G L Johnson
F T Liu
B S Coller
F V Chisari
Mitogen-activated protein (MAP) kinases act as transducers of extracellular signaling via tyrosine kinase-growth factor receptors and G-protein-linked receptors to elements regulating transcription. The activity, abundance, and localization of MAP kinase was investigated in normal and malignant neoplasia of the breast. In carcinoma of the breast, MAP kinase was heavily phosphorylated on tyrosyl residues and its activity elevated 5-10-fold over benign conditions, such as fibroadenoma and fibrocystic disease. By in situ reverse transcription-polymerase chain reaction, hyperexpression of MAP kinase mRNA can be localized to malignant, epithelial cells. Metastatic cells within involved lymph nodes of patients with breast cancer also display hyperexpression of MAP kinase. In spite of persistent activation via phosphorylation, MAP kinase expression is upregulated 5-20-fold and this hyperexpression may be a critical element to initiation as well as the metastatic potential of various forms of human breast cancer.
V S Sivaraman, H Wang, G J Nuovo, C C Malbon
At birth, transgenic mice, homozygous for the HIV-1 provirus pNL4-3, deleted in gag/pol, are normal in appearance and weight. Within several days after birth, the pups develop a syndrome characterized by dry, scaly, hyperkeratotic skin, growth failure, and death. The possibility that the homozygous embryos are being protected during gestation by a maternal factor led us to treat the newborn animals with various pregnancy-related hormones including human chorionic gonadotropin (hCG), estrogen, progesterone, and dexamethasone. Treatment with hCG prevented death, led to normal growth, and markedly reduced skin lesions. In contrast to the skin of the untreated homozygous pups, which expressed high levels of HIV mRNA and proteins (i.e., gp120 and Nef), the skin of the hCG-treated pups showed a marked reduction in both HIV mRNA and proteins. Discontinuation of hCG resulted in the reappearance of HIV transcripts and proteins, skin lesions, and growth failure resulting in death. In addition, HIV transcripts and proteins were reduced significantly in heterozygous mothers during pregnancy, but reappeared after parturition. Similarly, hCG treatment resulted in a decrease of HIV proteins in the skin of nonpregnant heterozygous transgenic mice. These findings suggest that the inhibiting effect of hCG on HIV expression may be clinically useful in the treatment of HIV infections, and may be responsible, during pregnancy, for the low transmission of HIV from infected mothers to their offspring.
S K De, C R Wohlenberg, N J Marinos, D Doodnauth, J L Bryant, A L Notkins
Cross-linking of allergen specific IgE bound to the high affinity IgE receptor (FC epsilonRI) on the surface of mast cells with multivalent allergens results in the release of both pre-formed and newly generated mediators, and in the manifestation of allergic symptoms. The expression of Fc epsilonRI, and the synthesis of IgE are therefore critical for the development of allergic diseases. In this study, we report that nasal mast cells (NMC) from patients with perennial allergic rhinitis (PAR) expressed significantly greater levels of the Fc epsilonRI, CD40L, IL-4, and IL-13 as compared to NMC from patients with chronic infective rhinitis (CIR). The level of Fc epsilonRI expression in NMC of PAR patients strongly correlated with the levels of serum total (r = 0.8, P < 0.003) and specific IgE (r = 0.89, P < 0.0004) antibodies. In addition, stimulation of NMC with IL-4, upregulated the Fc epsilonRIalpha chain expression both at the protein and mRNA levels, as detected by flow cytometry and reverse transcriptase-polymerase chain reaction. Furthermore, NMC from PAR, but not CIR, patients induced IgE synthesis by purified B cells in the presence of Der fII (mite antigen). These results suggest novel and critical roles for mast cells in promoting the allergic reaction through the increased expression of Fc epsilonRI and by enhancing and amplifying the IgE production, within the local microenvironment.
R Pawankar, M Okuda, H Yssel, K Okumura, C Ra
Aquaporin-2 (AQP2) mediates vasopressin-regulated collecting duct water permeability. Chronic heart failure (CHF) is characterized by abnormal renal water retention. We hypothetized that upregulation of aquaporin-2 water channel could account for the water retention in CHF. Male rats underwent either a left coronary artery ligation, a model of CHF, or were sham operated. 31-33 d after surgery, mean arterial pressure (MAP) and cardiac output were measured in conscious animals, and the animals were killed 24 h later. Cardiac output (CO) and plasma osmolality were significantly decreased and plasma vasopressin increased in the CHF as compared to the sham-operated rats. Both mRNA and protein AQP2 were significantly increased in the kidneys of the CHF rats. The effect of oral administration of a nonpeptide V2 vasopressin receptor antagonist, OPC 31260, was therefore investigated. OPC 31260 induced a significant increase in diuresis, decrease in urinary osmolality, and rise in plasma osmolality in the OPC 31260-treated CHF rats as compared to untreated CHF rats. The mRNA and protein AQP2 were significantly diminished in both cortex and inner medulla of the treated CHF rats. In conclusion, an early upregulation of AQP2 is present in CHF rats and this upregulation is inhibited by the administration of a V2 receptor antagonist. The results indicate a major role for vasopressin in the upregulation of AQP2 water channels and water retention in experimental CHF in the rat.
D L Xu, P Y Martin, M Ohara, J St John, T Pattison, X Meng, K Morris, J K Kim, R W Schrier
Urea transport in the kidney plays an important role in urinary concentration and nitrogen balance. Recently, three types of urea transporters have been cloned, UT1 and UT2 from rat and rabbit kidney and HUT11 from human bone marrow. To elucidate the physiological role of the latter urea transporter, we have isolated the rat homologue (UT3) of HUT11 and studied its distribution of expression and functional characteristics. UT3 cDNA encodes a 384 amino acid residue protein, which has 80% identity to the human HUT11 and 62% identity to rat UT2. Functional expression in Xenopus oocytes induced a large (approximately 50-fold) increase in the uptake of urea compared with water-injected oocytes. The uptake was inhibited by phloretin (0.75 mM) and pCMBS (0.5 mM) (55 and 32% inhibition, respectively). Northern analysis gave a single band of 3.8 kb in kidney inner and outer medulla, testis, brain, bone marrow, spleen, thymus, and lung. In situ hybridization of rat kidney revealed that UT3 mRNA is expressed in the inner stripe of the outer medulla, inner medulla, the papillary surface epithelium, and the transitional urinary epithelium of urinary tracts. Co-staining experiments using antibody against von Willebrand factor showed that UT3 mRNA in the inner stripe of the outer medulla is expressed in descending vasa recta. These data suggest that UT3 in kidney is involved in counter current exchange between ascending and descending vasa recta, to enhance the cortico-papillary osmolality gradient. In situ hybridization of testis revealed that UT3 is located in Sertoli cells of seminiferous tubules. The signal was only detected in Sertoli cells associated with the early stages of spermatocyte development, suggesting that urea may play a role in spermatogenesis.
H Tsukaguchi, C Shayakul, U V Berger, T Tokui, D Brown, M A Hediger
The expression of proinflammatory and immunoregulatory cytokines rapidly increases in the lungs after hemorrhage, and such alterations contribute to the frequent development of acute inflammatory lung injury in this setting. Blood loss also produces elevations in catecholamine concentrations in the pulmonary and systemic circulation. In the present experiments, we used alpha- and beta-adrenergic receptor blockade to examine in vivo interactions between hemorrhage-induced adrenergic stimulation and pulmonary cytokine expression. Treatment of mice with the alpha-adrenergic receptor antagonist phentolamine prevented not only the elevation in mRNA levels of IL-1beta, TNF-alpha, and TGF-beta1, the increase in IL-1beta protein, but also the activation of nuclear factor (NF)-KB and cyclic AMP response element binding protein, which occurred in lung cells of untreated animals during the first hour after hemorrhage. In contrast, treatment before hemorrhage with the beta-adrenergic receptor antagonist propranolol was associated with increases in mRNA levels for IL-1beta, TNF-alpha, and TGF-beta1, which were greater than those present in untreated hemorrhaged mice, and did not prevent hemorrhage-associated increases in lung IL-1beta protein. Treatment with propranolol prevented hemorrhage-induced phosphorylation of cyclic AMP response element binding protein, but increased hemorrhage-associated activation of NF-KB. These results demonstrate that hemorrhage initially increases pulmonary cytokine expression through alpha- but not beta-adrenergic stimulation, and suggest that such alpha-adrenergic-mediated effects occur through activation of the transcriptional regulatory factor NF-kappaB.
Y Le Tulzo, R Shenkar, D Kaneko, P Moine, G Fantuzzi, C A Dinarello, E Abraham
Although the high incidence of EBV-associated diffuse large cell lymphomas (DLCL) in HIV-1 infection is believed to be related to loss of immune control due to HIV-induced immune deficiency, it has been claimed that cytotoxic T lymphocyte (CTL) responses to EBV are longer lasting in HIV-1-infected persons than CTL directed against HIV-1 itself. We approached this apparent paradox by performing the first longitudinal study into the kinetics of EBV and HIV-specific CTL responses in HIV-infected patients progressing either to AIDS with non-Hodgkin's lymphoma (NHL) or AIDS with opportunistic infection (OI). Multiple samples were tested from HIV-1 seroconversion to AIDS-diagnosis. Four out of six patients that were either long-term asymptomatic or progressing to OI showed declining HIV-1 CTL precursor (CTLp) frequencies whereas EBV-CTLp remained stable, suggestive for HIV-1-specific immune exhaustion. In two patients rapidly progressing to AIDS-OI, a parallel decline of HIV-1- and EBV-CTL responses was seen, indicative for total collapse of cellular immunity. In all these six patients EBV-load remained low. However, in four out of five patients that progressed to DLCL, EBV-load was high and increasing several months preceding the NHL. In all five patients, EBV-CTLp decreased before the emergence of the NHL. Thus, our data show that in HIV-1 infection loss of HIV-1-specific T cell immunity is not necessarily paralleled by loss of EBV-specific T cell responses. The occurrence of AIDS-related DLCL is preceded by decreasing EBV-CTLp and increasing EBV load. Failing EBV-control might therefore be an important step in the pathogenesis of AIDS-related DLCL.
M J Kersten, M R Klein, A M Holwerda, F Miedema, M H van Oers
We demonstrate the direct involvement of increased collagenase activity in the cleavage of type II collagen in osteoarthritic human femoral condylar cartilage by developing and using antibodies reactive to carboxy-terminal (COL2-3/4C(short)) and amino-terminal (COL2-1/4N1) neoepitopes generated by cleavage of native human type II collagen by collagenase matrix metalloproteinase (MMP)-1 (collagenase-1), MMP-8 (collagenase-2), and MMP-13 (collagenase-3). A secondary cleavage followed the initial cleavage produced by these recombinant collagenases. This generated neoepitope COL2-1/4N2. There was significantly more COL2-3/4C(short) neoepitope in osteoarthritis (OA) compared to adult nonarthritic cartilages as determined by immunoassay of cartilage extracts. A synthetic preferential inhibitor of MMP-13 significantly reduced the unstimulated release in culture of neoepitope COL2-3/4C(short) from human osteoarthritic cartilage explants. These data suggest that collagenase(s) produced by chondrocytes is (are) involved in the cleavage and denaturation of type II collagen in articular cartilage, that this is increased in OA, and that MMP-13 may play a significant role in this process.
R C Billinghurst, L Dahlberg, M Ionescu, A Reiner, R Bourne, C Rorabeck, P Mitchell, J Hambor, O Diekmann, H Tschesche, J Chen, H Van Wart, A R Poole
The plasma membrane remodeling, including the early transverse redistribution of phosphatidylserine, is a general feature occurring in cells in which a death program has been induced. In most cases, studies of this kind have focused mainly on cells. In this study, we report a clear correlation between the degree of apoptosis induced by a variety of agents in several types of cultured cells and the amount of shed membrane microparticles captured in the corresponding supernatants by insolubilized annexin V, a protein showing a strong affinity for phosphatidylserine. Such particles carry membrane antigens specific of the cells they stem from, and through which capture is also feasible. Homologous circulating microparticles were captured in peripheral blood from individuals with HIV-1 infection. A substantial proportion bore CD4 antigen. In some cases, CD4+ particles could be detected even in the absence of circulating CD4+ T cells, testifying to the presence of such resident cells in lymphoid tissues. These results suggest that shed membrane particles are one of the hallmarks of programmed cell death, of particular interest when the corresponding cells are hardly accessible.
K Aupeix, B Hugel, T Martin, P Bischoff, H Lill, J L Pasquali, J M Freyssinet
In this report, we demonstrate that the T cell tropic strain of HIV, LAI, does not replicate in naive CD4 T cells stimulated by cross-linking CD3 and CD28. In contrast, LAI replicates well in memory CD4 T cells stimulated in the same way. Unlike this physiologically relevant stimulation, PHA stimulates productive LAI replication in both naive and memory T cells. These studies were conducted with highly purified (FACS-isolated) subsets of CD4 T cells identified by expression of both CD45RA and CD62L. Remixing of purified T cells showed that naive T cells do not suppress LAI replication in memory T cells and that memory T cells do not restore LAI expression in naive T cells. The suppression of productive LAI replication in naive T cells is not due to differential expression of viral coreceptors, nor is it due to inhibition of activation of the important HIV transcription factors, nuclear factor-kappaB and activator protein-1. The inherent resistance of naive T cells to productive HIV infection, coupled with their proliferative advantage as demonstrated here, provides a sound basis for proposed clinical therapies using ex vivo expansion and reinfusion of CD4 T cells from HIV-infected adults.
M Roederer, P A Raju, D K Mitra, L A Herzenberg, L A Herzenberg
Heparan sulfate (HS) proteoglycans play a key role in cell proliferation induced by basic fibroblast growth factor (FGF-2) and other heparin-binding growth factors. To modulate the involvement of HS, we have used a synthetic, nonsulfated polyanionic aromatic compound (RG-13577) that mimics functional features of heparin/HS. FGF-2-stimulated proliferation of vascular endothelial cells was markedly inhibited in the presence of 5-10 microg/ml compound RG-13577 (poly-4-hydroxyphenoxy acetic acid; Mr approximately 5 kD). Direct interaction between RG-13577 and FGF-2 was demonstrated by the ability of the former to compete with heparin on binding to FGF-2. RG-13577 inhibited FGF-2 binding to soluble- and cell surface-FGF receptor 1 (FGFR1). Unlike heparin, RG-13577 alone failed to mediate dimerization of FGF-2. Moreover, it abrogated heparin-mediated dimerization of FGF-2 and FGFR1, as well as FGF-2 mitogenic activity in HS-deficient F32 lymphoid cells. The antiproliferative effect of compound RG-13577 was associated with abrogation of FGF-2-induced tyrosine phosphorylation of FGFR1 and of cytoplasmic proteins involved in FGF-2 signal transduction, such as p90 and mitogen-activated protein kinase. A more effective inhibition of tyrosine phosphorylation was obtained after removal of the cell surface HS by heparinase. In contrast, tyrosine phosphorylation of an approximately 200-kD protein was stimulated by RG-13577, but not by heparin or FGF-2. RG-13577 prevented microvessel outgrowth from rat aortic rings embedded in a collagen gel. Development of nontoxic polyanionic compounds may provide an effective strategy to inhibit FGF-2-induced cell proliferation associated with angiogenesis, arteriosclerosis, and restenosis.
H Q Miao, D M Ornitz, E Aingorn, S A Ben-Sasson, I Vlodavsky
Thrombopoietin (TPO) regulates early and late stages of platelet formation as well as platelet activation. TPO exerts its effects by binding to the receptor, encoded by the protooncogene c-mpl, that is expressed in a large number of cells of hematopoietic origin. In this study, we evaluated the expression of c-Mpl and the effects of TPO on human polymorphonuclear cells (PMN). We demonstrate that PMN express the TPO receptor c-Mpl and that TPO induces STAT1 tyrosine phosphorylation and the formation of a serum inducible element complex containing STAT1. The analysis of biological effects of TPO on PMN demonstrated that TPO, at concentrations of 1-10 ng/ml, primes the response of PMN to n-formyl-met-leu-phe (FMLP) by inducing an early oxidative burst. TPO-induced priming on FMLP-stimulated PMN was also detected on the tyrosine phosphorylation of a protein with a molecular mass of approximately 28 kD. Moreover, we demonstrated that TPO by itself was able to stimulate, at doses ranging from 0.05 to 10 ng/ml, early release and delayed synthesis of interleukin 8 (IL-8). Thus, our data indicate that, in addition to sustaining megakaryocytopoiesis, TPO may have an important role in regulating PMN activation.
M F Brizzi, E Battaglia, A Rosso, P Strippoli, G Montrucchio, G Camussi, L Pegoraro
Diabetic nephropathy is a glomerular disease due to uncontrolled diabetes and genetic factors. It can be caused by glomerular hypertension produced by capillary vasodilation, due to diabetes, against constitutional glomerular resistance. As angiotensin II increases glomerular pressure, we studied the relationship between genetic polymorphisms in the renin-angiotensin system-angiotensin I converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II, subtype 1, receptor-and the renal involvement of insulin-dependent diabetic subjects with proliferative retinopathy: those exposed to the risk of nephropathy due to diabetes. Of 494 subjects recruited in 17 centers in France and Belgium (GENEDIAB Study), 157 (32%) had no nephropathy, 104 (21%) incipient (microalbuminuria), 126 (25 %) established (proteinuria), and 107 (22%) advanced (plasma creatinine > or = 150 micromol/liter or renal replacement therapy) nephropathy. The severity of renal involvement was associated with ACE insertion/deletion (I/D) polymorphism: chi2 for trend 5.135, P = 0.023; adjusted odds ratio attributable to the D allele 1.889 (95% CI 1.209-2.952, P = 0.0052). Renal involvement was not directly linked to other polymorphisms. However, ACE I-D and AGT M235T polymorphisms interacted significantly (P = 0.0166): in subjects with ACE ID and DD genotypes, renal involvement increased from the AGT MM to TT genotypes. Thus, genetic determinants that affect renal angiotensin II and kinin productions are risk factors for the progression of glomerular disease in uncontrolled insulin-dependent diabetic patients.
M Marre, X Jeunemaitre, Y Gallois, M Rodier, G Chatellier, C Sert, L Dusselier, Z Kahal, L Chaillous, S Halimi, A Muller, H Sackmann, B Bauduceau, F Bled, P Passa, F Alhenc-Gelas
We demonstrated previously that short term administration of recombinant beta-glucuronidase to newborn mice with mucopolysaccharidosis type VII reduced lysosomal storage in many tissues. Lysosomal storage accumulated gradually after cessation of enzyme replacement therapy. Mice alive at 1 yr of age had decreased bone deformities and less lysosomal storage in cortical neurons. Here we compare the effects of long term enzyme replacement initiated either at birth or at 6 wk of age, and of enzyme administration initiated at birth followed by syngeneic bone marrow transplantation (BMT) at 5 wk of age. Several mice from each treatment group lived to at least 1 yr of age. Liver and spleen samples had beta-glucuronidase levels ranging from 2.4 to 19.8% of normal and showed a parallel decrease in lysosomal storage. The combination of enzyme replacement therapy followed by BMT reduced lysosomal distension in meninges, corneal fibroblasts, and bone when compared with treatment with enzyme alone. Mice treated at birth had less lysosomal storage in some neurons of the brain and the skeletal dysplasia was less severe when compared to mice whose treatment was delayed until 6 wk of age. We conclude that both enzyme replacement alone and early enzyme replacement followed by BMT have long term positive effects on murine mucopolysaccharidosis type VII. In addition, treatment started at birth is far more effective than treatment initiated in young adults.
M S Sands, C Vogler, A Torrey, B Levy, B Gwynn, J Grubb, W S Sly, E H Birkenmeier
Lipoprotein lipase degrades triglycerides in plasma and as a byproduct produces HDL particles. Genetic variation in lipoprotein lipase may therefore affect cardiovascular risk. We tested 9,214 men and women from a general population sample and 948 patients with ischemic heart disease for the Asn291Ser substitution in lipoprotein lipase. The allele frequency in the general population was 0.024 and 0.026 for women and men, respectively. In comparison with noncarriers, female heterozygous probands had increased plasma triglycerides (delta = 0.23 mmol/liter), while HDL cholesterol was reduced in both female and male carriers (delta = 0.18 mmol/liter and delta = 0.11 mmol/liter, respectively). A similar phenotype was found in six homozygous carriers. On multiple logistic regression analysis, plasma triglycerides and HDL cholesterol were independent predictors of ischemic heart disease in both genders. On univariate analysis, odds ratios for ischemic heart disease in probands were 1.89 in women (95% CI: 1.19-3.01) and 0.90 in men (95% CI: 0.62-1.31), and on multivariate analysis were 1.98 in women (95% CI: 1.11-3.53) and 1.02 in men (95% CI: 0.65-1.60). This study demonstrates that a single common mutation in the lipoprotein lipase gene is associated with elevated plasma triglycerides and reduced HDL cholesterol levels, whereby carriers, in particular women, seem to be predisposed to ischemic heart disease. It cannot be excluded, however, that male carriers of this substitution may represent a subset of low-HDL individuals without raised triglycerides not predisposed to ischemic heart disease.
H H Wittrup, A Tybjaerg-Hansen, S Abildgaard, R Steffensen, P Schnohr, B G Nordestgaard
To analyze the human kappa chain repertoire and the influences that shape it, a single cell PCR technique was used that amplified Vkappa Jkappa rearrangements from genomic DNA of individual human B cells. More than 350 productive and 250 nonproductive Vkappa Jkappa rearrangements were sequenced. Nearly every functional Vkappa gene segment was used in rearrangements, although six Vkappa gene segments, A27, L2, L6, L12a, A17, and O12/O2 were used preferentially. Of these, A27, L2, L6, and L12a showed evidence of positive selection based on the variable region and not CDR3, whereas A17 was overrepresented because of a rearrangement bias based on molecular mechanisms. Utilization of Jkappa segments was also nonrandom, with Jkappa1 and Jkappa2 being overrepresented and Jkappa3 and Jkappa5 underrepresented in the nonproductive repertoire, implying a molecular basis for the bias. In B cells with two Vkappa Jkappa rearrangements, marked differences were noted in the Vkappa segments used for the initial and subsequent rearrangements, whereas Jkappa segments were used comparably. Junctional diversity was generated by n-nucleotide addition in 60% and by exonuclease trimming in 75% of the Vkappa Jkappa rearrangements analyzed. Despite this large degree of diversity, a strict CDR3 length was maintained in both productive and nonproductive rearrangements. More than 23% of the productive rearrangements, but only 7% of the nonproductive rearrangements contained somatic hypermutations. Mutations were significantly more frequent in Vkappa sequences derived from CD5- as compared with CD5+ B cells. These results document that the gene segment utilization within the Vkappa repertoire is biased by both intrinsic molecular processes as well as selection after light chain expression. Moreover, IgM+ memory cells with highly mutated kappa genes reside within the CD5- but not the CD5+ B cell compartment.
S J Foster, H P Brezinschek, R I Brezinschek, P E Lipsky
Human gastric mucosal epithelial cells display class II MHC, the expression of which is increased during Helicobacter pylori infection. These observations suggest that the gastric epithelium may participate as antigen-presenting cells (APC) during local immune responses. The increase in class II MHC expression occurs in parallel with an elevation in gastric CD4+ T cell numbers within and adjacent to the epithelium. Since the expression of either B7-1 (CD80) or B7-2 (CD86) on APC is required for the activation of T cells, it was important to establish human gastric epithelial cells expressed those surface ligands. The expression of B7-1 and B7-2 was detected on human gastric epithelial cell lines and freshly isolated epithelial cells from gastric biopsies with specific antibodies. B7-2 expression was higher than B7-1 at both protein and transcript levels and was increased after crosslinking class II MHC molecules on IFNgamma-treated epithelial cells and in cells pretreated with the combination of IFNgamma and H. pylori. Similarly, B7-2 expression was higher on gastric epithelial cells from H. pylori-infected tissues compared with those from uninfected specimens. To determine the function of these molecules on gastric epithelial cells, antibodies to B7-1 and B7-2 were shown to reduce the ability of the cells to stimulate alloreactive CD4+ T cells. These observations are the first to demonstrate that B7-1 and B7-2 are expressed on mucosal epithelial cells in situ. Thus, the expression of B7-1 and B7-2 by epithelial cells may allow them to act as APC in regulating local responses such as those that occur during infection with H. pylori.
G Ye, C Barrera, X Fan, W K Gourley, S E Crowe, P B Ernst, V E Reyes
The role of IFNgamma in the development of infection-driven interstitial pneumonitis in a model of murine graft-versus-host disease was investigated. Mice were given either syngeneic or allogeneic bone marrow transplants along with lung Pneumocystis carinii infections and were treated with either control mAb or anti-IFNgamma mAb. At day 21 after transplant, lung weights were elevated nearly twofold in all groups. By day 41, mice in all groups had cleared the P. carinii but only the mice given allogeneic transplants and anti-IFNgamma had increased lung weights. Increased lung weights in the anti-IFNgamma-treated mice corresponded to alveolar infiltration of eosinophils, neutrophils, and multinucleated giant cells and exacerbated interstitial pneumonitis compared with mice treated with control antibody. Intracellular staining indicated that there were 3- to 10-fold more CD4+ cells producing IFNgamma than those producing IL-4 in the lung lavages of mice given either syngeneic or allogeneic transplant. Treatment of transplanted mice with anti-IFNgamma resulted in a significant decrease in IFN-gamma-producing CD4+ and CD8+ cells in the lung lavages but no change in the number of IL-4-producing CD4+ cells. These data indicate that IFNgamma is critical for controlling the development of P. carinii-driven interstitial pneumonia after either syngeneic or allogeneic bone marrow transplant in mice.
B A Garvy, F Gigliotti, A G Harmsen
Heat shock protein 70 (HSP70) has been reported to be involved in the myocardial self-preservation system. To obtain the evidence that HSP70 plays a direct role in the protection from myocardial ischemia-reperfusion injury, rat hearts were transfected with human HSP70 gene by intracoronary infusion of hemagglutinating virus of Japan (HVJ)-liposome containing human HSP70 gene. The control hearts were infused with HVJ-liposome without the HSP70 gene. The hearts from whole-body heat-stressed or nontreated rats were also examined. Western blot and immunohistochemical analysis showed that apparent overexpression of HSP70 occurred in the gene transfected hearts and that gene transfection might be more effective for HSP70 induction than heat stress. In Langendorff perfusion, better functional recovery as well as less creatine phosphokinase leakage after ischemia were obtained in the gene transfected hearts with HSP70 than in the control or nontreated hearts. Furthermore, the gene transfected hearts showed better functional recovery than the heat-stressed hearts. These results indicated that overexpressed HSP70 plays a protective role in myocardial injury, suggesting the possibility that gene transfection with HSP70 may become a novel method for myocardial protection through enforcing the self-preservation systems.
K Suzuki, Y Sawa, Y Kaneda, H Ichikawa, R Shirakura, H Matsuda
To investigate abnormalities of airway epithelial ion transport underlying chronic inflammatory airway diseases, we performed electrophysiological, histological, and molecular biological experiments using rabbits exposed to SO2 as a model of bronchitis. By comparison with control, the SO2-exposed trachea exhibited decreased short circuit current (Isc) and conductance associated with increased potential difference. In normal trachea, apical ATP induced a transient Isc activation followed by a suppression, whereas the bronchitis model exhibited a prolonged activation without suppression. This pathological ATP response was abolished by diphenylamine 2-carboxylate or Cl--free bath solution. A significant increase in net Cl- flux toward the lumen was observed after ATP in our bronchitis model. Isoproterenol or adenosine evoked a sustained Isc increase in SO2-exposed, but not in normal, tracheas. The Northern blot analysis showed a strong expression of cystic fibrosis transmembrane conductance regulator (CFTR) mRNA in SO2-exposed epithelium. The immunohistochemical study revealed a positive label of CFTR on cells located luminally only in SO2-exposed rabbits. We concluded that the prolonged ATP response in our bronchitis model was of a superimposed normal and adenosine-activated current. The latter current was also activated by isoproterenol and appeared as a signature current for the bronchitis model airway. This was likely mediated by CFTR expressed in the course of chronic inflammation.
N Iwase, T Sasaki, S Shimura, T Fushimi, H Okayama, H Hoshi, T Irokawa, K Sasamori, K Takahashi, K Shirato
Escherichia coli that express Dr fimbriae and related adhesins recognize the common receptor decay accelerating factor. E. coli strains that express adhesins of the Dr family were postulated to be associated with cystitis (30-50%), pregnancy-associated pyelonephritis (30%), and chronic diarrhea (50%). In this study, we investigated the hypothesis that E. coli renal interstitial binding mediated by the Dr adhesin may be important for the development of chronic pyelonephritis. An insertional dra mutant, E. coli DR14, of the clinical E. coli isolate IH11128 bearing Dr fimbriae, was constructed and used to characterize persistence of infection and interstitial tropism in an experimental model of ascending pyelonephritis. Quantitative cultures of kidney homogenates indicated that Dr hemagglutinin positive (Dr+) E. coli IH11128 established a 1-yr colonization of renal tissue. In the Dr hemagglutinin negative (Dr-) group, 50% of animals cleared infection within 20 wk and 100% between 32 to 52 wk. Dr+ E. coli colonized the renal interstitium. Significant histological changes corresponding to tubulointerstitial nephritis including interstitial inflammation, fibrosis, and tubular atrophy were found in the kidney tissue of the Dr+ but not the Dr- group. A substantial amount of fimbrial antigen was detected in the parenchymal regions affected by interstitial inflammation and fibrosis. The obtained results are consistent with the hypothesis that mutation within the dra region, affecting E. coli binding to tubular basement membranes, prevented renal interstitial tropism and the development of the changes characteristically seen in tubulointerstitial nephritis.
P Goluszko, S L Moseley, L D Truong, A Kaul, J R Williford, R Selvarangan, S Nowicki, B Nowicki
A novel approach to reduce the anaphylactic activity of allergens is suggested. The strategy makes use of the presence of conformational immunoglobulin E (IgE) epitopes on one of the most common allergens. The three dimensional structure of the major birch pollen allergen, Bet v 1, was disrupted by expressing two parts of the Bet v 1 cDNA representing amino acids 1-74 and 75-160 in Escherichia coli. In contrast to the complete recombinant Bet v 1, the fragments showed almost no allergenicity and exhibited random coil conformation as analyzed by circular dichroism. Both nonanaphylactic fragments induced proliferation of human Bet v 1-specific T cell clones, indicating that they harbored all dominant T cell epitopes and therefore may be considered as a basis for the development of a safe and specific T cell immunotherapy.
S Vrtala, K Hirtenlehner, L Vangelista, A Pastore, H G Eichler, W R Sperr, P Valent, C Ebner, D Kraft, R Valenta
Recent studies using murine animal model systems indicate that clinical progression of autoimmune disease may be due to the sequential accumulation of neoautoreactivity characterized by extensive plasticity of self recognition. In the present study, we addressed the question of whether a similar paradigm of self recognition is implicated in the development of multiple sclerosis (MS), a demyelinating disease with a presumed autoimmune etiology. Our approach was to determine serial changes over a 12-18-mo period in response to an epitope-mapping series of 265 12-mer peptides of myelin proteolipid protein (PLP) by patients with isolated monosymptomatic demyelinating syndromes (IMDS), a group of distinct clinical disorders with variable rates of progression to MS. Our data showed that an extensive array of proteolipid protein peptides could elicit autoreactivity. Moreover, differential autoreactive patterns were evident within IMDS patient subpopulations. Monocentric monophasic IMDS patients with no evidence of prior subclinical disease typically showed fully sustained autoreactivity characterized by extensive plasticity, epitope focusing, shifting, and spreading of responses to new self determinants. In contrast, multicentric monophasic IMDS patients with putative evidence of prior asymptomatic lesion formation typically showed partially sustained autoreactivity characterized by abrupt abrogation of responses to an extensive array of self determinants. No sustained autoreactivity was observed in normal control subjects or in patients with other neurologic diseases. Our results indicate that self recognition associated with the development of MS is a developmental process characterized by autoreactive diversity, plasticity, and instability.
V K Tuohy, M Yu, B Weinstock-Guttman, R P Kinkel
Myotonic dystrophy is a dominantly inherited clinically variable multisystemic disorder, and has been found to be caused by heterozygosity for a trinucleotide repeat expansion mutation in the 3' untranslated region of a protein kinase gene (DM kinase). The mechanisms by which the expanded repeat in DNA results in a dominant biochemical defect and the varied clinical phenotype, is not known. We have recently proposed a model where disease pathogenesis may occur at the RNA level in myotonic dystrophy: the mutant DM kinase RNA with the expansion mutation may disrupt cellular RNA metabolism in some general manner, as evidenced by defects in RNA processing of the normal DM kinase gene in heterozygous patients (dominant negative RNA mutation). Here we further test this hypothesis by measuring RNA metabolism of other genes in patient muscle biopsies (nine adult onset myotonic dystrophy patients, two congenital muscular dystrophy patients, four normal controls, and four myopathic controls). We focused on the insulin receptor gene because of the documented insulin resistance of DM patients. We show that there is a significant decrease in insulin receptor RNA in both total RNA and RNA polyA+ pools relative to normal and myopathic control muscles (P < 0.002), measured relative to both dystrophin RNA and muscle sodium channel RNA. We also show reductions in insulin receptor protein. Our results reinforce the concept of a generalized RNA metabolism defect in myotonic dystrophy, and offer a possible molecular mechanism for the increased insulin resistance observed in many myotonic dystrophy patients.
A Morrone, E Pegoraro, C Angelini, E Zammarchi, G Marconi, E P Hoffman
To evaluate the role of tumor necrosis factor (TNF alpha) in bone loss resulting from estrogen deficiency, the effects of ovariectomy were explored in six-month-old transgenic mice expressing high blood levels of a soluble TNF receptor type I (sTNFR1)-FcIgG3 fusion protein, which neutralizes TNF alpha, and in their nontransgenic littermates used as controls. These transgenic mice were identical to control mice in bone mass (evaluated by bone mineral density and content) and strength. 12 weeks after ovariectomy, the decrease in bone mass and increase in osteocalcin (marker of bone turnover) found in control mice were not observed in transgenic mice, which were not different from sham-operated mice, transgenic or not. This observation suggests a critical role for TNF alpha in the pathogenesis of bone loss induced by estrogen deficiency, a common cause of morbidity in postmenopausal women.
P Ammann, R Rizzoli, J P Bonjour, S Bourrin, J M Meyer, P Vassalli, I Garcia
These studies were undertaken to determine the kinetic characteristics of high density lipoprotein (HDL) apo AI and cholesteryl ester transport in the hamster in vivo. Saturable HDL apo AI transport was demonstrated in the kidneys, adrenal glands, and liver. Saturable HDL cholesteryl ester transport was highest in the adrenal glands and liver. In the liver and adrenal glands, maximal transport rates (J(m)) for receptor dependent uptake were similar for the protein and cholesteryl ester moieties; however, the concentration of HDL necessary to achieve half-maximal transport (K(m)) was 20- to 30-fold higher for apo AI. Consequently, at normal plasma HDL concentrations, the clearance of HDL cholesteryl ester exceeded that of HDL apo AI by approximately 10-fold in the adrenal glands and by approximately fivefold in the liver. At normal HDL concentrations, the majority of HDL cholesteryl ester (76%) was cleared by the liver whereas the majority of HDL apo AI (77%) was cleared by extrahepatic tissues. The rate of HDL cholesteryl ester uptake by the liver equaled the rate of cholesterol acquisition by all extrahepatic tissues suggesting that HDL cholesteryl ester uptake by the liver accurately reflects the rate of "reverse cholesterol transport." Receptor dependent HDL cholesteryl ester uptake by the liver was maximal (saturated) at normal plasma HDL concentrations. Consequently, changes in plasma HDL concentrations are not accompanied by parallel changes in the delivery of HDL cholesteryl ester to the liver unless the number or affinity of transporters is also regulated.
L A Woollett, D K Spady
The congenital long QT syndrome (LQTS) is an inherited disorder characterized by a delay in cardiac cellular repolarization leading to cardiac arrhythmias and sudden death often in young people. One form of the disease (LQT3) involves mutations in the voltage-gated cardiac sodium channel. The potential for targeted suppression of the LQT defect was explored by heterologous expression of mutant channels in cultured human cells. Kinetic and steady state analysis revealed an enhanced apparent affinity for the predominantly charged, primary amine compound, mexiletine. The affinity of the mutant channels in the inactivated state was similar to the wild type (WT) channels (IC50 approximately 15-20 microM), but the late-opening channels were inhibited at significantly lower concentrations (IC50 = 2-3 microM) causing a preferential suppression of the late openings. The targeting of the defective behavior of the mutant channels has important implications for therapeutic intervention in this disease. The results provide insights for the selective suppression of the mutant phenotype by very low concentrations of drug and indicate that mexiletine equally suppresses the defect in all three known LQT3 mutants.
D W Wang, K Yazawa, N Makita, A L George Jr, P B Bennett
The local delivery of glucocorticoids to tissues significantly decreases mast cell number. This pharmacologic effect of glucocorticoids is believed to be one of the mechanisms by which glucocorticoids regulate allergic inflammation. To determine the mechanism by which glucocorticoids are able to exert this effect, we first applied the glucocorticoid fluocinonide to mouse dermis and observed that the decrease in mast cell number was associated with an increase in mast cell apoptosis. This did not appear to be due to a direct effect of the glucocorticoid on mast cells, as the addition of 0.01-1.0 microM of the glucocorticoid dexamethasone into stem cell factor (SCF)-dependent mast cell cultures did not enhance mast cell death. However, addition of dexamethasone to cultured fibroblasts did result in a downregulation of SCF mRNA and a significant decrease in SCF protein production. Similarly, immunohistochemistry performed on fluocinonide-treated mouse dermis revealed a decrease in immunoreactive SCF. Administration of SCF at sites of fluocinonide administration to the dermis abolished the mast cell-depleting effect of this glucocorticoid. Thus, glucocorticoids decrease tissue mast cell number by downregulating tissue SCF production required for the survival of local mast cells. This observation may be applicable to the design of improved strategies to treat mast cell-mediated disorders.
S Finotto, Y A Mekori, D D Metcalfe
Clinical conditions associated with local or systemic hypoxemia can lead to prothrombotic diatheses. This study was undertaken to establish a model of whole-animal hypoxia wherein oxygen deprivation by itself would be sufficient to trigger tissue thrombosis. Furthermore, this model was used to test the hypothesis that hypoxia-induced mononuclear phagocyte (MP) recruitment and tissue factor (TF) expression may trigger the local deposition of fibrin which occurs in response to oxygen deprivation. Using an environmental chamber in which inhaled oxygen tension was lowered to 6%, hypoxic induction of thrombosis was demonstrated in murine pulmonary vasculature by 8 h based upon: (a) immunohistologic evidence of fibrin formation in hypoxic lung tissue using an antifibrin antibody, confirmed by 22.5-nm strand periodicity by electron microscopy; (b) immunoblots revealing fibrin gamma-gamma chain dimers in lungs from hypoxic but not normoxic mice or hypoxic mice treated with hirudin; (c) accelerated deposition of 125I-fibrin/fibrinogen and 111In-labeled platelets in the lung tissue of hypoxic compared with normoxic animals; (d) reduction of tissue 125I-fibrin/fibrinogen accumulation in animals which had either been treated with hirudin or depleted of platelets before hypoxic exposure. Because immunohistochemical analysis of hypoxic pulmonary tissue revealed strong MP staining for TF, confirmed by increased TF RNA in hypoxic lungs, and because 111In-labeled murine MPs accumulated in hypoxic pulmonary tissue, we evaluated whether recruited MPs might be responsible for initiation of hypoxia-induced thrombosis. This hypothesis was supported by several lines of evidence: (a) MP depletion before hypoxia reduced thrombosis, as measured by reduced 125I-fibrin/fibrinogen deposition and reduced accumulation of cross-linked fibrin by immunoblot; (b) isolated murine MPs demonstrated increased TF immunostaining when exposed to hypoxia; and (c) administration of an anti-rabbit TF antibody that cross-reacts with murine TF decreased 125I-fibrin/fibrinogen accumulation and cross-linked fibrin accumulation in response to hypoxia in vivo. In summary, these studies using a novel in vivo model suggest that MP accumulation and TF expression may promote hypoxia-induced thrombosis.
C A Lawson, S D Yan, S F Yan, H Liao, Y S Zhou, J Sobel, W Kisiel, D M Stern, D J Pinsky
The highly regulated secretion of effector cytokines by CD4+ T cells plays a critical role in immune protection against pathogens such as cytomegalovirus. Here, we directly compare the frequency and functional characteristics of cytomegalovirus-specific CD4+ memory/effector T cells in normal and HIV+ subjects using a novel, highly efficient multiparameter flow cytometric assay that detects the rapid intracellular accumulation of cytokine(s) after short-term (6 h) in vitro antigen stimulation. Responses in this assay correlate precisely with independent measures of sensitization history (e.g., seroreactivity), and allow the simultaneous assessment of multiple cytokines in single effector T cells. Healthy HIV- individuals manifested an average of 0.71, 0.72, 0.38, and 0.06% CD4+ T cells responding to cytomegalovirus with gamma-IFN, TNF-alpha, IL-2, and IL-4 production, respectively, with the simultaneous production of gamma-IFN, TNF-alpha, and IL-2 being the most common effector phenotype. Significantly, overall cytomegalovirus-specific CD4+ effector frequencies were markedly higher among 40% of HIV+ subjects (2.7-8.0%), and demonstrated a predominately polarized gamma-IFN+/TNF-alpha+/IL-2-/IL-4- phenotype. In contrast, CD4+ effector frequencies for heterologous, nonubiquitous viruses such as the mumps virus were low or absent in the HIV+ group. These data suggest the existence of homeostatic mechanisms in HIV disease that selectively preserve memory T cell populations reactive with ubiquitous pathogens such as cytomegalovirus-likely at the expense of T cell memory to more sporadically encountered infectious agents.
S L Waldrop, C J Pitcher, D M Peterson, V C Maino, L J Picker
Mitochondria have been implicated in apoptosis, however, the precise mechanisms whereby mitochondria exert their effect are not clear. To gain further insights, we generated a panel of cells from ML-1a cells that were rendered respiration deficient by ethidium bromide treatment. Two respiration-deficient clones were subsequently reconstituted by fusion with platelets. Respiration-deficient clones were resistant to TNF-induced apoptosis, whereas ML-1a and reconstituted clones were sensitive. In contrast, inhibition of proliferation and induction of differentiation by TNF were still observed in respiration deficient clones, suggesting a selective requirement of respiration in TNF-induced apoptosis. Furthermore the apoptosis machinery is not completely altered in respiration-deficient cells because they underwent apoptosis after staurosporine treatment. Next, we showed that apoptosis induced by TNF and staurosporine were blocked by z-DEVD-CH2F, an inhibitor of CPP32-like cysteine protease, suggesting the involvement of CPP32-like protease in both apoptosis signaling pathways. Interestingly, TNF activated CPP32-like protease in the parental and reconstituted clones but not in respiration-deficient clones, and staurosporine in all clones. Thus, the apoptosis signaling block in respiration-deficient clones is located at a step before CPP32-like protease activation, which can be bypassed by staurosporine.
M Higuchi, B B Aggarwal, E T Yeh
Neonates exposed to parasite antigens (Ags) in utero may develop altered fetal immunity that could affect subsequent responses to infection. We hypothesized that cord blood lymphocytes (CBL) from offspring of mothers residing in an area highly endemic for schistosomiasis, filariasis, and tuberculosis in Kenya would either fail to respond or generate a predominantly Th2-associated cytokine response to helminth and mycobacterial antigens (PPD) in vitro compared to maternal PBMC. Kenyan CBL generated helminth Ag-specific IL-5 (range 29-194 pg/ml), IL-10 (121-2,115 pg/ml), and/or IFN-gamma (78 pg/ml-10.6 ng/ml) in 26, 46, and 57% of neonates, respectively (n = 40). PPD induced IFN-gamma in 30% of Kenyan CBL (range 79-1,896 pg/ml), but little or no IL-4 or IL-5. No Ag-specific IL-4, IL-5, or IFN-gamma release was detected by CBL obtained in the United States (n = 11). Ag-driven cytokine production was primarily CD4-dependent. Cytokine responses to helminth and mycobacterial Ags by maternal PBMC mirrored that observed in neonates. CBL from helminth infected and/or PPD-sensitized mothers produced more Ag-specific cytokines compared to CBL from uninfected mothers (P < 0.05). These data demonstrate that the human fetus develops similar patterns of cytokine production observed in adults and indicates that prenatal exposure may not lead to tolerance or altered fetal immunity. .
I Malhotra, J Ouma, A Wamachi, J Kioko, P Mungai, A Omollo, L Elson, D Koech, J W Kazura, C L King
Eotaxin is a potent and specific eosinophil chemoattractant that is mobilized in the respiratory epithelium after allergic stimulation. Pulmonary levels of eotaxin mRNA are known to increase after allergen exposure in sensitized animals. In this study we demonstrate that TNF alpha and IL-1beta induce the accumulation of eotaxin mRNA in the pulmonary epithelial cell lines A549 and BEAS 2B in a dose-dependent manner. Cytokine-induced A549 cell mRNA accumulation was maximal at 4 h and was significantly enhanced when the cells were costimulated with IFNgamma. TNFalpha- and IL-1beta-induced increases in eotaxin mRNA were diminished in a dose-dependent manner by the glucocorticoid dexamethasone and were augmented by the protein synthesis inhibitor cycloheximide. Cytokine-induced increases in eotaxin mRNA expression correlated with increased eotaxin protein production and secretion, and dexamethasone inhibition of cytokine-induced eotaxin mRNA augmentation was associated with diminished eotaxin protein secretion. These findings, together with the known kinetics of TNF alpha and IL-1beta mobilization in asthmatic airways and the potent eosinophil chemotactic effects of eotaxin, define a mechanism linking inflammatory cytokine mobilization to eosinophil recruitment that may be relevant to the pathogenesis of asthma.
C M Lilly, H Nakamura, H Kesselman, C Nagler-Anderson, K Asano, E A Garcia-Zepeda, M E Rothenberg, J M Drazen, A D Luster
The ability of HIV-1 to establish an infection and replicate to high copy number in CD4 lymphocytes is dependent on both the activation state of the cell and virus-encoded regulatory proteins that modulate viral gene expression. To study these required virus-cell interactions, we have used an in vitro cell model of acute HIV infection of quiescent, primary CD4 lymphocytes and subsequent induction of T cell activation and virus replication by lectin or CD3 receptor cross-linking. Experiments were done to determine if the capacity of HIV to establish infection and complete replication was impacted by the maturational state of the CD4 cell target or the specific signal induction pathway engaged during activation. Primary CD4 cells were FACS-sorted into the major phenotypic subsets representative of memory (CD45RO) and naive (CD45RA) cells. Levels of virus replication were compared between infection with wild-type NL4-3 virus and an isogenic mutant containing a deletion in nef regulatory gene. PHA mitogen stimulation was compared with anti-CD3, with and without anti-CD28 costimulation, for induction of cell proliferation and virus replication. In both infected and uninfected cells, the RA cell subset exhibited significantly greater response to CD3/CD28 stimulation than did the RO cell subset. In contrast, the majority of virus replication occurred consistently in the RO cell subset. Deletion of HIV nef function caused a severe reduction in viral replication, especially in the RA naive cell subset after CD3 induction. PCR analysis of viral DNA formation, during infection of quiescent cells, demonstrated that the observed differences in HIV replication capacity between RO and RA cell subsets were not due to inherent differences in cell susceptibility to infection. Our results indicate that HIV replication is enhanced selectively in CD45RO memory phenotype cells through the probable contribution of specialized cellular factors which are produced during CD3-initiated signal transduction.
C A Spina, H E Prince, D D Richman
In earlier studies, we provided statistical evidence that individual differences in the angiotensinogen gene, the precursor of the vasoactive hormone angiotensin II, constitute inherited predispositions to essential hypertension in humans. We have now identified a common variant in the proximal promoter, the presence of an adenine, instead of a guanine, 6 bp upstream from the initiation site of transcription, in significant association with the disorder. Tests of promoter activity and DNA binding studies with nuclear proteins suggest that this nucleotide substitution affects the basal transcription rate of the gene. These observations provide some biological insight about the possible mechanism of a genetic predisposition to essential hypertension; they may also have important evolutionary implications.
I Inoue, T Nakajima, C S Williams, J Quackenbush, R Puryear, M Powers, T Cheng, E H Ludwig, A M Sharma, A Hata, X Jeunemaitre, J M Lalouel
A number of cytokines, including basic fibroblast growth factor (bFGF), vascular endothelial growth factor (VEGF), oncostatin M (OSM), IL-6, and tumor necrosis factor alpha (TNF-alpha), have been postulated to have a role in the pathogenesis of Kaposi's sarcoma (KS). The proliferative effects of bFGF and OSM may be via their reported activation of the c-Jun NH2-terminal kinase (JNK) signaling pathway in KS cells. We now report that KS cells express a recently identified focal adhesion kinase termed RAFTK which appears in other cell systems to coordinate surface signals between cytokine and integrin receptors and the cytoskeleton as well as act downstream to modulate JNK activation. We also report that the tyrosine kinase receptor FLT-4, present on normal lymphatic endothelium, is robustly expressed in KS cells. Treatment of KS cells with VEGF-related protein (VRP), the ligand for the FLT-4 receptor, as well as with the cytokines bFGF, OSM, IL-6, VEGF, or TNF-alpha resulted in phosphorylation and activation of RAFTK. Following its activation, there was an enhanced association of RAFTK with the cytoskeletal protein paxillin. This association was mediated by the hydrophobic COOH-terminal domain of the kinase. Furthermore, JNK activity was increased in KS cells after VEGF or VRP stimulation. We postulate that in these tumor cells RAFTK may be activated by a diverse group of stimulatory cytokines and facilitate signal transduction to the cytoskeleton and downstream to the growth promoting JNK pathway.
Z Y Liu, R K Ganju, J F Wang, M A Ona, W C Hatch, T Zheng, S Avraham, P Gill, J E Groopman