The curtain rises on the renin-angiotensin system: AT2 receptors are in the spotlight.
The zebrafish: heritable disorders in transparent embryos.
Inhibition of HIV-1 replication by cyclopentenone prostaglandins in acutely infected human cells. Evidence for a transcriptional block.
C Rozera, A Carattoli, A De Marco, C Amici, C Giorgi, M G SantoroAbstract | Full text | PDF (Page 1795)
Cyclopentenone prostaglandins (PGs) inhibit virus replication in several DNA and RNA virus models, in vitro and in vivo. In the present report we demonstrate that the cyclopentenone prostaglandins PGA(1) and PGJ(2) at nontoxic concentrations can dramatically suppress HIV-1 replication during acute infection in CEM-SS cells. PGs did not affect HIV-1 adsorption, penetration, reverse transcriptase activity nor viral DNA accumulation in HIV-1 infected cells. A dramatic reduction in HIV-1 mRNA levels was detected up to 48-72 h after infection (p.i.) in PG-treated cells, and HIV-1 protein synthesis was greatly reduced by a single PG-treatment up to 96 h p.i. Repeated PGA(1)-treatments were effective in protecting CEM-SS cells by the cytopathic effect of the virus, and in dramatically reducing HIV-1 RNA levels up to 7 d after infection. The antiviral effect was not mediated by alterations in the expression of alpha-, beta-, or gamma-interferon,TNFalpha, TNFbeta, IL6, and IL10 in HIV-infected CEM-SS cells. The fact that prostaglandins are used clinically in the treatment of several diseases, suggests a potential use of cyclopentenone PGs in the treatment of HIV-infection.
Defective anion transport and marked spherocytosis with membrane instability caused by hereditary total deficiency of red cell band 3 in cattle due to a nonsense mutation.
M Inaba, A Yawata, I Koshino, K Sato, M Takeuchi, Y Takakuwa, S Manno, Y Yawata, A Kanzaki, J Sakai, A Ban, K Ono, Y MaedeAbstract | Full text | PDF (Page 1804)
We studied bovine subjects that exhibited a moderate uncompensated anemia with hereditary spherocytosis inherited in an autosomal incompletely dominant mode and retarded growth. Based on the results of SDS-PAGE, immunoblotting, and electron microscopic analysis by the freeze fracture method, we show here that the proband red cells lacked the band 3 protein completely. Sequence analysis of the proband band 3 cDNA and genomic DNA showed a C --> T substitution resulting in a nonsense mutation (CGA --> TGA; Arg --> Stop) at the position corresponding to codon 646 in human red cell band 3 cDNA. The proband red cells were deficient in spectrin, ankyrin, actin, and protein 4.2, resulting in a distorted and disrupted membrane skeletal network with decreased density. Therefore, the proband red cell membranes were extremely unstable and showed the loss of surface area in several distinct ways such as invagination, vesiculation, and extrusion of microvesicles, leading to the formation of spherocytes. Total deficiency of band 3 also resulted in defective Cl-/HCO3- exchange, causing mild acidosis with decreases in the HCO3- concentration and total CO2 in the proband blood. Our results demonstrate that band 3 indeed contributes to red cell membrane stability, CO2 transport, and acid-base homeostasis, but is not always essential to the survival of this mammal.
Urokinase is required for the pulmonary inflammatory response to Cryptococcus neoformans. A murine transgenic model.
M R Gyetko, G H Chen, R A McDonald, R Goodman, G B Huffnagle, C C Wilkinson, J A Fuller, G B ToewsAbstract | Full text | PDF (Page 1818)
Urokinase (uPA) is hypothesized to provide proteolytic activity enabling inflammatory cells to traverse tissues during recruitment, and it is implicated as a cytokine modulator. Definitive evaluation of these hypotheses in vivo has previously been impossible because uPA could not completely and irreversibly be eliminated. This limitation has been overcome through the development of uPA-deficient transgenic mice (uPA-/-). Using these mice, we evaluated the importance of uPA in the pulmonary inflammatory response to Cryptococcus neoformans (strain 52D). C. neoformans was inoculated into uPA-/- and control mice (uPA+/+), and cell recruitment to the lungs was quantitated. The number of CFU in lung, spleen and brain was determined to assess clearance, and survival curves were generated. By day 21 after inoculation, uPA-/- mice had markedly fewer pulmonary inflammatory (CD45+), CD4+, and CD11b/CD18+ cells compared with uPA+/+ controls (P<0.0007); pulmonary CFUs in the uPA-/- mice continued to increase, whereas CFUs diminished in uPA+/+ mice(P<0.005). In survival studies, only 3/19 uPA+/+ mice died, whereas 15/19 uPA-/- mice died (p<0.001). We have demonstrated that uPA is required for a pulmonary inflammatory response to C. neoformans. Lack of uPA results in inadequate cellular recruitment, uncontrolled infection, and death.
Constitutive activation of 5-lipoxygenase in the lungs of patients with idiopathic pulmonary fibrosis.
J Wilborn, M Bailie, M Coffey, M Burdick, R Strieter, M Peters-GoldenAbstract | Full text | PDF (Page 1827)
Idiopathic pulmonary fibrosis (IPF) is a progressive disorder characterized by inflammation, fibroblast proliferation, and accumulation of extracellular matrix proteins. Leukotrienes (LTs) are pro-inflammatory and pro-fibrogenic mediators derived from the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism. They are thought to play a role in a number of disease processes, but have received relatively little attention in investigations into the pathogenesis of IPF. In this study, we measured the levels of immunoreactive LTs B(4) and C(4) in homogenates of lung tissue obtained from patients with newly diagnosed, untreated IPF, as compared to levels measured in homogenates of uninvolved nonfibrotic lung tissue from patients undergoing resectional surgery for bronchogenic carcinoma. Compared to homogenates on nonfibrotic control lung, homogenates from IPF patients contained 15-fold more LTB(4) and 5-fold more LTC(4). IPF homogenate levels of LTB(4) were significantly correlated with histologic indices of both inflammation (r=0.861) and fibrosis (r=0.926). Activation of 5-LO is known from in vitro studies to be associated with localization of the enzyme at the nuclear membrane. Immunohistochemical staining for 5-LO protein in alveolar macrophages (AMs) demonstrated that such an "activated" localization pattern was significantly more frequent in IPF lung (19.2+/-3.3% of cells) than in control lung (9.3+/-0.9%); this localization pattern was rarely seen (3.2%) in sections from a truly normal transplant donor lung. Consistent with these data, AMs obtained from IPF patients by bronchoalveolar lavage, purified by adherence, and cultured in the absence of a stimulus for 16 h elaborated significantly greater amounts of LTB(4) and LTC(4) than did control AMs obtained from normal volunteers. These data indicate that the 5-LO pathway is constitutively activated in the lungs of patients with IPF, and the AM represents at least one cellular source of LT overproduction in this disorder. We speculate that LTs participate in the pathogenesis of IPF, and their overproduction in this disorder may be amenable to specific pharmacotherapy.
Nitric oxide inhibits viral replication in murine myocarditis.
C J Lowenstein, S L Hill, A Lafond-Walker, J Wu, G Allen, M Landavere, N R Rose, A HerskowitzAbstract | Full text | PDF (Page 1837)
Nitric oxide (NO) is a radical molecule that not only serves as a vasodilator and neurotransmitter but also acts as a cytotoxic effector molecule of the immune system. The inducible enzyme making NO, inducible NO synthase (iNOS), is transcriptionally activated by IFN-gamma and TNF-alpha, cytokines which are produced during viral infection. We show that iNOS is induced in mice infected with the Coxsackie B3 virus. Macrophages expressing iNOS are identified in the hearts and spleens of infected animals with an antibody raised against iNOS. Infected mice have increased titers of virus and a higher mortality when fed NOS inhibitors. Thus, viral infection induces iNOS in vivo, and NO inhibits viral replication. NO is a novel, nonspecific immune defense against viruses in vivo.
Hyperalphalipoproteinemia in human lecithin cholesterol acyltransferase transgenic rabbits. In vivo apolipoprotein A-I catabolism is delayed in a gene dose-dependent manner.
M E Brousseau, S Santamarina-Fojo, L A Zech, A M Bérard, B L Vaisman, S M Meyn, D Powell, H B Brewer Jr, J M HoegAbstract | Full text | PDF (Page 1844)
Lecithin cholesterol acyltransferase (LCAT) is an enzyme involved in the intravascular metabolism of high density lipoproteins (HDLs). Overexpression of human LCAT (hLCAT) in transgenic rabbits leads to gene dose-dependent increases of total and HDL cholesterol concentrations. To elucidate the mechanisms responsible for this effect, 131I-HDL apoA-I kinetics were assessed in age- and sex-matched groups of rabbits (n=3 each) with high, low, or no hLCAT expression. Mean total and HDL cholesterol concentrations (mg/dl), respectively, were 162+/-18 and 121+/-12 for high expressors (HE), 55+/-6 and 55+/-10 for low expressors (LE), and 29+/-2 and 28+/-4 for controls. Fast protein liquid chromatography analysis of plasma revealed that the HDL of both HE and LE were cholesteryl ester and phospholipid enriched, as compared with controls, with the greatest differences noted between HE and controls. These compositional changes resulted in an incremental shift in apparent HDL particle size which correlated directly with the level of hLCAT expression, such that HE had the largest HDL particles and controls the smallest. In vivo kinetic experiments demonstrated that the fractional catabolic rate(FCR, d(-1)) of apoA-I was slowest in HE (0.328+/-0.03) followed by LE (0.408+/-0.01) and, lastly, by controls (0.528+/-0.04). ApoA-I FCR was inversely associated with HDL cholesterol level (r=-0.851,P<0.01) and hLCAT activity (r=-0.816, P<0.01). These data indicate that fractional catabolic rate is the predominant mechanism by which hLCAT overexpression differentially modulates HDL concentrations in this animal model. We hypothesize that LCAT-induced changes in HDL composition and size ultimately reduce apoA-I catabolism by altering apoA-I conformation and/or HDL particle regeneration.
Leukemia inhibitory factor (LIF) stimulates proopiomelanocortin (POMC) expression in a corticotroph cell line. Role of STAT pathway.
We recently described the expression of leukemia inhibitory factor (LIF) in human fetal and murine corticotrophs. LIF and the related cytokine oncostatin M induced basal, and corticotropin-releasing hormone (CRH) induced proopiomelanocortin (POMC) mRNA and ACTH secretion in AtT20 cells. LIF signaling and regulation of POMC gene transcription were therefore tested. Dexamethasone inhibited both basal- and LIF-induced ACTH secretion (P<0.05) and LIF induction of ACTH was also attenuated by immuneutralization of either the LIF receptor (35%, P<0.05) or the gp130 affinity converter (41%, P<0.05). These antisera also attenuated basal ACTH secretion in the absence of added ligand (P<0.05). To examine intrapituitary LIF signaling, phosphorylation of post-receptor substrates was measured. 1 nM LIF rapidly induced tyrosyl phosphorylation of STAT 1 and STAT 3 proteins, as well as tyrosyl phosphorylation of a 115-kD protein, coimmunoprecipitated with STAT 1. The transfected rat POMC promoter -706/+64, fused to the luciferase reporter gene, was induced by LIF, which exerted strong (18-fold) synergy with CRH. Deletion of the major CRH responsive region in POMC (-323/-166) abolished CRH induction of transcription and severely limited LIF synergy. Although 8 bromo cAMP or forskolin modestly enhanced POMC transcription (2.8-fold), LIF markedly potentiated (7.4-fold) these cAMP activators. These results demonstrate that corticotroph LIF action is receptor mediated and involves activation of STAT signaling pathways. LIF potently synergizes with both CRH and cAMP induction of POMC transcription. This novel intrapituitary signaling mechanism may mediate a neuroimmune pituitary interface.
Pulsatile insulin release from mouse islets occurs in the absence of stimulated entry of Ca2+.
Pancreatic islets are known to respond to a raise of the glucose concentration with Ca2+ -induced 2-3-min pulses of insulin release. The reports of cyclic variations of circulating insulin in the fasting state made it important to explore whether insulin release is also pulsatile in the absence of stimulated entry of Ca2+. Individual pancreatic islets were isolated from a local colony of ob/ob mice and perifused under conditions allowing dual wavelength recordings of the cytoplasmic Ca2+ concentration ([Ca2+]i) with fura-2 and measurements of insulin with ELISA technique. At 3 mM of glucose, [Ca2+]i remained at a stable low level, but insulin was released in pulses with a frequency of 0.41+/-0.02 min-1, determined by Fourier transformation of original and autocorrelated data. Pulses of basal insulin release were also seen when glucose was omitted and 1 microM clonidine or 400 microM diazoxide was added to a glucose-free medium. The results indicate that pulsatile insulin release can be generated in the absence of stimulated entry of Ca2+. A tentative explanation for this phenomenon is inherent fluctuations in the ATP production of the beta cells.
Enzyme replacement therapy in a feline model of Maroteaux-Lamy syndrome.
A C Crawley, D A Brooks, V J Muller, B A Petersen, E L Isaac, J Bielicki, B M King, C D Boulter, A J Moore, N L Fazzalari, D S Anson, S Byers, J J HopwoodAbstract | Full text | PDF (Page 1864)
We report studies that suggest enzyme replacement therapy will result in a significant reduction in disease progression and tissue pathology in patients with Maroteaux-Lamy syndrome (Mucopolysaccharidosis type VI, MPS VI). A feline model for MPS VI was used to evaluate tissue distribution and clinical efficacy of three forms of recombinant human N-acetylgalactosamine-4-sulfatase (rh4S, EC 22.214.171.124). Intravenously administered rh4S was rapidly cleared from circulation. The majority of rh4S was distributed to liver, but was also detected in most other tissues. Tissue half-life was approximately 2-4 d. Three MPS VI cats given regular intravenous infusions of rh4S for up to 20 mo showed variable reduction of storage vacuoles in Kupffer cells and connective tissues, however cartilage chondrocytes remained vacuolated. Vertebral bone mineral volume was improved in two MPS VI cats in which therapy was initiated before skeletal maturity, and increased bone volume appeared to correlate with earlier age of onset of therapy. One cat showed greater mobility in response to therapy.
Induction of a negative autocrine loop by expression of sst2 somatostatin receptor in NIH 3T3 cells.
I Rauly, N Saint-Laurent, N Delesque, L Buscail, J P Estéve, N Vaysse, C SusiniAbstract | Full text | PDF (Page 1874)
The somatostatin receptor subtype sst2 mediates both activation of a tyrosine phosphatase activity and inhibition of cell proliferation induced by somatostatin analogues. In the absence of exogenous ligand, expression of sst2 in NIH 3T3 cells resulted in inhibition of cell growth. Polymerase chain reaction coupled to reverse transcription demonstrated that expression of sst2 in NIH 3T3 cells stimulated the expression of preprosomatostatin mRNA accompanied by a production of immunoreactive somatostatin-like peptide which corresponded predominantly to somatostatin 14. Moreover anti-somatostatin antibodies suppressed sst2-promoted inhibition of cell proliferation. Inhibition of cell proliferation associated with increased secretion of somatostatin-like immunoreactivity was also observed after expression of sst2 in human pancreatic tumor cells BxPC3 devoid of endogenous receptors. In addition, expression of sst2 in NIH 3T3 cells was associated with constitutive activation of tyrosine phosphatase PTP1C that resulted from enhanced expression of the protein. Blocking of PTP1C tyrosine phosphatase activity with orthovanadate or that of PTP1C protein with antisense PTP1C oligonucleotides decreased the sst2-induced inhibition of cell proliferation. These results, taken together, show that expression of sst2 in NIH 3T3 cells generated a negative autocrine loop by stimulating sst2 ligand production and amplifying PTP1C sst2-transducer. Sst2/ligand may function as a determinant factor involved in the negative growth control of cells.
Urea signaling in cultured murine inner medullary collecting duct (mIMCD3) cells involves protein kinase C, inositol 1,4,5-trisphosphate (IP3), and a putative receptor tyrosine kinase.
Urea, in concentrations unique to the renal medulla, increases transcription and protein expression of several immediate-early genes (IEGs) including the zinc finger-containing transcription factor, Egr-1. In the present study, the proximal 1.2 kb of the murine Egr-1 5' -flanking sequence conferred urea-responsiveness to a heterologous luciferase reporter gene when transiently transfected into renal medullary mIMCD3 cells,and this effect was comparable with that of the extremely potent immediate-early gene inducer, O-tetradecanoylphorbol 13-acetate (TPA). Urea inducibility of Egr-1 expression was protein kinase C (PKC)-dependent because staurosporine and calphostin C abrogated the urea effect, and down-regulation of PHC through chronic TPa treatment inhibited both urea-inducible Egr-1 protein expression and gene transcription. In addition, hyperosmotic urea increased inositol 1,4,5-trisphosphate (IP3) release from mIMCD3 cells and induced tyrosine phosphorylation of the receptor tyrosine kinase-specific phospholipase C (PLC) isoform, PLC-gamma. Importantly, urea-inducible Egr-1 expression was strongly genistein-sensitive, to a much greater extent than the comparable TPA-inducible Egr-1 expression. These data suggest that urea-inducible Egr-1 expression is a consequence of sequential PLC-gamma activation, IP3 release, and PKC activation. Urea-inducible PLC-gamma activation, in conjunction with the genistein-sensitivity of urea-inducible Egr-1 expression suggest the possibility of a cell surface or cytoplasmic urea-sensing receptor tyrosine kinase.
Monocytic cell type-specific transcriptional induction of collagenase.
Interstitial collagenase (MMP-1), a metalloproteinase produced by resident and inflammatory cells during connective tissue turnover, cleaves type I collagen fibrils. This catalytic event is rate limiting in remodeling of tissues rich in fibrillar collagen such as the skin and lungs. The regulation of collagenase expression is cell-type specific; bacterial LPS and zymosan, a yeast cell wall derivative, are potent inducers of collagenase expression in macrophages, but do not alter fibroblast collagenase expression. Since promoter elements controlling collagenase transcription in monocytic cells have not been previously defined, we sought to delineate responsive cis-acting elements of the collagenase promoter in transiently transfected human (U937) and murine (J774) monocytic cell lines. Deletion constructs containing as little as 72 bp of 5' -flanking sequence of the collagenase promoter were sufficient for LPS- or zymosan-mediated transcriptional induction, whereas phorbol inducibility exhibited an absolute requirement for upstream elements including the polyoma enhancer A-binding protein-3 site (-83 to -91) and TTCA sequence (-102 to -105) in both monocytic cells and fibroblasts. Mutagenesis of the activator protein-1 [AP-1] site at -72 abolished basal promoter activity and LPS/zymosan inducibility, while mutagenesis of an NF-kappaB-like site at -20 to -10 had no effect. Nuclear extracts from LPS- and zymosan-treated cells showed strong AP-1 activity by gel-shift analysis, and supershift analysis showed the AP-1 complexes contained specific members of both the jun and fos gene families. These data indicate that, in contrast to most LPS effects, AP-1, but not nuclear factor-kappaB, mediates LPS induction of collagenase transcription in macrophagelike cells. Furthermore, as compared to regulation by phorbol ester, collagenase induction in monocytic cells by cell wall derivatives of bacteria or yeast is largely independent of upstream promoter sequences.
Primary preventive and secondary interventionary effects of acetyl-L-carnitine on diabetic neuropathy in the bio-breeding Worcester rat.
A A Sima, H Ristic, A Merry, M Kamijo, S A Lattimer, M J Stevens, D A GreeneAbstract | Full text | PDF (Page 1900)
The abnormalities underlying diabetic neuropathy appear to be multiple and involve metabolic neuronal and vasomediated defects. The accumulation of long-chain fatty acids and impaired beta-oxidation due to deficiencies in carnitine and/or its esterified derivatives, such as acetyl-L-carnitine, may have deleterious effects. In the present study, we examined, in the diabetic bio-breeding Worcester rat, the short- and long-term effects of acetyl-L-carnitine administration on peripheral nerve polyols, myoinositol, Na+/K+ -ATPase, vasoactive prostaglandins, nerve conduction velocity, and pathologic changes. Short-term prevention (4 mo) with acetyl-L-carnitine had no effects on nerve polyols, but corrected the Na+/K+ -ATPase defect and was associated with 63% prevention of the nerve conduction defect and complete prevention of structural changes. Long-term prevention (8 mo) and intervention (from 4 to 8 mo) with acetyl-L-carnitine treatment normalized nerve PGE(1) whereas 6-keto PGF(1-alpha) and PGE(2) were unaffected. In the prevention study, the conduction defect was 73% prevented and structural abnormalities attenuated. Intervention with acetyl-L-carnitine resulted in 76% recovery of the conduction defect and corrected neuropathologic changes characteristic of 4-mo diabetic rats. Acetyl-L-carnitine treatment promoted nerve fiber regeneration, which was increased two-fold compared to nontreated diabetic rats. These results demonstrate that acetyl-L-carnitine has a preventive effect on the acute Na+/- K+_ATPase defect and a preventive and corrective effect on PGE1 in chronically diabetic nerve associated with improvements of nerve conduction velocity and pathologic changes.
Nitric oxide synthase (NOS3) and contractile responsiveness to adrenergic and cholinergic agonists in the heart. Regulation of NOS3 transcription in vitro and in vivo by cyclic adenosine monophosphate in rat cardiac myocytes.
Cardiac myocytes express the nitric oxide synthase isoform originally identified in constitutive nitric oxide synthase cells (NOS3), which mediates the attenuation by muscarinic cholinergic agonists of beta-adrenergic stimulation of L-type calcium current and contractility in these cells. However, calcium current and contractility in these cells. However, the reciprocal regulation of NOS3 activity in myocytes by agents that elevate cAMP has not been reported. In this study, we show that NOS3 and mRNA and protein levels in cardiac myocytes are reduced both in vitro after treatment with cAMP elevating drugs, and in vivo after 3 d of treatment with milrinone, a type III cAMP phosphodiesterase inhibitor. This effect on NOS3 activity by cAMP is cell type specific because treatment of cardiac microvascular endothelial cells in vitro or in vivo did not decrease NOS3 mRNA or protein in these cells. NOS3 downregulation in myocytes appeared to be at the level of transcription since there was no modification of NOS3 mRNA half-life by agents that increase intracellular cAMP. To determine the functional effects of NOS3 downregulation, we examined the contractile responsiveness of isolated electrically paced ventricular myocytes, isolated from animals that had been treated in vivo with milrinone, to the beta-adrenergic agonist isoproterenol and the muscarinic cholinergic agonist carbamylcholine. There was no difference in baseline contractile function in cells that had been pretreated with cAMP elevating agents compared to controls, but cells exposed to milrinone in vivo exhibited an accentuation in their contractile responsiveness to isoproterenol compared to controls and a loss of responsiveness to carbamylcholine. Downregulation of myocyte NOS3 by sustained elevation of cAMP may have important implications for the regulation of myocardial contractile state by the autonomic nervous system.
Angiotensin II-mediated hypertension in the rat increases vascular superoxide production via membrane NADH/NADPH oxidase activation. Contribution to alterations of vasomotor tone.
S Rajagopalan, S Kurz, T Münzel, M Tarpey, B A Freeman, K K Griendling, D G HarrisonAbstract | Full text | PDF (Page 1916)
We tested the hypothesis that angiotensin II-induced hypertension is associated with an increase in vascular .O2- production, and characterized the oxidase involved in this process. Infusion of angiotensin II (0.7 mg/kg per d) increased systolic blood pressure and doubled vascular .O2- production (assessed by lucigenin chemiluminescence), predominantly from the vascular media. NE infusion (2.75 mg/kg per d) produced a similar degree of hypertension, but did not increase vascular .O2- production. Studies using various enzyme inhibitors and vascular homogenates suggested that the predominant source of .O2- activated by angiotensin II infusion is an NADH/NADPH-dependent, membrane-bound oxidase. Angiotensin II-, but not NE-, induced hypertension was associated with impaired relaxations to acetylcholine, the calcium ionophore A23187, and nitroglycerin. These relaxations were variably corrected by treatment of vessels with liposome-encapsulated superoxide dismutase. When Losartan was administered concomitantly with angiotensin II, vascular .O2- production and relaxations were normalized, demonstrating a role for the angiotensin type-1 receptor in these processes. We conclude that forms of hypertension associated with elevated circulating levels of angiotensin II may have unique vascular effects not shared by other forms of hypertension because they increase vascular smooth muscle .O2- production via NADH/NADPH oxidase activation.
Stromelysin-3 expression promotes tumor take in nude mice.
A C Nöel, O Lefebvre, E Maquoi, L VanHoorde, M P Chenard, M Mareel, J M Foidart, P Basset, M C RioAbstract | Full text | PDF (Page 1924)
Stromelysin-3 (ST3) is a matrix metalloproteinase expressed in human carcinomas in ways suggesting that it may play a role in tumor progression. To test this possibility, we have performed gene transfer experiments using both anti-sense and sense ST3 expression vectors, and malignant cells either expressing (NIH 3T3 fibroblasts) or not (MCF7 epithelial cells) endogenous ST3. We have compared the ability of parental and transfected cells to cause subcutaneous tumor development in nude mice. 3T3 cells expressing anti-sense ST3 RNA showed reduced tumorigenicity, and MCF7 cells expressing mouse or human ST3 were associated with reduced tumor-free period leading to a significant increased tumor incidence(P<10(-4)). However, once established, the ST3 expressing tumors did not grow faster than those obtained with the parental MCF7 cell line. In addition, tumors obtained after sub-cutaneous injection of ST3-expressing or nonexpressing cells did not exhibit obvious histological differences, and careful examination did not reveal any local invasive tissue areas nor systemic metastases. These in vivo observations were in agreement with those obtained in vitro showing that ST3 expression did not modify proliferative nor invasive properties of transfected cells. Altogether, these results indicate that ST3 expression promotes tumor take in nude mice, presumably by favoring cancer cell survival in a tissue environment initially not permissive for tumor growth. These findings represent the first experimental evidence showing that ST3 can modulate cancer progression.
T lymphocyte recruitment by interleukin-8 (IL-8). IL-8-induced degranulation of neutrophils releases potent chemoattractants for human T lymphocytes both in vitro and in vivo.
IL-8 has been shown to be a human neutrophil and T cell chemoattractant in vitro. In an effort to assess the in vivo effects of IL-8 on human leukocyte migration, we examined the ability of rhIL-8 to induce human T cell infiltration using a human/mouse model in which SCID mice were administered human peripheral blood lymphocytes intraperitoneally, followed by subcutaneous injections of rhIL-8. rhIL-8 induced predominantly murine neutrophil accumulation by 4 h after administration while recombinant human macrophage inflammatory protein-1beta (rhMIP-1beta) induced both murine monocytes and human T cell infiltration during the same time period as determined by immunohistology. Interestingly, 72 h after chemokine administration, a marked human T cell infiltrate was observed in the IL-8 injection site suggesting that rhIL-8 may be acting indirectly possibly through a murine neutrophil-derived T cell chemoattractant. This hypothesis was confirmed using granulocyte-depleted SCID mice. Moreover, human neutrophils stimulated in vitro with IL-8 were found to release granule-derived factor(s) that induce in vitro T cell and monocyte chemotaxis and chemokinesis. This T cell and monocyte chemotactic activity was detected in extracts of both azurophilic and specific granules. Together, these results demonstrate that neutrophils store and release, upon stimulation with IL-8 or other neutrophil activators, chemoattractants that mediate T cell and monocyte accumulation at sites of inflammation.
The urokinase receptor (CD87) facilitates CD11b/CD18-mediated adhesion of human monocytes.
Urokinase receptors (uPAR; CD87) from complexes with complement receptor 3 (CR3) (CD11b/CD18), a beta2 integrin. In this study, we sought to determine if this association modulates the adhesive function of CR3. Both CR3 and uPAR concentrate at the ventral surface of fibrinogen-adherent human monocytes, and CR3-uPAR coupling increases substantially upon adhesion to fibrinogen. Pretreatment with anti-uPAR monoclonal antibody reduced adhesion to CR3 counterligands (fibrinogen and keyhole limpet hemocyanin) by 50%, but did not affect adhesion to fibronectin, a beta1 integrin counterligand. Antisense (AS) oligonucleotides were used to determine if selectively suppressing uPAR expression also modulates CR3 adhesive function. AS-uPAR oligo reduced CR3-dependent adhesion by 43+/-9% (P<0.01), but did not affect CR3-independent adhesion. To determine if the effects of uPAR are mediated through its ligand, monocytes were pre-treated with AS oligo to block uPA expression. Unlike the effects of blocking uPAR expression, AS-uPA oligo increased adhesion by 46% (P<0.005), and exogenous intact uPA, but not uPA fragments, reversed this effect. We conclude that complex formation with uPAR facilitates the adhesive functions of CR3. This function of uPAR is not dependent upon its occupancy with uPA, which negatively influences adhesion.
The role of cytokines, adhesion molecules, and chemokines in interleukin-2-induced lymphocytic infiltration in C57BL/6 mice.
J A Anderson, A B Lentsch, D J Hadjiminas, F N Miller, A W Martin, K Nakagawa, M J EdwardsAbstract | Full text | PDF (Page 1952)
IL-2 mediates the regression of certain malignancies, but clinical use is limited because of associated toxicities, including parenchymal lymphocytic infiltration with multiple organ failure. Secondarily induced cytokines are important mediators of IL-2 toxicity and IL-2-induced lymphocyte-endothelial adherence and trafficking. The recently discovered C-C chemokines, RANTES (regulated on activation, normal T expressed and secreted) and macrophage inflammatory protein-1alpha, have also been implicated in lymphocytic migration. We hypothesized that IL-2 alters cytokine, C-C chemokine, and adhesion molecule expression in association with parenchymal lymphocytic infiltration. C57BL/6 mice were injected with 3x10(5) IU of IL-2 or 0.1 ml of 5% dextrose intraperitoneally every 8 h for 6 d, then killed. IL-2 induced massive lymphocytic infiltration in the liver and lung and moderate infiltration in the kidney in association with organ edema and dysfunction. Immunostaining showed increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression in association with this organ-specific lymphocytic infiltration. Flow cytometry showed increased expression of the corresponding ligands (lymphocyte function-associated antigen-1 and very late antigen-4) on splenocytes. IL-2 increased TNF-alpha mRNA and protein expression in the liver. Organs infiltrated by lymphocytes had increased TNF-alpha mRNA, whereas RANTES mRNA was increased in all organs, regardless of lymphocytic infiltration. IL-2 toxicity involves organ-specific TNF-alpha and RANTES production with increased ICAM-1 and VCAM-1 expression as potential mechanisms facilitating lymphocytic infiltration and organ dysfunction.
Hypokalemia-induced downregulation of aquaporin-2 water channel expression in rat kidney medulla and cortex.
Prolonged hypokalemia causes vasopressin-resistant polyuria. We have recently shown that another cause of severe polyuria, chronic lithium therapy, is associated with decreased aquaporin-2 (AQP2) water channel expression (Marples, D., S. Christensen, E.I. Christensen, P.D. Ottosen, and S. Nielsen, 1995. J. Clin. Invest., 95: 1838-1845). Consequently, we studied the effect in rats of 11 days' potassium deprivation on urine production and AQP2 expression and distribution. Membrane fractions were prepared from one kidney, while the contralateral kidney was perfusion-fixed for immunocytochemistry. Immunoblotting and densitometry revealed a decrease in AQP2 levels to 27+/-3.4% of control levels (n=11, P<0.001) in inner medulla, and 34+/-15% of controls (n=5, P<0.05) in cortex. Urine production increased in parallel, from 11+/-1.4 to 30+/-4.4 ml/day (n=11, P<0.01). After return to a potassium-containing diet both urine output and AQP2 labels normalized within 7 d. Immunocytochemistry confirmed decreased AQP2 labeling in principal cells of both inner medullary and cortical collecting ducts. AQP2 labeling was predominantly associated with the apical plasma membrane and intracellular vesicles. Lithium treatment for 24 d caused a more extensive reduction of AQP2 levels, to 4+/-1% of control levels in the inner medulla and 4+/-2% in cortex, in association with severe polyuria. The similar degree of downregulation in medulla and cortex suggests that interstitial tonicity is not the major factor in the regulation of AQP2 expression. Consistent with this furosemide treatment did not alter AQP2 levels. In summary,hypokalemia, like lithium treatment, results in a decrease in AQP2 expression in rat collecting ducts, in parallel with the development of polyuria, and the degree of downregulation is consistent with the level of polyuria induced, supporting the view that there is a causative link.
Common T cell receptor clonotype in lacrimal glands and labial salivary glands from patients with Sjögren's syndrome.
I Matsumoto, K Tsubota, Y Satake, Y Kita, R Matsumura, H Murata, T Namekawa, K Nishioka, I Iwamoto, Y Saitoh, T SumidaAbstract | Full text | PDF (Page 1969)
Sjogren's syndrome (SS) is an autoimmune disease characterized by lymphocytic infiltration into lacrimal and salivary glands leading to symptomatic dry eyes and mouth. Immunohistological studies have clarified that the majority of infiltrating lymphocytes around the lacrimal glands and labial salivary glands are CD4 positive alphabeta T cells. To analyze the pathogenesis of T cells infiltrating into lacrimal and labial salivary glands, we examined T cell clonotype of these cells in both glands from four SS patients using PCR-single-strand conformation polymorphism (SSCP) and a sequencing method. SSCP analysis showed that some infiltrating T cells in both glands expand clonally, suggesting that the cells proliferate by antigen-driven stimulation. Intriguingly, six to sixteen identical T cell receptor (TCR) Vbeta genes were commonly found in lacrimal glands and labial salivary glands from individual patients. This indicates that some T cells infiltrating into both glands recognize the shared epitopes on autoantigens. Moreover, highly conserved amino acid sequence motifs were found in the TCR CDR3 region bearing the same TCR Vbeta family gene from four SS patients, supporting the notion that the shared epitopes on antigens are limited. In conclusion, these findings suggest that some autoreactive T cells infiltrating into the lips and eyes recognized restricted epitopes of a common autoantigen in patients with SS.
The subtype-2 (AT2) angiotensin receptor regulates renal cyclic guanosine 3', 5'-monophosphate and AT1 receptor-mediated prostaglandin E2 production in conscious rats.
The renal effects of angiotensin II(AII) are attributed to AT1 receptors. In contrast, the function of renal AT2 receptors in unknown. Using a microdialysis technique, we monitored changes in renal interstitial fluid (RIF) prostaglandin E2 (PGE2) and cyclic guanosine 3', 5'-monophosphate (cGMP) in response to dietary sodium (Na) depletion alone, or Na depletion or normal Na diet combined with the AT1 receptor blocker, Losartan, the AT2 receptor blocker, PD 123319 (PD), or angiotensin II, individually or combined in conscious rats. Na depletion significantly increased PGE2 and cGMP. During Na depletion, Losartan decreased PGE2 and did not change cGMP. In contrast, PD significantly increased PGE2 and decreased cGMP. Combined administration of Losartan and PD decreased PGE2 and cGMP. During normal Na diet, RIF PGE2 and cGMP increased in response to angiotensin II. Neither Losartan nor PD, individually or combined, changed RIF PGE2 or cGMP. Combined administration of angiotensin II and Losartan or PD produced a significant decrease in response of PGE2 and cGMP to angiotensin II, respectively. These data demonstrate that activation of the reninangiotensin system during Na depletion increases renal interstitial PGE2 and cGMP. The AT1 receptor mediates renal production of PGE2. The AT2 receptor mediates cGMP. AT2 blockade potentiates angiotensin-induced PGE2 production at the AT1 receptor.
Tumor suppression and inhibition of aneuploid cell accumulation in human brain tumor cells by ectopic overexpression of the cyclin-dependent kinase inhibitor p27KIP1.
To investigate how overexpression of p27KIP1, a downstream effector of TGF-beta and a universal cyclin-dependent kinase (CDK) inhibitor could influence the malignant phenotype of malignant human brain tumor cells, an adenovirus vector system was used to transfer the human p27KIP1 gene (Adp27KIP1) into the human astrocytoma cell line, U-373MG. Inhibition of CDK activity in Adp27KIP1-infected cells was indicated by inhibition of [3H]thymidine incorporation, an increase in cell doubling time and by cell cycle arrest in G1. Notably, ectopic overexpression of p27KIP1 was associated with a marked decrease in the accumulation of aneuploid cells. Diminished malignant potential of Adp27KIP1-infected cells was manifested by the loss of anchorage-independent growth in soft agar and by the inability to induce tumorgenesis in a xenograft model. These studies suggest that p27KIP1 is a tumor suppressor gene and supports the use of Adp27KIP1 for gene therapy of human brain tumors.
Oral L-arginine improves endothelium-dependent dilation in hypercholesterolemic young adults.
P Clarkson, M R Adams, A J Powe, A E Donald, R McCredie, J Robinson, S N McCarthy, A Keech, D S Celermajer, J E DeanfieldAbstract | Full text | PDF (Page 1989)
In hypercholesterolemic rabbits, oral L-arginine (the substrate for endothelium derived nitric oxide) attenuates endothelial dysfunction and atheroma formation, but the effect in hypercholesterolemic humans is unknown. Using high resolution external ultrasound, we studied arterial physiology in 27 hypercholesterolemic subjects aged 29+/-5 (19-40) years, with known endothelial dysfunction and LDL-cholesterol levels of 238+/-43 mg/dl. Each subject was studied before and after 4 wk of L-arginine (7 grams x 3/day) or placebo powder, with 4 wk washout, in a randomized double-blind crossover study. Brachial artery diameter was measured at rest, during increased flow (causing endothelium-dependent dilation, EDD) and after sublingual glyceryl trinitrate (causing endothelium-independent dilation). After oral L-arginine, plasma L-arginine levels rose from 115+/-103 to 231+/-125 micromol/liter (P<0.001), and EDD improved from 1.7+/-1.3 to 5.6+/-3.0% (P<0.001). In contrast there was no significant change in response to glyceryl trinitrate. After placebo there were no changes in endothelium-dependent or independent vascular responses. Lipid levels were unchanged after L-arginine and placebo. Dietary supplementation with L-arginine significantly improves EDD in hypercholesterolemic young adults, and this may impact favorably on the atherogenic process.