Host/pathogen interactions: series introduction.

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D G Guiney, M F Kagnoff

Complex oscillatory heart rhythm: a dance macabre.

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R L Verrier, B D Nearing, E G Lovett

Selectin ligands: will the real ones please stand up?

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A Varki

Sepsis is associated with increased mRNAs of the ubiquitin-proteasome proteolytic pathway in human skeletal muscle.

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Previous studies provided evidence that sepsis-induced muscle proteolysis in experimental animals is caused by increased ubiquitin-proteasome-dependent protein breakdown. It is not known if a similar mechanism accounts for muscle proteolysis in patients with sepsis. We determined mRNA levels for ubiquitin and the 20 S proteasome subunit HC3 by Northern blot analysis in muscle tissue from septic (n = 7) and non-septic (n = 11) patients. Plasma and muscle amino acid concentrations and concentrations in urine of 3-methylhistidine (3-MH), creatinine, and cortisol were measured at the time of surgery to assess the catabolic state of the patients. A three- to fourfold increase in mRNA levels for ubiquitin and HC3 was noted in muscle tissue from the septic patients concomitant with increased muscle levels of phenylalanine and 3-MH and reduced levels of glutamine. Total plasma amino acids were decreased by approximately 30% in the septic patients. The 3-MH/creatinine ratio in urine was almost doubled in septic patients. The cortisol levels in urine were higher in septic than in control patients but this difference did not reach statistical significance. The results suggest that sepsis is associated with increased mRNAs of the ubiquitin-proteasome pathway in human skeletal muscle.

Authors

G Tiao, S Hobler, J J Wang, T A Meyer, F A Luchette, J E Fischer, P O Hasselgren

Shared gamma(c) subunit within the human interleukin-7 receptor complex. A molecular basis for the pathogenesis of X-linked severe combined immunodeficiency.

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Genetic evidence suggests that mutations in the gamma(c) receptor subunit cause X-linked severe combined immunodeficiency (X-SCID). The gamma(c) subunit can be employed in receptor complexes for IL-2, -4, -7, -9, and -15, and the multiple signaling defects that would result from a defective gamma(c) chain in these receptors are proposed to cause the severe phenotype of X-SCID patients. Interestingly, gene disruption of either IL-7 or the IL-7 receptor (IL-7R) alpha subunit in mice leads to immunological defects that are similar to human X-SCID. These observations suggest the functional importance of gamma(c) in the IL-7R complex. In the present study, structure/function analyses of the IL-7R complex using a chimeric receptor system demonstrated that gamma(c) is indeed critical for IL-7R function. Nonetheless, only a limited portion of the cytoplasmic domain of gamma(c) is necessary for IL-7R signal transduction. Furthermore, replacement of the gamma(c) cytoplasmic domain by a severely truncated erythropoeitin receptor does not affect measured IL-7R signaling events. These findings support a model in which gamma(c) serves primarily to activate signal transduction by the IL-7R complex, while IL-7R alpha determines specific signaling events through its association with cytoplasmic signaling molecules. Finally, these studies are consistent with the hypothesis that the molecular pathogenesis of X-SCID is due primarily to gamma(c)-mediated defects in the IL-7/IL-7R system.

Authors

S Y Lai, J Molden, M A Goldsmith

Chemokine receptor usage by human eosinophils. The importance of CCR3 demonstrated using an antagonistic monoclonal antibody.

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Chemokines bind and signal through G-protein coupled seven transmembrane receptors. Various chemokine receptors are expressed on leukocytes, and these may impart selective homing of leukocyte subsets to sites of inflammation. Human eosinophils express the eotaxin receptor, CCR3, but respond to a variety of CC chemokines apart from eotaxin, including RANTES, monocyte chemotactic protein (MCP)-2, MCP-3, and MCP-4. Here we describe a mAb, 7B11, that is selective for CCR3 and has the properties of a true receptor antagonist. 7B11 blocked binding of various radiolabeled chemokines to either CCR3 transfectants, or eosinophils. Pretreatment of eosinophils with this mAb blocked chemotaxis and calcium flux induced by all CCR3 ligands. In all individuals examined, including allergic and eosinophilic donors, > 95% of the response of eosinophils to eotaxin, RANTES, MCP-2, MCP-3, and MCP-4 was shown to be mediated through CCR3. The IL-8 receptors, particularly CXCR2, were induced on IL-5 primed eosinophils, however these eosinophils responded to CC chemokines in the same manner as unprimed eosinophils. These results demonstrate the importance of CCR3 for eosinophil responses, and the feasibility of completely antagonizing this receptor.

Authors

H Heath, S Qin, P Rao, L Wu, G LaRosa, N Kassam, P D Ponath, C R Mackay

Voltage-gated calcium channel currents in human coronary myocytes. Regulation by cyclic GMP and nitric oxide.

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Voltage-gated Ca2+ channels contribute to the maintenance of contractile tone in vascular myocytes and are potential targets for vasodilating agents. There is no information available about their nature and regulation in human coronary arteries. We used the whole-cell voltage-clamp technique to characterize Ca2+-channel currents immediately after enzymatic dissociation and after primary culture of coronary myocytes taken from heart transplant patients. We recorded a dihydropyridine-sensitive L-type current in both freshly isolated and primary cultured cells. A T-type current was recorded only in culture. The L- (but not the T-) type current was inhibited by permeable analogues of cGMP in a dose-dependent manner. This effect was mimicked by the nitric oxide-generating agents S-nitroso-N-acetylpenicillamine (SNAP) and 3-morpholinosydnonimine which increased intracellular cGMP. Methylene blue, known to inhibit guanylate cyclase, antagonized the effect of SNAP. Inhibitions by SNAP and cGMP were not additive and seemed to occur through a common pathway. We conclude that (a) L-type Ca2+ channels are the major pathway for voltage-gated Ca2+ entry in human coronary myocytes; (b) their inhibition by agents stimulating nitric oxide and/or intracellular cGMP production is expected to contribute to vasorelaxation and may be involved in the therapeutic effect of nitrovasodilators; and (c) the expression of T-type Ca2+ channels in culture may be triggered by cell proliferation.

Authors

J F Quignard, J M Frapier, M C Harricane, B Albat, J Nargeot, S Richard

Loss of the polycystic kidney disease (PKD1) region of chromosome 16p13 in renal cyst cells supports a loss-of-function model for cyst pathogenesis.

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It is not known whether mutations in the PKD1 gene cause autosomal dominant polycystic kidney disease (PKD) by an activating (gain-of-function) or an inactivating (loss-of-function) model. We analyzed DNA from cyst epithelial cells for loss of heterozygosity (LOH) in the PKD1 region of chromosome 16p13 using microsatellite markers. 29 cysts from four patients were studied. Five cysts from three patients had chromosome 16p13 LOH. Four of the cysts had loss of two chromosome 16p13 markers that flank the PKD1 gene. In two patients, microsatellite analysis of family members was consistent with loss of the wild-type copy of PKD1 in the cysts. In the third patient, 16p13 LOH was detected in three separate cysts, all of which showed loss of the same alleles. Chromosome 3p21 LOH was detected in one cyst. No LOH was detected in four other genomic regions. These results demonstrate that some renal cyst epithelial cells exhibit clonal chromosomal abnormalities with loss of the wild-type copy of PKD1. This supports a loss-of-function model for autosomal dominant PKD, with a germline mutation inactivating one copy of PKD1 and somatic mutation or deletion inactivating the remaining wild-type copy.

Authors

J L Brasier, E P Henske

Impaired arterial neointima formation in mice with disruption of the plasminogen gene.

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To define the role of plasminogen (Plg) in the smooth muscle cell response after arterial wall injury, neointima formation was evaluated after electric injury of the femoral artery in plasminogen-deficient (Plg-/-) mice. The injury destroyed all medial smooth muscle cells, denuded the injured segment of intact endothelium, and induced transient platelet-rich mural thrombosis. In wild-type (Plg+/+) mice, vascular wound healing was characterized by lysis of the thrombus, transient infiltration of inflammatory cells, and progressive removal of necrotic debris and thrombosis. Topographic analysis revealed repopulation of the media and accumulation in the neointima of smooth muscle cells originating from the noninjured borders, which progressed into the necrotic center. In Plg-/- mice, wound healing was significantly impaired with delayed removal of necrotic debris, reduced leucocyte infiltration and smooth muscle cell accumulation, and decreased neointima formation. Smooth muscle cells accumulated at the uninjured borders, but failed to migrate into the necrotic center. Proliferation of smooth muscle cells was not affected by Plg deficiency. Evans blue staining revealed no genotypic differences in reendothelialization. Thus, Plg plays a significant role in vascular wound healing and arterial neointima formation after injury, most likely by affecting cellular migration.

Authors

P Carmeliet, L Moons, V Ploplis, E Plow, D Collen

Established immunity precludes adenovirus-mediated gene transfer in rat carotid arteries. Potential for immunosuppression and vector engineering to overcome barriers of immunity.

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Preclinical arterial gene transfer studies with adenoviral vectors are typically performed in laboratory animals that lack immunity to adenovirus. However, human patients are likely to have prior exposures to adenovirus that might affect: (a) the success of arterial gene transfer; (b) the duration of recombinant gene expression; and (c) the likelihood of a destructive immune response to transduced cells. We confirmed a high prevalence (57%) in adult humans of neutralizing antibodies to adenovirus type 5. We then used a rat model to establish a central role for the immune system in determining the success as well as the duration of recombinant gene expression after adenovirus-mediated gene transfer into isolated arterial segments. Vector-mediated recombinant gene expression, which was successful in naive rats and prolonged by immunosuppression, was unsuccessful in the presence of established immunity to adenovirus. 4 d of immunosuppressive therapy permitted arterial gene transfer and expression in immune rats, but at decreased levels. Ultraviolet-irradiated adenoviral vectors, which mimic advanced-generation vectors (reduced viral gene expression and relatively preserved capsid function), were less immunogenic than were nonirradiated vectors. A primary exposure to ultraviolet-irradiated (but not nonirradiated) vectors permitted expression of a recombinant gene after redelivery of the same vector. In conclusion, arterial gene transfer with current type 5 adenoviral vectors is unlikely to result in significant levels of gene expression in the majority of humans. Both immunosuppression and further engineering of the vector genome to decrease expression of viral genes show promise in circumventing barriers to adenovirus-mediated arterial gene transfer.

Authors

A H Schulick, G Vassalli, P F Dunn, G Dong, J J Rade, C Zamarron, D A Dichek

Deficiency of Src family kinases Fgr and Hck results in activation of erythrocyte K/Cl cotransport.

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Src-family kinases play a central role in regulation of hematopoietic cell functions. We found that mouse erythrocytes express the Src-family kinases Fgr and Hck, as well as Lyn. To directly test whether Fgr and Hck play any role in erythrocyte function, we analyzed red cells isolated from fgr-/-, hck-/-, and fgr-/- hck-/- knock-out mice. Mean corpuscular hemoglobin concentration and median density are increased, while K content is decreased, in fgr-/- hck-/- double-mutant erythrocytes compared with wild-type, fgr-/-, or hck-/- erythrocytes. Na/K pump and Na/K/Cl cotransport were not altered, but K/Cl cotransport activity was significantly and substantially higher (approximately three-fold) in fgr-/- hck-/- double-mutant erythrocytes. This enhanced K/Cl cotransport activity did not depend on cell age. In fact, in response to bleeding, K/Cl cotransport activity increased in parallel with reticulocytosis in wild-type erythrocytes, while abnormal K/Cl cotransport did not change as a consequence of reticulocytosis in fgr-/- hck-/- double-mutant erythrocytes. Okadaic acid, an inhibitor of a phosphatase that has been implicated in activation of the K/Cl cotransporter, inhibited K/Cl cotransport in wild-type and fgr-/- hck-/- double-mutant erythrocytes to a comparable extent. In contrast, staurosporine, an inhibitor of a kinase that has been suggested to negatively regulate this same phosphatase enhanced K/Cl cotransport in wild-type but not in fgr-/- hck-/- double-mutant erythrocytes. On the basis of these findings, we propose that Fgr and Hck are the kinases involved in the negative regulation of the K/Cl cotransporter-activating phosphatase. Abnormality of erythrocyte K/Cl cotransport in fgr-/- hck-/- double-mutant animals represents the first demonstration that Src-family kinases may be involved in regulation of membrane transport.

Authors

L De Franceschi, L Fumagalli, O Olivieri, R Corrocher, C A Lowell, G Berton

Transit time heterogeneity in canine small intestine: significance for oxygen transport.

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We previously found that local O2 extraction efficacy in isolated pump-perfused intestine was enhanced when systemic reflex vasoconstriction was stimulated by hypovolemia (Samsel, R.W., and P.T. Schumacker. 1994. J. Appl. Physiol. 77: 2291-2298). The microvascular mechanism underlying this beneficial effect could involve a redistribution of flow between mucosa and serosa, or an adjustment in the heterogeneity of perfusion within those regions. We measured regional blood flows and distributions of flow and capillary erythrocyte transit times in two segments of small intestine in anesthetized dogs (n = 10). Each vascularly isolated segment of intestine was pump-perfused under high flow (O2 supply-independent VO2) and low flow (O2 supply-dependent) conditions. During the first gut segment, the animal was kept normovolemic using i.v. fluids to minimize reflex vasoconstriction. During the second, the animal was hemorrhaged to augment vasoconstriction (n = 7), or kept normovolemic to control for the effects of time (n = 3). Blood flow distributions were measured using 15 microm radiolabeled microspheres. Tissue blood volume was measured using 99mTc-labeled red blood cells. Capillary volume was determined as the product of tissue blood volume and the histologically derived fraction of vascular volume in the capillaries. Transit times were calculated as the ratio of capillary volume to flow. Each gut segment was fixed and sectioned into 350 approximately 100 mg tissue pieces for analysis. Data revealed significant spatial heterogeneity of blood flow and capillary transit times in both mucosa and muscularis, with relative dispersions (SD/Mean) ranging from 23 to 97%. Hypovolemia caused an increase in flow heterogeneity in muscularis at both high and low flow states, and in mucosa under high flow conditions. However, hypovolemia also elicited changes in capillary volume, such that transit time heterogeneity remained unchanged. Augmentation of vasoconstrictor tone caused a redistribution of flow toward mucosa (P < 0.003) under high and low flow conditions. This redistribution correlated with the improvements in O2 extraction ratio (P = 0.022). Thus, the improvement in gut O2 extraction efficacy seen with increased vasoconstriction may be explained mostly by an intramural redistribution of flow between mucosa and muscularis. Capillary transit time heterogeneity remained unchanged, suggesting that this variable is tightly regulated.

Authors

H V Connolly, L A Maginniss, P T Schumacker

EWS-Fli1 antisense oligodeoxynucleotide inhibits proliferation of human Ewing's sarcoma and primitive neuroectodermal tumor cells.

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The translocation t(11;22) is a common chromosomal abnormality detected both in Ewing's sarcoma and in primitive neuroectodermal tumor cells. The translocation results in an EWS-Fli1 fusion gene, made up of the 5' half of the EWS gene on chromosome 22 fused to the 3' half of the Fli1 gene on chromosome 11. Recent studies have evaluated possible roles of the fusion gene products. However, the biological significance of EWS-Fli1 is still unknown. Using a competitive polymerase chain reaction technique, we show here that there might be a correlation between the expression levels of the EWS-Fli1 fusion gene and the proliferative activities of Ewing's sarcoma and primitive neuroectodermal tumor cells. When the EWS-Fli1 expression is inhibited by antisense oligodeoxynucleotides against the fusion RNA, the growth of the tumor cells is significantly reduced both in vitro and in vivo. The data further indicate the growth inhibition of the cells by the antisense sequence might be mediated by G0/G1 block in the cell cycle progression. These results suggest that EWS-Fli1 may play an important role in the proliferation of the tumor cells, and the EWS-Fli1 fusion RNA could be used as a target to inhibit the growth of Ewing's sarcoma and primitive neuroectodermal tumor with the specific antisense oligonucleotide.

Authors

K Tanaka, T Iwakuma, K Harimaya, H Sato, Y Iwamoto

Dramatic neuronal rescue with prolonged selective head cooling after ischemia in fetal lambs.

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Hypothermia has been proposed as a neuroprotective strategy. However, short-term cooling after hypoxia-ischemia is effective only if started immediately during resuscitation. The aim of this study was to determine whether prolonged head cooling, delayed into the late postinsult period, improves outcome from severe ischemia. Unanesthetized near term fetal sheep were subject to 30 min of cerebral ischemia. 90 min later they were randomized to either cooling (n = 9) or sham cooling (n = 7) for 72 h. Intrauterine cooling was induced by a coil around the fetal head, leading initially to a fall in extradural temperature of 5-10 degrees C, and a fall in esophageal temperature of 1.5-3 degrees C. Cooling was associated with mild transient systemic metabolic effects, but not with hypotension or altered fetal heart rate. Cerebral cooling reduced secondary cortical cytotoxic edema (P < 0.001). After 5 d of recovery there was greater residual electroencephalogram activity (-5.2+/-1.6 vs. -15.5+/-1.5 dB, P < 0.001) and a dramatic reduction in the extent of cortical infarction and neuronal loss in all regions assessed (e.g., 40 vs. 99% in the parasagittal cortex, P < 0.001). Selective head cooling, maintained throughout the secondary phase of injury, is noninvasive and safe and shows potential for improving neonatal outcome after perinatal asphyxia.

Authors

A J Gunn, T R Gunn, H H de Haan, C E Williams, P D Gluckman

Priming of human CD4+ antigen-specific T cells to undergo apoptosis by HIV-infected monocytes. A two-step mechanism involving the gp120 molecule.

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The study of the pathology of HIV-1 infection in chimpanzees supports the idea of the crucial role of HIV-infected monocytes in the pathogenesis of AIDS, although viral mechanisms that lead to T cell dysfunction and deletion during HIV infection are still unclear. We show here that HIV-1-infected antigen-presenting monocytes (APCs) are able to prime in vitro non-HIV-infected antigen-specific CD4+ T cell lines or peripheral blood CD4+ T cells to undergo apoptosis after antigen-specific restimulation. The priming of T cells for apoptosis occurs in the absence of HIV replication in the T cells. Priming for apoptosis required two concomitant signals present on the same APC, an antigenic stimulus and a second signal provided by the HIV gp120 protein as demonstrated by the use as APCs of EBV-LCLs infected with different recombinant deleted proviruses or transfected with different HIV proteins. These results provide a mechanism for the priming for apoptosis of T cells in HIV-infected patients, implicating a role for HIV-infected APCs in the induction of T cell dysfunction and depletion in AIDS.

Authors

F Cottrez, F Manca, A G Dalgleish, F Arenzana-Seisdedos, A Capron, H Groux

Mutation of a highly conserved residue of betaI spectrin associated with fatal and near-fatal neonatal hemolytic anemia.

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We studied an infant with severe nonimmune hemolytic anemia and hydrops fetalis at birth. His neonatal course was marked by ongoing hemolysis of undetermined etiology requiring repeated erythrocyte transfusions. He has remained transfusion-dependent for more than 2 yr. A previous sibling born with hemolytic anemia and hydrops fetalis died on the second day of life. Peripheral blood smears from the parents revealed rare elliptocytes. Examination of their erythrocyte membranes revealed abnormal mechanical stability as well as structural and functional abnormalities in spectrin. Genetic studies revealed that the proband and his deceased sister were homozygous for a mutation of betaIsigma1 spectrin, L2025R, in a region of spectrin that is critical for normal function. The importance of leucine in this position of the proposed triple helical model of spectrin repeats is highlighted by its evolutionary conservation in all beta spectrins from Drosophila to humans. Molecular modeling demonstrated the disruption of hydrophobic interactions in the interior of the triple helix critical for spectrin function caused by the replacement of the hydrophobic, uncharged leucine by a hydrophilic, positively charged arginine. This mutation must also be expressed in the betaIsigma2 spectrin found in muscle, yet pathologic and immunohistochemical examination of skeletal muscle from the deceased sibling was unremarkable.

Authors

P G Gallagher, M J Petruzzi, S A Weed, Z Zhang, S L Marchesi, N Mohandas, J S Morrow, B G Forget

Important role of tissue angiotensin-converting enzyme activity in the pathogenesis of coronary vascular and myocardial structural changes induced by long-term blockade of nitric oxide synthesis in rats.

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The long-term administration of N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide synthesis, produces coronary vascular remodeling and myocardial hypertrophy in animals. This study used a rat model to investigate the role of angiotensin I converting enzyme (ACE) in the pathogenesis of such changes. We studied the following groups, all of which received drug treatment in their drinking water: untreated controls, and those administered L-NAME, L-NAME, and an ACE inhibitor (ACEI), and L-NAME and hydralazine. Cardiovascular structural changes and tissue ACE activities were evaluated after the first, fourth, and eighth week of treatment. In rats treated with L-NAME alone, vascular remodeling was evident at the fourth and eighth week, and myocardial hypertrophy was present at the eighth week of treatment. The vascular and myocardial remodeling were characterized by increased tissue ACE activities and immunodetectable ACE in those tissues. These changes were markedly reduced by ACEI, but not by hydralazine treatment. Increased local ACE expression may thus be important in the pathogenesis of cardiovascular remodeling in this model.

Authors

M Takemoto, K Egashira, M Usui, K Numaguchi, H Tomita, H Tsutsui, H Shimokawa, K Sueishi, A Takeshita

Potentiation of beta-adrenergic signaling by adenoviral-mediated gene transfer in adult rabbit ventricular myocytes.

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Our laboratory has been testing the hypothesis that genetic modulation of the beta-adrenergic signaling cascade can enhance cardiac function. We have previously shown that transgenic mice with cardiac overexpression of either the human beta2-adrenergic receptor (beta2AR) or an inhibitor of the beta-adrenergic receptor kinase (betaARK), an enzyme that phosphorylates and uncouples agonist-bound receptors, have increased myocardial inotropy. We now have created recombinant adenoviruses encoding either the beta2AR (Adeno-beta2AR) or a peptide betaARK inhibitor (consisting of the carboxyl terminus of betaARK1, Adeno-betaARKct) and tested their ability to potentiate beta-adrenergic signaling in cultured adult rabbit ventricular myocytes. As assessed by radioligand binding, Adeno-beta2AR infection led to approximately 20-fold overexpression of beta-adrenergic receptors. Protein immunoblots demonstrated the presence of the Adeno-betaARKct transgene. Both transgenes significantly increased isoproterenol-stimulated cAMP as compared to myocytes infected with an adenovirus encoding beta-galactosidase (Adeno-betaGal) but did not affect the sarcolemmal adenylyl cyclase response to Forskolin or NaF. beta-Adrenergic agonist-induced desensitization was significantly inhibited in Adeno-betaARKct-infected myocytes (16+/-2%) as compared to Adeno-betaGal-infected myocytes (37+/-1%, P < 0.001). We conclude that recombinant adenoviral gene transfer of the beta2AR or an inhibitor of betaARK-mediated desensitization can potentiate beta-adrenergic signaling.

Authors

M H Drazner, K C Peppel, S Dyer, A O Grant, W J Koch, R J Lefkowitz

Hereditary vitamin D resistant rickets caused by a novel mutation in the vitamin D receptor that results in decreased affinity for hormone and cellular hyporesponsiveness.

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Mutations in the vitamin D receptor (VDR) result in target organ resistance to 1alpha,25-dihydroxyvitamin D [1,25(OH)2D3], the active form of vitamin D, and cause hereditary 1,25-dihydroxyvitamin D resistant rickets (HVDRR). We analyzed the VDR of a patient who exhibited three genetic diseases: HVDRR, congenital total lipodystrophy, and persistent mullerian duct syndrome. The patient was treated with extremely high dose calcitriol (12.5 microg/d) which normalized serum calcium and improved his rickets. Analysis of [3H]1,25(OH)2D3 binding in the patient's cultured fibroblasts showed normal abundance of VDR with only a slight decrease in binding affinity compared to normal fibroblasts when measured at 0 degrees C. The patient's fibroblasts demonstrated 1,25(OH)2D3-induction of 24-hydroxylase mRNA, but the effective dose was approximately fivefold higher than in control cells. Sequence analysis of the patient's VDR gene uncovered a single point mutation, H305Q. The recreated mutant VDR was transfected into COS-7 cells where it was 5 to 10-fold less responsive to 1,25(OH)2D3 in gene transactivation. The mutant VDR had an eightfold lower affinity for [3H]1,25(OH)2D3 than the normal VDR when measured at 24 degrees C. RFLP demonstrated that the patient was homozygous for the mutation while the parents were heterozygous. In conclusion, we describe a new ligand binding domain mutation in the VDR that causes HVDRR due to decreased affinity for 1,25(OH)2D3 which can be effectively treated with extremely high doses of hormone.

Authors

P J Malloy, T R Eccleshall, C Gross, L Van Maldergem, R Bouillon, D Feldman

Quasiperiodicity and chaos in cardiac fibrillation.

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In cardiac fibrillation, disorganized waves of electrical activity meander through the heart, and coherent contractile function is lost. We studied fibrillation in three stationary forms: in human chronic atrial fibrillation, in a stabilized form of canine ventricular fibrillation, and in fibrillation-like activity in thin sheets of canine and human ventricular tissue in vitro. We also created a computer model of fibrillation. In all four studies, evidence indicated that fibrillation arose through a quasiperiodic stage of period and amplitude modulation, thus exemplifying the "quasiperiodic transition to chaos" first suggested by Ruelle and Takens. This suggests that fibrillation is a form of spatio-temporal chaos, a finding that implies new therapeutic approaches.

Authors

A Garfinkel, P S Chen, D O Walter, H S Karagueuzian, B Kogan, S J Evans, M Karpoukhin, C Hwang, T Uchida, M Gotoh, O Nwasokwa, P Sager, J N Weiss

Lipopolysaccharide binding protein and soluble CD14 catalyze exchange of phospholipids.

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Lipopolysaccharide binding protein (LBP) is a plasma protein known to facilitate the diffusion of bacterial LPS (endotoxin). LBP catalyzes movement of LPS monomers from LPS aggregates to HDL particles, to phospholipid bilayers, and to a binding site on a second plasma protein, soluble CD14 (sCD14). sCD14 can hasten transfer by receiving an LPS monomer from an LPS aggregate, and then surrendering it to an HDL particle, thus acting as a soluble "shuttle" for an insoluble lipid. Here we show that LBP and sCD14 shuttle not only LPS, but also phospholipids. Phosphatidylinositol (PI), phosphatidylcholine, and a fluorescently labeled derivative of phosphatidylethanolamine (R-PE) are each transferred by LBP from membranes to HDL particles. The transfer could be observed using recombinant LBP and sCD14 or whole human plasma, and the plasma-mediated transfer of PI could be blocked by anti-LBP and partially inhibited by anti-CD14. sCD14 appears to act as a soluble shuttle for phospholipids since direct binding of PI and R-PE to sCD14 was observed and because addition of sCD14 accelerated transfer of these lipids. These studies define a new function for LBP and sCD14 and describe a novel mechanism for the transfer of phospholipids in blood. In further studies, we show evidence suggesting that LBP transfers LPS and phospholipids by reciprocal exchange: LBP-catalyzed binding of R-PE to LPS x sCD14 complexes was accompanied by the exit of LPS from sCD14, and LBP-catalyzed binding of R-PE to sCD14 was accelerated by prior binding of LPS to sCD14. Binding of one lipid is thus functionally coupled with the release of a second. These results suggest that LBP acts as a lipid exchange protein.

Authors

B Yu, E Hailman, S D Wright

Acute bacterial pneumonia in rats increases alveolar epithelial fluid clearance by a tumor necrosis factor-alpha-dependent mechanism.

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To study the rate and regulation of alveolar fluid clearance in acute pneumonia, we created a model of Pseudomonas aeruginosa pneumonia in rats. To measure alveolar liquid and protein clearance, we instilled into the airspaces a 5% bovine albumin solution with 1.5 microCi of 125I-human albumin, 24 h after intratracheal instillation of bacteria. The concentration of unlabeled and labeled protein in the distal airspaces over 1 h was used as an index of net alveolar fluid clearance. Since there was histologic evidence of alveolar epithelial injury, several methods were used to measure alveolar fluid clearance, including the use of experiments in rats with blood flow and the use of experiments in rats without blood flow, so that movement across the epithelial barrier would be minimized in the latter group. The results with each method were identical. We found that P. aeruginosa pneumonia increased alveolar liquid clearance over 1 h by 48% in studies with blood flow, and by 43% in rats without blood flow, compared with respective controls (P < 0.05). In both studies, this increase was inhibited with amiloride. However, propranolol had no inhibitory effect, thus ruling out a catecholamine-dependent mechanism to explain the increase in alveolar fluid clearance. An antitumor necrosis factor-alpha neutralizing antibody, instilled into the lung 5 min before bacteria, prevented the increase in alveolar liquid clearance in rats with pneumonia (P < 0.05). Also, TNFalpha (5 microg) instilled in normal rats increased alveolar liquid clearance by 43% over 1 h compared with control rats (P < 0.05). In normal rats instilled with TNFalpha, propranolol had no inhibitory effect. In conclusion, gram-negative pneumonia markedly upregulates net alveolar epithelial fluid clearance, in part by a TNFalpha-dependent mechanism. This finding provides a novel mechanism for the upregulation of alveolar epithelial sodium and fluid transport from the distal airspaces of the lung.

Authors

S Rezaiguia, C Garat, C Delclaux, M Meignan, J Fleury, P Legrand, M A Matthay, C Jayr

Interferon-gamma differentially regulates interleukin-12 and interleukin-10 production in leprosy.

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The ability of monocytes to influence the nature of the T cell response to microbial pathogens is mediated in part by the release of cytokines. Of particular importance is the release of IL-12 and IL-10 by cells of the monocyte/macrophage lineage upon encountering the infectious agent. IL-12 promotes cell mediated immunity (CMI) to intracellular pathogens by augmenting T-helper type 1 responses, whereas IL-10 downregulates these responses. The ability of IFN-gamma to modulate the balance between IL-12 and IL-10 production was examined by studying leprosy as a model. In response to Mycobacterium leprae stimulation, IFN-gamma differentially regulated IL-12 and IL-10 production resulting in upregulation of IL-12 release and downregulation of IL-10 release. Furthermore, we determined that the mechanism by which IFN-gamma downregulates IL-10 was through the induction of IL-12. The data suggest a model of lymphocyte-monocyte interaction whereby the relative presence or absence of IFN-gamma in the local microenvironment is a key determinant of the type of monocyte cytokine response, and hence the degree of CMI in the host response to infection.

Authors

D H Libraty, L E Airan, K Uyemura, D Jullien, B Spellberg, T H Rea, R L Modlin

Podocyte loss and progressive glomerular injury in type II diabetes.

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Kidney biopsies from Pima Indians with type II diabetes were analyzed. Subjects were classified clinically as having early diabetes (n = 10), microalbuminuria (n = 17), normoalbuminuria, despite a duration of diabetes equal to that of the subjects with microalbuminuria (n = 12), or clinical nephropathy (n = 12). Subjects with microalbuminuria exhibited moderate increases in glomerular and mesangial volume when compared with those with early diabetes, but could not be distinguished from subjects who remained normoalbuminuric after an equal duration of diabetes. Subjects with clinical nephropathy exhibited global glomerular sclerosis and more prominent structural abnormalities in nonsclerosed glomeruli. Marked mesangial expansion was accompanied by a further increase in total glomerular volume. Glomerular capillary surface area remained stable, but the glomerular basement membrane thickness was increased and podocyte foot processes were broadened. Broadening of podocyte foot processes was associated with a reduction in the number of podocytes per glomerulus and an increase in the surface area covered by remaining podocytes. These findings suggest that podocyte loss contributes to the progression of diabetic nephropathy.

Authors

M E Pagtalunan, P L Miller, S Jumping-Eagle, R G Nelson, B D Myers, H G Rennke, N S Coplon, L Sun, T W Meyer

Synergistic decrease of clonal proliferation, induction of differentiation, and apoptosis of acute promyelocytic leukemia cells after combined treatment with novel 20-epi vitamin D3 analogs and 9-cis retinoic acid.

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Abstract

Patients with acute promyelocytic leukemia (APL) usually relapse after all-trans retinoic acid (RA) treatment because this therapy fails to eradicate the malignant clone. Our data showed that KH 1060 and other 20-epi vitamin D3 analogs alone were potent inhibitors of clonal growth of NB4 cells, an APL cell line (ED50, approximately 5 x 10(-11) M). The combination of KH 1060 and 9-cis-RA synergistically and irreversibly enhanced this effect. Neither KH 1060 nor 9-cis-RA (10(-6) M, 3 d) were strong inducers of differentiation of NB4 cells. However, 98% of the cells underwent differentiation to a mature phenotype with features of both granulocytes and monocytes after exposure to a combination of both compounds. Apoptosis only increased after incubation of NB4 cells with 9-cis-RA alone (28%) or with a combination of 9-cis-RA plus KH1060 (32%). Immunohistochemistry showed that the bcl-2 protein decreased from nearly 100% of the wild-type NB4 cells to 2% after incubation with a combination of KH 1060 and 9-cis-RA, and the bax protein increased from 50% of wild-type NB4 cells to 92% after culture with both analogs (5 x 10(-7) M, 3 d). Western blot analysis paralleled these results. Studies of APL cells from one untreated individual paralleled our results with NB4 cells. Taken together, the data demonstrated that nearly all of the NB4 cells can be irreversibly induced to differentiate terminally when exposed to the combination of KH 1060 and 9-cis-RA.

Authors

E Elstner, M Linker-Israeli, J Le, T Umiel, P Michl, J W Said, L Binderup, J C Reed, H P Koeffler

Local ventromedial hypothalamus glucose perfusion blocks counterregulation during systemic hypoglycemia in awake rats.

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Abstract

The ventromedial hypothalamic nucleus (VMH) is necessary for the integrated hormonal response to hypoglycemia. To determine the role of the VMH as a glucose sensor, we performed experiments designed to specifically prevent glucopenia in the VMH, while producing hypoglycemia elsewhere. We used awake chronically catheterized rats, in which local VMH glucose perfusion (100 mM or 15 mM of D-glucose) was combined with a sequential euglycemic-hypoglycemic clamp. In two control groups the VMH was perfused either with (a) an iso-osmotic solution lacking glucose, or with (b) nonmetabolizable L-glucose (100 mM). During systemic hypoglycemia glucagon and catecholamine concentrations promptly increased in the control animals perfused with either 100 mM L-glucose or the iso-osmotic solution lacking glucose. In contrast, glucagon, epinephrine and norepinephrine release was inhibited in the animals in which the VMH was perfused with D-glucose; hormonal secretion was partially suppressed by the VMH perfusion with 15 mM D-glucose and suppressed by approximately 85% when the VMH was perfused with 100 mM D-glucose, as compared with the control groups. We conclude that the VMH must sense hypoglycemia for full activation of catecholamine and glucagon secretion and that it is a key glucose sensor for hypoglycemic counterregulation.

Authors

M A Borg, R S Sherwin, W P Borg, W V Tamborlane, G I Shulman