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J A Corbett

Publications and source records attributed to J A Corbett.

At least 37 records · Page 2Linked to original sources
PubMed1997

Evidence for the presence of type I IL-1 receptors on beta-cells of islets of Langerhans.

The cytokine interleukin-1beta (IL-1beta) has been shown to inhibit insulin secretion and destroy pancreatic islets by a mechanism that involves the expression of inducible nitric oxide synthase (iNOS), and the production of nitric oxide (NO). Insulin containing beta-cells, selectively destroyed during the development of autoimmune diabetes, appear to be the islet cellular source of iNOS following treatment with IL-1beta. In this study we have evaluated the presence of type I IL-1 signaling receptors on purified pancreatic beta-cells. We show that the interleukin-1 receptor antagonist protein (IRAP) prevents IL-1beta-induced nitrite formation and IL-1beta-induced inhibition of insulin secretion by isolated islets and primary beta-cells purified by fluorescence-activated cell sorting (FACS). The protective effects of IRAP correlate with an inhibition of IL-1beta-induced iNOS expression by islets and FACS purified beta-cells. To provide direct evidence to support beta-cell expression of IL-1 type I signaling receptors, we show that antiserum specific for the type I IL-1 receptor neutralizes IL-1beta-induced nitrite formation by RINm5F cells, and that RINm5F cells express the type I IL-1 receptor at the protein level. Using reverse transcriptase-polymerase chain reaction (RT-PCR), the expression of type I IL-1 signaling receptors by FACS purified beta-cells and not alpha-cells is demonstrated. These results provide direct support for the expression of type I IL-1 receptors by primary pancreatic beta-cells, the cell type selectively destroyed during the development of autoimmune diabetes.

Animals↗
PubMed1997

Interferon-gamma increases the sensitivity of islets of Langerhans for inducible nitric-oxide synthase expression induced by interleukin 1.

The purpose of this study was to evaluate the effects of interferon-gamma (IFN-gamma) alone and in combination with interleukin 1beta (IL-1beta) on inducible nitric-oxide synthase (iNOS) mRNA and protein expression, nitrite production, and insulin secretion by islets of Langerhans. Treatment of rat islets with IL-1beta results in a concentration-dependent increase in the production of nitrite that is maximal at 5 units/ml. Individually, 0. 1 unit/ml IL-1beta or 150 units/ml rat IFN-gamma do not stimulate iNOS expression or nitrite production by rat islets; however, in combination, these cytokines induce the expression of iNOS and the production of nitrite to levels similar in magnitude to the individual effects of 5 units/ml IL-1beta. The islet beta-cell, selectively destroyed during insulin-dependent diabetes mellitus, appears to be one islet cellular source of iNOS as 150 units/ml rat IFN-gamma and 0.1 unit/ml IL-1beta induced similar effects in primary beta-cells purified by fluorescence-activated cell sorting and in the rat insulinoma cell line, RINm5F. iNOS expression and nitrite production by rat islets in response to 150 units/ml rat IFN-gamma and 0.1 unit/ml IL-1beta are correlated with an inhibition of insulin secretion and islet degeneration that are prevented by the iNOS inhibitor aminoguanidine. The mechanism by which IFN-gamma increases the sensitivity of beta-cells for IL-1-induced iNOS expression appears to be associated with an increase in the stability of iNOS mRNA. Last, cellular damage during physical dispersion of islets results in the release of sufficient amounts of IL-1beta to induce iNOS expression and nitrite production in the presence of exogenously added rat IFN-gamma. The cellular source of IL-1beta under these conditions is believed to be resident islet macrophages as depletion of macrophages prior to dispersion prevents IFN-gamma-induced iNOS expression and nitrite formation by dispersed islet cells. These studies show that the T-lymphocyte cytokine, IFN-gamma, increases the sensitivity of rat islets to the effects of IL-1beta on iNOS expression and nitrite production by 10-fold, in part, through the stabilization of iNOS mRNA. Our studies also support an effector role for IFN-gamma, in concert with resident islet macrophage release of IL-1beta, in mediating beta-cell destruction during the development of autoimmune diabetes.

Animals↗
PubMed1997

Expression of neuregulins and their putative receptors, ErbB2 and ErbB3, is induced during Wallerian degeneration.

Schwann cell dedifferentiation and proliferation is a prerequisite to axonal regeneration in the injured peripheral nervous system. The neuregulin (NRG) family of growth and differentiation factors may play a particularly important role in this process, because these axon-associated molecules are potent Schwann cell mitogens and differentiation factors in vitro. We have examined Schwann cell DNA synthesis and the expression of NRGs and their receptors, the erbB membrane tyrosine kinases, in rat sciatic nerve, sensory ganglia, and spinal cord 0-30 d postaxotomy. Analysis of NRG cDNAs from these tissues revealed several novel splice variants and showed that cells endogenous to injured nerve express NRG mRNAs. A selective induction of mRNAs encoding the glial growth factor (GGF) subfamily of NRGs occurs in nerve beginning 3 d postaxotomy and thus coincides with the onset of Schwann cell DNA synthesis. In later stages of Wallerian degeneration, however, Schwann cell mitogenesis markedly decreases, whereas elevated GGF expression persists. Of the four known erbB kinases, Schwann cells express both erbB2 and erbB3 receptors over the entire interval studied. Expression of erbB2 and erbB3 is coordinately induced in response to axotomy, indicating that Schwann cell responses to NRGs may be modulated by changes in receptor density. Neuregulin (including transmembrane precursors) and erbB protein are associated with Schwann cells postaxotomy. Thus, in contrast to the concept of NRGs as axon-associated mitogens, our findings suggest that NRGs produced by Schwann cells themselves may be partially responsible for Schwann cell proliferation during Wallerian degeneration, probably acting via autocrine or paracrine mechanisms.

Animals↗
PubMed1997

Effects of aspirin on nitric oxide formation and de novo protein synthesis by RINm5F cells and rat islets.

Aspirin and aspirin-like drugs are the most commonly indicated agents for the treatment of inflammation. Mechanisms of action for these drugs, however, are not clearly understood. In this study, we examined the effects of aspirin on production of nitric oxide (NO), a proinflammatory mediator, and show that aspirin inhibits NO production by transformed pancreatic beta cells (RINm5F) and rat islets in a concentration-dependent manner with an IC50 value of approximately 3 mM. Therapeutic concentrations of aspirin (1-5 mM) that block NO production affected neither nuclear factor-kappaB activation nor inducible NO synthase (iNOS) mRNA transcription but potently inhibited iNOS protein expression by both RINm5F cells and rat islets. The effects of aspirin on islet function were examined by measuring glucose-stimulated insulin secretion in the presence of various concentrations of aspirin. Aspirin (1-5 mM) did not affect insulin secretion at basal or glucose-stimulated conditions, whereas higher concentrations of aspirin (10-20 mM) significantly increased basal insulin secretion. Aspirin at high concentrations of 10 and 20 mM inhibited de novo protein synthesis as demonstrated by inhibition of [35S]methionine incorporation into total islet protein and by inhibition of rabbit reticulocyte expression by Brome mosaic virus mRNA, suggesting that inhibition of iNOS expression at these high concentrations of aspirin may be due to the impairment of the translational machinery. These findings indicate that inhibition of iNOS expression and NO production may explain, in part, the beneficial effects of aspirin as an anti-inflammatory agent at therapeutic concentrations, whereas inhibition of de novo protein synthesis may possibly explain clinical and side effects of aspirin in the inflamed tissues and organs such as stomach and kidney that may accumulate high concentrations of aspirin.

Animals↗
PubMed1997

Phorbol esters stimulate muscle glucose transport by a mechanism distinct from the insulin and hypoxia pathways.

Glucose transport in skeletal muscle can be stimulated by insulin and also by contractions and hypoxia. Activation of protein kinase C (PKC) stimulates glucose transport in muscle and other insulin-responsive cells. This study was performed to determine if the diacylglycerol (DAG)/phorbol ester-sensitive PKC isoforms participate in insulin and/or hypoxia-stimulated glucose transport in skeletal muscle. The phorbol ester 12-deoxyphorbol 13-phenylacetate 20-acetate (dPPA) induced a three- to fourfold increase in glucose transport in rat epitrochlearis muscle. The effects of dPPA on glucose transport and on cell surface GLUT-4 were completely additive to the maximal effects of insulin or hypoxia. Phorbol ester treatment induced 5- to 10-fold increases in phosphorylation of the myristoylated alanine-rich C kinase substrate protein in muscle, whereas insulin and hypoxia had negligible effects. Calphostin C, an inhibitor of DAG-sensitive PKC isoforms, decreased glucose transport stimulation by dPPA but not by insulin or hypoxia. These results provide evidence that activation of DAG/phorbol ester-sensitive PKCs is not involved in the pathways by which either insulin or hypoxia stimulates muscle glucose transport. They also show that activation of this group of PKCs increases glucose transport by a mechanism that is independent of and additive to the effects of insulin or hypoxia.

Animals↗
PubMed1997

Inhibition of nitric oxide synthase attenuates NNMU-induced alveolar injury in vivo.

The purpose of this study was to determine if the acute alveolar injury induced by subcutaneous injections of N-nitroso-N-methylurethane (NNMU) in rats is mediated by nitric oxide (NO.). We show that intraperitoneal injections of the NO. synthase (NOS) inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine significantly attenuate the NNMU-induced alveolar injury as assessed by 1) normalization of the alveolar-arterial O2 difference, 2) attenuation of the lowered phospholipid-to-protein ratio in the crude surfactant pellet (CSP), 3) attenuation of the elevated minimal surface tension of the CSP, and 4) attenuation of polymorphonuclear neutrophilic infiltration into the alveolar space. Injections of N omega-nitro-D-arginine methyl ester, the inactive stereoisoform of L-NAME, did not affect the acute lung injury. Western blot analysis of whole lung homogenates demonstrate an elevated expression of transcriptionally inducible, Ca(2+)-independent NOS (iNOS) in NNMU-injected rats compared with control saline-injected rats. NOS inhibitors did not affect NNMU-induced iNOS expression. These investigations demonstrate that the inhibition of NOS attenuates NNMU-induced acute lung injury, suggesting a role for NO. in the progression of acute respiratory distress syndrome.

Animals↗
PubMed1997

Irreversible inhibition of metabolic function and islet destruction after a 36-hour exposure to interleukin-1beta.

The purpose of this study was to identify the duration of exposure of islets to interleukin 1beta (IL-1beta) that results in irreversible damage. Treatment of rat islets for 18 h with IL-1beta results in an inhibition of glucose-stimulated insulin secretion, mitochondrial aconitase activity, and total protein synthesis. The addition of N(G)-monomethyl-L-arginine (NMMA) or aminoguanidine to islets preincubated for 18 h with IL-1beta, followed by continued culture for 8 h (with both NMMA and IL-1beta), results in the recovery of islet secretory function, aconitase activity, and protein synthesis. However, islet metabolic function is irreversibly inhibited after a 36-h incubation with IL-1beta, as an additional 8-h incubation with NMMA or aminoguanidine does not stimulate the recovery of insulin secretion, aconitase activity, or protein synthesis. The irreversible inhibition of metabolic function correlates with the commitment of islets to destruction. Treatment of islets for 96 h with IL-1beta results in islet degeneration. NMMA, added to islets 24 h after the addition of IL-1beta, followed by continued culture for 72 h (with NMMA and IL-1beta), prevents islet degeneration. However, NMMA added to islets 36 h or 48 h after the addition of IL-1beta, followed by continued culture for a total of 96 h, does not prevent islet degeneration. New messenger RNA expression appears to be required for islet recovery from IL-1beta-induced damage as actinomycin D prevents the recovery of islet aconitase activity. Lastly, treatment of human islets with a combination of IL-1beta and interferon-gamma (IFNgamma) results in a potent inhibition of mitochondrial aconitase activity. NMMA, when cocultured with IL-1beta + IFNgamma, completely prevents cytokine-induced inhibition of human islet aconitase activity. NMMA, when added to human islets pretreated for 18 h with IL-1beta + IFNgamma, stimulates the recovery of mitochondrial aconitase activity after an additional 8 h incubation. These findings indicate that nitric oxide-induced islet damage is reversible; however, prolonged production of nitric oxide (after a 36-h exposure to IL-1beta) results in the irreversible inhibition of islet metabolic and secretory function.

Aconitate Hydratase↗
PubMed1996

Nitric oxide regulates interleukin 1 bioactivity released from murine macrophages.

The bioactivity of interleukin-1 (IL-1), a major proinflammatory cytokine, can be modulated by a variety of factors including inhibitors of IL-1 production and release and receptor blockade by IL-1 receptor antagonist and by binding to nonsignaling soluble receptors. This study demonstrates that the free radical nitric oxide (NO) is also a regulator of IL-1 bioactivity. Lipopolysaccharide-activated murine macrophage RAW264.7 cells, and lipopolysaccharide plus interferon-gamma-activated murine peritoneal macrophages release IL-1 bioactivity, which is increased 10-fold over control levels by 24 h. NG-Monomethyl -arginine (NMMA), a nitric oxide synthase (NOS) inhibitor, almost completely inhibits the release of IL-1 bioactivity from activated macrophages in a time- and concentration-dependent manner with an IC50 of 50 microM. IL-1 activity was determined by thymocyte proliferation bioassay and by a new spectrophotometric bioassay based on IL-1-specific induction of NOS and NO production by an insulinoma cell line, RINm5F. Neither NO nor NOS inhibitors present in the macrophage supernatant interfere with the bioassays. Aminoguanidine and iodonium diphenyl, mechanistically unrelated NOS inhibitors, also prevent the release of IL-1 activity from RAW 264.7 cells. The addition of the NO donor S-nitroso-acetylpenicillamine reconstituted the release of IL-1 bioactivity inhibited by NMMA in a concentration-dependent manner. NO appears to increase the amount of IL-1 protein released by activated macrophages as determined by enzyme-linked immunosorbent assay, but not by mechanisms involving cell death nor modification of IL-1 precursor processing. A cGMP donor, 8-bromo-cGMP, dose-dependently reverses NMMA inhibition of bioactive IL-1 release, suggesting that NO regulates IL-1 release by a cGMP-dependent mechanism. These observations suggest that NO stimulation of the activity of IL-1, a key mediator of the immune response, may be a potentially important mechanism for control of IL-1 activity in vivo.

Animals↗
PubMed1996

Nitric oxide production by the rat insulinoma cell line, RINm5F, Is specific for IL-1: a spectrophotometric IL-1 bioassay.

Cytokines inhibit glucose-induced insulin secretion from pancreatic beta-cells by stimulating the expression of nitric oxide synthase and the increased production of nitric oxide (NO). We have found that the rat insulinoma cell line, RINm5F, responds specifically and linearly to murine and human interleukin-1beta (IL-1beta) and IL-1alpha in the range of 0.1 to 1 unit/ml to produce nitric oxide. Other cytokines, including IL-2, IL-4, IL-6, IL-9, IL-11, IL-15, tumor necrosis factor-alpha, interferon-gamma, and lipopolysaccharide fail to stimulate nitric oxide formation by RINm5F cells either alone or in combination. In addition, these cytokines do not significantly potentiate or attenuate the IL-1 response. This unprecedented specificity to IL-1 has been further developed as a sensitive and specific assay for IL-1 bioactivity. Quantitation by this new bioassay of human IL-1beta and IL-1 released from activated murine peritoneal macrophages showed a close correlation with the quantitation of IL-1 by enzyme immunoassay (ELISA). This new bioassay, which is specific, nonradioactive and inexpensive, represents a significant improvement over current bioassays for IL-1.

Animals↗
PubMed1996

Characterization of the sphingomyelin content of isolated pancreatic islets. Evaluation of the role of sphingomyelin hydrolysis in the action of interleukin-1 to induce islet overproduction of nitric oxide.

Inflammatory cytokines may participate in the destruction of pancreatic islets during the pathogenesis of insulin-dependent diabetes mellitus, and the cytokine interleukin-1 (IL-1) strongly inhibits insulin secretion from rat pancreatic islets by a process which involves induction of expression of the inducible isoform of nitric oxide synthase and the overproduction of nitric oxide. The signaling events between IL-1 receptor occupancy and induction of nitric oxide synthase in rat islets involve activation of the transcriptional activator NFkappa B. Because sphingomyelin hydrolysis has been implicated as a signaling process both in NFkappa B activation and in IL-1 action in some cells, we have examined the potential involvement of sphingomyelin hydrolysis in the induction of islet nitric oxide overproduction by IL-1. Rat islet sphingomyelin pools were radiolabeled with [3H]choline, and sphingomyelin was then isolated by normal phase HPLC. Electrospray ionization-mass spectrometric analysis revealed islet sphingomyelin consists of at least 4 distinct molecular species, and the most abundant of them contained sphingosine as the long chain base and a residue of palmitic acid as the fatty acid substituent. Molecular species containing residues of stearic acid and arachidic acid were also observed. Neither interleukin-1 nor tumor necrosis factor-alpha was found to induce hydrolysis of islet sphingomyelin species, and neither an exogenous, cell-permeant ceramide species (N-acetyl-D-sphingosine) nor exogenous sphingomyelinase mimicked or potentiated the effect of IL-1 to increase rat islet nitric oxide generation, as reflected by nitrite production. Similar findings were obtained with RINm5F insulinoma cells and with mouse pancreatic islets. These findings provide the first information on the molecular species of sphingomyelin in pancreatic islets and suggest that sphingomyelin hydrolysis is not involved in the signaling pathway whereby IL-1 induces the overproduction of nitric oxide by pancreatic islets.

Animals↗
PubMed1996

Interleukin-1 enhances pancreatic islet arachidonic acid 12-lipoxygenase product generation by increasing substrate availability through a nitric oxide-dependent mechanism.

Interleukin-1 (IL-1) impairs insulin secretion from pancreatic islets and may contribute to the pathogenesis of insulin-dependent diabetes mellitus. IL-1 increases islet expression of nitric oxide (NO) synthase, and the resultant overproduction of NO participates in inhibition of insulin secretion because NO synthase inhibitors, e.g. NG-monomethyl-arginine (NMMA), prevent this inhibition. While exploring effects of IL-1 on islet arachidonic acid metabolism, we found that IL-1 increases islet production of the 12-lipoxygenase product 12-hydroxyeicosatetraenoic acid 12-(HETE). This effect requires NO production and is prevented by NMMA. Exploration of the mechanism of this effect indicates that it involves increased availability of the substrate arachidonic acid rather than enhanced expression of 12-lipoxygenase. Evidence supporting this conclusion includes the facts that IL-1 does not increase islet 12-lipoxygenase protein or mRNA levels and does not enhance islet conversion of exogenous arachidonate to 12-HETE. Mass spectrometric stereochemical analyses nonetheless indicate that 12-HETE produced by IL-1-treated islets consists only of the S-enantiomer and thus arises from enzyme action. IL-1 does enhance release of nonesterified arachidonate from islets, as measured by isotope dilution mass spectrometry, and this effect is suppressed by NMMA and mimicked by the NO-releasing compound 3-morpholinosydnonimine. Although IL-1 increases neither islet phospholipase A2 (PLA2) activities nor mRNA levels for cytosolic or secretory PLA2, a suicide substrate which inhibits an islet Ca(2+)-independent PLA2 prevents enhancement of islet arachidonate release by IL-1. IL-1 also impairs esterification of [3H8]arachidonate into islet phospholipids, and this effect is prevented by NMMA and mimicked by the mitochondrial ATP-synthase inhibitor oligomycin. Experiments with exogenous substrates indicate that NMMA does not inhibit and that the NO-releasing compound does not activate islet 12-lipoxygenase or PLA2 activities. These results indicate that a novel action of NO is to increase levels of nonesterified arachidonic acid in islets.

Animals↗
PubMed1996

Regulation of inducible nitric oxide synthase expression by macrophage purinoreceptors and calcium.

Macrophage activation is central to the progression of multiple diseases via the release of inflammatory mediators such as cytokines and nitric oxide. Despite the recognized overlap in the regulatory mechanisms involved in mediator production, little formation exists regarding receptor-initiated signaling pathways that coordinately control multiple end points, such as tumor necrosis factor-alpha (TNF-alpha) and nitric oxide production. In this study, the expression of inducible nitric oxide synthase (iNOS) in macrophages is shown to be regulated by calcium and by a purinoreceptor signaling system. The P2Y purinoreceptor partial agonist, 2-methylthio-ATP (2-MeS-ATP), inhibits the expression of iNOS induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma) in primary macrophages. Additionally, 2-MeS-ATP attenuates the expression of iNOS in macrophages isolated from CD-1 mice challenged with LPS, and it inhibits LPS-induced TNF-alpha and interleukin-1 alpha (IL-1 alpha) release, thereby preventing endotoxic death. Thus, purinoreceptors and calcium are likely to be critical for macrophage activation and the production of inflammatory mediators stimulated by LPS.

Adenosine Triphosphate↗
PubMed1996

Experimental allergic encephalomyelitis in the rat is inhibited by aminoguanidine, an inhibitor of nitric oxide synthase.

This study assessed the role of de novo nitric oxide (NO) production in the pathogenesis of experimental allergic encephalomyelitis (EAE) by using aminoguanidine (AG), an inhibitor of nitric oxide synthase (NOS), which preferentially inhibits the cytokine- and endotoxin-inducible isoform of NOS versus the constitutive isoforms consisting of endothelial and neuronal NOS. The maximum clinical severity of EAE and the duration of illness were significantly reduced or totally inhibited by twice daily subcutaneous injection of 100 mg/kg body weight AG. Histochemical staining for NADPH diaphorase, which detects enzymatic activity of NOS, revealed positive reactivity in untreated EAE rats both in parenchymal blood vessel walls and in anterior horn cell neurons, while normal rats and rats with EAE treated with AG showed predominantly the neuronal positivity. Moreover, this NADPH staining pattern was further supported by the immunohistochemical findings that endothelial NOS (eNOS) expression was increased in blood vessels in the inflamed lesions of untreated EAE rats and that inducible NOS (iNOS) was detected in some inflammatory cells, while treatment with AG could significantly reduce both iNOS and eNOS production. These results suggest that: (i) both iNOS and eNOS are upregulated in inflamed areas of the rat central nervous system in EAE; (ii) increased NO production plays a role in the development of clinical signs in EAE; and (iii) selective inhibitors of iNOS and/or eNOS may have therapeutic potential for the treatment of certain autoimmune diseases.

Animals↗
PubMed1996

Increased plasma kynurenine and its relationship to neopterin and tryptophan in Tourette's syndrome.

Fasting plasma levels of tryptophan, kynurenine and the pteridines, neopterin and tetrahydrobiopterin were measured in seven patients with Gilles de la Tourette syndrome (GTS) and 10 healthy controls. Plasma kynurenine was significantly elevated in the GTS patients. The lowest patient value was higher than the highest control value. Values for tryptophan, neopterin and tetrahydrobiopterin were similar in TS patients and controls. However, in TS patients only, there was a significant negative correlation between tryptophan and neopterin and a significant positive correlation between kynurenine and neopterin when controlling for tryptophan. This finding indicates that activation of cellular immune processes is a possible explanation for the rise in plasma kynurenine.

Adolescent↗
PubMed1996

Tyrosine kinase inhibitors prevent cytokine-induced expression of iNOS and COX-2 by human islets.

Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease that is characterized by selective destruction of insulin-secreting beta-cells. Cytokines have been implicated as effector molecules that participate in both islet inflammation and beta-cell destruction during the development of IDDM. In this study, the effects of cytokines on the expression of inducible nitric oxide synthase (iNOS) and inducible cyclooxygenase (COX-2) by human islets were examined. In combination, the cytokines, human recombinant interleukin-1 beta (IL-1 beta), human recombinant tumor necrosis factor-alpha (TNF-alpha), and human recombinant interferon-gamma (IFN-gamma), induce the time-dependent formation of nitrite and prostaglandin E2 (PGE2) by human islets. The nitric oxide synthase inhibitor NG-monomethyl-L-arginine (L-NMMA) completely inhibits cytokine-induced nitrite formation and attenuates PGE2 production by human islets. L-NMMA does not inhibit cytokine-induced expression of COX-2 by human islets, suggesting that nitric oxide may directly activate cyclooxygenase, an effect that has been previously demonstrated for isolated rat islets. This combination of cytokines (IL-1 beta, TNF-alpha, and IFN-gamma) also induces the expression of iNOS mRNA by human islets as demonstrated by both reverse transcriptase-polymerase chain reaction and Northern blot analysis. We further show that the tyrosine kinase inhibitors genistein and herbimycin A prevent IL-1 beta plus IFN-gamma-induced expression of COX-2 and iNOS and the production of PGE2 and nitric oxide by human islets. These results demonstrate that cytokines induce the expression of iNOS and COX-2 by human islets and that cytokine-induced expression of both COX-2 and iNOS by human islets appears to require the activation of a tyrosine kinase(s).

Arginine↗
PubMed1996

Interleukin 1-induced Fos and Jun do not regulate inducible nitric oxide synthase in rat islets of Langerhans and RINm5F cells.

Recent evidence indicates that nitric oxide (NO) produced after expression of inducible NO synthase (iNOS) mediates cytokine-induced inhibition of insulin secretion by pancreatic islets. The current studies were designed to characterize the involvement of immediate-early response genes, c-fos and c-jun, in interleukin 1 (IL-1)-induced expression of iNOS. iNOS messenger RNA (mRNA) expression by both rat islets and RINm5F cells was time dependent, with maximal expression observed after an approximately 3- to 6-h exposure to IL-1. IL-1 also stimulated rapid and transient expression of c-fos and c-jun by both rat islets and RINm5F cells, with maximal mRNA accumulation detected 30-60 min after IL-1 treatment. IL-1-induced protein synthesis of Fos and Jun was observed as early as 30 min, peaked between 3-5 h, and decreased by 8 h after IL-1 treatment. Temporal correlation of Fos and Jun expression and iNOS gene induction suggested that Fos and Jun might regulate iNOS gene transcription by rodent pancreatic beta-cells. The present study, however, indicates that IL-1 induced expression of Fos and Jun does not seem to participate in the regulation of iNOS and mRNA expression, because: 1) cycloheximide (1 microM) completely inhibited Fos expression but had no inhibitory effect on iNOS mRNA levels; and 2) tyrosine kinase inhibitors genistein and herbimycin A completely inhibited IL-1 induced iNOS expression but did not block c-fos and c-jun expression. These results indicate that two separate signaling pathways may exist for induction of c-fos and c- jun and iNOS genes and that de novo synthesis of Fos and Jun does not participate in the regulation of iNOS gene expression.

Animals↗