Biomedical subjects

M H Marino

Publications and source records attributed to M H Marino.

5 recordsLinked to original sources

PubMed1998

IL-1 produced and released endogenously within human islets inhibits beta cell function.

Resident macrophages have been suggested to participate in the initiation of beta cell damage during the development of autoimmune diabetes. The purpose of this study was to determine if the endogenous production and release of interleukin 1 (IL-1) in human islets of Langerhans by resident macrophages results in the inhibition of beta cell function. Treatment of human islets with a combination of tumor necrosis factor (TNF) + lipopolysaccharide (LPS) + interferon-gamma (IFN-gamma) stimulates inducible nitric oxide synthase (iNOS) expression, nitric oxide production, and inhibits glucose-stimulated insulin secretion. The IL-1 receptor antagonist protein (IRAP) prevents TNF + LPS + IFN-gamma-induced iNOS expression and nitrite production, and attenuates the inhibitory effects on glucose-stimulated insulin secretion by human islets. Inhibition of iNOS activity by aminoguanidine also attenuates TNF + LPS + IFN-gamma-induced inhibition of insulin secretion by human islets. These results indicate that the inhibitory effects of TNF + LPS + IFN-gamma are mediated by nitric oxide, produced by the actions of IL-1 released endogenously within human islets. Reverse transcriptase polymerase chain reaction was used to confirm that TNF + LPS + IFN-gamma stimulates the expression of both IL-1alpha and IL-1beta in human islets. Two forms of evidence indicate that resident macrophages are the human islet cellular source of IL-1: culture conditions that deplete islet lymphoid cells prevent TNF + LPS + IFN-gamma-induced iNOS expression, nitric oxide production, and IL-1 mRNA expression by human islets; and IL-1 and the macrophage surface marker CD69 colocalize in human islets treated with TNF + LPS + IFN-gamma as determined by immunohistochemical analysis. Lastly, nitric oxide production is not required for TNF + LPS + IFN-gamma-induced IL-1 release in human islets. However, cellular damage stimulates IL-1 release by islet macrophages. These findings support the hypothesis that activated islet macrophages may mediate beta cell damage during the development of insulin-dependent diabetes by releasing IL-1 in human islets followed by cytokine-induced iNOS expression by beta cells.

Enzyme Induction↗

PubMed1998

Inducible nitric oxide synthase and inflammation.

Nitric oxide (NO), derived from L-arginine (L-Arg) by the enzyme nitric oxide synthase (NOS), is involved in acute and chronic inflammatory events. In view of the complexity associated with the inflammatory response, the dissection of possible mechanisms by which NO modulates this response will be profitable in designing novel and more efficacious NOS inhibitors. In this review we describe the consequences associated with the induction of inducible nitric oxide synthase (iNOS) and its therapeutic implications.

Journal Article↗

PubMed1996

Nitric oxide: a key mediator in the early and late phase of carrageenan-induced rat paw inflammation.

1 The role of nitric oxide (NO) derived from constitutive and inducible nitric oxide synthase (cNOS and iNOS) and its relationship to oxygen-derived free radicals and prostaglandins (PG) was investigated in a carrageenan-induced model of acute hindpaw inflammation. 2 The intraplantar injection of carrageenan elicited an inflammatory response that was characterized by a time-dependent increase in paw oedema, neutrophil infiltration, and increased levels of nitrite/nitrate (NO2-/NO3-) and prostaglandin E2(PGE2) in the paw exudate. 3 Paw oedema was maximal by 6 h and remained elevated for 10 h following carrageenan administration. The non-selective cNOS/iNOS inhibitors, NG-monomethyl-L-arginine (L-NMMA) and NG-nitro-L-arginine methyl ester (L-NAME) given intravenously (30-300 mg kg-1) 1 h before or after carrageenan administration, inhibited paw oedema at all time points. 4 The selective iNOS inhibitors, N-iminoethyl-L-lysine (L-NIL) or aminoguanidine (AG), failed to inhibit carrageenan-induced paw oedema during the first 4 h following carrageenan administration, but inhibited paw oedema at subsequent time points (from 5-10 h). iNOS mRNA was detected between 3 to 10 h following carrageenan administration using ribonuclease protection assays. iNOS protein was first detected 6 h and was maximal 10 h following carrageenan administration as shown by Western blot analysis. Administration of the iNOS inhibitors 5 h after carrageenan (a time point where iNOS was expressed) inhibited paw oedema at all subsequent time points. Infiltrating neutrophils were not the source of iNOS since pretreatment with colchicine (2 mg kg-1) suppressed neutrophil infiltration, but did not inhibit the iNOS mRNA expression or the elevated NO2-/NO3- levels in the paw exudate. 5 Inhibition of paw oedema by the NOS inhibitors was associated with attenuation of both the NO2-/NO3- and PGE2 levels in the paw exudate. These inhibitors also reduced the neutrophil infiltration at the site of inflammation. 6 Recombinant human Cu/Zn superoxide dismutase coupled to polyethyleneglycol (PEGrhSOD; 12 x 10(3) u kg-1), administered intravenously either 30 min prior to or 1 h after carrageenan injection, inhibited paw oedema and neutrophil infiltration, but had no effect on NO2-/NO3- or PGE2 production in the paw exudate. The administration of catalase (40 x 10(3) u kg-1), given intraperitoneally 30 min before carrageenan administration, had no effect on paw oedema. Treatment with desferrioxamine (300 mg kg-1), given subcutaneously 1 h before carrageenan, inhibited paw oedema during the first 2 h after carrageenan administration, but not at later times. 7 These results suggest that the NO produced by cNOS is involved in the development of inflammation at early time points following carrageenan administration and that NO produced by iNOS is involved in the maintenance of the inflammatory response at later time points. The potential interactions of NO with superoxide anion and PG is discussed.

Animals↗

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↗

PubMed1995

Novel assay for the influenza virus M2 channel activity.

The influenza A M2 ion channel was expressed and activity characterized in Xenopus oocytes. Based on the activation properties of the channels, a high throughput, non-electrophysiological screening assay was developed in order to identify novel inhibitors of the channel. This will facilitate discovery of novel agents to treat influenza viral infections.

Animals↗