Heitmeier M R, Scarim A L, Corbett J A
The Edward A. Doisy Department of Biochemistry and Molecular Biology, St. Louis University School of Medicine, Saint Louis, Missouri 63104, USA.
J Biol Chem. 1997 May 23;272(21):13697-704. doi: 10.1074/jbc.272.21.13697.
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.
本研究的目的是评估单独使用干扰素-γ（IFN-γ）以及将其与白细胞介素1β（IL-1β）联合使用对诱导型一氧化氮合酶（iNOS）mRNA和蛋白表达、亚硝酸盐生成以及胰岛β细胞胰岛素分泌的影响。用IL-1β处理大鼠胰岛会导致亚硝酸盐生成呈浓度依赖性增加，在5单位/毫升时达到最大值。单独使用0.1单位/毫升的IL-1β或150单位/毫升的大鼠IFN-γ不会刺激大鼠胰岛的iNOS表达或亚硝酸盐生成；然而，联合使用时，这些细胞因子会诱导iNOS表达和亚硝酸盐生成，其水平与5单位/毫升IL-1β的单独作用相似。在胰岛素依赖型糖尿病中选择性被破坏的胰岛β细胞似乎是iNOS的一个胰岛细胞来源，因为150单位/毫升的大鼠IFN-γ和0.1单位/毫升的IL-1β在通过荧光激活细胞分选纯化的原代β细胞和大鼠胰岛素瘤细胞系RINm5F中诱导出相似的效应。大鼠胰岛对150单位/毫升的大鼠IFN-γ和0.1单位/毫升的IL-1β的反应中，iNOS表达和亚硝酸盐生成与胰岛素分泌抑制和胰岛退变相关，而iNOS抑制剂氨基胍可预防这种情况。IFN-γ增加β细胞对IL-1诱导的iNOS表达敏感性的机制似乎与iNOS mRNA稳定性增加有关。最后，胰岛物理分散过程中的细胞损伤会导致释放足够量的IL-1β，在添加外源性大鼠IFN-γ的情况下诱导iNOS表达和亚硝酸盐生成。在这些条件下，IL-1β的细胞来源被认为是胰岛驻留巨噬细胞，因为在分散前耗尽巨噬细胞可防止IFN-γ诱导分散的胰岛细胞的iNOS表达和亚硝酸盐形成。这些研究表明，T淋巴细胞细胞因子IFN-γ会使大鼠胰岛对IL-1β对iNOS表达和亚硝酸盐生成的影响的敏感性提高10倍，部分原因是通过稳定iNOS mRNA。我们的研究还支持IFN-γ与胰岛驻留巨噬细胞释放的IL-1β协同作用，在自身免疫性糖尿病发展过程中介导β细胞破坏的效应作用。
