Nitric oxide mediates IL-1beta stimulation of heat shock protein but not IL-1beta inhibition of glutamic acid decarboxylase.
Interleukin-1beta (IL-1beta) has been implicated to play an important role in the autoimmune beta cell lesion of insulin-dependent diabetes mellitus (IDDM) because of its inhibition of insulin secretion, direct islet cytotoxicity and alteration of islet cell antigen expression. We have previously demonstrated that IL-1beta inhibits glutamic acid decarboxylase-65 (GAD-65) and increases heat shock protein-70 (HSP-70) expression in islet cells. IL-1beta stimulates the inducible form of nitric oxide (NO) synthase and the resultant increased NO mediates many of IL-1beta's effects. In this study we investigated the role of the NO pathway in mediating the effects of IL-1beta on GAD-65 and HSP-70 expression and on insulin secretion. Islets isolated from Sprague-Dawley rats were cultured with IL-1beta and aminoguanidine (AG), an inhibitor of inducible NO synthase, individually and in combination for 24 h. Accumulated nitrite production, insulin release and islet expression of GAD-65 and HSP-70 were measured. We found that (1) IL-1beta at 10 U/ml increased nitrite production, inhibited insulin release, increased HSP-70 expression and decreased GAD-65 expression. (2) AG alone at 1 mM/ml had no effect on nitrite production, insulin release, GAD-65 and HSP-70 expression. (3) In combination, AG completely blocked IL-1beta increased nitrite production, reversed IL-1beta inhibited insulin release by approximately 50%, completely reversed IL-1beta increased HSP-70 expression, but did not reverse IL-1beta inhibited GAD-65 expression. Our findings indicate that the effect of IL-1beta on HSP-70 expression is mediated by NO production, whereas a NO-independent pathway is involved in the effect of IL-1beta on GAD-65 expression and insulin secretion.
Hao
W
W
Department of Medicine, University of Washington, Department of Veteran Affairs Puget Sound Health Care System, Seattle 98108, USA. weihao@u.washington.edu
Myhre
A P
AP
Palmer
J P
JP
D000818:Animals; D003922:Diabetes Mellitus, Type 1 / Q000209:etiology; D005968:Glutamate Decarboxylase / Q000037:antagonists & inhibitors*; D006146:Guanidines / Q000494:pharmacology; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007375:Interleukin-1 / Q000494:pharmacology*; D008297:Male; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II; D051381:Rats; D017207:Rats, Sprague-Dawley
D006146:Guanidines; D018840:HSP70 Heat-Shock Proteins; D007328:Insulin; D007375:Interleukin-1; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D005968:Glutamate Decarboxylase; C004479:pimagedine