Diabetes, Vol 47, Issue 10 1602-1608, Copyright © 1998 by American Diabetes Association

ARTICLES

Ciliary neurotrophic factor potentiates the beta-cell inhibitory effect of IL-1beta in rat pancreatic islets associated with increased nitric oxide synthesis and increased expression of inducible nitric oxide synthase

KA Wadt, CM Larsen, HU Andersen, K Nielsen, AE Karlsen and T Mandrup-Poulsen
Steno Diabetes Center, Gentofte, Denmark.

Proinflammatory cytokines are implicated as effector molecules in the pathogenesis of IDDM. Interleukin-6 (IL-6) alone or in combination with IL-1beta inhibits glucose-stimulated insulin release from isolated rat pancreatic islets by unknown mechanisms. Here we investigated 1) if the effects of IL-6 are mimicked by ciliary neurotrophic factor (CNTF), another member of the IL-6 family of cytokines signaling via gp130, 2) the possible cellular mechanisms for these effects, and 3) if islet endocrine cells are a source of CNTF. CNTF (20 ng/ml) potentiated IL-1beta-mediated (5-150 pg/ml) nitric oxide (NO) synthesis from neonatal Wistar rat islets by 31-116%, inhibition of accumulated insulin release by 34-49%, and inhibition insulin response to a 2-h glucose challenge by 31-36%. CNTF potentiated IL-1beta-mediated NO synthesis from RIN-5AH cells by 83%, and IL-1beta induced islet inducible NO-synthase (iNOS) mRNA expression fourfold. IL-6 (10 ng/ml) also potentiated IL-1beta-mediated NO synthesis and inhibition of insulin release, whereas beta-nerve growth factor (NGF) (5 or 50 ng/ml) had no effect. mRNA for CNTF was expressed in rat islets and in islet cell lines. In conclusion, CNTF is constitutively expressed in pancreatic beta-cells and potentiates the beta-cell inhibitory effect of IL-1beta in association with increased iNOS expression and NO synthesis, an effect shared by IL-6 but not by beta-NGF. These findings indicate that signaling via gp130 influences islet NO synthesis associated with iNOS expression. We hypothesize that CNTF released from destroyed beta-cells during the inflammatory islet lesion leading to IDDM may potentiate IL-1beta action on the beta-cells.
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