Protective Effect And Possible Mechanism Of Exendin-4on Interleukin-1β-induced Apoptosis In Murine Pancreaticβ-cells

OBJECTIVE: In the present study we used murine MIN6pancreaticβ-cells toexplore the protective effect of Exendin-4on IL-1β-induced apoptosis and thepossible mechanism.METHODS: Cell viability was determined by MTT assay,and apotosis andnecrosis by fluorescence microscopy after Hoechst33342-propidium iodide stainingand flow cytometric assay after staining with Annexin-Ⅴ-FITC-PI. The levels ofnitric oxide was measured by Griess reagent assay.Inmmunoblot analysis(Westernblot) was used to detect changes in protein expression,including iNOS and NF-κBp65fragment.RESULTS: Incubation of MIN6cells with IL-1β at range of5-40ng/ml for24hours significantly decreased cell viability (p<0.01), as well as increased the levels ofnitrite, the levels of cytoplasmic iNOS and nucleus NF-κBp65fragment in adose-dependent manner. Pretreated with Exendin-4,a long-acting GLP-1receptoragonist, at the concentration100nmol/L or N-Acetyl-L-cysteine(NAC) andNG-Nitro-L-arginine Methyl Ester(L-NAME) for24h or pyrrolidine dithiocarbamate(PDTC) for2h prior to exposure to IL-1β,partially protected the cells against IL-1β-induced toxicity in association with a reduction of the levels of nitrite and thepercentage of apoptosis.In parallel with these changes, exendin-4decreased theIL-1β-induced activation of NF-κB(P＜0.001) and decreased inducible nitric oxidesythase (P＜0.001),which is similar to L-NAME,PDTC or NAC,respectively.CONCLUSION:The results of our study indicate that GLP-1plays a protectiverole against IL-1β-induced apoptosis and necrosis in beta cells via down-regulation ofNF-κB-iNOS pathway. Exendin-4,a long-acting GLP-1receptor agonist is potentiallya highly effective therapeutic agent in protecting pancreaticβ-cells.