ABSTRACT
Objective The aims of the study were to investigate the effects of human islet amyloid polypeptide (hIAPP) on autophagy in INS-1 cells and its underlying mechanism,and to explore the role of autophagy in hIAPP-induced cytotoxicity and oxidative stress.Methods INS-1 cells were treated with hIAPP (10 μmol/L) for 24 h in the presence or absence of N-acetyl-L-cysteine (NAC),compound C,5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) and 3-methyladenine (3-MA),respectively.Transmission electron microscopy was used to observe the number of autophagosome in cells.Cell viability was determined by methyl thiazolyl tetrazolium (MTT) test.2',7'-dichlorofluorescin diacetate (DCFH-DA) assay was used to measure the relative levels of reactive oxygen species (ROS).Western blot was used to detect expression of adenosine monophosphate-activated protein kinase (AMPK) and autophagic markers p62 and microtubule associated protein 1 light chain3 (LC3).Results Treatment of INS-1 cells with hIAPP resulted in a significant increase in the number of autophagosomes and the expression of LC3-Ⅱ/LC3-Ⅰ (both P＜0.05).Meanwhile,treatment of INS-1 cells with hIAPP enhanced the level of ROS to 1.76 times of control cells (P＜0.01).Co-treatment with NAC,an antioxidant,inhibited hIAPP-induced ROS generation,and the expression of LC3-Ⅱ/LC3-Ⅰ and p-AMPK in the INS-1 cells (all P＜0.05).Pretreatment of INS-1 cells with AMPK inhibitor compound C suppressed hIAPP and AICAR,an activator of AMPK,induced expression of LC3-Ⅱ/LC3-Ⅰ and p-AMPK (all P＜0.05).Autophagic inhibitor 3-MA and compound C aggravated the hIAPP-induced cell death and ROS generation in INS-1 cells (All P＜0.05).The cytotoxic effects of hIAPP were significantly attenuated by co-treatment with AICAR (P＜0.05).Conclusion Autophagy may act as an adaptive mechanism to alleviate hIAPP-induced oxidative damage and toxicity in INS-1 cells.