[The effect of human islet amyloid polypeptide on autophagy in murine INS-1 cells and potential mechanisms]

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.