Inhibition of <scp>miR</scp> ‐33 Alleviates Inflammation Response in <scp> <i>Ctenopharyngodon idella</i> </scp> Kidney Cells Induced by Chloroquine/Lipopolysaccharide

A previous study in our laboratory revealed that microRNA-33 (miR-33) regulated autophagy initiation and inflammatory response by targeting Atg5; furthermore, in this study, chloroquine (CQ), lipopolysaccharide (LPS) and the miR-33 inhibitor were transfected into Ctenopharyngodon idella kidney (CIK) cells to explore whether miR-33 regulated late-stage autophagy and inflammatory response induced by LPS. The results showed that CQ inhibited the fusion of autophagosome and lysosome and significantly increased the secretion of pro-inflammatory cytokines (p < 0.05). Interestingly, miR-33 was also significantly upregulated after CQ incubation (p < 0.05). However, compared with the CQ group, the expression of beclin-1, atg5, atg7 and atg12 did not recover after inhibiting miR-33 (p > 0.05). But the expression of tnf-α, il-6, il-1β, il-8 and nf-κb, as well as the secretion of TNF-α, IL-6, IL-12 and IL-1β, were significantly downregulated, and the activities of ALP, SOD and CAT were significantly increased (p < 0.05). Furthermore, CIK cells were treated with LPS to construct an inflammation model, and miR-33 expression was significantly upregulated (p < 0.05). In contrast, the miR-33 inhibitor reversed the effects of LPS by decreasing the transcription levels of tnf-α, il-6, il-1β, il-8 and nf-κb; inhibiting the secretion of TNF-α, IL-6, IL-12 and IL-1β; and increasing the activities of ACP, ALP, SOD and CAT (p < 0.05). Taken together, the inhibition of miR-33 alleviated inflammatory response in CIK cells induced by CQ and LPS, but miR-33 regulated autophagy independently of CQ. These findings provided a theoretical foundation and a novel perspective for further understanding the mechanisms by which miR-33 regulated autophagy and inflammation in fish.