Hyperglycemia aggravates acute liver injury by promoting liver-resident macrophage NLRP3 inflammasome activation via the inhibition of AMPK/mTOR-mediated autophagy induction

Abstract

Although the detrimental effects of diabetes mellitus/hyperglycemia have been observed in many liver disease models, the function and mechanism of hyperglycemia regulating liver-resident macrophages, Kupffer cells (KCs), in thioacetamide (TAA)-induced liver injury remain largely unknown. In this study, we evaluated the role of hyperglycemia in regulating NOD-like receptor family pyrin domain-containing 3 protein (NLRP3) inflammasome activation by inhibiting autophagy induction in KCs in the TAA-induced liver injury model. Type I diabetes/hyperglycemia was induced by streptozotocin treatment. Compared with the control group, hyperglycemic mice exhibited a significant increase in intrahepatic inflammation and liver injury. Enhanced NLRP3 inflammasome activation was detected in KCs from hyperglycemic mice, as shown by increased gene induction and protein levels of NLRP3, cleaved caspase-1, apoptosis-associated speck-like protein containing a caspase recruitment domain and interleukin-1β, compared with control mice. NLRP3 inhibition by its antagonist CY-09 effectively suppressed inflammasome activation in KCs and attenuated liver injury in hyperglycemic mice. Furthermore, inhibited autophagy activation was revealed by transmission electron microscope detection, decreased LC3B protein expression and p-62 protein degradation in KCs isolated from TAA-stressed hyperglycemic mice. Interestingly, inhibited 5' AMP-activated protein kinase (AMPK) but enhanced mammalian target of rapamycin (mTOR) activation was found in KCs from TAA-stressed hyperglycemic mice. AMPK activation by its agonist 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) or mTOR signaling knockdown by small interfering RNA restored autophagy activation, and subsequently, inhibited NLRP3 inflammasome activation in KCs, leading to ultimately reduced TAA-induced liver injury in the hyperglycemic mice. Our findings demonstrated that hyperglycemia aggravated TAA-induced acute liver injury by promoting liver-resident macrophage NLRP3 inflammasome activation via inhibiting AMPK/mTOR-mediated autophagy. This study provided a novel target for prevention of toxin-induced acute liver injury under hyperglycemia.

Keywords: AMPK; mTOR; Kupffer cell; NLRP3 inflammasome; autophagy; hyperglycemia; liver injury; thioacetamide.