Pioglitazone ameliorates glomerular NLRP3 inflammasome activation in apolipoprotein E knockout mice with diabetes mellitus

OBJECTIVE: The NLRP3 inflammasome plays an important role in the pathogenesis of inflammation in diabetic nephropathy (DN). Pioglitazone (PIO) has been found to exert an anti-inflammatory effect in patients with diabetes mellitus, but it is still unclear whether PIO exhibits a similar effect in DN. We aimed to explore the effect and underlying mechanism of PIO on DN, as well as investigate if NLRP3 is a pharmacologic target of PIO. METHODS: We divided 48 apolipoprotein E (apoE) (-/-) mice into 4 groups: apoE (-/-), apoE (-/-) with PIO, diabetic apoE (-/-), and diabetic apoE (-/-) with PIO. Wild type male C57BL/6 mice were used as controls (n = 8 per group). After 8 weeks of PIO treatment, we examined the baseline characteristics and metabolic parameters of each group, and we used enzyme-linked immunosorbent assay (ELISA), western blot, and immunohistochemical staining to evaluate the expression levels of advanced glycation end products (AGEs), receptor for advanced glycation end products (RAGE), NLRP3, nuclear factor-kappa B (NF-κB), caspase-1, interleukin (IL)-18, and IL-1β in each group. RESULTS: Compared to the diabetic apoE (-/-) group, PIO treatment decreased blood glucose, cholesterol, serum blood urea nitrogen (BUN), and creatinine levels. It also depressed the glomerular mesangial expansion. PIO down-regulated expression of AGEs, RAGE, and NF-κB, all of which further depressed NLRP3, caspase-1, IL-18, and IL-1β levels. CONCLUSION: Pioglitazone can ameliorate diabetic renal damage, and this effect is related to the inhibition of renal AGE/RAGE axis activation and the down-regulation of NF-κB expression. These effects lead to a decline in NLRP3 levels and downstream secretion of inflammatory cytokines.