Novel complementary antitumour effects of celastrol and metformin by targeting IκBκB, apoptosis and NLRP3 inflammasome activation in diethylnitrosamine-induced murine hepatocarcinogenesis.

One promising strategy for minimizing chemotherapeutic resistance in hepatocellular carcinoma (HCC) is the use of effective chemosensitizers. We studied the complementary multi-targeted molecular mechanisms of metformin and celastrol in mice with diethylnitrosamine-induced HCC to investigate whether metformin could augment the sensitivity of HCC tissue to the effect of celastrol. Simultaneous administration of celastrol (2 mg/kg) and metformin (200 mg/kg) improved liver function, enhanced the histological picture and prolonged survival. Additionally, combination therapy exerted anti-inflammatory activity, as indicated by the decreased levels of TNF-α and IL-6. This protective role could be attributed to inhibition of inflammasome activation. Herein, our data revealed downregulated NLRP3 gene expression, suppressed caspase-1 activity and reduced levels of the active forms of IL-1β and IL-18. Under this condition, pyroptotic activity was suppressed. In contrast, in the celastrol and celastrol + metformin groups, the apoptotic potential was amplified, as revealed by the increase in the caspase-9 and caspase-3 levels and Bax:BCL-2 ratio. In addition to their repressive effect on the gene expression of NFκBp65, TNFR and TLR4, metformin and celastrol inhibited phosphorylation-induced activation of IκBκB and NFκBp65 and decreased IκBα degradation. Combination therapy with metformin and celastrol repressed markers of angiogenesis, metastasis and tumour proliferation, as revealed by the decreased hepatic levels of VEGF, MMP-2/9 and cyclin D1 mRNA, respectively. In conclusion, by inhibiting NLRP3 inflammasome and its prerequisite NFκB signalling, simultaneous administration of metformin and celastrol appears to have additive benefits in the treatment of HCC compared to cela monotherapy. This effect warrants further clinical investigation.