HSP60-mediated UPR^mt overactivation drives triptolide-induced hepatocellular lipoapoptosis

The mitochondrial unfolded protein response (UPR^mt) maintains proteostasis, but its dysregulation dictates cell fate. This study aimed to elucidate the signaling mechanism by which triptolide (TP), a bioactive component of Tripterygium wilfordii Hook. f., triggers hepatocellular Lipoapoptosis, focusing on HSP60-mediated UPR^mt overactivation.

A TP-induced mouse liver injury model was established. Serum biochemistry, histopathology, and liver proteomics were performed. Key proteins (HSP60, UPR^mt components, SREBP-1c, FASN, cleaved caspase-3) were validated by Western blot and RT-qPCR both in vivo and in AML-12 hepatocytes, while co-immunoprecipitation (Co-IP) was conducted in AML-12 cells. Functional validation used siRNA knockdown.

TP induced liver injury, lipid deposition, and apoptosis. Proteomic screening implicated UPR^mt activation, with HSP60 subsequently validated as a central upregulated component. TP downregulated MFN2 and upregulated HSP60, ClpP, DRP1, SREBP-1c, FASN, and cleaved caspase-3. Co-IP confirmed a direct HSP60-SREBP-1c interaction. Moreover, HSP60 knockdown attenuated the entire TP-induced cascade, including UPR^mt overactivation, mitochondrial dysfunction, lipid dysregulation, and apoptosis.

This study delineates a novel mitochondria-to-nucleus pathway wherein TP induces HSP60-mediated UPR^mt overactivation, which promotes SREBP-1c/FASN-driven lipid accumulation, culminating in lipoapoptosis. The "HSP60-UPR^mt-SREBP-1c/FASN-lipoapoptosis" axis links dysregulated organelle stress signaling to metabolic cell death. These findings establish HSP60 as a key signaling node and a potential therapeutic target for intercepting this pathological cascade.