Role of PML SUMOylation in arsenic trioxide-induced fibrosis in HSCs

Background: Arsenic trioxide (ATO) can bind directly to the human promyelocytic leukemia (PML) protein, leading to modification of PML by SUMOs. UBC9 is the only known E2-conjugating enzyme involved in SUMOylation. PML degradation via RNF4, an E3 ubiquitin ligases family member. PML is key organizer of nuclear bodies (NBs) that regulate many biological processes such as senescence, and DNA damage. ATO can activate the TGF beta/Smad signaling pathway, causing liver fibrosis. However, the roles of PML Sumoylation in ATO-induced liver fibrosis remain unclear. Objective: This study aimed to investigate the role of PML Sumoylation in the ATO-induced HSCs activation and to improve the mechanism of ATO-induced liver fibrosis. Methods: Hepatic stellate cells (HSCs) were treated with 2 mu mol/L ATO. Cell viability was detected by CCK-8 analysis. Immunoblot analysis and real-time quantitative PCR were used to detect the expression of IL-1 beta, TNF alpha, TGF-beta 1, p-Smad2/3, alpha-SMA, Collagen I and PML SUMOylation after silencing PML, UBC9, and RNF4, respectively. The formation of PML-NBs was observed by immunofluorescence staining. Results: 2 and 5 mu mol/L ATO intervention increased HSCs cell viability. ATO was able to significantly trigger PML SUMOylation and the formation of PML-NBs. Inhibition of SUMOylated PML by silencing UBC9, subsequently preventing the downregulation of HSCs activation indicators induced by ATO (P < 0.05). Conversely, enhancing SUMOylated PML accumulation by silencing RNF4, activating TGF beta/Smad signaling pathway, eventually promoting the induction of liver fibrosis. Conclusion: These results indicated that PML SUMOylation plays a critical role in the development of liver fibrosis induced by ATO.