Histone Deacetylase 2 Regulates Autophagy <i>via</i> ULK1-NLRP3-Pyroptosis Pathway Associated with the Inflammatory Response in Acute Liver Failure

Abstract

Background: Pyroptosis is new necrosis pattern of hepatocytes during liver inflammation in acute liver failure (ALF). The autophagy-NLRP3-pyroptosis pathway plays an important role in the process of cell damage. HDAC2 is a regulator of the autophagy protein ULK1. Methods: The role of HDAC2 on ULK1-NLRP3-pyroptosis pathway during ALF was decteced in clinlincal sample. It was investigated the mechanism in transfected cells and ALF mouse model. The RNA-seq technology revealed that ULK1 was a negative regulatory molecule by HDAC2. Findings: The results from clinical specimens showed that with the elevated liver severity, the levels of HDAC2, NLRP3, caspase 1, GSDMD, IL-18 and IL-1β in liver tissue increased gradually, the expression of ULK1 decreased. Targeting knockdown or overexpression of HDAC2 could accordingly up-regulate or down-regulate ULK1. Then NLRP3-pyroptosis pathway was inhibited and activated. The results of mass spectrometry showed that ULK1 K68 lysine site was modified by acetylation. The degree of acetylation of K68 site in ALF liver tissue was lower than normal liver tissue. Furthermore, the study using ULK1 acetyl-silencing mutants (K68R) showed that HDAC2 could hardly attenuat D-galactosamine (D-Gal) and TNF-α induced pyroptosis in K68R-transfected L02 cells. The ALF mouse was significantly attenuated by HDAC2 innibitor in mice model, leading to reduced liver tiusse pyroptosis and liver function. Duing the process of injury, HDAC2 and pyroptosis exserted the antagonistic effect with ULK1. Interpretation: HDAC2 in hepatocytes plays a pivotal role in an ULK1-NLRP3 pathway driven auto-amplification of pyroptosis in the inflammation and liver damage of ALF. One of the important mechanisms is that inhibition HDAC2 to reduce pyroptosis may be by modulating the K68 lysine site of ULK1. These results provide a treatment strategy against hepatocyte injury in ALF. Funding Statement: This work was supported by the Natural Science Foundation of China (81870413). Declaration of Interests: The authors declare that they have no conflicts of interests. Ethics Approval Statement: Animal experiments were approved by the Animal Ethics Committee of Renmin Hospital of Wuhan University. The ethical approval for research involving animal number was WDRM (Welfare) 20181018. The ALF patient and normal donor liver tissues were provided by the Liver Transplantation Center of Renmin Hospital of Wuhan University. The study was signed with informed consent of patient and agreed with Ethics Committee of Renmin Hospital of Wuhan University.