#4645 HISTONE LACTYLATION ENHANCES PERITONEAL FIBROSIS BY INDUCING PERITONEAL MESOTHELIAL CELL SENESCENCE

Abstract Background and Aims Peritoneal fibrosis (PF) is a serious complication limiting the application of peritoneal dialysis (PD). Histone lactylation has recently been found to increase with glycolysis and intracellular lactate levels, thereby mediating chronic organ damage. This study investigated the role and mechanism of histone lactylation in high glucose peritoneal dialysate-induced peritoneal fibrosis in mice. Method The PF mouse model induced by high glucose peritoneal dialysate was constructed by daily intraperitoneal injection of 4.25% glucose peritoneal dialysate combined with 40 mM Methylglyoxal for 2 weeks. We also used a lactylation enhancer (rotenone) and a lactylation inhibitor (oxamate) to validate the effects of histone lactylation in vivo and in vitro. The parietal peritoneum samples and cultured peritoneal mesothelial cells in various groups were analyzed for evidence of senescence, fibrosis, glycolysis, and histone lactylation levels. In addition, we generated DcR2 knockout mice to further verify the effects of histone lactylation on peritoneal mesothelial cell (PMCs) senescence by clearing senescent cells. Results In the PF group, the results of Masson staining and immunohistochemistry revealed increased peritoneal thickness and expression of fibrosis markers (α-SMA, Collagen I, and Fibronectin) and senescence markers (P16, P21, and DcR2) compared to the control group. We found that lactate and glycolysis levels were significantly higher in the PF group compared to the control group, and further immunoprecipitation results also showed enhanced levels of histone lactylation modifications in the PF group. We further found that the level of lactylation modification of H3K18la site increased significantly, suggesting that H3K18la site may play an important role in promoting PF. Similarly, in vitro, we verified that peritoneal mesothelial cells (PMCs) exhibited enhanced levels of lactate and lactylation in response to stimulation by high glucose, while we found an increasing expression of cell senescence phenotype (P16, P21, and DcR2) and senescence-associated cytokines secretion (IL-1β, IL-6, and TNF-α). By enhancing or inhibiting lactylation, we found that PMCs senescence was significantly enhanced in the lactylation-enhanced group, while the lactylation-inhibited group alleviated PMCs senescence induced by high glucose peritoneal dialysate. In the PF model of DcR2 knockout mice, compared with the wild group, there was no significant difference in the level of histone lactylation, while peritoneal thickness and the expression of markers of fibrosis markers (α-SMA, Collagen I, and Fibronectin) were significantly reduced. Conclusion Histone lactylation leads to peritoneal fibrosis induced by high glucose peritoneal dialysate by promoting PMSCs senescence. Histone lactylation may be a vital mechanism of peritoneal dialysis-related peritoneal fibrosis.