Introduction

Sepsis-associated encephalopathy (SAE) is a complication posing a significant risk to patient health and survival. Microglial polarization and inflammation are key to the pathological progression of SAE. The p65 subunit is a component of the nuclear factor-κB (NF-κB) family. This study aimed to clarify the role of p65 in microglial polarization.

Material and methods

Human microglial HMC3 cells were treated with lipopolysaccharide (LPS). Cell viability was measured using a CCK-8 kit. Proinflammatory cytokine levels were evaluated using an ELISA assay. qRT-PCR or western blot assays were used to estimate mRNA or protein levels. The proportion of microglial M1 polarization was assessed using flow cytometry. The m6A-modified high mobility group box 1 (HMGB1) levels were analyzed using MeRIP-qPCR. Dual-luciferase reporter, chromatin immunoprecipitation (ChIP), and RNA immunoprecipitation (RIP) assays were conducted to validate the interactions between p65 and methyltransferase-like 3 (METTL3) or between METTL3 and HMGB1.

Results

LPS promoted microglial M1 polarization and enhanced p65, METTL3, and HMGB1 expression. Further, the inhibition of p65 ameliorated the LPS-induced M1 microglial polarization. p65 promotes HMGB1 m6A methylation by transcriptionally activating METTL3. Under LPS treatment, p65 enhances microglial M1 polarization via METTL3 activation. METTL3 aggravates LPS-induced microglial M1 polarization by positively regulating HMGB1 m6A modification.

Conclusions

p65 increases LPS-induced M1 polarization by promoting METTL3-mediated m6A modification of HMGB1 in HMC3 cells.