Objective To explore the potential relationship between ubiquitination of transforming growth factor kinase 1(TAK1)/nuclear factor-κB(NF-κB)signaling pathway mediated by ring finger protein 99(RNF99)and septic acute respiratory distress syndrome(ARDS).Methods Plasmid and siRNA transfection were conducted to overexpress or knock down RNF99 in MLE12,and expressions of p65 phosphate and p65 protein were analyzed.The protein interaction between RNF99 and TRAF6 or TAK1 was analyzed by immunoprecipitation assay.Forty mice were randomly divided into WT plus PBS,WT plus LPS,RNF99 specific expression(TG)plus PBS,and TG plus LPS groups,with 10 mice in each group.Sepsis was induced by intraperitoneal injection of 30 mg/kg LPS.Results As compared with vector group,protein expression levels of TRAF6 and TAK1 in MLE12 cells decreased significantly in RNF99 group(P<0.05).Ubiquitinated TRAF6 protein increased in MLE12 cells with RNF99 knockdown.As compared with LPS plus vector group,phosphorylation level of p65 in MLE12 cells was signifi-cantly lower in LPS plus RNF99 group(P<0.05).As compared with si-NC group,protein expression levels of RNF99 and IκBα in si-RNF99 group decreased significantly(P<0.05).As compared with LPS plus si-NC group,phosphorylation level of p65 in LPS plus si-RNF99 group increased significantly(P<0.05).The staining percentage of CD68 macrophages in lung tissues was significantly lower in TG plus LPS group than in WT plus LPS group(P<0.05).Phosphorylation level of p65 in lung tissues was significantly lower in TG plus LPS group than in WT plus LPS group(P<0.05).Conclusion RNF99 regulates NF-κB signaling pathway by interacting with the key regulator of NF-κB signaling pathway(TRAF6/TAK1),and improves lung injury after intraperitoneal injection of LPS in mice.