Abstract: Objective To estimate the effect of E3 ubiquitin ligase RNF121 on the expression of proinflammatory cytokines in LPS-stimulated macrophages. Methods The level of RNF121 in mouse peritoneal macrophages treatment with LPS was detected by Weston-Blot. RNF121 expression was reduced by RNA interference (si-RNF121). After LPS stimulation, the mRNA levels of TNF-α and IL-6 in mouse peritoneal macrophages were detected by real-time quantitive PCR (q-PCR). The levels of TNF-α and IL-6 in supernatants were detected by ELISA. The level of phosphorylated p65 (p-p65) was detected by Weston-Blot. The NF-κB activity was measured by dual-luciferase assay. Results After treatment with LPS, the RNF121 protein level was significantly decreased (P<0.05) in macrophages. However, protease inhibitor MG132 can significantly increase the RNF121 protein level. Decreased the expression of RNF121 by si-RNF121 and stimulated by LPS in macrophages, TNF-α and IL-6 expression levels (mRNA and protein levels) were significantly decreased (P<0.05), and the transcription factor phosphorylated p65 (p-p65) was also significantly decreased (P<0.05). In addition, NF-κB activity was also decreased (P<0.05). Conclusions The E3 ubiquitin ligase RNF121 was involved in the regulation of the expression of TNF-α and IL-6 in innate immune responses in mouse macrophages by NF-κB pathway.

Key words: RNF121, NF-κB, LPS, innate immunity, macrophage