Tripartite Motif Containing 52 Positively Regulates NF-κB Signaling by Promoting IκBα Ubiquitination in Lipopolysaccharide-Treated Microglial Cell Activation.

BACKGROUND Microglial cell activation is the first response to spinal cord injury (SCI). The purpose of the study was to investigate the role and mechanism of tripartite motif containing 52 (TRIM52) in microglial cell activation and the inflammatory response. MATERIAL AND METHODS The cerebral cortex was isolated in rats, and primary microglial cells were subsequently incubated for 7 to 9 days and activated by lipopolysaccharide (LPS). TRIM52 overexpression and interference lentivirus were constructed, and primary microglial cells were transfected. Cytokine levels of interleukin-1ß and tumor necrosis factor-a were detected using enzyme-linked immunosorbent assay kits. TRIM52 mRNA expression and protein levels were examined by real-time polymerase chain reaction and nuclear factor-kappa B (NF-kappaB) and inhibitory kappa B-alpha (IkappaBalpha) protein expression were examined by western blot. The interaction between TRIM52 and IkappaBalpha was analyzed by co-immunoprecipitation (Co-IP) detection. Microglial marker Iba-1 and microglial cell activation marker OX-42 were detected by immunofluorescent staining. RESULTS Primary rat microglial cells were successfully isolated and activated by LPS. The expression levels of cytokines and TRIM52 and nuclear accumulation of NF-kappaB in microglial cells all increased in a dose-dependent manner with LPS. Cytokine and nuclear NF-kappaB levels decreased after TRIM52 knockdown, while the opposite expression pattern was found in microglial cells transfected with TRIM52 gene overexpression lentivirus. Co-IP revealed the association between TRIM52 and IkappaBalpha, and overexpressed TRIM52 promoted the ubiquitination of IkappaBalpha and significantly reduced its protein expression. CONCLUSIONS TRIM52 activated the NF-kappaB signaling pathway by promoting IkappaBalpha ubiquitination, thereby regulating LPS-induced microglial cell activation and the inflammatory response.