Effects of Christensenella minuta lipopolysaccharide on RAW 264.7 macrophages activation

Christensenella minuta ( C. minuta ) is a gram-negative gastrointestinal bacterium associated with weight loss . However, recent studies have shown that C. minuta might be a potential pathogen and thus limited its application in the control of obesity. Research into the genetic characteristics and pathogenicity of C. minuta remain elusive. As a major virulence factor of gram-negative bacteria, lipopolysaccharide (LPS) can induce various diseases . In this study, we report the complete genome sequence of C. minuta and have also identified some genes related to LPS biosynthesis. The structure of C. minuta LPS, detected by SDS-PAGE, was different from that of Escherichia coli ( E. coli ) LPS. The incubation of RAW 264.7 macrophages with C. minuta LPS resulted in lower levels of cellular proliferation , phagocytosis and nuclear factor-kappa B (NF-κB) activation as compared to incubation with E. coli LPS. Furthermore, the expression of pro-inflammatory cytokines, as well as nitric oxide and reactive oxygen species production, was induced in C. minuta LPS-treated cells but to a much lower extent than that by E. coli LPS. These findings show that C. minuta LPS acts as a weak agonist for RAW 264.7 macrophages and can only trigger a weak inflammatory response through the NF-κB signalling pathway . In conclusion, these results suggest that the toxicity of C. minuta LPS is significantly attenuated due to its atypical structure and weak agonist activity for RAW 264.7 macrophages.