Excision of mesenteric lymph nodes alters gut microbiota and impairs social dominance in adult mice

IntroductionMesenteric lymph nodes (MLNs) are central in immune anatomy. MLNs are associated with the composition of gut microbiota, affecting the central system and immune system. Gut microbiota was found to differ among individuals of different social hierarchies. Nowadays, excision of MLNs is more frequently involved in gastrointestinal surgery; however, the potential side effects of excision of MLNs on social dominance are still unknown. MethodsMLNs were removed from male mice (7-8 weeks old). Four weeks after MLN removal, social dominance test was performed to investigate social dominance; hippocampal and serum interleukin (IL)-1 beta, IL-10, and tumor necrosis factor-alpha (TNF-alpha) were investigated; and histopathology was used to evaluate local inflammation of the ileum. The composition of the gut microbiota was then examined to understand the possible mechanism, and finally intraperitoneal injection of IL-10 was used to validate the effect of IL-10 on social dominance. ResultsThere was a decrease in social dominance in the operation group compared to the control group, as well as a decrease in serum and hippocampal IL-10 levels, but no difference in serum and hippocampal IL-1 beta and TNF-alpha levels, and no local inflammation of the ileum after MLN removal. 16S rRNA sequencing analysis showed that the relative abundance of the class Clostridia was decreased in the operation group. This decrease was positively associated with serum IL-10 levels. Furthermore, intraperitoneal injection of IL-10 in a subset of mice increased social dominance. ConclusionsOur findings suggested that MLNs contributed to maintaining social dominance, which might be associated with reduced IL-10 and the imbalance of specific flora in gut microbiota.

Automated summary

Mesenteric lymph nodes (MLNs) play a crucial role in immune anatomy, being associated with gut microbiota composition and the central and immune systems. The excision of MLNs may have unknown side effects on social dominance. Our study showed that the removal of MLNs led to a decrease in social dominance and IL-10 levels in the serum and hippocampus. Additionally, the imbalance of specific flora in gut microbiota was observed. IL-10 injection increased social dominance, suggesting the importance of MLNs in maintaining social dominance.