Background: Simulated microgravity environment can lead to gastrointestinal motility disturbance. The pathogenesis of gastrointestinal motility disorders is closely related to the stem cell factor (SCF)/c-kit signaling pathway associated with intestinal flora and Cajal stromal cells. Moreover, intestinal flora can also affect the regulation of SCF/c-kit signaling pathway, thus affecting the expression of Cajal stromal cells. Cajal cells are the pacemakers of gastrointestinal motility.
Aim: To investigate the effects of Bifidobacterium lactis (B. lactis) BLa80 on the intestinal flora of rats in simulated microgravity and on the gastrointestinal motility-related SCF/c-kit pathway.
Methods: The internationally recognized tail suspension animal model was used to simulate the microgravity environment, and 30 rats were randomly divided into control group, tail suspension group and drug administration tail suspension group with 10 rats in each group for a total of 28 days. The tail group was given B. lactis BLa80 by intragastric administration, and the other two groups were given water intragastric administration, the concentration of intragastric administration was 0.1 g/mL, and each rat was 1 mL/day. Hematoxylin & eosin staining was used to observe the histopathological changes in each segment of the intestine of each group, and the expression levels of SCF, c-kit, extracellular signal-regulated kinase (ERK) and p-ERK in the gastric antrum of each group were detected by Western blotting and PCR. The fecal flora and mucosal flora of rats in each group were detected by 16S rRNA.
Results: Simulated microgravity resulted in severe exfoliation of villi of duodenum, jejunum and ileum in rats, marked damage, increased space between villi, loose arrangement, shortened columnar epithelium of colon, less folds, narrower mucosal thickness, reduced goblet cell number and crypts, and significant improvement after probiotic intervention. Simulated microgravity reduced the expressions of SCF and c-kit, and increased the expressions of ERK and P-ERK in the gastric antrum of rats. However, after probiotic intervention, the expressions of SCF and c-kit were increased, while the expressions of ERK and P-ERK were decreased, with statistical significance (P < 0.05). In addition, simulated microgravity can reduce the operational taxonomic unit (OTU) of the overall intestinal flora of rats, B. lactis BLa80 can increase the OTU of rats, simulated microgravity can reduce the overall richness and diversity of stool flora of rats, increase the abundance of firmicutes in stool flora of rats, and reduce the abundance of Bacteroides in stool flora of rats, most of which are mainly beneficial bacteria. Simulated microgravity can increase the overall richness and diversity of mucosal flora, increase the abundance of Bacteroides and Desulphurides in the rat mucosal flora, and decrease the abundance of firmicutes, most of which are proteobacteria. After probiotics intervention, the overall Bacteroidetes trend in simulated microgravity rats was increased.
Conclusion: B. lactis BLa80 can ameliorate intestinal mucosal injury, regulate intestinal flora, inhibit ERK expression, and activate the SCF/c-kit signaling pathway, which may have a facilitating effect on gastrointestinal motility in simulated microgravity rats.
Keywords: Gastrointestinal motility; Intestinal flora; Rat; Simulated microgravity; Stem cell factor/c-kit signaling pathway.
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