Abstract: Objective: To study the influence of spinal cord injury (SCI) in intestinal inflammation in the zebrafishes, and to clarify the effect of alleviating the intestinal inflammation of Lactobacillus rhamnosus GG (LGG) and its mechanism. Methods: Fourteen normal zebrafishes were randomly divided into normal diet group (n=7) and LGG group (n=7).After 21 d of feeding, intestinal tissues were taken and the expression levels of intestinal barrier-related molecules defensin beta-like 1 (DEFBL1), tight junction protein 2a (TJP2a), mucin 2.1 (MUC2.1) and mucin 5.3 (MUC5.3) in intestinal tissue of the zebrafishes were detected by RT-qPCR method. Forty eight operated zebrafishes were randomly divided into sham operation + normal diet group (n=12), sham operation + LGG group (n=12), SCI + normal diet group (n=12) and SCI + LGG group (n=12).After 25 d of feeding after injury (n=6 in each group), intestinal tissues were taken and the expression levels of intestinal inflammatory cytokines tumor necrosis factor-α (TNF-α), Toll-like receptor 2 (TLR-2) and interleukin-6 (IL-6) were detected by RT-qPCR method. After 7 d (n=3 in each group) and 28 d (n=3 in each group) of feeding after injury, the intestinal tissues were taken for high-throughput 16S rRNA sequencing of intestinal flora to detect the changes in intestinal flora. Results: Compared with normal diet group,the expression levels of DEFBL1 and TJP2a in intestinal tissue of the zebrafishes in LGG group were significantly increased(t=-2.387, P<0.05;t=-12.482, P<0.001), but the expression levels of MUC2.1 and MUC5.3 were significantly decreased (t=2.497, P<0.05;t=3.173, P<0.05). Compared with sham operation +normal diet group, the expression levels of TNF-α, TLR-2 and IL-6 mRNA in the intestinal tissue of the zebrafishes in SCI + normal diet group were increased significantly(P<0.05 or P<0.01);compared with SCI + normal diet group, the expression levels of TNF-α, TLR-2, and IL-6 in intestinal tissue of the zebrafishes in SCI + LGG group were decreased(P<0.05 or P<0.01).Compared with normal diet groups (sham + normal diet group and SCI + normal diet group), the abundance of pathogenic bacteria (Aeromonas and Vibrio) and conditioned pathogenic bacteria (Desulphomonas and Brevundimonas) in intestinal tissue of the zebrafishes in sham + LGG group and SCI + LGG group were significantly decreased. Conclusion: LGG can inhibit the intestinal inflammation caused by SCI in the zebrafishes, and its mechanism may be related to increasing the expression levels of intestinal barrier-related molecules and decreasing the abundance of intestinal pathogenic bacteria.

Key words: Lactobacillus rhamnosus, spinal cord injury, zebrafish, intestinal inflammation, intestinal bacteria