The Research Of Bacillus Subtilis,Enterococcus Faecalis Supernatants Regulating The Serotonin Transporter Expression In Post-infectious Irritable Bowel Syndrome Rats

Objects: Irritable bowel syndrome(IBS)is a common recurrent gastrointestinal chronic disease,which is physically and mentally harmful and brings great burden to patients’ economy.Post-infectious irritable bowel syndrome(PI-IBS)is an important clinical subtype of IBS.With many researches exploring the risk factors and pathogenesis of IBS,the understanding of the disease has been improved in recent years,but it’s still unclear.Many existing studies have shown that probiotics can relieve abdominal pain,abdominal distension,abnormal defecation and other symptoms safely and effectively in patients with IBS,at the same time,it can reduce anxiety,nervousness and other mental discomfort simultaneously,then consequently improve their life quality.Bacillus subtilis and Enterococcus faecalis,as two commonly used clinical probiotics,are widely used as adjuvant therapeutic drugs,yet the precise mechanism of their effect on IBS remains unknown.It is approved that abnormal metabolism of serotonin,which is mainly regulated by serotonin transporter(SERT),is closely related to the pathogenesis of IBS.The present study aimed to verify whether the supernatant of Bacillus subtilis and Enterococcus faecalis can regulate the expression of SERT in intestinal tissue of PI-IBS model rats.Method: 66 healthy adult SD male rats were divided into control group and model group.Campylobacter jejuni was given to the model group rats by intragastric administration to make PI-IBS rat model.The general physiological data and fecal excretion of bacteria were monitored and recorded regularly.When the rats in the model group stopped excreting bacteria,we detected the intestinal motility and colon SERT protein expression in both groups and affirmed that the animal model was effective.Then the rats in the model group were equally divided into 4 treatment groups,and they were treated respectively with phosphate buffer(Phosphate Buffer Saline,PBS)(group A),the supernatant of Bacillus subtilis(group B),the supernatant of Enterococcus faecalis(group C),the equal-volume mixed supernatant of Bacillus subtilis and Enterococcus faecalis(group D),2 ml/day,by intragastric administration.The control group(group M)was retained and treated with the same amount of PBS.During the 4-week experiment,an equal number of rats were randomly selected weekly from each group and sacrificed,and the expression of SERT protein in colon tissue was detected by Western-blot technique.SPSS 20.0 statistical software package was used for statistical analysis,LSD and Dunnett’s T3 methods were used to compare the difference between groups.Statistically,the difference was only considered significant when P<0.05.Results: During the whole process of treatment,SERT protein expression in group A was significantly lower than that in control group.As for the probiotic supernatant treatment group(group B,C,D),the expression of SERT protein in each group kept increasing by varying degrees until the 2nd week when reached the highest peak,yet began to decline during the subsequent 2 weeks: Group B decreased to the level of group A at the 3rd week and returned to 1.5 times the level of group A at the 4th week,while both group C and D kept decreasing significantly to the level of group A at the 4th week.Then between-group comparison was made: statistically,the SERT expression in group D was higher than that of group B in the first 3 weeks(P<0.01),but significantly lower at the 4th week(P<0.01);And group D was also higher than group C at the 2nd and 3rd week(P=0.027,P=0.029);Group C was significantly higher than group B in the 1st week and showed no statistical difference at other time(P<0.01).Conclusion: The supernatant of Bacillus subtilis and Enterococcus faecalis could both up-regulate the expression of SERT protein in the colon of PI-IBS rats.In the short-term treatment,combined bacteria supernatant up-regulated SERT greater than that of single bacteria supernatant,and single Enterococcus faecalis supernatant manifested better than that of Bacillus subtilis.While with the extension of treatment,the upregulation effect of these three kinds of bacteria supernatant decreased in varying degrees,especially in Enterococcus faecalis and combined bacteria supernatant.