The Research Of Lactobacillus Acidophilus And Bifidobacterium Longum Supernatants Regulating The Serotonin Transporter Expression In Intestinal Epithelial Cells

Objects: Irritable Bowel Syndrome(IBS)is a common clinical gastrointestinal functional disease with characteristic abdominal pain,abdominal distension or abdominal discomfort,which often accompanied by alterations in stool frequency or stool form.In recent years,studies have shown that serotonin(5-hydroxytryp-tamine,5-HT)and its transporter(Serotonin Transporter,SERT)metabolic disorders may play an important role in the pathogenesis of IBS.Many clinical trials have proved that probiotics have a significant effect for the treatment of IBS.Lactobacillus and Bifidobacterium are the most frequently reseached probiotics in IBS,in which Lactobacillus acidophilus and Bifidobacterium longum have been used as probiotics in clinical.However,the underlying mechanism of probiotics relieving the symptoms of IBS is yet unclear.Our previous studies have shown that Lactobacillus rhamnosus supernatant can up-regulate the expression of SERT in intestinal epithelial cells and mouse colon tissue.However,there is no study to confirm whether L.acidophilus and B.longum supernatant can also regulate SERT expression.Thus,the present study investigated the effects of the supernatants of L.acidophilus and B.longum on the expression of SERT mRNA and protein in intestinal epithelial cells.Methods: HT-29 and Caco-2 cells were treated with L.acidophilus supernatant and B.longum supernatant for 12 and 24 h,respectively.SERT m RNA levels were detected by RT-PCR.SERT protein levels were detected by Western-blot.The SPSS17.0 statistical software package was used for statistical analysis.The measurement data were expressed as mean ± standard deviation(x ± s).The one-way analysis of variance was used in the three groups.The LSD test was used when the variance was homogeneous.The Dunnett T3 method was used when the variance was not homogeneous.Differences were considered statistically significant if P <0.05.Results: The mRNA levels of SERT in HT-29 cells treated with 1:100,1:50,and1:20 dilutions of L.acidophilus supernatant for 12 h and 24 h were1.80-,2.24-,2.28-,and 2.04-,2.30-,2.80-fold higher than that in the control group,respectively(P<0.05,P<0.05,P<0.05,and P<0.05,P<0.05,P<0.05,respectively).SERT mRNA levels inCaco-2 cells treated with 1:100,1:50,and 1:20 dilutions of L.acidophilus supernatant for 12 h and 24 h were 1.20-,1.22-,1.61-,and 1.16-,1.50-,2.13-fold higher than that in the control group,respectively(P>0.05,P>0.05,P<0.05,and P>0.05,P<0.05,P<0.05,respectively).The SERT mRNA levels in HT-29 cells treated with dilutions1:100,1:50,and 1:20 of B.longum supernatant for 12 h and 24 h were 0.96-,1.90-,2.50-,and 2.58-,2.19-,3.21-fold higher than that in the control group,respectively(P>0.05,P<0.05,P<0.05,and P<0.05,P<0.05,P<0.05,respectively).The SERT mRNA levels in Caco-2 cells treated with 1:100,1:50,and 1:20 dilutions of B.longum supernatant for 12 h and 24 h were 1.25-,2.06-,1.83-,and 1.84-,2.23-,2.13-fold higher than that in the control group,respectively(P>0.05,P<0.05,P<0.05,and P<0.05,P<0.05,P<0.05,respectively).The expression of SERT protein in HT-29 and Caco-2 cells was also up-regulated by the supernatants of L.acidophilus and B.longum,which was approximately similar to that of the corresponding mRNA.Conclusion:(1)Lactobacillus acidophilus and Bifidobacterium longum supernatants can up-regulate the expression of SERTmRNA and SERT protein in intestinal epithelial cells;(2)It is time dependent and concentration dependent that Lactobacillus acidophilus and Bifidobacterium longum supernatants up-regulate the expression of SERT.