The Effect Of Lactobacillus On Tumor Necrosis Factor-α Secretion Of Cells

Background: The role of probiotics in health is being paid more and more attention. Lactobacillus is one of the most frequently used genera in probiotics. It has been used in the therapy of diseases with intestinal inflammation, such as IBD, IBS and chronic diarrhea. The medical value of lactobacillus is proved by many reliable clinical trials. The mechanism of probiotics to intestinal inflammation keeps unclear in spite of a number of researches focused on it. Intestine epithelial cells (IEC) and lamina propria cells constitute the gut barrier and may be involved in intestinal inflammation. Although their functions of suppressing inflammation have been studied respectively, a comparison is necessary to evaluate their roles in the interaction of probiotics and intestinal inflammation. Pro-inflammatory cytokines Tumor Necrosis Factor-α (TNF-α) exists in almost all inflammation. It can promote inflammation by triggering the inflammatory mediators cascade and activating neutrophils. TNF-α is appropriate to measure the intestinal inflammation.Aim: To investigate the effect of lactobacillus (Lactobacillus caseiCICC6002) on lipopolysaccharide (LPS) induced TNF-α secretion ofmonocytes (THP-1) and IECs (HT-29), with comparison of non-pathogen Escherichia coli (Escherichia coli DH5α).Method: Overnight culture (37℃, aerobic condition) of L asei, E coli in MRS, LB culture medium were collect, then cultured for 48 hours in RPMI medium. Bacteria conditioned medium (CM) were ultracentrifuged (100 000g×1lh, 4℃). HT-29 cells were cultured in DMEM medium. THP-1 cells were cultured in RPMI medium. LPS was used to induce secretion of THP-1 cells and HT-29 cells, with or without bacteria CM. released by cells was assayed by commercial enzyme linked immunosorbent assays (ELISA). Results were performed using analysis of t-test.Results: LPS induced TNF-α secretion of THP-1 cells (with or without bacterial CM) [956.39±374.45, 475.74±49.59, 829.62 ± 110.51 pg/ml] was significantly higher than basal secretion [100.96+48.95 pg/ml] (P<0.05). L casei CM exerted an inhibitory effect on LPS induced TNF-α secretion of THP-1 cells [475.74+49.59 pg/ml] (P<0.05). E coli CM didn't influence LPS induced TNF-α secretion of THP-1 cells [829.62 ± 110.51 pg/ml] (P>0.05) . Basal or LPS induced (with or without L casei CM) secretion of TNF-α by HT-29 cells was not detectable. Stimulated by LPS and E coli CM, the release of TNF-α by HT-29 cells was detected [10.94 ±6.32 pg/ml], but lower than that of THP-1 cells [829.62 ± 110.51 pg/ml] (P＜0.01).Conclusion: The probiotic bacterium L casei has anti-inflammatory properties. It may play an important role in inhibition of intestinal inflammation. L casei exerts its anti-inflammatory properties by inhibiting TNF-α secretion of monocytes.IEC is not involved in the inflammation inhibition mediated by L casei. E coli DH5α dose not show any anti-inflammatory properties.