Preventive effects of Escherichia coli strain Nissle 1917 with different courses and different doses on intestinal inflammation in murine model of colitis.

To analyze the in vivo effect of Escherichia coli Nissle 1917 (EcN) with different courses and different doses to Sprague-Dawley rats with trinitrobenzene sulfonic acid (TNBS)-induced colitis. The probiotic was orally administered with different courses of treatment (with or without pre-administration) and different doses (10(7)-10(9) CFU/day) to Sprague-Dawley rats with TNBS-induced colitis. Therapeutic effects, levels of cytokine in serum, mRNA and protein expression were analyzed. Oral EcN administration after TNBS-induced improved colitis dose dependently. In parallel, a reduction of disease activity index and colonic MPO activity together with a decreased level of TNF-α and a trend of increased IL-10 expression was detected. Pre-administration of 10(7)CFU/day EcN to TNBS-treated rats resulted in a significant protection against inflammatory response and colons isolated from these rats exhibited a more pronounced expression of ZO-1 than the other groups. In the group of pre-administration of 10(9)CFU/day, the condition was not improved but deteriorated. This study convincingly demonstrates that pre-administration of probiotic EcN with low dose is able to protect colitis of rats and mediate up-regulation of ZO-1 expression, but long-term of high-dose EcN may do harm to colitis.