Nicotine protects against DSS colitis through regulating microRNA-124 and STAT3 / 中国药理学与毒理学杂志

ABSTRACT

OBJECTIVE Although it is generally believed that nicotine accounts for the beneficial effect of smoking on ulcerative colitis, the underlying mechanisms remain not well understood. Our previous finding that nicotine inhibits inflammatory responses through inducing miRNA-124 prompted us to ask whether the miRNA is involved in the protective action of nicotine on UC. METHODS MiR-124 expres-sion in colon tissues and cells was determined by q-PCR and in situ hybridization.The effect of miR-124 on protective role of nicotine in ulcerative colitis was evaluated in DSS-treated mice and IL-6-treated Caco-2 colon epithelial cells. Expression of p-STAT3/STAT3 was detected by immunohistochemistry and Western-blot analysis. RESULTS miR-124 expression is upregulated in colon tissues from UC patients and DSS-induced colitis mice. Nicotine treatment further elevated miR-124 level in lympho-cytes isolated from human ulcerative colonic mucosa and ulcerative colon tissues from DSS mice,both in infiltrated lymphocytes and epithelial cells. Administration of nicotine also reduced weight loss, improved DAI and decreased HE score in DSS-induced colitis mice.Moreover,knockdown of miR-124 in vivo significantly diminished the beneficial effect of nicotine on murine colitis, and in vitro on IL-6-treated Caco-2 colon epithelial cells.Further analysis indicated that nicotine inhibited STAT3 activation in vivo and in IL-6-treated Caco-2 colon epithelial cells and Jurkat human T lymphocytes,in which miR-124 knockdown led to increased activation of STAT3. Blocking STAT3 activity alone is beneficial for DSS colitis and also abolished nicotine′s protective effect in this model.CONCLUSION These data indicated that nicotine exerts its protective action in UC through inducing miR-124 and its effect on STAT3, and suggest that the miR-124/STAT3 system is a potential target for the therapeutic intervention of UC.