Proc Natl Acad Sci U S A. 2007 Jan 30; [Epub ahead of print]
Substance P mediates antiapoptotic responses in human colonocytes by Akt activation.
Koon HW, Zhao D, Zhan Y, Moyer MP, Pothoulakis C.
Gastrointestinal Neuropeptide Center, Division of Gastroenterology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215.
We examined the hypothesis that substance P (SP) and the neurokinin-1 receptor (NK-1R), both in vitro and in vivo, promote mucosal healing during recovery from colitis by stimulating antiapoptotic pathways in human colonic epithelial cells. For the in vitro experiments, human nontransformed NCM460 colonocytes stably transfected with NK-1R (NCM460-NK-1R cells) were exposed to SP, and cell viability assays, TUNEL assays, and Western blot analyses were used to detect apoptotic and antiapoptotic pathways. SP exposure of NCM460-NK-1R colonocytes stimulated phosphorylation of the antiapoptotic molecule Akt and inhibited tamoxifen-induced cell death and apoptosis evaluated by the cell viability assay and poly(ADP-ribose) polymerase cleavage, respectively. SP-induced phosphorylation of Akt and cleavage of poly(ADP-ribose) polymerase were inhibited by blockade of integrin alphaVbeta3, Jak2, and activation of phosphatidylinositol 3-kinase. For the in vivo experiments, C57BL/6 mice, administered 5% dextran sulfate (DSS) dissolved in tap water for 5 days followed by a 5-day recovery period, were treated with the NK-1R antagonist CJ-12,255 or vehicle. Vehicle-treated mice showed increased colonic Akt phosphorylation and apoptosis compared with mice that received no DSS. In contrast, daily i.p. administration of CJ-12,255 for 5 days post-DSS suppressed Akt activation, exacerbated colitis, and enhanced apoptosis, and pharmacologic inhibition of Akt, either alone or together with CJ-12,255, produced a similar effect. Thus, SP, through NK-1R, possesses antiapoptotic effects in the colonic mucosa by activating Akt, which prevents apoptosis and mediates tissue recovery during colitis. |
