Neurokinin-1 receptor (NK-1R) expression is induced in human colonic epithelial cells by proinflammatory cytokines and mediates proliferation in response to substance P.
We have previously shown that the receptor for substance P (SP), neurokinin-1 receptor (NK-1R), is a marker of human mucosal but not peripheral mononuclear cells. In the present study, we investigate NK-1R expression in the human colonic mucosa in vivo, particularly in the epithelial cells. We investigate the influence of proinflammatory Th1 cytokines and SP on expression and function of NK-1R in colonic epithelial cells in vitro. Using in situ hybridization to detect NK-1R mRNA, and immunohistochemistry to detect NK-1R protein, colonic epithelial cells were found to express NK-1R in vivo. In contrast, colon epithelial cell lines (Caco-2, HT29, SW620, T84) were negative for NK-1R mRNA and protein. However, stimulation with a proinflammatory cytokine cocktail containing IFN-gamma, TNF-alpha, and IL-1beta, caused induction of NK-1R expression. Expression of NK-1R in human colonic epithelial cells in vivo may therefore reflect cytokine conditioning by the mucosal microenvironment. SP did not alter ion transport in monolayers of cytokine-treated T84 cells. While SP stimulated epithelial ion transport in colonic mucosae ex vivo, this was not a direct effect of SP on the epithelial cells, and appeared to be neurally mediated. However, SP (10(-10)-10(-8) M) elicited a dose-dependent proliferative effect on cytokine-stimulated, but not unstimulated, SW620 cells. Proliferation of the epithelial cells in response to SP was mediated specifically via cytokine-induced NK-1R, since an NK-1R-specific antagonist (Spantide 1) completely blocked SP-mediated proliferation in the cytokine-treated cells. Our results therefore demonstrate that proinflammatory cytokines induce expression of NK-1R in human colonic epithelial cell lines, and that SP induces proliferation of the epithelial cells via cytokine-induced NK-1R.
Goode
Triona
T
Department of Medicine, National University of Ireland, Cork, Ireland.
O'Connor
Terry
T
Hopkins
Ann
A
Moriarty
Derek
D
O'Sullivan
Gearld C
GC
Collins
J Kevin
JK
O'Donoghue
Diarmuid
D
Baird
Alan W
AW
O'Connell
Joe
J
Shanahan
Fergus
F
D018938:Caco-2 Cells; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D003106:Colon / Q000166:cytology; D016207:Cytokines / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D019073:HT29 Cells; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007413:Intestinal Mucosa / Q000378:metabolism; D017136:Ion Transport / Q000187:drug effects; D018040:Receptors, Neurokinin-1 / Q000096:biosynthesis*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013373:Substance P / Q000378:metabolism*
D016207:Cytokines; D018040:Receptors, Neurokinin-1; D013373:Substance P