Time-course expression of Toll-like receptors 2 and 4 in inflammatory bowel disease and homeostatic effect of VIP.
Toll-like receptor 2 (TLR2) and -4 mediate signals from a great variety of bacterial gut products, giving the host a panel of microbe-recognizing receptors. Under homeostatic conditions, TLRs act as protective receptors of the intestinal epithelium. When homeostasis is disrupted in diseases such as inflammatory bowel disease, TLR2 and -4 are deregulated. Our study demonstrates, by using a trinitrobenzene sulfonic acid-induced colitis model of Crohn's disease, the constitutive expression and the up-regulation of TLR2 and -4 at messenger and protein levels in colon extracts, as well as in macrophages, dendritic cells, and lymphocytes from mesenteric lymphoid nodes. Vasoactive intestinal peptide (VIP) treatment induced a decrease of TLR2 and -4 expressions approaching ethanol control levels. Our results suggest that VIP modulation of TLR2 and -4 could be explained by two possible mechanisms. The first one would be the secondary reduction of TLR2 and -4 caused by the VIP-mediated decrease of inflammatory mediators such as interleukin-1beta and interferon-gamma, which synergize with bacterial products, contributing to the amplification of TLR presence in the intestine. The other possible mechanism would involve a VIP-mediated decrease of nuclear factor-kappaB, which would cause a direct down-regulation of TLR expression. In summary, the resultant physiological effect is the decrease of TLR2 and -4 expressions to homeostatic levels. Our study describes for the first time the role of a peptide present in the gut microenvironment as an effective modulator of the initial steps of acute inflammation, acting at local and systemic levels and leading to the restoration of the homeostasis lost after an established inflammatory/autoimmune disease.
Gomariz
Rosa P
RP
Departamento de Biología Celular, Facultad de Biología, Universidad Complutense, 28040 Madrid, Spain. gomariz@bio.ucm.es
Arranz
Alicia
A
Abad
Catalina
C
Torroba
Marta
M
Martinez
Carmen
C
Rosignoli
Florencia
F
Garcia-Gómez
Maria
M
Leceta
Javier
J
Juarranz
Yasmina
Y
D000818:Animals; D001327:Autoimmune Diseases / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation / Q000187:drug effects*; D006706:Homeostasis / Q000187:drug effects*; D007249:Inflammation / Q000378:metabolism; D015212:Inflammatory Bowel Diseases / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D007274:Injections, Intraperitoneal; D007371:Interferon-gamma / Q000378:metabolism; D007375:Interleukin-1 / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000473:pathology; D008297:Male; D008562:Membrane Glycoproteins / Q000096:biosynthesis*; D051379:Mice; D008807:Mice, Inbred BALB C; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D011956:Receptors, Cell Surface / Q000096:biosynthesis*; D020127:Recovery of Function / Q000187:drug effects; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014302:Trinitrobenzenesulfonic Acid / Q000633:toxicity; D014660:Vasoactive Intestinal Peptide / Q000008:administration & dosage*
D007375:Interleukin-1; D008562:Membrane Glycoproteins; D018696:Neuroprotective Agents; D011956:Receptors, Cell Surface; D051195:Toll-Like Receptor 2; D051193:Toll-Like Receptors; D014660:Vasoactive Intestinal Peptide; D007371:Interferon-gamma; D014302:Trinitrobenzenesulfonic Acid