Urocortin 3 expression at baseline and during inflammation in the colon: corticotropin releasing factor receptors cross-talk.
Urocortins (Ucn1-3), members of the corticotropin-releasing factor (CRF) family of neuropeptides, are emerging as potent immunomodulators. Localized, cellular expression of Ucn1 and Ucn2, but not Ucn3, has been demonstrated during inflammation. Here, we investigated the role of Ucn3 in a rat model of Crohn's colitis and the relative contribution of CRF receptors (CRF1 and CRF2) in regulating Ucn3 expression at baseline and during inflammation. Ucn3 mRNA and peptide were ubiquitously expressed throughout the GI tract in naïve rats. Ucn3 immunoreactivity was seen in epithelial cells and myenteric neurons. On day 1 of colitis, Ucn3 mRNA levels decreased by 80% and did not recover to baseline even by day 9. Next, we ascertained pro- or anti-inflammatory actions of Ucn3 during colitis. Surprisingly, unlike observed anti-inflammatory actions of Ucn1, exogenous Ucn3 did not alter histopathological outcomes during colitis and neither did it alter levels of pro-inflammatory cytokines IL-6 and TNF-α. At baseline, colon-specific knockdown of CRF1, but not CRF2 decreased Ucn3 mRNA by 78%, whereas during colitis, Ucn3 mRNA levels increased after CRF1 knockdown. In cultured cells, co-expression of CRF1+CRF2 attenuated Ucn3-stimulated intracellular Ca(2+) peak by 48% as compared to cells expressing CRF2 alone. Phosphorylation of p38 kinase increased by 250% during colitis and was significantly attenuated after Ucn3 administration. Thus, our results suggest that a balanced and coordinated expression of CRF receptors is required for proper regulation of Ucn3 at baseline and during inflammation.
Department of Surgery, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
Shilpi
S
Mahajan
Department of Surgery, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
Min
M
Liao
Department of Surgery, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA; Jefferson Medical College, 1025 Walnut Street, Philadelphia, PA 19107, USA(1).
Paris
P
Barkan
Department of Endocrinology and Applied Medical Science, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Aoba-ku, Sendai, Miyagi 980-8575, Japan.
Kazuhiro
K
Takahashi
Department of Surgery, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA. Electronic address: Aditi.Bhargava@ucsfmedctr.org.
Aditi
A
Bhargava
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D003092:Colitis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D003106:Colon / Q000187:drug effects; D004195:Disease Models, Animal; D055785:Gene Knockdown Techniques; D008297:Male; D009929:Organ Size / Q000187:drug effects; D010766:Phosphorylation; D034622:RNA Interference; D017207:Rats, Sprague-Dawley; D018019:Receptors, Corticotropin-Releasing Hormone / Q000235:genetics / Q000378:metabolism; D012016:Reference Values; D013154:Spleen / Q000187:drug effects; D014302:Trinitrobenzenesulfonic Acid / Q000633:toxicity; D054832:Urocortins / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D000099052:CRF Receptor, Type 1
C101531:CRF receptor type 2; D018019:Receptors, Corticotropin-Releasing Hormone; D054832:Urocortins; D000099052:CRF Receptor, Type 1; D014302:Trinitrobenzenesulfonic Acid
Ca(2+) signaling; Crohn's colitis; Inflammation; MAPK; RNAi