Ghrelin stimulates interleukin-8 gene expression through protein kinase C-mediated NF-kappaB pathway in human colonic epithelial cells

Ghrelin, a newly identified gastric peptide, is known for its potent activity in growth hormone (GH) release and appetite. Although ghrelin is involved in several other responses such as stress and intestinal motility, its potential role in intestinal inflammation is not clear. Here, we show that expression of ghrelin and its receptor mRNA is significantly increased during acute experimental colitis in mice injected intracolonically with trinitrobenzene sulfate (TNBS). We found by PCR that ghrelin receptor mRNA is expressed in non-transformed human colonic epithelial NCM460 cells. Exposure of NCM460 cells stably transfected with ghrelin receptor mRNA to ghrelin, increased IkappaBalpha phosphorylation and its subsequent degradation. In addition, ghrelin stimulated NF-kappaB-binding activity and NF-kappaB p65 subunit phosphorylation, and induced IL-8 promoter activity and IL-8 protein secretion. Furthermore, our data show that ghrelin-induced IkappaBalpha and p65 phosphorylation was markedly reduced by pharmacological inhibitors of intracellular calcium mobilization (BAPTA/AM) and protein kinase C (GF 109203X). Pretreatment with BAPTA/AM or GF109203X also significantly attenuated ghrelin-induced IL-8 production. Together, our results strongly suggest that ghrelin may be a proinflammatory peptide in the colon. Ghrelin may participate in the pathophysiology of colonic inflammation by inducing PKC-dependent NF-kappaB activation and IL-8 production at the colonocyte level.