Dysregulation of innate immunity in ulcerative colitis patients who fail anti-tumor necrosis factor therapy.

AIM: To study the innate immune function in ulcerative colitis (UC) patients who fail to respond to anti-tumor necrosis factor (TNF) therapy. METHODS: Effects of anti-TNF therapy, inflammation and medications on innate immune function were assessed by measuring peripheral blood mononuclear cell (PBMC) cytokine expression from 18 inflammatory bowel disease patients pre- and 3 mo post-anti-TNF therapy. Toll-like receptor (TLR) expression and cytokine production post TLR stimulation was assessed in UC "responders" (n = 12) and "non-responders" (n = 12) and compared to healthy controls (n = 12). Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) levels were measured in blood to assess disease severity/activity and inflammation. Pro-inflammatory (TNF, IL-1ß, IL-6), immuno-regulatory (IL-10), Th1 (IL-12, IFNγ) and Th2 (IL-9, IL-13, IL-17A) cytokine expression was measured with enzyme-linked immunosorbent assay while TLR cellular composition and intracellular signalling was assessed with FACS. RESULTS: Prior to anti-TNF therapy, responders and non-responders had similar level of disease severity and activity. PBMC's ability to respond to TLR stimulation was not affected by TNF therapy, patient's severity of the disease and inflammation or their medication use. At baseline, non-responders had elevated innate but not adaptive immune responses compared to responders (P < 0.05). Following TLR stimulation, non-responders had consistently reduced innate cytokine responses to all TLRs compared to healthy controls (P < 0.01) and diminished TNF (P < 0.001) and IL-1ß (P < 0.01) production compared to responders. This innate immune dysfunction was associated with reduced number of circulating plasmacytoid dendritic cells (pDCs) (P < 0.01) but increased number of CD4+ regulatory T cells (Tregs) (P = 0.03) as well as intracellular accumulation of IRAK4 in non-responders following TLR-2, -4 and -7 activation (P < 0.001). CONCLUSION: Reduced innate immunity in non-responders may explain reduced efficacy to anti-TNF therapy. These serological markers may prove useful in predicting the outcome of costly anti-TNF therapy.

Prostaglandin E2 and polyenylphosphatidylcholine protect against intestinal fibrosis and regulate myofibroblast function.

BACKGROUND: Intestinal fibrosis is a serious and often recurrent complication of inflammatory bowel disease despite surgical intervention. The anti-fibrotic potential of prostaglandin E2 (PGE2) and polyenylphosphatidylcholine (PC) was investigated using the murine model of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced chronic intestinal inflammation and fibrosis, and murine and human intestinal myofibroblasts. METHODS: Mice were treated with TNBS enemas weekly for 2 or 6 weeks ± PGE2 (10 mg/kg/day orally) or PC (200 mg/kg/day orally). Inflammation and fibrosis were histologically assessed and scored. Pro-inflammatory cytokines, TLR4, and ECM-related gene expression from the colonic tissue and cultured myofibroblasts were assessed by RT-qPCR. The levels of α-SMA(+) staining and endogenous PGE2 in vivo were also assessed. RESULTS: Both PGE2 and PC treatment significantly decreased TNBS-induced intestinal inflammation and excess collagen deposition in vivo. This was accompanied by decreased α-SMA(+) staining in the lamina propria and lower collagen type I (COL1α1) expression. Endogenous PGE2 levels demonstrated that PC was not being converted into PGE2, thus mediating its effects primarily via PGE2-independent pathways. Both PGE2 and the PC isoform, 1,2-dilinoleoylphosphatidylcholine (DLPC), regulated primary mouse myofibroblast and CCD-18co COL1α1 production, and induced lower collagen type I to III and TGF-ß1 to TGF-ß3 ratios, demonstrating their ability to induced normal healing in the presence of phorbol 12-myristate 13-acetate (protein kinase C-dependent inducer of collagen production). CONCLUSION: PGE2 and PC both have potent anti-fibrogenic potentials in their ability to regulate inflammatory cell and myofibroblast accumulation within inflamed tissue, to decrease pro-inflammatory cytokine expression and to maintain normal healing in an inflammatory environment.