Gastroenterology

Gastroenterology

Volume 129, Issue 1, July 2005, Pages 131-141
Gastroenterology

Basic-alimentary tract
Mechanisms Underlying the Maintenance of Muscle Hypercontractility in a Model of Postinfective Gut Dysfunction

https://doi.org/10.1053/j.gastro.2005.03.049Get rights and content

Background & Aims: Acute gastroenteritis is a strong risk factor for the development of irritable bowel syndrome (IBS). We have developed an animal model in which transient acute infection leads to persistent muscle hypercontractility. Here, we investigate the mechanisms underlying the maintenance of this hypercontractility in the postinfective (PI) state. Methods: Muscle contraction and messenger RNA (mRNA) or protein expression of cytokines were examined from jejunal longitudinal muscle cells of NIH Swiss mice infected with Trichinella spiralis or incubated with or without cytokines. Results: During acute infection, interleukin (IL)-4 or IL-13, transforming growth factor (TGF)-β1, and cyclooxygenase (COX)-2 were increased in the muscle layer (P < .05). In the PI phase of the model, T helper (Th)2 cytokines returned to normal, but TGF-β1 remained in the muscle (P < .05). Exposure of muscle cells to IL-4 or IL-13 increased TGF-β1 (P < .01), COX-2 protein, and prostaglandin (PG)E2. Exposure of muscle cells to TGF-β1 increased PGE2 (P < .05) and COX-2 protein. Incubation of tissue with IL-4, IL-13, TGF-β1, or PGE2 enhanced carbachol-induced muscle cell contractility (P < .05). COX-2 inhibitor attenuated TGF-β1–induced muscle hypercontractility (P < .05). Conclusions: These results support the hypothesis that Th2 cytokines induce muscle hypercontractility during infection by a direct action on smooth muscle. The maintenance of hypercontractility results from Th2 cytokine-induced expression of TGF-β1 and the subsequent up-regulation of COX-2 and PGE2 at the level of the smooth muscle cell. We propose that PI gut dysfunction reflects mediator production in the neuromuscular tissues and that this may occur in PI-IBS.

Section snippets

Materials

The following materials were used in this study: collagenase (CLS type l), trypsin inhibitor, BSA, phenylmethylsulfonyl fluoride (PMSF), aprotinin, leupeptine, nonidet P-40, acrolein, PGE2, peroxidase conjugated-anti-goat/sheep IgG from Sigma Chemical (St. Louis, MO); HEPES from Bioshop Canada (Burlington, ON, Canada); IL-4, IL-13, TGF-β1, TGF-β1 immunoassay kit from R&D Systems (Minneapolis, MN); DMEM, antibiotic-antimycotic from Gibco BRL Life Technologies (Gaithersburg, MD); PGE2 assay kit

PCR for IL-4R and TGF-β Type IIR

As shown Figure 1, PCR products for IL-4Rα (241 base pairs for soluble IL-4R [sIL-4R] and 127 base pairs for membrane IL-4R [mIL-4R]) and 2 distinct forms of mouse TGF-β type IIR (526 base pairs for mTGF-βRII1 and 601 base pairs for mTGF-βRII2) were expressed on primary cultured muscle cells isolated from control mice (Figure 1).

T spiralis–Induced Muscle Hypercontractility

We next examined the characteristics of single muscle cells isolated from the longitudinal muscle layer from control and T spiralis–infected mice. In muscle from

Discussion

We used isolated smooth muscle cells in this study to localize the action of mediators expressed in the model because direct effects on muscle are more difficult to demonstrate in muscle strips because these retain intrinsic innervations.21 We showed that cells isolated from the longitudinal muscle layer of T spiralis–infected mice exhibited a substantially greater degree of shortening on exposure to carbachol than cells isolated from control mice. This finding indicates that the

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    Supported by a grant from the Canadian Institutes of Health Research (to S.M.C.) and from a Research Initiative Award (to H.A.) from the Canadian Association of Gastroenterology and AstraZeneca.

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