Endogenous IGF-I and α_vβ₃ integrin ligands regulate increased smooth muscle growth in TNBS-induced colitis

Abstract

Hazelgrove KB, Flynn RS, Qiao LY, Grider JR, Kuemmerle JF. Endogenous IGF-I and ␣v␤3 integrin ligands regulate increased smooth muscle growth in TNBS-induced colitis. Am J Physiol Gastrointest Liver Physiol 296: G1230 -G1237, 2009. First published April 9, 2009 doi:10.1152/ajpgi.90508.2008.-Endogenous insulinlike growth factor-I (IGF-I) regulates intestinal smooth muscle growth by concomitantly stimulating proliferation and inhibiting apoptosis. IGF-I-stimulated growth is augmented by the ␣v␤3 integrin ligands vitronectin and fibronectin. IGF-I expression in smooth muscle is increased in both TNBS-induced colitis and Crohn's disease. We hypothesized that intestinal inflammation increased vitronectin and fibronectin expression by smooth muscle and, along with IGF-I upregulation, increased intestinal muscle growth. Intestinal smooth muscle cells were examined 7 days following the induction of TNBS-induced colitis. Although ␣ v␤3 integrin expression was not altered by TNBSinduced colitis, vitronectin and fibronectin levels were increased by 80 Ϯ 10% and 90 Ϯ 15%, above control levels, respectively. Basal IGF-I receptor phosphorylation in inflamed muscle from TNBStreated rats was increased by 86 Ϯ 8% over vehicle-treated controls. Basal ERK1/2, p70S6 kinase, and GSK-3␤ phosphorylation in muscle cells of TNBS-treated rats were also increased by 140 -180%. TNBS treatment increased basal muscle cell proliferation by 130 Ϯ 15% and decreased apoptosis by 20 Ϯ 2% compared with that in vehicletreated controls. The changes in proliferation and apoptosis were reversed by an IGF-I receptor tyrosine kinase inhibitor or an ␣v␤3 integrin antagonist. The results suggest that smooth muscle hyperplasia in TNBS-induced colitis partly results from the upregulation of endogenous IGF-I and ligands of ␣ v␤3 integrin that mediate increased smooth muscle cell proliferation and decreased apoptosis. This paper has identified one mechanism regulating smooth muscle hyperplasia, a feature of stricture formation that occurs in the chronically inflamed intestine of TNBS-induced colitis and potentially Crohn's disease.

Differential immune and genetic responses in rat models of Crohn's colitis and ulcerative colitis

“…Our findings show that these differences relate to differential generation of growth factors in the two models; TNBS inflammation enhances the expressions of growth factors, such as IGF-1 and TGF-␤ in the muscularis externa. Our in vitro studies confirm that IGF-1 induces the proliferation of smooth muscle cells in culture (19), whereas TGF-␤ has no effect. On the other hand, both IGF-1 and TGF-␤ induce hypertrophy.…”

Hypercontractility of Intestinal Longitudinal Smooth Muscle Induced by Cytokines Is Mediated by the Nuclear Factor-κB/AMP-Activated Kinase/Myosin Light Chain Kinase Pathway

“…Colitis was induced with TNBS (2,4,6-trinitrobenzene sulphonic acid) as described previously (Hazelgrove et al, 2009;Alkahtani et al, 2013). Briefly, 6-to 8-week-old male adult C57BL/6J (Charles River Laboratories, Wilmington, MA) mice were fasted for 24 hours and lightly anesthesized with isoflurane; 100 ml of TNBS solution [2.5% in 50% ethanol (v/v)] was injected via a catheter advanced to 3 cm proximal to the anus via 1-ml syringe fitted with a catheter.…”

“…or TNF-a in vitro were based on our previous studies of colonic circular smooth muscle as described in Materials and Methods (Kuemmerle, 1998;Hu et al, 2007Hu et al, , 2008Hu et al, , 2009Hazelgrove et al, 2009;Alkahtani et al, 2013).…”

Jun kinase-induced overexpression of leukemia-associated Rho GEF (LARG) mediates sustained hypercontraction of longitudinal smooth muscle in inflammation

“…Colonic inflammation was induced with 2,4,6-trinitrobenzene sulfonic acid (TNBS) as described previously (2,14). All animal treatment protocols were approved by the Institutional Animal Care and Use Committee of Virginia Commonwealth University.…”

“…Mice were euthanized 3 days after the induction of inflammation. Colonic tissue from mice treated with TNBS exhibited typical histological characteristics of colitis (2,14). Two-to three-centimeter-long segments of the distal colon (starting from ϳ0.5 cm oral to the pelvic flexure) were removed, and muscle cells from longitudinal muscle layer were obtained.…”