Persistent and selective effects of inflammation on smooth muscle cell contractility in rat colitis

Abstract

Intestinal inflammation affects smooth muscle contractility contributing to altered motility, but changes to the individual smooth muscle cells are not well described. We used video microscopy to study the contractility of circular smooth muscle cells (CSMC) isolated from the rat mid-descending colon throughout the course of TNBS-induced colitis, measuring their shortening response to carbachol (CCh), 5-HT, histamine or high K(+). In control CSMC, CCh caused a maximal shortening response of 28 (2%), similar to that for 5-HT of 27 (1%), but by day 4 of colitis, these responses were decreased by 35% and 37%, respectively. By day 36, all aspects of cholinergic contraction returned to control levels, while 5-HT-induced contraction remained significantly attenuated. In contrast, the contractile responses to histamine remained similar at all time points. K(+)-induced contraction was impaired only on day 4, and the maximal response remained substantially greater than CCh or 5-HT. Colitis caused a 121% increase in CSMC length by day 2 that persisted through day 36, independent evidence for phenotypic change. We conclude that impaired CSMC contractility at both the receptor and non-receptor levels contribute to altered smooth muscle function during colitis. Persistent changes in contractile response remained detectable after resolution of inflammation, and similar events may occur in post-enteritis syndromes seen in humans.

Visceral and Somatic Hypersensitivity in TNBS-Induced Colitis in Rats

“…The intensity and duration of inflammation may very well be strain related. The study by Wells et al [38] used a different concentration of TNBS from our study which makes it difficult to compare the results to our findings. Our TNBS colitis data was most consistent with Morris' group's findings [40].…”

Cell culture retains contractile phenotype but epigenetically modulates cell-signaling proteins of excitation-contraction coupling in colon smooth muscle cells

“…In fact, expression of MYPT1 and G␣ q , downregulated during cell proliferation, was upregulated at 35 days. Despite the persistence of these changes, the contractile response of smooth muscle cells was normal at this time (35). By contrast, expression of contractile proteins continues to deteriorate in the in vitro environment, as they are cultured repeatedly (16).…”

Impaired acetylcholine-induced smooth muscle contraction in colitis involves altered calcium mobilization and AKT phosphorylation

“…Colitis was induced by instillation of 500 μl of 200 mM trinitrobenzene sulfonic acid (Fluka) dissolved in 50% ethanol into the colon 8 cm proximal to the anus, in animals under light anesthesia by inhalation of isofluorane as described earlier [7,19]. All procedures received prior approval from the University Animal Care Committee of Queen's University.…”

“…The isolation of colonic CSMC has been previously described [7,20]. Briefly, strips of circular smooth muscle were isolated from the mid-descending colon and placed into 4-2-hydroxyethyl-1-piperazineethanesulfonic acid (HEPES) physiological salt solution (HPSS)-digestion solution.…”

“…While there is evidence of structural plasticity, such as inflammationinduced hyperplasia and hypertrophy of the smooth muscle cell [1,2], and damage to the enteric nervous system [3,4], functional changes at the level of the individual smooth muscle cell are an important component of the altered motility seen in the intact tissue [5,6]. For example, circular smooth muscle cells (CSMC) were hypo-responsive to contractile agonists in the well-studied model of trinitrobenzene sulphonic acid (TNBS)-induced colitis in the rat, and this was related to changes to the function and expression of both muscarinic and serotonergic receptor systems [5,7].…”