Hydrogen Sulfide Improves Aberrant Gastric Smooth Muscle Function in Duchenne Muscular Dystrophy Mice

Abstract

Deficiency of dystrophin, a cytoskeletal protein localized in the inner face of the plasma membrane in skeletal, cardiac and smooth muscle, results in Duchenne Muscular Dystrophy (DMD). Through its interactions with extracellular matrix and plasma membrane proteins, dystrophin plays a role in contraction and signal transduction. In DMD, gastrointestinal disorders such as gastric dilation and intestinal pseudo‐obstruction resulting from altered motility have been reported. The role of dystrophin in the regulation of contractile protein expression and smooth muscle function, per se, is not known. Studies have suggested that inflammation contributes to the pathophysiology of DMD. Exogenous H2S had been shown to exert beneficial cardiovascular and gastrointestinal functions, probably via exerting anti‐inflammatory actions.AimTo test the hypothesis that a lack of dystrophin causes a decrease in contractile protein expression and smooth muscle function and that treatment with H2S restores the effects of dystrophin deficiency.MethodsThe role of dystrophin was examined using mice deficient in dystrophin alone (mdx) and mice deficient in dystrophin plus telomerase RNA (mdx/mTR), which exhibit increased disease severity. The effect of an orally‐active, slow releasing H2S agent (SG1002) was tested in mdx/mTR mice (40 mg/kg body weight in chow/every 3 days starting from 3 weeks to 9 months). Contraction in response to acetylcholine (ACh) was measured in gastric muscle strips isolated from mdx, mdx/mTR and SG1002‐treated mdx/mTR mice. Age‐matched control mice were used for each group. Contraction was also measured in muscle cells isolated from the stomach of control and mdx mice by scanning micrometry and expressed as the percent decrease in muscle cell length. Expression of contractile proteins such as smoothelin, caldesmon, calponin and tropomyosin was measured by qRT‐PCR and western blot.ResultsAcetylcholine‐induced contraction was reduced in muscle strips from mdx/mTR mice (19 ± 5 mN/100 mg tissue) compared to age‐matched 9‐month old control mice (34 ± 7 mN/100 mg tissue). Treatment of mdx/mTR mice with SG1002 restored contraction to above normal levels (56 ± 8 mN/100 mg tissue). Contraction was also reduced in mdx mice (22 ± 8 mN/100 mg tissue) compared to age‐matched 3‐month old control mice (40 ± 5 mN/100 mg tissue). Acetylcholine‐induced contraction was also decreased in gastric muscle cells from mdx mice (25 ± 3% decrease in cell length) compared to control mice (41 ± 5% decrease in cell length). Expression of contractile proteins was decreased in gastric smooth muscle from mdx and mdx/mTR mice compared to age‐matched controls. Treatment of mdx/mTR mice with SG1002 restored expression of contractile proteins to levels similar to control.ConclusionThe results support our hypothesis that dystrophin deficiency affects contractile protein expression leading to decreased muscle contraction. Furthermore, treatment with H2S restores gastric smooth muscle function and contractile protein expression suggesting therapeutic potential of H2S in the treatment of motility disorders in DMD.Support or Funding InformationSupported by DK15564, DK28300, DK34153, and HL133167.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.