Effect of endogenous hydrogen sulfide on the transwall gradient of the mouse colon circular smooth muscle. (5th February 2014)

• Record Type: Journal Article
• Authors: Sha, L.; Linden, D. R.; Farrugia, G.; Szurszewski, J. H.
• Is Part Of: Journal of physiology. Volume 592:Number 5(2014:Mar.)
• Page Start: 1077
• Page End: 1089
• Publication Date: 2014-02-05
• Subjects: Physiology -- Periodicals; 612.005
• DOI: 10.1113/jphysiol.2013.266841
• Languages: English
• ISSNs: 0022-3751

Abstract

<abstract abstract-type="main"> <title> <x xml:space="preserve">Abstract</x> </title> <sec id="tjp6035-sec-0010" sec-type="section"> <title>Key points</title> <p> <list id="tjp6035-list-0001" list-type="bullet"> <list-item> <p>A CO‐dependent transwall gradient of resting membrane potential exists across the circular muscle layer in the gastrointestinal tract; this gradient regulates the strength of phasic muscle contraction during electrical slow wave activity.</p> </list-item> <list-item> <p>H<sub>2</sub>S, CO and NO are endogenously generated in the muscle layers of the gut wall.</p> </list-item> <list-item> <p>Inhibiting the H<sub>2</sub>S producing enzyme CSE with the CSE inhibitor PAG had no significant effect on transwall resting membrane potential gradient in control preparations but significantly shifted the entire gradient in the depolarizing direction in preparations pretreated with the NO synthase (NOS) inhibitor <sc>l</sc>‐NNA.</p> </list-item> <list-item> <p>PAG significantly shifted the gradient in the depolarizing direction in mouse preparations lacking neuronal NOS (nNOS‐KO) and the gradient was significantly shifted in the depolarizing direction in mouse preparations lacking both nNOS and CSE (CSE‐KO–nNOS‐KO).</p> </list-item> <list-item> <p>NO production was significantly higher in CSE‐KO mouse preparations compared to wild‐type mouse preparations and the amplitude of NO‐mediated slow inhibitory junction potentials (S‐IJPs) was significantly higher in CSE‐KO mouse preparations compared to the amplitude of S‐IJPs in wild‐type mouse preparations.</p> </list-item> <list-item> <p>Nearly all submucosal neurons and myenteric neurons were CSE positive and 11% of submucosal neurons and 50% of myenteric neurons were nNOS positive.</p> </list-item> <list-item> <p>Our novel findings suggested that endogenous H<sub>2</sub>S is a stealth hyperpolarizing factor on smooth muscle cells and that endogenous H<sub>2</sub>S inhibits NO production from nNOS.</p> </list-item> </list> </p> </sec> <sec id="tjp6035-sec-0020" sec-type="section"> <title>Abstract</title> <p>A transwall gradient in resting membrane potential (RMP) exists across the circular muscle layer in the mouse colon. This gradient is dependent on endogenous generation of CO. H<sub>2</sub>S is also generated in muscle layers of the mouse colon. The effect of endogenously generated H<sub>2</sub>S on the transwall gradient is not known. The aim was to investigate the role of endogenous H<sub>2</sub>S. Our results showed that the CSE inhibitor <sc>dl</sc>‐propargylglycine (PAG, 500 μ<sc>m</sc>) had no effect on the transwall gradient. However, in preparations pretreated with the nitric oxide synthase inhibitor <italic>N</italic>‐nitro‐<sc>l</sc>‐arginine (<sc>l</sc>‐NNA, 200 μ<sc>m</sc>) and in nNOS‐knockout (KO) mouse preparations, PAG shifted the transwall gradient in the depolarizing direction. In CSE‐KO–nNOS‐KO mice, the gradient was shifted in the depolarizing direction. Endogenous generation of NO was significantly higher in muscle preparations of CSE‐KO mice compared to wild‐type (WT) mice. The amplitude of NO‐mediated slow inhibitory junction potentials (S‐IJPs) evoked by electric field stimulation was significantly higher in CSE‐KO mouse preparations compared to the amplitude of S‐IJPs in wild‐type mouse preparations. CSE was present in all submucosal ganglion neurons and in almost all myenteric ganglion neurons. Eleven per cent of CSE positive neurons in the submucosal plexus and 50% of CSE positive neurons in the myenteric plexus also contained nNOS. Our results suggest that endogenously generated H<sub>2</sub>S acts as a stealth hyperpolarizing factor on smooth muscle cells to maintain the CO‐dependent transwall gradient and inhibits NO production from nNOS.</p> </sec> </abstract>