title: Bimodal effect of oxidative stress in internal anal sphincter smooth muscle.
abstract: Changes in oxidative stress may affect basal tone and relaxation of the internal anal sphincter (IAS) smooth muscle in aging. We examined this issue by investigating the effects of the oxidative stress inducer 6-anilino-5,8-quinolinedione (LY-83583) in basal as well as U-46619-stimulated tone, and nonadrenergic, noncholinergic (NANC) relaxation in rat IAS. LY-83583, which works via generation of reactive oxygen species in living cells, produced a bimodal effect in IAS tone: lower concentrations (0.1 nM to 10 μM) produced a concentration-dependent increase, while higher concentrations (50-100 μM) produced a decrease in IAS tone. An increase in IAS tone by lower concentrations was associated with an increase in RhoA/Rho kinase (ROCK) activity. This was evident by the increase in RhoA/ROCK in the particulate fractions, in ROCK activity, and in the levels of phosphorylated (p) (Thr696)-myosin phosphatase target subunit 1 and p(Thr18/Ser19)-20-kDa myosin light chain. Conversely, higher concentrations of LY-83583 produced inhibitory effects on RhoA/ROCK. Interestingly, both the excitatory and inhibitory effects of LY-83583 in the IAS were reversed by superoxide dismutase. The excitatory effects of LY-83583 were found to resemble those with neuronal nitric oxide synthase (nNOS) inhibition by l-NNA, since it produced a significant increase in the IAS tone and attenuated NANC relaxation. These effects of LY-83583 and l-NNA were reversible by l-arginine. This suggests the role of nNOS inhibition and RhoA/ROCK activation in the increase in IAS tone by LY-83583. These data have important implications in the pathophysiology and therapeutic targeting of rectoanal disorders, especially associated with IAS dysfunction.
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania.
authors.forename: Jagmohan
authors.initials: J
authors.lastname: Singh
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania.
authors.forename: Sumit
authors.initials: S
authors.lastname: Kumar
authors.affiliation: Division of Gastroenterology and Hepatology, Department of Medicine, Jefferson Medical College of Thomas Jefferson University, Philadelphia, Pennsylvania.
authors.forename: Satish
authors.initials: S
authors.lastname: Rattan
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000634:Aminoquinolines / Q000494:pharmacology; D001003:Anal Canal / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D006162:Guanylate Cyclase / Q000037:antagonists & inhibitors; D043263:Myosin-Light-Chain Phosphatase / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000378:metabolism; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D054460:rho-Associated Kinases / Q000378:metabolism
chemical_list: D000634:Aminoquinolines; D014662:Vasoconstrictor Agents; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C041715:6-anilino-5,8-quinolinedione; D013482:Superoxide Dismutase; D054460:rho-Associated Kinases; D043263:Myosin-Light-Chain Phosphatase; D009218:Myosins; D006162:Guanylate Cyclase
keywords: neuronal nitric oxide synthase inhibition; oxidative stress; rhoa/rock; smooth muscle tone; superoxide anions