Augmentation of cGMP/PKG pathway and colonic motility by hydrogen sulfide

• Published in: American journal of physiology: Gastrointestinal and liver physiology 2017-10, Vol.313 (4), p.G330-G341
• Main Authors: Nalli, Ancy D, Bhattacharya, Sayak, Wang, Hongxia, Kendig, Derek M, Grider, John R, Murthy, Karnam S
• Format: Article
• Language: English
• Subjects: Animals; Calcitonin; Calcitonin gene-related peptide; Colon; Colon - physiology; Cyclic GMP; Cyclic GMP - metabolism; Cyclic GMP-Dependent Protein Kinases - metabolism; Cysteine; Female; Gastrointestinal Motility; Guanosine; Guanylate cyclase; Humans; Hydrogen sulfide; Hydrogen Sulfide - metabolism; Kinases; Male; Mice; Mice, Inbred C57BL; Mucosa; Muscle contraction; Muscle Contraction - physiology; Muscle, Smooth - physiology; Nitric oxide; Nitric Oxide - metabolism; Phosphodiesterase; Phosphorylation; Protein kinase; Protein kinase G; Rabbits; Ribonucleic acid; RNA; Signal Transduction - physiology; siRNA; Smooth muscle; Species Specificity; Sulfide; Up-Regulation - physiology
• ISSN: 0193-1857; 1522-1547
• DOI: 10.1152/ajpgi.00161.2017

Hydrogen sulfide (H S), like nitric oxide (NO), causes smooth muscle relaxation, but unlike NO, does not stimulate soluble guanylyl cyclase (sGC) activity and generate cyclic guanosine 5'-monophosphate (cGMP). The aim of this study was to investigate the interplay between NO and H S in colonic smooth muscle. In colonic smooth muscle from rabbit, mouse, and human, l-cysteine, substrate of cystathionine-γ-lyase (CSE), or NaHS, an H S donor, inhibited phosphodiesterase 5 (PDE5) activity and augmented the increase in cGMP levels, IP receptor phosphorylation at Ser (measured as a proxy for PKG activation), and muscle relaxation in response to NO donor nitrosoglutathione (GSNO), suggesting augmentation of cGMP/PKG pathway by H S. The inhibitory effect of l-cysteine, but not NaHS, on PDE5 activity was blocked in cells transfected with CSE siRNA or treated with CSE inhibitor d,l-propargylglycine (dl-PPG), suggesting activation of CSE and generation of H S in response to l-cysteine. H S levels were increased in response to l-cysteine, and the effect of l-cysteine was augmented by GSNO in a cGMP-dependent protein kinase-sensitive manner, suggesting augmentation of CSE/H S by cGMP/PKG pathway. As a result, GSNO-induced relaxation was inhibited by dl-PPG. In flat-sheet preparation of colon, l-cysteine augmented calcitonin gene-related peptide release in response to mucosal stimulation, and in intact segments, l-cysteine increased the velocity of pellet propulsion. These results demonstrate that in colonic smooth muscle, there is a novel interplay between NO and H S. NO generates H S via cGMP/PKG pathway, and H S, in turn, inhibits PDE5 activity and augments NO-induced cGMP levels. In the intact colon, H S promotes colonic transit. Hydrogen sulfide (H S) and nitric oxide (NO) are important regulators of gastrointestinal motility. The studies herein provide the cross talk between NO and H S signaling to mediate smooth muscle relaxation and colonic transit. H S inhibits phosphodiesterase 5 activity to augment cGMP levels in response to NO, which, in turn, via cGMP/PKG pathway, generates H S. These studies suggest that interventions targeted at restoring NO and H S homeostasis within the smooth muscle may provide novel therapeutic approaches to mitigate motility disorders.