Activation of distinct cAMP- and cGMP-dependent pathways by relaxant agents in isolated gastric muscle cells

Abstract

The mechanism of action of vasoactive intestinal peptide (VIP) was examined in isolated gastric and taenia coli muscle cells and compared with that of nitric oxide (NO), sodium nitroprusside (SNP), and isoproterenol. In gastric muscle cells, VIP stimulated NO production, increased adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 3',5'-cyclic monophosphate (cGMP) levels, and induced relaxation in a concentration-dependent fashion. The NO synthase inhibitor NG-nitro-L-arginine abolished NO and cGMP production and partly inhibited relaxation. The soluble guanylate cyclase inhibitor LY 83583 abolished cGMP production and partly inhibited relaxation. (R)-p-adenosine 3',5'-cyclic phosphorothioate [(R)-p-cAMPS], a preferential inhibitor of cAMP-dependent protein kinase (cAK), and KT5823, a preferential inhibitor of cGMP-dependent protein kinase (cGK), partly inhibited relaxation separately and abolished relaxation in combination. The pattern implied that VIP induced relaxation by activation of cAK and by NO-mediated stimulation of cGMP and activation of cGK. In taenia coli muscle cells, VIP did not increase NO production or cGMP levels: relaxation was accompanied by an increase in cAMP and was partly inhibited by (R)-p-cAMPS and KT5823 and abolished by a combination of both inhibitors. Isoproterenol increased only cAMP levels in both cell types, which induced relaxation by activating cAK at low concentrations of agonist and both cAK and cGK at high concentrations in a pattern identical to that observed with VIP in taenia coli muscle cells. SNP and NO increased only cGMP levels in both cell types, which induced relaxation by activating cGK only. We conclude that cAK and cGK can be activated separately and mediate relaxation independently.(ABSTRACT TRUNCATED AT 250 WORDS)

Relaxation Patterns of Human Gastric Corporal Smooth Muscle by Cyclic Nucleotides Producing Agents

“…In general, GI motility is regulated by various intrinsic and/or extrinsic factors of neurohormones. Among these factors, muscarinic cholinergic contraction and β-adrenergic relaxation as well as production of nitric oxide (NO) are well known (Schultz et al, 1977;Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Isoproterenol (ISO) and nitric oxide (NO) produce membrane hyperpolarization, decrease slow wave, and then inhibit contraction via activation of adenylate and guanylate cyclase in GI tract (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006).…”

“…Among these factors, muscarinic cholinergic contraction and β-adrenergic relaxation as well as production of nitric oxide (NO) are well known (Schultz et al, 1977;Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Isoproterenol (ISO) and nitric oxide (NO) produce membrane hyperpolarization, decrease slow wave, and then inhibit contraction via activation of adenylate and guanylate cyclase in GI tract (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Especially, NO is recognized as a neurotransmitter of nonadrenergic non-cholinergic (NANC) nerves in the myenteric plexus throughout the GI tract and is responsible for gastric receptive relaxation (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Tonini et al, 2000).…”

“…Isoproterenol (ISO) and nitric oxide (NO) produce membrane hyperpolarization, decrease slow wave, and then inhibit contraction via activation of adenylate and guanylate cyclase in GI tract (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Especially, NO is recognized as a neurotransmitter of nonadrenergic non-cholinergic (NANC) nerves in the myenteric plexus throughout the GI tract and is responsible for gastric receptive relaxation (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Tonini et al, 2000). In addition, sodium nitroprusside (SNP), known NO-releasing compound, is reported to stimulate guanylate cyclase and then increase intracellular guanosine 3',5'-cyclic monophosphate (cGMP) levels, while forskolin (FSK) to stimulate adenylate cyclase and then adenosine 3',5'-cyclic monophosphate (cAMP) levels in many smooth muscles, including GI tract (Katsuki et al, 1977;Huizinga et al, 1991;Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006).…”

“…Especially, NO is recognized as a neurotransmitter of nonadrenergic non-cholinergic (NANC) nerves in the myenteric plexus throughout the GI tract and is responsible for gastric receptive relaxation (Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Tonini et al, 2000). In addition, sodium nitroprusside (SNP), known NO-releasing compound, is reported to stimulate guanylate cyclase and then increase intracellular guanosine 3',5'-cyclic monophosphate (cGMP) levels, while forskolin (FSK) to stimulate adenylate cyclase and then adenosine 3',5'-cyclic monophosphate (cAMP) levels in many smooth muscles, including GI tract (Katsuki et al, 1977;Huizinga et al, 1991;Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Therefore, the resultant activation of cAMP-dependent protein kinase A (PKA) and cGMP-dependent protein kinase G (PKG) seems to be linked to the inhibitory effects of FSK, ISO and SNP (Schultz et al, 1977;Jin et al, 1993;Smith et al, 1993).…”

“…In addition, sodium nitroprusside (SNP), known NO-releasing compound, is reported to stimulate guanylate cyclase and then increase intracellular guanosine 3',5'-cyclic monophosphate (cGMP) levels, while forskolin (FSK) to stimulate adenylate cyclase and then adenosine 3',5'-cyclic monophosphate (cAMP) levels in many smooth muscles, including GI tract (Katsuki et al, 1977;Huizinga et al, 1991;Ozaki et al, 1992;Jin et al, 1993;Smith et al, 1993;Severi et al, 2006). Therefore, the resultant activation of cAMP-dependent protein kinase A (PKA) and cGMP-dependent protein kinase G (PKG) seems to be linked to the inhibitory effects of FSK, ISO and SNP (Schultz et al, 1977;Jin et al, 1993;Smith et al, 1993). /calmodulin-dependent protein kinase II (CaMKII) have been suggested to be involved in the inhibition mechanism of cAMP and cGMP (Koh and Sanders, 1996;Geeson et al, 2002;Yu et al, 2003;Zhu et al, 2005;Kim and Perrino, 2007).…”