Orthovanadate-Induced Vasoconstriction of Rat Mesenteric Arteries Is Mediated by Rho Kinase-Dependent Inhibition of Myosin Light Chain Phosphatase

Abstract

Key words myosin light chain phosphatase; orthovanadate; mesenteric artery Vanadium forms numerous inorganic compounds (vanadyl sulfate, sodium metavanadate, sodium orthovanadate (OVA), vanadium pentoxide) and complexes with organic compounds.1) Because of its structural similarity to phosphate, vanadate possesses various biochemical and pharmacological properties, such as the ability to inhibit ATPases 2) and protein tyrosine phosphatases (PTPases), 3) epidermal growth factor (EGF)-like mitogenic activity, 4) insulin-mimetic properties, 5) anti-apoptotic activities, 6) and antitumor or carcinogenic properties. 7,8) Vanadium compounds exert contractile effects on vascular and non-vascular smooth muscle, such as the guinea pig taenia coli, trachea, and gallbladder smooth muscle.9-11) The contractile effects of vanadates have been considered to be due to inhibition of PTPase, 9,11,12) but not ATPase, 13,14) because genistein, a protein tyrosine kinase inhibitor, attenuates vanadateinduced constriction. Vanadate-induced muscle constriction was regulated by activation of Rho kinase-dependent signaling in ileal longitudinal smooth muscle in guinea pigs, resulting in increased phosphorylation of the myosin light chain (MLC). 15)These reports showed that vanadates inhibited the activity of protein tyrosine phosphatases, leading to Rho kinase-dependent constriction. Recently, we reported that OVA induced Rho kinase-dependent constriction and phosphorylation of the myosin phosphatase target subunit 1 (MYPT1) of myosin light chain phosphatase (MLCP). OVA-induced phosphorylation of MYPT1 was regulated by the EGF receptor (EGFR) and Src, because inhibitors of EGFR and Src abolished phosphorylation of MYPT1.16) Furthermore, metalloproteinase inhibitor TAPI-0 (N-(R)-(2-(hydroxyaminocarbonyl) methyl]-4-methylpentanoyl-L-naphthylalanyl-L-alanine amide) and an inhibitor of heparin/EGF binding abrogated OVA-induced aortic constriction and phosphorylation of EGFR and MYPT1.16) This finding indicated that OVA transactivated EGFR in vascular smooth muscle cells (VSMCs) derived from the rat thoracic aorta. These findings indicate that OVA can influence smooth muscle constriction through EGFR and Rho kinase-dependent inactivation of MLCP. Furthermore, we showed that EGF induced Ca 2+ sensitization in vascular smooth muscle by Rho kinasedependent inactivation of MLCP through the extracellular signal-regulated kinases 1 and 2 (Erk1/2) and Erk1/2 kinase (MEK) pathway. 17) However, it is not clear whether OVA activates MEK and Erk1/2 signaling through the EGFR. In addition, it is unknown whether OVA induces constriction and phosphorylation of MYPT1 in mesenteric arteries in rats. Therefore, in this study, we aimed to determine whether OVA-induced constriction of rat superior mesenteric arteries is mediated by Src, EGFR, mitogen-activated protein kinase (MAPK) s, and Rho kinase.

A Lipid Emulsion Reverses Toxic-Dose Bupivacaine-Induced Vasodilation during Tyrosine Phosphorylation-Evoked Contraction in Isolated Rat Aortae

“…In agreement with previous reports, sodium orthovanadate induced protein tyrosine, PLC γ-1 and ERK phosphorylation [6,9]. In addition, the tyrosine kinase inhibitor genistein attenuated protein tyrosine and PLC γ-1 phosphorylation induced by sodium orthovanadate.…”

“…Similar to previous reports, genistein, Y-27632 and SP600125 highly attenuated sodium orthovanadate-induced contraction in the present study [6,7,8,9]. Furthermore, PD98059 has been previously shown to attenuate sodium orthovanadate-induced contraction in rat mesenteric arteries [9]. Consistently, in the current study, PD98059 and U-73122 inhibited the contraction evoked by sodium orthovanadate [9].…”

“…Furthermore, PD98059 has been previously shown to attenuate sodium orthovanadate-induced contraction in rat mesenteric arteries [9]. Consistently, in the current study, PD98059 and U-73122 inhibited the contraction evoked by sodium orthovanadate [9]. Taken together, these data indicate that the contraction induced by sodium orthovanadate appears to be primarily mediated by a pathway involving tyrosine kinase, JNK and Rho-kinase and partially by a pathway involving PLC γ-1 and ERK.…”

“…Genistein and Y-27632 have been reported to inhibit the contraction induced by sodium orthovanadate [6,7,8,9]. Similar to previous reports, genistein, Y-27632 and SP600125 highly attenuated sodium orthovanadate-induced contraction in the present study [6,7,8,9].…”

“…The tyrosine phosphatase inhibitor sodium orthovanadate causes tyrosine phosphorylation-mediated contraction via the inhibition of protein tyrosine dephosphorylation [6,7]. In addition, sodium orthovanadate-induced contraction involves Rho-kinase-induced myosin phosphatase target subunit 1 (MYPT1) phosphorylation, contributing to the inhibition of myosin light chain phosphatase, which is associated with calcium sensitization [8,9]. …”