Stretch Enhances Contraction of Bovine Coronary Arteries via an NAD(P)H Oxidase–Mediated Activation of the Extracellular Signal–Regulated Kinase Mitogen-Activated Protein Kinase Cascade

Abstract

Abstract-This study examines the effects of an increase in passive stretch in endothelium-removed bovine coronary artery on oxidant-induced changes in force generation. Increasing passive stretch on the arterial segments from 5 to 20 g for 20 minutes caused a subsequent increase (PϽ0.05) in force generation to 30 mmol/L KCl or 0.1 mol/L serotonin compared with the prestretch control response. Also associated with the passive stretch were increases in superoxide detection by lucigenin and a selective increase in extracellular signal-regulated kinase (ERK) mitogen-activated protein (MAP) kinase phosphorylation measured by Western analysis. The stretch-induced increase in force generation was eliminated by inhibition of the ERK pathway by the MEK inhibitor PD98059 but not by inhibitors of the p38 MAP kinase pathway (SB202190) or c-Jun N-terminal protein kinase pathway (SP200169). Additionally, stretch-induced increases in both ERK phosphorylation and force generation were attenuated by inhibition of tyrosine kinases (genistein), src (PP2), and specific sites on the epidermal growth factor receptor (EGFR) (AG1478). Probes for oxidant signaling, including NAD(P)H oxidase inhibitors (diphenyliodonium and apocynin) or enhancement of peroxide consumption (ebselen) but not inhibition of xanthine oxidase (allopurinol), attenuated the effects of stretch on both ERK phosphorylation and force generation. Furthermore, stretch caused an increase in EGFR phosphorylation and cytosolic to membrane translocation of the p47phox NAD(P)H oxidase subunit. Hydrogen peroxide also elicited contraction through EGFR phosphorylation and ERK. In summary, stretch seems to enhance force generation via ERK signaling through an EGFR/src-dependent mechanism activated by peroxide derived from a stretch-mediated activation of the NAD(P)H oxidase, a response that may contribute to hypertensive alterations in vascular reactivity. Key Words: stretch Ⅲ mitogen-activated protein kinases Ⅲ NAD(P)H oxidase Ⅲ hydrogen peroxide Ⅲ oxidant signaling T here is recent evidence that mechanical stretch can increase reactive oxygen species (ROS) production 1 and that ROS may be involved with the myogenic response of the microcirculation. 2 In addition, extracellular signal-regulated kinase (ERK), p38, and c-Jun N-terminal protein kinase (JNK), subsets of the mitogen-activated protein (MAP) kinases, have been shown to be activated by mechanical 3,4 and pulsatile 5-7 stretch as well as oxidants such as peroxide. 8 Recent studies on the mechanisms of myogenic responses have detected evidence that both the p38 and ERK MAP kinase pathways mediate this response. 9 However, myogenic responses are not observed in conduit arteries, and evidence for oxidant-induced activation of the MAP kinases has generally been derived from studies in cultured cells, and their subsequent involvement in stretch-induced contractile responses has not yet been established.Preliminary observations from our laboratory have demonstrated that brief stretching of the coronary vessels increases luc...

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