OBJECTIVENitric oxide (NO) elicits relaxation in vascular smooth muscle cells (VSMC) that is associated with guanylate cyclase (GC) and K(+) channel activation. In this study we determined the mechanisms that lead to ERK1/2 MAP kinase dephosphorylation in response to NO.METHODSVSMC were treated with the NO donor SNAP or sodium nitroprusside (SNP), and ERK1/2, Src homology (SH) 1 domain-containing protein tyrosine phosphatase (SHP-1), and Kv.1.2 phosphorylation were assessed by immunoprecipitation and Western blot analysis.RESULTSNO decreased basal ERK1/2 phosphorylation in a dose- and time-dependent manner. NO-induced ERK1/2 dephosphorylation was detected at 1 min and sustained for 30 min. Pre-treatment with the GC inhibitor ODQ or the protein tyrosine phosphatase inhibitor I prevented ERK1/2 dephosphorylation induced by SNAP. The inhibition of protein phosphatase 1A/2A had no effect on ERK1/2 dephosphorylation induced by SNAP. Treatment with cromakalim A, a nonspecific K(+) channel activator, also induced ERK1/2 dephosphorylation, while blockade of Kv.1.2 K(+) channels (AM92016 hydrochloride) prevented NO-induced ERK1/2 dephosphorylation. In addition, SNAP induced SHP-1 phosphorylation, and the Kv.1.2 dephosphorylation increase and SHP-1 phosphorylation was blocked by ODQ or AM92016. The basal interaction between ERK1/2 and SHP-1 was decreased in response to SNAP stimulation. SHP-1 also interacted with Kv.1.2 under basal conditions and participates in Kv.1.2 activation. Using the mouse mesenteric resistance artery, we found that ERK1/2 MAP kinase is involved in regulation of myogenic tone.CONCLUSIONThus, our study provides the first evidence that NO controls basal ERK1/2 phosphorylation by a signaling cascade that involves a dynamic signaling complex between cGMP, Kv.1.2 and SHP-1.

2005-01-01·European Journal of Pharmacology3区 · 医学

Tetraethylammonium exacerbates ischemic neuronal injury in rat cerebrocortical slice cultures

3区 · 医学

Article

作者: Toshiaki Kume ; Atsumi Shinohara ; Shinji Fujimoto ; Hiroshi Katsuki ; Akinori Akaike

We investigated potential contribution of K+ channel activity to regulation of ischemia-induced neuronal injury, using cerebrocortical slice cultures. Exposure of cultures to a glucose-free conditioning solution containing sodium azide and 2-deoxyglucose caused neuronal cell death as assessed by cellular uptake of propidium iodide, which was prevented by MK-801, an N-methyl-D-aspartate (NMDA) receptor antagonist. Application of tetraethylammonium markedly exacerbated ischemic neuronal injury. Charybdotoxin, a blocker of large-conductance Ca(2+)-activated K+ (BK(Ca)) channels, also augmented ischemic injury, whereas AM 92016, a blocker of delayed rectifier K+ channels, and dequalinium, a blocker of small-conductance Ca(2+)-activated K+ channels, had no significant effect. In addition, tetraethylammonium and charybdotoxin were effective in augmenting NMDA-induced neuronal injury. These results present unprecedented evidence for the ability of tetraethylammonium to enhance ischemic neuronal death, and suggest that BK(Ca) channels constitute an endogenous system to protect cortical neurons from ischemic injury, via prevention of NMDA receptor over-activation.

1996-04-01·Journal of Pharmacy and Pharmacology3区 · 医学

The In-vivo Cardiovascular Effects of a Putative Class III Anti-arrhythmic Drug, AM 92016

3区 · 医学

Article

作者: Kane, K A ; Wainwright, C L ; Hagerty, M J

AbstractAM 92016(1-(4-methanesulphonamidophenoxy)-3-(N-methyl-3–4-dichlorophenethylamino)-2-propanol benzoic acid salt), an oxypropanolamine analogue of sotalol, has been shown to possess Class III antiarrhythmic properties in-vitro at concentrations showing 1000 times more potency than sotalol. The aim of this study was to characterize the effects of AM 92016 in-vivo.When administered to anaesthetized guinea-pigs, AM 92016 (10 μg kg−1-5 mg kg−1) significantly increased heart rate, systolic arterial blood pressure, left ventricular systolic pressure and the contractile index dp/dtmax. AM 92016 also significantly decreased the QT interval of the electrocardiogram from 135 ± 10 to 105 ± 4 ms (5 mg kg−1). The time to onset of the first arrhythmia and ventricular fibrillation, induced by intravenous infusion of ouabain, was shortened in the presence of AM 92016. Ouabain-induced ventricular fibrillation occurred at 18 ± 5 and 12 ± 3 min (P < 005) in control and AM 92016-(1 mg kg−1) treated guinea-pigs, respectively. An infusion of AM 92016 (2.5 μg kg−1 min−1) to anaesthetized pigs significantly increased the total number of arrhythmias occurring following coronary artery occlusion from 266 ·26 in control pigs to 535 ± 148 (P < 005) in those receiving AM 92016. The time to onset of ventricular fibrillation was also significantly reduced in anaesthetized pigs from 24 ± 1 to 18 ± 3 min in the presence of AM 92016. The drug did not change haemodynamics in the anaesthetized pig.We conclude that AM 92016 exhibited proarrhythmic rather than antiarrhythmic activity when administered in-vivo to either guinea-pigs or pigs.

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