endothelin-1 and fasudil

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Acute Disease; Angioplasty, Balloon; Calcium Channel Blockers; Cell Membrane; Combined Modality Therapy; Endothelin-1; Hemoglobins; Humans; Muscle, Smooth, Vascular; Nicardipine; Nitric Oxide; Oxidative Stress; Subarachnoid Hemorrhage; Vasodilator Agents; Vasospasm, Intracranial; Verapamil

This study aims to study the effect of Rho kinase inhibitor fasudil on the expression endothelin-1 (ET-1) and nitric oxide (NO) in rats with hypoxic pulmonary hypertension (HPH).. Twenty-four male SD rats were randomly divided into three groups: control group, model group (HPH group) and HPH+fasudil group. The rat HPH model was established by intermittent hypoxia (IH) at atmospheric pressure. Mean pulmonary artery pressure (mPAP), right ventricular hypertrophy index (RVHI), ET-1 and NO levels, and pulmonary vascular structural changes were observed in all groups.. MPAP, RVHI and ET-1 levels were significantly higher in HPH group than in control group, while NO was significantly lower than in control group. In addition, mPAP, RVHI and ET-1 were significantly lower in the HPH+fasudil group than in the HPH group. In the HPH group, ET-1 level was significantly and positively correlated with mPAP and RVHI, NO was negatively correlated with mPAP and RVHI levels, and ET-1 level was significantly and negatively correlated with NO level. In the HPH group, pulmonary arteriolar walls were generally thickened, and lumen stenosis was obvious; while after fasudil treatment, pulmonary arteriolar wall thickening and stenosis degree were significantly reduced.. Fasudil can significantly reduce ET-l level and increase NO level in HPH rats, suppressing the development of pulmonary arterial hypertension.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Disease Models, Animal; Endothelin-1; Hypertension, Pulmonary; Male; Nitric Oxide; Protein Kinase Inhibitors; Rats; Rats, Sprague-Dawley

Endothelial dysfunction is one of the main pathological changes in Obstructive sleep apnoea (OSA). The Rho kinase (ROCK) pathway is associated with endothelial dysfunction. However, the interaction between ROCK and nuclear factor of activated T cells isoform c3 (NFATc3) in the development of this pathological response under chronic intermittent hypoxia (CIH) is unclear. To simulate the OSA model, we established a moderate CIH rat model by administering the fraction of inspired O2 (FiO2) from 21% to 9%, 20 times/h, 8 h/day for 3 weeks. Fasudil (ROCK inhibitor, 8 mg/kg/d, i.p.) was administrated in the rats exposed to CIH for 3 weeks. Our results demonstrated that CIH caused significantly endothelial dysfunction, accompanying with increased ET-1 level, decreased eNOS expression and NO production, which reduced ACh-induced vascular relaxation responses. Moreover, RhoA/ROCK-2/NFATc3 expressions were up-regulated. Fasudil significantly improved CIH induced endothelial dysfunction. Data suggested that the ROCK activation is necessary for endothelial dysfunction during CIH.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Aorta; Endothelin-1; Endothelium, Vascular; Hypoxia; Male; NFATC Transcription Factors; Nitric Oxide; Rats; Rats, Sprague-Dawley; rho-Associated Kinases; rhoA GTP-Binding Protein; Signal Transduction; Time Factors

Endothelin (ET)-1 and ET-2 cause potent long-lasting vasoconstrictions by tight binding to smooth muscle ETA receptors. We tested the hypotheses that different mechanisms mediate initiation and maintenance of arterial contractile responses to ET-1 and ET-2 and that this differs among vascular beds.. Segments of rat mesenteric resistance artery (MRA) and basilar artery (BA) were studied in wire myographs with and without functional antagonists.. Sensitivity and maximum of MRA contractile responses to ET-1 were not, or only moderately, reduced by stimulation of soluble GC, AC or K(+) -channels and by an inhibitor of receptor-operated ion channels. However, each of these reduced maintenance of ET-1 effects and relaxed ET-1-induced contractions in MRA. A calcium channel antagonist did not alter sensitivity, maximum and maintenance of ET-1 effects, but relaxed ET-1-induced contractions in MRA. A PLC inhibitor prevented contractile responses to ET-1 and ET-2 in MRA and BA, and relaxed ET-1- and ET-2-induced responses in MRA and ET-1 effects in BA. A Rho-kinase inhibitor did not modify sensitivity, maximum and maintenance of responses to both peptides in both arteries but relaxed ET-2, but not ET-1, effects in MRA and ET-1 effects in BA.. PLC played a key role in arterial contractile responses to ETs, but ET-1 and ET-2 initiated and maintained vasoconstriction through different mechanisms, and these differed between MRA and BA. Selective functional antagonism may be considered for agonist- and vascular bed selective pharmacotherapy of ET-related diseases.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Cerebral Arteries; Endothelin-1; Endothelin-2; Estrenes; Male; Mesenteric Arteries; Phosphodiesterase Inhibitors; Protein Kinase Inhibitors; Pyrrolidinones; Rats; Rats, Inbred WKY; rho-Associated Kinases; Type C Phospholipases; Vasoconstriction

Hepatic stellate cells are thought to play a role in modulating intrahepatic vascular resistance based on their capacity to contract via Rho signaling. We investigated the effect of a Rho-kinase inhibitor on ischemia-reperfusion injury in the steatotic liver.. Steatotic livers, induced by a choline-deficient diet in rats, were subjected to ischemia-reperfusion injury. Hepatic stellate cells isolated from steatotic livers were analyzed for contractility and Rho signaling activity. The portal pressure of the perfused rat liver and the survival rate after ischemia-reperfusion were also investigated.. Hepatic stellate cells from steatotic livers showed increased contractility and upregulation of Rho-kinase 2 compared with those from normal livers. Furthermore, endothelin-1 significantly enhanced the contractility and phosphorylation level of myosin light chain and cofilin in hepatic stellate cells isolated from steatotic livers. A specific Rho-kinase inhibitor, fasudil, significantly suppressed the contractility and decreased the phosphorylation levels of myosin light chain and cofilin. Serum levels of endothelin-1 were markedly increased after IR in rats with steatotic livers, whereas fasudil significantly decreased endothelin-1 serum levels. Rats with steatotic livers showed a significant increase in portal perfusion pressure after ischemia-reperfusion and a significant decrease in survival rate; fasudil treatment significantly reduced these effects.. Activation of Rho/Rho-kinase signaling in hepatic stellate cells isolated from steatotic livers is associated with an increased susceptibility to ischemia-reperfusion injury. A Rho-kinase inhibitor attenuated the activation of hepatic stellate cells isolated from steatotic livers and improved ischemia-reperfusion injury in steatotic rats.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Actin Depolymerizing Factors; Animals; Endothelin-1; Fatty Liver; Hepatic Stellate Cells; Liver; Male; Myosin Light Chains; Phosphorylation; Protein Kinase Inhibitors; Rats; Rats, Wistar; Reperfusion Injury; rho-Associated Kinases

Pulmonary hypertension (PH) in left ventricular dysfunction is attributable not only to backward failure of the left ventricle, but also to increased pulmonary vascular resistance (PVR) in some patients. Recently, Rho-kinase has been known as a potent growth stimulator and mediator of vasoconstriction, and Rho-kinase inhibitors could ameliorate PVR, little is known about the role of Rho-kinase in left ventricular dysfunction-induced PH. We utilized the ascending aortic-banded rat and assessed the effect of Rho-kinase inhibitor fasudil on the development of PH secondary to left ventricular dysfunction. Subsequently, in rats subjected to aortic banding for 6 weeks, there were increases in mean pulmonary arterial pressure, pulmonary arteriolar medial thickness, active RhoA, Rho-kinase II, Rho-kinase activity, endothelial nitric oxide synthase (eNOS) and endothelin-1(ET-1) concomitant with decreased levels in NO and cGMP in the lung. Treatment with fasudil at a dose of 30 mg/kg/day from days 1 to 28 or from days 29 to 42 decreased the mean pulmonary arterial pressure by 57% and 56%, right ventricular hypertrophy by 31% and 30%, pulmonary arteriolar medial thickness by 50% and 50%, and pulmonary expression of Rho-kinase II by 41% and 28%, respectively, as well as augmented pulmonary expression of eNOS by 16% and 31% and NO by 50% and 76%, respectively, when compared with the vehicle controls. In conclusion, these results suggest that inhibition of Rho-kinase may provide therapeutic potential for preventing and attenuating the development of PH in left ventricular dysfunction. Further translational study in human is needed to substantiate the findings.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Arterioles; Cyclic GMP; Endothelin-1; Hypertension, Pulmonary; Lung; Male; Nitric Oxide; Nitric Oxide Synthase Type III; Protein Kinase Inhibitors; Pulmonary Artery; Rats; Rats, Wistar; rho-Associated Kinases; Treatment Outcome; Ventricular Dysfunction, Left

To investigate the effects of fasudil, a Rho-associated coiled coil-forming protein kinase (ROCK) inhibitor, on normal or impaired optic nerve head (ONH) blood flow in a rabbit model.. ONH blood flow was measured by laser speckle flowgraphy. Changes in ONH blood flow were examined during a continuous intravenous infusion of fasudil with and without the application of N(G)-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor. Effects of topical fasudil on ONH blood flow were investigated in normal eyes or models of ocular circulation impairment induced by the application of endothelin (ET)-1. Visual-evoked potentials (VEPs) and morphologic and histologic changes were also analyzed in the ET-1-injected eyes.. A continuous intravenous infusion of fasudil had no significant effect on normal ONH blood flow, yet it prevented or improved the ONH blood flow impairment induced by the intravenous injection of L-NAME. Repeated intravitreal injections of ET-1 twice a week for 4 weeks decreased the ONH blood flow, prolonged the VEPs' implicit time, enlarged the optic cup, and decreased retinal ganglion cells. Multiple doses of topical fasudil ameliorated the ONH impairments caused by ET-1.. These results show that systemic or topical fasudil suppresses impairment of ONH blood flow, function, and morphology induced by L-NAME or ET-1. A ROCK inhibitor can be useful for the treatment of impaired ONH blood flow.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Administration, Topical; Animals; Blood Flow Velocity; Blood Pressure; Endothelin-1; Evoked Potentials, Visual; Infusions, Intravenous; Intraocular Pressure; Laser-Doppler Flowmetry; Male; NG-Nitroarginine Methyl Ester; Optic Disk; Protein Kinase Inhibitors; Rabbits; Regional Blood Flow; rho-Associated Kinases

Vasospasm of the cerebrovasculature is a common manifestation of blast-induced traumatic brain injury (bTBI) reported among combat casualties in the conflicts in Afghanistan and Iraq. Cerebral vasospasm occurs more frequently, and with earlier onset, in bTBI patients than in patients with other TBI injury modes, such as blunt force trauma. Though vasospasm is usually associated with the presence of subarachnoid hemorrhage (SAH), SAH is not required for vasospasm in bTBI, which suggests that the unique mechanics of blast injury could potentiate vasospasm onset, accounting for the increased incidence. Here, using theoretical and in vitro models, we show that a single rapid mechanical insult can induce vascular hypercontractility and remodeling, indicative of vasospasm initiation. We employed high-velocity stretching of engineered arterial lamellae to simulate the mechanical forces of a blast pulse on the vasculature. An hour after a simulated blast, injured tissues displayed altered intracellular calcium dynamics leading to hypersensitivity to contractile stimulus with endothelin-1. One day after simulated blast, tissues exhibited blast force dependent prolonged hypercontraction and vascular smooth muscle phenotype switching, indicative of remodeling. These results suggest that an acute, blast-like injury is sufficient to induce a hypercontraction-induced genetic switch that potentiates vascular remodeling, and cerebral vasospasm, in bTBI patients.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Algorithms; Arteries; Blast Injuries; Blotting, Western; Brain Injuries; Calcium; Calcium Channel Blockers; Cells, Cultured; Cytosol; Endothelin-1; Gene Expression; Humans; Military Medicine; Models, Biological; Muscle Contraction; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Myosin Heavy Chains; Reverse Transcriptase Polymerase Chain Reaction; Stress, Mechanical; Tissue Engineering; Vasospasm, Intracranial; Warfare

The physiologic role of smooth muscle structure in defining arterial function is poorly understood. We aimed to elucidate the relationship between vascular smooth muscle architecture and functional contractile output. Using microcontact printing and muscular thin film technology, we engineered in vitro vascular tissues with strictly defined geometries and tested their contractile function. In all tissues, vascular smooth muscle cells (VSMCs) were highly aligned with in vivo-like spindle architecture, and contracted physiologically in response to stimulation with endothelin-1. However, tissues wherein the VSMCs were forced into exaggerated spindle elongation exerted significantly greater contraction force per unit cross-sectional area than those with smaller aspect ratios. Moreover, this increased contraction did not occur in conjunction with an increase in traditionally measured contractile phenotype markers. These results suggest that cellular architecture within vascular tissues plays a significant role in conferring tissue function and that, in some systems, traditional phenotype characterization is not sufficient to define a functionally contractile population of VSMCs.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Actin Cytoskeleton; Cell Nucleus; Cell Shape; Cells, Cultured; Cytoskeletal Proteins; Dimethylpolysiloxanes; Dose-Response Relationship, Drug; Endothelin-1; Fibronectins; Humans; Laminin; Muscle Contraction; Muscle Proteins; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Myosin Heavy Chains; rho-Associated Kinases; Smooth Muscle Myosins; Tissue Engineering; Tissue Scaffolds; Umbilical Veins

Sleep apnea (SA) is defined as intermittent respiratory arrest during sleep and affects up to 20% of the adult population. SA is also associated with an increased incidence of hypertension and peripheral vascular disease. Exposing rodents to intermittent hypoxia during sleep mimics the cyclical hypoxia/normoxia of SA. We have previously shown that in mice and rats intermittent hypoxia induces ET-1 upregulation and systemic hypertension. Furthermore, intermittent hypoxia (IH) in mice increases nuclear factor of activated T cells isoform 3 (NFATc3) transcriptional activity in aorta and mesenteric arteries, whereas the calcineurin/NFAT inhibitor cyclosporin A prevents IH-induced hypertension. More importantly, NFATc3 knockout (KO) mice do not develop IH-induced hypertension. The goals of this study were to determine the role of NFATc3 in IH-induced arterial remodeling and whether IH-induced NFATc3 activation is mediated by ET-1. Oral administration of both a dual (bosentan) and a selective endothelin receptor type A antagonist (PD155080) during 2 days of IH exposure attenuated NFAT activation in aorta and mesenteric arteries. Rho kinase inhibition with fasudil also prevented IH-induced NFAT activation. Mesenteric artery cross-sectional wall thickness was increased by IH in wild-type (WT) and vehicle-treated mice but not in bosentan-treated and NFATc3 KO mice. The arterial remodeling in mesenteric arteries after IH was characterized by increased expression of the hypertrophic NFATc3 target smooth muscle-alpha-actin in WT but not in KO mice. These results indicate that ET-1 is an upstream activator of NFATc3 during intermittent hypoxia, contributing to the resultant hypertension and increased wall thickness.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Actins; Animals; Aorta, Thoracic; Bosentan; Dioxoles; Disease Models, Animal; Endothelin A Receptor Antagonists; Endothelin-1; Genes, Reporter; Hemodynamics; Hyperoxia; Hypertension; Male; Mesenteric Arteries; Mice; Mice, Inbred BALB C; Mice, Knockout; Mice, Transgenic; NFATC Transcription Factors; Promoter Regions, Genetic; Protein Kinase Inhibitors; Receptor, Endothelin A; rho-Associated Kinases; Sulfonamides; Time Factors

Chronic pulmonary hypertension in infancy and childhood is characterized by a fixed and progressive increase in pulmonary arterial pressure and resistance, pulmonary arterial remodeling, and right ventricular hypertrophy and systolic dysfunction. These abnormalities are replicated in neonatal rats chronically exposed to hypoxia from birth in which increased activity of Rho-kinase (ROCK) is critical to injury, as evidenced by preventive effects of ROCK inhibitors. Our objective in the present study was to examine the reversing effects of a late or rescue approach to treatment with a ROCK inhibitor on the pulmonary and cardiac manifestations of established chronic hypoxic pulmonary hypertension. Rat pups were exposed to air or hypoxia (13% O(2)) from postnatal day 1 and were treated with Y-27632 (15 mg/kg) or saline vehicle by twice daily subcutaneous injection commencing on day 14, for up to 7 days. Treatment with Y-27632 significantly attenuated right ventricular hypertrophy, reversed arterial wall remodeling, and completely normalized right ventricular systolic function in hypoxia-exposed animals. Reversal of arterial wall remodeling was accompanied by increased apoptosis and attenuated content of endothelin (ET)-1 and ET(A) receptors. Treatment of primary cultured juvenile rat pulmonary artery smooth muscle cells with Y-27632 attenuated serum-stimulated ROCK activity and proliferation and increased apoptosis. Smooth muscle apoptosis was also induced by short interfering RNA-mediated knockdown of ROCK-II, but not of ROCK-I. We conclude that sustained rescue treatment with a ROCK inhibitor reversed both the hemodynamic and structural abnormalities of chronic hypoxic pulmonary hypertension in juvenile rats and normalized right ventricular systolic function. Attenuated expression and activity of ET-1 and its A-type receptor on pulmonary arterial smooth muscle was a likely contributor to the stimulatory effects of ROCK inhibition on apoptosis. In addition, our data suggest that ROCK-II may be dominant in enhancing survival of pulmonary arterial smooth muscle.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Age Factors; Aging; Amides; Animals; Apoptosis; Cell Proliferation; Cells, Cultured; Chronic Disease; Disease Models, Animal; Endothelin-1; Hemodynamics; Hypertension, Pulmonary; Hypertrophy, Right Ventricular; Hypoxia; Injections, Subcutaneous; Muscle, Smooth, Vascular; Myocardium; Protein Kinase Inhibitors; Pulmonary Artery; Pyridines; Rats; Receptor, Endothelin A; rho-Associated Kinases; RNA Interference; Ventricular Dysfunction, Right; Ventricular Function, Right; Ventricular Remodeling

We aimed to compare the expression and function of molecular components of the RhoA/Rho-kinase signaling pathway in the contractile responses of detrusor, trigonal and urethral smooth muscle, using selective Rho-kinase inhibitors. Contractility studies and molecular approaches were employed to demonstrate the expression patterns and functional activity of the RhoA/Rho-kinase signaling pathway in the lower urinary tract. Frequency-response curves (1-32 Hz) and concentration-response curves (CRC) to carbachol (CCh, 0.01-30 microM), phenylephrine (PE, 0.01-300 microM) and endothelin-1 (ET-1, 0.01-100 nM) were significantly attenuated (p<0.01) following incubation with the Rho-kinase inhibitors H-1152 (0.1-1 microM), Y-27632 (1-10 microM) or HA-1077 (10 microM). Addition of Rho-kinase inhibitors also markedly reduced (p<0.01) the contractions evoked by either KCl (80 mM) or alpha,beta-methylene ATP (alpha,beta-mATP, 10 microM). Among the Rho-kinase inhibitors tested, H-1152 was approximately 9-16 times more potent than Y-27632 or HA-1077. In addition, basal tone of detrusor and trigonal strips was reduced following addition of Y-27632 (10 microM), H-1152 (1 microM) and HA-1077 (10 microM). The expression of RhoA, RhoGDI, leukemia-associated RhoGEF (LARG) and p115RhoGEF was similar among the detrusor, trigone and urethra, whereas Rho-kinase alpha, Rho-kinase beta and PDZ-RhoGEF protein levels were significantly lower in the urethra. Components of the RhoA/Rho-kinase signaling are expressed in detrusor, trigonal and urethral smooth muscle and dynamically regulate contraction and tone. Manipulation of RhoGEF expression may provide further understanding of mechanisms involving Ca(2+) sensitization in the lower urinary tract.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Adenosine Triphosphate; Amides; Animals; Atropine; Blotting, Western; Calcium Signaling; Dose-Response Relationship, Drug; Electric Stimulation; Endothelin-1; Enzyme Inhibitors; Guanine Nucleotide Dissociation Inhibitors; In Vitro Techniques; Intracellular Signaling Peptides and Proteins; Male; Muscle Contraction; Muscle, Smooth; Nifedipine; Protein Serine-Threonine Kinases; Pyridines; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; rho-Associated Kinases; rho-Specific Guanine Nucleotide Dissociation Inhibitors; rhoA GTP-Binding Protein; Urethra; Urinary Bladder

Endothelin-1 (ET-1), a potent vasoconstrictor, is believed to contribute to the pathogenesis of hypoxic pulmonary hypertension. Previously we demonstrated that contraction induced by ET-1 in intrapulmonary arteries (IPA) from chronically hypoxic (CH) rats occurred independently of changes in intracellular Ca2+ concentration ([Ca2+]i), suggesting that ET-1 increased Ca2+ sensitivity. The mechanisms underlying this effect are unclear but could involve the activation of myosin light chain kinase, Rho kinase, PKC, or tyrosine kinases (TKs), including those from the Src family. In this study, we examined the effect of pharmacological inhibitors of these kinases on maximum tension generated by IPA from CH rats (10% O2 for 21 days) in response to ET-1. Experiments were conducted in the presence of nifedipine, an L-type Ca2+ channel blocker, to isolate the component of contraction that occurred without a change in [Ca2+]i. The mean change in tension caused by ET-1 (10(-8) M) expressed as a percent of the maximum response to KCl was 184.0+/-39.0%. This response was markedly inhibited by the Rho kinase inhibitors Y-27632 and HA-1077 and the TK inhibitors genistein, tyrphostin A23, and PP2. In contrast, staurosporine and GF-109203X, inhibitors of PKC, had no significant inhibitory effect on the tension generated in response to ET-1. We conclude that the component of ET-1-induced contraction that occurs without a change in [Ca2+]i in IPA from CH rats requires activation of Rho kinase and TKs, but not PKC.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Amides; Animals; Azepines; Endothelin-1; Enzyme Inhibitors; Genistein; Hypoxia; Indoles; Intracellular Signaling Peptides and Proteins; Isometric Contraction; Male; Maleimides; Myosin-Light-Chain Kinase; Potassium Chloride; Protein Kinase C; Protein Serine-Threonine Kinases; Protein-Tyrosine Kinases; Pulmonary Artery; Pyridines; Pyrimidines; Rats; Rats, Wistar; rho-Associated Kinases; src-Family Kinases; Staurosporine; Vasoconstriction

Fasudil hydrochloride (AT877, hexahydro-1-(5-isoquinolinesulfonyl)-1H-1,4-diazepine hydrochloride, identical to HA1077) inhibits cerebral vasospasm after subarachnoid hemorrhage in experimental animals and humans. In the current study, the vasorelaxing mechanism of hydroxyfasudil, a hydroxylated metabolite of fasudil hydrochloride, was determined in the rabbit basilar artery. The effects of hydroxyfasudil on tension, intracellular Ca2+ concentration ([Ca2+]i), and phosphorylation of the myosin light chain were examined using the isolated and intact or permeabilized rabbit basilar artery without endothelium in vitro. In the intact rabbit basilar artery, hydroxyfasudil elicited a concentration-dependent relaxation of the artery precontracted with 1 nmol/L endothelin-1 (ET-1) plus 20 mmol/L KCl without any significant decrease in [Ca2+]i as determined by fura-2 microfluorometry (IC50: 5.1 +/- 4.6 micromol/L). The relaxation induced by hydroxyfasudil was accompanied with dephosphorylation of the myosin light chain. In the permeabilized preparation, hydroxyfasudil inhibited the contraction induced by ET-1, guanosine 5'-O-(3-thiotriphosphate), or the catalytic subunit of rho-associated kinase, but it did not inhibit Ca2+-induced contraction under the condition of inhibited myosin light chain phosphatase. Hydroxyfasudil showed a greater relaxant effect under decreased adenosine triphosphate (ATP) levels. The present study indicated that hydroxyfasudil relaxes the rabbit basilar artery mainly by disinhibiting myosin light chain phosphatase through the inhibition of rho-associated kinase and that this effect depends on the intracellular ATP concentration.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Adenosine Triphosphate; Animals; Basilar Artery; Calcium; Endothelin-1; Enzyme Activation; Guanosine 5'-O-(3-Thiotriphosphate); Kinetics; Male; Muscle Contraction; Muscle Relaxation; Muscle, Smooth, Vascular; Myosin-Light-Chain Phosphatase; Phorbol 12,13-Dibutyrate; Phosphoprotein Phosphatases; Protein Kinase C; Rabbits; Vasodilator Agents

Endothelin-1 (ET-1) induces severe pathologic conditions such as coronary spasm followed by vasospastic angina pectoris and acute myocardial infarction. The related pathophysiologic mechanisms have remained obscure. Endothelin-1 receptor (ET(A) and ET(B)) is reported to couple with several types of G protein-involved pathways that participate in phospholipase C activation and atrial myofibrils organization into sarcomeric units. Here we demonstrate that ET-1 induces histologic and pathologic dysfunction in the rabbit myocardium and that such pathologic events are prevented by the Rho-kinase inhibitor fasudil. Although the bolus injection of ET-1 (1.4 nmol/kg) via the auricular vein of the rabbit induced only transient T-wave elevation, irreversible, severe histologic changes were observed in papillary muscles of the ventricle, and multifocal myocardial necrosis with infiltration of neutrophils and macrophages in the left ventricle occurred. Oral administration of fasudil (10 mg/kg) significantly reduced the occurrence of myocardial injury determinants, whereas conventional Ca2+ channel blockers (nifedipine, diltiazem) and a K+ channel opener (nicorandil; 10 mg/kg, p.o. each) showed a lesser or no effect on such determinants. These results suggest that ET-1 induces severe myocardial dysfunction based not only on the occurrence of vasospastic ischemia but also on its direct effects on the myocardium.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Animals; Cell Movement; Diltiazem; Electrocardiography; Endothelin-1; Enzyme Inhibitors; Heart Ventricles; Macrophages; Male; Microscopy; Myocardial Ischemia; Necrosis; Neutrophils; Nicorandil; Nifedipine; Papillary Muscles; Rabbits; Random Allocation; Vasodilator Agents