p38 mitogen-activated protein kinase contributes to the diminished aortic contraction by endothelin-1 in DOCA-salt hypertensive rats

Pharmacological Inhibition of Mammalian Target of Rapamycin Attenuates Deoxycorticosterone Acetate Salt-Induced Hypertension and Related Pathophysiology: Regulation of Oxidative Stress, Inflammation, and Cardiovascular Hypertrophy in Male Rats

ABSTRACT

The present study aimed to explore the contribution of mammalian target of rapamycin (mTOR) in deoxycorticosterone acetate (DOCA) salt-induced hypertension and related pathophysiological changes in cardiovascular and renal tissues. DOCA salt loading resulted in an increase in systolic blood pressure, diastolic blood pressure, and mean blood pressure along with the activity of ribosomal protein S6, the effector protein of mTOR. Treatment with rapamycin, the selective inhibitor of mTOR, initiated at the fourth week of DOCA- salt administration normalized the systolic blood pressure and attenuated ribosomal protein S6 activity in the heart, aorta, and kidney. Cardiac and vascular hypertrophy, oxidative stress, and infiltration of macrophages (CD68+), the marker of inflammation, were also reduced in rapamycin-treated, DOCA-salt, hypertensive rats. In addition, renal hypertrophy and dysfunction were also reduced with rapamycin-treated hypertensive rats. Moreover, these pathophysiological changes in DOCA-salt hypertensive rats were associated with increased NADPH oxidase (NOX) activity, gp91phox (formerly NOX2) expression, ERK1/2, and p38 MAPK activities in the heart, aorta, and kidney were minimized by rapamycin. These data indicate that mTOR plays an important role in regulating blood pressure and the development of cardiovascular and renal pathophysiological changes, most likely due to increased NOX expression/activity, ERK1/2, and p38 MAPK activity with macrophages infiltration in the heart, kidney, and aorta. Pharmacological inhibition of mTOR and related signaling pathways could serve as a novel target for the treatment of hypertension.

O‑GlcNAcylation contributes to intermittent hypoxia‑associated vascular dysfunction via modulation of MAPKs but not CaMKII pathways

Intermittent hypoxia (IH) leads to vascular dysfunction, and O-linked-β-N-acetylglucosamine (O-GlcNAc)ylation may regulate vascular reactivity through the modulation of intracellular signaling. The present study hypothesized that O-GlcNAc modifications contributed to the vascular effects of acute IH (AIH) and chronic IH (CIH) through the MAPK and Ca²⁺/calmodulin-dependent kinase II (CaMKII) pathways. Rat aortic and mesenteric segments were incubated with DMSO, O-GlcNAcase (OGA) or O-GlcNAc transferase (OGT) inhibitor under either normoxic or AIH conditions for 3 h, and arterial function was then assessed. Meanwhile, arteries isolated from control and CIH rats were exposed to 3 h of incubation under normoxic conditions using DMSO, OGA or OGT as an inhibitor, before assessing arterial reactivity. CIH was found to increase the expression of vascular O-GlcNAc protein and OGT, phosphorylate p38 MAPK and ERK1/2, and decrease OGA levels, but it had no effects on phosphorylated CaMKII levels. OGA inhibition increased global O-GlcNAcylation and the phosphorylation of p38 MAPK, ERK1/2 and CaMKII, whereas OGT blockade had the opposite effects. OGA inhibition preserved acetylcholine-induced relaxation in AIH arteries, whereas OGT blockade attenuated the relaxation responses of arteries under normoxic conditions or undergoing AIH treatments. However, the impairment of acetylcholine dilation in CIH mesenteric arteries was improved. CIH artery contraction was increased following angiotensin II (Ang II) exposure. Blockade of p38 MAPK and ERK1/2, but not CaMKII, attenuated Ang II-induced contractile responses in CIH arteries isolated from the non-OGT inhibitor-treated groups. OGT inhibition significantly blocked contractile responses to Ang II and abolished the inhibitory effects of MAPK inhibitors. These findings indicated that O-GlcNAcylation regulates IH-induced vascular dysfunction, at least partly by modulating MAPK, but not CaMKII, signaling pathways.

MAPKs Are Highly Abundant but Do Not Contribute to α1-Adrenergic Contraction of Rat Saphenous Arteries in the Early Postnatal Period

Previously, the abundance of p42/44 and p38 MAPK proteins had been shown to be higher in arteries of 1- to 2-week-old compared to 2- to 3-month-old rats. However, the role of MAPKs in vascular tone regulation in early ontogenesis remains largely unexplored. We tested the hypothesis that the contribution of p42/44 and p38 MAPKs to the contraction of peripheral arteries is higher in the early postnatal period compared to adulthood. Saphenous arteries of 1- to 2-week-old and 2- to 3-month-old rats were studied using wire myography and western blotting. The α₁-adrenoceptor agonist methoxamine did not increase the phosphorylation level of p38 MAPK in either 1- to 2-week-old or 2- to 3-month-old rats. Accordingly, inhibition of p38 MAPK did not affect arterial contraction to methoxamine in either age group. Methoxamine increased the phosphorylation level of p42/44 MAPKs in arteries of 2- to 3-month-old and of p44 MAPK in 1- to 2-week-old rats. Inhibition of p42/44 MAPKs reduced methoxamine-induced contractions in arteries of 2- to 3-month-old, but not 1- to 2-week-old rats. Thus, despite a high abundance in arterial tissue, p38 and p42/44 MAPKs do not regulate contraction of the saphenous artery in the early postnatal period. However, p42/44 MAPK activity contributes to arterial contractions in adult rats.

Dietary supplementation of Huangshan Maofeng green tea preventing hypertension of older C57BL/6 mice induced by desoxycorticosterone acetate and salt

Senile hypertension affects the life quality of aged population. Dietary intervention plays a pivotal role in the prevention of hypertension. There are few reports concerning the effects and mechanisms of green tea supplementation preventing age related hypertension. The current study investigated the effect and mechanism of dietary supplement of Huangshan Maofeng green tea (HSMF) on prevention of hypertension induced by deoxycorticosterone acetate (DOCA) and salt in old C57BL/6 mice. Our results showed that HSMF dose-dependently prevented the increase of systolic blood pressure and diastolic blood pressure induced by DOCA plus salt (DS) at 51-week-old mice. And HSMF significantly reduced the agonists' stimulated contraction of mesenteric arteries isolated from the old mice. The expression of vasoconstrictor genes and inflammatory cytokines in aorta were suppressed observably by HSMF supplementation compared with DS group. The protein expression of PKCα in the aorta was dose-dependently decreased by HSMF compared to DS group. The phosphorylation level of MYPT1, CPI-17and MLC20 was also restrained by HSMF in the aorta. Furthermore, HSMF protected kidney by maintaining integrity of glomeruli and tubules and remarkably decreased the NGAL level in plasma. HSMF also suppressed the kidney inflammation by decreasing inflammatory cytokines expression and the macrophage infiltration. Our results proved that dietary supplement of HSMF remarkably improved the vascular functions and protected kidney injury, and thus prevented hypertension induced by DS in older C57BL/6 mice. Our data indicated that the dietary supplement of HSMF may potentially be used as a food additive for preventing hypertension for aged people.

Dysregulated mitogen-activated protein kinase and matrix metalloproteinase in ethanol-induced cavernosal dysfunction

We evaluated the effects of ethanol consumption on the mitogen-activated protein kinases (MAPK) and metalloproteinases (MMP) pathways in the rat cavernosal smooth muscle (CSM). Male Wistar rats were treated with ethanol (20% v/v) for 6 weeks. Quantitative real-time polymerase chain reaction experiments showed that ethanol consumption did not alter mRNA levels of p38MAPK, SAPK/JNK, ERK1/2, MMP-2, or MMP-9 in the rat CSM. Western immunoblotting experiments revealed decreased protein expression of p38MAPK and phosphorylation of SAPK/JNK in the CSM from ethanol-treated rats. Additionally, ethanol consumption decreased the expression of MMP-2. Functional assays showed that SP600125, an inhibitor of SAPK/JNK, prevented the increase in endothelin (ET)-1-induced contraction in the CSM from ethanol-treated rats. Treatment with ethanol decreased MMP-2 activity, but did not change net MMP activity in the rat CSM. Ethanol consumption increased the circulating levels of MMP-2, MMP-9, and TIMP-2 as well as the MMP-9/TIMP-1 ratio. The major finding of our study is that ethanol consumption down-regulates both MAPK and MMP pathways in the rat CSM, whereas it increases the circulating levels of MMP-9. Additionally, we found that SAPK/JNK plays a role in ethanol-induced increase on ET-1 contraction in the isolated rat CSM.

Anti-atherosclerotic plants which modulate the phenotype of vascular smooth muscle cells

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of global death, with atherosclerosis being a major contributor to this mortality. Several mechanisms are implicated in the pathogenesis of this disease. A key element in the development and progression of atherosclerotic lesions is the phenotype of vascular smooth muscle cells. Under pathophysiologic conditions such as injury, these cells switch from a contractile to a synthetic phenotype that often possesses high proliferative and migratory capacities.

PURPOSE

Despite major advances made in the management and treatment of atherosclerosis, mortality associated with this disease remains high. This mandates that other approaches be sought. Herbal medicine, especially for the treatment of CVD, has been gaining more attention in recent years. This is in no small part due to the evidence-based values associated with the consumption of many plants as well as the relatively cheaper prices, easier access and conventional folk medicine "inherited" over generations. Sections: In this review, we provide a brief introduction about the pathogenesis of atherosclerosis then we highlight the role of vascular smooth muscle cells in this disease, especially when a phenotypic switch of these cells arises. We then thoroughly discuss the various plants that show potentially beneficial effects as anti-atherosclerotic, with prime attention given to herbs and plants that inhibit the phenotypic switch of vascular smooth muscle cells.

CONCLUSION

Accumulating evidence provides the justification for the use of botanicals in the treatment or prevention of atherosclerosis. However, further studies, especially clinical ones, are warranted to better define several pharmacological parameters of these herbs, such as toxicity, tolerability, and efficacy.

Multiple activation mechanisms of serotonin-mediated contraction in the carotid arteries obtained from spontaneously hypertensive rats

Serotonin (5-hydroxytryptamine, 5-HT) is an important endogenous substance that regulates the vascular tone, and the abnormal signaling of 5-HT has been observed in the arteries under several pathophysiological conditions such as diabetes and hypertension. However, signaling pathways of 5-HT-mediated vasocontraction in hypertension remain unclear. Therefore, we tested the hypothesis that 5-HT-mediated contraction and contributions of various kinases such as mitogen-activated protein kinases (MAPKs), phosphoinositide 3-kinase (PI3K), Rho kinase (ROCK), and 3-phosphoinositide-dependent kinase 1 (PDK1) to the contraction would be altered in the carotid arteries obtained from spontaneously hypertensive rats (SHR) compared to control Wistar Kyoto (WKY) rats. In the carotid arteries from SHR (vs. those from WKY), (1) the 5-HT-mediated contraction was increased, whereas the norepinephrine-mediated contraction was not; (2) 5-HT-mediated contractions were partly inhibited by each kinase (extracellular signal-regulated kinase 1/2 (ERK1/2), p38 MAPK, c-Jun N-terminal kinase (JNK), PI3K, ROCK, and PDK1) inhibitor; and (3) 5-HT-stimulated phosphorylation of ERK1/2, p38 MAPK, JNK, myosin phosphatase target subunit 1 (MYPT1), and PDK1 was increased. The expression of ROCK2 but not ROCK1 was increased in the carotid arteries from SHR compared to WKY. The expression of 5-HT2A receptor, a major receptor of 5-HT-mediated contraction in rat carotid artery, was similar in carotid arteries between the two groups. These results suggest that 5-HT-mediated contraction was utilized multiple signaling pathways such as ERK1/2, p38 MAPK, JNK, PI3K, ROCK, and PDK1. Although 5-HT-mediated contraction was increased in the carotid arteries obtained from SHR, further studies are necessary to clarify how each kinase may integrate in the vascular smooth muscles under hypertension.

Diminished Lipid Raft SNAP23 Increases Blood Pressure by Inhibiting the Membrane Fluidity of Vascular Smooth-Muscle Cells

Synaptosomal-associated protein 23 (SNAP23) is involved in microvesicle trafficking and exocytosis in various cell types, but its functional role in blood pressure (BP) regulation has not yet been defined. Here, we found that lipid raft SNAP23 expression was much lower in vascular smooth-muscle cells (VSMCs) from spontaneously hypertensive rats (SHR) than in those from normotensive Wistar-Kyoto (WKY) rats. This led us to investigate the hypothesis that this lower expression may be linked to the spontaneous hypertension found in SHR. The expression level of lipid raft SNAP23 and the fluidity in the plasma membrane of VSMCs were lower in SHR than in WKY rats. Cholesterol content in the VSMC membrane was higher, but the secreted cholesterols found in VSMC-conditioned medium and in the blood serum were lower in SHR than in WKY rats. SNAP23 knockdown in WKY rat VSMCs reduced the membrane fluidity and increased the membrane cholesterol level. Systemic overexpression of SNAP23 in SHR resulted in an increase of cholesterol content in their serum, a decrease in cholesterol in their aorta and the reduction of their BP. Our findings suggest that the low expression of the lipid raft SNAP23 in VSMCs might be a potential cause for the characteristic hypertension of SHR.

Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress

OBJECTIVES

We hypothesized that chronic ethanol intake enhances vascular oxidative stress and induces hypertension through renin-angiotensin system (RAS) activation.

METHODS AND RESULTS

Male Wistar rats were treated with ethanol (20% v/v). The increase in blood pressure induced by ethanol was prevented by losartan (10mg/kg/day; p.o. gavage), a selective AT1 receptor antagonist. Chronic ethanol intake increased plasma renin activity (PRA), angiotensin converting enzyme (ACE) activity, plasma angiotensin I (ANG I) and angiotensin II (ANG II) levels and serum aldosterone levels. No differences on plasma osmolality and sodium or potassium levels were detected after treatment with ethanol. Ethanol consumption did not alter ACE activity, as well as the levels of ANG I and ANG II in the rat aorta or mesenteric arterial bed (MAB). Ethanol induced systemic and vascular oxidative stress (aorta and MAB) and these effects were prevented by losartan. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol was prevented by losartan. Ethanol intake did not alter protein expression of ACE, AT1 or AT2 receptors in both aorta and MAB. Aortas from ethanol-treated rats displayed decreased ERK1/2 phosphorylation and increased protein expression of SAPK/JNK. These responses were prevented by losartan. MAB from ethanol-treated rats displayed reduced phosphorylation of p38MAPK and ERK1/2 and losartan did not prevent these responses.

CONCLUSIONS

Our study provides novel evidence that chronic ethanol intake increases blood pressure, induces vascular oxidative stress and decreases nitric oxide (NO) bioavailability through AT1-dependent mechanisms.

A review of deoxycorticosterone acetate-salt hypertension and its relevance for cardiovascular physiotherapy research

[Purpose] The purpose of this review was to elucidate the deoxycorticosterone acetate (DOCA)-salt-related hypertensive mechanism and to contribute to future studies of cardiovascular physiotherapy. [Methods] This paper focuses on the signal transductions that control hypertension and its mechanisms. We include results reported by our laboratory in a literature review. [Results] Our results and the literature show the various mechanisms of DOCA-salt hypertension. [Conclusion] In this review paper, we carefully discuss the signal transduction in hypertension based on our studies and with reference to cardiovascular physiotherapy research.

A Review of Signal Transduction of Endothelin-1 and Mitogen-activated Protein Kinase-related Pain for Nanophysiotherapy

[Purpose] An understanding of pain is very important in the study of nanophysiotherapy. In this review, we summarize the mechanisms of endothelin-1 (ET-1)- and mitogen-activated protein kinase (MAPK)-related pain, and suggest their applications in pain physiotherapy. [Method] This review focuses on the signal transduction of pain and its mechanisms. [Results] Our reviews show that mechanisms of ET-1- and MAPK-related pain exist. [Conclusions] In this review article, we carefully discuss the signal transduction in ET-1- and MAPK-related pain with reference to pain nanophysiotherapy from the perspective of nanoparticle-associated signal transduction.

β-Adrenoceptors differentially regulate vascular tone and angiogenesis of rat aorta via ERK1/2 and p38

β-Adrenoceptors (β-ARs) modulate ERK1/2 and p38 in different cells, but little is known about the contribution of these signaling pathways to the function of β-ARs in vascular tissue. Immunoblotting analysis of rat aortic rings, primary endothelial (ECs) and smooth muscle cells (SMCs) isolated from aorta showed that β-AR stimulation with isoprenaline activated p38 in aortic rings and in both cultured cell types, whereas it had a dual effect on ERK1/2 phosphorylation, decreasing it in ECs while increasing it in SMCs. These effects were reversed by propranolol, which by itself increased p-ERK1/2 in ECs. Isoprenaline β-AR mediated vasodilation of aortic rings was potentiated by the ERK1/2 inhibitor, U0126, in the presence or absence of endothelium or L-NAME, whereas inhibition of p38 had no impact. Isoprenaline moderately decreased sprouting from aorta rings in the Matrigel angiogenesis assay; conversely propranolol not only prevented isoprenaline inhibition, but stimulated angiogenesis. ERK1/2 inhibition decreased angiogenesis, while a dramatic stimulation was observed by p38 blockade. Our results suggest that ERK1/2 activation after β-ARs stimulation in the smooth muscle hinders the vasodilator effect of isoprenaline, but in the endothelium β-ARs decreases ERK1/2 and increases p38 activity reducing therefore angiogenesis.

Waveform Analysis of the Brachial-ankle Pulse Wave Velocity in Hemiplegic Stroke Patients and Healthy Volunteers: A Pilot Study

[Purpose] Brachial-ankle pulse wave velocity (BaPWV), which has been reported as an index of arterial stiffness, is very closely related to cardiovascular risk factors. A high BaPWV indicates high cardiovascular risk. However, BaPWV and pressure waveforms after stroke are not fully understood. [Methods] BaPWV was measured in thirty-two subjects (twenty-two healthy volunteers and ten stroke patients) while they were in the supine position. It was measured in their bilateral upper and lower extremities. [Results] BaPWV was significantly increased in the stroke group compared with the healthy volunteers. It was also significantly increased on both the affected and non-affected sides of stroke patients in the stroke group. Furthermore, analysis of the pressure waveforms showed that the peak pressure was significantly increased in the stroke group compared with the control group. The peak pressure on both the affected and non-affected sides was also significantly greater than in the control group. However, the rise and decay times were significantly decreased in the stroke group compared with the control group. The rise and decay time on both the affected and non-affected sides were also significantly more decreased than in the control group. [Conclusion] The results demonstrated that increased BaPWV and changed pulse waves are closely associated with the pathologic states of hemiplegic stroke patients.

DJ-1/park7 modulates vasorelaxation and blood pressure via epigenetic modification of endothelial nitric oxide synthase

AIMS

DJ-1/park7, a multifunctional protein, may play essential roles in the vascular system. However, the function of DJ-1/park7 in vascular contractility has remained unclear. The present study was designed to investigate whether the DJ-1/park7 is involved in the regulation of vascular contractility and systolic blood pressure (SBP).

METHODS AND RESULTS

Norepinephrine (NE) elevated contraction in endothelium-intact vessels in a dose-dependent manner, to a greater extent in DJ-1/park7 knockout (DJ-1/park7(-/-)) mice than in wild-type (DJ-1/park7(+/+)) mice. Acetylcholine inhibited NE-evoked contraction in endothelium-intact vessels, and this was markedly impaired in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+). Nitric oxide (NO) production (82.1 ± 2.8% of control) and endothelial NO synthase (eNOS) expression (61.7 ± 8.9%) were lower, but H2O2 production (126.4 ± 8.6%) was higher, in endothelial cells from DJ-1/park7(-/-) mice than in those from DJ-1/park7(+/+) controls; these effects were reversed by DJ-1/park7-overexpressing endothelial cells from DJ-1/park7(-/-) mice. Histone deacetylase (HDAC)-1 recruitment and H3 histone acetylation at the eNOS promoter were elevated and diminished, respectively, in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+) controls. Moreover, SBP was significantly elevated in DJ-1/park7(-/-) mice compared with DJ-1/park7(+/+) controls, but this elevation was inhibited in mice treated with valproic acid, an inhibitor of Class I HDACs including HDAC-1.

CONCLUSION

These results demonstrate that DJ-1/park7 protein may be implicated in the regulation of vascular contractility and blood pressure, probably by the impairment of NO production through H2O2-mediated epigenetic inhibition of eNOS expression.

Involvement of the Tyr kinase/JNK pathway in carbachol-induced bronchial smooth muscle contraction in the rat

BACKGROUND

Tyrosine (Tyr) kinases and mitogen-activated protein kinases have been thought to participate in the contractile response in various smooth muscles. The aim of the current study was to investigate the involvement of the Tyr kinase pathway in the contraction of bronchial smooth muscle.

METHODS

Ring preparations of bronchi isolated from rats were suspended in an organ bath. Isometric contraction of circular smooth muscle was measured. Immunoblotting was used to examine the phosphorylation of c-Jun N-terminal kinasess (JNKs) in bronchial smooth muscle.

RESULTS

To examine the role of mitogen-activated protein kinase(s) in bronchial smooth muscle contraction, the effects of MPAK inhibitors were investigated in this study. The contraction induced by carbachol (CCh) was significantly inhibited by pretreatment with selective Tyr kinase inhibitors (genistein and ST638, n = 6, respectively), and a JNK inhibitor (SP600125, n = 6). The contractions induced by high K depolarization (n = 4), orthovanadate (a potent Tyr phosphatase inhibitor) and sodium fluoride (a G protein activator; NaF) were also significantly inhibited by selective Tyr kinase inhibitors and a JNK inhibitor (n = 4, respectively). However, the contraction induced by calyculin-A was not affected by SP600125. On the other hand, JNKs were phosphorylated by CCh (2.2 ± 0,4 [mean±SEM] fold increase). The JNK phosphorylation induced by CCh was significantly inhibited by SP600125 (n = 4).

CONCLUSION

These findings suggest that the Tyr kinase/JNK pathway may play a role in bronchial smooth muscle contraction. Strategies to inhibit JNK activation may represent a novel therapeutic approach for diseases involving airway obstruction, such as asthma and chronic obstructive pulmonary disease.

Effects of peroxisome proliferator-activated receptor-β activation in endothelin-dependent hypertension

AIMS

We analysed the chronic effects of the peroxisome proliferator-activated receptor β/δ (PPAR-β) agonist GW0742 on the renin-independent hypertension induced by deoxycorticosterone acetate (DOCA)-salt.

METHODS AND RESULTS

Rats were treated for 5 weeks with: control-vehicle, control-GW0742 (5 or 20 mg kg(-1) day(-1)), DOCA-vehicle, DOCA-GW0742 (5 or 20 mg kg(-1) day(-1)), DOCA-GSK0660 (1 mg kg(-1) day(-1)), and DOCA-GSK0660-GW0742. Rats receiving DOCA-vehicle showed increased systolic blood pressure, left ventricular and kidney weight indices, endothelin-1 (ET-1), and malondialdehyde plasma levels, urinary iso-PGF2α excretion, impaired endothelium-dependent relaxation to acetylcholine, and contraction to ET-1 when compared with controls. Aortic reactive oxygen species content, NADPH oxidase activity, and p47(phox), p22(phox), NOX-4, glutathione peroxidase 1, hemeoxygenase-1, and preproET-1 expression were increased, whereas catalase and regulators of G protein-coupled signalling proteins (RGS)5 expression were decreased in the DOCA-vehicle group. GW0742 prevented the development of hypertension in a dose-dependent manner but the reduction of renal and cardiac hypertrophy, systemic and vascular oxidative stress markers, and improvement of endothelial dysfunction were only observed after the higher dose. GW0742, at 20 mg kg(-1) day(-1), attenuated ET-1 contraction by increasing RGS5 expression and restored the intracellular redox balance by reducing NADPH-oxidase activity, and by increasing the antioxidant genes expression. The PPAR-β antagonist GSK0660 prevented all vascular changes induced by GW0742 but not its antihypertensive effects.

CONCLUSION

Vascular protective effects of GW0742 operate via PPAR-β by interference with the ET-1 signalling as a result of increased expression of RGS5 and up-regulation of antioxidant genes and via PPAR-β-independent mechanisms to decrease blood pressure.

DJ-1/park7 protects against neointimal formation via the inhibition of vascular smooth muscle cell growth

AIMS

DJ-1/park7 is a ubiquitously expressed multifunctional protein that plays essential roles in a variety of cells. However, its function in the vascular system has not been determined. We investigated the protective roles of DJ-1/park7 in vascular disorders, especially in neointimal hyperplasia.

METHODS AND RESULTS

DJ-1/park7 was strongly expressed in the neointimal layer, in which its oxidized form was predominant. Treatment of vascular smooth muscle cells (VSMCs) from the mouse aorta with H(2)O(2) increased the oxidation of DJ-1/park7 visualized on two-dimensional electrophoresis gels. The growth of VSMCs in FBS-containing media and the release of H(2)O(2) were significantly increased in DJ-1/park7(-/-) knockout mice compared with DJ-1/park7(+/+) wild-type mice. The expression of cyclin D1 and the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 were greater in VSMCs from the DJ-1/park7(-/-) aorta than from the DJ-1/park7(+/+) aorta. Both of these measures were inhibited by treatment with an ERK1/2 inhibitor or antioxidants and in DJ-1/park7-overexpressing cells. VSMC proliferation, cyclin D1 expression, and ERK1/2 phosphorylation in response to platelet-derived growth factor-BB were upregulated in DJ-1/park7(-/-) compared with DJ-1/park7(+/+) mice. VSMCs of DJ-1/park7(-/-) mice exhibited higher levels of sprout outgrowth of aortic strips and neointimal plaque formation elicited by carotid artery ligation compared with those of DJ-1/park7(+/+) mice.

CONCLUSION

These results indicate that DJ-1/park7 is involved in the growth of VSMCs, thereby inhibiting neointimal hyperplasia, and suggest that it might play protective roles in vascular remodelling.

Pravastatin normalizes ET-1-induced contraction in the aorta of type 2 diabetic OLETF rats by suppressing the KSR1/ERK complex

Endothelin (ET)-1 is a likely candidate for a key role in diabetic vascular complications. In the present study, we hypothesized that treatment with pravastatin (an inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase) would normalize the ET-1-induced contraction in aortas isolated from type 2 diabetic Otsuka Long-Evans Tokushima fatty (OLETF) rats. Contractile responses were examined by measuring isometric force in endothelium-denuded aortic helical strips from four groups: Long-Evans Tokushima Otsuka (LETO; genetic control), OLETF (type 2 diabetic), pravastatin-treated LETO, and pravastatin-treated OLETF rats. Both immunoblot analysis and immunoprecipitation assays were used to examine Src, protein phosphatase (PP)2A, kinase suppressor of Ras (KSR)1, and ERK signaling pathway protein levels and activities. In endothelium-denuded aortas isolated from OLETF rats at the chronic stage of diabetes (56–60 wk) (vs. those from age-matched LETO rats), we found the following: 1) ET-1-induced contraction was enhanced, 2) ERK1/2 phosphorylation was increased, 3) phosphorylations of KSR1 and PP2A were reduced (i.e., enhancement of the kinase active state), 4) ERK1/2-KSR1 complexes were increased, and 5) Src tyrosine kinase activity was diminished. Endothelium-denuded aortas isolated from OLETF rats treated with pravastatin (10 mg/kg po, daily for 4 wk) exhibited normalized ET-1-induced contractions and suppressed ET-1-stimulated ERK phosphorylation, with the associated phosphorylated KSR1 and phosphorylated PP2A levels being increased toward normal levels. These results suggest that in type 2 diabetic rats, pravastatin normalizes ET-1-induced contraction in aortic smooth muscle via a suppression of PP2A/KSR1/ERK activities after an enhancement of Src kinase activity.

Enhanced estradiol-induced vasorelaxation in aortas from type 2 diabetic mice may reflect a compensatory role of p38 MAPK-mediated eNOS activation

Cardiovascular problems are a major cause of morbidity and mortality, mainly due to coronary artery disease and atherosclerosis, in type 2 diabetes mellitus. However, female gender is a protective factor in the development of, for example, atherosclerosis and hypertension. One of the female hormones, 17β-estradiol (E2), is known to protect against the cardiovascular injury resulting from endothelial dysfunction, but the mechanism by which it does so remains unknown. Our hypothesis was that E2-mediated activation of Akt and mitogen-activated protein kinase (MAPK), and the subsequent endothelial NO synthase (eNOS) phosphorylation, might protect the aorta in diabetic mellitus. The experimental type 2 diabetic model we employed to test that hypothesis (female mice given streptozotocin and nicotinamide) is here termed fDM. In fDM aortas, we examined the E2-induced relaxation response and the associated protein activities. In control (age-matched, nondiabetic) aortas, E2 induced a vascular relaxation response that was mediated via Akt/eNOS and mitogen-activated/ERK-activating kinase (MEK)/eNOS pathways. In fDM aortas (vs. control aortas), (a) the E2-induced relaxation was enhanced, (b) the mediation of the response was different (via Akt/eNOS and p38 MAPK/eNOS pathways), and (c) E2 stimulation increased p38 MAPK and eNOS phosphorylations, decreased MEK phosphorylation, but did not alter estrogen receptor activity. We infer that at least in fDM aortas, E2 has beneficial effects (enhanced vascular relaxation and protection) that are mediated through Akt activation and (compensating for reduced MEK activation) p38 MAPK activation, leading to enhanced eNOS phosphorylation.

Rosuvastatin attenuates the elevation in blood pressure induced by overexpression of human C-reactive protein

C-reactive protein (CRP) has been shown to function as an inflammatory factor to induce endothelial dysfunction and hypertension in rats. The anti-inflammatory effects of statins suggest that they may attenuate CRP-induced endothelial dysfunction and hypertension in Sprague-Dawley rats. Male Sprague-Dawley rats were injected with an adeno-associated virus (AAV) to induce overexpression of human CRP (AAV-hCRP) or green fluorescent protein (GFP) control (AAV-GFP). At 2 months after injection, rats were administered rosuvastatin by daily oral gavage (10 mg kg(-1)) for 2 additional months. Rosuvastatin administration attenuated the increased blood pressure and loss of vascular endothelial nitric oxide synthase expression in AAV-hCRP-treated rats, and N-nitro-L-arginine methyl ester blocked its hypotensive effect. Rosuvastatin also activated phosphoinositide 3-kinases/Akt, and inhibited Rho kinase activity in aorta. Rosuvastatin reduced the production of reactive oxygen species through downregulation of nicotinamide adenine dinucleotide phosphate oxidase subunits, p22 phox and gp91 phox, and upregulation of superoxide dismutase 1 expression. Rosuvastatin attenuated the increase in blood pressure in AAV-hCRP-treated rats through endothelial protection and antioxidant effects. Our data reveals a novel mechanism through which statins may lower blood pressure.

c-Jun NH₂-terminal kinase contributes to dexmedetomidine-induced contraction in isolated rat aortic smooth muscle

PURPOSE

Dexmedetomidine, a full agonist of α2B-adrenoceptors, is used for analgesia and sedation in the intensive care units. Dexmedetomidine produces an initial transient hypertension due to the activation of post-junctional α2B-adrenoceptors on vascular smooth muscle cells (SMCs). The aims of this in vitro study were to identify mitogen-activated protein kinase (MAPK) isoforms that are primarily involved in full, α2B-adrenoceptor agonist, dexmedetomidine-induced contraction of isolated rat aortic SMCs.

MATERIALS AND METHODS

Rat thoracic aortic rings without endothelium were isolated and suspended for isometric tension recording. Cumulative dexmedetomidine (10⁻⁹ to 10⁻⁶ M) dose-response curves were generated in the presence or absence of extracellular signal-regulated kinase (ERK) inhibitor PD 98059, p38 MAPK inhibitor SB 203580, c-Jun NH₂-terminal kinase (JNK) inhibitor SP 600125, L-type calcium channel blocker (verapamil and nifedipine), and α₂-adrenoceptor inhibitor atipamezole. Dexmedetomidine-induced phosphorylation of ERK, JNK, and p38 MAPK in rat aortic SMCs was detected using Western blotting.

RESULTS

SP 600125 (10⁻⁶ to 10⁻⁵ M) attenuated dexmedetomidine-evoked contraction in a concentration- dependent manner, whereas PD 98059 had no effect on dexmedetomidine- induced contraction. SB 203580 (10⁻⁵ M) attenuated dexmedetomidine-induced contraction. Dexmedetomidine-evoked contractions were both abolished by atipamezole and attenuated by verapamil and nifedipine. Dexmedetomidine induced phosphorylation of JNK and p38 MAPK in rat aortic SMCs, but did not induce phosphorylation of ERK.

CONCLUSION

Dexmedetomidine-induced contraction involves a JNK- and p38 MAPK-mediated pathway downstream of α₂-adrenoceptor stimulation in rat aortic SMCs. In addition, dexmedetomidine-induced contractions are primarily dependent on calcium influx via L-type calcium channels.

3-morpholinosydnonimine participates in the attenuation of neointima formation via inhibition of annexin A2-mediated vascular smooth muscle cell migration

3-Morpholinosydnonimine (SIN-1) affects vascular smooth muscle cell migration and proliferation, processes essential for atherosclerosis. However, the mechanism by which SIN-1 exerts these effects has not been elucidated. We used 2-DE followed by MALDI-TOF/TOF MS to identify responses in protein expression to SIN-1 in rat aortic smooth muscle. Platelet-derived growth factor-BB increased cell migration and proliferation in rat aortic smooth muscle cells, and subsequent SIN-1 treatment inhibited it. Administration of SIN-1 in vivo attenuated neointima formation in balloon-injured rat carotid arteries. Proteomic analysis showed that glutathione peroxidase and 40S ribosomal protein S12 were differentially expressed in aortic strips exposed to SIN-1. Expression of annexin A2 was decreased by SIN-1. Platelet-derived growth factor-BB-induced cell migration was increased and inhibited in rat aortic smooth muscle cells with overexpression and knockdown of annexin A2 gene, respectively. The expression of annexin A2 was increased in vascular neointima compared with the intact control, which was inhibited by SIN-1 treatment. These results demonstrate that SIN-1 may attenuate vascular neointima formation by inhibiting annexin A2-mediated migration. Therefore, annexin A2 may be a potential target for therapeutic strategies for atherosclerosis.

Melatonin sensitizes human myometrial cells to oxytocin in a protein kinase C alpha/extracellular-signal regulated kinase-dependent manner

CONTEXT

Studies have shown that labor occurs primarily in the night/morning hours. Recently, we identified the human myometrium as a target for melatonin (MEL), the neuroendocrine output signal coding for circadian night.

OBJECTIVE

The purpose of this study was to determine the signaling pathway underlying the effects of MEL on contractility and the contractile machinery in immortalized human myometrial cells.

DESIGN

To ascertain the signaling pathway of MEL leading to its effects on myometrial contractility in vitro, we performed gel retraction assays with cells exposed to iodo-MEL (I-MEL) with or without oxytocin and the Rho kinase inhibitor Y27632. I-MEL effects on inositol trisphosphate (IP(3))/diacylglycerol (DAG)/protein kinase C (PKC) signaling were also investigated. Additionally, we assayed for caldesmon phosphorylation and ERK1/2 activation.

RESULTS

I-MEL was found to activate PKC alpha via the phospholipase C/IP(3)/DAG signaling pathway, which was confirmed by PKC enzyme assay. I-MEL did not affect myosin light chain phosphatase activity, and its effects on contractility were insensitive to Rho kinase inhibition. I-MEL did increase phosphorylation of ERK1/2 and caldesmon, which was inhibited by the MAPK kinase inhibitor PD98059 or the PKC inhibitor C1.

CONCLUSIONS

MEL sensitizes myometrial cells to subsequent procontractile signals in vitro through activation of the phospholipase C/IP(3)/DAG signaling pathway, resulting in specific activation of PKC alpha and ERK1/2, thereby phosphorylating caldesmon, which increases actin availability for myosin binding and cross-bridging. In vivo, this sensitization would provide a mechanism for the increased nocturnal uterine contractility and labor that has been observed in late-term human pregnancy.

Differential coupling of human endothelin type A receptor to G(q/11) and G(12) proteins: the functional significance of receptor expression level in generating multiple receptor signaling

This study examines the influence of receptor expression level on signaling pathways activated via endothelin type A receptor (ET(A)R) expressed in Chinese hamster ovary cells at 32,100 (ET(A)R-high-CHO) and 893 (ET(A)R-low-CHO) fmolmg protein(-1). Endothelin-1 (ET-1) elicited a sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), which was dependent on G(q/11) protein, phospholipase C (PLC), Na(+)/H(+) exchanger (NHE), and p38 mitogen-activated protein kinase (p38MAPK) in ET(A)R-high-CHO, whereas the sustained [Ca(2+)](i) increase was negligible in ET(A)R-low-CHO. Functional study with Cytosensor(TM) microphysiometer showed that ET-1 evoked an NHE1-mediated increase in extracellular acidification rate (ECAR) in ET(A)R-high-CHO and ET(A)R-low-CHO. In ET(A)R-high-CHO, the ECAR response at 30 min after ET-1 stimulation was insensitive to G(q/11) and PLC inhibitors, but sensitive to the p38MAPK inhibitor. In ET(A)R-low-CHO, the ECAR response at 30 min was sensitive to these inhibitors. Western blot analysis demonstrated that ET-1-induced p38MAPK phosphorylation in ET(A)R-low-CHO but not in ET(A)R-high-CHO was mediated via G(q/11) and PLC. The G(q/11)/PLC-independent p38MAPK phosphorylation in ET(A)R-high-CHO was suppressed by expression of the C terminus of G(alpha12) protein to disrupt receptor-G(12) protein coupling. These results provide evidence for multiple signaling pathways of ET(A)R that were activated via at least the G(q/11)/PLC/NHE, G(12)/p38MAPK/NHE, and G(q/11)/PLC/p38MAPK/NHE cascades in an expression level-dependent manner.

Diminished expression of dihydropteridine reductase is a potent biomarker for hypertensive vessels

To identify the new targets for hypertension, we analyzed the protein expression profiles of aortic smooth muscle in spontaneously hypertensive rats (SHR) of various ages during the development of hypertension, as well as in age-matched normotensive Wistar-Kyoto (WKY) rats, using a proteomic analysis. The expressions of seven proteins were altered in SHR compared with WKY rats. Of these proteins, NADH dehydrogenase 1alpha, GSTomega1, peroxi-redoxin I and transgelin were upregulated in SHR compared with WKY rats. On the other hand, the expression of HSP27 and Ran protein decreased in SHR. The diminution of dihydrobiopterin reductase, an enzyme located in the regeneration pathways of tetrahydrobiopterin (BH4), was also prominent in SHR. The results from a PCR analysis revealed that the expression of BH4 biosynthesis enzymes - GTP cyclohydrolase-1 and sepiapterin reductase - decreased and increased, respectively, in SHR compared with WKY rats. The level of BH4 was less in aortic strips from SHR than from WKY rats. Moreover, treatment with BH4 inhibited aortic smooth muscle contraction induced by serotonin. These results suggest that the deficiency in BH4 regeneration produced by diminished dihydrobiopterin reductase expression is involved in vascular disorders in hypertensive rats.

Cordycepin attenuates neointimal formation by inhibiting reactive oxygen species-mediated responses in vascular smooth muscle cells in rats

We determined the action mechanism of cordycepin, a major bioactive component of Cordyceps militaris, on responses of rat aortic smooth muscle cells (RASMCs) and on vascular disorders, especially neointimal formation. Cordycepin inhibited platelet-derived growth factor-BB (PDGF-BB)-induced RASMCs migration and proliferation in a dose-dependent manner. However, pre-treatment with N(omega)-nitro-L-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor, and 1,3-dipropyl-8-sulphophenylxanthine (DPSPX), an A(1)/A(2) adenosine-receptor antagonist, abolished the inhibitory role of cordycepin. Cordycepin suppressed the phosphorylation of p38 mitogen-activated protein kinase (p38 MAPK) and heat shock protein 27 (Hsp27), but not that of extracellular signal-regulated kinase (ERK) 1/2 in RASMCs stimulated by PDGF-BB. The production of reactive oxygen species (ROS), O(2)(-) and H(2)O(2), induced by PDGF-BB was abolished by the treatment of cordycepin. Moreover, the sprout outgrowth of aortic rings by PDGF-BB was inhibited by cordycepin. In vivo neointimal formation evoked by balloon-injury was significantly attenuated by the administration of cordycepin. These results demonstrate that cordycepin may exert inhibitory effects on PDGF-BB-induced migration and proliferation via interfering with adenosine receptor-mediated NOS pathways, thus resulting in the attenuation of neointima formation. In conclusion, cordycepin may be a potent, promising anti-atherosclerosis agent.

Olibanum extract inhibits vascular smooth muscle cell migration and proliferation in response to platelet-derived growth factor

Olibanum (Boswellia serrata) has been shown to have anti-inflammatory, anti-arthritic and anti-cancer effects. This study determined the role of a water extract of olibanum in platelet-derived growth factor (PDGF)-stimulated proliferation and migration of rat aortic smooth muscle cells (RASMCs). PDGF-BB induced the migration and proliferation of RASMCs that were inhibited by olibanum extract in a dose-dependent manner. The PDGF-BB-increased phosphorylation of p38 mitogen-activated protein kinase (MAPK); the heat shock protein (Hsp) 27 was significantly inhibited by the olibanum extract. The effects of PDGF-BB-induced extracellular signal-regulated kinase1/2 was not altered by the olibanum extract. Treatment with olibanum extract inhibited PDGF-BB-stimulated sprout out growth of aortic rings. These results suggest that the water extract of olibanum inhibits PDGF-BB-stimulated migration and proliferation in RASMCs as well as sprout out growth, which may be mediated by the inhibition of the p38 MAPK and Hsp27 pathways.

Fibrinogen-induced endothelin-1 production from endothelial cells

We previously demonstrated that fibrinogen (Fg) binding to the vascular endothelial intercellular adhesion molecule-1 (ICAM-1) leads to microvascular constriction in vivo and in vitro. Although a role of endothelin-1 (ET-1) in this Fg-induced vasoconstriction was suggested, the mechanism of action was not clear. In the current study, we tested the hypothesis that Fg-induced vasoconstriction results from ET-1 production by vascular endothelial cells (EC) and is mediated by activation of extracellular signal-regulated kinase -1/2 (ERK-1/2). Confluent, rat heart microvascular endothelial cells (RHMECs) were treated with one of the following: Fg (2 or 4 mg/ml), Fg (4 mg/ml) with ERK-1/2 kinase inhibitors (PD-98059 or U-0126), Fg (4 mg/ml) with an antibody against ICAM-1, or medium alone for 45 min. The amount of ET-1 formed and the concentration of released von Willebrand factor (vWF) in the cell culture medium were measured by ELISAs. Fg-induced exocytosis of Weibel-Palade bodies (WPBs) was assessed by immunocytochemistry. Phosphorylation of ERK-1/2 was detected by Western blot analysis. Fg caused a dose-dependent increase in ET-1 formation and release of vWF from the RHMECs. This Fg-induced increase in ET-1 production was inhibited by specific ERK-1/2 kinase inhibitors and by anti-ICAM-1 antibody. Immunocytochemical staining showed that an increase in Fg concentration enhanced exocytosis of WPBs in ECs. A specific endothelin type B receptor blocker, BQ-788, attenuated the enhanced phosphorylation of ERK-1/2 in ECs caused by increased Fg content in the culture medium. The presence of an endothelin converting enzyme inhibitor, SM-19712, slightly decreased Fg-induced phosphorylation of ERK-1/2, but inhibited production of Fg-induced ET-1 production. These results suggest that Fg-induced vasoconstriction may be mediated, in part, by activation of ERK-1/2 signaling and increased production of ET-1 that further increases EC ERK-1/2 signaling. Thus, an increased content of Fg may enhance vasoconstriction through increased production of ET-1.

Diabetic state, high plasma insulin and angiotensin II combine to augment endothelin-1-induced vasoconstriction via ETA receptors and ERK

BACKGROUND AND PURPOSE

Mechanisms associated with the enhanced contractile response to endothelin-1 in hyperinsulinaemic diabetes have been examined using the rat aorta. Functions for angiotensin II, endothelin-1 receptor expression and extracellular signal-regulated kinase (ERK) have been investigated.

EXPERIMENTAL APPROACH

Streptozotocin-induced diabetic rats were infused with angiotensin II or, following insulin treatment, were treated with losartan, an angiotensin II receptor antagonist. Contractions of aortic strips with or without endothelium, in response to endothelin-1 and angiotensin II, were examined in vitro. Aortic ET(A) receptors and ERK/MEK expression were measured by western blotting.

KEY RESULTS

Insulin-treated diabetic rats exhibited increases in plasma insulin, angiotensin II and endothelin-1. The systolic blood pressure and endothelin-1-induced contractile responses in aortae in vitro were enhanced in insulin-treated diabetic rats and blunted by chronic losartan administration. LY294002 (phosphatidylinositol 3-kinase inhibitor) and/or PD98059 (MEK inhibitor) diminished the enhanced contractile response to endothelin-1 in aortae from insulin-treated diabetic rats. ET(A) and ET(B) receptors, ERK-1/2 and MEK-1/2 protein expression and endothelin-1-stimulated ERK phosphorylation were all increased in aortae from insulin-treated diabetic rats. Such increases were blunted by chronic losartan administration. Endothelin-1-induced contraction was significantly higher in aortae from angiotensin II-infused diabetic rats. angiotensin II-infusion increased ERK phosphorylation, but the expression of endothelin receptors and ERK/MEK proteins remained unchanged.

CONCLUSIONS AND IMPLICATIONS

These results suggest that the combination of high plasma angiotensin II and insulin with a diabetic state induced enhancement of endothelin-1-induced vasoconstriction, ET(A) receptor expression and ERK expression/activity in the aorta. Losartan improved both the diabetes-related abnormalities and the diabetic hypertension.

Soluble form of vascular cell adhesion molecule 1 induces migration and proliferation of vascular smooth muscle cells

BACKGROUND

Serum levels of soluble vascular cell adhesion molecule 1 (sVCAM-1) shed from its membrane-bound form are elevated in hypertension. This study clarified the effects of sVCAM-1 on vascular responses in rat aortic smooth muscle cells (RASMCs).

METHODS

Boyden chamber, 5-bromo-2'-deoxyuridine incorporation and ex vivo aortic ring assays for migration and proliferation, and Western blot for the kinase activity were used.

RESULTS

Spontaneously hypertensive rats (SHR) and Wistar Kyoto (WKY) rats were compared functionally. sVCAM-1 increased RASMC migration and proliferation, which were greater in SHR compared with WKY rats. RASMCs expressed the very late antigen 4alpha receptor integrin with no difference between SHR and WKY rats. Inhibitors of phosphoinositide kinase 3 (PI3K) and spleen tyrosine kinase (Syk) and small interference RNA-Syk abolished the sVCAM-1-induced migration, proliferation and phosphorylation of focal adhesion kinase. The phosphorylation of Syk was significantly greater in RASMCs from SHR than from WKY rats. sVCAM-1 increased aortic sprout outgrowth, which was inhibited by inhibitors of PI3K and Syk.

CONCLUSIONS

This study suggests that sVCAM-1 promotes the RASMC migration and proliferation via the focal adhesion kinase pathway regulated by Syk and PI3K, and the altered sVCAM-1-induced responses during hypertension are closely associated with the increments in intracellular signal transmission.

p38 mitogen-activated protein kinase contributes to angiotensin II-stimulated migration of rat aortic smooth muscle cells

In this study, we clarified the intracellular mechanism of angiotensin II (Ang II) in promoting migration in rat aortic smooth muscle cells (RASMCs). RASMC migration was measured with the Boyden chamber assay, and the result was confirmed with an aortic sprout assay. The activities of kinases were investigated by western blot analysis. Ang II enhanced RASMC migration, which was chemotaxis directed, and induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK1/2), and heat shock protein 27 (Hsp27). Ang II-enhanced cell migration was inhibited by SB203580 (a p38 MAPK inhibitor) and piceatannol (a spleen tyrosine kinase inhibitor), but only partially by PD98059 (an ERK inhibitor) and PP2 (a Src inhibitor). The Ang II-stimulated phosphorylation of p38 MAPK and Hsp27 in RASMCs was inhibited by piceatannol and SB203580. The phosphorylation of ERK1/2 stimulated by Ang II was suppressed by PD98059, piceatannol, and PP2. Ang II increased the sprout outgrowth from aortic rings and this response was attenuated by pretreatment with SB203580, PD98059, PP2, or piceatannol. These results suggest that p38 MAPK contributes to the regulation of the Ang II-induced chemotactic migration of vascular smooth muscle cells, which is mediated by Hsp27 phosphorylation.

Transforming Growth Factor-β1 Impairs Endothelin-1-Mediated Contraction of Brain Vessels by Inducing Mitogen-Activated Protein (MAP) Kinase Phosphatase-1 and Inhibiting p38 MAP Kinase

Brain levels of transforming growth factor-beta1 (TGF-beta1) are increased in Alzheimer's disease and have been implicated in the associated cerebrovascular pathology. We recently reported that transgenic mice that overexpress TGF-beta1 (TGF+ mice) display, with aging, selectively reduced endothelin-1 (ET-1)-mediated contractions. Because ET-1 is a key regulator of cerebrovascular tone and homeostasis, we investigated how increased levels of TGF-beta1 could selectively alter this contractile response. We found that ETA receptors, via activation of p38 mitogen-activated protein (MAP) kinase, mediate the ET-1-induced contraction in mouse cerebral arteries, a response significantly decreased in aged TGF+ mice (-39%; p < 0.01) despite unaltered ETA receptor levels or affinity. In cerebrovascular smooth muscle cell cultures, long-term treatment with TGF-beta1 significantly decreased (>50%; p < 0.05) the ET-1-induced activation of the p38 MAPK/27-kDa heat shock protein (HSP27) signaling pathway. This occurred with no effect upstream to p38 MAP kinase but with the concomitant induction of mitogen-activated protein kinase phosphatase-1 (MKP-1) expression. Inhibition of MKP-1 expression with Ro-31-8220 or suppression of MKP-1 expression by short interfering RNA restored the ET-1-mediated p38 MAP kinase response. These results disclose a new role for long-term increases of TGF-beta1 in modulating cerebrovascular tone by dampening ET-1-mediated activation of the p38 MAPK/HSP27 signaling pathway. Such changes in ET-1-mediated signaling may help maintain vascular wall homeostasis by compensating for the diminished dilatory function induced by TGF-beta1 and amyloid-beta; brain levels of these two molecules are increased in patients with Alzheimer's disease.

Enhancement of receptor-operated cation current and TRPC6 expression in arterial smooth muscle cells of deoxycorticosterone acetate-salt hypertensive rats

OBJECTIVES

In deoxycorticosterone acetate (DOCA)-salt hypertensive rats, altered reactivity of blood vessels to vasoactive agonists is frequently associated with an elevation in blood pressure. Canonical transient receptor potential (TRPC) channels are believed to encode receptor-operated cation channels (ROC), the activation of which is involved in smooth muscle depolarization and vasoconstriction. The aims of the present study were to investigate whether the ROC current is increased in DOCA-hypertensive rats and determine whether aldosterone directly enhances the expression of TRPC.

METHODS

The nystatin-perforated patch-clamp technique was used for the recording of receptor-stimulated ion currents in mesenteric arterial smooth muscle cells, which were enzymatically dispersed from sham-operated and DOCA-salt hypertensive rats. Expressions of TRPCs were evaluated by reverse transcriptase-polymerase chain reaction (RT-PCR) and by Western blot analysis.

RESULTS

Receptor-stimulated currents activated by 5-hydroxytryptamine (serotonin) and norepinephrine were increased significantly in the mesenteric arterial smooth muscle cells of DOCA-salt hypertensive rats compared to sham-operated rats. Ion-substitution experiments revealed that the enhanced currents were cation currents (ROC currents). Enhanced expression of TRPC6 in mesenteric arteries from DOCA-salt hypertensive rats was demonstrated by real-time RT-PCR. Up-regulation of TRPC6 by aldosterone treatment in vitro was also observed in A7r5 cells by RT-PCR and in western blots.

CONCLUSION

These results suggest that aldosterone enhances TRPC6 expression and ROC currents in vascular smooth muscle cells, and that this may in turn contribute to altered vascular reactivity and to hypertension.

Schistosoma mansoni infection enhances host portal vein contraction: role of potassium channels and p38 MAP kinase

Murine Schistosoma mansoni infection is related to an increased contraction of portal vein in response to 5-hydroxytryptamine (5-HT). The present study addressed a putative alteration of ion channels and enzymes involved in vascular contraction. In control group, either inhibition of K+ channels sensitive to ATP (K(ATP)) or Ca2+ (BK(Ca)) increased 5-HT-induced contraction, but the same did not occur in infected mice. On the other hand, inhibition of p38 MAP kinase markedly decreased the vascular contraction to 5-HT in the infected mice with minor effects in the control group. Accordingly, we observed a higher density of phospho-p38 MAP kinase, that refers to the fully active state of the enzyme, in portal veins from infected mice as compared to control animals. These results suggest that the reduced function of K(ATP) and BK(Ca) channels along with an increased contribution of p38 MAP kinase contribute to the increased contraction of portal veins to 5-HT observed in murine schistosomiasis.

Analysis of peroxiredoxin decreasing oxidative stress in hypertensive aortic smooth muscle

To determine the role of peroxiredoxin (Prx) in response to oxidative stress and during hypertension in the vasculature, we identified Prx proteins and analyzed their antioxidant effects. Rat aortic smooth muscle contains all six Prxs (I-VI). Prx I, II, and VI shifted to its acidic site on two-dimensional polyacrylamide gel electrophoresis after exposure to H(2)O(2). The total expression of Prx I and VI was increased in response to H(2)O(2). The expression of Prx I, but not that of Prx II and VI, increases and the acidic form of Prx I and the sulfonic acid form of Prx (SO(3)H-Prx) are more strongly expressed in the aortic smooth muscle of hypertensive rats than in that of normotensive control rats. Prxs were also found in the mesenteric artery, heart, and kidney. The expression levels of Prx I and VI were increased in mesenteric artery, but not heart and kidney, from hypertensive rats compared with that from normotensive rats. These results suggest that Prxs play a crucial role against oxidative stress in vascular smooth muscles during hypertension.

Spleen tyrosine kinase participates in src-mediated migration and proliferation by PDGF-BB in rat aortic smooth muscle cells

Tyrosine kinases, Src and spleen tyrosine kinase (Syk), play crucial roles in cell responses to platelet-derived growth factor (PDGF) and may have their functional interactions. In this study, we focused on investigating the roles of Syk in the regulation of Src signaling in PDGF-mediated vascular cell responses. Migration, proliferation, and activity of kinases were determined in rat aortic smooth muscle cells (RASMCs). PDGF-BB (10 ng/mL) induced the migration and proliferation of RASMCs, which were significantly inhibited by PP2 (10 microM) and piceatannol (30 microM), inhibitors of Src and Syk, respectively. The phosphorylation of Syk induced by PDGF-BB was abolished by PP2. PDGF-BB increased the co-association of the PDGFbeta-receptor and the kinases, Src or Syk, and its maximal binding to Src was achieved in a shorter time than that to Syk. PDGF-BB stimulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) 1/2, which was inhibited by PP2 and piceatannol. PDGF-BB-induced proliferation and migration were inhibited by SB203580 (30 microM) and PD98059 (30 microM), inhibitors of p38 MAPK and ERK1/2, respectively. These results imply that Syk is regulated by Src kinase, which participates in migration and proliferation in response to PDGF-BB in RASMCs.

Proteomic profiling and identification of cofilin responding to oxidative stress in vascular smooth muscle

We used 2-DE and MALDI-TOF/TOF to identify proteins of vascular smooth muscle cells whose expression was or was not altered by exposure to 500 microM H2O2 for 30 min. We detected more than 800 proteins on silver-stained gels of whole protein extracts from rat aortic smooth muscle strips. Of these proteins, 135 clearly unaffected and 19 having levels altered by exposure to H2O2 were identified. Protein characterization revealed that the most prominent vascular smooth muscle proteins were those with antioxidant, cytoskeletal structure, or muscle contraction. In addition, cofilin, an isoform of the actin depolymerizing factor family, shifted to its basic site on the 2-DE gel as a result of H2O2 treatment. In Western blot analysis of proteins from A7r5 aortic smooth muscle cells, the phosphorylation, but not the expression, of cofilin was decreased by H2O2 in a dose-dependent manner. The H2O2-induced dephosphorylation of cofilin and apoptosis was inhibited by Na3VO4, an inhibitor of protein tyrosine phosphatase (PTP). These results suggest that cofilin is one of the proteins regulated by H2O2 treatment in vascular smooth muscle, and has an important role in the induction of vascular apoptosis through PTP-dependent mechanisms.

Serotonin-induced ion channel modulations in mesenteric artery myocytes from normotensive and DOCA-salt hypertensive rats

Although serotonin (5-hydroxytryptamine, 5-HT) has been found to be a potent vasoconstrictor, a pivotal role of 5-HT in the control of appetite and mood control by the modulation of neuronal synapse has also been proposed. Selective 5-HT reuptake inhibitors (SSRIs) are frequently used to suppress appetite and treat depressive disorder, and the target protein of SSRIs is the 5-HT transporter (5-HTT) in the neuronal synapse. However, SSRIs may increase the free 5-HT concentration in circulating blood because platelets and vascular smooth muscles express functional 5-HTT. In addition, enhanced vasoactive action of 5-HT and alterations in 5-HT receptor subtypes have been reported in some types of hypertension. Therefore, we can infer that the use of drugs such as SSRIs in some hypertensive patients is potentially risky. Altered functional expression of ion channels in vascular smooth muscle is suggested to be a mechanism for the enhanced vasoconstriction by vasoactive agonists, including 5-HT. In this brief review, we compared the electrophysiological properties of mesenteric artery myocytes and their modulation by 5-HT between sham-operated control and deoxycorticosterone acetate (DOCA)-salt hypertensive rats.

Endothelin-1 Induces Contraction via a Syk-Mediated p38 Mitogen-Activated Protein Kinase Pathway in Rat Aortic Smooth Muscle

Although spleen tyrosine kinase (Syk) has crucial roles in various cells, its function on vascular smooth muscle contraction has not been determined. In the present study, we performed experiments to determine if Syk contributes to the endothelin-1 (ET-1)-mediated contraction in rat aortic smooth muscle. ET-1-induced contraction of aortic strips was inhibited by piceatannol, PD98059, and SB203580, inhibitors of Syk, extracellular signal-regulated kinase 1/2 (ERK1/2), and p38 mitogen-activated protein kinase (MAPK), respectively. Piceatannol also attenuated high K(+)-induced contraction. ET-1 dose-dependently enhanced the activity of Syk and this was inhibited by piceatannol in both rat aortic strip and rat aortic smooth muscle cells. The phosphorylation of p38 MAPK and heat shock protein 27 (HSP27), but not that of ERK1/2, in response to ET-1 was inhibited by both piceatannol and SB203580. These results suggest that Syk may play an important role in the regulation of aortic smooth muscle contraction induced by ET-1, which may be mediated by the p38 MAPK/HSP27 signaling pathway.

Phorbol ester-induced contraction through p38 mitogen-activated protein kinase is diminished in aortas from DOCA-salt hypertensive rats

The role of mitogen-activated protein kinase (MAPK) in the decreased contractile response to phorbol ester in aortic smooth muscle strips from deoxycorticosterone acetate (DOCA)-salt hypertensive rats was examined. Norepinephrine (NE) evoked greater contractility in aortic strips from DOCA rats than in those of sham-operated rats. 12-Deoxyphorbol 13-isobutyrate (DPB) induced contraction in Ca2+-free medium, which was diminished in strips from DOCA rats compared to sham-operated rats. Vasoconstrictions induced by these stimulants were inhibited by SB203580 and PD098059, inhibitors of p38 MAPK and extracellular signal-regulated kinase (ERK) 1/2, respectively, in both strips. The phosphorylation of p38 MAPK and ERK1/2 induced by NE was greater in strips from DOCA rats compared to those from sham-operated rats, and this phosphorylation was inhibited by the kinase inhibitors. DPB increased the phosphorylation of p38 MAPK and ERK1/2 in strips from both animals, and the increment of p38 MAPK phosphorylation by the stimulant was diminished in strips from DOCA rats compared to sham-operated rats. These findings suggest that the Ca2+-independent contraction evoked by DPB results from the activation of MAPKs in rat aortic smooth muscle and that the attenuated contractility by DPB in DOCA rat appears to be associated with diminished p38 MAPK activity.

Adenosine restores angiotensin II-induced contractions by receptor-independent enhancement of calcium sensitivity in renal arterioles

Adenosine is coupled to energy metabolism and regulates tissue blood flow by modulating vascular resistance. In this study, we investigated isolated, perfused afferent arterioles of mice, which were subjected to desensitization during repeated applications of angiotensin II. Exogenously applied adenosine restores angiotensin II-induced contractions by increasing calcium sensitivity of the arterioles, along with augmented phosphorylation of the regulatory unit of the myosin light chain. Adenosine restores angiotensin II-induced contractions via intracellular action, because inhibition of adenosine receptors do not prevent restoration, but inhibition of NBTI sensitive adenosine transporters does. Restoration was prevented by inhibition of Rho-kinase, protein kinase C, and the p38 mitogen-activated protein kinase, which modulate myosin light chain phosphorylation and thus calcium sensitivity in the smooth muscle. Furthermore, adenosine application increased the intracellular ATP concentration in LuciHEK cells. The results of the study suggest that restoration of the angiotensin II-induced contraction by adenosine is attributable to the increase of the calcium sensitivity by phosphorylation of the myosin light chain. This can be an important component of vascular control during ischemic and hypoxic conditions. Additionally, this mechanism may contribute to the mediation of the tubuloglomerular feedback by adenosine in the juxtaglomerular apparatus of the kidney.

Serotonin depolarizes the membrane potential in rat mesenteric artery myocytes by decreasing voltage-gated K+ currents

We hypothesized that voltage-gated K+ (Kv) currents regulate the resting membrane potential (Em), and that serotonin (5-HT) causes Em depolarization by reducing Kv currents in rat mesenteric artery smooth muscle cells (MASMCs). The resting Em was about -40 mV in the nystatin-perforated patch configuration, and the inhibition of Kv currents by 4-aminopyridine caused marked Em depolarization. The inhibition of Ca2+-activated K+ (KCa) currents had no effect on Em. 5-HT (1 microM) depolarized Em by approximately 11 mV and reduced the Kv currents to approximately 63% of the control at -20 mV. Similar 5-HT effects were observed with the conventional whole-cell configuration with a weak Ca2+ buffer in the pipette solution, but not with a strong Ca2+ buffer. In the presence of tetraethylammonium (1mM), 5-HT caused Em depolarization similar to the control condition. These results indicate that the resting Em is largely under the regulation of Kv currents in rat MASMCs, and that 5-HT depolarizes Em by reducing Kv currents in a [Ca2+]i-dependent manner.