Rho kinase and protein kinase C involvement in vascular smooth muscle myofilament calcium sensitization in arteries from diabetic rats

Asymmetric Dimethylarginine Enables Depolarizing Spikes and Vasospasm in Mesenteric and Coronary Resistance Arteries

BACKGROUND

Increased vasoreactivity due to reduced endothelial NO bioavailability is an underlying feature of cardiovascular disease, including hypertension. In small resistance arteries, declining NO enhances vascular smooth muscle (VSM) reactivity partly by enabling rapid depolarizing Ca2+-based spikes that underlie vasospasm. The endogenous NO synthase inhibitor asymmetric dimethylarginine (ADMA) is metabolized by DDAH1 (dimethylarginine dimethylaminohydrolase 1) and elevated in cardiovascular disease. We hypothesized ADMA might enable VSM spikes and vasospasm by reducing NO bioavailability, which is opposed by DDAH1 activity and L-arginine.

METHODS

Rat isolated small mesenteric arteries and myogenic rat-isolated intraseptal coronary arteries (RCA) were studied using myography, VSM intracellular recording, Ca2+ imaging, and DDAH1 immunolabeling. Exogenous ADMA was used to inhibit NO synthase and a selective DDAH1 inhibitor, NG-(2-methoxyethyl) arginine, to assess the functional impact of ADMA metabolism.

RESULTS

ADMA enhanced rat-isolated small mesenteric arteries vasoreactivity to the α1-adrenoceptor agonist, phenylephrine by enabling T-type voltage-gated calcium channel-dependent depolarizing spikes. However, some endothelium-dependent NO-vasorelaxation remained, which was sensitive to DDAH1-inhibition with NG-(2-methoxyethyl) arginine. In myogenically active RCA, ADMA alone stimulated depolarizing Ca2+ spikes and marked vasoconstriction, while NO vasorelaxation was abolished. DDAH1 expression was greater in rat-isolated small mesenteric arteries endothelium compared with RCA, but low in VSM of both arteries. L-arginine prevented depolarizing spikes and protected NO-vasorelaxation in rat-isolated small mesenteric artery and RCA.

CONCLUSIONS

ADMA increases VSM electrical excitability enhancing vasoreactivity. Endothelial DDAH1 reduces this effect, and low levels of DDAH1 in RCAs may render them susceptible to endothelial dysfunction contributing to vasospasm, changes opposed by L-arginine.

Diabetic vascular diseases: molecular mechanisms and therapeutic strategies

Vascular complications of diabetes pose a severe threat to human health. Prevention and treatment protocols based on a single vascular complication are no longer suitable for the long-term management of patients with diabetes. Diabetic panvascular disease (DPD) is a clinical syndrome in which vessels of various sizes, including macrovessels and microvessels in the cardiac, cerebral, renal, ophthalmic, and peripheral systems of patients with diabetes, develop atherosclerosis as a common pathology. Pathological manifestations of DPDs usually manifest macrovascular atherosclerosis, as well as microvascular endothelial function impairment, basement membrane thickening, and microthrombosis. Cardiac, cerebral, and peripheral microangiopathy coexist with microangiopathy, while renal and retinal are predominantly microangiopathic. The following associations exist between DPDs: numerous similar molecular mechanisms, and risk-predictive relationships between diseases. Aggressive glycemic control combined with early comprehensive vascular intervention is the key to prevention and treatment. In addition to the widely recommended metformin, glucagon-like peptide-1 agonist, and sodium-glucose cotransporter-2 inhibitors, for the latest molecular mechanisms, aldose reductase inhibitors, peroxisome proliferator-activated receptor-γ agonizts, glucokinases agonizts, mitochondrial energy modulators, etc. are under active development. DPDs are proposed for patients to obtain more systematic clinical care requires a comprehensive diabetes care center focusing on panvascular diseases. This would leverage the advantages of a cross-disciplinary approach to achieve better integration of the pathogenesis and therapeutic evidence. Such a strategy would confer more clinical benefits to patients and promote the comprehensive development of DPD as a discipline.

Oxidative Regulation of Vascular Cav1.2 Channels Triggers Vascular Dysfunction in Hypertension-Related Disorders

Blood pressure is determined by cardiac output and peripheral vascular resistance. The L-type voltage-gated Ca²⁺ (Ca_v1.2) channel in small arteries and arterioles plays an essential role in regulating Ca²⁺ influx, vascular resistance, and blood pressure. Hypertension and preeclampsia are characterized by high blood pressure. In addition, diabetes has a high prevalence of hypertension. The etiology of these disorders remains elusive, involving the complex interplay of environmental and genetic factors. Common to these disorders are oxidative stress and vascular dysfunction. Reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria are primary sources of vascular oxidative stress, whereas dysfunction of the Ca_v1.2 channel confers increased vascular resistance in hypertension. This review will discuss the importance of ROS derived from NOXs and mitochondria in regulating vascular Ca_v1.2 and potential roles of ROS-mediated Ca_v1.2 dysfunction in aberrant vascular function in hypertension, diabetes, and preeclampsia.

Regulation of myosin light-chain phosphorylation and its roles in cardiovascular physiology and pathophysiology

The regulation of muscle contraction is a critical function in the cardiovascular system, and abnormalities may be life-threatening or cause illness. The common basic mechanism in muscle contraction is the interaction between the protein filaments myosin and actin. Although this interaction is primarily regulated by intracellular Ca²⁺, the primary targets and intracellular signaling pathways differ in vascular smooth muscle and cardiac muscle. Phosphorylation of the myosin regulatory light chain (RLC) is a primary molecular switch for smooth muscle contraction. The equilibrium between phosphorylated and unphosphorylated RLC is dynamically achieved through two enzymes, myosin light chain kinase, a Ca²⁺-dependent enzyme, and myosin phosphatase, which modifies the Ca²⁺ sensitivity of contractions. In cardiac muscle, the primary target protein for Ca²⁺ is troponin C on thin filaments; however, RLC phosphorylation also plays a modulatory role in contraction. This review summarizes recent advances in our understanding of the regulation, physiological function, and pathophysiological involvement of RLC phosphorylation in smooth and cardiac muscles.

Signalling pathway of U46619-induced vascular smooth muscle contraction in mouse coronary artery

BACKGROUND

Thromboxane A₂ (TXA₂ ) participates in many pathophysiological processes of coronary artery disease. However, its mechanism of TXA₂ -induced contraction in the coronary artery remains to be clarified. A multi myograph system was used to measure the isometric tension of the mouse coronary arteries and identify the effect and pathway of TXA₂ analogues U46619. Confocal laser scanning microscopy was used to measure the intracellular calcium concentration ([Ca²⁺ ]_i ) in mouse coronary artery smooth muscle cells. Results from the experiment had shown that contraction in coronary artery was generated by U46619 in a concentration-dependent manner, which was completely abolished by a specific TXA₂ receptor blocker, GR32191. PI-PLC inhibitors U73122 and D609 and Rho-Kinase inhibitor Y-27632 can block the U46619 elicited coronary artery contraction in a dose-dependent manner. Then, the vasoconstriction response to U46619 was obviously inhibited by two pan-PKC inhibitors chelerythrine or Gӧ6983, and a selective PKCδ inhibitor rottlerin, but was not blocked by a selective PKCζ inhibitor PKC-PS or a selective PKCβ inhibitor hispidin. Meanwhile, the PKC activator PDBu-induced vasoconstriction was significantly inhibited by 1 μmol/L nifedipine, then mostly inhibited by 100 μmol/L 2-APB and 10 μmol/L Y27632. We further found that the response to U46619 was inhibited, respectively, by three calcium channel blockers nifedipine, SKF96356 or 2-APB in a concentration-dependent manner. Although Store-operated Ca²⁺ (SOC) channels generated the increase of [Ca²⁺ ]_i in mouse coronary artery smooth muscle cells, SOC channels did not contribute to the vasoconstriction in mouse coronary arteries. Caffeine-induced sarcoplasmic reticulum (SR) Ca²⁺ release could obviously induce coronal vasoconstriction. In addition, NPPB, a cell membrane Ca²⁺ activated C1^- channel blocker, could obviously inhibit the U46619-induced vasoconstriction. The U46619-induced mouse coronary artery contraction was involved in the increase in [Ca²⁺ ]_i mediated by Cav1.2, TRPC channels and SR release through the activation of G-protein-coupled TP receptors and the kinases signalling pathway in TP downstream proteins, while SOC channels did not participate in the vasoconstriction.

Cellular and molecular effects of hyperglycemia on ion channels in vascular smooth muscle

Diabetes affects millions of people worldwide. This devastating disease dramatically increases the risk of developing cardiovascular disorders. A hallmark metabolic abnormality in diabetes is hyperglycemia, which contributes to the pathogenesis of cardiovascular complications. These cardiovascular complications are, at least in part, related to hyperglycemia-induced molecular and cellular changes in the cells making up blood vessels. Whereas the mechanisms mediating endothelial dysfunction during hyperglycemia have been extensively examined, much less is known about how hyperglycemia impacts vascular smooth muscle function. Vascular smooth muscle function is exquisitely regulated by many ion channels, including several members of the potassium (K+) channel superfamily and voltage-gated L-type Ca2+ channels. Modulation of vascular smooth muscle ion channels function by hyperglycemia is emerging as a key contributor to vascular dysfunction in diabetes. In this review, we summarize the current understanding of how diabetic hyperglycemia modulates the activity of these ion channels in vascular smooth muscle. We examine underlying mechanisms, general properties, and physiological relevance in the context of myogenic tone and vascular reactivity.

The ginsenoside metabolite compound K stimulates glucagon-like peptide-1 secretion in NCI-H716 cells by regulating the RhoA/ROCKs/YAP signaling pathway and cytoskeleton formation

Ginsenoside Rb1 has been shown to have antidiabetic and anti-inflammatory effects. Its major metabolite, compound K (CK), can stimulate the secretion of glucagon-like peptide-1 (GLP1), a gastrointestinal hormone that plays a vital role in regulating glucose metabolism. However, the mechanism underlying the regulation of GLP1 secretion by compound K has not been fully explored. This study was designed to investigate whether CK ameliorates incretin impairment by regulating the RhoA/ROCKs/YAP signaling pathway and cytoskeleton formation in NCI-H716 cells. Using NCI-H716 cells as a model cell line for GLP1 secretion, we analyzed the effect of CK on the expression of RhoA/ROCK/YAP pathway components. Our results suggest that the effect of CK on GLP1 secretion depends on the anti-inflammatory effect of CK. We also demonstrated that CK can affect the RhoA/ROCK/YAP pathway, which is downstream of transforming growth factor β1 (TGFβ1), by maintaining the capacity of intestinal differentiation. In addition, this effect was mediated by regulating F/G-actin dynamics. These results provide not only the mechanistic insight for the effect of CK on intestinal L cells but also the molecular basis for the further development of CK as a potential therapeutic agent to treat type 2 diabetes mellitus (T2D).

Conceptualizing Conduction as a Pliant Vasomotor response: Impact of Ca2+ fluxes and Ca2+ Sensitization

Coordinating blood flow to active tissue requires vasomotor responses to conduct among resistance arteries. Vasomotor spread is governed by the electrical and mechanical properties of vessels; the latter being linked to the sigmoid relations between membrane potential (VM), [Ca2+], and smooth muscle contractility. Proteins guiding electrical-to-tone translation are subject to regulation; thus, vasomotor conduction could be viewed as "pliant" to the current regulatory state. Using simple in silico approaches, we explored vasomotor pliancy and how the regulation of contractility impacts conduction along a skeletal muscle artery and a branching cerebrovascular network. Initial simulations revealed how limited electromechanical linearity affects the translation of electrical spread into arterial tone. Subtle changes to the VM-[Ca2+] or [Ca2+]-diameter relationship, akin to regulatory alterations in Ca2+ influx and Ca2+ sensitivity, modified the distance and amplitude of the conducted vasomotor response. Simultaneous changes to both relationships, consistent with agonist stimulation, augmented conduction although the effect varied with stimulus strength and polarity (depolarization vs hyperpolarization). Final simulations using our cerebrovascular network revealed how localized changes to the VM-[Ca2+] or [Ca2+]-diameter relationships could regionally shape conduction without interfering with the electrical spread. We conclude that regulatory changes to key effector proteins (e.g. L-type Ca2+ channels, myosin light chain phosphatase), integral to voltage translation, not only impact conducted vasomotor tone but likely blood flow delivery to active tissues.

NO-Releasing Nanoparticles Ameliorate Detrusor Overactivity in Transgenic Sickle Cell Mice via Restored NO/ROCK Signaling

Sickle cell disease (SCD) is associated with overactive bladder (OAB). Detrusor overactivity, a component of OAB, is present in an SCD mouse, but the molecular mechanisms for this condition are not well-defined. We hypothesize that nitric oxide (NO)/ ras homolog gene family (Rho) A/Rho-associated kinase (ROCK) dysregulation is a mechanism for detrusor overactivity and that NO-releasing nanoparticles (NO-nps), a novel NO delivery system, may serve to treat this condition. Male adult SCD transgenic, combined endothelial NO synthases (eNOSs) and neuronal NOS (nNOS) gene-deficient (dNOS^-/-), and wild-type (WT) mice were used. Empty nanoparticle or NO-np was injected into the bladder, followed by cystometric studies. The expression levels of phosphorylated eNOS (Ser-1177), protein kinase B (Akt) (Ser-473), nNOS (Ser-1412), and myosin phosphatase target subunit 1 (MYPT1) (Thr-696) were assessed in the bladder. SCD and dNOS^-/- mice had a greater (P < 0.05) number of voiding and nonvoiding contractions compared with WT mice, and they were normalized by NO-np treatment. eNOS (Ser-1177) and AKT (Ser-473) phosphorylation were decreased (P < 0.05) in the bladder of SCD compared with WT mice and reversed by NO-np. Phosphorylated MYPT1, a marker of the RhoA/ROCK pathway, was increased (P < 0.05) in the bladder of SCD mice compared with WT and reversed by NO-np. nNOS phosphorylation on positive (Ser-1412) regulatory site was decreased (P < 0.05) in the bladder of SCD mice compared with WT and was not affected by NO-np. NO-nps did not affect any of the measured parameters in WT mice. In conclusion, dysregulation of NO and RhoA/ROCK pathways is associated with detrusor overactivity in SCD mice; NO-np reverses these molecular derangements in the bladder and decreases detrusor overactivity. SIGNIFICANCE STATEMENT: Voiding abnormalities commonly affect patients with sickle cell disease (SCD) but are problematic to treat. Clarification of the science for this condition in an animal model of SCD may lead to improved interventions for it. Our findings suggest that novel topical delivery of a vasorelaxant agent nitric oxide into the bladder of these mice corrects overactive bladder by improving deranged bladder physiology regulatory signaling.

Hypoxic pulmonary vasoconstriction is lacking in rats with type 1 diabetes

Hypoxic pulmonary vasoconstriction (HPV) is the most important feature of intact lung circulation that matches local blood perfusion to ventilation. The main goal of this work was to study the effects of diabetes on the development of HPV in rats. The experimental design comprised diabetes mellitus induction by streptozotocin, video-morphometric measurements of the lumen area of intrapulmonary arteries (iPAs) using perfused lung tissue slices and patch-clamp techniques. It was shown that iPA lumen size was significantly reduced under physical and chemical hypoxia (7-10 mm Hg) in normal iPA, but, on the contrary, it clearly increased in diabetic lung slices. The amplitude of the outward K⁺ current in diabetic iPAs smooth muscle cells (SMCs) was two-fold greater than that seen in healthy cells. Chemical hypoxia led to significant decrease in the amplitude of the K⁺ outward current in healthy iPA SMCs while it was without effect in diabetic cells. The data obtained clearly indicate a significant dysregulation of vascular tone in pulmonary circulation under diabetes, ie diabetes damages the adaptive mechanism for regulating blood flow from poorly ventilated to better ventilated regions of the lung under hypoxia. This effect could be clinically important for patients with diabetes who have acute or chronic lung diseases associated with the lack of blood oxygenation.

Mechanisms of U46619-induced contraction in mouse intrarenal artery

Thromboxane A₂ (TXA₂ ) has been implicated in the pathogenesis of vascular complications, but the underlying mechanism remains unclear. The contraction of renal arterial rings in mice was measured by a Multi Myograph System. The intracellular calcium concentration ([Ca²⁺ ]_i ) in vascular smooth muscle cells (VSMCs) was obtained by using a fluo-4/AM dye and a confocal laser scanning microscopy. The results show that the U46619-induced vasoconstriction of renal artery was completely blocked by a TXA₂ receptor antagonist GR32191, significantly inhibited by a selective phospholipase C (PI-PLC) inhibitor U73122 at 10 μmol/L and partially inhibited by a Phosphatidylcholine - specific phospholipase C (PC-PLC) inhibitor D609 at 50 μmol/L. Moreover, the U46619-induced vasoconstriction was inhibited by a general protein kinase C (PKC) inhibitor chelerythrine at 10 μmol/L, and a selective PKCδ inhibitor rottlerin at 10 μmol/L. In addition, the PKC-induced vasoconstriction was partially inhibited by a Rho-kinase inhibitor Y-27632 at 10 μmol/L and was further completely inhibited together with a putative IP₃ receptor antagonist and store-operated Ca²⁺ (SOC) entry inhibitor 2-APB at 100 μmol/L. On the other hand, U46619-induced vasoconstriction was partially inhibited by L-type calcium channel (Cav1.2) inhibitor nifedipine at 1 μmol/L and 2-APB at 50 and 100 μmol/L. Last, U46619-induced vasoconstriction was partially inhibited by a cell membrane Ca²⁺ activated C1^- channel blocker 5-Nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) at 50 and 100 μmol/L. Our results suggest that the U46619-induced contraction of mouse intrarenal arteries is mediated by Cav1.2 and SOC channel, through the activation of thromboxane-prostanoid receptors and its downstream signaling pathway.

A Gs-coupled purinergic receptor boosts Ca2+ influx and vascular contractility during diabetic hyperglycemia

Elevated glucose increases vascular reactivity by promoting L-type Ca_V1.2 channel (LTCC) activity by protein kinase A (PKA). Yet, how glucose activates PKA is unknown. We hypothesized that a G_s-coupled P2Y receptor is an upstream activator of PKA mediating LTCC potentiation during diabetic hyperglycemia. Experiments in apyrase-treated cells suggested involvement of a P2Y receptor underlying the glucose effects on LTTCs. Using human tissue, expression for P2Y₁₁, the only G_s-coupled P2Y receptor, was detected in nanometer proximity to Ca_V1.2 and PKA. FRET-based experiments revealed that the selective P2Y₁₁ agonist NF546 and elevated glucose stimulate cAMP production resulting in enhanced PKA-dependent LTCC activity. These changes were blocked by the selective P2Y₁₁ inhibitor NF340. Comparable results were observed in mouse tissue, suggesting that a P2Y₁₁-like receptor is mediating the glucose response in these cells. These findings established a key role for P2Y₁₁ in regulating PKA-dependent LTCC function and vascular reactivity during diabetic hyperglycemia.

Fasudil ameliorates endothelial dysfunction in streptozotocin-induced diabetic rats: a possible role of Rho kinase

Endothelial dysfunction is a major contributor to the pathogenesis of vascular disease in diabetes mellitus and RhoA/Rho-kinase (ROCK) system appears to play a crucial role in this setting. The present study was conducted to investigate the effect of the selective ROCK inhibitor, fasudil, on diabetes-related endothelial dysfunction and elucidated its underlying mechanism(s). Diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ, 50 mg/kg), and fasudil (5 mg/kg per day) was orally administered for 8 weeks. Our results showed that fasudil administration attenuated the increased activity/expression of ROCK (627.5 ± 27 vs. 247.8 ± 19.1) and the NADPH oxidase subunits, NOX2 and p47phox, in diabetic rat aorta. Fasudil could reduce the elevated tumor necrosis factor (TNF)-α (70.2 ± 14.1 vs. 25.3 ± 5.2) and transforming growth factor (TGF-β) levels and restored the deficit in antioxidant level of the diabetic aorta. Additionally, fasudil markedly improved the endothelial dysfunction in the diabetic aorta (73.8 ± 8.1 vs. 47.42 ± 8.69) and corrected the dysregulated endothelial nitric oxide (eNOS) expression. In conclusion, the present study demonstrates that fasudil effectively ameliorates the endothelial dysfunction in STZ-induced diabetic rats through inhibition of the Rho/ROCK pathway and thereby reducing the TNF-α-mediated NADPH oxidase activation.

Ser1928 phosphorylation by PKA stimulates the L-type Ca2+ channel CaV1.2 and vasoconstriction during acute hyperglycemia and diabetes

Hypercontractility of arterial myocytes and enhanced vascular tone during diabetes are, in part, attributed to the effects of increased glucose (hyperglycemia) on L-type Ca_V1.2 channels. In murine arterial myocytes, kinase-dependent mechanisms mediate the increase in Ca_V1.2 activity in response to increased extracellular glucose. We identified a subpopulation of the Ca_V1.2 channel pore-forming subunit (α1_C) within nanometer proximity of protein kinase A (PKA) at the sarcolemma of murine and human arterial myocytes. This arrangement depended upon scaffolding of PKA by an A-kinase anchoring protein 150 (AKAP150) in mice. Glucose-mediated increases in Ca_V1.2 channel activity were associated with PKA activity, leading to α1_C phosphorylation at Ser¹⁹²⁸ Compared to arteries from low-fat diet (LFD)-fed mice and nondiabetic patients, arteries from high-fat diet (HFD)-fed mice and from diabetic patients had increased Ser¹⁹²⁸ phosphorylation and Ca_V1.2 activity. Arterial myocytes and arteries from mice lacking AKAP150 or expressing mutant AKAP150 unable to bind PKA did not exhibit increased Ser¹⁹²⁸ phosphorylation and Ca_V1.2 current density in response to increased glucose or to HFD. Consistent with a functional role for Ser¹⁹²⁸ phosphorylation, arterial myocytes and arteries from knockin mice expressing a Ca_V1.2 with Ser¹⁹²⁸ mutated to alanine (S1928A) lacked glucose-mediated increases in Ca_V1.2 activity and vasoconstriction. Furthermore, the HFD-induced increases in Ca_V1.2 current density and myogenic tone were prevented in S1928A knockin mice. These findings reveal an essential role for α1_C phosphorylation at Ser¹⁹²⁸ in stimulating Ca_V1.2 channel activity and vasoconstriction by AKAP-targeted PKA upon exposure to increased glucose and in diabetes.

Elevated Glucose Levels Promote Contractile and Cytoskeletal Gene Expression in Vascular Smooth Muscle via Rho/Protein Kinase C and Actin Polymerization

Both type 1 and type 2 diabetes are associated with increased risk of cardiovascular disease. This is in part attributed to the effects of hyperglycemia on vascular endothelial and smooth muscle cells, but the underlying mechanisms are not fully understood. In diabetic animal models, hyperglycemia results in hypercontractility of vascular smooth muscle possibly due to increased activation of Rho-kinase. The aim of the present study was to investigate the regulation of contractile smooth muscle markers by glucose and to determine the signaling pathways that are activated by hyperglycemia in smooth muscle cells. Microarray, quantitative PCR, and Western blot analyses revealed that both mRNA and protein expression of contractile smooth muscle markers were increased in isolated smooth muscle cells cultured under high compared with low glucose conditions. This effect was also observed in hyperglycemic Akita mice and in diabetic patients. Elevated glucose activated the protein kinase C and Rho/Rho-kinase signaling pathways and stimulated actin polymerization. Glucose-induced expression of contractile smooth muscle markers in cultured cells could be partially or completely repressed by inhibitors of advanced glycation end products, L-type calcium channels, protein kinase C, Rho-kinase, actin polymerization, and myocardin-related transcription factors. Furthermore, genetic ablation of the miR-143/145 cluster prevented the effects of glucose on smooth muscle marker expression. In conclusion, these data demonstrate a possible link between hyperglycemia and vascular disease states associated with smooth muscle contractility.

Nigella sativa seed decreases endothelial dysfunction in streptozotocin-induced diabetic rat aorta

OBJECTIVE

Diabetes is an important risk factor for cardiovascular events. The great percent of morbidity in patients with diabetes is due to endothelial dysfunction. The present study investigated the effects of hydroalcholic extract of Nigella sativa (N. sativa) on contractile and dilatation response of isolated aorta in streptozotocin (STZ)-induced diabetic rat.

MATERIALS AND METHODS

Rats were divided into six experimental groups (control, untreated STZ-diabetic, and N. sativa hydroalcholic extract or metformin-treated diabetic rats). Treated rats received N. sativa extract (100, 200, and 400 mg/kg) or metformin (300 mg/kg) by gavage, daily for 6 weeks. Isolated rat thoracic rings were mounted in an organ bath system then contractile and dilatation responses induced by phenylephrine (PE), acetylcholine (ACh), potassium chloride (KCl), and sodium nitroprusside (SNP) were evaluated in different situations.

RESULTS

The lower concentrations of N. sativa seed extract (DE 100 and DE 200) and metformin significantly reduced the contractile responses to higher concentrations of PE (10(-6) - 10(-5) M) compared to diabetic group (p<0.05 to p<0.01). The relaxation response to Ach 10(-8) M, was increased in DE 200 and metformin groups compared to diabetic group (p<0.05). The relaxation responses to Ach 10(-7) - 10(-5) M were significantly higher in all treated groups compared to diabetic group (p<0.05 to p<0.001).

CONCLUSION

Chronic administration of N. sativa seed extract has a significant hypoglycemic effect and improves aortic reactivity to vasoconstrictor and vasodilator agents in STZ-induced diabetic rats.

Increased Contractile Response to Noradrenaline Induced By Factors Associated with the Metabolic Syndrome in Cultured Small Mesenteric Arteries

This study investigated the effect of the metabolic syndrome associated risk factors hyperglycemia (glucose [Glc]), hyperinsulinemia (insulin [Ins]) and low-grade inflammation (tumor necrosis factor α [TNFα]) on the vasomotor responses of resistance arteries. Isolated small mesenteric arteries from 3-month-old Sprague-Dawley rats, were suspended for 21-23 h in tissue cultures containing either elevated Glc (30 mmol/l), Ins (100 nmol/l), TNFα (100 ng/ml) or combinations thereof. After incubation, the vascular response to noradrenaline (NA), phenylephrine, isoprenaline and NA in the presence of propranolol (10 µmol/l) was measured by wire myography.

RESULTS

Arteries exposed only to combinations of the risk factors showed a significant 1.6-fold increase in the contractile NA sensitivity, which suggests that complex combinations of metabolic risk factors might lead to changes in vascular tone.

Toll-like receptor 2 mediates vascular contraction and activates RhoA signaling in vascular smooth muscle cells from STZ-induced type 1 diabetic rats

Increased vascular smooth muscle cell (VSMC) contraction is an early and critical contributor to the pathogenesis of vascular dysfunction in diabetes; however, knowledge regarding the underlying mechanisms is scarce. Toll-like receptor 2 (TLR2), a well-known component of the innate immunity, is expressed in VSMC and recently has been identified to be systemically activated in diabetes. Whether TLR2 is locally activated in the diabetic blood vessels and have effect on contraction is not known. In the current study, we examined the role of TLR2 in increased vascular contraction in diabetes. Utilizing rat model of type 1 diabetes (induced by streptozotocin (STZ)), we demonstrated that aortas from STZ-diabetic rats exhibit increased expression of TLR2 and its adaptor protein, myeloid differentiation primary response 88 (MyD88), as well as enhanced protein-protein interaction between TLR2 and MyD88, suggesting a TLR2 signaling activation. Blockade of TLR2 in intact aortas using anti-TLR2 antibody attenuated increased vascular contraction in STZ-diabetic rat as assessed by wire myograph. Activation of TLR2 by specific ligand in primary aortic VSMC cultures triggered activation of RhoA which was exacerbated in cells from STZ-diabetic rats than control rats. Activation of RhoA was accompanied by phosphorylation and therefore activation of its downstream targets myosin phosphatase target subunit I and myosin light chain (markers of VSMC contraction). Taken together, these results provide evidence for the role of TLR2 in increased contraction in diabetic blood vessels that involves RhoA signaling. Thus, targeting vascular TLR2 offers a promising drug target to treat vascular dysfunction in diabetes.

Fasudil improves short-term echocardiographic parameters of diastolic function in patients with type 2 diabetes with preserved left ventricular ejection fraction: a pilot study

Left ventricular (LV) diastolic dysfunction is observed frequently in patients with type 2 diabetes; however, few studies have focused on the effect of the Rho-associated kinase inhibitor fasudil on cardiac performance in humans. We conducted a prospective pilot study to assess the impact of fasudil on LV diastolic function in patients with diabetes without systolic dysfunction. Two hundred and fifty eligible patients with type 2 diabetes (149 men [61.3 %] and 94 women [38.7 %]) with a mean age of 57.2 years were randomly assigned to fasudil (n = 122, 30 mg intravenously twice a day for 14 days) or placebo (n = 121) groups. Echocardiographic variables were measured at the baseline and 1 month after the intervention. Compared with the placebo group, the fasudil group showed a significant decrease in diastolic blood pressure and in the peak of late diastolic transmitral flow (Am) (P < 0.05 for both). Deceleration time (DT), isovolumic relaxation time (IVRT), the peak of early diastolic annular velocity (e'), the peak of late diastolic annular velocity, and E/e' also exhibited a significant improvement (all, P < 0.05) after fasudil administration. Furthermore, the Em/Am ratio and IVRT, DT, and E/e' values recorded after fasudil treatment in the subgroup with impaired LV relaxation significantly differed from the corresponding values in the subgroup with normal LV relaxation (all, P < 0.05). Fasudil improves short-term echocardiographic parameters of LV diastolic function in patients with type 2 diabetes with preserved left ventricular ejection fraction.

Dissociation of hyperglycemia from altered vascular contraction and relaxation mechanisms in caveolin-1 null mice

Hyperglycemia and endothelial dysfunction are associated with hypertension, but the specific causality and genetic underpinning are unclear. Caveolin-1 (cav-1) is a plasmalemmal anchoring protein and modulator of vascular function and glucose homeostasis. Cav-1 gene variants are associated with reduced insulin sensitivity in hypertensive individuals, and cav-1(-/-) mice show endothelial dysfunction, hyperglycemia, and increased blood pressure (BP). On the other hand, insulin-sensitizing therapy with metformin may inadequately control hyperglycemia while affecting the vascular outcome in certain patients with diabetes. To test whether the pressor and vascular changes in cav-1 deficiency states are related to hyperglycemia and to assess the vascular mechanisms of metformin under these conditions, wild-type (WT) and cav-1(-/-) mice were treated with either placebo or metformin (400 mg/kg daily for 21 days). BP and fasting blood glucose were in cav-1(-/-) > WT and did not change with metformin. Phenylephrine (Phe)- and KCl-induced aortic contraction was in cav-1(-/-) < WT; endothelium removal, the nitric-oxide synthase (NOS) blocker L-NAME (N(ω)-nitro-L-arginine methyl ester), or soluble guanylate cyclase (sGC) inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) enhanced Phe contraction, and metformin blunted this effect. Acetylcholine-induced relaxation was in cav-1(-/-) > WT, abolished by endothelium removal, L-NAME or ODQ, and reduced with metformin. Nitric oxide donor sodium nitroprusside was more potent in inducing relaxation in cav-1(-/-) than in WT, and metformin reversed this effect. Aortic eNOS, AMPK, and sGC were in cav-1(-/-) > WT, and metformin decreased total and phosphorylated eNOS and AMPK in cav-1(-/-). Thus, metformin inhibits both vascular contraction and NO-cGMP-dependent relaxation but does not affect BP or blood glucose in cav-1(-/-) mice, suggesting dissociation of hyperglycemia from altered vascular function in cav-1-deficiency states.

ROCK inhibitor, Y-27632, reduces FBS-induced structural alteration in organ-cultured mesenteric artery

Background

Chronic treatment with fetal bovine serum (FBS) causes gradual vasoconstriction, vascular wall thickening, and contractility reduction in organ-cultured vascular tissues. We have previously demonstrated that Rho-associated kinase (ROCK) inhibitors prevent the functional alterations of small arteries in response to the FBS treatment. Here, we tested a further hypothesis that the chronic inhibition of ROCK has a protective effect on FBS-induced structural alterations.

Methods

To verify the new hypothesis, the rabbit mesenteric arterial rings were cultured in FBS-supplemented culture medium with or without Y-27632, a reversible ROCK inhibitor and then western blot, immunohistochemistry, apoptosis assay, and electron microscopy were performed using organ-cultured arterial rings.

Results

Chronic treatment with Y-27632 maintained the arterial diameter by preventing FBS-induced gradual arterial constriction during organ culture. Y-27632 also reduced the apoptosis and the loss of contractile myosin and actin filaments of smooth muscle cells. In addition, Y-27632 protected the morphological integrity between the endothelial cell layer and smooth muscle cell layer by preventing endothelial cell detachment and platelet endothelial cell adhesion molecule (PECAM) expression decrement.

Conclusions

Chronic ROCK inhibition provides protective effects against FBS-stimulated structural in addition to functional alterations of vascular smooth muscle cells and endothelial cells. These results strongly suggest that the RhoA/ROCK signaling is crucial for maintaining the structural and functional phenotypes of vasculature, and hence, chronic ROCK inhibition may provide protective effects on excessive growth factor-related vascular diseases including hypertension and atherosclerosis.

Targeting of Rho kinase ameliorates impairment of diabetic endothelial function in intrarenal artery

Endothelial dysfunction in kidney vasculature is the initial and key element for nephropathy in diabetes mellitus. Accumulating evidence suggests the protective role of Rho kinase inhibitors in endothelial dysfunction via modulating eNOS activity and NO production. However, the role of Rho kinase in diabetes-related endothelial dysfunction in kidney vasculature and the relevant mechanisms remain unknown. We assessed whether pharmacological inhibition of Rho kinase attenuates endothelial dysfunction in intrarenal arteries from type 1 diabetic rats. Fasudil, a Rho kinase inhibitor effectively decreased the phosphorylated level of MYPT1 without affecting the expression of ROCKs in the kidney. Fasudil treatment showed no improvement in diabetes-related abnormality in metabolic indices, but it significantly ameliorated endothelial dysfunction in intrarenal arteries and lessened the mesangial matrix expansion in the kidney cortex. Mechanistically, superoxide production in the intrarenal artery and NOX4 member of NADPH oxidase in the renal cortex that contribute to diabetic nephropathy were also prevented by the Rho kinase inhibitor. In conclusion, the present results indicate that Rho kinase is involved in endothelial dysfunction in type 1 diabetes via enhancement of oxidative stress and provides new evidence for Rho kinase inhibitors as potential therapeutic agents for the treatment of diabetic nephropathy.

Acute Rho-kinase inhibition improves coronary dysfunction in vivo, in the early diabetic microcirculation

OBJECTIVES

Activation of RhoA/Rho-kinase (ROCK) is increasingly implicated in acute vasospasm and chronic vasoconstriction in major organ systems. Therefore we aimed to ascertain whether an increase in ROCK activity plays a role in the deterioration of coronary vascular function in early stage diabetes.

METHODS

Synchrotron radiation microangiography was used to determine in vivo coronary responses in diabetic (3 weeks post streptozotocin 65 mg/kg ip) and vehicle treated male Sprague-Dawley rats (n = 8 and 6). Changes in vessel number and calibre during vasodilator stimulation before and after blockade of nitric oxide synthase and cyclooxygenase were compared between rats. Acute responses to ROCK inhibitor, fasudil (10 mg/kg iv) was evaluated. Further, perivascular and myocardial fibrosis, arterial intimal thickening were assessed by histology, and capillary density, nitrotyrosine and ROCK1/2 expressions were evaluated by immunohistochemical staining.

RESULTS

Diabetic rats had significantly elevated plasma glucose (P < 0.001 vs control), but did not differ in fibrotic scores, media to lumen ratio, capillary density or baseline visible vessel number or calibre. Responses to acetylcholine and sodium nitroprusside stimulation were similar between groups. However, in comparison to control rats the diabetic rats showed more segmental constrictions during blockade, which were not completely alleviated by acetylcholine, but were alleviated by fasudil. Further, second order vessel branches in diabetic rats were significantly more dilated relative to baseline (37% vs 12% increase, P < 0.05) after fasudil treatment compared to control rats, while visible vessel number increased in both groups. ROCK2 expression was borderline greater in diabetic rat hearts (P < 0.053).

CONCLUSIONS

We found that ahead of the reported decline in coronary endothelial vasodilator function in diabetic rats there was moderate elevation in ROCK expression, more widespread segmental constriction when nitric oxide and prostacyclin production were inhibited and notably, increased calibre in second and third order small arteries-arterioles following ROCK inhibition. Based on nitrotyrosine staining oxidative stress was not significantly elevated in early diabetic rats. We conclude that tonic ROCK mediated vasoconstriction contributes to coronary vasomotor tone in early diabetes.

The protective effect of fasudil on the structure and function of cardiac mitochondria from rats with type 2 diabetes induced by streptozotocin with a high-fat diet is mediated by the attenuation of oxidative stress

Dysfunction of cardiac mitochondria appears to play a substantial role in cardiomyopathy or myocardial dysfunction and is a promising therapeutic target for many cardiovascular diseases. We investigated the effect of the Rho/Rho-associated protein kinase (ROCK) inhibitor fasudil on cardiac mitochondria from rats in which diabetes was induced by a combination of streptozotocin (STZ) and a sustained high-fat diet. Eight weeks after diabetes was induced by a single intraperitoneal injection of 50 mg/kg STZ followed by a sustained high-fat diet, either fasudil (5 mg/kg bid) or equivalent volumes of saline (control) were administered over four weeks. Fasudil significantly protected against the histopathologic changes of cardiac mitochondria in diabetic rats. Fasudil significantly reduced the abundances of the Rho A, ROCK 1, and ROCK 2 proteins, restored the activities of succinate dehydrogenase (SDH) and monoamine oxidase (MAO) in cardiac mitochondria, inhibited the opening of the mitochondrial permeability transition pore, and decreased the total antioxidant capacity, as well as levels of malonyldialdehyde, hydroxy radical, reduced glutathione, and superoxide dismutase in heart. Fasudil improved the structures of cardiac mitochondria and increased both SDH and MAO activities in cardiac mitochondria. These beneficial effects may be associated with the attenuation of oxidative stress caused by fasudil treatment.

Role of ROCK upregulation in endothelial and smooth muscle vascular functions in diabetic rat aorta

Background

The RhoA/ROCK signaling pathway mediates vascular smooth muscle contraction while endogenous NO induces vasodilation through its inhibition. Since myosin light chain phosphatase (MLCP) and eNOS are targeted by RhoA/ROCK upregulation then turn to lead abnormalities in vasculature, we aimed to examine whether less endothelial NO-production and inhibited eNOS together with an upregulation of RhoA/ROCK signaling pathway in thoracic aorta can play an important role in vascular dysfunction under hyperglycemia.

Methods

We used streptozotocin-injected rats, as a model of type 1 diabetes, and their lean controls to investigate the role of ROCK upregulation in the function of toracic aorta by using electrophysiological and biochemical techniques.

Results

The protein level of ROCK isoform ROCK2 was found to be 2.5-fold higher in endothelium-intact aortic rings of the diabetic rats compared to those of the controls while its level in endothelium-denuded rings was similar among these two groups. Phosphorylation level of eNOS in endothelium-intact rings from the diabetics was 50% less compared to that of the control. ROCK inhibitors, either Y27632 or HA1077, induced concentration-dependent relaxation with a marked left-shift in phenylephrine pre-contracted endothelium-intact rings from either diabetics or high glucose incubated controls while pretreatment of these rings with L-NAME abolished this shift, fully. Moreover, phosphorylation levels of both MLCP and MLC in endothelium-denuded rings were markedly higher in the diabetics than the controls.

Conclusion

We demonstrated that diabetes-induced vascular dysfunction can arise due to either inbition of eNOS, thereby less endothelial NO-production, either directly or indirectly, in part, due to an upregulation of ROCK2 by hyperglycemia. Additionally, our data demonstrate that high phosphorylation levels of both MLC and MLCP in endothelium-denuded rings can be due to a less endothelial NO-production dependent ROCK upregulation in the smooth muscle cells under hyperglycemia, as well.

Chronic supplementation of paeonol combined with danshensu for the improvement of vascular reactivity in the cerebral basilar artery of diabetic rats

One of the leading causes of death in the world is cerebrovascular disease. Numerous Chinese traditional medicines, such as Cortex Moutan (root bark of Paeonia suffruticosa Andrew) and Radix Salviae miltiorrhizae (root and rhizome of Salvia miltiorrhiza Bunge), protect against cerebrovascular diseases and exhibit anti-atherosclerotic effects. Traditional medicines have been routinely used for a long time in China. In addition, these two herbs are prescribed together in clinical practice. Therefore, the pharmacodynamic interactions between the active constituents of these two herbs, which are paeonol (Pae) and danshensu (DSS), should be particularly studied. The study of Pae and DSS can provide substantial foundations in understanding their mechanisms and empirical evidence to support clinical practice. This study investigated the effects and possible mechanisms of the pharmacodynamic interaction between Pae and DSS on cerebrovascular malfunctioning in diabetes. Experimental diabetes was induced in rats, which was then treated with Pae, DSS, and Pae + DSS for eight weeks. Afterward, cerebral arteries from all groups were isolated and equilibrated in an organ bath with Krebs buffer and ring tension. Effects of Pae, DSS, and Pae + DSS were observed on vessel relaxation with or without endothelium as well as on the basal tonus of vessels from normal and diabetic rats. Indexes about oxidative stress were also determined. We report that the cerebral arteries from diabetic rats show decreased vascular reactivity to acetylcholine (ACh) which was corrected in Pae, DSS, and Pae + DSS treated groups. Furthermore, phenylephrine (PE)-induced contraction response decreased in the treated groups. Phenylephrine and CaCl(2)-induced vasoconstrictions are partially inhibited in the three treated groups under Ca2+-free medium. Pre-incubated with tetraethylammonium, a non-selective K+ channel blocker, the antagonized relaxation responses increased in DSS and Pae + DSS treated diabetic groups compared with those in diabetic and Pae-treated diabetic groups. In addition, superoxide dismutase activity and thiobarbituric acid reactive substances content significantly changed in the presence of Pae + DSS. We therefore conclude that both Pae and DSS treatments prevent diabetes-induced vascular damage. Furthermore, Pae + DSS prove to be the most efficient treatment regimen. The combination of Pae and DSS produce significant protective effects through the reduction of oxidative stress and through intracellular Ca2+ regulatory mechanisms.

Fasudil, a Rho-kinase inhibitor, protects against excessive endurance exercise training-induced cardiac hypertrophy, apoptosis and fibrosis in rats

Excessive endurance exercise training (EEET) is accompanied by cardiac remodeling, changes in ventricular function and increased heart failure risk. Fasudil, a potent Rho-kinase inhibitor, has been demonstrated to blunt cardiomyocyte hypertrophy, cardiac remodeling, and heart failure progression in pre-clinical trials and has been approved for clinical use in Japan. We examined the in vivo bioefficacy of fasudil against EEET-induced cardiac remodeling and the underlying molecular mechanisms. Male Sprague-Dawley rats were randomly divided into three groups: sedentary control (SC), EEET, and EEET with fasudil treatment (EEET-F). Rats in EEET and EEET-F groups ran on a motorized treadmill for 12 weeks. The results revealed that EEET increased myocardial hypertrophy (LV weight/tibial length), myocyte cross-sectional area, hypertrophy-related pathways (IL6/STAT3-MEK5-ERK5, calcineurin-NFATc3, p38 and JNK MAPK), hypertrophic markers (ANP/BNP), pro-apoptotic molecules (cytochrome C, cleaved caspase-3 and PARP), and fibrosis-related pathways (FGF-2-ERK1/2) and fibrosis markers (uPA, MMP-9 and -2). These pathways were then expressed lower in the EEET-F group when compared with the EEET group. The cardiac hypertrophic level, apoptotic pathway and fibrosis signaling were further inhibited in the fasudil-treated group. We systematically investigated the possible signaling pathways leading to EEET-induced cardiac hypertrophy, apoptosis and fibrosis. We also provide evidence for the novel function of fasudil in suppressing EEET-induced cardiac remodeling and impairment by multiple mechanisms, which suggests that the RhoA signaling pathway contributes to EEET-induced cardiac remodeling and dysfunction.

Increased availability of angiotensin AT 1 receptors leads to sustained arterial constriction to angiotensin II in diabetes - role for Rho-kinase activation

BACKGROUND AND PURPOSE

Antagonists of angiotensin AT(1) receptors elicit beneficial vascular effects in diabetes mellitus. We hypothesized that diabetes induces sustained availability of AT(1) receptors, causing enhanced arterial constriction to angiotensin II.

EXPERIMENTAL APPROACH

To assess functional availability of AT(1) receptors, constrictions to successive applications of angiotensin II were measured in isolated skeletal muscle resistance arteries (∼150 µm) of Zucker diabetic fatty (ZDF) rats and of their controls (+/Fa), exposed acutely to high glucose concentrations (HG, 25 mM, 1 h). AT(1) receptors on cell membrane surface were measured by immunofluorescence.

KEY RESULTS

Angiotensin II-induced constrictions to first applications were greater in arteries of ZDF rats (maximum: 82 ± 3% original diameter) than in those from +/Fa rats (61 ± 5%). Constrictions to repeated angiotensin II administration were decreased in +/Fa arteries (20 ± 6%), but were maintained in ZDF arteries (67 ± 4%) and in +/Fa arteries vessels exposed to HG (65 ± 6%). In ZDF arteries and in HG-exposed +/Fa arteries, Rho-kinase activities were enhanced. The Rho-kinase inhibitor, Y27632 inhibited sustained constrictions to angiotensin II in ZDF arteries and in +/Fa arteries exposed to HG. Levels of surface AT(1) receptors on cultured vascular smooth muscle cells (VSMCs) were decreased by angiotensin II but were maintained in VSMCs exposed to HG. In VSMCs exposed to HG and treated with Y27632, angiotensin II decreased surface AT(1) receptors.

CONCLUSIONS AND IMPLICATIONS

In diabetes, elevated glucose concentrations activate Rho-kinase which inhibits internalization or facilitates recycling of AT(1) receptors, leading to increased functional availability of AT(1) receptors and sustained angiotensin II-induced arterial constriction.

Contribution of Rho-kinase to membrane excitability of murine colonic smooth muscle

BACKGROUND AND PURPOSE

The Rho-kinase pathway regulates agonist-induced contractions in several smooth muscles, including the intestine, urinary bladder and uterus, via dynamic changes in the Ca(2+) sensitivity of the contractile apparatus. However, there is evidence that Rho-kinase also modulates other cellular effectors such as ion channels.

EXPERIMENTAL APPROACH

We examined the regulation of colonic smooth muscle excitability by Rho-kinase using conventional microelectrode recording, isometric force measurements and patch-clamp techniques.

KEY RESULTS

The Rho-kinase inhibitors, Y-27632 and H-1152, decreased nerve-evoked on- and off-contractions elicited at a range of frequencies and durations. The Rho-kinase inhibitors decreased the spontaneous contractions and the responses to carbachol and substance P independently of neuronal inputs, suggesting Y-27632 acts directly on smooth muscle. The Rho-kinase inhibitors significantly reduced the depolarization in response to carbachol, an effect that cannot be due to regulation of Ca(2+) sensitization. Patch-clamp experiments showed that Rho-kinase inhibitors reduce GTPγS-activated non-selective cation currents.

CONCLUSIONS AND IMPLICATIONS

The Rho-kinase inhibitors decreased contractions evoked by nerve stimulation, carbachol and substance P. These effects were not solely due to inhibition of the Ca(2+) sensitization pathway, as the Rho-kinase inhibitors also inhibited the non-selective cation conductances activated by excitatory transmitters. Thus, Rho-kinase may regulate smooth muscle excitability mechanisms by regulating non-selective cation channels as well as changing the Ca(2+) sensitivity of the contractile apparatus.

3',4'-Dihydroxyflavonol reduces vascular contraction through Ca²⁺ desensitization in permeabilized rat mesenteric artery

3',4'-Dihydroxyflavonol (DiOHF) exerts endothelium-independent relaxation in rat aortic rings. In this study, we hypothesized that DiOHF reduces vascular contraction through Ca²⁺ desensitization in permeabilized third-order branches of rat mesenteric arteries. The third-order branches of rat mesenteric arteries were permeabilized with β-escin and subjected to tension measurement. Cumulative addition of phenylephrine (0.3-30 μM) produced concentration-dependent vascular contraction of endothelium-intact and endothelium-denuded arterial rings, which were inhibited by pretreatment with DiOHF (10, 30, or 100 μM). In addition, DiOHF dose-dependently decreased vascular contractions induced by 3.0 μM phenylephrine. β-Escin-permeabilized third-order branches of mesenteric arteries were contracted with Ca²⁺, NaF, or guanosine-5'-(γ-thio)triphosphate (GTPγS) 30 min after pretreatment with DiOHF or vehicle. Pretreatment with DiOHF for 30 min inhibited vascular contraction induced by cumulative additions of Ca²⁺ (pCa 9.0-6.0) or NaF (4.0-16.0 mM) in permeabilized arterial rings. Cumulative addition of DiOHF also reduced vascular contraction induced by Ca²⁺-controlled solution of pCa 6.0, 16.0 mM NaF, or 100 μM GTPγS in permeabilized arterial rings. DiOHF inhibited the increase in vascular tension provoked by calyculin A, even though it did not affect vascular tension already produced by calyculin A. DiOHF accelerated the relaxation induced by rapidly lowering Ca²⁺. DiOHF reduced vascular contraction through Ca²⁺ desensitization in permeabilized third-order branches of rat mesenteric arteries. These results suggest that DiOHF may have a therapeutic potential in the treatment of cardiovascular diseases.

Impaired Ca2+ handling in penile arteries from prediabetic Zucker rats: involvement of Rho kinase

Diabetes is associated with an increased vascular tone usually involved in the pathogenesis of diabetic cardiovascular complications such as hypertension, stroke, coronary artery disease, or erectile dysfunction (ED). Enhanced contractility of penile erectile tissue has been associated with augmented activity of the RhoA/Rho kinase (RhoK) pathway in models of diabetes-associated ED. The present study assessed whether abnormal vasoconstriction in penile arteries from prediabetic obese Zucker rats (OZRs) is due to changes in the intracellular Ca2+ concentration ([Ca2+]i) and/or in myofilament Ca2+ sensitivity. Penile arteries from OZRs and lean Zucker rats (LZRs) were mounted on microvascular myographs for simultaneous measurements of [Ca2+]i and tension. The relationships between [Ca2+]i and contraction for the α1-adrenergic vasoconstrictor phenylephrine (PE) were left shifted and steeper in OZRs compared with LZRs, although the magnitude of the contraction was similar in both groups. In contrast, the vasoconstriction induced by the thromboxane A2 receptor agonist U-46619 was augmented in arteries from OZRs, and this increase was associated with an increase in both the sensitivity and maximum responses to Ca2+. The RhoK inhibitor Y-27632 (10 μM) reduced the vasoconstriction induced by PE to a greater extent in OZRs than in LZRs, without altering Ca2+. Y-27632 inhibited with a greater potency the contraction elicited by high KCl in arteries from OZRs compared with LZRs without changing [Ca2+]i. RhoK-II expression was augmented in arteries from OZRs. These results suggest receptor-specific changes in the Ca2+ handling of penile arteries under conditions of metabolic syndrome. Whereas augmented vasoconstriction upon activation of the thromboxane A2 receptor is coupled to enhanced Ca2+ entry, a RhoK-mediated enhancement of myofilament Ca2+ sensitivity is coupled with the α1-adrenergic vasoconstriction in penile arteries from OZRs.

Rho-kinase, a common final path of various contractile bladder and ureter stimuli

Normal urinary bladder function is based on the proper contraction and relaxation of smooth muscle (SM), which constitutes the majority of the bladder wall. The contraction and relaxation of all SM involves a phosphorylation-dephosphorylation pathway involving the enzymes smooth muscle myosin light chain kinase (SMMLCK) and smooth muscle myosin light chain phosphatase (SMMLCP), respectively. Although originally thought to function just as a passive opposition to SMMLCK-driven SM contraction, it is now clear that SMMLCP activity is under an extremely complex molecular regulation via which SMMLCP inhibition can induce "calcium sensitization." This review provides a thorough summary of the literature regarding the molecular regulation of the SMMLCP with a focus on one of its major inhibitory pathways that is RhoA/Rho-kinase (ROK) including its activation pathways, effector molecules, and its roles in various pathological conditions associated with bladder dysfunction. Newly emerging roles of ROK outside of SM contractility are also discussed. It is concluded that the RhoA/ROK pathway is critical for the maintenance of basal SM tone of the urinary bladder and serves as a common final pathway of various contractile stimuli in rabbits, rats, mice, and pigs as well as humans. In addition, this pathway is upregulated in response to a number of pathological conditions associated with bladder SM dysfunction. Similarly, RhoA/Rho-kinase signaling is essential for normal ureteral function and development and is upregulated in response to ureteral outlet obstruction. In addition to its critical role in bladder SM function, a role of ROK in the urothelium is also beginning to emerge as well as roles for ROK in bladder infection and invasion and metastasis of bladder cancer.