Rho-kinase inhibition in the therapy of cardiovascular disease

TNF-α Plus IL-1β Induces Opposite Regulation of Cx43 Hemichannels and Gap Junctions in Mesangial Cells through a RhoA/ROCK-Dependent Pathway

Connexin 43 (Cx43) is expressed in kidney tissue where it forms hemichannels and gap junction channels. However, the possible functional relationship between these membrane channels and their role in damaged renal cells remains unknown. Here, analysis of ethidium uptake and thiobarbituric acid reactive species revealed that treatment with TNF-α plus IL-1β increases Cx43 hemichannel activity and oxidative stress in MES-13 cells (a cell line derived from mesangial cells), and in primary mesangial cells. The latter was also accompanied by a reduction in gap junctional communication, whereas Western blotting assays showed a progressive increase in phosphorylated MYPT (a target of RhoA/ROCK) and Cx43 upon TNF-α/IL-1β treatment. Additionally, inhibition of RhoA/ROCK strongly antagonized the TNF-α/IL-1β-induced activation of Cx43 hemichannels and reduction in gap junctional coupling. We propose that activation of Cx43 hemichannels and inhibition of cell-cell coupling during pro-inflammatory conditions could contribute to oxidative stress and damage of mesangial cells via the RhoA/ROCK pathway.

Role of a RhoA/ROCK-Dependent Pathway on Renal Connexin43 Regulation in the Angiotensin II-Induced Renal Damage

In various models of chronic kidney disease, the amount and localization of Cx43 in the nephron is known to increase, but the intracellular pathways that regulate these changes have not been identified. Therefore, we proposed that: "In the model of renal damage induced by infusion of angiotensin II (AngII), a RhoA/ROCK-dependent pathway, is activated and regulates the abundance of renal Cx43". In rats, we evaluated: 1) the time-point where the renal damage induced by AngII is no longer reversible; and 2) the involvement of a RhoA/ROCK-dependent pathway and its relationship with the amount of Cx43 in this irreversible stage. Systolic blood pressure (SBP) and renal function (urinary protein/urinary creatinine: Uprot/UCrea) were evaluated as systemic and organ outcomes, respectively. In kidney tissue, we also evaluated: 1) oxidative stress (amount of thiobarbituric acid reactive species), 2) inflammation (immunoperoxidase detection of the inflammatory markers ED-1 and IL-1β), 3) fibrosis (immune detection of type III collagen; Col III) and 4) activity of RhoA/ROCK (amount of phosphorylated MYPT1; p-MYPT1). The ratio Uprot/UCrea, SBP, oxidative stress, inflammation, amount of Cx43 and p-MYPT1 remained high 2 weeks after suspending AngII treatment in rats treated for 4 weeks with AngII. These responses were not observed in rats treated with AngII for less than 4 weeks, in which all measurements returned spontaneously close to the control values after suspending AngII treatment. Rats treated with AngII for 6 weeks and co-treated for the last 4 weeks with Fasudil, an inhibitor of ROCK, showed high SBP but did not present renal damage or increased amount of renal Cx43. Therefore, renal damage induced by AngII correlates with the activation of RhoA/ROCK and the increase in Cx43 amounts and can be prevented by inhibitors of this pathway.

Newer Therapies for Management of Stable Ischemic Heart Disease With Focus on Refractory Angina

Ischemic heart disease remains a major public health problem nationally and internationally. Stable ischemic heart disease (SIHD) is one of the clinical manifestations of ischemic heart disease and is generally characterized by episodes of reversible myocardial demand/supply mismatch, related to ischemia or hypoxia, which are usually inducible by exercise, emotion, or other stress and reproducible-but which may also be occurring spontaneously. Improvements in the treatment of acute coronary syndromes along with increasing prevalence of cardiovascular risk factors, including diabetes and obesity, have led to increasing population of patients with SIHD. A significant number of these continue to have severe angina despite medical management and revascularization procedures performed and may progress to refractory angina. This article reviews the newer therapies in the treatment of SIHD with special focus in treating patients with refractory angina.

Fasudil evokes vasodilatation of rat mesenteric vascular bed via Ca(2+) channels and Rho/ROCK pathway

As a Rho kinase (ROCK) inhibitor, fasudil has been used in clinical trials of several cardiovascular diseases. This study was to investigate the vasorelaxant effect of fasudil on resistance arterial rings including mesenteric, renal, ventral tail and basilar artery. We also examined the potential mechanisms of its vasodilatory action using mesenteric artery rings. A DMT multiwire myograph system was used to test the tension of isolated small arteries. K(+) channel blockers, NO-cGMP pathway blockers and Ca(2+)-free physiological salt solution (PSS) were employed to verify the underlying mechanisms. Fasudil (10(-7)-10(-4)M) relaxed four types of small artery rings pre-contracted by 60mmol/l KCl (pEC50: 6.01±0.09, 5.47±0.03, 5.54±0.04, and 5.72±0.10 for mesenteric, renal, ventral tail and basilar artery rings, respectively). Pre-incubation with fasudil (1, 3, or 10μmol/l) attenuated KCl (10-60mmol/l) and angiotensin II (Ang II; 1μmol/l)-induced vasoconstriction in mesenteric artery rings. Fasudil at the concentration of 10(-6)mol/l showed different relaxant potency in endothelium intact (pEC50:6.01±0.09) or denued (5.75±0.06) mesenteric artery. The influx and release of Ca(2+) were inhibited by fasudil. In addition, fasudil could block the increased phosphorylation level of myosin light chain (MLC) and myosin-binding subunit of myosin phosphatase (MYPT1) induced by Ang II. However, pretreatment with various K(+) channel blockers did not affect the relaxant effects of fasudil remarkably. The present results demonstrate that fasudil has a vasorelaxant effect on isolated rat resistance arteries, including mesenteric, renal, ventral tail and basilar artery, and may exert its action through the endothelium, Ca(2+) channels, and the Rho/ROCK pathway.

A review on ROCK-II inhibitors: From molecular modelling to synthesis

Rho kinase enzyme expressed in different disease conditions and involved in mediating vasoconstriction and vascular remodeling in the pathogenesis. There are two isoforms of Rho kinases, namely ROCK I and ROCK II, responsible for different physiological function due to difference in distribution, but almost similar in structure. The Rho kinase 2 belongs to AGC family and is widely distributed in brain, heart and muscles. It is responsible for contraction of vascular smooth muscles by calcium sensitization. Its defective and unwanted expression can lead to many medical conditions like multiple sclerosis, myocardial ischemia, inflammatory responses, etc. Many Rho kinase 1 and 2 inhibitors have been designed for Rho/Rho kinase pathway by use of molecular modeling studies. Most of the designed compounds have been modeled based on ROCK 1 enzyme. This article is focused on Rho kinase 2 inhibitors as there are many ways to improvise by use of Computer aided drug designing as very less quantum of research work carried out. Herein, the article highlights different stages of designing like docking, SAR and synthesis of ROCK inhibitors and recent advances. It also highlights future prospective to improve the activity.

Existing drugs and agents under investigation for pulmonary arterial hypertension

Pulmonary arterial hypertension is a progressive and debilitating disorder with an associated high morbidity and mortality rate. Significant advances in our understanding of the epidemiology, pathogenesis, and pathophysiology of pulmonary hypertension have occurred over the past several decades. This has allowed the development of new therapeutic options in this disease. Today, our selection of therapeutic modalities is broader, including calcium channel blockers, prostanoids, endothelin receptor antagonists, phosphodiesterase inhibitors, and soluble guanylate cyclase stimulators, but the disease remains fatal. This underscores the need for a continued search for novel therapies. Several potential pharmacologic agents for the treatment of pulmonary arterial hypertension are under clinical development and some promising results with these treatments have been reported. These agents include rho-kinase inhibitors, long-acting nonprostanoid prostacyclin receptor agonists, tyrosine protein kinase inhibitors, endothelial nitric oxide synthase couplers, synthetically produced vasoactive intestinal peptide, antagonists of the 5-HT2 receptors, and others. This article will review several of these promising new therapies and will discuss the current evidence regarding their potential benefit in pulmonary arterial hypertension.

Inhibitors of the ROCK serine/threonine kinases: key effectors of the RhoA small GTPase

Aberrant activation of the RhoA small GTPase has been implicated in cancer and other human diseases. Therefore, inhibitors of RhoA may have important therapeutic value. However, similar to the Ras small GTPases, RhoA itself is not considered a tractable target and is currently considered to be "undruggable." While recent efforts suggest that direct inhibitors of the Ras oncoprotein may yet be developed, the most promising directions for anti-Ras inhibitors involve inhibitors of protein kinases that are activated downstream of Ras. By analogy, protein kinases activated downstream of RhoA may provide more attractive directions for the development of anti-RhoA inhibitors. Among the multitude of RhoA effectors, the ROCK serine/threonine kinases have emerged as attractive targets for anti-RhoA drug discovery. In this review, we summarize the current status of the development of small molecule inhibitors of ROCK.

Barrier enhancing signals in pulmonary edema

Increased endothelial permeability and reduction of alveolar liquid clearance capacity are two leading pathogenic mechanisms of pulmonary edema, which is a major complication of acute lung injury, severe pneumonia, and acute respiratory distress syndrome, the pathologies characterized by unacceptably high rates of morbidity and mortality. Besides the success in protective ventilation strategies, no efficient pharmacological approaches exist to treat this devastating condition. Understanding of fundamental mechanisms involved in regulation of endothelial permeability is essential for development of barrier protective therapeutic strategies. Ongoing studies characterized specific barrier protective mechanisms and identified intracellular targets directly involved in regulation of endothelial permeability. Growing evidence suggests that, although each protective agonist triggers a unique pattern of signaling pathways, selected common mechanisms contributing to endothelial barrier protection may be shared by different barrier protective agents. Therefore, understanding of basic barrier protective mechanisms in pulmonary endothelium is essential for selection of optimal treatment of pulmonary edema of different etiology. This article focuses on mechanisms of lung vascular permeability, reviews major intracellular signaling cascades involved in endothelial monolayer barrier preservation and summarizes a current knowledge regarding recently identified compounds which either reduce pulmonary endothelial barrier disruption and hyperpermeability, or reverse preexisting lung vascular barrier compromise induced by pathologic insults.

Peripheral circulation

Blood flow (BF) increases with increasing exercise intensity in skeletal, respiratory, and cardiac muscle. In humans during maximal exercise intensities, 85% to 90% of total cardiac output is distributed to skeletal and cardiac muscle. During exercise BF increases modestly and heterogeneously to brain and decreases in gastrointestinal, reproductive, and renal tissues and shows little to no change in skin. If the duration of exercise is sufficient to increase body/core temperature, skin BF is also increased in humans. Because blood pressure changes little during exercise, changes in distribution of BF with incremental exercise result from changes in vascular conductance. These changes in distribution of BF throughout the body contribute to decreases in mixed venous oxygen content, serve to supply adequate oxygen to the active skeletal muscles, and support metabolism of other tissues while maintaining homeostasis. This review discusses the response of the peripheral circulation of humans to acute and chronic dynamic exercise and mechanisms responsible for these responses. This is accomplished in the context of leading the reader on a tour through the peripheral circulation during dynamic exercise. During this tour, we consider what is known about how each vascular bed controls BF during exercise and how these control mechanisms are modified by chronic physical activity/exercise training. The tour ends by comparing responses of the systemic circulation to those of the pulmonary circulation relative to the effects of exercise on the regional distribution of BF and mechanisms responsible for control of resistance/conductance in the systemic and pulmonary circulations.

Kamolonol suppresses angiotensin II-induced stress fiber formation and cellular hypertrophy through inhibition of Rho-associated kinase 2 activity

Kamolonol (7-[[(1R,2R,4R,4aS,5R,8aS)-4-hydroxy-1,2,4a,5-tetramethyl-6-oxo-3,4,5,7,8,8a-hexahydro-2H-naphthalen-1-yl]methoxy]chromen-2-one) is a sesquiterpene coumarin and an active component of gum extracts from Ferulaassafoetida. The aim of this study was to investigate the anti-fibrotic and anti-cellular hypertrophic effects of kamolonol, and further to explore its possible mechanism. Kamolonol (3-30μM) significantly inhibited stress fiber formation induced by angiotensin II (Ang II) in rat heart-derived H9c2 cells. Furthermore, kamolonol (3-30μM) showed a potent inhibitory effect on Ang II-induced cellular hypertrophy in H9c2 cells. Next, a Rho-associated kinase (ROCK) activity was measured because actin stress fiber formation and/or cellular hypertrophy are usually induced by the activation of ROCK. Rho-associated kinase 2 (ROCK2) studies using a time-resolved fluorescence resonance energy transfer (TR-FRET) showed that kamolonol possesses a potent ROCK2 inhibitory activity with IC50 values of 2.27μM, and has an ATP-competitive inhibitory mode. In validation study, pretreatment of kamolonol (3-30μM) for 2h decreased the Ang II-induced phosphorylation of myosin phosphatase 1 (MYPT1) and myosin light chain 2 (MLC2). Taken together, these results indicate that kamolonol suppresses Ang II-induced stress fiber formation and cellular hypertrophy, and propose that one mechanism underlying these anti-fibrotic and anti-cellular hypertrophic effects involves inhibition of the ROCK-MLC pathway.

Age-associated differences in gene expression in response to delayed anesthetic preconditioning

Evidence suggests that the protective benefits of anesthetic preconditioning (APC) are significantly attenuated in the aged myocardium. In this study, we investigated the effect of aging on gene expression in delayed APC. Hearts from Fischer 344 rats, age 4 or 24 months, were divided into five groups: control; ischemia/reperfusion (I/R); and delayed APC at 6, 12, and 24 h. Whole-genome array was studied using Affymetrix Rat Genome 230 2.0 array. Data were analyzed for significant ≥2.0-fold changes in gene expression. Microarray results were confirmed by quantitative real-time reverse transcription-polymerase chain reaction. Of the 28,000 genes represented on the Affymetrix Rat Genome 230 2.0 Microarray chip, 24 transcripts in 6 h APC, 28 in 12 h APC, and 28 in 24 h APC group displayed significant up-regulation in mRNA levels, and 70 transcripts in 6 h APC, 101 in 12 h APC, and 82 in 24 h APC displayed significant down-regulation in young rat hearts. These altered genes fall into functional categories of cell defense/death, cell structure, gene expression/protein synthesis, inflammatory response/growth/remodeling, and signaling/communication. Although alterations for some genes were in common, the numbers of changed genes in old rats were markedly and consistently lower than the young rats. Twenty-four hour delayed APC also significantly reduced infarct size and improved myocardial left ventricular function in young hearts, effects that were not observed in old rat hearts. We concluded that delayed APC profoundly and differentially affected gene expression profiles of the cardiomyocyte in an age-associated pattern. The impaired genomic response to delayed APC could underlie the loss of the protective benefits of preconditioning in aged hearts.

Ventricular-vascular interaction in heart failure

Nearly half of all patients who have heart failure have preserved ejection fraction (HFpEF). Patients who have HFpEF tend to be older, female, and hypertensive, and characteristically display increased ventricular and arterial stiffening. In this article, we discuss the pathophysiology of abnormal ventriculoarterial stiffening and how it affects ventricular function, cardiovascular hemodynamics, reserve capacity, and symptoms. We conclude by exploring how novel treatment strategies targeting abnormal ventricular-arterial interaction might prove useful in the treatment of patients who have HFpEF.

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.

New approaches to the treatment of pulmonary hypertension: from bench to bedside

Pulmonary hypertension (PH) is a severe, life-threatening disease for which there are no effective curative therapies. A diverse group of agents such as prostacyclins, endothelin antagonists, phosphodiesterase inhibitors, calcium channel blockers, diuretics, inotropic agents, and anticoagulants are used to treat PH; however, none of these agents have a marked effect upon survival. Among the new agents that promise treatment of PH are rho-kinase inhibitors and soluble guanylate cyclase stimulators. Although these new classes of agents have beneficial effects in experimental animal models and clinical studies, they are not selective in their actions on the pulmonary vascular bed. This manuscript reviews the actions of rho-kinase inhibitors and soluble guanylate cyclase stimulators on the pulmonary vascular bed. It is our hypothesis that these new agents may be more effective than current therapies in the treatment of PH. Moreover, new methods in the delivery of these agents to the lung need to be developed so that their main effects will be exerted in the pulmonary vascular bed and their systemic effects can be minimized or avoided.

Heart failure with preserved ejection fraction: pathophysiology, diagnosis, and treatment

Half of patients with heart failure (HF) have a preserved left ventricular ejection fraction (HFpEF). Morbidity and mortality in HFpEF are similar to values observed in patients with HF and reduced EF, yet no effective treatment has been identified. While early research focused on the importance of diastolic dysfunction in the pathophysiology of HFpEF, recent studies have revealed that multiple non-diastolic abnormalities in cardiovascular function also contribute. Diagnosis of HFpEF is frequently challenging and relies upon careful clinical evaluation, echo-Doppler cardiography, and invasive haemodynamic assessment. In this review, the principal mechanisms, diagnostic approaches, and clinical trials are reviewed, along with a discussion of novel treatment strategies that are currently under investigation or hold promise for the future.

Optimisation of 6-substituted isoquinolin-1-amine based ROCK-I inhibitors

Rho kinase is an important target implicated in a variety of cardiovascular diseases. Herein, we report the optimisation of the fragment derived ATP-competitive ROCK inhibitors 1 and 2 into lead compound 14A. The initial goal of improving ROCK-I potency relative to 1, whilst maintaining a good PK profile, was achieved through removal of the aminoisoquinoline basic centre. Lead 14A was equipotent against both ROCK-I and ROCK-II, showed good in vivo efficacy in the spontaneous hypertensive rat model, and was further optimised to demonstrate the scope for improving selectivity over PKA versus hydroxy Fasudil 3.

Rho-kinase signalling regulates CXC chemokine formation and leukocyte recruitment in colonic ischemia-reperfusion

BACKGROUND AND AIMS

Leukocyte recruitment is a key feature in ischemia-reperfusion (I/R)-induced tissue injury. The aim of the present study was to investigate the effect of Rho-kinase inhibition on I/R-provoked leukocyte recruitment in the colon.

METHODS

C57BL/6 mice were subjected to 30 min of ischemia by clamping of the superior mesenteric artery followed by 120 min of reperfusion. Intraperitoneal pretreatment with the selective Rho-kinase inhibitors fasudil (4-40 mg/kg) and Y-27632 (1-10 mg/kg) was administered prior to induction of colonic I/R. Leukocyte-endothelium interactions were analyzed by intravital fluorescence microscopy. Colonic content of tumour necrosis factor-alpha (TNF-alpha) and the CXC chemokines macrophage inflammatory protein-2 (MIP-2) and cytokine-induced neutrophil chemoattractant (KC) were determined by ELISA. Additionally, colonic activity of myeloperoxidase (MPO), a marker of leukocyte infiltration, and malondialdehyde (MDA), were quantified.

RESULTS

Fasudil and Y-27632 pretreatment decreased I/R-induced leukocyte rolling and adhesion by 76% and 96%, respectively. Moreover, Rho-kinase interference reduced formation of TNF-alpha, MIP-2 and KC by more than 68% in the reperfused colon. Additionally, the reperfusion-provoked increase in the levels of MPO and MDA in the colon decreased after Rho-kinase inhibition by 69% and 42%, respectively.

CONCLUSIONS

Our data demonstrate that inhibition of Rho-kinase activity decrease I/R-induced leukocyte rolling, adhesion and recruitment in the colon. Moreover, these findings show that Rho-kinase signalling regulates TNF-alpha and CXC chemokine formation as well as lipid peroxidation in the reperfused colon. Thus, targeting Rho-kinase signalling may be a useful strategy in order to protect against pathological inflammation in the colon.

Heart failure with preserved ejection fraction: pathophysiology and emerging therapies

Approximately half of patients with heart failure (HF) have a preserved ejection fraction (HFpEF). Morbidity and mortality are similar to HF with reduced EF (HFrEF), yet therapies with unequivocal benefit in HFrEF have not been shown to be effective in HFpEF. Recent studies have shown that the pathophysiology of HFpEF, initially believed to be due principally to diastolic dysfunction, is more complex. Appreciation of this complexity has shed new light into how HFpEF patients might respond to traditional HF treatments, while also suggesting new applications for novel therapies and strategies. In this review, we shall briefly review the pathophysiologic mechanisms in HFpEF, currently available clinical trial data, and finally explore new investigational therapies that are being developed and tested in ongoing and forthcoming trials.

Hit to lead account of the discovery of bisbenzamide and related ureidobenzamide inhibitors of Rho kinase

A highly selective series of bisbenzamide inhibitors of Rho-associated coiled-coil forming protein kinase (ROCK) and a related ureidobenzamide series, both identified by high throughput screening (HTS), are described. Details of the hit validation and lead generation process, including structure-activity relationship (SAR) studies, a selectivity assessment, target-independent profiling (TIP) results, and an analysis of functional activity using a rat aortic ring assay are discussed.

Prostanoid TP receptor-mediated impairment of cyclic AMP-dependent vasorelaxation is reversed by phosphodiesterase inhibitors

Activation of the thromboxane prostanoid (TP) receptor produces potent vasoconstriction, which contributes to the increased vascular tone and blood pressure. The present study was designed to examine the hypothesis that stimulation of prostanoid TP receptors impairs endothelium-independent relaxations to cyclic AMP-elevating agents via increasing the activity of phosphodiesterases (PDEs). Rat carotid arteries without endothelium were isolated and suspended in myograph for the measurement of changes in isometric tension; the tissue content of cyclic AMP was assayed by enzyme immunoassay kit; and prostanoid TP receptor was detected in vascular wall by immunohistochemistry and Western blot. In phenylephrine-contracted rings without endothelium, relaxations induced by isoprenaline (receptor-mediated) and forskolin (receptor-independent) were markedly reduced by the presence of a prostanoid TP receptor agonist, U46619; the attenuated relaxations were prevented by acute treatment with S18886, the selective prostanoid TP receptor antagonist, but not by protein kinase C inhibitors. The reduced relaxations were partially restored by IBMX (non-selective PDE inhibitor), cilostazol (PDE3 inhibitor), rolipram (PDE4 inhibitor) or by Y27632 (Rho kinase inhibitor), but not by T0156 (PDE5 inhibitor). U46619 diminished isoprenaline- or forskolin-stimulated rise in cyclic AMP and this effect was inhibited by cilostazol, rolipram or Y27632. The present results suggest that activation of prostanoid TP receptors impairs cyclic AMP-dependent vasorelaxations partly via PDE- and RhoA/Rho kinase-dependent mechanisms. Inhibitors of PDEs and Rho kinase may be useful in the treatment of cardiovascular complications.

Role of AKT-glycogen synthase kinase axis in monocyte activation in human beings with and without type 2 diabetes

Monocyte activation by chemokines is a vital trigger for initiation of atherosclerotic process. Circulating levels of platelet activating factor (PAF), a recognized chemokine, is known to be increased in type 2 diabetes that is linked to accelerated atherosclerosis. To explore the molecular basis we examined the signalling pathways involved in PAF induced monocyte activation. PAF increased migration in monocytes obtained from THP-1 cells, nondiabetic and diabetic subjects. This effect was blocked by AKT inhibition. It did so by phosphorylation of glycogen synthase kinase (GSK)-3βS⁹, which was completely blocked by AKT inhibition. Additionally, PAF induced GSK-3β phosphorylation was linked to Rac-1 activation and Rho-A inactivation leading to migration. Paradoxically, inhibition of GSK-3β phosphorylation also augmented monocyte migration in THP-1, ND and diabetic monocytes through phosphorylation of AKT and activation of Rho-A that was independent of GSK. This was validated when (i) overexpression of dominant negative mutants of Rho-A reversed GSK inhibitor induced monocyte migration and (ii) AKT inhibition blocked GSK inhibitor induced Rho-A activity. Constitutively active ARAP3 (Rho-GAP) appears to have a regulatory role in monocyte activity during GSK inhibition. Finally, inhibition of monocyte GSK-3β activity (by inhibitors and genetic manipulation) led to enhanced migration in diabetes compared to persons without diabetes. We conclude that diabetic monocytes show increased migratory capacity in response to GSK-3β inhibition. GSK inhibitors developed to treat the metabolic complications of diabetes should therefore be used with caution.

The pathogenic mechanisms of polyglutamine diseases and current therapeutic strategies

Expansion of CAG trinucleotide repeat within the coding region of several genes results in the production of proteins with expanded polyglutamine (PolyQ) stretch. The expression of these pathogenic proteins leads to PolyQ diseases, such as Huntington's disease or several types of spinocerebellar ataxias. This family of neurodegenerative disorders is characterized by constant progression of the symptoms and molecularly, by the accumulation of mutant proteins inside neurons causing their dysfunction and eventually death. So far, no effective therapy actually preventing the physical and/or mental decline has been developed. Experimental therapeutic strategies either target the levels or processing of mutant proteins in an attempt to prevent cellular deterioration, or they are aimed at the downstream pathologic effects to reverse or ameliorate the caused damages. Certain pathomechanistic aspects of PolyQ disorders are discussed here. Relevance of disease models and recent knowledge of therapeutic possibilities is reviewed and updated.

Pharmacological characterization of SAR407899, a novel rho-kinase inhibitor

Recent advances in basic and clinical research have identified Rho kinase as an important target potentially implicated in a variety of cardiovascular diseases. Rho kinase is a downstream mediator of RhoA that leads to stress fiber formation, membrane ruffling, smooth muscle contraction, and cell motility. Increased Rho-kinase activity is associated with vasoconstriction and elevated blood pressure. We identified a novel inhibitor of Rho kinase (SAR407899) and characterized its effects in biochemical, cellular, tissue-based, and in vivo assays. SAR407899 is an ATP-competitive Rho-kinase inhibitor, equipotent against human and rat-derived Rho-kinase 2 with inhibition constant values of 36 nM and 41 nM, respectively. It is highly selective in panel of 117 receptor and enzyme targets. SAR407899 is approximately 8-fold more active than fasudil. In vitro, SAR407899 demonstrated concentration-dependent inhibition of Rho-kinase-mediated phosphorylation of myosin phosphatase, thrombin-induced stress fiber formation, platelet-derived growth factor-induced proliferation, and monocyte chemotactic protein-1-stimulated chemotaxis. SAR407899 potently (mean IC(50) values: 122 to 280 nM) and species-independently relaxed precontracted isolated arteries of different species and different vascular beds. In vivo, over the dose range 3 to 30 mg/kg PO, SAR407899 lowered blood pressure in a variety of rodent models of arterial hypertension. The antihypertensive effect of SAR407899 was superior to that of fasudil and Y-27632. In conclusion, SAR407899 is a novel and potent selective Rho-kinase inhibitor with promising antihypertensive activity.

Sustained cardioprotection: exploring unconventional modalities

Since Murry et al. [Murry, C.E., Jennings, R.B., Reimer, K.A., 1986. Preconditioning with ischemia: a delay of lethal cell injury in ischemic myocardium. Circulation. 74, 1124-36.] initially reported on the powerful protective effects of ischemic preconditioning (PC), a plethora of experimental investigations have identified varied preconditioning protocols or mimetics to achieve cardioprotection. These stimuli predominantly act via archetypal mediators identified in associated signalling studies (including PI3-K, Akt, PKC, mitochondrial K(ATP) channels). Despite an intense research effort over the last 20 years, there remains a paucity of evidence that this protective paradigm is clinically exploitable. This may arise due to a number of drawbacks to conventional protection, including effects of age, disease, and interactions with other pharmacological agents. This encourages investigation of alternate strategies that trigger protection via unconventional signalling (distinct from conventional PC) and/or mediate sustained shifts in ischemic tolerance in hearts of varying age and disease status. This review considers briefly drawbacks to conventional PC, and focuses on alternate strategies for generating prolonged states of cardiac protection.

Control of pulmonary vascular tone during exercise in health and pulmonary hypertension

Despite the importance of the pulmonary circulation as a determinant of exercise capacity in health and disease, studies into the regulation of pulmonary vascular tone in the healthy lung during exercise are scarce. This review describes the current knowledge of the role of various endogenous vasoactive mechanisms in the control of pulmonary vascular tone at rest and during exercise. Recent studies demonstrate an important role for endothelial factors (NO and endothelin) and neurohumoral factors (noradrenaline, acetylcholine). Moreover, there is evidence that natriuretic peptides, reactive oxygen species and phosphodiesterase activity can influence resting pulmonary vascular tone, but their role in the control of pulmonary vascular tone during exercise remains to be determined. K-channels are purported end-effectors in control of pulmonary vascular tone. However, K(ATP) channels do not contribute to regulation of pulmonary vascular tone, while the role of K(V) and K(Ca) channels at rest and during exercise remains to be determined. Pulmonary hypertension is associated with alterations in pulmonary vascular function and structure, resulting in blunted pulmonary vasodilatation during exercise and impaired exercise capacity. Although there is a paucity of studies pertaining to the regulation of pulmonary vascular tone during exercise in idiopathic pulmonary hypertension, the few studies that have been performed in models of pulmonary hypertension secondary to left ventricular dysfunction suggest altered control of pulmonary vascular tone during exercise. Since the increased pulmonary vascular tone during exercise limits exercise capacity, future studies are needed to investigate the vasomotor mechanisms that are responsible for the blunted exercise-induced pulmonary vasodilatation in pulmonary hypertension.

Ventricular-vascular interaction in heart failure

Nearly half of all patients who have heart failure have preserved ejection fraction (HFpEF). Patients who have HFpEF tend to be older, female, and hypertensive, and characteristically display increased ventricular and arterial stiffening. In this article, we discuss the pathophysiology of abnormal ventriculoarterial stiffening and how it affects ventricular function, cardiovascular hemodynamics, reserve capacity, and symptoms. We conclude by exploring how novel treatment strategies targeting abnormal ventricular-arterial interaction might prove useful in the treatment of patients who have HFpEF.

ROCK inhibition and CNTF interact on intrinsic signalling pathways and differentially regulate survival and regeneration in retinal ganglion cells

Functional regeneration in the CNS is limited by lesion-induced neuronal apoptosis and an environment inhibiting axonal elongation. A principal, yet unresolved question is the interaction between these two major factors. We thus evaluated the role of pharmacological inhibition of rho kinase (ROCK), a key mediator of myelin-derived axonal growth inhibition and CNTF, a potent neurotrophic factor for retinal ganglion cells (RGC), in models of retinal ganglion cell apoptosis and neurite outgrowth/regeneration in vitro and in vivo. Here, we show for the first time that the ROCK inhibitor Y-27632 significantly enhanced survival of RGC in vitro and in vivo. In vitro, the co-application of CNTF and Y-27632 potentiated the effect of either substance alone. ROCK inhibition resulted in the activation of the intrinsic MAPK pathway, and the combination of CNTF and Y-27632 resulted in even more pronounced MAPK activation. While CNTF also induced STAT3 phosphorylation, the additional application of ROCK inhibitor surprisingly diminished the effects of CNTF on STAT3 phosphorylation. ROCK activity was also decreased in an additive manner by both substances. In vivo, both CNTF and Y-27632 enhanced regeneration of RGC into the non-permissive optic nerve crush model and additive effects were observed after combination treatment. Further evaluation using specific inhibitors delineate STAT3 as a negative regulator of neurite growth and positive regulator of cell survival, while MAPK and Akt support neurite growth. These results show that next to neurotrophic factors ROCK inhibition by Y-27632 potently supports survival of lesioned adult CNS neurons. Co-administration of CNTF and Y-27632 results in additive effects on neurite outgrowth and regeneration. The interaction of intracellular signalling pathways may, however, attenuate more pronounced synergy and has to be taken into account for future treatment strategies.

Rho kinase and Ca2+ entry mediate increased pulmonary and systemic vascular resistance in l-NAME-treated rats

The small GTP-binding protein and its downstream effector Rho kinase play an important role in the regulation of vasoconstrictor tone. Rho kinase activation maintains increased pulmonary vascular tone and mediates the vasoconstrictor response to nitric oxide (NO) synthesis inhibition in chronically hypoxic rats and in the ovine fetal lung. However, the role of Rho kinase in mediating pulmonary vasoconstriction after NO synthesis inhibition has not been examined in the intact rat. To address this question, cardiovascular responses to the Rho kinase inhibitor fasudil were studied at baseline and after administration of an NO synthesis inhibitor. In the intact rat, intravenous injections of fasudil cause dose-dependent decreases in systemic arterial pressure, small decreases in pulmonary arterial pressure, and increases in cardiac output. l-NAME caused a significant increase in pulmonary and systemic arterial pressures and a decrease in cardiac output. The intravenous injections of fasudil after l-NAME caused dose-dependent decreases in pulmonary and systemic arterial pressure and increases in cardiac output, and the percent decreases in pulmonary arterial pressure in response to the lower doses of fasudil were greater than decreases in systemic arterial pressure. The Ca++ entry blocker isradipine also decreased pulmonary and systemic arterial pressure in l-NAME-treated rats. Infusion of sodium nitroprusside restored pulmonary arterial pressure to baseline values after administration of l-NAME. These data provide evidence in support of the hypothesis that increases in pulmonary and systemic vascular resistance following l-NAME treatment are mediated by Rho kinase and Ca++ entry through L-type channels, and that responses to l-NAME can be reversed by an NO donor.

Inhibition of rho-kinase impairs fibroblast stress fiber formation, confluence, and contractility in vitro

Rho kinase is an enzyme that has been implicated in pathological wound healing. In our study, we aimed to characterize the dosages of Y-27632 (a competitive inhibitor of rho kinase) at which fibroblast stress fiber formation is inhibited, to determine the effect of Y-27632 on fibroblast confluence, and to determine the effect of varying concentrations of Y-27632 on fibroblast-mediated gel contraction. First, 3T3 fibroblasts were exposed to various concentrations of Y-27632, and stress fiber dissolution was assessed with immunofluorescence. Next, 10 microM Y-27632 was applied to 3T3 fibroblast monolayer cultures immediately after plating and at 8 hours after plating to determine the effect on fibroblast confluence. Finally, a three-dimensional model was used to assess the effect of Y-27632 on gel contraction. Increasing doses of Y-27632 resulted in a dose-dependent increase in stress fiber dissolution as well as a dose-dependent inhibition of gel contraction. Median number of days to confluence were 3, 5, and 6 after no, immediate, and delayed incubation with Y-27632, respectively (P < .05). Our results further characterize the dosages at which Y-27632 may be most effective in the modulation of wound contraction in burn patients. In addition, our confluence study suggests that patients need not necessarily be pretreated with Y-27632.

Small-molecule therapies for cardiac hypertrophy: moving beneath the cell surface

Pathological stress from cardiovascular disease stimulates hypertrophy of heart cells, which increases the risk of cardiac morbidity and mortality. Recent evidence has indicated that inhibiting such hypertrophy could be beneficial, encouraging drug discovery and development efforts for agents that could achieve this goal. Most existing therapies that have antihypertrophic effects target outside-in signalling in cardiac cells, but their effectiveness seems limited, and so attention has recently turned to the potential of targeting intracellular signalling pathways. Here, we focus on new developments with small-molecule inhibitors of cardiac hypertrophy, summarizing both agents that have been in or are poised for clinical testing, and pathways that offer further promising potential therapeutic targets.

Rho and ROCK signaling in VEGF-induced microvascular endothelial hyperpermeability

OBJECTIVES

Vascular endothelial growth factor (VEGF) plays an important role in the regulation of microvascular permeability under various physiological and pathological conditions. The authors tested the hypothesis that the small GTPase Rho and its downstream effector ROCK (Rho-associated coiled-coil-containing protein kinase) mediate VEGF-induced increases in venular permeability. They also investigated myosin light chain (MLC) phosphorylation and actin polymerization, two well-characterized targets of the Rho-ROCK pathway that are implicated in the regulation of endothelial barrier function.

METHODS

The apparent permeability coefficient of albumin (P(a)) was measured in intact isolated porcine coronary venules and in cultured coronary venular endothelial cell (CVEC) monolayers. RhoA activation was determined using a Rhotekin-agarose pull down assay. MLC phosphorylation was evaluated by immunoblotting with phospho-specific antibodies, and endothelial cellular F-actin was viewed using fluorescence microscopy.

RESULTS

VEGF increased P(a) in both isolated coronary venules and CVEC monolayers. The hyperpermeability response occurred in a similar time course to that of Rho activation, MLC phosphorylation, and actin stress fiber formation. Selective blockage of ROCK with Y27632 dose-dependently inhibited VEGF-induced venular hyperpermeability. Moreover, inhibition of either Rho with exoenzyme C3 or ROCK with Y-27632 attenuated VEGF-induced increases in permeability, MLC phosphorylation, and actin-stress fiber formation in CVEC monolayers.

CONCLUSIONS

Collectively, these findings suggest that the Rho-ROCK signal pathway contributes to VEGF-induced hyperpermeability. Myosin light-chain phosphorylation and actin stress fiber formation occur concomitantly with the increase in permeability upon VEGF stimulation.