The Function of Rho-Associated Kinases ROCK1 and ROCK2 in the Pathogenesis of Cardiovascular Disease

Selective inhibition of brain endothelial Rho-kinase-2 provides optimal protection of an in vitro blood-brain barrier from tissue-type plasminogen activator and plasmin

Rho-kinase (ROCK) inhibition, broadly utilised in cardiovascular disease, may protect the blood-brain barrier (BBB) during thrombolysis from rt-PA-induced damage. While the use of nonselective ROCK inhibitors like fasudil together with rt-PA may be hindered by possible hypotensive side-effects and inadequate capacity to block detrimental rt-PA activity in brain endothelial cells (BECs), selective ROCK-2 inhibition may overcome these limitations. Here, we examined ROCK-2 expression in major brain cells and compared the ability of fasudil and KD025, a selective ROCK-2 inhibitor, to attenuate rt-PA-induced BBB impairment in an in vitro human model. ROCK-2 was highly expressed relative to ROCK-1 in all human and mouse brain cell types and particularly enriched in rodent brain endothelial cells and astrocytes compared to neurons. KD025 was more potent than fasudil in attenuation of rt-PA- and plasminogen-induced BBB permeation under normoxia, but especially under stroke-like conditions. Importantly, only KD025, but not fasudil, was able to block rt-PA-dependent permeability increases, morphology changes and tight junction degradation in isolated BECs. Selective ROCK-2 inhibition further diminished rt-PA-triggered myosin phosphorylation, shape alterations and matrix metalloprotease activation in astrocytes. These findings highlight ROCK-2 as the key isoform driving BBB impairment and brain endothelial damage by rt-PA and the potential of KD025 to optimally protect the BBB during thrombolysis.

Membrane depolarization activates BK channels through ROCK-mediated β1 subunit surface trafficking to limit vasoconstriction

Membrane depolarization of smooth muscle cells (myocytes) in the small arteries that regulate regional organ blood flow leads to vasoconstriction. Membrane depolarization also activates large-conductance calcium (Ca²⁺)-activated potassium (BK) channels, which limits Ca²⁺ channel activity that promotes vasoconstriction, thus leading to vasodilation. We showed that in human and rat arterial myocytes, membrane depolarization rapidly increased the cell surface abundance of auxiliary BK β1 subunits but not that of the pore-forming BKα channels. Membrane depolarization stimulated voltage-dependent Ca²⁺ channels, leading to Ca²⁺ influx and the activation of Rho kinase (ROCK) 1 and 2. ROCK1/2-mediated activation of Rab11A promoted the delivery of β1 subunits to the plasma membrane by Rab11A-positive recycling endosomes. These additional β1 subunits associated with BKα channels already at the plasma membrane, leading to an increase in apparent Ca²⁺ sensitivity and activation of the channels in pressurized arterial myocytes and vasodilation. Thus, membrane depolarization activates BK channels through stimulation of ROCK- and Rab11A-dependent trafficking of β1 subunits to the surface of arterial myocytes.

The Role of Rho/Rho-Kinase Pathway in the Pathogenesis of Cholesteatoma

OBJECTIVE

To assess the role of Rho/Rho-kinase pathway in the pathogenesis of cholesteatoma.

MATERIALS AND METHODS

Thirty-eight patients with cholesteatoma, who had gone mastoidectomies were enrolled in this prospective study. Cholesteatomas matrix (CM) and a piece of the external ear canal skin (EECS as control) were taken and transferred to the liquid nitrogen and kept at -86 °C for Rho A and Rho-kinase (ROCK) analysis with Western blotting and commercial ELISA kits (Cell Biolabs Inc., San Diego, CA). The tissues were homogenized by an appropriate ice-cold lysis buffer. Following centrifugation, the supernatant was taken and total protein amount was detected by the Bradford method. Thereafter, tissue homogenates were subjected to sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis electrophoresis then transferred to nitrocellulose membrane where it was treated with specific monoclonal primary antibody against to ROCK-2 and HRP-conjugated seconder antibody, respectively. The protein blots were visualized with commercial x-ray film and dansitometrically analyzed by the Scion Image Program (Cell Biolabs Inc., San Diego, CA). In another series of experiments, Rho-kinase activities were assessed by ROCK-2 ELISA kits.

RESULTS

There were no statistical differences in Rho A translocation between CM and EECS. However, ROCK activity was found to be lower in CM than EECS as detected by ELISA kits. Furthermore, ROCK protein expression was also significantly lower in CM than EECS as demonstrated by Western blotting.

CONCLUSION

Given Rho-kinase could take essential roles in cell differentiation, the results of this study implicate that down-regulated Rho-kinase could be responsible for the keratinocyte undifferentiation seen in cholesteatoma pathogenesis.

Fn14 is regulated via the RhoA pathway and mediates nuclear factor-kappaB activation by Angiotensin II

Angiotesin II (Ang II) plays an important role in cardiac remodeling. Fibroblast growth factor inducible-14 (Fn14) is the smallest member of the tumor necrosis factor superfamily of receptors. Currently, little is known about the functional role of Fn14 in the heart. Chiefly, we observe the up-regulation of extracellular matrix in in vivo model. We therefore assess the expression and regulation of Fn14 in cardiomyocytes and in vivo models induced by Ang II. In order to study the regulation of Fn14, cardiac remodeling was established in rats and neonatal cardiomyocytes were used in in vitro model. As well, Ang II is able to strongly induce Fn14 expression in in vivo and in vitro models. Fn14 is mediated via RhoA pathways, since siRNA against RhoA prevented the expression of Fn14 in cardiomyocytes. Pretreatment of cardiomyoctes with siRNA against NF-κB and IκBα also decreased Fn14 expression induced by Ang II. We here describe for the first time Ang II regulation of Fn14 in in vivo and in vitro models via RhoA, NF-κB and NF-κB driven gene signaling pathway. In conclusion, Fn14 may be important in regulating the process of cardiac remodeling induced by Ang II.

Regulation of pulmonary endothelial barrier function by kinases

The pulmonary endothelium is the target of continuous physiological and pathological stimuli that affect its crucial barrier function. The regulation, defense, and repair of endothelial barrier function require complex biochemical processes. This review examines the role of endothelial phosphorylating enzymes, kinases, a class with profound, interdigitating influences on endothelial permeability and lung function.

Role of the Rho GTPase/Rho kinase signaling pathway in pathogenesis and treatment of glaucoma: Bench to bedside research

Glaucoma is a leading cause of irreversible blindness worldwide. Elevated intraocular pressure (IOP) is considered to be a predominant risk factor for primary open angle glaucoma, the most prevalent form of glaucoma. Although the etiological mechanisms responsible for increased IOP are not completely clear, impairment in aqueous humor (AH) drainage through the conventional or trabecular pathway is recognized to be a primary cause in glaucoma patients. Importantly, lowering of IOP has been demonstrated to reduce progression of vision loss and is a mainstay of treatment for all types of glaucoma. Currently however, there are limited therapeutic options available for lowering IOP especially as it relates to enhancement of AH outflow through the trabecular pathway. Towards addressing this challenge, bench and bedside research conducted over the course of the last decade and a half has identified the significance of inhibiting Rho kinase for lowering IOP. Rho kinase is a downstream effector of Rho GTPase signaling that regulates actomyosin dynamics in numerous cell types. Studies from several laboratories have demonstrated that inhibition of Rho kinase lowers IOP via relaxation of the trabecular meshwork which enhances AH outflow. By contrast, activation of Rho GTPase/Rho kinase signaling in the trabecular outflow pathway increases IOP by altering the contractile, cell adhesive and permeability barrier characteristics of the trabecular meshwork and Schlemm's canal tissues, and by influencing extracellular matrix production and fibrotic activity. This article, written in honor of the late David Epstein, MD, summarizes findings from both basic and clinical studies that have been instrumental for recognition of the importance of the Rho/Rho kinase signaling pathway in regulation of AH outflow, and in the development of Rho kinase inhibitors as promising IOP- lowering agents for glaucoma treatment.

Progress on the cardiotoxicity of sunitinib: Prognostic significance, mechanism and protective therapies

Tyrosine kinase inhibitors (TKIs) are multi-targeted anti-cancer agents effective in the treatment of renal cell carcinoma (RCC), imatinib-resistant gastrointestinal stromal tumor (GIST) and pancreatic cancer (PC). Targeting and inhibiting a wide range of oncogenically relevant receptor tyrosine kinases (RTKs), TKIs have been the golden standard treatment of several types of cancer. The cardiotoxicity of TKIs, however, has also emerged alongside their anti-cancer potencies and has attracted research attention. Over the past few years significant progress has been made in developing a deeper understanding of aspects such as extent of cardiotoxicity, prognostic implications and survival predictions, toxicological mechanisms, and potential cardioprotective therapies. In this review we focus on a typical TKI sunitinib and summarize the up-to-date knowledge of sunitinib-induced cardiac abnormalities reported in clinical studies, weighing their implications of prognostic values. We also examine recent findings in underlying mechanisms, and development of potential cardioprotective agents.

The effects of ripasudil (K-115), a Rho kinase inhibitor, on activation of human conjunctival fibroblasts

The most common cause of glaucoma surgery failure is scar formation induced by activation of wound-healing responses and resultant fibrosis at the surgical site. We investigated the effects of ripasudil, a Rho kinase inhibitor, on activation of human conjunctival fibroblasts (HConF). HConF were pretreated with different concentrations of ripasudil for 1 h before addition of transforming growth factor (TGF)-β2, followed by incubation for 48 h. TGF-β2-treated fibroblasts exhibited a significant increase in expression of α-smooth muscle actin (α-SMA), a marker of fibroblast-to-myofibroblast differentiation, and this increase was significantly suppressed, in a dose-dependent manner, by pretreatment with ripasudil. Ripasudil pretreatment also significantly attenuated TGF-β2-induced fibronectin production and collagen gel contraction. TGF-β2 increased both the number of viable cells and the number of cells in the G2/M phase of the cell cycle; these effects were attenuated by pretreatment with ripasudil. In addition, we explored the effects of ripasudil on stimulation of HConF by activated macrophages. Human monocytic cell line THP-1 cells were differentiated into M1 or M2 macrophage-like cells, and HConF were treated with conditioned media derived from these macrophages in the presence or absence of ripasudil. Conditioned medium from M2 macrophage-like cells induced a significant increase in α-SMA expression, viable cell numbers, and gel contraction, all of which were significantly suppressed by ripasudil. Thus, overall, ripasudil attenuated activation of human conjunctival fibroblasts. Ripasudil may be of therapeutic utility, preventing excessive scarring after glaucoma filtration surgery.

Focused Proteomics Revealed a Novel Rho-kinase Signaling Pathway in the Heart

Protein phosphorylation plays an important role in the physiological regulation of cardiac function. Myocardial contraction and pathogenesis of cardiac diseases have been reported to be associated with adaptive or maladaptive protein phosphorylation; however, phosphorylation signaling in the heart is not fully elucidated. We recently developed a novel kinase-interacting substrate screening (KISS) method for exhaustive screening of protein kinase substrates, using mass spectrometry and affinity chromatography. First, we examined protein phosphorylation by extracellular signal-regulated kinase (ERK) and protein kinase A (PKA), which has been relatively well studied in cardiomyocytes. The KISS method showed that ERK and PKA mediated the phosphorylation of known cardiac-substrates of each kinase such as Rps6ka1 and cTnI, respectively. Using this method, we found about 330 proteins as Rho-kinase-mediated substrates, whose substrate in cardiomyocytes is unknown. Among them, CARP/Ankrd1, a muscle ankyrin repeat protein, was confirmed as a novel Rho-kinase-mediated substrate. We also found that non-phosphorylatable form of CARP repressed cardiac hypertrophy-related gene Myosin light chain-2v (MLC-2v) promoter activity, and decreased cell size of heart derived H9c2 myoblasts more efficiently than wild type-CARP. Thus, focused proteomics enable us to reveal a novel signaling pathway in the heart.

The cytoskeleton as a novel target for treatment of renal fibrosis

The incidence of chronic kidney disease (CKD) is increasing, with an estimated prevalence of 12% in the United States (Synder et al., 2009). While CKD may progress to end-stage renal disease (ESRD), which necessitates renal replacement therapy, i.e. dialysis or transplantation, most CKD patients never reach ESRD due to the increased risk of death from cardiovascular disease. It is well-established that regardless of the initiating insult - most often diabetes or hypertension - fibrosis is the common pathogenic pathway that leads to progressive injury and organ dysfunction (Eddy, 2014; Duffield, 2014). As such, there has been extensive research into the molecular and cellular mechanisms of renal fibrosis; however, translation to effective therapeutic strategies has been limited. While a role for the disruption of the cytoskeleton, most notably the actin network, has been established in acute kidney injury over the past two decades, a role in regulating renal fibrosis and CKD is only recently emerging. This review will focus on the role of the cytoskeleton in regulating pro-fibrotic pathways in the kidney, as well as data suggesting that these pathways represent novel therapeutic targets to manage fibrosis and ultimately CKD.

Simultaneous Rho kinase inhibition in circulating leukocytes and in cardiovascular tissue in rats with high angiotensin converting enzyme levels

BACKGROUND

The small guanosine triphosphatase RhoA and its direct target Rho kinase (ROCK) play important roles in cardiovascular pathophysiology. Activated ROCK phosphorylates intracellular proteins with detrimental effects on cardiovascular remodeling. Increased ROCK activity in circulating leukocytes is observed in hypertension and in heart failure, but its relationship with ROCK activation in the myocardium and vessels is unknown. We hypothesized that ROCK activation and phosphorylation/activation of some of its key downstream molecules in the heart and arterial wall are reflected in circulating leukocytes.

METHODS

Phosphorylation of MYPT1, ERM and p38-MAPK and levels of p65-NF-κB were determined in the left ventricle (LV), aortic wall and circulating leukocytes in rats with high (Brown Norway, BN) and low (Lewis) angiotensin converting enzyme. A group of BN rats received the ROCK inhibitor fasudil (7days).

RESULTS

Compared to Lewis rats, in the BN group phosphorylated levels of MYPT1, ERM and p38-MAPK and levels of p65-NF-κB were increased (P<0.05) in the LV (67%, 92%, 52% and 98%, respectively); in the aortic wall (57%, 51%, 68% and 66%, respectively) and in circulating leukocytes (61%, 72%, 49% and 105%, respectively). Fasudil reduced all these levels to those observed in Lewis rats. Phosphorylated MYPT1, ERM, and p38-MAPK and levels of p65-NF-κB in circulating leukocytes were significantly correlated with their respective LV and aortic wall levels (excepting p65-NF-κB in aorta).

CONCLUSION

ROCK activity in circulating leukocytes reflects activation of this signaling pathway in the myocardium and aortic wall in this model, and supports its value as a potential cardiovascular remodeling marker.