HMG CoA reductase inhibition modulates VEGF-induced endothelial cell hyperpermeability by preventing RhoA activation and myosin regulatory light chain phosphorylation

Morphological landscape of endothelial cell networks reveals a functional role of glutamate receptors in angiogenesis

Angiogenesis plays a key role in several diseases including cancer, ischemic vascular disease, and Alzheimer's disease. Chemical genetic screening of endothelial tube formation provides a robust approach for identifying signalling components that impact microvascular network morphology as well as endothelial cell biology. However, the analysis of the resulting imaging datasets has been limited to a few phenotypic features such as the total tube length or the number of branching points. Here we developed a high content analysis framework for detailed quantification of various aspects of network morphology including network complexity, symmetry and topology. By applying our approach to a high content screen of 1,280 characterised drugs, we found that drugs that result in a similar phenotype share the same mechanism of action or common downstream signalling pathways. Our multiparametric analysis revealed that a group of glutamate receptor antagonists enhances branching and network connectivity. Using an integrative meta-analysis approach, we validated the link between these receptors and angiogenesis. We further found that the expression of these genes is associated with the prognosis of Alzheimer's patients. In conclusion, our work shows that detailed image analysis of complex endothelial phenotypes can reveal new insights into biological mechanisms modulating the morphogenesis of endothelial networks and identify potential therapeutics for angiogenesis-related diseases.

Identification of C3 as a therapeutic target for diabetic nephropathy by bioinformatics analysis

The pathogenesis of diabetic nephropathy is not completely understood, and the effects of existing treatments are not satisfactory. Various public platforms already contain extensive data for deeper bioinformatics analysis. From the GSE30529 dataset based on diabetic nephropathy tubular samples, we identified 345 genes through differential expression analysis and weighted gene coexpression correlation network analysis. GO annotations mainly included neutrophil activation, regulation of immune effector process, positive regulation of cytokine production and neutrophil-mediated immunity. KEGG pathways mostly included phagosome, complement and coagulation cascades, cell adhesion molecules and the AGE-RAGE signalling pathway in diabetic complications. Additional datasets were analysed to understand the mechanisms of differential gene expression from an epigenetic perspective. Differentially expressed miRNAs were obtained to construct a miRNA-mRNA network from the miRNA profiles in the GSE57674 dataset. The miR-1237-3p/SH2B3, miR-1238-5p/ZNF652 and miR-766-3p/TGFBI axes may be involved in diabetic nephropathy. The methylation levels of the 345 genes were also tested based on the gene methylation profiles of the GSE121820 dataset. The top 20 hub genes in the PPI network were discerned using the CytoHubba tool. Correlation analysis with GFR showed that SYK, CXCL1, LYN, VWF, ANXA1, C3, HLA-E, RHOA, SERPING1, EGF and KNG1 may be involved in diabetic nephropathy. Eight small molecule compounds were identified as potential therapeutic drugs using Connectivity Map.

Stearic acid methyl ester ​promotes migration of mesenchymal stem cells and accelerates cartilage defect repair

Background

Mesenchymal stem cells (MSCs) can be easily expanded without losing the ability of multilineage differentiation, including oesteogenic, chondrogenic and adipogenic differentiation. These characters make MSCs a promising cell resource for cartilage defect repair. MSCs could be recruited by inflammatory stimulation, then home to the injury tissues. However, its capacity of homing is extremely limited. Thus, it has become extremely necessary to develop an agent or a method, which can be used to enhance the efficiency of MSCs homing. This study investigates the effect of stearic acid methyl ester (SAME) on MSCs mobilisation and cartilage regeneration.

Methods

MSCs were isolated from femurs of Sprague-Dawley (SD) rats. MTT assay was used to detect effect of SAME on viability of MSCs. Transwell assay and wound healing assay were used to detect effect of SAME on migration of MSCs. RNA-seq, quantitative real-time PCR and western blot were performed to analyze the expression of RNAs and proteins. Colony forming assay and flow cytometry were used to evaluate the effect of SAME on MSCs mobilisation in vivo. A rat cartilage defect model was created to evaluate the effect of SAME on cartilage regeneration.

Results

We found that SAME could promote the migration of MSCs. Interestingly, we found SAME significantly increased the expression levels of Vav1 in MSCs. On the other hand, the enhanced migration ability of MSCs induced by SAME was retarded by Vav1 small interfering RNA (siRNA) and Rho-associated protein kinase 2 (ROCK2) inhibitor. In addition, we also checked the effect of SAME on mobilisation of MSCs in vivo. The results showed that SAME increased the number of MSCs in peripheral blood and enhanced the capacity of colony formation. Finally, using a cartilage defect model in rats, we found SAME could improve cartilage repair.

Conclusion

Our study demonstrates that SAME can enhance MSCs migration ability mainly through the Vav1/ROCK2 signaling pathway, which could contribute to the accelerated cartilage regeneration.

The translational potential of this article

These findings provide evidence that SAME could be used as a therapeutic reagent for MSCs mobilisation and cartilage regeneration.

Systemic Rho-kinase inhibition using fasudil in mice with oxygen-induced retinopathy

PURPOSE

To investigate the influence of the selective Rho-kinase (ROCK) inhibitor, fasudil, on the mRNA level of proinflammatory factors and the retinal vascular development in mice with oxygen-induced retinopathy (OIR).

METHODS

C57BL/6J mice underwent standard protocol for OIR induction from postnatal days 7 to 12. Subsequently, they received a daily intraperitoneal injection of fasudil or sodium chloride from P12 to P16. Analyses were performed using vascular staining on retinal flat mounts, RNA expression by qPCR, and immunohistochemistry on paraffin sections.

RESULTS

On retinal flat mounts, the proportion of avascular area and tuft formation did not differ between the fasudil and NaCl group. Immunohistochemical staining revealed a less intense staining with inflammatory markers after fasudil. Nevertheless, there were no differences on RNA level between the two groups.

CONCLUSIONS

In conclusion, our findings support that daily systemic application of fasudil does not decrease retinal neovascularization in rodents with oxygen-induced retinopathy. The results of our study together with the controversial results on the effects of different ROCK inhibitors from the literature makes it apparent that effects of ROCK inhibition are more complex, and further studies are necessary to analyze its potential therapeutic effects.

Repurposing simvastatin as a therapy for preterm labor: evidence from preclinical models

Preterm birth (PTB), the leading cause of neonatal morbidity and mortality, urgently requires novel therapeutic agents. Spontaneous PTB, resulting from preterm labor, is commonly caused by intrauterine infection/inflammation. Statins are well-established, cholesterol-lowering drugs that can reduce inflammation and inhibit vascular smooth muscle contraction. We show that simvastatin reduced the incidence of PTB in a validated intrauterine LPS-induced PTB mouse model, decreased uterine proinflammatory mRNA concentrations (IL-6, Cxcl1, and Ccl2), and reduced serum IL-6 concentration. In human myometrial cells, simvastatin reduced proinflammatory mediator mRNA and protein expression (IL-6 and IL-8) and increased anti-inflammatory cytokine mRNA expression (IL-10 and IL-13). Critically, simvastatin inhibited myometrial cell contraction, basally and during inflammation, and reduced phosphorylated myosin light chain concentration. Supplementation with mevalonate and geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, abolished these anticontractile effects, indicating that the Rho/Rho-associated protein kinase pathway is critically involved. Thus, simvastatin reduces PTB incidence in mice, inhibits myometrial contractions, and exhibits key anti-inflammatory effects, providing a rationale for investigation into the repurposing of statins to treat preterm labor in women.—Boyle, A. K., Rinaldi, S. F., Rossi, A. G., Saunders, P. T. K., Norman, J. E. Repurposing simvastatin as a therapy for preterm labor: evidence from preclinical models.

Statins Promote Cardiac Infarct Healing by Modulating Endothelial Barrier Function Revealed by Contrast-Enhanced Magnetic Resonance Imaging

OBJECTIVE

The endothelium has a crucial role in wound healing, acting as a barrier to control transit of leukocytes. Endothelial barrier function is impaired in atherosclerosis preceding myocardial infarction (MI). Besides lowering lipids, statins modulate endothelial function. Here, we noninvasively tested whether statins affect permeability at the inflammatory (day 3) and the reparative (day 7) phase of infarct healing post-MI using contrast-enhanced cardiac magnetic resonance imaging (MRI).

APPROACH AND RESULTS

Noninvasive permeability mapping by MRI after MI in C57BL/6, atherosclerotic ApoE^-/-, and statin-treated ApoE^-/- mice was correlated to subsequent left ventricular outcome by structural and functional cardiac MRI. Ex vivo histology, flow cytometry, and quantitative polymerase chain reaction were performed on infarct regions. Increased vascular permeability at ApoE^-/- infarcts was observed compared with C57BL/6 infarcts, predicting enhanced left ventricular dilation at day 21 post-MI by MRI volumetry. Statin treatment improved vascular barrier function at ApoE^-/- infarcts, indicated by reduced permeability. The infarcted tissue of ApoE^-/- mice 3 days post-MI displayed an unbalanced Vegfa(vascular endothelial growth factor A)/Angpt1 (angiopoetin-1) expression ratio (explaining leakage-prone vessels), associated with higher amounts of CD45⁺ leukocytes and inflammatory LY6C^hi monocytes. Statins reversed the unbalanced Vegfa/Angpt1 expression, normalizing endothelial barrier function at the infarct and blocking the augmented recruitment of inflammatory leukocytes in statin-treated ApoE^-/- mice.

CONCLUSIONS

Statins lowered permeability and reduced the transit of unfavorable inflammatory leukocytes into the infarcted tissue, consequently improving left ventricular outcome.

Rho-associated kinase signalling and the cancer microenvironment: novel biological implications and therapeutic opportunities

The Rho/ROCK pathway is involved in numerous pivotal cellular processes that have made it an area of intense study in cancer medicine, however, Rho-associated coiled-coil containing protein kinase (ROCK) inhibitors are yet to make an appearance in the clinical cancer setting. Their performance as an anti-cancer therapy has been varied in pre-clinical studies, however, they have been shown to be effective vasodilators in the treatment of hypertension and post-ischaemic stroke vasospasm. This review addresses the various roles the Rho/ROCK pathway plays in angiogenesis, tumour vascular tone and reciprocal feedback from the tumour microenvironment and explores the potential utility of ROCK inhibitors as effective vascular normalising agents. ROCK inhibitors may potentially enhance the delivery and efficacy of chemotherapy agents and improve the effectiveness of radiotherapy. As such, repurposing of these agents as adjuncts to standard treatments may significantly improve outcomes for patients with cancer. A deeper understanding of the controlled and dynamic regulation of the key components of the Rho pathway may lead to effective use of the Rho/ROCK inhibitors in the clinical management of cancer.

Between Rho(k) and a hard place: the relation between vessel wall stiffness, endothelial contractility, and cardiovascular disease

Vascular stiffness is a mechanical property of the vessel wall that affects blood pressure, permeability, and inflammation. As a result, vascular stiffness is a key driver of (chronic) human disorders, including pulmonary arterial hypertension, kidney disease, and atherosclerosis. Responses of the endothelium to stiffening involve integration of mechanical cues from various sources, including the extracellular matrix, smooth muscle cells, and the forces that derive from shear stress of blood. This response in turn affects endothelial cell contractility, which is an important property that regulates endothelial stiffness, permeability, and leukocyte-vessel wall interactions. Moreover, endothelial stiffening reduces nitric oxide production, which promotes smooth muscle cell contraction and vasoconstriction. In fact, vessel wall stiffening, and microcirculatory endothelial dysfunction, precedes hypertension and thus underlies the development of vascular disease. Here, we review the cross talk among vessel wall stiffening, endothelial contractility, and vascular disease, which is controlled by Rho-driven actomyosin contractility and cellular mechanotransduction. In addition to discussing the various inputs and relevant molecular events in the endothelium, we address which actomyosin-regulated changes at cell adhesion complexes are genetically associated with human cardiovascular disease. Finally, we discuss recent findings that broaden therapeutic options for targeting this important mechanical signaling pathway in vascular pathogenesis.

Sparse feature selection methods identify unexpected global cellular response to strontium-containing materials

Despite the increasing sophistication of biomaterials design and functional characterization studies, little is known regarding cells' global response to biomaterials. Here, we combined nontargeted holistic biological and physical science techniques to evaluate how simple strontium ion incorporation within the well-described biomaterial 45S5 bioactive glass (BG) influences the global response of human mesenchymal stem cells. Our objective analyses of whole gene-expression profiles, confirmed by standard molecular biology techniques, revealed that strontium-substituted BG up-regulated the isoprenoid pathway, suggesting an influence on both sterol metabolite synthesis and protein prenylation processes. This up-regulation was accompanied by increases in cellular and membrane cholesterol and lipid raft contents as determined by Raman spectroscopy mapping and total internal reflection fluorescence microscopy analyses and by an increase in cellular content of phosphorylated myosin II light chain. Our unexpected findings of this strong metabolic pathway regulation as a response to biomaterial composition highlight the benefits of discovery-driven nonreductionist approaches to gain a deeper understanding of global cell-material interactions and suggest alternative research routes for evaluating biomaterials to improve their design.

Rho kinase inhibition in diabetic kidney disease

Small GTPases of the Rho family and their down-stream effectors Rho associated kinases (ROCKs) are the molecules that converge a spectrum of pathophysiological signals triggered by the diabetic milieu and represent promising molecular targets for nephroprotective treatment in diabetes. The review discusses recent studies exploring the consequences of diabetes-induced Rho-ROCK activation in the kidney and the effects of ROCK inhibition (ROCKi) in experimental diabetic kidney disease (DKD). Studies in models of type 1 and type 2 diabetes have indicated blood pressure-independent nephroprotective actions of ROCKi in DKD. The underlying mechanisms include attenuation of diabetes-induced increases in renal expression of prosclerotic cytokines and extracellular matrix, anti-oxidant effects and protection of mitochondrial function, resulting in slower development of glomerulosclerosis and interstitial fibrosis. The studies have also shown antiproteinuric effects of ROCKi that could be related to reductions in permeability of the glomerular barrier and beneficial effects on podocytes. Glomerular haemodynamic mechanisms might also be involved. Despite remaining questions in this field, such as the effects in podocytes later in the course of DKD, specificity of currently available ROCKi, or the roles of individual ROCK isoforms, recent evidence in experimental diabetes suggests that ROCKi might in future broaden the spectrum of treatments available for patients with DKD. This is supported by the evidence generated in models of non-diabetic kidney disease and in clinical studies in patients with various cardiovascular disorders.

New insights into molecular mechanisms of diabetic kidney disease

Diabetic kidney disease remains a major microvascular complication of diabetes and the most common cause of chronic kidney failure requiring dialysis in the United States. Medical advances over the past century have substantially improved the management of diabetes mellitus and thereby have increased patient survival. However, current standards of care reduce but do not eliminate the risk of diabetic kidney disease, and further studies are warranted to define new strategies for reducing the risk of diabetic kidney disease. In this review, we highlight some of the novel and established molecular mechanisms that contribute to the development of the disease and its outcomes. In particular, we discuss recent advances in our understanding of the molecular mechanisms implicated in the pathogenesis and progression of diabetic kidney disease, with special emphasis on the mitochondrial oxidative stress and microRNA targets. Additionally, candidate genes associated with susceptibility to diabetic kidney disease and alterations in various cytokines, chemokines, and growth factors are addressed briefly.

Simvastatin alleviates hyperpermeability of glomerular endothelial cells in early-stage diabetic nephropathy by inhibition of RhoA/ROCK1

Background

Endothelial dysfunction is an early sign of diabetic cardiovascular disease and may contribute to progressive diabetic nephropathy (DN). There is increasing evidence that dysfunction of the endothelial tight junction is a crucial step in the development of endothelial hyperpermeability, but it is unknown whether this occurs in glomerular endothelial cells (GEnCs) during the progression of DN. We examined tight junction dysfunction of GEnCs during early-stage DN and the potential underlying mechanisms. We also examined the effect of simvastatin (3-Hydroxy-3-methylglutaryl CoA reductase inhibitor) on dysfunction of the tight junctions of cultured GEnCs and in db/db mice with early-stage DN.

Methods

We assessed the expression of occludin and ZO-1, two major components of the tight junction complex, in cultured rat GEnCs treated with high glucose and in 12 week-old db/db mice with early-stage DN. We also investigated activation of RhoA/ROCK1 signaling, GEnC permeability, and renal function of the mice.

Results

High glucose suppresses occludin expression and disrupts occludin/ZO-1 translocation in GEnCs. These changes were associated with increased permeability to albumin and activation of RhoA/ROCK1 signaling. Occludin and ZO-1 dysregulation also occurred in the glomeruli of mice with early-stage DN, and these abnormalities were accompanied by albuminuria and activation of RhoA/ROCK1 in isolated glomeruli. Simvastatin prevented high glucose or hyperglycemia-induced dysregulation of occludin and ZO-1 by inhibition of RhoA/ROCK1 signaling in cultured GEnCs and in db/db mice with early-stage DN.

Conclusion

Our results indicate that activation of RhoA/ROCK1 by high glucose disrupts the expression and translocation of occludin/ZO-1 and that simvastatin alleviates occludin/ZO-1 dysregulation and albuminuria by suppressing RhoA/ROCK1 signaling during early-stage DN. These results suggest a potential therapeutic strategy for preventing the onset of albuminuria in early-stage DN.

Rk1, a ginsenoside, is a new blocker of vascular leakage acting through actin structure remodeling

Endothelial barrier integrity is essential for vascular homeostasis and increased vascular permeability and has been implicated in many pathological processes, including diabetic retinopathy. Here, we investigated the effect of Rk1, a ginsenoside extracted from sun ginseng, on regulation of endothelial barrier function. In human retinal endothelial cells, Rk1 strongly inhibited permeability induced by VEGF, advanced glycation end-product, thrombin, or histamine. Furthermore, Rk1 significantly reduced the vessel leakiness of retina in a diabetic mouse model. This anti-permeability activity of Rk1 is correlated with enhanced stability and positioning of tight junction proteins at the boundary between cells. Signaling experiments revealed that Rk1 induces phosphorylation of myosin light chain and cortactin, which are critical regulators for the formation of the cortical actin ring structure and endothelial barrier. These findings raise the possibility that ginsenoside Rk1 could be exploited as a novel prototype compound for the prevention of human diseases that are characterized by vascular leakage.

Donor simvastatin treatment and cardiac allograft ischemia/reperfusion injury

Ischemia/reperfusion injury of a transplanted heart may result in serious early and late adverse effects such as primary graft dysfunction, increased allograft immunogenicity, and initiation of fibroproliferative cascades that compromise the survival of the recipient. Microvascular dysfunction has a central role in ischemia/reperfusion injury through increased vascular permeability, leukocyte adhesion and extravasation, thrombosis, vasoconstriction, and the no-reflow phenomenon. Here we review the involvement of microvascular endothelial cells and their surrounding pericytes in ischemia/reperfusion injury, and the pleiotropic, cholesterol-independent effects of statins on microvascular dysfunction. In addition, we delineate how the rapid vasculoprotective effects of statins could be used to protect cardiac allografts against ischemia/reperfusion injury by administering statins to the organ donor before graft removal and transplantation.

Endothelial cell-selective adhesion molecule in diabetic nephropathy

BACKGROUND

Endothelial cell-selective adhesion molecule (ESAM) contributes to the integrity of tight junctions and modulates endothelial function. ESAM has been linked to experimental diabetic nephropathy; its soluble fraction is related to atherosclerosis in humans. In this cross-sectional observational study, we describe for the first time serum ESAM in type 2 diabetic patients with different stages of chronic kidney disease (CKD) and its relationship to vascular endothelial growth factor-A (VEGF-A). Materials and methods  We included diabetic patients with different stages of CKD and controls. History, laboratory evaluation, serum ESAM and VEGF-A and urinary albumin/creatinine ratio were obtained.

RESULTS

Endothelial cell-selective adhesion molecule was higher in non-CKD diabetic patients 13.80 (6.15-18.70) ng/mL (n=45) than controls 7.30 (4.60-9.40) ng/mL (n=48), P=0.001. VEGF-A had a similar pattern: 71.3 (54.75-120.70) vs. 43.20 (30.1-65.90) pg/mL, P<0.0001. ESAM was 10.4 (5.6-17.4) ng/mL in predialysis CKD patients (n=59) and 22.35 (8.55-29.95) ng/mL in dialysis patients (n=36), P<0.001. Patients with glomerular filtration rate (GFR)<15 mL/min had the highest ESAM (P=0.003). ESAM was similar in normoalbuminuric, microalbuminuric and proteinuric patients. ESAM was directly correlated with the duration of diabetes (r(2)=0.048, P=0.009), C-reactive protein (r(2)=0.028, P=0.05), VEGF-A (r(2)=0.040, P=0.01) and inversely with HbA1C (r(2)=0.036, P=0.03), haemoglobin (r(2)=0.062, P=0.005) and albumin (r(2)=0.0·40, P=0.026). In multiple regression diabetes duration, HbA1C and VEGF-A were significant predictors of ESAM. In controls, ESAM was inversely related to VEGF (r(2)=037, P=0.01).

CONCLUSION

Endothelial cell-selective adhesion molecule and VEGF-A are higher in patients with diabetes than in controls. The highest ESAM is found in dialysis patients. ESAM correlates with diabetes duration and control, inflammation and VEGF-A in patients with diabetes, but not in controls.

Functions of nonmuscle myosin II in assembly of the cellular contractile system

The contractile system of nonmuscle cells consists of interconnected actomyosin networks and bundles anchored to focal adhesions. The initiation of the contractile system assembly is poorly understood structurally and mechanistically, whereas system's maturation heavily depends on nonmuscle myosin II (NMII). Using platinum replica electron microscopy in combination with fluorescence microscopy, we characterized the structural mechanisms of the contractile system assembly and roles of NMII at early stages of this process. We show that inhibition of NMII by a specific inhibitor, blebbistatin, in addition to known effects, such as disassembly of stress fibers and mature focal adhesions, also causes transformation of lamellipodia into unattached ruffles, loss of immature focal complexes, loss of cytoskeleton-associated NMII filaments and peripheral accumulation of activated, but unpolymerized NMII. After blebbistatin washout, assembly of the contractile system begins with quick and coordinated recovery of lamellipodia and focal complexes that occurs before reappearance of NMII bipolar filaments. The initial formation of focal complexes and subsequent assembly of NMII filaments preferentially occurred in association with filopodial bundles and concave actin bundles formed by filopodial roots at the lamellipodial base. Over time, accumulating NMII filaments help to transform the precursor structures, focal complexes and associated thin bundles, into stress fibers and mature focal adhesions. However, semi-sarcomeric organization of stress fibers develops at much slower rate. Together, our data suggest that activation of NMII motor activity by light chain phosphorylation occurs at the cell edge and is uncoupled from NMII assembly into bipolar filaments. We propose that activated, but unpolymerized NMII initiates focal complexes, thus providing traction for lamellipodial protrusion. Subsequently, the mechanical resistance of focal complexes activates a load-dependent mechanism of NMII polymerization in association with attached bundles, leading to assembly of stress fibers and maturation of focal adhesions.

Simvastatin reduces endotoxin-induced acute lung injury by decreasing neutrophil recruitment and radical formation

INTRODUCTION

Treatment of acute lung injury (ALI) remains an unsolved problem in intensive care medicine. As simvastatin exerts protective effects in inflammatory diseases we explored its effects on development of ALI and due to the importance of neutrophils in ALI also on neutrophil effector functions.

METHODS

C57Bl/6 mice were exposed to aerosolized LPS (500 µg/ml) for 30 min. The count of alveolar, interstitial, and intravasal neutrophils were assessed 4 h later by flow cytometry. Lung permeability changes were assessed by FITC-dextran clearance and albumin content in the BAL fluid. In vitro, we analyzed the effect of simvastatin on neutrophil adhesion, degranulation, apoptosis, and formation of reactive oxygen species. To monitor effects of simvastatin on bacterial clearance we performed phagocytosis and bacterial killing studies in vitro as well as sepsis experiments in mice.

RESULTS

Simvastatin treatment before and after onset of ALI reduces neutrophil influx into the lung as well as lung permeability indicating the protective role of simvastatin in ALI. Moreover, simvastatin reduces the formation of ROS species and adhesion of neutrophils without affecting apoptosis, bacterial phagocytosis and bacterial clearance.

CONCLUSION

Simvastatin reduces recruitment and activation of neutrophils hereby protecting from LPS-induced ALI. Our results imply a potential role for statins in the management of ALI.

Combined treatment of Aβ immunization with statin in a mouse model of Alzheimer's disease

We evaluated the therapeutic efficacy of combined treatment of Aβ-immunization with simvastatin in an Alzheimer mouse model at age 22 months. DNA prime-adenovirus boost immunization induced modest anti-Aβ titers and simvastatin increased the seropositive rate. Aβ-KLH was additionally administered to boost the titers. Irrespective of simvastatin, the immunization did not decrease cerebral Aβ deposits but increased soluble Aβ and tended to exacerbate amyloid angiopathy in the hippocampus. The immunization increased cerebral invasion of leukocytes and simvastatin counteracted the increase. Thus, modest anti-Aβ titers can increase soluble Aβ and simvastatin may reduce inflammation associated with vaccination in aged Alzheimer mouse models.

Dynamic regulation of vascular myosin light chain (MYL9) with injury and aging

BACKGROUND

Aging-associated changes in the cardiovascular system increase the risk for disease development and lead to profound alterations in vascular reactivity and stiffness. Elucidating the molecular response of arteries to injury and age will help understand the exaggerated remodeling of aging vessels.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the gene expression profile in a model of mechanical vascular injury in the iliac artery of aging (22 months old) and young rats (4 months old). We investigated aging-related variations in gene expression at 30 min, 3 d and 7 d post injury. We found that the Myosin Light Chain gene (MYL9) was the only gene differentially expressed in the aged versus young injured arteries at all time points studied, peaking at day 3 after injury (4.6 fold upregulation (p<0.05) in the smooth muscle cell layers. We confirmed this finding on an aging aortic microarray experiment available through NCBI's GEO database. We found that Myl9 was consistently upregulated with age in healthy rat aortas. To determine the arterial localization of Myl9 with age and injury, we performed immunohistochemistry for Myl9 in rat iliac arteries and found that in healthy and injured (30 days post injury) arteries, Myl9 expression increased with age in the endothelial layers.

CONCLUSIONS/SIGNIFICANCE

The consistent upregulation of the myosin light chain protein (Myl9) with age and injury in arterial tissue draws attention to the increased vascular permeability and to the age-caused predisposition to arterial constriction after balloon angioplasty.

Fasudil hydrochloride hydrate, a Rho-kinase inhibitor, suppresses high glucose-induced proliferation and collagen synthesis in rat cardiac fibroblasts

1. Hyperglycaemia promotes the proliferation of cardiac fibroblasts (CFs) and collagen synthesis in CFs. The objectives of the present study were to determine the effects of fasudil hydrochloride hydrate, a Rho-kinase (ROCK) inhibitor, on high glucose (HG)-induced proliferation of CFs and collagen production in rat CFs and to investigate the molecular mechanism of action of fasudil. 2. Rat CFs were cultured in Dulbecco's modified Eagle's medium, supplemented with 5.5 or 25 mmol/L d-glucose or 5.5 mmol/L d-glucose + 19.5 mmol/L mannose, in the presence of absence of fasudil (50 or 100 μmol/L). Proliferation was measured by the 3-(4,5-dimethyl-2 thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay, whereas the production of Type I collagen was evaluated using ELISA and the expression of ROCK1, c-Jun N-terminal kinase (JNK) and Type I procollagen mRNA was determined by reverse transcription-polymerase chain reaction. Intracellular Type I procollagen protein levels were evaluated using immunocytochemistry. Western blot analysis was used to evaluate the phosphorylation of myosin phosphatase target subunit 1 (MYPT1), JNK and Smad2/3, as well as c-jun protein levels. 3. Both concentrations of fasudil effectively inhibited HG (25 mmol/L d-glucose)-induced increases in the proliferation of CFs and collagen synthesis, concomitant with suppression of HG-induced upregulation of ROCK1 and JNK mRNA expression and c-jun protein levels, as well as the phosphorylation of MYPT1, JNK and Smad2/3. 4. These data suggest that ROCK activation is essential for the proliferation of CFs and collagen synthesis induced by HG. Fasudil suppressed HG-induced increases in the proliferation of CFs and collagen synthesis, which may be associated with inhibition of the JNK and transforming growth factor β/Smad pathways. The results of the present study indicate that inhibition of ROCK may be a novel therapeutic target for the prevention of diabetic cardiac fibrosis.

Rho kinase inhibition in diabetic nephropathy

PURPOSE OF REVIEW

The Rho GTPases and their downstream effectors Rho-associated kinases (ROCKs) appear to be the molecules that converge numerous pathophysiological signals triggered by the diabetic milieu and represent promising molecular targets for nephroprotective treatment in diabetes. The review discusses recent studies exploring the consequences of diabetes-induced Rho-ROCK activation in the kidney and the effects of ROCK inhibition (ROCKi) in experimental diabetic nephropathy.

RECENT FINDINGS

Recent studies in models of type 1 and type 2 diabetes have indicated blood-pressure-independent nephroprotective actions of ROCKi in diabetic nephropathy. The underlying mechanisms include attenuation of diabetes-induced increases in renal expression of prosclerotic cytokines and extracellular matrix, resulting in slower development of glomerulosclerosis and interstitial fibrosis. The studies have also shown antiproteinuric affects of ROCKi that could be related to reductions in permeability of glomerular barrier and beneficial effects on podocytes. Moreover hemodynamic mechanisms might be also involved.

SUMMARY

Despite remaining questions in this field, such as the specificity of currently available ROCKi, or the roles of individual ROCK isoforms, recent evidence in experimental diabetes, together with evidence generated in models of nondiabetic kidney disease and in clinical studies in patients with various cardiovascular disorders, suggest that ROCKi might in future broaden the spectrum of treatments available for patients with diabetic nephropathy.

Long-term diabetic complications may be ameliorated by targeting Rho kinase

This review addresses the roles of Rho/Rho-kinase (ROCK) pathway in the pathogenesis of diabetes complications. Diabetes can cause many serious complications and can result in physical disability or even increased mortality. However, there are not many effective ways to treat these complications. The small guanosine-5'-triphosphate-binding protein Rho and its downstream target Rho-kinase mediate important cellular functions, such as cell morphology, motility, secretion, proliferation, and gene expression. Recently, the Rho/Rho-kinase pathway has attracted a great deal of attention in diabetes-related research. These studies have provided evidence that the activity and gene expression of Rho-kinase are upregulated in some tissues in animal models of type 1 or type 2 diabetes and in cell lines cultured with high concentrations of glucose. Inhibitors of Rho-kinase could prevent or ameliorate the pathological changes in diabetic complications. The inhibitory effects of statins on the Rho/Rho-kinase signalling pathway may also play a role in the prevention of diabetic complications. However, the precise molecular mechanism by which the Rho/Roh-kinase pathway participates in the development or progression of diabetic complications has not been extensively investigated. This article evaluates the relationship between Rho/Roh-kinase activation and diabetic complications, as well as the roles of Roh-kinase inhibitors and statins in the complications of diabetes, with the objective of providing a novel target for the treatment of long-term diabetic complications.

Peptide nanofibers preconditioned with stem cell secretome are renoprotective

Stem cells may contribute to renal recovery following acute kidney injury, and this may occur through their secretion of cytokines, chemokines, and growth factors. Here, we developed an acellular, nanofiber-based preparation of self-assembled peptides to deliver the secretome of embryonic stem cells (ESCs). Using an integrated in vitro and in vivo approach, we found that nanofibers preconditioned with ESCs could reverse cell hyperpermeability and apoptosis in vitro and protect against lipopolysaccharide-induced acute kidney injury in vivo. The renoprotective effect of preconditioned nanofibers associated with an attenuation of Rho kinase activation. We also observed that the combined presence of follistatin, adiponectin, and secretory leukoprotease during preconditioning was essential to the renoprotective properties of the nanofibers. In summary, we developed a designer-peptide nanofiber that can serve as a delivery platform for the beneficial effects of stem cells without the problems of teratoma formation or limited cell engraftment and viability.

MicroRNA-29c is a signature microRNA under high glucose conditions that targets Sprouty homolog 1, and its in vivo knockdown prevents progression of diabetic nephropathy

Although several recent publications have suggested that microRNAs contribute to the pathogenesis of diabetic nephropathy, the role of miRNAs in vivo still remains poorly understood. Using an integrated in vitro and in vivo comparative miRNA expression array, we identified miR-29c as a signature miRNA in the diabetic environment. We validated our profiling array data by examining miR-29c expression in the kidney glomeruli obtained from db/db mice in vivo and in kidney microvascular endothelial cells and podocytes treated with high glucose in vitro. Functionally, we found that miR-29c induces cell apoptosis and increases extracellular matrix protein accumulation. Indeed, forced expression of miR-29c strongly induced podocyte apoptosis. Conversely, knockdown of miR-29c prevented high glucose-induced cell apoptosis. We also identified Sprouty homolog 1 (Spry1) as a direct target of miR-29c with a nearly perfect complementarity between miR-29c and the 3'-untranslated region (UTR) of mouse Spry1. Expression of miR-29c decreased the luciferase activity of Spry1 when co-transfected with the mouse Spry1 3'-UTR reporter construct. Overexpression of miR-29c decreased the levels of Spry1 protein and promoted activation of Rho kinase. Importantly, knockdown of miR-29c by a specific antisense oligonucleotide significantly reduced albuminuria and kidney mesangial matrix accumulation in the db/db mice model in vivo. These findings identify miR-29c as a novel target in diabetic nephropathy and provide new insights into the role of miR-29c in a previously unrecognized signaling cascade involving Spry1 and Rho kinase activation.

How increased VEGF induces glomerular hyperpermeability: a potential signaling pathway of Rac1 activation

Despite growing evidence for a pathogenic role of vascular endothelial growth factor (VEGF) in microvascular complications of diabetes, the underlying mechanism responsible for its detrimental effect remains unknown. In the current study, we hypothesized that some of the detrimental effects of VEGF on microvascular endothelial cells in the diabetic milieu stem from its aberrant signaling, which leads to perturbed tight junction assembly and increased endothelial permeability. Using an integrated in vitro approach, we investigated whether the effect of VEGF on endothelial cell permeability involves Rac1 GTPase activation and tight junction disassembly. Rac1 activity was detected by Western blotting in cell membrane protein as well as pull-down assay. The permeability of glomerular endothelial cells monolayer was detected as transendothelial electronic resistance. Then tyrosine phosphorylated occludin protein was detected by Western blotting after immunoprecipitation. N17Rac1 cells are obtained by transfection of glomerular endothelial cells with a dominant negative mutant of Rac1. The data obtained in this study indicate that activation of Rac1 GTPase contributes to VEGF-induced endothelial cell hyperpermeability. We also observed that Rac1 activation leads to increased endothelial permeability through tyrosine phosphorylation of occludin. Indeed, N17Rac1 cells dramatically attenuated the effect of VEGF on phospho-occludin and endothelial cell permeability. These results, when taken together, provide a framework for understanding the role of VEGF-induced Rac1/phospho-occludin pathway in the integrity of endothelial barrier function in the glomerulus.

Simvastatin attenuates ventilator-induced lung injury in mice

INTRODUCTION

Mechanical ventilation (MV) is a life saving intervention in acute respiratory failure without alternative. However, particularly in pre-injured lungs, even protective ventilation strategies may evoke ventilator-induced lung injury (VILI), which is characterized by pulmonary inflammation and vascular leakage. Adjuvant pharmacologic strategies in addition to lung protective ventilation to attenuate VILI are lacking. Simvastatin exhibited anti-inflammatory and endothelial barrier stabilizing properties in vitro and in vivo.

METHODS

Mice were ventilated (12 ml/kg; six hours) and subjected to simvastatin (20 mg/kg) or sham treatment. Pulmonary microvascular leakage, oxygenation, pulmonary and systemic neutrophil and monocyte counts and cytokine release in lung and blood plasma were assessed. Further, lung tissue was analyzed by electron microscopy.

RESULTS

Mechanical ventilation induced VILI, displayed by increased pulmonary microvascular leakage and endothelial injury, pulmonary recruitment of neutrophils and Gr-1high monocytes, and by liberation of inflammatory cytokines in the lungs. Further, VILI associated systemic inflammation characterized by blood leukocytosis and elevated plasma cytokines was observed. Simvastatin treatment limited pulmonary endothelial injury, attenuated pulmonary hyperpermeability, prevented the recruitment of leukocytes to the lung, reduced pulmonary cytokine levels and improved oxygenation in mechanically ventilated mice.

CONCLUSIONS

High-dose simvastatin attenuated VILI in mice by reducing MV-induced pulmonary inflammation and hyperpermeability.

ROCK as a Therapeutic Target of Diabetic Retinopathy

The increasing global prevalence of diabetes is a critical problem for public health. In particular, diabetic retinopathy, a prevalent ocular complication of diabetes mellitus, causes severe vision loss in working population. A better understanding of the pathogenesis and the development of new pharmacologic treatments are needed. This paper describes the relevance between Rho/ROCK pathway and the pathogenesis of diabetic retinopathy from its early to late stages. Moreover, the therapeutic potential of ROCK inhibitor in the total management of diabetic retinopathy is discussed.

Lovastatin inhibits the thrombin-induced loss of barrier integrity in bovine corneal endothelium

PURPOSE

Increased actomyosin contraction of the dense band of actin cytoskeleton at the apical junctional complex (perijunctional actomyosin ring, PAMR) breaks down the barrier integrity of corneal endothelium. This study has investigated the efficacy of statins, which inhibit activation of RhoA, in opposing the thrombin-induced loss of barrier integrity of monolayers of cultured bovine corneal endothelium.

METHODS

Myosin light chain (MLC) phosphorylation, a biochemical measure of actomyosin contraction, was assayed by urea-glycerol gel electrophoresis, followed by western blot analysis. The locus of MLC phosphorylation and changes in the organization of the PAMR were visualized by immunostaining. Phosphorylation of MYPT1, a regulatory subunit of myosin light-chain phosphatase (MLCP), was assessed by Western blot analysis to determine down-regulation of RhoA. The barrier integrity was assessed in terms of trans-endothelial electrical resistance (TER), and further confirmed by determining permeability to FITC dextran (10 kDa) and distribution of ZO-1, a marker of tight junctional assembly.

RESULTS

Lovastatin, a prototype of lipophilic statins, induced MLC dephosphorylation under basal conditions. It opposed increase in phosphorylation of MLC and MYPT1 in response to thrombin and nocodazole, agents known to activate RhoA in the endothelium. Pretreatment with the statin opposed the thrombin- and nocodazole-induced disruption of the PAMR and the thrombin-induced decline in TER. Lovastatin also opposed the thrombin- and nocodazole-induced increase in permeability to FITC dextran and redistribution of ZO-1. However, upon supplementation with GGPP (geranylgeranyl pyrophosphate), lovastatin failed to oppose the effects of thrombin and nocodazole on the PAMR, ppMLC, and ZO-1 distribution.

CONCLUSIONS

Lovastatin attenuates RhoA activation in the corneal endothelium presumably by reducing its isoprenylation. This underlies the suppression of the thrombin-induced loss in barrier integrity of the corneal endothelium.

Identification of microRNA-93 as a novel regulator of vascular endothelial growth factor in hyperglycemic conditions

Vascular endothelial growth factor (VEGF) is a dimeric glycoprotein that plays a crucial role in microvascular complications of diabetes, including diabetic nephropathy. However, the precise regulatory mechanisms governing VEGF expression in the diabetic milieu are still poorly understood. Here, we provide evidence that microRNA-93 (miR-93) regulates VEGF expression in experimental models of diabetes both in vitro and in vivo. Comparative microRNA expression profile arrays identified miR-93 as a signature microRNA in hyperglycemic conditions. We identified VEGF-A as a putative target of miR-93 in the kidney with a perfect complementarity between miR-93 and the 3'-untranslated region of vegfa in several species. When cotransfected with a luciferase reporter construct containing the mouse vegfa 3'-untranslated region, expression of miR-93 markedly decreased the luciferase activity. We showed that forced expression of miR-93 in cells abrogated VEGF protein secretion. Conversely, anti-miR-93 inhibitors increased VEGF release. Transfection of miR-93 also prevented the effect of high glucose on VEGF downstream targets. Using transgenic mice containing VEGF-LacZ bicistronic transcripts, we found that inhibition of glomerular miR-93 by peptide-conjugated morpholino oligomers elicited increased expression of VEGF. Our findings also indicate that high glucose decreases miR-93 expression by down-regulating the promoter of the host MCM7 gene. Taken together, our findings provide new insights into the role of miR-93 in VEGF signaling pathway and offer a potentially novel target in preventing the progression of diabetic nephropathy.

Diverse effects of statins on angiogenesis: new therapeutic avenues

Angiogenesis is an important process for a variety of physiologic and pathologic conditions. Different angiogenic modulating targets are under extensive investigation both experimentally and clinically. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the first-line agents used in hypercholesterolemia. They are also characterized by having other benefits apart from their lipid-lowering effects. Among these pleiotropic effects are the pro- and antiangiogenic properties of statins. The pleiotropic effects of statins and how they modulate new blood vessel formation are discussed in this review. The currently available data from both animal and human studies regarding the effects of statins on angiogenesis in ischemic heart disease, stroke, ocular diseases, and cancer are also reviewed. Statins are safe, orally available agents that may acquire novel therapeutic indications through their angiogenic modulating effects.

RhoA/ROCK signaling is essential for multiple aspects of VEGF-mediated angiogenesis

The small GTPase RhoA and its downstream effectors, ROCK1 and ROCK2, regulate a number of cellular processes, including cell motility, proliferation, survival, and permeability. Pharmacological inhibitors of the Rho pathway reportedly block angiogenesis; however, the molecular details of this inhibition are largely unknown. We demonstrate that vascular endothelial growth factor-A (VEGF) rapidly induces RhoA activation in endothelial cells (ECs). Moreover, the pharmacological inhibition of ROCK1/2 using 10 microM Y-27632 (the IC(50) for this compound in ECs) strongly disrupts vasculogenesis in pluripotent embryonic stem cell cultures, VEGF-mediated regenerative angiogenesis in ex vivo retinal explants, and VEGF-mediated in vitro EC tube formation. Furthermore, using small interfering RNA knockdown and mouse heterozygote knockouts of ROCK1 and ROCK2, we provide data indicating that VEGF-driven angiogenesis is largely mediated through ROCK2. These data demonstrate that Rho/ROCK signaling is an important mediator in a number of angiogenic processes, including EC migration, survival, and cell permeability, and suggest that Rho/ROCK inhibition may prove useful for the treatment of angiogenesis-related disorders.

Simvastatin reverses podocyte injury but not mesangial expansion in early stage type 2 diabetes mellitus

Statins may confer renal protection in a variety of glomerular diseases, including diabetic nephropathy (DN). However, various glomerular lesions have different etiologies and may have different responses to statins. This study was performed to determine the differential effects of simvastatin (SMV) on glomerular pathology including mesangial expansion and podocyte injury in a mouse model of early stage type 2 diabetes mellitus (DM). Type 2 DM was induced in male C57BL/6 mice by feeding a high fat diet (HF; 45 kcal% fat). After 22 weeks, one group of HF mice was treated with SMV (HF-SMV; 7 mug/day/g BW) and another group was treated with vehicle (HF-vehicle) for 4 weeks via osmotic mini-pump. A third group served as age-matched normal diet vehicle controls (ND-vehicle; 10 kcal% fat). At the end of treatment, glomerular morphology was evaluated in a blind manner to determine the progression of DN. Body weight, blood glucose, insulin, HDL-cholesterol and triglycerides, but not LDL-cholesterol, were increased in HF mice. Over the course of treatment, the 24-hour urinary albumin excretion (UAE) was unchanged in ND-vehicle. HF mice exhibited elevated UAE, which decreased with SMV, but was unchanged with vehicle. The absolute mesangial volume and the relative mesangial volume per glomerular volume increased in HF-vehicle and remained elevated with SMV treatment. The immuno-staining of nephrin, a protein marker of the integrity of podocyte slit diaphragms, was decreased in HF-vehicle; however, the nephrin quantity of the HF-SMV group was not different from ND-vehicle. It is concluded that SMV reverses podocyte damage, but does not affect mesangial expansion in the kidneys of early stage proteinuria of type 2 DM.

Molecular mechanisms of endothelial hyperpermeability: implications in inflammation

Endothelial hyperpermeability is a significant problem in vascular inflammation associated with trauma, ischaemia-reperfusion injury, sepsis, adult respiratory distress syndrome, diabetes, thrombosis and cancer. An important mechanism underlying this process is increased paracellular leakage of plasma fluid and protein. Inflammatory stimuli such as histamine, thrombin, vascular endothelial growth factor and activated neutrophils can cause dissociation of cell-cell junctions between endothelial cells as well as cytoskeleton contraction, leading to a widened intercellular space that facilitates transendothelial flux. Such structural changes initiate with agonist-receptor binding, followed by activation of intracellular signalling molecules including calcium, protein kinase C, tyrosine kinases, myosin light chain kinase, and small Rho-GTPases; these kinases and GTPases then phosphorylate or alter the conformation of different subcellular components that control cell-cell adhesion, resulting in paracellular hypermeability. Targeting key signalling molecules that mediate endothelial-junction-cytoskeleton dissociation demonstrates a therapeutic potential to improve vascular barrier function during inflammatory injury.

Statins normalize vascular lysyl oxidase down-regulation induced by proatherogenic risk factors

AIMS

Statins are lipid-lowering drugs widely used in the management of vascular diseases. Clinical and experimental evidence suggest that statins improve endothelial function by both cholesterol-lowering-dependent and -independent mechanisms. We have previously shown that endothelial dysfunction induced by risk factors and proinflammatory cytokines is associated with down-regulation of lysyl oxidase (LOX), a key enzyme modulating extracellular matrix maturation and vascular integrity. Our aim was to analyse whether statins could normalize LOX expression impaired by proatherogenic risk factors.

METHODS AND RESULTS

We observed that pharmacological concentrations of statins (atorvastatin and simvastatin) modulated LOX transcriptional activity, counteracting the down-regulation of LOX (at the mRNA, protein, and activity level) caused by tumour necrosis factor-alpha (TNFalpha) in porcine, bovine, and human aortic endothelial cells. Geranylgeraniol but not farnesol reversed this effect, suggesting the involvement of geranylgeranylated proteins. In accordance, inhibitors of RhoA/Rho kinase also counteracted LOX down-regulation caused by TNFalpha, and over-expression of a RhoA dominant-negative mutant mimicked statin effects. Statins were also able to counteract the decrease in LOX expression produced by atherogenic concentrations of LDL by a similar mechanism and to partially prevent the increase in endothelial permeability elicited by these lipoproteins. Finally, in the in vivo porcine model of hypercholesterolaemia, we observed that statins abrogated the reduction of vascular LOX expression triggered by high plasma levels of LDL.

CONCLUSION

These data indicate that statins normalize vascular LOX expression altered by atherogenic risk factors through a RhoA/Rho kinase-dependent mechanism. Thus, modulation of LOX by statins could contribute to vascular protection and to the cardiovascular risk reduction achieved by this therapy.

Dynamics of neutrophil extravasation and vascular permeability are uncoupled during aseptic cutaneous wounding

Transport of macromolecules and transmigration of leukocytes across vascular endothelium are regulated by a tight molecular junction, but the mechanisms by which these two inflammatory events are differentially controlled in time and magnitude during aseptic cutaneous wounding remain elusive. A real-time fluorescence imaging technique was developed to simultaneously track influx of Alexa 680-labeled albumin and genetically tagged enhanced green fluorescent protein-neutrophils [polymorphonuclear neutrophils (PMN)] within the wound bed. Vascular permeability increased approximately threefold more rapidly than the rate of PMN influx, reaching a maximum at 12 h, on the order of approximately 0.15% per minute versus approximately 0.05% per minute for PMN influx, which peaked at 18 h. Systemic depletion of PMN with antibody blocked their extravasation to the wound but did not alter the increase in vascular permeability. In contrast, pretreatment with antiplatelet GPIb decreased permeability by 25% and PMN influx by 50%. Hyperpermeability stimulated by the endothelium-specific agonists VEGF or thrombin at 24 h postwounding was completely inhibited by blocking Rho-kinase-dependent signaling, whereas less inhibition was observed at 1 h and neutrophil influx was not perturbed. These data suggest that in aseptic wounds, the endothelium maintains a tight junctional barrier to protein leakage that is independent of neutrophil transmigration, partially dependent on circulating platelets, and associated with Rho-kinase-dependent signaling.

The cerebral cavernous malformation signaling pathway promotes vascular integrity via Rho GTPases

Cerebral cavernous malformation (CCM) is a common vascular dysplasia that affects both systemic and CNS blood vessels. Loss of function mutations in the CCM2 gene cause CCM. Here we show that targeted disruption of Ccm2 in mice results in failed lumen formation and early embryonic death through an endothelial cell autonomous mechanism. We demonstrate that CCM2 regulates endothelial cytoskeletal architecture, cell-cell interactions and lumen formation. Heterozygosity at Ccm2, a genotype equivalent to human CCM, results in impaired endothelial barrier function. Because our biochemical studies indicate that loss of CCM2 results in activation of RHOA GTPase, we rescued the cellular phenotype and barrier function in heterozygous mice using simvastatin, a drug known to inhibit Rho GTPases. These data offer the prospect for pharmacologic treatment of a human vascular dysplasia using a widely available and safe drug.

Vascular endothelial growth factor and diabetic nephropathy

The field of vascular endothelial growth factor (VEGF) has recently witnessed a surge of research into its role in diabetic kidney disease. Based on its credentials as a potent inducer of vasopermeability and angiogenesis, podocyte-derived VEGF is believed to participate in the glomerular capillary hyperpermeability of macromolecules that potentially underlies the pathogenesis of diabetic albuminuria. The evidence for VEGF's role is relatively straightforward in animal models of diabetes, establishing that VEGF is upregulated in the diabetic kidney, that VEGF alone reproduces some aspects of diabetic glomerulopathy, and that antagonism of VEGF attenuates diabetic albuminuria and other associated features of the podocytopathy. However, the promise shown in the animal studies has not carried over as convincingly into the realm of human studies, as some investigators find a negative or no relationship between VEGF and diabetic nephropathy, whereas others find a positive correlation between the two. If VEGF does play a role in diabetic renal disease, its observed effects and known mechanisms seem to point squarely at the podocyte as a central target of the maladaptive VEGF overactivity.

Endothelial cell barrier protection by simvastatin: GTPase regulation and NADPH oxidase inhibition

The statins, hydroxy-3-methylglutaryl-CoA reductase inhibitors that lower serum cholesterol, exhibit myriad clinical benefits, including enhanced vascular integrity. One potential mechanism underlying increased endothelial cell (EC) barrier function is inhibition of geranylgeranylation, a covalent modification enabling translocation of the small GTPases Rho and Rac to the cell membrane. While RhoA inhibition attenuates actin stress fiber formation and promotes EC barrier function, Rac1 inhibition at the cell membrane potentially prevents activation of NADPH oxidase and subsequent generation of superoxides known to induce barrier disruption. We examined the relative regulatory effects of simvastatin on RhoA, Rac1, and NADPH oxidase activities in the context of human pulmonary artery EC barrier protection. Confluent EC treated with simvastatin demonstrated significantly decreased thrombin-induced FITC-dextran permeability, a reflection of vascular integrity, which was linked temporally to simvastatin-mediated actin cytoskeletal rearrangement. Compared with Rho inhibition alone (Y-27632), simvastatin afforded additional protection against thrombin-mediated barrier dysfunction and attenuated LPS-induced EC permeability and superoxide generation. Statin-mediated inhibition of both Rac translocation to the cell membrane and superoxide production were attenuated by geranylgeranyl pyrophosphate (GGPP), indicating that these effects are due to geranylgeranylation inhibition. Finally, thrombin-induced EC permeability was modestly attenuated by reduced Rac1 expression (small interfering RNA), whereas these effects were made more pronounced by simvastatin pretreatment. Together, these data suggest EC barrier protection by simvastatin is due to dual inhibitory effects on RhoA and Rac1 as well as the attenuation of superoxide generation by EC NADPH oxidase and contribute to the molecular mechanistic understanding of the modulation of EC barrier properties by simvastatin.

High glucose increases phosphocofilin via phosphorylation of LIM kinase due to Rho/Rho kinase activation in cultured pig proximal tubular epithelial cells

In proximal tubular epithelial cells (PTECs), depolymerization of actin by cofilin plays a crucial role in maintaining polarity and function. Cofilin is inactivated when phosphorylated by p-Lin-11/Isl-1/Mec-3 kinase (LIMK) to give p-cofilin. LIMK is phosphorylated by phosphorylated p21-activated kinase (PAK), a downstream signal of phosphoinositide 3-kinase (PI3K), or by Rho kinase (ROCK), and is dephosphorylated by slingshot (SSH). However, in PTECs the signaling pathways regulating phosphorylation and dephosphorylation of cofilin, and the influence of high glucose (HG) on these pathways remain to be elucidated. Here, we show that HG in cultured porcine PTECs (LLC-PK1) increases p-cofilin and p-LIMK1 beyond 6h and that the simultaneous presence of phlorizin reverses the increase. HG did not influence the levels of PI3K-p85, downstream signals to SSH1 and p-PAK1, and mRNA of cofilin, LIMK1 and SSH1. On the other hand, wortmannin and LY294002 markedly increased p-cofilin and p-LIMK1 without influencing on the level of SSH1 protein. HG-activated RhoA and ROCK2 beyond 3h, and phlorizin attenuated this activation. GF109203X inhibited HG-induced increase in membranous RhoA and ROCK2, and phorbol ester increased these proteins. Y27632 (a ROCK inhibitor) reversed HG-induced increases of p-cofilin and p-LIMK1. We conclude that HG increases p-cofilin by phosphorylating LIMK1 through activation of Rho/Rho kinase, probably due to diacylglycerol-sensitive PKC activation resulting from increased glucose influx. HG did not alter PI3K or its downstream signals, even though PI3K has a physiological role in maintaining the cofilin level by activating SSH1.

Antiangiogenic properties of fasudil, a potent Rho-Kinase inhibitor

PURPOSE

Vascular endothelial growth factor (VEGF) plays a pivotal role in pathological angiogenesis. In this study, we addressed the therapeutic potential of fasudil, a potent Rho-kinase inhibitor, for VEGF-elicited angiogenesis and also for the intracellular signalings induced by VEGF.

METHODS

In vitro, the inhibitory effects of fasudil on the VEGF-dependent VEGF receptor 2 (VEFGR2 or KDR), extracellular signal-related kinase (ERK) 1/2, Akt and myosin light chain (MLC) phosphorylation, as well as on the migration and proliferation of bovine retinal microvascular endothelial cells (BRECs) were analyzed with Western blotting, [3H]-thymidine uptake, and modified Boyden chamber assay. VEGF-elicited in vivo angiogenesis was analyzed with a mouse corneal micropocket assay coembedded with or without fasudil.

RESULTS

VEGF caused enhanced MLC phosphorylation of BRECs, which was almost completely attenuated by 10microM fasudil. VEGF-dependent phosphorylation of ERK1/2 and Akt were also partially but significantly attenuated by treatment with fasudil without affecting VEGFR2 (KDR) phosphorylation. Moreover, both VEGF-induced [3H]-thymidine uptake and the migration of BRECs were significantly inhibited in the presence of fasudil. Finally, VEGF-elicited angiogenesis in the corneal micropocket assay was potently attenuated by coembedding with fasudil (P < 0.01).

CONCLUSIONS

These findings indicate that fasudil might have a therapeutic potential for ocular angiogenic diseases. The antiangiogenic effect of fasudil appears to be mediated through the blockade not only of Rho-kinase signaling but also of ERK and Akt signaling.

Targeting of RhoA/ROCK signaling ameliorates progression of diabetic nephropathy independent of glucose control

OBJECTIVE

RhoA, a small GTPase protein, and its immediate downstream target, Rho kinase (ROCK), control a wide variety of signal transduction pathways. Recent studies have shown that fasudil, a selective ROCK inhibitor, may play a pivotal role in a number of pathological conditions, ranging from cardiovascular diseases to pulmonary hypertension and erectile dysfunction. Considerable evidence suggests that some of the beneficial effects of statins may also stem from their modulatory effects on RhoA/ROCK signaling. In the current study, we hypothesized that pharmacological blockade of the RhoA/ROCK pathway with either fasudil or simvastatin would ameliorate progression of diabetic nephropathy.

RESEARCH DESIGN AND METHODS

In two separate experiments, diabetic db/db mice received fasudil (10 mg x kg(-) x day(-) i.p.) or simvastatin (40 mg x kg(-) x day(-) p.o.) for 16 weeks. Untreated db/db and db/m mice served as controls.

RESULTS

The kidney cortices of untreated db/db mice displayed increased ROCK activity compared with db/m mice. The fasudil-treated mice exhibited a significant reduction in ROCK activity, albuminuria, glomerular collagen IV accumulation, and urinary collagen IV excretion compared with untreated db/db mice. Interestingly, blood glucose was unaffected by fasudil administration. Treatment with simvastatin significantly attenuated RhoA activation in the kidney cortices of db/db mice and resulted in a significant reduction of albuminuria and mesangial matrix expansion.

CONCLUSIONS

Based on these results, we propose that RhoA/ROCK blockade constitutes a novel approach to the treatment of diabetic nephropathy. Our data also suggest a critical role for RhoA/ROCK activation in the pathogenesis of diabetic nephropathy.

Adiponectin protects against angiotensin II or tumor necrosis factor alpha-induced endothelial cell monolayer hyperpermeability: role of cAMP/PKA signaling

OBJECTIVE

Angiotensin II (Ang II) and tumor necrosis factor (TNF)-alpha levels increase endothelial permeability, and we hypothesized that adiponectin suppressed these responses in a cAMP-dependent manner.

METHODS AND RESULTS

The effect of adiponectin on transendothelial electric resistance (TEER) and diffusion of albumin through human umbilical vein and bovine aortic endothelial cell monolayers induced by Ang II (100 nmol/L) or TNF-alpha (5 ng/mL) was measured. Treatment with the globular domain of adiponectin (3 mug/mL) for 16 hours abrogated the adverse TEER effect of TNF-alpha (-35 versus -12 Omega/cm(2) at 45 minutes, P<0.05) and Ang II (-25 versus -5 Omega/cm(2) at 45 minutes, P<0.01) and partially suppressed the increased diffusion of albumin with Ang II (40% versus 10% change, P<0.05) or TNF-alpha (40% versus 20% change, P<0.05). Full-length adiponectin also suppressed Ang II-induced monolayer hyperpermeability. Adiponectin treatment also suppressed Ang II-induced increased actin stress fiber development, intercellular gap formation, and beta-tubulin disassembly. Adiponectin increased cAMP levels, and its effects were abrogated by inhibition of adenylyl cyclase or cAMP-dependent protein kinase signaling.

CONCLUSIONS

Adiponectin protects the endothelial monolayer from Ang II or TNF-alpha-induced hyperpermeability by modulating microtubule and cytoskeleton stability via a cAMP/ PKA signaling cascade.

The Galpha12/13 family of heterotrimeric G proteins and the small GTPase RhoA link the Kaposi sarcoma-associated herpes virus G protein-coupled receptor to heme oxygenase-1 expression and tumorigenesis

Heme oxygenase-1 (HO-1), an inducible enzyme that metabolizes the heme group, is highly expressed in human Kaposi sarcoma lesions. Its expression is up-regulated by the G protein-coupled receptor from the Kaposi sarcoma-associated herpes virus (vGPCR). Although recent evidence shows that HO-1 contributes to vGPCR-induced tumorigenesis and vascular endothelial growth factor (VEGF) expression, the molecular steps that link vGPCR to HO-1 remain unknown. Here we show that vGPCR induces HO-1 expression and transformation through the Galpha(12/13) family of heterotrimeric G proteins and the small GTPase RhoA. Targeted small hairpin RNA knockdown expression of Galpha(12), Galpha(13), or RhoA and inhibition of RhoA activity impair vGPCR-induced transformation and ho-1 promoter activity. Knockdown expression of RhoA also reduces vGPCR-induced VEFG-A secretion and blocks tumor growth in a murine allograft tumor model. NIH-3T3 cells expressing constitutively activated Galpha(13) or RhoA implanted in nude mice develop tumors displaying spindle-shaped cells that express HO-1 and VEGF-A, similarly to vGPCR-derived tumors. RhoAQL-induced tumor growth is reduced 80% by small hairpin RNA-mediated knockdown expression of HO-1 in the implanted cells. Likewise, inhibition of HO-1 activity by chronic administration of the HO-1 inhibitor tin protoporphyrin IX to mice reduces RhoAQL-induced tumor growth by 70%. Our study shows that vGPCR induces HO-1 expression through the Galpha(12/13)/RhoA axes and shows for the first time a potential role for HO-1 as a therapeutic target in tumors where RhoA has oncogenic activity.

Inhibition of CXCL16 attenuates inflammatory and progressive phases of anti-glomerular basement membrane antibody-associated glomerulonephritis

Chemokines recruit and activate leukocytes during inflammation. CXCL16 is a recently discovered chemokine that is expressed as a transmembrane protein that is cleaved to form the active, soluble chemokine. We analyzed the role of CXCL16 in the development of inflammation and in the progression of the anti-glomerular basement membrane (GBM) antibody-induced experimental glomerulonephritis in Wistar-Kyoto rats. CXCL16 was expressed in glomerular endothelial cells and mediated adhesion of macrophages expressing CXCL16 and its cognate receptor, CXCR6. Glomerular infiltrates displayed a strong migratory response to soluble CXCL16. Soluble CXCL16 and its receptor CXCR6 were induced in nephritic glomeruli throughout the disease, and CXCL16 expression correlated with the up-regulation of ADAM10, suggesting that this disintegrin and metalloproteinase mediates the chemokine activity of CXCL16. Blocking CXCL16 in the acute inflammatory phase or progressive phase of established glomerulonephritis significantly attenuated monocyte/macrophage infiltration and glomerular injury; proteinuria also improved. We conclude that CXCL16/CXCR6 plays a critical role in stimulating leukocyte influx, which causes glomerular damage during anti-GBM glomerulonephritis. Blocking CXCL16 actions limits the progression of anti-GBM glomerulonephritis even when the disease is established.

Statins and the vascular endothelial inflammatory response

Statins reduce cholesterol synthesis and are widely used for the treatment of hyperlipidaemia and ischaemic heart disease. Besides their cholesterol-lowering effects, statins also possess broad immunomodulatory and anti-inflammatory properties. Vascular endothelial cells have a crucial role in the pathogenesis of inflammatory disease, and, alongside leukocytes and antigen-presenting cells, represent a key cellular target for statin therapy. Recent studies investigating how these drugs modify endothelial cell function demonstrate that the therapeutic effect of statins can be attributed, in part, to their action on the endothelium. Accordingly, statins attenuate endothelial MHC class II expression, increase endothelial nitric oxide synthase and fibrinolytic activity, decrease leukocyte adhesion and transmigration, and enhance resistance to local injurious stimuli. Many of these effects are brought about by the modulation of small GTPase function and the downregulation of proinflammatory gene expression.

Integrin alphavbeta5 regulates lung vascular permeability and pulmonary endothelial barrier function

Increased lung vascular permeability is an important contributor to respiratory failure in acute lung injury (ALI). We found that a function-blocking antibody against the integrin alphavbeta5 prevented development of lung vascular permeability in two different models of ALI: ischemia-reperfusion in rats (mediated by vascular endothelial growth factor [VEGF]) and ventilation-induced lung injury (VILI) in mice (mediated, at least in part, by transforming growth factor-beta [TGF-beta]). Knockout mice homozygous for a null mutation of the integrin beta5 subunit were also protected from lung vascular permeability in VILI. In pulmonary endothelial cells, both the genetic absence and blocking of alphavbeta5 prevented increases in monolayer permeability induced by VEGF, TGF-beta, and thrombin. Furthermore, actin stress fiber formation induced by each of these agonists was attenuated by blocking alphavbeta5, suggesting that alphavbeta5 regulates induced pulmonary endothelial permeability by facilitating interactions with the actin cytoskeleton. These results identify integrin alphavbeta5 as a central regulator of increased pulmonary vascular permeability and a potentially attractive therapeutic target in ALI.