Induction of connective tissue growth factor by angiotensin II: integration of signaling pathways

Promising Therapeutic Treatments for Cardiac Fibrosis: Herbal Plants and Their Extracts

Cardiac fibrosis is closely associated with multiple heart diseases, which are a prominent health issue in the global world. Neurohormones and cytokines play indispensable roles in cardiac fibrosis. Many signaling pathways participate in cardiac fibrosis as well. Cardiac fibrosis is due to impaired degradation of collagen and impaired fibroblast activation, and collagen accumulation results in increasing heart stiffness and inharmonious activity, leading to structure alterations and finally cardiac function decline. Herbal plants have been applied in traditional medicines for thousands of years. Because of their naturality, they have attracted much attention for use in resisting cardiac fibrosis in recent years. This review sheds light on several extracts from herbal plants, which are promising therapeutics for reversing cardiac fibrosis.

LRP1 protects against excessive superior mesenteric artery remodeling by modulating angiotensin II-mediated signaling

Vascular smooth muscle cells (vSMCs) exert a critical role in sensing and maintaining vascular integrity. These cells abundantly express the low-density lipoprotein receptor-related protein 1 (LRP1), a large endocytic signaling receptor that recognizes numerous ligands, including apolipoprotein E-rich lipoproteins, proteases, and protease-inhibitor complexes. We observed the spontaneous formation of aneurysms in the superior mesenteric artery (SMA) of both male and female mice in which LRP1 was genetically deleted in vSMCs (smLRP1-/- mice). Quantitative proteomics revealed elevated abundance of several proteins in smLRP1-/- mice that are known to be induced by angiotensin II-mediated (AngII-mediated) signaling, suggesting that this pathway was dysregulated. Administration of losartan, an AngII type I receptor antagonist, or an angiotensinogen antisense oligonucleotide to reduce plasma angiotensinogen concentrations restored the normal SMA phenotype in smLRP1-/- mice and prevented aneurysm formation. Additionally, using a vascular injury model, we noted excessive vascular remodeling and neointima formation in smLRP1-/- mice that was restored by losartan administration. Together, these findings reveal that LRP1 regulates vascular integrity and remodeling of the SMA by attenuating excessive AngII-mediated signaling.

MRTF: Basic Biology and Role in Kidney Disease

A lesser known but crucially important downstream effect of Rho family GTPases is the regulation of gene expression. This major role is mediated via the cytoskeleton, the organization of which dictates the nucleocytoplasmic shuttling of a set of transcription factors. Central among these is myocardin-related transcription factor (MRTF), which upon actin polymerization translocates to the nucleus and binds to its cognate partner, serum response factor (SRF). The MRTF/SRF complex then drives a large cohort of genes involved in cytoskeleton remodeling, contractility, extracellular matrix organization and many other processes. Accordingly, MRTF, activated by a variety of mechanical and chemical stimuli, affects a plethora of functions with physiological and pathological relevance. These include cell motility, development, metabolism and thus metastasis formation, inflammatory responses and—predominantly-organ fibrosis. The aim of this review is twofold: to provide an up-to-date summary about the basic biology and regulation of this versatile transcriptional coactivator; and to highlight its principal involvement in the pathobiology of kidney disease. Acting through both direct transcriptional and epigenetic mechanisms, MRTF plays a key (yet not fully appreciated) role in the induction of a profibrotic epithelial phenotype (PEP) as well as in fibroblast-myofibroblast transition, prime pathomechanisms in chronic kidney disease and renal fibrosis.

Connective tissue growth factor expression after angiotensin II exposure is dependent on transforming growth factor-β signaling via the canonical Smad-dependent pathway in hypertensive induced myocardial fibrosis

Introduction:

Transforming growth factor-β (TGF-β) and connective tissue growth factor (CTGF) are often described as the initial pro-fibrotic mediators upregulated early in fibrosis models dependent on angiotensin II (Ang-II). In the present study, we explore the mechanistic link between TGF-β and CTGF expression by using a novel TGF-β trap.

Materials and methods:

NIH/3T3 fibroblasts were subjected to TGF-β with or without TGF-β trap or 1D11 antibody, CTGF or CTGF plus TGF-β for six or 24 hours, and then used for quantitative real-time polymerase chain reaction (qRT-PCR) or immunocytochemistry. Male C57BL/6 mice were infused with Ang-II and randomly assigned TGF-β trap for six or 24 hours. Hearts were harvested for histological analyses, qRT-PCR and western blotting.

Results:

Exogenous TGF-β-induced fibroblasts resulted in significant upregulation of CTGF, TGF-β and type I collagen transcript levels in vitro. Additionally, TGF-β promoted the differentiation of fibroblasts into α-SMA⁺ myofibroblasts. CTGF expression was reduced by the addition of TGF-β trap or neutralizing antibody, confirming that its expression is dependent on TGF-β signaling. In contrast, exogenous CTGF did not appear to have an effect on fibroblast production of pro-fibrotic transcripts or fibroblast differentiation. Ang-II infusion in vivo led to a significant increase in TGF-β and CTGF mRNA expression at six and 24 hours with corresponding changes in Smad2 phosphorylation (pSmad2), indicative of increased TGF-β signaling. Ang-II animals that received the TGF-β trap demonstrated reduced CTGF mRNA levels and pSmad2 at six hours, suggesting that early CTGF expression is dependent on TGF-β signaling.

Conclusions:

We demonstrated that CTGF expression is dependent on TGF-β signaling both in vitro and in vivo in a model of myocardial fibrosis. This also suggests that early myocardial CTGF mRNA expression (six hours) after Ang-II exposure is likely dependent on latent TGF-β activation via the canonical Smad-dependent pathway in resident cardiac cells.

Effects and Mechanism of SO2 Inhalation on Rat Myocardial Collagen Fibers

Background

This study investigates the effects and mechanism of sulfur dioxide (SO₂) inhalation and exercise on rat myocardial collagen fiber.

Material/Methods

The rats were randomly divided into 4 groups: a control group (RG), an exercise group (EG), an SO₂ pollution group (SRG), and an SO₂ pollution and exercise group (SEG). Body weight, cardiac index, and left ventricular index in each group were compared. The myocardial hydroxyproline (Hyp) concentration was determined by pepsin acid hydrolysis. The interstitial myocardial collagen expression was measured by Sirius Red F3B in saturated carbazotic acid. The local myocardial angiotensin II type 1 receptor (AT1R) and connective tissue growth factor (CTGF) expression was tested by immunohistochemistry SABC method.

Results

Compared with RG, the weight growth rate of EG, SRG, and SEG decreased significantly (P<0.01). Compared with EG, the body weight growth rate of SEG significantly decreased (P<0.01) and cardiac index and left ventricular index decreased but without a significant difference. Compared with EG, myocardial Hyp and collagen concentration, myocardial collagen volume fraction (CVF), perivascular collagen area (PVCA), and the expression of AT1R and CTGF in myocardium of SEG increased significantly (P<0.01).

Conclusions

SO₂ inhalation and exercise will not only offset beneficial health effects of movement on the cardiovascular system, but also produce more unfavorable influences. People should pay attention to their environment when exercising, and try to avoid exercising in environments with SO₂ pollution.

CTGF Is Expressed During Cystic Remodeling in the PKD/Mhm (cy/+) Rat Model for Autosomal-Dominant Polycystic Kidney Disease (ADPKD)

Connective tissue growth factor (CTGF, also named CCN2) plays an important role in the development of tubulointerstitial fibrosis, which most critically determines the progression to end-stage renal failure in autosomal-dominant polycystic kidney disease (ADPKD), the most common genetically caused renal disease. We determined CTGF expression in a well-characterized animal model of human ADPKD, the PKD/Mhm (cy/+) rat. Kidneys of 12 weeks old (cy/+) as well as (+/+) non-affected rats were analyzed for CTGF RNA and protein expression by RT-PCR, Northern and Western blot analyses, in situ hybridization, and IHC. Besides the established expression of CTGF in glomerular cells in kidneys of wild-type (+/+) animals, in (cy/+) rats, CTGF mRNA and protein were robustly expressed in interstitial, stellate-shaped cells, located in a scattered pattern underlying the cystic epithelium and in focal areas of advanced tubulointerstitial remodeling. Renal CTGF mRNA and protein expression levels were significantly higher in (cy/+) rats compared with their (+/+) littermates. Detection of CTGF expression in cells adjacent to cystic epithelium and in areas of marked fibrosis suggests a role in the local response to cyst development and indicates that CTGF may be a relevant factor contributing to tubulointerstitial fibrosis in polycystic kidney disease.

CYP2J2 metabolites, epoxyeicosatrienoic acids, attenuate Ang II-induced cardiac fibrotic response by targeting Gα12/13

The arachidonic acid-cytochrome P450 2J2-epoxyeicosatrienoic acid (AA-CYP2J2-EET) metabolic pathway has been identified to be protective in the cardiovascular system. This study explored the effects of the AA-CYP2J2-EET metabolic pathway on cardiac fibrosis from the perspective of cardiac fibroblasts and underlying mechanisms. In in vivo studies, 8-week-old male CYP2J2 transgenic mice (aMHC-CYP2J2-Tr) and littermates were infused with angiotensin II (Ang II) or saline for 2 weeks. Results showed that CYP2J2 overexpression increased EET production. Meanwhile, impairment of cardiac function and fibrotic response were attenuated by CYP2J2 overexpression. The effects of CYP2J2 were associated with reduced activation of the α subunits of G12 family G proteins (Gα_12/13)/RhoA/Rho kinase (ROCK) cascade and elevation of the NO/cyclic guanosine monophosphate (cGMP) level in cardiac tissue. In in vitro studies, cardiac fibroblast activation, proliferation, migration, and collagen production induced by Ang II were associated with activation of the Gα_12/13/RhoA/ROCK pathway, which was inhibited by exogenous 11,12-EET. Moreover, silencing of Gα_12/13 or RhoA exerted similar effects as 11,12-EET. Furthermore, inhibitory effects of 11,12-EET on Gα_12/13 were blocked by NO/cGMP pathway inhibitors. Our findings indicate that enhancement of the AA-CYP2J2-EET metabolic pathway by CYP2J2 overexpression attenuates Ang II-induced cardiac dysfunction and fibrosis by reducing the fibrotic response of cardiac fibroblasts by targeting the Gα_12/13/RhoA/ROCK pathway via NO/cGMP signaling.

Role of connective tissue growth factor in vascular and renal damage associated with hypertension in rats. Interactions with angiotensin II

We have evaluated the role of connective tissue growth factor (CTGF) in vascular and renal damage associated with hypertension and possible interactions with angiotensin II (Ang II). Spontaneously hypertensive rats (SHR) were treated with either the Ang II receptor antagonist candesartan (C;2 mg/Kg-1/day-1) or antihypertensive triple therapy (TT; in mg/Kg-1/day-1 ;20 hydralazine +7 hydrochlorothiazide +0.15 reserpine) for 10 weeks. Wistar Kyoto rats were used as a normotensive control group. Hypertension was associated with an increase in aortic media area, media-to-lumen ratio and collagen density. Kidneys from SHR showed minimum renal alterations. Aorta and renal gene expression and immunostaining of CTGF were higher in SHR. Candesartan decreased arterial pressure, aortic media area, media-to-lumen ratio and collagen density. However, although arterial pressure decrease was comparable for both treatments,TT partially reduced these parameters. Candesartantreated rats showed lower levels of vascular CTGF expression, aortic media area, media-to-lumen ratio and collagen density than TT-treated animals. Treatments improve renal damage and reduce renal gene exp Pression and CTGF immunostaining in SHR in a similar manner.The results show that vascular and renal damage is associated with stimulation of CTGF gene and protein content.These results also might suggest that CTGF could be one downstream mediator of Ang II in hypertension-associated organ damage in SHR.

Signaling Crosstalk between Tubular Epithelial Cells and Interstitial Fibroblasts after Kidney Injury

BACKGROUND

A wide variety of kidney diseases ultimately lead to tubulointerstitial damage. The initial site of injury is usually the renal tubules, with activation of fibroblasts occurring later. Self-limited disease is characterized by transient cellular activation with timed deactivation and ultimately a return to normal functioning, whereas sustained responses characterize chronic disease and the development of irreversible fibrosis. The underlying molecular and cellular mechanisms of this cascade of events remain an area of active research. Current data overwhelmingly support a role for crosstalk between the tubular epithelium and the interstitial fibroblast that mediates both repair/regeneration and progressive disease. This epithelial-mesenchymal communication (EMC) is regulated by a variety of soluble ligands binding to cell surface receptors to induce intracellular signaling events.

SUMMARY

EMC is an important mechanism whereby tubular epithelium and fibroblasts/mesenchymal cells crosstalk to affect renal physiology and pathology. Numerous soluble factors such as sonic hedgehog, Wnt ligands, transforming growth factor-β, hepatocyte growth factor, connective tissue growth factor, and angiotensin II all participate in bidirectional EMC. Recent studies have also identified exosomes as a vehicle to mediate EMC during kidney injury. In general, while the short-term activity of EMC factors is renoprotective, prolonged activation of these factors leads to chronic disease and fibrosis.

KEY MESSAGES

The discovery of a complex and intricate system of communication between tubular cells and fibroblasts is a new paradigm in our understanding of renal fibrosis. An appreciation of both their regenerative and pathologic functions will inform the development and use of targeted therapeutic interventions.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]

The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.

Smooth muscle cell deletion of low-density lipoprotein receptor-related protein 1 augments angiotensin II-induced superior mesenteric arterial and ascending aortic aneurysms

OBJECTIVE

Low-density lipoprotein receptor-related protein 1 (LRP1), a multifunctional protein involved in endocytosis and cell signaling pathways, leads to several vascular pathologies when deleted in vascular smooth muscle cells (SMCs). The purpose of this study was to determine whether LRP1 deletion in SMCs influenced angiotensin II-induced arterial pathologies.

APPROACH AND RESULTS

LRP1 protein abundance was equivalent in selected arterial regions, but SMC-specific LRP1 depletion had no effect on abdominal and ascending aortic diameters in young mice. To determine the effects of LRP1 deficiency on angiotensin II vascular responses, SMC-specific LRP1 (smLRP1(+/+)) and smLRP1-deficient (smLRP1(-/-)) mice were infused with saline, angiotensin II, or norepinephrine. Several smLRP(-/-) mice died of superior mesenteric arterial (SMA) rupture during angiotensin II infusion. In surviving mice, angiotensin II profoundly augmented SMA dilation in smLRP1(-/-) mice. SMA dilation was blood pressure dependent as demonstrated by a similar response during norepinephrine infusion. SMA dilation was also associated with profound macrophage accumulation, but minimal elastin fragmentation. Angiotensin II infusion led to no significant differences in abdominal aorta diameters between smLRP1(+/+) and smLRP1(-/-) mice. In contrast, ascending aortic dilation was exacerbated markedly in angiotensin II-infused smLRP1(-/-) mice, but norepinephrine had no significant effect on either aortic region. Ascending aortas of smLRP1(-/-) mice infused with angiotensin II had minimal macrophage accumulation but significantly increased elastin fragmentation and mRNA abundance of several LRP1 ligands including MMP-2 (matrix metalloproteinase-2) and uPA (urokinase plasminogen activator).

CONCLUSIONS

smLRP1 deficiency had no effect on angiotensin II-induced abdominal aortic aneurysm formation. Conversely, angiotensin II infusion in smLRP1(-/-) mice exacerbated SMA and ascending aorta dilation. Dilation in these 2 regions had differential association with blood pressure and divergent pathological characteristics.

Adverse biventricular remodeling in isolated right ventricular hypertension is mediated by increased transforming growth factor-β1 signaling and is abrogated by angiotensin receptor blockade

The pressure-loaded right ventricle (RV) adversely affects left ventricular (LV) function. We recently found that these ventricular-ventricular interactions lead to LV myocardial fibrosis through transforming growth factor-β1 (TGF-β1) signaling. We investigated the mechanisms mediating biventricular fibrosis in RV afterload and their potential modification by angiotensin receptor blockade. An adjustable pulmonary artery band (PAB) was placed in rabbits. In sham-operated control rabbits, the band was left uninflated (n = 6). In the RV afterload group, the PAB was sequentially inflated to generate systemic RV pressure at 28 days (n = 8). In a third group, the PAB was inflated to systemic levels, and the angiotensin receptor blocker losartan was added (n = 6). Five weeks after surgery, the animals were killed for assessments of biventricular hypertrophy, fibrosis, apoptosis, and the components of their signaling pathways. PAB animals developed biventricular hypertrophy, fibrosis, and apoptosis, versus sham rabbits, in which these conditions were decreased with losartan. RV and LV TGF-β1, connective tissue growth factor (CTGF) (CCN2), endothelin-1 (ET-1), endothelin receptor B, and matrix metalloproteinase 2/9 mRNA levels were increased in PAB animals versus sham animals, and decreased with losartan. Given the marked biventricular CTGF up-regulation in PAB and down-regulation with losartan, we investigated CTGF signaling. RV and LV Smad 2/3/4 protein levels and LV RhoA mRNA levels were increased with PAB and reduced with losartan. In conclusion, isolated RV afterload induces biventricular fibrosis and apoptosis, which are reduced by angiotensin receptor blockade. Adverse ventricular-ventricular interactions induced by isolated RV afterload appear to be mediated through TGF-β1-CTGF and ET-1 pathways.

Glutathione S-transferase mu2 suppresses cancer cell metastasis in non-small cell lung cancer

Glutathione S-transferase mu2 (GST-M2) is a phase II detoxification enzyme. Low expression of GST-M2 in lung cancers is due to hypermethylation of its promoter. Lung cancer with the GST mu-null genotype is associated with shorter survival. However, a correlation between GST-M2 and important clinical parameters, as well as the migration of GST-M2-defective cells in lung cancer, has not been established. In the present study, we investigate the role of GST-M2 in cell migration and actin disassembly in lung cancer cells. GST-M2 and CCN2 mRNA levels were significantly reduced in non-small cell lung cancer (NSCLC) tumors when compared with matched normal lung tissues in 82 patients with NSCLC. We found that high expressions of both GST-M2 and CCN2 are correlated with favorable survival of patients with lung cancer when compared with similar patients without GST-M2 or CCN2 expression. GST-M2 can induce CCN2 expression by driving the CCN2 proximal promoter. Overexpression of GST-M2 decreases the formation of filopodia, resulting in remodeling of the reorganized cytoskeletons. Overexpression of GST-M2 significantly suppressed cancer cell migration on wound-healing assay. In addition, overexpression of GST-M2 dramatically reduced tumor growth and metastasis in a xenograft mouse model. These data highlight the potential of GST-M2 as a novel tumor suppressor. GST-M2 increases the expression of CCN2 in lung cancer cells, which inhibits cancer cell migration in lung cancer and animal models.

Angiotensin II-induced pro-fibrotic effects require p38MAPK activity and transforming growth factor beta 1 expression in skeletal muscle cells

Fibrotic disorders are typically characterised by excessive connective tissue and extracellular matrix (ECM) deposition that preclude the normal healing of different tissues. Several skeletal muscle dystrophies are characterised by extensive fibrosis. Among the factors involved in skeletal muscle fibrosis is angiotensin II (Ang-II), a key protein of the renin-angiotensin system (RAS). We previously demonstrated that myoblasts responded to Ang-II by increasing the ECM protein levels mediated by AT-1 receptors, implicating an Ang-II-induced reactive oxygen species (ROS) by a NAD(P)H oxidase-dependent mechanism. In this paper, we show that in myoblasts, Ang-II induced the increase of transforming growth factor beta 1 (TGF-β1) and connective tissue growth factor (CTGF) expression through its AT-1 receptor. This effect is dependent of the NAD(P)H oxidase (NOX)-induced ROS, as indicated by a decrease of the expression of both pro-fibrotic factors when the ROS production was inhibited via the NOX inhibitor apocynin. The increase in pro-fibrotic factors levels was paralleled by enhanced p38MAPK and ERK1/2 phosphorylation in response to Ang-II. However, only the p38MAPK activity was critical for the Ang-II-induced fibrotic effects, as indicated by the decrease in the Ang-II-induced TGF-β1 and CTGF expression and fibronectin levels by SB-203580, an inhibitor of the p38MAPK, but not by U0126, an inhibitor of ERK1/2 phosphorylation. Furthermore, we showed that the Ang-II-dependent p38MAPK activation, but not the ERK1/2 phosphorylation, was necessary for the NOX-derived ROS. In addition, we demonstrated that TGF-β1 expression was required for the Ang-II-induced pro-fibrotic effects evaluated by using SB-431542, an inhibitor of TGF-βRI kinase activity, and by knocking down TGF-β1 levels by shRNA technique. These results strongly suggest that the fibrotic response to Ang-II is mediated by the AT-1 receptor and requires the p38MAPK phosphorylation, NOX-induced ROS, and TGF-β1 expression increase mediated by Ang-II in skeletal muscle cells.

Matricellular proteins in cardiac adaptation and disease

The term matricellular proteins describes a family of structurally unrelated extracellular macromolecules that, unlike structural matrix proteins, do not play a primary role in tissue architecture, but are induced following injury and modulate cell-cell and cell-matrix interactions. When released to the matrix, matricellular proteins associate with growth factors, cytokines, and other bioactive effectors and bind to cell surface receptors transducing signaling cascades. Matricellular proteins are upregulated in the injured and remodeling heart and play an important role in regulation of inflammatory, reparative, fibrotic and angiogenic pathways. Thrombospondin (TSP)-1, -2, and -4 as well as tenascin-C and -X secreted protein acidic and rich in cysteine (SPARC), osteopontin, periostin, and members of the CCN family (including CCN1 and CCN2/connective tissue growth factor) are involved in a variety of cardiac pathophysiological conditions, including myocardial infarction, cardiac hypertrophy and fibrosis, aging-associated myocardial remodeling, myocarditis, diabetic cardiomyopathy, and valvular disease. This review discusses the properties and characteristics of the matricellular proteins and presents our current knowledge on their role in cardiac adaptation and disease. Understanding the role of matricellular proteins in myocardial pathophysiology and identification of the functional domains responsible for their actions may lead to design of peptides with therapeutic potential for patients with heart disease.

Simvastatin ameliorates angiotensin II-induced endothelial dysfunction through restoration of Rho-BH4-eNOS-NO pathway

Endothelial dysfunction contributes to the initiation and development of hypertension. We previously found that simvastatin moderately decreases blood pressure in 2-kidney-2-clip (2k2c) renal hypertension, but the precise mechanisms are still unclear. The present study was designed to examine the protective actions of simvastatin in 2k2c-evoked endothelial dysfunction and also delineate the underlying mechanisms. Here we show that 2k2c-induced elevation in plasma angiotensin II impaired acetylcholine-induced endothelium-dependent vascular relaxation, suppressed endothelial NO synthase (eNOS) activity and reduced nitric oxide (NO) production. Additionally, the levels of tetrahydrobiopterin (BH4), an essential cofactor of eNOS, as well as the activity of GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme for BH4 synthesis, were markedly reduced. Administration of simvastatin significantly improved acetylcholine-induced endothelium-dependent carotid arteries relaxation at 9 weeks in reno-hypertensive rats. Notably, GTPCH I activity, BH4 production, p-eNOS expression and NO levels in the vascular endothelium were elevated as a result of simvastatin administration. In cultured rat arterial endothelial cells, simvastatin restored BH4, GTPCH I activity and NO release impaired by angiotensin II, and pretreatment with mevalonate (MVA) or geranylgeranyl pyrophosphate (GGPP) abolished the beneficial effects exerted by simvastatin. Moreover, RhoA inhibitor C3 exoenzyme, Rho kinase inhibitor Y-27632 and dominant negative mutant of RhoA prevented BH4 and NO loss due to Ang II treatment. Taken together, normalization of BH4-eNOS-NO pathway at least in part accounts for the beneficial actions of simvastatin on vascular endothelium during 2k2c hypertension, and RhoA-Rho kinase pathway is involved in regulation of BH4 production.

Connective tissue growth factor (CTGF/CCN2) ELISA: a novel tool for monitoring fibrosis

BACKGROUND

Connective tissue growth factor (CTGF) has been identified as a key factor in the pathogenesis of diseases with significant fibrosis-related complications such as hepatitis, diabetes and renal transplantation. Increasing evidence shows that CTGF levels in plasma, serum and urine have promising biomarker applicability in these disorders.

OBJECTIVE

To present an overview of current knowledge on CTGF in various patient populations and the technical aspects of CTGF measurement by enzyme-linked immunosorbent assay (ELISA).

METHOD

We performed a comprehensive literature search by using electronic bibliographic databases.

CONCLUSION

CTGF is associated with disease severity parameters and outcome in fibrotic disease and may have diagnostic and prognostic values. However, CTGF ELISA needs standardization.

Effects of antiproteinuric intervention on elevated connective tissue growth factor (CTGF/CCN-2) plasma and urine levels in nondiabetic nephropathy

BACKGROUND AND OBJECTIVES

Connective tissue growth factor (CTGF/CCN-2) is a key player in fibrosis. Plasma CTGF levels predict end-stage renal disease and mortality in diabetic chronic kidney disease (CKD), supporting roles in intra- and extrarenal fibrosis. Few data are available on CTGF in nondiabetic CKD. We investigated CTGF levels and effects of antiproteinuric interventions in nondiabetic proteinuric CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In a crossover randomized controlled trial, 33 nondiabetic CKD patients (3.2 [2.5 to 4.0] g/24 h proteinuria) were treated during 6-week periods with placebo, ARB (100 mg/d losartan), and ARB plus diuretics (100 mg/d losartan plus 25 mg/d hydrochlorothiazide) combined with consecutively regular and low sodium diets (193 ± 62 versus 93 ± 52 mmol Na(+)/d).

RESULTS

CTGF was elevated in plasma (464 [387 to 556] pmol/L) and urine (205 [135 to 311] pmol/24 h) of patients compared with healthy controls (n = 21; 96 [86 to 108] pmol/L and 73 [55 to 98] pmol/24 h). Urinary CTGF was lowered by antiproteinuric intervention, in proportion to the reduction of proteinuria, with normalization during triple therapy (CTGF 99 [67 to 146] in CKD versus 73 [55 to 98] pmol/24 h in controls). In contrast, plasma CTGF was not affected.

CONCLUSIONS

Urinary and plasma CTGF are elevated in nondiabetic CKD. Only urinary CTGF is normalized by antiproteinuric intervention, consistent with amelioration of tubular dysfunction. The lack of effect on plasma CTGF suggests that its driving force might be independent of proteinuria and that short-term antiproteinuric interventions are not sufficient to correct the systemic profibrotic state in CKD.

Atorvastatin prevents left ventricular remodeling in spontaneously hypertensive rats

Statins improve left ventricular (LV) remodeling in spontaneously hypertensive rats (SHRs). This study was designed to investigate the effects of atorvastatin administered in the early stage on LV remodeling in SHRs, and to explore the underlying mechanisms.Sixteen male 8-week-old SHRs were randomized to receive distilled water (SHR-DW) or atorvastatin (SHR-ATV) for 12 weeks. Age-matched male Wistar-Kyoto (WKY) rats gavaged with distilled water served as controls. LV remodeling was evaluated, myocardial CTGF expression levels were detected using Western blotting, and cardiomyocyte apoptosis was detected with the TUNEL method.Compared with WKY and SHR-DW, atorvastatin treatment significantly decreased systolic blood pressure in SHRs; atorvastatin significantly inhibited LV remodeling, as indicated by the reduced LV weight/body weight ratio (SHR-ATV: 4.0 ± 0.4 versus SHR-DW: 4.7 ± 0.4 mg/g, P < 0.05), cardiomyocyte diameter (SHR-ATV: 16.2 ± 2.8 versus SHR-DW: 19.0 ± 1.0 µm, P < 0.05), and interstitial fibrosis (SHR-ATV: 3.3 ± 2.1 versus SHR-DW: 4.5 ± 1.8%, P < 0.05). Compared with WKY, myocardial CTGF expression was significantly increased and cardiomyocyte apoptosis decreased in SHRs. Compared with the SHR-DW group, atorvastatin treatment significantly inhibited myocardial CTGF expression (SHR-ATV: 0.69 ± 0.21 versus SHR-DW: 1.12 ± 0.27, P < 0.05) and induced cardiomyocyte apoptosis in SHRs (SHR-ATV: 5.2 ± 0.6 versus SHR-DW: 1.9 ± 0.3%, P < 0.05).The results indicate that early-stage administration of atorvastatin effectively prevented LV remodeling in SHRs, and that inhibition of myocardial CTGF expression and induction of cardiomyocyte apoptosis may be the underlying mechanisms.

Connective tissue growth factor and cardiac fibrosis

Cardiac fibrosis is a major pathogenic factor in a variety of cardiovascular diseases and refers to an excessive deposition of extracellular matrix components in the heart, which leads to cardiac dysfunction and eventually overt heart failure. Evidence is accumulating for a crucial role of connective tissue growth factor (CTGF) in fibrotic processes in several tissues including the heart. CTGF orchestrates the actions of important local factors evoking cardiac fibrosis. The central role of CTGF as a matricellular protein modulating the fibrotic process in cardiac remodelling makes it a possible biomarker for cardiac fibrosis and a potential candidate for therapeutic intervention to mitigate fibrosis in the heart.

Up-regulation of connective tissue growth factor in endothelial cells by the microtubule-destabilizing agent combretastatin A-4

Incubation of microvascular endothelial cells with combretastatin A-4 phosphate (CA-4P), a microtubule-destabilizing compound that preferentially targets tumor vessels, altered cell morphology and induced scattering of Golgi stacks. Concomitantly, CA-4P up-regulated connective tissue growth factor (CTGF/CCN2), a pleiotropic factor with antiangiogenic properties. In contrast to the effects of other microtubule-targeting agents such as colchicine or nocodazole, up-regulation of CTGF was only detectable in sparse cells, which were not embedded in a cell monolayer. Furthermore, CA-4P induced CTGF expression in endothelial cells, forming tube-like structures on basement membrane gels. Up-regulation of CTGF by CA-4P was dependent on Rho kinase signaling and was increased when p42/44 mitogen-activated protein kinase was inhibited. Additionally, FoxO transcription factors were identified as potent regulators of CTGF expression in endothelial cells. Activation of FoxO transcription factors by inhibition of phosphatidylinositol 3-kinase/AKT signaling resulted in a synergistic increase in CA-4P-mediated CTGF induction. CA-4P-mediated expression of CTGF was thus potentiated by the inhibition of kinase pathways, which are targets of novel antineoplastic drugs. Up-regulation of CTGF by low concentrations of CA-4P may thus occur in newly formed tumor vessels and contribute to the microvessel destabilization and antiangiogenic effects of CA-4P observed in vivo.

Pharmacological modulation of epithelial mesenchymal transition caused by angiotensin II. Role of ROCK and MAPK pathways

PURPOSE

Tubulointerstitial fibrosis is a final common pathway to end-stage chronic kidney diseases, which are characterized by elevated renal angiotensin II (AngII) production. This peptide participates in kidney damage inducing fibrosis and epithelial mesenchymal transition (EMT). Our aim was to describe potential therapeutic targets in AngII-induced EMT, investigating the blockade of different intracellular pathways.

METHODS

Studies were done in human tubular epithelial cells (HK2 cell line), evaluating changes in phenotype and EMT markers (Western blot and immunofluorescence).

RESULTS

Treatment of HK2 cells with AngII for 3 days caused transdifferentiation into myofibroblast-like cells. The blockade of MAPKs cascade, using specific inhibitors of p38 (SB203580), extracellular signal-regulated kinase1/2 (ERK; PD98059) and Jun N-terminal kinase (JNK) (SP600125), diminished AngII-induced EMT. The blockade of RhoA/ROCK pathway, by transfection of a RhoA dominant-negative vector or by ROCK inhibition with Y-27632 or fasudil, inhibited EMT caused by AngII. Connective tissue growth factor (CTGF) is a downstream mediator of AngII-induced EMT. MAPKs and ROCK inhibitors blocked CTGF overexpression induced by AngII. HMG-CoA reductase inhibitors, although blocked AngII-mediated kinases activation, only partially diminished EMT and did not regulate CTGF.

CONCLUSIONS

These data suggest a potential therapeutic use of kinase inhibitors in renal fibrosis.

TGF-beta signaling is dynamically regulated during the alveolarization of rodent and human lungs

Although transforming growth factor-beta (TGF-beta) signaling negatively regulates branching morphogenesis in early lung development, few studies to date have addressed the role of this family of growth factors during late lung development. We describe here that the expression, tissue localization, and activity of components of the TGF-beta signaling machinery are dynamically regulated during late lung development in the mouse and human. Pronounced changes in the expression and localization of the TGF-beta receptors Acvrl1, Tgfbr1, Tgfbr2, Tgfbr3, and endoglin, and the intracellular messengers Smad2, Smad3, Smad4, Smad6, and Smad7 were noted as mouse and human lungs progressed through the canalicular, saccular, and alveolar stages of development. TGF-beta signaling, assessed by phosphorylation of Smad2, was detected in the vascular and airway smooth muscle, as well as the alveolar and airway epithelium throughout late lung development. These data suggest that active TGF-beta signaling is required for normal late lung development.

SGK1-dependent upregulation of connective tissue growth factor by angiotensin II

Angiotensin II has previously been shown to trigger fibrosis, an effect involving connective tissue growth factor (CTGF). The signaling pathways linking angiotensin II to CTGF formation are, however, incompletely understood. A gene highly expressed in fibrosing tissue is the serum- and glucocorticoid-inducible kinase SGK1. The present study explored whether SGK1 is transcriptionally regulated by angiotensin II and participates in the angiotensin II-dependent regulation of CTGF expression. To this end, experiments have been performed in human kidney fibroblasts and mouse lung fibroblasts from gene-targeted mice lacking SGK1 (sgk1-/-) and their wild-type littermates (sgk1+/+). In human renal fibroblasts, SGK1 and CTGF protein expression were enhanced by angiotensin II (10 nM) within 4 h. In sgk1+/+ mouse fibroblasts, SGK1 transcript levels were significantly increased after 4 h of angiotensin II treatment. Angiotensin II stimulated both transcript and protein abundance of CTGF in fibroblasts from sgk1+/+ mice, effects significantly blunted in fibroblasts of sgk1-/- mice. In conclusion, angiotensin II stimulates the expression of SGK1, which is in turn required for the stimulating effect of angiotensin II on the expression of CTGF. Thus, SGK1 presumably contributes to the profibrotic effect of angiotensin II.

Inhibitory effect of interleukin-1beta on angiotensin II-induced connective tissue growth factor and type IV collagen production in cultured mesangial cells

Connective tissue growth factor (CTGF) is overexpressed in kidney diseases associated with extracellular matrix accumulation. Angiotensin II (ANG II) participates in renal fibrosis by the upregulation of growth factors, including CTGF, and extracellular matrix proteins, such as type IV collagen. During renal injury, ANG II and the macrophage-produced cytokine interleukin-1beta (IL-1beta) may be present simultaneously in the glomerular environment. However, there are no studies about the interaction between ANG II and IL-1beta in renal fibrosis. For this reason, in cultured mesangial cells (MC), we investigated whether IL-1beta could regulate ANG II-mediated collagen accumulation and the mechanisms underlying this process. In MC, CTGF is a downstream mediator of type IV collagen production induced by ANG II. IL-1beta did not increase the production of CTGF and type IV collagen but significantly inhibited ANG II-induced CTGF and type IV collagen overexpression. Moreover, IL-1beta also inhibited type IV collagen upregulation caused by exogenous recombinant CTGF. Matrix metalloproteinase-9 (MMP-9) is the main enzyme involved in type IV collagen degradation. In MC, coincubation of IL-1beta and ANG II caused a synergistic increase in MMP-9 gene expression and activity, associated with type IV collagen inhibition. The described IL-1beta effects were dependent on activation of ERK/MAPK but independent p38-MAPK, JNK, phosphatidylinositol 3-kinase/Akt, and Rho-associated kinase pathways. In summary, these data indicate that IL-1beta inhibited ANG II-mediated type IV collagen production, via CTGF downregulation, and increased type IV collagen degradation, through MMP-9 upregulation. Our in vitro data show that the proinflammatory cytokine IL-1beta abrogates ANG II-induced CTGF production, describing antagonistic activities of proinflammatory cytokines on ANG II actions.

Bacteria induce CTGF and CYR61 expression in epithelial cells in a lysophosphatidic acid receptor-dependent manner

Cysteine-rich protein 61 (Cyr61/CCN1) and connective tissue growth factor (CTGF/CCN2) are members of the CCN (CYR61, CTGF, nephroblastoma overexpressed gene) family and exert pleiotropic functions such as regulation of adhesion, migration, extracellular matrix deposition, or cell differentiation, and play an important role in wound healing. This study focused on the nature of the so far unknown CTGF and CYR61 mRNA expression of epithelial cells after infection with bacteria. We demonstrate that infection of epithelial cells with attenuated Yersinia enterocolitica lacking the virulence plasmid pYV leads to the expression of CYR61 and CTGF. Virulent Y. enterocolitica bearing the pYV virulence plasmid suppressed the mRNA expression of these genes. Yersinia-mediated inhibition of CTGF and CYR61 mRNA expression is partially mediated by the cysteine protease YopT. Further characterization of the Yersinia factors, which trigger CTGF and CYR61 mRNA expression, demonstrated that these factors were secreted and could be enriched in lipid extracts. Beside Yersinia, several other bacteria such as Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis, or Staphylococcus aureus, as well as supernatants of these bacteria induced CTGF and CYR61 expression. Blocking experiments with the lysophosphatidic acid (LPA) receptor-specific inhibitor Ki16425 suggest a general involvement of LPA receptors in bacteria-triggered CTGF and CYR61 expression. These data suggest that LPA receptor-dependent expression of CTGF and CYR61 represents a common host response after interaction with bacteria.

HMG-CoA Reductase Inhibitors Decrease Angiotensin II–Induced Vascular Fibrosis

3-hydroxy-3-methylglutaryl (HMG)-coenzyme A (CoA) reductase inhibitors (statins) present beneficial effects in cardiovascular diseases. Angiotensin II (Ang II) contributes to cardiovascular damage through the production of profibrotic factors, such as connective tissue growth factor (CTGF). Our aim was to investigate whether HMG-CoA reductase inhibitors could modulate Ang II responses, evaluating CTGF expression and the mechanisms underlying this process. In cultured vascular smooth muscle cells (VSMCs) atorvastatin and simvastatin inhibited Ang II–induced CTGF production. The inhibitory effect of statins on CTGF upregulation was reversed by mevalonate and geranylgeranylpyrophosphate, suggesting that RhoA inhibition could be involved in this process. In VSMCs, statins inhibited Ang II–induced Rho membrane localization and activation. In these cells Ang II regulated CTGF via RhoA/Rho kinase activation, as shown by inhibition of Rho with C3 exoenzyme, RhoA dominant-negative overexpression, and Rho kinase inhibition. Furthermore, activation of p38MAPK and JNK, and redox process were also involved in Ang II–mediated CTGF upregulation, and were downregulated by statins. In rats infused with Ang II (100 ng/kg per minute) for 2 weeks, treatment with atorvastatin (5 mg/kg per day) diminished aortic CTGF and Rho activation without blood pressure modification. Rho kinase inhibition decreased CTGF upregulation in rat aorta, mimicking statin effect. CTGF is a vascular fibrosis mediator. Statins diminished extracellular matrix (ECM) overexpression caused by Ang II in vivo and in vitro. In summary, HMG-CoA reductase inhibitors inhibit several intracellular signaling systems activated by Ang II (RhoA/Rho kinase and MAPK pathways and redox process) involved in the regulation of CTGF. Our results may explain, at least in part, some beneficial effects of statins in cardiovascular diseases.

Angiotensin II type 1 receptor blocker attenuates myocardial remodeling and preserves diastolic function in diabetic heart

Blockade of the renin-angiotensin system reduces cardiovascular morbidity and mortality in diabetic patients. Angiotensin II (Ang II) plays an important role in the structural and functional abnormalities of the diabetic heart. We investigated whether or not Ang II type 1 receptor blocker (ARB) could attenuate left ventricular (LV) remodeling in male mice with diabetes mellitus (DM) induced by the injection of streptozotocin (200 mg/kg, i.p.). Diabetic mice were treated with candesartan (1 mg/kg/day; DM+Candesartan, n=7) or vehicle (DM+Vehicle, n=7) for 8 weeks. Heart rate and aortic blood pressure were comparable between the groups. Normal systolic function was preserved in diabetic mice. In contrast, diastolic function was impaired in DM+Vehicle and was improved in DM+Candesartan, as assessed by the deceleration time of the peak velocity of transmitral diastolic flow (40.3+/-0.3 vs. 37.3+/-0.5 ms, p<0.01) and the time needed for relaxation of 50% maximal LV pressure to baseline value (tau; 10.6+/-0.7 vs. 8.7+/-0.6 ms, p<0.05) without significant changes in heart rate and aortic blood pressure. Improvement of LV diastolic function was accompanied by the attenuation of myocyte hypertrophy, interstitial fibrosis and apoptosis in association with the expression of connective tissue growth factor (CTGF) and myocardial oxidative stress. Moreover, candesartan directly inhibited Ang II-mediated induction of CTGF in cultured cardiac fibroblasts. ARB might be beneficial to prevent cardiac abnormalities in DM.

The up-regulation of angiotensin II receptor type 1 and connective tissue growth factor are involved in high-glucose-induced fibronectin production by cultured human dermal fibroblasts

BACKGROUND

The expansion of extracellular matrix in diabetes occur in many tissues, including skin, but the underlying mechanisms are poorly understood. We were interested to study whether the activation of angiotensin II/receptor type 1 pathway with the consequent involvement of CTGF may be the possible cause of high-glucose-induced matrix abnormalities in cultured dermal fibroblasts.

OBJECTIVE

We aimed to investigate the effect of high glucose on the generation of angiotensin II and the expression of angiotensin II receptors, and on the expression of CTGF mediating the fibronectin production in cultured human dermal fibroblasts.

METHODS

Cell culturing, ELISA, semi-quantitative RT-PCR, Western blotting.

RESULTS

High glucose treatment of cultured dermal fibroblasts led to: (1) the angiotensin II receptor type 1 was up-regulated at the level of mRNA and protein, unlike the receptor type 2; (2) the generation of angiotensin II and the mRNA expression of all components of the local renin-angiotensin system were not altered; (3) the mRNA and protein expression of CTGF was up-regulated, and this effect was cancelled by losartan; (4) the fibronectin production was increased, also was cancelled by losartan, while an anti-CTGF-neutralizing antibody only partly reduced it; (5) TGFbeta1 expression, the secretion of total and active TGFbeta1 were not changed; (6) the hyperosmotic action of high glucose had no effect.

CONCLUSION

The up-regulation of angiotensin II receptor type 1 and the consequent increase of CTGF expression, independently of TGFbeta1, participate in high-glucose-induced fibronectin production in cultured human dermal fibroblasts.

AGT and ACE genes influence classic mitral valve prolapse predisposition in Marfan patients

BACKGROUND

In Marfan syndrome, the mitral valve prolapse, ranging from nonclassic to classic form on the basis of the leaflet thickness, is a common condition characterized by a highly variable structural abnormality. We investigated the role of angiotensinogen (AGT) M235T, angiotensin converting enzyme (ACE) I/D and angiotensin II type 1 receptor (AT1R) A1166C polymorphisms in influencing the susceptibility to classic or non-classic mitral valve prolapse in Marfan patients.

METHODS

We studied 135 Marfan patients with mitral valve prolapse, diagnosed by echocardiography. AGT, ACE, and AT1R polymorphisms were identified by polymerase chain reaction-based restriction analysis.

RESULTS

The frequency of the ACE D, but not AGT 235T and AT1R 1166C allele, was significantly higher in patients with classic mitral valve prolapse in comparison to that observed in the non-classic one (p=0.03). The percentage of subjects with the contemporaneous presence of ACE D and AGT 235T alleles was significantly higher in the classic mitral valve prolapse group in comparison to the non-classic one (79% vs. 55%, respectively; p=0.008). The concomitant presence of these two alleles was associated with increased susceptibility to the classic mitral valve prolapse (OR 3.02, p=0.016).

CONCLUSIONS

Our findings show a possible role of ACE and AGT genes as predisposing factors to classic mitral valve prolapse in Marfan patients, thus suggesting a role of renin angiotensin system genes in modulating mitral valve abnormality, and the need for an interventional study with angiotensin II type 1 receptor antagonists, which considers the leaflet thickness progression in Marfan patients with MVP.

High glucose upregulates connective tissue growth factor expression in human vascular smooth muscle cells

Background

Connective tissue growth factor (CTGF) is a potent profibrotic factor, which is implicated in fibroblast proliferation, angiogenesis and extracellular matrix (ECM) synthesis. It is a downstream mediator of some of the effects of transforming growth factor β (TGFβ) and is potentially induced by hyperglycemia in human renal mesangial cells. However, whether high glucose could induce the CTGF expression in vascular smooth muscle cells (VSMCs) remains unknown. Therefore, this study was designed to test whether high glucose could regulate CTGF expression in human VSMC. The effect of modulating CTGF expression on VSMC proliferation and migration was further investigated.

Results

Expression of CTGF mRNA was up-regulated as early as 6 hours in cultured human VSMCs after exposed to high glucose condition, followed by ECM components (collagen type I and fibronectin) accumulation. The upregulation of CTGF mRNA appears to be TGFβ-dependent since anti-TGFβ antibody blocks the effect of high glucose on CTGF gene expression. A small interference RNA (siRNA) targeting CTGF mRNA (CTGF-siRNA) effectively suppressed CTGF up-regulation stimulated by high glucose up to 79% inhibition. As a consequence of decreased expression of CTGF gene, the deposition of ECM proteins in the VSMC was also declined. Moreover, CTGF-siRNA expressing vector partially inhibited the high glucose-induced VSMC proliferation and migration.

Conclusion

Our data suggest that in the development of macrovascular complications in diabetes, CTGF might be an important factor involved in the patho-physiological responses to high glucose in human VSMCs. In addition, the modulatory effects of CTGF-siRNA during this process suggest that specific targeting CTGF by RNA interference could be useful in preventing intimal hyperplasia in diabetic macrovascular complications.

Renal injury due to renin-angiotensin-aldosterone system activation of the transforming growth factor-beta pathway

Glomerulosclerosis, interstitial fibrosis, and tubular atrophy occur with end-stage kidney failure, irrespective of the primary etiology. The transforming growth factor-beta (TGF-beta) is a key factor in these alterations either directly, by stimulating synthesis of extracellular matrix components and reducing collagenase production, or indirectly through other profibrogenic factors such as connective tissue growth factor (CTGF). TGF-beta is important for the proliferation of intrarenal fibroblasts and the epithelial-mesenchymal transition through which tubular cells become fibroblasts. Although several factors induce TGF-beta expression in the kidney, one very interesting aspect is the link between the renin-angiotensin-aldosterone (Aldo) system (RAAS) and TGF-beta. Angiotensin II (ANG II) stimulates TGF-beta expression in the kidney by various mechanisms and upregulates receptors for TGF-beta. ANG II can directly phosphorylate Smads without inducing TGF-beta. Recent data provide compelling evidence that other components of the RAAS including ANG III, renin, and Aldo also activate the TGF-beta system. As direct modulation of the TGF-beta system is not yet feasible in humans, angiotensin-converting enzyme (ACE) inhibitors and angiotensin type 1 (AT1)-receptor blockers are currently the most potential drugs to interfere with this ANG II-mediated TGF-beta expression. This review highlights some current aspects of the interaction between the RAAS and the TGF-beta axis.

Modulation by bradykinin of angiotensin type 1 receptor-evoked RhoA activation of connective tissue growth factor expression in human lung fibroblasts

The mechanisms regulating the opposing physiological actions of bradykinin (BK) and angiotensin II (AngII) are not well understood. Here we investigate signaling interactions between these two effectors. Connective tissue growth factor (CTGF) expression in IMR-90, human lung fibroblasts, is used as the endpoint target. In these cells the BK B2 receptor (BKB2R) is expressed constitutively, while no binding of AngII is detected. An inducible expression system is used to insert AngII receptor 1 (AT1R) and to obtain a signal level in response to AngII at the magnitude of BK. AngII and BK activate G protein-coupled targets, arachidonate release from cellular phospholipid stores, and intracellular phosphatidylinositol turnover equally. Both activate ERK, JNK, and p38 equally. However, AngII activates, whereas BK inactivates, RhoA. AngII induces a rapid (1 h) CTGF mRNA expression. RhoA siRNA and RhoA activation inhibitor, Y-27632, markedly reduce the AngII effect. Simultaneous treatment with BK and AngII attenuates the AT1R action. Additionally, BK in the absence of AngII lowers CTGF mRNA expression below basal levels over a span of 4 h. An AT1R/BKB2R chimera lacking heterotrimeric G protein coupling continues to activate MAP kinases to the same extent as wild-type (WT) AT1R and BKB2R. However, the increase of CTGF mRNA expression by this mutant is low, almost identical with that obtained by the simultaneous treatment of the WT AT1R-expressing cells with BK and AngII. In this context the chimeric receptor displays the characteristics of both receptors. These data demonstrate that, in human lung fibroblasts, BK modulates the action of AngII through the small G protein RhoA, but in a Galphai/Galphaq-independent manner.

Microarray and phosphokinase screenings leading to studies on ERK and JNK regulation of connective tissue growth factor expression by angiotensin II 1a and bradykinin B2 receptors in Rat1 fibroblasts

Rat1 fibroblasts stably transfected with the rat angiotensin II (AngII) AT1a and bradykinin (BK) B2 receptor cDNAs gained the ability to bind Ang II and BK. Wild-type Rat1 cells bound neither ligand. Exposure to either effector led to characteristic Galphai and Galphaq signal cascades, the release of arachidonic acid (ARA), and the intracellular accumulation of inositol phosphates (IP). Microarray analyses in response to BK or AngII showed that both receptors markedly induce the CCN family genes, CTGF (CCN2) and Cyr61 (CCN1), as well as the vasculature-related genes, Cnn1 and Egr1. Real time PCR confirmed the increased expression of connective tissue growth factor (CTGF) mRNA. Combined sequence-based analysis of gene promoter regions with statistical prevalence analyses identified CREB, SRF, and ATF-1, downstream targets of ERK, and JNK, as prominent products of genes that are regulated by ligand binding to the BK or AngII receptors. The binding of AngII or BK markedly stimulated the phosphorylation and thus the activation of ERK2, JNK, and p38MAPK. A BKB2R and an AT1aR chimera which displayed only negligible G-protein-related signaling were constructed. Both mutant receptors continued to activate these kinases and stimulate CTGF expression. Inhibitors of ERK1/2 and JNK but not p38MAPK inhibited the BK- and AngII-stimulated expression of CTGF in cells expressing either the WT or mutant receptors, illustrating that ERK and JNK participate in the control of CTGF expression in a manner that appears to be independent of G-protein. Conversely, addition of BK or AngII to the cell line expressing WT AT1aR and BKB2R downregulated the expression of collagen alpha1(I) (COL1A1) mRNA. However, these effectors did not have this effect in cells expressing the mutant receptors. Thus, a robust G-protein related response is necessary for BK or AngII to affect COL1A1 expression.

Mechanical regulation of the Cyr61/CCN1 and CTGF/CCN2 proteins

Cells in various anatomical locations are constantly exposed to mechanical forces from shear, tensile and compressional forces. These forces are significantly exaggerated in a number of pathological conditions arising from various etiologies e.g., hypertension, obstruction and hemodynamic overload. Increasingly persuasive evidence suggests that altered mechanical signals induce local production of soluble factors that interfere with the physiologic properties of tissues and compromise normal functioning of organ systems. Two immediate early gene-encoded members of the family of the Cyr61/CTGF/Nov proteins referred to as cysteine-rich protein 61 (Cyr61/CCN1) and connective tissue growth factor (CTGF/CCN2), are highly expressed in several mechanical stress-related pathologies, which result from either increased externally applied or internally generated forces by the actin cytoskeleton. Both Cyr61 and CTGF are structurally related but functionally distinct multimodular proteins that are expressed in many organs and tissues only during specific developmental or pathological events. In vitro assessment of their biological activities revealed that Cyr61 expression induces a genetic reprogramming of angiogenic, adhesive and structural proteins while CTGF promotes distinctively extracellular matrix accumulation (i.e., type I collagen) which is the principal hallmark of fibrotic diseases. At the molecular level, expression of the Cyr61 and CTGF genes is regulated by alteration of cytoskeletal actin dynamics orchestrated by various components of the signaling machinery, i.e., small Rho GTPases, mitogen-activated protein kinases, and actin binding proteins. This review discusses the mechanical regulation of the Cyr61 and CTGF in various tissues and cell culture models with a special attention to the cytoskeletally based mechanisms involved in such regulation.

STAT3-independent inhibition of lysophosphatidic acid-mediated upregulation of connective tissue growth factor (CTGF) by cucurbitacin I

Cucurbitacins are recognised as anti-tumour agents because of their interference with STAT3 signalling, but may also affect the integrity of the actin cytoskeleton. In the present study the effect of cucurbitacin I was investigated in fibroblasts. In these cells, cucurbitacin I interfered with lysophosphatidic acid (LPA) signalling. It inhibited tyrosine phosphorylation of focal adhesion proteins and induction of connective tissue growth factor (CTGF), a potent profibrotic protein. Inhibition of Src family kinases with PP2, but not the inactive analogue PP3, also interfered with LPA-mediated tyrosine phosphorylation and induction of CTGF. Jak2-STAT3 signalling seemed to be the connecting link, because CTGF induction was sensitive to AG490, an inhibitor of Jak2, and cucurbitacin I, an inhibitor of Jak2 and STAT3. However, LPA did not activate tyrosine phosphorylation of STAT3. Furthermore, cucurbitacin I was as effective in STAT3 knock out cells as in control cells. Therefore, the inhibitory effect of cucurbitacin I was not related to inhibition of STAT3. Immunocytochemical analysis of cucurbitacin I-treated cells revealed disassembly of F-actin fibres, reorganisation into F-actin patches and resolution of focal adhesions. The phenotypic changes resembled changes observed after treatment of the cells with cytochalasin D, which has been shown to interfere with CTGF induction. Concentrations of cucurbitacin I, which have been shown to target Jak2-STAT3 signalling, thus, profoundly affect the actin cytoskeleton and may therefore modulate cell morphology, migration, adherence and gene expression also in non-tumour cells.

Lipoic acid supplementation prevents cyclosporine-induced hypertension and nephrotoxicity in spontaneously hypertensive rats

BACKGROUND

Cyclosporine (CsA) has significantly improved long-term survival after organ transplantations. Hypertension and nephrotoxicity are common side effects during CsA treatment and are aggravated by high salt intake.

OBJECTIVE

To examine whether lipoic acid (LA), a natural antioxidant that scavenges reactive oxygen species and regenerates/recycles endogenous antioxidants, could prevent CsA-induced hypertension and nephrotoxicity.

METHODS

Six-week-old spontaneously hypertensive rats (SHR) on a high-sodium diet (NaCl 6%) received CsA [5 mg/kg subcutaneously (s.c.)] alone or in combination with LA (0.5% w/w) for 6 weeks. Blood pressure, arterial functions, and tissue morphology were determined. Immunohistochemistry, quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and high-pressure liquid chromatography were used for kidney and heart samples.

RESULTS

CsA induced severe hypertension, cardiac hypertrophy, endothelial dysfunction, and pronounced albuminuria. Histologically, the kidneys showed severe thickening of the media of the afferent arteries with fibrinoid necrosis, perivascular monocyte/macrophage infiltration and nitrotyrosine overexpression. CsA induced the expression of fibrogenic connective tissue growth factor both in the heart and kidneys. The detrimental effects of CsA were associated with upregulation of myocardial atrial natriuretic peptide (ANP) mRNA expression, paradoxical activation of the renin-angiotensin system (RAS), induction of renal reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase, and overexpression of oxidative stress-induced transcription factor NRF2. LA lowered blood pressure, ameliorated cardiac hypertrophy and endothelial dysfunction, and totally normalized albuminuria. In LA-treated rats, renal and cardiac morphologies were indistinguishable from those of SHR controls. CsA-induced myocardial ANP and connective tissue growth factor (CTGF) mRNA overexpression, RAS activation, NADPH oxidase induction, and NRF2 overexpression were prevented by LA. LA induced the mRNA expression of gamma-glutamylcysteine ligase, the rate-limiting enzyme in glutathione synthesis, and markedly increased hepatic cysteine and glutathione concentrations.

CONCLUSIONS

Our findings suggest a salutary role for lipoic acid supplementation in the prevention of CsA-induced hypertension and nephrotoxicity, and underscore the importance of increased oxidative stress in the pathogenesis of CsA toxicity.

Contribution of Src-FAK signaling to the induction of connective tissue growth factor in renal fibroblasts

Expression of connective tissue growth factor (CTGF) is sensitive to reorganization of the actin cytoskeleton, but also to alterations in cell morphology due to extracellular forces, for example, cyclic stretching or mechanical loading. Dynamic alterations of focal adhesion proteins were thus proposed to modulate CTGF induction. Immortalized human renal fibroblasts were cultured in or on top of preformed collagen-1 gels. Proteins were detected by immunofluorescence and quantified by Western blotting. Fibroblasts cultured in/on collagen gels resembled cells in vivo by their spindle-like morphology, absence of actin stress fibers, small punctiform focal contacts, and low levels of CTGF expression. Disassembly of microtubules by short-term treatment with colchicine induced cell rounding, cortical recruitment of patchy F-actin, reorganization of focal contacts into strong clusters, and upregulation of CTGF, all of which were dependent on RhoA-Rho-kinase signaling. Clustering of focal adhesion sites activated Src-family kinases and focal adhesion kinase (FAK). Interference with Src activity by PP2 had no effect on the morphological alterations but decreased tyrosine phosphorylation of focal adhesion proteins and almost completely prevented upregulation of CTGF. Furthermore, inhibition of phosphatidylinositol 3-kinase reduced CTGF expression. On the other hand, when the fibroblasts were cultured on a rigid matrix, that is collagen-coated plates, strong focal complexes prevented the dynamic alterations, and RhoA-mediated upregulation of CTGF expression was independent of Src-FAK signaling. Assembly of focal adhesion proteins regulates CTGF expression, providing a link between actin network, adhesion receptors, and CTGF-mediated functions such as synthesis of extracellular matrix proteins.

Differential involvement of the integrin-linked kinase (ILK) in RhoA-dependent rearrangement of F-actin fibers and induction of connective tissue growth factor (CTGF)

The integrin-linked kinase (ILK) serves as an adapter protein to link the cytoplasmic domains of integrins with cytoskeletal components. Organization of the actin cytoskeleton is strongly influenced by the small GTPase RhoA, which also regulates gene expression. To investigate the impact of ILK deficiency on RhoA-mediated signaling we used ILK-deficient fibroblasts. The cytoskeleton of ILK (-/-) cells was characterized by less organized F-actin fibers, compared to wild type mouse fibroblasts. Stimulation of the cells with lysophosphatidic acid (LPA) or the microtubule disrupting agent colchicine increased polymerization of F-actin stress fibers in ILK (+/+) cells, whereas ILK (-/-) cells showed a network of short thin cortical actin fibers, cell rounding and finally detachment from the surface of the culture plates. The structural changes were primarily attributable to the activation of RhoA in both cell types. ILK deficiency also affected gene expression. The basal levels of several proteins related to fibroblast differentiation, such as connective tissue growth factor (CTGF), thrombospondin 1 and alpha smooth muscle actin, were reduced in ILK (-/-) cells. However, induction of CTGF expression by LPA or colchicine was comparable in ILK (+/+) and ILK (-/-) cells. Furthermore, stimulation of CTGF or thrombospondin by TGFbeta was not reduced by ILK deficiency. Inhibition of the RhoA-associated kinase or overexpression of dominant negative RhoA reduced the stimulated CTGF expression indicative of a role for RhoA signaling in CTGF expression. Taken together, ILK is involved in RhoA-dependent reorganization of the actin cytoskeleton, whereas activation of RhoA and RhoA-mediated gene expression is independent of ILK.

Advanced glycation end-product-induced mitogenesis and collagen production are dependent on angiotensin II and connective tissue growth factor in NRK-49F cells

Diabetic nephropathy (DN) is characterized by glomerulopathy and tubulointerstitial expansion followed by renal fibrosis. Angiotensin II (Ang II) and connective tissue growth factor (CTGF) are involved in the pathogenesis of DN, while Janus kinase 2 (JAK2) is important in advanced glycation end-product (AGE)-induced effects in renal interstitial (NRK-49F) fibroblasts. Thus, we studied the role of Ang II, CTGF, and JAK2 in AGE-induced effects in NRK-49F cells. We found that AGE (150 microg/ml) increased mitogenesis and type I collagen production at 7 days while Ang II (10(-7)M) increased mitogenesis and type I collagen production at 3 days. We also found that AGE (150 microg/ml) increased angiotensinogen protein at 2 days, which was attenuated by AG-490 (a JAK2 inhibitor). AGE (150 microg/ml) increased CTGF mRNA and protein expression at 3 and 5 days, respectively. Ang II (10(-7)M) increased CTGF mRNA and protein expression at 1 and 2 days, respectively, which were attenuated by AG-490. Moreover, losartan (a type I angiotensin receptor blocker) and captopril (an angiotensin converting enzyme inhibitor) attenuated AGE-induced CTGF mRNA/protein expression while attenuating AGE-induced mitogenesis and type I collagen production. AG-490 and CTGF antisense (but not sense) oligodeoxynucleotide (ODN) attenuated Ang II (10(-7)M) and AGE-induced mitogenesis and type I collagen production at 3 and 7 days, respectively. We concluded that AGE (150 microg/ml)-induced mitogenesis and type I collagen production are dependent on the Ang II-JAK2-CTGF pathway in NRK-49F cells. Moreover, Ang II-induced mitogenesis and type I collagen production are dependent on the JAK2-CTGF pathway.

Decreased perivascular fibrosis but not cardiac hypertrophy in ROCK1+/- haploinsufficient mice

BACKGROUND

Rho GTPase and its downstream target, Rho-associated kinase (ROCK), have been implicated in diverse cardiovascular diseases such as cardiac hypertrophy. However, pharmacological inhibitors of ROCK are not entirely specific, nor can they discriminate between the ROCK isoforms ROCK1 and ROCK2. To determine the specific role of ROCK1 in the development of cardiac hypertrophy, we generated ROCK1(+/-) haploinsufficient mice and determined whether cardiac hypertrophy and remodeling are decreased in these mice.

METHODS AND RESULTS

Litters of ROCK1(-/-) mice on C57Bl/6 background were markedly underrepresented, suggesting lethality in utero or postnatally. ROCK1(+/-) mice, however, are viable and fertile with no obvious phenotypic abnormalities. Basal blood pressure, heart rate, and cardiac dimension and function in ROCK1(+/-) mice were similar to those in wild-type (WT) littermates. Infusion of angiotensin II (400 ng.kg(-1).min(-1) for 28 days) or treatment with NG-nitro-L-arginine methyl ester (1 mg/mL in drinking water for 28 days) caused similar increases in systolic blood pressure, left ventricular wall thickness, left ventricular mass, ratio of heart weight to tibial length, and cardiomyocyte size in ROCK1(+/-) mice and WT littermates. In contrast, perivascular fibrosis in hearts was increased to a lesser extent in ROCK1(+/-) mice compared with WT littermates. This was associated with decreased expression of transforming growth factor-beta, connective tissue growth factor, and type III collagen. In addition, perivascular fibrosis induced by transaortic constriction or myocardial infarction was decreased in ROCK1(+/-) mice compared with WT littermates.

CONCLUSIONS

These findings indicate ROCK1 is critical for the development of cardiac fibrosis, but not hypertrophy, in response to various pathological conditions and suggest that signaling pathways leading to the hypertrophic and profibrotic response of the heart are distinct.

Inhibition of Rho-kinase by fasudil attenuated angiotensin II-induced cardiac hypertrophy in apolipoprotein E deficient mice

Recent evidence indicates that the GTPase activated Rho/Rho-kinase pathway contributes angiotensin II-induced cardiac hypertrophy and vascular remodeling. We tested this hypothesis in vivo by determining the effects of fasudil, a Rho-kinase inhibitor, on angiotensin II-induced cardiac hypertrophy, coronary vascular remodeling, and ventricular dysfunction. Six-month-old apolipoprotein E deficient (apoE-KO) mice were subcutaneously infused with angiotensin II (1.44 mg/kg/day) using an osmotic mini-pump. Mice were randomly assigned to either vehicle or fasudil (136 or 213 mg/kg/day in drinking water) group. Infusion of angiotensin II for 4 weeks resulted in cardiac enlargement, myocyte hypertrophy, and myocardial interstitial and coronary artery perivascular fibrosis. These changes were accompanied by reduced aortic flow velocity and acceleration rate. Cardiac gene expression levels of atrial natriuretic peptide (ANP) and collagen type III detected by real-time reverse transcriptase polymerase chain reaction were significantly increased in angiotensin II-infused mice. Treatment with fasudil dose-dependently attenuated angiotensin II-induced cardiac hypertrophy, prevented perivascular fibrosis, blunted the increase in ANP and collagen type III expression, and improved cardiac function, without changing blood pressure. These data are consistent with a role for Rho-kinase activation in angiotensin II-induced cardiac remodeling and vascular wall fibrosis.

Differential regulation of angiotensin II-induced expression of connective tissue growth factor by protein kinase C isoforms in the myocardium

Protein kinase C (PKC) and angiotensin II (AngII) can regulate cardiac function in pathological conditions such as in diabetes or ischemic heart disease. We have reported that expression of connective tissue growth factor (CTGF) is increased in the myocardium of diabetic mice. Now we showed that the increase in CTGF expression in cardiac tissues of streptozotocin-induced diabetic rats was reversed by captopril and islet cell transplantation. Infusion of AngII in rats increased CTGF mRNA expression by 15-fold, which was completely inhibited by co-infusion with AT1 receptor antagonist, candesartan. Similarly, incubation of cultured cardiomyocytes with AngII increased CTGF mRNA expression by 2-fold, which was blocked by candesartan and a general PKC inhibitor, GF109203X. The role of PKC isoform-dependent action was further studied using adenoviral vector-mediated gene transfer of dominant negative (dn) PKC or wild type PKC isoforms. Expression of dnPKCalpha, -epsilon, and -zeta isoforms suppressed AngII-induced CTGF expression in cardiomyocytes. In contrast, expression of dominant negative PKCdelta significantly increased AngII-induced CTGF expression, whereas expression of wild type PKCdelta inhibited this induction. This inhibitory effect was further confirmed in the myocardium of transgenic mice with cardiomyocyte-specific overexpression of PKCdelta (deltaTg mice). Thus, AngII can regulate CTGF expression in cardiomyocytes through a PKC activation-mediated pathway in an isoform-selective manner both in physiological and diabetic states and may contribute to the development of cardiac fibrosis in diabetic cardiomyopathy.

Magnesium supplementation prevents angiotensin II-induced myocardial damage and CTGF overexpression

OBJECTIVES AND DESIGN

Magnesium deficiency promotes vasoconstriction and myocardial damage. Recent studies provide evidence that Ang II mobilizes intracellular Mg through AT1 receptor-mediated pathways. We tested the hypothesis of whether magnesium supplementation prevents Ang II-induced myocardial damage and induction of the profibrotic connective tissue growth factor (CTGF).

METHODS

Four-week-old double transgenic rats harboring human renin and angiotensinogen genes (dTGR) were given dietary magnesium supplementation (0.6%) for 3 weeks. Control dTGR and normotensive Sprague-Dawley (SD) rats received normal diet (Mg 0.2%). Histopathological, immunohistochemical and mRNA analysis were used to detect the treatment-related effects of dietary magnesium in dTGR.

RESULTS

Magnesium (Mg) supplementation decreased blood pressure, ameliorated cardiac hypertrophy, protected against the development of Ang II-induced myocardial damage and increased serum ionized Mg2+ concentration (all variables P < 0.05). There was no difference in serum ionized Mg2+ concentration between dTGR and SD rats. Myocardial connective tissue growth factor (CTGF) mRNA and protein expressions were increased by 300% in dTGR (P < 0.05), especially in areas with myocardial infarctions and vascular inflammation. Magnesium supplementation prevented Ang II-induced myocardial CTGF overexpression (P < 0.05). Magnesium supplementation also improved the therapeutic effects of the calcineurin inhibitor tacrolimus, which produced marked hypomagnesemia when given as monotherapy.

CONCLUSION

Our findings suggest a salutary effect for magnesium supplementation in the treatment of Ang II-induced myocardial complications.