Angiotensin II upregulates transforming growth factor-beta type I receptor on rat vascular smooth muscle cells

Fibrillin-1 mutation contributes to Marfan syndrome by inhibiting Cav1.2-mediated cell proliferation in vascular smooth muscle cells

Marfan syndrome (MFS) is an autosomal dominant connective tissue disorder caused by mutation in fibrillin-1 (FBN1). However, the molecular mechanism underlying MFS remains poorly understood. The study aimed to explore how the L-type calcium channel (Ca_V1.2) modulates disease progression of MFS and to identify a potential effective target for attenuating MFS. KEGG enrichment analysis showed that the calcium signaling pathway gene set was significantly enriched. We demonstrated that FBN1 deficiency exhibited inhibition on both the expression of Cav1.2 and proliferation of vascular smooth muscle cells (VSMCs). Then, we examined whether FBN1 mediates Cav1.2 via regulating TGF-β1. Higher levels of TGF-β1 were observed in the serum and aortic tissues from patients with MFS. TGF-β1 modulated Cav1.2 expression in a concentration-dependent manner. We evaluated the role of Cav1.2 in MFS by small interfering RNA and Cav1.2 agonist Bay K8644. The effect of Cav1.2 on cell proliferation was dependent on c-Fos activity. These results demonstrated FBN1 deficiency decreased the expression levels of Cav1.2 via regulation of TGF-β1, and downregulation of Cav1.2 inhibited cell proliferation of human aortic smooth muscle cells (HASMCs) in MFS patients. These findings suggest that Cav1.2 may be an appealing therapeutic target for MFS.

Pharmacotherapeutic Approaches to Treatment of Muscular Dystrophies

Muscular dystrophies are a heterogeneous group of genetic muscle-wasting disorders that are subdivided based on the region of the body impacted by muscle weakness as well as the functional activity of the underlying genetic mutations. A common feature of the pathophysiology of muscular dystrophies is chronic inflammation associated with the replacement of muscle mass with fibrotic scarring. With the progression of these disorders, many patients suffer cardiomyopathies with fibrosis of the cardiac tissue. Anti-inflammatory glucocorticoids represent the standard of care for Duchenne muscular dystrophy, the most common muscular dystrophy worldwide; however, long-term exposure to glucocorticoids results in highly adverse side effects, limiting their use. Thus, it is important to develop new pharmacotherapeutic approaches to limit inflammation and fibrosis to reduce muscle damage and promote repair. Here, we examine the pathophysiology, genetic background, and emerging therapeutic strategies for muscular dystrophies.

Angiotensin receptor blockade and stereotactic body radiation therapy for early stage lung cancer ARB & SBRT for early stage lung cancer

Stereotactic body radiotherapy (SBRT) demonstrates excellent local control in early stage lung cancer, however a quarter of patients develop recurrence or distant metastasis. Transforming growth factor-beta (TGF-β) supports metastasis and treatment resistance, and angiotensin receptor blockade (ARB) indirectly suppresses TGF-β signaling. This study investigates whether patients taking ARBs while undergoing SBRT for early stage lung cancer exhibited improved overall survival (OS) or recurrence free survival (RFS) compared to patients not taking ARBs. This was a single institution retrospective analysis of 272 patients treated with SBRT for early stage lung cancer between 2009 and 2018. Patient health data was abstracted from the electronic medical record. OS and RFS were assessed using Kaplan-Meier method. Log-rank test was used to compare unadjusted survival between groups. Univariable and multivariable Cox proportional hazard regression models were used to estimate hazard ratios (HRs). Of 247 patients analyzed, 24 (10%) patients took ARBs for the duration of radiotherapy. There was no difference in mean age, median tumor diameter, or median biologic effective dose between patients taking ARBs or not. Patients taking ARBs exhibited increased OS (ARB = 96.7 mo.; no ARB = 43.3 mo.; HR = 0.25 [95% CI: 0.10 to 0.62, P = .003]) and increased RFS (median RFS, ARB = 64.3 mo.; No ARB = 35.1 mo.; HR = 0.26 [95% CI: 0.10 to 0.63, P = .003]). These effects were not seen in patients taking angiotensin converting enzyme inhibitors (ACEIs) or statins. ARB use while undergoing SBRT for early stage lung cancer may increase OS and RFS, but ACEI use does not show the same effect.

Marfan Syndrome and Autosomal Dominant Polycystic Kidney Disease: A Case of Rare Co-occurrence or Coincidence?

Background: Marfan syndrome (MFS) and autosomal dominant kidney disease (ADPKD) are two separate genetic disorders. The author describes the case of a young male with ADPKD who incidentally had Marfan-like features. A literature review was carried out to see if these two disorders could be linked. Case presentation: A young male presented for incidentally found renal cysts. Kidney function was well preserved, but the patient had positive family history of ADPKD. During routine follow-up, a history of aortic valve disease was mentioned. This, along with the patient’s tall, lean stature and long extremities raised the concern for MFS. A detailed physical examination and workup by other specialists confirmed a clinical diagnosis of MFS. They had no known family history of MFS. The patient has been followed at Associates in Kidney Care, Des Moines, Iowa, USA, for the past 2 years. Discussion: There are several reports of overlap of ADPKD and connective tissue disorders with an overlap of vascular disorders. ADPKD and MFS are caused by totally different mutations. However, the literature review showed that vascular abnormalities and connective tissue diseases may be more common with ADPKD. Studies have shown that there could be a common signalling pathway for connective tissue disorders when both genes are affected simultaneously. Further research is needed to identify these pathways. More frequent screening of vascular abnormalities might be warranted in those with both phenotypes.

Connective Tissue Disorders and Cardiovascular Complications: The Indomitable Role of Transforming Growth Factor-β Signaling

Marfan Syndrome (MFS) and Loeys-Dietz Syndrome (LDS) represent heritable connective tissue disorders that segregate with a similar pattern of cardiovascular defects (thoracic aortic aneurysm, mitral valve prolapse/regurgitation, and aortic dilatation with regurgitation). This pattern of cardiovascular defects appears to be expressed along a spectrum of severity in many heritable connective tissue disorders and raises suspicion of a relationship between the normal development of connective tissues and the cardiovascular system. With overwhelming evidence of the involvement of aberrant Transforming Growth Factor-beta (TGF-β) signaling in MFS and LDS, this signaling pathway may represent the common link in the relationship between connective tissue disorders and their associated cardiovascular complications. To further explore this hypothetical link, this chapter will review the TGF-β signaling pathway, the heritable connective tissue syndromes related to aberrant TGF-β signaling, and will discuss the pathogenic contribution of TGF-β to these syndromes with a primary focus on the cardiovascular system.

Pathophysiology and Pathogenesis of Marfan Syndrome

Marfan syndrome (MFS) is a systemic connective tissue disorder that is inherited in an autosomal dominant pattern with variable penetrance. While clinically this disease manifests in many different ways, the most life-threatening manifestations are related to cardiovascular complications including mitral valve prolapse, aortic insufficiency, dilatation of the aortic root, and aortic dissection. In the past 30 years, research efforts have not only identified the genetic locus responsible but have begun to elucidate the molecular pathogenesis underlying this disorder, allowing for the development of seemingly rational therapeutic strategies for treating affected individuals. In spite of these advancements, the cardiovascular complications still remain as the most life-threatening clinical manifestations. The present chapter will focus on the pathophysiology and clinical treatment of Marfan syndrome, providing an updated overview of the recent advancements in molecular genetics research and clinical trials, with an emphasis on how this information can focus future efforts toward finding betters ways to detect, diagnose, and treat this devastating condition.

Losartan prevents bladder fibrosis and protects renal function in rat with neurogenic paralysis bladder

AIMS

To investigate the effect of losartan on preventing bladder fibrosis and protecting renal function in rats with neurogenic paralysis bladder (NPB).

MATERIALS AND METHODS

Rats were assigned to the transecting spinal nerves group (TSNG), transecting spinal nerves + losartan group (LSTG), and control group (CG). On Day 32 postsurgery, bladder capacity (BC), bladder compliance (ΔC), bladder leakage pressure (P_ves.leak ) of TSNG and LSTG while BC, ΔC, and bladder threshold pressure (P_ves.thre ) of CG were measured by cystometry in each cohort. Renal function and the expression quantity of Angiotensin Ⅱ (Ang II) in blood were detected, in addition Ang II, Ang II Type 1 receptor (AT1), transformation growth factor β1 (TGFβ1), Collagen Ⅲ, and collagen fibrin in the bladder tissue were detected too.

RESULTS

ΔC in TSNG and LSTG decreased significantly compared to the CG. P_ves.leak in TSNG and LSTG were significantly higher than P_ves.thre in CG. Renal function of both TSNG and LSTG decreased significantly compared with the CG, but renal function in LSTG was better than in TSNG. Ang Ⅱ in blood and bladder tissue in TSNG and LSTG increased significantly compared with CG. AT1 was expressed in the bladder tissue of all rats. The TGFβ1, Collagen Ⅲ, and collagen fibrin expression level increased significantly in TSNG compared with LSTG and CG, while these levels were not significantly different between CG and LSTG.

CONCLUSION

Losartan might prevent NPB fibrosis by stopping the upregulated signaling of Ang II/AT1/TGFβ1 and consequently may reduce kidney damage from occurring.

Anti-hyperglycaemic effects of dioxidovanadium complex cis-[VO2(obz)py] avert kidney dysfunction in streptozotocin-induced diabetic male Sprague-Dawley rats

Despite the success of antidiabetic drugs in alleviation of hyperglycaemia, diabetic complications, including renal dysfunction, continue to be a burden. This raises the need to seek alternative therapies that will alleviate these complications. Accordingly, the aim of this study was to investigate the effects of dioxidovanadium(V) complex cis-[VO2(obz)py] on renal function in diabetic rats. Streptozotocin-induced diabetic rats were treated with cis-[VO2(obz)py] (40 mg·kg-1) twice every third day for five weeks. Diabetic untreated and insulin-treated rats served as the diabetic control and positive control, respectively. Blood glucose concentrations, water intake, urinary output, and mean arterial pressure (MAP) were monitored weekly for five weeks. Rats were then euthanized, and blood and kidney tissues were collected for biochemical analysis. Significant decreases in blood glucose concentrations, MAP, glomerular filtration rate (GFR), and SGLT2 expression, as well as plasma angiotensin and aldosterone concentrations, were observed in the treated groups compared with the diabetic control. The complex also increased urinary glucose concentrations, antioxidant enzymes GPx and SOD concentrations, and decreased MDA concentrations and kidney injury molecule (KIM-1) concentrations. These findings suggest that the anti-hyperglycaemic effects of this vanadium complex may ameliorate kidney dysfunction in diabetes.

Myofibroblasts and Fibrosis: Mitochondrial and Metabolic Control of Cellular Differentiation

Cardiac fibrosis is mediated by the activation of resident cardiac fibroblasts, which differentiate into myofibroblasts in response to injury or stress. Although myofibroblast formation is a physiological response to acute injury, such as myocardial infarction, myofibroblast persistence, as occurs in heart failure, contributes to maladaptive remodeling and progressive functional decline. Although traditional pathways of activation, such as TGFβ (transforming growth factor β) and AngII (angiotensin II), have been well characterized, less understood are the alterations in mitochondrial function and cellular metabolism that are necessary to initiate and sustain myofibroblast formation and function. In this review, we highlight recent reports detailing the mitochondrial and metabolic mechanisms that contribute to myofibroblast differentiation, persistence, and function with the hope of identifying novel therapeutic targets to treat, and potentially reverse, tissue organ fibrosis.

Ochratoxin A induces epithelial-to-mesenchymal transition and renal fibrosis through TGF-β/Smad2/3 and Wnt1/β-catenin signaling pathways in vitro and in vivo

Ochratoxin A (OTA) is a toxin produced by fungi such as Aspergillus spp. and Penicillium spp. The key target organ of OTA toxicity is the kidney, and it is known that epithelial-to-mesenchymal transition (EMT) leading to fibrosis is enhanced after long-term exposure of the kidney to OTA. However, the mechanisms responsible for this onset are not precisely known. Therefore, the purpose of this study was to investigate the mechanism of OTA-induced EMT and fibrosis in human proximal tubule HK-2 cells and mouse kidneys. Cells were treated for 48 h with various concentrations of OTA (50, 100, and 200 nM) and mice underwent oral administration of various doses of OTA (200 and 1000 μg/kg body weight) for 12 weeks. Blood urea nitrogen and creatinine levels were increased in the serum of OTA-treated mice, and fibrosis was observed in kidney tissues. Furthermore, alpha-smooth muscle actin (α-SMA) and fibronectin levels were increased, and E-cadherin level was decreased by OTA in both HK-2 cells and kidney tissues. In addition, the expression levels of TGF-β, smad2/3, and β-catenin were increased after OTA treatment. α-SMA, E-cadherin, and fibronectin were shown to be regulated by the activation of transcription factors, smad2/3 and β-catenin. These results demonstrated that OTA induces EMT and renal fibrosis through Smad2/3 and β-catenin signaling pathways in vitro and in vivo.

Fibrogenesis in LAMA2-Related Muscular Dystrophy Is a Central Tenet of Disease Etiology

LAMA2-related congenital muscular dystrophy, also known as MDC1A, is caused by loss-of-function mutations in the alpha2 chain of Laminin-211. Loss of this protein interrupts the connection between the muscle cell and its extracellular environment and results in an aggressive, congenital-onset muscular dystrophy characterized by severe hypotonia, lack of independent ambulation, and early mortality driven by respiratory complications and/or failure to thrive. Of the pathomechanisms of MDC1A, the earliest and most prominent is widespread and rampant fibrosis. Here, we will discuss some of the key drivers of fibrosis including TGF-beta and renin–angiotensin system signaling and consequences of these pathways including myofibroblast transdifferentiation and matrix remodeling. We will also highlight some of the differences in fibrogenesis in congenital muscular dystrophy (CMD) with that seen in Duchenne muscular dystrophy (DMD). Finally, we will connect the key signaling pathways in the pathogenesis of MDC1A to the current status of the therapeutic approaches that have been tested in the preclinical models of MDC1A to treat fibrosis.

Pathological cardiac remodeling occurs early in CKD mice from unilateral urinary obstruction, and is attenuated by Enalapril

Cardiovascular disease constitutes the leading cause of mortality in patients with chronic kidney disease (CKD) and end-stage renal disease. Despite increasing recognition of a close interplay between kidney dysfunction and cardiovascular disease, termed cardiorenal syndrome (CRS), the underlying mechanisms of CRS remain poorly understood. Here we report the development of pathological cardiac hypertrophy and fibrosis in early stage non-uremic CKD. Moderate kidney failure was induced three weeks after unilateral urinary obstruction (UUO) in mice. We observed pathological cardiac hypertrophy and increased fibrosis in UUO-induced CKD (UUO/CKD) animals. Further analysis indicated that this cardiac fibrosis was associated with increased expression of transforming growth factor β (TGF-β) along with significant upregulation of Smad 2/3 signaling in the heart. Moreover early treatment of UUO/CKD animals with an angiotensin-converting-enzyme inhibitor (ACE I), Enalapril, significantly attenuated cardiac fibrosis. Enalapril antagonized activation of the TGF-β signaling pathway in the UUO/CKD heart. In summary our study demonstrates the presence of pathological cardiac hypertrophy and fibrosis in mice early in UUO-induced CKD, in association with early activation of the TGF-β/Smad signaling pathway. We also demonstrate the beneficial effect of ACE I in alleviating this early fibrogenic process in the heart in UUO/CKD animals.

Balance and circumstance: The renin angiotensin system in wound healing and fibrosis

The tissue renin angiotensin system (tRAS) is a locally-acting master-modulator of tissue homeostasis and regeneration. Through these abilities, it is emerging as an attractive target for therapies aiming to restore tissue homeostasis in conditions associated with disturbed wound healing. The tRAS can be divided into two axes - one being pro-inflammatory and pro-fibrotic and one being anti-inflammatory and anti-fibrotic. However, the division of the axes is fuzzy and imperfect as the axes are codependent and the outcome of tRAS activation is determined by the context. Although the tRAS is a local system it shares its key enzymes, ligands and receptors with the systemic RAS and is consequently also targeted by repurposing of drugs developed against the systemic RAS to manage hypertension. With a focus on the skin we will here discuss the tRAS, its involvement in physiological and pathological wound healing, and the therapeutic aptitude of its targeting to treat chronic wounds and fibrosis.

A mutation update on the LDS-associated genes TGFB2/3 and SMAD2/3

The Loeys–Dietz syndrome (LDS) is a connective tissue disorder affecting the cardiovascular, skeletal, and ocular system. Most typically, LDS patients present with aortic aneurysms and arterial tortuosity, hypertelorism, and bifid/broad uvula or cleft palate. Initially, mutations in transforming growth factor‐β (TGF‐β) receptors (TGFBR1 and TGFBR2) were described to cause LDS, hereby leading to impaired TGF‐β signaling. More recently, TGF‐β ligands, TGFB2 and TGFB3, as well as intracellular downstream effectors of the TGF‐β pathway, SMAD2 and SMAD3, were shown to be involved in LDS. This emphasizes the role of disturbed TGF‐β signaling in LDS pathogenesis. Since most literature so far has focused on TGFBR1/2, we provide a comprehensive review on the known and some novel TGFB2/3 and SMAD2/3 mutations. For TGFB2 and SMAD3, the clinical manifestations, both of the patients previously described in the literature and our newly reported patients, are summarized in detail. This clearly indicates that LDS concerns a disorder with a broad phenotypical spectrum that is still emerging as more patients will be identified. All mutations described here are present in the corresponding Leiden Open Variant Database.

TGF-β Signaling in Control of Cardiovascular Function

Genetic studies in animals and humans indicate that gene mutations that functionally perturb transforming growth factor β (TGF-β) signaling are linked to specific hereditary vascular syndromes, including Osler-Rendu-Weber disease or hereditary hemorrhagic telangiectasia and Marfan syndrome. Disturbed TGF-β signaling can also cause nonhereditary disorders like atherosclerosis and cardiac fibrosis. Accordingly, cell culture studies using endothelial cells or smooth muscle cells (SMCs), cultured alone or together in two- or three-dimensional cell culture assays, on plastic or embedded in matrix, have shown that TGF-β has a pivotal effect on endothelial and SMC proliferation, differentiation, migration, tube formation, and sprouting. Moreover, TGF-β can stimulate endothelial-to-mesenchymal transition, a process shown to be of key importance in heart valve cushion formation and in various pathological vascular processes. Here, we discuss the roles of TGF-β in vasculogenesis, angiogenesis, and lymphangiogenesis and the deregulation of TGF-β signaling in cardiovascular diseases.

Comparison of the Effect of Aliskiren Versus Negative Controls on Aortic Stiffness in Patients With Marfan Syndrome Under Treatment With Atenolol

INTRODUCTION AND OBJECTIVES

The aim of this study was to evaluate the effect of aliskiren on aortic stiffness in patients with Marfan syndrome (MS).

METHODS

Twenty-eight MS patients (mean age ± standard deviation: 32.6 ± 10.6 years) were recruited from November 2009 to October 2014. All patients were receiving atenolol as standard beta-blocker therapy. A prospective randomization process was performed to assign participants to either aliskiren treatment (150-300mg orally per day) or no aliskiren treatment (negative control) in an open-label design. Central aortic distensibility and central pulsed wave velocity (PWV) by magnetic resonance imaging (MRI), peripheral PWV, central aortic blood pressure and augmentation index by peripheral tonometry, and aortic dilatation by echocardiography were examined initially and after 24 weeks. The primary endpoint was central aortic distensibility by MRI.

RESULTS

In analyses of differences between baseline and 24 weeks for the aliskiren treatment group vs the negative control group, central distensibility (overall; P = .26) and central PWV (0.2 ± 0.9 vs 0.03 ± 0.7 [m/s]; P = .79) by MRI were not significantly different. Central systolic aortic blood pressure tended to be lower by 14mmHg in patients in the aliskiren treatment group than in the control group (P = .09). A significant decrease in peripheral PWV (brachial-ankle PWV) in the aliskiren treatment group (-1.6 m/s) compared with the control group (+0.28 m/s) was noted (P = .005).

CONCLUSIONS

Among patients with MS, the addition of aliskiren to beta-blocker treatment did not significantly improve central aortic stiffness during a 24-week period.

Poricoic acid ZA, a novel RAS inhibitor, attenuates tubulo-interstitial fibrosis and podocyte injury by inhibiting TGF-β/Smad signaling pathway

BACKGROUND

The pathogenesis of tubulo-interstitial fibrosis and glomerulosclerosisis was characterized by cellular hypertrophy, extracellular matrix accumulation and podocyte detachment. Poricoic acid ZA (PZA) is a tetracyclic triterpenoid compound extracted from the surface layer of Poria cocos (LPC), which have been used extensively for diuretic and renoprotective effects.

METHODS

The anti-fibrotic effect of PZA is investigated in HK-2 cells and podocytes induced by TGF-β1 and angiotensin II (ANGII). qRT-PCR, siRNA, immunofluorescence staining, co-immunoprecipitation and Western blot analyses are used to evaluate the expression of RAS signaling, TGF-β/Smad pathway, epithelial-to-mesenchymal transition (EMT) and podocyte markers.

RESULTS

PZA restores the mRNA and protein expression of EMT in HK-2 cells. Specific TGF-β1-siRNA efficiently blocks ANGII-induced protein expression of TGF-β1 and further inhibits activated Smad signaling. PZA significantly attenuates up-regulation of angiotensinogen, renin, ACE and AT1. Further, PZA reverses up-regulation of TGFβRII and suppresses Smad proteins. Simultaneously, PZA inhibits the protein interaction of TGF-β receptor and Smads and PZA also inhibits activated RAS and TGF-β/Smad signaling cascade and up-regulates protein expression of podocyte markers and mitigates podocyte injury.

CONCLUSIONS

This study demonstrated the beneficial role of PZA in renal fibrosis and podocyte injury. Our study highlighted that PZA inhibits RAS and further suppresses TGF-β/Smad pathway through inhibiting Smad2/3 phosphorylation via blocking Smad2/3-TGFβRI protein interaction. PZA is implicated in activation of RAS/TGF-β/Smad axis in HK-2 cells and podocytes. PZA could be considered as a novel RAS inhibitor for treating CKD.

TGF-β Family Signaling in Connective Tissue and Skeletal Diseases

The transforming growth factor β (TGF-β) family of signaling molecules, which includes TGF-βs, activins, inhibins, and numerous bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs), has important functions in all cells and tissues, including soft connective tissues and the skeleton. Specific TGF-β family members play different roles in these tissues, and their activities are often balanced with those of other TGF-β family members and by interactions with other signaling pathways. Perturbations in TGF-β family pathways are associated with numerous human diseases with prominent involvement of the skeletal and cardiovascular systems. This review focuses on the role of this family of signaling molecules in the pathologies of connective tissues that manifest in rare genetic syndromes (e.g., syndromic presentations of thoracic aortic aneurysm), as well as in more common disorders (e.g., osteoarthritis and osteoporosis). Many of these diseases are caused by or result in pathological alterations of the complex relationship between the TGF-β family of signaling mediators and the extracellular matrix in connective tissues.

Marfan Syndrome: A Clinical Update

Marfan syndrome is a connective tissue disorder that can affect many organ systems. Affected patients present with orthopaedic manifestations of the syndrome during all phases of life. Pain caused by musculoskeletal abnormalities often requires definitive orthopaedic treatment. Orthopaedic surgeons must understand the phenotypes of Marfan syndrome so they can recognize when screening is warranted and can appropriately address the skeletal manifestations. Through medical advancements, patients with Marfan syndrome are living longer and more active lives. Knowledge of the latest diagnostic criteria for the disorder, as well as of advances in understanding the skeletal phenotype, clinical trials of medication therapy, and lifestyle considerations is important for orthopaedic surgeons who treat these patients because these clinicians often are the first to suspect Marfan syndrome and recommend screening.

Deletion of NF-κB/RelA in Angiotensin II-Sensitive Mesenchymal Cells Blocks Aortic Vascular Inflammation and Abdominal Aortic Aneurysm Formation

OBJECTIVE

Infusion of angiotensin II (Ang II) induces extracellular matrix remodeling and inflammation resulting in abdominal aortic aneurysms (AAAs) in normolipidemic mice. Although Ang II activates mesenchymal cells in the media and adventitia to become fibrogenic, the sentinel role of this mesenchymal population in modulating the inflammatory response and aneurysms is not known. We test the hypothesis that these fibrogenic mesenchymal cells play a critical role in Ang II-induced aortic wall vascular inflammation and AAA formation.

APPROACH AND RESULTS

Ang II infusion increased phospho-Ser536-RelA and interleukin (IL)-6 immunostaining in the abdominal aorta. In addition, aortic mRNA transcripts of RelA-dependent cytokines IL-6 and IL-1β were significantly elevated suggesting that Ang II functionally activates RelA signaling. To test the role of mesenchymal RelA in AAA formation, we generated RelA-CKO mice by administering tamoxifen to double transgenic mice harboring RelA-flox alleles and tamoxifen-inducible Col1a2 promoter-driven Cre recombinase (Col1a2-CreER^T). Tamoxifen administration to Col1a2-CreER^T•mT/mG mice induced Cre expression and RelA depletion in aortic smooth muscle cells and fibroblasts but not in endothelial cells. Infusion of Ang II significantly increased abdominal aortic diameter and the incidence of AAA in RelA wild-type but not in RelA-CKO mice, independent of changes in systolic blood pressure. Furthermore, mesenchymal cell-specific RelA-CKO mice exhibited decreased expression of IL-6 and IL-1β cytokines and decreased recruitment of C68+ and F4/80^lo•Ly6C^hi monocytes during Ang II infusion.

CONCLUSIONS

Fibrogenic mesenchymal RelA plays a causal role in Ang II-induced vascular inflammation and AAA in normolipidemic mice.

Genetic and Epigenetic Regulation of Aortic Aneurysms

Aneurysms are characterized by structural deterioration of the vascular wall leading to progressive dilatation and, potentially, rupture of the aorta. While aortic aneurysms often remain clinically silent, the morbidity and mortality associated with aneurysm expansion and rupture are considerable. Over 13,000 deaths annually in the United States are attributable to aortic aneurysm rupture with less than 1 in 3 persons with aortic aneurysm rupture surviving to surgical intervention. Environmental and epidemiologic risk factors including smoking, male gender, hypertension, older age, dyslipidemia, atherosclerosis, and family history are highly associated with abdominal aortic aneurysms, while heritable genetic mutations are commonly associated with aneurysms of the thoracic aorta. Similar to other forms of cardiovascular disease, family history, genetic variation, and heritable mutations modify the risk of aortic aneurysm formation and provide mechanistic insight into the pathogenesis of human aortic aneurysms. This review will examine the relationship between heritable genetic and epigenetic influences on thoracic and abdominal aortic aneurysm formation and rupture.

The effect of losartan on progressive aortic dilatation in patients with Marfan's syndrome: a meta-analysis of prospective randomized clinical trials

OBJECTIVE

To assess the effect of losartan therapy on progressive aortic dilatation and on clinical outcome in patients with Marfan's syndrome (MFS).

METHODS

The meta-analysis was instituted, which included studies identified by a systematic review of MEDLINE of peer-reviewed publications. Echocardiogram or MRI measurements of the aortic root dimension and outcome measures of death, cardiovascular surgery and aortic dissection or rupture were compared between patients who were treated and untreated with losartan therapy.

RESULTS

Six randomized trials with 1398 subjects met all the inclusion criteria and were included in the meta-analysis. Compared with non-losartan treatment, losartan therapy significantly decreased the rate of aortic dilatation (SMD=-0.13 with 95% CI -0.25 to 0.00, p=0.04). The clinical outcome beneficial was not observed in the losartan treatment group when compared with no losartan treatment group (odds ratio=1.04 with 95% CI of 0.57-1.87).

CONCLUSION

Given the current results of the meta-analysis and together with the lack of associated side effects, it would be reasonable to use losartan in MFS patients with aortic root dilatation. However, no clinical outcome benefits were observed in the losartan treatment group when compared with no losartan treatment group.

Angiotensin II Type 2 Receptor Decreases Transforming Growth Factor-β Type II Receptor Expression and Function in Human Renal Proximal Tubule Cells

Transforming growth factor-β (TGF-β), via its receptors, induces epithelial-mesenchymal transition (EMT) and plays an important role in the development of renal tubulointersitial fibrosis. Angiotensin II type 2 receptor (AT₂R), which mediates beneficial renal physiological functions, has received attention as a prospective therapeutic target for renoprotection. In this study, we investigated the effect and underlying mechanism of AT₂R on the TGF-β receptor II (TGF-βRII) expression and function in human proximal tubular cells (HK-2). Here, we show that the AT₂R agonist CGP42112A decreased TGF-βRII protein expression in a concentration- and time-dependent manner in HK-2 cells. The inhibitory effect of the AT₂R on TGF-βRII expression was blocked by the AT₂R antagonists PD123319 or PD123177. Stimulation with TGF-β1 enhanced EMT in HK-2 cells, which was prevented by pre-treatment with CGP42112A. One of mechanisms in this regulation is associated with the increased TGF-βRII degradation after activation of AT₂R. Furthermore, laser confocal immunofluorescence microscopy showed that AT₂R and TGF-βRII colocalized in HK-2 cells. AT₂R and TGF-βRII coimmunoprecipitated and this interaction was increased after AT₂R agonist stimulation for 30 min. The inhibitory effect of the AT₂R on TGF-βRII expression was also blocked by the nitric oxide synthase inhibitor L-NAME, indicating that nitric oxide is involved in the signaling pathway. Taken together, our study indicates that the renal AT₂R regulates TGF-βRII expression and function via the nitric oxide pathway, which may be important in the control of renal tubulointerstitial fibrosis.

Losartan Treatment Protects Retinal Ganglion Cells and Alters Scleral Remodeling in Experimental Glaucoma

Purpose

To determine if oral losartan treatment decreases the retinal ganglion cell (RGC) death caused by experimental intraocular pressure (IOP) elevation in mice.

Methods

We produced IOP increase in CD1 mice and performed unilateral optic nerve crush. Mice received oral losartan, spironolactone, enalapril, or no drug to test effects of inhibiting angiotensin receptors. IOP was monitored by Tonolab, and blood pressure was monitored by tail cuff device. RGC loss was measured in masked axon counts and RGC bodies by β-tubulin labeling. Scleral changes that could modulate RGC injury were measured including axial length, scleral thickness, and retinal layer thicknesses, pressure-strain behavior in inflation testing, and study of angiotensin receptors and pathways by reverse transcription polymerase chain reaction, Western blot, and immunohistochemistry.

Results

Losartan treatment prevented significant RGC loss (median loss = 2.5%, p = 0.13), while median loss with water, spironolactone, and enalapril treatments were 26%, 28% and 43%; p < 0.0001). The lower RGC loss with losartan was significantly less than the loss with spironolactone or enalapril (regression model p = 0.001; drug treatment group term p = 0.01). Both losartan and enalapril significantly lowered blood pressure (p< 0.001), but losartan was protective, while enalapril led to worse than water-treated RGC loss. RGC loss after crush injury was unaffected by losartan treatment (difference from control p = 0.9). Survival of RGC in cell culture was not prolonged by sartan treatment. Axonal transport blockade after 3 day IOP elevations was less in losartan-treated than in control glaucoma eyes (p = 0.007). Losartan inhibited effects of glaucoma, including reduction in extracellular signal-related kinase activity and modification of glaucoma-related changes in scleral thickness and creep under controlled IOP.

Conclusions

The neuroprotective effect of losartan in mouse glaucoma is associated with adaptive changes in the sclera expressed at the optic nerve head.

Atenolol versus losartan in children and young adults with Marfan's syndrome

BACKGROUND

Aortic-root dissection is the leading cause of death in Marfan's syndrome. Studies suggest that with regard to slowing aortic-root enlargement, losartan may be more effective than beta-blockers, the current standard therapy in most centers.

METHODS

We conducted a randomized trial comparing losartan with atenolol in children and young adults with Marfan's syndrome. The primary outcome was the rate of aortic-root enlargement, expressed as the change in the maximum aortic-root-diameter z score indexed to body-surface area (hereafter, aortic-root z score) over a 3-year period. Secondary outcomes included the rate of change in the absolute diameter of the aortic root; the rate of change in aortic regurgitation; the time to aortic dissection, aortic-root surgery, or death; somatic growth; and the incidence of adverse events.

RESULTS

From January 2007 through February 2011, a total of 21 clinical centers enrolled 608 participants, 6 months to 25 years of age (mean [±SD] age, 11.5±6.5 years in the atenolol group and 11.0±6.2 years in the losartan group), who had an aortic-root z score greater than 3.0. The baseline-adjusted rate of change in the mean (±SE) aortic-root z score did not differ significantly between the atenolol group and the losartan group (-0.139±0.013 and -0.107±0.013 standard-deviation units per year, respectively; P=0.08). Both slopes were significantly less than zero, indicating a decrease in the aortic-root diameter relative to body-surface area with either treatment. The 3-year rates of aortic-root surgery, aortic dissection, death, and a composite of these events did not differ significantly between the two treatment groups.

CONCLUSIONS

Among children and young adults with Marfan's syndrome who were randomly assigned to losartan or atenolol, we found no significant difference in the rate of aortic-root dilatation between the two treatment groups over a 3-year period. (Funded by the National Heart, Lung, and Blood Institute and others; ClinicalTrials.gov number, NCT00429364.).

Angiotensin receptor blockers: a panacea for Marfan syndrome and related disorders?

The study of mouse models for Marfan syndrome, an autosomal dominant connective tissue disorder caused by mutations in fibrillin-1 (FBN1), has shifted our understanding of the pathogenesis of thoracic aortic aneurysm significantly. Multiple lines of evidence support the notion that dysregulation of canonical and noncanonical transforming growth factor (TGF)β signaling is the responsible pathway in this and related thoracic aortic aneurysm conditions. This exciting knowledge has opened numerous new treatment options, including antagonism of the angiotensin II receptor blocker type 1 (AT1R). In this review, we summarize the current knowledge, the first human losartan Marfan trial results and future therapeutic perspectives for aortic disease in Marfan patients.

A Pkd1-Fbn1 genetic interaction implicates TGF-β signaling in the pathogenesis of vascular complications in autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common cause of renal failure that is due to mutations in two genes, PKD1 and PKD2. Vascular complications, including aneurysms, are a well recognized feature of ADPKD, and a subgroup of families exhibits traits reminiscent of Marfan syndrome (MFS). MFS is caused by mutations in fibrillin-1 (FBN1), which encodes an extracellular matrix protein with homology to latent TGF-β binding proteins. It was recently demonstrated that fibrillin-1 deficiency is associated with upregulation of TGF-β signaling. We investigated the overlap between ADPKD and MFS by breeding mice with targeted mutations in Pkd1 and Fbn1. Double heterozygotes displayed an exacerbation of the typical Fbn1 heterozygous aortic phenotype. We show that the basis of this genetic interaction results from further upregulation of TGF-β signaling caused by Pkd1 haploinsufficiency. In addition, we demonstrate that loss of PKD1 alone is sufficient to induce a heightened responsiveness to TGF-β. Our data link the interaction of two important diseases to a fundamental signaling pathway.

Losartan added to β-blockade therapy for aortic root dilation in Marfan syndrome: a randomized, open-label pilot study

OBJECTIVE

To assess the tolerability and efficacy of the investigational use of the angiotensin II receptor blocker losartan added to β-blockade (BB) to prevent progressive aortic root dilation in patients with Marfan syndrome (MFS).

PATIENTS AND METHODS

Between May 1, 2007, and September 31, 2011, 28 patients with MFS (11 males [39%]; mean ± SD age, 13.1±6.3 years) with recognized aortic root dilation (z score >2.0) and receiving BB (atenolol or propranolol) treatment were enrolled. They were randomized to receive BB (BB: 13 patients) or β-blockade and losartan (BB-L: 15 patients) for 35 months.

RESULTS

In the BB-L group, aortic root dilation was reduced with treatment, and the annual dilation rate of the aortic root was significantly lower than that of the BB group (0.10 mm/yr vs 0.89 mm/yr; P=.02). The absolute aortic diameters at the sinus of Valsalva, annulus, and sinotubular junction showed similar trends, with a reduced rate of dilation in the BB-L group (P=.02, P=.03, and P=.03, respectively). Five patients (33%) treated with BB-L were noted to have a reduced aortic root diameter. However, the differences between the groups regarding changes in aortic stiffness and cross-sectional compliance were not statistically significant.

CONCLUSION

This randomized, open-label, active controlled trial mostly based on a pediatric population demonstrated for the first time that losartan add-on BB therapy is safe and provides more effective protection to slow the progression of aortic root dilation than does BB treatment alone in patients with MFS.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT00651235.

Matrix-dependent perturbation of TGFβ signaling and disease

Transforming growth factor beta (TGFβ) is a multipotent cytokine that is sequestered in the extracellular matrix (ECM) through interactions with a number of ECM proteins. The ECM serves to concentrate latent TGFβ at sites of intended function, to influence the bioavailability and/or function of TGFβ activators, and perhaps to regulate the intrinsic performance of cell surface effectors of TGFβ signal propagation. The downstream consequences of TGFβ signaling cascades in turn provide feedback modulation of the ECM. This review covers recent examples of how genetic mutations in constituents of the ECM or TGFβ signaling cascade result in altered ECM homeostasis, cellular performance and ultimately disease, with an emphasis on emerging therapeutic strategies that seek to capitalize on this refined mechanistic understanding.

Losartan reduces trinitrobenzene sulphonic acid-induced colorectal fibrosis in rats

BACKGROUND

Intestinal fibrosis is a challenging clinical condition in several fibrostenosing enteropathies, particularly Crohn's disease. Currently, no effective preventive measures or medical therapies are available for intestinal fibrosis. Fibrosis, due to an abnormal accumulation of extracellular matrix proteins, is a chronic and progressive process mediated by cell⁄matrix⁄cytokine and growth factor interactions, but may be a reversible phenomenon. Of the several molecules regulating fibrogenesis, transforming growth factor-beta 1 (TGF-b1) appears to play a pivotal role; it is strongly induced by the local activation of angiotensin II. The levels of both TGF-b1 and angiotensin II are elevated in fibrostenosing Crohn's disease.

AIMS

To evaluate the in vivo effect of losartan - an angiotensin II receptor antagonist - on the course of chronic colitis-associated fibrosis and on TGF-b1 expression.

METHODS

Colitis was induced by intrarectal instillation of trinitrobenzene sulphonic acid (TNBS) (15 mg⁄mL) while losartan was administered orally daily by gavage (7 mg⁄kg⁄day) for 21 days. Three groups of rats were evaluated: control (n=10); TNBS treated (n=10); and TNBS + losartan treated (n=10). Inflammation and fibrosis of the colon were evaluated by macro- and microscopic score analysis. Colonic TGF-b1 levels was measured using ELISA.

RESULTS

Twenty-one days after induction, losartan significantly improved the macro- and microscopic scores of fibrosis in the colonic wall and reduced TGF-b1 concentration.

CONCLUSIONS

Prophylactic oral administration of losartan reduces the colorectal fibrosis complicating the TNBS-induced chronic colitis, an effect that appears to be mediated by a downregulation of TGF-b1 expression.

Noncanonical TGFβ signaling contributes to aortic aneurysm progression in Marfan syndrome mice

Transforming growth factor-β (TGFβ) signaling drives aneurysm progression in multiple disorders, including Marfan syndrome (MFS), and therapies that inhibit this signaling cascade are in clinical trials. TGFβ can stimulate multiple intracellular signaling pathways, but it is unclear which of these pathways drives aortic disease and, when inhibited, which result in disease amelioration. Here we show that extracellular signal-regulated kinase (ERK) 1 and 2 and Smad2 are activated in a mouse model of MFS, and both are inhibited by therapies directed against TGFβ. Whereas selective inhibition of ERK1/2 activation ameliorated aortic growth, Smad4 deficiency exacerbated aortic disease and caused premature death in MFS mice. Smad4-deficient MFS mice uniquely showed activation of Jun N-terminal kinase-1 (JNK1), and a JNK antagonist ameliorated aortic growth in MFS mice that lacked or retained full Smad4 expression. Thus, noncanonical (Smad-independent) TGFβ signaling is a prominent driver of aortic disease in MFS mice, and inhibition of the ERK1/2 or JNK1 pathways is a potential therapeutic strategy for the disease.

Angiotensin II type 2 receptor signaling attenuates aortic aneurysm in mice through ERK antagonism

Angiotensin II (AngII) mediates progression of aortic aneurysm, but the relative contribution of its type 1 (AT1) and type 2 (AT2) receptors remains unknown. We show that loss of AT2 expression accelerates the aberrant growth and rupture of the aorta in a mouse model of Marfan syndrome (MFS). The selective AT1 receptor blocker (ARB) losartan abrogated aneurysm progression in the mice; full protection required intact AT2 signaling. The angiotensin-converting enzyme inhibitor (ACEi) enalapril, which limits signaling through both receptors, was less effective. Both drugs attenuated canonical transforming growth factor-β (TGFβ) signaling in the aorta, but losartan uniquely inhibited TGFβ-mediated activation of extracellular signal-regulated kinase (ERK), by allowing continued signaling through AT2. These data highlight the protective nature of AT2 signaling and potentially inform the choice of therapies in MFS and related disorders.

Activation of the activin A-ALK-Smad pathway in systemic sclerosis

Systemic sclerosis (SSc) is a chronic disease of unknown etiology that is characterized by multiple tissue fibrosis. Transforming Growth Factor-beta (TGF-β) is thought to be the most important mediator that induces fibrosis. However, the molecular mechanisms by which fibrosis is induced have not been fully elucidated. In this study, the role of activin, a member of the TGF-β superfamily, was investigated in the pathogenesis of fibrosis in SSc. Serum activin A levels in patients with SSc were measured by ELISA, and the expression of the activin receptor type IB (ACVRIB/ALK4) and the activity of the signaling pathway via ACVRIB/ALK4 were investigated using western blotting. To evaluate a potential therapeutic strategy for SSc, we also attenuated the ACVRIB/ALK4 pathway using an inhibitor. Serum activin A levels were significantly higher in SSc patients than in normal controls. Activin A and ACVRIB/ALK4 expression were also higher in cultured SSc fibroblasts. Activin A stimulation induced phosphorylation of Smad2/3 and CTGF expression in SSc fibroblasts. Procollagen production and Col1α mRNA also increased upon stimulation by activin A. The basal level of Smad2/3 phosphorylation was higher in cultured SSc fibroblasts than in control cells, and treatment with the ALK4/5 inhibitor SB431542 prevented phosphorylation of Smad2/3 and CTGF expression. Furthermore, production of collagen was also induced by activin A. Activin A-ACVRIB/ALK4-Smad-dependent collagen production was augmented in SSc fibroblasts, suggesting the involvement of this signaling mechanism in SSc. Inhibition of the activin A-ACVRIB/ALK4-Smad pathway would be a new approach for the treatment of SSc.

TGFbeta-induced GRK2 expression attenuates AngII-regulated vascular smooth muscle cell proliferation and migration

Through diametric actions, the transforming growth factor beta (TGFbeta) and Angiotensin II (AngII) play important roles in regulating various biological responses such as cell proliferation and migration. Signaling initiated by TGFbeta and AngII occurs through two structurally and functionally distinct receptor super families,the serine/threonine kinase and G protein-coupled receptors (GPCRs). Previously, we identified the Gprotein-coupled receptor kinase-2 (GRK2), a key regulatory factor in the desensitization of GPCRs, as a direct downstream target of the TGFbeta signaling cascade. GRK2 acts through a negative feed-back loop mechanism to terminate TGFbeta-induced smad signaling. To investigate the impact of TGFbeta-induced GRK2 expression on GPCR signaling, we examined its effect on AngII signaling in vascular smooth muscle cells (VSMCs). In this study, we show that activation of the TGFbeta signaling cascade in VSMCs results in increased GRK2 expression levels, which consequently inhibits AngII-induced ERK phosphorylation and antagonizes AngII-induced VSMC proliferation and migration. Moreover, the inhibitory effect of TGFbeta on AngII signaling occurs at the Mek-Erk interface and is abrogated when an anti-sense oligonucleotide directed against GRK2 is used. Thus,we conclude that TGFbeta signaling antagonizes AngII-induced VSMC proliferation and migration through the inhibition of ERK phosphorylation and that GRK2 is a key factor mediating the cross-talk between these two receptor super families.

Rationale and design of a trial evaluating the effects of losartan vs. nebivolol vs. the association of both on the progression of aortic root dilation in Marfan syndrome with FBN1 gene mutations

BACKGROUND

The major clinical problem of Marfan syndrome (MFS) is the aortic root aneurysm, with risk of dissection when the root diameter approximates 5 cm. In MFS, a key molecule, transforming growth factor-beta (TGF-beta), normally bound to the extracellular matrix, is free and activated. In an experimental setting, TGF-beta blockade prevents the aortic root structural damage and dilatation. The angiotensin receptor 1 blockers (sartanics) exert an anti-TGF-beta effect; trials are now ongoing for evaluating the effect of losartan compared with atenolol in MFS. beta-Adrenergic blockers are the drugs most commonly used in MFS. The third-generation beta-adrenergic blocker nebivolol retains the beta-adrenergic blocker effects on heart rate and further exerts antistiffness effects, typically increased in MFS.

METHODS

The open-label phase III study will include 291 patients with MFS and proven FBN1 gene mutations, with aortic root dilation (z-score > or =2.5). The patients will be randomized to nebivolol, losartan and the combination of the two drugs. The primary end point is the comparative evaluation of the effects of losartan, nebivolol and the association of both on the progression of aortic root growth rate. Secondary end points include the pharmacokinetics of the two drugs, comparative evaluation of serum levels of total and active TGF-beta, quantitative assessment of the expression of the mutated gene (FBN1, both 5' and 3'), pharmacogenetic bases of drug responsiveness. The quality of life evaluation in the three groups will be assessed. Statistical evaluation includes an interim analysis at month 24 and conclusive analyses at month 48.

CONCLUSION

The present study will add information about pharmacological therapy in MFS, supporting the new application of angiotensin receptor 1 blockers and finding beta-adrenergic blockers that may give more specific effects. Moreover, the study will further deepen understanding of the pathogenetic mechanisms that are active in Marfan syndrome through the pharmacogenomic and transcriptomic mechanisms that may explain MFS phenotype variability.

AT1 antagonist modulates activin-like kinase 5 and TGF-beta receptor II in the developing kidney

Previous studies by our group have demonstrated that angiotensin-converting enzyme (ACE) inhibition in the developing kidney modulates transforming growth factor-beta receptors. Blocking of angiotensin II (ANG II) mainly through angiotensin II type 1 receptor (AT1) has been implicated in mediating this ACE inhibition. The present study was designed to investigate the effects of an AT1 antagonist, losartan, on transforming growth factor-beta1 (TGF-beta1), TGF-beta receptor I [TbetaRI, activin-like kinase (ALK)-1, ALK-5], TGF-beta receptor II (TbetaRII), and alpha-smooth muscle actin (alpha-SMA) expression in the developing kidney. Newborn rat pups were treated with losartan (30 mg/kg per day) or normal saline for 7 days. Kidneys were removed for immunohistochemistry, reverse transcription polymerase chain reaction (PCR), and Western blotting of TGF-beta1, ALK-1, ALK-5, TbetaRII, and alpha-SMA. Renal ALK-5 and TbetaRII protein expressions in the losartan-treated group were found to be significantly increased (P<0.05), whereas TGF-beta1, ALK-1, and alpha-SMA protein expressions were not changed by losartan treatment. The losartan-treated group also showed significantly increased mean tubular diameter and interstitial area of the kidney (P<0.05). These results suggest that AT1 inhibition in the developing kidney impairs renal growth and development and modulates the expression of ALK-5 and TbetaRII.

Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome

Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder.

TGF-beta1 increases proliferation of airway smooth muscle cells by phosphorylation of map kinases

BACKGROUND

Airway remodeling in asthma is the result of increased expression of connective tissue proteins, airway smooth muscle cell (ASMC) hyperplasia and hypertrophy. TGF-beta1 has been found to increase ASMC proliferation. The activation of mitogen-activated protein kinases (MAPKs), p38, ERK, and JNK, is critical to the signal transduction associated with cell proliferation. In the present study, we determined the role of phosphorylated MAPKs in TGF-beta1 induced ASMC proliferation.

METHODS

Confluent and growth-arrested bovine ASMCs were treated with TGF-beta1. Proliferation was measured by [3H]-thymidine incorporation and cell counting. Expressions of phosphorylated p38, ERK1/2, and JNK were determined by Western analysis.

RESULTS

In a concentration-dependent manner, TGF-beta1 increased [3H]-thymidine incorporation and cell number of ASMCs. TGF-beta1 also enhanced serum-induced ASMC proliferation. Although ASMCs cultured with TGF-beta1 had a significant increase in phosphorylated p38, ERK1/2, and JNK, the maximal phosphorylation of each MAPK had a varied onset after incubation with TGF-beta1. TGF-beta1 induced DNA synthesis was inhibited by SB 203580 or PD 98059, selective inhibitors of p38 and MAP kinase kinase (MEK), respectively. Antibodies against EGF, FGF-2, IGF-I, and PDGF did not inhibit the TGF-beta1 induced DNA synthesis.

CONCLUSION

Our data indicate that ASMCs proliferate in response to TGF-beta1, which is mediated by phosphorylation of p38 and ERK1/2. These findings suggest that TGF-beta1 which is expressed in airways of asthmatics may contribute to irreversible airway remodeling by enhancing ASMC proliferation.

Transforming growth factor beta receptor endoglin is expressed in cardiac fibroblasts and modulates profibrogenic actions of angiotensin II

Angiotensin II (Ang II) is a powerful mediator of adverse cardiac remodeling and fibrosis. However, the mechanisms of Ang II-induced myocardial fibrosis remain to be clarified. We postulated that Ang II alters transforming growth factor beta (TGF-beta) receptor expression, specifically that of endoglin, and thereby modulates cardiac fibroblast (CF) collagen metabolism. Experiments were conducted using CF from adult Sprague Dawley rats to determine the expression of TGF-beta1 receptors including endoglin, and the role of Ang II type 1 (AT1) and type 2 (AT2) receptors, and MAPK p42/44 in this process. The functional role of endoglin in modulating Ang II effects on matrix metalloproteinase-1 (MMP-1) and type I collagen expression was also analyzed. Endoglin gene and protein expression were consistently identified in quiescent CFs. Ang II increased the expression of endoglin mRNA and protein in a concentration and time-dependent manner, with no effect on TGF-beta receptors I and II expression. This effect was AT1 receptor mediated, because AT1 receptor antagonists valsartan, candesartan, and losartan inhibited Ang II-induced endoglin expression, whereas the AT2 receptor antagonist PD123319 had no effect. MAPKp42/44 inhibition attenuated Ang II-induced endoglin expression. Ang II-induced decrease in MMP-1 protein expression and increase in type I collagen protein expression were both blocked by a specific endoglin antibody. Hence, our results indicate that endoglin is upregulated in CFs by Ang II via the AT1 receptor and modulates profibrotic effects of Ang II. These findings provide novel insights into Ang II-induced cardiac remodeling.

Prevention of fibrosis in experimental colitis by captopril: the role of tgf-beta1

BACKGROUND & AIMS

There is a body of evidence to suggest that the local activation of angiotensin II (ANG II) plays a pivotal role in fibrogenic response involving the kidney, heart, lung, pancreas and liver. In such conditions, fibrosis is mediated, at least partially, through ANG II induction of the cytokine transforming growth factor-beta1 (TGF-beta1). Both ANG II and TGF-beta1 also seem to be involved in intestinal fibrosis and stenosis, particularly in Crohn's disease. The aim of the present study was, firstly, to determine the effects of the angiotensin-converting enzyme inhibitor, captopril, on colonic fibrosis in experimental colitis in rats and, secondly, to check the role of TGF-beta1 on these effects.

METHODS

Colitis was induced in rats by intracolonic administration of TNBS. Colonic fibrosis was assessed 21 days later by macroscopic and microscopic evaluation. Levels of collagen alpha1 gene expression, hydroxyproline, angiotensin II and TGF-beta1 proteins, and TGF-beta1 mRNA were measured on the colonic tissue.

RESULTS

In chronic colitis, captopril significantly reduced the score of macroscopic and histologic lesions, as well as the colonic tissue levels of collagen alpha1, hydroxyproline, ANG II and TGF-beta1 proteins, and TGF-beta1 mRNA.

CONCLUSIONS

These data demonstrate for the first time that the prophylactic administration of captopril is effective in preventing colonic fibrosis in TNBS-induced colitis. The antifibrotic action of captopril could be due to the blockade of TGFbeta-1 overexpression, and/or to a direct down-regulation of TGFbeta-1 transcript.

Effect of AT2 receptor on expression of AT1 and TGF-beta receptors in VSMCs from SHR

We recently reported that overexpression of the angiotensin II type 2 (AT2) receptor downregulates the AT1a receptor through the bradykinin/NO pathway in a ligand-independent manner in vascular smooth muscle cells (VSMCs). In the present study, we investigated the effect of AT2 receptor overexpression on the expression of the AT1a receptor and transforming growth factor-beta (TGF-beta) receptor subtypes in VSMCs from spontaneously hypertensive rats (SHR) and Wistar-Kyoto rats (WKY). Transfection of the AT2 receptor gene downregulated expression of the AT1a receptor in VSMCs from WKY, but did not affect expression of the AT1a receptor in VSMCs from SHR. Transfection of the AT2 receptor abolished DNA synthesis in response to angiotensin II in VSMCs from WKY; in VSMCs from SHR, basal DNA synthesis was suppressed, but DNA synthesis in response to Ang II was not altered. The NO substrate L-arginine augmented downregulation of the AT1a receptor in VSMCs from WKY, whereas it did not affect expression of the AT1a receptor in VSMCs from SHR. In response to AT2 receptor transfection, expression of TGF-beta type I receptor mRNA was suppressed significantly in VSMCs from WKY, whereas expression of TGF-beta type I receptor was not altered in VSMCs from SHR. These results suggest that the AT2 receptor downregulates AT1a and TGF-beta type I receptors in normal VSMCs, but not in SHR-derived VSMCs. The lack of downregulation of the AT1a receptor may contribute, in part, to the exaggerated growth of VSMCs from SHR.

Endoglin upregulation during experimental renal interstitial fibrosis in mice

The goal of the present study was to evaluate the role of endoglin, a transforming growth factor-beta1 (TGF-beta1) accessory receptor, in the pathogenesis of renal fibrosis. This was achieved by testing a model of tubulo-interstitial fibrosis induced by unilateral ureteral obstruction in endoglin heterozygous (Eng(+/-)) mice. Northern and Western blot analysis revealed that endoglin expression in kidneys of these mice was significantly reduced compared with Eng(+/+) littermates. Pronounced interstitial fibrosis induced by ureteral obstruction was confirmed histologically by Masson's trichromic staining and by increased immunostaining for fibronectin and laminin without significant differences between Eng(+/-) and Eng(+/+) mice. Ureteral obstruction induced significant increases in alpha2(I) and alpha1(IV) collagen, fibronectin, and TGF-beta1 mRNA levels, as well as in total kidney collagen but changes were similar in Eng(+/-) and Eng(+/+) mouse kidneys. Ureteral obstruction also induced a 2-fold increase in endoglin mRNA levels in both Eng(+/+) mice and Eng(+/-) mice, which was confirmed by Western blot analysis. Thus, the present study provides clear evidence that endoglin is upregulated in the kidneys of mice with interstitial fibrosis induced by unilateral ureteral ligation. However, Eng(+/-) mice do not show any changes in the severity of renal disease induced in this model when compared with normal mice, suggesting that the absolute level of endoglin is not critical for the effects of TGF-beta1 in the renal fibrosis process.

Angiotensin II stimulates migration of retinal microvascular pericytes: involvement of TGF-beta and PDGF-BB

We studied the promigratory effect of angiotensin II (ANG II) on cultured bovine retinal microvascular pericytes. ANG II stimulated migration of pericytes by 86% at 10(-8) M, but this effect was lost at 10(-4) M. Migratory responses were inhibited by the ANG II type 1 (AT(1)) receptor antagonist losartan but not by PD-123319, an AT(2) antagonist. Addition of PD-123319 to the 10(-4) M ANG II dose restored migratory responses. The promigratory effect of ANG II (10(-7) M) was reduced by 59% in absence of gradient. Although ANG II augmented the latent matrix metalloproteinase-2 (MMP-2) activity of the pericyte by 35%, it also doubled tissue inhibitors of MMPs. ANG II-induced migration was not altered by a broad-spectrum MMP inhibitor (GM6001); it was inhibited by ~50% by antibodies against transforming growth factor (TGF)-beta(1/2/3) and was abolished by antibodies against platelet-derived growth factor (PDGF)-BB. We conclude that ANG II induces chemotactic responses on retinal microvascular pericytes acting through the AT(1) receptor. This effect is opposed by the AT(2) receptor. ANG II-induced chemotaxis is mediated by PDGF-BB and involves TGF-beta, but it is independent of MMP activity. It is also independent of vascular endothelial growth factor (VEGF) because VEGF did not stimulate pericyte migration. ANG II can contribute to the regulation of retinal neovascularization by stimulating pericyte migration.

Angiotensin II via activation of type 1 receptor upregulates expression of endoglin in human coronary artery endothelial cells

Transforming growth factor-beta1 and its subtype receptor endoglin are key components in angiogenesis. We explored the role of angiotensin (Ang) II in the expression of endoglin and the underlying intracellular signaling mechanism in human coronary artery endothelial cells. Incubation of cells with Ang II upregulated endoglin expression in a concentration- and time-dependent manner (maximal effect with 10(-6) mol/L Ang II at 24 hours). The Ang II type 1 receptor blocker losartan, but not the type 2 receptor blocker PD 123,319, completely blocked the effect of Ang II. In parallel experiments, the mitogen-activated protein kinase inhibitor PD 098,059 fully inhibited the effect of Ang II on the expression of endoglin. Incubation of endothelial cells with Ang II also increased the expression of transforming growth factor-beta1 and -beta2 receptors and simultaneously decreased the levels of transforming growth factor-beta1. These effects of Ang II were also attenuated by losartan. We propose that Ang II via its type 1 receptor activation modulates the expression of transforming growth factor-beta1 receptors in human coronary endothelial cells. The activation of mitogen-activated protein kinase plays an important role in this process. These observations provide a new clue regarding the regulatory effect of Ang II on vascular remodeling after injury.

Effect of angiotensin II type 1 receptor blockade on experimental hepatic fibrogenesis

BACKGROUND/AIMS

The aim of this study was to investigate whether in the liver, as in other tissues, there is evidence that angiotensin II, acting via the angiotensin II type 1 receptor (AT1-R), plays a role in fibrogenesis.

METHODS

Sprague-Dawley rats were divided into three groups; sham, bile duct ligated (BDL) and BDL + AT1-R antagonist, irbesartan. Real time RT-PCR was utilised to assess gene expression of the AT1 receptor, TGF-beta1 and alpha1 (I) collagen in the liver. TGF-beta1 and alpha1 (I) collagen mRNA expression and localisation were also assessed by in situ hybridisation. TGF-beta1 activity was assessed by using the TGF-beta inducible gene product betaig-h3. Fibrosis was assessed by the Knodell scoring system, tissue hydroxyproline content and picro-sirius red staining.

RESULTS

Real time RT-PCR revealed that there was a 6-fold up-regulation in AT1 receptor expression in BDL animals compared with shams. This was associated with marked increases in TGF-beta1, betaig-h3 and alpha1 (I) collagen gene expression which were attenuated by AT1-RA treatment. However, AT1-RA therapy produced no significant change in liver histology or hydroxyproline content.

CONCLUSIONS

These results suggest that in the liver angiotensin II may play an important role in the fibrogenic response to injury. However, whether treatment with an AT1-RA will be of therapeutic benefit remains to be determined.