Angiotensin II induces myocyte enhancer factor 2- and calcineurin/nuclear factor of activated T cell-dependent transcriptional activation in vascular myocytes

Estrogen signaling as a bridge between the nucleus and mitochondria in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality worldwide. Epidemiological studies indicate that pre-menopausal women are more protected against the development of CVDs compared to men of the same age. This effect is attributed to the action/effects of sex steroid hormones on the cardiovascular system. In this context, estrogen modulates cardiovascular function in physiological and pathological conditions, being one of the main physiological cardioprotective agents. Here we describe the common pathways and mechanisms by which estrogens modulate the retrograde and anterograde communication between the nucleus and mitochondria, highlighting the role of genomic and non-genomic pathways mediated by estrogen receptors. Additionally, we discuss the presumable role of bromodomain-containing protein 4 (BRD4) in enhancing mitochondrial biogenesis and function in different CVD models and how this protein could act as a master regulator of estrogen protective activity. Altogether, this review focuses on estrogenic control in gene expression and molecular pathways, how this activity governs nucleus-mitochondria communication, and its projection for a future generation of strategies in CVDs treatment.

Vascular Health Triad in Humans With Hypertension-Not the Usual Suspects

Hypertension (HTN) affects more than one-third of the US population and remains the top risk factor for the development of cardiovascular disease (CVD). Identifying the underlying mechanisms for developing HTN are of critical importance because the risk of developing CVD doubles with ∼20 mmHg increase in systolic blood pressure (BP). Endothelial dysfunction, especially in the resistance arteries, is the primary site for initiation of sub-clinical HTN. Furthermore, inflammation and reactive oxygen and nitrogen species (ROS/RNS) not only influence the endothelium independently, but also have a synergistic influence on each other. Together, the interplay between inflammation, ROS and vascular dysfunction is referred to as the vascular health triad, and affects BP regulation in humans. While the interplay of the vascular health triad is well established, new underlying mechanistic targets are under investigation, including: Inducible nitric oxide synthase, hydrogen peroxide, hydrogen sulfide, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and nuclear factor activated T cells. This review outlines the role of these unusual suspects in vascular health and function in humans. This review connects the dots using these unusual suspects underlying inflammation, ROS and vascular dysfunction especially in individuals at risk of or with diagnosed HTN based on novel studies performed in humans.

The role of calmodulin and calmodulin-dependent protein kinases in the pathogenesis of atherosclerosis

Atherosclerosis is a chronic inflammatory disease that triggers severe thrombotic cardiovascular events, such as stroke and myocardial infarction. In atherosclerotic processes, both macrophages and vascular smooth muscle cells (VSMCs) are essential cell components in atheromata formation through proinflammatory cytokine secretion, defective efferocytosis, cell migration, and proliferation, primarily controlled by Ca²⁺-dependent signaling. Calmodulin (CaM), as a versatile Ca²+ sensor in diverse cell types, regulates a broad spectrum of Ca²⁺-dependent cell functions through the actions of downstream protein kinases. Thus, this review focuses on discussing how CaM and CaM-dependent kinases (CaMKs) regulate the functions of macrophages and VSMCs in atherosclerotic plaque development based on literature from open databases. A central theme in this review is a summary of the mechanisms and consequences underlying CaMK-mediated macrophage inflammation and apoptosis, which are the key processes in necrotic core formation in atherosclerosis. Another central theme is addressing the role of CaM and CaMK-dependent pathways in phenotypic modulation, migration, and proliferation of VSMCs in atherosclerotic progression. A complete understanding of CaM and CaMK-controlled individual processes involving macrophages and VSMCs in atherogenesis might provide helpful information for developing potential therapeutic targets and strategies.

Aging- and gender-related modulation of RAAS: potential implications in COVID-19 disease

Coronavirus disease 2019 (COVID-19) is a new infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). COVID-19 is frequently characterized by a marked inflammatory response with severe pneumonia and respiratory failure associated with multiorgan involvement. Some risk factors predispose patients to develop a more severe infection and to an increased mortality; among them, advanced age and male gender have been identified as major and independent risk factors for COVID-19 poor outcome. The renin-angiotensin-aldosterone system (RAAS) is strictly involved in COVID-19 because angiotensin converting enzyme 2 (ACE2) is the host receptor for SARS-CoV-2 and also converts pro-inflammatory angiotensin (Ang) II into anti-inflammatory Ang(1–7). In this review, we have addressed the effect of aging and gender on RAAS with emphasis on ACE2, pro-inflammatory Ang II/Ang II receptor 1 axis and anti-inflammatory Ang(1–7)/Mas receptor axis.

The pathophysiological role of angiotensin receptor-binding protein in hypertension and kidney diseases: Oshima Award Address 2019

Excessive activation of the tissue renin–angiotensin system through angiotensin II (Ang II) type 1 receptor (AT1R) plays a pivotal role in the pathogenesis of hypertension and related organ injury. AT1R-associated protein (ATRAP/Agtrap) was identified as a molecule specifically interacting with the carboxyl- terminal domain of AT1R. The results of in vitro studies showed that ATRAP suppresses Ang II-mediated pathological responses in cardiovascular cells by promoting AT1R internalization. With respect to the tissue distribution and regulation of ATRAP expression in vivo, ATRAP is broadly expressed in many tissues as is AT1R including kidney. The results of in vivo study employing genetic engineered mice with modified ATRAP expression showed that ATRAP inhibits cardiovascular injuries provoked by Ang II-induced hypertension, along with preserving physiological AT1R signaling. In addition, we have shown that ATRAP functions as an endogenous modulator so as to prevent hypertension in response to pathological stimuli, by regulating renal sodium handling. Furthermore, ATRAP may have an AT1R-independent function of renal proximal tubule to protect aging and fibrosis. These results suggest the clinical potential benefit of an ATRAP activation strategy in the treatment of hypertension and cardiorenal and vascular diseases.

Nanojunctions of the Sarcoplasmic Reticulum Deliver Site- and Function-Specific Calcium Signaling in Vascular Smooth Muscles

Vasoactive agents may induce myocyte contraction, dilation, and the switch from a contractile to a migratory-proliferative phenotype(s), which requires changes in gene expression. These processes are directed, in part, by Ca²⁺ signals, but how different Ca²⁺ signals are generated to select each function is enigmatic. We have previously proposed that the strategic positioning of Ca²⁺ pumps and release channels at membrane-membrane junctions of the sarcoplasmic reticulum (SR) demarcates cytoplasmic nanodomains, within which site- and function-specific Ca²⁺ signals arise. This chapter will describe how nanojunctions of the SR may: (1) define cytoplasmic nanospaces about the plasma membrane, mitochondria, contractile myofilaments, lysosomes, and the nucleus; (2) provide for functional segregation by restricting passive diffusion and by coordinating active ion transfer within a given nanospace via resident Ca²⁺ pumps and release channels; (3) select for contraction, relaxation, and/or changes in gene expression; and (4) facilitate the switch in myocyte phenotype through junctional reorganization. This should serve to highlight the need for further exploration of cellular nanojunctions and the mechanisms by which they operate, that will undoubtedly open up new therapeutic horizons.

Calcineurin/NFAT Activation-Dependence of Leptin Synthesis and Vascular Growth in Response to Mechanical Stretch

Background and Aims: Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca²⁺/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC) hypertrophy and leptin synthesis.

Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM) on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA, and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM), the selective calcineurin inhibitor FK506 (1 nM), and the ERK1/2 inhibitor PD98059 (1 μM). The transcription inhibitor actinomycin D (0.1 μM) and the translation inhibitor cycloheximide (1 mM) significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM). In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL), the ROCK inhibitor Y-27632 (10 μM), and the actin depolymerization agents Latrunculin B (50 nM) and cytochalasin D (1 μM) reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3.

Conclusions: Mechanical stretch-induced VSMC hypertrophy and leptin synthesis and secretion are mediated by Ca²⁺/calcineurin/NFAT activation. RhoA/ROCK and ERK1/2 activation are critical for mechanical stretch-induced calcineurin activation.

Role of CaMKII in Ang-II-dependent small artery remodeling

Angiotensin-II (Ang-II) is a well-established mediator of vascular remodeling. The multifunctional calcium-calmodulin-dependent kinase II (CaMKII) is activated by Ang-II and regulates Erk1/2 and Akt-dependent signaling in cultured smooth muscle cells in vitro. Its role in Ang-II-dependent vascular remodeling in vivo is far less defined. Using a model of transgenic CaMKII inhibition selectively in smooth muscle cells, we found that CaMKII inhibition exaggerated remodeling after chronic Ang-II treatment and agonist-dependent vasoconstriction in second-order mesenteric arteries. These findings were associated with increased mRNA and protein expression of smooth muscle structural proteins. As a potential mechanism, CaMKII reduced serum response factor-dependent transcriptional activity. In summary, our findings identify CaMKII as an important regulator of smooth muscle function in Ang-II hypertension in vivo.

Nuclear factor of activated T-cell isoform expression and regulation in human myometrium

BACKGROUND

During pregnancy, myometrial gene and protein expression is tightly regulated to accommodate fetal growth, promote quiescence and ultimately prepare for the onset of labour. It is proposed that changes in calcium signalling, may contribute to regulating gene expression and that nuclear factor of activated T-cell (NFAT) transcription factors (isoforms c1-c4) may be involved. Currently, there is little information regarding NFAT expression and regulation in myometrium.

METHODS

This study examined NFAT isoform mRNA expression in human myometrial tissue and cells from pregnant women using quantitative PCR. The effects of the Ca(2+) ionophore A23187 and in vitro stretch (25 % elongation, static strain; Flexercell FX-4000 Tension System) on NFAT expression were determined in cultured human myometrial cells.

RESULTS

Human myometrial tissue and cultured cells expressed NFATc1-c4 mRNA. NFATc2 gene expression in cultured cells was increased in response to 6 h stretch (11.5 fold, P < 0.001, n = 6) and calcium ionophore (A23187, 5 μM) treatment (20.6 fold, P < 0.001, n = 6). This response to stretch was significantly reduced (90 %, P < 0.001, n = 10) in the presence of an intracellular calcium chelator, BAPTA-AM (20 μM).

CONCLUSIONS

These data suggest that NFATc2 expression is regulated by intracellular calcium and in vitro stretch, and that the stretch response in human myometrial cells is dependent upon intracellular calcium signalling pathways. Our findings indicate a potentially unique role for NFATc2 in mediating stretch-induced gene expression per se and warrant further exploration in relation to the mechanisms promoting uterine smooth muscle growth in early pregnancy and/or labour.

Neuromedin B Restores Erectile Function by Protecting the Cavernous Body and the Nitrergic Nerves from Injury in a Diabetic Rat Model

Erectile dysfunction (ED) is a major health problem worldwide and affects approximately 75% of diabetic patients, likely due to severely damaged cavernous body. While screening for cytokines produced by adipose tissue-derived stem cells, we detected neuromedin B (NMB). To explore a potential treatment option for ED, we examined whether NMB was capable of restoring erectile function. We also examined the potential mechanism by which NMB could restore erectile function. Male Wistar rats were injected with streptozotocin (STZ) to induce diabetes. An adenovirus expressing NMB (AdNMB) was injected into the penis 6 weeks after STZ administration. Four weeks after the injection of AdNMB, erectile function, penile histology, and protein expression were analyzed. As assessed by the measurement of intracavernous pressure, AdNMB injection significantly restored erectile function compared with the injection of an adenovirus expressing green fluorescent protein. This restoration was associated with conservation of the cavernous body structure and neural nitric oxide synthase (nNOS)-expressing nerves, together with recovery of α-smooth muscle actin, vascular endothelial-cadherin, and nNOS expression. Furthermore, NMB significantly stimulated the survival of SH-SY5Y cells derived from human neuroblastoma tissue with characteristics similar to neurons. Collectively, these results suggested that NMB restored erectile function via protection of the cavernous body from injury and stimulation of the survival of the associated nerves. NMB may be useful to treat ED patients with a severely damaged cavernous body.

Phosphodiesterase 5 inhibition ameliorates angiontensin II-induced podocyte dysmotility via the protein kinase G-mediated downregulation of TRPC6 activity

The emerging role of the transient receptor potential cation channel isotype 6 (TRPC6) as a central contributor to various pathological processes affecting podocytes has generated interest in the development of therapeutics to modulate its function. Recent insights into the regulation of TRPC6 have revealed PKG as a potent negative modulator of TRPC6 conductance and associated signaling via its phosphorylation at two highly conserved amino acid residues: Thr(69)/Thr(70) (Thr(69) in mice and Thr(70) in humans) and Ser(321)/Ser(322) (Ser(321) in mice and Ser(322) in humans). Here, we tested the role of PKG in modulating TRPC6-dependent responses in primary and conditionally immortalized mouse podocytes. TRPC6 was phosphorylated at Thr(69) in nonstimulated podocytes, but this declined upon ANG II stimulation or overexpression of constitutively active calcineurin phosphatase. ANG II induced podocyte motility in an in vitro wound assay, and this was reduced 30-60% in cells overexpressing a phosphomimetic mutant TRPC6 (TRPC6T70E/S322E) or activated PKG (P < 0.05). Pretreatment of podocytes with the PKG agonists S-nitroso-N-acetyl-dl-penicillamine (nitric oxide donor), 8-bromo-cGMP, Bay 41-2772 (soluble guanylate cyclase activator), or phosphodiesterase 5 (PDE5) inhibitor 4-{[3',4'-(methylenedioxy)benzyl]amino}[7]-6-methoxyquinazoline attenuated ANG II-induced Thr(69) dephosphorylation and also inhibited TRPC6-dependent podocyte motility by 30-60%. These data reveal that PKG activation strategies, including PDE5 inhibition, ameliorate ANG II-induced podocyte dysmotility by targeting TRPC6 in podocytes, highlighting the potential therapeutic utility of these approaches to treat hyperactive TRPC6-dependent glomerular disease.

Adrenomedullin and angiopoietin-1 additively restore erectile function in diabetic rats: comparison with the combination therapy of vascular endothelial growth factor and angiopoietin-1

INTRODUCTION

Erectile dysfunction (ED) is a major health problem. We have shown that adrenomedullin (AM) restores erectile function in diabetic rats.

AIM

The aim of this study is to explore a better treatment for ED, we examined whether combination of AM and angiopoietin-1 (Ang-1) was more effective to treat ED than treatment with AM alone or Ang-1 alone. We also compared the effect of the combination therapy with that of treatment with vascular endothelial growth factor-A (VEGF-A).

METHODS

Male Wistar rats were injected with streptozotocin (STZ) to induce diabetes. Adenoviruses expressing AM (AdAM), Ang-1 (AdAng-1), and VEGF-A (AdVEGF-A) were injected into the penis 6 weeks after STZ administration. Erectile function, penile histology, and protein expression were analyzed 4 weeks after the injection of the adenoviruses.

MAIN OUTCOME MEASURES

Intracavernous pressure and mean arterial pressure were measured to evaluate erectile function. The morphology of the penis was analyzed by Elastica van Gieson stain and immunohistochemistry. The expression of α-smooth muscle actin (SMA), VE-cadherin and type I collagen was assessed by Western blot analysis.

RESULTS

Infection with AdAM plus AdAng-1 more effectively restored erectile function than infection with AdAM alone or AdAng-1 alone. This combination therapy restored erectile function to a level similar to that observed in the age-matched Wistar rats. Expression of SMA and VE-cadherin increased more significantly in the AdAM plus AdAng-1-treated group than in the AdAM- or AdAng-1-treated group. Although AdVEGF-A infection restored erectile function significantly, it also caused enlargement of the trabeculae of the cavernous body, aberrant angiogenesis, and overproduction of type I collagen.

CONCLUSIONS

These results suggested that combination therapy with AM and Ang-1 potently restored erectile function and normal morphology of the cavernous body compared with VEGF-A administration. This combination therapy will be useful to treat ED patients with a severely damaged cavernous body.

Adipocytes produce aldosterone through calcineurin-dependent signaling pathways: implications in diabetes mellitus-associated obesity and vascular dysfunction

We reported aldosterone as a novel adipocyte-derived factor that regulates vascular function. We aimed to investigate molecular mechanisms, signaling pathways, and functional significance of adipocyte-derived aldosterone and to test whether adipocyte-derived aldosterone is increased in diabetes mellitus-associated obesity, which contributes to vascular dysfunction. Studies were performed in the 3T3-L1 adipocyte cell line and mature adipocytes isolated from human and mouse (C57BL/6J) adipose tissue. Mesenteric arteries with and without perivascular fat and mature adipocytes were obtained from obese diabetic db/db and control db/+ mice. Aldosterone synthase (CYP11B2; mRNA and protein) was detected in 3T3-L1 and mature adipocytes, which secrete aldosterone basally and in response to angiotensin II (Ang II). In 3T3-L1 adipocytes, Ang II stimulation increased aldosterone secretion and CYP11B2 expression. Ang II effects were blunted by an Ang II type 1 receptor antagonist (candesartan) and inhibitors of calcineurin (cyclosporine A and FK506) and nuclear factor of activated T-cells (VIVIT). FAD286 (aldosterone synthase inhibitor) blunted adipocyte differentiation. In candesartan-treated db/db mice (1 mg/kg per day, 4 weeks) increased plasma aldosterone, CYP11B2 expression, and aldosterone secretion were reduced. Acetylcholine-induced relaxation in db/db mesenteric arteries containing perivascular fat was improved by eplerenone (mineralocorticoid receptor antagonist) without effect in db/+ mice. Adipocytes possess aldosterone synthase and produce aldosterone in an Ang II/Ang II type 1 receptor/calcineurin/nuclear factor of activated T-cells-dependent manner. Functionally adipocyte-derived aldosterone regulates adipocyte differentiation and vascular function in an autocrine and paracrine manner, respectively. These novel findings identify adipocytes as a putative link between aldosterone and vascular dysfunction in diabetes mellitus-associated obesity.

Back to your heart: ubiquitin proteasome system-regulated signal transduction

Awareness of the regulation of cell signaling by post-translational ubiquitination has emerged over the past 2 decades. Like phosphorylation, post-translational modification of proteins with ubiquitin can result in the regulation of numerous cellular functions, for example, the DNA damage response, apoptosis, cell growth, and the innate immune response. In this review, we discuss recently published mechanisms by which the ubiquitin proteasome system regulates key signal transduction pathways in the heart, including MAPK JNK, calcineurin, FOXO, p53, and estrogen receptors α and β. We then explore how ubiquitin proteasome system-specific regulation of these signal transduction pathways plays a role in the pathophysiology of common cardiac diseases, such as cardiac hypertrophy, heart failure, ischemia reperfusion injury, and diabetes. This article is part of a Special Section entitled "Post-translational Modification."

Adrenomedullin mediates adipose tissue-derived stem cell-induced restoration of erectile function in diabetic rats

INTRODUCTION

Erectile dysfunction (ED) is a major health problem. It is known that diabetic patients are more refractory to common treatments for ED.

AIM

To explore the better treatment for ED, we examined the effects of adipose-derived stem cells (ASC) on ED using a diabetic rat model. We also analyzed the cytokines produced by ASC and implicated in ASC-induced restoration of erectile function.

METHODS

Male Wistar rats were injected with streptozotocin (STZ) to induce diabetes. ASC or adenoviruses were injected into the penis 6 weeks after STZ administration. Erectile function, penile histology and protein expression were analyzed 4 weeks after the injection of ASC or adenoviruses.

MAIN OUTCOME MEASURES

Intracavernous pressure and mean arterial pressure were measured to evaluate erectile function. The morphology of the penis was analyzed by Elastica van Gieson stain and immunohistochemistry. The expression of proteins specific for vascular endothelial cells (VEC) was assessed by Western blot analysis.

RESULTS

ASC restored erectile function especially when they were cultured in medium containing growth factors for VEC. This restoration was associated with improvement in the histology of the cavernous body, and increased expression of VEC markers such as VE-cadherin and endothelial nitric oxide synthase (eNOS). When the expression of adrenomedullin (AM), a vasoactive peptide originally isolated from human pheochromocytoma tissue, was knocked down, the effect of ASC on ED was significantly diminished. Knockdown of AM was associated with decreased expressions of VE-cadherin and eNOS. Furthermore, overexpression of AM induced by adenovirus infection significantly improved erectile function in these diabetic rats. Overexpression of AM was associated with increased expressions of VE-cadherin and eNOS.

CONCLUSIONS

These results suggested that ASC have the potentials to restore erectile function and that AM produced by ASC plays a major role in the restoration of erectile function.

Regulator of calcineurin 1 mediates pathological vascular wall remodeling

Angiotensin-II–driven calcineurin activation and regulator of calcineurin-1 (Rcan-1) expression is required for pathological vascular remodeling in mice.

Artery wall remodeling, a major feature of diseases such as hypertension, restenosis, atherosclerosis, and aneurysm, involves changes in the tunica media mass that reduce or increase the vessel lumen. The identification of molecules involved in vessel remodeling could aid the development of improved treatments for these pathologies. Angiotensin II (AngII) is a key effector of aortic wall remodeling that contributes to aneurysm formation and restenosis through incompletely defined signaling pathways. We show that AngII induces vascular smooth muscle cell (VSMC) migration and vessel remodeling in mouse models of restenosis and aneurysm. These effects were prevented by pharmacological inhibition of calcineurin (CN) or lentiviral delivery of CN-inhibitory peptides. Whole-genome analysis revealed >1,500 AngII-regulated genes in VSMCs, with just 11 of them requiring CN activation. Of these, the most sensitive to CN activation was regulator of CN 1 (Rcan1). Rcan1 was strongly activated by AngII in vitro and in vivo and was required for AngII-induced VSMC migration. Remarkably, Rcan1^−/− mice were resistant to AngII-induced aneurysm and restenosis. Our results indicate that aneurysm formation and restenosis share mechanistic elements and identify Rcan1 as a potential therapeutic target for prevention of aneurysm and restenosis progression.

Captopril treatment induces hyperplasia but inhibits myonuclear accretion following severe myotrauma in murine skeletal muscle

The role of ANG II in skeletal muscle and satellite cell regulation is largely unknown. Cardiotoxin (CTX) was used to investigate whether muscle injury activates a local ANG II signaling system. Following injury, immunohistochelmistry (IHC) analysis revealed a robust increase in the intensity of angiotensinogen and angiotensin type 1 (AT1) receptor expression. As regeneration proceeded, however, AT1 and angiotensinogen were downregulated. Nuclear accretion and fiber formation were also assessed during muscle regeneration in mice treated with captopril (an angiotensin-converting enzyme inhibitor). When ANG II formation was blocked through the use of captopril, we observed a significantly reduced accretion of nuclei into myofibers (−25%), while tibialis anterior total fiber number was significantly increased +37%. This phenotype appeared to be due to alterations in satellite cell differentiation kinetics; captopril treatment led to sustained mRNA expression of markers associated with quiescence and proliferation (Myf5, Pax7) and simultaneously delayed or inhibited the expression of myogenin. IHC staining supported these findings, revealing that captopril treatment resulted in a strong trend ( P = 0.06) for a decrease in the proportion of myogenin-positive myoblasts. Furthermore, these observations were associated with a delay in muscle fiber maturation; captopril treatment resulted in sustained expression of embryonic myosin heavy chain. Collectively, these findings demonstrate that localized skeletal muscle angiotensin signaling is important to muscle fiber formation, myonuclear accretion, and satellite cell function.

Endothelin-1 contributes to increased NFATc3 activation by chronic hypoxia in pulmonary arteries

Chronic hypoxia (CH) activates the Ca(2+)-dependent transcription factor nuclear factor of activated T cells isoform c3 (NFATc3) in mouse pulmonary arteries. However, the mechanism of this response has not been explored. Since we have demonstrated that NFATc3 is required for CH-induced pulmonary arterial remodeling, establishing how CH activates NFATc3 is physiologically significant. The goal of this study was to test the hypothesis that endothelin-1 (ET-1) contributes to CH-induced NFATc3 activation. We propose that this mechanism requires increased pulmonary arterial smooth muscle cell (PASMC) intracellular Ca(2+) concentration ([Ca(2+)](i)) and stimulation of RhoA/Rho kinase (ROK), leading to calcineurin activation and actin cytoskeleton polymerization, respectively. We found that: 1) CH increases pulmonary arterial pre-pro-ET-1 mRNA expression and lung RhoA activity; 2) inhibition of ET receptors, calcineurin, L-type Ca(2+) channels, and ROK blunts CH-induced NFATc3 activation in isolated intrapulmonary arteries from NFAT-luciferase reporter mice; and 3) both ET-1-induced NFATc3 activation in isolated mouse pulmonary arteries ex vivo and ET-1-induced NFATc3-green fluorescence protein nuclear import in human PASMC depend on ROK and actin polymerization. This study suggests that CH increases ET-1 expression, thereby elevating PASMC [Ca(2+)](i) and RhoA/ROK activity. As previously demonstrated, elevated [Ca(2+)](i) is required to activate calcineurin, which dephosphorylates NFATc3, allowing its nuclear import. Here, we demonstrate that ROK increases actin polymerization, thus providing structural support for NFATc3 nuclear transport.

Selectivity and efficiency of late transgene expression by transcriptionally targeted oncolytic adenoviruses are dependent on the transgene insertion strategy

Key challenges facing cancer therapy are the development of tumor-specific drugs and potent multimodal regimens. Oncolytic adenoviruses possess the potential to realize both aims by restricting virus replication to tumors and inserting therapeutic genes into the virus genome, respectively. A major effort in this regard is to express transgenes in a tumor-specific manner without affecting virus replication. Using both luciferase as a sensitive reporter and genetic prodrug activation, we show that promoter control of E1A facilitates highly selective expression of transgenes inserted into the late transcription unit. This, however, required multistep optimization of late transgene expression. Transgene insertion via internal ribosome entry site (IRES), splice acceptor (SA), or viral 2A sequences resulted in replication-dependent expression. Unexpectedly, analyses in appropriate substrates and with matching control viruses revealed that IRES and SA, but not 2A, facilitated indirect transgene targeting via tyrosinase promoter control of E1A. Transgene expression via SA was more selective (up to 1,500-fold) but less effective than via IRES. Notably, we also revealed transgene-dependent interference with splicing. Hence, the prodrug convertase FCU1 (a cytosine deaminase-uracil phosphoribosyltransferase fusion protein) was expressed only after optimizing the sequence surrounding the SA site and mutating a cryptic splice site within the transgene. The resulting tyrosinase promoter-regulated and FCU1-encoding adenovirus combined effective oncolysis with targeted prodrug activation therapy of melanoma. Thus, prodrug activation showed potent bystander killing and increased cytotoxicity of the virus up to 10-fold. We conclude that armed oncolytic viruses can be improved substantially by comparing and optimizing strategies for targeted transgene expression, thereby implementing selective and multimodal cancer therapies.

Activation of NFAT signaling in podocytes causes glomerulosclerosis

Mutant forms of TRPC6 can activate NFAT-dependent transcription in vitro via calcium influx and activation of calcineurin. The same TRPC6 mutants can cause FSGS, but whether this involves an NFAT-dependent mechanism is unknown. Here, we generated mice that allow conditional induction of NFATc1. Mice with NFAT activation in nascent podocytes in utero developed proteinuria and glomerulosclerosis postnatally, resembling FSGS. NFAT activation in adult mice also caused progressive proteinuria and FSGS. Ultrastructural studies revealed podocyte foot process effacement and deposition of extracellular matrix. NFAT activation did not initially affect expression of podocin, synaptopodin, and nephrin but reduced their expression as glomerular injury progressed. In contrast, we observed upregulation of Wnt6 and Fzd9 in the mutant glomeruli before the onset of significant proteinuria, suggesting a potential role for Wnt signaling in the pathogenesis of NFAT-induced podocyte injury and FSGS. These results provide in vivo evidence for the involvement of NFAT signaling in podocytes, proteinuria, and glomerulosclerosis. Furthermore, this study suggests that NFAT activation may be a key intermediate step in the pathogenesis of mutant TRPC6-mediated FSGS and that suppression of NFAT activity may contribute to the antiproteinuric effects of calcineurin inhibitors.

Modulation of angiotensin II-mediated cardiac remodeling by the MEF2A target gene Xirp2

RATIONALE

The vasoactive peptide angiotensin II (Ang II) is a potent cardiotoxic hormone whose actions have been well studied, yet questions remain pertaining to the downstream factors that mediate its effects in cardiomyocytes.

OBJECTIVE

The in vivo role of the myocyte enhancer factor (MEF)2A target gene Xirp2 in Ang II-mediated cardiac remodeling was investigated.

METHODS AND RESULTS

Here we demonstrate that the MEF2A target gene Xirp2 (also known as cardiomyopathy associated gene 3 [CMYA3]) is an important effector of the Ang II signaling pathway in the heart. Xirp2 belongs to the evolutionarily conserved, muscle-specific, actin-binding Xin gene family and is significantly induced in the heart in response to systemic administration of Ang II. Initially, we characterized the Xirp2 promoter and demonstrate that Ang II activates Xirp2 expression by stimulating MEF2A transcriptional activity. To further characterize the role of Xirp2 downstream of Ang II signaling we generated mice harboring a hypomorphic allele of the Xirp2 gene that resulted in a marked reduction in its expression in the heart. In the absence of Ang II, adult Xirp2 hypomorphic mice displayed cardiac hypertrophy and increased beta myosin heavy chain expression. Strikingly, Xirp2 hypomorphic mice chronically infused with Ang II exhibited altered pathological cardiac remodeling including an attenuated hypertrophic response, as well as diminished fibrosis and apoptosis.

CONCLUSIONS

These findings reveal a novel MEF2A-Xirp2 pathway that functions downstream of Ang II signaling to modulate its pathological effects in the heart.

Regulatory polymorphism in transcription factor KLF5 at the MEF2 element alters the response to angiotensin II and is associated with human hypertension

Krüppel-like factor 5 (KLF5) is a zinc-finger-type transcription factor that mediates the tissue remodeling in cardiovascular diseases, such as atherosclerosis, restenosis, and cardiac hypertrophy. Our previous studies have shown that KLF5 is induced by angiotensin II (AII), although the precise molecular mechanism is not yet known. Here we analyzed regulatory single nucleotide polymorphisms (SNPs) within the KLF5 locus to identify clinically relevant signaling pathways linking AII and KLF5. One SNP was located at -1282 bp and was associated with an increased risk of hypertension: subjects with the A/A and A/G genotypes at -1282 were at significantly higher risk for hypertension than those with the G/G genotype. Interestingly, a reporter construct corresponding to the -1282G genotype showed much weaker responses to AII than a construct corresponding to -1282A. Electrophoretic mobility shift, chromatin immunoprecipitation, and reporter assays collectively showed that the -1282 SNP is located within a functional myocyte enhancer factor 2 (MEF2) binding site, and that the -1282G genotype disrupts the site and reduces the AII responsiveness of the promoter. Moreover, MEF2 activation via reactive oxygen species and p38 mitogen-activated protein kinase induced KLF5 expression in response to AII, and KLF5 and MEF2 were coexpressed in coronary atherosclerotic plaques. These results suggest that a novel signaling and transcription network involving MEF2A and KLF5 plays an important role in the pathogenesis of cardiovascular diseases such as hypertension.

Calmodulin kinase II is required for angiotensin II-mediated vascular smooth muscle hypertrophy

Despite our understanding that medial smooth muscle hypertrophy is a central feature of vascular remodeling, the molecular pathways underlying this pathology are still not well understood. Work over the past decade has illustrated a potential role for the multifunctional calmodulin-dependent kinase CaMKII in smooth muscle cell contraction, growth, and migration. Here we demonstrate that CaMKII is enriched in vascular smooth muscle (VSM) and that CaMKII inhibition blocks ANG II-dependent VSM cell hypertrophy in vitro and in vivo. Specifically, systemic CaMKII inhibition with KN-93 prevented ANG II-mediated hypertension and medial hypertrophy in vivo. Adenoviral transduction with the CaMKII peptide inhibitor CaMKIIN abrogated ANG II-induced VSM hypertrophy in vitro, which was augmented by overexpression of CaMKII-delta2. Finally, we identify the downstream signaling components critical for ANG II- and CaMKII-mediated VSM hypertrophy. Specifically, we demonstrate that CaMKII induces VSM hypertrophy by regulating histone deacetylase 4 (HDAC4) activity, thereby stimulating activity of the hypertrophic transcription factor MEF2. MEF2 transcription is activated by ANG II in vivo and abrogated by the CaMKII inhibitor KN-93. Together, our studies identify a complete pathway for ANG II-triggered arterial VSM hypertrophy and identify new potential therapeutic targets for chronic human hypertension.

Glycogen synthase kinase 3beta regulation of nuclear factor of activated T-cells isoform c1 in the vascular smooth muscle cell response to injury

The migration and proliferation of vascular smooth muscle cells (vSMCs) are critical events in neointima formation during atherosclerosis and restenosis. The transcription factor nuclear factor of activated T-cells-isoform c1 (NFATc1) is regulated by atherogenic cytokines, and has been implicated in the migratory and proliferative responses of vSMCs through the regulation of gene expression. In T-cells, calcineurin de-phosphorylates NFATc1, leading to its nuclear import, while glycogen synthase kinase 3 beta (GSK3beta) phosphorylates NFATc1 and promotes its nuclear export. However, the relationship between NFATc1 and GSK3beta has not been studied during SMC migration and proliferation. We investigated this by scrape wounding vSMCs in vitro, and studying wound repair. NFATc1 protein was transiently increased, reaching a peak at 8 h after wounding. Cell fractionation and immunocytochemistry revealed that NFATc1 accumulation in the nucleus was maximal at 4 h after injury, and this was coincident with a significant 9 fold increase in transcriptional activity. Silencing NFATc1 expression with siRNA or inhibition of NFAT with cyclosporin A (CsA) attenuated wound closure by vSMCs. Phospho-GSK3beta (inactive) increased to a peak at 30 min after injury, preceding the nuclear accumulation of NFATc1. Overexpression of a constitutively active mutant of GSK3beta delayed the nuclear accumulation of NFATc1, caused a 50% decrease in NFAT transcriptional activity, and attenuated vSMC wound repair. We conclude that NFATc1 promotes the vSMC response to injury, and that inhibition of GSK3beta is required for the activation of NFAT during wound repair.

Calcineurin is critical for sodium-induced neointimal formation in normotensive and hypertensive rats

It is well known that excessive intake of sodium chloride (sodium) is a risk factor for cardiovascular disease because it raises blood pressure. However, sodium loading reportedly promotes cardiovascular disease independently of its effect on blood pressure. To examine the mechanisms by which sodium loading promotes vascular inflammation independently of its effect on blood pressure, we examined the role of calcineurin in sodium loading-induced vascular inflammation using a wire injury model of the rat femoral artery. Calcineurin mRNA expression in the wire-injured femoral artery was significantly higher in sodium-loaded normotensive rats, such as Wistar-Kyoto (WKY) rats, than that in control WKY rats. Neointimal formation was also significantly enhanced in sodium-loaded WKY rats compared with control WKY rats. Gene transfer of an adenovirus expressing a dominant negative mutant of calcineurin (AdCalAΔC92Q) significantly suppressed neointimal formation in sodium-loaded WKY rats to a level similar to that observed in control WKY rats. Calcineurin expression and neointimal formation were more significantly enhanced in hypertensive rats, such as spontaneously hypertensive rats (SHRs), than those in control WKY rats. AdCalAΔC92Q infection significantly suppressed neointimal formation in SHRs to a level similar to that observed in control WKY rats. These results suggest that sodium loading promotes neointimal formation, even in normotensive rats, and that hypertension further stimulates neointimal formation. These results also suggest that calcineurin plays a pivotal role in this process.

Angiotensin II and tumor necrosis factor-alpha synergistically promote monocyte chemoattractant protein-1 expression: roles of NF-kappaB, p38, and reactive oxygen species

We examined whether ANG II and TNF-alpha cooperatively induce vascular inflammation using the expression of monocyte chemoattractant protein (MCP)-1 as a marker of vascular inflammation. ANG II and TNF-alpha stimulated MCP-1 expression in a synergistic manner in vascular smooth muscle cells. ANG II-induced MCP-1 expression was potently inhibited to a nonstimulated basal level by blockade of the p38-dependent pathway but only partially inhibited by blockade of the NF-kappaB-dependent pathway. In contrast, TNF-alpha-induced MCP-1 expression was potently suppressed by blockade of NF-kappaB activation but only modestly suppressed by blockade of p38 activation. ANG II- and TNF-alpha-induced activation of NF-kappaB- and p38-dependent pathways was partially inhibited by pharmacological inhibitors of ROS production. Furthermore, ANG II- and TNF-alpha-stimulated MCP-1 expression was partially suppressed by ROS inhibitors. We also examined whether endogenous ANG II and TNF-alpha cooperatively promote vascular inflammation in vivo using a wire injury model of the rat femoral artery. Blockade of both ANG II and TNF-alpha further suppressed neointimal formation, macrophage infiltration, and MCP-1 expression in an additive manner compared with blockade of ANG II or TNF-alpha alone. These results suggested that ANG II and TNF-alpha synergistically stimulate MCP-1 expression via the utilization of distinct intracellular signaling pathways (p38- and NFkappaB-dependent pathways) and that these pathways are activated in ROS-dependent and -independent manners. These results also suggest that ANG II and TNF-alpha cooperatively stimulate vascular inflammation in vivo as well as in vitro.

Role of sarco/endoplasmic reticulum calcium content and calcium ATPase activity in the control of cell growth and proliferation

Ca(2+), the main second messenger, is central to the regulation of cellular growth. There is increasing evidence that cellular growth and proliferation are supported by a continuous store-operated Ca(2+) influx. By controlling store refilling, the sarco/endoplasmic reticulum Ca(2+) ATPase (SERCA) also controls store-operated calcium entry and, thus, cell growth. In this review, we discuss data showing the involvement of SERCA in the regulation of proliferation and hypertrophy. First, we describe the Ca(2+)-related signaling pathways involved in cell growth. Then, we present evidence that SERCA controls proliferation of differentiated cells and hypertrophic growth of cardiomyocytes, and discuss the role of SERCA isoforms. Last, we consider the potential therapeutic applications of increasing SERCA activity for the treatment of cardiovascular diseases and of modulating SERCA and SR content for the treatment of cancer.

Myocyte enhancer factor 2B is involved in the inducible expression of NOX1/NADPH oxidase, a vascular superoxide-producing enzyme

NADPH oxidase is a major source of the superoxide produced in cardiovascular tissues. Expression of NOX1, a catalytic subunit of NADPH oxidase, is induced by various vasoactive factors, including angiotensin II, prostaglandin (PG) F(2alpha) and platelet-derived growth factor (PDGF). To clarify the molecular basis of this transcriptional activation, we delineated the promoter region of the NOX1 gene. RT-PCR and 5'-rapid amplification of cDNA ends-based analyses revealed a novel 5'-terminal exon of the rat NOX1 gene located approximately 28 kb upstream of the exon containing the start codon. Both PGF(2alpha) and PDGF enhanced the transcriptional activity of the - 3.6 kb 5'-flanking region of the NOX1 gene in A7r5 cells, a rat vascular smooth muscle cell line. A PGF(2alpha)-response element was located between -146 and -125 in the 5'-flanking region containing a consensus binding site for myocyte enhancer factor 2 (MEF2), to which binding of MEF2 was augmented by PGF(2alpha). Gene silencing of MEF2B by RNA interference significantly suppressed the expression of NOX1, while silencing of activating transcription factor (ATF)-1, previously implicated in up-regulation of NOX1, abolished the PGF(2alpha)- or PDGF-induced expression of MEF2B. These results indicate that superoxide production in vascular smooth muscle cells is regulated by the ATF-1-MEF2B cascade by induction of the expression of the NOX1 gene.

Mutation of delta-sarcoglycan is associated with Ca(2+) -dependent vascular remodeling in the Syrian hamster

We examined whether mutation of the delta-sarcoglycan gene, which causes dilated cardiomyopathy, also alters the vascular smooth muscle cell (VSMC) phenotype and arterial function in the Syrian hamster CHF 147. Thoracic aorta media thickness showed marked variability in diseased hamsters with zones of atrophy and hypertrophied segments. CHF-147 VSMCs displayed a proliferating/"synthetic" phenotype characterized by the absence of the smooth muscle myosin heavy chain SM2, dystrophin, and Ca(2+)-handling proteins, and the presence of cyclin D1. In freshly isolated VSMCs from CHF 147 hamsters, voltage-independent basal Ca(2+) channels showed enhanced activity similar to that in proliferating wild-type (WT) cells. The transcription factor NFAT (nuclear factor of activated T cells) was spontaneously active in freshly isolated CHF 147 VSMCs, as in proliferating VSMCs from WT hamsters. Mibefradil inhibited B-type channels, NFAT activity, and VSMC proliferation. CHF 147 hamsters had abundant apoptotic cells distributed in patches along the aorta, and clusters of inactive mitochondria were observed in 25% of isolated CHF 147 cells, whereas no such clusters were seen in WT cells. In conclusion, mutation of the delta-sarcoglycan gene increases plasma membrane permeability to Ca(2+), activates the Ca(2+)-regulated transcription factor NFAT, and leads to spontaneous mitochondrial aggregation, causing abnormal VSMC proliferation and apoptosis.

Xanthine oxidase-derived extracellular superoxide anions stimulate activator protein 1 activity and hypertrophy in human vascular smooth muscle via c-Jun N-terminal kinase and p38 mitogen-activated protein kinases

OBJECTIVE

Vascular xanthine oxidase (XO) activity has been found to be elevated in chronic vascular disease. Although a role for XO in endothelial dysfunction has been proposed, little is known about its influence on vascular smooth muscle maladaptive growth.

METHODS

The proliferative and hypertrophic response of human aortic smooth muscle cells (HASMC) stimulated with xanthine/xanthine oxidase (X/XO) was quantified by determining cell number, cell size and protein synthesis. The levels and activity of the growth-related transcription factor activator protein 1 (AP-1) and the activation of mitogen-activated protein kinase (MAPK) by X/XO were determined by either Western blot or transient transfection experiments.

RESULTS

X/XO did not affect HASMC proliferation, but led to enhanced planar cell surface area and protein synthesis. In addition, X/XO enhanced c-jun levels and AP-1 transcriptional activity. Although X/XO did not modify extracellular signal-regulated protein kinases 1/2 MAPK or Akt/PKB activity, it promoted the activation of c-Jun N-terminal kinase and p38 MAPK, which were both necessary for X/XO to increase AP-1 activity and cell size in HASMC cultures. Finally, the effects of X/XO on MAPK activation, AP-1 activity and cell size were dependent on the extracellular release of superoxide anions through the enzymatic activity of XO, as they were prevented by both superoxide dismutase and allopurinol.

CONCLUSION

X/XO exhibits hypertrophic properties for human vascular smooth muscle, which are mediated by redox-sensitive pathways involving MAPK activation. XO can therefore participate in the maladaptive vascular remodeling observed in chronic cardiovascular diseases exhibiting elevated vascular XO activity.

Novel blocker of NFAT activation inhibits IL-6 production in human myometrial arteries and reduces vascular smooth muscle cell proliferation

The calcineurin/nuclear factor of activated T cells (NFAT) signaling pathway has been found to play a role in regulating growth and differentiation in several cell types. However, the functional significance of NFAT in the vasculature is largely unclear. Here we show that NFATc1, NFATc3, and NFATc4 are expressed in human myometrial arteries. Confocal immunofluorescence and Western blot analysis revealed that endothelin-1 efficiently increases NFATc3 nuclear accumulation in native arteries. Endothelin-1 also stimulates NFAT-dependent transcriptional activity, as shown by a luciferase reporter assay. Both the agonist-induced NFAT nuclear accumulation and transcriptional activity were prevented by the calcineurin inhibitor CsA and by the novel NFAT blocker A-285222. Chronic inhibition of NFAT significantly reduced IL-6 production in intact myometrial arteries and inhibited cell proliferation in vascular smooth muscle cells cultured from explants from the same arteries. Furthermore, by using small interfering RNA-mediated reduction of NFATc3, we show that this isoform is involved in the regulation of cell proliferation. Protein synthesis in intact arteries was investigated using autoradiography of [(35)S]methionine incorporation in serum-free culture. Inhibition of NFAT signaling did not affect overall protein synthesis or specifically the synthesis rates of major proteins associated with the contractile/cytoskeletal system. An intact contractile phenotype under these conditions was also shown by unchanged force response to depolarization or agonist stimulation. Our results demonstrate NFAT expression and activation in native human vessels and point out A-285222 as a powerful pharmacological blocker of NFAT signaling in the vasculature.

An emerging role for calcineurin Aalpha in the development and function of the kidney

For many years, calcineurin has been a familiar molecule as a target of the immunosuppressive agents cyclosporin A and FK-506. Calcineurin inhibition interferes with T cell signaling by preventing activation of the transcription factor NFATc. However, calcineurin is expressed in most tissues in the body, and calcineurin inhibition undoubtedly alters many other cellular processes. As a result, serious side effects of calcineurin inhibitors regularly occur, including hypertension and renal dysfunction. Because nephrotoxicity is often a barrier to continued clinical use of calcineurin inhibitors, understanding the role of calcineurin in the kidney is of particular importance. Recent work has demonstrated that the two main isoforms of the catalytic subunit of calcineurin, Aalpha and Abeta, may have distinct functions, particularly in the kidney. Calcineurin isoforms may be differentially expressed, and/or the activity of each may be differentially regulated, leading to tissue-specific functions. Differences between the action of the two isoforms are most evident in knockout mice lacking each isoform. Mice lacking the beta-isoform are characterized principally by altered development and function of immune cells. alpha-Knockout mice, in contrast, can still be immune suppressed by cyclosporin A but display pervasive developmental defects, including renal dysfunction. Therefore, it is intriguing to consider that while the beta-isoform may be responsible for calcineurin action in T cells, the alpha-isoform may be the predominant catalytic isoform in the kidney. This conclusion, if correct, may have substantial clinical implication for novel strategies to selectively target calcineurin action in T cells without associated nephrotoxicity.

Transcription of the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase type 3 gene, ATP2A3, is regulated by the calcineurin/NFAT pathway in endothelial cells

Histamine, known to induce Ca2+ oscillations in endothelial cells, was used to alter Ca2+ cycling. Treatment of HUVEC (human umbilical-vein endothelial cell)-derived EA.hy926 cells with histamine for 1-3 days increased the levels of SERCA (sarcoplasmic/endoplasmic reticulum Ca2+-ATPase) 3, but not of SERCA 2b, transcripts and proteins. Promoter-reporter gene assays demonstrated that this increase in expression was due to activation of SERCA 3 gene transcription. The effect of histamine was abolished by mepyramine, but not by cimetidine, indicating that the H1 receptor, but not the H2 receptor, was involved. The histamine-induced up-regulation of SERCA 3 was abolished by cyclosporin A and by VIVIT, a peptide that prevents calcineurin and NFAT (nuclear factor of activated T-cells) from interacting, indicating involvement of the calcineurin/NFAT pathway. Histamine also induced the nuclear translocation of NFAT. NFAT did not directly bind to the SERCA 3 promoter, but activated Ets-1 (E twenty-six-1), which drives the expression of the SERCA 3 gene. Finally, cells treated with histamine and loaded with fura 2 exhibited an improved capacity in eliminating high cytosolic Ca2+ concentrations, in accordance with an increase in activity of a low-affinity Ca2+-ATPase, like SERCA 3. Thus chronic treatment of endothelial cells with histamine up-regulates SERCA 3 transcription. The effect of histamine is mediated by the H1R (histamine 1 receptor) and involves activation of the calcineurin/NFAT pathway. By increasing the rate of Ca2+ sequestration, up-regulation of SERCA 3 counteracts the cytosolic increase in Ca2+ concentration.

Convergence of protein kinase C and JAK-STAT signaling on transcription factor GATA-4

Angiotensin II (AII), a potent vasoactive hormone, acts on numerous organs via G-protein-coupled receptors and elicits cell-specific responses. At the level of the heart, AII stimulation alters gene transcription and leads to cardiomyocyte hypertrophy. Numerous intracellular signaling pathways are activated in this process; however, which of these directly link receptor activation to transcriptional regulation remains undefined. We used the atrial natriuretic factor (ANF) gene (NPPA) as a marker to elucidate the signaling cascades involved in AII transcriptional responses. We show that ANF transcription is activated directly by the AII type 1 receptor and precedes the development of myocyte hypertrophy. This response maps to STAT and GATA binding sites, and the two elements transcriptionally cooperate to mediate signaling through the JAK-STAT and protein kinase C (PKC)-GATA-4 pathways. PKC phosphorylation enhances GATA-4 DNA binding activity, and STAT-1 functionally and physically interacts with GATA-4 to synergistically activate AII and other growth factor-inducible promoters. Moreover, GATA factors are able to recruit STAT proteins to target promoters via GATA binding sites, which are sufficient to support synergy. Thus, STAT proteins can act as growth factor-inducible coactivators of tissue-specific transcription factors. Interactions between STAT and GATA proteins may provide a general paradigm for understanding cell specificity of cytokine and growth factor signaling.

Transcriptomic profiling of the canine tachycardia-induced heart failure model: global comparison to human and murine heart failure

Alterations of cardiac gene expression are central to ventricular dysfunction in human heart failure (HF). The canine tachycardia pacing-induced HF model is known to reproduce the main hemodynamic, echocardiographic and electrophysiological changes observed in human HF. In this study, we use this HF model to compare gene expression profiles in the left and right ventricles (LV, RV) of normal and end-stage failing canine hearts and compare the transcription profiles to those in human and murine models of HF. In end-stage HF, the LV exhibits down regulation of genes involved in energy production, cardiac contraction, and modulation of excitation-contraction coupling as compared with normal LV. The majority of transcriptomic changes between normal and end-stage canine HF were shared by the RV and LV. Genes down regulated only in the LV included those involved in aerobic energy production pathways, regulation of actin filament length, and enzyme-linked receptor protein signaling pathways. In normal canine hearts, genes encoding specific components of the contractile apparatus exhibit LV-RV asymmetric expression patterns; in failing hearts, cardiac fetal transcription factors MEF2 and MITF and the stress-responsive transcription factor ATF4 showed interventricular differences in expression. The comparison among the canine tachypacing, mouse transgenic, and human HF reveals that human disease involves down regulation of genes in a broad range of biological processes while experimentally induced HF is associated with down regulation of energy pathways, and that human ischemic HF and canine HF share a similar over representation of transcriptional pathways in the up regulated genes. This study provides insights into the molecular pathways leading to end-stage tachycardia-induced HF, and into global transcriptomic differences between the animal HF models and human HF.

Sarco/endoplasmic reticulum Ca2+-ATPase gene transfer reduces vascular smooth muscle cell proliferation and neointima formation in the rat

Proliferation of vascular smooth muscle cells (VSMC) is a primary cause of vascular disorders and is associated with major alterations in Ca2+ handling supported by loss of the sarco/endoplasmic reticulum calcium ATPase, SERCA2a. To determine the importance of SERCA2a in neointima formation, we have prevented loss of its expression by adenoviral gene transfer in a model of balloon injury of the rat carotid artery. Two weeks after injury, the intima/media ratio was significantly lower in SERCA2a-infected than in injured noninfected or injured beta-galactosidase-infected carotids (0.29+/-0.04 versus 0.89+/-0.19 and 0.72+/-0.14, respectively; P<0.05), and was comparable to that observed in control carotids (0.21+/-0.03). The pathways leading to proliferation were analyzed in serum-stimulated VSMC. Forced expression of SERCA2a arrested cell cycle at the G1 phase and prevented apoptosis. SERCA2a inhibits proliferation through inactivation of calcineurin (PP2B) and its target transcription factor NFAT (nuclear factor of activated T-cells) resulting in lowering of cyclin D1 and pRb levels. By using NFAT-competing peptide VIVIT, we showed that NFAT activity is strongly required to promote VSMC proliferation. In conclusion, we provide the first evidence that increasing SERCA2a activity inhibits VSMC proliferation and balloon injury-induced neointima formation.

Heritability and a Genome-Wide Linkage Scan for Arterial Stiffness, Wave Reflection, and Mean Arterial Pressure

Background— Arterial stiffness and mean arterial pressure variably contribute to systolic hypertension and increased cardiovascular risk. However, few prior community-based studies have evaluated the genetics of arterial stiffness and separate mean and pulsatile components of blood pressure.

Methods and Results— Using arterial tonometry, we evaluated heritability and linkage of forward and reflected wave amplitude, mean arterial pressure, and carotid-femoral pulse wave velocity (CFPWV) in 1480 participants representing 817 pedigrees in the Framingham Study offspring cohort. In 204 families with tonometry data, a genome-wide scan was performed with microsatellite markers that covered the genome at 10-cM intervals. Heritability estimates were moderate for reflected wave amplitude (h 2 =0.48), forward wave amplitude (h 2 =0.21), CFPWV (h 2 =0.40), and mean arterial pressure (h 2 =0.33). Variance components linkage analysis identified 2 regions of linkage for reflected wave amplitude: chromosome 4 at 181 cM (logarithm of odds [LOD]=4.93, permuted P =0.002) and chromosome 8 at 33 cM (LOD=3.27, permuted P =0.058). There was 1 region of linkage for forward wave amplitude on chromosome 7 at 174 cM (LOD=2.88, permuted P =0.017). There were several regions of suggestive linkage for CFPWV: chromosome 2 at 94 cM (LOD=2.46), chromosome 7 at 29 cM (LOD=2.50), chromosome 13 at 108 cm (LOD=2.10), and chromosome 15 at 108 cM (LOD=2.48). There was 1 region of suggestive linkage for mean arterial pressure on chromosome 1 at 192 cM (LOD=2.18).

Conclusions— Arterial stiffness measures and mean and pulsatile components of blood pressure are heritable and appear to have genetic determinants that may be linked to separate genetic loci in humans.

Conversion From Cyclosporine Microemulsion to Tacrolimus-Based Immunoprophylaxis Improves Cholesterol Profile in Heart Transplant Recipients With Treated but Persistent Dyslipidemia: The Canadian Multicentre Randomized Trial of Tacrolimus vs Cyclosporine Microemulsion

BACKGROUND

Tacrolimus improves lipid profile in renal and liver transplant recipients. The impact of conversion from cyclosporine microemulsion (Neoral) to tacrolimus (Prograf) in a large randomized study of stable heart transplant recipients with treated but persistent mild dyslipidemia is reported.

METHODS

One hundred twenty-nine long-term (>or=12 months) cyclosporine microemulsion-treated heart transplant recipients with low-density lipoprotein cholesterol >2.5 mmol/liter and/or a total cholesterol/high-density lipoprotein cholesterol ratio >4 were recruited for the study. Complete lipid profile was assessed before (baseline) and after 6 months of treatment with either cyclosporine microemulsion maintenance (n=64) or tacrolimus conversion (n=65).

RESULTS

At 6 months, tacrolimus-converted patients exhibited a greater decrease in total cholesterol (from 5.51 +/- 0.16 to 4.88 +/- 1.22 mmol/liter [tacrolimus], vs 5.61 +/- 1.36 to 5.38 +/- 0.87 mmol/liter [cyclosporine]; p = 0.0078). This decrease in cholesterol was caused largely by a decrease in low-density lipoprotein cholesterol (-0.41 +/- 0.54 [tacrolimus] vs -0.13 +/- 0.55 [cyclosporine]; p=0.0018). There were no changes in high-density lipoprotein cholesterol and triglyceride levels, but apolipoprotein B therapy was reduced in tacrolimus-converted vs cyclosporine-maintained patients (p=0.0003). By 6 months, 23.7% of tacrolimus- vs 6.7% of cyclosporine-treated patients met the target lipid levels for high-risk patients (p=0.0094). Conversion from cyclosporine to tacrolimus resulted in decreases in blood urea nitrogen, creatinine, and uric acid without any changes in glucose, HbA(1C), and insulin levels.

CONCLUSIONS

Conversion from cyclosporine microemulsion- to tacrolimus-based immunoprophylaxis resulted in decreased cholesterol, apolipoprotein B, urea, creatinine, and uric acid without any clinically evident perturbation of glucose metabolism in stable heart transplant recipients with treated but persistent mild dyslipidemia.

Regulation of intracellular Ca2+ and calcineurin by NO/PKG in proliferation of vascular smooth muscle cells

AIM

To determine whether Ca2+/calcineurin mediated the inhibitory effects of nitric oxide /cGMP-dependent protein kinase (NO/PKG) on the proliferation of vascular smooth muscle cells (VSMC).

METHODS

Proliferation and viability of primary VSMC from rat aorta were measured using [3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) assay and acridine orange and ethidium bromide staining, respectively. Cytosolic Ca2+ was determined by Fluo-3/AM. Calcineurin protein and its activity were assayed using immunoblotting and free inorganic phosphate analysis, respectively.

RESULTS

(+/-)-S-nitroso-N-acetyl-penicillamine (SNAP) and Sp-8-(4-chlorophenylthio)-guanosine-3',5'-cyclic monophosphorothioate (Sp-8-pCPT-cGMPS) decreased phenylephrine (PE)-induced proliferation of VSMC by 27.3% and 36.6%, respectively, but Rp-8-[(4-chlorophenyl)thio]-guanosine-3',5'-cyclic monophosphorothioate (Rp-8-pCPT-cGMPS) increased PE-induced proliferation of VSMC. SNAP, Sp-8-pCPT-cGMPS, and Rp-8-pCPT-cGMPS did not affect the viability of VSMC. Calcineurin protein was decreased by 63.1% and its activity was decreased by 59.7% in smooth muscle cells (SMC) pretreated with verapamil (Ver) and then stimulated by PE. In SMC pretreated with Ver, the absorbance of cells stimulated by PE decreased by 22.0% and was further inhibited by the additional treatment of SNAP and Sp-8-pCPT-cGMPS. In SMC pretreated with cyclosporin A (CsA), the absorbance of cells stimulated by PE decreased by 36.7%, but could not be further altered by the additional treatment of SNAP, Sp-8-pCPT-cGMPS, and Rp-8-pCPT-cGMPS. In addition, Ver inhibited PE-induced intracellular Ca2+ variations, which could be further inhibited by SNAP and Sp-8-pCPT-cGMPS, but not by Rp-8-pCPT-cGMPS. Moreover, the increase in calcineurin activity induced by PE was inhibited by SNAP and Sp-8-pCPT-cGMPS, but was promoted by Rp-8-pCPT-cGMPS.

CONCLUSION

NO/PKG regulates calcineurin activity via the modulation of intracellular Ca2+ concentration, and thus partially inhibits the proliferation of VSMC without affecting their viability.

Identification of calcium-modulating cyclophilin ligand (CAML) as transducer of angiotensin II-mediated nuclear factor of activated T cells (NFAT) activation

Angiotensin II (Ang II) plays a central role in cardiovascular physiology and disease. Ang II type I receptor (AT1) is thought to mediate most actions of Ang II. A novel AT1 receptor intracellular partner called AT1 receptor-associated protein (ATRAP) was identified, but its exact function has not been elucidated. A yeast two-hybrid screen using ATRAP as bait identified calcium-modulating cyclophilin ligand (CAML) as an ATRAP partner. Yeast two-hybrid and coimmunoprecipitation analysis demonstrated that the N-terminal hydrophilic domain of CAML (amino acids (aa) 1-189) mediates a specific interaction between ATRAP and CAML. Our analysis also showed that aa 40-82 of ATRAP contribute to this interaction. Bioluminescence resonance energy transfer and intracellular colocalization analysis by immunofluorescence in HEK293 cells verified this association within endoplasmic reticulum vesicular structures. Functionally, transcriptional reporter assays and RNA interference ATRAP experiments demonstrated that ATRAP knockdown increased nuclear factor of activated T cells (NFAT) activity. Overexpression of ATRAP decreased Ang II- or CAML-induced NFAT transcriptional activation, whereas an ATRAP-interacting domain of CAML (aa 1-189) sensitized NFAT activation in response to Ang II. These results indicate that CAML is an important signal transducer for the actions of Ang II in regulating the calcineurin-NFAT pathway and suggest that the interaction of CAML with ATRAP may mediate the Ang II actions in vascular physiology.

Calcineurin A-alpha but not A-beta is required for normal kidney development and function

Calcineurin is an important signaling molecule in the kidney and may be involved in a variety of processes. The phosphatase subunit of calcineurin (CnA) has three isoforms, alpha, beta, and gamma. In this study, we investigated the effect of loss of calcineurin A-alpha (CnA-alpha) or calcineurin A-beta (CnA-beta) on the development and function of the kidney. Total calcineurin expression and activity was significantly reduced in whole kidney homogenates from both CnA-alpha -/- and CnA-beta -/- mice. Kidneys of CnA-beta -/- mice appear normal and the mice develop with no phenotypic abnormalities. In contrast, kidneys of CnA-alpha -/- animals fail to fully develop. In particular, postnatal maturation of the nephrogenic zone (NZ) is defective. Within the NZ, glomeruli also fail to mature and lack mesangial cells. In addition to alterations in development, there is an absence of proliferation and an increase of cell death in the NZ with loss of CnA-alpha. Finally, increased collagen deposition is observed and serum creatinine levels are significantly increased in CnA-alpha -/- animals compared to wild-type littermates, indicating that kidney function is impaired. In summary, absence of CnA-alpha but not CnA-beta leads to a defect in normal maturation of the NZ and glomeruli, alterations in the cell cycle, and impaired kidney function.

NFATc3 Regulates Kv2.1 Expression in Arterial Smooth Muscle

Voltage-gated K+ (Kv) channels control the excitability of arterial smooth muscle. However, the molecular mechanisms regulating Kv channel function in smooth muscle remain unclear. We examined the hypothesis that the vasoactive peptide angiotensin II (Ang II) regulates arterial smooth muscle Kv channel function via calcineurin-dependent activation of the transcription factor NFAT. We found that sustained administration of Ang II decreased Kv currents (IKv) by reducing the expression of Kv2.1 K+ channel subunits. This effect of Ang II was independent of pressure but required Ca2+ influx through L-type Ca2+ channels. Consistent with our hypothesis, we found that calcineurin and NFATc3 are obligatory components of the signaling cascade mediating reduced IKv by Ang II. We conclude that sustained Ang II exposure increases smooth muscle Ca2+, which leads to activation of calcineurin and NFATc3, culminating in decreased Kv2.1 expression and reduced IKv function. These results support the novel concept that NFATc3 controls the excitability of arterial smooth muscle by regulating Kv2.1 expression.

Genome-Wide Scan for Pulse Pressure in the National Heart, Lung and Blood Institute’s Framingham Heart Study

The objective of this study was to assess heritability and identify chromosomal regions showing evidence of linkage to pulse pressure (PP), a simple indicator of proximal conduit vessel stiffness. Blood pressure data were analyzed for 8478 members of the National Heart, Lung and Blood Institute's (NHLBI) Framingham Heart Study. Long-term PP was defined using 2-stage analysis. First, the difference between systolic and diastolic blood pressure was averaged over all qualifying clinic examinations. In the second stage, mean PP was adjusted for mean age, time period of examination, and body mass index by regression analysis. PP values were available for 6421 individuals in 1593 families for heritability estimation and for 2492 individuals in 330 families for linkage analysis. Microsatellite markers covering the genome at 10 cM intervals were typed by the NHLBI Mammalian Genotyping Service; genome scan data were available on 1585 individuals with PP data. Heritability estimates of long-term PP accounting for hypertension treatment and for ignoring treatment were 0.52 and 0.51, respectively. Variance component linkage analysis identified several locations with suggestive evidence of linkage: chromosome 15 at 122 cM (logarithm of odds [LOD]=2.94), chromosome 7 at 71 cM (LOD=2.42), chromosome 5 at 53 cM (LOD=2.03), and chromosome 10 at 81 cM (LOD=1.83) for PP accounting for treatment. LOD scores were slightly lower when ignoring treatment, with the exception of a peak on chromosome 10 at 81 cM (LOD=2.58). In conclusion, we have demonstrated a substantial genetic component to PP and have identified 4 chromosomal regions that may harbor genes influencing vascular stiffness.

A ternary complex of transcription factors, Nishéd and NFATc4, and co-activator p300 bound to an intronic sequence, intronic regulatory element, is pivotal for the up-regulation of myosin light chain-2v gene in cardiac hypertrophy

Transcriptional up-regulation of the myosin light chain-2 (MLC-2v) gene is an established marker for hypertrophic response in cardiomyocytes. Despite the documentation on the role of several cis-elements in the MLC-2v gene and their cognate proteins in transcription, the mechanism that dictates the preferential increase in MLC-2v gene expression during myocardial hypertrophy has not been delineated. Here we describe the properties of a cardiac specific intronic activator element (IRE) that shares sequence homology with the repressor element, the cardiac specific sequence, in the chicken MLC-2v gene. The transcription factor, Nishéd, that recognizes both IRE and the cardiac specific sequence potentiates the transcription of the MLC-2v gene via interaction with another transcription factor, nuclear factor of activated T cells, and the co-activator p300 at the IRE site. Angiotensin II (Ang II), a potent agonist of hypertrophy, causes induction of the MLC-2v gene transcription, which correlates well with the enhanced binding of Nishéd-nuclear factor of the activated T cells-p300 complex to IRE in the gel mobility shift assay. Losartan, an antagonist of Ang II receptor (AT1), abolishes the agonist-dependent stimulation of IRE/protein interaction and the consequent increase in MLC-2v gene transcription. These results together have thus established a transcriptional role of IRE as a direct target sequence of Ang II-mediated signaling that appears to be pivotal in the mechanism underlying the up-regulation of the MLC-2v gene during cardiac hypertrophy.

Myocyte Enhancer Factor 2 Mediates Vascular Inflammation via the p38-Dependent Pathway

Although it has been established that myocyte enhancer factor 2 (MEF2) plays pivotal roles in the development of the cardiovascular system as well as skeletal muscle cells, little is known of its role in vascular inflammatory diseases such as atherosclerosis and restenosis after angioplasty. To investigate the role of MEF2 in vascular inflammation and that of p38 in the activation of MEF2, we infected cultured rat vascular smooth muscle cells (VSMCs) with an adenovirus construct expressing a dominant-negative mutant of MEF2A (MEF2ASA) or mitogen-activated protein kinase kinase 6 (MEK6AA), and examined their effects on the expression of monocyte chemoattractant protein-1 (MCP-1), which is known to play important roles in vascular inflammation. We also examined the role of MEF2 in vivo using a rat model of transluminal wire-induced injury of the femoral artery. Angiotensin II (Ang II)–induced expression of MCP-1 mRNA was significantly inhibited by infection with adenoviruses encoding MEF2ASA (AdMEF2ASA) or MEK6AA. Ang II–induced increase of MCP-1 promoter activity was also significantly suppressed by overexpression of MEF2ASA or MEK6AA. Ang II stimulated the transactivating function of MEF2A and this activation was inhibited by overexpression of MEK6AA. Infection with AdMEF2ASA suppressed MCP-1 expression in the femoral artery after the transluminal mechanical injury. AdMEF2ASA infection also inhibited macrophages infiltration and neointimal formation in the wire-injured femoral arteries. These results suggested that MEF2 activation via the p38-dependent pathway mediates vascular inflammation via stimulation of MCP-1 expression in VSMCs and macrophages infiltration.