Zhou-Yan Bian

Regulator of G protein signaling 5 protects against cardiac hypertrophy and fibrosis during biomechanical stress of pressure overload

The development of cardiac hypertrophy in response to increased hemodynamic load and neurohormonal stress is initially a compensatory response that may eventually lead to ventricular dilation and heart failure. Regulator of G protein signaling 5 (Rgs5) is a negative regulator of G protein-mediated signaling by inactivating Gα(q) and Gα(i), which mediate actions of most known vasoconstrictors. Previous studies have demonstrated that Rgs5 expresses among various cell types within mature heart and showed high levels of Rgs5 mRNA in monkey and human heart tissue by Northern blot analysis. However, the critical role of Rgs5 on cardiac remodeling remains unclear. To specifically determine the role of Rgs5 in pathological cardiac remodeling, we used transgenic mice with cardiac-specific overexpression of human Rgs5 gene and Rgs5−/− mice. Our results demonstrated that the transgenic mice were resistant to cardiac hypertrophy and fibrosis through inhibition of MEK-ERK1/2 signaling, whereas the Rgs5−/− mice displayed the opposite phenotype in response to pressure overload. These studies indicate that Rgs5 protein is a crucial component of the signaling pathway involved in cardiac remodeling and heart failure.

Role of Interferon Regulatory Factor 4 in the Regulation of Pathological Cardiac Hypertrophy

IRF4, a member of the interferon regulatory factor (IRF) family, was previously shown to be restricted in the immune system and involved in the differentiation of immune cells. However, we interestingly observed that IRF4 was also highly expressed in both human and animal hearts. Given that several transcription factors have been shown to regulate the pathological cardiac hypertrophy, we then ask whether IRF4, as a new transcription factor, plays a critical role in pressure overload–elicited cardiac remodeling. A transgenic mouse model with cardiac-specific overexpression of IRF4 was generated and subjected to an aortic banding for 4 to 8 weeks. Our results demonstrated that overexpression of IRF4 aggravated pressure overload–triggered cardiac hypertrophy, fibrosis, and dysfunction. Conversely, IRF4 knockout mice showed an attenuated hypertrophic response to chronic pressure overload. Mechanistically, we discovered that the expression and activation of cAMP response element–binding protein (CREB) were significantly increased in IRF4-overexpressing hearts, while being greatly reduced in IRF4-KO hearts on aortic banding, compared with control hearts, respectively. Similar results were observed in ex vivo cultured neonatal rat cardiomyocytes on the treatment with angiotensin II. Inactivation of CREB by dominant-negative mutation (dnCREB) offset the IRF4-mediated hypertrophic response in angiotensin II–treated myocytes. Furthermore, we identified that the promoter region of CREB contains 3 IRF4 binding sites. Altogether, these data indicate that IRF4 functions as a necessary modulator of hypertrophic response by activating the transcription of CREB in hearts. Thus, our study suggests that IRF4 might be a novel target for the treatment of pathological cardiac hypertrophy and failure.

Mineralized Tissue Formation by BMP2-transfected Pulp Stem Cells

Previously, in vitro differentiation of odontoblasts was shown for dental pulp stem cells (DPSCs) transfected with bone morphogenetic protein-2 (Bmp2). For this study, we hypothesized that such cells also show potential for mineralized tissue formation in vivo. DPSCs were transfected with Bmp2 and seeded onto a ceramic scaffold. These complexes were cultured in medium without dexamethasone, and thereafter placed subcutaneously in nude mice for 1, 4, and 12 weeks. Samples were evaluated by histology and real-time PCR for osteocalcin, bone sialoprotein, dentin sialophosphoprotein, and dentin matrix protein 1. Results indicated that only the transfected DPSCs showed obvious mineralized tissue generation, and 12 weeks of implantation gave the highest percentage of mineralized tissue formation (33 ± 7.3% of implant pore area). Real-time PCR confirmed these results. In conclusion, Bmp2-transfected DPSCs effectively show mineralized tissue formation upon ectopic implantation.

Lysosomal cysteine peptidase cathepsin L protects against cardiac hypertrophy through blocking AKT/GSK3β signaling

The lysosomal cysteine peptidase cathepsin L (CTSL) is an important lysosomal proteinase involved in a variety of cellular functions including intracellular protein turnover, epidermal homeostasis, and hair development. Deficiency of CTSL in mice results in a progressive dilated cardiomyopathy. In the present study, we tested the hypothesis that cardiac overexpression of human CTSL in the murine heart would protect against cardiac hypertrophy in vivo. The effects of constitutive human CTSL expression on cardiac hypertrophy were investigated using in vitro and in vivo models. Cardiac hypertrophy was produced by aortic banding (AB) in CTSL transgenic mice and control animals. The extent of cardiac hypertrophy was quantitated by two-dimensional and M-mode echocardiography as well as by molecular and pathological analyses of heart samples. Constitutive overexpression of human CTSL in the murine heart attenuated the hypertrophic response, markedly reduced apoptosis, and fibrosis. Cardiac function was also preserved in hearts with increased CTSL levels in response to hypertrophic stimuli. These beneficial effects were associated with attenuation of the Akt/GSK3β signaling cascade. Our in vitro studies further confirmed that CTSL expression in cardiomyocytes blunts cardiac hypertrophy through blocking of Akt/GSK3β signaling. The study indicates that CTSL improves cardiac function and inhibits cardiac hypertrophy, inflammation, and fibrosis through blocking Akt/GSK3β signaling.

Activating transcription factor 3 deficiency promotes cardiac hypertrophy, dysfunction, and fibrosis induced by pressure overload.

Activating transcription factor 3 (ATF3), which is encoded by an adaptive-response gene induced by various stimuli, plays an important role in the cardiovascular system. However, the effect of ATF3 on cardiac hypertrophy induced by a pathological stimulus has not been determined. Here, we investigated the effects of ATF3 deficiency on cardiac hypertrophy using in vitro and in vivo models. Aortic banding (AB) was performed to induce cardiac hypertrophy in mice. Cardiac hypertrophy was estimated by echocardiographic and hemodynamic measurements and by pathological and molecular analysis. ATF3 deficiency promoted cardiac hypertrophy, dysfunction and fibrosis after 4 weeks of AB compared to the wild type (WT) mice. Furthermore, enhanced activation of the MEK-ERK1/2 and JNK pathways was found in ATF3-knockout (KO) mice compared to WT mice. In vitro studies performed in cultured neonatal mouse cardiomyocytes confirmed that ATF3 deficiency promotes cardiomyocyte hypertrophy induced by angiotensin II, which was associated with the amplification of MEK-ERK1/2 and JNK signaling. Our results suggested that ATF3 plays a crucial role in the development of cardiac hypertrophy via negative regulation of the MEK-ERK1/2 and JNK pathways.

Allicin protects against cardiac hypertrophy and fibrosis via attenuating reactive oxygen species-dependent signaling pathways.

Increased oxidative stress has been associated with the pathogenesis of chronic cardiac hypertrophy and heart failure. Since allicin suppresses oxidative stress in vitro and in vivo, we hypothesized that allicin would inhibit cardiac hypertrophy through blocking oxidative stress-dependent signaling. We examined this hypothesis using primary cultured cardiac myocytes and fibroblasts and one well-established animal model of cardiac hypertrophy. Our results showed that allicin markedly inhibited hypertrophic responses induced by Ang II or pressure overload. The increased reactive oxygen species (ROS) generation and NADPH oxidase activity were significantly suppressed by allicin. Our further investigation revealed this inhibitory effect on cardiac hypertrophy was mediated by blocking the activation of ROS-dependent ERK1/2, JNK1/2 and AKT signaling pathways. Additional experiments demonstrated allicin abrogated inflammation and fibrosis by blocking the activation of nuclear factor-κB and Smad 2/3 signaling, respectively. The combination of these effects resulted in preserved cardiac function in response to cardiac stimuli. Consequently, these findings indicated that allicin protected cardiac function and prevented the development of cardiac hypertrophy through ROS-dependent mechanism involving multiple intracellular signaling.

Puerarin attenuates high-glucose-and diabetes-induced vascular smooth muscle cell proliferation by blocking PKCβ2/Rac1-dependent signaling

Oxidative stress has been implicated in several steps leading to the development of diabetic vascular complications. The purpose of this study was to determine the efficacy and the possible mechanism of puerarin on high-glucose (HG; 25 mM)-induced proliferation of cultured rat vascular smooth muscle cells (VSMCs) and neointimal formation in a carotid arterial balloon injury model of obese Zucker rats. Our data demonstrated that puerarin significantly inhibited rat VSMC proliferation as well as reactive oxygen species (ROS) generation and NADPH oxidase activity induced by HG treatment. Further studies revealed that HG treatment resulted in phosphorylation and membrane translocation of PKCbeta2 as well as Rac1, p47phox, and p67phox subunits, leading to NADPH oxidase activation. Puerarin treatment remarkably disrupted the phosphorylation and membrane translocation of PKCbeta2 as well as Rac1, p47phox, and p67phox subunits. Blocking PKCbeta2 by infection with AdDNPKCbeta2 also abolished HG-induced phosphorylation and membrane translocation of Rac1, p47phox, and p67phox subunits as well as ROS production and NADPH oxidase activation in VSMCs. In vivo neointimal formation of obese Zucker rats evoked by balloon injury was evidently attenuated by the administration of puerarin. These results demonstrate that puerarin may exert inhibitory effects on HG-induced VSMC proliferation via interfering with PKCbeta2/Rac1-dependent ROS pathways, thus resulting in the attenuation of neointimal formation in the context of hyperglycemia in diabetes mellitus.

Tumor Suppressor A20 Protects Against Cardiac Hypertrophy and Fibrosis by Blocking Transforming Growth Factor-β–Activated Kinase 1–Dependent Signaling

A20 or tumor necrosis factor–induced protein 3 is a negative regulator of nuclear factor &kgr;B signaling. A20 has been shown previously to attenuate cardiac hypertrophy in vitro and postmyocardial infarction remodeling in vivo. In the present study, we tested the hypothesis that overexpression of A20 in the murine heart would protect against cardiac hypertrophy in vivo. The effects of constitutive human A20 expression on cardiac hypertrophy were investigated using in vitro and in vivo models. Cardiac hypertrophy was produced by aortic banding in A20 transgenic mice and control animals. The extent of cardiac hypertrophy was quantitated by echocardiography, as well as by pathological and molecular analyses of heart samples. Constitutive overexpression of human A20 in the murine heart attenuated the hypertrophic response and markedly reduced inflammation, apoptosis, and fibrosis. Cardiac function was also preserved in hearts with increased A20 levels in response to hypertrophic stimuli. Western blot experiments further showed A20 expression markedly blocked transforming growth factor-&bgr;–activated kinase 1–dependent c-Jun N-terminal kinase/p38 signaling cascade but with no difference in either extracellular signal-regulated kinase 1/2 or AKT activation in vivo and in vitro. In cultured neonatal rat cardiac myocytes, [3H]proline incorporation and Western blot assays revealed that A20 expression suppressed transforming growth factor-&bgr;–induced collagen synthesis and transforming growth factor-&bgr;–activated kinase 1–dependent Smad 2/3/4 activation. In conclusion, A20 improves cardiac functions and inhibits cardiac hypertrophy, inflammation, apoptosis, and fibrosis by blocking transforming growth factor-&bgr;–activated kinase 1–dependent signaling.

Effect of bioaggregate on differentiation of human periodontal ligament fibroblasts

AIM To investigate the cytotoxicity of bioaggregate (BA; Innovative Bioceramix, Vancouver, BC, Canada) to human periodontal ligament (PDL) fibroblasts and its effect on differentiation of human PDL fibroblasts and to compare its performance to that of mineral trioxide aggregate (MTA; Dentsply, Tulsa, OK, USA). METHODOLOGY Cytotoxicity was assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay on days 1, 2, and 3 after incubation with BA or MTA. The influence of BA and MTA on differentiation of human PDL fibroblasts on days 3, 5, and 7 was evaluated by gene expression of alkaline phosphatase (ALP) and collagen type I (COLI) via quantitative real-time polymerase chain reaction (PCR). The data were analysed by one-way analysis of variance followed by Tukeys test. RESULTS Cell numbers in the BA group were similar to that of the control group throughout the culture period, whereas MTA suppressed the proliferation of fibroblasts. ALP expression was significantly increased in the BA group on day 7, whilst it was enhanced by MTA on day 3. Gene expression of COLI was induced by both BA and MTA compared to the control group. CONCLUSIONS Bioaggregate was nontoxic to human PDL fibroblasts and appeared to induce the differentiation of human PDL fibroblasts.

Gastrodin protects against cardiac hypertrophy and fibrosis.

Phenolic glucoside gastrodin (Gas), which is a main component extracted from the Chinese herbs Gastrodia elata Bl, is a well-known natural calcium antagonist with antioxidant and anti-inflammatory functions. It has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. Previous studies have shown that gastrodin possesses comprehensive pharmacological functions. However, very little is known about whether gastrodin has protective role on cardiac hypertrophy. The aim of this study was to determine whether gastrodin attenuates pressure overload-induced cardiac hypertrophy in mice and to clarify the underlying molecular mechanisms. Our data demonstrated that gastrodin prevented cardiac hypertrophy induced by aortic banding (AB), as assessed by heart weight/body weight and lung weight/body weight ratios, echocardiographic parameters, and gene expression of hypertrophic markers. The inhibitory effect of gastrodin on cardiac hypertrophy is mediated by ERK1/2 signaling and GATA-4 activation. Further studies showed that gastrodin attenuated fibrosis and collagen synthesis through abrogating ERK1/2 signaling pathway. Therefore, these findings indicated that gastrodin, which is a potentially safe and inexpensive therapy for clinical use, has protective potential in targeting cardiac hypertrophy and fibrosis through suppression of ERK1/2 signaling.