Heat shock transcription factor 1 protects heart after pressure overload through promoting myocardial angiogenesis in male mice

Astragaloside IV ameliorates pressure overload-induced heart failure by enhancing angiogenesis through HSF1/VEGF pathway

Astragaloside IV(AS-IV), the main active ingredient of Astragalus, has been used as a treatment for heart failure with favorable effects, but its molecular mechanism has not been fully elucidated. Network pharmacological analysis and molecular docking revealed that Heat shock transcription factor 1 (HSF1) is a potential target of AS-IV. We designed cellular and animal experiments to investigate the role and intrinsic molecular mechanisms of AS-IV in ameliorating pressure overload-induced heart failure. In cellular experiments, Myocardial microvascular endothelial cells (MMVECs) were cultured in isolation and stimulated by adding high and low concentrations of AS-IV, and a cell model with down-regulation of HSF1 expression was constructed by using siRNA technology. Changes in the expression of key molecules of HSF1/VEGF signaling pathway and differences in tube-forming ability were detected in different groups of cells using PCR, WB and tube-forming assay. In animal experiments, TAC technology was applied to establish a pressure overload-induced heart failure model in C57 mice, postoperative mice were ingested AS-IV by gavage, and adenoviral transfection technology was applied to construct a mouse model with down-regulation of HSF1 expression.Small animal ultrasound for cardiac function assessment, MASSON staining, CD31 immunohistochemistry, and Western blotting (WB) were performed on the mice. The results showed that AS-IV could promote the expression of key molecules of HSF1/VEGF signaling pathway, enhance the tube-forming ability of MMVECs, increase the density of myocardial capillaries, reduce myocardial fibrosis, and improve the cardiac function of mice with TAC.AS-IV could modulate the HSF1/VEGF signaling pathway to promote the angiogenesis and improve the pressure overload-induced heart failure.

Role of Oxygen Starvation in Right Ventricular Decompensation and Failure in Pulmonary Arterial Hypertension

Right ventricular (RV) function and eventually failure determine outcome in patients with pulmonary arterial hypertension (PAH). Initially, RV responds to an increased load caused by PAH with adaptive hypertrophy; however, eventually RV failure ensues. Unfortunately, it is unclear what causes the transition from compensated RV hypertrophy to decompensated RV failure. Moreover, at present, there are no therapies for RV failure; those for left ventricular (LV) failure are ineffective, and no therapies specifically targeting RV are available. Thus there is a clear need for understanding the biology of RV failure and differences in physiology and pathophysiology between RV and LV that can ultimately lead to development of such therapies. In this paper, we discuss RV adaptation and maladaptation in PAH, with a particular focus of oxygen delivery and hypoxia as the principal drivers of RV hypertrophy and failure, and attempt to pinpoint potential sites for therapy.

MicroRNA‑378: An important player in cardiovascular diseases (Review)

Cardiovascular disease (CVD) is a common chronic clinical condition and is the main cause of death in humans worldwide. Understanding the genetic and molecular mechanisms involved in the development of CVD is essential to develop effective prevention strategies and therapeutic measures. An increasing number of CVD‑related genetic studies have been conducted, including those on the potential roles of microRNAs (miRs). These studies have demonstrated that miR‑378 is involved in the pathological processes of CVD, including those of myocardial infarction, heart failure and coronary heart disease. Despite the potential importance of miR‑378 CVD, a comprehensive summary of the related literature is lacking. Thus, the present review aimed to summarize the findings of previous studies on the roles and mechanisms of miR‑378 in a variety of CVDs and provide an up‑to date basis for further r research targeting the prevention and treatment of CVDs.

Emerging role of heat shock proteins in cardiovascular diseases

Heat Shock Proteins (HSPs) are evolutionarily conserved proteins from prokaryotes to eukaryotes. They are ubiquitous proteins involved in key physiological and cellular pathways (viz. inflammation, immunity and apoptosis). Indeed, the survivability of the cells under various stressful conditions depends on appropriate levels of HSP expression. There is a growing line of evidence for the role of HSPs in regulating cardiovascular diseases (CVDs) (viz. hypertension, atherosclerosis, atrial fibrillation, cardiomyopathy and heart failure). Furthermore, studies indicate that a higher concentration of circulatory HSP antibodies correlate to CVDs; some are even potential markers for CVDs. The multifaceted roles of HSPs in regulating cellular signaling necessitate unraveling their links to pathophysiology of CVDs. This review aims to consolidate our understanding of transcriptional (via multiple transcription factors including HSF-1, NF-κB, CREB and STAT3) and post-transcriptional (via microRNAs including miR-1, miR-21 and miR-24) regulation of HSPs. The cytoprotective nature of HSPs catapults them to the limelight as modulators of cell survival. Yet another attractive prospect is the development of new therapeutic strategies against cardiovascular diseases (from hypertension to heart failure) by targeting the regulation of HSPs. Moreover, this review provides insights into how genetic variation of HSPs can contribute to the manifestation of CVDs. It would also offer a bird's eye view of the evolving role of different HSPs in the modulation and manifestation of cardiovascular disease.

Trimetazidine enhances myocardial angiogenesis in pressure overload-induced cardiac hypertrophy mice through directly activating Akt and promoting the binding of HSF1 to VEGF-A promoter

Latest clinical research shows that trimetazidine therapy during the perioperative period relieves endothelial dysfunction in patients with unstable angina induced by percutaneous coronary intervention. In this study we investigated the effects of TMZ on myocardial angiogenesis in pressure overload-induced cardiac hypertrophy mice. Cardiac hypertrophy was induced in mice by transverse aortic constriction (TAC) surgery. TAC mice were administered trimetazidine (2.8 mg/100 µL, i.g.) for 28 consecutive days. We showed that trimetazidine administration significantly increased blood vessel density in the left ventricular myocardium and abrogated cardiac dysfunction in TAC mice. Co-administration of a specific HSF1 inhibitor KRIBB11 (1.25 mg/100 µL, i.h.) abrogated the angiogenesis-promoting effects of trimetazidine in TAC mice. Using luciferase reporter and electrophoretic mobility shift assays we demonstrated that the transcription factor HSF1 bound to the promoter region of VEGF-A, and the transcriptional activity of HSF1 was enhanced upon trimetazidine treatment. In molecular docking analysis we found that trimetazidine directly bound to Akt via a hydrogen bond with Asp292 and a pi-pi bond with Trp80. In norepinephrine-treated HUVECs, we showed that trimetazidine significantly increased the phosphorylation of Akt and the synergistic nuclear translocation of Akt and HSF1, as well as the binding of Akt and HSF1 in the nucleus. These results suggest that trimetazidine enhances myocardial angiogenesis through a direct interaction with Akt and promotion of nuclear translocation of HSF1, and that trimetazidine may be used for the treatment of myocardial angiogenic disorders in hypertensive patients.

Salvianolic Acid Ameliorates Pressure Overload-Induced Cardiac Endothelial Dysfunction via Activating HIF1[Formula: see text]/HSF1/CD31 Pathway

Pressure overload is a major risk factor for various cardiovascular diseases. Disorders of the endothelium are involved in the pathological mechanisms of pressure, and maintaining endothelial function is a practical strategy to alleviate pressure overload-induced cardiac injury. In this study, we provided evidence that salvianolic acid, the active component of Danshen, a traditional Chinese herb medicine, preserved pressure overload-induced cardiac dysfunction via protecting endothelium. Male C57BL/6J mice were imposed with transverse aortic constriction to mimic pressure overload and treated with salvianolic acid (200[Formula: see text]mg/kg/day) or vehicle for 6 weeks. The hemodynamic and cardiac functional parameters were detected by the cardiac catheter and transthoracic echocardiography. The pathological measurements were conducted by heart hematoxylin-eosin, wheat germ agglutinin staining, Masson's trichrome staining, and immunofluorescence staining. Endothelial cell (EC) proliferation was estimated using the Cell Counting Kit-8, EC migration was evaluated by scratched assay, and EC integrity was observed by electron microscope. Salvianolic acid notably inhibited cardiac chamber enlargement, restrained cardiac contractile dysfunction, and repressed cardiac fibrosis caused by chronic pressure overload. Salvianolic acid maintained endothelial tight junction integrity by boosting the expression of CD31. Furthermore, the endothelial protective effect of salvianolic acid against pressure overload is dependent on the activation of hypoxia-inducible factor 1[Formula: see text], which consequently activated heat shock factor 1 and promoted CD31 expression. Our study uncovered that salvianolic acid protected cardiac ECs against pressure overload via a HIF1[Formula: see text]/HSF1/CD31 pathway, indicating a potential appliance of salvianolic acid in hypertensive heart disease.

AT1 receptor blocker inhibits HMGB1 expression in pressure overload-induced acute cardiac dysfunction by suppressing the MAPK/NF-κB signaling pathway

BACKGROUND

High-mobility group box 1 (HMGB1) expression not only peaks during the early phase of pressure overload (PO), but also serves a role in the pathogenesis of PO-induced cardiac remodeling. Meanwhile, angiotensin II type 1 (AT1) receptor blockers reverse PO-induced cardiac remodeling and repress the secretion of inflammatory factors. However, whether AT1 receptor inhibitors decrease HMGB1 expression in the early stages of PO remains unknown.

MATERIALS AND METHODS

PO mouse models were established using transverse aortic constriction (TAC), in which losartan was administrated. Transthoracic echocardiography was performed 3 days after the operation, and serum and cardiac HMGB1 expression, as well as the expression levels of related proteins were measured.

RESULTS

PO-induced acute cardiac dysfunction was observed 3 days after TAC, and was subsequently slightly, but not significantly relieved by losartan. The expression levels of HMGB1, tumor necrosis factor-α and interleukin-6 in both the serum and myocardium were upregulated in response to TAC, while they were significantly reduced by losartan. Moreover, the phosphorylation of extracellular signal-regulated kinases, p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) in the myocardium were significantly increased under PO, and this was also prevented by losartan.

CONCLUSION

These data suggest that losartan may downregulate the expression of HMGB1 in acute cardiac dysfunction induced by PO by inhibiting the MAPKs/NF-κB signaling pathway, which indicates a novel beneficial role of AT1 receptor antagonists in ameliorating cardiac remodeling under PO.

Chronic Benzene Exposure Aggravates Pressure Overload-Induced Cardiac Dysfunction

Benzene is a ubiquitous environmental pollutant abundant in household products, petrochemicals and cigarette smoke. Benzene is a well-known carcinogen in humans and experimental animals; however, little is known about the cardiovascular toxicity of benzene. Recent population-based studies indicate that benzene exposure is associated with an increased risk for heart failure. Nonetheless, it is unclear whether benzene exposure is sufficient to induce and/or exacerbate heart failure. We examined the effects of benzene (50 ppm, 6 h/day, 5 days/week, 6 weeks) or HEPA-filtered air exposure on transverse aortic constriction (TAC)-induced pressure overload in male C57BL/6J mice. Our data show that benzene exposure had no effect on cardiac function in the Sham group; however, it significantly compromised cardiac function as depicted by a significant decrease in fractional shortening and ejection fraction, as compared with TAC/Air-exposed mice. RNA-seq analysis of the cardiac tissue from the TAC/benzene-exposed mice showed a significant increase in several genes associated with adhesion molecules, cell-cell adhesion, inflammation, and stress response. In particular, neutrophils were implicated in our unbiased analyses. Indeed, immunofluorescence studies showed that TAC/benzene exposure promotes infiltration of CD11b+/S100A8+/myeloperoxidase+-positive neutrophils in the hearts by 3-fold. In vitro, the benzene metabolites, hydroquinone and catechol, induced the expression of P-selectin in cardiac microvascular endothelial cells by 5-fold and increased the adhesion of neutrophils to these endothelial cells by 1.5-2.0-fold. Benzene metabolite-induced adhesion of neutrophils to the endothelial cells was attenuated by anti-P-selectin antibody. Together, these data suggest that benzene exacerbates heart failure by promoting endothelial activation and neutrophil recruitment.

The regulatory roles of p53 in cardiovascular health and disease

Cardiovascular disease (CVD) remains the leading cause of mortality globally, so further investigation is required to identify its underlying mechanisms and potential targets for its prevention. The transcription factor p53 functions as a gatekeeper, regulating a myriad of genes to maintain normal cell functions. It has received a great deal of research attention as a tumor suppressor. In the past three decades, evidence has also shown a regulatory role for p53 in the heart. Basal p53 is essential for embryonic cardiac development; it is also necessary to maintain normal heart architecture and physiological function. In pathological cardiovascular circumstances, p53 expression is elevated in both patient samples and animal models. Elevated p53 plays a regulatory role via anti-angiogenesis, pro-programmed cell death, metabolism regulation, and cell cycle arrest regulation. This largely promotes the development of CVDs, particularly cardiac remodeling in the infarcted heart, hypertrophic cardiomyopathy, dilated cardiomyopathy, and diabetic cardiomyopathy. Roles for p53 have also been found in atherosclerosis and chemotherapy-induced cardiotoxicity. However, it has different roles in cardiomyocytes and non-myocytes, even in the same model. In this review, we describe the different effects of p53 in cardiovascular physiological and pathological conditions, in addition to potential CVD therapies targeting p53.

Angiotensin II Increases HMGB1 Expression in the Myocardium Through AT1 and AT2 Receptors When Under Pressure Overload

High-mobility group box 1 (HMGB1) is increased in the myocardium under pressure overload (PO) and is involved in PO-induced cardiac remodeling. The mechanisms of the upregulation of cardiac HMGB1 expression have not been fully elucidated. In the present study, a mouse transverse aortic constriction (TAC) model was used, and an angiotensin II (Ang II) type 1 (AT1) receptor inhibitor (losartan) or Ang II type 2 (AT2) receptor inhibitor (PD123319) was administrated to mice for 14 days. Cardiac myocytes were cultured and treated with Ang II for 5 minutes to 48 hours conditionally with the blockage of the AT1 or AT2 receptor. TAC-induced cardiac hypertrophy was observed at 14 days after the operation, which was partially reversed by losartan, but not by PD123319. Similarly, the upregulated HMGB1 expression levels observed in both the serum and myocardium induced by TAC were reduced by losartan. Elevated cardiac HMGB1 protein levels, but not mRNA or serum levels, were significantly decreased by PD123319. Furthermore, HMGB1 expression levels in culture media and cardiac myocytes were increased following Ang II treatment in vitro, positively associated with the duration of treatment. Similarly, Ang II-induced upregulation of HMGB1 in vitro was inhibited by both losartan and PD123319. These results suggest that upregulation of HMGB1 in serum and myocardium under PO, which are partially derived from cardiac myocytes, may be induced by Ang II via the AT1 and AT2 receptors. Additionally, amelioration of PO-induced cardiac hypertrophy following losartan treatment may be associated with the reduction of HMGB1 expression through the AT1 receptor.

HMGB1 Aggravates Pressure Overload-Induced Left Ventricular Dysfunction by Promoting Myocardial Fibrosis

Aim. Fibrosis had important effects on pressure overload-induced left ventricular (LV) dysfunction. High-mobility group box 1 (HMGB1), which was closely associated with fibrosis, was involved in the pressure overload-induced cardiac injury. This study determines the role of HMGB1 in LV dysfunction under pressure overload. Methods. Transverse aortic constriction (TAC) operation was performed on male C57BL/6J mice to build the model of pressure overload, while HMGB1 or PBS was injected into the LV wall. Cardiac function, collagen volume, and relevant genes were detected. Results. Echocardiography demonstrated that the levels of LV ejection fraction (LVEF) were markedly decreased on day 28 after TAC, which was consistent with raised collagen in the myocardium. Moreover, we found that the exposure of mice to TAC + HMGB1 is associated with higher mortality, BNP, and collagen volume in the myocardium and lower LVEF. In addition, real-time PCR showed that the expression of collagen type I, TGF-β, and MMP2 markedly increased in the myocardium after TAC, while HMGB1 overexpression further raised the TGF-β expression but not collagen type I and MMP2 expressions. Conclusion. This study indicated that exogenous HMGB1 overexpression in the myocardium aggravated the pressure overload-induced LV dysfunction by promoting cardiac fibrosis, which may be mediated by increasing the TGF-β expression.

Molecular Mechanism of HSF1-Upregulated ALDH2 by PKC in Ameliorating Pressure Overload-Induced Heart Failure in Mice

Evidences abound that HSF1 and ALDH2 are of cardioprotective effect, yet there is still no report on whether HSF1 can regulate ALDH2 to delay the occurrence of heart failure. We first established the pressure overload-induced heart failure model of mice by transverse aortic constriction (TAC) and discovered that, in the forming period of heart failure, changes of HSF1 and ALDH2 expression recorded the consistent trend. When HSF1 was upregulated/downregulated to delay/promote the occurrence of heart failure, PKC and ALDH2 also showed increased/decreased expression. And when ALDH2 was upregulated/downregulated, the role of HSF1 in delaying the occurrence of heart failure strengthened/weakened. Next, we used mechanical stretch to establish a pressure-stimulated myocardial hypertrophy model and discovered an increased expression of both HSF1 and ALDH2. When HSF1 was upregulated/downregulated to increase/decrease the expression of myocardial hypertrophy gene beta-MHC, PKC and ALDH2 recorded an increased/decreased expression. When an inhibitor was used to downregulate the expression of PKC in cardiomyocytes, we found that the role of HSF1 in upregulating ALDH2 beta-MHC weakened. These findings suggest that HSF1 can upregulate the expression of ALDH2 via PKC to promote pressure-stimulated myocardial compensatory hypertrophy, which is an important molecular pathway for HSF1 to ameliorate heart failure.

Mangiferin activates Nrf2 to attenuate cardiac fibrosis via redistributing glutaminolysis-derived glutamate

Cardiac injury is followed by fibrosis, characterized by myofibroblast activation. Excessive deposition of extracellular matrix (ECM) impairs the plasticity of myocardium and results in myocardial systolic and diastolic dysfunction. Mangiferin is a xanthonoid derivative rich in plants mangoes and iris unguicularis, exhibiting the ability to ameliorate metabolic disorders. This study aims to investigate whether mangiferin attenuates cardiac fibrosis via redox regulation. The transverse aortic constriction (TAC) in mice induced cardiac fibrosis with impaired heart function. Oral administration of mangiferin (50 mg/kg, 4 weeks) inhibited myofibroblast activation with reduced formation of ECM. The impaired left ventricular contractive function was also improved by mangiferin. TGF-β1 stimulation increased glutaminolysis to fuel intracellular glutamate pool for the increased demands of nutrients to support cardiac myofibroblast activation. Mangiferin degraded Keap1 to promote Nrf2 protein accumulation by improving its stability, leading to Nrf2 activation. Nrf2 transcriptionally promotes the synthesis of antioxidant proteins. By activating Nrf2, mangiferin promoted the synthesis of glutathione (GSH) in cardiac fibroblasts, likely due to the consumption of glutaminolysis-derived glutamate as a source. Meanwhile, mangiferin promoted the exchange of intracellular glutamate for the import of extracellular cystine to support GSH generation. As a result of redistribution, the reduced glutamate availability failed to support myofibroblast activation. In support of this, the addition of extracellular glutamate or α-ketoglutarate diminished the inhibitory effects of mangiferin on cardiac myofibroblast proliferation and activation. Moreover, cardiac knockdown of Nrf2 attenuated the cardioprotective effects of mangiferin in mice subjected to TAC. In conclusion, we demonstrated that activated myofibroblasts were sensitive to glutamate availability. Mangiferin activated Nrf2 and redistributed intracellular glutamate for the synthesis of GSH, consequently impairing cardiac myofibroblast activation due to decreased glutamate availability. These results address that pharmacological activation of Nrf2 could restrain cardiac fibrosis via metabolic regulation.

Heat shock transcription factor 1 regulates exercise-induced myocardial angiogenesis after pressure overload via HIF-1α/VEGF pathway

Exercise training is believed to have a positive effect on cardiac hypertrophy after hypertension. However, its mechanism is still not fully understood. Herein, our findings suggest that heat shock transcription factor 1 (HSF1) improves exercise‐initiated myocardial angiogenesis after pressure overload. A sustained narrowing of the diagonal aorta (TAC) and moderately‐ intense exercise training protocol were imposed on HSF1 heterozygote (KO) and their littermate wild‐type (WT) male mice. After two months, the cardiac function was assessed using the adaptive responses to exercise training, or TAC, or both of them such as catheterization and echocardiography. The HE stains assessed the area of myocyte cross‐sectional. The Western blot and real‐time PCR measured the levels of expression for heat shock factor 1 (HSF1), vascular endothelial growth factor (VEGF) and hypoxia inducible factor‐1 alpha (HIF‐1α) in cardiac tissues. The anti‐CD31 antibody immunohistochemical staining was done to examine how exercise training influenced cardiac ontogeny. The outcome illustrated that exercise training significantly improved the cardiac ontogeny in TAC mice, which was convoyed by elevated levels of expression for VEGF and HIF‐1α and preserved the heart microvascular density. More importantly, HSF1 deficiency impaired these effects induced by exercise training in TAC mice. In conclusion, exercise training encourages cardiac ontogeny by means of HSF1 activation and successive HIF‐1α/VEGF up‐regulation in endothelial cells during continued pressure overload.

Angiogenic Endothelial Cell Signaling in Cardiac Hypertrophy and Heart Failure

Endothelial cells are, by number, one of the most abundant cell types in the heart and active players in cardiac physiology and pathology. Coronary angiogenesis plays a vital role in maintaining cardiac vascularization and perfusion during physiological and pathological hypertrophy. On the other hand, a reduction in cardiac capillary density with subsequent tissue hypoxia, cell death and interstitial fibrosis contributes to the development of contractile dysfunction and heart failure, as suggested by clinical as well as experimental evidence. Although the molecular causes underlying the inadequate (with respect to the increased oxygen and energy demands of the hypertrophied cardiomyocyte) cardiac vascularization developing during pathological hypertrophy are incompletely understood. Research efforts over the past years have discovered interesting mediators and potential candidates involved in this process. In this review article, we will focus on the vascular changes occurring during cardiac hypertrophy and the transition toward heart failure both in human disease and preclinical models. We will summarize recent findings in transgenic mice and experimental models of cardiac hypertrophy on factors expressed and released from cardiomyocytes, pericytes and inflammatory cells involved in the paracrine (dys)regulation of cardiac angiogenesis. Moreover, we will discuss major signaling events of critical angiogenic ligands in endothelial cells and their possible disturbance by hypoxia or oxidative stress. In this regard, we will particularly highlight findings on negative regulators of angiogenesis, including protein tyrosine phosphatase-1B and tumor suppressor p53, and how they link signaling involved in cell growth and metabolic control to cardiac angiogenesis. Besides endothelial cell death, phenotypic conversion and acquisition of myofibroblast-like characteristics may also contribute to the development of cardiac fibrosis, the structural correlate of cardiac dysfunction. Factors secreted by (dysfunctional) endothelial cells and their effects on cardiomyocytes including hypertrophy, contractility and fibrosis, close the vicious circle of reciprocal cell-cell interactions within the heart during pathological hypertrophy remodeling.

Increased myocardial stiffness activates cardiac microvascular endothelial cell via VEGF paracrine signaling in cardiac hypertrophy

When the heart is subjected to an increased workload, mechanical stretch together with neurohumoral stimuli activate the "fetal gene program" and induce cardiac hypertrophy to optimize output. Due to a lack of effective methods/models to quantify and modulate cardiac mechanical properties, the connection between these properties and the development of cardiac hypertrophy remains largely unexplored. Here, we utilized an atomic force microscope (AFM) to directly measure the elastic modulus of the hypertrophic myocardium induced by pressure overload. Additionally, we investigated the effects of extracellular elasticity on angiogenesis, which provides blood and nutrition to support cardiomyocyte hypertrophic growth in this process. In response to pressure overload, the myocardium rapidly developed hypertrophy and correspondingly demonstrated a high elastic modulus property. This mechanical feature correlated with enhanced angiogenesis. Mechanistically, we found that a high elastic modulus promoted cultured cardiomyocytes to synthesize and paracrine vascular endothelial growth factor (VEGF) to activate cardiac microvascular endothelial cells. Further analysis showed that the increased elastic modulus enhanced the interaction between Talin1 and integrin β1 to activate the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/hypoxia-inducible factor 1α (Hif-1α) pathway, which contributed to VEGF production. Thus, our study revealed a critical role of the elastic modulus in regulating angiogenesis during the development of cardiac hypertrophy.

Downregulation of MiR-199b-5p Inducing Differentiation of Bone-Marrow Mesenchymal Stem Cells (BMSCs) Toward Cardiomyocyte-Like Cells via HSF1/HSP70 Pathway

BACKGROUND Bone-marrow mesenchymal stem cells (BMSCs) are pluripotent stem cells with potent self-renewal and differentiation ability that are widely used in transplantation of cell therapy. But the mechanism on microRNA (miRNA) regulating stem cell differentiation is complicated and unclear. The aim of this study was to investigate whether miR-199b-5p is involved in differentiation of cardiomyocyte-like cells and identify potential signal pathways in BMSCs. MATERIAL AND METHODS Mouse BMSCs were treated with 5-azacytidine and transfected by miR-199b-5p mimic and inhibitor, respectively. qRT-PCR was used to detect the expression of miR-199b-5p in BMSCs, 5-azacytidine treated BMSCs, and neonatal murine cardiomyocytes. The expression of cardiac specific genes and the HSF1/HSP70 signal pathway were examined by qRT-PCR or western blotting. The proliferation and migration of BMSCs were evaluated by CCK-8 assay and wound-healing assay. RESULTS The expression of miR-199b-5p decreased gradually in the process of differentiation of BMSCs toward cardiomyocyte-like cells. The expression of cardiac specific genes and HSF1/HSP70 were increased in the miR-199b-5p inhibitor group; however, the miR-199b-5p mimic group presented an opposite result. Both the miR-199b-5p inhibitor group and the miR-199b-5p mimic group had no influence on BMSCs proliferation and migration. Using lentivirus vectors bearing HSF1 shRNA to silence HSF1 and HSP70, the anticipated elevated expression effect of cardiac specific genes induced by miR-199b-5p inhibitor was suppressed. CONCLUSIONS Downregulation of miR-199b-5p induced differentiation of BMSCs toward cardiomyocyte-like cells partly via the HSF1/HSP70 signaling pathway, and had no influence on BMSCs proliferation and migration.

Role of heat shock transcription factor 1(HSF1)-upregulated macrophage in ameliorating pressure overload-induced heart failure in mice

In order to explore the role of macrophages in HSF1-mediated alleviation of heart failure, mice model of pressure overload-induced heart failure was established using transverse aortic constriction (TAC). Changes in cardiac function and morphology were studied in TAC and SHAM groups using ultrasonic device, tissue staining, electron microscopy, real-time quantitative polymerase chain reaction (RT-QPCR), and Western blotting. We found that mice in the TAC group showed evidence of impaired cardiac function and aggravation of fibrosis on ultrasonic and histopathological examination when compared to those in the SHAM group. The expressions of HSF1, LC3II/LC3I, Becline-1 and HIF-1, as well as autophagosome formation in TAC group were greater than that in SHAM group. On sub-group analyses in the TAC group, improved cardiac function and alleviation of fibrosis was observed in the HSF1 TG subgroup as compared to that in the wild type subgroup. Expressions of LC3II/LC3I, Becline-1 and HIF-1, too showed an obvious increase; and increased autophagosome formation was observed on electron microscopy. Opposite results were observed in the HSF1 KO subgroup. These results collectively suggest that in the pressure overload heart failure model, HSF1 promoted formation of macrophages by inducing upregulation of HIF-1 expression, through which heart failure was ameliorated.

MicroRNA-378 suppresses myocardial fibrosis through a paracrine mechanism at the early stage of cardiac hypertrophy following mechanical stress

Rationale: Excessive myocardial fibrosis is the main pathological process in the development of cardiac remodeling and heart failure; therefore, it is important to prevent excessive myocardial fibrosis. We determined that microRNA-378 (miR-378) is cardiac-enriched and highly repressed during cardiac remodeling. We therefore proposed that miR-378 has a critical role in regulation of cardiac fibrosis, and examined the effects of miR-378 on cardiac fibrosis after mechanical stress. Methods: Mechanical stress was respectively imposed on mice through a transverse aortic constriction (TAC) procedure and on cardiac fibroblasts by stretching silicon dishes. A chemically modified miR-378 mimic (Agomir) or an inhibitor (Antagomir) was administrated to mice by intravenous injection and to cells by direct addition to the culture medium. MiR-378 knockout mouse was constructed. Cardiac fibroblasts were cultured in the conditioned media from the cardiomyocytes with either miR-378 depletion or treatment with sphingomyelinase inhibitor GW4869. Quantitative real-time polymerase chain reaction analysis of gene and miRNA expression, Western blot analysis, immunochemistry and electron microscopy were performed to elucidate the mechanisms. Results: Mechanical stress induced significant increases in fibrotic responses, including myocardial fibrosis, fibroblast hyperplasia, and protein and gene expression of collagen and matrix metalloproteinases (MMPs) both in vivo and in vitro. All these fibrotic responses were attenuated by treatment with a chemically modified miR-378 mimic (Agomir) but were exaggerated by treatment with an inhibitor (Antagomir). MiR-378 knockout mouse models exhibited aggravated cardiac fibrosis after TAC. Media from the cardiomyocytes with either miR-378 depletion or treatment with sphingomyelinase inhibitor GW4869 enhanced the fibrotic responses of stimulated cardiac fibroblasts, confirming that miR-378 inhibits fibrosis in an extracellular vesicles-dependent secretory manner. Mechanistically, the miR-378-induced anti-fibrotic effects manifested partially through the suppression of p38 MAP kinase phosphorylation by targeting MKK6 in cardiac fibroblasts. Conclusions: miR-378 is secreted from cardiomyocytes following mechanical stress and acts as an inhibitor of excessive cardiac fibrosis through a paracrine mechanism.

Endogenous hormone 2-methoxyestradiol suppresses venous hypertension-induced angiogenesis through up- and down-regulating p53 and id-1

Brain arteriovenous malformations (AVMs) which associate with angiogenesis due to local hypertension, chronic cerebral ischaemia and tissue hypoxia usually lead to haemorrhage, however, the therapeutic medicine for the disease is still lacking. 2‐methoxyestradiol (2‐ME) has been shown effective in the anti‐angiogenic treatment. This study was conducted to examine whether and how 2‐ME could improve the vascular malformations. Intracranial venous hypertension (VH) model produced in adult male Sprague‐Dawley rats and culture of human umbilical vein endothelial cells (HUVECs) at the anoxia condition were used to induce in vivo and in vitro angiogenesis, respectively. Lentiviral vectors of ID‐1 and p53 genes and of their siRNA were intracranially injected into rats and transfected into HUVECs to overexpress and down‐regulate these molecules. 2‐ME treatment not only reduced the in vivo progression of brain tissue angiogenesis in the intracranial VH rats and the in vitro increases in microvasculature formation, cellular migration and HIF‐1α expression induced by anoxia in HUVECs but also reversed the up‐regulation of ID‐1 and down‐regulation of p53 in both the in vivo and in vitro angiogenesis models. All of the anti‐angiogenesis effects of 2‐ME observed in VH rats and anoxic HUVECs were abrogated by ID‐1 overexpression and p53 knockdown. Our data collectively suggest that 2‐ME treatment inhibits hypoxia/anoxia‐induced angiogenesis dependently on ID‐1 down‐regulation and p53 up‐regulation, providing a potential alternative medical treatment for un‐ruptured AVM patients.

Syndecan-4 deficiency accelerates the transition from compensated hypertrophy to heart failure following pressure overload

Increasing evidence suggests that a mismatch between angiogenesis and myocardial growth contributes to the transition from adaptive cardiac hypertrophy to heart failure following pressure overload. Syndecan-4 is a transmembrane proteoglycan that binds to growth factors and extracellular matrix proteins and is critical in focal adhesion formation. However, its effects on coronary angiogenesis during pressure overload-induced heart failure have not been studied. Here, we hypothesize that syndecan-4 modulates cardiac remodeling in response to pressure overload through its ability to regulate adaptive angiogenesis. Syndecan-4 knockout (syndecan-4 KO) and wild-type (WT) mice were subjected to pressure overload induced by transverse aortic constriction (TAC). Syndecan-4 KO mice exhibited reduced capillary density, attenuated cardiomyocyte size, and worsened left ventricular cardiac function after TAC surgery compared with WT mice. Moreover, syndecan-4 KO mice showed a significant decrease in protein kinase C alpha expression. Our data suggest that syndecan-4 is essential for the compensated hypertrophy and the maintenance of cardiac function during the process of heart failure following pressure overload.

Heat shock transcription factor 1 protects against pressure overload-induced cardiac fibrosis via Smad3

Abstract

Fibrotic cardiac muscle exhibits high stiffness and low compliance which are major risk factors of heart failure. Although heat shock transcription factor 1 (HSF1) was identified as an intrinsic cardioprotective factor, the role that HSF1 plays in cardiac fibrosis remains unclear. Our study aims to investigate the role of HSF1 in pressure overload-induced cardiac fibrosis and the underlying mechanism. HSF1 phosphorylation was significantly downregulated in transverse aortic constriction (TAC)-treated mouse hearts and mechanically stretched cardiac fibroblasts (cFBs). HSF1 transgenic (TG) mice, HSF1 deficient heterozygote (KO) mice, and their wild-type littermates were subjected to sham or TAC surgery for 4 weeks. HSF1 overexpression significantly attenuated pressure overload-induced cardiac fibrosis and dysfunction. Conversely, HSF1 KO mice showed deteriorated fibrotic response and cardiac dysfunction upon TAC. Moreover, we uncovered that overexpression of HSF1 protected against fibrotic response of cFBs to pressure overload. Mechanistically, we observed that the phosphorylation and the nuclear distribution of the Smad family member 3 (Smad3) were significantly decreased in HSF1-overexpressing mouse hearts, while being greatly increased in HSF1 KO mouse hearts upon TAC, compared to the control hearts, respectively. Similar alteration of Smad3 phosphorylation and nuclear distribution were found in isolated mouse cardiac fibroblasts and mechanically stretched cFBs. Constitutively active Smad3 blocked the anti-fibrotic effect of HSF1 in cFBs. Furthermore, we found a direct binding of phosphorylated HSF1 and Smad3, which can be suppressed by mechanical stress. In conclusion, the present study demonstrated for the first time that HSF1 acts as a novel negative regulator of cardiac fibrosis by blocking Smad3 activation.

Key messages

HSF1 activity is decreased in fibrotic hearts.

HSF1 overexpression attenuates pressure overload-induced cardiac fibrosis and dysfunction.

Deficiency of HSF1 deteriorates fibrotic response and cardiac dysfunction upon TAC.

HSF1 inhibits phosphorylation and nuclear distribution of Smad3 via direct binding to Smad3.

Active Smad3 blocks the anti-fibrotic effect of HSF1.

Electronic supplementary material

The online version of this article (doi:10.1007/s00109-016-1504-2) contains supplementary material, which is available to authorized users.

Role of miR-199b-5p in regulating angiogenesis in mouse myocardial microvascular endothelial cells through HSF1/VEGF pathway

Our study explored effects of miR-199b-5p on angiogenesis in mouse myocardial microvascular endothelial cells (MMVECs) and the involved working mechanisms. We applied explant culture to incubate C57/BL6 mouse MMVECs. Lipofection was used to transfect miR-199b-5p mimic, miR-199b-5p inhibitor and miR-199b-5p scramble respectively. MMVECs were divided into miR-199b-5p up-regulation, miR-199b-5p down-regulation and control groups based on above sequence. Expressions of miR-199b-5p, heat shock factor protein 1 (HSF1) mRNA were assessed by real-time quantitative polymerase chain reaction (RT-QPCR). Expressions of HSF1 and vascular endothelial growth factor (VEGF) were assessed by Western Blotting. Cell proliferation was assessed by CCK8. Tubule formation assay was conducted to assess formation of blood vessels. Results showed that miR-199b-5p up/down-regulation groups exhibited no obvious differences in the expressions of HSF1 mRNA compared to control group. However, miR-199b-5p up-regulation group recorded lower expressions of HSF1 and VEGF in the level of protein, and reduced cell proliferation and tubule formation. Whereas, miR-199b-5p down-regulation group presented the contrary results. The experiment indicated that miR-199b-5p can regulate proliferation and angiogenesis in mouse MMVECs through the pathway of HSF1/VEGF.

Role of HSF1-upregulated AC6 in ameliorating heart failure in mice

PURPOSE

Our previous studies discovered that Heat shock factor 1(HSF1) can alleviate pressure overload induced heart failure in mice. However, its molecular mechanisms are yet to be further explained. Many studies have already verified that Adenylyl Cyclase 6 (AC6) can ameliorate heart failure, but it is still unknown whether or not the pathway HSF1 is involved in the process. Our preliminary experiment showed that the expression level of AC6 is positively associated with HSF1. Therefore, in the present study, we aimed to explore whether HSF1 can play its role in ameliorating heart failure by regulating AC6, and how the potential internal mechanisms work.

METHODS

We applied the Transverse Aortic Constriction (TAC) for 4 weeks to develop the C57BL/6 mice pressure overload induced heart failure model. First, the mice were divided into TAC group and SHAM group. Changes in the cardiac function and morphology of the mice were observed by an ultrasonic device and Masson staining slices, expressions of AC6 mRNA were observed by RT-QPCR, expressions of HSF1 and proteinkinase A (PKA) were examined by Western Blotting, and the levels of cyclic adenosine monophosphate (cAMP) from aortic blood were measured by ELISA. Second, the TAC group were further divided into subgroups of HSF1 transgene mice, HSF1 knockout mice and wild type mice, followed by the aforesaid observations.

RESULTS

In the SHAM group, no obvious variations of cardiac function, AC6 mRNAHSF1, PKA, cAMP and other test results were found among each of the subgroups. Compared to the SHAM group, the TAC group presented clearly weakened heart functions, while, expressions of AC6 mRNA, HSF1, PKA and cAMP all recorded obvious increases. In the TAC group, compared to the WT subgroup, the HSF1 KO subgroup presented decreases in expressions of AC6 mRNA, HSF1, PKA and cAMP, and at the same time, the heart functions were weaker, while, the HSF1 TG subgroup recorded the contrary results.

CONCLUSION

In the pressure overload heart failure model, HSF1 can ameliorate heart failure by positively regulating the pathway of AC6/cAMP/PKA.

Extracellular high-mobility group box 1 mediates pressure overload-induced cardiac hypertrophy and heart failure

Inflammation plays a key role in pressure overload-induced cardiac hypertrophy and heart failure, but the mechanisms have not been fully elucidated. High-mobility group box 1 (HMGB1), which is increased in myocardium under pressure overload, may be involved in pressure overload-induced cardiac injury. The objectives of this study are to determine the role of HMGB1 in cardiac hypertrophy and cardiac dysfunction under pressure overload. Pressure overload was imposed on the heart of male wild-type mice by transverse aortic constriction (TAC), while recombinant HMGB1, HMGB1 box A (a competitive antagonist of HMGB1) or PBS was injected into the LV wall. Moreover, cardiac myocytes were cultured and given sustained mechanical stress. Transthoracic echocardiography was performed after the operation and sections for histological analyses were generated from paraffin-embedded hearts. Relevant proteins and genes were detected. Cardiac HMGB1 expression was increased after TAC, which was accompanied by its translocation from nucleus to both cytoplasm and intercellular space. Exogenous HMGB1 aggravated TAC-induced cardiac hypertrophy and cardiac dysfunction, as demonstrated by echocardiographic analyses, histological analyses and foetal cardiac genes detection. Nevertheless, the aforementioned pathological change induced by TAC could partially be reversed by HMGB1 inhibition. Consistent with the in vivo observations, mechanical stress evoked the release and synthesis of HMGB1 in cultured cardiac myocytes. This study indicates that the activated and up-regulated HMGB1 in myocardium, which might partially be derived from cardiac myocytes under pressure overload, may be of crucial importance in pressure overload-induced cardiac hypertrophy and cardiac dysfunction.

Upregulation of Nuclear Heat Shock Factor 1 Contributes to Tumor Angiogenesis and Poor Survival in Patients With Non-Small Cell Lung Cancer

BACKGROUND

The aim of this study was to detect the expression of heat shock factor 1 (HSF1) and microvessel density (MVD) in patients with non-small cell lung cancer (NSCLC) and to examine the relevance between HSF1 and angiogenesis, clinicopathologic factors, and prognosis.

METHODS

Immunohistochemical staining was used to examine the level of expression of HSF1 and CD34. MVD was used to detect the number of microvessels by counting CD34(+) endothelial cells. Their relationship with clinicopathologic factors and prognosis in patients with NSCLC was determined using IBM SPSS Statistics, version 19 (SPSS Inc, Chicago, IL).

RESULTS

The level of expression of HSF1 was increased significantly in NSCLC. HSF1 overexpression was observed in 45 patients and was significantly associated with MVD (p = 0.005). The overexpression of HSF1 was not associated with patient sex, age, tumor size, histologic type, or differentiation, but it was significantly associated with node metastasis (p = 0.005) and clinical stage (p = 0.006). HSF1 overexpression and high MVD were significantly associated with poor 5-year disease-free survival (p = 0.001 and p = 0.006, respectively). Patients with HSF1 overexpression and high MVD had a significantly poor overall survival (p = 0.006 and p = 0.019, respectively) and disease-specific survival (p = 0.005 and p = 0.016, respectively). Multivariate analysis showed that HSF1 overexpression was an independent prognosticator for poor overall, disease-specific, and disease-free survival (p = 0.040, p = 0.046, and p = 0.004, respectively).

CONCLUSIONS

Overexpression of HSF1 is common and significantly correlated with tumor angiogenesis in NSCLC. Patients with high HSF1 expression had poorer overall, disease-free, and disease-specific survival. These current findings suggest that HSF1 may serve as a novel prognostic marker and potential therapeutic target molecule for antiangiogenic therapy in patients with NSCLC.

Mitochondrial aldehyde dehydrogenase 2 plays protective roles in heart failure after myocardial infarction via suppression of the cytosolic JNK/p53 pathway in mice

Background

Increasing evidence suggests a critical role for mitochondrial aldehyde dehydrogenase 2 (ALDH2) in protection against cardiac injuries; however, the downstream cytosolic actions of this enzyme are largely undefined.

Methods and Results

Proteomic analysis identified a significant downregulation of mitochondrial ALDH2 in the heart of a rat heart failure model after myocardial infarction. The mechanistic insights underlying ALDH2 action were elucidated using murine models overexpressing ALDH2 or its mutant or with the ablation of the ALDH2 gene (ALDH2 knockout) and neonatal cardiomyocytes undergoing altered expression and activity of ALDH2. Left ventricle dilation and dysfunction and cardiomyocyte death after myocardial infarction were exacerbated in ALDH2‐knockout or ALDH2 mutant‐overexpressing mice but were significantly attenuated in ALDH2‐overexpressing mice. Using an anoxia model of cardiomyocytes with deficiency in ALDH2 activities, we observed prominent cardiomyocyte apoptosis and increased accumulation of the reactive aldehyde 4‐hydroxy‐2‐nonenal (4‐HNE). We subsequently examined the impacts of mitochondrial ALDH2 and 4‐HNE on the relevant cytosolic protective pathways. Our data documented 4‐HNE‐stimulated p53 upregulation via the phosphorylation of JNK, accompanying increased cardiomyocyte apoptosis that was attenuated by inhibition of p53. Importantly, elevation of 4‐HNE also triggered a reduction of the cytosolic HSP70, further corroborating cytosolic action of the 4‐HNE instigated by downregulation of mitochondrial ALDH2.

Conclusions

Downregulation of ALDH2 in the mitochondria induced an elevation of 4‐HNE, leading to cardiomyocyte apoptosis by subsequent inhibition of HSP70, phosphorylation of JNK, and activation of p53. This chain of molecular events took place in both the mitochondria and the cytosol, contributing to the mechanism underlying heart failure.

ANG II promotes IGF-IIR expression and cardiomyocyte apoptosis by inhibiting HSF1 via JNK activation and SIRT1 degradation

Hypertension-induced cardiac hypertrophy and apoptosis are major characteristics of early-stage heart failure. Our previous studies found that the activation of insulin-like growth factor receptor II (IGF-IIR) signaling was critical for hypertensive angiotensin II (ANG II)-induced cardiomyocyte apoptosis. However, the detailed mechanism by which ANG II regulates IGF-IIR in heart cells remains elusive. In this study, we found that ANG II activated its downstream kinase JNK to increase IGF-IIR expression through the ANG II receptor angiotensin type 1 receptor. JNK activation subsequently led to sirtuin 1 (SIRT1) degradation via the proteasome, thus preventing SIRT1 from deacetylating heat-shock transcription factor 1 (HSF1). The resulting increase in the acetylation of HSF1 impaired its ability to bind to the IGF-IIR promoter region (nt -748 to -585). HSF1 protected cardiomyocytes by acting as a repressor of IGF-IIR gene expression, and ANG II diminished this HSF1-mediated repression through enhanced acetylation, thus activating the IGF-IIR apoptosis pathway. Taken together, these results suggest that HSF1 represses IGF-IIR gene expression to protect cardiomyocytes. ANG II activates JNK to degrade SIRT1, resulting in HSF1 acetylation, which induces IGF-IIR expression and eventually results in cardiac hypertrophy and apoptosis. HSF1 could be a valuable target for developing treatments for cardiac diseases in hypertensive patients.

Urotensin II inhibited the proliferation of cardiac side population cells in mice during pressure overload by JNK-LRP6 signalling

Cardiac side population cells (CSPs) are promising cell resource for the regeneration in diseased heart as intrinsic cardiac stem cells. However, the relative low ratio of CSPs in the heart limited the ability of CSPs to repair heart and improve cardiac function effectively under pathophysiological condition. Which factors limiting the proliferation of CSPs in diseased heart are unclear. Here, we show that urotensin II (UII) regulates the proliferation of CSPs by c-Jun N-terminal kinase (JNK) and low density lipoprotein receptor-related protein 6 (LRP6) signalling during pressure overload. Pressure overload greatly upregulated UII level in plasma, UII receptor (UT) antagonist, urantide, promoted CSPs proliferation and improved cardiac dysfunction during chronic pressure overload. In cultured CSPs subjected to mechanical stretch (MS), UII significantly inhibited the proliferation by UT. Nanofluidic proteomic immunoassay showed that it is the JNK activation, but not the extracellular signal-regulated kinase signalling, that involved in the UII-inhibited- proliferation of CSPs during pressure overload. Further analysis in vitro indicated UII-induced-phospho-JNK regulates phosphorylation of LRP6 in cultured CSPs after MS, which is important in the inhibitory effect of UII on the CSPs during pressure overload. In conclusion, UII inhibited the proliferation of CSPs by JNK/LRP6 signalling during pressure overload. Pharmacological inhibition of UII promotes CSPs proliferation in mice, offering a possible therapeutic approach for cardiac failure induced by pressure overload.

The ginsenoside Rg1 prevents transverse aortic constriction-induced left ventricular hypertrophy and cardiac dysfunction by inhibiting fibrosis and enhancing angiogenesis

BACKGROUND

Ginsenoside Rg1, an important and active ingredient of Panax ginseng, has been shown to exert cardioprotective effects in vivo. The present study aimed to test the hypothesis that ginsenoside Rg1 attenuates cardiac dysfunction in a transverse aortic constriction (TAC)-induced left ventricular hypertrophy in vivo via proangiogenic and antifibrotic effects.

METHODS

This study investigated the effects of ginsenoside Rg1 in a rat model of TAC-induced left ventricular hypertrophy. Cardiac function was assessed by echocardiography. The antifibrotic and proangiogenic effects were assessed by histopathology and mRNA expression of procollagen I, III, and vascular endothelial growth factor (VEGF) through quantitative real-time PCR. The expression of phosphorylation of Akt, p38 mitogen-activated protein kinase (MAPK), hypoxia inducible factor-1 (HIF-1), and VEGF proteins were examined by Western blotting.

RESULTS

Ginsenoside Rg1 treatment significantly decreased TAC-induced myocardial fibrosis and left ventricular hypertrophy, and preserved cardiac function. Ginsenoside Rg1 administration enhanced angiogenesis by increasing the expression of HIF-1 and VEGF. These cardioprotective effects of ginsenoside Rg1 are partially related to the activation of phospho-Akt and inhibition of p38 MAPK.

CONCLUSIONS

Ginsenoside Rg1 exhibited protective effect against TAC-induced left ventricular hypertrophy and cardiac dysfunction, which is potentially associated with phospho-Akt activation and p38 MAPK inhibition.

Regulation of p53 by jagged1 contributes to angiotensin II-induced impairment of myocardial angiogenesis

Angiotensin II (AngII) is a major contributor to the development of heart failure, however, the molecular and cellular mechanisms still remain elucidative. Inadequate angiogenesis in myocardium leads to transition from cardiac hypertrophy to dysfunction, this study was therefore conducted to examine the effects of AngII on myocardial angiogenesis and the underlying mechanisms. AngII treatment significantly impaired angiogenetic responses, which were determined by counting the capillaries either in matrigel formed by cultured cardiac microvascular endothelial cells (CMVECs) or in myocardium of mice and by measuring the in vitro and in vivo production of VEGF proteins, and stimulated accumulation and phosphorylation of cytosolic p53 which led to increases in phosphorylated p53 and decreases of hypoxia inducible factor (Hif-1) in nucleus. All of these cellular and molecular events induced by AngII in CEMCs and hearts of mice were largely reduced by a p53 inhibitor, pifithrin-α (PFT-α). Interestingly, AngII stimulated the upregulation of Jagged1, a ligand of Notch, but it didn't affect the expression of Delta-like 4 (Dll-4), another ligand of Notch. Inhibition of p53 by PFT-α partly abolished this effect of AngII. Further experiments showed that knockdown ofJagged1 by addition of siRNA to cultured CMVECs dramatically declined AngII-stimulated accumulation and phosphorylation of p53 in cytosol, upregulation of phosphorylated p53 and downregulation of Hif-1 expression in nucleus, decrease of VEGF production and impairment of capillary-like tube formation by the cells. Our data collectively suggest that AngII impairs myocardial angiogenetic responses through p53-dependent downregulation of Hif-1 which is regulated by Jagged1/Notch1 signaling.

Possible role of NF-κB in hormesis during ageing

Hormesis in ageing is probably represented by mild stress-induced stimulation of protective mechanisms in cells and organisms resulting in biologically beneficial effects. Mild stress and hormetins may act on bifurcation points in the complex network of cell signaling and transcription factors, often turning homeodynamics to health or survival. Several signaling pathways activated by diverse stimuli and by stress response converge on NF-κB activation, resulting in a regulatory system characterized by high complexity. NF-κB behaves as a chaotic oscillator and it is increasingly recognized that the number of components that impinges upon phenotypic outcomes of signal transduction pathways may be higher than those taken into consideration from canonical pathway representations. NF-κB is closely related to other important upstream signaling networks, creating chaotic oscillators with other receptor-related kinases and targeting hubs for hormesis. The great bulk of natural hormetins acts on these signaling pathways, while NF-κB appears as a key regulatory factor in this context. Due to its tight relationship with main signaling system NF-κB plays a fundamental role in stress response, apoptosis and autophagy and appears to be a possible target for hormesis in ageing.

Small heat shock proteins in redox metabolism: implications for cardiovascular diseases

A timely review series on small heat shock proteins has to appropriately examine their fundamental properties and implications in the cardiovascular system since several members of this chaperone family exhibit robust expression in the myocardium and blood vessels. Due to energetic and metabolic demands, the cardiovascular system maintains a high mitochondrial activity but irreversible oxidative damage might ensue from increased production of reactive oxygen species. How equilibrium between their production and scavenging is achieved becomes paramount for physiological maintenance. For example, heat shock protein B1 (HSPB1) is implicated in maintaining this equilibrium or redox homeostasis by upholding the level of glutathione, a major redox mediator. Studies of gain or loss of function achieved by genetic manipulations have been highly informative for understanding the roles of those proteins. For example, genetic deficiency of several small heat shock proteins such as HSPB5 and HSPB2 is well-tolerated in heart cells whereas a single missense mutation causes human pathology. Such evidence highlights both the profound genetic redundancy observed among the multigene family of small heat shock proteins while underscoring the role proteotoxicity plays in driving disease pathogenesis. We will discuss the available data on small heat shock proteins in the cardiovascular system, redox metabolism and human diseases. From the medical perspective, we envision that such emerging knowledge of the multiple roles small heat shock proteins exert in the cardiovascular system will undoubtedly open new avenues for their identification and possible therapeutic targeting in humans. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Early treatment with fumagillin, an inhibitor of methionine aminopeptidase-2, prevents Pulmonary Hypertension in monocrotaline-injured rats

Pulmonary Hypertension (PH) is a pathophysiologic condition characterized by hypoxemia and right ventricular strain. Proliferation of fibroblasts, smooth muscle cells, and endothelial cells is central to the pathology of PH in animal models and in humans. Methionine aminopeptidase-2 (MetAP2) regulates proliferation in a variety of cell types including endothelial cells, smooth muscle cells, and fibroblasts. MetAP2 is inhibited irreversibly by the angiogenesis inhibitor fumagillin. We have previously found that inhibition of MetAP2 with fumagillin in bleomycin-injured mice decreased pulmonary fibrosis by selectively decreasing the proliferation of lung myofibroblasts. In this study, we investigated the role of fumagillin as a potential therapy in experimental PH. In vivo, treatment of rats with fumagillin early after monocrotaline injury prevented PH and right ventricular remodeling by decreasing the thickness of the medial layer of the pulmonary arteries. Treatment with fumagillin beginning two weeks after monocrotaline injury did not prevent PH but was associated with decreased right ventricular mass and decreased cardiomyocyte hypertrophy, suggesting a direct effect of fumagillin on right ventricular remodeling. Incubation of rat pulmonary artery smooth muscle cells (RPASMC) with fumagillin and MetAP2-targeting siRNA inhibited proliferation of RPASMC in vitro. Platelet-derived growth factor, a growth factor that is important in the pathogenesis of PH and stimulates proliferation of fibroblasts and smooth muscle cells, strongly increased expression of MetP2. By immunohistochemistry, we found that MetAP2 was expressed in the lesions of human pulmonary arterial hypertension. We propose that fumagillin may be an effective adjunctive therapy for treating PH in patients.

Association of Stat3 with HSF1 plays a critical role in G-CSF-induced cardio-protection against ischemia/reperfusion injury

Granulocyte colony-stimulating factor (G-CSF) has been shown to be cardio-protective against ischemia through activating Jak2/Stat3 pathway, however, the mechanism is unclear. Heat shock transcription factor 1 (HSF1), a definite endogenous protective protein in cardiomyocytes, may interact with Stat family under stress conditions. We hypothesized that G-CSF could induce cardio-protection against ischemia/reperfusion (I/R) through association of HSF1 with Stat3. To test the hypothesis, we built cardiac I/R injury model with HSF1 knockout (KO) mice and wild type (WT) mice by occlusion of the left anterior descending (LAD) coronary artery for 30min and subsequent release of the occlusion for 24h. These mice were administered with G-CSF (100μg/kg/day) or vehicle subcutaneously for 3days before surgery. As expected, G-CSF induced significant cardio-protections against I/R injury, characterized by higher ejection fraction (EF%), lower left ventricular end diastolic pressure (LVEDP), increased dp/dt value and decreased infarct area as compared with the vehicle treatment in WT mice. In HSF1-KO mice, however, these cardio-protections induced by G-CSF were greatly attenuated. Inhibition of oxidative stress-induced cardiomyocyte apoptosis by G-CSF also disappeared due to the deficiency of HSF1 in vitro and in vivo. Furthermore, G-CSF increased the phosphorylation and the association of Stat3 with HSF1, which enhanced transcriptional activity of HSF1. Inhibition of either Stat3 or HSF1 by pharmacological agents suppressed G-CSF-induced association of the two proteins and anti-apoptotic effect on cardiomyocytes. Our data suggest that G-CSF stimulates phosphorylation and association of Stat3 with HSF1 and therefore enhances transcriptional activity of HSF1, leading to the cardio-protection against I/R injury.

Proteostasis and REDOX state in the heart

Force-generating contractile cells of the myocardium must achieve and maintain their primary function as an efficient mechanical pump over the life span of the organism. Because only half of the cardiomyocytes can be replaced during the entire human life span, the maintenance strategy elicited by cardiac cells relies on uninterrupted renewal of their components, including proteins whose specialized functions constitute this complex and sophisticated contractile apparatus. Thus cardiac proteins are continuously synthesized and degraded to ensure proteome homeostasis, also termed "proteostasis." Once synthesized, proteins undergo additional folding, posttranslational modifications, and trafficking and/or become involved in protein-protein or protein-DNA interactions to exert their functions. This includes key transient interactions of cardiac proteins with molecular chaperones, which assist with quality control at multiple levels to prevent misfolding or to facilitate degradation. Importantly, cardiac proteome maintenance depends on the cellular environment and, in particular, the reduction-oxidation (REDOX) state, which is significantly different among cardiac organelles (e.g., mitochondria and endoplasmic reticulum). Taking into account the high metabolic activity for oxygen consumption and ATP production by mitochondria, it is a challenge for cardiac cells to maintain the REDOX state while preventing either excessive oxidative or reductive stress. A perturbed REDOX environment can affect protein handling and conformation (e.g., disulfide bonds), disrupt key structure-function relationships, and trigger a pathogenic cascade of protein aggregation, decreased cell survival, and increased organ dysfunction. This review covers current knowledge regarding the general domain of REDOX state and protein folding, specifically in cardiomyocytes under normal-healthy conditions and during disease states associated with morbidity and mortality in humans.