Inflammation and fibrosis in murine models of heart failure

Matrine Protects Cardiomyocytes Against Hyperglycemic Stress by Promoting Mitofusin 2-Induced Mitochondrial Fusion

Matrine, an active component of Sophora flavescens Ait root extracts, has been used in China for years to treat cancer and viral hepatitis. In the present study, we explored the effects of matrine on hyperglycemia-treated cardiomyocytes. Cardiomyocyte function, oxidative stress, cellular viability, and mitochondrial fusion were assessed through immunofluorescence, quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assays, and RNA interference. Matrine treatment suppressed hyperglycemia-induced oxidative stress in cardiomyocytes by upregulating transcription of nuclear factor erythroid 2-like 2 and heme oxygenase-1. Matrine also improved cardiomyocyte contractile and relaxation function during hyperglycemia, and it reduced hyperglycemia-induced cardiomyocyte death by inhibiting mitochondrial apoptosis. Matrine treatment increased the transcription of mitochondrial fusion-related genes and thus attenuated the proportion of fragmented mitochondria in cardiomyocytes. Inhibiting mitochondrial fusion by knocking down mitofusin 2 (Mfn2) abolished the cardioprotective effects of matrine during hyperglycemia. These results demonstrate that matrine could be an effective drug to alleviate hyperglycemia-induced cardiomyocyte damage by activating Mfn2-induced mitochondrial fusion.

SPARC production by bone marrow-derived cells contributes to myocardial fibrosis in pressure overload

In human heart failure and in murine hearts with left-ventricular pressure overload (LVPO), increases in fibrosis are associated with increases in myocardial stiffness. Secreted protein acidic and rich in cysteine (SPARC) is shown to be necessary for both cardiac fibrosis and increases in myocardial stiffness in response to LVPO; however, cellular sources of cardiac SPARC are incompletely defined. Irradiation and bone marrow transfer were undertaken to test the hypothesis that SPARC expression by bone marrow-derived cells is an important mediator of fibrosis in LVPO. In recipient SPARC-null mice transplanted with donor wild-type (WT) bone marrow and subjected to LVPO, levels of fibrosis similar to that of WT mice were found despite the lack of SPARC expression by resident cells. In recipient WT mice with donor SPARC-null bone marrow, significantly less fibrosis versus that of WT mice was found despite the expression of SPARC by resident cells. Increases in myocardial stiffness followed a similar pattern to that of collagen deposition. Myocardial macrophages were significantly reduced in SPARC-null mice with LVPO versus that of WT mice. Recipient SPARC-null mice transplanted with donor WT bone marrow exhibited an increase in cardiac macrophages versus that of SPARC-null LVPO and donor WT mice with recipient SPARC-null bone marrow. Expression of vascular cellular adhesion molecule (VCAM), a previously identified binding partner of SPARC, was assessed in all groups and with the exception of WT mice, increases in VCAM immunoreactivity with LVPO were observed. However, no differences in VCAM expression between bone marrow transplant groups were noted. In conclusion, SPARC expression by bone marrow-derived cells was critical for fibrotic deposition of collagen and influenced the expansion of myocardial macrophages in response to LVPO.NEW & NOTEWORTHY Myocardial fibrosis and the resultant increases in LV and myocardial stiffness represent pivotal consequences of chronic pressure overload (PO). In this study, a murine model of cardiac fibrosis induced by PO was used to demonstrate a critical function of SPARC in bone marrow-derived cells that drives cardiac fibrosis and increases in cardiac macrophages.

Reynoutrin Improves Ischemic Heart Failure in Rats Via Targeting S100A1

This study investigated the effects of reynoutrin on the improvement of ischemic heart failure (IHF) and its possible mechanism in rats. The rat heart failure model was established by permanently ligating the left anterior descending coronary artery (LAD) and administering different doses of reynoutrin. Cardiac function, inflammatory factors releasing, oxidative stress, cardiomyocytes apoptosis, and myocardial fibrosis were evaluated. Western blotting was used to determine protein expression levels of S100 calcium-binding protein A1 (S100A1), matrix metallopeptidase 2(MMP2), MMP9, phosphorylated (p-) p65, and transforming growth factor -β1 (TGF-β1) in myocardial tissue of the left ventricle. Results showed that reynoutrin significantly improved cardiac function, suppressed the release of inflammatory factors, reduced oxidative stress, inhibited cardiomyocytes apoptosis, and attenuated myocardial fibrosis in rats with IHF. In rat myocardial tissue, permanent LAD-ligation resulted in a significant down-regulation in S100A1 expression, whereas reynoutrin significantly up-regulated S100A1 protein expression while down-regulating MMP2, MMP9, p-p65, and TGF-β1 expressions. However, when S100A1 was knocked down in myocardial tissue, the above-mentioned positive effects of reynoutrin were significantly reversed. Reynoutrin is a potential natural drug for the treatment of IHF, and its mechanism of action involves the up-regulation of S100A1 expression, thereby inhibiting expressions of MMPs and the transcriptional activity of nuclear factor kappa-B.

CD11b is involved in coxsackievirus B3-induced viral myocarditis in mice by inducing Th17 cells

Viral myocarditis (VMC) caused by coxsackievirus B3 (CVB3) infection is a life-threatening disease. The cardiac damage during VMC is not mainly due to the direct cytotoxic effect of the virus on cardiomyocytes but mostly involves the induction of immune responses. Integrin CD11b plays an important role in immune response, for instance, in the induction of Th17 cells. However, the role of CD11b in the pathogenesis of VMC remains largely unknown. In the present study, a mouse model of VMC was established by CVB3 infection and CD11b was knocked down in the VMC mice by transfection with siRNA-CD11b. The expression of CD11b and IL-17 in heart tissues, frequency of Th17 cells in spleen tissues and serum IL-17 levels were measured using quantitative RT-PCR, Western blot, immunohistochemistry, flow cytometry and ELISA. Results showed that CVB3 infection caused the pathological changes in heart tissues with the increases in the following indexes: expression of CD11b and IL-17 in heart tissues, frequency of Th17 cells in spleen tissues and serum IL-17 levels. The expression of CD11b was positively correlated with IL-17 expression in heart tissues. Depletion of CD11b attenuated the damage caused by CVB3 and decreased the frequency of Th17 cells in spleen tissues as well as in IL-17, IL-23 and STAT3 expression in heart tissues. In summary, our findings reveal that disruption of CD11b function reduced CVB3-induced myocarditis, suggesting that CD11b may be a novel therapeutic target for VMC.

Huoxin Pill () Attenuates Cardiac Fibrosis by Suppressing TGF-β1/Smad2/3 Pathway in Isoproterenol-Induced Heart Failure Rats

OBJECTIVE

To evaluate the effects of Huoxin Pill (, HXP) on cardiac fibrosis and heart failure (HF) in isoproterenol (ISO)-induced HF rats.

METHODS

Thirty Wistar rats were randomly divided into 5 groups including control, HF, isosorbide mononitrate (ISMN), HXP low (HXP-L), and HXP high (HXP-H) groups (n=6 for each group) according to the complete randomization method. Rats were pretreated with ISMN (5 mg/kg daily), low concentration of HXP (10 mg/kg daily) or high concentration of HXP (30 mg/kg daily) or equal volume of saline by intragastric administration for 1 week, followed by intraperitoneal injection of ISO (10 mg/kg, 14 days), and continually intragastric administrated with above medicines or saline for additional 6 weeks. The effects of HXP treatment on the cardiac function, heart weight index (HWI), pathological changes, and collagen content were further assessed. Moreover, the role of HXP on activation of transforming growth factor- β 1 (TGF-β 1)/Smads pathway was further explored using immunohistochemistry (IHC) and Western-blot assay.

RESULTS

HXP treatment significantly alleviated the decrease of ejection fraction (EF) and fractional shortening (FS), while decreased the elevation of left ventricular end-systolic volume (LVESV) in ISO-induced HF rats (P<0.05). Moreover, HXP treatment obviously attenuated the increase of HWI and serum level of creatine kinase MB (CK-MB, P<0.05), as well as pathological changes in ISO-induced HF rats. Further determination indicated that HXP treatment alleviated the elevation of collagen I and collagen III protein expression in cardiac tissues of ISO-induced HF rats. Furthermore, HXP treatment significantly down-regulated the increase of TGF-β 1 and p-Smad2/3 protein expression in cardiac tissues of HF rats (P<0.05), while did not affect the expression of total Smad2/3.

CONCLUSIONS

HXP attenuated heart failure and cardiac fibrosis in ISO-induced HF rats by suppression of TGF-β 1/Smad2/3 pathway.

Total Glucosides of Peony Protect Cardiomyocytes against Oxidative Stress and Inflammation by Reversing Mitochondrial Dynamics and Bioenergetics

Total glucosides of peony (TGP) are used to treat rheumatoid arthritis and systemic lupus erythematosus. We explored the protective effects of TGP on cardiomyocyte oxidative stress and inflammation in the presence of hydrogen peroxide by focusing on mitochondrial dynamics and bioenergetics. Our study demonstrated that hydrogen peroxide significantly repressed cardiomyocyte viability and promoted cell apoptosis through induction of the mitochondrial death pathway. TGP treatment sustained cardiomyocyte viability, reduced cardiomyocyte apoptosis, and decreased inflammation and oxidative stress. Molecular investigation indicated that hydrogen peroxide caused mitochondrial dynamics disruption and bioenergetics reduction in cardiomyocytes, but this alteration could be normalized by TGP. We found that disruption of mitochondrial dynamics abolished the regulatory effects of TGP on mitochondrial bioenergetics; TGP modulated mitochondrial dynamics through the AMP-activated protein kinase (AMPK) pathway; and inhibition of AMPK alleviated the protective effects of TGP on mitochondria. Our results showed that TGP treatment reduces cardiomyocyte oxidative stress and inflammation in the presence of hydrogen peroxide by correcting mitochondrial dynamics and enhancing mitochondrial bioenergetics. Additionally, the regulatory effects of TGP on mitochondrial function seem to be mediated through the AMPK pathway. These findings are promising for myocardial injury in patients with rheumatoid arthritis and systemic lupus erythematosus.

X-ray diffraction and second harmonic imaging reveal new insights into structural alterations caused by pressure-overload in murine hearts

We demonstrate a label-free imaging approach to study cardiac remodeling of fibrotic and hypertrophic hearts, bridging scales from the whole organ down to the molecular level. To this end, we have used mice subjected to transverse aortic constriction and imaged adjacent cardiac tissue sections by microfocus X-ray diffraction and second harmonic generation (SHG) imaging. In this way, the acto-myosin structure was probed in a spatially resolved manner for entire heart sections. From the recorded diffraction data, spatial maps of diffraction intensity, anisotropy and orientation were obtained, and fully automated analysis depicted the acto-myosin filament spacing and direction. X-ray diffraction presented an overview of entire heart sections and revealed that in regions of severe cardiac remodeling the muscle mass is partly replaced by connective tissue and the acto-myosin lattice spacing is increased at these regions. SHG imaging revealed sub-cellular structure of cardiac tissue and complemented the findings from X-ray diffraction by revealing micro-level distortion of myofibrils, immune cell infiltration at regions of cardiac remodeling and the development of fibrosis down to the scale of a single collagen fibril. Overall, our results show that both X-ray diffraction and SHG imaging can be used for label-free and high-resolution visualization of cardiac remodeling and fibrosis progression at different stages in a cardiac pressure-overload mouse model that cannot be achieved by conventional histology.

Silencing of METTL3 attenuates cardiac fibrosis induced by myocardial infarction via inhibiting the activation of cardiac fibroblasts

Cardiac fibrosis is characterized by the activation of cardiac fibroblasts and accumulation of extracellular matrix. METTL3, a component of methyltransferase complex, participates in multiple biological processes associated with mammalian development and disease progression. However, the role of METTL3 in cardiac fibrosis is still unknown. We performed fibroblasts activation with TGF-β1 (20 ng/mL) in vitro and established in vivo mouse models with lentivirus to assess the effects of METTL3 on cardiac fibroblasts proliferation and collagen formation. Methylated RNA immunoprecipitation (MeRIP) was used to define the potential fibrosis-regulated gene. The expression level of METTL3 was increased in cardiac fibrotic tissue of mice with chronic myocardial infarction and cultured cardiac fibroblats (CFs) treated with TGF-β1. Enforced expression of METTL3 promoted proliferation and fibroblast-to-myofibroblast transition and collagens accumulation, while silence of METTL3 did the opposite. Silence of METTL3 by lentivirus carrying METTL3 siRNA markedly alleviated cardiac fibrosis in MI mice. Transcriptome and N6-methyladenosine (m⁶ A) profiling analyses revealed that the expression and m⁶ A level of collagen-related genes were altered after silence of METTL3. METTL3-mediated m⁶ A modification is critical for the development of cardiac fibrosis, providing a molecular target for manipulating fibrosis and the associated cardiac diseases.

Critical roles of macrophages in pressure overload-induced cardiac remodeling

Macrophages are integral components of the mammalian heart that show extensive expansion in response to various internal or external stimuli. After the onset of sustained pressure overload (PO), the accumulation of cardiac macrophages through local macrophage proliferation and monocyte migration has profound effects on the transition to cardiac hypertrophy and remodeling. In this review, we describe the heterogeneity and diversity of cardiac macrophages and summarize the current understanding of the important roles of macrophages in PO-induced cardiac remodeling. In addition, the possible mechanisms involved in macrophage modulation are also described. Finally, considering the significant effects of cardiac macrophages, we highlight their emerging role as therapeutic targets for alleviating pathological cardiac remodeling after PO.

Signaling via the Interleukin-10 Receptor Attenuates Cardiac Hypertrophy in Mice During Pressure Overload, but not Isoproterenol Infusion

Inflammation plays a key role during cardiac hypertrophy and the development of heart failure. Interleukin-10 (IL-10) is a major anti-inflammatory cytokine that is expressed in the heart and may play a crucial role in cardiac remodeling. Based on the evidence that IL-10 potentially reduces pathological hypertrophy, it was hypothesized that signaling via the IL-10 receptor (IL10R) in the heart produces a protective role in reducing cardiac hypertrophy. The aim of this study was to investigate the effects of the ablation of Il-10-r1 gene during pathological cardiac hypertrophy in mice. We found that IL-10R1 gene silencing in cultured cardiomyocytes diminished the anti-hypertrophic effect of Il-10 in TNF-α induced hypertrophy model. We then analyzed mice deficient in the Il-10-r1 gene (IL-10R1^-/- mice) and subjected them to transverse aortic constriction or isoproterenol infusion to induce pathological hypertrophy. In response to transverse aortic constriction for 2 weeks, IL-10R1^-/- mice displayed a significant increase in the hypertrophic response as indicated by heart weight/body weight ratio, which was accompanied by significant increases in cardiomyocyte surface area and interstitial fibrosis. In contrast, there was no difference in hypertrophic response to isoproterenol infusion (10 days) between the knockout and control groups. Analysis of cardiac function using echocardiography and invasive hemodynamic studies did not show any difference between the WT and IL-10R1^-/- groups, most likely due to the short term nature of the models. In conclusion, our data shows that signaling via the IL-10 receptor may produce protective effects against pressure overload-induced hypertrophy but not against β-adrenergic stimuli in the heart. Our data supports previous evidence that signaling modulated by IL-10 and its receptor may become a potential target to control pathological cardiac hypertrophy.

Matrine attenuates cardiomyocyte ischemia-reperfusion injury through activating AMPK/Sirt3 signaling pathway

Matrine has been found to affect cell viability and function. In the present study, we explored the cardioprotective role of matrine in cardiomyocyte damage under hypoxia/reoxygenation. In vitro, cardiomyocyte hypoxia/reoxygenation was used to mimic ischemia/reperfusion injury in the presence of matrine. After exposure to hypoxia/reoxygenation, cardiomyocyte viability was reduced and cell apoptosis was increased; this alteration was inhibited by matrine. At the molecular levels, Sirt3 and AMPK were significantly downregulated by hypoxia/reoxygenation injury whereas matrine administration was able to upregulate Sirt3 and AMPK expression and activity in the presence of hypoxia/reoxygenation. Interestingly, inhibition of Sirt3/AMPK pathway abolished the cardioprotective action of matrine on cardiomyocyte in the presence of hypoxia/reoxygenation injury, resulting into cardiomyocyte viability reduction and cell death augmentation. Altogether, our results demonstrated a novel role played by matrine in regulating cardiomyocyte viability and death in the presence of hypoxia/reoxygenation, with a potential application in the clinical practice for the treatment of patients with myocardial infarction.

Emerging therapies for right ventricular dysfunction and failure

Therapeutic options for right ventricular (RV) dysfunction and failure are strongly limited. Right heart failure (RHF) has been mostly addressed in the context of pulmonary arterial hypertension (PAH), where it is not possible to discern pulmonary vascular- and RV-directed effects of therapeutic approaches. In part, opposing pathomechanisms in RV and pulmonary vasculature, i.e., regarding apoptosis, angiogenesis and proliferation, complicate addressing RHF in PAH. Therapy effective for left heart failure is not applicable to RHF, e.g., inhibition of adrenoceptor signaling and of the renin-angiotensin system had no or only limited success. A number of experimental studies employing animal models for PAH or RV dysfunction or failure have identified beneficial effects of novel pharmacological agents, with most promising results obtained with modulators of metabolism and reactive oxygen species or inflammation, respectively. In addition, established PAH agents, in particular phosphodiesterase-5 inhibitors and soluble guanylate cyclase stimulators, may directly address RV integrity. Promising results are furthermore derived with microRNA (miRNA) and long non-coding RNA (lncRNA) blocking or mimetic strategies, which can target microvascular rarefaction, inflammation, metabolism or fibrotic and hypertrophic remodeling in the dysfunctional RV. Likewise, pre-clinical data demonstrate that cell-based therapies using stem or progenitor cells have beneficial effects on the RV, mainly by improving the microvascular system, however clinical success will largely depend on delivery routes. A particular option for PAH is targeted denervation of the pulmonary vasculature, given the sympathetic overdrive in PAH patients. Finally, acute and durable mechanical circulatory support are available for the right heart, which however has been tested mostly in RHF with concomitant left heart disease. Here, we aim to review current pharmacological, RNA- and cell-based therapeutic options and their potential to directly target the RV and to review available data for pulmonary artery denervation and mechanical circulatory support.

SERCA Overexpression Improves Mitochondrial Quality Control and Attenuates Cardiac Microvascular Ischemia-Reperfusion Injury

Despite significant advances in the treatment of myocardial ischemia-reperfusion (I/R) injury, coronary circulation is a so far neglected target of cardioprotection. In this study, we investigated the molecular mechanisms underlying I/R injury to cardiac microcirculation. Using gene delivery, we analyzed microvascular protective effects of sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) on the reperfused heart and examined the role of SERCA in regulating mitochondrial quality control in cardiac microvascular endothelial cells (CMECs). Our data showed that SERCA overexpression attenuates lumen stenosis, inhibits microthrombus formation, reduces inflammation response, and improves endothelium-dependent vascular relaxation. In vitro experiments demonstrated that SERCA overexpression improves endothelial viability, barrier integrity, and cytoskeleton assembly in CMECs. Mitochondrial quality control, including mitochondrial fusion, mitophagy, bioenergetics, and biogenesis, were disrupted by I/R injury but were restored by SERCA overexpression. SERCA overexpression also restored mitochondrial quality control by inhibiting calcium overload, inactivating xanthine oxidase (XO), and reducing intracellular/mitochondrial reactive oxygen species (ROS). Administration of exogenous XO or a calcium channel agonist abolished the protective effects of SERCA overexpression on mitochondrial quality control and offset the beneficial effects of SERCA overexpression after cardiac microvascular I/R injury. These findings indicate that SERCA overexpression may be an effective approach to targeting cardiac microvascular I/R injury by regulating calcium/XO/ROS signaling and preserving mitochondrial quality control.

Immune cell Dilemma in Ischemic Cardiomyopathy: To Heal or Not to Heal

Inflammation is a double-edged sword for sterile tissue injury such as in myocardial infarction (MI). After ischemic injury, inflammatory immune responses activate repair processes, clear tissue-debris, form a stable scar and initiate angiogenesis in the myocardium for efficient wound-healing. However, incomplete immune resolution or sustained low-grade inflammation lead to ischemic cardiomyopathy (IC) characterized by maladaptive tissue remodeling and left-ventricular dilatation. It is clear that a delicate balance of cytokines, chemokines, prostaglandins, resolvins, and the innate and adaptive immune systems is critical for adequate healing as both insufficient- or overt-activation of inflammatory responses can either enhance rupture incidence or exacerbate cardiac dysfunction in the long-term. Among all the players, immune cells are the most critical as they are not only a source for all of the inflammatory protein mediators, but are also a target. However, phenotypic complexities associated with different immune subtypes, their interdependence, phasic-activations and varied functionalities often make it difficult to segregate the effects of one immune cell from another. In this review, we briefly summarize the role of several innate and adaptive immune cells to acquaint readers with complex immune-networks that dictate the extent of wound-healing post-MI and maladaptive remodeling during IC.

Kruppel-like factor 10 protects against acute viral myocarditis by negatively regulating cardiac MCP-1 expression

Viral myocarditis (VMC) is a cardiac disease associated with myocardial inflammation and injury induced by virus infection. Cardiomyocytes have recently been regarded as key players in eliciting and modulating inflammation within the myocardium. Kruppel-like factor 10 (KLF10) is a crucial regulator of various pathological processes and plays different roles in a variety of diseases. However, its role in VMC induced by coxsackievirus B3 (CVB3) infection remains unknown. In this study, we report that cardiac KLF10 confers enhanced protection against viral myocarditis. We found that KLF10 expression was downregulated upon CVB3 infection. KLF10 deficiency enhanced cardiac viral replication and aggravated VMC progress. Bone marrow chimera experiments indicated that KLF10 expression in nonhematopoietic cells was involved in the pathogenesis of VMC. We further identified MCP-1 as a novel target of KLF10 in cardiomyocytes, and KLF10 cooperated with histone deacetylase 1 (HDAC1) to negatively regulate MCP-1 expression by binding its promoter, leading to activation of MCP-1 transcription and recruitment of Ly6C^high monocytes/macrophages into the myocardium. This novel mechanism of MCP-1 regulation by KLF10 might provide new insights into the pathogenesis of VMC and a potential therapeutic target for VMC.

Overexpression of Ubiquitin-Specific Protease 2 (USP2) in the Heart Suppressed Pressure Overload-Induced Cardiac Remodeling

Ubiquitin-specific protease 2 (USP2) is an important member of the deubiquitination system. GEO dataset revealed that USP2 was downregulated in the hearts under pressure overload. However, the cardiomyocyte-specific function of USP2 in the setting of pressure overload is unknown. In the current study, a mouse model of pressure overload was induced by transverse aortic constriction (TAC, 2 weeks). Overexpression of USP2 in the heart was conducted by AAV9 infection. Changes in heart histology were detected by Masson's trichrome staining and hematoxylin-eosin staining (H&E). Echocardiography was used to assess cardiac function. The size of cardiomyocytes was examined by wheat germ agglutinin (WGA) staining. Cardiac oxidative stress was detected by dihydroethidine staining. Our results showed that USP2 was downregulated in the cardiomyocytes following 2 weeks of TAC. Overexpression of cardiac USP2 preserved ventricular function following 2 weeks of TAC. Overexpression of cardiac USP2 inhibited TAC-induced cardiac remodeling, by suppressing cardiac hypertrophy, inhibiting inflammatory responses and fibrosis, and attenuating oxidative stress. Our findings reveal a previously unrecognized role of USP2 in regulating pressure overload-induced cardiac remodeling.

SERCA overexpression reduces reperfusion-mediated cardiac microvascular damage through inhibition of the calcium/MCU/mPTP/necroptosis signaling pathways

Endothelial cells lining the microvasculature are particularly vulnerable to the deleterious effects of cardiac ischemia/reperfusion (I/R) injury, a susceptibility that is partially mediated by dysregulated intracellular calcium signals. Sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) functions to recycle calcium from the cytosol back to the endoplasmic reticulum. The purpose of this study is to explore the roles and mechanisms of SERCA in protecting microcirculation against cardiac I/R injury. Our data showed that overexpression of SERCA significantly reduced I/R-induced luminal stenosis and vascular wall edema, possibly through normalization of the ratio between eNOS and ET-1. I/R-induced erythrocyte morphological changes in micro-vessels could be reversed by SERCA overexpression through transcriptional inhibition of the expression of adhesive factors. In addition, SERCA-sustained endothelial barrier integrity reduced the likelihood of inflammatory cells infiltrating the myocardium. Furthermore, we found that SERCA overexpression attenuated intracellular calcium overload, suppressed mitochondrial calcium uniporter (MCU) expression, and prevented the abnormal opening of mitochondrial permeability transition pores (mPTP) in I/R-treated cardiac microvascular endothelial cells (CMECs). Interestingly, the administration of calcium activator or MCU agonist induced endothelial necroptosis in vitro and thus abolished the microvascular protection afforded by SERCA in reperfused heart tissue in vivo. In conclusion, by using gene delivery strategies to specifically target SERCA in vitro and in vivo, we identify a potential novel pathway by which SERCA overexpression protects microcirculation against cardiac I/R injury in a manner dependent on the calcium/MCU/necroptosis pathway. These findings should be taken into consideration in the development of pharmacological strategies for therapeutic interventions against cardiac microvascular I/R injury.

Huoxin pill attenuates myocardial infarction-induced apoptosis and fibrosis via suppression of p53 and TGF-β1/Smad2/3 pathways

Huoxin Pill (HXP), a Traditional Chinese Medicine, is used widely to treat patients with coronary heart disease and angina pectoris in China. However, the underlying protective mechanism of HXP on cardiac apoptosis and fibrosis has never been evaluated. Therefore, the aim of this study was to investigate the role of HXP in a myocardial infarction (MI) mouse model. The mice were randomly divided into 3 groups and subjected to surgical ligation of the left anterior descending (LAD) coronary artery or sham surgery (n = 6 for each group) and treated with HXP (50 mg/kg/day) or saline by gavage for 2 weeks. At 2 weeks post MI, we found that HXP significantly enhanced myocardial function and attenuated the increase of heart weight index (HWI) and pathological changes in MI mice. RNA-sequencing and KEGG pathway analyses identified 660 differentially expressed genes and multiple enriched signaling pathways including p53 and TGF-β. In support of these findings, HXP attenuated cardiac apoptosis and decreased p53 and Bax protein expression, while increasing Bcl-2 protein expression in cardiac tissues of MI mice. Furthermore, HXP treatment inhibited cardiac fibrosis and significantly down-regulated TGF-β1 protein expression and Smad2/3 phosphorylation in cardiac tissues. In summary, HXP can improve cardiac function in mice after MI by attenuating cardiac apoptosis and fibrosis partly via supression of the p53/Bax/Bcl-2 and TGF-β1/Smad2/3 pathways.

Imaging tools for assessment of myocardial fibrosis in humans: the need for greater detail

Myocardial fibrosis is recognized as a key pathological process in the development of cardiac disease and a target for future therapeutics. Despite this recognition, the assessment of fibrosis is not a part of routine clinical practice. This is primarily due to the difficulties in obtaining an accurate assessment of fibrosis non-invasively. Moreover, there is a clear discrepancy between the understandings of myocardial fibrosis clinically where fibrosis is predominately studied with comparatively low-resolution medical imaging technologies like MRI compared with the basic science laboratories where fibrosis can be visualized invasively with high resolution using molecularly specific fluorescence microscopes at the microscopic and nanoscopic scales. In this article, we will first review current medical imaging technologies for assessing fibrosis including echo and MRI. We will then highlight the need for greater microscopic and nanoscopic analysis of human tissue and how this can be addressed through greater utilization of human tissue available through endomyocardial biopsies and cardiac surgeries. We will then describe the relatively new field of molecular imaging that promises to translate research findings to the clinical practice by non-invasively monitoring the molecular signature of fibrosis in patients.

Serum neprilysin levels are associated with myocardial stunning after ST-elevation myocardial infarction

Background

Left ventricular remodeling following ST-elevation myocardial infarction (STEMI) is associated with poor outcome, including heart failure (HF). Neprilysin inhibition leads to improved outcome in patients with altered left ventricular ejection fraction (LVEF).

Methods

We aimed to assess the association between serum levels of neprilysin and left ventricular (LV) volumes, function and remodeling in STEMI patients with successful myocardial reperfusion and no clinical sign of HF. Sixty-eight patients were admitted for STEMI and had both plasma neprilysin measurement at baseline and 3D transthoracic echocardiogram at baseline and after a median follow-up of 7 months. We compared 3 groups: a group with a low-level of plasma neprilysin (< 125 pg/mL, i.e. the lower limit of detection of the assay) and the two other groups were defined as being below or above the median value of the remaining samples.

Results

Median age was 58.5 ± 12.8 years and 56 (82.4%) were men. Median LVEF was 45.0 ± 8.5%. Baseline characteristics were comparable between groups (low-level of neprilysin group [≤125 pg/mL, n = 38], medium-level of neprilysin group [126–450 pg/mL, n = 15] and a high-level group [> 450 pg/mL, n = 15]). At baseline there was a non-significant trend towards lower end-diastolic volume (p = 0.07) but significantly lower LVEF in the high neprilysin group (46.4 ± 8.3%, 47.1 ± 8.1% and 39.1 ± 6.9%, p < 0.01). At follow-up, the magnitude of LVEF increase was significantly more important in the high neprilysin group compared to the other groups (p = 0.022 for relative change in LVEF and 6.6 ± 7.3%, 3.6 ± 9.0% and 11.3 ± 8.4%, p = 0.031 for absolute change in LVEF) resulting in similar LVEF levels at follow-up between all groups (53.0 ± 8.9%, 50.6 ± 9.7% and 50.4 ± 9.9%, p = 0.55).

Conclusions

Initial high neprilysin levels may identify patients with stunned myocardium early after STEMI, with a recovery of contractility leading to improved LVEF at follow-up. Future studies will have to assess the role of neprilysin in the setting of STEMI and the potential benefit of its blockade.

Bcl-2-associated athanogene 5 overexpression attenuates catecholamine-induced vascular endothelial cell apoptosis

Bcl-2 associated athanogene 5 (Bag5) is a novel endoplasmic reticulum (ER) regulator. However, its role in catecholamine-induced endothelial cells damage has not been fully understood. In our study, catecholamine was used to mimic hypertension-related endothelial cell damage. Then, western blots, enzyme-linked immunosorbent assay, immunofluorescence, quantitative polymerase chain reaction and pathway analysis were conducted to analyze the role of Bag5 in endothelial cell damage in response to catecholamine. Our results indicated that the endothelial cell viability was impaired by catecholamine. Interestingly, Bag5 overexpression significantly reversed endothelial cell viability. Mechanistically, Bag5 overexpression inhibited ER stress, attenuated oxidative stress and repressed inflammation in catecholamine-treated endothelial cells. These beneficial effects finally contributed to endothelial cell survival under catecholamine treatment. Pathway analysis demonstrated that Bag5 was under the control of the mitogen-activated protein kinase (MAPK)-extracellular-signal-regulated kinase (ERK) signaling pathway. Reactivation of the MAPK-ERK pathway could upregulate Bag5 expression and thus promote endothelial cell survival through inhibiting oxidative stress, ER stress, and inflammation. Altogether, our results illustrate that Bag5 overexpression sustains endothelial cell survival in response to catecholamine treatment. This finding identifies Bag5 downregulation and the inactivated MAPK-ERK pathway as potential mechanisms underlying catecholamine-induced endothelial cell damage.

Recombinant Human Brain Natriuretic Peptide Attenuates Myocardial Ischemia-Reperfusion Injury by Inhibiting CD4+ T Cell Proliferation via PI3K/AKT/mTOR Pathway Activation

Inflammation plays a major role in the development of myocardial ischemia-reperfusion (IR) injury. Recombinant human brain natriuretic peptide (rhBNP), a man-made version of a peptide that is elevated in heart failure, exhibits anti-inflammatory effects in various tissues. However, its role in myocardial IR injury remains unclear. In this study, we demonstrate that treatment with rhBNP provided protection for mice against myocardial IR injury as manifested by reduced infarct size and well-preserved myocardial, attenuated inflammatory infiltration and CD4⁺ T cell proliferation function, and inhibited expression of proinflammatory related genes. Furthermore, mechanistic studies revealed that rhBNP inhibited Jurkat T proliferation by promoting PI3K/AKT/mTOR phosphorylation. Collectively, our data suggest that the administration of rhBNP during IR injury could expand our understanding of the cardioprotective effects of rhBNP.

Oxidative stress-induced cardiomyocyte apoptosis is associated with dysregulated Akt/p53 signaling pathway

Oxidative stress may play a crucial role in cardiac and vascular abnormalities in different types of cardiovascular diseases. In the present study, we explored the mechanism underlying oxidative stress-mediated cardiomyocyte apoptosis with a focus on the Akt-p53 signaling pathway. In vitro, cardiomyocyte was cultured with different concentrations of hydrogen peroxide. Then, cardiomyocyte viability, apoptosis rate and signaling pathway were analyzed through ELISA, immunofluorescence, qPCR and western blots. The results indicated that oxidative stress caused cardiomyocyte apoptosis in a dose-dependent manner. Mechanistically, oxidative stress inhibited cardiomyocyte glucose metabolism and promoted lactic acid accumulation. Besides, oxidative stress triggered calcium overload in cardiomyocyte. Finally, we found that oxidative stress inhibited the activity of Akt pathway while activated p53 signaling pathway. Genetic knockdown of p53 abolished oxidative stress-mediated cardiomyocyte injury and death through regulating the expressions and activities of caspase-3 and Bax. Altogether, our results illustrate that oxidative stress is associated with cardiomyocyte apoptosis through a mechanism involving dysregulated Akt/p53 signaling pathway.

Regulatory Roles of Circular RNAs in Coronary Artery Disease

Coronary artery disease (CAD) is a cardiac disorder caused by abnormal structure or function of the coronary artery, which leads to myocardial ischemia and hypoxia. CAD is a major cause of morbidity and mortality worldwide. Although there are currently effective drug therapies, there is a pressing need to find novel molecular therapeutic targets for CAD. The development of molecular biology technology has allowed the recognition of circular RNAs (circRNAs) as a novel class of noncoding RNAs that regulate gene function. The pathological roles of circRNAs in CAD have not, however, been comprehensively summarized. In this article, we review published research linking circRNAs to CAD and summarize the regulatory roles of circRNAs in the pathogenesis of coronary atherosclerosis, myocardial infarction, ischemia/reperfusion injury, and ischemic heart failure.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

The Synthetic Curcumin Analogue GO-Y030 Effectively Suppresses the Development of Pressure Overload-induced Heart Failure in Mice

Curcumin is a naturally occurring p300-histone acetyltransferase (p300-HAT) inhibitor that suppresses cardiomyocyte hypertrophy and the development of heart failure in experimental animal models. To enhance the therapeutic potential of curcumin against heart failure, we produced a series of synthetic curcumin analogues and investigated their inhibitory activity against p300-HAT. The compound with the strongest activity was further evaluated to determine its effects on cardiomyocyte hypertrophy and pressure overload-induced heart failure in mice. We synthesised five synthetic curcumin analogues and found that a compound we have named GO-Y030 most strongly inhibited p300-HAT activity. Furthermore, 1 μM GO-Y030, in a manner equivalent to 10 µM curcumin, suppressed phenylephrine-induced hypertrophic responses in cultured cardiomyocytes. In mice undergoing transverse aortic constriction surgery, administration of GO-Y030 at a mere 1% of an equivalently-effective dose of curcumin significantly attenuated cardiac hypertrophy and systolic dysfunction. In addition, this low dose of GO-Y030 almost completely blocked histone H3K9 acetylation and eliminated left ventricular fibrosis. A low dose of the synthetic curcumin analogue GO-Y030 effectively inhibits p300-HAT activity and markedly suppresses the development of heart failure in mice.

BET Epigenetic Reader Proteins in Cardiovascular Transcriptional Programs

Epigenetic mechanisms involve the placing (writing) or removal (erasing) of histone modifications that allow heterochromatin to transition to the open, activated euchromatin state necessary for transcription. A third, less studied epigenetic pathway involves the reading of these specific histone marks once placed. The BETs (bromodomain and extraterminal-containing protein family), which includes BRD2, BRD3, and BRD4 and the testis-restricted BRDT, are epigenetic reader proteins that bind to specific acetylated lysine residues on histone tails where they facilitate the assembly of transcription complexes including transcription factors and transcriptional machinery like RNA Polymerase II. As reviewed here, considerable recent data establishes BETs as novel determinants of induced transcriptional programs in vascular cells, like endothelial cells and vascular smooth muscle cells, cardiac myocytes and inflammatory cells, like monocyte/macrophages, cellular settings where these epigenetic reader proteins couple proximal stimuli to chromatin, acting at super-enhancer regulatory regions to direct gene expression. BET inhibition, including the use of specific chemical BET inhibitors like JQ-1, has many reported effects in vivo in the cardiovascular setting, like decreasing atherosclerosis, angiogenesis, intimal hyperplasia, pulmonary arterial hypertension, and cardiac hypertrophy. At the same time, data in endothelial cells, adipocytes, and elsewhere suggest BETs also help regulate gene expression under basal conditions. Studies in the cardiovascular setting have highlighted BET action as a means of controlling gene expression in differentiation, cell identity, and cell state transitions, whether physiological or pathological, adaptive, or maladaptive. While distinct BET inhibitors are being pursued as therapies in oncology, a large prospective clinical cardiovascular outcome study investigating the BET inhibitor RVX-208 (now called apabetalone) has already been completed. Independent of this specific agent and this one trial or the numerous unanswered questions that remain, BETs have emerged as novel epigenetic players involved in the execution of coordinated transcriptional programs in cardiovascular health and disease.

Quantitative analysis of variability in an integrated model of human ventricular electrophysiology and β-adrenergic signaling

In ventricular myocytes, stimulation of β-adrenergic receptors activates critical cardiac signaling pathways, leading to shorter action potentials and increased contraction strength during the "fight-or-flight" response. These changes primarily result, at the cellular level, from the coordinated phosphorylation of multiple targets by protein kinase A. Although mathematical models of the intracellular signaling downstream of β-adrenergic receptor activation have previously been described, only a limited number of studies have explored quantitative interactions between intracellular signaling and electrophysiology in human ventricular myocytes. Accordingly, our objective was to develop an integrative mathematical model of β-adrenergic receptor signaling, electrophysiology, and intracellular calcium (Ca²⁺) handling in the healthy human ventricular myocyte. We combined published mathematical models of intracellular signaling and electrophysiology, then calibrated the model results against voltage clamp data and physiological changes occurring after stimulation of β-adrenergic receptors with isoproterenol. We subsequently: (1) explored how molecular variability in different categories of model parameters translated into phenotypic variability; (2) identified the most important parameters determining physiological cellular outputs in the model before and after β-adrenergic receptor stimulation; and (3) investigated which molecular level alterations can produce a phenotype indicative of heart failure with preserved ejection fraction (HFpEF). Major results included: (1) variability in parameters that controlled intracellular signaling caused qualitatively different behavior than variability in parameters controlling ion transport pathways; (2) the most important model parameters determining action potential duration and intracellular Ca²⁺ transient amplitude were generally consistent before and after β-adrenergic receptor stimulation, except for a shift in the importance of K⁺ currents in determining action potential duration; and (3) decreased Ca²⁺ uptake into the sarcoplasmic reticulum, increased Ca²⁺ extrusion through Na⁺/Ca²⁺ exchanger and decreased Ca²⁺ leak from the sarcoplasmic reticulum may contribute to HFpEF. Overall, this study provided novel insight into the phenotypic consequences of molecular variability, and our integrated model may be useful in the design and interpretation of future experimental studies of interactions between β-adrenergic signaling and cellular physiology in human ventricular myocytes.

Melatonin improves mitochondrial biogenesis through the AMPK/PGC1α pathway to attenuate ischemia/reperfusion-induced myocardial damage

Cardiac ischemia/reperfusion injury is associated with reduced mitochondrial turnover and regeneration. There is currently no effective approach to stimulate mitochondrial biogenesis in the reperfused myocardium. In this study, we investigated whether melatonin could increase mitochondrial biogenesis and thus promote mitochondrial homeostasis in cardiomyocytes. Cardiomyocytes were subjected to hypoxia/reoxygenation (H/R) injury with or without melatonin treatment, and various mitochondrial functions were measured. H/R injury repressed mitochondrial biogenesis in cardiomyocytes, whereas melatonin treatment restored mitochondrial biogenesis through the 5’ adenosine monophosphate-activated protein kinase (AMPK)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α) pathway. Melatonin enhanced mitochondrial metabolism, inhibited mitochondrial oxidative stress, induced mitochondrial fusion and prevented mitochondrial apoptosis in cardiomyocytes subjected to H/R injury. The melatonin-induced improvement in mitochondrial biogenesis was associated with increased cardiomyocyte survival during H/R injury. On the other hand, silencing of PGC1α attenuated the protective effects of melatonin on cardiomyocyte viability, thereby impairing mitochondrial bioenergetics, disrupting the mitochondrial morphology, and activating mitochondrial apoptosis. Thus, H/R injury suppressed mitochondrial biogenesis, while melatonin activated the AMPK/PGC1α pathway and restored mitochondrial biogenesis, ultimately protecting the reperfused heart.

New insights into the role of mitochondria in cardiac microvascular ischemia/reperfusion injury

As reperfusion therapies have become more widely used in acute myocardial infarction patients, ischemia-induced myocardial damage has been markedly reduced, but reperfusion-induced cardiac injury has become increasingly evident. The features of cardiac ischemia-reperfusion (I/R) injury include microvascular perfusion defects, platelet activation and sequential cardiomyocyte death due to additional ischemic events at the reperfusion stage. Microvascular obstruction, defined as a no-reflow phenomenon, determines the infarct zone, myocardial function and peri-operative mortality. Cardiac microvascular endothelial cell injury may occur much earlier and with much greater severity than cardiomyocyte injury. Endothelial cells contain fewer mitochondria than other cardiac cells, and several of the pathological alterations during cardiac microvascular I/R injury involve mitochondria, such as increased mitochondrial reactive oxygen species (mROS) levels and disturbed mitochondrial dynamics. Although mROS are necessary physiological second messengers, high mROS levels induce oxidative stress, endothelial senescence and apoptosis. Mitochondrial dynamics, including fission, fusion and mitophagy, determine the shape, distribution, size and function of mitochondria. These adaptive responses modify extracellular signals and orchestrate intracellular processes such as cell proliferation, migration, metabolism, angiogenesis, permeability transition, adhesive molecule expression, endothelial barrier function and anticoagulation. In this review, we discuss the involvement of mROS and mitochondrial morphofunction in cardiac microvascular I/R injury.

Irisin activates Opa1-induced mitophagy to protect cardiomyocytes against apoptosis following myocardial infarction

Myocardial infarction is characterized by sudden ischemia and cardiomyocyte death. Mitochondria have critical roles in regulating cardiomyocyte viability and can sustain damage under ischemic conditions. Mitophagy is a mechanism by which damaged mitochondria are removed by autophagy to maintain mitochondrial structure and function. We investigated the role of the dynamin-like GTPase optic atrophy 1 (Opa1) in mitophagy following myocardial infarction. Opa1 expression was downregulated in infarcted hearts in vivo and in hypoxia-treated cardiomyocytes in vitro. We found that Opa1 overexpression protected cardiomyocytes against hypoxia-induced damage and enhanced cell viability by inducing mitophagy. Opa1-induced mitophagy was activated by treatment with irisin, which protected cardiomyocytes from further damage following myocardial infarction. Opa1 knockdown abolished the cardioprotective effects of irisin resulting in an enhanced inflammatory response, increased oxidative stress, and mitochondrial dysfunction in cardiomyocytes. Our data indicate that Opa1 plays an important role in maintaining cardiomyocyte viability and mitochondrial function following myocardial infarction by inducing mitophagy. Irisin can activate Opa1-induced mitophagy and protect against cardiomyocyte injury following myocardial infarction.

Fibroblast growth factor-inducible 14 mediates macrophage infiltration in heart to promote pressure overload-induced cardiac dysfunction

AIMS

Heart failure (HF) is characterized by compromised cardiac structure and function. Previous work has identified a link between upregulation of pro-inflammatory cytokines and HF. Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) is a pro-inflammatory cytokine, which binds to fibroblast growth factor inducible 14 (Fn14), a ubiquitously expressed cell-surface receptor. The objective of this study was to investigate the role of TWEAK/Fn14 pathway in promoting cardiac inflammation under non ischemic stress conditions.

MAIN METHODS

Wild type (WT) and Fn14 knock out (Fn14^-/-) mice were subjected to pressure overload [transaortic constriction (TAC)] for 1 or 6 weeks. A subset of WT TAC animals were treated with the Fn14 antagonist L524-0366. Cardiac function was measured by echocardiography. Cardiac fibrosis and macrophage infiltration were quantified using immunohistochemistry and flow cytometry, respectively. Cardiac fibroblasts were isolated for quantifying TWEAK-induced chemokine release.

KEY FINDINGS

Fn14^-/- mice displayed improved cardiac function, reduced fibrosis and lower macrophage infiltration in heart compared to WT following TAC. L524-0366 mitigated maladaptive remodeling with TAC. TWEAK induced secretion of the pro-inflammatory chemokine, monocyte chemoattractant protein 1 from WT but not Fn14^-/- fibroblasts in vitro, in part through activation of non-canonical NF-κB signaling. Finally, Fn14 expression was increased in mouse following TAC and in human failing hearts.

SIGNIFICANCE

Our findings support an important role for the TWEAK/Fn14 promoting macrophage infiltration and fibrosis in heart under non-ischemic stress, with potential for therapeutic intervention to improve cardiac function in the setting of HF.

Pak2 inhibition promotes resveratrol-mediated glioblastoma A172 cell apoptosis via modulating the AMPK-YAP signaling pathway

As a polyphenolic compound, resveratrol (Res) is widely present in a variety of plants. Previous studies have shown that Res can inhibit various tumors. However, its role in c remains largely unexplored. In the present study, we first demonstrated that Res inhibited cell viability and induced apoptosis of glioblastoma A172 cell. Further experiments showed that Res induced mitochondrial dysfunction and activated the activity of caspase-9. Functional studies have found that Res treatment is associated with an increase in the expression of Pak2. Interestingly, inhibition of Pak2 could further augment the proapoptotic effect of Res. Mechanistically, Pak2 inhibition induced reactive oxygen species overproduction, mitochondria-JNK pathway activation, and AMPK-YAP axis suppression. However, overexpression of YAP could abolish the anticancer effects of Res and Pak2 inhibition, suggesting a necessary role played by the AMPK-YAP pathway in regulating cancer-suppressive actions of Res and Pak2 inhibition. Altogether, our results indicated that Res in combination with Pak2 inhibition could further enhance the anticancer property of Res and this effect is mediated via the AMPK-YAP pathway.

Sphingosine kinase 1 promotes cerebral ischemia-reperfusion injury through inducing ER stress and activating the NF-κB signaling pathway

Endoplasm reticulum stress and inflammation response have been found to be linked to cerebral ischemia-reperfusion (IR) injury. Sphingosine kinase 1 (SPHK1) has been reported to be a novel endoplasm reticulum regulator. The aim of our study is to figure out the role of SPHK1 in cerebral IR injury and verify whether it has an ability to regulate inflammation and endoplasm reticulum stress. Hydrogen peroxide was used to induce cerebral IR injury. Enzyme-linked immunosorbent assay, quantitative polymerase chain reaction, western blots, and immunofluorescence were used to measure the alterations of cell viability, inflammation response, and endoplasm reticulum stress. The results demonstrated that after exposure to hydrogen peroxide, cell viability was reduced whereas SPHK1 expression was significantly elevated. Knockdown of SPHK1 attenuated hydrogen peroxide-mediated cell death and reversed cell viability. Our data also demonstrated that SPHK1 deletion reduced endoplasm reticulum stress and alleviated inflammation response in hydrogen peroxide-treated cells. In addition, we also found that SHPK1 modulated endoplasm reticulum stress and inflammation response to through the NF-κB signaling pathway. Inhibition of NF-κB signaling pathway has similar results when compared with the cells with SPHK1 deletion. Altogether, our results demonstrated that SPHK1 upregulation, induced by hydrogen peroxide, is responsible for cerebral IR injury through inducing endoplasm reticulum stress and inflammation response in a manner working through the NF-κB signaling pathway. This finding provides new insight into the molecular mechanism to explain the neuron death induced by cerebral IR injury.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.

Fundc1-dependent mitophagy is obligatory to ischemic preconditioning-conferred renoprotection in ischemic AKI via suppression of Drp1-mediated mitochondrial fission

FUN14 domain-containing protein 1 (Fundc1)-dependent mitophagy, mainly activated by ischemic/hypoxic preconditioning, benefits acute myocardial reperfusion injury and chronic metabolic syndrome via sustaining mitochondrial homeostasis. Mitochondrial fission plays a pathogenic role in ischemic acute kidney injury (AKI) through perturbation of mitochondrial quality and activation of mitochondrial apoptosis. The aim of our study was to explore the role of Fundc1 mitophagy in ischemia preconditioning (IPC)-mediated renoprotection. Proximal tubule-specific Fundc1 knockout (Fundc1^PTKO) mice were subjected to ischemia reperfusion injury (IRI) and IPC prior to assessment of renal function, mitophagy, mitochondrial quality control, and Drp1-related mitochondrial fission. Following exposure to IPC, Fundc1 mitophagy was activated through post-transcriptional phosphorylation at Ser17. Interestingly, IRI-mediated renal injury, inflammation, and tubule cell death were mitigated by IPC whereas proximal tubule-specific Fundc1 knockout (Fundc1PTKO) mice abolished IPC-offered renoprotection. Mechanistically, IRI-evoked mitochondrial damage was improved by IPC whereas Fundc1 deficiency provoked mitochondrial abnormality, manifested by impaired mitochondrial quality and hyperactivated Drp1-dependent mitochondrial fission. Interestingly, Fundc1 deficiency-associated mitochondrial dysfunction was reversed by pharmacological inhibition of mitochondrial fission. In vivo, Fundc1 deletion-caused renal injury, severe pro-inflammatory response, and tubule cell death could be nullified by way of knockout Drp1 on Fundc1PTKO background. Finally, we also revealed that IPC triggered Fundc1 mitophagy activation through UNC-51-like kinase 1 (Ulk1) and Ulk1 ablation interrupted IPC-mediated Fundc1 activation and thus attenuated IPC-induced renoprotection. Fundc1 mitophagy, primarily driven by IPC, confers resistance to AKI through reconciliation of mitochondrial fission, implicating the therapeutic potential of targeting mitochondrial homeostasis for AKI.

Heart non-specific effector CD4+ T cells protect from postinflammatory fibrosis and cardiac dysfunction in experimental autoimmune myocarditis

Heart-specific CD4⁺ T cells have been implicated in development and progression of myocarditis in mice and in humans. Here, using mouse models of experimental autoimmune myocarditis (EAM) we investigated the role of heart non-specific CD4⁺ T cells in the progression of the disease. Heart non-specific CD4⁺ T cells were obtained from DO11.10 mice expressing transgenic T cell receptor recognizing chicken ovalbumin. We found that heart infiltrating CD4⁺ T cells expressed exclusively effector (T_eff) phenotype in the EAM model and in hearts of patients with lymphocytic myocarditis. Adoptive transfer experiments showed that while heart-specific T_eff infiltrated the heart shortly after injection, heart non-specific T_eff effectively accumulated during myocarditis and became the major heart-infiltrating CD4⁺ T cell subset at later stage. Restimulation of co-cultured heart-specific and heart non-specific CD4⁺ T cells with alpha-myosin heavy chain antigen showed mainly Th1/Th17 response for heart-specific T_eff and up-regulation of a distinct set of extracellular signalling molecules in heart non-specific T_eff. Adoptive transfer of heart non-specific T_eff in mice with myocarditis did not affect inflammation severity at the peak of disease, but protected the heart from adverse post-inflammatory fibrotic remodelling and cardiac dysfunction at later stages of disease. Furthermore, mouse and human T_eff stimulated in vitro with common gamma cytokines suppressed expression of profibrotic genes, reduced amount of α-smooth muscle actin filaments and decreased contraction of cardiac fibroblasts. In this study, we provided a proof-of-concept that heart non-specific T_eff cells could effectively contribute to myocarditis and protect the heart from the dilated cardiomyopathy outcome.

The role of lncRNA MALAT1 in cardiovascular disease

Cardiovascular disease (CVD) is the first leading cause of death worldwide. Understanding the molecular mechanism of signaling pathways involved in pathology of CVD is benefit for targeted therapeutics. Recently, long non-coding RNAs (lncRNAs) are found and involved in regulation of pathology of CVD at different levels. Among them, MALAT1 attracted more attention as it was profoundly expressed in endothelial cells or cardiomyocytes in response to the risk factors of CVD, such as hypoxia, high glucose, cytokine, and oxidative stress. In this review, we summarize recent progresses in research on the molecular mechanism of MALAT1 on regulating the pathophysiological processes of CVD as well as its potential therapeutic applications.

Gal-3 (Galectin-3) and KCa3.1 Mediate Heterogeneous Cell Coupling and Myocardial Fibrogenesis Driven by βAR (β-Adrenoceptor) Activation

Heart failure is associated with sympatho-βAR (β-adrenoceptor) activation and cardiac fibrosis. Gal-3 (galectin-3) and K_Ca3.1 channels that are upregulated in diverse cells of diseased heart are implicated in mediating myocardial inflammation and fibrosis. It remains unclear whether Gal-3 interacts with K_Ca3.1 leading to cardiac fibrosis in the setting of βAR activation. We tested the effect of K_Ca3.1 blocker TRAM-34 on cardiac fibrosis and inflammation in cardiac-restricted β₂-TG (β₂AR overexpressed transgenic) mice and determined K_Ca3.1 expression in β₂-TG×Gal-3^-/- mouse hearts. Mechanisms of K_Ca3.1 in mediating Gal-3 induced fibroblast activation were studied ex vivo. Expression of Gal-3 and K_Ca3.1 was elevated in β₂-TG hearts. Gal-3 gene deletion in β₂-TG mice decreased K_Ca3.1 expression in inflammatory cells but not in fibroblasts. Treatment of β₂-TG mice with TRAM-34 for 1 or 2 months significantly ameliorated cardiac inflammation and fibrosis and reduced Gal-3 level. In cultured fibroblasts, Gal-3 upregulated K_Ca3.1 expression and channel currents with enhanced membrane potential and Ca²⁺ entry through TRPV4 (transient receptor potential V4) and TRPC6 (transient receptor potential C6) channels leading to fibroblast activation. In conclusion, βAR stimulation promotes Gal-3 production that upregulates K_Ca3.1 channels in noncardiomyocyte cells and activates K_Ca3.1 channels in fibroblasts leading to hyperpolarization of membrane potential and Ca²⁺ entry via TRP channels. Gal-3-K_Ca3.1 signaling mobilizes diverse cells facilitating regional inflammation and fibroblast activation and hence myocardial fibrosis.

Computational tools for automated histological image analysis and quantification in cardiac tissue

Image processing and quantification is a routine and important task across disciplines in biomedical research. Understanding the effects of disease on the tissue and organ level often requires the use of images, however the process of interpreting those images into data which can be tested for significance is often time intensive, tedious and prone to inaccuracy or bias. When working within resource constraints, these different issues often present a trade-off between time invested in analysis and accuracy. To address these issues, we present two novel open source and publically available tools for automated analysis of histological cardiac tissue samples:

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Automated Fibrosis Analysis Tool (AFAT) for quantifying fibrosis; and

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Macrophage Analysis Tool (MAT) for quantifying infiltrating macrophages.

The TRPA1 Channel in the Cardiovascular System: Promising Features and Challenges

The transient receptor potential ankyrin 1 (TRPA1) channel is a calcium-permeable nonselective cation channel in the plasma membrane that belongs to the transient receptor potential (TRP) channel superfamily. Recent studies have suggested that the TRPA1 channel plays an essential role in the development and progression of several cardiovascular conditions, such as atherosclerosis, heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, arrhythmia, vasodilation, and hypertension. Activation of the TRPA1 channel has a protective effect against the development of atherosclerosis. Furthermore, TRPA1 channel activation elicits peripheral vasodilation and induces a biphasic blood pressure response. However, loss of channel expression or blockade of its activation suppressed heart failure, myocardial ischemia-reperfusion injury, myocardial fibrosis, and arrhythmia. In this paper, we review recent research progress on the TRPA1 channel and discuss its potential role in the cardiovascular system.

Ca2+ Signaling in Cardiac Fibroblasts and Fibrosis-Associated Heart Diseases

Cardiac fibrosis is the excessive deposition of extracellular matrix proteins by cardiac fibroblasts and myofibroblasts, and is a hallmark feature of most heart diseases, including arrhythmia, hypertrophy, and heart failure. This maladaptive process occurs in response to a variety of stimuli, including myocardial injury, inflammation, and mechanical overload. There are multiple signaling pathways and various cell types that influence the fibrogenesis cascade. Fibroblasts and myofibroblasts are central effectors. Although it is clear that Ca2+ signaling plays a vital role in this pathological process, what contributes to Ca2+ signaling in fibroblasts and myofibroblasts is still not wholly understood, chiefly because of the large and diverse number of receptors, transporters, and ion channels that influence intracellular Ca2+ signaling. Intracellular Ca2+ signals are generated by Ca2+ release from intracellular Ca2+ stores and by Ca2+ entry through a multitude of Ca2+-permeable ion channels in the plasma membrane. Over the past decade, the transient receptor potential (TRP) channels have emerged as one of the most important families of ion channels mediating Ca2+ signaling in cardiac fibroblasts. TRP channels are a superfamily of non-voltage-gated, Ca2+-permeable non-selective cation channels. Their ability to respond to various stimulating cues makes TRP channels effective sensors of the many different pathophysiological events that stimulate cardiac fibrogenesis. This review focuses on the mechanisms of Ca2+ signaling in fibroblast differentiation and fibrosis-associated heart diseases and will highlight recent advances in the understanding of the roles that TRP and other Ca2+-permeable channels play in cardiac fibrosis.

Liraglutide attenuates cardiac remodeling and improves heart function after abdominal aortic constriction through blocking angiotensin II type 1 receptor in rats

Objective

Angiotensin II (Ang II) is known to contribute to the pathogenesis of heart failure by eliciting cardiac remodeling and dysfunction. The glucagon-like peptide-1 (GLP-1) has been shown to exert cardioprotective effects in animals and patients. This study investigates whether GLP-1 receptor agonist liraglutide inhibits abdominal aortic constriction (AAC)-induced cardiac fibrosis and dysfunction through blocking Ang II type 1 receptor (AT1R) signaling.

Methods

Sprague-Dawley rats were subjected to sham operation and abdominal aortic banding procedure for 16 weeks. In treated rats, liraglutide (0.3 mg/kg) was subcutaneously injected twice daily or telmisartan (10 mg/kg/day), the AT1R blocker, was administered by gastric gavage.

Results

Relative to the animals with AAC, liraglutide reduced protein level of the AT1R and upregulated the AT2R, as evidenced by reduced ratio of AT1R/AT2R (0.59±0.04 vs. 0.91±0.06, p<0.05). Furthermore, the expression of angiotensin converting enzyme 2 was upregulated, tissue levels of malondialdehyde and B-type natriuretic peptide were reduced, and superoxide dismutase activity was increased. Along with a reduction in HW/BW ratio, cardiomyocyte hypertrophy was inhibited. In coincidence with these changes, liraglutide significantly decreased the populations of macrophages and myofibroblasts in the myocardium, which were accompanied by reduced protein levels of transforming growth factor beta1, Smad2/3/4, and upregulated smad7. The synthesis of collagen I and III was inhibited and collagen-rich fibrosis was attenuated. Consistent with these findings, cardiac systolic function was preserved, as shown by increased left ventricular systolic pressure (110±5 vs. 99±2 mmHg, p<0.05), ejection fraction (83%±2% vs. 69%±4%, p<0.05) and fraction shortening (49%±2% vs. 35%±3%, p<0.05). Treatment with telmisartan provided a comparable level of protection as compared with liraglutide in all the parameters measured.

Conclusion

Taken together, liraglutide ameliorates cardiac fibrosis and dysfunction, potentially via suppressing the AT1R-mediated events. These data indicate that liraglutide might be selected as an add-on drug to prevent the progression of heart failure.

Differential expression of coxsackievirus and adenovirus receptor in endomyocardial tissue of patients with myocarditis

Recent studies demonstrated that the expression of coxsackievirus and adenovirus receptor (CAR) is implicated in the pathophysiology of myocarditis. The aim of the present study was to assess the association between active and borderline myocarditis and CAR expression in endomyocardial tissues, and analyze the association between CAR expression and treatment response. An analytic, cross-sectional, retrospective study was performed in 26 patients with myocarditis and 10 control subjects without heart disease. Myocardial biopsies were obtained and CAR transcription was measured by reverse transcription-quantitative polymerase chain reaction analysis. The association between CAR mRNA levels and the response to immunosuppressive or conventional therapy (treatment responders, n=17; non-responders, n=9) or with the type of histological myocarditis (active myocarditis, n=16; borderline myocarditis, n=10) was analyzed. CAR transcription levels were significantly lower (P=0.012) in patients with myocarditis compared with controls, and a significant decrease was observed (P=0.023) in CAR mRNA levels among patients with borderline myocarditis compared with the no myocarditis group. Patients responding to therapy exhibited higher CAR mRNA levels (P=0.036) compared with patients not responding to treatment, as evaluated based on clinical and echocardiographic criteria (immunosuppressive therapy, n=8; conventional therapy, n=1). Myocarditis in non-responders was associated with fewer clinical manifestations and lower CAR mRNA levels. A significant difference was only found regarding the use of oral steroids in patients with active myocarditis who responded to treatment (P=0.02), with no difference in borderline myocarditis. In conclusion, the transcriptional level of CAR is low in the endomyocardial tissue of patients with myocarditis, and it is lower in borderline myocarditis and in non-responder patients. These findings may enable early identification of patients who may benefit from treatment and timely determination of prognosis.

Upregulation of Circular RNA CircNFIB Attenuates Cardiac Fibrosis by Sponging miR-433

Cardiac fibrosis is the pathological consequence of fibroblast proliferation and fibroblast-to-myofibroblast transition. As a new class of endogenous non-coding RNAs, circular RNAs (circRNAs) have been identified in many cardiovascular diseases including fibrosis, generally acting as microRNA (miRNA) sponges. Here, we report that the expression of circRNA-circNFIB was decreased in mice post-myocardial infarction heart samples, as well as in primary adult cardiac fibroblasts treated with TGF-β. Forced expression of circNFIB decreased cell proliferation in both NIH/3T3 cells and primary adult fibroblasts as evidenced by EdU incorporation. Conversely, inhibition of circNFIB promoted adult fibroblast proliferation. Furthermore, circNFIB was identified as a miR-433 endogenous sponge. Overexpression of circNFIB could attenuate pro-proliferative effects induced by the miR-433 mimic while inhibition of circNFIB exhibited opposite results. Finally, upregulation of circNFIB also reversed the expression levels of target genes and downstream signaling pathways of miR-433. In conclusion, circNFIB is critical for protection against cardiac fibrosis. The circNFIB-miR-433 axis may represent a novel therapeutic approach for treatment of fibrotic diseases.