G Protein-Coupled Estrogen Receptor 1 Mediates Acute Estrogen-Induced Cardioprotection via MEK/ERK/GSK-3β Pathway after Ischemia/Reperfusion

The Abl1 tyrosine kinase is a key player in doxorubicin-induced cardiomyopathy and its p53/p73 cell death mediated signaling differs in atrial and ventricular cardiomyocytes

BACKGROUND

Doxorubicin is an important anticancer drug, however, elicits dose-dependently cardiomyopathy. Given its mode of action, i.e. topoisomerase inhibition and DNA damage, we investigated genetic events associated with cardiomyopathy and searched for mechanism-based possibilities to alleviate cardiotoxicity. We treated rats at clinically relevant doses of doxorubicin. Histopathology and transmission electron microscopy (TEM) defined cardiac lesions, and transcriptomics unveiled cardiomyopathy-associated gene regulations. Genomic-footprints revealed critical components of Abl1-p53-signaling, and EMSA-assays evidenced Abl1 DNA-binding activity. Gene reporter assays confirmed Abl1 activity on p53-targets while immunohistochemistry/immunofluorescence microscopy demonstrated Abl1, p53&p73 signaling.

RESULTS

Doxorubicin treatment caused dose-dependently toxic cardiomyopathy, and TEM evidenced damaged mitochondria and myofibrillar disarray. Surviving cardiomyocytes repressed Parkin-1 and Bnip3-mediated mitophagy, stimulated dynamin-1-like dependent mitochondrial fission and induced anti-apoptotic Bag1 signaling. Thus, we observed induced mitochondrial biogenesis. Transcriptomics discovered heterogeneity in cellular responses with minimal overlap between treatments, and the data are highly suggestive for distinct cardiomyocyte (sub)populations which differed in their resilience and reparative capacity. Genome-wide footprints revealed Abl1 and p53 enriched binding sites in doxorubicin-regulated genes, and we confirmed Abl1 DNA-binding activity in EMSA-assays. Extraordinarily, Abl1 signaling differed in the heart with highly significant regulations of Abl1, p53 and p73 in atrial cardiomyocytes. Conversely, in ventricular cardiomyocytes, Abl1 solely-modulated p53-signaling that was BAX transcription-independent. Gene reporter assays established Abl1 cofactor activity for the p53-reporter PG13-luc, and ectopic Abl1 expression stimulated p53-mediated apoptosis.

CONCLUSIONS

The tyrosine kinase Abl1 is of critical importance in doxorubicin induced cardiomyopathy, and we propose its inhibition as means to diminish risk of cardiotoxicity.

Activation of G Protein-Coupled Estrogen Receptor (GPER) Negatively Modulates Cardiac Excitation-Contraction Coupling (ECC) through the PI3K/NOS/NO Pathway

The G-protein-coupled estrogen receptor (GPER) has been described to exert several cardioprotective effects. However, the exact mechanism involved in cardiac protection remains unclear. The aim of this study is to investigate the role of GPER activation on excitation-contraction coupling (ECC) and the possibility that such effect participates in cardioprotection. The cardiac myocytes of male Wistar rats were isolated with a digestive buffer and loaded with Fura-2-AM for the measurement of intracellular calcium transient (CaT). Sarcomere shortening (SS) and L-type calcium current (ICaL) were also registered. The confocal technique was used to measure nitric oxide (NO) production in cells loaded with DAF-FM-diacetate. Cardiac myocytes exposed to 17-β-estradiol (E2, 10 nM) or G-1 (1 μM) for fifteen minutes decreased CaT, SS, and ICaL. These effects were prevented using G-36 (antagonist of GPER, 1 μM), L-Name (NO synthase -NOS- inhibitor, 100 nM), or wortmannin (phosphoinositide-3-kinase -PI3K- inhibitor, 100 nM). Moreover, G1 increased NO production, and this effect was abolished in the presence of wortmannin. We concluded that the selective activation of GPER with E2 or G1 in the isolated cardiac myocytes of male rats induced a negative inotropic effect due to the reduction in ICaL and the decrease in CaT. Finally, the pathway that we proposed to be implicated in these effects is PI3K-NOS-NO.

Research progress on the protective effect of hormones and hormone drugs in myocardial ischemia-reperfusion injury

Ischemic heart disease (IHD) is a condition where the heart muscle does not receive enough blood flow, leading to cardiac dysfunction. Restoring blood flow to the coronary artery is an effective clinical therapy for myocardial ischemia. This strategy helps lower the size of the myocardial infarction and improves the prognosis of patients. Nevertheless, if the disrupted blood flow to the heart muscle is restored within a specific timeframe, it leads to more severe harm to the previously deprived heart tissue. This condition is referred to as myocardial ischemia/reperfusion injury (MIRI). Until now, there is a dearth of efficacious strategies to prevent and manage MIRI. Hormones are specialized substances that are produced directly into the circulation by endocrine organs or tissues in humans and animals, and they have particular effects on the body. Hormonal medications utilize human or animal hormones as their active components, encompassing sex hormones, adrenaline medications, thyroid hormone medications, and others. While several studies have examined the preventive properties of different endocrine hormones, such as estrogen and hormone analogs, on myocardial injury caused by ischemia-reperfusion, there are other hormone analogs whose mechanisms of action remain unexplained and whose safety cannot be assured. The current study is on hormones and hormone medications, elucidating the mechanism of hormone pharmaceuticals and emphasizing the cardioprotective effects of different endocrine hormones. It aims to provide guidance for the therapeutic use of drugs and offer direction for the examination of MIRI in clinical therapy.

Sex-Based Mechanisms of Cardiac Development and Function: Applications for Induced-Pluripotent Stem Cell Derived-Cardiomyocytes

Males and females exhibit intrinsic differences in the structure and function of the heart, while the prevalence and severity of cardiovascular disease vary in the two sexes. However, the mechanisms of this sex-based dimorphism are yet to be elucidated. Sex chromosomes and sex hormones are the main contributors to sex-based differences in cardiac physiology and pathophysiology. In recent years, the advances in induced pluripotent stem cell-derived cardiac models and multi-omic approaches have enabled a more comprehensive understanding of the sex-specific differences in the human heart. Here, we provide an overview of the roles of these two factors throughout cardiac development and explore the sex hormone signaling pathways involved. We will also discuss how the employment of stem cell-based cardiac models and single-cell RNA sequencing help us further investigate sex differences in healthy and diseased hearts.

The BKCa (slo) channel regulates the cardiac function of Drosophila

The large conductance, calcium, and voltage-active potassium channels (BKCa) were originally discovered in Drosophila melanogaster as slowpoke (slo). They are extensively characterized in fly models as ion channels for their roles in neurological and muscular function, as well as aging. BKCa is known to modulate cardiac rhythm and is localized to the mitochondria. Activation of mitochondrial BKCa causes cardioprotection from ischemia-reperfusion injury, possibly via modulating mitochondrial function in adult animal models. However, the role of BKCa in cardiac function is not well-characterized, partially due to its localization to the plasma membrane as well as intracellular membranes and the wide array of cells present in mammalian hearts. Here we demonstrate for the first time a direct role for BKCa in cardiac function and cardioprotection from IR injury using the Drosophila model system. We have also discovered that the BKCa channel plays a role in the functioning of aging hearts. Our study establishes the presence of BKCa in the fly heart and ascertains its role in aging heart function.

Aromatase enzyme: Paving the way for exploring aromatization for cardio-renal protection

Documented male-female differences in the risk of cardiovascular and chronic kidney diseases have been largely attributed to estrogens. The cardiovascular and renal protective effects of estrogens are mediated via the activation of estrogen receptors (ERα and ERβ) and G protein-coupled estrogen receptor, and involve interactions with the renin-angiotensin-aldosterone system. Aromatase, also called estrogen synthase, is a cytochrome P-450 enzyme that plays a pivotal role in the conversion of androgens into estrogens. Estrogens are biosynthesized in gonadal and extra-gonadal sites by the action of aromatase. Evidence suggests that aromatase inhibitors, which are used to treat high estrogen-related pathologies, are associated with the development of cardiovascular events. We review the potential role of aromatization in providing cardio-renal protection and highlight several meta-analysis studies on cardiovascular events associated with aromatase inhibitors. Overall, we present the potential of aromatase enzyme as a fundamental contributor to cardio-renal protection.

The G protein-coupled oestrogen receptor GPER in health and disease: an update

Oestrogens and their receptors contribute broadly to physiology and diseases. In premenopausal women, endogenous oestrogens protect against cardiovascular, metabolic and neurological diseases and are involved in hormone-sensitive cancers such as breast cancer. Oestrogens and oestrogen mimetics mediate their effects via the cytosolic and nuclear receptors oestrogen receptor-α (ERα) and oestrogen receptor-β (ERβ) and membrane subpopulations as well as the 7-transmembrane G protein-coupled oestrogen receptor (GPER). GPER, which dates back more than 450 million years in evolution, mediates both rapid signalling and transcriptional regulation. Oestrogen mimetics (such as phytooestrogens and xenooestrogens including endocrine disruptors) and licensed drugs such as selective oestrogen receptor modulators (SERMs) and downregulators (SERDs) also modulate oestrogen receptor activity in both health and disease. Following up on our previous Review of 2011, we herein summarize the progress made in the field of GPER research over the past decade. We will review molecular, cellular and pharmacological aspects of GPER signalling and function, its contribution to physiology, health and disease, and the potential of GPER to serve as a therapeutic target and prognostic indicator of numerous diseases. We also discuss the first clinical trial evaluating a GPER-selective drug and the opportunity of repurposing licensed drugs for the targeting of GPER in clinical medicine.

Mitofilin Heterozygote Mice Display an Increase in Myocardial Injury and Inflammation after Ischemia/Reperfusion

Mitochondrial inner membrane protein (Mitofilin/Mic60) is part of a big complex that constituent the mitochondrial inner membrane organizing system (MINOS), which plays a critical role in maintaining mitochondrial architecture and function. We recently showed that Mitofilin physically binds to Cyclophilin D, and disruption of this interaction promotes the opening of mitochondrial permeability transition pore (mPTP) and determines the extent of I/R injury. Here, we investigated whether Mitofilin knockout in the mouse enhances myocardial injury and inflammation after I/R injury. We found that full-body deletion (homozygote) of Mitofilin induces a lethal effect in the offspring and that a single allele expression of Mitofilin is sufficient to rescue the mouse phenotype in normal conditions. Using non-ischemic hearts from wild-type (WT) and Mitofilin+/- (HET) mice, we report that the mitochondria structure and calcium retention capacity (CRC) required to induce the opening of mPTP were similar in both groups. However, the levels of mitochondrial dynamics proteins involved in both fusion/fission, including MFN2, DRP1, and OPA1, were slightly reduced in Mitofilin+/- mice compared to WT. After I/R, the CRC and cardiac functional recovery were reduced while the mitochondria structure was more damaged, and myocardial infarct size was increased in Mitofilin+/- mice compared to WT. Mitofilin+/- mice exhibited an increase in the mtDNA release in the cytosol and ROS production, as well as dysregulated SLC25As (3, 5, 11, and 22) solute carrier function, compared to WT. In addition, Mitofilin+/- mice displayed an increase in the transcript of pro-inflammatory markers, including IL-6, ICAM, and TNF-α. These results suggest that Mitofilin knockdown induces mitochondrial cristae damage that promotes dysregulation of SLC25As solute carriers, leading to an increase in ROS production and reduction in CRC after I/R. These effects are associated with an increase in the mtDNA release into the cytosol, where it activates signaling cascades leading to nuclear transcription of pro-inflammatory cytokines that aggravate I/R injury.

The emerging role of estrogen's non-nuclear signaling in the cardiovascular disease

Sexual dimorphism exists in the epidemiology of cardiovascular disease (CVD), which indicates the involvement of sexual hormones in the pathophysiology of CVD. In particular, ample evidence has demonstrated estrogen's protective effect on the cardiovascular system. While estrogen receptors, bound to estrogen, act as a transcription factor which regulates gene expressions by binding to the specific DNA sequence, a subpopulation of estrogen receptors localized at the plasma membrane induces activation of intracellular signaling, called "non-nuclear signaling" or "membrane-initiated steroid signaling of estrogen". Although the precise molecular mechanism of non-nuclear signaling as well as its physiological impact was unclear for a long time, recent development of genetically modified animal models and pathway-selective estrogen receptor stimulant bring new insights into this pathway. We review the published experimental studies on non-nuclear signaling of estrogen, and summarize its role in cardiovascular system, especially focusing on: (1) the molecular mechanism of non-nuclear signaling; (2) the design of genetically modified animals and pathway-selective stimulant of estrogen receptor.

Gender differences in GRK2 in cardiovascular diseases and its interactions with estrogen

G protein-coupled receptor kinase 2 (GRK2) is a multifunctional protein involved in regulating G protein-coupled receptor (GPCR) and non-GPCR signaling in the body. In the cardiovascular system, increased expression of GRK2 has been implicated in the occurrence and development of several cardiovascular diseases (CVDs). Recent studies have found gender differences in GRK2 in the cardiovascular system under physiological and pathological conditions, where GRK2's expression and activity are increased in males than in females. The incidence of CVDs in premenopausal women is lower than in men of the same age, which is related to estrogen levels. Given the shared location of GRK2 and estrogen receptors, estrogen may interact with GRK2 by modulating vital molecules such as calmodulin (CaM), caveolin, RhoA, nitrate oxide (NO), and mouse double minute 2 homolog (Mdm2), via signaling pathways mediated by estrogen's genomic (ERα and ERβ), and non-genomic (GPER) receptors, conferring cardiovascular protection in females. Highlighting the gender differences in GRK2 and understanding its interaction with estrogen in the cardiovascular system is pertinent in treating gender-related CVDs. As a result, this article explores the gender differences of GRK2 in the cardiovascular system and its relationship with estrogen during disease conditions. Estrogen's protective and therapeutic effects and its mechanism on GRK2-related cardiovascular diseases have also been discussed.

Cardiovascular Disease in Women: What the Radiologist Needs to Know

BACKGROUND

 Sex-specific disparities are well documented for cardiovascular disease (CVD). There are differences in physiology and pathophysiology, pain perception, spectrum of disease, risk, therapeutic aspects, prognosis, and outcome. CVD represents a broad spectrum of disorders. This review focuses on cardiovascular and cardiac pathology.

METHOD

 This review summarizes the current state of the literature on cardiovascular disease in women from a radiological viewpoint. It aims to provide a deeper understanding of these differences and thereby alerts the reader to the potential of CT and MRI for diagnosing CVD in women. Special attention is paid to disparities in the underlying physiological and pathophysiological processes, clinical presentation, and the quality of care to provide a deep understanding of the topic. Cardiovascular and cardiac pathologies with a sex-specific pattern of disease are presented and typical CT and MRI findings are arranged and illustrated with imaging findings.

RESULTS AND CONCLUSION

 Sex-specific differences are not only sex hormonal in nature but are rooted in the epigenome and encompass a multitude of physiological systems. In fact, cardiovascular disease shows sex-specific characteristics spanning from incidence to clinical presentation, course of disease, and prognosis. This is of significance regarding pretest probabilities, the power of tests, imaging strategies, and interpretation of imaging results. Key sex-specific issues encompass obstructive and non-obstructive coronary artery disease (CAD), microvascular angina, myocardial infarction with non-obstructive CAD, and coronary artery dissection. Sex-specific patterns are also noted in myocardial disease and heart failure such as pregnancy-related heart disease, Takotsubo syndrome, and anthracycline-induced cardiotoxicity.

KEY POINTS

  · Cardiovascular diseases have sex-specific characteristics.. · Imaging strategies and interpretation of imaging results should be adjusted for women.. · Imaging helps in the improvement of the sex-specific management of cardiovascular disease..

Er-xian ameliorates myocardial ischemia-reperfusion injury in rats through RISK pathway involving estrogen receptors

Curculigo orchioides (CUR) and Epimedium (EPI) are traditional Chinese medicines with estrogen-like biological activity, called Xianmao and Xianlingpi (Er-xian) in Chinese. However, whether Er-xian exerts protective effects on myocardial ischemia-reperfusion injury (MIRI) is unknown. This study aimed to investigate the cardioprotective effects of Er-xian preconditioning against MIRI and the underlying mechanisms. CUR or EPI was administered intragastrically to aged female rats as a monotherapy or combination therapy. 2 weeks later, a rat MIRI model was established. Myocardial infarction size, myocardial morphology, cTnT, cell apoptosis rate, intracellular calcium concentration, mitochondrial permeability transition pore (MPTP) opening and reperfusion injury salvage kinase (RISK) signaling pathway molecules were observed after the surgery. To evaluate the mechanisms of Er-xian, estrogen receptors antagonists ICI 182780 and G15 were used. In this study, Er-xian notably alleviated myocardial tissue damage, maintained mitochondrial morphology, reduced infarct size and cardiac markers, and increased sera levels of E2. Moreover, Er-xian inhibited calcium overload and mPTP opening, and decreased cardiomyocyte apoptosis. We found that the dual therapy of CUR and EPI elicited more noticeable results than CUR or EPI monotherapy. The significant protective effects of Er-xian on ischemia-reperfusion myocardium were attributed to the up-regulation of AKT, ERK1/2 and GSK-3β phosphorylation levels. The cardioprotective effects of Er-xian were significantly reduced after estrogen receptor blockade, especially GPER30. These results indicate that Er-xian attenuates MIRI through RISK signaling pathway and estrogen receptors are the critical mediators.

The cardioprotective effects and mechanisms of naringenin in myocardial ischemia based on network pharmacology and experiment verification

Naringenin (Nar) is a natural flavonoid extracted from citrus fruits with abundant pharmacological properties against cardiac diseases, but existing studies are unsystematic and scattered. The present research systematically investigates the mechanism of action of Nar in the treatment of myocardial ischemia (MI). Network pharmacology was used to analyze the relevant targets of Nar against MI as well as the biological mechanisms. The protective effect of Nar was initially assessed in H9c2 cells induced by CoCl₂. In acutely isolated rat cardiomyocytes, Nar was further explored for effects on L-type Ca²⁺ currents, cell contractility and Ca²⁺ transients by using patch-clamp technique and Ion Optix system. Network pharmacology analysis indicated that Nar improved apoptosis, mitochondrial energy metabolism, inflammation and oxidative stress. Experimental validation demonstrated that Nar decreased ROS and MDA levels and increased antioxidant activity (e.g., GSH-P_X, SOD, and CAT), mitochondrial membrane potential, ATP and Ca²⁺-ATPase contents. Nar also markedly reduced inflammatory factor levels, apoptosis, and intracellular Ca²⁺ concentrations in H9c2 cells. Based on the experimental results, it is speculated that Ca²⁺ signals play an essential role in the process of Nar against MI. Thus, we further confirmed that Nar significantly inhibited the L-type Ca²⁺ currents, contractility and Ca²⁺ transients in acutely isolated cardiomyocytes. The inhibition of Ca²⁺ overload by Nar may be a novel cardioprotective mechanism. The present study may serve as a basis for future clinical research, and Nar as a Ca²⁺ channel inhibitor may provide new perspectives for the treatment of myocardial ischemic diseases.

Estrogen Receptor-β Agonists Modulate T-Lymphocyte Activation and Ameliorate Left Ventricular Remodeling During Chronic Heart Failure

BACKGROUND

CD4⁺ T cells temporally transition from protective to pathological during ischemic heart failure (HF; 8 weeks postmyocardial infarction). Cellular mechanisms mediating this shift are unknown.

METHODS

RNA-sequencing of cardiac CD4⁺ T cells and flow cytometric analysis of immune cells was conducted.

RESULTS

RNA-sequencing of CD4⁺ T cells from the failing hearts of male mice indicated activation of ER (estrogen receptor)-α signaling. Flow cytometric analysis showed that ERα in CD4⁺ T cells decreases significantly at 3-day postmyocardial infarction but increases during HF. To antagonize ERα, we tested a novel ERβ agonist (OSU-ERb-012) to inhibit T cells and blunt left ventricular remodeling. Proliferation assays showed that OSU-ERb-012 dose-dependently inhibited proliferation and proinflammatory cytokine expression in anti-CD3/CD28 stimulated splenic T cells isolated from both the sexes. For in vivo efficacy, 10- to 12-week-old male and ovariectomized female mice were randomized at 4 weeks postmyocardial infarction and treated with either vehicle or drug (60 mg/kg per day; oral). While vehicle-treated HF mice displayed progressive left ventricular dilatation with significantly increased end-systolic and end-diastolic volumes from 4 to 8 weeks postmyocardial infarction, treatment with OSU-ERb-012 significantly blunted these changes and stopped left ventricular remodeling in both the sexes. Reduction in tibia-normalized heart and left ventricular weights, cardiomyocyte hypertrophy and interstitial fibrosis further supported these results. Additionally, OSU-ERb-012 treatment selectively inhibited cardiac, splenic, and circulating CD4⁺ T cells without affecting other myeloid and lymphoid cells in the HF mice.

CONCLUSIONS

Our studies indicate that ERβ agonists and OSU-ERb-012, in particular, could be used as selective immunomodulatory drugs to inhibit CD4⁺ T cells during chronic HF.

RIP3 Translocation into Mitochondria Promotes Mitofilin Degradation to Increase Inflammation and Kidney Injury after Renal Ischemia-Reperfusion

The receptor-interacting protein kinase 3 (RIP3) has been reported to regulate programmed necrosis-necroptosis forms of cell death with important functions in inflammation. We investigated whether RIP3 translocates into mitochondria in response to renal ischemia-reperfusion (I/R) to interact with inner mitochondrial protein (Mitofilin) and promote mtDNA release into the cytosol. We found that release of mtDNA activates the cGAS-STING pathway, leading to increased nuclear transcription of pro-inflammatory markers that exacerbate renal I/R injury. Monolateral C57/6N and RIP3^-/- mice kidneys were subjected to 60 min of ischemia followed by either 12, 24, or 48 h of reperfusion. In WT mice, we found that renal I/R injury increased RIP3 levels, as well as its translocation into mitochondria. We observed that RIP3 interacts with Mitofilin, likely promoting its degradation, resulting in increased mitochondria damage and mtDNA release, activation of the cGAS-STING-p65 pathway, and increased transcription of pro-inflammatory markers. All of these effects observed in WT mice were decreased in RIP3^-/- mice. In HK-2, RIP3 overexpression or Mitofilin knockdown increased cell death by activating the cGAS-STING-p65 pathway. Together, this study point to an important role of the RIP3-Mitofilin axis in the initiation and development of renal I/R injury.

Mitochondrial Damage in Myocardial Ischemia/Reperfusion Injury and Application of Natural Plant Products

Ischemic heart disease (IHD) is currently one of the leading causes of death among cardiovascular diseases worldwide. In addition, blood reflow and reperfusion paradoxically also lead to further death of cardiomyocytes and increase the infarct size. Multiple evidences indicated that mitochondrial function and structural disorders were the basic driving force of IHD. We summed up the latest evidence of the basic associations and underlying mechanisms of mitochondrial damage in the event of ischemia/reperfusion (I/R) injury. This review then reviewed natural plant products (NPPs) which have been demonstrated to mitochondria-targeted therapeutic effects during I/R injury and the potential pathways involved. We realized that NPPs mainly maintained the integrality of mitochondria membrane and ameliorated dysfunction, such as improving abnormal mitochondrial calcium handling and inhibiting oxidative stress, so as to protect cardiomyocytes during I/R injury. This information will improve our knowledge of mitochondrial biology and I/R-induced injury's pathogenesis and exhibit that NPPs hold promise for translation into potential therapies that target mitochondria.

Emerging Roles for G Protein-Coupled Estrogen Receptor 1 in Cardio-Renal Health: Implications for Aging

Cardiovascular (CV) and renal diseases are increasingly prevalent in the United States and globally. CV-related mortality is the leading cause of death in the United States, while renal-related mortality is the 8th. Despite advanced therapeutics, both diseases persist, warranting continued exploration of disease mechanisms to develop novel therapeutics and advance clinical outcomes for cardio-renal health. CV and renal diseases increase with age, and there are sex differences evident in both the prevalence and progression of CV and renal disease. These age and sex differences seen in cardio-renal health implicate sex hormones as potentially important regulators to be studied. One such regulator is G protein-coupled estrogen receptor 1 (GPER1). GPER1 has been implicated in estrogen signaling and is expressed in a variety of tissues including the heart, vasculature, and kidney. GPER1 has been shown to be protective against CV and renal diseases in different experimental animal models. GPER1 actions involve multiple signaling pathways: interaction with aldosterone and endothelin-1 signaling, stimulation of the release of nitric oxide, and reduction in oxidative stress, inflammation, and immune infiltration. This review will discuss the current literature regarding GPER1 and cardio-renal health, particularly in the context of aging. Improving our understanding of GPER1-evoked mechanisms may reveal novel therapeutics aimed at improving cardio-renal health and clinical outcomes in the elderly.

Uncovering the molecular mechanisms of Ilex pubescens against myocardial ischemia-reperfusion injury using network pharmacology analysis and experimental pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Ilex pubescens (I. pubescens), has been widely used to treat cardiovascular disease (CVD) in South China. Several studies have revealed aspect of its phytochemistry and pharmacological activities in cardiovascular diseases, but its active compounds and mechanisms of action are still unclear. The aim of this study was to search for the active compounds and the pharmacological mechanisms of I. pubescens for myocardial ischemia-reperfusion injury (MI/RI) by an integrative pharmacology-based investigation.

MATERIALS AND METHODS

The main targets of compounds in I. pubescens were predicted using the TargetNet webserver (http://targetnet.scbdd.com). The network between compounds and predicted targets related to MI/RI and compounds was constructed. Functional enrichment analysis was performed to investigate the specific functions and pathways involved in the candidate I. pubescens targets acting on MI/RI, which were further validated by in vitro and in vivo experiments.

RESULTS

A total of 191 targets were predicted for 64 chemical compounds in I. pubescens. Following Venn's analysis, we found that 38 candidate targets of I. pubescens were associated with protective effects against MI/RI. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses showed that these targets were related to estrogen signaling pathway. Importantly, the cardioprotective effects of I. pubescens and its active compounds were evaluated and the regulatory effects on key targets of heat shock protein 90 alpha family class A member 1 (HSP90AA1) and Estrogen receptor 1 (ESRα) in estrogen signaling pathway were validated in vitro and in vivo.

CONCLUSION

Our discoveries revealed that I. pubescens ameliorated MI/RI by regulating HSP90AA1 and ESRα in estrogen signaling pathway.

Nuclear Receptors in Myocardial and Cerebral Ischemia-Mechanisms of Action and Therapeutic Strategies

Nearly 18 million people died from cardiovascular diseases in 2019, of these 85% were due to heart attack and stroke. The available therapies although efficacious, have narrow therapeutic window and long list of contraindications. Therefore, there is still an urgent need to find novel molecular targets that could protect the brain and heart against ischemia without evoking major side effects. Nuclear receptors are one of the promising targets for anti-ischemic drugs. Modulation of estrogen receptors (ERs) and peroxisome proliferator-activated receptors (PPARs) by their ligands is known to exert neuro-, and cardioprotective effects through anti-apoptotic, anti-inflammatory or anti-oxidant action. Recently, it has been shown that the expression of aryl hydrocarbon receptor (AhR) is strongly increased after brain or heart ischemia and evokes an activation of apoptosis or inflammation in injury site. We hypothesize that activation of ERs and PPARs and inhibition of AhR signaling pathways could be a promising strategy to protect the heart and the brain against ischemia. In this Review, we will discuss currently available knowledge on the mechanisms of action of ERs, PPARs and AhR in experimental models of stroke and myocardial infarction and future perspectives to use them as novel targets in cardiovascular diseases.

A-Kinase Anchoring Protein 2 Promotes Protection against Myocardial Infarction

Myocardial infarction (MI) is a leading cause of maladaptive cardiac remodeling and heart failure. In the damaged heart, loss of function is mainly due to cardiomyocyte death and remodeling of the cardiac tissue. The current study shows that A-kinase anchoring protein 2 (AKAP2) orchestrates cellular processes favoring cardioprotection in infarcted hearts. Induction of AKAP2 knockout (KO) in cardiomyocytes of adult mice increases infarct size and exacerbates cardiac dysfunction after MI, as visualized by increased left ventricular dilation and reduced fractional shortening and ejection fraction. In cardiomyocytes, AKAP2 forms a signaling complex with PKA and the steroid receptor co-activator 3 (Src3). Upon activation of cAMP signaling, the AKAP2/PKA/Src3 complex favors PKA-mediated phosphorylation and activation of estrogen receptor α (ERα). This results in the upregulation of ER-dependent genes involved in protection against apoptosis and angiogenesis, including Bcl2 and the vascular endothelial growth factor a (VEGFa). In line with these findings, cardiomyocyte-specific AKAP2 KO reduces Bcl2 and VEGFa expression, increases myocardial apoptosis and impairs the formation of new blood vessels in infarcted hearts. Collectively, our findings suggest that AKAP2 organizes a transcriptional complex that mediates pro-angiogenic and anti-apoptotic responses that protect infarcted hearts.

Sex-Gender Disparities in Cardiovascular Diseases: The Effects of Estrogen on eNOS, Lipid Profile, and NFATs During Catecholamine Stress

Cardiovascular diseases (CVDs) characterized by sex-gender differences remain a leading cause of death globally. Hence, it is imperative to understand the underlying mechanisms of CVDs pathogenesis and the possible factors influencing the sex-gender disparities in clinical demographics. Attempts to elucidate the underlying mechanisms over the recent decades have suggested the mechanistic roles of estrogen in modulating cardioprotective and immunoregulatory effect as a factor for the observed differences in the incidence of CVDs among premenopausal and post-menopausal women and men. This review from a pathomechanical perspective aims at illustrating the roles of estrogen (E2) in the modulation of stimuli signaling in the heart during chronic catecholamine stress (CCS). The probable mechanism employed by E2 to decrease the incidence of hypertension, coronary heart disease, and pathological cardiac hypertrophy in premenopausal women are discussed. Initially, signaling via estrogen receptors and β-adrenergic receptors (βARs) during physiological state and CCS were summarized. By reconciling the impact of estrogen deficiency and hyperstimulation of βARs, the discussions were centered on their implications in disruption of nitric oxide synthesis, dysregulation of lipid profiles, and upregulation of nuclear factor of activated T cells, which induces the aforementioned CVDs, respectively. Finally, updates on E2 therapies for maintaining cardiac health during menopause and suggestions for the advancement treatments were highlighted.

Estrogen Receptors: Therapeutic Perspectives for the Treatment of Cardiac Dysfunction after Myocardial Infarction

Estrogen receptors (ER) mediate functions beyond their endocrine roles, as modulation of cardiovascular, renal, and immune systems through anti-inflammatory and anti-apoptotic effects, preventing necrosis of cardiomyocytes and endothelial cells, and attenuating cardiac hypertrophy. Estradiol (E2) prevents cardiac dysfunction, increases nitric oxide synthesis, and reduces the proliferation of vascular cells, yielding protective effects, regardless of gender. Such actions are mediated by ER (ER-alpha (ERα), ER-beta (ERβ), or G protein-coupled ER (GPER)) through genomic or non-genomic pathways, which regulate cardiovascular function and prevent tissue remodeling. Despite the extensive knowledge on the cardioprotective effects of estrogen, clinical studies conducted on myocardial infarction (MI) and cardiovascular diseases still include favorable and unfavorable profiles. The purpose of this review is to provide up-to-date information regarding molecular, preclinical, and clinical aspects of cardiovascular E2 effects and ER modulation as a potential therapeutic target for the treatment of MI-induced cardiac dysfunction.

Estrogen Alleviates Sex-Dependent Differences in Lung Bacterial Clearance and Mortality Secondary to Bacterial Pneumonia after Traumatic Brain Injury

Traumatic brain injury (TBI) is the leading cause of injury-related death and disability in patients under the age of 46 years. Survivors of the initial injury often endure systemic complications such as pulmonary infection, and Pseudomonas aeruginosa is one of the most common causes of nosocomial pneumonia in intensive care units. Female patients are less likely to develop secondary pneumonia after TBI, and pre-clinical studies have revealed a salutary role for estrogen after trauma. Therefore, we hypothesized that female mice would experience less mortality after post-TBI pneumonia with P. aeruginosa. We employed a mouse model of TBI followed by P. aeruginosa pneumonia. Male mice had greater mortality and impaired lung bacterial clearance after post-TBI pneumonia compared with female mice. This was confirmed as a difference in sex hormones, as oophorectomized wild-type mice had mortality and lung bacterial clearance similar to male mice. There were differences in tumor necrosis factor-α secretion in male and female alveolar macrophages after P. aeruginosa infection. Finally, injection of male or oophorectomized wild-type female mice with estrogen restored lung bacterial clearance and prevented mortality. Our model of TBI followed by P. aeruginosa pneumonia is among the first to reveal sex dimorphism in secondary, long-term TBI complications.

The Protective of Baicalin on Myocardial Ischemia-Reperfusion Injury

BACKGROUND

The aim of this study was to explore the inhibitory effect of baicalin on myocardial apoptosis induced by Ischemia-Reperfusion (I/R).

METHODS

Sprague Dawley rats' heart and myocardial cells I/R model were established in vivo and vitro, then 100 mg/kg and 10 μmol/l baicalin were administrated, respectively. The experiment was randomly divided into 4 groups (n=10): Control; I/R; IR+DMEM; and I/R+baicalin groups. Postoperation, the Left Ventricular (LV) End-Diastolic Pressure (LVEDP), the maximum velocity of LV contraction (dP/dtmax) and the maximum velocity of LV diastole (dP/dtmin) were recorded by the transthoracic echocardiography; the myocardial apoptosis percentage was analyzed by Annexin VFITC/ PI and TUNEL staining, and the apoptosis gene and protein were detected by RT-PCR and western blot. Furthermore, the protein expression of the calcium-sensing receptor (CaSR) and ERK1/2 phosphorylation were observed by western blot and Fura-2-acetoxymethyl ester. Moreover, primary rats' cardiomyocytes were cultured and ERK1/2 specific inhibitor PD98059 was added to the culture medium. The cell survival rate, vitality and apoptosis were detected by MTT, lactate dehydrogenase (LDH) and TUNEL staining assay Kit, respectively.

RESULTS

Our present study showed that baicalin significantly improved LV hemodynamic parameters and myocardial apoptosis in myocardial I/R injury rats. Furthermore, we found that baicalin could down-regulate the protein expression of CaSR, but up-regulate the protein expression of ERK1/2. Furthermore, when the cells were pretreated with ERK1/2 inhibitor PD98059, the cells survival rate significantly decreased, but LDH activity and apoptosis significantly increased. The results indicated that the effect of baicalin on myocardial I/R injury could be inhibited by ERK1/2 inhibitor.

CONCLUSION

In conclusion, our data suggests that baicalin attenuates I/R-induced myocardial injury maybe through the suppression of the CaSR/ERK1/2 signaling pathway.

DOKI: Domain knowledge-driven inference method for reverse-engineering transcriptional regulatory relationships among genes in cancer

Efficient reverse-engineering methods are important for identifying transcriptional regulatory relationships among genes in cancer. These methods are becoming increasingly useful in this era where huge volumes of data are generated through the use of high-throughput technologies such as next-generation sequencing technologies and microarrays. However, it is important to improve current methods because of complications involved in modelling complex biological systems. In this paper, we present a novel approach, Domain Knowledge-driven Inference (DOKI), for identification of transcriptional regulatory relationships among genes, given a biological context such as cancer. Combining data normalization, the use of a probability distribution function and Kullback-Leibler Divergence, DOKI incorporates a domain knowledge-driven criterion to make determinations of the existence of regulatory relationships between given transcription factors and given specific gene targets. Characteristics of DOKI enable it to adequately handle complexities inherent in data, and accurately unearth linear and higher-order dependent relationships among genes. DOKI performed equally well with one established high-performing method and better than three other high-performing methods on relatively small data sets. However, it remarkably outperformed these methods on larger data sets to demonstrate its utility. Furthermore, we demonstrate the relevance of such inference algorithms for identifying novel relationships among genes in breast cancer, as some of the consensus results representing novel relationships were confirmed in previously published experimental results. Thus, DOKI will facilitate current efforts to gain etiological insights and help uncover new targeted therapies for various diseases.

Cardiac ischemia/reperfusion stress reduces inner mitochondrial membrane protein (mitofilin) levels during early reperfusion

Mitochondrial inner membrane protein (Mitofilin or Mic60) is a mitochondria-shaping protein that plays a key role in maintaining mitochondrial cristae structure and remodeling. We recently showed that Mitofilin knockdown in H9c2 myoblasts induces mitochondrial structural damage resulting in mitochondrial dysfunction that is responsible for cell death via apoptosis. Here, we investigated the role of Mitofilin regulation in ischemia/reperfusion (I/R) injury and studied the relationship between Mitofilin and Cyclophilin (CypD), a key regulator of mitochondrial permeability transition pore (mPTP) opening. C57Bl6 male mice hearts were subjected to different ischemia times (15, 30, or 45 min) followed by a 2 h reperfusion period, or 45 min ischemia followed by 0, 15, 30, 60, or 120 min reperfusion to determine the impact of ischemia or reperfusion times on Mitofilin levels and its interaction with CypD. We found that the increase in myocardial infarct size and the reduction of mitochondrial calcium retention capacity were concomitant with Mitofilin reduction as a function of ischemic duration. We also found that 15 min reperfusion after 45 min ischemia was sufficient to cause a reduction of Mitofilin levels compared to sham, while 45 min ischemia alone was not enough to cause a significant decrease of Mitofilin. We revealed that the c-terminus coiled-coiled domain of Mitofilin is important for its interaction with CypD and the deletion of this identified sequence resulted in a loss of Mitofilin-CypD link, dissipation of mitochondrial membrane potential and increase in cell death. A decrease of the levels of Mitofilin was also associated with mitochondrial structural integrity damage, increased reactive oxygen species (ROS) production, and calpain activity. Our results indicate that Mitofilin physically binds to CypD in the inner mitochondrial membrane and the disruption of this interaction may play a critical role in the increase of mitochondrial dysfunction and initiation of myocytes' death after I/R injury.

Inner mitochondrial membrane protein MPV17 mutant mice display increased myocardial injury after ischemia/reperfusion

MPV17 is an inner mitochondrial membrane protein whose mutation results in mitochondrial DNA (mtDNA) depletion diseases such as neurohepatopathy. MPV17 is expressed in several organs including the liver and kidneys. Here, we investigated its role and mechanism of action in cardiac ischemia/reperfusion (I/R) injury. Using isolated hearts from wild type and Mpv17 mutant (Mpv17^mut) mice, we found that mtDNA levels and normal cardiac function were similar between the groups. Furthermore, reactive oxygen species (ROS) generation, mitochondrial morphology, and calcium levels required to trigger mitochondrial permeability transition pore (mPTP) opening were all similar in normal/non-ischemic animals. However, following I/R, we found that mutant mice had poorer cardiac functional recovery and exhibited more mitochondrial structural damage. We also found that after I/R, Mpv17^mut heart mitochondria did not produce more ROS than wild type hearts but that calcium retention capacity was gravely compromised. Using immunoprecipitation and mass spectrometry, we identified ATP synthase, Cyclophilin D, MIC60 and GRP75 as proteins critical to mitochondrial cristae organization and calcium handling that interact with MPV17, and this interaction is reduced by I/R. Together our results suggest that MPV17 has a protective function in the heart and is necessary for recovery following insults to the heart.

The Role of Estrogen Receptors in Cardiovascular Disease

Cardiovascular Diseases (CVDs) are the leading cause of death globally. More than 17 million people die worldwide from CVD per year. There is considerable evidence suggesting that estrogen modulates cardiovascular physiology and function in both health and disease, and that it could potentially serve as a cardioprotective agent. The effects of estrogen on cardiovascular function are mediated by nuclear and membrane estrogen receptors (ERs), including estrogen receptor alpha (ERα), estrogen receptor beta (ERβ), and G-protein-coupled ER (GPR30 or GPER). Receptor binding in turn confers pleiotropic effects through both genomic and non-genomic signaling to maintain cardiovascular homeostasis. Each ER has been implicated in multiple pre-clinical cardiovascular disease models. This review will discuss current reports on the underlying molecular mechanisms of the ERs in regulating vascular pathology, with a special emphasis on hypertension, pulmonary hypertension, and atherosclerosis, as well as in regulating cardiac pathology, with a particular emphasis on ischemia/reperfusion injury, heart failure with reduced ejection fraction, and heart failure with preserved ejection fraction.

Crosstalk between GSK-3β-actuated molecular cascades and myocardial physiology

The finding of "glycogen synthase kinase-3" (GSK-3) was initially identified as a protein kinase that phosphorylate and inhibited glycogen synthase. However, it was soon discovered that GSK-3 also has significant impact in regulation of truly astonishing number of critical intracellular signaling pathways ranging from regulation of cell growth, neurology, heart failure, diabetes, aging, inflammation, and cancer. Recent studies have validated the feasibility of targeting GSK-3 for its vital therapeutic potential to maintain normal myocardial homeostasis, conversely, its loss is incompatible with life as it can abrupt cell cycle and endorse fatal cardiomyopathy. The current study focuses on its expanding therapeutic action in myocardial tissue, concentrating primarily on its role in diabetes-associated cardiac complication, apoptosis and metabolism, heart failure, cardiac hypertrophy, and myocardial infarction. The current report also includes the finding of our previous investigation that has shown the impact of GSK-3β inhibitor against diabetes-associated myocardial injury and experimentally induced myocardial infarction. We have also discussed some recent identified GSK-3β inhibitors for their cardio-protective potential. The crosstalk of various underlying mechanisms that highlight the significant role of GSK-3β in myocardial pathophysiology have been discussed in the present report. For these literatures, we will rely profoundly on our previous studies and those of others to reconcile some of the deceptive contradictions in the literature.

Reciprocality Between Estrogen Biology and Calcium Signaling in the Cardiovascular System

17β-Estradiol (E₂) is the main estrogenic hormone in the body and exerts many cardiovascular protective effects. Via three receptors known to date, including estrogen receptors α (ERα) and β (ERβ) and the G protein-coupled estrogen receptor 1 (GPER, aka GPR30), E₂ regulates numerous calcium-dependent activities in cardiovascular tissues. Nevertheless, effects of E₂ and its receptors on components of the calcium signaling machinery (CSM), the underlying mechanisms, and the linked functional impact are only beginning to be elucidated. A picture is emerging of the reciprocality between estrogen biology and Ca²⁺ signaling. Therein, E₂ and GPER, via both E₂-dependent and E₂-independent actions, moderate Ca²⁺-dependent activities; in turn, ERα and GPER are regulated by Ca²⁺ at the receptor level and downstream signaling via a feedforward loop. This article reviews current understanding of the effects of E₂ and its receptors on the cardiovascular CSM and vice versa with a focus on mechanisms and combined functional impact. An overview of the main CSM components in cardiovascular tissues will be first provided, followed by a brief review of estrogen receptors and their Ca²⁺-dependent regulation. The effects of estrogenic agonists to stimulate acute Ca²⁺ signals will then be reviewed. Subsequently, E₂-dependent and E₂-independent effects of GPER on components of the Ca²⁺ signals triggered by other stimuli will be discussed. Finally, a case study will illustrate how the many mechanisms are coordinated to moderate Ca²⁺-dependent activities in the cardiovascular system.

Chronic GPER1 Activation Protects Against Oxidative Stress-Induced Cardiomyoblast Death via Preservation of Mitochondrial Integrity and Deactivation of Mammalian Sterile-20-Like Kinase/Yes-Associated Protein Pathway

Introduction: Estrogen (17β-estradiol, E2) is well-known to induce cardioprotective effects against ischemia/reperfusion (I/R) injury. We recently reported that acute application of E2 at the onset of reperfusion in vivo induces cardioprotective effects against I/R injury via activation of its non-steroidal receptor, G protein-coupled estrogen receptor 1 (GPER1). Here, we investigated the impact and mechanism underlying chronic GPER1 activation in cultured H9c2 rat cardiomyoblasts. Methods: H9c2 rat cardiomyoblasts were cultured and pretreated with the cytotoxic agent H₂O₂ for 24 h and incubated in the presence of vehicle (control), GPER1 agonists E2 and G1, or GPER1 agonists supplemented with G15 (GPER1 antagonist) for 48 or 96 h. After treatment, cells were collected to measure the rate of cell death and viability using flow cytometry and Calcein AM assay or MTT assay, respectively. The resistance to opening of the mitochondrial permeability transition pore (mPTP), the mitochondrial membrane potential, and ATP production was assessed using fluorescence microscopy, and the mitochondrial structural integrity was observed with electron microscopy. The levels of the phosphorylation of mammalian sterile-20-like kinase (MST1) and yes-associated protein (YAP) were assessed by Western blot analysis in whole-cell lysate, while the expression levels of mitochondrial biogenesis genes, YAP target genes, and proapoptotic genes were measured by qRT-PCR. Results: We found that after H₂O₂ treatment, chronic E2/G1 treatment decreased cell death effect was associated with the prevention of the S phase of the cell cycle arrest compared to control. In the mitochondria, chronic E2/G1 activation treatment preserved the cristae morphology, and increased resistance to opening of mPTP, but with little change to mitochondrial fusion/fission. Additionally, chronic E2/G1 treatment predominantly reduced phosphorylation of MST1 and YAP, as well as increased MST1 and YAP protein levels. E2 treatment also upregulated the expression levels of TGF-β and PGC-1α mRNAs and downregulated PUMA and Bim mRNAs. Except for ATP production, all the E2 or G1 effects were prevented by the cotreatment with the GPER1 antagonist, G15. Conclusion: Together, these results indicate that chronic GPER1 activation with its agonists E2 or G1 treatment protects H9c2 cardiomyoblasts against oxidative stress-induced cell death and increases cell viability by preserving mitochondrial structure and function as well as delaying the opening of mPTP. These chronic GPER1 effects are associated with the deactivation of the non-canonical MST1/YAP mechanism that leads to genetic upregulation of cell growth genes (CTGF, CYR61, PGC-1α, and ANKRD1), and downregulation of proapoptotic genes (PUMA and Bim).

Protein kinase Cα mediates recovery of renal and mitochondrial functions following acute injury

Previously, we have shown that active protein kinase Cα (PKCα) promotes recovery of mitochondrial function after injury in vitro [Nowak G & Bakajsova D (2012) Am J Physiol Renal Physiol 303, F515-F526]. This study examined whether PKCα regulates recovery of mitochondrial and kidney functions after ischemia-induced acute injury (AKI) in vivo. Markers of kidney injury were increased after bilateral ischemia and returned to normal levels in wild-type (WT) mice. Maximum mitochondrial respiration and activities of respiratory complexes and F_o F₁ -ATPase decreased after ischemia and recovered in WT mice. Reperfusion after ischemia was accompanied by translocation of active PKCα to mitochondria. PKCα deletion reduced mitochondrial respiration and activities of respiratory complex I and F_o F₁ -ATPase in noninjured kidneys, indicating that PKCα is essential in developing fully functional renal mitochondria. These changes in PKCα-deficient mice were accompanied by lower levels of complex I subunits (NDUFA9 and NDUFS3) and the γ-subunit of F_o F₁ -ATPase. Also, lack of PKCα exacerbated ischemia-induced decreases in respiration, complex I and F_o F₁ -ATPase activities, and blocked their recovery after injury, indicating a crucial role of PKCα in promoting mitochondrial recovery after AKI. Further, PKCα deletion exacerbated acetylation and succinylation of key mitochondrial proteins of energy metabolism after ischemia due to decreases in deacetylase and desuccinylase (sirtuin3 and sirtuin5) levels in renal mitochondria. Thus, our data show a novel role for PKCα in regulating levels of mitochondrial sirtuins and acetylation and succinylation of key mitochondrial proteins. We conclude that PKCα deletion: (a) affects renal physiology by decreasing mitochondrial capacity for maximum respiration; (b) blocks recovery of mitochondrial functions, renal morphology, and functions after AKI; and (c) decreases survival after AKI. ENZYMES: Protein kinase C: EC 2.7.11.13; NADH : ubiquinone reductase (H⁺ -translocating; complex I): EC 7.1.1.2; FoF1-ATPase (H⁺ -transporting two-sector ATPase): EC 7.1.2.2; Succinate : ubiquinone oxidoreductase (complex II): EC 1.3.5.1; Ubiquinol : cytochrome-c reductase (complex III): EC 7.1.1.8; Cytochrome c oxidase (complex IV): EC 1.9.3.1; NAD-dependent protein deacetylase sirtuin-3, mitochondrial: EC 2.3.1.286; NAD-dependent protein deacetylase sirtuin-5, mitochondrial: EC 3.5.1.-; Proteinase K (peptidase K): EC 3.4.21.64.

Liproxstatin-1 protects the mouse myocardium against ischemia/reperfusion injury by decreasing VDAC1 levels and restoring GPX4 levels

Ferroptosis is a distinct iron-dependent mechanism of regulated cell death recognized in cancer and ischemia/reperfusion (I/R) injury of different organs. It has been reported that molecules such as liproxstatin-1 (Lip-1) inhibit ferroptosis and promote cell survival however, the mechanisms underlying this action are not clearly understood. We investigated the role and mechanism of Lip-1 in reducing cell death in the ischemic myocardium. Using an I/R model of isolated perfused mice hearts in which Lip-1 was given at the onset of reperfusion, we found that Lip-1 protects the heart by reducing myocardial infarct sizes and maintaining mitochondrial structural integrity and function. Further investigation revealed that Lip-1-induced cardioprotection is mediated by a reduction of VDAC1 levels and oligomerization, but not VDAC2/3. Lip-1 treatment also decreased mitochondrial reactive oxygen species production and rescued the reduction of the antioxidant GPX4 caused by I/R stress. Meanwhile, mitochondrial Ca²⁺ retention capacity needed to induce mitochondrial permeability transition pore opening did not change with Lip-1 treatment. Thus, we report that Lip-1 induces cardioprotective effects against I/R injury by reducing VDAC1 levels and restoring GPX4 levels.

Astragaloside IV attenuates myocardial ischemia/reperfusion injury in rats via inhibition of calcium-sensing receptor-mediated apoptotic signaling pathways

Astragaloside IV (AsIV) is an active saponin extracted from Astragalus membranaceus, which has shown cardioprotective effects in a number of experimental animals. In this study we investigated the molecular mechanisms by which AsIV attenuated the myocardial ischemia reperfusion (MI/R)-induced injury in vitro and in vivo by focusing on calcium-sensing receptor (CaSR) and extracellular signal-regulated kinase 1/2 (ERK1/2). Rat neonatal cardiac myocytes were subjected to a hypoxia/reoxygenation (H/R) procedure in vitro, which significantly decreased the cell viability, increased lactate dehydrogenase (LDH) release, induced cardiomyocyte apoptosis, and increased [Ca²⁺]_i. H/R also increased the expression of CaSR and decreased ERK1/2 phosphorylation levels in H/R-exposed myocytes. Pretreatment with AsIV (60 μmol/L) significantly improved the cell viability and decreased LDH release, attenuated myocyte apoptosis, decreased [Ca²⁺]_i and CaSR expression, and increased the ERK1/2 phosphorylation levels. The protective effects of AsIV against H/R injury were partially inhibited by co-treatment with a CaSR agonist, gadolinium chloride (GdCl₃) or with a specific ERK1/2 inhibitor U0126. For in vivo studies, a rat MI/R model was established. Pre-administration of AsIV (80 mg/kg every day, ig) significantly decreased the myocardium infarct size, creatine kinase-MB (CK-MB) production, serum cardiac troponin (cTnI) levels, and cardiomyocyte apoptosis in the rats with MI/R injury. The therapeutic effects of AsIV were associated with the downregulation of CaSR expression and upregulation of ERK1/2 phosphorylation in myocardial tissues. In summary, astragaloside IV attenuates myocardial I/R injury via inhibition of CaSR/ERK1/2 and the related apoptotic signaling pathways.

Sex Differences in Ischemia/Reperfusion Injury: The Role of Mitochondrial Permeability Transition

Brain and heart ischemia are among the leading causes of death and disability in both men and women, but there are significant sex differences in the incidence and severity of these diseases. Ca²⁺ dysregulation in response to ischemia/reperfusion injury (I/RI) is a well-recognized pathogenic mechanism leading to the death of affected cells. Excess intracellular Ca²⁺ causes mitochondrial matrix Ca²⁺ overload that can result in mitochondrial permeability transition (MPT), which can have severe consequences for mitochondrial function and trigger cell death. Recent findings indicate that estrogens and their related receptors are involved in the regulation of MPT, suggesting that sex differences in I/RI could be linked to estrogen-dependent modulation of mitochondrial Ca²⁺. Here, we review the evidence supporting sex differences in I/RI and the role of estrogen and estrogen receptors in producing these differences, the involvement of mitochondrial Ca²⁺ overload in disease pathogenesis, and the estrogen-dependent modulation of MPT that may contribute to sex differences.

Activation of G protein-coupled estrogen receptor protects intestine from ischemia/reperfusion injury in mice by protecting the crypt cell proliferation

The intestinal ischemia/reperfusion (I/R) injury is a common clinical event related with high mortality in patients undergoing surgery or trauma. Estrogen exerts salutary effect on intestinal I/R injury, but the receptor type is not totally understood. We aimed to identify whether the G protein-coupled estrogen receptor (GPER) could protect the intestine against I/R injury and explored the mechanism. Adult male C57BL/6 mice were subjected to intestinal I/R injury by clamping (45 min) of the superior mesenteric artery followed by 4 h of intestinal reperfusion. Our results revealed that the selective GPER blocker abolished the protective effect of estrogen on intestinal I/R injury. Selective GPER agonist G-1 significantly alleviated I/R-induced intestinal mucosal damage, neutrophil infiltration, up-regulation of TNF-α and cyclooxygenase-2 (Cox-2) expression, and restored impaired intestinal barrier function. G-1 could ameliorate the impaired crypt cell proliferation ability induced by I/R and restore the decrease in villus height and crypt depth. The up-regulation of inducible nitric oxide synthase (iNOS) expression after I/R treatment was attenuated by G-1 administration. Moreover, selective iNOS inhibitor had a similar effect with G-1 on promoting the proliferation of crypt cells in the intestinal I/R model. Both GPER and iNOS were expressed in leucine-rich repeat containing G-protein coupled receptor 5 (Lgr5) positive stem cells in crypt. Together, these findings demonstrate that GPER activation can prompt epithelial cell repair following intestinal injury, which occurred at least in part by inhibiting the iNOS expression in intestinal stem cells (ISCs). GPER may be a novel therapeutic target for intestinal I/R injury.

Regulation effects of melatonin on bone marrow mesenchymal stem cell differentiation

Melatonin's therapeutic potential has been highly underestimated because its biological functional roles are diverse and relevant mechanisms are complicated. Among the numerous biological activities of melatonin, its regulatory effects on pluripotent mesenchymal stem cells (MSCs), which are found in bone marrow stem cells (BMSCs) and adipose tissue (AD-MSC), have been recently proposed, which has received increasingly more attention in recent studies. Moreover, receptor-dependent and receptor-independent responses to melatonin are identified to occur in these cells by regulating signaling pathways, which drive the commitment and differentiation of MSCs into osteogenic, chondrogenic, or adipogenic lineages. Therefore, the aim of our current review is to summarize the evidence related to the utility of melatonin as a regulatory agent by focusing on its relationship with the differentiation of MSCs. In particular, we aimed to review its roles in promoting osteogenic and chondrogenic differentiation and the relevant signaling cascades involved. Also, the roles that melatonin and, particularly, its receptors play in these processes are highlighted.

The Role of 17β-Estradiol and Estrogen Receptors in Regulation of Ca2+ Channels and Mitochondrial Function in Cardiomyocytes

Numerous epidemiological, clinical, and animal studies showed that cardiac function and manifestation of cardiovascular diseases (CVDs) are different between males and females. The underlying reasons for these sex differences are definitely multifactorial, but major evidence points to a causal role of the sex steroid hormone 17β-estradiol (E2) and its receptors (ER) in the physiology and pathophysiology of the heart. Interestingly, it has been shown that cardiac calcium (Ca²⁺) ion channels and mitochondrial function are regulated in a sex-specific manner. Accurate mitochondrial function and Ca²⁺ signaling are of utmost importance for adequate heart function and crucial to maintaining the cardiovascular health. Due to the highly sensitive nature of these processes in the heart, this review article highlights the current knowledge regarding sex dimorphisms in the heart implicating the importance of E2 and ERs in the regulation of cardiac mitochondrial function and Ca²⁺ ion channels, thus the contractility. In particular, we provide an overview of in-vitro and in-vivo studies using either E2 deficiency; ER deficiency or selective ER activation, which suggest that E2 and ERs are strongly involved in these processes. In this context, this review also discusses the divergent E2-responses resulting from the activation of different ER subtypes in these processes. Detailed understanding of the E2 and ER-mediated molecular and cellular mechanisms in the heart under physiological and pathological conditions may help to design more specifically targeted drugs for the management of CVDs in men and women.

Non-genomic Effects of Estrogen on Cell Homeostasis and Remodeling With Special Focus on Cardiac Ischemia/Reperfusion Injury

This review takes into consideration the main mechanisms involved in cellular remodeling following an ischemic injury, with special focus on the possible role played by non-genomic estrogen effects. Sex differences have also been considered. In fact, cardiac ischemic events induce damage to different cellular components of the heart, such as cardiomyocytes, vascular cells, endothelial cells, and cardiac fibroblasts. The ability of the cardiovascular system to counteract an ischemic insult is orchestrated by these cell types and is carried out thanks to a number of complex molecular pathways, including genomic (slow) or non-genomic (fast) effects of estrogen. These pathways are probably responsible for differences observed between the two sexes. Literature suggests that male and female hearts, and, more in general, cardiovascular system cells, show significant differences in many parameters under both physiological and pathological conditions. In particular, many experimental studies dealing with sex differences in the cardiovascular system suggest a higher ability of females to respond to environmental insults in comparison with males. For instance, as cells from females are more effective in counteracting the ischemia/reperfusion injury if compared with males, a role for estrogen in this sex disparity has been hypothesized. However, the possible involvement of estrogen-dependent non-genomic effects on the cardiovascular system is still under debate. Further experimental studies, including sex-specific studies, are needed in order to shed further light on this matter.

Cardiotoxicity mechanisms of the combination of BRAF-inhibitors and MEK-inhibitors

Many new drugs have appeared in last years in the oncological treatment scenario. Each drug carries an important set of adverse events, not less, cardiovascular adverse events. This aspect is even more important considering the increasing use of combination therapies with two drugs, or three drugs as in some ongoing clinical trials. Besides it represents a growing problem for Cardiologists, that face it in every day clinical practice and that will face it probably more and more in the coming years. This work reviews the mechanism of action of BRAF-inhibitors and MEK-inhibitors used together, the pathophysiological mechanisms that lead to cardiovascular toxicity. Particularly, it focuses on hypertension and ejection fraction reduction development. Then, it follows the examination of published data for each combination therapy. A Literature research was carried out using Pubmed selecting review articles, original studies and clinical trials, but mainly focusing on phase 3 studies. This work aims to summarize the knowledge about BRAF-inhibitor and MEK-inhibitor treatment and its cardiovascular toxicity to make it usable and give the basic tools to Cardiologists and Oncologists for a better management of cancer patient undergoing this treatment. Besides a deeper knowledge of the cardiovascular adverse events linked to this treatment and the magnitude of their expression and frequency can lead to a targeted cardiological treatment.

Crosstalk between nuclear and G protein-coupled estrogen receptors

In 2005, two groups independently discovered that the G protein-coupled receptor GPR30 binds estradiol in cultured cells and, in response, initiates intracellular signaling cascades Revankar et al. (2005), Thomas et al. (2005). GPR30 is now referred to as GPER, the G-protein coupled estrogen receptor Prossnitz and Arterburn (2015). While studies in animal models are illuminating GPER function, there is controversy as to whether GPER acts as an autonomous estrogen receptor in vivo, or whether GPER interacts with nuclear estrogen receptor signaling pathways in response to estrogens. Here, we review the evidence that GPER acts as an autonomous estrogen receptor in vivo and discuss experimental approaches to test this hypothesis directly. We propose that the degree to which GPER influences nuclear estrogen receptor signaling likely depends on cell type, developmental stage and pathology.

Mitochondrial inner membrane protein (mitofilin) knockdown induces cell death by apoptosis via an AIF-PARP-dependent mechanism and cell cycle arrest

Mitofilin is an inner membrane protein that has been defined as a mitochondria-shaping protein in controlling and maintaining mitochondrial cristae structure and remodeling. We determined the role of mitofilin in cell survival by investigating the mechanism underlying mitofilin knockdown-induced cell death by apoptosis. Cultured H9c2 myoblasts and HEK 293 cells were treated with mitofilin siRNA or scrambled siRNA for 24 h. Cell death (apoptosis), caspase 3 activity and cell cycle phases were assessed by flow cytometry, while cytochrome c release and intracellular ATP production were measured by ELISA. Mitofilin, apoptosis-inducing factor (AIF) and poly(ADP-ribose) polymerase (PARP) expression were measured by Western blot analysis and calpain activity was assessed using a calpain activity kit. Mitochondrial images were taken using electron microscopy. We found that mitofilin knockdown increases apoptosis mainly via activation of the AIF-PARP pathway leading to nuclear fragmentation that is correlated with S phase arrest of the cell cycle. Knockdown of mitofilin also led to mitochondrial swelling and damage of cristae that is associated with the increase in reactive oxygen species production and mitochondrial calpain activity, as well as a marked decrease in intracellular ATP production and mitochondrial membrane potential. Together, these results indicate that mitofilin knockdown by siRNA increases calpain activity that presumably leads to mitochondrial structural degradation resulting in a critical reduction of mitochondrial function that is responsible for the increase in cell death by apoptosis via an AIF-PARP mechanism and associated with nuclear fragmentation, and S phase arrest of the cell cycle.

GPER modulators: Opportunity Nox on the heels of a class Akt

The (patho)physiology of estrogen and its receptors is complex. It is therefore not surprising that therapeutic approaches targeting this hormone include stimulation of its activity through supplementation with either the hormone itself or natural or synthetic agonists, inhibition of its activity through the use of antagonists or inhibitors of its synthesis, and tissue-selective modulation of its activity with biased ligands. The physiology of this hormone is further complicated by the existence of at least three receptors, the classical nuclear estrogen receptors α and β (ERα and ERβ), and the 7-transmembrane G protein-coupled estrogen receptor (GPER/GPR30), with overlapping but distinct pharmacologic profiles, particularly of anti-estrogenic ligands. GPER-selective ligands, as well as GPER knockout mice, have greatly aided our understanding of the physiological roles of GPER. Such ligands have revealed that GPER activation mediates many of the rapid cellular signaling events (including Ca2+ mobilization, ERK and PI3K/Akt activation) associated with estrogen activity, as opposed to the nuclear ERs that are traditionally described to function as ligand-induced transcriptional factors. Many of the salutary effects of estrogen throughout the body are reproduced by the GPER-selective agonist G-1, which, owing to its minimal effects on reproductive tissues, can be considered a non-feminizing estrogenic compound, and thus of potential therapeutic use in both women and men. On the contrary, until recently GPER-selective antagonists had predominantly found preclinical application in cancer models where estrogen stimulates cell growth and survival. This viewpoint changed recently with the discovery that GPER is associated with aging, particularly that of the cardiovascular system, where the GPER antagonist G36 reduced hypertension and GPER deficiency prevented cardiac fibrosis and vascular dysfunction with age, through the downregulation of Nox1 and as a consequence superoxide production. Thus, similar to the classical ERs, both agonists and antagonists of GPER may be of therapeutic benefit depending on the disease or condition to be treated.

Molecular pathways of oestrogen receptors and β-adrenergic receptors in cardiac cells: Recognition of their similarities, interactions and therapeutic value

Oestrogen receptors (ERs) and β-adrenergic receptors (βARs) play important roles in the cardiovascular system. Moreover, these receptors are expressed in cardiac myocytes and vascular tissues. Numerous experimental observations support the hypothesis that similarities and interactions exist between the signalling pathways of ERs (ERα, ERβ and GPR30) and βARs (β₁ AR, β₂ AR and β₃ AR). The recently discovered oestrogen receptor GPR30 shares structural features with the βARs, and this forms the basis for the interactions and functional overlap. GPR30 possesses protein kinase A (PKA) phosphorylation sites and PDZ binding motifs and interacts with A-kinase anchoring protein 5 (AKAP5), all of which enable its interaction with the βAR pathways. The interactions between ERs and βARs occur downstream of the G-protein-coupled receptor, through the G_αs and G_αi proteins. This review presents an up-to-date description of ERs and βARs and demonstrates functional synergism and interactions among these receptors in cardiac cells. We explore their signalling cascades and the mechanisms that orchestrate their interactions and propose new perspectives on the signalling patterns for the GPR30 based on its structural resemblance to the βARs. In addition, we explore the relevance of these interactions to cell physiology, drugs (especially β-blockers and calcium channel blockers) and cardioprotection. Furthermore, a receptor-independent mechanism for oestrogen and its influence on the expression of βARs and calcium-handling proteins are discussed. Finally, we highlight promising therapeutic avenues that can be derived from the shared pathways, especially the phosphatidylinositol-3-OH kinase (PI3K/Akt) pathway.

Neonatal cardiomyocyte hypertrophy induced by endothelin-1 is blocked by estradiol acting on GPER

Estradiol (E₂) prevents cardiac hypertrophy, and these protective actions are mediated by estrogen receptor (ER)α and ERβ. The G protein-coupled estrogen receptor (GPER) mediates many estrogenic effects, and its activation in the heart has been observed in ischemia and reperfusion injury or hypertension models; however, the underlying mechanisms need to be fully elucidated. Herein, we investigated whether the protective effect of E₂ against cardiomyocyte hypertrophy induced by endothelin-1 (ET-1) is mediated by GPER and the signaling pathways involved. Isolated neonatal female rat cardiomyocytes were treated with ET-1 (100 nmol/l) for 48 h in the presence or absence of E₂ (10 nmol/l) or GPER agonist G-1 (10 nmol/l) and GPER antagonist G-15 (10 nmol/l). ET-1 increased the surface area of cardiomyocytes, and this was associated with increased expression of atrial and brain natriuretic peptides. Additionally, ET-1 increased the phosphorylation of extracellular signal-related protein kinases-1/2 (ERK1/2). Notably, E₂ or G-1 abolished the hypertrophic actions of ET-1, and that was reversed by G-15. Likewise, E₂ reversed the ET-1-mediated increase of ERK1/2 phosphorylation as well as the decrease of phosphorylated Akt and its upstream activator 3-phosphoinositide-dependent protein kinase-1 (PDK1). These effects were inhibited by G-15, indicating that they are GPER dependent. Confirming the participation of GPER, siRNA silencing of GPER inhibited the antihypertrophic effect of E₂. In conclusion, E₂ plays a key role in antagonizing ET-1-induced hypertrophy in cultured neonatal cardiomyocytes through GPER signaling by a mechanism involving activation of the PDK1 pathway, which would prevent the increase of ERK1/2 activity and consequently the development of hypertrophy.

Activation of G protein-coupled oestrogen receptor 1 at the onset of reperfusion protects the myocardium against ischemia/reperfusion injury by reducing mitochondrial dysfunction and mitophagy

Background and Purpose

Recent evidence indicates that GPER (G protein‐coupled oestrogen receptor 1) mediates acute pre‐ischaemic oestrogen‐induced protection of the myocardium from ischaemia/reperfusion injury via a signalling cascade that includes PKC translocation, ERK1/2/ GSK‐3β phosphorylation and inhibition of the mitochondrial permeability transition pore (mPTP) opening. Here, we investigated the impact and mechanism involved in post‐ischaemic GPER activation in ischaemia/reperfusion injury. We determined whether GPER activation at the onset of reperfusion confers cardioprotective effects by protecting against mitochondrial impairment and mitophagy.

Experimental Approach

In vivo rat hearts were subjected to ischaemia followed by reperfusion with oestrogen (17β‐oestradiol, E2), E2 + G15, a GPER antagonist, or vehicle. Myocardial infarct size, the threshold for the opening of mPTP, mitophagy, mitochondrial membrane potential, ROS production, proteins ubiquitinated including cyclophilin D, and phosphorylation levels of ERK and GSK‐3β were measured.

Results

We found that post‐ischaemic E2 administration to both male and female ovariectomized‐rats reduced myocardial infarct size. Post‐ischaemic E2 administration preserved mitochondrial structural integrity and this was associated with a decrease in ROS production and increased mitochondrial membrane potential, as well as an increase in the mitochondrial Ca²⁺ load required to induce mPTP opening via activation of the MEK/ERK/GSK‐3β axis. Moreover, E2 reduced mitophagy via the PINK1/Parkin pathway involving LC3I, LC3II and p62 proteins. All these post‐ischaemic effects of E2 were abolished by G15 suggesting a GPER‐dependent mechanism.

Conclusion

These results indicate that post‐ischaemic GPER activation induces cardioprotective effects against ischaemia/reperfusion injury in males and females by protecting mitochondrial structural integrity and function and reducing mitophagy.

GPER modulates tone and coronary vascular reactivity in male and female rats

Compared with age-matched men, premenopausal women are largely protected from coronary artery disease, a difference that is lost after menopause. The effects of oestrogens are mediated by the activation of nuclear receptors (ERα and ERβ) and by the G protein-coupled oestrogen receptor (GPER). This study aims to evaluate the potential role of GPER in coronary circulation in female and male rats. The baseline coronary perfusion pressure (CPP) and the concentration-response curve with a GPER agonist (G-1) were evaluated in isolated hearts before and after the blockade of GPER. GPER, superoxide dismutase (SOD-2), catalase and gp91phox protein expression were assessed by Western blotting. Superoxide production was evaluated 'in situ' via dihydroethidium fluorescence (DHE). GPER blockade significantly increased the CPP in both groups, demonstrating the modulation of coronary tone by GPER. G-1 causes relaxation of the coronary bed in a concentration-dependent manner and was significantly higher in female rats. No differences were detected in GPER, SOD-2 and catalase protein expression. However, gp91phox expression and DHE fluorescence were higher in male rats, indicating elevated superoxide production. Therefore, GPER plays an important role in modulating coronary tone and reactivity in female and male rats. The observed differences in vascular reactivity may be related to the higher superoxide production in male rats. These findings help to elucidate the role of GPER-modulating coronary circulation, providing new information to develop a potential therapeutic target for the treatment of coronary heart disease.