Effect of Ischemia Reperfusion Injury and Epoxyeicosatrienoic Acids on Caveolin Expression in Mouse Myocardium:

The purified extract of steamed Panax ginseng protects cardiomyocyte from ischemic injury via caveolin-1 phosphorylation-mediating calcium influx

Background

Caveolin-1, the scaffolding protein of cholesterol-rich invaginations, plays an important role in store-operated Ca2+ influx and its phosphorylation at Tyr14 (p-caveolin-1) is vital to mobilize protection against myocardial ischemia (MI) injury. SOCE, comprising STIM1, ORAI1 and TRPC1, contributes to intracellular Ca2+ ([Ca2+]i) accumulation in cardiomyocytes. The purified extract of steamed Panax ginseng (EPG) attenuated [Ca2+]i overload against MI injury. Thus, the aim of this study was to investigate the possibility of EPG affecting p-caveolin-1 to further mediate SOCE/[Ca2+]i against MI injury in neonatal rat cardiomyocytes and a rat model.

Methods

PP2, an inhibitor of p-caveolin-1, was used. Cell viability, [Ca2+]i concentration were analyzed in cardiomyocytes. In rats, myocardial infarct size, pathological damages, apoptosis and cardiac fibrosis were evaluated, p-caveolin-1 and STIM1 were detected by immunofluorescence, and the levels of caveolin-1, STIM1, ORAI1 and TRPC1 were determined by RT-PCR and Western blot. And, release of LDH, cTnI and BNP was measured.

Results

EPG, ginsenosides accounting for 57.96%, suppressed release of LDH, cTnI and BNP, and protected cardiomyocytes by inhibiting Ca2+ influx. And, EPG significantly relieved myocardial infarct size, cardiac apoptosis, fibrosis, and ultrastructure abnormality. Moreover, EPG negatively regulated SOCE via increasing p-caveolin-1 protein, decreasing ORAI1 mRNA and protein levels of ORAI1, TRPC1 and STIM1. More importantly, inhibition of the p-caveolin-1 significantly suppressed all of the above cardioprotection of EPG.

Conclusions

Caveolin-1 phosphorylation is involved in the protective effects of EPG against MI injury via increasing p-caveolin-1 to negatively regulate SOCE/[Ca2+]i.

Arachidonic acid metabolism in health and disease

Arachidonic acid (AA), an n-6 essential fatty acid, is a major component of mammalian cells and can be released by phospholipase A2. Accumulating evidence indicates that AA plays essential biochemical roles, as it is the direct precursor of bioactive lipid metabolites of eicosanoids such as prostaglandins, leukotrienes, and epoxyeicosatrienoic acid obtained from three distinct enzymatic metabolic pathways: the cyclooxygenase pathway, lipoxygenase pathway, and cytochrome P450 pathway. AA metabolism is involved not only in cell differentiation, tissue development, and organ function but also in the progression of diseases, such as hepatic fibrosis, neurodegeneration, obesity, diabetes, and cancers. These eicosanoids are generally considered proinflammatory molecules, as they can trigger oxidative stress and stimulate the immune response. Therefore, interventions in AA metabolic pathways are effective ways to manage inflammatory-related diseases in the clinic. Currently, inhibitors targeting enzymes related to AA metabolic pathways are an important area of drug discovery. Moreover, many advances have also been made in clinical studies of AA metabolic inhibitors in combination with chemotherapy and immunotherapy. Herein, we review the discovery of AA and focus on AA metabolism in relation to health and diseases. Furthermore, inhibitors targeting AA metabolism are summarized, and potential clinical applications are discussed.

Pathophysiology and molecular mechanism of caveolin involved in myocardial protection strategies in ischemic conditioning

Multiple pathophysiological pathways are activated during the process of myocardial injury. Various cardioprotective strategies protect the myocardium from ischemia, infarction, and ischemia/reperfusion (I/R) injury through different targets, yet the clinical translation remains limited. Caveolae and its structure protein, caveolins, have been suggested as a bridge to transmit damage-preventing signals and mediate the protection of ultrastructure in cardiomyocytes under pathological conditions. In this review, we first briefly introduce caveolae and caveolins. Then we review the cardioprotective strategies mediated by caveolins through various pathophysiological pathways. Finally, some possible research directions are proposed to provide future experiments and clinical translation perspectives targeting caveolin based on the investigative evidence.

Epoxylipids and soluble epoxide hydrolase in heart diseases

Cardiovascular and heart diseases are leading causes of morbidity and mortality. Coronary artery endothelial and vascular dysfunction, inflammation, and mitochondrial dysfunction contribute to progression of heart diseases such as arrhythmias, congestive heart failure, and heart attacks. Classes of fatty acid epoxylipids and their enzymatic regulation by soluble epoxide hydrolase (sEH) have been implicated in coronary artery dysfunction, inflammation, and mitochondrial dysfunction in heart diseases. Likewise, genetic and pharmacological manipulations of epoxylipids have been demonstrated to have therapeutic benefits for heart diseases. Increasing epoxylipids reduce cardiac hypertrophy and fibrosis and improve cardiac function. Beneficial actions for epoxylipids have been demonstrated in cardiac ischemia reperfusion injury, electrical conductance abnormalities and arrhythmias, and ventricular tachycardia. This review discusses past and recent findings on the contribution of epoxylipids in heart diseases and the potential for their manipulation to treat heart attacks, arrhythmias, ventricular tachycardia, and heart failure.

Neuroretinal-Derived Caveolin-1 Promotes Endotoxin-Induced Inflammation in the Murine Retina

Purpose

The immune-privileged environment and complex organization of retinal tissue support the retina's essential role in visual function, yet confound inquiries into cell-specific inflammatory effects that lead to dysfunction and degeneration. Caveolin-1 (Cav1) is an integral membrane protein expressed in several retinal cell types and is implicated in immune regulation. However, whether Cav1 promotes or inhibits inflammatory processes in the retina (as well as in other tissues) remains unclear. Previously, we showed that global-Cav1 depletion resulted in reduced retinal inflammatory cytokine production but paradoxically elevated retinal immune cell infiltration. We hypothesized that these disparate responses are the result of differential cell-specific Cav1 functions in the retina.

Methods

We used Cre/lox technology to deplete Cav1 specifically in the neural retinal (NR) compartment to clarify the role NR-specific Cav1 (NR-Cav1) in the retinal immune response to intravitreal inflammatory challenge induced by activation of Toll-like receptor-4 (TLR4). We used multiplex protein suspension array and flow cytometry to evaluate innate immune activation. Additionally, we used bioinformatics assessment of differentially expressed membrane-associated proteins to infer relationships between NR-Cav1 and immune response pathways.

Results

NR-Cav1 depletion, which primarily affects Müller glia Cav1 expression, significantly altered immune response pathway regulators, decreased retinal inflammatory cytokine production, and reduced retinal immune cell infiltration in response to LPS-stimulated inflammatory induction.

Conclusions

Cav1 expression in the NR compartment promotes the innate TLR4-mediated retinal tissue immune response. Additionally, we have identified novel potential immune modulators differentially expressed with NR-Cav1 depletion. This study further clarifies the role of NR-Cav1 in retinal inflammation.

Soluble Epoxide Hydrolase Regulation of Lipid Mediators Limits Pain

The role of lipids in pain signaling is well established and built on decades of knowledge about the pain and inflammation produced by prostaglandin and leukotriene metabolites of cyclooxygenase and lipoxygenase metabolism, respectively. The analgesic properties of other lipid metabolites are more recently coming to light. Lipid metabolites have been observed to act directly at ion channels and G protein-coupled receptors on nociceptive neurons as well as act indirectly at cellular membranes. Cytochrome P450 metabolism of specifically long-chain fatty acids forms epoxide metabolites, the epoxy-fatty acids (EpFA). The biological role of these metabolites has been found to mediate analgesia in several types of pain pathology. EpFA act through a variety of direct and indirect mechanisms to limit pain and inflammation including nuclear receptor agonism, limiting endoplasmic reticulum stress and blocking mitochondrial dysfunction. Small molecule inhibitors of the soluble epoxide hydrolase can stabilize the EpFA in vivo, and this approach has demonstrated relief in preclinical modeled pain pathology. Moreover, the ability to block neuroinflammation extends the potential benefit of targeting soluble epoxide hydrolase to maintain EpFA for neuroprotection in neurodegenerative disease.

Milrinone Attenuates Heart and Lung Remote Injury after Abdominal Aortic Cross-Clamping

BACKGROUND

Phosphodiesterase enzymes play a pivotal role in the pathogenesis of ischemia/reperfusion (IR). We examined the role of milrinone (MIL), a phosphodiesterase 3 inhibitor, on remote injury of the heart and lung after abdominal aortic cross-clamping.

DESIGN

Experimental study.

METHODS

Twenty-one Wistar rats were divided into 3 groups: (1) control (C, n = 7), underwent laparotomy and exploration of abdominal aorta only; (2) IR (n = 7), normal saline was applied intraperitoneally (i.p) before IR induced by clamping of the abdominal aorta for 1 hr and then allowing reperfusion for 1 hr; and (3) MIL + IR (n = 7), MIL was given (0.5 mg/kg, i.p) before IR. After sacrification, the lungs and hearts were taken out for analyses and the tissue malondialdehyde (MDA) and glutathione (GSH) were studied. All tissues were examined under light microscopy and transmission electron microscopy (TEM). Expressions of caveolin (Cav)-1 in the lung and Cav-1 and Cav-3 in the heart were examined immunohistochemically.

RESULTS

The MIL + IR group had significantly a lower magnitude of oxidative stress than the IR group both in the lung and heart (lung: P = 0.03 for MDA and 0.001 for GSH and heart: P = 0.002 for MDA and 0.000 for GSH). In light microscopy, the MIL + IR group had statistically a lower total injury score than the IR group for both the lung and heart tissue (P = 0.03 and P = 0.04, respectively). In TEM, regression of mitochondrial degeneration and lamellar bodies in type II pneumocytes in the lungs and obvious improvements in disruption at the intercalated discs and mitochondrial degeneration in the hearts in the MIL + IR group were detected compared with the IR group. The expression of both Cav-1 and Cav-3 in the MIL + IR group was improved compared with the IR group (P = 0.03 for both).

CONCLUSIONS

MIL attenuates remote injury of heart and lung in lower body IR by inhibiting oxidative stress. Moreover, Cav-1 and Cav-3 might have a potential role in MIL-induced cardioprotection.

Mitochondrial Dysfunction and Inflammaging in Heart Failure: Novel Roles of CYP-Derived Epoxylipids

Age-associated changes leading to a decline in cardiac structure and function contribute to the increased susceptibility and incidence of cardiovascular diseases (CVD) in elderly individuals. Indeed, age is considered a risk factor for heart failure and serves as an important predictor for poor prognosis in elderly individuals. Effects stemming from chronic, low-grade inflammation, inflammaging, are considered important determinants in cardiac health; however, our understanding of the mechanisms involved remains unresolved. A steady decline in mitochondrial function is recognized as an important biological consequence found in the aging heart which contributes to the development of heart failure. Dysfunctional mitochondria contribute to increased cellular stress and an innate immune response by activating the NLRP-3 inflammasomes, which have a role in inflammaging and age-related CVD pathogenesis. Emerging evidence suggests a protective role for CYP450 epoxygenase metabolites of N-3 and N-6 polyunsaturated fatty acids (PUFA), epoxylipids, which modulate various aspects of the immune system and protect mitochondria. In this article, we provide insight into the potential roles N-3 and N-6 PUFA have modulating mitochondria, inflammaging and heart failure.

Buyang Huanwu Decoction Exerts Cardioprotective Effects through Targeting Angiogenesis via Caveolin-1/VEGF Signaling Pathway in Mice with Acute Myocardial Infarction

Background

Acute myocardial infarction (AMI) remains a leading cause of morbidity and mortality worldwide. The idea of therapeutic angiogenesis in ischemic myocardium is a promising strategy for MI patients. Buyang Huanwu decoction (BHD), a famous Chinese herbal prescription, exerted antioxidant, antiapoptotic, and anti-inflammatory effects, which contribute to cardio-/cerebral protection. Here, we aim to investigate the effects of BHD on angiogenesis through the caveolin-1 (Cav-1)/vascular endothelial growth factor (VEGF) pathway in MI model of mice.

Materials and Methods

C57BL/6 mice were randomly divided into 3 groups by the table of random number: (1) sham-operated group (sham, n = 15), (2) AMI group (AMI+sham, n = 20), and (3) BHD-treated group (AMI+BHD, n = 20). 2,3,5-Triphenyltetrazolium chloride solution stain was used to determine myocardial infarct size. Myocardial histopathology was tested using Masson staining and hematoxylin-eosin staining. CD31 immunofluorescence staining was used to analyze the angiogenesis in the infarction border zone. Western blot analysis, immunofluorescence staining, and/or real-time quantitative reverse transcription polymerase chain reaction was applied to test the expression of Cav-1, VEGF, vascular endothelial growth factor receptor 2 (VEGFR2), and/or phosphorylated extracellular signal-regulated kinase (p-ERK). All statistical analyses were performed using the SPSS 20.0 software and GraphPad Prism 6.05. Values of P < 0.05 were considered as statistically significant.

Results and Conclusion

Compared with the AMI group, the BHD-treated group showed a significant improvement in the heart weight/body weight ratio, echocardiography images, cardiac function, infarct size, Mason staining of the collagen deposition area, and density of microvessel in the infarction border zone (P < 0.05). Compared with the AMI group, BHD promoted the expression of Cav-1, VEGF, VEGFR2, and p-ERK in the infarction border zone after AMI. BHD could exert cardioprotective effects on the mouse model with AMI through targeting angiogenesis via Cav-1/VEGF signaling pathway.

Caveolin-1 facilitated KCNA5 expression, promoting breast cancer viability

Potassium voltage-gated channel subfamily A member 5 (KCNA5) is a voltage-gated potassium channel protein encoded by the KCNA5 gene. A large number of studies have shown that KCNA5 is associated with the survival of malignant tumors, including breast cancer, but the detailed mechanism remains inconclusive. Our previous study found that KCNA5 is co-expressed with a scaffolding protein, caveolin-1 in MCF-10A-neoT non-tumorigenic epithelial cell. In the present study, KCNA5 and caveolin-1 were expressed in breast cancer tissues and cell lines. Exposing MCF-10A-neoT to 2 mM of methyl-β-cyclodextrin, an agent to disrupt caveolae and lipid rafts led to a downregulation of caveolin-1 that reduced the expression of KCNA5. Furthermore, following caveolin-1 knockdown, the expression of KCNA5 was decreased in MDA-MB-231 human breast cancer and MCF-10A-neoT non-tumorigenic epithelial cell lines. In subsequent experiments, the MTT assay showed that increased caveolin-1 and KCNA5 expression promoted the survival of MCF-7 human breast cancer cells, but cell survival was not affected following KCNA5 overexpression alone. Using small interfering RNA technology, KCNA5-silenced MCF-10A-neoT cells were established and a decreased level of phosphorylated-AKT serine/threonine kinase (AKT) was observed in the cells compared with the parental cells. Overall, these results suggested that caveolin-1 facilitated KCNA5 expression and may be associated with AKT activation.

Modulation of mitochondrial dysfunction and endoplasmic reticulum stress are key mechanisms for the wide-ranging actions of epoxy fatty acids and soluble epoxide hydrolase inhibitors

The arachidonic acid cascade is arguably the most widely known biologic regulatory pathway. Decades after the seminal discoveries involving its cyclooxygenase and lipoxygenase branches, studies of this cascade remain an active area of research. The third and less widely known branch, the cytochrome P450 pathway leads to highly active oxygenated lipid mediators, epoxy fatty acids (EpFAs) and hydroxyeicosatetraenoic acids (HETEs), which are of similar potency to prostanoids and leukotrienes. Unlike the COX and LOX branches, no pharmaceuticals currently are marketed targeting the P450 branch. However, data support therapeutic benefits from modulating these regulatory lipid mediators. This is being approached by stabilizing or mimicking the EpFAs or even by altering the diet. These approaches lead to predominantly beneficial effects on a wide range of apparently unrelated states resulting in an enigma of how this small group of natural chemical mediators can have such diverse effects. EpFAs are degraded by soluble epoxide hydrolase (sEH) and stabilized by inhibiting this enzyme. In this review, we focus on interconnected aspects of reported mechanisms of action of EpFAs and inhibitors of soluble epoxide hydrolase (sEHI). The sEHI and EpFAs are commonly reported to maintain homeostasis under pathological conditions while remaining neutral under normal physiological conditions. Here we provide a conceptual framework for the unique and broad range of biological activities ascribed to epoxy fatty acids. We argue that their mechanism of action pivots on their ability to prevent mitochondrial dysfunction, to reduce subsequent ROS formation and to block resulting cellular signaling cascades, primarily the endoplasmic reticulum stress. By stabilizing the mitochondrial - ROS - ER stress axis, the range of activity of EpFAs and sEHI display an overlap with the disease conditions including diabetes, fibrosis, chronic pain, cardiovascular and neurodegenerative diseases, for which the above outlined mechanisms play key roles.

Helium postconditioning regulates expression of caveolin-1 and -3 and induces RISK pathway activation after ischaemia/reperfusion in cardiac tissue of rats

Caveolae, lipid enriched invaginations of the plasma membrane, are epicentres of cellular signal transduction. The structural proteins of caveolae, caveolins, regulate effector pathways in anaesthetic-induced cardioprotection, including the RISK pathway. Helium (He) postconditioning (HePoc) is known to mimic anaesthetic conditioning and to prevent damage from myocardial infarction. We hypothesize that HePoc regulates caveolin-1 and caveolin-3 (Cav-1 and Cav-3) expression in the rat heart and activates the RISK pathway. Male Wistar rats (n=8, each group) were subjected to 25min of cardiac ischaemia followed by reperfusion (I/R) for 5, 15 or 30min (I/R 5/15/30). The HePoc groups underwent I/R with 70% helium ventilation during reperfusion (IR+He 5/15/30min). Sham animals received surgical treatment without I/R. After each protocol blood and hearts were retrieved. Tissue was obtained from the area-at-risk (AAR) and non-area-at-risk (NAAR) and processed for western blot analyses and reverse-transcription-real-time-polymerase-chain-reaction (RT-qPCR). Protein analyses revealed increased amounts of Cav-1 and Cav-3 in the membrane of I/R+He15 (AAR: Cav-1, P<0.05; Cav-3, P<0.05; both vs. I/R15). In serum, Cav-3 was found to be elevated in I/R+He15 (P<0.05 vs. I/R15). RT-qPCR showed increased expression of Cav-1 in IR+He15 in AAR tissue (P<0.05 vs. I/R15). Phosphorylation of RISK pathway proteins pERK1/2 (AAR: P<0.05 vs. I/R15) and pAKT (AAR: P<0.05; NAAR P<0.05; both vs. I/R15) was elevated in the cytosolic fraction of I/R+He15. These results suggest that 15min of HePoc regulates Cav-1 and Cav-3 and activates RISK pathway kinases ERK1/2 and AKT. These processes might be crucially involved in HePoc mediated cardioprotection.

Sarcolemmal dependence of cardiac protection and stress-resistance: roles in aged or diseased hearts

Disruption of the sarcolemmal membrane is a defining feature of oncotic death in cardiac ischaemia-reperfusion (I-R), and its molecular makeup not only fundamentally governs this process but also affects multiple determinants of both myocardial I-R injury and responsiveness to cardioprotective stimuli. Beyond the influences of membrane lipids on the cytoprotective (and death) receptors intimately embedded within this bilayer, myocardial ionic homeostasis, substrate metabolism, intercellular communication and electrical conduction are all sensitive to sarcolemmal makeup, and critical to outcomes from I-R. As will be outlined in this review, these crucial sarcolemmal dependencies may underlie not only the negative effects of age and common co-morbidities on myocardial ischaemic tolerance but also the on-going challenge of implementing efficacious cardioprotection in patients suffering accidental or surgically induced I-R. We review evidence for the involvement of sarcolemmal makeup changes in the impairment of stress-resistance and cardioprotection observed with ageing and highly prevalent co-morbid conditions including diabetes and hypercholesterolaemia. A greater understanding of membrane changes with age/disease, and the inter-dependences of ischaemic tolerance and cardioprotection on sarcolemmal makeup, can facilitate the development of strategies to preserve membrane integrity and cell viability, and advance the challenging goal of implementing efficacious 'cardioprotection' in clinically relevant patient cohorts. Linked Articles This article is part of a themed section on Molecular Pharmacology of G Protein-Coupled Receptors. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v173.20/issuetoc.

Caveolin-1/-3: therapeutic targets for myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (I/R) injury is a major cause of morbidity and mortality worldwide. Caveolae, caveolin-1 (Cav-1), and caveolin-3 (Cav-3) are essential for the protective effects of conditioning against myocardial I/R injury. Caveolins are membrane-bound scaffolding proteins that compartmentalize and modulate signal transduction. In this review, we introduce caveolae and caveolins and briefly describe the interactions of caveolins in the cardiovascular diseases. We also review the roles of Cav-1/-3 in protection against myocardial ischemia and I/R injury, and in conditioning. Finally, we suggest several potential research avenues that may be of interest to clinicians and basic scientists. The information included, herein, is potentially useful for the design of future studies and should advance the investigation of caveolins as therapeutic targets.

Orally active epoxyeicosatrienoic acid analog does not exhibit antihypertensive and reno- or cardioprotective actions in two-kidney, one-clip Goldblatt hypertensive rats

This study examined the effects of a novel orally active 14,15-epoxyeicosatrienoic acid analog (EET-A) on blood pressure (BP) and myocardial infarct size (IS) in two-kidney, one-clip (2K1C) Goldblatt hypertensive rats during sustained phase of hypertension. Between days 31 and 35 after clip placement the rats were treated with EET-A and BP was monitored by radiotelemetry; sham-operated normotensive rats were used as controls. Tissue concentrations of epoxyeicosatrienoic acids served as a marker of production of epoxygenase metabolites. The rats were subjected to acute myocardial ischemia/reperfusion (I/R) injury and IS was determined. We found that EET-A treatment did not lower BP in 2K1C rats and did not alter availability of biologically active epoxygenase metabolites in 2K1C or in sham-operated rats. The myocardial IS was significantly smaller in untreated 2K1C rats as compared with normotensive controls and EET-A reduced it in controls but not in 2K1C rats. Our findings suggest that during the phase of sustained hypertension 2K1C Goldblatt hypertensive rats exhibit increased cardiac tolerance to I/R injury as compared with normotensive controls, and that in this animal model of human renovascular hypertension short-term treatment with EET-A does not induce any antihypertensive and cardioprotective actions.

Inhibition of soluble epoxide hydrolase increases coronary perfusion in mice

Roles of soluble epoxide hydrolase (sEH), the enzyme responsible for hydrolysis of epoxyeicosatrienoic acids (EETs) to their diols (DHETs), in the coronary circulation and cardiac function remain unknown. We tested the hypothesis that compromising EET hydrolysis/degradation, via sEH deficiency, lowers the coronary resistance to promote cardiac perfusion and function. Hearts were isolated from wild type (WT), sEH knockout (KO) mice and WT mice chronically treated with t-TUCB (sEH inhibitor), and perfused with constant flow at different pre-loads. Compared to WT controls, sEH-deficient hearts required significantly greater basal coronary flow to maintain the perfusion pressure at 100 mmHg and exhibited a greater reduction in vascular resistance during tension-induced heart work, implying a better coronary perfusion during cardiac performance. Cardiac contractility, characterized by developed tension in response to changes in preload, was potentially increased in sEH-KO hearts, manifested by an enlarged magnitude at each step-wise increase in end-diastolic to peak-systolic tension. 14,15-EEZE (EET antagonist) prevented the adaptation of coronary circulation in sEH null hearts whereas responses in WT hearts were sensitive to the inhibition of NO. Cardiac expression of EET synthases (CYP2J2/2C29) was comparable in both genotypic mice whereas, levels of 14,15-, 11,12- and 8,9-EETs were significantly higher in sEH-KO hearts, accompanied with lower levels of DHETs. In conclusion, the elevation of cardiac EETs, as a function of sEH deficiency, plays key roles in the adaptation of coronary flow and cardiac function.

Opioid receptors and cardioprotection - 'opioidergic conditioning' of the heart

Ischaemic heart disease (IHD) remains a major cause of morbidity/mortality globally, firmly established in Westernized or 'developed' countries and rising in prevalence in developing nations. Thus, cardioprotective therapies to limit myocardial damage with associated ischaemia-reperfusion (I-R), during infarction or surgical ischaemia, is a very important, although still elusive, clinical goal. The opioid receptor system, encompassing the δ (vas deferens), κ (ketocyclazocine) and μ (morphine) opioid receptors and their endogenous opioid ligands (endorphins, dynorphins, enkephalins), appears as a logical candidate for such exploitation. This regulatory system may orchestrate organism and organ responses to stress, induces mammalian hibernation and associated metabolic protection, triggers powerful adaptive stress resistance in response to ischaemia/hypoxia (preconditioning), and mediates cardiac benefit stemming from physical activity. In addition to direct myocardial actions, central opioid receptor signalling may also enhance the ability of the heart to withstand I-R injury. The δ- and κ-opioid receptors are strongly implicated in cardioprotection across models and species (including anti-infarct and anti-arrhythmic actions), with mixed evidence for μ opioid receptor-dependent protection in animal and human tissues. A small number of clinical trials have provided evidence of cardiac benefit from morphine or remifentanil in cardiopulmonary bypass or coronary angioplasty patients, although further trials of subtype-specific opioid receptor agonists are needed. The precise roles and utility of this GPCR family in healthy and diseased human myocardium, and in mediating central and peripheral survival responses, warrant further investigation, as do the putative negative influences of ageing, IHD co-morbidities, and relevant drugs on opioid receptor signalling and protective responses.

Epoxyeicosatrienoic acids and cardioprotection: the road to translation

Cardiovascular disease, including acute myocardial infarction (AMI), is the leading cause of morbidity and mortality globally, despite well-established treatments. The discovery and development of novel therapeutics that prevent the progression of devastating consequences following AMI are thus important in reducing the global burden of this devastating disease. Scientific evidence for the protective effects of epoxyeicosatrienoic acids (EETs) in the cardiovascular system is rapidly emerging and suggests that promoting the effects of these cytochrome P450-derived epoxyeicosanoids is a potentially viable clinical therapeutic strategy. Through a translational lens, this review will provide insight into the potential clinical utility of this therapeutic strategy for AMI by 1) outlining the known cardioprotective effects of EETs and underlying mechanisms demonstrated in preclinical models of AMI with a particular focus on myocardial ischemia-reperfusion injury, 2) describing studies in human cohorts that demonstrate a relationship between EETs and associated pathways with coronary artery disease risk, and 3) discussing preclinical and clinical areas that require further investigation in order to increase the probability of successfully translating this rapidly emerging body of evidence into a clinically applicable therapeutic strategy for AMI.

Role of caveolin-1 in atrial fibrillation as an anti-fibrotic signaling molecule in human atrial fibroblasts

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia in the general population; yet, the precise mechanisms resulting in AF are not fully understood. Caveolin-1 (Cav-1), the principal structural component of caveolae organelles in cardiac fibroblasts, is involved in several cardiovascular conditions; however, the study on its function in atrium, in particular, in AF, is still lacking. This report examines the hypothesis that Cav-1 confers an anti-AF effect by mediating atrial structural remodeling through its anti-fibrotic action. We evaluated the expression of Cav-1, transforming growth factor-β1 (TGF-β1), and fibrosis in atrial specimens of 13 patients with AF and 10 subjects with sinus rhythm, and found that the expression of Cav-1 was significantly downregulated, whereas TGF-β1 level, collagens I/III contents and atrial fibrosis were markedly increased, in AF. Western blot analysis demonstrated that treatment of human atrial fibroblasts (HAFs) with TGF-β1 resulted in a concentration- and time-dependent repression of Cav-1. Downregulation of Cav-1 with siRNA increased the TGF-β1-induced activation of Smad signal pathway and collagens production in HAFs. Furthermore, incubation of HAFs with the peptides derived from Cav-1 to achieve Cav-1 gain-of-function abolished the TGF-β1-induced production of collagens I/III and decreases of MMP-2/-9 expression. Therefore it was concluded that Cav-1 is an important anti-AF signaling mediator by conferring its anti-fibrotic effects in atrium.