Effect of hypercholesterolaemia on myocardial function, ischaemia-reperfusion injury and cardioprotection by preconditioning, postconditioning and remote conditioning

Cardioprotective potential of oleuropein, hydroxytyrosol, oleocanthal and their combination: Unravelling complementary effects on acute myocardial infarction and metabolic syndrome

Clinical studies have previously established the role of olive products in cardiovascular disease (CVD) prevention, whilst the identification of the responsible constituents for the beneficial effects is still pending. We sought to assess and compare the cardioprotective potential of oleuropein (OL), hydroxytyrosol (HT), oleocanthal (OC) and oleanolic Acid (OA), regarding Ischemia/Reperfusion Injury (IRI) and CVD risk factors alleviation. The scope of the study was to design a potent and safe combinatorial therapy for high-cardiovascular-risk patients on a bench-to-bedside approach. We evaluated the IRI-limiting potential of 6-weeks treatment with OL, HT, OC or OA at nutritional doses, in healthy and metabolic syndrome (MS)-burdened mice. Three combinatorial regimens were designed and the mixture with preponderant benefits (OL-HT-OC, Combo 2), including infarct sparing and antiglycemic potency, compared to the isolated compounds, was further investigated for its anti-atherosclerotic effects. In vivo experiments revealed that the combination regimen of Combo 2 presented the most favorable effects in limiting infarct size and hyperglycemia, which was selected to be further investigated in the clinical setting in Chronic Coronary Artery Syndrome (CCAS) patients. Cardiac function, inflammation markers and oxidative stress were assessed at baseline and after 4 weeks of treatment with the OL-HT-OC supplement in the clinical study. We found that OL, OC and OA significantly reduced infarct size in vivo compared to Controls. OL exhibited antihyperglycemic properties and OA attenuated hypercholesterolemia. OL-HT-OA, OL-HT-OC and OL-HT-OC-OA combination regimens were cardioprotective, whereas only OL-HT-OC mitigated hyperglycemia. Combo 2 cardioprotection was attributed to apoptosis suppression, enhanced antioxidant effects and upregulation of antioxidant enzymes. Additionally, it reduced atherosclerotic plaque extent in vivo. OL-HT-OC supplement ameliorated cardiac, vascular and endothelial function in the small-scale clinical study. Conclusively, OL-HT-OC combination therapy exerts potent cardioprotective, antihyperglycemic and anti-atherosclerotic properties in vivo, with remarkable and clinically translatable cardiovascular benefits in high-risk patients.

Electrocontractile remodeling of isolated cardiomyocytes induced during early-stage hypercholesterolemia

Hypercholesterolemia is one of the most important risk factors for cardiovascular diseases. However, it is mostly associated with vascular dysfunction and atherosclerotic lesions, while evidence of direct effects of hypercholesterolemia on cardiomyocytes and heart function is still incomplete and controversial. In this study, we assessed the direct effects of hypercholesterolemia on heart function and the electro-contractile properties of isolated cardiomyocytes. After 5 weeks, male Swiss mice fed with AIN-93 diet added with 1.25% cholesterol (CHO), developed an increase in total serum cholesterol levels and cardiomyocytes cholesterol content. These changes led to altered electrocardiographic records, with a shortening of the QT interval. Isolated cardiomyocytes displayed a shortening of the action potential duration with increased rate of depolarization, which was explained by increased IK, reduced ICa.L and altered INa voltage-dependent inactivation. Also, reduced diastolic [Ca2+]i was found with preserved adrenergic response and cellular contraction function. However, contraction of isolated hearts is impaired in isolated CHO hearts, before and after ischemia/reperfusion, although CHO heart was less susceptible to arrhythmic contractions. Overall, our results demonstrate that early hypercholesterolemia-driven increase in cellular cholesterol content is associated with direct modulation of the heart and cardiomyocytes' excitability, Ca2+ handling, and contraction.

Endothelial Protection by Sodium-Glucose Cotransporter 2 Inhibitors: A Literature Review of In Vitro and In Vivo Studies

Endothelial dysfunction often precedes the development of cardiovascular diseases, including heart failure. The cardioprotective benefits of sodium-glucose cotransporter 2 inhibitors (SGLT2is) could be explained by their favorable impact on the endothelium. In this review, we summarize the current knowledge on the direct in vitro effects of SGLT2is on endothelial cells, as well as the systematic observations in preclinical models. Four putative mechanisms are explored: oxidative stress, nitric oxide (NO)-mediated pathways, inflammation, and endothelial cell survival and proliferation. Both in vitro and in vivo studies suggest that SGLT2is share a class effect on attenuating reactive oxygen species (ROS) and on enhancing the NO bioavailability by increasing endothelial nitric oxide synthase activity and by reducing NO scavenging by ROS. Moreover, SGLT2is significantly suppress inflammation by preventing endothelial expression of adhesion receptors and pro-inflammatory chemokines in vivo, indicating another class effect for endothelial protection. However, in vitro studies have not consistently shown regulation of adhesion molecule expression by SGLT2is. While SGLT2is improve endothelial cell survival under cell death-inducing stimuli, their impact on angiogenesis remains uncertain. Further experimental studies are required to accurately determine the interplay among these mechanisms in various cardiovascular complications, including heart failure and acute myocardial infarction.

Identification of a mechanism promoting mitochondrial sterol accumulation during myocardial ischemia-reperfusion: role of TSPO and STAR

Hypercholesterolemia is a major risk factor for coronary artery diseases and cardiac ischemic events. Cholesterol per se could also have negative effects on the myocardium, independently from hypercholesterolemia. Previously, we reported that myocardial ischemia-reperfusion induces a deleterious build-up of mitochondrial cholesterol and oxysterols, which is potentiated by hypercholesterolemia and prevented by translocator protein (TSPO) ligands. Here, we studied the mechanism by which sterols accumulate in cardiac mitochondria and promote mitochondrial dysfunction. We performed myocardial ischemia-reperfusion in rats to evaluate mitochondrial function, TSPO, and steroidogenic acute regulatory protein (STAR) levels and the related mitochondrial concentrations of sterols. Rats were treated with the cholesterol synthesis inhibitor pravastatin or the TSPO ligand 4'-chlorodiazepam. We used Tspo deleted rats, which were phenotypically characterized. Inhibition of cholesterol synthesis reduced mitochondrial sterol accumulation and protected mitochondria during myocardial ischemia-reperfusion. We found that cardiac mitochondrial sterol accumulation is the consequence of enhanced influx of cholesterol and not of the inhibition of its mitochondrial metabolism during ischemia-reperfusion. Mitochondrial cholesterol accumulation at reperfusion was related to an increase in mitochondrial STAR but not to changes in TSPO levels. 4'-Chlorodiazepam inhibited this mechanism and prevented mitochondrial sterol accumulation and mitochondrial ischemia-reperfusion injury, underlying the close cooperation between STAR and TSPO. Conversely, Tspo deletion, which did not alter cardiac phenotype, abolished the effects of 4'-chlorodiazepam. This study reveals a novel mitochondrial interaction between TSPO and STAR to promote cholesterol and deleterious sterol mitochondrial accumulation during myocardial ischemia-reperfusion. This interaction regulates mitochondrial homeostasis and plays a key role during mitochondrial injury.

Dyslipidemia and Efficacy of Remote Ischemic Conditioning in Acute Moderate Ischemic Stroke: A Post Hoc Analysis of the RICAMIS Study

BACKGROUND

Ischemic conditioning-induced cardioprotection was attenuated by dyslipidemia in some animal and clinical studies, which is not investigated in patients with stroke. We conducted a post hoc analysis of the RICAMIS (Remote Ischemic Conditioning for Acute Moderate Ischemic Stroke) trial to investigate the association of dyslipidemia on admission with the efficacy of remote ischemic conditioning (RIC).

METHODS AND RESULTS

In this analysis, eligible patients were divided into dyslipidemia and normal-lipid groups according to the levels of 4 blood lipid profiles (total cholesterol, triglycerides, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol), which were further subdivided into RIC and control subgroups. We analyzed the differences in functional outcome between RIC and control subgroups in dyslipidemia and normal-lipid patients, respectively, and the interaction effects of RIC treatment with blood lipid levels were evaluated. Among 1776 patients from intention-to-treat analysis, 1419 patients with data of blood lipid profiles were included in the final analysis. A significantly higher proportion of modified Rankin Scale score 0 to 1 was identified in the RIC versus control subgroup across the normal-total cholesterol group (69.9% versus 63.5%; P=0.04), normal-triglycerides group (68.1% versus 60.5%; P=0.016), high-low-density lipoprotein cholesterol group (65.7% versus 57.7%; P=0.025), and normal-high-density lipoprotein cholesterol group (68.3% versus 60.5%; P=0.005). Similar statistical trends were found in the high-total cholesterol group (62.8% versus 55.5%; P=0.059), high-triglycerides group (67.8% versus 60.1%; P=0.099), normal-low-density lipoprotein cholesterol group (69.8% versus 63.7%; P=0.105), but no statistical significance was found in the low-high-density lipoprotein cholesterol group (63.4% versus 61%; P=0.705). Furthermore, no significant interaction effect of RIC intervention by blood lipid profiles was found. Similar results were obtained for lipids as continuous variables.

CONCLUSIONS

Blood lipids on admission was not associated with the neuroprotective effect of RIC.

Targeting the Translocator Protein (18 kDa) in Cardiac Diseases: State of the Art and Future Opportunities

Mitochondria dysfunctions are typical hallmarks of cardiac disorders (CDs). The multiple tasks of this energy-producing organelle are well documented, but its pathophysiologic involvement in several manifestations of heart diseases, such as altered electromechanical coupling, excitability, and arrhythmias, is still under investigation. The human 18 kDa translocator protein (TSPO) is a protein located on the outer mitochondrial membrane whose expression is altered in different pathological conditions, including CDs, making it an attractive therapeutic and diagnostic target. Currently, only a few TSPO ligands are employed in CDs and cardiac imaging. In this Perspective, we report an overview of the emerging role of TSPO at the heart level, focusing on the recent literature concerning the development of TSPO ligands used for fighting and imaging heart-related disease conditions. Accordingly, targeting TSPO might represent a successful strategy to achieve novel therapeutic and diagnostic strategies to unravel the fundamental mechanisms and to provide solutions to still unanswered questions in CDs.

Role of Erythropoiesis-Stimulating Agents in Cardiovascular Protection in CKD Patients: Reappraisal of Their Impact and Mechanisms

Erythropoiesis-stimulating agents (ESAs) have markedly reduced the need for blood transfusion for renal anemia and are included in standard therapies for patients with chronic kidney disease (CKD). Various protective effects of ESAs on the cardiovascular system have been discovered through basic research, and the effects have received much attention because the rates of cardiovascular events and mortality are high in CKD patients. However, randomized clinical trials did not provide strong evidence that ESAs exert cardioprotection in humans, including CKD patients. It is difficult to assess the cardioprotective effects of ESAs in CKD patients through the clinical data that has been reported to date because the relationship between hemoglobin level rather than ESA dose and cardiovascular event rates was examined in most studies. Interestingly, recent studies using a rat model of CKD showed that the infarct size-limiting effect of an ESA was lost when its dose was increased to a level that normalized blood hemoglobin levels, suggesting that the optimal dose of an ESA for myocardial protection is less than the dose required to normalize hemoglobin levels. Furthermore, animal models of traditional coronary risk factors or comorbidities were resistant to the cardioprotective effects of ESAs because of interruptions in signal-mediated mechanisms downstream of erythropoietin receptors. In this review, we briefly discuss basic and clinical data on the impact of anemia on coronary and systemic circulation, the effects of CKD on the cardiovascular system, and the multiple pharmacological actions of ESAs to examine whether the ESAs that are prescribed for renal anemia exert any cardioprotection in patients with CKD.

Modulation of the nitric oxide/cGMP pathway in cardiac contraction and relaxation: Potential role in heart failure treatment

Evidence exists that heart failure (HF) has an overall impact of 1-2 % in the global population being often associated with comorbidities that contribute to increased disease prevalence, hospitalization, and mortality. Recent advances in pharmacological approaches have significantly improved clinical outcomes for patients with vascular injury and HF. Nevertheless, there remains an unmet need to clarify the crucial role of nitric oxide/cyclic guanosine 3',5'-monophosphate (NO/cGMP) signalling in cardiac contraction and relaxation, to better identify the key mechanisms involved in the pathophysiology of myocardial dysfunction both with reduced (HFrEF) as well as preserved ejection fraction (HFpEF). Indeed, NO signalling plays a crucial role in cardiovascular homeostasis and its dysregulation induces a significant increase in oxidative and nitrosative stress, producing anatomical and physiological cardiac alterations that can lead to heart failure. The present review aims to examine the molecular mechanisms involved in the bioavailability of NO and its modulation of downstream pathways. In particular, we focus on the main therapeutic targets and emphasize the recent evidence of preclinical and clinical studies, describing the different emerging therapeutic strategies developed to counteract NO impaired signalling and cardiovascular disease (CVD) development.

Alleviating Effects of Ovatodiolide and Antcin K Supplements on High-Fat Diet-Induced Cardiovascular Dysfunction in ApoE-Knockout Mice by Attenuating Oxidative Stress

A high-fat diet (HFD) is a major risk factor for cardiovascular diseases. Many pure compounds have been demonstrated to be effective in treating cardiovascular diseases. In this study, we investigated the alleviating effects of oral ovatodiolide and antcin K (OAK) supplements on HFD-induced cardiovascular dysfunction in apolipoprotein E (ApoE)-knockout mice. Cardiovascular dysfunction was induced in ApoE-knockout mice by feeding them an HFD for 12 weeks. The degree of cardiovascular dysfunction was assessed through echocardiography, hematological and biochemical analyses, and immunofluorescence and immunohistochemical staining. The HFD-fed mice exhibited cardiovascular dysfunction-abnormal blood biochemical index. The arterial wall tissue exhibited the marked deposition of lipids, upregulated expression of vascular cell adhesion molecule-1 and CD36 receptors, and downregulated expression of the ABCA1 receptor. Macrophages isolated from the peritoneal cavity of the mice exhibited increased levels of lipid accumulation, reactive oxygen species, and CD11b expression but reduced mitochondrial membrane potential. The expression of superoxide dismutase 2 was downregulated and that of tumor necrosis factor-α was upregulated in the myocardial tissue. Oral OAK supplements twice a day for 12 weeks significantly mitigated HFD-induced cardiovascular dysfunction in the experimental mice. Oral OAK supplements appear to be a promising strategy for treating HFD-induced cardiovascular dysfunction. The underlying mechanisms may involve the reduction of lipid accumulation in the artery and oxidative stress and inflammation in the cardiovascular tissue.

Age-Dependent Effects of Remote Preconditioning in Hypertensive Rat Hearts are Associated With Activation of RISK Signaling

Remote ischemic preconditioning (RIPC) represents one of the forms of innate cardioprotection. While being effective in animal models, its application in humans has not been always beneficial, which might be attributed to the presence of various comorbidities, such as hypertension, or being related to the confounding factors, such as patients' sex and age. RIPC has been shown to mediate its cardioprotective effects through the activation of Reperfusion Injury Salvage Kinase (RISK) pathway in healthy animals, however, scarce evidence supports this effect of RIPC in the hearts of spontaneously hypertensive (SHR) rats, in particular, in relationship with aging. The study aimed to investigate the effectiveness of RIPC in male SHR rats of different age and to evaluate the role of RISK pathway in the effect of RIPC on cardiac ischemic tolerance. RIPC was performed using three cycles of inflation/deflation of the pressure cuff placed on the hind limb of anesthetized rats aged three, five and eight months. Subsequently, hearts were excised, Langendorff-perfused and exposed to 30-min global ischemia and 2-h reperfusion. Infarct-sparing and antiarrhythmic effects of RIPC were observed only in three and five months-old animals but not in eight months-old rats. Beneficial effects of RIPC were associated with increased activity of RISK and decreased apoptotic signaling only in three and five months-old animals. In conclusion, RIPC showed cardioprotective effects in SHR rats that were partially age-dependent and might be attributed to the differences in the activation of RISK pathway and various aspects of ischemia/reperfusion injury in aging animals.

Interaction of Cardiovascular Nonmodifiable Risk Factors, Comorbidities and Comedications With Ischemia/Reperfusion Injury and Cardioprotection by Pharmacological Treatments and Ischemic Conditioning

Preconditioning, postconditioning, and remote conditioning of the myocardium enhance the ability of the heart to withstand a prolonged ischemia/reperfusion insult and the potential to provide novel therapeutic paradigms for cardioprotection. While many signaling pathways leading to endogenous cardioprotection have been elucidated in experimental studies over the past 30 years, no cardioprotective drug is on the market yet for that indication. One likely major reason for this failure to translate cardioprotection into patient benefit is the lack of rigorous and systematic preclinical evaluation of promising cardioprotective therapies prior to their clinical evaluation, since ischemic heart disease in humans is a complex disorder caused by or associated with cardiovascular risk factors and comorbidities. These risk factors and comorbidities induce fundamental alterations in cellular signaling cascades that affect the development of ischemia/reperfusion injury and responses to cardioprotective interventions. Moreover, some of the medications used to treat these comorbidities may impact on cardioprotection by again modifying cellular signaling pathways. The aim of this article is to review the recent evidence that cardiovascular risk factors as well as comorbidities and their medications may modify the response to cardioprotective interventions. We emphasize the critical need for taking into account the presence of cardiovascular risk factors as well as comorbidities and their concomitant medications when designing preclinical studies for the identification and validation of cardioprotective drug targets and clinical studies. This will hopefully maximize the success rate of developing rational approaches to effective cardioprotective therapies for the majority of patients with multiple comorbidities. SIGNIFICANCE STATEMENT: Ischemic heart disease is a major cause of mortality; however, there are still no cardioprotective drugs on the market. Most studies on cardioprotection have been undertaken in animal models of ischemia/reperfusion in the absence of comorbidities; however, ischemic heart disease develops with other systemic disorders (e.g., hypertension, hyperlipidemia, diabetes, atherosclerosis). Here we focus on the preclinical and clinical evidence showing how these comorbidities and their routine medications affect ischemia/reperfusion injury and interfere with cardioprotective strategies.

Sericin-mediated improvement of dysmorphic cardiac mitochondria from hypercholesterolaemia is associated with maintaining mitochondrial dynamics, energy production, and mitochondrial structure

CONTEXT

Sericin is a component protein in the silkworm cocoon [Bombyx mori Linnaeus (Bombycidae)] that improves dysmorphic cardiac mitochondria under hypercholesterolemic conditions. This is the first study to explore cardiac mitochondrial proteins associated with sericin treatment.

OBJECTIVE

To investigate the mechanism of action of sericin in cardiac mitochondria under hypercholesterolaemia.

MATERIALS AND METHODS

Hypercholesterolaemia was induced in Wistar rats by feeding them 6% cholesterol-containing chow for 6 weeks. The hypercholesterolemic rats were separated into 2 groups (n = 6 for each): the sericin-treated (1,000 mg/kg daily) and nontreated groups. The treatment conditions were maintained for 4 weeks prior to cardiac mitochondria isolation. The mitochondrial structure was evaluated by immunolabeling electron microscopy, and differential mitochondrial protein expression was determined and quantitated by two-dimensional gel electrophoresis coupled with mass spectrometry.

RESULTS

A 32.22 ± 2.9% increase in the percent striated area of cardiac muscle was observed in sericin-treated hypercholesterolemic rats compared to the nontreatment group (4.18 ± 1.11%). Alterations in mitochondrial proteins, including upregulation of optic atrophy 1 (OPA1) and reduction of NADH-ubiquinone oxidoreductase 75 kDa subunit (NDUFS1) expression, are correlated with a reduction in mitochondrial apoptosis under sericin treatment. Differential proteomic observation also revealed that sericin may improve mitochondrial energy production by upregulating acetyl-CoA acetyltransferase (ACAT1) and NADH dehydrogenase 1α subcomplex subunit 10 (NDUFA10) expression.

DISCUSSION AND CONCLUSIONS

Sericin treatment could improve the dysmorphic mitochondrial structure, metabolism, and energy production of cardiac mitochondria under hypercholesterolaemia. These results suggest that sericin may be an alternative treatment molecule that is related to cardiac mitochondrial abnormalities.

The protective effect of remote ischemic conditioning is lost in patients with hypercholesterolemia

Remote ischemic conditioning (RIC), brief repetitive cycles of ischemia and reperfusion in remote tissues, is known to induce robust protection against myocardial ischemia-reperfusion (I/R) injury in preclinical studies. However, translation of the beneficial effects to the clinical setting has been challenging. A possibility is that comorbidities, including hypercholesterolemia, interfere with the protective mechanisms of RIC. The aim of this study was to test if hypercholesterolemia attenuates the efficacy of RIC in patients with hypercholesterolemia. Patients with familial hypercholesterolemia (FH) with high (≥5.5 mmol/L) low-density lipoprotein cholesterol (LDL-C), FH with low (≤2.5 mmol/L) and healthy control subjects (n = 12 in each group) were included. Flow-mediated vasodilatation (FMD) of the brachial artery was evaluated, before and after a 20-min period of forearm ischemia and 20 min reperfusion (I/R) as a measure of endothelial function. Study subjects were randomized to a RIC protocol consisting of four cycles of 5 min of leg ischemia or sham using a crossover design. Forearm I/R induced significant reduction in FMD in all three groups during the sham procedure. RIC protected from endothelial dysfunction induced by forearm ischemia-reperfusion in healthy controls [FMD baseline 2.8 ± 2.3 vs. FMD after I/R + RIC 4.5 ± 4.0%; means (SD)] and in patients with FH with low LDL-C (4.5 ± 3.5 vs. 4.4 ± 4.2%). By contrast, RIC fails to protect against I/R-induced endothelial dysfunction in patients with FH and high LDL-C (3.9 ± 3.0 vs. 1.1 ± 1.5%; P < 0.01). These findings provide the first evidence in humans that the protective effect of RIC is lost in patients with elevated cholesterol.NEW & NOTEWORTHY We investigated the impact of hypercholesterolemia on the protective effect of RIC on ischemia-reperfusion injury in a well-characterized patient population with isolated hypercholesterolemia. The results show that the protective effect of RIC is absent in patients with hypercholesterolemia but is apparent in patients with hypercholesterolemic following treatment with lipid-lowering drugs. The results are of importance for the understanding of how comorbidities affect the therapeutic potential of RIC.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Proprotein Convertase Subtilisin Kexin Type 9 (PCSK9) Deletion but Not Inhibition of Extracellular PCSK9 Reduces Infarct Sizes Ex Vivo but Not In Vivo

Hypoxia upregulates PCSK9 expression in the heart, and PCSK9 affects the function of myocytes. This study aimed to investigate the impact of PCSK9 on reperfusion injury in rats and mice fed normal or high-fat diets. Either the genetic knockout of PCSK9 (mice) or the antagonism of circulating PCSK9 via Pep2-8 (mice and rats) was used. Isolated perfused hearts were exposed to 45 min of ischemia followed by 120 min of reperfusion. In vivo, mice were fed normal or high-fat diets (2% cholesterol) for eight weeks prior to coronary artery occlusion (45 min of ischemia) and reperfusion (120 min). Ischemia/reperfusion upregulates PCSK9 expression (rats and mice) and releases it into the perfusate. The inhibition of extracellular PCSK9 does not affect infarct sizes or functional recovery. However, genetic deletion largely reduces infarct size and improves post-ischemic recovery in mice ex vivo but not in vivo. A high-fat diet reduced the survival rate during ischemia and reperfusion, but in a PCSK9-independent manner that was associated with increased plasma matrix metalloproteinase (MMP)9 activity. PCSK9 deletion, but not the inhibition of extracellular PCSK9, reduces infarct sizes in ex vivo hearts, but this effect is overridden in vivo by factors such as MMP9.

Hypercholesterolemia attenuates cardioprotection of ischemic preconditioning and postconditioning with α7 nicotinic acetylcholine receptor agonist by enhancing inflammation and inhibiting the PI3K/Akt/eNOS pathway

The present study aimed to evaluate the effects of hypercholesterolemia on cardioprotection of ischemic preconditioning and α7 nicotinic acetylcholine receptor (α7nAChR) agonist postconditioning and explore the potential mechanisms that hypercholesterolemia affected their cardioprotection. Hypercholesterolemic and normal rats were divided into the four groups that received the following treatments: i) Hypercholesterolemic control and normal control groups; ii) hypercholesterolemic ischemia/reperfusion (HI) and normal ischemia/reperfusion (NI) groups; iii) hypercholesterolemic ischemic preconditioning (HIPC) and normal ischemic preconditioning (NIPC) groups; and iv) hypercholesterolemic PNU282987 postconditioning (HPNU) and normal PNU282987 postconditioning (NPNU) groups. Serum lactate dehydrogenase (LDH), creatine kinase isoenzyme MB (CK-MB), cardiac troponin I (cTnI), tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) levels after ischemia/reperfusion were assayed. Furthermore, infarct size and expression levels of Akt, phosphorylated (p)-Akt and endothelial nitric oxide synthase (eNOS) in ischemic myocardium were assessed. Compared with the NI group, serum LDH, CK-MB, cTnI, TNF-α and IL-6 levels and infarct size were significantly decreased, and myocardial p-Akt/Akt and eNOS/GAPDH ratios were significantly increased in the NIPC and NPNU groups. Compared with the HI group, serum CK-MB, cTnI, TNF-α and IL-6 levels and infarct size were significantly decreased in the HIPC group; however, myocardial p-Akt/Akt and eNOS/GAPDH ratios did not significantly change in the HIPC group. Furthermore, there were no significant difference between the HI and HPNU groups in serum LDH, CK-MB, cTnI, TNF-α and IL-6 levels, infarct size, myocardial p-Akt/Akt and eNOS/GAPDH ratios. In conclusion, hypercholesterolemia could aggravate myocardial ischemia/reperfusion injury, attenuate cardioprotection of ischemic preconditioning and eliminate cardioprotection from α7nAChR agonist postconditioning by enhancing inflammation and inhibiting PI3K/Akt/eNOS pathway.

Finding inhibitors for PCSK9 using computational methods

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the key targets for atherosclerosis drug development as its binding with low-density lipoprotein receptor leads to atherosclerosis. The protein-ligand interaction helps to understand the actual mechanism for the pharmacological action. This research aims to discover the best inhibitory candidates targeting PCSK9. To start with, reported ACE inhibitors were incorporated into pharmacophore designing using PharmaGist to produce pharmacophore models. Selected models were later screened against the ZINC database using ZINCPHARMER to define potential drug candidates that were docked with the target protein to understand their interactions. Molecular docking revealed the top 10 drug candidates against PCSK9, with binding energies ranging from -9.8 kcal·mol^-1 to -8.2 kcal·mol^-1, which were analyzed for their pharmacokinetic properties and oral bioavailability. Some compounds were identified as plant-derived compounds like (S)-canadine, hesperetin or labetalol (an antihypertensive drug). Molecular dynamics results showed that these substances formed stable protein-ligand complexes. (S)-canadine-PCSK9 complex was the most stable with the lowest RMSD. It was concluded that (S)-canadine may act as a potential inhibitor against atherosclerosis for the development of new PCSK9 inhibitory drugs in future in vitro research.

Atorvastatin reverses high cholesterol-induced cardiac remodelling and regulates mitochondrial quality-control in a cholesterol-independent manner: An experimental study

Mitochondria are key regulators of cell fate, maintaining self-stability by a fine-tuned quality-control network including mitophagy, biogenesis, fission and fusion processes. Myocardial mitochondria can be impaired by hypercholesterolemia. Statins, such as atorvastatin, are considered the cornerstone in the management of hypercholesterolaemia primarily due to their marked cholesterol-lowering ability. The direct effect of atorvastatin on myocardial mitochondria remains unclear. We aimed to explore whether atorvastatin could attenuate myocardial mitochondrial defects induced by high cholesterol, and whether cycloastragenol, a potent telomerase activator, could be used as a potential complementary bioactive compound for obesity and hypercholesterolaemia treatment. We found that atorvastatin at a low dose (3 mg/kg) did not reduce elevated serum cholesterol, but reversed cardiac remodelling and dysfunction in C57BL/6J mice fed with high-fat diet (HFD). Atorvastatin reversed the upregulated mitophagy, mitochondrial fission and fusion, accompanied by mitochondrial biogenesis activation in HFD-fed mice hearts. Mitochondrial structural impairments were attenuated by atorvastatin in HFD-fed mice and oxidized low-density lipoprotein (ox-LDL) exposed HL-1 cardiomyocytes. The depolarized mitochondrial membrane potential and increased mitochondrial oxygen consumption rates in ox-LDL exposed HL-1 cells were recovered by atorvastatin. Furthermore, atorvastatin co-treated with cycloastragenol had better effects on reducing body weight, improving cardiac remodelling and dysfunction, and protecting mitochondria in high cholesterol. Conclusively, low-dose atorvastatin exhibited a cholesterol-independent cardioprotective effect through improving the mitochondrial quality-control network and repairing mitochondrial ultrastructure in high cholesterol. Atorvastatin plus cycloastragenol supplement therapy has a better effect on treating obesity and hypercholesterolaemia.

Thiol-based redox-active proteins as cardioprotective therapeutic agents in cardiovascular diseases

Thiol-based redox compounds, namely thioredoxins (Trxs), glutaredoxins (Grxs) and peroxiredoxins (Prxs), stand as a pivotal group of proteins involved in antioxidant processes and redox signaling. Glutaredoxins (Grxs) are considered as one of the major families of proteins involved in redox regulation by removal of S-glutathionylation and thereby reactivation of other enzymes with thiol-dependent activity. Grxs are also coupled to Trxs and Prxs recycling and thereby indirectly contribute to reactive oxygen species (ROS) detoxification. Peroxiredoxins (Prxs) are a ubiquitous family of peroxidases, which play an essential role in the detoxification of hydrogen peroxide, aliphatic and aromatic hydroperoxides, and peroxynitrite. The Trxs, Grxs and Prxs systems, which reversibly induce thiol modifications, regulate redox signaling involved in various biological events in the cardiovascular system. This review focuses on the current knowledge of the role of Trxs, Grxs and Prxs on cardiovascular pathologies and especially in cardiac hypertrophy, ischemia/reperfusion (I/R) injury and heart failure as well as in the presence of cardiovascular risk factors, such as hypertension, hyperlipidemia, hyperglycemia and metabolic syndrome. Further studies on the roles of thiol-dependent redox systems in the cardiovascular system will support the development of novel protective and therapeutic strategies against cardiovascular diseases.

Cyclic GMP modulating drugs in cardiovascular diseases: Mechanism-based network pharmacology

Mechanism-based therapy centred on the molecular understanding of disease-causing pathways in a given patient is still the exception rather than the rule in medicine, even in cardiology. However, recent successful drug developments centred around the second messenger cyclic guanosine-3′-5′-monophosphate (cGMP), which is regulating a number of cardiovascular disease modulating pathways, are about to provide novel targets for such a personalized cardiovascular therapy. Whether cGMP breakdown is inhibited or cGMP synthesis is stimulated via guanylyl cyclases or their upstream regulators in different cardiovascular disease phenotypes, the outcomes seem to be so far uniformly protective. Thus, a network of cGMP-modulating drugs has evolved that act in a mechanism-based, possibly causal manner in a number of cardiac conditions. What remains a challenge is the detection of cGMPopathy endotypes amongst cardiovascular disease phenotypes. Here, we review the growing clinical relevance of cGMP and provide a glimpse into the future on how drugs interfering with this pathway may change how we treat and diagnose cardiovascular diseases altogether.

Inclisiran-Silencing the Cholesterol, Speaking up the Prognosis

The reduction of circulating low-density lipoprotein-cholesterol (LDL-C) is a primary target in cardiovascular risk reduction due to its well-established benefits in terms of decreased mortality. Despite the use of statin therapy, 10%-20% of high- and very-high-risk patients do not reach their LDL-C targets. There is an urgent need for improved strategies to manage dyslipidemia, especially among patients with homozygous familial hypercholesterolemia, but also in patients with established cardiovascular disease who fail to achieve LDL goals despite combined statin, ezetimibe, and PCSK9 inhibitor (PCSK9i) therapy. Inclisiran is a disruptive, first-in-class small interfering RNA (siRNA)-based therapeutic developed for the treatment of hypercholesterolemia that inhibits proprotein convertase subtilisin-kexin type 9 (PCSK9) synthesis, thereby upregulating the number of LDL receptors on the hepatocytes, thus lowering the plasma LDL-C concentration. Inclisiran decreases the LDL-C levels by over 50% with one dose every 6 months, making it a simple and well-tolerated treatment strategy. In this review, we summarize the general information regarding (i) the role of LDL-C in atherosclerotic cardiovascular disease, (ii) data regarding the role of PCSK9 in cholesterol metabolism, (iii) pleiotropic effects of PCSK9, and (iv) the effects of PCSK9 silencing. In addition, we focus on inclisiran, in terms of its (i) mechanism of action, (ii) biological efficacy and safety, (iii) results from the ORION trials, (iv) benefits of its combination with statins, and (v) its potential future role in atherosclerotic cardiovascular disease.

Bladder Hyperactivity Induced by Oxidative Stress and Bladder Ischemia: A Review of Treatment Strategies with Antioxidants

Overactive bladder (OAB) syndrome, including frequency, urgency, nocturia and urgency incontinence, has a significantly negative impact on the quality-of-life scale (QoL) and can cause sufferer withdrawal from social activities. The occurrence of OAB can result from an imbalance between the production of pro-oxidants, such as free radicals and reactive species, and their elimination through protective mechanisms of antioxidant-induced oxidative stress. Several animal models, such as bladder ischemia/reperfusion (I/R), partial bladder outlet obstruction (PBOO) and ovarian hormone deficiency (OHD), have suggested that cyclic I/R during the micturition cycle induces oxidative stress, leading to bladder denervation, bladder afferent pathway sensitization and overexpression of bladder-damaging molecules, and finally resulting in bladder hyperactivity. Based on the results of previous animal experiments, the present review specifically focuses on four issues: (1) oxidative stress and antioxidant defense system; (2) oxidative stress in OAB and biomarkers of OAB; (3) OAB animal model; (4) potential nature/plant antioxidant treatment strategies for urinary dysfunction with OAB. Moreover, we organized the relationships between urinary dysfunction and oxidative stress biomarkers in urine, blood and bladder tissue. Reviewed information also revealed the summary of research findings for the effects of various antioxidants for treatment strategies for OAB.

Natural and synthetic antioxidants targeting cardiac oxidative stress and redox signaling in cardiometabolic diseases

Cardiometabolic diseases (CMDs) are metabolic diseases (e.g., obesity, diabetes, atherosclerosis, rare genetic metabolic diseases, etc.) associated with cardiac pathologies. Pathophysiology of most CMDs involves increased production of reactive oxygen species and impaired antioxidant defense systems, resulting in cardiac oxidative stress (OxS). To alleviate OxS, various antioxidants have been investigated in several diseases with conflicting results. Here we review the effect of CMDs on cardiac redox homeostasis, the role of OxS in cardiac pathologies, as well as experimental and clinical data on the therapeutic potential of natural antioxidants (including resveratrol, quercetin, curcumin, vitamins A, C, and E, coenzyme Q10, etc.), synthetic antioxidants (including N-acetylcysteine, SOD mimetics, mitoTEMPO, SkQ1, etc.), and promoters of antioxidant enzymes in CMDs. As no antioxidant indicated for the prevention and/or treatment of CMDs has reached the market despite the large number of preclinical and clinical studies, a sizeable translational gap is evident in this field. Thus, we also highlight potential underlying factors that may contribute to the failure of translation of antioxidant therapies in CMDs.

Influence of cardiometabolic comorbidities on myocardial function, infarction, and cardioprotection: Role of cardiac redox signaling

The morbidity and mortality from cardiovascular diseases (CVD) remain high. Metabolic diseases such as obesity, hyperlipidemia, diabetes mellitus (DM), non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) as well as hypertension are the most common comorbidities in patients with CVD. These comorbidities result in increased myocardial oxidative stress, mainly from increased activity of nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, mitochondria as well as downregulation of antioxidant defense systems. Oxidative and nitrosative stress play an important role in ischemia/reperfusion injury and may account for increased susceptibility of the myocardium to infarction and myocardial dysfunction in the presence of the comorbidities. Thus, while early reperfusion represents the most favorable therapeutic strategy to prevent ischemia/reperfusion injury, redox therapeutic strategies may provide additive benefits, especially in patients with heart failure. While oxidative and nitrosative stress are harmful, controlled release of reactive oxygen species is however important for cardioprotective signaling. In this review we summarize the current data on the effect of hypertension and major cardiometabolic comorbidities such as obesity, hyperlipidemia, DM, NAFLD/NASH on cardiac redox homeostasis as well as on ischemia/reperfusion injury and cardioprotection. We also review and discuss the therapeutic interventions that may restore the redox imbalance in the diseased myocardium in the presence of these comorbidities.

Co-morbidities and co-medications as confounders of cardioprotection-Does it matter in the clinical setting?

The translation of cardioprotection from robust experimental evidence to beneficial clinical outcome for patients suffering acute myocardial infarction or undergoing cardiovascular surgery has been largely disappointing. The present review attempts to critically analyse the evidence for confounders of cardioprotection in patients with acute myocardial infarction and in patients undergoing cardiovascular surgery. One reason that has been proposed to be responsible for such lack of translation is the confounding of cardioprotection by co-morbidities and co-medications. Whereas there is solid experimental evidence for such confounding of cardioprotection by single co-morbidities and co-medications, the clinical evidence from retrospective analyses of the limited number of clinical data is less robust. The best evidence for interference of co-medications is that for platelet inhibitors to recruit cardioprotection per se and thus limit the potential for further protection from myocardial infarction and for propofol anaesthesia to negate the protection from remote ischaemic conditioning in cardiovascular surgery. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

PCSK9 in Myocardial Infarction and Cardioprotection: Importance of Lipid Metabolism and Inflammation

Extensive evidence from epidemiologic, genetic, and clinical intervention studies has indisputably shown that elevated low-density lipoprotein cholesterol (LDL-C) concentrations play a central role in the pathophysiology of atherosclerotic cardiovascular disease. Apart from LDL-C, also triglycerides independently modulate cardiovascular risk. Reduction of proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a therapeutic target for reducing plasma LDL-C, but it is also associated with a reduction in triglyceride levels potentially through modulation of the expression of free fatty acid transporters. Preclinical data indicate that PCSK9 is up-regulated in the ischaemic heart and decreasing PCSK9 expression impacts on infarct size, post infarct inflammation and remodeling as well as cardiac dysfunction following ischaemia/reperfusion. Clinical data support that notion in that PCSK9 inhibition is associated with reductions in the incidence of myocardial infarction, stroke, and coronary revascularization and an improvement of endothelial function in subjects with increased cardiovascular risk. The aim of the current review is to summarize the current knowledge on the importance of free fatty acid metabolism on myocardial ischaemia/reperfusion injury and to provide an update on recent evidence on the role of hyperlipidemia and PCSK9 in myocardial infarction and cardioprotection.

Cardioprotective Effect of Novel Matrix Metalloproteinase Inhibitors

Background: We recently developed novel matrix metalloproteinase-2 (MMP-2) inhibitor small molecules for cardioprotection against ischemia/reperfusion injury and validated their efficacy in ischemia/reperfusion injury in cardiac myocytes. The aim of the present study was to test our lead compounds for cardioprotection in vivo in a rat model of acute myocardial infarction (AMI) in the presence or absence of hypercholesterolemia, one of the major comorbidities affecting cardioprotection. Methods: Normocholesterolemic adult male Wistar rats were subjected to 30 min of coronary occlusion followed by 120 min of reperfusion to induce AMI. MMP inhibitors (MMPI)-1154 and -1260 at 0.3, 1, and 3 µmol/kg, MMPI-1248 at 1, 3, and 10 µmol/kg were administered at the 25th min of ischemia intravenously. In separate groups, hypercholesterolemia was induced by a 12-week diet (2% cholesterol, 0.25% cholic acid), then the rats were subjected to the same AMI protocol and single doses of the MMPIs that showed the most efficacy in normocholesterolemic animals were tested in the hypercholesterolemic animals. Infarct size/area at risk was assessed at the end of reperfusion in all groups by standard Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining, and myocardial microvascular obstruction (MVO) was determined by thioflavine-S staining. Results: MMPI-1154 at 1 µmol/kg, MMPI-1260 at 3 µmol/kg and ischemic preconditioning (IPC) as the positive control reduced infarct size significantly; however, this effect was not seen in hypercholesterolemic animals. MVO in hypercholesterolemic animals decreased by IPC only. Conclusions: This is the first demonstration that MMPI-1154 and MMPI-1260 showed a dose-dependent infarct size reduction in an in vivo rat AMI model; however, single doses that showed the most efficacy in normocholesterolemic animals were abolished by hypercholesterolemia. The further development of these promising cardioprotective MMPIs should be continued with different dose ranges in the study of hypercholesterolemia and other comorbidities.

Pharmacological Inhibition of PTEN Restores Remote Ischemic Postconditioning Cardioprotection in Hypercholesterolemic Mice: Potential Role of PTEN/AKT/GSK3β SIGNALS

Although remote ischemic postconditioning (RIPC) was shown to confer cardioprotection against myocardial ischemia/reperfusion (I/R) injury in normal animals, whether RIPC-induced cardioprotection is altered in the presence of hypercholesterolemia, a comorbidity with acute myocardial infarction (AMI) patients has yet to be determined. Normal or 2% cholesterol chow was fed to male C57BL/6J mice for 12 weeks to induce hypercholesterolemia, then normal or hypercholesterolemic murine hearts were exposed to AMI by coronary artery ligation. RIPC was induced by four episodes of 5 min femoral artery occlusion followed by 5 min reperfusion immediately after myocardial reperfusion in mice. Following I/R, RIPC significantly attenuated postischemic infarct size, hindered cardiomyocyte apoptosis, improved cardiac systolic function, decreased phosphatase and tensin homolog deleted on chromosome ten (PTEN) expression, and further increased Akt and GSK-3β phosphorylation in non-hypercholesterolemic, but not in hypercholesterolemic mice. Application of the PTEN inhibitor bisperoxovanadium (BpV) (1.0 mg/kg) reduced postischemic infarct size, attenuated cardiomyocyte apoptosis, and improved cardiac dysfunction in normal, but not in hypercholesterolemic mice. Further, increased dose of BpV (2 mg/kg or 10 mg/kg) failed to rescue the detrimental effects of hypercholesterolemia on I/R in mice following I/R. Especially important, we demonstrated that the combination BpV and RIPC exerted marked cardioprotective effects both in normal and hypercholesterolemic mice with I/R, indicating that PTEN inhibition restores RIPC-elicited myocardial protection in the presence of hypercholesterolemia. Our results demonstrated that hypercholesterolemia attenuated RIPC-induced cardioprotection against I/R injury by alteration of PTEN/Akt/GSK3β signals, and inhibition of PTEN rescued RIPC-induced cardioprotection in the presence of hypercholesterolemia.

Effect of down-regulated miR-15b-5p expression on arrhythmia and myocardial apoptosis after myocardial ischemia reperfusion injury in mice

In this study, the regulation of miR-15b-5p on myocardial ischemia reperfusion (I/R) injury-induced arrhythmia and myocardial apoptosis was investigated in mice. We observed the change in miR-15b-5p expression after mice suffered from myocardial I/R injury and the change in myocardial injury, infarct size, apoptosis, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), superoxide dismutase (SOD) and malondialdehyde (MDA) after down-regulation of miR-15b-5p expression. The negative regulation of miR-15b-5p to KCNJ2 as well as whether cardioprotective effect formed by miR-15b-5p down-regulation relied on the increase of KNCJ2 expression were measured by dual-luciferase reporter assay system. miR-15b-5p expression increased and KCNJ2 mRNA and protein expressions decreased after myocardial ischemia reperfusion (all P < 0.05). miR-15b-5p negatively regulated KCNJ2 in a targeted way. Down-regulating miR-15b-5p expression or increasing KCNJ2 expression significantly decreased the incidence of arrhythmia, infarct size and apoptosis after myocardial I/R and lowered MDA content in the myocardial tissue as well as IL-6 and TNF-α content in the blood (all P < 0.05). KCNJ2 gene knockout reversed the above cardioprotective effect formed by miR-15b-5p down-regulation (P < 0.05). Down-regulating miR-15b-5p expression or up-regulating KCNJ2 expression improves arrhythmia after mice suffered from myocardial I/R injury and inhibits myocardial apoptosis.

The role of mitochondrial reactive oxygen species, NO and H2 S in ischaemia/reperfusion injury and cardioprotection

Redox signalling in mitochondria plays an important role in myocardial ischaemia/reperfusion (I/R) injury and in cardioprotection. Reactive oxygen and nitrogen species (ROS/RNS) modify cellular structures and functions by means of covalent changes in proteins including among others S‐nitros(yl)ation by nitric oxide (NO) and its derivatives, and S‐sulphydration by hydrogen sulphide (H₂S). Many enzymes are involved in the mitochondrial formation and handling of ROS, NO and H₂S under physiological and pathological conditions. In particular, the balance between formation and removal of reactive species is impaired during I/R favouring their accumulation. Therefore, various interventions aimed at decreasing mitochondrial ROS accumulation have been developed and have shown cardioprotective effects in experimental settings. However, ROS, NO and H₂S play also a role in endogenous cardioprotection, as in the case of ischaemic pre‐conditioning, so that preventing their increase might hamper self‐defence mechanisms. The aim of the present review was to provide a critical analysis of formation and role of reactive species, NO and H₂S in mitochondria, with a special emphasis on mechanisms of injury and protection that determine the fate of hearts subjected to I/R. The elucidation of the signalling pathways of ROS, NO and H₂S is likely to reveal novel molecular targets for cardioprotection that could be modulated by pharmacological agents to prevent I/R injury.

Mitochondrial Protection by PARP Inhibition

Inhibitors of the nuclear DNA damage sensor and signalling enzyme poly(ADP-ribose) polymerase (PARP) have recently been introduced in the therapy of cancers deficient in double-strand DNA break repair systems, and ongoing clinical trials aim to extend their use from other forms of cancer non-responsive to conventional treatments. Additionally, PARP inhibitors were suggested to be repurposed for oxidative stress-associated non-oncological diseases resulting in a devastating outcome, or requiring acute treatment. Their well-documented mitochondria- and cytoprotective effects form the basis of PARP inhibitors’ therapeutic use for non-oncological diseases, yet can limit their efficacy in the treatment of cancers. A better understanding of the processes involved in their protective effects may improve the PARP inhibitors’ therapeutic potential in the non-oncological indications. To this end, we endeavoured to summarise the basic features regarding mitochondrial structure and function, review the major PARP activation-induced cellular processes leading to mitochondrial damage, and discuss the role of PARP inhibition-mediated mitochondrial protection in several oxidative stress-associated diseases.

Pachymic acid protects against cerebral ischemia/reperfusion injury by the PI3K/Akt signaling pathway

Pachymic acid (PA) from medicinal fungus Poria cocos has a variety of pharmacological potentials. However, there are no reports of the effects of PA on cerebral ischemia/reperfusion (I/R) injury. The purpose of this study was to investigate the mechanisms of PA on cerebral I/R injury in rats. The effects of PA on cerebral infarction size, brain water content, neurological symptoms and cerebral blood flow were evaluated. Nissl staining was used to observe the damage of ischemic brain neurons after I/R in rats. Apoptosis of ischemic brain neurons after I/R was observed by TUNEL staining. The effect of PA on the expression of some components of PI3K/Akt was detected by Western blotting. PA significantly increased cerebral blood flow after I/R in rats, reduced infarct volume and brain water content, and downgrade neurological function scores, significantly reduced neuronal damage after I/R in rats, and significantly decreased neuronal apoptosis. The effect of PA on rat I/R can be eliminated by LY294002. In addition, PA significantly up-regulated the protein expression of p-PTEN (Ser380), p-PDK1 (Ser241), p-Akt (Ser473), pc-Raf (Ser259) and p-BAD (Ser136), and down-regulated Cleaved caspase protein expression. LY294002 can reverse the effect of PA on the expression of PI3K / Akt signaling pathway related protein in rats after I/R. PA had obviously neuroprotective effects on brain I/R injury and neuronal apoptosis, and its mechanism may be related to activation of PI3K / Akt signaling pathway.

Translational issues for mitoprotective agents as adjunct to reperfusion therapy in patients with ST-segment elevation myocardial infarction

Pre‐clinical studies have indicated that mitoprotective drugs may add cardioprotection beyond rapid revascularization, antiplatelet therapy and risk modification. We review the clinical efficacy of mitoprotective drugs that have progressed to clinical testing comprising cyclosporine A, KAI‐9803, MTP131 and TRO 40303. Whereas cyclosporine may reduce infarct size in patients undergoing primary angioplasty as evaluated by release of myocardial ischaemic biomarkers and infarct size imaging, the other drugs were not capable of demonstrating this effect in the clinical setting. The absent effect leaves the role of the mitochondrial permeability transition pore for reperfusion injury in humans unanswered and indicates that targeting one single mechanism to provide mitoprotection may not be efficient. Moreover, the lack of effect may relate to favourable outcome with current optimal therapy, but conditions such as age, sex, diabetes, dyslipidaemia and concurrent medications may also alter mitochondrial function. However, as long as the molecular structure of the pore remains unknown and specific inhibitors of its opening are lacking, the mitochondrial permeability transition pore remains a target for alleviation of reperfusion injury. Nevertheless, taking conditions such as ageing, sex, comorbidities and co‐medication into account may be of paramount importance during the design of pre‐clinical and clinical studies testing mitoprotective drugs.

Potential Role of Tocotrienols on Non-Communicable Diseases: A Review of Current Evidence

Tocotrienol (T3) is a subfamily of vitamin E known for its wide array of medicinal properties. This review aimed to summarize the health benefits of T3, particularly in prevention or treatment of non-communicable diseases (NCDs), including cardiovascular, musculoskeletal, metabolic, gastric, and skin disorders, as well as cancers. Studies showed that T3 could prevent various NCDs, by suppressing 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) in the mevalonate pathway, inflammatory response, oxidative stress, and alternating hormones. The efficacy of T3 in preventing/treating these NCDs is similar or greater compared to tocopherol (TF). TF may lower the efficacy of T3 because the efficacy of the combination of TF and T3 was lower than T3 alone in some studies. Data investigating the effects of T3 on osteoporosis, arthritis, and peptic ulcers in human are limited. The positive outcomes of T3 treatment obtained from the preclinical studies warrant further validation from clinical trials.

Hyperlipidaemia and cardioprotection: Animal models for translational studies

Hyperlipidaemia is a well-established risk factor for cardiovascular diseases and therefore, many animal model have been developed to mimic the human abnormal elevation of blood lipid levels. In parallel, extensive research for the alleviation of ischaemia/reperfusion injury has revealed that hyperlipidaemia is a major co-morbidity that attenuates the cardioprotective effect of conditioning strategies (preconditioning, postconditioning and remote conditioning) and that of pharmacological interventions by interfering with cardioprotective signalling pathways. In the present review article, we summarize the existing data on animal models of hypercholesterolaemia (total, low density and HDL abnormalities) and hypertriglyceridaemia used in ischaemia/reperfusion injury and protection from it. We also provide recommendations on preclinical animal models to be used for translations of the cardioprotective strategies into clinical practice. LINKED ARTICLES: This article is part of a themed issue on Risk factors, comorbidities, and comedications in cardioprotection. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.23/issuetoc.

A Comorbidity Model of Myocardial Ischemia/Reperfusion Injury and Hypercholesterolemia in Rat Cardiac Myocyte Cultures

Introduction

The use of comorbidity models is crucial in cardioprotective drug development. Hypercholesterolemia causes endothelial and myocardial dysfunction, as well as aggravates ischemia/reperfusion (I/R)-induced myocardial injury. Endogenous cardioprotective mechanisms against I/R are impaired in hyperlipidemic and hyperglycemic in vivo animal models. Therefore, our aim was to develop a medium throughput comorbidity cell-based test system of myocardial I/R injury, hypercholesterolemia and hyperglycemia that mimics comorbidity conditions.

Methods

Cardiac myocytes isolated from neonatal or adult rat hearts were cultured in control or in three different hypercholesterolemic media with increasing cholesterol content (hiChol) or hiChol + hyperglycemic medium, respectively. Each group was then subjected to simulated ischemia/reperfusion (SI/R) or corresponding normoxic condition, respectively. Cholesterol uptake was tested by Filipin staining in neonatal cardiac myocytes. Cell viability, total cell count and oxidative stress, i.e., total reactive oxygen species (ROS) and superoxide level were measured by fluorescent assays.

Results

Neonatal cardiac myocytes took up cholesterol from the different hiChol media at a concentration-dependent manner. In normoxia, viability of hiChol neonatal cardiac myocytes was not significantly changed, however, superoxide levels were increased as compared to vehicle. After SI/R, the viability of hiChol neonatal cardiac myocytes was decreased and total ROS level was increased as compared to vehicle. HiChol combined with hyperglycemia further aggravated cell death and oxidative stress in normoxic as well as in SI/R conditions. Viability of hiChol adult cardiac myocytes was significantly decreased and superoxide level was increased in normoxia and these changes were further aggravated by SI/R. HiChol combined with hyperglycemia further aggravated cell death, however level of oxidative stress increased only in normoxic condition.

Conclusion

HiChol rat cardiac myocytes showed reduction of cell viability and increased oxidative stress, which were further aggravated by SI/R and with additional hyperglycemia. This is the first demonstration that the combination of the current hypercholesterolemic medium and SI/R in cardiac myocytes mimics the cardiac pathology of the comorbid heart with I/R and hypercholesterolemia.

Regular transient limb ischemia prevents atherosclerosis progression in hypercholesterolemic rabbits

BACKGROUND

Endothelial dysfunction, the initial pathogenic factor in atherosclerosis, can be alleviated via transient limb ischemia. We observed the effects of regular transient limb ischemia (RTLI) on atherosclerosis in hypercholesterolemic rabbits.

METHODS

Twenty-eight rabbits were randomized to control, cholesterol, sham, ischemia groups (n = 7 each) between October 2010 and March 2011. They were fed a normal diet in the control group and hypercholesterolemic diet in other groups for 12 weeks. Six cycles of RTLI were performed once per day on the ischemia group. Serum samples were prepared to measure the total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) before the experiment (W0), at the end of weeks 4, 8, 12 (W4, W8, W12). The whole aorta was harvested at W12 and stained using Sudan IV to identify the plaque. The plaque area was measured using Image J. Results were analyzed by analysis of variance or rank sum test.

RESULTS

Concentrations of TC in the cholesterol group were higher than those in the control group at W4 (29.60 [23.75, 39.30] vs. 1.00 [0.80, 1.55], Z = -2.745, P = 0.006), W8 (41.78 [28.08, 47.37] vs. 0.35 [0.10, 0.68], Z = -2.739, P = 0.006), W12 (48.32 [40.04, 48.95] vs. 0.61 [0.50, 0.86], Z = -2.739, P = 0.006). Similar results were obtained for HDL-C and LDL-C. Serum concentrations of TC, HDL-C, and LDL-C in the hypercholesterolemic groups had no differences (all P > 0.05). The percentage of plaque area in the cholesterol group was higher than that in the control group (47.22 ± 23.89% vs. 0, Z = -2.986, P = 0.003). Square root of the percentage of plaque area was smaller in the ischemia group than that in the cholesterol (0.44 ± 0.13 vs. 0.67 ± 0.18, P = 0.014) or sham groups (0.44 ± 0.13 vs. 0.61 ± 0.12, P = 0.049).

CONCLUSION

In hypercholesterolemic rabbits, RTLI might prevent atherosclerosis progression by reducing the percentage of plaque area.

Impact of hyperglycemia on myocardial ischemia-reperfusion susceptibility and ischemic preconditioning in hearts from rats with type 2 diabetes

Background

The mechanisms underlying increased mortality in patients with diabetes and admission hyperglycemia after an acute coronary syndrome may involve reduced capacity for cardioprotection. We investigated the impact of hyperglycemia on exogenously activated cardioprotection by ischemic preconditioning (IPC) in hearts from rats with type 2 diabetes mellitus (T2DM) that were endogenously cardioprotected by an inherent mechanism, and the involvement of myocardial glucose uptake (MGU) and myocardial O-linked β-N-acetylglucosamine (O-GlcNAc).

Methods and results

In isolated, perfused rat hearts subjected to ischemia–reperfusion, infarct size (IS) was overall larger during hyper- ([Glucose] = 22 mmol/L]) than normoglycemia ([Glucose] = 11 mmol/L]) (p < 0.001). IS was smaller in 12-week old Zucker diabetic fatty rats with recent onset T2DM (fa/fa) than in rats without T2DM (fa/+) (n = 8 in each group) both during hyperglycemia (p < 0.05) and normoglycemia (p < 0.05). IPC (2 × 5 min cycles) reduced IS during normo- (p < 0.01 for both groups) but not during hyperglycemia independently of the presence of T2DM. During hyperglycemia, an intensified IPC stimulus (4 × 5 min cycles) reduced IS only in hearts from animals with T2DM (p < 0.05). IPC increased MGU and O-GlcNAc levels during reperfusion in animals with and without T2DM at normoglycemia (MGU: p < 0.05, O-GlcNAc: p < 0.01 for both groups) but not during hyperglycemia. Intensified IPC at hyperglycemia increased MGU (p < 0.05) and O-GlcNAc levels (p < 0.05) only in hearts from animals with T2DM.

Conclusion

While the effect of IPC is reduced during hyperglycemia in rats without T2DM, endogenous cardioprotection in animals with T2DM is not influenced by hyperglycemia and the capacity for exogenous cardioprotection by IPC is preserved. MGU and O-GlcNAc levels are increased by exogenously induced cardioprotection by IPC but not by endogenous cardioprotection in animals with T2DM reflecting different underlying mechanisms by exogenous and endogenous cardioprotection.

A novel ferulic acid derivative attenuates myocardial cell hypoxia reoxygenation injury through a succinate dehydrogenase dependent antioxidant mechanism

The molecular structure optimization aimed at definite target is expected to improve its anti-myocardial ischemia reperfusion (I/R) injury. Ferulic acid derivatives could probably attenuate myocardial I/R injury when optimized on account of definite target succinate dehydrogenase (SDH). Herein, an original compound hmy-paa (3-(4-hydroxy-3-methoxyphenyl)-N-(1H-pyrazol-3-yl)acrylamide), a combination of ferulic acid and active groups of enzyme inhibitor was synthesized, myocardial cell hypoxia reoxygenation (H/R) model were built, and SDH activity of myocardial cell was detected to investigate the effect of the derivative. Intriguingly, it could selectively inhibit SDH activity, and efficiently abate myocardial cell H/R injury. SDH is located in the mitochondrial inner membrane, and fluorescent hmy-paa could be observed to accumulate in cell and mitochondria through fluorescence inversion microscopy, which allows for more efficient SDH inhibition efficacy. By inhibiting SDH activity, hmy-paa could reduce oxidative damage by preventing excess production of intracellular reactive oxygen species as well as ensure energy production through the regulation of ATP level. The computational docking simulation exhibits a tightly bound mode between hmy-paa and SDH. Consequently, ferulic acid derivative hmy-paa is a new candidate for the treatment of myocardial H/R injury that exerts its therapeutic effect through a SDH dependent antioxidant mechanism. SDH could probably be a new target for drug discovery to alleviate myocardial I/R injury.

Pragmatic Analysis of Dyslipidemia Involvement in Coronary Artery Disease: A Narrative Review

Background

Dyslipidemia is the main factor involved in the occurrence and progression of coronary artery disease.

Objective

The research strategy is aimed at analyzing new data on the pathophysiology of dyslipidemia involvement in coronary artery disease, the modalities of atherogenic risk estimation and therapeutic advances.

Methods

Scientific articles published in PubMed from January 2017 to February 2018 were searched using the terms “dyslipidemia” and “ischemic heart disease”.

Results

PCSK9 contributes to the increase in serum levels of low-density lipoprotein-cholesterol and lipoprotein (a). The inflammation is involved in the progression of hyperlipidemia and atherosclerosis. Hypercholesterolemia changes the global cardiac gene expression profile and is thus involved in the increase of oxidative stress, mitochondrial dysfunction, and apoptosis initiated by inflammation. Coronary artery calcifications may estimate the risk of coronary events. The cardio-ankle vascular index evaluates the arterial stiffness and correlates with subclinical coronary atherosclerosis. The carotid plaque score is superior to carotid intima-media thickness for risk stratification in patients with familial hypercholesterolemia and both can independently predict coronary artery disease. The lipoprotein (a) and familial hypercholesterolemia have a synergistic role in predicting the risk of early onset and severity of coronary atherosclerosis. A decrease in atherosclerotic coronary plaque progression can be achieved in patients with plasma LDL-cholesterol levels below 70 mg/dL. A highly durable RNA interference therapeutic inhibitor of PCSK9 synthesis could be a future solution.

Conclusion

The prophylaxis and treatment of coronary artery disease in a dyslipidemic patient should be based on a careful assessment of cardio-vascular risk factors and individual metabolic particularities, so it may be personalized.

Lycopene restores the effect of ischemic postconditioning on myocardial ischemia‑reperfusion injury in hypercholesterolemic rats

Ischemic postconditioning (IPoC) has been demonstrated to prevent myocardial ischemia-reperfusion injury (MIRI), but its cardioprotective effect is abrogated by hypercholesterolemia. The aim of the present study was to determine whether lycopene (LP), a type of carotenoid, can restore the cardioprotective effect of IPoC in hypercholesterolemic rats. Male Wistar rats were fed a cholesterol-enriched diet for 12 weeks to establish a hypercholesterolemic model. The rat hearts were isolated and subjected to 30 min ischemia and 60 min reperfusion using a Langendorff apparatus. LP was administered to the rats intraperitoneally for 5 consecutive days prior to ischemia and reperfusion. Myocardial pathological changes, infarct size and cell apoptosis were measured by hematoxylin and eosin, triphenyltetrazolium chloride and TUNEL staining, respectively. The changes in endoplasmic reticulum (ER) stress markers, the reperfusion injury salvage kinase (RISK) pathway and mitochondrial apoptosis-related proteins were detected by western blotting. Overall, the results demonstrated that low-dose LP in combination with IPoC ameliorated myocardial histopathological changes, reduced the infarct size and release of cardiac enzymes, and decreased cardiomyocyte apoptosis in hypercholesterolemic rats, but no beneficial effects were achieved by the same dose of LP or IPoC treatment were used alone. Furthermore, the combination of LP and IPoC inhibited the expression of glucose-regulated protein 78 and C/EBP homologous protein, increased the phosphorylation levels of AKT, ERK1/2 and glycogen synthase kinase-3β, repressed mitochondrial permeability transition pore opening, and reduced the expression of cytochrome c, cleaved caspase-9 and cleaved caspase-3. Collectively, these findings demonstrated that LP can restore the cardioprotective effects of IPoC on MIRI in hypercholesterolemic rats, and this restoration by LP was mediated by inhibition of ER stress and reactivation of the RISK pathway in hypercholesterolemic rat myocardium.

Ischaemic and hypoxic conditioning: potential for protection of vital organs

NEW FINDINGS

What is the topic of this review? Remote ischaemic preconditioning (RIPC) and hypoxic preconditioning as novel therapeutic approaches for cardiac and neuroprotection. What advances does it highlight? There is improved understanding of mechanisms and signalling pathways associated with ischaemic and hypoxic preconditioning, and potential pitfalls with application of these therapies to clinical trials have been identified. Novel adaptations of preconditioning paradigms have also been developed, including intermittent hypoxia training, RIPC training and RIPC-exercise, extending their utility to chronic settings.

ABSTRACT

Myocardial infarction and stroke remain leading causes of death worldwide, despite extensive resources directed towards developing effective treatments. In this Symposium Report we highlight the potential applications of intermittent ischaemic and hypoxic conditioning protocols to combat the deleterious consequences of heart and brain ischaemia. Insights into mechanisms underlying the protective effects of intermittent hypoxia training are discussed, including the activation of hypoxia-inducible factor-1 and Nrf2 transcription factors, synthesis of antioxidant and ATP-generating enzymes, and a shift in microglia from pro- to anti-inflammatory phenotypes. Although there is little argument regarding the efficacy of remote ischaemic preconditioning (RIPC) in pre-clinical models, this strategy has not consistently translated into the clinical arena. This lack of translation may be related to the patient populations targeted thus far, and the anaesthetic regimen used in two of the major RIPC clinical trials. Additionally, we do not fully understand the mechanism through which RIPC protects the vital organs, and co-morbidities (e.g. hypercholesterolemia, diabetes) may interfere with its efficacy. Finally, novel adaptations have been made to extend RIPC to more chronic settings. One adaptation is RIPC-exercise (RIPC-X), an innovative paradigm that applies cyclical RIPC to blood flow restriction exercise (BFRE). Recent findings suggest that this novel exercise modality attenuates the exaggerated haemodynamic responses that may limit the use of conventional BFRE in some clinical settings. Collectively, intermittent ischaemic and hypoxic conditioning paradigms remain an exciting frontier for the protection against ischaemic injuries.

Naringenin Attenuates Myocardial Ischemia-Reperfusion Injury via cGMP-PKGIα Signaling and In Vivo and In Vitro Studies

Endoplasmic reticulum (ER) stress and oxidative stress contribute greatly to myocardial ischemia-reperfusion (MI/R) injury. Naringenin, a flavonoid derived from the citrus genus, exerts cardioprotective effects. However, the effects of naringenin on ER stress as well as oxidative stress under MI/R condition and the detailed mechanisms remain poorly defined. This study investigated the protective effect of naringenin on MI/R-injured heart with a focus on cyclic guanosine monophosphate- (cGMP-) dependent protein kinase (PKG) signaling. Sprague-Dawley rats were treated with naringenin (50 mg/kg/d) and subjected to MI/R surgery with or without KT5823 (2 mg/kg, a selective inhibitor of PKG) cotreatment. Cellular experiment was conducted on H9c2 cardiomyoblasts subjected to simulated ischemia-reperfusion treatment. Before the treatment, the cells were incubated with naringenin (80 μmol/L). PKGIα siRNA was employed to inhibit PKG signaling. Our in vivo and in vitro data showed that naringenin effectively improved heart function while it attenuated myocardial apoptosis and infarction. Furthermore, pretreatment with naringenin suppressed MI/R-induced oxidative stress as well as ER stress as evidenced by decreased superoxide generation, myocardial MDA level, gp91^phox expression, and phosphorylation of PERK, IRE1α, and EIF2α as well as reduced ATF6 and CHOP. Importantly, naringenin significantly activated myocardial cGMP-PKGIα signaling while inhibition of PKG signaling with KT5823 (in vivo) or siRNA (in vitro) not only abolished these actions but also blunted naringenin's inhibitory effects against oxidative stress and ER stress. In summary, our study demonstrates that naringenin treatment protects against MI/R injury by reducing oxidative stress and ER stress via cGMP-PKGIα signaling. Its cardioprotective effect deserves further clinical study.

Current Modalities and Mechanisms Underlying Cardioprotection by Ischemic Conditioning

Ischemic preconditioning is a process which serves to mitigate reperfusion injury. Preconditioning of the heart can be achieved through natural, pharmacological, and mechanical means. Mechanical preconditioning appears to have the greatest chance of good outcomes while methods employing pharmacologic preconditioning have been largely unsuccessful. Remote ischemic preconditioning achieves a cardioprotective effect by applying cycles of ischemia and reperfusion in a distal limb, stimulating the release of a neurohumoral cardioprotective factor incited by stimulation of afferent neurons. The cardioprotective factor stimulates the reperfusion injury salvage kinase (RISK) and survivor activator factor enhancement (SAFE) signaling cascades in cardiomyocytes which promote cell survival by the expression of anti-apoptotic genes and inhibition of the opening of mitochondrial permeability transition pores. Clinical application of ischemic preconditioning involving targets in the RISK and SAFE signaling appears promising in the treatment of acute myocardial infarction; however, clinical trials have yet to demonstrate additional benefit to current therapy.

Luteolin alleviates cardiac ischemia/reperfusion injury in the hypercholesterolemic rat via activating Akt/Nrf2 signaling

Myocardial ischemia/reperfusion (I/R) injury in hypercholesterolemia is associated with oxidative stress, while luteolin is known to reduce oxidative stress by activating Akt/nuclear factor erythroid-2-related factor 2 (Nrf2) signaling and alleviate cardiac I/R injury. Here, we investigated whether luteolin pretreatment diminishes myocardial I/R injury in hypercholesterolemic rats by activating Akt/Nrf2 signaling. Hypercholesterolemic rats were produced by 2% cholesterol diet for 8 weeks. Luteolin (100 mg/kg/day, i.g.) or LY294002 was administered for the last 2 weeks. The hearts were then isolated and subjected to 30 min of global ischemia followed by 120 min of reperfusion. Pretreatment with luteolin significantly improved left ventricular function throughout reperfusion, increased cardiac tissue viability, reduced coronary lactate dehydrogenase release and the myocardial malondialdehyde level, upregulated p-Akt and p-GSK3β expressions, inhibited nuclear translocation of Fyn, and activated Nrf2 function in hypercholesterolemic I/R rat hearts. All these improving effects of luteolin were significantly attenuated by LY294002. Ca2+-induced mitochondrial permeability transition pore (mPTP) opening and mitochondrial inner membrane potential reduction were significantly inhibited in ventricular myocytes isolated from luteolin-treated hypercholesterolemic rats, which were attenuated by LY294002. These results indicate that luteolin protects the hypercholesterolemic heart against I/R injury due to upregulation of Akt-mediated Nrf2 antioxidative function and inhibition of mPTP.

The role of microRNA-1 targeting of MAPK3 in myocardial ischemia-reperfusion injury in rats undergoing sevoflurane preconditioning via the PI3K/Akt pathway

Recent studies have uncovered the vital roles played by microRNAs in regulating cardiac injury. Among them, the cardiac enriched microRNA-1 (miR-1) has been extensively studied and proven to be detrimental to cardiac myocytes. Hence, the current study aimed to explore whether miR-1 affects myocardial ischemia-reperfusion injury (MIRI) in rats undergoing sevoflurane preconditioning and the underlying mechanism. After successful model establishment, rats with MIRI were transfected with mimics or inhibitors of miR-1, or siRNA against MAPK3, and then were injected with sevoflurane. A luciferase reporter gene assay was conducted to evaluate the targeting relationship between miR-1 and MAPK3. Reverse transcription quantitative polymerase chain reaction and Western blot analysis were employed to evaluate the expressions of miR-1, MAPK3, phosphatidylinositol 3-kinase (PI3K), and Akt. Additionally, the concentration of lactate dehydrogenase (LDH) was determined. Cell apoptosis and viability were assessed using TUNEL and cell counting kit-8 assays, and the ischemic area at risk and infarct size were detected using Evans blue and triphenyltetrazolium chloride staining. MAPK3 was found to be the target gene of miR-1. miR-1 expressed at a high level whereas MAPK3 expressed at a low level in MIRI rats. Overexpressing miR-1 or silencing MAPK3 blocked the PI3K/Akt pathway to increase cell apoptosis, ischemic area at risk, and infarct area but decreased cell viability and increased LDH concentration. In contrast, miR-1 downregulation abrogated the effects induced by miR-1 mimics or siRNA against MAPK3. These findings indicate that inhibition of miR-1 promotes MAPK3 to protect against MIRI in rats undergoing sevoflurane preconditioning through activation of the PI3K/Akt pathway.