ω-3 Polyunsaturated Fatty Acid Postconditioning Protects the Isolated Perfused Rat Heart from Ischemia-Reperfusion Injury

The Impact of Opioids on Epigenetic Modulation in Myocardial Ischemia and Reperfusion Injury: Focus on Non-coding RNAs

Myocardial ischemia-reperfusion injury (IRI) is a major issue in cardiovascular medicine, marked by tissue damage from the restoration of blood flow after ischemia. Opioids, known for their pain-relieving properties, have emerged as potential cardioprotective agents in IRI. Recent research suggests opioids influence epigenetic mechanisms-such as histone modifications and non-coding RNAs (ncRNAs)-which are essential for regulating gene expression and cellular responses during myocardial IRI. This review delves into how opioids like remifentanil affect histone modifications, DNA methylation, and ncRNAs, including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). Remifentanil postconditioning (RPC) reduces apoptosis in cardiomyocytes through histone deacetylation, specifically downregulating histone deacetylase 3 (HDAC3). Similarly, opioids impact miRNAs such as miR- 206 - 3p and miR- 320 - 3p, and lncRNAs like TINCR and UCA1, which influence apoptosis, inflammation, and oxidative stress. Understanding these interactions highlights the potential for opioid-based therapies in mitigating IRI-induced myocardial damage.

LDL receptor-related protein 5 selectively transports unesterified polyunsaturated fatty acids to intracellular compartments

Polyunsaturated fatty acids (PUFAs), which cannot be synthesized by animals and must be supplied from the diet, have been strongly associated with human health. However, the mechanisms for their accretion remain poorly understood. Here, we show that LDL receptor-related protein 5 (LRP5), but not its homolog LRP6, selectively transports unesterified PUFAs into a number of cell types. The LDLa ligand-binding repeats of LRP5 directly bind to PUFAs and are required and sufficient for PUFA transport. In contrast to the known PUFA transporters Mfsd2a, CD36 and FATP2, LRP5 transports unesterified PUFAs via internalization to intracellular compartments including lysosomes, and n-3 PUFAs depend on this transport mechanism to inhibit mTORC1. This LRP5-mediated PUFA transport mechanism suppresses extracellular trap formation in neutrophils and protects mice from myocardial injury during ischemia-reperfusion. Thus, this study reveals a biologically important mechanism for unesterified PUFA transport to intracellular compartments.

ACETYL-COA PRODUCTION BY OCTANOIC ACID ALLEVIATES ACUTE COMPARTMENT SYNDROME-INDUCED SKELETAL MUSCLE INJURY THROUGH REGULATING MITOPHAGY

ABSTRACT

Background: Treatment of acute compartment syndrome (ACS)-induced skeletal muscle injury remains a challenge. Previous studies have shown that octanoic acid is a promising treatment for ACS owing to its potential ability to regulate metabolic/epigenetic pathways in ischemic injury. The present study was designed to investigate the efficacy and underlying mechanism of octanoic acid in ACS-induced skeletal muscle injury. Methods: In this study, we established a saline infusion ACS rat model. Subsequently, we assessed the protective effects of sodium octanoate (NaO, sodium salt of octanoic acid) on ACS-induced skeletal muscle injury. Afterward, the level of acetyl-coenzyme A and histone acetylation in the skeletal muscle tissue were quantified. Moreover, we investigated the activation of the AMP-activated protein kinas pathway and the occurrence of mitophagy in the skeletal muscle tissue. Lastly, we scrutinized the expression of proteins associated with mitochondrial dynamics in the skeletal muscle tissue. Results: The administration of NaO attenuated muscle inflammation, alleviating oxidative stress and muscle edema. Moreover, NaO treatment enhanced muscle blood perfusion, leading to the inhibition of apoptosis-related skeletal muscle cell death after ACS. In addition, NaO demonstrated the ability to halt skeletal muscle fibrosis and enhance the functional recovery of muscle post-ACS. Further analysis indicates that NaO treatment increases the acetyl-CoA level in muscle and the process of histone acetylation by acetyl-CoA. Lastly, we found NaO treatment exerts a stimulatory impact on the activation of the AMPK pathway, thus promoting mitophagy and improving mitochondrial dynamics. Conclusion: Our findings indicate that octanoic acid may ameliorate skeletal muscle injury induced by ACS. Its protective effects may be attributed to the promotion of acetyl-CoA synthesis and histone acetylation within the muscular tissue, as well as its activation of the AMPK-related mitophagy pathway.

Targeting Ferroptosis against Ischemia/Reperfusion Cardiac Injury

Ischemic heart disease is a leading cause of death worldwide. Primarily, ischemia causes decreased oxygen supply, resulting in damage of the cardiac tissue. Naturally, reoxygenation has been recognized as the treatment of choice to recover blood flow through primary percutaneous coronary intervention. This treatment is the gold standard therapy to restore blood flow, but paradoxically it can also induce tissue injury. A number of different studies in animal models of acute myocardial infarction (AMI) suggest that ischemia-reperfusion injury (IRI) accounts for up to 50% of the final myocardial infarct size. Oxidative stress plays a critical role in the pathological process. Iron is an essential mineral required for a variety of vital biological functions but also has potentially toxic effects. A detrimental process induced by free iron is ferroptosis, a non-apoptotic type of programmed cell death. Accordingly, efforts to prevent ferroptosis in pathological settings have focused on the use of radical trapping antioxidants (RTAs), such as liproxstatin-1 (Lip-1). Hence, it is necessary to develop novel strategies to prevent cardiac IRI, thus improving the clinical outcome in patients with ischemic heart disease. The present review analyses the role of ferroptosis inhibition to prevent heart IRI, with special reference to Lip-1 as a promising drug in this clinicopathological context.

Effects of ω-3 PUFA and ascorbic acid combination on post-resuscitation myocardial function

Accumulating evidence demonstrated that administration of ω-3 polyunsaturated fatty acid (ω-3 PUFA) or ascorbic acid (AA) following cardiac arrest (CA) improves survival. Therefore, we investigate the effects of ω-3 PUFA combined with AA on myocardial function after CA and cardiopulmonary resuscitation (CPR) in a rat model. Thirty male rats were randomized into 5 groups: (1) sham; (2) control; (3) ω-3 PUFA; (4) AA; (5) ω-3 PUFA + AA. Ventricular fibrillation (VF) was induced and untreated for 6 min followed by defibrillation after 8 min of CPR. Infusion of drug or vehicle occurred at the start of CPR. Myocardial function and sublingual microcirculation were measured at baseline and after return of spontaneous circulation (ROSC). Heart tissues and blood were collected 6 h after ROSC. Myocardial function and sublingual microcirculation improvements were seen with ω-3 PUFA or AA compared to control after ROSC (p < 0.05). ω-3 PUFA + AA shows a better myocardial function than ω-3 PUFA or AA (p < 0.05). ω-3 PUFA or AA decreases pro-inflammatory cytokines, cTnI, myocardium malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) modified proteins compared to control (p < 0.05). ω-3 PUFA and AA combined have lower MDA and 4-HNE modified proteins than alone (p < 0.05). ω-3 PUFA or AA treatment reduces the severity of post-resuscitation myocardial dysfunction, improves sublingual microcirculation, decreases lipid peroxidation and systemic inflammation in the early phase of recovery following CA and resuscitation. A combination of ω-3 PUFA and AA treatment confers an additive effect in suppressing lipid peroxidation and improving myocardial function.

Mechanism of the hypoxia inducible factor 1/hypoxic response element pathway in rat myocardial ischemia/diazoxide post‑conditioning

Ischemic post-conditioning (IPO) and diazoxide post-conditioning (DPO) has been proven to reduce myocardial ischemia reperfusion injury (MIRI); however, the mechanisms of IPO/DPO are still not clear. The present study aimed to investigate whether mitochondrial ATP-sensitive potassium channels (mitoK_ATP) channels are activated by IPO/DPO, which may further activate the hypoxia inducible factor 1/hypoxic response element (HIF-1/HRE) pathway to mitigate MIRI. Using a Langendorff perfusion device, healthy male (250–300 g) Sprague Dawley rat hearts were randomly divided into the following groups. Group N was aerobically perfused with K-H solution for 120 min. Group ischaemia/reperfusion (I/R) was aerobically perfused for 20 min, then subjected to 40 min hypoxia plus 60 min reperfusion. Group IPO was treated like the I/R group, but with 10 sec of hypoxia plus 10 sec of reperfusion for six rounds before reperfusion. Group DPO was exposed to 50 µM diazoxide for 5 min before reperfusion and otherwise treated the same as group I/R. In groups IPO+5-hydroxydecanoic acid (5HD), DPO+5HD and I/R+5HD, exposure to 100 µM 5HD (a mitoK_ATP channel specific blocker) for 5 min before reperfusion as described for groups IPO, DPO and I/R, respectively. In groups IPO+2-methoxyestradiol (2ME2), DPO+2ME2 and I/R+2ME2, exposure to 2 µM 2ME2 (a HIF-1α specific blocker) for 10 min before reperfusion as described for groups IPO, DPO and I/R respectively. Cardiac hemodynamics, myocardial injury and the expression of HIF-1/HRE pathway [HIF-1α, heme oxygenase (HO-1), inducible nitric oxide synthase (iNOS) and vascular endothelial growth factor (VEGF)] were detected in each group. The infarct size and mitochondrial Flameng scores of groups IPO/DPO were significantly decreased compared with the I/R group (P<0.05), but the myocardial protective effects of IPO/DPO could be eliminated by 5HD or 2ME2 (P<0.05). In addition, IPO/DPO could increase the mRNA expression of HIF-1α and the downstream factors of the HIF-1/HRE pathway (the mRNA and protein expression of HO-1, iNOS and VEGF; P<0.05). However, the myocardial protective effects and the activation the HIF-1/HRE pathway mediated by IPO/DPO could be eliminated by 5HD or 2ME2 (P<0.05). Therefore, the activation of the HIF-1/HRE pathway by opening mitoK_ATP channels may work with the mechanism of IPO/DPO in reducing MIRI.

Urotensin-#receptor antagonist SB-706375 protected isolated rat heart from ischaemia-reperfusion injury by attenuating myocardial necrosis via RhoA/ROCK/RIP3 signalling pathway

SB-706375 is a selective receptor antagonist of human urotensin-II (hU-II), which can block the aorta contraction induced by hU-II in rats. The effect of SB-706375 on myocardial ischaemia-reperfusion (I/R) injury is unclear. The major objective of this study was to investigate whether SB-706375 has a protective effect on myocardial I/R injury in rats and explore its possible mechanisms. Isolated hearts of Adult Sprague-Dawley were perfused in a Langendorff apparatus, and haemodynamic parameters, lactate dehydrogenase (LDH), creatine phosphokinase-MB (CK-MB), cardiac troponin I (cTnI), RhoA, and the protein expressions of U-II receptor (UTR), receptor-interacting protein 3 (RIP3), Rho-associated coiled-coil-containing protein kinase 1 (ROCK1) and Rho-associated coiled-coil-containing protein kinase 2 (ROCK2) were assessed. We found that SB-706375 (1 × 10-6 and 1 × 10-5 mol/L) significantly inhibited the changes of haemodynamic parameters and reduced LDH and CK-MB activities and also cTnI level in the coronary effluents in the heart subjected to myocardial I/R injury. Further experiments studies showed that SB-706375 obviously prevented myocardial I/R increased RhoA activity and UTR, RIP3, ROCK1, and ROCK2 protein expressions. ROCK inhibition abolished the improving effect of SB-706375 on myocardial I/R-induced haemodynamic change in the isolated perfused rat heart. These findings suggested that SB-706375 provides cardio-protection against I/R injury in isolated rats by blocking UTR-RhoA/ROCK-RIP3 pathway.

About the controversies of the cardioprotective effect of n-3 polyunsaturated fatty acids (PUFAs) between animal studies and clinical meta-analyses: a review with several strategies to enhance the beneficial effects of n-3 PUFAs

Several meta-analyses describing the effect of n-3 polyunsaturated fatty acids on the survival rate of the victims of an acute coronary event do not clearly support a beneficial impact of these fatty acids. Yet, animal studies consistently show n-3 PUFA-induced protection against ischemia-reperfusion-induced myocardial injuries. The impact on reperfusion arrhythmias of these PUFAs is more controversial. The literature shows the anti-arrhythmic properties of circulating n-3 PUFAs. However, when these fatty acids are incorporated in the cardiac membrane, they protect the myocardial tissue vis a vis cellular damage but they can be either pro- or anti-arrhythmic during reperfusion, depending on the severity of tissue injuries. The latter elements can explain the lack of beneficial effect observed in the meta-analyses, but a proper use of n-3 PUFAs may provide advantages in terms of survival rate. This review discusses the different results obtained in humans and animals and presents several strategies to enhance the beneficial effects of n-3 PUFAs.

Cardiolipotoxicity, Inflammation, and Arrhythmias: Role for Interleukin-6 Molecular Mechanisms

Fatty acid infiltration of the myocardium, acquired in metabolic disorders (obesity, type-2 diabetes, insulin resistance, and hyperglycemia) is critically associated with the development of lipotoxic cardiomyopathy. According to a recent Presidential Advisory from the American Heart Association published in 2017, the current average dietary intake of saturated free-fatty acid (SFFA) in the US is 11–12%, which is significantly above the recommended <10%. Increased levels of circulating SFFAs (or lipotoxicity) may represent an unappreciated link that underlies increased vulnerability to cardiac dysfunction. Thus, an important objective is to identify novel targets that will inform pharmacological and genetic interventions for cardiomyopathies acquired through excessive consumption of diets rich in SFFAs. However, the molecular mechanisms involved are poorly understood. The increasing epidemic of metabolic disorders strongly implies an undeniable and critical need to further investigate SFFA mechanisms. A rapidly emerging and promising target for modulation by lipotoxicity is cytokine secretion and activation of pro-inflammatory signaling pathways. This objective can be advanced through fundamental mechanisms of cardiac electrical remodeling. In this review, we discuss cardiac ion channel modulation by SFFAs. We further highlight the contribution of downstream signaling pathways involving toll-like receptors and pathological increases in pro-inflammatory cytokines. Our expectation is that if we understand pathological remodeling of major cardiac ion channels from a perspective of lipotoxicity and inflammation, we may be able to develop safer and more effective therapies that will be beneficial to patients.