Angiotensin receptor-neprilysin inhibitior (thiorphan/irbesartan) decreased ischemia-reperfusion induced ventricular arrhythmias in rat; in vivo study

Involvement of Oxidative Stress and Antioxidants in Modification of Cardiac Dysfunction Due to Ischemia-Reperfusion Injury

Delayed reperfusion of the ischemic heart (I/R) is known to impair the recovery of cardiac function and produce a wide variety of myocardial defects, including ultrastructural damage, metabolic alterations, subcellular Ca2+-handling abnormalities, activation of proteases, and changes in cardiac gene expression. Although I/R injury has been reported to induce the formation of reactive oxygen species (ROS), inflammation, and intracellular Ca2+ overload, the generation of oxidative stress is considered to play a critical role in the development of cardiac dysfunction. Increases in the production of superoxide, hydroxyl radicals, and oxidants, such as hydrogen peroxide and hypochlorous acid, occur in hearts subjected to I/R injury. In fact, mitochondria are a major source of the excessive production of ROS in I/R hearts due to impairment in the electron transport system as well as activation of xanthine oxidase and NADPH oxidase. Nitric oxide synthase, mainly present in the endothelium, is also activated due to I/R injury, leading to the production of nitric oxide, which, upon combination with superoxide radicals, generates nitrosative stress. Alterations in cardiac function, sarcolemma, sarcoplasmic reticulum Ca2+-handling activities, mitochondrial oxidative phosphorylation, and protease activation due to I/R injury are simulated upon exposing the heart to the oxyradical-generating system (xanthine plus xanthine oxidase) or H2O2. On the other hand, the activation of endogenous antioxidants such as superoxide dismutase, catalase, glutathione peroxidase, and the concentration of a transcription factor (Nrf2), which modulates the expression of various endogenous antioxidants, is depressed due to I/R injury in hearts. Furthermore, pretreatment of hearts with antioxidants such as catalase plus superoxide dismutase, N-acetylcysteine, and mercaptopropionylglycerine has been observed to attenuate I/R-induced subcellular Ca2+ handling and changes in Ca2+-regulatory activities; additionally, it has been found to depress protease activation and improve the recovery of cardiac function. These observations indicate that oxidative stress is intimately involved in the pathological effects of I/R injury and different antioxidants attenuate I/R-induced subcellular alterations and improve the recovery of cardiac function. Thus, we are faced with the task of developing safe and effective antioxidants as well as agents for upregulating the expression of endogenous antioxidants for the therapy of I/R injury.

Interaction between ischemia-reperfusion injury and intestinal microecology in organ transplantation and its therapeutic prospects

Organ transplantation is a vital intervention for end-stage organ failure; however, ischemia-reperfusion injury is a complication of transplantation, affecting the prognosis and survival of transplant recipients. As a complex ecosystem, recent research has highlighted the role of the intestinal microecology in transplantation, revealing its significant interplay with ischemia-reperfusion injury. This review explores the interaction between ischemia-reperfusion injury and intestinal microecology, with a special focus on how ischemia-reperfusion injury affects intestinal microecology and how these microecological changes contribute to complications after organ transplantation, such as infection and rejection. Based on a comprehensive analysis of current research advances, this study proposes potential strategies to improve transplant outcomes, offering guidance for future research and clinical practice.

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

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

A comparative study between angiotensin receptor neprilysin inhibitor (thiorphan/irbesartan) with each of nitrate and carvedilol in a rat model of myocardial ischemic reperfusion injury

The combined angiotensin receptor neprilysin inhibitor is a promising cardioprotective pharmacological agent. This study investigated the beneficial effects of thiorphan (TH)/irbesartan (IRB), in myocardial ischemia-reperfusion (IR) injury, compared to each of nitroglycerin and carvedilol. Male Wistar rats were divided into five groups (10 rats/group): Sham, untreated I/R, TH/IRB + IR (0.1/10 mg/kg), nitroglycerin + IR (0.2 mg/kg), and carvedilol + IR (10 mg/kg). Mean arterial blood pressure, cardiac functions and arrhythmia incidence, duration and score were assessed. Cardiac levels of creatine kinase-MB (CK-MB), oxidative stress, endothelin-1, ATP, Na⁺ /K⁺ ATPase pump activity and mitochondria complexes activities were measured. Histopathological examination, Bcl/Bax immunohistochemistry studies and electron microscopy examination of left ventricle were performed. TH/IRB preserved the cardiac functions and mitochondrial complexes activities, mitigated cardiac damage, reduced oxidative stress and arrhythmia severity, improved the histopathological changes and decreased cardiac apoptosis. TH/IRB showed a comparable effect to each of nitroglycerin and carvedilol in alleviating the IR injury consequences. TH/IRB showed significant preservation of mitochondrial complexes activity I and II compared to nitroglycerin. TH/IRB significantly increased LVdP/dtmax and decreased oxidative stress, cardiac damage and endothelin-1 along with increasing the ATP content, Na⁺ /K⁺ ATPase pump activity and mitochondrial complexes activity when compared to carvedilol. TH/IRB showed a cardioprotective effect in reducing IR injury that is comparable to each of nitroglycerin and carvedilol that could be explained in part by its ability to preserve mitochondrial function, increase ATP, decrease oxidative stress as well as endothelin 1.

Angiotensin receptor-neprilysin inhibitor (thiorphan/irbesartan) improved cardiac function in a rat model of myocardial ischemic reperfusion injury

Mitochondria-mediated apoptosis plays a critical role in myocardial ischemia reperfusion (IR) injury and causes a negative impact on cardiac efficiency and function. The combined angiotensin receptor-neprilysin inhibitor (ARNI) is a promising cardioprotective pharmacological agent that could rescue the heart from IR injury. This study investigated the cardioprotective effect of thiorphan (TH) in combination with three different doses of irbesartan (IRB) on myocardial IR injury and detected the most effective dose combination. Male Wistar rats were used and divided into five groups (10 rats/group): (I) Sham, (II) ischemia-reperfusion I/R, (III) TH/IRB + IR (0.1/5 mg/kg), (IV) TH/IRB + IR (0.1/10 mg/kg), and (V) TH/IRB + IR (0.1/15 mg/kg) groups. Thiorphan and irbesartan were injected intraperitoneally 15 min before IR induction. Mean arterial blood pressure, left ventricular end diastolic pressure (LVEDP), left ventricular maximum rate of pressure (LVdp/dt_max ), and cardiac levels of creatine kinase-MB, malondialdehyde, superoxide dismutase, and endothelin-1 were measured. Cardiac mitochondria complexes activities, histopathological examination of myocardial tissues, immunohistochemistry studies for myocardial apoptosis (Bax and Bcl-2), and electron microscopy examination of left ventricle were performed. TH/IRB combination preserved cardiac functions and mitochondria complex activities and mitigated cardiac damage, oxidative stress, and apoptosis following IR. Also, there was an evident improvement in histopathological changes and electron microscopy examination of left ventricle compared with I/R group. TH/IRB in a dose of 0.1/10 mg/kg showed significant improvement compared with the other treated groups. Thiorphan/irbesartan improved cardiac functions following IR injury. This could be explained by the reported improvement of mitochondria complex activities and reduction of oxidative stress, endothelin-1, and apoptosis.

Alpha-lipoic acid treatment improves adverse cardiac remodelling in the diabetic heart - The role of cardiac hydrogen sulfide-synthesizing enzymes

INTRODUCTION

Alpha-lipoic acid (ALA) is a licensed drug for the treatment of diabetic neuropathy. We recently reported that it also improves diabetic cardiomyopathy (DCM) in type 2 diabetes mellitus (T2DM). In this study, we present evidence supporting our hypothesis that the cardioprotective effect of ALA is via upregulation of cardiac hydrogen sulfide (H₂S)-synthesizing enzymes.

METHODS

Following 12 h of overnight fasting, T2DM was induced in 23 out of 30 male Sprague-Dawley rats by intraperitoneal administration of nicotinamide (110 mg/kg) followed by streptozotocin (55 mg/kg) while the rest served as healthy control (HC). T2DM rats then received either oral administration of ALA (60 mg/kg/day; n = 7) or 40 mg/kg/day DL-propargylglycine (PAG, an endogenous H₂S inhibitor; n = 7) intraperitoneally for 6 weeks after which all rats were sacrificed and samples collected for analysis. Untreated T2DM rats served as diabetic control (DCM; n = 9).

RESULTS

T2DM resulted in weight loss, islet destruction, reduced pancreatic β-cell function and hyperglycemia. Histologically, DCM rats showed significant myocardial damage evidenced by myocardial degeneration, cardiomyocyte vacuolation and apoptosis, cardiac fibrosis and inflammation, which positively correlated with elevated levels of cardiac damage markers compared to HC rats (p < 0.001). These pathological alterations worsened significantly in PAG-treated rats (p < 0.05). However, ALA treatment restored normoinsulemia, normoglycemia, prevented DCM, and improved lipid and antioxidant status. Mechanistically, ALA significantly upregulated the expression of cardiac H₂S-synthesizing enzymes and increased plasma H₂S concentration compared to DCM rats (p < 0.001).

CONCLUSION

ALA preserves myocardial integrity in T2DM likely by maintaining the expression of cardiac H₂S-synthezing enzymes and increasing plasma H₂S level.

General anesthesia and electrocardiographic parameters in in vivo experiments involving rats

In in vivo cardiovascular or toxicological studies involving rat models, changes in selected electrocardiographic (ECG) parameters are monitored after various interventions to assess the origin and development of heart rhythm disorders. Each ECG parameter has diagnostic significance; as such, commonly evaluated ECG parameters, including heart rate, PR interval, P wave duration, P wave amplitude, QRS complex, QT and QTc interval duration, R wave and T wave amplitude, of rats under various types of general anesthesia were the focus of this study. Studies that performed in vivo cardiovascular or toxicological experiments in rats were retrieved from a search of the Web of Science database for articles published mainly between 2000 and 2021. In total, the search retrieved 123 articles. ECG parameters that were reported as baseline or control values were summarized and averages with ranges were calculated. It is important to be cautious when interpreting results and, in discussions addressing the mechanisms underlying a given type of arrhythmia, acknowledge that initial ECG parameters may already be affected to some extent by the general anesthesia as well as by sex and the time of day the experiments were performed.

Effect of sacubitril/valsartan on investigator-reported ventricular arrhythmias in PARADIGM-HF

Aims

Sudden death is a leading cause of mortality in heart failure with reduced ejection fraction (HFrEF). In PARADIGM‐HF, sacubitril/valsartan reduced the incidence of sudden death. The purpose of this post hoc study was to analyse the effect of sacubitril/valsartan, compared to enalapril, on the incidence of ventricular arrhythmias.

Methods and results

Adverse event reports related to ventricular arrhythmias were examined in PARADIGM‐HF. The effect of randomized treatment on two arrhythmia outcomes was analysed: ventricular arrhythmias and the composite of a ventricular arrhythmia, implantable cardioverter defibrillator (ICD) shock or resuscitated cardiac arrest. The risk of death related to a ventricular arrhythmia was examined in time‐updated models. The interaction between heart failure aetiology, or baseline ICD/cardiac resynchronization therapy‐defibrillator (CRT‐D) use, and the effect of sacubitril/valsartan was analysed. Of the 8399 participants, 333 (4.0%) reported a ventricular arrhythmia and 372 (4.4%) the composite arrhythmia outcome. Ventricular arrhythmias were associated with higher mortality. Compared with enalapril, sacubitril/valsartan reduced the risk of a ventricular arrhythmia (hazard ratio [HR] 0.76, 95% confidence interval [CI] 0.62–0.95; p = 0.015) and the composite arrhythmia outcome (HR 0.79, 95% CI 0.65–0.97; p = 0.025). The treatment effect was maintained after adjustment and accounting for the competing risk of death. Baseline ICD/CRT‐D use did not modify the effect of sacubitril/valsartan, but aetiology did: HR in patients with an ischaemic aetiology 0.93 (95% CI 0.71–1.21) versus 0.53 (95% CI 0.37–0.78) in those without an ischaemic aetiology (p for interaction = 0.020).

Conclusions

Sacubitril/valsartan reduced the incidence of investigator‐reported ventricular arrhythmias in patients with HFrEF. This effect may have been greater in patients with a non‐ischaemic aetiology.

Angiotensin Receptor Blocker and Neprilysin Inhibitor Suppresses Cardiac Dysfunction by Accelerating Myocardial Angiogenesis in Apolipoprotein E-Knockout Mice Fed a High-Fat Diet

Materials and Methods

Male apolipoprotein E-knockout mice fed a high-fat diet were divided into control (CTL), valsartan (30 mg/kg) (VAL), sacubitril (30 mg/kg) (SAC), and valsartan plus sacubitril (30 mg/kg each) (VAL/SAC) groups after 4 weeks of prefeeding and were subsequently treated for 12 weeks.

Results

The VAL/SAC group exhibited significantly higher serum brain natriuretic peptide levels; more subtle changes in left ventricular systolic diameter, fractional shortening, and ejection fraction, and significantly higher expression levels of natriuretic peptide precursor B and markers of angiogenesis, including clusters of differentiation 34, vascular endothelial growth factor A, and monocyte chemotactic protein 1, than the CTL group.

Conclusions

Valsartan plus sacubitril preserved left ventricular systolic function in apolipoprotein E-knockout mice fed a high-fat diet. This result suggests that myocardial angiogenic factors induced by ARNI might provide cardioprotective effects.