Implications of Oxidative and Nitrosative Post-Translational Modifications in Therapeutic Strategies against Reperfusion Damage

Valosin-containing protein acts as a target and mediator of S-nitrosylation in the heart through distinct mechanisms

S-nitrosylation (SNO) is an emerging paradigm of redox signaling protecting cells against oxidative stress in the heart. Our previous studies demonstrated that valosin-containing protein (VCP), an ATPase-associated protein, is a vital mediator protecting the heart against cardiac stress and ischemic injury. However, the molecular regulations conferred by VCP in the heart are not fully understood. In this study, we explored the potential role of VCP in cardiac protein SNO using multiple cardiac-specific genetically modified mouse models and various analytical techniques including biotin switch assay, liquid chromatography, mass spectrometry, and western blotting. Our results showed that cardiac-specific overexpression of VCP led to an overall increase in the levels of SNO-modified cardiac proteins in the transgenic (TG) vs. wild-type (WT) mice. Mass spectrometry analysis identified mitochondrial proteins involved in respiration, metabolism, and detoxification as primary targets of SNO modification in VCP-overexpressing mouse hearts. Particularly, we found that VCP itself underwent SNO modification at a specific cysteine residue in its N-domain. Additionally, our study demonstrated that glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a key enzyme in glycolysis, also experienced increased SNO in response to VCP overexpression. While deletion of inducible nitric oxide synthase (iNOS) in VCP TG mice did not affect VCP SNO, it did abolish SNO modification in mitochondrial complex proteins, suggesting a dual mechanism of regulation involving both iNOS-dependent and independent pathways. Overall, our findings shed light on post-translational modification of VCP in the heart, unveiling a previously unrecognized role for VCP in regulating cardiac protein SNO and offering new insights into its function in cardiac protection.

Expanding the Frontiers of Guardian Antioxidant Selenoproteins in Cardiovascular Pathophysiology

Significance: Physiological levels of reactive oxygen and nitrogen species (ROS/RNS) function as fundamental messengers for many cellular and developmental processes in the cardiovascular system. ROS/RNS involved in cardiac redox-signaling originate from diverse sources, and their levels are tightly controlled by key endogenous antioxidant systems that counteract their accumulation. However, dysregulated redox-stress resulting from inefficient removal of ROS/RNS leads to inflammation, mitochondrial dysfunction, and cell death, contributing to the development and progression of cardiovascular disease (CVD). Recent Advances: Basic and clinical studies demonstrate the critical role of selenium (Se) and selenoproteins (unique proteins that incorporate Se into their active site in the form of the 21st proteinogenic amino acid selenocysteine [Sec]), including glutathione peroxidase and thioredoxin reductase, in cardiovascular redox homeostasis, representing a first-line enzymatic antioxidant defense of the heart. Increasing attention has been paid to emerging selenoproteins in the endoplasmic reticulum (ER) (i.e., a multifunctional intracellular organelle whose disruption triggers cardiac inflammation and oxidative stress, leading to multiple CVD), which are crucially involved in redox balance, antioxidant activity, and calcium and ER homeostasis. Critical Issues: This review focuses on endogenous antioxidant strategies with therapeutic potential, particularly selenoproteins, which are very promising but deserve more detailed and clinical studies. Future Directions: The importance of selective selenoproteins in embryonic development and the consequences of their mutations and inborn errors highlight the need to improve knowledge of their biological function in myocardial redox signaling. This could facilitate the development of personalized approaches for the diagnosis, prevention, and treatment of CVD. Antioxid. Redox Signal. 40, 369-432.

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.

The influence of ambient temperature and polyphenols from plant leaves on growth and the response to oxidative and nitrosative stress in African nightcrawler earthworm, Eudrilus eugeniae (Kinberg, 1867)

Earthworms are one of the organisms that may be affected by climate change. Finding ways to help them deal with this problem is, therefore, important and necessary. The objective of this experiment was to understand the influence of ambient temperature and polyphenols from mulberry (Morus alba L.), almond (Terminalia catappa L.) and cassava (Manihot esculenta (L.) Crantz) leaves on growth, ferric reducing antioxidant power (FRAP), malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and nitric oxide (NO) concentration of the African night crawler, Eudrilus eugeniae (Kinberg, 1867) earthworm. The earthworms were cultured in 2 different conditions of ambient temperature, and in 4 types of substrate i.e. dairy cow faeces (BS), dairy cow faeces + mulberry leaves (BS + MA), almond leaves (BS + TC), and cassava leaves (BS + ME), respectively. At week 2 of the experiment, body weight, FRAP, MDA, H₂O₂ and NO were measured in the earthworms. It was found that the body weight gain (BWG) of the earthworms cultured in BS at cyclical temperature (26 + 1^oC - 34 + 1^oC - 26 + 1^oC, CyT) was higher than the constant temperature (26 ± 1 °C, CoT) (P < 0.05). FRAP of earthworms cultured in BS + TC was higher than in other groups (P < 0.05). MDA of earthworms cultured at CyT was higher than ambient temperature at CoT (P < 0.05). At CyT, the MDA of earthworms cultured in BS + MA was higher than that of those cultured in BS, BS + TC and BS + ME (P < 0.05). NO of earthworms at CoT was higher than at CyT(P < 0.05). At CoT, the NO of earthworms cultured in BS + TC was lower than that of those cultured in BS + MA and BS + ME (P < 0.05). H₂O₂ of earthworms at CoT was higher than those at CyT (P < 0.05). The level of H₂O₂ of the earthworms cultured in BS + ME at CoT was higher than at CyT (P < 0.05). In addition, the H₂O₂ of earthworms cultured in both ambient temperatures and cultured in BS + MA was higher than the other groups (P < 0.05). These phenomena indicated that low and high ambient temperatures induced nitrosative and oxidative stress in earthworms, respectively. Mulberry leaves are toxic to earthworms. On the other hand, almond leaves could reduce nitrosative stress in earthworms. While at the CoT, cassava leaves induced the production of H₂O₂ in the earthworms.

Modulation of Inula racemosa Hook Extract on Cardioprotection by Ischemic Preconditioning in Hyperlipidaemic Rats

Objectives

Hyperlipidemia (HL) is a major cause of ischemic heart diseases. The size-limiting effect of ischemic preconditioning (IPC), a cardioprotective phenomenon, is reduced in HL, possibly because of the opening of the mitochondrial permeability transition pore (MPTP). The objective of this study is to see what effect pretreatment with Inula racemosa Hook root extract (IrA) had on IPC-mediated cardioprotection on HL Wistar rat hearts. An isolated rat heart was mounted on the Langendorff heart array, and then ischemia reperfusion (I/R) and IPC cycles were performed. Atractyloside (Atr) is an MPTP opener.

Methods

The animals were divided into ten groups, each consisting of six rats (n = 6), to investigate the modulation of I. racemosa Hook extract on cardioprotection by IPC in HL hearts Sham control, I/R Control, IPC control, I/R + HL, I/R + IrA + HL, IPC + HL, IPC + NS + HL, IPC + IrA+ HL, IPC + Atr + oxidative stress, mitochondrial function, integrity, and hemodynamic parameters are evaluated for each group.

Results

The present experimental data show that pretreatment with IrA reduced the LDH, CK-MB, size of myocardial infarction, content of cardiac collagen, and ventricular fibrillation in all groups of HL rat hearts. This pretreatment also reduced the oxidative stress and mitochondrial dysfunction. Inhibition of MPTP opening by Atr diminished the effect of IrA on IPC-mediated cardioprotection in HL rats.

Conclusion

The study findings indicate that pretreatment with IrA e restores IPC-mediated cardioprotection in HL rats by inhibiting the MPTP opening.

Deciphering the Global Proteomic Profile Involved in Methylmercury-Induced Cerebellar Neurodegeneration and Motor Dysfunction in Adult Rats

Mercury is a ubiquitous pollutant in the environment with potential neurotoxic effects. Several populations are susceptible to mercurial exposure, especially methylmercury (MeHg) at low doses for long periods through food consumption. Given this, the present work aimed to assess the effects of long-term MeHg exposure on the cerebellum of rats from a translational perspective using a representative dose, assessing molecular, biochemical, morphological, and behavioral parameters. The model was produced by administering 40 µg/kg of MeHg for 60 days to adult male Wistar rats by oral gavage. As a result of this exposure, the animals presented motor deficits in open field and rotarod tests which were associated with an increase in total mercury content in cerebellar parenchyma, a reduction in antioxidant competence against peroxyl radicals, and increased nitrite and lipid peroxidation levels. The proteomic approach showed 317 modulated proteins. Such findings were associated with reductions in mature neuron and Purkinje cell densities and glial fibrillary acidic protein immunostained areas and increased microglial density. In addition, decreases in myelin basic protein and synaptophysin immunostaining were also observed. The results thus provided new evidence of the mechanisms underlying complex MeHg-induced neurodegeneration, especially the proteins underlying the biochemical and morphological features associated with motor dysfunction.

Custodiol HTK versus Plegisol: in-vitro comparison with the use of immature (H9C2) and mature (HCM) cardiomyocytes cultures

Background

Although cardioplegia is used since the ‘70s of the last century, debate on cardioprotection during cardio-surgical procedures is still actual. The selection of a particular method depends mainly on the preferences and experience of a specific center or even surgeon. Crystalloid cardioplegia is an aqueous ion solution similar to intracellular (Custodiol HTK) or extracellular (Plegisol) fluid. The potensional clinical advantages of relatively new idea of cardioplegia solution based on intracellular composition (Custodiol HTK) justifies futher research, but only a few used cultured cells in laboratory conditions.

Methods

In this study, the authors sought to compare Custodiol HTK with Plegisol cardioplegia solutions using an in-vitro model simulating cardioplegic arrest. The efficacy of myocardial protection during ischemia was investigated with susceptible indicators like the appearance of the deleterious effect of reactive oxygen species and oxidative stress markers. Immersed human cardiomyocytes and rat cardiomyoblasts H9C2 in cardioplegia for 4 h were examined for expression of oxidative stress markers (MnSOD, iNOS, HSP27), cardioplegic solutions cytotoxicity, and peroxidation damage of the cell’s lipids and proteins. All tests were performed after 0.5 h, 1 h, 2 h, and 4 h of incubation in identical physical and biological conditions, which is difficult to achieve in clinical trials.

Results

The lower cytotoxicity index performed on matured cells of human cardiomyocytes and highest dehydrogenase level showed after incubation with Custodiol HTK. This did not apply to tests on immature cells H9C2. Custodiol HTK induced significantly stronger iNOS expression. The decrease of HSP27 concentration has been instantaneous and maintained troughout the study only in both cultures incubated with Custodiol HTK. The other tests: lipid peroxidation, carbonyl groups concentration and MnSOD expression show no clear superiority evidence of used cardioplegic solutions.

Conclusions

Considering proceeded examinations on cultured cardiomyocytes, Custodiol HTK appears to be safer than Plegisol.

Targeting the mitochondrial permeability transition pore for drug discovery: Challenges and opportunities

Several drug targets have been amenable to drug discovery pursuit not until the characterization of the mitochondrial permeability transition pore (MPTP), a pore with an undefined molecular identity that forms on the inner mitochondrial membrane upon mitochondrial permeability transition (MPT) under the influence of calcium overload and oxidative stress. The opening of the pore which is presumed to cause cell death in certain human diseases also has implications under physiological parlance. Different models for this pore have been postulated following its first identification in the last six decades. The mitochondrial community has witnessed many protein candidates such as; voltage-dependent anion channel (VDAC), adenine nucleotide translocase (ANT), Mitochondrial phosphate carrier (PiC), Spastic Paralegin (SPG7), disordered proteins, and F1Fo ATPase. However, genetic studies have cast out most of these candidates with only F1Fo ATPase currently under intense argument. Cyclophilin D (CyPD) remains the widely accepted positive regulator of the MPTP known to date, but no drug candidate has emerged as its inhibitor, raising concern issues for therapeutics. Thus, in this review, we discuss various models of MPTP reported with the hope of stimulating further research in this field. We went beyond the classical description of the MPTP to ascribe a 'two-edged sword property' to the pore for therapeutic function in human disease because its inhibition and activation have pharmacological relevance. We suggested putative proteins upstream to CyPD that can regulate its activity and prevent cell deaths in neurodegenerative disease and ischemia-reperfusion injury.

Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Mitochondria are the central target of ischemic preconditioning and postconditioning cardioprotective strategies, which consist of either the application of brief intermittent ischemia/reperfusion (I/R) cycles or the administration of pharmacological agents. Such strategies reduce cardiac I/R injury by activating protective signaling pathways that prevent the exacerbated production of reactive oxygen/nitrogen species, inhibit opening of mitochondrial permeability transition pore and reduce apoptosis, maintaining normal mitochondrial function. Cardioprotection also involves the activation of mitochondrial quality control (MQC) processes, which replace defective mitochondria or eliminate mitochondrial debris, preserving the structure and function of the network of these organelles, and consequently ensuring homeostasis and survival of cardiomyocytes. Such processes include mitochondrial biogenesis, fission, fusion, mitophagy and mitochondrial-controlled cell death. This review updates recent advances in MQC mechanisms that are activated in the protection conferred by different cardiac conditioning interventions. Furthermore, the role of extracellular vesicles in mitochondrial protection and turnover of these organelles will be discussed. It is concluded that modulation of MQC mechanisms and recognition of mitochondrial targets could provide a potential and selective therapeutic approach for I/R-induced mitochondrial dysfunction.

Sitagliptin Modulates Oxidative, Nitrative and Halogenative Stress and Inflammatory Response in Rat Model of Hepatic Ischemia-Reperfusion

A possibility of repurposing sitagliptin, a well-established antidiabetic drug, for alleviating injury caused by ischemia-reperfusion (IR) is being researched. The aim of this study was to shed some light on the molecular background of the protective activity of sitagliptin during hepatic IR. The expression and/or concentration of inflammation and oxidative stress-involved factors have been determined in rat liver homogenates using quantitative RT-PCR and Luminex^® xMAP^® technology and markers of nitrative and halogenative stress were quantified using targeted metabolomics (LC-MS/MS). Animals (n = 36) divided into four groups were treated with sitagliptin (5 mg/kg) (S and SIR) or saline solution (C and IR), and the livers from IR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). The midkine expression (by 2.2-fold) and the free 3-nitrotyrosine (by 2.5-fold) and IL-10 (by 2-fold) concentration were significantly higher and the Nox4 expression was lower (by 9.4-fold) in the IR than the C animals. As compared to IR, the SIR animals had a lower expression of interleukin-6 (by 4.2-fold) and midkine (by 2-fold), a lower concentration of 3-nitrotyrosine (by 2.5-fold) and a higher Nox4 (by 2.9-fold) and 3-bromotyrosine (by 1.4-fold). In conclusion, IR disturbs the oxidative, nitrative and halogenative balance and aggravates the inflammatory response in the liver, which can be attenuated by low doses of sitagliptin.