Resolution of mitochondrial oxidant stress improves aged-cardiovascular performance

Progress in molecular mechanisms of coronary microvascular dysfunction

Coronary microvascular dysfunction is a high-risk factor for many cardiovascular events. However, because of multiple risk factors and limited understanding about its underlying pathophysiological mechanisms, it was easily misdiagnosed. Therefore, its clinical diagnosis and treatment were greatly restricted. Coronary microcirculation refers to microvessels that play an important role in the physiological regulation of myocardial perfusion and regulating blood flow distribution, fulfilling myocardial metabolic needs and moderating peripheral vascular resistance. In coronary microvascular dysfunction, vascular endothelial celldamage is a critical link. The main feature of early coronary microvascular dysfunction is the impairment of endothelial cell proliferation, adhesion, migration, apoptosis, and secretion. Moreover, coronary microvascular dysfunction risk factors include hyperglycemia, lipid metabolism disorders, ischemia-reperfusion injury, aging, and hypertension, similar to coronary atherosclerosis. There are various mechanisms by which these risk factors harm endothelial function and cause microcirculatory disturbances. Therefore, we reviewed coronary microvascular dysfunction's risk factors and pathogenesis in this article.

Cardiovascular aging: the mitochondrial influence

Age-associated cardiovascular disease is becoming progressively prevalent due to the increased lifespan of the population. However, the fundamental mechanisms underlying the aging process and the corresponding decline in tissue functions are still poorly understood. The heart has a very high energy demand and the cellular energy needed to sustain contraction is primarily generated by mitochondrial oxidative phosphorylation. Mitochondria are also involved in supporting various metabolic processes, as well as activation of the innate immune response and cell death pathways. Given the central role of mitochondria in energy metabolism and cell survival, the heart is highly susceptible to the effects of mitochondrial dysfunction. These key organelles have been implicated as underlying drivers of cardiac aging. Here, we review the evidence demonstrating the mitochondrial contribution to the cardiac aging process and disease susceptibility. We also discuss the potential mechanisms responsible for the age-related decline in mitochondrial function.

Novel Strategies in the Early Detection and Treatment of Endothelial Cell-Specific Mitochondrial Dysfunction in Coronary Artery Disease

Although elevated cholesterol and other recognised cardiovascular risk factors are important in the development of coronary artery disease (CAD) and heart attack, the susceptibility of humans to this fatal process is distinct from other animals. Mitochondrial dysfunction of cells in the arterial wall, particularly the endothelium, has been strongly implicated in the pathogenesis of CAD. In this manuscript, we review the established evidence and mechanisms in detail and explore the potential opportunities arising from analysing mitochondrial function in patient-derived cells such as endothelial colony-forming cells easily cultured from venous blood. We discuss how emerging technology and knowledge may allow us to measure mitochondrial dysfunction as a potential biomarker for diagnosis and risk management. We also discuss the "pros and cons" of animal models of atherosclerosis, and how patient-derived cell models may provide opportunities to develop novel therapies relevant for humans. Finally, we review several targets that potentially alleviate mitochondrial dysfunction working both via direct and indirect mechanisms and evaluate the effect of several classes of compounds in the cardiovascular context.

Mitochondrial calcium and reactive oxygen species in cardiovascular disease

Cardiomyocytes are one of the most mitochondria-rich cell types in the body, with ∼30-40% of the cell volume being composed of mitochondria. Mitochondria are well established as the primary site of adenosine triphosphate (ATP) generation in a beating cardiomyocyte, generating up to 90% of its ATP. Mitochondria have many functions in the cell, which could contribute to susceptibility to and development of cardiovascular disease (CVD). Mitochondria are key players in cell metabolism, ATP production, reactive oxygen species (ROS) production, and cell death. Mitochondrial calcium (Ca2+) plays a critical role in many of these pathways, and thus the dynamics of mitochondrial Ca2+ are important in regulating mitochondrial processes. Alterations in these varied and in many cases interrelated functions play an important role in CVD. This review will focus on the interrelationship of mitochondrial energetics, Ca2+, and ROS and their roles in CVD. Recent insights into the regulation and dysregulation of these pathways have led to some novel therapeutic approaches.

Targeting Mitochondria to Control Ageing and Senescence

Ageing is accompanied by a progressive impairment of cellular function and a systemic deterioration of tissues and organs, resulting in increased vulnerability to multiple diseases. Here, we review the interplay between two hallmarks of ageing, namely, mitochondrial dysfunction and cellular senescence. The targeting of specific mitochondrial features in senescent cells has the potential of delaying or even reverting the ageing process. A deeper and more comprehensive understanding of mitochondrial biology in senescent cells is necessary to effectively face this challenge. Here, we discuss the main alterations in mitochondrial functions and structure in both ageing and cellular senescence, highlighting the differences and similarities between the two processes. Moreover, we describe the treatments available to target these pathways and speculate on possible future directions of anti-ageing and anti-senescence therapies targeting mitochondria.

Effect of Mitochondrial Antioxidant (Mito-TEMPO) on Burn-Induced Cardiac Dysfunction

BACKGROUND

Imbalance of oxidants/antioxidants results in heart failure, contributing to mortality after burn injury. Cardiac mitochondria are a prime source of reactive oxygen species (ROS), and a mitochondrial-specific antioxidant may improve burn-induced cardiomyopathy. We hypothesize that the mitochondrial-specific antioxidant, Triphenylphosphonium chloride (Mito-TEMPO), could protect cardiac function after burn.

STUDY DESIGN

Male rats had a 60% total body surface area (TBSA) scald burn injury and were treated with/without Mito-TEMPO (7 mg/kg-1, intraperitoneal) and harvested at 24 hours post-burn. Echocardiography (ECHO) was used for measurement of heart function. Masson Trichrome and hematoxylin and eosin (H & E) staining were used for cardiac fibrosis and immune response. Qualitative polymerase chain reaction (qPCR) was used for mitochondrial DNA replication and gene expression.

RESULTS

Burn-induced cardiac dysfunction, fibrosis, and mitochondrial damage were assessed by measurement of mitochondrial function, DNA replication, and DNA-encoded electron transport chain-related gene expression. Mito-TEMPO partially improved the abnormal parameters. Burn-induced cardiac dysfunction was associated with crosstalk between the NFE2L2-ARE pathway, PDE5A-PKG pathway, PARP1-POLG-mtDNA replication pathway, and mitochondrial SIRT signaling.

CONCLUSIONS

Mito-TEMPO reversed burn-induced cardiac dysfunction by rescuing cardiac mitochondrial dysfunction. Mitochondria-targeted antioxidants may be an effective therapy for burn-induced cardiac dysfunction.

ZFHX3 knockdown dysregulates mitochondrial adaptations to tachypacing in atrial myocytes through enhanced oxidative stress and calcium overload

AIM

To investigate the role of zinc finger homeobox 3 gene (ZFHX3) in tachypacing-induced mitochondrial dysfunction and explore its molecular mechanisms and potential as a therapeutic target in atrial fibrillation (AF).

METHODS

Through a bioluminescent assay, a patch clamp, confocal fluorescence and fluorescence microscopy, microplate enzyme activity assays and Western blotting, we studied ATP and ADP production, mitochondrial electron transfer chain complex activities, ATP-sensitive potassium channels (I_KATP ), mitochondrial oxidative stress, Ca²⁺ content, and protein expression in control and ZFHX3 knockdown (KD) HL-1 cells subjected to 1 and 5-Hz pacing for 24 hours.

RESULTS

Compared with 1-Hz pacing, 5-Hz pacing increased ATP and ADP production, I_KATP , phosphorylated adenosine monophosphate-activated protein kinase and inositol 1,4,5-triphosphate (IP₃ ) receptor (IP₃ R) protein expression. Tachypacing induced mitochondrial oxidative stress and Ca²⁺ overload in both cell types. Furthermore, under 1- and 5-Hz pacing, ZFHX3 KD cells showed higher I_KATP , ATP and ADP production, mitochondrial oxidative stress and Ca²⁺ content than control cells. Under 5-Hz pacing, 2-aminoethoxydiphenyl borate (2-APB; 3 μmol/L, an IP₃ R inhibitor) and MitoTEMPO (10 µmol/L, a mitochondria-targeted antioxidant) reduced ADP and increased ATP production in both cell types; however, only 2-APB significantly reduced mitochondrial Ca²⁺ overload in control cells. Under 5-Hz pacing, mitochondrial oxidative stress was significantly reduced by both MitoTEMPO and 2-APB and only by 2-APB in control and ZFHX3 KD cells respectively.

CONCLUSION

ZFHX3 KD cells modulate mitochondrial adaptations to tachypacing in HL-1 cardiomyocytes through Ca²⁺ overload, oxidative stress and metabolic disorder. Targeting IP₃ R signalling or oxidative stress could reduce AF.

Riding the tiger - physiological and pathological effects of superoxide and hydrogen peroxide generated in the mitochondrial matrix

Elevated mitochondrial matrix superoxide and/or hydrogen peroxide concentrations drive a wide range of physiological responses and pathologies. Concentrations of superoxide and hydrogen peroxide in the mitochondrial matrix are set mainly by rates of production, the activities of superoxide dismutase-2 (SOD2) and peroxiredoxin-3 (PRDX3), and by diffusion of hydrogen peroxide to the cytosol. These considerations can be used to generate criteria for assessing whether changes in matrix superoxide or hydrogen peroxide are both necessary and sufficient to drive redox signaling and pathology: is a phenotype affected by suppressing superoxide and hydrogen peroxide production; by manipulating the levels of SOD2, PRDX3 or mitochondria-targeted catalase; and by adding mitochondria-targeted SOD/catalase mimetics or mitochondria-targeted antioxidants? Is the pathology associated with variants in SOD2 and PRDX3 genes? Filtering the large literature on mitochondrial redox signaling using these criteria highlights considerable evidence that mitochondrial superoxide and hydrogen peroxide drive physiological responses involved in cellular stress management, including apoptosis, autophagy, propagation of endoplasmic reticulum stress, cellular senescence, HIF1α signaling, and immune responses. They also affect cell proliferation, migration, differentiation, and the cell cycle. Filtering the huge literature on pathologies highlights strong experimental evidence that 30-40 pathologies may be driven by mitochondrial matrix superoxide or hydrogen peroxide. These can be grouped into overlapping and interacting categories: metabolic, cardiovascular, inflammatory, and neurological diseases; cancer; ischemia/reperfusion injury; aging and its diseases; external insults, and genetic diseases. Understanding the involvement of mitochondrial matrix superoxide and hydrogen peroxide concentrations in these diseases can facilitate the rational development of appropriate therapies.

Altered mitochondrial metabolism in the insulin-resistant heart

Obesity-induced insulin resistance and type 2 diabetes mellitus can ultimately result in various complications, including diabetic cardiomyopathy. In this case, cardiac dysfunction is characterized by metabolic disturbances such as impaired glucose oxidation and an increased reliance on fatty acid (FA) oxidation. Mitochondrial dysfunction has often been associated with the altered metabolic function in the diabetic heart, and may result from FA-induced lipotoxicity and uncoupling of oxidative phosphorylation. In this review, we address the metabolic changes in the diabetic heart, focusing on the loss of metabolic flexibility and cardiac mitochondrial function. We consider the alterations observed in mitochondrial substrate utilization, bioenergetics and dynamics, and highlight new areas of research which may improve our understanding of the cause and effect of cardiac mitochondrial dysfunction in diabetes. Finally, we explore how lifestyle (nutrition and exercise) and pharmacological interventions can prevent and treat metabolic and mitochondrial dysfunction in diabetes.

The Aging Heart: Mitophagy at the Center of Rejuvenation

Aging is associated with structural and functional changes in the heart and is a major risk factor in developing cardiovascular disease. Many recent studies have focused on increasing our understanding of the basis of aging at the cellular and molecular levels in various tissues, including the heart. It is known that there is an age-related decline in cellular quality control pathways such as autophagy and mitophagy, which leads to accumulation of potentially harmful cellular components in cardiac myocytes. There is evidence that diminished autophagy and mitophagy accelerate the aging process, while enhancement preserves cardiac homeostasis and extends life span. Here, we review the current knowledge of autophagy and mitophagy in aging and discuss how age-associated alterations in these processes contribute to cardiac aging and age-related cardiovascular diseases.

Improved Cardiovascular Function in Old Mice After N-Acetyl Cysteine and Glycine Supplemented Diet: Inflammation and Mitochondrial Factors

Metabolic, inflammatory, and functional changes occur in cardiovascular aging which may stem from oxidative stress and be remediable with antioxidants. Glutathione, an intracellular antioxidant, declines with aging, and supplementation with glutathione precursors, N-acetyl cysteine (NAC) and glycine (Gly), increases tissue glutathione. Thirty-month old mice were fed diets supplemented with NAC or NAC+Gly and, after 7 weeks, cardiac function and molecular studies were performed. The NAC+Gly supplementation improved diastolic function, increasing peak early filling velocity, and reducing relaxation time, left atrial volume, and left ventricle end diastolic pressure. By contrast, cardiac function did not improve with NAC alone. Both diet supplementations decreased cardiac levels of inflammatory mediators; only NAC+Gly reduced leukocyte infiltration. Several mitochondrial genes reduced with aging were upregulated in hearts by NAC+Gly diet supplementation. These Krebs cycle and oxidative phosphorylation enzymes, suggesting improved mitochondrial function, and permeabilized cardiac fibers from NAC+Gly-fed mice produced ATP from carbohydrate and fatty acid sources, whereas fibers from control old mice were less able to utilize fatty acids. Our data indicate that NAC+Gly supplementation can improve diastolic function in the old mouse and may have potential to prevent important morbidities for older people.

Trimetazidine and l‑carnitine prevent heart aging and cardiac metabolic impairment in rats via regulating cardiac metabolic substrates

BACKGROUND

This study aimed to investigate the effects of trimetazidine and l‑carnitine on heart aging and cardiac metabolism in the natural aging rats and explore the possible mechanism regarding the regulation of cardiac metabolic substrates.

METHODS

A total of 28 young (2-month-old) and 28 aged (14-month-old) male Sprague-Dawley rats were randomly allocated to the following groups: young control (YC, n = 8), young trimetazidine (YT, n = 10), young l‑carnitine (YL, n = 10), aging control (AC, n = 8), aging trimetazidine (AT, n = 10), and aging l‑carnitine (AL, n = 10). All rats were intragastrically treated with saline, trimetazidine, or l‑carnitine for 4 weeks. Blood sample parameters (MDA, SOD, Glu, TG, TC, LDL-c, HDL-c, AST, ALT, ALP, BUN, Cr, LDH), Echocardiographic paramerters, ATP levels of cardiac apex, cardiac pathology (HE staining and mitochondrial ultrastructures), and cardiac metabolism-related parameters (glucose transporter type-4[GLUT-4], carnitine palmitoyl transferase‑1[CPT-1]) were analyzed in each group.

RESULTS

The left ventricular ejection fractions were normal in most groups, with a higher value observed in the AT group than in the AC group. The AC group showed decreased ATP levels of cardiac apex compared with the YC group. But both trimetazidine and l‑carnitine attenuated the aging-induced decrease in ATP levels of cardiac apex. The AC group also showed increased myocardial fiber fragmentations and dissolutions, and interstitial proliferation compared with the YC group. However both trimetazidine and l‑carnitine protected against the aging-induced pathological changes in myocardium. Furthermore, both trimetazidine and l‑carnitine prevented mitochondria of cardiomyocytes from aging-induced injury. Both the AT and AL groups had significantly fewer focal cavitations and higher mitochondrial matrix electron densities than the AC group. GLUT-4 and CPT-1 protein levels were significantly lower while GLUT-4/CPT-1 ratios were higher in aging rats than YC rats. The AT and AL groups had significantly higher GLUT-4 and CPT-1 levels than the AC group, with more significant changes observed in the AT group.

CONCLUSIONS

Trimetazidine and l‑carnitine may partially improve the age-related changes of rat myocardial metabolisms and heart function via regulating cardiac metabolic substrates, with trimetazidine being superior. Interestingly, they may also reduce cardiac energy generation and impair mitochondrial structures in young rats. These findings suggest that age should be taken as an independent factor during the use of metabolic modulatory drugs in the patients with cardiovascular diseases because it may completely change the effects of drugs.

Mitochondria and aging: A role for the mitochondrial transition pore?

The cellular mechanisms responsible for aging are poorly understood. Aging is considered as a degenerative process induced by the accumulation of cellular lesions leading progressively to organ dysfunction and death. The free radical theory of aging has long been considered the most relevant to explain the mechanisms of aging. As the mitochondrion is an important source of reactive oxygen species (ROS), this organelle is regarded as a key intracellular player in this process and a large amount of data supports the role of mitochondrial ROS production during aging. Thus, mitochondrial ROS, oxidative damage, aging, and aging-dependent diseases are strongly connected. However, other features of mitochondrial physiology and dysfunction have been recently implicated in the development of the aging process. Here, we examine the potential role of the mitochondrial permeability transition pore (mPTP) in normal aging and in aging-associated diseases.

[The influence of Cytoflavin therapy on the cerebral hemodynamics in patients with various stages of hypertensive disease]

AIM

To study an influence of cytoflavin therapy on the cerebral hemodynamics in patients with various stages of hypertensive disease (HD).

MATERIAL AND METHODS

One hundred and forty patients with HD, I-III stages, were randomized into 2 groups: patients of group 1 received complex treatment (antihypertensive therapy and cytoflavin), patients of group 2 were treated with antihypertensive therapy. The control group consisted of 30 healthy people. The changes in cerebral hemodynamics using the algorithm of the complex ultrasound study of cerebral vascular system were assessed.

RESULTS

Disturbances of hemodynamics at all structural/functional levels of cerebral vascular system were found in all HD stages. There were a decrease in the blood flow through the common carotid, inner carotid, spinal and middle cerebral arteries, reactivity of veins of Rosenthal, blood flow through veins of Rosenthal and inner jugular veins and an increase of blood flow through spinal veins. The hemodynamic study showed that in group 1 there was the increase of blood flow through common carotid, inner carotid, middle cerebral arteries in stage I and through spinal arteries in stage I-II of HD; improvement of the reactivity of veins of Rosenthal, restoration of blood flow parameters through the veins of Rosenthal and inner jugular veins to control values, the decrease in blood flow velocity through the spinal veins in all HD stages.

CONCLUSION

HD is accompanied by the damage of all structural/functional levels of cerebral vascular system. The use of cytoflavin in the complex therapy of HD exerts a positive influence on the cerebral hemodynamics reducing the severity of arterial insufficiency in the initial stages of disease, improving microcirculation and venous hemodynamics in all HD stages.

Mitochondrial-Targeted Antioxidant Maintains Blood Flow, Mitochondrial Function, and Redox Balance in Old Mice Following Prolonged Limb Ischemia

Aging is a major factor in the decline of limb blood flow with ischemia. However, the underlying mechanism remains unclear. We investigated the role of mitochondrial reactive oxygen species (ROS) with regard to limb perfusion recovery in aging during ischemia. We performed femoral artery ligation in young and old mice with or without treatment with a scavenger of mitochondrial superoxide, MitoTEMPO (180 μg/kg/day, from pre-operative day 7 to post-operative day (POD) 21) infusion using an implanted mini-pump. The recoveries of cutaneous blood flow in the ischemic hind limb were lower in old mice than in young mice but were improved in MitoTEMPO-treated old mice. Mitochondrial DNA damage appeared in ischemic aged muscles but was eliminated by MitoTEMPO treatment. For POD 2, MitoTEMPO treatment suppressed the expression of p53 and the ratio of Bax/Bcl2 and upregulated the expression of hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF) in ischemic aged skeletal muscles. For POD 21, MitoTEMPO treatment preserved the expression of PGC-1α in ischemic aged skeletal muscle. The ischemic soleus of old mice showed a lower mitochondrial respiratory control ratio in POD 21 compared to young mice, which was recovered in MitoTEMPO-treated old mice. Scavenging of mitochondrial superoxide attenuated mitochondrial DNA damage and preserved the mitochondrial respiration, in addition to suppression of the expression of p53 and preservation of the expression of peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) in ischemic skeletal muscles with aging. Resolution of excessive mitochondrial superoxide could be an effective therapy to recover blood flow of skeletal muscle during ischemia in senescence.