Mitochondrial permeability transition pore opening as a promising therapeutic target in cardiac diseases

Permeabilization of the outer mitochondrial membrane: Mechanisms and consequences

Permeabilization of the outer mitochondrial membrane is а physiological process that can allow certain molecules to pass through it, such as low molecular weight solutes required for cellular respiration. This process is also important for the development of various modes of cell death. Depending on the severity of this process, cells can die by autophagy, apoptosis, or necrosis/necroptosis. Distinct types of pores can be opened at the outer mitochondrial membrane depending on physiological or pathological stimuli, and different mechanisms can be activated in order to open these pores. In this comprehensive review, all these types of permeabilization, the mechanisms of their activation, and their role in various diseases are discussed.

The role of miRNA-29b1 on the hypoxia-induced apoptosis in mammalian cardiomyocytes

Cardiomyocyte apoptosis is a complex biological process involving the interaction of many factors and signaling pathways. In hypoxic environment, cardiomyocytes may trigger apoptosis due to insufficient energy supply, increased production of oxygen free radicals, and disturbance of intracellular calcium ion balance. The present research aimed to investigate the role of microRNA-29b1 (miR-29b1) in hypoxia-treated cardiomyocytes and its potential mechanism involved. We established an in vitro ischemia model using AC16 and H9C2 cardiomyocytes through hypoxia treatment (1% O2, 48 h). Cell apoptosis was evaluated by flow cytometry using Annexin V FITC-PI staining assay. Moreover, we used Western blot and immunofluorescence analysis to determine the expression of Bcl-2, Bax caspase-3 and Cx43 proteins. We found that miR-29b1 protected AC16 and H9C2 cells from hypoxia-induced injury as evidence that miR-29b1 attenuated the effects of hypoxia treatment on AC16 and H9C2 cell apoptosis after hypoxia treatment. In conclusion, our findings suggest that miR-29b1 may have potential cardiovascular protective effects during ischemia-related myocardial injury.

Inhibition of the mPTP and Lipid Peroxidation Is Additively Protective Against I/R Injury

BACKGROUND

During myocardial ischemia/reperfusion (I/R) injury, high levels of matrix Ca2+ and reactive oxygen species (ROS) induce the opening of the mitochondrial permeability transition pore (mPTP), which causes mitochondrial dysfunction and ultimately necrotic death. However, the mechanisms of how these triggers individually or cooperatively open the pore have yet to be determined.

METHODS

Here, we use a combination of isolated mitochondrial assays and in vivo I/R surgery in mice. We challenged isolated liver and heart mitochondria with Ca2+, ROS, and Fe2+ to induce mitochondrial swelling. Using inhibitors of the mPTP (cyclosporine A or ADP) lipid peroxidation (ferrostatin-1, MitoQ), we determined how the triggers elicit mitochondrial damage. Additionally, we used the combination of inhibitors during I/R injury in mice to determine if dual inhibition of these pathways is additivity protective.

RESULTS

In the absence of Ca2+, we determined that ROS fails to trigger mPTP opening. Instead, high levels of ROS induce mitochondrial dysfunction and rupture independently of the mPTP through lipid peroxidation. As expected, Ca2+ in the absence of ROS induces mPTP-dependent mitochondrial swelling. Subtoxic levels of ROS and Ca2+ synergize to induce mPTP opening. Furthermore, this synergistic form of Ca2+- and ROS-induced mPTP opening persists in the absence of CypD (cyclophilin D), suggesting the existence of a CypD-independent mechanism for ROS sensitization of the mPTP. These ex vivo findings suggest that mitochondrial dysfunction may be achieved by multiple means during I/R injury. We determined that dual inhibition of the mPTP and lipid peroxidation is significantly more protective against I/R injury than individually targeting either pathway alone.

CONCLUSIONS

In the present study, we have investigated the relationship between Ca2+ and ROS, and how they individually or synergistically induce mitochondrial swelling. Our findings suggest that Ca2+ mediates mitochondrial damage through the opening of the mPTP, although ROS mediates its damaging effects through lipid peroxidation. However, subtoxic levels both Ca2+ and ROS can induce mPTP-mediated mitochondrial damage. Targeting both of these triggers to preserve mitochondria viability unveils a highly effective therapeutic approach for mitigating I/R injury.

Warm Cells, Hot Mitochondria: Achievements and Problems of Ultralocal Thermometry

Temperature is a crucial regulator of the rate and direction of biochemical reactions and cell processes. The recent data indicating the presence of local thermal gradients associated with the sites of high-rate thermogenesis, on the one hand, demonstrate the possibility for the existence of "thermal signaling" in a cell and, on the other, are criticized on the basis of thermodynamic calculations and models. Here, we review the main thermometric techniques and sensors developed for the determination of temperature inside living cells and diverse intracellular compartments. A comparative analysis is conducted of the results obtained using these methods for the cytosol, nucleus, endo-/sarcoplasmic reticulum, and mitochondria, as well as their biological consistency. Special attention is given to the limitations, possible sources of errors and ambiguities of the sensor's responses. The issue of biological temperature limits in cells and organelles is considered. It is concluded that the elaboration of experimental protocols for ultralocal temperature measurements that take into account both the characteristics of biological systems, as well as the properties and limitations of each type of sensor is of critical importance for the generation of reliable results and further progress in this field.

Mitochondrial Volume Regulation and Swelling Mechanisms in Cardiomyocytes

Mitochondrion, known as the "powerhouse" of the cell, regulates ion homeostasis, redox state, cell proliferation and differentiation, and lipid synthesis. The inner mitochondrial membrane (IMM) controls mitochondrial metabolism and function. It possesses high levels of proteins that account for ~70% of the membrane mass and are involved in the electron transport chain, oxidative phosphorylation, energy transfer, and ion transport, among others. The mitochondrial matrix volume plays a crucial role in IMM remodeling. Several ion transport mechanisms, particularly K+ and Ca2+, regulate matrix volume. Small increases in matrix volume through IMM alterations can activate mitochondrial respiration, whereas excessive swelling can impair the IMM topology and initiates mitochondria-mediated cell death. The opening of mitochondrial permeability transition pores, the well-characterized phenomenon with unknown molecular identity, in low- and high-conductance modes are involved in physiological and pathological increases of matrix volume. Despite extensive studies, the precise mechanisms underlying changes in matrix volume and IMM structural remodeling in response to energy and oxidative stressors remain unknown. This review summarizes and discusses previous studies on the mechanisms involved in regulating mitochondrial matrix volume, IMM remodeling, and the crosstalk between these processes.

Diplacone Isolated from Paulownia tomentosa Mature Fruit Induces Ferroptosis-Mediated Cell Death through Mitochondrial Ca2+ Influx and Mitochondrial Permeability Transition

The recently defined type of cell death ferroptosis has garnered significant attention as a potential new approach to cancer treatment owing to its more immunogenic nature when compared with apoptosis. Ferroptosis is characterized by the depletion of glutathione (GSH)/glutathione peroxidase-4 (GPx4) and iron-dependent lipid peroxidation. Diplacone (DP), a geranylated flavonoid compound found in Paulownia tomentosa fruit, has been identified to have anti-inflammatory and anti-radical activity. In this study, the potential anticancer activity of DP was explored against A549 human lung cancer cells. It was found that DP induced a form of cytotoxicity distinct from apoptosis, which was accompanied by extensive mitochondrial-derived cytoplasmic vacuoles. DP was also shown to increase mitochondrial Ca2+ influx, reactive oxygen species (ROS) production, and mitochondrial permeability transition (MPT) pore-opening. These changes led to decreases in mitochondrial membrane potential and DP-induced cell death. DP also induced lipid peroxidation and ATF3 expression, which are hallmarks of ferroptosis. The ferroptosis inhibitors ferrostatin-1 and liproxstatin-1 were effective in counteracting the DP-mediated ferroptosis-related features. Our results could contribute to the use of DP as a ferroptosis-inducing agent, enabling studies focusing on the relationship between ferroptosis and the immunogenic cell death of cancer cells.

UBA52 Attunes VDAC1-Mediated Mitochondrial Dysfunction and Dopaminergic Neuronal Death

Mitochondrial homeostasis regulates energy metabolism, calcium buffering, cell function, and apoptosis. The present study has been conducted to investigate the implications of the ubiquitin-encoding gene UBA52 in mitochondrial physiology. Transient expression of Myc-UBA52 in neurons significantly inhibited the rotenone-induced increase in reactive oxygen species generation, nitrite level, and depleted glutathione level. Mass spectrometric and coimmunoprecipitation data suggested the profound interaction of UBA52 with mitochondrial outer membrane channel protein, VDAC1 in both the wild-type and Myc-α-synuclein overexpressed neuronal cells and in the Parkinson's disease (PD)-specific substantia nigra and striatal region of the rat brain. In vitro ubiquitylation assay revealed that UBA52 participates in the ubiquitylation of VDAC1 through E3 ligase CHIP. Myc-UBA52 overexpression in neurons further improved the mitochondrial functionality and cell viability by preventing the alteration in mitochondrial membrane potential, mitochondrial complex I activity, and translocation of cytochrome c and p-Nrf2 along with the effect on intracellular calcium uptake, thus collectively inhibiting the opening of mitochondrial permeability transition pore. Additionally, Myc-UBA52 expression in neuronal cells offered protection against apoptotic and autophagic cell death. Altogether, our findings delineate a functional association between UBA52 and mitochondrial homeostasis, providing new insights into the deterrence of dopaminergic cell death during acute PD pathogenesis.

Multiple Sclerosis: Inflammatory and Neuroglial Aspects

Multiple sclerosis (MS) represents the most common acquired demyelinating disorder of the central nervous system (CNS). Its pathogenesis, in parallel with the well-established role of mechanisms pertaining to autoimmunity, involves several key functions of immune, glial and nerve cells. The disease's natural history is complex, heterogeneous and may evolve over a relapsing-remitting (RRMS) or progressive (PPMS/SPMS) course. Acute inflammation, driven by infiltration of peripheral cells in the CNS, is thought to be the most relevant process during the earliest phases and in RRMS, while disruption in glial and neural cells of pathways pertaining to energy metabolism, survival cascades, synaptic and ionic homeostasis are thought to be mostly relevant in long-standing disease, such as in progressive forms. In this complex scenario, many mechanisms originally thought to be distinctive of neurodegenerative disorders are being increasingly recognized as crucial from the beginning of the disease. The present review aims at highlighting mechanisms in common between MS, autoimmune diseases and biology of neurodegenerative disorders. In fact, there is an unmet need to explore new targets that might be involved as master regulators of autoimmunity, inflammation and survival of nerve cells.

ALDH2 attenuates ischemia and reperfusion injury through regulation of mitochondrial fusion and fission by PI3K/AKT/mTOR pathway in diabetic cardiomyopathy

The function of mitochondrial fusion and fission is one of the important factors causing ischemia-reperfusion (I/R) injury in diabetic myocardium. Aldehyde dehydrogenase 2 (ALDH2) is abundantly expressed in heart, which involved in the regulation of cellular energy metabolism and stress response. However, the mechanism of ALDH2 regulating mitochondrial fusion and fission in diabetic myocardial I/R injury has not been elucidated. In the present study, we found that the expression of ALDH2 was downregulated in rat diabetic myocardial I/R model. Functionally, the activation of ALDH2 resulted in the improvement of cardiac hemodynamic parameters and myocardial injury, which were abolished by the treatment of Daidzin, a specific inhibitor of ALDH2. In H9C2 cardiomyocyte hypoxia-reoxygenation model, ALDH2 regulated the dynamic balance of mitochondrial fusion and fission and maintained mitochondrial morphology stability. Meanwhile, ALDH2 reduced mitochondrial ROS levels, and apoptotic protein expression in cardiomyocytes, which was associated with the upregulation of phosphorylation (p-PI3K_Tyr458, p-AKT_Ser473, p-mTOR). Moreover, ALDH2 suppressed the mitoPTP opening through reducing 4-HNE. Therefore, our results demonstrated that ALDH2 alleviated the ischemia and reperfusion injury in diabetic cardiomyopathy through inhibition of mitoPTP opening and activation of PI3K/AKT/mTOR pathway.

Mechanisms of Mitochondrial Apoptosis-Mediated Meat Tenderization Based on Quantitative Phosphoproteomic Analysis

This study investigates the mechanism of phosphorylation in the regulation of apoptosis-mediated meat tenderization during postmortem aging. The results found that the pork muscle exhibited apoptotic potential at early postmortem (48 h) and showed more tenderness at late postmortem, as evidenced by the increase in mitochondrial membrane permeability (MMP), Ca2+ level, reactive oxygen species (ROS) content, and caspases activity at 0 h to 48 h, and decreases in ATP level at 0 h to 24 h and shear force at 12 h to 120 h (p < 0.05). Phosphoproteomic analysis revealed that phosphorylation regulated apoptosis by modulating ATP and calcium bindings as well as apoptotic signaling, which occurred within early 12 h and mainly occurred at 12 h to 48 h postmortem. Moreover, differential expression of phosphoproteins demonstrated that phosphorylation regulated oxidative stress-induced apoptosis and rigor mortis, thereby promoting the development of meat tenderness. Our results provide insights into the roles of phosphorylation in various physiological processes that affect meat tenderness.

Beneficial effects of Cyclosporine A in combination with Nortriptyline on germ cell-specific apoptosis, oxidative stress and epididymal sperm qualities following testicular ischemia/reperfusion in rats: a comparative study

Background

Testicular torsion is a pathological condition which needs emergency surgical intervention. However, after surgical reperfusion, oxidative stress factors cause to germ cell apoptosis. The study was planned to evaluate the efficacy of simultaneous use of Cyclosporine A (CsA) and Nortriptyline (Nort) to repair testicular damages in an experimental torsion/detorsion (T/D) rat model.

Methods

Male rats (n = 112) were allocated into 7 groups 16 each in; (Group 1); Control group, (Group 2); T/D group, (Group 3–4); CsA 1 and 5 mg/kg, (Group 5–6); Nort 2 and 10 mg/kg and (Group 7); concurrent group, CsA (1 mg/kg) + Nort (2 mg/kg). Right uni-lateral torsion was inducted by twisting testis 720 degrees in the clockwise direction for 1 h. For short-term and mid-term studies, lipid peroxidation, antioxidant enzyme activities, caspase-3 level, histopathological changes and germ cell apoptosis were evaluated. Moreover, in long-term investigation, semen analysis was performed.

Results

After T/D induction, testis abnormalities both functional and structural were appeared. Pre- and post-treatment with CsA and Nort, separately, reduced MDA and caspase-3 levels, normalized antioxidant levels, ameliorate tissue injury and improved sperm criteria.

Conclusion

The antioxidant and anti-apoptotic characteristics of CsA and Nort and their protective effects have been shown in our study. Concurrent administration of CsA and Nort in selected low-dose indicated a significant positive effect as compared to the individual drug interventions on the reversal of T/D induced oxidative stress in short-term, apoptosis, and histologic changes in mid-term, as well as semen criteria in the long-term appraisal.

CD137 Signal Mediates Cardiac Ischemia-Reperfusion Injury by Regulating the Necrosis of Cardiomyocytes

The injury of cardiomyocytes after ischemia-reperfusion is the main reason of cardiac dysfunction. Necrosis is one of the methods of programmed cell death and cardiomyocyte necrosis occurs in the process of reperfusion. The activation of CD137 signal is involved in various diseases. In vivo experiments proved that CD137^-/- mice have less heart damage than wild-type mice after ischemia-reperfusion. In vitro experiments, we found that after inhibiting the CD137 signal, the degree of necrosis of HL-1 cells was reduced and it was caused by reducing the Ca2 + overload in the mitochondria, which caused the reduction of mPTP opening. Ca2 + overload in mitochondria induced by activation of CD137 signal was caused by increased Ca2 + released into mitochondria by activation of IP3R and increased MCU level. These results indicate that CD137 signaling aggravates cardiac ischemia-reperfusion injury by inducing myocardial cell necrosis.

Chemotherapy Resistance: Role of Mitochondrial and Autophagic Components

Simple Summary

Chemotherapy resistance is a common occurrence during cancer treatment that cancer researchers are attempting to understand and overcome. Mitochondria are a crucial intracellular signaling core that are becoming important determinants of numerous aspects of cancer genesis and progression, such as metabolic reprogramming, metastatic capability, and chemotherapeutic resistance. Mitophagy, or selective autophagy of mitochondria, can influence both the efficacy of tumor chemotherapy and the degree of drug resistance. Regardless of the fact that mitochondria are well-known for coordinating ATP synthesis from cellular respiration in cellular bioenergetics, little is known its mitophagy regulation in chemoresistance. Recent advancements in mitochondrial research, mitophagy regulatory mechanisms, and their implications for our understanding of chemotherapy resistance are discussed in this review.

Abstract

Cancer chemotherapy resistance is one of the most critical obstacles in cancer therapy. One of the well-known mechanisms of chemotherapy resistance is the change in the mitochondrial death pathways which occur when cells are under stressful situations, such as chemotherapy. Mitophagy, or mitochondrial selective autophagy, is critical for cell quality control because it can efficiently break down, remove, and recycle defective or damaged mitochondria. As cancer cells use mitophagy to rapidly sweep away damaged mitochondria in order to mediate their own drug resistance, it influences the efficacy of tumor chemotherapy as well as the degree of drug resistance. Yet despite the importance of mitochondria and mitophagy in chemotherapy resistance, little is known about the precise mechanisms involved. As a consequence, identifying potential therapeutic targets by analyzing the signal pathways that govern mitophagy has become a vital research goal. In this paper, we review recent advances in mitochondrial research, mitophagy control mechanisms, and their implications for our understanding of chemotherapy resistance.

Analysis of Mitochondrial Function, Structure, and Intracellular Organization In Situ in Cardiomyocytes and Skeletal Muscles

Analysis of the function, structure, and intracellular organization of mitochondria is important for elucidating energy metabolism and intracellular energy transfer. In addition, basic and clinically oriented studies that investigate organ/tissue/cell dysfunction in various human diseases, including myopathies, cardiac/brain ischemia-reperfusion injuries, neurodegenerative diseases, cancer, and aging, require precise estimation of mitochondrial function. It should be noted that the main metabolic and functional characteristics of mitochondria obtained in situ (in permeabilized cells and tissue samples) and in vitro (in isolated organelles) are quite different, thereby compromising interpretations of experimental and clinical data. These differences are explained by the existence of the mitochondrial network, which possesses multiple interactions between the cytoplasm and other subcellular organelles. Metabolic and functional crosstalk between mitochondria and extra-mitochondrial cellular environments plays a crucial role in the regulation of mitochondrial metabolism and physiology. Therefore, it is important to analyze mitochondria in vivo or in situ without their isolation from the natural cellular environment. This review summarizes previous studies and discusses existing approaches and methods for the analysis of mitochondrial function, structure, and intracellular organization in situ.

Beta-Amyloid Instigates Dysfunction of Mitochondria in Cardiac Cells

Alzheimer's disease (AD) includes the formation of extracellular deposits comprising aggregated β-amyloid (Aβ) fibers associated with oxidative stress, inflammation, mitochondrial abnormalities, and neuronal loss. There is an associative link between AD and cardiac diseases; however, the mechanisms underlying the potential role of AD, particularly Aβ in cardiac cells, remain unknown. Here, we investigated the role of mitochondria in mediating the effects of Aβ1-40 and Aβ1-42 in cultured cardiomyocytes and primary coronary endothelial cells. Our results demonstrated that Aβ1-40 and Aβ1-42 are differently accumulated in cardiomyocytes and coronary endothelial cells. Aβ1-42 had more adverse effects than Aβ1-40 on cell viability and mitochondrial function in both types of cells. Mitochondrial and cellular ROS were significantly increased, whereas mitochondrial membrane potential and calcium retention capacity decreased in both types of cells in response to Aβ1-42. Mitochondrial dysfunction induced by Aβ was associated with apoptosis of the cells. The effects of Aβ1-42 on mitochondria and cell death were more evident in coronary endothelial cells. In addition, Aβ1-40 and Aβ1-42 significantly increased Ca2+ -induced swelling in mitochondria isolated from the intact rat hearts. In conclusion, this study demonstrates the toxic effects of Aβ on cell survival and mitochondria function in cardiac cells.

Quercetin and vitamin E ameliorate cardio-apoptotic risks in diabetic rats

Apoptosis is upregulated in all forms of diabetes, and the mitochondria act as target in diabetes pathophysiology. Quercetin and vitamin E have both shown usefulness in the delay of progression of diabetes-induced complications. However, their effect on the apoptotic process in diabetes mellitus is unknown. We hypothesize that quercetin treatment in diabetes may decrease the propensity for cardiomyocytic death via regulation of the mitochondria permeability transition (mPT) pore opening. Hearts from normal and streptozotocin-induced diabetic rats were used for the study. Low ionic strength heart mitochondria were used for swelling assay and mitochondrial lipid peroxidation (mLPO) activity was spectrophotometrically assessed. Levels of cytochrome c and caspase 3 and 9 were determined by immunohistochemistry, while lesions assessed by histology. Diabetic heart mPT pore showed larger amplitude swelling than control, while mLPO levels were increased in diabetic rats relative to control, this resulted in cytochrome c release. This initiated increased caspase 3 and 9 activity in diabetic rats (p < 0.05). Histology showed hemorrhagic lesions in diabetic rat hearts. Quercetin and vitamin E treatment reversed these effects, suggestive of their anti-apoptotic effect. Quercetin and vitamin E protection in diabetes is mediated by mPT pore inhibition and modulation of mitochondrial-mediated apoptosis.

Neurogenic Hypertension Mediated Mitochondrial Abnormality Leads to Cardiomyopathy: Contribution of UPRmt and Norepinephrine-miR- 18a-5p-HIF-1α Axis

Aims: Hypertension increases the risk of heart disease. Hallmark features of hypertensive heart disease is sympathoexcitation and cardiac mitochondrial abnormality. However, the molecular mechanisms for specifically neurally mediated mitochondrial abnormality and subsequent cardiac dysfunction are unclear. We hypothesized that enhanced sympatho-excitation to the heart elicits cardiac miR-18a-5p/HIF-1α and mitochondrial unfolded protein response (UPRmt) signaling that lead to mitochondrial abnormalities and consequent pathological cardiac remodeling. Methods and Results: Using a model of neurogenic hypertension (NG-HTN), induced by intracerebroventricular (ICV) infusion of Ang II (NG-HTN; 20 ng/min, 14 days, 0.5 μl/h, or Saline; Control, 0.9%) through osmotic mini-pumps in Sprague-Dawley rats (250-300 g), we attempted to identify a link between sympathoexcitation (norepinephrine; NE), miRNA and HIF-1α signaling and UPRmt to produce mitochondrial abnormalities resulting in cardiomyopathy. Cardiac remodeling, mitochondrial abnormality, and miRNA/HIF-1α signaling were assessed using histology, immunocytochemistry, electron microscopy, Western blotting or RT-qPCR. NG-HTN demonstrated increased sympatho-excitation with concomitant reduction in UPRmt, miRNA-18a-5p and increased level of HIF-1α in the heart. Our in silico analysis indicated that miR-18a-5p targets HIF-1α. Direct effects of NE on miRNA/HIF-1α signaling and mitochondrial abnormality examined using H9c2 rat cardiomyocytes showed NE reduces miR-18a-5p but increases HIF-1α. Electron microscopy revealed cardiac mitochondrial abnormality in NG-HTN, linked with hypertrophic cardiomyopathy and fibrosis. Mitochondrial unfolded protein response was decreased in NG-HTN indicating mitochondrial proteinopathy and proteotoxic stress, associated with increased mito-ROS and decreased mitochondrial membrane potential (ΔΨm), and oxidative phosphorylation. Further, there was reduced cardiac mitochondrial biogenesis and fusion, but increased mitochondrial fission, coupled with mitochondrial impaired TIM-TOM transport and UPRmt. Direct effects of NE on H9c2 rat cardiomyocytes also showed cardiomyocyte hypertrophy, increased mitochondrial ROS generation, and UPRmt corroborating the in vivo data. Conclusion: In conclusion, enhanced sympatho-excitation suppress miR-18a-5p/HIF-1α signaling and increased mitochondrial stress proteotoxicity, decreased UPRmt leading to decreased mitochondrial dynamics/OXPHOS/ΔΨm and ROS generation. Taken together, these results suggest that ROS induced mitochondrial transition pore opening activates pro-hypertrophy/fibrosis/inflammatory factors that induce pathological cardiac hypertrophy and fibrosis commonly observed in NG-HTN.

Lycopene Regulates Dietary Dityrosine-Induced Mitochondrial-Lipid Homeostasis by Increasing Mitochondrial Complex Activity

SCOPE

Dityrosine (DT), a marker of protein oxidation, is widely found in many high-protein foods. Dietary intake of DT induces myocardial oxidative stress injury and impairs energy metabolism. Lycopene is a common dietary supplement with antioxidant and mitochondrial-lipid homeostasis modulating abilities. This study aimed to examine the effects of lycopene on DT-induced disturbances in myocardial function and energy metabolism.

METHODS AND RESULTS

Four-week-old C57BL/6J mice received intragastric administration of either tyrosine (420 µg kg^-1 BW), DT (420 µg kg^-1 BW), or lycopene at high (10 mg kg^-1 BW) and low (5 mg kg^-1 BW) doses for 35 days. Lycopene administration effectively reduced oxidative stress, cardiac fatty acid accumulation, and cardiac hypertrophy and improved mitochondrial performance in DT-induced mice. In vitro experiments in H9c2 cells showed that DT directly inhibited the activity of the respiratory chain complex, whereas oxidative phosphorylation and β-oxidation gene expression is upregulated. Lycopene enhanced the activity of the complexes and inhibited ROS production caused by compensatory regulation.

CONCLUSION

Lycopene improves DT-mediated myocardial energy homeostasis disorder by promoting the activity of respiratory chain complexes I and IV and alleviates the accumulation of cardiac fatty acids and myocardial hypertrophy.

Role of the Mitochondrial Protein Import Machinery and Protein Processing in Heart Disease

Mitochondria are essential organelles for cellular energy production, metabolic homeostasis, calcium homeostasis, cell proliferation, and apoptosis. About 99% of mammalian mitochondrial proteins are encoded by the nuclear genome, synthesized as precursors in the cytosol, and imported into mitochondria by mitochondrial protein import machinery. Mitochondrial protein import systems function not only as independent units for protein translocation, but also are deeply integrated into a functional network of mitochondrial bioenergetics, protein quality control, mitochondrial dynamics and morphology, and interaction with other organelles. Mitochondrial protein import deficiency is linked to various diseases, including cardiovascular disease. In this review, we describe an emerging class of protein or genetic variations of components of the mitochondrial import machinery involved in heart disease. The major protein import pathways, including the presequence pathway (TIM23 pathway), the carrier pathway (TIM22 pathway), and the mitochondrial intermembrane space import and assembly machinery, related translocases, proteinases, and chaperones, are discussed here. This review highlights the importance of mitochondrial import machinery in heart disease, which deserves considerable attention, and further studies are urgently needed. Ultimately, this knowledge may be critical for the development of therapeutic strategies in heart disease.

Sleep/wake calcium dynamics, respiratory function, and ROS production in cardiac mitochondria

Introduction

Incidents of myocardial infarction and sudden cardiac arrest vary with time of the day, but the mechanism for this effect is not clear. We hypothesized that diurnal changes in the ability of cardiac mitochondria to control calcium homeostasis dictate vulnerability to cardiovascular events.

Objectives

Here we investigate mitochondrial calcium dynamics, respiratory function, and reactive oxygen species (ROS) production in mouse heart during different phases of wake versus sleep periods.

Methods

We assessed time-of-the-day dependence of calcium retention capacity of isolated heart mitochondria from young male C57BL6 mice. Rhythmicity of mitochondrial-dependent oxygen consumption, ROS production and transmembrane potential in homogenates were explored using the Oroboros O2k Station equipped with a fluorescence detection module. Changes in expression of essential clock and calcium dynamics genes/proteins were also determined at sleep versus wake time points.

Results

Our results demonstrate that cardiac mitochondria exhibit higher calcium retention capacity and higher rates of calcium uptake during sleep period. This was associated with higher expression of clock gene Bmal1, lower expression of per2, greater expression of MICU1 gene (mitochondrial calcium uptake 1), and lower expression of the mitochondrial transition pore regulator gene cyclophilin D. Protein levels of mitochondrial calcium uniporter (MCU), MICU2, and sodium/calcium exchanger (NCLX) were also higher at sleep onset relative to wake period. While complex I and II-dependent oxygen utilization and transmembrane potential of cardiac mitochondria were lower during sleep, ROS production was increased presumably due to mitochondrial calcium sequestration.

Conclusions

Taken together, our results indicate that retaining mitochondrial calcium in the heart during sleep dissipates membrane potential, slows respiratory activities, and increases ROS levels, which may contribute to increased vulnerability to cardiac stress during sleep-wake transition. This pronounced daily oscillations in mitochondrial functions pertaining to stress vulnerability may at least in part explain diurnal prevalence of cardiac pathologies.

Endothelial extracellular vesicles contain protective proteins and rescue ischemia-reperfusion injury in a human heart-on-chip

Extracellular vesicles (EVs) derived from various stem cell sources induce cardioprotective effects during ischemia-reperfusion injury (IRI). These have been attributed mainly to the antiapoptotic, proangiogenic, microRNA (miRNA) cargo within the stem cell-derived EVs. However, the mechanisms of EV-mediated endothelial signaling to cardiomyocytes, as well as their therapeutic potential toward ischemic myocardial injury, are not clear. EV content beyond miRNA that may contribute to cardioprotection has not been fully illuminated. This study characterized the protein cargo of human vascular endothelial EVs (EEVs) to identify lead cardioactive proteins and assessed the effect of EEVs on human laminar cardiac tissues (hlCTs) exposed to IRI. We mapped the protein content of human vascular EEVs and identified proteins that were previously associated with cellular metabolism, redox state, and calcium handling, among other processes. Analysis of the protein landscape of human cardiomyocytes revealed corresponding modifications induced by EEV treatment. To assess their human-specific cardioprotection in vitro, we developed a human heart-on-a-chip IRI assay using human stem cell-derived, engineered cardiac tissues. We found that EEVs alleviated cardiac cell death as well as the loss in contractile capacity during and after simulated IRI in an uptake- and dose-dependent manner. Moreover, we found that EEVs increased the respiratory capacity of normoxic cardiomyocytes. These results suggest that vascular EEVs rescue hlCTs exposed to IRI possibly by supplementing injured myocytes with cargo that supports multiple metabolic and salvage pathways and therefore may serve as a multitargeted therapy for IRI.

Role of Oxidative Stress in Reperfusion following Myocardial Ischemia and Its Treatments

Myocardial ischemia is a disease with high morbidity and mortality, for which reperfusion is currently the standard intervention. However, the reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MI/RI). Oxidative stress is one of the most important pathological mechanisms in reperfusion injury, which causes apoptosis, autophagy, inflammation, and some other damage in cardiomyocytes through multiple pathways, thus causing irreversible cardiomyocyte damage and cardiac dysfunction. This article reviews the pathological mechanisms of oxidative stress involved in reperfusion injury and the interventions for different pathways and targets, so as to form systematic treatments for oxidative stress-induced myocardial reperfusion injury and make up for the lack of monotherapy.

Overexpression of Transcripts Coding for Renin-b but Not for Renin-a Reduce Oxidative Stress and Increase Cardiomyoblast Survival under Starvation Conditions

A stimulated renin-angiotensin system is known to promote oxidative stress, apoptosis, necrosis and fibrosis. Renin transcripts (renin-b; renin-c) encoding a cytosolic renin isoform have been discovered that may in contrast to the commonly known secretory renin (renin-a) exert protective effects Here, we analyzed the effect of renin-a and renin-b overexpression in H9c2 cardiomyoblasts on apoptosis and necrosis as well as on potential mechanisms involved in cell death processes. To mimic ischemic conditions, cells were exposed to glucose starvation, anoxia or combined oxygen–glucose deprivation (OGD) for 24 h. Under OGD, control cells exhibited markedly increased necrotic and apoptotic cell death accompanied by enhanced ROS accumulation, loss of mitochondrial membrane potential and decreased ATP levels. The effects of OGD on necrosis were exaggerated in renin-a cells, but markedly diminished in renin-b cells. However, with respect to apoptosis, the effects of OGD were almost completely abolished in renin-b cells but interestingly also moderately diminished in renin-a cells. Under glucose depletion we found opposing responses between renin-a and renin-b cells; while the rate of necrosis and apoptosis was aggravated in renin-a cells, it was attenuated in renin-b cells. Based on our results, strategies targeting the regulation of cytosolic renin-b as well as the identification of pathways involved in the protective effects of renin-b may be helpful to improve the treatment of ischemia-relevant diseases.

Aconitine attenuates mitochondrial dysfunction of cardiomyocytes via promoting deacetylation of cyclophilin-D mediated by sirtuin-3

ETHNOPHARMACOLOGICAL RELEVANCE

Aconite is a processed product of seminal root of perennial herbaceous plant Aconitum Carmichaclii Debx. of Ranunculaceae. It has the effects of warming and tonifying heart yang and restoring yang to save from collapse. Aconitine is the main effective constituent of aconite and used to prevent and treat heart disease. However, how aconitine exerts myocardial protection is still poorly understood.

AIM OF THE STUDY

The present study aimed to investigate the effects of aconitine on mitochondrial dysfunction and explore its mechanism of action.

MATERIALS AND METHODS

The model of myocardial injury was induced by Angiotensin II (Ang II) (1 × 10-6 mol L-1), and H9c2 cells were incubated with different concentrations of aconitine. The effect of aconitine on mitochondrial was determined by flow cytometry, transmission electron microscopy, luciferase, Seahorse technique and Western blot. The effects of aconitine on sirtuin-3 (Sirt3) activity and Cyclophilin D (CypD) acetylation were detected by immunofluorescence, RT-PCR and co-immunoprecipitation.

RESULTS

We demonstrate that aconitine alleviates the energy metabolic dysfunction of H9c2 cells by activating Sirt3 to deacetylate CypD and inhibiting mitochondrial permeability transition pore (mPTP) opening. In cardiomyocytes, aconitine significantly reduced mitochondrial fragmentation, inhibited acetylation of CypD, suppressed the mPTP opening, mitigated mitochondrial OXPHOS disorders, and improved the synthesis ability of ATP. In contrast, Sirt3 deficiency abolished the effects of aconitine on mPTP and OXPHOS, indicating that aconitine improves mitochondrial function by activating Sirt3.

CONCLUSIONS

These results showed that aconitine attenuated the energy metabolism disorder by promoting Sirt3 expression and reducing CypD-mediated mPTP excess openness, rescuing mitochondrial function. Improve mitochondrial function may be a therapeutic approach for treating heart disease, which will generate fresh insight into the cardioprotective of aconitine.

A Balanced Act: The Effects of GH-GHR-IGF1 Axis on Mitochondrial Function

Mitochondrial function is multifaceted in response to cellular energy homeostasis and metabolism, with the generation of adenosine triphosphate (ATP) through the oxidative phosphorylation (OXPHOS) being one of their main functions. Selective elimination of mitochondria by mitophagy, in conjunction with mitochondrial biogenesis, regulates mitochondrial function that is required to meet metabolic demand or stress response. Growth hormone (GH) binds to the GH receptor (GHR) and induces the JAK2/STAT5 pathway to activate the synthesis of insulin-like growth factor 1 (IGF1). The GH–GHR–IGF1 axis has been recognized to play significant roles in somatic growth, including cell proliferation, differentiation, division, and survival. In this review, we describe recent discoveries providing evidence for the contribution of the GH–GHR–IGF1 axis on mitochondrial biogenesis, mitophagy (or autophagy), and mitochondrial function under multiple physiological conditions. This may further improve our understanding of the effects of the GH–GHR–IGF1 axis on mitochondrial function, which may be controlled by the delicate balance between mitochondrial biogenesis and mitophagy. Specifically, we also highlight the challenges that remain in this field.

MK2-Deficient Mice Are Bradycardic and Display Delayed Hypertrophic Remodeling in Response to a Chronic Increase in Afterload

Background

Mitogen‐activated protein kinase–activated protein kinase‐2 (MK2) is a protein serine/threonine kinase activated by p38α/β. Herein, we examine the cardiac phenotype of pan MK2‐null (MK2^−/−) mice.

Methods and Results

Survival curves for male MK2^+/+ and MK2^−/− mice did not differ (Mantel‐Cox test, P=0.580). At 12 weeks of age, MK2^−/− mice exhibited normal systolic function along with signs of possible early diastolic dysfunction; however, aging was not associated with an abnormal reduction in diastolic function. Both R‐R interval and P‐R segment durations were prolonged in MK2‐deficient mice. However, heart rates normalized when isolated hearts were perfused ex vivo in working mode. Ca²⁺ transients evoked by field stimulation or caffeine were similar in ventricular myocytes from MK2^+/+ and MK2^−/− mice. MK2^−/− mice had lower body temperature and an age‐dependent reduction in body weight. mRNA levels of key metabolic genes, including Ppargc1a, Acadm, Lipe, and Ucp3, were increased in hearts from MK2^−/− mice. For equivalent respiration rates, mitochondria from MK2^−/− hearts showed a significant decrease in Ca²⁺ sensitivity to mitochondrial permeability transition pore opening. Eight weeks of pressure overload increased left ventricular mass in MK2^+/+ and MK2^−/− mice; however, after 2 weeks the increase was significant in MK2^+/+ but not MK2^−/− mice. Finally, the pressure overload–induced decrease in systolic function was attenuated in MK2^−/− mice 2 weeks, but not 8 weeks, after constriction of the transverse aorta.

Conclusions

Collectively, these results implicate MK2 in (1) autonomic regulation of heart rate, (2) cardiac mitochondrial function, and (3) the early stages of myocardial remodeling in response to chronic pressure overload.

The newborn Fmr1 knockout mouse: a novel model of excess ubiquinone and closed mitochondrial permeability transition pore in the developing heart

BACKGROUND

Mitochondrial permeability transition pore (mPTP) closure triggers cardiomyocyte differentiation during development while pathological opening causes cell death during myocardial ischemia-reperfusion and heart failure. Ubiquinone modulates the mPTP; however, little is known about its mechanistic role in health and disease. We previously found excessive proton leak in newborn Fmr1 KO mouse forebrain caused by ubiquinone deficiency and increased open mPTP probability. Because of the physiological differences between the heart and brain during maturation, we hypothesized that developing Fmr1 KO cardiomyocyte mitochondria would demonstrate dissimilar features.

METHODS

Newborn male Fmr1 KO mice and controls were assessed. Respiratory chain enzyme activity, ubiquinone content, proton leak, and oxygen consumption were measured in cardiomyocyte mitochondria. Cardiac function was evaluated via echocardiography.

RESULTS

In contrast to controls, Fmr1 KO cardiomyocyte mitochondria demonstrated increased ubiquinone content and decreased proton leak. Leak was cyclosporine (CsA)-sensitive in controls and CsA-insensitive in Fmr1 KOs. There was no difference in absolute mitochondrial respiration or cardiac function between strains.

CONCLUSION

These findings establish the newborn Fmr1 KO mouse as a novel model of excess ubiquinone and closed mPTP in the developing heart. Such a model may help provide insight into the biology of cardiac development and pathophysiology of neonatal heart failure.

IMPACT

Ubiquinone is in excess and the mPTP is closed in the developing FXS heart. Strengthens evidence of open mPTP probability in the normally developing postnatal murine heart and provides new evidence for premature closure of the mPTP in Fmr1 mutants. Establishes a novel model of excess CoQ and a closed pore in the developing heart. Such a model will be a valuable tool used to better understand the role of ubiquinone and the mPTP in the neonatal heart in health and disease.

Interaction of Agaric Acid with the Adenine Nucleotide Translocase Induces Mitochondrial Oxidative Stress

Mitochondrial permeability transition is characterized by the opening of a transmembranal pore that switches membrane permeability from specific to nonspecific. This structure allows the free traffic of ions, metabolites, and water across the mitochondrial inner membrane. The opening of the permeability transition pore is triggered by oxidative stress along with calcium overload. In this work, we explored if oxidative stress is a consequence, rather than an effector of the pore opening, by evaluating the interaction of agaric acid with the adenine nucleotide translocase, a structural component of the permeability transition pore. We found that agaric acid induces transition pore opening, increases the generation of oxygen-derived reactive species, augments the oxidation of unsaturated fatty acids in the membrane, and promotes the detachment of cytochrome c from the inner membrane. The effect of agaric acid was inhibited by the antioxidant tamoxifen in association with decreased binding of the thiol reagent eosin-3 maleimide to the adenine nucleotide translocase. We conclude that agaric acid promotes the opening of the pore, increasing ROS production that exerts oxidative modification of critical thiols in the adenine nucleotide translocase.

Synergic effect of combined cyclosporin and melatonin protects the brain against acute ischemic reperfusion injury

BACKGROUND

This study tested whether combined cyclosporin-A (CsA) and melatonin (Mel) was superior to either one on protecting the brain against ischemia (occluded left-middle-cerebral-artery for 90-min)-reperfusion (for 14 days) injury.

METHODS AND RESULTS

Neuro-2a cells (N2a) were categorized into groups 1 (N2a), 2 (N2a-IR), 3 (N2a-IR-Mel), 4 (N2a-IR-CsA) and 5 (N2a-IR-CsA-Mel). in vitro results showed the protein expressions of cytosolic-cytochrome-C/mitochondrial-Bax/cleaved-capase-3/NOX-1/NOX-2 and flow-cytometric results of ROS (DCFDA/Mito-SOX) were highest in group 2, lowest in group 1, significantly lower in group 5 than in groups 3/4, but they showed no difference in groups 3/4 (all p < 0.001). Male-adult-SD rats (50) were equally categorized into groups 1 (sham-operated-control), 2 (IR), 3 (IR-CsA/20.0 mg/kg at 0.5/24/48 h intraperitoneally after IR), 4 (IR-Mel/50.0 mg/kg intraperitoneally at 30 min and 30 mg/kg at 6/24/48 h after IR) and 5 (IR-CsA-Mel). The brain-infarct-area (BIA) (at day-3 by TTC-stain) was lowest in group 1, highest in group 2, significantly lower in group 5 than groups 3/4, but it showed no difference between groups 3/4 whereas the brain-infarct-volume (at day 14 by MRI) was similar as BIA except for significantly lower in group 4 than in group 3 (all p < 0.0001). By day 14, microscopic finding showed the numbers of glial+/GFAP+/AQP + cells expressed an identical trend whereas the number of NeuN + cells exhibited an opposite pattern of BIA among the groups (all p < 0.0001). The protein expressions of oxidative-stress (NOX-1/NOX-2/p22phox/oxidized-protein), inflammatory (TNF-α/p-NF-κB/MMP-9), apoptotic (mitochondrial-Bax/caspase-3/PARP) and mitochondrial-damaged (Cyclophilin-D/DRP1/cytosolic-cytochrome-C) biomarkers displayed an identical pattern of BIA among the five groups (all p < 0.0001).

CONCLUSION

Combined CsA-Mel was superior to either CsA or Mel on protecting the brain against IR injury.

Immunological organ modification during Ex Vivo machine perfusion: The future of organ acceptance

Ex vivo machine perfusion (EVMP) has gained revitalized interest in recent years due to the increasing use of marginal organs which poorly tolerate the standard preservation method static cold storage (SCS). EVMP improves on SCS in a number of ways, most notably by the potential for reconditioning of the donor organ prior to transplantation without the ethical concerns associated with organ modulation before procurement. Immunomodulatory therapies administered during EVMP can influence innate and adaptive immune responses to reduce production of inflammatory molecules and polarize tissue-resident immune cells to a regulatory phenotype. The targeted inhibition of an inflammatory response can reduce ischemia-reperfusion injury following organ reoxygenation and therefore reduce incidence of graft dysfunction and rejection. Numerous approaches to modulate the inflammatory response have been applied in experimental models, with the ultimate goal of clinical translatability. Strategies to target the innate immune system include inhibiting inflammatory signaling pathways, upregulating anti-inflammatory mediators, and decreasing mitochondrial damage while those which target the adaptive immune system include mesenchymal stromal cells. Inhibitory RNA approaches target both the innate and adaptive immune systems with a focus on MHC knock-down. Future studies may address issues of therapeutic agent delivery through use of nanoparticles and explore novel strategies such as targeting co-inhibitory molecules to educate T-cells to a tolerogenic state. In this review, we summarize the cellular and acellular contributors to allograft dysfunction and rejection, discuss the strategies which have been employed pre-clinically during EVMP to modulate the donor organ immune environment, and suggest future directions for immunomodulatory EVMP studies.

Comprehensive Analysis of Zinc Derivatives Pro-proliferative, Anti-Apoptotic and Antimicrobial Effect on Human Fibroblasts and Keratinocytes in a Simulated, Nutrient-deficient Environment In Vitro

Zinc as therapeutic agent in skin and wound care has been known for centuries, but its role is controversial and comprehensive investigations in nutrient-deficient environments are lacking. We aimed to provide a broad analysis of different zinc derivatives on proliferation, apoptosis and antimicrobial properties in a simulated nutrient-deficient environment in vitro. Human fibroblasts (CRL2522) and keratinocytes (HaCaT) were treated with a broad concentration range (10 – 0.0001 µg/mL) of zinc-sulfate (ZnSO₄), -gluconate (ZnGluc) and -histidine (ZnHis) for 1-6 days under nutrient-deficient media conditions. Cell proliferation was investigated by XTT assay. Targeted analyzes in proliferation (E2F1, PCNA) and apoptosis (TP53) associated genes were performed via qRT-PCR and apoptosis was determined via FACS (annexin V/7-AAD staining). Antimicrobial efficacy was investigated using a quantitative suspension method against S. aureus, P. aeruginosa, E. coli, and C. albicans. The results indicated that 0.1 to 0.001 µg/mL Zn increased cell proliferation in both cell lines. Fibroblasts were more susceptible with significant proliferation peaks on days 2 & 6, and days 1 & 4 for keratinocytes. No relevant changes in gene expression were detected for E2F1 and PCNA nor for TP53. Annexin-V/7-AAD-staining of fibroblasts revealed a small, yet insignificant reduction of apoptosis induction for ZnGluc and ZnSO₄. ZnGluc and ZnSO₄ (0.1%) achieved high microbial reductions (4-5 log₁₀ reductions) against tested pathogens. ZnGluc and ZnSO₄ showed relevant pro-proliferative and antimicrobial, as well as tendential anti-apoptotic features in a simulated nutrient-deficient microenvironment in vitro. This further validates a potential benefit of local zinc treatment in deficient wound microenvironments.

Protective effects of catalpol on mitochondria of hepatocytes in cholestatic liver injury

Cholestasis, which is caused by the obstruction of bile flow, can lead to rapid organ injury, cell apoptosis and necrosis of hepatocytes, and may eventually develop into fibrosis and cirrhosis. Oxidative stress and mitochondrial dysfunction are the key pathogenic signs of hepatic cholestasis. Catalpol has pharmacological activities, including antioxidative and anti-inflammatory effects, and may relieve mitochondrial damage and restore mitochondrial membrane potential. However, the potential roles and mechanisms of catalpol in cholestasis-induced liver injury are not clear. In the present study, liver function-related indexes were measured in the serum of mice by commercial kits. In addition, levels of serum inflammatory factors were detected by ELISA. Hematoxylin and eosin staining was performed to observe histopathological changes, and mitochondrial membrane potential was detected using JC-1 staining. Mitochondrial adenosine triphosphate (ATP), reactive oxygen species (ROS) and malondialdehyde levels were determined using a luciferase reporter kit, flow cytometry and a thiobarbituric acid reactive substance assay kit, respectively. Western blotting was performed to detect the expression levels of apoptosis-related proteins in liver tissues. The findings revealed that catalpol reduced liver damage caused by cholestasis, improved the mitochondrial membrane potential, and increased the ATP content and glutathione content of cholestasis model mice. Moreover, catalpol also reduced the ROS level, inhibited lipid peroxidation, and regulated oxidative stress and apoptotic protein expression. Thus, the present study preliminarily confirmed that catalpol can reduce liver injury in a mouse model of cholestasis through inhibiting oxidative stress and enhancing mitochondrial membrane potential.

Non-secretory renin reduces oxidative stress and increases cardiomyoblast survival during glucose and oxygen deprivation

Although the renin-angiotensin system usually promotes oxidative stress and cell death, renin transcripts have been discovered, whose transcription product may be cardioprotective. These transcripts encode a non-secretory renin isoform that is localized in the cytosol and within mitochondria. Here we tested the hypotheses that cytosolic renin [ren(2-9)] expression promotes cell survival under hypoxia and glucose depletion by preserving the mitochondrial membrane potential (∆Ψ_m) and mitigating the accumulation of ROS. To simulate ischemic insults, we exposed H9c2 cells to glucose deprivation, anoxia or to combined oxygen-glucose deprivation (OGD) for 24 hours and determined renin expression. Furthermore, H9c2 cells transfected with the empty pIRES vector (pIRES cells) or ren(2-9) cDNA-containing vector [ren(2-9) cells] were analyzed for cell death, ∆Ψ_m, ATP levels, accumulation of ROS, and cytosolic Ca²⁺ content. In pIRES cells, expression of ren(1A-9) was stimulated under all three ischemia-related conditions. After OGD, the cells lost their ∆Ψ_m and exhibited enhanced ROS accumulation, increased cytosolic Ca²⁺ levels, decreased ATP levels as well as increased cell death. In contrast, ren(2-9) cells were markedly protected from these effects. Ren(2-9) appears to represent a protective response to OGD by reducing ROS generation and preserving mitochondrial functions. Therefore, it is a promising new target for the prevention of ischemia-induced myocardial damage.

Crosstalk between Mitochondria and Cytoskeleton in Cardiac Cells

Elucidation of the mitochondrial regulatory mechanisms for the understanding of muscle bioenergetics and the role of mitochondria is a fundamental problem in cellular physiology and pathophysiology. The cytoskeleton (microtubules, intermediate filaments, microfilaments) plays a central role in the maintenance of mitochondrial shape, location, and motility. In addition, numerous interactions between cytoskeletal proteins and mitochondria can actively participate in the regulation of mitochondrial respiration and oxidative phosphorylation. In cardiac and skeletal muscles, mitochondrial positions are tightly fixed, providing their regular arrangement and numerous interactions with other cellular structures such as sarcoplasmic reticulum and cytoskeleton. This can involve association of cytoskeletal proteins with voltage-dependent anion channel (VDAC), thereby, governing the permeability of the outer mitochondrial membrane (OMM) to metabolites, and regulating cell energy metabolism. Cardiomyocytes and myocardial fibers demonstrate regular arrangement of tubulin beta-II isoform entirely co-localized with mitochondria, in contrast to other isoforms of tubulin. This observation suggests the participation of tubulin beta-II in the regulation of OMM permeability through interaction with VDAC. The OMM permeability is also regulated by the specific isoform of cytolinker protein plectin. This review summarizes and discusses previous studies on the role of cytoskeletal proteins in the regulation of energy metabolism and mitochondrial function, adenosine triphosphate (ATP) production, and energy transfer.

Myocardial Adaptation in Pseudohypoxia: Signaling and Regulation of mPTP via Mitochondrial Connexin 43 and Cardiolipin

Therapies intended to mitigate cardiovascular complications cannot be applied in practice without detailed knowledge of molecular mechanisms. Mitochondria, as the end-effector of cardioprotection, represent one of the possible therapeutic approaches. The present review provides an overview of factors affecting the regulation processes of mitochondria at the level of mitochondrial permeability transition pores (mPTP) resulting in comprehensive myocardial protection. The regulation of mPTP seems to be an important part of the mechanisms for maintaining the energy equilibrium of the heart under pathological conditions. Mitochondrial connexin 43 is involved in the regulation process by inhibition of mPTP opening. These individual cardioprotective mechanisms can be interconnected in the process of mitochondrial oxidative phosphorylation resulting in the maintenance of adenosine triphosphate (ATP) production. In this context, the degree of mitochondrial membrane fluidity appears to be a key factor in the preservation of ATP synthase rotation required for ATP formation. Moreover, changes in the composition of the cardiolipin’s structure in the mitochondrial membrane can significantly affect the energy system under unfavorable conditions. This review aims to elucidate functional and structural changes of cardiac mitochondria subjected to preconditioning, with an emphasis on signaling pathways leading to mitochondrial energy maintenance during partial oxygen deprivation.

In silico simulation of reversible and irreversible swelling of mitochondria: The role of membrane rigidity

Mitochondria have been widely accepted as the main source of ATP in the cell. The inner mitochondrial membrane (IMM) is important for the maintenance of ATP production and other functions of mitochondria. The electron transport chain (ETC) generates an electrochemical gradient of protons known as the proton-motive force across the IMM and thus produces the mitochondrial membrane potential that is critical to ATP synthesis. One of the main factors regulating the structural and functional integrity of the IMM is the changes in the matrix volume. Mild (reversible) swelling regulates mitochondrial metabolism and function; however, excessive (irreversible) swelling causes mitochondrial dysfunction and cell death. The central mechanism of mitochondrial swelling includes the opening of non-selective channels known as permeability transition pores (PTPs) in the IMM by high mitochondrial Ca²⁺ and reactive oxygen species (ROS). The mechanisms of reversible and irreversible mitochondrial swelling and transition between these two states are still unknown. The present study elucidates an upgraded biophysical model of reversible and irreversible mitochondrial swelling dynamics. The model provides a description of the PTP regulation dynamics using an additional differential equation. The rigidity tensor was used in numerical simulations of the mitochondrial parameter dynamics with different initial conditions defined by Ca²⁺ concentration in the sarco/endoplasmic reticulum. We were able to estimate the values of the IMM rigidity tensor components by fitting the model to the previously reported experimental data. Overall, the model provides a better description of the reversible and irreversible mitochondrial swelling dynamics.

The Role of Mitochondria in the Mechanisms of Cardiac Ischemia-Reperfusion Injury

Mitochondria play a critical role in maintaining cellular function by ATP production. They are also a source of reactive oxygen species (ROS) and proapoptotic factors. The role of mitochondria has been established in many aspects of cell physiology/pathophysiology, including cell signaling. Mitochondria may deteriorate under various pathological conditions, including ischemia-reperfusion (IR) injury. Mitochondrial injury can be one of the main causes for cardiac and other tissue injuries by energy stress and overproduction of toxic reactive oxygen species, leading to oxidative stress, elevated calcium and apoptotic and necrotic cell death. However, the interplay among these processes in normal and pathological conditions is still poorly understood. Mitochondria play a critical role in cardiac IR injury, where they are directly involved in several pathophysiological mechanisms. We also discuss the role of mitochondria in the context of mitochondrial dynamics, specializations and heterogeneity. Also, we wanted to stress the existence of morphologically and functionally different mitochondrial subpopulations in the heart that may have different sensitivities to diseases and IR injury. Therefore, various cardioprotective interventions that modulate mitochondrial stability, dynamics and turnover, including various pharmacologic agents, specific mitochondrial antioxidants and uncouplers, and ischemic preconditioning can be considered as the main strategies to protect mitochondrial and cardiovascular function and thus enhance longevity.

Temporal dynamics of immune response following prolonged myocardial ischemia/reperfusion with and without cyclosporine A

Understanding the dynamics of the immune response following late myocardial reperfusion is critical for the development of immunomodulatory therapy for myocardial infarction (MI). Cyclosporine A (CSA) possesses multiple therapeutic applications for MI, but its effects on the inflammation caused by acute MI are not clear. This study aimed to determine the dynamics of the immune response following myocardial ischemia/reperfusion (I/R) and the effects of CSA in a mouse model of prolonged myocardial ischemia designated to represent the human condition of late reperfusion. Adult C57BL/6 mice were subjected to 90 min of closed-chest myocardial I/R, which induced severe myocardial injury and excessive inflammation in the heart. Multicomponent analysis of the immune response caused by prolonged I/R revealed that the peak of cytokines/chemokines in the systemic circulation was synchronized with the maximal influx of neutrophils and T-cells in the heart 1 day after MI. The peak of cytokine/chemokine secretion in the infarcted heart coincided with the maximal macrophage and natural killer cell infiltration on day 3 after MI. The cellular composition of the mediastinal lymph nodes changed similarly to that of the infarcted hearts. CSA (10 mg/kg/day) given after prolonged I/R impaired heart function, enlarged the resulting scar, and reduced heart vascularization. It did not change the content of immune cells in hearts exposed to prolonged I/R, but the levels of MCP-1 and MIP-1α (hearts) and IL-12 (hearts and serum) were significantly reduced in the CSA-treated group in comparison to the untreated group, indicating alterations in immune cell function. Our findings provide new knowledge necessary for the development of immunomodulatory therapy targeting the immune response after prolonged myocardial ischemia/reperfusion.

Comparison of multiple doses of cyclosporine A on germ cell apoptosis and epididymal sperm parameters after testicular ischemia/reperfusion in rats

Testicular torsion/detorsion (T/D) is an inflammatory problem in men genital system with infertility effects. Cyclosporine A (CsA) as an immunosuppressant medication, exerts anti-inflammatory properties in tissue injuries. We sought to compare the efficacy of 3 doses of CsA on oxidative stress, apoptosis and epididymal sperm quality after ipsilateral testicular T/D.

METHODS

96 mature male rats were divided into six groups 16 each in: Control group (Group1), Sham operated (Group2), In rest groups, the right testis was twisted 720° in a clockwise direction for 1 h; T/D + 0.1% dimethylsulfoxide) DMSO((Group3), and in groups 4-6; CsA were administered 1, 5, and 10 mg/kg, intravenously (iv) 30 and 90 min after torsion, respectively.

RESULTS

Tissue malondialdehyde (MDA) level and caspase-3 activity increased and catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities decreased in compared with control group 4 h after detorsion (p < .001). In six rats of each group 24 h after detorsion, histopathological changes and germ cell apoptosis were significantly deteriorated by determining mean of seminiferous tubules diameters (MSTD) and TUNEL assay. Moreover, 30 days after T/D, sperm concentration and motility were examined in rest of animals.

CONCLUSIONS

Pre- and post-reperfusion CsA diminished MDA and caspase-3levels and normalized antioxidant enzymes activities. Germ cell apoptosis was significantly reduced, as well as, MSTD and long-term sperm insults were improved. Inhibition of mitochondrial permeability transition pore opening is suggested mechanism for cell protection against testicular T/D insults.

UCP2 protect the heart from myocardial ischemia/reperfusion injury via induction of mitochondrial autophagy

Uncoupling protein 2 (UCP2), located in the mitochondrial inner membrane, is a predominant isoform of UCP that expressed in the heart and other tissues of human and rodent tissues. Nevertheless, its functional role during myocardial ischemia/reperfusion (I/R) is not entirely understood. Ischemic preconditioning (IPC) remarkably improved postischemic functional recovery followed by reduced lactate dehydrogenase (LDH) release with simultaneous upregulation of UCP2 in perfused myocardium. We then investigated the role of UCP2 in IPC-afforded cardioprotective effects on myocardial I/R injury with adenovirus-mediated in vivo UCP2 overexpression (AdUCP2) and knockdown (AdshUCP2). IPC-induced protective effects were mimicked by UCP2 overexpression, while which were abolished with silencing UCP2. Mechanistically, UCP2 overexpression significantly reinforced I/R-induced mitochondrial autophagy (mitophagy), as measured by biochemical hallmarks of mitochondrial autophagy. Moreover, primary cardiomyocytes infected with AdUCP2 increased simulated ischemia/reperfusion (sI/R)-induced mitophagy and therefore reversed impaired mitochondrial function. Finally, suppression of mitophagy with mdivi-1 in cultured cardiomyocytes abolished UCP2-afforded protective effect on sI/R-induced mitochondrial dysfunction and cell death. Our data identify a critical role for UCP2 against myocardial I/R injury through preventing the mitochondrial dysfunction through reinforcing mitophagy. Our findings reveal novel mechanisms of UCP2 in the cardioprotective effects during myocardial I/R.

Growth Hormone Receptor Gene is Essential for Chicken Mitochondrial Function In Vivo and In Vitro

The growth hormone receptor (GHR) gene is correlated with many phenotypic and physiological alternations in chicken, such as shorter shanks, lower body weight and muscle mass loss. However, the role of the GHR gene in mitochondrial function remains unknown in poultry. In this study, we assessed the function of mitochondria in sex-linked dwarf (SLD) chicken skeletal muscle and interfered with the expression of GHR in DF-1 cells to investigate the role of the GHR gene in chicken mitochondrial function both in vivo and in vitro. We found that the expression of key regulators of mitochondrial biogenesis and mitochondrial DNA (mtDNA)-encoded oxidative phosphorylation (OXPHOS) genes were downregulated and accompanied by reduced enzymatic activity of OXPHOS complexes in SLD chicken skeletal muscle and GHR knockdown cells. Then, we assessed mitochondrial function by measuring mitochondrial membrane potential (ΔΨm), mitochondrial swelling, reactive oxygen species (ROS) production, malondialdehyde (MDA) levels, ATP levels and the mitochondrial respiratory control ratio (RCR), and found that mitochondrial function was impaired in SLD chicken skeletal muscle and GHR knockdown cells. In addition, we also studied the morphology and structure of mitochondria in GHR knockdown cells by transmission electron microscopy (TEM) and MitoTracker staining. We found that knockdown of GHR could reduce mitochondrial number and alter mitochondrial structure in DF-1 cells. Above all, we demonstrated for the first time that the GHR gene is essential for chicken mitochondrial function in vivo and in vitro.

Therapeutic implications of novel peptides targeting ER-mitochondria Ca2+-flux systems

Intracellular Ca²⁺-flux systems located at the ER-mitochondrial axis govern mitochondrial Ca²⁺ balance and cell fate. Multiple yet incurable pathologies are characterized by insufficient or excessive Ca²⁺ fluxes toward the mitochondria, in turn leading to aberrant cell life or death dynamics. The discovery and ongoing molecular characterization of the main interorganellar Ca²⁺ gateways have resulted in a novel class of peptide tools able to regulate relevant protein-protein interactions (PPIs) underlying this signaling scenario. Here, we review peptides, molecularly derived from Ca²⁺-flux systems or their accessory proteins. We discuss how they alter Ca²⁺-signaling protein complexes and modulate cell survival in light of their forthcoming therapeutic applications.

Posttranslational modifications of mitochondrial fission and fusion proteins in cardiac physiology and pathophysiology

Mitochondrial fragmentation frequently occurs in chronic pathological conditions as seen in various human diseases. In fact, abnormal mitochondrial morphology and mitochondrial dysfunction are hallmarks of heart failure (HF) in both human patients and HF animal models. A link between mitochondrial fragmentation and cardiac pathologies has been widely proposed, but the physiological relevance of mitochondrial fission and fusion in the heart is still unclear. Recent studies have increasingly shown that posttranslational modifications (PTMs) of fission and fusion proteins are capable of directly modulating the stability, localization, and/or activity of these proteins. These PTMs include phosphorylation, acetylation, ubiquitination, conjugation of small ubiquitin-like modifier proteins, O-linked-N-acetyl-glucosamine glycosylation, and proteolysis. Thus, understanding the PTMs of fission and fusion proteins may allow us to understand the complexities that determine the balance of mitochondrial fission and fusion as well as mitochondrial function in various cell types and organs including cardiomyocytes and the heart. In this review, we summarize present knowledge regarding the function and regulation of mitochondrial fission and fusion in cardiomyocytes, specifically focusing on the PTMs of each mitochondrial fission/fusion protein. We also discuss the molecular mechanisms underlying abnormal mitochondrial morphology in HF and their contributions to the development of cardiac diseases, highlighting the crucial roles of PTMs of mitochondrial fission and fusion proteins. Finally, we discuss the future potential of manipulating PTMs of fission and fusion proteins as a therapeutic strategy for preventing and/or treating HF.

Adrenergic Regulation of Drp1-Driven Mitochondrial Fission in Cardiac Physio-Pathology

Abnormal mitochondrial morphology, especially fragmented mitochondria, and mitochondrial dysfunction are hallmarks of a variety of human diseases including heart failure (HF). Although emerging evidence suggests a link between mitochondrial fragmentation and cardiac dysfunction, it is still not well described which cardiac signaling pathway regulates mitochondrial morphology and function under pathophysiological conditions such as HF. Mitochondria change their shape and location via the activity of mitochondrial fission and fusion proteins. This mechanism is suggested as an important modulator for mitochondrial and cellular functions including bioenergetics, reactive oxygen species (ROS) generation, spatiotemporal dynamics of Ca²⁺ signaling, cell growth, and death in the mammalian cell- and tissue-specific manners. Recent reports show that a mitochondrial fission protein, dynamin-like/related protein 1 (DLP1/Drp1), is post-translationally modified via cell signaling pathways, which control its subcellular localization, stability, and activity in cardiomyocytes/heart. In this review, we summarize the possible molecular mechanisms for causing post-translational modifications (PTMs) of DLP1/Drp1 in cardiomyocytes, and further discuss how these PTMs of DLP1/Drp1 mediate abnormal mitochondrial morphology and mitochondrial dysfunction under adrenergic signaling activation that contributes to the development and progression of HF.

Acetylation of Mitochondrial Proteins in the Heart: The Role of SIRT3

A growing number of studies have demonstrated the role of post-translational modifications of proteins, particularly acetylation, in human diseases including neurodegenerative and cardiovascular diseases, diabetes, cancer, and in aging. Acetylation of mitochondrial proteins has been shown to be involved in the pathogenesis of cardiac diseases such as myocardial infarction (ischemia-reperfusion) and heart failure. Indeed, over 60% of mitochondrial proteins contain acetylation sites, and most of these proteins are involved in mitochondrial bioenergetics. Mitochondrial non-enzymatic acetylation is enabled by acetyl-coenzyme A abundance and serves as the primary pathway of acetylation in mitochondria. Hence, regulation of enzymatic deacetylation becomes the most important mechanism to control acetylation/deacetylation of mitochondrial proteins. Acetylation/deacetylation of mitochondrial proteins has been regarded as a key regulator of mitochondrial metabolism and function. Proteins are deacetylated by NAD⁺-dependent deacetylases known as sirtuins (SIRTs). Among seven sirtuin isoforms, only SIRT3, SIRT4, and SIRT5 are localized in the mitochondria. SIRT3 is the main mitochondrial sirtuin which plays a key role in maintaining metabolic and redox balance in the mitochondria under physiological and pathological conditions. SIRT3 regulates the enzymatic activity of proteins involved in fatty acid oxidation, tricarboxylic acid cycle, electron transport chain, and oxidative phosphorylation. Although many enzymes have been identified as targets for SIRT3, cardiac-specific SIRT3 effects and regulations could differ from those in non-cardiac tissues. Therefore, it is important to elucidate the contribution of SIRT3 and mitochondrial protein acetylation/deacetylation in mitochondrial metabolism and cardiac dysfunction. Here, we summarize previous studies and provide a comprehensive analysis of the role of SIRT3 in mitochondria metabolism and bioenergetics under physiological conditions and in cardiac diseases. In addition, the review discusses mitochondrial protein acetylation as a potential target for cardioprotection.