Mitochondrial Reactive Oxygen Species Formation Research Articles

Mitochondrial Creatine Kinase 2 (Ckmt2) as a Plasma-Based Biomarker for Evaluating Reperfusion Injury in Acute Myocardial Infarction.

Acute myocardial infarction (AMI), characterized by irreversible heart muscle damage and impaired cardiac function caused by myocardial ischemia, is a leading cause of global mortality. The damage associated with reperfusion, particularly mitochondrial dysfunction and reactive oxygen species (ROS) formation, has emerged as a crucial factor in the pathogenesis of cardiac diseases, leading to the recognition of mitochondrial proteins as potential markers for myocardial damage. This study aimed to identify differentially expressed proteins based on the type of cardiac injury, in particular those with and without reperfusion. Male C57Bl/6J mice were either left untreated, sham-operated, received non-reperfused AMI, or reperfused AMI. Twenty-four hours after the procedures, left ventricular (LV) function and morphological changes including infarct size were determined using echocardiography and triphenyl tetrazolium chloride (TTC) staining, respectively. In addition, plasma was isolated and subjected to untargeted mass spectrometry and, further on, the ELISA-based validation of candidate proteins. We identified mitochondrial creatine kinase 2 (Ckmt2) as a differentially regulated protein in plasma of mice with reperfused but not non-reperfused AMI. Elevated levels of Ckmt2 were significantly associated with infarct size and impaired LV function following reperfused AMI, suggesting a specific involvement in reperfusion damage. Our study highlights the potential of plasma Ckmt2 as a biomarker for assessing reperfusion injury and its impact on cardiac function and morphology in the acute phase of MI.

Manifesting the Dasatinib-gallic acid co-amorphous system to augment anticancer potential: Physicochemical characterization, in silico molecular simulation, ex vivo permeability, and in vitro efficacy

Dasatinib (DAB) has been explored for repurposing in the treatment of breast cancer (BC) due to its known effectiveness in treating leukemia, in addition to its role as a tyrosine kinase inhibitor. Gallic acid (GA) was chosen as a co-former due to its anticancer potential in BC, as demonstrated in several previous studies. DAB is a low-solubility drug, which is a significant hurdle for its oral bioavailability. To address this limitation, a DAB and GA co-amorphous (DAB-GA-CA) system was developed using liquid-assisted grinding and ball mill technology to enhance solubility, bioavailability, and anti-tumor efficacy. Physical characterization investigation revealed that the emergence of the halo diffractogram in PXRD, single glass transition temperature (Tg) value at 111.7 °C in DSC thermogram, and irregularly shaped blocks with loose, porous surfaces in SEM analysis indicated the formation of the DAB-GA-CA system at 1:1 M ratio. Furthermore, FTIR, Raman spectroscopy, in-silico molecular docking, and molecular dynamic studies confirmed the intermolecular hydrogen connections between DAB and GA. Moreover, the outcomes of the ligands (DAB and GA) and receptors (BCL-2, mTOR, estrogen receptor, and HER-2) docking studies demonstrated that both DAB and GA could interact with those receptors, leading to preventive action on BC cells. Additionally, the solubility and dissolution rate significantly improved at pH 6.8, and the permeability study indicated that DAB-GA-CA showed 1.9 times higher apparent permeability compared to crystalline DAB. Furthermore, in vitro cytotoxicity assessments of the DAB-GA-CA system revealed 3.42 times lower IC50 than free DAB. The mitochondrial membrane depolarization, apoptotic index, and reactive oxygen species formation in MCF-7 cells were also notably higher in the DAB-GA-CA system than in free DAB. Hence, this research suggests that the DAB-GA-CA system could substantially enhance oral delivery, solubility, and therapeutic efficacy.

Acid sphingomyelinase inhibition induces cerebral angiogenesis post-ischemia/reperfusion in an oxidative stress-dependent way and promotes endothelial survival by regulating mitochondrial metabolism

Acid sphingomyelinase (ASM) inhibitors are widely used for the treatment of post-stroke depression. They promote neurological recovery in animal stroke models via neurorestorative effects. In a previous study, we found that antidepressants including amitriptyline, fluoxetine, and desipramine increase cerebral angiogenesis post-ischemia/reperfusion (I/R) in an ASM-dependent way. To elucidate the underlying mechanisms, we investigated the effects of the functional ASM inhibitor amitriptyline in two models of I/R injury, that is, in human cerebral microvascular endothelial hCMEC/D3 cells exposed to oxygen-glucose deprivation and in mice exposed to middle cerebral artery occlusion (MCAO). In addition to our earlier studies, we now show that amitriptyline increased mitochondrial reactive oxygen species (ROS) formation in hCMEC/D3 cells and increased ROS formation in the vascular compartment of MCAO mice. ROS formation was instrumental for amitriptyline’s angiogenic effects. ROS formation did not result in excessive endothelial injury. Instead, amitriptyline induced a profound metabolic reprogramming of endothelial cells that comprised reduced endothelial proliferation, reduced mitochondrial energy metabolism, reduced endoplasmic reticulum stress, increased autophagy/mitophagy, stimulation of antioxidant responses and inhibition of apoptotic cell death. Specifically, the antioxidant heme oxygenase-1, which was upregulated by amitriptyline, mediated amitriptyline’s angiogenic effects. Thus, heme oxygenase-1 knockdown severely compromised angiogenesis and abolished amitriptyline’s angiogenic responses. Our data demonstrate that ASM inhibition reregulates a complex network of metabolic and mitochondrial responses post-I/R that contribute to cerebral angiogenesis without compromising endothelial survival.

Upregulation of Mitochondrial Sirt3 and Alleviation of the Inflammatory Phenotype in Macrophages by Estrogen.

Aging and comorbidities like type 2 diabetes and obesity contribute to the development of chronic systemic inflammation, which impacts the development of heart failure and vascular disease. Increasing evidence suggests a role of pro-inflammatory M1 macrophages in chronic inflammation. A shift of metabolism from mitochondrial oxidation to glycolysis is essential for the activation of the pro-inflammatory M1 phenotype. Thus, reprogramming the macrophage metabolism may alleviate the pro-inflammatory phenotype and protect against cardiovascular diseases. In the present study, we hypothesized that the activation of estrogen receptors leads to the elevation of the mitochondrial deacetylase Sirt3, which supports mitochondrial function and mitigates the pro-inflammatory phenotype in macrophages. Experiments were performed using the mouse macrophage cell line RAW264.7, as well as primary male or female murine bone marrow macrophages (BMMs). Macrophages were treated for 24 h with estradiol (E2) or vehicle (dextrin). The effect of E2 on Sirt3 expression was investigated in pro-inflammatory M1, anti-inflammatory/immunoregulatory M2, and naïve M0 macrophages. Mitochondrial respiration was measured by Seahorse assay, and protein expression and acetylation were determined by western blotting. E2 treatment upregulated mitochondrial Sirt3, reduced mitochondrial protein acetylation, and increased basal mitochondrial respiration in naïve RAW264.7 macrophages. Similar effects on Sirt3 expression and mitochondrial protein acetylation were observed in primary female but not in male murine BMMs. Although E2 upregulated Sirt3 in naïve M0, pro-inflammatory M1, and anti-inflammatory/immunoregulatory M2 macrophages, it reduced superoxide dismutase 2 acetylation and suppressed mitochondrial reactive oxygen species formation only in pro-inflammatory M1 macrophages. E2 alleviated the pro-inflammatory phenotype in M1 RAW264.7 cells. The study suggests that E2 treatment upregulates Sirt3 expression in macrophages. In primary BMMs, female-specific Sirt3 upregulation was observed. The Sirt3 upregulation was accompanied by mitochondrial protein deacetylation and the alleviation of the oxidative and pro-inflammatory phenotype in M1 macrophages. Thus, the E2-Sirt3 axis might be used in a therapeutic strategy to fight chronic systemic inflammation and prevent the development of inflammation-linked diseases.

Pathological Role of High Sugar in Mitochondrial Respiratory Chain Defect-Augmented Mitochondrial Stress.

According to many research groups, high glucose induces the overproduction of superoxide anions, with reactive oxygen species (ROS) generally being considered the link between high glucose levels and the toxicity seen at cellular levels. Respiratory complex anomalies can lead to the production of ROS. Calcium [Ca2+] at physiological levels serves as a second messenger in many physiological functions. Accordingly, mitochondrial calcium [Ca2+]m overload leads to ROS production, which can be lethal to the mitochondria through various mechanisms. F1F0-ATPase (ATP synthase or complex V) is the enzyme responsible for catalyzing the final step of oxidative phosphorylation. This is achieved by F1F0-ATPase coupling the translocation of protons in the mitochondrial intermembrane space and shuttling them to the mitochondrial matrix for ATP synthesis to take place. Mitochondrial complex V T8993G mutation specifically blocks the translocation of protons across the intermembrane space, thereby blocking ATP synthesis and, in turn, leading to Neuropathy, Ataxia, and Retinitis Pigmentosa (NARP) syndrome. This study seeks to explore the possibility of [Ca2+]m overload mediating the pathological roles of high glucose in defective respiratory chain-mediated mitochondrial stress. NARP cybrids are the in vitro experimental models of cells with F1FO-ATPase defects, with these cells harboring 98% of mtDNA T8993G mutations. Their counterparts, 143B osteosarcoma cell lines, are the parental cell lines used for comparison. We observed that NARP cells mediated and enhanced the death of cells (apoptosis) when incubated with hydrogen peroxide (H2O2) and high glucose, as depicted using the MTT assay of cell viability. Furthermore, using fluorescence probe-coupled laser scanning confocal imaging microscopy, NARP cells were found to significantly enable mitochondrial reactive oxygen species (mROS) formation and enhance the depolarization of the mitochondrial membrane potential (ΔΨm). Elucidating the mechanisms of sugar-enhanced toxicity on the mitochondria may, in the future, help to alleviate the symptoms of patients with NARP syndromes and other neurodegenerative diseases.

The inotropic and arrhythmogenic effects of acutely increased late INa are associated with elevated ROS but not oxidation of PKARIα.

Acute stimulation of the late sodium current (INaL) as pharmacologically induced by Anemonia toxin II (ATX-II) results in Na+-dependent Ca2+ overload and enhanced formation of reactive oxygen species (ROS). This is accompanied by an acute increase in the amplitude of the systolic Ca2+ transient. Ca2+ transient amplitude is determined by L-type Ca2+-mediated transsarcolemmal Ca2+ influx (ICa) into the cytosol and by systolic Ca2+ release from the sarcoplasmic reticulum (SR). Type-1 protein kinase A (PKARIα) becomes activated upon increased ROS and is capable of stimulating ICa, thereby sustaining the amplitude of the systolic Ca2+ transient upon oxidative stress. We aimed to investigate whether the increase of the systolic Ca2+ transient as acutely induced by INaL (by ATX-II) may involve stimulation of ICa through oxidized PKARIα. We used a transgenic mouse model in which PKARIα was made resistant to oxidative activation by homozygous knock-in replacement of redox-sensitive Cysteine 17 with Serine within the regulatory subunits of PKARIα (KI). ATX-II (at 1 nmol/L) was used to acutely enhance INaL in freshly isolated ventricular myocytes from KI and wild-type (WT) control mice. Epifluorescence and confocal imaging were used to assess intracellular Ca2+ handling and ROS formation. A ruptured-patch whole-cell voltage-clamp was used to measure INaL and ICa. The impact of acutely enhanced INaL on RIα dimer formation and PKA target structures was studied using Western blot analysis. ATX-II increased INaL to a similar extent in KI and WT cells, which was associated with significant cytosolic and mitochondrial ROS formation in both genotypes. Acutely activated Ca2+ handling in terms of increased Ca2+ transient amplitudes and elevated SR Ca2+ load was equally present in KI and WT cells. Likewise, cellular arrhythmias as approximated by non-triggered Ca2+ elevations during Ca2+ transient decay and by diastolic SR Ca2+-spark frequency occurred in a comparable manner in both genotypes. Most importantly and in contrast to our initial hypothesis, ATX-II did not alter the magnitude or inactivation kinetics of ICa in neither WT nor KI cells and did not result in PKARIα dimerization (i.e., oxidation) despite a clear prooxidant intracellular environment. The inotropic and arrhythmogenic effects of acutely increased INaL are associated with elevated ROS, but do not involve oxidation of PKARIα.

Protective Role of Ellagic Acid Against Ethanol-Induced Neurodevelopmental Disorders in Newborn Male Rats: Insights into Maintenance of Mitochondrial Function and Inhibition of Oxidative Stress.

Ellagic acid (EA) exerts, neuroprotective, mitoprotective, anti-oxidative and anti-inflammatory effects. We evaluated protective effect of EA on ethanol-induced fetal alcohol spectrum disorders (FASD). A total of 35 newborn male rats were used, divided into five groups, including; control (normal saline), ethanol (5.25 g/kg per day), ethanol (5.25 g/kg per day) + EA (10 mg/kg), ethanol (5.25 g/kg per day) + EA (20 mg/kg) and ethanol (5.25 g/kg per day) + EA (40 mg/kg). Thirty-six days after birth behavioral tests (Morris water maze and Elevated Plus Maze), tumor necrosis factor-α (TNF-α) levels, oxidative markers (malondialdehyde, glutathione and superoxide dismutase), mitochondrial examination such as succinate dehydrogenases (SDH) activity, mitochondrial swelling, mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) formation were analyzed. The results revealed that ethanol exposure adversely affected cognitive and mitochondrial functions and as well as induced oxidative stress and inflammation in brain tissue. However, EA (20 and 40 mg/kg) administration effectively prevented the toxic effects of ethanol in FASD model. These findings demonstrate that ethanol application significantly impairs the brain development via mitochondrial dysfunction and induction of oxidative stress. These data indicate that EA might be a useful compound for prevention of alcohol-induced FASD.

Does Cell-Type-Specific Silencing of Monoamine Oxidase B Interfere with the Development of Right Ventricle (RV) Hypertrophy or Right Ventricle Failure in Pulmonary Hypertension?

Increased mitochondrial reactive oxygen species (ROS) formation is important for the development of right ventricular (RV) hypertrophy (RVH) and failure (RVF) during pulmonary hypertension (PH). ROS molecules are produced in different compartments within the cell, with mitochondria known to produce the strongest ROS signal. Among ROS-forming mitochondrial proteins, outer-mitochondrial-membrane-located monoamine oxidases (MAOs, type A or B) are capable of degrading neurotransmitters, thereby producing large amounts of ROS. In mice, MAO-B is the dominant isoform, which is present in almost all cell types within the heart. We analyzed the effect of an inducible cardiomyocyte-specific knockout of MAO-B (cmMAO-B KO) for the development of RVH and RVF in mice. Right ventricular hypertrophy was induced by pulmonary artery banding (PAB). RV dimensions and function were measured through echocardiography. ROS production (dihydroethidium staining), protein kinase activity (PamStation device), and systemic hemodynamics (in vivo catheterization) were assessed. A significant decrease in ROS formation was measured in cmMAO-B KO mice during PAB compared to Cre-negative littermates, which was associated with reduced activity of protein kinases involved in hypertrophic growth. In contrast to littermates in which the RV was dilated and hypertrophied following PAB, RV dimensions were unaffected in response to PAB in cmMAO-B KO mice, and no decline in RV systolic function otherwise seen in littermates during PAB was measured in cmMAO-B KO mice. In conclusion, cmMAO-B KO mice are protected against RV dilatation, hypertrophy, and dysfunction following RV pressure overload compared to littermates. These results support the hypothesis that cmMAO-B is a key player in causing RV hypertrophy and failure during PH.

Mitochondrial peptides derived from exercising skeletal muscle increase oxidative stress in microvascular endothelial cells

Introduction: Mitochondria-derived peptides are newly discovered small bioactive peptides thought to communicate metabolic status to other cells. Two such peptides, MOTS-c and Humanin, have been shown to have particularly strong local and systemic regulatory effects on metabolism and oxidative stress in tissues, but their effect specifically on vascular endothelial cells remains unclear. Furthermore, it has been proposed that skeletal muscle is a source of MOTS-c and humanin during exercise but this has not been directly shown. Methods: In seven healthy young males, muscle interstitial fluid was collected from microdialysis probes in the thigh muscle, blood was drawn from femoral arterial and venous catheters and thigh muscle biopsies were obtained before and after one acute bout of exercise. In addition, muscle biopsies were obtained before and after 14 days of leg exercise training. Samples were analysed for MOTS-c, Humanin protein and mRNA. To test the effect of MOTS-c on the microvasculature, human endothelial cells derived from the muscle biopsies were incubated for three days with MOTS-c and analysed for mitochondrial respiration and formation of reactive oxygen species (ROS). Furthermore, mice were injected with MOTS-c for 4-weeks to investigate the in-vivo effect of vessels and microvascular endothelial cells. Data was analyzed by linear mixed models performed with R. Results: Acute exercise resulted in an 88% and 55% ( p<0.001) increase in MOTS-c and humanin concentration, respectively, in muscle dialysate, with no effect on the femoral arterial-venous plasma concentration differences. Both MOTS-c and humanin mRNA levels increased (by 20 and 26%; p<0.05) after acute exercise and were 43% and 35% ( p<0.05) higher, respectively, after 14 days of training. A period of MOTS-c treatment of endothelial cells increased mitochondrial respiration and ROS formation by 3-fold and 5-fold, respectively ( p<0.01). Muscle derived endothelial cells from mice injected for 4-weeks presented a similar mitochondrial respiration but a 4-fold ( p<0.05) higher ROS emission. Conclusion: interstitium in response to exercise, muscle is not a likely source of these peptides in plasma. Our data from in vitro and in vivo experiments suggest that treatment with MOTS-c does not influence endothelial metabolism but leads to increased oxidative stress in microvascular endothelial cells. The funding by Novo Nordisk Foundation (application number: 0070369) is gratefully acknowledged. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Anandamide and WIN 55212–2 Afford Protection in Rat Brain Mitochondria in a Toxic Model Induced by 3-Nitropropionic Acid: an In Vitro Study

Mitochondrial dysfunction plays a key role in the development of neurodegenerative disorders. In contrast, the regulation of the endocannabinoid system has been shown to promote neuroprotection in different neurotoxic paradigms. The existence of an active form of the cannabinoid receptor 1 (CB1R) in mitochondrial membranes (mitCB1R), which might exert its effects through the same signaling mechanisms as the cell membrane CB1R, has been shown to regulate mitochondrial activity. Although there is evidence suggesting that some cannabinoids may induce protective effects on isolated mitochondria, substantial evidence on the role of cannabinoids in mitochondria remains to be explored. In this work, we developed a toxic model of mitochondrial dysfunction induced by exposure of brain mitochondria to the succinate dehydrogenase inhibitor 3-nitropropionic acid (3-NP). Mitochondria were also pre-incubated with the endogenous agonist anandamide (AEA) and the synthetic CB1R agonist WIN 55212–2 to evaluate their protective effects. Mitochondrial reduction capacity, reactive oxygen species (ROS) formation, and mitochondrial swelling were assessed as toxic markers. While 3-NP decreased the mitochondrial reduction capacity and augmented mitochondrial ROS formation and swelling, both AEA and WIN 55212–2 ameliorated these toxic effects. To explore the possible involvement of mitCB1R activation on the protective effects of AEA and WIN 55212–2, mitochondria were also pre-incubated in the presence of the selective CB1R antagonist AM281, which completely reverted the protective effects of the cannabinoids to levels similar to those evoked by 3-NP. These results show partial protective effects of cannabinoids, suggesting that mitCB1R activation may be involved in the recovery of compromised mitochondrial activity, related to reduction of ROS formation and further prevention of mitochondrial swelling.

Clozapine suppresses NADPH oxidase activation, counteracts cytosolic H2O2, and triggers early onset mitochondrial dysfunction during adipogenesis of human liposarcoma SW872 cells

Long-term treatment of schizophrenia with clozapine (CLZ), an atypical antipsychotic drug, is associated with an increased incidence of metabolic disorders mediated by poorly understood mechanisms. We herein report that CLZ, while slowing down the morphological changes and lipid accumulation occurring during SW872 cell adipogenesis, also causes an early (day 3) inhibition of the expression/nuclear translocation of CAAT/enhancer-binding protein β and peroxisome proliferator-activated receptor γ. Under the same conditions, CLZ blunts NADPH oxidase-derived reactive oxygen species (ROS) by a dual mechanism involving enzyme inhibition and ROS scavenging. These effects were accompanied by hampered activation of the nuclear factor (erythroid-derived2)-like 2 (Nrf2)-dependent antioxidant responses compared to controls, and by an aggravated formation of mitochondrial superoxide. CLZ failed to exert ROS scavenging activities in the mitochondrial compartment but appeared to actively scavenge cytosolic H2O2 derived from mitochondrial superoxide. The early formation of mitochondrial ROS promoted by CLZ was also associated with signs of mitochondrial dysfunction. Some of the above findings were recapitulated using mouse embryonic fibroblasts.We conclude that the NADPH oxidase inhibitory and cytosolic ROS scavenging activities of CLZ slow down SW872 cell adipogenesis and suppress their Nrf2 activation, an event apparently connected with increased mitochondrial ROS formation, which is associated with insulin resistance and metabolic syndrome. Thus, the cellular events characterised herein may help to shed light on the more detailed molecular mechanisms explaining some of the adverse metabolic effects of CLZ.

Mitochondrial Reactive Oxygen Species Formation Determines ACSL4/LPCAT2-Mediated Ferroptosis.

Ferroptosis is a form of oxidative cell death that is characterized by enhanced lipid peroxidation and mitochondrial impairment. The enzymes acyl-CoA synthetase long-chain family member 4 (ACSL4) and lysophosphatidylcholine acyltransferase (LPCAT) play an essential role in the biosynthesis of polyunsaturated fatty acid (PUFA)-containing phospholipids, thereby providing the substrates for lipid peroxidation and promoting ferroptosis. To examine the impact of mitochondria in ACSL4/LPCAT2-driven ferroptosis, HEK293T cells overexpressing ACSL4 and LPCAT2 (OE) or empty vector controls (LV) were exposed to 1S, 3R-RSL3 (RSL3) for induction of ferroptosis. The ACSL4/LPCAT2 overexpression resulted in higher sensitivity against RSL3-induced cell death compared to LV-transfected controls. Moreover, mitochondrial parameters such as mitochondrial reactive oxygen species (ROS) formation, mitochondrial membrane potential, and mitochondrial respiration deteriorated in the OE cells, supporting the conclusion that mitochondria play a significant role in ACSL4/LPCAT2-driven ferroptosis. This was further confirmed through the protection of OE cells against RSL3-mediated cell death by the mitochondrial ROS scavenger mitoquinone (MitoQ), which exerted protection via antioxidative properties rather than through previously reported metabolic effects. Our findings implicate that mitochondrial ROS production and the accompanying organelle disintegration are essential for mediating oxidative cell death initiated through lipid peroxidation in ferroptosis.

In vivo measurement of mitochondrial ROS production in mouse models of photoreceptor degeneration

Retinitis pigmentosa (RP) is a disease characterised by photoreceptor cell death. It can be initiated by mutations in a number of different genes, primarily affecting rods, which will die first, resulting in loss of night vision. The secondary death of cones then leads to loss of visual acuity and blindness. We set out to investigate whether increased mitochondrial reactive oxygen species (ROS) formation, plays a role in this sequential photoreceptor degeneration. To do this we measured mitochondrial H2O2 production within mouse eyes in vivo using the mass spectrometric probe MitoB. We found higher levels of mitochondrial ROS that preceded photoreceptor loss in four mouse models of RP: Pde6brd1/rd1; Prhp2rds/rds; RPGR−/−; Cln6nclf. In contrast, there was no increase in mitochondrial ROS in loss of function models of vision loss (GNAT−/−, OGC), or where vision loss was not due to photoreceptor death (Cln3). Upregulation of Nrf2 transcriptional activity with dimethylfumarate (DMF) lowered mitochondrial ROS in RPGR−/− mice. These findings have important implications for the mechanism and treatment of RP.

Effects of Caffeic Acid on Multi-walled Carbon Nanotubes -Induced Mitochondrial Toxicity in Rat Kidney

: Multi-walled carbon nanotubes (MWCNTs) are being utilized in various fields. With regard to their numerous applications, MWCNT-induced toxicity has not been extensively investigated. Thus, the present study sheds light on the protective effect of caffeic acid (CA) on mitochondrial toxicity in the kidney caused by MWCNTs in Wistar rats employing the MTT assay as well as reactive oxygen species (ROS) indices, based on measuring glutathione (GSH), mitochondrial membrane potential (MMP), malondialdehyde (MDA), and catalase (CAT) activity. According to the MTT assay, using MWCNTs could significantly diminish mitochondrial viability based on doses. Furthermore, the study findings suggested that MWCNTs could reduce GSH content and CAT activity and subsequently improve mitochondrial ROS formation and damage the mitochondrial membrane of the kidney. The findings also implied that CA could protect renal mitochondria against toxicity induced by MWCNTs by lowering oxidative stress.

Importance of Mitochondria in Cardiac Pathologies: Focus on Uncoupling Proteins and Monoamine Oxidases.

On the one hand, reactive oxygen species (ROS) are involved in the onset and progression of a wide array of diseases. On the other hand, these are a part of signaling pathways related to cell metabolism, growth and survival. While ROS are produced at various cellular sites, in cardiomyocytes the largest amount of ROS is generated by mitochondria. Apart from the electron transport chain and various other proteins, uncoupling protein (UCP) and monoamine oxidases (MAO) have been proposed to modify mitochondrial ROS formation. Here, we review the recent information on UCP and MAO in cardiac injuries induced by ischemia-reperfusion (I/R) as well as protection from I/R and heart failure secondary to I/R injury or pressure overload. The current data in the literature suggest that I/R will preferentially upregulate UCP2 in cardiac tissue but not UCP3. Studies addressing the consequences of such induction are currently inconclusive because the precise function of UCP2 in cardiac tissue is not well understood, and tissue- and species-specific aspects complicate the situation. In general, UCP2 may reduce oxidative stress by mild uncoupling and both UCP2 and UCP3 affect substrate utilization in cardiac tissue, thereby modifying post-ischemic remodeling. MAOs are important for the physiological regulation of substrate concentrations. Upon increased expression and or activity of MAOs, however, the increased production of ROS and reactive aldehydes contribute to cardiac alterations such as hypertrophy, inflammation, irreversible cardiomyocyte injury, and failure.

Mitochondrial Coenzyme Q Redox Homeostasis and Reactive Oxygen Species Production.

Mitochondrial coenzyme Q (mtQ) of the inner mitochondrial membrane is a redox active mobile carrier in the respiratory chain that transfers electrons between reducing dehydrogenases and oxidizing pathway(s). mtQ is also involved in mitochondrial reactive oxygen species (mtROS) formation through the mitochondrial respiratory chain. Some mtQ-binding sites related to the respiratory chain can directly form the superoxide anion from semiubiquinone radicals. On the other hand, reduced mtQ (ubiquinol, mtQH2) recycles other antioxidants and directly acts on free radicals, preventing oxidative modifications. The redox state of the mtQ pool is a central bioenergetic patameter that alters in response to changes in mitochondrial function. It reflects mitochondrial bioenergetic activity and mtROS formation level, and thus the oxidative stress associated with the mitochondria. Surprisingly, there are few studies describing a direct relationship between the mtQ redox state and mtROS production under physiological and pathological conditions. Here, we provide a first overview of what is known about the factors affecting mtQ redox homeostasis and its relationship to mtROS production. We have proposed that the level of reduction (the endogenous redox state) of mtQ may be a useful indirect marker to assess total mtROS formation. A higher mtQ reduction level (mtQH2/mtQtotal) indicates greater mtROS formation. The mtQ reduction level, and thus the mtROS formation, depends on the size of the mtQ pool and the activity of the mtQ-reducing and mtQH2-oxidizing pathway(s) of respiratory chain. We focus on a number of physiological and pathophysiological factors affecting the amount of mtQ and thus its redox homeostasis and mtROS production level.

Rosiglitazone reduces diabetes angiopathy by inhibiting mitochondrial dysfunction dependent on regulating HSP22 expression

The effects of rosiglitazone (RSG) in patients with type 2 diabetes mellitus (T2DM) remain controversial. Here, we first used network pharmacology to identify the common targets of RSG in the treatment of diabetes angiopathy (DA). Enrichment analysis found that the common genes were involved in the inflammatory response, leukocyte cell-cell adhesion, mitochondrion organization and oxidative stress. Our previous research confirmed that heat shock protein 22 (HSP22) suppresses diabetes-induced endothelial activation and injury by inhibiting mitochondrial reactive oxygen species (mtROS) formation and dysfunction. We then constructed HSP22 knockout mice with T2DM to investigate whether RSG protected the vascular endothelium by upregulating HSP22. Our study suggested that RSG reduced vascular endothelial cell activation and injury by decreasing monocyte adhesion and cytokine secretion and simultaneously upregulating HSP22 expression. Mechanistically, RSG inhibited mitochondrial oxidative stress and dysfunction by regulating PPAR-γ in a manner partially dependent on expression of HSP22, resulting in reduced DA.

Pathological role of high sugar in mitochondrial respiratory chain defect - augmented mitochondrial stress.

Respiratory complex anomalies could lead to the production of ROS. Ca2+, at physiological levels serves as a second messenger in many physiological functions. However, a research group reported that mitochondrial calcium [Ca2+]m overload leads to ROS production which could be lethal to the mitochondria through various mechanisms. The F1F0-ATPase (ATP synthase or complex V) is the enzyme that is responsible for catalyzing the final step of oxidative phosphorylation. Mitochondrial complex V T8993G mutation specifically blocks the translocation of protons across the intermembrane space thereby blocking ATP synthesis leading to Neuropathy, Ataxia and Retinitis Pigmentosa Syndromes (NARP). The main aim undertaking this study is to explore the possibility of [Ca2+]m overload mediating the pathological roles of high glucose in defective respiratory chain mediated mitochondrial stress. The NARP cybrids are ordered and are established in vitro experimental models for the cells with F1FO-ATPase defects, these cells harbor 98% of mtDNA T8993G mutation. Their counterparts 143B osteosarcoma cell lines are the parental cell lines used for comparisons. We uncovered that, NARP cells mediated and enhanced the death of the cells (apoptosis) when incubated with hydrogen peroxide (H2O2) and high glucose respectively as depicted by the MTT assay of cell viability. Furthermore, using the fluorescence probe-coupled laser scanning confocal imaging microscopy, NARP cells significantly enabled mitochondrial reactive oxygen species (mROS) formation and enhanced the depolarization of the mitochondrial membrane potential (ΔΨm). Elucidating the mechanisms of sugar enhanced toxicity on mitochondria would help in the future to alleviate the symptoms of patients associated with Neuritis Ataxia Retinitis Pigmentosa (NARP) syndromes.

Down regulation of NDUFS1 is involved in the progression of parenteral-nutrition-associated liver disease by increasing Oxidative stress

Parenteral nutrition (PN)-associated liver disease (PNALD) is a common and life-threatening complication of patients receiving PN. However, its definitive pathology remains unclear. Ubiquinone oxidoreductase core subunit S1 (NDUFS1), which is the largest core subunit of mitochondrial complex I, could alter the mitochondrial reactive oxygen species (ROS) formation. The purpose of this study was to investigate the role of NDUFS1 in the pathogenesis of PNALD and its underlying mechanism. We performed hepatic proteomics analysis of PNALD patients, and established a PNALD rat model to verify the role of oxidative stress, NDUFS1, pyrin inflammasome, and IL-1β in the progression of PNALD.Proteomics analysis revealed the NDUFS1 expression was decreased in PNALD patients, and the differentially espressed proteins were involved in mitochondrial respiratory chain complex Ⅰ. Treatment with MitoQ or overexpression of NDUFS1 can alleviate the progression of PNALD by reducing oxidative stress. The expression of pyrin, caspase-1, and IL-1β was increased in PN rats. Pharmacological antagonism of pyrin by colchicine can alleviate liver injury and hepatic steatosis.NDUFS1 prevents PNALD pathogenesis by regulating oxidative stress. Pyrin inflammasome and IL-1β may participate in the process of PNALD development by suppressing the transcription of MTTP and impairing the secretion of VLDL. Oxidative stress reduction may be employed as a strategy in the prevention and treatment of PNALD.

Abstract P1101: Mitochondrial Ca Uniporter Complex, ROS And CaT Alternans

Background: Atrial calcium transient (CaT) alternans is defined as beat-to-beat alternation in CaT amplitude and is causally linked to atrial fibrillation (AF). Inhibition of mitochondrial Ca uptake via the mitochondrial Ca uniporter complex (MCUC) facilitates CaT alternans and can lead to an increase in mitochondrial reactive oxygen species(ROS) production that compromises the cellular antioxidative capacity. The objective was to determine the mechanisms through which mitochondrial Ca uptake and ROS production determine the susceptibility of atrial cells to develop CaT alternans. Methods: CaT alternans was measured in single rabbit left atrial myocytes with fluorescence microscopy using the fluorescent Ca indicator Cal-520/AM, and for simultaneous measurements of ROS and alternans, cells were loaded with CM-DCFDA and Cal-590/AM. CaT alternans was induced by increasing the pacing frequency until stable CaT alternans was observed. The degree of alternans was quantified as the alternans ratio (AR = 1 – S/L, where S/L is the ratio of the small to the large amplitude of a pair of alternating CaTs). Results: Exposure of LA myocytes to the specific MCUC inhibitor Ru360 increased the AR by 86%. However, the subsequent stimulation of mitochondrial Ca uptake with the MCUC activator spermine (Spm) decreased AR by 79% (p=0.028). Quercetin (a O2 .- scavenger) and Tempol (a superoxide dismutase mimetic) lowered CaT AR by 96% (p=0.0007) and 79% (p=0.0029), respectively. An oxidative challenge with tert-butylhydroperoxide (tBHP) increased AR by 140% (p=<0.0001), and the reducing agent dithiothreitol (DTT) decreased AR by 39% (p=0.0194). Moreover, DTT treatment rescued CaT alternans previously enhanced by tBHP. During CaT alternans the rate of ROS production increased by 23% (p=0.026), however Spm treatment attenuated the increased ROS production. Conclusion: An oxidizing environment facilitates the development of CaT alternans. During CaT alternans mitochondrial ROS formation is increased and involves MCUC activity.