Redox biology and the interface between bioenergetics, autophagy and circadian control of metabolism.

Understanding molecular mechanisms that underlie the recent emergence of metabolic diseases such as diabetes and heart failure has revealed the need for a multi-disciplinary research integrating the key metabolic pathways which change the susceptibility to environmental or pathologic stress. At the physiological level these include the circadian control of metabolism which aligns metabolism with temporal demand. The mitochondria play an important role in integrating the redox signals and metabolic flux in response to the changing activities associated with chronobiology, exercise and diet.

The Role of Autophagy, Mitophagy and Lysosomal Functions in Modulating Bioenergetics and Survival in the Context of Redox and Proteotoxic Damage: Implications for Neurodegenerative Diseases.

Redox and proteotoxic stress contributes to age-dependent accumulation of dysfunctional mitochondria and protein aggregates, and is associated with neurodegeneration. The free radical theory of aging inspired many studies using reactive species scavengers such as alpha-tocopherol, ascorbate and coenzyme Q to suppress the initiation of oxidative stress. However, clinical trials have had limited success in the treatment of neurodegenerative diseases.

Abrogation of Nrf2 impairs antioxidant signaling and promotes atrial hypertrophy in response to high-intensity exercise stress.

Background: Anomalies in myocardial structure involving myocyte growth, hypertrophy, differentiation, apoptosis, necrosis etc. affects its function and render cardiac tissue more vulnerable to the development of heart failure. Although oxidative stress has a well-established role in cardiac remodeling and dysfunction, the mechanisms linking redox state to atrial cardiomyocyte hypertrophic changes are poorly understood.

The immediate wound-induced oxidative burst of Saccharina latissima depends on light via photosynthetic electron transport.

Reactive oxygen species (ROS) produced by an oxidative burst are an important component of the wound response in algae, vascular plants, and animals. In all taxa, ROS production is usually attributed solely to a defense-related enzyme like NADPH-oxidase (Nox). However, here we show that the initial, wound-induced oxidative burst of the kelp Saccharina latissima depends on light and photosynthetic electron transport.

Disruption of nuclear factor (erythroid-derived-2)-like 2 antioxidant signaling: a mechanism for impaired activation of stem cells and delayed regeneration of skeletal muscle.

Recently we have reported that age-dependent decline in antioxidant levels accelerated apoptosis and skeletal muscle degeneration. Here, we demonstrate genetic ablation of the master cytoprotective transcription factor, nuclear factor (erythroid-derived-2)-like 2 (Nrf2), aggravates cardiotoxin (CTX)-induced tibialis anterior (TA) muscle damage. Disruption of Nrf2 signaling sustained the CTX-induced burden of reactive oxygen species together with compromised expression of antioxidant genes and proteins.

Endothelial Cell Bioenergetics and Mitochondrial DNA Damage Differ in Humans Having African or West Eurasian Maternal Ancestry.

Background: We hypothesized that endothelial cells having distinct mitochondrial genetic backgrounds would show variation in mitochondrial function and oxidative stress markers concordant with known differential cardiovascular disease susceptibilities. To test this hypothesis, mitochondrial bioenergetics were determined in endothelial cells from healthy individuals with African versus European maternal ancestries.

Methods And Results: Bioenergetics and mitochondrial DNA (mtDNA) damage were assessed in single-donor human umbilical vein endothelial cells belonging to mtDNA haplogroups H and L, representing West Eurasian and African maternal ancestries, respectively.

Mitochondrial thiol modification by a targeted electrophile inhibits metabolism in breast adenocarcinoma cells by inhibiting enzyme activity and protein levels.

Many cancer cells follow an aberrant metabolic program to maintain energy for rapid cell proliferation. Metabolic reprogramming often involves the upregulation of glutaminolysis to generate reducing equivalents for the electron transport chain and amino acids for protein synthesis. Critical enzymes involved in metabolism possess a reactive thiolate group, which can be modified by certain oxidants.

Hemodiafiltration and hemodialysis differently affect P wave duration and dispersion on the surface electrocardiogram.

Aim: The incidence of atrial fibrillation is increased during hemodialysis (HD); however, the effects of hemodiafiltration (HDF) on atrial arrhythmias have not been evaluated. The prolongation of the P wave and P dispersion (Pd) can predict atrial arrhythmias.

Methods: Data from 30 patients receiving HDF over a period of 3 months were collected; the same group of patients was then evaluated during treatment with conventional HD for at least another 3 months.

Mitochondrial oncobioenergetic index: A potential biomarker to predict progression from indolent to aggressive prostate cancer.

Mitochondrial function is influenced by alterations in oncogenes and tumor suppressor genes and changes in the microenvironment occurring during tumorigenesis. Therefore, we hypothesized that mitochondrial function will be stably and dynamically altered at each stage of the prostate tumor development. We tested this hypothesis in RWPE-1 cells and its tumorigenic clones with progressive malignant characteristics (RWPE-1 < WPE-NA22 < WPE-NB14 < WPE-NB11 < WPE-NB26) using high-throughput respirometry.

Pharmacological induction of ferritin prevents osteoblastic transformation of smooth muscle cells.

Vascular calcification is a frequent complication of atherosclerosis, diabetes and chronic kidney disease. In the latter group of patients, calcification is commonly seen in tunica media where smooth muscle cells (SMC) undergo osteoblastic transformation. Risk factors such as elevated phosphorus levels and vitamin D3 analogues have been identified.

Modification of platelet proteins by 4-hydroxynonenal: Potential Mechanisms for inhibition of aggregation and metabolism.

Platelet aggregation is an essential response to tissue injury and is associated with activation of pro-oxidant enzymes, such as cyclooxygenase, and is also a highly energetic process. The two central energetic pathways in the cell, glycolysis and mitochondrial oxidative phosphorylation, are susceptible to damage by reactive lipid species. Interestingly, how platelet metabolism is affected by the oxidative stress associated with aggregation is largely unexplored.

Mitochondrial DNA Polymerase POLG1 Disease Mutations and Germline Variants Promote Tumorigenic Properties.

Germline mutations in mitochondrial DNA polymerase gamma (POLG1) induce mitochondrial DNA (mtDNA) mutations, depletion, and decrease oxidative phosphorylation. Earlier, we identified somatic mutations in POLG1 and the contribution of these mutations in human cancer. However, a role for germline variations in POLG1 in human cancers is unknown.

Human REV3 DNA Polymerase Zeta Localizes to Mitochondria and Protects the Mitochondrial Genome.

To date, mitochondrial DNA polymerase γ (POLG) is the only polymerase known to be present in mammalian mitochondria. A dogma in the mitochondria field is that there is no other polymerase present in the mitochondria of mammalian cells. Here we demonstrate localization of REV3 DNA polymerase in the mammalian mitochondria.

Mitoepigenetics: The different shades of grey.

Epigenetic modifications of the nuclear genome have been well studied and it is established that these modifications play a key role in nuclear gene expression. However, the status of mitochondrial epigenetic modifications has not been delved in detail. The recent technological advancements in the genome analyzing tools and techniques, have helped in investigating mitochondrial epigenetic modifications with greater resolution and studies have indicated a regulatory role of the mitochondrial epigenome.

Defining the effects of storage on platelet bioenergetics: The role of increased proton leak.

The quality of platelets decreases over storage time, shortening their shelf life and potentially worsening transfusion outcomes. The changes in mitochondrial function associated with platelet storage are poorly defined and to address this we measured platelet bioenergetics in freshly isolated and stored platelets. We demonstrate that the hypotonic stress test stimulates both glycolysis and oxidative phosphorylation and the stored platelets showed a decreased recovery to this stress.

KEAP1-NRF2 signalling and autophagy in protection against oxidative and reductive proteotoxicity.

Maintaining cellular redox status to allow cell signalling to occur requires modulation of both the controlled production of oxidants and the thiol-reducing networks to allow specific regulatory post-translational modification of protein thiols. The oxidative stress hypothesis captured the concept that overproduction of oxidants can be proteotoxic, but failed to predict the recent finding that hyperactivation of the KEAP1-NRF2 system also leads to proteotoxicity. Furthermore, sustained activation of thiol redox networks by KEAP1-NRF2 induces a reductive stress, by decreasing the lifetime of necessary oxidative post-translational modifications required for normal metabolism or cell signalling.

Predicting storage-dependent damage to red blood cells using nitrite oxidation kinetics, peroxiredoxin-2 oxidation, and hemoglobin and free heme measurements.

Background: Storage-dependent damage to red blood cells (RBCs) varies significantly. Identifying RBC units that will undergo higher levels of hemolysis during storage may allow for more efficient inventory management decision-making. Oxidative-stress mediates storage-dependent damage to RBCs and will depend on the oxidant:antioxidant balance.

Decreased Bioenergetic Health Index in monocytes isolated from the pericardial fluid and blood of post-operative cardiac surgery patients.

Monitoring the bioenergetics of leucocytes is now emerging as an important approach in translational research to detect mitochondrial dysfunction in blood or other patient samples. Using the mitochondrial stress test, which involves the sequential addition of mitochondrial inhibitors to adherent leucocytes, we have calculated a single value, the Bioenergetic Health Index (BHI), which represents the mitochondrial function in cells isolated from patients. In the present report, we assess the BHI of monocytes isolated from the post-operative blood and post-operative pericardial fluid (PO-PCF) from patients undergoing cardiac surgery.

A Nitric Oxide-Releasing Self-Assembled Peptide Amphiphile Nanomatrix for Improving the Biocompatibility of Microporous Hollow Fibers.

Oxygenators are critical components of extracorporeal circuits used frequently in cardiopulmonary bypass and intensive care, but platelet activation and induction of a complex inflammatory response are usually observed with their use. To improve the biocompatibility of oxygenators, we developed a nitric oxide (NO)-releasing, self-assembled peptide amphiphile nanomatrix. The nanomatrix formed a homogenous coating over the microporous hollow fibers as demonstrated by scanning electron microscopy.

Novel Mechanisms for the Antifibrotic Action of Nintedanib.

Idiopathic pulmonary fibrosis (IPF) is a disease with relentless course and limited therapeutic options. Nintedanib (BIBF-1120) is a multiple tyrosine kinase inhibitor recently approved by the U.S.

Inhibition of the lymphocyte metabolic switch by the oxidative burst of human neutrophils.

Activation of the phagocytic NADPH oxidase-2 (NOX-2) in neutrophils is a critical process in the innate immune system and is associated with elevated local concentrations of superoxide, hydrogen peroxide (H2O2) and hypochlorous acid. Under pathological conditions, NOX-2 activity has been implicated in the development of autoimmunity, indicating a role in modulating lymphocyte effector function. Notably, T-cell clonal expansion and subsequent cytokine production requires a metabolic switch from mitochondrial respiration to aerobic glycolysis.

Red blood cell washing, nitrite therapy, and antiheme therapies prevent stored red blood cell toxicity after trauma-hemorrhage.

Transfusion of stored red blood cells (RBCs) is associated with increased morbidity and mortality in trauma patients. Pro-oxidant, pro-inflammatory, and nitric oxide (NO) scavenging properties of stored RBCs are thought to underlie this association. In this study we determined the effects of RBC washing and nitrite and antiheme therapy on stored RBC-dependent toxicity in the setting of trauma-induced hemorrhage.