Types Of Mitochondrial Dysfunction Research Articles

Advancing Anticancer Drug Discovery: Leveraging Metabolomics and Machine Learning for Mode of Action Prediction by Pattern Recognition.

A bottleneck in the development of new anti-cancer drugs is the recognition of their mode of action (MoA). Metabolomics combined with machine learning allowed to predict MoAs of novel anti-proliferative drug candidates, focusing on human prostate cancer cells (PC-3). As proof of concept, 38 drugs are studied with known effects on 16 key processes of cancer metabolism, profiling low molecular weight intermediates of the central carbon and cellular energy metabolism (CCEM) by LC-MS/MS. These metabolic patterns unveiled distinct MoAs, enabling accurate MoA predictions for novel agents by machine learning. The transferability of MoA predictions based on PC-3 cell treatments is validated with two other cancer cell models, i.e., breast cancer and Ewing's sarcoma, and show that correct MoA predictions for alternative cancer cells are possible, but still at some expense of prediction quality. Furthermore, metabolic profiles of treated cells yield insights into intracellular processes, exemplified for drugs inducing different types of mitochondrial dysfunction. Specifically, it is predicted that pentacyclic triterpenes inhibit oxidative phosphorylation and affect phospholipid biosynthesis, as confirmed by respiration parameters, lipidomics, and molecular docking. Using biochemical insights from individual drug treatments, this approach offers new opportunities, including the optimization of combinatorial drug applications.

The role of graphene quantum dots in mitigating lipid peroxidation.

Lipid peroxidation often underlies apoptosis and mitochondrial dysfunction, which are common pathological phenomena in neurodegenerative and lysosomal storage diseases. Graphene quantum dots (GQDs) have garnered considerable interest as a nanomedicine over the last several years due to their biocompatibility and ability to target cellular disorders associated with disease phenotypes. Recent work with cells containing α-synuclein aggregates (i.e., cells mimicking the onset of Parkinson's disease) has demonstrated that GQDs exhibit mitoprotective behavior. In these studies, GQDs were able to permeate the plasma membrane, inhibit mitochondrial deformation, and restore mitochondrial complex I activity. However, the mechanism by which GQDs interacted with mitochondria was neither examined nor understood. It is known that this type of mitochondrial dysfunction is associated with free radical-induced oxidative lipid damage. Therefore, we hypothesize that the observed mitoprotective properties of GQDs arise from the scavenging of reactive oxidative species that would otherwise interact with mitochondrial membranes. To test this hypothesis, we developed a system to examine lipid peroxidation in synthetic membranes while in the presence of GQDs. Here, we used the fluorescent sensor C11-BODIPY to monitor the kinetics of lipid peroxidation in the presence of hydroxyl free radicals. Comparison of peroxidation rates to first principles kinetic models confirmed that GQDs were indeed scavengers of free radicals. When membranes were incubated with GQDs, the lipid peroxidation rate decreased by 90%. Interestingly, when compared to other renowned antioxidants, such as ascorbic acid and Trolox, GQDs exhibited significantly higher antioxidant efficiency. Ascorbic acid and Trolox required substantially higher concentrations than GQDs to achieve comparable levels of reduction to lipid peroxidation rates. These results warrant further investigation of GQDs as a mitochondrial membrane protection agent.

Site-specific mitochondrial dysfunction in neurodegeneration

Mitochondria are essential for neuronal survival and mitochondrial dysfunction is a hallmark of neurodegeneration. The loss in mitochondrial energy production, oxidative stress, and changes in calcium handling are associated with neurodegenerative diseases; however, different sites and types of mitochondrial dysfunction are linked to distinct neuropathologies. Understanding the causal or correlative relationship between changes in mitochondria and neuropathology will lead to new therapeutic strategies. Here, we summarize the evidence of site-specific mitochondrial dysfunction and mitochondrial-related clinical trials for neurodegenerative diseases. We further discuss potential therapeutic approaches, such as mitochondrial transplantation, restoration of mitochondrial function, and pharmacological alleviation of mitochondrial dysfunction.

Age-related sex differences in the expression of important disease-linked mitochondrial proteins in mice

The prevalence and progression of many illnesses, such as neurodegenerative and cardiovascular diseases, obesity, and cancer, vary between women and men, often in an age-dependent manner. A joint hallmark of these diseases is some type of mitochondrial dysfunction. While several mitochondrial proteins are known to be regulated by sex hormones, the levels of those proteins have not been systematically analyzed with regard to sex and age, and studies that consider sex and/or age differences in the protein expression are very rare. In this study, we compared the expression patterns of physiologically important mitochondrial proteins in female and male C57BL/6N mice of age cohorts frequently used in experiments. We found that sex-related differences in the expression of uncoupling proteins 1 and 3 (UCP1 and UCP3) occur in an age-dependent manner. The sex-specific expression of UCP1 and UCP3 in brown adipose tissue (BAT) was inversely correlated with differences in body weight. Expression of UCP4 in the brain, Complex I in the spleen, and Complex II in the brain and BAT was least affected by the sex of the mouse. We further demonstrated that there are serious limitations in using VDAC1 and actin as markers in western blot analyses, due to their sex- and age-specific fluctuations. Our results confirm that sex and age are important parameters and should be taken into account by researchers who examine the mechanistic aspects of diseases.HighlightsThe levels of UCP1 and UCP3 protein expression differ between females and males in an age-dependent manner.Pre-pubertal expression of almost all proteins tested in this study does not depend on the sex of the mouse.Expression of VDAC1 and actin, which are often used as loading control proteins in western blot analysis, is tissue-specifically influenced by sex and age.

Exploring the Rationale for the Use of the Ketogenic Diet in the Treatment of Mental Health Disorders

(1) Background: The ketogenic diet (KD) was developed in the 1920s as a treatment for pediatric epilepsy and is emerging as a possible treatment option for certain mental health disorders. There is a link between certain mental health disorders and epilepsy, suggesting some commonality among underlying mechanisms. (2) Methods: The literature relating to mental disorders and the KD is sparse. The authors attempt to a narrative review of the existing literature to show that there may be validity to studying the KD as a treatment for certain mental health disorders. (3) Results: Various types of mitochondrial dysfunction and impaired oxidative metabolism have been identified in many mental health disorders (bipolar disorder, major depressive disorder, autism, schizophrenia, and others). Mitochondrial deficits may affect neuroplasticity and cause synaptic dysfunction, which could change brain structure and function in a way that might affect behavior. The KD has been associated with epigenetic changes in the genes associated with mitochondrial function. Chronic oxidative stress and inflammation have also been implicated in mental health disorders and may be reduced by the KD. The KD regulates glutamatergic transmission and may initiate extracellular changes as well, in a manner similar to pharmacological agents used to stabilize moods. The KD may be difficult for patient adherence and has been associated with many and potentially severe adverse effects. The role of the KD in addressing treatment-resistant pediatric epilepsy is established and epilepsy is comorbid with a number of mental health conditions. (4) Conclusions: There is a paucity of literature on this subject and there is no robust clinical evidence in support of the use of the KD for treating mental disorders but there are indications that the KD can reduce systemic inflammation, improve cerebral mitochondrial metabolism, and enhance endogenous antioxidation, all of which may be helpful in treating certain mental health conditions. The KD is also associated with serious health risks and clinicians must weigh risks versus benefits.

209 - Inhibition of respiratory chain Complex III irreversibly changes the mitochondria proteomic landscape

The role of mitochondria dysfunction in the pathogenesis of pulmonary hypertension (PH) is currently well-recognized. However, the particular mechanisms and the type of mitochondrial dysfunction are still being debated. We have recently shown that chronic inhibition of oxidative phosphorylation by Antimycin A (AA) results in increased pulmonary pressure and remodeled pulmonary arteries. AA (0.35mg/kg) was given to rats three times during first six days and lungs were analyzed 30 minutes (acute effect), 12 and 24 days (chronic effect) after the first AA injection. Mitochondria isolated from lungs were subjected to mass spectrometry and quantitative proteomic analysis to estimate changes in the isolated mitochondrial proteome over the course of disease development. Using a 4-fold change cutoff value, 48 mitochondrial proteins were discovered to be altered upon AA treatment, with 13 proteins exhibiting a significant difference. Our data indicate that proteomic data with applied 4-fold cutoff can completely distinguish between the control and 24-day groups using principal component analysis. Functional analysis of the proteome data revealed major downregulation of enzymes involved in fatty acids oxidation(ACDSB,HADH) and fatty acids transport(CPT1, ACSM5). Electron transport chain proteins showed mixed results with downregulation of Complex IV (COX1/2), altered Complex I subunits(NU4/5M) and assembly protein expression(NDUF4), and upregulation of ubiquinone biosynthesis (COQ3/7). Activation of ubiquinone biosynthesis could be explained as compensation for inhibition of mitochondrial respiration by AA. Mitochondrial machinery for importing proteins into the matrix(TIM9/10/13) was upregulated, but peptidases(LON,MPPA) that control the quality of matrix proteins were downregulated. Finally, proteins that regulate mitochondria morphology(MIRO2, PGAM5,TMM11) and degradation pathways (MIEAP,BCL2) were altered. Collectively, our data indicate that chronic inhibition of the respiratory chain for six days leads to irreversible changes in the proteomic landscape of mitochondria. These changes reprogram mitochondria to a different metabolic state and altered morphology that have been found in various models of PH and PH patients.

Mitochondrial Dysfunction: A Novel Potential Driver of Epithelial-to-Mesenchymal Transition in Cancer.

Epithelial-to-mesenchymal transition (EMT) allows epithelial cancer cells to assume mesenchymal features, endowing them with enhanced motility and invasiveness, thus enabling cancer dissemination and metastatic spread. The induction of EMT is orchestrated by EMT-inducing transcription factors that switch on the expression of “mesenchymal” genes and switch off the expression of “epithelial” genes. Mitochondrial dysfunction is a hallmark of cancer and has been associated with progression to a metastatic and drug-resistant phenotype. The mechanistic link between metastasis and mitochondrial dysfunction is gradually emerging. The discovery that mitochondrial dysfunction owing to deregulated mitophagy, depletion of the mitochondrial genome (mitochondrial DNA) or mutations in Krebs’ cycle enzymes, such as succinate dehydrogenase, fumarate hydratase, and isocitrate dehydrogenase, activate the EMT gene signature has provided evidence that mitochondrial dysfunction and EMT are interconnected. In this review, we provide an overview of the current knowledge on the role of different types of mitochondrial dysfunction in inducing EMT in cancer cells. We place emphasis on recent advances in the identification of signaling components in the mito-nuclear communication network initiated by dysfunctional mitochondria that promote cellular remodeling and EMT activation in cancer cells.

Assessment of ToxCast Phase II for Mitochondrial Liabilities Using a High-Throughput Respirometric Assay.

Previous high-throughput screens to identify mitochondrial toxicants used immortalized cell lines and focused on changes in mitochondrial membrane potential, which may not be sufficient and do not identify different types of mitochondrial dysfunction. Primary cultures of renal proximal tubule cells (RPTC) were examined with the Seahorse Extracellular Flux Analyzer to screen 676 compounds (5 μM; 1 h) from the ToxCast Phase II library for mitochondrial toxicants. Of the 676 compounds, 19 were classified as cytotoxicants, 376 were electron transport chain (ETC) inhibitors, and 5 were uncouplers. The remaining 276 compounds were examined after a 5-h exposure to identify slower acting mitochondrial toxicants. This experiment identified 3 cytotoxicants, 110 ETC inhibitors, and 163 compounds with no effect. A subset of the ToxCast Phase II library was also examined in immortalized human renal cells (HK2) to determine differences in susceptibility to mitochondrial toxicity. Of the 131 RPTC ETC inhibitors tested, only 14 were ETC inhibitors in HK2 cells. Of the 5 RPTC uncouplers, 1 compound was an uncoupler in HK2 cells. These results demonstrate that 73% (491/676) of the compounds in the ToxCast Phase II library compounds exhibit RPTC mitochondrial toxicity, overwhelmingly ETC inhibition. In contrast, renal HK2 cells are markedly less sensitive and only identified 6% of the compounds as mitochondrial toxicants. We suggest caution is needed when studying mitochondrial toxicity in immortalized cell lines. This information will provide mechanisms and chemical-based criteria for assessing and predicting mitochondrial liabilities of new drugs, consumer products, and environmental agents.

Oxidative stress induces mitochondrial dysfunction in a subset of autistic lymphoblastoid cell lines

There is an increasing recognition that mitochondrial dysfunction is associated with autism spectrum disorders. However, little attention has been given to the etiology of mitochondrial dysfunction and how mitochondrial abnormalities might interact with other physiological disturbances such as oxidative stress. Reserve capacity is a measure of the ability of the mitochondria to respond to physiological stress. In this study, we demonstrate, for the first time, that lymphoblastoid cell lines (LCLs) derived from children with autistic disorder (AD) have an abnormal mitochondrial reserve capacity before and after exposure to reactive oxygen species (ROS). Ten (44%) of 22 AD LCLs exhibited abnormally high reserve capacity at baseline and a sharp depletion of reserve capacity when challenged with ROS. This depletion of reserve capacity was found to be directly related to an atypical simultaneous increase in both proton-leak respiration and adenosine triphosphate-linked respiration in response to increased ROS in this AD LCL subgroup. In this AD LCL subgroup, 48-hour pretreatment with N-acetylcysteine, a glutathione precursor, prevented these abnormalities and improved glutathione metabolism, suggesting a role for altered glutathione metabolism associated with this type of mitochondrial dysfunction. The results of this study suggest that a significant subgroup of AD children may have alterations in mitochondrial function, which could render them more vulnerable to a pro-oxidant microenvironment as well as intrinsic and extrinsic sources of ROS such as immune activation and pro-oxidant environmental toxins. These findings are consistent with the notion that AD is caused by a combination of genetic and environmental factors.

Targeting mitochondria for cancer treatment - two types of mitochondrial dysfunction.

Two basic types of cancers were identified – those with the mitochondrial dysfunction in cancer cells (the Warburg effect) or in fibroblasts supplying energy rich metabolites to a cancer cell with functional mitochondria (the reverse Warburg effect). Inner membrane potential of the functional and dysfunctional mitochondria measured by fluorescent dyes (e.g. by Rhodamine 123) displays low and high values (apparent potential), respectively, which is in contrast to the level of oxidative metabolism. Mitochondrial dysfunction (full function) results in reduced (high) oxidative metabolism, low (high) real membrane potential, a simple layer (two layers) of transported protons around mitochondria, and high (low) damping of microtubule electric polar vibrations. Crucial modifications are caused by ordered water layer (exclusion zone). For the high oxidative metabolism one proton layer is at the mitochondrial membrane and the other at the outer rim of the ordered water layer. High and low damping of electric polar vibrations results in decreased and increased electromagnetic activity in cancer cells with the normal and the reverse Warburg effect, respectively. Due to nonlinear properties the electromagnetic frequency spectra of cancer cells and transformed fibroblasts are shifted in directions corresponding to their power deviations resulting in disturbances of interactions and escape from tissue control. The cancer cells and fibroblasts of the reverse Warburg effect tumors display frequency shifts in mutually opposite directions resulting in early generalization. High oxidative metabolism conditions high aggressiveness. Mitochondrial dysfunction, a gate to malignancy along the cancer transformation pathway, forms a narrow neck which could be convenient for cancer treatment.

Mitochondrial Genome Instability and ROS Enhance Intestinal Tumorigenesis in APC Min/+ Mice

Alterations in mitochondrial oxidative phosphorylation have long been documented in tumors. Other types of mitochondrial dysfunction, including altered reactive oxygen species (ROS) production and apoptosis, also can contribute to tumorigenesis and cancer phenotypes. Furthermore, mutation and altered amounts of mitochondrial DNA (mtDNA) have been observed in cancer cells. However, how mtDNA instability per se contributes to cancer remains largely undetermined. Mitochondrial transcription factor A (TFAM) is required for expression and maintenance of mtDNA. Tfam heterozygous knock-out (Tfam(+/-)) mice show mild mtDNA depletion, but have no overt phenotypes. We show that Tfam(+/-) mouse cells and tissues not only possess less mtDNA but also increased oxidative mtDNA damage. Crossing Tfam(+/-) mice to the adenomatous polyposis coli multiple intestinal neoplasia (APC(Min/+)) mouse cancer model revealed that mtDNA instability increases tumor number and growth in the small intestine. This was not a result of enhancement of Wnt/β-catenin signaling, but rather appears to involve a propensity for increased mitochondrial ROS production. Direct involvement of mitochondrial ROS in intestinal tumorigenesis was shown by crossing APC(Min/+) mice to those that have catalase targeted to mitochondria, which resulted in a significant reduction in tumorigenesis in the colon. Thus, mitochondrial genome instability and ROS enhance intestinal tumorigenesis and Tfam(+/-) mice are a relevant model to address the role of mtDNA instability in disease states in which mitochondrial dysfunction is implicated, such as cancer, neurodegeneration, and aging.

Mitochondrial medicine for neurodegenerative diseases

Mitochondrial dysfunction has been reported in a wide array of neurological disorders ranging from neuromuscular to neurodegenerative diseases. Recent studies on neurodegenerative diseases have revealed that mitochondrial pathology is generally found in inherited or sporadic neurodegenerative diseases and is believed to be involved in the pathophysiological process of these diseases. Commonly seen types of mitochondrial dysfunction in neurodegenerative diseases include excessive free radical generation, lowered ATP production, mitochondrial permeability transition, mitochondrial DNA lesions, perturbed mitochondrial dynamics and apoptosis. Mitochondrial medicine as an emerging therapeutic strategy targeted to mitochondrial dysfunction in neurodegenerative diseases has been proven to be of value, though this area of research is still at in its early stage. In this article, we report on recent progress in the development of several mitochondrial therapies including antioxidants, blockade of mitochondrial permeability transition, and mitochondrial gene therapy as evidence that mitochondrial medicine has promise in the treatment of neurodegenerative diseases.