Mitochondrial dysfunction as a trigger of innate immune responses and inflammation

In vitro cytotoxicity study of superparamagnetic iron oxide and silica nanoparticles on pneumocyte organelles

Inhalation is the main route of nanoparticles (NP) exposure during manufacturing. Although many mechanisms of toxicity have been described, the interaction of NP with relevant pneumocytes organelles is not widely understood. Considering that the physicochemical properties of NP influence their toxicological responses, the objective of this study was to evaluate whether exposure to different NP, crystalline Fe₃O₄ NP and amorphous SiO₂ NP could alter pneumocytes organelles in alveolar epithelial cells. To achieve this goal, cell viability, ultrastructural changes, lysosomal damage, mitochondrial membrane potential (MMP), lipid droplets (LD) formation and cytokines production were evaluated by MTT, electron microscopy, lysotracker red staining, JC-1, Oil Red staining and Milliplex® assay respectively. Both NP were observed within lamellar bodies (LB), lysosomes, and cytoplasm causing morphological changes. Exposure to SiO₂ NP at 6 h induced lysosomal activation, but not Fe₃O₄ NP. MMP decreased and LD increased at the highest concentrations after both NP exposure. Pro-inflammatory cytokines were released only after SiO₂ NP exposure at 48 h. These results indicate that SiO₂ NP have a greater impact than Fe₃O₄ NP on organelles responsible for energy, secretion, degradation and metabolism in pneumocytes leading to the development of respiratory disorders or the exacerbation of preexisting conditions. Therefore, the established biocompatibility for amorphous NP has to be reconsidered.

The role of mitophagy in innate immune responses triggered by mitochondrial stress

Mitochondria are important cellular organelles involved in many different functions, from energy generation and fatty acid oxidation to cell death regulation and immune responses. Accumulating evidence indicates that mitochondrial stress acts as a key trigger of innate immune responses. Critically, the dysfunctional mitochondria can be selectively eliminated by mitophagy. The elimination of dysfunctional mitochondria may function as an effective way employed by mitophagy to keep the immune system in check. In addition, mitophagy can be utilized by pathogens for immune evasion. In this review, we summarize how mitochondrial stress triggers innate immune responses and the roles of mitophagy in innate immunity and in infection, as well as the molecular mechanisms of mitophagy. Video Abstract.

Decoding the rosetta stone of mitonuclear communication

Cellular homeostasis in eukaryotic cells requires synchronized coordination of multiple organelles. A key role in this stage is played by mitochondria, which have recently emerged as highly interconnected and multifunctional hubs that process and coordinate diverse cellular functions. Beyond producing ATP, mitochondria generate key metabolites and are central to apoptotic and metabolic signaling pathways. Because most mitochondrial proteins are encoded in the nuclear genome, the biogenesis of new mitochondria and the maintenance of mitochondrial functions and flexibility critically depend upon effective mitonuclear communication. This review addresses the complex network of signaling molecules and pathways allowing mitochondria-nuclear communication and coordinated regulation of their independent but interconnected genomes, and discusses the extent to which dynamic communication between the two organelles has evolved for mutual benefit and for the overall maintenance of cellular and organismal fitness.

Mitochondrial Dysfunction and Kidney Stone Disease

Mitochondrion is a pivotal intracellular organelle that plays crucial roles in regulation of energy production, oxidative stress, calcium homeostasis, and apoptosis. Kidney stone disease (nephrolithiasis/urolithiasis), particularly calcium oxalate (CaOx; the most common type), has been shown to be associated with oxidative stress and tissue inflammation/injury. Recent evidence has demonstrated the involvement of mitochondrial dysfunction in CaOx crystal retention and aggregation as well as Randall’s plaque formation, all of which are the essential mechanisms for kidney stone formation. This review highlights the important roles of mitochondria in renal cell functions and provides the data obtained from previous investigations of mitochondria related to kidney stone disease. In addition, mechanisms for the involvement of mitochondrial dysfunction in the pathophysiology of kidney stone disease are summarized. Finally, future perspectives on the novel approach to prevent kidney stone formation by mitochondrial preservation are discussed.

The Impact of Mitochondrial Deficiencies in Neuromuscular Diseases

Neuromuscular diseases (NMDs) are a heterogeneous group of acquired or inherited rare disorders caused by injury or dysfunction of the anterior horn cells of the spinal cord (lower motor neurons), peripheral nerves, neuromuscular junctions, or skeletal muscles leading to muscle weakness and waste. Unfortunately, most of them entail serious or even fatal consequences. The prevalence rates among NMDs range between 1 and 10 per 100,000 population, but their rarity and diversity pose difficulties for healthcare and research. Some molecular hallmarks are being explored to elucidate the mechanisms triggering disease, to set the path for further advances. In fact, in the present review we outline the metabolic alterations of NMDs, mainly focusing on the role of mitochondria. The aim of the review is to discuss the mechanisms underlying energy production, oxidative stress generation, cell signaling, autophagy, and inflammation triggered or conditioned by the mitochondria. Briefly, increased levels of inflammation have been linked to reactive oxygen species (ROS) accumulation, which is key in mitochondrial genomic instability and mitochondrial respiratory chain (MRC) dysfunction. ROS burst, impaired autophagy, and increased inflammation are observed in many NMDs. Increasing knowledge of the etiology of NMDs will help to develop better diagnosis and treatments, eventually reducing the health and economic burden of NMDs for patients and healthcare systems.

[The role of mitochondria in pathological mechanisms of innate immunity in multiple]

The review discusses the role of mitochondria in multiple sclerosis (MS). Previously, damage to the mitochondria was regarded as a manifestation of secondary damage to axons and neurons, i.e. as a marker of neurodenegation. Recently, the role of mitochondria in the early stages of MS development, when they could participate in the activation of innate immunity and trigger activation of autoimmune responses of acquired immunity, has been increasingly discussed. The role of polymorphism mitochondrial DNA changes in MS is discussed.

Structural and functional insights into CWC27/CWC22 heterodimer linking the exon junction complex to spliceosomes

Human CWC27 is an uncharacterized splicing factor and mutations in its gene are linked to retinal degeneration and other developmental defects. We identify the splicing factor CWC22 as the major CWC27 partner. Both CWC27 and CWC22 are present in published B^act spliceosome structures, but no interacting domains are visible. Here, the structure of a CWC27/CWC22 heterodimer bound to the exon junction complex (EJC) core component eIF4A3 is solved at 3Å-resolution. According to spliceosomal structures, the EJC is recruited in the C complex, once CWC27 has left. Our 3D structure of the eIF4A3/CWC22/CWC27 complex is compatible with the B^act spliceosome structure but not with that of the C complex, where a CWC27 loop would clash with the EJC core subunit Y14. A CWC27/CWC22 building block might thus form an intermediate landing platform for eIF4A3 onto the B^act complex prior to its conversion into C complex. Knock-down of either CWC27 or CWC22 in immortalized retinal pigment epithelial cells affects numerous common genes, indicating that these proteins cooperate, targeting the same pathways. As the most up-regulated genes encode factors involved in inflammation, our findings suggest a possible link to the retinal degeneration associated with CWC27 deficiencies.

Effect of Triclosan Exposure on Developmental Competence in Parthenogenetic Porcine Embryo during Preimplantation

Triclosan (TCS) is included in various healthcare products because of its antimicrobial activity; therefore, many humans are exposed to TCS daily. While detrimental effects of TCS exposure have been reported in various species and cell types, the effects of TCS exposure on early embryonic development are largely unknown. The aim of this study was to determine if TCS exerts toxic effects during early embryonic development using porcine parthenogenetic embryos in vitro. Porcine parthenogenetic embryos were cultured in in vitro culture medium with 50 or 100 µM TCS for 6 days. Developmental parameters including cleavage and blastocyst formation rates, developmental kinetics, and the number of blastomeres were assessed. To determine the toxic effects of TCS, apoptosis, oxidative stress, and mitochondrial dysfunction were assessed. TCS exposure resulted in a significant decrease in 2-cell rate and blastocyst formation rate, as well as number of blastomeres, but not in the cleavage rate. TCS also increased the number of apoptotic blastomeres and the production of reactive oxygen species. Finally, TCS treatment resulted in a diffuse distribution of mitochondria and decreased the mitochondrial membrane potential. Our results showed that TCS exposure impaired porcine early embryonic development by inducing DNA damage, oxidative stress, and mitochondrial dysfunction.

Cardiometabolic risk factors are associated with immune cell mitochondrial respiration in humans

Modifiable cardiometabolic risk factors induce the release of proinflammatory cytokines and reactive oxygen species from circulating peripheral blood mononuclear cells (PBMCs), resulting in increased cardiovascular disease risk and compromised immune health. These changes may be driven by metabolic reprogramming of PBMCs, resulting in reduced mitochondrial respiration; however, this has not been fully tested. We aimed to determine the independent associations between cardiometabolic risk factors including BMI, blood pressure, fasting glucose, and plasma lipids with mitochondrial respiration in PBMCs isolated from generally healthy individuals (n = 21) across the adult lifespan (12 men/9 women; age, 56 ± 21 yr; age range, 22-78 yr; body mass index, 27.9 ± 5.7 kg/m²; blood pressure, 123 ± 16/72 ± 10 mmHg; glucose, 90 ± 14 mg/dL; low-density lipoprotein cholesterol (LDL-C), 111 ± 22 mg/dL; and high-density lipoprotein cholesterol (HDL-C), 62 ± 16 mg/dL). PBMCs were isolated from whole blood by density-dependent centrifugation and used to assess mitochondrial function by respirometry. Primary outcomes included basal and maximal oxygen consumption rate (OCR), which were subsequently used to determine spare respiratory capacity and OCR metabolic potential. After we corrected for systolic blood pressure (SBP), diastolic blood pressure (DBP), and blood glucose, LDL-C was negatively associated with maximal respiration (r = -0.56, P = 0.016), spare respiratory capacity (r = -0.58, P = 0.012), and OCR metabolic potential (r = -0.71, P = 0.0011). In addition, SBP was negatively associated with OCR metabolic potential (r = -0.62, P = 0.0056) after we corrected for DBP, blood glucose, and LDL-C. These data suggest a link between blood cholesterol, SBP, and mitochondrial health that may provide insight into how cardiometabolic risk factors contribute to impaired immune cell function.NEW & NOTEWORTHY Independent of other cardiometabolic risk factors, low-density lipoprotein cholesterol, and systolic blood pressure were found to be negatively associated with several parameters of mitochondrial respiration in peripheral blood mononuclear cells of healthy adults. These data suggest that low-density lipoprotein cholesterol and systolic blood pressure may induce metabolic reprogramming of immune cells, contributing to increased cardiovascular disease risk and impaired immune health.

Mitochondrial Dysfunction and Inflammaging in Heart Failure: Novel Roles of CYP-Derived Epoxylipids

Age-associated changes leading to a decline in cardiac structure and function contribute to the increased susceptibility and incidence of cardiovascular diseases (CVD) in elderly individuals. Indeed, age is considered a risk factor for heart failure and serves as an important predictor for poor prognosis in elderly individuals. Effects stemming from chronic, low-grade inflammation, inflammaging, are considered important determinants in cardiac health; however, our understanding of the mechanisms involved remains unresolved. A steady decline in mitochondrial function is recognized as an important biological consequence found in the aging heart which contributes to the development of heart failure. Dysfunctional mitochondria contribute to increased cellular stress and an innate immune response by activating the NLRP-3 inflammasomes, which have a role in inflammaging and age-related CVD pathogenesis. Emerging evidence suggests a protective role for CYP450 epoxygenase metabolites of N-3 and N-6 polyunsaturated fatty acids (PUFA), epoxylipids, which modulate various aspects of the immune system and protect mitochondria. In this article, we provide insight into the potential roles N-3 and N-6 PUFA have modulating mitochondria, inflammaging and heart failure.

The essential functions of mitochondrial dynamics in immune cells

Mitochondria are highly mobile organelles due to fission, fusion, transport, and mitophagy, and these processes are known as mitochondrial dynamics. Mitochondrial dynamics play an important role in energy production, cell division, cell differentiation, and cell death. In the past decade, numerous studies have revealed the importance of mitochondrial metabolism in immunity, and mitochondrial dynamics are essential for immune responses mediated by various cell types. In this review, we mainly discuss the role of mitochondrial dynamics in activation, differentiation, cytokine production, and the activity of related pathways in immune cells, particularly T cells, B cells, and other cells involved in the innate immune response.

Exploration of anti-inflammatory mechanism of forsythiaside A and forsythiaside B in CuSO4-induced inflammation in zebrafish by metabolomic and proteomic analyses

BACKGROUND

Inflammation is a general pathological phenomenon during severe disturbances to the homeostasis. Forsythiaside A (FA) and forsythiaside B (FB), isolated from the dried fruit of Forsythia suspensa (Thunb.) Vahl, are phenylethanoid compounds that show a significant anti-inflammatory effect. However, the properties and therapeutic mechanisms of this effect have not yet been systematically elucidated.

METHODS

In this study, the anti-inflammatory effects of FA and FB were investigated in CuSO₄-induced inflammation in zebrafish larvae. Intracellular generation of reactive oxygen species (ROS) and nitric oxide (NO) was investigated using fluorescence probes. Metabolomic and proteomic analyses using liquid chromatography-mass spectrometry were carried out to identify the expressions of metabolites and proteins associated with the anti-inflammatory mechanism of FA and FB. Quantitative polymerase chain reaction (PCR) was performed to detect the progressive changes in gene expression.

RESULTS

FA and FB inhibited neutrophils migration to the damaged neuromasts and remarkably reduced CuSO₄-induced ROS and NO generation in zebrafish larvae. Metabolomic analysis pointed to the involvement of nicotinate and nicotinamide metabolism, energy metabolism, pyrimidine metabolism, and purine metabolism. Proteomic analysis identified 146 differentially expressed proteins between the control and model groups. These included collagen [collagen type II alpha 1b precursor (col2a1b), collagen alpha-2(IX) chain precursor (col9a2), collagen type IX alpha I precursor (col9a1b)], nucleoside diphosphate kinase 3 isoform X1 (Nme3), WD repeat-containing protein 3 (Wdr3), and 28S ribosomal protein S7 mitochondrial precursor (Mrps7). FA and FB were shown to reverse the abnormal expressions of potential metabolite and protein biomarkers and alleviate CuSO₄-induced damage to the neuromasts in the zebrafish lateral line.

CONCLUSIONS

Our results indicate that FA and FB possess remarkable anti-inflammatory properties, protecting against CuSO₄-induced neuromasts damage in zebrafish larvae. The results also suggest a multi-component and multi-regulatory therapeutic mechanism for FA and FB.

Polydatin attenuates cadmium-induced oxidative stress via stimulating SOD activity and regulating mitochondrial function in Musca domestica larvae

Cadmium (Cd) is a widespread environment contaminant due to the development of electroplating and metallurgical industry. Cd can be enriched by organisms via food chain, causing the enlarged environmental problems and posing threats to the health of humans. Polydatin (PD), a natural stilbenoid compound derived from Polygonum cuspidatum, shows pronouncedly curative effect on oxidative damage. In this work, the protective effects of PD on oxidative damage induced by Cd in Musca domestica (housefly) larvae were evaluated. The larvae were exposed to Cd and/or PD, subsequently, the oxidative stress status, mitochondria activity, oxidative phosphorylation efficiency, and survival rate were assessed. Cd exposure generated significant increases of malondialdehyde (MDA), reactive oxygen species (ROS) and 8-hydroxy-2-deoxyguanosine (8-oxoG) in the housefly larvae, causing mitochondrial dysfunction and survival rate decline. Interestingly, pretreatment with PD exhibited obviously mitochondrial protective effects in the Cd-exposed larvae, as evidenced by reduced MDA, ROS and 8-oxoG levels, and increased activities of superoxide dismutase (SOD), mitochondrial electron transfer chain, and mitochondrial membrane potential, as well as respiratory control ratio. These results suggested that PD could attenuate Cd-induced damage via maintaining redox balance, stimulating SOD activity, and regulating mitochondria activity in housefly larvae. As a natural polyphenolic chemical, PD can act as a potential candidate compounds to relieve Cd injury.

Diverse roles of mtDNA in schizophrenia: Implications in its pathophysiology and as biomarker for cognitive impairment

Schizophrenia (SZ) is a mental disorder characterized by neurocognitive dysfunctions and a reduction in occupational and social functioning. Several studies have provided evidence for mitochondrial dysfunction in the pathophysiology of SZ. In this sense, it is known that the addition of genetic variations in mitochondrial DNA (mtDNA) impairs oxidative phosphorylation of enzymatic complexes in mitochondria, resulting in ATP depletion and subsequent enhancement of reactive oxygen species; this is associated with cellular degeneration and apoptosis observed in some neuropsychiatric disorders. As a consequence of mitochondrial dysfunction, an increase in circulating cell-free mtDNA fragments can occur, which has been observed in individuals with SZ. Moreover, due to the bacterial origin of mitochondria, these cell-free mtDNA fragments in blood plasma may induce inflammatory and immunogenic responses, especially when their release is enhanced in specific disease conditions. However, the exact mechanism by which mtDNA could be released into blood plasma is not yet clear. Therefore, the aims of this review article were to discuss the participation of mtDNA genetic variations in physiopathologic mechanisms of SZ, and to determine the status of the disease and the possible ensuing changes over time by using circulating cell-free mtDNA fragments as a biomarker.

Developmental regression and mitochondrial function in children with autism

BACKGROUND

Developmental regression (DR) occurs in about one-third of children with Autism Spectrum Disorder (ASD) yet it is poorly understood. Current evidence suggests that mitochondrial function in not normal in many children with ASD. However, the relationship between mitochondrial function and DR has not been well-studied in ASD.

METHODS

This cross-sectional study of 32 children, 2 to 8 years old with ASD, with (n = 11) and without (n = 12) DR, and non-ASD controls (n = 9) compared mitochondrial respiration and mtDNA damage and copy number between groups and their relation to standardized measures of ASD severity.

RESULTS

Individuals with ASD demonstrated lower ND1, ND4, and CYTB copy number (Ps < 0.01) as compared to controls. Children with ASD and DR had higher maximal oxygen consumption rate (Ps < 0.02), maximal respiratory capacity (P < 0.05), and reserve capacity (P = 0.01) than those with ASD without DR. Coupling Efficiency and Maximal Respiratory Capacity were associated with disruptive behaviors but these relationships were different for those with and without DR. Higher ND1 copy number was associated with better behavior.

CONCLUSIONS

This study suggests that individuals with ASD and DR may represent a unique metabolic endophenotype with distinct abnormalities in respiratory function that may put their mitochondria in a state of vulnerability. This may allow physiological stress to trigger mitochondrial decompensation as is seen clinically as DR. Since mitochondrial function was found to be related to ASD symptoms, the mitochondria could be a potential target for novel therapeutics. Additionally, identifying those with vulnerable mitochondrial before DR could result in prevention of ASD.

The Imbalance among Oxidative Biomarkers and Antioxidant Defense Systems in Thromboangiitis Obliterans (Winiwarter-Buerger Disease)

(1) Background: Thromboangiitis obliterans or Winiwarter-Buerger disease (WBD), is an inflammatory, thrombotic occlusive, peripheral vascular disease, usually occurring in young smokers. The pathophysiological mechanisms underlying the disease are not clearly understood. The aim of this study is to investigate the imbalance between oxidants and antioxidants occurring in these patients. (2) Patients and Methods: In this cross-sectional study, 22 male patients with WBD and 20 healthy male smoking habit matched control group were included. To evaluate the possible sources of oxidative stress, the antioxidant biomarkers, and the markers of lipid peroxidation and protein oxidation, serum samples were analyzed for total oxidative status (TOS), total antioxidant capacity (TAC), myeloperoxidase (MPO), coenzyme Q10 (CoQ10), superoxide dismutase (SOD), glutathione reductase (GR), malondialdehyde (MDA), and protein carbonyl (PC) activity and/or content. (3) Results: The circulating levels of TOS, TAC, and CoQ10 were significantly higher in WBD patients, with respect to healthy smokers as controls. No significant difference was found among the serum level of PC, total cholesterol, MPO, and GR activity in WBD patients and healthy smoker controls. The activity of SOD and the mean serum level of MDA were significantly lower in WBD patients, with respect to healthy smoker controls. (4) Conclusion: Considerably high levels of oxidative stress were detected in WBD patients, which were greater than the antioxidant capacity. The low level of MDA may be associated with the enzymatic degradation of lipid peroxidation products. High levels of CoQ10 and low levels of SOD may be related to a harmful oxidative cooperation, leading to the vasoconstriction of WBD, representing a promising tool to discern possible different clinical risks of this poorly understood peripheral occlusive disease.

Chlorpyrifos induces redox imbalance-dependent inflammation in common carp lymphocyte through dysfunction of T-cell receptor γ

Chlorpyrifos is a poisonous pesticide that is highly toxic to fish and aquatic organisms. However, there are fewer reports about how chlorpyrifos influences the redox balance of immune cells. Herein, the head kidney tissue treated with chlorpyrifos to do transcriptome analysis and TCR γ was screened out. Subsequently, we established TCR γ knockdown and overexpression carp head kidney lymphocyte models, respectively, by using RNA interference and pcDNA3.1. Real-time PCR, fluorescent staining, oxidation and antioxidant kit were used to detect the related factors. We found that TCR γ knockdown significantly increased the mRNA expression of HSP70 and HSP90 and decreased the mRNA expression of SOD and CAT. Meanwhile, TCR γ knockdown reduced the activities of GSH, GSG-PX, T-AOC, CAT and SOD and increased the content of MDA and H₂ O₂ and activities of iNOS. Adverse results were obtained in TCR γ overexpression group. Additionally, TCR γ knockdown significantly increased the mRNA expression of IFN-γ, IL-1β, IL-8, IL-10, Nrf2 and NF-κB, but relieved TCR γ overexpression, in which the process of inflammation was activated. Our results reported here indicated that chlorpyrifos induces redox imbalance-dependent inflammation in common carp lymphocyte through dysfunction of T-cell receptor γ, and HSPs play potential protective role in entire process.

Age- and Organ-Specific Differences in Mitochondrial Bioenergetics in Brown Norway Rats

Mitochondria play a central role in energy homeostasis and act as regulatory checkpoints for downstream metabolic responses and cell senescence processes during an entire life span. Acute or chronic environmental toxicant exposures have shown deleterious organ-specific human health issues at various life stages. Since mitochondria are a prime target for ensuing cellular bioenergetics responses and senescence, it is essential to understand mitochondrial bioenergetic responses in different organs over multiple life stages. Therefore, in the present study, we evaluated mitochondrial bioenergetic parameters in the liver, lung, and heart in four diverse age groups (young: 1 month; adult: 4 months; middle-aged: 12 months; old-aged: 24 month) using male Brown Norway rats as a model of aging (n = 5 sample size/organ/age group) and compared them with our previously published results on brain. Real-time mitochondrial bioenergetic parameters (i.e., State III, State IV, and State V) were measured using the Seahorse Extracellular Flux Analyzer. Additionally, mitochondrial enzyme pyruvate dehydrogenase complex (PDHC), Complex I, Complex II, and Complex IV activities were measured using Synergy HT plate reader. Our results indicated that nearly in all parameters, significant age- and organ-specific interactions were observed. We observed age-specific declines in State III (i.e., ATP synthesis rate) responses in both the heart and lung, where opposite was observed in the liver as age advances. Across the age, the heart has highest enzyme activities than the liver and lung. Interestingly, heart and liver mitochondrial bioenergetic rates and enzyme activities remain higher than the lung, which specifies their higher metabolic capabilities than the lung. Amongst all, bioenergetic rates and enzyme activities in the lung remain lowest suggesting the lung may display higher vulnerability and lower resilience to environmental toxicants during aging than other organs tested here. Overall, these age- and organ-specific findings may facilitate a more contextualized understanding of mitochondrial bioenergetic outcomes when considering the interactions of age-related sensitivities with exposure to chemical stressors from the environment.

CpG-ODN-mediated TLR9 innate immune signalling and calcium dyshomeostasis converge on the NFκB inhibitory protein IκBβ to drive IL1α and IL1β expression

Sterile inflammation contributes to many pathological states associated with mitochondrial injury. Mitochondrial injury disrupts calcium homeostasis and results in the release of CpG-rich mitochondrial DNA. The role of CpG-stimulated TLR9 innate immune signalling and sterile inflammation is well studied; however, how calcium dyshomeostasis affects this signalling is unknown. Therefore, we interrogated the relationship beτween intracellular calcium and CpG-induced TLR9 signalling in murine macrophages. We found that CpG-ODN-induced NFκB-dependent IL1α and IL1β expression was significantly attenuated by both calcium chelation and calcineurin inhibition, a finding mediated by inhibition of degradation of the NFκB inhibitory protein IκBβ. In contrast, calcium ionophore exposure increased CpG-induced IκBβ degradation and IL1α and IL1β expression. These results demonstrate that through its effect on IκBβ degradation, increased intracellular Ca²⁺ drives a pro-inflammatory TLR9-mediated innate immune response. These results have implications for the study of innate immune signalling downstream of mitochondrial stress and injury.

Tuberculosis infection and lung adenocarcinoma: Mendelian randomization and pathway analysis of genome-wide association study data from never-smoking Asian women

We investigated whether genetic susceptibility to tuberculosis (TB) influences lung adenocarcinoma development among never-smokers using TB genome-wide association study (GWAS) results within the Female Lung Cancer Consortium in Asia. Pathway analysis with the adaptive rank truncated product method was used to assess the association between a TB-related gene-set and lung adenocarcinoma using GWAS data from 5512 lung adenocarcinoma cases and 6277 controls. The gene-set consisted of 31 genes containing known/suggestive associations with genetic variants from previous TB-GWAS. Subsequently, we followed-up with Mendelian Randomization to evaluate the association between TB and lung adenocarcinoma using three genome-wide significant variants from previous TB-GWAS in East Asians. The TB-related gene-set was associated with lung adenocarcinoma (p = 0.016). Additionally, the Mendelian Randomization showed an association between TB and lung adenocarcinoma (OR = 1.31, 95% CI: 1.03, 1.66, p = 0.027). Our findings support TB as a causal risk factor for lung cancer development among never-smoking Asian women.

The Metabolic Remodelling in Lung Cancer and Its Putative Consequence in Therapy Response

Lung cancer is the leading cause of cancer-related deaths worldwide in both men and women. Conventional chemotherapy has failed to provide long-term benefits for many patients and in the past decade, important advances were made to understand the underlying molecular/genetic mechanisms of lung cancer, allowing the unfolding of several other pathological entities. Considering these molecular subtypes, and the appearance of promising targeted therapies, an effective personalized control of the disease has emerged, nonetheless benefiting a small proportion of patients. Although immunotherapy has also appeared as a new hope, it is still not accessible to the majority of patients with lung cancer.The metabolism of energy and biomass is the basis of cellular survival. This is true for normal cells under physiological conditions and it is also true for pathophysiologically altered cells, such as cancer cells. Thus, knowledge of the metabolic remodelling that occurs in cancer cells in the sense of, on one hand, surviving in the microenvironment of the organ in which the tumour develops and, on the other hand, escaping from drugs conditioned microenvironment, is essential to understand the disease and to develop new therapeutic approaches.

Role of Mitochondria in the Redox Signaling Network and Its Outcomes in High Impact Inflammatory Syndromes

Inflammation is associated with the release of soluble mediators that drive cellular activation and migration of inflammatory leukocytes to the site of injury, together with endothelial expression of adhesion molecules, and increased vascular permeability. It is a stepwise tightly regulated process that has been evolved to cope with a wide range of different inflammatory stimuli. However, under certain physiopathological conditions, the inflammatory response overwhelms local regulatory mechanisms and leads to systemic inflammation that, in turn, might affect metabolism in distant tissues and organs. In this sense, as mitochondria are able to perceive signals of inflammation is one of the first organelles to be affected by a dysregulation in the systemic inflammatory response, it has been associated with the progression of the physiopathological mechanisms. Mitochondria are also an important source of ROS (reactive oxygen species) within most mammalian cells and are therefore highly involved in oxidative stress. ROS production might contribute to mitochondrial damage in a range of pathologies and is also important in a complex redox signaling network from the organelle to the rest of the cell. Therefore, a role for ROS generated by mitochondria in regulating inflammatory signaling was postulated and mitochondria have been implicated in multiple aspects of the inflammatory response. An inflammatory condition that affects mitochondrial function in different organs is the exposure to air particulate matter (PM). Both after acute and chronic pollutants exposure, PM uptake by alveolar macrophages have been described to induce local cell activation and recruitment, cytokine release, and pulmonary inflammation. Afterwards, inflammatory mediators have been shown to be able to reach the bloodstream and induce a systemic response that affects metabolism in distant organs different from the lung. In this proinflammatory environment, impaired mitochondrial function that leads to bioenergetic dysfunction and enhanced production of oxidants have been shown to affect tissue homeostasis and organ function. In the present review, we aim to discuss the latest insights into the cellular and molecular mechanisms that link systemic inflammation and mitochondrial dysfunction in different organs, taking the exposure to air pollutants as a case model.

Maintenance of mitochondrial function by astaxanthin protects against bisphenol A-induced kidney toxicity in rats

Bisphenol A (BPA), a global environmental pollutant, has been reported to have the potential to induced organs toxicity. This study explored the potential benefits of astaxanthin (ATX), a natural antioxidant, against BPA toxicity in the kidney, and explored whether mitochondria are involved in this condition. Male Wistar rats were fed with a vehicle, BPA, BPA plus ATX, ATX and were evaluated after five weeks. ATX treatment significantly reversed BPA-induced changes in body weight, kidney/body weight, and renal function related markers. When treated simultaneously with ATX, the imbalance of the oxidative-antioxidant status caused by BPA was also alleviated. The high expression of BPA-induced pro-inflammatory cytokines were inhibited by ATX treatment. ATX treatment also lessened the effects of BPA-induced caspase-3, -8, -9 and -10 gene expression and enzyme activity. The benefits of ATX were associated with enhanced mitochondrial function, which led to increased mitochondrial-encoded gene expression, mitochondrial copy number, and increased mitochondrial respiratory chain complex enzyme activity. Our results demonstrate the efficacy of ATX in protecting BPA-induced kidney damage, in part by regulating oxidative imbalance and improving mitochondrial function. Collectively, these findings provide a new perspective for the rational use of ATX in the treatment of BPA-induced kidney disease.

SS-31 reduces inflammation and oxidative stress through the inhibition of Fis1 expression in lipopolysaccharide-stimulated microglia

SS-31 is a kind of mitochondrion-targeted peptide. Recent studies indicated significant neuroprotective effects of SS-31. In this study, we investigated that SS-31 protected the murine cultured microglial cells (BV-2) against lipopolysaccharide (LPS)-induced inflammation and oxidative stress through stabilizing mitochondrial morphology. The morphological study showed that SS-31 preserved LPS-induced mitochondrial ultrastructure by reducing the fission protein 1 (Fis1) expression. Flow cytometry and Western blot verified that SS-31 defended the BV-2 cells against LPS-stimulated inflammation and oxidative stress via suppressing Fis1. To sum up, our study represents that SS-31 preserves BV-2 cells from LPS-stimulated inflammation and oxidative stress by down-regulating the Fis1 expression.

HIV-1 infection alters energy metabolism in the brain: Contributions to HIV-associated neurocognitive disorders

The brain is particularly sensitive to changes in energy supply. Defects in glucose utilization and mitochondrial dysfunction are hallmarks of nearly all neurodegenerative diseases and are also associated with the cognitive decline that occurs as the brain ages. Chronic neuroinflammation driven by glial activation is commonly implicated as a contributing factor to neurodegeneration and cognitive impairment. Human immunodeficiency virus-1 (HIV-1) disrupts normal brain homeostasis and leads to a spectrum of HIV-associated neurocognitive disorders (HAND). HIV-1 activates stress responses in the brain and triggers a state of chronic neuroinflammation. Growing evidence suggests that inflammatory processes and bioenergetics are interconnected in the propagation of neuronal dysfunction. Clinical studies of people living with HIV and basic research support the notion that HIV-1 creates an environment in the CNS that interrupts normal metabolic processes at the cellular level to collectively alter whole brain metabolism. In this review, we highlight reports of abnormal brain metabolism from clinical studies and animal models of HIV-1. We also describe diverse CNS cell-specific changes in bioenergetics associated with HIV-1. Moreover, we propose that attention should be given to adjunctive therapies that combat sources of metabolic dysfunction as a mean to improve and/or prevent neurocognitive impairments.

Islet-immune interactions in type 1 diabetes: the nexus of beta cell destruction

Recent studies in Type 1 Diabetes (T1D) support an emerging model of disease pathogenesis that involves intrinsic β-cell fragility combined with defects in both innate and adaptive immune cell regulation. This combination of defects induces systematic changes leading to organ-level atrophy and dysfunction of both the endocrine and exocrine portions of the pancreas, ultimately culminating in insulin deficiency and β-cell destruction. In this review, we discuss the animal model data and human tissue studies that have informed our current understanding of the cross-talk that occurs between β-cells, the resident stroma, and immune cells that potentiate T1D. Specifically, we will review the cellular and molecular signatures emerging from studies on tissues derived from organ procurement programs, focusing on in situ defects occurring within the T1D islet microenvironment, many of which are not yet detectable by standard peripheral blood biomarkers. In addition to improved access to organ donor tissues, various methodological advances, including immune receptor repertoire sequencing and single-cell molecular profiling, are poised to improve our understanding of antigen-specific autoimmunity during disease development. Collectively, the knowledge gains from these studies at the islet-immune interface are enhancing our understanding of T1D heterogeneity, likely to be an essential component for instructing future efforts to develop targeted interventions to restore immune tolerance and preserve β-cell mass and function.

Linking Mitochondrial Dysfunction to Organismal and Population Health in the Context of Environmental Pollutants: Progress and Considerations for Mitochondrial Adverse Outcome Pathways

Mitochondria are key targets of many environmental contaminants, because specific chemicals can interact directly with mitochondrial proteins, lipids, and ribonucleic acids. These direct interactions serve as molecular initiating events that impede adenosine triphosphate production and other critical functions that mitochondria serve within the cell (e.g., calcium and metal homeostasis, apoptosis, immune signaling, redox balance). A limited but growing number of adverse outcome pathways (AOPs) have been proposed to associate mitochondrial dysfunction with effects at organismal and population levels. These pathways involve key events such as altered membrane potential, mitochondrial fission/fusion, and mitochondrial DNA damage, among others. The present critical review and analysis reveals current progress on AOPs involving mitochondrial dysfunction, and, using a network-based computational approach, identifies the localization of mitochondrial molecular initiating events and key events within multiple existing AOPs. We also present 2 case studies, the first examining the interaction between mitochondria and immunotoxicity, and the second examining the role of early mitochondrial dysfunction in the context of behavior (i.e., locomotor activity). We discuss limitations in our current understanding of mitochondrial AOPs and highlight opportunities for clarifying their details. Advancing our knowledge of key event relationships within the AOP framework will require high-throughput datasets that permit the development and testing of chemical-agnostic AOPs, as well as high-resolution research that will enhance the mechanistic testing and validation of these key event relationships. Given the wide range of chemicals that affect mitochondria, and the centrality of energy production and signaling to ecologically important outcomes such as pathogen defense, homeostasis, growth, and reproduction, a better understanding of mitochondrial AOPs is expected to play a significant, if not central, role in environmental toxicology. Environ Toxicol Chem 2019;38:1625-1634. © 2019 SETAC.

Unexpected inflammation in the sympathetic ganglia in thromboangiitis obliterans: more likely sterile or infectious induced inflammation?

Introduction

The aim of this study was to determine if the inflammation of the sympathetic ganglia (SG) in thromboangiitis obliterans (TAO) is induced by an infectious pathogen inside or if it is a reactive sterile inflammation.

Methods

For the purpose of this study, the gene expression of high-mobility group box 1 (HMGB1), toll-like receptor 4 (TLR4), toll-like receptor 9 (TLR9), and the receptor for advanced glycation end-products (RAGE) were evaluated on the complementary DNA (cDNA) of the SG tissues of 24 TAO patients and two controls with hyperhidrosis by real-time polymerase chain reaction (PCR) and analysed by the Pfaffl method.

Results

The gene expression of HMGB1 and TLR9 increased by about 25- and 2-fold changes in the SG of the TAO patients, respectively. However, there was no change in the gene expression of TLR4 or RAGE.

Conclusion

It appears that the inflammation in the SG of TAO patients is more likely a sterile inflammation, and its trigger may be mitochondrial DNA (mtDNA). Cadmium in cigarettes could be responsible for the induction of mtDNA release to the cell cytoplasm. In addition, the high expression of HMGB1 may play a role in the pathogenesis of TAO and may be responsible for both clinical manifestation of the disease and the imaging findings. Moreover, HMGB1 may be a target for treatment protocols for TAO. Further studies are highly recommended.

Mitochondrial dysfunction and chronic lung disease

The functions of body gradually decrease as the age increases, leading to a higher frequency of incidence of age-related diseases. Diseases associated with aging in the respiratory system include chronic obstructive pulmonary disease (COPD), IPF (idiopathic pulmonary fibrosis), asthma, lung cancer, and so on. The mitochondrial dysfunction is not only a sign of aging, but also is a disease trigger. This article aims to explain mitochondrial dysfunction as an aging marker, and its role in aging diseases of lung. We also discuss whether the mitochondria can be used as a target for the treatment of aging lung disease.

Inflammation and Metabolism in Cancer Cell-Mitochondria Key Player

Cancer metabolism is an essential aspect of tumorigenesis, as cancer cells have increased energy requirements in comparison to normal cells. Thus, an enhanced metabolism is needed in order to accommodate tumor cells' accelerated biological functions, including increased proliferation, vigorous migration during metastasis, and adaptation to different tissues from the primary invasion site. In this context, the assessment of tumor cell metabolic pathways generates crucial data pertaining to the mechanisms through which tumor cells survive and grow in a milieu of host defense mechanisms. Indeed, various studies have demonstrated that the metabolic signature of tumors is heterogeneous. Furthermore, these metabolic changes induce the exacerbated production of several molecules, which result in alterations that aid an inflammatory milieu. The therapeutic armentarium for oncology should thus include metabolic and inflammation regulators. Our expanding knowledge of the metabolic behavior of tumor cells, whether from solid tumors or hematologic malignancies, may provide the basis for the development of tailor-made cancer therapies.

A network biology approach to unraveling inherited axonopathies

Inherited axonopathies represent a spectrum of disorders unified by the common pathological mechanism of length-dependent axonal degeneration. Progressive axonal degeneration can lead to both Charcot-Marie-Tooth type 2 (CMT2) and Hereditary Spastic Paraplegia (HSP) depending on the affected neurons: peripheral motor and sensory nerves or central nervous system axons of the corticospinal tract and dorsal columns, respectively. Inherited axonopathies display an extreme degree of genetic heterogeneity of Mendelian high-penetrance genes. High locus heterogeneity is potentially advantageous to deciphering disease etiology by providing avenues to explore biological pathways in an unbiased fashion. Here, we investigate ‘gene modules’ in inherited axonopathies through a network-based analysis of the Human Integrated Protein-Protein Interaction rEference (HIPPIE) database. We demonstrate that CMT2 and HSP disease proteins are significantly more connected than randomly expected. We define these connected disease proteins as ‘proto-modules’ and show the topological relationship of these proto-modules by evaluating their overlap through a shortest-path based measurement. In particular, we observe that the CMT2 and HSP proto-modules significantly overlapped, demonstrating a shared genetic etiology. Comparison of both modules with other diseases revealed an overlapping relationship between HSP and hereditary ataxia and between CMT2 + HSP and hereditary ataxia. We then use the DIseAse Module Detection (DIAMOnD) algorithm to expand the proto-modules into comprehensive disease modules. Analysis of disease modules thus obtained reveals an enrichment of ribosomal proteins and pathways likely central to inherited axonopathy pathogenesis, including protein processing in the endoplasmic reticulum, spliceosome, and mRNA processing. Furthermore, we determine pathways specific to each axonopathy by analyzing the difference of the axonopathy modules. CMT2-specific pathways include glycolysis and gluconeogenesis-related processes, while HSP-specific pathways include processes involved in viral infection response. Unbiased characterization of inherited axonopathy disease modules will provide novel candidate disease genes, improve interpretation of candidate genes identified through patient data, and guide therapy development.

Association between mitochondrial DNA and cognitive impairment in schizophrenia: study protocol for a Mexican population

BACKGROUND

Circulating cell-free mitochondrial DNA (cf-mtDNA) fragments in blood plasma have been reported in patients with schizophrenia (SZ). Although the relationship of cf-mtDNA to the cognitive status of patients with SZ has not yet been explored, it is known that cognitive impairment in SZ compromises the functional and social capacity of these patients and diminishes their quality of life. In this sense, the assessment of the severity of cognitive impairment in a Mexican population with SZ and its association with cf-mtDNA levels in blood plasma may provide the possibility of using cf-mtDNA as a biomarker to determine the status of the disease and the possible ensuing changes over time.

METHODS

Subjects for a case-control study will be recruited. cf-mtDNA obtained from blood plasma will be quantified by real-time polymerase chain reaction, using melting curve technology with SYBR green as amplification marker. Patients with SZ will be grouped into those with severe, mild, and no cognitive impairment according to Montreal Cognitive Assessment scale scores, to determine differences between cognitive performance and cf-mtDNA levels in blood plasma.

ETHICS AND COMMUNICATION

This study has been approved by the ethics and investigation committees of the High Specialty Regional Hospital of Mental Health (Hospital Regional de Alta Especialidad de Salud Mental); project No. HRAESM/DG/RP/1128/2018. We plan to communicate our research findings in scientific conferences and in peer-reviewed journals.

CONCLUSION

It is known that cognitive dysfunction provokes negative effects in an SZ patient´s life. This project aims to provide better knowledge about the role of cf-mtDNA in the pathogenesis of cognitive impairment in SZ, as an attempt to achieve improvements to the existing treatments, thereby helping to prevent major cognitive deterioration.

Deletion of the Mitochondrial Complex-IV Cofactor Heme A:Farnesyltransferase Causes Focal Segmental Glomerulosclerosis and Interferon Response

Mutations in mitochondrial DNA as well as nuclear-encoded mitochondrial proteins have been reported to cause tubulointerstitial kidney diseases and focal segmental glomerulosclerosis (FSGS). Recently, genes and pathways affecting mitochondrial turnover and permeability have been implicated in adult-onset FSGS. Furthermore, dysfunctioning mitochondria may be capable of engaging intracellular innate immune-sensing pathways. To determine the impact of mitochondrial dysfunction in FSGS and secondary innate immune responses, we generated Cre/loxP transgenic mice to generate a loss-of-function deletion mutation of the complex IV assembly cofactor heme A:farnesyltransferase (COX10) restricted to cells of the developing nephrons. These mice develop severe, early-onset FSGS with innate immune activation and die prematurely with kidney failure. Mutant kidneys showed loss of glomerular and tubular epithelial function, epithelial apoptosis, and, in addition, a marked interferon response. In vitro modeling of Cox10 deletion in primary kidney epithelium compromises oxygen consumption, ATP generation, and induces oxidative stress. In addition, loss of Cox10 triggers a selective interferon response, which may be caused by the leak of mitochondrial DNA into the cytosol activating the intracellular DNA sensor, stimulator of interferon genes. This new animal model provides a mechanism to study mitochondrial dysfunction in vivo and demonstrates a direct link between mitochondrial dysfunction and intracellular innate immune response.

Mitochondrial Toxicity

Recent decades have seen a rapid increase in reported toxic effects of drugs and pollutants on mitochondria. Researchers have also documented many genetic differences leading to mitochondrial diseases, currently reported to affect ∼1 person in 4,300, creating a large number of potential gene-environment interactions in mitochondrial toxicity. We briefly review this history, and then highlight cutting-edge areas of mitochondrial research including the role of mitochondrial reactive oxygen species in signaling; increased understanding of fundamental biological processes involved in mitochondrial homeostasis (DNA maintenance and mutagenesis, mitochondrial stress response pathways, fusion and fission, autophagy and biogenesis, and exocytosis); systemic effects resulting from mitochondrial stresses in specific cell types; mitochondrial involvement in immune function; the growing evidence of long-term effects of mitochondrial toxicity; mitochondrial-epigenetic cross-talk; and newer approaches to test chemicals for mitochondrial toxicity. We also discuss the potential importance of hormetic effects of mitochondrial stressors. Finally, we comment on future areas of research we consider critical for mitochondrial toxicology, including increased integration of clinical, experimental laboratory, and epidemiological (human and wildlife) studies; improved understanding of biomarkers in the human population; and incorporation of other factors that affect mitochondria, such as diet, exercise, age, and nonchemical stressors.

Antipurinergic therapy for autism-An in-depth review

Are the symptoms of autism caused by a treatable metabolic syndrome that traces to the abnormal persistence of a normal, alternative functional state of mitochondria? A small clinical trial published in 2017 suggests this is possible. Based on a new unifying theory of pathogenesis for autism called the cell danger response (CDR) hypothesis, this study of 10 boys, ages 5-14years, showed that all 5 boys who received antipurinergic therapy (APT) with a single intravenous dose of suramin experienced improvements in all the core symptoms of autism that lasted for 5-8weeks. Language, social interaction, restricted interests, and repetitive movements all improved. Two children who were non-verbal spoke their first sentences. None of these improvements were observed in the placebo group. Larger and longer studies are needed to confirm this promising discovery. This review introduces the concept of M2 (anti-inflammatory) and M1 (pro-inflammatory) mitochondria that are polarized along a functional continuum according to cell stress. The pathophysiology of the CDR, the complementary functions of M1 and M2 mitochondria, relevant gene-environment interactions, and the metabolic underpinnings of behavior are discussed as foundation stones for understanding the improvements in ASD behaviors produced by antipurinergic therapy in this small clinical trial.

Mitochondrial dysfunction in glial cells: Implications for neuronal homeostasis and survival

Mitochondrial dysfunction is central to the pathogenesis of neurological disorders. Neurons rely on oxidative phosphorylation to meet their energy requirements and thus alterations in mitochondrial function are linked to energy failure and neuronal cell death. Furthermore, in neurons, dysfunctional mitochondria are reported to increase the steady-state levels of reactive oxygen species derived from the leakage of electrons from the electron transport chain. Research aimed at understanding mitochondrial dysfunction and its role in neurological disorders has been primarily geared towards neurons. In contrast, the effects of mitochondrial dysfunction in glial cells' function and its implication for neuronal homeostasis and brain function has been largely understudied. Unlike neurons and oligodendrocytes, astrocytes and microglia do not degenerate upon the impairment of mitochondrial function, as they rely primarily on glycolysis to produce energy and have a higher antioxidant capacity than neurons. However, recent evidence highlights the role of mitochondrial metabolism and signaling in glial cell function. In this work, we review the functional role of mitochondria in glial cells and the evidence regarding its potential role regulating neuronal homeostasis and disease progression.

Mitochondrial fusion, fission, and mitochondrial toxicity

Mitochondrial dynamics are regulated by two sets of opposed processes: mitochondrial fusion and fission, and mitochondrial biogenesis and degradation (including mitophagy), as well as processes such as intracellular transport. These processes maintain mitochondrial homeostasis, regulate mitochondrial form, volume and function, and are increasingly understood to be critical components of the cellular stress response. Mitochondrial dynamics vary based on developmental stage and age, cell type, environmental factors, and genetic background. Indeed, many mitochondrial homeostasis genes are human disease genes. Emerging evidence indicates that deficiencies in these genes often sensitize to environmental exposures, yet can also be protective under certain circumstances. Inhibition of mitochondrial dynamics also affects elimination of irreparable mitochondrial DNA (mtDNA) damage and transmission of mtDNA mutations. We briefly review the basic biology of mitodynamic processes with a focus on mitochondrial fusion and fission, discuss what is known and unknown regarding how these processes respond to chemical and other stressors, and review the literature on interactions between mitochondrial toxicity and genetic variation in mitochondrial fusion and fission genes. Finally, we suggest areas for future research, including elucidating the full range of mitodynamic responses from low to high-level exposures, and from acute to chronic exposures; detailed examination of the physiological consequences of mitodynamic alterations in different cell types; mechanism-based testing of mitotoxicant interactions with interindividual variability in mitodynamics processes; and incorporating other environmental variables that affect mitochondria, such as diet and exercise.

The use of high-throughput screening techniques to evaluate mitochondrial toxicity

Toxicologists and chemical regulators depend on accurate and effective methods to evaluate and predict the toxicity of thousands of current and future compounds. Robust high-throughput screening (HTS) experiments have the potential to efficiently test large numbers of chemical compounds for effects on biological pathways. HTS assays can be utilized to examine chemical toxicity across multiple mechanisms of action, experimental models, concentrations, and lengths of exposure. Many agricultural, industrial, and pharmaceutical chemicals classified as harmful to human and environmental health exert their effects through the mechanism of mitochondrial toxicity. Mitochondrial toxicants are compounds that cause a decrease in the number of mitochondria within a cell, and/or decrease the ability of mitochondria to perform normal functions including producing adenosine triphosphate (ATP) and maintaining cellular homeostasis. Mitochondrial dysfunction can lead to apoptosis, necrosis, altered metabolism, muscle weakness, neurodegeneration, decreased organ function, and eventually disease or death of the whole organism. The development of HTS techniques to identify mitochondrial toxicants will provide extensive databases with essential connections between mechanistic mitochondrial toxicity and chemical structure. Computational and bioinformatics approaches can be used to evaluate compound databases for specific chemical structures associated with toxicity, with the goal of developing quantitative structure-activity relationship (QSAR) models and mitochondrial toxicophores. Ultimately these predictive models will facilitate the identification of mitochondrial liabilities in consumer products, industrial compounds, pharmaceuticals and environmental hazards.

Clinical effects of chemical exposures on mitochondrial function

Mitochondria are critical for the provision of ATP for cellular energy requirements. Tissue and organ functions are dependent on adequate ATP production, especially when energy demand is high. Mitochondria also play a role in a vast array of important biochemical pathways including apoptosis, generation and detoxification of reactive oxygen species, intracellular calcium regulation, steroid hormone and heme synthesis, and lipid metabolism. The complexity of mitochondrial structure and function facilitates its diverse roles but also enhances its vulnerability. Primary disorders of mitochondrial bioenergetics, or Primary Mitochondrial Diseases (PMD) are due to inherited genetic defects in the nuclear or mitochondrial genomes that result in defective oxidative phosphorylation capacity and cellular energy production. Secondary mitochondrial dysfunction is observed in a wide range of diseases such as Alzheimer's and Parkinson's disease. Several lines of evidence suggest that environmental exposures cause substantial mitochondrial dysfunction. Whereby literature from experimental and human studies on exposures associated with Alzheimer's and Parkinson's diseases exist, the significance of exposures as potential triggers in Primary Mitochondrial Disease (PMD) is an emerging clinical question that has not been systematically studied.