Mitochondrial dysfunction in T cells of patients with systemic lupus erythematosus

Targeting ferroptosis in autoimmune diseases: Mechanisms and therapeutic prospects

Ferroptosis is a form of regulated cell death that relies on iron and exhibits unique characteristics, including disrupted iron balance, reduced antioxidant defenses, and abnormal lipid peroxidation. Recent research suggests that ferroptosis is associated with the onset and progression of autoimmune disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), inflammatory bowel disease (IBD), and multiple sclerosis (MS). However, the precise effects and molecular mechanisms remain incompletely understood. This article presents an overview of how ferroptosis mechanisms contribute to the development and advancement of autoimmune diseases, as well as the involvement of various immune cells in linking ferroptosis to autoimmune conditions. It also explores potential drug targets within the ferroptosis pathway and recent advancements in therapeutic approaches aimed at preventing and treating autoimmune diseases by targeting ferroptosis. Lastly, the article discusses the challenges and opportunities in utilizing ferroptosis as a potential therapeutic avenue for autoimmune disorders.

Advances in the study of ferroptosis and its relationship to autoimmune diseases

Ferroptosis represents a novel mode of programmed cell death characterized by the intracellular accumulation of iron and lipid peroxidation, culminating in oxidative stress and subsequent cell demise. Mounting evidence demonstrates that ferroptosis contributes significantly to the onset and progression of diverse pathological conditions and diseases, including infections, neurodegenerative disorders, tissue ischemia-reperfusion injury, and immune dysregulation. Recent investigations have underscored the pivotal role of ferroptosis in the pathogenesis of rheumatoid arthritis, ulcerative colitis, systemic lupus erythematosus, and asthma. This review provides a comprehensive overview of the current understanding of the regulatory mechanisms governing ferroptosis, particularly its interplay with iron, lipid, and amino acid metabolism. Furthermore, we explore the implications of ferroptosis in autoimmune diseases and deliberate on its potential as a promising therapeutic target for diverse autoimmune disorders.

Glycolysis inhibition functionally reprograms T follicular helper cells and reverses lupus

Systemic lupus erythematosus (SLE) is an autoimmune disease in which the production of pathogenic autoantibodies depends on T follicular helper (T FH ) cells. This study was designed to investigate the mechanisms by which inhibition of glycolysis with 2-deoxy-d-glucose (2DG) reduces the expansion of T FH cells and the associated autoantibody production in lupus-prone mice. Integrated cellular, transcriptomic, epigenetic and metabolic analyses showed that 2DG reversed the enhanced cell expansion and effector functions, as well as mitochondrial and lysosomal defects in lupus T FH cells, which include an increased chaperone-mediated autophagy induced by TLR7 activation. Importantly, adoptive transfer of 2DG-reprogrammed T FH cells protected lupus-prone mice from disease progression. Orthologs of genes responsive to 2DG in murine lupus T FH cells were overexpressed in the T FH cells of SLE patients, suggesting a therapeutic potential of targeting glycolysis to eliminate aberrant T FH cells and curb the production of autoantibodies inducing tissue damage.

Mitochondrial Dysfunction and Fatigue in Sjögren's Disease

Objectives

Sjögren's disease (SjD) is a common exocrine disorder typified by chronic inflammation and dryness, but also profound fatigue, suggesting a pathological basis in cellular bioenergetics. In healthy states, damaged or dysfunctional mitochondrial components are broken down and recycled by mitophagy, a specialized form of autophagy. In many autoimmune disorders, however, evidence suggests that dysfunctional mitophagy allows poorly functioning mitochondria to persist and contribute to a cellular milieu with elevated reactive oxygen species. We hypothesized that mitophagic processes are dysregulated in SjD and that dysfunctional mitochondria contribute to overall fatigue. We sought to link fatigue with mitochondrial dysfunction directly in SjD, heretofore unexamined, and further sought to assess the pathogenic extent and implications of dysregulated mitophagy in SjD.

Methods

We isolated pan T cells via negative selection from the peripheral blood mononuclear cells of 17 SjD and 8 age-matched healthy subjects, all of whom completed fatigue questionnaires prior to phlebotomy. Isolated T cells were analyzed for mitochondrial oxygen consumption rate (OCR) and glycolysis using Seahorse, and linear correlations with fatigue measures were assessed. A mitophagy transcriptional signature in SjD was identified by reanalysis of whole-blood microarray data from 190 SjD and 32 healthy subjects. Differential expression analyses were performed by case/control and subgroup analyses comparing SjD patients by mitophagy transcriptional cluster against healthy subjects followed by bioinformatic interpretation using gene set enrichment analysis.

Results

Basal OCR, ATP-linked respiration, maximal respiration, and reserve capacity were significantly lower in SjD compared to healthy subjects with no observed differences in non-mitochondrial respiration, basal glycolysis, or glycolytic stress. SjD lymphocytic mitochondria show structural alterations compared to healthy subjects. Fatigue scores related to pain/discomfort in SjD correlated with the altered OCR. Results from subgroup analyses by mitophagic SjD clusters revealed highly variable inter-cluster differentially expressed genes (DEGs) and expanded the number of SjD-associated gene targets by tenfold within the same dataset.

Conclusion

Mitochondrial dysfunction, associated with fatigue, is a significant problem in SjD and warrants further investigation.

Dermatologic Manifestations of Mitochondrial Dysfunction: A Review of the Literature

Mitochondria are eukaryotic cellular organelles that function in energy metabolism, ROS production, and programmed cell death. Cutaneous epithelial and hair follicle dermal papilla cells are energy-rich cells that thereby may be affected by mitochondrial dysfunction and DNA mutation accumulation. In this review, we aimed to summarize the medical literature assessing dermatologic conditions and outcomes associated with mitochondrial dysfunction. A search of PubMed and Embase was performed with subsequent handsearching to retrieve additional relevant articles. Mitochondrial DNA (mtDNA) deletions, mutation accumulation, and damage are associated with phenotypic signs of cutaneous aging, hair loss, and impaired wound healing. In addition, several dermatologic conditions are associated with aberrant mitochondrial activity, such as systemic lupus erythematosus, psoriasis, vitiligo, and atopic dermatitis. Mouse model studies have better established causality between mitochondrial damage and dermatologic outcomes, with some depicting reversibility upon restoration of mitochondrial function. Mitochondrial function mediates a variety of dermatologic conditions, and mitochondrial components may be a promising target for therapeutic strategies.

Reduced mitochondrial-encoded NADH dehydrogenase 6 gene expression drives inflammatory CD4+T cells in patients with systemic lupus erythematosus

Abnormal mitochondrial function has been implicated in the progression of systemic lupus erythematosus (SLE), the prototypical autoimmune disease, yet the underlying cause remains unclear. In this study, mitochondrial-encoded NADH dehydrogenase 6 gene (MT-ND6) was identified as having increased m6A methylation and decreased expression in peripheral blood mononuclear cells of SLE patients by MeRIP-seq analysis. MT-ND6 expression was negatively correlated with SLE disease activity index score and 24-h urine protein level, and lower in patients with positive anti-Sm or anti-dsDNA antibodies. With the reduction of MT-ND6 levels, CD4+ T cells in SLE patients exhibited mitochondrial dysfunction, as evidenced by increased levels of reactive oxygen species (ROS) and mitochondrial ROS and insufficient ATP production. Accordingly, in vitro MT-ND6 silencing induced abnormalities in the above mitochondrial indicators in CD4+ T cells, and promoted the development of both transcription and inflammatory factors in these cells. In contrast, treatment with targeted mitochondrial antioxidants largely counteracted the silencing effect of MT-MD6. Thus, reduced MT-ND6 in SLE patients may lead to mitochondrial dysfunction through ROS overproduction, thereby promoting inflammatory CD4+ T cells.

The underestimated role of mitochondria in vitiligo: From oxidative stress to inflammation and cell death

Vitiligo is an acquired depigmentary disorder characterized by the depletion of melanocytes in the skin. Mitochondria shoulder multiple functions in cells, such as production of ATP, maintenance of redox balance, initiation of inflammation and regulation of cell death. Increasing evidence has implicated the involvement of mitochondria in the pathogenesis of vitiligo. Mitochondria alteration will cause the abnormalities of mitochondria functions mentioned above, ultimately leading to melanocyte loss through various cell death modes. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a critical role in mitochondrial homeostasis, and the downregulation of Nrf2 in vitiligo may correlate with mitochondria damage, making both mitochondria and Nrf2 promising targets in treatment of vitiligo. In this review, we aim to discuss the alterations of mitochondria and its role in the pathogenesis of vitiligo.

Therapeutic Dosage of Antipsychotic Drug Aripiprazole Induces Persistent Mitochondrial Hyperpolarisation, Moderate Oxidative Stress in Liver Cells, and Haemolysis

Aripiprazole has fewer metabolic side effects than other antipsychotics; however, there are some severe ones in the liver, leading to drug-induced liver injury. Repeated treatment with aripiprazole affects cell division. Since this process requires a lot of energy, we decided to investigate the impact of aripiprazole on rat liver cells and mitochondria as the main source of cellular energy production by measuring the mitochondrial membrane potential, respiration, adenosine triphosphate (ATP) production, oxidative stress, antioxidative response, and human blood haemolysis. Here, we report that mitochondrial hyperpolarisation from aripiprazole treatment is accompanied by higher reactive oxygen species (ROS) production and increased antioxidative response. Lower mitochondrial and increased glycolytic ATP synthesis demand more glucose through glycolysis for equal ATP production and may change the partition between the glycolysis and pentose phosphate pathway in the liver. The uniform low amounts of the haemolysis of erythrocytes in the presence of aripiprazole in 25 individuals indicate lower quantities of the reduced form of nicotinamide adenine dinucleotide phosphate (NADPH+H+), which is in accordance with a decreased activity of glucose 6-phosphate dehydrogenase and the lower dehydrogenase activity upon aripiprazole treatment. The lower activity of glucose 6-phosphate dehydrogenase supports a shift to glycolysis, thus rescuing the decreased mitochondrial ATP synthesis. The putative reduction in NADPH+H+ did not seem to affect the oxidised-to-reduced glutathione ratio, as it remained equal to that in the untreated cells. The effect of aripiprazole on glutathione reduction is likely through direct binding, thus reducing its total amount. As a consequence, the low haemolysis of human erythrocytes was observed. Aripiprazole causes moderate perturbations in metabolism, possibly with one defect rescuing the other. The result of the increased antioxidant enzyme activity upon treatment with aripiprazole is increased resilience to oxidative stress, which makes it an effective drug for schizophrenia in which oxidative stress is constantly present because of disease and treatment.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

Glucose metabolic reprogramming in autoimmune diseases

Autoimmune diseases are conditions in which the immune system mistakenly targets and damages healthy tissue in the body. In recent decades, the incidence of autoimmune diseases has increased, resulting in a significant disease burden. The current autoimmune therapies focus on targeting inflammation or inducing immunosuppression rather than addressing the underlying cause of the diseases. The activity of metabolic pathways is elevated in autoimmune diseases, and metabolic changes are increasingly recognized as important pathogenic processes underlying these. Therefore, metabolically targeted therapies may represent an important strategy for treating autoimmune diseases. This review provides a comprehensive overview of the evidence surrounding glucose metabolic reprogramming and its potential applications in drug discovery and development for autoimmune diseases, such as type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, and systemic sclerosis.

Chemical Profile, Antioxidant and Anti-Inflammatory Potency of Extracts of Vitex madiensis Oliv. and Crossopteryx febrifuga (Afzel ex G. Don)

Vitex madiensis Oliv. (Lamiaceae) and Crossopteryx febrifuga (Rubiaceae), two plants commonly used in traditional African medicines to treat malaria and pain, were studied either to determine their chemical profiles or to evaluate their antioxidant and anti-inflammatory activities. In this study, we investigated leaves, trunk bark, root bark and fruits methanolic extracts of both plants in order to find out which part of the plant is responsible for the activity. The analyses of the chemical profiles allowed us to confirm the presence of several ecdysteroids, especially 20-hydroxyecdysone in some parts of V. madiensis and to highlight the presence of organic acids and phenol derivatives in C. febrifuga. Among the four parts of the plants studied, only the fruits extract of C. febrifuga could present anti-inflammatory activity by decreasing ROS production. The leaves and trunk bark extracts of V. madiensis showed significant free radical scavenging activity compared to ascorbic acid, and the same extracts decrease ROS production significantly. The activity of these two extracts could be explained by the presence of ecdysteroids and flavonoids. The ROS production inhibition of V. madiensis is particularly interesting to investigate with further analyses.

The Potential Role of Ferroptosis in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that is accompanied with autoantibody production and inflammation. Other features of SLE pathogenesis include iron accumulation, oxidative stress, and lipid peroxidation, which are also major biochemical characteristics of ferroptosis, a novel non-apoptotic regulated form of cell death. To date, ferroptosis has been demonstrated to be an important driver of lupus progression, and several ferroptosis inhibitors have therapeutic effect in lupus-prone mice. Given the emerging link between ferroptosis and SLE, it can be postulated that ferroptosis is an integral component in the vicious cycle of immune dysfunction, inflammation, and tissue damage in SLE pathogenesis. In this review, we summarize the potential links between ferroptosis and SLE, with the aim of elucidating the underlying pathogenic mechanism of ferroptosis in lupus, and providing a new promising therapeutic strategy for SLE.

T cell metabolism and possible therapeutic targets in systemic lupus erythematosus: a narrative review

In the immunopathogenesis of systemic lupus erythematosus (SLE), there is a dysregulation of specific immune cells, including T cells. The metabolic reprogramming in T cells causes different effects. Metabolic programs are critical checkpoints in immune responses and are involved in the etiology of autoimmune disease. For instance, resting lymphocytes generate energy through oxidative phosphorylation (OXPHOS) and fatty acid oxidation (FAO), whereas activated lymphocytes rapidly shift to the glycolytic pathway. Specifically, mitochondrial dysfunction, oxidative stress, abnormal metabolism (including glucose, lipid, and amino acid metabolism), and mTOR signaling are hallmarks of T lymphocyte metabolic dysfunction in SLE. Herein it is summarized how metabolic defects contribute to T cell responses in SLE, and some epigenetic alterations involved in the disease. Finally, it is shown how metabolic defects could be modified therapeutically.

Targeting mitochondria in dermatological therapy: Beyond oxidative damage and skin aging

INTRODUCTION

The analysis of the role of the mitochondria in oxidative damage and skin aging is a significant aspect of dermatological research. Mitochondria generate most reactive oxygen species (ROS); however, excessive ROS are cytotoxic and DNA-damaging and promote (photo-)aging. ROS also possesses key physiological and regulatory functions and mitochondrial dysfunction is prominent in several skin diseases including skin cancers. Although many standard dermatotherapeutics modulate mitochondrial function, dermatological therapy rarely targets the mitochondria. Accordingly, there is a rationale for "mitochondrial dermatology"-based approaches to be applied to therapeutic research.

AREAS COVERED

This paper examines the functions of mitochondria in cutaneous physiology beyond energy (ATP) and ROS production. Keratinocyte differentiation and epidermal barrier maintenance, appendage morphogenesis and homeostasis, photoaging and skin cancer are considered. Based on related PubMed search results, the paper evaluates thyroid hormones, glucocorticoids, Vitamin D3 derivatives, retinoids, cannabinoid receptor agonists, PPARγ agonists, thyrotropin, and thyrotropin-releasing hormone as instructive lead compounds. Moreover, the mitochondrial protein MPZL3 as a promising new drug target for future "mitochondrial dermatology" is highlighted.

EXPERT OPINION

Future dermatological therapeutic research should have a mitochondrial medicine emphasis. Focusing on selected lead agents, protein targets, in silico drug design, and model diseases will fertilize a mito-centric approach.

Redox Homeostasis Involvement in the Pharmacological Effects of Metformin in Systemic Lupus Erythematosus

Significance: Metformin has been proposed as a treatment for systemic lupus erythematosus (SLE). The primary target of metformin, the electron transport chain complex I in the mitochondria, is associated with redox homeostasis in immune cells, which plays a critical role in the pathogenesis of autoimmune diseases. This review addresses the evidence and knowledge gaps on whether a beneficial effect of metformin in lupus may be due to a restoration of a balanced redox state. Recent Advances: Clinical trials in SLE patients with mild-to-moderate disease activity and preclinical studies in mice have provided encouraging results for metformin. The mechanism by which this therapeutic effect was achieved is largely unknown. Metformin regulates redox homeostasis in a context-specific manner. Multiple cell types contribute to SLE, with evidence of increased mitochondrial oxidative stress in T cells and neutrophils. Critical Issues: The major knowledge gaps are whether the efficacy of metformin is linked to a restored redox homeostasis in the immune system, and if it does, in which cell types it occurs? We also need to know which patients may have a better response to metformin, and whether it corresponds to a specific mechanism? Finally, the identification of biomarkers to predict treatment outcomes would be of great value. Future Directions: Mechanistic studies must address the context-dependent pharmacological effects of metformin. Multiple cell types as well as a complex disease etiology should be considered. These studies must integrate the rapid advances made in understanding how metabolic programs direct the effector functions of immune cells. Antioxid. Redox Signal. 36, 462-479.

Mitochondrial DNA genetic variants are associated with systemic lupus erythematosus susceptibility, glucocorticoids efficacy, and prognosis

OBJECTIVE

To investigate the associations of mitochondrial DNA (mtDNA) genetic variants with systemic lupus erythematosus (SLE) susceptibility, glucocorticoids (GCs) efficacy, and prognosis.

METHODS

Our study was done in two stages. First, we performed the whole mitochondrial genome sequencing in 100 patients and 100 controls to initially screen potential mtDNA variants associated with disease and glucocorticoids efficacy. Then, we validated the results in an independent set of samples. In total, 605 SLE patients and 604 normal controls were included in our two-stage study. A two-stage efficacy study was conducted in 512 patients treated with GCs for 12 weeks. We also explored the association between mtDNA variants and SLE prognosis.

RESULTS

In the combined sample, four mtDNA variants (A4833G, T5108C, G14569A, CA514-515-) were associated with SLE susceptibility (all P  BH<0.05). We confirmed that T16362C was related to GCs efficacy (P  BH=0.014). Significant associations were detected between T16362C and T16519C and the efficacy of GCs in females with SLE (P  BH<0.05). In the prognosis study, variants A4833G (P  BH=0.003) and G14569A (P  BH=9.744 × 1 0 -4) substantially increased SLE relapse risk. Female patients harbouring variants T5108C and T16362C were more prone to relapse (P  BH<0.05). Haplotype analysis showed that haplogroup G was linked with SLE susceptibility (P  BH=0.001) and prognosis (P  BH=0.013). Moreover, mtDNA variants-environment interactions were observed.

CONCLUSION

We identified novel mtDNA genetic variants that were associated with SLE susceptibility, GCs efficacy, and prognosis. Interactions between mtDNA variants and environmental factors were related to SLE risk and GCs efficacy. Our findings provide important information for future understanding the occurrence and development of SLE.

Metabolic preconditioning in CD4+ T cells restores inducible immune tolerance in lupus-prone mice

Autoimmune disease has presented an insurmountable barrier to restoration of durable immune tolerance. Previous studies indicate that chronic therapy with metabolic inhibitors can reduce autoimmune inflammation, but it remains unknown whether acute metabolic modulation enables permanent immune tolerance to be established. In an animal model of lupus, we determined that targeting glucose metabolism with 2-deoxyglucose (2DG) and mitochondrial metabolism with metformin enables endogenous immune tolerance mechanisms to respond to tolerance induction. A 2-week course of 2DG and metformin, when combined with tolerance-inducing therapy anti-CD45RB, prevented renal deposition of autoantibodies for 6 months after initial treatment and restored tolerance induction to allografts in lupus-prone mice. The restoration of durable immune tolerance was linked to changes in T cell surface glycosylation patterns, illustrating a role for glycoregulation in immune tolerance. These findings indicate that metabolic therapy may be applied as a powerful preconditioning to reinvigorate tolerance mechanisms in autoimmune and transplant settings that resist current immune therapies.

IRGM1 links mitochondrial quality control to autoimmunity

Mitochondrial abnormalities have been noted in lupus, but the causes and consequences remain obscure. Autophagy-related genes ATG5, ATG7 and IRGM have been previously implicated in autoimmune disease. We reasoned that failure to clear defective mitochondria via mitophagy might be a foundational driver in autoimmunity by licensing mitochondrial DNA-dependent induction of type I interferon. Here, we show that mice lacking the GTPase IRGM1 (IRGM homolog) exhibited a type I interferonopathy with autoimmune features. Irgm1 deletion impaired the execution of mitophagy with cell-specific consequences. In fibroblasts, mitochondrial DNA soiling of the cytosol induced cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-dependent type I interferon, whereas in macrophages, lysosomal Toll-like receptor 7 was activated. In vivo, Irgm1-/- tissues exhibited mosaic dependency upon nucleic acid receptors. Whereas salivary and lacrimal gland autoimmune pathology was abolished and lung pathology was attenuated by cGAS and STING deletion, pancreatic pathology remained unchanged. These findings reveal fundamental connections between mitochondrial quality control and tissue-selective autoimmune disease.

An exacerbated metabolism and mitochondrial reactive oxygen species contribute to mitochondrial alterations and apoptosis in CD4 T cells during the acute phase of Trypanosoma cruzi infection

Chagas disease caused by Trypanosoma cruzi parasite is an endemic infection in America. It is well known that T. cruzi causes a strong immunosuppression during the acute phase of infection. However, it is not clear whether T. cruzi infection is related to metabolic alterations in CD4 T cells that prevent downstream effector function. Here, we evaluated the CD4 T cell metabolic and mitochondrial profiles from non-infected (NI), acute phase (AP) and chronic phase (CP) T. cruzi infected mice. CD4 T cells from all groups showed increased glucose uptake after stimulation. Moreover, the bioenergetic analysis revealed a rise in glycolysis and a higher oxidative metabolism in CD4 T cells from the AP. These cells showed increased proton leak and uncoupling protein 3 (UCP3) expression that correlated with mitochondrial ROS (mROS) accumulation, mitochondrial membrane potential (MMP) depolarization and expression of PD-1. In addition, CD4 T cells with mitochondrial alteration displayed an activated phenotype, and were less functional and more prone to apoptosis. In contrast, mitochondrial alterations were not observed during in vivo activation of CD4 T cells in a model of OVA-immunization. The Mn-superoxide dismutase (SOD2) expression, which is involved in mROS detoxification, was increased during the AP and CP of infection. Remarkably, the apoptosis observed in CD4 T cells with MMP depolarization was prevented by incubation with N-acetyl cysteine (NAC). Thus, our results showed that infection triggered an exacerbated metabolism together with mROS production in CD4 T cells from the AP of infection. However, antioxidant availability may not be sufficient to avoid mitochondrial alterations rendering these cells more susceptible to apoptosis. Our investigation is the first to demonstrate an association between a disturbed metabolism and an impaired CD4 T cell response during T. cruzi infection.

Oxidative Stress in Autoimmune Diseases: An Under Dealt Malice

Oxidative stress is the off-balance of antioxidants and free radicals. All kinds of diseases and disorders give rise to oxidative damage including autoimmune diseases. An autoimmune disorder is a pathological condition characterized by the breakdown of self-tolerance of the immune system in the body. Immunological processes against tissues and organs lead to enhanced oxidative stress and, in turn, misbalance of oxidative stress aggravates the pathobiology of the disease. Highly reactive nature of free radicals, for example hydroxyl and superoxide ions, alters DNA, protein, and lipids in the body which augment the pathologic processes of diseases. The damaged biomolecules are responsible for systemic complications and secondary disease co-morbidities. In this review, we discuss the role of oxidative stress in some incapacitating autoimmune diseases like Rheumatoid arthritis, Systemic Lupus Erythematosus, Type 1 Diabetes, and Multiple Sclerosis. Oxidative stress plays a central and course defining role in these diseases and it has become a necessity to study the pathological mechanism involved in oxidative stress to better understand and offer treatment holistically. Presently there are no clinically available parameters for measurement and treatment of pathological oxidative stress, therefore it requires intensive research. Probably, in the future, the discovery of easily detectable markers of oxidative stress can aid in the diagnosis, prognosis, and treatment of progressively destructive autoimmune diseases.

The Role of Mitochondria in Systemic Lupus Erythematosus: A Glimpse of Various Pathogenetic Mechanisms

BACKGROUND

Systemic Lupus Erythematosus (SLE) is a polysystem autoimmune disease that adversely affects human health. Various organs can be affected, including the kidney or brain. Traditional treatment methods for SLE primarily rely on glucocorticoids and immunosuppressors. Unfortunately, these therapeutic agents cannot prevent a high recurrence rate after SLE remission. Therefore, novel therapeutic targets are urgently required.

METHODS

A systematic search of the published literature regarding the abnormal structure and function of mitochondria in SLE and therapies targeting mitochondria was performed in several databases.

RESULTS

Accumulating evidence indicates that mitochondrial dysfunction plays important roles in the pathogenesis of SLE, including influencing mitochondrial DNA damage, mitochondrial dynamics change, abnormal mitochondrial biogenesis and energy metabolism, mitophagy, oxidative stress, inflammatory reactions, apoptosis and NETosis. Further investigation of mitochondrial pathophysiological roles will result in further clarification of SLE. Specific lupus-induced organ damage also exhibits characteristic mitochondrial changes.

CONCLUSION

This review aimed to summarize the current research on the role of mitochondrial dysfunction in SLE, which will necessarily provide potential novel therapeutic targets for SLE.

The Influence of Reactive Oxygen Species in the Immune System and Pathogenesis of Multiple Sclerosis

Multiple roles have been indicated for reactive oxygen species (ROS) in the immune system in recent years. ROS have been extensively studied due to their ability to damage DNA and other subcellular structures. Noticeably, they have been identified as a pivotal second messenger for T-cell receptor signaling and T-cell activation and participate in antigen cross-presentation and chemotaxis. As an agent with direct toxic effects on cells, ROS lead to the initiation of the autoimmune response. Moreover, ROS levels are regulated by antioxidant systems, which include enzymatic and nonenzymatic antioxidants. Enzymatic antioxidants include superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase. Nonenzymatic antioxidants contain vitamins C, A, and E, glutathione, and thioredoxin. Particularly, cellular antioxidant systems have important functions in maintaining the redox system homeostasis. This review will discuss the significant roles of ROS generation and antioxidant systems under normal conditions, in the immune system, and pathogenesis of multiple sclerosis.

Mitochondria in skin health, aging, and disease

The skin is a high turnover organ, and its constant renewal depends on the rapid proliferation of its progenitor cells. The energy requirement for these metabolically active cells is met by mitochondrial respiration, an ATP generating process driven by a series of protein complexes collectively known as the electron transport chain (ETC) that is located on the inner membrane of the mitochondria. However, reactive oxygen species (ROS) like superoxide, singlet oxygen, peroxides are inevitably produced during respiration and disrupt macromolecular and cellular structures if not quenched by the antioxidant system. The oxidative damage caused by mitochondrial ROS production has been established as the molecular basis of multiple pathophysiological conditions, including aging and cancer. Not surprisingly, the mitochondria are the primary organelle affected during chronological and UV-induced skin aging, the phenotypic manifestations of which are the direct consequence of mitochondrial dysfunction. Also, deletions and other aberrations in the mitochondrial DNA (mtDNA) are frequent in photo-aged skin and skin cancer lesions. Recent studies have revealed a more innate role of the mitochondria in maintaining skin homeostasis and pigmentation, which are affected when the essential mitochondrial functions are impaired. Some common and rare skin disorders have a mitochondrial involvement and include dermal manifestations of primary mitochondrial diseases as well as congenital skin diseases caused by damaged mitochondria. With studies increasingly supporting the close association between mitochondria and skin health, its therapeutic targeting in the skin-either via an ATP production boost or free radical scavenging-has gained attention from clinicians and aestheticians alike. Numerous bioactive compounds have been identified that improve mitochondrial functions and have proved effective against aged and diseased skin. In this review, we discuss the essential role of mitochondria in regulating normal and abnormal skin physiology and the possibility of targeting this organelle in various skin disorders.

T cell Metabolism in Lupus

Abnormal T cell responses are central to the development of autoimmunity and organ damage in systemic lupus erythematosus. Following stimulation, naïve T cells undergo rapid proliferation, differentiation and cytokine production. Since the initial report, approximately two decades ago, that engagement of CD28 enhances glycolysis but PD-1 and CTLA-4 decrease it, significant information has been generated which has linked metabolic reprogramming with the fate of differentiating T cell in health and autoimmunity. Herein we summarize how defects in mitochondrial dysfunction, oxidative stress, glycolysis, glutaminolysis and lipid metabolism contribute to pro-inflammatory T cell responses in systemic lupus erythematosus and discuss how metabolic defects can be exploited therapeutically.

Immunometabolic disorders in the pathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus is a chronic autoimmune disease connected with complex and unclear disorders of the immune system, which causes inflammation of body tissues and internal organs. It leads to the formation of anti-nuclear antibodies (ANA) and immune complexes. Numerous immune system disorders and dysfunctions in the biochemical processes can occur in the course of the disease, and a wide range of abnormalities associated with cellular respiratory processes and mitochondrial function have been documented. The following paper presents the current understanding of the contribution of these disorders to the pathogenesis of lupus.

Metabolism and Autoimmune Responses: The microRNA Connection

Distinct metabolic pathways are known to regulate growth, differentiation, survival, and activation of immune cells by providing energy and specific biosynthetic precursors. Compelling experimental evidence demonstrates that effector T cell functions are coupled with profound changes in cellular metabolism. Importantly, the effector T cell-dependent “anti-self” response characterizing the autoimmune diseases is accompanied by significant metabolic alterations. MicroRNAs (miRNAs), evolutionary conserved small non-coding RNA molecules that affect gene expression by binding to target messenger RNAs, are now known to regulate multiple functions of effector T cells, including the strength of their activation, thus contributing to immune homeostasis. In this review, we will examine the most recent studies that describe miRNA direct involvement in the metabolic reprogramming that marks effector T cell functions. In particular, we will focus on the work showing a connection between miRNA regulatory function and the molecular network dysregulation that leads to metabolic pathway derangement in autoimmunity. Finally, we will also speculate on the possibility that the interplay between miRNAs and metabolism in T cells may help identify novel miRNA-based therapeutic strategies to treat effector T cell immunometabolic alterations in pathological conditions such as autoimmunity and chronic inflammation.

Molecular and Cellular Bases of Immunosenescence, Inflammation, and Cardiovascular Complications Mimicking "Inflammaging" in Patients with Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an archetype of systemic autoimmune disease, characterized by the presence of diverse autoantibodies and chronic inflammation. There are multiple factors involved in lupus pathogenesis, including genetic/epigenetic predisposition, sexual hormone imbalance, environmental stimulants, mental/psychological stresses, and undefined events. Recently, many authors noted that "inflammaging", consisting of immunosenescence and inflammation, is a common feature in aging people and patients with SLE. It is conceivable that chronic oxidative stresses originating from mitochondrial dysfunction, defective bioenergetics, abnormal immunometabolism, and premature telomere erosion may accelerate immune cell senescence in patients with SLE. The mitochondrial dysfunctions in SLE have been extensively investigated in recent years. The molecular basis of normoglycemic metabolic syndrome has been found to be relevant to the production of advanced glycosylated and nitrosative end products. Besides, immunosenescence, autoimmunity, endothelial cell damage, and decreased tissue regeneration could be the results of premature telomere erosion in patients with SLE. Herein, the molecular and cellular bases of inflammaging and cardiovascular complications in SLE patients will be extensively reviewed from the aspects of mitochondrial dysfunctions, abnormal bioenergetics/immunometabolism, and telomere/telomerase disequilibrium.

Metabolism of T Lymphocytes in Health and Disease

Adaptive immune responses that occur in infection, cancer, and autoimmune as well as allergic diseases involve the participation of T cells. T cells travel throughout the body searching for antigens, which are recognized via the major histocompatibility complexes. In the healthy organism, these T cells maintain metabolic quiescence until they encounter a potentially cognate antigen. Once activated, e.g., during an infection or tissue damage, T cells switch their metabolic program to gain energy and building blocks to maintain cellular homeostasis and to fulfill their specific immune functions involving clonal expansion and/or differentiation into effector and memory T cells to ultimately ensure host survival. Thus, differences in metabolism in healthy and pathogenic T cells provide an explanation for dysfunctionality of T-cell responses in metabolic disorders, autoimmunity, and cancer. Here, we summarize current knowledge on T-cell metabolism during the maintenance of homeostasis, activation, and differentiation as well as over the course of time that memory is generated in health and in diseased states such as autoimmunity and cancer.

Use the Protonmotive Force: Mitochondrial Uncoupling and Reactive Oxygen Species

Mitochondrial respiration results in an electrochemical proton gradient, or protonmotive force (pmf), across the mitochondrial inner membrane. The pmf is a form of potential energy consisting of charge (∆ψ_m) and chemical (∆pH) components, that together drive ATP production. In a process called uncoupling, proton leak into the mitochondrial matrix independent of ATP production dissipates the pmf and energy is lost as heat. Other events can directly dissipate the pmf independent of ATP production as well, such as chemical exposure or mechanisms involving regulated mitochondrial membrane electrolyte transport. Uncoupling has defined roles in metabolic plasticity and can be linked through signal transduction to physiologic events. In the latter case, the pmf impacts mitochondrial reactive oxygen species (ROS) production. Although capable of molecular damage, ROS also have signaling properties that depend on the timing, location, and quantity of their production. In this review, we provide a general overview of mitochondrial ROS production, mechanisms of uncoupling, and how these work in tandem to affect physiology and pathologies, including obesity, cardiovascular disease, and immunity. Overall, we highlight that isolated bioenergetic models-mitochondria and cells-only partially recapitulate the complex link between the pmf and ROS signaling that occurs in vivo.

Two-photon microscopy imaging of oxidative stress in human living erythrocytes

Red blood cells (RBCs) are known to be the most suitable cells to study oxidative stress, which is implicated in the etiopathology of many human diseases. The goal of the current study was to develop a new effective approach for assessing oxidative stress in human living RBCs using two-photon microscopy. To mimic oxidative stress in human living RBCs, an in vitro model was generated followed by two-photon microscopy imaging. The results revealed that oxidative stress is clearly visible on the two-photon microscopy images of RBCs under oxidative stress compared to no fluorescence in controls (P<0.0001). This novel approach for oxidative stress investigation in human living RBCs could efficiently be applied in clinical research and antioxidant compounds testing.

T cells display mitochondria hyperpolarization in human type 1 diabetes

T lymphocytes constitute a major effector cell population in autoimmune type 1 diabetes. Despite essential functions of mitochondria in regulating activation, proliferation, and apoptosis of T cells, little is known regarding T cell metabolism in the progression of human type 1 diabetes. In this study, we report, using two independent cohorts, that T cells from patients with type 1 diabetes exhibited mitochondrial inner-membrane hyperpolarization (MHP). Increased MHP was a general phenotype observed in T cell subsets irrespective of prior antigen exposure, and was not correlated with HbA1C levels, subject age, or duration of diabetes. Elevated T cell MHP was not detected in subjects with type 2 diabetes. T cell MHP was associated with increased activation-induced IFNγ production, and activation-induced IFNγ was linked to mitochondria-specific ROS production. T cells from subjects with type 1 diabetes also exhibited lower intracellular ATP levels. In conclusion, intrinsic mitochondrial dysfunction observed in type 1 diabetes alters mitochondrial ATP and IFNγ production; the latter is correlated with ROS generation. These changes impact T cell bioenergetics and function.

Immunometabolism in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease mediated by pathogenic autoantibodies directed against nucleoprotein complexes. Beyond the activation of autoreactive B cells, this process involves dysregulation in many other types of immune cells, including CD4⁺ T cells, dendritic cells, macrophages and neutrophils. Metabolic substrate utilization and integration of cues from energy sensors are critical checkpoints of effector functions in the immune system, with common as well as cell-specific programmes. Patients with SLE and lupus-prone mice present with activated metabolism of CD4⁺ T cells, and the use of metabolic inhibitors to normalize these features is associated with therapeutic effects. Far less is known about the metabolic requirements of B cells and myeloid cells in SLE. This article reviews current knowledge of the alterations in metabolism of immune cells in patients with SLE and mouse models of lupus in the context of what is known about the metabolic regulation of these cells during normal immune responses. How these alterations might contribute to lupus pathogenesis and how they can be targeted therapeutically are also discussed.

Reactive oxygen species induce virus-independent MAVS oligomerization in systemic lupus erythematosus

The increased expression of genes induced by type I interferon (IFN) is characteristic of viral infections and systemic lupus erythematosus (SLE). We showed that mitochondrial antiviral signaling (MAVS) protein, which normally forms a complex with retinoic acid gene I (RIG-I)-like helicases during viral infection, was activated by oxidative stress independently of RIG-I helicases. We found that chemically generated oxidative stress stimulated the formation of MAVS oligomers, which led to mitochondrial hyperpolarization and decreased adenosine triphosphate production and spare respiratory capacity, responses that were not observed in similarly treated cells lacking MAVS. Peripheral blood lymphocytes of SLE patients also showed spontaneous MAVS oligomerization that correlated with the increased secretion of type I IFN and mitochondrial oxidative stress. Furthermore, inhibition of mitochondrial reactive oxygen species (ROS) by the mitochondria-targeted antioxidant MitoQ prevented MAVS oligomerization and type I IFN production. ROS-dependent MAVS oligomerization and type I IFN production were reduced in cells expressing the MAVS-C79F variant, which occurs in 30% of sub-Saharan Africans and is linked with reduced type I IFN secretion and milder disease in SLE patients. Patients expressing the MAVS-C79F variant also had reduced amounts of oligomerized MAVS in their plasma compared to healthy controls. Together, our findings suggest that oxidative stress-induced MAVS oligomerization in SLE patients may contribute to the type I IFN signature that is characteristic of this syndrome.

RNA-seq Analysis Reveals Unique Transcriptome Signatures in Systemic Lupus Erythematosus Patients with Distinct Autoantibody Specificities

Systemic lupus erythematosus (SLE) patients exhibit immense heterogeneity which is challenging from the diagnostic perspective. Emerging high throughput sequencing technologies have been proved to be a useful platform to understand the complex and dynamic disease processes. SLE patients categorised based on autoantibody specificities are reported to have differential immuno-regulatory mechanisms. Therefore, we performed RNA-seq analysis to identify transcriptomics of SLE patients with distinguished autoantibody specificities. The SLE patients were segregated into three subsets based on the type of autoantibodies present in their sera (anti-dsDNA+ group with anti-dsDNA autoantibody alone; anti-ENA+ group having autoantibodies against extractable nuclear antigens (ENA) only, and anti-dsDNA+ENA+ group having autoantibodies to both dsDNA and ENA). Global transcriptome profiling for each SLE patients subsets was performed using Illumina® Hiseq-2000 platform. The biological relevance of dysregulated transcripts in each SLE subsets was assessed by ingenuity pathway analysis (IPA) software. We observed that dysregulation in the transcriptome expression pattern was clearly distinct in each SLE patients subsets. IPA analysis of transcripts uniquely expressed in different SLE groups revealed specific biological pathways to be affected in each SLE subsets. Multiple cytokine signaling pathways were specifically dysregulated in anti-dsDNA+ patients whereas Interferon signaling was predominantly dysregulated in anti-ENA+ patients. In anti-dsDNA+ENA+ patients regulation of actin based motility by Rho pathway was significantly affected. The granulocyte gene signature was a common feature to all SLE subsets; however, anti-dsDNA+ group showed relatively predominant expression of these genes. Dysregulation of Plasma cell related transcripts were higher in anti-dsDNA+ and anti-ENA+ patients as compared to anti-dsDNA+ ENA+. Association of specific canonical pathways with the uniquely expressed transcripts in each SLE subgroup indicates that specific immunological disease mechanisms are operative in distinct SLE patients' subsets. This 'sub-grouping' approach could further be useful for clinical evaluation of SLE patients and devising targeted therapeutics.

Dexamethasone provoked mitochondrial perturbations in thymus: Possible role of N-acetylglucosamine in restoration of mitochondrial function

Thymus mitochondria play a crucial role in immune function. This study identifies the novel protective role of N-Acetylglucosamine (NAG) in dexamethasone (DEX) induced mitochondrial perturbations in mice thymus. Mice were induced with DEX (5mg/kg) and treated with NAG i.p. (266μg/kg, 400μg/kg and 800μg/kg) for 14 days, Withanolide A (800μg/kg) has been used as positive control. Dose dependent treatment of NAG against DEX significantly restored the mitochondrial enzyme levels (ICDH, KDH, SDH and MDH) and elevated the mitochondrial glutathione antioxidants defense (GSH, SOD, GPX and GST) thus improving the ATP status which was confirmed by ultrastructural alterations in mitochondria and nucleus using TEM studies. Further histopathological studies also revealed that NAG attenuate DEX induced thymotoxicity. Finally, the study concludes that dose dependent treatment of NAG supports a potential role in preventing DEX induced thymotoxicity and NAG acts as a beneficial pharmacological intervention in the DEX induced thymic repercussions.

Oxidative Stress and Treg and Th17 Dysfunction in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease that involves multiple organ systems. The pathogenic mechanisms that cause SLE remain unclear; however, it is well recognized that the immune balance is disturbed and that this imbalance contributes to the autoimmune symptoms of SLE. Oxidative stress represents an imbalance between the production and manifestation of reactive oxygen species and the ability of the biological system to readily detoxify the reactive intermediates or to repair the resulting damage. In humans, oxidative stress is involved in many diseases, including atherosclerosis, myocardial infarction, and autoimmune diseases. Numerous studies have confirmed that oxidative stress plays an important role in the pathogenesis of SLE. This review mainly focuses on the recent research advances with respect to oxidative stress and regulatory T (Treg)/helper T 17 (Th17) cell dysfunction in the pathogenesis of SLE.

Neuroimaging of translocator protein in patients with systemic lupus erythematosus: a pilot study using [11C]DPA-713 positron emission tomography

Objective Inflammation secondary to autoantibody-mediated effects occurring in multiple organs is a hallmark of systemic lupus erythematosus (SLE). The inflammatory response to SLE-mediated damage in brain parenchyma has been postulated in both normal and cognitively impaired individuals. Our goal is to use molecular imaging to investigate the distribution within the brain of the mitochondrial translocator protein (TSPO) that is upregulated during glial cell activation, and is considered as a marker of brain injury and repair. Methods We sought to characterize TSPO distribution in the brain of SLE patients using positron emission tomography (PET) and [¹¹C]DPA-713 (DPA), a radiopharmaceutical that targets TSPO. We imaged 11 healthy controls and 10 patients with SLE (years of diagnosis: 13.0 ± 7.7), all between the ages of 22 and 52.

RESULTS

Among the nine brain regions studied, no statistically significant increases in DPA binding were observed in SLE. Instead, there was a significant decrease in TSPO distribution in the cerebellum and hippocampus of SLE patients, as compared to healthy controls. Such decreases were most significant in cognitively normal SLE subjects, but showed pseudo-normalization in those with cognitive impairment, due to higher cerebellar and hippocampal DPA binding in the cognitively impaired (versus normal) SLE brain. Conclusions Results from this pilot study suggest a link between diminished regional TSPO expression in the brain of patients with SLE, as well as possible glial cell activation within the cerebellum and hippocampus of cognitively impaired individuals with SLE. Further studies are needed to elucidate how mitochondrial dysfunction and glial cell activation may act together in SLE and SLE-mediated neurocognitive deficits.

Structural differences in diarylheptanoids analogues from Alnus viridis and Alnus glutinosa influence their activity and selectivity towards cancer cells

Diarylheptanoids represent a group of plant secondary metabolites that possess multiple biological properties and are increasingly recognized for their therapeutic potential. A comparative study was performed on structurally analogous diarylheptanoids isolated from the bark of green (Alnus viridis) and black alder (Alnus glutinosa) to address their biological effects and determine structure-activity relationship. The structures and configurations of all compounds were elucidated by NMR, HR-ESI-MS, UV and IR. Diarylheptanoids actions were studied in human non-small cell lung carcinoma cells (NCI-H460) and normal keratinocytes (HaCaT). A. viridis compounds 3v, 5v, 8v and 9v that possess a carbonyl group at C-3 were considerably more potent than compounds without this group. A. viridis/A. glutinosa analogue pairs, 5v/5g and 9v/9g, which differ in the presence of 3' and 3″-OH groups, were evaluated for anticancer activity and selectivity. 5v and 9v that do not possess 3' and 3″-OH groups showed significantly higher cytotoxicity compared to analogues 5g and 9g. In addition, these two A. viridis compounds induced a more prominent apoptosis in both cell lines and an increase in subG0 cell cycle phase, compared to their A. glutinosa analogues. 5v and 9v treatment triggered intracellular superoxide anion accumulation and notably decreased mitochondrial transmembrane potential. In HaCaT cells, 9v and 9g with a 4,5 double bond caused a more prominent loss of mitochondrial transmembrane potential compared to 5v and 5g which possess a 5-methoxy group instead. Although green alder diarylheptanoids 5v and 9v displayed higher cytotoxicity, their analogues from black alder 5g and 9g could be more favorable for therapeutic use since they were more active in cancer cells than in normal keratinocytes. These results indicate that minor differences in the chemical structure can greatly influence the effect of diarylheptanoids on apoptosis and redox status and determine their selectivity towards cancer cells.

Association of mtDNA M/N haplogroups with systemic lupus erythematosus: a case-control study of Han Chinese women

To investigate whether mitochondrial DNA haplogroups M or N are related to occurrence or manifestations of systemic lupus erythematosus (SLE), we collected M/N haplogrouping and clinical characteristics from 868 Han Chinese women with SLE, as well as for 870 age-matched healthy Han Chinese control women. M/N haplogroups were determined in all subjects using allele-specific amplification. The frequency of M haplogroup in all patients was 429 (49.4%) and the frequency of N haplogroup, 439 (50.6%). The corresponding frequencies in controls were 456 (52.4%) and 414 (47.6%) (P = 0.213). Among women older than 50 years at onset age, the N haplogroup was significantly higher in patients than in healthy controls (59.6% vs 41.7%, P = 0.042). The N haplogroup was associated with significantly higher risk for certain SLE characteristics: hematological system damage (OR 2.128, 95%CI 1.610 to 2.813), skin impairment (OR 1.873, 95%CI 1.428 to 2.457), neurological disturbance (OR 3.956, 95%CI 1.874 to 8.352) and alopecia (OR 1.322, 95%CI 1.007 to 1.737 ). Our results suggest that in Han Chinese women, the mtDNA N haplogroup is associated with higher risk of late-onset SLE, skin impairment, neurological disturbance, hematological system damage and alopecia.

Mitochondrial dysfunction: a neglected component of skin diseases

Aberrant mitochondrial structure and function influence tissue homeostasis and thereby contribute to multiple human disorders and ageing. Ten per cent of patients with primary mitochondrial disorders present skin manifestations that can be categorized into hair abnormalities, rashes, pigmentation abnormalities and acrocyanosis. Less attention has been paid to the fact that several disorders of the skin are linked to alterations of mitochondrial energy metabolism. This review article summarizes the contribution of mitochondrial pathology to both common and rare skin diseases. We explore the intriguing observation that a wide array of skin disorders presents with primary or secondary mitochondrial pathology and that a variety of molecular defects can cause dysfunctional mitochondria. Among them are mutations in mitochondrial- and nuclear DNA-encoded subunits and assembly factors of oxidative phosphorylation (OXPHOS) complexes; mutations in intermediate filament proteins involved in linking, moving and shaping of mitochondria; and disorders of mitochondrial DNA metabolism, fatty acid metabolism and heme synthesis. Thus, we assume that mitochondrial involvement is the rule rather than the exception in skin diseases. We conclude the article by discussing how improving mitochondrial function can be beneficial for aged skin and can be used as an adjunct therapy for certain skin disorders. Consideration of mitochondrial energy metabolism in the skin creates a new perspective for both dermatologists and experts in metabolic disease.

Mitochondrial DNA damage is associated with damage accrual and disease duration in patients with systemic lupus erythematosus

OBJECTIVE

To determine the extent of mitochondrial DNA (mtDNA) damage in systemic lupus erythematosus (SLE) patients compared to healthy subjects and to determine the factors associated with mtDNA damage among SLE patients.

METHODS

A cross-sectional study was performed in 86 SLE patients (per American College of Rheumatology classification criteria) and 86 healthy individuals matched for age and gender. Peripheral blood mononuclear cells (PBMCs) were collected from subjects to assess the relative amounts of mtDNA damage. Quantitative polymerase chain reaction assay was used to measure the frequency of mtDNA lesions and mtDNA abundance. Socioeconomic-demographic features, clinical manifestations, pharmacologic treatment, disease activity, and damage accrual were determined. Statistical analyses were performed using t test, pairwise correlation, and Pearson's chi-square test (or Fisher's exact test) as appropriate.

RESULTS

Among SLE patients, 93.0% were women. The mean (SD) age was 38.0 (10.4) years and the mean (SD) disease duration was 8.7 (7.5) years. SLE patients exhibited increased levels of mtDNA damage as shown by higher levels of mtDNA lesions and decreased mtDNA abundance as compared to healthy individuals. There was a negative correlation between disease damage and mtDNA abundance and a positive correlation between mtDNA lesions and disease duration. No association was found between disease activity and mtDNA damage.

CONCLUSION

PBMCs from SLE patients exhibited more mtDNA damage compared to healthy subjects. Higher levels of mtDNA damage were observed among SLE patients with major organ involvement and damage accrual. These results suggest that mtDNA damage have a potential role in the pathogenesis of SLE.

Damaged mitochondria in Fanconi anemia - an isolated event or a general phenomenon?

Fanconi anemia (FA) is known as an inherited bone marrow failure syndrome associated with cancer predisposition and susceptibility to a number of DNA damaging stimuli, along with a number of clinical features such as upper limb malformations, increased diabetes incidence and typical anomalies in skin pigmentation. The proteins encoded by FA-defective genes (FANC proteins) display well-established roles in DNA damage and repair pathways. Moreover, some independent studies have revealed that mitochondrial dysfunction (MDF) is also involved in FA phenotype. Unconfined to FA, we have shown that other syndromes featuring DNA damage and repair (such as ataxia-telangiectasia, AT, and Werner syndrome, WS) display MDF-related phenotypes, along with oxidative stress (OS) that, altogether, may play major roles in these diseases. Experimental and clinical studies are warranted in the prospect of future therapies to be focused on compounds scavenging reactive oxygen species (ROS) as well as protecting mitochondrial functions.

Oxidative stress and its biomarkers in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune inflammatory disease whose etiology remains largely unknown. The uncontrolled oxidative stress in SLE contributes to functional oxidative modifications of cellular protein, lipid and DNA and consequences of oxidative modification play a crucial role in immunomodulation and trigger autoimmunity. Measurements of oxidative modified protein, lipid and DNA in biological samples from SLE patients may assist in the elucidation of the pathophysiological mechanisms of the oxidative stress-related damage, the prediction of disease prognosis and the selection of adequate treatment in the early stage of disease. Application of these biomarkers in disease may indicate the early effectiveness of the therapy. This review is intended to provide an overview of various reactive oxygen species (ROS) formed during the state of disease and their biomarkers linking with disease. The first part of the review presents biochemistry and pathophysiology of ROS and antioxidant system in disease. The second part of the review discusses the recent development of oxidative stress biomarkers that relates pathogenesis in SLE patients and animal model. Finally, this review also describes the reported clinical trials of antioxidant in the disease that have evaluated the efficacy of antioxidant in the management of disease with ongoing conventional therapy.

Interaction between glutathione and apoptosis in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by imbalance redox state and increased apoptosis. The activation, proliferation and cell death of lymphocytes are dependent on intracellular levels of glutathione and controlled production of reactive oxygen species (ROS). Changes in the intracellular redox environment of cells, through oxygen-derived free radical production known as oxidative stress, have been reported to be critical for cellular immune dysfunction, activation of apoptotic enzymes and apoptosis. The shift in the cellular GSH-to-GSSG redox balance in favor of the oxidized species, GSSG, constitutes an important signal that can decide the fate of the abnormal apoptosis in the disease. The current review will focus on four main areas: (1) general description of oxidative stress markers in SLE, (2) alteration of redox state and complication of disease, (3) role of redox mechanisms in the initiation and execution phases of apoptosis, and (4) intracellular glutathione and its checkpoints with lymphocyte apoptosis which represent novel targets for pharmacological intervention in SLE.

Antioxidant treatment regulates the humoral immune response during acute viral infection

Generation of reactive oxygen intermediates (ROI) following antigen receptor ligation is critical to promote cellular responses. However, the effect of antioxidant treatment on humoral immunity during a viral infection was unknown. Mice were infected with lymphocytic choriomeningitis virus (LCMV) and treated with Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), a superoxide dismutase mimetic, from days 0 to 8 postinfection. On day 8, at the peak of the splenic response in vehicle-treated mice, virus-specific IgM and IgG antibody-secreting cells (ASC) were decreased 22- and 457-fold in MnTBAP-treated animals. By day 38, LCMV-specific IgG ASC were decreased 5-fold in the bone marrow of drug-treated mice, and virus-specific antibodies were of lower affinity. Interestingly, antioxidant treatment had no effect on the number of LCMV-specific IgG memory B cells. In addition to decreases in ASC, MnTBAP treatment decreased the number of functional virus-specific CD4(+) T cells. The decreased numbers of ASC observed on day 8 in drug-treated mice were due to a combination of Bim-mediated cell death and decreased proliferation. Together, these data demonstrate that ROI regulate antiviral ASC expansion and have important implications for understanding the effects of antioxidants on humoral immunity during infection and immunization.

Peroxiredoxin II regulates effector and secondary memory CD8+ T cell responses

Reactive oxygen intermediates (ROI) generated in response to receptor stimulation play an important role in cellular responses. However, the effect of increased H(2)O(2) on an antigen-specific CD8(+) T cell response was unknown. Following T cell receptor (TCR) stimulation, the expression and oxidation of peroxiredoxin II (PrdxII), a critical antioxidant enzyme, increased in CD8(+) T cells. Deletion of PrdxII increased ROI, S phase entry, division, and death during in vitro division. During primary acute viral and bacterial infection, the number of effector CD8(+) T cells in PrdxII-deficient mice was increased, while the number of memory cells were similar to those of the wild-type cells. Adoptive transfer of P14 TCR transgenic cells demonstrated that the increased expansion of effector cells was T cell autonomous. After rechallenge, effector CD8(+) T cells in mutant animals were more skewed to memory phenotype than cells from wild-type mice, resulting in a larger secondary memory CD8(+) T cell pool. During chronic viral infection, increased antigen-specific CD8(+) T cells accumulated in the spleens of PrdxII mutant mice, causing mortality. These results demonstrate that PrdxII controls effector CD8(+) T cell expansion, secondary memory generation, and immunopathology.

Metabolic regulation of organelle homeostasis in lupus T cells

Abnormal T-cell signaling and activation are characteristic features in systemic lupus erythematosus (SLE). Lupus T cells are shifted toward an over-activated state, important signaling pathways are rewired, and signaling molecules are replaced. Disturbances in metabolic and organelle homeostasis, importantly within the mitochondrial, endosomal, and autophagosomal compartments, underlie the changes in signal transduction. Mitochondrial hyperpolarization, enhanced endosomal recycling, and dysregulated autophagy are hallmarks of pathologic organelle homeostasis in SLE. This review is focused on the metabolic checkpoints of endosomal traffic that control immunological synapse formation and mitophagy and may thus serve as targets for treatment in SLE.

Leukocyte mitochondrial DNA alteration in systemic lupus erythematosus and its relevance to the susceptibility to lupus nephritis

The role of mitochondrial DNA (mtDNA) alterations in the pathophysiology of systemic lupus erythematosus (SLE) remains unclear. We investigated sequence variations in the D310 region and copy number change of mtDNA in 85 SLE patients and 45 normal subjects. Leukocyte DNA and RNA were extracted from leukocytes of the peripheral venous blood. The D310 sequence variations and copy number of mtDNA, and mRNA expression levels of mtDNA-encoded genes in leukocytes were determined by quantitative real-time polymerase chain reaction (Q-PCR) and PCR-based direct sequencing, respectively. We found that leukocyte mtDNA in SLE patients exhibited higher frequency of D310 heteroplasmy (69.4% vs. 48.9%, p = 0.022) and more D310 variants (2.2 vs. 1.7, p = 0.014) than those found in controls. Among normal controls and patients with low, medium or high SLE disease activity index (SLEDAI), an ever-increasing frequency of D310 heteroplasmy was observed (p = 0.021). Leukocyte mtDNA copy number tended to be low in patients of high SLEDAI group (p = 0.068), especially in those harboring mtDNA with D310 heteroplasmy (p = 0.020). Moreover, the mtDNA copy number was positively correlated with the mRNA level of mtDNA-encoded ND1 (NADH dehydrogenase subunit 1) (p = 0.041) and ATPase 6 (ATP synthase subunit 6) (p = 0.030) genes. Patients with more D310 variants were more susceptible to lupus nephritis (p = 0.035). Taken together, our findings suggest that decrease in the mtDNA copy number and increase in D310 heteroplasmy of mtDNA are related to the development and progression of SLE, and that the patients harboring more D310 variants of mtDNA are more susceptible to lupus nephritis.

Murine lupus susceptibility locus Sle1c2 mediates CD4+ T cell activation and maps to estrogen-related receptor γ

Sle1c is a sublocus of the NZM2410-derived Sle1 major lupus susceptibility locus. We have shown previously that Sle1c contributes to lupus pathogenesis by conferring increased CD4(+) T cell activation and increased susceptibility to chronic graft-versus-host disease (cGVHD), which mapped to the centromeric portion of the locus. In this study, we have refined the centromeric sublocus to a 675-kb interval, termed Sle1c2. Mice from recombinant congenic strains expressing Sle1c2 exhibited increased CD4(+) T cell intrinsic activation and cGVHD susceptibility, similar to mice with the parental Sle1c. In addition, B6.Sle1c2 mice displayed a robust expansion of IFN-γ-expressing T cells. NZB complementation studies showed that Sle1c2 expression exacerbated B cell activation, autoantibody production, and renal pathology, verifying that Sle1c2 contributes to lupus pathogenesis. The Sle1c2 interval contains two genes, only one of which, Esrrg, is expressed in T cells. B6.Sle1c2 CD4(+) T cells expressed less Esrrg than B6 CD4(+) T cells, and Esrrg expression was correlated negatively with CD4(+) T cell activation. Esrrg encodes an orphan nuclear receptor that regulates oxidative metabolism and mitochondrial functions. In accordance with reduced Esrrg expression, B6.Sle1c2 CD4(+) T cells present reduced mitochondrial mass and altered mitochondrial functions as well as altered metabolic pathway utilization when compared with B6 CD4(+) T cells. Taken together, we propose Esrrg as a novel lupus susceptibility gene regulating CD4(+) T cell function through their mitochondrial metabolism.