Metabolic interventions improve HBV envelope-specific T-cell responses in patients with chronic hepatitis B

BACKGROUND

Restoration of HBV-specific T cell immunity is a promising approach for the functional cure of chronic Hepatitis B (CHB), necessitating the development of valid assays to boost and monitor HBV-specific T cell responses in patients with CHB.

METHODS

We analyzed hepatitis B virus (HBV) core- and envelope (env)-specific T cell responses using in vitro expanded peripheral blood mononuclear cells (PBMCs) from patients with CHB exhibiting different immunological phases, including immune tolerance (IT), immune activation (IA), inactive carrier (IC), and HBeAg-negative hepatitis (ENEG). Additionally, we evaluated the effects of metabolic interventions, including mitochondria-targeted antioxidants (MTA), polyphenolic compounds, and ACAT inhibitors (iACAT), on HBV-specific T-cell functionality.

RESULTS

We found that HBV core- and env-specific T cell responses were finely coordinated and more profound in IC and ENEG than in the IT and IA stages. HBV env-specific T cells were more dysfunctional but prone to respond to metabolic interventions using MTA, iACAT, and polyphenolic compounds than HBV core-specific T-cells. The responsiveness of HBV env-specific T cells to metabolic interventions can be predicted by the eosinophil (EO) count and the coefficient of variation of red blood cell distribution width (RDW-CV).

CONCLUSION

These findings may provide valuable information for metabolically invigorating HBV-specific T-cells to treat CHB.

Mitochondria in cell senescence: A Friend or Foe?

Cell senescence denotes cell growth arrest in response to continuous replication or stresses damaging DNA or mitochondria. Mounting research suggests that cell senescence attributes to aging-associated failing organ function and diseases. Conversely, it participates in embryonic tissue maturation, wound healing, tissue regeneration, and tumor suppression. The acute or chronic properties and microenvironment may explain the double faces of senescence. Senescent cells display unique characteristics. In particular, its mitochondria become elongated with altered metabolomes and dynamics. Accordingly, mitochondria reform their function to produce more reactive oxygen species at the cost of low ATP production. Meanwhile, destructed mitochondrial unfolded protein responses further break the delicate proteostasis fostering mitochondrial dysfunction. Additionally, the release of mitochondrial damage-associated molecular patterns, mitochondrial Ca²⁺ overload, and altered NAD⁺ level intertwine other cellular organelle strengthening senescence. These findings further intrigue researchers to develop anti-senescence interventions. Applying mitochondrial-targeted antioxidants reduces cell senescence and mitigates aging by restoring mitochondrial function and attenuating oxidative stress. Metformin and caloric restriction also manifest senescent rescuing effects by increasing mitochondria efficiency and alleviating oxidative damage. On the other hand, Bcl2 family protein inhibitors eradicate senescent cells by inducing apoptosis to facilitate cancer chemotherapy. This review describes the different aspects of mitochondrial changes in senescence and highlights the recent progress of some anti-senescence strategies.

MitoQ demonstrates connexin- and p53-mediated cancer chemoprevention in N-nitrosodiethylamine-induced hepatocarcinogenesis rodent model

Cancer chemoprevention is an approach that offers huge potential for preventing/retarding carcinogenesis. MitoQ is well-known and extensively studied mitochondria-targeted antioxidants for its applications in diseases linked with oxidative stress. In the present study chemopreventive potential of mitoQ was studied with a focus on the role of gap-junctions and p53 at an advanced stage of HCC. BALB/c mice model of hepatocarcinogenesis was established using N-nitrosodiethylamine as a carcinogen (200 mg/kg b. w., cumulative dose, intraperitoneally). The chemopreventive effect of mitoQ was studied by pre-protecting animals with mitoQ (0.125 mg/kg b. w., orally once a week) till the termination of the study. The tumors developed in the course of the study were histopathologically analyzed and statistically evaluated. The mechanistic role of mitoQ was investigated in terms of mitochondrial oxidative stress, expression of 8-OHdG, Cx26, Cx32, p53 and status of gap-junctional intercellular communication (GJIC) in tumors. Chemopreventive activity of mitoQ was evident from improved survival of animals, significantly (p ≤ 0.05) lower tumor multiplicity, tumor incidence and a total number of tumors. MitoQ treatment significantly (p ≤ 0.05) decreased mitochondrial oxidative stress as indicated by reduced mtROS and mtLPO. Increased staining intensity of 8-OHdG and internalization of Cx26, Cx32 which was observed in hepatic tumors was reduced upon mitoQ treatment. Furthermore, the expression of Cx26, Cx32 and p53 was significantly increased along with improvement in GJIC in mitoQ treatment group. MitoQ demonstrated its chemopreventive potential probably by regulating mtROS, connexins and p53 in hepatocarcinogenesis.

Contributions and Limitations of Mitochondria-Targeted and Non-Targeted Antioxidants in the Treatment of Parkinsonism: an Updated Review

As conventional therapeutics can only treat the symptoms of Parkinson's disease (PD), major focus of research in recent times is to slow down or prevent the progression of neuronal degeneration in PD. Non-targeted antioxidants have been an integral part of the conventional therapeutics regimen; however, their importance have lessened over time because of their controversial outcomes in clinical PD trials. Inability to permeate and localize within the mitochondria remains the main drawback on the part of non-targeted antioxidants inspite of possessing free radical scavenging properties. In contrast, mitochondrial-targeted antioxidants (MTAs), a special class of compounds have emerged having high advantages over non-targeted antioxidants by virtue of efficient pharmacokinetics and better absorption rate with capability to localize many fold inside the mitochondrial matrix. Preclinical experimentations indicate that MTAs have the potential to act as better alternatives compared to conventional non-targeted antioxidants in treating PD; however, sufficient clinical trials have not been conducted to investigate the efficacies of MTAs in treating PD. Controversial clinical outcomes on the part of non-targeted antioxidants and lack of clinical trials involving MTAs have made it difficult to go ahead with a direct comparison and in turn have slowed down the progress of development of safer and better alternate strategies in treating PD. This review provides an insight on the roles MTAs and non-targeted antioxidants have played in the treatment of PD till date in preclinical and clinical settings and discusses about the limitations of mitochondria-targeted and non-targeted antioxidants that can be resolved for developing effective strategies in treating Parkinsonism.

Mitochondriotropic antioxidant based on caffeic acid AntiOxCIN4 activates Nrf2-dependent antioxidant defenses and quality control mechanisms to antagonize oxidative stress-induced cell damage

Mitochondria are key organelles involved in cellular survival, differentiation, and death induction. In this regard, mitochondrial morphology and/or function alterations are involved in stress-induced adaptive pathways, priming mitochondria for mitophagy or apoptosis induction. We have previously shown that the mitochondriotropic antioxidant AntiOxCIN₄ (100 μM; 48 h) presented significant cytoprotective effect without affecting the viability of human hepatoma-derived (HepG2) cells. Moreover, AntiOxCIN₄ (12.5 μM; 72 h) caused a mild increase of reactive oxygen species (ROS) levels without toxicity to primary human skin fibroblasts (PHSF). As Nrf2 is a master regulator of the oxidative stress response inducing antioxidant-encoding gene expression, we hypothesized that AntiOxCIN₄ could increase the resistance of human hepatoma-derived HepG2 to oxidative stress by Nrf2-dependent mechanisms, in a process mediated by mitochondrial ROS (mtROS). Here we showed that after an initial decrease in oxygen consumption paralleled by a moderate increase in superoxide anion levels, AntiOxCIN₄ led to a time-dependent Nrf2 translocation to the nucleus. This was followed later by a 1.5-fold increase in basal respiration and a 1.2-fold increase in extracellular acidification. AntiOxCIN₄ treatment enhanced mitochondrial quality by triggering the clearance of defective organelles by autophagy and/or mitophagy, coupled with increased mitochondrial biogenesis. AntiOxCIN₄ also up-regulated the cellular antioxidant defense system. AntiOxCIN₄ seems to have the ability to maintain hepatocyte redox homeostasis, regulating the electrophilic/nucleophilic tone, and preserve cellular physiological functions. The obtained data open a new avenue to explore the effects of AntiOxCIN₄ in the context of preserving hepatic mitochondrial function in disorders, such as NASH/NAFLD and type II diabetes.

Are mitochondria the main contributor of reactive oxygen species in cells?

Physiologists often assume that mitochondria are the main producers of reactive oxygen species (ROS) in cells. Consequently, in biomedicine, mitochondria are considered as important targets for therapeutic treatments, and in evolutionary biology, they are considered as mediators of life-history tradeoffs. Surprisingly, data supporting such an assumption are lacking, at least partially due to the technical difficulties in accurately measuring the level of ROS produced by different subcellular compartments in intact cells. In this Commentary, we first review three potential reasons underlying the misassumption of mitochondrial dominance in the production of cellular ROS. We then introduce some other major sites/enzymes responsible for cellular ROS production. With the use of a recently developed cell-based assay, we further discuss the contribution of mitochondria to the total rate of ROS release in cell lines and primary cells of different species. In these cells, the contribution of mitochondria varies between cell types but mitochondria are never the main source of cellular ROS. This indicates that although mitochondria are one of the significant sources of cellular ROS, they are not necessarily the main contributor under normal conditions. Intriguingly, similar findings were also observed in cells under a variety of stressors, life-history strategies and pathological stages, in which the rates of cellular ROS production were significantly enhanced. Finally, we make recommendations for designing future studies. We hope this paper will encourage investigators to carefully consider non-mitochondrial sources of cellular ROS in their study systems or models.

Oxidative stress-based therapeutics in COPD

Oxidative stress is a major driving mechanism in the pathogenesis of COPD. There is increased oxidative stress in the lungs of COPD patients due to exogenous oxidants in cigarette smoke and air pollution and due to endogenous generation of reactive oxygen species by inflammatory and structural cells in the lung. Mitochondrial oxidative stress may be particularly important in COPD. There is also a reduction in antioxidant defences, with inactivation of several antioxidant enzymes and the transcription factors Nrf2 and FOXO that regulate multiple antioxidant genes. Increased systemic oxidative stress may exacerbate comorbidities and contribute to skeletal muscle weakness. Oxidative stress amplifies chronic inflammation, stimulates fibrosis and emphysema, causes corticosteroid resistance, accelerates lung aging, causes DNA damage and stimulates formation of autoantibodies. This suggests that treating oxidative stress by antioxidants or enhancing endogenous antioxidants should be an effective strategy to treat the underlying pathogenetic mechanisms of COPD. Most clinical studies in COPD have been conducted using glutathione-generating antioxidants such as N-acetylcysteine, carbocysteine and erdosteine, which reduce exacerbations in COPD patients, but it is not certain whether this is due to their antioxidant or mucolytic properties. Dietary antioxidants have so far not shown to be clinically effective in COPD. There is a search for more effective antioxidants, which include superoxide dismutase mimetics, NADPH oxidase inhibitors, mitochondria-targeted antioxidants and Nrf2 activators.

Triphenylphosphonium (TPP)-Based Antioxidants: A New Perspective on Antioxidant Design

Mitochondrial oxidative damage and dysfunction contribute to a wide range of human diseases. Considering the limitation of conventional antioxidants and that mitochondria are the main source of reactive oxygen species (ROS) which induce oxidative damage, mitochondria-targeted antioxidants which can selectively block mitochondrial oxidative damage and prevent various types of cell death have been widely developed. As a lipophilic cation, triphenylphosphonium (TPP) has been commonly used in designing mitochondria-targeted antioxidants. Conjugated with the TPP moiety, antioxidants can achieve more than 1000-fold higher mitochondrial concentration depending on cell membrane potentials and mitochondrial membrane potentials. Herein we discuss the deficiencies of conventional antioxidants and the advantages of mitochondrial targeting, and review various types of TPP-based mitochondria-targeted antioxidants. These provide theoretical and background support for the design of new anti-oxidant.

Mitochondrial dysfunction and oxidative stress in metabolic disorders - A step towards mitochondria based therapeutic strategies

Mitochondria are the powerhouses of the cell and are involved in essential functions of the cell, including ATP production, intracellular Ca2+ regulation, reactive oxygen species production & scavenging, regulation of apoptotic cell death and activation of the caspase family of proteases. Mitochondrial dysfunction and oxidative stress are largely involved in aging, cancer, age-related neurodegenerative and metabolic syndrome. In the last decade, tremendous progress has been made in understanding mitochondrial structure, function and their physiology in metabolic syndromes such as diabetes, obesity, stroke and hypertension, and heart disease. Further, progress has also been made in developing therapeutic strategies, including lifestyle interventions (healthy diet and regular exercise), pharmacological strategies and mitochondria-targeted approaches. These strategies were mainly focused to reduce mitochondrial dysfunction and oxidative stress and to maintain mitochondrial quality in metabolic syndromes. The purpose of our article is to highlight the recent progress on the mitochondrial role in metabolic syndromes and also summarize the progress of mitochondria-targeted molecules as therapeutic targets to treat metabolic syndromes. This article is part of a Special Issue entitled: Oxidative Stress and Mitochondrial Quality in Diabetes/Obesity and Critical Illness Spectrum of Diseases - edited by P. Hemachandra Reddy.

Mitochondria-Targeted Molecules as Potential Drugs to Treat Patients With Alzheimer's Disease

Alzheimer's disease (AD) is the most common multifactorial mental illness affecting the elderly population in the world. Its prevalence increases as person ages. There is no known drug or agent that can delay or prevent the AD and its progression. Extensive research has revealed that multiple cellular pathways involved, including amyloid beta production, mitochondrial structural and functional changes, hyperphosphorylation of Tau and NFT formation, inflammatory responses, and neuronal loss in AD pathogenesis. Amyloid beta-induced synaptic damage, mitochondrial abnormalities, and phosphorylated Tau are major areas of present research investigations. Synaptic pathology and mitochondrial oxidative damage are early events in disease process. In this chapter, a systematic literature survey has been conducted and presented a summary of antioxidants used in (1) AD mouse models, (2) elderly populations, and (3) randomized clinical trials in AD patients. This chapter highlights the recent progress in developing and testing mitochondria-targeted molecules using AD cell cultures and AD mouse models. This chapter also discusses recent research on AD pathogenesis and therapeutics, focusing on mitochondria-targeted molecules as potential therapeutic targets to delay or prevent AD progression.

Therapeutic Strategies for Mitochondrial Dysfunction and Oxidative Stress in Age-Related Metabolic Disorders

Mitochondria are complex, intercellular organelles present in the cells and are involved in multiple roles including ATP formation, free radicals generation and scavenging, calcium homeostasis, cellular differentiation, and cell death. Many studies depicted the involvement of mitochondrial dysfunction and oxidative damage in aging and pathogenesis of age-related metabolic disorders and neurodegenerative diseases. Remarkable advancements have been made in understanding the structure, function, and physiology of mitochondria in metabolic disorders such as diabetes, obesity, cardiovascular diseases, and stroke. Further, much progress has been done in the improvement of therapeutic strategies, including lifestyle interventions, pharmacological, and mitochondria-targeted therapeutic approaches. These strategies were mainly focused to reduce the mitochondrial dysfunction caused by oxidative stress and to retain the mitochondrial health in various diseases. In this chapter, we have highlighted the involvement of mitochondrial dysfunction in the pathophysiology of various disorders and recent progress in the development of mitochondria-targeted molecules as therapeutic measures for metabolic disorders.

Results of a Multicenter, Randomized, Double-Masked, Placebo-Controlled Clinical Study of the Efficacy and Safety of Visomitin Eye Drops in Patients with Dry Eye Syndrome

INTRODUCTION

This article presents the results of an international, multicenter, randomized, double-masked, placebo-controlled clinical study of Visomitin (Mitotech LLC, Moscow, Russian Federation) eye drops in patients with dry eye syndrome (DES). Visomitin is the first registered (in Russia) drug with a mitochondria-targeted antioxidant (SkQ1) as the active ingredient.

METHODS

In this multicenter (10 sites) study of 240 subjects with DES, study drug (Visomitin or placebo) was self-administered three times daily (TID) for 6 weeks, followed by a 6-week follow-up period. Seven in-office study visits occurred every 2 weeks during both the treatment and follow-up periods. Efficacy measures included Schirmer's test, tear break-up time, fluorescein staining, meniscus height, and visual acuity. Safety measures included adverse events, slit lamp biomicroscopy, tonometry, blood pressure, and heart rate. Tolerability was also evaluated.

RESULTS

This clinical study showed the effectiveness of Visomitin eye drops in the treatment of signs and symptoms of DES compared with placebo. The study showed that a 6-week course of TID topical instillation of Visomitin significantly improved the functional state of the cornea; Visomitin increased tear film stability and reduced corneal damage. Significant reduction of dry eye symptoms (such as dryness, burning, grittiness, and blurred vision) was also observed.

CONCLUSION

Based on the results of this study, Visomitin is effective and safe for use in eye patients with DES for protection from corneal damage.

FUNDING

Mitotech LLC.

The mitochondria-targeted antioxidant MitoQ extends lifespan and improves healthspan of a transgenic Caenorhabditis elegans model of Alzheimer disease

β-Amyloid (Aβ)-induced toxicity and oxidative stress have been postulated to play critical roles in the pathogenic mechanism of Alzheimer disease (AD). We investigated the in vivo ability of a mitochondria-targeted antioxidant, MitoQ, to protect against Aβ-induced toxicity and oxidative stress in a Caenorhabditis elegans model overexpressing human Aβ. Impairment of electron transport chain (ETC) enzymatic activity and mitochondrial dysfunction are early features of AD. We show that MitoQ extends lifespan, delays Aβ-induced paralysis, ameliorates depletion of the mitochondrial lipid cardiolipin, and protects complexes IV and I of the ETC. Despite its protective effects on lifespan, healthspan, and ETC function, we find that MitoQ does not reduce DCFDA fluorescence, protein carbonyl levels or modulate steadystate ATP levels or oxygen consumption rate. Moreover, MitoQ does not attenuate mitochondrial DNA (mtDNA) oxidative damage. In agreement with its design, the protective effects of MitoQ appear to be targeted specifically to the mitochondrial membrane and our findings suggest that MitoQ may have therapeutic potential for Aβ- and oxidative stress-associated neurodegenerative disorders, particularly AD.

Cationic antioxidants as a powerful tool against mitochondrial oxidative stress

This review describes evidence that mitochondrial reactive oxygen species (mROS) are of great importance under many physiological and pathological conditions. The most demonstrative indications favoring this conclusion originate from recent discoveries of the in vivo effects of mitochondria-targeted antioxidants (MitoQ and SkQs). The latter compounds look promising in treating several incurable pathologies as well as aging.