Mitochondrial generation of superoxide and hydrogen peroxide as the source of mitochondrial redox signaling

Pitfalls of Mitochondrial Redox Signaling Research

Redox signaling from mitochondria (mt) to the cytosol and plasma membrane (PM) has been scarcely reported, such as in the case of hypoxic cell adaptation or (2-oxo-) 2-keto-isocaproate (KIC) β-like-oxidation stimulating insulin secretion in pancreatic β-cells. Mutual redox state influence between mitochondrial major compartments, the matrix and the intracristal space, and the cytosol is therefore derived theoretically in this article to predict possible conditions, when mt-to-cytosol and mt-to-PM signals may occur, as well as conditions in which the cytosolic redox signaling is not overwhelmed by the mitochondrial antioxidant capacity. Possible peroxiredoxin 3 participation in mt-to-cytosol redox signaling is discussed, as well as another specific case, whereby mitochondrial superoxide release is diminished, whereas the matrix MnSOD is activated. As a result, the enhanced conversion to H2O2 allows H2O2 diffusion into the cytosol, where it could be a predominant component of the H2O2 release. In both of these ways, mt-to-cytosol and mt-to-PM signals may be realized. Finally, the use of redox-sensitive probes is discussed, which disturb redox equilibria, and hence add a surplus redox-buffering to the compartment, where they are localized. Specifically, when attempts to quantify net H2O2 fluxes are to be made, this should be taken into account.

Changes in the Mitochondria in the Aging Process-Can α-Tocopherol Affect Them?

Aerobic organisms use molecular oxygen in several reactions, including those in which the oxidation of substrate molecules is coupled to oxygen reduction to produce large amounts of metabolic energy. The utilization of oxygen is associated with the production of ROS, which can damage biological macromolecules but also act as signaling molecules, regulating numerous cellular processes. Mitochondria are the cellular sites where most of the metabolic energy is produced and perform numerous physiological functions by acting as regulatory hubs of cellular metabolism. They retain the remnants of their bacterial ancestors, including an independent genome that encodes part of their protein equipment; they have an accurate quality control system; and control of cellular functions also depends on communication with the nucleus. During aging, mitochondria can undergo dysfunctions, some of which are mediated by ROS. In this review, after a description of how aging affects the mitochondrial quality and quality control system and the involvement of mitochondria in inflammation, we report information on how vitamin E, the main fat-soluble antioxidant, can protect mitochondria from age-related changes. The information in this regard is scarce and limited to some tissues and some aspects of mitochondrial alterations in aging. Improving knowledge of the effects of vitamin E on aging is essential to defining an optimal strategy for healthy aging.

Redox regulation in diabetic kidney disease

Diabetic kidney disease (DKD) is one of the most devastating complications of diabetes mellitus, where currently there is no cure available. Several important mechanisms contribute to the pathogenesis of this complication, with oxidative stress being one of the key factors. The past decades have seen a large number of publications with various aspects of this topic; however, the specific details of redox regulation in DKD are still unclear. This is partly because redox biology is very complex, coupled with a complex and heterogeneous organ with numerous cell types. Furthermore, often times terms such as "oxidative stress" or reactive oxygen species are used as a general term to cover a wide and rich variety of reactive species and their differing reactions. However, no reactive species are the same, and not all of them are capable of biologically relevant reactions or "redox signaling." The goal of this review is to provide a biochemical background for an array of specific reactive oxygen species types with varying reactivity and specificity in the kidney as well as highlight some of the advances in redox biology that are paving the way to a better understanding of DKD development and risk.

Effects of ROS pathway inhibitors and NADH and FADH2 linked substrates on mitochondrial bioenergetics and ROS emission in the heart and kidney cortex and outer medulla

Mitochondria are major sources of reactive oxygen species (ROS), which play important roles in both physiological and pathological processes. However, the specific contributions of different ROS production and scavenging components in the mitochondria of metabolically active tissues such as heart and kidney cortex and outer medulla (OM) are not well understood. Therefore, the goal of this study was to determine contributions of different ROS production and scavenging components and provide detailed comparisons of mitochondrial respiration, bioenergetics, ROS emission between the heart and kidney cortex and OM using tissues obtained from the same Sprague-Dawley rat under identical conditions and perturbations. Specifically, data were obtained using both NADH-linked substrate pyruvate + malate and FADH2-linked substrate succinate followed by additions of inhibitors of different components of the electron transport chain (ETC) and oxidative phosphorylation (OxPhos) and other ROS production and scavenging systems. Currently, there is limited data available for the mitochondria of kidney cortex and OM, the two major energy-consuming tissues in the body only next to the heart, and scarce quantitative information on the interplay between mitochondrial ROS production and scavenging systems in the three tissues. The findings from this study demonstrate significant differences in mitochondrial respiratory and bioenergetic functions and ROS emission among the three tissues. The results quantify the rates of ROS production from different complexes of the ETC, identify the complexes responsible for variations in mitochondrial membrane depolarization and regulations of ROS production, and quantify the contributions of ROS scavenging enzymes towards overall mitochondrial ROS emission. These findings advance our fundamental knowledge of tissue-specific and substrate-dependent mitochondrial respiratory and bioenergetic functions and ROS emission. This is important given the critical role that excess ROS production, oxidative stress, and mitochondrial dysfunction in the heart and kidney cortex and OM play in the pathogenesis of cardiovascular and renal diseases, including salt-sensitive hypertension.

Searching for molecular hypoxia sensors among oxygen-dependent enzymes

The ability to sense and respond to changes in cellular oxygen levels is critical for aerobic organisms and requires a molecular oxygen sensor. The prototypical sensor is the oxygen-dependent enzyme PHD: hypoxia inhibits its ability to hydroxylate the transcription factor HIF, causing HIF to accumulate and trigger the classic HIF-dependent hypoxia response. A small handful of other oxygen sensors are known, all of which are oxygen-dependent enzymes. However, hundreds of oxygen-dependent enzymes exist among aerobic organisms, raising the possibility that additional sensors remain to be discovered. This review summarizes known and potential hypoxia sensors among human O2-dependent enzymes and highlights their possible roles in hypoxia-related adaptation and diseases.

Oxidative Stress: A Suitable Therapeutic Target for Optic Nerve Diseases?

Optic nerve disorders encompass a wide spectrum of conditions characterized by the loss of retinal ganglion cells (RGCs) and subsequent degeneration of the optic nerve. The etiology of these disorders can vary significantly, but emerging research highlights the crucial role of oxidative stress, an imbalance in the redox status characterized by an excess of reactive oxygen species (ROS), in driving cell death through apoptosis, autophagy, and inflammation. This review provides an overview of ROS-related processes underlying four extensively studied optic nerve diseases: glaucoma, Leber's hereditary optic neuropathy (LHON), anterior ischemic optic neuropathy (AION), and optic neuritis (ON). Furthermore, we present preclinical findings on antioxidants, with the objective of evaluating the potential therapeutic benefits of targeting oxidative stress in the treatment of optic neuropathies.

Advances in exercise to alleviate sarcopenia in older adults by improving mitochondrial dysfunction

Sarcopenia is a chronic degenerative disease affecting primarily older adults. A growing aging population is gradually increasing the number of patients suffering from sarcopenia, placing increasing financial pressure on patients' families and society in general. There is a strong link between mitochondrial dysfunction and sarcopenia pathogenesis. As a result, treating sarcopenia by improving mitochondrial dysfunction is an effective strategy. Numerous studies have demonstrated that exercise has a positive effect on mitochondrial dysfunction when treating sarcopenia. Exercise promotes mitochondrial biogenesis and mitochondrial fusion/division to add new mitochondria or improve dysfunctional mitochondria while maintaining mitochondrial calcium homeostasis, mitochondrial antioxidant defense system, and mitochondrial autophagy to promote normal mitochondrial function. Furthermore, exercise can reduce mitochondrial damage caused by aging by inhibiting mitochondrial oxidative stress, mitochondrial DNA damage, and mitochondrial apoptosis. Exercise effectiveness depends on several factors, including exercise duration, exercise intensity, and exercise form. Therefore, Moderate-intensity exercise over 4 weeks potentially mitigates sarcopenia in older adults by ameliorating mitochondrial dysfunction. HIIT has demonstrated potential as a viable approach to addressing sarcopenia in aged rats. However, further investigation is required to validate its efficacy in treating sarcopenia in older adults.

Fluorescence microscopy imaging of mitochondrial metabolism in cancer cells

Mitochondrial metabolism is an important contributor to cancer cell survival and proliferation that coexists with enhanced glycolytic activity. Measuring mitochondrial activity is useful to characterize cancer metabolism patterns, to identify metabolic vulnerabilities and to identify new drug targets. Optical imaging, especially fluorescent microscopy, is one of the most valuable tools for studying mitochondrial bioenergetics because it provides semiquantitative and quantitative readouts as well as spatiotemporal resolution of mitochondrial metabolism. This review aims to acquaint the reader with microscopy imaging techniques currently used to determine mitochondrial membrane potential (ΔΨm), nicotinamide adenine dinucleotide (NADH), ATP and reactive oxygen species (ROS) that are major readouts of mitochondrial metabolism. We describe features, advantages, and limitations of the most used fluorescence imaging modalities: widefield, confocal and multiphoton microscopy, and fluorescent lifetime imaging (FLIM). We also discus relevant aspects of image processing. We briefly describe the role and production of NADH, NADHP, flavins and various ROS including superoxide and hydrogen peroxide and discuss how these parameters can be analyzed by fluorescent microscopy. We also explain the importance, value, and limitations of label-free autofluorescence imaging of NAD(P)H and FAD. Practical hints for the use of fluorescent probes and newly developed sensors for imaging ΔΨm, ATP and ROS are described. Overall, we provide updated information about the use of microscopy to study cancer metabolism that will be of interest to all investigators regardless of their level of expertise in the field.

MFN2-mediated mitochondrial fusion facilitates acute hypobaric hypoxia-induced cardiac dysfunction by increasing glucose catabolism and ROS production

BACKGROUND

Rapid ascent to high-altitude environment which is characterized by acute hypobaric hypoxia (HH) may increase the risk of cardiac dysfunction. However, the potential regulatory mechanisms and prevention strategies for acute HH-induced cardiac dysfunction have not been fully clarified. Mitofusin 2 (MFN2) is highly expressed in the heart and is involved in the regulation of mitochondrial fusion and cell metabolism. To date, however, the significance of MFN2 in the heart under acute HH has not been investigated.

METHODS AND RESULTS

Our study revealed that MFN2 upregulation in hearts of mice during acute HH led to cardiac dysfunction. In vitro experiments showed that the decrease in oxygen concentration induced upregulation of MFN2, impairing cardiomyocyte contractility and increasing the risk of QT prolongation. Additionally, acute HH-induced MFN2 upregulation promoted glucose catabolism and led to excessive mitochondrial reactive oxygen species (ROS) production in cardiomyocytes, ultimately resulting in decreased mitochondrial function. Furthermore, co-immunoprecipitation (co-IP) and mass spectrometry analyses indicated that MFN2 interacted with the NADH-ubiquinone oxidoreductase 23 kDa subunit (NDUFS8). Specifically, acute HH-induced MFN2 upregulation increased NDUFS8-dependent complex I activity.

CONCLUSIONS

Taken together, our studies provide the first direct evidence that MFN2 upregulation exacerbates acute HH-induced cardiac dysfunction by increasing glucose catabolism and ROS production.

GENERAL SIGNIFICANCE

Our studies indicate that MFN2 may be a promising therapeutic target for cardiac dysfunction under acute HH.

Anti-Inflammatory and Antioxidant Effects of Leaves and Sheath from Bamboo (Phyllostacys edulis J. Houz)

Bamboo (Phyllostacys edulis J. Houz) has become an emerging forest resource of economic and ecological significance with health benefits. Since the beneficial effects of the non-edible parts of bamboo have not been thoroughly explored, we characterized in this study bamboo leaf (BL) and sheath (BS) extracts. The total phenol and flavonoid content (TPC and TFC), antioxidant activity (ABTS, DPPH, FRAP and β-carotene bleaching test) and anti-inflammatory properties were determined. Leaves exhibited a TPC value of 73.92 mg equivalent (eq) gallic acid/g fresh weight (FW) and a TFC value of 56.75 mg eq quercetin/g FW. Ultra-High-Performance Liquid Chromatography (UHPLC) coupled with photo diode array detector (PDA) analysis revealed evidence for the presence of protocatechuic acid, isoorientin, orientin and isovitexin in BL, whereas BS was rich in phenolic acids. Both samples demonstrated a significant ability to scavenge radicals against ABTS^·+, with an inhibitory concentration of 50% of 3.07 μg/mL for BL and 6.78 μg/mL for BS. At a concentration of 0.1 and 0.2 mg/mL, BS decreased reactive oxygen species production without hampering cell viability in HepG2 liver cells, while at the same concentrations, BL exhibited cytotoxicity in HepG2 cells. In addition, 0.1 and 0.2 mg/mL BS and BL reduced Interleukin-6 and Monocyte Chemoattractant Protein-1 production in human lipopolysaccharide-stimulated THP-1 macrophages, without affecting cell viability. These findings highlight the anti-inflammatory and antioxidant properties of BL and BS, corroborating their different potential applications in the nutraceutical, cosmetic and pharmaceutical industries.

Targeting Oxidative Stress with Polyphenols to Fight Liver Diseases

Reactive oxygen species (ROS) are important second messengers in many metabolic processes and signaling pathways. Disruption of the balance between ROS generation and antioxidant defenses results in the overproduction of ROS and subsequent oxidative damage to biomolecules and cellular components that disturb cellular function. Oxidative stress contributes to the initiation and progression of many liver pathologies such as ischemia-reperfusion injury (LIRI), non-alcoholic fatty liver disease (NAFLD), and hepatocellular carcinoma (HCC). Therefore, controlling ROS production is an attractive therapeutic strategy in relation to their treatment. In recent years, increasing evidence has supported the therapeutic effects of polyphenols on liver injury via the regulation of ROS levels. In the current review, we summarize the effects of polyphenols, such as quercetin, resveratrol, and curcumin, on oxidative damage during conditions that induce liver injury, such as LIRI, NAFLD, and HCC.

Mitochondrial calcium and reactive oxygen species in cardiovascular disease

Cardiomyocytes are one of the most mitochondria-rich cell types in the body, with ∼30-40% of the cell volume being composed of mitochondria. Mitochondria are well established as the primary site of adenosine triphosphate (ATP) generation in a beating cardiomyocyte, generating up to 90% of its ATP. Mitochondria have many functions in the cell, which could contribute to susceptibility to and development of cardiovascular disease (CVD). Mitochondria are key players in cell metabolism, ATP production, reactive oxygen species (ROS) production, and cell death. Mitochondrial calcium (Ca2+) plays a critical role in many of these pathways, and thus the dynamics of mitochondrial Ca2+ are important in regulating mitochondrial processes. Alterations in these varied and in many cases interrelated functions play an important role in CVD. This review will focus on the interrelationship of mitochondrial energetics, Ca2+, and ROS and their roles in CVD. Recent insights into the regulation and dysregulation of these pathways have led to some novel therapeutic approaches.

S-nitroso-glutathione (GSNO) inhibits hydrogen peroxide production by alpha-ketoglutarate dehydrogenase: An investigation into sex and diet effects

Pyruvate dehydrogenase (PDH) and α-ketoglutarate dehydrogenase (KGDH) are vital sources of hydrogen peroxide (H₂O₂) and key sites for redox regulation. Here, we report KGDH is more sensitive to inhibition by S-nitroso-glutathione (GSNO) when compared to PDH and deactivation of both enzymes by nitro modification is affected by sex and diet. Liver mitochondria from male C57BL/6N mice displayed a robust inhibition of H₂O₂ production after exposure to 500-2000 μM GSNO. H₂O₂ genesis by PDH was not significantly affected by GSNO. Purified KGDH of porcine heart origin displayed a ∼82% decrease in H₂O₂ generating activity at 500 μM GSNO, which was mirrored by a decrease in NADH production. By contrast, H₂O₂- and NADH-producing activity of purified PDH was only minimally affected by an incubation in 500 μM GSNO. Incubations in GSNO had no significant effect on the H₂O₂-generating activity of KGDH and PDH in female liver mitochondria when compared to samples collected from males, which was attributed to higher GSNO reductase (GSNOR) activity. High fat feeding augmented the GSNO-mediated inhibition of KGDH in liver mitochondria from male mice. Exposure of male mice to a HFD also resulted in a significant decrease in the GSNO-mediated inhibition of H₂O₂ genesis by PDH, an effect not observed in mice fed a control-matched diet (CD). Female mice displayed higher resistance to the GSNO-induced inhibition of H₂O₂ production, regardless of being fed a CD or HFD. However, exposure to a HFD did result in a small but significant decrease in H₂O₂ production by KGDH and PDH when female liver mitochondria were treated with GSNO. Although, the effect was less when compared to their male counterparts. Collectively, we show for the first time GSNO deactivates H₂O₂ production by α-keto acid dehydrogenases and we demonstrate that sex and diet are determinants for the nitro-inhibition of both KGDH and PDH.

Suppression of superoxide/hydrogen peroxide production at mitochondrial site IQ decreases fat accumulation, improves glucose tolerance and normalizes fasting insulin concentration in mice fed a high-fat diet

We developed S1QEL1.719, a novel bioavailable S1QEL (suppressor of site I_Q electron leak). S1QEL1.719 prevented superoxide/hydrogen peroxide production at site I_Q of mitochondrial complex I in vitro. The free concentration giving half-maximal suppression (IC₅₀) was 52 nM. Even at 50-fold higher concentrations S1QEL1.719 did not inhibit superoxide/hydrogen peroxide production from other sites. The IC₅₀ for inhibition of complex I electron flow was 500-fold higher than the IC₅₀ for suppression of superoxide/hydrogen peroxide production from site I_Q. S1QEL1.719 was used to test the metabolic effects of suppressing superoxide/hydrogen peroxide production from site I_Qin vivo. C57BL/6J male mice fed a high-fat chow for one, two or eight weeks had increased body fat, decreased glucose tolerance, and increased fasting insulin concentrations, classic symptoms of metabolic syndrome. Daily prophylactic or therapeutic oral treatment of high-fat-fed animals with S1QEL1.719 decreased fat accumulation, strongly protected against decreased glucose tolerance and prevented or reversed the increase in fasting insulin level. Free exposures in plasma and liver at C_max were 1-4 fold the IC₅₀ for suppression of superoxide/hydrogen peroxide production at site I_Q and substantially below levels that inhibit electron flow through complex I. These results show that the production of superoxide/hydrogen peroxide from mitochondrial site I_Qin vivo is necessary for the induction and maintenance of glucose intolerance caused by a high-fat diet in mice. They raise the possibility that oral administration of S1QELs may be beneficial in metabolic syndrome.

Reactive oxygen species in biological media are they friend or foe? Major In vivo and In vitro sensing challenges

The role of Reactive Oxygen Species (ROS) on biological media has been shifting over the years, as the knowledge on the complex mechanism that lies in underneath their production and overall results has been growing. It has been known for some time that these species are associated with a number of health conditions. However, they also participate in the immunoactivation cascade process, and can have an active role in theranostics. Macrophages, for example, react to the presence of pathogens through ROS production, potentially allowing the development of new therapeutic strategies. However, their short lifetime and limited spatial distribution of ROS have been limiting factors to the development and understanding of this phenomenon. Even though, ROS have shown successful theranostic applications, e.g., photodynamic therapy, their wide applicability has been hampered by the lack of effective tools for monitoring these processes in real time. Thus the development of innovative sensing strategies for in vivo monitoring of the balance between ROS concentration and the resultant immune response is of the utmost relevance. Such knowledge could lead to major breakthroughs towards the development of more effective treatments for neurodegenerative diseases. Within this review we will present the current understanding on the interaction mechanisms of ROS with biological systems and their overall effect. Additionally, the most promising sensing tools developed so far, for both in vivo and in vitro tracking will be presented along with their main limitations and advantages. This review focuses on the four main ROS that have been studied these are: singlet oxygen species, hydrogen peroxide, hydroxyl radical and superoxide anion.

Bioinspired Structure Regulation of Apyrase-Like Nanozyme with Intracellular-Generated H2O2 for Tumor Catalytic Therapy

Adenosine triphosphate (ATP) is the major resource of energy supply in tumor activity. Therefore, improving ATP consumption efficiencies is a promising approach for cancer therapy. Herein, inspired by the H₂O₂-involved structure regulation effect during the catalysis of natural protein enzymes, we developed an artificial H₂O₂-driven ATP catalysis-promoting system, the Ce-based metal-organic framework (Ce-MOF), for catalytic cancer therapy. In the presence of H₂O₂, the hydrolysis ATP activity of Ce-MOF(H₂O₂) was enhanced by around 1.6 times. Taking advantage of the endogenous H₂O₂ in cancerous cells, catalytic hydrolysis for intracellular ATP of the Ce-MOF achieves the inhibition of cancerous cell growth, which involves damaged mitochondrial function and autophagy-associated cell death. Furthermore, in vivo studies suggest that the Ce-MOF has a good tumor inhibition effect. The artificial H₂O₂-driven ATP catalysis-promoting system not only demonstrates high catalytic ATP consumption efficiencies for cancer therapy but also highlights a bioinspired strategy to expedite nanozyme research in both design and applied sciences.

Relevant Membrane Transport Proteins as Possible Gatekeepers for Effective Pharmacological Ascorbate Treatment in Cancer

Despite the increasing number of newly diagnosed malignancies worldwide, therapeutic options for some tumor diseases are unfortunately still limited. Interestingly, preclinical but also some clinical data suggest that the administration of pharmacological ascorbate seems to respond well, especially in some aggressively growing tumor entities. The membrane transport and channel proteins are highly relevant for the use of pharmacological ascorbate in cancer therapy and are involved in the transfer of active substances such as ascorbate, hydrogen peroxide, and iron that predominantly must enter malignant cells to induce antiproliferative effects and especially ferroptosis. In this review, the relevant conveying proteins from cellular surfaces are presented as an integral part of the efficacy of pharmacological ascorbate, considering the already known genetic and functional features in tumor tissues. Accordingly, candidates for diagnostic markers and therapeutic targets are mentioned.

Chemotherapy induced oxidative stress in the ovary: drug-dependent mechanisms and potential interventions†

Cancer incidence and relative survival are expected to increase over the next few decades. With the majority of patients receiving combinatorial chemotherapy, an increasing proportion of patients experience long-term side effects from treatment-including reproductive disorders and infertility. A limited number of studies have examined mechanisms of single-agent chemotherapy-induced gonadotoxicity, with chemotherapy-induced oxidative stress being implicated in the loss of reproductive functions. Current methods of female fertility preservation are costly, invasive, only moderately successful, and seldom presented to cancer patients. The potential of antioxidants to alleviate chemotherapy has been overlooked at a time when it is becoming increasingly important to develop strategies to protect reproductive functions during chemotherapy. This review will summarize the importance of reactive oxygen species homeostasis in reproduction, chemotherapy-induced mitochondrial dysfunction in oocytes, chemotherapy-induced oxidative stress, and several promising natural adjuvants.

Phytochemical composition and antioxidant activities of some wild edible plants locally consumed by rural communities in northern Uganda

Background

Acalypha rhomboidea, Asystacia gangetica, Crassocephalum sacrobasis, Crotalaria ochroleuca, Heterosis rotundifolia, Hibiscus cannabinus, Hibiscus sp., Hibiscus surratensis, Ipomoea eriocarpa, Maerua angolensis, Senna obtusifolia and Vigna membranacea are among the common wild edible plants in the Acholi sub-region, northern Uganda. This study evaluated the phytochemical constituents and antioxidant potential of the plants.

Methods

Fresh leaves collected from each plant species were air-dried under shade. The phytochemical contents of the ethanol and petroleum ether extracts were determined using standard protocols. The antioxidant content of the methanolic extracts was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay.

Results

Preliminary phytochemical analyses indicated the presence of tannins, reducing compounds, alkaloids, flavonoids, flavons aglycones, flavanosides, anthracenosides, anthocyanosides, volatile oils, coumarins, steroid glycosides, sterols and triterpenes. However, the extracts did not contain any emodols and saponins. The results of the quantitative phytochemical analysis showed that the contents of different phytochemicals detected varied significantly (p < 0.05) among the selected plants. The amount of tannins in mg/g (gallic acid equivalent) of dry weight varied from 3.90 ± 0.16 in C. ochroleuca to 10.41 ± 0.78 in I. eriocarpa, total flavonoids in RE, mg/g dry matter from 4.07 ± 0.11 in I. eriocarpa to 14.94 ± 0.08 in S. obtusifolia. Total alkaloids in mg/100 g ranged from 1.59 ± 0.30 in I. eriocarpa to 6.37 ± 0.24 in Hibiscus sp. Total phenolic content in GAE, mg/g dry matter ranged from 13.39 ± 0.26 in A. rhomboidea to 64.25 ± 0.54 in I. eriocarpa. The in vitro antioxidant assays revealed substantial free radical scavenging activity in all the plants. Antioxidant activity expressed as IC50 (ppm) ranged from 13.39 for A. rhomboidea to 64.84 for I. eriocarpa, compared to 12.82 for ascorbic acid standard. The total phenolic compounds and total tannins had significant and positive correlations with DPPH free radical scavenging activity.

Conclusion

The findings of this study provide evidence that the species are good natural sources of phytochemicals and antioxidants, whose regular consumption could provide human health benefits by protecting against oxidative stress related diseases. Further research is needed on the structural characterization of the phytochemicals, profiling the plant extracts with high antioxidant activity and determining the antimicrobial activities.

Oxidative stress: The nexus of obesity and cognitive dysfunction in diabetes

Obesity has been associated with oxidative stress. Obese patients are at increased risk for diabetic cognitive dysfunction, indicating a pathological link between obesity, oxidative stress, and diabetic cognitive dysfunction. Obesity can induce the biological process of oxidative stress by disrupting the adipose microenvironment (adipocytes, macrophages), mediating low-grade chronic inflammation, and mitochondrial dysfunction (mitochondrial division, fusion). Furthermore, oxidative stress can be implicated in insulin resistance, inflammation in neural tissues, and lipid metabolism disorders, affecting cognitive dysfunction in diabetics.

Human hair proteins as natural reactive oxygen species scavengers for in vitro applications

Human hair proteins are recognized for their intrinsically high cysteine content. They can be solubilized while preserving their highly reductive thiol groups for free radical scavenging applications. The presence of aromatic and nucleophilic amino acids such as methionine, serine, phenylalanine, and threonine further contribute to the antioxidative potential of this material. Herein, utilizing the DPPH (2,2-diphenyl-1-picrylhydrazyl) and acellular 2',7'-dichlorodihydrofluorescein diacetate (H₂ DCFDA) assays, keratins are demonstrated to possess the highest radical scavenging activity among the studied hair proteins. Consequently, protection against hydrogen peroxide-induced oxidative stress in human dermal fibroblasts (HDFs) cultured in human hair keratin supplemented media is demonstrated. Quenching of reactive oxygen species in the HDF is observed using the CellROX Green dye and the expression levels of antioxidant (HMOX1, SOD2, GPX1) and tumor suppressor (TP53) genes is analyzed using qPCR. Collectively, this study presents further evidence and demonstrates the in vitro application potential of hair proteins, especially keratins, as an antioxidizing supplement.

Emerging drugs targeting cellular redox homeostasis to eliminate acute myeloid leukemia stem cells

Acute myeloid leukemia (AML) is a very heterogeneous group of disorders with large differences in the percentage of immature blasts that presently are classified according to the specific mutations that trigger malignant proliferation among thousands of mutations reported thus far. It is an aggressive disease for which few targeted therapies are available and still has a high recurrence rate and low overall survival. The main reason for AML relapse is believed to be due to leukemic stem cells (LSCs) that have unlimited self-renewal capacity and long residence in a quiescent state, which promote greater resistance to traditional therapies for this cancer. AML LSCs have low oxidative stress levels, which appear to be caused by a combination of low mitochondrial activity and high activity of ROS-removing pathways. In this sense, oxidative stress has been thought to be an important new potential target for the treatment of AML patients, targeting the eradication of AML LSCs. The aim of this review is to discuss some drugs that induce oxidative stress to direct new goals for future research focusing on redox imbalance as an effective strategy to eliminate AML LSCs.

Antioxidants attenuate mitochondrial oxidative damage through the Nrf2 pathway: A promising therapeutic strategy for stroke

Stroke represents one of the leading causes of disability and death worldwide. Reactive oxygen species overproduction-induced oxidative stress in mitochondria results in mitochondrial DNA damage, mitochondrial autophagy (mitophagy), inflammation, and apoptosis during the pathologic progression of stroke. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator that induces the transcription of a wide range of antioxidant genes to attenuate mitochondrial oxidative stress. Different antioxidative compounds, including polyphenols, mitochondrial antioxidants, triterpenoids, and others, have been shown to be able to activate Nrf2 and, thus, exert neuroprotective effects on stroke by ameliorating mitochondrial oxidative damage. In this review, we briefly discussed the role of mitochondrial oxidative stress in the pathophysiology of stroke and focused on the protective effects of antioxidative compounds through attenuating mitochondrial oxidative damage by activating Nrf2 in stroke. In conclusion, these antioxidants may represent novel therapeutic strategies against stroke.

Site IQ in mitochondrial complex I generates S1QEL-sensitive superoxide/hydrogen peroxide in both the reverse and forward reactions

Superoxide/hydrogen peroxide production by site IQ in complex I of the electron transport chain is conventionally assayed during reverse electron transport (RET) from ubiquinol to NAD. However, S1QELs (specific suppressors of superoxide/hydrogen peroxide production by site IQ) have potent effects in cells and in vivo during presumed forward electron transport (FET). Therefore, we tested whether site IQ generates S1QEL-sensitive superoxide/hydrogen peroxide during FET (site IQf), or alternatively, whether RET and associated S1QEL-sensitive superoxide/hydrogen peroxide production (site IQr) occurs in cells under normal conditions. We introduce an assay to determine if electron flow through complex I is thermodynamically forward or reverse: on blocking electron flow through complex I, the endogenous matrix NAD pool will become more reduced if flow before the challenge was forward, but more oxidised if flow was reverse. Using this assay we show in the model system of isolated rat skeletal muscle mitochondria that superoxide/hydrogen peroxide production by site IQ can be equally great whether RET or FET is running. We show that sites IQr and IQf are equally sensitive to S1QELs, and to rotenone and piericidin A, inhibitors that block the Q-site of complex I. We exclude the possibility that some sub-fraction of the mitochondrial population running site IQr during FET is responsible for S1QEL-sensitive superoxide/hydrogen peroxide production by site IQ. Finally, we show that superoxide/hydrogen peroxide production by site IQ in cells occurs during FET, and is S1QEL-sensitive.

Antioxidant Status and Biotechnological Potential of New Vischeria vischeri (Eustigmatophyceae) Soil Strains in Enrichment Cultures

The functional state of enrichment cultures of the Eustigmatophycean strains Vischeria vischeri MZ-E3 and MZ-E4 after 25-day cultivation in the BBM medium was studied. The concentrations of chlorophyll a, total carotenoids, protein, vitamins A and E, fatty acid peroxidation product content, an antioxidant enzyme, and succinate dehydrogenase activity were measured. MZ-E3 succinate dehydrogenase activity was significantly higher by 2.21 times; the MZ-E4 strain had 2.94 times higher glutathione peroxidase activity. The MZ-E3 antioxidant activity index and the MZ-E3 unsaturation of fatty acids were 1.3 and 1.25 times higher than the MZ-E4. The retinol and α-tocopherol content of the MZ-E3 was 28.6% and 38.76% higher than MZ-E4. The main fatty acid profile differences were the 3.46-fold and 3.92-fold higher stearic and eicosapentaenoic acid content in the MZ-E4 biomass. MZ-E3 had higher antioxidant, energy, and metabolic and photosynthetic status than MZ-E4. The antioxidant status of the studied strains showed the dependence of the adaptive mechanisms of each, associated with differences in the ecological conditions of the biotopes from which they were isolated. These strains are promising for producing α-tocopherol and biomass enriched with omega-3 and omega-6 fatty acids.

KRIT1: A Traffic Warden at the Busy Crossroads Between Redox Signaling and the Pathogenesis of Cerebral Cavernous Malformation Disease

Significance: KRIT1 (Krev interaction trapped 1) is a scaffolding protein that plays a critical role in vascular morphogenesis and homeostasis. Its loss-of-function has been unequivocally associated with the pathogenesis of Cerebral Cavernous Malformation (CCM), a major cerebrovascular disease of genetic origin characterized by defective endothelial cell-cell adhesion and ensuing structural alterations and hyperpermeability in brain capillaries. KRIT1 contributes to the maintenance of endothelial barrier function by stabilizing the integrity of adherens junctions and inhibiting the formation of actin stress fibers. Recent Advances: Among the multiple regulatory mechanisms proposed so far, significant evidence accumulated over the past decade has clearly shown that the role of KRIT1 in the stability of endothelial barriers, including the blood-brain barrier, is largely based on its involvement in the complex machinery governing cellular redox homeostasis and responses to oxidative stress and inflammation. KRIT1 loss-of-function has, indeed, been demonstrated to cause an impairment of major redox-sensitive mechanisms involved in spatiotemporal regulation of cell adhesion and signaling, which ultimately leads to decreased cell-cell junction stability and enhanced sensitivity to oxidative stress and inflammation. Critical Issues: This review explores the redox mechanisms that influence endothelial cell adhesion and barrier function, focusing on the role of KRIT1 in such mechanisms. We propose that this supports a novel model wherein redox signaling forms the common link between the various pathogenetic mechanisms and therapeutic approaches hitherto associated with CCM disease. Future Directions: A comprehensive characterization of the role of KRIT1 in redox control of endothelial barrier physiology and defense against oxy-inflammatory insults will provide valuable insights into the development of precision medicine strategies. Antioxid. Redox Signal. 38, 496-528.

The role of mitochondria in the peri-implant microenvironment

NEW FINDINGS

What is the topic of this review? In this review, we consider the key role of mitochondria in the peri-implant milieu, including the regulation of mitochondrial reactive oxygen species and mitochondrial metabolism in angiogenesis, the polarization of macrophage immune responses, and bone formation and bone resorption during osseointegration. What advances does it highlight? Mitochondria contribute to the behaviours of peri-implant cell lines based on metabolic and reactive oxygen species signalling modulations, which will contribute to the research field and the development of new treatment strategies for improving implant success.

ABSTRACT

Osseointegration is a dynamic biological process in the local microenvironment adjacent to a bone implant, which is crucial for implant performance and success of the implant surgery. Recently, the role of mitochondria in the peri-implant microenvironment during osseointegration has gained much attention. Mitochondrial regulation has been verified to be essential for cellular events in osseointegration and as a therapeutic target for peri-implant diseases in the peri-implant microenvironment. In this review, we summarize our current knowledge of the key role of mitochondria in the peri-implant milieu, including the regulation of mitochondrial reactive oxygen species and mitochondrial metabolism in angiogenesis, the polarization of macrophage immune responses, and bone formation and resorption during osseointegration, which will contribute to the research field and the development of new treatment strategies to improve implant success. In addition, we indicate limitations in our current understanding of the regulation of mitochondria in osseointegration and suggest topics for further study.

The Cys/N-degron pathway in the ubiquitin-proteasome system and autophagy

The N-degron pathway is a degradative system in which the N-terminal residues of proteins modulate the half-lives of proteins and other cellular materials. The majority of amino acids in the genetic code have the potential to induce cis or trans degradation in diverse processes, which requires selective recognition between N-degrons and cognate N-recognins. Of particular interest is the Cys/N-degron branch, in which the N-terminal cysteine (Nt-Cys) induces proteolysis via either the ubiquitin (Ub)-proteasome system (UPS) or the autophagy-lysosome pathway (ALP), depending on physiological conditions. Recent studies provided new insights into the central role of Nt-Cys in sensing the fluctuating levels of oxygen and reactive oxygen species (ROS). Here, we discuss the components, regulations, and functions of the Cys/N-degron pathway.

Ubiquinone deficiency drives reverse electron transport to disrupt hepatic metabolic homeostasis in obesity

Mitochondrial reactive oxygen species (mROS) are central to physiology. While excess mROS production has been associated with several disease states, its precise sources, regulation, and mechanism of generation in vivo remain unknown, limiting translational efforts. Here we show that in obesity, hepatic ubiquinone (Q) synthesis is impaired, which raises the QH 2 /Q ratio, driving excessive mROS production via reverse electron transport (RET) from site I Q in complex I. Using multiple complementary genetic and pharmacological models in vivo we demonstrated that RET is critical for metabolic health. In patients with steatosis, the hepatic Q biosynthetic program is also suppressed, and the QH 2 /Q ratio positively correlates with disease severity. Our data identify a highly selective mechanism for pathological mROS production in obesity, which can be targeted to protect metabolic homeostasis.

Breast cancer cells that preferentially metastasize to lung or bone are more glycolytic, synthesize serine at greater rates, and consume less ATP and NADPH than parent MDA-MB-231 cells

Gene expression signatures associated with breast cancer metastases suggest that metabolic re-wiring is important for metastatic growth in lungs, bones, and other organs. However, since pathway fluxes depend on additional factors such as ATP demand, allosteric effects, and post-translational modification, flux analysis is necessary to conclusively establish phenotypes. In this study, the metabolic phenotypes of breast cancer cell lines with low (T47D) or high (MDA-MB-231) metastatic potential, as well as lung (LM)- and bone (BoM)-homing lines derived from MDA-MB-231 cells, were assessed by ¹³C metabolite labeling from [1,2-¹³C] glucose or [5-¹³C] glutamine and the rates of nutrient and oxygen consumption and lactate production. MDA-MB-231 and T47D cells produced 55 and 63%, respectively, of ATP from oxidative phosphorylation, whereas LM and BoM cells were more glycolytic, deriving only 20-25% of their ATP from mitochondria. ATP demand by BoM and LM cells was approximately half the rate of the parent cells. Of the anabolic fluxes assessed, nucleotide synthesis was the major ATP consumer for all cell lines. Glycolytic NADH production by LM cells exceeded the rate at which it could be oxidized by mitochondria, suggesting that the malate-aspartate shuttle was not involved in re-oxidation of these reducing equivalents. Serine synthesis was undetectable in MDA-MB-231 cells, whereas 3-5% of glucose was shunted to serine by LM and BoM lines. Proliferation rates of T47D, BoM, and LM lines tightly correlated with their respiration-normalized NADPH production rates. In contrast, MDA-MB-231 cells produced NADPH and GSH at higher rates, suggesting this line is more oxidatively stressed. Approximately half to two-thirds of NADPH produced by T47D, MDA-MB-231, and BoM cells was from the oxidative PPP, whereas the majority in LM cells was from the folate cycle. All four cell lines used the non-oxidative PPP to produce pentose phosphates, although this was most prominent for LM cells. Taken together, the metabolic phenotypes of LM and BoM lines differed from the parent line and from each other, supporting the metabolic re-wiring hypothesis as a feature of metastasis to lung and bone.

Site-specific phosphorylation of tau impacts mitochondrial biology and response to stressors

Phosphorylation of tau at sites associated with Alzheimer's disease (AD) likely plays a role in the disease progression. Mitochondrial impairment, correlating with increased presence of phosphorylated tau, has been identified as a contributing factor to neurodegenerative processes in AD. However, how tau phosphorylated at specific sites impacts mitochondrial function has not been fully defined. We examined how AD-relevant phosphomimetics of tau impact selected aspects of mitochondrial biology. To mimic phosphorylation at AD-associated sites, the Ser/Thr sites in wild-type GFP tagged-tau (T4) were converted to glutamic acid (E) to make pseudophosphorylated GFP tagged-Ser-396/404 (2EC) and GFP tagged-Thr-231/Ser-235 (2EM) constructs. These constructs were expressed in neuronal HT22 cells and their impact on specific mitochondrial functions and responses to stressors were measured. Phosphomimetic tau altered mitochondrial distribution. Specifically, mitochondria accumulated in the soma of cells expressing either 2EC or 2EM, and neurite-like extensions in 2EC cells were shorter. Additionally, ATP levels were reduced in both 2EC and 2EM expressing cells, and ROS production increased in 2EC cells during oxidation of succinate when compared to T4 expressing cells. Thapsigargin reduced mitochondrial membrane potential (Ψ m ) and increased ROS production in both 2EC and 2EM cells relative to T4 cells, with no significant difference in the effects of rotenone. These results show that tau phosphorylation at specific AD-relevant epitopes negatively affects mitochondria, with the extent of dysfunction and stress response varying according to the sites of phosphorylation. Altogether, these findings extend our understanding of potential mechanisms whereby phosphorylated tau promotes mitochondria dysfunction in tauopathies, including AD.

Funding information

R01 AG067617.

Role of Metal Cations of Copper, Iron, and Aluminum and Multifunctional Ligands in Alzheimer's Disease: Experimental and Computational Insights

Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people around the world. Even though the causes of AD are not completely understood due to its multifactorial nature, some neuropathological hallmarks of its development have been related to the high concentration of some metal cations. These roles include the participation of these metal cations in the production of reactive oxygen species, which have been involved in neuronal damage. In order to avoid the increment in the oxidative stress, multifunctional ligands used to coordinate these metal cations have been proposed as a possible treatment to AD. In this review, we present the recent advances in experimental and computational works aiming to understand the role of two redox active and essential transition-metal cations (Cu and Fe) and one nonbiological metal (Al) and the recent proposals on the development of multifunctional ligands to stop or revert the damaging effects promoted by these metal cations.

Tetrathiomolybdate Decreases the Expression of Alkaline Phosphatase in Dermal Papilla Cells by Increasing Mitochondrial ROS Production

Dermal papilla cells (DPCs) play important roles in hair growth regulation. However, strategies to regrow hair are lacking. Here, global proteomic profiling identified the tetrathiomolybdate (TM)-mediated inactivation of copper (Cu) depletion-dependent mitochondrial cytochrome c oxidase (COX) as the primary metabolic defect in DPCs, leading to decreased Adenosine Triphosphate (ATP) production, mitochondrial membrane potential depolarization, increased total cellular reactive oxygen species (ROS) levels, and reduced expression of the key marker of hair growth in DPCs. By using several known mitochondrial inhibitors, we found that excessive ROS production was responsible for the impairment of DPC function. We therefore subsequently showed that two ROS scavengers, N-acetyl cysteine (NAC) and ascorbic acid (AA), partially prevented the TM- and ROS-mediated inhibition of alkaline phosphatase (ALP). Overall, these findings established a direct link between Cu and the key marker of DPCs, whereby copper depletion strongly impaired the key marker of hair growth in the DPCs by increasing excessive ROS production.

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

Calcium and Reactive Oxygen Species Signaling Interplays in Cardiac Physiology and Pathologies

Mitochondria are key players in energy production, critical activity for the smooth functioning of energy-demanding organs such as the muscles, brain, and heart. Therefore, dysregulation or alterations in mitochondrial bioenergetics primarily perturb these organs. Within the cell, mitochondria are the major site of reactive oxygen species (ROS) production through the activity of different enzymes since it is one of the organelles with the major availability of oxygen. ROS can act as signaling molecules in a number of different pathways by modulating calcium (Ca2+) signaling. Interactions among ROS and calcium signaling can be considered bidirectional, with ROS regulating cellular Ca2+ signaling, whereas Ca2+ signaling is essential for ROS production. In particular, we will discuss how alterations in the crosstalk between ROS and Ca2+ can lead to mitochondrial bioenergetics dysfunctions and the consequent damage to tissues at high energy demand, such as the heart. Changes in Ca2+ can induce mitochondrial alterations associated with reduced ATP production and increased production of ROS. These changes in Ca2+ levels and ROS generation completely paralyze cardiac contractility. Thus, ROS can hinder the excitation-contraction coupling, inducing arrhythmias, hypertrophy, apoptosis, or necrosis of cardiac cells. These interplays in the cardiovascular system are the focus of this review.

The isothiocyanate sulforaphane prevents mitochondrial impairment and neuroinflammation in the human dopaminergic SH-SY5Y and in the mouse microglial BV2 cells: role for heme oxygenase-1

Sulforaphane (SFN) promotes protective effects in different cell types. Nonetheless, it remains to be clarified by which mechanism SFN exerts benefits in mammalian cells. Mitochondria are a major source of adenosine triphosphate (ATP) and reactive species in nucleated cells. Mitochondrial impairment result in cellular redox biology disruption, bioenergetic status collapse, and inflammation. Evidence suggest that mitochondrial dysfunction plays a role in neurological disorders. Since a cure was not discovered yet to some of these diseases, investigating strategies to promote mitochondrial protection is pharmacologically relevant and may improve life quality of patients suffering from these maladies. Natural molecules, such as SFN, are potent inducers of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and, consequently, stimulate the expression of genes whose products, such as heme oxygenase-1 (HO-1), induce cytoprotective actions in mammalian tissues. In this work, we investigated whether SFN (5 µM) would be capable to prevent the dysfunctions caused by chlorpyrifos (CPF) on the human dopaminergic SH-SY5Y cells. Moreover, we examined the effects of a pretreatment with SFN at the same concentration on the mouse microglial BV2 cells stimulated by lipopolysaccharide (LPS) in an experimental model of neuroinflammation. SFN prevented the mitochondrial impairment and the neuroinflammation caused by the chemical stressors in both cell types. Inhibition of heme oxygenase-1 (HO-1) suppressed the mitochondrial protection and anti-inflammatory action afforded by SFN in this experimental model. Overall, SFN promoted cytoprotection by a mechanism dependent on the HO-1 enzyme in the SH-SY5Y and BV2 cells.

The air-breathing Alaska blackfish (Dallia pectoralis) suppresses brain mitochondrial reactive oxygen species to survive cold hypoxic winters

The Alaska blackfish (Dallia pectoralis) is the only air-breathing fish in the Arctic. In the summer, a modified esophagus allows the fish to extract oxygen from the air, but this behavior is not possible in the winter because of ice and snow cover. The lack of oxygen (hypoxia) and near freezing temperatures in winter is expected to severely compromise metabolism, and yet remarkably, overwintering Alaska blackfish remain active. To maintain energy balance in the brain and limit the accumulation of reactive oxygen species (ROS), we hypothesized that cold hypoxic conditions would trigger brain mitochondrial remodeling in the Alaska blackfish. To address this hypothesis, fish were acclimated to warm (15 °C) normoxia, cold (5 °C) normoxia or cold hypoxia (5 °C, 2.1-4.2 kPa; no air access) for 5-8 weeks. Mitochondrial respiration, ADP affinity and H₂0₂ production were measured at 10 °C in isolated brain homogenates with an Oroboros respirometer. Cold acclimation and chronic hypoxia had no effects on mitochondrial aerobic capacity or ADP affinity. However, cold acclimation in normoxia led to a suppression of brain mitochondrial H₂0₂ production, which persisted and became more pronounced in the cold hypoxic fish. Overall, our study suggests cold acclimation supresses ROS production in Alaska blackfish, which may protect the fish from oxidative stress when oxygen becomes limited during winter.

Skeletal Muscle Mitochondrial Dysfunction in Chronic Obstructive Pulmonary Disease: Underlying Mechanisms and Physical Therapy Perspectives

Skeletal muscle dysfunction (SMD) is a prevalent extrapulmonary complication and a significant independent prognostic factor in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial dysfunction is one of the core factors that damage structure and function in COPD skeletal muscle and is closely related to smoke exposure, hypoxia, and insufficient physical activity. The currently known phenotypes of mitochondrial dysfunction are reduced mitochondrial content and biogenesis, impaired activity of mitochondrial respiratory chain complexes, and increased mitochondrial reactive oxygen species production. Significant progress has been made in research on physical therapy (PT), which has broad prospects for treating the abovementioned potential mitochondrial-function changes in COPD skeletal muscle. In terms of specific types of PT, exercise therapy can directly act on mitochondria and improve COPD SMD by increasing mitochondrial density, regulating mitochondrial biogenesis, upregulating mitochondrial respiratory function, and reducing oxidative stress. However, improvements in mitochondrial-dysfunction phenotype in COPD skeletal muscle due to different exercise strategies are not entirely consistent. Therefore, based on the elucidation of this phenotype, in this study, we analyzed the effect of exercise on mitochondrial dysfunction in COPD skeletal muscle and the regulatory mechanism thereof. We also provided a theoretical basis for exercise programs to rehabilitate this condition.

CuATSM effectively ameliorates ALS patient astrocyte-mediated motor neuron toxicity in human in vitro models of amyotrophic lateral sclerosis

Patient diversity and unknown disease cause are major challenges for drug development and clinical trial design for amyotrophic lateral sclerosis (ALS). Transgenic animal models do not adequately reflect the heterogeneity of ALS. Direct reprogramming of patient fibroblasts to neuronal progenitor cells and subsequent differentiation into patient astrocytes allows rapid generation of disease relevant cell types. Thus, this methodology can facilitate compound testing in a diverse genetic background resulting in a more representative population for therapeutic evaluation. Here, we used established co-culture assays with motor neurons and reprogrammed patient skin-derived astrocytes (iAs) to evaluate the effects of (SP-4-2)-[[2,2'-(1,2-dimethyl-1,2-ethanediylidene)bis[N-methylhydrazinecarbothioamidato-κN² ,κS]](2-)]-copper (CuATSM), currently in clinical trial for ALS in Australia. Pretreatment of iAs with CuATSM had a differential effect on neuronal survival following co-culture with healthy motor neurons. Using this assay, we identified responding and non-responding cell lines for both sporadic and familial ALS (mutant SOD1 and C9ORF72). Importantly, elevated mitochondrial respiration was the common denominator in all CuATSM-responders, a metabolic phenotype not observed in non-responders. Pre-treatment of iAs with CuATSM restored mitochondrial activity to levels comparable to healthy controls. Hence, this metabolic parameter might allow selection of patient subpopulations best suited for CuATSM treatment. Moreover, CuATSM might have additional therapeutic value for mitochondrial disorders. Enhanced understanding of patient-specific cellular and molecular profiles could help improve clinical trial design in the future.

Potential candidates from marine and terrestrial resources targeting mitochondrial inhibition: Insights from the molecular approach

Mitochondria are the target sites for multiple disease manifestations, for which it is appealing to researchers' attention for advanced pharmacological interventions. Mitochondrial inhibitors from natural sources are of therapeutic interest due to their promising benefits on physiological complications. Mitochondrial complexes I, II, III, IV, and V are the most common sites for the induction of inhibition by drug candidates, henceforth alleviating the manifestations, prevalence, as well as severity of diseases. Though there are few therapeutic options currently available on the market. However, it is crucial to develop new candidates from natural resources, as mitochondria-targeting abnormalities are rising to a greater extent. Marine and terrestrial sources possess plenty of bioactive compounds that are appeared to be effective in this regard. Ample research investigations have been performed to appraise the potentiality of these compounds in terms of mitochondrial disorders. So, this review outlines the role of terrestrial and marine-derived compounds in mitochondrial inhibition as well as their clinical status too. Additionally, mitochondrial regulation and, therefore, the significance of mitochondrial inhibition by terrestrial and marine-derived compounds in drug discovery are also discussed.

Inclusion of the in-chain sulfur in 3-thiaCTU increases the efficiency of mitochondrial targeting and cell killing by anticancer aryl-urea fatty acids

Mitochondria in tumor cells are functionally different from those in normal cells and could be targeted to develop new anticancer agents. We showed recently that the aryl-ureido fatty acid CTU is the prototype of a new class of mitochondrion-targeted agents that kill cancer cells by increasing the production of reactive oxygen species (ROS), activating endoplasmic reticulum (ER)-stress and promoting apoptosis. However, prolonged treatment with high doses of CTU were required for in vivo anti-tumor activity. Thus, new strategies are now required to produce agents that have enhanced anticancer activity over CTU. In the present study we prepared a novel aryl-urea termed 3-thiaCTU, that contained an in-chain sulfur heteroatom, for evaluation in tumor cell lines and in mice carrying tumor xenografts. The principal finding to emerge was that 3-thiaCTU was several-fold more active than CTU in the activation of aryl-urea mechanisms that promoted cancer cell killing. Thus, in in vitro studies 3-thiaCTU disrupted the mitochondrial membrane potential, increased ROS production, activated ER-stress and promoted tumor cell apoptosis more effectively than CTU. 3-ThiaCTU was also significantly more active than CTUin vivo in mice that carried MDA-MB-231 cell xenografts. Compared to CTU, 3-thiaCTU prevented tumor growth more effectively and at much lower doses. These findings indicate that, in comparison to CTU, 3-thiaCTU is an aryl-urea with markedly enhanced activity that could now be suitable for development as a novel anticancer agent.

Coordinated regulation of the mitochondrial retrograde response by circadian clock regulators and ANAC017

Mitochondrial retrograde signaling (MRS) supports photosynthetic function under a variety of conditions. Induction of mitochondrial dysfunction with myxothiazol (a specific inhibitor of the mitochondrial bc₁ complex) or antimycin A (an inhibitor of the mitochondrial bc₁ complex and cyclic electron transport in the chloroplast under light conditions) in the light and dark revealed diurnal control of MRS. This was evidenced by (1) significantly enhanced binding of ANAC017 to promoters in the light compared with the dark in Arabidopsis plants treated with myxothiazol (but not antimycin A), (2) overlap in the experimentally determined binding sites for ANAC017 and circadian clock regulators in the promoters of ANAC013 and AOX1a, (3) a diurnal expression pattern for ANAC017 and transcription factors it regulates, (4) altered expression of ANAC017-regulated genes in circadian clock mutants with and without myxothiazol treatment, and (5) a decrease in the magnitude of LHY and CCA1 expression in an ANAC017-overexpressing line and protein-protein interaction between ANAC017 and PIF4. This study also shows a large difference in transcriptome responses to antimycin A and myxothiazol in the dark: these responses are ANAC017 independent, observed in shoots and roots, similar to biotic challenge and salicylic acid responses, and involve ERF and ZAT transcription factors. This suggests that antimycin A treatment stimulates a second MRS pathway that is mediated or converges with salicylic acid signaling and provides a merging point with chloroplast retrograde signaling.

Ovarian Cancer: A Landscape of Mitochondria with Emphasis on Mitochondrial Dynamics

Ovarian cancer (OC) represents the main cause of death from gynecological malignancies in western countries. Altered cellular and mitochondrial metabolism are considered hallmarks in cancer disease. Several mitochondrial aspects have been found altered in OC, such as the oxidative phosphorylation system, oxidative stress and mitochondrial dynamics. Mitochondrial dynamics includes cristae remodeling, fusion, and fission processes forming a dynamic mitochondrial network. Alteration of mitochondrial dynamics is associated with metabolic change in tumour development and, in particular, the mitochondrial shaping proteins appear also to be responsible for the chemosensitivity and/or chemoresistance in OC. In this review a focus on the mitochondrial dynamics in OC cells is presented.

Grape seed proanthocyanidin extract targets p66Shc to regulate mitochondrial biogenesis and dynamics in diabetic kidney disease

Mitochondrial biogenesis and dynamics are associated with renal mitochondrial dysfunction and the pathophysiological development of diabetic kidney disease (DKD). Decreased p66Shc expression prevents DKD progression by significantly regulating mitochondrial function. Grape seed proanthocyanidin extract (GSPE) is a potential therapeutic medicine for multiple kinds of diseases. The effect of GSPE on the mitochondrial function and p66Shc in DKD has not been elucidated. Hence, we decided to identify p66Shc as a therapeutic target candidate to probe whether GSPE has a renal protective effect in DKD and explored the underlying mechanisms.

METHODS

In vivo, rats were intraperitoneally injected with streptozotocin (STZ) and treated with GSPE. Biochemical changes, mitochondrial morphology, the ultrastructure of nephrons, and protein expression of mitochondrial biogenesis (SIRT1, PGC-1α, NRF1, TFAM) and dynamics (DRP1, MFN1) were determined. In vitro, HK-2 cells were transfected with p66Shc and treated with GSPE to evaluate changes in cell apoptosis, reactive oxygen species (ROS), mitochondrial quality, the protein expression.

RESULTS

In vivo, GSPE significantly improved the renal function of rats, with less proteinuria and a lower apoptosis rate in the injured renal tissue. Besides, GSPE treatment increased SIRT1, PGC-1α, NRF1, TFAM, and MFN1 expression, decreased p66Shc and DRP1 expression. In vitro, overexpression of p66Shc decreased the resistance of HK-2 cells to high glucose toxicity, as shown by increased apoptosis and ROS production, decreased mitochondrial quality and mitochondrial biogenesis, and disturbed mitochondrial dynamic homeostasis, ultimately leading to mitochondrial dysfunction. While GSPE treatment reduced p66Shc expression and reversed these changes.

CONCLUSION

GSPE can maintain the balance between mitochondrial biogenesis and dynamics by negatively regulating p66Shc expression.

Impact of a Saccharomyces cerevisiae fermentation product during an intestinal barrier challenge in lactating Holstein cows on ileal microbiota and markers of tissue structure and immunity

Feeding a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during periods of metabolic stress is beneficial to the health of dairy cows partially through its effect on the gut microbiota. Whether SCFP alters the ileal microbiota in lactating cows during intestinal challenges induced by feed restriction (FR) is not known. We used 16S rRNA sequencing to assess if feeding SCFP during FR to induce gut barrier dysfunction alters microbiota profiles in the ileum. The mRNA abundance of key genes associated with tissue structures and immunity was also detected. Multiparous cows (97.1 ± 7.6 days in milk (DIM); n = 7 per treatment) fed a control diet or the control plus 19 g/d NutriTek for 9 wk were subjected to an FR challenge for 5 d, during which they were fed 40% of their ad libitum intake from the 7 d before FR. All cows were slaughtered at the end of FR. DNA extracted from ileal digesta was subjected to PacBio Full-Length 16S rRNA gene sequencing. High-quality amplicon sequence analyses were performed with Targeted Amplicon Diversity Analysis and MicrobiomeAnalyst. Functional analysis was performed and analyzed using PICRUSt and STAMP. Feeding SCFP did not (P > 0.05) alter dry matter intake, milk yield, or milk components during FR. In addition, SCFP supplementation tended (P = 0.07) to increase the relative abundance of Proteobacteria and Bifidobacterium animalis. Compared with controls, feeding SCFP increased the relative abundance of Lactobacillales (P = 0.03). Gluconokinase, oligosaccharide reducing-end xylanase, and 3-hydroxy acid dehydrogenase were among the enzymes overrepresented (P < 0.05) in response to feeding SCFP. Cows fed SCFP had a lower representation of adenosylcobalamin biosynthesis I (early cobalt insertion) and pyrimidine deoxyribonucleotides de novo biosynthesis III (P < 0.05). Subsets of the Firmicutes genus, Bacteroidota phylum, and Treponema genus were correlated with the mRNA abundance of genes associated with ileal integrity (GCNT3, GALNT5, B3GNT3, FN1, ITGA2, LAMB2) and inflammation (AOX1, GPX8, CXCL12, CXCL14, CCL4, SAA3). Our data indicated that the moderate FR induced dysfunction of the ileal microbiome, but feeding SCFP increased the abundance of some beneficial gut probiotic bacteria and other species related to tissue structures and immunity.

Protein S-glutathionylation and sex dimorphic effects on hydrogen peroxide production by dihydroorotate dehydrogenase in liver mitochondria

Dihydroorotate dehydrogenase (DHODH) oxidizes dihydroorotate to orotate for pyrimidine biosynthesis, donating electrons to the ubiquinone (UQ) pool of mitochondria. DHODH has a measurable rate for hydrogen peroxide (H₂O₂) production and thus contributes to cellular changes in redox tone. Protein S-glutathionylation serves as a negative feedback loop for the inhibition of H₂O₂ by several α-keto acid dehydrogenases and respiratory complexes in mitochondria, as well as ROS sources in liver cytoplasm. Here, we report this redox signaling mechanism also inhibits H₂O₂ production by DHODH in liver mitochondria isolated from male and female C57BL6N mice. We discovered that low amounts of the glutathionylation catalyst, disulfiram (50-500 nM), almost abolished H₂O₂ production by DHODH in mitochondria from male mice. Similar results were collected with diamide, however, higher doses (1000-5000 μM) were required to elicit this effect. Disulfiram and diamide also significantly suppressed H₂O₂ production by DHODH in female liver mitochondria. However, liver mitochondria from female mice were more resistant to disulfiram or diamide-mediated inhibition of H₂O₂ genesis when compared to samples from males. Analysis of the impact of disulfiram and diamide on DHODH activity revealed that both compounds inhibited the dehydrogenase directly, however the effect was less in female mice. Additionally, disulfiram and diamide impeded the use of dihydroorotate fueled oxidative phosphorylation in mitochondria from males and females, although samples collected from female rodents displayed more resistance to this inhibition. Taken together, our findings demonstrate H₂O₂ production by DHODH can be inhibited by glutathionylation and sex can impact this redox modification.

Free radicals: Relationship to Human Diseases and Potential Therapeutic applications

Reactive species are highly-reactive enzymatically, or non-enzymatically produced compounds with important roles in physiological and pathophysiological cellular processes. Although reactive species represent an extensively researched topic in biomedical sciences, many aspects of their roles and functions remain unclear. This review aims to systematically summarize findings regarding the biochemical characteristics of various types of reactive species and specify the localization and mechanisms of their production in cells. In addition, we discuss the specific roles of free radicals in cellular physiology, focusing on the current lines of research that aim to identify the reactive oxygen species-initiated cascades of reactions resulting in adaptive or pathological cellular responses. Finally, we present recent findings regarding the therapeutic modulations of intracellular levels of reactive oxygen species, which may have substantial significance in developing novel agents for treating several diseases.

Reflections on the state of diabetes research and prospects for treatment

Research on the etiology and treatment of diabetes has made substantial progress. As a result, several new classes of anti-diabetic drugs have been introduced in clinical practice. Nonetheless, the number of patients achieving glycemic control targets has not increased for the past 20 years. Two areas of unmet medical need are the restoration of insulin sensitivity and the reversal of pancreatic beta cell failure. In this review, we integrate research advances in transcriptional regulation of insulin action and pathophysiology of beta cell dedifferentiation with their potential impact on prospects of a durable "cure" for patients suffering from type 2 diabetes.

Comparing the Impact of NIR, Visible and UV Light on ROS Upregulation via Photoacceptors of Mitochondrial Complexes in Normal, Immune and Cancer Cells

The effect of UV/visible/NIR light (380/450/530/650/808/1064 nm) on ROS generation, mitochondrial activity and viability is experimentally compared in human neuroblastoma cancer cells. The absorption of photons by mitochondrial photoacceptors in Complexes I, III and IV is in detail investigated by sequential blocking with selective pharmaceutical blockers. Complex I absorbs UV/blue light by heme P450, resulting in a very high rate (14 times) of ROS generation leading to cell death. Complex III absorbs green light, by cytochromes b, c1 and c, and possesses less ability for ROS production (seven times), so that only irradiation lower than 10 mW cm^-2 causes an increase in cell viability. Complex IV is well-known as the primary photoacceptor for red/NIR light. Light of 650/808 nm at 10-100 mW cm^-2 generates a physiological ROS level about 20% of a basal concentration, which enhance mitochondrial activity and cell survival, while 1064 nm light does not show any distinguished effects. Further, ROS generation induced by low-intensity red/NIR light is compared in neurons, immune and cancer cells. Red light seems to more rapidly stimulate ROS production, mitochondrial activity and cell survival than 808 nm. At the same time, different cell lines demonstrate slightly various rates of ROS generation, peculiar to their cellular physiology.