Oxidative Stress, Inflammation, and Activators of Mitochondrial Biogenesis: Tempol Targets in the Diaphragm Muscle of Exercise Trained-mdx Mice

Pharmacology and macrophage modulation of HPGDS inhibitor PK007 demonstrate reduced disease severity in DMD-affected muscles of the mdx mouse model

BACKGROUND

Duchenne Muscular Dystrophy (DMD) is an X-linked disease characterised by chronic inflammation, progressive muscle damage, and muscle loss. Typically, initial symptoms affect lower limb muscles, including the gastrocnemius (GA), tibialis anterior (TA), and extensor digitorum longus (EDL). During the acute phase of DMD, particularly in boys aged 2-8 years, muscle damage resulting in necrosis (myonecrosis) involves a complex immune-inflammatory response. Prostaglandin D2 (PGD2) is recognised for enhancing pro-inflammatory chemokine and interleukin signalling and recruiting infiltrating immune cells such as pro-inflammatory macrophages, exacerbating myonecrosis.

METHODS

To reduce levels of PGD2, a novel hematopoietic prostaglandin D2 synthase (HPGDS) inhibitor, PK007, was characterised (i) for potency and pharmacokinetic profiles and then tested in the mdx mouse model of DMD during the acute early onset of disease progression. Juvenile mdx and wild type (WT) C57Bl/10Scsn mice were orally treated with PK007 and control vehicle solution for 10 days, from postnatal day 18 to 28. This builds upon a previous study with PK007 with (ii) additional analyses of disease progression assessed for muscle grip strength, metabolic and locomotor activity, myonecrosis in a wide range of muscles (3 from hindlimb, diaphragm, heart, and tongue), macrophage infiltration and pro-inflammatory cytokines (TNF-α, IL-1β and iNOS).

RESULTS

PK007 exhibited high potency (17.23 ± 12 nM), a long half-life (3.0 ± 0.3 h), and good oral bioavailability (81%). Treatment with PK007 decreased serum PGD2 levels (33.36%) in mdx mice compared to control (vehicle-treated) mdx mice. In mdx mice (compared with controls), PK007 enhanced grip strength (69.05% increase) and improved locomotor activity (69.05% increase). Histological analysis revealed a significant reduction in the total myonecrotic area in PK007-treated GA (49.75%), TA (73.87%), EDL (60.31%), diaphragm (48.02%), and tongue (37.93%) muscles of mdx mice (compared with controls). Additionally, PK007 decreased macrophage cell area by 55.56% in GA and 47.83% in EDL muscles. Further expression of pro-inflammatory cytokines and enzymes such as TNF-α, IL-1β and iNOS were significantly reduced in PK007 treated mice. These results demonstrate that PK007 significantly reduces the inflammatory response, protects muscles from necrosis and increases strength in juvenile mdx mice.

CONCLUSION

This study lays a strong foundation for progressing the use of HPDGS inhibitors such as PK007, which specifically inhibit PGD2 and reduce inflammation, as a viable therapeutic approach for DMD. This approach protects dystrophic muscles from necrosis and reduces the severity of this debilitating disease, improving outcomes and quality of life.

Functional Foods, a Hope to Delay Muscle Dystrophy Progression: A Potential Role for Omega Fatty Acids

Functional foods, thanks to their basic nutritional properties, can have physiological benefits and can alleviate the symptoms of many chronic diseases. They contain active components deriving either from plant or animal sources, and they show anti-inflammatory, cardiotonic, and antioxidant pharmacological activities that could be useful in preventing oxidative damage and inflammatory processes in a variety of disorders. There is evidence from in vitro, in vivo, and clinical observational studies that some compounds have significant effects in modulating the muscular dystrophy phenotype, which is characterized by fibrosis, myofiber necrotic cell death, inflammation, oxidative stress, and dysfunctional mitochondria. This review involves collecting data from the main medical databases and detailing the key features involved in muscular dystrophy progression and the relevance of fatty-acid compounds as diet supplements in the management of the disease. Omega fatty acids improve the dystrophic phenotype in terms of fibrosis and inflammation reduction, stimulating mitochondrial activity and antioxidant systems. Omega fatty acids could play a crucial role as food supplementation to delay dystrophy progression. This overview appears extremely relevant for researchers who are studying these molecules as valid alternatives to glucocorticoids, that today remain the only recognized pharmacological cure for dystrophic patients.

LED therapy modulates M1/M2 macrophage phenotypes and mitigates dystrophic features in treadmill-trained mdx mice

The mdx mouse phenotype, aggravated by chronic exercise on a treadmill, makes this murine model more reliable for the study of Duchenne muscular dystrophy (DMD) and allows the efficacy of therapeutic interventions to be evaluated. This study aims to investigate the effects of photobiomodulation by light-emitting diode (LED) therapy on functional, biochemical and morphological parameters in treadmill-trained adult mdx animals. Mdx mice were trained for 30 min of treadmill running at a speed of 12 m/min, twice a week for 4 weeks. The LED therapy (850 nm) was applied twice a week to the quadriceps muscle throughout the treadmill running period. LED therapy improved behavioral activity (open field) and muscle function (grip strength and four limb hanging test). Functional benefits correlated with reduced muscle damage; a decrease in the inflammatory process; modulation of the regenerative muscular process and calcium signalling pathways; and a decrease in oxidative stress markers. The striking finding of this work is that LED therapy leads to a shift from the M1 to M2 macrophage phenotype in the treadmill-trained mdx mice, enhancing tissue repair and mitigating the dystrophic features. Our data also imply that the beneficial effects of LED therapy in the dystrophic muscle correlate with the interplay between calcium, oxidative stress and inflammation signalling pathways. Together, these results suggest that photobiomodulation could be a potential adjuvant therapy for dystrophinopathies.

Differential tempol effects in prostatic cancer: angiogenesis and short- and long-term treatments

Prostate cancer (PCa) is the second cause of cancer death among men worldwide. Several processes are involved in the development and progression of PCa such as angiogenesis, inflammation and oxidative stress. The present study investigated the effect of short- or long-term Tempol treatment at different stages of prostate adenocarcinoma progression, focusing on angiogenic, proliferative, and stromal remodeling processes in TRAMP mice. The dorsolateral lobe of the prostate of TRAMP mice were evaluated at two different stages of PCa progression; early and late stages. Early stage was again divided into, short- or long-term. 50 mg/kg Tempol dose was administered orally. The results demonstrated that Tempol mitigated the prostate histopathological lesion progressions in the TRAMP mice in all treated groups. However, Tempol increased molecules involved in the angiogenic process such as CD31 and VEGFR2 relative frequencies, particularly in long-term treatment. In addition, Tempol upregulated molecule levels involved in angiogenesis and stromal remodeling process VEGF, TGF-β1, VE-cadherin and vimentin, particularly, in T8-16 group. Thus, it was concluded that Tempol treatment delayed prostatic lesion progression in the dorsolateral lobe of the TRAMP mice. However, Tempol also led to pro-angiogenic effects and glandular stromal microenvironment imbalance, especially, in the long-term treatment.

Tempol effect on oxidative and mitochondrial markers in preclinical models for prostate cancer

Background

Tempol is a redox-cycling nitroxide considered a potent antioxidant. The present study investigated the tempol effects on oxidative stress and mitochondrial markers on prostate cancer (PCa).

Methods

PC-3 and LnCaP cells were exposed to tempol. Cell viability test, western blot and Amplex Red analyses were performed. In vivo, five experimental groups evaluated tempol effects in the early (CT12 and TPL12 groups) and late stages (CT20, TPL20-I, and TLP20-II) of PCa development. The TPL groups were treated with 50 or 100 mg/kg tempol doses. Control groups received water as the vehicle. The ventral lobe of the prostate and the blood were collected and submitted to western blotting or enzymatic activity analyses.

Results

In vitro, tempol decreased cell viability and differentially altered the H2O2 content for PC-3 and LNCaP. Tempol increased SOD2 levels in both cell lines and did not alter Catalase protein levels. In vivo, tempol increased SOD2 levels in the early stage and did not change Catalase levels in the different PCa stages. Systemically, tempol decreased SOD2 levels in the late-stage and improved redox status in the early and late stages, which was confirmed by reduced LDH in tempol groups. Alterations on energetic metabolism and oxidative phosphorylation were observed in TRAMP model.

Conclusion

Tempol can be considered a beneficial therapy for PCa treatment considering its antioxidant and low toxicity properties, however the PCa progression must be evaluated to get successful therapy.

Trilobatin contributes to the improvement of myopathy in a mouse model of Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) occurs due to genetic mutations that lead to a deficiency in dystrophin production and consequent progressive degeneration of skeletal muscle fibres, through oxidative stress and an exacerbated inflammatory process. The flavonoid trilobatin (TLB) demonstrates antioxidant and anti-inflammatory potential. Its high safety profile and effective action make it a potent therapy for the process of dystrophic muscle myonecrosis. Thus, we sought to investigate the action of TLB on damage in a DMD model, the mdx mouse. Eight-week-old male animals were treated with 160 mg/kg/day of trilobatin for 8 weeks. Control animals were treated with saline. Following treatment, muscle strength, serum creatine kinase (CK) levels, histopathology (necrotic myofibres, regenerated fibres/central nuclei, Feret's diameter and inflammatory area) and the levels of catalase and NF-κB (western blotting) of the quadriceps (QUA), diaphragm (DIA) and tibialis anterior (TA) muscles were measured. TLB was able to significantly increase muscle strength and reduce serum CK levels in dystrophic animals. The QUA of mdx mice showed a reduction in catalase and the number of fibres with a centralized nucleus after treatment with TLB. In the DIA of dystrophic animals, TLB reduced the necrotic myofibres, inflammatory area and NF-κB and increased the number of regenerated fibres and the total fibre diameter. In TA, TLB increased the number of regenerated fibres and reduced catalase levels in these animals. It is concluded that in the mdx experimental model, treatment with TLB was beneficial in the treatment of DMD.

LEDT and Idebenone treatment modulate autophagy and improve regenerative capacity in the dystrophic muscle through an AMPK-pathway

PURPOSE

Considering the difficulties and challenges in Duchenne muscular dystrophy (DMD) treatment, such as the adverse effects of glucocorticoids, which are the main medical prescription used by dystrophic patients, new treatment concepts for dystrophic therapy are very necessary. Thus, in this study, we explore the effects of photobiomodulation (PBM; a non-invasive therapy) and Idebenone (IDE) treatment (a potent antioxidant), applied alone or in association, in dystrophic muscle cells and the quadriceps muscle, with special focus on autophagy and regenerative pathways.

METHODS

For the in vitro studies, the dystrophic primary muscle cells received 0.5J LEDT and 0.06μM IDE; and for the in vivo studies, the dystrophic quadriceps muscle received 3J LEDT and the mdx mice were treated with 200mg/kg IDE.

RESULTS

LEDT and IDE treatment modulate autophagy by increasing autophagy markers (SQSTM1/p62, Beclin and Parkin) and signaling pathways (AMPK and TGF-β). Concomitantly, the treatments prevented muscle degeneration by reducing the number of IgG-positive fibers and the fibers with a central nucleus; decreasing the fibrotic area; up-regulating the myogenin and MCH-slow levels; and down-regulating the MyoD and MHC-fast levels.

CONCLUSION

These results suggest that LEDT and IDE treatments enhance autophagy and prevented muscle degeneration in the dystrophic muscle of the experimental model. These findings illustrate the potential efficacy of LEDT and IDE treatment as an alternative therapy focused on muscle recovery in the dystrophic patient.

Effects of Dityrosine on Lactic Acid Metabolism in Mice Gastrocnemius Muscle During Endurance Exercise via the Oxidative Stress-Induced Mitochondria Damage

Dityrosine (Dityr) has been detected in commercial food as a product of protein oxidation and has been shown to pose a threat to human health. This study aims to investigate whether Dityr causes a decrease in lactic acid metabolism in the gastrocnemius muscle during endurance exercise. C57BL/6 mice were administered Dityr or saline by gavage for 13 weeks and underwent an endurance exercise test on a treadmill. Dityr caused a severe reduction in motion displacement and endurance time, along with a significant increase in lactic acid accumulation in the blood and gastrocnemius muscle in mice after exercise. Dityr induced significant mitochondrial defects in the gastrocnemius muscle of mice. Additionally, Dityr induced serious oxidative stress in the gastrocnemius muscle, accompanied by inflammation, which might be one of the causes of mitochondrial dysfunction. Moreover, significant apoptosis in the gastrocnemius muscle increased after exposure to Dityr. This study confirmed that Dityr induced oxidative stress in the gastrocnemius muscle, which further caused significant mitochondrial damage in the gastrocnemius muscle cell, resulting in decreased capacity of lactic acid metabolism and finally affected performance in endurance exercise. This may be one of the possible mechanisms by which highly oxidized foods cause a decreased muscle energy metabolism.

Antioxidant effects of LEDT in dystrophic muscle cells: involvement of PGC-1α and UCP-3 pathways

PURPOSE

Reactive oxygen species and mitochondrial dysfunction play a crucial role in the pathophysiology of Duchenne muscular dystrophy (DMD). The light-emitting diode therapy (LEDT) showed beneficial effects on the dystrophic muscles. However, the mechanisms of this therapy influence the molecular pathways in the dystrophic muscles, particularly related to antioxidant effects, which still needs to be elucidated. The current study provides muscle cell-specific insights into the effect of LEDT, 48 h post-irradiation, on oxidative stress and mitochondrial parameters in the dystrophic primary muscle cells in culture.

METHODS

Dystrophic primary muscle cells were submitted to LEDT, at multiple wavelengths (420 nm, 470 nm, 660 nm and 850 nm), 0.5 J dose, and evaluated after 48 h based on oxidative stress markers, antioxidant enzymatic system and biogenesis, and functional mitochondrial parameters.

RESULTS

The mdx muscle cells treated with LEDT showed a significant reduction of H2O2 production and 4-HNE, catalase, SOD-2, and GR levels. Upregulation of UCP3 was observed with all wavelengths while upregulation of PGC-1α and a slight upregulation of electron transport chain complexes III and V was only observed following 850 nm LEDT. In addition, the mitochondrial membrane potential and mitochondrial mass mostly tended to be increased following LEDT, while parameters like O2·- production tended to be decreased.

CONCLUSION

The data shown here highlight the potential of LEDT as a therapeutic agent for DMD through its antioxidant action by modulating PGC-1α and UCP3 levels.

LED therapy plus idebenone treatment targeting calcium and mitochondrial signaling pathways in dystrophic muscle cells

Intracellular calcium dysregulation, oxidative stress, and mitochondrial dysfunction are some of the main pathway contributors towards disease progression in Duchenne muscular dystrophy (DMD). This study is aimed at investigating the effects of light emitting diode therapy (LEDT) and idebenone antioxidant treatment, applied alone or together in dystrophic primary muscle cells from mdx mice, the experimental model of DMD. Mdx primary muscle cells were submitted to LEDT and idebenone treatment and evaluated for cytotoxic effects and calcium and mitochondrial signaling pathways. LEDT and idebenone treatment showed no cytotoxic effects on the dystrophic muscle cells. Regarding the calcium pathways, after LEDT and idebenone treatment, a significant reduction in intracellular calcium content, calpain-1, calsequestrin, and sarcolipin levels, was observed. In addition, a significant reduction in oxidative stress level markers, such as H2O2, and 4-HNE levels, was observed. Regarding mitochondrial signaling pathways, a significant increase in oxidative capacity (by OCR and OXPHOS levels) was observed. In addition, the PGC-1α, SIRT-1, and PPARδ levels were significantly higher in the LEDT plus idebenone treated-dystrophic muscle cells. Together, the findings suggest that LEDT and idebenone treatment, alone or in conjunction, can modulate the calcium and mitochondrial signaling pathways, such as SLN, SERCA 1, and PGC-1α, contributing towards the improvement of the dystrophic phenotype in mdx muscle cells. In addition, data from the LEDT plus idebenone treatment showed slightly better results than those of each separate treatment in terms of SLN, OXPHOS, and SIRT-1.

Modulation of Mitochondrial Metabolic Parameters and Antioxidant Enzymes in Healthy and Glaucomatous Trabecular Meshwork Cells with Hybrid Small Molecule SA-2

Oxidative stress (OS)-induced mitochondrial damage is a risk factor for primary open-angle glaucoma (POAG). Mitochondria-targeted novel antioxidant therapies could unearth promising drug candidates for the management of POAG. Previously, our dual-acting hybrid molecule SA-2 with nitric oxide-donating and antioxidant activity reduced intraocular pressure and improved aqueous humor outflow in rodent eyes. Here, we examined the mechanistic role of SA-2 in trabecular meshwork (TM) cells in vitro and measured the activity of intracellular antioxidant enzymes during OS. Primary human TM cells isolated from normal (hNTM) or glaucomatous (hGTM) post-mortem donors and transformed glaucomatous TM cells (GTM-3) were used for in vitro assays. We examined the effect of SA-2 on oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) in vitro using Seahorse Analyzer with or without the oxidant, tert-butyl hydroperoxide (TBHP) treatment. Concentrations of total antioxidant enzymes, catalase (CAT), malondialdehyde (MDA), and glutathione peroxidase (GPx) were measured. We observed significant protection of both hNTM and hGTM cells from TBHP-induced cell death by SA-2. Antioxidant enzymes were elevated in SA-2-treated cells compared to TBHP-treated cells. In addition, SA-2 demonstrated an increase in mitochondrial metabolic parameters. Altogether, SA-2 protected both normal and glaucomatous TM cells from OS via increasing mitochondrial energy parameters and the activity of antioxidant enzymes.

Tempol differential effect on prostate cancer inflammation: In vitro and in vivo evaluation

BACKGROUND

Tempol is a redox-cycling nitroxide that acts directly on inflammation. However, few studies have reported the use of tempol in prostate cancer (PCa). The present study investigated the effects of tempol on inflammation related to NF-κB signaling, using hormone-dependent or hormone-independent cell lines and the transgenic adenocarcinoma of the mouse prostate PCa animal model in the early and late stages of cancer progression.

METHODS

PC-3 and LnCaP cells were exposed to different tempol doses in vitro, and cell viability assays were performed. The optimal treatment dose was chosen for subsequent analysis using western blotting. Five experimental groups were evaluated in vivo to test for tempol effects in the early (CT12 and TPL12 groups) and late stages (CT20, TPL20-I, and TLP20-II) of PCa development. The TPL groups were treated with 50 or 100 mg/kg tempol. All control groups received water as the vehicle. The ventral lobe of the prostate was collected and subjected to immunohistochemical and western blot analysis.

RESULTS

Tempol treatment reduced cellular proliferation in vitro and improved prostatic morphology in vivo, thereby decreasing tumor progression. Tempol reduced inflammation in preclinical models, and downregulated the initial inflammatory signaling through toll-like receptors, not always mediated by the MyD88 pathway. In addition, it upregulated iκB-α and iκB -β levels, leading to a decrease in NF-κB, TNF-α, and other inflammatory markers. Tempol also influenced cell survival markers.

CONCLUSIONS

Tempol can be considered a beneficial therapy for PCa treatment owing to its anti-inflammatory and antiproliferative effects. Nevertheless, the action of tempol was different depending on the degree of the prostatic lesion in vivo and hormone reliance in vitro. This indicates that tempol plays a multifaceted role in the prostatic tissue environment.

Cilostazol attenuates oxidative stress and apoptosis in the quadriceps muscle of the dystrophic mouse experimental model

Duchenne muscular dystrophy (DMD) is the most severe and frequent form of muscular dystrophy. The mdx mouse is one of the most widely used experimental models to understand aspects of the biology of dystrophic skeletal muscles and the mechanisms of DMD. Oxidative stress and apoptosis are present in early stages of the disease in mdx mice. The high production of reactive oxygen species (ROS) causes activation of apoptotic death regulatory proteins due to DNA damage and breakdown of nuclear and mitochondrial membranes. The quadriceps (QUA) muscle of the mdx mouse is a good tool to study oxidative events. Previous studies have demonstrated that cilostazol exerts an anti-oxidant effect by decreasing the production of reactive oxygen species (ROS). The present study aimed to evaluate the ability of cilostazol to modulate oxidative stress and apoptosis in the QUA muscle of mdx mice. Fourteen-day-old mdx mice received cilostazol or saline for 14 days. C57BL/10 mice were used as a control. In the QUA muscle of mdx mice, cilostazol treatment decreased ROS production (-74%), the number of lipofuscin granules (-47%), lipid peroxidation (-11%), and the number of apoptotic cells (-66%). Thus cilostazol showed anti-oxidant and anti-apoptotic action in the QUA muscle of mdx mice.

The new challenge of “exercise + X″ therapy for Duchenne muscular dystrophy—Individualized identification of exercise tolerance and precise implementation of exercise intervention

Duchenne muscular dystrophy (DMD) is an X-linked recessive fatal muscular disease. Gene therapy, cell therapy, and drug therapy are currently the most widely used treatments for DMD. However, many experiments on animals and humans suggested that appropriate exercise could improve the effectiveness of such precision medicine treatment, thereby improving patient’s muscle quality and function. Due to the striated muscle damage of DMD individuals, there are still many debates about whether DMD animals or patients can exercise, how to exercise, when to exercise best, and how to exercise effectively. The purpose of this review is to summarize and investigate the scientific basis and efficacy of exercise as an adjuvant therapy for DMD gene therapy, cell therapy and drug therapy, as well as to present the theoretical framework and optional strategies of “exercise + X″″ combination therapy.

Antioxidant effects of bis-indole alkaloid indigo and related signaling pathways in the experimental model of Duchenne muscular dystrophy

Indigo is a bis-indolic alkaloid that has antioxidant and anti-inflammatory effects reported in literature and is a promissory compound for treating chronic inflammatory diseases. This fact prompted to investigate the effects of this alkaloid in the experimental model of Duchenne muscular dystrophy. The main aim of this study was to evaluate the potential role of the indigo on oxidative stress and related signaling pathways in primary skeletal muscle cell cultures and in the diaphragm muscle from mdx mice. The MTT and Neutral Red assays showed no indigo dose-dependent toxicities in mdx muscle cells at concentrations analyzed (3.12, 6.25, 12.50, and 25.00 μg/mL). Antioxidant effect of indigo, in mdx muscle cells and diaphragm muscle, was demonstrated by reduction in 4-HNE content, H2O2 levels, DHE reaction, and lipofuscin granules. A significant decrease in the inflammatory process was identified by a reduction on TNF and NF-κB levels, on inflammatory area, and on macrophage infiltration in the dystrophic sample, after indigo treatment. Upregulation of PGC-1α and SIRT1 in dystrophic muscle cells treated with indigo was also observed. These results suggest the potential of indigo as a therapeutic agent for muscular dystrophy, through their action anti-inflammatory, antioxidant, and modulator of SIRT1/PGC-1α pathway.

Cross-talk between TRPC-1, mTOR, PGC-1α and PPARδ in the dystrophic muscle cells treated with tempol

Background Ca2+ dysregulation and oxidative damage appear to have a central role in Duchenne muscular dystrophy (DMD) progression. The current study provides muscle cell-specific insights into the effect of Tempol on the TRPC 1 channel; on the positive and negative regulators of muscle cell differentiation; on the antioxidant enzymatic system; on the activators of mitochondrial biogenesis; and on the inflammatory process in the dystrophic primary muscle cells in culture.

METHODS

Mdx myotubes were treated with Tempol (5 mM) for 24 h. Untreated mdx myotubes and C57BL/10 myotubes were used as controls.

RESULTS

The Trypan Blue, MTT and Live/Dead Cell assays showed that Tempol (5 mM) presented no cytotoxic effect on the dystrophic muscle cells. The Tempol treated-mdx muscle cells showed significantly lower levels in the fluorescence intensity of intracellular calcium; TRPC-1 channel; MyoD; H₂O₂ and O₂^•- production; 4-HNE levels; SOD2, CAT and GPx levels; and TNF levels. On the other hand, SOD, CAT and GR mRNA relative expression were significantly higher in Tempol treated-mdx muscle cells. In addition, higher levels of Myogenin, MHC-Slow, mTOR, PGC-1α and PPARδ were also observed in Tempol treated-mdx muscle cells.

CONCLUSION

Our findings demonstrated that Tempol decreased intracellular calcium and oxidative stress in primary dystrophic muscle cells, promoting a cross-talk between TRPC-1, mTOR, PGC-1α and PPARδ.

XJB-5-131 Is a Mild Uncoupler of Oxidative Phosphorylation

BACKGROUND

Mitochondria (MT) are energy "powerhouses" of the cell and the decline in their function from oxidative damage is strongly correlated in many diseases. To suppress oxygen damage, we have developed and applied XJB-5-131 as a targeted platform for neutralizing reactive oxygen species (ROS) directly in MT. Although the beneficial activity of XJB-5-131 is well documented, the mechanism of its protective effects is not yet fully understood.

OBJECTIVE

Here, we elucidate the mechanism of protection for XJB-5-131, a mitochondrial targeted antioxidant and electron scavenger.

METHODS

The Seahorse Flux Analyzer was used to probe the respiratory states of isolated mouse brain mitochondria treated with XJB-5-131 compared to controls.

RESULTS

Surprisingly, there is no direct impact of XJB-5-131 radical scavenger on the electron flow through the electron transport chain. Rather, XJB-5-131 is a mild uncoupler of oxidative phosphorylation. The nitroxide moiety in XJB-5-131 acts as a superoxide dismutase mimic, which both extracts or donates electrons during redox reactions. The electron scavenging activity of XJB-5-131 prevents the leakage of electrons and reduces formation of superoxide anion, thereby reducing ROS.

CONCLUSION

We show here that XJB-5-131 is a mild uncoupler of oxidative phosphorylation in MT. The mild uncoupling property of XJB-5-131 arises from its redox properties, which exert a protective effect by reducing ROS-induced damage without sacrificing energy production. Because mitochondrial decline is a common and central feature of toxicity, the favorable properties of XJB-5-131 are likely to be useful in treating Huntington's disease and a wide spectrum of neurodegenerative diseases for which oxidative damage is a key component. The mild uncoupling properties of XJB-5-131 suggest a valuable mechanism of action for the design of clinically effective antioxidants.

The Interplay of Mitophagy and Inflammation in Duchenne Muscular Dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked neuromuscular disease caused by a pathogenic disruption of the DYSTROPHIN gene that results in non-functional dystrophin protein. DMD patients experience loss of ambulation, cardiac arrhythmia, metabolic syndrome, and respiratory failure. At the molecular level, the lack of dystrophin in the muscle results in myofiber death, fibrotic infiltration, and mitochondrial dysfunction. There is no cure for DMD, although dystrophin-replacement gene therapies and exon-skipping approaches are being pursued in clinical trials. Mitochondrial dysfunction is one of the first cellular changes seen in DMD myofibers, occurring prior to muscle disease onset and progresses with disease severity. This is seen by reduced mitochondrial function, abnormal mitochondrial morphology and impaired mitophagy (degradation of damaged mitochondria). Dysfunctional mitochondria release high levels of reactive oxygen species (ROS), which can activate pro-inflammatory pathways such as IL-1β and IL-6. Impaired mitophagy in DMD results in increased inflammation and further aggravates disease pathology, evidenced by increased muscle damage and increased fibrosis. This review will focus on the critical interplay between mitophagy and inflammation in Duchenne muscular dystrophy as a pathological mechanism, as well as describe both candidate and established therapeutic targets that regulate these pathways.