Assessment of mitochondrial respiratory chain enzymatic activities on tissues and cultured cells

Rapid and slow thawing of Takifugu rubripes fillets: TMT-labeled proteomics analysis, biochemical and morphological comparison

This study aimed to investigate how running water (rapid, R) and ice-water (slow, I) thawing methods affect the quality of Takifugu rubripes fillets. Thawing shrinkage and changes in extractable proteins quantified by tandem mass tag (TMT)-labeled quantitative proteomics were compared. The results showed that the rapidly thawed fillets were quickly underwent greater shrinkage, and the smaller gap areas were reduced by 7.5 % compared to slow thawing. Compared with fresh fish fillets, the outflow of proteins such as ATP synthase, NADH dehydrogenase, and aconitase within mitochondria increased in both thawing methods that presents cell membrane damage and significant disruptions in mitochondrial structure. The pyruvate dehydrogenase and cytochrome c were significantly upregulated in slow-thawing group. Whereas myosin and structural proteins including the Z-line related were significantly upregulated in the rapid-thawing group. These differential proteins serve as crucial markers for elucidating mechanism involved in muscle quality deterioration under different thawing conditions.

Mitochondrial complex I deficiency occurs in skeletal muscle of a subgroup of individuals with Parkinson's disease

BACKGROUND

Widespread neuronal mitochondrial complex I (CI) deficiency was recently reported to be a characteristic in a subgroup of individuals with idiopathic Parkinson's disease (PD). Here, we sought to determine whether a CI-deficient subgroup could be discerned using clinically accessible muscle biopsies. We further hypothesized that the inconsistency of previous findings of mitochondrial respiratory impairment in PD muscle may be due to interindividual variation, with respiratory deficiency only occurring in a subgroup of cases.

METHODS

Using a cross-sectional design, vastus lateralis needle biopsies were collected from 83 individuals with PD and 29 neurologically healthy controls and analyzed by immunohistochemistry for CI and complex IV (CIV), cytochrome c oxidase/succinate dehydrogenase (COX/SDH) histochemistry, and spectrophotometric activity assays of complexes I-IV. Mitochondrial DNA (mtDNA) copy number, deletions, and point variation were analyzed in single muscle fibers and bulk biopsy samples.

RESULTS

We show that PD muscle exhibits reduced CI activity at the group level, with 9% of cases falling below two standard deviations of the control group. In contrast, the activities of CII-CIV are not significantly different between the PD and control groups. No quantitative change of CI or CIV is detected, and the observed functional CI deficiency is not associated with mtDNA abnormalities.

CONCLUSIONS

Our findings support the existence of a PD subpopulation characterized by CI pathology in skeletal muscle and suggest that stratification by extra-neural mitochondrial dysfunction may be informative for selecting individuals for clinical trials.

Fructose-Induced Impairment of Liver and Skeletal Muscle Metabolism Is Prevented by Administration of Shouchella clausii Spores by Preserving Mitochondrial Function and Insulin Sensitivity

The objective of the study was to evaluate the efficacy of S. clausii spores (SF174) in counteracting the deleterious effects of dietary fructose. Thirty-days old male Wistar rats were treated for 6 weeks: control group: 0.5 mL of 10% sucrose solution (without probiotics); fructose group: 0.5 mL of 10% sucrose solution + high-fructose diet (without probiotics); SF174 group: 0.5 mL of 10% sucrose solution containing SF174 (5 × 10⁹ CFU) + high-fructose diet. Fructose intake induced an increase in proinflammatory cytokines in portal plasma, liver, and skeletal muscle, a decrease in insulin sensitivity in both tissues and a condition of hepatic steatosis. An increase in the mitochondrial activity in the liver and a decrease in skeletal muscle were evidenced, together with an increase in the thiobarbituric acid reactive substances (TBARS) levels and a decrease in the antioxidant enzyme activity. All the above alterations were counteracted by probiotic administration. We here demonstrate for the first time that S. clausii SF174 counteracts low-grade inflammation and insulin resistance induced by fructose, protects mitochondria from changes in oxidative capacity, and maintains unaltered the oxidative balance. Therefore, S. clausii SF174 administration can be an effective strategy to prevent the unhealthy consequences of dietary fructose.

Fucoxanthinol Mitigates the Cytotoxic Effect of Chlorpyrifos and MPTP on the Dopaminergic Differentiation of SH-SY5Y Human Neuroblastoma Cells

This study investigates the neuroprotective effects of fucoxanthinol (FXL) against the toxic activities of two compounds known to induce neurotoxic effects in humans and animals. MPTP (1-methyl- 4-phenyl- 1,2,3,6-tetrahydropyridine) induces Parkinson's disease (PD)-like phenotypes by inhibiting mitochondrial complex I in dopaminergic neurons. Chlorpyrifos (CPF), another neurotoxic agent, is associated with acute and long-term neurotoxicity primarily through acetylcholinesterase (AChE) inhibition. FXL demonstrated the ability to reverse the neurotoxic effects of CPF and MPTP in SH-SY5Y dopaminergic neuronal cell models. Treatment with FXL enhances mitochondrial function in SH-SY5Y cells exposed to CPF and MPTP, as demonstrated by increased levels of Adenosine triphosphate (ATP), mitochondrial membrane potential (MMP), mitochondrial complexes activities, and oxygen consumption rates, pyruvate dehydrogenase (PDH) activities, and mitophagy pathways. This improvement highlights FXL's ability to counteract the mitochondrial dysfunction induced by these neurotoxic agents. Additionally, FXL reduces oxidative damage and enhances cell viability. At the molecular level, the neuroprotective effects were also associated with the modulation of apoptotic cell markers, including Bcl- 2 and the oxidative damage markers. Molecular docking data further support the outcomes of our in vitro studies. Multivariable analysis highlights the neuroprotective effects of FXL. These findings indicate the potential of FXL to mitigate CPF- and MPTP-induced neurotoxicity, suggesting its promise as a therapeutic agent for managing neuronal damage observe in PD.

Attenuation of cisplatin-induced acute kidney injury by sanguinarine: modulation of oxidative stress, inflammation, and cellular damage

Introduction

Cisplatin (CP)-induced acute kidney injury (AKI) is a significant side effect of CP chemotherapy, driven by oxidative stress and inflammation. Sanguinarine (SANG), an alkaloid from the rhizomes of Sanguinaria canadensis and poppy-fumaria species, exhibits antioxidant and anti-inflammatory properties. This study examined SANG's effect on CP-induced AKI in mice and its underlying mechanisms.

Methods

Mice were orally administered 5 mg/kg SANG for 10 days. On the seventh day, they received a single intraperitoneal CP injection (20 mg/kg) and were sacrificed on the 11th day.

Results

SANG significantly improved CP-induced decreases in body weight, water intake, urine volume, relative kidney weight, creatinine clearance, albumin-to-creatinine ratio, and plasma urea and creatinine levels. It also reduced elevated plasma neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, cystatin C, and adiponectin levels, as well as renal markers of inflammation and oxidative stress induced by CP administration. SANG normalized kidney mitochondrial dysfunction, DNA damage, and apoptosis caused by CP. It also inhibited the CP-induced increase in the expression of phosphorylated nuclear factor-κB and autophagy markers in the kidney. Histological analysis showed that SANG reduced acute tubular necrosis and intraluminal protein accumulation due to CP.

Discussion

In conclusion, SANG mitigated CP-induced AKI by reducing inflammation, oxidative stress, DNA damage, apoptosis, and autophagy. Pending more comprehensive pharmacological and toxicological assessments, SANG may be regarded as a potential therapeutic agent for mitigating CP-induced AKI.

Recent advances in the role of gasotransmitters in necroptosis

Necroptosis is a finely regulated programmed cell death process involving complex molecular mechanisms and signal transduction networks. Among them, receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein are the key molecules regulating this process. In recent years, gasotransmitters such as nitric oxide, carbon monoxide and hydrogen sulfide have been suggested to play a regulatory role in necroptosis. This paper reviews the evidence that these gasotransmitters are involved in the regulation of necroptosis by influencing the production of reactive oxygen species, regulating the modification of S subunits of RIPK1 and RIPK3, regulating inflammatory mediators, and signal transduction. In addition, this review explores the potential therapeutic applications of these gasotransmitters in pathological conditions such as cardiovascular disease and ischemia-reperfusion injury. Although some studies have revealed the important role of gasotransmitters in necroptosis, the specific mechanism of action is still not fully understood. Future research is needed to further elucidate the molecular mechanisms of gasotransmitters in precisely regulating necroptosis, which will help develop new therapeutic strategies to prevent and treat related diseases.

Vitamin D Alleviates Heavy Metal-Induced Cytotoxic Effects on Human Bone Osteoblasts Via the Induction of Bioenergetic Disruption, Oxidative Stress, and Apoptosis

Cadmium (Cd) and lead (Pb) are heavy metals (HMs) that persistently contaminate the ecosystem, and bioaccumulation in bones is a health concern. We used biochemical and molecular assays to assess the cytoprotective effect of vitamin D (VD) on Cd- and Pd-induced chemical toxicity of human bone osteoblasts in vitro. Exposing Cd and Pb to human osteoblast cultures at concentrations of 0.1-1000 µM for 24-72 h significantly reduced osteoblast viability in an exposure time- and concentration-dependent manner. The cytotoxic effect of Cd on osteoblasts was more severe than Pb's, with 72-h exposure estimated half maximal effective concentration (EC50) of 8 and 12 µM, respectively, and VD (1 and 10 nM) alleviated cytotoxicity. Bioenergetics assays of ATP, mitochondrial membrane potential, and mitochondrial complex I and III activity showed that both Cd and Pb (1 and 10 µM) inhibited cellular bioenergetics after 72-h exposure. Cd and Pb increased lipid peroxidation and reactive oxygen species with reduced catalase/superoxide dismutase antioxidant activities and increased activity of caspases -3, -8, and -9. Co-treatment with VD (1 and 10 nM) counteracted bioenergetic disruption, oxidative damage, and apoptosis in a concentration-dependent manner. These findings suggest that VD is effective in managing the toxic effects of environmental pollutants and in treating bone diseases characterized by oxidative stress, apoptosis, and bioenergetic disruption.

Xanthocillin X Dimethyl Ether Exhibits Anti-Proliferative Effect on Triple-Negative Breast Cancer by Depletion of Mitochondrial Heme

Triple-negative breast cancer (TNBC) presents a significant therapeutic challenge due to the absence of specific targeted treatments. In this study, we explored the therapeutic potential of xanthocillin X dimethyl ether (XanDME), a naturally occurring isocyanide isolated from the marine fungus Scedosporium apiospermum, on TNBC. To elucidate the underlying mechanism, we initially demonstrated that XanDME directly binds to hemin, the oxidized form of heme, in vitro, corroborating previous reports. This interaction led to the depletion of intracellular regulatory heme. We further established that XanDME translocates into the mitochondria, where it interacts with crucial hemoproteins, namely cytochromes. The binding of XanDME with mitochondrial cytochromes disrupts the electron transport chain (ETC), inhibits the activity of mitochondrial complexes, and inactivates mitochondrial respiration. The inhibitory activity of XanDME on mitochondrial function significantly contributes to its anti-TNBC effects, as observed both in vitro and in vivo. Our study underscores the potential of XanDME against TNBC, warranting further investigations.

Could the inhibition of systemic NLRP3 inflammasome mediate central redox effects of yerba mate? An in silico and pre-clinical translational approach

ETHNOPHARMACOLOGICAL RELEVANCE

Empirically, Ilex paraguariensis A. St. Hil, or yerba-mate, has been used by natives of South America as a stimulant. Nowadays, this plant has gained popularity due to its neuroprotective effects. However, there are few studies on the biochemical-molecular mechanisms of action involved in its effect.

AIM OF THE STUDY

Chemically characterize an aqueous extract of yerba mate (YME) and evaluate if it could suppress the aberrant inflammatory response related to neurodegeneration.

MATERIALS AND METHODS

Macrophages and microglia cells were exposed to lipopolysaccharide (LPS; 100 ng/mL) plus nigericin (100 μM) or quinolinic acid (QA; 5 mM). Cellular viability, oxidative, and inflammatory markers were evaluated. Chemical matrix (HPLC - DAD), antioxidant activity, safety profile in vitro and in vivo, and an in silico docking of main targets were also assessed.

RESULTS

Pre-treatment with YME (15 μg/mL) prevented impairments in redox metabolism and inflammatory markers in BV-2 cells. In macrophages, YME showed similar results to MCC950, an inflammasome inhibitor. YME presented 282.88 mg EAG/g total phenolic content and a redox capacity of 32.94 ± 1.30 μg/mL (IC50), and its major compounds were chlorogenic acid > rutin > ferulic acid > catechin > sinapic acid. Chlorogenic acid and rutin presented a high affinity to the MCC950 region. Additionally, YME did not cause genotoxicity and was safe in vivo.

CONCLUSION

YME has significantly affected macrophages and microglia by regulating the NLRP3 inflammatory pathway.

Decreased Complex I Activity in Blood lymphocytes Correlates with Idiopathic Pulmonary Fibrosis Severity

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease linked to aging. Mitochondrial dysfunction in circulating T cells, often caused by disruption of mitochondrial DNA (mtDNA), may play a role in age-related conditions like IPF. In our previous study, we found high mtDNA mutational loads in blood lymphocytes from IPF patients, especially in regions critical for mtDNA expression. Since Complex I of the electron transport chain, partly encoded by mtDNA, is essential for energy production, we conducted a preliminary study on its activity. We found significantly reduced Complex I activity (p < 0.001) in lymphocytes from 40 IPF patients compared to 40 controls, which was positively correlated with lung function decline, specifically in functional vital capacity and diffusing capacity for carbon monoxide. These findings indicate that T cell mitochondrial dysfunction is associated with disease progression in IPF. Future work will explore the mechanisms linking T cell mitochondrial disruption with fibrosis, potentially uncovering new therapeutic targets.

Selenoprotein O Promotes Melanoma Metastasis and Regulates Mitochondrial Complex II Activity

Evolutionarily conserved selenoprotein O (SELENOO) catalyzes a posttranslational protein modification known as AMPylation that is essential for the oxidative stress response in bacteria and yeast. Given that oxidative stress experienced in the blood limits survival of metastasizing melanoma cells, SELENOO might be able to affect metastatic potential. However, further work is needed to elucidate the substrates and functional relevance of the mammalian homolog of SELENOO. In this study, we revealed that SELENOO promotes cancer metastasis and identified substrates of SELENOO in mammalian mitochondria. In patients with melanoma, high SELENOO expression was correlated with metastasis and poor overall survival. In a murine model of spontaneous melanoma metastasis, SELENOO deficiency significantly reduced metastasis to distant visceral organs, which could be rescued by treatment with the antioxidant N-acetylcysteine. Mechanistically, SELENOO AMPylated multiple mitochondrial substrates, including succinate dehydrogenase subunit A, one of the four key subunits of mitochondrial complex II. Consistently, SELENOO-deficient cells featured increased mitochondrial complex II activity. Together, these findings demonstrate that SELENOO deficiency limits melanoma metastasis by modulating mitochondrial function and oxidative stress. Significance: SELENOO alters mitochondrial function and supports metastasis in melanoma, highlighting the impact of SELENOO-mediated posttranslational modification of mitochondrial substrates and selenoproteins in cancer progression.

Reduced expression of the serotonin transporter impacts mitochondria in a sexually dimorphic manner

Neuropsychiatric and neurodevelopmental disorders are complex conditions that arise from a variety of interacting genetic and environmental factors. Among these factors, altered serotonergic signalling and mitochondrial dysfunction are strongly implicated, with a growing body of evidence to suggesting that serotonergic signalling is an important regulator of mitochondrial biogenesis. The serotonin transporter (SERT) functions to regulate synaptic 5-HT, and human allelic variants of the serotonin reuptake transporter-linked polymorphic region (5-HTTLPR) are associated with reduced SERT expression and increased susceptibility for developing neuropsychiatric disorders. Using the heterozygous (HET) variant of the SERT knockout rat to model reduced SERT expression, Western blotting was used to measure the abundance of TOMM20 and the complex I protein MT-CO1 as metrics for mitochondrial mass and abundance of respiratory complex IV. Mitochondrial activity was determined by dye reduction. We found sex-based and region-specific differences in mitochondrial mass and activity and that male and females show differing responses to reduced SERT expression. Our findings suggest that the sexually dimorphic differences in serotonergic signalling impact mitochondrial function and that these differences may be important for understanding sex differences in neuropsychiatric and neurodevelopmental disorders.

Fucoxanthin mitigates mercury-induced mitochondrial toxicity in the human ovarian granulosa cell line

Mercury (Hg) is known to be a hazardous toxin with a significant negative impact on female reproduction through mechanisms that remain unclear. The carotenoid fucoxanthin (FX) is an antioxidant with several positive effects on human health. This study aimed to examine the potential protective role of FX in reducing the Hg-induced bioenergetic disturbances in a human ovarian granulosa cell line model. (methods briefly) Hg was found to reduce the viability of granulosa cells in a concentration-dependent manner, with an estimated 72-hour EC50 of 10 µM. In contrast, FX (10 and 20 µM) improved cell viability. Hg (1 and 10 µM) significantly reduced cellular ATP levels, mitochondrial membrane potential, oxygen consumption rates, and lactate production. Additionally, Hg impaired the activities and kinetics of mitochondrial complexes I and III and reduced the expression of mitochondrial genes ND1, ND5, cytochrome B, cytochrome C oxidase, and ATP synthase subunits 6 and 8. According to tests on mitochondrial membranes, Hg increased membrane fluidity by reducing saturated fatty acid levels and increasing those of unsaturated fatty acids. Hg also promoted mitochondrial swelling and enhanced the inner mitochondrial membrane permeability to hydrogen and potassium ions. FX (10 µM) was shown to mitigate the negative effects of Hg on the viability of treated granulosa cells, bioenergetics parameters, and mitochondrial membrane integrity in a concentration-dependent manner. Based on these findings, bioenergetic disruption may be a key underlying cause of Hg-induced ovarian dysfunction. Furthermore, FX may have a potential therapeutic role in treating ovarian disorders caused by Hg-induced disruption of granulosa cell bioenergetics.

Interactive effects of elevated temperature and venlafaxine on mitochondrial respiration and enzymatic capacity in Nile tilapia (Oreochromis niloticus)

Warming events are becoming more frequent and extreme in aquatic environments worldwide. Concurrently, many environments are polluted with biologically active compounds such as pharmaceuticals. Understanding how these challenges interact is critical for understanding the climate crisis, as contaminants may modulate how ectotherms respond to heat stress or vice versa. One potential site for these heat × contaminant interactions is the mitochondrion, which is central to metabolism, implicated in thermal tolerance, and evolutionarily conserved. Using high-resolution respirometry, we investigated how acute warming (to 35 °C, 40 °C, or 45 °C from 25 °C) impacted the respiration, coupling, and metabolic capacity of liver mitochondria isolated from Nile tilapia, and how exposure to environmentally relevant levels of the ubiquitous antidepressant venlafaxine modulated those effects. Mitochondria exposed to hotter temperatures had higher respiration rates and decreased respiratory control ratio compared to mitochondria exposed to cooler temperatures. The depressive effects of venlafaxine on respiration rates through complex I and II or complex II only (State 3 and State 4), as well as complex IV-linked respiration, were mild except in mitochondria exposed to high temperatures, suggesting an interactive effect of warming and contaminant exposure. Finally, we found that the maximal enzyme activity of intact mitochondria (represented by mitochondrial respiration) showed a different pattern of response to warming and venlafaxine compared to its underlying components (as reflected by the activity of succinate dehydrogenase [complex II] and cytochrome c oxidase [complex IV]), demonstrating the value of incorporating both interactive and reductive approaches in understanding how mitochondria cope with anthropogenic changes in the environment.

Functional compartmentalization of hepatic mitochondrial subpopulations during MASH progression

The role of peridroplet mitochondria (PDM) in diseased liver, such as during the progression of metabolic dysfunction-associated steatohepatitis (MASH), remains unknown. We isolated hepatic cytoplasmic mitochondria (CM) and PDM from a mouse model of diet-induced MASLD/MASH to characterize their functions from simple steatosis to advanced MASH, using chow-fed mice as controls. Our findings show an inverse relationship between hepatic CM and PDM levels from healthy to steatosis to advanced MASH. Proteomics analysis revealed these two mitochondrial populations are compositionally and functionally distinct. We found that hepatic PDM are more bioenergetically active than CM, with higher pyruvate oxidation capacity in both healthy and diseased liver. Higher respiration capacity of PDM was associated with elevated OXPHOS protein complexes and increased TCA cycle flux. In contrast, CM showed higher fatty acid oxidation capacity with MASH progression. Transmission electron microscopy revealed larger and elongated mitochondria during healthy and early steatosis, which appeared small and fragmented during MASH progression. These changes coincided with higher MFN2 protein levels in hepatic PDM and higher DRP1 protein levels in hepatic CM. These findings highlight the distinct roles of hepatic CM and PDM in MASLD progression towards MASH.

Mitochondrial Dysfunction in Neurodegenerative Diseases

Mitochondrial dysfunction represents a pivotal characteristic of numerous neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. These conditions, distinguished by unique clinical and pathological features, exhibit shared pathways leading to neuronal damage, all of which are closely associated with mitochondrial dysfunction. The high metabolic requirements of neurons make even minor mitochondrial deficiencies highly impactful, driving oxidative stress, energy deficits, and aberrant protein processing. Growing evidence from genetic, biochemical, and cellular investigations associates impaired electron transport chain activity and disrupted quality-control mechanisms, such as mitophagy, with the initial phases of disease progression. Furthermore, the overproduction of reactive oxygen species and persistent neuroinflammation can establish feedforward cycles that exacerbate neuronal deterioration. Recent clinical research has increasingly focused on interventions aimed at enhancing mitochondrial resilience-through antioxidants, small molecules that modulate the balance of mitochondrial fusion and fission, or gene-based therapeutic strategies. Concurrently, initiatives to identify dependable mitochondrial biomarkers seek to detect pathological changes prior to the manifestation of overt symptoms. By integrating the current body of knowledge, this review emphasizes the critical role of preserving mitochondrial homeostasis as a viable therapeutic approach. It also addresses the complexities of translating these findings into clinical practice and underscores the potential of innovative strategies designed to delay or potentially halt neurodegenerative processes.

Grape Seed Extract Pretreatment Prevents Mitochondrial Dysfunction and NLRP3 Inflammasome-Induced Inflammatory Response in Glial Cells Exposed to Paroxetine and Quinolinic Acid

Depression is a neuropsychiatric disorder that affects thousands of people around the world. Drug therapy is the main approach for treating this disease, but its use can cause side effects on cells. This study aimed to examine the impact of antidepressant drugs from different classes on glial (BV-2) cells in the presence or absence of grape seed extract (GSE) and quinolinic acid (QA; 1.5 mM). Cells were treated with GSE (50 μg/mL; 23 h) and then exposed to non-cytotoxic concentrations of bupropion, imipramine, paroxetine, trazodone, and venlafaxine (27-181 µM; 1 h). Principal Component Analysis (PCA) was conducted to demonstrate the best combination of drug and extract treatment. Cell viability, adenosine triphosphate (ATP) production, reactive oxygen species (ROS) and nitric oxide (NO) levels, oxidative damage to lipids (TBARS), superoxide dismutase (SOD) activity, apoptosis, and NLR family pyrin domain containing 3 (NLRP3) genetic expression were evaluated by spectrophotometry, qRT-PCR, or flow cytometry. Mitochondrial markers (CI: NADH-CoQ reductase and CIV: cytochrome c oxidase) were also studied. GSE prevented the increment in levels of ROS (13.73-72.11%), TBARS (44.1-92.77%), NO (9.5-16%), SOD (68.44-212.29%) activity, and apoptosis (10.06-17.3%) caused by antidepressant drugs. Furthermore, it prevented impairments in complexes I (22-71.5%) and IV (7.5-92.5%) activities and ATP production (8-46%). GSE also prevented the NLRP3 overexpression in BV-2 activated by QA (62%), and paroxetine (46%), defined by PCA. Our study evidences that GSE can restore redox equilibrium and prevent inflammation caused by antidepressants and/or QA in a glial microenvironment.

Formation of I2+III2 supercomplex rescues respiratory chain defects

Mitochondrial electron transport chain (ETC) complexes partition between free complexes and quaternary assemblies known as supercomplexes (SCs). However, the physiological requirement for SCs and the mechanisms regulating their formation remain controversial. Here, we show that genetic perturbations in mammalian ETC complex III (CIII) biogenesis stimulate the formation of a specialized extra-large SC (SC-XL) with a structure of I2+III2, resolved at 3.7 Å by cryoelectron microscopy (cryo-EM). SC-XL formation increases mitochondrial cristae density, reduces CIII reactive oxygen species (ROS), and sustains normal respiration despite a 70% reduction in CIII activity, effectively rescuing CIII deficiency. Consequently, inhibiting SC-XL formation in CIII mutants using the Uqcrc1DEL:E258-D260 contact site mutation leads to respiratory decompensation. Lastly, SC-XL formation promotes fatty acid oxidation (FAO) and protects against ischemic heart failure in mice. Our study uncovers an unexpected plasticity in the mammalian ETC, where structural adaptations mitigate intrinsic perturbations, and suggests that manipulating SC-XL formation is a potential therapeutic strategy for mitochondrial dysfunction.

CRISPR-Cas9 mediated knockout of NDUFS4 in human iPSCs: A model for mitochondrial complex I deficiency

Mitochondrial diseases, often caused by defects in complex I (CI) of the oxidative phosphorylation system, currently lack curative treatments. Human-relevant, high-throughput drug screening platforms are crucial for the discovery of effective therapeutics, with induced pluripotent stem cells (iPSCs) emerging as a valuable technology for this purpose. Here, we present a novel iPSC model of NDUFS4-related CI deficiency that displays a strong metabolic phenotype in the pluripotent state. Human iPSCs were edited using CRISPR-Cas9 to target the NDUFS4 gene, generating isogenic NDUFS4 knockout (KO) cell lines. Sanger sequencing detected heterozygous biallelic deletions, whereas no indel mutations were found in isogenic control cells. Western blotting confirmed the absence of NDUFS4 protein in KO iPSCs and CI enzyme kinetics showed a ~56 % reduction in activity compared to isogenic controls. Comprehensive metabolomic profiling revealed a distinct metabolic phenotype in NDUFS4 KO iPSCs, predominantly associated with an elevated NADH/NAD+ ratio, consistent with alterations observed in other models of mitochondrial dysfunction. Additionally, β-lapachone, a recognized NAD+ modulator, alleviated reductive stress in KO iPSCs by modifying the redox state in both the cytosol and mitochondria. Although undifferentiated iPSCs cannot fully replicate the complex cellular dynamics of the disease seen in vivo, these findings highlight the utility of iPSCs in providing a relevant metabolic milieu that can facilitate early-stage, high-throughput exploration of therapeutic strategies for mitochondrial dysfunction.

Melatonin induces fiber switching by improvement of mitochondrial oxidative capacity and function via NRF2/RCAN/MEF2 in the vastus lateralis muscle from both sex Zücker diabetic fatty rats

The positive role of melatonin in obesity control and skeletal muscle (SKM) preservation is well known. We recently showed that melatonin improves vastus lateralis muscle (VL) fiber oxidative phenotype. However, fiber type characterization, mitochondrial function, and molecular mechanisms that underlie VL fiber switching by melatonin are still undefined. Our study aims to investigate whether melatonin induces fiber switching by NRF2/RCAN/MEF2 pathway activation and mitochondrial oxidative metabolism modulation in the VL of both sex Zücker diabetic fatty (ZDF) rats. 5-Weeks-old male and female ZDF rats (N = 16) and their age-matched lean littermates (ZL) were subdivided into two subgroups: control (C) and orally treated with melatonin (M) (10 mg/kg/day) for 12 weeks. Interestingly, melatonin increased oxidative fibers amounts (Types I and IIa) counteracting the decreased levels found in the VL of obese-diabetic rats, and upregulated NRF2, calcineurin and MEF2 expression. Melatonin also restored the mitochondrial oxidative capacity increasing the respiratory control ratio (RCR) in both sex and phenotype rats through the reduction of the proton leak component of respiration (state 4). Melatonin also improved the VL mitochondrial phosphorylation coefficient and modulated the total oxygen consumption by enhancing complex I, III and IV activity, and fatty acid oxidation (FAO) in both sex obese-diabetic rats, decreasing in male and increasing in female the complex II oxygen consumption. These findings suggest that melatonin treatment induces fiber switching in SKM improving mitochondrial functionality by NRF2/RCAN/MEF2 pathway activation.

Co-delivery of curcumin-resveratrol-carnosic acid complex promotes neurogenesis and cognitive recovery in a rodent model of repeated mild traumatic brain injury

Repeated traumatic brain injury has grown in importance as sports-related injuries have increased. Repetitive mild TBI (rmTBI) increases the risk of developing neurodegenerative diseases such as Alzheimer's and Parkinson's diseases, as well as chronic comorbidities like PTSD, depression, substance abuse and neuroendocrine functions. However, no effective therapeutic strategies have been reported for the effective management of TBI. Herein, we examined the effectiveness of co-delivery of the phytonutrients curcumin, trans-resveratrol, and carnosic acid as a bioavailable complex (CGM+) in managing rmTBI in the rodent model. The rats were randomly assigned to sham, rmTBI, and CGM+ (300 mg/kg b.wt.) groups for a total of 21 days. On Days 6 and 7, all animals, except those in the sham group, were subjected to repeated mild traumatic brain injury (rmTBI). The CGM+ group received supplementation throughout the 21 days, while the other groups received a vehicle. Neurological severity score (NSS) was assessed 24 h after the last injury, and behavioral tests were completed within 14 days post-injury. Samples for the biochemical analysis were collected after euthanasia. CGM+ supplementation significantly decreased the sensory-motor deficits associated with rmTBI. Following TBI, the CGM+ group demonstrated enhanced memory and low-stress levels. Furthermore, CGM+ has been shown to modulate neurotransmitter levels and promote neurogenesis. The biochemical and molecular analysis revealed that CGM+ promotes recovery following rmTBI by modulating mitochondrial bioenergetics and BDNF pathways. The findings indicate that CGM+ can be used to manage cognitive and sensory-motor defects caused by rmTBI, such as in the case of sports injuries.

Blackberry extract prevents lipopolysaccharide-induced depressive-like behavior in female mice: implications for redox status, inflammation, and brain enzymes

This study evaluated the effects of Rubus sp. extract on behavioral and neurochemical parameters in female mice submitted to experimental model of depression induced by lipopolysaccharide (LPS). The results indicated that Rubus sp. extract protected against depressive-like behavior induced by LPS. Moreover, the administration of Rubus sp. extract was effective in preventing the increase in reactive species and nitrites levels, as well as the decrease in catalase activity induced by LPS in the cerebral cortex. In the serum, the Rubus sp. extract was effective in preventing the decrease in catalase activity induced by LPS. Treatment with Rubus sp. extract attenuated the increase in acetylcholinesterase activity induced by LPS in the cerebral cortex. Finally, blackberry extract also downregulated IL-1β levels in cerebral cortex. In conclusion, our findings demonstrated that treatment with Rubus sp. exerted antidepressant, antioxidant, anticholinesterase and anti-inflammatory effects in a model of depressive - like behavior induced by LPS in female mice. This highlights Rubus sp. as a potential therapeutic agent for individuals with major depressive disorder.

Comparative analysis of cold-stored apheresis platelet units in additive solution with or without pathogen reduction: Implications of cytochrome c supplementation

BACKGROUND

Platelets are limited in supply, and the preservation of platelet function during storage remains challenging. Novel storage approaches are being explored to improve platelet quality, extend shelf life, and reduce risk of infection. This study sought to elucidate platelet function in cold-stored apheresis units in additive solution (platelet additive solution [PAS]) and subjected to pathogen reduction (PR) as well as the impact of cytochrome c (cyt c) supplementation. We hypothesized that the PR would decrease stored platelet function, regardless of cyt c supplementation.

METHODS

Platelet apheresis units (PAS) were collected (N = 5 volunteers) and divided into PR or no PR (PAS) and supplemented with vehicle or cyt c (100 μM). Units were stored at 4°C for 15 days, sequential aliquots were removed, and platelet/mitochondrial respiratory function and biochemical parameters were analyzed.

RESULTS

There was no difference in platelet aggregation in response to adenosine diphosphate between PAS and PR platelets. Aggregation function in response to arachidonic acid was higher in PR versus PAS platelets. Maximum clot strength was not different between PAS and PR from Day 0 to Day 5 but declined in PR platelets on Days 10 and 15. Oxygen consumption declined at the same rate in PAS and PR platelets, while rate of lactate and TCO 2 decrease was greater in PR platelets than in PAS platelets. Supplementation with cyt c did not alter platelet function or biochemical parameters in PAS or PR platelets.

CONCLUSION

Platelet additive solution and PR platelets show similar declines in respiratory capacity, and biochemical parameters during cold storage, but PR platelets demonstrated significantly increased arachidonic acid-induced aggregation across all time points. Further understanding this mechanism may provide a means to prolong platelet shelf life.

Selective deficiency of mitochondrial respiratory complex I subunits Ndufs4/6 causes tumor immunogenicity

Cancer cells frequently rewire their metabolism to support proliferation and evade immune surveillance, but little is known about metabolic targets that could increase immune surveillance. Here we show a specific means of mitochondrial respiratory complex I (CI) inhibition that improves tumor immunogenicity and sensitivity to immune checkpoint blockade (ICB). Targeted genetic deletion of either Ndufs4 or Ndufs6, but not other CI subunits, induces an immune-dependent growth attenuation in melanoma and breast cancer models. We show that deletion of Ndufs4 induces expression of the major histocompatibility complex (MHC) class I co-activator Nlrc5 and antigen presentation machinery components, most notably H2-K1. This induction of MHC-related genes is driven by a pyruvate dehydrogenase-dependent accumulation of mitochondrial acetyl-CoA, which leads to an increase in histone H3K27 acetylation within the Nlrc5 and H2-K1 promoters. Taken together, this work shows that selective CI inhibition restricts tumor growth and that specific targeting of Ndufs4 or Ndufs6 increases T cell surveillance and ICB responsiveness.

Mitochondrial diseases: from molecular mechanisms to therapeutic advances

Mitochondria are essential for cellular function and viability, serving as central hubs of metabolism and signaling. They possess various metabolic and quality control mechanisms crucial for maintaining normal cellular activities. Mitochondrial genetic disorders can arise from a wide range of mutations in either mitochondrial or nuclear DNA, which encode mitochondrial proteins or other contents. These genetic defects can lead to a breakdown of mitochondrial function and metabolism, such as the collapse of oxidative phosphorylation, one of the mitochondria's most critical functions. Mitochondrial diseases, a common group of genetic disorders, are characterized by significant phenotypic and genetic heterogeneity. Clinical symptoms can manifest in various systems and organs throughout the body, with differing degrees and forms of severity. The complexity of the relationship between mitochondria and mitochondrial diseases results in an inadequate understanding of the genotype-phenotype correlation of these diseases, historically making diagnosis and treatment challenging and often leading to unsatisfactory clinical outcomes. However, recent advancements in research and technology have significantly improved our understanding and management of these conditions. Clinical translations of mitochondria-related therapies are actively progressing. This review focuses on the physiological mechanisms of mitochondria, the pathogenesis of mitochondrial diseases, and potential diagnostic and therapeutic applications. Additionally, this review discusses future perspectives on mitochondrial genetic diseases.

Endonuclease G promotes hepatic mitochondrial respiration by selectively increasing mitochondrial tRNAThr production

Mitochondrial endonuclease G (EndoG) contributes to chromosomal degradation when it is released from mitochondria during apoptosis. It is presumed to also have a mitochondrial function because EndoG deficiency causes mitochondrial dysfunction. However, the mechanism by which EndoG regulates mitochondrial function is not known. Fat accumulation in metabolic dysfunction-associated steatotic liver disease (MASLD), which is more common in men, is caused in part by mitochondrial dysfunction. EndoG expression is reduced in MASLD liver, and EndoG deficiency causes MASLD in an obesity-independent manner but only in males. EndoG promotes mitochondrial respiration by resolving mitochondrial tRNA/DNA hybrids formed during mtDNA transcription by recruiting RNA helicase DHX30 to unwind them. EndoG also cleaves off the 3'-end of the H-strand transcript that can prevent mt-tRNAThr precursor cloverleaf-folding, and processing, which increases mt-tRNAThr production and mitochondrial translation. Using fluorescent lifetime imaging microscopy technology to visualize oxygen consumption at the individual mitochondrion level, we found that EndoG deficiency leads to the selective loss of a mitochondrial subpopulation with high-oxygen consumption. This defect was reversed with mt-tRNAThr supplementation. Thus, EndoG promotes mitochondrial respiration by selectively regulating the production of mt-tRNAThr in male mice.

Ndufs4 knockout mice with isolated complex I deficiency engage a futile adaptive brain response

Paediatric Leigh syndrome (LS) is an early-onset and fatal neurodegenerative disorder lacking treatment options. LS is frequently caused by mutations in the NDUFS4 gene, encoding an accessory subunit of mitochondrial complex I (CI), the first complex of the oxidative phosphorylation (OXPHOS) system. Whole-body Ndufs4 knockout (KO) mice (WB-KO mice) are widely used to study isolated CI deficiency, LS pathology and interventions. These animals develop a brain-specific phenotype via an incompletely understood pathomechanism. Here we performed a quantitative analysis of the sub-brain proteome in six-weeks old WB-KO mice vs. wildtype (WT) mice. Brain regions comprised of a brain slice (BrSl), cerebellum (CB), cerebral cortex (CC), hippocampus (HC), inferior colliculus (IC), and superior colliculus (SC). Proteome analysis demonstrated similarities between CC/HC, and between IC/SC, whereas BrSl and CB differed from these two groups and each other. All brain regions displayed greatly reduced levels of two CI structural subunits (NDUFS4, NDUFA12) and an increased level of the CI assembly factor NDUFAF2. The level of CI-Q module subunits was significantly more reduced in IC/SC than in BrSl/CB/CC/HC, whereas other OXPHOS complex levels were not reduced. Gene ontology and pathway analysis demonstrated specific and common proteome changes between brain regions. Across brain regions, upregulation of cold-shock-associated proteins, mitochondrial fatty acid (FA) oxidation and synthesis (mtFAS) were the most prominent. FA-related pathways were predominantly upregulated in CB and HC. Based upon these results, we argue that stimulation of these pathways is futile and pro-pathological and discuss alternative strategies for therapeutic intervention in LS. SIGNIFICANCE: The Ndufs4 knockout mouse model is currently the most relevant and most widely used animal model to study the brain-linked pathophysiology of human Leigh Syndrome (LS) and intervention strategies. We demonstrate that the Ndufs4 knockout brain engages futile and pro-pathological responses. These responses explain both negative and positive outcomes of intervention studies in Leigh Syndrome mice and patients, thereby guiding novel intervention opportunities.

Inducible and reversible SOD2 knockdown in mouse skeletal muscle drives impaired pyruvate oxidation and reduced metabolic flexibility

INTRODUCTION

Skeletal muscle mitochondrial dysfunction is a key characteristic of aging muscle and contributes to age related diseases such as sarcopenia, frailty, and type 2 diabetes. Mitochondrial oxidative stress has been implicated as a driving factor in these age-related diseases, however whether it is a cause, or a consequence of mitochondrial dysfunction remains to be determined. The development of flexible genetic models is an important tool to test the mechanistic role of mitochondrial oxidative stress on skeletal muscle metabolic dysfunction. We characterize a new model of inducible and reversible mitochondrial redox stress using a tetracycline controlled skeletal muscle specific short hairpin RNA targeted to superoxide dismutase 2 (iSOD2).

METHODS

iSOD2 KD and control (CON) animals were administered doxycycline for 3- or 12- weeks and followed for up to 24 weeks and mitochondrial respiration and muscle contraction were measured to define the time course of SOD2 KD and muscle functional changes and recovery.

RESULTS

Maximum knockdown of SOD2 protein occurred by 6 weeks and recovered by 24 weeks after DOX treatment. Mitochondrial aconitase activity and maximum mitochondrial respiration declined in KD muscle by 12 weeks and recovered by 24 weeks. There were no significant differences in antioxidant or mitochondrial biogenesis genes between groups. Twelve-week KD showed a small, but significant decrease in muscle fatigue resistance. The primary phenotype was reduced metabolic flexibility characterized by impaired pyruvate driven respiration when other substrates are present. The pyruvate dehydrogenase kinase inhibitor dichloroacetate partially restored pyruvate driven respiration, while the thiol reductant DTT did not.

CONCLUSION

We use a model of inducible and reversible skeletal muscle SOD2 knockdown to demonstrate that elevated matrix superoxide reversibly impairs mitochondrial substrate flexibility characterized by impaired pyruvate oxidation. Despite the bioenergetic effect, the limited change in gene expression suggests that the elevated redox stress in this model is confined to the mitochondrial matrix.

A Comparison of the Mitochondrial Performance between Migratory and Sedentary Mimid Thrushes

Birds exhibit a variety of migration strategies. Because sustained flapping flight requires the production of elevated levels of energy compared to typical daily activities, migratory birds are well-documented to have several physiological adaptations to support the energy demands of migration. However, even though mitochondria are the source of ATP that powers flight, the respiratory performance of the mitochondria is almost unstudied in the context of migration. We hypothesized that migratory species would have higher mitochondrial respiratory performance during migration compared to species that do not migrate. To test this hypothesis, we compared variables related to mitochondrial respiratory function between two confamilial bird species-the migratory Gray Catbird (Dumetella carolinensis) and the non-migratory Northern Mockingbird (Mimus polyglottos). Birds were captured at the same location along the Alabama Gulf Coast, where we assumed that Gray Catbirds were migrants and where resident Northern Mockingbirds live year-round. We found a trend in citrate synthase activity, which suggests that Gray Catbirds have a greater mitochondrial volume in their pectoralis muscle, but we observed no other differences in mitochondrial respiration or complex enzymatic activities between individuals from the migrant vs. the non-migrant species. However, when we assessed the catbirds included in our study using well-established indicators of migratory physiology, birds fell into two groups: a group with physiological parameters indicating a physiology of birds engaged in migration and a group with the physiology of birds not migrating. Thus, our comparison included catbirds that appeared to be outside of migratory condition. When we compared the mitochondrial performance of these three groups, we found that the mitochondrial respiratory capacity of migrating catbirds was very similar to that of Northern Mockingbirds, while the catbirds judged to be not migrating were lowest. One explanation for these observations is these species display very different daily flight behaviors. While the mockingbirds we sampled were not breeding nor migrating, they are highly active birds, living in the open and engaging in flapping flights throughout each day. In contrast, Gray Catbirds live in shrubs and fly infrequently when not migrating. Such differences in baseline energy needs likely confounded our attempt to study adaptations to migration.

Mechanisms that Alter Capacity for Adenosine Triphosphate Production and Oxidative Phosphorylation: Insights from Avian Migration

Avian migration is among the most energetically demanding feats observed in animals. Studies evaluating the physiological underpinnings of migration have repeatedly shown that migratory birds display numerous adaptations that ultimately supply the flight muscle mitochondria with abundant fuel and oxygen during long-distance flights. To make use of this high input, the organs and mitochondria of migrants are predicted to display several traits that maximize their capacity to produce adenosine triphosphate (ATP). This review aims to introduce readers to several mechanisms by which organs and mitochondria can alter their capacity for oxidative phosphorylation and ATP production. The role of organ size, mitochondrial volume, substrate, and oxygen delivery to the electron transport system are discussed. A central theme of this review is the role of changes in electron chain complex activity, mitochondrial morphology and dynamics, and supercomplexes in allowing avian migrants and other taxa to alter the performance of the electron transport system with predictable shifts in demand. It is my hope that this review will serve as a springboard for future studies exploring the mechanisms that alter bioenergetic capacity across animal species.

Detoxification of hydrogen sulfide by synthetic heme model compounds

Hydrogen sulfide is a lethal toxic gas that disrupts cellular respiration in the mitochondrial system. Currently, no antidote is available for the clinical treatment of hydrogen sulfide poisoning. In this study, we investigated the function of iron(III)porphyrin complexes as hydrogen sulfide scavengers in water and evaluated their potential use as therapeutic agents for hydrogen sulfide poisoning. The compounds, named met-hemoCD-P and met-hemoCD-I, are composed of iron(III)porphyrin complexed with per-methylated β-cyclodextrin dimers that contain a pyridine (met-hemoCD-P) or imidazole axial fifth ligand that is coordinated to Fe(III) (met-hemoCD-I). These compounds formed stable HS-Fe(III) complexes under physiological conditions, with binding constants of 1.2 × 105 and 2.5 × 106 M-1 for met-hemoCD-P and met-hemoCD-I, respectively. The binding constant of met-hemoCD-I was 10-times higher than that reported for native human met-hemoglobin at pH 7.4 and 25oC. Electron paramagnetic resonance (EPR) spectroscopy and H2S quantification assays revealed that after SH- was coordinated to met-hemoCD-I, it was efficiently converted to nontoxic sulfite and sulfate ions via homolytic cleavage of the HS-Fe(III) bond followed by aerobic oxidation. Mouse animal experiments revealed that the survival rate was significantly improved when NaSH-treated mice were injected with met-hemoCD-I. After the injection, mitochondrial CcO function in brain and heart tissues recovered, and met-hemoCD-I injected was excreted in the urine without chemical decomposition.

Consequences of Early Maternal Deprivation on Neuroinflammation and Mitochondrial Dynamics in the Central Nervous System of Male and Female Rats

Early life stress (ELS) is associated with an increased risk for neuropsychiatric disorders, and both neuroinflammation and mitochondrial dysfunction seem to be central to mental health. Herein, using an animal model of ELS, a single episode of maternal deprivation (MD, 24 h on pnd 9) extensively documented to elicit behavioural anomalies in male and female Wistar rats, we investigated its consequences in terms of neuroinflammation and mitochondrial dynamics in the prefrontal cortex (PFC) and the hippocampal formation (HCF). MD differentially affected the brain content of cytokines: MD induced a transient increase in pro-inflammatory cytokines (IL-1β and IL-6) in the PFC, as well as in the levels of the anti-inflammatory cytokine IL-10 in the HCF. MD also induced a significant decrease mitochondria citrate synthase activity, but MD did not exert significant changes in mitochondria Complex IV activity, revealing a generalized decrease in mitochondrial density without any change in mitochondrial respiration. In the present study, we demonstrate that MD induces neuroinflammatory processes in specific brain regions. Additional research is needed to better understand the temporal pattern of such changes, their impact on the developing brain, and their participation in the already well-known behavioural consequences of MD.

Autologous mitochondrial transplant for acute cerebral ischemia: Phase 1 trial results and review

The results of a Phase 1 trial of autologous mitochondrial transplantation for the treatment of acute ischemic stroke during mechanical thrombectomy are presented. Standardized methods were used to isolate viable autologous mitochondria in the acute clinical setting, allowing for timely transplantation within the ischemic window. No significant adverse events were observed with the endovascular approach during reperfusion therapy. Safety outcomes in study participants were comparable to those of matched controls who did not undergo transplantation. This study represents the first use of mitochondrial transplantation in the human brain, highlighting specific logistical challenges related to the acute clinical setting, such as limited tissue samples and constrained time for isolation and transplantation. We also review the opportunities and challenges associated with further clinical translation of mitochondrial transplantation in the context of acute cerebral ischemia and beyond.

Mitochondrial proteome analysis reveals that an augmented cytochrome c oxidase assembly and activity potentiates respiratory capacity in sarcoma

Mitochondrial oxidative phosphorylation (OXPHOS) is an obligatory process in sarcoma. Despite that, the metabolic programming of sarcoma mitochondria is still unknown. To obtain a comprehensive metabolic insight of mitochondria, we developed a mouse fibrosarcoma model by injecting 3-methylcholanthrene and compared mitochondrial proteomes between sarcoma and its contralateral normal muscle using mass spectrometry. Our study identified ∼449 proteins listed in the SwissProt databases, and all the data sets are available via ProteomeXchange with the identifier PXD044903. In sarcoma, 49 mitochondrial proteins were found differentially expressed, including 36 proteins up-regulated and 13 proteins down-regulated, with the significance of p-value <0.05 and the log2[fold change] > 1 and < -1 as compared to normal muscle. Our data revealed that various anaplerotic reactions actively replenish the TCA cycle in sarcoma. The comparative expression profile and Western blotting analysis of OXPHOS subunits showed that complex-IV subunits, MT-CO3 and COX6A1, were significantly up-regulated in sarcoma vs. normal muscle. Further, biochemical and physiological assays confirmed enhanced complex-IV specific enzymatic and supercomplex activities with a concomitant increase of oxygen consumption rate in sarcoma mitochondria compared to normal muscle. Validation with human post-operative sarcoma tissues also confirms an increased MT-CO3 expression compared to normal tissue counterparts. Thus, our data comprehensively analyses the mitochondrial proteome and identifies augmented complex-IV assembly and activity in sarcoma.

Biochemical Alterations and Motor Dysfunctions in Corpus Striatum of Rats Brain Exposed to Azo Dyes

Azo food dyes are prohibited in most countries, but their injudicious use is still reported particularly in the developing Nations. Continuous use of contaminated food raises health concerns and given this the present study designed to investigate the effects of 3 non-permitted azo dyes (metanil yellow - MY, malachite green - MG, and sudan III - SIII) on neurobehavioral, neurochemicals, mitochondrial dysfunction, oxidative stress, and histopathological changes in the corpus striatum of rats. Rats were grouped and treated with MY (430 mg/kg), MG (13.75 mg/kg), SIII (250 mg/kg) & mixture (YGR) (MY 143.33 + MG 4.52 + SIII 83.33 mg/kg) p.o. for 60 days showed a significant decrease in grip strength and motor activity, the activity of acetylcholinesterase (AChE), monoamine oxidase - B (MAO-B), and mitochondrial complex I and II compared to the control. The treated groups showed a significant increase in lipid peroxidation and a decrease in the level of reduced glutathione, superoxide dismutase, and catalase as compared to the control. Histopathology of the corpus striatum revealed immense damage. Data from the present study correlate between azo dyes and changes in the behavior of rats which have been associated with the altered biochemicals and neurochemicals activities. In conclusion, exposure to azo dyes caused neurotoxicity involving motor impairments associated with enhanced oxidative stress, mitochondrial dysfunctions, AChE and MAO-B inhibition, and neuronal damage in the corpus striatum of rats.

Melatonin Reduces Mito-Inflammation in Ischaemic Hippocampal HT22 Cells and Modulates the cGAS-STING Cytosolic DNA Sensing Pathway and FGF21 Release

Mitochondrial dysfunction is a key event in many pathological conditions, including neurodegenerative processes. When mitochondria are damaged, they release damage-associated molecular patterns (DAMPs) that activate mito-inflammation. The present study assessed mito-inflammation after in vitro oxygen-glucose deprivation as a representation of ischaemia, followed by reoxygenation (OGD/R) of HT22 cells and modulation of the inflammatory response by melatonin. We observed that melatonin prevented mitochondrial structural damage and dysfunction caused by OGD/R. Melatonin reduced oxidative damage and preserved the enzymatic activity for complexes I, III and IV, encoded by mitochondrial DNA, which were reduced by OGD/R. No effect was observed on complex II activity encoded by nuclear DNA. The release of mtDNA into the cytosol was also prevented with a consequent reduction of the cGAS-STING pathway and IFNβ and IL-6 production. Interestingly, melatonin also increased the early release of the fibroblast growth factor-21 (FGF-21), a mitokine secreted in response to mitochondrial stress. These data indicate that melatonin reduces mito-inflammation and modulates FGF-21 release, further highlighting the key role of this molecule in preserving mitochondrial integrity in OGD/R deprivation-type ischaemic brain injury.

Risperidone-induced bioenergetic disruption in the isolated human peripheral blood monocytes

Risperidone (RIS) is a widely used antipsychotic drug with reported alteration in immune response. The current study investigated mitochondrial disruption as the underlying mechanism of RIS-induced immunotoxicity in isolated human peripheral blood monocytes (hPBM). RIS was cytotoxic to hPBM in exposure duration and concentration-dependent patterns. Functionally, RIS was shown to increase the release of IL-6, TNF-α, and IL-8 with a decrease in test particle phagocytosis in concertation and exposure time-based patterns. It was found that RIS decreased ATP production in isolated monocytes' mitochondria, with an estimated EC50 of around 70 μM after 24 h with parallel inhibition of mitochondrial complexes I and III activities and decreased mitochondrial membrane potential and oxygen consumption rates with increased lactate production from by the treated cells in comparison to controls. Structurally, RIS in 100 μM concentration significantly increased the mitochondrial membrane fluidity with significant increase in increased unsaturated/saturated fatty acids ratios of the mitochondrial membranes of the treated cells. Interestingly, water-soluble CoQ10 formulation significantly decreased the cytotoxic effect of RIS and improved the phagocytic activity of RIS-treated cells. To conclude, the current data suggests mitochondrial disruption as the underlying mechanism of RIS-induced immunotoxicity with shown protective effect of water-soluble CoQ10 formulation.

Fucoxanthin alleviates the cytotoxic effects of cadmium and lead on a human osteoblast cell line

OBJECTIVE

Cadmium (Cd) and lead (Pb) are non-biodegradable heavy metals (HMs) that persistently contaminate ecosystems and accumulate in bones, where they exert harmful effects. This study aimed to investigate the protective effect of fucoxanthin (FX) against the chemical toxicity induced by Cd and Pb in human bone osteoblasts in vitro, using various biochemical and molecular assays.

METHODS

The effect of metals and FX on osteoblasts viability was assayed by MTT, then the effect of Pb, Cd, and FX on the cells' mitochondrial parameters was studied via assays for ATP, mitochondrial membrane potential (MMP), mitochondrial complexes, and lactate production. Also, the effect of metals on oxidative stress was assessed by reactive oxygen species, lipid peroxidation and antioxidant enzymes assays. Also the effect of FX and metals on apoptosis caspases and related genes was assessed.

RESULTS

When Cd and Pb were added to human osteoblast cultures at concentrations ranging from 1-20 μM for 72 h, they significantly reduced osteoblast viability in a time and concentration-dependent manner. The cytotoxic effect of Cd on osteoblasts was greater than that of Pb, with estimated EC50 of 8 and 12 μM, respectively, after 72 h of exposure. FX (10 and 20 μM) alleviated the cytotoxicity of the metals. Bioenergetics assays, including ATP, MMP, and mitochondrial complexes I and III activities, revealed that HMs at 1 and 10 μM concentrations inhibited cellular bioenergetics after 72 h of exposure. Cd and Pb also increased lipid peroxidation and reactive oxygen species while reducing catalase and superoxide dismutase antioxidant activities and oxidative stress-related genes. This was accompanied by increased caspases -3, -8, and - 9 and Bax/bCl-2 ratio. Co-treatment with FX (10 and 20 μM) mitigated the disruption of bioenergetics, oxidative damage, and apoptosis induced by the metals, showing a concentration-dependent pattern to varying extents.

CONCLUSION

These findings strongly support the role of FX in managing toxicities induced by environmental pollutants in bones and in addressing bone diseases associated with molecular bases of oxidative stress, apoptosis, and bioenergetic disruption.

Structural basis of respiratory complex adaptation to cold temperatures

In response to cold, mammals activate brown fat for respiratory-dependent thermogenesis reliant on the electron transport chain. Yet, the structural basis of respiratory complex adaptation upon cold exposure remains elusive. Herein, we combined thermoregulatory physiology and cryoelectron microscopy (cryo-EM) to study endogenous respiratory supercomplexes from mice exposed to different temperatures. A cold-induced conformation of CI:III2 (termed type 2) supercomplex was identified with a ∼25° rotation of CIII2 around its inter-dimer axis, shortening inter-complex Q exchange space, and exhibiting catalytic states that favor electron transfer. Large-scale supercomplex simulations in mitochondrial membranes reveal how lipid-protein arrangements stabilize type 2 complexes to enhance catalytic activity. Together, our cryo-EM studies, multiscale simulations, and biochemical analyses unveil the thermoregulatory mechanisms and dynamics of increased respiratory capacity in brown fat at the structural and energetic level.

Mass Spectrometry Probe Combined with Machine Learning to Capture the Relationship between Metabolites and Mitochondrial Complex Activity at the Whole-Cell Level

Mitochondrial complex activity controls a multitude of physiological processes by regulating the cellular metabolism. Current methods for evaluating mitochondrial complex activity mainly focus on single metabolic reactions within mitochondria. These methods often require fresh samples in large quantities for mitochondria purification or intact mitochondrial membranes for real-time monitoring. Confronting these limitations, we shifted the analytical perspective toward interactive metabolic networks at the whole-cell level to reflect mitochondrial complex activity. To this end, we compiled a panel of mitochondrial respiratory chain-mapped metabolites (MRCMs), whose perturbations theoretically provide an overall reflection on mitochondrial complex activity. By introducing N-dimethyl-p-phenylenediamine and N-methyl-p-phenylenediamine as a pair of mass spectrometry probes, an ultraperformance liquid chromatography-tandem mass spectrometry method with high sensitivity (LLOQ as low as 0.2 fmol) was developed to obtain accurate quantitative data of MRCMs. Machine learning was then combined to capture the relationship between MRCMs and mitochondrial complex activity. Using Complex I as a proof-of-concept, we identified NADH, alanine, and phosphoenolpyruvate as metabolites associated with Complex I activity based on the whole-cell level. The effectiveness of using their concentrations to reflect Complex I activity was further validated in external data sets. Hence, by capturing the relationship between metabolites and mitochondrial complex activity at the whole-cell level, this study explores a novel analytical paradigm for the interrogation of mitochondrial complex activity, offering a favorable complement to existing methods particularly when sample quantities, type, and treatment timeliness pose challenges. More importantly, it shifts the focus from individual metabolic reactions within mitochondria to a more comprehensive view of an interactive metabolic network, which should serve as a promising direction for future research into the functional architecture between mitochondrial complexes and metabolites.

40 Hz light preserves synaptic plasticity and mitochondrial function in Alzheimer's disease model

Alzheimer's disease (AD) is the most prevalent type of dementia. Its causes are not fully understood, but it is now known that factors like mitochondrial dysfunction, oxidative stress, and compromised ion channels contribute to its onset and progression. Flickering light therapy has shown promise in AD treatment, though its mechanisms remain unclear. In this study, we used a rat model of streptozotocin (STZ)-induced AD to evaluate the effects of 40 Hz flickering light therapy. Rats received intracerebroventricular (ICV) STZ injections, and 7 days after, they were exposed to 40 Hz flickering light for 15 min daily over seven days. Cognitive and memory functions were assessed using Morris water maze, novel object recognition, and passive avoidance tests. STZ-induced AD rats exhibited cognitive decline, elevated reactive oxygen species, amyloid beta accumulation, decreased serotonin and dopamine levels, and impaired mitochondrial function. However, light therapy prevented these effects, preserving cognitive function and synaptic plasticity. Additionally, flickering light restored mitochondrial metabolites and normalized ATP-insensitive mitochondrial calcium-sensitive potassium (mitoBKCa) channel activity, which was otherwise downregulated in AD rats. Our findings suggest that 40 Hz flickering light therapy could be a promising treatment for neurodegenerative disorders like AD by preserving synaptic and mitochondrial function.

Coptisine exerts anti-tumour effects in triple-negative breast cancer by targeting mitochondrial complex I

BACKGROUND AND PURPOSE

Triple-negative breast cancer (TNBC) has a poor prognosis due to limited therapeutic options. Recent studies have shown that TNBC is highly dependent on mitochondrial oxidative phosphorylation. The aim of this study was to investigate the potential of coptisine, a novel compound that inhibits the complex I of the mitochondrial electron transport chain (ETC), as a treatment for TNBC.

EXPERIMENTAL APPROACH

In this study, mitochondrial metabolism in TNBC was analysed by bioinformatics. In vitro and in vivo experiments (in mice) were conducted to evaluate the potential of coptisine as an ETC complex I-targeting therapeutic agent and to investigate the molecular mechanisms underlying coptisine-induced mitochondrial dysfunction. The therapeutic effect of coptisine was assessed in TNBC cells and xenograft mouse model.

KEY RESULTS

We demonstrated that mitochondrial ETC I was responsible for this metabolic vulnerability in TNBC. Furthermore, a naturally occurring compound, coptisine, exhibited specific inhibitory activity against this complex I. Treatment with coptisine significantly inhibited mitochondrial functions, reprogrammed cellular metabolism, induced apoptosis and ultimately inhibited the proliferation of TNBC cells. Additionally, coptisine administration induced prominent growth inhibition that was dependent on the presence of a functional complex I in xenograft mouse models.

CONCLUSION AND IMPLICATIONS

Altogether, these findings suggest the promising potential of coptisine as a potent ETC complex I inhibitor to target the metabolic vulnerability of TNBC.

Candida albicans PPR proteins are required for the expression of respiratory Complex I subunits

Pentatricopeptide repeat (PPR) proteins bind RNA and are present in mitochondria and chloroplasts of Eukaryota. In fungi, they are responsible for controlling mitochondrial genome expression, mainly on the posttranscriptional level. Candida albicans is a human opportunistic pathogen with a facultative anaerobic metabolism which, unlike the model yeast Saccharomyces cerevisiae, possesses mitochondrially encoded respiratory Complex I (CI) subunits and does not tolerate loss of mtDNA. We characterized the function of 4 PPR proteins of C. albicans that lack orthologs in S. cerevisiae and found that they are required for the expression of mitochondrially encoded CI subunits. We demonstrated that these proteins localize to mitochondria and are essential to maintain the respiratory capacity of cells. Deletion of genes encoding these PPR proteins results in changes in steady-state levels of mitochondrial RNAs and proteins. We demonstrated that C. albicans cells lacking CaPpr4, CaPpr11, and CaPpr13 proteins show no CI assembly, whereas the lack of CaPpr7p results in a decreased CI activity. CaPpr13p is required to maintain the bicistronic NAD4L-NAD5 mRNA, whereas the other 3 PPR proteins are likely involved in translation-related assembly of mitochondrially encoded CI subunits. In addition, we show that CaAep3p, which is an ortholog of ScAep3p, performs the evolutionary conserved function of controlling expression of the ATP8-ATP6 mRNA. We also show that C. albicans cells lacking PPR proteins express a higher level of the inducible alternative oxidase (AOX2) which likely rescues respiratory defects and compensates for oxidative stress.

Omega-3 Attenuates Disrupted Neurotransmission and Partially Protects Metabolic Dysfunction Caused by Obesity in Wistar Rats

Omega-3 (n3) is a polyunsaturated fatty acid well known for its anti-inflammatory and neuroprotective properties. Obesity is linked to chronic inflammation that disrupts metabolism, the intestine physiology and the central nervous system functioning. This study aims to determine if n3 supplementation can interfere with the effects of obesity on the mitochondrial activity, intestinal barrier, and neurotransmitter levels in the brain of Wistar rats that received cafeteria diet (CAF). We examined adipose tissue, skeletal muscle, plasma, intestine, and the cerebral cortex of four groups: CT (control diet), CTn3 (control diet with n3 supplementation), CAF, and CAFn3 (CAF and n3). Diets were offered for 13 weeks, with n3 supplementation in the final 5 weeks. Adipose tissue Electron Transport Chain complexes I, II, and III showed higher activity in CAF groups, as did complexes III and IV in skeletal muscle. Acetate levels in plasma were reduced in CAF groups, and Lipopolysaccharide (LPS) was higher in the CAF group but reduced in CAFn3 group. Claudin-5 in the intestine was lower in CAF groups, with no n3 supplementation effect. In the cerebral cortex, dopamine levels were decreased with CAF, which was reversed by n3. DOPAC, a dopamine metabolite, also showed a supplementation effect, and HVA, a diet effect. Serotonin levels increased in the CAF group that received supplementation. Therefore, we demonstrate disturbances in mitochondria, plasma, intestine and brain of rats submitted to CAF and the potential benefit of n3 supplementation in endotoxemia and neurotransmitter levels.

Mitochondrial transplantation attenuates lipopolysaccharide-induced acute respiratory distress syndrome

BACKGROUND

The mitochondria are essential organelles not only providing cellular energy in the form of ATP, but also regulating the inflammatory response and the cell death program. Mitochondrial dysfunction has been associated with various human diseases, including metabolic syndromes as well as inflammatory and neurodegenerative diseases. Acute respiratory distress syndrome (ARDS) is an acute pulmonary disorder characterized by uncontrolled alveolar inflammation, apoptotic lung epithelial/endothelial cells, and pulmonary edema. Despite the high mortality of ARDS, an effective pharmacotherapy to treat this disease has not been established yet. Therefore, identifying a novel targeted therapy for ARDS is important. Recently, exogenous mitochondrial transplantation was reported to be beneficial for treating mitochondrial dysfunction. The current study aimed to investigate the therapeutic effect of mitochondrial transplantation on ARDS in vitro and in vivo.

METHODS

Mitochondria were isolated from human stem cells. For in vitro efficacy of mitochondrial transplantation on the inflammation and cell death, murine alveolar macrophages MH-S and human pulmonary microvascular endothelial cells HPMECs were exposed to LPS, respectively. The ARDS mice model established by a single intratracheal instillation of LPS was used for in vivo efficacy of intravenously treated mitochondria.

RESULTS

Our results showed that the mitochondria isolated from human stem cells exhibited an anti-inflammatory effect against alveolar macrophages and an anti-apoptotic effect against the alveolar epithelial cells. Furthermore, intravenous mitochondrial treatment was associated with the attenuation of lung injury in the LPS-induced ARDS mice.

CONCLUSION

Dual effects of mitochondria on anti-inflammation and anti-apoptosis support the potential of mitochondrial transplantation as a novel therapeutic strategy for ARDS.

Inducible and reversible SOD2 knockdown in mouse skeletal muscle drives impaired pyruvate oxidation and reduced metabolic flexibility

Introduction

Skeletal muscle mitochondrial dysfunction is a key characteristic of aging muscle and contributes to age related diseases such as sarcopenia, frailty, and type 2 diabetes. Mitochondrial oxidative distress has been implicated as a driving factor in these age-related diseases, however whether it is a cause, or a consequence of mitochondrial dysfunction remains to be determined. The development of more flexible genetic models is an important tool to test the mechanistic role of mitochondrial oxidative stress on skeletal muscle metabolic dysfunction. We characterize a new model of inducible and reversible mitochondrial redox stress using a tetracycline controlled skeletal muscle specific short hairpin RNA targeted to superoxide dismutase 2 (iSOD2).

Methods

iSOD2 KD and control (CON) animals were administered doxycycline for 3- or 12- weeks and followed for up to 24 weeks and mitochondrial respiration and muscle contraction were measured to define the time course of SOD2 KD and muscle functional changes and recovery.

Results

Maximum knockdown of SOD2 protein occurred by 6 weeks and recovered by 24 weeks after DOX treatment. Mitochondrial aconitase activity and maximum mitochondrial respiration declined in KD muscle by 12 weeks and recovered by 24 weeks. There were minimal changes in gene expression between KD and CON muscle. Twelve-week KD showed a small, but significant decrease in muscle fatigue resistance. The primary phenotype was reduced metabolic flexibility characterized by impaired pyruvate driven respiration when other substrates are present. The pyruvate dehydrogenase kinase inhibitor dichloroacetate partially restored pyruvate driven respiration, while the thiol reductant DTT did not.

Conclusion

We use a model of inducible and reversible skeletal muscle SOD2 knockdown to demonstrate that elevated matrix superoxide reversibly impairs mitochondrial substrate flexibility characterized by impaired pyruvate oxidation. Despite the bioenergetic effect, the limited change in gene expression suggests that the elevated redox stress in this model is confined to the mitochondrial matrix.

N-acetylaspartate promotes glycolytic-to-oxidative fiber-type switch and resistance to atrophic stimuli in myotubes

N-acetylaspartate (NAA) is a neuronal metabolite that can be extruded in extracellular fluids and whose blood concentration increases in several neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Aspartoacylase (ASPA) is the enzyme responsible for NAA breakdown. It is abundantly expressed in skeletal muscle and most other human tissues, but the role of NAA catabolism in the periphery is largely neglected. Here we demonstrate that NAA treatment of differentiated C2C12 muscle cells increases lipid turnover, mitochondrial biogenesis and oxidative metabolism at the expense of glycolysis. These effects were ascribed to NAA catabolism, as CRISPR/Cas9 ASPA KO cells are insensitive to NAA administration. Moreover, the metabolic switch induced by NAA was associated with an augmented resistance to atrophic stimuli. Consistently with in vitro results, SOD1-G93A ALS mice show an increase in ASPA levels in those muscles undergoing the glycolytic to oxidative switch during the disease course. The impact of NAA on the metabolism and resistance capability of myotubes supports a role for this metabolite in the phenotypical adaptations of skeletal muscle in neuromuscular disorders.

Neurotoxic mechanisms of dexamethasone in SH-SY5Y neuroblastoma cells: Insights into bioenergetics, oxidative stress, and apoptosis

Despite the known therapeutic uses of dexamethasone (DEX), the specific mechanisms underlying its neurotoxic effects in neuronal cells, particularly in undifferentiated human neuroblastoma (SH-SY5Y) cells, remain inadequately understood. This study aims to elucidate these mechanisms, emphasizing bioenergetics, oxidative stress, and apoptosis, thereby providing novel insights into the cellular vulnerabilities induced by chronic DEX exposure. The findings revealed significant reductions in cell viability, altered membrane integrity with LDH leakage, decreased intracellular ATP production, and the electron transport chain complexes I and III activity inhibition. DEX significantly increased the release of the reactive species and peroxidation of lipids, as well as of Nrf2 expression. At the same time, it simultaneously led to a decline in the activities of the antioxidant catalase and superoxide dismutase enzymes, along with a depletion of glutathione reserves. The apoptosis process was exhibited by a significant elevation of caspases 3 and 8 activities with overexpression of mRNA BAX, inhibition of BCL-2, and a significant upregulation of the BAX/BCL-2 ratio. Assessment of neuronal development genes (GAP43, CAMK2A, CAMK2B, TUBB3, and Wnts) by quantitative PCR assay showed increased expression of CAMK2A, CAMK2B, and Wnt3a with a significant reduction in GAP43 mRNA levels. Collectively, this study proved that DEX was cytotoxic to SH-SY5Y via bioenergetic disruption, mitochondrial dysfunction, oxidative stress, and apoptosis.

Effects of polyvinyl chloride and low-density polyethylene microplastics on oxidative stress and mitochondria function of earthworm (Eisenia fetida)

Plastics are widely used worldwide due to their convenience. However, microplastics (MPs) accumulation poses a serious threat to ecosystem health. Therefore, understanding the effects of MPs on living organisms within their native ecosystem is crucial. Previous studies have primarily focused on the impacts of MPs in aquatic environments, whereas the effects of MPs on terrestrial ecosystems have remained largely understudied. Therefore, our study assessed the impacts of MPs on soil ecosystems by characterizing their toxic effects on earthworms (Eisenia fetida). Here, we exposed earthworms to two representative plastics within soil environments: polyvinyl chloride (PVC) and low-density polyethylene (LDPE). Given the known link between MPs and oxidative stress, we next quantified oxidative stress markers and mitochondrial function to assess the effects of MPs on the redox metabolism of earthworms. Mitochondria are crucial metabolic organelles that generate reactive oxygen species via uncontrolled ATP production. Our findings demonstrated that MPs exert different effects depending on their type. Neither the PVC-exposed groups nor the LDPE-exposed groups exhibited changes in oxidative stress, as worked by the action of superoxide dismutase (SOD) and glutathione (GSH). While treatment of the two types of MP did not significantly affect the amount of reactive oxygen species/reactive nitrogen species (ROS/RNS) generated, PVC exhibited a more pronounced effect on antioxidant system compared to LDPE. However, mitochondrial function was markedly decreased in the group exposed to high LDPE concentrations, suggesting that the examined LDPE concentrations were too low to activate compensatory mechanisms. Collectively, our findings demonstrated that exposure of MPs not only influences the antioxidant defense mechanisms of earthworms but also alters their mitochondrial function depending on their types.