Mitochondrial Respiratory Chain Activity Research Articles

Distinct Essentiality of the Mitochondrial Respiratory Chain in Proliferating Cells in Vivo

Mitochondrial respiratory chain (RC) activity is essential for in vivo cell proliferation, particularly in cancer, CD4+ and CD8+ T cells, and endothelial cells involving ATP production and biosynthesis. The RC is essential for the oxidative tricarboxylic acid (TCA) cycle to produce intermediates that funnel into anabolic pathways to synthesize lipids, proteins, and nucleotides. By contrast, mitochondrial respiration has a distinct role in other proliferating cells including regulatory T cells (Tregs) and stem cells whereby mitochondria are dispensable for in vivo cell proliferation but determine cell fate and function through several signaling mechanisms. In this review, we discuss how the mitochondrial RC is an anabolic engine that supports the proliferation of cancer cells, CD4+ and CD8+ T cells, and endothelial cells while mitochondria serve as central hubs that integrate metabolic signals to control Treg and stem cell fate and function in vivo.

Systemic messenger RNA replacement therapy is effective in a novel clinically relevant model of acute intermittent porphyria developed in non-human primates

ObjectiveAcute intermittent porphyria (AIP) is a rare metabolic disorder caused by haploinsufficiency of hepatic porphobilinogen deaminase (PBGD), the third enzyme of the heme biosynthesis. Individuals with AIP experience neurovisceral attacks...

Strobilurin X acts as an anticancer drug by inhibiting protein synthesis and suppressing mitochondrial respiratory chain activity

PurposeStrobilurins act as antifungal agents by inhibiting the mitochondrial respiratory chain. The cytotoxic activity of strobilurins, focusing on its anticancer activities, has been reported. However, the mechanisms involved in these activities remain unclear.MethodsThe cytotoxic effects of strobilurin X isolated from the mycelium of Mucidula. venosolamellata were examined in human cancer cell lines (A549 and HeLa) and normal fibroblasts (WI-38).ResultsStrobilurin X significantly decreased the viability of A549 and HeLa cells compared to that in the WI-38 cells after 48 h of exposure. The EC50 values for cytotoxicity in the A549, HeLa, and WI-38 cells were 3.4, 5.4, and 16.8 μg/mL, respectively. Strobilurin X inhibited the mitochondrial respiratory chain and enhanced the release of lactate in the A549 cells. The IC50 value of strobilurin X against the mitochondrial respiratory chain complex III activity was 139.8 ng/mL. The cytotoxicity induced by strobilurin X was not completely rescued after adding uridine, methyl pyruvate, or N-acetyl cysteine. Furthermore, pharmacological approaches demonstrated that strobilurin X failed to modulate the mitogen-activated protein kinase family and phosphoinositide 3-kinase-Akt pathways; alternatively, it suppressed protein synthesis independent of uridine.ConclusionStrobilurin X induced cytotoxicity by blocking the mitochondrial respiratory chain and suppressing protein synthesis. These findings may aid in the development of novel anticancer drugs using strobilurins.

Mitochondrial citrate transporters Ctp1-Yhm2 and respiratory chain: A coordinated functional connection in Saccharomyces cerevisiae metabolism

The mitochondrial inner membrane contains some hydrophobic proteins that mediate the exchange of metabolites between the mitochondrial matrix and the cytosol. Ctp1 and Yhm2 are two carrier proteins in the yeast Saccharomyces cerevisiae responsible for the transport of citrate, a tricarboxylate involved in several metabolic pathways.Since these proteins also contribute to respiratory metabolism, in this study we investigated for the first time whether changes in citrate transport can affect the structural organization and functional properties of respiratory complexes.Through experiments in yeast mutant cells in which the gene encoding Ctp1 or Yhm2 was deleted, we found that in the absence of either mitochondrial citrate transporter, mitochondrial respiration was impaired. Structural analysis of the respiratory complexes III and IV revealed different expression levels of the catalytic and supernumerary subunits in the Δctp1 and Δyhm2 strains. In addition, Δyhm2 mitochondria appeared to be more sensitive than Δctp1 to the oxidative damage.Our results provide the first evidence for a coordinated modulation of mitochondrial citrate transport and respiratory chain activity in S. cerevisiae metabolism.

Tetrahedral framework nucleic acids’ role in facilitating chronic diabetic wound repair via the endoplasmic reticulum-mitochondrial pathway

Under diabetic circumstances, keratinocytes are constantly exposed to hyperglycaemic micromilieu, leading to disrupted differentiation and increased chronic wound susceptibility during to sustained endoplasmic reticulum (ER) stress (ERS) and mitochondrial dysfunction during hyperglycaemia. As mitochondrial respiratory chain activity is a primary generator of intracellular reactive oxygen species (ROS), we postulated that tFNAs could potentially boost mitochondrial function and energy metabolism in the presence of oxidative stress. To this end, we first explored the ER-mitochondrial (ER-MITO) axis-associated intracellular transportation of tetrahedral framework nucleic acids (tFNAs). tFNAs are transported to the ER and mitochondria via caveolae-mediated endocytosis, thereby regulating the ER-MITO axis. Additionally, tFNAs reduce ERS by downregulating PERK-ATF 4-CHOP, thereby stabilising mitochondrial dynamics, improving energy metabolism, maintaining membrane potential polarisation, and scavenging generated reactive oxygen species to counteract oxidative stress during hyperglycaemia. Consequently, tFNAs restore cell proliferation, migration, and differentiation and enhance chronic wound healing and skin graft survival. Furthermore, tFNAs repaired the diabetic skin mechanical barrier, underscoring their versatility of ER-MITO axis modulation. Overall, this study highlights the importance of tFNAs in ER-MITO axis modulation and a novel therapeutic approach for chronic diabetic wound healing.

Exploring the Interplay between Mitochondrial DNA and Lifestyle Factors in the Pathogenesis of Psychiatric Disorders

The objectives of this study were to investigate the interaction of mitochondrial DNA (mtDNA) and lifestyle factors in the development of psychiatric disorders and to gain greater insight into their pathogenesis and comorbidity. We analyzed data from approximately 150,000 individuals from the UK Biobank. Mitochondrial gene-by-environment interaction studies (mtGEIS) were performed to assess the relationships between mtDNA and psychiatric disorders, such as anxiety, depression, and self-harm. These disorders were defined using diagnostic and severity indicators derived from the General Anxiety Disorder (GAD-7) and Patient Health Questionnaire (PHQ-9). Smoking and drinking behaviors were characterized based on UK Biobank criteria. For the mtGEIS, logistic and linear regression models from PLINK 2.0 were employed, accounting for covariates like age, sex, PC1-10, Townsend Deprivation Index (TDI), and educational attainment. We also conducted sex-stratified analyses to detect any gender-specific effects. Our findings highlighted significant associations between mtDNA and three psychiatric disorders. Moreover, the interplay between mtDNA and lifestyle factors showed significant associations with psychiatric disorders (all P values < 0.05). Specifically, two mutant loci, T5004C (BAnx_self=−0.0026, BDep_self=−0.0024, BSelf−harm=−0.0018) and G9123A (BAnx_self=−0.0030, BDep_self=−0.0024, BSelf−harm=−0.0017), were found to reduce the risk of three disorders after interacting with alcohol. Sex-specific differences were also observed. In summary, the expression of mitochondrial genes could be modulated by lifestyle factors like smoking and drinking, potentially affecting psychiatric disorders. These habits might influence mitochondrial respiratory chain activity and the replication and transcriptional regulation of mitochondrial genes, culminating in changes in mitochondrial functionality and subsequently psychiatric disorders.

Mitochondrial Esterase Activity Measured at the Single Organelle Level by Nano-flow Cytometry.

Monitoring mitochondrial esterase activity is crucial not only for investigating mitochondrial metabolism but also for assessing the effectiveness of mitochondrial-targeting prodrugs. However, accurately detecting esterase activity within mitochondria poses challenges due to its ubiquitous presence in cells and the uncontrolled localization of fluorogenic probes. To overcome this hurdle and reveal variations among different mitochondria, we isolated mitochondria and preserved their activity and functionality in a buffered environment. Subsequently, we utilized a laboratory-built nano-flow cytometer in conjunction with an esterase-responsive calcein-AM fluorescent probe to measure the esterase activity of individual mitochondria. This approach enabled us to investigate the influence of temperature, pH, metal ions, and various compounds on the mitochondrial esterase activity without any interference from other cellular constituents. Interestingly, we observed a decline in the mitochondrial esterase activity following the administration of mitochondrial respiratory chain inhibitors. Furthermore, we found that mitochondrial esterase activity was notably higher in the presence of a high concentration of ATP compared to that of ADP and AMP. Additionally, we noticed a correlation between elevated levels of complex IV and increased mitochondrial esterase activity. These findings suggest a functional connection between the mitochondrial respiratory chain and mitochondrial esterase activity. Moreover, we detected an upsurge in mitochondrial esterase activity during the early stages of apoptosis, while cellular esterase activity decreased. This highlights the significance of analyzing enzyme activity within specific organelle subregions. In summary, the integration of a nano-flow cytometer and fluorescent dyes introduces a novel method for quantifying mitochondrial enzyme activity with the potential to uncover the alterations and unique functions of other mitochondrial enzymes.

Combining Porous Se@SiO2 Nanocomposites and dECM Enhances the Myogenic Differentiation of Adipose-Derived Stem Cells.

Volumetric Muscle Loss (VML) denotes the traumatic loss of skeletal muscle, a condition that can result in chronic functional impairment and even disability. While the body can naturally repair injured skeletal muscle within a limited scope, patients experiencing local and severe muscle loss due to VML surpass the compensatory capacity of the muscle itself. Currently, clinical treatments for VML are constrained and demonstrate minimal efficacy. Selenium, a recognized antioxidant, plays a crucial role in regulating cell differentiation, anti-inflammatory responses, and various other physiological functions. We engineered a porous Se@SiO2 nanocomposite (SeNPs) with the purpose of releasing selenium continuously and gradually. This nanocomposite was subsequently combined with a decellularized extracellular matrix (dECM) to explore their collaborative protective and stimulatory effects on the myogenic differentiation of adipose-derived mesenchymal stem cells (ADSCs). The influence of dECM and NPs on the myogenic level, reactive oxygen species (ROS) production, and mitochondrial respiratory chain (MRC) activity of ADSCs was evaluated using Western Blot, ELISA, and Immunofluorescence assay. Our findings demonstrate that the concurrent application of SeNPs and dECM effectively mitigates the apoptosis and intracellular ROS levels in ADSCs. Furthermore, the combination of dECM with SeNPs significantly upregulated the expression of key myogenic markers, including MYOD, MYOG, Desmin, and myosin heavy chain in ADSCs. Notably, this combination also led to an increase in both the number of mitochondria and the respiratory chain activity in ADSCs. The concurrent application of SeNPs and dECM effectively diminishes ROS production, boosts mitochondrial function, and stimulates the myogenic differentiation of ADSCs. This study lays the groundwork for future treatments of VML utilizing the combination of SeNPs and dECM.

Regular exercise attenuates alcoholic myopathy in zebrafish by modulating mitochondrial homeostasis.

Alcoholic myopathy is caused by chronic consumption of alcohol (ethanol) and is characterized by weakness and atrophy of skeletal muscle. Regular exercise is one of the important ways to prevent or alleviate skeletal muscle myopathy. However, the beneficial effects and the exact mechanisms underlying regular exercise on alcohol myopathy remain unclear. In this study, a model of alcoholic myopathy was established using zebrafish soaked in 0.5% ethanol. Additionally, these zebrafish were intervened to swim for 8 weeks at an exercise intensity of 30% of the absolute critical swimming speed (Ucrit), aiming to explore the beneficial effects and underlying mechanisms of regular exercise on alcoholic myopathy. This study found that regular exercise inhibited protein degradation, improved locomotion ability, and increased muscle fiber cross-sectional area (CSA) in ethanol-treated zebrafish. In addition, regular exercise increases the functional activity of mitochondrial respiratory chain (MRC) complexes and upregulates the expression levels of MRC complexes. Regular exercise can also improve oxidative stress and mitochondrial dynamics in zebrafish skeletal muscle induced by ethanol. Additionally, regular exercise can activate mitochondrial biogenesis and inhibit mitochondrial unfolded protein response (UPRmt). Together, our results suggest regular exercise is an effective intervention strategy to improve mitochondrial homeostasis to attenuate alcoholic myopathy.

Dietary Marine Hydrolysate Improves Memory Performance and Social Behavior through Gut Microbiota Remodeling during Aging.

Aging is characterized by a decline in social behavior and cognitive functions leading to a decrease in life quality. In a previous study, we show that a fish hydrolysate supplementation prevents age-related decline in spatial short-term memory and long-term memory and anxiety-like behavior and improves the stress response in aged mice. The aim of this study was to determine the effects of a fish hydrolysate enriched with EPA/DHA or not on the cognitive ability and social interaction during aging and the biological mechanisms involved. We showed for the first time that a fish hydrolysate enriched with EPA/DHA or not improved memory performance and preference for social novelty that were diminished by aging. These changes were associated with the modulation of the gut microbiota, normalization of corticosterone, and modulation of the expression of genes involved in the mitochondrial respiratory chain, circadian clock, neuroprotection, and antioxidant activity. Thus, these changes may contribute to the observed improvements in social behavior and memory and reinforced the innovative character of fish hydrolysate in the prevention of age-related impairments.

Diversities in Leigh Syndrome Associated with MT-ATP6 Gene Variants.

Leigh syndrome (LS) is clinically and genetically heterogeneous and presents defective mitochondrial bioenergetics. Patients present neurological symptoms and imagiological features that may result in early death [1]. The LS has been associated with mitochondrial DNA (mtDNA) variants, e.g., m.8993T>G (L156R) and m.8993T>C (L156P), in the MT-ATP6 gene. They lead to the substitution of a highly conserved amino acid in subunit 6 of ATP synthase, affecting the F0 domain and ATP synthesis [1-3]. We present five cases with m.8993T>G and a family harbouring m.8993T>C+m.1555A>G (proband and four relatives). Our laboratory received 48 samples from LS-suspected patients. The samples (various tissues) were assessed for bioenergetics (activity of mitochondrial respiratory chain (MRC) complexes, ubiquinone content) and genetic analyses (mtDNA copy number, Sequencing and PCR-RFLP) by established protocols. Bioenergetics were assessed in 5 patients (various tissues) with varying levels of MRC/ATP synthase impairment. Six cases had a mtDNA pathogenic variant in the 8993 nucleotide associated with LS. Five cases presented the m.8993T>G variant, one of which (P5) possibly de novo. This variant was homoplasmy (P1-3) or very high heteroplasmy (P4/5, 90-95%). Of the four patients with bioenergetics assessment, three (P1/3/4) had deficiencies of MRC complexes, and P5 had small deficits. The other case (familial, proband and 4 relatives) presented a combination of m.1555A>G (homoplasmy) and m.8993T>C (heteroplasmy) variants. The proband presents m.8993T>C in 95% heteroplasmy and 85-35% in three relatives. All have m.1555A>G in homoplasmy, including the fourth relative without m.8993T>C. A deficiency (31%) was found in complex V activity in muscle for proband. We present a case series of patients harbouring pathogenic variants in the 8993 nucleotide of mtDNA, which have been associated with LS and impairment of MRC's complex V. These cases highlight the variability in clinical symptoms and their severity, as well as genetic heterogeneity within LS. Many patients will not present a classic pathogenic variant and there are many cases of asymptomatic relatives (carriers). It is important to get a broader view of the cases - classical methods and multiple tissue analysis are still valuable tools for the comprehensive characterization of patients.

Mitochondrial respiratory chain activity is associated with severity, corticosteroid response and prognosis of alcoholic hepatitis.

Little is known about the extent of mitochondrial respiratory chain (MRC) activity dysfunction in patients with alcoholic hepatitis (AH). We aimed to assess the hepatic MRC activity in AH patients and its potential impact on the severity and prognosis of this life-threatening liver disease. MRC complexes were measured in liver biopsies of 98 AH patients (non-severe, 17; severe, 81) and in 12 histologically normal livers (NL). Severity was assessed according to Maddrey's Index and MELD score. Corticosteroid response rate and cumulative mortality were also evaluated. The activity of the five MRC complexes was markedly decreased in the liver of AH patients compared with that of NL subjects, being significantly lower in patients with severe AH than in those with non-severe AH. There was a negative correlation between the activity of all MRC complexes and the severity of AH. Interestingly, only complex I and III activities showed a significant positive correlation with the corticosteroid response rate and a significant negative correlation with the mortality rate at all-time points studied. In a multivariate regression analysis, besides the MELD score and the corticosteroid response rate, complex I activity was significantly associated with 3-month mortality (OR=6.03; p= 0.034) and complex III activity with 6-month mortality (OR=4.70; p= 0.041) in AH patients. Our results indicate that MRC activity is markedly decreased in the liver of AH patients, and, particularly, the impairment of MRC complexes I and III activity appears to have a significant impact on the clinical outcomes of patients with AH.

P047 Osteopontin in colitis-associated carcinoma (CAC)

Abstract Background Inflammatory bowel disease (IBD) patients pose a lifelong risk of developing colitis-associated carcinoma (CAC). Current understanding and mechanisms of CAC development stem from murine CAC models while studies on human CAC carcinogenesis are scarce. Thus, we aimed to understand CAC carcinogenesis, using human samples from patients suffering from Crohn′s disease (CD), CD-associated CAC (CD-CAC), ulcerative colitis (UC), and UC-associated CAC (UC-CAC) and further validated the findings in vitro. Methods We obtained FFPE specimens from 40 patients that suffered from either one of the IBDs or CACs and furthermore inflammation-free healthy controls (10 patients per group). These samples were micro-dissected, followed by RNA isolation and Nanostring gene expression analysis. Our data revealed a strong upregulation of SPP1 (Secreted Phosphoprotein-1) gene encoding for osteopontin (OPN) upon comparing heathy controls to IBD and to CAC. We then used in vitro-models to elucidate the mechanism of OPN-induced carcinogenesis. We stimulated intestinal epithelial cell lines HT-29/B6 and T84 cells with rhOPN (recombinant human OPN), following bulk RNAseq. We validated the findings using Seahorse assay for analysis of mitochondrial respiration (determining oxygen consumption rate, OCR). Western phospho-blots were done to unravel signal transduction events. Results Nanostring gene expression data revealed the following: (i) SPP1 gene encoding for OPN and epithelial-to-mesenchymal (EMT) transcription factors fibronectin-1 (FN1) and ZEB1 were strongly upregulated in UC-CAC and CD-CAC patients when compared to UC and CD. (ii) IL17-pathway genes were significantly downregulated in UC-CAC patients. (iii) Tight junction and polarity genes were altered in both UC-CAC and CD-CAC patients. rhOPN stimulation in vitro to HT29/B6 and T84 cells excluded OPN as the trigger of EMT but uncovered upregulated mitochondrial respiratory chain genes as a potential trigger for tumour cell proliferation. Validation of RNAseq findings by Seahorse assay revealed that after sequential injections of oligomycin, FCCP, rotenone and antimycin A both, HT-29/B6 and T84 cells, had higher basal and maximal OCRs in response to rhOPN (Fig. 1). T84, but not HT-29/B6 cells also showed an upregulated ATP production in response to rhOPN. Conclusion SPP1 expression correlates with CAC carcinogenesis. Putative underlying pathways rather include modulation of mitochondrial respiratory chain activity by differential gene expression than induction of EMT.

Surface Defects Regulate the in Vivo Bioenergetic Response of Earthworm Eisenia fetida Coelomocytes to Molybdenum Disulfide Nanosheets.

Two-dimensional molybdenum disulfide (2D MoS2) nanomaterials are seeing increased use in several areas, and this will lead to their inevitable release into soils. Surface defects can occur on MoS2 nanosheets during synthesis or during environmental aging processes. The mechanisms of MoS2 nanosheet toxicity to soil invertebrates and the role of surface defects in that toxicity have not been fully elucidated. We integrated traditional toxicity end points, targeted energy metabolomics, and transcriptomics to compare the mechanistic differences in the toxicity of defect-free and defect-rich MoS2 nanosheets (DF-MoS2 and DR-MoS2) to Eisenia fetida using a coelomocyte-based in vivo assessment model. After organism-level exposure to DF-MoS2 for 96 h at 10 and 100 mg Mo/L, cellular reactive oxygen species (ROS) levels were elevated by 25.6-96.6% and the activity of mitochondrial respiratory electron transport chain (Mito-RETC) complex III was inhibited by 9.7-19.4%. The tricarboxylic acid cycling and glycolysis were also disrupted. DF-MoS2 preferentially up-regulated subcellular component motility processes related to microtubules and caused mitochondrial fission. Unlike DF-MoS2, DR-MoS2 triggered an increased degree of mitochondrial fusion, as well as more severe oxidative stress. The activities of Mito-RETC complexes (I, III, IV, V) associated with oxidative phosphorylation were significantly inhibited by 22.8-68.6%. Meanwhile, apoptotic pathways were activated upon DR-MoS2 exposure, which together with the depolarization of mitochondrial membrane potential, mediated significant apoptosis. In turn, genes related to cellular homeostasis and energy release were up-regulated to compensate for DR-MoS2-induced energy deprivation. Our study indicates that MoS2 nanosheets have nanospecific effects on E. fetida and also that the role of surface defects from synthesis or that accumulate from environmental impacts needs to be fully considered when evaluating the toxicity of these 2D materials.

SERS uncovers the link between conformation of cytochrome c heme and mitochondrial membrane potential

The balance between the mitochondrial respiratory chain activity and the cell's needs in ATP ensures optimal cellular function. Cytochrome c is an essential component of the electron transport chain (ETC), which regulates ETC activity, oxygen consumption, ATP synthesis and can initiate apoptosis. The impact of conformational changes in cytochrome c on its function is not understood for the lack of access to these changes in intact mitochondria. We have developed a novel sensor that uses unique properties of label-free surface-enhanced Raman spectroscopy (SERS) to identify conformational changes in heme of cytochrome c and to elucidate their role in functioning mitochondria. We have verified that molecule bond vibrations assessed by SERS are a reliable indicator of the heme conformation during changes in the inner mitochondrial membrane potential and ETC activity. We have demonstrated that cytochrome c heme reversibly switches between planar and ruffled conformations in response to the inner mitochondrial membrane potential (ΔΨ) and H+ concentration in the intermembrane space. This regulates the efficiency of the mitochondrial respiratory chain, thus, adjusting the mitochondrial respiration to the cell's consumption of ATP and the overall activity. We have found that under hypertensive conditions cytochrome c heme loses its sensitivity to ΔΨ that can affect the regulation of ETC activity. The ability of the proposed SERS-based sensor to track mitochondrial function opens broad perspectives in cell bioenergetics.

No Cardiomyopathy or Skeletal Muscle Weakness in an Organismal Model of Barth Syndrome - Is Metabolism the Basis for Its Neutropenia?

Introduction: Barth syndrome (BTHS) is a rare X-linked mitochondrial disease due to a mutation in TAFAZZIN, which encodes tafazzin, a phospholipid-lysophospholipid transacylase. Defects in tafazzin lead to a life-threatening cardiomyopathy, neutropenia, skeletal muscle weakness, growth delay and 3-methylglutaconic aciduria (3-MGC). Tafazzin is required for the normal biogenesis of cardiolipin (CL). CL is a phospholipid of the inner mitochondrial membrane and required for the activity of mitochondrial respiratory chain. Absence of tafazzin reduces CL. Monolysocardiolipins (MLCLs), intermediates in remodeling, are increased in a variety of tissues from BTHS patients. Two of the greatest obstacles to understanding the pathophysiology of BTHS and developing more effective therapies are the rarity of the disease and absence of an organismal models. Wide variability of phenotypes exists among BTHS patients and mouse models. Zebrafish provide an excellent vertebrate model for studying heart, blood, and muscle development and disease. In particular, zebrafish harbor a single homologous gene for tafazzin, and there is 60% amino acid conservation between humans and fish. Methods and Results: We created a zebrafish mutant line using CRISPR/cas9 targeting for the tafazzin exon 3. The new mutation resulted in deletion of 1 bp that cause a frame shift and a premature termination codon resulting in protein truncation. Unexpectedly and interestingly, homozygous mutants for this mutation (tafazzin-/-) survive for at least ten months without a visible phenotype. They are fertile and have viable progeny. We incrossed the homozygous mutants (tafazzin-/-) and study the descendants comparing to an incross of homozygous wildtype (tafazzin+/+) siblings. The maternal zygotic (MZ) mutants showed neutropenia at 5 days post fertilization (dpf) and reduced taz mRNA levels. Using RT-qPCR, we observed an upregulation of mRNA of the three key enzymes of glycolysis (gck, pfkmb, pyrk), unfolded protein response (UPR) markers (chop, bip, atf6, edem) and p53 pathway activation (tp53, bax, mdm2, cdkn2ab, ccng1) at 15 dpf. We next determined whether tafazzin-deficient zebrafish exhibited lipid dysregulation similar to that observed in BTHS patients. Whole larvae extracts at 15 dpf showed a significant increase ratio of MLCL:CL and increased levels of 3-MGC acid. Surprisingly, the tafazzin-/- MZ did not develop cardiac defects at 2 months. Conclusions: Our novel zebrafish tafazzin mutants recapitulate some features of BTHS patients, prominently the neutropenia. We are currently studying effects in ATP production and ROS production and metabolites in the tafazzin-deficient zebrafish. This new organismal model will be critical to gain new knowledge into its pathogenesis. More importantly, characterization of how zebrafish metabolizes CL differently from humans can lead to design of small molecule therapy, mitochondrial repair approaches, or dietary modifications for BTHS patients.

Inhibition of glutaminolysis restores mitochondrial function in senescent stem cells.

Mitochondrial dysfunction, a hallmark of aging, has been associated with the onset of aging phenotypes and age-related diseases. Here, we report that impaired mitochondrial function is associated with increased glutamine catabolism in senescent human mesenchymal stem cells (MSCs) and myofibroblasts derived from patients suffering from Hutchinson-Gilford progeria syndrome. Increased glutaminase (GLS1) activity accompanied by loss of urea transporter SLC14A1 induces urea accumulation, mitochondrial dysfunction, and DNA damage. Conversely, blocking GLS1 activity restores mitochondrial function and leads to amelioration of aging hallmarks. Interestingly, GLS1 expression is regulated through the JNK pathway, as demonstrated by chemical and genetic inhibition. In agreement with our invitro findings, tissues isolated from aged or progeria mice display increased urea accumulation and GLS1 activity, concomitant with declined mitochondrial function. Inhibition of glutaminolysis in progeria mice improves mitochondrial respiratory chain activity, suggesting that targeting glutaminolysis may be a promising strategy for restoring age-associated loss of mitochondrial function.

Mitochondrial dysfunction due to in vitro exposure to atrazine and its metabolite in striatum.

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) has beendescribed as a potential toxic for dopaminergic metabolism both in vivo and in vitro. Its main metabolite diamino-chloro triazine (DACT) has been shown to achieve higher levels in brain tissue than atrazine. The aim of this study was to evaluate the in vitro effects of atrazine and DACT on striatal mitochondrial function, active oxygen species generation, and nitric oxide (NO) content. Incubation of mitochondria with atrazine (10 µM) was not able to modify oxygen consumption. However, a 50% increase in malate-glutamate state 4 respiratory rates was observed after DACT treatment (100 µM) without changes in respiratory state 3. Atrazine was able to inhibit complex I-III activity by 30% and DACT induced a tendency to decrease by 17% in the striatum. Regardingreactive oxygen species(ROS), DACT increased H2 O2 production by 43%. Also, superoxide anion levels were higher (14%) after atrazine exposure than in control mitochondria. Incubation of striatal mitochondria with atrazine and DACT induced membrane depolarization by 15% and 19%, respectively. Also, atrazine increased NO content by 10% but no significant changes were observed after exposure of mitochondria to DACT. Glutathione peroxidase activity was inhibited (56%) by DACT and atrazine inhibited superoxide dismutase activity by 60%. Also, cardiolipin oxidation (15%) was observed after atrazine treatment. Summing up, the obtained results suggest that in vitro atrazine and DACT induce ROS production affecting striatal mitochondrial function. The atrazine effects would be attributed to a direct effect on the mitochondrialrespiratory chain and superoxide dismutase activity while DACT appears to disturb glutathione-related enzyme system.

Megaconial congenital muscular dystrophy due to novel CHKB variants: a case report and literature review

BackgroundCholine kinase beta (CHKB) catalyzes the first step in the de novo biosynthesis of phosphatidyl choline and phosphatidylethanolamine via the Kennedy pathway. Derangement of this pathway might also influence the homeostasis of mitochondrial membranes.Autosomal recessive CHKB mutations cause a rare form of congenital muscular dystrophy known as megaconial congenital muscular dystrophy (MCMD).Case presentationWe describe a novel proband presenting MCMD due to unpublished CHKB mutations. The patient is a 6-year-old boy who came to our attention for cognitive impairment and slowly progressive muscular weakness. He was the first son of non-consanguineous healthy parents from Sri Lanka. Neurological examination showed proximal weakness at four limbs, weak osteotendinous reflexes, Gowers’ maneuver, and waddling gate. Creatine kinase levels were mildly increased. EMG and brain MRI were normal. Left quadriceps skeletal muscle biopsy showed a myopathic pattern with nuclear centralizations and connective tissue increase. Histological and histochemical staining suggested subsarcolemmal localization and dimensional increase of mitochondria. Ultrastructural analysis confirmed the presence of enlarged (“megaconial”) mitochondria. Direct sequencing of CHKB identified two novel defects: the c.1060G > C (p.Gly354Arg) substitution and the c.448-56_29del intronic deletion, segregating from father and mother, respectively. Subcloning of RT-PCR amplicons from patient’s muscle RNA showed that c.448-56_29del results in the partial retention (14 nucleotides) of intron 3, altering physiological splicing and transcript stability. Biochemical studies showed reduced levels of the mitochondrial fission factor DRP1 and the severe impairment of mitochondrial respiratory chain activity in patient’s muscle compared to controls.ConclusionsThis report expands the molecular findings associated with MCMD and confirms the importance of considering CHKB variants in the differential diagnosis of patients presenting with muscular dystrophy and mental retardation. The clinical outcome of MCMD patients seems to be influenced by CHKB molecular defects. Histological and ultrastructural examination of muscle biopsy directed molecular studies and allowed the identification and characterization of an intronic mutation, usually escaping standard molecular testing.

Role of TRPA1/TRPV1 in acute ozone exposure induced murine model of airway inflammation and bronchial hyperresponsiveness.

BackgroundTransient receptor potential (TRP) ankyrin 1 (TRPA1) and vanilloid 1 (TRPV1) mediate the development of lung injury and inflammation. This study investigated the role and mechanism of the TRPA1/TRPV1 pathway in airway inflammation and bronchial hyperresponsiveness (BHR) induced by acute ozone exposure.MethodsC57BL/6 mice (8–10 weeks) were intraperitoneally injected with phosphate buffered saline (PBS), A967079 (TRPA1 inhibitor) or AMG9810 (TRPV1 inhibitor) 1 h before or after ozone exposure (2.5 ppm, 3 h). BHR, cell counts in bronchoalveolar lavage (BAL) fluid, oxidative stress biomarkers, inflammatory cytokines, TRPA1 and TPRV1 protein levels, mitochondrial dynamics- and mitophagy-related protein levels, and activities of mitochondrial respiratory chain (MRC) in lung were measured.ResultsThe preventive treatment effect was similar to the therapeutic treatment effect. Both A967079 and AMG9810 intervention suppressed BHR, inflammatory cytokines, total BAL fluid cells, malondialdehyde (MDA) levels and inflammatory cytokines mRNA including Substance P (SP), Keratinocyte-Derived Chemokine (KC), interleukin-18 (IL-18) and chemokine (C-X-C motif) ligand 8 (CXCL8) expression, and enhanced reduced glutathione (GSH)/oxidized glutathione (GSSG) levels compared with ozone-exposed mice. A967079 and AMG9810 intervention inhibited dynamin-related protein (DRP1), mitochondrial fission factor (MFF), Parkinson protein 2 E3 ubiquitin protein ligase (PARK2) and Sequestosome 1 (SQSTM1)/p62 expression, increased Optic atrophy 1 (OPA1), mitofusin 2 (MFN2) and PTEN-induced putative kinase 1 (PINK1) expression, and up-regulated the activities of MRC complex III and V in lung tissue.ConclusionsThe results show that both TRPA1 and TRPV1 pathways are involved in acute ozone exposure-induced airway inflammation and BHR and influence oxidative stress, mitochondrial quality control and MRC activity, which could be a potential target for clinical therapy of respiratory diseases.