Upregulation of TFAM and mitochondria copy number in human lymphoblastoid cells

Metabolic Reprogramming in Epstein-Barr Virus Associated Diseases

Epstein-Barr virus (EBV) is the first human cancer-causing viral pathogen to be discovered; it has been epidemiologically associated with a wide range of diseases, including cancers, autoimmunity, and hyperinflammatory disorders. Its evolutionary success is underpinned by coordinated expression of viral transcription factors (EBV nuclear antigens), signaling proteins (EBV latent membrane proteins), and noncoding RNAs, which orchestrate cell transformation, immune evasion, and dissemination. Each of those activities entails significant metabolic rewiring, which is achieved by viral subversion of key host metabolic regulators such as the mammalian target of rapamycin (mTOR), MYC, and hypoxia-inducible factor (HIF). In this review, we systemically discuss how EBV-encoded factors regulate metabolism to achieve viral persistence and propagation, as well as potential research questions and directions in EBV-driven metabolism.

Spatheliachromen mitigates methylglyoxal-induced myotube atrophy by activating Nrf2, inhibiting ubiquitin-mediated protein degradation, and restoring mitochondrial function

BACKGROUND

Methylglyoxal (MGO) is a potent precursor of glycative stress that leads to oxidative stress and muscle atrophy in diabetes. Spatheliachromen (FPATM-20), derived from Ficus pumila var. awkeotsang, exhibited potential antioxidant activity.

PURPOSE

This study aimed to evaluate the potential impact and underlying mechanisms of FPATM-20 on MGO-induced myotube atrophy and mitochondrial dysfunction in mouse skeletal C2C12 myotubes.

METHODS

Atrophic and antioxidant factors were evaluated using immunofluorescence, enzyme-linked immunosorbent assay, and western blotting. Mitochondrial function was assessed using the ATP assay and Seahorse Cell Mito Stress Test. The glycogen content was determined using periodic acid-Schiff staining. Molecular docking was performed to determine the interaction between FPATM-20 and Keap1.

RESULTS

In myotubes treated with MGO, FPATM-20 activated the Nrf2 pathway, reduced ROS levels, enhanced antioxidant defense, and increased glycogen content. FPATM-20 improved myotube viability and size, upregulated myosin heavy chain (MyHC) expression, modulated ubiquitin-proteasome molecules (nuclear FoxO3a, atrogin-1, MuRF-1, and p62/SQSTM1), and inhibited apoptosis (Bax/Bcl-2 ratio and cleaved caspase 3). Moreover, FPATM-20 restored mitochondrial function, including mitochondrial membrane potential, mitochondrial oxygen consumption rate, and mitochondrial biogenesis pathway (nuclear PGC-1α/TFAM/FNDC5). The inhibition of Nrf2 with ML385 reversed the effects of FPATM-20 on MGO. Furthermore, molecular docking confirmed the binding of FPATM-20 to Keap1, a suppressor of Nrf2, showing the crucial role of Nrf2 in protective effects.

CONCLUSIONS

FPATM-20 protects myotubes from MGO toxicity by activating the Nrf2 antioxidant defense, reducing protein degradation and apoptosis, and enhancing mitochondrial function. Thus, FPATM-20 may be a novel agent for preventing skeletal muscle atrophy.

Investigation of the possible effects of night shift on telomere length and mtDNA copy number in nurses

In this study, we aimed to investigate the impacts of altered circadian rhythm on telomere length and mtDNA copy number (mtDNA-CN) in nurses working night shifts. In our study, 52 healthy nurses working in shifts at Ondokuz Mayıs University Hospital and 45 healthy control subjects working during the day were included. qRT-PCR technique was used for the determination of telomere length and mtDNA-CN. It was observed that the shift-work group had poor sleep quality (p = 0.004), feeling tired (p < 0.01) and stressed (p = 0.02) more than control group working during the day. Nurses working in shifts were found to have 1.18 times longer telomeres with respect to the control group working during the day (p = 0.005). When compared among shift workers, poor sleep quality and insufficient sleep duration shortened telomeres (r = 0.32; p = 0.02). There was no statistically significantdisparity regarding mtDNA-CN among the nurses working in shifts and the control group working during the day (p = 0.07). Insufficient sleep was associated with decreased mtDNA-CN when shift-working nurses were compared according to sleep quality (p = 0.006). Furthermore, mtDNA-CN of nurses with poor sleep quality was correlated with lower mtDNA-CN in comparison to nurses with good sleep quality (r = 0.284; p = 0.04). The mtDNA-CN of the nurses was positively associated with the sleep duration the night sleep before the night shift (r = 0.32; p = 0.02). Inadequate sleep duration and quality were observed to cause a reduction in mtDNA-CN of nurses. In conclusion, it has been observed that poor sleep quality and duration are related to shortened telomere length and decreased mtDNA-CN in night shift nurses.

A state-of-the-science review of using mitochondrial DNA copy number as a biomarker for environmental exposure

Mitochondria are bioenergetic, biosynthetic, and signaling organelles in eukaryotes, and contain their own genomes, mitochondrial DNA (mtDNA), to supply energy to cells by generating ATP via oxidative phosphorylation. Therefore, the threat to mitochondria' integrity and health resulting from environmental exposure could induce adverse health effects in organisms. In this review, we summarized the association between mtDNA copy number (mtDNAcn), and environmental exposures as reported in the literature. We conducted a literature search in the Web of Science using [Mitochondrial DNA copy number] and [Exposure] as two keywords and employed three selection criteria for the final inclusion of 97 papers for review. The consensus of data was that mtDNAcn could be used as a plausible biomarker for cumulative exposures to environmental chemical and physical agents. In order to furtherly expand the application of mtDNAcn in ecological and environmental health research, we suggested a series of algorithms aiming to standardize the calculation of mtDNAcn based on the PCR results in this review. We also discussed the pitfalls of using whole blood/plasma samples for mtDNAcn measurements and regard buccal cells a plausible and practical alternative. Finally, we recognized the importance of better understanding the mechanistic analysis and regulatory mechanism of mtDNAcn, in particular the signals release and regulation pathways. We believe that the development of using mtDNAcn as an exposure biomarker will revolutionize the evaluation of chronic sub-lethal toxicity of chemicals to organisms in ecological and environmental health research that has not yet been implemented.

Mitochondrial DNA copy number is associated with incident chronic kidney disease and proteinuria in the AIDS linked to the intravenous experience cohort

We evaluated the prospective association of mitochondrial DNA copy number (mtDNA CN) with markers of kidney function among a cohort of persons who inject drugs (PWID). This is a Prospective cohort study nested in the AIDS linked to the intravenous experience cohort (community-based cohort of PWID in Baltimore, MD). mtDNA CN was measured at two time-points 5 years apart using a real-time polymerase chain reaction. Kidney function (estimated glomerular filtration rate [eGFR], serum creatinine, urine protein) was measured annually. We used linear mixed effects models to evaluate kidney function trajectories (N = 946) and Cox regression models to assess hazard of incident CKD (eGFR < 60 at two consecutive visits, N = 739) and proteinuria (urine protein:creatinine ratio > 200, N = 573) by level of mtDNA CN (Low [lowest quartile], vs high [other three quartiles]. Models were adjusted for demographic and behavioral characteristics, HIV and/or HCV infection, and comorbidity burden. Low mtDNA CN was independently associated with higher hazard of incident CKD (aHR: 2.33, 95% CI 1.42, 3.80) and proteinuria (aHR: 1.42, 95% CI 1.04, 1.96). Participants with low mtDNA CN had greater declines in eGFR and greater increases in serum creatinine over time. Low mtDNA CN is associated with more rapid kidney function decline and risk of incident CKD and proteinuria.

HEK293T Cells with TFAM Disruption by CRISPR-Cas9 as a Model for Mitochondrial Regulation

The mitochondrial transcription factor A (TFAM) is considered a key factor in mitochondrial DNA (mtDNA) copy number. Given that the regulation of active copies of mtDNA is still not fully understood, we investigated the effects of CRISPR-Cas9 gene editing of TFAM in human embryonic kidney (HEK) 293T cells on mtDNA copy number. The aim of this study was to generate a new in vitro model by CRISPR-Cas9 system by editing the TFAM locus in HEK293T cells. Among the resulting single-cell clones, seven had high mutation rates (67-96%) and showed a decrease in mtDNA copy number compared to control. Cell staining with Mitotracker Red showed a reduction in fluorescence in the edited cells compared to the non-edited cells. Our findings suggest that the mtDNA copy number is directly related to TFAM control and its disruption results in interference with mitochondrial stability and maintenance.

Neurobiological Opportunities in Diabetic Polyneuropathy

This review highlights a selection of potential translational directions for the treatment of diabetic polyneuropathy (DPN) currently irreversible and without approved interventions beyond pain management. The list does not include all diabetic targets that have been generated over several decades of research but focuses on newer work. The emphasis is firstly on approaches that support the viability and growth of peripheral neurons and their ability to withstand a barrage of diabetic alterations. We include a section describing Schwann cell targets and finally how mitochondrial damage has been a common element in discussing neuropathic damage. Most of the molecules and pathways described here have not yet reached clinical trials, but many trials have been negative to date. Nonetheless, these failures clear the pathway for new thoughts over reversing DPN.

Brain Atrophy and White Matter Damage Linked to Peripheral Bioenergetic Deficits in the Neurodegenerative Disease FXTAS

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurodegenerative disorder affecting subjects (premutation carriers) with a 55-200 CGG-trinucleotide expansion in the 5'UTR of the fragile X mental retardation 1 gene (FMR1) typically after age 50. As both the presence of white matter hyperintensities (WMHs) and atrophied gray matter on magnetic resonance imaging (MRI) are linked to age-dependent decline in cognition, here we tested whether MRI outcomes (WMH volume (WMHV) and brain volume) were correlated with mitochondrial bioenergetics from peripheral blood monocytic cells in 87 carriers with and without FXTAS. As a parameter assessing cumulative damage, WMHV was correlated to both FXTAS stages and age, and brain volume discriminated between carriers and non-carriers. Similarly, mitochondrial mass and ATP production showed an age-dependent decline across all participants, but in contrast to WMHV, only FADH2-linked ATP production was significantly reduced in carriers vs. non-carriers. In carriers, WMHV negatively correlated with ATP production sustained by glucose-glutamine and FADH2-linked substrates, whereas brain volume was positively associated with the latter and mitochondrial mass. The observed correlations between peripheral mitochondrial bioenergetics and MRI findings-and the lack of correlations with FXTAS diagnosis/stages-may stem from early brain bioenergetic deficits even before overt FXTAS symptoms and/or imaging findings.

MiR-193b deregulation is associated with Parkinson's disease

PGC-1α/FNDC5/BDNF has found to be a critical pathway in neurodegeneration. MicroRNAs (miR(NA)s) are non-coding regulatory RNAs whose dysregulation has been observed in multiple neurological disorders, and miRNA-mediated gene deregulation plays a decisive role in PD. Here, candidate miRNA was chosen based on the literature survey and in silico studies. Chronic and acute models of PD were created using MPP+-treated SH-SY5Y cells. Twenty PD patients and 20 healthy volunteers were recruited. RT-qPCR was performed to assess the expression of miRNA and genes. Severe mitochondrial dysfunction induced by acute MPP+ treatment instigated compensatory mechanisms through enhancing expression of PGC-1α/FNDC5/BDNF pathway genes, while chronic MPP+ toxicity led to down-regulated levels of the genes in SH-SY5Y cells. PD peripheral blood mononuclear cells (PBMCs) also showed decreased expression of target genes. There were significant changes in the level of miR-193b in both models, as well as PD PBMCs. Moreover, miR-193b overexpression significantly affected PGC-1α, FNDC5 and TFAM levels. Interestingly, down-regulations of PGC-1α, FNDC5, BDNF and TFAM were inversely correlated with miR-193b up-regulation in PD PBMCs. This study showed the deregulation of PGC-1α/FNDC5/BDNF pathway in PD models and PBMCs, verifying its importance in neurodegeneration. Our findings also revealed that miR-193b functions in PD development, possibly through regulating PGC-1α/FNDC5/BDNF pathway, suggesting miR-193b as a potential biomarker for PD diagnosis.

Epigenetic alteration of mitochondrial biogenesis regulatory genes in arsenic exposed individuals (with and without skin lesions) and in skin cancer tissues: A case control study

Chronic arsenic toxicity has become a global concern due to its adverse pathophysiological outcome and carcinogenic potential. It is already established that arsenic induced reactive oxygen species alters mitochondrial functionality. Major regulatory genes for mitochondrial biogenesis, i.e., PGC1α, Tfam, NRF1and NRF2 are located in the nucleus. As a result, mitochondria-nucleus crosstalk is crucial for proper mitochondrial function. This previous hypothesis led us to investigateinvolvement of epigenetic alteration behindenhanced mitochondrial biogenesis in chronic arsenic exposure. An extensive case-control study was conducted with 390 study participants (unexposed, exposed without skin lesion, exposed with skin lesion and exposed skin tumour) from highly arsenic exposed areas ofWest Bengal, India. Methylation specific PCRrevealed significant promoter hypomethylation oftwo key biogenesis regulatory genes, PGC1αandTfam in arsenic exposed individuals and also in skin tumour tissues. Linear regression analysis indicated significant negative correlation between urinary arsenic concentration and promoter methylation status. Increased expression of biogenesis regulatory genes wasobtained by quantitative real-time PCR analysis. Moreover, altered mitochondrial fusion-fission regulatory gene expression was also observed in skin tumour tissues. miR663, having tumour suppressor gene like function was known to be epigenetically regulated through mitochondrial retrograde signal. Promoter hypermethylation with significantly decreased expression of miR663 was found in skin cancer tissues compared to non-cancerous control tissue. In conclusion, results indicated crucial role of epigenetic alteration in arsenic induced mitochondrial biogenesis and arsenical skin carcinogenesis for the first time. However, further mechanistic studies are necessary for detailed understanding of mitochondria-nucleus crosstalk in arsenic perturbation.

Beauvericin alters the expression of genes coding for key proteins of the mitochondrial chain in ovine cumulus-oocyte complexes

Beauvericin (BEA) is a member of the enniatin family of mycotoxins which has received increasing interest because of frequent occurrence in food and feed. By its ionophoric properties, BEA is able to alter membrane ion permeability uncoupling oxidative phosphorylation. It was also shown to alter oocyte mitochondrial function. In this study, the effects of BEA at 0.5, 1, ,3 and 5 μmol/L on expression of genes coding for key proteins of the mitochondrial chain in ovine oocytes and cumulus cells were evaluated at different time points of in vitro maturation (IVM), germinal vesicle (GV; t = 0), metaphase I (MI; t = 7 h), and metaphase II (MII; t = 24 h). The expression of nuclear (TFAM, NDUFA12, UQCRH, COX4, ATP5O) and mitochondrial (ND1, COX1, COX2, ATP6, ATP8) genes coding for proteins of Complexes I, III, IV, and V was analyzed by qRT-PCR. After BEA exposure, perturbed expression of all genes was observed in cumulus cells and in oocytes at the MI stage (7 h IVM). Expression of ND1, UQCRH, COX4 and ATP5O was downregulated in cumulus cells and upregulated in oocytes starting from 0.5 μmol/L BEA. Expression of TFAM, NDUFA12, COX1, COX2, ATP6, and ATP8 was upregulated starting from 1 μmol/L in cumulus cells and from 3 μmol/L in oocytes. Cumulus cells and oocytes displayed different gene expression patterns upon BEA exposure. The downregulation in cumulus cells of four genes coding for proteins of mitochondrial complexes could represent a major toxic event induced by BEA on the cumulus-oocyte complex which may result in mitochondrial functional alteration.

Modified level of miR-376a is associated with Parkinson's disease

Parkinson's disease (PD) is a frequent progressive neurodegenerative disorder. Impaired mitochondrial function is a major feature of sporadic PD. Some susceptibility or causative genes detected in PD are strongly associated with mitochondrial dysfunction including PGC1α, TFAM and GSK3β. microRNAs (miRNAs) are non‐coding RNAs whose altered levels are proven in disparate PD models and human brains. Therefore, the aim of this study was to detect modulations of miRs upstream of PGC1α, TFAM and GSK3β in association with PD onset and progress. In this study, a total of 33 PD subjects and 25 healthy volunteers were recruited. Candidate miRNA (miR‐376a) was selected through target prediction tools and literature survey. Chronic and acute in vitro PD models were created by MPP⁺‐intoxicated SHSY5Y cells. The levels of miR‐376a and aforementioned genes were assessed by RT‐qPCR. The expression of target genes was decreased in chronic model while there were dramatically up‐regulated levels of those genes in acute model of PD. miR‐376a was strongly altered in both acute and chronic PD models as well as PBMCs of PD patients. Our results also showed overexpression of PGC1α, and TFAM in PBMCs is inversely correlated with down‐regulation of miR‐376a, suggesting that miR‐376a possibly has an impact on PD pathogenesis through regulation of these genes which are involved in mitochondrial function. miR‐376a expression in PD‐derived PBMCs was also correlated with disease severity and may serve as a potential biomarker for PD diagnosis. This is the first study showing altered levels of miR‐376a in PD models and PBMCs, suggesting the probable role of this miRNA in PD pathogenesis. The present study also proposed TFAM and PGC1α as target genes of miR‐376a for the first time, through which it possibly can exert its impact on PD pathogenesis.

Whole mitochondria genome mutational spectrum in occupationally exposed lead subjects

Lead is a public health hazard substance affecting millions of people worldwide especially those who are occupationally exposed. Our study aimed to investigate the effect of occupational lead exposure on mitochondria DNA (mtDNA). By sequencing the whole mitochondria genome, we identified 25 unique variants in lead exposed subjects affecting 10 protein coding genes in the order of MT-ND1, MT-ND2, MT-CO2, MT-ATP8, MT-ATP6, MT-CO3, MT-ND3, MT-ND4, MT-ND5, and MT-CYB. Mitochondria functional analysis revealed that exposure to lead can reduce reactive oxygen species (ROS) levels, alter mitochondria membrane potential (MMP) and increase mitochondrial mass (MM). This was further supported by mtDNA copy number analysis which was increased in lead exposed individuals compared to unexposed control group indicating the compensatory mechanism that lead has in stabilizing the mitochondria. This is the first report of mtDNA mutation and copy number analysis in occupationally lead exposed subjects where we identified mtDNA mutation signature associated with lead exposure thus providing evidence for altered molecular mechanism to compensate mitochondrial oxidative stress.

Role of mitochondria in diabetic peripheral neuropathy: Influencing the NAD+-dependent SIRT1-PGC-1α-TFAM pathway

Survival of human peripheral nervous system neurons and associated distal axons is highly dependent on energy. Diabetes invokes a maladaptation in glucose and lipid energy metabolism in adult sensory neurons, axons and Schwann cells. Mitochondrial (Mt) dysfunction has been implicated as an etiological factor in failure of energy homeostasis that results in a low intrinsic aerobic capacity within the neuron. Over time, this energy failure can lead to neuronal and axonal degeneration and results in increased oxidative injury in the neuron and axon. One of the key pathways that is impaired in diabetic peripheral neuropathy (DPN) is the energy sensing pathway comprising the nicotinamide-adenine dinucleotide (NAD⁺)-dependent Sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor-γ coactivator α (PGC-1α)/Mt transcription factor A (TFAM or mtTFA) signaling pathway. Knockout of PGC-1α exacerbates DPN, whereas overexpression of human TFAM is protective. LY379268, a selective metabolomic glutamate receptor 2/3 (mGluR2/3) receptor agonist, also upregulates the SIRT1/PGC-1α/TFAM signaling pathway and prevents DPN through glutamate recycling in Schwann/satellite glial (SG) cells and by improving dorsal root ganglion (DRG) neuronal Mt function. Furthermore, administration of nicotinamide riboside (NR), a precursor of NAD⁺, prevents and reverses DPN, in part by increasing NAD⁺ levels and SIRT1 activity. In summary, we review the role of NAD⁺, mitochondria and the SIRT1-PGC-1α-TFAM pathway both from the perspective of pathogenesis and therapy in DPN.

Investigating mitonuclear interactions in human admixed populations

To function properly, mitochondria utilize products of 37 mitochondrial and >1,000 nuclear genes, which should be compatible with each other. Discordance between mitochondrial and nuclear genetic ancestry could contribute to phenotypic variation in admixed populations. Here, we explored potential mitonuclear incompatibility in six admixed human populations from the Americas: African Americans, African Caribbeans, Colombians, Mexicans, Peruvians and Puerto Ricans. By comparing nuclear versus mitochondrial ancestry in these populations, we first show that mitochondrial DNA (mtDNA) copy number decreases with increasing discordance between nuclear and mtDNA ancestry. The direction of this effect is consistent across mtDNA haplogroups of different geographic origins. This observation indicates suboptimal regulation of mtDNA replication when its components are encoded by nuclear and mtDNA genes with different ancestry. Second, while most populations analysed exhibit no such trend, in African Americans and Puerto Ricans, we find a significant enrichment of ancestry at nuclear-encoded mitochondrial genes towards the source populations contributing the most prevalent mtDNA haplogroups (African and Native American, respectively). This possibly reflects compensatory effects of selection in recovering mitonuclear interactions optimized in the source populations. Our results provide evidence of mitonuclear interactions in human admixed populations and we discuss their implications for human health and disease.

p53 increase mitochondrial copy number via up-regulation of mitochondrial transcription factor A in colorectal cancer

In colorectal cancer, no study has been carried out discovering the relationship among p53, mitochondrial transcription factor A (TFAM) expression and change of mitochondrial DNA (mtDNA) copy number. In our study, co-expression of p53 and TFAM was observed in colon adenocarcinoma tissues, paracancerous tissues and 9 colorectal cancer cell lines. Then, a significant linear correlation was established between either p53 or TFAM expression and advanced TNM stage, positive lymph nodes and low 5-year survival rate in patients with colon adenocarcinoma. Additionally, advanced TNM stage, large tumor burden, presence of distant metastasis, and high TFAM expression were significantly related to poor overall 5-years survival. Moreover, alteration of p53 expression could change TFAM expression but TFAM could not influence p53 expression, and p53 could enhance TFAM expression via binding to TFAM promoter. While, both of p53 and TFAM expression could incrase mtDNA copy number in vitro. In conclusions, p53 might incrase mtDNA copy number through its regulation on TFAM expression via TFAMpromoter.

Lymphocytes eject interferogenic mitochondrial DNA webs in response to CpG and non-CpG oligodeoxynucleotides of class C

Circulating mitochondrial DNA (mtDNA) is receiving increasing attention as a danger-associated molecular pattern in conditions such as autoimmunity, cancer, and trauma. We report here that human lymphocytes [B cells, T cells, natural killer (NK) cells], monocytes, and neutrophils derived from healthy blood donors, as well as B cells from chronic lymphocytic leukemia patients, rapidly eject mtDNA as web filament structures upon recognition of CpG and non-CpG oligodeoxynucleotides of class C. The release was quenched by ZnCl₂, independent of cell death (apoptosis, necrosis, necroptosis, autophagy), and continued in the presence of TLR9 signaling inhibitors. B-cell mtDNA webs were distinct from neutrophil extracellular traps concerning structure, reactive oxygen species (ROS) dependence, and were devoid of antibacterial proteins. mtDNA webs acted as rapid (within minutes) messengers, priming antiviral type I IFN production. In summary, our findings point at a previously unrecognized role for lymphocytes in antimicrobial defense, utilizing mtDNA webs as signals in synergy with cytokines and natural antibodies, and cast light on the interplay between mitochondria and the immune system.

Gene expression and proliferation biomarkers for antidepressant treatment resistance

The neurotrophic hypothesis of depression suggests an association between effects on neuroplasticity and clinical response to antidepressant drug therapy. We studied individual variability in antidepressant drug effects on cell proliferation in lymphoblastoid cell lines (LCLs) from n=25 therapy-resistant patients versus n=25 first-line therapy responders from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Furthermore, the variability in gene expression of genes associated with cell proliferation was analyzed for tentative candidate genes for prediction of individual LCL donor's treatment response. Cell proliferation was quantified by EdU (5-ethynyl-2'-deoxyuridine) assays after 21-day incubation of LCLs with fluoxetine (0.5 ng μl-1) and citalopram (0.3 ng μl-1) as developed and described earlier. Gene expression of a panel of candidate genes derived from genome-wide expression analyses of antidepressant effects on cell proliferation of LCLs from the Munich Antidepressant Response Signature (MARS) study was analyzed by real-time PCR. Significant differences in in vitro cell proliferation effects were detected between the group of LCLs from first-line therapy responders and LCLs from treatment-resistant patients. Gene expression analysis of the candidate gene panel revealed and confirmed influence of the candidate genes ABCB1, FZD7 and WNT2B on antidepressant drug resistance. The potential of these genes as tentative biomarkers for antidepressant drug resistance was confirmed. In vitro cell proliferation testing may serve as functional biomarker for individual neuroplasticity effects of antidepressants.

Differences between the genomes of lymphoblastoid cell lines and blood-derived samples

Lymphoblastoid cell lines (LCLs) represent a convenient research tool for expanding the amount of biologic material available from an individual. LCLs are commonly used as reference materials, most notably from the Genome in a Bottle Consortium. However, the question remains how faithfully LCL-derived genome assemblies represent the germline genome of the donor individual as compared to the genome assemblies derived from peripheral blood mononuclear cells. We present an in-depth comparison of a large collection of LCL- and peripheral blood mononuclear cell-derived genomes in terms of distributions of coverage and copy number alterations. We found significant differences in the depth of coverage and copy number calls, which may be driven by differential replication timing. Importantly, these copy number changes preferentially affect regions closer to genes and with higher GC content. This suggests that genomic studies based on LCLs may display locus-specific biases, and that conclusions based on analysis of depth of coverage and copy number variation may require further scrutiny.

IL-4 promotes asymmetric dimethylarginine accumulation, oxo-nitrative stress, and hypoxic response-induced mitochondrial loss in airway epithelial cells

BACKGROUND

Obesity is known to increase asthma risk and severity. Increased levels of asymmetric dimethylarginine (ADMA), an endogenous nitric oxide synthase inhibitor, are associated with mitochondrial toxicity, asthma, and metabolic syndrome. IL-4 upregulates the expression of protein arginine methyltransferases, which are essential for ADMA formation. Importantly, cross-talk between IL-4, ADMA, and mitochondrial dysfunction could explain how obesity and IL-4 can synergize to exacerbate allergic inflammation.

OBJECTIVE

We sought to investigate how IL-4, a key asthma-associated cytokine, can influence ADMA-related effects on lungs.

METHODS

BEAS2B (bronchial epithelial) cells were treated with IL-4 followed by ADMA and investigated for oxo-nitrative stress and resultant mitochondrial toxicity after 48 hours by using flow cytometry, confocal imaging, immunoblotting, and fluorimetric assays.

RESULTS

IL-4-induced mitotoxicity in BEAS2B cells was significantly higher in the presence of exogenous ADMA. IL-4 treatment led to proteolytic degradation of dimethylarginine dimethylaminohydrolase 2, which catabolizes ADMA. IL-4 pretreatment was associated with increased intracellular ADMA accumulation and increased ADMA-induced mitotoxicity. Airway epithelial cells treated with IL-4 followed by ADMA showed exaggerated oxo-nitrative stress and potent induction of the cellular hypoxic response, despite normoxic conditions. The hypoxic response was associated with reduced mitochondrial function but was reversible by overexpression of the mitochondrial biogenesis factor, mitochondrial transcription factor A.

CONCLUSION

We conclude that IL-4 promotes intracellular ADMA accumulation, leading to mitochondrial loss through oxo-nitrative stress and hypoxic response. This provides a novel understanding of how obesity, with high ADMA levels, and asthma, with high IL-4 levels, might potentiate each other and highlights the potential of mitochondrial-targeted therapeutics in obese subjects with asthma.

Mitochondrial biology: From molecules to diseases

As an integral part of the cell, mitochondria play a pivotal role in the regulation of energy metabolism, signaling pathways, cell differentiation, cell proliferation and cell death. Mitochondrion with its own genetic material has characteristics distinct from those of the nuclear counterpart and its dysregulation is associated with a myriad of diseases. The discovery of interplay between the nuclear and mitochondrial genes, and various post-transcriptional modifications associated with their products has added excitement in the field. This has led to a better understanding of the basic mitochondrial function in normal and disease states, and is important for diagnosis and prognosis of a large number of disorders. The Fourth Annual Conference of Society for Mitochondrial Research and Medicine - India (SMRM) was titled "Mitochondrial Biology: from Molecules to Disease". The conference was organized by K. Satyamoorthy and K. Thangaraj at School of Life Sciences, Manipal University, Manipal, India, during 8-9 December, 2014. The aim of the conference was to bring researchers and clinicians to a common platform; create an opportunity for networking between laboratories; and to discuss about the recent development in mitochondrial biology, diagnosis, and therapy. This review summarizes the key outcomes of the conference.

Mitochondrial transcription factor A regulation of mitochondrial degeneration in experimental diabetic neuropathy

Oxidative stress-induced mitochondrial dysfunction and mitochondrial DNA (mtDNA) damage in peripheral neurons is considered to be important in the development of diabetic neuropathy. Mitochondrial transcription factor A (TFAM) wraps mtDNA and promotes mtDNA replication and transcription. We studied whether overexpression of TFAM reverses experimental peripheral diabetic neuropathy using TFAM transgenic mice (TFAM Tg) that express human TFAM (hTFAM). Levels of mouse mtDNA and the total TFAM (mouse TFAM + hTFAM) in the dorsal root ganglion (DRG) increased by approximately twofold in the TFAM Tg mice compared with control (WT) mice. WT and TFAM Tg mice were made diabetic by the administration of streptozotocin. Neuropathy end points were motor and sensory nerve conduction velocities, mechanical allodynia, thermal nociception, and intraepidermal nerve fiber density (IENFD). In the DRG neurons, mtDNA copy number and damage to mtDNA were quantified by qPCR, and TFAM levels were measured by Western blot. Mice with 16-wk duration of diabetes developed motor and sensory nerve conduction deficits, behavioral deficits, and intraepidermal nerve fiber loss. All of these changes were mostly prevented in diabetic TFAM Tg mice and were independent of changes in blood parameters. Mice with 16 wk of diabetes had a 40% decrease in mtDNA copy number compared with nondiabetic mice (P < 0.01). Importantly, the mtDNA copy number in diabetic TFAM Tg mice reached the same level as that of WT nondiabetic mice. In comparison, there was upregulation of mtDNA and TFAM in 6-wk diabetic mice, suggesting that TFAM activation could be a therapeutic strategy to treat peripheral neuropathy.

Indoxyl sulfate-induced oxidative stress, mitochondrial dysfunction, and impaired biogenesis are partly protected by vitamin C and N-acetylcysteine

Indoxyl sulfate (IS) contributes to oxidative stress and endothelial dysfunction in chronic kidney disease patients. However, the role of mitochondria in IS-induced oxidative stress is not very clear. In this study, we examined whether mitochondria play a pivotal role in modulating the effects of antioxidants during IS treatment. In the context of human umbilical vein endothelial cells, we found that IS had a dose-dependent antiproliferative effect. In addition, we used flow cytometry to demonstrate that the level of reactive oxygen species increased in a dose-dependent manner after treatment with IS. High doses of IS also corresponded to increased mitochondrial depolarization and decreased mitochondrial DNA copy number and mitochondrial mass. However, these effects could be reversed by the addition of antioxidants, namely, vitamin C and N-acetylcysteine. Thus, our results suggest that IS-induced oxidative stress and antiproliferative effect can be attributed to mitochondrial dysfunction and impaired biogenesis and that these processes can be protected by treatment with antioxidants.

Expression of mitochondrial regulators PGC1α and TFAM as putative markers of subtype and chemoresistance in epithelial ovarian carcinoma

Epithelial ovarian carcinoma (EOC), the major cause of gynaecological cancer death, is a heterogeneous disease classified into five subtypes. Each subtype has distinct clinical characteristics and is associated with different genetic risk factors and molecular events, but all are treated with surgery and platinum/taxane regimes. Tumour progression and chemoresistance is generally associated with major metabolic alterations, notably altered mitochondrial function(s). Here, we report for the first time that the expression of the mitochondrial regulators PGC1α and TFAM varies between EOC subtypes; furthermore, we have identified a profile in clear-cell carcinoma consisting of undetectability of PGC1α/TFAM, and low ERα/Ki-67. By contrast, high-grade serous carcinomas were characterised by a converse state of PGC1α/TFAM, ERα positivity and a high Ki-67 index. Interestingly, loss of PGC1α/TFAM and ERα was found also in a non-clear cell EOC cell line made highly resistant to platinum in vitro. Similar to clear-cell carcinomas, these resistant cells also showed accumulation of glycogen. Altogether, our data provide mechanistic insights into the chemoresistant nature of ovarian clear-cell carcinomas. Furthermore, these findings corroborate the need to take into account the diversity of EOC and to develop subtype specific treatment strategies.