Assaying Mitochondrial Respiration as an Indicator of Cellular Metabolism and Fitness

Mitochondria-containing extracellular vesicles from mouse vs. human brain endothelial cells for ischemic stroke therapy

Ischemic stroke-induced mitochondrial dysfunction in the blood-brain barrier-forming brain endothelial cells (BECs) results in long-term neurological dysfunction post-stroke. We previously reported data from a pilot study where intravenous administration of human BEC (hBEC)-derived mitochondria-containing extracellular vesicles (EVs) showed a potential efficacy signal in a mouse middle cerebral artery occlusion (MCAo) model of stroke. We hypothesized that EVs harvested from donor species homologous to the recipient species (e.g., mouse) may improve therapeutic efficacy, and therefore, use of mouse BEC (mBEC)-derived EVs may improve post-stroke outcomes in MCAo mice. We investigated potential differences in the mitochondria transfer of EVs derived from the same species as the recipient cell (mBEC-EVs and recipient mBECs or hBECs-EVs and recipient hBECs) vs. cross-species EVs and recipient cells (mBEC-EVs and recipient hBECs or vice versa). Our results showed that while both hBEC- and mBEC-EVs transferred EV mitochondria, mBEC-EVs outperformed hBEC-EVs in increasing ATP levels and improved recipient mBEC mitochondrial function via increasing oxygen consumption rates. mBEC-EVs significantly reduced brain infarct volume and neurological deficit scores compared to vehicle-injected MCAo mice. The superior therapeutic efficacy of mBEC-EVs in MCAo mice support the continued use of mBEC-EVs to optimize the therapeutic potential of mitochondria-containing EVs in preclinical mouse models.

Ling-gui-zhu-gan promotes adipocytes browning via targeting the miR-27b/PRDM16 pathway in 3T3-L1 cells

Introduction: Obesity, a global epidemic, is caused by an imbalance between energy intake and expenditure. The induction of white adipose browning to increase heat production has emerged as a potential effective strategy to address obesity. Ling-gui-zhu-gan (LGZG), a traditional Chinese medicine formula, has been proved to achieve promising results to combat obesity and related metabolic diseases, yet the mechanisms remain largely unexplored. This study aimed to elucidate the anti-obesity properties and the mechanisms of LGZG by investigating its browning effect on 3T3-L1 adipocytes. Methods: LGZG-containing serum obtained by oral administration of LGZG to animals was added to 3T3-L1 adipocytes to simulate in vivo conditions. Results: The results showed that 49 compounds were identified in LGZG-containing serum by UHPLC-Q-Orbitrap HRMS, including compounds such as atractylenolides and polyporenic acid C, etc. LGZG-containing serum alleviated the lipid accumulation and decreased both intracellular and extracellular triglyceride contents in a dose-dependent manner. This reduction is accompanied by enhanced mitochondrial respiratory and heat production function. Mechanistically, LGZG-containing serum led to a decrease in miR-27b expression and an increase in the mRNA and protein levels of browning-related markers, including UCP1, PRDM16, PGC-1α, PPARγ, CTBP1, and CTBP2. Further investigation using miR-27b mimic transfection confirmed that miR-27b/PRDM16 pathway might be a potential mechanism by which LGZG-containing serum promotes browning of 3T3-L1 adipocytes. Discussion: These results underscore the therapeutic potential of LGZG in addressing obesity and its associated metabolic disorders through the promotion of adipose browning.

Protective effects of 2,4-dinitrophenol in okadaic acid-induced cellular model of Alzheimer's disease

Alzheimer's disease (AD) research started several decades ago and despite the many efforts employed to develop new treatments or approaches to slow and/or revert disease progression, AD treatment remains an unsolved issue. Knowing that mitochondria loss of function is a central hub for many AD-associated pathophysiological processes, there has been renewed interest in exploring mitochondria as targets for intervention. In this perspective, the present study was aimed to investigate the possible beneficial effects of 2,4 dinitrophenol (DNP), a mitochondrial uncoupler agent, in an in vitro model of AD. Retinoic acid-induced differentiated SH-SY5Y cells were incubated with okadaic acid (OA), a neurotoxin often used as an AD experimental model, and/or with DNP. OA caused a decrease in neuronal cells viability, induced multiple mitochondrial anomalies including increased levels of reactive oxygen species, decreased bioenergetics and mitochondria content markers, and an altered mitochondria morphology. OA-treated cells also presented increased lipid peroxidation levels, and overactivation of tau related kinases (GSK3β, ERK1/2 and AMPK) alongside with a significant augment in tau protein phosphorylation levels. Interestingly, DNP co-treatment ameliorated and rescued OA-induced detrimental effects not only on mitochondria but also but also reinstated signaling pathways homeostasis and ameliorated tau pathology. Overall, our results show for the first time that DNP has the potential to preserve mitochondria homeostasis under a toxic insult, like OA exposure, as well as to reestablish cellular signaling homeostasis. These observations foster the idea that DNP, as a mitochondrial modulator, might represent a new avenue for treatment of AD.

Mitochondria-containing extracellular vesicles from mouse vs . human brain endothelial cells for ischemic stroke therapy

Ischemic stroke-induced mitochondrial dysfunction in the blood-brain barrier-forming brain endothelial cells ( BECs ) results in long-term neurological dysfunction post-stroke. We previously data from a pilot study where intravenous administration of human BEC ( hBEC )-derived mitochondria-containing extracellular vesicles ( EVs ) showed a potential efficacy signal in a mouse middle cerebral artery occlusion ( MCAo ) model of stroke. We hypothesized that EVs harvested from donor species homologous to the recipient species ( e.g., mouse) may improve therapeutic efficacy, and therefore, use of mouse BEC ( mBEC )-derived EVs may improve post-stroke outcomes in MCAo mice. We investigated potential differences in the mitochondria transfer of EVs derived from the same species as the recipient cell (mBEC-EVs and recipient mBECs or hBECs-EVs and recipient hBECs) vs . cross-species EVs and recipient cells (mBEC-EVs and recipient hBECs or vice versa ). Our results showed that while both hBEC- and mBEC-EVs transferred EV mitochondria, mBEC-EVs outperformed hBEC-EVs in increasing ATP levels and improved recipient mBEC mitochondrial function via increasing oxygen consumption rates. mBEC-EVs significantly reduced brain infarct volume and neurological deficit scores compared to vehicle-injected MCAo mice. The superior therapeutic efficacy of mBEC-EVs in a mouse MCAo stroke support the continued use of mBEC-EVs to optimize the therapeutic potential of mitochondria-containing EVs in preclinical mouse models.

Improvement in Epigenetic Aging Clock Induced by BioBran Containing Rice Kefiran in Relation to Various Biomarkers: A Pilot Study

Many lifestyle-related diseases such as cancer, dementia, myocardial infarction, and stroke are known to be caused by aging, and the WHO's ICD-11 (International Classification of Diseases, 11th edition) created the code "aging-related" in 2022. In other words, aging is irreversible but aging-related diseases are reversible, so taking measures to treat them is important for health longevity and preventing other diseases. Therefore, in this study, we used BioBran containing rice kefiran as an approach to improve aging. Rice kefiran has been reported to improve the intestinal microflora, regulate the intestines, and have anti-aging effects. BioBran has also been reported to have antioxidant effects and improve liver function, and human studies have shown that it affects the diversity of the intestinal microbiota. Quantitative measures of aging that correlate with disease risk are now available through the epigenetic clock test, which examines the entire gene sequence and determines biological age based on the methylation level. Horvath's Clock is the best known of many epigenetic clock tests and was published by Steve Horvath in 2013. In this study, we examine the effect of using Horvath's Clock to improve aging and report on the results, which show a certain effect.

J24335 exerts neuroprotective effects against 6-hydroxydopamine-induced lesions in PC12 cells and mice

Parkinson's disease is the second most prevalent age-related neurodegenerative disease and disrupts the lives of people aged >60 years. Meanwhile, single-target drugs becoming inapplicable as PD pathogenesis diversifies. Mitochondrial dysfunction and neurotoxicity have been shown to be relevant to the pathogenesis of PD. The novel synthetic compound J24335 (11-Hydroxy-1-(8-methoxy-5-(trifluoromethyl)quinolin-2-yl)undecan-1-one oxime), which has been researched similarly to J2326, has the potential to be a multi-targeted drug and alleviate these lesions. Therefore, we investigated the mechanism of action and potential neuroprotective function of J24335 against 6-OHDA-induced neurotoxicity in mice, and in PC12 cell models. The key target of action of J24335 was also screened. MTT assay, LDH assay, flow cytometry, RT-PCR, LC-MS, OCR and ECAR detection, and Western Blot analysis were performed to characterize the neuroprotective effects of J24335 on PC12 cells and its potential mechanism. Behavioral tests and immunohistochemistry were used to evaluate behavioral changes and brain lesions in mice. Moreover, bioinformatics was employed to assess the drug-likeness of J24335 and screen its potential targets. J24335 attenuated the degradation of mitochondrial membrane potential and enhanced glucose metabolism and mitochondrial biosynthesis to ameliorate 6-OHDA-induced mitochondrial dysfunction. Animal behavioral tests demonstrated that J24335 markedly improved motor function and loss of TH-positive neurons and dopaminergic nerve fibers, and contributed to an increase in the levels of dopamine and its metabolites in brain tissue. The activation of both the CREB/PGC-1α/NRF-1/TFAM and PKA/Akt/GSK-3β pathways was a major contributor to the neuroprotective effects of J24335. Furthermore, bioinformatics predictions revealed that J24335 is a low toxicity and highly BBB permeable compound targeting 8 key genes (SRC, EGFR, ERBB2, SYK, MAPK14, LYN, NTRK1 and PTPN1). Molecular docking suggested a strong and stable binding between J24335 and the 8 core targets. Taken together, our results indicated that J24335, as a multi-targeted neuroprotective agent with promising therapeutic potential for PD, could protect against 6-OHDA-induced neurotoxicity via two potential pathways in mice and PC12 cells.

Cutaneous Redox Senescence

Our current understanding of skin cell senescence involves the role of environmental stressors (UV, O3, cigarette smoke, particulate matter, etc.), lifestyle (diet, exercise, etc.) as well as genetic factors (metabolic changes, hormonal, etc.). The common mechanism of action of these stressors is the disturbance of cellular redox balance characterized by increased free radicals and reactive oxygen species (ROS), and when these overload the intrinsic antioxidant defense system, it can lead to an oxidative stress cellular condition. The main redox mechanisms that activate cellular senescence in the skin involve (1) the oxidative damage of telomeres causing their shortening; (2) the oxidation of proteomes and DNA damage; (3) an a in lysosomal mass through the increased activity of resident enzymes such as senescence-associated β-galactosidase (SA-β-gal) as well as other proteins that are products of lysosomal activity; (4) and the increased expression of SASP, in particular pro-inflammatory cytokines transcriptionally regulated by NF-κB. However, the main targets of ROS on the skin are the proteome (oxi-proteome), followed by telomeres, nucleic acids (DNAs), lipids, proteins, and cytoplasmic organelles. As a result, cell cycle arrest pathways, lipid peroxidation, increased lysosomal content and dysfunctional mitochondria, and SASP synthesis occur. Furthermore, oxidative stress in skin cells increases the activity of p16INK4A and p53 as inhibitors of Rb and CDks, which are important for maintaining the cell cycle. p53 also promotes the inactivation of mTOR-mediated autophagic and apoptotic pathways, leading to senescence. However, these markers alone cannot establish the state of cellular senescence, and multiple analyses are encouraged for confirmation. An updated and more comprehensive approach to investigating skin senescence should include further assays of ox-inflammatory molecular pathways that can consolidate the understanding of cutaneous redox senescence.

The protective effect of Luteolin on chicken spleen lymphocytes from ammonia poisoning through mitochondria and balancing energy metabolism disorders

Ammonia poses a significant challenge in the contemporary intensive breeding industry, resulting in substantial economic losses. Despite this, there is a dearth of research investigating efficacious strategies to prevent ammonia poisoning in poultry. Consequently, the objective of this study was to investigate the molecular mechanisms through which Luteolin (Lut) safeguards mitochondria and restores equilibrium to energy metabolism disorders, thereby shielding chicken spleen lymphocytes from the detrimental effects of ammonia poisoning. Chicken spleen lymphocytes were categorized into 3 distinct groups: the control group, the ammonia group (with the addition of 1 mmol/L of ammonium chloride), and the Lut group (with the treatment of 0.5 μg/mL of Lut for 12 h followed by the addition of 1 mmol/L of ammonium chloride). These groups were then cultured for a duration of 24 h. To investigate the potential protective effect of Lut on lymphocytes exposed to ammonia, various techniques were employed, including CCK-8 analysis, ultrastructural observation, reagent kit methodology, fluorescence microscopy, and quantitative real-time PCR (qRT-PCR). The findings indicate that Lut has the potential to mitigate the morphological damage of mitochondria caused by ammonia poisoning. Additionally, it can counteract the decline in mitochondrial membrane potential, ATP content, and ATPase activities (specifically Na+/K+-ATPase, Ca2+-ATPase, Mg2+-ATPase, and Ca/Mg2+-ATPase) following exposure to ammonia in lymphocytes. Lut also has the ability to regulate the expression of genes involved in mitochondrial fusion (Opa1, Mfn1, and Mfn2) and division (Drp1 and Mff) in spleen lymphocytes after ammonia exposure. This regulation leads to a balanced energy metabolism (HK1, HK2, LDHA, LDHB, PFK, PK, SDHB, and ACO2) and provides protection against ammonia poisoning.

α-Ketoglutarate Attenuates Hyperlipidemia-Induced Endothelial Damage by Activating the Erk-Nrf2 Signaling Pathway to Inhibit Oxidative Stress and Mitochondrial Dysfunction

Aims: α-Ketoglutarate (AKG) is an intermediate of the tricarboxylic acid cycle and a key hub linking amino acid metabolism and glucose oxidation. Previous studies have shown that AKG improved cardiovascular diseases such as myocardial infarction and myocardial hypertrophy through antioxidant and lipid-lowering characteristics. However, its protective effect and mechanism on endothelial injury caused by hyperlipidemia have not been elucidated yet. In this study, we tested whether AKG possesses protective effects on hyperlipidemia-induced endothelial injury and studied the mechanism. Results: AKG administration both in vivo, and in vitro significantly suppressed the hyperlipidemia-induced endothelial damage, regulated ET-1 and nitric oxide levels, and reduced the inflammatory factor interleukin-6 and matrix metallopeptidase-1 by inhibiting oxidative stress and mitochondrial dysfunction. The protective effects were achieved by the mechanism of activating the Nrf2 phase II system through the ERK signaling pathway. Innovation: These results reveal the role of the AKG-ERK-Nrf2 signaling pathway in the prevention of hyperlipidemia-induced endothelial damage, and suggest that AKG, as a mitochondria-targeting nutrient, is a potential drug for the treatment of endothelial damage in hyperlipidemia. Conclusion: AKG ameliorated the hyperlipidemia-induced endothelial damage and inflammatory response by inhibiting oxidative stress and mitochondrial dysfunction. Antioxid. Redox Signal. 39, 777-793.

Carvedilol Phenocopies PGC-1α Overexpression to Alleviate Oxidative Stress, Mitochondrial Dysfunction and Prevent Doxorubicin-Induced Toxicity in Human iPSC-Derived Cardiomyocytes

Doxorubicin (DOX), one of the most effective and widely used anticancer drugs, has the major limitation of cancer treatment-related cardiotoxicity (CTRTOX) in the clinic. Reactive oxygen species (ROS) generation and mitochondrial dysfunction are well-known consequences of DOX-induced injury to cardiomyocytes. This study aimed to explore the mitochondrial functional consequences and associated mechanisms of pretreatment with carvedilol, a ß-blocking agent known to exert protection against DOX toxicity. When disease modeling was performed using cultured rat cardiac muscle cells (H9c2 cells) and human iPSC-derived cardiomyocytes (iPSC-CMs), we found that prophylactic carvedilol mitigated not only the DOX-induced suppression of mitochondrial function but that the mitochondrial functional readout of carvedilol-pretreated cells mimicked the readout of cells overexpressing the major regulator of mitochondrial biogenesis, PGC-1α. Carvedilol pretreatment reduces mitochondrial oxidants, decreases cell death in both H9c2 cells and human iPSC-CM and maintains the cellular 'redox poise' as determined by sustained expression of the redox sensor Keap1 and prevention of DOX-induced Nrf2 nuclear translocation. These results indicate that, in addition to the already known ROS-scavenging effects, carvedilol has a hitherto unrecognized pro-reducing property against the oxidizing conditions induced by DOX treatment, the sequalae of DOX-induced mitochondrial dysfunction and compromised cell viability. The novel findings of our preclinical studies suggest future trial design of carvedilol prophylaxis, such as prescreening for redox state, might be an alternative strategy for preventing oxidative stress writ large in lieu of the current lack of clinical evidence for ROS-scavenging agents.

Oxygen consumption rate to evaluate mitochondrial dysfunction and toxicity in cardiomyocytes

The increase in the types and complexity of diseases has led to significant advances in diagnostic techniques and the availability of effective therapies. Recent studies have focused on the role of mitochondrial dysfunction in the pathogenesis of cardiovascular diseases (CVDs). Mitochondria are important organelles in cells that generate energy. Besides the production of adenosine triphosphate (ATP), the energy currency of cells, mitochondria are also involved in thermogenesis, control of intracellular calcium ions (Ca2+), apoptosis, regulation of reactive oxygen species (ROS), and inflammation. Mitochondrial dysfunction has been implicated in several diseases including cancer, diabetes, some genetic diseases, and neurogenerative and metabolic diseases. Furthermore, the cardiomyocytes of the heart are rich in mitochondria due to the large energy requirement for optimal cardiac function. One of the main causes of cardiac tissue injuries is believed to be mitochondrial dysfunction, which occurs via complicated pathways which have not yet been completely elucidated. There are various types of mitochondrial dysfunction including mitochondrial morphological change, unbalanced levels of substances to maintain mitochondria, mitochondrial damage by drugs, and mitochondrial deletion and synthesis errors. Most of mitochondrial dysfunctions are linked with symptoms and diseases, thus we focus on parts of mitochondrial dysfunction about fission and fusion in cardiomyocytes, and ways to understand the mechanism of cardiomyocyte damage by detecting oxygen consumption levels in the mitochondria.

Molecular Oxygen Levels and Percentages of DNA Damage in TPN Patients

Total parenteral nutrition (TPN) is a life-saving therapy for patients with intestinal failure, but it carries the risk of complications, including an increase in liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) after long-term use. Patients receiving chronic TPN are also exposed to metabolic stress from both the underlying disease and parenteral nutrition. The aim of this study was to compare the concentration of liver transaminases AST and ALT in relation to the rate of oxygen consumption in platelet mitochondria in patients receiving long-term TPN with the degree of oxidative stress induced by lipid emulsions, and to explain their role in cellular energy metabolism and changes in the liver based on the percentage of genomic DNA damage. The study group consisted of 86 TPN patients, while the control group consisted of 86 healthy volunteers who were fed only orally. The results of the study showed that the percentage of molecular oxygen depended on the type of lipid emulsion supplied. Analyzing time on TPN as a factor, we observed a decrease in percentage genomic DNA damage and an increase in percentage molecular oxygen in cells. It remains unclear whether TPN has a direct effect on genomic DNA damage and the level of molecular oxygen in cells during the course of treatment. In conclusion, this study provides important insights into the potential effects of TPN on liver enzymes and cellular metabolism. Further research is needed to better understand the underlying mechanisms and to develop strategies to minimize the risk of complications associated with TPN.

VEGF affects mitochondrial ROS generation in glioma cells and acts as a radioresistance factor

Vascular endothelial growth factor (VEGF) is closely related to angiogenesis. Anticancer therapy by inhibiting VEGF signaling is well established. However, the role of VEGF in cell-cell communication during the response to ionizing radiation is not well understood. Here, we examined the role of VEGF on radiosensitivity of cells. The addition of recombinant VEGF (rVEGF) on cultured rat C6 glioma cells showed a radioprotective effects on X-ray irradiation and reduced oxidative stress. These effects were also observed by endogenous VEGF in supernatant of C6 glioma cells. Reduction of oxidative stress by VEGF is suggested to underlie the radioprotective effects. The mechanism of VEGF-induced reduction of oxidative stress was indicated by a decreased oxygen consumption rate (OCR) in mitochondria. However, the number of DNA double-strand breaks (DSB) immediately after irradiation was not reduced by the treatment with VEGF. These results suggest that VEGF plays a role in cell survival after irradiation by controlling the oxidative condition through mitochondrial function that is independent of the efficiency of DSB induction.

Methods to Evaluate Changes in Mitochondrial Structure and Function in Cancer

Mitochondria are regulators of key cellular processes, including energy production and redox homeostasis. Mitochondrial dysfunction is associated with various human diseases, including cancer. Importantly, both structural and functional changes can alter mitochondrial function. Morphologic and quantifiable changes in mitochondria can affect their function and contribute to disease. Structural mitochondrial changes include alterations in cristae morphology, mitochondrial DNA integrity and quantity, and dynamics, such as fission and fusion. Functional parameters related to mitochondrial biology include the production of reactive oxygen species, bioenergetic capacity, calcium retention, and membrane potential. Although these parameters can occur independently of one another, changes in mitochondrial structure and function are often interrelated. Thus, evaluating changes in both mitochondrial structure and function is crucial to understanding the molecular events involved in disease onset and progression. This review focuses on the relationship between alterations in mitochondrial structure and function and cancer, with a particular emphasis on gynecologic malignancies. Selecting methods with tractable parameters may be critical to identifying and targeting mitochondria-related therapeutic options. Methods to measure changes in mitochondrial structure and function, with the associated benefits and limitations, are summarized.

PGC 1α-Mediates Mitochondrial Damage in the Liver by Inhibiting the Mitochondrial Respiratory Chain as a Non-cholinergic Mechanism of Repeated Low-Level Soman Exposure

This work aimed to assess whether mitochondrial damage in the liver induced by subacute soman exposure is caused by peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) and whether PGC-1α regulates mitochondrial respiratory chain damage. Toxicity mechanism research may provide theoretical support for developing anti-toxic drugs in the future. First, a soman animal model was established in male Sprague-Dawley (SD) rats by subcutaneous soman injection. Then, liver damage was biochemically evaluated, and acetylcholinesterase (AChE) activity was also determined. Transmission electron microscopy (TEM) was performed to examine liver mitochondrial damage, and high-resolution respirometry was carried out for assessing mitochondrial respiration function. In addition, complex I-IV levels were quantitatively evaluated in isolated liver mitochondria by enzyme-linked immunosorbent assay (ELISA). PGC-1α levels were detected with a Jess capillary-based immunoassay device. Finally, oxidative stress was analyzed by quantifying superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), oxidized glutathione (GSSG), and reactive oxygen species (ROS) levels. Repeated low-level soman exposure did not alter AChE activity, while increasing morphological damage of liver mitochondria and liver enzyme levels in rat homogenates. Complex I, II and I + II activities were 2.33, 4.95, and 5.22 times lower after treatment compared with the control group, respectively. Among complexes I-IV, I-III decreased significantly (p < 0.05), and PGC-1α levels were 1.82 times lower after soman exposure than in the control group. Subacute soman exposure significantly increased mitochondrial ROS production, which may cause oxidate stress. These findings indicated dysregulated mitochondrial energy metabolism involves PGC-1α protein expression imbalance, revealing non-cholinergic mechanisms for soman toxicity.

Mitochondria-containing extracellular vesicles (EV) reduce mouse brain infarct sizes and EV/HSP27 protect ischemic brain endothelial cultures

Ischemic stroke causes brain endothelial cell (BEC) death and damages tight junction integrity of the blood-brain barrier (BBB). We harnessed the innate mitochondrial load of BEC-derived extracellular vesicles (EVs) and utilized mixtures of EV/exogenous 27 kDa heat shock protein (HSP27) as a one-two punch strategy to increase BEC survival (via EV mitochondria) and preserve their tight junction integrity (via HSP27 effects). We demonstrated that the medium-to-large (m/lEV) but not small EVs (sEV) transferred their mitochondrial load, that subsequently colocalized with the mitochondrial network of the recipient primary human BECs. Recipient BECs treated with m/lEVs showed increased relative ATP levels and mitochondrial function. To determine if the m/lEV-meditated increase in recipient BEC ATP levels was associated with m/lEV mitochondria, we isolated m/lEVs from donor BECs pre-treated with oligomycin A (OGM, mitochondria electron transport complex V inhibitor), referred to as OGM-m/lEVs. BECs treated with naïve m/lEVs showed a significant increase in ATP levels compared to untreated OGD cells, OGM-m/lEVs treated BECs showed a loss of ATP levels suggesting that the m/lEV-mediated increase in ATP levels is likely a function of their innate mitochondrial load. In contrast, sEV-mediated ATP increases were not affected by inhibition of mitochondrial function in the donor BECs. Intravenously administered m/lEVs showed a reduction in brain infarct sizes compared to vehicle-injected mice in a mouse middle cerebral artery occlusion model of ischemic stroke. We formulated binary mixtures of human recombinant HSP27 protein with EVs: EV/HSP27 and ternary mixtures of HSP27 and EVs with a cationic polymer, poly (ethylene glycol)-b-poly (diethyltriamine): (PEG-DET/HSP27)/EV. (PEG-DET/HSP27)/EV and EV/HSP27 mixtures decreased the paracellular permeability of small and large molecular mass fluorescent tracers in oxygen glucose-deprived primary human BECs. This one-two punch approach to increase BEC metabolic function and tight junction integrity may be a promising strategy for BBB protection and prevention of long-term neurological dysfunction post-ischemic stroke.

Single-cell profiling of healthy human kidney reveals features of sex-based transcriptional programs and tissue-specific immunity

Knowledge of the transcriptional programs underpinning the functions of human kidney cell populations at homeostasis is limited. We present a single-cell perspective of healthy human kidney from 19 living donors, with equal contribution from males and females, profiling the transcriptome of 27677 cells to map human kidney at high resolution. Sex-based differences in gene expression within proximal tubular cells were observed, specifically, increased anti-oxidant metallothionein genes in females and aerobic metabolism-related genes in males. Functional differences in metabolism were confirmed in proximal tubular cells, with male cells exhibiting higher oxidative phosphorylation and higher levels of energy precursor metabolites. We identified kidney-specific lymphocyte populations with unique transcriptional profiles indicative of kidney-adapted functions. Significant heterogeneity in myeloid cells was observed, with a MRC1+LYVE1+FOLR2+C1QC+ population representing a predominant population in healthy kidney. This study provides a detailed cellular map of healthy human kidney, and explores the complexity of parenchymal and kidney-resident immune cells.

Cardiolipin nanodisks confer protection against doxorubicin-induced mitochondrial dysfunction

Doxorubicin (DOX) is an aqueous soluble anthracycline therapeutic widely used in cancer treatment. Although DOX anti-cancer activity is dose-dependent, increased dosage enhances the risk of cardiotoxicity. Despite intensive investigation, the molecular basis of this undesirable side effect has yet to be established. In addition to serving as a DNA intercalation agent, DOX is known to bind to the signature mitochondrial phospholipid, cardiolipin (CL). Consistent with this, DOX associates with aqueous soluble nanoparticles, termed nanodisks (ND), comprised solely of CL and an apolipoprotein scaffold. Fluorescence microscopy analysis revealed that DOX uptake, and targeting to the nucleus of cultured hepatocarcinoma (HepG2) or breast cancer (MCF7) cells, was unaffected by its association with CL-ND. Subsequent studies revealed that free DOX and DOX-CL-ND were equivalent in terms of growth inhibition activity in both cell lines. By contrast, in studies with H9C2 cardiomyocytes, DOX-CL-ND induced a lesser concentration-dependent decline in cell viability than free DOX. Whereas incubation of H9C2 cardiomyocytes with free DOX caused a steep decline in maximal oxygen consumption rate, DOX-CL-ND treated cells were largely unaffected. The data indicate that association of DOX with CL-ND does not diminish its cancer cell growth inhibition activity yet confers protection to cardiomyocytes from DOX-induced effects on aerobic respiration. This study illustrates that interaction with CL plays a role in DOX-induced mitochondrial dysfunction and suggests CL-ND provide a tool for investigating the mechanistic basis of DOX-induced cardiotoxicity.

Measurement of oxygen consumption rates of human renal proximal tubule cells in an array of organ-on-chip devices to monitor drug-induced metabolic shifts

Measurement of cell metabolism in moderate-throughput to high-throughput organ-on-chip (OOC) systems would expand the range of data collected for studying drug effects or disease in physiologically relevant tissue models. However, current measurement approaches rely on fluorescent imaging or colorimetric assays that are focused on endpoints, require labels or added substrates, and lack real-time data. Here, we integrated optical-based oxygen sensors in a high-throughput OOC platform and developed an approach for monitoring cell metabolic activity in an array of membrane bilayer devices. Each membrane bilayer device supported a culture of human renal proximal tubule epithelial cells on a porous membrane suspended between two microchannels and exposed to controlled, unidirectional perfusion and physiologically relevant shear stress for several days. For the first time, we measured changes in oxygen in a membrane bilayer format and used a finite element analysis model to estimate cell oxygen consumption rates (OCRs), allowing comparison with OCRs from other cell culture systems. Finally, we demonstrated label-free detection of metabolic shifts in human renal proximal tubule cells following exposure to FCCP, a drug known for increasing cell oxygen consumption, as well as oligomycin and antimycin A, drugs known for decreasing cell oxygen consumption. The capability to measure cell OCRs and detect metabolic shifts in an array of membrane bilayer devices contained within an industry standard microtiter plate format will be valuable for analyzing flow-responsive and physiologically complex tissues during drug development and disease research.

Restoration of Mitochondrial Function Is Essential in the Endothelium-Dependent Vasodilation Induced by Acacetin in Hypertensive Rats

Mitochondrial dysfunction in the endothelium contributes to the progression of hypertension and plays an obligatory role in modulating vascular tone. Acacetin is a natural flavonoid compound that has been shown to possess multiple beneficial effects, including vasodilatation. However, whether acacetin could improve endothelial function in hypertension by protecting against mitochondria-dependent apoptosis remains to be determined. The mean arterial pressure (MAP) in Wistar Kyoto (WKY) rats, spontaneously hypertensive rats (SHR) administered with acacetin intraperitoneally for 2 h or intragastrically for six weeks were examined. The endothelial injury was evaluated by immunofluorescent staining and a transmission electron microscope (TEM). Vascular tension measurement was performed to assess the protective effect of acacetin on mesenteric arteries. Endothelial injury in the pathogenesis of SHR was modeled in HUVECs treated with Angiotensin II (Ang II). Mitochondria-dependent apoptosis, the opening of Mitochondrial Permeability Transition Pore (mPTP) and mitochondrial dynamics proteins were determined by fluorescence activated cell sorting (FACS), immunofluorescence staining and western blot. Acacetin administered intraperitoneally greatly reduced MAP in SHR by mediating a more pronounced endothelium-dependent dilatation in mesenteric arteries, and the vascular dilatation was reduced remarkably by NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthesis. While acacetin administered intragastrically for six weeks had no apparent effect on MAP, it improved the endothelium-dependent dilatation in SHR by activating the AKT/eNOS pathway and protecting against the abnormalities of endothelium and mitochondria. Furthermore, acacetin remarkably inhibited Ang II induced apoptosis by inhibiting the increased expression of Cyclophilin D (CypD), promoted the opening of mPTP, ROS generation, ATP loss and disturbance of dynamin-related protein 1 (DRP1)/optic atrophy1 (OPA1) dynamics in HUVECs. This study suggests that acacetin protected against endothelial dysfunction in hypertension by activating the AKT/eNOS pathway and modulating mitochondrial function by targeting mPTP and DRP1/OPA1-dependent dynamics.

Evaluation of a Serum-Free Medium for Human Epithelial and Stromal Cell Culture

Over the past decade, growing demand from many domains (research, cosmetics, pharmaceutical industries, etc.) has given rise to significant expansion of the number of in vitro cell cultures. Despite the widespread use of fetal bovine serum, many issues remain. Among them, the whole constitution of most serums remains unknown and is subject to significant variations. Furthermore, the presence of potential contamination and xenogeny elements is challenging for clinical applications, while limited production is an obstacle to the growing demand. To circumvent these issues, a Serum-Free Medium (SFM) has been developed to culture dermal and vesical fibroblasts and their corresponding epithelial cells, namely, keratinocytes and urothelial cells. To assess the impact of SFM on these cells, proliferation, clonogenic and metabolic assays have been compared over three passages to conditions associated with the use of a classic Fetal Bovine Serum-Containing Medium (FBSCM). The results showed that the SFM enabled fibroblast and epithelial cell proliferation while maintaining a morphology, cell size and metabolism similar to those of FBSCM. SFM has repeatedly been found to be better suited for epithelial cell proliferation and clonogenicity. Fibroblasts and epithelial cells also showed more significant mitochondrial metabolism in the SFM compared to the FBSCM condition. However, the SFM may need further optimization to improve fibroblast proliferation.

Enhancing and stabilization of cord blood regulatory T-cell suppressive function by human mesenchymal stem cell (MSC)-derived exosomes

FOXP3+ regulatory T cells (Tregs) are central to maintaining peripheral tolerance and immune homeostasis. They have the potential to be developed as a cellular therapy to treat various clinical ailments such as autoimmune disorders, inflammatory diseases and to improve transplantation outcomes. However, a major question remains whether Tregs can persist and exert their function effectively in a disease state, where a broad spectrum of inflammatory mediators could inactivate Tregs. In this study, we investigated the potential of mesenchymal stem cell (MSC)-derived exosomes to promote and sustain Tregs function. MSC-conditioned media (MSC-CM) cultured Tregs were more suppressive in both polyclonal and allogeneic responses and were resistant to inflammatory stimulation in vitro compared with the controls. A similar enhancement of Treg function was also observed by culturing Tregs with MSC-derived exosomes alone. The enhanced suppressive activity and stability of Treg cultured in MSC-CM was reduced when exosomes were depleted from MSC-CM. We identified that MSC-derived exosomes could upregulate the expression of LC3(II/I), phosphorylate Jak3 and Stat5 to promote Treg survival, and regulate FOXP3 expression in Tregs. Overall, our study demonstrates that MSC-derived exosomes are capable of enhancing Hucb-Tregs function and stability by activating autophagy and Stat5 signalling pathways. Our findings provide a strong rationale for utilizing MSC-derived exosomes as an effective strategy to enhance Treg function, and improve the overall Tregs-based cell therapy landscape.

IFNγ Regulates NAD+ Metabolism to Promote the Respiratory Burst in Human Monocytes

IFNγ is an essential and pleiotropic activator of human monocytes, but little is known about the changes in cellular metabolism required for IFNγ-induced activation. We sought to elucidate the mechanisms by which IFNγ reprograms monocyte metabolism to support its immunologic activities. We found that IFNγ increased oxygen consumption rates (OCR) in monocytes, indicative of reactive oxygen species generation by both mitochondria and NADPH oxidase. Transcriptional profiling revealed that this oxidative phenotype was driven by IFNγ-induced reprogramming of NAD+ metabolism, which is dependent on nicotinamide phosphoribosyltransferase (NAMPT)-mediated NAD+ salvage to generate NADH and NADPH for oxidation by mitochondrial complex I and NADPH oxidase, respectively. Consistent with this pathway, monocytes from patients with gain-of-function mutations in STAT1 demonstrated higher than normal OCR. Whereas chemical or genetic disruption of mitochondrial complex I (rotenone treatment or Leigh Syndrome patient monocytes) or NADPH oxidase (DPI treatment or chronic granulomatous disease (CGD) patient monocytes) reduced OCR. Interestingly, inhibition of NAMPT in healthy monocytes completely abrogated the IFNγ-induced oxygen consumption, comparable to levels observed in CGD monocytes. These data identify an IFNγ-induced, NAMPT-dependent, NAD+ salvage pathway that is critical for IFNγ activation of human monocytes.

Macrophage metabolism in the intestine is compartment specific and regulated by the microbiota

Intestinal macrophages play a vital role in the maintenance of gut homeostasis through signals derived from the microbiota. We previously demonstrated that microbial-derived metabolites can shape the metabolic functions of macrophages. Here, we show that antibiotic-induced disruption of the intestinal microbiota dramatically alters both the local metabolite environment and the metabolic functions of macrophages in the colon. Broad-spectrum antibiotic administration in mice increased the expression of the large neutral amino acid transporter LAT1 and accordingly, amino acid uptake. Subsequently, antibiotic administration enhanced the metabolic functions of colonic macrophages, increasing phosphorylation of components of mammalian/mechanistic target of rapamycin signalling pathways, with increased expression of genes involved in glycolysis and oxidative phosphorylation (OXPHOS), increased mitochondrial function, increased rate of extracellular acidification (ECAR; measure of glycolysis) and increased rate of oxygen consumption (OCR; measure of OXPHOS). Small bowel macrophages were less metabolically active than their colonic counterparts, with macrophage metabolism in the small intestine being independent of the microbiota. Finally, we reveal tissue-resident Tim4⁺  CD4⁺ macrophages exhibit enhanced fatty acid uptake alongside reduced fatty acid synthesis compared to recruited macrophages. Thus, the microbiota shapes gut macrophage metabolism in a compartment-specific manner, with important implications for monocyte recruitment and macrophage differentiation.

Morphine-induced modulation of Nrf2-antioxidant response element signaling pathway in primary human brain microvascular endothelial cells

Morphine is one of the most potent opioid analgesic used for pain treatment. Morphine action in the central nervous system requires crossing the blood-brain barrier. Due to the controversial relationship between morphine and oxidative stress, the potential pro- or antioxidant effects of morphine in the blood-brain barrier is important to be understood, as oxidative stress could cause its disruption and predispose to neurodegenerative diseases. However, investigation is scarce in human brain endothelial cells. Therefore, the present study evaluated the impact of morphine exposure at three different concentrations (1, 10 and 100 µM) for 24 h and 48 h on primary human brain microvascular endothelial cells. A quantitative data-independent acquisition mass spectrometry strategy was used to analyze proteome modulations. Almost 3000 proteins were quantified of which 217 were reported to be significantly regulated in at least one condition versus untreated control. Pathway enrichment analysis unveiled dysregulation of the Nrf2 pathway involved in oxidative stress response. Seahorse assay underlined mitochondria dysfunctions, which were supported by significant expression modulations of relevant mitochondrial proteins. In conclusion, our study revealed the dysregulation of the Nrf2 pathway and mitochondria dysfunctions after morphine exposure, highlighting a potential redox imbalance in human brain endothelial cells.

Anti-HIV Drugs Cause Mitochondrial Dysfunction in Monocyte-Derived Macrophages

Combination antiretroviral therapy (cART) dramatically changed the face of the HIV/AIDS pandemic, making it one of the most prominent medical breakthroughs of the past 3 decades. However, as the life span of persons living with HIV (PLWH) continues to approach that of the general population, the same cannot be said regarding their quality of life. PLWH are affected by comorbid conditions such as high blood pressure, diabetes, and neurocognitive impairment at a higher rate and increased severity than their age-matched counterparts. PLWH also have higher levels of inflammation, the drivers of which are not entirely clear. As cART treatment is lifelong, we assessed here the effects of cART, independent of HIV, on primary human monocyte-derived macrophages (MDMs). MDMs were unskewed or skewed to an alternative phenotype and treated with Atripla or Triumeq, two first-line cART treatments. We report that Triumeq skewed alternative MDMs toward an inflammatory nonsenescent phenotype. Both Atripla and Triumeq caused mitochondrial dysfunction, specifically efavirenz and abacavir. Additionally, transcriptome sequencing (RNA-seq) demonstrated that both Atripla and Triumeq caused differential regulation of genes involved in immune regulation and cell cycle and DNA repair. Collectively, our data demonstrate that cART, independent of HIV, alters the MDM phenotype. This suggests that cART may contribute to cell dysregulation in PLWH that subsequently results in increased susceptibility to comorbidities.

Comparative study of two isothiazolinone biocides, 1,2-benzisothiazolin-3-one (BIT) and 4,5-dichloro-2-n-octyl-isothiazolin-3-one (DCOIT), on barrier function and mitochondrial bioenergetics using murine brain endothelial cell line (bEND.3)

Isothiazolinone (IT) biocides are potent antibacterial substances used as preservatives and disinfectants. These biocides exert differing biocidal effects and display environmental stability based upon chemical structure. In agreement with our recent study reporting that 2-n-octyl-4-isothiazolin-3-one (OIT) induced dysfunction of the blood-brain barrier (BBB), the potential adverse health effects of two IT biocides 1,2-benzisothiazolin-3-one (BIT) and 4,5-dichloro-2-n-octyl-isothiazolin-3-one (DCOIT) were compared using brain endothelial cells (ECs) derived from murine brain endothelial cell line (bEND.3). BIT possesses an unchlorinated IT ring structure and used as a preservative in cleaning products. DCOIT contains a chlorinated IT ring structure and employed as an antifouling agent in paints. Data demonstrated that DCOIT altered cellular metabolism at a lower concentration than BIT. Both BIT and DCOIT increased reactive oxygen species (ROS) generation at the mitochondrial and cellular levels. However, the effect of DCOIT on glutathione (GSH) levels appeared to be greater than BIT. While mitochondrial membrane potential (MMP) was decreased in both BIT- and DCOIT-exposed cells, direct disturbance in mitochondrial bioenergetic flux was only observed in BIT-treated ECs. Taken together, IT biocides produced toxicity in brain EC and barrier dysfunction, but at different concentration ranges suggesting distinct differing mechanisms related to chemical structure.

Paraquat-induced cholesterol biosynthesis proteins dysregulation in human brain microvascular endothelial cells

Despite Paraquat (PQ) being banned in several countries, it is still one of the most commonly used herbicides in agriculture. This compound is known to induce damaging effects on human and animal brain cells by generating Reactive Oxygen Species (ROS). However, there is few evidence of PQ effect on Human Brain Microvascular Endothelial Cells (HBMECs), one of the major component of the Blood–Brain Barrier (BBB). The present study aimed at unraveling biological mechanisms associated to the exposure of 1, 10 and 100 µM of PQ for 24 h on HBMECs. High-throughput mass spectrometry-based proteomics using data-independent acquisition (DIA) was applied. Biological pathway enrichment and cellular assays such as mitochondrial respiration and cholesterol level were performed to verify proteomics results. A total of 3753 proteins were quantified out of which 419 were significantly modulated by paraquat exposure. Biological pathway enrichment revealed the ubiquinone metabolism, a pathway directly linked to mitochondrial complex I proteins, confirming the well-known mechanism of PQ inducing oxidative stress. Additionally, this study also described the cholesterol biosynthesis modulation on HBMECs not yet described. In conclusion, our data indicate the toxic effect of PQ on HBMECs by downregulating proteins involved in mitochondrial complex I and cholesterol pathways.

Ex vivo Assessment of Mitochondrial Function in Human Peripheral Blood Mononuclear Cells Using XF Analyzer

Cellular health and function, as we know today, depend on a large extent on mitochondrial function. The essential function of mitochondria is the energy production, more precisely ATP production, via oxidative phosphorylation. Mitochondrial energy production parameters therefore represent important biomarkers. Studies on human cells have mainly been performed on in vitro cell cultures. However, peripheral blood mononuclear cells (PBMCs) are particularly suitable for such examinations. That's why this protocol describes a method to measure key parameters of mitochondrial function in freshly isolated PBMCs with the latest technology, the XF Analyzer. For this ex vivo approach PBMCs are first isolated out of human anticoagulated blood. Next, they are attached to the surface of special microplates pre-coated with Poly-D-Lysine. During the subsequent measurement of oxygen consumption rate (OCR) as well as extracellular acidification rate (ECAR) the stress reagents oligomycin, carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), rotenone and antimycin A are injected. Several mitochondrial parameters can be calculated from the results obtained. The application of this protocol allows the analysis of various influences, such as pharmaceuticals or environmental factors, on human cells.

Mitochondrial miR-181a-5p promotes glucose metabolism reprogramming in liver cancer by regulating the electron transport chain

Liver cancer and other malignant tumor cells rely on the glycolytic pathway to obtain energy (i.e. the Warburg effect); however, the underlying mechanism is unclear. Mitochondria are sites of oxidative phosphorylation and adenosine triphosphate (ATP) production. The 13 constituent respiratory chain proteins encoded by the mitochondrial genome (namely, mtDNA) play essential roles. We found that in human hepatocellular carcinoma (HCC) tissues, 11 out of the 13 mtDNA-encoded genes exhibited decreased mRNA levels and 5 genes displayed decreased protein levels, including the cytochrome B (mt-CYB) and cytochrome C oxidase II (mt-CO2) genes. Mitochondrial gene sequencing revealed abnormalities in the levels of a large number of mitochondrial miRNAs (mitomiRs). MicroRNA-181a-5p (mir-181a-5p), which potentially targets genes encoding mt-CYB and mt-CO2 protein, was screened out from 549 downregulated mitomiRs via bioinformatic analysis. After overexpression of mitomiR-181a-5p, mt-CYB and mt-CO2 levels were reduced in HCC cells, and the mitochondrial membrane potential (MMP) maintained by the electron transport chain (ETC) was decreased. Furthermore, the expression of hexokinase 2 (HK2) and glucose transporter type 1 (GLUT1) was upregulated, accompanied by elevated glucose, lactic acid release, and activity of lactate dehydrogenase (LDH). In vivo experiments confirmed that constitutive mitomiR-181a-5p expression caused reprogramming of glucose metabolism and promoted tumor growth and early lung metastasis in liver cancer. In summary, the present study reveals the important role of mitomiRs in glucose metabolism reprogramming in liver cancer, which is of considerable value in exploring new therapeutic targets for HCC.

Targeting breast cancer metabolism with a novel inhibitor of mitochondrial ATP synthesis

Inhibitors of mitochondrial respiration and ATP synthesis may promote the selective killing of respiration-competent cancer cells that are critical for tumor progression. We previously reported that CADD522, a small molecule inhibitor of the RUNX2 transcription factor, has potential for breast cancer treatment. In the current study, we show that CADD522 inhibits mitochondrial oxidative phosphorylation by decreasing the mitochondrial oxygen consumption rate (OCR) and ATP production in human breast cancer cells in a RUNX2-independent manner. The enzyme activity of mitochondrial ATP synthase was inhibited by CADD522 treatment. Importantly, results from cellular thermal shift assays that detect drug-induced protein stabilization revealed that CADD522 interacts with both α and β subunits of the F1-ATP synthase complex. Differential scanning fluorimetry also demonstrated interaction of α subunits of the F1-ATP synthase to CADD522. These results suggest that CADD522 might target the enzymatic F1 subunits in the ATP synthase complex. CADD522 increased the levels of intracellular reactive oxygen species (ROS), which was prevented by MitoQ, a mitochondria-targeted antioxidant, suggesting that cancer cells exposed to CADD522 may elevate ROS from mitochondria. CADD522-increased mitochondrial ROS levels were enhanced by exogenously added pro-oxidants such as hydrogen peroxide or tert-butyl hydroperoxide. Conversely, CADD522-mediated cell growth inhibition was blocked by N-acetyl-l-cysteine, a general ROS scavenger. Therefore, CADD522 may exert its antitumor activity by increasing mitochondrial driven cellular ROS levels. Collectively, our data suggest in vitro proof-of-concept that supports inhibition of mitochondrial ATP synthase and ROS generation as contributors to the effectiveness of CADD522 in suppression of tumor growth.

Potent Anticancer Effect of the Natural Steroidal Saponin Gracillin Is Produced by Inhibiting Glycolysis and Oxidative Phosphorylation-Mediated Bioenergetics

Metabolic rewiring to utilize aerobic glycolysis is a hallmark of cancer. However, recent findings suggest the role of mitochondria in energy generation in cancer cells and the metabolic switch to oxidative phosphorylation (OXPHOS) in response to the blockade of glycolysis. We previously demonstrated that the antitumor effect of gracillin occurs through the inhibition of mitochondrial complex II-mediated energy production. Here, we investigated the potential of gracillin as an anticancer agent targeting both glycolysis and OXPHOS in breast and lung cancer cells. Along with the reduction in adenosine triphosphate (ATP) production, gracillin markedly suppresses the production of several glycolysis-associated metabolites. A docking analysis and enzyme assay suggested phosphoglycerate kinase 1 (PGK1) is a potential target for the antiglycolytic effect of gracillin. Gracillin reduced the viability and colony formation ability of breast cancer cells by inducing apoptosis. Gracillin displayed efficacious antitumor effects in mice bearing breast cancer cell line or breast cancer patient-derived tumor xenografts with no overt changes in body weight. An analysis of publicly available datasets further suggested that PGK1 expression is associated with metastasis status and poor prognosis in patients with breast cancer. These results suggest that gracillin is a natural anticancer agent that inhibits both glycolysis and mitochondria-mediated bioenergetics.

A genetic toolkit for the analysis of metabolic changes in Drosophila provides new insights into metabolic responses to stress and malignant transformation

Regulation of the energetic metabolism occurs fundamentally at the cellular level, so analytical strategies must aim to attain single cell resolution to fully embrace its inherent complexity. We have developed methods to utilize a toolset of metabolic FRET sensors for assessing lactate, pyruvate and 2-oxoglutarate levels of Drosophila tissues in vivo by imaging techniques. We show here how the energetic metabolism is altered by hypoxia: While some larval tissues respond to low oxygen levels by executing a metabolic switch towards lactic fermentation, the fat body and salivary glands do not alter their energetic metabolism. Analysis of tumor metabolism revealed that depending on the genetic background, some tumors undergo a lactogenic switch typical of the Warburg effect, while other tumors do not. This toolset allows for developmental and physiologic studies in genetically manipulated Drosophila individuals in vivo.

Isolation and Differentiation of Primary Myoblasts from Mouse Skeletal Muscle Explants

Primary myoblasts are undifferentiated proliferating precursors of skeletal muscle. They can be cultured and studied as muscle precursors or induced to differentiate into later stages of muscle development. The protocol provided here describes a robust method for the isolation and culture of a highly proliferative population of myoblast cells from young adult mouse skeletal muscle explants. These cells are useful for the study of the metabolic properties of skeletal muscle of different mouse models, as well as in other downstream applications such as transfection with exogenous DNA or transduction with viral expression vectors. The level of differentiation and metabolic profile of these cells depends on the length of exposure, and composition of the media used to induce myoblast differentiation. These methods provide a robust system for the study of mouse muscle cell metabolism ex vivo. Importantly, unlike in vivo models, the methods described here provide a cell population that can be expanded and studied with high levels of reproducibility.

FASN activity is important for the initial stages of the induction of senescence

Senescent cells accumulate in several tissues during ageing and contribute to several pathological processes such as ageing and cancer. Senescence induction is a complex process not well defined yet and is characterized by a series of molecular changes acquired after an initial growth arrest. We found that fatty acid synthase (FASN) levels increase during the induction of senescence in mouse hepatic stellate cells and human primary fibroblasts. Importantly, we also observed a significant increase in FASN levels during ageing in mouse liver tissues. To probe the central role of FASN in senescence induction, we used a small-molecule inhibitor of FASN activity, C75. We found that C75 treatment prevented the induction of senescence in mouse and human senescent cells. Importantly, C75 also reduced the expression of the signature SASP factors interleukin 1α (IL-1α), IL-1β and IL-6, and suppressed the secretion of small extracellular vesicles. These findings were confirmed using a shRNA targeting FASN. In addition, we find that FASN inhibition induces metabolic changes in senescent cells. Our work underscores the importance of C75 as a pharmacological inhibitor for reducing the impact of senescent cell accumulation.

Live-Imaging Readouts and Cell Models for Phenotypic Profiling of Mitochondrial Function

Mitochondria are best known as the powerhouses of the cells but their cellular role goes far beyond energy production; among others, they have a pivotal function in cellular calcium and redox homeostasis. Mitochondrial dysfunction is often associated with severe and relatively rare disorders with an unmet therapeutic need. Given their central integrating role in multiple cellular pathways, mitochondrial dysfunction is also relevant in the pathogenesis of various other, more common, human pathologies. Here we discuss how live-cell high content microscopy can be used for image-based phenotypic profiling to assess mitochondrial (dys) function. From this perspective, we discuss a selection of live-cell fluorescent reporters and imaging strategies and discuss the pros/cons of human cell models in mitochondrial research. We also present an overview of live-cell high content microscopy applications used to detect disease-associated cellular phenotypes and perform cell-based drug screening.

Leucine supplementation attenuates macrophage foam-cell formation: Studies in humans, mice, and cultured macrophages

Whereas atherogenicity of dietary lipids has been largely studied, relatively little is known about the possible contribution of dietary amino acids to macrophage foam-cell formation, a hallmark of early atherogenesis. Recently, we showed that leucine has antiatherogenic properties in the macrophage model system. In this study, an in-depth investigation of the role of leucine in macrophage lipid metabolism was conducted by supplementing humans, mice, or cultured macrophages with leucine. Macrophage incubation with serum obtained from healthy adults supplemented with leucine (5 g/d, 3 weeks) significantly decreased cellular cholesterol mass by inhibiting the rate of cholesterol biosynthesis and increasing cholesterol efflux from macrophages. Similarly, leucine supplementation to C57BL/6 mice (8 weeks) resulted in decreased cholesterol content in their harvested peritoneal macrophages (MPM) in relation with reduced cholesterol biosynthesis rate. Studies in J774A.1 murine macrophages revealed that leucine dose-dependently decreased cellular cholesterol and triglyceride mass. Macrophages treated with leucine (0.2 mM) showed attenuated uptake of very low-density lipoproteins and triglyceride biosynthesis rate, with a concurrent down-regulation of diacylglycerol acyltransferase-1, a key enzyme catalyzing triglyceride biosynthesis in macrophages. Similar effects were observed when macrophages were treated with α-ketoisocaproate, a key leucine metabolite. Finally, both in vivo and in vitro leucine supplementation significantly improved macrophage mitochondrial respiration and ATP production. The above studies, conducted in human, mice, and cultured macrophages, highlight a protective role for leucine attenuating macrophage foam-cell formation by mechanisms related to the metabolism of cholesterol, triglycerides, and energy production. © 2018 BioFactors, 44(3):245-262, 2018.

Patient-derived lymphoblastoid cell lines harboring mitochondrial DNA mutations as tool for small molecule drug discovery

Objective

Mitochondrial diseases are a group of devastating disorders for which there is no transformative cure. The majority of therapies for mitochondrial disease—approved, previously tested, or currently in development—are small molecules. The implementation of better cell-based models of mitochondrial disease can accelerate and improve the accuracy of small molecule drug discovery. The objective of this study is to evaluate the use of patient-derived lymphoblastoid cell lines for small molecule research in mitochondrial disease.

Results

Five lymphoblastoid cell lines derived from mitochondrial disease patients harboring point mutations in mtND1, mtND4, or mtATP6 were characterized in two high throughput assays assessing mitochondrial function. In a pilot “clinical trial in a dish” experiment, the efficacy of idebenone—an approved therapy for mitochondrial disease—on the lymphoblastoid cell lines was tested. Idebenone increased the basal respiration of all lymphoblastoid cell lines except those harboring the 8993T>G point mutation in mtATP6. Our results posit lymphoblastoid cell lines as a strong model for mitochondrial disease research with small molecules and have implications for the clinical efficacy of idebenone.

The phenotype of peritoneal mouse macrophages depends on the mitochondria and ATP/ADP homeostasis

Different macrophage subtypes have different morphologies/shapes and functions. Naïve M0 macrophages are elongated. Pro-inflammatory M1 that produce the bactericidal molecule iNos are round. Anti-inflammatory M2 macrophages that produce the pro-healing enzyme Arg-1 are highly elongated. We showed previously that the morphologies of M0 and M2 but not M1 macrophages are RhoA-dependent. Macrophage-specific deletion of RhoA causes the extreme elongation (hummingbird phenotype) of M0 and M2 but not M1 macrophages. The M1 and M2 macrophages also differ in their metabolic status. Here, we studied the effect of the oxidative phosphorylation inhibitors, antimycin A and oligomycin A, at a suboptimal dose, which depolarizes mitochondria but does not eliminate mitochondrial functions, on the mitochondria/energy production and phenotype of wild-type and RhoA-deleted M0, M1 and M2 peritoneal mouse macrophages. We found that, while untreated M1 macrophages had the lowest and the M2 had the highest level of ATP the ATP/ADP ratio was nearly identical between M0, M1 and M2 macrophages. Inhibitor treatment resulted in approximately 60% increase in ATP level and ATP/ADP ratio in M0 and M2 macrophages, and decrease in the level of filamentous (F) actin, and these changes correlated with a drastic shortening/tail retraction of M0 and M2 macrophages, and decreased expression of Arg-1 in M2 macrophages. The treatment of M1 macrophages caused only a 30% increase in the ATP level and ATP/ADP ratio, and while it did not affect the shape of M1 macrophages, it increased the production of iNos. This indicates that the maintenance of mouse macrophage phenotypes depends on mitochondrial function and ATP/ADP homeostasis.