In vitro characterization of mitochondrial function and structure in rat and human cells with a deficiency of the NADH: ubiquinone oxidoreductase Ndufc2 subunit

Cis-eQTLs in seven duck tissues identify novel candidate genes for growth and carcass traits

BACKGROUND

Expression quantitative trait loci (eQTL) studies aim to understand the influence of genetic variants on gene expression. The colocalization of eQTL mapping and GWAS strategy could help identify essential candidate genes and causal DNA variants vital to complex traits in human and many farm animals. However, eQTL mapping has not been conducted in ducks. It is desirable to know whether eQTLs within GWAS signals contributed to duck economic traits.

RESULTS

In this study, we conducted an eQTL analysis using publicly available RNA sequencing data from 820 samples, focusing on liver, muscle, blood, adipose, ovary, spleen, and lung tissues. We identified 113,374 cis-eQTLs for 12,266 genes, a substantial fraction 39.1% of which were discovered in at least two tissues. The cis-eQTLs of blood were less conserved across tissues, while cis-eQTLs from any tissue exhibit a strong sharing pattern to liver tissue. Colocalization between cis-eQTLs and genome-wide association studies (GWAS) of 50 traits uncovered new associations between gene expression and potential loci influencing growth and carcass traits. SRSF4, GSS, and IGF2BP1 in liver, NDUFC2 in muscle, ELF3 in adipose, and RUNDC1 in blood could serve as the candidate genes for duck growth and carcass traits.

CONCLUSIONS

Our findings highlight substantial differences in genetic regulation of gene expression across duck primary tissues, shedding light on potential mechanisms through which candidate genes may impact growth and carcass traits. Furthermore, this availability of eQTL data offers a valuable resource for deciphering further genetic association signals that may arise from ongoing extensive endeavors aimed at enhancing duck production traits.

Mitochondrial Dysfunction in Heart Failure: From Pathophysiological Mechanisms to Therapeutic Opportunities

Mitochondrial dysfunction, a feature of heart failure, leads to a progressive decline in bioenergetic reserve capacity, consisting in a shift of energy production from mitochondrial fatty acid oxidation to glycolytic pathways. This adaptive process of cardiomyocytes does not represent an effective strategy to increase the energy supply and to restore the energy homeostasis in heart failure, thus contributing to a vicious circle and to disease progression. The increased oxidative stress causes cardiomyocyte apoptosis, dysregulation of calcium homeostasis, damage of proteins and lipids, leakage of mitochondrial DNA, and inflammatory responses, finally stimulating different signaling pathways which lead to cardiac remodeling and failure. Furthermore, the parallel neurohormonal dysregulation with angiotensin II, endothelin-1, and sympatho-adrenergic overactivation, which occurs in heart failure, stimulates ventricular cardiomyocyte hypertrophy and aggravates the cellular damage. In this review, we will discuss the pathophysiological mechanisms related to mitochondrial dysfunction, which are mainly dependent on increased oxidative stress and perturbation of the dynamics of membrane potential and are associated with heart failure development and progression. We will also provide an overview of the potential implication of mitochondria as an attractive therapeutic target in the management and recovery process in heart failure.

Abnormal expression of sphingolipid-metabolizing enzymes in the heart of spontaneously hypertensive rat models

Sphingolipids exert important roles within the cardiovascular system and related diseases. Perturbed sphingolipid metabolism was previously reported in cerebral and renal tissues of spontaneously hypertensive rats (SHR). Specific defects related to the synthesis of sphingolipids and to the metabolism of Sphingosine-1-Phospahte (S1P) were exclusively identified in the stroke-prone (SHRSP) with the respect to the stroke-resistant (SHRSR) strain. In this study, we explored any existing perturbation in either protein or gene expression of enzymes involved in the sphingolipid pathways in cardiac tissue from both SHRSP and SHRSR strains, compared to the normotensive Wistar Kyoto (WKY) strain. The two hypertensive rat models showed an overall perturbation of the expression of different enzymes involved in the sphingolipid metabolism in the heart. In particular, whereas the expression of the S1P-metabolizing-enzyme, SPHK2, was significantly reduced in both SHR strains, SGPL1 protein levels were decreased only in SHRSP. The protein levels of S1P receptors 1-3 were reduced only in the cardiac tissue of SHRSP, whereas S1PR2 levels were reduced in both SHR strains. The de novo synthesis of sphingolipids was aberrant in the two hypertensive strains. A significant reduction of mRNA expression of the Sgms1 and Smpd3 enzymes, implicated in the metabolism of sphingomyelin, was found in both hypertensive strains. Interestingly, Smpd2, devoted to sphingomyelin degradation, was reduced only in the heart of SHRSP. In conclusion, alterations in the expression of sphingolipid-metabolizing enzymes may be involved in the susceptibility to cardiac damage of hypertensive rat strains. Specific differences detected in the SHRSP, however, deserve further elucidation.

NDUFC2 deficiency exacerbates endothelial mesenchymal transformation during ischemia-reperfusion via NLRP3

Ischemic stroke is the main type of cerebrovascular disease. Emergency thrombectomy combined with medication therapy is currently the primary treatment for stroke. Inflammation and oxidative stress induced by ischemia-reperfusion cause secondary damage to blood vessels, especially endothelial mesenchymal transformation (EndoMT). However, much is still unclear about the role of EndoMT in ischemia-reperfusion. In this study, an in vivo ischemia-reperfusion model was established by transient middle cerebral artery occlusion (tMCAO) in wild-type (WT) C57BL/6 mice and NLRP3 (NOD-like receptor thermal protein domain associated protein 3) knockout (KO) C57BL/6 mice. An in vitro ischemia-reperfusion model was established by oxygen glucose deprivation and reoxygenation (OGD/R) of human brain microvascular endothelial cells (HBMECs). α-SMA (alpha smooth muscle actin), CD31 (platelet endothelial cell adhesion molecule-1, PECAM-1/CD31), NDUFC2 (NADH: ubiquinone oxidoreductase subunit C2), and NLRP3 were used to evaluate EndoMT and inflammation. Real-time PCR measured superoxide dismutase 1 (SOD1) and catalase (CAT) mRNA expression to evaluate oxidative stress levels. NLRP3 was activated by ischemia-reperfusion injury and NLRP3 inactivation inhibited the EndoMT in tMCAO mice. Further experiments demonstrated that OGD/R treatment induced NLRP3 activation and EndoMT in HBMECs, which resulted in NDUFC2 deficiency. NDUFC2 overexpression suppressed NLRP3 activation and EndoMT in HBMECs induced by OGD/R. Moreover, NDUFC2 overexpression rescued SOD1 and CAT mRNA expression. These results demonstrated that NDUFC2 deficiency decreased the antioxidant levels, leading to NLRP3 activation and EndoMT during ischemia-reperfusion injury and suggesting that NDUFC2 is a potential drug target for the treatment of ischemic stroke.

Polymorphic variants at NDUFC2, encoding a mitochondrial complex I subunit, associate with cardiac hypertrophy in human hypertension

BACKGROUND

A dysfunction of NADH dehydrogenase, the mitochondrial Complex I (CI), associated with the development of left ventricular hypertrophy (LVH) in previous experimental studies. A deficiency of Ndufc2 (subunit of CI) impairs CI activity causing severe mitochondrial dysfunction. The T allele at NDUFC2/rs11237379 variant associates with reduced gene expression and impaired mitochondrial function. The present study tested the association of both NDUFC2/rs11237379 and NDUFC2/rs641836 variants with LVH in hypertensive patients. In vitro studies explored the impact of reduced Ndufc2 expression in isolated cardiomyocytes.

METHODS

Two-hundred-forty-six subjects (147 male, 59.7%), with a mean age of 59 ± 15 years, were included for the genetic association analysis. Ndufc2 silencing was performed in both H9c2 and rat primary cardiomyocytes to explore the hypertrophy development and the underlying signaling pathway.

RESULTS

The TT genotype at NDUFC2/rs11237379 associated with significantly reduced gene expression. Multivariate analysis revealed that patients carrying this genotype showed significant differences for septal thickness (p = 0.07), posterior wall thickness (p = 0.008), RWT (p = 0.021), LV mass/BSA (p = 0.03), compared to subjects carrying either CC or CT genotypes. Patients carrying the A allele at NDUFC2/rs641836 showed significant differences for septal thickness (p = 0.017), posterior wall thickness (p = 0.011), LV mass (p = 0.003), LV mass/BSA (p = 0.002) and LV mass/height2.7(p = 0.010) after adjustment for covariates. In-vitro, the Ndufc2 deficiency-dependent mitochondrial dysfunction caused cardiomyocyte hypertrophy, pointing to SIRT3-AMPK-AKT-MnSOD as a major underlying signaling pathway.

CONCLUSIONS

We demonstrated for the first time a significant association of NDUFC2 variants with LVH in human hypertension and highlight a key role of Ndufc2 deficiency-dependent CI mitochondrial dysfunction on increased susceptibility to cardiac hypertrophy development.

Atrial natriuretic peptide stimulates autophagy/mitophagy and improves mitochondrial function in chronic heart failure

Mitochondrial dysfunction, causing increased reactive oxygen species (ROS) production, is a molecular feature of heart failure (HF). A defective antioxidant response and mitophagic flux were reported in circulating leucocytes of patients with chronic HF and reduced ejection fraction (HFrEF). Atrial natriuretic peptide (ANP) exerts many cardiac beneficial effects, including the ability to protect cardiomyocytes by promoting autophagy. We tested the impact of ANP on autophagy/mitophagy, altered mitochondrial structure and function and increased oxidative stress in HFrEF patients by both ex vivo and in vivo approaches. The ex vivo study included thirteen HFrEF patients whose peripheral blood mononuclear cells (PBMCs) were isolated and treated with αANP (10^-11 M) for 4 h. The in vivo study included six HFrEF patients who received sacubitril/valsartan for two months. PBMCs were characterized before and after treatment. Both approaches analyzed mitochondrial structure and functionality. We found that levels of αANP increased upon sacubitril/valsartan, whereas levels of NT-proBNP decreased. Both the ex vivo direct exposure to αANP and the higher αANP level upon in vivo treatment with sacubitril/valsartan caused: (i) improvement of mitochondrial membrane potential; (ii) stimulation of the autophagic process; (iii) significant reduction of mitochondrial mass-index of mitophagy stimulation-and upregulation of mitophagy-related genes; (iv) reduction of mitochondrial damage with increased inner mitochondrial membrane (IMM)/outer mitochondrial membrane (OMM) index and reduced ROS generation. Herein we demonstrate that αANP stimulates both autophagy and mitophagy responses, counteracts mitochondrial dysfunction, and damages ultimately reducing mitochondrial oxidative stress generation in PBMCs from chronic HF patients. These properties were confirmed upon sacubitril/valsartan administration, a pivotal drug in HFrEF treatment.

Beneficial Effects of Citrus Bergamia Polyphenolic Fraction on Saline Load-Induced Injury in Primary Cerebral Endothelial Cells from the Stroke-Prone Spontaneously Hypertensive Rat Model

High salt load is a known noxious stimulus for vascular cells and a risk factor for cardiovascular diseases in both animal models and humans. The stroke-prone spontaneously hypertensive rat (SHRSP) accelerates stroke predisposition upon high-salt dietary feeding. We previously demonstrated that high salt load causes severe injury in primary cerebral endothelial cells isolated from SHRSP. This cellular model offers a unique opportunity to test the impact of substances toward the mechanisms underlying high-salt-induced vascular damage. We tested the effects of a bergamot polyphenolic fraction (BPF) on high-salt-induced injury in SHRSP cerebral endothelial cells. Cells were exposed to 20 mM NaCl for 72 h either in the absence or the presence of BPF. As a result, we confirmed that high salt load increased cellular ROS level, reduced viability, impaired angiogenesis, and caused mitochondrial dysfunction with a significant increase in mitochondrial oxidative stress. The addition of BPF reduced oxidative stress, rescued cell viability and angiogenesis, and recovered mitochondrial function with a significant decrease in mitochondrial oxidative stress. In conclusion, BPF counteracts the key molecular mechanisms underlying high-salt-induced endothelial cell damage. This natural antioxidant substance may represent a valuable adjuvant to treat vascular disorders.

Mass Spectrometry-Based Quantitative Proteomics Analysis for Better Understanding of Telomeric Zinc Finger-Associated Protein-Induced Pathogenesis in Cardiomyocytes

Telomere length is highly related to cardiovascular diseases. Telomeric zinc finger-associated protein (TZAP) directly binds to telomeric TTAGGG repeats via zinc finger domains and triggers the initiation of the telomere trimming process. However, proteomics analysis of TZAP in cardiomyocytes is slightly unknown. In our study, TZAP was overexpressed by adenovirus transfection in cultured H9c2 cardiomyocytes, and then mass spectrometry-based quantitative proteomics research strategies, including Gene Ontology analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, subcellular localizations, predicted functional domains, and protein-protein interaction (PPI) analysis, were performed to explore TZAP-induced potential pathogenesis in cardiomyocytes. A total of 184 upregulated and 228 downregulated differentially expressed proteins (DEPs) were identified among identified 5693 quantifiable proteins in TZAP-overexpressed cardiomyocytes. These DEPs were mainly distributed in the nucleus, cytoplasm, and plasma membrane. DEPs were enriched in biological processes including cardiac muscle cell contraction, acute inflammatory response, cell-cell junction assembly, and macromolecule biosynthetic process. They were enriched in 9 KEGG pathways, including Hippo signaling pathway, protein digestion and absorption, and cytokine receptor interaction, and enriched in 17 protein domains, including translation initiation factor 1A/IF-1, class I histocompatibility antigen, and zinc finger. PPI analysis indicated that TZAP interacted with NDUFC2, Gja1, and HDAC2. Further, as proteins closely related to cardiovascular function, the mRNA levels of BRD4, Gja1, HDAC2, MAP2K3, Plakophilin 4, and Syndecan 1 significantly decreased, while Trpm7, clusterin, and NDUFC2 remarkably increased in TZAP-overexpressed cardiomyocytes by RT-PCR assay, which were consistent with the proteomics analysis. Collectively, we provided candidate proteins and enrichment pathways in TZAP-overexpressed cardiomyocytes, which need further investigation.

Impact of a NDUFC2 Variant on the Occurrence of Acute Coronary Syndromes

Background

Among several potential mechanisms, mitochondrial dysfunction has been proposed to be involved in the pathogenesis of coronary artery disease (CAD). A mitochondrial complex I deficiency severely impairs cardiovascular health and contributes to CAD development. Previous evidence highlighted a key role of NDUFC2, a subunit of complex I, deficiency in the increased occurrence of renal and cerebrovascular damage in an animal model of hypertension, and of juvenile ischemic stroke occurrence in humans. Furthermore, a significant decrease of NDUFC2 mRNA was detected in peripheral blood mononuclear cells from patients experiencing acute coronary syndrome (ACS). The T allele at NDUFC2/rs23117379 variant is known to associate with reduced gene expression and mitochondrial dysfunction.

Objective

In the present study we tested the impact of the T/C NDUFC2/rs23117379 variant on occurrence of ACS in a prospective cohort of CAD patients (n = 260).

Results

Hypertension, smoking habit, diabetes and hypercholesterolemia were present in a large proportion of patients. Non-ST-elevation myocardial infarction (NSTEMI) represented the most frequent type of ACS (44%, n = 115), followed by ST-elevation myocardial infarction (STEMI) (34%, n = 88) and unstable angina (22%, n = 57). The alleles/genotypes distribution for T/C at NDUFC2/rs23117379 revealed that the TT genotype was associated with a trend toward the development of ACS at an earlier age (TT 61 ± 12, CT 65 ± 12 and CC 66 ± 11 years; p = 0.051 after adjustment for gender, hypertension, smoking habit, diabetes and hypercholesterolemia) and with a significant predictive role for ACS recurrence (hazard ratio [HR]1.671; 95% confidence interval [CI], 1.138–2.472; p = 0.009).

Conclusions

Our findings are consistent with a deleterious effect of NDUFC2 deficiency on acute coronary events predisposition and further support a role of the NDUFC2/rs23117379 variant as a genetic cardiovascular risk factor.

The Mysterious Multitude: Structural Perspective on the Accessory Subunits of Respiratory Complex I

Complex I (CI) is the largest protein complex in the mitochondrial oxidative phosphorylation electron transport chain of the inner mitochondrial membrane and plays a key role in the transport of electrons from reduced substrates to molecular oxygen. CI is composed of 14 core subunits that are conserved across species and an increasing number of accessory subunits from bacteria to mammals. The fact that adding accessory subunits incurs costs of protein production and import suggests that these subunits play important physiological roles. Accordingly, knockout studies have demonstrated that accessory subunits are essential for CI assembly and function. Furthermore, clinical studies have shown that amino acid substitutions in accessory subunits lead to several debilitating and fatal CI deficiencies. Nevertheless, the specific roles of CI’s accessory subunits have remained mysterious. In this review, we explore the possible roles of each of mammalian CI’s 31 accessory subunits by integrating recent high-resolution CI structures with knockout, assembly, and clinical studies. Thus, we develop a framework of experimentally testable hypotheses for the function of the accessory subunits. We believe that this framework will provide inroads towards the complete understanding of mitochondrial CI physiology and help to develop strategies for the treatment of CI deficiencies.

Trehalose, a natural disaccharide, reduces stroke occurrence in the stroke-prone spontaneously hypertensive rat

Cerebrovascular disease, a frequent complication of hypertension, is a major public health issue for which novel therapeutic and preventive approaches are needed. Autophagy activation is emerging as a potential therapeutic and preventive strategy toward stroke. Among usual activators of autophagy, the natural disaccharide trehalose (TRE) has been reported to be beneficial in preclinical models of neurodegenerative diseases, atherosclerosis and myocardial infarction. In this study, we tested for the first time the effects of TRE in the stroke-prone spontaneously hypertensive rat (SHRSP) fed with a high-salt stroke permissive diet (JD). We found that TRE reduced stroke occurrence and renal damage in high salt-fed SHRSP. TRE was also able to decrease systolic blood pressure. Through ex-vivo studies, we assessed the beneficial effect of TRE on the vascular function of high salt-fed SHRSP. At the molecular level, TRE restored brain autophagy and reduced mitochondrial mass, along with the improvement of mitochondrial function. The beneficial effects of TRE were associated with increased nuclear translocation of TFEB, a transcriptional activator of autophagy. Our results suggest that TRE may be considered as a natural compound efficacious for the prevention of hypertension-related target organ damage, with particular regard to stroke and renal damage.

Mitochondria-related changes and metabolic dysfunction in low prognosis patients under the POSEIDON classification

STUDY QUESTION

What is the relationship between mitochondria of granulosa cells (GCs) and age and ovarian function in the patients under the POSEIDON classification?

SUMMARY ANSWER

Our results revealed obvious abnormal mitochondrial-related changes in low prognosis IVF population, where age and the function of ovarian reserve exerted a divergent effect on mitochondrial content and function.

WHAT IS KNOWN ALREADY

Mitochondria have an important role in the cross-talk between GCs and oocytes. However, factors affecting mitochondria of GCs and related mechanisms are still poorly understood.

STUDY DESIGN, SIZE, DURATION

GCs samples were obtained from 119 infertile women undergoing IVF from September 2020 to February 2021. Six groups were investigated by the POSEIDON stratification: young with normal prognosis (C1), aging with normal prognosis (C2), young and low prognosis group with normal ovarian reserve (NOR) (G1), aging and low prognosis group with NOR (G2), young and low prognosis group with diminished ovarian reserve (DOR) (G3), and aging and low prognosis group with DOR (G4).

PARTICIPANTS/MATERIALS, SETTING, METHODS

The morphology of GC mitochondria was observed by transmission electron microscopy. MtDNA copy number and mitochondrial replication-related genes were detected by real-time quantitative PCR (qPCR). Mitochondrial membrane potential (MMP) and cytosolic reactive oxygen species (ROS) were detected by confocal microscopy. Cellular glycolysis and aerobic respiratory capacity were analyzed by Seahorse XFe96 Analyzer, and related gene expression and protein levels were assessed by qPCR and Western blot.

MAIN RESULTS AND THE ROLE OF CHANCE

Compared to the normal prognosis groups, mitochondrial morphology was impaired in the low prognosis groups, where the young groups (G1, G3) with low prognosis showed phenotypes undergoing oxidative stress (round, vacuolated, swollen with decreased matrix density) and the aging groups (G2, G4) revealed typical aging characteristics (an irregular shape with heterogeneous matrix density and cord-like cristae). Additionally, the degree of corresponding change and damage was more obvious in patients with DOR (G3, G4) regardless of age. For mitochondrial content, the mtDNA copy number in GCs was significantly negatively correlated with age in the low prognosis groups (β = -0.373, P = 0.005). Interestingly, the relationship between mtDNA copy number and anti-Mullerian hormone score differed between the two age groups with low prognosis, with a negative correlation in the young groups (β = -0.639, P = 0.049) and a positive correlation in the aging groups (β = 0.505, P = 0.039). In addition, significantly reduced mitochondrial activity (MMP, ROS) and cell metabolism (both glycolysis and OXPHOS) were observed in the low prognosis groups, with the most obvious decrease being observed in the DOR population. However, the metabolism of the GCs in normal prognosis aging women (C2) shifted from OXPHOS to anaerobic glycolysis.

LIMITATIONS, REASONS FOR CAUTION

Owing to the difficulties involved in primary GC collection and culture, the sample size was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Mitochondrial abnormality is closely linked to the low prognostic outcome in IVF patients. Supplementing the functional mitochondrial content or improving mitochondrial function by autologous mitochondrial transfer or mitochondrial-related regulating drugs may help improve the clinical outcomes in patients with a low prognosis, especially for those with DOR.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the National Natural Science Foundation of China (No. 21737001), the Peking University Clinical Medicine + X Youth Project (PKU2020LCXQ011), the Research and Development Program of Peking University People's Hospital (No. RDH2017-03; No. RDX2019-06) and the Application of Clinical Features of Capital Special Subject (Z171100001017130). There were no competing interests.

TRIAL REGISTRATION NUMBER

This study was registered with the Chinese Clinical Trial Register (Clinical Trial Number: ChiCTR2100045531).

The oncogene AAMDC links PI3K-AKT-mTOR signaling with metabolic reprograming in estrogen receptor-positive breast cancer

Adipogenesis associated Mth938 domain containing (AAMDC) represents an uncharacterized oncogene amplified in aggressive estrogen receptor-positive breast cancers. We uncover that AAMDC regulates the expression of several metabolic enzymes involved in the one-carbon folate and methionine cycles, and lipid metabolism. We show that AAMDC controls PI3K-AKT-mTOR signaling, regulating the translation of ATF4 and MYC and modulating the transcriptional activity of AAMDC-dependent promoters. High AAMDC expression is associated with sensitization to dactolisib and everolimus, and these PI3K-mTOR inhibitors exhibit synergistic interactions with anti-estrogens in IntClust2 models. Ectopic AAMDC expression is sufficient to activate AKT signaling, resulting in estrogen-independent tumor growth. Thus, AAMDC-overexpressing tumors may be sensitive to PI3K-mTORC1 blockers in combination with anti-estrogens. Lastly, we provide evidence that AAMDC can interact with the RabGTPase-activating protein RabGAP1L, and that AAMDC, RabGAP1L, and Rab7a colocalize in endolysosomes. The discovery of the RabGAP1L-AAMDC assembly platform provides insights for the design of selective blockers to target malignancies having the AAMDC amplification.

Myosin light chain kinase mediates intestinal barrier dysfunction following simulated microgravity based on proteomic strategy

Microgravity induces injury of intestinal barrier. However, the underlying mechanism remains unclear. The present study aimed to investigate the pathological change of intestinal mucosa induced by long term simulated microgravity and to explore its etiological mechanism using a proteomic approach. The well accepted tail-suspended rat model was used to simulate microgravity. The damage of rat small intestine was evaluated via histological and molecular test, and a label-free comparative proteomic strategy was used to determine the molecular mechanism. Simulated microgravity for 21 days damaged intestine barrier with decreased numbers of the goblet cells, large intercellular space, and down-regulated adhesion molecules, accompanied by increased intestinal permeability. Proteomic analysis identified 416 differentially expressed proteins and showed simulated microgravity dramatically down-regulated the adhesion molecules and deteriorated several pathways for metabolism, focal adhesion, and regulation of actin cytoskeleton. Western-blot analysis confirmed that myosin regulatory light chain (MLC) 12B was significantly down-regulated, while rho-associated protein kinase, myosin light chain kinase (MLCK), and phosphorylated MLC were dramatically up-regulated. Taken together, these data reveal that down-regulation of adhesion molecules and MLCK dependent up-regulation MLC phosphorylation mediate intestinal barrier dysfunction during simulated microgravity injury. Our results also indicate that regulation of epithelial MLCK is a potential target for the therapeutic treatment of microgravity injury.

Resveratrol Regulates the Expression of Genes Involved in CoQ Synthesis in Liver in Mice Fed with High Fat Diet

Resveratrol (RSV) is a bioactive natural molecule that induces antioxidant activity and increases protection against oxidative damage. RSV could be used to mitigate damages associated to metabolic diseases and aging. Particularly, RSV regulates different aspects of mitochondrial metabolism. However, no information is available about the effects of RSV on Coenzyme Q (CoQ), a central component in the mitochondrial electron transport chain. Here, we report for the first time that RSV modulates COQ genes and parameters associated to metabolic syndrome in mice. Mice fed with high fat diet (HFD) presented a higher weight gain, triglycerides (TGs) and cholesterol levels while RSV reverted TGs to control level but not weight or cholesterol. HFD induced a decrease of COQs gene mRNA level, whereas RSV reversed this decrease in most of the COQs genes. However, RSV did not show effect on CoQ₉, CoQ₁₀ and total CoQ levels, neither in CoQ-dependent antioxidant enzymes. HFD influenced mitochondrial dynamics and mitophagy markers. RSV modulated the levels of PINK1 and PARKIN and their ratio, indicating modulation of mitophagy. In summary, we report that RSV influences some of the metabolic adaptations of HFD affecting mitochondrial physiology while also regulates COQs gene expression levels in a process that can be associated with mitochondrial dynamics and turnover.

Integrative assessment of low-dose gamma radiation effects on Daphnia magna reproduction: Toxicity pathway assembly and AOP development

High energy gamma radiation is potentially hazardous to organisms, including aquatic invertebrates. Although extensively studied in a number of invertebrate species, knowledge on effects induced by gamma radiation is to a large extent limited to the induction of oxidative stress and DNA damage at the molecular/cellular level, or survival, growth and reproduction at the organismal level. As the knowledge of causal relationships between effects occurring at different levels of biological organization is scarce, the ability to provide mechanistic explanation for observed adverse effects is limited, and thus development of Adverse Outcome Pathways (AOPs) and larger scale implementation into next generation hazard and risk predictions is restricted. The present study was therefore conducted to assess the effects of high-energy gamma radiation from cobalt-60 across multiple levels of biological organization (i.e., molecular, cellular, tissue, organ and individual) and characterize the major toxicity pathways leading to impaired reproduction in the model freshwater crustacean Daphnia magna (water flea). Following gamma exposure, a number of bioassays were integrated to measure relevant toxicological endpoints such as gene expression, reactive oxygen species (ROS), lipid peroxidation (LPO), neutral lipid storage, adenosine triphosphate (ATP) content, apoptosis, ovary histology and reproduction. A non-monotonic pattern was consistently observed across the levels of biological organization, albeit with some variation at the lower end of the dose-rate scale, indicating a complex response to radiation doses. By integrating results from different bioassays, a novel pathway network describing the key toxicity pathways involved in the reproductive effects of gamma radiation were proposed, such as DNA damage-oocyte apoptosis pathway, LPO-ATP depletion pathway, calcium influx-endocrine disruption pathway and DNA hypermethylation pathway. Three novel AOPs were proposed for oxidative stressor-mediated excessive ROS formation leading to reproductive effect, and thus introducing the world's first AOPs for non-chemical stressors in aquatic invertebrates.

Pharmacological restoration of autophagy reduces hypertension-related stroke occurrence

The identification of the mechanisms predisposing to stroke may improve its preventive and therapeutic strategies in patients with essential hypertension. The role of macroautophagy/autophagy in the development of hypertension-related stroke needs to be clarified. We hypothesized that a defective autophagy may favor hypertension-related spontaneous stroke by promoting mitochondrial dysfunction. We studied autophagy in the stroke-prone spontaneously hypertensive (SHRSP) rat, which represents a clinically relevant model of stroke associated with high blood pressure. We assessed autophagy, mitophagy and NAD⁺:NADH levels in brains of SHRSP and stroke-resistant SHR fed with high salt diet. Vascular smooth muscle cells silenced for the mitochondrial complex I subunit Ndufc2 gene (NADH:ubiquinone oxidoreductase subunit C2) and cerebral endothelial cells isolated from SHRSP were also used to assess autophagy/mitophagy and mitochondrial function in response to high salt levels. We found a reduction of autophagy in brains of high salt-fed SHRSP. Autophagy impairment was associated with NDUFC2 downregulation, mitochondrial dysfunction and NAD⁺ depletion. Restoration of NAD⁺ levels by nicotinamide administration reactivated autophagy and reduced stroke development in SHRSP. A selective reactivation of autophagy/mitophagy by Tat-Beclin 1 also reduced stroke occurrence, restored autophagy/mitophagy and improved mitochondrial function. Endothelial progenitor cells (EPCs) from subjects homozygous for the thymine allele variant at NDUFC2/rs11237379, which is associated with NDUFC2 deficiency and increased stroke risk, displayed an impairment of autophagy and increased senescence in response to high salt levels. EPC senescence was rescued by Tat-Beclin 1. Pharmacological activation of autophagy may represent a novel therapeutic strategy to reduce stroke occurrence in hypertension.

ABBREVIATIONS

10 VSMCs: aortic vascular smooth muscle cells; COX4I1/COX IV: cytochrome c oxidase subunit 4I1; ECs: endothelial cells; EPCs: endothelial progenitor cells; JD: Japanese-style diet; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; NAD: nicotinamide adenine dinucleotide; NDUFC2: NADH:ubiquinone oxidoreductase subunit C2; NMN: nicotinamide mononucleotide; RD: regular diet; SHRSP: stroke-prone spontaneously hypertensive rat; SHRSR: stroke-resistant spontaneously hypertensive rat.

Circulating Leukocytes and Oxidative Stress in Cardiovascular Diseases: A State of the Art

Increased oxidative stress from both mitochondrial and cytosolic sources contributes to the development and the progression of cardiovascular diseases (CVDs), and it is a target of therapeutic interventions. The numerous efforts made over the last decades in order to develop tools able to monitor the oxidative stress level in patients affected by CVDs rely on the need to gain information on the disease state. However, this goal has not been satisfactorily accomplished until now. Among others, the isolation of circulating leukocytes to measure their oxidant level offers a valid, noninvasive challenge that has been tested in few pathological contexts, including hypertension, atherosclerosis and its clinical manifestations, and heart failure. Since leukocytes circulate in the blood stream, it is expected that they might reflect quite closely both systemic and cardiovascular oxidative stress and provide useful information on the pathological condition. The results of the studies discussed in the present review article are promising. They highlight the importance of measuring oxidative stress level in circulating mononuclear cells in different CVDs with a consistent correlation between degree of oxidative stress and severity of CVD and of its complications. Importantly, they also point to a double role of leukocytes, both as a marker of disease condition and as a direct contributor to disease progression. Finally, they show that the oxidative stress level of leukocytes reflects the impact of therapeutic interventions. It is likely that the isolation of leukocytes and the measurement of oxidative stress, once adequately developed, may represent an eligible tool for both research and clinical purposes to monitor the role of oxidative stress on the promotion and progression of CVDs, as well as the impact of therapies.

Mitochondrial complex I deficiency and cardiovascular diseases: current evidence and future directions

Compelling evidence demonstrates the emerging role of mitochondrial complex I deficiency in the onset and development of cardiovascular diseases (CVDs). In particular, defects in single subunits of mitochondrial complex I have been associated with cardiac hypertrophy, ischemia/reperfusion injury, as well as diabetic complications and stroke in pre-clinical studies. Moreover, data obtained in humans revealed that genes coding for complex I proteins were associated with different CVDs. In this review, we discuss recent experimental studies that underline the contributory role of mitochondrial complex I deficiency in the etiopathogenesis of several CVDs, with a particular focus on those involving loss of function models of mitochondrial complex I. We also discuss human studies and potential therapeutic strategies able to rescue mitochondrial function in CVDs.

Developmental Dioxin Exposure Alters the Methylome of Adult Male Zebrafish Gonads

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a persistent environmental toxicant and endocrine disrupting compound with reproductive and developmental effects in humans and model organisms, including zebrafish. Our previous microarray and histological studies found defects in spermatogenesis and fertility of zebrafish in response to acute developmental TCDD exposure. These effects are apparent following exposure during reproductive development, modeling fetal basis of adult-onset disease. Some outcomes of these previous studies (reduced fertility, changes in sex ratio, transcriptomic alterations) are also transgenerational – persisting to unexposed generations – through the male germline. We hypothesized that DNA methylation could be a possible mechanism for these reproductive effects and performed whole genome bisulfite sequencing (WGBS), which identifies whole genome DNA methylation status at the base pair level, on testes of adult zebrafish exposed to TCDD (two separate hour-long exposures to 50 pg/mL TCDD at 3 and 7 weeks post fertilization). In response to TCDD exposure, multiple genes were differentially methylated; many of which are involved in reproductive processes or epigenetic modifications, suggesting a role of DNA methylation in later-life health outcomes. Additionally, several differentially methylated genes corresponded with gene expression changes identified in TCDD-exposed zebrafish testes, indicating a potential link between DNA methylation and gene expression. Ingenuity pathway analysis of WGBS and microarray data revealed genes involved in reproductive processes and development, RNA regulation, the cell cycle, and cellular morphology and development. We conclude that site-specific changes in DNA methylation of adult zebrafish testes occur in response to acute developmental TCDD exposure.

iTRAQ-based proteomic profiling of Pycnoporus sanguineus in response to co-existed tetrabromobisphenol A (TBBPA) and hexavalent chromium

In current study, we investigated the changes of proteome profiles of Pycnoporus sanguineus after a single exposure of Cr(VI), TBBPA and a combined exposure of TBBPA and Cr(VI), with the goal of illuminating the cellular mechanisms involved in the interactions of co-existed TBBPA and Cr(VI) with the cells of P. sanguineus at the protein level. The results revealed that some ATP-binding cassette (ABC) transporters were obviously induced by these pollutants to accelerate the transportation, transformation and detoxification of TBBPA and Cr(VI). Cr(VI) could inhibit the bioremoval of its organic co-pollutants TBBPA through suppressing the expression of several key proteins related to the metabolism of TBBPA by P. sanguineus, including two cytochrome P450s, pentachlorophenol 4-monooxygenase and glutathione S-transferases. Furthermore, Cr(VI) possibly reduced the cell vitality and growth of P. sanguineus by enhancing the expression of imidazole glycerol phosphate synthase as well as by decreasing the abundances of proteins associated with the intracellular metabolic processes, such as the tricarboxylic acid cycle, purine metabolism and glutathione biosynthesis, thereby adversely affecting the biotransformation of TBBPA. Cr(VI) also inhibited the expression of peptidyl prolyl cis/trans isomerases, thus causing the damage of cell membrane integrity. In addition, some important proteins participated in the resistance to Cr(VI) toxicity were observed to up-regulate, including heat shock proteins, 26S proteasome, peroxiredoxins and three critical proteins implicated in S-adenosyl methionine synthesis, which contributed to reducing the hazard of Cr(VI) to P. sanguineus. The results of this study provide novel insights into the physiological responses and molecular mechanism of white rot fungi P. sanguineus to the stress of concomitant TBBPA and Cr(VI).

Chronic heart failure is characterized by altered mitochondrial function and structure in circulating leucocytes

Oxidative stress is currently viewed as a key factor in the genesis and progression of Heart Failure (HF). The aim of this study was to characterize the mitochondrial changes linked to oxidative stress generation in circulating peripheral blood mononuclear cells isolated from chronic HF patients (HF_PBMCs) in order to highlight the involvement of mitochondrial dysfunction in the pathophysiology of HF.

To assess the production of reactive oxygen species (ROS), mitochondrial function and ultrastructure and the mitophagic flux in circulating PBMCs we enrolled 15 patients with HF and a control group of ten healthy subjects. The HF_PBMCs showed a mitochondrial population consisting of damaged and less functional organelles responsible of higher superoxide anion production both at baseline and under in vitro stress conditions, with evidence of cellular apoptosis. Although the mitophagic flux at baseline was enhanced in HF_PBMCs at level similar to those that could be achieved in control PBMCs only under inflammatory stress conditions, the activation of mitophagy was unable to preserve a proper mitochondrial dynamics upon stress stimuli in HF.

In summary, circulating HF_PBMCs show structural and functional derangements of mitochondria with overproduction of reactive oxidant species. This mitochondrial failure sustains a leucocyte dysfunctional status in the blood that may contribute to development and persistence of stress conditions within the cardiovascular system in HF.

The Double-Edged Sword Profile of Redox Signaling: Oxidative Events As Molecular Switches in the Balance between Cell Physiology and Cancer

The intracellular redox state in the cell depends on the balance between the level of reactive oxygen species (ROS) and the activity of defensive systems including antioxidant enzymes. This balance is a dynamic process that can change in relation to many factors and/or stimuli induced within the cell. ROS production is derived from physiological metabolic events. For instance, mitochondria represent the major ROS sources during oxidative phosphorylation, but other systems, such as NADPH oxidase or specific enzymes in certain metabolisms, may account for ROS production as well. Whereas high levels of ROS perturb the cell environment, causing oxidative damage to biological macromolecules, low levels of ROS can exert a functional role in the cell, influencing the activity of specific enzymes or modulating some intracellular signaling cascades. Of particular interest appears to be the role of ROS in tumor systems not only because ROS are known to be tumorigenic but also because tumor cells are able to modify their redox state, regulating ROS production to sustain tumor growth and proliferation. Overall, the scope of this review was to critically discuss the most recent findings pertaining to ROS physiological roles as well as to highlight the controversial involvement of ROS in tumor systems.