Role of mitochondrial respiration in sensitization of copper-deficient yeast to cisplatin-induced cytotoxicity

Vitamin D deficiency has been linked to a reduction in skeletal muscle function and oxidative capacity; however, the mechanistic bases of these impairments are poorly understood. The biological actions of vitamin D are carried out via the binding of 1α,25-dihydroxyvitamin D3 (1α,25(OH)2D3) to the vitamin D receptor (VDR). Recent evidence has linked 1α,25(OH)2D3 to the regulation of skeletal muscle mitochondrial function in vitro; however, little is known with regard to the role of the VDR in this process. To examine the regulatory role of the VDR in skeletal muscle mitochondrial function, we used lentivirus-mediated shRNA silencing of the VDR in C2C12 myoblasts (VDR-KD) and examined mitochondrial respiration and protein content compared with an shRNA scrambled control. VDR protein content was reduced by ~95% in myoblasts and myotubes ( P < 0.001). VDR-KD myoblasts displayed a 30%, 30%, and 36% reduction in basal, coupled, and maximal respiration, respectively ( P < 0.05). This phenotype was maintained in VDR-KD myotubes, displaying a 34%, 33%, and 48% reduction in basal, coupled, and maximal respiration ( P < 0.05). Furthermore, ATP production derived from oxidative phosphorylation (ATPOx) was reduced by 20%, suggesting intrinsic impairments within the mitochondria following VDR-KD. However, despite the observed functional decrements, mitochondrial protein content, as well as markers of mitochondrial fission were unchanged. In summary, we highlight a direct role for the VDR in regulating skeletal muscle mitochondrial respiration in vitro, providing a potential mechanism as to how vitamin D deficiency might impact upon skeletal muscle oxidative capacity.

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Nitric oxide synthase inhibitors negatively regulate respiration in isolated rodent cardiac and brain mitochondria

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00720.2019 ◽

2020 ◽

Vol 318 (2) ◽

pp. H295-H300 ◽

Cited By ~ 1

Author(s):

Siva S. V. P. Sakamuri ◽

Jared A. Sperling ◽

Wesley R. Evans ◽

Monica H. Dholakia ◽

Aaron L. Albuck ◽

...

Keyword(s):

Nitric Oxide ◽

Mitochondrial Respiration ◽

Isolated Heart ◽

Protein S ◽

Brain Mitochondria ◽

Respiratory Parameters ◽

Nos Inhibitors ◽

Consumption Rates ◽

Nos Isoforms

Nitric oxide (NO) is known to exert inhibitory control on mitochondrial respiration in the heart and brain. Evidence supports the presence of NO synthase (NOS) in the mitochondria (mtNOS) of cells; however, the functional role of mtNOS in the regulation of mitochondrial respiration is unclear. Our objective was to examine the effect of NOS inhibitors on mitochondrial respiration and protein S-nitrosylation. Freshly isolated cardiac and brain nonsynaptosomal mitochondria were incubated with selective inhibitors of neuronal (nNOS; ARL-17477, 1 µmol/L) or endothelial [eNOS; N5-(1-iminoethyl)-l-ornithine, NIO, 1 µmol/L] NOS isoforms. Mitochondrial respiratory parameters were calculated from the oxygen consumption rates measured using Agilent Seahorse XFe24 analyzer. Expression of NOS isoforms in the mitochondria was confirmed by immunoprecipitation and Western blot analysis. In addition, we determined the protein S-nitrosylation by biotin-switch method followed by immunoblotting. nNOS inhibitor decreased the state IIIu respiration in cardiac mitochondria and both state III and state IIIu respiration in brain mitochondria. In contrast, eNOS inhibitor had no effect on the respiration in the mitochondria from both heart and brain. Interestingly, NOS inhibitors reduced the levels of protein S-nitrosylation only in brain mitochondria, but nNOS and eNOS immunoreactivity was observed in the cardiac and brain mitochondrial lysates. Thus, the effects of NOS inhibitors on S-nitrosylation of mitochondrial proteins and mitochondrial respiration confirm the existence of functionally active NOS isoforms in the mitochondria. Notably, our study presents first evidence of the positive regulation of mitochondrial respiration by mitochondrial nNOS contrary to the current dogma representing the inhibitory role attributed to NOS isoforms. NEW & NOTEWORTHY Existence and the role of nitric oxide synthases in the mitochondria are controversial. We report for the first time that mitochondrial nNOS positively regulates respiration in isolated heart and brain mitochondria, thus challenging the existing dogma that NO is inhibitory to mitochondrial respiration. We have also demonstrated reduced protein S-nitrosylation by NOS inhibition in isolated mitochondria, supporting the presence of functional mitochondrial NOS.

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Cardioprotection by modulation of mitochondrial respiration during ischemia–reperfusion: Role of apoptosis-inducing factor

Biochemical and Biophysical Research Communications ◽

10.1016/j.bbrc.2013.05.033 ◽

2013 ◽

Vol 435 (4) ◽

pp. 627-633 ◽

Cited By ~ 14

Author(s):

Aijun Xu ◽

Karol Szczepanek ◽

Ying Hu ◽

Edward J. Lesnefsky ◽

Qun Chen

Keyword(s):

Mitochondrial Respiration ◽

Ischemia Reperfusion ◽

Apoptosis Inducing Factor

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Succinate Accumulation Is Associated with a Shift of Mitochondrial Respiratory Control and HIF-1α Upregulation in PTEN Negative Prostate Cancer Cells

International Journal of Molecular Sciences ◽

10.3390/ijms19072129 ◽

2018 ◽

Vol 19 (7) ◽

pp. 2129 ◽

Cited By ~ 5

Author(s):

Anja Weber ◽

Helmut Klocker ◽

Herbert Oberacher ◽

Erich Gnaiger ◽

Hannes Neuwirt ◽

...

Keyword(s):

Prostate Cancer ◽

Cell Growth ◽

Mitochondrial Respiration ◽

Respiratory Control ◽

Phosphatase And Tensin Homolog ◽

Permeabilized Cells ◽

Tensin Homolog ◽

Viable Cells ◽

Sodium Dependent

The idea of using metabolic aberrations as targets for diagnosis or therapeutic intervention has recently gained increasing interest. In a previous study, our group discovered intriguing differences in the oxidative mitochondrial respiration capacity of benign and prostate cancer (PCa) cells. In particular, we found that PCa cells had a higher total respiratory activity than benign cells. Moreover, PCa cells showed a substantial shift towards succinate-supported mitochondrial respiration compared to benign cells, indicating a re-programming of respiratory control. This study aimed to investigate the role of succinate and its main plasma membrane transporter NaDC3 (sodium-dependent dicarboxylate transporter member 3) in PCa cells and to determine whether targeting succinate metabolism can be potentially used to inhibit PCa cell growth. Using high-resolution respirometry analysis, we observed that ROUTINE respiration in viable cells and succinate-supported respiration in permeabilized cells was higher in cells lacking the tumor suppressor phosphatase and tensin-homolog deleted on chromosome 10 (PTEN), which is frequently lost in PCa. In addition, loss of PTEN was associated with increased intracellular succinate accumulation and higher expression of NaDC3. However, siRNA-mediated knockdown of NaDC3 only moderately influenced succinate metabolism and did not affect PCa cell growth. By contrast, mersalyl acid—a broad acting inhibitor of dicarboxylic acid carriers—strongly interfered with intracellular succinate levels and resulted in reduced numbers of PCa cells. These findings suggest that blocking NaDC3 alone is insufficient to intervene with altered succinate metabolism associated with PCa. In conclusion, our data provide evidence that loss of PTEN is associated with increased succinate accumulation and enhanced succinate-supported respiration, which cannot be overcome by inhibiting the succinate transporter NaDC3 alone.

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The role of Asprosin in patients with dilated cardiomyopathy

BMC Cardiovascular Disorders ◽

10.1186/s12872-020-01680-1 ◽

2020 ◽

Vol 20 (1) ◽

Author(s):

Ming-Shien Wen ◽

Chao-Yung Wang ◽

Jih-Kai Yeh ◽

Chun-Chi Chen ◽

Ming-Lung Tsai ◽

...

Keyword(s):

Dilated Cardiomyopathy ◽

Mitochondrial Respiration ◽

Cardiovascular Events ◽

Molecular Mechanisms ◽

Major Adverse Cardiovascular Events ◽

Study Cohort ◽

Protective Mechanisms ◽

Mitochondrial Functions ◽

And Function

Abstract Background Asprosin is a novel fasting glucogenic adipokine discovered in 2016. Asprosin induces rapid glucose releases from the liver. However, its molecular mechanisms and function are still unclear. Adaptation of energy substrates from fatty acid to glucose is recently considered a novel therapeutic target in heart failure treatment. We hypothesized that the asprosin is able to modulate cardiac mitochondrial functions and has important prognostic implications in dilated cardiomyopathy (DCM) patients. Methods We prospectively enrolled 50 patients (86% male, mean age 55 ± 13 years) with DCM and followed their 5-year major adverse cardiovascular events from 2012 to 2017. Comparing with healthy individuals, DCM patients had higher asprosin levels (191.2 versus 79.7 ng/mL, P < 0.01). Results During the 5-year follow-up in the study cohort, 16 (32.0%) patients experienced adverse cardiovascular events. Patients with lower asprosin levels (< 210 ng/mL) were associated with increased risks of adverse clinical outcomes with a hazard ratio of 7.94 (95% CI 1.88–33.50, P = 0.005) when compared patients with higher asprosin levels (≥ 210 ng/mL). Using cardiomyoblasts as a cellular model, we showed that asprosin prevented hypoxia-induced cell death and enhanced mitochondrial respiration and proton leak under hypoxia. Conclusions In patients with DCM, elevated plasma asprosin levels are associated with less adverse cardiovascular events in five years. The underlying protective mechanisms of asprosin may be linked to its functions relating to enhanced mitochondrial respiration under hypoxia.

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Activation of Mitochondrial STAT3 Increases Mitochondrial Respiration and Inhibits Oxidative Stress in Chronic Lymphocytic Leukemic Cells

Blood ◽

10.1182/blood.v118.21.287.287 ◽

2011 ◽

Vol 118 (21) ◽

pp. 287-287 ◽

Cited By ~ 2

Author(s):

Li Jia ◽

Nadiha Uddin ◽

John G. Gribben

Keyword(s):

Cell Death ◽

Free Radical ◽

Oxidative Damage ◽

Mitochondrial Function ◽

Mitochondrial Respiration ◽

Mitochondrial Mass ◽

Free Radical Generation ◽

Atp Turnover ◽

Radical Generation

Abstract Abstract 287 Chronic lymphocytic leukemia (CLL) is a malignant disease occurring in the elderly and remains incurable. CLL is characterized by resistance to both spontaneous and induced apoptosis aided by changes induced by the tumor microenvironment. STAT3 is a signal responsive transcription factor that plays pivotal roles in tumorigensis in a number of malignancies including CLL. STAT3 resides in an inactive form in the cytoplasm of non-stimulated cells and in response to various cytokines and growth factors present in the microenvironment is activated through JAK-mediated phosphorylation of two residues, tyrosine 705 (Y705) and serine 727 (S727). Phosphorylation of this critical tyrosine residue (Y705) induces STAT3 dimerization through phosphotyrosine-SH2 domain interaction and. once dimerized, enters the nucleus and activates a broad array of target genes. The role of serine phosphorylation (S727) is less understood. It has been reported that STAT3 is constitutively phosphorylated on S727 and pS727-STAT3, not pY705-STAT3, binds DNA and activates transcription in CLL cells. However, it has also been reported that STAT3 is present in the mitochondria both in cell lines and primary liver and heart of mouse models, where it is one of the components of the mitochondrial electron transport chain (mETC) and plays an important role in mitochondrial respiration. The active form of mitochondrial STAT3 is pS727-STAT3 and it is crucial for Ras-dependent transformation by sustaining altered glycolytic and oxidative phosphorylation activities characteristic of cancer cells. It is unknown whether STAT3 regulates mitochondrial function in CLL. We therefore investigated whether activated STAT3 regulates mitochondrial respiration in CLL and whether it is important for CLL cell survival. Screening by Western blotting in untreated CLL patients' samples (n=16 )revealed that both pS727-STAT3 and pY705-STAT3 were constitutively expressed and we demonstrated correlation of the expression levels between these two active forms. Using fluorescent microscopy and cellular protein fractionation, both pS727-STAT3 and pY705-STAT3 showed mitochondrial localization in CLL cells. Stimulation of CLL cells with IL-10 induced STAT3 activation and both active forms of STAT3 exhibited mitochondrial translocation. The JAK inhibitor AG490 prevented STAT3 translocation to the mitochondria and led to reduction of mitochondrial mass and expression of cytochrome c oxidase IV (COX IV), one of the components of mETC. Knockdown of STAT3 RNA also decreased COX IV expression. Flow cytometry studies demonstrated that activation of STAT3 by IL-10 prevented depolarization of mitochondrial membrane potential and free radical generation by CLL cells, but inhibition of STAT3 induced mitochondrial oxidative damage and CLL cell death. The role of STAT3 activation by IL-10 on mitochondrial respiration was determined using a Seahorse XF Extracellular Flux Analyzer and demonstrated significantly increased coupled and uncoupled mitochondrial respiration and ATP turnover. Inhibition of STAT3 by AG490 reduced mitochondrial respiration and ATP turnover. However, decreased mitochondrial respiration did not provoke glycolytic capacity in CLL cells, indicating that CLL cells mainly rely on mitochondria for energetic needs. In summary, we demonstrate that activated STAT3 targets mitochondria and increases mitochondrial respiration and ATP turnover in CLL cells. This enables increased bioenergetic mitochondrial function and also prevents oxidative damage of CLL cells. Inhibition of STAT3 reduces mitochondrial mass and function but increases free radical generation and promotes CLL cell death. We therefore propose that mitochondrial STAT3 could be a therapeutic target for the treatment of CLL. Disclosures: Gribben: Roche: Honoraria; Celgene: Honoraria; GSK: Honoraria; Mundipharma: Honoraria; Gilead: Honoraria; Pharmacyclics: Honoraria.

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P24. The role of nitrite in nitroglycerin-mediated inhibition of mitochondrial respiration and ROS formation

Nitric Oxide ◽

10.1016/j.niox.2011.03.255 ◽

2011 ◽

Vol 24 ◽

pp. S25

Author(s):

Peter Dungel ◽

Susanne Haindl ◽

Tircia Behling ◽

Heinz Redl ◽

Andrey Kozlov

Keyword(s):

Mitochondrial Respiration ◽

Ros Formation

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