| 1. |
- Fujita, Hidetoshi, et al.
(author)
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The E3 ligase synoviolin controls body weight and mitochondrial biogenesis through negative regulation of PGC-1 beta
- 2015
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In: EMBO Journal. - : EMBO. - 1460-2075 .- 0261-4189. ; 34:8, s. 1042-1055
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Journal article (peer-reviewed)abstract
- Obesity is a major global public health problem, and understanding its pathogenesis is critical for identifying a cure. In this study, a gene knockout strategy was used in post-neonatal mice to delete synoviolin (Syvn) 1/Hrd1/Der3, an ER-resident E3 ubiquitin ligase with known roles in homeostasis maintenance. Syvn1 deficiency resulted in weight loss and lower accumulation of white adipose tissue in otherwise wild-type animals as well as in genetically obese (ob/ob and db/db) and adipose tissue-specific knockout mice as compared to control animals. SYVN1 interacted with and ubiquitinated the thermogenic coactivator peroxisome proliferator-activated receptor coactivator (PGC)-1 beta, and Syvn1 mutants showed upregulation of PGC-1 beta target genes and increase in mitochondrion number, respiration, and basal energy expenditure in adipose tissue relative to control animals. Moreover, the selective SYVN1 inhibitor LS-102 abolished the negative regulation of PGC-1 beta by SYVN1 and prevented weight gain in mice. Thus, SYVN1 is a novel post-translational regulator of PGC-1 beta and a potential therapeutic target in obesity treatment.
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| 2. |
- Hansson, Magnus, et al.
(author)
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Calcium-induced generation of reactive oxygen species in brain mitochondria is mediated by permeability transition.
- 2008
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In: Free Radical Biology & Medicine. - : Elsevier BV. - 0891-5849. ; 45, s. 284-294
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Journal article (peer-reviewed)abstract
- Mitochondrial uptake of calcium in excitotoxicity is associated with subsequent increase in reactive oxygen species (ROS) generation and delayed cellular calcium deregulation in ischemic and neurodegenerative insults. The mechanisms linking mitochondrial calcium uptake and ROS production remain unknown but activation of the mitochondrial permeability transition (mPT) may be one such mechanism. In the present study, calcium increased ROS generation in isolated rodent brain and human liver mitochondria undergoing mPT despite an associated loss of membrane potential, NADH and respiration. Unspecific permeabilization of the inner mitochondrial membrane by alamethicin likewise increased ROS independently of calcium, and the ROS increase was further potentiated if NAD(H) was added to the system. Importantly, calcium per se did not induce a ROS increase unless mPT was triggered. Twenty-one cyclosporin A analogs were evaluated for inhibition of calcium-induced ROS and their efficacy clearly paralleled their potency of inhibiting mPT-mediated mitochondrial swelling. We conclude that while intact respiring mitochondria possess powerful antioxidant capability, mPT induces a dysregulated oxidative state with loss of GSH- and NADPH-dependent ROS detoxification. We propose that mPT is a significant cause of pathological ROS generation in excitotoxic cell death.
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| 3. |
- Hansson, Magnus, et al.
(author)
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Cyclophilin D-sensitive mitochondrial permeability transition in adult human brain and liver mitochondria.
- 2011
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In: Journal of Neurotrauma. - : Mary Ann Liebert Inc. - 1557-9042 .- 0897-7151. ; 28, s. 143-153
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Journal article (peer-reviewed)abstract
- The mitochondrial permeability transition (mPT) is considered to be a major cause of cell death under a variety of pathophysiological conditions of the CNS and other organs. Pharmacological inhibition or genetic knock-out of the matrix protein cyclophilin D (CypD) prevents mPT and cell degeneration in several models of brain injury. Provided that findings in animal models can be translatable to human disease, pharmacological inhibition of mPT offers a promising therapeutic target. The objective of this study was to validate the presence of a CypD-sensitive mPT in adult human brain and liver mitochondria. In order to perform functional characterization of human mitochondria, fresh tissue samples were obtained during hemorrhage or tumor surgery and mitochondria were rapidly isolated. Mitochondrial calcium retention capacity, a quantitative assay for mPT, was significantly increased by the CypD inhibitor cyclosporin A in both human brain and liver mitochondria, whereas thiol-reactive compounds and oxidants sensitized mitochondria to calcium-induced mPT. Brain mitochondria underwent swelling upon calcium overload, which was reversible upon calcium removal. To further explore mPT of human mitochondria, liver mitochondria were demonstrated to exhibit several classical features of the mPT phenomenon such as calcium-induced loss of membrane potential and respiratory coupling, as well as release of the pro-apoptotic protein cytochrome c. It is concluded that adult viable human brain and liver mitochondria possess an active CypD-sensitive mPT. The present findings support the rationale of CypD and mPT inhibition as pharmacological targets in acute and chronic neurodegeneration.
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| 4. |
- Hansson, Magnus, et al.
(author)
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Increased potassium conductance of brain mitochondria induces resistance to permeability transition by enhancing matrix volume.
- 2010
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In: Journal of Biological Chemistry. - 1083-351X. ; 285, s. 741-750
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Journal article (peer-reviewed)abstract
- Modulation of K+ conductance of the inner mitochondrial membrane has been proposed to mediate preconditioning in ischemia-reperfusion injury. The mechanism is not entirely understood but it has been linked to a decreased activation of mitochondrial permeability transition (mPT). In the present study, K+ channel activity was mimicked by picomolar concentrations of valinomycin. Isolated brain mitochondria were exposed to continuous infusions of calcium. Monitoring of extramitochondrial Ca2+ and mitochondrial respiration provided a quantitative assay for mPT-sensitivity by determining calcium retention capacity (CRC). Valinomycin and cyclophilin D-inhibition separately and additively increased CRC. Comparable degrees of respiratory uncoupling induced by increased K+ or H+ conductance had opposite effects on mPT sensitivity. Protonophores dose-dependently decreased CRC, demonstrating that so-called mild uncoupling was not beneficial per se. The putative mitoKATP channel opener diazoxide did not mimic the effect of valinomycin. An alkaline matrix pH was required in order for mitochondria to retain calcium, but increased K+ conductance did not result in augmented DeltapH. The beneficial effect of valinomycin on CRC was not mediated by H2O2-induced PKCepsilon activation. In contrast, increased K+ conductance reduced H2O2 generation during calcium infusion. Lowering the osmolarity of the buffer induced an increase in mitochondrial volume and improved CRC similar to valinomycin without inducing uncoupling or otherwise affecting respiration. We propose that increased potassium conductance in brain mitochondria may cause a direct physiological effect on matrix volume inducing resistance to pathological calcium challenges.
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| 5. |
- Hara, Naomi, et al.
(author)
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Metabolomic Analyses of Brain Tissue in Sepsis Induced by Cecal Ligation Reveal Specific Redox Alterations-Protective Effects of the Oxygen Radical Scavenger Edaravone.
- 2015
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In: Shock. - 1540-0514. ; 44:6, s. 578-584
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Journal article (peer-reviewed)abstract
- The pathophysiology of sepsis-associated encephalopathy (SAE) is complex and remains incompletely elucidated. Dysregulated reactive oxygen species (ROS) production and mitochondrial-mediated necrotic-apoptotic pathway have been proposed as part of the pathogenesis. The present study aimed at analyzing the preventive effect of the free radical scavenger edaravone on sepsis-induced brain alterations. Sepsis was induced by cecal ligation and puncture (CLP) and the mice were divided into three groups-CLP vehicle (CLPV), CLP and edaravone (MCI-186, 3-methyl-1-phenyl-2-pyrazolin-5-one) (CLPE), and sham-operated (Sham). Mice in CLPV and CLPE were injected with saline or edaravone intraperitoneally at a dose of 10 mg/kg twice daily. The treatments were initiated 4 days prior to the surgical procedure. Mortality, histological changes, electron microscopy (EM), and expression of Bcl-2 family genes (Bcl-2 and Bax) were analyzed in selected brain regions. CLPE showed significant improvement in survival compared with CLPV 18 h postinduction of sepsis (P < 0.05). At the same time point, pathohistological analysis also showed marked reduction of neuronal cell death in both parietal cortex and hippocampus in the CLPE (P < 0.05). RT-PCR and immunoblotting directed at the Bcl-2 family revealed increased Bax mRNA levels in hippocampus at 12 h in CLPV as well as an increased Bax/Bcl-2 protein ratio, changes that were significantly suppressed in CLPE. In conclusion, our study suggests that sepsis induced by cecal ligation alters cerebral redox status and supports a proapoptotic phenotype. The free radical scavenger edavarone reduces mortality of septic mice and protects against sepsis-induced neuronal cell death.
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| 6. |
- Kobayashi, Takayuki, et al.
(author)
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Disease Outcome and Brain Metabolomics of Cyclophilin-D Knockout Mice in Sepsis
- 2022
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In: International Journal of Molecular Sciences. - : MDPI AG. - 1661-6596 .- 1422-0067. ; 23:2
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Journal article (peer-reviewed)abstract
- Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction resulting from a systemic inflammatory response to infection, but the mechanism remains unclear. The mitochondrial permeability transition pore (MPTP) could play a central role in the neuronal dysfunction, induction of apoptosis, and cell death in SAE. The mitochondrial isomerase cyclophilin D (CypD) is known to control the sensitivity of MPTP induction. We, therefore, established a cecal ligation and puncture (CLP) model, which is the gold standard in sepsis research, using CypD knockout (CypD KO) mice, and analyzed the disease phenotype and the possible molecular mechanism of SAE through metabolomic analyses of brain tissue. A comparison of adult, male wild-type, and CypD KO mice demonstrated statistically significant differences in body temperature, mortality, and histological changes. In the metabolomic analysis, the main finding was the maintenance of reduced glutathione (GSH) levels and the reduced glutathione/oxidized glutathione (GSH/GSSG) ratio in the KO animals following CLP. In conclusion, we demonstrate that CypD is implicated in the pathogenesis of SAE, possibly related to the inhibition of MPTP induction and, as a consequence, the decreased production of ROS and other free radicals, thereby protecting mitochondrial and cellular function.
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| 7. |
- Li, Ping-An, et al.
(author)
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Amelioration by cyclosporin A of brain damage following 5 or 10 min of ischemia in rats subjected to preischemic hyperglycemia
- 1997
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In: Brain Research. - 1872-6240. ; 753:1, s. 133-140
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Journal article (peer-reviewed)abstract
- It has recently been shown that the immunosuppressant cyclosporin A (CsA) dramatically ameliorates the selective neuronal necrosis which results from 10 min of forebrain ischemia in rats. Since CsA is a virtually specific blocker of the mitochondrial permeability transition (MPT) pore which is assembled under adverse conditions, such as mitochondrial calcium accumulation and oxidative stress, the results suggest that the delayed neuronal death is due to an MPT. In the present study we explored whether CsA can also ameliorate the aggravated brain damage which is observed in hyperglycemic subjects, and which encompasses rapidly evolving neuronal lesions, edema, and postischemic seizures. Anaesthetised rats with a plasma glucose concentration of approximately 13 mM were subjected to 10 min of forebrain ischemia, and allowed a recovery period of 7 days. In these animals, CsA prevented seizure from occurring and virtually eliminated neuronal necrosis. In order to allow even higher plasma glucose values (approximately 20 mM) to be studied, with long-term recovery, the duration of ischemia had to be reduced to 5 min. Again, CsA suppressed seizure activity and reduced neuronal damage. However, the effects were not as marked or consistent as in the 10 min group, suggesting that excessive tissue acidosis recruits mechanisms of damage which are not sensitive to CsA.
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| 8. |
- Morota, Saori, et al.
(author)
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Evaluation of putative inhibitors of mitochondrial permeability transition for brain disorders - Specificity vs. toxicity.
- 2009
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In: Experimental Neurology. - : Elsevier BV. - 0014-4886. ; 218, s. 353-362
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Journal article (peer-reviewed)abstract
- Inhibition of mitochondrial permeability transition (mPT) has emerged as a promising approach for neuroprotection and development of well-tolerated mPT inhibitors with favorable blood-brain barrier penetration is highly warranted. In a recent study, 28 clinically available drugs with a common heterocyclic structure were identified as mPT inhibitors e.g. trifluoperazine, promethazine and nortriptyline. In addition, neuroprotection by structurally unrelated drugs e.g. neurosteroids, 4-hydroxy-tamoxifen and trimetazidine has been attributed to direct inhibition of mPT. The regulation of mPT is complex and highly dependent on the prevailing experimental conditions. Several features of mPT, such as swelling, depolarization or NADH oxidation, can also occur independently of the mPT phenomenon. Here, in isolated rodent brain-derived and human liver mitochondria, we re-evaluate drugs promoted as potent mPT inhibitors. We address the definition of an mPT inhibitor and present strategies to reliably detect mPT inhibition in vitro. Surprisingly, none of the 12 compounds tested displayed convincing mPT inhibition or effects comparable to cyclophilin D inhibition by the non-immunosuppressive cyclophilin inhibitor D-MeAla(3)-EtVal(4)-Cyclosporin (Debio 025). Propofol and 2-aminoethoxydiphenyl borate (2-APB) inhibited swelling in de-energized mitochondria but did not increase calcium retention capacity (CRC). Progesterone, trifluoperazine, allopregnanolone and 4-hydroxy-tamoxifen dose-dependently reduced CRC and respiratory control and were thus toxic rather than beneficial to mitochondrial function. Interestingly, topiramate increased CRC at high concentrations likely by a mechanism separate from direct mPT inhibition. We conclude that a clinically relevant mPT inhibitor should have a mitochondrial target and increase mitochondrial calcium retention at concentrations which can be translated to human use.
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| 9. |
- Morota, Saori, et al.
(author)
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Spinal cord mitochondria display lower calcium retention capacity compared with brain mitochondria without inherent differences in sensitivity to cyclophilin D inhibition
- 2007
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In: Journal of Neurochemistry. - : Wiley. - 1471-4159 .- 0022-3042. ; 103:5, s. 2066-2076
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Journal article (peer-reviewed)abstract
- The mitochondrial permeability transition (mPT) is a potential pathogenic mechanism in neurodegeneration. Varying sensitivity to calcium-induced mPT has been demonstrated for regions within the CNS possibly correlating with vulnerability following insults. The spinal cord is selectively vulnerable in e.g. amyotrophic lateral sclerosis and increased mPT sensitivity of mitochondria derived from the spinal cord has previously been demonstrated. In this study, we introduce whole-body hypothermia prior to removal of CNS tissue to minimize the effects of differential tissue extraction prior to isolation of spinal cord and cortical brain mitochondria. Spinal cord mitochondria were able to retain considerably less calcium when administered as continuous infusion, which was not related to a general increased sensitivity of the mPT to calcium, its desensitization to calcium by the cyclophilin D inhibitor cyclosporin-A, or to differences in respiratory parameters. Spinal cord mitochondria maintained a higher concentration of extramitochondrial calcium during infusion than brain mitochondria possibly related to an increased set-point concentration for calcium uptake. A hampered transport and retention capacity of calcium may translate into an increased susceptibility of the spinal cord to neurodegenerative processes involving calcium-mediated damage.
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| 10. |
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