Psammaplin A and Its Analogs Attenuate Oxidative Stress in Neuronal Cells through Peroxisome Proliferator-Activated Receptor γ Activation.

Psammaplins are sulfur containing bromotyrosine alkaloids that have shown antitumor activity through the inhibition of class I histone deacetylases (HDACs). The cytotoxic properties of psammaplin A (1), the parent compound, are related to peroxisome proliferator-activated receptor γ (PPARγ) activation, but the mechanism of action of its analogs psammaplin K (2) and bisaprasin (3) has not been elucidated. In this study, the protective effects against oxidative stress of compounds 1-3, isolated from the sponge Aplysinella rhax, were evaluated in SH-SY5Y cells. The compounds improved cell survival, recovered glutathione (GSH) content, and reduced reactive oxygen species (ROS) release at nanomolar concentrations. Psammaplins restored mitochondrial membrane potential by blocking mitochondrial permeability transition pore opening and reducing cyclophilin D expression. This effect was mediated by the capacity of 1-3 to activate PPARγ, enhancing gene expression of the antioxidant enzymes catalase, nuclear factor E2-related factor 2 (Nrf2), and glutathione peroxidase. Finally, HDAC3 activity was reduced by 1-3 under oxidative stress conditions. This work is the first description of the neuroprotective activity of 1 at low concentrations and the mechanism of action of 2 and 3. Moreover, it links for the first time the previously described effects of 1 in HDAC3 and PPARγ signaling, opening a new research field for the therapeutic potential of this compound family.

S-adenosylmethionine induces mitochondrial dysfunction, permeability transition pore opening and redox imbalance in subcellular preparations of rat liver.

S-adenosylmethionine (AdoMet) predominantly accumulates in tissues and biological fluids of patients affected by liver dysmethylating diseases, particularly glycine N-methyltransferase, S-adenosylhomocysteine hydrolase and adenosine kinase deficiencies, as well as in some hepatic mtDNA depletion syndromes, whose pathogenesis of liver dysfunction is still poorly established. Therefore, in the present work, we investigated the effects of S-adenosylmethionine (AdoMet) on mitochondrial functions and redox homeostasis in rat liver. AdoMet decreased mitochondrial membrane potential and Ca2+ retention capacity, and these effects were fully prevented by cyclosporin A and ADP, indicating mitochondrial permeability transition (mPT) induction. It was also verified that the thiol-alkylating agent NEM prevented AdoMet-induced ΔΨm dissipation, implying a role for thiol oxidation in the mPT pore opening. AdoMet also increased ROS production and provoked protein and lipid oxidation. Furthermore, AdoMet reduced GSH levels and the activities of aconitase and α-ketoglutarate dehydrogenase. Free radical scavengers attenuated AdoMet effects on lipid peroxidation and GSH levels, supporting a role of ROS in these effects. It is therefore presumed that disturbance of mitochondrial functions associated with mPT and redox unbalance may represent relevant pathomechanisms of liver damage provoked by AdoMet in disorders in which this metabolite accumulates.

Cryptotanshinone Ameliorates Doxorubicin-Induced Cardiotoxicity by Targeting Akt-GSK-3ß-mPTP Pathway In Vitro.

Cardiotoxicity is one of the main side effects of doxorubicin (Dox) treatment. Dox could induce oxidative stress, leading to an opening of the mitochondrial permeability transition pore (mPTP) and apoptosis in cardiomyocytes. Previous studies have shown that Cryptotanshinone (Cts) has potential cardioprotective effects, but its role in Dox-induced cardiotoxicity (DIC) remains unknown. A Dox-stimulated H9C2 cell model was established. The effects of Cts on cell viability, reactive oxygen species (ROS), superoxide ion accumulation, apoptosis and mitochondrial membrane potential (MMP) were evaluated. Expressions of proteins in Akt-GSK-3ß pathway were detected by Western blot. An Akt inhibitor was applied to investigate the effects of Cts on the Akt-GSK-3ß pathway. The effects of Cts on the binding of p-GSK-3ß to ANT and the formation of the ANT-CypD complex were explored by immunoprecipitation assay. The results showed that Cts could increase cell viability, reduce ROS levels, inhibit apoptosis and protect mitochondrial membrane integrity. Cts increased phosphorylated levels of Akt and GSK-3ß. After cells were co-treated with an Akt inhibitor, the effects of Cts were abolished. An immunoprecipitation assay showed that Cts significantly increased GSK-3ß-ANT interaction and attenuated Dox-induced formation of the ANT-CypD complex, thereby inhibiting opening of the mPTP. In conclusion, Cts could ameliorate oxidative stress and apoptosis via the Akt-GSK-3ß-mPTP pathway.

Melatonin alleviates angiotensin-II-induced cardiac hypertrophy via activating MICU1 pathway.

Mitochondrial calcium uptake 1 (MICU1) is a pivotal molecule in maintaining mitochondrial homeostasis under stress conditions. However, it is unclear whether MICU1 attenuates mitochondrial stress in angiotensin II (Ang-II)-induced cardiac hypertrophy or if it has a role in the function of melatonin. Here, small-interfering RNAs against MICU1 or adenovirus-based plasmids encoding MICU1 were delivered into left ventricles of mice or incubated with neonatal murine ventricular myocytes (NMVMs) for 48 h. MICU1 expression was depressed in hypertrophic myocardia and MICU1 knockdown aggravated Ang-II-induced cardiac hypertrophy in vivo and in vitro. In contrast, MICU1 upregulation decreased cardiomyocyte susceptibility to hypertrophic stress. Ang-II administration, particularly in NMVMs with MICU1 knockdown, led to significantly increased reactive oxygen species (ROS) overload, altered mitochondrial morphology, and suppressed mitochondrial function, all of which were reversed by MICU1 supplementation. Moreover, peroxisome proliferator-activated receptor gamma coactivator 1-α (PGC-1α)/MICU1 expression in hypertrophic myocardia increased with melatonin. Melatonin ameliorated excessive ROS generation, promoted mitochondrial function, and attenuated cardiac hypertrophy in control but not MICU1 knockdown NMVMs or mice. Collectively, our results demonstrate that MICU1 attenuates Ang-II-induced cardiac hypertrophy by inhibiting mitochondria-derived oxidative stress. MICU1 activation may be the mechanism underlying melatonin-induced protection against myocardial hypertrophy.

ATP Synthase Subunit a Supports Permeability Transition in Yeast Lacking Dimerization Subunits and Modulates yPTP Conductance.

BACKGROUND/AIMS: Mitochondrial ATP synthase, in addition to being involved in ATP synthesis, is involved in permeability transition pore (PTP) formation, which precedes apoptosis in mammalian cells and programmed cell death in yeast. Mutations in genes encoding ATP synthase subunits cause neuromuscular disorders and have been identified in cancer samples. PTP is also involved in pathology. We previously found that in Saccharomyces cerevisiae, two mutations in ATP synthase subunit a (atp6-P163S and atp6-K90E, equivalent to those detected in prostate and thyroid cancer samples, respectively) in the OM45-GFP background affected ROS and calcium homeostasis and delayed yeast PTP (yPTP) induction upon calcium treatment by modulating the dynamics of ATP synthase dimer/oligomer formation. The Om45 protein is a component of the porin complex, which is equivalent to mammalian VDAC. We aimed to investigate yPTP function in atp6-P163S and atp6-K90E mutants lacking the e and g dimerization subunits of ATP synthase. METHODS: Triple mutants with the atp6-P163S or atp6-K90E mutation, the OM45-GFP gene and deletion of the TIM11 gene encoding subunit e were constructed by crossing and tetrad dissection. In spores capable of growing, the original atp6 mutations reverted to wild type, and two compensatory mutations, namely, atp6-C33S-T215C, were selected. The effects of these mutations on cellular physiology, mitochondrial morphology, bioenergetics and permeability transition (PT) were analyzed by fluorescence and electron microscopy, mitochondrial respiration, ATP synthase activity, calcium retention capacity and swelling assays. RESULTS: The atp6-C33S-T215C mutations in the OM45-GFP background led to delayed growth at elevated temperature on both fermentative and respiratory media and increased sensitivity to high calcium ions concentration or hydrogen peroxide in the medium. The ATP synthase activity was reduced by approximately 50% and mitochondrial network was hyperfused in these cells grown at elevated temperature. The atp6-C33S-T215C stabilized ATP synthase dimers and restored the yPTP properties in Tim11∆ cells. In OM45-GFP cells, in which Tim11 is present, these mutations increased the fraction of swollen mitochondria by up to 85% vs 60% in the wild type, although the time required for calcium release doubled. CONCLUSION: ATP synthase subunit e is essential in the S. cerevisiae atp6-P163S and atp6-K90E mutants. In addition to subunits e and g, subunit a is critical for yPTP induction and conduction. The increased yPTP conduction decrease the S. cerevisiae cell fitness.

CypD deficiency confers neuroprotection against mitochondrial abnormality caused by lead in SH-SY5Y cell.

Mitochondrial permeability transition (MPT), which is mainly regulated by cyclophilin D (CypD) encoded by ppif gene, is an early event that occurs during mitochondrial stimuli exposure. Lead (Pb) induces MPT and subsequently causes mitochondrial abnormality, followed by events, including oxidative stress and cell death. Here, we generated a ppif-/- SH-SY5Y cell line to determine the role of CypD in Pb-induced mitochondrial abnormality. CypD deficiency significantly blocked mitochondrial permeability transition pore (MPTP) opening and inhibited mitochondrial membrane potential (MMP) collapse, as well as mitochondrial structure damage and fragmentation caused by Pb. Mitochondria fragmentation and MMP collapse, accompanying with Pb-induced downregulation of Glut1 and Glut3 and inactivation of AMPK signaling pathway, could impair the energy supply in wildtype cells. Meanwhile, ppif knockout can alleviate these impairments and maintain the energy supply. In addition, reactive oxygen species accumulation and cell death caused by Pb can also be attenuated by ppif knockout, thereby promoting cell survival. Our study tends to identify CypD as an important contributor to Pb-induced mitochondrial abnormality and provides a potential strategy to inhibit Pb neurotoxicity.

L-Cystathionine Protects against Homocysteine-Induced Mitochondria-Dependent Apoptosis of Vascular Endothelial Cells.

The study was aimed at investigating the effects of L-cystathionine on vascular endothelial cell apoptosis and its mechanisms. Cultured human umbilical vein endothelial cells (HUVECs) were used in the study. Apoptosis of vascular endothelial cells was induced by homocysteine. Apoptosis, mitochondrial superoxide anion, mitochondrial membrane potential, mitochondrial permeability transition pore (MPTP) opening, and caspase-9 and caspase-3 activities were examined. Expression of Bax, Bcl-2, and cleaved caspase-3 was tested and BTSA1, a Bax agonist, and HUVEC Bax overexpression was used in the study. Results showed that homocysteine obviously induced the apoptosis of HUVECs, and this effect was significantly attenuated by the pretreatment with L-cystathionine. Furthermore, L-cystathionine decreased the production of mitochondrial superoxide anion and the expression of Bax and restrained its translocation to mitochondria, increased mitochondrial membrane potential, inhibited mitochondrial permeability transition pore (MPTP) opening, suppressed the leakage of cytochrome c from mitochondria into the cytoplasm, and downregulated activities of caspase-9 and caspase-3. However, BTSA1, a Bax agonist, or Bax overexpression successfully abolished the inhibitory effect of L-cystathionine on Hcy-induced MPTP opening, caspase-9 and caspase-3 activation, and HUVEC apoptosis. Taken together, our results indicated that L-cystathionine could protect against homocysteine-induced mitochondria-dependent apoptosis of HUVECs.

Liproxstatin-1 protects the mouse myocardium against ischemia/reperfusion injury by decreasing VDAC1 levels and restoring GPX4 levels.

Ferroptosis is a distinct iron-dependent mechanism of regulated cell death recognized in cancer and ischemia/reperfusion (I/R) injury of different organs. It has been reported that molecules such as liproxstatin-1 (Lip-1) inhibit ferroptosis and promote cell survival however, the mechanisms underlying this action are not clearly understood. We investigated the role and mechanism of Lip-1 in reducing cell death in the ischemic myocardium. Using an I/R model of isolated perfused mice hearts in which Lip-1 was given at the onset of reperfusion, we found that Lip-1 protects the heart by reducing myocardial infarct sizes and maintaining mitochondrial structural integrity and function. Further investigation revealed that Lip-1-induced cardioprotection is mediated by a reduction of VDAC1 levels and oligomerization, but not VDAC2/3. Lip-1 treatment also decreased mitochondrial reactive oxygen species production and rescued the reduction of the antioxidant GPX4 caused by I/R stress. Meanwhile, mitochondrial Ca2+ retention capacity needed to induce mitochondrial permeability transition pore opening did not change with Lip-1 treatment. Thus, we report that Lip-1 induces cardioprotective effects against I/R injury by reducing VDAC1 levels and restoring GPX4 levels.

Fusaricidin-Type Compounds Create Pores in Mitochondrial and Plasma Membranes of Mammalian Cells.

Fusaricidins and related LI-F compounds are effective bactericides and fungicides. Recently, we have found that they are highly toxic to mammalian cells. Here, we studied the effect of fusaricidin-type compounds (FTCs) on the membranes of mammalian cells. Ethanol extracts from Paenibacillus polymyxa strains, RS10 and I/Sim, were fractionated and analyzed by HPLC and mass spectrometry. The effects of FTCs on mitochondrial functions and integrity were studied by standard methods: measurements of swelling, membrane potential (ΔΨm), respiration rate, cytochrome c release, and pore sizes. Superoxide flashes were registered by 3,7-dihydro-2-methyl-6-(4-methoxyphenyl)imidazol[1,2-a]pyrazine-3-one (MCLA). Plasma membrane permeability was assessed by propidium iodide (PI) staining and ATP release. FTCs caused the permeabilization of the inner mitochondria membrane (IMM) to ions and low-molecular-weight (~750 Da) solutes. The permeabilization did not depend on the permeability transition pore (mPTP) but was strongly dependent on ΔΨm. Fusaricidins A plus B, LI-F05a, and LI-F05b-LI-F07b permeabilized IMM with comparable efficiency. They created pores and affected mitochondrial functions and integrity similarly to mPTP opening. They permeabilized the sperm cell plasma membrane to ATP and PI. Thus, the formation of pores in polarized membranes underlays the toxicity of FTCs to mammals. Besides, FTCs appeared to be superior reference compounds for mPTP studies.

Nutritional preconditioning induced by astragaloside â £ on isolated hearts and cardiomyocytes against myocardial ischemia injury via improving Bcl-2-mediated mitochondrial function.

Ischemic preconditioning and pharmacological preconditioning are common strategies to prevent lethal myocardial injury, especially nutritional preconditioning (NPC). In this study, we investigated the effects of astragaloside IV (Ast), as an NPC agent, on myocardium suffered anoxia/reoxygenation (A/R) injury. Rats received 5 mg/kg Ast daily for 3 weeks by intragastric administration. Then, hearts were harvested and underwent A/R treatment using a Langendorff apparatus. Ast- pretreatment significantly promoted functional recovery of the myocardium, reduced infarct size, and oxidative stress, and decreased the apoptotic index. Similar findings were demonstrated in H9c2 cardiomyocytes that were pretreated with Ast for 24 h. Moreover, Ast-pretreatment significantly upregulated Bcl-2 expression, especially in mitochondria. The effects of Ast treatment against A/R injury were also reflected by increased antioxidant potential, inhibited reactive oxygen species (ROS) burst, increased oxygen consumption rate, maintained mitochondrial membrane potential (MMP), inhibited mitochondrial permeability transition pore (mPTP) opening, and prevented apoptosis. Selective inhibition of Bcl-2 by ABT-737 decreased myocardial injury protection of Ast. Ast-pretreatment resulted in NPC- related effects against A/R, and mitochondria may be the target of a cascade of events elicited by upregulating Bcl-2 expression, promoting translocation of Bcl-2 into mitochondria, maintaining MMP, inhibiting ROS bursts, thereby leading to recovery of mitochondrial respiration, preventing mPTP opening, decreasing cytochrome C release, preventing apoptosis, and ultimately alleviating myocardial injury.

Epigallocatechin gallate prevents mitochondrial impairment and cell apoptosis by regulating miR-30a/p53 axis.

PURPOSE: This study was designed to investigate whether EGCG prevents cardiac I/R mitochondrial impairment and cell apoptosis by regulating miR-30a/p53 axis. METHODS: The H9c2 cardiomyocytes hypoxia/reoxygenation (H/R) model in vitro and myocardial ischemia /reperfusion (I/R) model in vivo were made, with or without EGCG treatment. The levels of I/R-induced creatine kinase-MB (CK-MB) and the release of lactate dehydrogenase (LDH), as well as the adenosine triphosphate (ATP) and cardiac functional impairment were examined. Stablely transfecting miR-30a mimic or inhibitor in H9c2 cardiomyocytes was built. The expression of miR-30a, p53 and related proteins in cells was measured by western blotting and qRT-PCR. Cell viability and apoptosis were examined using CCK-8 assay and flow cytometry. The content of reactive oxygen species (ROS), mitochondrial permeability transition pores (MPTP) opening and mitochondrial transmembrane potential (ΔΨm) in cells was measured by fluorescent probes. The levels of miR-30a and p53, some related proteins expression and apoptosis in the cardiac muscle tissues were determined by quantitative real-time PCR (qRT-PCR), H&E staining, western blotting and TUNEL assays. RESULTS: We found that EGCG preconditioning significantly decreased the levels of CK-MB and LDH, increased the activity of ATP, reduced the apoptotic rate and partially preserved heart function. Furthermore, EGCG decreased ROS levels, MPTP opening and depolarization of ΔΨm, and improved the activity of post-I/R cardiomyocyte. The beneficial effect of EGCG was associated with restored levels of miR-30a expression in the I/R injury that correspond to p53 mRNA downregulation. The regulatory effect of EGCG was greatly enhanced by miR-30a mimic and suppressed by miR-30a inhibitor. More importantly, EGCG pretreatment inhibited the expression of mitochondrial apoptotic related proteins downstream of the miR-30a/p53 pathway. CONCLUSION: This study demonstrated that EGCG pretreatment may attenuate mitochondrial impairment and myocardial apoptosis by regulation of miR-30a/p53 axis.

Pharmacological inhibition of Bax-induced cell death: Bax-inhibiting peptides and small compounds inhibiting Bax.

IMPACT STATEMENT: Bax induces mitochondria-dependent programed cell death. While cytotoxic drugs activating Bax have been developed for cancer treatment, clinically effective therapeutics suppressing Bax-induced cell death rescuing essential cells have not been developed. This mini-review will summarize previously reported Bax inhibitors including peptides, small compounds, and antibodies. We will discuss potential applications and the future direction of these Bax inhibitors.

High doses of sodium tungstate can promote mitochondrial dysfunction and oxidative stress in isolated mitochondria.

Tungstate (W) is recognized as an agent of environmental pollution and a substitute to depleted uranium. According to some preliminary studies, tungstate toxicity is related to the formation of reactive oxygen species (ROS) under abnormal pathological conditions. The kidneys and liver are the main tungstate accumulation sites and important targets of tungstate toxicity. Since the mitochondrion is the main ROS production site, we evaluated the mechanistic toxicity of tungstate in isolated mitochondria for the first time, following a two-step ultracentrifugation method. Our findings demonstrated that tungstate-induced mitochondrial dysfunction is related to the increased formation of ROS, lipid peroxidation, and potential membrane collapse, correlated with the amelioration of adenosine triphosphate and glutathione contents. The present study indicated that mitochondrial dysfunction was associated with disruptive effects on the mitochondrial respiratory chain and opening of mitochondrial permeability transition (MPT) pores, which is correlated with cytochrome c release. Our findings suggest that high concentrations of tungstate (2 mM)-favored MPT pore opening in the inner membranes of liver and kidney mitochondria of rats. Besides, the results indicated higher tungstate susceptibility in the kidneys, compared with the liver.

Salvianolic Acid A Protects Neonatal Cardiomyocytes Against Hypoxia/Reoxygenation-Induced Injury by Preserving Mitochondrial Function and Activating Akt/GSK-3ß Signals.

OBJECTIVE: To investigate the effects of salvianolic acid A (SAA) on cardiomyocyte apoptosis and mitochondrial dysfunction in response to hypoxia/reoxygenation (H/R) injury and to determine whether the Akt signaling pathway might play a role. METHODS: An in vitro model of H/R injury was used to study outcomes on primary cultured neonatal rat cardiomyocytes. The cardiomyocytes were treated with 12.5, 25, 50 µg/mL SAA at the beginning of hypoxia and reoxygenation, respectively. Adenosine triphospate (ATP) and reactive oxygen species (ROS) levels were assayed. Cell apoptosis was evaluated by flow cytometry and the expression of cleaved-caspase 3, Bax and Bcl-2 were detected by Western blotting. The effects of SAA on mitochondrial dysfunction were examined by determining the mitochondrial membrane potential (△Ψm) and mitochondrial permeability transition pore (mPTP), followed by the phosphorylation of Akt (p-Akt) and GSK-3ß (p-GSK-3ß), which were measured by Western blotting. RESULTS: SAA significantly preserved ATP levels and reduced ROS production. Importantly, SAA markedly reduced the number of apoptotic cells and decreased cleaved-caspase 3 expression levels, while also reducing the ratio of Bax/Bcl-2. Furthermore, SAA prevented the loss of △Ψm and inhibited the activation of mPTP. Western blotting experiments further revealed that SAA significantly increased the expression of p-Akt and p-GSK-3ß, and the increase in p-GSK-3ß expression was attenuated after inhibition of the Akt signaling pathway with LY294002. CONCLUSION: SAA has a protective effect on cardiomyocyte H/R injury; the underlying mechanism may be related to the preservation of mitochondrial function and the activation of the Akt/GSK-3ß signaling pathway.

Rhein reverses doxorubicin resistance in SMMC-7721 liver cancer cells by inhibiting energy metabolism and inducing mitochondrial permeability transition pore opening.

Rhein, a monomeric anthraquinone obtained from the plant herb species Polygonum multiflorum and P. cuspidatum, has been proposed to have anticancer activity. This activity has been suggested to be associated with mitochondrial injury due to the induction of mitochondrial permeability transition pore (mPTP) opening. In this study, the effects of 5-80 µM rhein on cell viability, half-maximal inhibitory concentration (IC50 value), resistance index, and apoptosis were assessed in the liver cancer cell lines SMMC-7721 and SMMC-7721/DOX (doxorubicin-resistant cells). Rhein (10-80 µM) significantly reduced the viability of both cell lines; 20 µM rhein significantly increased sensitivity to DOX and increased apoptosis in SMMC-7721 cells, but reversed resistance to DOX by 7.24-fold in SMMC-7721/DOX cells. Treatment with rhein increased accumulation of DOX in SMMC-7721/DOX cells, inhibited mitochondrial energy metabolism, decreased cellular ATP, and ADP levels, and altered the ratio of ATP to ADP. These effects may result from the binding of rhein with voltage-dependent ion channels (VDACs), adenine nucleotide translocase (ANT), and cyclophilin D, affecting their function and leading to the inhibition of ATP transport by VDACs and ANT. ATP synthesis was greatly reduced and mitochondrial inner membrane potential decreased. Together, these results indicate that rhein could reverse drug resistance in SMMC-7721/DOX cells by inhibiting energy metabolism and inducing mPTP opening. © 2018 BioFactors, 45(1):85-96, 2019.

Toxicity of some broad-spectrum antibacterials in normal rat liver: the role of mitochondrial membrane permeability transition pore.

Ciprofloxacin (CIP) and Amoxycillin/Clavulanate (AC) are broad-spectrum antibiotics that are commonly administered for treatment of various bacterial infections. Studies have reported the antiproliferative and apoptotic activities of CIP in several cancer cell lines while AC has been implicated in drug-induced liver injury. We investigated the influence of CIP and AC on mitochondrial Permeability Transition (mPT) pore, ATPase activity, and cytochrome C release of normal Rat Liver Mitochondria (RLM) spectrophotometrically. In vitro, CIP and AC induced the opening of the mPT pore in a concentration-dependent manner with evidence of cytochrome C release maximally at 70 µg/ml by 13 and 10 folds, respectively. In vivo, CIP (100, 200 mg/kgbw) significantly induced mPT pore opening with induction folds of 2.4 and 2.6, respectively. However, low dose of AC (10 mg/kgbw) had no effect whatsoever on the mPT pore while higher dose (30 mg/kgbw) significantly induced pore opening by 3.4 folds. Similarly, CIP(100 mg/kgbw) and AC (30 mg/kgbw), significantly enhanced RLM ATPase activity, induced cytochrome C release and increased levels of RLM malondialdehyde generation and triggered the activation of caspases-9 and 3 in liver post-mitochondrial fraction. There were also significant (p<0.05) elevation in levels of serum aminotransferases and white blood cell count. Our results show that prolonged use of Ciprofloxacin and Amoxicillin Clavulanate could result in mitochondrial membrane breakdown via induction of opening of mPT pore leading to expulsion of cytochrome C, lipid peroxidation and decrease in energy content in healthy liver cells. These drugs should therefore be used with caution.

Dual role of inorganic polyphosphate in cardiac myocytes: The importance of polyP chain length for energy metabolism and mPTP activation.

We have previously demonstrated that inorganic polyphosphate (polyP) is a potent activator of the mitochondrial permeability transition pore (mPTP) in cardiac myocytes. PolyP depletion protected against Ca2+-induced mPTP opening, however it did not prevent and even exacerbated cell death during ischemia-reperfusion (I/R). The central goal of this study was to investigate potential molecular mechanisms underlying these dichotomous effects of polyP on mitochondrial function. We utilized a Langendorff-perfused heart model of I/R to monitor changes in polyP size and chain length at baseline, 20 min no-flow ischemia, and 15 min reperfusion. Freshly isolated cardiac myocytes and mitochondria from C57BL/6J (WT) and cyclophilin D knock-out (CypD KO) mice were used to measure polyP uptake, mPTP activity, mitochondrial membrane potential, respiration and ATP generation. We found that I/R induced a significant decrease in polyP chain length. We, therefore, tested, the ability of synthetic polyPs with different chain length to accumulate in mitochondria and induce mPTP. Both short and long chain polyPs accumulated in mitochondria in oligomycin-sensitive manner implicating potential involvement of mitochondrial ATP synthase in polyP transport. Notably, only short-chain polyP activated mPTP in WT myocytes, and this effect was prevented by mPTP inhibitor cyclosprorin A and absent in CypD KO myocytes. To the contrary, long-chain polyP suppressed mPTP activation, and enhanced ADP-linked respiration and ATP production. Our data indicate that 1) effect of polyP on cardiac function strongly depends on polymer chain length; and 2) short-chain polyPs (as increased in ischemia-reperfusion) induce mPTP and mitochondrial uncoupling, while long-chain polyPs contribute to energy generation and cell metabolism.

[Impacts of aluminum on sperm quality and sperm mitochondria in male rats].

OBJECTIVE: To study the impacts of aluminum chloride (AlCl3) on the sperm quality, sperm mitochondrial membrane potential (MMP) and sperm mitochondrial membrane permeability transition pore (MPTP) function of male rats, and the possible mechanisms of AlCl3 inducing the declination of sperm quality. METHODS: According to the median lethal dose (LD50) of AlCl3・6H2O in drinking water, we randomly assigned 96 male Wistar rats weighing 180－200 g to four groups of equal number and fed them with AlCl3 aqueous drinking water at 256.72 mg/kg/d (1/5 LD50, high-dose group), 128.36 mg/kg/d (1/10 LD50, medium-dose group), 64.18 mg/kg/d (1/20 LD50, low-dose group) and 0 mg/kg/d (control group), respectively, all for 16 weeks. Then, we examined the quality of the epididymal sperm of the rats, observed the morphology of the sperm mitochondria under the transmission electron microscope, and determined the MMP level of the sperm mitochondria and the function of the MPTP by flow cytometry. RESULTS: The percentage of progressively motile sperm was significantly decreased in the low-, medium- and high-dose AlCl3 groups as compared with that in the control group (ï¼»46.49 ± 5.37ï¼½%, ï¼»33.50 ± 8.75ï¼½% and ï¼»16.94 ± 5.00ï¼½% vs ï¼»66.28 ± 5.68ï¼½%, P < 0.01), that of dead sperm was remarkably increased (ï¼»19.73 ± 5.57ï¼½%, ï¼»35.80 ± 5.90ï¼½% and ï¼»55.19 ± 4.97ï¼½% vs ï¼»12.71 ± 4.84ï¼½%, P < 0.01), and so was that of morphologically abnormal sperm (ï¼»19.06 ± 2.44ï¼½%, ï¼»23.78 ± 3.29ï¼½% and ï¼»32.06 ± 4.65ï¼½% vs ï¼»14.56 ± 1.62ï¼½%, P < 0.01). Sperm mitochondrial swelling was aggravated in the AlCl3-exposed rats in a dose-dependent manner. The sperm MMP level was significantly lower in the low-, medium- and high-dose AlCl3 groups than in the control (ï¼»60.88 ± 7.37ï¼½%, ï¼»51.54 ± 6.12ï¼½% and ï¼»37.70 ± 7.44ï¼½% vs ï¼»74.35±4.67ï¼½%, P < 0.01), with a negative correlation to the dose of AlCl3 (rs = －0.819, P < 0.01), while the pathologically open MPTP was markedly higher in the former three than in the latter group (ï¼»27.80 ± 5.74ï¼½%, ï¼»36.58 ± 6.67ï¼½% and ï¼»64.95 ± 8.07ï¼½% vs ï¼»15.37 ± 7.13ï¼½%, P < 0.01), with a positive correlation to the dose of AlCl3 (rs = 0.867, P < 0.01). CONCLUSIONS: Exposure to aluminum can cause sperm mitochondrial swelling, decrease the sperm MMP level, induce pathological opening of the MPTP, and consequently reduce sperm quality in male rats.

Cyclophilin D, Somehow a Master Regulator of Mitochondrial Function.

Cyclophilin D (CyPD) is an important mitochondrial chaperone protein whose mechanism of action remains a mystery. It is well known for regulating mitochondrial function and coupling of the electron transport chain and ATP synthesis by controlling the mitochondrial permeability transition pore (PTP), but more recent evidence suggests that it may regulate electron transport chain activity. Given its identification as a peptidyl-prolyl, cis-trans isomerase (PPIase), CyPD, is thought to be involved in mitochondrial protein folding, but very few reports demonstrate the presence of this activity. By contrast, CyPD may also perform a scaffolding function, as it binds to a number of important proteins in the mitochondrial matrix and inner mitochondrial membrane. From a clinical perspective, inhibiting CyPD to inhibit PTP opening protects against ischemia⁻reperfusion injury, making modulation of CyPD activity a potentially important therapeutic goal, but the lack of knowledge about the mechanisms of CyPD's actions remains problematic for such therapies. Thus, the important yet enigmatic nature of CyPD somehow makes it a master regulator, yet a troublemaker, for mitochondrial function.

Erinacine Facilitates the Opening of the Mitochondrial Permeability Transition Pore Through the Inhibition of the PI3K/ Akt/GSK-3ß Signaling Pathway in Human Hepatocellular Carcinoma.

BACKGROUND/AIMS: Erinacine, which is extracted from the medicinal mushroom Hericium erinaceus, is known to play anticancer roles in human cancers. The following study aims to investigate the role of erinacine in the opening of the mitochondrial permeability transition pore (MPTP) in hepatocellular carcinoma (HCC) through the PI3K/Akt/GSK-3ß signaling pathway and highlights the applicability of erinacine in HCC treatments. METHODS: HCC and paracancerous tissues were obtained from 85 HCC patients who've undergone surgical resection. Immunohistochemistry was adopted to detect positive expression of PI3K, Akt, and GSK-3ß. Treatment of HepG-2 with LY294002 (an inhibitor of the PI3K/Akt/GSK-3ß signaling pathway) and different concentration of erinacine was performed to determine the involvement of LY294002 in erinacine action. The expressions of PI3K, Akt, GSK-3ß, CyclinD1, Vimentin, ß-catenin, Bcl-2, E-cadherin, Bax, and caspase-9 were determined by RT-qPCR and Western blot analysis. Cell viability, colony formation rate, migration, invasion, cycle, and apoptosis were detected by MTT, colony formation, wound healing assay, Transwell assay, and flow cytometry, respectively. The size and weight of xenograft tumors were observed in nude mice. Mitochondrial membrane potential in HepG-2 was determined using laser scanning confocal microscopy following JC-1 staining. Mitochondrial Ca2+ indicator Rhod-2, AM was used to detect the changes of mitochondrial Ca2+, while western blot analysis was employed to detect the presence levels of cytochrome C (cyt-C). RESULTS: The results revealed that PI3K, Akt, and GSK-3ß were up-regulated in HCC tissues. Erinacine or LY294002 led to a decrease in mitochondrial membrane potential, increase in intracellular mitochondrial Ca2+, and the release of cyt-C in mitochondria. In addition, Erinacine was found to decrease the mitochondrial membrane potential, expression of PI3K, Akt, GSK-3ß, CyclinD1, Vimentin, ß-catenin, and Bcl-2, cell proliferation, colony formation ability, migration, invasion, and xenograft tumor size, while E-cadherin, Bax, and caspase-9 expression, and cell apoptosis were elevated in a dose-dependent manner. Erinacine also stimulated the effects of LY294002 on the HCC. Following the addition of 500 µM Erinacine and MPTP opening inhibitor CsA, we found that the mitochondrial membrane potential level increased, while mitochondrial Ca2+ and Cyt-C decreased from the mitochondria. CONCLUSION: The results from the study demonstrated that erinacine induced MPTP opening, facilitates the release of cyt-C, and inhibited cell proliferation, migration, and invasion, while it promotes apoptosis by inactivating the PI3K/Akt/GSK-3ß signaling pathway, preventing the progression of HCC.