The cytotoxic, genotoxic and mitotoxic effects of Atractylis gummifera extract in vitro.

Background: The Mediterranean thistle Atractylis gummifera L. (Asteraceae; AG) has diterpenoid glucosides; atractyloside and carboxyatractyloside that interact with mitochondrial protein adenine nucleotide translocator (ANT) and resulted in ATP inhibition. Despite its well-known toxicity, acute poisonings still occur with this plant. Although most symptoms are attributed to ANT and diterpenoids interaction, in-depth investigation of the effects of AG extract on various cellular processes has not been performed. Objective/method: We tested in vitro induction of mitochondrial permeability transition pore (MPTP) opening in bovine liver mitochondria and evaluated its cytotoxicity and genotoxicity using Allium cepa test. Cell division, mitotic index (MI) and total chromosomal and mitotic aberrations (TAs), that all seem potentially affected by ATP shortage, were studied in root cells of Allium cepa exposed to Atractylis gummifera extract. Results: With the two different doses of two purified AG fractions, stronger induction of MPTP was observed compared to the induction with the standard pure atracyloside. Aqueous AG extract exerted inhibition root growth in A. cepa at 6 different doses. The TAs was increased in a dose-dependent manner too, while mitotic index was decreased at the same doses. Evaluation of mitotic phases revealed mitodepressive effect of AG on A. cepa roots. Conclusion: this work highlights cellular and mitochondrial adverse effects of Atractylis gummifera extracts. A purified fraction that likely corresponds to ATR derivatives induces MPTP opening leading to swelling of mitochondria and its dysfunction. Allium cepa test provides the evidence for A. gummifera genotoxicity and cytotoxicity.

Study on the mechanism of Wuzi-Yanzong-Wan-medicated serum interfering with the mitochondrial permeability transition pore in the GC-2 cell induced by atractyloside.

Wuzi-Yanzong-Wan (WZYZW) is a classic prescription for male infertility. Our previous investigation has demonstrated that it can inhibit sperm apoptosis via affecting mitochondria, but the underlying mechanisms are unclear. The purpose of the present study was to explore the actions of WZYZW on mitochondrial permeability transition pore (mPTP) in mouse spermatocyte cell line (GC-2 cells) opened by atractyloside (ATR). At first, WZYZW-medicated serum was prepared from rats following oral administration of WZYZW for 7 days. GC-2 cells were divided into control group, model group, positive group, as well as 5%, 10%, 15% WZYZW-medicated serum group. Cyclosporine A (CsA) was used as a positive control. 50 µmol·L-1 ATR was added after drugs incubation. Cell viability was assessed using CCK-8. Apoptosis was detected using flow cytometry and TUNEL method. The opening of mPTP and mitochondrial membrane potential (MMP) were detected by Calcein AM and JC-1 fluorescent probe respectively. The mRNA and protein levels of voltage-dependent anion channel 1 (VDAC1), cyclophilin D (CypD), adenine nucleotide translocator (ANT), cytochrome C (Cyt C), caspase 3, 9 were detected by RT-PCR (real time quantity PCR) and Western blotting respectively. The results demonstrated that mPTP of GC-2 cells was opened after 24 hours of ATR treatment, resulting in decreased MMP and increased apoptosis. Pre-protection with WZYZ-medicated serum and CsA inhibited the opening of mPTP of GC-2 cells induced by ATR associated with increased MMP and decreased apoptosis. Moreover, the results of RT-qPCR and WB suggested that WZYZW-medicated serum could significantly reduce the mRNA and protein levels of VDAC1 and CypD, Caspase-3, 9 and CytC, as well as a increased ratio of Bcl/Bax. However, ANT was not significantly affected. Therefore, these findings indicated that WZYZW inhibited mitochondrial mediated apoptosis by attenuating the opening of mPTP in GC-2 cells. WZYZW-medicated serum inhibited the expressions of VDAC1 and CypD and increased the expression of Bcl-2, which affected the opening of mPTP and exerted protective and anti-apoptotic effects on GC-2 cell induced by ATR.

Investigating the Broad Matrix-Gate Network in the Mitochondrial ADP/ATP Carrier through Molecular Dynamics Simulations.

The mitochondrial ADP/ATP carrier (AAC) exports ATP and imports ADP through alternating between cytosol-open (c-) and matrix-open (m-) states. The salt bridge networks near the matrix side (m-gate) and cytosol side (c-gate) are thought to be crucial for state transitions, yet our knowledge on these networks is still limited. In the current work, we focus on more conserved m-gate network in the c-state AAC. All-atom molecular dynamics (MD) simulations on a variety of mutants and the CATR-AAC complex have revealed that: (1) without involvement of other positive residues, the charged residues from the three Px[DE]xx[KR] motifs only are prone to form symmetrical inter-helical network; (2) R235 plays a determinant role for the asymmetry in m-gate network of AAC; (3) R235 significantly strengthens the interactions between H3 and H5; (4) R79 exhibits more significant impact on m-gate than R279; (5) CATR promotes symmetry in m-gate mainly through separating R234 from D231 and fixing R79; (6) vulnerability of the H2-H3 interface near matrix side could be functionally important. Our results provide new insights into the highly conserved yet variable m-gate network in the big mitochondrial carrier family.

Knockdown of forkhead box protein P1 alleviates hypoxia reoxygenation injury in H9c2 cells through regulating Pik3ip1/Akt/eNOS and ROS/mPTP pathway.

Forkhead box protein P1 (Foxp1) exerts an extensive array of physiological and pathophysiological impacts on the cardiovascular system. However, the exact function of myocardial Foxp1 in myocardial ischemic reperfusion injury (MIRI) stays largely vague. The hypoxia reoxygenation model of H9c2 cells (the rat ventricular myoblasts) closely mimics myocardial ischemia-reperfusion injury. This report intends to research the effects and mechanisms underlying Foxp1 on H9c2 cells in response to hypoxia (12 h)/reoxygenation (4 h) (HR) stimulation. Expressions of Foxp1 and Phosphatidylinositol 3-kinase interacting protein 1 (Pik3ip1) were both upregulated in ischemia/reperfusion (IR)/HR-induced injury. Stimulation through HR led to marked increases in cellular apoptosis, mitochondrial dysfunction, and superoxide generation in H9c2 cells, which were rescued with knockdown of Foxp1 by siRNA. Silence of Foxp1 depressed expression of Pik3ip1 directly activated the PI3K/Akt/eNOS pathway and promoted nitric oxide (NO) release. Moreover, the knockdown of Foxp1 blunted HR-induced enhancement of reactive oxygen species (ROS) generation, thus alleviating excessive persistence of mitochondrial permeability transition pore (mPTP) opening and decreased mitochondrial apoptosis-associated protein expressions in H9c2 cells. Meanwhile, these cardioprotective effects can be abolished by LY294002, NG-nitro-L-arginine methyl ester (L-NAME), and Atractyloside (ATR), respectively. In summary, our findings indicated that knockdown of Foxp1 prevented HR-induced encouragement of apoptosis and oxidative stress via PI3K/Akt/eNOS signaling activation by targeting Pik3ip1 and improved mitochondrial function by inhibiting ROS-mediated mPTP opening. Inhibition of Foxp1 may be a promising therapeutic avenue for MIRI.

Study on the mechanism of Wuzi-Yanzong-Wan-medicated serum interfering with the mitochondrial permeability transition pore in the GC-2 cell induced by atractyloside / 中国天然药物

Wuzi-Yanzong-Wan (WZYZW) is a classic prescription for male infertility. Our previous investigation has demonstrated that it can inhibit sperm apoptosis via affecting mitochondria, but the underlying mechanisms are unclear. The purpose of the present study was to explore the actions of WZYZW on mitochondrial permeability transition pore (mPTP) in mouse spermatocyte cell line (GC-2 cells) opened by atractyloside (ATR). At first, WZYZW-medicated serum was prepared from rats following oral administration of WZYZW for 7 days. GC-2 cells were divided into control group, model group, positive group, as well as 5%, 10%, 15% WZYZW-medicated serum group. Cyclosporine A (CsA) was used as a positive control. 50 μmol·L-1 ATR was added after drugs incubation. Cell viability was assessed using CCK-8. Apoptosis was detected using flow cytometry and TUNEL method. The opening of mPTP and mitochondrial membrane potential (MMP) were detected by Calcein AM and JC-1 fluorescent probe respectively. The mRNA and protein levels of voltage-dependent anion channel 1 (VDAC1), cyclophilin D (CypD), adenine nucleotide translocator (ANT), cytochrome C (Cyt C), caspase 3, 9 were detected by RT-PCR (real time quantity PCR) and Western blotting respectively. The results demonstrated that mPTP of GC-2 cells was opened after 24 hours of ATR treatment, resulting in decreased MMP and increased apoptosis. Pre-protection with WZYZ-medicated serum and CsA inhibited the opening of mPTP of GC-2 cells induced by ATR associated with increased MMP and decreased apoptosis. Moreover, the results of RT-qPCR and WB suggested that WZYZW-medicated serum could significantly reduce the mRNA and protein levels of VDAC1 and CypD, Caspase-3, 9 and CytC, as well as a increased ratio of Bcl/Bax. However, ANT was not significantly affected. Therefore, these findings indicated that WZYZW inhibited mitochondrial mediated apoptosis by attenuating the opening of mPTP in GC-2 cells. WZYZW-medicated serum inhibited the expressions of VDAC1 and CypD and increased the expression of Bcl-2, which affected the opening of mPTP and exerted protective and anti-apoptotic effects on GC-2 cell induced by ATR.

The newborn Fmr1 knockout mouse: a novel model of excess ubiquinone and closed mitochondrial permeability transition pore in the developing heart.

BACKGROUND: Mitochondrial permeability transition pore (mPTP) closure triggers cardiomyocyte differentiation during development while pathological opening causes cell death during myocardial ischemia-reperfusion and heart failure. Ubiquinone modulates the mPTP; however, little is known about its mechanistic role in health and disease. We previously found excessive proton leak in newborn Fmr1 KO mouse forebrain caused by ubiquinone deficiency and increased open mPTP probability. Because of the physiological differences between the heart and brain during maturation, we hypothesized that developing Fmr1 KO cardiomyocyte mitochondria would demonstrate dissimilar features. METHODS: Newborn male Fmr1 KO mice and controls were assessed. Respiratory chain enzyme activity, ubiquinone content, proton leak, and oxygen consumption were measured in cardiomyocyte mitochondria. Cardiac function was evaluated via echocardiography. RESULTS: In contrast to controls, Fmr1 KO cardiomyocyte mitochondria demonstrated increased ubiquinone content and decreased proton leak. Leak was cyclosporine (CsA)-sensitive in controls and CsA-insensitive in Fmr1 KOs. There was no difference in absolute mitochondrial respiration or cardiac function between strains. CONCLUSION: These findings establish the newborn Fmr1 KO mouse as a novel model of excess ubiquinone and closed mPTP in the developing heart. Such a model may help provide insight into the biology of cardiac development and pathophysiology of neonatal heart failure. IMPACT: Ubiquinone is in excess and the mPTP is closed in the developing FXS heart. Strengthens evidence of open mPTP probability in the normally developing postnatal murine heart and provides new evidence for premature closure of the mPTP in Fmr1 mutants. Establishes a novel model of excess CoQ and a closed pore in the developing heart. Such a model will be a valuable tool used to better understand the role of ubiquinone and the mPTP in the neonatal heart in health and disease.

Limb Ischemic Postconditioning Alleviates Postcardiac Arrest Syndrome through the Inhibition of Mitochondrial Permeability Transition Pore Opening in a Porcine Model.

OBJECTIVE: Previously, the opening of mitochondrial permeability transition pore (mPTP) was confirmed to play a key role in the pathophysiology of postcardiac arrest syndrome (PCAS). Recently, we demonstrated that limb ischemic postconditioning (LIpostC) alleviated cardiac and cerebral injuries after cardiac arrest and resuscitation. In this study, we investigated whether LIpostC would alleviate the severity of PCAS through inhibiting mPTP opening. METHODS: Twenty-four male domestic pigs weighing 37 ± 2 kg were randomly divided into three groups: control, LIpostC, and LIpostC+atractyloside (Atr, the mPTP opener). Atr (10 mg/kg) was intravenously injected 30 mins prior to the induction of cardiac arrest. The animals were subjected to 10 mins of untreated ventricular fibrillation and 5 mins of cardiopulmonary resuscitation. Coincident with the beginning of cardiopulmonary resuscitation, LIpostC was induced by four cycles of 5 mins of limb ischemia and then 5 mins of reperfusion. The resuscitated animals were monitored for 4 hrs and observed for an additional 68 hrs. RESULTS: After resuscitation, systemic inflammation and multiple organ injuries were observed in all resuscitated animals. However, postresuscitation systemic inflammation was significantly milder in the LIpostC group than in the control group. Myocardial, lung, and brain injuries after resuscitation were significantly improved in the LIpostC group compared to the control group. Nevertheless, pretreatment with Atr abolished all the protective effects induced by LIpostC. CONCLUSION: LIpostC significantly alleviated the severity of PCAS, in which the protective mechanism was associated with the inhibition of mPTP opening.

CMap analysis identifies Atractyloside as a potential drug candidate for type 2 diabetes based on integration of metabolomics and transcriptomics.

BACKGROUND: This research aimed at exploring the mechanisms of alterations of metabolites and pathways in T2D from the perspective of metabolomics and transcriptomics, as well as uncovering novel drug candidate for T2D treatment. METHODS: Metabolites in human plasma from 42 T2D patients and 45 non-diabetic volunteers were detected by liquid chromatography-mass spectrometer (LC-MS). Microarray dataset of the transcriptome was obtained from Gene Expression Omnibus (GEO) database. Kyoto Encyclopedia of Genes and Genomes (KEGG) database was used to conduct pathway enrichment analysis. Connectivity Map (CMap) was employed to select potential drugs for T2D therapy. In vivo assay was performed to verify above findings. The protein expression levels of ME1, ME2 and MDH1 were detected by Western blot to determine the status of NAD/NADH cofactor system. RESULTS: In our study, differentially expressed metabolites were selected out between healthy samples and T2D samples with selection criteria P value < .05, |Fold Change| > 2, including N-acetylglutamate and Malate. Genes set enrichment analysis (GSEA) revealed that 34 pathways were significantly enriched in T2D. Based on CMap analysis and animal experiments, Atractyloside was identified as a potential novel drug for T2D treatment via targeting ME1, ME2 and MDH1 and regulating the NAD/NADH cofactor system. CONCLUSION: The present research revealed differentially expressed metabolites and genes, as well as significantly altered pathways in T2D via an integration of metabolomics, transcriptomics and CMap analysis. It was also demonstrated that comprehensive analysis based on metabolomics and transcriptomics was an effective approach for identification and verification of metabolic biomarkers and alternated pathways.

Bioavailability and Biological Effects of 2- O-ß-d-Glucopyranosyl-carboxyatractyligenin from Green Coffee in Caenorhabditis elegans.

Targeted analysis of Coffea arabica and Coffea canephora green coffees (total sample size n = 57) confirmed 2- O-ß-d-glucopyranosyl-carboxyatractyligenin (6) as the quantitatively dominating carboxyatractyligenin derivative. Its abundance in Arabicas (2425 ± 549 nmol/g, n = 48) exceeded that in Robustas (34 ± 12 nmol/g, n = 9) roughly by a factor of 70. Coffee processing involving heat (e.g., steam treatment and decaffeination) reduced concentrations of 6 and increased those of the decarboxylated derivative. The bioavailability of compound 6 in Caenorhabditis elegans was demonstrated by ultraperformance liquid chromatography-tandem mass spectrometry analysis of extracts prepared from nematode cultures incubated in a liquid medium containing 6. A toxicity assay performed to assess the impact of 6 in vivo showed a 20-fold higher median lethal dose (LD50 = 11.7 ± 1.2 mM) concentration compared to that of the known phytotoxic adenine-nucleotide transporters inhibitor carboxyatractyloside (2, LD50 = 0.61 ± 0.05 mM), whereas 1 mM 6 and 0.1 mM 2 were sufficient to decrease the survival of wild type C. elegans, already 10-20-fold lower doses reduced reproduction. Because the insulin/insulin-like growth factors signaling cascade (IIS) is a key regulator of life span and stress resistance, the impact of compound 6 on the survival of long-living daf-2 C. elegans was tested. As the susceptibility of these nematodes to 6 was as high as that in wild type, an impact on central metabolic processes independent of IIS was suggested. Analysis of the in vivo adenosine triphosphate (ATP) content of adult C. elegans revealed no changes after 1 and 24 h, but a 50% reduction after treatment with 1 mM 6 during the entire postembryonic development. These data speak for a developmental-stage-dependent modulation of the ATP pool by 6.

Atractyligenin, a terpenoid isolated from coffee silverskin, inhibits cutaneous photoaging.

Ultraviolet (UV) light exposure-induced photoaging of the skin is a multifactorial process involving both extrinsic and intrinsic cellular mechanisms. Several naturally occurring products are known to confer protection against UV light-induced skin damage. Our preliminary studies confirmed that the ethyl acetate fraction of coffee silverskin exhibits inhibitory effects on matrix metalloproteases (MMPs). Furthermore, we previously isolated and identified atractyligenin, which has MMP-inhibitory activity, from the silverskin ethyl acetate fraction. The aim of this study was to elucidate the anti-photoaging effects of atractyligenin on human dermal fibroblasts and the underlying mechanism. Human dermal fibroblasts were exposed to 8 J/cm2 UVA radiation, and cell viability was analyzed by MTT assay. The fluorescent dye 2', 7'-dichlorodihydrofluorescein diacetate (H2DCF-DA) was used to measure the intracellular reactive oxygen species (ROS) levels. Our study showed that atractyligenin significantly suppressed the expression of UVA-induced MMPs by inhibiting intracellular ROS production. Atractyligenin treatment reduced c-Jun phosphorylation and c-Fos expression by inhibiting the mitogen-activated protein kinase (MAPK) signaling pathway activated by UVA irradiation. Additionally, treatment with atractyligenin contributed to the homeostasis of collagen by restoring the loss of collagen absorption-related receptor Endo180 and altered fibroblast morphology induced by UVA irradiation. These results indicate that atractyligenin isolated from coffee silverskin inhibits multiple pathways in the human skin photoaging process and is thus a potential candidate for treatment or prevention of photoaging.

Nutritional Preconditioning of Apigenin Alleviates Myocardial Ischemia/Reperfusion Injury via the Mitochondrial Pathway Mediated by Notch1/Hes1.

Apigenin (Api), a natural flavone found in high amounts in several herbs, has shown potent cardioprotective effects in clinical studies, although the underlying mechanisms are not clear. We hypothesized that Api protects the myocardium from simulated ischemia/reperfusion (SI/R) injury via nutritional preconditioning (NPC). Rats fed with Api-containing food showed improvement in cardiac functions; lactate dehydrogenase (LDH) and creatine phosphokinase (CPK) activities; infarct size; apoptosis rates; malondialdehyde (MDA) levels; caspase-3, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities; and ferric reducing antioxidant power (FRAP) compared to those fed standard chow following SI/R injury. In addition, Api pretreatment significantly improved the viability, decreased the LDH activity and intracellular reactive oxygen species (ROS) generation, alleviated the loss of mitochondrial membrane potential (MMP), prevented the opening of the mitochondrial permeability transition pore (mPTP), and decreased the caspase-3 activity, cytochrome c (Cyt C) release, and apoptosis induced by SI/R in primary cardiomyocytes. Mechanistically, Api upregulated Hes1 expression and was functionally neutralized by the Notch1 γ-secretase inhibitor GSI, as well as the mPTP opener atractyloside (Atr). Taken together, Api protected the myocardium against SI/R injury via the mitochondrial pathway mediated by the Notch1/Hes1 signaling pathway.

[Role of mitochondrial permeability transition pore in mediating the effect of endomorphin-1 postconditioning against myocardial ischemia-reperfusion injury in rats].

OBJECTIVE: To investigate the role of mitochondrial permeability transition pore (MPTP) opening in mediating the effect of endomorphine-1 postconditioning to alleviate myocardial ischemia-reperfusion (IR) injury in rats. METHODS: Forty-five male SD rats were randomized equally for sham operation, myocardial IR injury, endomorphin-1 postconditioning, atractyloside (a MPTP opener) postconditioning, or endomorphin-1 + atractyloside postconditioning. The hemodynamic param-eters of the rats were monitored in real time via carotid artery cannulation to the left ventricle. After reperfusion, plasma samples were collected for biochemical analyses. The size of myocardial infarct area was detected using Evans blue and TTC double staining, and the myocardial expressions of apoptosis-related proteins Bax, Bcl-2 and cleaved caspase-3 were analyzed using Western blotting. RESULTS: Myocardial IR injury resulted in significantly decreased heart rate and blood pressure in the rats (P<0.05). Compared with those in IR group, the rats with endomorphin-1 postconditioning showed significantly increased heart rate and blood pressure (P<0.05), lowered contents or activities of LDH, CK-MB, cTnI, IL-6, TNF-α, Cyt-C and MDA in the plasma (P<0.05), increased plasma SOD activity (P<0.05), reduced size of myocardial infarction, decreased myocardial expression of Bax and cleaved caspase-3 protein (P<0.05), and increased myocardial expression of Bcl-2 protein (P<0.05). All these changes induced by endomorphin-1 were obviously reversed by atractyloside postconditioning (P<0.05). CONCLUSION: Endomorphin-1 postconditioning protects against myocardial IR injury in rats probably by inhibiting the opening of MPTP and reducing cardiac myocyte apoptosis via down-regulating cleaved caspase-3 expression.

Inhibition of mitochondrial permeability transition pore opening contributes to cannabinoid type 1 receptor agonist ACEA-induced neuroprotection.

Cannabinoid type 1 (CB1) receptor agonist arachidonyl-2-chloroethylamide (ACEA) induces neuroprotection against brain ischemia, and the mechanism, however, is still elusive. In this study, we used bilateral common carotid artery occlusion (BCCAO) in mice and oxygen-glucose deprivation (OGD) in primary cultured neurons to mimic brain ischemic injury, and hypothesized that cannabinoid CB1 receptor agonist ACEA protects ischemic neurons via inhibiting the opening of mitochondrial permeability transition pore (MPTP). In vivo, we found that BCCAO treatment reduced the neurological functions, increased the number of apoptotic neuronal cells and deteriorated the mitochondrial morphology in the ischemic brain tissue. And in vitro, we observed that OGD injury reduced cell viability, mitochondrial function and anti-oxidant SOD2 expression, increased lactate dehydrogenase (LDH), mitochondrial cytochrome C (Cyto C) and apoptosis-inducing factor (AIF) releases, elevated the cell apoptosis and mitochondrial superoxide level. And the CB1 receptor agonist ACEA significantly abolished the BCCAO and OGD-induced neuronal injury above. However, the MPTP opener atractyloside (Atr) markedly reversed the ACEA-induced neuroprotective effects, inhibited the mitochondrial Cyto C and AIF releases and relieved the mitochondrial swelling, but the MPTP inhibitor cyclosporin A (CsA) did not cause significant effects on the ACEA-induced neuroprotection above. These findings indicated that inhibition of MPTP opening may be involved in the cannabinoid CB1 receptor agonist ACEA-induced neuroprotection.

Binding characterization of the targeting drug AIMPILA to AFP receptors in human tumor xenografts.

The main objective of this study was the characterization of preclinical tumor models based on their expression of alpha-fetoprotein receptor (RECAF) for targeting cancer cells with a new non-covalent complex (AIMPILA) containing alpha-fetoprotein as the carrier and Atractyloside as an apoptosis-inducing agent. For that purpose, we measured the amount of RECAF in the homogenates of the grafted tumors T47D and SW620 and in HepG2 cell extracts. We also determined the alpha-fetoprotein binding specificity of the targeting drug AIMPILA using a solid-phase chemiluminescent assay with AIMPILA-Acrdidinium. We found that RECAF is practically absent from healthy mice tissues (100 Units/mg) where in malignant cells, the amount of alpha-fetoprotein receptors follows this order: T47D (9152 Units/mg) > HepG2 (4865 Units/mg) > SW620 (2839 Units/mg). This agrees with our findings regarding AIMPILA-induced tumor growth inhibition (T47D (T/C = 22%) > HepG2 (T/C = 51%) > SW620 (T/C = 70%), where T/C is the ratio of tumor volume in treated vs control animals). Our results demonstrate that the therapeutic response to the targeting drug AIMPILA strongly depends on the RECAF expression by human tumors and confirms the choice of the tumor models used for an AIMPILA preclinical study.

Sasanquasaponin-induced cardioprotection involves inhibition of mPTP opening via attenuating intracellular chloride accumulation.

Sasanquasaponin (SQS) has been reported to elicit cardioprotection by suppressing hypoxia/reoxygenation (H/R)-induced elevation of intracellular chloride ion concentration ([Cl-]i). Given that the increased [Cl-]i is involved to modulate the mitochondrial permeability transition pore (mPTP), we herein sought to further investigate the role of mPTP in the cardioprotective effect of SQS on H/R injury. H9c2 cells were incubated for 24h with or without 10µM SQS followed by H/R. The involvement of mPTP was determined with a specific mPTP agonist atractyloside (ATR). The results showed that SQS attenuated H/R-induced the elevation of [Cl-]i, accompanied by reduction of lactate dehydrogenase release and increase of cell viability. Moreover, SQS suppressed mPTP opening, and protected mitochondria, as indicated by preserved mitochondrial membrane potential and respiratory chain complex activities, decreased mitochondrial reactive oxygen species generation, and increased ATP content. Interestingly, extracellular Cl--free condition created by replacing Cl- with equimolar gluconate resulted in a decrease in [Cl-]i and induced protective effects similar to SQS preconditioning, whereas pharmacologically opening of the mPTP with ATR abolished all the protective effects induced by SQS or Cl--free, including suppression of mPTP opening, maintenance of mitochondrial membrane potential, and subsequent improvement of mitochondrial function. The above results allow us to conclude that SQS-induced cardioprotection may be mediated by preserving the mitochondrial function through preventing mPTP opening via inhibition of H/R-induced elevation of [Cl-]i.

Sevoflurane pre-conditioning increases phosphorylation of Erk1/2 and HO-1 expression via inhibition of mPTP in primary rat cortical neurons exposed to OGD/R.

BACKGROUND: As an indispensable clinical inhalation anesthetic, sevoflurane is widely used for peri-operative sedation. The neuroprotective effect of sevoflurane pre-conditioning against cerebral ischemia/reperfusion has been gradually realized, but the underlying mechanism during the early reperfusion period has not been established. METHOD: Primary cultured cortical neurons were treated with 2% sevoflurane pre-conditioning for 30min, exposed to oxygen-glucose deprivation for 90min, and followed by 60min of reperfusion (OGD/R). Additionally, neuronal cells were treated with an inhibitor of extracellular signal-related kinases 1 and 2 (Erk1/2) phosphorylation (PD98059), a mPTP opener (atractyloside), or a mPTP opening inhibitor (cyclosporine A) before sevoflurane pre-conditioning. RESULT: Sevoflurane pre-conditioning decreased neuronal apoptosis (assessed by TUNEL), oxidative stress (assessed by malondialdehyde [MDA], superoxide dismutase [SOD], and heme oxygenase [HO]-1), and opening of mitochondrial permeability transition pores [mPTPs] (assessed by calcein-cobalt), but increased neuronal viability (assessed by MTT) and mitochondrial membrane potential (assessed by JC-1) after OGD/R exposure compared with OGD/R treatment alone. Pre-treatment with the mPTP opener and inhibitor of Erk1/2 phosphorylation abolished the protective effect induced by sevoflurane pre-conditioning. Pre-treatment with the mPTP opener attenuated the phosphorylation of Erk1/2 in mitochondria of neuronal cultures exposed to OGD/R induced by sevoflurane pre-conditioning. The mPTP opening inhibitor, like sevoflurane pre-conditioning, increased phosphorylation of Erk1/2 after OGD/R exposure, while PD98059 failed to reverse inhibition of mPTP opening in cultures exposed to OGD/R induced by sevoflurane pre-conditioning. CONCLUSION: The neuroprotective mechanism of sevoflurane pre-conditioning might be associated with increased Erk1/2 phosphorylation in mitochondria via inhibition of mPTP opening in the early reperfusion period.

Intracellular Renin Inhibits Mitochondrial Permeability Transition Pore via Activated Mitochondrial Extracellular Signal-Regulated Kinase (ERK) 1/2 during Ischemia in Diabetic Hearts.

Although beneficial effects of non-secreting intracellular renin (ns-renin) against ischemia have been reported, the precise mechanism remains unclear. In this study, we investigated the roles of ns-renin and mitochondrial extracellular signal-related kinase (ERK) 1/2 on mitochondrial permeability transition pore (mPTP) opening during ischemia in diabetes mellitus (DM) hearts. When isolated hearts from Wistar rats (non-DM hearts) and Goto-Kakizaki rats (DM hearts) were subjected to ischemia for 70 min by left anterior descending coronary artery ligation, DM hearts exhibited higher left ventricular (LV) developed pressure and lower LV end-diastolic pressure than non-DM hearts, suggesting ischemic resistance. In addition, DM hearts showed increased intracellular renin (int-renin, including secreting and non-secreting renin) in the ischemic area, and a direct renin inhibitor (DRI; aliskiren) attenuated ischemic resistance in DM hearts. ERK1/2 was significantly phosphorylated after ischemia in both whole cell and mitochondrial fractions in DM hearts. In isolated mitochondria from DM hearts, rat recombinant renin (r-renin) significantly phosphorylated mitochondrial ERK1/2, and hyperpolarized mitochondrial membrane potential (ΔΨm) in a U0126 (an inhibitor of mitogen-activated protein kinases/ERK kinases)-sensitive manner. R-renin also attenuated atractyloside (Atr, an mPTP opener)-induced ΔΨm depolarization and Atr-induced mitochondrial swelling in an U0126-sensitive manner in isolated mitochondria from DM hearts. Furthermore, U0126 attenuated ischemic resistance in DM hearts, whereas it did not alter the hemodynamics in non-DM hearts. Our results suggest that the increased int-renin during ischemia may inhibit mPTP opening through activation of mitochondrial ERK1/2, which may be involved in ischemic resistance in DM hearts.

Morphine-Induced Preconditioning: Involvement of Protein Kinase A and Mitochondrial Permeability Transition Pore.

BACKGROUND: Morphine induces myocardial preconditioning (M-PC) via activation of mitochondrial large conductance Ca2+-sensitive potassium (mKCa) channels. An upstream regulator of mKCa channels is protein kinase A (PKA). Furthermore, mKCa channel activation regulates mitochondrial bioenergetics and thereby prevents opening of the mitochondrial permeability transition pore (mPTP). Here, we investigated in the rat heart in vivo whether 1) M-PC is mediated by activation of PKA, and 2) pharmacological opening of the mPTP abolishes the cardioprotective effect of M-PC and 3) M-PC is critically dependent on STAT3 activation, which is located upstream of mPTP within the signalling pathway. METHODS: Male Wistar rats were randomised to six groups (each n = 6). All animals underwent 25 minutes of regional myocardial ischemia and 120 minutes of reperfusion. Control animals (Con) were not further treated. Morphine preconditioning was initiated by intravenous administration of 0.3 mg/kg morphine (M-PC). The PKA blocker H-89 (10 µg/kg) was investigated with and without morphine (H-89+M-PC, H-89). We determined the effect of mPTP opening with atractyloside (5 mg/kg) with and without morphine (Atr+M-PC, Atr). Furthermore, the effect of morphine on PKA activity was tested in isolated adult rat cardiomyocytes. In further experiments in isolated hearts we tested the protective properties of morphine in the presence of STAT3 inhibition, and whether pharmacological prevention of the mPTP-opening by cyclosporine A (CsA) is cardioprotective in the presence of STAT3 inhibition. RESULTS: Morphine reduced infarct size from 64±5% to 39±9% (P<0.05 vs. Con). H-89 completely blocked preconditioning by morphine (64±9%; P<0.05 vs. M-PC), but H-89 itself had not effect on infarct size (61±10%; P>0.05 vs. Con). Also, atractyloside abolished infarct size reduction of morphine completely (65±9%; P<0.05 vs. M-PC) but had no influence on infarct size itself (64±5%; P>0.05 vs. Con). In isolated hearts STAT3 inhibitor Stattic completely abolished morphine-induced preconditioning. Administration of Stattic and mPTP inhibitor cyclosporine A reduced infarct size to 31±6% (Stat+CsA, P<0.05 vs. Con). Cyclosporine A alone reduced infarct size to 26±7% (CsA P<0.05 vs. Con). In cardiomyocytes, PKA activity was increased by morphine. CONCLUSION: Our data suggest that morphine-induced cardioprotection is mediated by STAT3-activation and inhibition of mPTP, with STA3 located upstream of mPTP. There is some evidence that protein kinase A is involved within the signalling pathway.

To involvement the conformation of the adenine nucleotide translocase in opening the Tl(+)-induced permeability transition pore in Ca(2+)-loaded rat liver mitochondria.

The conformation of adenine nucleotide translocase (ANT) has a profound impact in opening the mitochondrial permeability transition pore (MPTP) in the inner membrane. Fixing the ANT in 'c' conformation by phenylarsine oxide (PAO), tert-butylhydroperoxide (tBHP), and carboxyatractyloside as well as the interaction of 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) with mitochondrial thiols markedly attenuated the ability of ADP to inhibit the MPTP opening. We earlier found (Korotkov and Saris, 2011) that calcium load of rat liver mitochondria in medium containing TlNO3 and KNO3 stimulated the Tl(+)-induced MPTP opening in the inner mitochondrial membrane. The MPTP opening as well as followed increase in swelling, a drop in membrane potential (ΔΨmito), and a decrease in state 3, state 4, and 2,4-dinitrophenol-uncoupled respiration were visibly enhanced in the presence of PAO, tBHP, DIDS, and carboxyatractyloside. However, these effects were markedly inhibited by ADP and membrane-penetrant hydrophobic thiol reagent, N-ethylmaleimide (NEM) which fix the ANT in 'm' conformation. Cyclosporine A additionally potentiated these effects of ADP and NEM. Our data suggest that conformational changes of the ANT may be directly involved in the opening of the Tl(+)-induced MPTP in the inner membrane of Ca(2+)-loaded rat liver mitochondria. Using the Tl(+)-induced MPTP model is discussed in terms finding new transition pore inhibitors and inducers among different chemical and natural compounds.

Identification of new highly selective inhibitors of the human ADP/ATP carriers by molecular docking and in vitro transport assays.

Mitochondrial carriers are proteins that shuttle a variety of metabolites, nucleotides and coenzymes across the inner mitochondrial membrane. The mitochondrial ADP/ATP carriers (AACs) specifically translocate the ATP synthesized within mitochondria to the cytosol in exchange for the cytosolic ADP, playing a key role in energy production, in promoting cell viability and regulating mitochondrial permeability transition pore opening. In Homo sapiens four genes code for AACs with different tissue distribution and expression patterns. Since AACs are dysregulated in several cancer types, the employment of known and new AAC inhibitors might be crucial for inducing mitochondrial-mediated apoptosis in cancer cells. Albeit carboxyatractyloside (CATR) and bongkrekic acid (BKA) are known to be powerful and highly selective AAC inhibitors, able to induce mitochondrial dysfunction at molecular level and poisoning at physiological level, we estimated here for the first time their affinity for the human recombinant AAC2 by in vitro transport assays. We found that the inhibition constants of CATR and BKA are 4 nM and 2.0 µM, respectively. For finding new AAC inhibitors we also performed a docking-based virtual screening of an in-house developed chemical library and we identified about 100 ligands showing high affinity for the AAC2 binding region. By testing 13 commercially available molecules, out of the 100 predicted candidates, we found that 2 of them, namely suramin and chebulinic acid, are competitive AAC2 inhibitors with inhibition constants 0.3 µM and 2.1 µM, respectively. We also demonstrated that chebulinic acid and suramin are "highly selective" AAC2 inhibitors, since they poorly inhibit other human mitochondrial carriers (namely ORC1, APC1 and AGC1).