Inhibitor Of Mitochondrial Permeability Transition Pore Research Articles

Mitochondrial aldehyde dehydrogenase activity protects against lipopolysaccharide‑induced cardiac dysfunction in rats.

Myocardial dysfunction in sepsis is associated with an increased risk of mortality. The mitochondrial aldehyde dehydrogenase (ALDH2) enzyme is crucial for protecting the heart from ischemic injury. The aim of the present study was to determine the role of ALDH2 in cardiac dysfunction induced by lipopolysaccharide (LPS). Male rats were treated intraperitoneally with LPS, and their stroke volume and cardiac output were evaluated using an M‑mode echocardiograph. The expression levels and activity of ALDH2, nitric oxide content and inducible nitric oxide synthase (iNOS) activity, and the opening of the mitochondrial permeability transition pore (MPTP) were also evaluated. Treatment with LPS (5, 10, or 20 mg/kg) resulted in a steady decrease in cardiac output and stroke volume. The ALDH2 activity was decreased in a dose‑dependent manner; however, the ALDH2 protein expression levels remained unchanged. Alda‑1, a specific activator of ALDH2, increased the activity of ALDH2 and lessened LPS‑induced cardiac dysfunction. A marked opening of the MPTP was observed 12 h following treatment with LPS, which was prevented by Alda‑1. The improvement in cardiac function in response to treatment with Alda‑1, was partially prevented by treatment with the MPTP inhibitor atractyloside. LPS treatment induced an increase in iNOS activation and inhibition of ALDH2 activity. The iNOS selective inhibitor, aminoguanidine, partially reversed the LPS‑induced ALDH2 activity decrease and MPTP opening. These results indicate that ALDH2 activity may have a role in protecting against LPS‑induced cardiac dysfunction. The potential mechanism may involve inhibition of MPTP opening and iNOS expression.

Ursolic acid triggers nonprogrammed death (necrosis) in human glioblastoma multiforme DBTRG-05MG cells through MPT pore opening and ATP decline.

Ursolic acid, a natural pentacyclic triterpenic acid, possesses anticancer potential and diverse biological effects, but its correlation with glioblastoma multiforme cells and different modes of cell death is unclear. We studied the cellular actions of human glioblastoma multiforme DBTRG-05MG cells after ursolic acid treatment and explored cell-selective killing effect of necrotic death as a cell fate. Ursolic acid effectively reversed temozolomide resistance and reduced DBTRG-05MG cell viability. Surprisingly, ursolic acid failed to stimulate the apoptosis- and autophagy-related signaling networks. The necrotic death was characterized by annexin V/propidium iodide double-positive detection and release of high-mobility group protein B1 and lactate dehydrogenase. These ursolic acid elicited responses were accompanied by reactive oxygen species generation and glutathione depletion. Rapid mitochondrial dysfunction was paralleled by the preferential induction of necrosis, rather than apoptotic death. Mitochondrial permeability transition (MPT) is a phenomenon to provide the onset of mitochondrial depolarization during cellular necrosis. The opening of MPT pores that were mechanistically regulated by cyclophilin D, and adenosine triphosphate decline occurred in treated necrotic DBTRG-05MG cells. Cyclosporine A (an MPT pore inhibitor) prevented ursolic acid-provoked necrotic death and the acid-involved key regulators. Our study is the first to report that ursolic acid-modified mitochondrial function triggers defective death by necrosis in DBTRG-05MG cells rather than augmenting programmed death.

The C Ring of the F1Fo ATP Synthase Forms the Mitochondrial Permeability Transition Pore: A Critical Appraisal.

The C Ring of the F1Fo ATP Synthase Forms the Mitochondrial Permeability Transition Pore: A Critical Appraisal.

Y3 +, La3 +, and some bivalent metals inhibited the opening of the Tl+-induced permeability transition pore in Ca2 +-loaded rat liver mitochondria

We showed earlier that diminution of 2,4-dinitrophenol (DNP)-stimulated respiration and increase of both mitochondrial swelling and electrochemical potential (ΔΨmito) dissipation in medium containing TlNO3 and KNO3 were caused by opening of Tl+-induced mitochondrial permeability transition pore (MPTP) in the inner membrane of Ca2+-loaded rat liver mitochondria. The MPTP opening was studied in the presence of bivalent metal ions (Sr2+, Ba2+, Mn2+, Co2+ and Ni2+), trivalent metal ions (Y3+ and La3+), and ruthenium red. We found that these metal ions (except Ba2+ and Co2+) as well as ruthenium red inhibited to the MPTP opening that manifested in preventing both diminution of the DNP-stimulated respiration and increase of the swelling and of the ΔΨmito dissipation in medium containing TlNO3, KNO3, and Ca2+. Inhibition of the MPTP opening by Sr2+ and Mn2+ is suggested because of their interaction with high affinity Ca2+ sites, facing the matrix side and participating in the MPTP opening. The inhibitory effects of metal ions (Y3+, La3+, and Ni2+), and ruthenium red are accordingly discussed in regard to competitive and noncompetitive inhibition of the mitochondrial Ca2+-uniporter. High concentrations (50μM) of Y3+ and La3+ favored of MPTP opening in the inner membrane of rat liver mitochondria in Ca2+ free medium containing TlNO3. The latter MPTP opening was markedly eliminated by MPTP inhibitors (cyclosporine A and ADP).

Effects of Panax quinquefolium saponin on phosphatidylinositol 3-kinase/serine threonine kinase pathway of neonatal rat myocardial cells subjected to hypoxia.

To explore the effects of Panax Quinquefolium Saponin (PQS) on phosphatidylinositol 3-kinase/serine threonine kinase (PI3K/Akt) pathway of neonatal rat myocardial cells subjected to hypoxia. Neonatal rat myocardial cells were cultured in vitro. After the myocardial cell injury was induced by hypoxia, the cells were randomized into 5 groups: the normal group, the model group, the positive control group (Ciclosporin A, 2 µ mol/L), the low-dose PQS group (PQSL, 25mg/L), and the high-dose PQS group (PQSH, 50 mg/L). Morphology and behavior of myocardial cells were observed under an inverted microscope. Apoptosis rate and lactate dehydrogenase (LDH) leakage rate of myocardial cells were determined by colorimetry. Mitochondrial transmembrane potential was assessed using a fluorexon laser. Phospho-glycogen synthase kinase (GSK)-3β and phospho-Akt as well as cytochrome C were determined by Western blot LDH leakage in the Ciclosporin A group, PQSH group and PQSL group reduced progressively compared with the model group (P<0.05). Akt and GSK-3β was strongly phosphorylated after treatment with Ciclosporin A and PQS compared with the model group (P<0.05, P<0.01). Compared with the model group (16.41±1.74; 35.28±6.30), both the integrated optical density of mitochondrial permeability transition pore (MPTP) and the mitochondrial transmembrane potential significantly increased in the PQSH group (42.74±2.12; 71.36±6.54) and the PQSL group (39.58±1.49; 66.99±5.45; P<0.05, P<0.01). However, the protein of cytochrome C outside the mitochondrion decreased in the PQSH group (273.66±14.61) and the PQSL group (259.62±17.31) compared with the model group (502.41±17.76; P<0.05). Through activation of the PI3K/Akt pathway and inhibition of the MPTP, PQS might protect the heart against ischemia injury and apoptosis of myocardial cells.

Dimebon Attenuates the A&amp;#946;-Induced Mitochondrial Permeabilization

The currently available experimental data supports the hypothesis that the neuroprotective effect of dimebon is related to the protection of the brain-mitochondria from neurodegeneration. In this study, the influence of dimebon on mitochondria was investigated to gain a better understanding of the neuroprotective effects of this drug. Here, we demonstrate that dimebon enhances the resistance of the isolated rat brain and liver mitochondria to the induction of mitochondrial permeability transition (MPT) by calcium ions even in the presence of atractyloside, a MPT pore (MPTP) opener, but is ineffective against atractyloside-induced mitochondria swelling. Unlike cyclosporine A (CsA), a MPTP inhibitor, Dimebon does not influence the adenine nucleotide translocase (ANT) conformational changes and is not able to prevent the MPT of de-energized mitochondria. Using three different assays, and using amyloid-β peptide for inducing mitochondrial toxicity, we show that the influence of dimebon on the calcium retention capacity (CRC) of mitochondria depends on the mode of calcium addition. No obvious influence of dimebon on CRC was observed under the conditions of calcium infusion in the pump mode but the increase of CRC of rat brain mitochondria was observed when calcium was added in the bolus mode; the addition of calcium in the single pulse mode led to the increase of the lag period of calcium efflux from mitochondria. From these studies it is shown that dimebon is effective against amyloid-β (Aβ) potentiated mitochondrial swelling and decrease of calcium retention capacity (CRC) of the brain mitochondria.

Cinnamic anilides as new mitochondrial permeability transition pore inhibitors endowed with ischemia-reperfusion injury protective effect in vivo.

In this account, we report the development of a series of substituted cinnamic anilides that represents a novel class of mitochondrial permeability transition pore (mPTP) inhibitors. Initial class expansion led to the establishment of the basic structural requirements for activity and to the identification of derivatives with inhibitory potency higher than that of the standard inhibitor cyclosporine-A (CsA). These compounds can inhibit mPTP opening in response to several stimuli including calcium overload, oxidative stress, and thiol cross-linkers. The activity of the cinnamic anilide mPTP inhibitors turned out to be additive with that of CsA, suggesting for these inhibitors a molecular target different from cyclophylin-D. In vitro and in vivo data are presented for (E)-3-(4-fluoro-3-hydroxy-phenyl)-N-naphthalen-1-yl-acrylamide 22, one of the most interesting compounds in this series, able to attenuate opening of the mPTP and limit reperfusion injury in a rabbit model of acute myocardial infarction.

The effect of ATP-dependent K(+)-channel opener on transmembrane potassium exchange and reactive oxygen species production upon the opening of mitochondrial pore

The effect of mitochondrial ATP-dependent K(+)-channel (K(+)ATP-channel) opener diazoxide (DZ) on transmembrane potassium exchange and reactive oxygen species (ROS) formation under the opening of mitochondrial permeability transition pore (MPTP) was studied in rat liver mitochondria. The activation of K(+)-cycling (K(+)-uptake and K(+)/H(+)-exchange) by DZ was established with peak effect at < or = 500 nM. It was shown that MPTP opening as well resulted in the activation of K(+)-cycling together with simultaneous activation of Ca(2+)-cycle in mitochondria. In the absence of depolarization Ca(2+)-cycle is supported by MPTP and Ca(2+)-uniporter. The stimulation of K(+)/H(+)-exchange by MPTP opening led to the activation of K(+)-cycle, but further activation of K(+)/H(+)-exchange resulted in MPTP inhibition. Under the same conditions the decrease in mitochondrial ROS production was observed. It was proposed that the decrease in ROS formation together with K(+)/H(+)-exchange activation could be the constituents of the complex effect of MPTP inhibition induced by K(+)ATP-channel opener.

Apoptosis of THP-1 Derived Macrophages Induced by Sonodynamic Therapy Using a New Sonosensitizer Hydroxyl Acetylated Curcumin

Curcumin is extracted from the rhizomes of the traditional Chinese herb Curcuma longa. Our previous study indicated curcumin was able to function as a sonosensitizer. Hydroxyl acylated curcumin was synthesized from curcumin to eliminate the unstable hydroxy perssad in our group. The potential use of Hydroxyl acylated curcumin as a sonosensitizer for sonodynamic therapy (SDT) requires further exploration. This study investigated the sonodynamic effect of Hydroxyl acylated curcumin on THP-1 macrophage. THP-1 macrophages were cultured with Hydroxyl acylated curcumin at a concentration of 5.0 μg/mL for 4 hours and then exposed to pulse ultrasound irradiation (0.5 W/cm2 with 1.0 MHz ) for 5 min, 10 min and 15 min. Six hours later, cell viability decreased significantly by CCK-8 assay. After ultrasound irradiation, the ratio of apoptosis and necrosis in SDT group was higher than that in control, Hydroxyl acylated curcumin alone and ultrasound alone. Moreover, the apoptotic rate was higher than necrotic rate with the flow cytometry analysis. Furthermore, Hydroxyl acylated curcumin-SDT induced reactive oxygen species (ROS) generation in THP-1 macrophages immediately after the ultrasound treatment while ROS generation was reduced significantly with the scavenger of singlet oxygen Sodium azide (NaN3). Hydroxyl acylated curcumin-SDT led to a conspicuous loss of mitochondrial membrane potential (MMP) compared with other groups, while MMP was increased significantly with the scavenger of singlet oxygen Sodium azide (NaN3), ROS inhibitor N-acetyl cysteine (NAC) and Mitochondrial Permeability Transition Pore (MPTP) inhibitor Cyclosporin A (CsA). The cytochrome C, cleaved-Caspase-9, cleaved-Caspase-3 and cleaved-PARP upregulated after SDT through Western blotting. These findings suggested that Hydroxyl acylated curcumin under low-intensity ultrasound had sonodynamic effect on THP-1 macrophages via generation of intracellular singlet oxygen and mitochondria-caspase signaling pathway, indicating that Hydroxyl acylated curcumin could be used as a novel sonosensitizer in SDT for atherosclerosis.

Consequences of tributyltin chloride induced stress in Leydig cells: An ex-vivo approach

Tributyltin (TBT), a member of the organotin family, is a known endocrine disruptor. It persists long in the environment and is widely used in various industrial applications. This study was planned to understand its toxic influence on Leydig cells isolated from 28 day old wistar rats. In-vitro exposure to TBT-Chloride (TBTC) (300–3000nM) reduced cell viability (DNA fragmentation, nuclear condensation and MTT assay) and affected testosterone production. TBTC induced both apoptotic and necrotic cell death (AnnexinV/PI binding assay). Involvement of calcium (Ca2+), redox imbalance (ROS, GSH and TBARS) and mitochondria in TBTC toxicity was evaluated by using Ca2+ inhibitors (BAPTA-AM, EGTA, Ruthenium Red), free radical scavengers (NAC, C-Phycocyanin) and mitochondrial permeability transition pore inhibitor (Cyclosporine A). Protein expression analysis of phosphorylated MAPKinases (ERK1/2, JNK1/2, & p38), steroidogenic proteins (3β-HSD, StAR & TSPO) and apoptotic proteins (Bax, Bcl2) illustrates the cytotoxic and anti-steroidogenic activity of TBTC.

Resveratrol protects astrocytes against traumatic brain injury through inhibiting apoptotic and autophagic cell death

Traumatic brain injury (TBI) is often caused by accidents that damage the brain. TBI can induce glutamate excitotoxicity and lead to neuronal and glial cell death. In this study, we investigated the mechanism of cell death during the secondary damage caused by TBI in vivo and in vitro, as well as the protective effect of resveratrol (RV). Here we report that glycogen synthase kinase-3β (GSK-3β) activation and microtubule-associated protein light chain 3 processing were induced in rat brains exposed to TBI. In the in vitro TBI model, apoptotic and autophagic cell death were induced through glutamate-mediated GSK-3β activation in normal CTX TNA2 astrocytes. The GSK-3β inhibitor SB216763 or transfection of GSK-3β small-interfering RNA increases cell survival. By contrast, overexpression of GSK-3β enhanced glutamate excitotoxicity. Administration of RV reduced cell death in CTX TNA2 astrocytes by suppressing reactive oxygen species (ROS)-mediated GSK-3β activation, the mechanism by which RV also exerted protective effects in vivo. Mitochondrial damages, including the opening of mitochondrial permeability transition pore (MPTP) and mitochondrial depolarization, were induced by glutamate through the ROS/GSK-3β pathway. Moreover, cyclosporine A, an MPTP inhibitor, suppressed mitochondrial damage and the percentages of cells undergoing autophagy and apoptosis and thereby increased cell survival. Taken together, our results demonstrated that cell death occurring after TBI is induced through the ROS/GSK-3β/mitochondria signaling pathway and that administration of RV can increase cell survival by suppressing GSK-3β-mediated autophagy and apoptosis. Therefore, the results indicated that resveratrol may serve as a potential therapeutic agent in the treatment of TBI.

Induction of autophagy restores the loss of sevoflurane cardiac preconditioning seen with prolonged ischemic insult

Sevoflurane preconditioning against myocardial ischemia-reperfusion injury is lost if the ischemic insult is too long. Emerging evidence suggests that induction of autophagy may also confer cardioprotection against ischemia-reperfusion injury. We examined whether induction of autophagy prolongs sevoflurane preconditioning protection during a longer ischemic insult. Isolated guinea pigs hearts were subjected to 30 or 45min ischemia, followed by 120min reperfusion (control). Anesthetic preconditioning was elicited with 2% sevoflurane for 10min prior to ischemia (SEVO-30, SEVO-45). Chloramphenicol (autophagy upregulator, 300µM) was administered starting 20min before ischemia and throughout reperfusion in SEVO-45 (SEVO-45+CAP). To inhibit autophagy, 3-methyladenine (10μM) was administered during sevoflurane administration in SEVO-45+CAP. Infarct size was determined by triphenyltetrazolium chloride stain. Tissue samples were obtained before ischemia to determine autophagy-related protein (microtubule-associated protein light chain I and II: LC3-I, II), Akt and glycogen synthase kinase 3β (GSK3β) expression using Western blot analysis. The effect of autophagy on calcium-induced mitochondrial permeability transition pore (MPTP) opening in isolated calcein-loaded mitochondria was assessed. Electron microscopy was used to detect autophagosomes. Infarct size was significantly reduced in SEVO-30, but not in SEVO-45. Chloramphenicol restored sevoflurane preconditioning lost by 45min ischemia. There were more abundant autophagozomes and LC3-II expression was significantly increased in SEVO-45+CAP. Induction of autophagy before ischemia enhanced GSK3β phosphorylation and inhibition of calcium-induced MPTP opening. These effects were abolished by 3-methyladenine. Pre-ischemic induction of autophagy restores sevoflurane preconditioning lost by longer ischemic insult. This effect is associated with enhanced inhibition of MPTP by autophagy.

The Novel Heterocyclic Trioxirane [(1,3,5-Tris Oxiran-2-yl)Methyl)-1,3,5-Triazinane-2,4,6-Trione (TATT)] Exhibits a Better Anticancer Effect than Platinum-Based Chemotherapy by Induction of Apoptosis and Curcumin Further Enhances its Chemosensitivity

The heterocyclic trioxirane compound [1,3,5-tris((oxiran-2-yl)methyl)-1,3,5-triazinane-2,4,6-trione (TATT)] is a synthetic compound which has been used as an experimental anticancer agent in human clinical trials. Curcumin, an active natural compound in turmeric and curry, is an ingredient commonly used in the traditional diet of many Asian countries. In the present study, we observed that TATT exhibited a better anticancer effect on chemoresistant human colorectal cancer HT-29 cells and displayed less cytotoxicity on normal human umbilical vein endothelial cells, compared with FDA-approved anticancer drugs (cisplatin, carboplatin, or oxaliplatin) using MTT assay. TATT also induced a stronger apoptotic effect than that seen with the three studied anticancer drugs, as characterized by externalization of phosphatidylserine using flow cytometry. Administration of caspase 8-specific inhibitor (z-IETD-fmk) and mitochondrial permeability transition pore inhibitor (cyclosporin A) demonstrated that TATT-induced apoptosis proceeded via both extrinsic and intrinsic signaling pathways. It is noteworthy that coadministration of curcumin further significantly increased TATT-induced cytotoxicity, externalization of phosphatidylserine (representing early apoptosis), and the percentages of cells at the sub-G1 phase (representing late apoptosis), producing an additivity and/or synergistic effect, and vice versa. Suppression of nuclear NF-κB was involved in curcumin-enhanced chemosensitivity of TATT. Overall, our data indicate that TATT exerts a chemotherapeutic effect on colorectal cancer cells and coadministration of curcumin enhances the treatment effect of TATT.

The role of mitochondrial permeability transition pore in regulating the shedding of the platelet GPIbα ectodomain

Agonists induce platelet activation or apoptosis with concomitant shedding of the platelet receptor glycoprotein Ibα (GPIbα) ectodomain in a disintegrin and metalloproteinase 17 (ADAM17)-dependent mechanism. Mitochondrial permeability transition pore (MPTP) plays a pivotal role in platelet activation or apoptosis. However, its impact on ADAM17-mediated GPIbα ectodomain shedding remains unclear. Here, we aimed to test the hypothesis that MPTP regulates ADAM17-dependent GPIbα ectodomain shedding. We showed that calcium ionophore A23187- or thrombin plus collagen-induced GPIbα ectodomain shedding was partially inhibited by a MPTP inhibitor, and a MPTP potentiator promoted A23187-induced GPIbα cleavage. Furthermore, A23187-induced elevation of mitochondrial Ca2+ levels was blocked by the mitochondrial calcium uniporter (MCU) inhibitor Ru360 or treatment with the membrane-permeable Ca2+ chelator BAPTA-AM. We also demonstrated that an increase in mitochondrial Ca2+ levels triggered MPTP opening, as revealed by the examination of mitochondrial inner transmembrane potential depolarization. In addition, A23187 induced-mitochondrial reactive oxygen species (ROS) generation was blocked by the MPTP inhibitor or by treatment with the mitochondria-targeted ROS scavenger. Lastly, A23187-induced GPIbα shedding was partially blocked by inhibitors of either ROS or calpain, and was completely inhibited when platelets were exposed to both inhibitors. Therefore, these observations indicate that MPTP opening triggered mitochondrial ROS production, which plays an important role in regulating ADAM17-mediated shedding of the GPIbα ectodomain in A23187-treated platelets.

Влияние активатора АТР -зависимого K+-канала на функциональное состояние и открывание циклоспоринчувствительной поры в митохондриях печени крыс

The effect of mitochondrial ATP-dependent K(+)-channel (K+(ATP)-channel) opener diazoxide (DZ) on the oxygen consumption, functional state and the opening of cyclosporine-sensitive pore in the rat liver mitochondria has been studied. It has been established that K+(ATP)-channel activation results in the increase of the oxygen consumption rate (V4(s)) and the uncoupling due to the acceleration of K(+)-cycling, the decrease in state 3 respiration rate (V3) and the respiratory control ratio (RCR). Under K+(ATP)-channel activation an inhibition of oxidative phosphorylation takes place which reduces the rate of ATP synthesis and hydrolysis as well as ATP production and consequently results in the seeming increase of P/O ratio. It has been shown that the increase in ATP-dependent K(+)-uptake accompanied by the opening of mitochondrial permeability transition pore (MPTP) leads to dramatic uncoupling of the respiratory chain due to simultaneous activation of K(+)- and Ca(2+)-cycling supported by MPTP and Ca(2+)-uniporter as well as K(+)-channels and K+/H(+)-exchange. K+(ATP)-channel activation leads to the partial inhibition of MPTP, but insufficient for the restoration of mitochondrial functions. Elimination of Ca(2+)-cycling after MPTP opening is necessary to return mitochondrial functions back to the control level which shows that MPTP could serve as the mechanism of reversible modulation of bioenergetic effects of K+(ATP)-channel activation.

Coumaric Acid Induces Mitochondrial Damage and Oxidative-Mediated Cell Death of Human Endothelial Cells

Evidence that higher natural antioxidants (NA) intake provides cardiovascular protection is contradictory. The endothelium plays a pivotal role in cardiovascular homeostasis, and for this reason, the molecular events resulting from the interaction of NA with endothelial cells (ECs) are actively investigated. Here, we show that moderately high doses of coumaric acid (CA) induced intracellular reactive oxygen species (ROS) production, mitochondrial membrane depolarization and ECs death. Treatment of ECs with cyclosporine A, a mitochondrial permeability transition pore inhibitor, prevented the oxidative-mediated cell damage indicating mitochondrial involvement in CA-induced ECs impairment. CA-induced intracellular ROS generation was counteracted by the specific cytochrome P450 (CYP) 2C9 inhibitor sulfaphenazole (SPZ). SPZ also prevented CA-induced mitochondrial membrane depolarization and ECs death, implicating CYP2C9 in mediating the cellular response upon CA treatment. Our results indicate that moderately high doses of CA can promote CYP2C9-mediated oxidative stress eliciting mitochondrial-dependent ECs death and may pave the way toward mechanistic insight into NA effects on cardiovascular cells.

The mitochondrial permeability transition pore as a target for cardioprotection in hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy, and is the leading cause of sudden cardiac death in the young and a major cause of heart failure [1]. Numerous studies have shown that myocardial ischemia caused by an inability to increase myocardial blood flow (MBF) during stress contribute to the pathophysiology of HCM and are associated with adverse left ventricular (LV) remodelling and systolic dysfunction [1]. Numerous studies have shown that myocardial ischemia, which is caused by an inability to increase myocardial blood flow (MBF) during stress, contributes to the pathophysiology of HCM and is associated with adverse left ventricular (LV) remodelling and systolic dysfunction. In this regard the opening of the mitochondrial permeability transition pore (MPTP) at the onset of reperfusion is a critical determinant of cardiomyocyte death following myocardial ischaemiareperfusion injury (IRI) [2, 3]. Pharmacological inhibition of MPTP opening at the onset of reperfusion, using agents such as ciclosporin-A (CsA), has been reported to reduce myocardial infarct (MI) size in animal models of IRI [4]. Importantly, MPTP inhibition at the time of myocardial reperfusion has been demonstrated to protect human atrial cardiomyocytes and trabeculae, harvested from patients undergoing coronary artery bypass graft (CABG) surgery, against simulated IRI [5]. Furthermore, CsA has been reported to be reduce MI size in patients when administered at the time of myocardial reperfusion [6, 7]. MPTP inhibition can also be achieved by pharmacologically activating pro-survival kinases such as Akt and Erk1/2 using the HMG Co-A reductase inhibitor, atorvastatin [8]. Experimental animal studies have demonstrated a reduction in MI size with the administration of atorvastatin at reperfusion in both animal and human heart tissue models of simulated IRI [8, 9]. Whilst these cardioprotective mechanisms are known to operate in the setting of “normal” myocardium, little is understood about potential cardioprotective signaling pathways in HCM. The ability of pharmacological agents to inhibit MPTP opening as a strategy for limiting myocardial IRI, may provide a novel therapeutic intervention for patients with HCM. Therefore, in the current study, the overall objective was to demonstrate the MPTP to be a viable target for cardioprotection in patients with HCM.

Betanodavirus: Mitochondrial disruption and necrotic cell death

Betanodaviruses cause viral nervous necrosis, an infectious neuropathological condition in fish that is characterized by necrosis of the central nervous system, including the brain and retina. This disease can cause mass mortality in larval and juvenile populations of several teleost species and is of global economic importance. The mechanism of brain and retina damage during betanodavirus infection is poorly understood. In this review, we will focus recent results that highlight betanodavirus infection-induced molecular death mechanisms in vitro. Betanodavirus can induce host cellular death and post-apoptotic necrosis in fish cells. Betanodavirus-induced necrotic cell death is also correlated with loss of mitochondrial membrane potential in fish cells, as this necrotic cell death is blocked by the mitochondrial membrane permeability transition pore inhibitor bongkrekic acid and the expression of the anti-apoptotic Bcl-2 family member zfBcl-xL. Moreover, this mitochondria-mediated necrotic cell death may require a caspase-independent pathway. A possible cellular death pathway involving mitochondrial function and the modulator zfBcl-xs is discussed which may provide new insights into the necrotic pathogenesis of betanodavirus.

DNA Damage and Cell Cycle Arrest Induced by Protoporphyrin IX in Sarcoma 180 Cells

Background: Porphyrin derivatives have been widely used in photodynamic therapy as effective sensitizers. Protoporphyrin IX (PpIX), a well-known hematoporphyrin derivative component, shows great potential to enhance light induced tumor cell damage. However, PpIX alone could also exert anti-tumor effects. The mechanisms underlying those direct effects are incompletely understood. This study thus investigated the putative mechanisms underlying the anti-tumor effects of PpIX on sarcoma 180 (S180) cells. Methods: S180 cells were treated with different concentrations of PpIX. Following the treatment, cell viability was evaluated by the 3-(4, 5- dimethylthiazol-2-yl)-2, 5-diphenyltetrazoliumbromide (MTT) assay; Disruption of mitochondrial membrane potential was measured by flow cytometry; The trans-location of apoptosis inducer factor (AIF) from mitochondria to nucleus was visualized by confocal laser scanning microscopy; DNA damage was detected by single cell gel electrophoresis; Cell cycle distribution was analyzed by DNA content with flow cytometry; Cell cycle associated proteins were detected by western blotting. Results: PpIX (≥ 1 µg/ml) significantly inhibited proliferation and reduced viability of S180 cells in a dose-dependent manner. PpIX rapidly and significantly triggered mitochondrial membrane depolarization, AIF (apoptosis inducer factor) translocation from mitochondria to nucleus and DNA damage, effects partially relieved by the specific inhibitor of MPTP (mitochondrial permeability transition pore). Furthermore, S phase arrest and upregulation of the related proteins of P53 and P21 were observed following 12 and 24 h PpIX exposure. Conclusion: PpIX could inhibit tumor cell proliferation by induction of DNA damage and cell cycle arrest in the S phase.

Sevoflurane preconditioning improves mitochondrial function and long-term neurologic sequelae after transient cerebral ischemia

Anesthetic preconditioning appears to be a viable strategy to treat ischemic cerebral injury. Here we investigated 1) whether the protection conferred by sevoflurane preconditioning sustains in time; 2) whether sevoflurane preconditioning diminishes mitochondrial dysfunction following cerebral ischemia; and 3) whether mitochondrial permeability transition pore plays a crucial role in the sevoflurane preconditioning. Laboratory investigation. University research laboratory. : Sprague-Dawley rats. Rats underwent 2 hrs of focal cerebral ischemia induced by middle cerebral artery occlusion. Preconditioning was elicited with sevoflurane (2.3%) for 60 mins at 24 hrs before ischemia. The involvement of mitochondrial permeability transition pore was determined with a mitochondrial permeability transition pore opener atractyloside and a specific mitochondrial permeability transition pore inhibitor cyclosporin A. In vitro study was performed on acutely isolated mitochondria subjected to calcium overload. Sevoflurane preconditioning significantly decreased the infarct size by 35.9% (95% confidence interval 6.5-28.4, p < .001). This reduction of injury volume was associated with a long-term improvement of neurological function according to modified neurological severity score (F = 13.6, p = .001) and sticky-tape test (F = 29.1, p < .001) for 42 days after ischemia. Furthermore, sevoflurane preconditioning markedly protected mitochondria, as indicated by preserved respiratory chain complex activities and membrane potential, lowered mitochondrial hydrogen-peroxide production, and attenuated mitochondrial permeability transition pore opening. Isolated mitochondria also demonstrated a reduced sensitivity to Ca-induced mitochondrial permeability transition pore opening after pre-exposure to sevoflurane in vitro (95% confidence interval 24.2-196.5,p = .006). Inhibiting mitochondrial permeability transition pore using cyclosporin A resulted in protective effects similar to those seen with sevoflurane preconditioning, whereas pharmacologically opening the mitochondrial permeability transition pore with atractyloside abrogated all the positive effects of sevoflurane preconditioning and cyclosporin A, including suppression of mitochondrial permeability transition pore opening, counteraction of mitochondria-dependent apoptotic pathway, and subsequent histological and behavioral improvements. Sevoflurane preconditioning protects mitochondria from cerebral ischemia/reperfusion injury and ameliorates long-term neurological deficits. Inhibition of mitochondrial permeability transition pore opening is a crucial step in mediating the neuroprotection of sevoflurane preconditioning.