Permeability Transition Pore Inhibitor Research Articles

The anti-apoptotic role of Ginkgolide B via mitochondrial permeability transition pore inhibition in retinal ischemia-reperfusion

This research delves into the effectiveness of Ginkgolide B (GB), a compound from Ginkgo biloba, in combating cell death caused by glaucoma, with a focus on mitochondrial impairment and the mitochondrial permeability transition pore (mPTP). Utilizing models of high intraocular pressure and in vitro glaucoma simulations, the study investigates GB's impact on retinal progenitor cells (RPCs) under oxygen-glucose deprivation/reperfusion (OGD/R) and in a rat glaucoma model. The study methodologies included apoptosis assessment, apoptotic marker analysis via Western blot, and mitochondrial structure and function evaluation. The findings reveal that GB notably decreases apoptosis in RPCs exposed to OGD/R in vitro, and reduces ischemia-reperfusion damage in vivo. GB's protective role is attributed to its ability to preserve mitochondrial integrity, maintain membrane potential, regulate calcium levels, and inhibit mPTP opening. These results underscore GB's potential as a therapeutic agent for acute primary angle-closure glaucoma, highlighting its capability to alleviate mitochondrial damage and apoptosis in RPCs and retinal nerve fiber layer cells.

Effects of Concomitant Use of N-acetylcysteine and Cyclosporine A on Acetaminophen-induced Acute Kidney Injury in Mice

Background: Acetaminophen (APAP), a commonly used analgesic, causes acute kidney injury (AKI) in overdose although it is rare. Mitochondrial dysfunction plays a major role in the pathophysiology of renal damage, although the exact molecular mechanism is unknown. This study aimed to evaluate the potential therapeutic effect of cyclosporin A (CsA), a mitochondrial membrane permeability transition pore (MPTP) inhibitor, with N-acetylcysteine (NAC) in APAP-induced AKI. Methods: Male BALB/c mice were divided into control, APAP, APAP+NAC, APAP+CsA and APAP+NAC+CsA groups (n=6). A single dose of APAP (400 mg/kg) was administered intraperitoneally. All other treatments (1200 mg/kg NAC, 50 mg/kg CsA) were performed intraperitoneally 3 h after APAP administration. All animals were decapitated and blood samples and kidney tissue samples were collected for evaluation. Serum creatinine (Cr) and blood urea nitrogen (BUN) levels were measured. The kidney tissue 8-hydroxy-deoxyguanosine (8-OHdG), cytochrome c (Cytc) and 3-nitrotyrosine (3-NT) levels and cytochrome c (Cytc) expressions were determined. Result: Increased Cr and BUN levels, histopathological examinations and expressions of 8-OHdG, 3-NT and Cytc were detected in the APAP group. Combined NAC+CsA treatment sufficiently reversed oxidative stress, serum Cr and BUN levels and histopathological alterations induced by APAP. Moreover, cytc levels and renal tubular injury were remarkably reduced by combined drug treatment compared to the APAP+NAC group. These data suggest that the therapeutic effect of combined NAC+CsA treatment in mice with APAP-induced nephrotoxicity can be related to the combination of the antioxidant effect of NAC and the mitochondrial MPTP inhibitor effect of CsA.

The dynamic relationship between inorganic polyphosphate and adenosine triphosphate in human non-small cell lung cancer H1299 cells.

Inorganic polyphosphate (polyP) plays a vital role in cellular energy metabolism and signaling, owing to its structure and high-energy phosphate bonds. Intracellular ATP functions both as a cellular energy source and a key factor in cell death, and ATP dynamics in tumor cells are crucial for advancing cancer therapy. In this study, we explored the interplay between polyP and ATP in cellular energy metabolism. Treatment with polyP did not affect cell proliferation of human non-small cell lung cancer H1299 and human glioblastoma T98G cell lines as compared to their respective control cells until 72 h post-treatment. The mitochondrial membrane potential (MMP) in polyP-treated cells was low, contrasting with the time-dependent increase observed in control cells. While the ATP content increased over time in untreated and Na-phosphate-treated control cells, it remained unchanged in polyP-treated cells. Furthermore, the addition of cyclosporine A, a mitochondrial permeability transition pore (mPTP) inhibitor, failed to restore ATP levels in polyP-treated cells. We performed lactate assays and western blot analysis to evaluate the effect of polyP on glucose metabolism and found no significant differences in lactate secretion or glucose-6-phosphate dehydrogenase (G6PD) activity between polyP-treated and control cells. Additional pyruvate restored MMP but had no effect on the cellular ATP content in polyP-treated cells. We observed no correlation between the Warburg effect and glucose metabolism during ATP depletion in polyP-treated cells. Further investigation is warranted to explore the roles of polyP and ATP in cancer cell energy metabolism, which might offer potential avenues for therapeutic interventions.

Pharmaceutical Manipulation of Mitochondrial F0F1-ATP Synthase Enables Imaging and Protection of Myocardial Ischemia/Reperfusion Injury Through Stress-induced Selective Enrichment.

To rescue ischemic myocardium from progressing to myocardial infarction, timely identification of the infarct size and reperfusion is crucial. However, fast and accurate identification, as well as the targeted protection of injured cardiomyocytes following ischemia/reperfusion (I/R)injury, remain significantly challenging. Here, a near infrared heptamethine dye IR-780 is shown that has the potential to quickly monitor the area at risk following I/R injury by selectively entering the cardiomyocytes of the at-risk heart tissues. Preconditioning with IR-780 or timely IR-780 administration before reperfusion significantly protects the heart from ischemia and oxidative stress-induced cell death, myocardial remodeling, and heart failure in both rat and pig models. Furthermore, IR-780 can directly bind to F0F1-ATP synthase of cardiomyocytes, rapidly decrease the mitochondrial membrane potential, and subsequently slow down the mitochondrial energy metabolism, which induces the mitochondria into a "quiescent state" and results in mitochondrial permeability transition pore inhibition by preventing mitochondrial calcium overload. Collectively, the findings show the feasibility of IR-780-based imaging and protection strategy for I/R injury in a preclinical context and indicate that moderate mitochondrial function depression is a mode of action that can be targeted in the development of cardioprotective reagents.

An ex vivo screening using mouse brain mitochondria identified seco-cycline D as an inhibitor of mitochondrial permeability transition pore

Mitochondrial dysfunction is implicated in neuropsychiatric disorders. Inhibition of mitochondrial permeability transition pore (mPTP) and thereby enhancement of mitochondrial Ca2+ retention capacity (CRC) is a promising treatment strategy. Here, we screened 1718 compounds to search for drug candidates inhibiting mPTP by measuring their effects on CRC in mitochondria isolated from mouse brains. We identified seco-cycline D (SCD) as an active compound. SCD and its derivative were more potent than a known mPTP inhibitor, cyclosporine A (CsA). The mechanism of action of SCD was suggested likely to be different from CsA that acts on cyclophilin D. Repeated administration of SCD decreased ischemic area in a middle cerebral artery occlusion model in mice. These results suggest that SCD is a useful probe to explore mPTP function.

IP3R-dependent mitochondrial dysfunction mediates C5b-9-induced ferroptosis in trichloroethylene-caused immune kidney injury.

Patients with occupational medicamentose-like dermatitis due to trichloroethylene often suffer from immune kidney injury. Our previous study reveals that C5b-9-dependent cytosolic Ca2+ overload-induced ferroptosis is involved in trichloroethylene sensitized kidney injury. However, how C5b-9 causes cytosolic Ca2+ rise and the specific mechanism whereby overloaded Ca2+ induces ferroptosis remain unknown. The purpose of our study was to explore the role of IP3R-dependent mitochondrial dysfunction in C5b-9 mediated ferroptosis in trichloroethylene sensitized kidney. Our results showed that IP3R was activated, and mitochondrial membrane potential was decreased in the renal epithelial cells of trichloroethylene-sensitized mice, and these changes were antagonized by CD59, a C5b-9 inhibitory protein. Moreover, this phenomenon was reproduced in a C5b-9-attacked HK-2 cell model. Further investigation showed that RNA interference with IP3R not only alleviated C5b-9-induced cytosolic Ca2+ overload and mitochondrial membrane potential loss but also attenuated C5b-9-induced ferroptosis in HK-2 cells. Mechanistically, IP3R-dependent cytosolic Ca2+ overload activated the mitochondrial permeability transition pore, resulting in the loss of mitochondrial membrane potential and ferroptosis of HK-2 cells. Finally, cyclosporin A, a mitochondrial permeability transition pore inhibitor, not only ameliorated IP3R-dependent mitochondrial dysfunction but also blocked C5b-9-induced ferroptosis. Taken together, these results suggest that IP3R-dependent mitochondrial dysfunction plays an important role in trichloroethylene sensitized renal tubular ferroptosis.

AZD5438 a GSK-3a/b and CDK inhibitor is antiapoptotic modulates mitochondrial activity and protects human neurons from mitochondrial toxins

We previously reported that kenpaullone, which inhibits GSK-3a/b and CDKs inhibited CCCP mediated mitochondrial depolarisation and augments the mitochondrial network. To investigate the actions of this class of drug further, we compared the ability of kenpaullone, alsterpaullone, 1-azakenapaullone, AZD5438, AT7519 (CDK and GSK-3a/b inhibitors) and dexpramipexole and olesoxime (mitochondrial permeability transition pore inhibitors) to prevent CCCP mediated mitochondrial depolarisation and found that AZD5438 and AT7519, were the most effective. Furthermore, treatment with AZD5438 alone increased the complexity of the mitochondrial network. We also found that AZD5438 prevented the rotenone induced decrease in PGC-1alpha and TOM20 levels and that it mediated powerful anti-apoptotic effects and promoted glycolytic respiration. Importantly, experiments in human iPSC derived cortical and midbrain neurons showed AZD5438 mediated significant protective effects, preventing the neuronal cell death, and collapse in the neurite and mitochondrial network associated with rotenone treatment. These results suggest drugs that target GSK-3a/b and CDKs should be developed and assessed further as they may have significant therapeutic potential.

1,3,8-Triazaspiro[4.5]decane Derivatives Inhibit Permeability Transition Pores through a FO-ATP Synthase c Subunit Glu119-Independent Mechanism That Prevents Oligomycin A-Related Side Effects

Permeability transition pore (PTP) molecular composition and activity modulation have been a matter of research for several years, especially due to their importance in ischemia reperfusion injury (IRI). Notably, c subunit of ATP synthase (Csub) has been identified as one of the PTP-forming proteins and as a target for cardioprotection. Oligomycin A is a well-known Csub interactor that has been chemically modified in-depth for proposed new pharmacological approaches against cardiac reperfusion injury. Indeed, by taking advantage of its scaffold and through focused chemical improvements, innovative Csub-dependent PTP inhibitors (1,3,8-Triazaspiro[4.5]decane) have been synthetized in the past. Interestingly, four critical amino acids have been found to be involved in Oligomycin A-Csub binding in yeast. However, their position on the human sequence is unknown, as is their function in PTP inhibition. The aims of this study are to (i) identify for the first time the topologically equivalent residues in the human Csub sequence; (ii) provide their in vitro validation in Oligomycin A-mediated PTP inhibition and (iii) understand their relevance in the binding of 1,3,8-Triazaspiro[4.5]decane small molecules, as Oligomycin A derivatives, in order to provide insights into Csub interactions. Notably, in this study we demonstrated that 1,3,8-Triazaspiro[4.5]decane derivatives inhibit permeability transition pores through a FO-ATP synthase c subunit Glu119-independent mechanism that prevents Oligomycin A-related side effects.

Specific Features of Mitochondrial Dysfunction under Conditions of Ferroptosis Induced by t-Butylhydroperoxide and Iron: Protective Role of the Inhibitors of Lipid Peroxidation and Mitochondrial Permeability Transition Pore Opening

Recent studies have indicated the critical importance of mitochondria in the induction and progression of ferroptosis. There is evidence indicating that tert-butyl hydroperoxide (TBH), a lipid-soluble organic peroxide, is capable of inducing ferroptosis-type cell death. We investigated the effect of TBH on the induction of nonspecific membrane permeability measured by mitochondrial swelling and on oxidative phosphorylation and NADH oxidation assessed by NADH fluo rescence. TBH and iron, as well as their combinations, induced, with a respective decrease in the lag phase, the swelling of mitochondria, inhibited oxidative phosphorylation and stimulated NADH oxidation. The lipid radical scavenger butylhydroxytoluene (BHT), the inhibitor of mitochondrial phospholipase iPLA2γ bromoenol lactone (BEL), and the inhibitor of the mitochondrial permeability transition pore (MPTP) opening cyclosporine A (CsA) were equally effective in protecting these mitochondrial functions. The radical-trapping antioxidant ferrostatin-1, a known indicator of ferroptotic alteration, restricted the swelling but was less effective than BHT. ADP and oligomycin significantly decelerated iron- and TBH-induced swelling, confirming the involvement of MPTP opening in mitochondrial dysfunction. Thus, our data showed the participation of phospholipase activation, lipid peroxidation, and the MPTP opening in the mitochondria-dependent ferroptosis. Presumably, their involvement took place at different stages of membrane damage initiated by ferroptotic stimuli.

Requirement for ER-mitochondria Ca2+ transfer, ROS production and mPTP formation in L-asparaginase-induced apoptosis of acute lymphoblastic leukemia cells.

Acute lymphoblastic leukemia (aLL) is a malignant cancer in the blood and bone marrow characterized by rapid expansion of lymphoblasts. It is a common pediatric cancer and the principal basis of cancer death in children. Previously, we reported that L-asparaginase, a key component of acute lymphoblastic leukemia chemotherapy, causes IP3R-mediated ER Ca2+ release, which contributes to a fatal rise in [Ca2+]cyt, eliciting aLL cell apoptosis via upregulation of the Ca2+-regulated caspase pathway (Blood, 133, 2222-2232). However, the cellular events leading to the rise in [Ca2+]cyt following L-asparaginase-induced ER Ca2+ release remain obscure. Here, we show that in acute lymphoblastic leukemia cells, L-asparaginase causes mitochondrial permeability transition pore (mPTP) formation that is dependent on IP3R-mediated ER Ca2+ release. This is substantiated by the lack of L-asparaginase-induced ER Ca2+ release and loss of mitochondrial permeability transition pore formation in cells depleted of HAP1, a key component of the functional IP3R/HAP1/Htt ER Ca2+ channel. L-asparaginase induces ER Ca2+ transfer into mitochondria, which evokes an increase in reactive oxygen species (ROS) level. L-asparaginase-induced rise in mitochondrial Ca2+ and reactive oxygen species production cause mitochondrial permeability transition pore formation that then leads to an increase in [Ca2+]cyt. Such rise in [Ca2+]cyt is inhibited by Ruthenium red (RuR), an inhibitor of the mitochondrial calcium uniporter (MCU) that is required for mitochondrial Ca2+ uptake, and cyclosporine A (CsA), an mitochondrial permeability transition pore inhibitor. Blocking ER-mitochondria Ca2+ transfer, mitochondrial ROS production, and/or mitochondrial permeability transition pore formation inhibit L-asparaginase-induced apoptosis. Taken together, these findings fill in the gaps in our understanding of the Ca2+-mediated mechanisms behind L-asparaginase-induced apoptosis in acute lymphoblastic leukemia cells.

Mu opioid receptor-mediated release of endolysosome iron increases levels of mitochondrial iron, reactive oxygen species, and cell death.

Opioids including morphine and DAMGO activate mu-opioid receptors (MOR), increase intracellular reactive oxygen species (ROS) levels, and induce cell death. Ferrous iron (Fe2+) through Fenton-like chemistry increases ROS levels and endolysosomes are "master regulators of iron metabolism" and contain readily-releasable Fe2+ stores. However, mechanisms underlying opioid-induced changes in endolysosome iron homeostasis and downstream-signaling events remain unclear. We used SH-SY5Y neuroblastoma cells, flow cytometry, and confocal microscopy to measure Fe2+ and ROS levels and cell death. Morphine and DAMGO de-acidified endolysosomes, decreased endolysosome Fe2+ levels, increased cytosol and mitochondria Fe2+ and ROS levels, depolarized mitochondrial membrane potential, and induced cell death; effects blocked by the nonselective MOR antagonist naloxone and the selective MOR antagonist β-funaltrexamine (β-FNA). Deferoxamine, an endolysosome-iron chelator, inhibited opioid agonist-induced increases in cytosolic and mitochondrial Fe2+ and ROS. Opioid-induced efflux of endolysosome Fe2+ and subsequent Fe2+ accumulation in mitochondria were blocked by the endolysosome-resident two-pore channel inhibitor NED-19 and the mitochondrial permeability transition pore inhibitor TRO. Opioid agonist-induced increases in cytosolic and mitochondrial Fe2+ and ROS as well as cell death appear downstream of endolysosome de-acidification and Fe2+ efflux from the endolysosome iron pool that is sufficient to affect other organelles.

Alisporivir Normalizes Mitochondrial Function of Primary Mouse Lung Endothelial Cells Under Conditions of Hyperglycemia

Effect of alisporivir (a mitochondrial permeability transition pore inhibitor) on the development of mitochondrial dysfunction under hyperglycemic conditions in the primary culture of mouse lung endothelial cells was investigated in this work. We demonstrated that hyperglycemia (30 mM glucose for 24 h) leads to the decrease in viability of the pulmonary endotheliocytes, causes mitochondrial dysfunction manifested by the drop in membrane potential and increase in superoxide anion generation as well as facilitates opening of the mitochondrial permeability transition pore (MPT pore). Incubation of endothelial cells with 5 µM alisporivir under hyperglycemic conditions leads to the increase in cell viability, restoration of the membrane potential level and of the MPT pore opening activity to control values. Hyperglycemia causes increased mitophagy in the lung endothelial cells: we observed increase in the degree of colocalization of mitochondria and lysosomes and upregulation of the Parkin gene expression. Alisporivir restores these parameters back to the levels observed in the control cells. Hyperglycemia results in the increase in the expression of the Drp1 gene in endotheliocytes responsible for synthesis of the protein involved in the process of mitochondria fission. Alisporivir does not significantly alter expression of the genes. The paper discusses mechanisms of the effect of alisporivir on mitochondrial dysfunction in murine pulmonary endotheliocytes under conditions of hyperglycemia.Electronic supplementary materialThe online version contains supplementary material available at 10.1134/S0006297922070033.

Inhibiting Succinate Release Worsens Cardiac Reperfusion Injury by Enhancing Mitochondrial Reactive Oxygen Species Generation.

BackgroundThe metabolite succinate accumulates during cardiac ischemia. Within 5 minutes of reperfusion, succinate returns to baseline levels via both its release from cells and oxidation by mitochondrial complex II. The latter drives reactive oxygen species (ROS) generation and subsequent opening of the mitochondrial permeability transition (PT) pore, leading to cell death. Targeting succinate dynamics (accumulation/oxidation/release) may be therapeutically beneficial in cardiac ischemia–reperfusion (IR) injury. It has been proposed that blocking MCT1 (monocarboxylate transporter 1) may be beneficial in IR injury, by preventing succinate release and subsequent engagement of downstream inflammatory signaling pathways. In contrast, herein we hypothesized that blocking MCT1 would retain succinate in cells, exacerbating ROS generation and IR injury.Methods and ResultsUsing the mitochondrial ROS probe mitoSOX and a custom‐built murine heart perfusion rig built into a spectrofluorometer, we measured ROS generation in situ during the first moments of reperfusion. We found that acute MCT1 inhibition enhanced mitochondrial ROS generation at reperfusion and worsened IR injury (recovery of function and infarct size). Both of these effects were abrogated by tandem inhibition of mitochondrial complex II, suggesting that succinate retention worsens IR because it drives more mitochondrial ROS generation. Furthermore, using the PT pore inhibitor cyclosporin A, along with monitoring of PT pore opening via the mitochondrial membrane potential indicator tetramethylrhodamine ethyl ester, we herein provide evidence that ROS generation during early reperfusion is upstream of the PT pore, not downstream as proposed by others. In addition, pore opening was exacerbated by MCT1 inhibition.ConclusionsTogether, these findings highlight the importance of succinate dynamics and mitochondrial ROS generation as key determinants of PT pore opening and IR injury outcomes.

SS-31, a Mitochondria-Targeting Peptide, Ameliorates Kidney Disease.

Mitochondria are essential for eukaryotic cell activity and function, and their dysfunction is associated with the development and progression of renal diseases. In recent years, there has been a rapid development in mitochondria-targeting pharmacological strategies as mitochondrial biogenesis, morphology, and function, as well as dynamic changes in mitochondria, have been studied in disease states. Mitochondria-targeting drugs include nicotinamide mononucleotide, which supplements the NAD+ pool; mitochondria-targeted protective compounds, such as MitoQ; the antioxidant coenzyme, Q10; and cyclosporin A, an inhibitor of the mitochondrial permeability transition pore. However, traditional drugs targeting mitochondria have limited clinical applications due to their inability to be effectively absorbed by mitochondria in vivo and their high toxicity. Recently, SS-31, a mitochondria-targeting antioxidant, has received significant research attention as it decreases mitochondrial reactive oxygen species production and prevents mitochondrial depolarization, mitochondrial permeability transition pore formation, and Ca2+-induced mitochondrial swelling, and has no effects on normal mitochondria. At present, few studies have evaluated the effects of SS-31 against renal diseases, and the mechanism underlying its action is unclear. In this review, we first discuss the pharmacokinetics of SS-31 and the possible mechanisms underlying its protective effects against renal diseases. Then, we analyze its renal disease-improving effects in various experimental models, including animal and cell models, and summarize the clinical evidence of its benefits in renal disease treatment. Finally, the potential mechanism underlying the action of SS-31 against renal diseases is explored to lay a foundation for future preclinical studies and for the evaluation of its clinical applications.

Attenuation of hepatic ischemia‑reperfusion injury by adipose stem cell‑derived exosome treatment via ERK1/2 and GSK‑3β signaling pathways.

Exosomes are an emerging therapeutic tool for the treatment of tissue injuries. In the present study, the protective effect of isolated exosomes from adipose-derived stem cells (ADSCs-exo) against hepatic ischemia-reperfusion (I/R) injury was explored. Hepatic I/R injury was achieved by inducing ischemia for 60 min followed by reperfusion for 2 and 6 h. Pre-treatment with ADSCs-exo revealed a significant reduction in necrosis and apoptosis in liver tissue induced by I/R injury. Hypoxic oxidative stress was managed by exosome-mediated reduced reactive oxygen species and increased superoxide dismutase that in turn protected mitochondrial damage and apoptosis. Reduction in inflammatory mediators such as IL-1β and TNF-α was also observed and protection of hepatocytes from I/R injury was evidenced by a significant decrease in biochemical markers of liver damage (alanine transaminase, aspartate transaminase and lactate dehydrogenase). Exosomal prostaglandin E2 (PGE2)-mediated ERK1/2 and GSK-3β phosphorylation were revealed to increase Bcl-2 and decrease Bax expression with mitochondrial permeability transition pore-inhibition which may be considered a prime mechanism of exosome-mediated hepatoprotection. In conclusion, our results indicated that ADSCs-exo pre-treatment is effective in protecting liver I/R injury.

Abstract 13594: Cyclosporine-A Reduces Myocardial Damage in Donation After Circulatory Death Hearts

Background: Mitochondria contribute to ischemia and reperfusion injury (IRI) in donation after circulatory death (DCD) donor hearts. Cyclosporine A (CyA), an inhibitor of mitochondrial permeability transition pore (MPTP) opening, limits IRI. CyA administration at the onset of reperfusion is essential for therapeutic efficacy. DCD heart transplantation (HTx) is a unique setting for controlled administration of CyA. Hypothesis: CyA administered to DCD hearts during reperfusion is cardioprotective. Methods: Under general anesthesia Sprague Dawley rats underwent simulated clinical DCD setup with a global ischemia of 25 minutes. Control beating-heart donor (CBD) hearts served as controls (n=10). Hearts were reanimated ex-vivo with Krebs-Henseleit buffer (KH) perfusion at 37 o C for 90 minutes. DCD hearts were randomly assigned to receive CyA (0.5mM) or DMSO added to KH buffer for the first 15 minutes of perfusion (n=10 each). The hearts were collected to measure oxidative phosphorylation (OXPHOS) and calcium retention capacity (CRC). Additional CBD (n=5) and DCD (with or without CyA, n=15) hearts underwent heterotopic HTx in recipient rats to measure developed pressure (DP) and rate pressure product (RPP) at 48 hours. Results: Compared to CBD hearts, OXPHOS in DCD hearts was significantly reduced. CyA improved OXPHOS and was similar to CBD hearts. CRC was reduced in DCD hearts compared to CBD hearts (317 vs.578nM/mg) and was increased with CyA treatment (413 vs. 317nM/mg; p<0.05, Figure). Infarct size decreased significantly with CyA treatment (15% vs. 25%). In transplanted DCD hearts, DP and RPP were significantly reduced compared to CBD hearts (80 vs.153mmHg and 17639 vs. 29545mmHg*bpm). CyA treatment improved DP (124vs.80mmHg; p<0.05) and RPP (35491vs.17639mmHg*bpm; p<0.05) which was comparable to CBD hearts. Conclusions: CyA administered at reperfusion reduces mitochondrial damage, limits infarct size, and preserves function in transplanted DCD hearts.

TASK-1 regulates mitochondrial function under hypoxia

TASK-1, TWIK-related acid-sensitive potassium channel 1, is a member of the two-pore- domain potassium channel family. It is constitutively active at resting potentials and strongly expressed in the heart. However, little is known about the role of TASK-1 channels in hypoxia. A cellular model of hypoxia and reoxygenation from rat heart-derived H9c2 cells or TASK-1 deficient HEK293T cells was employed to explore the role of TASK-1 channels in cytoprotection against hypoxia. The cell viability assay revealed that TASK-1 expression increased the number of viable cells subjected to 2 h of hypoxia followed by 2 h of reoxygenation (H/R). To dissect the protective role of TASK-1 on mitochondrial function, mitochondrial membrane potential (MMP) was assessed by tetramethylrhodamine fluorescence. It was demonstrated that MMP was significantly decreased by H/R, but it was maintained by TASK-1 expression or pretreatment with cyclosporin A, an inhibitor of mitochondrial permeability transition pore (mPTP). The effect of cyclosporin A on MMP was not further altered by TASK-1 expression. Moreover, TASK-1 expression significantly blocked cytochrome c release induced by H/R. While a small fraction of endogenous TASK-1 was found to colocalize with the mitochondrial marker MitoTracker in H9c2 cells, H/R did not alter the extent of colocalization of TASK-1 with MitoTracker. The total TASK-1 protein level was not significantly affected by H/R. In summary, we provided the evidence that TASK-1 channels confer cytoprotection against hypoxia-reoxygenation injury, possibly by their capacity of maintaining the mitochondrial membrane potential via inhibiting MPTP opening.

Effect of the Non-Immunosuppressive MPT Pore Inhibitor Alisporivir on the Functioning of Heart Mitochondria in Dystrophin-Deficient mdx Mice.

Supporting mitochondrial function is one of the therapeutic strategies that improve the functioning of skeletal muscle in Duchenne muscular dystrophy (DMD). In this work, we studied the effect of a non-immunosuppressive inhibitor of mitochondrial permeability transition pore (MPTP) alisporivir (5 mg/kg/day), reducing the intensity of the necrotic process and inflammation in skeletal muscles on the cardiac phenotype of dystrophin-deficient mdx mice. We found that the heart mitochondria of mdx mice show an increase in the intensity of oxidative phosphorylation and an increase in the resistance of organelles to the MPT pore opening. Alisporivir had no significant effect on the hyperfunctionalization of the heart mitochondria of mdx mice, and the state of the heart mitochondria of wild-type animals did not affect the dynamics of organelles but significantly suppressed mitochondrial biogenesis and reduced the amount of mtDNA in the heart muscle. Moreover, alisporivir suppressed mitochondrial biogenesis in the heart of wild-type mice. Alisporivir treatment resulted in a decrease in heart weight in mdx mice, which was associated with a significant modification of the transmission of excitation in the heart. The latter was also noted in the case of WT mice treated with alisporivir. The paper discusses the prospects for using alisporivir to correct the function of heart mitochondria in DMD.

Effects of Tl+ on the inner membrane thiol groups, respiration, and swelling in succinate-energized rat liver mitochondria were modified by thiol reagents.

The effects of both Tl+ and thiol reagents were studied on the content of the inner membrane free SH-groups, detected with Ellman reagent, and the inner membrane potential as well as swelling and respiration of succinate-energized rat liver mitochondria in medium containing TlNO3 and KNO3. These effects resulted in a rise in swelling and a decrease in the content, the potential, and mitochondrial respiration in 3 and 2,4-dinitrophenol-uncoupled states. A maximal effect was seen when phenylarsine oxide reacting with thiol groups recessed into the hydrophobic regions of the membrane. Compared with phenylarsine oxide, the effective concentrations of other reagents were approximately one order of magnitude higher in experiments with mersalyl and 4,4'-diisothiocyanostilbene-2,2'-disulfonate, and two orders of magnitude higher in experiments with tert-butyl hydroperoxide and diamide. The above effects of Tl+ and the thiol reagents became even more pronounced with calcium overload of mitochondria. However, the effects were suppressed by inhibitors of the mitochondrial permeability transition pore (cyclosporine A, ADP, and n-ethylmaleimide). These findings suggest that opening of the pore induced by Tl+ in the inner membrane can be dependent on the conformation state of the adenine nucleotide translocase, which depends on the activity of its thiol groups.

CD36 Promotes Platelet Phosphatidylserine Exposure through MAP Kinase ERK5

Dyslipidemic conditions can promote atherosclerotic plaque instability and rupture, leading to thrombosis that can cause life threatening complications. Thrombosis in this setting is augmented by circulating oxidized lipids on oxidized low density lipoprotein particles (oxLDL) that are recognized by key scavenger receptors. CD36 is a major platelet scavenger receptor that recognizes oxLDL and consequently promotes a prothrombotic platelet phenotype through multiple signaling pathways. We previously reported that recognition of oxLDL by CD36 generates specific reactive oxygen species through Src family kinases and NADPH oxidase. These species modulate redox sensitive signaling, such as the activation of the oxidant sensor MAP kinase ERK5, leading to platelet integrin activation, aggregation, and thrombus formation. Although ERK5 was a key effector for CD36 to promote thrombosis, the downstream signaling mechanisms are unclear. We hypothesize that CD36 promotes a procoagulant phenotype that requires ERK5. Platelets isolated and washed from healthy human donors were stimulated with buffer, native low-density lipoprotein (LDL), or oxLDL, and were stained with fluorophore-conjugated Annexin V or Lactadherin to detect exposure of procoagulant phosphatidylserine (PS). OxLDL-stimulated platelets showed dose-dependent 13.4 ± 2.8% and 18.5 ± 3.5% increases in Lactadherin binding at 50 and 100μg/mL oxLDL compared to control LDL (p=0.026; p<0.01), and a rapid binding within 5 min (11.0±0.35%, p<0.001). Furthermore, pre-treatment with oxLDL followed by addition of convulxin, a snake venom that activates platelets through the collagen signaling receptor GPVI, showed a 58.1 ± 4.62% increase in Lactadherin binding compared to oxLDL and convulxin alone (p<0.0001). Addition of ADP or thrombin, agonists that activates specific G-protein coupled receptors, following pre-treatment with oxLDL did not enhance Lactadherin binding. Platelets treated with FA6, a monoclonal CD36 antibody which prevents oxLDL binding, or BIX02188, an ERK5 inhibitor, showed an 80-90% decrease in Annexin V binding (p=0.039; p=0.02) after oxLDL exposure compared to a control non-immunizing IgG or DMSO. To link known pathways for PS exposure with oxLDL-induced PS exposure, platelets were stimulated with oxLDL followed by treatment with Z-VAD-FMK, a “pan” caspase inhibitor, or cyclosporin A, a cyclophilin D/mitochondrial permeability transition pore inhibitor. Z-VAD-FMK treated platelets showed 68% decrease in Lactadherin binding compared to control DMSO (p=0.0196), whereas cyclosporin A did not inhibit Lactadherin binding. Relevance of CD36/ERK5-mediated PS exposure was demonstrated using an in vivo arterial thrombosis model that relies on autologous transplantation of the epigastric artery, which has an adventitial surface that serves as a collagen-rich thrombogenic substrate for thrombosis, into the carotid artery. This model of thrombosis was chosen due to the potential impact of free radical generation in the standard ferric chloride or Rose Bengal-mediated arterial thrombosis models. Bone marrows from platelet ERK5-deficient mice (ERK5 flox/Pf4-cre+) or control mice (ERK5 flox/flox) were transplanted into irradiated atherogenic apoE null mice fed a high fat or control diet. Fibrin deposition, detected by a fluorophore-conjugated antibody to fibrin, was enhanced in hyperlipidemic conditions for mice with platelet ERK5. High fat diet-fed chimeric mice without ERK5 or animals on control diet do not show enhanced fibrin deposition. In conclusion, oxLDL promoted PS exposure through a CD36-Src family kinases-ERK5-caspase-dependent mechanism. PS exposure by this pathway potentially enhances fibrin deposition in an atherogenic arterial in vivo thrombosis model, which suggests a role for CD36 and ERK5 in thrombosis and coagulation in dyslipidemic conditions. DisclosuresNo relevant conflicts of interest to declare.