The Protective Effect of Uridine in a Rotenone-Induced Model of Parkinson's Disease: The Role of the Mitochondrial ATP-Dependent Potassium Channel.

The effect of the modulators of the mitochondrial ATP-dependent potassium channel (mitoKATP) on the structural and biochemical alterations in the substantia nigra and brain tissues was studied in a rat model of Parkinson's disease induced by rotenone. It was found that, in experimental parkinsonism accompanied by characteristic motor deficits, both neurons and the myelin sheath of nerve fibers in the substantia nigra were affected. Changes in energy and ion exchange in brain mitochondria were also revealed. The nucleoside uridine, which is a source for the synthesis of the mitoKATP channel opener uridine diphosphate, was able to dose-dependently decrease behavioral disorders and prevent the death of animals, which occurred for about 50% of animals in the model. Uridine prevented disturbances in redox, energy, and ion exchanges in brain mitochondria, and eliminated alterations in their structure and the myelin sheath in the substantia nigra. Cytochemical examination showed that uridine restored the indicators of oxidative phosphorylation and glycolysis in peripheral blood lymphocytes. The specific blocker of the mitoKATP channel, 5-hydroxydecanoate, eliminated the positive effects of uridine, suggesting that this channel is involved in neuroprotection. Taken together, these findings indicate the promise of using the natural metabolite uridine as a new drug to prevent and, possibly, stop the progression of Parkinson's disease.

Cultivation of human skin cells under physiological oxygen concentration modulates expression of skin significant genes and response to hydroxy acids.

Physiological oxygen concentration (physioxia) ranges from 1 to 8% in human tissues while many researchers cultivate mammalian cells under an atmospheric concentration of 21% (hyperoxia). Oxygen is one of the significant gases which functions in human cells including energy production in mitochondria, metabolism in peroxidase, and transcription of various genes in company with HIF (Hypoxia-inducible factors) in the nucleus. Thus, mammalian cell culture should be deliberated on the oxygen concentration to mimic in vivo physiology. Here, we studied if the cultivation of human skin cells under physiological conditions could affect skin significant genes in barrier functions and dermal matrix formation. We further examined that some representative active ingredients in dermatology such as glycolic acid, gluconolactone, and salicylic acid work in different ways depending on the oxygen concentration. Taken together, we present the importance of oxygen concentration in skin cell culture for proper screening of novel ingredients as well as the mechanistic study of skin cell regulation.

Autophagy contributes to angiotensin II induced dysfunction of HUVECs.

BACKGROUND: Signal transduction of Angiotensin II (Ang II) induced autophagy and its role in Ang II-induced dysfunction of HUVECs are still unclear. METHODS: HUVECs are stimulated with different doses of Ang II (10-9-10-5 mol/L) for different time (6-48 hours). Autophagy-related protein markers: LC3, Beclin-1 and SQSTM1/p62 are measured by western blot. RESULTS: Incubation with Ang II increases autophagic flux (Beclin-1, autophagosomes formation, and degradation of SQSTM1/p62, LC3-I). Increased autophagic levels are inhibited by pretreatment with Ang II type 1 receptor (AT1) blocker (Candesartan), NADPH Oxidase inhibitor (apocycin), mitochondrial KATP channels inhibitor (5-hydroxydecanoate, 5HD). 3-Methyladenine (inhibitors of autophagy) and rapamycin (activator of autophagy) respectively inhibits or activates Ang II-induced autophagy levels. Ang II decreases phosphorylation of endothelial nitric oxide synthase (eNOS) and NO production in HUVECs. L-NAME (NOS inhibitor) totally mimics the actions of Ang II on eNOS, NO production and autophagy levels. Rapamycin further decreases NO production combined with Ang II. Silence Atg5 completely reverses Ang II-activated autophagy levels. CONCLUSIONS: Our results demonstrate that Ang II stimulation increases autophagy levels via AT1 receptor, NADPH oxidase, mitochondrial KATP channel, eNOS, Atg5 signal pathway in HUVECs, and activation of autophagy contributes to Ang II induced dysfunction of HUVECs.

Ex Vivo Live Full-Thickness Porcine Skin Model as a Versatile In Vitro Testing Method for Skin Barrier Research.

Since the European Union (EU) announced their animal testing ban in 2013, all animal experiments related to cosmetics have been prohibited, creating a demand for alternatives to animal experiments for skin studies. Here, we investigated whether an ex vivo live porcine skin model can be employed to study the safety and skin barrier-improving effects of hydroxyacids widely used in cosmetics for keratolytic peels. Glycolic acid (1-10%), salicylic acid (0.2-2%), and lactobionic acid (1.2-12%) were used as representative substances for α-hydroxyacid (AHA), ß-hydroxyacid (BHA), and polyhydroxyacid (PHA), respectively. When hydroxyacids were applied at high concentrations on the porcine skin every other day for 6 days, tissue viability was reduced to 50-80%, suggesting that the toxicity of cosmetic ingredients can be evaluated with this model. Based on tissue viability, the treatment scheme was changed to a single exposure for 20 min. The protective effects of a single exposure of hydroxyacids on skin barrier function were evaluated by examining rhodamine permeability and epidermal structural components of barrier function using immunohistochemistry (IHC) and immunofluorescence (IF) staining. Lactobionic acid (PHAs) improved skin barrier function most compared to other AHAs and BHAs. Most importantly, trans-epidermal water loss (TEWL), an important functional marker of skin barrier function, could be measured with this model, which confirmed the significant skin barrier-protective effects of PHAs. Collectively, we demonstrated that the ex vivo live full-thickness porcine skin model can be an excellent alternative to animal experiments for skin studies on the safety and efficacy of cosmetic ingredients.

New Hydroxydecanoic Acid Derivatives Produced by an Dndophytic Yeast Aureobasidium pullulans AJF1 from Flowers of Aconitum carmichaeli.

Endophytes have been recognized as a source for structurally novel and biologically active secondary metabolites. Among the host plants for endophytes, some medicinal plants that produce pharmaceuticals have been reported to carry endophytes, which could also produce bioactive secondary metabolites. In this study, the medicinal plant Aconitum carmichaeli was selected as a potential source for endophytes. An endophytic microorganism, Aureobasidium pullulans AJF1, harbored in the flower of Aconitum carmichaeli, was cultured on a large scale and extracted with an organic solvent. Extensive chemical investigation of the extracts resulted in isolation of three lipid type compounds (1-3), which were identified to be (3R,5R)-3,5-dihydroxydecanoic acid (1), (3R,5R)-3-(((3R,5R)-3,5-dihydroxydecanoyl)oxy)-5-hydroxydecanoic acid (2), and (3R,5R)-3-(((3R,5R)-5-(((3R,5R)-3,5-dihydroxydecanoyl)oxy)-3-hydroxydecanoyl)oxy)-5-hydroxydecanoic acid (3) by chemical methods in combination with spectral analysis. Compounds 2 and 3 had new structures. Absolute configurations of the isolated compounds (1-3) were established using modified Mosher's method together with analysis of NMR data for their acetonide derivatives. All the isolates (1-3) were evaluated for antibiotic activities against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, and their cytotoxicities against MCF-7 cancer cells. Unfortunately, they showed low antibiotic activities and cytotoxic activities.

Dynamic Restructuring of the Myocardial Mitochondria in Response to Uridine Modulation of the Activity of Mitochondrial ATP-Dependent Potassium Channel under Conditions of Acute Hypoxic Hypoxia.

We studied the effects of in vivo modulation of activity of mitochondrial ATP-dependent potassium channel (mitoKATP) by uridine on the morphofunctional state of mitochondria in rat cardiomyocytes under conditions of acute hypoxia. Preinjection of uridine to animals reduced the number of structurally modified mitochondria, but had practically no effect on their morphogenesis after hypoxia. Uridine in vivo stimulated the formation of micromitochondria and their release into the cytoplasm. The number of "maternal" mitochondria containing three and more new micromitochondria, increased as well. The use of mitoKATP blocker 5-hydroxydecanoate in parallel with uridine abolished its protective effect, as it significantly inhibited the formation of micromitochondria in rat cardiomyocytes after acute hypoxic exposure.

PI3K-AKT Pathway Protects Cardiomyocytes Against Hypoxia-Induced Apoptosis by MitoKATP-Mediated Mitochondrial Translocation of pAKT.

BACKGROUND/AIMS: The phosphatidylinositol-3-kinase -AKT (PI3K-AKT) is an important intracellular signal pathway in regulating cell proliferation, differentiation and apoptosis. In previous studies, we've demonstrated that PI3K-AKT pathway protects cardiomyocytes from ischemic and hypoxic apoptosis through mitochondrial function. However, the molecular mechanisms underlying hypoxia-induced cardiomyocyte apoptosis via PI3K-AKT pathway remain ill-defined. Here, we addressed this question. METHODS: Cardiomyocytes were exposed to hypoxia, with/without different inhibitors and then protein levels were assessed by Western blotting. RESULTS: We found that the PI3K-AKT pathway was activated in cardiomyocytes that were exposed to hypoxia. Moreover, the phospho-AKT (pAKT) translocated from cytosol to mitochondria via mitochondrial adenosine triphosphate-dependent potassium (mitoKATP), leading to an increase in cytochrome c oxidase (CcO) activity to suppress apoptosis. On the other hand, the mitoKATP specific blocker, 5-hydroxydecanote (5-HD), or suppression of CcO using siRNA, inhibited the pAKT mitochondrial translocation to maintain the CcO activity, resulting in mitochondrial dysfunction and cellular apoptosis induced by hypoxia. CONCLUSION: These findings suggest that the anti-apoptotic effect of the PI3K-AKT pathway through pAKT translocation to mitochondrial via mitoKATP may be conducted through modification of CcO activity.

Dual Effects of Alpha-Hydroxy Acids on the Skin.

AHAs are organic acids with one hydroxyl group attached to the alpha position of the acid. AHAs including glycolic acid, lactic acid, malic acid, tartaric acid, and citric acid are often used extensively in cosmetic formulations. AHAs have been used as superficial peeling agents as well as to ameliorate the appearance of keratoses and acne in dermatology. However, caution should be exercised in relation to certain adverse reactions among patients using products with AHAs, including swelling, burning, and pruritus. Whether AHAs enhance or decrease photo damage of the skin remains unclear, compelling us to ask the question, is AHA a friend or a foe of the skin? The aim of this manuscript is to review the various biological effects and mechanisms of AHAs on human keratinocytes and in an animal model. We conclude that whether AHA is a friend or foe of human skin depends on its concentration. These mechanisms of AHAs are currently well understood, aiding the development of novel approaches for the prevention of UV-induced skin damage.

The Opening of ATP-Sensitive K+ Channels Protects H9c2 Cardiac Cells Against the High Glucose-Induced Injury and Inflammation by Inhibiting the ROS-TLR4-Necroptosis Pathway.

BACKGROUND/AIMS: Hyperglycemia activates multiple signaling molecules, including reactive oxygen species (ROS), toll-like receptor 4 (TLR4), receptor-interacting protein 3 (RIP3, a kinase promoting necroptosis), which mediate hyperglycemia-induced cardiac injury. This study explored whether inhibition of ROS-TLR4-necroptosis pathway contributed to the protection of ATP-sensitive K+ (KATP) channel opening against high glucose-induced cardiac injury and inflammation. METHODS: H9c2 cardiac cells were treated with 35 mM glucose (HG) to establish a model of HG-induced insults. The expression of RIP3 and TLR4 were tested by western blot. Generation of ROS, cell viability, mitochondrial membrane potential (MMP) and secretion of inflammatory cytokines were measured as injury indexes. RESULTS: HG increased the expression of TLR4 and RIP3. Necrostatin-1 (Nec-1, an inhibitor of necroptosis) or TAK-242 (an inhibitor of TLR4) co-treatment attenuated HG-induced up-regulation of RIP3. Diazoxide (DZ, a mitochondrial KATP channel opener) or pinacidil (Pin, a non-selective KATP channel opener) or N-acetyl-L-cysteine (NAC, a ROS scavenger) pre-treatment blocked the up-regulation of TLR4 and RIP3. Furthermore, pre-treatment with DZ or Pin or NAC, or co-treatment with TAK-242 or Nec-1 attenuated HG-induced a decrease in cell viability, and increases in ROS generation, MMP loss and inflammatory cytokines secretion. However, 5-hydroxy decanoic acid (5-HD, a mitochondrial KATP channel blocker) or glibenclamide (Gli, a non-selective KATP channel blocker) pre-treatment did not aggravate HG-induced injury and inflammation. CONCLUSION: KATP channel opening protects H9c2 cells against HG-induced injury and inflammation by inhibiting ROS-TLR4-necroptosis pathway.

DNA Transfection to Mesenchymal Stem Cells Using a Novel Type of Pseudodendrimer Based on 2,2-Bis(hydroxymethyl)propionic Acid.

In the search for effective vehicles to carry genetic material into cells, we present here new pseudodendrimers that consist of a hyperbranched polyester core surrounded by amino-terminated 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) dendrons. The pseudodendrimers are readily synthesized from commercial hyperbranched bis-MPA polyesters of the second, third, and fourth generations and third-generation bis-MPA dendrons, bearing eight peripheral glycine moieties, coupled by the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). This approach provides globular macromolecular structures bearing 128, 256, and 512 terminal amino groups, and these can complex pDNA. The toxicity of the three pseudodendrimers was studied on two cell lines, mesenchymal stem cells, and HeLa, and it was demonstrated that these compounds do not affect negatively cell viability up to 72 h. The complexation with DNA was investigated in terms of N-to-P ratio and dendriplex stability. The three generations were found to promote internalizing of pDNA into mesenchymal stem cells (MSCs), and their transfection capacity was compared with two nonviral commercial transfection agents, Lipofectamine and TransIT-X2. The highest generations were able to transfect these cells at levels comparable to both commercial reagents.

Effect of dexmedetomidine on cerebral ischemia-reperfusion rats by activating mitochondrial ATP-sensitive potassium channel.

The aim of the study reported here was to evaluate whether the mitochondrial ATP-sensitive potassium (mitoKATP) channel could participate in the effect of dexmedetomidine on cerebral ischemia-reperfusion (I/R) rats. Forty rats were randomly assigned into 5 groups: sham operation (S) group; cerebral I/R group; dexmedetomidine (D) group; 5-hydroxydecanoate (5-HD) group; 5-HD + D group. The cerebral I/R were produced by 2 h right middle cerebral artery occlusion followed by 24 h reperfusion. Dexmedetomidine (50µg/kg) was injected intraperitoneally before ischemia and after the onset of reperfusion. 5-HD (30 mg/kg) was injected intraperitoneally at 1 h before ischemia. The neurological deficit score (NDS) and the levels of super oxide dismutase (SOD), malondialdehyde (MDA), myeloperoxidase (MPO), Interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α) were evaluated. Compared to group S, NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly higher, and SOD levels were significantly lower in the other groups (P < 0.05). Compared to group I/R,NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly lower, and SOD level was significantly higher in group D (P < 0.05). Compared to group D, NDS and the levels of MDA, MPO, IL-6 and TNF-α were significantly higher, and SOD level was significantly lower in group5-HD + D (P < 0.05). The activation of the mitoKATP channel could contribute to the protective effect of dexmedetomidine on rats induced by focal cerebral ischemia-reperfusion injury.

Myocardial triggers involved in activation of remote ischaemic preconditioning.

NEW FINDINGS: What is the central question of this study? Ischaemia-reperfusion of peripheral tissues protects the heart from subsequent myocardial ischaemia-reperfusion injury, a phenomenon referred to as remote ischaemic preconditioning (rIPC). This study evaluated the possible myocardial triggers of rIPC. What is the main finding and its importance? Remote ischaemic preconditioning reduces infarct size through a vagal pathway and a mechanism involving phosphorylation of Akt and endothelial nitric oxide synthase, opening of mitochondrial ATP-dependent K(+) channels and an increase in mitochondrial H2 O2 production. All these phenomena occur before the myocardial ischaemia; hence, they could act as 'triggers' of rIPC. It has been proposed that remote ischaemic preconditioning (rIPC) activates a parasympathetic neural pathway. However, the myocardial intracellular mechanism of rIPC remains unclear. Here, we characterized some of the intracellular signals participating as rIPC triggers. Isolated rat hearts were subjected to 30 min of global ischaemia and 120 min of reperfusion (Non-rIPC group). In a second group, before the isolation of the heart, an rIPC protocol (three cycles of hindlimb ischaemia-reperfusion) was performed. The infarct size was measured with tetrazolium staining. Expression/phosphorylation of Akt and endothelial nitric oxide synthase (eNOS) and mitochondrial H2 O2 production were evaluated at the end of the rIPC protocol, before myocardial ischaemia-reperfusion. The rIPC significantly decreased the infarct size and induced Akt and eNOS phosphorylation. The protective effect on infarct size was abolished by cervical vagal section, l-NAME (an NO synthesis inhibitor) and 5-hydroxydecanoate (a mitochondrial ATP-dependent K(+) channel blocker). Mitochondrial production of H2 O2 was increased by rIPC, whereas it was abolished by cervical vagal section, l-NAME and 5-hydroxydecanoate. We conclude that rIPC activates a parasympathetic vagal pathway and a mechanism involving the phosphorylation of Akt and eNOS, the opening of mitochondrial ATP-dependent K(+) channels and the release of H2 O2 by the mitochondria. All these phenomena occur before myocardial ischaemia and could act as triggers of rIPC.

Bioenergetic and volume regulatory effects of mitoKATP channel modulators protect against hypoxia-reoxygenation-induced mitochondrial dysfunction.

The mitochondrial ATP-sensitive K(+) (mitoKATP) channel plays a significant role in mitochondrial physiology and protects against ischemic reperfusion injury in mammals. Although fish frequently face oxygen fluctuations in their environment, the role of the mitoKATP channel in regulating the responses to oxygen stress is rarely investigated in this class of animals. To elucidate whether and how the mitoKATP channel protects against hypoxia-reoxygenation (H-R)-induced mitochondrial dysfunction in fish, we first determined the mitochondrial bioenergetic effects of two key modulators of the channel, diazoxide and 5-hydroxydecanoate (5-HD), using a wide range of doses. Subsequently, the effects of low and high doses of the modulators on mitochondrial bioenergetics and volume under normoxia and after H-R using buffers with and without magnesium and ATP (Mg-ATP) were tested. In the absence of Mg-ATP (mitoKATP channel open), both low and high doses of diazoxide improved mitochondrial coupling, but only the high dose of 5-HD reversed the post-H-R coupling-enhancing effect of diazoxide. In the presence of Mg-ATP (mitoKATP channel closed), diazoxide at the low dose improved coupling post-H-R, and this effect was abolished by 5-HD at the low dose. Interestingly, both low and high doses of diazoxide reversed H-R-induced swelling under mitoKATP channel open conditions, but this effect was not sensitive to 5-HD. Under mitoKATP channel closed conditions, diazoxide at the low dose protected the mitochondria from H-R-induced swelling and 5-HD at the low dose reversed this effect. In contrast, diazoxide at the high dose failed to reduce the swelling caused by H-R, and the addition of the high dose of 5-HD enhanced mitochondrial swelling. Overall, our study showed that in the presence of Mg-ATP, both opening of mitoKATP channels and bioenergetic effects of diazoxide were protective against H-R in fish mitochondria, while in the absence of Mg-ATP only the bioenergetic effect of diazoxide was protective.

The novel H2S-donor 4-carboxyphenyl isothiocyanate promotes cardioprotective effects against ischemia/reperfusion injury through activation of mitoKATP channels and reduction of oxidative stress.

The endogenous gasotransmitter hydrogen sulphide (H2S) is an important regulator of the cardiovascular system, particularly of myocardial function. Moreover, H2S exhibits cardioprotective activity against ischemia/reperfusion (I/R) or hypoxic injury, and is considered an important mediator of "ischemic preconditioning", through activation of mitochondrial potassium channels, reduction of oxidative stress, activation of the endogenous "anti-oxidant machinery" and limitation of inflammatory responses. Accordingly, H2S-donors, i.e. pro-drugs able to generate exogenous H2S, are viewed as promising therapeutic agents for a number of cardiovascular diseases. The novel H2S-donor 4-carboxy phenyl-isothiocyanate (4CPI), whose vasorelaxing effects were recently reported, was tested here in different experimental models of myocardial I/R. In Langendorff-perfused rat hearts subjected to I/R, 4CPI significantly improved the post-ischemic recovery of myocardial functional parameters and limited tissue injury. These effects were antagonized by 5-hydroxydecanoic acid (a blocker of mitoKATP channels). Moreover, 4CPI inhibited the formation of reactive oxygen species. We found the whole battery of H2S-producing enzymes to be present in myocardial tissue: cystathionine γ-lyase (CSE), cystathionine ß-synthase (CBS) and 3-mercaptopyruvate sulfurtransferase (MPST). Notably, 4CPI down-regulated the post-ischemic expression of CSE. In Langendorff-perfused mouse hearts, 4CPI reduced the post-ischemic release of norepinephrine and the incidence of ventricular arrhythmias. In both rat and mouse hearts, 4CPI did not affect the degranulation of resident mast cells. In isolated rat cardiac mitochondria, 4CPI partially depolarized the mitochondrial membrane potential; this effect was antagonized by ATP (i.e., the physiological inhibitor of KATP channels). Moreover, 4CPI abrogated calcium uptake in the mitochondrial matrix. Finally, in an in vivo model of acute myocardial infarction in rats, 4CPI significantly decreased I/R-induced tissue injury. In conclusion, H2S-donors, and in particular isothiocyanate-based H2S-releasing drugs like 4CPI, can actually be considered a suitable pharmacological option in anti-ischemic therapy.

The Effects of Fentanyl on Hepatic Mitochondrial Function.

BACKGROUND: Remifentanil interferes with hepatic mitochondrial function. The aim of the present study was to evaluate whether hepatic mitochondrial function is affected by fentanyl, a more widely used opioid than remifentanil. METHODS: Human hepatoma HepG2 cells were exposed to fentanyl or pretreated with naloxone (an opioid receptor antagonist) or 5-hydroxydecanoate (5-HD, an inhibitor of mitochondrial adenosine triphosphate (ATP)-sensitive potassium [mitoKATP] channels), followed by incubation with fentanyl. Mitochondrial function and metabolism were then analyzed. RESULTS: Fentanyl marginally reduced maximal mitochondrial complex-specific respiration rates using exogenous substrates (decrease in medians: 11%-18%; P = 0.003-0.001) but did not affect basal cellular respiration rates (P = 0.834). The effect on stimulated respiration was prevented by preincubation with naloxone or 5-HD. Fentanyl reduced cellular ATP content in a dose-dependent manner (P < 0.001), an effect that was not significantly prevented by 5-HD and not explained by increased total ATPase concentration. However, in vitro ATPase activity of recombinant human permeability glycoprotein (an ATP-dependent drug efflux transporter) was significantly stimulated by fentanyl (P = 0.004). CONCLUSIONS: Our data suggest that fentanyl reduces stimulated mitochondrial respiration of cultured human hepatocytes by a mechanism that is blocked by a mitoKATP channel antagonist. Increased energy requirements for fentanyl efflux transport may offer an explanation for the substantial decrease in cellular ATP concentration.

The cardioprotective effect of naringenin against ischemia-reperfusion injury through activation of ATP-sensitive potassium channel in rat.

Naringenin (Nari) has antioxidative and anti-atherosclerosis effects, and activation of ATP-sensitive potassium channel (KATP) can offer cardiac protection. We hypothesized that Nari protects the heart against ischemia-reperfusion (I-R) injury through activation of KATP. Isolated hearts from adult male Sprague-Dawley rats experienced a 30-min global ischemia followed by 60-min reperfusion (120 min for the infarct size determination). The hearts were treated with Nari (NARI); Nari plus glibenclamide (GLI), a non-specific ATP-sensitive potassium channel blocker (NARI+GLI); and Nari plus 5-hydroxy decanoic acid (5-HD), a mitochondrial membrane ATP-sensitive potassium channel blocker (NARI+5-HD). The left ventricular pressure, lactate dehydrogenates (LDH) in coronary effluent, superoxide dismutase (SOD) and malondialdehyde (MDA) in myocardium, and myocardial infarct area were measured. Nari above 2.5 µmol/L improved the recovery of left ventricular function, decreased LDH in coronary effluent, and reduced myocardial infarct area. The SOD activity was increased and MDA was decreased in Nari-treated myocardium. The cardioprotective effect of Nari was canceled by GLI and 5-HD. In conclusion, Nari has a cardioprotective effect against I-R injury, which may be carried out through activating ATP-sensitive potassium channels in both cell and mitochondrial membrane, and enhancing myocardial antioxidant capacity.

Sevoflurane postconditioning affects post-ischaemic myocardial mitochondrial ATP-sensitive potassium channel function and apoptosis in ageing rats.

This study investigated the effect of sevoflurane postconditioning on post-ischaemic cardiac function, infarct size, myocardial mitochondrial ATP-sensitive potassium channel (mitoKATP) function and apoptosis in ageing rats to determine the possible mechanism underlying the cardioprotective property of sevoflurane. Ageing rat hearts were isolated and attached to a Langendorff apparatus. The hearts were then exposed or not to sevoflurane postconditioning in the presence or absence of 100 µmol/L 5-hydroxydecanoate (5-HD), a selective mitoKATP inhibitor. The infarct size was measured by triphenyltetrazolium chloride (TTC) staining. Mitochondrial morphology was observed by electron microscopy and scored using FlaMeng semiquantitative analysis. In addition, the expression levels of Bax, Bcl-2, and cytochrome-C (Cyt-C) were determined by Western blot analysis at the end of reperfusion. Sevoflurane postconditioning increased coronary flow, improved functional recovery, reduced Bax/Bcl-2 and Cyt-C phosphorylation levels, and decreased mitochondrial lesion severity and the extent of apoptosis. The protective effects of sevoflurane postconditioning were prevented by the mitoKATP inhibitor 5-HD. Sevoflurane postconditioning significantly protected the function of ageing hearts that were subjected to ischaemia and reperfusion, and these protective effects were mediated by mitoKATP opening.

Lidocaine relaxation in isolated rat aortic rings is enhanced by endothelial removal: possible role of Kv, KATP channels and A2a receptor crosstalk.

BACKGROUND: Lidocaine is an approved local anesthetic and Class 1B antiarrhythmic with a number of ancillary properties. Our aim was to investigate lidocaine's vasoreactivity properties in intact versus denuded rat thoracic aortic rings, and the effect of inhibitors of nitric oxide (NO), prostenoids, voltage-dependent Kv and KATP channels, membrane Na+/K+ pump, and A2a and A2b receptors. METHODS: Aortic rings were harvested from adult male Sprague Dawley rats and equilibrated in an organ bath containing oxygenated, modified Krebs-Henseleit solution, pH 7.4, 37 °C. The rings were pre-contracted sub-maximally with 0.3 µM norepinephrine (NE), and the effect of increasing lidocaine concentrations was examined. Rings were tested for viability after each experiment with maximally dilating 100 µM papaverine. The drugs 4-aminopyridine (4-AP), glibenclamide, 5-hydroxydecanoate, ouabain, 8-(3-chlorostyryl) caffeine and PSB-0788 were examined. RESULTS: All drugs tested had no significant effect on basal tension. Lidocaine relaxation in intact rings was biphasic between 1 and 10 µM (Phase 1) and 10 and 1000 µM (Phase 2). Mechanical removal of the endothelium resulted in further relaxation, and at lower concentrations ring sensitivity (% relaxation per µM lidocaine) significantly increased 3.5 times compared to intact rings. The relaxing factor(s) responsible for enhancing ring relaxation did not appear to be NO- or prostacyclin-dependent, as L-NAME and indomethacin had little or no effect on intact ring relaxation. In denuded rings, lidocaine relaxation was completely abolished by Kv channel inhibition and significantly reduced by antagonists of the MitoKATP channel, and to a lesser extent the SarcKATP channel. Curiously, A2a subtype receptor antagonism significantly inhibited lidocaine relaxation above 100 µM, but not the A2b receptor. CONCLUSIONS: We show that lidocaine relaxation in rat thoracic aorta was biphasic and significantly enhanced by endothelial removal, which did not appear to be NO or prostacyclin dependent. The unknown factor(s) responsible for enhanced relaxation was significantly reduced by Kv inhibition, 5-HD inhibition, and A2a subtype inhibition indicating a potential role for crosstalk in lidocaine's vasoreactivity.

Role of Vitamin C in Cardioprotection of Ischemia/Reperfusion Injury by Activation of Mitochondrial KATP Channel.

How to provide effective prevention and treatment of myocardial ischemia/reperfusion (I/R) injury and study of the mechanism underlying I/R injury are hotspots of current research. This study aimed to elucidate the effect and cardioprotective mechanism of vitamin C (VC) on myocardial I/R injury. Our study introduced two different I/R models: I/R in vitro and oxygen-glucose deprivation/recovery (OGD/R) in primary neonatal rat cardiac myocytes. We used the mitochondrial permeability transition pore (mPTP) opener lonidamine (LND) and the mitochondrial KATP (mitoKATP) channel inhibitor 5-hydroxydecanoate (5-HD) to analyze the underlying mechanisms. We found that post-treatment with VC decreased I/R injury in our models. Post-treatment with VC significantly decreased I/R-induced injury, attenuated apoptosis, and maintained the functional integrity of mitochondria via alleviation of Ca(2+) overload, reactive oxygen species burst, inhibition of the opening of mPTP, and prevention of mitochondrial membrane potential (ΔΨm) depolarization. VC post-treatment increased the phosphorylation of Akt and glycogen synthase kinase (GSK)-3ß. The present results demonstrate that VC might protect the myocardium from I/R-induced injury by inhibiting the mPTP opening via activation of mitoKATP channels. VC mediates cardioprotection via activation of the phosphatidyl inositol 3-kinase (PI3K)-Akt signaling pathway. These findings may contribute toward the development of novel strategies for clinical cardioprotection against I/R injury.

The unfolded protein response in the therapeutic effect of hydroxy-DHA against Alzheimer's disease.

The unfolded protein response (UPR) and autophagy are two cellular processes involved in the clearing of intracellular misfolded proteins. Both pathways are targets for molecules that may serve as treatments for several diseases, including neurodegenerative disorders like Alzheimer's disease (AD). In the present work, we show that 2-hydroxy-DHA (HDHA), a docosahexaenoic acid (DHA) derivate that restores cognitive function in a transgenic mouse model of AD, modulates UPR and autophagy in differentiated neuron-like SH-SY5Y cells. Mild therapeutic HDHA exposure induced UPR activation, characterized by the up-regulation of the molecular chaperone Bip as well as PERK-mediated stimulation of eIF2α phosphorylation. Key proteins involved in initiating autophagy, such as beclin-1, and several Atg proteins involved in autophagosome maturation (Atg3, Atg5, Atg12 and Atg7), were also up-regulated on exposure to HDHA. Moreover, when HDHA-mediated autophagy was studied after amyloid-ß peptide (Aß) stimulation to mimic the neurotoxic environment of AD, it was associated with increased cell survival, suggesting that HDHA driven modulation of this process at least in part mediates the neuroprotective effects of this new anti-neurodegenerative drug. The present results in part explain the pharmacological effects of HDHA inducing full recovery of the cognitive scores in murine models of AD.