Alternative Targets for Modulators of Mitochondrial Potassium Channels.

Mitochondrial potassium channels control potassium influx into the mitochondrial matrix and thus regulate mitochondrial membrane potential, volume, respiration, and synthesis of reactive oxygen species (ROS). It has been found that pharmacological activation of mitochondrial potassium channels during ischemia/reperfusion (I/R) injury activates cytoprotective mechanisms resulting in increased cell survival. In cancer cells, the inhibition of these channels leads to increased cell death. Therefore, mitochondrial potassium channels are intriguing targets for the development of new pharmacological strategies. In most cases, however, the substances that modulate the mitochondrial potassium channels have a few alternative targets in the cell. This may result in unexpected or unwanted effects induced by these compounds. In our review, we briefly present the various classes of mitochondrial potassium (mitoK) channels and describe the chemical compounds that modulate their activity. We also describe examples of the multidirectional activity of the activators and inhibitors of mitochondrial potassium channels.

Modulation of mitochondrial respiration rate and calcium-induced swelling by new cromakalim analogues.

A cellular model of cardiomyocytes (H9c2 cell line) and mitochondria isolated from mouse liver were used to understand the drug action of BPDZ490 and BPDZ711, two benzopyran analogues of the reference potassium channel opener cromakalim, on mitochondrial respiratory parameters and swelling, by comparing their effects with those of the parent compound cromakalim. For these three compounds, the oxygen consumption rate (OCR) was determined by high-resolution respirometry (HRR) and their impact on adenosine triphosphate (ATP) production and calcium-induced mitochondrial swelling was investigated. Cromakalim did not modify neither the OCR of H9c2 cells and the ATP production nor the Ca-induced swelling. By contrast, the cromakalim analogue BPDZ490 (1) induced a strong increase of OCR, while the other benzopyran analogue BPDZ711 (2) caused a marked slowdown. For both compounds, 1 displayed a biphasic behavior while 2 still showed an inhibitory effect. Both compounds 1 and 2 were also found to decrease the ATP synthesis, with pronounced effect for 2, while cromakalim remained without effect. Overall, these results indicate that cromakalim, as parent molecule, does not induce per se any direct effect on mitochondrial respiratory function neither on whole cells nor on isolated mitochondria whereas both benzopyran analogues 1 and 2 display totally opposite behavior profiles, suggesting that compound 1, by increasing the maximal respiration capacity, might behave as a mild uncoupling agent and compound 2 is taken as an inhibitor of the mitochondrial electron-transfer chain.

Screening Technologies for Inward Rectifier Potassium Channels: Discovery of New Blockers and Activators.

K+ channels play a critical role in maintaining the normal electrical activity of excitable cells by setting the cell resting membrane potential and by determining the shape and duration of the action potential. In nonexcitable cells, K+ channels establish electrochemical gradients necessary for maintaining salt and volume homeostasis of body fluids. Inward rectifier K+ (Kir) channels typically conduct larger inward currents than outward currents, resulting in an inwardly rectifying current versus voltage relationship. This property of inward rectification results from the voltage-dependent block of the channels by intracellular polyvalent cations and makes these channels uniquely designed for maintaining the resting potential near the K+ equilibrium potential (EK). The Kir family of channels consist of seven subfamilies of channels (Kir1.x through Kir7.x) that include the classic inward rectifier (Kir2.x) channel, the G-protein-gated inward rectifier K+ (GIRK) (Kir3.x), and the adenosine triphosphate (ATP)-sensitive (KATP) (Kir 6.x) channels as well as the renal Kir1.1 (ROMK), Kir4.1, and Kir7.1 channels. These channels not only function to regulate electrical/electrolyte transport activity, but also serve as effector molecules for G-protein-coupled receptors (GPCRs) and as molecular sensors for cell metabolism. Of significance, Kir channels represent promising pharmacological targets for treating a number of clinical conditions, including cardiac arrhythmias, anxiety, chronic pain, and hypertension. This review provides a brief background on the structure, function, and pharmacology of Kir channels and then focuses on describing and evaluating current high-throughput screening (HTS) technologies, such as membrane potential-sensitive fluorescent dye assays, ion flux measurements, and automated patch clamp systems used for Kir channel drug discovery.

In Vitro Effects of Eicosapentaenoic and Docosahexaenoic Acid on the Vascular Tone of a Human Saphenous Vein: Influence of Precontractile Agents.

BACKGROUND: Cardiovascular effects of omega-3 polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have been widely reported. However, there are limited studies concerning their effects on human blood vessels. Therefore, the aim of this study was to investigate the direct vascular effects of EPA and DHA on the human saphenous vein (SV) precontracted with either prostaglandin F2α (PGF2α), or thromboxane A2 analogue (U46619), or norepinephrine (NE). Moreover, we aimed to investigate the protein expression of free fatty acid receptor 4 (FFAR4) in human SV. METHODS: Pretreatment of human SV rings with EPA and DHA (100 µM, 30 min) was tested on vascular reactivity induced by PGF2α (10 nM to 5 µM), NE (10 nM to 100 µM), and U46619 (1 nM to 100 nM). In addition, direct relaxant effects of EPA/DHA (1-100 µM) were tested in human SV rings precontracted by PGF2α, NE, and U46619. Furthermore, the involvement of potassium channels on their vascular effects was investigated in the presence of the nonselective K+ channel inhibitor tetraethylammonium chloride. RESULTS: Pretreatment with EPA and DHA resulted in a significant decrease in vascular reactivity induced by U46619 and PGF2α compared to NE. In the presence of TEA, the relaxant effects of EPA and DHA were significantly decreased in SV preparations precontracted by U46619 and PGF2α for DHA. Furthermore, FFAR-4 protein was expressed in tissue extracts of human SV. CONCLUSIONS: Our study demonstrates that both EPA and DHA reduce the increased vascular tone elicited by contractile agents on the human SV and that the direct vasorelaxant effect is likely to involve potassium channels.

Cardamom extract induces cell proliferation by increasing potassium currents in NIH3T3 cell line.

Amommum subulatum (Roxb.) or Cardamom extract is known to have anti-inflammatory and neuroprotective effects towards many gastrointestinal related problems. However, uptill now different fractions of cardamom extract on fibroblasts with respect to potassium channel activity have not been investigated. Therefore, present study investigated the effects of different fractions of cardamom extract on potassium channels in non-tumor NIH3T3 cell line. Phytochemical analysis of hydroalcoholic, n-hexane, butane and ethyl acetate fractions of cardamom extracts were purified and isolated by thin layer chromatography (TLC). 3T3 cells were cultured and incubated with hydroalcohol (1-2 µ/ml), n-hexane (1 µ/ml), butane (2 µ/ml) and ethyl acetate (1-2 µ/ml) for 5 hrs at 37°C. Modulation in potassium currents were recorded by whole-cell patch clamp method. The data showed two constituents Cineol (C10H18O) and Terpinyl acetate (C10H17OOCCH3) by TLC method. The present study shows that the constituents in n-hexane, hydro alcohol (1 µ/ml) and ethyl acetate (2 µ/ml) significantly increased (p<0.01) the potassium outward rectifying currents from NIH3T3 cells when compared to untreated controls cells. Whereas, butanol fraction (2 µ/ml) significantly decreased (p<0.01) the inward rectifying currents when compared to controls. Moreover hydroalcoholic and n-hexane fractions have increased the proliferation in 3T3 cell line. On the other hand butanol and ethyl acetate did not induce proliferation in 3T3 cells. Taken together, our data suggested that cardamom extract contains constituents that increased K+ currents, cell migration and proliferation and are involved in wound healing.

A Computational Method for Unveiling the Target Promiscuity of Pharmacologically Active Compounds.

Drug discovery is governed by the desire to find ligands with defined modes of action. It has been realized that even designated selective drugs may have more macromolecular targets than is commonly thought. Consequently, it will be mandatory to consider multitarget activity for the design of future medicines. Computational models assist medicinal chemists in this effort by helping to eliminate unsuitable lead structures and spot undesired drug effects early in the discovery process. Here, we present a straightforward computational method to find previously unknown targets of pharmacologically active compounds. Validation experiments revealed hitherto unknown targets of the natural product resveratrol and the nonsteroidal anti-inflammatory drug celecoxib. The obtained results advocate machine learning for polypharmacology-based molecular design, drug re-purposing, and the "de-orphaning" of phenotypic drug effects.

Nicorandil modulated macrophages activation and polarization via NF-κb signaling pathway.

Nicorandil, a drug with both nitrate-like and ATP-sensitive potassium (KATP) channel-activating properties, has been well demonstrated in various aspects of myocardial infarction (MI), especially in inhibiting cell apoptosis and increasing coronary flow. However, the role of nicorandil in regulating inflammation and angiogenesis following myocardial infarction is still unrevealed. In the present study, we explored the effect of nicorandil on macrophage phenotype transition and inflammation regulation and the potential underlying mechanisms. For the phenotype transition and phagocytosis ability of macrophages detection, flow cytometry analysis was used. The inflammation factors were measured with ELISA and qRT-PCR. Western blot was used to assess the levels of NF-κb and its target genes and VEGF expression. The tube formation ability of endothelial cells was examined on matrigel. We discovered that nicorandil can obviously inhibit the differentiation of monocytes into mature macrophages and decrease M1 phenotype transition both in peritoneal macrophages and cultured macrophage cell line in normal or hypoxia and serum deprivation (H/SD) conditions. Meanwhile, nicorandil can induce an anti-inflammatory M2 phenotype. Thereby, nicorandil regulated macrophages switching to M1/M2 status. Our data further showed that NF-κb and the expression of its target genes were pivotal players in the regulation of macrophages phenotype. Besides, we also showed that nicorandil can promote the tube formation and VEGF expression in endothelial cells. We concluded that nicorandil may serve as an effective modulator of NF-κb signaling pathway during the pathogenesis of MI via regulating M1/M2 status and promoting angiogenesis.

IK channel activation increases tumor growth and induces differential behavioral responses in two breast epithelial cell lines.

Many potassium channel families are over-expressed in cancer, but their mechanistic role in disease progression is poorly understood. Potassium channels modulate membrane potential (Vmem) and thereby influence calcium ion dynamics and other voltage-sensitive signaling mechanisms, potentially acting as transcriptional regulators. This study investigated the differential response to over-expression and activation of a cancer-associated potassium channel, the intermediate conductance calcium-activated potassium channel (IK), on aggressive behaviors in mammary epithelial and breast cancer cell lines. IK was over-expressed in the highly metastatic breast cancer cell line MDA-MB-231 and the spontaneously immortalized breast epithelial cell line MCF-10A, and the effect on cancer-associated behaviors was assessed. IK over-expression increased primary tumor growth and metastasis of MDA-MB-231 in orthotopic xenografts, demonstrating for the first time in any cancer type that increased IK is sufficient to promote cancer aggression. The primary tumors had similar vascularization as determined by CD31 staining and similar histological characteristics. Interestingly, despite the increased in vivo growth and metastasis, neither IK over-expression nor activation with agonist had a significant effect on MDA-MB-231 proliferation, invasion, or migration in vitro. In contrast, IK decreased MCF-10A proliferation and invasion through Matrigel but had no effect on migration in a scratch-wound assay. We conclude that IK activity is sufficient to promote cell aggression in vivo. Our data provide novel evidence supporting IK and downstream signaling networks as potential targets for cancer therapies.

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.

Persistent mitoKATP Activation Is Involved in the Isoflurane-induced Cytotoxicity.

Isoflurane exposure induces apoptosis in cultured cells and in the developing brain, while the underlying mechanism remains largely unclarified. This study was designed to determine whether the disruption of mitoKATP-mediated ATP balance was involved in the cytotoxicity of isoflurane. Human neuroglioma cells U251 and 7-day-old mice were treated with isoflurane. A specific mitoKATP antagonist 5-HD was used, and the cellular ATP levels, NAD+/NADH ratios, and mitochondrial transmembrane potential (ΔΨm) were measured. Our data showed that the blockage of mitoKATP by 5-HD mitigated the isoflurane-induced ΔΨm disruption, reactive oxygen species (ROS) accumulation, and apoptosis in U251 cells. Moreover, we found that the toxic effect of isoflurane was not observed in the first 2-h exposure; instead, the cellular ATP levels and NAD+/NADH ratios were markedly increased. The reduction of ATP levels and NAD+/NADH ratios was only detected after this initial phase. This dynamical effect of isoflurane was blocked by 5-HD. In contrast, a ROS scavenger NAC sustained the isoflurane-induced ATP elevation. Similar results were observed in animal studies. And again, 5-HD attenuated isoflurane-induced cognitive disorders in the Intellicage test, a system that assesses place learning behavior in a social environment. Our study uncovered a potential mechanism underlying isoflurane's toxicity with a therapeutic future.

Iptakalim influences the proliferation and apoptosis of human pulmonary artery smooth muscle cells.

The aim of the present study was to determine the effect of an ATP-sensitive K+ (KATP) channel opener iptakalim (IPT) on the proliferation and apoptosis of human pulmonary artery smooth muscle cells (HPASMCs), and examine the potential value of IPT to hypoxic pulmonary hyper-tension (HPH) at a cellular level. HPASMCs were divided into the control, ET-1, ET-1+IPT and ET-1+IPT+glibenclamide (GLI) groups. GLI was administered 30 min prior to ET-1 and IPT. The 4 groups were incubated with corresponding reagents for 24 h. Cell viability was evaluated using a CCK-8 assay, cell proliferation by 5-ethynyl-2'-deoxyuridine (EdU) incorporation assay, and cell apoptosis via the expression of apoptosis-related proteins, i.e., Bcl-2-associated X protein (Bax) and B-cell lymphoma 2 (Bcl-2) using western blotting. We incubated HPASMCs with varying concentrations of ET-1 for 24, 48 and 72 h, and found that cell survival rate was increased in a dose-dependent manner (P<0.05) rather than in a time-dependent manner (P>0.05). After co-incubation of HPASMCs with varying concentrations of IPT and ET-1 for 24 h, the cell survival rate was decreased in a dose-dependent manner. The cell survival rate in the IPT+ET-1 group was significantly lower than that in the ET-1 group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1 group were higher than those in the control group, and the expression of Bax/Bcl-2 was lower than the control group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1+IPT group were lower than those in the ET-1 group, and the expression of Bax/Bcl-2 was higher than that in the ET-1 group (P<0.05). The cell viability (P<0.05) and proliferation (P<0.05) in the ET-1+IPT+GLI group were higher than those in the ET-1+IPT group, and the expression of Bax/Bcl-2 was lower than that in the ET-1+IPT group (P<0.05). In conclusion, IPT inhibited ET-1­induced HPASMC proliferation and promoted cell apoptosis. Thus, it may play an important role in the treatment of HPH.

Diazoxide accelerates wound healing by improving EPC function.

Endothelial cell dysfunction is the primary cause of microvascular complications in diabetes. Diazoxide enables beta cells to rest by reversibly suppressing glucose-induced insulin secretion by opening ATP-sensitive K+ channels in the beta cells. This study investigated the role of diazoxide in wound healing in mice with streptozotocin (STZ)-induced diabetes and explored the possible mechanisms of its effect. Compared to the controls, mice with STZ-induced diabetes exhibited significantly impaired wound healing. Diazoxide treatment (30 mg/kg/d, intragastrically) for 28 days accelerated wound closure and stimulated angiogenesis in the diabetic mice. Circulating endothelial progenitor cells (EPCs) increased significantly in the diazoxide-treated diabetic mice. The adhesion, migration, and tube formation abilities of bone marrow (BM)-EPCs were impaired by diabetes, and these impairments were improved by diazoxide treatment. The expression of both p53 and TSP-1 increased in diabetic mice compared to that in the controls, and these increases were inhibited significantly by diazoxide treatment. In vitro, diazoxide treatment improved the impaired BM-EPC function and diminished the increased expression of p53 and TSP-1 in cultured BM-EPCs caused by high glucose levels. We conclude that diazoxide improved BM-EPC function in mice with STZ-induced diabetes, possibly via a p53- and TSP-1-dependent pathway.

Potential role of microRNA-7 in the anti-neuroinflammation effects of nicorandil in astrocytes induced by oxygen-glucose deprivation.

BACKGROUND: It is generally recognized that the inflammatory reaction in glia is one of the important pathological factors in brain ischemic injury. Our previous study has revealed that opening ATP-sensitive potassium (K-ATP) channels could attenuate glial inflammation induced by ischemic stroke. However, the detailed mechanisms are not well known. METHODS: Primary cultured astrocytes separated from C57BL/6 mice were subjected to oxygen-glucose deprivation (OGD); cellular injuries were determined via observing the changes of cellular morphology and cell viability. MicroRNA (miR) and messenger RNA (mRNA) level was validated by real-time PCR. The interaction between microRNA and the target was confirmed via dual luciferase reporter gene assay. Expressions of proteins and inflammatory cytokines were respectively assessed by western blotting and enzyme-linked immunosorbent assay. RESULTS: OGD resulted in astrocytic damage, which was prevented by K-ATP channel opener nicorandil. Notably, we found that OGD significantly downregulated miR-7 and upregulated Herpud2. Our further study proved that miR-7 targeted Herpud2 3'UTR, which encoded endoplasmic reticulum (ER) stress protein-HERP2. Correspondingly, our results showed that OGD increased the levels of ER stress proteins along with significant elevations of pro-inflammatory cytokines, including tumor necrosis factor α (TNF-α) and interleukin 1ß (IL-1ß). Pretreatment with nicorandil could remarkably upregulate miR-7, depress the ER-related protein expressions including glucose-regulated protein 78 (GRP78), C/EBP-homologous protein (CHOP), and Caspase-12, and thereby attenuate inflammatory responses and astrocytic damages. CONCLUSIONS: These findings demonstrate that opening K-ATP channels protects astrocytes against OGD-mediated neuroinflammation. Potentially, miR-7-targeted ER stress acts as a key molecular brake on neuroinflammation.

Flavonoid galetin 3,6-dimethyl ether attenuates guinea pig ileum contraction through K(+) channel activation and decrease in cytosolic calcium concentration.

Flavonoid galetin 3,6-dimethyl ether (FGAL) has been isolated from the aerial parts of Piptadenia stipulaceae and has shown a spasmolytic effect in guinea pig ileum. Thus, we aimed to characterize its relaxant mechanism of action. FGAL exhibited a higher relaxant effect on ileum pre-contracted by histamine (EC50=1.9±0.4×10(-7) M) than by KCl (EC50=2.6±0.5×10(-6) M) or carbachol (EC50=1.8±0.4×10(-6) M). The flavonoid inhibited the cumulative contractions to histamine, as well as to CaCl2 in depolarizing medium nominally Ca(2+)-free. The flavonoid relaxed the ileum pre-contracted by S-(-)-Bay K8644 (EC50=9.5±1.9×10(-6) M) but less potently pre-contracted by KCl or histamine. CsCl attenuated the relaxant effect of FGAL (EC50=1.1±0.3×10(-6) M), but apamin or tetraethylammonium (1mM) had no effect (EC50=2.6±0.2×10(-7) and 1.6±0.3×10(-7) M, respectively), ruling out the involvement of small and big conductance Ca(2+)-activated K(+) channels (SKCa and BKCa, respectively). Either 4-aminopyridine or glibenclamide attenuated the relaxant effect of FGAL (EC50=1.8±0.2×10(-6) and 1.5±0.5×10(-6) M, respectively), indicating the involvement of voltage- and ATP-sensitive K(+) channels (KV and KATP, respectively). FGAL did not alter the viability of intestinal myocytes in the MTT assay and decreased (88%) Fluo-4 fluorescence, indicating a decrease in cytosolic Ca(2+) concentration. Therefore, the relaxant mechanism of FGAL involves pseudo-irreversible noncompetitive antagonism of histaminergic receptors, KV and KATP activation and blockade of CaV1, thus leading to a reduction in cytosolic Ca(2+) levels.

Adenosine Triphosphate-Sensitive Potassium Channel Kir Subunits Implicated in Cardioprotection by Diazoxide.

BACKGROUND: ATP-sensitive potassium (K(ATP)) channel openers provide cardioprotection in multiple models. Ion flux at an unidentified mitochondrial K(ATP) channel has been proposed as the mechanism. The renal outer medullary kidney potassium channel subunit, potassium inward rectifying (Kir)1.1, has been implicated as a mitochondrial channel pore-forming subunit. We hypothesized that subunit Kir1.1 is involved in cardioprotection (maintenance of volume homeostasis and contractility) of the K(ATP) channel opener diazoxide (DZX) during stress (exposure to hyperkalemic cardioplegia [CPG]) at the myocyte and mitochondrial levels. METHODS AND RESULTS: Kir subunit inhibitor Tertiapin Q (TPN-Q) was utilized to evaluate response to stress. Mouse ventricular mitochondrial volume was measured in the following groups: isolation buffer; 200 µmol/L of ATP; 100 µmol/L of DZX+200 µmol/L of ATP; or 100 µmol/L of DZX+200 µmol/L of ATP+TPN-Q (500 or 100 nmol/L). Myocytes were exposed to Tyrode's solution (5 minutes), test solution (Tyrode's, cardioplegia [CPG], CPG+DZX, CPG+DZX+TPN-Q, Tyrode's+TPN-Q, or CPG+TPN-Q), N=12 for all (10 minutes); followed by Tyrode's (5 minutes). Volumes were compared. TPN-Q, with or without DZX, did not alter mitochondrial or myocyte volume. Stress (CPG) resulted in myocyte swelling and reduced contractility that was prevented by DZX. TPN-Q prevented the cardioprotection afforded by DZX (volume homeostasis and maintenance of contractility). CONCLUSIONS: TPN-Q inhibited myocyte cardioprotection provided by DZX during stress; however, it did not alter mitochondrial volume. Because TPN-Q inhibits Kir1.1, Kir3.1, and Kir3.4, these data support that any of these Kir subunits could be involved in the cardioprotection afforded by diazoxide. However, these data suggest that mitochondrial swelling by diazoxide does not involve Kir1.1, 3.1, or 3.4.

Beneficial effects of adenosine triphosphate-sensitive K+ channel opener on liver ischemia/reperfusion injury.

AIM: To investigate the effect of diazoxide administration on liver ischemia/reperfusion injury. METHODS: Wistar male rats underwent partial liver ischemia performed by clamping the pedicle from the medium and left anterior lateral segments for 1 h under mechanical ventilation. They were divided into 3 groups: Control Group, rats submitted to liver manipulation, Saline Group, rats received saline, and Diazoxide Group, rats received intravenous injection diazoxide (3.5 mg/kg) 15 min before liver reperfusion. 4 h and 24 h after reperfusion, blood was collected for determination of aspartate transaminase (AST), alanine transaminase (ALT), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), interleukin-10 (IL-10), nitrite/nitrate, creatinine and tumor growth factor-ß1 (TGF-ß1). Liver tissues were assembled for mitochondrial oxidation and phosphorylation, malondialdehyde (MDA) content, and histologic analysis. Pulmonary vascular permeability and myeloperoxidase (MPO) were also determined. RESULTS: Four hours after reperfusion the diazoxide group presented with significant reduction of AST (2009 ± 257 U/L vs 3523 ± 424 U/L, P = 0.005); ALT (1794 ± 295 U/L vs 3316 ± 413 U/L, P = 0.005); TNF-α (17 ± 9 pg/mL vs 152 ± 43 pg/mL, P = 0.013; IL-6 (62 ± 18 pg/mL vs 281 ± 92 pg/mL); IL-10 (40 ± 9 pg/mL vs 78 ± 10 pg/mL P = 0.03), and nitrite/nitrate (3.8 ± 0.9 µmol/L vs 10.2 ± 2.4 µmol/L, P = 0.025) when compared to the saline group. A significant reduction in liver mitochondrial dysfunction was observed in the diazoxide group compared to the saline group (P < 0.05). No differences in liver MDA content, serum creatinine, pulmonary vascular permeability and MPO activity were observed between groups. Twenty four hours after reperfusion the diazoxide group showed a reduction of AST (495 ± 78 U/L vs 978 ± 192 U/L, P = 0.032); ALT (335 ± 59 U/L vs 742 ± 182 U/L, P = 0.048), and TGF-ß1 (11 ± 1 ng/mL vs 17 ± 0.5 ng/mL, P = 0.004) serum levels when compared to the saline group. The control group did not present alterations when compared to the diazoxide and saline groups. CONCLUSION: Diazoxide maintains liver mitochondrial function, increases liver tolerance to ischemia/reperfusion injury, and reduces the systemic inflammatory response. These effects require further evaluation for using in a clinical setting.

Targeting solid tumours with potassium channel activators. A return to fundamentals?

From a pharmacological point of view nicotinamide and minoxidil are potassium channel activators. Nicotinamide is used as a radiosensitizer in ARCON (accelerated radiotherapy combined with carbogen breathing and nicotinamide) therapeutic strategy with promising results but not confirmed so far. Minoxidil has never been considered by radiotherapists. Based from recent pathophysiological considerations we suggest a new perspective for the use of these two "old" molecules in order to target solid tumours.

[The role of adenosine Al receptors and mitochondrial K+ATP channels in the mechanism of increasing the resistance to acute hypoxia in the combined effects of hypoxia and hypercapnia].

We studied the role of the role of mitoK+ATp channels and Al-adenosine receptor in the mechanism of increasing the resistance to acute hypoxia after hypoxic, hypercapnic and hypercapnic-hypoxic preconditioning. It is shown that mitochondrial ATP-sensitive potassium channels and Al-adenosine receptors, an important mechanism of preconditioning have a high value to increase the resistance to acute hypoxia/ischemia in the combined effect of hypoxia and hypercapnia. However, with regard to the adenosine receptor, this mechanism is realized without the participation hypercapnic component, which apparently starts neuroprotection without activation of the adenosine Al receptors.