Dietary Omega-3 Polyunsaturated Fatty Acids Alter Fatty Acid Composition of Lipids and CYP2E1 Expression in Rat Liver Tissue.

Omega-3 polyunsaturated fatty acids (PUFAs) are used for the treatment and prevention of numerous pathologies in humans. As recently found, PUFAs play significantly protective roles in liver, cardiovascular system and kidney. They also are widely used in total parenteral nutrition. We evaluated the effect of omega-3 PUFA consumption on liver fatty acid composition and the expression of CYP2E1, one of the key enzymes in detoxification and prooxidant systems of liver cells. To estimate the oxidative stress in liver tissue, the antioxidant status and the level of lipid peroxidation were determined in a rodent model. Animals were divided into two groups: control (n = 10) and experimental (n = 10). Epadol-containing omega-3 PUFA fish oil capsules were administered to Wistar rats within 4 weeks (0.1 mL/100 g b.w./day). The consumption of omega-3 PUFAs resulted in changes of fatty acid composition of liver tissue. A significant increase was detected in the α-linolenic, eicosapentaenoic and docosahexaenoic acid content (5.1-, 16-, and 1.3-fold, respectively, p < 0.05), while the content of linoleic and arachidonic acid was reduced (1.7- and 3.2-fold, respectively, p < 0.05). This caused significant increases in the omega-3:omega-6 ratio. Consumption of omega-3 PUFAs led to a 3-fold (p < 0.05) increase in CYP2E1 content, which could entail enhanced Nrf2 expression levels and increases in the HO-1 content in rat liver. The alteration in CYP2E1 expression did not have an impact on the level of lipid peroxidation and on the prooxidant/antioxidant balance.

Effects of fluorine-containing opener of ATP-sensitive potassium channels, pinacidil-derivative flocalin, on cardiac voltage-gated sodium and calcium channels.

Fluorine-containing pinacidil-derivative flocalin is an effective adenosine triphosphate-sensitive potassium (K(ATP))-channel opener with pronounced vasodilatory, cardioprotective effects and low general toxicity. By activating cardiac K(ATP) channels, flocalin hyperpolarizes cardiac myocytes, decreases their excitability, reduces Ca(2+) entry, and inhibits Ca(2+)-dependent signalling processes. Since our previous studies indicated that the drug also influences the rate of rise and amplitude of the cardiomyocyte's action potential, here we have investigated its possible actions on depolarizing inward currents through voltage-gated sodium (VGSC) and L-type calcium (VGCC) channels. Experiments were conducted on cultured cardiac myocytes prepared from the whole hearts of neonatal rats and maintained in culture for 1-3 days using whole-cell patch-clamp technique with no distinction of myocyte's type. Flocalin concentration dependently inhibited the Na(+) inward current through VGSCs with IC(50) = 17.4 µM and a maximal extent of 0.54, slowed down its inactivation kinetics, and hyperpolarized steady-state inactivation by 5.6 mV. The drug also inhibited calcium current through L-type VGCCs with IC(50) = 24.1 µM and a maximal block of 0.38, without affecting its inactivation but producing 5.3-mV hyperpolarization shifting of steady-state activation. Inhibition of both depolarizing currents by flocalin in addition to its ability to open K(ATP) channels enhances the suppressive action of the drug on cardiac excitability and broadens its pharmacological effects. Since, according to our previous data, cardiac K(ATP)-channel opening by flocalin occurs with ЕC(50) = 8 µM, the possibility of partial blockade of VGSC and L-type VGCCs should be considered when determining the therapeutic concentrations of the compound during its use as a cardioprotector.

Sarcolemmal cardiac K(ATP) channels as a target for the cardioprotective effects of the fluorine-containing pinacidil analogue, flocalin.

BACKGROUND AND PURPOSE: A class of drugs known as K(ATP) -channel openers induce cardioprotection. This study examined the effects of the novel K(ATP) -channel opener, the fluorine-containing pinacidil derivative, flocalin, on cardiac-specific K(ATP) -channels, excitability of native cardiac myocytes and on the ischaemic heart. EXPERIMENTAL APPROACH: The action of flocalin was investigated on: (i) membrane currents through cardiac-specific K(ATP) -channels (I(KATP) ) formed by K(IR) 6.2/SUR2A heterologously expressed in HEK-293 cells (HEK-293(6.2/2A) ); (ii) excitability and intracellular Ca²(+) ([Ca²(+) ](i) ) transients of cultured rat neonatal cardiac myocytes; and (iii) functional and ultrastructural characteristics of isolated guinea-pig hearts subjected to ischaemia-reperfusion. KEY RESULTS: Flocalin concentration-dependently activated a glibenclamide-sensitive I(KATP) in HEK-293(6.2/2A) cells with an EC50= 8.1 ± 0.4 µM. In cardiac myocytes, flocalin (5 µM) hyperpolarized resting potential by 3-5 mV, markedly shortened action potential duration, reduced the amplitude of [Ca²(+) ](i) transients by 2-3-fold and suppressed contraction. The magnitude and extent of reversibility of these effects depended on the type of cardiac myocytes. In isolated hearts, perfusion with 5 µmol·L⁻¹ flocalin, before inducing ischaemia, facilitated restoration of contraction during reperfusion, decreased the number of extrasystoles, prevented the appearance of coronary vasoconstriction and reduced damage to the cardiac tissue at the ultrastructural level (state of myofibrils, membrane integrity, mitochondrial cristae structure). CONCLUSION AND IMPLICATIONS: Flocalin induced potent cardioprotection by activating cardiac-type K(ATP) -channels with all the benefits of the presence of fluorine group in the drug structure: higher lipophilicity, decreased toxicity, resistance to oxidation and thermal degradation, decreased metabolism in the organism and prolonged therapeutic action.

Cardioprotective effect of 5-lipoxygenase gene (ALOX5) silencing in ischemia-reperfusion.

It is well known that 5-lipoxygenase derivates of arachidonic acid play an important pathogenic role during myocardial infarction. Therefore, the gene encoding arachidonate 5-lipoxygenase (ALOX5) appears to be an attractive target for RNA interference (RNAi) application. In experiments on cultivated cardiomyocytes with anoxia-reoxygenation (AR) and in vivo using rat model of heart ischemia-reperfusion (IR) we determined influence of ALOX5 silencing on myocardial cell death. ALOX5 silencing was quantified using real-time PCR, semi-quantitative PCR, and evaluation of LTC(4) concentration in cardiac tissue. A 4.7-fold decrease of ALOX5 expression (P < 0.05) was observed in isolated cardiomyocytes together with a reduced number of necrotic cardiomyocytes (P < 0.05), increased number live (P < 0.05) and unchanged number of apoptotic cells during AR of cardiomyocytes. Downregulation of ALOX5 expression in myocardial tissue by 19% (P < 0.05) resulted in a 3.8-fold reduction of infarct size in an open chest rat model of heart IR (P < 0.05). Thus, RNAi targeting of ALOX5 protects heart cells against IR injury both in culture and in vivo.