Comparative Analysis of Infarct Size Limiting Activity of δ-Opioid Receptor Agonists in Reperfused Heart In Vivo.

The study examined the effects of δ-opioid receptor (OR) agonists on infarct size on cardiac ischemia (45 min) and reperfusion (120 min) in vivo model in rats narcotized with α-chloralose. The OR agonists were injected intravenously 5 min prior to reperfusion, OR antagonists were administered 10 min before reperfusion. A selective δ-OR agonist BW373U86 (1 mg/kg) reduced the infarct size/area at risk ratio. A selective δ1-OR agonist DPDPE injected in the doses of 0.1 or 0.969 mg/kg produced no effect on infarct size. The selective δ2-OR agonist deltorphin II (0.12 mg/kg) reduced infarct size/area at risk ratio by 2 times. The δ-OR agonist p-Cl-Phe-DPDPE (1 mg/kg) reduced infarct size/area at risk ratio by 40%. Naltrexone and naloxone methiodide, the peripheral OR antagonists, and selective δ2-OR antagonist naltriben prevented the infarct size limiting effect of deltorphin II. Therefore, activation of peripheral δ2-OR enhanced cardiac resistance against toxic action of reperfusion. During reperfusion, deltorphin II demonstrated the most pronounced cardioprotective activity.

Prospects of Using of κ-Opioid Receptor Agonists U-50,488 and ICI 199,441 for Improving Heart Resistance to Ischemia/Reperfusion.

We studied the ability of the agonist of κ1-opioid receptors U-50,488 in doses of 0.1 and 1 mg/kg to simulate ischemic pre- and postconditioning of the heart and κ-opioid receptors ICI 199,441 in a dose of 0.1 mg/kg to simulate the antiarrhythmic effect of heart preconditioning. The duration of ischemia was 10 or 45 min and the duration of reperfusion was 10 min or 2 h. Administration of 1 mg/kg U-50,488 both before ischemia and 5 min before reperfusion produced a pronounced antiarrhythmic effect. U-50,488 injected 5 min before reperfusion 2-fold reduced the ratio of infarction to risk area. Administration of ICI 199,441 in a dose of 0.1 mg/kg 15 min before ischemia produced a potent antiarrhythmic effect. Antiarrhythmic effect of κ-opioid receptor agonists depended on activation of κ-opioid receptors.

Role of cyclic nucleotides and NO synthase in mechanisms of cardioprotective effects of cannabinoid HU-210.

Isolated perfused rat heart was subjected to global ischemia (45 min) followed by reperfusion (30 min). Under these conditions, the level of creatine phosphokinase in the perfusate increased by 4.5 times. Perfusion (10 min) of the isolated heart with a solution containing cannabinoid HU-210 (0.1 or 1.0 µmol/liter) was followed by a 2-fold decrease in creatine phosphokinase level in the perfusate. The cardioprotective effect of HU-210 remained unchanged under condition of NO synthase inhibition. Cannabinoid HU-210 reduced the concentration of cAMP in the myocardium by 2 times during reperfusion, but did not affect it before and during ischemia. This agent also did not change the level of cGMP in the myocardium before and during ischemia and during reperfusion. The results of the experiment suggest that the cardioprotective effect of HU-210 can be determined by a decrease in cAMP level in the myocardium during reperfusion. cGMP and NO synthase do not contribute to cytoprotective effect of HU-210.

Comparative analysis of early and delayed cardioprotective and antiarrhythmic efficacy of hypoxic preconditioning.

Hypoxic preconditioning produces an infarct-limiting effect both in the early and delayed periods. The increase in heart resistance to ischemia-repefusion was more pronounced after early preconditioning. Hypoxic preconditioning did not change heart resistance to the arrhythmogenic effect of coronary occlusion and reperfusion.

[Perspective of use of agonists of adenosine and opioid receptors for prevention of reperfusion damages of heart. Analysis of experimental and clinical data].

In Russia inhospital lethality after acute myocardial infarction is 16.5-16.7%. The part of patients perishes even after recanalisation of infarct-related coronary artery as a result of reperfusion cardiac injury. Experimental data indicate that adenosine receptor agonists and opioids can prevent reperfusion damages of heart that is mimic postconditioning phenomena. Data of clinical observation show that adenosine during intravenous infusion or intracoronary administration during thrombolysis or percutaneous coronary intervention exert infarct reducing effect and eliminate manifestation of of "no-reflow" phenomenon. Clinical data indicate that morphine is able to prevent cardiac reperfusion injury in human. Thus, analysis of published data testifies that adenosine and opioid receptor agonists can be prototype for development of drugs for prophylaxis of reperfusion heart injury.

[Signaling mechanism of cardioprotective effects of opioids].

It has been established that G(i/o)-proteins are an intermediate link that provides intracellular signaling between opioid receptors and protein kinases. Our investigations have shown that protein kinase C is involved in realization of the anti-necrotic and anti-apoptotic effects of opioids. PI3 and Akt kinases are involved in the cardioprotective effect of opioids. MEK1/2, ERK1/2, Src and JAK2 kinases play an important role in the cardioprotective effect of opioids. Further study of the participation of JNK, p70s6K and GRK2 in the opioid-induced increase of cardiac tolerance to ischemia and reperfusion is required. NO-synthase plays an important role in the cardioprotective action of opioids. Transactivation of opioid and adenosine receptors is an important element in the development of cardiac tolerance to ischemia and reperfusion. Opioid transactivation of EGF receptor is a connecting link between opioid receptors and ERK1/2 and PI3 kinase cascades.

Variability of the biological activity of oxidized titanium implants.

Oxidized titanium is a biologically inert material, but bioinertness reduces biomechanical characteristics of titanium implants. Modification of the structure of oxide surface layer of BT 5-1 titanium by increasing its thickness (by 1.7 times) and pore diameter (by 1.4 times) and by adding phosphorus, aluminum, and zinc oxides to its composition leads to radical modification of its biological characteristics. These implants acquire osteoinductive properties in in vivo systems not found in pure or oxidized BT 1-00 titanium and fairly well maintain in vitro growth of mesenchymal cells.

[Mediated role of NO-syntase, protein kinase C and KATP-channels in realization of cardioprotective impact of cannabinoid HU-210].

It was shown that perfusion of the isolated heart of rat with solution containing the CB1- and CB2-receptor agonist HU-210 at concentrations of 0.1 or 1.0 microM/L for a duration of 10 min at 20 min before global ischemia (45 min) and reperfusion (30 min) promotes a twofold decrease in creatine kinase levels in coronary effluent. It was established that KATP channel blockade by glibenclamide (1 microM/L) or inhibition of protein kinase C (2 microM/L) by chelerythrine abolishes the cardioprotective effect of HU-210. The inhibitor of NO synthase L-NAME (1 microM/L) had no effect on the anti-necrotic effect of HU-210. Thus, the intracellular signaling mechanism of the cardioprotective effect of the CB-agonist HU-210 involves the activation of KATP channels and protein kinase C without the participation of NO-synthase.

[Perspective of creation of drugs on basis of opioids increasing cardiac tolerance to pathogenic impact of ischemia reperfusion].

It was established that delta- and kappa1-opioid receptor (OR) stimulation both in vivo and in vitro promotes a decrease of infarct size/area at risk (IS/AAR) ratio during ischemia and reperfusion of heart. mu-OR activation increases a tolerance of isolated perfused heart to impact of ischemia and reperfusion but has no effect on IS/AAR index in vivo. The ORL1-receptor agonist nociceptin does not exert IS/AAR ratio in vivo. Delta- and kappa1-OR stimulation prevents cardiomyocyte apoptosis during ischemia and reperfusion of heart. The delta- and kappa1-OR agonists mimic infarct-reducing effect of postconditioning. The OR inhibition does not impact IS/AAR index both in vivo and in vitro. The delta1-, delta2- and kappa1-OR agonists are the most perspective group of opioids for creation of drugs increasing cardiac tolerance to pathogenic impact of ischemia and reperfusion.

Opioid peptide deltorphin II simulates the cardioprotective effect of ischemic preconditioning: role of δ2-opioid receptors, protein kinase C, and K(ATP) channels.

The cardioprotective properties of a δ2-opioid receptor agonist deltorphin II were studied in rats with coronary occlusion and reperfusion. Opioid receptor ligands and inhibitors (glybenclamide, chelerythrine, and 5-hydroxydecanoate) were injected intravenously before ischemia and reperfusion. A δ2-opioid receptor agonist deltorphin II significantly decreased the infarction zone/risk zone index. This effect was abolished by naltrexone, naloxone methiodide, and δ2-opioid receptor antagonist naltriben, but not by a δ1-opioid receptor antagonist BNTX. The infarct-limiting effect of deltorphin II was not observed after inhibition of protein kinase C or blockade of mitochondrial K(ATP) channels.

Antiarrhythmic activity of phytoadaptogens in short-term ischemia-reperfusion of the heart and postinfarction cardiosclerosis.

A course of treatment (16 mg/kg orally during 5 days) by Aralia mandshurica or Rhodiola rosea extracts reduced the incidence of ischemic and reperfusion ventricular arrhythmias during 10-min ischemia and 10-min reperfusion. Extracts of Eleutherococcus senticosus, Leuzea carthamoides, and Panax ginseng did not change the incidence of ischemic and reperfusion arrhythmias. Chronic treatment by aralia, rhodiola, and eleutherococcus elevated the ventricular fibrillation threshold in rats with postinfarction cardiosclerosis. Ginseng and leuzea did not change this parameter in rats with postinfarction cardiosclerosis.

[Cardioprotective, inotropic, and anti-arrhythmia properties of a complex adaptogen "Tonizid"].

We have studied the new complex plant adaptogen preparation tonizid containing dry extracts of Aralia mandshurica, Panax ginseng, Rhodiola rosea, and Eleutherococcus senticosus. The course administration (5 days) of tonizid led to a decrease in the ratio of necrotic zone size/risk area during a 45-min local ischemia and a 2-hr reperfusion in artificially ventilated chloralose anaesthetized rats. This compound decreased the necrotic zone but did not change the size of the risk area. Tonizid also prevented an appearance of ventricular fibrillation during a 45-min coronary artery occlusion, but did not affect the incidence of ventricular arrhythmias during a brief ischemia and reperfusion. In a separate series of experiments, tonizid was administered during 5 days to rats with postinfarction cardiac sclerosis, which was formed 45 days after coronary artery occlusion. In this case, tonizid dose-dependently elevated the ventricular fibrillation threshold. The experiments in vitro were performed on a model of 35-min total ischemia and 30-min reperfusion of isolated rat heart using the Langendorff technique. The course administration of tonizid attenuated the reperfusion-induced decrease in the left ventricular pressure and the rate of contraction. However, tonizid did not prevent a reperfusion-induced reduction in the heart rate, a decrease in the rate of relaxation, and an increase in the final diastolic pressure. Tonizid decreased the creatine kinase levels in the venous effluent from isolated rat heart during reperfusion. At the same time, the plant adaptogen did not affect the incidence of ventricular arrhythmias and coronary flow. It is suggested that tonizid can be used as an adaptogen drug attenuating the contractility dysfunction and preventing an appearance of irreversible cardiomyocyte damage during ischemia and reperfusion. Tonizid exhibits cardioprotective and antifibrillatory properties during acute cardiac ischemia/reperfusion and postinfarction cardiac fibrosis.

[Role of cannabinoid receptors in regulation of cardiac tolerance to ischemia and reperfusion].

Coronary artery occlusion (45 min) and reperfusion (2 h) were modeled in vivo in anesthetized artificially ventilated Wistar rats. Total ischemia (45 min) and reperfusion (30 min) of the isolated rat heart were performed in vitro. The selective agonist of cannabinoid (CB) receptors HU-210 was injected intravenously at a dose of 0.1 mg/kg 15 min prior to the coronary artery ligation. The selective CB1 antagonist SR141716A and the selective CB2 antagonist SR144528 were injected intravenously 25 min prior to ischemia. In vitro, HU-210 and SR141716A were added to the perfusion solution at the final concentrations of 0.1 microM prior to total ischemia. Preliminary injection of HU-210 reduced the infarct size-to-area at risk (IS/AAR) ratio in vivo. This cardioprotective effect was completely abolished by SR141716A but remained after SR144528 injection. Both antagonists had no effect on the IS/AAR ratio. Preliminary injection of the K(ATP) channel blocker glibenclamide did not abolish the cardioprotective effect of HU-210. The addition of HU-210 prior to ischemia reduced the creatine phosphokinase (CPK) level in the coronary effluent and decreased left ventricular developed pressure. SR141716A alone had no effect on cardiac contractility and CPK levels. These results suggest that cardiac CB1 receptor activation increases cardiac tolerance to ischemia-reperfusion and has a negative effect on the cardiac pump function. Endogenous cannabinoids are not involved in the regulation of cardiac contractility and tolerance to ischemia and reperfusion. ATP-sensitive E+ channels are not involved in the mechanism of the cardioprotective effect of HU-210.

[Significance of cardiac cannabinoid receptors in regulation of cardiac rhythm, myocardial contractility, and electrophysiologic processes in heart].

Intravenous administration of cannabinoid (CB) receptor agonists (HU-210, 0.1 mg/kg; ACPA, 0.125 mg/kg; methanandamide, 2.5 mg/kg; and anandamide, 2.5 mg/kg) induced bradycardia in chloralose-anesthetized rats irrespective of the solubilization method. Methanandamide, HU-210, and ACPA had no effect on the electrophysiological activity in the heart, while anandamide increased the duration of the QRS complex. The negative chronotropic effect of HU-210 was due to CB1 receptor activation since is was not observed after CB1 receptor blockade by SR141716A (1 mg/kg intravenously) but was present after pretreatment with CB2 receptor antagonist SR144528 (1 mg/kg intravenously). CB receptor antagonists SR141716A and SR144528 had no effect on cardiac rhythm or ECG indices. Hence, in the intact heart, endogenous CB receptor agonists are not involved in the regulation of cardiac rhythm and electrophysiological processes. The chronotropic effect of CBs was independent of the autonomic nervous system because it remained significant after autonomic ganglion blockade by hexamethonium (1 mg/kg intravenously). CB receptor activation by HU-210 (0.1 and 1 microM) in vitro decreased the rate and force of isolated heart contractions, the rates of contraction and relaxation, and end diastolic pressure. The negative chronotropic effect of HU-210 was less pronounced in vitro than in vivo. The maximum inotropic effect of HU-210 was reached at the concentration of 0.1 microM.

[ROLE OF OPIOID RECEPTORS IN THE REGULATION OF RESISTANCE OF HEART TO IMPACT OF ISCHEMIA-REPERFUSION].

Activation of m-, d1-, d2- and k1-opioid receptors increases cardiac resistance to ischemia-reperfusion. The cardioprotective effect of opioids in many cases appears to be associated with the activation of the peripheral OR. However, when it comes to non-peptide agonists OR able to cross the blood-brain barrier, we cannot exclude the involvement of central opioid receptors in cardioprotection. Endogenous opioids are not involved in the regulation of cardiac tolerance to ischemia- reperfusion in non-adapted animals. Stimulation of k1- and d1-OP may exert delayed cardioprotective effect. Activation d- and k1-OP reduces the intensity of cardiomyocyte apoptosis after reperfusion. The results of studies related to the inotropic effect of opioids during reperfusion of the heart remain highly controversial.

[THE ROLE OF THE ENDOGENOUS CANNABINOID SYSTEM IN THE FORMATION OF THE GENERAL ADAPTATION SYNDROME].

Nonopioid stress-induced analgesia is the consequence of activation of CB1 receptors by the increased level of 2-arachidonoyl glycerol, anandamide in the periaqueductal gray matter in the midbrain. The activation of cannabinoid CB1 receptors inhibits stress-induced ulcerogenesis due to the strengthening of the antioxidant defense of the gastric mucosa. CB1 receptor antagonists promote an increase in ACTH and corticosterone concentrations in the blood of intact animals, the knockout of the gene encoding the CB1 receptor exhibits the same effect. Antagonists of CB1 receptors enhance the stressor elevation of ACTH and corticosterone levels in the blood of experimental animals. It was found an increase in stress-induced elevation of corticosterone and ACTH levels in the blood of mice with a knockout of the gene encoding the CB1 receptor. An increase in the endogenous anandamide level or disturbance of the reuptake of endogenous cannabi-noids after application of pharmacological agents promotes reducing corticosterone level in stressed animals. Consequently, endogenous cannabinoids inhibit basal and suppress stress-induced activity of the hypothalamic-pituitary-adrenal axis. The indicated regulation is carried out on the level of the hypothalamus, pituitary and adrenal cortex. Stimulation of central cannabinoid receptors leads to an activation of the sympathetic system. The activation of peripheral CB1 receptors leads to inhibition of norepinephrine release from sympathetic terminals and epinephrine release from the adrenal glands. The endogenous CB1 receptor agonists play an anxiolytic role and prevent the occurrence of pathological anxiety.

[MIMICKING ISCHEMIC PRECONDITIONING PHENOMENON THROUGH THE IMPACT ON THE CANNABINOID RECEPTORS: ROLE OF PROTEIN KINASE AND NO-SYNTHASE].

It was established that CB 1-receptors stimulation mimic preconditioning phenomena. Since the cardioprotective effect of cannabinoid HU-210 is occurred both in the experiments in vivo and in the experiments in vitro there are reasons to believe that the protective effect of HU-210 is me- diated via an activation of cardiac CB1-receptors. It is established that the cardioprotective effect of cannabinoid HU-2 10 is depends upon a stimulation ofprotein kinase C whereas NO-synthase is not involved in protective impact of CB1-receptor stimulation.

[The anti-arrhythmic effect of the selective sigma-receptor antagonist DuP 734 [1-(cyclopropylmethyl)-4-(2'-(4''-fluorophenyl)-2'-oxoethyl)piper idine HBr]]. / Antiaritmicheskii éffekt selektivnogo antagonista sigma-retseptorov DuP734 [1-(tsiklopropilmetil)-4-(2'-(4''-fluorofenil)-2'-oksoétil)piperidin HBr].

It was demonstrated on models of epinephrine-, CaCl2-, and aconitine-induced arrhythmias that the sigma-receptor antagonist DuP734 possesses high antiarrhythmic activity in a dose of 1 mg/kg. The sigma-receptor agonist-(+)SKF10,047 promoted the development of ventricular fibrillation. Atropine had no effect on the antiarrhythmic properties of DuP734. "Chemical sympathectomy" of the myocardium with the ganglion-blocking agent hexamethonium also did not affect the proarrhythmic properties of (+)SKF10,047. It is supposed that selective sigma-receptor blocking agents may be highly effective antiarrhythmic drugs.

The anti-arrhythmia properties of the functional opioid agonist orphanin FQ (nociceptin). / Antiaritmicheskie svoistva funktsional'nogo agonista opioidov orfanina FQ (notsitseptina).

It was shown that the agonist of peripheral ORL1 receptors nociceptine raises heart resistance to the antiarrhythmic effect of aconitine. The antiarrhythmic effect of nociceptine is not connected with a change in the tonus of the autonomous nervous system or with an effect on opiate receptors. It is assumed that the antiarrhythmic properties of nociceptine are realized through inhibition of Na+/Ca2+ metabolism or blockade of rapid Na(+) channels of the cardiomyocytes.

[The anti-arrhythmic activity of agonists of the peripheral mu-opiate receptors]. / Antiaritmicheskaia aktivnost' agonistov perifericheskikh mu-opiatnykh retseptorov.

It was shown that the agonists of peripheral mu-receptors DALBA and PLO17 increase the resistance of the heart to adrenaline, aconitine, ischemic, reperfusion, and CaCl2-induced arrhythmias and also raise the threshold of ventricular fibrillation in postinfarction cardiosclerosis. The antagonists of mu-receptors naloxon and STAR removed these effects. The ganglion-blocking agent hexamethonium had no influence on the antiarrhythmic effect of DALBA. It is supposed that the autonomic nervous system does not play any essential role in the mechanism of the antiarrhythmic effect of agonists of peripheral mu-receptors.