Morphine preconditioning confers cardioprotection in doxorubicin-induced failing rat hearts via ERK/GSK-3β pathway independent of PI3K/Akt.

Preconditioning against myocardial ischemia-reperfusion (I/R) injury can be suppressed in some pathological conditions. This study was designed to investigate whether morphine preconditioning (MPC) exerts cardioprotection in doxorubicin (DOX)-induced heart failure in rats and the mechanisms involved. Phosphatidylinositol-3 kinase/protein kinase B (PI3K/Akt), extracellular signal-regulated kinase (ERK) and glycogen synthase kinase (GSK)-3β pathways were examined.

The function of calcineurin and ERK1/2 signal in the antihypertrophic effects of kappa-opioid receptor stimulation on myocardial hypertrophy induced by isoprenaline.

The aim of the present study, performed in an in vitro model of cardiac hypertrophy, was to examine the possible function of calcineurin and ERK1/2 in the inhibitory effects of kappa-opioid receptor stimulation on Ca2+ transients and myocardial hypertrophy induced by beta1-adrenoceptor stimulation. We determined the effects of trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamid methanesulfonate salt (U50,488H), a selective kappa-opioid receptor agonist, on the enhancement of spontaneous Ca2+ transients and the induction of hypertrophy by isoprenaline, a beta-adrenoceptor agonist, in cultured neonatal ventricular myocytes. Total protein content, [3H]leucine incorporation and cell size were used as indices of hypertrophy; calcineurin activity and phospho-ERK1/2 level were determined by immunoblotting.

Ionic mechanisms underlying cardiac toxicity of the organochloride solvent trichloromethane.

Trichloromethane (chloroform) is widely used for industrial chemical synthesis and also as an organic solvent in laboratories or ingredient of pesticides. Sudden death resulted from cardiac arrhythmias has been reported in clinic with acute trichloromethane intoxication. The present study was designed to investigate ionic mechanisms underlying arrhythmogenic effect (cardiac toxicity) of trichloromethane in isolated rat hearts and ventricular myocytes and HEK 293 cells stably expressing human Nav1.

Intracerebroventricular administration of morphine confers remote cardioprotection--role of opioid receptors and calmodulin.

The current study aimed to delineate the mechanism of remote preconditioning by intracerebroventricular morphine (RMPC) against myocardial ischemia-reperfusion injury. Male Sprague-Dawley rats were given an intracerebroventricular morphine injection before myocardial ischemia and reperfusion injury. Ischemia-reperfusion injury was achieved by 30min of left coronary artery occlusion followed by 120min of reperfusion.

Polyol pathway impairs the function of SERCA and RyR in ischemic-reperfused rat hearts by increasing oxidative modifications of these proteins.

A number of studies have shown that the polyol pathway, consisting of aldose reductase (AR) and sorbitol dehydrogenase (SDH), contributes to ischemia-reperfusion (I/R)-induced myocardial infarction due to depletion of ATP. In this report we show that the polyol pathway in I/R heart also contributes to the impairment of sacro/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and ryanodine receptor (RyR), two key players in Ca(2+) signaling that regulate cardiac contraction. Rat hearts were isolated and retrogradely perfused with either Krebs' buffer containing 1 microM AR inhibitor, zopolrestat, or 200 nM SDH inhibitor, CP-170,711, and challenged by 30 min of regional ischemia and 45 min of reperfusion.

Protein kinase C mediates the effects of delta-opioid receptor stimulation on survival and apoptosis in neonatal cardiomyocytes cultured in serum-deprived condition.

The aims of the present study were to determine whether Delta opioid receptor (delta-OR) stimulation improved the survival of cardiomyocytes cultured in serum-deprived conditions, which impaired their growth. [D-Ala2, D-Leu5]-enkephalin (DADLE), a selective delta-OR agonist, at a concentration range of 0.1 micromol/L to 10 micromol/L for 48 h increased the viability of the cardiomyocyte under serum deprivation conditions.

Effects of remifentanil on intracellular Ca(2+) and its transients induced by electrical stimulation and caffeine in rat ventricular myocytes.

Background: Preconditioning with remifentanil confers cardioprotection. Since Ca(2+) overload is a precipitating factor of injury, we determined the effects of remefentanil on intracellular Ca(2+) ([Ca(2+)](i)) and its transients induced by electrical stimulation and caffeine, which reflects Ca(2+) handling by Ca(2+) handling proteins, in rat ventricular myocytes.

Methods: Freshly isolated adult male Sprague-Dawley rat myocytes were loaded with Fura-2/AM and [Ca](i) was determined by spectrofluorometry.

Testosterone-augmented contractile responses to alpha1- and beta1-adrenoceptor stimulation are associated with increased activities of RyR, SERCA, and NCX in the heart.

We hypothesized that testosterone at physiological levels enhances cardiac contractile responses to stimulation of both alpha(1)- and beta(1)-adrenoceptors by increasing Ca(2+) release from the sarcoplasmic reticulum (SR) and speedier removal of Ca(2+) from cytosol via Ca(2+)-regulatory proteins. We first determined the left ventricular developed pressure, velocity of contraction and relaxation, and heart rate in perfused hearts isolated from control rats, orchiectomized rats, and orchiectomized rats without and with testosterone replacement (200 microg/100 g body wt) in the presence of norepinephrine (10(-7) M), the alpha(1)-adrenoceptor agonist phenylephrine (10(-6) M), or the nonselective beta-adrenoceptor agonist isoprenaline (10(-7) M) in the presence of 5 x 10(-7) M ICI-118,551, a beta(2)-adrenoceptor antagonist. Next, we determined the amplitudes of intracellular Ca(2+) concentration transients induced by electrical stimulation or caffeine, which represent, respectively, Ca(2+) release via the ryanodine receptor (RyR) or releasable Ca(2+) in the SR, in ventricular myocytes isolated from the three groups of rats.

Intrathecal morphine preconditioning induces cardioprotection via activation of delta, kappa, and mu opioid receptors in rats.

Background: Small doses of intrathecal morphine provide cardioprotection similar to that conferred by IV morphine. However, the extent of intrathecal morphine preconditioning (IT-MPC) relative to that resulting from ischemic preconditioning (IPC) is unknown. Further, it is uncertain whether IT-MPC is mediated by opioid receptor dependent pathways.

kappa-Opioid receptor stimulation inhibits augmentation of Ca(2+) transient and hypertrophy induced by isoprenaline in neonatal rat ventricular myocytes - Role of CaMKIIdelta(B).

We aimed to further define the pathway mediating the inhibitory effects of kappa-opioid receptor stimulation on Ca(2+) transients and hypertrophic responses to beta(1)-adrenoceptor stimulation. We determined the effects of trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamid methanesulfonate salt (U50,488H), a selective kappa-opioid receptor agonist, on the enhancement of spontaneous Ca(2+) transients and the induction of hypertrophy by isoprenaline, a beta-adrenoceptor agonist, in cultured neonatal ventricular myocytes. The results were compared with those found with KN93, a selective Ca(2+)/calmodulin-dependent kinase (CaMKII) inhibitor, propranolol, a beta-adrenoceptor antagonist, and verapamil, a L-type Ca(2+) channel antagonist.

Polyol pathway mediates iron-induced oxidative injury in ischemic-reperfused rat heart.

Recent studies have shown that the polyol pathway is involved in ischemia-reperfusion (I/R)-induced myocardial infarction, but the mechanism is unclear. We previously found that lack of aldose reductase (AR), the first enzyme of the polyol pathway, attenuated the increase in transferrin (Tf) level in I/R brain, suggesting that AR contributes to iron-catalyzed free radical-induced damage. We therefore investigated if this mechanism occurs in I/R hearts.

2-hydroxyoleic acid affects cardiomyocyte [Ca2+]i transient and contractility in a region-dependent manner.

Monounsaturated fatty acids such as oleic acid are cardioprotective, modify the physicochemical properties of cardiomyocyte membranes, and affect the electrical stability of these cells by regulating the conductance of ion channels. We have designed a nonhydrolysable oleic acid derivative, 2-hydroxyoleic acid (2-OHOA), which regulates membrane lipid structure and cell signaling, resulting in beneficial cardiovascular effects. We previously demonstrated that 2-OHOA induces PKA activation and PKCalpha translocation to the membrane; both pathways are thought to regulate transient outward K(+) current (I(to)) depending on the stimulus and the species used.

delta-Opioid receptor stimulation enhances the growth of neonatal rat ventricular myocytes via the extracellular signal-regulated kinase pathway.

1. The aims of the present study were to determine whether delta-opioid receptor stimulation enhanced proliferation of and to investigate the role of the extracellular signal-regulated kinase (ERK) pathway in ventricular myocytes from neonatal rats. 2.

Involvement of voltage-gated K+ and Na+ channels in gastric epithelial cell migration.

Epithelial cell migration plays an important role in gastrointestinal mucosal repair. We previously reported that multiple functional ion channels, including a Ba(2+)-sensitive K(+) inward rectifier K(ir)1.2, 4-aminopyridine (4-AP)-sensitive voltage-gated K(+) channels K(v)1.

Cardioprotection by the female sex hormone -- interaction with the beta₁-adrenoceptor and its signaling pathways.

Estrogen is a steroid and the predominant female sex hormone in the body. Ovariectomised (OVX) adult female rats exhibit greater myocardial injury compared to the sham rats following ischemic insult in the presence of beta-adrenoceptor stimulation. Estrogen replacement restores the response of OVX female rats to ischemic/beta-adrenoceptor stimulation to that of normal female rats, providing evidence for a cardioprotective role of estrogen during ischemic insult.

Testosterone and cardioprotection against myocardial ischemia.

Male gender is a risk factor for cardiovascular diseases. Testosterone being the main male sex hormone is therefore believed to be responsible for the deleterious effect of the male. However, there are recent studies showing that testosterone level is lower in patients with ischemic heart diseases, and testosterone treatment alleviates the symptoms.

Role of reverse mode Na+/Ca2+ exchanger in the cardioprotection of metabolic inhibition preconditioning in rat ventricular myocytes.

This study determined the role of the reverse mode Na(+)/Ca(2+) exchanger (NCX) in cardioprotection of metabolic inhibition preconditioning in isolated ventricular myocyctes. Activity of the reverse mode NCX was assessed by changes of [Ca(2+)](i) upon withdrawal of extracellular Na(+). [Ca(2+)](i) was measured by spectrofluorometry, using Fura-2 as Ca(2+) indicator.

Chronic intermittent hypoxia alters Ca2+ handling in rat cardiomyocytes by augmented Na+/Ca2+ exchange and ryanodine receptor activities in ischemia-reperfusion.

This study examined Ca(2+) handling mechanisms involved in cardioprotection induced by chronic intermittent hypoxia (CIH) against ischemia-reperfusion (I/R) injury. Adult male Sprague-Dawley rats were exposed to 10% inspired O(2) continuously for 6 h daily from 3, 7, and 14 days. In isolated perfused hearts subjected to I/R, CIH-induced cardioprotection was most significant in the 7-day group with less infarct size and lactate dehydrogenase release, compared with the normoxic group.

Altered Ca(2+) handling by ryanodine receptor and Na(+)-Ca(2+) exchange in the heart from ovariectomized rats: role of protein kinase A.

Our previous study has demonstrated that ovariectomy (Ovx) significantly increased the left ventricular developed pressure (LVDP) and the maximal rate of developed pressure over time (+/-dP/dt(max)) in the isolated perfused rat heart and the effects were reversed by female sex hormone replacement. In the present investigation, we studied the effects of Ovx for 6 wk on Ca(2+) homeostasis that determines the contractile function. Particular emphasis was given to Ca(2+) handling by ryanodine receptor (RyR) and Na(+)-Ca(2+) exchange (NCX).

kappa-opioid receptor stimulation inhibits cardiac hypertrophy induced by beta1-adrenoceptor stimulation in the rat.

To test the hypothesis that kappa-opioid receptor stimulation inhibits cardiac hypertrophy induced by beta1-adrenoceptor stimulation, we determined the effects of trans-(+/-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide methanesulfonate salt (U50,488H), a selective kappa-opioid receptor agonist, on cardiac hypertrophy induced by isoprenaline, a selective beta-adrenoceptor agonist, in neonatal ventricular myocytes upon blockade of beta2-adrenoceptor. Hypertrophy of cardiomyocytes was determined by increases in (i) total protein content; (ii) [3H]leucine incorporation; and iii) cell size. 10 micromol/l isoprenaline increased all three parameters.

Testosterone is required for delayed cardioprotection and enhanced heat shock protein 70 expression induced by preconditioning.

Ischemic preconditioning fails to confer immediate cardioprotection in the absence of testosterone, indicating that the hormone is required for the process. Here we set out to determine whether testosterone is also necessary for delayed cardioprotection and, if so, how it acts. Male Sprague Dawley rats (7-8 wk) underwent sham operation or gonadectomy without (G) or with testosterone replacement (GT) for 8 wk.

Attenuation of mitochondrial, but not cytosolic, Ca2+ overload reduces myocardial injury induced by ischemia and reperfusion.

Aim: Attenuation of mitochondrial Ca2+ ([Ca2+]m), but not cytosolic Ca2+ ([Ca2+]c), overload improves contractile recovery. We hypothesized that attenuation of [Ca2+]m, but not [Ca2+]c, overload confers cardioprotection against ischemia/reperfusion-induced injury.

Methods: Infarct size from isolated perfused rat heart, cell viability, and electrically-induced Ca2+ transient in isolated rat ventricular myocytes were measured.

Further study on the role of HSP70 on Ca2+ homeostasis in rat ventricular myocytes subjected to simulated ischemia.

We hypothesized that activation of heat shock protein 70 (HSP70) by preconditioning, which is known to confer delayed cardioprotection, attenuates the impaired handling of Ca(2+) at multiple sites. To test the hypothesis, we determined how the ryanodine receptor (RyR), sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA), and Na(+)/Ca(2+) exchanger (NCX) handled Ca(2+) in rat ventricular myocytes preconditioned with a kappa-opioid receptor agonist, U50488H (UP), followed by blockade of HSP70 with a selective antisense oligonucleotide and subsequently subjected to simulated ischemia. We determined the following: 1) the Ca(2+) transients induced by electrical stimulation and caffeine, which provide the overall picture of Ca(2+) homeostasis; 2) expression of RyR, SERCA, and NCX; and 3) Ca(2+) fluxes via NCX by the use of (45)Ca(2+) in the rat ventricular myocyte.

In vitro electrophysiologic effects of morphine in rabbit ventricular myocytes.

Background: Morphine is widely used in patients undergoing surgical operations and is also reported to mediate cardioprotection of preconditioning. The current study determined effects of morphine at therapeutic to pharmacologic concentrations on cardiac action potential, L-type Ca2+ current (ICa.L), delayed rectifier K+ current (IK), and inward rectifier K+ current (IK1) in isolated rabbit ventricular myocytes.

The K(Ca) channel as a trigger for the cardioprotection induced by kappa-opioid receptor stimulation -- its relationship with protein kinase C.

We first determined whether the cardioprotection resulting from kappa opioid receptor (kappa-OR) stimulation was blocked by the K(Ca) channel inhibitor, paxilline (Pax), administered before or during ischaemic insults in vitro. In isolated rat hearts, 30 min of ischaemia and 120 min of reperfusion induced infarction and increased lactate dehydrogenase (LDH) release. In isolated ventricular myocytes subjected to 5 min of metabolic inhibition and anoxia followed by 10 min of reperfusion, the percentage of live cells and the amplitude of the electrically induced intracellular Ca(2+) ([Ca(2+)](i)) transient decreased, while diastolic [Ca(2+)](i) increased.