Nitric Oxide/Glucose Transporter Type 4 Pathway Mediates Cardioprotection against Ischemia/Reperfusion Injury under Hyperglycemic and Diabetic Conditions in Rats.

INTRODUCTION: The comorbidities of ischemic heart disease (IHD) and diabetes mellitus (DM) compromise the protection of the diabetic heart from ischemia/reperfusion (I/R) injury. We hypothesized that manipulation of reperfusion injury salvage kinase (RISK) and survivor activating factor enhancement (SAFE) pathways might protect the diabetic heart, and intervention of these pathways could be a new avenue for potentially protecting the diabetic heart. METHODS: All hearts were subjected to 30-min ischemia and 30-min reperfusion. During reperfusion, hearts were exposed to molecules proven to protect the heart from I/R injury. The hemodynamic data were collected using suitable software. The infarct size, troponin T levels, and protein levels in hearts were evaluated. RESULTS: Both cyclosporine-A and nitric oxide donor (SNAP) infusion at reperfusion protected 4-week diabetic hearts from I/R injury. However, 6-week diabetic hearts were protected only by SNAP, but not cyclosporin-A. These treatments significantly (p < 0.05) improved cardiac hemodynamics and decreased infarct size. CONCLUSIONS: The administration of SNAP to diabetic hearts protected both 4- and 6-week diabetic hearts; however, cyclosporine-A protected only the 4-week diabetic hearts. The eNOS/GLUT-4 pathway executed the SNAP-mediated cardioprotection.

High-Density Lipoprotein Signaling via Sphingosine-1-Phosphate Receptors Safeguards Spontaneously Hypertensive Rats against Myocardial Ischemia/Reperfusion Injury.

BACKGROUND: High-density lipoprotein (HDL) protects against ischemia/reperfusion (I/R) injury via signaling through scavenger-receptor class B type-I (SR-BI) and sphingosine-1-phosphate receptors (S1PRs). We recently reported that HDL protects the hearts of spontaneously hypertensive rats (SHRs) against I/R injury in an SR-BI-dependent manner. OBJECTIVE: In this study, we examined the role of S1PRs in HDL-induced protection against myocardial I/R injury in hypertensive rats. METHODS: Hearts from Wistar Kyoto rats (WKYs) and SHRs were subjected to I/R injury using a modified Langendorff system. The hearts were treated with or without HDL in the presence or absence of a receptor- or kinase-specific antagonist. Cardiac hemodynamics and infarct size were measured. Target proteins were analyzed by immunoblotting and ELISA, and nitrite levels were measured using Greis reagent. RESULTS: HDL protected the hearts of WKYs and SHRs against I/R injury. HDL, however, was more protective in WKYs. HDL protection in SHRs required lipid uptake via SR-BI and S1PR1 and S1PR3 but not S1PR2. The hearts from SHRs expressed significantly lower levels of S1PR3 than the hearts from WKYs. HDL differentially activated mediators of the SAFE and RISK pathways in WKYs and SHRs and resulted in nitric oxide generation. Blockage of these pathways abrogated HDL effects. CONCLUSIONS: HDL protects against myocardial I/R injury in normotensive and hypertensive rats, albeit to varying degrees. HDL protection in hearts from hypertensive rodents involved SR-BI-mediated lipid uptake coupled with signaling through S1PR1 and S1PR3. The extent of HDL-induced cardiac protection is directly proportional to S1PR3 expression levels. Mechanistically, the safeguarding effects of HDL involved activation of the SAFE and RISK pathways and the generation of nitric oxide.

Impaired Insulin Signaling Alters Mediators of Hippocampal Synaptic Dynamics/Plasticity: A Possible Mechanism of Hyperglycemia-Induced Cognitive Impairment.

Alzheimer's disease (AD) is a neurological condition that affects the elderly and is characterized by progressive and irreversible neurodegeneration in the cerebral cortex [...].

Renin-Angiotensin System Antagonism Protects the Diabetic Heart from Ischemia/Reperfusion Injury in Variable Hyperglycemia Duration Settings by a Glucose Transporter Type 4-Mediated Pathway.

BACKGROUND: Diabetes mellitus (DM) is a risk factor for cardiovascular diseases, specifically, the ischemic heart diseases (IHD). The renin-angiotensin system (RAS) affects the heart directly and indirectly. However, its role in the protection of the heart against I/R injury is not completely understood. The aim of the current study was to evaluate the efficacy of the angiotensin-converting enzyme (ACE) inhibitor and Angiotensin II receptor (AT1R) blocker or a combination thereof in protection of the heart from I/R injury. METHODS: Hearts isolated from adult male Wistar rats (n = 8) were subjected to high glucose levels; acute hyperglycemia or streptozotocin (STZ)-induced diabetes were used in this study. Hearts were subjected to I/R injury, treated with Captopril, an ACE inhibitor; Losartan, an AT1R antagonist; or a combination thereof. Hemodynamics data were measured using a suitable software for that purpose. Additionally, infarct size was evaluated using 2,3,5-Triphenyltetrazolium chloride (TTC) staining. The levels of apoptosis markers (caspase-3 and -8), antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), nitric oxide synthase (eNOS), and glucose transporter type 4 (GLUT-4) protein levels were evaluated by Western blotting. Pro-inflammatory and anti-inflammatory cytokines levels were evaluated by enzyme-linked immunosorbent assay (ELISA). RESULTS: Captopril and Losartan alone or in combination abolished the effect of I/R injury in hearts subjected to acute hyperglycemia or STZ-induced diabetes. There was a significant (p < 0.05) recovery in hemodynamics, infarct size, and apoptosis markers following the treatment with Captopril, Losartan, or their combination. Treatment with Captopril, Losartan, or their combination significantly (p < 0.05) reduced pro-inflammatory cytokines and increased GLUT-4 protein levels. CONCLUSIONS: The blockade of the RAS system protected the diabetic heart from I/R injury. This protection followed a pathway that utilizes GLUT-4 to decrease the apoptosis markers, pro-inflammatory cytokines, and to increase the anti-inflammatory cytokines. This protection seems to employ a pathway which is not involving ERK1/2 and eNOS.

Effects of Apocynin, a NADPH Oxidase Inhibitor, in the Protection of the Heart from Ischemia/Reperfusion Injury.

Ischemia and perfusion (I/R) induce inflammation and oxidative stress, which play a notable role in tissue damage. The aim of this study was to investigate the role of an NADPH oxidase inhibitor (apocynin) in the protection of the heart from I/R injury. Hearts isolated from Wistar rats (n = 8 per group) were perfused with a modified Langendorff preparation. Left ventricular (LV) contractility and cardiovascular hemodynamics were evaluated by a data acquisition program, and infarct size was evaluated by 2,3,5-Triphenyl-2H-tetrazolium chloride (TTC) staining. Furthermore, the effect of apocynin on the pro-inflammatory cytokines (IL-1ß, IL-6 and TNF-α) and anti-inflammatory cytokine (IL-10) was evaluated using an enzyme linked immunosorbent assay (ELISA). Hearts were subjected to 30 min of regional ischemia, produced by ligation of the left anterior descending (LAD) coronary artery, followed by 30 min of reperfusion. Hearts were infused with apocynin before ischemia, during ischemia or at reperfusion. To understand the potential pathways of apocynin protection of the heart, a nitric oxide donor (S-nitroso-N-acetylpenicillamine, SNAP), nitric oxide blocker (N (gamma)-nitro-L-arginine methyl ester, L-Name), nicotinic acid adenine dinucleotide phosphate (NAADP) inhibiter (Ned-K), cyclic adenosine diphosphate ribose (cADPR) agonist, or CD38 blocker (Thiazoloquin (az)olin (on)e compound, 78c) was infused with apocynin. Antioxidants were evaluated by measuring superoxide dismutase (SOD) and catalase (CAT) activity. Apocynin infusion before ischemia or at reperfusion protected the heart by normalizing cardiac hemodynamics and decreasing the infarct size. Apocynin treatment resulted in a significant (p < 0.05) decrease in pro-inflammatory cytokine levels and a significant increase (p < 0.05) in anti-inflammatory and antioxidant levels. Apocynin infusion protected the heart by improving LV hemodynamics and coronary vascular dynamics. This treatment decreased the infarct size and inflammatory cytokine levels and increased anti-inflammatory cytokine and antioxidant levels. This protection follows a pathway involving CD38, nitric oxide and acidic stores.

Early time course of oxidative stress in hippocampal synaptosomes and cognitive loss following impaired insulin signaling in rats: Development of sporadic Alzheimer's disease.

Oxidative stress, caused by impaired insulin signaling, plays a pivotal role in the pathogenesis of sporadic Alzheimer's disease (sAD). We investigated the oxidative stress parameters in the synaptosomes prepared from the hippocampus tissue in order to identify their potential role in sAD development in intraperitoneal (IP) and intracerebroventricular (ICV) streptozotocin (STZ) injections models of insulin signaling impairment. Rats were harvested 1, 3, or 6 weeks post treatment. Spatial learning and memory, several antioxidants and oxidative stress markers were analyzed. Results showed a significant deficit in learning and memory in rats injected with STZ through IP and ICV routes. Glutathione, glutathione/oxidized glutathione, glutathione S-transferase, glutathione peroxidase, glutathione reductase, catalase, superoxide dismutase(SOD)-total, Zn/Cu(SOD), Mn/Fe(SOD) are significantly decreased in IP-STZ and ICV-STZ groups at 1, 3, and 6 weeks after STZ injection. Oxidized glutathione, thiobarbituric acid reactive species, glucose 6-Phosphate dehydrogenase, protein carbonyls, 4-Hydroxynonenal, and 3-Nitrotyrosine are significantly increased in IP-STZ and ICV-STZ groups at 1,3, and 6 weeks after STZ injection. Changes in oxidative stress parameters in ICV-STZ groups are greater than IP-STZ groups. STZ treatment induced cognitive impairments by 3-W and 6-W, and it was significantly correlated with the extent of oxidative damage. In conclusion, STZ administration through ICV route is deleterious in causing early synaptosomal oxidative damage that exacerbated with time and correlated with cognitive impairments. Our data implicate the involvement of oxidative stress as an early feature of sAD and provide insights into the behavioral and biochemical changes over the course of disease development.

Mitigating Cardiotoxicity of Dendrimers: Angiotensin-(1-7) via Its Mas Receptor Ameliorates PAMAM-Induced Cardiac Dysfunction in the Isolated Mammalian Heart.

AIM: The influence of the physiochemical properties of dendrimer nanoparticles on cardiac contractility and hemodynamics are not known. Herein, we investigated (a) the effect of polyamidoamine (PAMAM) dendrimer generation (G7, G6, G5, G4 and G3) and surface chemistry (-NH2, -COOH and -OH) on cardiac function in mammalian hearts following ischemia-reperfusion (I/R) injury, and (b) determined if any PAMAM-induced cardiotoxicity could be mitigated by Angiotensin-(1-7) (Ang-(1-7), a cardioprotective agent. METHODS: Hearts isolated from male Wistar rats underwent regional I/R and/or treatment with different PAMAM dendrimers, Ang-(1-7) or its MAS receptors antagonists. Thirty minutes of regional ischemia through ligation of the left anterior descending coronary artery was followed by 30 min of reperfusion. All treatments were initiated 5 min prior to reperfusion and maintained during the first 10 min of reperfusion. Cardiac function parameters for left ventricular contractility, hemodynamics and vascular dynamics data were acquired digitally, whereas cardiac enzymes and infarct size were used as measures of cardiac injury. RESULTS: Treatment of isolated hearts with increasing doses of G7 PAMAM dendrimer progressively exacerbated recovery of cardiac contractility and hemodynamic parameters post-I/R injury. Impairment of cardiac function was progressively less on decreasing dendrimer generation with G3 exhibiting little or no cardiotoxicity. Cationic PAMAMs (-NH2) were more toxic than anionic (-COOH), with neutral PAMAMs (-OH) exhibiting the least cardiotoxicity. Cationic G7 PAMAM-induced cardiac dysfunction was significantly reversed by Ang-(1-7) administration. These cardioprotective effects of Ang-(1-7) were significantly revoked by administration of the MAS receptor antagonists, A779 and D-Pro7-Ang-(1-7). CONCLUSIONS: PAMAM dendrimers can impair the recovery of hearts from I/R injury in a dose-, dendrimer-generation-(size) and surface-charge dependent manner. Importantly, PAMAM-induced cardiotoxicity could be mitigated by Ang-(1-7) acting through its MAS receptor. Thus, this study highlights the activation of Ang-(1-7)/Mas receptor axis as a novel strategy to overcome dendrimer-induced cardiotoxicity.

Gum Arabic protects the rat heart from ischemia/reperfusion injury through anti-inflammatory and antioxidant pathways.

Gum Arabic (GA) is a plant exudate with antioxidant and anti-inflammatory effects. GA has shown promise in protection from and treatment of kidney failure, however, its role in the protection of the heart from ischemia and reperfusion (I/R) has not been investigated. This study investigated the antioxidant and anti-inflammatory effects of Gum Arabic (GA) in the protection of the heart against ischemia/reperfusion (I/R) injury. Langendorff-perfused Wistar rat hearts were divided into seven groups. One group which was subjected to I/R with no other treatment served as the control group. The second group was subjected to buffer perfusion with no ischemia (sham group). The third group was perfused with GA in the absence of ischemia (sham + GA). The rest of the hearts were isolated from rats that had been treated with GA for 4 or 2 weeks in the drinking water, or GA that had been infused intravenously 2 h before sacrifice or added to perfusion buffer at reperfusion. Hemodynamics data were digitally computed; infarct size was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining and cardiomyocyte injury was assessed by quantifying creatine kinase (CK) and lactate dehydrogenase (LDH) enzymes. The total oxidants (TOS) and antioxidants (TAS), superoxide dismutase (SOD) and pro- and anti-inflammatory cytokines levels were estimated by ELISA. GA treatment for 2 weeks, 4 weeks or 2 hours before sacrifice resulted in a significant (P < 0.05) improvement in cardiac hemodynamics and reduction in infarct size and cardiac enzyme levels compared to respective controls. However, GA administration at the time of reperfusion did not protect the hearts against I/R injury. Furthermore, GA treatment decreased the pro-inflammatory and anti-inflammatory cytokines levels. The levels of TOS in the effluent were significantly decreased (P < 0.05) and SOD levels were significantly (P < 0.05) increased by GA administration. GA protected the heart against I/R injury when administered for 2 or 4 weeks or when infused 2 hours before sacrifice. GA treatment decreased the total oxidants levels, the pro-inflammatory cytokines TNF-α, IL-1ß and IL-6 protein levels and increases SOD and anti-inflammatory cytokine IL-10 protein levels.

Discrepancy between the Actions of Glucagon-like Peptide-1 Receptor Ligands in the Protection of the Heart against Ischemia Reperfusion Injury.

Tirzepatide is a dual glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) receptor agonist and a promising therapy for type 2 diabetes mellitus (T2DM). GLP-1 is an incretin hormone with therapeutic potential beyond type 2 diabetes mellitus. However, GLP-1 is rapidly degraded by dipeptdyl peptidase-IV (DPP-IV) to GLP-1 (9-36). Exendin-4 (Ex-4) is a DPP-IV-resistant GLP-1 receptor agonist which, when truncated to Ex-4 (9-39), acts as a GLP-1 receptor antagonist. In the present study, hearts isolated from Wistar rats (n = 8 per group) were perfused with a modified Langendorff preparation. Left ventricular (LV) contractility and cardiovascular hemodynamics were evaluated by a data acquisition program and infarct size was evaluated by 2,3,5-Triphenyl-2H-tetrazolium chloride (TTC) staining and cardiac enzyme levels. Hearts were subjected to 30 min regional ischemia, produced by ligation of the left anterior descending (LAD) coronary artery followed by 30 min reperfusion. Hearts were treated during reperfusion with either the non-lipidated precursor of tirzepatide (NLT), GLP-1, GLP-1 (9-36), or Ex-4 in the presence or absence of Ex-4 (9-39). Infusion of GLP-1 (9-36) or Ex-4 protected the heart against I/R injury (p > 0.01) by normalizing cardiac hemodynamic and enzyme levels. Neither GLP-1, NLT, nor Ex-4 (9-39) showed any protection. Interestingly, Ex-4 (9-39) blocked Ex-4-mediated protection but not that of GLP-1 (9-36). These data suggest that Ex-4-mediated protection is GLP-1-receptor-dependent but GLP-1 (9-36)-mediated protection is not.

High Density Lipoprotein Reduces Blood Pressure and Protects Spontaneously Hypertensive Rats Against Myocardial Ischemia-Reperfusion Injury in an SR-BI Dependent Manner.

Background: Hypertension is a key risk factor in the development of cardiovascular diseases. Elevation in blood pressure alters high density lipoprotein (HDL) function and composition. The exact role of HDL in cardiovascular complications observed in hypertension is however not clearly understood. HDL protected against myocardial ischemia/reperfusion (I/R) injury in normotensive rats. Nonetheless, it's not clear if restoration of HDL function and/or composition protects against myocardial I/R injury in spontaneously hypertensive rats (SHR). Objectives: In this study we tested the effect of HDL treatment on I/R injury in Wistar Kyoto rats (WKY) and SHR and investigated the possible underlying mechanism(s). Methods: HDL (900 ng/kg/min) or vehicle were continuously administered to 11-week old WKY and SHR for 1 week (chronic treatment). Blood pressure was measured before and after treatment. Hearts were subjected to I/R injury using a modified Langendorff system. Another set of rats were treated with HDL administered at reperfusion (acute treatment) in the presence or absence of scavenger receptor class B type-I (SR-BI) blocking antibody. Cardiac hemodynamics were computed and cardiac enzyme release and infarct size were measured. Total cholesterol (TC) and HDL-cholesterol (HDL-C) were enzymatically assayed. Markers of autophagy and inflammation were detected by immunoblotting and ELISA, respectively. Results: HDL treatment did not increase TC or HDL-C levels in SHR or WKY, yet it significantly (P < 0.01) reduced systolic and diastolic blood pressure in SHR. Chronic and acute HDL treatment significantly (P < 0.05) protected WKY and SHR against myocardial I/R injury. Chronic HDL treatment was significantly (P < 0.05) more protective in SHR whereas acute HDL treatment induced significantly (P < 0.05) greater protection in WKY. The extent of HDL induced protection was proportional to the expression levels of cardiac SR-BI and blockage of SR-BI completely abolished HDL mediated protection in SHR. Chronic HDL treatment significantly (P < 0.05) reduced markers of autophagy and inflammation in hypertensive rats. Conclusions: We demonstrate a novel anti-hypertensive and a cardioprotective effect of HDL against myocardial I/R injury in SHR, the magnitude of which is directly related to the expression levels of cardiac SR-BI. Mechanistically, chronic HDL treatment protected SHR hearts by reducing autophagy and inflammation.

Nanotoxicology of Dendrimers in the Mammalian Heart: ex vivo and in vivo Administration of G6 PAMAM Nanoparticles Impairs Recovery of Cardiac Function Following Ischemia-Reperfusion Injury.

AIM: The effects of polyamidoamine (PAMAM) dendrimers on the mammalian heart are not completely understood. In this study, we have investigated the effects of a sixth-generation cationic dendrimer (G6 PAMAM) on cardiac function in control and diabetic rat hearts following ischemia-reperfusion (I/R) injury. METHODS: Isolated hearts from healthy non-diabetic (Ctr) male Wistar rats were subjected to ischemia and reperfusion (I/R). LV contractility and hemodynamics data were computed digitally whereas cardiac damage following I/R injury was assessed by measuring cardiac enzymes. For ex vivo acute exposure experiments, G6 PAMAM was administered during the first 10 mins of reperfusion in Ctr animals. In chronic in vivo studies, nondiabetic rats (Ctr) received either vehicle or daily i.p. injections of G6 PAMAM (40 mg/kg) for 4 weeks. Diabetic (D) animals received either vehicle or daily i.p. injections of G6 PAMAM (10, 20 or 40 mg/kg) for 4 weeks. The impact of G6 PAMAM on pacing-postconditioning (PPC) was also studied in Ctr and D rats. RESULTS: In ex vivo studies, acute administration of G6 PAMAM to isolated Ctr hearts during reperfusion dose-dependently impaired recovery of cardiac hemodynamics and vascular dynamics parameters following I/R injury. Chronic daily i.p. injections of G6 PAMAM significantly (P<0.01) impaired recovery of cardiac function following I/R injury in nondiabetic animals but this was not generally observed in diabetic animals except for CF which was impaired by about 50%. G6 PAMAM treatment completely blocked the protective effects of PPC in the Ctr animals. CONCLUSION: Acute ex vivo or chronic in vivo treatment with naked G6 PAMAM dendrimer can significantly compromise recovery of non-diabetic hearts from I/R injury and can further negate the beneficial effects of PPC. Our findings are therefore extremely important in the nanotoxicological evaluation of G6 PAMAM dendrimers for potential clinical applications in physiological and pathological settings.

Expression of Concern to: The role of ACE2, angiotensin-(1-7) and Mas1 receptor axis in glucocorticoid-induced intrauterine growth restriction.

An amendment to this paper has been published and can be accessed via the original article.

Effects of Cardiac Hypertrophy, Diabetes, Aging, and Pregnancy on the Cardioprotective Effects of Postconditioning in Male and Female Rats.

BACKGROUND: Aging, left ventricular hypertrophy (LVH), diabetes mellitus, and pregnancy are well-recognized risk factors that increase the prevalence of cardio-ischemic events and are linked to poor clinical recovery following acute myocardial infarction. The coexistence of these risk factors with ischemic heart disease (IHD) deteriorates disease prognosis and could potentially lead to fatal arrhythmias and heart failure. The objective of this study was to investigate the vulnerability of hearts with aging, LVH, diabetes, and pregnancy to ischemic insult and their response to pacing postconditioning- (PPC-) induced heart protection. METHODS: Hearts isolated from aged, spontaneously hypertensive and diabetic male and female rats and hearts from pregnant female rats (n=8 per group) were subjected to coronary occlusion followed by reperfusion using a modified Langendorff system. Hemodynamics data were computed digitally, and cardiac damage was accessed by measurements of infarct size and cardiac enzyme release. RESULTS: There were no significant differences in the vulnerability of all hearts to ischemic insult compared to their respective controls. PPC improved cardiac hemodynamics and reduced infarct size and cardiac enzyme release in hearts isolated from aged and spontaneously hypertensive female rats and female rats with hypertrophied hearts subjected to PPC (P < 0.001). Aged or hypertrophied male hearts were not protected by PPC maneuver. Moreover, the protective effects of PPC were lost in diabetic male and female hearts although retained in hearts from pregnant rats. CONCLUSIONS: We demonstrate that aging, LVH, diabetes mellitus, and pregnancy do not affect cardiac vulnerability to ischemic insult. Moreover, PPC mediates cardioprotection in a gender-specific manner in aged and spontaneously hypertensive rats. Diabetes mellitus provokes the protective effects of PPC on both genders equally. Finally, we demonstrate that PPC is a new cardioprotective maneuver in hearts from pregnant female rats.

Lead exposure induces oxidative stress, apoptosis, and attenuates protection of cardiac myocytes against ischemia-reperfusion injury.

Disrupting role of lead toxicity in heart functions and prognosis of cardiovascular diseases is not well known. This study investigated the interference of lead in heart functions and pacing postconditioning-mediated protection to the heart from ischemia-reperfusion injury. Lead exposure decreased the body weight and increased the heart weight in male rats (p < 0.001). Long-term lead exposure (45 days exposure to lead) increased total oxidant levels (p < 0.001) in the heart. Furthermore, lead exposure abrogated the pacing postconditioning-mediated protection from ischemia-reperfusion injury. The latter effect showed an association with reduced total antioxidants levels (p < 0.001). In the short-term study (5 days exposure to lead), pacing postconditioning protected the heart from ischemia-reperfusion injury despite the reduced total antioxidant levels (p < 0.001). Lead toxicity caused a drastic increase in the heart weight in male rats and apoptosis. The induced oxidative stress showed association with the lack of pacing postconditioning-mediated protection of the heart. However, long-term lead exposure eliminated pacing postconditioning-mediated protection of the heart from ischemia-reperfusion injury.

Acute Intravenous Infusion of Immunoglobulins Protects Against Myocardial Ischemia-Reperfusion Injury Through Inhibition of Caspase-3.

BACKGROUND/AIMS: To investigate the cardioprotective effects of intravenous immunoglobulins (IVIG) in rats subjected to regional myocardial ischemia reperfusion (I/R). METHODS: Langendorff-perfused rat hearts were used in this study. Hearts subjected to regional ischemia served as a negative untreated control. The effects of IVIG pre- and post-ischemic treatment on left ventricular function, coronary vascular dynamics and contractility were assessed. IVIG were administered in either a low or high dose. The infarct size was determined using triphenyltetrazolium chloride and through biochemical assays using the measured creatine kinase and lactate dehydrogenase levels. Apoptosis was evaluated by the TUNEL assay, and the caspase-3 expression level was assessed by immunoblotting. The cytokine levels were measured by ELISA. RESULTS: Low and high doses of immunoglobulins administered 2 hours before sacrifice, before the ischemic insult or at reperfusion resulted in a significant improvement in cardiac hemodynamics, coronary vascular dynamics and heart contractility. A significant decrease in the infarct size and cardiac enzymes was also evident compared to those in the control. IVIG administered as an infusion at reperfusion or pre-treatment resulted in a marked decrease in myocyte apoptosis, which was associated with decreased levels of caspase-3 expression in the supernatants of homogenized left ventricles. Infusion of IVIG both pre-ischemia and at reperfusion did not show the same protective effects. CONCLUSIONS: This study demonstrates a novel protection to the heart by low and high doses of IVIG given either pre- or post-ischemia.

Understanding pacing postconditioning-mediated cardiac protection: a role of oxidative stress and a synergistic effect of adenosine

We and others have demonstrated a protective role for pacing postconditioning (PPC) against ischemia/reperfusion (I/R) injury in the heart; however, the underlying mechanisms behind these protective effects are not completely understood. In this study, we wanted to further characterize PPC-mediated cardiac protection, specifically identify optimal pacing sites; examine the role of oxidative stress; and test the existence of a potential synergistic effect between PPC and adenosine. Isolated rat hearts were subjected to coronary occlusion followed by reperfusion. PPC involved three, 30 s, episodes of alternating left ventricular (LV) and right atrial (RA) pacing. Multiple pacing protocols with different pacing electrode locations were used. To test the involvement of oxidative stress, target-specific agonists or antagonists were infused at the beginning of reperfusion. Hemodynamic data were digitally recorded, and cardiac enzymes, oxidant, and antioxidant status were chemically measured. Pacing at the LV or RV but not at the heart apex or base significantly (P < 0.001) protected against ischemia-reperfusion injury. PPC-mediated protection was completely abrogated in the presence of reactive oxygen species (ROS) scavenger, ebselen; peroxynitrite (ONOO-) scavenger, uric acid; and nitric oxide synthase inhibitor, L-NAME. Nitric oxide (NO) donor, snap, however significantly (P < 0.05) protected the heart against I/R injury in the absence of PPC. The protective effects of PPC were significantly improved by adenosine. PPC-stimulated protection can be achieved by alternating LV and RA pacing applied at the beginning of reperfusion. NO, ROS, and the product of their interaction ONOO− play a significant role in PPC-induced cardiac protection. Finally, the protective effects of PPC can be synergized with adenosine (AU)

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Understanding pacing postconditioning-mediated cardiac protection: a role of oxidative stress and a synergistic effect of adenosine.

We and others have demonstrated a protective role for pacing postconditioning (PPC) against ischemia/reperfusion (I/R) injury in the heart; however, the underlying mechanisms behind these protective effects are not completely understood. In this study, we wanted to further characterize PPC-mediated cardiac protection, specifically identify optimal pacing sites; examine the role of oxidative stress; and test the existence of a potential synergistic effect between PPC and adenosine. Isolated rat hearts were subjected to coronary occlusion followed by reperfusion. PPC involved three, 30 s, episodes of alternating left ventricular (LV) and right atrial (RA) pacing. Multiple pacing protocols with different pacing electrode locations were used. To test the involvement of oxidative stress, target-specific agonists or antagonists were infused at the beginning of reperfusion. Hemodynamic data were digitally recorded, and cardiac enzymes, oxidant, and antioxidant status were chemically measured. Pacing at the LV or RV but not at the heart apex or base significantly (P < 0.001) protected against ischemia-reperfusion injury. PPC-mediated protection was completely abrogated in the presence of reactive oxygen species (ROS) scavenger, ebselen; peroxynitrite (ONOO-) scavenger, uric acid; and nitric oxide synthase inhibitor, L-NAME. Nitric oxide (NO) donor, snap, however significantly (P < 0.05) protected the heart against I/R injury in the absence of PPC. The protective effects of PPC were significantly improved by adenosine. PPC-stimulated protection can be achieved by alternating LV and RA pacing applied at the beginning of reperfusion. NO, ROS, and the product of their interaction ONOO- play a significant role in PPC-induced cardiac protection. Finally, the protective effects of PPC can be synergized with adenosine.

The role of ACE2, angiotensin-(1-7) and Mas1 receptor axis in glucocorticoid-induced intrauterine growth restriction.

BACKGROUND: Plasma and urine levels of the potent vasodilator Ang-(1-7) are elevated in mid and late pregnancy and are correlated with elevated placental angiogenesis, fetal blood flow, and rapid fetal growth. We hypothesized that Ang-(1-7), its receptor (Mas1) and the enzymes involved in Ang-(1-7) production (ACE2 and Membrane metallo-endopeptidase; MME) are down regulated in response to glucocorticoid administration contributing to IUGR. METHODS: Pregnant female Sprague-Dawley rats were injected with dexamethasone (DEX; 0.4 mg/kg/day) starting from 14 day gestation (dg) till sacrifice at 19 or 21 dg while control groups were injected with saline (n = 6/group). The gene and protein expression of ACE2, MME, Ang-(1-7) and Mas1 receptor in the placental labyrinth (LZ) and basal zones (BZ) were studied. RESULTS: DEX administration caused a reduction in LZ weight at 19 and 21 dg (p < 0.001). IUGR, as shown by decreased fetal weights, was evident in DEX treated rats at 21 dg (p < 0.01). ACE2 gene expression was elevated in the LZ of control placentas at 21 dg (p < 0.01) compared to 19 dg and DEX prevented this rise at both gene (p < 0.01) and protein levels (p < 0.05). In addition, Ang-(1-7) protein expression in LZ was significantly reduced in DEX treated rats at 21 dg (p < 0.05). On the other hand, Mas1 and MME were upregulated in LZ at 21 dg in both groups (p < 0.05 and p < 0.001, respectively). CONCLUSION: The results of this study indicate that a reduced expression of ACE2 and Ang-(1-7) in the placenta by DEX treatment may be responsible for IUGR and consequent disease programming later in life.

The Interplay between the Renin Angiotensin System and Pacing Postconditioning Induced Cardiac Protection.

BACKGROUND: Accumulating evidence suggests a cardioprotective role of pacing postconditioning (PPC) maneuvers in animal models and more recently in humans. The procedure however remains to be optimized and its interaction with physiological systems remains to be further explored. The renin angiotensin system (RAS) plays a dual role in ischemia/reperfusion (I/R) injury. The interaction between RAS and PPC induced cardiac protection is however not clearly understood. We have recently demonstrated that angiotensin (1-7) via Mas receptor played a significant role in PPC mediated cardiac protection against I/R injury. OBJECTIVE: The objective of this study was to investigate the role of angiotensin converting enzyme (ACE)-chymase-angiotensin II (Ang II)-angiotensin receptor 1 (AT1) axes of RAS in PPC mediated cardiac protection. METHODS: Isolated rat hearts were subjected to I/R (control) or PPC in the presence or absence of Ang II, chymostatin (inhibitor of locally produced Ang II), ACE blocker (captopril) or AT1 antagonist (irbesartan). Hemodynamics data was computed digitally and infarct size was determined histologically using TTC staining and biochemically by measuring creatine kinase (CK) and lactate dehydrogenase levels. RESULTS: Cardiac hemodynamics were significantly (P<0.001) improved and infarct size and cardiac enzymes were significantly (P<0.001) reduced in hearts subjected to PPC relative to hearts subjected to I/R injury. Exogenous administration of Ang II did not affect I/R injury or PPC mediated protection. Nonetheless inhibition of endogenously synthesized Ang II protected against I/R induced cardiac damage yet did not block or augment the protective effects of PPC. The administration of AT1 antagonist did not alleviate I/R induced damage. Interestingly it abrogated PPC induced cardiac protection in isolated rat hearts. Finally, PPC induced protection and blockade of locally produced Ang II involved enhanced activation of ERK1/2 and Akt components of the reperfusion injury salvage kinase (RISK) pathway. CONCLUSIONS: This study demonstrate a novel role of endogenously produced Ang II in mediating I/R injury and highlights the significance of AT1 signaling in PPC mediated cardiac protection in isolated rodents hearts ex vivo. The interaction between Ang II-AT1 and PPC appears to involve alterations in the activation state of ERK1/2 and Akt components of the RISK pathway.

Discrepancy in calcium release from the sarcoplasmic reticulum and intracellular acidic stores for the protection of the heart against ischemia/reperfusion injury

We and others have demonstrated a protective effect of pacing postconditioning (PPC) against ischemia/reperfusion (I/R) injury. However, the mechanisms underlying this protection are not completely clear. In the present study, we evaluated the effects of calcium release from the sarcoplasmic reticulum (SR) and the novel intracellular acidic stores (AS). Isolated rat hearts (n = 6 per group) were subjected to coronary occlusion followed by reperfusion using a modified Langendorff system. Cardiac hemodynamics and contractility were assessed using a data acquisition program, and cardiac injury was evaluated by creatine kinase (CK) and lactate dehydrogenase (LDH) levels. Hearts were subjected to 30 min of regional ischemia, produced by ligation of the left anterior descending (LAD) coronary artery, followed by 30 min of reperfusion. The hearts were also subjected to PPC (3 cycles of 30 s of left ventricle (LV) pacing alternated with 30 s of right atrium (RA) pacing) and/or were treated during reperfusion with agonists or antagonists of release of calcium from SR or AS. PPC significantly (P < 0.05) normalized LV, contractility, and coronary vascular dynamics and significantly (P < 0.001) decreased heart enzyme levels compared to the control treatments. The blockade of SR calcium release resulted in a significant (P < 0.01) recovery in LV function and contractility and a significant reduction in CK and LDH levels (P < 0.01) when applied alone or in combination with PPC. Interestingly, the release of calcium from AS alone or in combination with PPC significantly improved LV function and contractility (P < 0.05) and significantly decreased the CK and LDH levels (P < 0.01) compared to the control treatments. An additive effect was produced when agonism of calcium release from AS or blockade of calcium release from the SR was combined with PPC. Calcium release from AS and blockade of calcium release from the SR protect the heart against I/R. Combining calcium release from acidic stores or blockade of calcium release from the SR with PPC produced a synergistic protective effect (AU)

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