Potentilla reptans L. postconditioning protects reperfusion injury via the RISK/SAFE pathways in an isolated rat heart

Background Our previous study indicated that Potentilla reptans root has a preconditioning effect by its antioxidant and anti-apoptotic effects in an isolated rat heart ischemia/reperfusion (IR) model. In the present study, we investigated the post-conditioning cardio-protective effects of Potentilla reptans and its active substances. Methods The ethyl acetate fraction of P. reptans root (Et) was subjected to an IR model under 30 min of ischemia and 100 min of reperfusion. To investigate the postconditioning effect, Et was perfused for 15 min at the early phase of reperfusion. RISK/SAFE pathway inhibitors, 5HD and L-NAME, were applied individually 10 min before the ischemia, either alone or in combination with Et during the early reperfusion phase. The hemodynamic factors and ventricular arrhythmia were calculated during the reperfusion. Oxidative stress, apoptosis markers, GSK-3β and SGK1 proteins were assessed at the end of experiments. Results Et postconditioning (Etpost) significantly reduced the infarct size, arrhythmia score, ventricular fibrillation incidence, and enhanced the hemodynamic parameters by decreasing the MDA level and increasing expression of Nrf2, SOD and CAT activities. Meanwhile, Etpost increased the BCl-2/BAX ratio and decreased Caspase-3 expression. The cardioprotective effect of Etpost was abrogated by L-NAME, Wortmannin (a PI3K/Akt inhibitor), and AG490 (a JAK/STAT3 inhibitor). Finally, Etpost reduced the expression of GSK-3β and SGK1 proteins pertaining to the IR group. Conclusion P. reptans reveals the post-conditioning effects via the Nrf2 pathway, NO release, and the RISK/SAFE pathway. Also, Etpost decreased apoptotic indexes by inhibiting GSK-3β and SGK1 expressions. Hence, our data suggest that Etpost can be a suitable natural candidate to protect cardiomyocytes during reperfusion injury.

Abstract 12508: Nicotinamide Restores Tissue NAD + and Improves Mouse Survival After Cardiac Arrest

Introduction: Metabolic suppression in the ischemic heart is characterized by NAD + depletion. How nicotinamide (NAM) supplementation affects NAD + repletion and cardiac arrest outcomes is unknown. Hypothesis: We hypothesized that NAM supplementation restores tissue NAD + and promotes glucose oxidation and sorbitol clearance, resulting in improved cardiac function and survival in a mouse model of cardiac arrest. Methods: Adult C57BL6 mice were subjected to an established KCL-induced 8 min cardiac arrest, randomly assigned to receive saline (NS) or 100 mg/kg NAM during cardiopulmonary resuscitation (CPR). Survival, MAP, ETCO 2, and ECG were monitored for 4 h after the return of spontaneous circulation (ROSC). Direct cardiac effects were assessed using a cardiomyocyte stunning model and an isolated rat heart Langendroff model to measure the contraction recovery and cardiac function, respectively. NAD + , lactate and ATP were measured by assay kits and AMPK phosphorylation was measured by Western blot. Results: Cardiomyocyte NAD + content decreased from 4.51 ± 0.03 nMol/g pre-ischemia to 2.69 ± 0.42 nMol/g at the end of ischemia. Treatment with 0.01 mM NAM completely restored the cellular level of NAD + and improved contractile recovery by 10 min reperfusion (58.1 ± 7.3% of baseline contractile velocity vs.18.5 ± 3.7% in control cells). NAM administered immediately after ROSC significantly improved mouse survival, with 10/10 survival at 4 h as compared to 5/10 in the NS group. NAM-treated mice displayed improved NAD + content in hearts obtained at 4 h post-ROSC compared to saline treated hearts (4.5 ± 0.1 nMol/g vs. 2.4 ± 0.1 nMol/g). NAM significantly reduced sorbitol accumulation in heart from saline control of 20.4 ± 2.7 μMol/g to 7.2 ± 1.5 μMol/g at 30 min post-ROSC, indicating less glucose shunting to polyol pathway. Cardiac contractile function was completely recovered with 1 mM NAM treatment in the isolated perfused rat heart. Compared with buffer control, NAM treatment increased heart content of NAD + , lactate, ATP and phosphorylated AMPK. Conclusion: NAM is efficacious for restoring cardiac NAD + and promotes metabolic and contractile recovery, with improved survival of cardiac arrest.

Potential Interaction of Fresh Garlic with Metformin during Ischemia-Reperfusion Induced Cardiac Injury in Diabetic Rats

Background and objectives. Diabetes mellitus is a metabolic illness related to numerous organ damage, dysfunctions, and renal malfunction. In diabetes, oxidative stress plays a crucial part in the biochemical and pathological alterations linked to myocardial ischemia-reperfusion injury (IRI). In this study, an effort was made to evaluate the possible interaction of garlic (Allium sativum) (250 mg/kg) with the biguanide derivative, metformin (MET) (70 mg/kg), on IRI induced myocardial dysfunction in the isolated rat heart. Methods. The study was undertaken on both normoglycemic and alloxan (90 mg/kg) induced diabetic Sprague Dawley rats weighing 150–250 g. At the completion of the treatment phase (30 days for garlic, 250 mg/kg, oral; 10 days for MET, 70 mg/kg, oral), rats were anesthetized and mounted on the modified Langendorff’s apparatus. IRI was produced by myocardial no-flow global ischemia. Developed tension (DT) and heart rate (HR) were recorded both before and after ischemia. The perfusate was collected to estimate the leakage of cardiac biomarkers (Creatine Kinase-MB: CK-MB and Lactate dehydrogenase: LDH). Hearts were removed from the setup and utilized to prepare heart tissue homogenate (HTH) and histological slides. The endogenous antioxidants, superoxide dismutase (SOD) and catalase (CAT), in addition to oxidative thiobarbituric acid substances (TBS), were estimated in HTH. Results. The hemodynamic parameters, including percentage recovery in HR and DT, were found significantly higher in animals pretreated with garlic and MET in diabetic rats (DR). Both SOD and CAT enzyme activities increased significantly while TBS levels were reduced in the HTH of animals treated with garlic and MET. The cardiac markers CK-MB and LDH levels also increased in HTH with a corresponding decrease in the perfusate. The histopathological changes in the heart and pancreas demonstrated noticeable protection of the tissues due to pretreatment with garlic and MET. Taken together, these findings advocate that reactive oxygen species derived from hyperglycemia execute an important function in myocardial global IRI; the therapy of garlic homogenate was found to be effective in alleviating these toxic effects. Conclusion. The combined therapy of MET and garlic provided synergistic cardioprotection, implying that garlic seems to possess promise in lowering toxic parameters by protecting diabetic induced myocardial injury.

Stimulation of mitochondrial hydrogen sulfide and glutathione production improves Frank-Starling response of the rat heart via NO-dependent pathway

The Frank-Starling response of the heart is known to be mediated by NO signaling, which is regulated by GSH and H2S. We hypothesized that stimulation of endogenous H2S or GSH synthesis improve Frank-Starling response . Wistar male rats were injected with propargylglycine (PAG, 11.3mg/kg-1, 40min,n=12), an inhibitor of H2S producing enzyme (cystationine-γ-lyase) and L-cysteine (121mg/kg-1, 30min,n=20), a precursor of H2S and GSH. Pretreatment with PAG or L-cysteine separately slightly improved P-V dependence of the isolated rat heart, but combination of PAG and L-cysteine (n=12) improved heart contractile activity. H2S content, cNOS activity, nitrate reductase activity and nitrite content increased by 2, 3.83, 2.5 and 1.3 times in cardiac mitochondria as well as GSH and GSSG levels increased by 2.24 and 1.86 times in heart homogenates of PAG+L-cysteine group comparing to control (all P<0.05). Inhibition of glutathione with DL-buthionine-sulfoximine (22.2mg/kg-1, 40min, n=6) drastically decreased Frank-Starling response of the heart and prevented PAG+L-cysteine induced increase of GSH and GSSG levels (BSO+PAG+L-cysteine,n=9). Inhibitor of NOS, N-nitro-L-arginine-methylester hydrochloride (40min, 27mg/kg-1), abolished positive inotropy induced by PAG+L-cysteine pretreatment (L-NAME+PAG+L-cysteine,n=7). Thus, PAG+L-cysteine administration improves Frank-Starling response with up-regulation of mitochondrial H2S, glutathione and NO synthesis that might be promising approach in treatment of myocardial dysfunction.

Dose-dependent Effects of Perfluorocarbon Based Blood Substitute Perftoran on Cardyodinamics in Animal Model of Ischemia-reperfusion Injury

The main goal of this study was to investigate the cardioprotective properties in terms of effects on cardiodynamics of perfluorocarbon emulsion in ex vivo-induced ischemic-reperfusion injury of an isolated rat heart. The first part of the study aims to determine the dose of 10% perfluoroemulsion (PFT) that will show the best cardioprotective effect in rats on ex vivo-induced ischemic / reperfusion injury of an isolated rat heart. Depending on whether the animals received saline or PFT, the animals were divided into a control or experimental group, and depending on the application of a dose (8, 12, 16 ml / kg body weight) of saline or PFT. At a dose of 8 ml / kg, the results indicate statistically significantly lower values ​​of the maximum pressure growth rate in the group treated with 10% PFT compared to the control group treated with saline at R5 and R25 points. At a dose of 12 ml / kg, the maximum left ventricular pressure growth rate differed statistically significantly in the PFT group, ie there was an increase in this parameter at points R25 and R30, and the minimum left ventricular pressure growth rate in R15-R30 compared to saline-treated group. At a dose of 16 ml / kg, PFT also had a statistically significant effect on the change in cardiodynamic parameters in an isolated rat heart organ. Based on all the above, we can conclude that Peftoran administered immediately before ischemia (1 hour) has less positive effects on myocardial function in a model of an isolated rat heart compared to earlier administration (10 and 20 hours). Also, the effects of 10% peftoran solution are more pronounced if there is a longer period of time from application to ischemia, ie immediate application of peftoran before ischemia (1 hour) gave the weakest effects on the change of cardiodynamics of isolated rat heart.

miRNA-27a Transcription Activated by c-Fos Regulates Myocardial Ischemia-Reperfusion Injury by Targeting ATAD3a

MicroRNA-27a (miR-27a) has been implicated in myocardial ischemia-reperfusion injury (MIRI), but the underlying mechanism is not well understood. This study is aimed at determining the role of miR-27a in MIRI and at investigating upstream molecules that regulate miR-27a expression and its downstream target genes. miR-27a expression was significantly upregulated in myocardia exposed to ischemia/reperfusion (I/R) and cardiomyocytes exposed to hypoxia/reoxygenation (H/R). c-Fos could regulate miR-27a expression by binding to its promoter region. Moreover, overexpression of miR-27a led to a decrease in cell viability, an increase in LDH and CK-MB secretion, and an increase in apoptosis rates. In contrast, suppression of miR-27a expression resulted in the opposite effects. ATPase family AAA-domain-containing protein 3A (ATAD3a) was identified as a target of miR-27a. miR-27a regulated the translocation of apoptosis-inducing factor (AIF) from the mitochondria to the nucleus and H/R-induced apoptosis via the regulation of ATAD3a. It was found that inhibiting miR-27a in vivo by injecting a miR-27a sponge could ameliorate MIRI in an isolated rat heart model. In conclusion, our study demonstrated that c-Fos functions as an upstream regulator of miR-27a and that miR-27a regulates the translocation of AIF from the mitochondria to the nucleus by targeting ATAD3a, thereby contributing to MIRI. These findings provide new insight into the role of the c-Fos/miR-27a/ATAD3a axis in MIRI.

Pre-ischemic Lactate Levels Affect Post-ischemic Recovery in an Isolated Rat Heart Model of Donation After Circulatory Death (DCD)

Introduction: Donation after circulatory death (DCD) could substantially improve donor heart availability. In DCD, the heart is not only exposed to a period of warm ischemia, but also to a damaging pre-ischemic phase. We hypothesized that the DCD-relevant pre-ischemic lactate levels negatively affect the post-ischemic functional and mitochondrial recovery in an isolated rat heart model of DCD.Methods: Isolated, working rat hearts underwent 28.5′ of global ischemia and 60′ of reperfusion. Prior to ischemia, hearts were perfused with one of three pre-ischemic lactate levels: no lactate (0 Lac), physiologic lactate (0.5 mM; 0.5 Lac), or DCD-relevant lactate (1 mM; 1 Lac). In a fourth group, an inhibitor of the mitochondrial calcium uniporter was added in reperfusion to 1 Lac hearts (1 Lac + Ru360).Results: During reperfusion, left ventricular work (heart rate-developed pressure product) was significantly greater in 0.5 Lac hearts compared to 0 Lac or 1 Lac. In 1 vs. 0.5 Lac hearts, in parallel with a decreased function, cellular and mitochondrial damage was greater, tissue calcium content tended to increase, while oxidative stress damage tended to decrease. The addition of Ru360 to 1 Lac hearts partially abrogated the negative effects of the DCD-relevant pre-ischemic lactate levels (greater post-ischemic left ventricular work and less cytochrome c release in 1 Lac+Ru360 vs. 1 Lac).Conclusion: DCD-relevant levels of pre-ischemic lactate (1 mM) reduce contractile, cellular, and mitochondrial recovery during reperfusion compared to physiologic lactate levels. Inhibition of mitochondrial calcium uptake during early reperfusion improves the post-ischemic recovery of 1 Lac hearts, indicating calcium overload as a potential therapeutic reperfusion target for DCD hearts.

The dose-dependent effect of chronic Verapamil treatment on cardiac function in isolated rat heart with Hypertension

Funding Acknowledgements Type of funding sources: None. Introduction Verapamil, a calcium channel blocker, is used for treatment of hypertension, paroxysmal supraventricular tachycardia and angina pectoris. It primarily blocks L-type calcium channels preventing excessive influx of calcium into cardiomyocytes, leading to negative inotropic effect, and smooth muscle cells resulting in reduced relaxation of vasculature. With calcium antagonism it also causes negative chronotropic effect. However, there is no data on it’s dose-dependent effects on cardiac dynamic parameters and heart rate on isolated rat heart with hypertension. Purpose To investigate chronic, dose-dependent effects of Verapamil on cardiodynamic parameters in isolated rat heart with hypertension. Methods The present 4-week study was carried out on 24 spontaneously hypertensive Wistar Kyoto male rats (6 weeks old): Control (n = 6), rats treated with 0.5 mg/kg/day of Verapamil (n = 6), rats treated with 5 mg/kg/day of Verapamil (n = 6) and rats treated with 50 mg/kg/day of Verapamil (n = 6). Isolated rat hearts were perfused on Langendorff perfusion apparatus. Results Chronic, low-dose Verapamil treatment significantly depressed function of all cardiodynamic parameters of the hypertensive heart when compared to the rats treated with higher doses of Verapamil (p &lt; 0.001), except on the coronary flow and heart rate when compared to the Control (p= 0.137; p = 1.000, respectively). There was no significant differences between Verapamil in middle dose (5 mg/kg/day) and the Control group in inotropic (p = 0.415) and lusitropic (p = 1.000) effects, while it significantly lowered values of coronary flow (p = 0.002). It achieved significantly lower inotropic, lusitropic and chronotropic effects (p &lt; 0.001) than high Verapamil dose and significantly better inotropic (p = 0.017), lusitropic (p &lt; 0.001), but not chronotropic effects than low-dose Verapamil treatment (p = 0.179). High-dose, chronic treatment with Verapamil significantly intensified function of the isolated rat heart with hypertension when compared to Control and lower doses of Verapamil (p &lt; 0.001), without significant effects on coronary flow (p = 0.363). Conclusions Chronic treatment with Verapamil in high dose achieved better inotropic, chronotropic and lusitropic effects than treatment in low and middle doses of Verapamil, without significant effects on coronary flow. There is dose-depended effect of chronic Verapamil treatment on cardiac function of isolated rat heart with hypertension.