Isolated Rat Hearts Research Articles

The role of thiazole acetate derivatives on isolated heart and blood vessels in experimental rats

Background and objectivesThough various drugs are available in the market for cardiovascular diseases, search for an efficacious and patient friendly drug is an ongoing process. The effect of synthesized thiazole compounds on isolated rat heart and isolated rat blood vessel to determine their potential as newer therapeutic agents. Materials and methodsSix thiazole acetate compounds were examined for their function on isolated heart and blood arteries utilizing standardized experimental models after being characterized and identified in the laboratory. Anesthetized Wistar albino rats' hearts were removed and placed on a Langendorff setup. The percentage change in developed tension and heart rate owing to injecting each thiazole acetate compound in the developed tension and heart rate were seen and recorded in an isolated heart that was mounted in a retrograde fashion using Krebs Henseleit solution. Similarly, anesthetized rats' thoracic aortas were separated, and responses to the standard drug phenylephrine and different thiazole acetate derivatives were examined. The pharmacological effect of the specific thiazole compound was determined by the percentage change in contractile response. ResultEach of the six thiazole acetate derivatives was injected at 1 nM, 10 nM, 100 nM, 1 M, 10 M, and 100 M concentrations. All six (T1 to T6) chemicals investigated in the present study had no significant effect on developed tension or heart rate. There was a nosignificant change in the percentage contraction after injecting 1 nM 3 nM,10 nM, 30 nM, 100 nM, 300 nM, 1 M, 3 M, 10 M, and 30 M,100 M,300 M (cumulative dose) of T1, T3, T4, T5, and T6, while T2 (- ethyl-4-methyl-2-aminothiazole) showed contractile effect in the form of vasoconstrictor activity, which was 30 % of that produced by phenylephrine. Interpretation and conclusionThiazole acetate derivatives did not show any cardiovascular effects except ethyl-4-methyl-2-aminothiazole, which showed a slight vascular contractile response as compared to phenylephrine. A more thorough examination of the utilization of thiazole derivatives is required to establish their potential significance in the cardiovascular system.

Triiodothyronine improves contractile recovery of human atrial trabeculae after hypoxia/reoxygenation

BackgroundIn patients undergoing interventional or surgical coronary revascularization, subclinical hypothyroidism is common and associated with worse outcome, including the need for postoperative inotropic support. In isolated rat hearts with global ischemia/reperfusion, exogenous triiodothyronine (T3) reduces infarct size. Aim of this study was, to investigate whether or not exogenous T3 protects human myocardium from ischemia/reperfusion injury. MethodsRight atrial trabeculae from patients undergoing routine coronary artery bypass grafting were isolated and transferred to Tyrode's buffer. Electrically initiated (1 Hz) contractile stress (mN/mm2) was recorded for 10 min at baseline (95% O2/ 5% CO2, glucose). Sixty min hypoxia were induced by changing buffer gas and increasing stimulation rate (95% N2/ 5% CO2, choline chloride, 3 Hz) before return to reoxygenation for 30 min. T3 (500 μg/l) vs. NaOH (solvent control) was administered A) throughout (n = 11 vs. n = 9) or B) only 15 min before and during reoxygenation (n = 12 vs. n = 13). Western blot analyses of established cardioprotective signaling proteins were performed. ResultsAt baseline, contractile stress was comparable. T3 improved the cumulative recovery of contractile stress during reoxygenation from 41 ± 16 with NaOH to 55 ± 11% of baseline with T3, when given continuously in A or from 52 ± 13 with NaOH to 63 ± 11% of baseline with T3 when given just before and during reoxygenation in B. The ratio of mitochondrial complex I matrix arm to membrane NADH:ubiquinone oxidoreductase subunits (NDUF)V2 to NDUFA9 was reduced, reflecting increased complex I activity. ConclusionT3 increases contractile recovery of human right atrial trabeculae from hypoxia/reoxygenation.

Regulation of lipid peroxidation in mitochondria by nitroglycerine

The mechanisms of lipid oxidation under the application of nitroglycerine (NG) were studied in isolated rat heart and liver mitochondria. Dose-dependent formation of diene conjugates (DC), leukotriene C4 (LTC4) and thromboxane B2 (TxB2) was shown. To disclose the mechanisms regulating lipid peroxidation in mitochondria, we studied the effect of NG application on the formation of prooxidants (H2O2 and free Fe2+), as well as xanthine oxidase and mtNOS activity as main sources of ROS and RNS. Based on the correlation dependences, we have found that DC, LTC4, and TxB2 formation was strongly dependent on hydroperoxide production and free divalent iron release in mitochondria. Also, DC formation exhibited the dependence on Ca2+ uptake in mitochondria. No dependence of lipid oxidation on xanthine oxidase activity was found. In heart, but not liver mitochondria, DC, LTC4, and TxB2 exhibited strong dependence on mtNOS activity, but were independent of nitrosothiols formation. This indicated that lipid oxidation was independent of direct protein nitrosylation caused by NG application. No dependence of lipid oxidation on mtNOS activity in liver was found, which agreed with much higher mtNOS activity in heart mitochondria, and suppression of mtNOS activity in liver mitochondria at high doses of NG. So, we came to the conclusion that under NG application ROS overproduction and free Fe2+ release promoted both enzymatic and non-enzymatic lipid oxidation in heart and liver mitochondria. Also, we hypothesized that RNS overproduction due to the elevated mtNOS activity in the heart could largely contribute to lipid peroxidation and promote much faster increase in the formation of lipid oxidation products in heart as compared to liver mitochondria, especially at high doses of NG. Obtained correlation dependences allowed us disclose free iron, hydroperoxide, and mtNOS activity as principal factors affecting lipid peroxidation in mitochondria under NG application.

Cardiac Electrophysiological Changes and Downregulated Connexin 43 Prompts Reperfusion Arrhythmias Induced by Hypothermic Ischemia-Reperfusion Injury in Isolated Rat Hearts.

The purpose of this study was to determine the utility of the monophasic action potential (MAP) changes as an arrhythmic biomarker in hypothermic ischemia-reperfusion. The hypothermic ischemia-reperfusion model was subjected to 60min of cardioplegic arrest while the isolated rat hearts were preserved with a multidose cold K-H solution at 4°C. During the reperfusion period, the heart's arrhythmia and monophasic action potential were also monitored. The myocardial damage was assessed using HE and TTC stains. Immunohistochemistry and Western blotting were used to assess the expression and distribution of Connexin 43 (Cx43) and Akt. Collectively, prolonged action potential durations, increased dispersion of repolarization, and downregulated and lateralized Cx43 all contribute to the derangement of electrical impulse propagation that may underlie arrhythmogenesis in the cold ischemic heart following cardioplegic arrest. MAP might be used as a biomarker for arrhythmias caused by hypothermic ischemia-reperfusion.

Impact of exercise training on mitochondrial dynamics during ischemia-reperfusion

Mitochondrial fission is a key trigger of cardiac ischemia-reperfusion injuries (IR) injuries. Despite exercise training (ExTr) is known as an efficient strategy to protect the heart, its impact on the dynamic of the mitochondrial network remain to be investigated. To evaluate the impact of ExTr on the process of mitochondrial fission during IR. Isolated hearts from ExTr or Sedentary (Sed) rats were subjected to IR. Hearts samples were collected after 10 min of reperfusion for biochemical assays or electron microscopic analysis. Finally, DHR123 was used to detect ROS production on isolated cardiomyocytes treated or not with the mitochondrial fission inhibitor Mdivi1. We confirmed on isolated rat hearts that ExTr reduced heart sensitivity to IR. This was associated with lower ROS production evaluated by DHE fluorescence and higher mitochondria Ca2+ retention capacities. We next confirmed that IR was associated with mitochondrial fission as well as the translocation and activation of the Dynamin related protein 1 (Drp1), known as the central regulator of mitochondrial fission. Interestingly, ExTr limited both the activation of Drp1 and the fission of mitochondria. We also reported that ExTr tended to increase the level of Mfn2, known as a central regulator of mitochondrial fusion. Finally, on isolated cardiomyocytes stimulated with H2O2 to mimic IR, we reported that Mdivi1 impact the level of ROS production only in Sed cells. This confirms that mitochondrial fission was more pronounced in Sed cells and contributes to increased ROS production during IR. Altogether, our results support the hypothesis that ExTr is able to modulate the dynamic of the mitochondrial network during IR, which could participate to exercise-induced cardioprotection.

Corrigendum for Skyschally et al., volume 315, 2018, p. H159–H172

CorrigendumCorrigendum for Skyschally et al., volume 315, 2018, p. H159–H172Published Online:24 May 2022https://doi.org/10.1152/ajpheart.00152.2018_COROriginal articleMoreSectionsPDF (179 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmailWeChat Skyschally A, Kleinbongard P, Lieder H, Gedik N, Stoian L, Amanakis G, Elbers E, Heusch G. Humoral transfer and intramyocardial signal transduction of protection by remote ischemic perconditioning in pigs, rats, and mice. Am J Physiol Heart Circ Physiol 315: H159–H172, 2018. First published March 23, 2018. doi:10.1152/ajpheart.00152.2018.In the published article, there was an error in Fig. 5, A and B. Due to an internal calibration error and an improper focus of the fluorescence detector over the well plates containing the samples, the reported absolute numbers for mitochondrial ATP and ROS formation were incorrect by an order of magnitude. The authors were unable to reconstruct the true absolute numbers and have requested the removal of these data. The authors apologize for this error and state that it does not change the scientific conclusions of the article in any way. The corrected Fig. 5 with revised legend appears below.Figure 5.Mitochondrial calcium retention capacity in isolated rat hearts with infusion of pig plasma. A and B: original data removed. C and D: data without (C) and with (D) cyclosporin A. TC, time control; I/R, ischemia-reperfusion; pPLA, plasma taken from pigs after placebo (PLA); pRPER, plasma taken from pigs after remote ischemic perconditioning (RPER); aliquots of pPLA and pRPER samples (individual open symbols with the same shape within pPLA or pRPER represent plasma samples from the same pig, respectively) were retested in rat hearts subjected to reperfusion injury salvage kinase (RISK; +RISK-BL) or survivor activating factor enhancement (SAFE; +SAFE-BL) blockade, respectively. Closed symbols: means ± SD; *P < 0.05 vs. TC, #P < 0.05 vs. pRPER and I/R (one-way ANOVA; Fisher’s LSD post hoc tests). LSD, least significant difference.Download figureDownload PowerPointThis article has no references to display. Download PDF Previous Back to Top FiguresReferencesRelatedInformationRelated articlesHumoral transfer and intramyocardial signal transduction of protection by remote ischemic perconditioning in pigs, rats, and mice 09 Jul 2018American Journal of Physiology-Heart and Circulatory Physiology More from this issue > Volume 322Issue 6June 2022Pages H1086-H1086 Crossmark Copyright & PermissionsCopyright © 2022 the American Physiological Society.https://doi.org/10.1152/ajpheart.00152.2018_CORPubMed35608821History Published online 24 May 2022 Published in print 1 June 2022 Metrics Downloaded 103 times

The Role of Phosphocreatine in the Perconditioning and Postconditioning of Isolated Rat Heart

Abstract The present study strives to assess the cardioprotective role of phosphocreatine as an agent for postconditioning and perconditioning of isolated rat heart. Rat hearts (n=30) were perfused with a Langendorff apparatus and randomly assigned to three groups subjected to 20 minutes of global ischemia and 30 minutes of reperfusion: control group (untreated rat hearts), postconditioning group (hearts treated with 0.2 mmol/l of phosphocreatine during the first 5 minutes of reperfusion), and perconditioning group (hearts treated with 0.2 mmol/l of phosphocreatine during the first 5 minutes of ischemia). During the experimental protocol, cardiodynamic parameters were evaluated, while oxidative stress parameters such as superoxide anion radical, hydrogen peroxide, nitrites and index of lipid peroxidation were determined in coronary venous effluent. Postconditioning and perconditioning with phosphocreatine improved contractile function, heart rate and coronary flow, while the examined oxidative stress parameters in coronary venous effluent were significantly reduced in groups of treated rat hearts. The results of this study indicate that phosphocreatine has the potential as a therapeutic agent for perconditioning and postconditioning the heart in ischemia reperfusion injury.

Dose-dependent effects of perfluorocarbon-based blood substitute on cardiac function in myocardial ischemia-reperfusion injury.

The main goal of this study was to investigate the cardioprotective properties in terms of effects on cardiodynamics of perfluorocarbon emulsion (PFE) in ex vivo-induced ischemia-reperfusion injury of an isolated rat heart. The first part of the study aimed to determine the dose of 10% perfluoroemulsion (PFE) that would show the best cardioprotective effect in rats on ex vivo-induced ischemia-reperfusion injury of an isolated rat heart. Depending on whether the animals received saline or PFE, the animals were divided into a control or experimental group. They were also grouped depending on the applied dose (8, 12, 16ml/kg body weight) of saline or PFE. We observed the huge changes in almost all parameters in the PFE groups in comparison with IR group without any pre-treatment. Calculated in percent, dp/dt max was the most changed parameter in group treated with 8mg/kg, while the dp/dt min, SLVP, DLVP, HR, and CF were the most changed in group treated with 16mg/kg 10h before ischemia. The effects of 10% PFE are more pronounced if there is a longer period of time from application to ischemia, i.e., immediate application of PFE before ischemia (1h) gave the weakest effects on the change of cardiodynamics of isolated rat heart. Therefore, the future of PFE use is in new indications and application methods, and PFE can also be referred to as antihypoxic and antiischemic blood substitute with mild membranotropic effects.

Porosity-based heterojunctions enable leadless optoelectronic modulation of tissues.

Homo- and heterojunctions play essential roles in semiconductor-based devices such as field-effect transistors, solar cells, photodetectors and light-emitting diodes. Semiconductor junctions have been recently used to optically trigger biological modulation via photovoltaic or photoelectrochemical mechanisms. The creation of heterojunctions typically involves materials with different doping or composition, which leads to high cost, complex fabrications and potential side effects at biointerfaces. Here we show that a porosity-based heterojunction, a largely overlooked system in materials science, can yield an efficient photoelectrochemical response from the semiconductor surface. Using self-limiting stain etching, we create a nanoporous/non-porous, soft-hard heterojunction in p-type silicon within seconds under ambient conditions. Upon surface oxidation, the heterojunction yields a strong photoelectrochemical response in saline. Without any interconnects or metal modifications, the heterojunction enables efficient non-genetic optoelectronic stimulation of isolated rat hearts ex vivo and sciatic nerves in vivo with optical power comparable to optogenetics, and with near-infrared capabilities.

Creatine phosphate administration in cardiac ischemia-reperfusion injury in rats: focus on differences between preconditioning, perconditioning, and postconditioning protocols.

The aim of this study was to examine and compare the influence of preconditioning, perconditioning, and postconditioning with creatine phosphate (PCr) on functional recovery and production of prooxidants in isolated rat hearts subjected to ex vivo ischemic-reperfusion (I-R) injury on a Langendorff apparatus. Wistar albino rats (male, n=40) were divided into four groups: control and groups in which PCr (0.5mmol/L, 5 min) was perfused before (Pre group), after (Post group), or during (Per group) ex vivo induced ischemia. PCr application was associated with the great benefits of preserving cardiac contractility (in Pre group 100.96% for +(dP/dt max) and 97.61% for -(dP/dt max), in Per group 96.72% for +(dP/dt max) and 95.60% for -(dP/dt max), and in Post group 143.84% for +(dP/dt max) and 104.36% for -(dP/dt max) in relation to the stabilization). In addition, PCr application prevented the increase in prooxidative markers during I-R injury in all therapeutic modalities. The most intensive benefits in the current investigation were observed when PCr was applied during the period of ischemia because the lowest fluctuations in the parameters of cardiac function and oxidative stress were observed. Overall, the results of this study highlight PCr-induced cardioprotection with promising prospects for future clinical use.

The effects of chronic, dose-dependent administration of dronedarone and amiodarone on cardiodynamics and oxidative stress parameters of isolated rat heart with hypertension

Abstract Funding Acknowledgements Type of funding sources: None. Background Amiodarone represents the most widely used antiarrhythmic drug with an indication for administration in heart failure (HF) with many of its side effects. Dronedarone reduces the risk of recurrent atrial fibrillation, with increased mortality due to worsening HF, but necessary experimental data is missing. Purpose Investigate chronic, dose-dependent effects of Dronedarone and Amiodarone on cardiodynamic and oxidative stress of spontaneusly hypertensive rat (SHR) heart. Methods The present study was carried out on 42 SHR Wistar Kyoto male rats: Control (n=6), and 6 experimental groups treated by oral lavage for 4 weeks: rats treated with 100 mg/kg of Amiodarone (n=6), rats treated with 50 mg/kg of Amiodarone (n=6), rats treated with 10 mg/kg of Amiodarone (n=6), rats treated with 50 mg/kg of Dronedarone (n=6), rats treated with 10 mg/kg of Dronedarone (n=6) and rats treated with 5 mg/kg of Dronedarone (n=6). Isolated rat hearts were perfused by Langendorff perfusion apparatus and following cardiodynamic parameters were continuously registered: dp/dt max, dp/dt min, systolic left ventricular pressure, diastolic left ventricular pressure, heart rate and coronary flow on each of predetermined values of coronary perfused pressure. Parameters of oxidative stress were determined spectrophotometrically. Results Amiodarone in the low dose significantly improved dp/dt max and dt/dt min, this effect was less pronounced in the middle dose of Amiodarone, while Amiodarone in the high dose significantly decreased all parameters of cardiac function. Amiodarone in low dose significantly increased levels of parameters of oxidative stress including levels of O2- and nitrites, when compared to other doses of Amiodarone. Significant changes in cardiac function were also observed in Dronedarone treated rats, however function was significantly decreased in all Dronedarone groups. Dronedarone severely depressed cardiac function with dose-dependent effect. Comparison between Amiodarone and Dronedarone groups revealed that Amiodarone was better in improvement of cardiac function in all dose-regimes (Figure 1). Dronedarone significantly lowered levels of H2O2 and TBARS without dose-dependent effect, concentrations of O2-, NO2- remained unchanged. Amiodarone increased O2-, NO2- and TBARS with a dose-dependent effect. When compared to Amiodarone, Dronedarone lowered all oxidative stress parameters in high, middle and low-dose (Figure 2.) Conclusion Dose-dependent, chronic administration of Dronedarone severely depressed SHR cardiac function. Amiodarone shows less pronaunced effects in high and middle dose, while low dose increased cardiac function. By comparing the effects of Amiodarone and Dronedarone, Amiodarone showed better effects on SHR cardiac function in all doses, while Dronedarone significantly reduced parameters of oxidative stress in all doses, when compared to their parallel doses of Amiodarone.

Human platelet‐mediated transfer of cardioprotection by remote ischemic conditioning is abrogated by aspirin, but not by ticagrelor

BackgroundRepeated ischemia/reperfusion in a tissue/organ remote from the heart (remote ischemic conditioning, RIC) protects against injury from sustained myocardial ischemia/reperfusion (I/R). Platelets are considered as mediators/targets of RIC´s protection. We have recently reported that infusion of washed platelets, taken from healthy volunteers after RIC, reduced infarct size (IS) in isolated rat hearts (FASEB Journal 2021; 35; S1; DOI: 10.1096/fasebj.2021.35.S1.03444). Anti‐platelet drugs are potential confounders of RIC.AimTo study the impact of anti‐platelet drugs, the cyclooxygenase inhibitor aspirin and the P2Y12 inhibitor ticagrelor, on the platelet‐mediated transfer of cardioprotection.MethodsWe included 18 healthy volunteers. As a contemporary control, volunteers were subjected to RIC through 3 x 5 min blood pressure cuff inflation at 200 mmHg on the left upper arm/ 5 min deflation. After at least 2 weeks, these volunteers were again subjected to RIC 3 hours after pretreatment with oral aspirin (500‐1000 mg) and again at least another 2 weeks later 2 hours after pretreatment with oral ticagrelor (180 mg). Venous blood samples were taken before RIC and 60 min after RIC, respectively. Washed platelets were prepared using apyrase, prostaglandin E1 and citrated Tyrode‐buffer. The platelet count was adjusted to 2.5 x 105platelets/µL. The functionality of washed platelets was tested in response to thrombin (1U/ml), aggregation measured with turbodimetric light transmission aggregometry and expressed as the increase in light transmission in percent of control. Platelet preparations with an aggregation &lt;60% were discarded. Male Lewis rats were sacrificed, their hearts isolated and perfused at constant pressure with buffer. Washed platelets before and after RIC, respectively, were infused for 8 min (2.5 x 104 platelets/µL) into rat hearts before global 30 min/ 120 min I/R. IS was demarcated by triphenyl tetrazolium chloride staining and calculated in percent of ventricular mass.ResultsWe confirm, that infusion of platelets after RIC reduces IS in isolated hearts with global I/R (Figure). This platelet‐mediated transfer of cardioprotection was abrogated by aspirin‐pretreatment of the volunteers (Figure). Platelets before RIC from ticagrelor‐pretreated volunteers reduced IS per se; nevertheless, platelets after RIC further reduced IS (Figure).ConclusionHuman platelets serve as carriers for RIC’s cardioprotective signal through an aspirin‐sensitive and thus cyclooxygenase‐dependent mechanism. The P2Y12 inhibitor ticagrelor per se induces a cardioprotective platelet‐dependent signal, which is further enhanced by RIC. The precise signal transfer from the platelets to the myocardium and the nature of the platelet‐derived factors remain to be further identified.

Remote ischemic preconditioning promotes cardioprotection through a central nervous system dependent mechanism

Remote ischemic preconditioning (rIPC) is the phenomenon of brief periods of ischemia and reperfusion applied to a distant organ promote cardioprotection against a subsequent ischemia/reperfusion injury (I/R). Although a neurohumoral hypothesis has been proposed, the cardioprotective mechanisms of rIPC have not been fully elucidated. We investigated whether rIPC could induce cardioprotection in a pithed Wistar rat model hypothesizing that the absence of central nervous system (CNS) structures would prevent its cardioprotective effect. rIPC protocol consisting of 3 cycles of 4 minutes of ischemia and 4 minutes of reperfusion was applied to the left posterior extremity of male Wistar rats. I/R was induced surgically by left coronary descending artery ligation for 30 minutes followed by 2h of reperfusion. Isolated rat hearts were perfused in a Langendorff system to measure coronary vascular resistance (CVR). Finally, the infarct size was evaluated by Evans blue and triphenyltetrazolium staining. rIPC reduced the infarct size of the ischemic hearts; however, this effect was abolished in pithed rats. rIPC also prevented the rise of CVR of ischemic hearts while there was no difference compared to pithed rats. We concluded that rIPC reduces the infarct size of hearts during I/R preserving the coronary artery tone through a CNS‐dependent mechanism.

Teriflunomide treatment exacerbates cardiac ischemia reperfusion injury in isolated rat hearts.

PurposePrevious work suggests that Dihydroorotate dehydrogenase (DHODH) inhibition via teriflunomide (TERI) may provide protection in multiple disease models. To date, little is known about the effect of TERI on the heart. This study was performed to assess the potential effects of TERI on cardiac ischemia reperfusion injury.MethodsMale and female rat hearts were subjected to global ischemia (25 min) and reperfusion (120 min) on a Langendorff apparatus. Hearts were given either DMSO (VEH) or teriflunomide (TERI) for 5 min prior to induction of ischemia and during the reperfusion period. Left ventricular pressure, ECG, coronary flow, and infarct size were determined using established methods. Mitochondrial respiration was assessed via respirometry.ResultsPerfusion of hearts with TERI led to no acute effects in any values measured across 500 pM–50 nM doses. However, following ischemia–reperfusion injury, we found that 50 nM TERI-treated hearts had an increase in myocardial infarction (p < 0.001). In 50 nM TERI-treated hearts, we also observed a marked increase in the severity of contracture (p < 0.001) at an earlier time-point (p = 0.004), as well as reductions in coronary flow (p = 0.037), left ventricular pressure development (p = 0.025), and the rate-pressure product (p = 0.008). No differences in mitochondrial respiration were observed with 50 nM TERI treatment (p = 0.24–0.87).ConclusionThis study suggests that treatment with TERI leads to more negative outcomes following cardiac ischemia reperfusion, and administration of TERI to at-risk populations should receive special considerations.

Effect of subchronic use of sodium nitrite on the functional parameters of an isolated rat heart

Introduction. The active development of agriculture with the widespread use of nitrogen-containing fertilizers, increased consumption of processed meat products containing sodium nitrite as a preservative, inevitably leads to an increase in the nitrogen load on the human body and can cause the development of cardiovascular diseases. Materials and methods. The cardiotoxic effect of sodium nitrite was evaluated on a model of an isolated rat heart with subchronic intragastric administration for 28 days at doses of 0.03; 0.3; 3.0 mg/kg. Results. The use of sodium nitrite leads to dilation of the coronary vessels and myocardium, inhibition of the contractile activity of the heart, disruption of its electrical activity in the form of a shortening of the QT interval associated with an increased risk of ventricular fibrillation, and a tendency to increase the amplitude of the T wave, which indicates myocardial ischemia. In a stress test with total ischemia, it was revealed that the magnitude of the change in the parameters characterizing the restoration of myocardial function under reperfusion conditions is inversely proportional to the dose of sodium nitrite used. Limitations. The study was performed only on male white rats more prone to the development of cardiovascular pathology. Conclusion. With subchronic administration, sodium nitrite has cardiotoxicity at a dose of 0.028 mg/kg, which is twice lower than the WHO-established permissible daily intake for humans (0.06 mg/kg).

Long-term administration of fisetin was not as effective as short term in ameliorating IR injury in isolated rat heart.

The current study aims to determine the comparative efficacy of fisetin in reducing myocardial ischemia–reperfusion injury (IR) in isolated rat hearts when the drug was given either oral or intraperitoneal (ip) for short-term and long-term administration. Rats treated with fisetin (20 mg/kg-oral/ip) for short (30 min prior to surgery) and long (15 days prior to surgery followed by 1-day washout) duration were subjected to myocardial IR using Langendorf perfusion system. Hemodynamics, cardiac injury, mitochondrial functional assessment, and fisetin levels were estimated. Unlike the long-term administration of fisetin, the short-term treated-rat heart exhibited significant cardioprotection, measured via hemodynamic indices (RPP in mmHg × beats/min × 10 ^ 4: IR — 4 ± 0.1, FIPS — 2.49 ± 0.18, FIPL — 1.87 ± 0.14), reduced infarct size (in % area of infarct: IR — 38 ± 5, FIPS — 17 ± 1, FOS — 14 ± 2), improved mitochondrial ETC enzyme activity (NQR activity in IFM: FIPS — 0.25 ± 0.016, FIPL — 0.20 ± 0.02), and declined oxidative stress (GSH in IFM: FIPS — 1.52 ± 0.14, FIPL — 1.25 ± 0.22). However, no significant difference in the protection was observed between the animals treated with oral or intraperitoneally administered fisetin. Single dose of fisetin administration before IR protocol was more effective than 15 days of fisetin-treated drug followed by 1-day washout, thus may not be suitable for long-term dietary supplement for post-surgical cardiac rehabilitation.

Graphene oxide nanoflackes prevent reperfussion injury of Langerdorff isolated rat heart providing antioxidative activity in situ

Carbon materials possess powerful antioxidant activity that might be promising for the development of new generation treatment of cardiovascular diseases, ischemic conditions, and reperfusion injury. The present study aimed to characterize the structure of nanosized graphene oxide (GrO) sample and evaluate the antioxidant efficacy of GrO in situ models of oxidative stress widely used in pre-clinical studies. The structure and surface chemistry of the initial samples were analyzed via LDS, RAMAN, LDI, TPD-MS, and FTIR methods. The GrO showed a strong ability to scavenge DPPH, hydroxyl, and superoxide anion free radicals and have a total antioxidant capacity. The DFT quantum-chemical calculation demonstrated the radical scavenging effect of GrO proceeding due to the physical adsorption of the free radical on the surface. For evaluation of the antioxidant effect of GrO in situ, we used the model of ischemia-reperfusion (I/R) of Langendorff isolated rat heart. We revealed that intravenous pretreatment of Wistar male rats with GrO significantly increased resistance of myocardium to I/R, improved restoration of heart function, prevented non-effective oxygen utilization, and I/R induced reactive oxygen species production in cardiac tissue. Thus, our data demonstrate the perspective of further use of GrO for the development of antiischemic therapy.

Macrophage-Derived Extracellular Vesicles (EVs) Have Functional and Metabolic Effects on Cardiac Grafts in a Preclinical Model of Donation After Circulatory Death (DCD)

<h3>Purpose</h3> Donation after circulatory death (DCD) could substantially increase cardiac graft availability. Cardiac ischemia and reperfusion, as occurs during DCD, can trigger the recruitment of macrophages as well as their polarization from the M0 to M1 state, which may occur in parallel with increased glycogen turnover and pentose phosphate flux. Extracellular vesicles (EVs) can transmit the metabolic status of their parent cell to recipient cells. As post-ischemic glucose metabolism is recognized to affect the cardiac recovery, we investigated the effects of M0 and M1 macrophage-derived EV administration during reperfusion on post-ischemic functional recovery and glucose metabolism using an isolated rat heart model of DCD. <h3>Methods</h3> Hearts isolated from adult, male rats were aerobically perfused for 20 minutes, followed by 27 minutes continued perfusion or 27 minutes of warm, global ischemia, and 60 minutes aerobic reperfusion with or without the intravascular administration of EVs. Four experimental groups were examined: 1) continued perfusion, no EVs (No ISCH); 2) ischemia, no EVs (ISCH); 3) ischemia with EVs from M0 macrophages (ISCH M0); 4) ischemia with EVs from M1 macrophages (ISCH M1). Contractile and metabolic post-ischemic recovery were evaluated. Data are reported as mean ± standard deviation. <h3>Results</h3> Left ventricular (LV) work (heart rate-developed pressure product) at 60 minutes reperfusion was significantly decreased in ISCH (17 ± 3) and ISCH M1 (19 ± 3), but not in ISCH M0 (22 ± 3), compared to No ISCH (26 ± 4 mmHg*beats*min^{−1 *}10³; p<0.05 for both). Rates of glycolysis during reperfusion were not different among groups; however, glycogen content was significantly lower after 60 min reperfusion in ISCH M1 (8 ± 2) compared to ISCH M0 (17 ± 3 μmol/g dry; p<0.05). <h3>Conclusion</h3> The ischemia-induced reduction in left ventricular work was improved with M0-, but not M1-, derived EVs. M0 and M1-derived EVs also differentially affected glucose metabolism; M1-macrophage derived EVs limited glycogen content, possibly by increasing glycogen use or turnover and stimulating recipient cells to mimic parent cell metabolic phenotypes. Circulating EVs in the ex-situ perfusion of DCD hearts may be possible targets for modulating metabolic function and optimizing graft recovery following warm ischemia.

Δ9-Tetrahydrocannabinol (Δ9-THC) Improves Ischemia/Reperfusion Heart Dysfunction and Might Serve as a Cardioprotective Agent in the Future Treatment.

Ischemia/reperfusion (I/R) is a pivotal mechanism of organ injury during clinical stetting for example for cardiopulmonary bypasses. The generation of reactive oxygen species (ROS) during I/R induces oxidative stress that promotes endothelial dysfunction, DNA dissociation and local inflammation. In turn, those processes induce cytokine release, resulting in damage to cellular structures and cell death. One of the major psychoactive compounds of Cannabis is delta-9-tetrahydrocannabinol (Δ9-THC), which is known as an anti-inflammatory mediator. Our research aimed to test if Δ9-THC may be protective in the treatment of cardiovascular system dysfunction arising from I/R heart injury. Two experimental models were used: isolated rat hearts perfused with the Langendorff method and human cardiac myocytes (HCM) culture. Rat hearts and HCM underwent ex vivo/chemical in vitro I/R protocol with/without Δ9-THC treatment. The following parameters were measured: cell metabolic activity, morphology changes, cell damage as lactate dehydrogenase (LDH) activity, ceramide kinase (CERK) activity, ROS level, total antioxidant capacity (TAC) and heart hemodynamic parameters. Δ9-THC protected the heart, as evidenced by the improved recovery of cardiac function (p < 0.05, N = 3-6). Cells subjected to I/R showed lower cytoplasmic LDH activity, and 10 μM Δ9-THC treatment reduced cell injury and increased LDH content (p = 0.019, N = 6-9). Morphology changes of HCM-spherical shape, vacuolisation of cytoplasm and swollen mitochondria-were inhibited due to Δ9-THC treatment. I/R condition affected cell viability, but 10 μM Δ9-THC decreased the number of dead cells (p = 0.005, N = 6-9). The total level of CERK was lower in the I/R group, reflecting oxidative/nitrosative stress changes. The administration of Δ9-THC effectively increased the production of CERK to the level of aerobic control (p = 0.028, N = 6-9). ROS level was significantly decreased in I/R cells (p = 0.007, N = 6-8), confirming oxidative stress, while administration of 10 μM Δ9-THC enhanced TAC in cardiomyocytes subjected to I/R (p = 0.010, N = 6-8). Δ9-THC promotes the viability of cardiomyocytes, improves their metabolic activity, decreases cell damage and restores heart mechanical function, serving as a cardioprotective. We proposed the use of Δ9-THC as a cardioprotective drug to be, administered before onset of I/R protocol.

Cytochrome c Oxidase Inhibition by ATP Decreases Mitochondrial ROS Production.

This study addresses the eventual consequence of cytochrome c oxidase (CytOx) inhibition by ATP at high ATP/ADP ratio in isolated rat heart mitochondria. Earlier, it has been demonstrated that the mechanism of allosteric ATP inhibition of CytOx is one of the key regulations of mitochondrial functions. It is relevant that aiming to maintain a high ATP/ADP ratio for the measurement of CytOx activity effectuating the enzymatic inhibition as well as mitochondrial respiration, optimal concentration of mitochondria is critically important. Likewise, only at this concentration, were the differences in ΔΨm and ROS concentrations measured under various conditions significant. Moreover, when CytOx activity was inhibited in the presence of ATP, mitochondrial respiration and ΔΨm both remained static, while the ROS production was markedly decreased. Consubstantial results were found when the electron transport chain was inhibited by antimycin A, letting only CytOx remain functional to support the energy production. This seems to corroborate that the decrease in mitochondrial ROS production is solely the effect of ATP binding to CytOx which results in static respiration as well as membrane potential.