Reperfusion Phase Research Articles

A-355 Comparison of Arterial and Venous Whole Blood Samples Analyzed on the QuantraSystem With the QPlusand QStatCartridges

Abstract Background The Quantra Hemostasis System (HemoSonics, LLC) is a cartridge-based viscoelastic testing system used to monitor the coagulation status of whole blood samples. The clinical performance of the System with the QPlus and QStat Cartridges was demonstrated in patients undergoing surgical procedures using venous blood samples. However, depending on the nature of the surgical procedure, arterial or venous samples may be more accessible for testing. It is currently unknown if differences exist between the two samples for the Quantra System. This study compared QPlus and QStat parameters measurements in venous and arterial blood samples collected in parallel from patients undergoing cardiac or liver transplant surgery. Methods Two studies were conducted according to CLSI EP09. The cardiac study enrolled 50 adult patients undergoing cardiac surgery utilizing cardiopulmonary bypass to evaluate QPlus parameters. Matching arterial and venous samples were obtained at two time points: during bypass and post-protamine. The liver study enrolled 25 adult patients undergoing liver transplantation to evaluate QStat parameters. Matching arterial and venous samples from were obtained at three time points: baseline, anhepatic and reperfusion phases. All arterial samples were drawn from an existing arterial catheter whereas venous samples were drawn from the venous side of the bypass circuit or from the central venous catheter (proximal port to minimize infusion contamination). Linear regression analysis and means comparison (paired t-test) were used to assess whether the two sample types provided equivalent results, Results Table 1 provides the mean values for each parameter determined for venous and arterial samples. None of the parameters showed a significant difference between sample types (P > 0.05). Additionally, the linear regression analysis show strong correlation between the results for each parameter. Conclusions Both studies demonstrated that venous and arterial whole blood samples provide equivalent results on the Quantra System with the QPlus and QStat Cartridges.

Controlled automated reperfusion of the whole body after cardiac arrest: Device profile of the CARL system.

Cardiac arrest is associated with high mortality rates and severe neurological impairments. One of the underlying mechanisms is global ischemia-reperfusion injury of the body, particularly the brain. Strategies to mitigate this may thus improve favorable neurological outcomes. The use of extracorporeal cardiopulmonary membrane oxygenation (ECMO) during CA has been shown to improve survival, but available systems are vastly unable to deliver goal-oriented resuscitation to control patient's individual physical and chemical needs during reperfusion. Recently, controlled automated reperfusion of the whoLe body (CARL), a pulsatile ECMO with arterial blood-gas analysis, has been introduced to deliver goal-directed reperfusion therapy during the post-arrest phase. This review focuses on the device profile and use of CARL. Specifically, we reviewed the published literature to summarize data regarding its technical features and potential benefits in ECPR. Peri-arrest, mitigating severe IRI with ECMO, might be the next step toward augmenting survival rates and neurological recovery. To this end, CARL is a promising extracorporeal oxygenation device that improves the early reperfusion phase after resuscitation.

Abstract Tu143: Hsp90β Facilitates Cell Death During Acute Cardiac Ischemia/Reperfusion Injury

Myocardial infarction (MI), which caused 110,000 deaths in America in 2020, occurs following a complete blockage (ischemia) in one or more of the coronary arteries. Additionally, clearing the blockage (reperfusion) causes massive cell death, resulting in permanent tissue damage in the heart. Preventing cell death in IR injury is key to improving patient outcome in this disease. Molecular chaperones have emerged as promising targets in IR injury due to their pro-survival functions. However, the role of Hsp90β, the most abundant and constitutively active chaperone, in IR injury has not been fully elucidated. Therefore, we generated a cardiac-specific Hsp90β conditional knockout (cKO) mouse model to address it. To our surprise, current preliminary results suggest that cardiac-specific Hsp90β ablation reduces myocardial damage during IR injury, as Hsp90β cKO mice showed reduced infarct size compared to control. Opening of the mitochondrial permeability transition pore (mPTP) is the major driver of necrotic cell death during early reperfusion. Isolated mitochondria from the hearts of Hsp90β cKO mice show decreased sensitivity to mPTP opening during calcium overload, suggesting that it may be one of the cardioprotective mechanisms mediated by Hsp90β ablation. The Hsp90β cKO hearts also display an anti-apoptotic shift of the BAX/BCL2 apoptotic rheostat, suggesting the heart will be more resistant to apoptotic cell death during late reperfusion phase as well. Findings from this study will help us understand the role of Hsp90β in cell death activation during IR injury. In the future, we plan to investigate the underlying protective mechanisms mediated by Hsp90β ablation.

COMPARATIVE ANALYSIS OF MECHANISMS OF ACTION OF PEPTIDE TOXINS, INHIBITORS OF CALCIUM AND SODIUM CHANNELS, UNDER ISCHEMIA/REPERFUSION

Ischemia contributes to many pathological conditions encountered in clinical practice. Besides, subsequent reperfusion may worsen tissue damage, exacerbating injuries caused by ischemia. Shifts in the balance of calcium and sodium ions play a major role in the development of ischemia-reperfusion injury. Inhibitors of calcium and sodium ion channels located on the membrane surface can help to avoid a sharp disturbance in the ion balance. Although such inhibitors reduce cell death, their mechanisms of action differ. The aim of the study is to conduct a comparative analysis of the mechanisms of action of peptide inhibitors of calcium and sodium channels on ischemia-reperfusion damage to epithelial cells. Materials and Methods. Peptide synthesizer was used for toxin synthesis. Chromatography and mass spectrometry were used for quality control. Analysis of cell death, changes in calcium and sodium ion concentrations, and pH levels were performed using fluorescent dyes and a multimodal reader. Results. It was found that peptide inhibitors of calcium and sodium channels reduce apoptosis and necrosis levels in CHO-K1 culture under simulated ischemia/reperfusion. The calcium channel inhibitor reduces cell death by lowering calcium and sodium ion concentrations and maintaining physiological pH levels throughout the reperfusion phase. The sodium channel inhibitor reduces death by lowering calcium and increasing sodium concentrations, and by maintaining an elevated pH throughout the reperfusion phase. Conclusion. Although both calcium and sodium concentrations as well as their mutual influence play an important role in the development of ischemia-reperfusion injury, inhibition of certain channels has different effects on intracellular processes with the same result, namely reduced cell death.

Neuroprotective effects of MK-801 against cerebral ischemia reperfusion

Introduction& Objective: Cerebral ischemia/reperfusion (I/R) injury, the second cause of death globally, involves increased NMDA receptor activity leading to neuronal damage due to excessive sodium and calcium ion entry. Therefore, targeting NMDA receptor may potentially reduce cell death induced by brain injury. Our study aimed to investigate the role of NMDA receptors in hippocampal neuronal activity induced by I/R. MethodsIn this study, Wistar rats were divided into four groups: sham, I/R, I/R + MK801, and I/R + NMDA. Cerebral I/R injury was induced by temporarily occluding the common and vertebral carotid arteries, followed by reperfusion. MK801 or NMDA was administered to the rats after a specific reperfusion time. Neuronal density and cell morphology in the hippocampal CA1 region were assessed using Nissl and H&E staining. The expression of BDNF, p-CREB, and c-fos was evaluated through Western blot analysis. Additionally, neuronal activity in CA1 pyramidal neurons were examined using single unit recording technique. ResultsOur results showed that cerebral I/R injury caused significant damage to CA1 pyramidal neurons compared to the sham group. However, treatment with MK-801 improved hippocampal cell survival compared to the I/R group. Furthermore, MK-801 administration in I/R rats increased BDNF, c-fos, and p-CREB levels while decreasing cleaved caspase-3 activity compared to the I/R group. Additionally, electrophysiological data showed that MK-801 increased firing rates of CA1 pyramidal neurons during the reperfusion phase. ConclusionMK-801 shows promise as a therapeutic agent for cerebral I/R injury by enhancing cell survival, upregulating neuroplasticity factors, and increasing firing rates of CA1 pyramidal neurons. It exerts a specific protective effect against cerebral I/R injury.

Galanin Coordinates Macrophage-Associated Fibro-Inflammatory Response and Mitochondrial Integrity in Myocardial Infarction Reperfusion Injury.

Myocardial infarction activates an intense fibro-inflammatory reaction that is essential for cardiac remodeling and heart failure (HF). Bioactive peptide galanin plays a critical role in regulating cardiovascular homeostasis; however, its specific functional relevance in post-infarction fibro-inflammatory reprogramming remains obscure. Here, we show that galanin coordinates the fibro-inflammatory trajectory and mitochondrial integrity in post-infarction reperfusion injury. Aberrant deposition of collagen was associated with a marked increase in CD68-positive macrophage infiltration in cardiac tissue in mice subjected to myocardial ischemia/reperfusion (I/R) for 14 days compared to sham controls. Furthermore, we found that the myocardial expression level of a specific marker of M2 macrophages, CD206, was significantly down-regulated in I/R-challenged mice. In contrast, galanin treatment started during the reperfusion phase blunted the fibro-inflammatory responses and promoted the expression of CD206 in I/R-remodeled hearts. In addition, we found that the anti-apoptotic and anti-hypertrophic effects of galanin were associated with the preservation of mitochondrial integrity and promotion of mitochondrial biogenesis. These findings depict galanin as a key arbitrator of fibro-inflammatory responses to cardiac I/R injury and offer a promising therapeutic trajectory for the treatment of post-infarct cardiovascular complications.

#2037 Mitochondrial fumarate promotes ischemia/reperfusion-induced tubular injury

Abstract Background and Aims Mitochondrial dysfunction, a characteristic pathological feature of renal Ischemic/reperfusion injury (I/RI), predisposes tubular epithelial cells to maintain an inflammatory microenvironment, however, the exact mechanisms through which mitochondrial dysfunction modulates the induction of tubular injury remains incompletely understood. Method ESI-QTRAP-MS/MS approach was used to characterize the targeted metabolic profiling of kidney with I/RI. Tubule injury, mitochondrial dysfunction and fumarate level were evaluated using qPCR, transmission electron microscopy, ELISA, and immunohistochemistry. Results We demonstrated that tubule injury occurs at the phase of reperfusion in murine models of I/RI. Meanwhile, the enhanced glycolysis and mitochondrial dysfunction are found to be associated with tubule injury. Further, we found that tubular fumarate, which resulted from fumarate hydratase deficiency and released from dysfunctional mitochondria, promotes tubular injury. Mechanistically, fumarate induces tubular injury through causing disturbance of glutathione (GSH) hemostasis. Suppression of GSH with buthionine sulphoximine administration could deteriorate the fumarate inhibition-mediated tubule injury recovery. Reactive oxygen species/NF-κB signaling activation plays a vital role in fumarate-mediated tubule injury. Conclusion Our studies demonstrated that the mitochondrial-derived fumarate promotes tubular epithelial cells injury in renal I/RI. This finding represents a previously unrecognized mechanism for hypoxia-induced TECs injury. Blockade of fumarate-mediated ROS/NF-κB signaling activation may serve as a novel therapeutic approach to ameliorate hypoxic tubule injury.

#337 Renal 3D photoacoustic imaging and contrast-enhanced ultrasound to assess oxygenation and perfusion and to predict fibrosis after ischemia-reperfusion

Abstract Background and Aims Renal 3D photo-acoustic imaging (3D-PAI) and contrast-enhanced ultrasound (CEUS) are promising tools in mice models to assess repeatedly and non-invasively renal ischemia-reperfusion (RIR) consequences and damages, or their improvement by nephroprotective strategies like mild therapeutic hypothermia (mTH), at the early phase of reperfusion as well as in the chronic late phase. Method C57Bl6 mice underwent 15 minutes of unilateral renal vascular clamping, with body temperature at 37°C (RIR-37°C, n=7) or mTH at 34°C (RIR-34°C, n=7), or a sham procedure (Sham, n=5). Renal volume and oxygen saturation (sO2-3D; corresponding to the percentage of oxyhemoglobin over the total hemoglobin content) were measured with 3D-PAI (3D reconstruction of the whole kidney through multi-plane acquisition with an automatized mobile support), and renal perfusion parameters (rBV, mTT, rBF) with CEUS (“destruction-replenishment” model of intravenous microbubbles), performed with VEVO3100 echograph (Fujifilm Visualsonic) 1 week before RIR (basal), 20 minutes after reperfusion, and 1 month after. Renal fibrosis was quantified at 1 month with Masson's trichrome coloration on histological samples. Data were compared with Mann-Whitney test or Wilcoxon test (paired data) as appropriate. Correlation was tested by Spearman test. All animal procedures were approved by the Ethics Committee. Results Sham showed no significant changes during follow-up. RIR-37°C led to renal hypotrophy (volume on 3D-PAI) and fibrosis at 1 month, compared to RIR-34°C (median volume 76 IQR [71-119] vs 143 IQR[108-180] mm3; p=0.03), and those parameters were correlated (R=−0.49; p=0.03). In RIR-37°C, sO2-3D tended to lower at 20 minutes compared to basal values (median sO2-3D 37 IQR [37-44] vs 49 IQR [36-57]%; p=0.08), but not in RIR-34°C (p > 0.99), and these early variations of sO2-3D were correlated with fibrosis at 1 month (R=−0.48; p=0.04). Renal perfusion was altered in RIR-37°C at 20 minutes compared to basal values (median rBV 73 IQR [46-105] vs 100 IQR [89-126] a.u.; p=0.047), and remained altered at 1 month (median rBV 71 IQR [57-83] a.u.; p=0.03), but not in RIR-34°C (p=0.47 at both 20 minutes and 1 month). Renal perfusion early alterations at 20 minutes were correlated with late alterations at 1 month (R=0.63; p=0.005), and tended to correlate with fibrosis (R=−0.41; p=0.08). Conclusion Renal 3D-PAI (on the whole 3D-reconstructed kidney) and CEUS can detect early alterations of renal perfusion and oxygen saturation after RIR, and predict chronic disturbances of perfusion and the onset of fibrosis, as well as the protection conferred by mTH. 3D-PAI can also be used to evaluate non-invasively renal volume as a surrogate of renal fibrosis after RIR.

Reproducibility and sex differences in muscle oxygenation during brachial artery occlusion in healthy participants.

Near-infrared spectroscopy (NIRS) measurement is a widely used technique to measure muscle oxygenation. A knowledge of the reproducibility of NIRS measurements is essential for the correct interpretation of data. Our aim was to test the reproducibility and sex differences of NIRS measurements during brachial artery occlusion in healthy participants. An NIRS device was used to measure muscle oxygenation and microvascular function during a 5 min brachial occlusion. Muscle oxygen consumption (mVO2) and tissue saturation index (TSI%) were used. The occlusion test was performed three times on separate days for males (n = 13, 28 ± 8 years) and females (n = 13, 29 ± 7 years). During the occlusion phase, the reproducibility of mVO2 was excellent (intraclass correlation; ICC = 0.90). During the reperfusion phase, the maximal change in TSI% revealed the best reproducibility (ICC = 0.77). There were no sex differences in reproducibility. Male participants had higher muscle oxygenation during occlusion (mVO2, 0.054 ± 0.010 vs. 0.038 ± 0.012 mLO2/min/100 g, p = 0.001, male and female, respectively). There were no sex differences during the reperfusion phase. The reproducibility of NIRS to measure muscle oxygenation and microvascular function during circulation occlusion and reperfusion is good to excellent. Muscle oxygen capacity measured during occlusion is higher in males compared to females, and there are no sex differences in microvascular function during the reperfusion phase.

Autosis: a new form of cell death in myocardial ischemia-reperfusion injury.

Cardiomyocytes undergo a variety of cell death events during myocardial ischemia‒reperfusion injury (MIRI). Understanding the causes of cardiomyocyte mortality is critical for the prevention and treatment of MIRI. Among the various types of cell death, autosis is a recently identified type of autophagic cell death with distinct morphological and chemical characteristics. Autosis can be attenuated by autophagy inhibitors but not reversed by apoptosis or necrosis inhibitors. In recent years, it has been shown that during the late phase of reperfusion, autosis is activated, which exacerbates myocardial injury. This article describes the characteristics of autosis, autophagic cell death, and the relationship between autophagic cell death and autosis; reviews the mechanism of autosis in MIRI; and discusses its clinical significance.

HSPA12A maintains aerobic glycolytic homeostasis and Histone3 lactylation in cardiomyocytes to attenuate myocardial ischemia/reperfusion injury.

Myocardial ischemia/reperfusion (MI/R) injury is a major cause of adverse outcomes of revascularization following myocardial infarction. Anaerobic glycolysis during myocardial ischemia is well studied, but the role of aerobic glycolysis during the early phase of reperfusion is incompletely understood. Lactylation of Histone H3 (H3) is an epigenetic indicator of the glycolytic switch. Heat shock protein A12A (HSPA12A) is an atypic member of the HSP70 family. In the present study, we report that, during reperfusion following myocardial ischemia, HSPA12A was downregulated and aerobic glycolytic flux was decreased in cardiomyocytes. Notably, HSPA12A KO in mice exacerbated MI/R-induced aerobic glycolysis decrease, cardiomyocyte death, and cardiac dysfunction. Gain- and loss-of-function studies demonstrated that HSPA12A was required to support cardiomyocyte survival upon hypoxia/reoxygenation (H/R) challenge and that its protective effects were mediated by maintaining aerobic glycolytic homeostasis for H3 lactylation. Further analyses revealed that HSPA12A increased Smurf1-mediated Hif1α protein stability, thus increasing glycolytic gene expression to maintain appropriate aerobic glycolytic activity to sustain H3 lactylation during reperfusion and, ultimately, improving cardiomyocyte survival to attenuate MI/R injury.

Realtime assessment of vascular occlusion and reperfusion in animal models of intraoperative imaging- a pilot study.

Intraoperative monitoring of blood flow (BF) remains vital to guiding surgical decisions. Here, we report the use of SurgeON™ Blood Flow Monitor (BFM), a prototype system that attaches to surgical microscopes and implements laser speckle contrast imaging (LSCI) to noninvasively obtain and present vascular BF information in real-time within the microscope's eyepiece. The ability of SurgeON BFM to monitor BF status during reversible vascular occlusion procedures was investigated in two large animal models: occlusion of saphenous veins in six NZW rabbit hindlimbs and clipping of middle cerebral artery (MCA) branches in four Dorset sheep brain hemispheres. SurgeON BFM acquired, presented, and stored LSCI-based blood flow velocity index (BFVi) data and performed indocyanine green video angiography (ICG-VA) for corroboration. Stored BFVi data were analyzed for each phase: pre-occlusion (baseline), with the vessel occluded (occlusion), and after reversal of occlusion (re-perfusion). In saphenous veins, BFVi relative to baseline reduced to 5.2±3.7 % during occlusion and returned to 102.9±14.9 % during re-perfusion. Unlike ICG-VA, SurgeON BFM was able to monitor reduced BFVi and characterize re-perfusion robustly during five serial occlusion procedures conducted 2-5 min apart on the same vessel. Across four sheep MCA vessels, BFVi reduced to 18.6±7.7 % and returned to 120.1±27.8 % of baseline during occlusion and re-perfusion phases, respectively. SurgeON BFM can noninvasively monitor vascular occlusion status and provide intuitive visualization of BF information in real-time to an operating surgeon. This technology may find application in vascular, plastic, and neurovascular surgery.

Muscle Oxygen Extraction during Vascular Occlusion Test in Physically Very Active versus Inactive Healthy Men: A Comparative Study.

An increase in the delivery and use of oxygen to the musculature in physically active subjects are determinants of improving health-related aerobic capacity. Additional health benefits, such as an increase in the muscle mass and a decrease in fat mass, principally in the legs, could be achieved with weekly global physical activity levels of more than 300 min. The objective was to compare the muscle vascular and metabolic profiles of physically very active and inactive subjects. Twenty healthy men participated in the study; ten were assigned to the physically very active group (25.5 ± 4.2 years; 72.7 ± 8.1 kg; 173.7 ± 7.6 cm) and ten to the physically inactive group (30.0 ± 7.4 years; 74.9 ± 11.8 kg; 173.0 ± 6.4 cm). The level of physical activity was determined by the Global Physical Activity Questionnaire (GPAQ). A resting vascular occlusion test (5 min of an ischemic phase and 3 min of a reperfusion phase) was used, whereas a near-field infrared spectroscopy (NIRS) device was used to evaluate the muscle oxygenation in the right vastus lateralis of the quadriceps muscle. The area under the curve of the deoxyhemoglobin (HHb) during the ischemic phase and above the curve of the tissue saturation index (TSI) during the reperfusion phase were obtained to determine muscle metabolic and vascular responses, respectively. Physically very active group showed a higher absolute HHb (3331.9 ± 995.7 vs. 6182.7 ± 1632.5 mmol/s) and lower TSI (7615.0 ± 1111.9 vs. 5420.0 ± 781.4 %/s) and relative to body weight (46.3 ± 14.6 vs. 84.4 ± 27.1 mmol/s/kg and 106.0 ± 20.6 vs. 73.6 ± 13.8 %/s/kg, respectively), muscle mass (369.9 ± 122.2 vs. 707.5 ± 225.8 mmol/kg and 829.7 ± 163.4 vs. 611.9 ± 154.2 %/s/kg) and fat mass (1760.8 ± 522.9 vs. 2981.0 ± 1239.9 mmol/s/kg and 4160.0 ± 1257.3 vs. ±2638.4 ± 994.3 %/s/kg, respectively) than physically inactive subjects. A negative correlation was observed between HHb levels and TSI (r = -0.6; p < 0.05). Physically very active men (>300 min/week) present better muscle oxidative metabolism and perfusion and perform significantly more physical activity than physically inactive subjects. Extra benefits for vascular health and muscle oxidative metabolism are achieved when a subject becomes physically very active, as recommended by the World Health Organization. In addition, a higher level of physical activity determined by GPAQ is related to better vascular function and oxidative metabolism of the main locomotor musculature, i.e., the quadriceps.

Remotely Triggered LAD Occlusion Using a Balloon Catheter in Spontaneously Breathing Mice.

Acute myocardial infarction (AMI) is a prevalent and high-mortality cardiovascular condition. Despite advancements in revascularization strategies for AMI, it frequently leads to myocardial ischemia-reperfusion injury (IRI), amplifying cardiac damage. Murine models serve as vital tools for investigating both acute injury and chronic myocardial remodeling in vivo. This study presents a unique closed-chest technique for remotely inducing myocardial IRI in mice, enabling the investigation of the very early phase of occlusion and reperfusion using in-vivo imaging such as MRI or PET. The protocol utilizes a remote occlusion method, allowing precise control over ischemia initiation after chest closure. It reduces surgical trauma, enables spontaneous breathing, and enhances experimental consistency. What sets this technique apart is its potential for simultaneous noninvasive imaging, including ultrasound and magnetic resonance imaging (MRI), during occlusion and reperfusion events. It offers a unique opportunity to analyze tissue responses in almost real-time, providing critical insights into processes during ischemia and reperfusion. Extensive systematic testing of this innovative approach was conducted, measuring cardiac necrosis markers for infarction, assessing the area at risk using contrast-enhanced MRI, and staining infarcts at the scar maturation stage. Through these investigations, emphasis was placed on the value of the proposed tool in advancing research approaches to myocardial ischemia-reperfusion injury and accelerating the development of targeted interventions. Preliminary findings demonstrating the feasibility of combining the proposed innovative experimental protocol with noninvasive imaging techniques are presented herein. These initial results highlight the benefit of utilizing the purpose-built animal cradle to remotely induce myocardial ischemia while simultaneously conducting MRI scans.

Oxidation–reduction imaging of myoglobin reveals two-phase oxidation in the reperfused myocardium

Myocardial infarction (MI) is a serious acute cardiovascular syndrome that causes myocardial injury due to blood flow obstruction to a specific myocardial area. Under ischemic–reperfusion settings, a burst of reactive oxygen species is generated, leading to redox imbalance that could be attributed to several molecules, including myoglobin. Myoglobin is dynamic and exhibits various oxidation–reduction states that have been an early subject of attention in the food industry, specifically for meat consumers. However, rarely if ever have the myoglobin optical properties been used to measure the severity of MI. In the current study, we develop a novel imaging pipeline that integrates tissue clearing, confocal and light sheet fluorescence microscopy, combined with imaging analysis, and processing tools to investigate and characterize the oxidation–reduction states of myoglobin in the ischemic area of the cleared myocardium post-MI. Using spectral imaging, we have characterized the endogenous fluorescence of the myocardium and demonstrated that it is partly composed by fluorescence of myoglobin. Under ischemia–reperfusion experimental settings, we report that the infarcted myocardium spectral signature is similar to that of oxidized myoglobin signal that peaks 3 h post-reperfusion and decreases with cardioprotection. The infarct size assessed by oxidation–reduction imaging at 3 h post-reperfusion was correlated to the one estimated with late gadolinium enhancement MRI at 24 h post-reperfusion. In conclusion, this original work suggests that the redox state of myoglobin can be used as a promising imaging biomarker for characterizing and estimating the size of the MI during early phases of reperfusion.

Reduction of left ventricular diastolic pressure as a key regulator of infarct coronary flow under mechanical left ventricular support.

Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Acute mechanical left ventricular (LV) support has been suggested to improve infarct tissue perfusion. However, its regulatory mechanism remains unclear. We investigated the physiological mechanisms in six Yorkshire pigs, which were subjected to 90-min balloon occlusion of the left anterior descending artery. During the acute reperfusion phase, LV support using an Impella heart pump was initiated. LV pressure, coronary flow and pressure of the infarct artery were simultaneously recorded to evaluate the impact of LV support on coronary physiology. Coronary wave intensity was calculated to understand the forces regulating coronary flow. Significant increases in coronary flow velocity and its area under the curve were found after mechanical LV support. Among the coronary flow-regulating factors, coronary pressure was increased mainly during the late diastolic phase with less pulsatility. Meanwhile, LV pressure was reduced throughout diastole resulting in significant and consistent elevation of coronary driving pressure. Interestingly, the duration of diastole was prolonged with LV support. In the wave intensity analysis, the duration between backward suction and pushing waves was extended, indicating that earlier myocardial relaxation and delayed contraction contributed to the extension of diastole. In conclusion, mechanical LV support increases infarct coronary flow by extending diastole and augmenting coronary driving pressure. These changes were mainly driven by reduced LV diastolic pressure, indicatingthat the key regulator of coronary flow under mechanical LV support is downstream of the coronary artery, rather than upstream. Our study highlights the importance of LV diastolic pressure in infarct coronary flow regulation. KEY POINTS: Restoring ischaemic myocardial tissue perfusion is crucial for minimizing infarct size. Although mechanical left ventricular (LV) support has been suggested to improve infarct coronary flow, its specific mechanism remains to be clarified. LV support reduced LV pressure, and elevated coronary pressure during the late diastolic phase, resulting in high coronary driving pressure. This study demonstrated for the first time that mechanical LV support extends diastolic phase, leading to increased infarct coronary flow. Future studies should evaluate the correlation between improved infarct coronary flow and resulting infarct size.

Mitochondrial fumarate promotes ischemia/reperfusion-induced tubular injury.

Mitochondrial dysfunction, a characteristic pathological feature of renal Ischemic/reperfusion injury (I/RI), predisposes tubular epithelial cells to maintain an inflammatory microenvironment, however, the exact mechanisms through which mitochondrial dysfunction modulates the induction of tubular injury remains incompletely understood. ESI-QTRAP-MS/MS approach was used to characterize the targeted metabolic profiling of kidney with I/RI. Tubule injury, mitochondrial dysfunction, and fumarate level were evaluated using qPCR, transmission electron microscopy, ELISA, and immunohistochemistry. We demonstrated that tubule injury occurred at the phase of reperfusion in murine model of I/RI. Meanwhile, enhanced glycolysis and mitochondrial dysfunction were found to be associated with tubule injury. Further, we found that tubular fumarate, which resulted from fumarate hydratase deficiency and released from dysfunctional mitochondria, promoted tubular injury. Mechanistically, fumarate induced tubular injury by causing disturbance of glutathione (GSH) hemostasis. Suppression of GSH with buthionine sulphoximine administration could deteriorate the fumarate inhibition-mediated tubule injury recovery. Reactive oxygen species/NF-κB signaling activation played a vital role in fumarate-mediated tubule injury. Our studies demonstrated that the mitochondrial-derived fumarate promotes tubular epithelial cell injury in renal I/RI. Blockade of fumarate-mediated ROS/NF-κB signaling activation may serve as a novel therapeutic approach to ameliorate hypoxic tubule injury.

Comprehensive overview of the role of mitochondrial dysfunction in the pathogenesis of acute kidney ischemia-reperfusion injury: a narrative review.

Acute kidney ischemia-reperfusion (IR) injury is a life-threatening condition that predisposes individuals to chronic kidney disease. Since the kidney is one of the most energy-demanding organs in the human body and mitochondria are the powerhouse of cells, mitochondrial dysfunction plays a central role in the pathogenesis of IR-induced acute kidney injury. Mitochondrial dysfunction causes a reduction in adenosine triphosphate production, loss of mitochondrial dynamics (represented by persistent fragmentation), and impaired mitophagy. Furthermore, the pathological accumulation of succinate resulting from fumarate reduction under oxygen deprivation (ischemia) in the reverse flux of the Krebs cycle can eventually lead to a burst of reactive oxygen species driven by reverse electron transfer during the reperfusion phase. Accumulating evidence indicates that improving mitochondrial function, biogenesis, and dynamics, and normalizing metabolic reprogramming within the mitochondria have the potential to preserve kidney function during IR injury and prevent progression to chronic kidney disease. In this review, we summarize recent advances in understanding the detrimental role of metabolic reprogramming and mitochondrial dysfunction in IR injury and explore potential therapeutic strategies for treating kidney IR injury.

Abstract WP301: STAT3 Inhibition Reduces Infarct and Neuroinflammation in Experimental Stroke

Signal Transducer and Activator of Transcription 3 (STAT3) activation is increased in the brain following cerebral ischemia. STAT3, a transcription factor, is a positive regulator of cell survival and is implicated in cytoprotection following ischemia in multiple cell types, including neurons and endothelial cells. We hypothesized that pharmacological inhibition of STAT3 activation in mice during the reperfusion phase after middle cerebral artery occlusion (MCAO) will lead to increased infarct size. We subjected mice to 1-hour MCAO, following which they received STAT3 inhibitor Stattic (20 mg/kg), or vehicle, for 24 hours delivered subcutaneously via osmotic pump. Twenty-four hours later, infarct was measured by TTC and inflammatory cells were measured by flow cytometry. For experiments involving splenectomy, spleens were surgically removed 14 days prior to MCAO surgery. Surprisingly, we found that STAT3 inhibition reduces infarct after MCAO, with infarct in the hemisphere reducing from 49.90 ± 2.44 % in vehicle to 32.86 ± 1.55 % in Stattic-treated mice. Since STAT3 is involved in inflammatory processes, as well as cytoprotection, this led us to hypothesize that the reduction in infarct we observe may be due to decreased inflammation. We carried out FACS analysis and observed that Stattic inhibits MCAO-induced infiltration of B-, T- and dendritic cells into the brain. Neutrophil and monocyte infiltration into the brain were unaffected by Stattic. Since MCAO is known to induce splenic atrophy, with spleen size being inversely proportional to infarct volume, we measured spleen weights. Interestingly Stattic-treated mice had larger spleens (66.31 ± 5.40 g) compared to vehicle-treated mice (46.43 ± 4.60 g), indicating a dampened peripheral immune response upon inhibition of STAT3. Furthermore, Stattic was no longer effective in reducing infarct size in splenectomized mice. We conclude that pharmacological inhibition of STAT3 reduces infarct following MCAO, with the mechanism of protection involving differential regulation of the peripheral immune response.

Effects of occlusion pressure on hemodynamic responses recorded by near-infrared spectroscopy across two visits.

Ischemic Preconditioning (IPC) has emerged as a promising approach to mitigate the impact of hypoxia on physiological functions. However, the heterogeneity of occlusion pressures for inducing arterial occlusion has led to inconsistent hemodynamic outcomes across studies. This study aims to evaluate the peripheral hemodynamic responses to partial and total blood-flow occlusions on the left arm at rest, using absolute or individualized pressures, on two occasions. Thirty-five young males volunteered to participate in this study. IPC procedure (3 × 7-min) was performed on the left upper arm with cuff pressures at 50mmHg (G1), 50mmHg over the systolic blood pressure (SBP + 50mmHg) (G2) or 250mmHg (G3). NIRS-derived parameters were assessed for each occlusion and reperfusion phase in the brachioradialis. Results showed a significantly lower magnitude of deoxygenation (TSIAUC) for G1 compared to G2 (-1959.2 ± 1417.4 vs. -10908.1 ± 1607.5, P < 0.001) and G3 -1959.2 ± 1417.4 vs. -11079.3 ± 1828.1, P < 0.001), without differences between G2 and G3. However, G3 showed a significantly faster reoxygenation only for tissue saturation index (TSIslope) compared to G2 (1.3 ± 0.1 vs. 1.0 ± 0.2, P = 0.010), but without differences in the speed of recovery of deoxyhemoglobin [(HHb) slope], or in the magnitude of post-occlusive hyperemia (PORH). Besides TSI reoxygenation speed, G2 and G3 elicit comparable resting hemodynamic responses measured by NIRS. Thus, this study highlights the practicality and effectiveness of using relative occlusion pressures based on systolic blood pressure (SBP) rather than relying on excessively high absolute pressures.