Postischemic Reperfusion Research Articles

Meprin β expression associated with decreased proximal tubule PKA Cβ levels in ischemia/reperfusion‐induced acute kidney injury

Ischemia/ reperfusion (IR) is a leading cause of acute kidney injury (AKI). Meprins are metalloproteases that are expressed abundantly in the brush border membranes of renal proximal tubules (PTs). The levels of expression and the localization of meprins were previously shown to associate with IR‐induced AKI. Studies from our group showed that meprin B proteolytically cleaves three isoforms of the catalytic subunit of PKA, namely, PKA Cα1, Cβ1, and Cβ2. The cleavage by meprin B resulted in decreased kinase activity of these PKA C isoforms. Furthermore, the total levels of PKA C were significantly decreased in the meprin expressing PTs at 3h post‐IR when compared to distal tubules which are deficient in meprins. The objective of the current study was to determine which of the PKA C isoforms is impacted by meprin B and thus involved in the IR‐response mediated by meprin β. To this end, surgical procedures were used to induce unilateral IR (with contralateral nephrectomy) in 12‐week old wild‐type (WT) and meprin β knockout (βKO) mice on a C57BL/6 background. Kidney tissues were harvested at 6h post IR. Kidney proteins were extracted and fractionated into BBM‐, cytosolic‐, and nuclear‐enriched fractions. Western blot analysis was used to determine the levels of Cα and Cβ in the cytosolic‐ and nuclear‐enriched fractions. Immunofluorescence staining was used to determine the localization of PKA C (total), Cβ, and Cα. Statistical analysis utilized 2‐way ANOVA. The total levels of PKA C decreased in kidneys from WT mice subjected to IR but not in βKO counterparts. However, use of isoform‐specific antibodies demonstrated increases in the levels of Cβ but not Cα in the cytosolic‐ and nuclear‐enriched fractions. Two Cβ protein bands (41 and 37 kDa) were detected in cytosolic‐ and one band (41 kDa) in nuclear‐enriched fractions. The levels of the 41 kDa Cβ protein species were higher in lysates from WT kidneys at 6h post‐IR (P=0.0001). In contrast, the 37 kDa species, which was detected in nuclear‐enriched fractions only, decreased in βKO (P=0.002) but not in WT kidneys subjected to IR. A closer histological analysis of kidney sections showed that the level of damage to the brush borders was not uniform in all proximal tubules. More importantly, immunohistochemical analysis showed that the PKA Cβ levels decreased in damaged/injured meprin β expressing PTs but appeared to increase in intact PTs. These changes were not observed in PTs from meprin βKO kidneys. Individual interstitial cells (presumed to be resident macrophages) also stained positively for Cβ in WT but not in βKO kidney sections. Taken together, the data suggest that the PKA Cβ isoform is involved in the response to IR‐induced renal injury. The Cβ levels are known to be abundant in lymphoid tissue but our data indicate expression in immune cells resident in kidney tissue as well as epithelial tubular cells in response to IR‐induced AKI. More studies are needed to determine the response genes mediated by PKA Cβ signaling in IR to increase our understanding of how meprins modulate kidney injury in mice.Support or Funding InformationThis study was supported by the National Institute of Health/National Institutes of General Medical Sciences (NIGMS) Grant #s SC3GM102049 and SC1GM118271

Chronic reperfusion mediates restoring the integrity of c‐type cytochrome, limiting superoxide overproduction, and conferring reconditioning mitochondrial function in the postischemic heart

BackgroundA serious consequence of acute myocardial ischemia‐reperfusion injury (acute I/R) is oxidative damage which causes mitochondrial dysfunction. Such I/R‐induced mitochondrial dysfunction is observed as impaired state‐3 respiration and overproduction of superoxide. The cascading ROS (reactive oxygen species) propagates heme damage on the array of mitochondrial electron transport chain and cytochrome c (cytc), adding insult to myocardial injury. Chronic reperfusion partially restores mitochondrial function in the postischemic myocardium.MethodsWe employed proteomic analysis with native polyacrylamide gel electrophoresis (native‐PAGE) and LC‐MS/MS to identify heme impairment involved in interrupting the thioether bond formation between c‐type heme and holocytochrome focusing on two key mitochondrial ETC components: complex III (CxIII) and cyt c in the mitochondria of sham control as well as the mitochondria isolated from the infarct region of rat hearts subjected to 30‐min of coronary ligation and 24‐h (acute I/R) and 4‐week (chronic I/R) of reperfusion in vivo. The profile of heme in the mitochondria was assessed by differential UV/VIS spectral analysis. Ubiquinol (Q2H2)‐mediated SOD1‐inhibitable cytochrome c reduction was used to assay superoxide generation by the CxIII in mitochondria.ResultsWe detected carbamidomethylated C122 and C125 of the cytochrome c1 subunit of CxIII from alkylation of Cx3 exclusively in the mitochondria of acute I/R heart [detection of the tryptic peptide ion of CxxCH motif: 120QVC122(cam)SSC125(cam)HSMDYVAYR134, m/z 931.88512+, cam denotes carbamidomethylation by iodoacetamide]. The result was consistent with defect of thioether bonds formation of heme c1 and heme damage indicated by UV/VIS spectral analysis of mitochondria following acute I/R. Mitochondria from the infarct region of acute I/R have shown impaired enzymatic activity of CxIII and increased Q2H2‐mediated superoxide generation by CxIII. Acute I/R also mediated down‐regulation of cytochrome c heme lyase or holo cytochrome c synthetase (HCCS), further aggravating CxIII injury and associated mitochondrial dysfunction caused by thioether defect of c‐type cytochrome. In the mitochondria of risk region after chronic I/R (4‐week postischemic reperfusion), we have observed partial restoration of CxIII activity, protein expression of HCCS, integrity of c‐type heme, and decreasing Q2H2‐mediated superoxide generation. However, we have further observed that chronic reperfusion significantly down regulated the ratio of c‐type heme per c‐type cytochrome and associated c‐type cytochrome biogenesis.ConclusionAcute I/R mediates CxIII injury and aggravates mitochondrial dysfunction via impairing the thioether bonds of c‐type heme in the ETC components and increasing ROS production, whereas chronic reperfusion restores the integrity of c‐type cytochrome with downregulation of its biogenesis and limits ROS produciton.Support or Funding InformationNHLBI/NIH, HL083237

Characterization of a CholesteroNitrone (ISQ-201), a Novel Drug Candidate for the Treatment of Ischemic Stroke.

Nitrones have a well-recognized capacity as spin-traps and are considered powerful free radical scavengers, which are two important issues in hypoxia-induced oxidative stress and cell death in brain ischemia. Consequently, nitrones have been proposed as therapeutic agents in acute ischemic stroke (AIS). In this paper, we update the biological and pharmacological characterization of ISQ-201, a previously identified cholesteronitrone hybrid with antioxidant and neuroprotective activity. This study characterizes ISQ-201 as a neuroprotective agent against the hypoxia-induced ischemic injury. Transitory four-vessel occlusion and middle cerebral artery occlusion (tMCAO) were used to induce cerebral ischemia. Functional outcomes were determined using neurofunctional tests. Infarct area, neuronal death, and apoptosis induction were evaluated. In addition, ISQ-201 reactivity towards free radicals was studied in a theoretical model. ISQ-201 significantly decreased the ischemia-induced neuronal death and apoptosis, in a dose-dependent manner, showing its therapeutic effect when administered up until 6 h after post-ischemic reperfusion onset, effects that remained after 3 months from the ischemic episode. Furthermore, ISQ-201 significantly reduced infarct volume, leading to recovery of the motor function in the tMCAO model. Finally, the theoretical study confirmed the reactivity of ISQ-201 towards hydroxyl radicals. The results reported here prompted us to suggest ISQ-201 as a promising candidate for the treatment of AIS.

Iron, Insulin and Coronary Heart Disease Emphasis on the Generation of Sudden Death and Occult Diabetes (And Why Donating Blood Can Reduce Cardiovascular Death)

Dysregulated glucose metabolism promote inflammation in monocytes and macrophages from patients with atherosclerotic coronary artery disease. Men with metabolic syndrome are at increased risk for sudden cardiac death, and the incident sudden death is not explained by obesity or traditional cardiovascular risk factors (Kurl, 2016), but the ingested nutritional iron. Individuals with increased abdominal adiposity exhibit an increased risk of heart failure, in spite of there are oweweigtht or not (Cavalera, 2014), because the insulin resistance contribute to increased myocardial fibrosis in the absence of hypertension (Quilliot, 2005). Iron overload, and plasma viscosity contributes to cardiovascular risk in the general population, particularly in men (Van der A, 2005; Junker, 1998). Iron influences glucose metabolism, even in the absence of significant iron overload, and its reduction may alleviate coronary heart disease and reduced or prevent their complications: High stored or free iron levels (measured by serum ferritin or catalytic iron concentrations) elevate risk for development of coronary atherosclerosis, because labile iron accelerates endothelial dysfunction and originates oxidative injury that promotes systemic and vascular inflammation, phrothrombotic conditions and insulin resistance (Williams, 2002). High serum ferritin is strongly and independently associated with acute myocardial infarction and constitutes a novel risk factor in acute sudden event (Holay, 2012). Iron plays a direct and causal role in diabetes pathogenesis mediated both by β-cell failure and insulin resistance (Simcox, 2013). In the general population, body iron stores are positively associated with the development of glucose intolerance, type 2 diabetes and gestational diabetes. In this way, blood donation significant drops in the incidence of cardiovascular events, as well as in procedures such as percutaneous transluminal coronary angioplasty and coronary artery bypass grafting (Holsworth, 2013): frequent blood donations decreased iron stores in healthy volunteers, improving insulin sensitivity and hemodynamic parameters. Iron and oxygen-derived free radicals are important in the pathogenesis of postischemic reperfusion injury and contributes substantially to endothelial dysfunction in acute coronary syndromes (Chekanov, 2002; Duffy, 2001) , and a high iron diet potentially increase ischemic damage induced by transient ischemia and early reperfusion (García-Yébenes, 2012) in animals and humans. Iron, hyperinsulinemia, and hyperglycemia act in concert to up regulate free-radical reactions (Facchini, 2000) and this metal excess accelerated the development of atherosclerosis and its accumulation may promotes illness, particularly, ischemic cardiovascular diseases. Insulin resistance in macrophages promotes formation of a necrotic core in atherosclerotic plaques by enhancing macrophage apoptosis, and exposure it to circulating blood in the event of plaque rupture can precipitate thrombosis, leading to unstable angina pectoris, myocardial infarction and sudden death (Rask.Madsen, 2012, rev). In humans phlebotomy slows progression of peripheral vascular disease and blood donation lowers significantly the risk of myocardial infarction (Salonen, 1998), particularly in insulin-resistant subjects. On the contrary, exogenous iron into healthy individuals provoked endothelial dysfunction accompanied by increased generation of superoxide radical in whole blood (Vinchi, 2014, rev). A causal relationship between pre-diabetes and cardiovascular disease exist (Ford, 2010, rev). Humans lack effective mechanisms to excrete excess iron, and excessive dietary iron uptake cause iron deposition in heart, and pancreas (Kulaksis, 2008) leading to sudden death and occult diabetes mellitus. Iron play an underappreciated role in the development of insulin resistance and insulin resistance-induced heart failure. In a chronic and acute way, Insulin resistance is an early and major factor in the development of heart failure and acute iron induced insulin resistance in cardiomyocytes (Sung, 2019). 1- Introduction 2- Catalytic Iron; Irreversible Oxidizer 3- Excess Hemoglobin and Cardiocerebrovascular Pathology 4- Free Iron as a promoter of Ischemic Heart Disease 5- Excess Ferritin and pathogenesis of Endothelial Dysfunction 6- Hyperinsulinemia as a Sudden Death Promoter. The determining role of Iron 7- Iron accumulated in excess and pathogenesis of Diabetes: High hemoglobin versus High Ferritin 8- Iron and atherosclerosis. The evidence 9- Blood Donation. Cardiovascular Pathology Protector

Nanoparticle formulation and in vitro efficacy testing of the mitoNEET ligand NL-1 for drug delivery in a brain endothelial model of ischemic reperfusion-injury.

Ischemic reperfusion injury after a stroke is a leading cause of mortality and disability due to neuronal loss and tissue damage. Mitochondrial dysfunction plays a major role in the reperfusion-injury sequelae, and offers an attractive drug target. Mitochondrial derived reactive oxygen species (ROS) and resultant apoptotic cascade are among the primary mechanisms of neuronal death following ischemia and reperfusion injury. Here we optimized a nanoparticle formulation for the mitoNEET ligand NL-1, to target mitochondrial dysfunction post ischemic reperfusion (IR) injury. NL-1, a hydrophobic drug, was formulated using PLGA polymers with a particle size and entrapment efficiency of 123.9±17.1nm and 59.7±10.1%, respectively. The formulation was characterized for physical state of NL-1, in vitro release, uptake and nanoparticle localization. A near complete uptake of nanoparticles was found to occur by three hours, with the process being energy-dependent and occurring via caveolar mediated endocytosis. The fluorescent nanoparticles were found to localize in the cytoplasm of the endothelial cells. An in vitro oxygen glucose deprivation (OGD) model to mimic IR was employed for in vitro efficacy testing in murine brain vascular endothelium cells (bEND.3 cells). Efficacy studies showed that both NL-1 and the nanoparticles loaded with NL-1 had a protective activity against peroxide generation, and displayed improved cellular viability, as seen via reduction in cellular apoptosis. Finally, PLGA nanoparticles were found to have a non-toxic profile in vitro, and were found to be safe for intravenous administration. This study lays the preliminary work for potential use of mitoNEET as a target and NL-1 as a therapeutic for the treatment of cerebral ischemia and reperfusion injury.

Erythropoietin Derived Peptide Improved Endoplasmic Reticulum Stress and Ischemia-Reperfusion Related Cellular and Renal Injury.

Ischemia-reperfusion (IR) injury often affects transplant and native kidneys alike. IR injury is one of the main causes of acute kidney injury (AKI) and further associated with the progression of chronic kidney disease. Our previous study revealed the renoprotection of erythropoietin derived cyclic helix-B surface peptide (CHBP) against IR injury. However, the precise role and underlying mechanism of endoplasmic reticulum stress (ERS) in the injury and the renoprotection induced by IR or CHBP, respectively, have not been fully defined. This study using mouse kidney epithelial cells (TCMK-1) revealed that the level of CHOP (a key marker of ERS), PERK, and JNK (regulators of CHOP) was gradually increased by the prolonged time of hydrogen peroxide (H2O2) stimulation. In addition, CHOP mRNA and protein were significantly reduced by small interfering RNA (siRNA) target CHOP, as were apoptotic and inflammatory mediator caspase-3 and HMGB-1, and early apoptosis. Furthermore, CHOP mRNA was correlated positively with PERK protein, active caspase-3, HMGB-1 and apoptosis, but negatively with cell viability in vitro, while CHOP protein was also correlated positively with the level of tubulointerstitial damage and active caspase-3 protein in vivo. Finally, CHBP improved the viability of TCMK-1 cells subjected to H2O2 stimulation time-dependently, with reduced level of CHOP mRNA. CHBP also inhibited the increase of CHOP protein, not only in TCMK-1 cells, but also in the IR injury kidneys at 2 weeks. Moreover, CHBP reduced the expression of PERK mRNA and protein, JNK and HMGB-1 protein, as well as early and later apoptosis. In addition, raised CHOP at 12 h post IR injury might be an early time window for intervention. In conclusion, the differential role of ERS and CHBP in IR-related injury was proved in mouse TCMK-1 cells and kidneys, in which the mechanistic signaling pathway was associated with CHOP/PERK/JNK, HMGB-1/caspase-3, and apoptosis. CHOP might be a potential biomarker and CHBP might be therapeutic drug for IR-induced AKI.

Cardiovascular effects of DWORF (dwarf open reading frame) peptide in normal and ischaemia/reperfused isolated rat hearts

The novel peptide dwarf open reading frame (DWORF), highly conserved across species and expressed almost exclusively in cardiac ventricular muscle, may play a role in cardiac physiology and pathophysiology. The effect of direct administration of DWORF in the intact heart has not previously been examined. Accordingly, we investigated the cardiac effects of DWORF (1−30 nM) in normal isolated perfused rat hearts and hearts undergoing ischaemia/reperfusion (I/R) injury, and evaluated potential mechanisms of action. Exogenous DWORF at the top dose (30 nM) increased perfusion pressure (PP) in normal hearts, which indicates coronary vasoconstriction; and during post-ischaemic reperfusion, DWORF increased PP in a dose-dependent manner. In I/R hearts, DWORF at the top dose also increased left ventricular end-diastolic pressure and maximum and minimum derivatives of left ventricular pressure noted dP/dt(max) and dP/dt(min), respectively, without affecting developed pressure (DP). Co-infusion of DWORF with Diltiazem, an l-type Ca2+ channel blocker (1μM), in I/R hearts attenuated the falls in DP, dP/dt(max) and dP/dt(min) observed with Diltiazem alone. DWORF co-infusion with both Diltiazem and Y27632 (1μM) (a Rho-Kinase inhibitor) reversed the coronary vasodilator effect of the inhibitors administered alone. In conclusion, we provide the first evidence that DWORF has coronary vasoconstrictor actions in normal hearts and when administered during reperfusion in an ex-vivo model of cardiac I/R injury, and also exhibits positive cardiac inotropic activity in the latter setting. DWORF’s effect on ventricular contractile function appears to be dependent on the l-type Ca2+ channel, whereas Rho-Kinase activity may be related to the coronary vasoconstrictor effects of DWORF.

Extracorporeal membrane oxygenation mitigates myocardial injury and improves survival in porcine model of ventricular fibrillation cardiac arrest

IntroductionDespite decades of improved strategy in conventional cardiopulmonary resuscitation (CCPR), survival rates of favorable neurological outcome after cardiac arrest (CA) remains poor. It is indicated that the survival rate of successful resuscitation of extracorporeal membrane oxygenation (ECMO) is superior to that of CCPR. But the effect of ECMO in heart is unclear. We aimed to investigate whether ECMO produces cardiac protection by ameliorating post-ischemia reperfusion myocardial injury and myocardial apoptosis.MethodsAfter undergoing 8-min untreated ventricle fibrillation (VF) and 6-min basic life support, 20 male pigs were ultimately used in this study and randomly divided into two groups: CCPR group (n = 10) and extracorporeal CPR (ECPR) group (n = 10). Hemodynamics and blood samples were obtained at baseline and 1, 2, 4, and 6 h during resuscitation. The successfully resuscitated pigs were sacrificed at 6 h after return of spontaneous circulation (ROSC), and the hearts were removed and analyzed under electron microscopy, and immunohistochemistry, quantitative real-time polymerase chain reaction, and immunofluorescence staining assay were performed to evaluate myocardial injury and myocardial apoptosis.ResultsThere were no significant differences at basic hemodynamic status between the two groups. The survival rate of ECPR was significantly higher than CCPR group (10/10 [100%] vs. 4/10 [40%], P = 0.04). Compared to CCPR group, ECPR group exhibited a better outcome in hemodynamic function. Cardiac function was significantly impaired after ROSC in both groups, but left ventricular ejection fraction (LVEF) was significantly elevated in ECPR group than CCPR group. The expression of myocardial injury biomarkers (CK-MB, cTNI, H-FABP), endothelial injury biomarker (sP-selectin), and cardiac function biomarker (BNP) were remarkably increased after ROSC in both groups, but low levels in ECPR group than in CCPR group. Cardiomyocytes injury was attenuated in ECPR group under transmission electron microscopy (TEM). Typical apoptotic nuclei of cardiomyocytes were significantly reduced and oxidative damage were attenuated in ECPR group.ConclusionsDuring prolonged VF-induced CA, ECPR contributes to improving hemodynamics, attenuating myocardial ischemia-reperfusion injury, ameliorating myocardial ultra structure, improving cardiac function, and elevating survival rate by preventing oxidative damage, regulating energy metabolism, inhibiting cardiomyocyte apoptosis.

Progenitor/Stem Cell Delivery by Suprarenal Aorta Route in Acute Kidney Injury

Progenitor/stem cell-based kidney regenerative strategies are a key step towards the development of novel therapeutic regimens for kidney disease treatment. However, the route of cell delivery, e.g., intravenous, intra-arterial, or intra-parenchymal, may affect the efficiency for kidney repair in different models of acute and chronic injury. Here, we describe a protocol of intra-aorta progenitor/stem cell injection in rats following either acute ischemia-reperfusion injury or acute proteinuria induced by puromycin aminonucleoside (PAN) – the experimental prototype of human minimal change disease and early stages of focal and segmental glomerulosclerosis. Vascular clips were applied across both renal pedicles for 35 min, or a single dose of PAN was injected via intra-peritoneal route, respectively. Subsequently, 2 x 106 stem cells [green fluorescent protein (GFP)-labeled c-Kit+ progenitor/stem cells or GFP-mesenchymal stem cells] or saline were injected into the suprarenal aorta, above the renal arteries, after application of a vascular clip to the abdominal aorta below the renal arteries. This approach contributed to engraftment rates of ∼10% at day 8 post ischemia-reperfusion injury, when c-Kit+ progenitor/stem cells were injected, which accelerated kidney recovery. Similar rates of engraftment were found after PAN-induced podocyte damage at day 21. With practice and gentle surgical technique, 100% of the rats could be injected successfully, and, in the week following injection, ∼ 85% of the injected rats will recover completely. Given the similarities in mammals, much of the data obtained from intra-arterial delivery of progenitor/stem cells in rodents can be tested in translational research and clinical trials with endovascular catheters in humans.

Argon Inhalation for 24 Hours After Onset of Permanent Focal Cerebral Ischemia in Rats Provides Neuroprotection and Improves Neurologic Outcome.

We tested the hypothesis that prolonged inhalation of 70% argon for 24 hours after in vivo permanent or temporary stroke provides neuroprotection and improves neurologic outcome and overall recovery after 7 days. Controlled, randomized, double-blinded laboratory study. Animal research laboratories. Adult Wistar male rats (n = 110). Rats were subjected to permanent or temporary focal cerebral ischemia via middle cerebral artery occlusion, followed by inhalation of 70% argon or nitrogen in 30% oxygen for 24 hours. On postoperative day 7, a 48-point neuroscore and histologic lesion size were assessed. After argon inhalation for 24 hours immediately following "severe permanent ischemia" induction, neurologic outcome (neuroscore, p = 0.034), overall recovery (body weight, p = 0.02), and infarct volume (total infarct volume, p = 0.0001; cortical infarct volume, p = 0.0003; subcortical infarct volume, p = 0.0001) were significantly improved. When 24-hour argon treatment was delayed for 2 hours after permanent stroke induction or until after postischemic reperfusion treatment, neurologic outcomes remained significantly improved (neuroscore, p = 0.043 and p = 0.014, respectively), as was overall recovery (body weight, p = 0.015), compared with nitrogen treatment. However, infarct volume and 7-day mortality were not significantly reduced when argon treatment was delayed. Neurologic outcome (neuroscore), overall recovery (body weight), and infarct volumes were significantly improved after 24-hour inhalation of 70% argon administered immediately after severe permanent stroke induction. Neurologic outcome and overall recovery were also significantly improved even when argon treatment was delayed for 2 hours or until after reperfusion.

Neuroprotection mediated by remote preconditioning is associated with a decrease in systemic oxidative stress and changes in brain and blood glutamate concentration

It has been shown that ischemia of remote organs can generate resistance to ischemic conditions within sensitive brain tissues. However, only limited information about its mechanism is available. In the present paper, we used hind-limb ischemia by tourniquet to generate early remote ischemic tolerance in rats. The main objective was to investigate the role of glutamate in the process of neuroprotection and discover parameters that are affected in the blood of ischemia-affected animals. Our results showed that pretreatment with a hind-limb tourniquet caused a decrease in neurodegeneration by about 30%. However, we did not observe neurological deficit recovery. When compared to ischemia, glutamate concentration decreased in all observed brain regions (cortex, CA1 and dentate gyrus of hippocampus), regardless of their sensitivity to blood restrictions. In contrast to this, the blood levels raised significantly from 26% to 29% during the first four days of postischemic reperfusion. Pretreatment of animals reduced systemic oxidative stress—as represented by lymphocytic DNA damage—by about 80%, while changes in blood antioxidant enzymes (catalase, superoxide dismutase) were not detected.With these data we can further hypothesize that hind-limb-tourniquet preconditioning could accelerate brain-to-blood efflux of glutamate which could positively impact neuronal survival of ischemia-affected brain regions. Moreover, remote preconditioning improved systemic oxidative stress and did not seem to be affected by enzymatic antioxidant defenses in the blood.

Effect of dexmedetomidine on ischemia-reperfusion injury of liver and kidney tissues in experimental diabetes and hepatic ischemia-reperfusion injury induced rats

Background: Reperfusion following ischemia can lead to more injuries than ischemia itself especially in diabetic patients. The aim of this study was to evaluate the effect of dexmedetomidine on ischemia-reperfusion injury (IRI) in rats with have hepatic IRI and diabetes mellitus.

Cardioprotective Actions of the Annexin-A1 N-Terminal Peptide, Ac2-26, Against Myocardial Infarction.

The anti-inflammatory, pro-resolving annexin-A1 protein acts as an endogenous brake against exaggerated cardiac necrosis, inflammation, and fibrosis following myocardial infarction (MI) in vivo. Little is known, however, regarding the cardioprotective actions of the N-terminal-derived peptide of annexin A1, Ac2-26, particularly beyond its anti-necrotic actions in the first few hours after an ischemic insult. In this study, we tested the hypothesis that exogenous Ac2-26 limits cardiac injury in vitro and in vivo. Firstly, we demonstrated that Ac2-26 limits cardiomyocyte death both in vitro and in mice subjected to ischemia-reperfusion (I-R) injury in vivo (Ac2-26, 1 mg/kg, i.v. just prior to post-ischemic reperfusion). Further, Ac2-26 (1 mg/kg i.v.) reduced cardiac inflammation (after 48 h reperfusion), as well as both cardiac fibrosis and apoptosis (after 7-days reperfusion). Lastly, we investigated whether Ac2-26 preserved cardiac function after MI. Ac2-26 (1 mg/kg/day s.c., osmotic pump) delayed early cardiac dysfunction 1 week post MI, but elicited no further improvement 4 weeks after MI. Taken together, our data demonstrate the first evidence that Ac2-26 not only preserves cardiomyocyte survival in vitro, but also offers cardioprotection beyond the first few hours after an ischemic insult in vivo. Annexin-A1 mimetics thus represent a potential new therapy to improve cardiac outcomes after MI.

Prevention of Vascular Congestion Improves Renal Recovery and Function Post Renal Ischemia‐Reperfusion in Male Spontaneous Hypertensive Rats

Acute kidney injury (AKI) due to ischemia‐reperfusion (IR) is a serious and frequent complication in clinical settings and often progresses to kidney failure. The male gender is associated with greater severity and mortality following AKI, and young males have a greater prevalence of hypertension vs. age‐matched females. Despite the widespread prevalence of hypertension as a common co‐morbid condition with AKI, the impact of established hypertension on the progression of renal injury post‐AKI in either sex is poorly understood. Vascular congestion in the outer medulla is an early event occurring after IR, and congestion has been linked to worse renal outcomes following IR. The present study tested the hypothesis that increased vascular congestion in hypertensive males leads to impaired renal recovery compared to hypertensive females following renal IR. 13 wk old male and female normotensive Sprague Dawley rats (SD) and Spontaneous Hypertensive Rats (SHR) were subjected to sham or 25‐minute warm bilateral ischemia followed by reperfusion (n=6). Blood and urine were collected at 24 hrs and 7 days after IR; kidneys were harvested at 7 days for histological analysis. IR increased plasma creatinine (Pcr), BUN and proteinuria in all groups compared to respective sham controls at 24 hrs, with a sex difference in IR‐induced increases in Pcr observed in SD but not in SHR (SD Scr: Psex*IR<0.05; SHR Pcr: Psex*IR=0.4). At 7 days post‐IR, Pcr and BUN remained elevated only in male SHR compared to sham control (Pcr: PIR=0.03; BUN: PIR<0.05); Pcr and BUN returned to sham levels in all other groups. Histological examination of SHR kidneys at 7 days post‐IR showed sustained increases in vascular congestion (PIR=0.01; Psex*IR=0.002), damaged tubules (PIR=0.0003; Psex*IR=0.0019) and tubular cell apoptosis (P IR=0.001; Psex*IR=0.001) compared to sham controls in male SHR but not in females. Further, to study the role of IR induced vascular congestion on impaired recovery and loss of renal function in male SHR, additional SHR were pretreated with heparin (1500U/kg, n=6) prior to IR. Pre‐treatment with heparin prevented IR‐induced vascular congestion (PIR*Heparin=0.04) and tubular damage (PIR*Heparin=0.02) and improved renal function in male SHR 7 days post‐IR (Scr‐PIR*Heparin<0.05; BUN: PIR*Heparin=0.02) compared to heparin treated sham controls. Heparin pretreatment did not alter kidney function in female SHR 7 days post‐IR (Pcr‐PIR*Heparin=0.9; BUN: PIR*Heparin=0.2). In conclusion, our data demonstrated that persistent IR‐induced vascular congestion is a major driving factor to long‐term impaired renal recovery post IR in hypertensive males.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Blood Biomarkers of Parenchymal Damage in Ischemic Stroke Patients Treated With Revascularization Therapies.

Purpose:Postischemic reperfusion injury may exacerbate cerebral damage and capillary dysfunction, leading to brain edema (BE), hemorrhagic transformation (HT), necrosis, and injury from free radicals with subsequent infarct growth (IG). Several plasmatic biomarkers involved in the ischemic cascade have been studied in relation to radiological and clinical outcomes of reperfusion injury in ischemic stroke with heterogeneous results. This article provides a brief overview of the contribution of circulating biomarkers to the pathophysiology of parenchymal damage in ischemic stroke patients treated with revascularization therapies.Methods:We included full reports with measurements of plasma markers in patients with acute ischemic stroke treated with revascularization therapies.Findings:Our research included a large number of observational studies investigating a possible role of circulating biomarkers in the development of parenchymal damage after acute stroke treatments. To make the results clearer, we divided the review in 4 sections, exploring the relation of different biomarkers with each of the indicators of parenchymal damage (HT, BE, IG, recanalization).Discussion and conclusion:Definite conclusions are difficult to draw because of heterogeneity across studies. However, our review seems to confirm an association between some circulating biomarkers (particularly matrix metalloproteinase-9) and occurrence of parenchymal damage in ischemic stroke patients treated with revascularization therapies.

Phosphatidylserine-microbubble targeting-activated microglia/macrophage in inflammation combined with ultrasound for breaking through the blood\u2013brain barrier

Background and purposeInflammatory reaction plays a crucial role in cerebral ischemia reperfusion (IR) injury. It has been shown that activated microglia long-term existed in cerebral ischemia and induced second injury. Therefore, we hypothesize that prepared phosphatidylserine (PS)-modified microbubbles (PS-MBs) combined with ultrasound-targeted microbubble destruction (UTMD) can safely open the blood–brain barrier (BBB) and target activated microglia for inflammatory area in the later stage of ischemia reperfusion.MethodsTo verify our hypothesis, rat model of IR was established, then the change of activated microglia/macrophage (M/M) and permeability of BBB at 1, 7, 14, and 21 days could be clearly observed post IR. And the activated M/M still can be observed during the whole experiment.ResultsThe Evans blue extravasation of BBB gradually declined from day 1 to day 21. Compared to the control group, microbubbles containing PS were taken up more by activated M/M (approximately twofold) both in vitro and in vivo.ConclusionsPS-MBs combined with ultrasound (US) exposure could safely open BBB, and the resulting PS nanoparticles (PS-NPs) could further target activated M/M in the neuroinflammation.

The Post-Ischemic Increase in GluA2 Ser880 Phosphorylation Involves NADPH Oxidase

Most 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propanoic acid receptors (AMPARs) expressed on adult hippocampal pyramidal neurons contain the edited form of GluA2 (Q607R) and are thus impermeable to Ca2+/Zn2+ entry. Following ischemic injury, these receptors undergo a subunit composition change, switching from a GluA2-containing Ca2+/Zn2+-impermeable AMPAR to a GluA2-lacking Ca2+/Zn2+-permeable AMPAR. Recent studies indicate that an oxidative stress signaling pathway is responsible for the I/R-induced changes in AMPAR subunit composition. Studies suggest that nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase), a superoxide generator, is the source that initiates the oxidative stress-signaling cascade during post-ischemic reperfusion. The objective of the present study was to determine if suppression of NADPH oxidase activity prevents the increase in phosphorylation and subsequent internalization of the GluA2 AMPAR subunit during reperfusion of post-ischemic hippocampal slices. In this study, we demonstrated that exposure of adult rat hippocampal slices to oxygen glucose deprivation/reperfusion (OGD/R) results in an increase in Ser880 phosphorylation of the GluA2 subunit. The increase in Ser880 phosphorylation resulted in the dissociation of GluA2 from the scaffolding proteins Glutamate receptor-interacting protein 1 (GRIP1) and AMPAR binding protein (ABP), thus enabling the association of GluA2 with protein interacting with C kinase 1 (PICK1). OGD/R also resulted in an increase in the association of activated protein kinase C ? (PKC?) with PICK1. We have found that pharmacological inhibition of NADPH oxidase with apocynin diminishes the OGD/R-induced increase in activated PKC? association with PICK1 and subsequent Ser880 phosphorylation of GluA2. Suppression of NADPH oxidase activity also blunted OGD/R-induced decreased association of GluA2 with the scaffolding proteins GRIP1 and ABP. Protein phosphatase 2A (PP2A), which regulates PKC? activity by dephosphorylating the kinase, was inactivated by OGD/R-induced increase in tyrosine phosphorylation of the phosphatase (Y307). Inhibition of NADPH oxidase activity ameliorated OGD/R-induced PP2A phosphorylation and inactivation. Our findings are consistent with a model of OGD/R-induced Ser880 phosphorylation of GluA2 that implicates NADPH oxidase mediated inactivation of PP2A and sustained PKC? phosphorylation of GluA2.

Regulatory T Cells Promote Apelin-Mediated Sprouting Angiogenesis in Type 2 Diabetes

The role of CD4+ Tcells in the ischemic tissues of T2D patients remains unclear. Here, we report that T2D patients' vascular density was negatively correlated with the number of infiltrating CD4+ Tcells after ischemic injury. Th1 was the predominant subset, and Th1-derived IFN-γ and TNF-α directly impaired human angiogenesis. We then blocked CD4+ Tcell infiltration into the ischemic tissues of both Leprdb/db and diet-induced obese T2D mice. Genome-wide RNA sequencing shows an increased proliferative and angiogenic capability of diabetic ECs in ischemic tissues. Moreover, wire myography shows enhanced EC function and laser Doppler imaging reveals improved post-ischemic blood reperfusion. Mechanistically, functional revascularization after CD4 coreceptor blockade was mediated by Tregs. Genetic lineage tracing via Cdh5-CreER and Apln-CreER and coculture assays further illustrate that Tregs increased vascular density and induced de novo sprouting angiogenesis in a paracrine manner. Taken together, our results reveal that Th1 impaired while Tregs promoted functional post-ischemic revascularization in obesity and diabetes.

Cerebral blood perfusion deficits using dynamic susceptibility contrast MRI with gadolinium chelates in rats with post-ischemic reperfusion without significant dynamic contrast-enhanced MRI-derived vessel permeabilities: A cautionary note

In this study, we quantified perfusion deficits using dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) with an extravasating contrast agent (CA). We also investigated the efficacy of leakage compensation from CA pre-load in brains from post-ischemic rat models without significant dynamic contrast-enhanced MRI (DCE-MRI)-derived vessel wall permeability. DSC measurements were obtained using fast (0.3 s) echo-planar imaging in both normal rats and rats with transient middle carotid artery occlusion (MCAO) (1-h MCAO, 24-h reperfusion) after successive administrations of gadoterate meglumine (Dotarem) and intravascular superparamagnetic iron oxide nanoparticles (SPION). The relative cerebral blood volume (CBV) and cerebral blood flow (CBF) values acquired using Dotarem were significantly underestimated (~20%) when compared to those acquired using SPION in ipsilesional post-ischemic brain regions. A slight overestimation of relative mean transit time was observed. Areas with underestimated CBV and CBF values from the corresponding error maps encompassed the area of infarcted tissue (apparent diffusion coefficient < 500 μm2/s) and mostly coincided with the area wherein conspicuous longitudinal relaxation time differences were observed pre- vs. post-injection of Dotarem. The DSC measurements with significant pre-load (0.3 mmol·kg-1) of Dotarem displayed minimal perfusion deficits when compared to those determined using the reference intravascular SPION.

Infarct-Sparing Effect of Adenosine A2B Receptor Agonist Is Primarily Due to Its Action on Splenic Leukocytes Via a PI3K/Akt/IL-10 Pathway

BackgroundAdenosine A2B receptor (A2BAR) agonist reduces myocardial reperfusion injury by acting on inflammatory cells. Recently, a cardiosplenic axis was shown to mediate the myocardial postischemic reperfusion injury. This study aimed to explore whether the infarct-squaring effect of A2BAR agonist was primarily due to its action on splenic leukocytes. MethodsC57BL6 (wild type [WT]) mice underwent 40 min of left coronary artery occlusion followed by 60 min of reperfusion. A2BAR knockout (KO) and interleukin (IL)-10KO mice served as donors for splenic leukocytes. Acute splenectomy was performed 30 min before ischemia. The acute splenic leukocyte adoptive transfer was performed by injecting 5 × 106 live splenic leukocytes into splenectomized mice. BAY 60-6583, an A2BAR agonist, was injected by i.v. 15 min before ischemia. The infarct size (IS) was determined using 2,3,5-triphenyltetrazolium chloride and Phthalo blue staining. The expression of p-Akt and IL-10 was estimated by Western blotting. Immunofluorescence staining assessed the localization of IL-10 expression. ResultsBAY 60-6583 reduced the myocardial IS in intact mice but failed to reduce the same in splenectomized mice, which had a smaller IS than intact mice. BAY 60-6583 reduced the IS in splenectomized mice with the acute transfer of WT splenic leukocytes; however, it did not protect the heart of splenectomized mice with the acute transfer of A2BRKO splenic leukocytes. Furthermore, BAY 60-6583 increased the levels of p-Akt and IL-10 in the WT spleen. Moreover, it did not exert any protective effect in IL-10KO mice. ConclusionsA2BAR activation before ischemia stimulated the IL-10 production in splenic leukocytes via a PI3K/Akt pathway, thereby exerting anti-inflammatory effects that limited the myocardial reperfusion injury.