Inhibition of the Keap1-Nrf2 protein-protein interaction protects retinal cells and ameliorates retinal ischemia-reperfusion injury.

The Nrf2-Keap1 pathway regulates transcription of a wide array of antioxidant and cytoprotective genes and offers critical protection against oxidative stress. This pathway has demonstrated benefit for a variety of retinal conditions. Retinal ischemia plays a pivotal role in many vision threatening diseases. Retinal vascular endothelial cells are an important participant in ischemic injury. In this setting, Nrf2 provides a protective pathway via amelioration of oxidative stress and inflammation. In this study, we investigated a potent small molecule inhibitor of the Nrf2-Keap1 protein-protein interaction (PPI), CPUY192018, for its therapeutic potential in retinal cells and retinal ischemia-reperfusion injury. In human retinal endothelial cells (HREC), treatment with CPUY192018 increased Nrf2 protein levels and nuclear translocation, stimulated Nrf2-ARE-induced transcriptional capacity, and induced Nrf2 target gene expression. Furthermore, CPUY192018 protected HREC against oxidative stress and inflammatory activation. CPUY192018 also activated Nrf2 and suppressed inflammatory response in macrophages. In the retinal ischemia-reperfusion (I/R) model, administration of CPUY192018 induced Nrf2 target gene activation in the retina. Both systemic and topical treatment with CPUY192018 rescued visual function after ischemia-reperfusion injury. Taken together, these findings indicate that small molecule Keap1-Nrf2 PPI inhibitors can activate the Nrf2 pathway in the retina and provide protection against retinal ischemic and inflammatory injury, suggesting Keap1-Nrf2 PPI inhibition in the treatment of retinal conditions.

Efficacy and Safety of Tranexamic Acid in Pediatric Patients Undergoing Cardiac Surgery: A Single-Center Experience.

Aims: This study evaluated the efficacy and safety of tranexamic acid (TXA) undergoing cardiac surgery. Methods: Using a retrospective cohort study design, 2,026 consecutive pediatric patients who underwent surgical repair of atrial or ventricular septal defect or complete repair of Tetralogy of Fallot were included, and divided into a control group and a TXA group. Results: Compared with that in the control group, there were statistically significant reduction of both the 12-h and total postoperative blood loss in the TXA group [6.573 ± 0.144 vs. 5.499 ± 0.133 ml kg-1, mean difference (MD) 1.074 ml kg-1, p < 0.001; 12.183 ± 0.298 vs. 9.973 ± 0.276 ml kg-1, MD, 2.210 ml kg-1, p < 0.001]. There was a statistically significant reduction of the MD of 12-h postoperative blood loss due to TXA in patients aged < 1 year compared with that in patients aged ≥1 year (MD, 1.544 vs. 0.681 ml kg-1, P = 0.007). There were statistically significant reduction of the MD of both the 12-h and total postoperative blood loss due to TXA in patients weighing < 10 kg compared with that in patients weighing ≥10 kg (MD, 1.542 vs. 0.456 ml kg-1, P < 0.001, and MD, 2.195 vs. 0.929 ml kg-1, P = 0.036, respectively). There was a statistically significant reduction of the MD of total postoperative blood loss due to TXA in cyanotic patients compared with that in acyanotic patients (MD, 3.381 vs. 1.038 ml kg-1, P = 0.002). There was no significant difference in the postoperative volume or exposure of allogeneic transfusion, in-hospital morbidity or mortality between the groups. Conclusions: TXA took effects in reduction of postoperative blood loss but not the allogeneic transfusion requirement in pediatric patients undergoing cardiac surgery, particularly in infants weighing < 10 kg and cyanotic children. Moreover, the study suggested the use of TXA was safe in pediatric cardiac surgery.

Epidemiology of acute kidney injury among paediatric patients after repair of anomalous origin of the left coronary artery from the pulmonary artery.

OBJECTIVES: Acute kidney injury (AKI) is a prevalent complication after the surgical repair of paediatric cardiac defects and is associated with poor outcomes. Insufficient renal perfusion secondary to severe myocardial dysfunction in neonates is most likely an independent risk factor in patients undergoing repair for anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA). We retrospectively investigated the epidemiology and outcomes of children with ALCAPA who developed AKI after repair. METHODS: Eighty-nine children underwent left coronary reimplantation. The paediatric-modified risk, injury, failure, loss and end-stage (p-RIFLE) criteria were used to diagnose AKI. RESULTS: The incidence of AKI was 67.4% (60/89) in our study. Among the patient cohort with AKI, 23 (38.3%) were diagnosed with acute kidney injury/failure (I/F) (20 with acute kidney injury and 3 with acute kidney failure). Poor cardiac function (left ventricular ejection fraction < 35%) prior to surgery was a significant contributing factor associated with the onset of AKI [odds ratio (OR) 5.55, 95% confidential interval (CI) 1.39-22.13; P = 0.015], while a longer duration from diagnosis to surgical repair (OR 0.97, 95% CI 0.95-1.00; P = 0.049) and a higher preoperative albumin level (OR 0.83, 95% CI 0.70-0.99; P = 0.041) were found to lower the risk of AKI. Neither the severity of preoperative mitral regurgitation nor mitral annuloplasty was associated with the onset of AKI. After reimplantation, there was 1 death in the no-AKI group and 2 deaths in the AKI/F group (P = 0.356); the remaining patients survived until hospital discharge. The median follow-up time was 46.5 months (34.0-63.25). During follow-up, patients in the AKI cohort were seen more often by specialists and reassessed more often by echocardiography. CONCLUSIONS: Paediatric AKI after ALCAPA repair occurs at a relatively higher incidence than that suggested by previous reports and is linked to poor clinical outcomes. Preoperative cardiac dysfunction (left ventricular ejection fraction < 35%) is strongly associated with AKI. The beneficial effect of delaying surgery seen in some of our cases warrants further investigation, as it is not concordant with standard teaching regarding the timing of surgery for ALCAPA.

Long non-coding RNA CASC2 suppresses pulmonary artery smooth muscle cell proliferation and phenotypic switch in hypoxia-induced pulmonary hypertension.

BACKGROUND: In this study, we aimed to investigate whether and how lncRNA CASC2 was involved in hypoxia-induced pulmonary hypertension (PH)-related vascular remodeling. METHODS: The expression of lncRNAs or mRNAs was detected by qRT-PCR, and western blot analysis or immunochemistry was employed for detecting the protein expression. Cell number assay and EdU (5-ethynyl-2'-deoxyuridine) staining were performed to assess cell proliferation. Besides, flow cytometry and wound healing assay were employed for assessments of cell apoptosis and cell migration, respectively. Rat model of hypoxic PH was established and the hemodynamic measurements were performed. Hematoxylin and eosin (HE) and Masson's trichrome staining were carried out for pulmonary artery morphometric analysis. RESULTS: The expression of lncRNA CASC2 was decreased in hypoxia-induced rat pulmonary arterial tissues and pulmonary artery smooth muscle cells (PASMCs). Up-regulation of lncRNA CASC2 inhibited cell proliferation, migration yet enhanced apoptosis in vitro and in vivo in hypoxia-induced PH. Western blot analysis and immunochemistry showed that up-regulation of lncRNA CASC2 greatly decreased the expression of phenotype switch-related marker α-SMA in hypoxia-induced PH. Furthermore, it was indicated by the pulmonary artery morphometric analysis that lncRNA CASC2 suppressed vascular remodeling of hypoxia-induced rat pulmonary arterial tissues. CONCLUSION: LncRNA CASC2 inhibited cell proliferation, migration and phenotypic switch of PASMCs to inhibit the vascular remodeling in hypoxia-induced PH.

Levosimendan confers perioperative renoprotection in severe patients undergoing cardiac surgery: A systematic review and meta-analysis / 中国胸心血管外科临床杂志

@#Objective    To evaluate the effect of levosimendan on acute kidney injury (AKI) in patients with left ventricular dysfunction (preoperative left ventricular ejection fraction≤40.0%) undergoing cardiac surgery. Methods    A systematic review and meta-analysis was conducted based on a comprehensive search of the randomized controlled trial (RCT) from PubMed, EMbase and The Cochrane Library (up to Jan 2018). The clinical endpoints included the incidence of AKI and need for renal replacement therapy (RRT), mortality, mechanic ventilation (MV) duration and intensive care unit (ICU) stay. Random-effect model was used for the potential clinical inconsistency. All analyses were performed by RevMan 5.3 and Stata 12.0. Results    Thirteen trials with a total of 2 046 patients were selected. Compared with controls, levosimendan significantly reduced the incidence of postoperative AKI (OR=0.44, P=0.000 1, I2=0%), the risk of RRT (OR=0.63, P=0.02, I2=0%) and the mortality (OR=0.49, P<0.000 1, I2=0%). Levosimendan also shortened the postoperative MV duration (WMD=–5.62, P=0.07, I2=93%) and ICU stay (WMD=–1.50, P=0.005, I2=98%). Conclusion    The present meta-analysis suggests that perioperative levosimendan for patients with left ventricular ejection fraction≤40.0%undergoing cardiac surgery reduces the incidence of AKI, RRT and death, as well as shortens MV duration and ICU stay.

Levosimendan for Pediatric Anomalous Left Coronary Artery From the Pulmonary Artery Undergoing Repair: A Single-Center Experience.

Objectives: Our aim was to retrospectively evaluate the benefit of levosimendan in certain complicated congenital heart procedures such as the pediatric anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) with moderate or severe cardiac dysfunction and its repair. Study Design: We enrolled 40 pediatric patients with ALCAPA and moderate or severe left ventricular dysfunction. Patients who had a preoperative left ventricular ejection fraction (LVEF) of 50% or less and had undergone the surgical correction of their coronary artery through cardiopulmonary bypass met the criteria of our study. Twenty patients were given 0.1-0.2 µg/kg/min levosimendan at the induction of anesthesia, which lasted for 24 h. The remaining 20 patients were not given levosimendan. Results: The mean preoperative LVEF in the levosimendan group was significantly lower than that in the non-levosimendan group (22.5 ± 10.7% vs. 31.8 ± 8.1%, p = 0.004). On postoperative day 7, the LVEF in the levosimendan group was still significantly lower (27.1 ± 8.9% vs. 37.5 ± 11.0%, p = 0.002). There was no significant difference in ΔLVEF detected on day 7 [median 30.8%, interquartile range (IQR) -4.4 to 63.5% vs. median 15.1%, IQR -3.5 to 40.0%, p = 0.560] or at follow-up of about 180 days (median 123.5%, IQR 56.1-222.6% vs. median 80.0%, IQR 36.4-131.3%, p = 0.064). There was no significant difference between the two groups in postoperative vasoactive-inotropic score (VIS) at any of the time points of 1, 6, 12, 24, and 48 h (p = 0.093). Three patients had to be supported by extracorporeal membrane oxygenation when difficulty appeared in weaning off cardiopulmonary bypass because of low cardiac output in the non-levosimendan group, but no patient needed extracorporeal membrane oxygenation after levosimendan infusion (p = 0.231). The length of intensive care unit stay (median 10.5 days, IQR 7.3-39.3 days vs. median 4.0 days, IQR 2.0-10.0 days, p = 0.002) and duration of mechanical ventilation (median 146.0 h, IQR 76.5-888.0 h vs. median 27.0 h, IQR 11.0-75.0 h, p = 0.002) were revealed to be longer in the levosimendan group. Peritoneal dialysis occurred in eight patients (40%) in the levosimendan group and two patients (10%) in the non-levosimendan group (p = 0.028). No significant difference was revealed in all-cause mortality within 180 days, which occurred in two patients (10%) in the levosimendan group and one (5%) in the non-levosimendan group (p = 1.00). Conclusion: Levosimendan's unique pharmacological properties have strong potential for cardiac function recovery among pediatric patients with ALCAPA with impaired left ventricular function who have undergone surgical repair.However, any improvement from levosimendan on postoperative outcomes or mortality was not substantiated by this study and must be investigated further.

Fibrinogen Concentrate in Cardiovascular Surgery: A Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Postoperative bleeding remains a frequent complication after cardiovascular surgery and may contribute to serious morbidity and mortality. Observational studies have suggested a relationship between low endogenous plasma fibrinogen concentration and increased risk of postoperative blood loss in cardiac surgery. Although the transfusion of fibrinogen concentrate has been increasing, potential benefits and risks associated with perioperative fibrinogen supplementation in cardiovascular surgery are not fully understood. METHODS: PubMed, Cochrane Library, Ovid MEDLINE, Embase, Web of Science, and China National Knowledge Infrastructure were searched on January 15, 2017, with automated updates searched until February 15, 2018, to identify all randomized controlled trials (RCTs) of fibrinogen concentrate, whether for prophylaxis or treatment of bleeding, in adults undergoing cardiovascular surgery. All RCTs comparing fibrinogen infusion versus any other comparator (placebo/standard of care or another active comparator) in adult cardiovascular surgery and reporting at least 1 predefined clinical outcome were included. The random-effects model was used to calculate risk ratios and weighted mean differences (95% confidence interval [CI]) for dichotomous and continuous variables, respectively. Subgroup analyses by fibrinogen dose and by baseline risk for bleeding were preplanned. RESULTS: A total of 8 RCTs of fibrinogen concentrate in adults (n = 597) of mixed risk or high risk undergoing cardiovascular surgery were included. Compared to placebo or inactive control, perioperative fibrinogen concentrate did not significantly impact risk of all-cause mortality (risk ratio, 0.41; 95% CI, 0.12-1.38; I = 10%; P = .15). Fibrinogen significantly reduced incidence of allogeneic red blood cell transfusion (risk ratio, 0.64; 95% CI, 0.49-0.83; I = 0%; P = .001). No significant differences were found for other clinical outcomes. Subgroup analyses were unremarkable when analyzed according to fibrinogen dose, time of infusion initiation, mean cardiopulmonary bypass time, and rotational thromboelastometry/fibrinogen temogram use (all P values for subgroup interaction were nonsignificant). CONCLUSIONS: Current evidence remains insufficient to support or refute routine perioperative administration of fibrinogen concentrate in patients undergoing cardiovascular surgery. Fibrinogen concentrate may reduce the need for additional allogeneic blood product transfusion in cardiovascular surgery patients at high risk or with evidence of bleeding. However, no definitive advantage was found for reduction in risk of mortality or other clinically relevant outcomes. The small number of clinical events within existing randomized trials suggests that further well-designed studies of adequate power and duration to measure all-cause mortality, stroke, myocardial infarction, reoperation, and thromboembolic events should be conducted. Future studies should also address cost-effectiveness relative to standard of care.

A Mouse Model of Retinal Ischemia-Reperfusion Injury Through Elevation of Intraocular Pressure.

Retinal ischemia-reperfusion (I/R) is a pathophysiological process contributing to cellular damage in multiple ocular conditions, including glaucoma, diabetic retinopathy, and retinal vascular occlusions. Rodent models of I/R injury are providing significant insights into mechanisms and treatment strategies for human I/R injury, especially with regard to neurodegenerative damage in the retinal neurovascular unit. Presented here is a protocol for inducing retinal I/R injury in mice through elevation of intraocular pressure (IOP). In this protocol, the ocular anterior chamber is cannulated with a needle, through which flows the drip of an elevated saline reservoir. Using this drip to raise IOP above systolic arterial blood pressure, a practitioner temporarily halts inner retinal blood flow (ischemia). When circulation is reinstated (reperfusion) by removal of the cannula, severe cellular damage ensues, resulting ultimately in retinal neurodegeneration. Recent studies demonstrate inflammation, vascular permeability, and capillary degeneration as additional elements of this model. Compared to alternative retinal I/R methodologies, such as retinal arterial ligation, retinal I/R injury by elevated IOP offers advantages in its anatomical specificity, experimental tractability, and technical accessibility, presenting itself as a valuable tool for examining neuronal pathogenesis and therapy in the retinal neurovascular unit.

Nrf2 promotes reparative angiogenesis through regulation of NADPH oxidase-2 in oxygen-induced retinopathy.

Revascularization of ischemic tissue is a highly desirable outcome in multiple diseases, including cardiovascular diseases and ischemic retinopathies. Oxidative stress and inflammation are both known to play a role in suppressing reparative angiogenesis in ischemic disease models including oxygen-induced retinopathy (OIR), but the regulatory molecules governing these pathophysiologic processes in retinal ischemia are largely unknown. Nrf2 is a major stress-response transcription factor that has been implicated in regulating ischemic angiogenesis in the retina and other tissue beds. Using Nrf2-deficient mice, we investigated the effects of Nrf2 in regulating revascularization and modulating the retinal tissue milieu during ischemia. Strikingly, Nrf2's beneficial effect on reparative angiogenesis only became manifested in the later phase of ischemia in OIR, from postnatal day 14 (P14) to P17. This was temporally associated with a reduction in both oxidative stress and inflammatory mediators in wild-type compared to Nrf2-/- mice. Nrf2-/- retinas exhibited an increase in VEGF but also induction of anti-angiogenic Dll4/Notch signaling. NADPH oxidase (NOX), and especially NOX2, is a major pathogenic molecule and a particularly important contributor to oxidative stress in multiple retinal disease processes. Nrf2-/- mice exhibited a significant exacerbation of NOX2 induction in OIR that manifested in the later phases of ischemia. Pharmacologic inhibition of NADPH oxidase abrogated the adverse effect of Nrf2 deficiency on reparative angiogenesis. Taken together, this suggests that Nrf2 is an important regulator of the retinal milieu during tissue ischemia, and that the Nrf2/NOX2 balance may play a critical role in determining the fate of ischemic revascularization.

Levosimendan for Prevention of Acute Kidney Injury After Cardiac Surgery: A Meta-analysis of Randomized Controlled Trials.

BACKGROUND: Levosimendan has been shown to confer direct renoprotection in renal endotoxemic and ischemia-reperfusion injury and could increase renal blood flow in patients with low-cardiac-output heart failure. Results from clinical trials of levosimendan on acute kidney injury (AKI) following cardiac surgery are controversial. STUDY DESIGN: A random-effect meta-analysis was conducted based on evidence from PubMed, EMBASE, and Cochrane Library. SETTINGS & POPULATION: Adult patients undergoing cardiac surgery. SELECTION CRITERIA FOR STUDIES: Randomized controlled trials comparing the renal effect of levosimendan versus placebo or other inotropic drugs during cardiac surgery. INTERVENTION: Perioperative levosimendan continuous infusion at a rate of 0.1 to 0.2µg/kg/min following a loading dose (6-24µg/kg) for 24 hours or only 1 loading dose (24µg/kg) within 1 hour. OUTCOMES: AKI, need for renal replacement therapy, mechanical ventilation duration, intensive care unit stay during hospitalization, and postoperative mortality (in-hospital or within 30 days). RESULTS: 13 trials with a total of 1,345 study patients were selected. Compared with controls, levosimendan reduced the incidence of postoperative AKI (40/460 vs 78/499; OR, 0.51; 95% CI, 0.34-0.76; P=0.001; I(2)=0.0%), renal replacement therapy (22/492 vs 49/491; OR, 0.43; 95% CI, 0.25-0.76; P=0.002; I(2)=0.0%), postoperative mortality (35/658 vs 94/657; OR, 0.41; 95% CI, 0.27-0.62; P<0.001; I(2)=0.0%), mechanical ventilation duration (in days; n=235; weighted mean difference, -0.34; 95% CI, -0.58 to -0.09; P=0.007], and intensive care unit stay (in days; n=500; weighted mean difference, -2.2; 95% CI, -4.21 to -0.13; P=0.04). LIMITATIONS: Different definitions for AKI among studies. Small sample size for some trials. CONCLUSIONS: Perioperative administration of levosimendan in patients undergoing cardiac surgery may reduce complications. Future trials are needed to determine the dose effect of levosimendan in improving outcomes, especially in patients with decreased baseline kidney function.

Nrf2 in ischemic neurons promotes retinal vascular regeneration through regulation of semaphorin 6A.

Delayed revascularization of ischemic neural tissue is a major impediment to preservation of function in central nervous system (CNS) diseases including stroke and ischemic retinopathies. Therapeutic strategies allowing rapid revascularization are greatly needed to reduce ischemia-induced cellular damage and suppress harmful pathologic neovascularization. However, key mechanisms governing vascular recovery in ischemic CNS, including regulatory molecules governing the transition from tissue injury to tissue repair, are largely unknown. NF-E2-related factor 2 (Nrf2) is a major stress-response transcription factor well known for its cell-intrinsic cytoprotective function. However, its role in cell-cell crosstalk is less appreciated. Here we report that Nrf2 is highly activated in ischemic retina and promotes revascularization by modulating neurons in their paracrine regulation of endothelial cells. Global Nrf2 deficiency strongly suppresses retinal revascularization and increases pathologic neovascularization in a mouse model of ischemic retinopathy. Conditional knockout studies demonstrate a major role for neuronal Nrf2 in vascular regrowth into avascular retina. Deletion of neuronal Nrf2 results in semaphorin 6A (Sema6A) induction in hypoxic/ischemic retinal ganglion cells in a hypoxia-inducible factor-1 alpha (HIF-1α)-dependent fashion. Sema6A expression increases in avascular inner retina and colocalizes with Nrf2 in human fetal eyes. Extracellular Sema6A leads to dose-dependent suppression of the migratory phenotype of endothelial cells through activation of Notch signaling. Lentiviral-mediated delivery of Sema6A small hairpin RNA (shRNA) abrogates the defective retinal revascularization in Nrf2-deficient mice. Importantly, pharmacologic Nrf2 activation promotes reparative angiogenesis and suppresses pathologic neovascularization. Our findings reveal a unique function of Nrf2 in reprogramming ischemic tissue toward neurovascular repair via Sema6A regulation, providing a potential therapeutic strategy for ischemic retinal and CNS diseases.

Neuroprotective role of Nrf2 for retinal ganglion cells in ischemia-reperfusion.

Retinal ischemia plays a critical role in multiple vision-threatening diseases and leads to death of retinal neurons, particularly ganglion cells. Oxidative stress plays an important role in this ganglion cell loss. Nrf2 (NF-E2-related factor 2) is a major regulator of the antioxidant response, and its role in the retina is increasingly appreciated. We investigated the potential retinal neuroprotective function of Nrf2 after ischemia-reperfusion (I/R) injury. In an experimental model of retinal I/R, Nrf2 knockout mice exhibited much greater loss of neuronal cells in the ganglion cell layer than wild-type mice. Primary retinal ganglion cells isolated from Nrf2 knockout mice exhibited decreased cell viability compared to wild-type retinal ganglion cells, demonstrating the cell-intrinsic protective role of Nrf2. The retinal neuronal cell line 661W exhibited reduced cell viability following siRNA-mediated knockdown of Nrf2 under conditions of oxidative stress, and this was associated with exacerbation of increase in reactive oxygen species. The synthetic triterpenoid CDDO-Im (2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide), a potent Nrf2 activator, inhibited reactive oxygen species increase in cultured 661W under oxidative stress conditions and increased neuronal cell survival after I/R injury in wild-type, but not Nrf2 knockout mice. Our findings indicate that Nrf2 exhibits a retinal neuroprotective function in I/R and suggest that pharmacologic activation of Nrf2 could be a therapeutic strategy. Oxidative stress is thought to be an important mediator of retinal ganglion cell death in ischemia-reperfusion injury. We found that the transcription factor NF-E2-related factor 2 (Nrf2), a major regulator of oxidative stress, is an important endogenous neuroprotective molecule in retinal ganglion cells in ischemia-reperfusion, exerting a cell-autonomous protective effect.  The triterpenoid 2-Cyano-3,12-dioxooleana-1,9-dien-28-imidazolide (CDDO-Im) reduces neurodegeneration following ischemia-reperfusion in an Nrf2-dependent fashion. This suggests that Nrf2-activating drugs including triterpenoids could be a therapeutic strategy for retinal neuroprotection.

Restoration of autophagic flux in myocardial tissues is required for cardioprotection of sevoflurane postconditioning in rats.

AIM: Sevoflurane postconditioning (SpostC) has been shown to protect the heart from ischemia-reperfusion (I/R) injury. In this study, we examined whether SpostC affected autophagic flux in myocardial tissues that contributed to its cardioprotective effects in rats following acute I/R injury. METHODS: SD rats underwent 30 min of left anterior descending coronary artery ligation followed by 120 min of reperfusion. The rats were subjected to inhalation of 2.4% (v/v) sevoflurane during the first 5 min of reperfusion, and chloroquine (10 mg/kg, ip) was injected 1 h before I/R. Myocardial infarct size was estimated using TTC staining. Autophagosomes in myocardial tissues were detected under TEM. Expression of LC3B-II, beclin-1, p62/SQSTM1, cathepsin B, caspase-3 and cleaved PARP was assessed using Western blot analysis. Plasma cardiac troponin I was measured using ELISA. Cardiomyocyte apoptosis was evaluated with TUNEL staining. RESULTS: I/R procedure produced severe myocardium infarct and apoptosis accompanied by markedly increased number of autophagosomes, as well as increased levels of LC3B-II, beclin-1 and p62 in myocardial tissues. SpostC significantly reduced infarct size, attenuated myocardial apoptosis, restored intact autophagic flux and improved the lysosomal function in myocardial tissues. Administration of chloroquine that blocked autophagic flux abrogated the cardioprotective effects of SpostC. CONCLUSION: SpostC exerts its cardioprotective effects in rats following I/R injury via restoring autophagic flux in myocardial tissues.

Delayed remote preconditioning induces cardioprotection: role of heme oxygenase-1.

BACKGROUND: The role of heme oxygenase-1 (HO-1) in the cardioprotection induced by delayed remote ischemic preconditioning (DRIPC) has not been investigated. Therefore, this study was designed to investigate whether HO-1 is involved in DRIPC-mediated cardioprotection in an isolated perfused rat heart model. MATERIALS AND METHODS: Isolated rat hearts were subjected to 30 min ischemia followed by 60 min reperfusion. DRIPC (four cycles 5-min occlusion and 5-min reflow at the unilateral hind limb once per day for 1, 2, or 3 d before heart isolation, abbreviated as D1RIPC, D2RIPC, or D3RIPC respectively). Infarct size, myocardial troponin levels, and heart function were measured. The protein and messenger RNA levels of HO-1 were determined. RESULTS: DRIPC facilitated postischemic cardiac functional recovery and decreased cardiac enzyme release. The infarct size-limiting effect of DRIPC was more pronounced in the D3RIPC group (10.22 ± 2.57%) than the D1RIPC group (22.34 ± 4.02%, P < 0.001) or the D2RIPC group (14.60 ± 3.13%, P = 0.034). These effects in the D1RIPC group could be blocked by Zinc Protoporphyrin IX (ZnPP) (an HO-1 specific inhibitor). DRIPC-mediated cardioprotection was associated with enhanced HO-1 protein expression (D1RIPC, 0.11 ± 0.03; versus 0.15 ± 0.06 in the D2RIPC group, P = 0.06; versus 0.20 ± 0.04 in the D3RIPC group, P = 0.04) and messenger RNA levels of HO-1 expression. CONCLUSIONS: Our findings suggest that HO-1 is involved in the cardioprotection induced by DRIPC, and that increase in the number of preconditioning stimuli may enhance cardioprotective effects accompanied with increased HO-1 level.

NRF2 plays a protective role in diabetic retinopathy in mice.

AIMS/HYPOTHESIS: Although much is known about the pathophysiological processes contributing to diabetic retinopathy (DR), the role of protective pathways has received less attention. The transcription factor nuclear factor erythroid-2-related factor 2 (also known as NFE2L2 or NRF2) is an important regulator of oxidative stress and also has anti-inflammatory effects. The objective of this study was to explore the potential role of NRF2 as a protective mechanism in DR. METHODS: Retinal expression of NRF2 was investigated in human donor and mouse eyes by immunohistochemistry. The effect of NRF2 modulation on oxidative stress was studied in the human Müller cell line MIO-M1. Non-diabetic and streptozotocin-induced diabetic wild-type and Nrf2 knockout mice were evaluated for multiple DR endpoints. RESULTS: NRF2 was expressed prominently in Müller glial cells and astrocytes in both human and mouse retinas. In cultured MIO-M1 cells, NRF2 inhibition significantly decreased antioxidant gene expression and exacerbated tert-butyl hydroperoxide- and hydrogen peroxide-induced oxidative stress. NRF2 activation strongly increased NRF2 target gene expression and suppressed oxidant-induced reactive oxygen species. Diabetic mice exhibited retinal NRF2 activation, indicated by nuclear translocation. Superoxide levels were significantly increased by diabetes in Nrf2 knockout mice as compared with wild-type mice. Diabetic Nrf2 knockout mice exhibited a reduction in retinal glutathione and an increase in TNF-α protein compared with wild-type mice. Nrf2 knockout mice exhibited early onset of blood-retina barrier dysfunction and exacerbation of neuronal dysfunction in diabetes. CONCLUSIONS/INTERPRETATION: These results indicate that NRF2 is an important protective factor regulating the progression of DR and suggest enhancement of the NRF2 pathway as a potential therapeutic strategy.

Nrf2 acts cell-autonomously in endothelium to regulate tip cell formation and vascular branching.

Angiogenesis, in which new blood vessels form via endothelial cell (EC) sprouting from existing vessels, is a critical event in embryonic development and multiple disease processes. Many insights have been made into key EC receptors and ligands/growth factors that govern sprouting angiogenesis, but intracellular molecular mechanisms of this process are not well understood. NF-E2-related factor 2 (Nrf2) is a transcription factor well-known for regulating the stress response in multiple pathologic settings, but its role in development is less appreciated. Here, we show that Nrf2 is increased and activated during vascular development. Global deletion of Nrf2 resulted in reduction of vascular density as well as EC sprouting. This was also observed with specific deletion of Nrf2 in ECs, but not with deletion of Nrf2 in the surrounding nonvascular tissue. Nrf2 deletion resulted in increased delta-like ligand 4 (Dll4) expression and Notch activity in ECs. Blockade of Dll4 or Notch signaling restored the vascular phenotype in Nrf2 KOs. Constitutive activation of endothelial Nrf2 enhanced EC sprouting and vascularization by suppression of Dll4/Notch signaling in vivo and in vitro. Nrf2 activation in ECs suppressed Dll4 expression under normoxia and hypoxia and inhibited Dll4-induced Notch signaling. Activation of Nrf2 blocked VEGF induction of VEGFR2-PI3K/Akt and downregulated HIF-2α in ECs, which may serve as important mechanisms for Nrf2 inhibition of Dll4 and Notch signaling. Our data reveal a function for Nrf2 in promoting the angiogenic sprouting phenotype in vascular ECs.

Sevoflurane postconditioning alleviates action potential duration shortening and L-type calcium current suppression induced by ischemia/reperfusion injury in rat epicardial myocytes.

BACKGROUND: It has been proved that sevoflurane postconditioning (SpostC) could protect the heart against myocardial ischemia/reperfusion injury, however, there has been few research focused on the electrophysiological effects of SpostC. The objective of the study was to investigate the effects of SpostC on action potential duration (APD) and L-type calcium current (I(Ca, L)) in isolated cardiomyocytes. METHODS: Langendorff perfused SD rat hearts were randomly assigned to one of the time control (TC), ischemia/reperfusion (I/R, 25 minutes of ischemia followed by 30 minutes of reperfusion), and SpostC (postconditioned with 3% sevoflurane) groups. At the end of reperfusion, epicardial myocytes were dissociated enzymatically for patch clamp studies. RESULTS: Sevoflurane directly prolonged APD and decreased peak I(Ca, L) densities in epicardial myocytes of the TC group (P < 0.05). I/R injury shortened APD and decreased peak I(Ca, L) densities in epicardial myocytes of the I/R group (P < 0.05). SpostC prolonged APD and increased peak I(Ca, L) densities in epicardial myocytes exposed to I/R injury (P < 0.05). SpostC decreased intracellular reactive oxygen species (ROS) levels, reduced the incidence of ventricular tachycardia and ventricular fibrillation, and decreased reperfusion arrhythmia scores compared with the I/R group (all P < 0.05). CONCLUSIONS: SpostC attenuates APD shortening and I(Ca, L) suppression induced by I/R injury. The regulation of APD and I(Ca, L) by SpostC might be related with intracellular ROS modulation, which contributes to the alleviation of reperfusion ventricular arrhythmia.

Stenting technique, gender, and age are associated with cardioprotection by ischaemic postconditioning in primary coronary intervention: a systematic review of 10 randomized trials.

AIMS: We sought to perform a systematic review and meta-analysis to evaluate the potential factors affecting ischaemic postconditioning (IPoC) for patients with ST-segment elevation acute myocardial infarction (STEMI) in primary percutaneous coronary intervention (PCI). METHODS AND RESULTS: Ten randomized controlled trials (RCTs) on IPoC reporting myocardial enzyme levels or left ventricular ejection fraction (LVEF) in a total of 560 STEMI patients were identified in PubMed, EMBase, and Cochrane Library (up to February 2012). Compared with controls, IPoC significantly reduced elevated cardiac enzyme levels [standardized mean difference = -0.84; 95% confidential interval (CI): -1.26 to -0.43; P < 0.00001; heterogeneity test, I(2) = 81.0%] and improved LVEF [weighted mean difference (WMD) = 3.98%; 95% CI: 1.27-6.70%; P = 0.004; heterogeneity test, I(2) = 87.1%]. The effect on LVEF remained significant after 1 year (WMD = 5.04%; 95% CI: 4.20-5.88%; P < 0.00001; heterogeneity test, I(2) = 0.0%). Univariate meta-regression analysis suggested that the major sources of significant heterogeneity (P < 0.1) were the use of direct-stenting technique (%) (coefficient = -0.886; P = 0.069; adjusted R(2) = 0.34) and male proportion (%) (coefficient = -0.022; P = 0.098; adjusted R(2) = 0.28) for myocardial enzyme levels, and age (coefficient = -1.34; P = 0.025; adjusted R(2)= 0.55) for LVEF (%). Subsequent multivariate regression and subgroup analysis confirmed these results. CONCLUSION: Available evidence from this systematic review and meta-analysis of 10 RCTs suggests that IPoC may confer cardioprotection in terms of myocardial enzyme levels and LVEF for STEMI during primary PCI. These effects are more pronounced among young and male patients, and those in whom direct-stenting techniques were used. Future studies should focus on the mortality in high-quality, large-scale clinical trials with long-term follow-up.

MEF2C ablation in endothelial cells reduces retinal vessel loss and suppresses pathologic retinal neovascularization in oxygen-induced retinopathy.

Ischemic retinopathies, including retinopathy of prematurity and diabetic retinopathy, are major causes of blindness. Both have two phases, vessel loss and consequent hypoxia-driven pathologic retinal neovascularization, yet relatively little is known about the transcription factors regulating these processes. Myocyte enhancer factor 2 (MEF2) C, a member of the MEF2 family of transcription factors that plays an important role in multiple developmental programs, including the cardiovascular system, seems to have a significant functional role in the vasculature. We, therefore, generated endothelial cell (EC)-specific MEF2C-deficient mice and explored the role of MEF2C in retinal vascularization during normal development and in a mouse model of oxygen-induced retinopathy. Ablation of MEF2C did not cause appreciable defects in normal retinal vascular development. However, MEF2C ablation in ECs suppressed vessel loss in oxygen-induced retinopathy and strongly promoted vascular regrowth, consequently reducing retinal avascularity. This finding was associated with suppression of pathologic retinal angiogenesis and blood-retinal barrier dysfunction. MEF2C knockdown in cultured retinal ECs using small-interfering RNAs rescued ECs from death and stimulated tube formation under stress conditions, confirming the endothelial-autonomous and antiangiogenic roles of MEF2C. HO-1 was induced by MEF2C knockdown in vitro and may play a role in the proangiogenic effect of MEF2C knockdown on retinal EC tube formation. Thus, MEF2C may play an antiangiogenic role in retinal ECs under stress conditions, and modulation of MEF2C may prevent pathologic retinal neovascularization.

Sevoflurane postconditioning attenuates reperfusion-induced ventricular arrhythmias in isolated rat hearts exposed to ischemia/reperfusion injury.

Sevoflurane postconditioning has been proven to protect the hearts against ischemia/reperfusion injury, manifested mainly by improved cardiac function, reduced myocardial specific biomarker release, and decreased infarct size. This study is to observe the effects of sevoflurane postconditioning on reperfusion-induced ventricular arrhythmias and reactive oxygen species generation in Langendorff perfused rat hearts. Compared with the unprotected hearts subjected to 25 min of global ischemia followed by 30 min of reperfusion, exposure of 3% sevoflurane during the first 15 min of reperfusion significantly improved cardiac function, reduced cardiac troponin I release, decreased infarct size and attenuated reperfusion-induced ventricular arrhythmia. Further analysis on arrhythmia during the 30 min of reperfusion showed that, sevoflurane postconditioning decreased both the duration and incidence of ventricular tachycardia and ventricular fibrillation. In the meantime, intracellular malondialdehyde and reactive oxygen species levels were also reduced. These above results demonstrate that sevoflurane postconditioning protects the hearts against ischemia/reperfusion injury and attenuates reperfusion-induced arrhythmia, which may be associated with the regulation of lipid peroxidation and reactive oxygen species generation.