Reperfusion injury and reactive oxygen species: The evolution of a concept

Libidibia ferrea Fruit Crude Extract and Fractions Show Anti-Inflammatory, Antioxidant, and Antinociceptive Effect In Vivo and Increase Cell Viability In Vitro

Background

Libidibia ferrea (L. ferrea) is found throughout the northeastern region of Brazil, where it has been used in folk medicine with beneficial effects on many inflammatory disorders.

Purpose

This study investigated the phytochemical composition of the crude extract and fractions of L. ferrea fruit and evaluated its anti-inflammatory and antinociceptive activities in vivo and effect on cell viability in vitro.

Methods

Characterization of polyphenols present in crude extract (CE), hydroalcoholic fractions of 20-80% ethanol (CE20, CE40, CE60, and CE80), aqueous fraction (AqF), and ethyl acetate (EAF) fractions of L. ferrea fruit was performed by chromatographic analysis. Anti-inflammatory activity was evaluated by using a carrageenan-induced peritonitis model submitted to a leukocyte migration assay and myeloperoxidase activity (MPO) analysis. Total glutathione and malondialdehyde (MDA) levels were assessed to evaluate the oxidative stress level. Antinociceptive activity was evaluated by acetic acid-induced abdominal writhing and hot plate test. In vitro cell viability was determined by using MTT assay in a mouse embryonic fibroblast cell line (3T3 cells).

Results

Chromatography revealed the presence of ellagic acid content in EAF (3.06), CE (2.96), and CE40 (2.89). Gallic acid was found in EAF (12.03), CE 20 (4.43), and CE (3.99). L. ferrea crude extract and all fractions significantly reduced leukocyte migration and MPO activity (p<0.001). L. ferrea antioxidant effect was observed through high levels of total glutathione and reduction of MDA levels (p<0.001). Acetic acid-induced nociception was significantly inhibited after administration of L. ferrea crude extract and all fractions (p<0.001). Crude extract and all fractions significantly increased the viability of the 3T3 cell line (p<0.05).

Conclusions

The appropriate extraction procedure preserves the chemical components of L. ferrea fruit, such as gallic acid and ellargic acid. Crude extract and fractions of L. ferrea fruit exhibited anti-inflammatory, antioxidant, antinociceptive activities in vivo and enhanced cell viability in vitro.

Physiological effects of altering oxygenation during kidney normothermic machine perfusion

Kidney normothermic machine perfusion (NMP) has historically used a 95% O₂-5% CO₂ gas mixture. Using a porcine model of organ retrieval, NMP, and reperfusion, we tested the hypothesis that reducing perfusate oxygenation ( PpO2 ) would be detrimental to renal function and cause injury. In the minimal ischemic injury experiment, kidneys sustained 10 min of warm ischemia and 2 h of static cold storage before 1 h of NMP with either 95%, 25%, or 12% O₂ with 5% CO₂ and N₂ balance. In the clinical injury experiment, kidneys with 10-min warm ischemia and 17-h static cold storage underwent 1-h NMP with the above gas combinations or 18-h static cold storage as a control. They were then reperfused with whole blood and 95% O₂ for 3 h. Overall, reducing PpO2 did not significantly influence renal function in either experiment. Furthermore, there were no differences in the injury markers urinary neutrophil gelatinase-associated lipocalin or tissue high-motility group box protein 1. In the minimal ischemic injury experiment, a PpO2 of 25% significantly reduced renal blood flow and increased vascular resistance. Oxygen delivery, consumption, and extraction (oxygen extraction ratio) were significantly greater at 95% PpO2 . In the clinical injury experiment, renal blood flow was significantly increased at 25% PpO2 and Na⁺ excretion decreased. At 95% PpO2 , the oxygen content and oxygen extraction ratio were significantly increased. During reperfusion, renal blood flow was significantly increased in the 25% group. The control group pH was significantly decreased compared with the 25% group. Our data suggest that reducing PpO2 during NMP does not have detrimental effects on renal function or markers of injury.

Protective Effects of Galium verum L. Extract against Cardiac Ischemia/Reperfusion Injury in Spontaneously Hypertensive Rats

Galium verum L. (G. verum, lady's bedstraw) is a perennial herbaceous plant, belonging to the Rubiaceae family. It has been widely used throughout history due to multiple therapeutic properties. However, the effects of this plant species on functional recovery of the heart after ischemia have still not been fully clarified. Therefore, the aim of our study was to examine the effects of methanol extract of G. verum on myocardial ischemia/reperfusion (I/R) injury in spontaneously hypertensive rats (SHR), with a special emphasis on the role of oxidative stress. Rats involved in the research were divided randomly into two groups: control (spontaneously hypertensive rats (SHR)) and G. verum group, including SHR rats treated with the G. verum extract (500 mg/kg body weight per os) for 4 weeks. At the end of the treatment, in vivo cardiac function was assessed by echocardiography. Rats were sacrificed and blood samples were taken for spectrophotometric determination of systemic redox state. Hearts from all rats were isolated and retrogradely perfused according to the Langendorff technique. After a stabilization period, hearts were subjected to 20-minute ischemia, followed by 30-minute reperfusion. Levels of prooxidants were spectrophotometrically measured in coronary venous effluent, while antioxidant enzymes activity was assessed in heart tissue. Cell morphology was evaluated by hematoxylin and eosin (HE) staining. 4-week treatment with G. verum extract alleviated left ventricular hypertrophy and considerably improved in vivo cardiac function. Furthermore, G. verum extract preserved cardiac contractility, systolic function, and coronary vasodilatory response after ischemia. Moreover, it alleviated I/R-induced structural damage of the heart. Additionally, G. verum extract led to a drop in the generation of most of the measured prooxidants, thus mitigating cardiac oxidative damage. Promising potential of G. verum in the present study may be a basis for further researches which would fully clarify the mechanisms through which this plant species triggers cardioprotection.

Protective effects of Nesfatin-1 peptide on cerebral ischemia reperfusion injury via inhibition of neuronal cell death and enhancement of antioxidant defenses

Nesfatin-1 is a novel peptide with anorexigenic and anti-hyperglycemic properties. According to previous studies, this multi-functional peptide protects dopaminergic cells against neurotoxicity via anti-apoptotic effects. In addition, Nesfatin-1 protects myocardial tissue after myocardial infarction via anti-inflammatory and anti-apoptotic mechanisms. In this study, we investigated the neuroprotective effects of nesfatin-1 against cerebral ischemia reperfusion injury in the CA1 area of hippocampus in rats. 56 male Wistar rats (240-270 g) were randomly selected and allocated into four groups: (1) sham, (2) nesfatin-1, (3) ischemia/reperfusion, (4) ischemia/reperfusion+nesfatin-1. Cerebral ischemia induced by the occlusion of the common carotid arteries for 20 min was followed by reperfusion. Saline as a vehicle and nesfatin-1 (20 μg/kg) were injected intraperitoneally (IP) at the start of cerebral reperfusion. Apoptotic and necrotic cell death was detected by TUNEL and Nissl staining. Malondialdehyde (MDA) and antioxidant enzymes (GSH and SOD) levels were measured by the ELISA method. The results showed that cerebral ischemia increased the apoptotic and necrotic cell death in the CA1 area of hippocampus, while, treatment with nesfatin-1significantly reduced apoptotic and necrotic cell death. Moreover, the MDA levels of the hippocampus in ischemic rats were higher, whereas in nesfatin-1-treated rats the MDA levels were decreased. Furthermore, the SOD and GSH levels in the ischemic rats were decreased, whilst in ischemic rats treated with nesfatin-1, the SOD and GSH levels were increased. This study for the first time found that nesfatin-1 treatment improves CA1 hippocampus injuries after cerebral ischemia through preventing neuronal cell death and enhancement of antioxidant defenses.

Fangchinoline Ameliorates the Expressions of Angiogenic Molecule in Cerebral Ischemia Induced Neuronal Degeneration in Neonatal Rats

Background

Present investigation evaluates the beneficial effect of fangchinoline on cerebral ischemia induced neuronal degeneration in neonatal rats and also postulates the possible mechanism of its action.

Methodology

Cerebral ischemia was produced by the ligation of right common carotid artery in neonatal rats on postnatal day 5 (P5) and further pups were treated with fangchinoline 3, 10 and 30 mg/kg, i.p. for the period of 3 days. Effect of fangchinoline was estimated by determining the brain injury and enzyme linked immunosorbent assay (ELISA) method was used for the estimation of pro-inflammatory mediators and markers of oxidative stress in the cerebral tissues of neonatal rats. Moreover western blot assay and histopathology study was also performed on the brain tissue.

Results

Result of this investigation reveals that the percentage of brain injury significantly reduces and enhancement of myelin basic protein in the cerebral tissues of fangchinoline than ischemic group. Treatment with fangchinoline attenuates the altered level of proinflammatory mediators and markers of oxidative stress in the cerebral tissue of cerebral ischemia induced neuronal injury neonatal rats. Moreover expressions of inducible nitric oxide synthtase (iNOS), vascular endothelial growth factor (VEGF), p53 and nuclear receptor factor-2 (Nrf2) in the brain tissue attenuated by fangchinoline treated group.

Conclusion

In conclusion, fangchinoline ameliorates the cerebral ischemia induced neuronal injury in neonatal rats by enhancing angiogenesis molecules.

The Tri-phasic Role of Hydrogen Peroxide in Blood-Brain Barrier Endothelial cells

Hydrogen peroxide (H₂O₂) plays an important role physiologically as the second messenger and pathologically as an inducer of oxidative stress in injury, ischemia and other conditions. However, it is unclear how H₂O₂ influences various cellular functions in health and disease differentially, particularly in the blood-brain barrier (BBB). We hypothesized that the change in cellular concentrations of H₂O₂ is a major contributor in regulation of angiogenesis, barrier integrity/permeability and cell death/apoptosis in BBB endothelial cells. Rat brain microvascular endothelial cells were exposed to various concentrations of H₂O₂ (1 nM to 25 mM). BBB tight junction protein (zonula ocludens-1; ZO-1) localization and expression, cytoskeletal organization, monolayer permeability, angiogenesis, cell viability and apoptosis were evaluated. H₂O₂ at low concentrations (0.001 μM to 1 μM) increased endothelial cell tube formation indicating enhanced angiogenesis. H₂O₂ at 100 μM and above induced monolayer hyperpermeability significantly (p < 0.05). H₂O₂ at 10 mM and above decreased cell viability and induced apoptosis (p < 0.05). There was a decrease of ZO-1 tight junction localization with 100 μm H₂O₂, but had no effect on protein expression. Cytoskeletal disorganizations were observed starting at 1 μm. In conclusion H₂O₂ influences angiogenesis, permeability, and cell death/apoptosis in a tri-phasic and concentration-dependent manner in microvascular endothelial cells of the blood-brain barrier.

Protective Effect of Ethyl Pyruvate against Myocardial Ischemia Reperfusion Injury through Regulations of ROS-Related NLRP3 Inflammasome Activation

Emerging evidence indicates the pronounced role of inflammasome activation linked to reactive oxygen species (ROS) in the sterile inflammatory response triggered by ischemia/reperfusion (I/R) injury. Ethyl pyruvate (EP) is an antioxidant and conveys myocardial protection against I/R injury, while the exact mechanisms remain elusive. We aimed to investigate the effect of EP on myocardial I/R injury through mechanisms related to ROS and inflammasome regulation. The rats were randomly assigned to four groups: (1) sham, (2) I/R-control (IRC), (3) EP-pretreatment + I/R, and (4) I/R + EP-posttreatment. I/R was induced by a 30 min ligation of the left anterior descending artery followed by 4 h of reperfusion. EP (50 mg/kg) was administered intraperitoneally at 1 h before ischemia (pretreatment) or upon reperfusion (posttreatment). Both pre- and post-EP treatment resulted in significant reductions in myocardial infarct size (by 34% and 31%, respectively) and neutrophil infiltration. I/R-induced myocardial expressions of NADPH oxidase-4, carnitine palmitoyltransferase 1A, and thioredoxin-interacting protein (TXNIP) were mitigated by EP. EP treatment was associated with diminished inflammasome activation (NOD-like receptor 3 (NLRP3), apoptosis-associated speck-like protein, and caspase-1) and interleukin-1β induced by I/R. I/R-induced phosphorylation of ERK and p38 were also mitigated with EP treatments. In H9c2 cells, hypoxia-induced TXNIP and NLRP3 expressions were inhibited by EP and to a lesser degree by U0126 (MEK inhibitor) and SB203580 (p38 inhibitor) as well. EP's downstream protective mechanisms in myocardial I/R injury would include mitigation of ROS-mediated NLRP3 inflammasome upregulation and its associated pathways, partly via inhibition of hypoxia-induced phosphorylation of ERK and p38.

Protective efficacy of dinitrosyl iron complexes with reduced glutathione in cardioplegia and reperfusion

Disturbed homeostasis of nitric oxide (NO) is one of the causes of myocardial ischemia/reperfusion (I/R) injury during open-heart surgery. This study was designed to explore mechanisms of action of dinitrosyl iron complexes with reduced glutathione ({(GS^-)₂Fe⁺(NO⁺)₂}⁺, DNIC-GS) added to crystalloid cardioplegia or reperfusion solution in isolated working rat hearts. Hearts of male Wistar rats were subjected to cardioplegic arrest by St. Thomas' Hospital cardioplegic solution (STH) and normothermic global ischemia followed by reperfusion. DNIC-GS were used with STH or during early reperfusion. Lactate dehydrogenase (LDH) activity in the coronary effluent and myocardial contents of adenine nucleotides, phosphocreatine, and lactate were determined spectrophotometrically. Reactive oxygen species (ROS) formation in the coronary effluent and myocardial DNIC content was assessed by EPR technique. Cardioplegia or reperfusion with DNIC-GS significantly improved recovery of coronary flow and cardiac function compared with control. Carboxy-[2-(4-carboxyphenyl)-4,4,5,5-tetramethyl-imidozoline-1-oxy-3-oxide] (C-PTIO), a selective NO scavenger, reduced/abolished protective action of DNIC-GS. Enhanced recovery of cardiac function with DNIC-GS reduced LDH release in the coronary effluent, augmented recovery of myocardial energy state, and decreased formation of ROS-generating systems at reperfusion. Beneficial effects of DNIC-GS were related to the transfer of [Fe(NO)₂] cores to thiol groups of myocardial proteins to form intracellular DNIC pools. The study concluded that DNIC-GS is a promising adjunct agent for metabolic and antioxidant protection of the heart during cardioplegic arrest and reperfusion.

miR-191 secreted by platelet-derived microvesicles induced apoptosis of renal tubular epithelial cells and participated in renal ischemia-reperfusion injury via inhibiting CBS

In this study, we aimed to reveal the role of miR-191 in apoptosis of renal tubular epithelial cells and in the involvement of renal ischemia-reperfusion injury. Renal transplantation rat model was established. miR-191 and Cystathionine-β-synthase (CBS) were measured by qRT-PCR and Western blot. The regulation of miR-191 on CBS was detected by luciferase reporter assay. We found miR-191 expression in platelets and platelet microvesicles (P-MVs) of patients and model rats was significantly upregulated than that of health and normal rats. Also, mRNA and protein levels of CBS in renal tissues of patients were significantly downregulated than that of health and normal rats. We also found that P-MVs could transfer miR-191 to HK-2 cells. Luciferase reporter assay showed that CBS was a direct target of miR-191. In addition, we proved that P-MVs-secreted miR-191 inhibited CBS expression in HK-2 cells, and P-MVs-secreted miR-191 promoted HK-2 cell apoptosis via CBS. Finally, we verified the trends of CBS expressions, HK-2 cell apoptosis and apoptosis-related proteins in vivo were similar as the trends in vitro. Therefore, CBS was a direct target of miR-191, and miR-191 could transfer to HK-2 cells via P-MVs to decrease the expression of CBS, thus to promote cell apoptosis and renal IR injury.

Early hypoxemia burden is strongly associated with severe intracranial hemorrhage in preterm infants

OBJECTIVES

The objective of this study was to define the association between the burden of severe hypoxemia (SpO₂ ≤70%) in the first week of life and development of severe ICH (grade III/IV) in preterm infants.

STUDY DESIGN

Infants born at <32 weeks or weighing <1500 g underwent prospective SpO₂ recording from birth through 7 days. Severe hypoxemia burden was calculated as the percentage of the error-corrected recording where SpO₂ ≤70%. Binary logistic regression was used to model the relationship between hypoxemia burden and severe ICH.

RESULTS

A total of 163.3 million valid SpO₂ data points were collected from 645 infants with mean EGA = 27.7 ± 2.6 weeks, BW = 1005 ± 291 g; 38/645 (6%) developed severe ICH. There was a greater mean hypoxemia burden for infants with severe ICH (3%) compared to those without (0.1%) and remained significant when controlling for multiple confounding factors.

CONCLUSION

The severe hypoxemia burden in the first week of life is strongly associated with severe ICH.

Risk factors for mortality in paediatric cardiac ICU patients managed with extracorporeal membrane oxygenation

BACKGROUND

Veno-arterial extracorporeal membrane oxygenation is frequently used in patients with cardiac disease. We evaluated short-term outcomes and identified factors associated with hospital mortality in cardiac patients supported with veno-arterial extracorporeal membrane oxygenation.

METHODS

A retrospective review of patients supported with veno-arterial extracorporeal membrane oxygenation at a university-affiliated children's hospital was performed.

RESULTS

A total of 253 patients with cardiac disease managed with extracorporeal membrane oxygenation were identified; survival to discharge was 48%, which significantly improved from 39% in an earlier era (1995-2001) (p=0.01). Patients were categorised into surgical versus non-surgical groups on the basis of whether they had undergone cardiac surgery before or not, respectively. The most common indication for extracorporeal membrane oxygenation was extracorporeal cardiopulmonary resuscitation: 96 (51%) in the surgical group and 45 (68%) in the non-surgical group. In a multiple covariate analysis, single-ventricle physiology (p=0.01), duration of extracorporeal membrane oxygenation (p&lt;0.01), and length of hospital stay (p=0.03) were associated with hospital mortality. Weekend or night shift cannulation was associated with mortality in non-surgical patients (p=0.05).

CONCLUSION

We report improvement in survival compared with an earlier era in cardiac patients supported with extracorporeal membrane oxygenation. Single-ventricle physiology continues to negatively impact survival, along with evidence of organ dysfunction during extracorporeal membrane oxygenation, duration of extracorporeal membrane oxygenation, and length of stay.

How Acute Kidney Injury Contributes to Renal Fibrosis

Acute kidney injury (AKI) is a widespread clinical syndrome directly associated with patient short-term and long-term morbidity and mortality. During the last decade, the incidence rate of AKI has been increasing, the repeated and severe episodes of AKI have been recognized as a major risk factor chronic kidney diseases (CKD) and end-stage kidney disease (ESRD) leading to global disease burden. Proposed pathological processes and risk factors that add to the transition of AKI to CKD and ESRD include severity and frequency of kidney injury, older age, gender, genetics and chronic health conditions like diabetes, hypertension, and obesity. Therefore, there is a great interest in learning about the mechanism of AKI leading to renal fibrosis, the ultimate renal lesions of CKD. Over the last several years, a significant attention has been given to the field of renal fibrosis with impressive progression in knowing the mechanism of renal fibrosis to detailed cellular characterization and molecular pathways implicated in tubulointerstitial fibrosis. Research and clinical trial are underway for emerging biomarkers detecting early kidney injury, predicting kidney disease progression and developing strategies to efficiently treat AKI and to minimize AKI progression to CKD and ESRD. Specific interventions to prevent renal fibrosis are still experimental. Potential therapeutic advances based on those molecular mechanisms will hopefully offer promising insights into the development of new therapeutic interventions for patients in the near future.

Stabilization of p22phox by Hypoxia Promotes Pulmonary Hypertension

AIMS

Hypoxia and reactive oxygen species (ROS) have been shown to play a role in the pathogenesis of pulmonary hypertension (PH), a potentially fatal disorder characterized by pulmonary vascular remodeling, elevated pulmonary arterial pressure, and right ventricular hypertrophy. However, how they are linked in the context of PH is not completely understood. We, therefore, investigated the role of the NADPH oxidase subunit p22phox in the response to hypoxia both in vitro and in vivo.

RESULTS

We found that hypoxia decreased ubiquitinylation and proteasomal degradation of p22phox dependent on prolyl hydroxylases (PHDs) and the E3 ubiquitin ligase protein von Hippel Lindau (pVHL), which resulted in p22phox stabilization and accumulation. p22phox promoted vascular proliferation, migration, and angiogenesis under normoxia and hypoxia. Increased levels of p22phox were also detected in lungs and hearts from mice with hypoxia-induced PH. Mice harboring a point mutation (Y121H) in the p22phox gene, which resulted in decreased p22phox stability and subsequent loss of this protein, were protected against hypoxia-induced PH. Mechanistically, p22phox contributed to ROS generation under normoxia, hypoxia, and hypoxia/reoxygenation. p22phox increased the levels and activity of HIF1α, the major cellular regulator of hypoxia adaptation, under normoxia and hypoxia, possibly by decreasing the levels of the PHD cofactors ascorbate and iron(II), and it contributed to the downregulation of the tumor suppressor miR-140 by hypoxia.

INNOVATION

These data identify p22phox as an important regulator of the hypoxia response both in vitro and in vivo.

CONCLUSION

p22phox-dependent NADPH oxidases contribute to the pathophysiology of PH induced by hypoxia.

Biomechanistic insights into the roles of oxidative stress in generating complex neurological disorders

Neurological diseases like Alzheimer's disease, epilepsy, parkinsonism, depression, Huntington's disease and amyotrophic lateral sclerosis prevailing globally are considered to be deeply influenced by oxidative stress-based changes in the biochemical settings of the organs. The excess oxygen concentration triggers the production of reactive oxygen species, and even the intrinsic antioxidant enzyme system, i.e. SOD, CAT and GSHPx, fails to manage their levels and keep them under desirable limits. This consequently leads to oxidation of protein, lipids and nucleic acids in the brain resulting in apoptosis, proteopathy, proteasomes and mitochondrion dysfunction, glial cell activation as well as neuroinflammation. The present exploration deals with the evidence-based mechanism of oxidative stress towards development of key neurological diseases along with the involved biomechanistics and biomaterials.

Complement factor and T-cell interactions during alloimmune inflammation in transplantation

Complement factor and T-cell signaling during an effective alloimmune response plays a key role in transplant-associated injury, which leads to the progression of chronic rejection (CR). During an alloimmune response, activated complement factors (C3a and C5a) bind to their corresponding receptors (C3aR and C5aR) on a number of lymphocytes, including T-regulatory cells (Tregs), and these cell-molecular interactions have been vital to modulate an effective immune response to/from Th1-effector cell and Treg activities, which result in massive inflammation, microvascular impairments, and fibrotic remodeling. Involvement of the complement-mediated cell signaling during transplantation signifies a crucial role of complement components as a key therapeutic switch to regulate ongoing inflammatory state, and further to avoid the progression of CR of the transplanted organ. This review highlights the role of complement-T cell interactions, and how these interactions shunt the effector immune response during alloimmune inflammation in transplantation, which could be a novel therapeutic tool to protect a transplanted organ and avoid progression of CR.

Late failure of cerebral autoregulation in hypoxic-ischemic encephalopathy is associated with brain injury: a pilot study

BACKGROUND

Post-resuscitation reperfusion following hypoxic-ischemia (HIE) is associated with secondary brain injury in neonates.

OBJECTIVE

To quantify the association between perfusion exceeding autoregulatory limits and brain injury.

APPROACH

Continuous mean arterial blood pressure (MABP) and cerebral near-infrared spectroscopy (NIRS) data were prospectively collected from infants with HIE. Cerebral oximetry index (COx) was calculated as a moving correlation coefficient between MABP and NIRS. Upper and lower limits of autoregulation were identified by transition from negative to positive correlation. The proportion of time MABP above (hyperperfusion) and below (hypoperfusion) autoregulatory limits was calculated during therapeutic hypothermia (days 1-3).

MAIN RESULTS

Sixteen infants were included; injury was noted in 7/16. There was no significance in hyperperfusion burden between injured and uninjured infants during day one (7% versus 10%, p  =  0.88) or two (4% versus 2%, p  =  0.88), but there was a marked increase for injured infants on day three (54% versus 14%, p  =  0.02). There was a corollary decrease in hypoperfusion for injured versus uninjured infants on day 3 (6% versus 24%, p  =  0.05).

SIGNIFICANCE

HIE infants with brain injury have a late failure of cerebral autoregulation, manifested as a hyperperfusion burden, suggesting pathologic events are active on day 3 of hypothermia. This finding may help to identify infants which might need additional neuroprotection.

Metabolic syndrome and cancer risk: The role of xanthine oxidoreductase

Obesity and related pathologies such as diabetes and metabolic syndrome are associated with chronic inflammation and cancer. The serum level of xanthine oxidoreductase (XOR) is correlated to obesity-associated metabolic disorders. XOR can play a role in the pathogenesis of both metabolic syndrome and cancer through the inflammatory response and the oxidative stress elicited by the products of its activity. The reactive oxygen and nitrogen species and the uric acid derived from XOR concur to the development of hypertension, dyslipidemia and insulin resistance and participate in both cell transformation and proliferation, as well as in the progression and metastasis process. Despite the availability of different drugs to inhibit in vivo XOR activity, the complexity of XOR inhibition effects should be carefully considered before clinical application, save in the case of symptomatic hyperuricemia.

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Metabolic syndrome (MS) increases the risk of cancer development.

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Xanthine oxidoreductase (XOR) plays a role in both MS and cancer.

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Uric acid, ROS and RNS produced by XOR cause inflammation and oxidative stress.

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Inflammation and oxidative stress contribute to the pathogenesis of MS and cancer.

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XOR activity can be pharmacologically controlled.

Remote ischemic per-conditioning protects against renal ischemia-reperfusion injury via suppressing gene expression of TLR4 and TNF-α in rat model

The pathogenesis of renal ischemia-reperfusion injury (IRI) involves both inflammatory processes and oxidative stress in the kidney. This study determined whether remote ischemic per-conditioning (RIPerC) is mediated by toll-like receptor 4 (TLR4) signaling pathway in rats. Renal IR injury was induced by occluding renal arteries for 45 min followed by 24 h of reperfusion. RIPerC included 4 cycles of 2 min of ischemia of the left femoral artery followed by 3 min of reperfusion performed at the start of renal ischemia. Rats were divided into sham, IR, and RIPerC groups. At the end of the reperfusion period, urine, blood and tissue samples were gathered. IR created kidney dysfunction, as ascertained by a significant decrease in creatinine clearance and a significant increase in sodium fractional excretion. These changes occurred in concert with a decrease in the activities of glutathione peroxidase, catalase, and superoxide dismutase with an increment in malondialdehyde levels, mRNA expression levels of TLR4 and tumor necrosis factor α (TNF-α), and histological damage in renal tissues. RIPerC treatment diminished all these changes. This study demonstrates that RIPerC has protective effects on the kidney after renal IR, which might be related to the inhibition of the TLR4 signaling pathway and augmentation of antioxidant systems.

Protective effects of tetramethylpyrazine analogue Z-11 on cerebral ischemia reperfusion injury

The aim of our study was to investigate the effects of a new synthetic compound (E) -1- (E) -1- (2- hydroxy -5- chlorophenyl) -3- (3, 5, 6- three methyl pyrazine -2- based) -2- propylene -1 ketone, Z-11, a tetramethylpyrazine analogue, on cerebral ischemia reperfusion injury and the underlying mechanism. 240-260 g adult male Wistar rats were subjected to middle cerebral artery occlusion for 2 h, followed by 22 h of reperfusion. Z-11 (1.7, 3.4 and 6.8 mg/kg, i.p.), Edaravone (3 mg/kg, i.p.) and DMSO (1‰, i.p.) was administered at 2 h after the onset of ischemia. The rats' neurological score, infarct volume, and body weight change were tested, and some oxidative stress markers such as superoxide dismutase (SOD) activity, glutathione (GSH) and malondialdehyde (MDA) contents were evaluated after 22 h of reperfusion. Results showed that neurologic deficit, infarct volume and body weight change were ameliorated after cerebral ischemia reperfusion, and that Z-11 exhibits an excellent effect at a dosage of 6.8 mg/kg. This dose also reduced the content of MDA, and upregulated SOD activity and GSH content. Similarly, 6.8 mg/kg Z-11 treatment inhibited the reactive oxygen species content and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, with the protein levels of Ras-related C3 botulinum toxin substrate1(Rac-1) and mitogenic oxidase (Nox2) downregulated even further. Moreover, the protein levels of nuclear factor erythroid 2-related factor 2 (Nrf2) and its downstream anti-oxidant protein heme oxygenase-1 (HO-1) were upregulated. This indicates that Z-11 could play a protective role in cerebral ischemia-reperfusion injury, and that the protective effect of Z-11 may be related to improvements in the antioxidant capacity of brain tissue. The mechanisms are associated with enhancing oxidant defence systems via the activation of Nrf2/HO-1 and Rac-1/NADPH oxidase pathways.

Metabolic reprogramming by the S-nitroso-CoA reductase system protects against kidney injury

Endothelial nitric oxide synthase (eNOS) is protective against kidney injury, but the molecular mechanisms of this protection are poorly understood^1,2. Nitric oxide-based cellular signalling is generally mediated by protein S-nitrosylation, the oxidative modification of Cys residues to form S-nitrosothiols (SNOs). S-nitrosylation regulates proteins in all functional classes, and is controlled by enzymatic machinery that includes S-nitrosylases and denitrosylases, which add and remove SNO from proteins, respectively^3,4. In Saccharomyces cerevisiae, the classic metabolic intermediate co-enzyme A (CoA) serves as an endogenous source of SNOs through its conjugation with nitric oxide to form S-nitroso-CoA (SNO-CoA), and S-nitrosylation of proteins by SNO-CoA is governed by its cognate denitrosylase, SNO-CoA reductase (SCoR)⁵. Mammals possess a functional homologue of yeast SCoR, an aldo-keto reductase family member (AKR1A1)⁵ with an unknown physiological role. Here we report that the SNO-CoA-AKR1A1 system is highly expressed in renal proximal tubules, where it transduces the activity of eNOS in reprogramming intermediary metabolism, thereby protecting kidneys against acute kidney injury. Specifically, deletion of Akr1a1 in mice to reduce SCoR activity increased protein S-nitrosylation, protected against acute kidney injury and improved survival, whereas this protection was lost when Enos (also known as Nos3) was also deleted. Metabolic profiling coupled with unbiased mass spectrometry-based SNO-protein identification revealed that protection by the SNO-CoA-SCoR system is mediated by inhibitory S-nitrosylation of pyruvate kinase M2 (PKM2) through a novel locus of regulation, thereby balancing fuel utilization (through glycolysis) with redox protection (through the pentose phosphate shunt). Targeted deletion of PKM2 from mouse proximal tubules recapitulated precisely the protective and mechanistic effects of S-nitrosylation in Akr1a1^-/- mice, whereas Cys-mutant PKM2, which is refractory to S-nitrosylation, negated SNO-CoA bioactivity. Our results identify a physiological function of the SNO-CoA-SCoR system in mammals, describe new regulation of renal metabolism and of PKM2 in differentiated tissues, and offer a novel perspective on kidney injury with therapeutic implications.

Light-induced oxidant production by fluorescent proteins

Oxidants play an important role in the cell and are involved in many redox processes. Oxidant concentrations are maintained through coordinated production and removal systems. The dysregulation of oxidant homeostasis is a hallmark of many disease pathologies. The local oxidant microdomain is crucial for the initiation of many redox signaling events; however, methods to control oxidant product are limited. Some fluorescent proteins, including GFP, TagRFP, KillerRed, miniSOG, and their derivatives, generate oxidants in response to light. These genetically-encoded photosensitizers produce singlet oxygen and superoxide upon illumination and offer spatial and temporal control over oxidant production. In this review, we will examine the photosensitization properties of fluorescent proteins and their application to redox biology. Emerging concepts of selective oxidant species production via photosensitization and the impact of light on biological systems are discussed.

FGF21 protects myocardial ischemia-reperfusion injury through reduction of miR-145-mediated autophagy

AIMS

Fibroblast growth factor 21 (FGF21) plays a critical role in protecting against myocardial ischemia/reperfusion (I/R) injury. However, the molecular mechanism is not completely understood. Here, we aimed to examine whether miRNA-145 (miR-145) is involved in FGF21 protection against myocardial I/R injury through angiopoietin-2 (Angpt2) and autophagy.

METHODS

We established a rat myocardial I/R model and H9c2 hypoxia/reoxygenation (H/R) model. After administration of FGF21 in the rat I/R model, the infarct size, morphological changes and apoptosis in myocardium were determined by 2,3,5-triphenyltetrazolium chloride (TTC), hematoxylin and eosin (HE), and Masson's trichrome staining, and TUNEL assay, respectively. The expression levels of miR-145 and Angpt2 were evaluated by quantitative real-time PCR (qRT-PCR), Western blotting and immunohistochemical (IHC) staining. The activity of lactate dehydrogenase (LDH), TNF-α and IL-6 were assayed. Using a dual-luciferase reporter system, the targeted role of miR-145 on Angpt2 was studied. After transfection with miR-145 inhibitor, H9c2 cells were subjected to stimulated H/R with or without FGF21 treatment. The expression of Angpt2 was assessed while cell apoptosis and cell migration assays were performed.

RESULTS

FGF21 significantly decreased infarction after I/R, ameliorated I/R-induced cell apoptosis, and inhibited I/R-induced LDH, TNF-α and IL-6 in serum. FGF21 inhibited I/R-induced decrease in miR-145 level, increase in Angpt2 expression and decrease in autophagy; FGF21 also upregulated LC3-B and Beclin1 levels. miR-145 directly targeted Angpt2. The roles of FGF21 in expression of miR-145 and Angpt2 and activation of autophagy after H/R were reversed by miR-145 inhibitor. In addition, the FGF21-inhibited cell apoptosis and FGF21-promoted migration after H/R were restored by miR-145 inhibitor.

CONCLUSION

FGF21 protects myocardial cells against I/R injury by promoting an increase in miR-145 levels and autophagy while inhibiting Angpt2 expression, suggesting a novel therapeutic strategy for protecting against myocardial I/R injury.

Rivastigmine prevents injury induced by ischemia and reperfusion in rat liver

PURPOSE

To evaluate whether pre-treatment with rivastigmine is able to attenuate the I/R induced lesions in rat liver.

METHODS

SHAM animals or those submitted to I/R, non-treated or pre-treated with rivastigminine (2mg/kg) either 50 or 15 minutes before ischemia, were used. After I/R protocol, these animals were killed and their livers were harvested to measurement of the mitochondrial swelling as well as the malondialdehyde (MDA), nitrite and nitrate tissue concentration. Blood was also harvested for serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) determinations.

RESULTS

I/R promoted a significant increase of mitochondrial swelling in the studied animals. This increase of mitochondrial swelling was partially prevented by rivastigmine, but only if administered 50 minutes before ischemia. No significant modification of MDA, nitrite or nitrate tissue concentrations was observed in consequence of I/R, followed or not by rivastigmine treatments. In addition, I/R elevated both AST and ALT. These elevations of serum enzymes were not reversed by the different rivastigmine treatments.

CONCLUSIONS

Rivastigmine administered 50 minutes before ischemia attenuates I/R-induced mitochondrial swelling, that indicates liver injury. This protective effect may be related to a greater stimulation of α7nAChR present in the Kupffer cells by the non-methabolized ACh, leading to an attenuation of I/R-induced inflammation.

Taurine activates glycine and GABAA receptor currents in anoxia-tolerant painted turtle pyramidal neurons

Unlike anoxia-intolerant mammals, painted turtles can survive extended periods without oxygen. This is partly accomplished by an anoxia-mediated increase in gamma-aminobutyric acid (GABA) release, which activates GABA receptors and mediates spike arrest in turtle neurons via shunting inhibition. Extracellular taurine levels also increase during anoxia; why this occurs is unknown but it is speculated that glycine and/or GABA_A/B receptors are involved. Given the general importance of inhibitory neurotransmission in the anoxia-tolerant painted turtle brain, we investigated the function of taurine as an inhibitory neuromodulator in turtle pyramidal neurons. Using whole-cell patch-clamp electrophysiological methods to record from neurons within a cortical brain sheet, we found that taurine depolarized membrane potential by ∼8 mV, increased whole-cell conductance ∼2-fold, and induced an inward current that possessed characteristics similar to GABA- and glycine-evoked currents. These effects were mitigated following glycine receptor antagonism with strychnine and GABA_A receptor antagonism with gabazine, bicuculine or picrotoxin, but were unchanged following GABA_B or glutamatergic receptor inhibition. These data indicate that a high concentration of taurine in vitro mediates its effects through both glycine and GABA_A receptors, and suggests that taurine, in addition to GABA, inhibits neuronal activity during anoxia in the turtle cortex.

Silybum marianum provides cardioprotection and limits adverse remodeling post-myocardial infarction by mitigating oxidative stress and reactive fibrosis

AIMS

Milk thistle (Silybum marianum; SM) is an herb commonly used for hepatoprotection with antioxidant and antifibrotic properties. We investigated in pigs the cardiac effects of SM intake during the acute phase of myocardial infarction (MI) and remodeling period post-MI.

METHODS

Study-1 tested the effect of SM use on the acute phase of MI. Hence, animals were distributed to a control group or to receive SM prior infarction (1.5 h ischemia). Animals were sacrificed after 2.5 h of reperfusion. Study-2 tested the effect of SM use in the cardiac remodeling phase. Accordingly, animals received for 10 d diet ± SM prior MI and followed the same regime for 3 weeks and then sacrificed. Study-3 tested the effect of SM in a non-infarcted heart; therefore, animals received for 10 d diet ± SM and then sacrificed.

RESULTS

Animals taking SM before MI showed a reduction in cardiac damage (decreased oxidative damage, ROS production and xanthine oxidase levels; preserved mitochondrial function; and increased myocardial salvage; p < 0.05) versus controls. Animals that remained on chronic SM intake post-MI improved left ventricular remodeling. This was associated with the attenuation of the TGFß1/TßRs/SMAD2/3 signaling, lower myofibroblast transdifferentiation and collagen content in the border zone (p < 0.05 vs. all other groups). Cardiac contractility improved in animals taking SM (p < 0.05 vs. post-MI-control). No changes in cardiac function or fibrosis were detected in animals on SM but without MI.

CONCLUSION

Intake of SM protects the heart against the deleterious effects of an MI and favors cardiac healing. These benefits may be attributed to the antioxidant and antifibrotic properties of SM.

Stress-induced antioxidant defense and protein chaperone response in the freeze-tolerant wood frog Rana sylvatica

Freeze tolerance is an adaptive response utilized by the wood frog Rana sylvatica to endure the sub-zero temperatures of winter. Survival of whole body freezing requires wood frogs to trigger cryoprotective mechanisms to deal with potential injuries associated with conversion of 65-70% of total body water into ice, including multiple consequences of ice formation such as cessation of blood flow and cell dehydration caused by water loss into ice masses. To understand how wood frogs defend against these stressors, we measured the expression of proteins known to be involved in the antioxidant defense and protein chaperone stress responses in brain and heart of wood frogs comparing freezing, anoxia, and dehydration stress. Our results showed that most stress proteins were regulated in a tissue- and stress-specific manner. Notably, protein levels of the cytosolic superoxide dismutase (SOD1) were upregulated by 1.37 ± 0.11-fold in frozen brain, whereas the mitochondrial SOD2 isoform rose by 1.38 ± 0.37-fold in the heart during freezing. Catalase protein levels were upregulated by 3.01 ± 0.47-fold in the brain under anoxia stress, but remained unchanged in the heart. Similar context-specific regulatory patterns were also observed for the heat shock protein (Hsp) molecular chaperones. Hsp27 protein was down-regulated in the brain across the three stress conditions, whereas the mitochondrial Hsp60 was upregulated in anoxic brain by 1.73 ± 0.38-fold and by 2.13 ± 0.57-fold in the frozen heart. Overall, our study provides a snapshot of the regulatory expression of stress proteins in wood frogs under harsh environment conditions and shows that they are controlled in a tissue- and stress-specific manner.

Origin and Consequences of Necroinflammation

When cells undergo necrotic cell death in either physiological or pathophysiological settings in vivo, they release highly immunogenic intracellular molecules and organelles into the interstitium and thereby represent the strongest known trigger of the immune system. With our increasing understanding of necrosis as a regulated and genetically determined process (RN, regulated necrosis), necrosis and necroinflammation can be pharmacologically prevented. This review discusses our current knowledge about signaling pathways of necrotic cell death as the origin of necroinflammation. Multiple pathways of RN such as necroptosis, ferroptosis, and pyroptosis have been evolutionary conserved most likely because of their differences in immunogenicity. As the consequence of necrosis, however, all necrotic cells release damage associated molecular patterns (DAMPs) that have been extensively investigated over the last two decades. Analysis of necroinflammation allows characterizing specific signatures for each particular pathway of cell death. While all RN-pathways share the release of DAMPs in general, most of them actively regulate the immune system by the additional expression and/or maturation of either pro- or anti-inflammatory cytokines/chemokines. In addition, DAMPs have been demonstrated to modulate the process of regeneration. For the purpose of better understanding of necroinflammation, we introduce a novel classification of DAMPs in this review to help detect the relative contribution of each RN-pathway to certain physiological and pathophysiological conditions.

Experimental diabetes mellitus exacerbates ischemia/reperfusion-induced myocardial injury by promoting mitochondrial fission: Role of down-regulation of myocardial Sirt1 and subsequent Akt/Drp1 interaction

Diabetes mellitus (DM) has a negative impact on clinical outcomes for patients with myocardial infarction. The aim of the present study was to assess whether decreased myocardial levels of Sirtuin1 (Sirt1) contribute to the increased susceptibility of the diabetic myocardium to ischemia/reperfusion (I/R) injury. In vivo, myocardial levels of Sirt1 expression and activity were decreased in mice with STZ-induced DM. Increasing Sirt1 activity prevented the DM-induced exacerbation of myocardial mitochondrial fission, apoptosis and dysfunction elicited by I/R. In vitro, anoxia/reoxygenation (A/R) challenge of cardiomyocytes (CM) that were preconditioned with high glucose (HG-CM) resulted in an exacerbation of the A/R-induced mitochondrial fission, oxidant production and CM apoptosis; effects reversed by increasing Sirt1 protein/activity. Inhibition of Drp1 prevented the exacerbated CM mitochondrial fission and oxidant production after A/R challenge of HG-CM. Decreased Sirt1 in HG-CM was associated with decreased Akt phosphorylation. Inhibition of Akt had no effect on CM Sirt1 levels, but further increased Drp1 activation. Increasing Sirt1 levels prevented the decrease in Akt phosphorylation and Drp1 activation in A/R challenged HG-CM. In conclusion: our data indicate that the increased vulnerability of the diabetic myocardium to I/R-induced apoptosis/dysfunction is attributable, in part, to decreased myocardial Sirt1 activity which leads to a decrease in Akt activation, an increase in Drp1 activity, culminating in excessive mitochondrial fission and ROS production.

Metabolomic Profiling Reveals That Reprogramming of Cerebral Glucose Metabolism Is Involved in Ischemic Preconditioning-Induced Neuroprotection in a Rodent Model of Ischemic Stroke

Ischemic tolerance renders the brain resistant to ischemia-reperfusion (I/R) injury as a result of the activation of endogenous adaptive responses triggered by various types of preconditioning. The complex underlying metabolic mechanisms responsible for the neuroprotection of cerebral ischemic preconditioning (IPC) remain elusive. Herein, gas chromatography-mass spectrometry (GC-MS) technique was applied to delineate the dynamic changes of brain metabolome in a rodent model of ischemic stroke (transient occlusion of the middle cerebral artery, tMCAO), alone or after pretreatment with nonlethal ischemic tolerance induction (transient occlusion of the bilateral common carotid arteries, tBCCAO). Metabolomic analysis showed that accumulation of glucose (concentration increased more than 4 fold) and glycolytic intermediates is the prominent feature of brain I/R-induced metabolic disturbance. IPC attenuated brain I/R damage by subduing postischemic hyperglycolysis, increasing the pentose phosphate pathway (PPP) flux and promoting the utilization of β-hydroxybutyrate. The expression analysis of pivotal genes and proteins involved in relevant metabolic pathways revealed that the downregulation of AMP-activated protein kinase (AMPK)-mediated glucose transporter-1 (GLUT-1) and 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-3 (PFKFB3) and reduced mRNA levels of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) subunits were associated with IPC-induced metabolic flexibility, which allows the brain to be more capable of withstanding severe I/R insults. The present study provided mechanistic insights into the metabolic signature of IPC and indicated that adaptively modulating brain glucose metabolism could be an effective approach for the therapeutic intervention of ischemic stroke.

Inadequate ubiquitination-proteasome coupling contributes to myocardial ischemia-reperfusion injury

The ubiquitin-proteasome system (UPS) degrades a protein molecule via 2 main steps: ubiquitination and proteasomal degradation. Extraproteasomal ubiquitin receptors are thought to couple the 2 steps, but this proposition has not been tested in vivo with vertebrates. More importantly, impaired UPS performance plays a major role in cardiac pathogenesis, including myocardial ischemia-reperfusion injury (IRI), but the molecular basis of UPS impairment remains poorly understood. Ubiquilin1 is a bona fide extraproteasomal ubiquitin receptor. Here, we report that mice with a cardiomyocyte-restricted knockout of Ubiquilin1 (Ubqln1-CKO mice) accumulated a surrogate UPS substrate (GFPdgn) and increased myocardial ubiquitinated proteins without altering proteasome activities, resulting in late-onset cardiomyopathy and a markedly shortened life span. When subject to regional myocardial ischemia-reperfusion, young Ubqln1-CKO mice showed substantially exacerbated cardiac malfunction and enlarged infarct size, and conversely, mice with transgenic Ubqln1 overexpression displayed attenuated IRI. Furthermore, Ubqln1 overexpression facilitated proteasomal degradation of oxidized proteins and the degradation of a UPS surrogate substrate in cultured cardiomyocytes without increasing autophagic flux. These findings demonstrate that Ubiquilin1 is essential to cardiac ubiquitination-proteasome coupling and that an inadequacy in the coupling represents a major pathogenic factor for myocardial IRI; therefore, strategies to strengthen coupling have the potential to reduce IRI.

Remote post-conditioning and allopurinol reduce ischemia-reperfusion injury in an infra-renal ischemia model

BACKGROUND:

The aim of this study was to evaluate the effects of the antioxidant allopurinol and ischemic post-conditioning on the deleterious effects of ischemia followed by reperfusion (I/R) in a standardized model of ischemia involving infra-renal aortic occlusion in rats.

METHODS:

The animals were randomly divided into five groups: (A) animals not subjected to ischemia; (B) animals subjected to 2 h of ischemia and reperfusion only once; (C) animals given an allopurinol dose by gavage, then subjected to 2 h of ischemia and reperfusion only once; (D) animals subjected to 2 h of ischemia and post-conditioning and (E) animals that received allopurinol, then subjected to 2 h of ischemia and post-conditioning. The blood samples and small intestine segments were harvested for analysis after 3 days.

RESULTS:

The protective effects of the use of allopurinol and ischemic post-conditioning were observed by measuring aspartate aminotransferase, alanine aminotransferase and lactate levels. The benefits of post-conditioning were evident from the total antioxidant capacity and creatinine levels, but these could not ascertain any positive effects of allopurinol. The histological analysis of mesentery revealed that both methods were effective in minimizing the harmful effects of the ischemia and reperfusion process.

CONCLUSION:

Individual protocols significantly reduced I/R systemic injuries, but no additional protection was observed when the two strategies were combined.

The Role of Hydrogen Peroxide in Redox-Dependent Signaling: Homeostatic and Pathological Responses in Mammalian Cells

Hydrogen peroxide (H₂O₂) is an important metabolite involved in most of the redox metabolism reactions and processes of the cells. H₂O₂ is recognized as one of the main molecules in the sensing, modulation and signaling of redox metabolism, and it is acting as a second messenger together with hydrogen sulfide (H₂S) and nitric oxide (NO). These second messengers activate in turn a cascade of downstream proteins via specific oxidations leading to a metabolic response of the cell. This metabolic response can determine proliferation, survival or death of the cell depending on which downstream pathways (homeostatic, pathological, or protective) have been activated. The cells have several sources of H₂O₂ and cellular systems strictly control its concentration in different subcellular compartments. This review summarizes research on the role played by H₂O₂ in signaling pathways of eukaryotic cells and how this signaling leads to homeostatic or pathological responses.

Chick Embryo: A Preclinical Model for Understanding Ischemia-Reperfusion Mechanism

Ischemia-reperfusion (I/R)-related disorders, such as stroke, myocardial infarction, and peripheral vascular disease, are among the most frequent causes of disease and death. Tissue injury or death may result from the initial ischemic insult, primarily determined by the magnitude and duration of the interruption in blood supply and then by the subsequent reperfusion-induced damage. Various in vitro and in vivo models are currently available to study I/R mechanism in the brain and other tissues. However, thus far, no in ovo I/R model has been reported for understanding the I/R mechanisms and for faster drug screening. Here, we developed an in ovo Hook model of I/R by occluding and releasing the right vitelline artery of a chick embryo at 72 h of development. To validate the model and elucidate various underlying survival and death mechanisms, we employed imaging (Doppler blood flow imaging), biochemical, and blotting techniques and evaluated the cell death mechanism: autophagy and inflammation caused by I/R. In conclusion, the present model is useful in parallel with established in vitro and in vivo I/R models to understand the mechanisms of I/R development and its treatment.

Cellular responses of hyaluronic acid-coated chitosan nanoparticles

In recent years, nanotechnology has been proven to offer promising biomedical applications for in vivo diagnostics and drug delivery, stressing the importance of thoroughly investigating the biocompatibility of potentially translatable nanoparticles (NPs). Herein, we report the cellular responses of uncoated chitosan NPs (CS NPs) and hyaluronic acid-coated chitosan NPs (HA-CS NPs) when introduced into Chinese hamster ovary cells (CHO-K1) in a dose-dependent manner (2.5, 0.25, 0.025, 0.0025, and 0.00025 mg mL-1) at two time points (24 and 48 h). MTS assay, cell proliferation, showed a decrease in the viability of cells when treated with 0.25 and 2.5 mg mL-1 CS NPs. When exposed to high doses of CS NPs, the lactate dehydrogenase (LDH) enzyme started to leak out of the cells and the cellular levels of mitochondrial potentials were significantly reduced accompanied by a high production of intracellular reactive oxygen species (ROS). Our study provides molecular evidence of the biocompatibility offered by HA-CS NPs, through ROS scavenging capabilities rescuing cells from the oxidative stress, showing no observed cellular stress and thereby revealing the promising effect of anionic hyaluronic acid to significantly reduce the cytotoxicity of CS NPs. Our findings are important to accelerate the translation and utilization of HA-CS NPs in drug delivery, demonstrating the pronounced effect of surface modifications on modulating the biological responses.

Heart specific knockout of Ndufs4 ameliorates ischemia reperfusion injury

RATIONALE

Ischemic heart disease (IHD) is a leading cause of mortality. The most effective intervention for IHD is reperfusion, which ironically causes ischemia reperfusion (I/R) injury mainly due to oxidative stress-induced cardiomyocyte death. The exact mechanism and site of reactive oxygen species (ROS) generation during I/R injury remain elusive.

OBJECTIVE

We aim to test the hypothesis that Complex I-mediated forward and reverse electron flows are the major source of ROS in I/R injury of the heart.

METHODS AND RESULTS

We used a genetic model of mitochondrial Complex I deficiency, in which a Complex I assembling subunit, Ndufs4 was knocked out in the heart (Ndufs4H-/-). The Langendorff perfused Ndufs4H-/- hearts exhibited significantly reduced infarct size (45.3 ± 5.5% in wild type vs 20.9 ± 8.1% in Ndufs4H-/-), recovered contractile function, and maintained mitochondrial membrane potential after no flow ischemia and subsequent reperfusion. In cultured adult cardiomyocytes from Ndufs4H-/- mice, I/R mimetic treatments caused minimal cell death. Reintroducing Ndufs4 in Ndufs4H-/- cardiomyocytes abolished the protection. Mitochondrial NADH declined much slower in Ndufs4H-/- cardiomyocytes during reperfusion suggesting decreased forward electron flow. Mitochondrial flashes, a marker for mitochondrial respiration, were inhibited in Ndufs4H-/- cardiomyocytes at baseline and during I/R, which was accompanied by preserved aconitase activity suggesting lack of oxidative damage. Finally, pharmacological blockade of forward and reverse electron flow at Complex I inhibited I/R-induced cell death.

CONCLUSIONS

These results provide the first genetic evidence supporting the central role of mitochondrial Complex I in I/R injury of mouse heart. The study also suggests that both forward and reverse electron flows underlie oxidative cardiomyocyte death during reperfusion.

The role of mitochondrial cardiolipin in heart function and its implication in cardiac disease

Mitochondria play an essential role in the energy metabolism of the heart. Many of the essential functions are associated with mitochondrial membranes and oxidative phosphorylation driven by the respiratory chain. Mitochondrial membranes are unique in the cell as they contain the phospholipid cardiolipin. The important role of cardiolipin in cardiovascular health is highlighted by several cardiac diseases, in which cardiolipin plays a fundamental role. Barth syndrome, Sengers syndrome, and Dilated cardiomyopathy with ataxia (DCMA) are genetic disorders, which affect cardiolipin biosynthesis. Other cardiovascular diseases including ischemia/reperfusion injury and heart failure are also associated with changes in the cardiolipin pool. Here, we summarize molecular functions of cardiolipin in mitochondrial biogenesis and morphology. We highlight the role of cardiolipin for the respiratory chain, metabolite carriers, and mitochondrial metabolism and describe links to apoptosis and mitochondria specific autophagy (mitophagy) with possible implications in cardiac disease.