NADPH oxidases as a source of oxidative stress and molecular target in ischemia/reperfusion injury

Methylene blue-induced neuronal protective mechanism against hypoxia-reoxygenation stress

Brain ischemia and reperfusion (I/R) injury occurs in various pathological conditions, but there is no effective treatment currently available in clinical practice. Methylene blue (MB) is a century-old drug with a newly discovered protective function in the ischemic stroke model. In the current investigation we studied the MB-induced neuroprotective mechanism focusing on stabilization and activation of hypoxia-inducible factor-1α (HIF-1α) in an in vitro oxygen and glucose deprivation (OGD)-reoxygenation model.

METHODS

HT22 cells were exposed to OGD (0.1% O2, 6h) and reoxygenation (21% O2, 24h). Cell viability was determined with the calcein AM assay. The dynamic change of intracellular O2 concentration was monitored by fluorescence lifetime imaging microscopy (FLTIM). Glucose uptake was quantified using the 2-[N-(7-Nitrobenz-2-Oxa-1,3-Diazol-4-yl)Amino]-2-Deoxy-d-Glucose (2-NBDG) assay. ATP concentration and glycolytic enzyme activity were examined by spectrophotometry. Protein content changes were measured by immunoblot: HIF-1α, prolyl hydroxylase 2 (PHD2), erythropoietin (EPO), Akt, mTOR, and PIP5K. The contribution of HIF-1α activation in the MB-induced neuroprotective mechanism was confirmed by blocking HIF-1α activation with 2-methoxyestradiol-2 (2-MeOE2) and by transiently transfecting constitutively active HIF-1α.

RESULTS

MB increases cell viability by about 50% vs. OGD control. Compared to the corresponding control, MB increases intracellular O2 concentration and glucose uptake as well as the activities of hexokinase and G-6-PDH, and ATP concentration. MB activates the EPO signaling pathway with a corresponding increase in HIF-1α. Phosphorylation of Akt was significantly increased with MB treatment followed by activation of the mTOR pathway. Importantly, we observed, MB increased nuclear translocation of HIF-1α vs. control (about three folds), which was shown by a ratio of nuclear:cytoplasmic HIF-1α protein content.

CONCLUSION

We conclude that MB protects the hippocampus-derived neuronal cells against OGD-reoxygenation injury by enhancing energy metabolism and increasing HIF-1α protein content accompanied by an activation of the EPO signaling pathway.

Nuclear cardiac myosin light chain 2 modulates NADPH oxidase 2 expression in myocardium: a novel function beyond muscle contraction

Recent studies demonstrated that NADPH oxidase 2 (NOX2) expression in myocardium after ischemia-reperfusion (IR) is significantly upregulated. However, the underlying mechanisms remain unknown. This study aims to determine if nuclear cardiac myosin light chain 2 (MYL2), a well-known regulatory subunit of myosin, functions as a transcription factor to promote NOX2 expression following myocardial IR in a phosphorylation-dependent manner. We examined the phosphorylation status of nuclear MYL2 (p-MYL2) in a rat model of myocardial IR (left main coronary artery subjected to 1 h ligation and 3 h reperfusion) injury, which showed IR injury and upregulated NOX2 expression as expected, accompanied by elevated H₂O₂ and nuclear p-MYL2 levels; these effects were attenuated by inhibition of myosin light chain kinase (MLCK). Next, we explored the functional relationship of nuclear p-MYL2 with NOX2 expression in H9c2 cell model of hypoxia-reoxygenation (HR) injury. In agreement with our in vivo findings, HR treatment increased apoptosis, NOX2 expression, nuclear p-MYL2 and H₂O₂ levels, and the increases were ameliorated by inhibition of MLCK or knockdown of MYL2. Finally, molecular biology techniques including co-immunoprecipitation (Co-IP), chromatin immunoprecipitation (ChIP), DNA pull-down and luciferase reporter gene assay were utilized to decipher the molecular mechanisms. We found that nuclear p-MYL2 binds to the consensus sequence AGCTCC in NOX2 gene promoter, interacts with RNA polymerase II and transcription factor IIB to form a transcription preinitiation complex, and thus activates NOX2 gene transcription. Our results demonstrate that nuclear MYL2 plays an important role in IR injury by transcriptionally upregulating NOX2 expression to enhance oxidative stress in a phosphorylation-dependent manner.

Nitric Oxide Bioavailability in Obstructive Sleep Apnea: Interplay of Asymmetric Dimethylarginine and Free Radicals

Obstructive sleep apnea (OSA) occurs in 2% of middle-aged women and 4% of middle-aged men and is considered an independent risk factor for cerebrovascular and cardiovascular diseases. Nitric oxide (NO) is an important endothelium derived vasodilating substance that plays a critical role in maintaining vascular homeostasis. Low levels of NO are associated with impaired endothelial function. Asymmetric dimethylarginine (ADMA), an analogue of L-arginine, is a naturally occurring product of metabolism found in the human circulation. Elevated levels of ADMA inhibit NO synthesis while oxidative stress decreases its bioavailability, so impairing endothelial function and promoting atherosclerosis. Several clinical trials report increased oxidative stress and ADMA levels in patients with OSA. This review discusses the role of oxidative stress and increased ADMA levels in cardiovascular disease resulting from OSA.

Oxidative stress in fungi: its function in signal transduction, interaction with plant hosts, and lignocellulose degradation

In this review article, we want to present an overview of oxidative stress in fungal cells in relation to signal transduction, interaction of fungi with plant hosts, and lignocellulose degradation. We will discuss external oxidative stress which may occur through the interaction with other microorganisms or plant hosts as well as internally generated oxidative stress, which can for instance originate from NADPH oxidases or “leaky” mitochondria and may be modulated by the peroxiredoxin system or by protein disulfide isomerases thus contributing to redox signaling. Analyzing redox signaling in fungi with the tools of molecular genetics is presently only in its beginning. However, it is already clear that redox signaling in fungal cells often is linked to cell differentiation (like the formation of perithecia), virulence (in plant pathogens), hyphal growth and the successful passage through the stationary phase.

Effect of atorvastatin on serum oxidative stress and N-terminal brain natriuretic peptide expression in rats

OBJECTIVE

To investigate the effect of atorvastatin on serum oxidative stress and N-terminal brain natriuretic peptide expression in rats.

METHODS

A total of 40 healthy male SD rats were randomly divided into the sham group (Group A, n=10, saline 5 mL/d), ischemia-reperfusion group (Group B, n=10, saline 5 mL/d), atorvastatin group (Group C, n=10, atorvastatin 20 mg/kg · d), atorvastatin + N-amino-arginine group (Group D, n=10, atorvastatin 20 mg/kg · d + N-amino arginine 15 mg/kg). Myocardial ischemia-reperfusion rat model was established after 3 days of gavage. N-amino arginine 15 mg/kg was given by tail vein injection 15 min before ischemia. After reperfusion, enzymology indicators such us creatine kinase (CK) and lactate dehydrogenase and the oxidative stress parameters such as nitric oxide (NO), malondialdehyde (MDA) and total superoxide dismutase (TSOD), and n-terminal pro-brain natriuretic peptide (NT-proBNP) expression was detected by immunohistochemistry.

RESULTS

LDH and CK levels of group A were significantly lower than the other three groups, and group B was the highest. There was significant difference between group B and group C (P<0.05), and no significant difference between group B and group D (P>0.05). MDA levels in group B were significantly higher than the other three groups. The lowest was group A, followed by group C, the difference among groups was significantly (P<0.05). TSOD and NO levels in group B was the lowest, the level in group A was the highest, followed by group C, the difference among groups was significant (P<0.05). NT-proBNP level in group B was significantly higher than the other three groups, the lowest was group A, followed by group C, the difference among groups was significant (P<0.05).

CONCLUSIONS

Atorvastatin has a protective effect on the myocardial injury in the myocardial ischemia and reperfusion rats. It can increase NO synthesis and decrease MDA content, increase serum TSOD activity and the oxidative stress effect, meanwhile protect myocardial cells and reduce myocardial injury.

Elatoside C protects the heart from ischaemia/reperfusion injury through the modulation of oxidative stress and intracellular Ca²⁺ homeostasis

BACKGROUND

We have previously shown that Elatoside C reduces cardiomyocyte apoptosis during ischaemia/reperfusion (I/R). Here, we investigated whether Elatoside C improves heart function in isolated rat hearts subjected to I/R and elucidated the potential mechanisms involved in Elatoside C-induced protection.

METHODS AND RESULTS

Isolated rat hearts were subjected to global ischaemia followed by reperfusion in the absence or presence of Elatoside C. We found that Elatoside C significantly attenuated cardiac dysfunction and depressed oxidative stress induced by I/R. Consistently, Elatoside C prevented I/R-induced mitochondrial dysfunction, which was evident by the inhibition of mitochondrial ROS production, mitochondrial permeability transition pore (mPTP) opening, cytochrome c release from the mitochondria and Bax translocation. Moreover, Elatoside C improved abnormal calcium handling during I/R, including increasing sarcoplasmic reticulum Ca(2+) ATPase (SERCA2) activity, alleviating [Ca(2+)]ER depletion, and reducing the expression levels of ER stress protein markers. All of these protective effects of Elatoside C were partially abolished by the PI3K/Akt inhibitor LY294002, ERK1/2 inhibitor PD98059, and JAK2/STAT3 inhibitor AG490. Further assessment in isolated cardiomyocytes showed that Elatoside C maintained the Ca(2+) transients and cell shortening against I/R.

CONCLUSIONS

Elatoside C protects against cardiac injury during I/R by attenuating oxidative stress and [Ca(2+)]i overload through the activation of both the reperfusion injury salvage kinase (RISK) pathway (including PI3K/Akt and ERK1/2) and the survivor activating factor enhancement (SAFE) pathway (including JAK2/STAT3) and, subsequently, inhibiting the opening of mPTPs.

Apocynum venetum Leaf Attenuates Myocardial Ischemia/Reperfusion Injury by Inhibiting Oxidative Stress

Apocynum venetum, a Chinese medicinal herb, is reported to be neuroprotective. However, whether Apocynum venetum leaf extract (AVLE) protects against ischemic myocardium remains elusive. Our present study was aimed to observe the effects of AVLE preconditioning on myocardial ischemia/reperfusion (MI/R) injury and to investigate the possible mechanisms. Rats were treated with AVLE (500 mg/kg/d, o.g.) or distilled water once daily for one week. Afterward, all the animals were subjected to 30 min of myocardial ischemia followed by 4 h of reperfusion. AVLE preconditioning for one week significantly improved cardiac function following MI/R. Meanwhile, AVLE reduced infarct size, plasma creatine kinase (CK)/lactate dehydrogenase (LDH) activities and myocardial apoptosis at the end of reperfusion in rat hearts. Moreover, AVLE preconditioning significantly inhibited superoxide generation, gp91phox expression, malonaldialdehyde formation and enhanced superoxide dismutase (SOD) activity in I/R hearts. Furthermore, AVLE treatment increased Akt and extracellular regulated protein kinases 1/2 (ERK1/2) phosphorylations in I/R rat heart. Either the Phosphatidylinositide 3-kinase (PI3K) inhibitor wortmannin or the ERK1/2 inhibitor PD98059 blocked AVLE-stimulated anti-oxidative effects and cardioprotection. Our study demonstrated for the first time that AVLE reduces oxidative stress and exerts cardioprotection against MI/R injury in rats.

Angiotensin II triggers apoptosis via enhancement of NADPH oxidase-dependent oxidative stress in a dopaminergic neuronal cell line

Numerous studies reveal that Angiotensin II (Ang II), the main effector of renin-angiotensin system, contributes to the pathogenesis of Parkinson's disease (PD) via triggering dopaminergic cell loss. However, the underlying mechanisms remain largely unclear. In the current study, by using CATH.a cell, a dopaminergic neuronal cell line stably expressing Angiotensin II type 1 receptor (AT1R) and Angiotensin II type 2 receptor (AT2R), we showed that Ang II treatment triggered cell apoptosis in a dose-dependent manner, providing the first evidence that apoptotic cell death contributed to the dopaminergic cell loss induced by Ang II. Ang II treatment also led to a significant increment in intracellular reactive oxygen species generation, which could be fully abolished by nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors apocynin or diphenylene iodonium, indicating that Ang II enhanced oxidative stress via a NADPH oxidase-dependent manner. More importantly, inhibition of oxidative stress by NADPH oxidase inhibitors partially attenuated cell apoptosis caused by Ang II, implying that the enhancement of NADPH oxidase-dependent oxidative stress contributed to the cell apoptosis triggered by Ang II. Furthermore, the Ang II-induced oxidative stress and subsequent apoptosis could be completely abolished by AT1R blocker losartan rather than AT2R blocker PD1223319, suggesting that the aforementioned detrimental effects of Ang II are mediated by AT1R. In summary, these findings have deepened our understanding on the role of Ang II in PD pathogenesis, and support the use of AT1R blockers in the treatment of this devastating disease.

Therapeutic Effects of PPAR α on Neuronal Death and Microvascular Impairment

Peroxisome-proliferator activated receptor-alpha (PPARα) is a broadly expressed nuclear hormone receptor and is a transcription factor for diverse target genes possessing a PPAR response element (PPRE) in the promoter region. The PPRE is highly conserved, and PPARs thus regulate transcription of an extensive array of target genes involved in energy metabolism, vascular function, oxidative stress, inflammation, and many other biological processes. PPARα has potent protective effects against neuronal cell death and microvascular impairment, which have been attributed in part to its antioxidant and anti-inflammatory properties. Here we discuss PPARα's effects in neurodegenerative and microvascular diseases and also recent clinical findings that identified therapeutic effects of a PPARα agonist in diabetic microvascular complications.

Oxidative stress contributes to orthopedic trauma-induced acute kidney injury in obese rats

After trauma, obese patients have an increased risk of developing acute kidney injury (AKI). We have demonstrated that obese Zucker (OZ) rats, but not lean Zucker (LZ) rats, develop AKI 24 h after orthopedic trauma. ROS have been implicated in the pathophysiology of AKI in models of critical illness. However, the contribution of ROS to trauma-induced AKI in the setting of obesity has not been determined. We hypothesized that AKI in OZ rats after trauma is mediated by increased oxidative stress. Male LZ and OZ rats were divided into control and trauma groups, with a subset receiving treatment after trauma with the antioxidant apocynin (50 mg/kg ip, 2 mM in drinking water). The day after trauma, glomerular filtration rate, plasma creatinine, urine kidney injury molecule-1, and albumin excretion as well as renal oxidant and antioxidant activity were measured. After trauma, compared with LZ rats, OZ rats exhibited a significant decrease in glomerular filtration rate along with significant increases in plasma creatinine and urine kidney injury molecule-1 and albumin excretion. Additionally, oxidative stress was significantly increased in OZ rats, as evidenced by increased renal NADPH oxidase activity and urine lipid peroxidation products (thiobarbituric acid-reactive substances), and OZ rats also had suppressed renal superoxide dismutase activity. Apocynin treatment significantly decreased oxidative stress and AKI in OZ rats but had minimal effects in LZ rats. These results suggest that ROS play an important role in AKI in OZ rats after traumatic injury and that ROS may be a potential future therapeutic target in the obese after trauma.

Targeting tumour hypoxia to prevent cancer metastasis. From biology, biosensing and technology to drug development: the METOXIA consortium

The hypoxic areas of solid cancers represent a negative prognostic factor irrespective of which treatment modality is chosen for the patient. Still, after almost 80 years of focus on the problems created by hypoxia in solid tumours, we still largely lack methods to deal efficiently with these treatment-resistant cells. The consequences of this lack may be serious for many patients: Not only is there a negative correlation between the hypoxic fraction in tumours and the outcome of radiotherapy as well as many types of chemotherapy, a correlation has been shown between the hypoxic fraction in tumours and cancer metastasis. Thus, on a fundamental basis the great variety of problems related to hypoxia in cancer treatment has to do with the broad range of functions oxygen (and lack of oxygen) have in cells and tissues. Therefore, activation-deactivation of oxygen-regulated cascades related to metabolism or external signalling are important areas for the identification of mechanisms as potential targets for hypoxia-specific treatment. Also the chemistry related to reactive oxygen radicals (ROS) and the biological handling of ROS are part of the problem complex. The problem is further complicated by the great variety in oxygen concentrations found in tissues. For tumour hypoxia to be used as a marker for individualisation of treatment there is a need for non-invasive methods to measure oxygen routinely in patient tumours. A large-scale collaborative EU-financed project 2009-2014 denoted METOXIA has studied all the mentioned aspects of hypoxia with the aim of selecting potential targets for new hypoxia-specific therapy and develop the first stage of tests for this therapy. A new non-invasive PET-imaging method based on the 2-nitroimidazole [(18)F]-HX4 was found to be promising in a clinical trial on NSCLC patients. New preclinical models for testing of the metastatic potential of cells were developed, both in vitro (2D as well as 3D models) and in mice (orthotopic grafting). Low density quantitative real-time polymerase chain reaction (qPCR)-based assays were developed measuring multiple hypoxia-responsive markers in parallel to identify tumour hypoxia-related patterns of gene expression. As possible targets for new therapy two main regulatory cascades were prioritised: The hypoxia-inducible-factor (HIF)-regulated cascades operating at moderate to weak hypoxia (<1% O(2)), and the unfolded protein response (UPR) activated by endoplasmatic reticulum (ER) stress and operating at more severe hypoxia (<0.2%). The prioritised targets were the HIF-regulated proteins carbonic anhydrase IX (CAIX), the lactate transporter MCT4 and the PERK/eIF2α/ATF4-arm of the UPR. The METOXIA project has developed patented compounds targeting CAIX with a preclinical documented effect. Since hypoxia-specific treatments alone are not curative they will have to be combined with traditional anti-cancer therapy to eradicate the aerobic cancer cell population as well.

GYY4137 protects against myocardial ischemia and reperfusion injury by attenuating oxidative stress and apoptosis in rats

Hydrogen sulfide (H₂S) is a gasotransmitter that regulates cardiovascular functions. The present study aimed to determine the protective effect of slow-releasing H₂S donor GYY4137 on myocardial ischemia and reperfusion (I/R) injury and to investigate the possible signaling mechanisms involved. Male Sprague-Dawley rats were treated with GYY4137 at 12.5 mg/(kg·day), 25 mg/(kg·day) or 50 mg/(kg·day) intraperitoneally for 7 days. Then, rats were subjected to 30 minutes of left anterior descending coronary artery occlusion followed by reperfusion for 24 hours. We found that GYY4137 increased the cardiac ejection fraction and fractional shortening, reduced the ischemia area, alleviated histological injury and decreased plasma creatine kinase after myocardial I/R. Both H₂S concentration in plasma and cystathionine-γ-lyase (CSE) activity in the myocardium were enhanced in the GYY4137 treated groups. GYY4137 also decreased malondialdehyde and myeloperoxidase levels in serum, attenuated superoxide anion level and suppressed phosphorylation of mitogen activated protein kinases in the myocardium after I/R. Meanwhile, GYY4137 increased the expression of Bcl-2 but decreased the expression of Bax, caspase-3 activity and apoptosis in the myocardium. The data suggest that GYY4137 protects against myocardial ischemia and reperfusion injury by attenuating oxidative stress and apoptosis.

The quest for selective nox inhibitors and therapeutics: challenges, triumphs and pitfalls

SIGNIFICANCE

Numerous studies in animal models and human subjects corroborate that elevated levels of reactive oxygen species (ROS) play a pivotal role in the progression of multiple diseases. As a major source of ROS in many organ systems, the NADPH oxidase (Nox) has become a prime target for therapeutic development.

RECENT ADVANCES

In recent years, intense efforts have been dedicated to the development of pan- and isoform-specific Nox inhibitors as opposed to antioxidants that proved ineffective in clinical trials. Over the past decade, an array of compounds has been proposed in an attempt to fill this void.

CRITICAL ISSUES

Although many of these compounds have proven effective as Nox enzyme family inhibitors, isoform specificity has posed a formidable challenge to the scientific community. This review surveys the most prominent Nox inhibitors, and discusses potential isoform specificity, known mechanisms of action, and shortcomings. Some of these inhibitors hold substantial promise as targeted therapeutics.

FUTURE DIRECTIONS

Increased insight into the mechanisms of action and regulation of this family of enzymes as well as atomic structures of key Nox subunits are expected to give way to a broader spectrum of more potent, efficacious, and specific molecules. These lead molecules will assuredly serve as a basis for drug development aimed at treating a wide array of diseases associated with increased Nox activity.

Protective and antioxidant effects of PPARα in the ischemic retina

PURPOSE

Previous studies have demonstrated that peroxisome proliferator-activated receptor-alpha (PPARα) agonists have therapeutic effects in diabetic retinopathy, although the mechanism of action remains incompletely understood. The purpose of this study was to evaluate PPARα's protective effects in the ischemic retina, and to delineate its molecular mechanism of action.

METHODS

For the oxygen-induced retinopathy (OIR) model, wild-type (WT), and PPARα knockout (PPARα(-/-)) mice were exposed to 75% O₂ from postnatal day 7 (P7) to P12 and treated with the PPARα agonist fenofibric acid (Feno-FA) from P12 to P16. At P17, the effects of Feno-FA on retinal glial fibrillary acidic protein (GFAP) expression, apoptotic DNA cleavage, and TUNEL labeling were analyzed. Cultured retinal cells were exposed to CoCl₂ to induce hypoxia, and TUNEL staining and 5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein dye were used to measure apoptosis and reactive oxygen species (ROS) generation. Western blotting was used to measure GFAP levels and cell signaling.

RESULTS

Feno-FA decreased retinal apoptosis and oxidative stress in WT but not PPARα(-/-) OIR mice. Peroxisome proliferator-activated receptor-alpha knockout OIR mice showed increased retinal cell death and glial activation in comparison to WT OIR mice. Feno-FA treatment and PPARα overexpression protected cultured retinal cells from hypoxic cell death and decreased ROS levels. Nuclear hypoxia-inducible factor-α (HIF-1α) and nicotine adenine dinucleotide phosphate oxidase-4 (Nox 4) were increased in OIR retinas and downregulated by Feno-FA in WT but not in PPARα(-/-) mice.

CONCLUSIONS

Peroxisome proliferator-activated receptor-alpha has a potent antiapoptotic effect in the ischemic retina. This protective effect may be mediated in part through downregulation of HIF-1α/Nox 4 and consequently alleviation of oxidative stress.

Regulated necrosis: the expanding network of non-apoptotic cell death pathways

Cell death research was revitalized by the understanding that necrosis can occur in a highly regulated and genetically controlled manner. Although RIPK1 (receptor-interacting protein kinase 1)- and RIPK3-MLKL (mixed lineage kinase domain-like)-mediated necroptosis is the most understood form of regulated necrosis, other examples of this process are emerging, including cell death mechanisms known as parthanatos, oxytosis, ferroptosis, NETosis, pyronecrosis and pyroptosis. Elucidating how these pathways of regulated necrosis are interconnected at the molecular level should enable this process to be therapeutically targeted.

Redox control of enzymatic functions: The electronics of life's circuitry

The field of redox biology has changed tremendously over the past 20 years. Formerly regarded as bi-products of the aerobic metabolism exclusively involved in tissue damage, reactive oxygen species (ROS) are now recognized as active participants of cell signaling events in health and in disease. In this sense, ROS and the more recently defined reactive nitrogen species (RNS) are, just like hormones and second messengers, acting as fundamental orchestrators of cell signaling pathways. The chemical modification of enzymes by ROS and RNS (that result in functional enzymatic alterations) accounts for a considerable fraction of the transient and persistent perturbations imposed by variations in oxidant levels. Upregulation of ROS and RNS in response to stress is a common cellular response that foments adaptation to a variety of physiologic alterations (hypoxia, hyperoxia, starvation, and cytokine production). Frequently, these are beneficial and increase the organisms' resistance against subsequent acute stress (preconditioning). Differently, the sustained ROS/RNS-dependent rerouting of signaling produces irreversible alterations in cellular functioning, often leading to pathogenic events. Thus, the duration and reversibility of protein oxidations define whether complex organisms remain "electronically" healthy. Among the 20 essential amino acids, four are particularly susceptible to oxidation: cysteine, methionine, tyrosine, and tryptophan. Here, we will critically review the mechanisms, implications, and repair systems involved in the redox modifications of these residues in proteins while analyzing well-characterized prototypic examples. Occasionally, we will discuss potential consequences of amino acid oxidation and speculate on the biologic necessity for such events in the context of adaptative redox signaling. © 2014 IUBMB Life, 66(3):167-181, 2014.

Attenuation of urokinase activity during experimental ischaemia protects the cerebral barrier from damage through regulation of matrix metalloproteinase-2 and NAD(P)H oxidase

Ischaemic injury impairs the integrity of the blood-brain barrier (BBB). In this study, we investigated the molecular causes of this defect with regard to the putative correlations among NAD(P)H oxidase, plasminogen-plasmin system components, and matrix metalloproteinases. Hence, the activities of NAD(P)H oxidase, matrix metalloproteinase-2, urokinase-type plasminogen activator (uPA), and tissue-type plasminogen activator (tPA), and superoxide anion levels, were assessed in human brain microvascular endothelial cells (HBMECs) exposed to oxygen-glucose deprivation (OGD) alone or OGD followed by reperfusion (OGD + R). The integrity of an in vitro model of BBB comprising HBMECs and astrocytes was studied by measuring transendothelial electrical resistance and the paracellular flux of albumin. OGD with or without reperfusion (OGD ± R) radically perturbed barrier function while concurrently enhancing uPA, tPA and NAD(P)H oxidase activities and superoxide anion release in HBMECs. Pharmacological inactivation of NAD(P)H oxidase attenuated OGD ± R-mediated BBB damage through modulation of matrix metalloproteinase-2 and tPA, but not uPA activity. Overactivation of NAD(P)H oxidase in HBMECs via cDNA electroporation of its p22-phox subunit confirmed the involvement of tPA in oxidase-mediated BBB disruption. Interestingly, blockade of uPA or uPA receptor preserved normal BBB function by neutralizing both NAD(P)H oxidase and matrix metalloproteinase-2 activities. Hence, selective targeting of uPA after ischaemic strokes may protect cerebral barrier integrity and function by concomitantly attenuating basement membrane degradation and oxidative stress.

The anti-oxidative role of micro-vesicles derived from human Wharton-Jelly mesenchymal stromal cells through NOX2/gp91(phox) suppression in alleviating renal ischemia-reperfusion injury in rats

Oxidative stress is known as one of the main contributors in renal ischemia/reperfusion injury (IRI). Here we hypothesized that Micro-vesicles (MVs) derived from human Wharton Jelly mesenchymal stromal cells (hWJMSCs) could protect kidney against IRI through mitigating oxidative stress. MVs isolated from hWJMSCs conditioned medium were injected intravenously in rats immediately after unilateral kidney ischemia for 60 min. The animals were sacrificed at 24h, 48h and 2 weeks respectively after reperfusion. Our results show that the expression of NOX2 and reactive oxygen species (ROS) in injured kidney tissues was declined and the oxidative stress was alleviated in MVs group at 24h and 48h in parallel with the reduced apoptosis and enhanced proliferation of cells. IRI-initiated fibrosis was abrogated by MVs coincident with renal function amelioration at 2 weeks. NOX2 was also found down-regulated by MVs both in human umbilical vein endothelial cells (HUVEC) and NRK-52E cell line under hypoxia injury model in vitro. In conclusion, a single administration of hWJMSC-MVs might protect the kidney by alleviation of the oxidative stress in the early stage of kidney IRI through suppressing NOX2 expression. Moreover, it could reduce the fibrosis and improved renal function.

L-3-n-Butylphthalide protects rats' cardiomyocytes from ischaemia/reperfusion-induced apoptosis by affecting the mitochondrial apoptosis pathway

AIMS

This study investigated the role of L-3-n-Butylphthalide (NBP) in cardiac protection.

METHODS

The left anterior descending coronary arteries (LAD) of the rats were occluded for 30 min following by 2-h reperfusion to make the ischaemia/reperfusion models. Neonatal cardiomyocytes were cultured and subjected to hypoxia. L-3-n-Butylphthalide was administered intraperitoneally 2 h before the surgery and right after the reperfusion in the in vivo experiments or added to the culture medium in vitro. Haemodynamic parameters were recorded to evaluate the cardiac functions, triphenyltetrazolium chloride (TTC) and Evens blue staining were used to determine the area of risk and infarct area, apoptotic cell numbers were counted with terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) staining. Western blotting was used to determine the apoptotic protein levels and immune staining to determine the translocation of Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) protein.

RESULTS

Our research showed for the first time that L-3-n-Butylphthalide had great effects in improving cardiac hemodynamic function and decreasing cardiac infarct areas and apoptotic cell numbers in the peri-infarct areas. The apoptotic signals investigation showed that L-3-n-Butylphthalide affected the mitochondrial pathway including Bcl-2 protein expression, inhibition of caspase 3 activation and cytochrome C releasing. Besides, Glyceraldehyde-3-phosphate dehydrogenase protein translocation was inhibited by L-3-n-Butylphthalide treatment, and this effect was mediated by endogenous reactive oxygen species (ROS).

CONCLUSION

L-3-n-Butylphthalide protects cardiomyocytes from ischaemia/reperfusion-induced apoptosis by antioxidant effect and affecting mitochondrial apoptotic pathway.

NADPH oxidase 1 and its derived reactive oxygen species mediated tissue injury and repair

Reactive oxygen species are mostly viewed to cause oxidative damage to various cells and induce organ dysfunction after ischemia-reperfusion injury. However, they are also considered as crucial molecules for cellular signal transduction in biology. NADPH oxidase, whose only function is reactive oxygen species production, has been extensively investigated in many cell types especially phagocytes. The deficiency of NADPH oxidase extends the process of inflammation and delays tissue repair, which causes chronic granulomatous disease in patients. NADPH oxidase 1, one member of the NADPH oxidase family, is not only constitutively expressed in a variety of tissues, but also induced to increase expression in both mRNA and protein levels under many circumstances. NADPH oxidase 1 and its derived reactive oxygen species are suggested to be able to regulate inflammation reaction, cell proliferation and migration, and extracellular matrix synthesis, which contribute to the processes of tissue injury and repair.

Salvianolic acid B attenuates spinal cord ischemia-reperfusion-induced neuronal injury and oxidative stress by activating the extracellular signal-regulated kinase pathway in rats

BACKGROUND

Salvianolic acid B (SalB), the main bioactive compound isolated from the traditional Chinese medicinal herb broad Radix Salviae Miltiorrhizae exerts a spectrum of pharmacologic activities. We investigated the effects of SalB treatment in a rat model of spinal cord ischemia and reperfusion (I/R) injury and the underlying mechanism.

MATERIALS AND METHODS

SalB was administered at 1, 10, or 50 mg/kg after spinal cord ischemia. The potential protective effects on spinal cord injury were determined by spinal cord edema, infarct volume, and motor function assessment of the hind limbs.

RESULTS

SalB treatment significantly decreased spinal cord edema and infarct volume and preserved motor function of the hind limbs in a dose-dependent manner. SalB administration ameliorated the generation of oxidative products and preserved antioxidant defense activities in the injured spinal cord at both 4 and 24 h after I/R injury. Moreover, SalB prolonged the I/R injury-induced activation of extracellular signal-regulated kinase (ERK), and blocking ERK activation with PD98059 partially prevented the neuroprotective effects of SalB.

CONCLUSIONS

These findings demonstrate the neuroprotective effects of SalB in a spinal cord I/R injury model and suggest that SalB-induced neuroprotection was mediated by ERK activation.

Moderate hypoxia followed by reoxygenation results in blood-brain barrier breakdown via oxidative stress-dependent tight-junction protein disruption

Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O2, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2',7'-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this process.

AKIP1 expression modulates mitochondrial function in rat neonatal cardiomyocytes

A kinase interacting protein 1 (AKIP1) is a molecular regulator of protein kinase A and nuclear factor kappa B signalling. Recent evidence suggests AKIP1 is increased in response to cardiac stress, modulates acute ischemic stress response, and is localized to mitochondria in cardiomyocytes. The mitochondrial function of AKIP1 is, however, still elusive. Here, we investigated the mitochondrial function of AKIP1 in a neonatal cardiomyocyte model of phenylephrine (PE)-induced hypertrophy. Using a seahorse flux analyzer we show that PE stimulated the mitochondrial oxygen consumption rate (OCR) in cardiomyocytes. This was partially dependent on PE mediated AKIP1 induction, since silencing of AKIP1 attenuated the increase in OCR. Interestingly, AKIP1 overexpression alone was sufficient to stimulate mitochondrial OCR and in particular ATP-linked OCR. This was also true when pyruvate was used as a substrate, indicating that it was independent of glycolytic flux. The increase in OCR was independent of mitochondrial biogenesis, changes in ETC density or altered mitochondrial membrane potential. In fact, the respiratory flux was elevated per amount of ETC, possibly through enhanced ETC coupling. Furthermore, overexpression of AKIP1 reduced and silencing of AKIP1 increased mitochondrial superoxide production, suggesting that AKIP1 modulates the efficiency of electron flux through the ETC. Together, this suggests that AKIP1 overexpression improves mitochondrial function to enhance respiration without excess superoxide generation, thereby implicating a role for AKIP1 in mitochondrial stress adaptation. Upregulation of AKIP1 during different forms of cardiac stress may therefore be an adaptive mechanism to protect the heart.

NADPH oxidase enzymes in skin fibrosis: molecular targets and therapeutic agents

Fibrosis is characterized by the excessive deposition of extracellular matrix components eventually resulting in organ dysfunction and failure. In dermatology, fibrosis is the hallmark component of many skin diseases, including systemic sclerosis, graft-versus-host disease, hypertrophic scars, keloids, nephrogenic systemic fibrosis, porphyria cutanea tarda, restrictive dermopathy and other conditions. Fibrotic skin disorders may be debilitating and impair quality of life. There are few FDA-approved anti-fibrotic drugs; thus, research in this area is crucial in addressing this deficiency. Recent investigations elucidating the pathogenesis of skin fibrosis have implicated endogenous reactive oxygen species produced by the multicomponent nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) enzyme complex. In this review, we discuss Nox enzymes and their role in skin fibrosis. An overview of the Nox enzyme family is presented and their role in the pathogenesis of skin fibrosis is discussed. The mechanisms by which Nox enzymes influence specific fibrotic skin disorders are also reviewed. Finally, we describe the therapeutic approaches to ameliorate skin fibrosis by directly targeting Nox enzymes with the use of statins, p47phox subunit modulators, or GKT137831, a competitive inhibitor of Nox enzymes. Nox enzymes can also be targeted indirectly via scavenging ROS with antioxidants. We believe that Nox modulators are worthy of further investigation and have the potential to transform the management of skin fibrosis by dermatologists.

Achyranthes bidentata polypeptides reduces oxidative stress and exerts protective effects against myocardial ischemic/reperfusion injury in rats

Achyranthes bidentata, a Chinese medicinal herb, is reported to be neuroprotective. However, its role in cardioprotection remains largely unknown. Our present study aimed to investigate the effects of Achyranthes bidentata polypeptides (ABPP) preconditioning on myocardial ischemia/reperfusion (MI/R) injury and to test the possible mechanisms. Rats were treated with ABPP (10 mg/kg/d, i.p.) or saline once daily for one week. Afterward, all the animals were subjected to 30 min of myocardial ischemia followed by 4 h of reperfusion. ABPP preconditioning for one week significantly improved cardiac function following MI/R. Meanwhile, ABPP reduced infarct size, plasma creatine kinase (CK)/lactate dehydrogenase (LDH) activities and myocardial apoptosis at the end of reperfusion in rat hearts. Moreover, ABPP preconditioning significantly inhibited superoxide generation, gp91^phox expression, malonaldialdehyde formation and enhanced superoxide dismutase activity in I/R hearts. Furthermore, ABPP treatment inhibited PTEN expression and increased Akt phosphorylation in I/R rat heart. PI3K inhibitor wortmannin blocked Akt activation, and abolished ABPP-stimulated anti-oxidant effect and cardioprotection. Our study demonstrated for the first time that ABPP reduces oxidative stress and exerts cardioprotection against MI/R injury in rats. Inhibition of PTEN and activation of Akt may contribute to the anti-oxidant capacity and cardioprotection of ABPP.

Biological importance of reactive oxygen species in relation to difficulties of treating pathologies involving oxidative stress by exogenous antioxidants

Findings about involvement of reactive oxygen species (ROS) not only in defense processes, but also in a number of pathologies, stimulated discussion about their role in etiopathogenesis of various diseases. Yet questions regarding the role of ROS in tissue injury, whether ROS may serve as a common cause of different disorders or whether their uncontrolled production is just a manifestation of the processes involved, remain unexplained. Dogmatically, increased ROS formation is considered to be responsible for development of the so-called free-radical diseases. The present review discusses importance of ROS in various biological processes, including origin of life, evolution, genome plasticity, maintaining homeostasis and organism protection. This may be a reason why no significant benefit was found when exogenous antioxidants were used to treat free-radical diseases, even though their causality was primarily attributed to ROS. Here, we postulate that ROS unlikely play a causal role in tissue damage, but may readily be involved in signaling processes and as such in mediating tissue healing rather than injuring. This concept is thus in a contradiction to traditional understanding of ROS as deleterious agents. Nonetheless, under conditions of failing autoregulation, ROS may attack integral cellular components, cause cell death and deteriorate the evolving injury.

Role of oxidative stress in chemical allergens induced skin cells activation

Allergic contact dermatitis (ACD) is an important occupational and environmental disease caused by topical exposure to chemical allergens. It describes the adverse effects that may results when exposure to a chemical elicits a T cell-mediated inflammatory skin disease. The ability of contact sensitizers to induce the oxidative stress pathway in keratinocytes and dendritic cells has been confirmed by several authors. Reactive oxygen species (ROS) can serve as essential second messengers mediating cellular responses resulting in immune cells activation. Oxidative stress may be the starter point, as it leads to the activation of transcription factors and signaling pathways, including NF-kB and p38 MAPK, which leads to the release of cytokines and chemokines. ROS are also involved in the activation of the NLRP3/NALP3 inflammasome, which is required to direct the proteolytic maturation of inflammatory cytokines such as IL-1β and IL-18, which are all integral to the process of dendritic cells mobilization, migration and functional maturation. Moreover, emerging evidence correlates ROS to changes in the constitution of the extracellular microenvironment found to facilitate ACD. The purpose of this review is to provide both conceptual and technical frameworks on the role of oxidative stress in chemical allergy.