NADPH Oxidase as a Therapeutic Target for Neuroprotection against Ischaemic Stroke: Future Perspectives

Role of the telomeric factor TRF2 in post-hypoxic brain damages

The neuronal excitotoxicity that follows reoxygenation after a hypoxic period may contribute to epilepsy, Alzheimer's disease, Parkinson's disease and various disorders that are related to inadequate supplement of oxygen in neurons. Therefore, counteracting the deleterious effects of post-hypoxic stress is an interesting strategy to treat a large spectrum of neurodegenerative diseases. Here, we show that the expression of the key telomere protecting protein Trf2 decreases in the brain of mice submitted to a post-hypoxic stress. Moreover, downregulating the expression of Terf2 in hippocampal neural cells of unchallenged mice triggers an excitotoxicity-like phenotype including glutamate overexpression and behavioral alterations while overexpressing Terf2 in hippocampal neural cells of mice subjected to a post-hypoxic treatment prevents brain damages. Moreover, Terf2 overexpression in culture neurons counteracts the oxidative stress triggered by glutamate. Finally, we provide evidence that the effect of Terf2 downregulation on excitotoxicity involves Sirt3 repression leading to mitochondrial dysfunction. We propose that increasing the level of Terf2 expression is a potential strategy to reduce post-hypoxic stress damages.

Fasudil mediates neuroprotection in ischemia/reperfusion by modulating the ROCK-PPARα-NOX axis

PURPOSE

Cerebral ischemia-reperfusion (I/R) is a neurovascular disorder that leads to brain injury. In mice, Fasudil improves nerve injury induced by I/R. However, it is unclear if this is mediated by increased peroxisome proliferator-activated receptor-α (PPARα) expression and reduced oxidative damage. This study aimed to investigate the neuroprotective mechanism of action of Fasudil.

METHODS

MCAO (Middle cerebral artery occlusion) was performed in male C57BL/6J wild-type and PPARα KO mice between September 2021 to April 2023. Mice were treated with Fasudil and saline; 2,3,5-Triphenyltetrazolium chloride (TTC) staining was performed to analyze cerebral infarction. PPARα and Rho-associated protein kinase (ROCK) expression were detected using Western blot, and the expression of NADPH subunit Nox2 mRNA was detected using real-time polymerase chain reaction. The NADPH oxidase activity level and reactive oxygen species (ROS) content were also investigated.

RESULTS

After cerebral ischemia, the volume of cerebral necrosis was reduced in wild-type mice treated with Fasudil. The expression of PPARα was increased, while ROCK was decreased. Nox2 mRNA expression, NADPH oxidase activity, and ROS content decreased. There were no significant changes in cerebral necrosis volumes, NADPH oxidase activity, and ROS content in the PPARα KO mice treated with Fasudil.

CONCLUSIONS

In mice, the neuroprotective effect of Fasudil depends on the expression of PPARα induced by ROCK-PPARα-NOX axis-mediated reduction in ROS and associated oxidative damage.

Glycosylation of Quercetin by Selected Entomopathogenic Filamentous Fungi and Prediction of Its Products' Bioactivity

Quercetin is the most abundant flavonoid in food products, including berries, apples, cauliflower, tea, cabbage, nuts, onions, red wine and fruit juices. It exhibits various biological activities and is used for medical applications, such as treating allergic, inflammatory and metabolic disorders, ophthalmic and cardiovascular diseases, and arthritis. However, its low water solubility may limit quercetin's therapeutic potential. One method of increasing the solubility of active compounds is their coupling to polar molecules, such as sugars. The attachment of a glucose unit impacts the stability and solubility of flavonoids and often determines their bioavailability and bioactivity. Entomopathogenic fungi are biocatalysts well known for their ability to attach glucose and its 4-O-methyl derivative to bioactive compounds, including flavonoids. We investigated the ability of cultures of entomopathogenic fungi belonging to Beauveria, Isaria, Metapochonia, Lecanicillium and Metarhizium genera to biotransform quercetin. Three major glycosylation products were detected: (1), 7-O-β-D-(4″-O-methylglucopyranosyl)-quercetin, (2) 3-O-β-D-(4″-O-methylglucopyranosyl)-quercetin and (3) 3-O-β-D-(glucopyranosyl)-quercetin. The results show evident variability of the biotransformation process, both between strains of the tested biocatalysts from different species and between strains of the same species. Pharmacokinetic and pharmacodynamic properties of the obtained compounds were predicted with the use of cheminformatics tools. The study showed that the obtained compounds may have applications as effective modulators of intestinal flora and may be stronger hepato-, cardio- and vasoprotectants and free radical scavengers than quercetin.

Activation of peripheral TRPM8 mitigates ischemic stroke by topically applied menthol

Background

No reports exist as to neuroprotective effects associated with topical activation of transient receptor potential melastatin 8 (TRPM8), a noted cold receptor. In the present study, we identified whether activating peripheral TRPM8 can be an adjuvant therapy for ischemic stroke.

Methods

Menthol, an agonist of TRPM8, was applied orally or topically to all paws or back of the mouse after middle cerebral artery occlusion (MCAO). We used Trpm8 gene knockout (Trpm8^−/−) mice or TRPM8 antagonist and lidocaine to validate the roles of TRPM8 and peripheral nerve conduction in menthol against ischemic stroke.

Results

Application of menthol 16% to paw derma attenuated infarct volumes and ameliorated sensorimotor deficits in stroke mice induced by MCAO. The benefits of topically applied menthol were associated with reductions in oxidative stress, neuroinflammation and infiltration of monocytes and macrophages in ischemic brains. Antagonizing TRPM8 or Trpm8 knockout dulls the neuroprotective effects of topically application of menthol against MCAO. Immunohistochemistry analyses revealed significantly higher TRPM8 expression in skin tissue samples obtained from the paws compared with skin from the backs, which was reflected by significantly smaller infarct lesion volumes and better sensorimotor function in mice treated with menthol on the paws compared with the back. Blocking conduction of peripheral nerve in the four paws reversed the neuroprotective effects of topical menthol administrated to paws. On the other hand, oral menthol dosing did not assist with recovery from MCAO in our study.

Conclusion

Our results suggested that activation of peripheral TRPM8 expressed in the derma tissue of limbs with sufficient concentration of menthol is beneficial to stroke recovery. Topical application of menthol on hands and feet could be a novel and simple-to-use therapeutic strategy for stroke patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02553-4.

Fatty Acids: An Insight into the Pathogenesis of Neurodegenerative Diseases and Therapeutic Potential

One of the most common lipids in the human body is palmitic acid (PA), a saturated fatty acid with essential functions in brain cells. PA is used by cells as an energy source, besides being a precursor of signaling molecules and protein tilting across the membrane. Although PA plays physiological functions in the brain, its excessive accumulation leads to detrimental effects on brain cells, causing lipotoxicity. This mechanism involves the activation of toll-like receptors (TLR) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathways, with the consequent release of pro-inflammatory cytokines, increased production of reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, and autophagy impairment. Importantly, some of the cellular changes induced by PA lead to an augmented susceptibility to the development of Alzheimer's and Parkinson´s diseases. Considering the complexity of the response to PA and the intrinsic differences of the brain, in this review, we provide an overview of the molecular and cellular effects of PA on different brain cells and their possible relationships with neurodegenerative diseases (NDs). Furthermore, we propose the use of other fatty acids, such as oleic acid or linoleic acid, as potential therapeutic approaches against NDs, as these fatty acids can counteract PA's negative effects on cells.

Detection strategies for superoxide anion: A review

Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. Superoxide anion (O₂^-.), one kind of ROS, is the single-electron reduction product of oxygen molecules, which mainly exists in plants and animals, and is closely related to many inflammatory diseases. In the field of biomedicine, with the deepening understanding of superoxide anion, more and more detection methods have been developed. This review mainly introduces the detection techniques for superoxide anion in recent years.

Oxidative Stress, Neuroinflammation, and NADPH Oxidase: Implications in the Pathogenesis and Treatment of Alzheimer's Disease

NADPH oxidase as an important source of intracellular reactive oxygen species (ROS) has gained enormous importance over the years, and the detailed structures of all the isoenzymes of the NADPH oxidase family and their regulation have been well explored. The enzyme has been implicated in a variety of diseases including neurodegenerative diseases. The present brief review examines the body of evidence that links NADPH oxidase with the genesis and progression of Alzheimer's disease (AD). In short, evidence suggests that microglial activation and inflammatory response in the AD brain is associated with increased production of ROS by microglial NADPH oxidase. Along with other inflammatory mediators, ROS take part in neuronal degeneration and enhance the microglial activation process. The review also evaluates the current state of NADPH oxidase inhibitors as potential disease-modifying agents for AD.

Regulation of Superoxide by BAP31 through Its Effect on p22phox and Keap1/Nrf2/HO-1 Signaling Pathway in Microglia

Reactive oxygen species (ROS) production by activation of microglia is considered to be a major cause of neuronal dysfunction, which can lead to damage and death through direct oxidative damage to neuronal macromolecules or derangement of neuronal redox signaling circuits. BAP31, an integral ER membrane protein, has been defined as a regulatory molecule in the CNS. Our latest studies have found that BAP31 deficiency leads to activation of microglia. In this study, we discovered that BAP31 deficiency upregulated LPS-induced superoxide anion production in BV2 cells and mice by upregulating the expression level of p22^phox and by inhibiting the activation of Nrf2-HO-1 signaling. Knockdown of p22^phox/keap1 or use of an NADPH oxidase inhibitor (apocynin) reversed the production of superoxide anion and inflammatory cytokines, which then reduced neuronal damage and death in vitro and in vivo. These results suggest that BAP31 deficiency contributes to microglia-related superoxide anion production and neuroinflammation through p22^phox and keap1. Furthermore, the excess superoxide anion cooperated with inflammatory cytokines to induce the damage and death of neurons. Thus, we determined that BAP31 is an important regulator in superoxide anion production and neuroinflammation, and the downstream regulators or agonists of BAP31 could therefore be considered as potential therapeutic targets in microglial-related superoxide anion production and neuroinflammation.

Microglial metabolic disturbances and neuroinflammation in cerebral infarction

Cerebral ischemia/reperfusion injury activates microglia, resident immune cells in the brain, and allows the infiltration of circulating immune cells into the ischemic lesions. Microglia play both exacerbating and protective roles in pathological processes and are thus often referred to as "double-edged swords." In ischemic brains, blood-borne macrophages play a role that is distinct from that of resident activated microglia. Recently, the metabolic alteration of immune cells in the pathogenesis of inflammatory disorders including cerebral infarction has become a critical target for investigation. We begin this review by describing the multifaceted functions of microglia in cerebral infarction. Next, we focus on the metabolic alterations that occur in microglia during pathological processes. We also discuss morphological changes that take place in the mitochondria, leading to functional disturbances, accompanied by alterations in microglial function. Moreover, we describe the involvement of the reactive oxygen species that are produced during aberrant metabolic activity. Finally, we discuss therapeutic strategies to ameliorate aggravative changes in metabolism.

How to Improve the Antioxidant Defense in Asphyxiated Newborns-Lessons from Animal Models

Oxygen free radicals have been implicated in brain damage after neonatal asphyxia. In the early phase of asphyxia/reoxygenation, changes in antioxidant enzyme activity play a pivotal role in switching on and off the cascade of events that can kill the neurons. Hypoxia/ischemia (H/I) forces the brain to activate endogenous mechanisms (e.g., antioxidant enzymes) to compensate for the lost or broken neural circuits. It is important to evaluate therapies to enhance the self-protective capacity of the brain. In animal models, decreased body temperature during neonatal asphyxia has been shown to increase cerebral antioxidant capacity. However, in preterm or severely asphyxiated newborns this therapy, rather than beneficial seems to be harmful. Thus, seeking new therapeutic approaches to prevent anoxia-induced complications is crucial. Pharmacotherapy with deferoxamine (DFO) is commonly recognized as a beneficial regimen for H/I insult. DFO, via iron chelation, reduces oxidative stress. It also assures an optimal antioxidant protection minimizing depletion of the antioxidant enzymes as well as low molecular antioxidants. In the present review, some aspects of recently acquired insight into the therapeutic effects of hypothermia and DFO in promoting neuronal survival after H/I are discussed.

Metabolomics coupled with SystemsDock reveal the protective effect and the potential active components of Naozhenning granule against traumatic brain injury

ETHNOPHARMACOLOGICAL RELEVANCE

Naozhenning granule (NZN), a widely traditional Chinese medicine (TCM) prescription with a long history of clinical, which is mainly used in the treatment of concussion, cerebral post-traumatic syndrome, consists of Di Huang (Radix of Rehmannia glutinosa (Gaertn.) DC.), Dang Gui (Radix of Angelica sinensis (Oliv.) Diels), Chen Pi (Pericarpium of Citrus reticulata Blanco), Dan shen (Radix of Salvia Miltiorrhiza Bunge.), Di Long (Pheretima aspergillum (E. Perrier)), Mu Dan Pi (Cortex of Paeonia suffruticosa Andrews), Suan Zao Ren (Semen of Ziziphus jujuba Mill.), Chuan Xiong (Rhizoma of Ligusticum striatum DC.), Zhu Ru (Phyllostachys nigra (Lodd. Ex Lindl.) Munro), Bai Zi Ren (Semen of Platycladus orientalis (L.) Franco) and Fu Ling (sclerotium of Poria cocos (Schw.)Wolf).

AIM OF THE STUDY

This study aimed to unravel the mechanism and material basis of NZN against traumatic brain injury.

MATERIALS AND METHODS

In this study, a ¹H nuclear magnetic resonance (NMR) based metabolomic approach combined with systemsDock was employed to study the protective effect of NZN against traumatic brain injury using a cerebral concussion rat model. The morris water maze test and biochemical indexes were used to evaluate the efficacy of NZN.

RESULTS

The results of morris water maze test suggested NZN can improve the spatial learning and memory of model rats, and the superoxide dismutas (SOD) and malonyldialdehyde (MDA) level indicated that the effect of NZN was related with the regulation of oxidative stress. Multivariate analysis revealed that the effect of NZN was related with regulation of 18 brain metabolites, and the corresponding metabolic pathways were further revealed by MetPA analysis. 13 serum absorbed components were found to hit the targets both related with the metabolic regulation and cerebral trauma through systemsDock-aided molecular docking experiments, and these compounds might be served as the active compounds in NZN against cerebral trauma.

CONCLUSION

¹H-NMR based metabolomics and molecular docking provided the insights for the synergistic mechanisms and the potential active compounds of NZN in treating cerebral trauma. However, the bioactive compounds and their synergistic effect need to be further validated.

Reperfusion injury as a target for diminishing infarct size

Therapies for preventing reperfusion injury (RI) have been widely studied. However, the attempts to transfer cardioprotective therapies for reducing RI from experiments into clinical practice have been so far unsuccessful. Pathophysiological mechanisms of RI are complicated and compose of many pathways e.g. hypercontracture-mediated sarcolemma rupture, mitochondrial permeability transition pore persistent opening, reactive oxygen species formation, inflammation and no-reflow phenomenon. Based on research, it cannot be determined which mechanism dominates, probably they cooperate with a domination of one or another in different clinical circumstances. Our hypothesis is, that only intervention that at the same time interferes with different (all?) pathways of RI may turn out to be effective in decreasing the final area of infarction.

Exploring the effects of Gastrodia elata Blume on the treatment of cerebral ischemia-reperfusion injury using UPLC-Q/TOF-MS-based plasma metabolomics

Gastrodia elata Blume (Orchidaceae, GEB) is a medicinal plant that has been widely used in the treatment of cerebrovascular disease. This study explored the protective effects of GEB against cerebral ischemia-reperfusion using Information-Dependent Acquisition (IDA)-mediated UPLC-Q/TOF-MS-based plasma metabolomics. Cerebral ischemia-reperfusion (IR) injury was induced in male Wistar rats using the Zea Longa method. Biochemical and histological assays were performed to evaluate the therapeutic effects of GEB on IR rats. We found that the neurobehavioral scores and infarction areas of GEB and nimodipine treated groups were dramatically lower than those of the IR groups. Hematoxylin and Eosin (HE) staining and TdT-mediated dUTP Nick-End Labeling (TUNEL) showed that GEB significantly improved neuronal injury and prevented neuronal apoptosis. Biochemical analysis revealed that GEB prevented cerebral ischemia-reperfusion injury by regulating inflammation and oxidative injury. Through ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry-metabolomics-based approaches, 43 plasma metabolites related to GEB treatment were detected, 6 of which significantly differed (p < 0.05) between the model and GEB groups. The levels of l-histidine, sphinganine, thymine, spermidine and deoxycytidine in the IR group were significantly higher than those in the sham group, but decreased following GEB treatment. Arachidonic acid levels were lower in the IR group, but dramatically increased in response to GEB. Pharmacodynamics and metabolomics confirmed that the mechanism of GEB in the treatment of cerebral ischemia was not only related to the reduction of inflammation, oxidation, neurotoxicity, and apoptosis, but also mediated through arachidonic acid metabolism, histidine metabolism, pyrimidine metabolism, arginine and proline metabolism, sphingolipid metabolism, and glycerophospholipid metabolism in vivo.

Search for new pharmacological targets for increasing the efficiency of correction of cardiovascular diseases

Introduction: Cardiovascular disease (CVD) is the leading cause of death worldwide: no other reason causes as many deaths a year as CVD. An estimated 17.9 million people died of CVD in 2016, accounting for 31% of all deaths in the world. People with CVD or at high risk for these diseases (due to one or more risk factors, such as high blood pressure, diabetes, hyperlipidemia, or an already developed disease) need early detection and assistance through counseling and, if necessary, taking medication.

Ways to find new targets for the correction of endothelium-associated pathology: The basis of the modern therapy for arterial hypertension and other cardiovascular diseases is the postulate of the need to correct endothelial dysfunction as an indication of the adequacy of antihypertensive and other types of treatment. Lowering blood pressure (BP) without normalizing endothelial function cannot be considered a successfully resolved clinical task. Currently, there are no drugs for specific pharmacological correction of endothelial dysfunction in cardiovascular diseases, and the search for new targets for pharmacological correction of endothelial dysfunction is one of the main tasks of pharmacology.

The Role of Mitochondrial and Endoplasmic Reticulum Reactive Oxygen Species Production in Models of Perinatal Brain Injury

Significance: Perinatal brain injury is caused by hypoxia-ischemia (HI) in term neonates, perinatal arterial stroke, and infection/inflammation leading to devastating long-term neurodevelopmental deficits. Therapeutic hypothermia is the only currently available treatment but is not successful in more than 50% of term neonates suffering from hypoxic-ischemic encephalopathy. Thus, there is an urgent unmet need for alternative or adjunct therapies. Reactive oxygen species (ROS) are important for physiological signaling, however, their overproduction/accumulation from mitochondria and endoplasmic reticulum (ER) during HI aggravate cell death. Recent Advances and Critical Issues: Mechanisms underlying ER stress-associated ROS production have been primarily elucidated using either non-neuronal cells or adult neurodegenerative experimental models. Findings from mature brain cannot be simply transferred to the immature brain. Therefore, age-specific studies investigating ER stress modulators may help investigate ER stress-associated ROS pathways in the immature brain. New therapeutics such as mitochondrial site-specific ROS inhibitors that selectively inhibit superoxide (O2•-)/hydrogen peroxide (H2O2) production are currently being developed. Future Directions: Because ER stress and oxidative stress accentuate each other, a combinatorial therapy utilizing both antioxidants and ER stress inhibitors may prove to be more protective against perinatal brain injury. Moreover, multiple relevant targets need to be identified for targeting ROS before they are formed. The role of organelle-specific ROS in brain repair needs investigation. Antioxid. Redox Signal. 31, 643-663.

Examining the relationship between astrocyte dysfunction and neurodegeneration in ALS using hiPSCs

Amyotrophic lateral sclerosis (ALS) is a complex and fatal neurodegenerative disease for which the causes of disease onset and progression remain unclear. Recent advances in human induced pluripotent stem cell (hiPSC)-based models permit the study of the genetic factors associated with ALS in patient-derived neural cell types, including motor neurons and glia. While astrocyte dysfunction has traditionally been thought to exacerbate disease progression, astrocytic dysfunction may play a more direct role in disease initiation and progression. Such non-cell autonomous mechanisms expand the potential targets of therapeutic intervention, but only a handful of ALS risk-associated genes have been examined for their impact on astrocyte dysfunction and neurodegeneration. This review summarizes what is currently known about astrocyte function in ALS and suggests ways in which hiPSC-based models can be used to more effectively study the role of astrocytes in neurodegenerative disease.

Brain metabonomics study of the antidepressant-like effect of Xiaoyaosan on the CUMS-depression rats by 1H NMR analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Xiaoyaosan (XYS), a famous TCM prescription with a long history of clinical use for relieving a wide variety of depression symptoms, consists of Radix Bupleuri (Bupleurum chinense DC.), Radix Angelicae Sinensis (Angelica sinensis (Oliv.) Diels), Radix PaeoniaeAlba (Paeonia lactiflora Pall.), Rhizoma Atractylodis Macrocepha lae (Atractylodes macrocephala Koidz.), Poria (Poria cocos (Schw.)Wolf), Radix Glycyrrhizae (Glycyrrhiza uralensis Fisch.), Herba Menthae Haplocalycis (Mentha haplocalyx Briq.), and Rhizoma Zin-giberis Recens (Zingiber officinale Rosc.).

AIM OF THE STUDY

We aimed to characterize the diversity and variation of two kinds metabolites of brain, i.e. aqueous and lipophilic metabolites, gaining comprehensive insights into the metabolic processes of depression-like behavior, and to reveal the mechanisms of antidepressant-like effects of XYS.

MATERIALS AND METHODS

We first established a CUMS (Chronic Unpredictable Mild Stress)-induced depression-like behavior model. We then extracted both aqueous and lipophilic metabolites of rat brains by a two-phase extraction method, which were subsequently characterized by two differential sequences of ¹H nuclear magnetic resonance (NMR). Multivariate analysis including Principal Components Analysis (PCA) and Orthogonal Partial Least Squares-Discriminate Analysis (OPLS-DA) was applied.

RESULTS

Metabolic profiling by PCA indicated that XYS significantly reversed the metabolic perturbation caused by CUMS. OPLS-DA showed a total of 15 metabolites including 6 lipophilic and 9 aqueous metabolites was screened as potential biomarkers involved in CUMS-induced depression-like behavior. On top of this, five pathways including (1)D-glutamine and D-glutamate metabolism, (2) valine, leucine and isoleucine biosynthesis, (3) alanine, aspartate and glutamate metabolism, (4) taurine and hypotaurine metabolism and (5) arginine and proline metabolism were recognized as the most influenced pathways associated with the process of CUMS-induced depression-like behavior. Notably, XYS significantly reversed abnormality of 5 aqueous and 4 lipophilic metabolites to normal, suggesting that XYS synergistically mediated abnormalities of multiple pathways (1), (3), (4) and (5).

CONCLUSIONS

It is the first report to investigate the antidepressant-like effects and underlying mechanisms of XYS from the perspective of brain metabolites. In a broad sense, this study brings novel and valuable insights to evaluate the efficacy of traditional Chinese medicine (TCM), to interpret mechanisms, and to provide the theoretical basis for further research on therapeutic mechanisms in clinical practice.

Reactive Oxygen Species Formation in the Brain at Different Oxygen Levels: The Role of Hypoxia Inducible Factors

Hypoxia inducible factor (HIF) is the master oxygen sensor within cells and is central to the regulation of cell responses to varying oxygen levels. HIF activation during hypoxia ensures optimum ATP production and cell integrity, and is associated both directly and indirectly with reactive oxygen species (ROS) formation. HIF activation can either reduce ROS formation by suppressing the function of mitochondrial tricarboxylic acid cycle (TCA cycle), or increase ROS formation via NADPH oxidase (NOX), a target gene of HIF pathway. ROS is an unavoidable consequence of aerobic metabolism. In normal conditions (i.e., physioxia), ROS is produced at minimal levels and acts as a signaling molecule subject to the dedicated balance between ROS production and scavenging. Changes in oxygen concentrations affect ROS formation. When ROS levels exceed defense mechanisms, ROS causes oxidative stress. Increased ROS levels can also be a contributing factor to HIF stabilization during hypoxia and reoxygenation. In this review, we systemically review HIF activation and ROS formation in the brain during hypoxia and hypoxia/reoxygenation. We will then explore the literature describing how changes in HIF levels might provide pharmacological targets for effective ischaemic stroke treatment. HIF accumulation in the brain via HIF prolyl hydroxylase (PHD) inhibition is proposed as an effective therapy for ischaemia stroke due to its antioxidation and anti-inflammatory properties in addition to HIF pro-survival signaling. PHD is a key regulator of HIF levels in cells. Pharmacological inhibition of PHD increases HIF levels in normoxia (i.e., at 20.9% O₂ level). Preconditioning with HIF PHD inhibitors show a neuroprotective effect in both in vitro and in vivo ischaemia stroke models, but post-stroke treatment with PHD inhibitors remains debatable. HIF PHD inhibition during reperfusion can reduce ROS formation and activate a number of cellular survival pathways. Given agents targeting individual molecules in the ischaemic cascade (e.g., antioxidants) fail to be translated in the clinic setting, thus far, HIF pathway targeting and thereby impacting entire physiological networks is a promising drug target for reducing the adverse effects of ischaemic stroke.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

Contribution of Zinc-Dependent Delayed Calcium Influx via TRPC5 in Oxidative Neuronal Death and its Prevention by Novel TRPC Antagonist

Oxidative stress is a key mediator of neuronal death in acute brain injuries, such as epilepsy, trauma, and stroke. Although it is accompanied by diverse cellular changes, increases in levels of intracellular zinc ion (Zn²⁺) and calcium ion (Ca²⁺) may play a critical causative role in oxidative neuronal death. However, the mechanistic link between Zn²⁺ and Ca²⁺ dyshomeostasis in neurons during oxidative stress is not well-understood. Here, we show that the exposure of cortical neurons to H₂O₂ led to a zinc-triggered calcium influx, which resulted in neuronal death. The cyclin-dependent kinase inhibitor, NU6027, inhibited H₂O₂-induced Ca²⁺ increases and subsequent cell death in cortical neurons, without affecting the early increase in Zn²⁺. Therefore, we attempted to identify the zinc-regulated Ca²⁺ pathway that was inhibited by NU6027. The expression profile in cortical neurons identified transient receptor potential cation channel 5 (TRPC5) as a candidate that is known to involve in the generation of epileptiform burst firing and epileptic neuronal death (Phelan KD et al. 2012a; Phelan KD et al. 2013b). NU6027 inhibited basal and zinc-augmented TRPC5 currents in TRPC5-overexpressing HEK293 cells. Consistently, cortical neurons from TRPC5 knockout mice were highly resistant to H₂O₂-induced death. Moreover, NU6027 is neuroprotective in kainate-treated epileptic rats. Our results demonstrate that TRPC5 is a novel therapeutic target against oxidative neuronal injury in prolonged seizures and that NU6027 is a potent inhibitor of TRPC5.

Mitochondrial GSH Systems in CA1 Pyramidal Cells and Astrocytes React Differently during Oxygen-Glucose Deprivation and Reperfusion

Pyramidal cells and astrocytes have differential susceptibility to oxygen-glucose deprivation and reperfusion (OGD-RP). It is known that excessive reactive oxygen species (ROS) in mitochondria initiates cell death, while glutathione (GSH) is one of the major defenses against ROS. Although it is known that astrocytes contain a higher concentration of GSH than neurons, and that astrocytes can provide neurons with GSH, we are unaware of a detailed and quantitative examination of the dynamic changes in the mitochondrial GSH system in the two cell types during OGD-RP. Here, we determined mitochondrial membrane potential and the degrees of oxidation of the mitochondrially targeted roGFP-based sensors for hydrogen peroxide (OxD_P) and GSH (OxD_G). We also developed a method to estimate the mitochondrial GSH (mGSH) concentration in single cells in the CA1 region of organotypic hippocampal slice cultures at several time-points during OGD-RP. We find that mitochondrial membrane potential drops in pyramidal cells during OGD while it is relatively stable in astrocytes. In both types of cell, the mitochondrial membrane potential decreases during RP. During OGD-RP, mitochondrial peroxide levels are the same. Astrocytic mGSH is more than four times higher than pyramidal cell mGSH (3.2 vs 0.7 mM). Astrocytic mGSH is drained from mitochondria during OGD, whereas in pyramidal cells it remains fairly constant. OxD_GSH prior to and during OGD is lower (less oxidized) in pyramidal cells than in astrocytes, but the two nearly converge during RP. The larger changes of redox status in the GSH system in pyramidal cells than astrocytes is an upstream sign of the higher mortality of the pyramidal cells after facing an insult. The pattern of [mGSH] changes in the two cell types could be recognized as another mechanism by which astrocytes protect neurons from transient, extreme conditions.

Acid-base alterations in ESRD and effects of hemodialysis

Acid-base alterations in patients with kidney failure and on hemodialysis (HD) treatment contribute to (1) intradialytic hypercapnia and hypoxia, (2) hemodynamic instability and cardiac arrhythmia, (3) systemic inflammation, and (4) a number of associated electrolyte alterations including potentiating effects of hypokalemia, hypocalcemia and, chronically, soft-tissue and vascular calcification, imparting poor prognosis and mortality. This paper discusses acid-base regulation and pathogenesis of dysregulation in patients with kidney failure. Major organ and systemic effects of acid-base perturbations with a specific focus on kidney failure patients on HD are emphasized, and potential mitigating strategies proposed. The high rate of HD-related complications, specifically those that can be accounted for by rapid and steep acid-base perturbations imposed by HD treatment, attests to the pressing need for investigations to establish a better dialysis regimen.

A H2O2-Responsive Theranostic Probe for Endothelial Injury Imaging and Protection

Overproduction of H₂O₂ causes oxidative stress and is the hallmark of vascular diseases. Tracking native H₂O₂ in the endothelium is therefore indispensable to gain fundamental insights into this pathogenesis. Previous fluorescent probes for H₂O₂ imaging were generally arylboronates which were decomposed to emissive arylphenols in response to H₂O₂. Except the issue of specificity challenged by peroxynitrite, boric acid by-produced in this process is actually a waste with unknown biological effects. Therefore, improvements could be envisioned if a therapeutic agent is by-produced instead. Herein, we came up with a "click-to-release-two" strategy and demonstrate that dual functional probes could be devised by linking a fluorophore with a therapeutic agent via a H₂O₂-responsive bond. As a proof of concept, probe AP consisting of a 2-(2'-hydroxyphenyl) benzothiazole fluorophore and an aspirin moiety has been prepared and confirmed for its theranostic effects. This probe features high specificity towards H₂O₂ than other reactive species including peroxynitrite. Its capability to image and ameliorate endothelial injury has been verified both in vitro and in vivo. Noteworthy, as a result of its endothelial-protective effect, AP also works well to reduce thrombosis formation in zebrafish model.

NADPH Oxidase Contributes to Photoreceptor Degeneration in Constitutively Active RAC1 Mice

Purpose

The active form of small GTPase RAC1 is required for activation of NADPH oxidase (NOX), which in turn generates reactive oxygen species (ROS) in nonphagocytic cells. We explored whether NOX-induced oxidative stress contributes to rod degeneration in retinas expressing constitutively active (CA) RAC1.

Methods

Transgenic (Tg)–CA-RAC1 mice were given apocynin (10 mg/kg, intraperitoneal), a NOX inhibitor, or vehicle daily for up to 13 weeks. Superoxide production and oxidative damage were assessed by dihydroethidium staining and by protein carbonyls and malondialdehyde levels, respectively. Outer nuclear layer (ONL) cells were counted and electroretinogram (ERG) amplitudes measured in Tg-CA-RAC1 mice. Outer nuclear layer cells were counted in wild-type (WT) mice after transfer of CA-Rac1 gene by subretinal injection of AAV8-pOpsin-CA Rac1-GFP.

Results

Transgenic-CA-RAC1 retinas had significantly fewer photoreceptor cells and more apoptotic ONL cells than WT controls from postnatal week (Pw) 3 to Pw13. Superoxide accumulation and protein and lipid oxidation were increased in Tg-CA-RAC1 retinas and were reduced in mice treated with apocynin. Apocynin reduced the loss of photoreceptors and increased the rod ERG a- and b-wave amplitudes when compared with vehicle-injected transgenic controls. Photoreceptor loss was also observed in regions of adult WT retina transduced with AAV8-pOpsin-CA Rac1-GFP but not in neighboring regions that were not transduced or in AAV8-pOpsin-GFP–transduced retinas.

Conclusions

Constitutively active RAC1 promotes photoreceptor cell death by oxidative damage that occurs, at least partially, through NOX-induced ROS. Reactive oxygen species are likely involved in multiple forms of retinal degenerations, and our results support investigating RAC1 inhibition as a therapeutic approach that targets this disease pathway.

Targeting oxidative stress for the treatment of ischemic stroke: Upstream and downstream therapeutic strategies

Excessive oxygen and its chemical derivatives, namely reactive oxygen species (ROS), produce oxidative stress that has been known to lead to cell injury in ischemic stroke. ROS can damage macromolecules such as proteins and lipids and leads to cell autophagy, apoptosis, and necrosis to the cells. This review describes studies on the generation of ROS, its role in the pathogenesis of ischemic stroke, and recent development in therapeutic strategies in reducing oxidative stress after ischemic stroke.

(1)H NMR-based metabonomics revealed protective effect of Naodesheng bioactive extract on ischemic stroke rats

ETHNOPHARMACOLOGICAL RELEVANCE

Stroke is a leading cause of death and disability in the world. However, current therapies are limited. Naodesheng, a widely used traditional Chinese medicine prescription, has shown a good clinical curative effect on ischemic stroke. Also, Naodesheng has been suggested to have neuroprotective effect on focal cerebral ischemia rats, but the underlying molecular mechanism remains unclear.

AIM OF THE STUDY

The present study was designed to evaluate the effect of Naodesheng bioactive extract on the metabolic changes in brain tissue, plasma and urine induced by cerebral ischemia perfusion injury, and explore the possible metabolic mechanisms by using a (1)H NMR-based metabonomics approach.

MATERIALS AND METHODS

A middle cerebral artery occlusion rat model was established and confirmed by the experiments of neurobehavioral abnormality evaluation, brain tissue TTC staining and pathological examination. The metabolic changes in brain tissue, plasma and urine were then assessed by a (1)H NMR technique combined with multivariate statistical analysis method.

RESULTS

These NMR data showed that cerebral ischemia reperfusion induced great metabolic disorders in brain tissue, plasma and urine metabolisms. However, Naodesheng bioactive extract could reverse most of the imbalanced metabolites. Meanwhile, it was found that both the medium and high dosages of Naodesheng bioactive extract were more effective on the metabolic changes than the low dosage, consistent with histopathological assessments.

CONCLUSIONS

These results revealed that Naodesheng had protective effect on ischemic stroke rats and the underlying mechanisms involved multiple metabolic pathways, including energy metabolism, amino acid metabolism, oxidative stress and inflammatory injury. The present study could provide evidence that metabonomics revealed its capacity to evaluate the holistic efficacy of traditional Chinese medicine and explore the underlying mechanisms.

Antioxidants as therapeutics in the intensive care unit: Have we ticked the redox boxes?

Critically ill patients are under oxidative stress and antioxidant administration reasonably emerged as a promising approach to combat the aberrant redox homeostasis in this patient cohort. However, the results of the antioxidant treatments in the intensive care unit are conflicting and inconclusive. The main objective of the present review is to highlight some inherent, yet widely overlooked redox-related issues about the equivocal effectiveness of antioxidants in the intensive care unit, beyond methodological considerations. In particular, the discrepancy in the literature partially stems from: (1) the largely unspecified role of reactive species in disease onset and progression, (2) our fragmentary understanding on the interplay between inflammation and oxidative stress, (3) the complex spatiotemporal specificity of in vivo redox biology, (4) the pleiotropic effects of antioxidants and (5) the divergent effects of antioxidants according to the temporal administration pattern. In addition, two novel and sophisticated practices with promising pre-clinical results are presented: (1) the selective neutralization of reactive species in key organelles after they are formed (i.e., in mitochondria) and (2) the targeted complete inhibition of dominant reactive species sources (i.e., NADPH oxidases). Finally, the reductive potential of NADPH as a key pharmacological target for redox therapies is rationalized. In light of the above, the recontextualization of knowledge from basic redox biology to translational medicine seems imperative to perform more realistic in vivo studies in the fast-growing field of critical care pharmacology.

Chronic Pancreatitis Correlates With Increased Risk of Cerebrovascular Disease: A Retrospective Population-Based Cohort Study in Taiwan

The aim of this study is to explore whether there is a relationship between chronic pancreatitis and cerebrovascular disease in Taiwan. Using the claims data of the Taiwan National Health Insurance Program, we identified 16,672 subjects aged 20 to 84 years with a new diagnosis of chronic pancreatitis from 2000 to 2010 as the chronic pancreatitis group. We randomly selected 65,877 subjects aged 20 to 84 years without chronic pancreatitis as the nonchronic pancreatitis group. Both groups were matched by sex, age, comorbidities, and the index year of diagnosing chronic pancreatitis. The incidence of cerebrovascular disease at the end of 2011 was measured. The multivariable Cox proportional hazards regression model was used to measure the hazard ratio (HR) and 95% confidence interval (CI) for cerebrovascular disease risk associated with chronic pancreatitis and other comorbidities. The overall incidence of cerebrovascular disease was 1.24-fold greater in the chronic pancreatitis group than that in the nonchronic pancreatitis group (14.2 vs. 11.5 per 1000 person-years, 95% CI = 1.19-1.30). After controlling for confounding factors, the adjusted HR of cerebrovascular disease was 1.27 (95% CI = 1.19-1.36) for the chronic pancreatitis group as compared with the nonchronic pancreatitis group. Woman (adjusted HR = 1.41, 95% CI = 1.31-1.51), age (every 1 year, HR = 1.04, 95% CI = 1.04-1.05), atrial fibrillation (adjusted HR = 1.23, 95% CI = 1.02-1.48), chronic kidney disease (adjusted HR = 1.48, 95% CI = 1.31-1.67), chronic obstructive pulmonary disease (adjusted HR = 1.27, 95% CI = 1.16-1.40), diabetes mellitus (adjusted HR = 1.82, 95% CI = 1.72-1.92), hypertension (adjusted HR = 1.66, 95% CI = 1.56-1.76), and peripheral atherosclerosis (adjusted HR = 1.26, 95% CI = 1.06-1.51) were other factors significantly associated with cerebrovascular disease. Chronic pancreatitis is associated with increased hazard of subsequent cerebrovascular disease.

Optimized real-time monitoring of glutathione redox status in single pyramidal neurons in organotypic hippocampal slices during oxygen-glucose deprivation and reperfusion

A redox-sensitive Grx1-roGFP2 fusion protein was introduced by transfection into single pyramidal neurons in the CA1 subfield of organotypic hippocampal slice cultures (OHSCs). We assessed changes in the GSH system in neuronal cytoplasm and mitochondria during oxygen-glucose deprivation and reperfusion (OGD/RP), an in vitro model of stroke. Pyramidal cells in a narrow range of depths below the surface of the OHSC were transfected by gene gun or single-cell electroporation with cyto- or mito-Grx1-roGFP2. To mimic the conditions of acute stroke, we developed an optimized superfusion system with the capability of rapid and reproducible exchange of the solution bathing the OHSCs. Measurements of pO2 as a function of tissue depth show that in the region containing the transfected cells, the pO2 is well-controlled. We also found that the pO2 changes on the same time scale as changes in intracranial pressure, cerebral blood flow, and pO2 during acute stroke. Determining the reduction potential, EGSH, from the ratiometric fluorescence signal requires an absolute intensity measurement during calibration of the Grx1-roGFP2. Using the signal from cotransfected tdTomato as an internal standard during calibration improves quantitative measurements of Grx1-roGFP2 redox status and allows EGSH to be determined. EGSH becomes more reducing during OGD and more oxidizing during RP in mitochondria while changes in cytoplasm are not significant compared with controls.

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

Reperfusion injury, the paradoxical tissue response that is manifested by blood flow-deprived and oxygen-starved organs following the restoration of blood flow and tissue oxygenation, has been a focus of basic and clinical research for over 4-decades. While a variety of molecular mechanisms have been proposed to explain this phenomenon, excess production of reactive oxygen species (ROS) continues to receive much attention as a critical factor in the genesis of reperfusion injury. As a consequence, considerable effort has been devoted to identifying the dominant cellular and enzymatic sources of excess ROS production following ischemia-reperfusion (I/R). Of the potential ROS sources described to date, xanthine oxidase, NADPH oxidase (Nox), mitochondria, and uncoupled nitric oxide synthase have gained a status as the most likely contributors to reperfusion-induced oxidative stress and represent priority targets for therapeutic intervention against reperfusion-induced organ dysfunction and tissue damage. Although all four enzymatic sources are present in most tissues and are likely to play some role in reperfusion injury, priority and emphasis has been given to specific ROS sources that are enriched in certain tissues, such as xanthine oxidase in the gastrointestinal tract and mitochondria in the metabolically active heart and brain. The possibility that multiple ROS sources contribute to reperfusion injury in most tissues is supported by evidence demonstrating that redox-signaling enables ROS produced by one enzymatic source (e.g., Nox) to activate and enhance ROS production by a second source (e.g., mitochondria). This review provides a synopsis of the evidence implicating ROS in reperfusion injury, the clinical implications of this phenomenon, and summarizes current understanding of the four most frequently invoked enzymatic sources of ROS production in post-ischemic tissue.

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Reperfusion injury is implicated in a variety of human diseases and disorders.

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Evidence implicating ROS in reperfusion injury continues to grow.

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Several enzymes are candidate sources of ROS in post-ischemic tissue.

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Inter-enzymatic ROS-dependent signaling enhances the oxidative stress caused by I/R.

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Proteomic analysis of the hippocampus in naïve and ischemic-preconditioned rat

The hippocampus exhibits regional differences in vulnerability to ischemia, wherein pyramidal cells in the CA1 region are vulnerable to ischemia while pyramidal cells in the CA3 region and granule cells in the dentate gyrus (DG) region are relatively ischemia resistant. However, pyramidal cells in the CA1 region reportedly exhibit ischemic tolerance following exposure to a brief non-lethal period of ischemia known as ischemic preconditioning. In this study, we used proteomic analysis to examine the difference in protein expression between naïve rat CA1 and CA3/DG regions, as well as the altered protein expression in the CA1 region after 3min of ischemic preconditioning. Proteomic analysis identified ubiquitin carboxyl-terminal hydrolase isozyme L1 (UCH-L1), glutathione S-transferase μ5 (GSTμ5), glutamine synthetase (GS), and dynamin-1 as proteins with differential expression levels in naïve CA1 and CA3/DG regions. The difference in expression levels of GSTμ5 and GS between these two regions was further confirmed by western blot. Our analysis also identified aconitase2, α-tubulin, protein-l-isoaspartate O-methiltransferase (PIMT), and voltage-dependent anion channel 1 (VDCA1) as proteins with down-regulated expression levels in the CA1 region following 3min ischemic preconditioning. The decrease in the expression of aconitase2 was also confirmed by western blot and immunohistochemical staining. The present results suggest that GSTμ5 and GS may be associated with ischemia-resistance in the CA3/DG region and that aconitase2 may play a part in the ischemic tolerance in the CA1 region.

Reactive oxygen species in psoriasis and psoriasis arthritis: relevance to human disease

Psoriasis (Ps) is a chronic, immune-mediated, skin inflammatory disease affecting up to 3% of the population worldwide. Different environmental triggers initiate this complex multifactorial syndrome. Many individuals affected by Ps (6-26%) develop inflammatory disease in other organs, often in the joints as in psoriasis arthritis (PsA). Animal models that reflect the typical Ps syndrome, including both skin and joint pathology as in Ps and PsA, are valuable tools for dissecting disease pathways leading to clinical manifestations. In this context, we developed a new acute Ps and PsA-like disease model that appears after exposure to Saccharomyces cerevisiae mannan in certain mouse strains. The disease was found to be triggered by mannan-activated macrophages, leading to the activation of a pathogenic interleukin-17 pathway involving innate lymphocytes. Interestingly, the production of reactive oxygen species protected the mice from the triggering of this pathway and ameliorated Ps and PsA development.

Nox2 knockout delays infarct progression and increases vascular recovery through angiogenesis in mice following ischaemic stroke with reperfusion

Evidence suggests the NADPH oxidases contribute to ischaemic stroke injury and Nox2 is the most widely studied subtype in the context of stroke. There is still conjecture however regarding the benefits of inhibiting Nox2 to improve stroke outcome. The current study aimed to examine the temporal effects of genetic Nox2 deletion on neuronal loss after ischaemic stroke using knockout (KO) mice with 6, 24 and 72 hour recovery. Transient cerebral ischaemia was induced via intraluminal filament occlusion and resulted in reduced infarct volumes in Nox2 KO mice at 24 h post-stroke compared to wild-type controls. No protection was evident at either 6 h or 72 h post-stroke, with both genotypes exhibiting similar volumes of damage. Reactive oxygen species were detected using dihydroethidium and were co-localised with neurons and microglia in both genotypes using immunofluorescent double-labelling. The effect of Nox2 deletion on vascular damage and recovery was also examined 24 h and 72 h post-stroke using an antibody against laminin. Blood vessel density was decreased in the ischaemic core of both genotypes 24 h post-stroke and returned to pre-stroke levels only in Nox2 KO mice by 72 h. Overall, these results are the first to show that genetic Nox2 deletion merely delays the progression of neuronal loss after stroke but does not prevent it. Additionally, we show for the first time that Nox2 deletion increases re-vascularisation of the damaged brain by 72 h, which may be important in promoting endogenous brain repair mechanisms that rely on re-vascularisation.