Elucidation of 7,8-dihydroxy flavone in complexing with the oxidative stress-inducing enzymes, its impact on radical quenching and DNA damage: an in silico and in vitro approach

Oxidative stress (OS) has been attributed to the progression of various disorders, including cancer, diabetes, and cardiovascular diseases. Several antioxidant compounds and free radical quenchers have been shown to mitigate oxidative stress. However, large-scale randomized controlled trials of such compounds on chronic disease aversion have yielded paradoxical and disappointing results due to the constrained cognizance of their oxidative mechanisms and therapeutic targets. The current study sought to identify the potential therapeutic targets of 7,8-Dihydroxyflavone (7,8-DHF) by analyzing its interactions with the enzymes implicated in oxidative stress and also to explore its radicle quenching potential and prophylactic impact on the H2O2-induced DNA damage. Through the in silco approach, we investigated the antioxidant potential of 7,8-DHF by evaluating its interactions with the human oxidative stress-inducing enzymes such as myeloperoxidase (MPO), NADPH oxidase (NOX), nitric oxide synthase (NOS), and xanthine oxidase (XO) and a comparative analysis of those interactions with known antioxidants (Ascorbic acid, Melatonin, Tocopherol) used as controls. The best-scoring complex was adopted for the simulation analysis in investigating protein-ligand conformational dynamics. The in vitro radicle quenching potential was evaluated by performing a spectrum of antioxidant assays, and radical quenching was observed in a dose-dependent fashion with IC50 values of < 60 µM/mL. Further, we probed its anti-hemolytic potential and prophylactic impact in avian erythrocytes subjected to H2O2-induced hemolysis and DNA damage by implementing hemolysis and comet assays. The protective effect was more pronounced at higher concentrations of the drug.Communicated by Ramaswamy H. Sarma.

Hypochlorous acid derived from microglial myeloperoxidase could mediate high-mobility group box 1 release from neurons to amplify brain damage in cerebral ischemia-reperfusion injury

Myeloperoxidase (MPO) plays critical role in the pathology of cerebral ischemia-reperfusion (I/R) injury via producing hypochlorous acid (HOCl) and inducing oxidative modification of proteins. High-mobility group box 1 (HMGB1) oxidation, particularly disulfide HMGB1 formation, facilitates the secretion and release of HMGB1 and activates neuroinflammation, aggravating cerebral I/R injury. However, the cellular sources of MPO/HOCl in ischemic brain injury are unclear yet. Whether HOCl could promote HMGB1 secretion and release remains unknown. In the present study, we investigated the roles of microglia-derived MPO/HOCl in mediating HMGB1 translocation and secretion, and aggravating the brain damage and blood-brain barrier (BBB) disruption in cerebral I/R injury. In vitro, under the co-culture conditions with microglia BV cells but not the single culture conditions, oxygen-glucose deprivation/reoxygenation (OGD/R) significantly increased MPO/HOCl expression in PC12 cells. After the cells were exposed to OGD/R, MPO-containing exosomes derived from BV2 cells were released and transferred to PC12 cells, increasing MPO/HOCl in the PC12 cells. The HOCl promoted disulfide HMGB1 translocation and secretion and aggravated OGD/R-induced apoptosis. In vivo, SD rats were subjected to 2 h of middle cerebral artery occlusion (MCAO) plus different periods of reperfusion. Increased MPO/HOCl production was observed at the reperfusion stage, accomplished with enlarged infarct volume, aggravated BBB disruption and neurological dysfunctions. Treatment of MPO inhibitor 4-aminobenzoic acid hydrazide (4-ABAH) and HOCl scavenger taurine reversed those changes. HOCl was colocalized with cytoplasm transferred HMGB1, which was blocked by taurine in rat I/R-injured brain. We finally performed a clinical investigation and found that plasma HOCl concentration was positively correlated with infarct volume and neurological deficit scores in ischemic stroke patients. Taken together, we conclude that ischemia/hypoxia could activate microglia to release MPO-containing exosomes that transfer MPO to adjacent cells for HOCl production; Subsequently, the production of HOCl could mediate the translocation and secretion of disulfide HMGB1 that aggravates cerebral I/R injury. Furthermore, plasma HOCl level could be a novel biomarker for indexing brain damage in ischemic stroke patients.

Sterile inflammation induces vasculopathy and chronic lung injury in murine sickle cell disease

Murine sickle cell disease (SCD) results in damage to multiple organs, likely mediated first by vasculopathy. While the mechanisms inducing vascular damage remain to be determined, nitric oxide bioavailability and sterile inflammation are both considered to play major roles in vasculopathy. Here, we investigate the effects of high mobility group box-1 (HMGB1), a pro-inflammatory damage-associated molecular pattern (DAMP) molecule on endothelial-dependent vasodilation and lung morphometrics, a structural index of damage in sickle (SS) mice. SS mice were treated with either phosphate-buffered saline (PBS), hE-HMGB1-BP, an hE dual-domain peptide that binds and removes HMGB1 from the circulation via the liver, 1-[4-(aminocarbonyl)-2-methylphenyl]-5-[4-(1H-imidazol-1-yl)phenyl]-1H-pyrrole-2-propanoic acid (N6022) or N-acetyl-lysyltyrosylcysteine amide (KYC) for three weeks. Human umbilical vein endothelial cells (HUVEC) were treated with recombinant HMGB1 (r-HMGB1), which increases S-nitrosoglutathione reductase (GSNOR) expression by ∼80%, demonstrating a direct effect of HMGB1 to increase GSNOR. Treatment of SS mice with hE-HMGB1-BP reduced plasma HMGB1 in SS mice to control levels and reduced GSNOR expression in facialis arteries isolated from SS mice by ∼20%. These changes were associated with improved endothelial-dependent vasodilation. Treatment of SS mice with N6022 also improved vasodilation in SS mice suggesting that targeting GSNOR also improves vasodilation. SCD decreased protein nitrosothiols (SNOs) and radial alveolar counts (RAC) and increased GSNOR expression and mean linear intercepts (MLI) in lungs from SS mice. The marked changes in pulmonary morphometrics and GSNOR expression throughout the lung parenchyma in SS mice were improved by treating with either hE-HMGB1-BP or KYC. These data demonstrate that murine SCD induces vasculopathy and chronic lung disease by an HMGB1- and GSNOR-dependent mechanism and suggest that HMGB1 and GSNOR might be effective therapeutic targets for reducing vasculopathy and chronic lung disease in humans with SCD.

Gene expression analysis of oxidative stress-related genes in the apical, middle, and basal turns of the cochlea

It can be observed from aminoglycoside-induced hair cell damage that the cochlea basal turn is more susceptible to trauma than the apex. Drug-induced hearing loss is closely related to oxidative damage. The basilar membrane directly exposed to these ototoxic drugs exhibits differences in damage, indicating that there is an inherent difference in the sensitivity to oxidative damage from the apex to the base of the cochlea. It has been reported that the morphology and characteristics of the cochlea vary from the apex to the base. Therefore, we investigated oxidative stress-related gene expression profiles in the apical, middle, and basal turns of the cochlea. The Oxidative Stress RT2 Profiler™ PCR Array revealed that three of the 84 genes (Mb, Mpo, and Ncf1) were upregulated in the middle turn compared to their level in the apical turn. Moreover, eight genes (Mb, Duox1, Ncf1, Ngb, Fmo2, Gpx3, Mpo, and Gstk1) were upregulated in the basal turn compared to their level in the apical turn. The qPCR verification data were similar to that of the PCR Array. We found that MPO was expressed in the rat cochlea and protected against gentamicin-induced hair cell death. This study summarized the data for the gradient of expression of oxidative stress-related genes in the cochlea and found potential candidate targets for prevention of ototoxic deafness, which may provide new insights for cochlear pathology.

The Roles of Neutrophil-Derived Myeloperoxidase (MPO) in Diseases: The New Progress

Myeloperoxidase (MPO) is a heme-containing peroxidase, mainly expressed in neutrophils and, to a lesser extent, in monocytes. MPO is known to have a broad bactericidal ability via catalyzing the reaction of Cl- with H2O2 to produce a strong oxidant, hypochlorous acid (HOCl). However, the overproduction of MPO-derived oxidants has drawn attention to its detrimental role, especially in diseases characterized by acute or chronic inflammation. Broadly speaking, MPO and its derived oxidants are involved in the pathological processes of diseases mainly through the oxidation of biomolecules, which promotes inflammation and oxidative stress. Meanwhile, some researchers found that MPO deficiency or using MPO inhibitors could attenuate inflammation and tissue injuries. Taken together, MPO might be a promising target for both prognostic and therapeutic interventions. Therefore, understanding the role of MPO in the progress of various diseases is of great value. This review provides a comprehensive analysis of the diverse roles of MPO in the progression of several diseases, including cardiovascular diseases (CVDs), neurodegenerative diseases, cancers, renal diseases, and lung diseases (including COVID-19). This information serves as a valuable reference for subsequent mechanistic research and drug development.

Neuroinflammatory Biomarkers in the Brain, Cerebrospinal Fluid, and Blood After Ischemic Stroke

The most frequent type of stroke, known as ischemic stroke (IS), is a significant global public health issue. The pathological process of IS and post-IS episodes has not yet been fully explored, but neuroinflammation has been identified as one of the key processes. Biomarkers are objective indicators used to assess normal or pathological processes, evaluate responses to treatment, and predict outcomes, and some biomarkers can also be used as therapeutic targets. After IS, various molecules are produced by different cell types, such as microglia, astrocytes, infiltrating leukocytes, endothelial cells, and damaged neurons, that participate in the neuroinflammatory response within the ischemic brain region. These molecules may either promote or inhibit neuroinflammation and may be released into extracellular spaces, including cerebrospinal fluid (CSF) and blood, due to reasons such as BBB damage. These neuroinflammatory molecules should be valued as biomarkers to monitor whether their expression levels in the blood, CSF, and brain correlate with the diagnosis and prognosis of IS patients or whether they have potential as therapeutic targets. In addition, although some molecules do not directly participate in the process of neuroinflammation, they have been reported to have potential diagnostic or therapeutic value against post-IS neuroinflammation, and these molecules will also be listed. In this review, we summarize the neuroinflammatory biomarkers in the brain, CSF, and blood after an IS episode and the potential value of these biomarkers for the diagnosis, treatment, and prognosis of IS patients.

Folic acid protects against age-associated apoptosis and telomere attrition of neural stem cells in senescence-accelerated mouse prone 8

Folic acid (FA) could improve cognitive performance and attenuate brain cell injury in the aging brain; FA supplementation is also associated with inhibiting neural stem cell (NSC) apoptosis. However, its role in age-associated telomere attrition remains unclear. We hypothesized that FA supplementation attenuates age-associated apoptosis of NSCs in mice via alleviating telomere attrition in senescence-accelerated mouse prone 8 (SAMP8). In this study, 4-month-old male SAMP8 mice were assigned equal numbers to four different diet groups (n = 15). Fifteen age-matched senescence-accelerated mouse resistant 1 mice, fed with the FA-normal diet, were used as the standard aging control group. After FA treatment for 6 months, all mice were sacrificed. NSC apoptosis, proliferation, oxidative damage, and telomere length were evaluated by immunofluorescence and Q-fluorescent in situ hybridization. The results showed that FA supplementation inhibited age-associated NSC apoptosis and prevented telomere attrition in the cerebral cortex of SAMP8 mice. Importantly, this effect might be explained by the decreased levels of oxidative damage. In conclusion, we demonstrate it may be one of the mechanisms by which FA inhibits age-associated NSC apoptosis by alleviating telomere length shortening.

Sirtuins and redox signaling interplay in neurogenesis, neurodegenerative diseases, and neural cell reprogramming

Since the discovery of Neural Stem Cells (NSCs) there are still mechanism to be clarified, such as the role of mitochondrial metabolism in the regulation of endogenous adult neurogenesis and its implication in neurodegeneration. Although stem cells require glycolysis to maintain their stemness, they can perform oxidative phosphorylation and it is becoming more and more evident that mitochondria are central players, not only for ATP production but also for neuronal differentiation's steps regulation, through their ability to handle cellular redox state, intracellular signaling, epigenetic state of the cell, as well as the gut microbiota-brain axis, upon dietary influences. In this scenario, the 8-oxoguanine DNA glycosylase (OGG1) repair system would link mitochondrial DNA integrity to the modulation of neural differentiation. On the other side, there is an increasing interest in NSCs generation, from induced pluripotent stem cells, as a clinical model for neurodegenerative diseases (NDs), although this methodology still presents several drawbacks, mainly related to the reprogramming process. Indeed, high levels of reactive oxygen species (ROS), associated with telomere shortening, genomic instability, and defective mitochondrial dynamics, lead to pluripotency limitation and reprogramming efficiency's reduction. Moreover, while a physiological or moderate ROS increase serves as a signaling mechanism, to activate differentiation and suppress self-renewal, excessive oxidative stress is a common feature of NDs and aging. This ROS-dependent regulatory effect might be modulated by newly identified ROS suppressors, including the NAD⁺-dependent deacetylase enzymes family called Sirtuins (SIRTs). Recently, the importance of subcellular localization of NAD synthesis has been coupled to different roles for NAD in chromatin stability, DNA repair, circadian rhythms, and longevity. SIRTs have been described as involved in the control of both telomere's chromatin state and expression of nuclear gene involved in the regulation of mitochondrial gene expression, as well as in several NDs and aging. SIRTs are ubiquitously expressed in the mammalian brain, where they play important roles. In this review we summarize the current knowledge on how SIRTs-dependent modulation of mitochondrial metabolism could impact on neurogenesis and neurodegeneration, focusing mainly on ROS function and their role in SIRTs-mediated cell reprogramming and telomere protection.

Neutrophil Extracellular Traps in Cerebral Ischemia/Reperfusion Injury: Friend and Foe

Cerebral ischemic injury, one of the leading causes of morbidity and mortality worldwide, triggers various central nervous system (CNS) diseases, including acute ischemic stroke (AIS) and chronic ischemia-induced Alzheimer's disease (AD). Currently, targeted therapies are urgently needed to address neurological disorders caused by cerebral ischemia/reperfusion injury (CI/RI), and the emergence of neutrophil extracellular traps (NETs) may be able to relieve the pressure. Neutrophils are precursors to brain injury following ischemic stroke and exert complicated functions. NETs extracellularly release reticular complexes of neutrophils, i.e., double-stranded DNA (dsDNA), histones, and granulins. Paradoxically, NETs play a dual role, friend and foe, under different conditions, for example, physiological circumstances, infection, neurodegeneration, and ischemia/reperfusion. Increasing evidence indicates that NETs exert anti-inflammatory effects by degrading cytokines and chemokines through protease at a relatively stable and moderate level under physiological conditions, while excessive amounts of NETs release (NETosis) irritated by CI/RI exacerbate the inflammatory response and aggravate thrombosis, disrupt the blood-brain barrier (BBB), and initiates sequential neuron injury and tissue damage. This review provides a comprehensive overview of the machinery of NETs formation and the role of an abnormal cascade of NETs in CI/RI, as well as other ischemia-induced neurological diseases. Herein, we highlight the potential of NETs as a therapeutic target against ischemic stroke that may inspire translational research and innovative clinical approaches.

Non-Canonical Functions of Myeloperoxidase in Immune Regulation, Tissue Inflammation and Cancer

Myeloperoxidase (MPO) is one of the most abundantly expressed proteins in neutrophils. It serves as a critical component of the antimicrobial defense system, facilitating microbial killing via generation of reactive oxygen species (ROS). Interestingly, emerging evidence indicates that in addition to the well-recognized canonical antimicrobial function of MPO, it can directly or indirectly impact immune cells and tissue responses in homeostatic and disease states. Here, we highlight the emerging non-canonical functions of MPO, including its impact on neutrophil longevity, activation and trafficking in inflammation, its interactions with other immune cells, and how these interactions shape disease outcomes. We further discuss MPO interactions with barrier forming endothelial and epithelial cells, specialized cells of the central nervous system (CNS) and its involvement in cancer progression. Such diverse function and the MPO association with numerous inflammatory disorders make it an attractive target for therapies aimed at resolving inflammation and limiting inflammation-associated tissue damage. However, while considering MPO inhibition as a potential therapy, one must account for the diverse impact of MPO activity on various cellular compartments both in health and disease.

The role of neutrophils in the dysfunction of central nervous system barriers

Leukocyte migration into the central nervous system (CNS) represents a central process in the development of neurological diseases with a detrimental inflammatory component. Infiltrating neutrophils have been detected inside the brain of patients with several neuroinflammatory disorders, including stroke, multiple sclerosis and Alzheimer’s disease. During inflammatory responses, these highly reactive innate immune cells can rapidly extravasate and release a plethora of pro-inflammatory and cytotoxic factors, potentially inducing significant collateral tissue damage. Indeed, several studies have shown that neutrophils promote blood-brain barrier damage and increased vascular permeability during neuroinflammatory diseases. Recent studies have shown that neutrophils migrate into the meninges and choroid plexus, suggesting these cells can also damage the blood-cerebrospinal fluid barrier (BCSFB). In this review, we discuss the emerging role of neutrophils in the dysfunction of brain barriers across different neuroinflammatory conditions and describe the molecular basis and cellular interplays involved in neutrophil-mediated injury of the CNS borders.

Fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid: a comparative study

MPO-derived oxidants including HOCl contribute to tissue damage and the initiation and propagation of inflammatory diseases. The search for small molecule inhibitors of myeloperoxidase, as molecular tools and potential drugs, requires the application of high throughput screening assays based on monitoring the activity of myeloperoxidase. In this study, we have compared three classes of fluorescent probes for monitoring myeloperoxidase-derived hypochlorous acid, including boronate-, aminophenyl- and thiol-based fluorogenic probes and we show that all three classes of probes are suitable for this purpose. However, probes based on the coumarin fluorophore turned out to be not reliable indicators of the inhibitors’ potency. We have also determined the rate constants of the reaction between HOCl and the probes and they are equal to 1.8 × 10⁴ M⁻¹s⁻¹ for coumarin boronic acid (CBA), 1.1 × 10⁴ M⁻¹s⁻¹ for fluorescein based boronic acid (FLBA), 3.1 × 10⁴ M⁻¹s⁻¹ for 7-(p-aminophenyl)-coumarin (APC), 1.6 × 10⁴ M⁻¹s⁻¹ for 3’-(p-aminophenyl)-fluorescein (APF), and 1 × 10⁷ M⁻¹s⁻¹ for 4-thiomorpholino-7-nitrobenz-2-oxa-1,3-diazole (NBD-TM). The high reaction rate constant of NBD-TM with HOCl makes this probe the most reliable tool to monitor HOCl formation in the presence of compounds showing HOCl-scavenging activity.

Neuroprotective effects of catechin and quercetin in experimental Parkinsonism through modulation of dopamine metabolism and expression of IL-1β, TNF-α, NF-κB, IκKB, and p53 genes in male Wistar rats

The neurobehavioral, brain redox-stabilizing and neurochemical modulatory properties of catechin and quercetin in rotenone-induced Parkinsonism, and the involvement of NF-κB-mediated inflammation, were investigated. Male Wistar rats subcutaneously administered with multiple doses of 1.5mg/kg rotenone were post-treated with 5-20mg/kg catechin or quercetin. This was followed by neurobehavioral evaluation, biochemical estimations, and assessment of neurotransmitter metabolism in the striatum. Expression of genes involved in the canonical pathway for the activation of NF-κB mediated inflammation (IL-1β, TNF-α, NF-κB, and IκKB) and the pro-apoptotic gene, p53, in the striatum was determined by RT-qPCR. Catechin and quercetin mitigated neurobehavioral deficits caused by rotenone. Both flavonoids attenuated striatal redox stress and neurochemical dysfunction, optimized disturbed dopamine metabolism, and improved depletion of neuron density caused by rotenone toxicity. While administration of catechin produced a more pronounced attenuating effect on IL-1β, TNF-α, and p53 genes, the attenuating effect of quercetin (20mg/kg) was more pronounced on NF-κB and IκKB gene expressions when compared to the group administered with rotenone only. Comparatively, quercetin demonstrated superior protection against rotenone neurotoxicity. It is concluded that catechin and quercetin have potential relevance in Parkinson's disease therapy through amelioration of redox stress, optimization of dopamine metabolism, and modulation of anti-inflammatory and anti-apoptotic pathways.

Myeloperoxidase: a new target for the treatment of stroke?

Myeloperoxidase is an important inflammatory factor in the myeloid system, primarily expressed in neutrophils and microglia. Myeloperoxidase and its active products participate in the occurrence and development of hemorrhagic and ischemic stroke, including damage to the blood-brain barrier and brain. As a specific inflammatory marker, myeloperoxidase can be used in the evaluation of vascular disease occurrence and development in stroke, and a large amount of experimental and clinical data has indicated that the inhibition or lack of myeloperoxidase has positive impacts on stroke prognosis. Many studies have also shown that there is a correlation between the overexpression of myeloperoxidase and the risk of stroke. The occurrence of stroke not only refers to the first occurrence but also includes recurrence. Therefore, myeloperoxidase is significant for the clinical evaluation and prognosis of stroke. This paper reviews the potential role played by myeloperoxidase in the development of vascular injury and secondary brain injury after stroke and explores the effects of inhibiting myeloperoxidase on stroke prognosis. This paper also analyzes the significance of myeloperoxidase etiology in the occurrence and development of stroke and discusses whether myeloperoxidase can be used as a target for the treatment and prediction of stroke.

Microglia and Macrophages in Neuroprotection, Neurogenesis, and Emerging Therapies for Stroke

Stroke remains the number one cause of morbidity in the United States. Within weeks to months after an ischemic event, there is a resolution of inflammation and evidence of neurogenesis; however, years following a stroke, there is evidence of chronic inflammation in the central nervous system, possibly by the persistence of an autoimmune response to brain antigens as a result of ischemia. The mechanisms underlying the involvement of macrophage and microglial activation after stroke are widely acknowledged as having a role in ischemic stroke pathology; thus, modulating inflammation and neurological recovery is a hopeful strategy for treating the long-term outcomes after ischemic injury. Current treatments fail to provide neuroprotective or neurorestorative benefits after stroke; therefore, to ameliorate brain injury-induced deficits, therapies must alter both the initial response to injury and the subsequent inflammatory process. This review will address differences in macrophage and microglia nomenclature and summarize recent work in elucidating the mechanisms of macrophage and microglial participation in antigen presentation, neuroprotection, angiogenesis, neurogenesis, synaptic remodeling, and immune modulating strategies for treating the long-term outcomes after ischemic injury.

Neuropathy - Exponent of Accelerated Involution in Uremia: The Role of Carbamylation

Premature loss of functional integrity of the nervous system in chronic renal failure (CRF) as a consequence of persistent biological activities of the general uremic milieu is almost identical to its structural and functional involution during the process of physiological ageing, but disproportionate and independent of chronological age. In the hyperuremic status of CRF (urea - carbamide), forced carbamylation, as a non-enzymatic post-translational modification (NEPTM) of proteins and amino acids, by changing their biological properties and decreasing proteolysis capacity, represents pathogenetic potential of intensified molecular ageing and accelerated, pathological involution. Physiological predisposition and the exposure of neuropathy before complications of other organs and organ systems in CRF, due to the simultaneous and mutually pathogenetically related uremic lesion and the tissue and vascular segment of the nervous system, direct interest towards proteomic analytical techniques of quantification of carbamylated products as biomarkers of uremic neurotoxicity. Hypothetically, identical to the already established applications of other NEPTM products in practice, they have the potential of clinical methodology in the evaluation of uremic neuropathy and its contribution to the general prediction, but also to the change of the conventional CRF classification. In addition, the identification and therapeutic control of the substrate of accelerated involution, responsible for the amplification of not only neurological but also general degenerative processes in CRF, is attractive in the context of the well-known attitude towards aging.

Neutrophil Enzyme Myeloperoxidase Modulates Neuronal Response in a Model of Subarachnoid Hemorrhage by Venous Injury

[Figure: see text].

Taohong Siwu Decoction Regulates Cell Necrosis and Neuroinflammation in the Rat Middle Cerebral Artery Occlusion Model

Cell necrosis and neuroinflammation play an important role in brain injury induced by ischemic stroke. Previous studies reported that Taohong Siwu decoction (THSWD)can reduce heart muscle cell necrosis and has anti-inflammatory properties. In this study, we investigated the effects of THSWD on cell necrosis and neuroinflammation in a rat model of middle cerebral artery occlusion (MCAO). Thirty-six male Sprague-Dawley (SD) rats were randomly divided into three groups with 12 rats in each group. They were the sham operation group, MCAO model group, and MCAO + THSWD group. We used ELISA to determine the levels of TNF-α, Mcp-1, and IL-1β inflammatory factors in rat serum, qRT-PCR to detect the expression of TNF-α, Mcp-1 and IL-1β mRNA in rat brain, and immunohistochemistry to detect the number of microglia and neutrophils in rat brain. qRT-PCR and Western blot were used to detect the mRNA and protein expression levels of IBA-1 and MPO inflammatory factors and the TNF-α/RIP1/RIP3/MLKL pathway in the rat brain and protein expression levels. Compared with the sham operation group, the expression of MCP-1, IL-1β, IBA-1, and MPO inflammatory factors and the TNF-α/RIP1/RIP3/MLKL pathway were significantly upregulated in the MCAO group. Compared with the MCAO group, the expressions of MCP-1, IL-1β, IBA-1, and MPO inflammatory factors and the TNF-α/RIP1/RIP3/MLKL pathway were significantly downregulated in the MCAO + THSWD group. THSWD can reduce the expression levels of MCP-1, IL-1β, IBA-1, and MPO inflammatory factors as well as the TNF-α/RIP1/RIP3/MLKL pathway. Meanwhile, it can reduce the necrosis and inflammation of brain cells after cerebral ischemia, so as to protect the brain tissue of rats.

Neuroprotective effect of 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline mediated via regulation of antioxidant system and inhibition of inflammation and apoptosis in a rat model of cerebral ischemia/reperfusion

The aim of the study was the assessment of the neuroprotective potential of 6-hydroxy-2,2,4-trimethyl-1,2-dihydroquinoline (DHQ) and its effect on inflammation, apoptosis, and transcriptional regulation of the antioxidant system in cerebral ischemia/reperfusion (CIR) in rats. The CIR rat model was constructed using the bilateral common carotid artery occlusion followed by reoxygenation. DHQ was administered at a dose of 50 mg/kg for three days. Histological staining was performed using hematoxylin and eosin. The level of S100B protein, 8-hydroxy-2-deoxyguanosine, and 8-isoprostane was assessed using an enzyme immunoassay. The intensity of apoptosis was assessed based on the activity of caspases and DNA fragmentation. The activity of enzymes was measured spectrophotometrically, the level of gene transcripts was assessed by real-time PCR. DHQ reduced the histopathological changes and normalized levels of S100B, lactate, pyruvate, and HIF-1 mRNA in the CIR rat model. In addition, DHQ decreased the oxidative stress markers in animals with a pathology. The tested compound also inhibited inflammation by decreasing the activity of myeloperoxidase, expression of interleukins and Nfkb2. DHQ-treated rats with CIR showed decreased caspase activity, DNA fragmentation, and AIF expression. DHQ changed activity of antioxidant enzymes to the control values, decreased the expression of Cat, Gsr, and Nfe2l2, which was overexpressed in CIR, and activated the expression of Sod1, Gpx1, Gsta2, and Foxo1. DHQ showed a neuroprotective effect on CIR in rats. The neuroprotective effect involve mechanisms such as the inhibition of oxidative stress, leading to a reduction in the inflammatory response and apoptosis and the modulation of the antioxidant defense components.

N-acetyl-lysyltyrosylcysteine amide, a novel systems pharmacology agent, reduces bronchopulmonary dysplasia in hyperoxic neonatal rat pups

Bronchopulmonary dysplasia (BPD) is caused primarily by oxidative stress and inflammation. To induce BPD, neonatal rat pups were raised in hyperoxic (>90% O₂) environments from day one (P1) until day ten (P10) and treated with N-acetyl-lysyltyrosylcysteine amide (KYC). In vivo studies showed that KYC improved lung complexity, reduced myeloperoxidase (MPO) positive (+) myeloid cell counts, MPO protein, chlorotyrosine formation, increased endothelial cell CD31 expression, decreased 8-OH-dG and Cox-1/Cox-2, HMGB1, RAGE, TLR4, increased weight gain and improved survival in hyperoxic pups. EPR studies confirmed that MPO reaction mixtures oxidized KYC to a KYC thiyl radical. Adding recombinant HMGB1 to the MPO reaction mixture containing KYC resulted in KYC thiylation of HMGB1. In rat lung microvascular endothelial cell (RLMVEC) cultures, KYC thiylation of RLMVEC proteins was increased the most in RLMVEC cultures treated with MPO + H₂O₂, followed by H₂O₂, and then KYC alone. KYC treatment of hyperoxic pups decreased total HMGB1 in lung lysates, increased KYC thiylation of HMGB1, terminal HMGB1 thiol oxidation, decreased HMGB1 association with TLR4 and RAGE, and shifted HMGB1 in lung lysates from a non-acetylated to a lysyl-acetylated isoform, suggesting that KYC reduced lung cell death and that recruited immune cells had become the primary source of HMGB1 released into the hyperoxic lungs. MPO-dependent and independent KYC-thiylation of Keap1 were both increased in RLMVEC cultures. Treating hyperoxic pups with KYC increased KYC thiylation and S-glutathionylation of Keap1, and Nrf2 activation. These data suggest that KYC is a novel system pharmacological agent that exploits MPO to inhibit toxic oxidant production and is oxidized into a thiyl radical that inactivates HMGB1, activates Nrf2, and increases antioxidant enzyme expression to improve lung complexity and reduce BPD in hyperoxic rat pups.

Artesunate Provides Neuroprotection against Cerebral Ischemia-Reperfusion Injury via the TLR-4/NF-κB Pathway in Rats

Inflammation has an important role in ischemia-reperfusion (I/R) injury. Artesunate (ART) has anti-microbial and anti-inflammatory pharmacological activities, and it is used for various types of serious malaria, including cerebral malaria. ART maintains a high concentration in the brain but little is known about the neuroprotective effect of ART against brain I/R injury. We studied the neuroprotection of ART against brain I/R injury and its underlying mechanism. In this study, rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h. After 24 h of reperfusion, neurological deficits, cerebrum water content, infarct volume, hematoxylin-eosin (H&E)-staining, myeloperoxidase (MPO) activity, and proinflammatory cytokine levels were measured. Administration of 20, 40, 80, and 160 mg/kg ART intraperitoneally (i.p.) 10 min after MCAO significantly decreased brain water content and improved neurological deficits in a dose-dependent manner. An 80 mg/kg dosage was optimal. ART significantly reduced infarct volume, suppressed MPO activity and diminished the expressions of toll-like receptor (TLR)-4, MyD88, nuclear factor-κB (NF-κB), tumor necrosis factor (TNF)-α, and interleukin (IL)-6 in the area of the ischemic cortex. The neuroprotective action of ART against focal cerebral I/R injury might be due to the attenuation of inflammation through the TLR-4/NF-κB pathway.

Allicin alleviated acrylamide-induced NLRP3 inflammasome activation via oxidative stress and endoplasmic reticulum stress in Kupffer cells and SD rats liver

Acrylamide (AA) in heat-processed food leads to widespread concerns due to its hepatotoxicity. Allicin, a plant-derived antioxidant, possesses a significant protective effect on AA-induced hepatotoxicity, but the mechanism is still unclear. Herein, we investigated the mechanism in Kupffer cells and SD rats liver. Molecular docking, molecular dynamics simulation and LigPlus software speculated that allicin inhibited the activity of CYP2E1 expression by binding to its amino acid residues Phe116, Phe207, Leu210, Phe298, Ala299, Thr303, Val364 and Phe478 through hydrophobic interactions. Allicin decreased the reactive oxygen species (ROS) release and CYP2E1 protein expression and then alleviated the appearance of OS. Meanwhile, allicin significantly reduced ERS characteristic proteins GRP78, CHOP and UPR branch IRE1α pathway key proteins p-IRE, p-ASK, TRAF2 and XBP-1s expression. Simultaneously, allicin ameliorated OS and ERS activation, which inhibited the activation of the MAPK and NF-κB pathways, and down-regulated JNK, ERK, p38, p65 and IκBα phosphorylation. Allicin pre-treatment inhibited AA-induced inflammation as evidenced by reducing NLRP3 inflammasome activation, decreasing Cleaved-Caspase-1 expression as well as IL-1β, IL-18, IL-6 and TNF-α secretion. Taken together, our data provide new insights into possible signaling pathways involved in allicin attenuating AA-induced hepatotoxicity in vivo and in vitro.

Oxidative Stress at the Crossroads of Aging, Stroke and Depression

Epidemiologic studies have shown that in the aging society, a person dies from stroke every 3 minutes and 42 seconds, and vast numbers of people experience depression around the globe. The high prevalence and disability rates of stroke and depression introduce enormous challenges to public health. Accumulating evidence reveals that stroke is tightly associated with depression, and both diseases are linked to oxidative stress (OS). This review summarizes the mechanisms of OS and OS-mediated pathological processes, such as inflammation, apoptosis, and the microbial-gut-brain axis in stroke and depression. Pathological changes can lead to neuronal cell death, neurological deficits, and brain injury through DNA damage and the oxidation of lipids and proteins, which exacerbate the development of these two disorders. Additionally, aging accelerates the progression of stroke and depression by overactive OS and reduced antioxidant defenses. This review also discusses the efficacy and safety of several antioxidants and antidepressants in stroke and depression. Herein, we propose a crosstalk between OS, aging, stroke, and depression, and provide potential therapeutic strategies for the treatment of stroke and depression.

Myeloperoxidase: A versatile mediator of endothelial dysfunction and therapeutic target during cardiovascular disease

Myeloperoxidase (MPO) is a prominent mammalian heme peroxidase and a fundamental component of the innate immune response against microbial pathogens. In recent times, MPO has received considerable attention as a key oxidative enzyme capable of impairing the bioactivity of nitric oxide (NO) and promoting endothelial dysfunction; a clinically relevant event that manifests throughout the development of inflammatory cardiovascular disease. Increasing evidence indicates that during cardiovascular disease, MPO is released intravascularly by activated leukocytes resulting in its transport and sequestration within the vascular endothelium. At this site, MPO catalyzes various oxidative reactions that are capable of promoting vascular inflammation and impairing NO bioactivity and endothelial function. In particular, MPO catalyzes the production of the potent oxidant hypochlorous acid (HOCl) and the catalytic consumption of NO via the enzyme's NO oxidase activity. An emerging paradigm is the ability of MPO to also influence endothelial function via non-catalytic, cytokine-like activities. In this review article we discuss the implications of our increasing knowledge of the versatility of MPO's actions as a mediator of cardiovascular disease and endothelial dysfunction for the development of new pharmacological agents capable of effectively combating MPO's pathogenic activities. More specifically, we will (i) discuss the various transport mechanisms by which MPO accumulates into the endothelium of inflamed or diseased arteries, (ii) detail the clinical and basic scientific evidence identifying MPO as a significant cause of endothelial dysfunction and cardiovascular disease, (iii) provide an up-to-date coverage on the different oxidative mechanisms by which MPO can impair endothelial function during cardiovascular disease including an evaluation of the contributions of MPO-catalyzed HOCl production and NO oxidation, and (iv) outline the novel non-enzymatic mechanisms of MPO and their potential contribution to endothelial dysfunction. Finally, we deliver a detailed appraisal of the different pharmacological strategies available for targeting the catalytic and non-catalytic modes-of-action of MPO in order to protect against endothelial dysfunction in cardiovascular disease.

Glia and Neural Stem and Progenitor Cells of the Healthy and Ischemic Brain: The Workplace for the Wnt Signaling Pathway

Wnt signaling plays an important role in the self-renewal, fate-commitment and survival of the neural stem/progenitor cells (NS/PCs) of the adult central nervous system (CNS). Ischemic stroke impairs the proper functioning of the CNS and, therefore, active Wnt signaling may prevent, ameliorate, or even reverse the negative effects of ischemic brain injury. In this review, we provide the current knowledge of Wnt signaling in the adult CNS, its status in diverse cell types, and the Wnt pathway’s impact on the properties of NS/PCs and glial cells in the context of ischemic injury. Finally, we summarize promising strategies that might be considered for stroke therapy, and we outline possible future directions of the field.

Myeloperoxidase: a potential therapeutic target for coronary artery disease

INTRODUCTION

Coronary artery disease (CAD) poses significant morbidity and mortality globally. Despite significant advances in treatment interventions, residual cardiovascular risks remain unchecked. Recent clinical trials have shed light on the potential therapeutic benefits of targeting anti-inflammatory pathways. Myeloperoxidase (MPO) plays an important role in atherosclerotic plaque formation and destabilization of the fibrous cap; both increase the risk of atherosclerotic cardiovascular disease and especially CAD.

AREAS COVERED

This article examines the role of MPO in the pathogenesis of atherosclerotic CAD and the mechanistic data from several key therapeutic drug targets. There have been numerous interesting studies on prototype compounds that directly or indirectly attenuate the enzymatic activities of MPO, and subsequently exhibit atheroprotective effects; these include aminobenzoic acid hydrazide, ferulic acid derivative (INV-315), thiouracil derivatives (PF-1355 and PF-06282999), 2-thioxanthines derivative (AZM198), triazolopyrimidines, acetaminophen, N-acetyl lysyltyrosylcysteine (KYC), flavonoids, and alternative substrates such as thiocyanate and nitroxide radical.

EXPERT OPINION

Future investigations must determine if the cardiovascular benefits of direct systemic inhibition of MPO outweigh the risk of immune dysfunction, which may be less likely to arise with alternative substrates or MPO inhibitors that selectively attenuate atherogenic effects of MPO.

Bioinformatics-Based Study to Investigate Potential Differentially Expressed Genes and miRNAs in Pediatric Sepsis

BACKGROUND Sepsis is an extremely common health issue with a considerable mortality rate in children. Our understanding about the pathogenic mechanisms of sepsis is limited. The aim of this study was to identify the differential expression genes (DEGs) in pediatric sepsis through comprehensive analysis, and to provide specific insights for the clinical sepsis therapies in children. MATERIAL AND METHODS Three pediatric gene expression profiles (GSE25504, GSE26378, GSE26440) were downloaded from the Gene Expression Omnibus (GEO) database. The difference expression genes (DEGs) between pediatric sepsis and normal control group were screened with the GEO2R online tool. The Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses of the DEGs were performed. Cytoscape with CytoHubba were used to identify the hub genes. Finally, NetworkAnalyst was used to construct the targeted microRNAs (miRNAs) of the hub genes. RESULTS Totally, 160 overlapping upward genes and 61 downward genes were identified. In addition, 5 KEGG pathways, including hematopoietic cell lineage, Staphylococcus aureus infection, starch and sucrose metabolism, osteoclast differentiation, and tumor necrosis factor (TNF) signaling pathway, were significantly enriched using a database for labeling, visualization, and synthetic discovery. In combination with the results of the protein-protein interaction (PPI) network and CytoHubba, 9 hub genes including ITGAM, TLR8, IL1ß, MMP9, MPO, FPR2, ELANE, SPI1, and C3AR1 were selected. Combined with DEG-miRNAs visualization, 5 miRNAs, including has-miR-204-5p, has-miR-211-5p, has-miR-590-5p, and has-miR-21-5p, were predicted as possibly the key miRNAs. CONCLUSIONS Our findings will contribute to identification of potential biomarkers and novel strategies for pediatric sepsis treatment.

Targeting Myeloperoxidase (MPO) Mediated Oxidative Stress and Inflammation for Reducing Brain Ischemia Injury: Potential Application of Natural Compounds

Oxidative stress and inflammation are two critical pathological processes of cerebral ischemia-reperfusion injury. Myeloperoxidase (MPO) is a critical inflammatory enzyme and therapeutic target triggering both oxidative stress and neuroinflammation in the pathological process of cerebral ischemia-reperfusion injury. MPO is presented in infiltrated neutrophils, activated microglial cells, neurons, and astrocytes in the ischemic brain. Activation of MPO can catalyze the reaction of chloride and H2O2 to produce HOCl. MPO also mediates oxidative stress by promoting the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), modulating the polarization and inflammation-related signaling pathways in microglia and neutrophils. MPO can be a therapeutic target for attenuating oxidative damage and neuroinflammation in ischemic stroke. Targeting MPO with inhibitors or gene deficiency significantly reduced brain infarction and improved neurological outcomes. This article discusses the important roles of MPO in mediating oxidative stress and neuroinflammation during cerebral ischemia-reperfusion injury and reviews the current understanding of the underlying mechanisms. Furthermore, we summarize the active compounds from medicinal herbs with potential as MPO inhibitors for anti-oxidative stress and anti-inflammation to attenuate cerebral ischemia-reperfusion injury, and as adjunct therapeutic agents for extending the window of thrombolytic treatment. We highlight that targeting MPO could be a promising strategy for alleviating ischemic brain injury, which merits further translational study.

Myeloperoxidase and Septic Conditions Disrupt Sphingolipid Homeostasis in Murine Brain Capillaries In Vivo and Immortalized Human Brain Endothelial Cells In Vitro

During inflammation, activated leukocytes release cytotoxic mediators that compromise blood-brain barrier (BBB) function. Under inflammatory conditions, myeloperoxidase (MPO) is critically involved in inflicting BBB damage. We used genetic and pharmacological approaches to investigate whether MPO induces aberrant lipid homeostasis at the BBB in a murine endotoxemia model. To corroborate findings in a human system we studied the impact of sera from sepsis and non-sepsis patients on brain endothelial cells (hCMEC/D3). In response to endotoxin, the fatty acid, ceramide, and sphingomyelin content of isolated mouse brain capillaries dropped and barrier dysfunction occurred. In mice, genetic deficiency or pharmacological inhibition of MPO abolished these alterations. Studies in metabolic cages revealed increased physical activity and less pronounced sickness behavior of MPO-/- compared to wild-type mice in response to sepsis. In hCMEC/D3 cells, exogenous tumor necrosis factor α (TNFα) potently regulated gene expression of pro-inflammatory cytokines and a set of genes involved in sphingolipid (SL) homeostasis. Notably, treatment of hCMEC/D3 cells with sera from septic patients reduced cellular ceramide concentrations and induced barrier and mitochondrial dysfunction. In summary, our in vivo and in vitro data revealed that inflammatory mediators including MPO, TNFα induce dysfunctional SL homeostasis in brain endothelial cells. Genetic and pharmacological inhibition of MPO attenuated endotoxin-induced alterations in SL homeostasis in vivo, highlighting the potential role of MPO as drug target to treat inflammation-induced brain dysfunction.

Ezetimibe Attenuates Oxidative Stress and Neuroinflammation via the AMPK/Nrf2/TXNIP Pathway after MCAO in Rats

Oxidative stress and neuroinflammation play essential roles in ischemic stroke-induced brain injury. Previous studies have reported that Ezetimibe (Eze) exerts antioxidative stress and anti-inflammatory properties in hepatocytes. In the present study, we investigated the effects of Eze on oxidative stress and neuroinflammation in a rat middle cerebral artery occlusion (MCAO) model. One hundred and ninety-eight male Sprague-Dawley rats were used. Animals assigned to MCAO were given either Eze or its control. To explore the downstream signaling of Eze, the following interventions were given: AMPK inhibitor dorsomorphin and nuclear factor erythroid 2-related factor 2 (Nrf2) siRNA. Intranasal administration of Eze, 1 h post-MCAO, further increased the endogenous p-AMPK expression, reducing brain infarction, neurologic deficits, neutrophil infiltration, microglia/macrophage activation, number of dihydroethidium- (DHE-) positive cells, and malonaldehyde (MDA) levels. Specifically, treatment with Eze increased the expression of p-AMPK, Nrf2, and HO-1; Romo-1, thioredoxin-interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3), Cleaved Caspase-1, and IL-1β were reduced. Dorsomorphin and Nrf2 siRNA reversed the protective effects of Eze. In summary, Eze decreases oxidative stress and subsequent neuroinflammation via activation of the AMPK/Nrf2/TXNIP pathway after MCAO in rats. Therefore, Eze may be a potential therapeutic approach for ischemic stroke patients.

Inhibition of Calcium/Calmodulin-Dependent Protein Kinase IIα Suppresses Oxidative Stress in Cerebral Ischemic Rats Through Targeting Glucose 6-Phosphate Dehydrogenase

Ischemic stroke is a leading cause of mortality and morbidity worldwide, and oxidative stress plays a significant role in the ischemia stage and reperfusion stage. Previous studies have indicated that both calcium/calmodulin-dependent protein kinase II (CaMKII) and glucose 6-phosphate dehydrogenase (G6PD) are involved in the oxidative stress. Thus, the aim of this study was to investigate the roles of CaMKIIα, an important isoform of CaMKII, and G6PD in a rat model of middle cerebral artery occlusion (MCAO). Intracerebroventricular injection of small interfering ribonucleic acid (siRNA) for CaMKIIα was performed at 48 h pre-MCAO surgery. Immunofluorescence Staining and western blot were performed to detect the expression of p-CaMKIIα and G6PD in the cortices. 2, 3, 5-Triphenyltetrazolium chloride (TTC) staining was performed to investigate the infarct volume. In addition, neurological deficit, reactive oxygen species (ROS), ratio of reduced-to-oxidized glutathione (GSH/GSSG) and ratio of reduced-to-oxidized oxidized nicotinamide adenine dinucleotide phosphate (NADPH/NADP⁺) were assessed. The results indicated that both p-CaMKIIα and G6PD were widely located in the neurons and astrocytes, and their expression was gradually increased in the cortices after MCAO, which was accompanied by increased level of ROS and decreased levels of GSH/GSSG and NADPH/NADP⁺. However, after treatment with siRNA for CaMKIIα, p-CaMKIIα expression was decreased and G6PD expression was increased. Moreover, inhibition of CaMKIIα improved the neurological deficit, reduced the infarct volume, decreased the level of ROS and increased the levels of GSH/GSSG and NADPH/NADP⁺. The results suggested that CaMKIIα inhibition exerted neuroprotective effects through regulating G6PD expression, which provides a new target for prevention and treatment of stroke.

The Impact of Uremic Toxins on Cerebrovascular and Cognitive Disorders

Individuals at all stages of chronic kidney disease (CKD) have a higher risk of developing cognitive disorders and dementia. Stroke is also highly prevalent in this population and is associated with a higher risk of neurological deterioration, in-hospital mortality, and poor functional outcomes. Evidence from in vitro studies and in vivo animal experiments suggests that accumulation of uremic toxins may contribute to the pathogenesis of stroke and amplify vascular damage, leading to cognitive disorders and dementia. This review summarizes current evidence on the mechanisms by which uremic toxins may favour the occurrence of cerebrovascular diseases and neurological complications in CKD.