Peroxiredoxin 2 battles poly(ADP-ribose) polymerase 1- and p53-dependent prodeath pathways after ischemic injury

PARP-1 dependent cell death pathway (Parthanatos) mediates early brain injury after subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a neurological condition with high mortality and poor prognosis, and there are currently no effective therapeutic drugs available. Poly (ADP-ribose) polymerase 1 (PARP-1) dependent cell death pathway-parthanatos is closely associated with stroke. We investigated improvements in neurological function, oxidative stress, blood-brain barrier and parthanatos-related protein expression in rats with SAH after intraperitoneal administration of PARP-1 inhibitor (AG14361). Our study found that the expression of parthanatos-related proteins was significantly increased after SAH. Immunofluorescence staining showed increased expression of apoptosis-inducing factor (AIF) in the nucleus after SAH. Administration of PARP-1 inhibitor significantly reduced malondialdehyde (MDA) level and the expression of parthanatos-related proteins. Immunofluorescence staining showed that PARP-1 inhibitor reduced the expression of 8-hydroxy-2' -deoxyguanosine (8-OHdG) and thus reduced oxidative stress. Moreover, PARP-1 inhibitor could inhibit inflammation-associated proteins level and neuronal apoptosis, protect the blood-brain barrier and significantly improve neurological function after SAH. These results suggest that PARP-1 inhibitor can significantly improve SAH, and the underlying mechanism may be through inhibiting parthanatos pathway.

The atypical antidepressant tianeptine confers neuroprotection against oxygen-glucose deprivation

Proregenerative and neuroprotective effects of antidepressants are an important topic of inquiry in neuropsychiatric research. Oxygen-glucose deprivation (OGD) mimics key aspects of ischemic injury in vitro. Here, we studied the effects of 24-h pretreatment with serotonin (5-HT), citalopram (CIT), fluoxetine (FLU), and tianeptine (TIA) on primary mouse cortical neurons subjected to transient OGD. 5-HT (50 μM) significantly enhanced neuron viability as measured by MTT assay and reduced cell death and LDH release. CIT (10 μM) and FLU (1 μM) did not increase the effects of 5-HT and neither antidepressant conferred neuroprotection in the absence of supplemental 5-HT in serum-free cell culture medium. By contrast, pre-treatment with TIA (10 μM) resulted in robust neuroprotection, even in the absence of 5-HT. Furthermore, TIA inhibited mRNA transcription of candidate genes related to cell death and hypoxia and attenuated lipid peroxidation, a hallmark of neuronal injury. Finally, deep RNA sequencing of primary neurons subjected to OGD demonstrated that OGD induces many pathways relating to cell survival, the inflammation-immune response, synaptic dysregulation and apoptosis, and that TIA pretreatment counteracted these effects of OGD. In conclusion, this study highlights the comparative strength of the 5-HT independent neuroprotective effects of TIA and identifies the molecular pathways involved.

Nrf2 Plays a Key Role in Erythropoiesis during Aging

Aging is characterized by increased oxidation and reduced efficiency of cytoprotective mechanisms. Nuclear factor erythroid-2-related factor (Nrf2) is a key transcription factor, controlling the expression of multiple antioxidant proteins. Here, we show that Nrf2-/- mice displayed an age-dependent anemia, due to the combined contributions of reduced red cell lifespan and ineffective erythropoiesis, suggesting a role of Nrf2 in erythroid biology during aging. Mechanistically, we found that the expression of antioxidants during aging is mediated by activation of Nrf2 function by peroxiredoxin-2. The absence of Nrf2 resulted in persistent oxidation and overactivation of adaptive systems such as the unfolded protein response (UPR) system and autophagy in Nrf2-/- mouse erythroblasts. As Nrf2 is involved in the expression of autophagy-related proteins such as autophagy-related protein (Atg) 4-5 and p62, we found impairment of late phase of autophagy in Nrf2-/- mouse erythroblasts. The overactivation of the UPR system and impaired autophagy drove apoptosis of Nrf2-/- mouse erythroblasts via caspase-3 activation. As a proof of concept for the role of oxidation, we treated Nrf2-/- mice with astaxanthin, an antioxidant, in the form of poly (lactic-co-glycolic acid) (PLGA)-loaded nanoparticles (ATS-NPs) to improve its bioavailability. ATS-NPs ameliorated the age-dependent anemia and decreased ineffective erythropoiesis in Nrf2-/- mice. In summary, we propose that Nrf2 plays a key role in limiting age-related oxidation, ensuring erythroid maturation and growth during aging.

Implications and progression of peroxiredoxin 2 (PRDX2) in various human diseases

Peroxiredoxin 2 (PRDX2), a characteristic 2-Cys enzyme is one of the foremost effective scavenger proteins against reactive oxygen species (ROS) and hydrogen peroxide (H2O2) defending cells against oxidative stress. Dysregulation of this antioxidant raises the quantity of ROS and oxidative stress implicated in several diseases. PRDX2 lowers the generation of ROS that takes part in controlling several signalling pathways occurring in neurons, protecting them from stress caused by oxidation and an inflammatory harm. Depending on the aetiological variables, the kind of cancer, and the stage of tumour development, PRDX2 may behave either as an onco-suppressor or a promoter. However, overexpression of PRDX2 may be linked to the development of numerous cancers, including those of the colon, cervix, breast, and prostate. PRDX2 also plays a beneficial effect in inflammatory diseases. PRDX2 being a thiol-specific peroxidase, is known to control proinflammatory reactions. The spilling of PRDX2, on the other hand, accelerates cognitive impairment following a stroke by triggering an inflammatory reflex. PRDX2 expression patterns in vascular cells tend to be crucial to its involvement in cardiovascular diseases. In vascular smooth muscle cells, if the protein tyrosine phosphatase is restricted, PRDX2 could avoid the neointimal thickening which relies on platelet derived growth factor (PDGF), a vital component of vascular remodelling. A proper PRDX2 balance is therefore crucial. The imbalance causes a number of illnesses, including cancers, inflammatory diseases, cardiovascular ailments, and neurological and neurodegenerative problems which are discussed in this review.

Dihydromyricetin confers cerebroprotection against subarachnoid hemorrhage via the Nrf2-dependent Prx2 signaling cascade

BACKGROUND

Several clinical and experimental studies have shown that therapeutic strategies targeting oxidative damage are beneficial for subarachnoid hemorrhage (SAH). A brain-permeable flavonoid, dihydromyricetin (DHM), can modulate redox/oxidative stress and has cerebroprotective effects in several neurological disorders. The effects of DHM on post-SAH early brain injury (EBI) and the underlying mechanism have yet to be clarified.

PURPOSE

This work investigated a potential role for DHM in SAH, together with the underlying mechanisms.

METHODS

Cerebroprotection by DHM was studied using a SAH rat model and primary cortical neurons. Atorvastatin (Ato) was a positive control drug in this investigation. The effects of DHM on behavior after SAH were evaluated by performing the neurological rotarod and Morris water maze tests, as well as by examining its effects on brain morphology and on the molecular and functional phenotypes of primary cortical neurons using dichlorodihydrofluorescein diacetate (DCFH-DA), immunofluorescent staining, biochemical analysis, and Western blot.

RESULTS

DHM was found to significantly reduce the amount of reactive oxygen species (ROS), suppress mitochondrial disruption, and increase intrinsic antioxidant enzymatic activity following SAH. DHM also significantly reduced neuronal apoptosis in SAH rats and improved short- and long-term neurological functions. DHM induced significant increases in peroxiredoxin 2 (Prx2) and nuclear factor erythroid 2-related factor 2 (Nrf2) expression, while decreasing phosphorylation of p38 and apoptotic signal-regulated kinase 1 (ASK1). In contrast, reduction of Prx2 expression using small interfering ribonucleic acid or by inhibiting Nrf2 with ML385 attenuated the neuroprotective effect of DHM against SAH. Moreover, DHM dose-dependently inhibited oxidative damage, decreased neuronal apoptosis, and increased the viability of primary cultured neurons in vitro. These positive effects were associated with Nrf2 activation and stimulation of Prx2 signaling, whereas ML385 attenuated the beneficial effects.

CONCLUSION

These results reveal that DHM protects against SAH primarily by modulating the Prx2 signaling cascade through the Nrf2-dependent pathway. Hence, DHM could be a valuable therapeutic candidate for SAH treatment.

Mechanism of action of Daqinjiao decoction in treating cerebral small vessel disease explored using network pharmacology and molecular docking technology

BACKGROUND AND PURPOSE

Cerebral small vessel disease (CSVD) is a clinically commonly-seen slow-progressing cerebral vascular disease. As a classic Chinese formula for the treatment of stroke, Daqinjiao Decoction (DQJD) is now used to treat CSVD with desirable effect. Since the mechanism of action is still unclear, this article will explore the therapeutic effect and mechanism of action of the formula using network pharmacology technology.

METHODS

The major chemical components and potential target genes of DQJD were screened by bioinformatics. The key targets in CSVD were identified based on network modules. Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were performed. Pharmacodynamics of the decoction was evaluated by establishing a rat model with bilateral common carotid artery occlusion in the brain. Molecular docking, Western blot analysis and quantitative real-time polymerase chain reaction (QRT-PCR) were performed to confirm the effectiveness of targets in related pathways.

RESULTS

Network pharmacology showed that 16 targets and 30 pathways were involved in the DQJD-targeted pathway network. Results revealed that DQJD might play a role by targeting the key targets including Caspse3 and P53 and regulating the P53 signaling pathway. Cognitive function and neuronal cell changes of rats were evaluated using Morris water maze, open field test and HE staining. It was indicated that DQJD could keep the nerve cells intact and neatly arranged. The decoction could improve the memory and learning ability of rats compared with the model group. It decreased the protein and mRNA expression levels of Caspse3 and P53 significantly (p<0.01).

CONCLUSION

The study shows that baicalein, quercetin and wogonin, the effective components of DQJD, may regulate multiple signaling pathways by targeting the targets like Caspse3 and P53 and treat CSVD by reducing the damage to brain nerve cells.

Poly (ADP-ribose) polymerase: An Overview of Mechanistic Approaches and Therapeutic Opportunities in the Management of Stroke

Stroke is one of the leading causes of morbidity and mortality accompanied by blood supply loss to a particular brain area. Several mechanistic approaches such as inhibition of poly (ADP-ribose) polymerase, therapies against tissue thrombosis, and neutrophils lead to stroke's therapeutic intervention. Evidence obtained with the poly (ADP-ribose) polymerase (PARP) inhibition and animals having a deficiency of PARP enzymes; represented the role of PARP in cerebral stroke, ischemia/reperfusion, and neurotrauma. PARP is a nuclear enzyme superfamily with various isoforms, each with different structural domains and functions, and out of all, PARP-1 is the best-characterized member. It has been shown to perform multiple physiological as well as pathological processes, including its role in inflammation, oxidative stress, apoptosis, and mitochondrial dysfunction. The enzyme interacts with NF-κB, p53, and other transcriptional factors to regulate survival and cell death and modulates multiple downstream signaling pathways. Clinical trials have also been conducted using PARP inhibitors for numerous disorders and have shown positive results. However, additional information is yet to be established for the therapeutic intervention of PARP inhibitors in stroke. These agents' utilization appears to be challenging due to their unknown potential long-term side effects. PARP activity increased during ischemia, but its inhibition provided significant neuroprotection. Despite the increased interest in PARP as a pharmacological modulator for novel therapeutic therapies, the current review focused on stroke and poly ADP-ribosylation.

An integrated chemo-informatics and in vitro experimental approach repurposes acarbose as a post-ischemic neuro-protectant

The increasing prevalence of ischemic stroke combined with limited therapeutic options highlights the compelling need for continued research into the development of future neuro-therapeutics. Death-Associated Protein Kinase 1 (DAPK1) and p53 protein-protein interaction serve as a signaling point for the convergence of apoptosis and necrosis in cerebral ischemia. In this study, we used an integrated chemo-informatics and in vitro experimental drug repurposing strategy to screen potential small-molecule inhibitors of DAPK1-p53 interaction from the United States of America Food and Drug Administration (FDA) approved drug database exhibiting post-ischemic neuroprotective and neuro-regenerative efficacy and mechanisms. The computational docking and molecular dynamics simulation of FDA-approved drugs followed by an in vitro experimental validation identified acarbose, an anti-diabetic medication and caloric restriction mimetic as a potential inhibitor of DAPK1-p53 interaction. The evaluation of post-ischemic neuroprotective and regenerative efficacy and mechanisms of action for acarbose was carried out using a set of experimental methods, including cell viability, proliferation and differentiation assays, fluorescence staining, and gene expression analysis. Post-ischemic administration of acarbose conferred significant neuroprotection against ischemia-reperfusion injury in vitro. The reduced fluorescence emission in cells stained with _pS²⁰ supported the potential of acarbose in inhibiting the DAPK1-p53 interaction. Acarbose prevented mitochondrial and lysosomal dysfunction, and favorably modulated gene expression related to cell survival, inflammation, and regeneration. BrdU staining and neurite outgrowth assay showed a significant increase in cell proliferation and differentiation in acarbose-treated group. This is the first study known to provide mechanistic insight into the post-ischemic neuroprotective and neuro-regenerative potential of acarbose. Our results provide a strong basis for preclinical studies to evaluate the safety and neuroprotective efficacy of acarbose against ischemic stroke.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-022-03130-5.

Quantitative proteomic analysis of cervical cancer based on TMT-labeled quantitative proteomics

Cervical cancer is the second most common gynecological malignancy, which immensely threatens the well-being of women. However, the pathogenesis of cervical cancer is still unclear. Using tandem mass tags-labeled quantitative proteomic technology and bioinformatics tools, we analyzed the exfoliated cervical cells from the normal and cervical cancer groups to establish a cancer-specific protein profile, thereby identifying key proteins related to cervical oncogenesis. When compared with the normal group, a total of 351 differentially expressed proteins were identified in the cervical cancer group, including 247 up-regulated and 104 down-regulated proteins. Gene ontology function annotation revealed that the differentially expressed proteins were mainly involved in the single-multicellular organism process, multicellular organismal process, and negative regulation of biological process. These proteins were discerned to play a role in the extracellular membrane-bounded organelle, exosome of cell components, protein binding, structural molecule activity, and enzyme binding of molecular functions. The results of Kyoto Encyclopedia of Genes and Genomes signaling pathway enrichment proved that these differentially expressed proteins were mainly involved in PI3K - Akt, ECM-receptor interaction, complement and coagulation cascades, and other signaling pathways. Particularly, peroxiredoxin-2 may be involved in cervical tumor oncogenesis through inhibition of apoptosis signaling. SIGNIFICANCE: In this study, we determined that the proteins of the cervical cancer group exhibited qualitative and quantitative changes, and a total of 351 differentially expressed proteins were identified. The functions and signaling pathways of these differentially expressed proteins have laid a theoretical foundation for elucidating the molecular mechanism of cervical cancer.

Synthesis, characterization, DFT calculation, antioxidant activity, ADMET and molecular docking of thiosemicarbazide derivatives and their Cu (II) complexes

In this work, new thiosemicarbazides (ECA-1, ECA-2) and their Cu (II) complexes (ECA-1-Cu, ECA-2-Cu) were synthesized and their structures were characterized by ¹H NMR, ¹³C NMR, FT-IR, LC-MS, UV-Vis, and thermogravimetric analysis methods. Also, the surface morphology of the all compounds were examined by SEM (Scanning Electron Microscope). In the second stage, in vitro antioxidant capacity of the obtained compounds was investigated. The evaluation of the antioxidant properties of both synthesized ligands and complexes in this study was carried out by DPPH and FRAP methods. According to the results, both complexes exhibited more antioxidant capacity than the corresponding ligands. When antioxidant effects are compared for DPPH (SC₅₀ = 5.27 ± 0.05 μM) and for FRAP (7845.69 ± 16.75 mmolTE/g), compound ECA-2-Cu appears to have the best inhibition effect. The complexes were found non-electrolytic in nature with melting point of above 250 °C, and electronic spectra and magnetic behavior demonstrated that the complexes were found to be tetrahedral geometry. Further, in silico the ADMET properties which studies are a significant role in improving and predicting drug compounds were calculated using web-based platforms. The theoretical calculations were made using the method of Density Functional Theory (Frontier molecular orbital analyze and Nonlinear optical properties). Also, molecular docking studies were performed to evaluate the binding interactions between the ligand and complex compounds and Human Peroxiredoxin 2. Both in vitro and in silico results indicated that synthesized compounds could act as potent antioxidant agents.

Mechanisms Underlying the Protective Effect of the Peroxiredoxin-6 Are Mediated via the Protection of Astrocytes during Ischemia/Reoxygenation

Ischemia-like conditions reflect almost the entire spectrum of events that occur during cerebral ischemia, including the induction of oxidative stress, Ca²⁺ overload, glutamate excitotoxicity, and activation of necrosis and apoptosis in brain cells. Mechanisms for the protective effects of the antioxidant enzyme peroxiredoxin-6 (Prx-6) on hippocampal cells during oxygen-glucose deprivation/reoxygenation (OGD/R) were investigated. Using the methods of fluorescence microscopy, inhibitory analysis, vitality tests and PCR, it was shown that 24-h incubation of mixed hippocampal cell cultures with Prx-6 does not affect the generation of a reversible phase of a OGD-induced rise in Ca²⁺ ions in cytosol ([Ca²⁺]_i), but inhibits a global increase in [Ca²⁺]_i in astrocytes completely and in neurons by 70%. In addition, after 40 min of OGD, cell necrosis is suppressed, especially in the astrocyte population. This effect is associated with the complex action of Prx-6 on neuroglial networks. As an antioxidant, Prx-6 has a more pronounced and astrocyte-directed effect, compared to the exogenous antioxidant vitamin E (Vit E). Prx-6 inhibits ROS production in mitochondria by increasing the antioxidant capacity of cells and altering the expression of genes encoding redox status proteins. Due to the close bond between [Ca²⁺]_i and intracellular ROS, this effect of Prx-6 is one of its protective mechanisms. Moreover, Prx-6 effectively suppresses not only necrosis, but also apoptosis during OGD and reoxygenation. Incubation with Prx-6 leads to activation of the basic expression of genes encoding protective kinases—PI3K, CaMKII, PKC, anti-apoptotic proteins—Stat3 and Bcl-2, while inhibiting the expression of signaling kinases and factors involved in apoptosis activation—Ikk, Src, NF-κb, Caspase-3, p53, Fas, etc. This effect on the basic expression of the genome leads to the cell preconditions, which is expressed in the inhibition of caspase-3 during OGD/reoxygenation. A significant effect of Prx-6 is directed on suppression of the level of pro-inflammatory cytokine IL-1β and factor TNFα, as well as genes encoding NMDA- and kainate receptor subunits, which was established for the first time for this antioxidant enzyme. The protective effect of Prx-6 is due to its antioxidant properties, since mutant Prx-6 (mutPrx-6, Prx6-C47S) leads to polar opposite effects, contributing to oxidative stress, activation of apoptosis and cell death through receptor action on TLR4.

Manickam D. Targeting the blood-brain barrier for the delivery of stroke therapies

A variety of neuroprotectants have shown promise in treating ischemic stroke, yet their delivery to the brain remains a challenge. The endothelial cells lining the blood-brain barrier (BBB) are emerging as a dynamic factor in the response to neurological injury and disease, and the endothelial-neuronal matrix coupling is fundamentally neuroprotective. In this review, we discuss approaches that target the endothelium for drug delivery both across the BBB and to the BBB as a viable strategy to facilitate neuroprotective effects, using the example of brain-derived neurotrophic factor (BDNF). We highlight the advances in cell-derived extracellular vesicles (EVs) used for CNS targeting and drug delivery. We also discuss the potential of engineered EVs as a potent strategy to deliver BDNF or other drug candidates to the ischemic brain, particularly when coupled with internal components like mitochondria that may increase cellular energetics in injured endothelial cells.

Astaxanthin ameliorates oxidative stress and neuronal apoptosis via SIRT1/NRF2/Prx2/ASK1/p38 after traumatic brain injury in mice

BACKGROUND AND PURPOSE

Oxidative stress and neuronal apoptosis play key roles in traumatic brain injury. We investigated the protective effects of astaxanthin against traumatic brain injury and its underlying mechanisms of action.

EXPERIMENTAL APPROACH

A weight-drop model of traumatic brain injury in vivo and hydrogen peroxide exposure in vitro model were established. Brain oedema, behaviour tests, western blot, biochemical analysis, lesion volume, histopathological study and cell viability were performed.

KEY RESULTS

Astaxanthin significantly reduced oxidative insults on Days 1, 3 and 7 after traumatic brain injury. Neuronal apoptosis was also ameliorated on Day 3. Additionally, astaxanthin improved neurological functions up to 3 weeks after traumatic brain injury. Astaxanthin treatment dramatically enhanced the expression of peroxiredoxin 2 (Prx2), nuclear factor-erythroid 2-related factor 2 (NRF2/Nrf2) and sirtuin 1 (SIRT1), while it down-regulated the phosphorylation of apoptosis signal-regulating kinase 1 (ASK1) and p38. Inhibition of Prx2 by siRNA injection reversed the beneficial effects of astaxanthin against traumatic brain injury. Additionally, Nrf2 knockout prevented the neuroprotective effects of astaxanthin in traumatic brain injury. In contrast, overexpression of Prx2 in Nrf2 knockout mice attenuated the secondary brain injury after traumatic brain injury. Moreover, inhibiting SIRT1 by EX527 dramatically inhibited the neuroprotective effects of astaxanthin and suppressed SIRT1/Nrf2/Prx2/ASK1/p38 pathway both in vivo and in vitro.

CONCLUSION AND IMPLICATIONS

Astaxanthin improved the neurological functions and protected the brain from injury after traumatic brain injury, primarily by reducing oxidative stress and neuronal death via SIRT1/Nrf2/Prx2/ASK1/p38 signalling pathway and might be a new candidate to ameliorate traumatic brain injury.

Enhanced thioredoxin, glutathione and Nrf2 antioxidant systems by safflower extract and aceglutamide attenuate cerebral ischaemia/reperfusion injury

A large number of reactive oxygen species (ROS) aggravate cerebral damage after ischaemia/reperfusion (I/R). Glutathione (GSH), thioredoxin (Trx) and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) represent three major antioxidant systems and play vital roles in affecting each other in eliminating ROS. Identification of drugs targeting triple antioxidant systems simultaneously is vital for inhibiting oxidative damage after cerebral I/R. This study investigated the protective effect of safflower extract and aceglutamide (SAAG) against cerebral I/R injury through modulating multiple antioxidant systems of GSH, Trx and Nrf2 and identified each role of its component acegluatminde (AG) and safflower extract (SA) on these systems. Safflower extract and aceglutamide and its two components decreased neurological deficit scores, infarction rate, apoptosis and oxidative damage after cerebral I/R while enhanced cell viability, decreased reactive oxygen species and nitric oxide level in H₂ O₂ -induced PC12 cell model. Importantly, compared to its two components, SAAG demonstrated more effective enhancement of GSH, Nrf2 and Trx systems and a better protection against cerebral I/R injury. The enhanced antioxidant systems prevented ASK1 activation and suppressed subsequent p38 and JNK cascade-mediated apoptosis. Moreover, inhibition of Trx and Nrf2 systems by auranofin and ML385 abolished SAAG-mediated protection, respectively. Thus, enhanced triple systems by SAAG played a better protective role than those by SA or AG via inhibition of ASK1 cascades. This research provided evidence for the necessity of combination drugs from the perspective of multiple antioxidant systems. Furthermore, it also offers references for the study of combination drugs and inspires novel treatments for ischaemic stroke.

Effects of Peroxiredoxin 2 in Neurological Disorders: A Review of its Molecular Mechanisms

Oxidative stress and neuroinflammation are closely related to the pathological processes of neurological disorders. Peroxiredoxin 2 (Prdx2) is an abundant antioxidant enzyme in the central nervous system. Prdx2 reduces the production of reactive oxygen species and participates in regulating various signaling pathways in neurons by catalyzing hydrogen peroxide (H₂O₂), thereby protecting neurons against oxidative stress and an inflammatory injury. However, the spillage of Prdx2, as damage-associated molecular patterns, accelerates brain damage after stroke by activating an inflammatory response. The post-translational modifications of Prdx2 also affect its enzyme activity. This review focuses on the effects of Prdx2 and its molecular mechanisms in various neurological disorders.

Peroxiredoxin 1/2 protects brain against H2O2-induced apoptosis after subarachnoid hemorrhage

Recent studies suggest that peroxiredoxin1/2 (Prx1/2) may be involved in the pathophysiology of postischemic inflammatory responses in the brain. In this study, we assessed the distribution and function of Prx1/2 in mice after experimental subarachnoid hemorrhage (SAH). We investigated the distribution of Prx1/2 in the brains of mice both in vivo and in vitro using immunofluorescence staining. The expression of Prx1/2 after SAH was determined by Western blot. Adenanthin was used to inhibit Prx1/2 function, and Prx1/2 overexpression was achieved by injecting adeno-associated virus. Oxidative stress and neuronal apoptosis were assessed both in vivo and in vitro. The neurologic function, inflammatory response, and related cellular signals were analyzed. The results showed that Prx1 was mainly expressed in astrocytes, and Prx2 was abundant in neurons. The expression of Prx1/2 was elevated after SAH, and their expression levels peaked before proinflammatory cytokines. Inhibiting Prx1/2 promoted neuronal apoptosis by increasing the hydrogen peroxide (H₂O₂) levels via the apoptosis signal-regulating kinase 1/p38 pathway. By contrast, overexpression of Prx1/2 attenuated oxidative stress and neuronal apoptosis after SAH. Thus, early expression of Prx1/2 may protect the brain from oxidative damage after SAH and may provide a novel target for treating SAH.-Lu, Y., Zhang, X.-S., Zhou, X.-M., Gao, Y.-Y., Chen, C.-L., Liu, J.-P., Ye, Z.-N., Zhang, Z.-H., Wu, L.-Y., Li, W., Hang, C.-H. Peroxiredoxin 1/2 protects brain against H₂O₂-induced apoptosis after subarachnoid hemorrhage.

Downregulation of peroxiredoxin II suppresses the proliferation and metastasis of gastric cancer cells

Peroxiredoxin (Prx) II is an imperative member of the superfamily of peroxidases. It serves an essential role in scavenging organic hydroperoxide and H2O2. It is involved in the development of various malignant tumors. In order to investigate the significance of Prx II expressions level in gastric cancer (GC), downregulation of Prx II was performed to investigate its role in the proliferation and migration of gastric adenocarcinoma cells. In GC cells and 45 GC specimens, the mRNA and protein expression levels of Prx II were determined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis, respectively. The Prx II expression profile in another 116 GC specimens was also detected with immunohistochemistry (IHC). The changes in the proliferation and migration of MKN45 and MGC-803 cells folllowing transfection with small interfering RNA (siRNA) were detected by cell counting kit (CCK)-8, western blot analysis, and Transwell migration and invasion assays. The results revealed that the expression of Prx II in GC tissues and GC cells were significantly upregulated compared with the normal control. There was a significant association between the expression level of Prx II and various factors, including tumor size, histological differentiation, the depth of invasion, the stage of tumor-node-metastasis (TNM) and lymph node metastasis in GC (P<0.05). Survival in patients with higher Prx II expression was significantly decreased compared with those with lower Prx II expression (P<0.01). Prx II, depth of invasion, lymph node metastasis and distant metastasis were identified as independent prognosis factors of GC (P<0.05). Knockdown of Prx II significantly suppressed the proliferation and the migration of GC cells. These experiments revealed that Prx II promotes the development of GC, affecting the survival of patients with GC.

Mitochondria and neuroprotection in stroke: Cationic arginine-rich peptides (CARPs) as a novel class of mitochondria-targeted neuroprotective therapeutics

Stroke is the second leading cause of death globally and represents a major cause of devastating long-term disability. Despite sustained efforts to develop clinically effective neuroprotective therapies, presently there is no clinically available neuroprotective agent for stroke. As a central mediator of neurodamaging events in stroke, mitochondria are recognised as a critical neuroprotective target, and as such, provide a focus for developing mitochondrial-targeted therapeutics. In recent years, cationic arginine-rich peptides (CARPs) have been identified as a novel class of neuroprotective agent with several demonstrated mechanisms of action, including their ability to target mitochondria and exert positive effects on the organelle. This review provides an overview on neuronal mitochondrial dysfunction in ischaemic stroke pathophysiology and highlights the potential beneficial effects of CARPs on mitochondria in the ischaemic brain following stroke.

Danger signals in stroke and their role on microglia activation after ischemia

Ischemic stroke is a major cause of death. Besides the direct damage resulting from oxygen and glucose deprivation, sterile inflammation plays a pivotal role in increasing cellular death. Damaged-associated molecular patterns (DAMPs) are passively released from dying cells and activate the innate immune system. Thus, they take part in the direct and rapid activation of the inflammatory response after stroke onset. In this review the role of the most important DAMPs, high mobility group box 1, heat and cold shock proteins, purines, and peroxiredoxins, are addressed. Moreover, intracellular pathways activated by DAMPs in microglia are illuminated.

Reactive Oxygen Species in Metabolic and Inflammatory Signaling

Reactive oxygen species (ROS) are well known for their role in mediating both physiological and pathophysiological signal transduction. Enzymes and subcellular compartments that typically produce ROS are associated with metabolic regulation, and diseases associated with metabolic dysfunction may be influenced by changes in redox balance. In this review, we summarize the current literature surrounding ROS and their role in metabolic and inflammatory regulation, focusing on ROS signal transduction and its relationship to disease progression. In particular, we examine ROS production in compartments such as the cytoplasm, mitochondria, peroxisome, and endoplasmic reticulum and discuss how ROS influence metabolic processes such as proteasome function, autophagy, and general inflammatory signaling. We also summarize and highlight the role of ROS in the regulation metabolic/inflammatory diseases including atherosclerosis, diabetes mellitus, and stroke. In order to develop therapies that target oxidative signaling, it is vital to understand the balance ROS signaling plays in both physiology and pathophysiology, and how manipulation of this balance and the identity of the ROS may influence cellular and tissue homeostasis. An increased understanding of specific sources of ROS production and an appreciation for how ROS influence cellular metabolism may help guide us in the effort to treat cardiovascular diseases.

Oxidative stress and DNA damage after cerebral ischemia: Potential therapeutic targets to repair the genome and improve stroke recovery

The past two decades have witnessed remarkable advances in oxidative stress research, particularly in the context of ischemic brain injury. Oxidative stress in ischemic tissues compromises the integrity of the genome, resulting in DNA lesions, cell death in neurons, glial cells, and vascular cells, and impairments in neurological recovery after stroke. As DNA is particularly vulnerable to oxidative attack, cells have evolved the ability to induce multiple DNA repair mechanisms, including base excision repair (BER), nucleotide excision repair (NER) and non-homogenous endpoint jointing (NHEJ). Defective DNA repair is tightly correlated with worse neurological outcomes after stroke, whereas upregulation of DNA repair enzymes, such as APE1, OGG1, and XRCC1, improves long-term functional recovery following stroke. Indeed, DNA damage and repair are now known to play critical roles in fundamental aspects of stroke recovery, such as neurogenesis, white matter recovery, and neurovascular unit remodeling. Several DNA repair enzymes are essential for comprehensive neural repair mechanisms after stroke, including Polβ and NEIL3 for neurogenesis, APE1 for white matter repair, Gadd45b for axonal regeneration, and DNA-PKs for neurovascular remodeling. This review discusses the emerging role of DNA damage and repair in functional recovery after stroke and highlights the contribution of DNA repair to regenerative elements after stroke. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Redox Signaling Mediated by Thioredoxin and Glutathione Systems in the Central Nervous System

SIGNIFICANCE

The thioredoxin (Trx) and glutathione (GSH) systems play important roles in maintaining the redox balance in the brain, a tissue that is prone to oxidative stress due to its high-energy demand. These two disulfide reductase systems are active in various areas of the brain and are considered to be critical antioxidant systems in the central nervous system (CNS). Various neuronal disorders have been characterized to have imbalanced redox homeostasis. Recent Advances: In addition to their detrimental effects, recent studies have highlighted that reactive oxygen species/reactive nitrogen species (ROS/RNS) act as critical signaling molecules by modifying thiols in proteins. The Trx and GSH systems, which reversibly regulate thiol modifications, regulate redox signaling involved in various biological events in the CNS.

CRITICAL ISSUES

In this review, we focus on the following: (i) how ROS/RNS are produced and mediate signaling in CNS; (ii) how Trx and GSH systems regulate redox signaling by catalyzing reversible thiol modifications; (iii) how dysfunction of the Trx and GSH systems causes alterations of cellular redox signaling in human neuronal diseases; and (iv) the effects of certain small molecules that target thiol-based signaling pathways in the CNS.

FUTURE DIRECTIONS

Further study on the roles of thiol-dependent redox systems in the CNS will improve our understanding of the pathogenesis of many human neuronal disorders and also help to develop novel protective and therapeutic strategies against neuronal diseases. Antioxid. Redox Signal. 27, 989-1010.

Diagnostic performance of peroxiredoxin 1 to determine time-of-onset of acute cerebral infarction

Accurately determining time-of-onset of cerebral infarction is important to clearly identify patients who could benefit from reperfusion therapies. We assessed the kinetics of peroxiredoxin 1 (PRDX1), a protein involved in oxidative stress during the acute phase of ischemia, and its ability to determine stroke onset in a population of patients with known onset of less than 24 hours and in a control group. Median PRDX1 levels were significantly higher in stroke patients compared to controls. PRDX1 levels were also higher from blood samples withdrawn before vs. after 3 hours following stroke onset, and before vs. after 6 hours. ROC analysis with area under the curve (AUC), sensitivity (Se) and specificity (Sp) determined from the Youden index was performed to assess the ability of PRDX1 levels to determine onset. Diagnostic performances of PRDX1 levels were defined by an AUC of 69%, Se of 53% and Sp of 86% for identifying cerebral infarction occurring <3 hours, and an AUC of 68%, Se of 49% and Sp of 88% for cerebral infarction occurring <6 hours. These first results suggest that PRDX1 levels could be the basis of a new method using biomarkers for determining cerebral infarction onset.

SIRT1 exerts neuroprotective effects by attenuating cerebral ischemia/reperfusion-induced injury via targeting p53/microRNA-22

The aim of this study was to investigate whether the SIRT1 exerts neuroprotective effects by attenuating cerebral ischemia/reperfusion-induced injury (CIRI) via targeting p53/microRNA-22. We found that the overexpression of sirtuin 1 (SIRT1) decreased the infarct volume, suppressed p53 protein expression and activated microRNA-22 expression following CIRI. An injection of lipopolysaccharide (LPS, 1 mg/ml; Sigma, St. Louis, MO USA) into the corpus callosum was used to induce CIRI in rats. The infarct volume and neurological deficit score were used to examine the effects of SIRT1 on CIRI. Furthermore, the overexpression of SIRT1 was found to suppress caspase-3 activity, inhibit the activation of the Bax signaling pathway, reduce tumor necrosis factor-α (TNF-α) and interleukin (IL)-6) activity, decrease cyclooxygenase (COX)‑2 and inducible nitric oxide synthase (iNOS) protein expression, and increase IL-10 activity following CIRI. Following the downregulation of SIRT1, p53 protein expression was significantly increased, microRNA-22 expression was inhibited, caspase-3 activity was increased and the Bax signaling pathway was activated. In addition, the activity of TNF-α and IL-6 was was enhanced, COX-2 and iNOS protein expression was increased, and IL-10 activity was reduced following CIRI. Thus, the data from our study suggest that SIRT1 attenuates CIRI by targeting the p53/microRNA-22 axix, while suppressing apoptosis, inflammation, COX-2 and iNOS expression.

Protein profiling reveals antioxidant and signaling activities of NAP (Davunetide) in rodent hippocampus exposed to hypobaric hypoxia

NAP (davunetide) is a clinical octapeptide and reportedly possesses neuroprotective, neurotrophic and cognitive protective properties. The information for NAP-mediated neuroproteome changes and associated signaling pathways during hypoxia will help in drug development programmes across the world. In the present study, we have evaluated the antioxidant activities of NAP in rat hippocampus exposed to hypobaric hypoxia (25,000 ft, 282 mm Hg) for 3, 6 and 12 h respectively. Using 2D-gel electrophoresis (2D-GE) with matrix-assisted laser desorption ionization time of flight (MALDI-TOF/TOF) mass spectrometry, we have identified altered expression of 80 proteins in NAP-supplemented hippocampus after hypoxia. Pathway analysis revealed that NAP supplementation significantly regulated oxidative stress response, oxidoreductase activity and cellular response to stress pathways during hypoxia. Additionally, NAP supplementation also regulated energy production pathways along with AMP-activated protein kinase (AMPK) signaling and signaling by Rho family GTPases pathways. We observed higher expression of antioxidant Sod1, Eno1, Prdx2 and Prdx5 proteins that were subsequently validated by Western blotting. A higher level of Prdx2 was also observed by immunohistochemistry in NAP-supplemented hippocampus during hypoxia. In corroboration, we are able to detect significant lower level of protein carbonyls in NAP-supplemented hypoxic hippocampus suggesting amelioration of oxidant molecules by NAP supplementation. These results emphasize the antioxidant and signaling properties of NAP in rodent hippocampus during hypobaric hypoxia.