Time-dependent change of in vivo optical imaging of oxidative stress in a mouse stroke model

The Role of Nrf2 in Relieving Cerebral Ischemia-Reperfusion Injury

Ischemic stroke includes two related pathological damage processes: brain injury caused by primary ischemia and secondary ischemia reperfusion (I/R) injury. I/R injury has become a worldwide health problem. Unfortunately, there is still a lack of satisfactory drugs for ameliorating cerebral I/R damage. Nrf2 is a vital endogenous antioxidant protein, which combines with Keap1 to maintain a dormant state under physiological conditions. When pathological changes such as I/R occurs, Nrf2 dissociates from Keap1 and activates the expression of downstream antioxidant proteins to exert a protective effect. Recent research have shown that the activated Nrf2 not only effectively inhibits oxidative stress, but also performs the ability to repair the function of compromised mitochondria, alleviate endoplasmic reticulum stress, eliminate inflammatory response, reduce blood-brain barrier permeability, inhibit neuronal apoptosis, enhance the neural network remolding, thereby exerting significant protective effects in alleviating the injuries caused by cell oxygen-glucose deprivation, or animal cerebral I/R. However, no definite clinical application report demonstrated the efficacy of Nrf2 activators in the treatment of cerebral I/R. Therefore, further efforts are needed to elaborate the role of Nrf2 activators in the treatment of cerebral I/R. Here, we reviewed the possible mechanisms underlying its potential pharmacological benefits in alleviating cerebral I/R injury, so as to provide a theoretical basis for studying its mechanism and developing Nrf2 activators.

Brain Pericytes Acquire Stemness via the Nrf2-Dependent Antioxidant System

Pericytes (PCs) are a mural support cell population elongated at intervals along the walls of capillaries. Recent studies reported that PCs are multipotent cells that are activated in response to tissue injury and contribute to the regenerative process. Using a C.B-17 mouse model of ischemic stroke, it has been proposed that normal brain pericytes (nPCs) are converted to ischemic pericytes (iPCs), some of which function as multipotent stem cells. Furthermore, oxygen-glucose deprivation (OGD) promoted mesenchymal-epithelial transition in nPCs; however, nestin was not induced under OGD conditions. Therefore, further studies are needed to elucidate the PC reprogramming phenomenon. We herein isolated nPCs from the cortex of C.B-17 mice, and compared the traits of iPCs and nPCs. The results obtained showed that nPCs and iPCs shared common pericytic markers. Furthermore, intercellular levels of reactive oxygen species and the nuclear accumulation of nuclear factor erythroid-2-related factor 2 (Nrf2), a key player in antioxidant defenses, were higher in iPCs than in nPCs. OGD/reoxygenation and a treatment with tBHQ, an Nrf2 inducer, increased nestin levels in nPCs. Moreover, epithelial marker levels, including nestin, Sox2, and CDH1 (E-cadherin) mRNAs, were elevated in Nrf2-overexpressing PCs, which formed neurosphere-like cell clusters that differentiated into Tuj1-positive neurons. The present results demonstrate that oxidative stress and Nrf2 are required for the generation of stem cells after stroke and will contribute to the development of novel therapeutic strategies for ischemic stroke.

Antioxidant Therapy in Oxidative Stress-Induced Neurodegenerative Diseases: Role of Nanoparticle-Based Drug Delivery Systems in Clinical Translation

Free radicals are formed as a part of normal metabolic activities but are neutralized by the endogenous antioxidants present in cells/tissue, thus maintaining the redox balance. This redox balance is disrupted in certain neuropathophysiological conditions, causing oxidative stress, which is implicated in several progressive neurodegenerative diseases. Following neuronal injury, secondary injury progression is also caused by excessive production of free radicals. Highly reactive free radicals, mainly the reactive oxygen species (ROS) and reactive nitrogen species (RNS), damage the cell membrane, proteins, and DNA, which triggers a self-propagating inflammatory cascade of degenerative events. Dysfunctional mitochondria under oxidative stress conditions are considered a key mediator in progressive neurodegeneration. Exogenous delivery of antioxidants holds promise to alleviate oxidative stress to regain the redox balance. In this regard, natural and synthetic antioxidants have been evaluated. Despite promising results in preclinical studies, clinical translation of antioxidants as a therapy to treat neurodegenerative diseases remains elusive. The issues could be their low bioavailability, instability, limited transport to the target tissue, and/or poor antioxidant capacity, requiring repeated and high dosing, which cannot be administered to humans because of dose-limiting toxicity. Our laboratory is investigating nanoparticle-mediated delivery of antioxidant enzymes to address some of the above issues. Apart from being endogenous, the main advantage of antioxidant enzymes is their catalytic mechanism of action; hence, they are significantly more effective at lower doses in detoxifying the deleterious effects of free radicals than nonenzymatic antioxidants. This review provides a comprehensive analysis of the potential of antioxidant therapy, challenges in their clinical translation, and the role nanoparticles/drug delivery systems could play in addressing these challenges.

In Vivo Imaging of Oxidative and Hypoxic Stresses in Mice Model of Amyotrophic Lateral Sclerosis

Oxidative and hypoxic stresses are associated with the degeneration of both motor neurons and skeletal muscles in amyotrophic lateral sclerosis (ALS). In vivo bioluminescent imaging is used to monitor cellular responses to oxidative and hypoxic stresses in living ALS model mice bearing G93A-human Cu/Zn superoxide dismutase (SOD1) longitudinally using the IVIS spectrum imaging system. Double transgenic mice bearing both Keap1-dependent oxidative stress detector No-48 (OKD48) and G93A-SOD1 are useful for in vivo imaging of oxidative stress in ALS. We developed a bioluminescence resonance energy transfer (BRET) probe that is regulated by HIF-1α-specific ubiquitin-proteasome system. G93A-SOD1 mice injected with the BRET probe are useful to investigate the spatiotemporal responses to hypoxic stress in ALS. In this chapter, we introduce a practical protocol of in vivo imaging of both oxidative and hypoxic stress in ALS model mice.

Ginkgolide With Intravenous Alteplase Thrombolysis in Acute Ischemic Stroke Improving Neurological Function: A Multicenter, Cluster-Randomized Trial (GIANT)

Background and Purpose: We aimed to investigate the effect of Ginkgolide® treatment on neurological function in patients receiving intravenous (IV) recombinant tissue plasminogen activator (rt-PA). Methods: This cluster randomized controlled trial included acute ischemic stroke patients in 24 centers randomized to intervention of intravenous Ginkgolide® or control group within the first 24 h after IV rt-PA therapy (IVT). Clinical outcome at 90 days was assessed with modified Rankin Scale (mRS) score and dichotomized into good outcome (0-2) and poor outcome (3-6). Hemorrhagic transformation represented the conversion of a bland infarction into an area of hemorrhage by computed tomography. Symptomatic intracerebral hemorrhage (sICH) was defined as cerebral hemorrhagic transformation in combination with clinical deterioration of National Institutes of Health Stroke Scale (NIHSS) score ≥4 points at 7-day or if the hemorrhage was likely to be the cause of the clinical deterioration. We performed logistic regression analysis and propensity score matching analysis to investigate the impact of Ginkgolide® treatment with IV rt-PA on good outcome, hemorrhagic transformation and sICH, respectively. Results: A total of 1113 patients were finally included and 513 (46.1%) were in the intervention group. Patients in the Ginkgolide® group were more likely to have good outcomes (78.6 vs. 66.7%, p < 0.01) and lower rate of sICH (0 vs. 2.72%, p < 0.01), compared with patients in the control group. The intra-cluster correlation coefficient (ICC) for good outcome at 90 days was 0.033. Binary logistic regression analysis revealed that treatment with Ginkgolide® was independently associated with 90-day mRS in patients with IV rt-PA therapy (OR 1.498; 95% CI 1.006-2.029, p = 0.009). After propensity score matching, conditional logistic regression showed intervention with Ginkgolide® was significantly associated with 90-day good outcome (OR 1.513; 95% CI 1.073-2.132, p = 0.018). No significant difference in hemorrhage transformation was seen between the 2 matched cohorts (OR 0.885; 95% CI 0.450-1.741, p = 0.724). Conclusion: Using Ginkgolide® within 24-hour after IV rt-PA is effective and safe and might be recommended in combination with rtPA therapy in acute ischemic stroke. Clinical Trial Registration: http://www.clinicaltrials.gov, identifier NCT03772847.

The Keap1/Nrf2-ARE signaling pathway is involved in atrazine induced dopaminergic neurons degeneration via microglia activation

OBJECTIVE

To investigate the mechanisms of ATR-induced dopaminergic toxicity by microglia activation and the response of the Keap1/ Nrf2- ARE signaling pathway.

METHODS

Wistar rats were treated with 50, 100 and 200 mg/kg ATR and BV-2 microglia cells were treated with 50, 100 μM ATR or 100 ng/mL LPS, respectively. Rats behavioral responses and histopathological changes were monitored. Immunohistochemical and immunofluorescence analysis detected Iba-1 and TH⁺ cells in rats. Keap1/Nrf2-ARE signaling-related proteins and inflammatory factors from BV-2 cells and rats were detected using ELISA, Western blot and Real-time PCR.

RESULTS

After ATR treatment, the grip strength of Wistar rats was significantly decreased, and anxiety were clearly observed. TH⁺ neurons were reduced, however, the number of microglia cells and Iba-1 levels were increased clearly in SN. The release of ROS, TNF-α and IL-Iβ were increased, and levels of SOD and GSH-Px were significantly decreased. Keap1 mRNA expression and protein levels were decreased, while nuclear Nrf2 mRNA expression and protein levels were both increased in vivo and in vitro.

CONCLUSION

ATR could significantly activate microglia and exacerbate neurotoxicity and neuroinflammation, leading to accelerate dopaminergic neuron cell death by inhibiting Keap1/Nrf2-ARE signaling pathway.

The Nrf2 Pathway in Ischemic Stroke: A Review

Ischemic stroke, characterized by the sudden loss of blood flow in specific area(s) of the brain, is the leading cause of permanent disability and is among the leading causes of death worldwide. The only approved pharmacological treatment for acute ischemic stroke (intravenous thrombolysis with recombinant tissue plasminogen activator) has significant clinical limitations and does not consider the complex set of events taking place after the onset of ischemic stroke (ischemic cascade), which is characterized by significant pro-oxidative events. The transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates the expression of a great number of antioxidant and/or defense proteins, has been pointed as a potential pharmacological target involved in the mitigation of deleterious oxidative events taking place at the ischemic cascade. This review summarizes studies concerning the protective role of Nrf2 in experimental models of ischemic stroke, emphasizing molecular events resulting from ischemic stroke that are, in parallel, modulated by Nrf2. Considering the acute nature of ischemic stroke, we discuss the challenges in using a putative pharmacological strategy (Nrf2 activator) that relies upon transcription, translation and metabolically active cells in treating ischemic stroke patients.

Caffeine and Its Neuroprotective Role in Ischemic Events: A Mechanism Dependent on Adenosine Receptors

Ischemia is characterized by a transient, insufficient, or permanent interruption of blood flow to a tissue, which leads to an inadequate glucose and oxygen supply. The nervous tissue is highly active, and it closely depends on glucose and oxygen to satisfy its metabolic demand. Therefore, ischemic conditions promote cell death and lead to a secondary wave of cell damage that progressively spreads to the neighborhood areas, called penumbra. Brain ischemia is one of the main causes of deaths and summed with retinal ischemia comprises one of the principal reasons of disability. Although several studies have been performed to investigate the mechanisms of damage to find protective/preventive interventions, an effective treatment does not exist yet. Adenosine is a well-described neuromodulator in the central nervous system (CNS), and acts through four subtypes of G-protein-coupled receptors. Adenosine receptors, especially A₁ and A_2A receptors, are the main targets of caffeine in daily consumption doses. Accordingly, caffeine has been greatly studied in the context of CNS pathologies. In fact, adenosine system, as well as caffeine, is involved in neuroprotection effects in different pathological situations. Therefore, the present review focuses on the role of adenosine/caffeine in CNS, brain and retina, ischemic events.

Antioxidative effects of a novel dietary supplement Neumentix in a mouse stroke model

BACKGROUND

During an acute stroke, reactive oxygen species are overproduced and the endogenous antioxidative defense systems are disrupted. Therefore, antioxidative therapy can be a promising scheme to reduce the severity of stroke. Neumentix is a novel antioxidative supplement produced from a patented mint line and contains a high content of rosmarinic acid (RA). Although Neumentix has proven diverse efficacy and safety in clinical trials, its effect on strokes is unclear.

METHODS

Mice that were treated with Neumentix or vehicle for 14 days underwent transient middle cerebral artery occlusion (tMCAO) for 60 min. Mice were sacrificed 5 days after tMCAO.

RESULTS

Neumentix preserved body weight after tMCAO, showed a high antioxidative effect in serum, and reduced infarction volume compared to the vehicle. The expression of 4-hydroxy-2-nonenal, Nε-(carboxymethyl) lysine, and 8-hydroxy-2'-deoxyguanosine was reduced in Neumentix-treated mice.

CONCLUSION

The antioxidative effect of Neumentix was confirmed. This is the first report to demonstrate the antioxidative effect of Neumentix on strokes.

Neuroprotective effect of CuATSM in mice stroke model by ameliorating oxidative stress

Cu-diacetyl-bis (N4-methylthiosemicarbazone) (CuATSM) has both anti-oxidative and anti-inflammatory activities, but its therapeutic efficacy for oxidative stress has not been thoroughly investigated in acute ischemic stroke. Here, the present study was designed to assess the efficacies of CuATSM in acute ischemic stroke by comparing with the standard neuroprotective reagent edaravone. Mice were subjected to transient middle cerebral occlusion (tMCAO) for 60 min, and then intravenously administrated with CuATSM (1.5 mg/kg) or edaravone (3 mg/kg) just after the reperfusion, and examined at 1 and 3 d. Compared with the vehicle group, CuATSM treatment decreased infarct volumes and oxidative stress at 3d after tMCAO, which was further enhanced by combined CuATSM + edaravone treatment as compared with single CuATSM group, but not improve neurobehaviors. The present study demonstrated that CuATSM showed strong antioxidative and neuroprotective effects in acute ischemic stroke, which was enhanced by the combination with edaravone.

A Polyphenolic Complex Attenuates Inflammatory Response and Blood- Brain Barrier Disruption

BACKGROUND

Cerebral ischemia causes a strong inflammatory response. Neumentix is a dietary supplement containing 14.9% rosmarinic acid and 29.9% total phenolic content, which has been proved to be beneficial against inflammatory response. Therefore, Neumentix's effect on anti-inflammatory and blood brain barrier (BBB) disruption in transient middle cerebral artery occlusion (tMCAO) model mice is investigated in this study.

METHODS

After the pretreatment of vehicle or Neumentix 134 mg/kg/d, intraperitoneal injection (i.p.) (containing rosmarinic acid 20 mg/kg/d) for 14 days, mice were subjected to tMCAO for 60 min and kept receiving vehicle or Neumentix daily 5 days afterward.

RESULTS

Neumentix treatment ameliorated neurobehavioral impairment in the corner test (5d after tMCAO, **P<0.01), reduced infarct volume (#P<0.05), suppressed expression of ionized calciumbinding adapter molecule-1 (Iba-1), tumor necrosis factor alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) (###P<0.001), and improved the integrity of BBB (§P<0.05) at 5 days after tMCAO.

CONCLUSION

The present study provided an evidence of Neumentix's anti-inflammatory and neuroprotection effect against BBB disruption on experimental tMCAO model mice, suggesting that Neumentix could be a potential therapeutic agent for stroke.

The neuroprotective mechanisms of ginkgolides and bilobalide in cerebral ischemic injury: a literature review

The incidence and mortality of strokes have increased over the past three decades in China. Ischemic strokes can cause a sequence of detrimental events in patients, including increased permeability and dysfunction of the blood-brain barrier, brain edema, metabolic disturbance, endoplasmic reticulum stress, autophagy, oxidative stress, inflammation, neuron death and apoptosis, and cognitive impairment. Thrombolysis using recombinant tissue plasminogen activator (rtPA) and mechanical embolectomy with a retrievable stent are two recognized strategies to achieve reperfusion after a stroke. Nevertheless, rtPA has a narrow therapeutic timeframe, and mechanical embolectomy has limited rates of good neurological outcomes. EGb761 is a standardized and extensively studied extract of Ginkgo biloba leaves. The ginkgolides and bilobalide that constitute a critical part of EGb761 have demonstrated protective properties towards cerebral injury. Ginkgolides include Ginkgolide A (GA), Ginkgolide B (GB), Ginkgolide C (GC), Ginkgolide J (GJ), Ginkgolide K (GK), Ginkgolide L (GL), and Ginkgolide M (GM). This review seeks to elucidate the neuroprotective effects and mechanisms of ginkgolides, especially GA and GB, and bilobalide in cerebral injury following ischemic strokes.

Dynamic cell type-specific expression of Nrf2 after traumatic brain injury in mice

Nrf2 plays a pivotal role in antioxidant response and anti-inflammation after traumatic brain injury (TBI), and its deletion aggravates TBI-induced brain damage. Previous studies have demonstrated that Nrf2 is activated post TBI, but dynamic changes in expression and cell type-specific characteristics remain unclear. In this study, the Feeney weight-drop contusion model was conducted to mimic TBI, and the ipsilateral cerebral cortex was collected at 1, 3, 7 and 14 days post TBI (dpi). Nrf2 protein levels were observed by western blot. Cell type-specific localization of Nrf2 after TBI was detected at different time intervals by double immunofluorescence staining. NeuN, GFAP, IBA1 and NG2 were used as cell type-specific markers to neurons, astrocytes, microglia and NG2 glia, respectively. After TBI, Nrf2 protein levels peaked at 1 dpi. Robust transient Nrf2 accumulation was co-localized with neurons, which was predominant at 1 dpi. Continuous weak Nrf2 expression was detected in activated astrocytes, and the number of double positive cells peaked at 7 dpi. Inducible widespread immunostaining of Nrf2 was observed in the nucleus of the microglia, and the number of Nrf2+ microglia peaked at 7 dpi. In addition, we also explored colocalization of Nrf2 in NG2 glia, in which the percentage of Nrf2+ in NG2 glia reached a climax at 3 dpi. This study reveals that the accumulation of endogenous Nrf2 might mediate different pathophysical roles in neurons and glias after TBI, the cell-type specific and time-dependent expression provide insights to explain the roles of Nrf2 in different neural cells.

Critical Role of Nrf2 in Experimental Ischemic Stroke

Ischemic stroke is one of the leading causes of death and long-term disability worldwide; however, effective clinical approaches are still limited. The transcriptional factor Nrf2 is a master regulator in cellular and organismal defense against endogenous and exogenous stressors by coordinating basal and stress-inducible activation of multiple cytoprotective genes. The Nrf2 network not only tightly controls redox homeostasis but also regulates multiple intermediary metabolic processes. Therefore, targeting Nrf2 has emerged as an attractive therapeutic strategy for the prevention and treatment of CNS diseases including stroke. Here, the current understanding of the Nrf2 regulatory network is critically examined to present evidence for the contribution of Nrf2 pathway in rodent ischemic stroke models. This review outlines the literature for Nrf2 studies in preclinical stroke and focuses on the in vivo evidence for the role of Nrf2 in primary and secondary brain injuries. The dynamic change and functional importance of Nrf2 signaling, as well as Nrf2 targeted intervention, are revealed in permanent, transient, and global cerebral ischemia models. In addition, key considerations, pitfalls, and future potentials for Nrf2 studies in preclinical stroke investigation are discussed.

Neuroprotective effects of SMTP-44D in mice stroke model in relation to neurovascular unit and trophic coupling

Stachybotrys microspora triprenyl phenol (SMTP)-44D has both anti-oxidative and anti-inflammatory activities, but its efficacy has not been proved in relation to the pathological changes of neurovascular unit (NVU) and neurovascular trophic coupling (NVTC) in ischemic stroke. Here, the present study was designed to assess the efficacies of SMTP-44D, moreover, compared with the standard neuroprotective reagent edaravone in ischemic brains. ICR mice were subjected to transient middle cerebral artery occlusion (tMCAO) for 60 min, SMTP-44D (10 mg/kg) or edaravone (3 mg/kg) was intravenously administrated through subclavian vein just after the reperfusion, and these mice were examined at 1, 3, and 7 d after reperfusion. Compared with the vehicle group, SMTP-44D treatment revealed obvious ameliorations in clinical scores and infarct volume, meanwhile, markedly suppressed the accumulations of 4-HNE, 8-OHdG, nitrotyrosine, RAGE, TNF-α, Iba-1, and cleaved caspase-3 after tMCAO. In addition, SMTP-44D significantly prevented the dissociation of NVU and improved the intensity of NAGO/BDNF and the number of BDNF/TrkB and BDNF/NeuN double positive cells. These effects of SMTP-44D in reducing oxidative and inflammatory stresses were similar to or stronger than those of edaravone. The present study demonstrated that SMTP-44D showed strong anti-oxidative, anti-inflammatory, and anti-apoptotic effects, moreover, the drug also significantly improved the NVU damage and NVTC in the ischemic brain.