A small-molecule-inducible Nrf2-mediated antioxidant response provides effective prophylaxis against cerebral ischemia in vivo

Genistein attenuates brain damage induced by transient cerebral ischemia through up-regulation of Nrf2 expression in ovariectomized rats

OBJECTIVE

Postmenopausal women possess higher incidence of stroke and worse prognosis. Although estrogen replacement therapy has obvious neuroprotective effects against stroke, it is always accompanied with several adverse effects and undesired outcomes. Genistein, a natural phytoestrogen, has been indicated to be a potential neuroprotective alternative for postmenopausal women against stroke. However, the role and mechanism of genistein's neuroprotective effects against stroke in ovariectomized rats have rarely been explored.

METHODS

In this study, ovariectomized rats were treated with genistein (10 mg/kg) or vehicle daily for two weeks before they received middle cerebral artery occlusion (MCAO) and reperfusion. After 72 hours of reperfusion, the neurological function was evaluated by Garcia test, infarct volume was detected by 2,3,5-triphenyltetrazolium chloride staining, and neuronal damage was detected by Nissl staining. In addition, ROS production and the expression of Nrf2, NQO1 and cleaved-Caspase3 in the ischemic penumbra were detected.

RESULTS

The results showed that genistein treatment significantly improved the neurological outcome, reduced infarct volume, increased Nrf2 and NQO1 expression, and reduced ROS production and cleaved-Caspase3 expression in ovariectomized rats.

DISCUSSION

Our findings indicated that treatment with genistein could alleviated oxidative stress injury induced by cerebral ischemia in ovariectomized rats via promoting Nrf2 and NQO1 expression, which provide a new molecular mechanism for the neuroprotective effects of genistein against stroke in postmenopausal women.

Targeting the Nrf2-Heme Oxygenase-1 Axis after Intracerebral Hemorrhage

BACKGROUND

Injury to cells adjacent to an intracerebral hemorrhage (ICH) is likely mediated at least in part by toxins released from the hematoma that initiate complex and interacting injury cascades. Pharmacotherapies targeting a single toxin or pathway, even if consistently effective in controlled experimental models, have a high likelihood of failure in a variable clinical setting. Nuclear factor erythroid-2 related factor 2 (Nrf2) regulates the expression of heme oxygenase-1 (HO-1) and multiple other proteins with antioxidant and antiinflammatory effects, and may be a target of interest after ICH.

METHODS

Studies that tested the effect of HO and Nrf2 in models relevant to ICH are summarized, with an effort to reconcile conflicting data by consideration of methodological limitations.

RESULTS

In vitro studies demonstrated that Nrf2 activators rapidly increased HO-1 expression in astrocytes, and reduced their vulnerability to hemoglobin or hemin. Modulating HO-1 expression via genetic approaches yielded similar results. Systemic treatment with small molecule Nrf2 activators increased HO-1 expression in perivascular cells, particularly astrocytes. When tested in mouse or rat ICH models, Nrf2 activators were consistently protective, improving barrier function and attenuating edema, inflammation, neuronal loss and neurological deficits. These effects were mimicked by selective astrocyte HO-1 overexpression in transgenic mice.

CONCLUSION

Systemic treatment with Nrf2 activators after ICH is protective in rodents. Two compounds, dimethyl fumarate and hemin, are currently approved for treatment of multiple sclerosis and acute porphyria, respectively, and have acceptable safety profiles over years of clinical use. Further development of these drugs as ICH therapeutics seems warranted.

6'-O-Galloylpaeoniflorin Attenuates Cerebral Ischemia Reperfusion-Induced Neuroinflammation and Oxidative Stress via PI3K/Akt/Nrf2 Activation

6'-O-galloylpaeoniflorin (GPF), a galloylated derivative of paeoniflorin isolated from peony root, has been proven to possess antioxidant potential. In this present study, we revealed that GPF treatment exerted significant neuroprotection of PC12 cells following OGD, as evidenced by a reduction of oxidative stress, inflammatory response, cellular injury, and apoptosis in vitro. Furthermore, treatment with GPF increased the levels of phosphorylated Akt (p-Akt) and nuclear factor-erythroid 2-related factor 2 (Nrf2), as well as promoted Nrf2 translocation in PC12 cells, which could be inhibited by Ly294002, an inhibitor of phosphoinositide 3-kinase (PI3K). In addition, Nrf2 knockdown or Ly294002 treatment significantly attenuated the antioxidant, anti-inflammatory, and antiapoptotic activities of GPF in vitro. In vivo studies indicated that GPF treatment significantly reduced infarct volume and improved neurological deficits in rats subjected to CIRI, as well as decreased oxidative stress, inflammation, and apoptosis, which could be inhibited by administration of Ly294002. In conclusion, these results revealed that GPF possesses neuroprotective effects against oxidative stress, inflammation, and apoptosis after ischemia-reperfusion insult via activation of the PI3K/Akt/Nrf2 pathway.

Nuclear factor erythroid-2-related factor regulates LRWD1 expression and cellular adaptation to oxidative stress in human embryonal carcinoma cells

Leucine-rich repeats and WD repeat domain-containing protein 1 (LRWD1) is implicated in the regulation of signal transduction, transcription, RNA processing and tumor development. However, LRWD1 transcriptional regulation is not fully understood. This study aimed to investigate the relationship between LRWD1 expression and reactive oxygen species (ROS) level in human embryonal carcinoma cell line, NT2/D1 cells, which will help in understanding the transcriptional regulatory role of ROS in cells. Results showed that the exposure of NT2/D1 cells to various concentrations of hydrogen peroxide (H₂O₂) and the nitric oxide (NO) donor sodium nitroprusside (SNP) caused a significant increase in the mRNA and protein expression of LRWD1. In addition, LRWD1 promoter luciferase reporter assay, and Chromatin Immunoprecipitation assay (CHIP assay) showed that nuclear factor erythroid-2-related factor (Nrf2) was involved in the regulation of LRWD1 expression in response to oxidative stress. The involvement of Nrf2 was confirmed by shRNA-mediated knockdown of Nrf2 in NT2/D1 cells, which caused a significant decrease in LRWD1 expression in response to oxidative stress. Similarly, LRWD1 knockdown resulted in the accumulation of H₂O₂ and superoxide anion radical (O2-). Blocking ROS production by N-acetyl cysteine (NAC) protected NT2/D1 shLRWD1cells from H₂O₂-induced cell death. Collectively, oxidative stress increased LRWD1 expression through a Nrf2-dependent mechanism, which plays an important role in cellular adaptation to oxidative stress. These results highlight an evidence, on the molecular level, about LRWD1 transcriptional regulation under oxidative stress.

Tert-butylhydroquinone post-treatment attenuates neonatal hypoxic-ischemic brain damage in rats

Hypoxic-ischemic (HI) encephalopathy is a leading cause of dire mortality and morbidity in neonates. Unfortunately, no effective therapies have been developed as of yet. Oxidative stress plays a critical role in pathogenesis and progression of neonatal HI. Previously, as a Nrf2 activator, tert-butylhydroquinone (TBHQ) has been demonstrated to exert neuroprotection on brain trauma and ischemic stroke models, as well as oxidative stress-induced cytotoxicity in neurons. It is, however, still unknown whether TBHQ administration can protect against oxidative stress in neonatal HI brain injury. This study was undertaken to determine the neuroprotective effects and mechanisms of TBHQ post-treatment on neonatal HI brain damage. Using a neonatal HI rat model, we demonstrated that TBHQ markedly abated oxidative stress compared to the HI group, as evidenced by decreased oxidative stress indexes, enhanced Nrf2 nuclear accumulation and DNA binding activity, and up-regulated expression of Nrf2 downstream antioxidative genes. Administration of TBHQ likewise significantly suppressed reactive gliosis and release of inflammatory cytokines, and inhibited apoptosis and neuronal degeneration in the neonatal rat cerebral cortex. In addition, infarct size and neuronal damage were attenuated distinctly. These beneficial effects were accompanied by improved neurological reflex and motor coordination as well as amelioration of spatial learning and memory deficits. Overall, our results provide the first documentation of the beneficial effects of TBHQ in neonatal HI model, in part conferred by activation of Nrf2 mediated antioxidative signaling pathways.

Disruption of Central Antioxidant Property of Nuclear Factor Erythroid 2-Related Factor 2 Worsens Circulatory Homeostasis with Baroreflex Dysfunction in Heart Failure

Heart failure is defined as a disruption of circulatory homeostasis. We have demonstrated that baroreflex dysfunction strikingly disrupts circulatory homeostasis. Moreover, previous many reports have suggested that central excess oxidative stress causes sympathoexcitation in heart failure. However, the central mechanisms of baroreflex dysfunction with oxidative stress has not been fully clarified. Our hypothesis was that the impairment of central antioxidant property would worsen circulatory homeostasis with baroreflex dysfunction in heart failure. As the major antioxidant property in the brain, we focused on nuclear factor erythroid 2-related factor 2 (Nrf2; cytoprotective transcription factor). Hemodynamic and baroreflex function in conscious state were assessed by the radio-telemetry system. In the heart failure treated with intracerebroventricular (ICV) infusion of angiotensin II type 1 receptor blocker (ARB), sympathetic activation and brain oxidative stress were significantly lower, and baroreflex sensitivity and volume tolerance were significantly higher than in heart failure treated with vehicle. ICV infusion of Nrf2 activator decreased sympathetic activation and brain oxidative stress, and increased baroreflex sensitivity and volume tolerance to a greater extent than ARB. In conclusion, the disruption of central antioxidant property of Nrf2 worsened circulatory homeostasis with baroreflex dysfunction in heart failure.

Therapeutic Potential of the Activators of the Nuclear Factor Erythroid 2-Related Factor 2-Antioxidant Response Element Pathway in Brain Disorders

Oxidative stress is recognized as an important mediator of brain disorders. Nevertheless, there are few antioxidants approved for brain diseases. There are two types of mechanisms as antioxidant systems in vivo, antioxidants and antioxidant enzymes. Antioxidants are consumed by the reaction with reactive oxygen species. Thus, it is important to maintain high concentrations at the requisite site. On the other hand, antioxidant capacity is maintained for around a half-day to one day once antioxidant enzymes are induced. Therefore, low molecular-weight compounds that could induce antioxidant enzymes are considered to be suitable for the treatment and prevention of brain diseases. The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway is known as a system for inducing these antioxidant enzymes. Here, the potential for low molecular-weight compounds capable of activating the Nrf2-ARE pathway to become therapeutic agents for brain diseases is discussed.

Berberine activates Nrf2 nuclear translocation and inhibits apoptosis induced by high glucose in renal tubular epithelial cells through a phosphatidylinositol 3-kinase/Akt-dependent mechanism

Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Berberine (BBR) is identified as a potential anti-diabetic herbal medicine due to its beneficial effects on insulin sensitivity, glucose metabolism and glycolysis. In this study, the underlying mechanisms involved in the protective effects of BBR on high glucose-induced apoptosis were explored using cultured renal tubular epithelial cells (NRK-52E cells) and human kidney proximal tubular cell line (HK-2 cells). We identified the pivotal role of phosphatidylinositol 3-kinase (PI3K)/Akt in BBR cellular defense mechanisms and revealed the novel effect of BBR on nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2) and heme oxygenase (HO)-1 in NRK-52E and HK-2 cells. BBR attenuated reactive oxygen species production, antioxidant defense (GSH and SOD) and oxidant-sensitive proteins (Nrf2 and HO-1), which also were blocked by LY294002 (an inhibitor of PI3K) in HG-treated NRK-52E and HK-2 cells. Furthermore, BBR improved mitochondrial function by increasing mitochondrial membrane potential. BBR-induced anti-apoptotic function was demonstrated by decreasing apoptotic proteins (cytochrome c, Bax, caspase3 and caspase9). All these findings suggest that BBR exerts the anti-apoptosis effects through activation of PI3K/Akt signal pathways and leads to activation of Nrf2 and induction of Nrf2 target genes, and consequently protecting the renal tubular epithelial cells from HG-induced apoptosis.

Spirulina diet to lactating mothers protects the antioxidant system and reduces inflammation in post-natal brain after systemic inflammation

OBJECTIVES

This study concerns: (1) the long-term effects of peripheral lipopolysaccharide (LPS) in neonatal rats on inflammation and antioxidant parameters in brain and (2) the effects of a Spirulina-enriched diet given to lactating mothers on protective and inflammatory parameters in brains of suckling pups subjected to peripheral inflammation.

METHODS

Five-day old rat pups were treated with LPS (i.p. 2 mg/kg). After 3, 7, 30, and 65 days, mRNA, miRNA, and protein levels of pro-inflammatory cytokines and the Nuclear factor E2-related factor 2 (Nrf2)-system were examined. In a sub-group, a Spirulina-enriched diet was given to the mothers 24 hours before the pups were treated with LPS, then the effects on antioxidant and inflammatory parameters were evaluated.

RESULTS

The main findings were: (1) interleukin 1 beta (IL-1β) was upregulated in cortex 3, 7, and 30 days after LPS treatment, (2) Nrf2 and the catalytic subunit of γ-glutamylcysteinyl ligase were decreased in cortex 7 days after LPS in parallel with increased levels of phosphorylated p38 and decreased levels of histone H3 acetylation, and (3) a Spirulina-enriched diet to lactating mothers normalized both the increased IL-1β expression and the decreased antioxidant parameters after LPS. The protective effects of Spirulina were correlated with decreased levels of phosphorylated p38 and high levels of the antioxidant miRNA-146a.

DISCUSSION

A Spirulina diet given to lactating mothers can protect against neuroinflammation and decreased antioxidant defence in brain of suckling pups subjected to peripheral inflammation, possibly via decreased activation of p38 and high levels of the antioxidant miRNA-146a.

The Interrelation between Reactive Oxygen Species and Autophagy in Neurological Disorders

Neurological function deficits due to cerebral ischemia or neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) have long been considered a thorny issue in clinical treatment. Recovery after neurologic impairment is fairly limited, which poses a major threat to health and quality of life. Accumulating evidences support that ROS and autophagy are both implicated in the onset and development of neurological disorders. Notably, oxidative stress triggered by excess of ROS not only puts the brain in a vulnerable state but also enhances the virulence of other pathogenic factors, just like mitochondrial dysfunction, which is described as the culprit of nerve cell damage. Nevertheless, autophagy is proposed as a subtle cellular defense mode against destructive stimulus by timely removal of damaged and cytotoxic substance. Emerging evidence suggests that the interplay of ROS and autophagy may establish a determinant role in the modulation of neuronal homeostasis. However, the underlying regulatory mechanisms are still largely unexplored. This review sets out to afford an overview of the crosstalk between ROS and autophagy and discusses relevant molecular mechanisms in cerebral ischemia, AD, and PD, so as to provide new insights into promising therapeutic targets for the abovementioned neurological conditions.

Nrf2-dependent persistent oxidative stress results in stress-induced vulnerability to depression

Stressful life events produce a state of vulnerability to depression in some individuals. The mechanisms that contribute to vulnerability to depression remain poorly understood. A rat model of intense stress (social defeat (SD), first hit) produced vulnerability to depression in 40% of animals. Only vulnerable animals developed a depression-like phenotype after a second stressful hit (chronic mild stress). We found that this vulnerability to depression resulted from a persistent state of oxidative stress, which was reversed by treatment with antioxidants. This persistent state of oxidative stress was due to low brain-derived neurotrophic factor (BDNF) levels, which characterized the vulnerable animals. We found that BDNF constitutively controlled the nuclear translocation of the master redox-sensitive transcription factor Nrf2, which activates antioxidant defenses. Low BDNF levels in vulnerable animals prevented Nrf2 translocation and consequently prevented the activation of detoxifying/antioxidant enzymes, ultimately resulting in the generation of sustained oxidative stress. Activating Nrf2 translocation restored redox homeostasis and reversed vulnerability to depression. This mechanism was confirmed in Nrf2-null mice. The mice displayed high levels of oxidative stress and were inherently vulnerable to depression, but this phenotype was reversed by treatment with antioxidants. Our data reveal a novel role for BDNF in controlling redox homeostasis and provide a mechanistic explanation for post-stress vulnerability to depression while suggesting ways to reverse it. Because numerous enzymatic reactions produce reactive oxygen species that must then be cleared, the finding that BDNF controls endogenous redox homeostasis opens new avenues for investigation.

Progesterone Provides the Pleiotropic Neuroprotective Effect on Traumatic Brain Injury Through the Nrf2/ARE Signaling Pathway

Objective

This study was to investigate the role of Nrf2/ARE signaling pathway in the pleiotropic neuroprotective effect of progesterone (PROG) on traumatic brain injury (TBI).

Methods

The Nrf2-knockout (Nrf2−/−) and C57 mice were respectively subjected to a lateral cortical impact injury caused by a free-falling object and randomly divided into three groups: sham-operated, trauma, and trauma + PROG treatment group. The PROG treatment group was given PROG (32 mg/kg of body weight, intraperitoneal injection) immediately after injury. For all groups, a series of brain samples were obtained after trauma at 24 and 72 h, respectively. The cerebral edema was evaluated; the expression of IL-1β, IL-6, and TNF-α was measured using ELISA array, and the apoptosis index was detected by TUNEL. Flow cytometry was used to detect the intracellular calcium concentration.

Results

The water content, the apoptosis index, the levels of inflammatory cytokine, and the intracellular calcium ion were significantly decreased with the PROG treatment in C57 mice with TBI model. However, the effect of PROG on TBI was not found in the Nrf2−/− mouse model of TBI.

Conclusions

PROG reduced cerebral edema, apoptosis, inflammatory reaction, and intracellular calcium ion overload effects after TBI. These beneficial effects were not seen in the Nrf2−/− mouse model of TBI. The results from this study suggested that the Nrf2/ARE signal pathway may be involved in the pleiotropic neuroprotective effect of PROG on TBI.

MIND4-17 protects retinal pigment epithelium cells and retinal ganglion cells from UV

Nrf2 activation would efficiently protect retinal cells from UV radiation (UVR). Recent studies have developed a Nrf2-targeting thiazole-containing compound MIND4-17, which activates Nrf2 through blocking its association with Keap1. In the current study, we demonstrated that pretreatment with MIND4-17 efficiently protected retinal pigment epithelium (RPE) cells (RPEs) and retinal ganglion cells (RGCs) from UVR. UVR-induced apoptosis in the retinal cells was also largely attenuated by MIND4-17 pretreatment. MIND4-17 presumably separated Nrf2 from Keap1, allowing its stabilization and accumulation in retinal cells, which then translocated to cell nuclei and promoted transcription of ARE-dependent anti-oxidant genes, including HO1, NQO1 and GCLM. Significantly, shRNA-mediated knockdown of Nrf2 almost completely abolished MIND4-17-induced cytoprotection against UVR. Further studies showed that MIND4-17 largely ameliorated UVR-induced ROS production, lipid peroxidation and DNA damages in RPEs and RGCs. Together, MIND4-17 protects retinal cells from UVR by activating Nrf2 signaling.

MHY1485 ameliorates UV-induced skin cell damages via activating mTOR-Nrf2 signaling

Ultra Violet (UV)-caused skin cell damage is a main cause of skin cancer. Here, we studied the activity of MHY1485, a mTOR activator, in UV-treated skin cells. In primary human skin keratinocytes, HaCaT keratinocytes and human skin fibroblasts, MHY1485 ameliorated UV-induced cell death and apoptosis. mTOR activation is required for MHY1485-induced above cytoprotective actions. mTOR kinase inhibitors (OSI-027, AZD-8055 and AZD-2014) or mTOR shRNA knockdown almost abolished MHY1485-induced cytoprotection. Further, MHY1485 treatment in skin cells activated mTOR downstream NF-E2-related factor 2 (Nrf2) signaling, causing Nrf2 Ser-40 phosphorylation, stabilization/upregulation and nuclear translocation, as well as mRNA expression of Nrf2-dictated genes. Contrarily, Nrf2 knockdown or S40T mutation almost nullified MHY1485-induced cytoprotection. MHY1485 suppressed UV-induced reactive oxygen species production and DNA single strand breaks in skin keratinocytes and fibroblasts. Together, we conclude that MHY1485 inhibits UV-induced skin cell damages via activating mTOR-Nrf2 signaling.

Tert-butylhydroquinone attenuates oxidative stress and inflammation in hypothalamic paraventricular nucleus in high salt-induced hypertension

Excessive oxidative stress and inflammation in hypothalamic paraventricular nucleus (PVN) are implicated in the pathogenesis of hypertension. It is reported that tert-butylhydroquinone (tBHQ), a nuclear factor erythroid 2-related factor 2(Nrf2)-inducer, has a variety of pharmacological activities such as anti-oxidation and anti-inflammatory effect. The objective of this study was to investigate the effects of tBHQ in high salt induced hypertension and to identify whether the beneficial effects were induced by inhibiting PVN oxidative stress and inflammation. Male Sprague-Dawley rats were fed with high salt diet (HS, 8% NaCl) or normal salt diet (NS, 0.3% NaCl). These rats were administration of tBHQ (150mg/kg/d) by oral gavage for 16 weeks. Our results showed that high salt intake resulted in higher mean arterial pressure, cardiac hypertrophy as well as increased plasma level of norepinephrine and interleukin (IL)-1β, IL-6 compared with NS rats. It increased PVN level of reactive oxygen species, gp91^phox, IL-1β, IL-6, p-IKKβ and nuclear factor-kappa B (NF-κB) activity, decreased PVN level of Nrf2 and Cu/Zn-SOD. Chronic administration of tBHQ significantly attenuated these changes in HS rats. These data suggest that the protective effects of tBHQ in salt induced hypertension are partly due to inhibiting oxidative stress and inflammation in PVN.

Central administration of tert-butylhydroquinone attenuates hypertension via regulating Nrf2 signaling in the hypothalamic paraventricular nucleus of hypertensive rats

Reactive oxygen species (ROS) in the paraventricular nucleus (PVN) play a pivotal role in the pathogenesis of hypertension. Nuclear factor E2-related factor-2 (Nrf2) is an important transcription factor that modulates cell antioxidant defense response against oxidative stress. The present study aimed to explore the efficacy of PVN administration of tert-butylhydroquinone (tBHQ), a selective Nrf2 activator, in hypertensive rats. 16-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats were used in this study. These rats were chronic bilateral PVN infusion of tBHQ (0.8μg/day), or oxygen free radical scavenger tempol (20μg/h), or vehicle for 2weeks. SHR rats had higher mean arterial pressure (MAP), plasma norepinephrine (NE) levels, and sympathetic nerve activity (RSNA) and lower PVN levels of Nrf2, hemeoxygenase-1 (HO-1), superoxide dismutase-1 (SOD1) and catalase (CAT) as compared with those in the WKY group. Bilateral PVN infusion of tBHQ or tempol significantly reduced MAP, RSNA, plasma NE levels in SHR rats. In addition, tBHQ treatment enhanced the nuclear accumulation of Nrf2 and increased the expression of HO-1, CAT and SOD1 in SHR rats. Furthermore, tBHQ attenuated PVN levels of ROS, the expression of proinflammatory cytokines and restored the imbalance of neurotransmitters in PVN. Knockdown of Nrf2 in the PVN by adeno-associated virus mediated small interfering RNA abrogated the protective effects of tBHQ on hypertension. These findings suggest that PVN administration of tBHQ can attenuate hypertension by activation of the Nrf2-mediated signaling pathway.

Activation of Nrf2-driven antioxidant enzymes by cardamonin confers neuroprotection of PC12 cells against oxidative damage

Oxidative stress represents a disorder of the redox equilibrium between the production of free radicals and the capability of cells to eliminate them. As subversion of this redox balance is thought to initiate various diseases, living cells maintain a redox equilibrium diligently. More and more pieces of evidence show that oxidative stress has already become a common risk factor in the pathogenesis of neurodegenerative disorders. So, considerable importance has been given to the prevention of oxidative stress as a potential therapeutic strategy. It is well known that the Nrf2-ARE pathway represents one of the most important cellular endogenous defense mechanisms against oxidative stress. Activation of Nrf2 signaling induces the transcriptional regulation of multiple ARE-dependent antioxidant defense genes. Here, we showed that cardamonin (CD), a chalcone isolated from Alpinia katsumadai, attenuated cell death induced by hydrogen peroxide (H₂O₂) and 6-hydroxydopamine (6-OHDA) in PC12 cells. Pretreatment of PC12 cells with CD dose-dependently upregulated the expression of phase II antioxidant molecules governed by Nrf2. In contrast, CD failed to provide neuroprotection after silencing Nrf2 expression, indicating that this cytoprotection may be mediated by the activation of transcription factor Nrf2. Our results demonstrate that CD is a novel small molecule activator of Nrf2 in PC12 cells, and suggest that CD may be a potential candidate for the prevention of oxidative stress-mediated neurodegenerative disorders.

Commiphora molmol Modulates Glutamate-Nitric Oxide-cGMP and Nrf2/ARE/HO-1 Pathways and Attenuates Oxidative Stress and Hematological Alterations in Hyperammonemic Rats

Hyperammonemia is a serious complication of liver disease and may lead to encephalopathy and death. This study investigated the effects of Commiphora molmol resin on oxidative stress, inflammation, and hematological alterations in ammonium chloride- (NH₄Cl-) induced hyperammonemic rats, with an emphasis on the glutamate-NO-cGMP and Nrf2/ARE/HO-1 signaling pathways. Rats received NH₄Cl and C. molmol for 8 weeks. NH₄Cl-induced rats showed significant increase in blood ammonia, liver function markers, and tumor necrosis factor-alpha (TNF-α). Concurrent supplementation of C. molmol significantly decreased circulating ammonia, liver function markers, and TNF-α in hyperammonemic rats. C. molmol suppressed lipid peroxidation and nitric oxide and enhanced the antioxidant defenses in the liver, kidney, and cerebrum of hyperammonemic rats. C. molmol significantly upregulated Nrf2 and HO-1 and decreased glutamine and nitric oxide synthase, soluble guanylate cyclase, and Na⁺/K⁺-ATPase expression in the cerebrum of NH₄Cl-induced hyperammonemic rats. Hyperammonemia was also associated with hematological and coagulation system alterations. These alterations were reversed by C. molmol. Our findings demonstrated that C. molmol attenuates ammonia-induced liver injury, oxidative stress, inflammation, and hematological alterations. This study points to the modulatory effect of C. molmol on glutamate-NO-cGMP and Nrf2/ARE/HO-1 pathways in hyperammonemia. Therefore, C. molmol might be a promising protective agent against hyperammonemia.

Tissue kallikrein protects against ischemic stroke by suppressing TLR4/NF-κB and activating Nrf2 signaling pathway in rats

Brain damage following cerebral ischemia-reperfusion (I/R) is a complicated pathophysiological course, in which inflammation and oxidative stress have been suggested to serve an important role. Toll-like receptor 4 (TLR4) has been suggested to be involved in secondary inflammatory process in cerebral ischemia. Nuclear factor erythroid 2-related factor 2 (Nrf2), an important regulator of the antioxidant host defense, maintains the cellular redox homeostasis. Tissue kallikrein (TK) has been proven to elicit a variety of biological effects in ischemic stroke through its anti-inflammatory and anti-oxidant properties. However, the mechanisms underlying its beneficial effects remain poorly defined. The present study examined the hypothesis that TK attenuates ischemic cerebral injury via the TLR4/nuclear factor-κB (NF-κB) and Nrf2 signaling pathways. Using a transient rat middle cerebral artery occlusion (MCAO) model, the effects of immediate and delayed TK treatment subsequent to reperfusion were investigated. The neurological deficits, infarct size, and the expression of TLR4/NF-κB and Nrf2 pathway in ischemic brain tissues were measured at 24 following MCAO. The results indicated that TK immediate treatment significantly improved neurological deficits and reduced the infarct size, accompanied by the inhibition of TLR4 and NF-κB levels, and the activation of Nrf2 pathway. Furthermore, TK delayed treatment also exerted neuroprotection against I/R injury. However, the neuroprotective effect of TK immediate treatment was better compared with that of TK delayed treatment. In conclusion, the results indicated that TK protected the brain against ischemic injury in rats after MCAO through its anti-oxidative and anti-inflammatory effects. Suppression of TLR4/NF-κB and activation of the Nrf2 pathway contributed to the neuroprotective effects induced by TK in cerebral ischemia. Therefore, TK may provide an effective intervention with a wider therapeutic window for ischemic stroke.

Attenuation of diabetic nephropathy by Sanziguben Granule inhibiting EMT through Nrf2-mediated anti-oxidative effects in streptozotocin (STZ)-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetic nephropathy (DN) is an acute and serious diabetic complication characterized by renal hypertrophy and renal fibrosis with the expansion of extracellular matrices. Diabetic nephropathy has become a major cause of end-stage kidney disease. Sanziguben Granule (SZGB) is a compound prescription which has been widely applied in clinical medicine for the prevention and treatment of diabetic nephropathy as well as for acute and chronic kidney injuries. However, the mechanism of protective effects of SZGB in DN remains unclear.

MATERIALS AND METHODS

In this research, we investigated the effects of SZGB on renal interstitial fibrosis, antioxidant proficiency, and apoptosis in streptozotocin (STZ)-induced diabetic rats. Diabetic rats were prepared by performing a right uninephrectomy along with a single intraperitoneal injection of STZ. Rats were divided into six groups including sham, DN, SZGB-D, SZGB-Z, SZGB-G and fosinopril. SZGB and fosinopril were given to rats by gavage for 12 weeks. Samples from urine, blood and kidneys were collected for biochemical, histological, immunohistochemical and western blot analyses.

RESULTS

We found that rats treated with SZGB showed reduced 24-h urinary protein excretion along with reduced serum total cholesterol (TC) and triglyceride (TG) levels. SZGB was also shown to prevent the disruption of catalase activity and reduce serum urea, creatinine, and renal malondialdehyde while increasing glutathione levels. Moreover, SZGB administration markedly improved the expression levels of E-cadherin, 4-HNE, Nrf2, HO-1, and Bcl-2, while it decreased the expression levels of Vimentin, α-SMA and Cleaved caspase-3 in the kidneys of diabetic rats. The renoprotective effects of SZGB was believed to be mediated by its antioxidant capacity, and SZGB treatment attenuated renal fibrosis through stimulating the nuclear factor erythroid-2-related factor 2 (Nrf2) signaling pathway in the diabetic kidneys.

CONCLUSIONS

Therefore, it is suggested that SZGB can restrain epithelial-mesenchymal transition (EMT) through stimulating the Nrf2 pathway, which improves renal interstitial fibrosis in DN.

skn-1 is required for interneuron sensory integration and foraging behavior in Caenorhabditis elegans

Nrf2/skn-1, a transcription factor known to mediate adaptive responses of cells to stress, also regulates energy metabolism in response to changes in nutrient availability. The ability to locate food sources depends upon chemosensation. Here we show that Nrf2/skn-1 is expressed in olfactory interneurons, and is required for proper integration of multiple food-related sensory cues in Caenorhabditis elegans. Compared to wild type worms, skn-1 mutants fail to perceive that food density is limiting, and display altered chemo- and thermotactic responses. These behavioral deficits are associated with aberrant AIY interneuron morphology and migration in skn-1 mutants. Both skn-1-dependent AIY autonomous and non-autonomous mechanisms regulate the neural circuitry underlying multisensory integration of environmental cues related to energy acquisition.

Nrf2-ARE signaling provides neuroprotection in traumatic brain injury via modulation of the ubiquitin proteasome system

The nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway exhibits protective effects in a variety of neurological diseases. However, the role of this pathway in traumatic brain injury (TBI) is not fully understood. This study investigates whether the Nrf2-ARE pathway provides neuroprotection following TBI via regulation of the ubiquitin proteasome system (UPS), and examines the involvement of this pathway in redox homeostasis. We found that activation the Nrf2-ARE pathway can mitigate secondary brain injury induced by TBI. Furthermore, we found that inhibiting the Nrf2-ARE pathway weakened the UPS following TBI. Treatment of TBI with the proteasome inhibitor, MG132, increased neuronal apoptosis, and evidence of brain water content was found. These data suggest that the Nrf2-ARE pathway provides neuroprotection following TBI via modulation of the UPS. In addition, the results indicated that the content of glutathione (GSH) was significantly increased after activation of Nrf2, and the level of ROS decreased; however, this effect contradictory in the Nrf2 knockout mice. Further studies found that treatment with the ROS agonist, ferric ammonium citrate (FAC), resulted in additional damage exerted by the ubiquitin proteasome pathways, and a significant increase in the amount of ubiquitinated proteins. In contrast, the activity of the ubiquitin proteasome pathways was vastly enhanced, and the level of ubiquitination proteins was significantly decreased following treatment with the inhibitor, N-acetylcysteine (NAC). The above mentioned results were also verified in in vitro experiments. In conclusion, the activation the Nrf2-ARE pathway improves neurological impairment caused by TBI via modulation of the UPS, and the redox homeostasis is one of the vital regulatory mechanisms.

Exploring effects of remote ischemic preconditioning in a pig model of hypothermic circulatory arrest

OBJECTIVES

During aortic and cardiac surgery, risks for mortality and morbidity are inevitable. Surgical setups involving deep hypothermic circulatory arrest (DHCA) are effective to achieve organ protection against ischemic injury. The aim of this study was to identify humoural factors mediating additive protective effects of remote ischemic preconditioning (RIPC) in a porcine model of DHCA.

DESIGN

Twenty-two pigs were randomized into the RIPC group (n = 11) and the control group (n = 11). The RIPC group underwent four 5-minute hind limb ischemia-reperfusion cycles prior to cardiopulmonary bypass and DHCA. All animals underwent identical surgical procedures including 60 min DHCA at 18 °C. Blood samples were collected from vena cava and sagittal sinus at several time points. After the 8-hour follow-up period, the brain, heart, and kidney tissue samples were collected for tissue analyses.

RESULTS

Serum levels of brain damage marker S100B recovered faster in the RIPC group, after 4 hours of the arrest, (p < .05). Systemic lactate levels were lower and cardiac index was higher in the RIPC group postoperatively. Immunohistochemical cerebellum regional scores of antioxidant response regulator Nrf2 were better in the RIPC group (mean: 1.1, IQR: 0.0-2.5) compared with the control group (mean: 0.0, IQR: 0.0-0.0), reaching borderline statistical significance (p = .064). RIPC induced detectable modulations of plasma proteome and metabolites.

CONCLUSIONS

The faster recovery of S100B, lower systemic lactate levels and favourable regional antioxidant response suggest possible neuronal cellular and mitochondrial protection by RIPC, whereas better cardiac index underlines functional effects of RIPC. The exact humoural factor remains unclear.

The Role of Astrocytes in Neuroprotection after Brain Stroke: Potential in Cell Therapy

Astrocytes are commonly involved in negative responses through their hyperreactivity and glial scar formation in excitotoxic and/or mechanical injuries. But, astrocytes are also specialized glial cells of the nervous system that perform multiple homeostatic functions for the survival and maintenance of the neurovascular unit. Astrocytes have neuroprotective, angiogenic, immunomodulatory, neurogenic, and antioxidant properties and modulate synaptic function. This makes them excellent candidates as a source of neuroprotection and neurorestoration in tissues affected by ischemia/reperfusion, when some of their deregulated genes can be controlled. Therefore, this review analyzes pro-survival responses of astrocytes that would allow their use in cell therapy strategies.

Down-regulation of microRNA-142-5p attenuates oxygen-glucose deprivation and reoxygenation-induced neuron injury through up-regulating Nrf2/ARE signaling pathway

MicroRNAs (miRNAs) play vital roles in regulating neuron survival during cerebral ischemia/reperfusion injury. miR-142-5p is reported to be an important regulator of cellular survival. However, little is known about the role of miR-142-5p in regulating neuron survival during cerebral ischemia/reperfusion injury. In this study, we aimed to investigate the precise function and mechanism of miR-142-5p in the regulation of neuron ischemia/reperfusion injury using a cellular model of oxygen-glucose deprivation and reoxygenation (OGD/R)-induced injury in hippocampal neurons in vitro. We found that miR-142-5p was induced in hippocampal neurons with OGD/R treatment. The inhibition of miR-142-5p attenuated OGD/R-induced cell injury and oxidative stress, whereas the overexpression of miR-142-5p aggravated them. Nuclear factor erythroid 2-related factor 2 (Nrf2) was identified as a target gene of miR-142-5p. Moreover, miR-142-5p regulated Nrf2 expression and downstream signaling. Knockdown of Nrf2 abolished the protective effects of miR-142-5p suppression. In addition, we showed an inverse correlation relationship between miR-142-5p and Nrf2 in an in vivo model of middle cerebral artery occlusion in rats. Taken together, these results suggest that miR-142-5p contributes to OGD/R-induced cell injury and the down-regulation of miR-142-5p attenuates OGD/R-induced neuron injury through promoting Nrf2 expression. Our study provides a novel insight into understanding the molecular pathogenesis of cerebral ischemia/reperfusion injury and indicates a potential therapeutic target for the treatment of cerebral ischemia/reperfusion injury.

Acute exposure to chlorpyrifos caused NADPH oxidase mediated oxidative stress and neurotoxicity in a striatal cell model of Huntington's disease

We hypothesized that expression of mutant Huntingtin (HTT) would modulate the neurotoxicity of the commonly used organophosphate insecticide, chlorpyrifos (CPF), revealing cellular mechanisms underlying neurodegeneration. Using a mouse striatal cell model of HD, we report that mutant HD cells are more susceptible to CPF-induced cytotoxicity as compared to wild-type. This CPF-induced cytotoxicity caused increased production of reactive oxygen species, reduced glutathione levels, decreased superoxide dismutase activity, and increased malondialdehyde levels in mutant HD cells relative to wild-type. Furthermore, we show that co-treatment with antioxidant agents attenuated the CPF-induced ROS levels and cytotoxicity. Co-treatment with a NADPH oxidase (NOX) inhibitor, apocynin, also attenuated the CPF-induced ROS production and neurotoxicity. CPF caused increased NOX activity in mutant HD lines that was ameliorated following co-treatment with apocynin. Finally, CPF-induced neurotoxicity significantly increased the protein expression of nuclear factor erythroid 2-related factor (Nrf2) in mutant HD cells as compared to wild-type. This study is the first report of CPF-induced toxicity in HD pathophysiology and suggests that mutant HTT and CPF exhibit a disease-toxicant interaction wherein expression of mutant HTT enhances CPF-induced neurotoxicity via a NOX-mediated oxidative stress mechanism to cause neuronal loss in the full length HTT expressing striatal cells.

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

Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a pivotal role in cellular defense against oxidative stress damage after ischemic stroke. In the present study, we examined the time-dependent change of in vivo optical imaging of oxidative stress after stroke with Keap1-dependent oxidative stress detector (OKD) mice. OKD mice were subjected to transient middle cerebral artery occlusion (tMCAO) for 45 min, and in vivo optical signals were detected during the pre-operative period, 12 h, 1 d, 3 d, and 7 d after tMCAO. Ex vivo imaging was performed immediately after obtaining in vivo optical signals at 1 d after tMCAO. Immunohistochemical analyses and infarct volume were also examined after in vivo imaging at each period. The in vivo signals showed a peak at 1 d after tMCAO that was slightly correlated to infarct volume. The strong ex vivo signals, which were detected in the peri-ischemic area, corresponded to endogenous Nrf2 expression. Moreover, endogenous Nrf2 expression was detected mainly in neurons followed by oligodendrocytes and pericytes, but only slightly in astrocytes, microglia, endothelial cells. The present study successfully demonstrated the temporal change of in vivo imaging of oxidative stress after tMCAO, which is consistent with strong expression of endogenous Nrf2 in the peri-ischemic area with a similar time course. © 2017 Wiley Periodicals, Inc.

Kelch-like ECH-associated Protein 1-dependent Nuclear Factor-E2–related Factor 2 Activation in Relation to Antioxidation Induced by Sevoflurane Preconditioning

Background

The authors have reported that antioxidative effects play a crucial role in the volatile anesthetic-induced neuroprotection. Accumulated evidence shows that endogenous antioxidation could be up-regulated by nuclear factor-E2–related factor 2 through multiple pathways. However, whether nuclear factor-E2–related factor 2 activation is modulated by sevoflurane preconditioning and, if so, what is the signaling cascade underlying upstream of this activation are still unknown.

Methods

Sevoflurane preconditioning in mice was performed with sevoflurane (2.5%) 1 h per day for five consecutive days. Focal cerebral ischemia/reperfusion injury was induced by middle cerebral artery occlusion. Expression of nuclear factor-E2–related factor 2, kelch-like ECH-associated protein 1, manganese superoxide dismutase, thioredoxin-1, and nicotinamide adenine dinucleotide phosphate quinolone oxidoreductase-1 was detected (n = 6). The antioxidant activities and oxidative product expression were also examined. To determine the role of kelch-like ECH-associated protein 1 inhibition-dependent nuclear factor-E2–related factor 2 activation in sevoflurane preconditioning-induced neuroprotection, the kelch-like ECH–associated protein 1-nuclear factor-E2–related factor 2 signal was modulated by nuclear factor-E2–related factor 2 knockout, kelch-like ECH-associated protein 1 overexpression lentivirus, and kelch-like ECH-associated protein 1 deficiency small interfering RNA (n = 8). The infarct volume, neurologic scores, and cellular apoptosis were assessed.

Results

Sevoflurane preconditioning elicited neuroprotection and increased nuclear factor-E2–related factor 2 nuclear translocation, which in turn up-regulated endogenous antioxidation and reduced oxidative injury. Sevoflurane preconditioning reduced kelch-like ECH-associated protein 1 expression. Nuclear factor-E2–related factor 2 ablation abolished neuroprotection and reversed sevoflurane preconditioning by mediating the up-regulation of antioxidants. Kelch-like ECH-associated protein 1 overexpression reversed nuclear factor-E2–related factor 2 up-regulation and abolished the neuroprotection induced by sevoflurane preconditioning. Kelch-like ECH-associated protein 1 small interfering RNA administration improved nuclear factor-E2–related factor 2 expression and the outcome of mice subjected to ischemia/reperfusion injury.

Conclusions

Kelch-like ECH-associated protein 1 down-regulation–dependent nuclear factor-E2–related factor 2 activation underlies the ability of sevoflurane preconditioning to activate the endogenous antioxidant response, which elicits its neuroprotection.

Post-translational Activation of Glutamate Cysteine Ligase with Dimercaprol: A NOVEL MECHANISM OF INHIBITING NEUROINFLAMMATION IN VITRO

Neuroinflammation and oxidative stress are hallmarks of various neurological diseases. However, whether and how the redox processes control neuroinflammation is incompletely understood. We hypothesized that increasing cellular glutathione (GSH) levels would inhibit neuroinflammation. A series of thiol compounds were identified to elevate cellular GSH levels by a novel approach (i.e. post-translational activation of glutamate cysteine ligase (GCL), the rate-limiting enzyme in GSH biosynthesis). These small thiol-containing compounds were examined for their ability to increase intracellular GSH levels in a murine microglial cell line (BV2), of which dimercaprol (2,3-dimercapto-1-propanol (DMP)) was found to be the most effective compound. DMP increased GCL activity and decreased LPS-induced production of pro-inflammatory cytokines and inducible nitric-oxide synthase induction in BV2 cells in a concentration-dependent manner. The ability of DMP to elevate GSH levels and attenuate LPS-induced pro-inflammatory cytokine production was inhibited by buthionine sulfoximine, an inhibitor of GCL. DMP increased the expression of GCL holoenzyme without altering the expression of its subunits or Nrf2 target proteins (NQO1 and HO-1), suggesting a post-translational mechanism. DMP attenuated LPS-induced MAPK activation in BV2 cells, suggesting the MAPK pathway as the signaling mechanism underlying the effect of DMP. Finally, the ability of DMP to increase GSH via GCL activation was observed in mixed cerebrocortical cultures and N27 dopaminergic cells. Together, the data demonstrate a novel mechanism of GSH elevation by post-translational activation of GCL. Post-translational activation of GCL offers a novel targeted approach to control inflammation in chronic neuronal disorders associated with impaired adaptive responses.

Activation of anti-oxidant Nrf2 signaling by substituted trans stilbenes

Nrf2, which is a member of the cap'n'collar family of transcription factors, is a major regulator of phase II detoxification and anti-oxidant genes as well as anti-inflammatory and neuroprotective genes. The importance of inflammation and oxidative stress in many chronic diseases supports the concept that activation of anti-oxidant Nrf2 signaling may have therapeutic potential. A number of Nrf2 activators have entered into clinical trials. Nrf2 exists in the cytosol in complex with its binding partner Keap1, which is a thiol-rich redox-sensing protein. In response to oxidative and electrophilic stress, select cysteine residues of Keap1 are modified, which locks Keap1 in the Nrf2-Keap1 complex and allows newly synthesized Nrf2 to enter the nucleus. Numerous Nrf2-activating chemicals, including a number of natural products, are electrophiles that modify Keap1, often by Michael addition, leading to activation of Nrf2. One concern with the design of Nrf2 activators that are electrophilic covalent modifiers of Keap1 is the issue of selectivity. In the present study, substituted trans stilbenes were identified as activators of Nrf2. These activators of Nrf2 are not highly electrophilic and therefore are unlikely to activate Nrf2 through covalent modification of Keap1. Dose-response studies demonstrated that a range of substituents on either ring of the trans stilbenes, especially fluorine and methoxy substituents, influenced not only the sensitivity to activation, reflected in EC₅₀ values, but also the extent of activation, which suggests that multiple mechanisms are involved in the activation of Nrf2. The stilbene backbone appears to be a privileged scaffold for development of a new class of Nrf2 activators.

Activation of Nrf2/ARE signaling pathway attenuates lanthanum chloride induced injuries in primary rat astrocytes

Lanthanum (La) exposure can lead to learning and memory disorder in animals; however, the underlying mechanism of La induced neurotoxicity is still unknown.

5-HMF attenuates striatum oxidative damage via Nrf2/ARE signaling pathway following transient global cerebral ischemia

Recent studies have shown 5-hydroxymethyl-2-furfural (5-HMF) has favorable biological effects, and its neuroprotection in a variety of neurological diseases has been noted. Our previous study showed that treatment of 5-HMF led to protection against permanent global cerebral ischemia. However, the underlying mechanisms in cerebral ischemic injury are not fully understood. This study was conducted to investigate the neuroprotective effect of 5-HMF and elucidate the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathway mechanism in the striatum after transient global cerebral ischemia. C57BL/6 mice were subjected to bilateral common carotid artery occlusion for 20 min and sacrificed 24 h after reperfusion. 5-HMF (12 mg/kg) or an equal volume of vehicle was intraperitoneally injected 30 min before ischemia and 5 min after the onset of reperfusion. At 24 h after reperfusion, neurological function was evaluated by neurological disability status scale, locomotor activity test and inclined beam walking test. Histological injury of the striatum was observed by cresyl violet staining and terminal deoxynucleotidyl transferase (TdT)-mediated dNTP nick end labeling (TUNEL) staining. Oxidative stress was evaluated by the carbonyl groups introduced into proteins, and malondialdehyde (MDA) levels. An enzyme-linked immunosorbent assay (ELISA)-based measurement was used to detect Nrf2 DNA binding activity. Nrf2 and its downstream ARE pathway protein expression such as heme oxygenase-1, NAD (P)H:quinone oxidoreductase 1, glutamate-cysteine ligase catalytic subunit and glutamate-cysteine ligase modulatory subunit were detected by western blot. Our results showed that 5-HMF treatment significantly ameliorated neurological deficits, reduced brain water content, attenuated striatum neuronal damage, decreased the carbonyl groups and MDA levels, and activated Nrf2/ARE signaling pathway. Taken together, these results demonstrated that 5-HMF exerted significant antioxidant and neuroprotective effects following transient cerebral ischemia, possibly through the activation of the Nrf2/ARE signaling pathway.

Ebselen Preserves Tissue-Engineered Cell Sheets and their Stem Cells in Hypothermic Conditions

Clinical trials have been performed using autologous tissue-engineered epithelial cell sheets for corneal regenerative medicine. To improve stem cell-based therapy for convenient clinical practice, new techniques are required for preserving reconstructed tissues and their stem/progenitor cells until they are ready for use. In the present study, we screened potential preservative agents and developed a novel medium for preserving the cell sheets and their stem/progenitor cells; the effects were evaluated with a luciferase-based viability assay. Nrf2 activators, specifically ebselen, could maintain high ATP levels during preservation. Ebselen also showed a strong influence on maintenance of the viability, morphology, and stem cell function of the cell sheets preserved under hypothermia by protecting them from reactive oxygen species-induced damage. Furthermore, ebselen drastically improved the preservation performance of human cornea tissues and their stem cells. Therefore, ebselen shows good potential as a useful preservation agent in regenerative medicine as well as in cornea transplantation.

Adaptive regulation of the brain's antioxidant defences by neurons and astrocytes

The human brain generally remains structurally and functionally sound for many decades, despite the post-mitotic and non-regenerative nature of neurons. This is testament to the brain's profound capacity for homeostasis: both neurons and glia have in-built mechanisms that enable them to mount adaptive or protective responses to potentially challenging situations, ensuring that cellular viability and functionality is maintained. The high and variable metabolic and mitochondrial activity of neurons places several demands on the brain, including the task of neutralizing the associated reactive oxygen species (ROS) produced, to limit the accumulation of oxidative damage. Astrocytes play a key role in providing antioxidant support to nearby neurons, and redox regulation of the astrocytic Nrf2 pathway represents a powerful homeostatic regulator of the large cohort of Nrf2-regulated antioxidant genes that they express. In contrast, the Nrf2 pathway is weak in neurons, robbing them of this particular homeostatic device. However, many neuronal antioxidant genes are controlled by synaptic activity, enabling activity-dependent increases in ROS production to be offset by enhanced antioxidant capacity of both glutathione and thioredoxin-peroxiredoxin systems. These distinct homeostatic mechanisms in neurons and astrocytes together combine to promote neuronal resistance to oxidative insults. Future investigations into signaling between distinct cell types within the neuro-glial unit are likely to uncover further mechanisms underlying redox homeostasis in the brain.

Fumarate modulates the immune/inflammatory response and rescues nerve cells and neurological function after stroke in rats

BACKGROUND

Dimethyl fumarate (DMF), working via its metabolite monomethylfumarate (MMF), acts as a potent antioxidant and immunomodulator in animal models of neurologic disease and in patients with multiple sclerosis. These properties and their translational potential led us to investigate whether DMF/MMF could also protect at-risk and/or dying neurons in models of ischemic stroke in vitro and in vivo. Although the antioxidant effects have been partially addressed, the benefits of DMF immunomodulation after ischemic stroke still need to be explored.

METHODS

In vitro neuronal culture with oxygen-glucose deprivation and rats with middle cerebral artery occlusion were subjected to DMF/MMF treatment. Live/dead cell counting and LDH assay, as well as behavioral deficits, plasma cytokine assay, western blots, real-time PCR (Q-PCR) and immunofluorescence staining, were used to evaluate the mechanisms and neurological outcomes.

RESULTS

We found that MMF significantly rescued cortical neurons from oxygen-glucose deprivation (OGD) in culture and suppressed pro-inflammatory cytokines produced by primary mixed neuron/glia cultures subjected to OGD. In rats, DMF treatment significantly decreased infarction volume by nearly 40 % and significantly improved neurobehavioral deficits after middle cerebral artery occlusion (MCAO). In the acute early phase (72 h after MCAO), DMF induced the expression of transcription factor Nrf2 and its downstream mediator HO-1, important for the protection of infarcted cells against oxidative stress. In addition to its antioxidant role, DMF also acted as a potent immunomodulator, reducing the infiltration of neutrophils and T cells and the number of activated microglia/macrophages in the infarct region by more than 50 % by 7-14 days after MCAO. Concomitantly, the levels of potentially harmful pro-inflammatory cytokines were greatly reduced in the plasma and brain and in OGD neuron/glia cultures.

CONCLUSIONS

We conclude that DMF is neuroprotective in experimental stroke because of its potent immunomodulatory and antioxidant effects and thus may be useful as a novel therapeutic agent to treat stroke in patients.

Ischemic post-conditioning attenuates acute lung injury induced by intestinal ischemia-reperfusion in mice: role of Nrf2

Intestinal ischemic post-conditioning (IPo) protects against lung injury induced by intestinal ischemia-reperfusion (IIR) partly through promotion of expression and function of heme oxygenase-1 (HO-1). NF-E2-related factor-2 (Nrf2) is a key transcription factor that interacts with HO-1 and regulates antioxidant defense. However, the role of Nrf2 in IPo protection of IIR-induced pulmonary injury is not completely understood. Here we show that IPo significantly attenuated IIR-induced lung injury and suppressed oxidative stress and systemic inflammatory responses. IPo also increased the expression of both Nrf2 and HO-1. Consistently, the beneficial effects of IPo were abolished by ATRA and Brusatol, potent inhibitors of Nrf2. Moreover, the Nrf2 agonist t-BHQ showed similar activity as IPo. Taken together, our data suggest that Nrf2 activity, along with HO-1, plays an important role in the protective effects of IPo against IIR-induced acute lung injury.

Sulforaphane activates the cerebral vascular Nrf2-ARE pathway and suppresses inflammation to attenuate cerebral vasospasm in rat with subarachnoid hemorrhage

Nrf2-ARE pathway reportedly plays a protective role in several central nervous system diseases. No study has explored the role of the Nrf2-ARE pathway in cerebral vasospasm(CVS) after subarachnoid hemorrhage(SAH). The purpose of the present study was to investigate the activation of the cerebral vascular Nrf2-ARE pathway and to determine the potential role of this pathway in the development of CVS following SAH. We investigated whether the administration of sulforaphane (SFN, a specific Nrf2 activator) modulated vascular caliber, Nrf2-ARE pathway activity, proinflammatory cytokine expression, and clinical behavior in a rat model of SAH. A two-hemorrhage protocol was used to generate an animal model of SAH in male Sprague-Dawley rats. Administration of SFN to these rats following SAH enhanced the activity of the Nrf2-ARE pathway and suppressed the release of proinflammatory cytokines. Vasospasm was markedly attenuated in the basilar arteries after SFN therapy. Additionally, SFN administration significantly ameliorated two behavioral functions disrupted by SAH. These results suggest that SFN has a therapeutic benefit in post-SAH, and this may be due to elevated Nrf2-ARE pathway activity and inhibition of cerebral vascular proinflammatory cytokine expression.

Protective Effects of Berberine on Renal Injury in Streptozotocin (STZ)-Induced Diabetic Mice

Diabetic nephropathy (DN) is a serious diabetic complication with renal hypertrophy and expansion of extracellular matrices in renal fibrosis. Epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells may be involved in the main mechanism. Berberine (BBR) has been shown to have antifibrotic effects in liver, kidney and lung. However, the mechanism of cytoprotective effects of BBR in DN is still unclear. In this study, we investigated the curative effects of BBR on tubulointerstitial fibrosis in streptozotocin (STZ)-induced diabetic mice and the high glucose (HG)-induced EMT in NRK 52E cells. We found that BBR treatment attenuated renal fibrosis by activating the nuclear factor-erythroid 2-related factor 2 (Nrf2) signaling pathway in the diabetic kidneys. Further revealed that BBR abrogated HG-induced EMT and oxidative stress in relation not only with the activation of Nrf2 and two Nrf2-targeted antioxidative genes (NQO-1 and HO-1), but also with the suppressing the activation of TGF-β/Smad signaling pathway. Importantly, knockdown Nrf2 with siRNA not only abolished the BBR-induced expression of HO-1 and NQO-1 but also removed the inhibitory effect of BBR on HG-induced activation of TGF-β/Smad signaling as well as the anti-fibrosis effects. The data from present study suggest that BBR can ameliorate tubulointerstitial fibrosis in DN by activating Nrf2 pathway and inhibiting TGF-β/Smad/EMT signaling activity.

Cell-specific overactivation of nuclear erythroid 2 p45-related factor 2-mediated gene expression in myeloid cells decreases hepatic ischemia/reperfusion injury

Hepatic ischemia/reperfusion injury (IRI) is an unavoidable consequence of liver transplantation that can lead to postoperative hepatic dysfunction. Myeloid cells that include Kupffer cells, monocytes, and neutrophils contribute to the inflammatory response and cellular injury observed during hepatic IRI. We hypothesize that overactivation of the nuclear erythroid 2 p45-related factor 2 (Nrf2)-antioxidant response element (ARE) pathway in myeloid cells leads to decreased cellular damage after hepatic IRI. We constructed transgenic mice with constitutively active nuclear erythroid 2 p45-related factor 2 (caNrf2) that over activates the Nrf2-ARE pathway in myeloid cells (lysozyme M cre recombinase [LysMcre]+/caNrf2+, n = 9), and their littermate controls lacking transgene expression (LysMcre+/caNrf2-, n = 11). The mice underwent either sham or partial hepatic ischemia surgery, with 60 minutes of ischemia followed by 6 hours of reperfusion. After IRI, LysMcre+/caNrf2+ mice demonstrated significantly decreased serum alanine aminotransferase and decreased areas of necrosis. Immunohistochemistry and immunoblot of caspase 3 showed a significantly decreased cleaved to full-length caspase 3 ratio in LysMcre+/caNrf2+ animals. Lymphocyte antigen 6 complex locus G and CD68 staining demonstrated reduced inflammatory cell infiltration. LysMcre+/caNrf2+ animals also had significantly decreased gene expression of proinflammatory cytokines, including interleukin (IL) 1β, IL6, tumor necrosis factor α, chemokine (C-C motif) ligand 2, and chemokine (C-X-C motif) ligand 10, and significantly decreased levels of 8-isoprostanes. In our model, Nrf2 overactivation in myeloid cells leads to decreased hepatocellular damage, necrosis, apoptosis, inflammation, and oxidative stress. Pharmacologic targeting of the Nrf2-ARE pathway in myeloid cells may be a novel strategy to mitigate hepatic IRI. Liver Transplantation 22 1115-1128 2016 AASLD.

β-Lapachone increases phase II antioxidant enzyme expression via NQO1-AMPK/PI3K-Nrf2/ARE signaling in rat primary astrocytes

β-Lapachone (β-LAP) is a naturally occurring quinine that exerts a number of pharmacological actions including antibacterial, antifungal, antimalarial, and antitumor activities. In the present study, we investigated whether β-LAP has an antioxidant effect in rat primary astrocytes. β-LAP suppressed intracellular reactive oxygen species (ROS) production induced by hydrogen peroxide and inhibited astroglial cell death. It also increased astrocytic expression of phase II antioxidant enzymes such as heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase 1 (NQO1), manganese superoxide dismutase (MnSOD), and catalase. Further mechanistic studies revealed that β-LAP activated AMPK and Akt, and pretreatment of cells with an AMPK inhibitor (compound C) or PI3K/Akt inhibitor (LY294002) suppressed β-LAP-induced antioxidant enzyme expression by inhibiting Nrf2/antioxidant response element (ARE) signaling. Compound C also decreased Akt phosphorylation, suggesting that AMPK is upstream of PI3K/Akt. Furthermore, the AMPK activator 5-aminoimidazole-4-carboxamide 1-β-d-ribofuranoside mimicked the effect of β-LAP by increasing Akt phosphorylation and ARE-mediated transcription, suggesting that AMPK plays a pivotal role in β-LAP-mediated antioxidant enzyme expression. Because β-LAP effects are usually associated with NQO1 activity, we examined the effect of NQO1 knockdown on antioxidant enzyme expression. Small interfering RNA (siRNA) specific for NQO1 inhibited β-LAP-induced AMPK/Akt phosphorylation and downstream antioxidant enzyme expression. Collectively, the results suggest that β-LAP increases antioxidant enzyme gene expression in astrocytes by modulating NQO1-AMPK/PI3K-Nrf2/ARE signaling.

A novel nuclear factor erythroid 2-related factor 2 (Nrf2) activator RS9 attenuates brain injury after ischemia reperfusion in mice

Recanalization of occluded vessels leads to ischemia-reperfusion injury (IRI), with oxidative stress as one of the main causes of injury, despite the fact that recanalization therapy is the most effective treatment for ischemic stroke. The nuclear factor erythroid 2-related factor 2 (Nrf2) is one of the transcription factors which has an essential role in protection against oxidative stress. RS9 is a novel Nrf2 activator obtained from bardoxolone methyl (BARD), an Nrf2 activator that has already been tested in a clinical trial, using a biotransformation technique. RS9 has been reported to lead to higher Nrf2 activation and less cytotoxicity than BARD. In this study, we investigated the effects of RS9 on IRI. Mice were intraperitoneally treated immediately after 2h of transient middle cerebral artery occlusion (MCAO) with a vehicle solution or 0.2mg/kg of RS9. Post-onset treatment of RS9 attenuated the infarct volume and improved neurological deficits 22h after reperfusion. RS9 activated Nrf2 2 and 6h after reperfusion and activated heme oxygenase-1 at 6 and 22h after reperfusion. RS9 also attenuated the phosphorylation of NF-κB p65 2 and 6h after reperfusion. Finally, RS9 improved the survival rate and neurological deficits 7days after MCAO. Our results suggest that the activation of Nrf2 by RS9 has a neuroprotective effect, mediated by attenuating both oxidative stress and neuroinflammation, and that RS9 is an effective therapeutic candidate for the treatment of IRI.

Nuclear Factor Erythroid 2-Related Factor 2 (Nrf2) Mediates Neuroprotection in Traumatic Brain Injury at Least in Part by Inactivating Microglia

Background

Microglial activation has been reported to be involved in traumatic brain injury (TBI). Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a significant role in protecting against TBI-induced secondary brain injury. However, the exact mechanism is not clearly understood. The present study aimed to explore whether Nrf2 protects against TBI partly by regulating microglia function.

Material/Methods

Microglia cells were isolated from C57BL/6 mouse brains (postnatal day 1–3). The expression of Nrf2 was suppressed by transfection with Nrf2-specific small interfering RNA (siRNA), and overexpressed by transfections with pcDNA3.1-Nrf2. The expression of Nrf2 was confirmed by real-time PCR and Western blotting. After transfection, cell viability, phagocytic ability, and the expression of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α and interleukin (IL)-6) were determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay, phagocytosis assay, and enzyme-linked immunosorbent assay (ELISA), respectively.

Results

mRNA and protein expression levels of Nrf2 were significantly reduced by transfection with Nrf2-specific siRNA (both P<0.05) but were elevated by transfection with pcDNA3.1-Nrf2 (both P<0.01). The cell viability, phagocytic ability, and the expression of TNF-α and IL-6 were all significantly reduced by overexpression of Nrf2 but were significantly increased by silencing of Nrf2 compared with the control group.

Conclusions

Our results suggest that Nrf2 protects against TBI, at least part by regulating microglia function.