Ferrous Iron Induces Nrf2 Expression in Mouse Brain Astrocytes to Prevent Neurotoxicity

The Role of Glia in Wilson's Disease: Clinical, Neuroimaging, Neuropathological and Molecular Perspectives

Wilson's disease (WD) is inherited in an autosomal recessive manner and is caused by pathogenic variants of the ATP7B gene, which are responsible for impaired copper transport in the cell, inhibition of copper binding to apoceruloplasmin, and biliary excretion. This leads to the accumulation of copper in the tissues. Copper accumulation in the CNS leads to the neurological and psychiatric symptoms of WD. Abnormalities of copper metabolism in WD are associated with impaired iron metabolism. Both of these elements are redox active and may contribute to neuropathology. It has long been assumed that among parenchymal cells, astrocytes have the greatest impact on copper and iron homeostasis in the brain. Capillary endothelial cells are separated from the neuropil by astrocyte terminal legs, putting astrocytes in an ideal position to regulate the transport of iron and copper to other brain cells and protect them if metals breach the blood-brain barrier. Astrocytes are responsible for, among other things, maintaining extracellular ion homeostasis, modulating synaptic transmission and plasticity, obtaining metabolites, and protecting the brain against oxidative stress and toxins. However, excess copper and/or iron causes an increase in the number of astrocytes and their morphological changes observed in neuropathological studies, as well as a loss of the copper/iron storage function leading to macromolecule peroxidation and neuronal loss through apoptosis, autophagy, or cuproptosis/ferroptosis. The molecular mechanisms explaining the possible role of glia in copper- and iron-induced neurodegeneration in WD are largely understood from studies of neuropathology in Parkinson's disease and Alzheimer's disease. Understanding the mechanisms of glial involvement in neuroprotection/neurotoxicity is important for explaining the pathomechanisms of neuronal death in WD and, in the future, perhaps for developing more effective diagnostic/treatment methods.

Management of ROS and Regulatory Cell Death in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury (MIRI) is fatal to patients, leading to cardiomyocyte death and myocardial remodeling. Reactive oxygen species (ROS) and oxidative stress play important roles in MIRI. There is a complex crosstalk between ROS and regulatory cell deaths (RCD) in cardiomyocytes, such as apoptosis, pyroptosis, autophagy, and ferroptosis. ROS is a double-edged sword. A reasonable level of ROS maintains the normal physiological activity of myocardial cells. However, during myocardial ischemia-reperfusion, excessive ROS generation accelerates myocardial damage through a variety of biological pathways. ROS regulates cardiomyocyte RCD through various molecular mechanisms. Targeting the removal of excess ROS has been considered an effective way to reverse myocardial damage. Many studies have applied antioxidant drugs or new advanced materials to reduce ROS levels to alleviate MIRI. Although the road from laboratory to clinic has been difficult, many scholars still persevere. This article reviews the molecular mechanisms of ROS inhibition to regulate cardiomyocyte RCD, with a view to providing new insights into prevention and treatment strategies for MIRI.

Acetylated oligopeptide and N-acetylcysteine protect against iron overload-induced dentate gyrus hippocampal degeneration through upregulation of Nestin and Nrf2/HO-1 and downregulation of MMP-9/TIMP-1 and GFAP

Iron accumulation in the brain causes oxidative stress, blood-brain barrier (BBB) breakdown, and neurodegeneration. We examined the preventive effects of acetylated oligopeptides (AOP) from whey protein on iron-induced hippocampal damage compared to N-acetyl cysteine (NAC). This 5-week study used 40 male albino rats. At the start, all rats received 150 mg/kg/day of oral NAC for a week. The 40 animals were then randomly divided into four groups: Group I (control) received a normal diet; Group II (iron overload) received 60 mg/kg/day intraperitoneal iron dextran 5 days a week for 4 weeks; Group III (NAC group) received 150 mg/kg/day NAC and iron dextran; and Group IV (AOP group) received 150 mg/kg/day AOP and iron dextran. Enzyme-linked immunosorbent assay, spectrophotometry, and qRT-PCR were used to measure MMP-9, tissue inhibitor metalloproteinase-1 (TIMP-1), MDA, reduced glutathione (GSH) levels, and nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) gene expression. Histopathological and immunohistochemical detection of nestin, claudin, caspase, and GFAP was also done. MMP-9, TIMP-1, MDA, caspase, and GFAP rose in the iron overload group, while GSH, Nrf2, HO-1, nestin, and claudin decreased. The NAC and AOP administrations improved iron overload-induced biochemical and histological alterations. We found that AOP and NAC can protect the brain hippocampus from iron overload, improve BBB disruption, and provide neuroprotection with mostly no significant difference from healthy controls.

Ferroptosis regulation through Nrf2 and implications for neurodegenerative diseases

This article provides an overview of the background knowledge of ferroptosis in the nervous system, as well as the key role of nuclear factor E2-related factor 2 (Nrf2) in regulating ferroptosis. The article takes Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS) as the starting point to explore the close association between Nrf2 and ferroptosis, which is of clear and significant importance for understanding the mechanism of neurodegenerative diseases (NDs) based on oxidative stress (OS). Accumulating evidence links ferroptosis to the pathogenesis of NDs. As the disease progresses, damage to the antioxidant system, excessive OS, and altered Nrf2 expression levels, especially the inhibition of ferroptosis by lipid peroxidation inhibitors and adaptive enhancement of Nrf2 signaling, demonstrate the potential clinical significance of Nrf2 in detecting and identifying ferroptosis, as well as targeted therapy for neuronal loss and mitochondrial dysfunction. These findings provide new insights and possibilities for the treatment and prevention of NDs.

Interactions Between the Ubiquitin-Proteasome System, Nrf2, and the Cannabinoidome as Protective Strategies to Combat Neurodegeneration: Review on Experimental Evidence

Neurodegenerative disorders are chronic brain diseases that affect humans worldwide. Although many different factors are thought to be involved in the pathogenesis of these disorders, alterations in several key elements such as the ubiquitin-proteasome system (UPS), the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, and the endocannabinoid system (ECS or endocannabinoidome) have been implicated in their etiology. Impairment of these elements has been linked to the origin and progression of neurodegenerative disorders, while their potentiation is thought to promote neuronal survival and overall neuroprotection, as proved with several experimental models. These key neuroprotective pathways can interact and indirectly activate each other. In this review, we summarize the neuroprotective potential of the UPS, ECS, and Nrf2 signaling, both separately and combined, pinpointing their role as a potential therapeutic approach against several hallmarks of neurodegeneration.

Metal profiling in coronary ischemia-reperfusion injury: Implications for KEAP1/NRF2 regulated redox signaling

Coronary ischemia-reperfusion (IR) injury results from a blockage of blood supply to the heart followed by restoration of perfusion, leading to oxidative stress induced pathological processes. Nuclear factor erythroid 2-related factor 2 (NRF2), a master antioxidant transcription factor, plays a key role in regulating redox signaling. Over the past decades, the field of metallomics has provided novel insights into the mechanism of pro-oxidant and antioxidant pathological processes. Both redox-active (e.g. Fe and Cu) and redox-inert (e.g. Zn and Mg) metals play unique roles in establishing redox balance under IR injury. Notably, Zn protects against oxidative stress in coronary IR injury by serving as a cofactor of antioxidant enzymes such as superoxide dismutase [Cu-Zn] (SOD1) and proteins such as metallothionein (MT) and KEAP1/NRF2 mediated antioxidant defenses. An increase in labile Zn2+ inhibits proteasomal degradation and ubiquitination of NRF2 by modifying KEAP1 and glycogen synthase kinase 3β (GSK3β) conformations. Fe and Cu catalyse the formation of reactive oxygen species via the Fenton reaction and also serve as cofactors of antioxidant enzymes and can activate NRF2 antioxidant signaling. We review the evidence that Zn and redox-active metals Fe and Cu affect redox signaling in coronary cells during IR and the mechanisms by which oxidative stress influences cellular metal content. In view of the unique double-edged characteristics of metals, we aim to bridge the role of metals and NRF2 regulated redox signaling to antioxidant defenses in IR injury, with a long-term aim of informing the design and application of novel therapeutics.

Molecular therapy of cardiac ischemia-reperfusion injury based on mitochondria and ferroptosis

Excessive death of myocardial cells can lead to various cardiovascular diseases and even develop into heart failure, so developing ideal treatment plans based on pathogenesis is of great significance for cardiopathy. After the heart undergoes ischemia‒reperfusion (I/R), myocardial cells accumulate a large amount of peroxides, leading to mitochondrial dysfunction and inducing ferroptosis. Ferroptosis is a form of iron-dependent regulatory cell death (RCD) caused by imbalanced redox and iron metabolism that leads to severe cell damage through the accumulation of peroxides. The mechanism of ferroptosis is highly correlated with mitochondrial metabolism. Myocardial cells are rich in a large number of mitochondria, which serve as energy supply centers and are prone to producing reactive oxygen species (ROS), providing opportunities for oxidative stress caused by ferroptosis. Ferroptosis is related to various cardiovascular diseases, and potential treatment methods designed around ferroptosis may alter the pathological progression of cardiovascular diseases. Therefore, this review investigates the regulatory mechanisms of ferroptosis, exploring the close pathological and physiological connections between ferroptosis and mitochondrial and cardiac I/R injury. Targeting ferroptosis and mitochondria for intervention may be an effective plan for preventing and treating cardiac I/R injury.

Baicalein and luteolin inhibit ischemia/reperfusion-induced ferroptosis in rat cardiomyocytes

BACKGROUND

Ischemia/reperfusion (I/R) is associated with severe cellular damage and death. Ferroptosis, a new form of regulated cell death caused by the accumulation of iron-mediated lipid peroxidation, has been found in several diseases including I/R injury, which was reported to be suppressed by flavonoids. Baicalein (BAI) and luteolin (Lut) are flavonoids and were shown to reduce the myocardial I/R injury. BAI was found to suppress ferroptosis in cancer cells via reducing reactive oxygen species (ROS) generation. However, the anti-ferroptosis effect of Lut on ferroptosis has not been reported. This study aimed to investigate whether ferroptosis reduction contributes to the BAI- and Lut-protected cardiomyocytes.

METHODS

This research used erastin, RSL3, and Fe-SP to induce ferroptosis. Cell viability was examined using MTT assay. Annexin V-FITC, CM-H₂DCFDA, and Phen Green SK diacetate (PGSK) fluorescent intensity were detected to analyze apoptotsis, ROS levels, and Fe²⁺ concentrations, respectively. qPCR and Western blot analysis were conducted to detect the levels of mRNA and protein, respectively.

RESULTS

Our data show that BAI and Lut protected cardiomyocytes against ferroptosis caused by ferroptosis inducers and I/R. Moreover, both BAI and Lut decreased ROS and malondialdehyde (MDA) generation and the protein levels of ferroptosis markers, and restored Glutathione peroxidase 4 (GPX4) protein levels in cardiomyocytes reduced by ferroptosis inducers. BAI and Lut reduced the I/R-induced myocardium infarction and decreased the levels of Acsl4 and Ptgs2 mRNA.

CONCLUSIONS

BAI and Lut could protect the cardiomyocytes against the I/R-induced ferroptosis via suppressing accumulation of ROS and MDA.

The Roles of Iron and Ferroptosis in Human Chronic Diseases

Ferroptosis, an iron-dependent novel type of cell death, has been characterized as an excessive accumulation of lipid peroxides and reactive oxygen species. A growing number of studies demonstrate that ferroptosis not only plays an important role in the pathogenesis and progression of chronic diseases, but also functions differently in different diseases. As a double-edged sword, activation of ferroptosis could potently inhibit tumor growth and increase sensitivity to chemotherapy and immunotherapy in various cancer settings. Therefore, the development of more efficacious ferroptosis agonists or inhibitors remains the mainstay of ferroptosis-targeting strategy for cancer therapeutics or cardiovascular and cerebrovascular diseases and neurodegenerative diseases therapeutics.

The emerging roles of ferroptosis in cells of the central nervous system

Ferroptosis is morphologically characterized by shrunken mitochondria and biochemically characterized by iron overload, lipid peroxidation and lipid reactive oxygen species (ROS) accumulation; these phenomena are suppressed by iron chelation, genetic inhibition of cellular iron uptake, and intervention on other pathways such as lipid metabolism. The induction of ferroptosis may be related to pathological cellular conditions in the central nervous system (CNS); thus, ferroptosis may cause disability via CNS damage. Here, we review the role of ferroptosis in the main cells of the CNS, including glial cells, neurons, and pericytes; in various diseases of the CNS; and in the interaction of glia and neurons in CNS diseases. Some small molecules and traditional Chinese drugs which inhibit ferroptosis in cells of the CNS are shown as potential therapeutic strategies for neurological diseases.

Pathogenesis of α-Synuclein in Parkinson's Disease: From a Neuron-Glia Crosstalk Perspective

Parkinson's disease (PD) is a progressive neurodegenerative disorder. The classical behavioral defects of PD patients involve motor symptoms such as bradykinesia, tremor, and rigidity, as well as non-motor symptoms such as anosmia, depression, and cognitive impairment. Pathologically, the progressive loss of dopaminergic (DA) neurons in the substantia nigra (SN) and the accumulation of α-synuclein (α-syn)-composed Lewy bodies (LBs) and Lewy neurites (LNs) are key hallmarks. Glia are more than mere bystanders that simply support neurons, they actively contribute to almost every aspect of neuronal development and function; glial dysregulation has been implicated in a series of neurodegenerative diseases including PD. Importantly, amounting evidence has added glial activation and neuroinflammation as new features of PD onset and progression. Thus, gaining a better understanding of glia, especially neuron-glia crosstalk, will not only provide insight into brain physiology events but also advance our knowledge of PD pathologies. This review addresses the current understanding of α-syn pathogenesis in PD, with a focus on neuron-glia crosstalk. Particularly, the transmission of α-syn between neurons and glia, α-syn-induced glial activation, and feedbacks of glial activation on DA neuron degeneration are thoroughly discussed. In addition, α-syn aggregation, iron deposition, and glial activation in regulating DA neuron ferroptosis in PD are covered. Lastly, we summarize the preclinical and clinical therapies, especially targeting glia, in PD treatments.

Modulation of Cellular Circadian Rhythms by Secondary Metabolites of Lichens

Background

Most mammalian cells harbor molecular circadian clocks that synchronize physiological functions with the 24-h day-night cycle. Disruption of circadian rhythms, through genetic or environmental changes, promotes the development of disorders like obesity, cardiovascular diseases, and cancer. At the cellular level, circadian, mitotic, and redox cycles are functionally coupled. Evernic (EA) and usnic acid (UA), two lichen secondary metabolites, show various pharmacological activities including anti-oxidative, anti-inflammatory, and neuroprotective action. All these effects have likewise been associated with a functional circadian clock.

Hypothesis/Purpose

To test, if the lichen compounds EA and UA modulate circadian clock function at the cellular level.

Methods

We used three different cell lines and two circadian luminescence reporter systems for evaluating dose- and time-dependent effects of EA/UA treatment on cellular clock regulation at high temporal resolution. Output parameters studied were circadian luminescence rhythm period, amplitude, phase, and dampening rate.

Results

Both compounds had marked effects on clock rhythm amplitudes and dampening independent of cell type, with UA generally showing a higher efficiency than EA. Only in fibroblast cells, significant effects on clock period were observed for UA treated cells showing shorter and EA treated cells showing longer period lengths. Transient treatment of mouse embryonic fibroblasts at different phases had only minor clock resetting effects for both compounds.

Conclusion

Secondary metabolites of lichen alter cellular circadian clocks through amplitude reduction and increased rhythm dampening.

The Multifaceted Neurotoxicity of Astrocytes in Ageing and Age-Related Neurodegenerative Diseases: A Translational Perspective

In a healthy physiological context, astrocytes are multitasking cells contributing to central nervous system (CNS) homeostasis, defense, and immunity. In cell culture or rodent models of age-related neurodegenerative diseases (NDDs), such as Alzheimer’s disease (AD) and Parkinson’s disease (PD), numerous studies have shown that astrocytes can adopt neurotoxic phenotypes that could enhance disease progression. Chronic inflammatory responses, oxidative stress, unbalanced phagocytosis, or alteration of their core physiological roles are the main manifestations of their detrimental states. However, if astrocytes are directly involved in brain deterioration by exerting neurotoxic functions in patients with NDDs is still controversial. The large spectrum of NDDs, with often overlapping pathologies, and the technical challenges associated with the study of human brain samples complexify the analysis of astrocyte involvement in specific neurodegenerative cascades. With this review, we aim to provide a translational overview about the multi-facets of astrocyte neurotoxicity ranging from in vitro findings over mouse and human cell-based studies to rodent NDDs research and finally evidence from patient-related research. We also discuss the role of ageing in astrocytes encompassing changes in physiology and response to pathologic stimuli and how this may prime detrimental responses in NDDs. To conclude, we discuss how potentially therapeutic strategies could be adopted to alleviate or reverse astrocytic toxicity and their potential to impact neurodegeneration and dementia progression in patients.

Emerging Mechanisms and Disease Implications of Ferroptosis: Potential Applications of Natural Products

Ferroptosis, a newly discovered form of regulatory cell death (RCD), has been demonstrated to be distinct from other types of RCD, such as apoptosis, necroptosis, and autophagy. Ferroptosis is characterized by iron-dependent lipid peroxidation and oxidative perturbation, and is inhibited by iron chelators and lipophilic antioxidants. This process is regulated by specific pathways and is implicated in diverse biological contexts, mainly including iron homeostasis, lipid metabolism, and glutathione metabolism. A large body of evidence suggests that ferroptosis is interrelated with various physiological and pathological processes, including tumor progression (neuro)degenerative diseases, and hepatic and renal failure. There is an urgent need for the discovery of novel effective ferroptosis-modulating compounds, even though some experimental reagents and approved clinical drugs have been well documented to have anti- or pro-ferroptotic properties. This review outlines recent advances in molecular mechanisms of the ferroptotic death process and discusses its multiple roles in diverse pathophysiological contexts. Furthermore, we summarize chemical compounds and natural products, that act as inducers or inhibitors of ferroptosis in the prevention and treatment of various diseases. Herein, it is particularly highlighted that natural products show promising prospects in ferroptosis-associated (adjuvant) therapy with unique advantages of having multiple components, multiple biotargets and slight side effects.

Xanthohumol Protects the Rat Myocardium against Ischemia/Reperfusion Injury-Induced Ferroptosis

Ferroptosis is an iron-dependent form of cell death caused by the inactivation of glutathione peroxidase 4 (GPX4) and accumulation of lipid peroxides. Ferroptosis has been found to participate in the ischemia-reperfusion (I/R) injury, leading to heart dysfunction and myocardial cell death. Xanthohumol (XN), a prenylated flavonoid isolated from Humulus lupulus, has multiple pharmacological activities, such as anti-inflammatory and antioxidant. This study is aimed at investigating whether XN could attenuate the I/R-induced ferroptosis in cardiomyocytes and the underlying mechanisms. Cardiomyocytes were treated with Fe-SP and RSL3, and the rat hearts were treated with I/R. The results from the present study show that XN was able to protect cardiomyocytes against Fe-SP- and RSL3-induced ferroptotic cell death by decreasing the production of lipid peroxidation and ROS, chelating iron, reducing the NRF2 protein level, and modulating the protein levels of GPX4. Moreover, XN significantly decreased the mRNA levels of ferroptosis markers, Ptgs2 and Acsl4, and the protein levels of ACSL4 and NRF2 and modulated the protein levels of GPX4 in I/R-treated hearts. The findings from the present study suggest that XN might have the therapeutic potential for the I/R-induced ferroptosis injury.

Effects of lipoic acid supplementation on age- and iron-induced memory impairment, mitochondrial DNA damage and antioxidant responses

PURPOSE

To investigate the effects of lipoic acid (LA) supplementation during adulthood combined with supplementation later in life or LA administration only at old age on age-induced cognitive dysfunction, mitochondrial DNA deletions, caspase 3 and antioxidant response enzymes expression in iron-treated rats.

METHODS

Male rats were submitted to iron treatment (30 mg/kg body wt of Carbonyl iron) from 12 to 14th post-natal days. Iron-treated rats received LA supplementation (50 mg/kg, daily) in adulthood and old age or at old age only for 21 days. Memory, mitochondrial DNA (mtDNA) complex I deletions, caspase 3 mRNA expression and antioxidant response enzymes mRNA expression were analyzed in the hippocampus.

RESULTS

LA administration in adulthood combined with treatment later in life was able to reverse age-induced effects on object recognition and inhibitory avoidance memory, as well as on mtDNA deletions, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, and antioxidant enzymes disruption induced by iron in aged rats. LA treatment only at old age reversed iron-induced effects to a lesser extent when compared to the combined treatment.

CONCLUSION

The present findings support the view that LA supplementation may be considered as an adjuvant against mitochondrial damage and cognitive decline related to aging and neurodegenerative disorders.

Targeting NRF2 to suppress ferroptosis in brain injury

Brain injury is accompanied by serious iron metabolism disorder and oxidative stress. As a novel form of regulated cell death (RCD) depending on lipid peroxidation caused by iron overload, ferroptosis (FPT) further aggravates brain injury, which is different from apoptosis, autophagy and other traditional cell death in terms of biochemistry, morphology and genetics. Noteworthy, transcriptional regulator NRF2 plays a key role in the cell antioxidant system, and many genes related to FPT are under the control of NRF2, including genes for iron regulation, thiol-dependent antioxidant system, enzymatic detoxification of RCS and carbonyls, NADPH regeneration and ROS sources from mitochondria or extra-mitochondria, which place NRF2 in the key position of regulating the ferroptotic death. Importantly, NRF2 can reduce iron load and resist FPT. In the future, it is expected to open up a new way to treat brain injury by targeting NRF2 to alleviate FPT in brain.

[The role of ferroptosis in chronic diseases]

Recently, ferroptosis, an iron-dependent novel type of cell death, has been characterized as an excessive accumulation of lipid peroxides and reactive oxygen species. Emerging studies demonstrate that ferroptosis not only plays an important role in the pathogenesis and progression of chronic diseases, but also functions differently in the different disease context. Notably, it is shown that activation of ferroptosis could potently inhibit tumor growth and increase sensitivity to chemotherapy and immunotherapy in various cancer settings. As a result, the development of more efficacious ferroptosis agonists remains the mainstay of ferroptosis-targeting strategy for cancer therapeutics. By contrast, in non-cancerous chronic diseases, including cardiovascular & cerebrovascular diseases and neurodegenerative diseases, ferroptosis functions as a risk factor to promote these diseases progression through triggering or accelerating tissue injury. As a matter of fact, blocking ferroptosis has been demonstrated to effectively prevent ischemia-reperfusion heart disease in preclinical animal models. Therefore, it is a promising field to develope potent ferroptosis inhibitors for preventing and treating cardiovascular & cerebrovascular diseases and neurodegenerative diseases. In this article, we summarize the most recent progress on ferroptosis in chronic diseases, and draw attention to the possible clinical impact of this recently emerged ferroptosis modalities.

Nrf2 and Ferroptosis: A New Research Direction for Neurodegenerative Diseases

Ferroptosis is a kind of regulated cell death (RCD) caused by the redox state disorder of intracellular microenvironment controlled by glutathione (GSH) peroxidase 4 (GPX4), which is inhibited by iron chelators and lipophilic antioxidants. In addition to classical regulatory mechanisms, new regulatory factors for ferroptosis have been discovered in recent years, such as the P53 pathway, the activating transcription factor (ATF)3/4 pathway, Beclin 1 (BECN1) pathway, and some non-coding RNA. Ferroptosis is closely related to cancer treatment, neurodegenerative diseases, ischemia–reperfusion of organ, neurotoxicity, and others, in particular, in the field of neurodegenerative diseases treatment has aroused people’s interest. The nuclear factor E2 related factor 2 (Nrf2/NFE2L2) has been proved to play a key role in neurodegenerative disease treatment and ferroptosis regulation. Ferroptosis promotes the progression of neurodegenerative diseases, while the expression of Nrf2 and its target genes (Ho-1, Nqo-1, and Trx) has been declined with aging; therefore, there is still insufficient evidence for ferroptosis and Nrf2 regulatory networks in the field of neurodegenerative diseases. In this review, we will provide a brief overview of ferroptosis regulatory mechanisms, as well as an emphasis on the mechanism of Nrf2 regulating ferroptosis. We also highlight the role of ferroptosis and Nrf2 during the process of neurodegenerative diseases and investigate a theoretical basis for further research on the relationship between Nrf2 and ferroptosis in the process of neurodegenerative diseases treatment.

Exosomal Nrf2: From anti-oxidant and anti-inflammation response to wound healing and tissue regeneration in aged-related diseases

Accumulation of oxidative stress in cells is an essential feature of cellular senescence and aging. This phenomenon is involved in different age-related diseases through dysregulation of homeostasis and impairing repair and regeneration (wound healing) capacity, which can suppress antioxidant responses such as the activity of antioxidant enzymes and damaged protein clearance system. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor which regulates basal and inducible expression pattern of specific genes (antioxidants and detoxifications) through antioxidant element response (ARE) sites in the stress condition, specifically in chronic and age-related stresses. Nrf2 maintains cellular redox hemostasis and promotes rejuvenation. Exosomes are nanoscale vesicles that are released by various cells to actively regulate the complex cellular signaling networks. Exosomal-Nrf2 and exosomal-Nrf2-mediated products can modulate oxidative hemostasis in target cells to induce tissue repairing with therapeutic proposes, and regeneration capability. In this study, we summarized the role of exosomal-Nrf2 in different age-related diseases, including diabetic foot ulcers, atherosclerosis, chronic heart failure, reproductive cell failures, and neurodegenerative diseases. In addition, we briefly explained the crosstalk between plant exosomes and mammalian cell metabolism in the benefit of cellular stress suppression.

Pentraxin 3 contributes to neurogenesis after traumatic brain injury in mice

Emerging evidence indicates that pentraxin 3 is an acute-phase protein that is linked with the immune response to inflammation. It is also a newly discovered marker of anti-inflammatory A2 reactive astrocytes, and potentially has multiple protective effects in stroke; however, its role in the adult brain after traumatic brain injury is unknown. In the present study, a moderate model of traumatic brain injury in mice was established using controlled cortical impact. The models were intraventricularly injected with recombinant pentraxin 3 (the recombinant pentraxin 3 group) or an equal volume of vehicle (the control group). The sham-operated mice underwent craniotomy, but did not undergo the controlled cortical impact. The potential neuroprotective and neuroregenerative roles of pentraxin 3 were investigated on days 14 and 21 after traumatic brain injury. Western blot assay showed that the expression of endogenous pentraxin 3 was increased after traumatic brain injury in mice. Furthermore, the neurological severity test and wire grip test revealed that recombinant pentraxin 3 treatment reduced the neurological severity score and increased the wire grip score, suggesting an improved recovery of sensory-motor functions. The Morris water maze results demonstrated that recombinant pentraxin 3 treatment reduced the latency to the platform, increased the time spent in the correct quadrant, and increased the number of times traveled across the platform, thus suggesting an improved recovery of cognitive function. In addition, to investigate the effects of pentraxin 3 on astrocytes, specific markers of A2 astrocytes were detected in primary astrocyte cultures in vitro using western blot assay. The results demonstrated that pentraxin 3 administration activates A2 astrocytes. To explore the protective mechanisms of pentraxin 3, immunofluorescence staining was used. Intraventricular injection of recombinant pentraxin 3 increased neuronal maintenance in the peri-injured cortex and ipsilateral hippocampus, increased the number of doublecortin-positive neural progenitor cells in the subventricular and subgranular zones, and increased the number of bromodeoxyuridine (proliferation) and neuronal nuclear antigen (mature neuron) double-labeled cells in the hippocampus and peri-injured cortex. Pentraxin 3 administration also increased the number of neurospheres and the number of bromodeoxyuridine and doublecortin double-labeled cells in neurospheres, and enhanced the proliferation of neural progenitor cells in primary neural progenitor cell cultures in vitro. In conclusion, recombinant pentraxin 3 administration activated A2 astrocytes, and consequently improved the recovery of neural function by increasing neuronal survival and enhancing neurogenesis. All experiments were approved by the Animal Ethics Committee of the First Affiliated Hospital of Chongqing Medical University, China on March 1, 2016.

Crosstalk of Nrf2 with the Trace Elements Selenium, Iron, Zinc, and Copper

Trace elements, like Cu, Zn, Fe, or Se, are important for the proper functioning of antioxidant enzymes. However, in excessive amounts, they can also act as pro-oxidants. Accordingly, trace elements influence redox-modulated signaling pathways, such as the Nrf2 pathway. Vice versa, Nrf2 target genes belong to the group of transport and metal binding proteins. In order to investigate whether Nrf2 directly regulates the systemic trace element status, we used mice to study the effect of a constitutive, whole-body Nrf2 knockout on the systemic status of Cu, Zn, Fe, and Se. As the loss of selenoproteins under Se-deprived conditions has been described to further enhance Nrf2 activity, we additionally analyzed the combination of Nrf2 knockout with feeding diets that provide either suboptimal, adequate, or supplemented amounts of Se. Experiments revealed that the Nrf2 knockout partially affected the trace element concentrations of Cu, Zn, Fe, or Se in the intestine, liver, and/or plasma. However, aside from Fe, the other three trace elements were only marginally modulated in an Nrf2-dependent manner. Selenium deficiency mainly resulted in increased plasma Zn levels. One putative mediator could be the metal regulatory transcription factor 1, which was up-regulated with an increasing Se supply and downregulated in Se-supplemented Nrf2 knockout mice.

Astragaloside IV and ferulic acid synergistically promote neurite outgrowth through Nrf2 activation

Recently, nuclear factor (erythroid-derived 2)-like 2 (Nrf2) have nuclear localization and nuclear exclusion signals and shuttle between the cytoplasm and the nucleus. Thus, we hypothesised that astragaloside IV (AS-IV) induction nuclear import of Nrf2 and ferulic acid (FA) inhibition nuclear export of Nrf2 contribute to synergistic antioxidant effects of combination of FA and AS-IV (FA/AS-IV). Here, we have demonstrated that FA/AS-IV enhances neurite outgrowth of PC12 cells challenged with lead acetate (PbAc) via antioxidant properties in a synergistic manner. Concomitantly, FA/AS-IV significantly promotes Nrf2 activation and induces "phase-II'' enzymes during PbAc toxicity, compared with either FA or AS-IV alone. Interestingly, FA but not AS-IV activates the extracellular signal-regulated kinases 1 and 2 (ERK1/2), leading to an increase in both de novo synthesis of Nrf2 and nuclear import of Nrf2. Simultaneously, AS-IV but not FA suppresses Fyn phosphorylation via Akt-mediated inhibition of GSK-3β, which inhibited nuclear export of Nrf2. Importantly, dual activation of both ERK1/2 and Akt by FA/AS-IV in PC12 cells challenged with PbAc is mediated by independent mechanisms, which are supported by pharmacological inhibitors. Collectively, these results support the notion that the FA/AS-IV may be promising in therapy for lead developmental neurotoxicity. This combination deserves further study in vivo.

Circadian control of BDNF-mediated Nrf2 activation in astrocytes protects dopaminergic neurons from ferroptosis

Astrocyte-neuron interactions protect neurons from iron-mediated toxicity. As dopamine can be metabolized to reactive quinones, dopaminergic neurons are susceptible to oxidative damage and ferroptosis-like induced cell death. Detoxification enzymes are required to protect neurons. Brain-derived neurotrophic factor (BDNF) plays a key role in the regulation of redox sensitive transcription factor Nrf2 in astrocytes and metabolic cooperation between astrocytes and neurons. This article reviews the importance of BDNF and astrocyte-neuron interactions in the protection of neurons against oxidative damages in rodent brains. We previously proposed that BDNF activates Nrf2 via the truncated TrkB.T1 and p75^NTR receptor complex in astrocytes. Stimulation by BDNF generates the signaling molecule ceramide, which activates PKCζ leading to induction of the CK2-Nrf2 signaling axis. As a cell clock regulates p75^NTR expression, we suggested that BDNF effectively activates Nrf2 in astrocytes during the rest phase. In contrast, neurons express both TrkB.FL and TrkB.T1, and TrkB.FL tyrosine kinase activity inhibits p75^NTR-dependent ceramide generation and internalizes p75^NTR. Therefore, BDNF may not effectively activate Nrf2 in neurons. Notably, neurons only weakly activate detoxification and antioxidant enzymes/proteins via the Nrf2-ARE signaling axis. Thus, astrocytes may provide relevant transcripts and/or proteins to neurons via microparticles/exosomes increasing neuronal resistance to oxidative stress. Circadian increases in the levels of circulating glucocorticoids may further facilitate material transfer from astrocytes to neurons via the stimulation of pannexin 1 channels-P2X7R signaling pathway in astrocytes at the beginning of the active phase. Dysregulation of astrocyte-neuron interactions could therefore contribute to the pathogenesis of neurodegenerative diseases including Parkinson's disease.

Ferroptosis and Its Role in Diverse Brain Diseases

Ferroptosis is a recently identified, iron-regulated, non-apoptotic form of cell death. It is characterized by cellular accumulation of lipid reactive oxygen species that ultimately leads to oxidative stress and cell death. Although first identified in cancer cells, ferroptosis has been shown to have significant implications in several neurologic diseases, such as ischemic and hemorrhagic stroke, Alzheimer's disease, and Parkinson's disease. This review summarizes current research on ferroptosis, its underlying mechanisms, and its role in the progression of different neurologic diseases. Understanding the role of ferroptosis could provide valuable information regarding treatment and prevention of these devastating diseases.

Mechanisms of Endogenous Neuroprotective Effects of Astrocytes in Brain Injury

Astrocytes, once believed to serve only as "glue" for the structural support of neurons, have been demonstrated to serve critical functions for the maintenance and protection of neurons, especially under conditions of acute or chronic injury. There are at least seven distinct mechanisms by which astrocytes protect neurons from damage; these are (1) protection against glutamate toxicity, (2) protection against redox stress, (3) mediation of mitochondrial repair mechanisms, (4) protection against glucose-induced metabolic stress, (5) protection against iron toxicity, (6) modulation of the immune response in the brain, and (7) maintenance of tissue homeostasis in the presence of DNA damage. Astrocytes support these critical functions through specialized responses to stress or toxic conditions. The detoxifying activities of astrocytes are essential for maintenance of the microenvironment surrounding neurons and in whole tissue homeostasis. Improved understanding of the mechanisms by which astrocytes protect the brain could lead to the development of novel targets for the development of neuroprotective strategies.

Spatial-temporal expression of NDRG2 in brain tissues in a rat model of intracerebral hemorrhage: A pilot study

N-myc downstream regulated gene 2 (NDRG2) was a member of the N-myc down regulated gene family which belongs to the alpha/beta hydrolase superfamily and played important roles in cell death. To date, the expression and effects of NDRG2 in brain after intracerebral hemorrhage (ICH) are unclear. In this study, we investigated the spatial-temporal expression of NDRG2 in brain tissues in a rat model of ICH. The expression levels of NDRG2 were tested in 3h, 6h, 12h, 24h, 48h, 72h, and 7d after ICH by western blot analysis. The results showed that the NDRG2 levels were increased and peaked at 24h after ICH, and then declined subsequently. Meanwhile, we also examined the NDRG2 cellular localization in brain tissues by immunofluorescence analysis with NeuN and GFAP (biomarker of neuron and astrocytes respectively). The results demonstrated that NDRG2 was mainly expressed in astrocytes, but not neurons, after ICH. Additionally, the results of double staining indicated that the rate of NDRG2- and TUNEL -positive cells was significantly higher in the brain tissues in rats after ICH. The roles of NDRG2 in ICH needed further investigation and inhibiting the expression of NDRG2 may have potential therapeutic effects in ICH.