Oxidative injury triggers autophagy in astrocytes: the role of endogenous zinc

Emerging Perspectives in Zinc Transporter Research in Prostate Cancer: An Updated Review

Dysregulation of zinc and zinc transporters families has been associated with the genesis and progression of prostate cancer. The prostate epithelium utilizes two types of zinc transporters, the ZIP (Zrt-, Irt-related Protein) and the ZnTs (Zinc Transporter), to transport zinc from the blood plasma to the gland lumen. ZIP transporters uptake zinc from extracellular space and organelle lumen, while ZnT transporters release zinc outside the cells or to organelle lumen. In prostate cancer, a commonly observed low zinc concentration in prostate tissue has been correlated with downregulations of certain ZIPs (e.g., ZIP1, ZIP2, ZIP3, ZIP14) and upregulations of specific ZnTs (e.g., ZnT1, ZnT9, ZnT10). These alterations may enable cancer cells to adapt to toxic high zinc levels. While zinc supplementation has been suggested as a potential therapy for this type of cancer, studies have yielded inconsistent results because some trials have indicated that zinc supplementation could exacerbate cancer risk. The reason for this discrepancy remains unclear, but given the high molecular and genetic variability present in prostate tumors, it is plausible that some zinc transporters-comprising 14 ZIP and 10 ZnT members-could be dysregulated in others patterns that promote cancer. From this perspective, this review highlights novel dysregulation, such as ZIP-Up/ZnT-Down, observed in prostate cancer cell lines for ZIP4, ZIP8, ZnT2, ZnT4, ZnT5, etc. Additionally, an in silico analysis of an available microarray from mouse models of prostate cancer (Nkx3.1;Pten) predicts similar dysregulation pattern for ZIP4, ZIP8, and ZnT2, which appear in early stages of prostate cancer progression. Furthermore, similar dysregulation patterns are supported by an in silico analysis of RNA-seq data from human cancer tumors available in cBioPortal. We discuss how these dysregulations of zinc transporters could impact zinc supplementation trials, particularly focusing on how the ZIP-Up/ZnT-Down dysregulation through various mechanisms might promote prostate cancer progression.

Herpes Simplex Virus type 1 inhibits autophagy in glial cells but requires ATG5 for the success of viral replication

Herpes Simplex Virus type 1 (HSV-1) 1 is a neurotropic virus that has been associated with neurodegenerative disorders. The dysregulation of autophagy by HSV-1 has been proposed as a potential cause of neurodegeneration. While studies have extensively tackled the interaction between autophagy and HSV-1 in neurons, research in glial cells is currently limited. Our studies demonstrate that HSV-1 inhibits, but not completely blocks, the formation of autophagosomes in human oligodendroglioma- and astrocytoma- derived cell lines. These findings have been confirmed in murine oligodendrocyte precursor cells (OPCs). Finally, this study investigates the impact of autophagy on HSV-1 infection in glial cells. While the lack of basal autophagy in LC3B knockout glial cells does not have a significant effect on viral infection, cells without the autophagy-related protein ATG5 exhibit reduced viral production. The absence of ATG5 leads to a decrease in the transcription and replication of viral genes, as well as a delay in the initial stages of the formation of HSV-1 replication compartments. These findings indicate that while autophagy may not play a significant role in antiviral defense in glial cells, HSV-1 may be inhibiting autophagy to exploit non-canonical functions of certain components of the autophagic machinery, such as ATG5, to benefit its lifecycle.

Cadmium exposure induces necroptosis of porcine spleen via ROS-mediated activation of STAT1/RIPK3 signaling pathway

Cadmium (Cd), a heavy metal, is used in a wide range of applications, such as plastics, electroplating process, electronics, and so forth. Due to its bioaccumulation ability, Cd can contaminate soil, water, air and food. To determine the effect of Cd exposure on the necroptosis in pig spleen and its mechanistic investigation, we constructed a model in pigs by feeding them food containing 20 mg/kg Cd. In this study, we analyzed the effects of Cd exposure on pig spleen through HE staining, Quantitative real-time PCR (qRT-PCR), Western blot (WB), and principal component analysis (PCA). Results show that Cd exposure can destroy the structure and function of pig spleen, which is closely related to necroptosis. Further results show that Cd exposure can induce necroptosis through ROS-mediated activation of Signal transducer and activator of transcription 1/Receptor-Interacting Serine/Threonine-Protein Kinase 3 (STAT1/RIPK3) signaling pathway in pig spleen. Additionally, Cd exposure also can affect the stability of mitochondrial-associated endoplasmic reticulum membrane (MAMs) structure, which also contributes to the process of necroptosis. Our study provides insights into the physiological toxicity caused by Cd exposure.

Autophagy in the retinal neurovascular unit: New perspectives into diabetic retinopathy

Diabetic retinopathy (DR) is one of the most prevalent retinal disorders worldwide, and it is a major cause of vision impairment in individuals of productive age. Research has demonstrated the significance of autophagy in DR, which is a critical intracellular homeostasis mechanism required for the destruction and recovery of cytoplasmic components. Autophagy maintains the physiological function of senescent and impaired organelles under stress situations, thereby regulating cell fate via various signals. As the retina's functional and fundamental unit, the retinal neurovascular unit (NVU) is critical in keeping the retinal environment's stability and supporting the needs of retinal metabolism. However, autophagy is essential for the normal NVU structure and function. We discuss the strong association between DR and autophagy in this review, as well as the many kinds of autophagy and its crucial physiological activities in the retina. By evaluating the pathological changes of retinal NVU in DR and the latest advancements in the molecular mechanisms of autophagy that may be involved in the pathophysiology of DR in NVU, we seek to propose new ideas and methods for the prevention and treatment of DR.

Zinc enhances autophagic flux and lysosomal function through transcription factor EB activation and V-ATPase assembly

The stimulation of autophagy or lysosomes has been considered therapeutic for neurodegenerative disorders because the accumulation of misfolded proteins is commonly observed in the brains of individuals with these diseases. Although zinc is known to play critical roles in the functions of lysosomes and autophagy, the mechanism behind this regulatory relationship remains unclear. Therefore, in this study, we examined which mechanism is involved in zinc-mediated activation of autophagy and lysosome. Exposure to zinc at a sub-lethal concentration activated autophagy in a concentration-dependent manner in mRFP-GFP-LC3-expressing H4 glioma cells. Zinc also rescued the blocking of autophagic flux arrested by pharmaceutical de-acidification. Co-treatment with zinc attenuated the chloroquine (CQ)-induced increase in the number and size of mRFP-GFP-LC3 puncta in H4 cells and accumulation of p62 by CQ or ammonium chloride in both H4 and mouse cerebrocortical cultures. Zinc rapidly induced the expression of cathepsin B (CTSB) and cathepsin D (CTSD), representative lysosomal proteases in neurons, which appeared likely to be mediated by transcription factor EB (TFEB). We observed the translocation of TFEB from neurite to nucleus and the dephosphorylation of TFEB by zinc. The addition of cycloheximide, a chemical inhibitor of protein synthesis, inhibited the activity of CTSB and CTSD at 8 h after zinc exposure but not at 1 h, indicating that only late lysosomal activation was dependent on the synthesis of CTSB and CTSD proteins. At the very early time point, the activation of cathepsins was mediated by an increased assembly of V-ATPase on lysosomes and resultant lysosomal acidification. Finally, considering that P301L mutation in tau protein causes frontotemporal dementia through aggressive tau accumulation, we investigated whether zinc reduces the accumulation of protein aggregates in SK-N-BE(2)-C neuroblastoma cells expressing wild-type tau or mutant P301L-tau. Zinc markedly attenuated the levels of phosphorylated tau and total tau as well as p62 in both wild-type and mutant tau-overexpressing cells. We also observed that zinc was more effective than rapamycin at inducing TFEB-dependent CTSB and CTSD expression and V-ATPase-dependent lysosomal acidification and CTSB/CTSD activation. These results suggest that the regulation of zinc homeostasis could be a new approach for developing treatments for neurodegenerative diseases, including Alzheimer’s and Parkinson’s.

Free radical biology in neurological manifestations: mechanisms to therapeutics interventions

Recent advancements and growing attention about free radicals (ROS) and redox signaling enable the scientific fraternity to consider their involvement in the pathophysiology of inflammatory diseases, metabolic disorders, and neurological defects. Free radicals increase the concentration of reactive oxygen and nitrogen species in the biological system through different endogenous sources and thus increased the overall oxidative stress. An increase in oxidative stress causes cell death through different signaling mechanisms such as mitochondrial impairment, cell-cycle arrest, DNA damage response, inflammation, negative regulation of protein, and lipid peroxidation. Thus, an appropriate balance between free radicals and antioxidants becomes crucial to maintain physiological function. Since the 1brain requires high oxygen for its functioning, it is highly vulnerable to free radical generation and enhanced ROS in the brain adversely affects axonal regeneration and synaptic plasticity, which results in neuronal cell death. In addition, increased ROS in the brain alters various signaling pathways such as apoptosis, autophagy, inflammation and microglial activation, DNA damage response, and cell-cycle arrest, leading to memory and learning defects. Mounting evidence suggests the potential involvement of micro-RNAs, circular-RNAs, natural and dietary compounds, synthetic inhibitors, and heat-shock proteins as therapeutic agents to combat neurological diseases. Herein, we explain the mechanism of free radical generation and its role in mitochondrial, protein, and lipid peroxidation biology. Further, we discuss the negative role of free radicals in synaptic plasticity and axonal regeneration through the modulation of various signaling molecules and also in the involvement of free radicals in various neurological diseases and their potential therapeutic approaches. The primary cause of free radical generation is drug overdosing, industrial air pollution, toxic heavy metals, ionizing radiation, smoking, alcohol, pesticides, and ultraviolet radiation. Excessive generation of free radicals inside the cell R1Q1 increases reactive oxygen and nitrogen species, which causes oxidative damage. An increase in oxidative damage alters different cellular pathways and processes such as mitochondrial impairment, DNA damage response, cell cycle arrest, and inflammatory response, leading to pathogenesis and progression of neurodegenerative disease other neurological defects.

Research progress on astrocyte autophagy in ischemic stroke

Ischemic stroke is a highly disabling and potentially fatal disease. After ischemic stroke, autophagy plays a key regulatory role as an intracellular catabolic pathway for misfolded proteins and damaged organelles. Mounting evidence indicates that astrocytes are strongly linked to the occurrence and development of cerebral ischemia. In recent years, great progress has been made in the investigation of astrocyte autophagy during ischemic stroke. This article summarizes the roles and potential mechanisms of astrocyte autophagy in ischemic stroke, briefly expounds on the crosstalk of astrocyte autophagy with pathological mechanisms and its potential protective effect on neurons, and reviews astrocytic autophagy-targeted therapeutic methods for cerebral ischemia. The broader aim of the report is to provide new perspectives and strategies for the treatment of cerebral ischemia and a reference for future research on cerebral ischemia.

Zinc Deficiency Induces Autophagy in HT-22 Mouse Hippocampal Neuronal Cell Line

Zinc is a trace metal vital for various functions in nerve cells, although the effect of zinc deficiency on neuronal autophagy remains unclear. This study aimed to elucidate whether zinc deficiency induced by treatment with N, N, N′, N′-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN), a zinc chelator, affects and alters autophagy activity. In cell viability assays, TPEN showed cytotoxicity in HT-22 cells. TPEN treatment also increased LC3-II levels and the ratio of LC3-II to LC3-I. Western blot analysis showed that phospho-AMP-activated protein kinase levels and the ratio of phospho-AMP-activated protein kinase to total AMP-activated protein kinase increased. Protein levels of the mammalian target of rapamycin and sirtuin 1 decreased following TPEN treatment. When TPEN-treated HT-22 cells were cotreated with autophagy inhibitors, 3-methyladenine (1 mM), or bafilomycin A1 (3 nM), the TPEN-induced decrease in cell viability was exacerbated. Cotreatment with chloroquine (10 μM) partially restored cell viability. The study showed that zinc deficiency induces autophagy and may be cytoprotective in neurons. We expect our results to add a new perspective to our understanding of the neuronal pathology related to zinc deficiency.

Zinc in Cognitive Impairment and Aging

Zinc, an essential micronutrient for life, was first discovered in 1869 and later found to be indispensable for the normal development of plants and for the normal growth of rats and birds. Zinc plays an important role in many physiological and pathological processes in normal mammalian brain development, especially in the development of the central nervous system. Zinc deficiency can lead to neurodegenerative diseases, mental abnormalities, sleep disorders, tumors, vascular diseases, and other pathological conditions, which can cause cognitive impairment and premature aging. This study aimed to review the important effects of zinc and zinc-associated proteins in cognitive impairment and aging, to reveal its molecular mechanism, and to highlight potential interventions for zinc-associated aging and cognitive impairments.

Cross-Talk between Amyloid, Tau Protein and Free Radicals in Post-Ischemic Brain Neurodegeneration in the Form of Alzheimer’s Disease Proteinopathy

Recent years have seen remarkable progress in research into free radicals oxidative stress, particularly in the context of post-ischemic recirculation brain injury. Oxidative stress in post-ischemic tissues violates the integrity of the genome, causing DNA damage, death of neuronal, glial and vascular cells, and impaired neurological outcome after brain ischemia. Indeed, it is now known that DNA damage and repair play a key role in post-stroke white and gray matter remodeling, and restoring the integrity of the blood-brain barrier. This review will present one of the newly characterized mechanisms that emerged with genomic and proteomic development that led to brain ischemia to a new level of post-ischemic neuropathological mechanisms, such as the presence of amyloid plaques and the development of neurofibrillary tangles, which further exacerbate oxidative stress. Finally, we hypothesize that modified amyloid and the tau protein, along with the oxidative stress generated, are new key elements in the vicious circle important in the development of post-ischemic neurodegeneration in a type of Alzheimer’s disease proteinopathy.

Cholesterol Dysmetabolism in Alzheimer's Disease: A Starring Role for Astrocytes?

In recent decades, the impairment of cholesterol metabolism in the pathogenesis of Alzheimer’s disease (AD) has been intensively investigated, and it has been recognized to affect amyloid β (Aβ) production and clearance, tau phosphorylation, neuroinflammation and degeneration. In particular, the key role of cholesterol oxidation products, named oxysterols, has emerged. Brain cholesterol metabolism is independent from that of peripheral tissues and it must be preserved in order to guarantee cerebral functions. Among the cells that help maintain brain cholesterol homeostasis, astrocytes play a starring role since they deliver de novo synthesized cholesterol to neurons. In addition, other physiological roles of astrocytes are to modulate synaptic transmission and plasticity and support neurons providing energy. In the AD brain, astrocytes undergo significant morphological and functional changes that contribute to AD onset and development. However, the extent of this contribution and the role played by oxysterols are still unclear. Here we review the current understanding of the physiological role exerted by astrocytes in the brain and their contribution to AD pathogenesis. In particular, we focus on the impact of cholesterol dysmetabolism on astrocyte functions suggesting new potential approaches to develop therapeutic strategies aimed at counteracting AD development.

Dietary and Physiological Effects of Zinc on the Immune System

Evidence for the importance of zinc for all immune cells and for mounting an efficient and balanced immune response to various environmental stressors has been accumulating in recent years. This article describes the role of zinc in fundamental biological processes and summarizes our current knowledge of zinc's effect on hematopoiesis, including differentiation into immune cell subtypes. In addition, the important role of zinc during activation and function of immune cells is detailed and associated with the specific immune responses to bacteria, parasites, and viruses. The association of zinc with autoimmune reactions and cancers as diseases with increased or decreased immune responses is also discussed. This article provides a broad overview of the manifold roles that zinc, or its deficiency, plays in physiology and during various diseases. Consequently, we discuss why zinc supplementation should be considered, especially for people at risk of deficiency. Expected final online publication date for the Annual Review of Nutrition, Volume 41 is September 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

HIF-1α in the Crosstalk Between Reactive Oxygen Species and Autophagy Process: A Review in Multiple Sclerosis

Cellular stress can lead to the production of reactive oxygen species (ROS) while autophagy, as a catabolic pathway, protects the cells against stress. Autophagy in its turn plays a pivotal role in the pathophysiology of multiple sclerosis (MS). In the current review, we first summarized the contribution of ROS and autophagy to MS pathogenesis. Then probable crosstalk between these two pathways through HIF-1α for the first time has been proposed with the hope of employing a better understanding of MS pathophysiology and probable therapeutic approaches.

Oxidative stress induced by methomyl exposure reduces the quality of early embryo development in mice

Methomyl is a widely used carbamate insecticide and environmental oestrogen that has adverse effects on the reproductive system. However, there have been no reports on the effect of methomyl on early embryos in mammals. In this study, we explored the effect of methomyl exposure on the quality of early embryonic development in mice and the possible mechanisms. During in vitro culture, different concentrations of methomyl (10, 20, 30 and 35 μM) were added to mouse zygote medium. The results showed that methomyl had an adverse effect on early embryonic development. Compared with the control group, the addition of 30 μM methomyl significantly reduced the rate of early embryo blastocyst formation. Methomyl exposure can increase oxidative stress and impair mitochondrial function, which may be the cause of blastocyst formation. In addition, we found that methomyl exposure promoted apoptosis and autophagy in mouse blastocysts. The toxic effect of methomyl on early embryos may be the result of oxidative stress induction. Taken together, our results indicate that methomyl can cause embryonic development defects in mice, thereby reducing the quality of early embryo development.

Interplay Between Autophagy and Zinc

Autophagy is a conserved catabolic process that plays an important role in cellular homeostasis. The study of the interplay between autophagy and zinc has gained interest over the last years. Multiple studies have indicated that zinc stimulates autophagy and is critical for basal and induced autophagy in mammalian cells. Conversely, autophagy is induced by zinc starvation in yeast. There are no studies analyzing the role of zinc in either Microautophagy or Chaperone-Mediated-Autophagy. The mechanisms by which zinc modulates autophagy are still poorly understood. Studies examining loss of function of genes involved in cellular zinc homeostasis have provided novel insights into the role of zinc in autophagy. Autophagy may help cells adapt to changes in zinc availability in medium by controlling zinc mobilization, recycling, and secretion. Zinc is a key player in toxic and protective autophagy.

Autophagy in Multiple Sclerosis: Two Sides of the Same Coin

Multiple sclerosis (MS) is a complex auto-immune disorder of the central nervous system (CNS) that involves a range of CNS and immune cells. MS is characterized by chronic neuroinflammation, demyelination, and neuronal loss, but the molecular causes of this disease remain poorly understood. One cellular process that could provide insight into MS pathophysiology and also be a possible therapeutic avenue, is autophagy. Autophagy is an intracellular degradative pathway essential to maintain cellular homeostasis, particularly in neurons as defects in autophagy lead to neurodegeneration. One of the functions of autophagy is to maintain cellular homeostasis by eliminating defective or superfluous proteins, complexes, and organelles, preventing the accumulation of potentially cytotoxic damage. Importantly, there is also an intimate and intricate interplay between autophagy and multiple aspects of both innate and adaptive immunity. Thus, autophagy is implicated in two of the main hallmarks of MS, neurodegeneration, and inflammation, making it especially important to understand how this pathway contributes to MS manifestation and progression. This review summarizes the current knowledge about autophagy in MS, in particular how it contributes to our understanding of MS pathology and its potential as a novel therapeutic target.

Mammalian Sterile 20-Like Kinase (MST) 1/2: Crucial Players in Nervous and Immune System and Neurological Disorders

As central components of the Hippo signaling pathway in mammals, the mammalian sterile 20-like kinase 1 (MST1) and MST2 protein kinases regulate cell proliferation, survival, and death and are involved in the homeostasis of many tissues. Recent studies have elucidated the roles of MST1 and MST2 in the nervous system and immune system, particularly in neurological disorders, which are influenced by aging. In this review, we provide a comprehensive overview of these research areas. First, the activation mechanisms and roles of MST1 and MST2 in neurons, non-neuronal cells, and immune cells are introduced. The roles of MST1 and MST2 in neurological disorders, including brain tumors, cerebrovascular diseases, neurodegenerative disorders, and neuromuscular disorders, are then presented. Finally, the existing obstacles for further research are discussed. Collectively, the information compiled herein provides a common framework for the function of MST1 and MST2 in the nervous system, should contribute to the design of further experiments, and sheds light on potential treatments for aging associated neurological disorders.

A role of metallothionein-3 in radiation-induced autophagy in glioma cells

Although metallothionein-3 (MT3), a brain-enriched form of metallothioneins, has been linked to Alzheimer's disease, little is known regarding the role of MT3 in glioma. As MT3 plays a role in autophagy in astrocytes, here, we investigated its role in irradiated glioma cells. Irradiation increased autophagy flux in GL261 glioma cells as evidenced by increased levels of LC3-II but decreased levels of p62 (SQSTM1). Indicating that autophagy plays a cytoprotective role in glioma cell survival following irradiation, measures inhibiting autophagy flux at various steps decreased their clonogenic survival of irradiated GL261 as well as SF295 and U251 glioma cells. Knockdown of MT3 with siRNA in irradiated glioma cells induced arrested autophagy, and decreased cell survival. At the same time, the accumulation of labile zinc in lysosomes was markedly attenuated by MT3 knockdown. Indicating that such zinc accumulation was important in autophagy flux, chelation of zinc with tetrakis-(2-pyridylmethyl)ethylenediamine (TPEN), induced arrested autophagy in and reduced survival of GL261 cells following irradiation. Suggesting a possible mechanism for arrested autophagy, MT3 knockdown and zinc chelation were found to impair lysosomal acidification. Since autophagy flux plays a cytoprotective role in irradiated glioma cells, present results suggest that MT3 and zinc may be regarded as possible therapeutic targets to sensitize glioma cells to ionizing radiation therapy.

l-carnitine supplementation during in vitro culture regulates oxidative stress in embryos from bovine aged oocytes

Aging oocytes undergo various molecular, cellular, and biochemical changes. Aging of oocytes results in reduced embryo developmental capacity and blastocyst quality, which is thought to be caused partly by the accumulation of reactive oxygen species (ROS). This study aimed to determine the effect of l-carnitine (LC) on the development of embryos formed from aged oocytes in vitro. The development and quality of the blastocysts in the LC-treated group were significantly higher than those in the untreated aged group after in vitro fertilization (IVF). In addition, after LC treatment, the level of intracellular ROS in aged group significantly decreased, and glutathione (GSH) levels significantly increased compared with those in the untreated aged group. There was no significant difference in the mitochondrial membrane potential among the three groups. Moreover, ROS could induce autophagy and LC3 antibody was widely used as a marker for detecting autophagy. The fluorescence intensity of LC3 in the aged group was significantly higher than that of LC3 in the LC-treated group. Furthermore, Real-time reverse transcriptase-polymerase chain reaction showed that the mRNA levels of antioxidation genes GPX4 and SOD1 were significantly higher in embryos from LC-treated group than in those from the untreated aged group. In summary, our results indicated that LC can improve the developmental capacity of embryos from aging oocytes in vitro by reducing oxidative stress.

Astrocytes autophagy in aging and neurodegenerative disorders

Astrocytes can serve multiple functions in maintaining cellular homeostasis of the central nervous system (CNS), and normal functions for autophagy in astrocytes is considered to have very vital roles in the pathogenesis of aging and neurodegenerative diseases. Autophagy is a major intracellular lysosomal (or its yeast analog, vacuolar) clearance pathways involved in the degradation and recycling of long-lived proteins, oxidatively damaged proteins and dysfunctional organelles by lysosomes. Current evidence has shown that autophagy might influence inflammation, oxidative stress, aging and function of astrocytes. Although the interrelation between autophagy and inflammation, oxidative stress, aging or neurological disorders have been addressed in detail, the influence of astrocytes mediated-autophagy in aging and neurodegenerative disorders has yet to be fully reviewed. In this review, we will summarize the most up-to-date findings and highlight the role of autophagy in astrocytes and link autophagy of astrocytes to aging and neurodegenerative diseases. Due to the prominent roles of astrocytic autophagy in age-related neurodegenerative diseases, we believe that we can provide new suggestions for the treatment of these disorders.

Zinc Oxide Nanoparticles Induce Autophagy and Apoptosis via Oxidative Injury and Pro-Inflammatory Cytokines in Primary Astrocyte Cultures

The present study examined the potential toxic concentrations of zinc oxide nanoparticles (ZnO NPs) and associated autophagy and apoptosis-related injuries in primary neocortical astrocyte cultures. Concentrations of ZnO NPs ≥3 μg/mL induced significant toxicity in the astrocytes. At 24 h after exposure to the ZnO NPs, transmission electron microscopy revealed swelling of the endoplasmic reticulum (ER) and increased numbers of autophagolysosomes in the cultured astrocytes, and increased levels of LC3 (microtubule-associated protein 1 light chain 3)-mediated autophagy were identified by flow cytometry. Apoptosis induced by ZnO NP exposure was confirmed by the elevation of caspase-3/7 activity and 4′,6′-diamidino-2-phenylindole (DAPI) staining. Significant (p < 0.05) changes in the levels of glutathione peroxidase, superoxide dismutase, tumor necrosis factor (TNF-α), and interleukin-6 were observed by enzyme-linked immunoassay (ELISA) assay following the exposure of astrocyte cultures to ZnO NPs. Phosphatidylinositol 3-kinase (PI3K)/mitogen-activated protein kinase (MAPK) dual activation was induced by ZnO NPs in a dose-dependent manner. Additionally, the Akt (protein kinase B) inhibitor BML257 and the mTOR (mammalian target of rapamycin) inhibitor rapamycin contributed to the survival of astrocytes. Inhibitors of cyclooxygenase-2 and lipoxygenase attenuated ZnO NP-induced toxicity. Calcium-modulating compounds, antioxidants, and zinc/iron chelators also decreased ZnO NP-induced toxicity. Together, these results suggest that ZnO NP-induced autophagy and apoptosis may be associated with oxidative stress and the inflammatory process in primary astrocyte cultures.

Lysosome-specific sensing and imaging of pH variations in vitro and in vivo utilizing a near-infrared boron complex

A NIR lysosome-targeting boron complex has been developed based on hemicyanine for monitoring pH variations in vitro and in vivo.

Superiority of SpiroZin2 Versus FluoZin-3 for monitoring vesicular Zn2+ allows tracking of lysosomal Zn2+ pools

Small-molecule fluorescent probes are powerful and ubiquitous tools for measuring the concentration and distribution of analytes in living cells. However, accurate characterization of these analytes requires rigorous evaluation of cell-to-cell heterogeneity in fluorescence intensities and intracellular distribution of probes. In this study, we perform a parallel and systematic comparison of two small-molecule fluorescent vesicular Zn²⁺ probes, FluoZin-3 AM and SpiroZin2, to evaluate each probe for measurement of vesicular Zn²⁺ pools. Our results reveal that SpiroZin2 is a specific lysosomal vesicular Zn²⁺ probe and affords uniform measurement of resting Zn²⁺ levels at the single cell level with proper calibration. In contrast, FluoZin-3 AM produces highly variable fluorescence intensities and non-specifically localizes in the cytosol and multiple vesicular compartments. We further applied SpiroZin2 to lactating mouse mammary epithelial cells and detected a transient increase of lysosomal free Zn²⁺ at 24-hour after lactation hormone treatment, which implies that lysosomes play a role in the regulation of Zn²⁺ homeostasis during lactation. This study demonstrates the need for critical characterization of small-molecule fluorescent probes to define the concentration and localization of analytes in different cell populations, and reveals SpiroZin2 to be capable of reporting diverse perturbations to lysosomal Zn²⁺.

Impaired Autophagy of GABAergic Interneurons in Neuropathic Pain

Neuropathic pain (NP) is caused by lesions of the peripheral fibers and central neurons in the somatosensory nervous system and affects 7-10% of the general population. Although the distinct cause of neuropathic pain has been investigated in primary afferent neurons over the years, pain modulation by central sensitization remains controversial. NP is believed to be driven by cell type-specific spinal synaptic plasticity in the dorsal horn. Upon intense afferent stimulation, spinothalamic tract neurons are potentiated, whereas GABAergic interneurons are inhibited leading to long-term depression. Growing evidences suggest that the inhibition of GABAergic neurons plays pivotal roles in the manifestation of neuropathic and inflammatory pain states. Downregulation of GABA transmission and impairment of GABAergic interneurons in the dorsal horn are critical consequences after spinal cord and peripheral nerve injuries. These impairments in GABAergic interneurons may be associated with dysfunctional autophagy, resulting in neuropathic pain. Here, we review an emerging number of investigations that suggest a pivotal role of impaired autophagy of GABAergic interneurons in NP. We discuss relevant research spurring the development of new targets and therapeutic agents of NP and emphasize the need for a multidisciplinary approach to manage NP in the future.

Zinc mitigates renal ischemia-reperfusion injury in rats by modulating oxidative stress, endoplasmic reticulum stress, and autophagy

Oxidative stress is a major factor involved in the pathogenesis of renal ischemia/reperfusion (I/R). Exogenous zinc (Zn) was suggested as a potent antioxidant; however, the mechanism by which it strengthens the organ resistance against the effects of reactive oxygen species (ROS) is not yet investigated. The present study aims to determine whether acute zinc chloride (ZnCl₂ ) administration could attenuate endoplasmic reticulum (ER) stress, autophagy, and inflammation after renal I/R. Rats were subjected to either sham operation (Sham group, n = 6), or 1 hr of bilateral ischemia followed by 2 hr of reperfusion (I/R groups, n = 6), or they received ZnCl₂ orally 24 hr and 30 min before ischemia (ZnCl₂ group, n = 6). Rats were subjected to 1 hr of bilateral renal ischemia followed by 2 hr of reperfusion (I/R group, n = 6). Our results showed that ZnCl₂ enhances renal function and reduces cytolysis (p < 0,05). In addition, it increased significantly the activities of antioxidant enzymes (SOD, CAT, and GPX) and the level of GSH in comparison to I/R (p < 0,05). Interestingly, ZnCl₂ treatment resulted in significant decreased ER stress, as reflected by GRP78, ATF-6,p-eIF-2α, XPB-1, and CHOP downregulaion. Rats undergoing ZnCl₂ treatment demonstrated a low expression of autophagy parameters (Beclin-1 and LAMP-2), which was correlated with low induction of apoptosis (caspase-9, caspase-3, and p-JNK), and reduction of inflammation (IL-1ß, IL-6, and MCP-1) (p < 0,05). In conclusion, we demonstrated the potential effect of Zn supplementation to modulate ER pathway and autophagic process after I/R.

Polyamine Metabolism and Oxidative Protein Folding in the ER as ROS-Producing Systems Neglected in Virology

Reactive oxygen species (ROS) are produced in various cell compartments by an array of enzymes and processes. An excess of ROS production can be hazardous for normal cell functioning, whereas at normal levels, ROS act as vital regulators of many signal transduction pathways and transcription factors. ROS production is affected by a wide range of viruses. However, to date, the impact of viral infections has been studied only in respect to selected ROS-generating enzymes. The role of several ROS-generating and -scavenging enzymes or cellular systems in viral infections has never been addressed. In this review, we focus on the roles of biogenic polyamines and oxidative protein folding in the endoplasmic reticulum (ER) and their interplay with viruses. Polyamines act as ROS scavengers, however, their catabolism is accompanied by H₂O₂ production. Hydrogen peroxide is also produced during oxidative protein folding, with ER oxidoreductin 1 (Ero1) being a major source of oxidative equivalents. In addition, Ero1 controls Ca²⁺ efflux from the ER in response to e.g., ER stress. Here, we briefly summarize the current knowledge on the physiological roles of biogenic polyamines and the role of Ero1 at the ER, and present available data on their interplay with viral infections.

Effect of zinc intake on hepatic autophagy during acute alcohol intoxication

Autophagy is a conserved mechanism that plays a housekeeping role by eliminating protein aggregates and damaged organelles. Recent studies have demonstrated that acute ethanol intoxication induces hepatic autophagy in mice. The effect of dietary zinc intake on hepatic autophagic flux during ethanol intoxication has not been evaluated using animal models. Herein, we investigated whether zinc deficiency and excess can affect autophagic flux in the liver in mice and in human hepatoma cells acutely exposed to ethanol. A mouse model of binge ethanol feeding was utilized to analyze the effect of low, adequate, and high zinc intake on hepatic autophagic flux during ethanol intoxication. Autophagic flux was inferred by analyzing LC3II/LC3I ratio, protein levels of p62/SQSTM1, Beclin1 and Atg7, and phosphorylation of 4EBP1. In addition, the degradation of the fusion protein LC3-GFP and the formation of autophagosomes and autolysosomes were evaluated in cells. Ethanol treatment stimulated autophagy in mice and cells. High zinc intake resulted in enhanced autophagy in mice exposed to ethanol. Conversely, zinc deficiency was consistently associated with impaired ethanol-induced autophagy in mice and cells. Zinc-deficient mice exhibited a high degree of ethanol-driven steatosis. Furthermore, zinc depletion increased apoptosis in cells exposed to ethanol. The results of this study suggest that adequate zinc intake is necessary for proper stimulation of autophagy by ethanol. Poor zinc status is commonly found among alcoholics and could likely contribute to faulty autophagy.

Free Radical Damage in Ischemia-Reperfusion Injury: An Obstacle in Acute Ischemic Stroke after Revascularization Therapy

Acute ischemic stroke is a common cause of morbidity and mortality worldwide. Thrombolysis with recombinant tissue plasminogen activator and endovascular thrombectomy are the main revascularization therapies for acute ischemic stroke. However, ischemia-reperfusion injury after revascularization therapy can result in worsening outcomes. Among all possible pathological mechanisms of ischemia-reperfusion injury, free radical damage (mainly oxidative/nitrosative stress injury) has been found to play a key role in the process. Free radicals lead to protein dysfunction, DNA damage, and lipid peroxidation, resulting in cell death. Additionally, free radical damage has a strong connection with inducing hemorrhagic transformation and cerebral edema, which are the major complications of revascularization therapy, and mainly influencing neurological outcomes due to the disruption of the blood-brain barrier. In order to get a better clinical prognosis, more and more studies focus on the pharmaceutical and nonpharmaceutical neuroprotective therapies against free radical damage. This review discusses the pathological mechanisms of free radicals in ischemia-reperfusion injury and adjunctive neuroprotective therapies combined with revascularization therapy against free radical damage.

Salvianolic acid B protects hepatocytes from H2O2 injury by stabilizing the lysosomal membrane

AIM

To investigate the capability of salvianolic acid B (Sal B) to protect hepatocytes from hydrogen peroxide (H2O2)/carbon tetrachloride (CCl4)-induced lysosomal membrane permeabilization.

METHODS

Cell Counting Kit-8 assay was used to measure cell viability. Apoptosis and death were assayed through flow cytometry. BrdU incorporation was used to detect cell proliferation. Serum alanine aminotransferase activity and liver malondialdehyde (MDA) content were measured. Liver histopathological changes were evaluated using hematoxylin-eosin staining. Lysosomal membrane permeability was detected with LysoTracker Green-labeled probes and acridine orange staining. The levels of protein carbonyl content (PCC), cathepsins (Cat)B/D, and lysosome-associated membrane protein 1 (LAMP1) were evaluated through western blotting. Cytosol CatB activity analysis was performed with chemiluminescence detection. The mRNA level of LAMP1 was evaluated through quantitative real-time polymerase chain reaction.

RESULTS

Results indicated that H2O2 induced cell injury/death. Sal B attenuated H2O2-induced cell apoptosis and death, restored the inhibition of proliferation, decreased the amount of PCC, and stabilized the lysosome membrane by increasing the LAMP1 protein level and antagonizing CatB/D leakage into the cytosol. CCl4 also triggered hepatocyte death. Furthermore, Sal B effectively rescued hepatocytes by increasing LAMP1 expression and by reducing lysosomal enzyme translocation to the cytosol.

CONCLUSION

Sal B protected mouse embryonic hepatocytes from H2O2/CCl4-induced injury/death by stabilizing the lysosomal membrane.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Autophagy associated cytotoxicity and cellular uptake mechanisms of bismuth nanoparticles in human kidney cells

Bismuth compounds have been used for treatment of bacterial infection, and recently bismuth nanoparticles (BiNP) were synthesized for imaging and diagnostic purpose, while safety concern of bismuth cannot be ignored. Here, we prepared ultrasmall BiNP and showed an enhanced tumor imaging, but BiNP revealed a differentiated cytotoxicity in human embryonic kidney 293 cells (HEK293) compared to other cell types. For the first time, we found that BiNP can induce autophagy, shown as the increase of monodansylcadaverine fluorescence staining and the amount of LC3II that can be inhibited by 3-MA. BiNP were capable of entering cells in a dose and time dependent manner by fluorescence and element detection methods BiNP were found to be localized in the cytoplasm observed by transmission electron microscopy and intracellular bismuth element confirmed by energy dispersive X-ray analysis. Using endocytic inhibitors, BiNP were found to require ATP and endosomal trafficking pathways for their cellular uptake. Internalized BiNP did not co-localize with EEA1, but co-localized with Lysotracker/LAMP1/LAMP2 at late time points, indicating BiNP may be retained in the non-early endosomal vacuoles and late endosomes. With our novel finding of bismuth induced autophagy and endocytic mechanisms, potential approaches may be applied to reduce the toxicity by bismuth.

Zinc starvation induces autophagy in yeast

Zinc is an essential nutrient for all forms of life. Within cells, most zinc is bound to protein. Because zinc serves as a catalytic or structural cofactor for many proteins, cells must maintain zinc homeostasis under severely zinc-deficient conditions. In yeast, the transcription factor Zap1 controls the expression of genes required for uptake and mobilization of zinc, but to date the fate of existing zinc-binding proteins under zinc starvation remains poorly understood. Autophagy is an evolutionarily conserved cellular degradation/recycling process in which cytoplasmic proteins and organelles are sequestered for degradation in the vacuole/lysosome. In this study, we investigated how autophagy functions under zinc starvation. Zinc depletion induced non-selective autophagy, which is important for zinc-limited growth. Induction of autophagy by zinc starvation was not directly related to transcriptional activation of Zap1. Instead, TORC1 inactivation directed zinc starvation-induced autophagy. Abundant zinc proteins, such as Adh1, Fba1, and ribosomal protein Rpl37, were degraded in an autophagy-dependent manner. But the targets of autophagy were not restricted to zinc-binding proteins. When cellular zinc is severely depleted, this non-selective autophagy plays a role in releasing zinc from the degraded proteins and recycling zinc for other essential purposes.

The mucolipin-1 (TRPML1) ion channel, transmembrane-163 (TMEM163) protein, and lysosomal zinc handling

Lysosomes are emerging as important players in cellular zinc ion (Zn²⁺) homeostasis. The series of work on Zn2+ accumulation in the neuronal lysosomes and the mounting evidence on the role of lysosomal Zn²⁺ in cell death during mammary gland involution set a biological precedent for the central role of the lysosomes in cellular Zn²⁺ handling. Such a role appears to involve cytoprotection on the one hand, and cell death on the other. The recent series of work began to identify the molecular determinants of the lysosomal Zn²⁺ handling. In addition to zinc transporters (ZnT) of the solute-carrier family type 30A (SLC30A), the lysosomal ion channel TRPML1 and the poorly understood novel transporter TMEM163 have been shown to play a role in the Zn²⁺ uptake by the lysosomes. In this review, we summarize the current knowledge on molecular determinants of the lysosomal Zn²⁺ handling, uptake, and release pathways, as well as discuss their possible roles in health and disease.

Inhibition of autophagy blocks cathepsins-tBid-mitochondrial apoptotic signaling pathway via stabilization of lysosomal membrane in ischemic astrocytes

Our previous study and others have demonstrated that autophagy is activated in ischemic astrocytes and contributes to astrocytic cell death. However, the mechanisms of ischemia-induced autophagy remain largely unknown. In this study, we established a rat's model of permanent middle cerebral artery occlusion (pMCAO) and an in vitro oxygen and glucose deprivation (OGD) model. Autophagy was inhibited by either pharmacological treatment with 3-methyladenine (3-MA) and wortmannin (Wort) or genetic treatment with knockdown of Atg5 in primary cultured astrocytes and knockout of Atg5 in mouse embryonic fibroblast (MEF) cells, respectively. We found that pharmacological or genetic inhibition of autophagy reversed pMCAO or OGD-induced increase in LC3-II, active cathepsin B and L, tBid, active caspase-3 and cytoplastic cytochrome c (Cyt-c), and suppressed the injury-induced reduction in mitochondrial Cyt-c in ischemic cortex, in injured astrocytes and MEF cells. Immunofluorescence analysis showed that 3-MA or Wort treatment reversed OGD-induced release of cathepsin B and L from the lysosome to the cytoplasm and activation of caspase-3 in the astrocytes. Furthermore, treatment of 3-MA or Wort decreased OGD-induced increase in lysosomal membrane permeability and enhanced OGD-induced upregulation of lysosomal heat shock protein 70.1B (Hsp70.1B) in astrocytes. Inhibition of autophagy by 3-MA or Wort reduced infarction volume in rats and protected OGD-induced astrocytic cell injury. A non-selective caspase inhibitor z-VAD-fmk or a specific caspase-3 inhibitor Q-DEVD-OPh also rescued OGD-induced astrocytic cell injury. In conclusion, our presenting data suggest that inhibition of autophagy blocks cathepsins–tBid–mitochondrial apoptotic signaling pathway via stabilization of lysosomal membranes, possibly due to upregulation of the lysosomal Hsp70.1B in ischemic astrocytes.

Near-Infrared Probe Based on Rhodamine Derivative for Highly Sensitive and Selective Lysosomal pH Tracking

The development of near-infrared fluorescent probes with low pK_a, high selectivity, high photostability, and high sensitivity for lysosomal pH detection is of great importance. In the present work, we developed a novel near-infrared lysosomal pH probe (Lyso-hNR) based on a rhodamine derivative. Lyso-hNR showed fast, highly sensitive, and highly selective fluorescence response to acidic pH caused by the H⁺-induced structure changes from the nonfluorescent spirolactam form to the highly emissive open-ring form. Lyso-hNR displays a significant fluorescence enhancement at 650 nm (over 280-fold) from pH 7.0 to 4.0 with a pK_a value of 5.04. Live cell imaging data revealed that Lyso-hNR can selectively monitor lysosomal pH changes with excellent photostability and low cytotoxicity. In addition, Lyso-hNR can be successfully used in tracking lysosomal pH changes induced by chloroquine and those during apoptosis. All these features render Lyso-hNR a promising candidate to investigate lysosome-associated physiological and pathological processes.

A reversible ratiometric two-photon lysosome-targeted probe for real-time monitoring of pH changes in living cells

A reversible ratiometric two-photon lysosome-targeted probe that can monitor real-time pH changes in living cells.

Involvement of Programmed Cell Death in Neurotoxicity of Metallic Nanoparticles: Recent Advances and Future Perspectives

The widespread application of metallic nanoparticles (NPs) or NP-based products has increased the risk of exposure to NPs in humans. The brain is an important organ that is more susceptible to exogenous stimuli. Moreover, any impairment to the brain is irreversible. Recently, several in vivo studies have found that metallic NPs can be absorbed into the animal body and then translocated into the brain, mainly through the blood-brain barrier and olfactory pathway after systemic administration. Furthermore, metallic NPs can cross the placental barrier to accumulate in the fetal brain, causing developmental neurotoxicity on exposure during pregnancy. Therefore, metallic NPs become a big threat to the brain. However, the mechanisms underlying the neurotoxicity of metallic NPs remain unclear. Programmed cell death (PCD), which is different from necrosis, is defined as active cell death and is regulated by certain genes. PCD can be mainly classified into apoptosis, autophagy, necroptosis, and pyroptosis. It is involved in brain development, neurodegenerative disorders, psychiatric disorders, and brain injury. Given the pivotal role of PCD in neurological functions, we reviewed relevant articles and tried to summarize the recent advances and future perspectives of PCD involvement in the neurotoxicity of metallic NPs, with the purpose of comprehensively understanding the neurotoxic mechanisms of NPs.

A conditional proteomics approach to identify proteins involved in zinc homeostasis

Zinc signaling and dynamics play significant roles in many physiological responses and diseases. To understand the physiological roles of zinc in detail, comprehensive identification of proteins under high concentration of mobile zinc ion is crucial. We developed a 'conditional proteomics' approach to identify proteins involved in zinc homeostasis based on a chemical proteomic strategy that utilizes designer zinc-responsive labeling reagents to tag such proteins and quantitative mass spectrometry for their identification. We used this method to elucidate zinc dyshomeostasis induced by nitric-oxide-triggered oxidative stress in glioma cells, and we unveiled dynamic changes of the zinc-related proteomes. Moreover, we characterized unknown zinc-rich vesicles generated by oxidative stress as endoplasmic-reticulum- and Golgi-related vesicles.

Dehydroandrographolide, an iNOS inhibitor, extracted from Andrographis paniculata (Burm.f.) Nees, induces autophagy in human oral cancer cells

Autophagy, which is constitutively executed at the basal level in all cells, promotes cellular homeostasis by regulating the turnover of organelles and proteins. Andrographolide and dehydroandrographolide (DA) are the two principle components of Andrographis paniculata (Burm.f.) Nees. and are the main contributors to its therapeutic properties. However, the pharmacological activities of dehydroandrographolide (DA) remain unclear. In this study, DA induces oral cancer cell death by activating autophagy. Treatment with autophagy inhibitors inhibited DA-induced human oral cancer cell death. In addition, DA increased LC3-II expression and reduced p53 expression in a time- and concentration-dependent manner. Furthermore, DA induced autophagy and decreased cell viability through modulation of p53 expression. DA-induced autophagy was triggered by an activation of JNK1/2 and an inhibition of Akt and p38. In conclusion, this study demonstrated that DA induced autophagy in human oral cancer cells by modulating p53 expression, activating JNK1/2, and inhibiting Akt and p38. Finally, an administration of DA effectively suppressed the tumor formation in the oral carcinoma xenograft model in vivo. This is the first study to reveal the novel function of DA in activating autophagy, suggesting that DA could serve as a new and potential chemopreventive agent for treating human oral cancer.

58-F, a flavanone from Ophiopogon japonicus, prevents hepatocyte death by decreasing lysosomal membrane permeability

Lysosome membrane permeabilization (LMP) has been implicated in cell death. In the present study, we investigated the relationship between cell death and H₂O₂-/CCl₄-induced LMP in hepatocytes in vitro and following acute liver injury in vivo. The key finding was that H₂O₂ triggered LMP by oxidative stress, as evidenced by a suppression of LAMP1 expression, a reduction in LysoTracker Green and AO staining, and the leakage of proton and cathepsin B/D from the lysosome to the cytoplasm, resulting in cell death. CCl₄ also triggered hepatocyte death by decreasing lysosome LAMP1 expression and by inducing the accumulation of products of peroxidative lipids and oxidized proteins. Furthermore, a novel compound 5,8-dimethoxy-6-methyl-7-hydroxy-3-3(2-hydroxy-4-methoxybenzyl) chroman-4-one (58-F) was extracted from Ophiopogon japonicus and served as a potential therapeutic drug. In vivo and in vitro results showed that 58-F effectively rescued hepatocytes by decreasing LMP and by inducing lysosomal enzyme translocation to the cytosol.

ROS and intracellular ion channels

Oxidative stress is a well-known driver of numerous pathological processes involving protein and lipid peroxidation and DNA damage. The resulting increase of pro-apoptotic pressure drives tissue damage in a host of conditions, including ischemic stroke and reperfusion injury, diabetes, death in acute pancreatitis and neurodegenerative diseases. Somewhat less frequently discussed, but arguably as important, is the signaling function of oxidative stress stemming from the ability of oxidative stress to modulate ion channel activity. The evidence for the modulation of the intracellular ion channels and transporters by oxidative stress is constantly emerging and such evidence suggests new regulatory and pathological circuits that can be explored towards new treatments for diseases in which oxidative stress is an issue. In this review we summarize the current knowledge on the effects of oxidative stress on the intracellular ion channels and transporters and their role in cell function.

MP Resulting in Autophagic Cell Death of Microglia through Zinc Changes against Spinal Cord Injury

Methylprednisolone pulse therapy (MPPT), as a public recognized therapy of spinal cord injury (SCI), is doubted recently, and the exact mechanism of MP on SCI is unclear. This study sought to investigate the exact effect of MP on SCI. We examined the effect of MP in a model of SCI in vivo and an LPS induced model in vitro. We found that administration of MP produced an increase in the Basso, Beattie, and Bresnahan scores and motor neurons counts of injured rats. Besides the number of activated microglia was apparently reduced by MP in vivo, and Beclin-1 dependent autophagic cell death of microglia was induced by MP in LPS induced model. At the same time, MP increases cellular zinc concentration and level of ZIP8, and TPEN could revert effect of MP on autophagic cell death of microglia. Finally, we have found that MP could inhibit NF-κβ in LPS induced model. These results show that the MP could result in autophagic cell death of microglia, which mainly depends on increasing cellular labile zinc, and may be associated with inhibition of NF-κβ, and that MP can produce neuroprotective effect in SCI.

Role of autophagy in the pathogenesis of multiple sclerosis

Autophagy plays an important role in maintaining the cellular homeostasis. One of its functions is to degrade unnecessary organelles and proteins for energy recycling or amino-acids for cell survival. Ablation of autophagy leads to neurodegeneration. Multiple sclerosis (MS), a permanent neurological impairment typical of chronic inflammatory demyelinating disorder, is an auto-immune disease of the central nervous system (CNS). Autophagy is tightly linked to the innate and adaptive immune systems during the autoimmune process, and several studies have shown that autophagy directly participates in the progress of MS or experimental autoimmune encephalomyelitis (EAE, a mouse model of MS). Dysfunction of mitochondria that intensively influences the autophagy pathway is one of the important factors in the pathogenesis of MS. Autophagy-related gene (ATG) 5 and immune-related GTPase M (IRGM) 1 are increased, while ATG16L2 is decreased, in T-cells in EAE and active relapsing-remitting MS brains. Administration of rapamycin, an inhibitor of mammalian target of rapamycin ( mTOR), ameliorates relapsing-remitting EAE. Inflammation and oxidative stress are increased in MS lesions and EAE, but Lamp2 and the LC3-II/LC3-I ratio are decreased. Furthermore, autophagy in various glial cells plays important roles in regulating neuro-inflammation in the CNS, implying potential roles in MS. In this review, we discuss the role of autophagy in the peripheral immune system and the CNS in neuroinflammation associated with the pathogenesis of MS.

Autophagy Mediates Astrocyte Death During Zinc-Potentiated Ischemia--Reperfusion Injury

Pathological release of excess zinc ions and the resultant increase in intracellular zinc has been implicated in ischemic brain cell death, although the underlying mechanisms are not fully understood. Since zinc promotes the formation of the autophagic signal, reactive oxygen species (ROS), and increases autophagy, a known mechanism of cell death, we hypothesized that autophagy is involved in zinc-induced hypoxic cell death. To study this hypothesis, we determined the effect of zinc on autophagy and ROS generation in C8-D1A astrocytes subjected to hypoxia and rexoygenation (H/R), simulating ischemic stroke. C8-D1A astrocytes subjected to 3-h hypoxia and 18-h reoxygenation exhibited dramatically increased autophagy and astrocyte cell death in the presence of 100 μM zinc. Pharmacological inhibition of autophagy decreased zinc-potentiated H/R-induced cell death, while scavenging ROS reduced both autophagy and cell death caused by zinc-potentiated H/R. These data indicate that zinc-potentiated increases in ROS lead to over-exuberant autophagy and increased cell death in H/R-treated astrocytes. Furthermore, our elucidation of this novel mechanism indicates that modulation of autophagy, ROS, and zinc levels may be useful targets in decreasing brain damage during stroke.

Astrocytes and lysosomal storage diseases

Lysosomal storage diseases (LSDs) encompass a wide range of disorders characterized by inborn errors of lysosomal function. The majority of LSDs result from genetic defects in lysosomal enzymes, although some arise from mutations in lysosomal proteins that lack known enzymatic activity. Neuropathological abnormalities are a feature of several LSDs and when severe, represent an important determinant in disease outcome. Glial dysfunction, particularly in astrocytes, is also observed in numerous LSDs and has been suggested to impact neurodegeneration. This review will discuss the potential role of astrocytes in LSDs and highlight the possibility of targeting glia as a beneficial strategy to counteract the neuropathology associated with LSDs.