Cu(II) disrupts autophagy-mediated lysosomal degradation of oligomeric Aβ in microglia via mTOR-TFEB pathway

Dehydroandrographolide ameliorates doxorubicin-mediated cardiotoxicity by regulating autophagy through the mTOR-TFEB pathway

The clinical application of doxorubicin (DOX) was limited by the serious cardiotoxicity. The traditional Chinese medicine Andrographis paniculata and its principal active component (Dehydroandrographolide, DA) have been well known for their diverse cardiovascular protective effects. However, the effects of DA on DOX-induced cardiotoxicity (DIC) were still unknown. In this study, we evaluated the effects and revealed the potential mechanisms of DA on DIC both in vivo and in vitro. The effects of DA on DIC were systematically assessed by echocardiography and histological assays. Western blot and flow cytometry were used to measure apoptosis of cardiomyocytes. Transmission electron microscopy and StubRFP-SensGFP-LC3 lentivirus were further used to assay autophagic flux. Our results showed that DA administration significantly improved cardiac function and attenuated DOX-induced cardiomyocyte apoptosis. Mechanically, DA restored autophagic flux and lysosome functions via inhibiting DOX-induced mTOR signal pathway activation and increasing the translocation of TFEB to the nucleus. However, activation of mTOR or knockdown of TFEB significantly inhibited the protective effects of DA against DIC by impacting lysosomal functions and autophagic flux. In conclusion, our results revealed that DA might be a potential cardioprotective agent against DIC.

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.

Copper in cancer: From pathogenesis to therapy

One of the basic trace elements for the structure and metabolism of human tissue is copper. However, as a heavy metal, excessive intake or abnormal accumulation of copper in the body can cause inevitable damage to the organism because copper can result in direct injury to various cell components or disruption of the redox balance, eventually leading to cell death. Interestingly, a growing body of research reports that diverse cancers have raised serum and tumor copper levels. Tumor cells depend on more copper for their metabolism than normal cells, and a decrease in copper or copper overload can have a detrimental effect on tumor cells. New modalities for identifying and characterizing copper-dependent signals offer translational opportunities for tumor therapy, but their mechanisms remain unclear. Therefore, this article summarizes what we currently know about the correlation between copper and cancer and describes the characteristics of copper metabolism in tumor cells and the prospective application of copper-derived therapeutics.

Missing heritability of Wilson disease: a search for the uncharacterized mutations

Wilson disease (WD), a copper metabolism disorder caused by mutations in ATP7B, manifests heterogeneous clinical features. Interestingly, in a fraction of clinically diagnosed WD patients, mutations in ATP7B appears to be missing. In this review we discuss the plausible explanations of this missing heritability and propose a workflow that can identify the hidden mutations. Mutation analyses of WD generally includes targeted sequencing of ATP7B exons, exon-intron boundaries, and rarely, the proximal promoter region. We propose that variants in the distal cis-regulatory elements and/or deep intronic variants that impact splicing might well represent the hidden mutations. Heterozygous del/ins that remain refractory to conventional PCR-sequencing method may also represent such mutations. In this review, we also hypothesize that mutations in the key copper metabolism genes, like, ATOX1, COMMD1, and SLC31A1, could possibly lead to a WD-like phenotype. In fact, WD does present overlapping symptoms with other rare genetic disorders; hence, the possibility of a misdiagnosis and thus adding to missing heritability cannot be excluded. In this regard, it seems that whole-genome analysis will provide a comprehensive and rapid molecular diagnosis of WD. However, considering the associated cost for such a strategy, we propose an alternative customized screening schema of WD which include targeted sequencing of ATP7B locus as well as other key copper metabolism genes. Success of such a schema has been tested in a pilot study.

Probable Reasons for Neuron Copper Deficiency in the Brain of Patients with Alzheimer’s Disease: The Complex Role of Amyloid

Alzheimer’s disease is a progressive neurodegenerative disorder that eventually leads the affected patients to die. The appearance of senile plaques in the brains of Alzheimer’s patients is known as a main symptom of this disease. The plaques consist of different components, and according to numerous reports, their main components include beta-amyloid peptide and transition metals such as copper. In this disease, metal dyshomeostasis leads the number of copper ions to simultaneously increase in the plaques and decrease in neurons. Copper ions are essential for proper brain functioning, and one of the possible mechanisms of neuronal death in Alzheimer’s disease is the copper depletion of neurons. However, the reason for the copper depletion is as yet unknown. Based on the available evidence, we suggest two possible reasons: the first is copper released from neurons (along with beta-amyloid peptides), which is deposited outside the neurons, and the second is the uptake of copper ions by activated microglia.

Induction of autophagy via the ROS-dependent AMPK-mTOR pathway protects copper-induced spermatogenesis disorder

Copper (Cu) is a necessary micronutrient at lower concentration, while excessive Cu exposure or Cu homeostasis disorders can lead to toxicity. The mechanism of male reproductive toxicity induced by Cu is still unknown. This study aims to investigate whether autophagy plays an important role in copper-induced spermatogenesis disorder in vivo and vitro. The present study showed that copper sulfate (CuSO₄) might significantly promote autophagy level in the testis and mouse-derived spermatogonia cell line GC-1 spg cells. Concurrently, CuSO₄ could induce autophagy via AMPK-mTOR pathway that downregulated p-mTOR/mTOR and subsequently upregulated p-AMPKα/AMPKα as well as p-ULK1/ULK1. In the meanwhile, CuSO₄ treatment could also increase expression levels of the autophagy-related proteins. Then, the role of oxidative stress in CuSO₄-induced autophagy was investigated. The findings demonstrated that oxidative stress inhibitor (NAC) attenuated CuSO₄-induced autophagy in vivo and vitro, reversing the activation for AMPK-mTOR pathway. Additionally, the study also investigated how autophagy worked under the spermatogenesis disorder induced by CuSO₄. Inhibition of autophagy could decrease cell viability, and enhance the ROS accumulation and apoptosis in the GC-1 cells, meanwhile, the spermatogenesis disorder, oxidative stress and histopathological changes were increased in the testis. Furthermore, co-treatment with the apoptosis inhibitor (Z-VAD-FMK) could decrease the spermatogenesis disorder but not influence autophagy. Besides, the crosslink between autophagy and ferroptosis were also measured, the data showed that inhibition of autophagy could suppress CuSO₄-induced ferroptosis in in vivo and vitro. Altogether, abovementioned results indicated that CuSO₄ induced autophagy via oxidative stress-dependent AMPK-mTOR pathway in the GC-1 cells and testis, and autophagy activation possibly led to the generation of protection mechanism through oxidative damage and apoptosis inhibition, however, autophagy also aggravate CuSO₄ toxicology through promoting ferroptosis. Overall, autophagy plays a positive role for attenuating CuSO₄-induced testicular damage and spermatogenesis disorder. Our study provides a possible targeted therapy for Cu overload-induced reproduction toxicology.

Novel Insight into Functions of Transcription Factor EB (TFEB) in Alzheimer’s Disease and Parkinson’s Disease

A key pathological feature of neurodegenerative diseases (NDs) such as Alzheimer's disease (AD) and Parkinson's disease (PD) is the accumulation of aggregated and misfolded protein aggregates with limited effective therapeutic agents. TFEB (transcription factor EB), a key regulator of lysosomal biogenesis and autophagy, plays a pivotal role in the degradation of protein aggregates and has thus been regarded as a promising therapeutic target for these NDs. Here, we systematically summarize the molecular mechanisms and function of TFEB regulation. We then discuss the roles of TFEB and autophagy-lysosome pathways in major neurodegenerative diseases including AD and PD. Finally, we illustrate small molecule TFEB activators with protective roles in NDs animal models, which show great potential for being further developed into novel anti-neurodegenerative agents. Overall, targeting TFEB for enhancing lysosomal biogenesis and autophagy may represent a promising opportunity for the discovery of disease-modifying therapeutics for neurodegenerative disorders though more in-depth basic and clinical studies are required in the future.

Direct Interaction of ATP7B and LC3B Proteins Suggests a Cooperative Role of Copper Transportation and Autophagy

Macroautophagy/autophagy plays an important role in cellular copper clearance. The means by which the copper metabolism and autophagy pathways interact mechanistically is vastly unexplored. Dysfunctional ATP7B, a copper-transporting ATPase, is involved in the development of monogenic Wilson disease, a disorder characterized by disturbed copper transport. Using in silico prediction, we found that ATP7B contains a number of potential binding sites for LC3, a central protein in the autophagy pathway, the so-called LC3 interaction regions (LIRs). The conserved LIR3, located at the C-terminal end of ATP7B, was found to directly interact with LC3B in vitro. Replacing the two conserved hydrophobic residues W1452 and L1455 of LIR3 significantly reduced interaction. Furthermore, autophagy was induced in normal human hepatocellular carcinoma cells (HepG2) leading to enhanced colocalization of ATP7B and LC3B on the autophagosome membranes. By contrast, HepG2 cells deficient of ATP7B (HepG2 ATP7B^-/-) showed autophagy deficiency at elevated copper condition. This phenotype was complemented by heterologous ATP7B expression. These findings suggest a cooperative role of ATP7B and LC3B in autophagy-mediated copper clearance.

Microglia and Astrocytes in Alzheimer's Disease in the Context of the Aberrant Copper Homeostasis Hypothesis

Evidence of copper's (Cu) involvement in Alzheimer's disease (AD) is available, but information on Cu involvement in microglia and astrocytes during the course of AD has yet to be structurally discussed. This review deals with this matter in an attempt to provide an updated discussion on the role of reactive glia challenged by excess labile Cu in a wide picture that embraces all the major processes identified as playing a role in toxicity induced by an imbalance of Cu in AD.

mtROS-mediated Akt/AMPK/mTOR pathway was involved in Copper-induced autophagy and it attenuates Copper-induced apoptosis in RAW264.7 mouse monocytes

Copper (Cu) is a trace element necessary in animals as well as human beings. However, excessive Cu is toxic to immunocytes, but the precise mechanism is largely unclear so far. This work was conducted aiming to examine the Cu-mediated autophagy mechanism together with its role in Cu toxicology in RAW264.7 cells. Here, we demonstrated that CuSO4 reduced the cell viability depending on its dose. CuSO4 could obviously increase autophagy in RAW264.7 cells. According to the obtained results, CuSO4 induced autophagy through Akt/AMPK/mTOR pathway which characterized by down regulation of p-Akt (Ser473)/Akt, p-mTOR/mTOR, p-ULK1(Ser757)/ULK1 and subsequent up-regulation of p-AMPKα/AMPKα and p-ULK1(Ser555)/ULK1. Furthermore, CuSO4 significantly induced the production of mitochondrial reactive oxygen species (mtROS). In addition, CuSO4-mediated apoptosis and autophagy might be suppressed through suppressing mtROS generation by exposure to Mito-TEMPO. Intriguingly, autophagy promotion with rapamycin could decrease the apoptosis and the inhibition of autophagy with knock down Atg5 could enhance the apoptosis induced by CuSO4. Moreover, our results suggested that mtROS is the original cause in CuSO4-induced apoptosis and autophagy. Additionally, CuSO4 induced autophagy through mtROS-dependent Akt/AMPK/mTOR signalling pathwayin RAW264.7 cells. Moreover, autophagy activation might potentially generate a protection mechanism for improving CuSO4-induced RAW264.7 cell apoptosis.