Endoplasmic reticulum dysfunction in neurological disease

Exploring the nexus of cGAS STING pathway in neurodegenerative terrain: A therapeutic odyssey

By detecting and responding to cytosolic DNA, the cGAS STING pathway regulates the innate immune responses bymediatinginflammatory reactions and antiviral defense. Thederegulation and modification of this system have been linked to variousneurodegenerative diseases like AD, PD and ALS. Accumulation of tau protein and Aβ aggregates to activate the pathway and releases neuroinflammatory cytokines which accelerates neuronal dysfunction and cognitive impairment as the symptom of AD. Similarly, in PD Alpha-synuclein aggregates activate the cGAS STING pathway and regulate the neuroinflammation and oxidative stress. In ALS, mutation of the genes causes the activation of the pathway which leads to motor neuron degeneration. Alteration of the cGAS STING pathway also leads to mitochondrial dysfunction and impaired autophagy. Preclinical investigations of AD, PD, and ALS animal models showed that STING pathway inhibitors reduced inflammation and improved neurological outcomes and modulators of the cGAS STING pathway may treat these neurodegenerative disorders. In this review we focus on the fact thatneuroinflammation, neuronal dysfunction, and various disease progressions can be treated byaltering the cGAS STING pathway. Understanding the processes and creating specific interventions for this route may offer new treatments for these terrible illnesses.

Fu's subcutaneous needling promotes axonal regeneration and remyelination by inhibiting inflammation and endoplasmic reticulum stress

Fu's subcutaneous needling (FSN) is a traditional Chinese acupuncture procedure used to treat pain-related neurological disorders. Moreover, the regulation of inflammatory cytokines may provide a favorable environment for peripheral nerve regeneration. In light of this, FSN may be an important novel therapeutic strategy to alleviate pain associated with peripheral neuropathy; however, the underlying molecular mechanisms remain unclear. This study revealed that patients who had osteoarthritis with peripheral neuropathic pain significantly recovered after 1 to 2 weeks of FSN treatment according to the visual analog scale, Western Ontario and McMaster Universities Osteoarthritis Index, Lequesne index, walking speed, and passive range of motion. Similarly, we demonstrated that FSN treatment in an animal model of chronic constriction injury (CCI) significantly improved sciatic nerve pain using paw withdrawal thresholds, sciatic functional index scores, and compound muscle action potential amplitude tests. In addition, transmission electron microscopy images of sciatic nerve tissue showed that FSN effectively reduced axonal swelling, abnormal myelin sheaths, and the number of organelle vacuoles in CCI-induced animals. Mechanistically, RNA sequencing and gene set enrichment analysis revealed significantly reduced inflammatory pathways, neurotransmitters, and endoplasmic reticulum stress pathways and increased nerve regeneration factors in the FSN+CCI group, compared with that in the CCI group. Finally, immunohistochemistry, immunoblotting and enzyme-linked immunosorbent assay showed similar results in the dorsal root ganglia and sciatic nerve. Our findings suggest that FSN can effectively ameliorate peripheral neuropathic pain by regulate inflammation and endoplasmic reticulum stress, thereby determine its beneficial application in patients with peripheral nerve injuries.

Intramolecular Charge Transfer Inhibition Strategy toward a Desired Solvatochromic Fluorescent Platform: Visualization of Duple Organelles and Detection of Carbon Dioxide

Solvatochromic fluorescent probes are crucial molecular tools to investigate and aggregate proteins' fold, visualize fine structures in biomembranes, and label different organelles in dual emission colors. However, solvatochromic fluorogens often displayed a weak emission at high polarity, hindering their bioimaging applications. To resolve this problem, herein, we propose an intramolecular charge transfer (ICT) inhibition strategy. The probe was designed with a single electronic donor and two acceptors in order to split and inhibit the ICT procedure. As a result, the probe displayed an intense emission at both low and high polarities and showed a large emission shift (84 nm) upon polarity change. Using the probe, we successfully imaged lipid droplets and the endoplasmic reticulum in different fluorescence colors. Moreover, the different degrees of lipid accumulation by oleic acid, stearic acid, and cholesterol (oleic acid > stearic acid > cholesterol) have been revealed. The lipid accumulation induced by the three lipids could be rapidly consumed under lipid-less conditions, and the lipids with stearic acid were the most difficult to be consumed. The biological results could facilitate the understanding and treatment of lipid accumulation and obesity. Furthermore, utilizing the polarity increase of diethylamine after the reaction with CO2, the ratiometric detection of CO2 has been achieved for the first time with the probe.

Dose-dependent effects of silver nanoparticles on cell death modes in mouse blastocysts induced via endoplasmic reticulum stress and mitochondrial apoptosis

In view of the rapidly expanding medical and commercial applications of silver nanoparticles (AgNPs), their potential health risks and environmental effects are a significant growing concern. Earlier research by our group uncovered the embryotoxic potential of AgNPs, showing detrimental impacts of these nanoparticles on both pre- and post-implantation embryonic development. In the current study, we showed that low (50-100 μM) and high (200-400 μM) dose ranges of AgNPs trigger distinct cell death programs affecting mouse embryo development and further explored the underlying mechanisms. Treatment with low concentrations of AgNPs (50-100 μM) triggered ROS generation, in turn, inducing mitochondria-dependent apoptosis, and ultimately, harmful effects on embryo implantation, post-implantation development, and fetal development. Notably, high concentrations of AgNPs (200-400 μM) evoked more high-level ROS generation and endoplasmic reticulum (ER) stress-mediated necrosis. Interestingly, pre-incubation with Trolox, a strong antioxidant, reduced ROS generation in the group treated with 200-400 μM AgNPs to the level induced by 50-100 μM AgNPs, resulting in switching of the cell death mode from necrosis to apoptosis and a significant improvement in the impairment of embryonic development. Our findings additionally indicate that activation of PAK2 is a crucial step in AgNP-triggered apoptosis and sequent detrimental effects on embryonic development. Based on the collective results, we propose that the levels of ROS generated by AgNP treatment of embryos serve as a critical regulator of cell death type, leading to differential degrees of damage to embryo implantation, post-implantation development and fetal development through triggering apoptosis, necrosis or other cell death signaling cascades.

Endoplasmic reticulum's role in multiple sclerosis, exploring potential biomarkers, and pioneering therapeutic strategies: a comprehensive review of literature

BACKGROUD

Multiple Sclerosis (MS) is a complex and chronic autoimmune disease that affects the central nervous system. Inflammation and demyelination characterize it, which results in a range of neurological impairments. The increasing worldwide occurrence of MS, affecting an estimated 2.8 million individuals in 2020, highlights the urgent requirement for further research to tackle the significant impact it has on individuals and healthcare systems globally.

OBJECTIVE

In this study, we wanted to explore the complex function of the endoplasmic reticulum (ER) in the origin, development, and resolution of MS, emphasizing its importance in neuroinflammatory illnesses. The ER has become a central focus in comprehending the pathogenesis of MS. Upon reviewing the literature, we observed a lack of thorough analysis that explores the involvement of endoplasmic reticulum stress in multiple sclerosis. Thus, we aimed through this research to examine the correlations between ER stress and its influence on immunological dysregulation, demyelination, and neurodegeneration in MS.

FINDINGS

Based on the latest clinical trials, we suggested theories that explore possible biomarkers linked to ER stress and the unfolded protein response. Identifying molecules that are suggestive of early stages of illness and can serve as prognostic tools for improving our understanding of the heterogeneity of MS and offering novel approaches for managing the disease. Finally, through our comprehensive search, we wanted to offer a plan for future research, suggesting new and creative methods for managing MS and encouraging the creation of specific treatments that aim to reduce the impact of MS on individuals worldwide.

Biotoxicity of paraquat to lung cells mediated by endoplasmic reticulum-mitochondria interaction

The high lethality caused by paraquat (PQ) poisoning has attracted much attention in public and human health due to its high toxicity and lethality. However, the understanding of the mechanism of PQ-induced apoptosis from the perspective of organelles, especially inter-organelle interactions, is still scarce. Exploring the linkage of multiple organelles during PQ poisoning and the molecular mechanisms of PQ poisoning under its mediation will help to gain insight into the mode of PQ poisoning at the organelle level. In this study, we observed that a certain dose of PQ gavage induced oxidative stress, mitochondrial dysfunction and endoplasmic reticulum stress in rat lung tissue cells. PQ toxicity led to the occurrence of Ca2+ overload in the endoplasmic reticulum, and the activated BIP and CHOP pathways directly/indirectly led to the expression of apoptogenic factors Caspase family factors. In addition, PQ promoted Ca2+ release from the endoplasmic reticulum and Ca2+ uptake by mitochondria, which induced the disruption of Bax/Bcl-2 channel proteins in response to the IP3R/RyR/VDAC1&2/MCU Ca2+ axis thereby leading to the release of CytoC, which ultimately induced endoplasmic reticulum stress and apoptotic cell death. In addition, 10 differential proteins were screened and validated by proteomics that may act as upstream and downstream active factors of mitochondria-endoplasmic reticulum interaction-mediated biotoxicity. Our findings provide new perspectives for researchers to explore the toxicity mechanisms of PQ to reduce their adverse effects.

Mitigating Traumatic Brain Injury: A Narrative Review of Supplementation and Dietary Protocols

Traumatic brain injuries (TBIs) constitute a significant public health issue and a major source of disability and death in the United States and worldwide. TBIs are strongly associated with high morbidity and mortality rates, resulting in a host of negative health outcomes and long-term complications and placing a heavy financial burden on healthcare systems. One promising avenue for the prevention and treatment of brain injuries is the design of TBI-specific supplementation and dietary protocols centred around nutraceuticals and biochemical compounds whose mechanisms of action have been shown to interfere with, and potentially alleviate, some of the neurophysiological processes triggered by TBI. For example, evidence suggests that creatine monohydrate and omega-3 fatty acids (DHA and EPA) help decrease inflammation, reduce neural damage and maintain adequate energy supply to the brain following injury. Similarly, melatonin supplementation may improve some of the sleep disturbances often experienced post-TBI. The scope of this narrative review is to summarise the available literature on the neuroprotective effects of selected nutrients in the context of TBI-related outcomes and provide an evidence-based overview of supplementation and dietary protocols that may be considered in individuals affected by-or at high risk for-concussion and more severe head traumas. Prophylactic and/or therapeutic compounds under investigation include creatine monohydrate, omega-3 fatty acids, BCAAs, riboflavin, choline, magnesium, berry anthocyanins, Boswellia serrata, enzogenol, N-Acetylcysteine and melatonin. Results from this analysis are also placed in the context of assessing and addressing important health-related and physiological parameters in the peri-impact period such as premorbid nutrient and metabolic health status, blood glucose regulation and thermoregulation following injury, caffeine consumption and sleep behaviours. As clinical evidence in this research field is rapidly emerging, a comprehensive approach including appropriate nutritional interventions has the potential to mitigate some of the physical, neurological, and emotional damage inflicted by TBIs, promote timely and effective recovery, and inform policymakers in the development of prevention strategies.

Concurrent Subcellular Delivery of Hydrogen Sulfide and a Payload with Near-Infrared Light

Hydrogen sulfide (H2S) is a gaseous signaling molecule, exerting crucial regulatory functions in organelles and cellular environments. H2S exhibits high therapeutic potential and synergistic effects with other drugs, and its potency is notably enhanced through organelle-specific targeting. Yet, the navigation of light-activated H2S donors to specific organelles remains absent. Here, we report the first organelle-specific photocage that simultaneously delivers H2S and a payload with subcellular precision to mitochondria of live human cells using tissue-penetrating near-infrared light as a trigger. The fluorogenic payload enables real-time monitoring of the process, and we demonstrate the concurrent uncaging in mitochondria through a combination of fluorescence microscopy and mitochondria-specific fluorescent probes. We anticipate that these photocages will permit the precise delivery of H2S-drug combinations with exceptional spatiotemporal control, thereby driving the harnessing of known synergistic effects and the discovery of novel therapeutic strategies.

Neuroprotective effects of flavonoids: endoplasmic reticulum as the target

The incidence of neurological disorders, particularly age-related neurodegenerative pathologies, exhibits an alarming upward trend, while current pharmacological interventions seldom achieve curative outcomes. Despite their diverse clinical presentations, neurological diseases often share a common pathological thread: the aberrant accumulation of misfolded proteins within the endoplasmic reticulum (ER). This phenomenon, known as ER stress, arises when the cell's intrinsic quality control mechanisms fail to cope with the protein-folding burden. Consequently, misfolded proteins accumulate in the ER lumen, triggering a cascade of cellular stress responses. Recognizing this challenge, researchers have intensified their efforts over the past two decades to explore natural compounds that could potentially slow or even reverse these devastating pathologies. Flavonoids constitute a vast and heterogeneous class of plant polyphenols, with over 10,000 identified from diverse natural sources such as wines, vegetables, medicinal plants, and organic products. Flavonoids are generally divided into six different subclasses: anthocyanidins, flavanones, flavones, flavonols, isoflavones, and flavonols. The diverse family of flavonoids, featuring a common phenolic ring backbone adorned with varying hydroxyl groups and additional modifications, exerts its antioxidant activity by inhibiting the formation of ROS, as evidenced by research. Also, studies suggest that polyphenols such as flavonoids can regulate ER stress through apoptosis and autophagy. By understanding these mechanisms, we can unlock the potential of flavonoids as novel therapeutic agents for neurodegenerative disorders. Therefore, this review critically examines the literature exploring the modulatory effects of flavonoids on various steps of the ER stress in neurological disorders.

Multi-omics integration of scRNA-seq time series data predicts new intervention points for Parkinson's disease

Parkinson's disease (PD) is a complex neurodegenerative disorder without a cure. The onset of PD symptoms corresponds to 50% loss of midbrain dopaminergic (mDA) neurons, limiting early-stage understanding of PD. To shed light on early PD development, we study time series scRNA-seq datasets of mDA neurons obtained from patient-derived induced pluripotent stem cell differentiation. We develop a new data integration method based on Non-negative Matrix Tri-Factorization that integrates these datasets with molecular interaction networks, producing condition-specific "gene embeddings". By mining these embeddings, we predict 193 PD-related genes that are largely supported (49.7%) in the literature and are specific to the investigated PINK1 mutation. Enrichment analysis in Kyoto Encyclopedia of Genes and Genomes pathways highlights 10 PD-related molecular mechanisms perturbed during early PD development. Finally, investigating the top 20 prioritized genes reveals 12 previously unrecognized genes associated with PD that represent interesting drug targets.

The protective role of sesame oil against Parkinson's-like disease induced by manganese in rats

Chronic exposure to manganese (Mn) results in motor dysfunction, biochemical and pathological alterations in the brain. Oxidative stress, inflammation, and dysfunction of dopaminergic and GABAergic systems stimulate activating transcription factor-6 (ATF-6) and protein kinase RNA-like ER kinase (PERK) leading to apoptosis. This study aimed to investigate the protective effect of sesame oil (SO) against Mn-induced neurotoxicity. Rats received 25 mg/kg MnCl2 and were concomitantly treated with 2.5, 5, or 8 ml/kg of SO for 5 weeks. Mn-induced motor dysfunction was indicated by significant decreases in the time taken by rats to fall during the rotarod test and in the number of movements observed during the open field test. Also, Mn resulted in neuronal degeneration as observed by histological staining. The striatal levels of lipid peroxides and reduced glutathione (oxidative stress markers), interleukin-6 and tumor necrosis factor-α (inflammatory markers) were significantly elevated. Mn significantly reduced the levels of dopamine and Bcl-2, while GABA, PERK, ATF-6, Bax, and caspase-3 were increased. Interestingly, all SO doses, especially at 8 ml/kg, significantly improved locomotor activity, biochemical deviations and reduced neuronal degeneration. In conclusion, SO may provide potential therapeutic benefits in enhancing motor performance and promoting neuronal survival in individuals highly exposed to Mn.

Identification of cuproptosis-realated key genes and pathways in Parkinson's disease via bioinformatics analysis

INTRODUCTION

Parkinson's disease (PD) is the second most common worldwide age-related neurodegenerative disorder without effective treatments. Cuproptosis is a newly proposed conception of cell death extensively studied in oncological diseases. Currently, whether cuproptosis contributes to PD remains largely unclear.

METHODS

The dataset GSE22491 was studied as the training dataset, and GSE100054 was the validation dataset. According to the expression levels of cuproptosis-related genes (CRGs) and differentially expressed genes (DEGs) between PD patients and normal samples, we obtained the differentially expressed CRGs. The protein-protein interaction (PPI) network was achieved through the Search Tool for the Retrieval of Interacting Genes. Meanwhile, the disease-associated module genes were screened from the weighted gene co-expression network analysis (WGCNA). Afterward, the intersection genes of WGCNA and PPI were obtained and enriched using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). Subsequently, the key genes were identified from the datasets. The receiver operating characteristic curves were plotted and a PPI network was constructed, and the PD-related miRNAs and key genes-related miRNAs were intersected and enriched. Finally, the 2 hub genes were verified via qRT-PCR in the cell model of the PD and the control group.

RESULTS

525 DEGs in the dataset GSE22491 were identified, including 128 upregulated genes and 397 downregulated genes. Based on the PPI network, 41 genes were obtained. Additionally, the dataset was integrated into 34 modules by WGCNA. 36 intersection genes found from WGCNA and PPI were significantly abundant in 7 pathways. The expression levels of the genes were validated, and 2 key genes were obtained, namely peptidase inhibitor 3 (PI3) and neuroserpin family I member 1 (SERPINI1). PD-related miRNAs and key genes-related miRNAs were intersected into 29 miRNAs including hsa-miR-30c-2-3p. At last, the qRT-PCR results of 2 hub genes showed that the expressions of mRNA were up-regulated in PD.

CONCLUSION

Taken together, this study demonstrates the coordination of cuproptosis in PD. The key genes and miRNAs offer novel perspectives in the pathogenesis and molecular targeting treatment for PD.

Phthalates Induce Neurotoxicity by Disrupting the Mfn2-PERK Axis-Mediated Endoplasmic Reticulum-Mitochondria Interaction

Di-(2-ethylhexyl) phthalate (DEHP), as the most common phthalate, has been extensively used as a plasticizer to improve the plasticity of agricultural products, which pose severe harm to human health. Mitochondrial dynamics and endoplasmic reticulum (ER) homeostasis are indispensable for maintaining mitochondria-associated ER membrane (MAM) integrity. In this study, we aimed to explore the effect of DEHP on the nervous system and its association with the ER-mitochondria interaction. Here, we showed that DEHP caused morphological changes, motor deficits, cognitive impairments, and blood-brain barrier disruption in the brain. DEHP triggered ER stress, which is mainly mediated by protein kinase R-like endoplasmic reticulum kinase (PERK) signaling. Moreover, DEHP-induced mitofusin-2 (Mfn2) downregulation results in imbalance of the mitochondrial dynamics. Interestingly, DEHP exposure impaired MAMs by inhibiting the Mfn2-PERK interaction. Above all, this study elucidates the disruption of the Mfn2-PERK axis-mediated ER-mitochondria interaction as a phthalate-induced neurotoxicity that could be potentially developed as a novel therapy for neurological diseases.

Endoplasmic reticulum stress and its role in various neurodegenerative diseases

The Endoplasmic reticulum (ER), a critical cellular organelle, maintains cellular homeostasis by regulating calcium levels and orchestrating essential functions such as protein synthesis, folding, and lipid production. A pivotal aspect of ER function is its role in protein quality control. When misfolded proteins accumulate within the ER due to factors like protein folding chaperone dysfunction, toxicity, oxidative stress, or inflammation, it triggers the Unfolded protein response (UPR). The UPR involves the activation of chaperones like calnexin, calreticulin, glucose-regulating protein 78 (GRP78), and Glucose-regulating protein 94 (GRP94), along with oxidoreductases like protein disulphide isomerases (PDIs). Cells employ the Endoplasmic reticulum-associated degradation (ERAD) mechanism to counteract protein misfolding. ERAD disruption causes the detachment of GRP78 from transmembrane proteins, initiating a cascade involving Inositol-requiring kinase/endoribonuclease 1 (IRE1), Activating transcription factor 6 (ATF6), and Protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathways. The accumulation and deposition of misfolded proteins within the cell are hallmarks of numerous neurodegenerative diseases. These aberrant proteins disrupt normal neuronal signalling and contribute to impaired cellular homeostasis, including oxidative stress and compromised protein degradation pathways. In essence, ER stress is defined as the cellular response to the accumulation of misfolded proteins in the endoplasmic reticulum, encompassing a series of signalling pathways and molecular events that aim to restore cellular homeostasis. This comprehensive review explores ER stress and its profound implications for the pathogenesis and progression of neurodegenerative diseases.

ALKBH5 protects against stroke by reducing endoplasmic reticulum stress-dependent inflammation injury via the STAT5/PERK/EIF2α/CHOP signaling pathway in an m6A-YTHDF1-dependent manner

BACKGROUND

Endoplasmic reticulum (ER) stress causes neuroinflammation and neuronal apoptosis during ischemic stroke progression. This study has investigated the role of ALKBH5 in ER stress during ischemic stroke progression.

METHODS

In vivo and in vitro models of ischemic stroke were established by middle cerebral artery occlusion (MCAO) and OGD/R treatment, respectively. Cerebral infarct size was detected using triphenyltetrazolium chloride staining (TTC), and pathological changes were examined using histological staining. The levels of inflammatory factors were analyzed using Enzyme-linked immunosorbent assay. Cell counting kit-8 assay and flow cytometry were used to measure cell viability and apoptosis, respectively. The global m6A level was detected using the commercial kit, and STAT5 mRNA m6A level was determined using methylated RNA binding protein immunoprecipitation (Me-RIP). ALKBH5, YTHDF1, and STAT5 interactions were analyzed using RIP and RNA pull-down assays.

RESULTS

ALKBH5 was upregulated in MCAO animals and OGD/R cell models. ALKBH5 knockdown exacerbated ER stress, neuroinflammation, and neuronal apoptosis in brain tissues and neuronal cells. ALKBH5 inhibited STAT5 mRNA stability and expression in an m6A-YTHDF1-dependent manner. STAT5 promoted ER stress by activating the PERK/eIF2/CHOP signaling pathway. Furthermore, STAT5 knockdown reversed the effects of ALKBH5 knockdown on OGD/R-induced ER stress and neuroinflammation in HT22 cells.

CONCLUSION

ALKBH5 knockdown exacerbated ischemic stroke by increasing ER stress-dependent neuroinflammation and neuronal apoptosis via the STAT5/PERK/EIF2α/CHOP signaling pathway in an m6A-YTHDF1-dependent manner.

Acacetin inhibits activation of microglia to improve neuroinflammation after subarachnoid hemorrhage through the PERK signaling pathway mediated autophagy

PURPOSE

To explore the effect of acacetin on subarachnoid hemorrhage (SAH) and its possible mechanism.

METHODS

SAH model of rat was established, and intraperitoneally injected with three doses of acacetin. To verify the role of PERK pathway, we used the CCT020312 (PERK inhibitor) and Tunicamycin (activators of endoplasmic reticulum stress). The SAH score, neurological function score, brain edema content, and Evans blue (EB) exudate were evaluated. Western blot was used to determine the expression of inflammation-associated proteins and PERK pathway. The activation of microglia was also determined through Iba-1 detection. TEM and immunofluorescence staining of LC3B were performed to observe the autophagy degree of SAH rats after acacetin. Tunel/NeuN staining, HE and Nissl' staining were performed for neuronal damage.

RESULTS

Acacetin increased the neurological function score, reduce brain water content, Evans blue exudation and SAH scores. The microglia in cerebral cortex were activated after SAH, while acacetin could inhibit its activation, and decreased the expression of TNF-α and IL-6 proteins. The pathological staining showed the severe neuronal damage and increased neuronal apoptosis after SAH, while acacetin could improve these pathological changes. We also visualized the alleviated autophagy after acacetin. The expression of Beclin1 and ATF4 proteins were increased, but acacetin could inhibit them. Acacetin also inactivated PERK pathway, which could improve the neuronal injury and neuroinflammation after SAH, inhibit the microglia activation and the overactivated autophagy through PERK pathway.

CONCLUSION

Acacetin may alleviate neuroinflammation and neuronal damage through PERK pathway, thus having the protective effect on EBI after SAH.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

Bioorthogonal Chemistry in Cellular Organelles

While bioorthogonal reactions are routinely employed in living cells and organisms, their application within individual organelles remains limited. In this review, we highlight diverse examples of bioorthogonal reactions used to investigate the roles of biomolecules and biological processes as well as advanced imaging techniques within cellular organelles. These innovations hold great promise for therapeutic interventions in personalized medicine and precision therapies. We also address existing challenges related to the selectivity and trafficking of subcellular dynamics. Organelle-targeted bioorthogonal reactions have the potential to significantly advance our understanding of cellular organization and function, provide new pathways for basic research and clinical applications, and shape the direction of cell biology and medical research.

Chromene-based BioAIEgens: 'in-water' synthesis, regiostructure-dependent fluorescence and ER-specific imaging

Exploration of artificial aggregation-induced emission luminogens (AIEgens) has garnered extensive interest in the past two decades. In particular, AIEgens possessing natural characteristics (BioAIEgens) have received more attention recently due to the advantages of biocompatibility, sustainability and renewability. However, the extremely limited number of BioAIEgens extracted from natural sources have retarded their development. Herein, a new class of BioAIEgens based on the natural scaffold of chromene have been facilely synthesized via green reactions in a water system. These compounds show regiostructure-, polymorphism- and substituent-dependent fluorescence, which clearly illustrates the close relationship between the macroscopic properties and hierarchical structure of aggregates. Due to the superior biocompatibility of the natural scaffold, chromene-based BioAIEgens can specifically target the endoplasmic reticulum (ER) via the introduction of tosyl amide. This work has provided a new chromene scaffold for functional BioAIEgens on the basis of green and sustainable 'in-water' synthesis, applicable regiostructure-dependent fluorescence, and effective ER-specific imaging.

Key Subdomains of Cerebral Dopamine Neurotrophic Factor Regulate Its Protective Function in 6-Hydroxydopamine-Lesioned PC12 Cells

Cerebral dopamine neurotrophic factor (CDNF) is a unique neurotrophic factor (NTF) that has shown significant neuroprotective and neurorestorative functions on midbrain dopaminergic neurons. The secondary structure of human CDNF protein contains eight α-helices. We previously found that two key helices, α1 and α7, regulated the intracellular trafficking and secretion of CDNF protein in different manners. The α1 mutation (M1) induced most CDNF proteins to reside in the endoplasmic reticulum and little be secreted extracellularly, while the α7 mutation (M7) caused the majority of CDNF proteins to be secreted out of the cells and little reside in the cells. However, the regulation of the two mutants on the function of CDNF remains unclear. In this study, we investigated the effects of M1 and M7 on the protective activity of CDNF in PC12 cells, which were treated with 6-hydroxydopamine (6-OHDA) to mimic Parkinson's disease. We found that both M1 and M7 could promote survival and inhibit apoptosis more effectively than Wt in 6-OHDA-lesioned PC12 cells. Therefore, these findings will advance our understanding of the important regulation of subdomains on the function of NTFs.

Regulation of cortical hyperexcitability in amyotrophic lateral sclerosis: focusing on glial mechanisms

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder characterized by the loss of both upper and lower motor neurons, resulting in muscle weakness, atrophy, paralysis, and eventually death. Motor cortical hyperexcitability is a common phenomenon observed at the presymptomatic stage of ALS. Both cell-autonomous (the intrinsic properties of motor neurons) and non-cell-autonomous mechanisms (cells other than motor neurons) are believed to contribute to cortical hyperexcitability. Decoding the pathological relevance of these dynamic changes in motor neurons and glial cells has remained a major challenge. This review summarizes the evidence of cortical hyperexcitability from both clinical and preclinical research, as well as the underlying mechanisms. We discuss the potential role of glial cells, particularly microglia, in regulating abnormal neuronal activity during the disease progression. Identifying early changes such as neuronal hyperexcitability in the motor system may provide new insights for earlier diagnosis of ALS and reveal novel targets to halt the disease progression.

BEDwARS: a robust Bayesian approach to bulk gene expression deconvolution with noisy reference signatures

Differential gene expression in bulk transcriptomics data can reflect change of transcript abundance within a cell type and/or change in the proportions of cell types. Expression deconvolution methods can help differentiate these scenarios. BEDwARS is a Bayesian deconvolution method designed to address differences between reference signatures of cell types and corresponding true signatures underlying bulk transcriptomic profiles. BEDwARS is more robust to noisy reference signatures and outperforms leading in-class methods for estimating cell type proportions and signatures. Application of BEDwARS to dihydropyridine dehydrogenase deficiency identified the possible involvement of ciliopathy and impaired translational control in the etiology of the disorder.

Fibin regulates cardiomyocyte hypertrophy and causes protein-aggregate-associated cardiomyopathy in vivo

Despite the identification of numerous molecular pathways modulating cardiac hypertrophy its pathogenesis is not completely understood. In this study we define an unexpected role for Fibin ("fin bud initiation factor homolog") in cardiomyocyte hypertrophy. Via gene expression profiling in hypertrophic murine hearts after transverse aortic constriction we found a significant induction of Fibin. Moreover, Fibin was upregulated in another mouse model of cardiac hypertrophy (calcineurin-transgenics) as well as in patients with dilated cardiomyopathy. Immunoflourescence microscopy revealed subcellular localization of Fibin at the sarcomeric z-disc. Overexpression of Fibin in neonatal rat ventricular cardiomyocytes revealed a strong anti-hypertrophic effect through inhibiting both, NFAT- and SRF-dependent signalling. In contrast, transgenic mice with cardiac-restricted overexpression of Fibin developed dilated cardiomyopathy, accompanied by induction of hypertrophy-associated genes. Moreover, Fibin overexpression accelerated the progression to heart failure in the presence of prohypertrophic stimuli such as pressure overload and calcineurin overexpression. Histological and ultrastructural analyses surprisingly showed large protein aggregates containing Fibin. On the molecular level, aggregate formation was accompanied by an induction of the unfolded protein response subsequent UPR-mediated apoptosis and autophagy. Taken together, we identified Fibin as a novel potent negative regulator of cardiomyocyte hypertrophy in vitro. Yet, heart-specific Fibin overexpression in vivo causes development of a protein-aggregate-associated cardiomyopathy. Because of close similarities to myofibrillar myopathies, Fibin represents a candidate gene for cardiomyopathy and Fibin transgenic mice may provide additional mechanistic insight into aggregate formation in these diseases.

Discovery of a Potent and Selective CDKL5/GSK3 Chemical Probe That Is Neuroprotective

Despite mediating several essential processes in the brain, including during development, cyclin-dependent kinase-like 5 (CDKL5) remains a poorly characterized human protein kinase. Accordingly, its substrates, functions, and regulatory mechanisms have not been fully described. We realized that availability of a potent and selective small molecule probe targeting CDKL5 could enable illumination of its roles in normal development as well as in diseases where it has become aberrant due to mutation. We prepared analogs of AT-7519, a compound that has advanced to phase II clinical trials and is a known inhibitor of several cyclin-dependent kinases (CDKs) and cyclin-dependent kinase-like kinases (CDKLs). We identified analog 2 as a highly potent and cell-active chemical probe for CDKL5/GSK3 (glycogen synthase kinase 3). Evaluation of its kinome-wide selectivity confirmed that analog 2 demonstrates excellent selectivity and only retains GSK3α/β affinity. We next demonstrated the inhibition of downstream CDKL5 and GSK3α/β signaling and solved a co-crystal structure of analog 2 bound to human CDKL5. A structurally similar analog (4) proved to lack CDKL5 affinity and maintain potent and selective inhibition of GSK3α/β, making it a suitable negative control. Finally, we used our chemical probe pair (2 and 4) to demonstrate that inhibition of CDKL5 and/or GSK3α/β promotes the survival of human motor neurons exposed to endoplasmic reticulum stress. We have demonstrated a neuroprotective phenotype elicited by our chemical probe pair and exemplified the utility of our compounds to characterize the role of CDKL5/GSK3 in neurons and beyond.

Immunomodulatory therapy with glatiramer acetate reduces endoplasmic reticulum stress and mitochondrial dysfunction in experimental autoimmune encephalomyelitis

Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are found in lesions of multiple sclerosis (MS) and animal models of MS such as experimental autoimmune encephalomyelitis (EAE), and may contribute to the neuronal loss that underlies permanent impairment. We investigated whether glatiramer acetate (GA) can reduce these changes in the spinal cords of chronic EAE mice by using routine histology, immunostaining, and electron microscopy. EAE spinal cord tissue exhibited increased inflammation, demyelination, mitochondrial dysfunction, ER stress, downregulation of NAD+ dependent pathways, and increased neuronal death. GA reversed these pathological changes, suggesting that immunomodulating therapy can indirectly induce neuroprotective effects in the CNS by mediating ER stress.

Brain injury triggers cell-type-specific and time-dependent endoplasmic reticulum stress responses

The unfolded protein response (UPR) is a signal transduction network that responds to endoplasmic reticulum (ER) stress by coordinating protein homeostasis to maintain cell viability. The UPR can also trigger cell death when adaptive responses fail to improve protein homeostasis. Despite accumulating evidence suggesting that the UPR plays a role in neurodegenerative diseases and brain insults, our understanding of how ER stress is induced under neuropathological conditions is limited. Here, we investigated the cell- and time-specific patterns of the ER stress response after brain injury using ER stress-activated indicator (ERAI) mice, which enable monitoring of the UPR in vivo via increased fluorescence of a spliced XBP-1 protein fused with the green fluorescent protein (GFP) variant Venus. Following cortical stab injury of ERAI mice, the GFP signal and number of GFP⁺ cells increased in the ipsilateral cortex throughout the observation period (6 h to 7 days post-injury), confirming the induction of the UPR. GFP signals were observed in injured neurons early (from 6 h) after brain injury. However, non-neuronal cells, mainly endothelial cells followed by astrocytes, accounted for the majority of GFP⁺ cells after brain injury. Similar results were obtained in a mouse model of focal cerebral ischemia. These findings suggest that activation of the UPR in both neuronal and non-neuronal cells, especially endothelial cells and astrocytes, may play an important role in and could be a potential therapeutic target for acute brain injuries.

Neuronal endoplasmic reticulum architecture and roles in axonal physiology

The endoplasmic reticulum (ER) is the largest membrane compartment within eukaryotic cells and is emerging as a key coordinator of many cellular processes. The ER can modulate local calcium fluxes and communicate with other organelles like the plasma membrane. The importance of ER in neuronal processes such as neurite growth, axon repair and neurotransmission has recently gained much attention. In this review, we highlight the importance of the ER tubular network in axonal homeostasis and discuss how the generation and maintenance of the thin tubular ER network in axons and synapses, requires a cooperative effort of ER-shaping proteins, cytoskeleton and autophagy processes.

A Potent and Selective CDKL5/GSK3 Chemical Probe is Neuroprotective

Despite mediating several essential processes in the brain, including during development, cyclin-dependent kinase-like 5 (CDKL5) remains a poorly characterized human protein kinase. Accordingly, its substrates, functions, and regulatory mechanisms have not been fully described. We realized that availability of a potent and selective small molecule probe targeting CDKL5 could enable illumination of its roles in normal development as well as in diseases where it has become aberrant due to mutation. We prepared analogs of AT-7519, a known inhibitor of several cyclin dependent and cyclin-dependent kinase-like kinases that has been advanced into Phase II clinical trials. We identified analog 2 as a highly potent and cell-active chemical probe for CDKL5/GSK3 (glycogen synthase kinase 3). Evaluation of its kinome-wide selectivity confirmed that analog 2 demonstrates excellent selectivity and only retains GSK3α/β affinity. As confirmation that our chemical probe is a high-quality tool to use in directed biological studies, we demonstrated inhibition of downstream CDKL5 and GSK3α/β signaling and solved a co-crystal structure of analog 2 bound to CDKL5. A structurally similar analog ( 4 ) proved to lack CDKL5 affinity and maintain potent and selective inhibition of GSK3α/β. Finally, we used our chemical probe pair ( 2 and 4 ) to demonstrate that inhibition of CDKL5 and/or GSK3α/β promotes the survival of human motor neurons exposed to endoplasmic reticulum (ER) stress. We have demonstrated a neuroprotective phenotype elicited by our chemical probe pair and exemplified the utility of our compounds to characterize the role of CDKL5/GSK3 in neurons and beyond.

Biological Effects of Black Phosphorus Nanomaterials on Mammalian Cells and Animals

The remarkable progress of applied black phosphorus nanomaterials (BPNMs) is attributed to BP's outstanding properties. Due to its potential for applications, environmental release and subsequent human exposure are virtually inevitable. Therefore, how BPNMs impact biological systems and human health needs to be considered. In this comprehensive Minireview, the most recent advancements in understanding the mechanisms and regulation factors of BPNMs' endogenous toxicity to mammalian systems are presented. These achievements lay the groundwork for an understanding of its biological effects, aimed towards establishing regulatory principles to minimize the adverse health impacts.

Melatonin Can Modulate Neurodegenerative Diseases by Regulating Endoplasmic Reticulum Stress

As people age, their risks of developing degenerative diseases such as cancer, diabetes, Parkinson's Disease (PD), Alzheimer's Disease (AD), rheumatoid arthritis, and osteoporosis are generally increasing. Millions of people worldwide suffer from these diseases as they age. In most countries, neurodegenerative diseases are generally recognized as the number one cause afflicting the elderly. Endoplasmic reticulum (ER) stress has been suggested to be associated with some human neurological diseases, such as PD and AD. Melatonin, a neuroendocrine hormone mainly synthesized in the pineal gland, is involved in pleiotropically biological functions, including the control of the circadian rhythm, immune enhancement, and antioxidant, anti-aging, and anti-tumor effects. Although there are many papers on the prevention or suppression of diseases by melatonin, there are very few papers about the effects of melatonin on ER stress in neurons and neurodegenerative diseases. This paper aims to summarize and present the effects of melatonin reported so far, focusing on its effects on neurons and neurodegenerative diseases related to ER stress. Studies have shown that the primary target molecule of ER stress for melatonin is CHOP, and PERK and GRP78/BiP are the secondary target molecules. Therefore, melatonin is crucial in protecting neurons and treating neurodegeneration against ER stress.

Neuroprotective Strategies for Stroke by Natural Products: Advances and Perspectives

Cerebral ischemic stroke is a disease with high prevalence and incidence. Its management focuses on rapid reperfusion with intravenous thrombolysis and endovascular thrombectomy. Both therapeutic strategies reduce disability, but the therapy time window is short, and the risk of bleeding is high. Natural products (NPs) have played a key role in drug discovery, especially for cancer and infectious diseases. However, they have made little progress in clinical translation and pose challenges to the treatment of stroke. Recently, with the investigation of precise mechanisms in cerebral ischemic stroke and the technological development of NP-based drug discovery, NPs are addressing these challenges and opening up new opportunities in cerebral stroke. Thus, in this review, we first summarize the structure and function of diverse NPs, including flavonoids, phenols, terpenes, lactones, quinones, alkaloids, and glycosides. Then we propose the comprehensive neuroprotective mechanism of NPs in cerebral ischemic stroke, which involves complex cascade processes of oxidative stress, mitochondrial damage, apoptosis or ferroptosis-related cell death, inflammatory response, and disruption of the blood-brain barrier (BBB). Overall, we stress the neuroprotective effect of NPs and their mechanism on cerebral ischemic stroke for a better understanding of the advances and perspective in NPs application that may provide a rationale for the development of innovative therapeutic regimens in ischemic stroke.

A KO mouse model for the lncRNA Lhx1os produces motor neuron alterations and locomotor impairment

Here, we describe a conserved motor neuron-specific long non-coding RNA, Lhx1os, whose knockout in mice produces motor impairment and postnatal reduction of mature motor neurons (MNs). The ER stress-response pathway result specifically altered with the downregulation of factors involved in the unfolded protein response (UPR). Lhx1os was found to bind the ER-associated PDIA3 disulfide isomerase and to affect the expression of the same set of genes controlled by this protein, indicating that the two factors act in conjunction to modulate the UPR. Altogether, the observed phenotype and function of Lhx1os indicate its important role in the control of MN homeostasis and function.

Leptin alleviates endoplasmic reticulum stress induced by cerebral ischemia/reperfusion injury via the PI3K/Akt signaling pathway

BACKGROUND

Cerebral ischemic/reperfusion injury (CIRI) is a key factor for the prognosis of ischemic stroke (IS), the leading disease in terms of global disability and fatality rates. Recent studies have shown that endoplasmic reticulum stress (ERS) may be a target against CIRI and that leptin, a peptide hormone, has neuroprotective activity to mitigate CIRI.

METHODS

An in vitro CIRI model was induced in primary cortical neurons by oxygen-glucose deprivation and reoxygenation (OGD/R) after pretreatment with LY294002 (10 µmol/L) and/or leptin (0.4 mg/L), and cell viability, neuronal morphology and endoplasmic reticulum (ER) dysfunction were evaluated. An in vivo CIRI model was established in rats by middle cerebral artery occlusion and reperfusion (MCAO/R) after the injection of LY294002 (10 μmol/L) and/or leptin (1 mg/kg), and neurological function, infarct volume, cerebral pathological changes, the expression of ERS-related proteins and cell apoptosis were examined.

RESULTS

In vitro, leptin treatment improved the cell survival rate, ameliorated neuronal pathological morphology and alleviated OGD/R-induced ERS. In vivo, administration of leptin significantly reduced the infarct volume, neurological deficit scores and neuronal apoptosis as well as pathological alterations. In addition, leptin suppressed MCAO/R-induced ERS and may decrease apoptosis by inhibiting ERS-related death and caspase 3 activation. It also regulated expression of the antiapoptotic protein Bcl-2 and the proapoptotic protein Bax in the cortex. Furthermore, the inhibitory effect of leptin on ERS was significantly decreased by the effective phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002.

CONCLUSIONS

These results confirm that ERS plays an important role in CIRI and that leptin can inhibit the activation of ERS through the PI3K/Akt pathway, thereby alleviating CIRI. These findings provide novel therapeutic targets for IS.

CdTe quantum dots trigger oxidative stress and endoplasmic reticulum stress-induced apoptosis and autophagy in rat Schwann cell line RSC96

In the current study, the cytotoxicity and mechanisms of cadmium telluride quantum dots (CdTe QDs) on RSC96 cells were evaluated by exposing different doses of CdTe QDs for 24 h. Two types of cell death, including apoptosis and autophagy, as well as two important organelles, mitochondria and endoplasmic reticulum, were focused after CdTe QDs exposure. The results showed that CdTe QDs induced apoptosis in RSC96 cells in a concentration-dependent manner; promoted the accumulation of intracellular reactive oxygen species; decreased the mitochondrial membrane potential; caused the release of cytochrome c; and also increased the expression of Bcl-2 associated X protein, caspase-3, and cytochrome c proteins and decreased the expression of Bcl-2 protein. Further results also confirmed that CdTe QDs could be internalized by RSC96 cells, and the exposure and internalization of CdTe QDs could induce excessive endoplasmic reticulum stress in the cells, and the expression levels of binding immunoglobulin protein, C/EBP homologous protein, and caspase12 proteins were increased in a concentration-dependent manner. Moreover, autophagy-related proteins LC3II, Beclin1, and P62 all increased after CdTe QDs exposure, suggesting that CdTe QDs exposure both promoted autophagosome formation and inhibited autophagosome degradation, and that CdTe QDs affected the autophagic flow in RSC96 cells. In conclusion, CdTe QDs are able to cause apoptosis and autophagy in RSC96 cells through mitochondrial and endoplasmic reticulum stress pathways, and the possible neurotoxicity of CdTe QDs should be further investigated.

The functions of IRE1α in neurodegenerative diseases: Beyond ER stress

Inositol-requiring enzyme 1 α (IRE1α) is a type I transmembrane protein that resides in the endoplasmic reticulum (ER). IRE1α, which is the primary sensor of ER stress, has been proven to maintain intracellular protein homeostasis by activating X-box binding protein 1 (XBP1). Further studies have revealed novel physiological functions of the IRE1α, such as its roles in mRNA and protein degradation, inflammation, immunity, cell proliferation and cell death. Therefore, the function of IRE1α is not limited to its role in ER stress; IRE1α is also important for regulating other processes related to cellular physiology. Furthermore, IRE1α plays a key role in neurodegenerative diseases that are caused by the phosphorylation of Tau protein, the accumulation of α-synuclein (α-syn) and the toxic effects of mutant Huntingtin (mHtt). Therefore, targeting IRE1α is a valuable approach for treating neurodegenerative diseases and regulating cell functions. This review discusses the role of IRE1α in different cellular processes, and emphasizes the importance of IRE1α in neurodegenerative diseases.

Green Synthesis of Platinum Nanoparticles for Biomedical Applications

The diverse biological properties of platinum nanoparticles (PtNPs) make them ideal for use in the development of new tools in therapy, diagnostics, and other biomedical purposes. "Green" PtNPs synthesis is of great interest as it is eco-friendly, less energy-consuming and minimizes the amount of toxic by-products. This review is devoted to the biosynthesis properties of platinum nanoparticles based on living organisms (bacteria, fungi, algae, and plants) use. The participation of various biological compounds in PtNPs synthesis is highlighted. The biological activities of "green" platinum nanoparticles (antimicrobial, anticancer, antioxidant, etc.), the proposed mechanisms of influence on target cells and the potential for their further biomedical application are discussed.

Neurodegenerative Disorder Risk in Krabbe Disease Carriers

Krabbe disease (KD) is a rare autosomal recessive disorder caused by mutations in the galactocerebrosidase gene (GALC). Defective GALC causes aberrant metabolism of galactolipids present almost exclusively in myelin, with consequent demyelinization and neurodegeneration of the central and peripheral nervous system (NS). KD shares some similar features with other neuropathies and heterozygous carriers of GALC mutations are emerging with an increased risk in developing NS disorders. In this work, we set out to identify possible variations in the proteomic profile of KD-carrier brain to identify altered pathways that may imbalance its homeostasis and that may be associated with neurological disorders. The differential analysis performed on whole brains from 33-day-old twitcher (galc -/-), heterozygous (galc +/-), and wild-type mice highlighted the dysregulation of several multifunctional factors in both heterozygous and twitcher mice. Notably, the KD-carrier mouse, despite its normal phenotype, presents the deregulation of vimentin, receptor of activated protein C kinase 1 (RACK1), myelin basic protein (MBP), 2',3'-cyclic-nucleotide 3'-phosphodiesterase (CNP), transitional endoplasmic reticulum ATPase (VCP), and N-myc downstream regulated gene 1 protein (NDRG1) as well as changes in the ubiquitinated-protein pattern. Our findings suggest the carrier may be affected by dysfunctions classically associated with neurodegeneration: (i) alteration of (mechano) signaling and intracellular trafficking, (ii) a generalized affection of proteostasis and lipid metabolism, with possible defects in myelin composition and turnover, and (iii) mitochondrion and energy supply dysfunctions.

Subcellular Delivery of Hydrogen Sulfide Using Small Molecule Donors Impacts Organelle Stress

Hydrogen sulfide (H₂S) is an endogenously produced gaseous signaling molecule with important roles in regulating organelle function and stress. Because of its high reactivity, targeted delivery of H₂S using small molecule H₂S donors has garnered significant interest to minimize off-target effects. Although mitochondrially targeted H₂S donors, such as AP39, have been reported previously and exhibit significantly higher potency than nontargeted donors, the expansion of targeted H₂S delivery to other subcellular organelles remains largely absent. To fill this key unmet need, we report a library of organelle-targeted H₂S donors that localize H₂S delivery to specific subcellular organelles, including the Golgi apparatus, lysosome, endoplasmic reticulum, and mitochondria. We measured H₂S production in vitro from each donor, confirmed the localization of H₂S delivery using organelle-specific H₂S responsive fluorescent probes, and demonstrated enhanced potency of these targeted H₂S donors in providing protection against organelle-specific stress. We anticipate this class of targeted H₂S donors will enable future studies of subcellular roles of H₂S and the pathways by which H₂S alleviates subcellular organelle stress.

Cocoa Extract Provides Protection against 6-OHDA Toxicity in SH-SY5Y Dopaminergic Neurons by Targeting PERK

Parkinson’s disease (PD) represents one of the most common neurodegenerative disorders, characterized by a dopamine (DA) deficiency in striatal synapses and misfolded toxic α-synuclein aggregates with concomitant cytotoxicity. In this regard, the misfolded proteins accumulation in neurodegenerative disorders induces a remarkable perturbations of endoplasmic reticulum (ER) homeostasis leading to persistent ER stress, which in turn, effects protein synthesis, modification, and folding quality control. A large body of evidence suggests that natural products target the ER stress signaling pathway, exerting a potential action in cancers, diabetes, cardiovascular and neurodegenerative diseases. This study aims to assess the neuroprotective effect of cocoa extract and its purified fractions against a cellular model of Parkinson’s disease represented by 6-hydroxydopamine (6-OHDA)-induced SH-SY5Y human neuroblastoma. Our findings demonstrate, for the first time, the ability of cocoa to specifically targets PERK sensor, with significant antioxidant and antiapoptotic activities as both crude and fractioning extracts. In addition, cocoa also showed antiapoptotic properties in 3D cell model and a notable ability to inhibit the accumulation of α-synuclein in 6-OHDA-induced cells. Overall, these results indicate that cocoa exerts neuroprotective effects suggesting a novel possible strategy to prevent or, at least, mitigate neurodegenerative disorders, such as PD.

ER stress and UPR in Alzheimer's disease: mechanisms, pathogenesis, treatments

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by gradual loss of memory and cognitive function, which constitutes a heavy burden on the healthcare system globally. Current therapeutics to interfere with the underlying disease process in AD is still under development. Although many efforts have centered on the toxic forms of Aβ to effectively tackle AD, considering the unsatisfactory results so far it is vital to examine other targets and therapeutic approaches as well. The endoplasmic reticulum (ER) stress refers to the build-up of unfolded or misfolded proteins within the ER, thus, perturbing the ER and cellular homeostasis. Emerging evidence indicates that ER stress contributes to the onset and development of AD. A thorough elucidation of ER stress machinery in AD pathology may help to open up new therapeutic avenues in the management of this devastating condition to relieve the cognitive dementia symptoms. Herein, we aim at deciphering the unique role of ER stress in AD pathogenesis, reviewing key findings, and existing controversy in an attempt to summarize plausible therapeutic interventions in the management of AD pathophysiology.

A Pipeline for Natural Small Molecule Inhibitors of Endoplasmic Reticulum Stress

The homeostasis of eukaryotic cells is inseverable of that of the endoplasmic reticulum (ER). The main function of this organelle is the synthesis and folding of a significant portion of cellular proteins, while it is also the major calcium reservoir of the cell. Upon unresolved ER stress, a set of stress response signaling pathways that are collectively labeled as the unfolded protein response (UPR) is activated. Prolonged or intense activation of this molecular machinery may be deleterious. It is known that compromised ER homeostasis, and consequent UPR activation, characterizes the pathogenesis of neurodegenerative diseases. In an effort to discover new small molecules capable of countering ER stress, we subjected a panel of over 100 natural molecules to a battery of assays designed to evaluate several hallmarks of ER stress. The protective potential of these compounds against ER stress was evaluated at the levels of calcium homeostasis, key gene and protein expression, and levels of protein aggregation in fibroblasts. The most promising compounds were subsequently tested in neuronal cells. This framework resulted in the identification of several bioactive molecules capable of countering ER stress and deleterious events associated to it. Delphinidin stands out as the most promising candidate against neurodegeneration. This compound significantly inhibited the expression of UPR biomarkers, and displayed a strong potential to inhibit protein aggregation in the two aforementioned cell models. Our results indicate that natural products may be a valuable resource in the development of an effective therapeutic strategy against ER stress-related diseases.

The disturbance of protein synthesis/degradation homeostasis is a common trait of age-related neurodegenerative disorders

Protein homeostasis or "proteostasis" represent the process that regulates the balance of the intracellular functional and "healthy" proteins. Proteostasis is fundamental to preserve physiological metabolic processes in the cell and it allow to respond to any given stimulus as the expression of components of the proteostasis network is customized according to the proteomic demands of different cellular environments. In conditions that promote unfolding/misfolding of proteins chaperones act as signaling molecules inducing extreme measures to either fix the problem or destroy unfolded proteins. When the chaperone machinery fails under pathological insults unfolded proteins induce the endoplasmic reticulum (ER) stress activating the unfolded protein response (UPR) machinery. The activation of the UPR restores ER proteostasis primarily through the transcriptional remodeling of ER protein folding, trafficking, and degradation pathways, such as the ubiquitin proteasome system (UPS). If these mechanisms do not manage to clear the aberrant proteins, proteasome overload and become defective, and misfolded proteins may form aggregates thus extending the UPR mechanism. These aggregates are then attempted to be cleared by macroautophagy. Impaired proteostasis promote the accumulation of misfolded proteins that exacerbate the damage to chaperones, surveillance systems and/or degradative activities. Remarkably, the removal of toxic misfolded proteins is critical for all cells, but it is especially significant in neurons since these cannot be readily replaced. In neurons, the maintenance of efficient proteostasis is essential to healthy aging since the dysregulation of the proteostasis network can lead to neurodegenerative disease. Each of these brain pathologies is characterized by the repeated misfolding of one of more peculiar proteins, which evade both the protein folding machinery and cellular degradation mechanisms and begins to form aggregates that nucleate out into large fibrillar aggregates. In this chapter we describe the mechanisms, associated with faulty proteostasis, that promote the formation of protein aggregates, amyloid fibrils, intracellular, and extracellular inclusions in the most common nondegenerative disorders also referred to as protein misfolding disorders.

A HBDI-Based Fluorescent Probe for Labeling Endoplasmic Reticulum in Living Cells

The endoplasmic reticulum (ER) is an important organelle in eukaryotic cells and is closely involved in the synthesis and processing of proteins, as well as the storage, regulation, and release of calcium. A series of signaling pathways within the ER play a crucial part in the pathogenesis of various diseases, including cancer. Thus, it is necessary to design ER-targeting probes to monitor these signaling pathways. Additionally, precision medicine also requires new ER-targeting group to facilitate the delivery of drug cargoes to the ER. However, only a limited number of ER-targeting groups have been used for the design of fluorescent probes for ER imaging in living cells, as well as the development of ER-targeted drug delivery systems. Herein, a new ER-targeting fluorescent probe (BDI-ER) was designed and prepared. BDI-ER contains the hydrophilic fluorophore, derived from the core structure of GFP, and two hydrophobic octadecane chains. The amphipathic nature of BDI-ER facilitates localization in the ER. Live cell imaging demonstrated selective localization of BDI-ER towards ER compared to other organelles. Additionally, co-localization imaging in various cell lines indicate that BDI-ER is effective at targeting the ER.

Fluorescent probes for biomolecule detection under environmental stress

The use of fluorescent probes in visible detection has been developed over the last several decades. Biomolecules are essential in the biological processes of organisms, and their distribution and concentration are largely influenced by environmental factors. Significant advances have occurred in the applications of fluorescent probes for the detection of the dynamic localization and quantity of biomolecules during various environmental stress-induced physiological and pathological processes. Herein, we summarize representative examples of small molecule-based fluorescent probes that provide bimolecular information when the organism is under environmental stress. The discussion includes strategies for the design of smart small-molecule fluorescent probes, in addition to their applications in biomolecule imaging under environmental stresses, such as hypoxia, ischemia-reperfusion, hyperthermia/hypothermia, organic/inorganic chemical exposure, oxidative/reductive stress, high glucose stimulation, and drug treatment-induced toxicity. We believe that comprehensive insight into the beneficial applications of fluorescent probes in biomolecule detection under environmental stress should enable the further development and effective application of fluorescent probes in the biochemical and biomedical fields.

Regulation of endoplasmic reticulum stress by hesperetin: Focus on antitumor and cytoprotective effects

BACKGROUND

Cancer is still an all-times issue due to a large and even increasing number of deaths. Impaired genes regulating cell proliferation and apoptosis are targets for the development of novel cancer treatments.

HYPOTHESIS

Increased transcription of NADPH oxidase activator (NOXA), Bcl2-like11 (BIM), BH3-only proteins and p53 unregulated apoptosis modulator (PUMA) is caused by the imbalance between pro- and anti-apoptotic Bcl-2 proteins due to endoplasmic reticulum (ER) stress. The membranous network of ER is present in all eukaryotic cells. ER stress facilitates the interaction between Bax and PUMA, triggering the release of cytochrome C. As a main intracellular organelle, ER is responsible for translocation as well as post-translation modification and protein folding.

RESULTS

Hesperetin is a cytoprotective flavonone, which acts against ER stress and protects from cell damage induced by reactive oxygen species (ROS) and reactive nitrogen species (RNS). Hesperetin inhibits lipid peroxidation induced by Fe²⁺ and l-ascorbic acid in rat brain homogenates.

CONCLUSION

This review deals with the anticancer effects of hesperetin regarding the regulation of ER stress as a principal mechanism in the pathogenesis of tumors.

Low-dose silver nanoparticles plus methyl mercury exert embryotoxic effects on mouse blastocysts via endoplasmic reticulum stress and mitochondrial apoptosis

The health and environmental impacts of the increasing commercial use of silver nanoparticles (AgNPs) are a growing concern. Methyl mercury (MeHg) is a potent toxin that biotransforms from mercury or inorganic mercury compounds in waterways and causes dangerous environmental contamination. However, the potential interactions and combined effects of AgNPs and MeHg are yet to be established. In the current study, we showed that low/non-embryotoxic doses of AgNPs and MeHg interact synergistically to induce embryotoxicity and further explored the underlying mechanisms affecting mouse embryo development. Notably, co-treatment with noncytotoxic concentrations of AgNPs (10 μM) and MeHg (0.1 μM) triggered apoptotic processes and embryotoxicity in mouse blastocysts and evoked intracellular reactive oxygen species (ROS) generation, which was effectively blocked by preincubation with 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), a classic antioxidant. Further experiments demonstrated that ROS serve as a key upstream inducer of endoplasmic reticulum (ER) stress and mitochondria-dependent apoptotic processes in AgNP/MeHg-induced injury of mouse embryo implantation and pre- and postimplantation development. Our results collectively indicate that AgNP and MeHg at non-embryotoxic concentrations can synergistically evoke ROS, ultimately causing embryotoxicity through promotion of ER stress and mitochondria-dependent apoptotic signaling cascades.

Glucose metabolism and AD: evidence for a potential diabetes type 3

BACKGROUND

Alzheimer's disease is the most prevalent cause of dementia in the elderly. Neuronal death and synaptic dysfunctions are considered the main hallmarks of this disease. The latter could be directly associated to an impaired metabolism. In particular, glucose metabolism impairment has demonstrated to be a key regulatory element in the onset and progression of AD, which is why nowadays AD is considered the type 3 diabetes.

METHODS

We provide a thread regarding the influence of glucose metabolism in AD from three different perspectives: (i) as a regulator of the energy source, (ii) through several metabolic alterations, such as insulin resistance, that modify peripheral signaling pathways that influence activation of the immune system (e.g., insulin resistance, diabetes, etc.), and (iii) as modulators of various key post-translational modifications for protein aggregation, for example, influence on tau hyperphosphorylation and other important modifications, which determine its self-aggregating behavior and hence Alzheimer's pathogenesis.

CONCLUSIONS

In this revision, we observed a 3 edge-action in which glucose metabolism impairment is acting in the progression of AD: as blockade of energy source (e.g., mitochondrial dysfunction), through metabolic dysregulation and post-translational modifications in key proteins, such as tau. Therefore, the latter would sustain the current hypothesis that AD is, in fact, the novel diabetes type 3.

Inhibition of the ISR abrogates mGluR5-dependent long-term depression and spatial memory deficits in a rat model of Alzheimer's disease

Soluble amyloid-β-protein (Aβ) oligomers, a major hallmark of AD, trigger the integrated stress response (ISR) via multiple pathologies including neuronal hyperactivation, microvascular hypoxia, and neuroinflammation. Increasing eIF2α phosphorylation, the core event of ISR, facilitates metabotropic glutamate receptor (mGluR)-dependent long-term depression (LTD), and suppressing its phosphorylation has the opposite effect. Having found the facilitation of mGluR5-LTD by Aβ in live rats, we wondered if suppressing eIF2α phosphorylation cascade would protect against the synaptic plasticity and cognitive disrupting effects of Aβ. We demonstrate here that the facilitation of mGluR5-LTD in a delayed rat model by single i.c.v. injection of synthetic Aβ_1-42. Systemic administration of the small-molecule inhibitor of the ISR called ISRIB (trans-isomer) prevents Aβ-facilitated LTD and abrogates spatial learning and memory deficits in the hippocampus in exogenous synthetic Aβ-injected rats. Moreover, ex vivo evidence indicates that ISRIB normalizes protein synthesis in the hippocampus. Targeting the ISR by suppressing the eIF2α phosphorylation cascade with the eIF2B activator ISRIB may provide protective effects against the synaptic and cognitive disruptive effects of Aβ which likely mediate the early stage of sporadic AD.

Fluorescent probes for targeting endoplasmic reticulum: design strategies and their applications

Advances in developing organic fluorescent probes and fluorescence imaging techniques have enhanced our understanding of cell biology. The endoplasmic reticulum (ER) is a dynamic structure that plays a crucial role in protein synthesis, post-translational modifications, and lipid metabolism. The malfunction of ER contributes to several physiological and pathological conditions. Therefore, the investigations on the imaging and role of ER have attracted a lot of attention. Due to their simplicity, synthetic tunability, photostability, high quantum yields, easier cellular uptake, and lower cytotoxicity, organic fluorophores offer invaluable tools for the precision targeting of various cellular organelles and probe ER dynamics. The precision staining is made possible by incorporating specific functional groups having preferential and local organelle biomolecular interactions. For instance, functional moieties such as methyl sulfonamide, sulfonylurea, and pentafluorophenyl assist in ER targeting and thus have become essential tools to probe a deeper understanding of their dynamics. Furthermore, dual-function fluorescent probes that simultaneously image ER and detect specific physiological parameters or biological analytes were achieved by introducing special recognition or chemically reactive sites. This article attempts to comprehensively capture various design strategies currently employed by researchers utilizing small organic molecules to target the ER and detect specific analytes.