Repurposed drugs targeting eIF2α-P-mediated translational repression prevent neurodegeneration in mice

Pharmacological Regulation of Heat Shock Response via Aptamer-Antidote Couple

Heat shock factor 1 (HSF1) orchestrates the cellular heat shock response (HSR) by binding to heat shock elements (HSEs) in the promoters of genes encoding heat shock proteins (HSPs). In a nonstressed state, HSF1 exists in a dormant complex with HSP90 and other chaperones. Upon cellular stress or upon inhibition of HSP90, HSF1 dissociates from the complex and activates the expression of HSPs to mitigate protein misfolding and aggregation. This study explores the potential of RNA aptamers selected against HSP90 to modulate HSF1 activity, with a role in Huntington's disease model characterized by protein aggregation. Selected aptamers disrupted the HSP90-HSF1 interaction, enhancing the binding of HSF1 with HSEs. This upregulated heat shock response (HSR) and reduced aggregation of Q74-huntingtin in Neuro 2a cells with improved cell survival. Designed antidote sequences could reverse the effect of the aptamers on the HSF1-HSE interaction, allowing for fine-tuning of HSR. Chronic activation of stress response pathways is deleterious for cellular fitness. Our findings suggest that coupling an antidote with an aptamer offers a novel therapeutic strategy to regulate cellular proteostasis under disease conditions.

Inhibition of the Integrated Stress Response Prevents Natural Forgetting and Corrects Accelerated Forgetting Associated with Epilepsy

The neural mechanisms underlying the natural and maladaptive forgetting of established memory remain largely unknown. Brain disease states might hijack the physiological forgetting mechanisms, resulting in maladaptive forgetting such as accelerated forgetting that contributes to cognitive decline in various neurologic conditions including epilepsy. Based on the key role of the integrated stress response (ISR) in memory storage and maintenance, we determined whether the ISR underpins natural and accelerated forgetting. Here, based on the object location recognition (OLR) and novel object recognition (NOR) paradigms in mice, we found that the ISR was activated while an established memory was naturally forgotten, which was denoted by increased levels of phosphorylated eukaryotic translation initiation factor 2α (eIF2α) and activating transcription factor 4 (ATF4), and reduced general protein synthesis. Multiple administrations of ISRIB, a small molecule ISR inhibitor, during the memory retention interval attenuated the ISR activation, and prevented the natural forgetting of established OLR and NOR memories. At the same time, a single injection of ISRIB has no effect on natural forgetting and memory retrieval. Moreover, administration of pentylenetetrazole (PTZ), an inducer of epileptic seizures, during the memory retention interval provoked the ISR activation and accelerated forgetting, which was corrected by ISRIB treatment. Together, our findings suggest that the ISR is critically involved in natural forgetting and accelerated forgetting associated with epilepsy, and pharmacological inhibition of the ISR may emerge as a novel intervention strategy for accelerated forgetting in patients with epilepsy.

Redox regulation of lung endothelial PERK, unfolded protein response (UPR) and proliferation via NOX1: Targeted inhibition as a potential therapy for PAH

AIMS

Reactive oxygen species (ROS) play an important role in the pathogenesis of pulmonary arterial hypertension (PAH) and NADPH oxidases (NOXs) as sources of ROS are implicated in the development of the disease. We previously showed that NOX isozyme 1 (NOX1)-derived ROS contributes to pulmonary vascular endothelial cell (EC) proliferation in response to PAH triggers in vitro. However, whether and how NOX1 is involved in PAH in vivo have not been explored nor has NOX1 been examined as a viable and effective therapeutic disease target.

METHODS AND RESULTS

Herein, infusion of mice exposed to Sugen/hypoxia (10 % O2) with a specific NOX1 inhibitor, NOXA1ds, delivered via osmotic minipumps (i.p.), significantly suppressed pathological changes in hemodynamic parameters characteristic of PAH. Furthermore, lungs of human patients with idiopathic PAH (iPAH) and exploratory RNA-seq analysis of hypoxic human pulmonary ECs, in which NOX1 was suppressed, were probed. The findings showed a clear indication of NOX1 in the promotion of both protein disulfide isomerase (PDI) and the unfolded protein response (UPR; in particular, the PERK arm of the pathway including eIF2α and ATF4) leading to proliferation. In aggregate, these results are consistent with a causal role for NOX1 in the development of mouse and human PAH and reveal a novel and mechanistic pathway by which NOX1 activates the UPR response during EC proliferation.

CONCLUSION

NOX1 promotes phenotypic changes in ECs that are pivotal to proliferation and PAH through activation of the UPR. Taken together, our results are consistent with selective inhibition of NOX1 as a novel modality for attenuating PAH.

Homeostasis control in health and disease by the unfolded protein response

Cells rely on the endoplasmic reticulum (ER) to fold and assemble newly synthesized transmembrane and secretory proteins - essential for cellular structure-function and for both intracellular and intercellular communication. To ensure the operative fidelity of the ER, eukaryotic cells leverage the unfolded protein response (UPR) - a stress-sensing and signalling network that maintains homeostasis by rebalancing the biosynthetic capacity of the ER according to need. The metazoan UPR can also redirect signalling from cytoprotective adaptation to programmed cell death if homeostasis restoration fails. As such, the UPR benefits multicellular organisms by preserving optimally functioning cells while removing damaged ones. Nevertheless, dysregulation of the UPR can be harmful. In this Review, we discuss the UPR and its regulatory processes as a paradigm in health and disease. We highlight important recent advances in molecular and mechanistic understanding of the UPR that enable greater precision in designing and developing innovative strategies to harness its potential for therapeutic gain. We underscore the rheostatic character of the UPR, its contextual nature and critical open questions for its further elucidation.

A unified model for the origins of spongiform degeneration and other neuropathological features in prion diseases

Decades after their initial observation in prion-infected brain tissues, the identities of virus-like dense particles, varicose tubules, and oval bodies containing parallel bands and fibrils have remained elusive. Our recent work revealed that a phenotype of dilation of the endoplasmic reticulum (ER), most notable for the perinuclear space (PNS), contributes to spongiform degeneration. To assess the significance of this phenotype for the etiology of prion diseases, we explored whether it can be functionally linked to other neuropathological hallmarks observed in these diseases, as this would indicate it to be a central event. Having surveyed the neuropathological record and other distant literature niches, we propose a model in which pathogenic forms of the prion protein poison raft domains, including essential Na+, K+-ATPases (NKAs) embedded within them, thereby triggering an ER-centered cellular rescue program coordinated by the unfolded protein response (UPR). The execution of this program stalls general protein synthesis, causing the deterioration of synaptic spines. As the disease progresses, cells selectively increase sterol biosynthesis, along with ribosome and ER biogenesis. These adaptive rescue attempts cause morphological changes to the ER which manifest as ER dilation or ER hypertrophy in a manner that is influenced by Ca2+ influx into the cell. The nuclear-to-cytoplasmic transport of mRNAs and tRNAs interrupts in late stage disease, thereby depriving ribosomes of supplies and inducing them to aggregate into a paracrystalline form. In support of this model, we share previously reported data, whose features are consistent with the interpretation that 1) the phenotype of ER dilation is observed in major prion diseases, 2) varicose tubules and oval bodies represent ER hypertrophy, and 3) virus-like dense particles are paracrystalline aggregates of inactive ribosomes.

Trazodone, dibenzoylmethane and tauroursodeoxycholic acid do not prevent motor dysfunction and neurodegeneration in Marinesco-Sjögren syndrome mice

There is no cure for Marinesco-Sjögren syndrome (MSS), a genetic multisystem disease linked to loss-of-function mutations in the SIL1 gene, encoding a BiP co-chaperone. Previously, we showed that the PERK kinase inhibitor GSK2606414 delays cerebellar Purkinje cell (PC) degeneration and the onset of ataxia in the woozy mouse model of MSS. However, GSK2606414 is toxic to the pancreas and does not completely rescue the woozy phenotype. The present study tested trazodone and dibenzoylmethane (DBM), which partially inhibit PERK signaling with neuroprotective effects and no pancreatic toxicity. We also tested the chemical chaperone tauroursodeoxycholic acid (TUDCA), which protects MSS patients' cells from stress-induced apoptosis. Mice were chronically treated for five weeks, starting from a presymptomatic stage. Trazodone was given 40 mg/kg daily by intraperitoneal (ip) injection. DBM was given 0.5% in the diet ad libitum. TUDCA was given either 0.4% in the diet, or 500 mg/kg ip every three days. None of the treatments prevented motor dysfunction or PC degeneration in woozy mice, as assessed by beam walking, rotarod test, and calbindin immunohistochemistry. Only trazodone slightly boosted beam walking performance, but this effect was not related to inhibition of PERK signaling. Pharmacokinetic studies excluded that the lack of effect was due to altered drug metabolism in woozy mice. These results indicate that trazodone, DBM and TUDCA, at dosing regimens active in other neurodegenerative disease mouse models, have no disease-modifying effect in a preclinical model of MSS. This underscores the difficulty of translating neuroprotective strategies from other conditions to MSS, highlighting the need for more targeted therapeutic approaches.

The mitochondrial integrated stress response: A novel approach to anti-aging and pro-longevity

The ISR is a cellular signaling pathway that responds to various physiological changes and types of stimulation. The mitochondrial integrated stress response (ISRmt) is a stress response specific to mitochondria which is initiated by eIF2α phosphorylation and is responsive to mitochondrial stressors. The ISRmt triggers diverse metabolic responses reliant on activating transcription factor 4 (ATF4). The preliminary phases of ISRmt can provoke an adaptive stress response that antagonizes age-related diseases and promotes longevity. In this review, we provide an overview of the molecular mechanisms of the ISRmt, with a particular focus on its potential as a therapeutic target for age-related disease and the promotion of longevity.

Unravelling the interplay between ER stress, UPR and the cGAS-STING pathway: Implications for osteoarthritis pathogenesis and treatment strategy

Osteoarthritis (OA) is a debilitating chronic degenerative disease affecting the whole joint organ leading to pain and disability. Cellular stress and injuries trigger inflammation and the onset of pathophysiological changes ensue after irreparable damage and inability to resolve inflammation, impeding the completion of the healing process. Extracellular matrix (ECM) degradation leads to dysregulated joint tissue metabolism. The reparative effort induces the proliferation of hypertrophic chondrocytes and matrix protein synthesis. Aberrant protein synthesis leads to endoplasmic reticulum (ER) stress and chondrocyte apoptosis with consequent cartilage matrix loss. These events in a vicious cycle perpetuate inflammation, hindering the restoration of normal tissue homeostasis. Recent evidence suggests that inflammatory responses and chondrocyte apoptosis could be caused by the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) signalling axis in response to DNA damage. It has been reported that there is a crosstalk between ER stress and cGAS-STING signalling in cellular senescence and other diseases. Based on recent evidence, this review discusses the role of ER stress, Unfolded Protein Response (UPR) and cGAS-STING pathway in mediating inflammatory responses in OA.

Safety and efficacy of memantine and trazodone versus placebo for motor neuron disease (MND SMART): stage two interim analysis from the first cycle of a phase 3, multiarm, multistage, randomised, adaptive platform trial

BACKGROUND

Motor neuron disease represents a group of progressive and incurable diseases that are characterised by selective loss of motor neurons, resulting in an urgent need for rapid identification of effective disease-modifying therapies. The MND SMART trial aims to test the safety and efficacy of promising interventions efficiently and definitively against a single contemporaneous placebo control group. We now report results of the stage two interim analysis for memantine and trazodone.

METHODS

MND SMART is an investigator-led, phase 3, double-blind, placebo-controlled, multiarm, multistage, randomised, adaptive platform trial recruiting at 20 hospital centres in the UK. Individuals older than 18 years with a confirmed diagnosis of either amyotrophic lateral sclerosis classified by the revised El Escorial criteria, primary lateral sclerosis, progressive muscular atrophy, or progressive bulbar palsy, regardless of disease duration, were eligible for screening. Participants were randomised (1:1:1) to receive oral trazodone 200 mg once a day, oral memantine 20 mg once a day, or matched placebo using a computer-generated minimisation algorithm delivered via a secure web-based system. Co-primary outcome measures were clinical functioning, measured by rate of change in the Amyotrophic Lateral Sclerosis Functional Rating Scale Revised (ALSFRS-R), and survival. Comparisons were conducted in four stages, with predefined criteria for stopping at the end of stages one and two. We report interim analysis from the stage two results, which was done when 100 participants per group (excluding long survivors, defined as >8 years since diagnosis at baseline) completed a minimum of 12 months of follow-up for the candidate investigational medicinal products. The trial is registered on the European Clinical Trials Registry, 2019-000099-41, and ClinicalTrials.gov, NCT04302870, and is ongoing.

FINDINGS

Between Feb 27, 2020, and July 24, 2023 (database lock for interim analysis two), 554 people with a motor neuron disease were randomly allocated to memantine (183 [33%]), trazodone (185 [33%]), or placebo (186 [34%]). The primary interim analysis population comprised 530 participants, of whom 175 (33%) had been allocated memantine, 175 (33%) had been allocated trazodone, and 180 (34%) had been allocated placebo. Over 12 months of follow-up, the mean rate of change per month in ALSFRS-R was -0·650 for memantine, -0·625 for trazodone, and -0·655 for placebo (memantine versus placebo estimated mean difference 0·033, one-sided 90% CI lower level -0·085; one-sided p=0·36; trazodone vs placebo: 0·065, -0·051; one-sided p=0·24). The one-sided p values were both above the significance threshold of 10%, indicating that neither memantine nor trazodone groups met the criteria for continuation. There were 483 participants with at least one adverse event (145 [77%] on placebo, 170 [91%] on memantine, and 168 [90%] on trazodone). There were 88 participants with at least one serious adverse event (37 [20%] on memantine, 27 [14%] on trazodone, and 24 [13%] on placebo). A total of 11 serious adverse event led to treatment discontinuation. There was no survival difference between comparisons, with 49 deaths in the memantine group, 52 deaths in the trazodone group, and 48 deaths in the placebo group.

INTERPRETATION

Neither memantine nor trazodone improved efficacy outcomes compared with placebo. This result is sufficiently powered to warrant no further testing of trazodone or memantine in motor neuron disease at the doses evaluated in this study. The multiarm multistage design shows important benefits in reducing the time, cost, and participant numbers to reach a definitive result.

FUNDING

The Euan MacDonald Centre, MND Scotland, My Name'5 Doddie Foundation, and Baillie Gifford.

Genetic knock-in of EIF2AK3 variants reveals differences in PERK activity in mouse liver and pancreas under endoplasmic reticulum stress

Common single-nucleotide variants (SNVs) of eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3) slightly increase the risk of disorders in the periphery and the central nervous system. EIF2AK3 encodes protein kinase RNA-like endoplasmic reticulum kinase (PERK), a key regulator of ER stress. Three exonic EIF2AK3 SNVs form the PERK-B haplotype, which is present in 28% of the global population. Importantly, the precise impact of these SNVs on PERK activity remains elusive. In this study, we demonstrate that PERK-B SNVs do not alter PERK expression or basal activity in vitro and in the novel triple knock-in mice expressing the exonic PERK-B SNVs in vivo. However, the kinase activity of PERK-B protein is higher than that of PERK-A in a cell-free assay and in mouse liver homogenates. Pancreatic tissue in PERK-B/B mice also exhibit increased susceptibility to apoptosis under acute ER stress. Monocyte-derived macrophages from PERK-B/B mice exhibit higher PERK activity than those from PERK-A/A mice, albeit with minimal functional consequences at acute timepoints. The subtle PERK-B-driven effects observed in liver and pancreas during acute stress implicate PERK as a contributor to disease susceptibility. The novel PERK-B mouse model provides valuable insights into ER stress-induced PERK activity, aiding the understanding of the genetic basis of disorders associated with ER stress.

Defective regulation of the eIF2-eIF2B translational axis underlies depressive-like behavior in mice and correlates with major depressive disorder in humans

Major depressive disorder (MDD) is a significant cause of disability in adults worldwide. However, the underlying causes and mechanisms of MDD are not fully understood, and many patients are refractory to available therapeutic options. Impaired control of brain mRNA translation underlies several neurodevelopmental and neurodegenerative conditions, including autism spectrum disorders and Alzheimer's disease (AD). Nonetheless, a potential role for mechanisms associated with impaired translational control in depressive-like behavior remains elusive. A key pathway controlling translation initiation relies on the phosphorylation of the α subunit of eukaryotic initiation factor 2 (eIF2α-P) which, in turn, blocks the guanine exchange factor activity of eIF2B, thereby reducing global translation rates. Here we report that the expression of EIF2B5 (which codes for eIF2Bε, the catalytic subunit of eIF2B) is reduced in postmortem MDD prefrontal cortex from two distinct human cohorts and in the frontal cortex of social isolation-induced depressive-like behavior model mice. Further, pharmacological treatment with anisomycin or with salubrinal, an inhibitor of the eIF2α phosphatase GADD34, induces depressive-like behavior in adult C57BL/6J mice. Salubrinal-induced depressive-like behavior is blocked by ISRIB, a compound that directly activates eIF2B regardless of the phosphorylation status of eIF2α, suggesting that increased eIF2α-P promotes depressive-like states. Taken together, our results suggest that impaired eIF2-associated translational control may participate in the pathophysiology of MDD, and underscore eIF2-eIF2B translational axis as a potential target for the development of novel approaches for MDD and related mood disorders.

Pathogenic tau induces an adaptive elevation in mRNA translation rate at early stages of disease

Alterations in the rate and accuracy of messenger RNA (mRNA) translation are associated with aging and several neurodegenerative disorders, including Alzheimer's disease and related tauopathies. We previously reported that error-containing RNA that are normally cleared via nonsense-mediated mRNA decay (NMD), a key RNA surveillance mechanism, are translated in the adult brain of a Drosophila model of tauopathy. In the current study, we find that newly-synthesized peptides and translation machinery accumulate within nuclear envelope invaginations that occur as a consequence of tau pathology, and that the rate of mRNA translation is globally elevated in early stages of disease in adult brains of Drosophila models of tauopathy. Polysome profiling from adult heads of tau transgenic Drosophila reveals the preferential translation of specific mRNA that have been previously linked to neurodegeneration. Unexpectedly, we find that panneuronal elevation of NMD further elevates the global translation rate in tau transgenic Drosophila, as does treatment with rapamycin. As NMD activation and rapamycin both suppress tau-induced neurodegeneration, their shared effect on translation suggests that elevated rates of mRNA translation are an early adaptive mechanism to limit neurodegeneration. Our work provides compelling evidence that tau-induced deficits in NMD reshape the tau translatome by increasing translation of RNA that are normally repressed in healthy cells.

Time-Dependent Potentiation of the PERK Branch of UPR by GPR68 Offers Protection in Brain Ischemia

BACKGROUND

In ischemia, acidosis occurs in/around injured tissue and parallels disease progression. Therefore, targeting an acid-sensitive receptor offers unique advantages in achieving the spatial and temporal specificity required for therapeutic interventions. We previously demonstrated that increased expression of GPR68 (G protein-coupled receptor 68), a proton-sensitive G protein-coupled receptor, mitigates ischemic brain injury. Here, we investigated the mechanism underlying GPR68-dependent protection.

METHODS

We performed biochemical and molecular analyses to examine poststroke signaling. We used in vitro brain slice cultures and in vivo mouse transient middle cerebral artery occlusion (tMCAO) models to investigate ischemia-induced injuries.

RESULTS

GPR68 deletion reduced PERK (protein kinase R-like ER kinase) expression in mouse brain. Compared with the wild-type mice, the GPR68-/- (knockout) mice exhibited a faster decline in eIF2α (eukaryotic initiation factor-2α) phosphorylation after tMCAO. Ogerin, a positive modulator of GPR68, stimulated eIF2α phosphorylation at 3 to 6 hours after tMCAO, primarily in the ipsilateral brain tissue. Consistent with the changes in eIF2α phosphorylation, Ogerin enhanced tMCAO-induced reduction in protein synthesis in ipsilateral brain tissue. In organotypic cortical slices, Ogerin reduced pH 6 and oxygen-glucose deprivation-induced neurotoxicity. Following tMCAO, intravenous delivery of Ogerin reduced brain infarction in wild-type but not knockout mice. Coapplication of a PERK inhibitor abolished Ogerin-induced protection. Delayed Ogerin delivery at 5 hours after tMCAO remained protective, and Ogerin has a similar protective effect in females. Correlated with these findings, tMCAO induced GPR68 expression at 6 hours, and Ogerin alters post-tMCAO proinflammatory/anti-inflammatory cytokine/chemokine expression profile.

CONCLUSIONS

These data demonstrate that GPR68 potentiation leads to neuroprotection, at least in part, through enhancing PERK-eIF2α activation in ischemic tissue but has little impact on healthy tissue.

Protein tyrosine phosphatase receptor type O serves as a key regulator of insulin resistance-induced α-synuclein aggregation in Parkinson's disease

Insulin resistance (IR) was found to be a critical element in the pathogenesis of Parkinson's disease (PD), facilitating abnormal α-synuclein (α-Syn) aggregation in neurons and thus promoting PD development. However, how IR contributes to abnormal α-Syn aggregation remains ill-defined. Here, we analyzed six PD postmortem brain transcriptome datasets to reveal module genes implicated in IR-mediated α-Syn aggregation. In addition, we induced IR in cultured dopaminergic (DA) neurons overexpressing α-Syn to identify IR-modulated differentially expressed genes (DEGs). Integrated analysis of data from PD patients and cultured neurons revealed 226 genes involved in α-Syn aggregation under IR conditions, of which 53 exhibited differential expression between PD patients and controls. Subsequently, we conducted an integrated analysis of the 53 IR-modulated genes employing transcriptome data from PD patients with different Braak stages and DA neuron subclasses with varying α-Syn aggregation scores. Protein tyrosine phosphatase receptor type O (PTPRO) was identified to be closely associated with PD progression and α-Syn aggregation. Experimental validation in a cultured PD cell model confirmed that both mRNA and protein of PTPRO were reduced under IR conditions, and the downregulation of PTPRO significantly facilitated α-Syn aggregation and cell death. Collectively, our findings identified PTPRO as a key regulator in IR-mediated α-Syn aggregation and uncovered its prospective utility as a therapeutic target in PD patients with IR.

Unfolded protein response markers Grp78 and eIF2alpha are upregulated with increasing alpha-synuclein levels in Lewy body disease

AIMS

Endoplasmic reticulum stress followed by the unfolded protein response is one of the cellular mechanisms contributing to the progression of α-synuclein pathology in Parkinson's disease and other Lewy body diseases. We aimed to investigate the activation of endoplasmic reticulum stress and its correlation with α-synuclein pathology in human post-mortem brain tissue.

METHODS

We analysed brain tissue from 45 subjects-14 symptomatic patients with Lewy body disease, 19 subjects with incidental Lewy body disease, and 12 healthy controls. The analysed brain regions included the medulla, pons, midbrain, striatum, amygdala and entorhinal, temporal, frontal and occipital cortex. We analysed activation of endoplasmic reticulum stress via levels of the unfolded protein response-related proteins (Grp78, eIF2α) and endoplasmic reticulum stress-regulating neurotrophic factors (MANF, CDNF).

RESULTS

We showed that regional levels of two endoplasmic reticulum-localised neurotrophic factors, MANF and CDNF, did not change in response to accumulating α-synuclein pathology. The concentration of MANF negatively correlated with age in specific regions. eIF2α was upregulated in the striatum of Lewy body disease patients and correlated with increased α-synuclein levels. We found the upregulation of chaperone Grp78 in the amygdala and nigral dopaminergic neurons of Lewy body disease patients. Grp78 levels in the amygdala strongly correlated with soluble α-synuclein levels.

CONCLUSIONS

Our data suggest a strong but regionally specific change in Grp78 and eIF2α levels, which positively correlates with soluble α-synuclein levels. Additionally, MANF levels decreased in dopaminergic neurons in the substantia nigra. Our research suggests that endoplasmic reticulum stress activation is not associated with Lewy pathology but rather with soluble α-synuclein concentration and disease progression.

Downregulation of ATF-4 Attenuates the Endoplasmic Reticulum Stress-Mediated Neuroinflammation and Cognitive Impairment in Experimentally Induced Alzheimer's Disease Model

Protein aggregation is invariably associated with the inflammation as a factor in Alzheimer's disease (AD). We investigated the interaction between downstream factors of endoplasmic reticulum (ER) stress pathway and inflammation, with implications in cognitive impairment in AD. Amyloid-β (Aβ)(1-42) was administered by bilateral intracerebroventricular (icv) injection in the brain of adult male Wistar rats to experimentally develop AD. The cognitive impairment was assessed by measuring behavioral parameters such as Morris water maze and novel object recognition tests. Levels of pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α and anti-inflammatory cytokines IL-4 and IL-10 were measured by the enzyme-linked immunosorbent assay (ELISA) in different rat brain regions. Inflammatory marker proteins such as cyclo-oxygenase (COX)-2 and phosphorylation of nuclear factor kappa B (NF-КB) (p65) were measured by the western blotting. Gene expression of ER stress downstream factors such as ATF-4, CHOP, and GADD-34 was analyzed by qRT-PCR. Histological studies were performed to check Aβ accumulation and neuronal degeneration. Integrated stress response inhibitor (ISRIB) was used to confirm the specific role of ER stress-mediated inflammation in cognitive impairment. Administration of Aβ(1-42) resulted in alteration in levels of inflammatory cytokines, inflammatory proteins, and mRNA levels of ER stress downstream factors. ISRIB treatment resulted in attenuation of Aβ(1-42)-induced ER stress, inflammation, neurodegeneration, and cognitive impairment in rats. These results indicate that ER stress-mediated inflammation potentiates the cognitive impairment in AD. An understanding of cascade of events, interaction of ER stress which was a hallmark of the present investigation together with inflammation and modulation of downstream signalling factors could serve as potent biomarkers to study AD progression.

The integrated stress response in brain diseases: A double-edged sword for proteostasis and synapses

The integrated stress response (ISR) is a highly conserved biochemical pathway that regulates protein synthesis. The ISR is activated in response to diverse stressors to restore cellular homeostasis. As such, the ISR is implicated in a wide range of diseases, including brain disorders. However, in the brain, the ISR also has potent influence on processes beyond proteostasis, namely synaptic plasticity, learning and memory. Thus, in the setting of brain diseases, ISR activity may have dual effects on proteostasis and synaptic function. In this review, we consider the ISR's contribution to brain disorders through the lens of its potential effects on synaptic plasticity. From these examples, we illustrate that at times ISR activity may be a "double-edged sword". We also highlight its potential as a therapeutic target to improve circuit function in brain diseases independent of its role in disease pathogenesis.

Navigating the landscape of the unfolded protein response in CD8+ T cells

Endoplasmic reticulum stress occurs due to large amounts of misfolded proteins, hypoxia, nutrient deprivation, and more. The unfolded protein is a complex intracellular signaling network designed to operate under this stress. Composed of three individual arms, inositol-requiring enzyme 1, protein kinase RNA-like ER kinase, and activating transcription factor-6, the unfolded protein response looks to resolve stress and return to proteostasis. The CD8+ T cell is a critical cell type for the adaptive immune system. The unfolded protein response has been shown to have a wide-ranging spectrum of effects on CD8+ T cells. CD8+ T cells undergo cellular stress during activation and due to environmental insults. However, the magnitude of the effects this response has on CD8+ T cells is still understudied. Thus, studying these pathways is important to unraveling the inner machinations of these powerful cells. In this review, we will highlight the recent literature in this field, summarize the three pathways of the unfolded protein response, and discuss their roles in CD8+ T cell biology and functionality.

Structured and disordered regions of Ataxin-2 contribute differently to the specificity and efficiency of mRNP granule formation

Ataxin-2 (ATXN2) is a gene implicated in spinocerebellar ataxia type II (SCA2), amyotrophic lateral sclerosis (ALS) and Parkinsonism. The encoded protein is a therapeutic target for ALS and related conditions. ATXN2 (or Atx2 in insects) can function in translational activation, translational repression, mRNA stability and in the assembly of mRNP-granules, a process mediated by intrinsically disordered regions (IDRs). Previous work has shown that the LSm (Like-Sm) domain of Atx2, which can help stimulate mRNA translation, antagonizes mRNP-granule assembly. Here we advance these findings through a series of experiments on Drosophila and human Ataxin-2 proteins. Results of Targets of RNA Binding Proteins Identified by Editing (TRIBE), co-localization and immunoprecipitation experiments indicate that a polyA-binding protein (PABP) interacting, PAM2 motif of Ataxin-2 may be a major determinant of the mRNA and protein content of Ataxin-2 mRNP granules. Experiments with transgenic Drosophila indicate that while the Atx2-LSm domain may protect against neurodegeneration, structured PAM2- and unstructured IDR- interactions both support Atx2-induced cytotoxicity. Taken together, the data lead to a proposal for how Ataxin-2 interactions are remodelled during translational control and how structured and non-structured interactions contribute differently to the specificity and efficiency of RNP granule condensation as well as to neurodegeneration.

Protein translation: biological processes and therapeutic strategies for human diseases

Protein translation is a tightly regulated cellular process that is essential for gene expression and protein synthesis. The deregulation of this process is increasingly recognized as a critical factor in the pathogenesis of various human diseases. In this review, we discuss how deregulated translation can lead to aberrant protein synthesis, altered cellular functions, and disease progression. We explore the key mechanisms contributing to the deregulation of protein translation, including functional alterations in translation factors, tRNA, mRNA, and ribosome function. Deregulated translation leads to abnormal protein expression, disrupted cellular signaling, and perturbed cellular functions- all of which contribute to disease pathogenesis. The development of ribosome profiling techniques along with mass spectrometry-based proteomics, mRNA sequencing and single-cell approaches have opened new avenues for detecting diseases related to translation errors. Importantly, we highlight recent advances in therapies targeting translation-related disorders and their potential applications in neurodegenerative diseases, cancer, infectious diseases, and cardiovascular diseases. Moreover, the growing interest lies in targeted therapies aimed at restoring precise control over translation in diseased cells is discussed. In conclusion, this comprehensive review underscores the critical role of protein translation in disease and its potential as a therapeutic target. Advancements in understanding the molecular mechanisms of protein translation deregulation, coupled with the development of targeted therapies, offer promising avenues for improving disease outcomes in various human diseases. Additionally, it will unlock doors to the possibility of precision medicine by offering personalized therapies and a deeper understanding of the molecular underpinnings of diseases in the future.

Potential Alzheimer's early biomarkers in a transgenic rat model and benefits of diazoxide/dibenzoylmethane co-treatment on spatial memory and AD-pathology

Alzheimer's disease (AD) is the major form of dementia prevalent in older adults and with a high incidence in females. Identification of early biomarkers is essential for preventive intervention to delay its progression. Furthermore, due to its multifactorial nature, a multi-target approach could be therapeutically beneficial. Our studies included 4- (pre-pathology) and 11-month (mild-pathology) TgF344-AD rats, a transgenic Alzheimer's model that exhibits age-dependent AD progression. We identified two potential early biomarker genes for AD, early growth response 2 (EGR2) and histone 1H2AA (HIST1H2AA), in the hippocampus of 4-month females. Out of 17,168 genes analyzed by RNA sequencing, expression of these two genes was significantly altered in 4-month TgF344-AD rats compared to wild-type littermates. We also evaluated co-treatment with diazoxide (DZ), a potassium channel activator, and dibenzoylmethane (DIB), which inhibits eIF2α-P activity, on TgF344-AD and wild-type rats. DZ/DIB-treatment mitigated spatial memory deficits and buildup of hippocampal Aβ plaques and tau PHF in 11-month TgF344-AD rats but had no effect on wild-type littermates. To our knowledge, this preclinical study is the first to report EGR2 and HIST1H2AA as potential AD biomarkers in females, and the benefits of DZ/DIB-treatment in AD. Evaluations across multiple AD-related models is warranted to corroborate our findings.

Trazodone rescues dysregulated synaptic and mitochondrial nascent proteomes in prion neurodegeneration

The unfolded protein response (UPR) is rapidly gaining momentum as a therapeutic target for protein misfolding neurodegenerative diseases, in which its overactivation results in sustained translational repression leading to synapse loss and neurodegeneration. In mouse models of these disorders, from Alzheimer's to prion disease, modulation of the pathway-including by the licensed drug, trazodone-restores global protein synthesis rates with profound neuroprotective effects. However, the precise nature of the translational impairment, in particular the specific proteins affected in disease, and their response to therapeutic UPR modulation are poorly understood. We used non-canonical amino acid tagging (NCAT) to measure de novo protein synthesis in the brains of prion-diseased mice with and without trazodone treatment, in both whole hippocampus and cell-specifically. During disease the predominant nascent proteome changes occur in synaptic, cytoskeletal and mitochondrial proteins in both hippocampal neurons and astrocytes. Remarkably, trazodone treatment for just 2 weeks largely restored the whole disease nascent proteome in the hippocampus to that of healthy, uninfected mice, predominantly with recovery of proteins involved in synaptic and mitochondrial function. In parallel, trazodone treatment restored the disease-associated decline in synapses and mitochondria and their function to wild-type levels. In conclusion, this study increases our understanding of how translational repression contributes to neurodegeneration through synaptic and mitochondrial toxicity via depletion of key proteins essential for their function. Further, it provides new insights into the neuroprotective mechanisms of trazodone through reversal of this toxicity, relevant for the treatment of neurodegenerative diseases via translational modulation.

Lithium: effects in animal models of vanishing white matter are not promising

Vanishing white matter (VWM) is a devastating autosomal recessive leukodystrophy, resulting in neurological deterioration and premature death, and without curative treatment. Pathogenic hypomorphic variants in subunits of the eukaryotic initiation factor 2B (eIF2B) cause VWM. eIF2B is required for regulating the integrated stress response (ISR), a physiological response to cellular stress. In patients' central nervous system, reduced eIF2B activity causes deregulation of the ISR. In VWM mouse models, the extent of ISR deregulation correlates with disease severity. One approach to restoring eIF2B activity is by inhibition of GSK3β, a kinase that phosphorylates eIF2B and reduces its activity. Lithium, an inhibitor of GSK3β, is thus expected to stimulate eIF2B activity and ameliorate VWM symptoms. The effects of lithium were tested in zebrafish and mouse VWM models. Lithium improved motor behavior in homozygous eif2b5 mutant zebrafish. In lithium-treated 2b4he2b5ho mutant mice, a paradoxical increase in some ISR transcripts was found. Furthermore, at the dosage tested, lithium induced significant polydipsia in both healthy controls and 2b4he2b5ho mutant mice and did not increase the expression of other markers of lithium efficacy. In conclusion, lithium is not a drug of choice for further development in VWM based on the limited or lack of efficacy and significant side-effect profile.

Vanishing white matter

"Vanishing white matter" (VWM) is a leukodystrophy caused by autosomal recessive pathogenic variants in the genes encoding the subunits of eukaryotic initiation factor 2B (eIF2B). Disease onset and disease course are extremely variable. Onset varies from the antenatal period until senescence. The age of onset is predictive of disease severity. VWM is characterized by chronic neurologic deterioration and, additionally, episodes of rapid and major neurologic decline, provoked by stresses such as febrile infections and minor head trauma. The disease is dominated by degeneration of the white matter of the central nervous system due to dysfunction of oligodendrocytes and in particular astrocytes. Organs other than the brain are rarely affected, with the exception of the ovaries. The reason for the selective vulnerability of the white matter of the central nervous system and, less consistently, the ovaries is poorly understood. eIF2B is a central regulatory factor in the integrated stress response (ISR). Genetic variants decrease eIF2B activity and thereby cause constitutive activation of the ISR downstream of eIF2B. Strikingly, the ISR is specifically activated in astrocytes. Modulation of eIF2B activity and ISR activation in VWM mouse models impacts disease severity, revealing eIF2B-regulated pathways as potential druggable targets.

Post-Translational Modifications in Tau and Their Roles in Alzheimer's Pathology

Microtubule-Associated Protein Tau (also known as tau) has been shown to accumulate into paired helical filaments and neurofibrillary tangles, which are known hallmarks of Alzheimer's disease (AD) pathology. Decades of research have shown that tau protein undergoes extensive post-translational modifications (PTMs), which can alter the protein's structure, function, and dynamics and impact the various properties such as solubility, aggregation, localization, and homeostasis. There is a vast amount of information describing the impact and role of different PTMs in AD pathology and neuroprotection. However, the complex interplay between these PTMs remains elusive. Therefore, in this review, we aim to comprehend the key post-translational modifications occurring in tau and summarize potential connections to clarify their impact on the physiology and pathophysiology of tau. Further, we describe how different computational modeling methods have helped in understanding the impact of PTMs on the structure and functions of the tau protein. Finally, we highlight the tau PTM-related therapeutics strategies that are explored for the development of AD therapy.

Mutant-Huntingtin Molecular Pathways Elucidate New Targets for Drug Repurposing

The spectrum of neurodegenerative diseases known today is quite extensive. The complexities of their research and treatment lie not only in their diversity. Even many years of struggle and narrowly focused research on common pathologies such as Alzheimer's, Parkinson's, and other brain diseases have not brought cures for these illnesses. What can be said about orphan diseases? In particular, Huntington's disease (HD), despite affecting a smaller part of the human population, still attracts many researchers. This disorder is known to result from a mutation in the HTT gene, but having this information still does not simplify the task of drug development and studying the mechanisms of disease progression. Nonetheless, the data accumulated over the years and their analysis provide a good basis for further research. Here, we review studies devoted to understanding the mechanisms of HD. We analyze genes and molecular pathways involved in HD pathogenesis to describe the action of repurposed drugs and try to find new therapeutic targets.

Simple model systems reveal conserved mechanisms of Alzheimer's disease and related tauopathies

The lack of effective therapies that slow the progression of Alzheimer's disease (AD) and related tauopathies highlights the need for a more comprehensive understanding of the fundamental cellular mechanisms underlying these diseases. Model organisms, including yeast, worms, and flies, provide simple systems with which to investigate the mechanisms of disease. The evolutionary conservation of cellular pathways regulating proteostasis and stress response in these organisms facilitates the study of genetic factors that contribute to, or protect against, neurodegeneration. Here, we review genetic modifiers of neurodegeneration and related cellular pathways identified in the budding yeast Saccharomyces cerevisiae, the nematode Caenorhabditis elegans, and the fruit fly Drosophila melanogaster, focusing on models of AD and related tauopathies. We further address the potential of simple model systems to better understand the fundamental mechanisms that lead to AD and other neurodegenerative disorders.

Repaglinide Induces ATF6 Processing and Neuroprotection in Transgenic SOD1G93A Mice

The interaction of the activating transcription factor 6 (ATF6), a key effector of the unfolded protein response (UPR) in the endoplasmic reticulum, with the neuronal calcium sensor Downstream Regulatory Element Antagonist Modulator (DREAM) is a potential therapeutic target in neurodegeneration. Modulation of the ATF6-DREAM interaction with repaglinide (RP) induced neuroprotection in a model of Huntington's disease. Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with no cure, characterized by the progressive loss of motoneurons resulting in muscle denervation, atrophy, paralysis, and death. The aim of this work was to investigate the potential therapeutic significance of DREAM as a target for intervention in ALS. We found that the expression of the DREAM protein was reduced in the spinal cord of SOD1G93A mice compared to wild-type littermates. RP treatment improved motor strength and reduced the expression of the ALS progression marker collagen type XIXα1 (Col19α1 mRNA) in the quadriceps muscle in SOD1G93A mice. Moreover, treated SOD1G93A mice showed reduced motoneuron loss and glial activation and increased ATF6 processing in the spinal cord. These results indicate that the modulation of the DREAM-ATF6 interaction ameliorates ALS symptoms in SOD1G93A mice.

Astrocytic deletion of protein kinase R-like ER kinase (PERK) does not affect learning and memory in aged mice but worsens outcome from experimental stroke

Aging is associated with cognitive decline and is the main risk factor for a myriad of conditions including neurodegeneration and stroke. Concomitant with aging is the progressive accumulation of misfolded proteins and loss of proteostasis. Accumulation of misfolded proteins in the endoplasmic reticulum (ER) leads to ER stress and activation of the unfolded protein response (UPR). The UPR is mediated, in part, by the eukaryotic initiation factor 2α (eIF2α) kinase protein kinase R-like ER kinase (PERK). Phosphorylation of eIF2α reduces protein translation as an adaptive mechanism but this also opposes synaptic plasticity. PERK, and other eIF2α kinases, have been widely studied in neurons where they modulate both cognitive function and response to injury. The impact of astrocytic PERK signaling in cognitive processes was previously unknown. To examine this, we deleted PERK from astrocytes (AstroPERKKO ) and examined the impact on cognitive functions in middle-aged and old mice of both sexes. Additionally, we tested the outcome following experimental stroke using the transient middle cerebral artery occlusion (MCAO) model. Tests of short-term and long-term learning and memory as well as of cognitive flexibility in middle-aged and old mice revealed that astrocytic PERK does not regulate these processes. Following MCAO, AstroPERKKO had increased morbidity and mortality. Collectively, our data demonstrate that astrocytic PERK has limited impact on cognitive function and has a more prominent role in the response to neural injury.

RGC-specific ATF4 and/or CHOP deletion rescues glaucomatous neurodegeneration and visual function

Endoplasmic reticulum (ER) stress has been linked with various acute and chronic neurodegenerative diseases. We previously found that optic nerve (ON) injury and diseases induce neuronal ER stress in retinal ganglion cells (RGCs). We further demonstrated that germline deletion of CHOP preserves the structure and function of both RGC somata and axons in mouse glaucoma models. Here we report that RGC-specific deletion of CHOP and/or its upstream regulator ATF4 synergistically promotes RGC and ON survival and preserves visual function in mouse ON crush and silicone oil-induced ocular hypertension (SOHU) glaucoma models. Consistently, topical application of the ATF4/CHOP chemical inhibitor ISRIB or RGC-specific CRISPR-mediated knockdown of the ATF4 downstream effector Gadd45a also delivers significant neuroprotection in the SOHU glaucoma model. These studies suggest that blocking the neuronal intrinsic ATF4/CHOP axis of ER stress is a promising neuroprotection strategy for neurodegeneration.

The integrated stress response in cancer progression: a force for plasticity and resistance

During their quest for growth, adaptation, and survival, cancer cells create a favorable environment through the manipulation of normal cellular mechanisms. They increase anabolic processes, including protein synthesis, to facilitate uncontrolled proliferation and deplete the tumor microenvironment of resources. As a dynamic adaptation to the self-imposed oncogenic stress, cancer cells promptly hijack translational control to alter gene expression. Rewiring the cellular proteome shifts the phenotypic balance between growth and adaptation to promote therapeutic resistance and cancer cell survival. The integrated stress response (ISR) is a key translational program activated by oncogenic stress that is utilized to fine-tune protein synthesis and adjust to environmental barriers. Here, we focus on the role of ISR signaling for driving cancer progression. We highlight mechanisms of regulation for distinct mRNA translation downstream of the ISR, expand on oncogenic signaling utilizing the ISR in response to environmental stresses, and pinpoint the impact this has for cancer cell plasticity during resistance to therapy. There is an ongoing need for innovative drug targets in cancer treatment, and modulating ISR activity may provide a unique avenue for clinical benefit.

PERK signaling promotes mitochondrial elongation by remodeling membrane phosphatidic acid

Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are linked in the onset and pathogenesis of numerous diseases. This has led to considerable interest in defining the mechanisms responsible for regulating mitochondria during ER stress. The PERK signaling arm of the unfolded protein response (UPR) has emerged as a prominent ER stress-responsive signaling pathway that regulates diverse aspects of mitochondrial biology. Here, we show that PERK activity promotes adaptive remodeling of mitochondrial membrane phosphatidic acid (PA) to induce protective mitochondrial elongation during acute ER stress. We find that PERK activity is required for ER stress-dependent increases in both cellular PA and YME1L-dependent degradation of the intramitochondrial PA transporter PRELID1. These two processes lead to the accumulation of PA on the outer mitochondrial membrane where it can induce mitochondrial elongation by inhibiting mitochondrial fission. Our results establish a new role for PERK in the adaptive remodeling of mitochondrial phospholipids and demonstrate that PERK-dependent PA regulation adapts organellar shape in response to ER stress.

Clinical Neurobiology of Sleep and Wakefulness

OBJECTIVE

This article focuses on novel neuronal mechanisms of sleep and wakefulness and relates basic science developments with potential translational implications in circadian neurobiology, pharmacology, behavioral factors, and the recently integrated potential pathways of sleep-related motor inhibition.

LATEST DEVELOPMENTS

During the past decade, remarkable advances in the molecular biology of sleep and wakefulness have taken place, opening a promising path for the understanding of clinical sleep disorders. Newly gained insights include the role of astrocytes in sleep brain homeostasis through the glymphatic system, the promotion of memory consolidation during states of reduced cholinergic activity during slow wave sleep, and the differential functions of melatonin receptors involving regulation of both circadian rhythm and sleep initiation. Ongoing investigations exploring sleep and circadian rhythm disruptions are beginning to unlock pathophysiologic aspects of neurologic, psychiatric, and medical disorders.

ESSENTIAL POINTS

An understanding of sleep and circadian neurobiology provides coherent and biologically credible approaches to treatments, including the identification of potential targets for neuromodulation.

Radotinib Decreases Prion Propagation and Prolongs Survival Times in Models of Prion Disease

The conversion of cellular prion protein (PrPC) into pathogenic prion isoforms (PrPSc) and the mutation of PRNP are definite causes of prion diseases. Unfortunately, without exception, prion diseases are untreatable and fatal neurodegenerative disorders; therefore, one area of research focuses on identifying medicines that can delay the progression of these diseases. According to the concept of drug repositioning, we investigated the efficacy of the c-Abl tyrosine kinase inhibitor radotinib, which is a drug that is approved for the treatment of chronic myeloid leukemia, in the treatment of disease progression in prion models, including prion-infected cell models, Tga20 and hamster cerebellar slice culture models, and 263K scrapie-infected hamster models. Radotinib inhibited PrPSc deposition in neuronal ZW13-2 cells that were infected with the 22L or 139A scrapie strains and in cerebellar slice cultures that were infected with the 22L or 263K scrapie strains. Interestingly, hamsters that were intraperitoneally injected with the 263K scrapie strain and intragastrically treated with radotinib (100 mg/kg) exhibited prolonged survival times (159 ± 28.6 days) compared to nontreated hamsters (135 ± 9.9 days) as well as reduced PrPSc deposition and ameliorated pathology. However, intraperitoneal injection of radotinib exerted a smaller effect on the survival rate of the hamsters. Additionally, we found that different concentrations of radotinib (60, 100, and 200 mg/kg) had similar effects on survival time, but this effect was not observed after treatment with a low dose (30 mg/kg) of radotinib. Interestingly, when radotinib was administered 4 or 8 weeks after prion inoculation, the treated hamsters survived longer than the vehicle-treated hamsters. Additionally, a pharmacokinetic assay revealed that radotinib effectively crossed the blood-brain barrier. Based on our findings, we suggest that radotinib is a new candidate anti-prion drug that could possibly be used to treat prion diseases and promote the remission of symptoms.

Inhibition of Protein Aggregation and Endoplasmic Reticulum Stress as a Targeted Therapy for α-Synucleinopathy

α-synuclein (α-syn) is an intrinsically disordered protein abundant in the central nervous system. Physiologically, the protein regulates vesicle trafficking and neurotransmitter release in the presynaptic terminals. Pathologies related to misfolding and aggregation of α-syn are referred to as α-synucleinopathies, and they constitute a frequent cause of neurodegeneration. The most common α-synucleinopathy, Parkinson's disease (PD), is caused by abnormal accumulation of α-syn in the dopaminergic neurons of the midbrain. This results in protein overload, activation of endoplasmic reticulum (ER) stress, and, ultimately, neural cell apoptosis and neurodegeneration. To date, the available treatment options for PD are only symptomatic and rely on dopamine replacement therapy or palliative surgery. As the prevalence of PD has skyrocketed in recent years, there is a pending issue for development of new disease-modifying strategies. These include anti-aggregative agents that target α-syn directly (gene therapy, small molecules and immunization), indirectly (modulators of ER stress, oxidative stress and clearance pathways) or combine both actions (natural compounds). Herein, we provide an overview on the characteristic features of the structure and pathogenic mechanisms of α-syn that could be targeted with novel molecular-based therapies.

Dibenzoylmethane ameliorates adiposity-mediated neuroinflammatory response and inflammation-mediated neuronal cell death in mouse microglia and neuronal cells

Dibenzoylmethane (DBM), a licorice-derived component, has numerous health benefits. The current study aimed to investigate the effect of DBM on adiposity-induced neuroinflammatory/oxidative response and microglial activation-induced neuronal cell damage. For this research, BV2 and HT22 cells were cultured using adipcyte- and microglia-conditioned media, respectively. DBM effectively suppressed lipopolysaccharide-induced productions in inducible nitric oxide synthase and cyclooxygenase2. Interleukin (IL)-6, monocyte chemoattractant protein-1, IL-1β, and tumor necrosis factor-α levels were also downregulated by DBM. In adipocyte-conditioned medium (ACM)-cultured BV2 cells, DBM effectively decreased ACM-induced generation of nitric oxide, reactive oxygen species, and inflammatory cytokines by activating nuclear factor erythroid 2-related factor 2/heme oxygenase-1 signaling and reducing nuclear factor kappa-light-chain-enhancer of activated B cells. In BV2-conditioned medium (BVM)-cultured neuron cells, DBM recovered the BVM-induced reduction of neuronal cell viability, thereby regulating B-cell lymphoma 2 (BCL2), BCL2-associated X (BAX), and cleaved caspase-3 protein expression. Taken together, DBM suppressed adiposity-induced inflammation/oxidative responses and inflammation-induced neuronal cell death.

Early and late chaperone intervention therapy boosts XBP1s and ADAM10, restores proteostasis, and rescues learning in Alzheimer's Disease mice

Alzheimer's disease (AD) is a debilitating neurodegenerative disorder that is pervasive among the aging population. Two distinct phenotypes of AD are deficits in cognition and proteostasis, including chronic activation of the unfolded protein response (UPR) and aberrant Aβ production. It is unknown if restoring proteostasis by reducing chronic and aberrant UPR activation in AD can improve pathology and cognition. Here, we present data using an APP knock-in mouse model of AD and several protein chaperone supplementation paradigms, including a late-stage intervention. We show that supplementing protein chaperones systemically and locally in the hippocampus reduces PERK signaling and increases XBP1s, which is associated with increased ADAM10 and decreased Aβ42. Importantly, chaperone treatment improves cognition which is correlated with increased CREB phosphorylation and BDNF. Together, this data suggests that chaperone treatment restores proteostasis in a mouse model of AD and that this restoration is associated with improved cognition and reduced pathology.

One-sentence summary

Chaperone therapy in a mouse model of Alzheimer's disease improves cognition by reducing chronic UPR activity.

Proteostasis failure exacerbates neuronal circuit dysfunction and sleep impairments in Alzheimer's disease

Failed proteostasis is a well-documented feature of Alzheimer's disease, particularly, reduced protein degradation and clearance. However, the contribution of failed proteostasis to neuronal circuit dysfunction is an emerging concept in neurodegenerative research and will prove critical in understanding cognitive decline. Our objective is to convey Alzheimer's disease progression with the growing evidence for a bidirectional relationship of sleep disruption and proteostasis failure. Proteostasis dysfunction and tauopathy in Alzheimer's disease disrupts neurons that regulate the sleep-wake cycle, which presents behavior as impaired slow wave and rapid eye movement sleep patterns. Subsequent sleep loss further impairs protein clearance. Sleep loss is a defined feature seen early in many neurodegenerative disorders and contributes to memory impairments in Alzheimer's disease. Canonical pathological hallmarks, β-amyloid, and tau, directly disrupt sleep, and neurodegeneration of locus coeruleus, hippocampal and hypothalamic neurons from tau proteinopathy causes disruption of the neuronal circuitry of sleep. Acting in a positive-feedback-loop, sleep loss and circadian rhythm disruption then increase spread of β-amyloid and tau, through impairments of proteasome, autophagy, unfolded protein response and glymphatic clearance. This phenomenon extends beyond β-amyloid and tau, with interactions of sleep impairment with the homeostasis of TDP-43, α-synuclein, FUS, and huntingtin proteins, implicating sleep loss as an important consideration in an array of neurodegenerative diseases and in cases of mixed neuropathology. Critically, the dynamics of this interaction in the neurodegenerative environment are not fully elucidated and are deserving of further discussion and research. Finally, we propose sleep-enhancing therapeutics as potential interventions for promoting healthy proteostasis, including β-amyloid and tau clearance, mechanistically linking these processes. With further clinical and preclinical research, we propose this dynamic interaction as a diagnostic and therapeutic framework, informing precise single- and combinatorial-treatments for Alzheimer's disease and other brain disorders.

Experimental and computational studies of silver(I) dibenzoylmethane-based complexes, interaction with DNA/RNA/BSA biomolecules, and in vitro cytotoxic activity

Two silver(I) complexes of composition [Ag₂(L)₂] (1) and [Ag(L)(PPh₃)₂](2) (HL = dibenzoyl- methane, PPh₃ = triphenylphosphine) were synthesized and characterized by elemental analysis, FTIR, NMR, XRPD, and UV-visible spectra. The molecular structures of the studied ligands and Ag(I) complexes have been characterized using Density Function Theory (DFT) calculations. This analysis has enabled us to determine the reactivity and the coordination site(s) for each ligand. Ag(I) ion is found to be coordinated with the ligand's oxygens in almost a linear fashion in complex (1), while in complex (2) it adopts a tetrahedral geometry. The interaction compounds with biomolecules; calf thymus (ct DNA), yeast-tRNA, and bovine serum albumin (BSA) were investigated using both absorption and fluorescence spectroscopy. The in vitro cytotoxic studies of the complexes against normal human lung fibroblast (WI38), cancerous breast (MDA-MB-231), mammary gland breast (MCF7), hepatocellular (HePG2), and prostate (PC3) cell lines indicated that the complexes are highly toxic to the cancer cells but less toxic towards the normal one when compared with the ligand. Flow cytometric results showed that complex (1) induced cell cycle arrest at the G2/M phase, and complex (2) at G2/M and S phases. Moreover, the results of apoptotic genes (caspase3 and p53) and anti-apoptotic (Bcl2) led us to suggest an apoptotic killing mechanism of cells rather than a necrotic one.

Investigating the Neuroprotective and Neuroregenerative Effect of Trazodone Regarding Behavioral Recovery in a BL6C57 Mice Stroke Model

Stroke is a major cause of death and disability worldwide. Between 1990 and 2010, its global burden increased notably with reference to the absolute number of incident events, number of deaths, and disability-adjusted life-years lost. Trazodone is a triazolopyridine derivative that was approved for more than 40 years as monotherapy or in combination with other antidepressant drugs for the treatment of major depressive disorder in adult patients. The aim was investigated if trazodone can improve behavioural outcome after stroke in a mice model of middle cerebral artery occlusion (MCAo) due to the potential neuroprotective and neurodegenerative effects by using three behavioural tests: adhesive tape test, beam test and hole board test. Trazodone administration show modest improvements regarding the motor-sensorial function after stroke especially in the acute post-stroke phase in aged and young animals. The antidepressant effect of the drug was observed in the post-stroke period in aged animals and to a lesser extent in young animals. Future research is needed to evaluate the effects of trazodone at the cellular level to be sure that it has no benefit in stroke patients who do not suffer from depression.

Defective proteostasis in Alzheimer's disease

The homeostasis of cellular proteins, or proteostasis, is critical for neuronal function and for brain processes, including learning and memory. Increasing evidence indicates that defective proteostasis contributes to the progression of neurodegenerative disorders, including Alzheimer's disease (AD), the most prevalent form of dementia in the elderly. Proteostasis comprises a set of cellular mechanisms that control protein synthesis, folding, post-translational modification and degradation, all of which are deregulated in AD. Importantly, deregulation of proteostasis plays a key role in synapse dysfunction and in memory impairment, the major clinical manifestation of AD. Here, we discuss molecular pathways involved in protein synthesis and degradation that are altered in AD, and possible pharmacological approaches to correct these defects.

Systematic, comprehensive, evidence-based approach to identify neuroprotective interventions for motor neuron disease: using systematic reviews to inform expert consensus

OBJECTIVES

Motor neuron disease (MND) is an incurable progressive neurodegenerative disease with limited treatment options. There is a pressing need for innovation in identifying therapies to take to clinical trial. Here, we detail a systematic and structured evidence-based approach to inform consensus decision making to select the first two drugs for evaluation in Motor Neuron Disease-Systematic Multi-arm Adaptive Randomised Trial (MND-SMART: NCT04302870), an adaptive platform trial. We aim to identify and prioritise candidate drugs which have the best available evidence for efficacy, acceptable safety profiles and are feasible for evaluation within the trial protocol.

METHODS

We conducted a two-stage systematic review to identify potential neuroprotective interventions. First, we reviewed clinical studies in MND, Alzheimer's disease, Huntington's disease, Parkinson's disease and multiple sclerosis, identifying drugs described in at least one MND publication or publications in two or more other diseases. We scored and ranked drugs using a metric evaluating safety, efficacy, study size and study quality. In stage two, we reviewed efficacy of drugs in MND animal models, multicellular eukaryotic models and human induced pluripotent stem cell (iPSC) studies. An expert panel reviewed candidate drugs over two shortlisting rounds and a final selection round, considering the systematic review findings, late breaking evidence, mechanistic plausibility, safety, tolerability and feasibility of evaluation in MND-SMART.

RESULTS

From the clinical review, we identified 595 interventions. 66 drugs met our drug/disease logic. Of these, 22 drugs with supportive clinical and preclinical evidence were shortlisted at round 1. Seven drugs proceeded to round 2. The panel reached a consensus to evaluate memantine and trazodone as the first two arms of MND-SMART.

DISCUSSION

For future drug selection, we will incorporate automation tools, text-mining and machine learning techniques to the systematic reviews and consider data generated from other domains, including high-throughput phenotypic screening of human iPSCs.

Brain FNDC5/Irisin Expression in Patients and Mouse Models of Major Depression

Major depressive disorder (MDD) is a major cause of disability in adults. MDD is both a comorbidity and a risk factor for Alzheimer's disease (AD), and regular physical exercise has been associated with reduced incidence and severity of MDD and AD. Irisin is an exercise-induced myokine derived from proteolytic processing of fibronectin type III domain-containing protein 5 (FNDC5). FNDC5/irisin is reduced in the brains of AD patients and mouse models. However, whether brain FNDC5/irisin expression is altered in depression remains elusive. Here, we investigate changes in fndc5 expression in postmortem brain tissue from MDD individuals and mouse models of depression. We found decreased fndc5 expression in the MDD prefrontal cortex, both with and without psychotic traits. We further demonstrate that the induction of depressive-like behavior in male mice by lipopolysaccharide decreased fndc5 expression in the frontal cortex, but not in the hippocampus. Conversely, chronic corticosterone administration increased fndc5 expression in the frontal cortex, but not in the hippocampus. Social isolation in mice did not result in altered fndc5 expression in either frontal cortex or hippocampus. Finally, fluoxetine, but not other antidepressants, increased fndc5 gene expression in the mouse frontal cortex. Results indicate a region-specific modulation of fndc5 in depressive-like behavior and by antidepressant in mice. Our finding of decreased prefrontal cortex fndc5 expression in MDD individuals differs from results in mice, highlighting the importance of carefully interpreting observations in mice. The reduction in fndc5 mRNA suggests that decreased central FNDC5/irisin could comprise a shared pathologic mechanism between MDD and AD.

The neuroprotective effects of targeting key factors of neuronal cell death in neurodegenerative diseases: The role of ER stress, oxidative stress, and neuroinflammation

Neuronal loss is one of the striking causes of various central nervous system (CNS) disorders, including major neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and Amyotrophic lateral sclerosis (ALS). Although these diseases have different features and clinical manifestations, they share some common mechanisms of disease pathology. Progressive regional loss of neurons in patients is responsible for motor, memory, and cognitive dysfunctions, leading to disabilities and death. Neuronal cell death in neurodegenerative diseases is linked to various pathways and conditions. Protein misfolding and aggregation, mitochondrial dysfunction, generation of reactive oxygen species (ROS), and activation of the innate immune response are the most critical hallmarks of most common neurodegenerative diseases. Thus, endoplasmic reticulum (ER) stress, oxidative stress, and neuroinflammation are the major pathological factors of neuronal cell death. Even though the exact mechanisms are not fully discovered, the notable role of mentioned factors in neuronal loss is well known. On this basis, researchers have been prompted to investigate the neuroprotective effects of targeting underlying pathways to determine a promising therapeutic approach to disease treatment. This review provides an overview of the role of ER stress, oxidative stress, and neuroinflammation in neuronal cell death, mainly discussing the neuroprotective effects of targeting pathways or molecules involved in these pathological factors.

Mitochondria inter-organelle relationships in cancer protein aggregation

Mitochondria are physically associated with other organelles, such as ER and lysosomes, forming a complex network that is crucial for cell homeostasis regulation. Inter-organelle relationships are finely regulated by both tether systems, which maintain physical proximity, and by signaling cues that induce the exchange of molecular information to regulate metabolism, Ca²⁺ homeostasis, redox state, nutrient availability, and proteostasis. The coordinated action of the organelles is engaged in the cellular integrated stress response. In any case, pathological conditions alter functional communication and efficient rescue pathway activation, leading to cell distress exacerbation and eventually cell death. Among these detrimental signals, misfolded protein accumulation and aggregation cause major damage to the cells, since defects in protein clearance systems worsen cell toxicity. A cause for protein aggregation is often a defective mitochondrial redox balance, and the ER freshly translated misfolded proteins and/or a deficient lysosome-mediated clearance system. All these features aggravate mitochondrial damage and enhance proteotoxic stress. This review aims to gather the current knowledge about the complex liaison between mitochondria, ER, and lysosomes in facing proteotoxic stress and protein aggregation, highlighting both causes and consequences. Particularly, specific focus will be pointed to cancer, a pathology in which inter-organelle relations in protein aggregation have been poorly investigated.

Endoplasmic Reticulum Stress Signaling and Neuronal Cell Death

Besides protein processing, the endoplasmic reticulum (ER) has several other functions such as lipid synthesis, the transfer of molecules to other cellular compartments, and the regulation of Ca²⁺ homeostasis. Before leaving the organelle, proteins must be folded and post-translationally modified. Protein folding and revision require molecular chaperones and a favorable ER environment. When in stressful situations, ER luminal conditions or chaperone capacity are altered, and the cell activates signaling cascades to restore a favorable folding environment triggering the so-called unfolded protein response (UPR) that can lead to autophagy to preserve cell integrity. However, when the UPR is disrupted or insufficient, cell death occurs. This review examines the links between UPR signaling, cell-protective responses, and death following ER stress with a particular focus on those mechanisms that operate in neurons.

Molecular and cellular events linking variants in the histone demethylase KDM5C to the intellectual disability disorder Claes-Jensen syndrome

The widespread availability of genetic testing for those with neurodevelopmental disorders has highlighted the importance of many genes necessary for the proper development and function of the nervous system. One gene found to be genetically altered in the X-linked intellectual disability disorder Claes-Jensen syndrome is KDM5C, which encodes a histone demethylase that regulates transcription by altering chromatin. While the genetic link between KDM5C and cognitive (dys)function is clear, how KDM5C functions to control transcriptional programs within neurons to impact their growth and activity remains the subject of ongoing research. Here, we review our current knowledge of Claes-Jensen syndrome and discuss important new data using model organisms that have revealed the importance of KDM5C in regulating aspects of neuronal development and function. Continued research into the molecular and cellular activities regulated by KDM5C is expected to provide critical etiological insights into Claes-Jensen syndrome and highlight potential targets for developing therapies to improve the quality of life of those affected.

Differential Response to Three Antidepressants in Patients with Major Depressive Episode Who Suffered Covid-19-Related Trauma

BACKGROUND

The Covid 19 pandemic might have impacted response to drug treatment in major depressive episode (MDE). We compared responses to three different antidepressant drugs, i.e., vortioxetine, sertraline, and trazodone, in outpatients with MDE during Major Depressive Disorder (MDD), Bipolar Disorder (BD), or schizophrenia and related psychoses (SSOPDs) during two time periods, i.e., before and after suffering Covid-19-related trauma.

METHODS

We conducted an observational study on clinically stabilised for at least 6 months outpatients with MDE during the course of MDD (N=58), BD (N=33), or SSOPDs (N=51). Patients, whose baseline assessments of Montgomery-Åsberg Rating Scale (MADRS), Hamilton Anxiety Rating Scale (Ham-A), Brief Psychiatric Rating Scale (BPRS), Visual Analogue Scale for Craving (VAS-crav) and World Health Organization Quality of Life, Brief version (WHOQOL-BREF) were available, were recruited at the time they suffered Covid-19-related traumas. Fifty patients, prior to the pandemic, when they were clinically stable, were treated with 15 mg/die vortioxetine, 44 with 450 mg/die trazodone, and 48 with 150 mg/die sertraline. After experiencing a major Covid-19-related personal trauma, patients showed clinical worsening which required dosage adjustment (20 mg/day vortioxetine; 600 mg/day trazodone, and 200 mg/day sertraline) and, for some of them, hospitalisation. Scores on the MADRS, Ham-A, BPRS, VAS-crav and WHOQOL-BREF were compared drug-wise and genderwise with Student's t test for continuous variables and Χ2 for categorical variables.

RESULTS

The sample consisted of 142 outpatients (age, mean 39.63 ± 16.84; 70 men and 72 women); women were older than men (mean age 43.18 ± 17.61 vs. 35.98 ± 15.30; p=0.01). The two genders did not differ on other variables. For all treatments, worsening symptoms were observed at the time of trauma, followed by slow recovery with treatment readjustment. Trauma-related worsening in patients on vortioxetine was less intense than patients on the other two antidepressants and recovery was faster. All drugs were associated with an improvement in QoL. The vortioxetine group showed a lower hospitalisation rate (24%) than sertraline (35.4%) and trazodone (38.6%), but this was not significant (p=0.27).

CONCLUSION

All drugs improved symptoms of Covid-19 trauma in patients with MDE, with vortioxetine showing a small advantage. No differences between vortioxetine, sertraline and trazodone were found as concerning the need for hospitalisation.