Unfolded proteins and endoplasmic reticulum stress in neurodegenerative disorders

Perfluorooctanoic acid (PFOA) activates astrogliosis-associated neuroinflammation through ER stress-autophagy axis

Perfluorooctanoic acid (PFOA), a perfluoroalkyl acid, induces neuroinflammation. However, present understanding regarding its fundamental role in neuroinflammation remains limited. Therefore, in this study, we aimed to clarify the potential association between PFOA and astrocyte activation via the modulation of the endoplasmic reticulum (ER) stress-autophagy axis. The results obtained revealed that PFOA activated astroglia in A-172 astrocytoma cells and primary astrocytes by upregulating the expression levels of autophagy-related proteins (ATG5, BECN1, SQSTM1, and MAP1LC3B-II). It also activated autophagy in A-172 astrocytoma cells and primary astrocytes via the upstream activation of ER stress-related proteins, such as ATF4, GRP78, and CHOP. Further, the pharmacological inhibition of ER stress as well as autophagy prevented PFOA-induced activation of astrogliosis in PFOA-treated A-172 cells and primary astrocytes. We also observed that PFOA-mediated activation of GFAP upregulated the transcription of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6. These findings confirmed the existence of a relationship between ER stress-induced autophagy and astrogliosis in PFOA-treated astrocytes, suggesting that targeting the ER stress-autophagy axis may be a potential therapeutic strategy for reducing PFOA-induced neuroinflammation.

Skeletal muscle atrophy induced by aging and disuse atrophy are strongly associated with the upregulation of the endoplasmic stress protein CHOP in rats

BACKGROUND

While canonical anabolic and proteolytic pathways have been well examined in the context of skeletal muscle proteostasis, the roles of endoplasmic reticulum stress (ERS) and the induced unfolded protein response (UPR) are underappreciated. Thus, we aimed to determine whether aging and/or disuse atrophy in rats altered skeletal muscle ERS/UPR markers.

METHODS AND RESULTS

Soleus (SOL) and plantaris (PLT) muscles of 3-month-old (mo), 6 mo, 12 mo, 18 mo, and 24 mo rats (9-10 per group, 48 in total) were analyzed for UPR proteins with further analysis performed on the protein CHOP. The gastrocnemius muscles of 4 mo rats that had undergone hindlimb immobilization (HLI, n = 12) or sham casting (CTL, n = 12) were analyzed for similar targets as well as more extensive CHOP-related targets. CHOP protein was greater in the PLT and SOL of 18 and 24 mo rats versus other age groups (P < 0.05). Moreover, negative correlations existed between CHOP expression and normalized PLT (R=-0.702, P < 0.001) and SOL (R=-0.658, P < 0.001) muscle weights in all rats analyzed at different ages. CHOP protein expression was also greater in the gastrocnemius of HLI versus CTL rats (P < 0.001), and a negative correlation existed between CHOP protein expression and normalized muscle weights in these rats (R=-0.814, P < 0.001). Nuclear CHOP protein levels (P < 0.010) and genes transcriptionally regulated by CHOP were also greater in HLI versus CTL rats (P < 0.001) implicating transcriptional activity of CHOP is elevated during disuse atrophy.

CONCLUSIONS

CHOP is operative during aging- and disuse-induced skeletal muscle atrophy in rodents, and more research is needed to determine if CHOP is a key mechanistic driver of these processes.

C/EBP Homologous Protein Expression in Retinal Ganglion Cells Induces Neurodegeneration in Mice

The progressive loss of retinal ganglion cell (RGC) axons leading to irreversible loss of vision is the pathological hallmark of glaucoma. However, the pathological mechanisms of RGC degeneration are not completely understood. Here, we investigated the role of chronic endoplasmic reticulum (ER) stress in glaucomatous neurodegeneration. To evaluate whether chronic ER stress-induced transcriptional factors, activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP) are induced in RGCs; we utilized human donor tissue and the microbead occlusion model of glaucoma. Additionally, we performed the intravitreal injection of adeno-associated virus (AAV) 2 to express CHOP selectively in RGCs in C57BL/6 mice and evaluated its effect on RGC function and structure by pattern electroretinogram (PERG) and whole-mount retina staining with the RBPMS antibody. Here, we report that the ATF4-CHOP pathway is activated in the retinas of human glaucoma donor eyes and a mouse model of ocular hypertension. Further, the expression of CHOP in RGCs led to a significant loss of function, as evidenced by reduced PERG. Notably, the expression of CHOP in the retina induced a significant structural loss of RGCs within 15 weeks of injection. Altogether, our studies indicate that the expression of CHOP in RGCs leads to neurodegeneration in mice.

CUMS induces depressive-like behaviors and cognition impairment by activating the ERS-NLRP3 signaling pathway in mice

BACKGROUND AND OBJECTIVE

Endoplasmic reticulum stress (ERS), as a primary defense mechanism against stress, is closely related to mental disorders, but its pathogenesis is still unclear. This research seeks to explore the influence of ERS-nucleotide-bound oligomerized domain-like receptor protein 3 (NLRP3) signaling on mice's depressive-like behaviors and cognitive impairment.

DESIGN AND METHOD

We carried out a study on 32 male C57BL/6J mice to investigate how chronic unpredictable mild stress (CUMS) can give rise to depressive-like behaviors and cognitive dysfunction, randomly dividing them into control, model, inhibitor, and agonist groups. We utilized ELISA to quantify dopamine (DA) and 5-hydroxytryptamine (5-HT) levels. Using Nissl and hematoxylin and eosin (H&E) staining, we assessed the number and morphology of hippocampal neurons and cells. Western blot and immunofluorescence staining detected the changes in ERS and inflammation-related pathways in the hippocampus.

RESULTS

CUMS could induce ERS and activate NLRP3 inflammasome, causing neuronal damage and histopathological changes, eventually leading to depressive-like behaviors and cognitive impairment in mice. The abnormal activation of NLRP3 inflammasome could be restored by ERS blocker 4-phenyl butyric acid (PBA), thus reducing neuronal damage, and ameliorating depressive-like behaviors and cognitive disorder in mice.

CONCLUSION

Our study demonstrates a previously unknown link between ERS and NLRP3 inflammasome in CUMS mice. The ERS-NLRP3 signaling pathway may be activated by CUMS, potentially resulting in mice exhibiting depressive-like behaviors and cognitive dysfunction. Theoretical foundations for elucidating the pathogenesis of depression, as well as its prevention and treatment, will be established through the results.

A Structural Effect of the Antioxidant Curcuminoids on the Aβ(1-42) Amyloid Peptide

Investigating amyloid-β (Aβ) peptides in solution is essential during the initial stages of developing lead compounds that can influence Aβ fibrillation while the peptide is still in a soluble state. The tendency of the Aβ(1-42) peptide to misfold in solution, correlated to the aetiology of Alzheimer's disease (AD), is one of the main hindrances to characterising its aggregation kinetics in a cell-mimetic environment. Moreover, the Aβ(1-42) aggregation triggers the unfolded protein response (UPR) in the endoplasmic reticulum (ER), leading to cellular dysfunction and multiple cell death modalities, exacerbated by reactive oxygen species (ROS), which damage cellular components and trigger inflammation. Antioxidants like curcumin, a derivative of Curcuma longa, help mitigate ER stress by scavenging ROS and enhancing antioxidant enzymes. Furthermore, evidence in the literature highlights the effect of curcumin on the secondary structure of Aβ(1-42). This explorative study investigates the Aβ(1-42) peptide conformational behaviour in the presence of curcumin and six derivatives using circular dichroism (CD) to explore their interactions with lipid bilayers, potentially preventing aggregate formation. The results suggest that the synthetic tetrahydrocurcumin (THC) derivative interacts with the amyloid peptide in all the systems presented, while cyclocurcumin (CYC) and bisdemethoxycurcumin (BMDC) only interact when the peptide is in a less stable conformation. Molecular dynamics simulations helped visualise the curcuminoids' effect in an aqueous system and hypothesise the importance of the peptide surface exposition to the solvent, differently modulated by the curcumin derivatives.

Proteostasis disruption and senescence in Alzheimer's disease pathways to neurodegeneration

Alzheimer's Disease (AD) is a progressive neurological disease associated with behavioral abnormalities, memory loss, and cognitive impairment that cause major causes of dementia in the elderly. The pathogenetic processes cause complex effects on brain function and AD progression. The proper protein homeostasis, or proteostasis, is critical for cell health. AD causes the buildup of misfolded proteins, particularly tau and amyloid-beta, to break down proteostasis, such aggregates are toxic to neurons and play a critical role in AD pathogenesis. The rise of cellular senescence is accompanied by aging, marked by irreversible cell cycle arrest and the release of pro-inflammatory proteins. Senescent cell build-up in the brains of AD patients exacerbates neuroinflammation and neuronal degeneration. These cells senescence-associated secretory phenotype (SASP) also disturbs the brain environment. When proteostasis failure and cellular senescence coalesce, a cycle is generated that compounds each other. While senescent cells contribute to proteostasis breakdown through inflammatory and degradative processes, misfolded proteins induce cellular stress and senescence. The principal aspects of the neurodegenerative processes in AD are the interaction of cellular senescence and proteostasis failure. This review explores the interconnected roles of proteostasis disruption and cellular senescence in the pathways leading to neurodegeneration in AD.

Quantitative Imaging of Regional Cerebral Protein Synthesis in Clinical Alzheimer's Disease by [11C]Leucine PET

PURPOSE

Protein synthesis is essential to maintain integrity and function of the human brain, and protein synthesis is associated specifically with the formation of long-term memory. Experimental and clinical observations indicate that this process is disturbed in Alzheimer's dementia and other neurodegenerative diseases. In-vivo investigation with positron emission tomography (PET) using [11C]leucine provides a unique possibility to measure regional cerebral protein synthesis (rCPS) rates in human brain and to determine whether it is altered in Alzheimer's disease (AD), and thus may provide a target for future therapeutic interventions.

PROCEDURES

In this first human study, we measured rCPS by [11C]leucine PET in four patients with AD (age 57-73 years) and compared the results with six healthy controls (three of whom were age matched and the other three were young controls). Quantification of rCPS also required measurement of amino acid (AA) levels and of free and protein-bound [11C]leucine in plasma during the 90 min PET scans conducted following at least six hours of fasting.

RESULTS

Rates of rCPS measured in absolute units of nmol/g/min ranged between 1.81 and 2.53 in AD patients, 2.10 and 2.54 in matched controls, and 2.21 to 2.35 in the young controls. Mean and median values did not show significant differences between the groups. Rates of rCPS also depended upon whether corrections for plasma AA levels were included in the calculations. When considering regional values relative to the corpus callosum as a reference region, there was a tendency towards impairment of rCPS in patients, which was most prominent in the parietal cortex, but did not reach significance. Similar findings were observed with normalisation of rCPS to global cortical mean.

CONCLUSIONS

In summary, this first human study assessing regional protein synthesis with [11C]leucine in AD has demonstrated where the sources of variance in measurements of cerebral protein synthesis may arise, along with the potential magnitude of this variance. This study also indicates that there is a tendency towards impairment of rCPS in patients with Alzheimer's disease, which requires further investigation including possible partial volume effects due to atrophy.

Exome sequencing revealed variants in SGCA and SIL1 genes underlying limb girdle muscular dystrophy and Marinesco-Sjögren syndrome patients

BACKGROUND

Inherited neuromuscular (NMD) and neurodegenerative diseases (NDD) belong to two distinct categories that disturb different components of the nervous system, leading to a variety of different symptoms and clinical manifestations. Both NMD and NDD are a heterogeneous group of genetic conditions. Genetic variations in the SGCA and SIL1 genes have been implicated in causing Limb Girdle Muscular Dystrophy (LGMD), a type of neuromuscular disorder, and Marinesco-Sjögren Syndrome (MSS) which is a neurodegenerative disorder.

METHODS

In the present study, we have investigated four patients presenting LGMD and five patients with MSS features. After collecting detailed clinical and family history, necessary laboratory investigations, including estimation of a skeletal muscle marker enzyme serum creatine kinase (CK), nerve conduction study (NCS), electromyography (EMG), echocardiography (Echo), Magnetic resonance imaging (MRI -brain), CT-brain and X-rays were performed. Whole exome followed by Sanger sequencing was employed to search for the disease-causing variants.

RESULTS

Physical examination in LGMD patients revealed poor muscle tone and facing difficulty in straightening up from the floor. Clinical history revealed frequent falls and strenuousness in climbing stairs. They started toe-walking in early childhood. Laboratory investigations confirmed elevated CK levels and abnormal NCS and EMG. The MSS patients showed abnormalities in gate and jerking movement, abnormal speech, and strabismus with cataract. MRI-brain showed cerebral atrophy in some MSS patients with elevated CK levels. Whole exome sequencing revealed a nonsense variant [c.C574T, p.(Arg192*)] in the SGCA gene and a frameshift [c.936dupG, p.(Leu313AlaFs*39)] in the SIL1 gene in LGMD and MSS patients, respectively.

CONCLUSION

Our study emphasizes the significance of integrating clinical and genetic analyses for precise diagnosis and tailored management strategies in inherited NMD and NDD disorders. To the best of our knowledge, this is the first study documenting SGCA and SIL1 recurrent variants in subcontinent populations with few rare clinical features. The recurrent mutations expanding the global understanding of the mutation's geographic and ethnic distribution and contributing valuable epidemiological data. The study will facilitate genetic counseling for families experiencing similar clinical features, both within Pakistani populations and in other regions.

Therapeutic Implications and Regulations of Protein Post-translational Modifications in Parkinsons Disease

Parkinsons disease (PD) is a neurodegenerative disorder characterized by dopaminergic neuron loss and alpha-synuclein aggregation. This comprehensive review examines the intricate role of post-translational modifications (PTMs) in PD pathogenesis, focusing on DNA methylation, histone modifications, phosphorylation, SUMOylation, and ubiquitination. Targeted PTM modulation, particularly in key proteins like Parkin, DJ1, and PINK1, emerges as a promising therapeutic strategy for mitigating dopaminergic degeneration in PD. Dysregulated PTMs significantly contribute to the accumulation of toxic protein aggregates and dopaminergic neuronal dysfunction observed in PD. Targeting PTMs, including epigenetic strategies, addressing aberrant phosphorylation events, and modulating SUMOylation processes, provides potential avenues for intervention. The ubiquitin-proteasome system, governed by enzymes like Parkin and Nedd4, offers potential targets for clearing misfolded proteins and developing disease-modifying interventions. Compounds like ginkgolic acid, SUMO E1 enzyme inhibitors, and natural compounds like Indole-3-carbinol illustrate the feasibility of modulating PTMs for therapeutic purposes in PD. This review underscores the therapeutic potential of PTM-targeted interventions in modulating PD-related pathways, emphasizing the need for further research in this promising area of Parkinsons disease therapeutics.

Unraveling the path to osteoarthritis management: targeting chondrocyte apoptosis for therapeutic intervention

Osteoarthritis (OA) is a chronic disease affecting joints and further causing disabilities. This disease affects around 240 million people worldwide. It is a multifactorial disease, and its etiology is difficult to determine. Although numerous therapeutic strategies are available, the therapies are aimed at reducing pain and improving patients' quality of life. Hence, there is an urgent need to develop disease-modifying drugs (DMOAD) that can reverse or halt OA progression. Apoptosis is a cell removal process that is important in maintaining homeostatic mechanisms in the development and sustaining cell population. The apoptosis of chondrocytes is believed to play an important role in OA progression due to poor chondrocytes self-repair abilities to maintain the extracellular matrix (ECM). Hence, targeting chondrocyte apoptosis can be one of the potential therapeutic strategies in OA management. There are various mediators and targets available to inhibit apoptosis such as autophagy, endoplasmic reticulum (ER) stress, oxidative stress, and inflammation. As such, this review highlights the importance and potential targets that can be aimed to reduce chondrocyte apoptosis.

Bacillus amyloliquefaciens attenuates the intestinal permeability, oxidative stress and endoplasmic reticulum stress: transcriptome and microbiome analyses in weaned piglets

Endoplasmic reticulum (ER) stress is related to oxidative stress (OS) and leads to intestinal injury. Bacillus amyloliquefaciens SC06 (SC06) can regulate OS, but its roles in intestinal ER stress remains unclear. Using a 2 × 2 factorial design, 32 weaned piglets were treated by two SC06 levels (0 or 1 × 108 CFU/g), either with or without diquat (DQ) injection. We found that SC06 increased growth performance, decreased ileal permeability, OS and ER stress in DQ-treated piglets. Transcriptome showed that differentially expressed genes (DEGs) induced by DQ were enriched in NF-κB signaling pathway. DEGs between DQ- and SC06 + DQ-treated piglets were enriched in glutathione metabolism pathway. Ileal microbiome revealed that the SC06 + DQ treatment decreased Clostridium and increased Actinobacillus. Correlations were found between microbiota and ER stress genes. In conclusion, dietary SC06 supplementation increased the performance, decreased the permeability, OS and ER stress in weaned piglets by regulating ileal genes and microbiota.

DDIT3/CHOP promotes LPS/ATP-induced pyroptosis in osteoblasts via mitophagy inhibition

Inflammatory environments can trigger endoplasmic reticulum (ER) stress and lead to pyroptosis in various tissues and cells, including liver, brain, and immune cells. As a key factor of ER stress, DNA damage-inducible transcript 3 (DDIT3)/CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is upregulated in osteoblasts during inflammatory stimulation. DDIT3/CHOP may therefore regulate osteoblast pyroptosis in inflammatory conditions. During this investigation, we found that lipopolysaccharides (LPS)/adenosine 5'-triphosphate (ATP) stimulation in vitro induced osteoblasts to undergo pyroptosis, and the expression of DDIT3/CHOP was increased during this process. The overexpression of DDIT3/CHOP further promoted osteoblast pyroptosis as evidenced by the increased expression of the inflammasome NLR family pyrin domain containing 3 (NLRP3) and ratios of caspase-1 p20/caspase-1 and cleaved gasdermin D (GSDMD)/GSDMD. To explore the specific mechanism of this effect, we found through fluorescence imaging and Western blot analysis that LPS/ATP stimulation promoted PTEN-induced kinase 1 (PINK1)/E3 ubiquitin-protein ligase parkin (Parkin)-mediated mitophagy in osteoblasts, and this alteration was suppressed by the DDIT3/CHOP overexpression, resulting in increased ratio of pyroptosis compared with the control groups. The impact of DDIT3/CHOP on pyroptosis in osteoblasts was reversed by the application of carbonyl cyanide 3-chlorophenylhydrazone (CCCP), a specific mitophagy agonist. Therefore, our data demonstrated that DDIT3/CHOP promotes osteoblast pyroptosis by inhibiting PINK1/Parkin-mediated mitophagy in an inflammatory environment.

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.

ATF5-regulated Mitochondrial Unfolded Protein Response Attenuates Neuronal Damage in Epileptic Rat by Reducing Endoplasmic Reticulum Stress Through Mitochondrial ROS

Endoplasmic reticulum (ER) dysfunction caused by excessive ER stress is a crucial mechanism underlying seizures-induced neuronal injury. Studies have shown that mitochondrial reactive oxygen species (ROS) are closely related to ER stress, and our previous study showed that activating transcription factor 5 (ATF5)-regulated mitochondrial unfolded protein response (mtUPR) modulated mitochondrial ROS generation in a hippocampal neuronal culture model of seizures. However, the effects of ATF5-regulated mtUPR on ER stress and the underlying mechanisms remain uncertain in epilepsy. In this study, ATF5 upregulation by lentivirus infection attenuated seizures-induced neuronal damage and apoptosis in a rat model of pilocarpine-induced epilepsy, whereas ATF5 downregulation by lentivirus infection had the opposite effects. ATF5 upregulation potentiated mtUPR by increasing the expression of mitochondrial chaperone heat shock protein 60 (HSP60) and caseinolytic protease proteolytic subunit (ClpP) and reducing mitochondrial ROS generation in pilocarpine-induced seizures in rats. Additionally, upregulation of ATF5 reduced the expression of glucose-regulated protein 78 (GRP78), protein kinase RNA-like endoplasmic reticulum kinase (PERK), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP), suggesting suppression of ER stress; Moreover, ATF5 upregulation attenuated apoptosis-related proteins such as B-cell lymphoma-2 (BCL2) downregulation, BCL2-associated X (BAX) and cleaved-caspase-3 upregulation. However, ATF5 downregulation exerted the opposite effects. Furthermore, pretreatment with the mitochondria-targeted antioxidant mito-TEMPO attenuated the harmful effects of ATF5 downregulation on ER stress and neuronal apoptosis by reducing mitochondrial ROS generation. Overall, our study suggested that ATF5-regulated mtUPR exerted neuroprotective effects against pilocarpine-induced seizures in rats and the underlying mechanisms might involve mitochondrial ROS-mediated ER stress.

Infection of epithelioma papulosum cyprini (EPC) cells with spring viremia of carp virus (SVCV) induces autophagy and apoptosis through endoplasmic reticulum stress

Spring viremia of carp virus (SVCV) is a lethal freshwater pathogen of cyprinid fish that has caused significant economic losses to aquaculture. To reduce the economic losses caused by SVCV, its pathogenic mechanism needs to be studied more thoroughly. Here, we report for the first time that SVCV infection of Epithelioma papulosum cyprini (EPC) cells can induce cellular autophagy and apoptosis through endoplasmic reticulum stress. The presence of autophagic vesicles in infected EPC cells was shown by transmission electron microscopy. Quantitative fluorescence PCR and Western blot results showed that p62 mRNA expression was decreased, and the expression of Beclin1 and LC3 mRNA was increased. The p62 protein was decreased, and the Beclin1 protein and LC3 were increased in the endoplasmic reticulum stress activation state. To further clarify the mode of death of SVCV-infected EPC cells, we examined caspase3, caspase9, BCL-2, and Bax mRNA, which showed that they were all increased. Apoptosis of SVCV-infected cells increased upon activation of endoplasmic reticulum stress. Our results suggest that endoplasmic reticulum stress can regulate SVCV infection-induced autophagy and apoptosis. The results of this study provide theoretical data for the pathogenesis of SVCV and lay the foundation for future drug development and vaccine construction.

Primary Hypothyroidism and Alzheimer's Disease: A Tale of Two

Hypothyroidism (HPT) HPT could be a risk factor for the development and progression of Alzheimer's disease (AD). In addition, progressive neurodegeneration in AD may affect the metabolism of thyroid hormones (THs) in the brain causing local brain HPT. Hence, the present review aimed to clarify the potential association between HPT and AD. HPT promotes the progression of AD by inducing the production of amyloid beta (Aβ) and tau protein phosphorylation with the development of synaptic plasticity and memory dysfunction. Besides, the metabolism of THs is dysregulated in AD due to the accumulation of Aβ and tau protein phosphorylation leading to local brain HPT. Additionally, HPT can affect AD neuropathology through various mechanistic pathways including dysregulation of transthyretin, oxidative stress, ER stress, autophagy dysfunction mitochondrial dysfunction, and inhibition of brain-derived neurotrophic factor. Taken together there is a potential link between HPT and AD, as HPT adversely impacts AD neuropathology and the reverse is also true.

Pathological Impact of Tau Proteolytical Process on Neuronal and Mitochondrial Function: a Crucial Role in Alzheimer's Disease

Tau protein plays a pivotal role in the central nervous system (CNS), participating in microtubule stability, axonal transport, and synaptic communication. Research interest has focused on studying the role of post-translational tau modifications in mitochondrial failure, oxidative damage, and synaptic impairment in Alzheimer's disease (AD). Soluble tau forms produced by its pathological cleaved induced by caspases could lead to neuronal injury contributing to oxidative damage and cognitive decline in AD. For example, the presence of tau cleaved by caspase-3 has been suggested as a relevant factor in AD and is considered a previous event before neurofibrillary tangles (NFTs) formation.Interestingly, we and others have shown that caspase-cleaved tau in N- or C- terminal sites induce mitochondrial bioenergetics defects, axonal transport impairment, neuronal injury, and cognitive decline in neuronal cells and murine models. All these abnormalities are considered relevant in the early neurodegenerative manifestations such as memory and cognitive failure reported in AD. Therefore, in this review, we will discuss for the first time the importance of truncated tau by caspases activation in the pathogenesis of AD and how its negative actions could impact neuronal function.

UPR-Induced miR-616 Inhibits Human Breast Cancer Cell Growth and Migration by Targeting c-MYC

C/EBP homologous protein (CHOP), also known as growth arrest and DNA damage-inducible protein 153 (GADD153), belongs to the CCAAT/enhancer-binding protein (C/EBP) family. CHOP expression is induced by unfolded protein response (UPR), and sustained CHOP activation acts as a pivotal trigger for ER stress-induced apoptosis. MicroRNA-616 is located within an intron of the CHOP gene. However, the regulation of miR-616 expression during UPR and its function in breast cancer is not clearly understood. Here we show that the expression of miR-616 and CHOP (host gene of miR-616) is downregulated in human breast cancer. Both miR-5p/-3p arms of miR-616 are expressed with levels of the 5p arm higher than the 3p arm. During conditions of ER stress, the expression of miR-616-5p and miR-616-3p arms was concordantly increased primarily through the PERK pathway. Our results show that ectopic expression of miR-616 significantly suppressed cell proliferation and colony formation, whereas knockout of miR-616 increased it. We found that miR-616 represses c-MYC expression via binding sites located in its protein coding region. Furthermore, we show that miR-616 exerted growth inhibitory effects on cells by suppressing c-MYC expression. Our results establish a new role for the CHOP locus by providing evidence that miR-616 can inhibit cell proliferation by targeting c-MYC. In summary, our results suggest a dual function for the CHOP locus, where CHOP protein and miR-616 can cooperate to inhibit cancer progression.

Therapeutic potential of endoplasmic reticulum stress inhibitors in the treatment of diabetic peripheral neuropathy

Endoplasmic stress response, the unfolded protein response (UPR), is a homeostatic signaling pathway comprising transmembrane sensors that get activated upon alterations in ER luminal environment. Studies suggest a relation between activated UPR pathways and several disease states such as Parkinson, Alzheimer, inflammatory bowel disease, tumor growth, and metabolic syndrome. Diabetic peripheral neuropathy (DPN), a common microvascular complication of diabetes-related chronic hyperglycemia, causes chronic pain, loss of sensation, foot ulcers, amputations, allodynia, hyperalgesia, paresthesia, and spontaneous pain. Factors like disrupted calcium signaling, dyslipidemia, hyperglycemia, inflammation, insulin signaling, and oxidative stress disturb the UPR sensor levels manifesting as DPN. We discuss new effective therapeutic alternatives for DPN that can be developed by targeting UPR pathways like synthetic ER stress inhibitors like 4-PhenylButyric acid (4-PBA), Sephin 1, Salubrinal and natural ER stress inhibitors like Tauroursodeoxycholic acid (TUDCA), Cordycepin, Proanthocyanidins, Crocin, Purple Rice extract and cyanidin and Caffeic Acid Phenethyl Ester (CAPE).

Curcumae radix Reduces Endoplasmic Reticulum Stress in Mice with Chronic Neuroinflammation

Endoplasmic reticulum (ER) stress is a condition in which the ER protein-folding machinery is impaired, leading to the accumulation of improperly folded proteins and triggering an unfolded-protein response. Excessive ER stress causes cell death and contributes to the development of chronic diseases. Interestingly, there is a bidirectional relationship between ER stress and the nuclear factor-kappa B (NF-κB) pathway. Curcumin, a natural polyphenolic compound found in Curcumae radix, exerts its neuroprotective effects by regulating ER stress and inflammation. Therefore, investigating the potential protective and regulatory effects of curcumin on ER stress, inflammation, and neurodegeneration under chronic neuroinflammatory conditions is of great interest. Mice were pretreated with Curcumae radix extract (CRE) for 19 days and then treated with CRE plus lipopolysaccharide for 1 week. We monitored pro-inflammatory cytokine levels in the serum and ER stress-, inflammation-, and neurodegeneration-related markers in the mouse cerebrum and hippocampus using Western blotting and qRT-PCR. CRE reduced Interleukin-1 beta levels in the blood and brain of mice with lipopolysaccharide-induced chronic inflammation. CRE also suppressed the expression of markers related to the ER stress and NF-κB signaling pathways. The expression of neurodegeneration-related markers was reduced in the mouse cerebrum and hippocampus. CRE exerts neuroprotective effects under chronic inflammatory conditions via multifaceted anti-inflammatory and ER stress-pathway regulatory mechanisms.

Hepatic Proteomics Analysis Reveals Attenuated Endoplasmic Reticulum Stress in Lactiplantibacillus plantarum-Treated Oxidatively Stressed Broilers

Endoplasmic reticulum (ER) stress plays important roles in oxidative stress (OS), contributing to liver injury. Lactiplantibacillus plantarum P8 (P8) was reported to regulate broiler OS and the gut microbiota in broilers, but its roles in hepatic ER stress remain unclear. In the present study, the role of P8 in liver OS and ER stress was evaluated, and proteomics was performed to determine the mechanism. Results revealed that P8 treatment decreased liver OS and ER stress in dexamethasone (DEX)-induced oxidatively stressed broilers. Proteomics showed that differentially expressed proteins (DEPs) induced by DEX cover the "cellular response to unfold protein" term. Moreover, the DEPs (GGT5, TXNDC12, and SRM) between DEX- and DEX + P8-treated broilers were related to OS and ER stress and enriched in the glutathione metabolism pathway. RT-qPCR further confirmed the results of proteomics. In conclusion, P8 attenuates hepatic OS and ER stress by regulating GGT5, TXNDC12, SRM, and glutathione metabolism in broilers.

Natural antioxidants that act against Alzheimer's disease through modulation of the NRF2 pathway: a focus on their molecular mechanisms of action

Characterized by a complex pathophysiology that includes the intraneuronal formation of neurofibrillary tangles and the extracellular deposition of β-amyloid plaques, Alzheimer's disease (AD) is a terminal neurodegenerative disease that causes dementia in older adults. Oxidative stress in the brain is considered as one of the contributing factors to the pathogenesis of AD, and thus, antioxidants have attracted much interest as potential therapeutic agents against the disorder. Natural antioxidants are typically characterized by low acute and chronic toxicity, which facilitates their potential therapeutic application. One important molecular target for the beneficial effects of natural antioxidants is the nuclear factor erythroid-derived 2-related factor 2 (NFE2L2/NRF2). NRF2 is a key transcription factor that orchestrates the cellular antioxidant response through regulating the expression of oxidative stress-related genes harboring the antioxidant response element (ARE) in their promoters. Indeed, in the case of excessive oxidative damage, NRF2 migrates to the nucleus and binds to ARE, activating the transcription of antioxidant protector genes. There is increasing evidence that NRF2 is implicated in AD pathology through dysfunction and altered localization, which renders it as a potential therapeutic target for AD. Thus, this review summarizes the most recent (2018-2023) advances on the NRF2-modulating activity of natural antioxidants observed in vitro and in AD animal models. This information will help elucidate the molecular mechanisms governing the antioxidant activity of such phytochemicals to highlight their therapeutic potential against common neurodegenerative diseases, such as AD.

Exogenous Hydrogen Sulfide Induces A375 Melanoma Cell Apoptosis Through Overactivation of the Unfolded Protein Response

Purpose

Melanomas are highly malignant and rapidly develop drug resistance due to dysregulated apoptosis. Therefore, pro-apoptotic agents could be effective for the management of melanoma. Hydrogen sulfide is ubiquitous in the body, and exogenous hydrogen sulfide has been reported to show inhibitory and pro-apoptotic effects on cancer cells. However, whether high concentrations of exogenous hydrogen sulfide have pro-apoptotic effects on melanoma and its mechanisms remain unknown. Hence, this study aimed to explore the pro-apoptotic effects and mechanisms of exogenous hydrogen sulfide on the A375 melanoma cell line treated with a hydrogen sulfide donor (NaHS).

Methods

The cell proliferation test, flow cytometric analysis, Hoechst 33258 staining, and Western blotting of B-cell lymphoma 2 and cleaved caspase-3 were used to explore the pro-apoptotic effects of hydrogen sulfide on A375 cells. The transcriptional profile of NaHS-treated A375 cells was further explored via high-throughput sequencing. Western blotting of phosphorylated inositol-requiring enzyme 1α (p-IRE1α), phosphorylated protein kinase R-like ER kinase (p-PERK), phosphorylated eukaryotic translation initiation factor 2α (p-eIF2α), C/EBP homologous protein, glucose-regulating protein 78, IRE1α, PERK, and eIF2α was performed to verify the changes in the transcriptional profile.

Results

NaHS inhibited A375 melanoma cell proliferation and induced apoptosis. The endoplasmic reticulum stress unfolded protein response and apoptosis-associated gene expression was upregulated in NaHS-treated A375 melanoma cells. The overactivation of the unfolded protein response and increase in endoplasmic reticulum stress was verified at the protein level.

Conclusion

Treatment with NaHS increased endoplasmic reticulum stress, which triggered the overactivation of the unfolded protein response and ultimately lead to melanoma cell apoptosis. The pro-apoptotic effect of NaHS suggests that it can be explored as a potential therapeutic agent in melanoma.

Physical Exercise Decreases Endoplasmic Reticulum Stress in Central and Peripheral Tissues of Rodents: A Systematic Review

Endoplasmic reticulum stress (ER stress) affects many tissues and contributes to the development and severity of chronic diseases. In contrast, regular physical exercise (PE) has been considered a powerful tool to prevent and control several chronic diseases. The present systematic review aimed to evaluate the impact of different PE protocols on ER stress markers in central and peripheral tissues in rodents. The eligibility criteria were based on PICOS (population: rodents; intervention: physical exercise/physical training; control: animals that did not undergo training; outcomes: endoplasmic reticulum stress; studies: experimental). The PubMed/Medline, Science Direct, Scopus, and Scielo databases were analyzed systematically. Quality assessment was performed using SYRCLE's risk of bias tool for animal studies. The results were qualitatively synthesized. Initially, we obtained a total of 2.490 articles. After excluding duplicates, 30 studies were considered eligible. Sixteen studies were excluded for not meeting the eligibility criteria. Therefore, 14 articles were included. The PE protocol showed decreased levels/expression of markers of ER stress in the central and peripheral tissues of rodents. PE can decrease ER stress by reducing cellular stress in the cardiac, brain, and skeletal muscle tissues in rodents. However, robust PE protocols must be considered, including frequency, duration, and intensity, to optimize the PE benefits of counteracting ER stress and its associated conditions.

RNA-sequencing Reveals Differentially Expressed Genes of Laying Hens Fed Baihu Decoction Under Heat Shock

Egg production, an important economic trait in the poultry industry, is sensitive to heat stress. The hypothalamus is a crucial center for thermoregulation by detecting temperature changes and regulating the autonomic nervous system in poultry. Baihu decoction (BH), which contains four ingredients (Rhizoma Anemarrhenae, Gypsum Fibrosum, Radix Glycyrrhizae, and Semen Oryzae Nonglutinosae), is a traditional Chinese medicinal formula for clearing heat. Our study aimed to investigate the changes in gene transcription levels in the hypothalamus of laying hens treated with heat stress with and without BH using RNA sequencing. A total of 223 differentially expressed genes (DEGs) were identified in the heat-treated group compared with the control group and 613 DEGs were identified in the BH group compared with the heat-treated group. Heat shock led to significant changes in the expression of multiple genes involved in the "neuroactive ligand-receptor interaction" pathway. Moreover, feeding BH led to significant upregulation in the expression of eight genes encoding heat shock proteins (HSPs), which were highlighted as candidates to control the "protein processing in the endoplasmic reticulum (ER)" pathway. These results provide the novel insight that BH responds to heat stress by participating in regulation of the ER signaling pathway and HSPs expression.

Substance abuse and neurodegenerative diseases: focus on ferroptosis

Psychostimulants and alcohol are widely abused substances with the adverse effects on global public health. Substance abuse seriously harms people's health and causes various diseases, especially neurodegenerative diseases. Neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). The pathogenesis of neurodegenerative diseases is complex and diverse, usually involving oxidative stress, mitochondrial dysfunction, metal homeostasis disorder, and neuro-inflammation. The precise molecular mechanisms underlying neurodegeneration remain unclear, which is a major obstacle to therapeutic approaches. Therefore, it is urgent to improve the understanding of the molecular mechanisms of neurodegenerative processes and to identify the therapeutic targets for treatment and prevention. Ferroptosis is a regulatory cell necrosis caused by iron ion catalysis and lipid peroxidation induced by reactive oxygen species (ROS), which is thought to be associated with nervous system diseases, particularly neurodegenerative diseases. This review overviewed the ferroptosis process and explored the relationship of ferroptosis with substance abuse and neurodegenerative diseases, which provides a new way to study the molecular mechanisms of neurodegenerative diseases induced by alcohol, cocaine, and methamphetamine (MA), and also provides the potential therapeutic targets for substance abuse-induced neurodegenerative diseases.

Hakuna MAM-Tata: Investigating the role of mitochondrial-associated membranes in ALS

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease leading to selective and progressive motor neuron (MN) death. Despite significant heterogeneity in pathogenic and clinical terms, MN demise ultimately unifies patients. Across the many disturbances in neuronal biology present in the disease and its models, two common trends are loss of calcium homeostasis and dysregulations in lipid metabolism. Since both mitochondria and endoplasmic reticulum (ER) are essential in these functions, their intertwin through the so-called mitochondrial-associated membranes (MAMs) should be relevant in this disease. In this review, we present a short overview of MAMs functional aspects and how its dysfunction could explain a substantial part of the cellular disarrangements in ALS's natural history. MAMs are hubs for lipid synthesis, integrating glycerophospholipids, sphingolipids, and cholesteryl ester metabolism. These lipids are essential for membrane biology, so there should be a close coupling to cellular energy demands, a role that MAMs may partially fulfill. Not surprisingly, MAMs are also host part of calcium signaling to mitochondria, so their impairment could lead to mitochondrial dysfunction, affecting oxidative phosphorylation and enhancing the vulnerability of MNs. We present data supporting that MAMs' maladaptation could be essential to MNs' vulnerability in ALS.

Role of UCHL1 in the pathogenesis of neurodegenerative diseases and brain injury

UCHL1 is a multifunctional protein expressed at high concentrations in neurons in the brain and spinal cord. UCHL1 plays important roles in regulating the level of cellular free ubiquitin and redox state as well as the degradation of select proteins. This review focuses on the potential role of UCHL1 in the pathogenesis of neurodegenerative diseases and brain injury and recovery. Subjects addressed in the review include 1) Normal physiological functions of UCHL1. 2) Posttranslational modification sites and splice variants that alter the function of UCHL1 and mouse models with mutations and deletions of UCHL1. 3) The hypothesized role and pathogenic mechanisms of UCHL1 in neurodegenerative diseases and brain injury. 4) Potential therapeutic strategies targeting UCHL1 in these disorders.

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.

Neurotrophins in the Neuropathophysiology, Course, and Complications of Obstructive Sleep Apnea-A Narrative Review

Obstructive sleep apnea (OSA) is a disorder characterized by chronic intermittent hypoxia and sleep fragmentation due to recurring airway collapse during sleep. It is highly prevalent in modern societies, and due to its pleiotropic influence on the organism and numerous sequelae, it burdens patients and physicians. Neurotrophins (NTs), proteins that modulate the functioning and development of the central nervous system, such as brain-derived neurotrophic factor (BDNF), have been associated with OSA, primarily due to their probable involvement in offsetting the decline in cognitive functions which accompanies OSA. However, NTs influence multiple aspects of biological functioning, such as immunity. Thus, extensive evaluation of their role in OSA might enlighten the mechanism behind some of its elusive features, such as the increased risk of developing an immune-mediated disease or the association of OSA with cardiovascular diseases. In this review, we examine the interactions between NTs and OSA and discuss their contribution to OSA pathophysiology, complications, as well as comorbidities.

The mechanism and relevant mediators associated with neuronal apoptosis and potential therapeutic targets in subarachnoid hemorrhage

Subarachnoid hemorrhage (SAH) is a dominant cause of death and disability worldwide. A sharp increase in intracranial pressure after SAH leads to a reduction in cerebral perfusion and insufficient blood supply for neurons, which subsequently promotes a series of pathophysiological responses leading to neuronal death. Many previous experimental studies have reported that excitotoxicity, mitochondrial death pathways, the release of free radicals, protein misfolding, apoptosis, necrosis, autophagy, and inflammation are involved solely or in combination in this disorder. Among them, irreversible neuronal apoptosis plays a key role in both short- and long-term prognoses after SAH. Neuronal apoptosis occurs through multiple pathways including extrinsic, mitochondrial, endoplasmic reticulum, p53 and oxidative stress. Meanwhile, a large number of blood contents enter the subarachnoid space after SAH, and the secondary metabolites, including oxygenated hemoglobin and heme, further aggravate the destruction of the blood-brain barrier and vasogenic and cytotoxic brain edema, causing early brain injury and delayed cerebral ischemia, and ultimately increasing neuronal apoptosis. Even there is no clear and effective therapeutic strategy for SAH thus far, but by understanding apoptosis, we might excavate new ideas and approaches, as targeting the upstream and downstream molecules of apoptosis-related pathways shows promise in the treatment of SAH. In this review, we summarize the existing evidence on molecules and related drugs or molecules involved in the apoptotic pathway after SAH, which provides a possible target or new strategy for the treatment of SAH.

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.

New Frontiers on ER Stress Modulation: Are TRP Channels the Leading Actors?

The endoplasmic reticulum (ER) is a dynamic structure, playing multiple roles including calcium storage, protein synthesis and lipid metabolism. During cellular stress, variations in ER homeostasis and its functioning occur. This condition is referred as ER stress and generates a cascade of signaling events termed unfolded protein response (UPR), activated as adaptative response to mitigate the ER stress condition. In this regard, calcium levels play a pivotal role in ER homeostasis and therefore in cell fate regulation since calcium signaling is implicated in a plethora of physiological processes, but also in disease conditions such as neurodegeneration, cancer and metabolic disorders. A large body of emerging evidence highlighted the functional role of TRP channels and their ability to promote cell survival or death depending on endoplasmic reticulum stress resolution, making them an attractive target. Thus, in this review we focused on the TRP channels' correlation to UPR-mediated ER stress in disease pathogenesis, providing an overview of their implication in the activation of this cellular response.

Measurement of Protein Synthesis Rate in Rat by [11C]Leucine PET Imaging: Application to the TgF344-AD Model of Alzheimer’s Disease

Long-term memory requires stable protein synthesis and is altered in Alzheimer’s disease (AD). This study aimed to implement a method to measure the cerebral protein synthesis rate (PSR) with [11C]leucine PET in vivo in rats and evaluate potential PSR alterations longitudinally (6, 12 and 18 months old) in the TgF344-AD rat model of AD. Wistar, wild-type (WT) and TgF344-AD rats (TG) were scanned for 60 min with [11C]leucine. Arterial blood activity was monitored online and with discrete whole blood and plasma samples by γ-counting in Wistar rats, WT (n = 4) and TG (n = 5). Unlabelled amino acids were measured in plasma. The sensitivity of [11C]leucine PET to measure alterations in PSR was assessed in Wistar rats by injection of PSR inhibitor anisomycin before PET acquisition. Anisomycin administration significantly reduced the net uptake rate constant (Kcplx) of [11C]leucine and PSR, proving the suitability of the method. For the longitudinal study, averaged population-based input functions were used to calculate PSR. We found a significant genotype effect on PSR (decrease in TG vs WT) only in the globus pallidus. This study suggests that [11C]leucine PET is sensitive enough to measure brain PSR in rat but that cross-sectional design with individual input function should be preferred.

Inhibitory effect of (pro)renin receptor decoy inhibitor PRO20 on endoplasmic reticulum stress during cardiac remodeling

Background: Ectopic activation of renin-angiotensin-system contributes to cardiovascular and renal diseases. (Pro)renin receptor (PRR) binds to renin and prorenin, participating in the progression of nephrology. However, whether PRR could be considered as a therapeutic target for cardiac remodeling and heart failure remains unknown.

Materials and methods: Transverse aortic constriction (TAC) surgery was performed to establish a mouse model of chronic pressure overload-induced cardiac remodeling. Neonatal rat cardiomyocytes (CMs) and cardiac fibroblasts (CFs) were isolated and stimulated by Angiotensin II (Ang II). PRR decoy inhibitor PRO20 was synthesized and used to evaluate its effect on cardiac remodeling.

Results: Soluble PRR and PRR were significantly upregulated in TAC-induced cardiac remodeling and Ang II-treated CMs and CFs. Results of In vivo experiments showed that suppression of PRR by PRO20 significantly retarded cardiac remodeling and heart failure indicated by morphological and echocardiographic analyses. In vitro experiments, PRO20 inhibited CM hypertrophy, and also alleviated CF activation, proliferation and extracellular matrix synthesis. Mechanically, PRO20 enhanced intracellular cAMP levels, but not affected cGMP levels in CMs and CFs. Moreover, treatment of PRO20 in CFs markedly attenuated the production of reactive oxygen species and phosphorylation of IRE1 and PERK, two well-identified markers of endoplasmic reticulum (ER) stress. Accordingly, administration of PRO20 reversed ER stressor thapsigargin-induced CM hypertrophy and CF activation/migration.

Conclusion: Taken together, these findings suggest that inhibition of PRR by PRO20 attenuates cardiac remodeling through increasing cAMP levels and reducing ER stress in both CMs and CFs.

4-Phenylbutyrate Mitigates the Motor Impairment and Dopaminergic Neuronal Death During Parkinson's Disease Pathology via Targeting VDAC1 Mediated Mitochondrial Function and Astrocytes Activation

Parkinson's disease (PD) is a progressive motor neurodegenerative disorder significantly associated with protein aggregation related neurodegenerative mechanisms. In view of no disease modifying drugs, the present study was targeted to investigate the therapeutic effects of pharmacological agent 4-phenylbutyric acid (4PBA) in PD pathology. 4PBA is an FDA approved monocarboxylic acid with inhibitory activity towards histone deacetylase and clinically treats urea cycle disorder. First, we observed the significant protective effects of 4PBA on PD specific neuromuscular coordination, level of tyrosine hydroxylase, α-synuclein level and neurotransmitter dopamine in both substantia nigra and striatal regions of the experimental rat model of PD. Further results revealed that treatment with 4PBA drug exhibited significant protection against disease related oxidative stress and augmented nitrite levels. The disease pathology-related depletion in mitochondrial membrane potential and augmented level of calcium as well as mitochondrion membrane located VDAC1 protein level and cytochrome-c translocation were also significantly attenuated with 4PBA administration. Inhibited neuronal apoptosis and restored neuronal morphology were also observed with 4PBA treatment as measured by level of pro-apoptotic proteins t-Bid, Bax and cleaved caspase-3 along with cresyl violet staining in both substantia nigra and striatal regions. Lastly, PD-linked astrocyte activation was significantly inhibited with 4PBA treatment. Altogether, our findings suggest that 4PBA exerts broad-spectrum neuroprotective effects in PD animal model.

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.

Hydrogen Sulfide Plays an Important Role by Regulating Endoplasmic Reticulum Stress in Diabetes-Related Diseases

Endoplasmic reticulum (ER) plays important roles in protein synthesis, protein folding and modification, lipid biosynthesis, calcium storage, and detoxification. ER homeostasis is destroyed by physiological and pharmacological stressors, resulting in the accumulation of misfolded proteins, which causes ER stress. More and more studies have shown that ER stress contributes to the pathogenesis of many diseases, such as diabetes, inflammation, neurodegenerative diseases, cancer, and autoimmune diseases. As a toxic gas, H₂S has, in recent years, been considered the third most important gas signal molecule after NO and CO. H₂S has been found to have many important physiological functions and to play an important role in many pathological and physiological processes. Recent evidence shows that H₂S improves the body’s defenses to many diseases, including diabetes, by regulating ER stress, but its mechanism has not yet been fully understood. We therefore reviewed recent studies of the role of H₂S in improving diabetes-related diseases by regulating ER stress and carefully analyzed its mechanism in order to provide a theoretical reference for future research.

Neurobiological Links between Stress, Brain Injury, and Disease

Stress, which refers to a combination of physiological, neuroendocrine, behavioral, and emotional responses to novel or threatening stimuli, is essentially a defensive adaptation under physiological conditions. However, strong and long-lasting stress can lead to psychological and pathological damage. Growing evidence suggests that patients suffering from mild and moderate brain injuries and diseases often show severe neurological dysfunction and experience severe and persistent stressful events or environmental stimuli, whether in the acute, subacute, or recovery stage. Previous studies have shown that stress has a remarkable influence on key brain regions and brain diseases. The mechanisms through which stress affects the brain are diverse, including activation of endoplasmic reticulum stress (ERS), apoptosis, oxidative stress, and excitatory/inhibitory neuron imbalance, and may lead to behavioral and cognitive deficits. The impact of stress on brain diseases is complex and involves impediment of recovery, aggravation of cognitive impairment, and neurodegeneration. This review summarizes various stress models and their applications and then discusses the effects and mechanisms of stress on key brain regions—including the hippocampus, hypothalamus, amygdala, and prefrontal cortex—and in brain injuries and diseases—including Alzheimer’s disease, stroke, traumatic brain injury, and epilepsy. Lastly, this review highlights psychological interventions and potential therapeutic targets for patients with brain injuries and diseases who experience severe and persistent stressful events.

Endoplasmic Reticulum Stress and Its Role in Homeostasis and Immunity of Central and Peripheral Neurons

Neuronal cells are specialists for rapid transfer and translation of information. Their electrical properties relay on a precise regulation of ion levels while their communication via neurotransmitters and neuropeptides depends on a high protein and lipid turnover. The endoplasmic Reticulum (ER) is fundamental to provide these necessary requirements for optimal neuronal function. Accumulation of misfolded proteins in the ER lumen, reactive oxygen species and exogenous stimulants like infections, chemical irritants and mechanical harm can induce ER stress, often followed by an ER stress response to reinstate cellular homeostasis. Imbedded between glial-, endothelial-, stromal-, and immune cells neurons are constantly in communication and influenced by their local environment. In this review, we discuss concepts of tissue homeostasis and innate immunity in the central and peripheral nervous system with a focus on its influence on ER stress, the unfolded protein response, and implications for health and disease.

Potential Role of MANF, an ER Stress Responsive Neurotrophic Factor, in Protecting Against Alcohol Neurotoxicity

Alcohol exposure during pregnancy is harmful to the fetus and causes a wide range of long-lasting physiological and neurocognitive impairments, collectively referred to as fetal alcohol spectrum disorders (FASD). The neurobehavioral deficits observed in FASD result from structural and functional damages in the brain, with neurodegeneration being the most destructive consequence. Currently, there are no therapies for FASD. It is exigent to delineate the underlying mechanisms of alcohol neurotoxicity and develop an effective strategy of treatment. ER stress, caused by the accumulation of unfolded/misfolded proteins in the ER, is the hallmark of many neurodegenerative diseases, including alcohol-induced neurodegeneration. Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a newly discovered endoplasmic reticulum (ER) stress responsive neurotrophic factor that regulates diverse neuronal functions. This review summarizes the recent findings revealing the effects of MANF on the CNS and its protective role against neurodegeneration. Particularly, we focus the role of MANF on alcohol-induced ER stress and neurodegeneration and discuss the therapeutic potential of MANF in treating alcohol neurotoxicity such as FASD.

ER Stress in COVID-19 and Parkinson’s Disease: In Vitro and In Silico Evidences

The outbreak of COVID-19 caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) signifies a serious worldwide concern to public health. Both transcriptome and proteome of SARS-CoV-2-infected cells synergize the progression of infection in host, which may exacerbate symptoms and/or progression of other chronic diseases such as Parkinson’s disease (PD). Oxidative stress is a well-known cause of endoplasmic reticulum (ER) stress observed in both SARS-CoV-2 and PD. In the current study, we aimed to explore the influence of PKR-like ER kinase (PERK) stress pathway under SARS-CoV-2-mediated infection and in human cell model of PD. Furthermore, we investigated whether they are interconnected and if the ER stress inhibitors could inhibit cell death and provide cellular protection. To achieve this aim, we have incorporated in silico analysis obtained from gene set enrichment analysis (GSEA), a literature review and laboratory data. The neurotoxin, 6-hydroxy dopamine (6OHDA), was used to mimic the biochemical and neuropathological characteristics of PD by inducing oxidative stress in dopamine-containing neurons differentiated from ReNVM cell line (dDCNs). Furthermore, we explored if ER stress influences activation of caspases-2, -4 and -8 in SARS-CoV-2 and in stressed dDCNs. Our laboratory data using Western blot, immunocytochemistry and 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) analyses indicated that 6OHDA-induced toxicity triggered activation of caspases-2, -4 and -8 in dDCNs. Under SARS-CoV-2 infection of different cell types, GSEA revealed cell-specific sensitivities to oxidative and ER stresses. Cardiomyocytes and type II alveolar epithelial-like cells were more vulnerable to oxidative stress than neural cells. On the other side, only cardiomyocytes activated the unfolded protein response, however, the PERK pathway was operative in both cardiomyocytes and neural cells. In addition, caspase-4 activation by a SARS-CoV-2 was observed via in silico analyses. These results demonstrate that the ER stress pathway under oxidative stress in SARS-CoV-2 and PD are interconnected using diverse pathways. Furthermore, our results using the ER stress inhibitor and caspase specific inhibitors provided cellular protection suggesting that the use of specific inhibitors can provide effective therapeutic approaches for the treatment of COVID-19 and PD.

Identification of Novel Oxindole Compounds That Suppress ER Stress-Induced Cell Death as Chemical Chaperones

Endoplasmic reticulum (ER) stress and oxidative stress lead to protein misfolding, and the resulting accumulation of protein aggregates is often associated with the pathogenesis of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and prion disease. Small molecules preventing these pathogenic processes may be effective interventions for such neurodegenerative disorders. In this paper, we identify several novel oxindole compounds that can prevent ER stress- and oxidative stress-induced cell death. Among them, derivatives of the lead compound GIF-0726-r in which a hydrogen atom at the oxindole ring 5 position is substituted with a methyl (GIF-0852-r), bromine (GIF-0854-r), or nitro (GIF-0856-r) group potently suppressed global ER stress. Furthermore, GIF-0854-r and -0856-r prevented protein aggregate accumulation in vitro and in cultured hippocampal HT22 neuronal cells, indicating that these two compounds function effectively as chemical chaperones. In addition, GIF-0852-r, -0854-r, and -0856-r prevented glutamate-induced oxytosis and erastin-induced ferroptosis. Collectively, these results suggest that the novel oxindole compounds GIF-0854-r and -0856-r may be useful therapeutics against protein-misfolding diseases as well as valuable research tools for studying the molecular mechanisms of ER and oxidative stress.

Post-treatment with apocynin at a lower dose regulates the UPR branch of eIF2α and XBP-1 pathways after stroke

Stroke leads to disturbance in the physiology of the ER (Endoplasmic Reticulum) that triggers UPR (Unfolded Protein Response) pathways aimed to compensate neuronal cell damage. However, sustained UPR causes stressful conditions in the ER lumen forming abnormal protein aggregates. Stroke-induced oxidative stress also amalgamates with UPR to safeguard and ensure the proper functioning of brain cells. Thus we tested the effect of apocynin (a potent antioxidant) post-treatment in experimental stroke on the outcome of ER stress and UPR branch pathways. We administered a low dose of apocynin at 1 mg/kg (intraperitoneal) to adult Sprague-Dawley rats subjected to Middle Cerebral Artery Occlusion (MCAO) for two-time points. The first dose immediately after re-establishing the blood flow and another at 6 h of reperfusion. Apocynin post-treatment significantly reduced ROS (Reactive Oxygen Species) generation at an early reperfusion time point of 4 h. It preserved neuronal morphology, dendritic spine density, reduced protein aggregation, and brain damage after 24 h of reperfusion. Apocynin post-treatment regulates the two UPR branch pathways in our experimental paradigm. 1) Down-regulation of eIF2α (Eukaryotic Initiation Factor 2α) phosphorylation, and CHOP (C/EBP homologous protein) 2) by reducing the XBP-1 (X-Box binding Protein-1) mRNA splicing downstream to PERK (Protein Kinase RNA-Like ER Kinase) and IRE1α (Inositol Requiring Enzyme 1alpha) UPR pathways, respectively. Bioinformatics prediction showed that apocynin has binding sites for PERK (Protein Kinase RNA-Like ER Kinase) and IRE1α proteins. The amino acid residues interacting with apocynin were Cys891 and Gln889 (for PERK), and the amino acids Ser726, Arg722, and Ala719 (for IRE1α) lying within their activation loop. Overall, these studies indicate that apocynin post-treatment might regulate ER stress/UPR pathways and minimize stroke brain damage, thus having implications for developing newer strategies for stroke treatment.

DA-9805 protects dopaminergic neurons from endoplasmic reticulum stress and inflammation

Parkinson's disease (PD) is a multifactorial neurodegenerative disease with damages to mitochondria and endoplasmic reticulum (ER), followed by neuroinflammation. We previously reported that a triple herbal extract DA-9805 in experimental PD toxin-models had neuroprotective effects by alleviating mitochondrial damage and oxidative stress. In the present study, we investigated whether DA-9805 could suppress ER stress and neuroinflammation in vitro and/or in vivo. Pre-treatment with DA-9805 (1 μg/ml) attenuated upregulation of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP) and cleaved caspase-3 in SH-SY5Y neuroblastoma cells treated with thapsigargin (1 µg/ml) or tunicamycin (2 µg/ml). In addition, DA-9805 prevented the production of IL-1β, IL-6, TNF-α and nitric oxide through inhibition of NF-κB activation in BV2 microglial cells stimulated with lipopolysaccharides (LPS). Intraperitoneal injection of LPS (10 mg/kg) into mice can induce acute neuroinflammation and dopaminergic neuronal cell death. Oral administration of DA-9805 (10 or 30 mg/kg/day for 3 days before LPS injection) prevented loss of dopaminergic neurons and activation of microglia and astrocytes in the substantia nigra in LPS-injected mouse models. Taken together, these results indicate that DA-9805 can effectively prevent ER stress and neuroinflammation, suggesting that DA-9805 is a multitargeting and disease-modifying therapeutic candidate for PD.

Adipose-derived stem cells (ADSCs) inhibit the expression of anti-apoptosis proteins through up-regulation of ATF4 on breast cancer cells

Background

While current basic studies indicate adipose-derived stem cells (ADSCs) can promote cell proliferation, clinical trials have shown no significant difference in breast cancer recurrence rates for patients with or without autologous fat grafting (AFG). In this study we attempted to explore the underlying mechanism for these contradictory results.

Methods

ADSCs and umbilical mesenchymal stem cells (UMSCs) were co-cultured with breast cancer cells (MCF-7 and MDA-MB-231), and the cell viability analyzed by CCK-8 cell proliferation assay, TUNEL assay and immunofluorescence assay. In addition, real-time quantitative polymerase chain reaction (RT-qPCR) experiments and Western blot analysis were used to detect the mRNA and protein expression of activating transcription factor 4 (ATF4) and its downstream gene (MCL1 & BCL2), respectively.

Results

Co-cultured ADSCs could promote cell proliferation and cell apoptosis, and up-regulate ATF4 expression both in MCF-7 and MDA-MB-231. While co-cultured UMSCs could only promote cell apoptosis in MCF-7. Interestingly, we found that when co-cultured ADSCs, the expression of MCL1 and BCL2 protein was decreased, even if their mRNA expression was up-regulated both in MCF-7 and MDA-MB-231.

Conclusions

Co-cultured ADSCs can up-regulate ATF4 expression, then interfere with the translation process of MCL1 and BCL2 mRNA and induce cell apoptosis. These data provide insight into the safety characteristics of AFG.

EETs/sEHi alleviates nociception by blocking the crosslink between endoplasmic reticulum stress and neuroinflammation in a central poststroke pain model

Background

Central post-stroke pain (CPSP) is a chronic and intolerable neuropathic pain syndrome following a cerebral vascular insult, which negatively impacts the quality of life of stroke survivors but currently lacks efficacious treatments. Though its underlying mechanism remains unclear, clinical features of hyperalgesia and allodynia indicate central sensitization due to excessive neuroinflammation. Recently, the crosslink between neuroinflammation and endoplasmic reticulum (ER) stress has been identified in diverse types of diseases. Nevertheless, whether this interaction contributes to pain development remains unanswered. Epoxyeicosatrienoic acids (EETs)/soluble epoxy hydrolase inhibitors (sEHi) are emerging targets that play a significant role in pain and neuroinflammatory regulation. Moreover, recent studies have revealed that EETs are effective in attenuating ER stress. In this study, we hypothesized that ER stress around the stroke site may activate glial cells and lead to further inflammatory cascades, which constitute a positive feedback loop resulting in central sensitization and CPSP. Additionally, we tested whether EETs/sEHi could attenuate CPSP by suppressing ER stress and neuroinflammation, as well as their vicious cycle, in a rat model of CPSP.

Methods

Young male SD rats were used to induce CPSP using a model of thalamic hemorrhage and were then treated with TPPU (sEHi) alone or in combination with 14,15-EET or 14,15-epoxyeicosa-5(Z)-enoic acid (14,15-EEZE, the EET antagonist), tunicamycin (Tm, ER stress inducer), or 4-PBA (ER stress inhibitor). Nociceptive behaviors, ER stress markers, JNK and p38 (two well-recognized inflammatory kinases of mitogen-activated protein kinase (MAPK) signaling) expression, and glial cell activation were assessed. In addition, some healthy rats were intrathalamically microinjected with Tm or lipopolysaccharide (LPS) to test the interaction between ER stress and neuroinflammation in central pain.

Results

Analysis of the perithalamic lesion tissue from the brain of CPSP rats demonstrated decreased soluble epoxy hydrolase (sEH) expression, which was accompanied by increased expression of ER stress markers, including BIP, p-IRE, p-PERK, and ATF6. In addition, inflammatory kinases (p-p38 and p-JNK) were upregulated and glial cells were activated. Intrathalamic injection of sEHi (TPPU) increased the paw withdrawal mechanical threshold (PWMT), reduced hallmarks of ER stress and MAPK signaling, and restrained the activation of microglia and astrocytes around the lesion site. However, the analgesic effect of TPPU was completely abolished by 14,15-EEZE. Moreover, microinjection of Tm into the thalamic ventral posterior lateral (VPL) nucleus of healthy rats induced mechanical allodynia and activated MAPK-mediated neuroinflammatory signaling; lipopolysaccharide (LPS) administration led to activation of ER stress along the injected site in healthy rats.

Conclusions

The present study provides evidence that the interaction between ER stress and neuroinflammation is involved in the mechanism of CPSP. Combined with the previously reported EET/sEHi effects on antinociception and neuroprotection, therapy with agents that target EET signaling may serve as a multi-functional approach in central neuropathic pain by attenuating ER stress, excessive neuroinflammation, and subsequent central sensitization. The use of these agents within a proper time window could not only curtail further nerve injury but also produce an analgesic effect.

From psychiatry to neurology: Psychedelics as prospective therapeutics for neurodegenerative disorders

The studies of psychedelics, especially psychedelic tryptamines like psilocybin, are rapidly gaining interest in neuroscience research. Much of this interest stems from recent clinical studies demonstrating that they have a unique ability to improve the debilitating symptoms of major depressive disorder (MDD) long-term after only a single treatment. Indeed, the Food and Drug Administration (FDA) has recently designated two Phase III clinical trials studying the ability of psilocybin to treat forms of MDD with "Breakthrough Therapy" status. If successful, the use of psychedelics to treat psychiatric diseases like depression would be revolutionary. As more evidence appears in the scientific literature to support their use in psychiatry to treat MDD on and substance use disorders (SUD), recent studies with rodents revealed that their therapeutic effects might extend beyond treating MDD and SUD. For example, psychedelics may have efficacy in the treatment and prevention of brain injury and neurodegenerative diseases such as Alzheimer's Disease. Preclinical work has highlighted psychedelics' ability to induce neuroplasticity and synaptogenesis, and neural progenitor cell proliferation. Psychedelics may also act as immunomodulators by reducing levels of proinflammatory biomarkers, including IL-1β, IL-6, and tumor necrosis factor-α (TNF-α). Their exact molecular mechanisms, and induction of cellular interactions, especially between neural and glial cells, leading to therapeutic efficacy, remain to be determined. In this review, we discuss recent findings and information on how psychedelics may act therapeutically on cells within the central nervous system (CNS) during brain injuries and neurodegenerative diseases.

Using genetic testing to diagnose Kennedy's disease: a case report and literature review

Theoretical basis: Kennedy's disease (KD) is also known as spinal bulbar muscular dystrophy. Because the symptoms of KD are similar to most neuromuscular diseases, it is difficult to make a rapid clinical diagnosis. Patient case: We report the case of a 50-year-old man who was diagnosed with "lumbar disc herniation" five years ago because of progressive proximal limb weakness. After his initial diagnosis, his condition worsened gradually, and a muscle biopsy was performed 3 years ago, and he was then diagnosed with "motor neuron disease", but he had no such family history. His physical examination showed female breast development, erectile dysfunction, a weakness of the quadriceps femoris, a bilateral tendon reflex, and atrophy of the tongue muscle. One year ago, it was found that his blood sugar had increased, and when oral hypoglycemic drugs were given, his blood glucose control was not ideal. At the same time, it was found that his creatine kinase continued to increase significantly. He was admitted to the hospital again because of the aggravation of his walking difficulties. Diagnosis: A laboratory examination showed elevated creatine kinase, an impaired glucose tolerance, and abnormal lactate values. The diagnosis was confirmed using a genetic analysis, which showed a repeated amplification of CAG in the androgen receptor gene. Intervention measures and results: After this diagnosis, the patient had a good prognosis after receiving symptomatic treatment. Lesson: Genetic testing is the key to the diagnosis of KD. Clinicians should make a differential diagnosis, an early diagnosis, and provide treatment as soon as possible according to the patient's clinical manifestations and laboratory examination.