Endoplasmic Reticulum Stress Signaling and Neuronal Cell Death

Parkinson's Disease: The Neurodegenerative Enigma Under the "Undercurrent" of Endoplasmic Reticulum Stress

Parkinson's disease (PD), a prevalent neurodegenerative disorder, demonstrates the critical involvement of endoplasmic reticulum stress (ERS) in its pathogenesis. This review comprehensively examines the role and molecular mechanisms of ERS in PD. ERS represents a cellular stress response triggered by imbalances in endoplasmic reticulum (ER) homeostasis, induced by factors such as hypoxia and misfolded protein aggregation, which activate the unfolded protein response (UPR) through the inositol-requiring enzyme 1 (IRE1), protein kinase R-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6) pathways. Clinical, animal model, and cellular studies have consistently demonstrated a strong association between PD and ERS. Abnormal expression of ERS-related molecules in PD patients' brains and cerebrospinal fluid (CSF) correlates with disease progression. In animal models (e.g., Drosophila and mice), ERS inhibition alleviates dopaminergic neuronal damage. Cellular experiments reveal that PD-mimicking pathological conditions induce ERS, while interactions between ERS and mitochondrial dysfunction promote neuronal apoptosis. Mechanistically, (1) pathological aggregation of α-synuclein (α-syn) and ERS mutually reinforce dopaminergic neuron damage; (2) leucine-rich repeat kinase 2 (LRRK2) gene mutations induce ERS through thrombospondin-1 (THBS1)/transforming growth factor beta 1 (TGF-β1) interactions; (3) molecules such as Parkin and PTEN-induced kinase 1 (PINK1) regulate ERS in PD. Furthermore, ERS interacts with mitochondrial dysfunction, oxidative stress, and neuroinflammation to exacerbate neuronal injury. Emerging therapeutic strategies show significant potential, including artificial intelligence (AI)-assisted drug design targeting ERS pathways and precision medicine approaches exploring non-pharmacological interventions such as personalized electroacupuncture. Future research should focus on elucidating ERS-related mechanisms and identifying novel therapeutic targets to develop more effective treatments for PD patients, ultimately improving their quality of life.

Endoplasmic reticulum stress and unfolded protein response: Roles in skeletal muscle atrophy

Skeletal muscle atrophy is commonly present in various pathological states, posing a huge burden on society and patients. Increased protein hydrolysis, decreased protein synthesis, inflammatory response, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress (ERS) and unfolded protein response (UPR) are all important molecular mechanisms involved in the occurrence and development of skeletal muscle atrophy. The potential mechanisms of ERS and UPR in skeletal muscle atrophy are extremely complex and have not yet been fully elucidated. This article elucidates the molecular mechanisms of ERS and UPR, and discusses their effects on different types of muscle atrophy (muscle atrophy caused by disuse, cachexia, chronic kidney disease (CKD), diabetes mellitus (DM), amyotrophic lateral sclerosis (ALS), spinal muscular atrophy (SMA), spinal and bulbar muscular atrophy (SBMA), aging, sarcopenia, obesity, and starvation), and explores the preventive and therapeutic strategies targeting ERS and UPR in skeletal muscle atrophy, including inhibitor therapy and drug therapy. This review aims to emphasize the importance of endoplasmic reticulum (ER) in maintaining skeletal muscle homeostasis, which helps us further understand the molecular mechanisms of skeletal muscle atrophy and provides new ideas and insights for the development of effective therapeutic drugs and preventive measures for skeletal muscle atrophy.

Chinese Tuina ameliorates muscle damage by regulating endoplasmic reticulum stress and autophagy in a rat model of skeletal muscle contusion

Chinese Tuina has been used to treat skeletal muscle contusion (SMC) for a long time in China, yet its efficacy and mechanisms remain unclear. Previous studies have shown the vital roles of endoplasmic reticulum (ER) stress and autophagy during injured skeletal muscle recovery, we postulated that Chinese Tuina could expedite the healing of SMC by fine-tuning these processes. In this study, we established a rat model of SMC through weight-dropping and divided the rats into three groups: SMC, SMC+Tuina, and SMC+Tuina+ 3-methyladenine (3-MA) groups, while using untreated normal SD rats as a control. We assessed gait and edema via CatWalk gait analysis and swelling measurements, respectively. Tumor necrosis factor-α (TNF-α) expression was determined by immunohistochemistry (IHC). Morphological and ultrastructural alterations in the damaged muscle tissue were examined using hematoxylin and eosin (HE) staining and transmission electron microscopy (TEM), respectively. Expression of GRP78, LC3B and FAM134b was determined by western blot, and Colocalization of LC3B and FAM134b was examined by immunofluorescence. SMC+Tuina exhibited significantly improved gait and reduced edema. SMC+Tuina showed improvements in morphology and ultrastructure of damaged muscles, as well as decreased expression of TNF-α. Additionally, in SMC+Tuina, expression of GRP78 was downregulated, while expressions of FAM134 and LC3B were upregulated, and colocalization of FAM134 and LC3B was also enhanced. However, autophagy inhibitor 3-MA weakened the aforementioned effects of Chinese Tuina. The obtained results indicated that Chinese Tuina has a positive therapeutic effect in rats with SMC, potentially by promoting autophagy to reduce inflammation and ER stress.

PSMC2 promotes resistance against temozolomide in glioblastoma via suppressing JNK-mediated autophagic cell death

Temozolomide is universally used to treat glioblastoma due to its unique ability to cross the blood-brain barrier and inhibit tumor growth through DNA alkylation. However, over time, the inevitable emergence of resistance to temozolomide impedes successful treatment of this cancer. As a result, there is an urgent need to identify new therapeutic targets to improve treatment outcomes for this malignancy. In this work, acquired temozolomide-resistant glioblastoma cell lines LN18 (LN18-TR) and T98G (T98G-TR) exhibited stronger aggressiveness and lower endoplasmic reticulum (ER) stress than their parental cells.. Besides, temozolomide resistance was associated with elevated proteasome activity that suppressed ER stress, which was restored upon inhibition of the proteasome with MG132. Specifically, our study revealed that the 19S proteasomal regulatory subunit PSMC2, which was overexpressed in adapted temozolomide-resistant glioblastoma cells, reduced pro-death autophagy and decreased temozolomide sensitivity in parental cells when overexpressed. While autophagy increased in parental cells following temozolomide treatment, it was not elevated in temozolomide-resistant glioblastoma cells. Genetic suppression of PSMC2 triggered the JNK signalling pathway causing phosphorylation of BCL2, allowing Beclin1 to be released from the BCL2-Beclin1 complex. This boosted autophagosome nucleation, increased pro-death autophagy, and restored apoptosis in temozolomide-resistant glioblastoma cells. Finally, targeting PSMC2 provided a unique method for interrupting autophagy-mediated ER stress maintenance and temozolomide resistance in glioblastoma.

Endoplasmic reticulum stress in liver fibrosis: Mechanisms and therapeutic potential

This paper reviews the important role of endoplasmic reticulum stress in the patho mechanism of liver fibrosis and its potential as a potential target for the treatment of liver fibrosis. Liver fibrosis is the result of sustained inflammation and injury to the liver due to a variety of factors, triggering excessive deposition of extracellular matrix and fibrous scar formation, which in turn leads to loss of liver function and a variety of related complications. Endoplasmic reticulum stress is one of the characteristics of chronic liver disease and is closely related to the pathological process of chronic liver disease, including alcohol-related liver disease, viral hepatitis, and liver fibrosis. The unfolded protein response is one of the important response mechanisms to endoplasmic reticulum stress. It is associated with several pathological aspects of liver fibrosis and the maintenance of endoplasmic reticulum homeostasis. Interventions targeting endoplasmic reticulum stress for the treatment of liver fibrosis have potential research and application value. An in-depth understanding of the biological basis of endoplasmic reticulum stress is also needed in the treatment of liver fibrosis, as well as the development of more effective drugs and interventions to accurately regulate the endoplasmic reticulum signaling network, to achieve the restoration and maintenance of endoplasmic reticulum homeostasis at the cellular and organ levels, and to further promote the reversal of the pathological process of liver fibrosis.

Unravelling the impact of QRICH1 modulation on endoplasmic reticulum stress and neuronal apoptosis in traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major public health concern with high morbidity and mortality rates. Secondary brain injury, marked by inflammatory responses and apoptosis, worsens TBI outcomes. The endoplasmic reticulum stress (ERS) response has been implicated in secondary brain injury, with Glutamine Rich 1 Gene (QRICH1) emerging as a potential mediator. However, the precise role of QRICH1 in TBI pathogenesis and its therapeutic implications remain unclear.

METHODS

Controlled cortical impact mouse and Lipopolysaccharide-stimulated primary neuron models were used. Behavioral assessments, including the modified Garcia score, Y-maze test, and open-field test, were used to evaluate postoperative recovery in mice. QRICH1 neuron conditional knockout (cKO) mice were used to assess QRICH1 function, whereas adeno-associated virus (AAV)-mediated gene manipulation was used to modulate QRICH1 expression in cortical neurons.

RESULTS

QRICH1 expression was upregulated in the brain tissue of TBI mice, particularly 24 h post-injury, as shown by western blot analysis and immunofluorescence staining. QRICH1 is localized within neuronal nuclei, suggesting a role in cellular stress responses. QRICH1 cKO improved behavioral outcomes post-TBI, whereas AAV-mediated QRICH1 overexpression exacerbated secondary brain injury, characterized by increased ERS-related protein expression and neuronal death. Conversely, AAV-mediated QRICH1 knockdown reduced secondary brain injury as evidenced by decreased ERS-related protein expression and neuronal death.

CONCLUSION

QRICH1 plays a critical role in exacerbating ERS and apoptosis, and influences neuronal fate in secondary brain injury. Its involvement in the ERS pathway and in the induction of neuronal apoptosis post-TBI highlights QRICH1 as a potential therapeutic target for TBI treatment.

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.

Shrimp Shapes a Nitrite Tolerance Trait via Regulating Autophagy and Apoptosis

Nitrite is a significant toxic substance that causes acute toxicity in aquatic animals. However, the molecular mechanisms underlying nitrite tolerance remain largely unidentified. Here, we investigated the physiological and transcriptomic profiles of nitrite-sensitive and nitrite-tolerant families of the white shrimp Penaeus vannamei under nitrite stress. Exposure to a lethal concentration of nitrite for 72 h caused higher mortality, higher nitrite accumulation, and more severe physiological damage in both the hemolymph and hepatopancreas of nitrite-sensitive families than in nitrite-tolerant families. This damage manifested as hepatic tubular deformation, hepatocyte necrosis, decreased hemocyte counts, lowered phagocytic activity in hemocytes, elevated production of reactive oxygen species (ROS), and decreased AKP enzyme activity. Furthermore, transcriptomic analysis revealed an upregulation in protein processing in the endoplasmic reticulum (ER) in the nitrite-tolerant families, triggering apoptosis- and autophagy-related pathways in the hemocytes and hepatopancreas upon nitrite exposure. Additionally, TUNEL staining and transmission electron microscopy (TEM) experiments revealed that the tolerant families may mitigate nitrite toxicity by modulating autophagy and apoptosis. Collectively, our results provide a valuable foundation for exploring the molecular mechanisms underlying nitrite tolerance in shrimp, which could facilitate the targeted breeding of shrimp germplasm with enhanced nitrite tolerance in aquaculture.

The Interplay Between Endoplasmic Reticulum Stress and Ferroptosis in Neurological Diseases

Many studies in the open literature have highlighted the critical roles of endoplasmic reticulum stress and ferroptosis in neurological diseases such as neurodegenerative diseases, brain injuries, and depression, indicating that they are involved in the onset and progression of these diseases. Therefore, it is essential to explore the regulatory mechanisms and potential interventions targeting endoplasmic reticulum stress and ferroptosis in neurological diseases. However, most existing research has primarily focused on the unidirectional mechanisms of endoplasmic reticulum stress and ferroptosis within the nervous system, with a lack of in-depth investigations into their interactions. In this paper, we first present an overview of the pathogenesis of endoplasmic reticulum stress and ferroptosis, along with their roles in neurological diseases. We then summarize the latest findings on the interaction mechanism between endoplasmic reticulum stress and ferroptosis from the perspectives of calcium iron homeostasis, reactive oxygen species, microenvironment, and related factors. Finally, we explore the potential molecular mechanisms and targeted interventions associated with endoplasmic reticulum stress and ferroptosis in neurological diseases.

Exogenous hydrogen sulfide improves non-alcoholic fatty liver disease by inhibiting endoplasmic reticulum stress/NLRP3 inflammasome pathway

Non-alcoholic fatty liver disease (NAFLD) is a common chronic liver disease worldwide, and its exact pathogenesis has not been fully studied. Hydrogen sulfide (H2S) is the third gas signaling molecule discovered in mammals, following nitric oxide and carbon monoxide. It has the effects of anti-inflammation, anti-apoptosis, and so on, thereby playing an important role in many diseases. However, the role and mechanism of exogenous H2S in NAFLD are not fully understood. In this study, we constructed in vitro and in vivo NAFLD models by feeding mice a high-fat diet and stimulating hepatocytes with palmitic acid, respectively, to investigate the improvement effect and mechanism of exogenous H2S on NAFLD. The results showed that NaHS (a donor of H2S) treatment alleviated lipid accumulation, inflammation, apoptosis and pyroptosis, and downregulated endoplasmic reticulum (ER) stress and nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NRRP3) inflammasome in NAFLD. The activation of NLRP3 inflammasome weakened NaHS improvement of NAFLD, indicating that exogenous H2S ameliorated NAFLD by inhibiting NLRP3 inflammasome-mediated lipid synthesis, inflammation, apoptosis and pyroptosis. Similarly, the activation of ER stress weakened NaHS improvement of NAFLD and NaHS inhibition of NLRP3 inflammasome, indicating that exogenous H2S suppressed NLRP3 inflammasome by downregulating ER stress, thus improving NAFLD. Additionally, the protein expressions of NLRP3 and cleaved caspase-1 were downregulated after inhibiting the reactive oxygen species (ROS)/extracellular signal-regulated kinases (ERK) and ROS/thioredoxin-interacting protein (TXNIP) pathways, indicating that ER stress activated NLRP3 inflammasome through the ROS/ERK and ROS/TXNIP pathways. In conclusion, our results indicated that exogenous H2S inhibited NLRP3 inflammasome-mediated hepatocytes inflammation, lipid synthesis, apoptosis and pyroptosis by downregulating ER stress, thereby improving NAFLD; Furthermore, ER stress activated NLRP3 inflammasome through the ROS/ERK and ROS/TXNIP pathways in NAFLD. ER stress/NLRP3 inflammasome is expected to become a new target of H2S for treating NAFLD.

Effects of Herpud1 in Methamphetamine-induced Neuronal Apoptosis

INTRODUCTION

Methamphetamine (METH) is an illicit psychoactive substance that can damage various organs in the body, especially the nervous system. We hypothesized that expression of homocysteine-inducible endoplasmic reticulum-resident with ubiquitin-like domain member 1 (Herpud1) protein would alleviate the induction of apoptosis following METH administration.

METHODS

To test this hypothesis, we analysed the changes in Herpud1 expression and apoptosis in PC12 cells under different concentrations and exposure times of METH. Moreover, we examined the effects of Herpud1 knockdown on METH-induced neuronal apoptosis. Flow cytometry and Western blot analyses were used to evaluate apoptosis levels and the expression of apoptotic markers (cleaved caspase-3) in PC12 cells following Herpud1 knockdown by synthetic small interfering RNA (siRNA).

RESULTS

Our results showed that Herpud1 expression was upregulated in PC12 cells following METH treatment, while endoplasmic reticulum stress (ERS) and apoptosis were also increased. Conversely, Herpud1 knockdown reduced METH-induced ERS and apoptosis levels in vitro.

CONCLUSION

These results suggest that Herpud1 plays an essential role in METH-induced neuronal ERS and apoptosis and may represent a potential therapeutic gene target in METH-induced neurotoxicity.

Pulsed radiofrequency alleviates neuropathic pain by upregulating MG53 to inhibit microglial activation

BACKGROUND

Patients with neuropathic pain (NP) have significantly lower quality of life. Because the pathophysiology of NP is not fully understood, there is a lack of effective treatment for it in clinic. This study set out to investigate the precise mechanism by which pulsed radiofrequency (PRF) alleviated NP.

METHOD

The rat models of chronic constriction injury of the sciatic nerve (CCI) were established to simulate the occurrence of NP, following with measuring MWT and TWL to evaluate the pain of the rats. HE staining was utilized to observe the rat spinal cord tissue pathology. The expression of MG53, ATF4 and CHOP was evaluated by qRT-PCR and WB, while the expression of inflammatory factors was measured by ELISA. In addition, immunofluorescence assay was used to detect the expression of MG53 and Iba-1.

RESULT

PRF treatment alleviated NP in CCI rats, as well as upregulating the expression of MG53 and inhibiting microglial activation. After MG53 knockdown, the remission of NP by PRF was significantly weakened, but microglial activation and endoplasmic reticulum stress (ERS) exhibited enhancement. Therefore, PRF inhibited microglial activation by upregulating MG53. After injection of ERS inducer in CCI rats, the inhibition effect of overexpressed MG53 on microglial activation and its alleviation effect on NP were reversed. Consequently, MG53 played a role in suppressing microglial activation by mediating the inhibition of ERS.

CONCLUSION

PRF attenuated microglial activation by upregulating MG53 to inhibit ERS, resulting in the alleviation of NP in CCI rats.

Endoplasmic reticulum stress induces renal fibrosis in high‑fat diet mice via the TGF‑β/SMAD pathway

The aim of the present study was to investigate the role and mechanism of endoplasmic reticulum stress (ERS) in kidney injury caused by high‑fat diet (HFD). An obese mouse model was established via HFD feeding and intervention was performed by intraperitoneal injection of the ERS inhibitor salubrinal (Sal). Changes in the body and kidney weight and serum biochemical indices of the mice were determined. Hematoxylin and eosin and Masson staining were used to observe the pathological changes of renal tissues. Reverse transcription‑quantitative PCR and western blotting were used to observe the expression of ERS‑related proteins and TGF‑β/SMAD pathway‑related proteins. Immunohistochemistry was employed to explore the distribution of these proteins. Compared with those in the control group, the weight gain, lipid metabolism disorders and deterioration of renal function in the model group were greater. Malondialdehyde was elevated and superoxide dismutase was decreased in renal tissues. The mRNA and protein levels of TGF‑β1, SMAD2/3, α‑smooth muscle actin, collagen I, glucose‑regulated protein 78 and C/EBP‑homologous protein were markedly elevated, whereas SMAD7 was markedly decreased. Sal markedly inhibited the aforementioned effects. This investigation revealed a link between ERS and renal injury caused by HFD. ERS in HFD‑fed mice triggers renal fibrosis through the TGF‑β/SMAD pathway.

The role of microRNAs regulation of endoplasmic reticulum stress in ischemia-reperfusion injury: A review

The endoplasmic reticulum (ER) is an important organelle in eukaryotic cells, responsible for a range of biological functions such as the secretion, modification and folding of proteins, maintaining Ca2+ homeostasis and the synthesis of steroids/lipids, secreted proteins and membrane proteins. When cells are affected by internal or external factors, including abnormal energy metabolism, disrupted Ca2+ balance, altered glycosylation, drug toxicity, and so on, the unfolded or misfolded proteins accumulate in the ER, leading to the unfolded protein response (UPR) and ER stress. The abnormal ER stress has been reported to be involved in various pathological processes. MicroRNAs (miRNAs) are non-coding RNAs with the length of approximately 19-25 nucleotides. They control the expression of multiple genes through posttranscriptional gene silencing in eukaryotes or some viruses. Increasing evidence indicates that miRNAs are involved in various cellular functions and biological processes, such as cell proliferation and differentiation, growth and development, and metabolic homeostasis. Hence, miRNAs participate in multiple pathological processes. Recently, many studies have shown that miRNAs play an important role by regulating ER stress in ischemia-reperfusion (I/R) injury, but the relevant mechanisms are not fully understood. In this review, we reviewed the current understanding of ER stress, as well as the biogenesis and function of miRNAs, and focused on the role of miRNAs regulation of ER stress in I/R injury, with the aim of providing new targets for the treatment of I/R injury.

SIRT1-Dependent Neuroprotection by Resveratrol in TOCP-Induced Spinal Cord Injury: Modulation of ER Stress and Autophagic Flux

This study explores the neuroprotective effects of resveratrol (Resv) against tri-o-cresyl phosphate (TOCP)-induced neurotoxicity in the spinal cord of adult hens. It is well documented that TOCP exposure causes significant neurodegeneration via mechanisms that involve endoplasmic reticulum (ER) stress and impaired autophagy. In this experiment, adult hens were assigned to one of four groups: Control, Resv, TOCP, and TOCP + Resv. The spinal cord tissues were examined through transmission electron microscopy, hematoxylin and eosin (HE) staining, Nissl staining, and Western blotting to evaluate key proteins associated with ER stress and autophagy. Additionally, RT-qPCR and immunofluorescence were employed to measure sirtuin1 (SIRT1) expression. The findings revealed that TOCP induced severe ultrastructural damage, including disrupted myelin sheaths, dilated ER, and extensive neurodegeneration, as confirmed by histological evaluations. The expression levels of GRP78, p-PERK, p-eIF2α, ATF4, CHOP, Beclin-1, P62, and LC3-II were also significantly elevated by TOCP. However, Resv treatment markedly attenuated these pathological changes by reducing ER stress, restoring autophagic flux, and upregulating SIRT1 expression, preserving spinal cord integrity. These results indicate that Resv can effectively counteract TOCP-induced neurotoxicity by modulating ER stress and autophagy, underscoring its potential as a therapeutic agent for neuroprotection.

PIGK defects induce apoptosis in Purkinje cells and acceleration of neuroectodermal differentiation

Biallelic mutations in PIGK cause GPI biosynthesis defect 22 (GPIBD22), characterized with developmental delay, hypotonia, and cerebellar atrophy. The understanding of the underlying causes is limited due to the lack of suitable disease models. To address this gap, we generated a mouse model with PIGK deficits, specifically in Purkinje cells (Pcp2-cko) and an induced pluripotent stem cell (iPSC) model using the c.87dupT mutant (KI) found in GPIBD22 patients. Pcp2-cko mice demonstrated cerebellar atrophy, ataxia and progressive Purkinje cells loss which were accompanied by increased apoptosis and neuroinflammation. Similarly, KI iPSCs exhibited increased apoptosis and accelerated neural rosette formation, indicating that PIGK defects could impact early neural differentiation that confirmed by the RNA-Seq results of neural progenitor cells (NPCs). The increased apoptosis and accelerated NPC differentiation in KI iPSCs are associated with excessive unfolded protein response (UPR) pathway activation, and can be rescued by UPR pathway inhibitor. Our study reveals potential pathogenic mechanism of GPIBD22 and providing new insights into the therapeutic strategy for GPIBD.

Involvement of spinal NADPH oxidase 4 and endoplasmic reticulum stress in morphine-tolerant rats

Morphine tolerance (MT) is currently a challenging issue related to intractable pain treatment. Studies have shown that reactive oxygen species (ROSs) derived from NADPH oxidase (NOX) and produced in response to endoplasmic reticulum (ER) stress participate in MT development. However, which NOX subtype initiates ER stress during MT development is unclear. NOX4 is mainly expressed on intracellular membranes, such as the ER and mitochondrial membranes, and its sole function is to produce ROS. Whether NOX4 is activated during MT development and the mechanisms underlying the association between NOX4 and ER stress during this process still need to be confirmed. In our study, we used the classic morphine-tolerant rat model and evaluated the analgesic effect of intrathecally injected morphine through a hot water tail-flick assay. Our research demonstrated for the first time that chronic morphine administration upregulates NOX4 expression in the spinal cord by activating three ER stress sensors, protein kinase RNA-like ER kinase (PERK), inositol-requiring enzyme 1 (IRE1) and activating transcription factor 6 (ATF6), subsequently leading to the activation of microtubule-associated protein 1 light chain 3 b (LC3B) and P62 (a well-known autophagy marker) in GABAergic neurons. Our results may suggest that regulating NOX4 and the key mechanism underlying ER stress or autophagy may be a promising strategy to treat and prevent MT development.

Effect of Voluntary Wheel Running on Anxiety- and Depression-Like Behaviors in Fluoride-Exposed Mice

Fluoride, an environmental toxicant, could induce endoplasmic reticulum stress (ERS) in neuronal cells ultimately leading to apoptosis and emotional dysfunction. Meanwhile, voluntary wheel running contributes to mitigate anxiety and depression. Our investigation aimed to study the effect of voluntary wheel running on anxiety- and depression-like behaviors in fluoride-exposure mice. The results showed that exposure to 100 mg/L sodium fluoride (NaF) for 6 months can induce anxiety- and depression-like behavior in mice. Fluorosis mice subjected to voluntary wheel running have less anxiety- and depression-like behaviors. Nissl and TUNEL staining demonstrated that fluoride led to a reduced proportion of Nissl body area in the cerebral cortex and an increased apoptotic ratio of nerve cells in the cerebral cortex. In contrast, these pathologic damages were improved in voluntary wheel running mice exposed to NaF. Moreover, the expressions of mRNA in the cerebral cortex GABA, GAD65, GAD67, DR, vGLU, 5-HT1A, BDNF, NMDAR1, and Bcl2 were downregulated and the levels of c-fos, GRP78, PERK, eIF2α, CHOP, Caspase-12, and Caspase-3 mRNA were upregulated in mice exposed to fluoride. NaF treatment had increased the PERK, ATF6, IRE1, p-eIF2α, and Caspase-3 protein levels and reduced the expressions of proteins, including GAD67, VGAT, BDNF, NMDAR1, PSD95, and SYN. By contrast, fluorosis mice subjected to voluntary wheel running enhanced the expression of GAD65, GAD67, VGAT, and neuroplasticity-related proteins in mice and inhibited the PERK-CHOP pathway. It is worth noting that the correlation between the amount of exercise and the behavioral indicators as well as neurotransmitter levels was found. In conclusion, voluntary wheel running inhibits the fluoride-induced ERS and GRP78 expression through the PERK-CHOP pathway and plays an anti-apoptotic role, ultimately ameliorating emotional dysfunction in NaF-exposed mice.

The Role and Interactive Mechanism of Endoplasmic Reticulum Stress and Ferroptosis in Musculoskeletal Disorders

Endoplasmic reticulum (ER) stress is a cellular phenomenon that arises in response to the accumulation of misfolded proteins within the ER. This process triggers the activation of a signalling pathway known as the unfolded protein response (UPR), which aims to restore ER homeostasis by reducing protein synthesis, increasing protein degradation, and promoting proper protein folding. However, excessive ER stress can perturb regular cellular function and contribute to the development of diverse pathological conditions. As is well known, ferroptosis is a kind of programmed cell death characterized by the accumulation of lipid peroxides and iron-dependent reactive oxygen species (ROS), resulting in oxidative harm to cellular structures. In recent years, there has been increasing evidence indicating that ferroptosis occurs in musculoskeletal disorders (MSDs), with emerging recognition of the complex relationship between ER stress and ferroptosis. This review presents a summary of ER stress and the ferroptosis pathway. Most importantly, it delves into the significance of ER stress in the ferroptosis process within diverse skeletal or muscle cell types. Furthermore, we highlight the potential benefits of targeting the correlation between ER stress and ferroptosis in treating degenerative MSDs.

Leveraging explainable deep learning methodologies to elucidate the biological underpinnings of Huntington's disease using single-cell RNA sequencing data

BACKGROUND

Huntington's disease (HD) is a hereditary neurological disorder caused by mutations in HTT, leading to neuronal degeneration. Traditionally, HD is associated with the misfolding and aggregation of mutant huntingtin due to an extended polyglutamine domain encoded by an expanded CAG tract. However, recent research has also highlighted the role of global transcriptional dysregulation in HD pathology. However, understanding the intricate relationship between mRNA expression and HD at the cellular level remains challenging. Our study aimed to elucidate the underlying mechanisms of HD pathology using single-cell sequencing data.

RESULTS

We used single-cell RNA sequencing analysis to determine differential gene expression patterns between healthy and HD cells. HD cells were effectively modeled using a residual neural network (ResNet), which outperformed traditional and convolutional neural networks. Despite the efficacy of our approach, the F1 score for the test set was 96.53%. Using the SHapley Additive exPlanations (SHAP) algorithm, we identified genes influencing HD prediction and revealed their roles in HD pathobiology, such as in the regulation of cellular iron metabolism and mitochondrial function. SHAP analysis also revealed low-abundance genes that were overlooked by traditional differential expression analysis, emphasizing its effectiveness in identifying biologically relevant genes for distinguishing between healthy and HD cells. Overall, the integration of single-cell RNA sequencing data and deep learning models provides valuable insights into HD pathology.

CONCLUSION

We developed the model capable of analyzing HD at single-cell transcriptomic level.

Dietary bitter ginger-derived zerumbone improved memory performance during aging through inhibition of the PERK/CHOP-dependent endoplasmic reticulum stress pathway

PERK/CHOP pathway-mediated excessive endoplasmic reticulum (ER) stress is closely linked to aging-related cognitive impairment (ARCD). Zerumbone (ZB), a naturally occurring sesquiterpene molecule obtained from dietary bitter ginger, has garnered significant interest due to its diverse range of biological properties. It is unclear, though, if ZB can reduce ARCD by preventing ER stress that is dependent on the PERK/CHOP pathway. Here, the PERK-CHOP ER stress pathway was the main focus of an evaluation of the effects and mechanisms of ZB for attenuating ARCD in D-galactose (D-gal)-induced aging mice and SH-SY5Y cells. According to our findings, ZB not only greatly decreased neuronal impairment both in vitro and in vivo, but also significantly alleviated learning and memory failure in vivo. ZB significantly reduced the activation of the PERK/CHOP pathway and neuronal apoptosis in vitro and in vivo, exhibiting the down-regulation of GRP78, p-PREK/PERK, and CHOP expression levels, in addition to suppressing oxidative damage (MDA drop and SOD rise). Comparable outcomes were noted in SH-SY5Y cells subjected to severe ER stress caused by TM. On the other hand, 4-PBA, an ER stress inhibitor, considerably reversed these modifications. Remarkably, CCT020312 (a PERK activator) dramatically overrode the inhibitory effects of ZB on the PERK/CHOP pathway and neuronal death in D-gal-induced SH-SY5Y cells. In contrast, GSK2606414 (a PERK inhibitor) significantly increased these effects of ZB. In summary, our results suggested that ZB prevented D-gal-induced cognitive deficits by blocking the PERK/CHOP-dependent ER stress pathway and apoptosis, suggesting that ZB might be a natural sesquiterpene molecule that relieves ARCD.

Polydatin ameliorates early brain injury after subarachnoid hemorrhage through up-regulating SIRT1 to suppress endoplasmic reticulum stress

Objective

This study aims to investigate the inhibitory effect of Polydatin (PD) on endoplasmic reticulum (ER) stress following subarachnoid hemorrhage (SAH) and to elucidate the underlying mechanisms.

Methods

A standard intravascular puncture model was established to mimic SAH in mice. Neurological functions were assessed using neurological scoring, Grip test, and Morris water maze. Brain edema and Evans blue extravasation were measured to evaluate blood-brain barrier permeability. Western blot and quantitative real-time polymerase chain reaction (PCR) analyses were performed to examine protein and mRNA expressions related to ER stress. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining was used to detect cell apoptosis, and transmission electron microscopy was used to observe the ultrastructure of the endoplasmic reticulum.

Results

The results indicated that PD significantly reduced brain edema and Evans blue extravasation after SAH, improving neurological function. Compared to the SAH group, the expression levels of ER stress-related proteins including glucose-regulated protein 78 (GRP78), phosphorylated protein kinase R-like endoplasmic reticulum kinase (p-PERK), phosphorylated eukaryotic initiation factor 2α (p-eIF2α), activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP), were significantly lower in the PD-treated group. Moreover, PD significantly enhances the protein expression of Sirtuin 1 (SIRT1). Validation with sh-SIRT1 confirmed the critical role of SIRT1 in ER stress, with PD's inhibitory effect on ER stress being dependent on SIRT1 expression. Additionally, PD attenuated ER stress-mediated neuronal apoptosis and SAH-induced ferroptosis through upregulation of SIRT1.

Conclusion

PD alleviates ER stress following SAH by upregulating SIRT1 expression, thereby mitigating early brain injury. The protective effects of PD are mediated through SIRT1, which inhibits ER stress and reduces neuronal apoptosis and ferroptosis.

Nicotinamide riboside ameliorates survival time and motor dysfunction in an MPTP-Induced Parkinson's disease zebrafish model through effects on glucose metabolism and endoplasmic reticulum stress

Nicotinamide riboside (NR) is a precursor and exogenous supplement of nicotinamide adenine dinucleotide (NAD+). NR has been shown to play a beneficial role in a variety of neurodegenerative diseases. A phase 1 clinical trial identified NR as a potential neuroprotective therapy for Parkinson's disease (PD). However, the mechanism of action of NR in PD has not been fully elucidated. Therefore, the present study aimed to investigate the potential effects of NR on a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in zebrafish and its underlying mechanisms. The results showed that NR improved motor dysfunction, survival time, dopamine neurons, and peripheral neurons, as well as the NAD+ levels in the MPTP-affected PD zebrafish model. In addition, transcriptome sequencing analysis revealed that, after NR treatment, differentially expressed genes were significantly enriched in the glucose metabolism and protein processing pathways in the endoplasmic reticulum (ER). Quantitative PCR (qPCR) revealed that the mRNA levels of the glycoheterotrophic enzyme (involved in glucose metabolism) were significantly decreased, and the glycolytic enzyme mRNA expression levels were significantly increased. The results of the non-targeted metabolomic analysis showed that NR treatment significantly increased the levels of metabolites such as nicotinic acid ,nicotinamide, d-glucose (from the gluconeogenesis and glycolysis metabolism pathways) and some glucogenic amino acids, such as glutamine. Importantly, NR ameliorated MPTP-induced endoplasmic reticulum stress (ERS) in the PD zebrafish model through the Perk-Eif2α-Atf4-Chop pathway. These results highlight the neuroprotective effect of NR in the present PD zebrafish model through modulation of glucose metabolism and ERS via the Perk-Eif2α-Atf4-Chop pathway and provide valuable mechanistic insights into the treatment of PD.

Endoplasmic Reticulum Stress Differently Modulates the Release of IL-6 and IL-8 Cytokines in Human Glial Cells

Endoplasmic reticulum (ER) stress is a significant player in the pathophysiology of various neurodegenerative and neuropsychiatric disorders. Despite the established link between ER stress and inflammatory pathways, there remains a need for deeper exploration of the specific cellular mechanisms underlying ER stress-mediated neuroinflammation. This study aimed to investigate how the severity of ER stress (triggered by different concentrations of tunicamycin) can impact the release of proinflammatory cytokines IL-6 and IL-8 from astrocytes and microglia, comparing the effects with those induced by well-known immunostimulants-tumor necrosis factor alpha (TNF-α) or lipopolysaccharide (LPS). Mild ER stress has a distinct effect on the cytokine release compared to more intense stress levels, i.e., diminished IL-6 production was accompanied by an increase in IL-8 level, which was significantly more pronounced in astrocytes than in microglia. On the contrary, prolonged or more severe ER stress induced inflammation in glial cells, leading to a time- and concentration-dependent buildup of proinflammatory IL-6, but unlike inflammatory agents, an ER stress inducer diminished IL-8 secretions by glial cells. The differences could hold importance in identifying ER stress markers as potential drug targets for the treatment of neurodegenerative diseases or mood disorders, yet this requires confirmation in more complex animal studies.

The battle between host antiviral innate immunity and immune evasion by cytomegalovirus

Cytomegalovirus (CMV) has successfully established a long-lasting latent infection in humans due to its ability to counteract the host antiviral innate immune response. During coevolution with the host, the virus has evolved various evasion techniques to evade the host's innate immune surveillance. At present, there is still no vaccine available for the prevention and treatment of CMV infection, and the interaction between CMV infection and host antiviral innate immunity is still not well understood. However, ongoing studies will offer new insights into how to treat and prevent CMV infection and its related diseases. Here, we update recent studies on how CMV evades antiviral innate immunity, with a focus on how CMV proteins target and disrupt critical adaptors of antiviral innate immune signaling pathways. This review also discusses some classic intrinsic cellular defences that are crucial to the fight against viral invasion. A comprehensive review of the evasion mechanisms of antiviral innate immunity by CMV will help investigators identify new therapeutic targets and develop vaccines against CMV infection.

Emerging insights into Lipocalin-2: Unraveling its role in Parkinson's Disease

Parkinson's disease (PD) ranks as the second most prevalent neurodegenerative disorder globally, marked by a complex pathogenesis. Lipocalin-2 (LCN2) emerges as a crucial factor during the progression of PD. Belonging to the lipocalin family, LCN2 is integral to several biological functions, including glial cell activation, iron homeostasis regulation, immune response, inflammatory reactions, and oxidative stress mitigation. Substantial research has highlighted marked increases in LCN2 expression within the substantia nigra (SN), cerebrospinal fluid (CSF), and blood of individuals with PD. This review focuses on the pathological roles of LCN2 in neuroinflammation, aging, neuronal damage, and iron dysregulation in PD. It aims to explore the underlying mechanisms of LCN2 in the disease and potential therapeutic targets that could inform future treatment strategies.

Beyond PDE4 inhibition: A comprehensive review on downstream cAMP signaling in the central nervous system

Cyclic adenosine monophosphate (cAMP) is a key second messenger that regulates signal transduction pathways pivotal for numerous biological functions. Intracellular cAMP levels are spatiotemporally regulated by their hydrolyzing enzymes called phosphodiesterases (PDEs). It has been shown that increased cAMP levels in the central nervous system (CNS) promote neuroplasticity, neurotransmission, neuronal survival, and myelination while suppressing neuroinflammation. Thus, elevating cAMP levels through PDE inhibition provides a therapeutic approach for multiple CNS disorders, including multiple sclerosis, stroke, spinal cord injury, amyotrophic lateral sclerosis, traumatic brain injury, and Alzheimer's disease. In particular, inhibition of the cAMP-specific PDE4 subfamily is widely studied because of its high expression in the CNS. So far, the clinical translation of full PDE4 inhibitors has been hampered because of dose-limiting side effects. Hence, focusing on signaling cascades downstream activated upon PDE4 inhibition presents a promising strategy, offering novel and pharmacologically safe targets for treating CNS disorders. Yet, the underlying downstream signaling pathways activated upon PDE(4) inhibition remain partially elusive. This review provides a comprehensive overview of the existing knowledge regarding downstream mediators of cAMP signaling induced by PDE4 inhibition or cAMP stimulators. Furthermore, we highlight existing gaps and future perspectives that may incentivize additional downstream research concerning PDE(4) inhibition, thereby providing novel therapeutic approaches for CNS disorders.

Emerging insights into the role of NLRP3 inflammasome and endoplasmic reticulum stress in renal diseases

NLRP3 inflammasome is a key component of the innate immune system, mediating the activation of caspase-1, and the maturity and secretion of the pro-inflammatory cytokine interleukin (IL)-1beta (IL-1β) and IL-18 to cope with microbial infections and cell injury. The NLRP3 inflammasome is activated by various endogenous danger signals, microorganisms and environmental stimuli, including urate, extracellular adenosine triphosphate (ATP) and cholesterol crystals. Increasing evidence indicates that the abnormal activation of NLRP3 is involved in multiple diseases including renal diseases. Hence, clarifying the mechanism of action of NLRP3 inflammasome in different diseases can help prevent and treat various diseases. Endoplasmic reticulum (ER) is an important organelle which participates in cell homeostasis maintenance and protein quality control. The unfolded protein response (UPR) and ER stress are caused by the excessive accumulation of unfolded or misfolded proteins in ER to recover ER homeostasis. Many factors can cause ER stress, including inflammation, hypoxia, environmental toxins, viral infections, glucose deficiency, changes in Ca2+ level and oxidative stress. The dysfunction of ER stress participates in multiple diseases, such as renal diseases. Many previous studies have shown that NLRP3 inflammasome and ER stress play an important role in renal diseases. However, the relevant mechanisms are not yet fully clear. Herein, we focus on the current understanding of the role and mechanism of ER stress and NLRP3 inflammasome in renal diseases, hoping to provide theoretical references for future related researches.

Newsights of endoplasmic reticulum in hypoxia

The endoplasmic reticulum (ER) is important to cells because of its essential functions, including synthesizing three major nutrients and ion transport. When cellular homeostasis is disrupted, ER quality control (ERQC) system is activated effectively to remove misfolded and unfolded proteins through ER-phagy, ER-related degradation (ERAD), and molecular chaperones. When unfolded protein response (UPR) and ER stress are activated, the cell may be suffering a huge blow, and the most probable consequence is apoptosis. The membrane contact points between the ER and sub-organelles contribute to communication between the organelles. The decrease in oxygen concentration affects the morphology and structure of the ER, thereby affecting its function and further disrupting the stable state of cells, leading to the occurrence of disease. In this study, we describe the functions of ER-, ERQC-, and ER-related membrane contact points and their changes under hypoxia, which will help us further understand ER and treat ER-related diseases.

Malformation of the endoplasmic reticulum system evolving into giant inclusions and Auer bodies in acute promyelocytic leukemia: an ultrastructural study of 6 cases

The endoplasmic reticulum（ER）is the largest membranous network serving as a region for protein, lipid and steroid synthesis, transport and storage. Detailed information about ER-cisternae, ER-tubules and rough endoplasmic reticulum (rER) is scarce in human blood cells. This study describes a series of giant inclusions and Auer bodies in promyeloblasts in six patients with acute promyelocytic leukemia (APL), by light microscopy, transmission electron microscopy (TEM) and cytochemical stains. TEM revealed that giant inclusions and pro-Auer bodies were associated with rER and surrounded by tubular structures composed of degenerated or redundant membrane in promyeloblasts, which corresponded with elements of the ER system. This paper reveals that in the promyeloblasts of APL, ER is the source of and transforms progressively into giant inclusions and Auer bodies.

Orexins in apoptosis: a dual regulatory role

The orexins, also referred to as hypocretins, are neuropeptides that originate from the lateral hypothalamus (LH) region of the brain. They are composed of two small peptides, orexin-A, and orexin-B, which are broadly distributed throughout the central and peripheral nervous systems. Orexins are recognized to regulate diverse functions, involving energy homeostasis, the sleep-wake cycle, stress responses, and reward-seeking behaviors. Additionally, it is suggested that orexin-A deficiency is linked to sleepiness and narcolepsy. The orexins bind to their respective receptors, the orexin receptor type 1 (OX1R) and type 2 (OX2R), and activate different signaling pathways, which results in the mediation of various physiological functions. Orexin receptors are widely expressed in different parts of the body, including the skin, muscles, lungs, and bone marrow. The expression levels of orexins and their receptors play a crucial role in apoptosis, which makes them a potential target for clinical treatment of various disorders. This article delves into the significance of orexins and orexin receptors in the process of apoptosis, highlighting their expression levels and their potential contributions to different diseases. The article offers an overview of the existing understanding of the orexin/receptor system and how it influences the regulation of apoptosis.

Selenium Nanoparticles in Protecting the Brain from Stroke: Possible Signaling and Metabolic Mechanisms

Strokes rank as the second most common cause of mortality and disability in the human population across the world. Currently, available methods of treating or preventing strokes have significant limitations, primarily the need to use high doses of drugs due to the presence of the blood-brain barrier. In the last decade, increasing attention has been paid to the capabilities of nanotechnology. However, the vast majority of research in this area is focused on the mechanisms of anticancer and antiviral effects of nanoparticles. In our opinion, not enough attention is paid to the neuroprotective mechanisms of nanomaterials. In this review, we attempted to summarize the key molecular mechanisms of brain cell damage during ischemia. We discussed the current literature regarding the use of various nanomaterials for the treatment of strokes. In this review, we examined the features of all known nanomaterials, the possibility of which are currently being studied for the treatment of strokes. In this regard, the positive and negative properties of nanomaterials for the treatment of strokes have been identified. Particular attention in the review was paid to nanoselenium since selenium is a vital microelement and is part of very important and little-studied proteins, e.g., selenoproteins and selenium-containing proteins. An analysis of modern studies of the cytoprotective effects of nanoselenium made it possible to establish the mechanisms of acute and chronic protective effects of selenium nanoparticles. In this review, we aimed to combine all the available information regarding the neuroprotective properties and mechanisms of action of nanoparticles in neurodegenerative processes, especially in cerebral ischemia.

Metal organic layers enabled cell surface engineering coupling biomembrane fusion for dynamic membrane proteome profiling

Systematically dissecting the highly dynamic and tightly communicating membrane proteome of living cells is essential for the system-level understanding of fundamental cellular processes and intricate relationship between membrane-bound organelles constructed through membrane traffic. While extensive efforts have been made to enrich membrane proteins, their comprehensive analysis with high selectivity and deep coverage remains a challenge, especially at the living cell state. To address this problem, we developed the cell surface engineering coupling biomembrane fusion method to map the whole membrane proteome from the plasma membrane to various organelle membranes taking advantage of the exquisite interaction between two-dimensional metal-organic layers and phospholipid bilayers on the membrane. This approach, which bypassed conventional biochemical fractionation and ultracentrifugation, facilitated the enrichment of membrane proteins in their native phospholipid bilayer environment, helping to map the membrane proteome with a specificity of 77% and realizing the deep coverage of the HeLa membrane proteome (5087 membrane proteins). Furthermore, membrane N-phosphoproteome was profiled by integrating the N-phosphoproteome analysis strategy, and the dynamic membrane proteome during apoptosis was deciphered in combination with quantitative proteomics. The features of membrane protein N-phosphorylation modifications and many differential proteins during apoptosis associated with mitochondrial dynamics and ER homeostasis were found. The method provided a simple and robust strategy for efficient analysis of membrane proteome, offered a reliable platform for research on membrane-related cell dynamic events and expanded the application of metal-organic layers.

USP7 attenuates endoplasmic reticulum stress-induced apoptotic cell death through deubiquitination and stabilization of FBXO7

Parkinson's disease (PD) is a common neurodegenerative disease (NDD) characterized by the loss of dopaminergic neurons in the substantia nigra. Similar to other NDDs, the buildup of toxic protein aggregates in PD leads to progressive neuronal loss, culminating in neurodegeneration. Accumulating evidence indicates that alterations in subcellular organelles, particularly the endoplasmic reticulum (ER), are critically involved in pathological neurodegenerative events in NDDs, including PD. Mutations in the F-box only protein 7 (FBXO7 or PARK15) gene have been found to cause early onset autosomal recessive familiar PD. FBXO7 functions as an adaptor protein in the Skp1-Cullin1-F-box protein (SCF) E3 ubiquitin ligase complex, which promotes substrate ubiquitination. Although FBXO7 is involved in the ubiquitination of various target proteins, little is known about the upstream regulatory mechanism of FBXO7 and/or its modulator(s). Ubiquitin specific protease 7 (USP7) is a deubiquitinating enzyme that regulates the balance between protein synthesis and degradation by removing ubiquitin from target substrates. The role of USP7 in various types of cancer is well-established; however, its role in NDDs has not been elucidated to date. In this study, we identified that USP7 acts as a novel regulator of FBXO7, positively regulating the stability of FBXO7 through Lys48-linked deubiquitination. Moreover, USP7 was found to mitigate ER stress-induced cytotoxicity and apoptosis by preventing the proteasomal degradation of FBXO7. Taken together, our study suggests that the functional relationship between FBXO7 and USP7 may play a crucial role in ER stress-induced apoptosis and the pathogenesis of PD.

Cadmium-induced pyroptosis is mediated by PERK/TXNIP/NLRP3 signaling in SH-SY5Y cells

Cadmium (Cd) is a hypertoxic heavy metal that may be exposed to environmental pollutants by humans and animals. It can lead to cognitive disfunction, and is linked to neurodegenerative diseases. Cadmium reportedly can induce endoplasmic reticulum (ER) stress, but few studies have concentrated on it in nerve cells, and the connection between ER stress and neuroinflammation. In this study, in vitro experiments on SH-SY5Y neuroblastoma cells were carried out. We aimed at exploring whether Cd attributed to the cell pyroptosis and the role of PERK in promoting this form of cell damage which can induce strong inflammatory responses. Our results demonstrated that CdCl2 treatment induced excess reactive oxygen species (ROS) production, caused significant modifications in the expression of PERK and increased TXNIP, NLRP3, IL-1β, IL-18, and caspase1 in SH-SY5Y cells. In addition, scavenging ROS with N-acetylcysteine or inhibiting the expression of PERK by using GSK2606414, rescued the SH-SY5Y cells from cadmium-induced pyroptosis. In conclusion, the results suggest that Cd induces pyroptotic death of SH-SY5Y cells through ER stress, and this may be the potential mechanism of Cd incurring neurological diseases.

Neuroprotective Effects of Albizia lebbeck (L.) Benth. Leaf Extract against Glutamate-Induced Endoplasmic Reticulum Stress and Apoptosis in Human Microglial Cells

Endoplasmic reticulum (ER) stress caused by excessive glutamate in the central nervous system leads to neurodegeneration. Albizia lebbeck (L.) Benth. has been reported to possess neuroprotective properties. We aimed to investigate the effect and mechanism of A. lebbeck leaf extracts on glutamate-induced neurotoxicity and apoptosis linked to ER stress using human microglial HMC3 cells. A. lebbeck leaves were extracted using hexane (AHE), mixed solvents, and ethanol. Each different extract was evaluated for cytotoxic effects on HMC3 cells, and then non-cytotoxic concentrations of the extracts were pretreated with the cells, followed by glutamate. Our results showed that AHE treatment exhibited the highest protective effect and was thus selected for finding the mechanistic approach. AHE inhibited the specific ER stress proteins (calpain1 and caspase-12). AHE also suppressed the apoptotic proteins (Bax, cytochrome c, cleaved caspase-9, and cleaved caspase-3); however, it also increased the antiapoptotic Bcl-2 protein. Remarkably, AHE increased cellular antioxidant activities (SOD, CAT, and GPx). To support the activation of antioxidant defense and inhibition of apoptosis in our HMC3 cell model, the bioactive phytochemicals within AHE were identified by HPLC analysis. We found that AHE had high levels of carotenoids (α-carotene, β-carotene, and lutein) and flavonoids (quercetin, luteolin, and kaempferol). Our novel findings indicate that AHE can inhibit glutamate-induced neurotoxicity via ER stress and apoptosis signaling pathways by activating cellular antioxidant enzymes in HMC3 cells, suggesting a potential mechanism for neuroprotection. As such, A. lebbeck leaf might potentially represent a promising source and novel alternative approach for preventing neurodegenerative diseases.

Marchf6 E3 ubiquitin ligase critically regulates endoplasmic reticulum stress, ferroptosis, and metabolic homeostasis in POMC neurons

The metabolic prohormone pro-opiomelanocortin (POMC) is generally translocated into the endoplasmic reticulum (ER) for entry into the secretory pathway. Patients with mutations within the signal peptide (SP) of POMC or its adjoining segment develop metabolic disorders. However, the existence, metabolic fate, and functional outcomes of cytosol-retained POMC remain unclear. Here, we show that SP-uncleaved POMC is produced in the cytosol of POMC neuronal cells, thus inducing ER stress and ferroptotic cell death. Mechanistically, the cytosol-retained POMC sequesters the chaperone Hspa5 and subsequently accelerates degradation of the glutathione peroxidase Gpx4, a core regulator of ferroptosis, via the chaperone-mediated autophagy. We also show that the Marchf6 E3 ubiquitin ligase mediates the degradation of cytosol-retained POMC, thereby preventing ER stress and ferroptosis. Furthermore, POMC-Cre-mediated Marchf6-deficient mice exhibit hyperphagia, reduced energy expenditure, and weight gain. These findings suggest that Marchf6 is a critical regulator of ER stress, ferroptosis, and metabolic homeostasis in POMC neurons.

Ultrastructural and Molecular Investigation on Peripheral Leukocytes in Alzheimer's Disease Patients

Thriving literature underlines white blood cell involvement in the inflammatory processes of Alzheimer's Disease (AD). Among leukocytes, lymphocytes have been considered sentinels of neuroinflammation for years, but recent findings highlighted the pivotal role of neutrophils. Since neutrophils that infiltrate the brain through the brain vascular vessels may affect the immune function of microglia in the brain, a close investigation of the interaction between these cells is important in understanding neuroinflammatory phenomena and the immunological aftermaths that follow. This study aimed to observe how peripheral leukocyte features change at different stages of AD to identify potential molecular markers when the first features of pathological neurodegeneration arise. For this purpose, the examined patients were divided into Mild Cognitive Impairment (MCI) and severely impaired patients (DAT) based on their Cognitive Dementia Rating (CDR). The evaluation of the neutrophil-to-lymphocytes ratio and the morphology and function of leukocytes showed a close relationship between the ultrastructural and the molecular features in AD progression and suggested putative markers for the early stages of the disease.

Genetic Networks of Alzheimer's Disease, Aging, and Longevity in Humans

Human genomic analysis and genome-wide association studies (GWAS) have identified genes that are risk factors for early and late-onset Alzheimer's disease (AD genes). Although the genetics of aging and longevity have been extensively studied, previous studies have focused on a specific set of genes that have been shown to contribute to or are a risk factor for AD. Thus, the connections among the genes involved in AD, aging, and longevity are not well understood. Here, we identified the genetic interaction networks (referred to as pathways) of aging and longevity within the context of AD by using a gene set enrichment analysis by Reactome that cross-references more than 100 bioinformatic databases to allow interpretation of the biological functions of gene sets through a wide variety of gene networks. We validated the pathways with a threshold of p-value < 1.00 × 10^-5 using the databases to extract lists of 356 AD genes, 307 aging-related (AR) genes, and 357 longevity genes. There was a broad range of biological pathways involved in AR and longevity genes shared with AD genes. AR genes identified 261 pathways within the threshold of p < 1.00 × 10^-5, of which 26 pathways (10% of AR gene pathways) were further identified by overlapping genes among AD and AR genes. The overlapped pathways included gene expression (p = 4.05 × 10^-11) including ApoE, SOD2, TP53, and TGFB1 (p = 2.84 × 10^-10); protein metabolism and SUMOylation, including E3 ligases and target proteins (p = 1.08 × 10^-7); ERBB4 signal transduction (p = 2.69 × 10^-6); the immune system, including IL-3 and IL-13 (p = 3.83 × 10^-6); programmed cell death (p = 4.36 × 10^-6); and platelet degranulation (p = 8.16 × 10^-6), among others. Longevity genes identified 49 pathways within the threshold, of which 12 pathways (24% of longevity gene pathways) were further identified by overlapping genes among AD and longevity genes. They include the immune system, including IL-3 and IL-13 (p = 7.64 × 10^-8), plasma lipoprotein assembly, remodeling and clearance (p < 4.02 × 10^-6), and the metabolism of fat-soluble vitamins (p = 1.96 × 10^-5). Thus, this study provides shared genetic hallmarks of aging, longevity, and AD backed up by statistical significance. We discuss the significant genes involved in these pathways, including TP53, FOXO, SUMOylation, IL4, IL6, APOE, and CEPT, and suggest that mapping the gene network pathways provide a useful basis for further medical research on AD and healthy aging.