Involvement Of Endoplasmic Reticulum Stress Research Articles

Nimbolide protects against diabetic cardiomyopathy by regulating endoplasmic reticulum stress and mitochondrial function via the Akt/mTOR pathway

Nimbolide has been demonstrated to possess protective properties against gestational diabetes mellitus and diabetic retinopathy. However, the role and molecular mechanism of nimbolide in diabetic cardiomyopathy (DCM) remain unknown. Diabetes was induced in rats via a single injection of streptozotocin (STZ) and then the diabetic rats were administered nimbolide (5mg/kg and 20mg/kg) or dimethyl sulfoxide daily for 12 weeks. H9c2 cardiomyocytes were exposed to high glucose (25mM glucose) to mimic DCM in vitro. The protective effects of nimbolide against DCM were evaluated in vivo and in vitro. The potential molecular mechanism of nimbolide in DCM was further explored. We found that nimbolide dose-dependently decreased blood glucose and improved body weight of diabetic rats. Additionally, nimbolide dose-dependently improved cardiac function, alleviated myocardial injury/fibrosis, and inhibited endoplasmic reticulum (ER) stress and apoptosis in diabetic rats. Moreover, nimbolide dose-dependently improved mitochondrial function and inhibited the Akt/mTOR signaling. We consistently demonstrated the cardioprotective effects of nimbolide in an in vitro model of DCM. The involvement of ER stress and mitochondrial pathways were further confirmed by using inhibitors of ER stress and mitochondrial division. By applying a specific Akt inhibitor SC66, the cardioprotective effects of nimbolide were partially blocked. Our study indicated that nimbolide alleviated DCM by activating Akt/mTOR pathway. Nimbolide may be a novel therapeutic agent for DCM treatment.

Glucose Induces ER Stress Response-Mediated Peritoneal Mesothelial Cell Death.

Peritoneal dialysis (PD) fluid, which contains a high concentration of glucose, is involved in peritoneal damage after long-term use. The mechanisms through which glucose induces damage to the mesothelium have not been clearly elucidated. Although, endoplasmic reticulum (ER) stress response is associated with several diseases, the involvement of ER stress in peritoneal damage has not yet been demonstrated. Primary-cultured rat peritoneal mesothelial cells (RPMCs) and rat PD model were used to investigate the influence of glucose on the peritoneum. Cells treated with glucose were examined for cytotoxicity, induction of apoptosis, and activation of the ER stress pathway. Glucose treatment of RPMCs induced cell death at concentrations higher than 3%. Annexin V positive, that is a feature of apoptosis, occurred in dead cells. Treatment with glucose led to the activation of protein kinase R-like ER kinase (PERK) and eukaryotic translation initiation factor-2α (eIF-2α). Glucose also induced the expression and nuclear translocation of homologous protein C/EBP. Cell death was rescued by the integrated stress response inhibitor, ISRIB, which suppresses the integrated stress response pathway, including ER stress. Glucose in PD fluid induces PERK/eIF-2α-mediated ER stress in RPMCs, resulting in apoptosis. This cellular stress may cause peritoneal damage in patients receiving PD.

Comprehensive analysis of an endoplasmic reticulum stress-related gene prediction model and immune infiltration in idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease. This study aimed to investigate the involvement of endoplasmic reticulum stress (ERS) in IPF and explore its correlation with immune infiltration. ERS-related differentially expressed genes (ERSRDEGs) were identified by intersecting differentially expressed genes (DEGs) from three Gene Expression Omnibus datasets with ERS-related gene sets. Gene Set Variation Analysis and Gene Ontology were used to explore the potential biological mechanisms underlying ERS. A nomogram was developed using the risk signature derived from the ERSRDEGs to perform risk assessment. The diagnostic value of the risk signature was evaluated using receiver operating characteristics, calibration, and decision curve analyses. The ERS score of patients with IPF was measured using a single-sample Gene Set Enrichment Analysis (ssGSEA) algorithm. Subsequently, a prognostic model based on the ERS scores was established. The proportion of immune cell infiltration was assessed using the ssGSEA and CIBERSORT algorithms. Finally, the expression of ERSRDEGs was validated in vivo and in vitro via RT-qPCR. This study developed an 8-ERSRDEGs signature. Based on the expression of these genes, we constructed a diagnostic nomogram model in which agouti-related neuropeptide had a significantly greater impact on the model. The area under the curve values for the predictive value of the ERSRDEGs signature were 0.975 and 1.000 for GSE70866 and GSE110147, respectively. We developed a prognostic model based on the ERS scores of patients with IPF. Furthermore, we classified patients with IPF into two subtypes based on their signatures. The RT-qPCR validation results supported the reliability of most of our conclusions. We developed and verified a risk model using eight ERSRDEGs. These eight genes can potentially affect the progression of IPF by regulating ERS and immune responses.

Endoplasmic reticulum stress, autophagy, neuroinflammation, and sigma 1 receptors as contributors to depression and its treatment.

The etiological factors contributing to depression and other neuropsychiatric disorders are largely undefined. Endoplasmic reticulum stress pathways and autophagy are well-defined mechanisms that play critical functions in recognizing and resolving cellular stress and are possible targets for the pathophysiology and treatment of psychiatric and neurologic illnesses. An increasing number of studies indicate the involvement of endoplasmic reticulum stress and autophagy in the control of neuroinflammation, a contributing factor to multiple neuropsychiatric illnesses. Initial inflammatory triggers induce endoplasmic reticulum stress, leading to neuroinflammatory responses. Subsequently, induction of autophagy by neurosteroids and other signaling pathways that converge on autophagy induction are thought to participate in resolving neuroinflammation. The aim of this review is to summarize our current understanding of the molecular mechanisms governing the induction of endoplasmic reticulum stress, autophagy, and neuroinflammation in the central nervous system. Studies focused on innate immune factors, including neurosteroids with anti-inflammatory roles will be reviewed. In the context of depression, animal models that led to our current understanding of molecular mechanisms underlying depression will be highlighted, including the roles of sigma 1 receptors and pharmacological agents that dampen endoplasmic reticulum stress and associated neuroinflammation.

Excessive ER-phagy contributes to ochratoxin A-induced apoptosis.

The nephrotoxic secondary fungal metabolite ochratoxin A (OTA) is ubiquitously existed in foodstuffs and feeds. Although our earlier research provided preliminary evidence that endoplasmic reticulum (ER) was crucial in OTA-induced nephrotoxicity, more research is necessary to understand the fine-tune mechanisms involving ER stress (ERS), ER-phagy, and apoptosis. In the present study, the cell viability and protein expressions of human proximal tubule epithelial (HK-2) cells in response to OTA and/or chloroquine/rapamycin/sodium phenylbutyrate/tunicamycin were determined via cell viability assay, apoptosis analysis, and Western blot analysis. The findings showed that a 24 h-treatment of 0.25-4μM OTA could significantly reduced the cell viability (P<0.05), which notably increased with the addition of chloroquine and sodium phenylbutyrate, while decreased with the addition of rapamycin and tunicamycin as compared to group OTA (P<0.05). A 24 h-treatment of 1-4μM OTA could markedly induce apoptosis via increasing the protein expressions of GRP78, p-eIF2α, Chop, LC3B-II, Bak, and Bax, and inhibiting the protein expressions of DDRGK1, UBA5, Lonp1, Tex264, FAM134B, p-mTOR, p62, and Bcl-2 in HK-2cells (P<0.05). In conclusion, OTA activated ERS, unfolded protein response, and subsequent excessive ER-phagy, thus inducing apoptosis, and the vicious cycle between excessive ER-phagy and ERS could further promote apoptosis in vitro.

Endoplasmic Reticulum Stress in the Diagnosis and Treatment of Diseases

Endoplasmic reticulum (ER) stress is a protective stress response of cells that takes place when the ER has a significant amount of unfolded and misfolded proteins. Endoplasmic reticulum stress that is prolonged and severe and the unfolded protein response it produces start the apoptotic cascade. Apoptosis brought on by endoplasmic reticulum stress has been demonstrated to be a crucial entry point for the detection and treatment of illnesses. Both Alzheimer's disease and pulmonary fibrosis are difficult to treat, and both are linked to aberrant apoptosis. As a result, one of the crucial research areas is the involvement of endoplasmic reticulum stress in the treatment of pulmonary fibrosis and Alzheimer's disease. At present, COVID-19 pneumonia is prevalent in the world and has become one of the main causes of pulmonary fibrosis. At the same time, recent studies have shown that people who are positive for COVID-19 are more likely to suffer from Alzheimer's disease. Therefore, the diagnosis and treatment of these two diseases are particularly important today. The purpose of this paper is to explore the triggering mechanism and physiological characterization of ER stress, and the prospects for the treatment and diagnosis of pulmonary interstitial fibrosis and Alzheimer's syndrome, which are still difficult to overcome.

Involvement of endoplasmic reticulum stress in trigeminal ganglion corneal neuron injury in dry eye disease.

Dry eye disease (DED) is a multifactorial disease with a high prevalence worldwide. Uncomfortable corneal sensations severely affect daily life in DED patients. Hence, corneal neuron injury is a vital pathogenesis in DED. Notably, endoplasmic reticulum stress (ERS) plays a role in peripheral neuron injury. However, the role of ERS in DED corneal neuron injury is still far from being clear. In this study, we established an environmental DED (eDED) model in vivo and a hyperosmotic DED model in vitro. Subsequently, trigeminal ganglion (TG) corneal neurons were retrograde labeled by WGA-Alexa Fluor 555, and fluorescence-activated cell sorting was used to collect targeted corneal neurons for RNA sequencing in mice. Our results revealed that TG corneal neuron injury but not apoptosis in DED. ERS-related genes and proteins were upregulated in TG corneal neurons of the eDED mice. ERS inhibition alleviated TG corneal neuron's ERS-related injury. Therefore, ERS-induced TG corneal neuron injury may be an important pathomechanism and provide a promising therapeutic approach to DED.

CRELD2, endoplasmic reticulum stress, and human diseases.

CRELD2, a member of the cysteine-rich epidermal growth factor-like domain (CRELD) protein family, is both an endoplasmic reticulum (ER)-resident protein and a secretory factor. The expression and secretion of CRELD2 are dramatically induced by ER stress. CRELD2 is ubiquitously expressed in multiple tissues at different levels, suggesting its crucial and diverse roles in different tissues. Recent studies suggest that CRELD2 is associated with cartilage/bone metabolism homeostasis and pathological conditions involving ER stress such as chronic liver diseases, cardiovascular diseases, kidney diseases, and cancer. Herein, we first summarize ER stress and then critically review recent advances in the knowledge of the characteristics and functions of CRELD2 in various human diseases. Furthermore, we highlight challenges and present future directions to elucidate the roles of CRELD2 in human health and disease.

Involvement of endoplasmic reticulum stress in rifampicin-induced liver injury.

Rifampicin is a first-line antituberculosis drug. Hepatocyte toxicity caused by rifampicin is a significant clinical problem. However, the specific mechanism by which rifampicin causes liver injury is still poorly understood. Endoplasmic reticulum (ER) stress can have both protective and proapoptotic effects on an organism, depending on the environmental state of the organism. While causing cholestasis and oxidative stress in the liver, rifampicin also activates ER stress in different ways, including bile acid accumulation and cytochrome p450 (CYP) enzyme-induced toxic drug metabolites via pregnane X receptor (PXR). The short-term stress response helps the organism resist toxicity, but when persisting, the response aggravates liver damage. Therefore, ER stress may be closely related to the "adaptive" mechanism and the apoptotic toxicity of rifampicin. This article reviews the functional characteristics of ER stress and its potentially pathogenic role in liver injury caused by rifampicin.

Endoplasmic reticulum stress-regulated high temperature requirement A1 (HTRA1) modulates invasion and angiogenesis-related genes in human trophoblasts

The pathogenesis of hypertensive disorder of pregnancy (HDP), which affects about 10% of pregnant women, is still incompletely understood. Our previous study showed that endoplasmic reticulum (ER) stress influences high-temperature requirement A serine peptidase 1 (HTRA1) expression and trophoblast invasion. However, the involvement of ER stress in the regulation of HTRA subtype expression and pathophysiology of HDP has not been characterized in extravillous trophoblasts (EVTs). To investigate this, HTR8/SVneo EVTs cell line was treated with the ER stress inducers Thapsigargin (Thap) or Tunicamycin (Tuni). Treatment with either Thap or Tuni inhibited trophoblast invasion, reduced HTRA1 and HTRA3 expression, but did not alter HTRA2 or HTRA4 expression. Knockdown of HTRA1 or HTRA3 also inhibited trophoblast invasion. Furthermore, treatment with either ER stress inducer or HTRA1 silencing increased the ratio of soluble fms-like tyrosine kinase-1/placental growth factor (sFLT1/PlGF), which is a marker of HDP. Immunohistochemical analysis revealed that HTRA1 is localized to EVTs and the endometrial decidua in the placenta of patients with HDP. These results suggest that factors that cause ER stress could result in the inhibition of EVTs invasion via HTRA1.

Effect of Dietary 4-Phenylbuthyric Acid Supplementation on Acute Heat-Stress-Induced Hyperthermia in Broiler Chickens.

Simple SummaryHeat stress (HS) induces endoplasmic reticulum (ER) stress and disrupts the ER and cellular homeostasis. A recent study showed that ER stress was induced in broiler chickens under severe and acute HS; however, it was unclear how the alleviation of ER stress affects the physiological state of broiler chickens. Therefore, this study aimed to investigate the ameliorative effects of an ER stress alleviator, 4-phenylbutyric acid (4-PBA), which is a chemical chaperone that reduces ER stress, on the body temperature response, energy metabolic state, and cellular ER stress in HS-exposed birds. 4-PBA supplementation did not negatively affect the growth rate. In addition, 4-PBA suppressed the HS-induced ER stress response in skeletal muscle. Surprisingly, 4-PBA significantly decreased body temperature elevation in HS birds. The present study showed that the ER stress, alleviated by 4-PBA, might contribute to the induction of heat tolerance in broiler chickens.Hot, humid weather causes heat stress (HS) in broiler chickens, which can lead to high mortality. A recent study found that HS causes endoplasmic reticulum (ER) stress. However, the possible involvement of ER stress in HS-induced physiological alterations in broiler chickens is unclear. This study aimed to evaluate the effect of the dietary supplementation of 4-phenylbutyric acid (4-PBA), an alleviator of ER stress, in acute HS-exposed young broiler chickens. Twenty-eight 14-day-old male broiler chickens (ROSS 308) were divided into two groups and fed either a control diet or a diet containing 4-PBA (5.25 g per kg of diet feed) for 10 days. At 24 days old, each group of chickens was kept in thermoneutral (24 ± 0.5 °C) or acute HS (36 ± 0.5 °C) conditions for 2 h. The results showed that thermoneutral birds supplemented with 4-PBA exhibited no negative effects in terms of broiler body weight gain and tissue weight compared to non-supplemental birds. HS increased body temperature in both the control and 4-PBA groups, but the elevation was significantly lower in the 4-PBA group than in the control group. The plasma non-esterified fatty acid concentration was significantly increased by HS treatment in non-supplemental groups, while the increase was partially attenuated in the 4-PBA group. Moreover, 4-PBA prevented HS-induced gene elevation of the ER stress markers GRP78 and GRP94 in the skeletal muscle. These findings suggest that the 4-PBA effect may be specific to the skeletal muscle in HS-exposed birds and that 4-PBA supplementation attenuated HS-induced muscle ER stress, which could be associated with a supplementation of the body temperature elevation and lipolysis.

Chronic exposure to environmentally relevant levels of di(2-ethylhexyl) phthalate (DEHP) disrupts lipid metabolism associated with SBP-1/SREBP and ER stress in C. elegans

DEHP is commonly found in the environment, biota, food, and humans, raising significant health concerns. Whether developmental stage and exposure duration modify the obesogenic effects of DEHP is unclear, especially the underlying mechanisms by which chronic exposure to DEHP as well as its metabolites remain largely unknown. This study investigated the obesogenic effects of chronic DEHP exposure, with levels below environmentally-relevant amounts and provide the mechanism in Caenorhabditis elegans. We show that early-life DEHP exposure resulted in an increased lipid and triglyceride (TG) accumulation mainly attributed to DEHP itself, not its metabolite mono-2-ethylhexyl phthalate (MEHP). In addition, developmental stage and exposure timing influence DEHP-induced TG accumulation and chronic DEHP exposure resulted in the most significant effect. Analysis of fatty acid composition shows that chronic DEHP exposure altered fatty acid composition and TG, resulting in an increased ω-6/ω-3 ratio. The increased TG content by chronic DEHP exposure required lipogenic genes fat-6, fat-7, pod-2, fasn-1, and sbp-1. Moreover, chronic DEHP exposure induced XBP-1-mediated endoplasmic reticulum (ER) stress which might lead to up-regulation of sbp-1. This study suggests the possible involvement of ER stress and SBP-1/SREBP-mediated lipogenesis in chronic DEHP-induced obesogenic effects. Results from this study implies that chronic exposure to DEHP disrupts lipid metabolism, which is likely conserved across species due to evolutionary conservation of molecular mechanisms, raising concerns in ecological and human health.

Hidden Agenda - The Involvement of Endoplasmic Reticulum Stress and Unfolded Protein Response in Inflammation-Induced Muscle Wasting.

Critically ill patients at the intensive care unit (ICU) often develop a generalized weakness, called ICU-acquired weakness (ICUAW). A major contributor to ICUAW is muscle atrophy, a loss of skeletal muscle mass and function. Skeletal muscle assures almost all of the vital functions of our body. It adapts rapidly in response to physiological as well as pathological stress, such as inactivity, immobilization, and inflammation. In response to a reduced workload or inflammation muscle atrophy develops. Recent work suggests that adaptive or maladaptive processes in the endoplasmic reticulum (ER), also known as sarcoplasmic reticulum, contributes to this process. In muscle cells, the ER is a highly specialized cellular organelle that assures calcium homeostasis and therefore muscle contraction. The ER also assures correct folding of proteins that are secreted or localized to the cell membrane. Protein folding is a highly error prone process and accumulation of misfolded or unfolded proteins can cause ER stress, which is counteracted by the activation of a signaling network known as the unfolded protein response (UPR). Three ER membrane residing molecules, protein kinase R-like endoplasmic reticulum kinase (PERK), inositol requiring protein 1a (IRE1a), and activating transcription factor 6 (ATF6) initiate the UPR. The UPR aims to restore ER homeostasis by reducing overall protein synthesis and increasing gene expression of various ER chaperone proteins. If ER stress persists or cannot be resolved cell death pathways are activated. Although, ER stress-induced UPR pathways are known to be important for regulation of skeletal muscle mass and function as well as for inflammation and immune response its function in ICUAW is still elusive. Given recent advances in the development of ER stress modifying molecules for neurodegenerative diseases and cancer, it is important to know whether or not therapeutic interventions in ER stress pathways have favorable effects and these compounds can be used to prevent or treat ICUAW. In this review, we focus on the role of ER stress-induced UPR in skeletal muscle during critical illness and in response to predisposing risk factors such as immobilization, starvation and inflammation as well as ICUAW treatment to foster research for this devastating clinical problem.

Peptidylarginine deiminase 2 promotes T helper 17-like T cell activation and activated T cell-autonomous death (ACAD) through an endoplasmic reticulum stress and autophagy coupling mechanism

Peptididylarginine deiminase type 2 (PADI2) catalyzes the conversion of arginine residues to citrulline residues on proteins. We demonstrate that PADI2 induces T cell activation and investigate how PADI2 promotes activated T cell autonomous death (ACAD). In activated Jurkat T cells, overexpression of PADI2 significantly increases citrullinated proteins and induces endoplasmic reticulum (ER) stress and unfolded protein response (UPR) signaling, ultimately resulting in the expression of autophagy-related proteins and autophagy. PADI2 promoted autophagy and resulted in the early degradation of p62 and the light chain 3B (LC3B)-II accumulation. In Jurkat T cells, silencing the autophagy-related gene (Atg) 12 protein inhibits PADI2-mediated autophagy and promotes ER stress and apoptosis, whereas overexpression of Atg12 decreased ER stress and prolonged autophagy to promote cell survival. Additionally, PADI2 regulates T cell activation and the production of Th17 cytokines in Jurkat T cells (interleukins 6, IL-17A, IL-17F, IL-21, and IL-22). In Jurkat T cells, silencing IL-6 promotes autophagy mediated by PADI2 and inhibits PADI2-induced apoptosis, whereas silencing Beclin-1 increases the activation and survival of Th17-like T cells while decreasing autophagy and apoptosis. PADI2 silencing alleviates ER stress caused by PADI2 and decreases cytokine expression associated with Th17-like T cell activation and ACAD. We propose that PADI2 was involved in Th17 lymphocyte ACAD via a mechanism involving ER stress and autophagy that was tightly regulated by PADI2-mediated citrullination. These findings suggest that inhibiting Th17 T cell activation and the development of severe autoimmune diseases may be possible through the use of novel antagonists that specifically target PADI2.

Involvement of endoplasmic reticulum stress and cell death by synthesized Pa-PDT in oral squamous cell carcinoma cells

Background/purposePhotodynamic therapy (PDT) is a therapeutic alternative for malignant tumors that uses a photosensitizer. This study examined whether synthesized Pheophorbide a (Pa) -PDT induced apoptosis and autophagy involving endoplasmic reticulum (ER) stress in oral squamous cell carcinoma (OSCC) cells. Materials and methodsHuman OSCC cells were treated with Pa-PDT, and cell proliferation was examined by MTT assay. Apoptosis and autophagy were measured using Western blot analysis. ER stress was examined using RT-PCR and Western blot analysis. In vivo murine OSCC animal model were treated with intratumoral (IT) Pa-PDT, and investigated the therapeutic effect. ResultsPa-PDT significantly inhibited the proliferation of human OSCC cells in a dose-dependent manner. Pa-PDT induced intrinsic apoptotic cell death and also induced autophagy. Pa-PDT induced ER stress which was observed as demonstrated by the up-regulation of the ER stress marker. Inhibition of the ER stress pathway using 4-phenylbutyric acid (PBA) decreased CHOP and induced inhibition of cell deaths. In addition, the inhibition of ER stress enhanced Pa-PDT mediated autophagy. IT Pa-PDT significantly inhibited the tumor growth and induced apoptosis, autophagy and ER stress in vivo OSCC cells transplanted model. ConclusionThis study showed that synthesized Pa-PDT induced ER stress trigger apoptosis and apoptotic cell death pathways in OSCC cells. The inhibition of ER stress declined Pa-PDT mediated cytotoxicity with an increase of autophagy. These results may provide Pa-PDT exerts anti-tumor effects through ER stress pathway in OSCC cells and may provide a basis for developing Pa-PDT targeting ER stress as a therapy for OSCC.

5-Hydroxymethylfurfural Alleviates Inflammatory Lung Injury by Inhibiting Endoplasmic Reticulum Stress and NLRP3 Inflammasome Activation.

5-Hydroxymethylfurfural (5-HMF) is a common reaction product during heat processing and the preparation of many types of foods and Traditional Chinese Medicine formulations. The aim of this study was to evaluate the protective effect of 5-HMF on endotoxin-induced acute lung injury (ALI) and the underlying mechanisms. Our findings indicate that 5-HMF attenuated lipopolysaccharide (LPS)-induced ALI in mice by mitigating alveolar destruction, neutrophil infiltration and the release of inflammatory cytokines. Furthermore, the activation of macrophages and human monocytes in response to LPS was remarkably suppressed by 5-HMF in vitro through inhibiting the NF-κB signaling pathway, NLRP3 inflammasome activation and endoplasmic reticulum (ER) stress. The inhibitory effect of 5-HMF on NLRP3 inflammasome was reversed by overexpressing ATF4 or CHOP, indicating the involvement of ER stress in the negative regulation of 5-HMF on NLRP3 inflammasome-mediated inflammation. Consistent with this, the ameliorative effect of 5-HMF on in vivo pulmonary dysfunction were reversed by the ER stress inducer tunicamycin. In conclusion, our findings elucidate the anti-inflammatory and protective efficacy of 5-HMF in LPS-induced acute lung injury, and also demonstrate the key mechanism of its action against NLRP3 inflammasome-related inflammatory disorders via the inhibition of ER stress.

Abstract 14071: Gut Microbial Metabolite Trimethylamine N-oxide Enhances Endoplasmic Reticular Stress and Promotes Endothelial Dysfunction

Background: The intestinal microbe-derived metabolite trimethylamine N-oxide (TMAO) is known to the increase risk of cardiovascular diseases (CVDs). Endothelial dysfunction is associated with most forms of CVDs and is characterized by damage to the endoplasmic reticulum (ER). The current study was aimed to investigate the involvement of endoplasmic reticulum stress (ERS)-mediated protein kinase R-like endoplasmic reticulum kinase (PERK) signaling in TMAO induced endothelial dysfunction. Methods and Results: Biochemical analysis showed that PERK, CHOP, IRE-1α, AFT-4, eIF2 α which are indicative of ER stress, increased significantly in a dose dependent manner in response to TMAO treatment in endothelial cells. Western blot and immunofluorescent analysis showed significant increase in the phosphorylation of PERK and eIF2α along with upregulation of CHOP, IRE-1α and AFT-4 in TMAO group (30μM) compared to the control group (n=4/group; p&lt;0.05). TMAO (30μM) treatment for 24h induced mitochondrial dysfunction as evidenced by decreased mitochondrial membrane potential, increased mitochondrial ROS levels, and also enhanced endothelial cell permeability compared to the control (n=6/group; p&lt;0.05) . Furthermore, treatment with a PERK inhibitor (GSK2606414, 50nM, 24h) inhibited TMAO-induced phosphorylation of ER stress-related proteins, PERK and eIF2α and downregulated IRE1α, AFT-4 and CHOP and protected against increased endothelial cell permeability and mitochondrial ROS production. Conclusion: Our findings suggest that TMAO induced endothelial dysfunction through the ER stress-mediated PERK- eIF2 α -ATF4signaling pathway. Treatment with PERK inhibitors like (GSK2606414) could be a novel therapeutic strategy in TMAO-induced endothelial dysfunction.

Etiological Value of Sterile Inflammation in Preeclampsia: Is It a Non-Infectious Pregnancy Complication?

Understanding of sterile inflammation and its associated biological triggers and diseases is still at the elementary stage. This becomes more warranted in cases where infections are not associated with the pathology. Detrimental effects of bacterial and viral infections on the immune responses at the maternal-fetal interface as well as pregnancy outcomes have been well documented. However, an infection-induced etiology is not thought to be a major contributing component to severe pregnancy complications such as preeclampsia (PE) and gestational diabetes. How is then an inflammatory signal thought to be associated with these pregnancy complications? It is not clear what type of inflammation is involved in the onset of PE-like features. We opine that sterile inflammation regulated by the inflammasome-gasdermins-caspase-1 axis is a contributory factor to the onset of PE. We hypothesize that increased production and release of damage-associated molecular patterns (DAMPs) or Alarmins such as high-mobility group box1 (HMGB1), cell-free fetal DNA, uric acid, the NOD-like receptor pyrin-containing receptor 3 (NLRP3) inflammasome, IL-1β and IL-18 occur in the PE placenta. Some of these molecules have already been observed in the placenta from women with PE. Mechanistically, emerging evidence has demonstrated that excessive placental endoplasmic reticulum (ER) stress, impaired autophagy and gasdermine D (GSDMD)-mediated intrinsic pyroptosis are key events that contribute to systemic sterile inflammation in patients with PE, especially early-onset PE (e-PE). In this review, we highlight the advances on the roles of sterile inflammation and inflammatory signaling cascades involving ER stress, autophagy deficiency and pyroptosis in PE pathophysiology. Deciphering the mechanisms underlying these inflammatory pathways may provide potential diagnostic biomarkers and facilitate the development of therapeutic strategies to treat this devastating disease.

Involvement of endoplasmic reticulum stress in rotenone-induced leber hereditary optic neuropathy model and the discovery of new therapeutic agents

Leber hereditary optic neuropathy (LHON) is caused by mitochondrial DNA mutations and is the most common inherited mitochondrial disease. It is responsible for central vision loss in young adulthood. However, the precise mechanisms of onset are unknown. This study aimed to elucidate the mechanisms underlying LHON pathology and to discover new therapeutic agents. First, we assessed whether rotenone, a mitochondrial complex Ⅰ inhibitor, induced retinal degeneration such as that in LHON in a mouse model. Rotenone decreased the thickness of the inner retina and increased the expression levels of 8-hydroxy-2′-deoxyguanosine (8-OHdG) and immunoglobulin heavy-chain binding protein (BiP). Second, we assessed whether rotenone reproduces LHON pathologies on RGC-5, a neural progenitor cell derived from the retina. Rotenone increased the cell death rate, ROS production and the expression levels of ER stress markers. During chemical compounds screening, we used anti-oxidative compounds, ER stress inhibitors and anti-inflammatory compounds in a rotenone-induced in vitro model. We found that SUN N8075, an ER stress inhibitor, reduced mitochondrial ROS production and improved the mitochondrial membrane potential. Consequently, the ER stress response is strongly related to the pathologies of LHON, and ER stress inhibitors may have a protective effect against LHON.

Sigma-1 Receptor Promotes Mitochondrial Bioenergetics by Orchestrating ER Ca2+ Leak during Early ER Stress.

The endoplasmic reticulum (ER) is a complex, multifunctional organelle of eukaryotic cells and responsible for the trafficking and processing of nearly 30% of all human proteins. Any disturbance to these processes can cause ER stress, which initiates an adaptive mechanism called unfolded protein response (UPR) to restore ER functions and homeostasis. Mitochondrial ATP production is necessary to meet the high energy demand of the UPR, while the molecular mechanisms of ER to mitochondria crosstalk under such stress conditions remain mainly enigmatic. Thus, better understanding the regulation of mitochondrial bioenergetics during ER stress is essential to combat many pathologies involving ER stress, the UPR, and mitochondria. This article investigates the role of Sigma-1 Receptor (S1R), an ER chaperone, has in enhancing mitochondrial bioenergetics during early ER stress using human neuroblastoma cell lines. Our results show that inducing ER stress with tunicamycin, a known ER stressor, greatly enhances mitochondrial bioenergetics in a time- and S1R-dependent manner. This is achieved by enhanced ER Ca2+ leak directed towards mitochondria by S1R during the early phase of ER stress. Our data point to the importance of S1R in promoting mitochondrial bioenergetics and maintaining balanced H2O2 metabolism during early ER stress.