Chemical Chaperones to Inhibit Endoplasmic Reticulum Stress: Implications in Diseases

Endoplasmic reticulum stress as a driver and therapeutic target for kidney disease

The endoplasmic reticulum (ER) has crucial roles in metabolically active cells, including protein translation, protein folding and quality control, lipid biosynthesis, and calcium homeostasis. Adverse metabolic conditions or pathogenic genetic variants that cause misfolding and accumulation of proteins within the ER of kidney cells initiate an injurious process known as ER stress that contributes to kidney disease and its cardiovascular complications. Initiation of ER stress activates the unfolded protein response (UPR), a cellular defence mechanism that functions to restore ER homeostasis. However, severe or chronic ER stress rewires the UPR to activate deleterious pathways that exacerbate inflammation, apoptosis and fibrosis, resulting in kidney injury. This insidious crosstalk between ER stress, UPR activation, oxidative stress and inflammation forms a vicious cycle that drives kidney disease and vascular damage. Furthermore, genetic variants that disrupt protein-folding mechanisms trigger ER stress, as evidenced in autosomal-dominant tubulointerstitial kidney disease and Fabry disease. Emerging therapeutic strategies that enhance protein-folding capacity and reduce the burden of ER stress have shown promising results in kidney diseases. Thus, integrating knowledge of how genetic variants cause protein misfolding and ER stress into clinical practice will enhance treatment strategies and potentially improve outcomes for various kidney diseases and their vascular complications.

Single-nucleus transcriptional profiling of the placenta reveals the syncytiotrophoblast stress response to COVID-19

BACKGROUND

COVID-19 in pregnancy is associated with placental immune activation, inflammation, and vascular malperfusion, but its impact on syncytiotrophoblast biology and function is unclear.

OBJECTIVE

This study aimed to determine the effects of maternal COVID-19 on placental syncytiotrophoblasts using single-nucleus transcriptional profiling and to compare placental stress responses in COVID-19 and preeclampsia.

STUDY DESIGN

For transcriptional characterization of syncytiotrophoblasts, we used the single-nucleus RNA sequencing platform, single-cell combinatorial indexing RNA sequencing (sci-RNA-seq3), to profile placental villi and fetal membranes from unvaccinated patients with symptomatic COVID-19 at birth (n = 4), gestational age-matched controls (n = 4), and a case of critical COVID-19 in the second trimester with delivery at term (n = 1). Clustering of nuclei and differential gene expression analysis was performed in Seurat. Gene ontology analysis was conducted using Enrichr. High-confidence transcriptional target analysis was used to identify key transcription factor nodes governing the syncytiotrophoblast response to maternal SARS-CoV-2 infection. Bioinformatic approaches were further used to compare the COVID-19 dataset to published preeclampsia gene signatures. Tissue analysis, including immunofluorescence, was conducted to validate the transcriptional data and to compare COVID-19 and preeclampsia placental histology for an expanded cohort of placentas: controls (n = 6), asymptomatic COVID-19 (n = 3), symptomatic COVID-19 (n = 5), and preeclampsia with severe features (n = 7).

RESULTS

The analyzed dataset comprised 15 cell clusters and 47,889 nuclei. We identified 3 clusters of syncytiotrophoblasts representing fusing and mature nuclei with overlapping but distinct transcriptional responses to COVID-19. Bioinformatic analyses indicated that COVID-19 is associated with the following alterations in syncytiotrophoblasts: (1) endoplasmic reticulum stress and activation of stress signaling pathways, including the unfolded protein response and integrated stress response; (2) regulation of gene expression by CCAAT/enhancer-binding protein beta (CEBPB), a master transcription factor of the syncytiotrophoblast lineage; and (3) upregulation of preeclampsia-associated genes. Using complementary methods, we confirmed increased levels of stress response proteins (eg, BiP, G3BP1) in syncytiotrophoblasts, unfolded protein response signaling (spliced XBP1 mRNA), and CEBPB activation (phosphorylation) in COVID-19. Increased cytotrophoblast proliferation (Ki-67) was also detected in COVID-19, consistent with a trophoblast response to injury. Markers of stress detected in preeclampsia demonstrated similarities in the placental stress phenotype of COVID-19 and preeclampsia.

CONCLUSION

Maternal COVID-19 is associated with syncytiotrophoblast endoplasmic reticulum stress and activation of the syncytiotrophoblast lineage transcription factor, CEBPB. Similarities between syncytiotrophoblast stress in COVID-19 and preeclampsia provide insights into their clinical association.

Pharmacological landscape of endoplasmic reticulum stress: Uncovering therapeutic avenues for metabolic diseases

The endoplasmic reticulum (ER) plays a fundamental role in maintaining cellular homeostasis by ensuring proper protein folding, lipid metabolism, and calcium regulation. However, disruptions to ER function, known as ER stress, activate the unfolded protein response (UPR) to restore balance. Chronic or unresolved ER stress contributes to metabolic dysfunctions, including insulin resistance, non-alcoholic fatty liver disease (NAFLD), and neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Recent studies have also highlighted the importance of mitochondria-ER contact sites (MERCs) and ER-associated inflammation in disease progression. This review explores the current pharmacological landscape targeting ER stress, focusing on therapeutic strategies for rare metabolic and neurodegenerative diseases. It examines small molecules such as tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA), repurposed drugs like 17-AAG (17-N-allylamino-17demethoxygeldanamycin (tanespimycin)) and berberine, and phytochemicals such as resveratrol and hesperidin. Additionally, it discusses emerging therapeutic areas, including soluble epoxide hydrolase (sEH) inhibitors for metabolic disorders and MERCs modulation for neurological diseases. The review emphasizes challenges in translating these therapies to clinical applications, such as toxicity, off-target effects, limited bioavailability, and the lack of large-scale randomized controlled trials (RCTs). It also highlights the potential of personalized medicine approaches and pharmacogenomics in optimizing ER stress-targeting therapies.

Artificial enforcement of the unfolded protein response reduces disease features in multiple preclinical models of ALS/FTD

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are part of a spectrum of diseases that share several causative genes, resulting in a combinatory of motor and cognitive symptoms and abnormal protein aggregation. Multiple unbiased studies have revealed that proteostasis impairment at the level of the endoplasmic reticulum (ER) is a transversal pathogenic feature of ALS/FTD. The transcription factor XBP1s is a master regulator of the unfolded protein response (UPR), the main adaptive pathway to cope with ER stress. Here, we provide evidence of suboptimal activation of the UPR in ALS/FTD models under experimental ER stress. To artificially engage the UPR, we intracerebroventricularly administrated adeno-associated viruses (AAVs) to express the active form of XBP1 (XBP1s) in the nervous system of ALS/FTD models. XBP1s expression improved motor performance and extended lifespan of mutant SOD1 mice, associated with reduced protein aggregation. AAV-XBP1s administration also attenuated disease progression in models of TDP-43 and C9orf72 pathogenesis. Proteomic profiling of spinal cord tissue revealed that XBP1s overexpression improved proteostasis and modulated the expression of a cluster of synaptic and cell morphology proteins. Our results suggest that strategies to improve ER proteostasis may serve as a pan-therapeutic strategy to treat ALS/FTD.

The interplay between gut microbiota and the unfolded protein response: Implications for intestinal homeostasis preservation and dysbiosis-related diseases

The unfolded protein response (UPR) is a complex intracellular signal transduction system that orchestrates the cellular response during Endoplasmic Reticulum (ER) stress conditions to reestablish cellular proteostasis. If, on one side, prolonged ER stress conditions can lead to programmed cell death and autophagy as a cytoprotective mechanism, on the other, unresolved ER stress and improper UPR activation represent a perilous condition able to trigger or exacerbate inflammatory responses. Notably, intestinal and immune cells experience ER stress physiologically due to their high protein secretory rate. Indeed, there is evidence of UPR's involvement in both physiological and pathological intestinal conditions, while less is known about its bidirectional interaction with gut microbiota. However, gut microbes and their metabolites can influence ER stress and UPR pathways, and, in turn, ER stress conditions can shape gut microbiota composition, with important implications for overall intestinal health. Thus, targeting UPR components is an intriguing strategy for treating ER stress-linked dysbiosis and diseases, particularly intestinal inflammation.

The Therapeutic Potential of Gut-Microbiota-Derived Metabolite 4-Phenylbutyric Acid in Escherichia coli-Induced Colitis

Pathogenic Escherichia coli (E. coli) is a widely distributed pathogen that can cause varying degrees of zoonotic diseases, and infected animals often experience intestinal inflammation accompanied by diarrhea and dysbiosis. Previously, for the first time, we isolated Escherichia coli primarily of type B2 from a large-scale dairy farm in Yunnan, China. The 16s rRNA sequencing showed significant differences in the gut microbiota of calves infected with B2 E. coli, with higher abundance of harmful bacteria and lower abundance of beneficial bacteria compared with healthy calves. The metabolomics indicated that the concentrations of oxoadipic acid, 16-oxopalmitate, oerillyl alcohol, palmitoleic acid, and 4-phenylbutyrate (4-PBA) were significantly higher in the healthy group than in the infected group. The mouse model was established to assess the regulatory effect of 4-PBA on E. coli-induced colitis. Both oral administration of 4-PBA and fecal microbiota transplantation (FMT) had strong resistance to E. coli infection, improved survival rate and body weight, reduced intestinal tissue damage, decreased the levels of pro-inflammatory cytokines (TNF-α, IL-6, and IL-1β), and restrained TLR4/MyD88/NF-κB pathway. Our study demonstrated that 4-PBA could relieve E. coli-induced colitis by improving gut microbiota structure and inhibiting the expression of pro-inflammatory cytokines through the TLR4/MyD88/NF-κB pathway. The present finding reveals the therapeutic potential of the gut-microbiota-derived metabolite 4-PBA for the treatment of colitis caused by E. coli.

Unfolded protein response: An essential element of intestinal homeostasis and a potential therapeutic target for inflammatory bowel disease

Different physiological and pathological situations can produce alterations in the cell's endoplasmic reticulum (ER), leading to a condition known as ER stress, which can trigger an intricate intracellular signal transduction system known as the unfolded protein response (UPR). UPR is primarily tailored to restore proteostasis and ER equilibrium; otherwise, if ER stress persists, it can cause programmed cell death as a cytoprotective mechanism and drive inflammatory processes. Therefore, since intestinal cells strongly rely on UPR for their biological functions and unbalanced UPR has been linked to inflammatory, metabolic, and immune disorders, here we discussed the role of the UPR within the intestinal tract, focusing on the UPR contribution to inflammatory bowel disease development. Importantly, we also highlighted the promising potential of UPR components as therapeutic targets for intestinal inflammatory diseases.

Targeting endoplasmic reticulum stress as a potential therapeutic strategy for diabetic cardiomyopathy

Endoplasmic reticulum (ER) is an essential organelle involved in vesicular transport, calcium handling, protein synthesis and folding, and lipid biosynthesis and metabolism. ER stress occurs when ER homeostasis is disrupted by the accumulation of unfolded and/or misfolded proteins in the ER lumen. Adaptive pathways of the unfolded protein response (UPR) are activated to maintain ER homeostasis. In obesity and type 2 diabetes mellitus (T2DM), accumulating data indicate that persistent ER stress due to maladaptive UPR interacts with insulin/leptin signaling, which may be the potential and central mechanistic link between obesity-/T2DM-induced metabolic dysregulation (chronic hyperglycemia, dyslipidemia and lipotoxicity in cardiomyocytes), insulin/leptin resistance and the development of diabetic cardiomyopathy (DiabCM). Meanwhile, these pathological conditions further exacerbate ER stress. However, their interrelationships and the underlying molecular mechanisms are not fully understood. A deeper understanding of ER stress-mediated pathways in DiabCM is needed to develop novel therapeutic strategies. The aim of this review is to discuss the crosstalk between ER stress and leptin/insulin signaling and their involvement in the development of DiabCM focusing on mitochondria-associated ER membranes and chronic inflammation. We also present the current direction of drug development and important considerations for translational research into targeting ER stress for the treatment of DiabCM.

Transcriptome profiling reveals novel insights into the regulation of calcium ion and detoxification genes driving chlorantraniliprole resistance in Spodoptera exigua

Since the commercialization of diamide insecticides, including chlorantraniliprole, in 2007, the overuse of diamide insecticides for over a decade has resulted in excessive chlorantraniliprole resistance in Spodoptera exigua, causing continuous economic losses. While RyR target-site mutations and detoxification enzymes such as cytochrome P450 have been studied as the leading causes of resistance, previous studies, including functional research and synergistic tests, have not confirmed a clear correlation between these factors and the development of resistance. Thus, transcriptome analysis was employed to investigate alternative strategies beyond mutation(s) in RyR or metabolic factors involving detoxification pathways that allow diamide-resistance S. exigua to counteract the calcium ion imbalances induced by chlorantraniliprole effectively. Diamide-resistant, susceptible strains and its F1-hybrid of S. exigua were used for the RNAseq-based differentially expressed gene (DEG) analysis. In total 4669 genes were differentially expressed, with 2809 upregulated and 1860 downregulated in the resistant strain compared to the susceptible strain. GO, KEGG enrichment and orthologous analyses demonstrated that genes involved in metabolic factors were overrepresented in the resistant strain. In particular, overexpressed endoplasmic reticulum (ER)-related calcium ion homeostasis and cell stability-associated genes were newly identified in resistant strain. The selected differentially expressed genes were validated then with qPCR. These genes were inferred to induce cell stability to overcome ER stress derived from calcium ion imbalance caused by chlorantraniliprole. These results provide advanced insights into the critical roles of calcium ion homeostasis- and cell stability-related genes in conferring diamide insecticide resistance.

Lead (Pb) Induces Osteotoxicity Through the Activation of Mutually Reinforced ER Stress and ROS in MC3T3-E1 Cells

Lead (Pb) is the most common contaminant of heavy metals and is widely present in the environment. Destruction of bone structure, malformation of bone development, and loss of bone mass are important pathological features of lead-exposed individuals. However, the exact molecular mechanisms associated with lead exposure and osteogenic injury are still not fully understood. MC3T3-E1 mouse embryonic osteoblast is a cell line widely used in osteoblast cytology. It can differentiate into mature osteoblasts and express bone-specific genes in cell culture. The doses of 1, 2, and 4 mM Pb were adopted to study the toxicity of Pb on MC3T3-E1 proliferation and differentiation. In this study, the results show that Pb increases the expression of apoptosis-related proteins, including PARP1, cleaved caspase-3, Bax, and cleaved caspase-9. More importantly, Pb activated endoplasmic reticulum stress and oxidative stress, as evident by elevated PERK/ATF4/CHOP and ROS/NRF2 signaling pathway. Pb induced ROS production in MC3T3-E1 cells through endoplasmic reticulum stress and produced a lethal effect. NAC mitigated these effects. Endoplasmic reticulum stress inhibitor 4-PBA can block the ER stress pathway, reduce ROS production, and enhance cell viability. In addition, studies have shown that ERO1 activation in the ER stress pathway is responsible for inducing ROS production. ROS produced by the mitochondrial pathway also aggravates ER stress. This study suggests that Pb induces MC3T3-E1 cell apoptosis by inducing PERK-mediated ER stress and NRF2-mediated oxidative stress via mutual enhancement, which may be an important mechanism leading to skeletal toxicity.

Endoplasmic Reticulum Stress in Bronchopulmonary Dysplasia: Contributor or Consequence?

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity. Oxidative stress (OS) and inflammation are the major contributors to BPD. Despite aggressive treatments, BPD prevalence remains unchanged, which underscores the urgent need to explore more potential therapies. The endoplasmic reticulum (ER) plays crucial roles in surfactant and protein synthesis, assisting mitochondrial function, and maintaining metabolic homeostasis. Under OS, disturbed metabolism and protein folding transform the ER structure to refold proteins and help degrade non-essential proteins to resume cell homeostasis. When OS becomes excessive, the endogenous chaperone will leave the three ER stress sensors to allow subsequent changes, including cell death and senescence, impairing the growth potential of organs. The contributing role of ER stress in BPD is confirmed by reproducing the BPD phenotype in rat pups by ER stress inducers. Although chemical chaperones attenuate BPD, ER stress is still associated with cellular senescence. N-acetyl-lysyltyrosylcysteine amide (KYC) is a myeloperoxidase inhibitor that attenuates ER stress and senescence as a systems pharmacology agent. In this review, we describe the role of ER stress in BPD and discuss the therapeutic potentials of chemical chaperones and KYC, highlighting their promising role in future therapeutic interventions.

Loss of Fic causes progressive neurodegeneration in a Drosophila model of hereditary spastic paraplegia

Hereditary Spastic Paraplegia (HSP) is a group of rare inherited disorders characterized by progressive weakness and spasticity of the legs. Recent newly discovered biallelic variants in the gene FICD were found in patients with a highly similar phenotype to early onset HSP. FICD encodes filamentation induced by cAMP domain protein. FICD is involved in the AMPylation and deAMPylation protein modifications of the endoplasmic reticulum (ER) chaperone BIP, a major constituent of the ER that regulates the unfolded protein response. Although several biochemical properties of FICD have been characterized, the neurological function of FICD and the pathological mechanism underlying HSP are unknown. We established a Drosophila model to gain mechanistic understanding of the function of FICD in HSP pathogenesis, and specifically the role of BIP in neuromuscular physiology. Our studies on Drosophila Fic null mutants uncovered that loss of Fic resulted in locomotor impairment and reduced levels of BIP in the motor neuron circuitry, as well as increased reactive oxygen species (ROS) in the ventral nerve cord of Fic null mutants. Finally, feeding Drosophila Fic null mutants with chemical chaperones PBA or TUDCA, or treatment of patient fibroblasts with PBA, reduced the ROS accumulation. The neuronal phenotypes of Fic null mutants recapitulate several clinical features of HSP patients and further reveal cellular patho-mechanisms. By modeling FICD in Drosophila, we provide potential targets for intervention for HSP, and advance fundamental biology that is important for understanding related rare and common neuromuscular diseases.

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.

Inhibition of ER stress using tauroursodeoxycholic acid rescues obesity-evoked cardiac remodeling and contractile anomalies through regulation of ferroptosis

Interrupted ER homeostasis contributes to the etiology of obesity cardiomyopathy although it remains elusive how ER stress evokes cardiac anomalies in obesity. Our study evaluated the impact of ER stress inhibition on cardiac anomalies in obesity. Lean and ob/ob obese mice received chemical ER chaperone tauroursodeoxycholic acid (TUDCA, 50 mg/kg/d, p.o.) for 35 days prior to evaluation of glucose sensitivity, echocardiographic, myocardial geometric, cardiomyocyte mechanical and subcellular Ca2+ property, mitochondrial integrity, oxidative stress, apoptosis, and ferroptosis. Intracellular Ca2+ governing domains including sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) were monitored by45Ca2+uptake and immunoblotting. Our results noted that TUDCA alleviated myocardial remodeling (fibrosis, hypertrophy, enlarged LVESD), echocardiographic anomalies (compromised fractional shortening and ejection fraction), cardiomyocyte contractile dysfunction (amplitude and velocity of cell shortening, relengthening time) and intracellular Ca2+ anomalies (compromised subcellular Ca2+ release, clearance and SERCA function), mitochondrial damage (collapsed membrane potential, downregulated mitochondrial elements and ultrastructural alteration), ER stress (GRP78, eIF2α and ATF4), oxidative stress, apoptosis and ferroptosis [downregulated SLC7A11, GPx4 and upregulated transferrin receptor (TFRC)] without affecting global glucose sensitivity and serum Fe2+ in obese mice. Obesity-evoked change in HSP90, phospholamban and Na+-Ca2+ exchanger was spared by the chemical ER chaperone. Moreover, in vitro results noted that TUDCA, PERK inhibitor GSK2606414, TFRC neutralizing antibody and ferroptosis inhibitor LIP1 mitigated palmitic acid-elicited changes in lipid peroxidation and mechanical function. Our findings favored a role for ferroptosis in obesity cardiomyopathy downstream of ER stress.

Protective Effects and Mechanisms of Inhibiting Endoplasmic Reticulum Stress on Cold Seawater Immersion Combined with Hemorrhagic Shock

Purpose

Cold seawater immersion aggravates hemorrhagic shock-induced homeostasis imbalance and organ dysfunction, leading to increased mortality. Previous studies have shown that treatments targeting oxidative stress and mitochondrial dysfunction have limited efficacy for cold seawater immersion combined with hemorrhagic shock (SIHS). Thus, the mechanisms responsible for SIHS need further investigation.

Methods and Results

Data from the hemorrhagic shock transcriptome and cold seawater immersion targets used for bioinformatics analysis revealed the involvement of endoplasmic reticulum stress (ERS) in SIHS occurrence and progression. Based on these findings, the effects and possible mechanism of inhibiting ERS in SIHS rats were investigated. SIHS causes a lethal triad and impairment of vital organ function, leading to death. Compared to lactated Ringer's solution, the ERS inhibitor 4-phenylbutyric acid (PBA)significantly ameliorated acidosis and coagulopathy and protected vital organ function while prolonging survival and the golden treatment time. Through target screening and validation, 7 targets were identified for the ERS inhibitor PBA for the treatment of SIHS, among which S1PR1, MMP8 and CFTR may play more important roles.

Conclusion

ERS plays a crucial role in the progression of SIHS. Inhibition of ERS caused by SIHS alleviates the lethal triad, protects organ function, and prolongs survival and the golden treatment time. The ERS inhibitor PBA may be an effective therapeutic measure for treating SIHS.

Stress and the domestic cat: have humans accidentally created an animal mimic of neurodegeneration?

Many neurodegenerative diseases (NDD) appear to share commonality of origin, chronic ER stress. The endoplasmic reticulum (ER) is a dynamic organelle, functioning as a major site of protein synthesis and protein posttranslational modifications, required for proper folding. ER stress can occur because of external stimuli, such as oxidative stress or neuroinflammatory cytokines, creating the ER luminal environment permissive for the accumulation of aggregated and misfolded proteins. Unresolvable ER stress upregulates a highly conserved pathway, the unfolded protein response (UPR). Maladaptive chronic activation of UPR components leads to apoptotic neuronal death. In addition to other factors, physiological responses to stressors are emerging as a significant risk factor in the etiology and pathogenesis of NDD. Owned cats share a common environment with people, being exposed to many of the same stressors as people and additional pressures due to their "quasi" domesticated status. Feline Cognitive Dysfunction Syndrome (fCDS) presents many of the same disease hallmarks as human NDD. The prevalence of fCDS is rapidly increasing as more people welcome cats as companions. Barely recognized 20 years ago, veterinarians and scientists are in infancy stages in understanding what is a very complex disease. This review will describe how cats may represent an unexplored animal mimetic phenotype for human NDD with stressors as potential triggering mechanisms. We will consider how multiple variations of stressful events over the short-life span of a cat could affect neuronal loss or glial dysfunction and ultimately tip the balance towards dementia.

LIM homeobox 1 (LHX1) induces endoplasmic reticulum stress and promotes preterm birth

Background

Premature birth (PTB) is a major cause of neonatal mortality and has enduring consequences. LIM Homeobox 1 (LHX1) is vital in embryonic organogenesis, while Inositol-Requiring Enzyme 1 (IRE-1) regulates endoplasmic reticulum stress (ERS). This study explores whether IRE-1 impacts PTB via LHX1 modulation.

Methods

We analyzed LHX1 expression in placental samples from PTB patients and examined its impact on the viability, migration, invasion, and apoptosis of the human placental trophoblast cell line HTR8/Svneo, particularly when treated with the ERS inducer tunicamycin (TM). We also assessed the levels of ERS-related genes and autophagy activation in response to LHX1 deficiency. To gain mechanistic insights, we evaluated the ERS-mediated activation of the IRE-1/XBP1/CHOP signaling pathway in LHX1-silenced HTR8/Svneo cells. Additionally, we examined the transcriptional activation of IRE-1 and the binding of LHX1 to the IRE-1 promoter in HTR8/Svneo cells. We overexpressed IRE-1 in LHX1-silenced HTR8/Svneo cells to assess its effects on cell viability, migration, invasion, apoptosis, and autophagy. Finally, we induced LHX1 knockdown in mice through intraperitoneal injections of tunicamycin (TM) and Sh-LHX1 over a 24-h period to evaluate PTB symptoms.

Results

We observed LHX1 overexpression in placental tissue from PTB cases and TM-induced HTR8/Svneo cells. LHX1 depletion enhanced cell viability, migration, and invasion while reducing autophagy and apoptosis. This reduction in LHX1 led to decreased levels of IRE-1, XBP1, CHOP, and other ERS-related genes, indicating LHX1's role in ERS induction and the activation of the IRE-1/XBP1/CHOP pathway. Mechanistically, LHX1 was found to bind to the IRE-1 promoter, inducing its transcriptional activation. Notably, overexpressing IRE-1 counteracted the impact of LHX1 depletion on trophoblast cell behavior, suggesting that LHX1 modulates IRE-1. In line with our in vitro studies, LHX1 knockdown ameliorated PTB symptoms in TM-treated mice.

Conclusion

LHX1 contributes to the progression of PTB by regulating the IRE-1-XBP1-CHOP pathway.

A Proximity Complementation Assay to Identify Small Molecules That Enhance the Traffic of ABCA4 Misfolding Variants

ABCA4-related retinopathy is the most common inherited Mendelian eye disorder worldwide, caused by biallelic variants in the ATP-binding cassette transporter ABCA4. To date, over 2200 ABCA4 variants have been identified, including missense, nonsense, indels, splice site and deep intronic defects. Notably, more than 60% are missense variants that can lead to protein misfolding, mistrafficking and degradation. Currently no approved therapies target ABCA4. In this study, we demonstrate that ABCA4 misfolding variants are temperature-sensitive and reduced temperature growth (30 °C) improves their traffic to the plasma membrane, suggesting the folding of these variants could be rescuable. Consequently, an in vitro platform was developed for the rapid and robust detection of ABCA4 traffic to the plasma membrane in transiently transfected cells. The system was used to assess selected candidate small molecules that were reported to improve the folding or traffic of other ABC transporters. Two candidates, 4-PBA and AICAR, were identified and validated for their ability to enhance both wild-type ABCA4 and variant trafficking to the cell surface in cell culture. We envision that this platform could serve as a primary screen for more sophisticated in vitro testing, enabling the discovery of breakthrough agents to rescue ABCA4 protein defects and mitigate ABCA4-related retinopathy.

PBA alleviates cadmium-induced mouse spermatogonia apoptosis by suppressing endoplasmic reticulum stress

OBJECTIVE

Endoplasmic reticulum (ER) stress mediates Cd-caused germ cell apoptosis in testis. The effects of 4-phenylbutyric acid (PBA), a classical chaperone, were investigated on Cd-induced apoptosis in mouse GC-1 spermatogonia cells.

METHODS

The cells were pretreated with PBA before Cd exposure. TUNEL and flow cytometry assays were applied to determine apoptosis. Some key biomarkers of ER stress were analyzed using RT-PCR and western blot.

RESULTS

as expected, the apoptotic cells exposed to Cd apparently increased. The mRNA and protein expression levels of GRP78 and ATF6α, were elevated in the Cd groups. Additional experiments displayed that Cd notably increased IRE1α and JNK phosphorylation, and upregulated XBP-1 mRNA and protein expression. Moreover, p-eIF2α and CHOP expressions were clearly elevated in the Cd groups. Interestingly, PBA almost completely inhibited ER stress and protected spermatogonia against apoptosis induced by Cd.

CONCLUSION

PBA alleviated Cd-induced ER stress and spermatogonia apoptosis, and may have the therapeutic role in Cd-induced male reproductive toxicity.

Multifaceted roles and regulation of nucleotide-binding oligomerization domain containing proteins

Nucleotide-binding oligomerization domain-containing proteins, NOD1 and NOD2, are cytosolic receptors that recognize dipeptides and tripeptides derived from the bacterial cell wall component peptidoglycan (PGN). During the past two decades, studies have revealed several roles for NODs beyond detecting PGN fragments, including activation of an innate immune anti-viral response, NOD-mediated autophagy, and ER stress induced inflammation. Recent studies have also clarified the dynamic regulation of NODs at cellular membranes to generate specific and balanced immune responses. This review will describe how NOD1 and NOD2 detect microbes and cellular stress and detail the molecular mechanisms that regulate activation and signaling while highlighting new evidence and the impact on inflammatory disease pathogenesis.