Chronic Endoplasmic Reticulum Research Articles

Misprocessing of Alpha-Galactosidase A, Endoplasmic Reticulum Stress, and the Unfolded Protein Response

Background Classic Fabry disease is caused by GLA mutations that result in loss of enzymatic activity of alpha-galactosidase A, lysosomal storage of globotriaosylceramide, and a resulting multisystemic disease. In non-classic Fabry disease, patients have some preserved alpha-galactosidase A activity and a milder disease course. Heterozygous females may also be affected. While Fabry disease pathogenesis has been mostly attributed to catalytic deficiency of mutated alpha-galactosidase A, lysosomal storage and impairment of lysosomal functions, other pathogenic factors may contribute, especially in non-classic Fabry disease. Methods We characterized the genetic, clinical, biochemical, molecular, cellular and organ pathology correlates of the p.L394P alpha-galactosidase A variant that was identified initially in six individuals with kidney failure by the Czech national screening program for Fabry disease and by further screening in additional 24 family members. Results Clinical findings in affected males revealed a milder clinical course with ∼15% residual alpha-galactosidase A activity with normal plasma lyso-globotriaosylceramide levels and abnormally low ratio of these values. None of the four available kidney biopsies showed lysosomal storage. Laboratory investigations documented intracellular retention of mutated alpha-galactosidase A with resulting endoplasmic reticulum stress and the unfolded protein response, which were alleviated with BRD4780, a small molecule clearing misfolded proteins from the early secretory compartment. We observed similar findings of endoplasmic reticulum stress and unfolded protein response in five kidney biopsies with several other classic and non-classic Fabry disease missense alpha-galactosidase A variants. Conclusions We identified defective proteostasis of mutated alpha-galactosidase A resulting in chronic endoplasmic reticulum stress and unfolded protein response of alpha-galactosidase A expressing cells as a contributor to Fabry disease pathogenesis.

Abstract LB191: A genome-wide CRISPR-based functional screen uncovers the KLF4-Survivin/BIRC5 signaling pathways as a key regulator of cell fate following endoplasmic reticulum stress: Implications for tumor growth and therapeutic targeting

Abstract The growth and spread of tumors involve intricate interactions with the surrounding tissue microenvironment. As a tumor develops, it faces various stresses from its microenvironment, including hypoxia, nutrient deficiency, and acidosis. In response to these challenges, cancer cells can hijack existing cytoprotective mechanisms, such as the Unfolded Protein Response (UPR). The UPR activates signaling pathways at the translational and later transcriptional levels to alleviate cellular stress and prevent cell death. However, under unresolved or chronic endoplasmic reticulum (ER) stress, the UPR may paradoxically promote cell death. The precise mechanisms through which the UPR influences cellular fate during ER stress remain poorly understood. To address this knowledge gap, we employed a functional CRISPR-based genetic knockout screen to identify novel regulators of the UPR. Using a lentiviral genome-wide CRISPR-Cas9 knockout library, we identified over-represented sgRNAs (associated with pro-apoptotic genes) and underrepresented sgRNAs (associated with pro-survival genes) following ER stress induced by thapsigargin and tunicamycin. One of the top candidates identified was Survivin/BIRC5, a protein with anti-apoptotic and cell cycle regulatory activities and which is overexpressed in tumor cells compared to healthy tissues. Functional studies revealed that genetic or pharmacological inhibition of Survivin expression enhanced ER stress-induced apoptosis, but not apoptosis in response to other forms of stress. These findings were validated in multiple cancer cell lines, ruling out off-target effects. Mechanistically, ER stress led to PERK-dependent downregulation of Survivin, and overexpression of Survivin blocked Thapsigargin-induced apoptosis. In vivo xenograft models showed that combining Survivin ablation with PERK inhibition significantly delayed tumor growth and improved overall survival. Through a combination of bioinformatics analysis and loss-of-function studies, we identified the transcription factor KLF4 as a mediator of PERK-dependent effects on Survivin repression. Notably, CRISPR-mediated KLF4 knockout successfully rescued Survivin levels post-ER stress. Additionally, an analysis of TCGA data across various tumor types provided supporting evidence of a negative correlation between KLF4 and Survivin expression. In summary, this study unveils a novel regulatory axis, PERK-KLF4-Survivin, as a key determinant of cell fate in the cellular responses to ER stress. Targeting Survivin in conjunction with PERK inhibition showed promising antitumor effects in vivo. Citation Format: Nektaria M. Leli, Hengxi Liu, Souvik Dey, Lauren Brady, Carlo Salas Salinas, Victoria Wu, Spiros Tastsoglou, Giorgos Skoufos, Ioannis Verginadis, Ilias Karagounis, Artemis G. Hatzigeorgiou, Constantinos Koumenis. A genome-wide CRISPR-based functional screen uncovers the KLF4-Survivin/BIRC5 signaling pathways as a key regulator of cell fate following endoplasmic reticulum stress: Implications for tumor growth and therapeutic targeting [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB191.

Chronic endoplasmic reticulum stress in myotonic dystrophy type 2 promotes autoimmunity via mitochondrial DNA release

Myotonic dystrophy type 2 (DM2) is a tetranucleotide CCTG repeat expansion disease associated with an increased prevalence of autoimmunity. Here, we identified an elevated type I interferon (IFN) signature in peripheral blood mononuclear cells and primary fibroblasts of DM2 patients as a trigger of chronic immune stimulation. Although RNA-repeat accumulation was prevalent in the cytosol of DM2-patient fibroblasts, type-I IFN release did not depend on innate RNA immune sensors but rather the DNA sensor cGAS and the prevalence of mitochondrial DNA (mtDNA) in the cytoplasm. Sublethal mtDNA release was promoted by a chronic activation of the ATF6 branch of the unfolded protein response (UPR) in reaction to RNA-repeat accumulation and non-AUG translated tetrapeptide expansion proteins. ATF6-dependent mtDNA release and resulting cGAS/STING activation could also be recapitulated in human THP-1 monocytes exposed to chronic endoplasmic reticulum (ER) stress. Altogether, our study demonstrates a novel mechanism by which large repeat expansions cause chronic endoplasmic reticulum stress and associated mtDNA leakage. This mtDNA is, in turn, sensed by the cGAS/STING pathway and induces a type-I IFN response predisposing to autoimmunity. Elucidating this pathway reveals new potential therapeutic targets for autoimmune disorders associated with repeat expansion diseases.

Adaptive responses of neuronal cells to chronic endoplasmic reticulum (ER) stress

Accumulation of misfolded proteins or perturbation of calcium homeostasis leads to endoplasmic reticulum (ER) stress and is linked to the pathogenesis of neurodegenerative diseases. Hence, understanding the ability of neuronal cells to cope with chronic ER stress is of fundamental interest. Interestingly, several brain areas uphold functions that enable them to resist challenges associated with neurodegeneration. Here, we established novel clonal mouse hippocampal (HT22) cell lines that are resistant to prolonged (chronic) ER stress induced by thapsigargin (TgR) or tunicamycin (TmR) as in vitro models to study the adaption to ER stress. Morphologically, we observed a significant increase in vesicular und autophagosomal structures in both resistant lines and ‘giant lysosomes’, especially striking in TgR cells. While autophagic activity increased under ER stress, lysosomal function appeared slightly impaired; in both cell lines, we observed enhanced ER-phagy. However, proteomic analyses revealed that various protein clusters and signaling pathways were differentially regulated in TgR versus TmR cells in response to chronic ER stress. Additionally, bioenergetic analyses in both resistant cell lines showed a shift toward aerobic glycolysis (‘Warburg effect’) and a defective complex I of the oxidative phosphorylation (OXPHOS) machinery. Furthermore, ER stress-resistant cells differentially activated the unfolded protein response (UPR) comprising IRE1α and ATF6 pathways. These findings display the wide portfolio of adaptive responses of neuronal cells to chronic ER stress. ER stress-resistant neuronal cells could be the basis to uncover molecular modulators of adaptation, resistance, and neuroprotection as potential pharmacological targets for preventing neurodegeneration.

Large HBV Surface Protein-Induced Unfolded Protein Response Dynamically Regulates p27 Degradation in Hepatocellular Carcinoma Progression.

Up to 50% of hepatocellular carcinoma (HCC) is caused by hepatitis B virus (HBV) infection, and the surface protein of HBV is essential for the progression of HBV-related HCC. The expression of large HBV surface antigen (LHB) is presented in HBV-associated HCC tissues and is significantly associated with the development of HCC. Gene set enrichment analysis revealed that LHB overexpression regulates the cell cycle process. Excess LHB in HCC cells induced chronic endoplasmic reticulum (ER) stress and was significantly correlated with tumor growth in vivo. Cell cycle analysis showed that cell cycle progression from G1 to S phase was greatly enhanced in vitro. We identified intensive crosstalk between ER stress and cell cycle progression in HCC. As an important regulator of the G1/S checkpoint, p27 was transcriptionally upregulated by transcription factors ATF4 and XBP1s, downstream of the unfolded protein response pathway. Moreover, LHB-induced ER stress promoted internal ribosome-entry-site-mediated selective translation of p27, and E3 ubiquitin ligase HRD1-mediated p27 ubiquitination and degradation. Ultimately, the decrease in p27 protein levels reduced G1/S arrest and promoted the progress of HCC by regulating the cell cycle.

MicroRNA Biogenesis in Cell Senescence Induced by Chronic Endoplasmic Reticulum Stress

MicroRNA Biogenesis in Cell Senescence Induced by Chronic Endoplasmic Reticulum Stress

MicroRNA Biogenesis during Cellular Senesence Induced by Chronic Stress of the Endoplasmic Reticulum

MicroRNAs are small non-coding regulatory RNAs about 22 nt long, post-transcriptional and transcriptional regulators of gene expression that stabilize the cellular phenotype and play an important role in differentiation, development, and apoptosis. MicroRNA biogenesis includes several precisely controlled post-transcriptional stages of processing and transport, including cytoplasmic cleavage of pre-miRNA by type III ribonuclease DICER with the formation of a mature duplex included in the RISC complex. The role of miRNA and its biogenesis are not well understood in such an important process as cellular stress. Cellular stress is a non-specific cellular response to non-physiological stimuli that can switch a cell to death or cellular senescence. The global decrease in microRNA levels is a key feature of cancer cells and an important reason for the formation of a malignant phenotype. In this work, using flow cytometry and high-throughput analysis of gene expression, we showed that chronic endoplasmic reticulum (ER) stress, one of the types of cellular stress associated with impaired protein folding in the ER, leads to the formation of a cellular aging phenotype in fibroblast-like FRSN cells. Despite the fact that acute ER stress can reduce miRNA biogenesis, chronic stress does not lead to a significant drop in global miRNA expression and is accompanied by only a slight decrease in DICER1 mRNA expression. Under chronic ER stress, we found an increase in cell population heterogeneity in terms of lysosomal beta-galactosidase activity, which does not exclude induced or initial cell heterogeneity and in terms of expression of microRNA biogenesis pathway components.

Brief Oxygen Exposure after Traumatic Brain Injury Hastens Recovery and Promotes Adaptive Chronic Endoplasmic Reticulum Stress Responses.

Traumatic brain injury (TBI) is a major public health concern, particularly in adolescents who have a higher mortality and incidence of visual pathway injury compared to adult patients. Likewise, we have found disparities between adult and adolescent TBI outcomes in rodents. Most interestingly, adolescents suffer a prolonged apneic period immediately post-injury, leading to higher mortality; therefore, we implemented a brief oxygen exposure paradigm to circumvent this increased mortality. Adolescent male mice experienced a closed-head weight-drop TBI and were then exposed to 100% O2 until normal breathing returned or recovered in room air. We followed mice for 7 and 30 days and assessed their optokinetic response; retinal ganglion cell loss; axonal degeneration; glial reactivity; and retinal ER stress protein levels. O2 reduced adolescent mortality by 40%, improved post-injury visual acuity, and reduced axonal degeneration and gliosis in optical projection regions. ER stress protein expression was altered in injured mice, and mice given O2 utilized different ER stress pathways in a time-dependent manner. Finally, O2 exposure may be mediating these ER stress responses through regulation of the redox-sensitive ER folding protein ERO1α, which has been linked to a reduction in the toxic effects of free radicals in other animal models of ER stress.

PERK prevents rhodopsin degradation during retinitis pigmentosa by inhibiting IRE1-induced autophagy.

Chronic endoplasmic reticulum (ER) stress is the underlying cause of many degenerative diseases, including autosomal dominant retinitis pigmentosa (adRP). In adRP, mutant rhodopsins accumulate and cause ER stress. This destabilizes wild-type rhodopsin and triggers photoreceptor cell degeneration. To reveal the mechanisms by which these mutant rhodopsins exert their dominant-negative effects, we established an in vivo fluorescence reporter system to monitor mutant and wild-type rhodopsin in Drosophila. By performing a genome-wide genetic screen, we found that PERK signaling plays a key role in maintaining rhodopsin homeostasis by attenuating IRE1 activities. Degradation of wild-type rhodopsin is mediated by selective autophagy of ER, which is induced by uncontrolled IRE1/XBP1 signaling and insufficient proteasome activities. Moreover, upregulation of PERK signaling prevents autophagy and suppresses retinal degeneration in the adRP model. These findings establish a pathological role for autophagy in this neurodegenerative condition and indicate that promoting PERK activity could be used to treat ER stress-related neuropathies, including adRP.

Purposed potential Alzheimer’s Disease treatment based on the results from current primary research models

Alzheimer’s Disease is one of the most known neurodegenerative diseases that causes over 100,000 deaths till now. The pathology of Alzheimer’s Disease is still not fully clear, but the most widely accepted pathology is the chronic endoplasmic reticulum (ER) stress caused by neurotoxicity via amyloid beta (Aß) plaques and intracellular tau tangles. In Alzheimer's patients, the abnormal Aß plaques and tau tangles cause oxidative stress and induce chronic ER stress, which can hardly be relieved by the normal UPR pathway. One potential treatment for rescuing the excessive ER stress caused by Aß accumulation in human neural cells is the Salubrinal (Sal) treatment. Amentoflavone (AF) treatment is a plausible treatment to alleviate cell death stress due to pyroptosis in Alzheimer's patients. Latrepirdine (LAT) is a treatment that can induce autophagy with the help of ATG5. Mitophagy is a special form of autophagy that degrades dysfunctional mitochondria and does not function well in Alzheimer's patients. Treatment like NMN, UA, and AC can effectively induce mitophagy, decrease memory loss, and relieve common Alzheimer’s pathology like Aß plaques and tau tangles. In this review, the primary research on four key mechanisms in Alzheimer's etiology - UPR pathway(apoptosis), pyroptosis, autophagy and mitophagy - will be discussed and some potential treatments targeting these four mechanisms will be briefly introduced with the primary research results.

CDNF rescues motor neurons in models of amyotrophic lateral sclerosis by targeting endoplasmic reticulum stress.

Amyotrophic lateral sclerosis is a progressive neurodegenerative disease that affects motor neurons in the spinal cord, brainstem and motor cortex, leading to paralysis and eventually to death within 3-5 years of symptom onset. To date, no cure or effective therapy is available. The role of chronic endoplasmic reticulum stress in the pathophysiology of amyotrophic lateral sclerosis, as well as a potential drug target, has received increasing attention. Here, we investigated the mode of action and therapeutic effect of the endoplasmic reticulum-resident protein cerebral dopamine neurotrophic factor in three preclinical models of amyotrophic lateral sclerosis, exhibiting different disease development and aetiology: (i) the conditional choline acetyltransferase-tTA/TRE-hTDP43-M337V rat model previously described; (ii) the widely used SOD1-G93A mouse model; and (iii) a novel slow-progressive TDP43-M337V mouse model. To specifically analyse the endoplasmic reticulum stress response in motor neurons, we used three main methods: (i) primary cultures of motor neurons derived from embryonic Day 13 embryos; (ii) immunohistochemical analyses of spinal cord sections with choline acetyltransferase as spinal motor neuron marker; and (iii) quantitative polymerase chain reaction analyses of lumbar motor neurons isolated via laser microdissection. We show that intracerebroventricular administration of cerebral dopamine neurotrophic factor significantly halts the progression of the disease and improves motor behaviour in TDP43-M337V and SOD1-G93A rodent models of amyotrophic lateral sclerosis. Cerebral dopamine neurotrophic factor rescues motor neurons in vitro and in vivo from endoplasmic reticulum stress-associated cell death and its beneficial effect is independent of genetic disease aetiology. Notably, cerebral dopamine neurotrophic factor regulates the unfolded protein response initiated by transducers IRE1α, PERK and ATF6, thereby enhancing motor neuron survival. Thus, cerebral dopamine neurotrophic factor holds great promise for the design of new rational treatments for amyotrophic lateral sclerosis.

Antitumor T‐cell function requires CPEB4‐mediated adaptation to chronic endoplasmic reticulum stress

Tumor growth is influenced by a complex network of interactions between multiple cell types in the tumor microenvironment (TME). These constrained conditions trigger the endoplasmic reticulum (ER) stress response, which extensively reprograms mRNA translation. When uncontrolled over time, chronic ER stress impairs the antitumor effector function of CD8 T lymphocytes. How cells promote adaptation to chronic stress in the TME without the detrimental effects of the terminal unfolded protein response (UPR) is unknown. Here, we find that, in effector CD8 T lymphocytes, RNA‐binding protein CPEB4 constitutes a new branch of the UPR that allows cells to adapt to sustained ER stress, yet remains decoupled from the terminal UPR. ER stress, induced during CD8 T‐cell activation and effector function, triggers CPEB4 expression. CPEB4 then mediates chronic stress adaptation to maintain cellular fitness, allowing effector molecule production and cytotoxic activity. Accordingly, this branch of the UPR is required for the antitumor effector function of T lymphocytes, and its disruption in these cells exacerbates tumor growth.

MicroRNA Biogenesis in Cell Senescence Induced by Chronic Endoplasmic Reticulum Stress

MicroRNAs are small noncoding RNAs that regulate gene expression; stabilize the cell phenotype; and play an important role in cell differentiation, development, and apoptosis. A canonical microRNA biogenesis pathway includes several posttranscriptional steps of processing and transport and ends with cytoplasmic cleavage of pre-miRNA by type III ribonuclease DICER to form a mature duplex, which is included in RISC. MicroRNA biogenesis and role in cell stress are still poorly understood. Using flow cytometry and high-throughput analysis of gene expression, we have shown that chronic endoplasmic reticulum (ER) stress, which is associated with improper protein folding in the ER, induce a cellular senescence phenotype in fibroblast-like FRSN cells. While acute ER stress can reduce miRNA biogenesis, chronic stress does not cause a significant drop in global microRNA expression and is accompanied by only a slight decrease in DICER1 mRNA expression. Heterogeneity with respect to lysosomal β-galactosidase activity was found to increase in the cell population exposed to ER stress. We do not exclude induced cell heterogeneity regarding expression of components of the microRNA biogenesis pathway.

Redox stress and metal dys-homeostasis appear as hallmarks of early prion disease pathogenesis in mice

Neurodegenerative diseases are associated with a multitude of dysfunctional cellular pathways. One major contributory factor is a redox stress challenge during the development of several protein misfolding conditions including Alzheimer's (AD), Parkinson's disease (PD), and less common conditions such as Creutzfeldt Jakob disease (CJD). CJD is caused by misfolding of the neuronal prion protein and is characterised by a neurotoxic unfolded protein response involving chronic endoplasmic reticulum stress, reduced protein translation and spongiosis leading subsequently to synaptic and neuronal loss. Here we have characterised prion disease in mice to assess redox stress components including nitrergic and oxidative markers associated with neuroinflammatory activation. Aberrant regulation of the homeostasis of several redox metals contributes to the overall cellular redox stress and we have identified altered levels of iron, copper, zinc, and manganese in the hippocampus of prion diseased mice. Our data show that early in disease, there is evidence for oxidative stress in conjunction with reduced antioxidant superoxide dismutase mRNA and protein expression. Moreover, expression of divalent metal transporter proteins was reduced for Atp7b, Atox1, Slc11a2, Slc39a14 at 6–7 weeks but increased for Slc39a14 and Mt1 at 10 weeks of disease. Our data present evidence for a strong pro-oxidant environment and altered redox metal homeostasis in early disease pathology which both may be contributory factors to aggravating this protein misfolding disease.

FKBP11 rewires UPR signaling to promote glucose homeostasis in type 2 diabetes and obesity

Chronic endoplasmic reticulum (ER) stress and sustained activation of unfolded protein response (UPR) signaling contribute to the development of type 2 diabetes in obesity. UPR signaling is a complex signaling pathway, which is still being explored in many different cellular processes. Here, we demonstrate that FK506-binding protein 11 (FKBP11), which is transcriptionally regulated by XBP1s, is severely reduced in the livers of obese mice. Restoring hepatic FKBP11 expression in obese mice initiates an atypical UPR signaling pathway marked by rewiring of PERK signaling toward NRF2, away from the eIF2α-ATF4 axis of the UPR. This alteration in UPR signaling establishes glucose homeostasis without changing hepatic ER stress, food consumption, or body weight. We conclude that ER stress during obesity can be beneficially rewired to promote glucose homeostasis. These findings may uncover possible new avenues in the development of novel approaches to treat diseases marked by ER stress.

Myocilin Gene Mutation Induced Autophagy Activation Causes Dysfunction of Trabecular Meshwork Cells.

Trabecular meshwork dysfunction is the main cause of primary open angle glaucoma (POAG) associated with elevated intraocular pressure (IOP). Mutant myocilin causes glaucoma mainly via elevating IOP. Previously we have found that accumulated Asn 450 Tyr (N450Y) mutant myocilin impairs human trabecular meshwork (TM) cells by inducing chronic endoplasmic reticulum (ER) stress response in vitro. However, it is unclear how ER stress leads to TM damage and whether N450Y myocilin mutation is associated with POAG in vivo. Here we found that N450Y mutant myocilin induces autophagy, which worsens cell viability, whereas inhibition of autophagy increases viability and decreases cell death in human TM cells. Furthermore, we construct a transgenic mouse model of N450Y myocilin mutation (Tg-MYOCN450Y) and Tg-MYOCN450Y mice exhibiting glaucoma phenotypes: IOP elevation, retinal ganglion cell loss and visual impairment. Consistent with our published in vitro studies, mutant myocilin fails to secrete into aqueous humor, causes ER stress and actives autophagy in Tg-MYOCN450Y mice, and aqueous humor dynamics are altered in Tg-MYOCN450Y mice. In summary, our studies demonstrate that activation of autophagy is correlated with pathogenesis of POAG.

NRF2-mediated SIRT3 induction protects hepatocytes from ER stress-induced liver injury.

Chronic endoplasmic reticulum (ER) stress in hepatocytes plays a role in the pathogenesis of nonalcoholic fatty liver disease. Therefore, given the association between oxidative stress, mitochondrial dysfunction, and ER stress, our study investigated the role of NRF2-mediated SIRT3 activation in ER stress. SIRT3, a sirtuin, was predicted as the target of NRF2 based on bioinformatic analyses and animal experiments. Nrf2 abrogation diminished mitochondrial DNA content in hepatocytes with Ppargc1α and Cpt1a inhibition, whereas its overexpression enhanced oxygen consumption. Further, chromatin immunoprecipitation and luciferase reporter assays indicated that NRF2 induced SIRT3 through the antioxidant responsive element (ARE) sites comprising the -641 to -631bp and -419 to -409bp regions. In tunicamycin-induced ER stress conditions and liver injury animal models following ER stress, NRF2levels were highly correlated with SIRT3. Nrf2 deficiency enhanced the tunicamycin-mediated induction of CHOP, which was attenuated by Sirt3 overexpression. Further, Sirt3 delivery to hepatocytes in Nrf2knockout mice prevented tunicamycin from increasing mortality by decreasing ER stress. SIRT3 was upregulated in livers of patients with nonalcoholic liver diseases, whereas lower SIRT3 expression coincided with more severe disease conditions. Taken together, our findings indicated that NRF2-mediated SIRT3 induction protects hepatocytes from ER stress-induced injury, which may contribute to the inhibition of liver disease progression.

Probiotics Supplements Reduce ER Stress and Gut Inflammation Associated with Gliadin Intake in a Mouse Model of Gluten Sensitivity.

Exposure to gluten, a protein present in wheat rye and barley, is the major inducer for human Celiac Disease (CD), a chronic autoimmune enteropathy. CD occurs in about 1% worldwide population, in genetically predisposed individuals bearing human leukocyte antigen (HLA) DQ2/DQ8. Gut epithelial cell stress and the innate immune activation are responsible for the breaking oral tolerance to gliadin, a gluten component. To date, the only treatment available for CD is a long-term gluten-free diet. Several studies have shown that an altered composition of the intestinal microbiota (dysbiosis) could play a key role in the pathogenesis of CD through the modulation of intestinal permeability and the regulation of the immune system. Here, we show that gliadin induces a chronic endoplasmic reticulum (ER) stress condition in the small intestine of a gluten-sensitive mouse model and that the coadministration of probiotics efficiently attenuates both the unfolded protein response (UPR) and gut inflammation. Moreover, the composition of probiotics formulations might differ in their activity at molecular level, especially toward the three axes of the UPR. Therefore, probiotics administration might potentially represent a new valuable strategy to treat gluten-sensitive patients, such as those affected by CD.

FOXA3 induction under endoplasmic reticulum stress contributes to non-alcoholic fatty liver disease

Chronic endoplasmic reticulum (ER) stress in the liver has been shown to play a causative role in non-alcoholic fatty liver disease (NAFLD) progression, yet the underlying molecular mechanisms remain to be elucidated. Forkhead box A3 (FOXA3), a member of the FOX family, plays critical roles in metabolic homeostasis, although its possible functions in ER stress and fatty liver progression are unknown. Adenoviral delivery, siRNA delivery, and genetic knockout mice were used to crease FOXA3 gain- or loss-of-function models. Tunicamycin (TM) and a high-fat diet (HFD) were used to induce acute or chronic ER stress in mice. Chromatin immunoprecipiation (ChIP)-seq, luciferase assay, and adenoviral-mediated downstream gene manipulations were performed to reveal the transcriptional axis involved. Key axis protein levels in livers from healthy donors and patients with NAFLD were assessed via immunohistochemical staining. FOXA3 transcription is specifically induced by XBP1s upon ER stress. FOXA3 exacerbates the excessive lipid accumulation caused by the acute ER-inducer TM, whereas FOXA3 deficiency in hepatocytes and mice alleviates it. Importantly, FOXA3 deficiency in mice reduced diet-induced chronic ER stress, fatty liver, and insulin resistance. In addition, FOXA3 suppression via siRNA or adeno-associated virus delivery ameliorated the fatty liver phenotype in HFD-fed and db/db mice. Mechanistically, ChIP-Seq analysis revealed that FOXA3 directly regulates Period1 (Per1) transcription, which in turn promotes the expression of lipogenic genes, including Srebp1c, thus enhancing lipid synthesis. Of pathophysiological significance, FOXA3, PER1, and SREBP1c levels were increased in livers of obese mice and patients with NAFLD. The present study identified FOXA3 as the bridging molecule that links ER stress and NAFLD progression. Our results highlighted the role of the XBP1s-FOXA3-PER1/Srebp1c transcriptional axis in the development of NAFLD and identified FOXA3 as a potential therapeutic target for fatty liver disease. The molecular mechanisms linking endoplasmic reticulum stress to non-alcoholic fatty liver disease (NAFLD) progression remain undefined. Herein, via invitro and invivo analysis, we identified Forkhead box A3 (FOXA3) as a key bridging molecule. Of pathophysiological significance, FOXA3 protein levels were increased in livers of obese mice and patients with NAFLD, indicating that FOXA3 could be a potential therapeutic target in fatty liver disease.

Role of Oxidative Stress in the Pathogenesis of Non-Alcoholic Fatty Liver Disease: Implications for Prevention and Therapy

Oxidative stress (OxS) is considered a major factor in the pathophysiology of inflammatory chronic liver diseases, including non-alcoholic liver disease (NAFLD). Chronic impairment of lipid metabolism is closely related to alterations of the oxidant/antioxidant balance, which affect metabolism-related organelles, leading to cellular lipotoxicity, lipid peroxidation, chronic endoplasmic reticulum (ER) stress, and mitochondrial dysfunction. Increased OxS also triggers hepatocytes stress pathways, leading to inflammation and fibrogenesis, contributing to the progression of non-alcoholic steatohepatitis (NASH). The antioxidant response, regulated by the Nrf2/ARE pathway, is a key component in this process and counteracts oxidative stress-induced damage, contributing to the restoration of normal lipid metabolism. Therefore, modulation of the antioxidant response emerges as an interesting target to prevent NAFLD development and progression. This review highlights the link between disturbed lipid metabolism and oxidative stress in the context of NAFLD. In addition, emerging potential therapies based on antioxidant effects and their likely molecular targets are discussed.