Interactions Between Autophagy and the Unfolded Protein Response: Implications for Inflammatory Bowel Disease

Endoplasmic reticulum stress in gut inflammation: Implications for ulcerative colitis and Crohn's disease

Eukaryotic cells contain the endoplasmic reticulum (ER), a prevalent and intricate membranous structural system. During the development of inflammatory bowel disease (IBD), the stress on the ER and the start of the unfolded protein response are very important. Some chemicals, including 4μ8C, small molecule agonists of X-box binding protein 1, and ISRIB, work on the inositol-requiring enzyme 1, turn on transcription factor 6, and activate protein kinase RNA-like ER kinase pathways. This may help ease the symptoms of IBD. Researchers investigating the gut microbiota have discovered a correlation between ER stress and it. This suggests that changing the gut microbiota could help make new medicines for IBD. This study looks at how ER stress works and how it contributes to the emergence of IBD. It also talks about its possible clinical importance as a therapeutic target and looks into new ways to treat this condition.

Characterisation of autophagy induction by the thiopurine drugs azathioprine, mercaptopurine and thioguanine in THP-1 macrophages

Activating autophagy may be therapeutically beneficial, and we have previously shown that azathioprine (AZA), an immunomodulatory drug, induces autophagy. Here, we evaluated the induction of autophagy by the thiopurines AZA, mercaptopurine (6-MP) and thioguanine (6-TG) in THP-1 macrophages and investigated the mechanism of action in the context of this cellular process. The cytotoxicity of thiopurines was evaluated using an LDH assay. Induction of endogenous LC3 by thiopurines was evaluated using immunostaining. To confirm autophagy activation by thiopurines, a GFP-RFP-LC3 reporter plasmid was used to monitor the maturation of autophagosomes to autolysosomes. Induction of apoptosis by thiopurines was evaluated using Annexin V/PI staining, and ER stress was assessed via RT‒PCR analysis of XBP1 splicing. To gain insight into the mechanism of action of thiopurines, mTORC1 activity and eIF2α-S51 phosphorylation were evaluated by immunoblotting. Thiopurines were not cytotoxic to cells and induced strong time- and concentration-dependent autophagy. Thiopurines activate autophagy with complete progression through the pathway. Induction of autophagy by thiopurines occurred independently of apoptosis and ER stress. Immunoblotting revealed that AZA inhibited mTORC1 activity, and AZA and 6-TG increased eIF2α-S51 phosphorylation. In contrast, 6-MP had a minor effect on either signalling pathway. Thiopurines are strong inducers of autophagy, and autophagy induction should be considered among the mechanisms responsible for patient response to thiopurines.

Mesalazine alleviated the symptoms of spontaneous colitis in interleukin-10 knockout mice by regulating the STAT3/NF-κB signaling pathway

BACKGROUND

Excessive endoplasmic reticulum (ER) stress in intestinal epithelial cells can lead to damage to the intestinal mucosal barrier, activate the signal transducer and activator of transcription 3 (STAT3)/nuclear factor kappa B (NF-κB) signaling pathway, and exacerbate the inflammatory response, thus participating in the pathogenesis of ulcerative colitis (UC). Mesalazine is a commonly used drug in the clinical treatment of UC. However, further studies are needed to determine whether mesalazine regulates the ER stress of intestinal epithelial cells, down-regulates the STAT3/NF-κB pathway to play a role in the treatment of UC.

AIM

To study the therapeutic effects of mesalazine on spontaneous colitis in interleukin-10 (IL-10)-/- mice.

METHODS

The 24-week-old IL-10-/- mice with spontaneous colitis were divided into the model group and the 5-amino salicylic acid group. Littermates of wild-type mice of the same age group served as the control. There were eight mice in each group, four males and four females. The severity of symptoms of spontaneous colitis in IL-10-/- mice was assessed using disease activity index scores. On day 15, the mice were sacrificed. The colon length was measured, and the histopathological changes and ultrastructure of colonic epithelial cells were detected. The protein expressions of STAT3, p-STAT3, NF-κB, IκB, p-IκB, and glucose-regulated protein 78 were identified using Western blotting. The STAT3 and NF-κB mRNA expressions were identified using real-time polymerase chain reaction. The glucose-regulated protein 78 and C/EBP homologous protein expressions in colon sections were detected using immunofluorescence.

RESULTS

Mesalazine reduced the symptoms of spontaneous colitis in IL-10 knockout mice and the histopathological damage of colonic tissues, and alleviated the ER stress in epithelial cells of colitis mice. Western blotting and quantitative real-time polymerase chain reaction results showed that the STAT3/NF-κB pathway in the colon tissue of model mice was activated, suggesting that this pathway was involved in the pathogenesis of UC and might become a potential therapeutic target. Mesalazine could down-regulate the protein expressions of p-STAT3, NF-κB and p-IκB, and down-regulate the mRNA expression of STAT3 and NF-κB.

CONCLUSION

Mesalazine may play a protective role in UC by reducing ER stress by regulating the STAT3/NF-κB signaling pathway.

In Vitro Inhibition of Endoplasmic Reticulum Stress: A Promising Therapeutic Strategy for Patients with Crohn's Disease

BACKGROUND

Crohn's disease (CD) is an inflammatory bowel disease marked by an abnormal immune response and excessive pro-inflammatory cytokines, leading to impaired protein processing and endoplasmic reticulum (ER) stress. This stress, caused by the accumulation of misfolded proteins, triggers the unfolded protein response (UPR) through IRE1/Xbp-1, PERK/eIF2α, and ATF6 pathways, which are linked to intestinal inflammation. This study aimed to investigate ER stress in CD patients' intestinal mucosa and evaluate phenylbutyrate (PBA) as an ER stress inhibitor.

METHODS

Colon biopsies from CD patients and controls were cultured under five conditions, including 4-PBA treatments. Real-time PCR, cytokine level, and immunohistochemistry were performed.

RESULTS

Immunohistochemistry revealed that ER stress was activated in CD patients' intestinal epithelial cells and lamina propria cells. PERK/eIF2α, but not IRE1/Xbp-1 or ATF6, was upregulated in CD patients compared to controls. UPR-related genes (STC2, CALR, HSPA5, HSP90B1) were also elevated in CD patients. PBA treatment significantly reduced ER stress and UPR markers while decreasing apoptotic markers like DDIT3. Pro-inflammatory cytokines, such as IL-1β, IL-6, IL-17, TNF- α, and sCD40L, were significantly reduced after PBA treatment.

CONCLUSION

ER stress and UPR pathways are activated in CD colonic mucosa, and PBA reduces these markers, suggesting potential therapeutic benefits for CD-related inflammation.

The SERPINB4 gene mutation identified in twin patients with Crohn's disease impaires the intestinal epithelial cell functions

Crohn's disease (CD) is a chronic inflammatory autoimmune disease of unknown etiology. To identify new targets related to the initiation of CD, we screened a pair of twins with CD, which is a rare phenomenon in the Chinese population, for genetic susceptibility factors. Whole-exome sequencing (WES) of these patients revealed a mutation in their SERPINB4 gene. Therefore, we studied a wider clinical cohort of patients with CD or ulcerous colitis (UC), healthy individuals, and those with a family history of CD for this mutation by Sanger sequencing. The single-nucleotide difference in the SERPINB4 gene, which was unique to the twin patients with CD, led to the substitution of lysine by a glutamic acid residue. Functional analysis indicated that this mutation of SERPINB4 inhibited the proliferation, colony formation, wound healing, and migration of intestinal epithelial cells (IECs). Furthermore, mutation of SERPINB4 induced apoptosis and activated apoptosis-related proteins in IECs, and a caspase inhibitor significantly reduced these effects. Transcriptome sequencing revealed that the expression of genes encoding proinflammatory proteins (IL1B, IL6, IL17, IL24, CCL2, and CXCR2) and key proteins in the immune response (S100A9, MMP3, and MYC) was significantly upregulated during SERPINB4 mutant-induced apoptosis. Thus, the heterozygous SERPINB4 gene mutation causes the dysfunction of IECs, which would disrupt the intestinal epithelial barrier and contribute to the development of intestinal inflammation. The activation of SERPINB4 might represent a novel therapeutic target for inflammatory bowel disease.

Exploring the Connections: Autophagy, Gut Microbiota, and Inflammatory Bowel Disease Pathogenesis

Inflammatory Bowel Disease (IBD), which includes Crohn's disease and ulcerative colitis, represents a complex and growing global health issue with a multifaceted origin. This review delves into the intricate relationship between gut microbiota, autophagy, and the development of IBD. The gut microbiota, a diverse community of microorganisms, plays a vital role in maintaining gut health, while imbalances in this microbial community, known as dysbiosis, are linked to IBD. Autophagy, a process by which cells recycle their components, is essential for gut homeostasis and the regulation of immune responses. When autophagy is impaired and dysbiosis occurs, they individually contribute to IBD, with their combined impact intensifying inflammation. The interconnectedness of gut microbiota, autophagy, and the host's immune system is central to the onset of IBD. The review also examines how diet influences gut microbiota and its subsequent effects on IBD. It highlights the therapeutic potential of targeting the microbiota and modulating autophagic pathways as treatment strategies for IBD. Understanding these interactions could lead to personalized therapies within the rapidly advancing fields of microbiome research and immunology.

Autophagy: A potential target for natural products in the treatment of ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease primarily affecting the mucosa of the colon and rectum. UC is characterized by recurrent episodes, often necessitating lifelong medication use, imposing a significant burden on patients. Current conventional and advanced treatments for UC have the disadvantages of insufficient efficiency, susceptibility to drug resistance, and notable adverse effects. Therefore, developing effective and safe drugs has become an urgent need. Autophagy is an intracellular degradation process that plays an important role in intestinal homeostasis. Emerging evidence suggests that aberrant autophagy is involved in the development of UC, and modulating autophagy can effectively alleviate experimental colitis. A growing number of studies have established that autophagy can interplay with endoplasmic reticulum stress, gut microbiota, apoptosis, and the NLRP3 inflammasome, all of which contribute to the pathogenesis of UC. In addition, a variety of intestinal epithelial cells, including absorptive cells, goblet cells, and Paneth cells, as well as other cell types like neutrophils, antigen-presenting cells, and stem cells in the gut, mediate the development of UC through autophagy. To date, many studies have found that natural products hold the potential to exert therapeutic effects on UC by regulating autophagy. This review focuses on the possible effects and pharmacological mechanisms of natural products to alleviate UC with autophagy as a potential target in recent years, aiming to provide a basis for new drug development.

New insights into the unfolded protein response (UPR)-anterior gradient 2 (AGR2) pathway in the regulation of intestinal barrier function in weaned piglets

Sustained dysfunction of the intestinal barrier caused by early weaning is a major factor that induces postweaning diarrhea in weaned piglets. In both healthy and diseased states, the intestinal barrier is regulated by goblet cells. Alterations in the characteristics of goblet cells are linked to intestinal barrier dysfunction and inflammatory conditions during pathogenic infections. In this review, we summarize the current understanding of the mechanisms of the unfolded protein response (UPR) and anterior gradient 2 (AGR2) in maintaining intestinal barrier function and how modifications to these systems affect mucus barrier characteristics and goblet cell dysregulation. We highlight a novel mechanism underlying the UPR-AGR2 pathway, which affects goblet cell differentiation and maturation and the synthesis and secretion of mucin by regulating epidermal growth factor receptor and mucin 2. This study provides a theoretical basis and new insights into the regulation of intestinal health in weaned piglets.

Lentinula edodes extract increases goblet cell number and Muc2 expression in an intestinal inflammatory model of Trichinella spiralis infection

AHCC® is a standardized extract of cultured mushroom (Lentinula edodes) mycelia with a wide variety of therapeutic effects including anti-inflammatory, antitumor and antiviral effects. Trichinellosis, a food-borne parasitic zoonosis is caused by the nematode Trichinella spp. Infection with Trichinella is characterized by the induction of a Th1-type response at the beginning of the intestinal phase, followed by a dominant Th2-type response which is essential for parasite expulsion. The aim of this study was to evaluate the immunomodulatory effect of AHCC® in a murine model of Trichinella spiralis infection. Swiss CD1 mice were infected with T. spiralis larvae and treated with AHCC®. Standard treatment with albendazole (ABZ) was used as control in the assessment of parasite burden. The small intestine was taken out and the proximal segment was evaluated for several parameters: gene expression of immune and stress-reticulum mediators, histological damage score, goblet cell count and Mucin 2 (Muc2) gene expression. AHCC® modulated expression levels of both Th1 and Th2 cytokines and reduced histological damage score. In addition, AHCC® diminished the number of adults of T. spiralis in treated animals. AHCC® treatment anticipates T. spiralis expulsion and increases goblet cell number and Muc2 gene expression.

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

Background/purpose

Photodynamic 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 methods

Human 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.

Results

Pa-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.

Conclusion

This 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.

Mucins Dynamics in Physiological and Pathological Conditions

Maintaining intestinal health requires clear segregation between epithelial cells and luminal microbes. The intestinal mucus layer, produced by goblet cells (GCs), is a key element in maintaining the functional protection of the epithelium. The importance of the gut mucus barrier is highlighted in mice lacking Muc2, the major form of secreted mucins. These mice show closer bacterial residence to epithelial cells, develop spontaneous colitis and became moribund when infected with the attaching and effacing pathogen, Citrobacter rodentium. Furthermore, numerous observations have associated GCs and mucus layer dysfunction to the pathogenesis of inflammatory bowel disease (IBD). However, the molecular mechanisms that regulate the physiology of GCs and the mucus layer remain obscured. In this review, we consider novel findings describing divergent functionality and expression profiles of GCs subtypes within intestinal crypts. We also discuss internal (host) and external (diets and bacteria) factors that modulate different aspects of the mucus layer as well as the contribution of an altered mucus barrier to the onset of IBD.

Intestinal stricture in Crohn's disease: A 2020 update

Crohn's disease (CD) is a chronic and relapsing-remitting inflammatory disorder of the gastrointestinal tract. Approximately 70% of patients inevitably develop fibrosis-associated intestinal stricture after 10 years of CD diagnosis, which seriously affects their quality of life. Current therapies play limited role in preventing or reversing the process of fibrosis and no specific anti-fibrotic therapy is yet available. Nearly half of patients thus have no alternative but to receive surgery. The potential mechanisms of intestinal fibrosis remain poorly understood; extracellular matrix remodeling, aberrant immune response, intestinal microbiome imbalance and creeping fat might exert fundamental influences on the multiple physiological and pathophysiological processes. Recently, the emerging new diagnostic techniques have markedly promoted an accurate assessment of intestinal stricture by distinguishing fibrosis from inflammation, which is crucial for guiding treatment and predicting prognosis. In this review, we concisely summarized the key studies published in the year 2020 covering pathogenesis, diagnostic modalities, and therapeutic strategy of intestinal stricture. A comprehensive and timely review of the updated researches in intestinal stricture could provide insight to further elucidate its pathogenesis and identify novel drug targets with anti-fibrotic potentiality.

Beclin-1, an autophagy-related protein, is associated with the disease severity of COVID-19

Aims

Coronavirus disease 2019 (COVID-19), which is a highly contagious disease, is an ongoing outbreak worldwide with high morbidity and mortality. The approaches targeting the autophagy processes might have promising diagnostic and therapeutic values against Coronavirus infection. Here, we aimed to investigate the relationship of Beclin-1 (BECN1), an autophagy-related protein, with blood parameters and the clinical severity in patients with COVID-19.

Materials and methods

We enrolled 108 patients with COVID-19 and 21 healthy controls in this study, from September 2020 to January 2021 and divided all patients into two groups according to the severity of the disease: The non-severe group and the severe group. BECN1 levels and blood parameters were measured with Enzyme-Linked Absorbent Assay and routine techniques, respectively.

Key findings

Serum BECN1 levels were increased in patients with COVID-19 compared to the healthy controls, and its concentrations were significantly higher in the severe group than in the non-severe group (p < 0.001). BECN1 levels showed a significantly positive correlation with coagulation markers such as D-dimer and Fibrinogen (FIB) and inflammation markers such as C-reactive protein (CRP), Procalcitonin (PCT), Ferritin and biochemical markers such as Blood urea nitrogen and Lactate dehydrogenase (p < 0.001). We detected that areas under the ROC curve for BECN1, D-dimer, FIB, PCT, CRP and Ferritin were 0.8662, 0.9110, 0.8278, 0.9996 and 0.9284, respectively (p < 0.0001).

Significance

BECN1 may serve as a predictive biomarker in evaluating the disease severity of COVID-19. Our data suggest that BECN1 mediated-autophagy modulation might have a promising value in improving the clinical outcomes of COVID-19.

Ghrelin Inhibits Intestinal Epithelial Cell Apoptosis Through the Unfolded Protein Response Pathway in Ulcerative Colitis

Ulcerative colitis (UC) is a type of inflammatory bowel disease (IBD) that occurs in the lining of the rectum and colon. Apoptosis of the intestinal epithelial cells (IECs) is common in active UC patients. Ghrelin is reported to be downregulated in apoptosis of IECs induced by tumor necrosis factor-α (TNF-α). Therefore, we hypothesized that ghrelin might play an antiapoptotic role in UC progression, which was investigated using in vitro and in vivo studies. The TNF-α-treated Caco-2 cell model and mouse colitis model induced by dextran sulfate sodium (DSS) or 2,4,6-trinitrobenzenesulfonic acid (TNBS) were established and employed. We found that ghrelin could inhibit the apoptosis of Caco-2 cells induced by TNF-α, which could be disturbed by [D-lys3]-GHRP-6, the antagonist of ghrelin receptor GHS-R1a. Similarly, in the DSS- and TNBS-induced mouse colitis models, ghrelin could also protect intestinal tissues from apoptosis in DSS- and TNBS-induced colitis depending on GHS-R1a. Furthermore, ghrelin modulated the unfolded protein response (UPR) pathway and regulated the expressions of caspase-3, BAX, and Bcl-2, which contributed to the inhibition of cell apoptosis. In conclusion, ghrelin protects IECs from apoptosis during the pathogenesis of colitis by regulating the UPR pathway.

The Role of Autophagy in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory disease, including ulcerative colitis (UC) and Crohn’s disease (CD). The abnormality of inflammatory and immune responses in the intestine contributes to the pathogenesis and progression of IBD. Autophagy is a vital catabolic process in cells. Recent studies report that autophagy is highly involved in various kinds of diseases, especially inflammation-related diseases, such as IBD. In this review, the biological characteristics of autophagy and its role in IBD will be described and discussed based on recent literature. In addition, several therapies for IBD through modulating the inflammasome and intestinal microbiota taking advantage of autophagy regulation will be introduced. We aim to bring new insight in the exploration of mechanisms for IBD and development of novel therapeutic strategies against IBD.

Unfolded Protein Response and Crohn’s Diseases: A Molecular Mechanism of Wound Healing in the Gut

Endoplasmic reticulum (ER) stress triggers a series of signaling and transcriptional events termed the unfolded protein response (UPR). Severe ER stress is associated with the development of fibrosis in different organs, including lung, liver, kidney, heart, and intestine. ER stress is an essential response of epithelial and immune cells in the pathogenesis of Inflammatory Bowel Disease (IBD), including Crohn’s disease (CD). Intestinal epithelial cells are susceptible to ER stress-mediated damage due to secretion of a large amount of proteins that are involved in mucosal defense. In other cells, ER stress is linked to myofibroblast activation, extracellular matrix production, macrophage polarization, and immune cell differentiation. This review focuses on the role of the UPR in the pathogenesis in IBD from an immunologic perspective. The roles of macrophage and mesenchymal cells in the UPR from in vitro and in vivo animal models are discussed. The links between ER stress and other signaling pathways, such as senescence and autophagy, are introduced. Recent advances in the understanding of the epigenetic regulation of the UPR signaling are also updated here. The future directions of development of the UPR research and therapeutic strategies to manipulate ER stress levels are also reviewed.

Targeted deletion of Atg5 in intestinal epithelial cells promotes dextran sodium sulfate-induced colitis

Autophagy-associated genes have been identified as susceptible loci for inflammatory bowel disease. We investigated the role of a core autophagy factor, Atg5, in the development of dextran sodium sulfate (DSS)-induced colitis. Intestinal epithelial cell (IEC)-specific Atg5 gene deficient mice (Atg5 ^ΔIEC mice) were generated by cross of Atg5-floxed mice (Atg5 ^fl/fl ) with transgenic mice expressing Cre-recombinase driven by the villin promotor. Mice were given three cycles of 1.5% DSS in drinking water for 5 days and regular water for 14 days over a 60-day period. The dysfunction of autophagy characterized by a marked accumulation of p62 protein, a substrate for autophagy degradation, was detected in epithelial cells in the non-inflamed and inflamed mucosa of inflammatory bowel disease patients. DSS-colitis was exacerbated in Atg5 ^ΔIEC mice compared to control Atg5 ^fl/fl mice. Phosphorylation of inositol-requiring transmembrane kinase/endonuclease1α (IRE1α), a sensor for endoplasmic reticulum stress, and c-Jun N-terminal kinase, a downstream target of IRE1α, were significantly enhanced in IECs in DSS-treated Atg5 ^ΔIEC mice. Accumulation of phosphorylated IRE1α was enhanced by the treatment with chloroquine, an autophagy inhibitor. Apoptotic IECs were more abundant in DSS-treated Atg5 ^ΔIEC mice. These findings suggest that Atg5 suppresses endoplasmic reticulum stress-induced apoptosis of IECs via the degradation of excess p-IRE1α.

Endoplasmic Reticulum Stress in Subepithelial Myofibroblasts Increases the TGF-β1 Activity That Regulates Fibrosis in Crohn's Disease

BACKGROUND

Endoplasmic reticulum (ER) stress is an essential response of epithelial and immune cells to inflammation in Crohn's disease. The presence and mechanisms that might regulate the ER stress response in subepithelial myofibroblasts (SEMFs) and its role in the development of fibrosis in patients with Crohn's disease have not been examined.

METHODS

Subepithelial myofibroblasts were isolated from the affected ileum and normal ileum of patients with each Montreal phenotype of Crohn's disease and from normal ileum in non-Crohn's subjects. Binding of GRP78 to latent TGF-β1 and its subcellular trafficking was examined using proximity ligation-hybridization assay (PLA). The effects of XBP1 and ATF6 on TGF-β1 expression were measured using DNA-ChIP and luciferase reporter assay. Endoplasmic reticulum stress components, TGF-β1, and collagen levels were analyzed in SEMF transfected with siRNA-mediated knockdown of DNMT1 and GRP78 or with DNMT1 inhibitor 5-Azacytidine or with overexpression of miR-199a-5p.

RESULTS

In SEMF of strictured ileum from patients with B2 Crohn's disease, expression of ER stress sensors increased significantly. Tunicamycin elicited time-dependent increase in GRP78 protein levels, direct interaction with latent TGF-β1, and activated TGF-β1 signaling. The TGFB1 DNA-binding activity of ATF-6α and XBP1 were significantly increased and elicited increased TGFB1 transcription in SEMF-isolated from affected ileum. The levels of ER stress components, TGF-β1, and collagen expression in SEMF were significantly decreased following knockdown of DNMT1 or GRP78 by 5-Azacytidine treatment or overexpression of miR-199a-5p.

CONCLUSIONS

Endoplasmic reticulum stress is present in SEMF of patients susceptible to fibrostenotic Crohn's disease and can contribute to development of fibrosis. Targeting ER stress may represent a novel therapeutic target to prevent fibrosis in patients with fibrostenotic Crohn's disease.

MSTN Attenuates Cardiac Hypertrophy through Inhibition of Excessive Cardiac Autophagy by Blocking AMPK /mTOR and miR-128/PPARγ/NF-κB

Cardiac hypertrophy, a response of the heart to increased workload, is a major risk factor for heart failure. Myostatin (MSTN) is an inhibitor of myogenesis, regulating the number and size of skeletal myocytes. In recent years, cardiomyocyte autophagy also has been considered to be involved in controlling the hypertrophic response. However, less is known about the detailed mechanism of MSTN on cardiac hypertrophy via regulation of cardiomyocyte autophagy. In this study, we found that the deletion of MSTN potentiated abdominal aorta coarctation (AAC) and angiotensin II (Ang II)-induced pathological cardiac hypertrophy and cardiac autophagy; however, AAC and Ang II-induced cardiac hypertrophic phenotype and cardiac autophagy were dramatically diminished by MSTN in vivo and in vitro. Mechanistically, the anti-hypertrophic and anti-autophagic effects mediated by MSTN in response to pathological stimuli were associated with the direct inactivation of activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) and activation of the peroxisome proliferator-activated receptor gamma (PPARγ)/nuclear factor κB (NF-κB) signaling pathway. Additionally, miR-128 aggravated the progression of cardiac hypertrophy through suppressing its target PPARγ. Furthermore, MSTN downregulated miR-128 expression induced by AAC and Ang II. Taken together, MSTN significantly blunts pathological cardiac hypertrophy and dysfunction, at least in part, by inhibiting excessive cardiac autophagy via blocking AMPK/mTOR and miR-128/PPARγ/NF-κB signaling pathways.

Sirtuin 1 alleviates endoplasmic reticulum stress-mediated apoptosis of intestinal epithelial cells in ulcerative colitis

BACKGROUND

Sirtuin 1 (SIRT1) is a nicotinamide adenine dinucleotide (NAD⁺)-dependent protein deacetylase that is involved in various diseases, including cancers, metabolic diseases, and inflammation-associated diseases. However, the role of SIRT1 in ulcerative colitis (UC) is still confusing.

AIM

To investigate the role of SIRT1 in intestinal epithelial cells (IECs) in UC and further explore the underlying mechanisms.

METHODS

We developed a coculture model using macrophages and Caco-2 cells. After treatment with the SIRT1 activator SRT1720 or inhibitor nicotinamide (NAM), the expression of occludin and zona occludens 1 (ZO-1) was assessed by Western blot analysis. Annexin V-APC/7-AAD assays were performed to evaluate Caco-2 apoptosis. Dextran sodium sulfate (DSS)-induced colitis mice were exposed to SRT1720 or NAM for 7 d. Transferase-mediated dUTP nick-end labeling (TUNEL) assays were conducted to assess apoptosis in colon tissues. The expression levels of glucose-regulated protein 78 (GRP78), CCAAT/enhancer-binding protein homologous protein (CHOP), caspase-12, caspase-9, and caspase-3 in Caco-2 cells and the colon tissues of treated mice were examined by quantitative real-time PCR and Western blot.

RESULTS

SRT1720 treatment increased the protein levels of occludin and ZO-1 and inhibited Caco-2 apoptosis, whereas NAM administration caused the opposite effects. DSS-induced colitis mice treated with SRT1720 had a lower disease activity index (P < 0.01), histological score (P < 0.001), inflammatory cytokine levels (P < 0.01), and apoptotic cell rate (P < 0.01), while exposure to NAM caused the opposite effects. Moreover, SIRT1 activation reduced the expression levels of GRP78, CHOP, cleaved caspase-12, cleaved caspase-9, and cleaved caspase-3 in Caco-2 cells and the colon tissues of treated mice.

CONCLUSION

SIRT1 activation reduces apoptosis of IECs via the suppression of endoplasmic reticulum stress-mediated apoptosis-associated molecules CHOP and caspase-12. SIRT1 activation may be a potential therapeutic strategy for UC.

Targeting Autophagy for Overcoming Resistance to Anti-EGFR Treatments

Epidermal growth factor receptor (EGFR) plays critical roles in cell proliferation, tumorigenesis, and anti-cancer drug resistance. Overexpression and somatic mutations of EGFR result in enhanced cancer cell survival. Therefore, EGFR can be a target for the development of anti-cancer therapy. Patients with cancers, including non-small cell lung cancers (NSCLC), have been shown to response to EGFR-tyrosine kinase inhibitors (EGFR-TKIs) and anti-EGFR antibodies. However, resistance to these anti-EGFR treatments has developed. Autophagy has emerged as a potential mechanism involved in the acquired resistance to anti-EGFR treatments. Anti-EGFR treatments can induce autophagy and result in resistance to anti-EGFR treatments. Autophagy is a programmed catabolic process stimulated by various stimuli. It promotes cellular survival under these stress conditions. Under normal conditions, EGFR-activated phosphoinositide 3-kinase (PI3K)/AKT serine/threonine kinase (AKT)/mammalian target of rapamycin (mTOR) signaling inhibits autophagy while EGFR/rat sarcoma viral oncogene homolog (RAS)/mitogen-activated protein kinase kinase (MEK)/mitogen-activated protein kinase (MAPK) signaling promotes autophagy. Thus, targeting autophagy may overcome resistance to anti-EGFR treatments. Inhibitors targeting autophagy and EGFR signaling have been under development. In this review, we discuss crosstalk between EGFR signaling and autophagy. We also assess whether autophagy inhibition, along with anti-EGFR treatments, might represent a promising approach to overcome resistance to anti-EGFR treatments in various cancers. In addition, we discuss new developments concerning anti-autophagy therapeutics for overcoming resistance to anti-EGFR treatments in various cancers.

The Resolution of Intestinal Inflammation: The Peace-Keeper's Perspective

The uncontrolled activation of the immune system toward antigens contained in the gut lumen in genetically predisposed subjects is believed to be the leading cause of inflammatory bowel disease (IBD). Two not mutually exclusive hypotheses can explain the pathogenic process leading to IBD. The first and mostly explored hypothesis states that the loss of tolerance toward gut microbiota antigens generates an aberrant inflammatory response that is perpetuated by continuous and unavoidable exposure to the triggering antigens. However, the discovery that the resolution of inflammation is not the mere consequence of clearing inflammatory triggers and diluting pro-inflammatory factors, but rather an active process in which molecular and cellular elements are involved, implies that a defect in the pro-resolving mechanisms might cause chronic inflammation in different immune-mediated diseases, including IBD. Here we review data on pro-resolving and counter-regulatory mechanisms involved in the resolution of inflammation, aiming to identify their possible involvement in the pathogenesis of IBD.

Colonic epithelial cell diversity in health and inflammatory bowel disease

The colonic epithelium facilitates host-microorganism interactions to control mucosal immunity, coordinate nutrient recycling and form a mucus barrier. Breakdown of the epithelial barrier underpins inflammatory bowel disease (IBD). However, the specific contributions of each epithelial-cell subtype to this process are unknown. Here we profile single colonic epithelial cells from patients with IBD and unaffected controls. We identify previously unknown cellular subtypes, including gradients of progenitor cells, colonocytes and goblet cells within intestinal crypts. At the top of the crypts, we find a previously unknown absorptive cell, expressing the proton channel OTOP2 and the satiety peptide uroguanylin, that senses pH and is dysregulated in inflammation and cancer. In IBD, we observe a positional remodelling of goblet cells that coincides with downregulation of WFDC2-an antiprotease molecule that we find to be expressed by goblet cells and that inhibits bacterial growth. In vivo, WFDC2 preserves the integrity of tight junctions between epithelial cells and prevents invasion by commensal bacteria and mucosal inflammation. We delineate markers and transcriptional states, identify a colonic epithelial cell and uncover fundamental determinants of barrier breakdown in IBD.