Autophagy and Gastrointestinal Diseases

From macroautophagy to mitophagy: Unveiling the hidden role of mitophagy in gastrointestinal disorders

In this editorial, we comment on an article titled “Morphological and biochemical characteristics associated with autophagy in gastrointestinal diseases”, which was published in a recent issue of the World Journal of Gastroenterology. We focused on the statement that “autophagy is closely related to the digestion, secretion, and regeneration of gastrointestinal cells”. With advancing research, autophagy, and particularly the pivotal role of the macroautophagy in maintaining cellular equilibrium and stress response in the gastrointestinal system, has garnered extensive study. However, the significance of mitophagy, a unique selective autophagy pathway with ubiquitin-dependent and independent variants, should not be overlooked. In recent decades, mitophagy has been shown to be closely related to the occurrence and development of gastrointestinal diseases, especially inflammatory bowel disease, gastric cancer, and colorectal cancer. The interplay between mitophagy and mitochondrial quality control is crucial for elucidating disease mechanisms, as well as for the development of novel treatment strategies. Exploring the pathogenesis behind gastrointestinal diseases and providing individualized and efficient treatment for patients are subjects we have been exploring. This article reviews the potential mechanism of mitophagy in gastrointestinal diseases with the hope of providing new ideas for diagnosis and treatment.

Therapeutic effects of curculigoside on cyclophosphamide-induced premature ovarian failure in mice

OBJECTIVE

The main purpose of this study was to elucidate the anti-apoptotic effects of curculigoside (CUR) on ovarian granulosa cells (GCs) in a mouse model of cyclophosphamide (CTX)-induced premature ovarian failure (POF).

METHOD

Intraperitoneal injection of CTX (100 mg/kg body weight) induced POF in mice. Thirty-six female mice were divided into six groups: blank group; POF model group; low-dose CUR group; medium-dose CUR group; high-dose CUR group; and estradiol benzoate group. Mice were orally administered for 28 consecutive days. Twenty-four hours after the completion of treatment, mice were weighed and euthanized, and blood was collected from the eyeball under anesthesia. The ovaries were surgically separated and weighed, and the ovarian index was calculated. Hematoxylin-eosin (HE) staining was used to observe follicular development and corpus luteum morphology in the ovaries. Serum levels of follicle stimulating hormone (FSH), anti-Müllerian hormone (AMH) and estradiol (E2) were measured. Superoxide dismutase (SOD) activity, glutathione peroxidase (GSH-Px) content and malondialdehyde (MDA) levels in ovarian tissue were determined. The GC apoptosis level was measured. Western blotting was used to detect protein expression levels of Beclin-1, LC3, P62, AKT, p-AKT, mTOR and p-mTOR in the ovaries.

RESULTS

The results showed that CUR can improve body weight and ovarian index; promote follicular development and reduce follicular atresia; improve FSH, AMH and E2 levels; downregulate MDA levels and restore antioxidant enzyme activity; inhibit the autophagy level; activate the AKT/mTOR signaling pathway; and alleviate GC apoptosis.

CONCLUSION

CUR improves POF by activating the AKT/mTOR signaling pathway, inhibiting autophagy and alleviating GC apoptosis.

Ghrelin in Focus: Dissecting Its Critical Roles in Gastrointestinal Pathologies and Therapies

This review elucidates the critical role of ghrelin, a peptide hormone mainly synthesized in the stomach in various gastrointestinal (GI) diseases. Ghrelin participates in diverse biological functions ranging from appetite regulation to impacting autophagy and apoptosis. In sepsis, it reduces intestinal barrier damage by inhibiting inflammatory responses, enhancing GI blood flow, and modulating cellular processes like autophagy and apoptosis. Notably, in inflammatory bowel disease (IBD), serum ghrelin levels serve as markers for distinguishing between active and remission phases, underscoring its potential in IBD treatment. In gastric cancer, ghrelin acts as an early risk marker, and due to its significant role in increasing the proliferation and migration of gastric cancer cells, the ghrelin-GHS-R axis is poised to become a target for gastric cancer treatment. The role of ghrelin in colorectal cancer (CRC) remains controversial; however, ghrelin analogs have demonstrated substantial benefits in treating cachexia associated with CRC, highlighting the therapeutic potential of ghrelin. Nonetheless, the complex interplay between ghrelin's protective and potential tumorigenic effects necessitates a cautious approach to its therapeutic application. In post-GI surgery scenarios, ghrelin and its analogs could be instrumental in enhancing recovery and reducing complications. This article accentuates ghrelin's multifunctionality, shedding light on its influence on disease mechanisms, including inflammatory responses and cancer progression, and examines its therapeutic potential in GI surgeries and disorders, advocating for continued research in this evolving field.

Induction mechanisms of autophagy and endoplasmic reticulum stress in intestinal ischemia-reperfusion injury, inflammatory bowel disease, and colorectal cancer

In recent years, the incidence of intestinal ischemia-reperfusion injury (II/RI), inflammatory bowel disease (IBD), and colorectal cancer (CRC) has been gradually increasing, posing significant threats to human health. Autophagy and endoplasmic reticulum stress (ERS) play important roles in II/RI. Damage caused by ischemia and cellular stress can activate ERS, which in turn initiates autophagy to clear damaged organelles and abnormal proteins, thereby alleviating ERS and maintaining the intestinal environment. In IBD, chronic inflammation damages intestinal tissues and activates autophagy and ERS. Autophagy is initiated by upregulating ATG genes and downregulating factors that inhibit autophagy, thereby clearing abnormal proteins, damaged organelles, and bacteria. Simultaneously, persistent inflammatory stimulation can also trigger ERS, leading to protein imbalance and abnormal folding in the ER lumen. The activation of ERS can maintain cellular homeostasis by initiating the autophagy process, thereby reducing inflammatory responses and cell apoptosis in the intestine. In CRC, excessive cell proliferation and protein synthesis lead to increased ERS. The activation of ERS, regulated by signaling pathways such as IRE1α and PERK, can initiate autophagy to clear abnormal proteins and damaged organelles, thereby reducing the negative effects of ERS. It can be seen that autophagy and ERS play a crucial regulatory role in the development of intestinal diseases. Therefore, the progress in targeted therapy for intestinal diseases based on autophagy and ERS provides novel strategies for managing intestinal diseases. In this paper, we review the advances in regulation of autophagy and ERS in intestinal diseases, emphasizing the potential molecular mechanisms for therapeutic applications.

Therapeutic effects and potential mechanisms of endoscopic submucosal injection of mesenchymal stem cells on chronic atrophic gastritis

Previous studies have demonstrated the rejuvenating and restorative actions of mesenchymal stem cells (MSCs) in multiple diseases, but their role in reversing chronic atrophic gastritis (CAG) is not well understood owing to their low efficiency in homing to the stomach. In this work, we investigated the therapeutic effect of umbilical cord-derived MSCs (UC-MSCs) on CAG by endoscopic submucosal injection and preliminarily explored possible mechanisms in vitro. MSCs and normal saline (NS) were injected into the submucosa of the stomach in randomly grouped CAG rabbits. Therapeutic effects on serum indices and histopathology of the gastric mucosa were analyzed in vivo at 30 and 60 days after MSCs injection. GES-1 cells were co-cultured with MSCs in vitro using a Transwell system and cell viability, proliferation, and migration ability were detected. Additionally, in view of the potential mechanisms, the relative protein expression levels of apoptosis, autophagy and inflammation in vitro were explored by Western Blotting. We found that submucosal injection of MSCs up-regulated serum indices (G-17, PGI and PGI/PGII) and alleviated histopathological damage to the gastric mucosa in CAG rabbits. Co-culture of GES-1 cells with MSCs improved cell viability, proliferation, and migration ability, while suppressing apoptosis. We also observed a reduction in the expression of apoptosis indicators, including Bax and cleaved caspase-3, in GES-1 cells after co-culture with MSCs in vitro. Our findings suggest that submucosal injection of MSCs is a promising approach for reversing CAG, and attenuating apoptosis plays a potential role in this process.

Electroacupuncture Alleviates Functional Constipation in Mice by Activating Enteric Glial Cell Autophagy via PI3K/AKT/mTOR Signaling

OBJECTIVE

To investigate autophagy-related mechanisms of electroacupuncture (EA) action in improving gastrointestinal motility in mice with functional constipation (FC).

METHODS

According to a random number table, the Kunming mice were divided into the normal control, FC and EA groups in Experiment I. The autophagy inhibitor 3-methyladenine (3-MA) was used to observe whether it antagonized the effects of EA in Experiment II. An FC model was established by diphenoxylate gavage. Then the mice were treated with EA stimulation at Tianshu (ST 25) and Shangjuxu (ST 37) acupoints. The first black stool defecation time, the number, weight, and water content of 8-h feces, and intestinal transit rate were used to assess intestinal transit. Colonic tissues underwent histopathological assessment, and the expressions of autophagy markers microtubule-associated protein 1 light chain 3 (LC3) and Beclin-1 were detected by immunohistochemical staining. The expressions of phosphoinositide 3-kinases (PI3K)-protein kinase B (AKT)-mammalian target of rapamycin (mTOR) signaling pathway members were investigated by Western blot and quantitative reverse transcription-polymerase chain reaction, respectively. The relationship between enteric glial cells (EGCs) and autophagy was observed by confocal immunofluorescence microscopy, localization analysis, and electron microscopy.

RESULTS

EA treatment shortened the first black stool defecation time, increased the number, weight, and water content of 8-h feces, and improved the intestinal transit rate in FC mice (P<0.01). In terms of a putative autophagy mechanism, EA treatment promoted the expressions of LC3 and Beclin-1 proteins in the colonic tissue of FC mice (P<0.05), with glial fibrillary acidic protein (GFAP) and LC3 significantly colocalized. Furthermore, EA promoted colonic autophagy in FC mice by inhibiting PI3K/AKT/mTOR signaling (P<0.05 or P<0.01). The positive effect of EA on intestinal motility in FC mice was blocked by 3-MA.

CONCLUSION

EA treatment can inhibit PI3K/AKT/mTOR signaling in the colonic tissues of FC mice, thereby promoting EGCs autophagy to improve intestinal motility.

Quercetin Ameliorates Lipopolysaccharide-Induced Duodenal Inflammation through Modulating Autophagy, Programmed Cell Death and Intestinal Mucosal Barrier Function in Chicken Embryos

Diarrhea has been a global health problem for centuries, and the treatment has become increasingly difficult duo to the antibiotics overuse and resistance. Quercetin is a common flavonoid of extracts of vegetables, fruits, and traditional Chinese herbs, however, the mechanism of quercetin alleviating LPS-induced duodenal inflammation remains elusive. Specific pathogen-free chicken embryos (n = 120) were allocated to groups including control, PBS with or without alcohol, LPS (125 ng/egg) with or without quercetin (10, 20, or 40 nmol/egg, respectively), and quercetin groups (10, 20, or 40 nmol/egg). Fifteen day-old embryonated eggs were inoculated with abovementioned solutions via the allantoic cavity. At embryonic day 19, the duodena of the embryos were collected for histopathological examination, RNA extraction and real-time polymerase chain reaction, immunohistochemical investigations, and Western blotting. The results demonstrated quercetin enhanced the inflammatory cell infiltration in the Peyer's patch of the intestinal mucosa after LPS induction. The LPS-induced expressions of these inflammation-related factors (TLR4, IL-1β, MMP3, MMP9, NFKB1, IFNγ, IL-8, IL-6) were completely blocked by quercetin. Quercetin also decreased the protein expression of TLR4, IL-1β, MMP3, and MMP9 after LPS induction. Quercetin could down-regulate autophagy gene expression (ATG5, LC3-1, LC3-2, and LKB1), and decreased the protein expression of ATG5, and LC3-1/LC3-2 after LPS induction. Quercetin treatment prevented LPS-induced increases of the gene expressions of programmed cell death factors (TNFα, Fas, CASP1, CASP3, CASP12, Drp1, and RIPK1); meanwhile, quercetin decreased the protein expression of CASP1 and CASP3 after LPS challenge. LPS reduced the gene expression of mucin 2, but upregulated the mRNA and protein expression of claudin 1, occludin, and ZO-1, and this was balanced by quercetin. This evidence suggests that quercetin can alleviate duodenal inflammation induced by LPS through modulating autophagy, programmed cell death, intestinal barrier function.

Autophagy in gastrointestinal cancers

Gastrointestinal cancers are a group of cancers occurred in gastrointestinal tissues with high morbidity and mortality rate. Although numerous studies were conducted on the investigation of gastrointestinal cancers, the real mechanisms haven’t been discovered, and no effective methods of prevention and treatment of gastrointestinal cancers have been developed. Autophagy, a vital catabolic process in organisms, have been proven to participate in various mechanisms and signaling pathways, thus producing a regulatory effect on various diseases. The role of autophagy in gastrointestinal cancers remains unclear due to its high complexity. In this review, firstly, the biological features of autophagy will be introduced. Secondly, the role of autophagy in three popular gastrointestinal cancers, namely esophageal cancer, gastric cancer, and colorectal cancer will be described and discussed by reviewing the related literature. We aimed to bring novel insights in exploring the real mechanisms for gastrointestinal cancers and developing effective and efficient therapeutic methods to treat gastrointestinal cancers.

Gliadin Peptide P31-43 Induces mTOR/NFkβ Activation and Reduces Autophagy: The Role of Lactobacillus paracasei CBA L74 Postbiotc

Celiac disease (CD) is an autoimmune disease characterized by an altered immune response stimulated by gliadin peptides that are not digested and cause damage to the intestinal mucosa. The aim of this study was to investigate whether the postbiotic Lactobacillus paracasei (LP) could prevent the action of gliadin peptides on mTOR, autophagy, and the inflammatory response. Most of the experiments performed were conducted on intestinal epithelial cells Caco-2 treated with a peptic-tryptic digest of gliadin (PTG) and P31-43. Furthermore, we pretreated the Caco-2 with the postbiotic LP before treatment with the previously described stimuli. In both cases, we evaluated the levels of pmTOR, p70S6k, and p4EBP-1 for the mTOR pathway, pNFkβ, and pERK for inflammation and LC 3 and p62 for autophagy. For autophagy, we also used immunofluorescence analysis. Using intestinal organoids derivate from celiac (CD) patients, we analyzed the effect of gliadin after postbiotic pretreatment with LP on inflammation marker NFkβ. Through these experiments, we showed that gliadin peptides are able to induce the increase of the inflammatory response in a more complex model of intestinal epithelial cells. LP postbiotic was able to induce autophagy in Caco-2 cells and prevent gliadin effects. In conclusion, postbiotic pretreatment with LP could be considered for in vivo clinical trials.

16S rRNA sequencing-based evaluation of the protective effects of Hua-Zhuo-Jie-Du on rats with chronic atrophic gastritis

Background

Disturbance of the intestinal flora is a pathogenic factor for chronic atrophic gastritis (CAG). Hua-Zhuo-Jie-Du (HZJD) has been shown to be an effective Chinese herbal preparation for treating CAG. However, the effects of HZJD on the intestinal flora of CAG is unclear. In this study, we probed the regulating effects of HZJD on intestinal microbes in CAG rats using 16S rRNA gene sequencing.

Methods

High-performance liquid chromatography (HPLC) analysis was used to perform quality control of HZJD preparations. We then administered 1-methyl-3-nitro-1-nitrosoguanidine (200 μg/ml) to Sprague–Dawley rats to establish a CAG model. HZJD and vitacoenzyme were administered orally to these rats over a 10 week period. Hematoxylin and eosin (H&E) staining was performed to observe the histopathology of CAG rats. A rarefaction curve, species accumulation curve, Chao1 index, and ACE index were calculated to assess the alpha diversity. Principal component analysis (PCA), non-metric multi-dimensional scaling (NMDS), and unweighted pair group method with arithmetic mean (UPGMA) were conducted to examine the beta diversity. The LEfSe method was used to identify differential bacteria. Differential function analysis used PCA based on KEGG function prediction.

Results

HPLC showed that our HZJD preparation method was feasible. H&E staining showed that HZJD significantly improved the pathological state of the gastric mucosa in CAG rats. The rarefaction curve and species accumulation curve showed that the sequencing data were reasonable. The Chao1 and ACE indices were significantly increased in CAG rats compared to the N group. Following HZJD and vitacoenzyme treatment, the Chao1 and ACE indices were decreased. PCA, NMDS, and UPGMA results showed that the M group was separated from the N, HZJD, and V groups, and LEfSe results showed that the relative abundance of Akkermansia, Oscillospira, Prevotella, and CF231 were significantly higher in the N group. Proteobacteria and Escherichia were significantly enriched in the M group, Allobaculum, Bacteroides, Jeotgalicoccus, Corynebacterium, and Sporosarcina were significantly enriched in the V group, and Firmicutes, Lactobacillus, and Turicibacter were significantly enriched in the HZJD group.

Conclusion

HZJD exhibited a therapeutic effect on the intestinal flora of CAG rats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-022-03542-z.

Therapeutic effects of placenta derived-, umbilical cord derived-, and adipose tissue derived-mesenchymal stem cells in chronic Helicobacter pylori infection: comparison and novel mechanisms

Supported with significant rejuvenating and regenerating actions of mesenchymal stem cells (MSCs) in various gastrointestinal diseases including Helicobacter pylori (H. pylori)-associated gastric diseases, we have compared these actions among placenta derived-MSCs (PD-MSCs), umbilical cord derived-MSCs (UC-MSCs), and adipose tissue derived-MSCs (AD-MSCs) and explored contributing genes implicated in rejuvenation of H. pylori-chronic atrophic gastritis (CAG) and tumorigenesis. In this study adopting H. pylori-initiated, high salt diet-promoted gastric carcinogenesis model, we have administered three kinds of MSCs around 15-18 weeks in H. pylori infected C57BL/6 mice and sacrificed at 24 and 48 weeks, respectively, in order to either assess the rejuvenating capability or anti-tumorigenesis. At 24 weeks, MSCs all led to significantly mitigated atrophic gastritis, for which significant inductions of autophagy, preservation of tumor suppressive 15-PGDH, attenuated apoptosis, and efficient efferocytosis was imposed with MSCs administration during atrophic gastritis. At 48 weeks, MSCs administered during H. pylori-associated atrophic gastritis afforded significant blocking the progression of CAG, as evidenced with statistically significant reduction in H. pylori-associated gastric tumor (p<0.05) accompanied with significant decreases in IL-1β, COX-2, STAT3, and NF-κB. Combined together with the changes of stanniocalcin-1 (STC-1), thrombospondin-1 (TSP-1), and IL-10 known as biomarkers reflecting stem cell activities at 48 weeks after H. pylori, PD-MSCs among MSCs afforded the best rejuvenating action against H. pylori-associated CAG via additional actions of efferocytosis, autophagy, and anti-apoptosis at 24 weeks. In conclusion, MSCs, especially PD-MSCs, exerted rejuvenating actions against H. pylori-associated CAG via anti-mutagenesis of IL-10, CD-36, ATG5 and cancer suppressive influences of STC-1, TSP-1, and 15-PGDH.

Autophagy and Digestive Disorders: Advances in Understanding and Therapeutic Approaches

The gastrointestinal (GI) tract is a series of hollow organs that is responsible for the digestion and absorption of ingested foods and the excretion of waste. Any changes in the GI tract can lead to GI disorders. GI disorders are highly prevalent in the population and account for substantial morbidity, mortality, and healthcare utilization. GI disorders can be functional, or organic with structural changes. Functional GI disorders include functional dyspepsia and irritable bowel syndrome. Organic GI disorders include inflammation of the GI tract due to chronic infection, drugs, trauma, and other causes. Recent studies have highlighted a new explanatory mechanism for GI disorders. It has been suggested that autophagy, an intracellular homeostatic mechanism, also plays an important role in the pathogenesis of GI disorders. Autophagy has three primary forms: macroautophagy, microautophagy, and chaperone-mediated autophagy. It may affect intestinal homeostasis, host defense against intestinal pathogens, regulation of the gut microbiota, and innate and adaptive immunity. Drugs targeting autophagy could, therefore, have therapeutic potential for treating GI disorders. In this review, we provide an overview of current understanding regarding the evidence for autophagy in GI diseases and updates on potential treatments, including drugs and complementary and alternative medicines.

The Ketogenic Diet Reduces the Harmful Effects of Stress on Gut Mitochondrial Biogenesis in a Rat Model of Irritable Bowel Syndrome

Functional alterations in irritable bowel syndrome have been associated with defects in bioenergetics and the mitochondrial network. Effects of high fat, adequate-protein, low carbohydrate ketogenic diet (KD) involve oxidative stress, inflammation, mitochondrial function, and biogenesis. The aim was to evaluate the KD efficacy in reducing the effects of stress on gut mitochondria. Newborn Wistar rats were exposed to maternal deprivation to induce IBS in adulthood. Intestinal inflammation (COX-2 and TRL-4); cellular redox status (SOD 1, SOD 2, PrxIII, mtDNA oxidatively modified purines); mitochondrial biogenesis (PPAR-γ, PGC-1α, COX-4, mtDNA content); and autophagy (Beclin-1, LC3 II) were evaluated in the colon of exposed rats fed with KD (IBD-KD) or standard diet (IBS-Std), and in unexposed controls (Ctrl). IBS-Std rats showed dysfunctional mitochondrial biogenesis (PPAR-γ, PGC-1α, COX-4, and mtDNA contents lower than in Ctrl) associated with inflammation and increased oxidative stress (higher levels of COX-2 and TLR-4, SOD 1, SOD 2, PrxIII, and oxidatively modified purines than in Ctrl). Loss of autophagy efficacy appeared from reduced levels of Beclin-1 and LC3 II. Feeding of animals with KD elicited compensatory mechanisms able to reduce inflammation, oxidative stress, restore mitochondrial function, and baseline autophagy, possibly via the upregulation of the PPAR-γ/PGC-1α axis.

Modeling Potential Autophagy Pathways in COVID-19 and Sarcoidosis

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and mainly affects the lungs. Sarcoidosis is an autoinflammatory disease characterized by the diffusion of granulomas in the lungs and other organs. Here, we discuss how the two diseases might involve some common mechanistic cellular pathways around the regulation of autophagy.