Coexistence of apoptosis, pyroptosis, and necroptosis pathways in celiac disease

From Inflammasomes to Pyroptosis: Molecular Mechanisms in Chronic Intestinal Diseases - Opportunity or Challenge?

Pyroptosis is a unique form of programmed cell death characterized by intense inflammation. It involves the activation of Gasdermin proteins, which form membrane pores, leading to rapid cell rupture and the release of inflammatory molecules. Unlike other types of cell death, pyroptosis has distinct activation mechanisms and plays a complex role in chronic intestinal diseases, including inflammatory bowel disease, intestinal fibrosis, chronic infectious enteritis, and colorectal cancer. This review comprehensively examines how pyroptosis influences disease development and progression while exploring the therapeutic potential of targeting pyroptosis-related pathways. Moreover, the complex interplay between gut microbiota and pyroptosis is summarized, highlighting its critical role in the pathogenesis of chronic intestinal disorders. A deeper understanding of pyroptosis-related mechanisms in these diseases may provide valuable insights for future research and contribute to the development of innovative therapeutic strategies in gastroenterology.

Neurotensin receptor agonist PD149163 modulates LPS-induced enterocyte apoptosis by downregulating TNFR pathway and executioner caspase 3 in endotoxemic mice: insights from in vivo and in silico study

This study was designed to evaluate the dose-dependent efficacy of neurotensin receptor-1 (NTSR1) agonist PD149163 in the amelioration of the lipopolysaccharide (LPS)-induced apoptosis in the gastrointestinal tract (GIT) of mice. PD149163 is an analogue of NTS, a GIT tri-decapeptide with anti-inflammatory and anti-oxidative effects. Swiss-albino mice (female/8 weeks/25 ± 2.5 g) were divided into six groups: control; LPS, LPS + PD149163L, and LPS + PD149163H groups were treated with LPS (0.2 μmol/L/kgBW; 5 days), followed by exposure of PD149163 to LPS + PD149163L (10.6 μmol/L/kgBW), and LPS + PD149163H (21.2 μmol/L/kgBW) for 28 days. OnlyPD149163L (10.6 μmol/L/kgBW) and onlyPD149163H (21.2 μmol/L/kgBW) groups were maintained for 28 days. Both the LPS and PD149163 were given intraperitoneally. PD149163 treatment for 4 weeks alleviated the LPS-induced enterocyte apoptosis in a dose-dependent manner. LPS-induced excessive levels of caspase-3, tumour necrosis factor-α, and leptin (biomarkers of LPS-induced apoptosis) in plasma were decreased by PD149163H treatment. Moreover, LPS-induced gut oxidative stress was ameliorated by PD149163H supplementation, as evidenced by the decreased content of malondialdehyde, lipid-hydroperoxide and increased level of superoxide-dismutase, catalase. Furthermore, PD149163H mediated elevation of the plasma anti-apoptotic protein (B-cell leukaemia/lymphoma-2) along with the NTS level contributed to the modulation of LPS-induced enterocyte apoptosis, reflected in histopathology. In vivo results were substantiated with in silico molecular docking analysis that predicted the binding of PD149163-TLR4 complex, suggesting that PD149163 can act as a TLR4 modulator and inhibit the activation of TLR4. The role of PD149163 in ameliorating GIT apoptosis by its anti-apoptotic and antioxidative effects is suggested. Further research may provide significant insights into the therapeutic intervention of PD149163 in apoptosis-related diseases of GIT.

Inflammasomes in Intestinal Disease: Mechanisms of Activation and Therapeutic Strategies

NOD-like receptors (NLRs) are a family of cytosolic pattern recognition receptors (PRRs) implicated in the innate immune sensing of pathogens and damage signals. NLRs act as sensors in multi-protein complexes called inflammasomes. Inflammasome activity is necessary for the maintenance of intestinal homeostasis, although their aberrant activation contributes to the pathogenesis of several gastrointestinal diseases. In this review, we summarize the main features of the predominant types of inflammasomes involved in gastrointestinal immune responses and their implications in intestinal disease, including Irritable Bowel Syndrome (IBS), Inflammatory Bowel Disease (IBD), celiac disease, and Colorectal Cancer (CRC). In addition, we report therapeutic discoveries that target the inflammasome pathway, highlighting promising novel therapeutic strategies in the treatment of intestinal diseases. Collectively, our understanding of the mechanisms of intestinal inflammasome activation and their interactions with other immune pathways appear to be not fully elucidated. Moreover, the clinical relevance of the efficacy of inflammasome inhibitors has not been evaluated. Despite these limitations, a greater understanding of the effectiveness, specificity, and reliability of pharmacological and natural inhibitors that target inflammasome components could be an opportunity to develop new therapeutic options for the treatment of intestinal disease.

Oxysophocarpine Prevents the Glutamate-Induced Apoptosis of HT-22 Cells via the Nrf2/HO-1 Signaling Pathway

Oxysophocarpine (OSC), a quinolizidine alkaloid, shows neuroprotective potential, though its mechanisms are unclear. The aim of the present study was to investigate the neuroprotective effects of OSC through the nuclear factor erythroid 2-related factor 2 (Nrf2)/ heme oxygenase-1 (HO-1) signaling pathway using the HT-22 cell line. Assessments of cell viability were conducted utilizing the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Assessments of oxidative stress (OS) were conducted through the quantification of reactive oxygen species (ROS). The integrity of the mitochondrial membrane potential (MMP) was scrutinized using fluorescent probe technology. Apoptosis levels were quantified using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. The trafficking of Nrf2 within the cell nucleus was examined through immunofluorescence analysis. Furthermore, Western blotting (WB) was applied to evaluate the expression levels of proteins implicated in apoptosis and the Nrf2/HO-1 pathway. To further probe the influence of OSC on the overexpression of antioxidant enzymes, cells were subjected to transfection with HO-1 siRNA. The results showed that OSC inhibited glutamate-induced OS, as evidenced by reduced cell viability and ROS levels. Furthermore, the apoptotic condition induced by glutamate in HT-22 cells was significantly reduced following OSC treatment. More interestingly, the Nrf2/HO-1 signaling pathway was upregulated following OSC treatment. These results suggest that OSC can exert neuroprotective effects by regulating the Nrf2/HO-1 pathway to inhibit neuronal cell apoptosis, potentially aiding in the treatment of neurodegenerative diseases.

Specific deletion of Mettl3 in IECs triggers the development of spontaneous colitis and dysbiosis of T lymphocytes in mice

The enzymatic core component of m6A writer complex, Mettl3, plays a crucial role in facilitating the development and progress of gastric and colorectal cancer (CRC). However, its underlying mechanism in regulating intestinal inflammation remains unclear and poorly investigated. First, the characteristics of Mettl3 expression in inflammatory bowel diseases (IBD) patients were examined. Afterward, we generated the mice line with intestinal epithelial cells (IECs)-specific deletion of Mettl3 verified by various experiments. We continuously recorded and compared the physiological status including survival rate etc. between the two groups. Subsequently, we took advantage of staining assays to analyze mucosal damage and immune infiltration of Mettl3WT and Mettl3KO primary IECs. Bulk RNA sequencing was used to pursuit the differential expression of genes (DEGs) and associated signaling pathways after losing Mettl3. Pyroptosis-related proteins were to determine whether cell death was caused by pyroptosis. Eventually, CyTOF was performed to probe the difference of CD45+ cells, especially CD3e+ T-cell clusters after losing Mettl3. In IBD patients, Mettl3 was highly expressed in the inner-nucleus of IECs while significantly decreased upon acute intestinal inflammation. IECs-specific deletion of Mettl3 KO mice triggered a wasting phenotype and developed spontaneous colitis. The survival rate, body weight, and intestinal length observed from 2 to 8 weeks of Mettl3KO mice were significantly lower than Mettl3WT mice. The degree of mucosal damage and immune infiltration in Mettl3KO were even more serious than in their WT littermate. Bulk RNA sequencing demonstrated that DEGs were dramatically enriched in NOD-signaling pathways due to the loss of Mettl3. The colonic epithelium was more prone to pyroptosis after losing Mettl3. Subsequently, CyTOF revealed that T cells have altered significantly in Mettl3KO. Furthermore, there was abnormal proliferation of CD4+ T and markedly exhaustion of CD8 + T in Mettl3KO mice. In severe IBD patients, Mettl3 is located in the inner-nucleus of IECs and declined when intestinal inflammation occurs. Subsequently, Mettl3 prevented mice from developing colitis.

Duodenal mucosa of untreated celiac disease patients has altered expression of the GAS6 and PROS1 and the negative regulator tyrosine kinase TAM receptors subfamily

Celiac disease (CD) is an immune-driven disease characterized by tissue damage in the small intestine of genetically-susceptible individuals. We evaluated here a crucial immune regulatory pathway involving TYRO3, AXL, and MERTK (TAM) receptors and their ligands PROS1 and GAS6 in duodenal biopsies of controls and CD patients. We found increased GAS6 expression associated with downregulation of PROS1 and variable TAM receptors levels in duodenum tissue of CD patients. Interestingly, CD3+ lymphocytes, CD68+, CD11c+ myeloid and epithelial cells, showed differential expressions of TAM components comparing CD vs controls. Principal component analysis revealed a clear segregation of two groups of CD patients based on TAM components and IFN signaling. In vitro validation demonstrated that monocytes, T lymphocytes and epithelial cells upregulated TAM components in response to IFN stimulation. Our findings highlight a dysregulated TAM axis in CD related to IFN signaling and contribute to a deeper understanding of the pathophysiology of CD.