Inhibition of C3a/C3aR Axis in Diverse Stages of Ulcerative Colitis Affected the Prognosis of UC by Modulating the Pyroptosis and Expression of Caspase-11

Da-yuan-yin decoction alleviates ulcerative colitis by inhibiting complement activation, LPS-TLR4/NF-κB signaling pathway and NET formation

ETHNOPHARMACOLOGICAL RELEVANCE

Da-yuan-yin decoction (DYY) is a classical traditional Chinese medicine prescription for ulcerative colitis (UC).

AIM OF STUDY

This study explored the protective effects and mechanisms of DYY on UC.

MATERIALS AND METHODS

The mice were fed 2.5% dextran sulfate sodium (DSS) for 7 days to establish UC. On the second day, DYY (0.4 g/kg, 0.8 g/kg, 1.6 g/kg) was orally administered daily for 7 consecutive days. The colon tissues and serum were measured by histopathological examination and biochemical analysis.

RESULTS

DYY significantly reduced the disease activity index (DAI) and severity of colon shortening and alleviated pathological changes in the colon tissue. DYY restored the protein expression of intestinal tight junction (TJ) protein (ZO-1, occludin and claudin-3). DYY remarkably decreased the level of lipopolysaccharide (LPS), Lactic acid (LA), circulating free DNA (cfDNA), complement (C3, C3a, C3c, C3aR1, C5a and C5aR1) and regulated the levels of inflammatory cytokines in serum. DYY significantly inhibited the expressions of nuclear factor kappa-B p65 (NF-κB p65) and Toll-like receptor 4 (TLR4), citrullinated histone H3 (CitH3) and myeloperoxidase (MPO), reactive oxygen species (ROS) peptidylarginine deiminase 4 (PAD4) and CD 11b, the mRNA levels of PADI4, MPO and ELANE in colon tissues.

CONCLUSIONS

DYY significantly attenuated DSS-induced UC, which was related with regulating the inflammatory response by the inhibition of complement activation, the LPS-TLR4/NF-κB signaling pathway and neutrophil extracellular traps (NETs) formation. DYY is a potential therapeutic agent for UC.

Pyroptosis in health and disease: mechanisms, regulation and clinical perspective

Pyroptosis is a type of programmed cell death characterized by cell swelling and osmotic lysis, resulting in cytomembrane rupture and release of immunostimulatory components, which play a role in several pathological processes. Significant cellular responses to various stimuli involve the formation of inflammasomes, maturation of inflammatory caspases, and caspase-mediated cleavage of gasdermin. The function of pyroptosis in disease is complex but not a simple angelic or demonic role. While inflammatory diseases such as sepsis are associated with uncontrollable pyroptosis, the potent immune response induced by pyroptosis can be exploited as a therapeutic target for anti-tumor therapy. Thus, a comprehensive review of the role of pyroptosis in disease is crucial for further research and clinical translation from bench to bedside. In this review, we summarize the recent advancements in understanding the role of pyroptosis in disease, covering the related development history, molecular mechanisms including canonical, non-canonical, caspase 3/8, and granzyme-mediated pathways, and its regulatory function in health and multiple diseases. Moreover, this review also provides updates on promising therapeutic strategies by applying novel small molecule inhibitors and traditional medicines to regulate pyroptosis. The present dilemmas and future directions in the landscape of pyroptosis are also discussed from a clinical perspective, providing clues for scientists to develop novel drugs targeting pyroptosis.

Natural compounds target programmed cell death (PCD) signaling mechanism to treat ulcerative colitis: a review

Ulcerative colitis (UC) is a nonspecific inflammatory bowel disease characterized by abdominal pain, bloody diarrhea, weight loss, and colon shortening. However, UC is difficult to cure due to its high drug resistance rate and easy recurrence. Moreover, long-term inflammation and increased disease severity can lead to the development of colon cancer in some patients. Programmed cell death (PCD) is a gene-regulated cell death process that includes apoptosis, autophagy, necroptosis, ferroptosis, and pyroptosis. PCD plays a crucial role in maintaining body homeostasis and the development of organs and tissues. Abnormal PCD signaling is observed in the pathological process of UC, such as activating the apoptosis signaling pathway to promote the progression of UC. Targeting PCD may be a therapeutic strategy, and natural compounds have shown great potential in modulating key targets of PCD to treat UC. For instance, baicalin can regulate cell apoptosis to alleviate inflammatory infiltration and pathological damage. This review focuses on the specific expression of PCD and its interaction with multiple signaling pathways, such as NF-κB, Nrf2, MAPK, JAK/STAT, PI3K/AKT, NLRP3, GPX4, Bcl-2, etc., to elucidate the role of natural compounds in targeting PCD for the treatment of UC. This review used (ulcerative colitis) (programmed cell death) and (natural products) as keywords to search the related studies in PubMed and the Web of Science, and CNKI database of the past 10 years. This work retrieved 72 studies (65 from the past 5 years and 7 from the past 10 years), which aims to provide new treatment strategies for UC patients and serves as a foundation for the development of new drugs.

Revisiting the relationship between complement and ulcerative colitis

Ulcerative colitis (UC) is an inflammatory bowel disorder (IBD) characterized by relapsing chronic inflammation of the colon that causes continuous mucosal inflammation. The global incidence of UC is steadily increasing. Immune mechanisms are involved in the pathogenesis of UC, of which complement is shown to play a critical role by inducing local chronic inflammatory responses that promote tissue damage. However, the function of various complement components in the development of UC is complex and even paradoxical. Some components (e.g. C1q, CD46, CD55, CD59, and C6) are shown to safeguard the intestinal barrier and reduce intestinal inflammation, while others (e.g. C3, C5, C5a) can exacerbate intestinal damage and accelerate the development of UC. The complement system was originally thought to function primarily in an extracellular mode; however, recent evidence indicates that it can also act intracellularly as the complosome. The current study provides an overview of current studies on complement and its role in the development of UC. While there are few studies that describe how intracellular complement contributes to UC, we discuss potential future directions based on related publications. We also highlight novel methods that target complement for IBD treatment.

The Role of Caspase-11 and Pyroptosis in the Regulation of Inflammation in Peri-Implantitis

Peri-implantitis is an important cause of oral implant failure. In the past, TLR4 and TLR2 in the Toll-like family were generally considered as the key immune recognition receptors regulating peri-implantitis. However, under the guidance of this theory, there are still some unexplainable peri-implantitis symptoms. With the discovery of novel intracellular LPS receptor Caspase-11, a new understanding of inflammatory signaling and immune regulation in the development of peri-implantitis has been gained. However, the regulatory role of Caspase-11 in peri-implantitis and its crosstalk with the TLR4 pathway remain unclear. The therapeutic effect of drugs targeting Caspase-11 on peri-implantitis is still in its early stages. In view of this situation, this paper reviews the possible role of Caspase-11 in peri-implant inflammation, elaborated the entry process of LPS and the activation mechanism of Caspase-11, and analyzes the differences in Caspase-11 between commonly studied animals, mice and humans. The current research hotspots and challenges are also analyzed to provide new insights and ideas for researchers.

Regulatory Roles of Flavonoids in Caspase-11 Non-Canonical Inflammasome-Mediated Inflammatory Responses and Diseases

Inflammasomes are multiprotein complexes that activate inflammatory responses by inducing pyroptosis and secretion of pro-inflammatory cytokines. Along with many previous studies on inflammatory responses and diseases induced by canonical inflammasomes, an increasing number of studies have demonstrated that non-canonical inflammasomes, such as mouse caspase-11 and human caspase-4 inflammasomes, are emerging key players in inflammatory responses and various diseases. Flavonoids are natural bioactive compounds found in plants, fruits, vegetables, and teas and have pharmacological properties in a wide range of human diseases. Many studies have successfully demonstrated that flavonoids play an anti-inflammatory role and ameliorate many inflammatory diseases by inhibiting canonical inflammasomes. Others have demonstrated the anti-inflammatory roles of flavonoids in inflammatory responses and various diseases, with a new mechanism by which flavonoids inhibit non-canonical inflammasomes. This review discusses recent studies that have investigated the anti-inflammatory roles and pharmacological properties of flavonoids in inflammatory responses and diseases induced by non-canonical inflammasomes and further provides insight into developing flavonoid-based therapeutics as potential nutraceuticals against human inflammatory diseases.

Fucoidan mitigates gastric ulcer injury through managing inflammation, oxidative stress, and NLRP3-mediated pyroptosis

This study aimed to elucidate the gastro-protective effect of fucoidan against ethanol-induced gastric ulcer mediated via NLRP3-induced pyroptosis as an underlying mechanism, not yet assessed in prior research. Forty-eight male Albino mice were divided into six groups: Group I (normal control), group II (Ulcer/ethanol control), group III (Omeprazole + ethanol), group IV (fucoidan 25 mg + ethanol), group V (fucoidan 50 mg + ethanol) and group VI (fucoidan only). Fucoidan was administered orally for seven consecutive days followed by ulcer induction by a single oral dose of ethanol. Using colorimetric analysis, ELISA, qRT-PCR, histological assessment, and immunohistochemical studies, the results revealed that ethanol-induced ulcer exhibited an ulcer score of 42.5 ± 5.1 and a significant increase (p < 0.05) in malondialdehyde (MDA), nuclear factor kappa B (NF-κB), and interleukin 6 (IL-6) with a significant decrease in the gastro-protective mediators, prostaglandin E2 (PGE2), superoxide dismutase (SOD) and glutathione (GSH), accompanied with an increase in NLRP3, interleukin 1β (IL-1β), interleukin 18 (IL-18), caspase 1, caspase 11, gasdermin D, and toll-like receptor 4 (TLR4), compared with the normal control. Pre-treatment with fucoidan showed a comparable result with omeprazole. Additionally, pre-treatments elevated the levels of the gastro-protective mediators and lessened oxidative stress, relative to the positive control findings. Conclusively, fucoidan has a promising gastro-protective role by inhibiting inflammation and pyroptosis.

Echinacea purpurea (L.) Moench extract suppresses inflammation by inhibition of C3a/C3aR signaling pathway in TNBS-induced ulcerative colitis rats

ETHNOPHARMACOLOGICAL RELEVANCE

Echinacea purpurea (L.) Moench (EP) is a perennial herbaceous flowering plant, commonly known as purple conical flower. It was widely used to treat skin inflammation and gastrointestinal diseases.

AIM OF STUDY

Ulcerative colitis (UC) is a chronic and nonspecific inflammatory disease. Recent evidence shows that immune disorders are involved in the pathogenesis of UC. To evaluate the protective effect of Echinacea purpurea (L.) Moench exact (EE) on UC and explore the role of complement system in the treatment of UC.

MATERIALS AND METHODS

UC model was induced in rats by 2,4,6-trinitrobenzene sulfonic acid (TNBS), and then rats were administered with EE for 10 days. Collect colon tissues for analysis of relevant mechanisms.

RESULTS

EE could reduce the weight loss and diarrhea of UC rats. In addition, EE could improve the integrity of intestinal epithelial barrier in UC rats. EE inhibited the level of proinflammatory cytokines and promoted the antioxidation. Furthermore, EE suppressed the expression of C3aR, CFB, CD55, TLR4 and NLRP3.

CONCLUSION

These results indicate that EE may achieve therapeutic effect by inhibiting C3a/C3aR signal pathway, suggesting that EE may be used as a medicinal plant to alleviate UC.

The potential mechanism of huazhuojiedu decoction in the treatment of ulcerative colitis based on network pharmacology and experimental validation

Huazhuojiedu decoction (HZJDD), a traditional Chinese medicine prescription, has been clinically proven to be an effective treatment for ulcerative colitis (UC). However, the mechanism of HZJDD in the treatment of UC remains unclear. This study combined network pharmacology with experimental validation to explore the potential mechanism of HZJDD on UC. First, the relationship network diagrams between HZJDD and UC were established based on multiple databases. Then, the HZJDD-UC intersection genes target network was constructed and Gene Ontology-Biological processes (GO-BP) analysis was performed to discover the potential pharmacological mechanism. Finally, the results of GO-BP were verified in dextran sulfate sodium salt (DSS) induced UC rats. The network pharmacology results showed that 119 active components and 146 potential targets were screened for HZJDD, and six of the top 15 biological processes belonged to inflammatory response, cellular response to hypoxia, and cellular response to lipopolysaccharide (LPS). The GO-BP results indicated that the mechanism of HZJDD treatment of UC was related to inflammation, oxidative stress, and the regulation of LPS. Animal experiments showed that HZJDD could significantly reduce the disease activity index (DAI) score, improve colon length, and effectively repair the histomorphological and micromorphological changes in DSS-induced UC rats. Moreover, HZJDD reduced the expressions of CRP, TNF-α, IL-6, LPS, IL-1β, and IL-18; downregulated the activity of MDA; and upregulated the activities of CAT, GSH, and SOD in DSS-induced UC rats. Furthermore, HZJDD suppressed the expression of the NLRP3/caspase-1 signaling pathway at the gene and protein levels to inhibit pyroptosis. Network pharmacology and animal experiments showed that HZJDD exerted a therapeutic effect on DSS-induced UC rats by reducing inflammation, oxidative stress, and restraining the NLRP3/caspase-1 signaling pathway to inhibit pyroptosis.

The anti-alcoholism drug disulfiram effectively ameliorates ulcerative colitis through suppressing oxidative stresses-associated pyroptotic cell death and cellular inflammation in colonic cells

BACKGROUND

Oxidative stress, cell pyroptosis and inflammation are considered as important pathogenic factors for ulcerative colitis (UC) development, and the traditional anti-alcoholism drug disulfiram (DSF) has recently been reported to exert its regulating effects on all the above cellular functions, which makes DSF as ideal therapeutic agent for UC treatment, but this issue has not been fully studied.

METHODS

Dextran sulfate sodium (DSS)-induced animal models in C57BL/6J mice and lipopolysaccharide (LPS)-induced cellular models in colonic cell lines (HT-29 and Caco-2) for UC were respectively established. Cytokine secretion was determined by ELISA. Cell viability and proliferation were evaluated by MTT assay and EdU assay. Real-Time qPCR, Western Blot, immunofluorescent staining assay and immunohistochemistry (IHC) were employed to evaluate gene expressions. The correlations of the genes in the clinical tissues were analyzed by using the Pearson Correlation analysis.

RESULTS

DSF restrained oxidative stress, pyroptotic cell death and cellular inflammation in UC models in vitro and in vivo, and elimination of Reactive Oxygen Species (ROS) by N-acetyl-l-cysteine (NAC) rescued cell viability in LPS-treated colonic cells (HT-29 and Caco-2). Further experiments suggested that a glycogen synthase kinase-3β (GSK-3β)/Nrf2/NLRP3 signaling cascade played critical role in this process. Mechanistically, DSF downregulated GSK-3β and NLRP3, whereas upregulated Nrf2 in LPS-treated colonic cells. Also, the regulating effects of DSF on Nrf2 and NLRP3 were abrogated by upregulating GSK-3β. Moreover, upregulation of GSK-3β abolished the protective effects of DSF on LPS-treated colonic cells.

CONCLUSIONS

Taken together, data of this study indicated that DSF restrained oxidative damages-related pyroptotic cell death and inflammation via regulating the GSK-3β/Nrf2/NLRP3 pathway, leading to the suppression of LPS-induced UC development.

Inhibition of the C3a receptor attenuates sepsis-induced acute lung injury by suppressing pyroptosis of the pulmonary vascular endothelial cells

Acute lung injury (ALI) is the leading cause of bacterial sepsis-related death because of disrupted pulmonary endothelial barrier, resulting in protein-rich pulmonary oedema, an influx of pro-inflammatory cells and refractory hypoxaemia. Several studies have reported that C3a levels are significantly higher in organs with sepsis and their peripheral organs and are closely associated with organ dysfunction and poor prognosis in sepsis. However, the role of the C3a complement in sepsis ALI remains unclear. Therefore, this study aimed to investigate the important role and mechanism of C3a in preventing the occurrence of pyroptosis (a pro-inflammatory form of cell death) to protect the lung endothelial cells (ECs) in sepsis-induced ALI. A septic mouse model was established with cecal ligation and puncture (CLP), which demonstrated that C3a mediated EC pyroptosis through its C3aR receptor. Furthermore, inhibition of the C3a-C3aR axis could block both NLRP3/caspase-1 and caspase-11 pathways, thus preventing pulmonary EC from pyroptosis. These results indicate that inhibition of the C3A-C3AR complement axis can inhibit pulmonary vascular EC pyroptosis, a potential target for the treatment of ALI.

Complement induces podocyte pyroptosis in membranous nephropathy by mediating mitochondrial dysfunction

Podocyte damage mediated by in situ complement activation in the glomeruli is a key factor in the pathogenesis of membranous nephropathy (MN), but the molecular mechanism has not been fully elucidated. Pyroptosis is a special type of programmed cell death, mediate inflammatory response and induce tissue injury. However, it is not clear whether pyroptosis is involved in the development and progression of MN. Here, we report that pyroptosis plays an important role in promoting podocyte injury in MN. We first observed the occurrence of pyroptosis in the kidneys of MN patients and validated that complement stimulation triggered pyroptosis in podocytes and that inhibiting pyroptosis reversed complement-induced podocyte damage in vitro. In addition, stimulation of complement caused mitochondrial depolarization and reactive oxygen species (ROS) production in podocytes, and inhibition of ROS reversed complement-induced pyroptosis in podocytes. Interestingly, inhibition of pyroptosis in turn partially alleviated these effects. Furthermore, we also found the involvement of pyroptosis in the kidneys of passive Heymann nephritis (PHN) rats, and inhibitors of pyroptosis-related molecules relieved PHN-induced kidney damage in vivo. Our findings demonstrate that pyroptosis plays a critical role in complement-induced podocyte damage in MN and mitochondrial dysfunction is an important mechanism underlying this process. It provides new insight that pyroptosis may serve as a novel therapeutic target for MN treatment in future studies.

Network pharmacology for systematic understanding of Schisandrin B reduces the epithelial cells injury of colitis through regulating pyroptosis by AMPK/Nrf2/NLRP3 inflammasome

Ulcerative colitis (UC) is a chronic inflammatory disease with increasing incidence and prevalence in many countries. The purpose of this study is to explore the function of Schisandrin B and its underlying molecular mechanisms in colitis.

In this study, mice with colitis were induced by giving 2.0% dextran sulfate sodium (DSS, MP) in the drinking water for seven days. Furthermore, TCMSP server and GEO DataSets were used to analyze the mechanism of Schisandrin B in colitis.

It was found that Schisandrin B presented colitis in mice model. At the same time, Schisandrin B not only reduced inflammation in vivo and vitro model of colitis, but also suppressed the nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 (NLRP3) inflammasome in vivo and vitro model of colitis. In addition, Schisandrin B induced AMP-activated protein kinase (AMPK) / Nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway in model of colitis, and regulated AMPK protein at 316 sites. The inhibition of AMPK reduced the anti-inflammation effects of Schisandrin B on NLRP3 inflammasome. Apart from that, Schisandrin B decreased reactive oxygen species (ROS)-induced mitochondrial damage and reduced epithelial cells damage of colitis through regulating pyroptosis.

Collectively, our novel findings for first time showed that, Schisandrin B suppressed NLRP3 inflammasome activation-mediated interleukin-1beta (IL-1β) level and pyroptosis in intestinal epithelial cells of colitis model through the activation of AMPK/Nrf2 dependent signaling-ROS-induced mitochondrial damage, which may be a significant therapeutic approach in the treatment of acute colitis.

Pyroptosis by caspase-11 inflammasome-Gasdermin D pathway in autoimmune diseases

Inflammasomes are a group of supramolecular complexes primarily comprise a sensor, adaptor protein and an effector. Among them, canonical inflammasomes are assembled by one specific pattern recognition receptor, the adaptor protein apoptosis-associated speck-like protein containing a CARD and procaspase-1. Murine caspase-11 and its human ortholog caspase-4/5 are identified as cytosolic sensors which directly responds to LPS. Once gaining access to cytosol, LPS further trigger inflammasome activation in noncanonical way. Downstream pore-forming Gasdermin D is a pyroptosis executioner. Emerging evidence announced in recent years demonstrate the vital role played by caspase-11 non-canonical inflammasome in a range of autoimmune diseases. Pharmacological ablation of caspase-11 and its related effector results in potent therapeutic effects. Though recent advances have highlighted the potential of caspase-11 as a drug target, the understanding of caspase-11 molecular activation and regulation mechanism remains to be limited and thus hampered the discovery and progression of novel inhibitors. Here in this timeline review, we explored how caspase-11 get involved in the pathogenesis of autoimmune diseases, we also collected the reported small-molecular caspase-11 inhibitors. Moreover, the clinical implications and therapeutic potential of caspase-11 inhibitors are discussed. Targeting non-canonical inflammasomes is a promising strategy for autoimmune diseases treatment, while information about the toxicity and physiological disposition of the promising caspase-11 inhibitors need to be supplemented before they can be translated from bench to bedside.