[Inflammatory bowel diseases and inflammasome]

Ziziphus jujuba Miller Ethanol Extract Restores Disrupted Intestinal Barrier Function via Tight Junction Recovery and Reduces Inflammation

Inflammatory bowel disease (IBD) is a chronic inflammatory condition caused by the disruption of the intestinal barrier. The intestinal barrier is maintained by tight junctions (TJs), which sustain intestinal homeostasis and prevent pathogens from entering the microbiome and mucosal tissues. Ziziphus jujuba Miller (Z. jujuba) is a natural substance that has been used in traditional medicine as a therapy for a variety of diseases. However, in IBD, the efficacy of Z. jujuba is unknown. Therefore, we evaluated ZJB in Caco2 cells and a dextran sodium sulfate (DSS)-induced mouse model to demonstrate its efficacy in IBD. Z. jujuba extracts were prepared using 70% ethanol and were named ZJB. ZJB was found to be non-cytotoxic and to have excellent antioxidant effects. We confirmed its anti-inflammatory properties via the down-regulation of inflammatory factors, including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). To evaluate the effects of ZJB on intestinal barrier function and TJ improvement, the trans-epithelial electrical resistance (TEER) and fluorescein isothiocyanate-dextran 4 kDa (FITC-Dextran 4) permeability were assessed. The TEER value increased by 61.389% and permeability decreased by 27.348% in the 200 μg/mL ZJB group compared with the 50 ng/mL IL-6 group after 24 h. Additionally, ZJB alleviated body weight loss, reduced the disease activity index (DAI) score, and induced colon shortening in 5% DSS-induced mice; inflammatory cytokines, tumor necrosis factor (TNF)-α, and interleukin (IL)-6 were down-regulated in the serum. TJ proteins, such as Zonula occludens (ZO)-1 and occludin, were up-regulated by ZJB in an impaired Caco2 mouse model. Additionally, according to the liquid chromatography results, in tandem with mass spectrometry (LC-MS/MS) analysis, seven active ingredients were detected in ZJB. In conclusion, ZJB down-regulated inflammatory factors, protected intestinal barrier function, and increased TJ proteins. It is thus a safe, natural substance with the potential to be used as a therapeutic agent in IBD treatment.

Mechanism by which oleracein E alleviates TNBS-induced ulcerative colitis

OBJECTIVE

This study aimed to investigate the effect of oleracein E (OE) in improving 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced ulcerative colitis (UC).

METHODS

Lipopolysaccharide (LPS) was used to induce a UC cell model, and TNBS was used to induce a UC rat model. ELISA was performed to assess the levels of inflammatory factors (IL-1β, TNF-α, and IL-6). Moreover, the activities of catalase (CAT), myeloperoxidase (MPO), and malonaldehyde (MDA) were detected by kits. Western blotting was performed to assess related proteins of the Nrf2/HO-1 signaling pathway, tight junction protein (ZO-1, Occludin, and claudin-2) expression levels, and apoptosis-related proteins (Bcl2, Bax, and cleaved caspase 3). Flow cytometry was used to analyze ROS levels. The morphology of colon tissues and the apoptosis of cells were detected by HE and TUNEL staining, respectively.

RESULTS

OE significantly increased the activity of CAT and decreased the activity of MPO in LPS-induced Caco-2 cells and TNBS-induced UC rats. However, the levels of IL-1β, IL-6, and TNF-α were markedly reduced both in vivo and in vitro. In addition, OE significantly increased the levels of Nrf2/HO-1 signaling pathway-related proteins and tight junction proteins and inhibited cell apoptosis. HE staining showed that OE significantly decreased the severity of acute TNBS-induced colitis in rats.

CONCLUSION

OE may exert a regulatory effect on ameliorating intestinal barrier injury and reducing inflammation and oxidative stress levels by activating the Nrf2/HO-1 pathway.

CY-09 Alleviates the Depression-like Behaviors via Inhibiting NLRP3 Inflammasome-Mediated Neuroinflammation in Lipopolysaccharide-Induced Mice

Depression is a serious mental illness, mainly characterized as large mood swings and sleep, diet, and cognitive function disorders. NLPR3, one of the inflammasomes that can be activated by a variety of stimuli to promote the maturation and secretion of pro-inflammatory cytokines, has been considered to be involved in the pathophysiology of depression. In this study, the putative role of CY-09, a selective and direct inhibitor of NLRP3, was evaluated in the lipopolysaccharide (LPS)-induced mice. The results of the study indicated that CY-09 significantly decreased the levels of NLRP3 in the hippocampus of LPS-induced mice. In addition, CY-09 increased the sucrose preference and shortened the immobility time in LPS-induced mice, suggesting the antidepressant-like effects of inhibiting NLRP3 inflammasome. Biochemical analysis showed that LPS significantly activated the NLRP3/ASC/cytokine signaling pathway and caused microglial activation, while CY-09 prevented the changes. Moreover, CY-09 increased the brain-derived neurotrophic factor (BDNF) only in microglia but not in the whole hippocampus. Meanwhile, CY-09 did not promote neurogenesis in the hippocampus of LPS mice. In conclusion, the results of the study showed that the antidepressant-like effects of NLRP3 inhibitor CY-09 were mediated by alleviating neuroinflammation in microglia and independent of the neurotrophic function in the hippocampus.

Emerging mechanisms of pyroptosis and its therapeutic strategy in cancer

Pyroptosis, a type of inflammatory programmed cell death, is triggered by caspase cleavage of gasdermin family proteins. Based on accumulating evidence, pyroptosis is closely associated with tumour development, but the molecular mechanism underlying pyroptosis activation and the signalling pathways regulated by pyroptosis remain unclear. In this review, we first briefly introduce the definition, morphological characteristics, and activation pathways of pyroptosis and the effect of pyroptosis on anticancer immunity. Then we review recent progress concerning the complex role of pyroptosis in various tumours. Importantly, we summarise various FDA-approved chemotherapy drugs or natural compounds that exerted antitumor properties by inducing pyroptosis of cancer cells. Moreover, we also focus on the current application of nanotechnology-induced pyroptosis in tumour therapy. In addition, some unsolved problems and potential future research directions are also raised.

Esculetin inhibits the pyroptosis of microvascular endothelial cells through NF-κB /NLFP3 signaling pathway

The effect of Esculetin on pyroptosis and its possible mechanism in endothelium were explored. 10 μg/mL LPS and 0.5 mM ATP were used to stimulate the rat intestinal microvascular endothelial cells. Then add different concentrations of Esculetin (20μM, 40 μM) to the culture medium containing LPS and ATP culturing for 24 h. The expression of p-NF-κB p65, NF-κB p65, I-κB, p-I-κB, NLRP3, ASC, caspase-1, and gasdermin-D were detected by Western blot, and the release level of IL-18 and IL-1β were measured by ELISA. The NLRP3 inhibitor MCC950 was used at the concentration of 10 μM for 4 h to disentangle the potential mechanism of the influence of Esculetin on pyroptosis. In our experiments, the expression of gasdermin-d and important proteins of NF-κB and NLRP3 signaling pathways were inhibited by Esculetin. Besides, Esculetin also attenuated the morphological changes like swelling rupture and pores on the membrane caused by pyroptosis thereby protecting cells from being damaged by pyroptosis. Combining with the effect of Esculetin on proteins above and its protective effect on cell morphology, we believe that Esculetin has an anti-pyroptosis effect. The inhibiting pyroptosis effects mentioned above are similar to MCC950, which means the anti-pyroptosis effects of Esculetin are associated with the NLRP3 signaling pathway. In conclusion, Esculetin inhibits the pyroptosis of microvascular endothelial cells through the NF-κB/NLFP3 signaling pathway and is expected to be conducive in treating pyroptosis-related diseases.

IL-1β and the Intestinal Epithelial Tight Junction Barrier

The intestinal epithelial tight junction (TJ) barrier controls the paracellular permeation of contents from the intestinal lumen into the intestinal tissue and systemic circulation. A defective intestinal TJ barrier has been implicated as an important pathogenic factor in inflammatory diseases of the gut including Crohn's disease, ulcerative colitis, necrotizing enterocolitis, and celiac disease. Previous studies have shown that pro-inflammatory cytokines, which are produced during intestinal inflammation, including interleukin-1β (IL-1β), tumor necrosis factor-α, and interferon-γ, have important intestinal TJ barrier-modulating actions. Recent studies have shown that the IL-1β-induced increase in intestinal TJ permeability is an important contributing factor of intestinal inflammation. The IL-1β-induced increase in intestinal TJ permeability is mediated by regulatory signaling pathways and activation of nuclear transcription factor nuclear factor-κB, myosin light chain kinase gene activation, and post-transcriptional occludin gene modulation by microRNA and contributes to the intestinal inflammatory process. In this review, the regulatory role of IL-1β on intestinal TJ barrier, the intracellular mechanisms that mediate the IL-1β modulation of intestinal TJ permeability, and the potential therapeutic targeting of the TJ barrier are discussed.

Gut Microbiota-Mediated Transformation of Coptisine Into a Novel Metabolite 8-Oxocoptisine: Insight Into Its Superior Anti-Colitis Effect

Coptisine (COP) is a bioactive isoquinoline alkaloid derived from Coptis Chinemsis Franch, which is traditionally applied for the management of colitis. However, the blood concentration of COP was extremely low, and its gut microbiota-mediated metabolites were thought to contribute to its prominent bioactivities. To comparatively elucidate the protective effect and underlying mechanism of COP and its novel gut microbiota metabolite (8-oxocoptisine, OCOP) against colitis, we used dextran sulfate sodium (DSS) to induce colitis in mice. Clinical symptoms, microscopic alternation, immune-inflammatory parameters for colitis were estimated. The results indicated that OCOP dramatically ameliorated disease activity index (DAI), the shortening of colon length and colonic histopathological deteriorations. OCOP treatment also suppressed the mRNA expression and release of inflammatory mediators (TGF-β, TNF-α, IL-6, IL-18, IL-1β and IFN-γ) and elevated the transcriptional and translational levels of anti-inflammatory cytokine (IL-10) as well as the mRNA expression levels of adhesion molecules (ICAM-1 and VCAM-1). Besides, the activation of NF-κB pathway and NLRP3 inflammasome was markedly inhibited by OCOP. Furthermore, OCOP displayed superior anti-colitis effect to COP, and was similar to MSZ with much smaller dosage. Taken together, the protective effect of OCOP against DSS-induced colitis might be intimately related to inhibition of NF-κB pathway and NLRP3 inflammasome. And the findings indicated that OCOP might have greater potential than COP to be further exploited as a promising candidate in the treatment of colitis.

Walnut oil alleviates DSS-induced colitis in mice by inhibiting NLRP3 inflammasome activation and regulating gut microbiota

Ulcerative colitis (UC) has become a global disease and closely related to changes in intestinal oxidative stress, inflammatory factors and gut microbiota. Furthermore, the NLRP3 inflammasome activation is a key cause in the pathogenesis of dextran sulfate sodium (DSS)-induced colitis. Recent data showed the potential antioxidative and anti-inflammatory advantage of walnut oil, which widely used in traditional medicine and has become a dietary supplement for some patients. Therefore, we investigated whether walnut oil exerts an anti-inflammatory effect on DSS-induced colitis mice by targeting NLRP3 inflammasome and gut microbiota. Our data showed that walnut oil ameliorated the pathological morphology, decreased the reactive oxygen species (ROS) production and pro-inflammatory cytokines release, down-regulated the related gene proteins expression of NLRP3/ASC/Caspase-1 inflammatory pathway, inhibited apoptosis, shifted from more pathogens towards probiotics, and increased the levels of short-chain fatty acids (SCFAs) in DSS-induced damaging process. Collectively, our study concludes that walnut oil exerts anti-inflammatory effect on DSS-induced colitis in mice by inhibiting the NLRP3 inflammasome activation and modulating gut microbiota, and may be a prominent functional food candidate for UC treatment.

NLRP3 deletion inhibits inflammation-driven mouse lung tumorigenesis induced by benzo(a)pyrene and lipopolysaccharide

Background

Inflammatory micro-environment has been proposed to play a critical role in lung tumorigenesis. NLRP3 is known as an intracellular receptor involving inflammation and has been reported which is increasingly associated with tumor development, but the role in inflammation-driven lung cancer has not been fully clarified. In this study, we investigated whether lipopolysaccharide (LPS)-induced pulmonary inflammation could contribute to lung tumorigenesis induced by benzo(a)pyrene [B(a)p] in C57BL/6J mice and the role of NLRP3 in the pathogenesis.

Methods

NLRP3−/− mice and C57BL/6J mice (wide-type, WT) were instilled intratracheally with B(a)p (1 mg/mouse) once a week for 4 times [the week of the last time of B(a)p treatment named Week 0], and mice were then instilled intratracheally with LPS at Week 3, 2.5 μg/mouse, once every three weeks for 5 times. At Week 30, the incidence, number, size and histopathology of lung tumor were analyzed.

Results

Mice exposed to B(a)p or B(a)p plus LPS could induce lung tumors, whereas LPS or vehicles treatment could not induce lung tumorigenesis. In WT mice, B(a)p plus LPS exposure significantly increased tumor incidence, mean tumor count and tumor size of visible tumors of lungs compared with B(a)p treatment alone, and NLRP3 deletion inhibited lung tumorigenesis induced by B(a)p or B(a)p plus LPS. Histopathological examination found LPS-induced pulmonary inflammatory changes enhanced lung tumorigenesis induced by B(a)p in WT mice, deletion of NLRP3 improved the inflammatory changes induced by LPS and the number and size of pathological tumor nests induced by B(a)p or B(a)p plus LPS. In addition, we found B(a)p treatment and B(a)p plus LPS treatment predominately induced the development of adenoma.

Conclusion

LPS enhanced B(a)p-induced lung tumorigenesis in WT and NLRP3−/− mice of C57BL/6J strain, and NLRP3 deletion inhibits lung tumorigenesis induced by B(a)p or B(a)p plus LPS.

Structural characteristics and hepatoprotective potential of Aralia elata root bark polysaccharides and their effects on SCFAs produced by intestinal flora metabolism

The structural characteristics of the polysaccharides from Aralia elata root barks (AERP) were systematically investigated by FT-IR, HPSEC-ELSD and colorimetric methods as well as by GCMS based monosaccharide compositions, Smith degradations, and methylation analysis. The result showed average molecular weights of AERP were between 42.7 kDa and 93.9 kDa. AERP was composed of Ara, Rha, GlcA, Man, Glc, and Gal in a molar ratio of 22.2: 10.3: 8.1: 32.7: 5.7: 21.2 along with a small number of sulfate (3.38%) and acetyl (4.87%) groups. The abundant glycosidic linkages of Man, Ara, Gal, and Rha were observed as more than 90% of all the monosaccharides detected. Studies to evaluate hepatoprotective potentials of AERP showed that they had potent hepatoprotective effects in vivo in carbon tetrachloride-induced acute liver injury (CIALI) in mice by histopathological evaluation, biochemical examinations and ELISA assays. GCMS was further used to determine the effects of AERP on the chemical profiles of nine common short-chain fatty acids (SCFAs) produced by intestinal flora metabolism in CIALI mice. These findings not only provide novel insights into the pharmacological actions of AERP on the protection from CIALI in mice, but they also demonstrate that determining SCFA profiles by targeted GC-MS metabolomics is an effective technique to investigate the molecular mechanisms of the effects of plant polysaccharides on intestinal flora metabolism.

New Perspectives on the Potential Role of Aquaporins (AQPs) in the Physiology of Inflammation

Aquaporins (AQPs) are emerging, in the last few decades, as critical proteins regulating water fluid homeostasis in cells involved in inflammation. AQPs represent a family of ubiquitous membrane channels that regulate osmotically water flux in various tissues and sometimes the transport of small solutes, including glycerol. Extensive data indicate that AQPs, working as water channel proteins, regulate not only cell migration, but also common events essential for inflammatory response. The involvement of AQPs in several inflammatory processes, as demonstrated by their dysregulation both in human and animal diseases, identifies their new role in protection and response to different noxious stimuli, including bacterial infection. This contribution could represent a new key to clarify the dilemma of host-pathogen communications, and opens up new scenarios regarding the investigation of the modulation of specific AQPs, as target for new pharmacological therapies. This review provides updated information on the underlying mechanisms of AQPs in the regulation of inflammatory responses in mammals and discusses the broad spectrum of options that can be tailored for different diseases and their pharmacological treatment.

Activation of NLRP3 Inflammasome in Inflammatory Bowel Disease: Differences Between Crohn's Disease and Ulcerative Colitis

BACKGROUND

NLRP3 inflammasome is a multimolecular cytosol complex that, when activated, contributes to the cleavage of pro-interleukin (IL)-1β to IL-1β.

AIMS

To investigate NLRP3 inflammasome activation in inflammatory bowel disease.

METHODS

Peripheral blood mononuclear cells from Crohn's disease (CD), ulcerative colitis (UC) patients and controls were stimulated with LPS in the absence or presence of MSU. After incubation, concentrations of IL-1β, IL-6, and TNFα were measured in cell supernatants and concentration of pro-IL-1β was measured in cell lysates. NLRP3 activation was defined as more than 30% increase in IL-1β production after MSU addition. In separate experiments, PBMCs were lysed for RNA isolation transcripts of IL-1β, TNFα, NLRP3, and CASP1 were measured by RT-PCR. DNA was isolated from CD patients for ATG16L1 gene genotyping.

RESULTS

NLRP3 inflammasome was activated in 60% of CD patients compared to 28.6% of controls (p = 0.042); no significant difference was detected between UC and controls. Among UC patients, NLRP3 activation was associated (p = 0.008) with long-standing disease (>1.5 years). IL-1β levels were significantly higher in CD patents in comparison with controls (p = 0.032). No difference was detected in the levels of IL-6, TNFα, pro-IL-1β and in the numbers IL-1β, TNFα, NLRP3, and CASP1 transcripts among groups. IL-1β production was similar between carriers of wild-type and of SNP alleles of the rs2241880.

CONCLUSIONS

NLRP3 inflammasome is activated in CD patients and in UC patients with long-standing disease.

Human hepatocytes express absent in melanoma 2 and respond to hepatitis B virus with interleukin-18 expression

Absent in melanoma 2 (AIM2) is a recently recognized cytoplasmic receptor which could sense cytoplasmic double-stranded DNA (dsDNA). After AIM2 detects the presence of parasitic nucleic acids (dsDNA) derived from invasive bacteria or viral genomes (for example, vaccinia virus and cytomegalovirus) within infected cells, AIM2 inflammasome could be formed. The formed AIM2 inflammasome could induce innate immune response and increase expressions of IL-1β and IL-18. Hepatitis B virus (HBV) is a hepatotropic, non-cytopathic double-stranded DNA virus. The immune response to viral antigens or virus is thought to be responsible for both liver damage and viral clearance in patients with HBV infection. However, there are no reports about whether AIM2 inflammasome exists in hepatocytes. In the present study, we investigated the presence and activity of AIM2 inflammasome in human hepatocytes. We found that AIM2 was expressed in cytoplasm of hepatocytes, and IL-18 expression was increased after AIM2 sensed HBV in hepatocytes in vitro. These results showed that AIM2 inflammasome was active in hepatocytes. We also found that hepatic AIM2 expression of chronic hepatitis B (CHB) patients was higher than that of controls. Hepatic AIM2 expression levels were positively correlated to the severity of liver inflammation. IL-18 is already considered to be associated with hepatic injury during HBV infection. In conclusion, we, therefore, believe that AIM2 inflammasome in hepatocytes might play an important role in the development and maintenance of HBV-related hepatitis.

[Roles of enteric microbial composition and metabolism in health and diseases]

A complex microbiota colonizes mucosal layers in different regions of the human gut. In the healthy state, the microbial communities provide nutrients and energy to the host via fermentation of non-digestible dietary components in the large intestine. In contrast, they can play roles in inflammation and infection, including gastrointestinal diseases and metabolic syndrome such as obesity. However, because of the complexity of the microbial community, the functional connections between the enteric microbiota and metabolism are less well understood. Nevertheless, major progress has been made in defining dominant bacterial species, community profiles, and systemic characteristics that produce stable microbiota beneficial to health, and in identifying their roles in enteric metabolism. Through studies in both mice and humans, we are recently in a better position to understand what effect the enteric microbiota has on the metabolism by improving energy yield from food and modulating dietary components. Achieving better knowledge of this information may provide insights into new possibilities that reconstitution of enteric microbiota via diet can provide the maintenance of healthy state and therapeutic/preventive strategies against metabolic syndrome such as obesity. This review focuses on enteric microbial composition and metabolism on healthy and diseased states.

A novel pathway by which the environmental toxin 4-Nonylphenol may promote an inflammatory response in inflammatory bowel disease

Background 4-Nonylphenol is a ubiquitous environmental toxin that is formed as a byproduct in the manufacturing and/or sewage treatment of regular household items. Previous work in our lab has implicated 4-NP in the progression of autoimmune diseases such as inflammatory bowel disease in which macrophages mistakenly attack the intestinal linings, causing chronic inflammation. Several key pro-and anti-inflammatory molecules have been shown to be involved in the manifestation of this disease, including IL-23A, COX-2, IL-8, TLR-4, and IL-10. Material and Methods 4-NP's effects on these known mediators of IBD were effectively analyzed using a novel model for IBD, by which 4-NP may promote an inflammatory response. Data were collected using DNA Microarray, RT-PCR, and ELISA, after 48 hour treatment of U937 histiocytic lymphocyte cells and COLO320DM human intestinal epithelial cells with 1 nM and 5 nM concentrations of 4-NP. Results Significant dysregulation of the expression of both pro- and anti-inflammatory genes was observed in U937 cells that would promote and prolong inflammation. However, TLR-4, IL-8, and COX-2 gene expressions showed unprecedented effects in COLO320DM cells suggesting that these genes mediate apoptotic processes within the gastrointestinal tract. Conclusions Overall, our results suggest that 4-NP administration engenders immune responses linked to apoptotic processes via dysregulation of macrophage signaling. In sum, 4-NP appears to increases the risk of developing inflammatory bowel disease by promoting or prolonging adverse progression of inflammation in the gastrointestinal tract.