NLRP3 inflammasome has a protective effect against oxazolone-induced colitis: a possible role in ulcerative colitis

Gut instinct: harnessing the power of probiotics to tame pathogenic signaling pathways in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease (IBD) marked by persistent inflammation of the mucosal lining of the large intestine, leading to debilitating symptoms and reduced quality of life. Emerging evidence suggests that an imbalance of the gut microbiota plays a crucial role in UC pathogenesis, and various signaling pathways are implicated in the dysregulated immune response. Probiotics are live microorganisms that confer health benefits to the host, have attracted significant attention for their potential to restore gut microbial balance and ameliorate inflammation in UC. Recent studies have elucidated the mechanisms by which probiotics modulate these signaling pathways, often by producing anti-inflammatory molecules and promoting regulatory immune cell function. For example, probiotics can inhibit the nuclear factor-κB (NF-κB) pathway by stabilizing Inhibitor of kappa B alpha (IκBα), dampening the production of proinflammatory cytokines. Similarly, probiotics can modulate the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway, suppressing the activation of STAT1 and STAT3 and thus reducing the inflammatory response. A better understanding of the underlying mechanisms of probiotics in modulating pathogenic signaling pathways in UC will pave the way for developing more effective probiotic-based therapies. In this review, we explore the mechanistic role of probiotics in the attenuation of pathogenic signaling pathways, including NF-κB, JAK/STAT, mitogen-activated protein kinases (MAPKs), Wnt/β-catenin, the nucleotide-binding domain (NOD)-, leucine-rich repeat (LRR)- and pyrin domain-containing protein 3 (NLRP3) inflammasome, Toll-like receptors (TLRs), interleukin-23 (IL-23)/IL-17 signaling pathway in UC.

Role of inflammation and evidence for the use of colchicine in patients with acute coronary syndrome

Acute Coronary Syndrome (ACS) significantly contributes to cardiovascular death worldwide. ACS may arise from the disruption of an atherosclerotic plaque, ultimately leading to acute ischemia and myocardial infarction. In the pathogenesis of atherosclerosis, inflammation assumes a pivotal role, not solely in the initiation and complications of atherosclerotic plaque formation, but also in the myocardial response to ischemic insult. Acute inflammatory processes, coupled with time to reperfusion, orchestrate ischemic and reperfusion injuries, dictating infarct magnitude and acute left ventricular (LV) remodeling. Conversely, chronic inflammation, alongside neurohumoral activation, governs persistent LV remodeling. The interplay between chronic LV remodeling and recurrent ischemic episodes delineates the progression of the disease toward heart failure and cardiovascular death. Colchicine exerts anti-inflammatory properties affecting both the myocardium and atherosclerotic plaque by modulating the activity of monocyte/macrophages, neutrophils, and platelets. This modulation can potentially result in a more favorable LV remodeling and forestalls the recurrence of ACS. This narrative review aims to delineate the role of inflammation across the different phases of ACS pathophysiology and describe the mechanistic underpinnings of colchicine, exploring its purported role in modulating each of these stages.

Protective effects of sinomenine against dextran sulfate sodium-induced ulcerative colitis in rats via alteration of HO-1/Nrf2 and inflammatory pathway

BACKGROUND

Dextran Sulfate Sodium (DSS) induces ulcerative colitis (UC), a type of inflammatory bowel disease (IBD) that leads to inflammation, swelling, and ulcers in the large intestine. The aim of this experimental study is to examine how sinomenine, a plant-derived alkaloid, can prevent or reduce the damage caused by DSS in the colon and rectum of rats.

MATERIAL AND METHODS

Induction of ulcerative colitis (UC) in rats was achieved by orally administering a 2% Dextran Sulfate Sodium (DSS) solution, while the rats concurrently received oral administrations of sinomenine and sulfasalazine. The food, water intake was estimated. The body weight, disease activity index (DAI), colon length and spleen index estimated. Antioxidant, cytokines, inflammatory parameters and mRNA expression were estimated. The composition of gut microbiota was analyzed at both the phylum and genus levels in the fecal samples obtained from all groups of rats.

RESULTS

Sinomenine treatment enhanced the body weight, colon length and reduced the DAI, spleen index. Sinomenine treatment remarkably suppressed the level of NO, MPO, ICAM-1, and VCAM-1 along with alteration of antioxidant parameters such as SOD, CAT, GPx, GR and MDA. Sinomenine treatment also decreased the cytokines like TNF-α, IL-1, IL-1β, IL-6, IL-10, IL-17, IL-18 in the serum and colon tissue; inflammatory parameters viz., PAF, COX-2, PGE2, iNOS, NF-κB; matrix metalloproteinases level such as MMP-1 and MMP-2. Sinomenine significantly (P < 0.001) enhanced the level of HO-1 and Nrf2. Sinomenine altered the mRNA expression of RIP1, RIP3, DRP3, NLRP3, IL-1β, caspase-1 and IL-18. Sinomenine remarkably altered the relative abundance of gut microbiota like firmicutes, Bacteroidetes, F/B ratio, Verrucomicrobia, and Actinobacteria.

CONCLUSION

The results clearly indicate that sinomenine demonstrated a protective effect against DSS-induced inflammation, potentially through the modulation of inflammatory pathways and gut microbiota.

Management of ulcerative colitis by dichloroacetate: Impact on NFATC1/NLRP3/IL1B signaling based on bioinformatics analysis combined with in vivo experimental verification

The inflammatory response in ulcerative colitis (UC) could be relieved by the conventional immunomodulatory agents; 5-aminosalicylic acid, corticosteroids, or azathioprine. However, the low remission rates and the intolerance to these agents necessitate investigation of gene expression signature in UC that could influence the therapeutic efficacy of drugs, as well as the interference with persistence genes by novel therapeutic option. Three microarray datasets (GSE66407, GSE38713 and GSE14580) from the NCBI-GEO database were utilized. Differentially expressed genes between samples of patients with UC and healthy ones were analyzed using R software. In addition, in vivo study using oxazolone-induced UC in BALB/c mice was carried out to investigate the proposed therapeutic efficacy of dichloroacetate (DCA). The bioinformatics analysis revealed the persistence of NLRP3, NFATC1, and IL1B in UC despite treatment with common therapeutic agents. DCA administration to oxazolone-treated mice showed remarkable interference with those persistence genes. Western blotting analysis for NLRP3, NFATC1, nuclear/total NF-κB, and cleaved caspase-1 revealed the ability of DCA to reduce the expression levels of these proteins in oxazolone-treated mice. Additionally, the inflammatory cytokines IL-1β and IL-13 were reduced in colonic tissue by DCA treatment. The therapeutic efficacy of DCA was further confirmed by the apparent reduction in histopathological scoring, disease activity index, and the normalization of colon length. Therefore, DCA could be suggested as a novel and promising therapeutic option in UC based on its ability to interfere with the persistence of NFATC1/NLRP3/IL1B signaling. That merits further safety/toxicological pre-clinical assessment and update of bioavailability/metabolism data prior to clinical investigation.

Exploring the role of IL-1β in inflammatory bowel disease pathogenesis

Interleukin 1β (IL-1β) is a significant mediator of inflammation and tissue damage in IBD. The balance between IL-1β and its endogenous inhibitor-IL-1Ra-, plays a critical role in both initiation and regulation of inflammation. However, the precise role of IL-1β as a causative factor in IBD or simply a consequence of inflammation remains unclear. This review summarizes current knowledge on the molecular and cellular characteristics of IL-1β, describes the existing evidence on the role of this cytokine as a modulator of intestinal homeostasis and an activator of inflammatory responses, and also discusses the role of microRNAs in the regulation of IL-1β-related inflammatory responses in IBD. Current evidence indicates that IL-1β is involved in several aspects during IBD as it greatly contributes to the induction of pro-inflammatory responses through the recruitment and activation of immune cells to the gut mucosa. In parallel, IL-1β is involved in the intestinal barrier disruption and modulates the differentiation and function of T helper (Th) cells by activating the Th17 cell differentiation, known to be involved in the pathogenesis of IBD. Dysbiosis in the gut can also stimulate immune cells to release IL-1β, which, in turn, promotes inflammation. Lastly, increasing evidence pinpoints the central role of miRNAs involvement in IL-1β-related signaling during IBD, particularly in the maintenance of homeostasis within the intestinal epithelium. In conclusion, given the crucial role of IL-1β in the promotion of inflammation and immune responses in IBD, the targeting of this cytokine or its receptors represents a promising therapeutic approach. Further research into the IL-1β-associated post-transcriptional modifications may elucidate the intricate role of this cytokine in immunomodulation.

Dandelion polysaccharide treatment protects against dextran sodium sulfate-induced colitis by suppressing NF-κB/NLRP3 inflammasome-mediated inflammation and activating Nrf2 in mouse colon

The treatment of ulcerative colitis (UC) is still an intractable medical problem. Polysaccharides are promising candidates for the treatment of UC and have received widespread attention in recent years. The objective of this study was to explore the protective effect and underlying mechanism of dandelion polysaccharide (DP) on dextran sulfate sodium (DSS)-induced colitis in mice. Our results showed that oral administration of DP could dramatically alleviate colonic lesions, as evidenced by reduced DAI scores, shortening of colon length, and ameliorating pathologic abnormalities in colons. Additionally, the expressions of pro-inflammatory factors (TNF-α, IL-1β, and IL-6) and the infiltration of inflammation-regulation cells, marked by myeloperoxidase and F4/80, were also inhibited after DP treatment. Moreover, DP treatment also markedly suppressed the nuclear translocation of NF-κB-p65 and the activation of the NLRP3 inflammasome. Furthermore, DP also activated the Nrf2/HO-1 pathway and reduced the oxidative stress induced by DSS. Overall, these results suggest that DP could be a promising novel therapeutic approach for the treatment of UC.

A randomized, double-blind phase 1b study evaluating the safety, tolerability, pharmacokinetics and pharmacodynamics of the NLRP3 inhibitor selnoflast in patients with moderate to severe active ulcerative colitis

BACKGROUND

The NLRP3 inflammasome drives release of pro-inflammatory cytokines including interleukin (IL)-1β and IL-18 and is a potential target for ulcerative colitis (UC). Selnoflast (RO7486967) is an orally active, potent, selective and reversible small molecule NLRP3 inhibitor. We conducted a randomized, placebo-controlled Phase 1b study to assess the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics (PD) of selnoflast.

METHODS

Nineteen adults with previous diagnosis of UC and current active moderate to severe disease were randomized 2:1 to selnoflast or placebo for 7 days. A dose of 450 mg QD (once daily) was selected to achieve 90% IL-1β inhibition in plasma and colon tissue. Consecutive blood, sigmoid colon biopsies and stool samples were analyzed for a variety of PD markers. Safety and PK were also evaluated.

RESULTS

Selnoflast was well-tolerated. Plasma concentrations increased rapidly after oral administration, reaching Tmax 1 h post-dose. Mean plasma concentrations stayed above the IL-1β IC90 level throughout the dosing interval (mean Ctrough on Day 1 and Day 5: 2.55 μg/mL and 2.66 μg/mL, respectively). At steady state, post-dose selnoflast concentrations in sigmoid colon (5-20 μg/g) were above the IC90 . Production of IL-1β was reduced in whole blood following ex vivo stimulation with lipopolysaccharide (LPS) (in the selnoflast arm). No changes were observed in plasma IL-18 levels. There were no meaningful differences in the expression of an IL-1-related gene signature in sigmoid colon tissue, and no differences in the expression of stool biomarkers.

CONCLUSIONS

Selnoflast was safe and well-tolerated. Selnoflast 450 mg QD achieved plasma and tissue exposure predicted to maintain IL-1β IC90 over the dosing interval. However, PD biomarker results showed no robust differences between treatment arms, suggesting no major therapeutic effects are to be expected in UC. The limitations of this study are its small sample size and indirect assessment of the effect on IL-1β in tissue.

TRIAL REGISTRATION

ISRCTN16847938.

The 'speck'-tacular oversight of the NLRP3-pyroptosis pathway on gastrointestinal inflammatory diseases and tumorigenesis

The NLRP3 inflammasome is an intracellular sensor and an essential component of the innate immune system involved in danger recognition. An important hallmark of inflammasome activation is the formation of a single supramolecular punctum, known as a speck, per cell, which is the site where the pro-inflammatory cytokines IL-1β and IL-18 are converted into their bioactive form. Speck also provides the platform for gasdermin D protein activation, whose N-terminus domain perforates the plasma membrane, allowing the release of mature cytokines alongside with a highly inflammatory form of cell death, namely pyroptosis. Although controlled NLRP3 inflammasome-pyroptosis pathway activation preserves mucosal immunity homeostasis and contributes to host defense, a prolonged trigger is deleterious and could lead, in genetically predisposed subjects, to the onset of inflammatory bowel disease, including Crohn's disease and ulcerative colitis, as well as to gastrointestinal cancer. Experimental evidence shows that the NLRP3 inflammasome has both protective and pathogenic abilities. In this review we highlight the impact of the NLRP3-pyroptosis axis on the pathophysiology of the gastrointestinal tract at molecular level, focusing on newly discovered features bearing pro- and anti-inflammatory and neoplastic activity, and on targeted therapies tested in preclinical and clinical trials.

Treatment of Ulcerative Colitis by Cationic Liposome Delivered NLRP3 siRNA

Purpose

The abnormal activation of NLRP3 inflammasome is related to the occurrence and development of ulcerative colitis (UC). However, the ideal drug and delivery system remain important factors limiting the targeting of NLRP3 inflammasome in UC therapy. Gene therapy by delivering siRNA is effective in treating various diseases. Therefore, delivering siNLRP3 using an ideal vector for UC treatment is necessary.

Materials and Methods

Nanoparticles delivering siNLRP3 were developed based on cationic liposome (CLP/siNLRP3). Their ability to inhibit NLRP3 inflammasome activation was monitored using Western blot (WB) and Enzyme-linked Immunosorbent Assay (ELISA). The ASC oligomerization in LPS-primed peritoneal macrophages (PMs) was detected by WB and immunofluorescence. Moreover, we assessed the role of CLP/siNLRP3 on dextran sodium sulfate (DSS)-induced UC by examining NLRP3 levels, pro-inflammatory cytokines expression, and disease-associated index (DAI). Flow cytometry (FCM) was used to detect the contents of macrophages and T cells. Finally, we assessed the safety of CLP/siNLRP3.

Results

The prepared CLP was spherical, with a small particle size (94 nm) and low permeability. The CLP could efficiently protect siNLRP3 from degradation and then deliver siNLRP3 into PMs, inhibiting NLRP3 inflammasome activation. Also, the CLP/siNLRP3 could inhibit the secretion of mature IL-1β and IL-18 from PMs, thereby achieving a favorable anti-inflammation effect. In vivo, CLP/siNLRP3 could effectively alleviate intestinal injury in UC mice, which was attributed to down-regulating levels of IL-1β and IL-18, inhibiting infiltration of macrophages and other immune cells, and the polarization of M1 macrophages. Finally, pathological testing of tissue sections and blood biochemical tests showed no significant toxic effects of CLP/siNLRP3.

Conclusion

We introduced a prospective approach for the efficient delivery of siRNA in vitro and in vivo with high safety and stability, which was found to have great potential in treating NLRP3-driven diseases in an RNA-silencing manner.

Pien Tze Huang attenuated acetaminophen-induced liver injury by autophagy mediated-NLRP3 inflammasome inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

Pien Tze Huang is a classic traditional Chinese medicinal product, used for inflammatory diseases as stated in Chinese Pharmacopoeia. In particular, it is effective in treating liver diseases and pro-inflammatory conditions. Acetaminophen (APAP) is a widely used analgesic drug, but its over-dose is associated with acute liver failure where the clinical approved antidote treatment is limited. Inflammation has been considered as one of the therapeutic targets against APAP-induced liver injury.

AIM OF THE STUDY

We aimed to explore the therapeutic potential of Pien Tze Huang tablet (PTH) on protecting liver against APAP-induced liver injury through its strong anti-inflammatory pharmacological action.

MATERIALS AND METHODS

Wild-type C57BL/6 mice were given PTH (75, 150 and 300 mg/kg) by oral gavage 3 days before the APAP injection (400 mg/kg). The protective effect of PTH was assessed by aspartate aminotransferase (AST) and alanine transaminase (ALT) levels and pathological staining. The mechanisms underlying PTH's hepatoprotective effects were investigated in nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) knock-out (NLRP3^-/-), over expression NLRP3 (oe-NLRP3) mice, and wild-type mice with the injection of autophagy inhibitor (3-methyladenine, 3-MA).

RESULTS

APAP-exposed mice resulted in evident liver injury which was evidenced by hepatic necrosis and elevated levels of AST and ALT in the wild-type C57BL/6 mice. PTH dose-dependently reduced ALT, AST and upregulated autophagy activity. In addition, PTH significantly reduced elevated levels of proinflammatory cytokines and NLRP3 inflammasome. The liver protective effect of PTH (300 mg/kg) was still obvious in the oe-NLRP3 mice, however, it became insignificant in the NLRP3^-/- mice. When PTH (300 mg/kg) was co-treated with 3-MA to the wild-type C57BL/6 mice, the NLRP3 inhibition were reversed when autophagy was blocked.

CONCLUSION

PTH exerted a beneficial effect in protecting liver against APAP-induced liver injury. The underlying molecular mechanism was associated with the NLRP3 inflammasome inhibition which was likely driven by the upregulated autophagy activity. Our study underpins the traditional use of PTH in protecting liver through its anti-inflammatory action.

The NLRP3 inflammasome: contributions to inflammation-related diseases

The NOD-like receptor protein 3 (NLRP3) inflammasome is a protein complex that regulates innate immune responses by activating caspase-1 and the inflammatory cytokines interleukin (IL)-1β and IL-18. Multiple studies have demonstrated the importance of the NLRP3 inflammasome in the development of immune and inflammation-related diseases, including arthritis, Alzheimer's disease, inflammatory bowel disease, and other autoimmune and autoinflammatory diseases. This review first explains the activation and regulatory mechanism of the NLRP3 inflammasome. Secondly, we focus on the role of the NLRP3 inflammasome in various inflammation-related diseases. Finally, we look forward to new methods for targeting the NLRP3 inflammasome to treat inflammation-related diseases, and provide new ideas for clinical treatment.

Pulsatilla chinensis saponins improve SCFAs regulating GPR43-NLRP3 signaling pathway in the treatment of ulcerative colitis

ETHNOPHARMACOLOGICAL RELEVANCE

Pulsatilla decoction has been extensively used to treat ulcerative colitis (UC) in recent years. Pulsatilla chinensis saponin (PRS), the active ingredient of its monarch medicine Pulsatilla chinensis (Bunge) Regel, plays a crucial role in the treatment of UC, but its specific mechanism of action has not been fully elucidated.

AIM OF THE STUDY

This study aims to investigate the protective effect and possible mechanism of PRS on DSS-induced ulcerative colitis in rats.

MATERIALS AND METHODS

In this study, the DSS-induced colitis model was used to explore the metabolism and absorption of PRS under UC, detect the content of short-chain fatty acids (SCFAs) in colon tissue, the expression of receptor G Protein-Coupled Receptor 43 (GPR43) protein and inflammasome NLRP3, and observe the expression level of IL-1β, IL-6 and TNF-α in colon tissue. The protective effect of the PRS was also observed.

RESULTS

It was found that in the UC group, the absorption rate and extent of drugs increased, and the elimination was accelerated. Compared with the control group, PRS increased the content of short-chain fatty acids (SCFAs) in colon tissue, promoted the expression of SCFAs receptor GPR43 protein, inhibited the activation of the NLRP3 inflammasome, and decreased the content of IL-1β, IL-6 and TNF-α. PRS protects the colon in DSS-induced inflammatory bowel disease by increasing the content of SCFAs, promoting the expression of GPR43 protein, inhibiting the activation of the NLRP3 inflammasome, and reversing the increase in IL-1β, IL-6 and TNF-α levels.

CONCLUSIONS

PRS can increase the content of colonic SCFAs, activate the GPR43-NLRP3 signaling pathway, and reduce the levels of pro-inflammatory cytokines, thereby improving the symptoms of DSS-induced colitis.

Inhibition of CD82 improves colitis by increasing NLRP3 deubiquitination by BRCC3

CD82 is a transmembrane protein that is involved in cancer suppression and activates immune cells; however, information on the NLRP3 inflammasome is limited. Herein, we show that although CD82 suppressed the activation of the NLRP3 inflammasome in vivo and in vitro, CD82 deficiency decreased the severity of colitis in mice. Furthermore, two binding partners of CD82, NLRP3 and BRCC3, were identified. CD82 binding to these partners increased the degradation of NLRP3 by blocking BRCC3-dependent K63-specific deubiquitination. Previous studies have shown that CD82-specific bacteria in the colon microbiota called Bacteroides vulgatus (B. vulgatus) regulated the expression of CD82 and promoted the activation of the NLRP3 inflammasome. Accordingly, we observed that B. vulgatus administration increased mouse survival by mediating CD82 expression and activating NLRP3 in mice with colitis. Overall, this study showed that CD82 suppression reduced the pathogenesis of colitis by elevating the activation of the NLRP3 inflammasome through BRCC3-dependent K63 deubiquitination. Based on our findings, we propose that B. vulgatus is a novel therapeutic candidate for colitis.

A Protective Role of NOD2 on Oxazolone-induced Intestinal Inflammation Through IL-1β-mediated Signalling Pathway

BACKGROUND AND AIMS

NOD2 has emerged as a critical player in the induction of both Th1 and Th2 responses for potentiation and polarisation of antigen-dependent immunity. Loss-of-function mutations in the NOD2-encoding gene and deregulation of its downstream signalling pathway have been linked to Crohn's disease. Although it is well documented that NOD2 is capable of sensing bacterial muramyl dipeptide, it remains counter-intuitive to link development of overt intestinal inflammation to a loss of bacterial-induced inflammatory response. We hypothesised that a T helper bias could also contribute to an autoimmune-like colitis different from inflammation that is fully fledged by Th1 type cells.

METHODS

An oedematous bowel wall with a mixed Th1/Th2 response was induced in mice by intrarectal instillation of the haptenating agent oxazolone. Survival and clinical scoring were evaluated. At several time points after instillation, colonic damage was assessed by macroscopic and microscopic observations. To evaluate the involvement of NOD2 in immunochemical phenomena, quantitative polymerase chain reaction [PCR] and flow cytometry analysis were performed. Bone marrow chimera experimentation allowed us to evaluate the role of haematopoietic/non-hematopoietic NOD2-expressing cells.

RESULTS

Herein, we identified a key regulatory circuit whereby NOD2-mediated sensing of a muramyl dipeptide [MDP] by radio-resistant cells improves colitis with a mixed Th1/Th2 response that is induced by oxazolone. Genetic ablation of either Nod2 or Ripk2 precipitated oxazolone colitis that is predominantly linked to a lack of interferon-gamma. Bone marrow chimera experiments revealed that inactivation of Nod2 signalling in non-haematopoietic cells is causing a biased M1-M2 polarisation of macrophages and a decreased frequency of splenic regulatory T cells that correlates with an impaired activation of CD4 + T cells within mesenteric lymph nodes. Mechanistically, mice were protected from oxazolone-induced colitis upon administration of MDP in an interleukin-1- and interleukin-23-dependent manner.

CONCLUSIONS

These findings indicate that Nod2 signalling may prevent pathological conversion of T helper cells for maintenance of tissue homeostasis.

An IBD-associated pathobiont synergises with NSAID to promote colitis which is blocked by NLRP3 inflammasome and Caspase-8 inhibitors

Conflicting evidence exists on the association between consumption of non-steroidal anti-inflammatory drugs (NSAIDs) and symptomatic worsening of inflammatory bowel disease (IBD). We hypothesized that the heterogeneous prevalence of pathobionts [e.g., adherent-invasive Escherichia coli (AIEC)], might explain this inconsistent NSAIDs/IBD correlation. Using IL10^-/- mice, we found that NSAID aggravated colitis in AIEC-colonized animals. This was accompanied by activation of the NLRP3 inflammasome, Caspase-8, apoptosis, and pyroptosis, features not seen in mice exposed to AIEC or NSAID alone, revealing an AIEC/NSAID synergistic effect. Inhibition of NLRP3 or Caspase-8 activity ameliorated colitis, with reduction in NLRP3 inflammasome activation, cell death markers, activated T-cells and macrophages, improved histology, and increased abundance of Clostridium cluster XIVa species. Our findings provide new insights into how NSAIDs and an opportunistic gut-pathobiont can synergize to worsen IBD symptoms. Targeting the NLRP3 inflammasome or Caspase-8 could be a potential therapeutic strategy in IBD patients with gut inflammation, which is worsened by NSAIDs.

NLRP3 inflammasome activation By 17β-estradiol is a potential therapeutic target in hepatocellular carcinoma treatment

Hepatocellular carcinoma (HCC) is one of the most common cancers worldwide, and it mostly arises as a consequence of persistent chronic inflammation. Recently, NLRP3 inflammasome has caught the attention of many research groups due to its involvement in different types of cancer. However, its direct role in HCC remains elusive. Our study aimed to evaluate the role of NLRP3 inflammasome and pyroptosis in HCC and to clarify the potential mechanism by which 17β-estradiol (E2) can be used as a protective factor against HCC. NLRP3, caspase-1 (CASP1) as well as gasdermin-D (GSDMD) mRNA expression levels were assessed in human HCC tissues and adjacent non-cancerous liver tissues. Also, HepG2 HCC cells were cultured and treated with E2, followed by detection of the mRNA levels of these three genes. Our results revealed that NLRP3, CASP1, and GSDMD mRNA expressions were significantly lower in HCC tissues than in controls, and this under-expression was closely correlated with advanced HCC stages and grades. In contrast, HepG2 HCC cells displayed significantly higher expression levels of NLRP3 inflammasome components and GSDMD in the two E2-treated groups compared to the untreated group. Also, NLRP3, CASP1, and GSDMD mRNA expression levels were positively correlated with each other. This study confirmed that lack of NLRP3 inflammasome is involved in HCC progression and 17β-estradiol-induced activation of NLRP3 inflammasome may be effective in HCC treatment as it inhibited tumor cell growth and proliferation by triggering CASP1-dependent pyroptosis in HCC cells.

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.

Virulence-related gene wx2 of Toxoplasma gondii regulated host immune response via classic pyroptosis pathway

BACKGROUND

Toxoplasma gondii is known as the most successful parasite, which can regulate the host immune response through a variety of ways to achieve immune escape. We previously reported that a novel gene wx2 of T. gondii may be a virulence-related molecule. The objective of this study was to explore the mechanism of wx2 regulating host immune response.

METHODS

The wx2 knockout strain (RH^wx2-/- strain) and complementary strain (RH^wx2+/+ strain) were constructed by the CRISPR/Cas9 technique, and the virulence of the wx2 gene was detected and changes in pyroptosis-related molecules were observed.

RESULTS

Compared with the wild RH and RH^wx2+/+ strain groups, the survival time for mice infected with the RH^wx2-/- strain was prolonged to a certain extent. The mRNA levels of pyroptosis-related molecules of caspase-1, NLRP3, and GSDMD and et al. in mouse lymphocytes in vivo and RAW267.4 cells in vitro infected with RH^wx2-/- strain increased to different degrees, compared with infected with wild RH strain and RH^wx2+/+ strain. As with the mRNA level, the protein level of caspase-1, caspase-1 p20, IL-1β, NLRP3, GSDMD-FL, GSDMD-N, and phosphorylation level of NF-κB (p65) were also significantly increased. These data suggest that wx2 may regulate the host immune response through the pyroptosis pathway. In infected RAW264.7 cells at 48 h post-infection, the levels of Th1-type cytokines of IFN-γ, Th2-type cytokines such as IL-13, Th17-type cytokine of IL-17 in cells infected with RH^wx2-/- were significantly higher than those of RH and RH^wx2+/+ strains, suggesting that the wx2 may inhibit the host's immune response.

CONCLUSION

wx2 is a virulence related gene of T. gondii, and may be involved in host immune regulation by inhibiting the pyroptosis pathway.

DNA sensor-associated type I interferon signaling is increased in ulcerative colitis and induces JAK-dependent inflammatory cell death in colonic organoids

DNA sensor pathways can initiate inflammasome, cell death, and type I interferon (IFN) signaling in immune-mediated inflammatory diseases (IMIDs), including type I interferonopathies. We investigated the involvement of these pathways in the pathogenesis of ulcerative colitis (UC) by analyzing the expression of DNA sensor, inflammasome, and type I IFN biomarker genes in colonic mucosal biopsy tissue from control (n = 31), inactive UC (n = 31), active UC (n = 33), and a UC single-cell RNA-Seq dataset. The effects of type I IFN (IFN-β), IFN-γ, and TNF-α on gene expression, cytokine production, and cell death were investigated in human colonic organoids. In organoids treated with cytokines alone, or in combination with NLR family pyrin domain-containing 3 (NLRP3), caspase, or JAK inhibitors, cell death was measured, and supernatants were assayed for IL-1β/IL-18/CXCL10. The expression of DNA sensor pathway genes-PYHIN family members [absent in melanoma 2 (AIM2), IFI16, myeloid cell nuclear differentiation antigen (MNDA), and pyrin and HIN domain family member 1 (PYHIN1)- as well as Z-DNA-binding protein 1 (ZBP1), cyclic GMP-AMP synthase (cGAS), and DDX41 was increased in active UC and expressed in a cell type-restricted pattern. Inflammasome genes (CASP1, IL1B, and IL18), type I IFN inducers [stimulator of interferon response cGAMP interactor 1 (STING), TBK1, and IRF3), IFNB1, and type I IFN biomarker genes (OAS2, IFIT2, and MX2) were also increased in active UC. Cotreatment of organoids with IFN-β or IFN-γ in combination with TNFα increased expression of IFI16, ZBP1, CASP1, cGAS, and STING induced cell death and IL-1β/IL-18 secretion. This inflammatory cell death was blocked by the JAK inhibitor tofacitinib but not by inflammasome or caspase inhibitors. Increased type I IFN activity may drive elevated expression of DNA sensor genes and JAK-dependent but inflammasome-independent inflammatory cell death of colonic epithelial cells in UC.NEW & NOTEWORTHY This study found that patients with active UC have significantly increased colonic gene expression of cytosolic DNA sensor, inflammasome, STING, and type I IFN signaling pathways. The type I IFN, IFN-β, in combination with TNF-α induced JAK-dependent but NLRP3 and inflammasome-independent inflammatory cell death of colonic organoids. This novel inflammatory cell death phenotype is relevant to UC immunopathology and may partially explain the efficacy of the JAKinibs tofacitinib and upadacitinib in patients with UC.

NLRP3 inflammasome in digestive diseases: From mechanism to therapy

Digestive system diseases remain a formidable challenge to human health. NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is the most characteristic multimeric protein complex and is involved in a wide range of digestive diseases as intracellular innate immune sensors. It has emerged as a research hotspot in recent years. In this context, we provide a comprehensive review of NLRP3 inflammasome priming and activation in the pathogenesis of digestive diseases, including clinical and preclinical studies. Moreover, the scientific evidence of small-molecule chemical drugs, biologics, and phytochemicals, which acts on different steps of the NLRP3 inflammasome, is reviewed. Above all, deep interrogation of the NLRP3 inflammasome is a better insight of the pathomechanism of digestive diseases. We believe that the NLRP3 inflammasome will hold promise as a novel valuable target and research direction for treating digestive disorders.

Proinflammatory role of basophils in oxazolone-induced chronic intestinal inflammation

BACKGROUND AND AIM

The functions of basophils have not been elucidated until recently because of their rarity. However, with recent developments in basophil-specific antibodies and basophil-deficient animals, the roles of basophils in various diseases related to chronic inflammation have been clarified. In this study, we aimed to investigate the roles of basophils in human ulcerative colitis (UC) and oxazolone (OXA) colitis using genetically engineered Mcpt8^DTR mice.

METHODS

Immunohistochemical staining of human colon specimens was performed to examine the involvement of basophils in the pathogenesis of UC. We examined the correlation between the number of infiltrating basophils and the UC endoscopic index of severity (UCEIS), Mayo score, and Matts score. We also examined the correlation between eosinophil count and basophil infiltration. In murine experiments, we examined whether basophil infiltration was involved in OXA-induced colitis and whether basophil depletion improved inflammation in Mcpt8^DTR mice.

RESULTS

Colonic basophil infiltration was significantly increased in patients with UC. There were significant correlations between UCEIS, Mayo score, Matts score, and the number of infiltrating basophils. In murine OXA-induced colitis, a significant increase in basophil infiltration was observed. When basophils were depleted by diphtheria toxin in Mcpt8^DTR mice, inflammation improved significantly and mRNA expression of some proinflammatory cytokines, including Tnf-α and Ifn-γ decreased significantly.

CONCLUSION

Basophil infiltration correlated with endoscopic, clinical, and pathological scores in human UC independently of eosinophil infiltration, and depletion of basophils ameliorated mucosal inflammation in murine OXA-induced colitis, collectively suggesting that basophils exert a proinflammatory role in chronic intestinal inflammation such as UC.

Investigating the Role of the NLRP3 Inflammasome Pathway in Acute Intestinal Inflammation: Use of THP-1 Knockout Cell Lines in an Advanced Triple Culture Model

The NLRP3 inflammasome plays an important role in intestinal homeostasis as well as inflammation. However, in vivo studies investigating the role of the NLRP3 inflammasome in inflammatory bowel disease (IBD) report contrasting results, leaving it unclear if the NLRP3 inflammasome augments or attenuates intestinal inflammation. To investigate the role of the NLRP3/caspase-1 pathway in a model of acute intestinal inflammation, we modified a previously established in vitro triple culture model of the healthy and inflamed intestine (Caco-2/HT29-MTX-E12/THP-1). Using THP-1 knockout cell lines, we analyzed how the NLRP3 inflammasome and its downstream enzyme caspase-1 (CASP1) affect inflammatory parameters including barrier integrity and cytotoxicity, as well as gene expression and secretion of pro-inflammatory cytokines and mucus. Furthermore, we investigated differences in inflammation-mediated cytotoxicity towards enterocyte-like (Caco-2) or goblet-like (HT29-MTX-E12) epithelial cells. As a complementary approach, inflammation-related cytotoxicity and gene expression of cytokines was analyzed in intestinal tissue explants from wildtype (WT) and Nlrp3^-/- mice. Induction of intestinal inflammation impaired the barrier, caused cytotoxicity, and altered gene expression of pro-inflammatory cytokines and mucins in vitro, while the knockout of NLRP3 and CASP1 in THP 1 cells led to attenuation of these inflammatory parameters. The knockout of CASP1 tended to show a slightly stronger attenuating effect compared to the NLRP3 knockout model. We also found that the inflammation-mediated death of goblet-like cells is NLRP3/caspase-1 dependent. Furthermore, inflammation-related cytotoxicity and upregulation of pro-inflammatory cytokines was present in ileal tissue explants from WT, but not Nlrp3^-/- mice. The here presented observations indicate a pro-inflammatory and adverse role of the NLRP3 inflammasome in macrophages during acute intestinal inflammation.

Dual Role of Chitin as the Double Edged Sword in Controlling the NLRP3 Inflammasome Driven Gastrointestinal and Gynaecological Tumours

The role of NLRP3 in the tumour microenvironment is elusive. In some cancers, the activation of NLRP3 causes a worse prognosis and in some cancers, NLRP3 increases chances of survivability. However, in many cases where NLRP3 has a protumorigenic role, inhibition of NLRP3 would be a crucial step in therapy. Consequently, activation of NLRP3 would be of essence when inflammation is required. Although many ways of inhibiting and activating NLRP3 in cancers have been discussed before, not a lot of focus has been given to chitin and chitosan in this context. The availability of these marine compounds and their versatility in dealing with inflammation needs to be investigated further in relation with cancers, along with other natural extracts. In this review, the effects of NLRP3 on gastrointestinal and gynaecological cancers and the impact of different natural extracts on NLRP3s with special emphasis on chitin and chitosan is discussed. A research gap in using chitin derivatives as anti/pro-inflammatory agents in cancer treatment has been highlighted.

NLRP3 Inflammasome Inhibitor OLT1177 Suppresses Onset of Inflammation in Mice with Dextran Sulfate Sodium-Induced Colitis

BACKGROUND AND AIMS

NLRP3 inflammasomes have been reported to have a key role in the initiation and perpetuation of inflammatory bowel diseases (IBD). Here we investigated the effects of OLT1177, a selective inhibitor of NLRP3 inflammasomes, in mice with dextran sulfate sodium (DSS)-induced colitis.

METHODS

C57BL/6J mice were given drinking water containing 3% DSS for 5 days. OLT1177 was administered for 5 days during the induction phase (simultaneously with DSS treatment) or the recovery phase (after the DSS treatment ended). The body weight and disease activity index were monitored daily. The mice were sacrificed 10 days after the start of the experiment, and the severity of inflammation in the colon was determined based on histological and biochemical analyses.

RESULTS

Administration of OLT1177 during the induction phase effectively suppressed DSS colitis in terms of weight loss, disease activity index, histological score, and expression of inflammatory cytokines compared to the DSS group. In contrast, OLT1177 administration during the recovery phase did not significantly affect the colitis disease course or the results of histological analyses.

CONCLUSIONS

OLT1177 was effective in preventing the onset of DSS colitis in mice. These results could guide the use of OLT1177 as a therapy for human IBD.

Multi-Strain-Probiotic-Loaded Nanoparticles Reduced Colon Inflammation and Orchestrated the Expressions of Tight Junction, NLRP3 Inflammasome and Caspase-1 Genes in DSS-Induced Colitis Model

Gut modulation by multi-strain probiotics (MSPs) is considered an effective strategy for treating inflammatory bowel disease (IBD). The combination of nanomaterial-based MSPs can improve their viability and resistance and can allow their targeted release in the gastrointestinal tract to be achieved. Thus, our aim is to investigate the prospective role of MSP integration into nanomaterials (MSPNPs) and the underlying molecular mechanisms supporting their application as an alternative therapy for IBD using a colitis rat model. To induce the colitis model, rats received 5% DSS, and the efficacy of disease progression after oral administration of MSPNPs was assessed by evaluating the severity of clinical signs, inflammatory response, expressions of tight-junction-related genes and NLRP3 inflammasome and caspase-1 genes, microbial composition and histopathological examination of colonic tissues. The oral administration of MSPNPs successfully alleviated the colonic damage induced by DSS as proved by the reduced severity of clinical signs and fecal calprotectin levels. Compared with the untreated DSS-induced control group, the high activities of colonic NO and MPO and serum CRP levels were prominently reduced in rats treated with MSPNPs. Of note, colonic inflammation in the group treated with MSPNPs was ameliorated by downstreaming NLRP3 inflammasome, caspase-1, IL-18 and IL-1β expressions. After colitis onset, treatment with MSPNPs was more effective than that with free MSPs in restoring the expressions of tight-junction-related genes (upregulation of occludin, ZO-1, JAM, MUC and FABP-2) and beneficial gut microbiota. Interestingly, treatment with MSPNPs accelerated the healing of intestinal epithelium as detected in histopathological findings. In conclusion, the incorporation of MPSs into nanomaterials is recommended as a perspective strategy to overcome the challenges they face and augment their therapeutic role for treating of colitis.

Structural Characteristics of Inulin and Microcrystalline Cellulose and Their Effect on Ameliorating Colitis and Altering Colonic Microbiota in Dextran Sodium Sulfate-Induced Colitic Mice

Several studies have reported that dietary fibers (DFs) from plants may exert beneficial effects on inflammatory bowel disease. In the present study, we investigated the structural differences of soluble DF (inulin) and insoluble DF (microcrystalline cellulose, MCC) and their effects on the intestinal barrier integrity, gut microbiota community, and inflammation response in mice with dextran sodium sulfate (DSS)-induced colitis. Mice were fed for 21 days with diets containing inulin or MCC (2.5 g/kg body weight), and colitis was induced by administration of DSS (4% w/v) in drinking water during the last 8 days of experimentation. The results showed that inulin and MCC differ in morphology and structure. MCC exhibited a smaller particle size, a larger specific surface area, and higher thermal stability than inulin. In addition, both inulin and MCC restored various physical signs (body weight, colon weight and length, disease activity index score, and infiltration of inflammatory cells), gut barrier function (as evidenced by the increased expression of claudin-3, claudin-7, ZO-2, occludin, JAM-2, and MUC-3 and the decreased activity of myeloperoxidase activity), downregulation of mRNA expression of proinflammatory cytokines (caspase-1, NLPR3, TLR4, TNF-α, and IL-1β), and modulation of colon microbiota community. Taken together, the present study demonstrates that DFs differ in morphology and structure and ameliorate DSS-induced colitis in mice by blocking proinflammatory cytokines, reinforcing gut barrier integrity, and modulating gut microbiota. Therefore, DFs, especially inulin, are promising dietary supplements to alleviate intestinal inflammation.

In COVID-19, NLRP3 inflammasome genetic variants are associated with critical disease and these effects are partly mediated by the sickness symptom complex: a nomothetic network approach

In coronavirus disease (COVID-19), the nucleotide-binding domain, leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) inflammasome is activated in response to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Acute infections are accompanied by a sickness symptom complex (SSC) which is highly conserved and protects against infections and hyperinflammation. The aim of this study is to delineate the associations of COVID-19, SSC and NLPR3 rs10157379 T > C and NLPR3 rs10754558 C > G variants; and the protective role of SSC in SARS-CoV-2 infection. We recruited COVID-19 patients, 308 with critical, 63 with moderate and 157 with mild disease. Increased SSC protects against SARS, critical disease, and death due to COVID-19. Increasing age, male sex and rs10754558 CG significantly reduce SSC protection. The rs10157379 CT and rs10754558 GG genotypes are positively associated with SARS. Partial Least Squares analysis shows that a) 41.8% of the variance in critical COVID-19 symptoms is explained by SSC and oxygen saturation (inversely associated), inflammation, chest computed tomography abnormalities, increased body mass index, SARS and age (positively associated); and b) the effects of the NLRP3 rs10157379 and rs10754558 variants on critical COVID-19 are mediated via SSC (protective) and SARS (detrimental). SSC includes anosmia and dysgeusia, and maybe gastrointestinal symptoms. In conclusion, intersections among the rs10754558 variant, age, and sex increase risk towards critical COVID-19 by attenuating SSC. NLRP3 variants play an important role in SARS, and severe and critical COVID-19 especially in elderly male individuals with reduced SSC and with increased BMI, hypertension, and diabetes type 2.

Intervention of 3-aminobenzamide against Dextran Sulphate Sodium induced colitis in mice: Investigations on molecular mechanisms

Various preclinical and clinical studies reported that Poly [ADP-ribose] polymerase 1 plays significant role in all acute and chronic inflammatory diseases with different etiopathogenesis. The present study aims to investigate the protective effect of 3-aminobenzamide in Dextran Sulphate Sodium induced ulcerative colitis and associated molecular mechanisms. Ulcerative colitis in male BALB/c mice was induced using Dextran sulphate sodium (3 %w/v) for 3 cycles with 7 days recovery period in-between. 3-aminobenzamide was administered at the doses of 5, 10 and 20 mg/kg starting from the I^st week of remission period and was continued till the termination of the experiment. The effect of 3-aminbenzamide was evaluated using biochemical parameters, histopathological evaluations, ELISA, immunohistochemistry, immunofluorescence and Western blot analysis. All the doses of 3-aminobenzamide (5 mg/kg; 10 mg/kg and 20 mg/kg) ameliorated the severity of ulcerative colitis by modulating various molecular targets such as poly[ADP-ribose] polymerase 1, nuclear factor kappa-light-chain-enhancer of activated B cells, NLR family pyrin domain containing 3, apoptosis-associated speck-like protein containing a caspase-recruitment domain, cysteine aspartases, interleukin-1β, proliferating cell nuclear antigen, sirtuin 1, adenosine monophosphate-activated protein kinase, tumour necrosis factor-α and catalase. However, the lower doses (5 and 10 mg/kg) exerted more prominent effects in comparison to the high dose (20 mg/kg). Further, 3-aminobenzamide treatment restored the intestinal integrity by increasing the expression of occludin and significantly ameliorated ulcerative colitis associated elevated lipopolysaccharides, oxidative and nitrosative stress, cellular damage and apoptosis. Lower doses of 3-aminobenzamide showed more prominent protective effects against ulcerative colitis associated damage as compared to higher dose.

SUCNR1 Mediates the Priming Step of the Inflammasome in Intestinal Epithelial Cells: Relevance in Ulcerative Colitis

Intestinal epithelial cells (IECs) constitute a defensive physical barrier in mucosal tissues and their disruption is involved in the etiopathogenesis of several inflammatory pathologies, such as Ulcerative Colitis (UC). Recently, the succinate receptor SUCNR1 was associated with the activation of inflammatory pathways in several cell types, but little is known about its role in IECs. We aimed to analyze the role of SUCNR1 in the inflammasome priming and its relevance in UC. Inflammatory and inflammasome markers and SUCNR1 were analyzed in HT29 cells treated with succinate and/or an inflammatory cocktail and transfected with SUCNR1 siRNA in a murine DSS model, and in intestinal resections from 15 UC and non-IBD patients. Results showed that this receptor mediated the inflammasome, priming both in vitro in HT29 cells and in vivo in a murine chronic DSS-colitis model. Moreover, SUNCR1 was also found to be involved in the activation of the inflammatory pathways NFкB and ERK pathways, even in basal conditions, since the transient knock-down of this receptor significantly reduced the constitutive levels of pERK-1/2 and pNFкB and impaired LPS-induced inflammation. Finally, UC patients showed a significant increase in the expression of SUCNR1 and several inflammasome components which correlated positively and significantly. Therefore, our results demonstrated a role for SUCNR1 in basal and stimulated inflammatory pathways in intestinal epithelial cells and suggested a pivotal role for this receptor in inflammasome activation in UC.

The Pro-tumor and Anti-tumor Effects of NLRP3 Inflammasome as a New Therapeutic Option for Colon Cancer: a Meta-analysis of Pre-clinical Studies

In this review, we aimed to elaborate on these findings and explore how NLRP3 inflammasome affects CRC and which mechanism could be a potential therapeutic target. For this purpose, major indexing databases consist of Cochrane central, ISI web of science (WOS), PubMed/Medline, Scopus, and EMBASE were systematically searched using standard terms without any language, study region, or type restrictions. After applying the exclusion criteria, the main properties of 12 articles on 326 animals included in this meta-analysis. Of 12, eight were about an anti-tumoral effect, and four were on a pro-tumoral effect of the inflammasome. NLRP3 inhibition reduced IL-1β (SMD: -4.14, 95% CI: -5.49, -2.79, P < 0.00001, I² = 76%), TNFα (SMD: -2.18, 95% CI: -3.23, -1.13, P < 0.00001, I² = 82%), and IL-18 (SMD: -2.27, 95% CI: -3.38, -1.16, P = 0.0002, I² = 74%) significantly contrasted with the model controls. Colons harvested from NLRP3 inhibition groups showed significant truncation compared with the model controls (SMD: -1.75, 95% CI: -2.69, -0.81, P = 0.0003, I² = 60%). We demonstrated significantly decreased tumorigenesis following NLRP3 inactivation, as well as an increased survival rate compared with the model controls. To translate anti-cancer agents based on anti-NLRP3 from bench to bedside, it is necessary to identify the molecules that selectively target NLRP3 or its downstream pathways in malignant cells, as well as considering metabolic heterogeneity and the mechanisms causing such cancer-connected heterogeneity. Other studies are needed to separate the molecular and functional complexity of this network.SummarySecretion of IL-1β is contingent upon activation of the inflammasome complex of NLRP3. It has been suggested that activation of this complex necessitates two signals. One of these signals is made available by activation of toll-like-receptor (TLR)-mediated NF-kappa and actuates the IL-1β precursor synthesis and NLRP3 assembly. Another signal is conceivable to be mediated by hazard signals e.g., the purinergic P2X7 receptor stimulated by Adenosine triphosphate or other stimuli resulting in the efflux of potassium.

Forsythiaside A alleviates methotrexate-induced intestinal mucositis in rats by modulating the NLRP3 signaling pathways

Most chemotherapeutic drugs can kill the tumor cells, but also cause a vast damage to body, such as intestinal mucositis (IM). The present study was design to find out the effect of Forsythiaside A (FTA) on chemotherapeutic-induced IM in rats. Briefly, for 3 consecutive days, male Sprague-Dawley rats were treated with 7 mg / kg methotrexate (MTX) to establish IM and simultaneously administered with 40 or 80 mg / kg FTA for 7 days. Our results showed that the final body weight and daily food intake were increased, and the disease activity index was reduced in the MTX group after FTA treatment. The MTX group showed the pathological alterations like the inflammatory cells infiltration, the mucosal layer destruction, glands expansion, intestinal villi structure disorder and goblet cells reduction, while we found that 80 mg / kg FTA treatment displayed evident reversal effects. ELISA further suggested that TNF-α, IL-1β and IL-18 levels in serum in MTX-induced rats were reduced after 80 mg / kg FTA treatment. Moreover, FTA decreased the number of leukocytes, neutrophils and lymphocytes in peripheral blood. Western blot and immunofluorescence results indicated that the expression levels of NLRP3, cleaved caspase 1, cleaved IL-1β and CD68 positive rate were down-regulated in MTX-induced rats after 80 mg / kg FTA intervention. The findings of the current study suggested that FTA effectively inhibited MTX-induced IM in rats by attenuating the activation of the NLRP3 signaling pathways.

Type 2 immunity in intestinal homeostasis and inflammatory bowel disease

Type 2 immune responses commonly emerge during allergic reactions or infections with helminth parasites. Most of the cytokines associated with type 2 immune responses are IL-4, IL-5, and IL13, which are mainly produced by T helper 2 cells (T_H2), eosinophils, basophils, mast cells, and group 2 innate lymphoid cells (ILC2s). Over the course of evolution, humans have developed type 2 immune responses to fight infections and to protect tissues from the potential collateral damage caused by inflammation. For example, worm parasites induce potent type 2 immune responses, which are needed to simultaneously clear the pathogen and to promote tissue repair following injury. Due to the strong type 2 immune responses induced by helminths, which can promote tissue repair in the damaged epithelium, their use has been suggested as a possible treatment for inflammatory bowel disease (IBD); however, the role of type 2 immune responses in the initiation and progression of IBD is not fully understood. In this review, we discuss the molecular and cellular mechanisms that regulate type 2 immune responses during intestinal homeostasis, and we briefly discuss the scarce evidence linking type 2 immune responses with the aetiology of IBD.

Akkermansia muciniphila Alleviates Dextran Sulfate Sodium (DSS)-Induced Acute Colitis by NLRP3 Activation

Akkermansia muciniphila has been proved to play a crucial role in the progression of colitis, but its underlying mechanism remains inconclusive. In this study, we aim to investigate the effect of A. muciniphila on the development of acute colitis and explore the underlying mechanism. We found that the fecal level of A. muciniphila was decreased in ulcerative colitis (UC) patients compared to the healthy people in the GMrepo database. Oral administration of A. muciniphila strain BAA-835 significantly ameliorated the symptoms in dextran sulfate sodium (DSS)-induced acute colitis, evidenced by decreased body weight loss, colon length shortening, and colon histological inflammatory score. In addition, the number of goblet cells and the mucin family were enhanced after A. muciniphila treatment. Furthermore, proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), and monocyte chemoattractant protein 1 (MCP-1) had a downward trend. Mechanistically, the expression of NLRP3, caspase-1 p20, and IL-1β p17 were upregulated in A. muciniphila-treated mice. Additionally, the colon tissues from high-A. muciniphila UC patients had a higher NLRP3 expression than that from low-A. muciniphila UC patients. Moreover, the upregulation of NLRP3 was observed in mouse macrophage Raw264.7 cells and bone marrow-derived macrophage (BMDM) cells after incubation with A. muciniphila. To clarify whether the protective effect of A. muciniphila in colitis depends on NLRP3, we performed the NLRP3-deficient assay in NLRP3-/- mice in vivo. The evidence showed that NLRP3 deficiency eliminated the protective effects of A. muciniphila in acute colitis. In conclusion, A. muciniphila alleviates DSS-induced acute colitis by NLRP3 activation, which enriches the mechanism and provides a new prospect for the probiotic-based treatment of colitis. IMPORTANCE The gut microbiota and host immune response interaction influences the progression of intestinal inflammatory disease. As a well-recognized next-generation probiotic, Akkermansia muciniphila has been proved to play a crucial role in the progression of colitis, but its underlying mechanism remains inconclusive. We found that oral administration of A. muciniphila strain BAA-835 significantly ameliorated the symptoms of acute colitis. Mechanistically, the expression of NLRP3 was upregulated in the A. muciniphila group, and the protective effect of A. muciniphila in colitis depends on NLRP3 activation. This enriches the mechanism and provides a new prospect for the probiotic-based treatment of colitis, which would promote a deeper understanding of the complex characteristics of A. muciniphila and provide guidance for the treatment of human colitis in the future.

Advances in the Relationship Between Pyroptosis and Diabetic Neuropathy

Pyroptosis is a novel programmed cell death process that promotes the release of interleukin-1β (IL-1β) and interleukin-18 (IL-18) by activating inflammasomes and gasdermin D (GSDMD), leading to cell swelling and rupture. Pyroptosis is involved in the regulation of the occurrence and development of cardiovascular and cerebrovascular diseases, tumors, and nerve injury. Diabetes is a metabolic disorder characterized by long-term hyperglycemia, insulin resistance, and chronic inflammation. The people have paid more and more attention to the relationship between pyroptosis, diabetes, and its complications, especially its important regulatory significance in diabetic neurological diseases, such as diabetic encephalopathy (DE) and diabetic peripheral neuropathy (DPN). This article will give an in-depth overview of the relationship between pyroptosis, diabetes, and its related neuropathy, and discuss the regulatory pathway and significance of pyroptosis in diabetes-associated neuropathy.

NLRP3 Inflammasome: Checkpoint Connecting Innate and Adaptive Immunity in Autoimmune Diseases

Autoimmune diseases are a broad spectrum of human diseases that are characterized by the breakdown of immune tolerance and the production of autoantibodies. Recently, dysfunction of innate and adaptive immunity is considered to be a key step in the initiation and maintenance of autoimmune diseases. NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a multimeric protein complex, which can detect exogenous pathogen irritants and endogenous danger signals. The main function of NLRP3 inflammasome is to promote secretion of interleukin (IL)-1β and IL-18, and pyroptosis mediated by caspase-1. Served as a checkpoint in innate and adaptive immunity, aberrant activation and regulation of NLRP3 inflammasome plays an important role in the pathogenesis of autoimmune diseases. This paper reviewed the roles of NLRP3 inflammasome in autoimmune diseases, which shows NLRP3 inflammasome may be a potential target for autoimmune diseases deserved further study.

Quyu Shengxin Decoction Alleviates DSS-Induced Ulcerative Colitis in Mice by Suppressing RIP1/RIP3/NLRP3 Signalling

Purpose

To study the therapeutic effect of Quyu (QY) Shengxin (SX) decoction (QYSXD) in mice with dextran sulfate sodium- (DSS-) induced ulcerative colitis and to investigate the effects of QYSXD on the regulation of the receptor-interacting protein kinase 1 (RIP1)/receptor-interacting protein kinase 3 (RIP3)/nucleotide-binding oligomerization domain-like receptor family pyrin domain protein 3 (NLRP3) signaling pathway.

Method

Thirty-six mice were randomly divided into the following 6 groups: the experimental group (QYSX group), the model group (DSS group), the positive control group (5-aminosalicylic acid (5-ASA) group), the control group, the first component group (QY group), and the second component group (SX group). Each group included 6 mice. Ulcerative colitis (UC) was induced in the mice by providing 3.5% DSS in drinking water. The mice were weighed every day to evaluate the disease activity index (DAI). After 7 days, the mice were sacrificed, and colonic tissues were obtained for colon length measurement. The morphological changes in the colon and the pathological scores of the mice in each group were observed by hematoxylin-eosin (HE) staining. The messenger ribonucleic acid (mRNA) and protein expression levels of RIP1, RIP3, dynamin-related protein 1 (Drp1), NLRP3, cysteinyl aspartate specific proteinase-1 (caspase-1), interleukin (IL)-1β, and IL-18 in the colon tissues of the mice in each group were detected and compared by real-time quantitative reverse transcription PCR (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). The levels of RIP1, RIP3, NLRP3, IL-1β, and IL-8 in the colonic mucosa were detected by ELISA. Western blotting was used to compare the protein expression of Drp1, caspase-1, mitochondrial fission protein 1 (FIS1), and mitophagy-associated protein light chain 3a/b (LC3a/b) among groups. The levels of reactive oxygen species (ROS) in the colonic mucosal cells were compared by immunofluorescence.

Results

Compared with those in the DSS group, the mice with DSS-induced colitis in the QYSX group exhibited clearly higher body weights (P < 0.05) and DAI scores (P < 0.05). The colon lengths of the mice in the QYSX group were longer than those in the DSS group (P < 0.05), and the pathological score of the QYSX group was lower than that of the DSS group (P < 0.05). The RIP1, RIP3, Drp1, IL-1β, IL-18, and caspase-1 mRNA levels in the QYSX, 5-ASA, SX, and QY groups were significantly lower than those in the DSS group (P < 0.05), but there were no differences between the QYSX group and the 5-ASA group. The levels of RIP1, RIP3, NLRP3, IL-1β, and IL-18 in the QYSX group were lower than those in the DSS group (P < 0.01). The levels of Drp1, caspase-1, FIS1, and LC3a/b in the QYSX group and the 5-ASA group were lower than those in the DSS group (P < 0.05). The levels of ROS in the colonic mucosal cells in the QYSX, 5-ASA, and QY groups were lower than those in the DSS group (P < 0.05).

Conclusion

QYSXD has certain therapeutic effects on DSS-induced colitis in mice and may be as effective as 5-ASA. QY and SX decoctions also have certain effects on colitis; however, these decoctions are not as beneficial as QYSXD. QYSXD may ameliorate colitis by inhibiting the expression of RIP1/RIP3/NLRP3 pathway-related proteins and reversing mitochondrial dysfunction to control inflammation.

Genotype-phenotype associations of polymorphisms within the gene locus of NOD-like receptor pyrin domain containing 3 in Swiss inflammatory bowel disease patients

Background

Genetic variations within the regulatory region of the gene encoding NOD-like receptor pyrin domain containing 3 (NLRP3) have been associated with Crohn’s Disease (CD). NLRP3 is part of the NLRP3-inflammasome that mediates the maturation of IL-1β and IL-18. Carrying the major allele of the single nucleotide polymorphisms (SNPs) rs10733113, rs4353135 and rs55646866 is associated with an increased risk for CD. We here studied the impact of these polymorphisms on clinical characteristics in patients of the Swiss IBD Cohort Study (SIBDCS).

Methods

We included 981 Crohn’s disease (CD) patients and 690 ulcerative colitis (UC) patients of the SIBDCS. We analyzed whether three CD-associated NLRP3 polymorphisms have an impact on the clinical disease course in these patients.

Results

In CD patients presence of the major allele (G) of rs10733113 was associated with less surgeries and lower maximal CDAI and a similar trend was observed for rs55646866 and rs4353135. Presence of the major allele of all three SNPs was negatively correlated to maximal CDAI. In UC patients homozygous genotype for the major allele (CC) for rs55646866 was associated with a higher age at diagnosis and a higher MTWAI index. Homozygous genotype for the major allele of all three polymorphisms was associated with a higher number of ambulatory visits and longer hospital stays.

Conclusions

In CD patients presence of the major allele of all three polymorphisms was associated with markers of a less severe disease course, while in UC the homozygous genotype for all major alleles suggested a more severe disease activity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12876-021-01880-9.

hucMSC-derived exosomes attenuate colitis by regulating macrophage pyroptosis via the miR-378a-5p/NLRP3 axis

Background

Human umbilical cord mesenchymal stem cell (hucMSC)-derived exosomes are recognized as novel cell-free therapeutic agents for inflammatory bowel disease (IBD), a condition caused by dysregulated intestinal mucosal immunity. In this event, macrophage pyroptosis, a process of cell death following the activation of NLRP3 (NOD-like receptor family, pyrin domain-containing 3) inflammasomes, is believed to partially account for inflammatory reactions. However, the role of macrophage pyroptosis in the process of hucMSC-derived exosomes alleviating colitis remains unknown. This study aimed at exploring the therapeutic effect and mechanism of hucMSC-derived exosomes on colitis repair.

Methods

In vivo, we used BALB/c mice to establish a dextran sulfate sodium (DSS)-induced colitis model and administrated hucMSC-derived exosomes intravenously to estimate its curative effect. Human myeloid leukemia mononuclear (THP-1) cells and mouse peritoneal macrophages (MPMs) were stimulated with lipopolysaccharides (LPS) and Nigericin to activate NLRP3 inflammasomes, which simulated an inflammation environment in vitro. A microRNA mimic was used to verify the role of miR-378a-5p/NLRP3 axis in the colitis repair.

Results

hucMSC-derived exosomes inhibited the activation of NLRP3 inflammasomes in the mouse colon. The secretion of interleukin (IL)-18, IL-1β, and Caspase-1 cleavage was suppressed, resulting in reduced cell pyroptosis. The same outcome was observed in the in vitro cell experiments, where the co-culture of THP-1 cells and MPMs with hucMSC-derived exosomes caused decreased expression of NLRP3 inflammasomes and increased cell survival. Furthermore, miR-378a-5p was highly expressed in hucMSC-derived exosomes and played a vital function in colitis repair.

Conclusion

hucMSC-derived exosomes carrying miR-378a-5p inhibited NLRP3 inflammasomes and abrogated cell pyroptosis to protect against DSS-induced colitis.

Systems biology approach highlights mechanistic differences between Crohn's disease and ulcerative colitis

The molecular mechanisms of IBD have been the subject of intensive exploration. We, therefore, assembled the available information into a suite of causal biological network models, which offer comprehensive visualization of the processes underlying IBD. Scientific text was curated by using Biological Expression Language (BEL) and compiled with OpenBEL 3.0.0. Network properties were analysed by Cytoscape. Network perturbation amplitudes were computed to score the network models with transcriptomic data from public data repositories. The IBD network model suite consists of three independent models that represent signalling pathways that contribute to IBD. In the “intestinal permeability” model, programmed cell death factors were downregulated in CD and upregulated in UC. In the “inflammation” model, PPARG, IL6, and IFN-associated pathways were prominent regulatory factors in both diseases. In the “wound healing” model, factors promoting wound healing were upregulated in CD and downregulated in UC. Scoring of publicly available transcriptomic datasets onto these network models demonstrated that the IBD models capture the perturbation in each dataset accurately. The IBD network model suite can provide better mechanistic insights of the transcriptional changes in IBD and constitutes a valuable tool in personalized medicine to further understand individual drug responses in IBD.

Targeting the NLRP3 Inflammasome as a New Therapeutic Option for Overcoming Cancer

Inflammasomes are multiprotein complexes that regulate the maturation and secretion of the proinflammatory cytokines interleukin-1beta (IL-1β and interleukin-18 (IL-18) in response to various intracellular stimuli. As a member of the inflammasomes family, NLRP3 is the most studied and best characterized inflammasome and has been shown to be involved in several pathologies. Recent findings have made it increasingly apparent that the NLRP3 inflammasome may also play a central role in tumorigenesis, and it has attracted attention as a potential anticancer therapy target. In this review, we discuss the role of NLRP3 in the development and progression of cancer, offering a detailed summary of NLRP3 inflammasome activation (and inhibition) in the pathogenesis of various forms of cancer. Moreover, we focus on the therapeutic potential of targeting NLRP3 for cancer therapy, emphasizing how understanding NLRP3 inflammasome-dependent cancer mechanisms might guide the development of new drugs that target the inflammatory response of tumor-associated cells.

Therapeutic implications of inflammasome in inflammatory bowel disease

Inflammatory bowel disease (IBD) remains a persistent health problem with a global burden surging over 6.8 million cases currently. Clinical pathology of IBD is complicated; however, hyperactive inflammatory and immune responses in the gut is shown to be one of the persistent causes of the disease. Human gut inflammasome, the activator of innate immune system is believed to be a primary underlying cause for the pathology and is largely associated with the progression of IBD. To manage IBD, there is a need to fully understand the role of inflammasome activation in IBD. Since inflammasome potentially play a significant role in IBD, systemic modulation of inflammasome may provide an effective therapeutic and clinical approach to control IBD symptoms. In this review, we have focused on this association between IBD and gut inflammasome, and recent advances in the research and therapeutic strategies for IBD. We have discussed inflammasomes and their components, outcomes from the experimental animals and human studies, inflammasome inhibitors, and developments in the inflammasome-targeted therapies for IBD.

Role of nucleotide binding oligomerization domain-like receptor protein 3 inflammasome in stress-induced gastric injury

BACKGROUND AND AIM

The inflammasomes promote pro-caspase-1 cleavage, leading to processing of pro-interleukin (IL)-1β into its mature form. We investigated the role of the IL-1β and nucleotide binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome in gastric injury in mice receiving water-immersion restraint stress (WIRS), focusing on the cyclooxygenase (COX)-2/prostaglandin (PG) E₂ axis.

METHODS

To induce gastric injury, the mice were placed in a restraint cage and immersed in the water bath to the level of the xiphoid process. Protein levels of mature caspase-1 and IL-1β were assessed by western blotting.

RESULTS

Water-immersion restraint stress induced gastric injury with increase in IL-1β expression by activation of NLRP3 inflammasome. Exogenous IL-1β attenuated the injury, whereas anti-IL-1β neutralizing antibody and IL-1β receptor antibody aggravated it. NLRP3^-/- and caspase-1^-/- mice enhanced the injury with reducing of mature IL-1β, and this aggravation was reduced by exogenous IL-1β supplementation. Toll-like receptor 4^-/- mice were hyporesponsive to WIRS in terms of mature IL-1β production. Rabeprazole attenuated the injury with preventing inflammasome activation. WIRS injured the stomach with promotion of COX-2 mRNA and PGE₂ production, and exogenous IL-1β enhanced these molecules, while IL-1β immunoneutralization exerted opposite effect. PGE₂ supplementation abolished the hypersensitivity in NLRP3^-/- and caspase-1^-/- mice through negative regulation of inflammatory cytokines.

CONCLUSION

These results suggest that NLRP3 inflammasome-derived IL-1β plays a protective role in stress-induced gastric injury via activation of the COX-2/PGE₂ axis. Toll-like receptor 4 signaling and gastric acid may be involved in NLRP3 inflammasome activation.

Specific NLRP3 inflammasome inhibitors: promising therapeutic agents for inflammatory diseases

Innate immunity serves as a first line of defence against danger signals, invading pathogens and microbes. The inflammasomes, as pattern recognition receptors, sense these danger signals to initiate pro-inflammatory cascades. The nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3) inflammasome is the most well characterised inflammasome, and its aberrant activation is implicated in many inflammatory diseases. In the past decade, targeting the NLRP3 inflammasome has become an emerging strategy for inflammatory diseases. To avoid off-target immunosuppressive effects, specific NLRP3 inhibitors have been developed and show promising therapeutic effects. This review discusses the therapeutic effects and clinical perspectives of specific NLRP3 inhibitors, as well as recent progress in the development of these inhibitors for the treatment of inflammatory diseases.

Evaluation of the therapeutic effects of mycophenolate mofetil targeting Nrf-2 and NLRP3 inflammasome in acetic acid induced ulcerative colitis in rats

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that increases the risk of colorectal cancer. UC is highly associated with the disturbance of the immune system leading to oxidative stress and chronic inflammation of intestine. Therefore, the current study was conducted to investigate the potential anti-oxidant and anti-inflammatory effects of MMF against acetic acid-induced UC that might be associated with the regulation of Nrf-2 and NLRP3 inflammasome signaling. UC was induced in Sprague-Dawley rats by intracolonic instillation of acetic acid. Forty-eight hours post UC induction, MMF (50 mg/kg/day, orally) was given for 8 consecutive days. Then, colon tissues and blood samples were collected. Results showed that MMF significantly attenuated the acetic acid-induced functional, biochemical, and inflammatory injuries in colon. MMF significantly decreased oxidative stress as indicated by the decreased malondialdehyde concentration and the increased total antioxidant capacity, glutathione, catalase, and superoxide dismutase concentrations in colon tissues. MMF also significantly increased Nrf-2 and decreased NLRP3 inflammasome expressions. Moreover, MMF decreased expression of interferon-gamma and increased expression of interferon-alpha. MMF also significantly decreased expression of pro-inflammatory cytokines, interleukin (IL)-1β and IL-18. These results suggest that MMF has antioxidant and anti-inflammatory effects against acetic acid-induced UC through the upregulation of Nrf-2, and INF-α expression in addition to the suppression of NLRP3 inflammasome and subsequent release of IL1β, IL-18 and INF-γ.

Role of pattern recognition receptors and the microbiota in neurological disorders

In recent years, the gut microbiota has been increasingly implicated in the development of many extraintestinal disorders, including neurodevelopmental and neurodegenerative disorders. Despite this growing connection, our understanding of the precise mechanisms behind these effects is currently lacking. Pattern recognition receptors (PRRs) are important innate immune proteins expressed on the surface and within the cytoplasm of a multitude of cells, both immune and otherwise, including epithelial, endothelial and neuronal. PRRs comprise four major subfamilies: the Toll-like receptors (TLRs), the nucleotide-binding oligomerization domain leucine rich repeats-containing receptors (NLRs), the retinoic acid inducible gene 1-like receptors and the C-type lectin receptors. Recognition of commensal bacteria by PRRs is critical for maintaining host-microbe interactions and homeostasis, including behaviour. The expression of PRRs on multiple cell types makes them a highly interesting and novel target for regulation of host-microbe signalling, which may lead to gut-brain signalling. Emerging evidence indicates that two of the four known families of PRRs (the NLRs and the TLRs) are involved in the pathogenesis of neurodevelopmental and neurodegenerative disorders via the gut-brain axis. Taken together, increasing evidence supports a role for these PRRs in the development of neurological disorders, including Alzheimer's disease, Parkinson's disease and multiple sclerosis, via the microbiota-gut-brain axis.

Posttranslational modifications as therapeutic targets for intestinal disorders

A variety of biological processes are regulated by posttranslational modifications. Posttranslational modifications including phosphorylation, ubiquitination, glycosylation, and proteolytic cleavage, control diverse physiological functions in the gastrointestinal tract. Therefore, a better understanding of their implications in intestinal diseases, including inflammatory bowel disease, irritable bowel syndrome, celiac disease, and colorectal cancer would provide a basis for the identification of novel biomarkers as well as attractive therapeutic targets. Posttranslational modifications can be common denominators, as well as distinct biomarkers, characterizing pathological differences of various intestinal diseases. This review provides experimental evidence that identifies changes in posttranslational modifications from patient samples, primary cells, or cell lines in intestinal disorders, and a summary of carefully selected information on the use of pharmacological modulators of protein modifications as therapeutic options.

Effects of mild moxibustion on intestinal microbiome and NLRP3 inflammasome in rats with 5-fluorouracil-induced intestinal mucositis

OBJECTIVE

The present study investigated how mild moxibustion treatment affects the intestinal microbiome and expression of NLRP3-related immune factors in a rat model of intestinal mucositis (IM) induced with 5-fluorouracil (5-Fu).

METHODS

Forty male Sprague-Dawley rats were randomly divided into control, chemotherapy, moxibustion and probiotics groups. The IM rat model was established by intraperitoneal injection of 5-Fu. Mild moxibustion treatment and intragastric probiotic administration were provided once daily for 15 days. Tissue morphology, serum levels of inflammatory factors and the expression levels of tight junction proteins, caspase-1, gasdermin D and NLRP3 were evaluated in colon tissue, through hematoxylin and eosin staining, electron microscopy, enzyme-linked immunosorbent assay, Western blotting, quantitative real-time reverse transcription polymerase chain reaction and immunofluorescence. Gut microbiome profiling was conducted through 16S rRNA amplicon sequencing.

RESULTS

Moxibustion and probiotic treatments significantly increased the expression levels of tight junction proteins, reduced cell apoptosis and the expression levels of caspase-1, gasdermin D and NLRP3; they also decreased the serum levels of tumor necrosis factor-α, interleukin (IL)-6, IL-1β and IL-18, while increasing serum levels of IL-10. Moxibustion and probiotic treatments also corrected the reduction in α-diversity and β-diversity in IM rats, greatly increased the proportion of the dominant bacterial genus Lactobacillus and reduced the abundance of the genera Roseburia and Escherichia in chemotherapy-treated rats to levels observed in healthy animals. We also found that these dominant genera were firmly correlated with the regulation of pyroptosis-associated proteins and inflammatory factors. Finally, moxibustion and probiotic treatments elicited similar effects in regulating intestinal host-microbial homeostasis and the expression of NLRP3 inflammasome-related factors.

CONCLUSION

Moxibustion exerts its therapeutic effect on IM by ameliorating mucosal damage and reducing inflammation. Moreover, moxibustion modulates the gut microbiota, likely via decreasing the expression levels of the NLRP3 inflammasome.

Mutual Interplay of Host Immune System and Gut Microbiota in the Immunopathology of Atherosclerosis

Inflammation is the key for the initiation and progression of atherosclerosis. Accumulating evidence has revealed that an altered gut microbiome (dysbiosis) triggers both local and systemic inflammation to cause chronic inflammatory diseases, including atherosclerosis. There have been some microbiome-relevant pro-inflammatory mechanisms proposed to link the relationships between dysbiosis and atherosclerosis such as gut permeability disruption, trigger of innate immunity from lipopolysaccharide (LPS), and generation of proatherogenic metabolites, such as trimethylamine N-oxide (TMAO). Meanwhile, immune responses, such as inflammasome activation and cytokine production, could reshape both composition and function of the microbiota. In fact, the immune system delicately modulates the interplay between microbiota and atherogenesis. Recent clinical trials have suggested the potential of immunomodulation as a treatment strategy of atherosclerosis. Here in this review, we present current knowledge regarding to the roles of microbiota in contributing atherosclerotic pathogenesis and highlight translational perspectives by discussing the mutual interplay between microbiota and immune system on atherogenesis.

Heat shock transcription factor 2 reduces the secretion of IL-1β by inhibiting NLRP3 inflammasome activation in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease with unknown aetiology. As a pro-inflammatory cytokine, interleukin-1β (IL-1β) plays a critical, damaging role in UC. Heat shock proteins (HSPs) are important anti-inflammatory factors that maintain intestinal epithelial cells (IECs) homeostasis. Heat shock transcription factor 2 (HSF2) is an important regulator of HSPs. In our previous research, we found that HSF2 is highly expressed in UC, is negatively related to colon inflammation of mice, and inhibits the expression of IL-1β, but the specific mechanism is still unclear. As a product of the NLRP3 inflammasome, the expression of IL-1β is closely related to NLRP3 inflammasome activation. Therefore, we hypothesised that HSF2 affects the secretion of IL-1β by regulating activation of the NLRP3 inflammasome. In this study, hsf^-/- DSS model mice showed highest levels of expression of the NLRP3 inflammasome and the secretion of IL-1β. In Caco-2 cells, the levels of expression of the NLRP3 inflammasome and the secretion of IL-1β were inhibited by overexpression of HSF2, and inhibited HSF2 increased activation of the NLRP3 inflammasome and the secretion of IL-1β. These findings indicated that HSF2 might be an important target for inflammatory modulation in UC.

Contradictory Effects of NLRP3 Inflammasome Regulatory Mechanisms in Colitis

The inflammasome is an intracellular molecular complex, which is mainly involved in innate immunity. Inflammasomes are formed in response to danger signals, associated with infection and injury, and mainly regulate the secretion of interleukin-1β and interleukin-18. Inflammasome dysregulation is known to be associated with various diseases and conditions, and its regulatory mechanisms have become of great interest in recent years. In the colon, inflammasomes have been reported to be associated with autophagy and the microbiota, and their dysregulation contributes to colitis and. However, the detailed role of inflammasomes in inflammatory bowel disease is still under debate because the mechanisms that regulate the inflammasome are complex and the inflammasome components and cytokines show seemingly contradictory multiple effects. Herein, we comprehensively review the literature on inflammasome functioning in the colon and describe the complex interactions of the NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome components with inflammatory cytokines, autophagy, and the microbiota in experimental colitis models and patients with inflammatory bowel disease.