The transcription factor Cdx2 regulates inflammasome activity through expression of the NLRP3 suppressor TRIM31 to maintain intestinal homeostasis

Updated insights into the molecular networks for NLRP3 inflammasome activation

Over the past decade, significant advances have been made in our understanding of how NACHT-, leucine-rich-repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasomes are activated. These findings provide detailed insights into the transcriptional and posttranslational regulatory processes, the structural-functional relationship of the activation processes, and the spatiotemporal dynamics of NLRP3 activation. Notably, the multifaceted mechanisms underlying the licensing of NLRP3 inflammasome activation constitute a focal point of intense research. Extensive research has revealed the interactions of NLRP3 and its inflammasome components with partner molecules in terms of positive and negative regulation. In this Review, we provide the current understanding of the complex molecular networks that play pivotal roles in regulating NLRP3 inflammasome priming, licensing and assembly. In addition, we highlight the intricate and interconnected mechanisms involved in the activation of the NLRP3 inflammasome and the associated regulatory pathways. Furthermore, we discuss recent advances in the development of therapeutic strategies targeting the NLRP3 inflammasome to identify potential therapeutics for NLRP3-associated inflammatory diseases. As research continues to uncover the intricacies of the molecular networks governing NLRP3 activation, novel approaches for therapeutic interventions against NLRP3-related pathologies are emerging.

Therapeutic potential of quercitrin in intervertebral disc degeneration: Targeting pyroptosis and inflammation

BACKGROUND

Intervertebral disc degeneration (IDD) is the predominant cause of low back pain (LBP), that leads to significant disability and imposes a substantial socioeconomic burden. Despite its prevalence, effective treatment for IDD has yet to be fully established. This study aimed to explore the therapeutic potential of quercitrin (QUE) in IDD development and to elucidate its underlying mechanisms.

METHODS

In vitro, we investigated the effects of QUE on ECM metabolism, inflammatory response and pyroptosis in IL-1β-stimulated nucleus pulposus cells (NPCs), along with the potential mechanisms. In vivo, mice lumbar spinal instability (LSI) was established to determined the impact of QUE on IDD progression.

RESULTS

QUE significantly alleviated inflammation and maintained the ECM homeostasis under IL-1β stimulation in NPCs. Moreover, QUE appeared to inhibit pyroptosis, which was closely related to intense inflammatory response. Notably, the protective effects of QUE were abrogated upon inhibition of TRIM31 activity, indicating that TRIM31 mediated pyroptosis suppression is crucial for the therapeutic effects of QUE.

CONCLUSION

QUE plays an important role in alleviating pyroptosis and inflammation within NPCs, thereby slowing the progression of IDD. Therefore, QUE might emerge as a promising therapeutic candidate for IDD, holding the potential for clinical application in the future.

Valtrate alleviates inflammation by targeting USP9X to enhance NLRP3 degradation

BACKGROUND

The NLRP3 inflammasome is a key regulator of innate immunity and plays a critical role in the pathogenesis of various inflammatory diseases. Regulating NLRP3 has emerged as a promising strategy for the development of anti-inflammatory therapies. Valtrate (Val), a natural compound derived from Valeriana officinalis Jones, has demonstrated significant anti-inflammatory activity. However, its precise mechanism of action remains unclear.

PURPOSE

This study elucidates the molecular mechanisms of Val suppressing NLRP3 inflammasome activation.

METHODS

We screened 100 natural compounds for anti-pyroptotic in lipopolysaccharide (LPS)/nigericin-stimulated THP-1 cells and bone marrow-derived macrophages (BMDMs) using lactate dehydrogenase (LDH) release assays. Val's effect on NLRP3 were assessed via immunoblotting and ELISA. Target identification employed DARTS, proteomics, thermal shift assay (TSA), microscale thermophoresis (MST), and molecular dynamics (MD) simulations. In vivo efficacy was evaluated in acetaminophen (APAP)- and LPS-induced liver injury models.

RESULTS

Val potently inhibited pyroptosis (99.20 % LDH reduction) and selectively degraded NLRP3 via post-translation mechanisms (PTMs) without altering its mRNA. DARTS and CETSA confirmed that Val directly interacts with the C2 fragment of USP9X without inhibiting its enzymatic activity, while RMSD, RMSF, and Gibbs energy landscape analyses supported its stable binding to USP9X, which was further confirmed by MST. Mechanistically, Val downregulated USP9X protein expression and promoted K48- and K63-linked ubiquitination and proteasomal degradation of NLRP3. In vivo, Val exhibited therapeutic potential in murine models of acute liver injury induced by APAP and LPS. Val reduced serum ALT and AST levels, inflammatory cytokines, and liver injury (histopathological analysis (H&E) and TUNEL).

CONCLUSION

This study uncovers an unrecognized mechanism by which Val attenuates NLRP3 inflammasome activation by disrupting the USP9X-NLRP3 axis, thereby promoting NLRP3 ubiquitination and proteasomal degradation. Notably, Val down-regulates USP9X protein levels without impairing its catalytic activity, representing a distinct mechanism from existing USP9X inhibitors. These findings not only deepen our understanding of Val's anti-inflammatory action but also underscore its promise as a lead compound for the development of novel therapeutics targeting NLRP3-driven inflammatory diseases.

Mechanisms and therapeutic strategies for NLRP3 degradation via post-translational modifications in ubiquitin-proteasome and autophagy lysosomal pathway

The NLRP3 inflammasome is crucial for immune responses. However, its overactivation can lead to severe inflammatory diseases, underscoring its importance as a target for therapeutic intervention. Although numerous inhibitors targeting NLRP3 exist, regulating its degradation offers an alternative and promising strategy to suppress its activation. The degradation of NLRP3 is primarily mediated by the proteasomal and autophagic pathways. The review not only elaborates on the traditional concepts of ubiquitination and NLRP3 degradation but also investigates the important roles of indirect regulatory modifications, such as phosphorylation, acetylation, ubiquitin-like modifications, and palmitoylation-key post-translational modifications (PTMs) that influence NLRP3 degradation. Additionally, we also discuss the potential targets that may affect NLRP3 degradation during the proteasomal and autophagic pathways. By unraveling these complex regulatory mechanisms, the review aims to enhance the understanding of NLRP3 regulation and its implications for developing therapeutic strategies to combat inflammatory diseases.

CDX2 and SATB2 loss are associated with myeloid cell infiltration and poor survival in colorectal cancer

BACKGROUND

Caudal-type homeobox 2 (CDX2) and special AT-rich sequence-binding protein 2 (SATB2) are transcription factors playing important roles in intestinal homeostasis and participating in the regulation of intestinal inflammation. In colorectal cancer (CRC), reduced expression levels of CDX2 and SATB2 have been associated with poor differentiation and worse survival. However, their prognostic significance still needs further clarification, and the associations between CDX2 and SATB2 and immune cell infiltration into the CRC microenvironment are largely unknown.

METHODS

We analyzed CDX2 and SATB2 expression in two large cohorts of stages I-IV CRC patients (N = 2302) and analyzed their associations with clinicopathologic parameters, the density of local immune cells (determined with three multiplex immunohistochemistry panels and conventional immunohistochemistry), and survival.

RESULTS

In mismatch repair-proficient tumors, reduced CDX2 and SATB2 expression were associated with higher densities of immature monocytic cells, macrophages, and M2-like macrophages. Low expression of CDX2 was associated with shorter cancer-specific survival independent of conventional prognostic parameters in both cohorts. In the larger cohort, adjusted hazard ratio (HR) for negative (vs. high) CDX2 expression was 3.62 (95% CI 2.08-6.31, ptrend < 0.0001), and adjusted HR for negative (vs. high) SATB2 level was 1.61 (95% CI 0.97-2.67, ptrend = 0.002).

CONCLUSION

This study indicates that reduced CDX2 and SATB2 expression levels are associated with myeloid cell infiltration in the CRC microenvironment and represent markers for poor outcome. These findings highlight the potential of CDX2 and SATB2 as biomarkers for classifying CRC patients and support their role in regulating the tumor microenvironment.

Loss of Trim31 Worsens Cardiac Remodeling in a Mouse Model of Heart Failure by Enhancing the Activation of the NLRP3 Inflammasome

Tripartite motif-containing protein 31 (Trim31) is known to be involved in various pathological conditions, including heart diseases. Nonetheless, its specific involvement in heart failure (HF) has yet to be determined. In this study, we examined the function and mechanism of Trim31 in HF by using mice with cardiac-specific knockout (cKO) of Trim31. The HF mouse model was induced via the subcutaneous injection of isoproterenol (ISO). We observed a decrease in Trim31 expression in the heart tissues of mice with HF. Compared with wild-type (WT) mice, Trim31 cKO mice presented more severe characteristics of HF, including worsened cardiac dysfunction, hypertrophy, and fibrosis. However, these symptoms in Trim31 cKO mice were significantly reversed when they received an intramyocardial injection of recombinant adeno-associated virus (AAV) expressing Trim31. Excessive activation of the NLRP3 inflammasome, manifested by increased levels of NLRP3, ASC, cleaved Caspase-1, cleaved GSDMD, IL-1β, and IL-18, was observed in Trim31 cKO mice with HF. However, Trim31 overexpression effectively reversed the NLRP3 inflammasome activation in Trim31 cKO mice with HF. Selective inhibition of the NLRP3 inflammasome with the NLRP3 inhibitor MCC950 effectively reversed the worsened cardiac dysfunction, hypertrophy, and fibrosis observed in Trim31 cKO mice with HF. Overall, the findings from this study reveal a crucial role of Trim31 in HF. Trim31 deficiency may contribute to the progression of HF by promoting cardiac hypertrophy, fibrosis, and inflammation by facilitating the activation of the NLRP3 inflammasome. Therefore, Trim31 may hold significant potential as a therapeutic target for the treatment of HF.

Trim31 deficiency exacerbates airway inflammation in asthma by enhancing the activation of the NLRP3 inflammasome

Tripartite motif (Trim) 31 is important for numerous inflammatory diseases. However, whether Trim31 regulates airway inflammation in asthma remains undetermined. The present work explored the role of Trim31 in airway inflammation in asthmatic mice established by ovalbumin (OVA) stimulation. Trim31 expression was markedly downregulated in the lungs of asthmatic mice. Compared with wild-type (WT) mice, Trim31-/- mice showed more severe pathological changes accompanied by increased inflammatory cell infiltration after OVA induction. House dust mite (HDM) stimulation evoked airway epithelial cell injury and inflammation, which were exacerbated by Trim31 silencing or attenuated by Trim31 overexpression. Further examination revealed that Trim31 deficiency exacerbated the activation of the NLRP3 inflammasome in OVA-induced asthmatic mice and HDM-stimulated airway epithelial cells. The inhibition of NLRP3 markedly diminished the Trim31 silencing-mediated enhancement of HDM-induced injury and inflammation in airway epithelial cells. In conclusion, this work demonstrates that Trim31 acts as a crucial mediator of airway inflammation in asthma. Trim31 deficiency may contribute to the progression of asthma by increasing NLRP3 inflammasome activation, suggesting that Trim31 is a potential therapeutic target for asthma.

Britannilactone 1-O-acetate induced ubiquitination of NLRP3 inflammasome through TRIM31 as a protective mechanism against reflux esophagitis-induced esophageal injury

BACKGROUND

Reflux esophagitis (RE) is a disease in which inflammation of the esophageal mucosa owing to the reflux of gastric contents into the esophagus results in cytokine damage. Britannilactone 1-O-acetate (Brt) has anti-inflammatory effects, significantly inhibiting the activation of the NLRP3 inflammasome, leading to a decrease in inflammatory factors including IL-1 β, IL-6, and TNF-α. However, the mechanism underlying its protective effect against RE-induced esophageal injury remains unclear. In the present study, we investigated the protective mechanism of TRIM31 against NLRP3 ubiquitination-induced RE both in vivo and in vitro.

METHODS

A model of RE was established in vivo in rats by the method of "4.2 mm pyloric clamp + 2/3 fundoplication". In vitro, the mod was constructed by using HET-1A (esophageal epithelial cells) and exposing the cells to acid, bile salts, and acidic bile salts. The 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide (MTT) assay was used to screen the concentration of administered drugs, and the viability of HET-1A cells in each group. HE staining was used to assess the degree of pathological damage in esophageal tissues. Toluidine blue staining was used to detect whether the protective function of the esophageal epithelial barrier was damaged and restored. The enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of IL-1 β, IL-6, and TNF-α factors in serum. Immunohistochemistry (IHC) was used to detect the expression level of NLRP3 in esophageal tissues. The molecular docking and Co-immunoprecipitation assay (Co-IP assay) were used to detect the TRIM31 interacts with NLRP3. Western blotting detected the Claudin-4, Claudin-5, The G-protein-coupled receptor calcium-sensitive receptor (CaSR), NLRP3, TRIM31, ASC, C-Caspase1, and Caspase1 protein expression levels.

RESULTS

Brt could alleviate RE inflammatory responses by modulating serum levels of IL-1 β, IL-6, and TNF-α. It also activated the expression of NLRP3, ASC, Caspase 1, and C-Caspase-1 in HET-1A cells. Brt also attenuated TRIM31/NLRP3-induced pathological injury in rats with RE through a molecular mechanism consistent with the in vitro results.

CONCLUSIONS

Brt promotes the ubiquitination of NLRP3 through TRIM31 and attenuates esophageal epithelial damage induced by RE caused by acidic bile salt exposure. This study provides valuable insights into the mechanism of action of Brt in the treatment of RE and highlights its promising application in the prevention of NLRP3 inflammatory vesicle-associated inflammatory pathological injury.

E3 ubiquitin ligase TRIM31: A potential therapeutic target

Ubiquitination is a key mechanism for post-translational protein modification, affecting protein localization, metabolism, degradation and various cellular physiological processes. Dysregulation of ubiquitination is associated with the pathogenesis of various diseases, such as tumors and cardiovascular diseases, making it a primary area of interest in biochemical research and drug development endeavors. E3 ubiquitin ligases play a pivotal role in modulating the ubiquitination of substrate proteins through their unique recognition functions. TRIM31, a member of the TRIM family of E3 ubiquitin ligases, is aberrantly expressed in different pathophysiological conditions. The biological function of TRIM31 is associated with the occurrence and development of diverse diseases. TRIM31 has been demonstrated to inhibit inflammation by promoting ubiquitin-proteasome-mediated degradation of the sensing protein NLRP3 in the inflammasome. TRIM31 mediates ubiquitination of MAVS, inducing the formation of prion-like aggregates, and triggering innate antiviral immune responses. TRIM31 is also implicated in tumor pathophysiology through its ability to promote ubiquitination of the tumor suppressor protein p53. These findings indicate that TRIM31 is a potential therapeutic target, and subsequent in-depth research of TRIM31 is anticipated to provide information on its clinical application in therapy.

ACV with/without IVM: a new talk on intestinal CDX2 and muscular CD34 and Cyclin D1 during Trichinella spiralis infection

The current study assessed the efficacy of Acyclovir (ACV) and Ivermectin (IVM) as monotherapies and combined treatments for intestinal and muscular stages of Trichinella spiralis infection. One-hundred Swiss albino mice received orally 250 ± 50 infectious larvae and were divided into infected-untreated (Group-1), IVM-treated (Group-2), ACV-treated (Group-3), combined IVM+ACV (Group-4), and healthy controls (Group-5). Each group was subdivided into subgroup-A-enteric phase (10 mice, sacrificed day-7 p.i.) and subgroup-B-muscular phase (10 mice, sacrificed day-35 p.i.). Survival rate and body weight were recorded. Parasite burden and intestinal histopathology were assessed. In addition, immunohistochemical expression of epithelial CDX2 in the intestinal phase and CyclinD1 as well as CD34 in the muscular phase were evaluated. Compared, IVM and ACV monotherapies showed insignificant differences in the amelioration of enteric histopathology, except for lymphocytic counts. In the muscle phase, monotherapies showed variable disruptions in the encapsulated larvae. Compared with monotherapies, the combined treatment performed relatively better improvement of intestinal inflammation and reduction in the enteric and muscular parasite burden. CDX2 and CyclinD1 positively correlated with intestinal inflammation and parasite burden, while CD34 showed a negative correlation. CDX2 positively correlated with CyclinD1. CD34 negatively correlated with CDX2 and CyclinD1. IVM +ACV significantly ameliorated CDX2, CyclinD1, and CD34 expressions compared with monotherapies. Conclusion. T. spiralis infection-associated inflammation induced CDX2 and CyclinD1 expressions, whereas CD34 was reduced. The molecular tumorigenic effect of the nematode remains questionable. Nevertheless, IVM +ACV appeared to be a promising anthelminthic anti-inflammatory combination that, in parallel, rectified CDX2, CyclinD1, and CD34 expressions.

Inhibition of Immunoproteasome Attenuates NLRP3 Inflammasome Response by Regulating E3 Ubiquitin Ligase TRIM31

Excessive secretion of pro-inflammatory cytokines leads to the disruption of intestinal barrier in inflammatory bowel disease (IBD). The inflammatory cytokine tumor necrosis factor alpha (TNFα) induces the assembly of the NLRP3 inflammasome, resulting in the augmented secretion of inflammatory cytokines implicated in the pathogenesis of inflammatory bowel disease (IBD). TNFα has also been known to induce the formation of immunoproteasome (IP), which incorporates immunosubunits LMP2, LMP7, and MECL-1. Inhibition of IP activity using the IP subunit LMP2-specific inhibitor YU102, a peptide epoxyketone, decreased the protein levels of NLRP3 and increased the K48-linked polyubiquitination levels of NLRP3 in TNFα-stimulated intestinal epithelial cells. We observed that inhibition of IP activity caused an increase in the protein level of the ubiquitin E3 ligase, tripartite motif-containing protein 31 (TRIM31). TRIM31 facilitated K48-linked polyubiquitination and proteasomal degradation of NLRP3 with an enhanced interaction between NLRP3 and TRIM31 in intestinal epithelial cells. In addition, IP inhibition using YU102 ameliorated the symptoms of colitis in the model mice inflicted with dextran sodium sulfate (DSS). Administration of YU102 in the DSS-treated colitis model mice caused suppression of the NLRP3 protein levels and accompanied inflammatory cytokine release in the intestinal epithelium. Taken together, we demonstrated that inhibiting IP under inflammatory conditions induces E3 ligase TRIM31-mediated NLRP3 degradation, leading to attenuation of the NLRP3 inflammatory response that triggers disruption of intestinal barrier.

Arabinose confers protection against intestinal injury by improving integrity of intestinal mucosal barrier

There is a growing amount of research that highlights the significant involvement of metabolic imbalance and the inflammatory response in the advancement of colitis. Arabinose is a naturally occurring bioactive monosaccharide that plays a crucial role in the metabolic processes and synthesis of many compounds in living organisms. However, the more detailed molecular mechanism by which the administration of arabinose alleviates the progression of colitis and its associated carcinogenesis is still not fully understood. In the present study, arabinose is recognized as a significant and inherent protector of the intestinal mucosal barrier through its role in preserving the integrity of tight junctions within the intestines. Also, it is important to note that there is a positive correlation between the severity of inflammatory bowel disease (IBD) and colorectal cancer (CRC), as well as chemically-induced colitis in mice, and lower levels of arabinose in the bloodstream. In two mouse models of colitis, caused by dextran sodium sulfate (DSS) or by spontaneous colitis in IL-10-/- mice, damage to the intestinal mucosa was reduced by giving the mice arabinose. When arabinose is administrated to model with colitis, it sets off a chain of events that help keep the lysosomes together and stop cathepsin B from being released. During the progression of intestinal epithelial injury, this process blocks myosin light chain kinase (MLCK) from damaging tight junctions and causing mitochondrial dysfunction. In summary, the results of the study have provided evidence supporting the beneficial effects of arabinose in mitigating the progression of colitis. This is achieved through its ability to avoid dysregulation of the intestinal barrier. Consequently, arabinose may hold promise as a therapeutic supplementation for the management of colitis.

The prognostic potential of CDX2 in colorectal cancer: Harmonizing biology and clinical practice

Adjuvant chemotherapy following surgical intervention remains the primary treatment option for patients with localized colorectal cancer (CRC). However, a significant proportion of patients will have an unfavorable outcome after current forms of chemotherapy. While reflecting the increasing complexity of CRC, the clinical application of molecular biomarkers provides information that can be utilized to guide therapeutic strategies. Among these, caudal-related homeobox transcription factor 2 (CDX2) emerges as a biomarker of both prognosis and relapse after therapy. CDX2 is a key transcription factor that controls intestinal fate. Although rarely mutated in CRC, loss of CDX2 expression has been reported mostly in right-sided, microsatellite-unstable tumors and is associated with aggressive carcinomas. The pathological assessment of CDX2 by immunohistochemistry can thus identify patients with high-risk CRC, but the evaluation of CDX2 expression remains challenging in a substantial proportion of patients. In this review, we discuss the roles of CDX2 in homeostasis and CRC and the alterations that lead to protein expression loss. Furthermore, we review the clinical significance of CDX2 assessment, with a particular focus on its current use as a biomarker for pathological evaluation and clinical decision-making. Finally, we attempt to clarify the molecular implications of CDX2 deficiency, ultimately providing insights for a more precise evaluation of CDX2 protein expression.

An update on the role of TRIM/NLRP3 signaling pathway in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease of large and medium arteries that includes lipid metabolism disorder and recruitment of immune cells to the artery wall. An increasing number of studies have confirmed that inflammasome over-activation is associated with the onset and progression of atherosclerosis. The NLRP3 inflammasome, in particular, has been proven to increase the incidence rate of cardiovascular diseases (CVD) by promoting pro-inflammatory cytokine release and reducing plaque stability. The strict control of inflammasome and prevention of excessive inflammatory reactions have been the research focus of inflammatory diseases. Tripartite motif (TRIM) is a protein family with a conservative structure and rapid evolution. Several studies have demonstrated the TRIM family's regulatory role in mediating inflammation. This review aims to clarify the relationship between TRIMs and NLRP3 inflammasome and provide insights for future research and treatment discovery.

Comparative Transcriptomic Analysis Reveals the Functionally Segmented Intestine in Tunicate Ascidian

The vertebrate intestinal system consists of separate segments that remarkably differ in morphology and function. However, the origin of intestinal segmentation remains unclear. In this study, we investigated the segmentation of the intestine in a tunicate ascidian species, Ciona savignyi, by performing RNA sequencing. The gene expression profiles showed that the whole intestine was separated into three segments. Digestion, ion transport and signal transduction, and immune-related pathway genes were enriched in the proximal, middle, and distal parts of the intestine, respectively, implying that digestion, absorption, and immune function appear to be regional specializations in the ascidian intestine. We further performed a multi-species comparison analysis and found that the Ciona intestine showed a similar gene expression pattern to vertebrates, indicating tunicates and vertebrates might share the conserved intestinal functions. Intriguingly, vertebrate pancreatic homologous genes were expressed in the digestive segment of the Ciona intestine, suggesting that the proximal intestine might play the part of pancreatic functions in C. savignyi. Our results demonstrate that the tunicate intestine can be functionally separated into three distinct segments, which are comparable to the corresponding regions of the vertebrate intestinal system, offering insights into the functional evolution of the digestive system in chordates.

The role and mechanism of flavonoid herbal natural products in ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory disease of the intestine that presents clinically with abdominal pain, mucopurulent stools, and posterior urgency. The lesions of UC are mainly concentrated in the rectal and colonic mucosa and submucosa. For patients with mild to moderate UC, the best pharmacological treatment includes glucocorticoids, immunosuppressants, antibiotics, and biologics, but the long-term application can have serious toxic side effects. Currently, nearly 40% of UC patients are treated with herbal natural products in combination with traditional medications to reduce the incidence of toxic side effects. Flavonoid herbal natural products are the most widely distributed polyphenols in plants and fruits, which have certain antioxidant and anti-inflammatory activities. Flavonoid herbal natural products have achieved remarkable efficacy in the treatment of UC. The pharmacological mechanisms are related to anti-inflammation, promotion of mucosal healing, maintenance of intestinal immune homeostasis, and regulation of intestinal flora. In this paper, we summarize the flavonoid components of anti-ulcerative colitis and their mechanisms reported in the past 10 years, to provide a basis for rational clinical use and the development of new anti-ulcerative colitis drugs.