Discovery of Triazinone Derivatives as Novel, Specific, and Direct NLRP3 Inflammasome Inhibitors for the Treatment of DSS-Induced Ulcerative Colitis

Coptisine alleviates colitis through modulating gut microbiota and inhibiting TXNIP/NLRP3 inflammasome

ETHNOPHARMACOLOGICAL RELEVANCE

Ulcerative colitis (UC) is a disease involving the enteric canal which is characterised by chronisch inflammatory reaction. Coptisine (COP), the distinctive component of Coptis chinensis Franch., is famous for its anti-inflammation, antioxidation, anti-bacteria, and anti-cancer. Earlier researches certified that COP is a prospective remedy for colitis, but the mechanism of colitis and the therapeutical target of COP are deficiently elucidated.

AIM OF THIS STUDY

In this follow-up study, we adopted dextran sulfate sodium (DSS)-elicited UC model to further elucidate the possible mechanism of COP on UC in mice.

MATERIALS AND METHODS

COP and the positive drug sulfasalazine (SASP) were administered by oral gavage in DSS-induced colitis mouse model. Oxidative stress, inflammatory cytokines, intestinal barrier permeability, protein expression of the TXNIP/NLRP3 inflammasome pathway and intestinal microbiome structure were assessed.

RESULTS

Among this investigation, our team discovered that COP could mitigate DSS-elicited UC in murines, with prominent amelioration in weight loss, disease activity index, intestinal permeability (serum diamine oxidase and D-lactate), contracted colonal length and histologic alterations. Furthermore, COP greatly lowered the generation of pro-inflammatory factors, malondialdehyde (MDA) activity and reactive oxygen species (ROS) level, while increased superoxide dismutase (SOD) activity in colonal tissues. Additionally, COP downmodulated the proteic expressions of thioredoxin-interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein (ASC), caspase-1, IL-1β and IL-18. Enteric microbiome sequencing displayed that DSS and COP tremendously influenced the constitution and diversity of enteric microbes in DSS-elicited UC murines. Besides, COP elevated the abundance of probiotic bacteria Bacteroidota, Akkermansia_muciniphila and Bacteroides_acidifaciens, lowered the proportions of potential pathogenic bacteria, such as Lachnospiraceae, Acetatifactor_muris, Clostridium_XlVa, Alistipes and Oscillibacter, and reduced the ratio of Bacillota/Bacteroidota, which vastly helped to reverse the enteric microbiome to a balanceable condition. Alterations in these bacteria were strongly correlated with the colitis relative index.

CONCLUSION

The mechanism of COP against UC is connected with the suppression of TXNIP/NLRP3 inflammasome signalling pathway and the adjustment of the enteric microbiome profiles. The proofs offer new understandings upon the anti-UC function of COP, which might be a prospective candidate against UC.

NLRP3 inflammasome and its role in autoimmune diseases: A promising therapeutic target

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 IL-1β and IL-18. Numerous studies have highlighted its crucial role in the pathogenesis and development of inflammatory bowel disease, rheumatoid arthritis, systemic lupus erythematosus, autoimmune thyroid diseases, and other autoimmune diseases. Therefore, investigating the underlying mechanisms of NLRP3 in disease and targeted drug therapies holds clinical significance. This review summarizes the structure, assembly, and activation mechanisms of the NLRP3 inflammasome, focusing on its role and involvement in various autoimmune diseases. This review also identifies studies where the involvement of the NLRP3 inflammasome in the disease mechanism within the same disease appears contradictory, as well as differences in NLRP3-related gene polymorphisms among different ethnic groups. Additionally, the latest therapeutic advances in targeting the NLRP3 inflammasome for autoimmune diseases are outlined, and novel clinical perspectives are discussed. Conclusively, this review provides a consolidated source of information on the NLRP3 inflammasome and may guide future research efforts that have the potential to positively impact patient outcomes.

Discovery of novel biphenyl-sulfonamide analogues as NLRP3 inflammasome inhibitors

The aberrant activation of NLRP3 inflammasome has been observed in various human diseases. Targeting the NLRP3 protein with small molecule inhibitors shows immense potential as an effective strategy for disease intervention. Herein, a series of novel biphenyl-sulfonamide NLRP3 inflammasome inhibitors were designed and synthesized. The representative compound H28 was identified as potent and specific NLRP3 inflammasome inhibitor with IC50 values of 0.57 μM. Preliminary mechanistic studies have revealed that compound H28 exhibits direct binding to the NLRP3 protein (KD: 1.15 μM), effectively inhibiting the assembly and activation of the NLRP3 inflammasome. The results in a mouse acute peritonitis model revealed that H28 effectively inhibit the NLRP3 inflammasome pathway, demonstrating their anti-inflammatory properties. Our findings strongly support the further development of H28 as potential lead compound for treating NLRP3-related diseases.

Discovery of Potent, Orally Bioavailable, Tricyclic NLRP3 Inhibitors

NLRP3 is a molecular sensor recognizing a wide range of danger signals. Its activation leads to the assembly of an inflammasome that allows for activation of caspase-1 and subsequent maturation of IL-1β and IL-18, as well as cleavage of Gasdermin-d and pyroptotic cell death. The NLRP3 inflammasome has been implicated in a plethora of diseases including gout, type 2 diabetes, atherosclerosis, Alzheimer's disease, and cancer. In this publication, we describe the discovery of a novel, tricyclic, NLRP3-binding scaffold by high-throughput screening. The hit (1) could be optimized into an advanced compound NP3-562 demonstrating excellent potency in human whole blood and full inhibition of IL-1β release in a mouse acute peritonitis model at 30 mg/kg po dose. An X-ray structure of NP3-562 bound to the NLRP3 NACHT domain revealed a unique binding mode as compared to the known sulfonylurea-based inhibitors. In addition, NP3-562 shows also a good overall development profile.

SLC6A14 promotes ulcerative colitis progression by facilitating NLRP3 inflammasome-mediated pyroptosis

BACKGROUND

Ulcerative colitis (UC) is an inflammatory condition with frequent relapse and recurrence. Evidence suggests the involvement of SLC6A14 in UC pathogenesis, but the central regulator remains unknown.

AIM

To explore the role of SLC6A14 in UC-associated pyroptosis.

METHODS

Quantitative real-time polymerase chain reaction (qRT-PCR), immunoblotting, and immunohistochemical were used to assess SLC6A14 in human UC tissues. Lipopolysaccharide (LPS) was used to induce inflammation in FHC and NCM460 cells and model enteritis, and SLC6A14 levels were assessed. Pyroptosis markers were quantified using enzyme-linked immunosorbent assay, Western blotting, and qRT-PCR, and EdU incubation, CCK-8 assays and flow cytometry were used to examine proliferation and apoptosis. Mouse models of UC were used for verification.

RESULTS

SLC6A14 was increased and correlated with NLRP3 in UC tissues. LPS-induced FHC and NCM460 cells showed increased SLC6A14 levels. Reducing SLC6A14 increased cell proliferation and suppressed apoptosis. Reducing SLC6A14 decreased pyroptosis-associated proteins (ASC, IL-1β, IL-18, NLRP3). NLRP3 overexpression counteracted the effects of sh-SLC6A14 on LPS-induced FHC and NCM460 cell pyroptosis. SLC6A14 improved the mucosa in mice with dextran sulfate sodium-induced colitis.

CONCLUSION

SLC6A14 promotes UC pyroptosis by regulating NLRP3, suggesting the therapeutic potential of modulating the SLC6A14/NLRP3 axis.