Tabersonine, a natural NLRP3 inhibitor, suppresses inflammasome activation in macrophages and attenuate NLRP3-driven diseases in mice

Macrophage‑driven pathogenesis in acute lung injury/acute respiratory disease syndrome: Harnessing natural products for therapeutic interventions (Review)

Acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) is a common respiratory disease characterized by hypoxemia and respiratory distress. It is associated with high morbidity and mortality. Due to the complex pathogenesis of ALI, the clinical management of patients with ALI/ARDS is challenging, resulting in numerous post‑treatment sequelae and compromising the quality of life of patients. Macrophages, as a class of innate immune cells, play an important role in ALI/ARDS. In recent years, the functions and phenotypes of macrophages have been better understood due to the development of flow cytometry, immunofluorescence, single‑cell sequencing and spatial genomics. However, no macrophage‑targeted drugs for the treatment of ALI/ARDS currently exist in clinical practice. Natural products are important for drug development, and it has been shown that numerous natural compounds from herbal medicine can alleviate ALI/ARDS caused by various factors by modulating macrophage abnormalities. In the present review, the natural products from herbal medicine that can modulate macrophage abnormalities in ALI/ARDS to treat ALI/ARDS are introduced, and their mechanisms of action, discovered in the previous five years (2019‑2024), are presented. This will provide novel ideas and directions for further research, to develop new drugs for the treatment of ALI/ARDS.

MCC950 promotes diabetic wound healing through modulating macrophage polarization in an MDSC-dependent manner

Diabetic foot ulcers (DFUs) are serious skin injuries whereby the wound healing process is frequently stalled in the inflammatory phase. Currently, there is a lack of effective therapeutic strategies. MCC950, a highly selective nod-like receptor family pyrin domain containing 3 (NLRP3) inhibitor, has been reported to show strong anti-inflammation effects in many diseases. In this study, we unveiled the role of MCC950 in DFU mice model and its underlying molecular mechanisms. MCC950 could significantly accelerate diabetic wound healing, as shown by shortened healing time and better healing quality. Moreover, increased M2 phenotype macrophages and decreased pro-inflammatory genes were observed in MCC950-treated DFU mice. Additionally, myeloid-derived suppressor cells (MDSCs) were significantly increased in blood, spleen and wound tissues at different time courses. Specifically, MCC950 could recruit more MDSCs in an early phase in DFU mice, exerting an anti-inflammation effect. We identified the cell crosstalk between macrophages and MDSCs with MCC950 treatment process. Depleting MDSCs in vivo could eliminate the therapeutic effect of MCC950 on diabetic wound healing through inhibiting M2 macrophage polarization. Besides, MDSCs isolated from the wounds of MCC950 or saline treated mice were cocultured with bone marrow derived macrophage (BMDM) in a transwell system. Results confirmed that MDSCs sorted from MCC950 treated mice caused a significant increased percentage of M2 macrophages. Collectively, our findings suggest that the administration of MCC950 has the potential to accelerate diabetic wound healing by promoting M2 macrophage polarization in an MDSC-dependent manner. This study provides valuable insights into the utilization of pharmacological agents for DFU treatment.

The role of quercetin in NLRP3-associated inflammation

Quercetin is a natural flavonoid that is widely found in fruits and vegetables. As an important flavonoid, it exhibits a wide range of biological activities, including antioxidant, anti-inflammatory, antiviral, immunomodulatory, and analgesic activities. Quercetin exerts powerful antioxidant activity by regulating glutathione, enzyme activity, and the production of reactive oxygen species (ROS). Quercetin exerts powerful anti-inflammatory effects by acting on the Nod-like receptor protein 3 (NLRP3) inflammasome. In diabetes, quercetin has been shown to improve insulin sensitivity and reduce high blood sugar level, while, in neurological diseases, it potentially prevents neuronal degeneration and cognitive decline by regulating neuroinflammation. In addition, in liver diseases, quercetin may improve liver inflammation and fibrosis by regulating the NLRP3 activity. In addition, quercetin may improve inflammation in other diseases based on the NLRP3 inflammasome. With this background, in this review, we have discussed the progress in the study on the mechanism of quercetin toward improving inflammation via NLRP3 inflammasome in the past decade. In addition, from the perspective of quercetin glycoside derivatives, the anti-inflammatory mechanism of hyperoside, rutin, and isoquercetin based on NLRP3 inflammasome has been discussed. Moreover, we have discussed the pharmacokinetics of quercetin and its nanoformulation application, with the aim to provide new ideas for further research on the anti-inflammatory effect of quercetin and its glycoside derivatives based on NLRP3 inflammasome, as well as in drug development and application.

Angelica sinensis Polysaccharide Alleviates Staphylococcus aureus-Induced Mastitis by Regulating The Intestinal Flora and Gut Metabolites

The modulation of intestinal flora by various polysaccharides has been shown to mitigate disease progression. Recent research reveals a significant link between intestinal flora and the progression of mastitis. This study demonstrates that the oral administration of Angelica sinensis polysaccharide (ASP) reduces mammary inflammation and blood-milk barrier (BMB) damage induced by Staphylococcus aureus in mice, primarily through the modulation of intestinal flora. The beneficial effects of ASP were negated when antibiotics disrupted the gut microbiota in mice. Furthermore, fecal microbiota transplantation (FMT) from ASP-treated mice to recipients markedly alleviated symptoms of S. aureus-induced mastitis. Oral ASP not only enhances gut microbial diversity but also shifts its composition, increasing the abundance of Lachnospiraceae_NK4A136 while reducing Erysipelatoclostridium. Metabolomic analysis revealed that ASP alters intestinal metabolic pathways, elevating levels of metabolites, such as tabersonine and riboflavin. Notably, tabersonine was found to ameliorate S. aureus-induced mastitis. These results suggest that targeting intestinal flora and metabolism through polysaccharides could serve as a promising strategy for mastitis intervention and potentially for other infectious diseases, as well.

Intracerebroventricular infusion of secretoneurin inhibits neuronal NLRP3-Apoptosis pathway and preserves learning and memory after cerebral ischemia

Transient global cerebral ischemia (GCI) results in delayed neuronal death, primarily apoptosis, in the hippocampal CA1 subregion, which leads to severe cognitive deficits. While therapeutic hypothermia is an approved treatment for patients following cardiac arrest, it is associated with various adverse effects. Secretoneurin (SN) is an evolutionarily conserved neuropeptide generated in the brain, adrenal medulla and other endocrine tissues. In this study, SN was infused into the rat brain by intracerebroventricular injection 1 day after GCI, and we demonstrated that SN could significantly preserve spatial learning and memory in the Barnes maze tasks examined on days 14-17 after GCI. To further investigate underlying pathways involved, we demonstrated that, on day 5 after GCI, SN could significantly inhibit GCI-induced expression levels of Apoptosis Inducing Factor (AIF) and cleaved-PARP1, as well as neuronal apoptosis and synaptic loss in the hippocampal CA1 region. Additionally, SN could attenuate GCI-induced activation of both caspase-1 and caspase-3, and the levels of pro-inflammatory cytokines IL-1β and IL-18 in the CA1 region. Mechanically, we observed that treatment with SN effectively inhibited NLRP3 protein elevation and the bindings of NLRP3-ASC and ASC-caspase-1 in hippocampal neurons after GCI. In summary, our data indicate that SN could effectively attenuate NLRP3 inflammasome formation, as well as the activation of caspase-1 and -3, the production of pro-inflammatory cytokines, and ultimately the neuronal apoptotic loss induced by GCI. Potential neuronal pyroptosis, or caspase-1-dependent cell death, could also be involved in ischemic neuronal death, which needs further investigation.

NLRP3 inflammasome in atherosclerosis: Mechanisms and targeted therapies

Atherosclerosis (AS) is the primary pathology behind various cardiovascular diseases and the leading cause of death and disability globally. Recent evidence suggests that AS is a chronic vascular inflammatory disease caused by multiple factors. In this context, the NLRP3 inflammasome, acting as a signal transducer of the immune system, plays a critical role in the onset and progression of AS. The NLRP3 inflammasome is involved in endothelial injury, foam cell formation, and pyroptosis in AS. Therefore, targeting the NLRP3 inflammasome offers a new treatment strategy for AS. This review highlights the latest insights into AS pathogenesis and the pharmacological therapies targeting the NLRP3 inflammasome, focusing on optimal targets for small molecule inhibitors. These insights are valuable for rational drug design and the pharmacological assessment of new targeted NLRP3 inflammasome inhibitors in treating AS.

The STAT3 inhibitor B9 alleviates lipopolysaccharide-induced acute lung injury through its anti-inflammatory effects

The development of acute lung injury (ALI), a common respiratory condition with multiple causes, is significantly influenced by the pro-inflammatory environment of signal transducer and activator of transcription 3 (STAT3) in macrophages. Our study aimed to evaluate the anti-inflammatory effects of B9 (N-(4-hydroxyphenyl)-9, 10-dioxo-9, 10-dihydroanthracene-2-sulfonamide), a novel inhibitor targeting the STAT3 SH2 domain, in macrophages and to assess its therapeutic potential for ALI using a mouse model of lipopolysaccharide (LPS)-induced ALI. We found that B9 (30 mg/kg) significantly reduced lung pathological damage and neutrophil infiltration caused by the intratracheal administration of LPS. Additionally, the high expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in alveolar lavage fluid was also inhibited by B9 treatment. The decreased expression of CD86 and increased CD206 in lung tissue demonstrated the anti-inflammatory effect of B9, which was due to its inhibition of the STAT3 signaling pathway in macrophages of ALI mice. Furthermore, B9 suppressed the activation of RAW264.7 cells induced by LPS, characterized by its ability to inhibit the activation of iNOS and STAT3 in a dose-dependent manner, as well as reduce the secretion of IL-6 and IL-1β. The in vivo preliminary safety evaluation indicated that B9 had a favorable safety profile at the administered doses. These results suggest that B9 exerts a therapeutic effect on LPS-induced ALI, potentially by preventing the phosphorylation of STAT3 Y705 and S727 without affecting the STAT3 protein level. Taken together, these findings provide a foundation for developing B9 as a novel anti-inflammatory agent for ameliorating LPS-induced ALI.

Tabersonine Enhances Olaparib Sensitivity through FHL1-Mediated Epithelial-Mesenchymal Transition in an Ovarian Tumor

Ovarian cancer (OVC) is one of the most aggressive gynecological malignancies worldwide. Although olaparib treatment has shown favorable outcomes against the treatment of OVC, its effectiveness remains limited in some OVC patients. Investigating new strategies to improve the therapeutic efficacy of olaparib against OVC is imperative. Our study identified tabersonine, a natural indole alkaloid, for its potential to increase the chemosensitivity of olaparib in OVC. The combined treatment of olaparib and tabersonine synergistically inhibited cell proliferation in OVC cells and suppressed tumor growth in A2780 xenografts. The combined treatment effectively suppressed epithelial-mesenchymal transition (EMT) by altering the expression of E-cadherin, N-cadherin, and vimentin and induced DNA damage responses. Integrating quantitative proteomics, FHL1 was identified as a potential regulator to modulate EMT after tabersonine treatment. Increased expression of FHL1 was induced by tabersonine treatment, while downregulation of FHL1 reversed the inhibitory effects of tabersonine on OVC cells by mediating EMT. In vivo findings further reflected that the combined treatment of tabersonine and olaparib significantly inhibited tumor growth and OVC metastasis through upregulation of FHL1. Our findings reveal the role of tabersonine in improving the sensitivity of olaparib in OVC through FHL1-mediated EMT, suggesting that tabersonine holds promise for future application in OVC treatment.

Britannin as a novel NLRP3 inhibitor, suppresses inflammasome activation in macrophages and alleviates NLRP3-related diseases in mice

Overactivation of the NLRP3 inflammasomes induces production of pro-inflammatory cytokines and drives pathological processes. Pharmacological inhibition of NLRP3 is an explicit strategy for the treatment of inflammatory diseases. Thus far no drug specifically targeting NLRP3 has been approved by the FDA for clinical use. This study was aimed to discover novel NLRP3 inhibitors that could suppress NLRP3-mediated pyroptosis. We screened 95 natural products from our in-house library for their inhibitory activity on IL-1β secretion in LPS + ATP-challenged BMDMs, found that Britannin exerted the most potent inhibitory effect with an IC50 value of 3.630 µM. We showed that Britannin (1, 5, 10 µM) dose-dependently inhibited secretion of the cleaved Caspase-1 (p20) and the mature IL-1β, and suppressed NLRP3-mediated pyroptosis in both murine and human macrophages. We demonstrated that Britannin specifically inhibited the activation step of NLRP3 inflammasome in BMDMs via interrupting the assembly step, especially the interaction between NLRP3 and NEK7. We revealed that Britannin directly bound to NLRP3 NACHT domain at Arg335 and Gly271. Moreover, Britannin suppressed NLRP3 activation in an ATPase-independent way, suggesting it as a lead compound for design and development of novel NLRP3 inhibitors. In mouse models of MSU-induced gouty arthritis and LPS-induced acute lung injury (ALI), administration of Britannin (20 mg/kg, i.p.) significantly alleviated NLRP3-mediated inflammation; the therapeutic effects of Britannin were dismissed by NLRP3 knockout. In conclusion, Britannin is an effective natural NLRP3 inhibitor and a potential lead compound for the development of drugs targeting NLRP3.

Brazilin is a natural product inhibitor of the NLRP3 inflammasome

Excessive or aberrant NLRP3 inflammasome activation has been implicated in the progression and initiation of many inflammatory conditions; however, currently no NLRP3 inflammasome inhibitors have been approved for therapeutic use in the clinic. Here we have identified that the natural product brazilin effectively inhibits both priming and activation of the NLRP3 inflammasome in cultured murine macrophages, a human iPSC microglial cell line and in a mouse model of acute peritoneal inflammation. Through computational modeling, we predict that brazilin can adopt a favorable binding pose within a site of the NLRP3 protein which is essential for its conformational activation. Our results not only encourage further evaluation of brazilin as a therapeutic agent for NLRP3-related inflammatory diseases, but also introduce this small-molecule as a promising scaffold structure for the development of derivative NLRP3 inhibitor compounds.

Acacetin inhibits inflammation by blocking MAPK/NF-κB pathways and NLRP3 inflammasome activation

Objective: Our preliminary research indicates that acacetin modulates the nucleotide-binding oligomerization domain (NOD)-like receptor pyrin domain containing 3 (NLRP3) inflammasome, providing protection against Alzheimer's Disease (AD) and cerebral ischemic reperfusion injury. The mechanisms of acacetin to inhibit the activation of the NLRP3 inflammasome remain fully elucidated. This study aims to investigate the effects and potential mechanisms of acacetin on various agonists induced NLRP3 inflammasome activation. Methods: A model for the NLRP3 inflammasome activation was established in mouse bone marrow-derived macrophages (BMDMs) using Monosodium Urate (MSU), Nigericin, Adenosine Triphosphate (ATP), and Pam3CSK4, separately. Western blot analysis (WB) was employed to detect Pro-caspase-1, Pro-Interleukin-1β (Pro-IL-1β) in cell lysates, and caspase-1, IL-1β in supernatants. Enzyme-Linked Immunosorbent Assay (ELISA) was used to measured the release of IL-1β, IL-18, and Tumor Necrosis Factor-alpha (TNF-α) in cell supernatants to assess the impact of acacetin on NLRP3 inflammasome activation. The lactate dehydrogenase (LDH) release was also assessed. The Nuclear Factor Kappa B (NF-κB) and Mitogen-Activated Protein Kinase (MAPK) signaling pathways related proteins were evaluated by WB, and NF-κB nuclear translocation was observed via laser scanning confocal microscopy (LSCM). Disuccinimidyl Suberate (DSS) cross-linking was employed to detect oligomerization of Apoptosis-associated Speck-like protein containing a Caspase Recruitment Domain (ASC), and LSCM was also used to observe Reactive Oxygen Species (ROS) production. Inductively Coupled Plasma (ICP) and N-(6-methoxyquinolyl) acetoethyl ester (MQAE) assays were utilized to determined the effects of acacetin on the efflux of potassium (K+) and chloride (Cl-) ions. Results: Acacetin inhibited NLRP3 inflammasome activation induced by various agonists, reducing the release of TNF-α, IL-1β, IL-18, and LDH. It suppressed the expression of Lipopolysaccharides (LPS)-activated Phosphorylated ERK (p-ERK), p-JNK, and p-p38, inhibited NF-κB p65 phosphorylation and nuclear translocation. Acacetin also reduced ROS production and inhibited ASC aggregation, thus suppressing NLRP3 inflammasome activation. Notably, acacetin did not affect K+ and Cl-ions efflux during the activation process. Conclusion: Acacetin shows inhibitory effects on both the priming and assembly processes of the NLRP3 inflammasome, positioning it as a promising new candidate for the treatment of NLRP3 inflammasome-related diseases.

Targeting NLRP3 Inflammasome: Structure, Function, and Inhibitors

Inflammasomes are multimeric protein complexes that can detect various physiological stimuli and danger signals. As a result, they perform a crucial function in the innate immune response. The NLRP3 inflammasome, as a vital constituent of the inflammasome family, is significant in defending against pathogen invasion and preserving cellhomeostasis. NLRP3 inflammasome dysregulation is connected to various pathological conditions, including inflammatory diseases, cancer, and cardiovascular and neurodegenerative diseases. This profile makes NLRP3 an applicable target for treating related diseases, and therefore, there are rising NLRP3 inhibitors disclosed for therapy. Herein, we summarized the updated advances in the structure, function, and inhibitors of NLRP3 inflammasome. Moreover, we aimed to provide an overview of the existing products and future directions for drug research and development.

A review of studies on the implication of NLRP3 inflammasome for Parkinson's disease and related candidate treatment targets

Parkinson's disease (PD) is a neurodegenerative disease for which the prevalence is second only to Alzheimer's disease (AD). This disease primarily affects people of middle and old age, significantly impacting their health and quality of life. The main pathological features include the degenerative nigrostriatal dopaminergic (DA) neuron loss and Lewy body (LB) formation. Currently, available PD medications primarily aim to alleviate clinical symptoms, however, there is no universally recognized therapy worldwide that effectively prevents, clinically treats, stops, or reverses the disease. Consequently, the evaluation and exploration of potential therapeutic targets for PD are of utmost importance. Nevertheless, the pathophysiology of PD remains unknown, and neuroinflammation mediated by inflammatory cytokines that prompts neuron death is fundamental for the progression of PD. The nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key complex of proteins linking the neuroinflammatory cascade in PD. Moreover, mounting evidence suggests that traditional Chinese medicine (TCM) alleviates PD by suppressing the NLRP3 inflammasome. This article aims to comprehensively review the available studies on the composition and activating mechanism of the NLRP3 inflammasome, along with its significance in PD pathogenesis and potential treatment targets. We also review natural products or synthetic compounds which reduce neuroinflammation via modulating NLRP3 inflammasome activity, aiming to identify new targets for future PD diagnosis and treatment through the exploration of NLRP3 inhibitors. Additionally, this review offers valuable references for developing new PD treatment methods.