Thrombin cleaves IL-33 and modulates IL-33-activated allergic lung inflammation

Biological mechanisms and therapeutic prospects of interleukin-33 in pathogenesis and treatment of allergic disease

Allergic diseases significantly impact the quality of life of people around the world. Cytokines play a crucial role in regulating the immune system. Due to their importance in pro-inflammatory mechanisms, cytokines are used to understand pathogenesis and serve as biomarkers in many diseases. One such cytokine is interleukin-33, a member of the IL-1 family, including IL- 1α, IL-1β, and IL-18. The IL-33 receptor is a heterodimer of IL-1 receptor-like 1 and IL-1 receptor accessory protein. IL-33 plays a critical role in regulating innate and adaptive immune responses. The primary targets of IL-33 in vivo are tissue-resident immune cells, including mast cells, group 2 innate lymphoid cells, regulatory T cells, T helper 2 cells, eosinophils, basophils, dendritic cells, Th1 cells, CD8 + T cells, NK cells, iNKT cells, B cells, neutrophils, and macrophages. However, IL-33 appears to act as an alarm signal that is promptly released by producing cells under cellular damage or stress conditions. IL-33 regulates signaling and various biological functions, including induction of pro-inflammatory cytokines, regulation of cell proliferation, and involvement in tissue remodeling. IL-33 is fundamental in immune-related diseases and plays a critical role in the control of inflammation. Recently, IL-33 has been shown to significantly impact allergic diseases, primarily by inducing Th2 immune responses. IL-33 is a key regulator of mast cell function and a promising therapeutic target for treating allergic diseases. This review provides an overview of the current understanding of the role of IL-33 in allergy pathogenesis and potential clinical approaches.

Construction of safer hirudin-derived peptides with enhanced anticoagulant properties based on C-terminal active residue adaptation and modification

INTRODUCTION

Hirudin exerts anticoagulant effects by inhibiting the binding and catalytic activity of thrombin to fibrinogen. However, its rigid N-terminal region irreversibly occupies the thrombin catalytic center, raising concerns about potential bleeding.

OBJECTIVES

In this study, a novel lead compound, WPHVC_V1, which is based on the competitive binding mechanism of the hirudin variant WPHV_C, was developed and validated for in vitro and in vivo activity and safety.

METHODS

Saturation mutagenesis, molecular dynamics simulations and mutant protein activity assays were used to elucidate the competitive anticoagulant mechanism between WPHV_C and thrombin. Next, a recombinantly expressed tyrosylprotein sulfotransferase was used to modify and confirm the sulfation site on the C-terminal tyrosine of hirudin. Finally, a multisite aromatic amino acid mutation strategy was implemented to design and synthesize the lead anticoagulant, WPHVC_V1.

RESULTS

The acidic amino acid cluster in WPHV_C formed strong electrostatic interactions with the positively charged thrombin exosite I, blocking fibrinogen binding. The introduction of aromatic amino acids further stabilized the complex through π-π stacking and π-cation interactions. For example, mutation of 13E to A decreased the free energy of dissociation (ΔG) from 19.27 to 10.93 kcal·mol-1 and shortened the thrombin time (TT) from 42.00 s to 30.94 s, whereas mutation of 26 K to W increased the ΔG to 24.70 kcal·mol-1 and prolonged TT to 51.92 s. In addition, the aromatic effect of 20Y, combined with sulfation, synergistically enhanced binding. Based on these findings, the newly designed WPHVC_V1 showed a ΔG of 37.24 kcal·mol-1 and, at 0.1 mg/ml, increased TT/APTT/PT from 41.72/14.38/15.86 s (WPHV_C) to 62.08/23.38/22.22 s. In in vivo studies, WPHVC_V1 achieved tail thrombus inhibition in the mouse tail by reducing the length of the thrombus from 3.562 cm in CK to 1.853 cm (1.729 cm for sodium heparin and 2.530 cm for WPHV_C), completely inhibited thrombus formation in a carotid artery model and reduced tail bleeding time by 35.2 s compared with heparin sodium. Safety evaluations revealed that WPHVC_V1 did not cause hemolysis, had no significant effect on blood pressure or cause pathological changes in major organs.

CONCLUSION

These findings provide an initial foundation and sequence reference for the development of safe and effective anticoagulant drugs with potential for clinical translation.

Role and mechanism of IL-33 in bacteria infection related gastric cancer continuum: From inflammation to tumor progression

Gastric cancer, a globally prevalent malignant tumor, is characterized by low early diagnosis rate, high metastasis rate, and poor prognosis, particularly in East Asia, Eastern Europe, and South America. Helicobacter pylori (H. pylori) is recognized as the primary risk factor for gastric cancer. However, the fact that fewer than 3 % of infected individuals develop cancer suggests that other bacteria may also influence gastric carcinogenesis. A diverse community of microorganisms may interact with H. pylori, thereby driving disease progression. Here, the role of the cytokine IL-33, a member of the IL-1 family, is scrutinized. Its production can be induced by H. pylori through the activation of specific signaling pathways, and it contributes to the inflammatory environment by promoting the release of pro-inflammatory cytokines. This article reviews the conflicting evidence regarding IL-33's role in the progression from gastritis to gastric cancer and discusses the potential therapeutic implications of targeting the IL-33/ST2 axis, with various antibodies and inhibitors in development or undergoing clinical trials for inflammatory diseases. However, the role of IL-33 in gastric cancer treatment remains to be fully elucidated, with its effects potentially dependent on the cellular context and stage of cancer progression. In summary, this review provides a comprehensive overview of the intricate relationship between gastric microbiota, IL-33, and gastritis - gastric cancer transition, offering insights into potential therapeutic targets and the development of novel treatment strategies.

Activation of the Coagulation Cascade as a Universal Danger Sign

Hemostasis is a mechanism that stops bleeding from an injured vessel, involves multiple interlinked steps, culminating in the formation of a "clot" sealing the damaged area. Moreover, it has long been recognized that inflammation also provokes the activation of the coagulation system. However, there has been an increasing amount of evidence revealing the immune function of the hemostasis system. This review collects and analyzes the results of the experimental studies and data from clinical observations confirming the inflammatory function of hemostasis. Here, we summarize the latest knowledge of the pathways in immune system activation under the influence of coagulation factors. The data analyzed allow us to consider the components of hemostasis as receptors recognizing «foreign» or damaged «self» or/and as «self» damage signals that initiate and reinforce inflammation and affect the direction of the adaptive immune response. To sum up, the findings collected in the review allow us to classify the coagulation factors, such as Damage-Associated Molecular Patterns that break down the conventional concepts of the coagulation system.

Triptolide alleviates allergic airway inflammation by inhibiting group 2 innate lymphoid cell function

Group 2 innate lymphoid cells (ILC2s) produce the type 2 cytokines IL-5 and IL-13 and contribute to type 2 immune responses, such as allergic airway inflammation. However, specific drugs, especially traditional Chinese medicines, that target lung ILC2s have rarely been reported. Here, we demonstrate that triptolide ameliorates allergic airway inflammation by suppressing ILC2 activation. IL-33, which is produced mainly by epithelial cells, is the most powerful cytokine for activating ILC2s. Triptolide-treated ILC2s were found to be functionally impaired in response to interleukin (IL)-33 challenge. RNA-seq analysis revealed that triptolide impaired ILC2 function through inflammation-related signalling pathways. ILC2-related genes were up- and down-regulated under the treatment with TPL such as Adrb2, Nmur1, tnfsf11, IL-5, IL-13, IL-9 and so on. Interestingly, we observed not only preventive but also therapeutic effects of triptolide on allergic airway inflammation, indicating that triptolide may serve as a promising traditional Chinese medicine for the treatment of allergic airway inflammation by targeting ILC2s.

E3 ligase RNF128 restricts A. alternata-induced ILC2 activation and type 2 immune response in the murine lung

Allergic airway inflammation is a universal airway disease induced by inhaling allergens. Published data show that RNF128, an E3 ligase, promotes Th2 activation in the OVA-induced asthma model. Recent advances have shown that group 2 innate lymphoid cells (ILC2s) produce the cytokines IL-5 and IL-13 to mediate type 2 immune response. However, whether RNF128 regulates ILC2-dependent allergic lung inflammation remains unclear. In this study, we observed greater expression of the E3 ligase RNF128 in ILC2s than in other immune cells. RNF128 deficiency caused a selective increase in the number of peripheral mature ILC2s, and mice with RNF128 deficiency were more susceptible to Alternaria alternata (A. alternata) -induced allergic lung inflammation. Furthermore, RNF128 deficiency increased recruitment of eosinophils and levels of IL-5 and IL-13 in the bronchoalveolar lavage fluid. RNF128 effectively inhibited the expansion of ILC2s and the number of IL-5- and IL-13-producing ILC2s. Specially, RNF128 deficiency promoted the expression of the interleukin-33 (IL-33) receptor ST2 in A. alternata-induced allergic lung inflammation. Above all, our study demonstrated that RNF128 played a key role in A. alternata-induced ILC2 activation and type 2 immune response, suggesting that RNF128 may be an effective therapeutic target for allergic lung inflammation initiated by ILC2s.

Alarmins and their pivotal role in the pathogenesis of spontaneous abortion: insights for therapeutic intervention

Alarmins are a class of molecules released when affected cells damaged or undergo apoptosis. They contain various chemotactic and immunomodulatory proteins or peptides. These molecules regulate the immune response by interacting with pattern recognition receptors (PRRs) and play important roles in inflammatory response, tissue repair, infection defense, and cancer treatment. Spontaneous abortion (SA) is a common pregnancy-related disease, and its pathogenesis has been puzzling clinicians, so it needs to be further studied. In this paper, we first reviewed the research status of various alarmins and SA, focusing on the role of high mobility box 1 (HMGB1), interleukin33 (IL-33), interleukin1β (IL-1β) and S-100 protein (S100 protein) in immune response, inflammation, embryonic development and abortion. Subsequently, this paper summarized the effect of alarmins on pregnancy outcome by influencing angiogenesis-related factors. Finally, from the perspective of aseptic inflammation, the pro-inflammatory signaling pathways involved in various alarmins and their targeted drugs were reviewed. By focusing on specific molecules in alarmins and their receptors and signaling pathways, we can more accurately conduct drug research and development. The purpose of this review is to explore the role of alarmins in SA, and provide important references for early detection of abortion risk, revealing the disease mechanism, developing new therapies and improving the prognosis of patients.

Application of Nanoparticles for Immunotherapy of Allergic Rhinitis

Allergen Immunotherapy (AIT) is the only etiological therapeutic method available for allergic rhinitis (AR). Currently, several options for AIT in the market, such as subcutaneous immunotherapy (SCIT) and sublingual immunotherapy (SLIT), have different routes of administration. These traditional methods have achieved encouraging outcomes in clinic. However, the side effects associated with these methods have raised the need for innovative approaches for AIT that improve safety, shorten the course of treatment and increase local drug concentration. Nanoparticles (NPs) are particles ranging in size from 1 to 100 nm, which have been hired as potential adjuvants for AIT. NPs can be employed as agents for modulating immune responses in AR or/and carriers for loading proteins, peptides or DNA molecules. This review focuses on different kinds of nanoparticle delivery systems, including chitosan nanoparticles, exosomes, metal nanoparticles, and viral nanoparticles. We summarized the advantages and limitations of NPs for the treatment of allergic rhinitis. Overall, NPs are expected to be a therapeutic option for AR, which requires more in-depth studies and long-term therapeutic validation.

The production, function, and clinical applications of IL-33 in type 2 inflammation-related respiratory diseases

Epithelial-derived IL-33 (Interleukin-33), as a member of alarm signals, is a chemical substance produced under harmful stimuli that can promote innate immunity and activate adaptive immune responses. Type 2 inflammation refers to inflammation primarily mediated by Type 2 helper T cells (Th2), Type 2 innate lymphoid cells (ILC2), and related cytokines. Type 2 inflammation manifests in various forms in the lungs, with diseases such as asthma and chronic obstructive pulmonary disease chronic obstructive pulmonary disease (COPD) closely associated with Type 2 inflammation. Recent research suggests that IL-33 has a promoting effect on Type 2 inflammation in the lungs and can be regarded as an alarm signal for Type 2 inflammation. This article provides an overview of the mechanisms and related targets of IL-33 in the development of lung diseases caused by Type 2 inflammation, and summarizes the associated treatment methods. Analyzing lung diseases from a new perspective through the alarm of Type 2 inflammation helps to gain a deeper understanding of the pathogenesis of these related lung diseases. This, in turn, facilitates a better understanding of the latest treatment methods and potential therapeutic targets for diseases, with the expectation that targeting lL-33 can propose new strategies for disease prevention.

Discovery and Characterization of Panaxatriol as a Novel Thrombin Inhibitor from Panax notoginseng Using a Combination of Computational and Experimental Approaches

Thrombin is a crucial enzyme in the coagulation cascade, and inhibitors of thrombin have been extensively studied as potential antithrombotic agents. The objective of this study was to identify natural inhibitors of thrombin from Panax notoginseng and evaluate their biological activity in vitro and binding characteristics. A combined approach involving molecular docking, thrombin inhibition assays, surface plasmon resonance, and molecular dynamics simulation was utilized to identify natural thrombin inhibitors. The results demonstrated that panaxatriol directly inhibits thrombin, with an IC50 of 10.3 µM. Binding studies using surface plasmon resonance revealed that panaxatriol interacts with thrombin, with a KD value of 7.8 µM. Molecular dynamics analysis indicated that the thrombin-panaxatriol system reached equilibrium rapidly with minimal fluctuations, and the calculated binding free energy was - 23.8 kcal/mol. The interaction between panaxatriol and thrombin involves the amino acid residues Glu146, Glu192, Gly216, Gly219, Tyr60A, and Trp60D. This interaction provides a mechanistic basis for further optimizing panaxatriol as a thrombin inhibitor. Our study has shown that panaxatriol serves as a direct thrombin inhibitor, laying the groundwork for further research and development of novel thrombin inhibitors.

Biomarkers in Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin condition. The pathogenesis involves genetic, environmental, and immunological factors as well as a barrier dysfunction of the epidermis. Biomarkers may play a significant role in diagnosis, severity assessment, and treatment monitoring of AD. They are categorizable into diagnostic and prognostic as well as severity and stratification biomarkers, offering the potential for a more personalized treatment approach. Although there have been tremendous therapeutic advancements with interleukin (IL) antagonists and Janus kinase (JAK) inhibitors, the domain of biomarkers still requires further research to clarify their place in the diagnosis and prognosis of AD to unravel a better scientific basis for personalized medical care for patients with AD. This article reviews the various biomarkers in relation to the different AD phenotypes and endotypes.

Interleukin-33/serum stimulation-2 pathway: Regulatory mechanisms and emerging implications in immune and inflammatory diseases

Interleukin (IL)- 33, a nuclear factor and pleiotropic cytokine of the IL-1 family, is gaining attention owing to its important role in chronic inflammatory and autoimmune diseases. This review extends our knowledge of the effects exerted by IL-33 on target cells by binding to its specific receptor serum stimulation-2 (ST2). Depending on the tissue context, IL-33 performs multiple functions encompassing host defence, immune response, initiation and amplification of inflammation, tissue repair, and homeostasis. The levels and activity of IL-33 in the body are controlled by complex IL-33-targeting regulatory pathways. The unique temporal and spatial expression patterns of IL-33 are associated with host homeostasis and the development of immune and inflammatory disorders. Therefore, understanding the origin, function, and processes of IL-33 under various conditions is crucial. This review summarises the regulatory mechanisms underlying the IL-33/ST2 signalling axis and its potential role and clinical significance in immune and inflammatory diseases, and discusses the current complex and conflicting findings related to IL-33 in host responses.

Recruitment of PVT1 Enhances YTHDC1-Mediated m6A Modification of IL-33 in Hyperoxia-Induced Lung Injury During Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease that specifically affects preterm infants. Oxygen therapy administered to treat BPD can lead to hyperoxia-induced lung injury, characterized by apoptosis of lung alveolar epithelial cells. Our epitranscriptomic microarray analysis of normal mice lungs and hyperoxia-stimulated mice lungs revealed elevated RNA expression levels of IL-33, as well as increased m6A RNA methylation levels of IL-33 and PVT1 in the hyperoxia-stimulated lungs. This study aimed to investigate the role of the PVT1/IL-33 axis in BPD. A mouse model of BPD was established through hyperoxia induction, and lung histological changes were assessed by hematoxylin-eosin staining. Parameters such as radial alveolar count and mean chord length were measured to assess lung function. Mouse and human lung alveolar epithelial cells (MLE12 and A549, respectively) were stimulated with hyperoxia to create an in vitro BPD model. Cell apoptosis was detected using Western blotting and flow cytometry analysis. Our results demonstrated that silencing PVT1 suppressed apoptosis in MLE12 and A549 cells and improved lung function in hyperoxia-stimulated lungs. Additionally, IL-33 reversed the effects of PVT1 both in vivo and in vitro. Through online bioinformatics analysis and RNA-binding protein immunoprecipitation assays, YTHDC1 was identified as a RNA-binding protein (RBP) for both PVT1 and IL-33. We found that PVT1 positively regulated IL-33 expression by recruiting YTHDC1 to mediate m6A modification of IL-33. In conclusion, silencing PVT1 demonstrated beneficial effects in alleviating BPD by facilitating YTHDC1-mediated m6A modification of IL-33. Inhibition of the PVT1/IL-33 axis to suppress apoptosis in lung alveolar epithelial cells may hold promise as a therapeutic approach for managing hyperoxia-induced lung injury in BPD.

Role of IL-33-ST2 pathway in regulating inflammation: current evidence and future perspectives

Interleukin (IL)-33 is an alarmin of the IL-1 superfamily localized to the nucleus of expressing cells, such as endothelial cells, epithelial cells, and fibroblasts. In response to cellular damage or stress, IL-33 is released and activates innate immune responses in some immune and structural cells via its receptor interleukin-1 receptor like-1 (IL-1RL1 or ST2). Recently, IL-33 has become a hot topic of research because of its role in pulmonary inflammation. The IL-33-ST2 signaling pathway plays a pro-inflammatory role by activating the type 2 inflammatory response, producing type 2 cytokines and chemokines. Elevated levels of IL-33 and ST2 have been observed in chronic pulmonary obstructive disease (COPD). Notably, IL-33 is present in COPD induced by cigarette smoke or acute inflammations. The role of IL-33 in sepsis is becoming increasingly prominent, and understanding its significance in the treatment of sepsis associated with high mortality is critical. In addition to its pro-inflammatory effects, the IL-33-ST2 axis appears to play a role in bacterial clearance and tissue repair. In this review, we focused on the role of the IL-33-ST2 axis in sepsis, asthma, and COPD and summarized the therapeutic targets associated with this axis, providing a basis for future treatment.

Strategies targeting IL-33/ST2 axis in the treatment of allergic diseases

Interleukin-33 (IL-33) and its receptor Serum Stimulation-2 (ST2, also called Il1rl1) are members of the IL-1 superfamily that plays a crucial role in allergic diseases. The interaction of IL-33 and ST2 mainly activates NF-κB signaling and MAPK signaling via the MyD88/IRAK/TRAF6 module, resulting in the production and secretion of pro-inflammatory cytokines. The IL-33/ST2 axis participates in the pathogenesis of allergic diseases, and therefore serves as a promising strategy for allergy treatment. In recent years, strategies blocking IL-33/ST2 through targeting regulation of IL-33 and ST2 or targeting the molecules involved in the signal transduction have been extensively studied mostly in animal models. These studies provide various potential therapeutic agents other than antibodies, such as small molecules, nucleic acids and traditional Chinese medicines. Herein, we reviewed potential targets and agents targeting IL-33/ST2 axis in the treatment of allergic diseases, providing directions for further investigations on treatments for IL-33 induced allergic diseases.

Solar ultraviolet B radiation promotes α-MSH secretion to attenuate the function of ILC2s via the pituitary-lung axis

The immunomodulatory effects of ultraviolet B (UVB) radiation in human diseases have been described. Whether type 2 lung inflammation is directly affected by solar ultraviolet (UV) radiation is not fully understood. Here, we show a possible negative correlation between solar UVB radiation and asthmatic inflammation in humans and mice. UVB exposure to the eyes induces hypothalamus-pituitary activation and α-melanocyte-stimulating hormone (α-MSH) accumulation in the serum to suppress allergic airway inflammation by targeting group 2 innate lymphoid cells (ILC2) through the MC5R receptor in mice. The α-MSH/MC5R interaction limits ILC2 function through attenuation of JAK/STAT and NF-κB signaling. Consistently, we observe that the plasma α-MSH concentration is negatively correlated with the number and function of ILC2s in the peripheral blood mononuclear cells (PBMC) of patients with asthma. We provide insights into how solar UVB radiation-driven neuroendocrine α-MSH restricts ILC2-mediated lung inflammation and offer a possible strategy for controlling allergic diseases.

A novel anti-IL-33 antibody recognizes an epitope FVLHN of IL-33 and has a therapeutic effect on inflammatory diseases

As a crucial member of the Interleukin-1 (IL-1) family, IL-33 plays an indispensable role in modulating inflammatory responses. Here, we developed an effective anti-human IL-33 monoclonal antibody (mAb) named 5H8. Importantly, we have identified an epitope (FVLHN) of IL-33 protein as a recognition sequence for 5H8, which plays an important role in mediating the biological activity of IL-33. We observed that 5H8 significantly suppressed IL-33-induced IL-6 expression in bone marrow cells and mast cells in a dose-dependent manner in vitro. Furthermore, 5H8 effectively relievedHDM-induced asthma and PR8-induced acute lung injury in vivo. These findings indicate that targeting the FVLHN epitope is critical for inhibiting IL-33 function. In addition, wedetected that the Tm value of 5H8 was 66.47℃ and the KD value was 173.0 pM, which reflected that 5H8 had good thermal stability and high affinity. Taken together, our data suggest that our newly developed 5H8 antibody has potential as a therapeutic antibody for treating inflammatory diseases.

HTR2A agonists play a therapeutic role by restricting ILC2 activation in papain-induced lung inflammation

Group 2 innate lymphoid cells (ILC2s) are a category of heterogeneous cells that produce the cytokines IL-5 and IL-13, which mediate the type 2 immune response. However, specific drug targets on lung ILC2s have rarely been reported. Previous studies have shown that type 2 cytokines, such as IL-5 and IL-13, are related to depression. Here, we demonstrated the negative correlation between the depression-associated monoamine neurotransmitter serotonin and secretion of the cytokines IL-5 and IL-13 by ILC2s in individuals with depression. Interestingly, serotonin ameliorates papain-induced lung inflammation by suppressing ILC2 activation. Our data showed that the serotonin receptor HTR2A was highly expressed on ILC2s from mouse lungs and human PBMCs. Furthermore, an HTR2A selective agonist (DOI) impaired ILC2 activation and alleviated the type 2 immune response in vivo and in vitro. Mice with ILC2-specific depletion of HTR2A (Il5cre/+·Htr2aflox/flox mice) abolished the DOI-mediated inhibition of ILC2s in a papain-induced mouse model of inflammation. In conclusion, serotonin and DOI could restrict the type 2 lung immune response, indicating a potential treatment strategy for type 2 lung inflammation by targeting HTR2A on ST2+ ILC2s.