IL-17A neutralizing antibody attenuates eosinophilic meningitis caused by Angiostrongylus cantonensis by involving IL-17RA/Traf6/NF-κB signaling

[Mechanism of IL-17 Signaling Pathway in Spleen Inflammatory Response Induced by Altitude Hypoxia in Mice]

Objective

To explore the mechanism of spleen tissue inflammatory response induced by altitude hypoxia in mice.

Methods

C57BL/6 mice were randomly assigned to a plain, i.e., low-altitude, normoxia group and an altitude hypoxia group, with 5 mice in each group. In the plain normoxia group, the mice were kept in a normoxic environment at the altitude of 400 m above sea level (with an oxygen concentration of 19.88%). The mice in the altitude hypoxia group were kept in an environment at the altitude of 4200 m above sea level (with an oxygen concentration of 14.23%) to establish the animal model of altitude hypoxia. On day 30, spleen tissues were collected to determine the splenic index. HE staining was performed to observe the histopathological changes in the spleen tissues of the mice. Real time fluorogenic quantitative PCR (RT-qPCR) and Western blot were conducted to determine the mRNA and protein expressions of interleukin (IL)-6, IL-12, and IL-1β in the spleen tissue of the mice. High-throughput transcriptome sequencing was performed with RNA sequencing (RNA-seq). KEGG enrichment analysis was performed for the differentially expressed genes (DEGs). The DEGs in the key pathways were verified by RT-qPCR.

Results

Compared with the plain normoxia group, the mice exposed to high-altitude hypoxic environment had decreased spleen index (P<0.05) and exhibited such pathological changes as decreased white pulp, enlarged germinal center, blurred edge, and venous congestion. The mRNA and protein expression levels of IL-6, IL-12, and IL-1β in the spleen tissue of mice in the altitude hypoxia group were up-regulated (P<0.05). According to the results of transcriptome sequencing and KEGG pathway enrichment analysis, 4218 DEGs were enriched in 178 enrichment pathways (P<0.05). DEGs were significantly enriched in multiple pathways associated with immunity and inflammation, such as T cell receptor signaling pathway, TNF signaling pathway, and IL-17 signaling pathway (P<0.05) in the spleen of mice exposed to high-altitude hypoxic environment. Among them, IL-17 signaling pathway and the downstream inflammatory factors were highly up-regulated (P<0.05). Compared with the plain normoxia group, the mRNA expression levels of key genes in the IL-17 signaling pathway, including IL-17, IL-17R, and mitogen-activated protein kinase genes (MAPKs), and the downstream inflammatory factors, including matrix metallopeptidase 9 (MMP9), S100 calcium binding protein A8 gene (S100A8), S100 calcium binding protein A9 gene (S100A9), and tumor necrosis factor α (TNF-α), were up-regulated or down-regulated (P<0.05) in the altitude hypoxia group. According to the validation of RT-qPCR results, the mRNA expression levels of DEGs were consistent with the RNA-seq results.

Conclusion

Altitude hypoxia can induce inflammatory response in the mouse spleen tissue by activating IL-17 signaling pathway and promoting the release of downstream inflammatory factors.

An IL-17-EGFR-TRAF4 axis contributes to the alleviation of lung inflammation in severe influenza

Excessive inflammation is a postulated cause of severe disease and death in respiratory virus infections. In response to severe influenza virus infection, adoptively transferred naïve hemagglutinin-specific CD4⁺ T cells from CD4⁺ TCR-transgenic 6.5 mice drive an IFN-γ-producing Th1 response in wild-type mice. It helps in virus clearance but also causes collateral damage and disease aggravation. The donor 6.5 mice have all the CD4⁺ T cells with TCR specificity toward influenza hemagglutinin. Still, the infected 6.5 mice do not suffer from robust inflammation and grave outcome. The initial Th1 response wanes with time, and a prominent Th17 response of recent thymic emigrants alleviates inflammation and bestows protection in 6.5 mice. Our results suggest that viral neuraminidase-activated TGF-β of the Th1 cells guides the Th17 evolution, and IL-17 signaling through the non-canonical IL-17 receptor EGFR activates the scaffold protein TRAF4 more than TRAF6 during alleviation of lung inflammation in severe influenza.

IL-17/IL-17 Receptor Pathway-Mediated Inflammatory Response in Apostichopus japonicus Supports the Conserved Functions of Cytokines in Invertebrates

Inflammation participates in host defenses against infectious agents and contributes to the pathophysiology of many diseases. IL-17 is a well-known proinflammatory cytokine that contributes to various aspects of inflammation in vertebrates. However, the functional role of invertebrate IL-17 in inflammatory regulation is not well understood. In this study, we first established an inflammatory model in the Vibrio splendidus-challenged sea cucumber Apostichopus japonicus (Echinodermata). Typical inflammatory symptoms, such as increased coelomocyte infiltration, tissue vacuoles, and tissue fractures, were observed in the V. splendidus-infected and diseased tissue of the body wall. Interestingly, A. japonicus IL-17 (AjIL-17) expression in the body wall and coelomocytes was positively correlated with the development of inflammation. The administration of purified recombinant AjIL-17 protein also directly promoted inflammation in A. japonicus Through genome searches and ZDOCK prediction, a novel IL-17R counterpart containing FNIII and hypothetical TIR domains was identified in the sea cucumber genome. Coimmunoprecipitation, far-Western blotting, and laser confocal microscopy confirmed that AjIL-17R could bind AjIL-17. A subsequent cross-linking assay revealed that the AjIL-17 dimer mediates the inflammatory response by the specific binding of dimeric AjIL-17R upon pathogen infection. Moreover, silencing AjIL-17R significantly attenuated the LPS- or exogenous AjIL-17-mediated inflammatory response. Functional analysis revealed that AjIL-17/AjIL-17R modulated inflammatory responses by promoting A. japonicus TRAF6 ubiquitination and p65 nuclear translocation and evenly mediated coelomocyte proliferation and migration. Taken together, our results provide functional evidence that IL-17 is a conserved cytokine in invertebrates and vertebrates associated with inflammatory regulation via the IL-17-IL-17R-TRAF6 axis.

Deoxyhypusine synthase promotes a pro-inflammatory macrophage phenotype

The metabolic inflammation (meta-inflammation) of obesity is characterized by proinflammatory macrophage infiltration into adipose tissue. Catalysis by deoxyhypusine synthase (DHPS) modifies the translation factor eIF5A to generate a hypusine (Hyp) residue. Hypusinated eIF5A (eIF5A^Hyp) controls the translation of mRNAs involved in inflammation, but its role in meta-inflammation has not been elucidated. Levels of eIF5A^Hyp were found to be increased in adipose tissue macrophages from obese mice and in murine macrophages activated to a proinflammatory M1-like state. Global proteomics and transcriptomics revealed that DHPS deficiency in macrophages altered the abundance of proteins involved in NF-κB signaling, likely through translational control of their respective mRNAs. DHPS deficiency in myeloid cells of obese mice suppressed M1 macrophage accumulation in adipose tissue and improved glucose tolerance. These findings indicate that DHPS promotes the post-transcriptional regulation of a subset of mRNAs governing inflammation and chemotaxis in macrophages and contributes to a proinflammatory M1-like phenotype.

Generation and characterization of a humanized anti-IL-17A rabbit monoclonal antibody

Interleukin-17A (IL-17A) produced by Th17 cells, contributes to the pathogenesis of various autoimmune diseases by stimulating the release of cytokines and chemokines and its regulation. Anti-IL-17A antibody which blocks the function of IL-17A has been proved to be an effective treatment of autoimmune disease. The aim of our study was to generate a potential humanized anti-IL-17A therapeutic monoclonal antibody (mAb) through a comprehensive panel of in vitro and in vivo biological activity studies, as well as physicochemical characterization. HZD37-5, a humanized monoclonal antibody specifically recognizing N78 loci of IL-17A, binds to human and rhesus monkeys, blocks IL-17 induced signal transduction and the release of IL-6, IL-8, CXCL-1 and G-GSF. In an in vivo efficacy mouse model, HZD37-5 significantly inhibited human IL-17A induced-keratinocyte chemoattractant (KC) secretion in a dose-dependent manner. The pharmacokinetics (PK) study result of HZD37-5 in rhesus monkeys indicated that HZD37-5 had favorable PK characteristics with limited distribution (78.0-78.8 ml/kg), slow elimination (5.00-6.45 ml/day/kg), long half-life (9.1-10.7 days) and high bioavailability (103%) following a single IV or SC dose at 1.5 mg/kg. These findings provided a comprehensive preclinical characterization of HZD37-5 and supported that it may be developed as a potential therapeutic for the treatment of autoimmune diseases, including psoriasis, psoriatic arthritis, axial spondyloarthritis, etc.

The role of dendritic cells derived osteoclasts in bone destruction diseases

The bone is previously considered as a dominant organ involved in the processes of locomotion. However, in the past two decades, a large number of studies have suggested that the skeletal system closely coordinated with the immune system so as to result in the emerging area of 'osteoimmunology'. In the evolution of many kinds of bone destruction-related diseases, osteoclasts could differentiate from dendritic cells, which contributed to increased expression of osteoclast-related membrane receptors and relatively higher activity of bone destruction, inducing severe bone destruction under inflammatory conditions. Numerous factors could influence the interaction between osteoclasts and dendritic cells, contributing to the pathogenesis of several bone diseases in the context of inflammation, including both immunocytes and a large number of cytokines. In addition, the products of osteoclasts released from bone destruction area serve as important signals for the differentiation and activation of immature dendritic cells. Therefore, the border between the dendritic cell-related immune response and osteoclast-related bone destruction has gradually unravelled. Dendritic cells and osteoclasts cooperate with each other to mediate bone destruction and bone remodelling under inflammatory conditions. In this review, we will pay attention to the interactions between dendritic cells and osteoclasts in physiological and pathological conditions to further understand the skeletal system and identify potential new therapeutic targets for the future by summarizing their significant roles and molecular mechanisms in bone destruction.

Interleukin 17A Derived from γδ T Cell Induces Demyelination of the Brain in Angiostrongylus cantonensis Infection

Angiostrongylus cantonensis infection is a typical cause of eosinophilic encephalitis (EM), which has been reported to induce serious damage in the central nervous system. Both parasite and host factors contribute to the onset of EM, but the related immune-inflammation pathogenesis remains poorly characterised. An A. cantonensis infection model was generated through the infection of mice by gavage. Transmission electron microscopy and immunohistochemistry were used to assess the pathologic changes in the brain. The mRNA expression of inflammatory factors was tested using qRT-PCR. A combination of flow cytometry and western blotting was used to evaluate the alteration of leukocytes and related cytokines. A critical role of IL-17 was found by injecting IL-17A monoclonal antibody into naïve and A. cantonensis-infected mice. A. cantonensis larvae altered the immune homeostasis in the brain, leading to the destruction of myelin sheaths and activation of microglia and macrophage. During this process, IL-17A accumulation was observed, and IL-17RA was expressed in oligodendrocytes and microglia during the infection. Notably, γδ T cell was the major origin of IL-17A production induced by the parasite. After an IL-17A-neutralising antibody was applied, alterations in myelination and the state of the microglia/macrophage were discovered; the neurobehavioural scores of the mice also improved. Our study reveals one unrecognised impact of the γδ T cells in parasitic encephalopathy and emphasises that blocking IL-17A signalling can attenuate microglia and macrophage activation, thus reducing CNS demyelination and ameliorating the neurobehavioural deficit in A. cantonensis-infected mice.