Abstract
Background
Interleukin (IL)-33 is expressed in a healthy brain and plays a pivotal role in several neuropathologies, as protective or contributing to the development of cerebral diseases ...associated with cognitive impairments. However, the role of IL-33 in the brain is poorly understood, raising the question of its involvement in immunoregulatory mechanisms.
Methods
We administered recombinant IL-33 (rmIL-33) by intra-hippocampal injection to C57BL/6 J (WT) and IL-1αβ deficient mice. Chronic minocycline administration was performed and cognitive functions were examined trough spatial habituation test. Hippocampal inflammatory responses were investigated by RT-qPCR. The microglia activation was assessed using immunohistological staining and fluorescence-activated cell sorting (FACS).
Results
We showed that IL-33 administration in mice led to a spatial memory performance defect associated with an increase of inflammatory markers in the hippocampus while minocycline administration limited the inflammatory response. Quantitative assessment of glial cell activation in situ demonstrated an increase of proximal intersections per radius in each part of the hippocampus. Moreover, rmIL-33 significantly promoted the outgrowth of microglial processes. Fluorescence-activated cell sorting analysis on isolated microglia, revealed overexpression of IL-1β, 48 h post-rmIL-33 administration. This microglial reactivity was closely related to the onset of cognitive disturbance. Finally, we demonstrated that IL-1αβ deficient mice were resistant to cognitive disorders after intra-hippocampal IL-33 injection.
Conclusion
Thus, hippocampal IL-33 induced an inflammatory state, including IL-1β overexpression by microglia cells, being causative of the cognitive impairment. These results highlight the pathological role for IL-33 in the central nervous system, independently of a specific neuropathological model.
The receptor NLRP3 is involved in the formation of the NLRP3 inflammasome that activates caspase-1 and mediates the release of interleukin 1β (IL-1β) and IL-18. Whether NLRP3 can shape immunological ...function independently of inflammasomes is unclear. We found that NLRP3 expression in CD4(+) T cells specifically supported a T helper type 2 (TH2) transcriptional program in a cell-intrinsic manner. NLRP3, but not the inflammasome adaptor ASC or caspase-1, positively regulated a TH2 program. In TH2 cells, NLRP3 bound the Il4 promoter and transactivated it in conjunction with the transcription factor IRF4. Nlrp3-deficient TH2 cells supported melanoma tumor growth in an IL-4-dependent manner and also promoted asthma-like symptoms. Our results demonstrate the ability of NLRP3 to act as a key transcription factor in TH2 differentiation.
To the Editor: G-quadruplex (G4) DNA abundance in immunoglobulin switch (S) regions (see Fig E1 and the Methods section in this article's Online Repository at www.jacionline.org) might promote ...transcriptional pausing and occurrence of DNA nicks.1 In vitro, such structured DNA favors oligomerization and activity of activation-induced deaminase (AID).2 Orientation-dependent class-switch recombination (CSR) optimally occurs with G-rich DNA on the nontemplate strand.3 However, AT-rich Xenopus laevis S-regions support CSR in an orientation-independent manner and it was rather proposed that palindromes forming stem loops are mandatory for CSR, the role of G4-DNA remaining controversial.4 Pharmacological G4-stabilizing agents are potential anticancer drugs with telomerase inhibitory activity and potential to slow expression of some oncogene promoters.5 Their effect on CSR is unknown. ...some but not all functional aspects of airway allergy (airway compliance and lung eosinophil peroxidase activity) improved under RHPS4 treatment (see Fig E6 in this article's Online Repository at www.jacionline.org). CSR in B cells is modulated by multiple cis-regulatory elements, notably 3' IgH enhancers promoting AID recruitment.6,7 Convergent data suggest that CSR is favored by G-rich S-region transcripts forming RNA/DNA hybrids on the template strand, exposing single-stranded R-loops on the nontemplate strand, and differentially recruiting AID to initiate double-strand breaks instead of mutations.3 G4-DNA defining “G-loops” on the nontemplate strand may also help recruit CSR factors.8 AID binding to G4-containing transcripts might finally confer trans activity to such transcripts.9 We now show that low doses of a G4-DNA stabilizing agent documented for anticancer activity directly dampen CSR in vitro.
Stimulator of interferon genes (STING) contributes to immune responses against tumors and may control viral infection including SARS-CoV-2 infection. However, activation of the STING pathway by ...airway silica or smoke exposure leads to cell death, self-dsDNA release, and STING/type I IFN dependent acute lung inflammation/ARDS. The inflammatory response induced by a synthetic non-nucleotide-based diABZI STING agonist, in comparison to the natural cyclic dinucleotide cGAMP, is unknown. A low dose of diABZI (1 µg by endotracheal route for 3 consecutive days) triggered an acute neutrophilic inflammation, disruption of the respiratory barrier, DNA release with NET formation, PANoptosis cell death, and inflammatory cytokines with type I IFN dependent acute lung inflammation. Downstream upregulation of DNA sensors including cGAS, DDX41, IFI204, as well as NLRP3 and AIM2 inflammasomes, suggested a secondary inflammatory response to dsDNA as a danger signal. DNase I treatment, inhibition of NET formation together with an investigation in gene-deficient mice highlighted extracellular DNA and TLR9, but not cGAS, as central to diABZI-induced neutrophilic response. Therefore, activation of acute cell death with DNA release may lead to ARDS which may be modeled by diABZI. These results show that airway targeting by STING activator as a therapeutic strategy for infection may enhance lung inflammation with severe ARDS. STING agonist diABZI induces neutrophilic lung inflammation and PANoptosis A, Airway STING priming induce a neutrophilic lung inflammation with epithelial barrier damage, double-stranded DNA release in the bronchoalvelolar space, cell death, NETosis and type I interferon release. B, 1. The diamidobenzimidazole (diABZI), a STING agonist is internalized into the cytoplasm through unknown receptor and induce the activation and dimerization of STING followed by TBK1/IRF3 phosporylation leading to type I IFN response. STING activation also leads to NF-kB activation and the production of pro-inflammatory cytokines TNFα and IL-6. 2. The activation of TNFR1 and IFNAR1 signaling pathway results in ZBP1 and RIPK3/ASC/CASP8 activation leading to MLKL phosphorylation and necroptosis induction. 3. This can also leads to Caspase-3 cleavage and apoptosis induction. 4. Self-dsDNA or mtDNA sensing by NLRP3 or AIM2 induces inflammsome formation leading to Gasdermin D cleavage enabling Gasdermin D pore formation and the release mature IL-1β and pyroptosis. NLRP3 inflammasome formation can be enhanced by the ZBP1/RIPK3/CASP8 complex. 5. A second signal of STING activation with diABZI induces cell death and the release of self-DNA which is sensed by cGAS and form 2'3'-cGAMP leading to STING hyper activation, the amplification of TBK1/IRF3 and NF-kB pathway and the subsequent production of IFN-I and inflammatory TNFα and IL-6. This also leads to IFI204 and DDX41 upregulation thus, amplifying the inflammatory loop. The upregulation of apoptosis, pyroptosis and necroptosis is indicative of STING-dependent PANoptosis.
Objectives
Inhibitors of bromodomain and extra terminal domain (BET) proteins are a new and growing class of anti‐cancer drugs, which decrease oncogene expression by targeting superenhancers. ...Antibody production is another physiological process relying on superenhancers, and it remains to be clarified whether potential immunomodulatory properties of BET inhibitors might impact humoral immunity and allergy.
Methods
We thus evaluated humoral immune responses and their Th2 context in vitro and in vivo in mice following treatment with the classical BET‐inhibitor JQ1. We quantified immunoglobulin (Ig) and antibody production by B cells either stimulated in vitro or obtained from immunised mice. JQ1 effects on class switching and activation‐induced deaminase loading were determined, together with modifications of B, T follicular helper (Tfh) and T helper 2 (Th2) populations. JQ1 was finally tested in B‐cell‐dependent models of immune disorders.
Results
Bromodomain and extra terminal domain inhibition reduced class switching, Ig expression on B cells and antibody secretion and was correlated with decreased numbers of Tfh cells. However, JQ1 strongly increased the proportion of GATA3+ Th2 cells and the secretion of corresponding cytokines. In a mouse allergic model of lung inflammation, JQ1 did not affect eosinophil infiltration or mucus production but enhanced Th2 cytokine production and aggravated clinical manifestations.
Conclusion
Altogether, BET inhibition thus interweaves intrinsic negative effects on B cells with a parallel complex reshaping of T‐cell polarisation which can increase type 2 cytokines and eventually promote B‐cell‐dependent immunopathology. These opposite and potentially hazardous immunomodulatory effects raise concerns for clinical use of BET inhibitors in patients with immune disorders.
While bromodomain and extra terminal domain inhibition reduces class switching, antibody secretion and T follicular helper cell number, this treatment increases the proportion of GATA3+ T helper 2 cells and the secretion of corresponding cytokines. In a mouse model of lung inflammation, JQ1 thus aggravates rather than improves clinical manifestations.
Silica particles induce lung inflammation and fibrosis. Here we show that stimulator of interferon genes (STING) is essential for silica-induced lung inflammation. In mice, silica induces lung cell ...death and self-dsDNA release in the bronchoalveolar space that activates STING pathway. Degradation of extracellular self-dsDNA by DNase I inhibits silica-induced STING activation and the downstream type I IFN response. Patients with silicosis have increased circulating dsDNA and CXCL10 in sputum, and patients with fibrotic interstitial lung disease display STING activation and CXCL10 in the lung. In vitro, while mitochondrial dsDNA is sensed by cGAS-STING in dendritic cells, in macrophages extracellular dsDNA activates STING independent of cGAS after silica exposure. These results reveal an essential function of STING-mediated self-dsDNA sensing after silica exposure, and identify DNase I as a potential therapy for silica-induced lung inflammation.
T helper (Th)17 cells producing interleukin (IL)-17 play a role in autoimmune and allergic inflammation. Here, we show that IL-23 induces IL-17 in the lung and IL-17 is required during antigen ...sensitization to develop allergic asthma, as shown in IL-17R-deficient mice. Since IL-17 expression increased further upon antigen challenge, we addressed its function in the effector phase. Most strikingly, neutralization of IL-17 augmented the allergic response in sensitized mice. Conversely, exogenous IL-17 reduced pulmonary eosinophil recruitment and bronchial hyperreactivity, demonstrating a novel regulatory role of IL-17. Mechanistically, IL-17 down modulated eosinophil-chemokine eotaxin (CCL11) and thymus- and activation-regulated chemokine/CCL17 (TARC) in lungs in vivo and ex vivo upon antigen restimulation. In vitro, IL-17 reduced TARC production in dendritic cells (DCs)-the major source of TARC-and antigen uptake by DCs and IL-5 and IL-13 production in regional lymph nodes. Furthermore, IL-17 is regulated in an IL-4-dependent manner since mice deficient for IL-4Ralpha signaling showed a marked increase in IL-17 concentration with inhibited eosinophil recruitment. Therefore, endogenous IL-17 is controlled by IL-4 and has a dual role. Although it is essential during antigen sensitization to establish allergic asthma, in sensitized mice IL-17 attenuates the allergic response by inhibiting DCs and chemokine synthesis.
IL‐33, a new member of the IL‐1 family cytokine, is involved in Th2‐type responses in a wide range of diseases and signals through the ST2 receptor expressed on many immune cells. Since the effects ...of IL‐33 on DCs remain controversial, we investigated the ability of IL‐33 to modulate DC functions in vitro and in vivo. Here, we report that IL‐33 activates myeloid DCs to produce IL‐6, IL‐1b, TNF, CCL17 and to express high levels of CD40, CD80 OX40L and CCR7. Importantly, IL‐33‐activated DCs prime naive lymphocytes to produce the Th2 cytokines IL‐5 and IL‐13, but not IL‐4. In vivo, IL‐33 exposure induces DC recruitment and activation in the lung. Using an OVA‐induced allergic lung inflammation model, we demonstrate that the reduced airway inflammation in ST2‐deficient mice correlates with the failure in DC activation and migration to the draining LN. Finally, we show that adoptive transfer of IL‐33‐activated DCs exacerbates lung inflammation in a DC‐driven model of allergic airway inflammation. These data demonstrate for the first time that IL‐33 activates DCs during antigen presentation and thereby drives a Th2‐type response in allergic lung inflammation.
MyD88, the common adapter involved in TLR, IL-1, and IL-18 receptor signaling, is essential for the control of acute Mycobacterium tuberculosis (MTB) infection. Although TLR2, TLR4, and TLR9 have ...been implicated in the response to mycobacteria, gene disruption for these TLRs impairs only the long-term control of MTB infection. Here, we addressed the respective role of IL-1 and IL-18 receptor pathways in the MyD88-dependent control of acute MTB infection. Mice deficient for IL-1R1, IL-18R, or Toll-IL-1R domain-containing adaptor protein (TIRAP) were compared with MyD88-deficient mice in an acute model of aerogenic MTB infection. Although primary MyD88-deficient macrophages and dendritic cells were defective in cytokine production in response to mycobacterial stimulation, IL-1R1-deficient macrophages exhibited only a reduced IL-12p40 secretion with unaffected TNF, IL-6, and NO production and up-regulation of costimulatory molecules CD40 and CD86. Aerogenic MTB infection of IL-1R1-deficient mice was lethal within 4 wk with 2-log higher bacterial load in the lung and necrotic pneumonia but efficient pulmonary CD4 and CD8 T cell responses, as seen in MyD88-deficient mice. Mice deficient for IL-18R or TIRAP controlled acute MTB infection. These data demonstrate that absence of IL-1R signal leads to a dramatic defect of early control of MTB infection similar to that seen in the absence of MyD88, whereas IL-18R and TIRAP are dispensable, and that IL-1, together with IL-1-induced innate response, might account for most of MyD88-dependent host response to control acute MTB infection.
This study aimed at evaluating the effects of the micro-immunotherapy medicine (MIM) 2LEID, both in vitro and in vivo, on several components of the innate and adaptive immune system. MIM increased ...the phagocytic activity of macrophages, and it augmented the expression of the activation markers CD69 and HLA-DR in NK cells and monocytes/macrophages, respectively. The effect of MIM was evaluated in a model of respiratory infection induced by
virus administration to immunocompetent mice in which it was able to improve neutrophil recruitment within the lungs (
= 0.1051) and slightly increased the circulating levels of IgM (
= 0.1655). Furthermore, MIM stimulated the proliferation of CD3-primed T lymphocytes and decreased the secretion of the immunosuppressive cytokine IL-10 in CD14
-derived macrophages. Human umbilical vein endothelial cells were finally used to explore the effect of MIM on endothelial cells, in which it slightly increased the expression of immune-related markers such as HLA-I, CD137L, GITRL, PD-L1 and ICAM-1. In conclusion, the present study suggests that MIM might be a promising nonspecific (without antigen specificity) immunostimulant drug in preventing and early treating respiratory infections, but not only exclusively, as it would gently support several facets of the immune system and host defenses.
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