12/15-Lipoxygenase Regulates IL-33-Induced Eosinophilic Airway Inflammation in Mice.

Dysregulated fatty acid metabolism is clinically associated with eosinophilic allergic diseases, including severe asthma and chronic rhinosinusitis. This study aimed to demonstrate the role of 12/15-lipoxygenase (12/15-LOX) in interleukin (IL)-33-induced eosinophilic airway inflammation; to this end, we used 12/15-LOX-deficient mice, which displayed augmented IL-33-induced lung inflammation, characterized by an increased number of infiltrated eosinophils and group 2 innate lymphoid cells (ILC2s) in the airway. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based lipidomics revealed that the levels of a series of 12/15-LOX-derived metabolites were significantly decreased, and application of 14(S)-hydroxy docosahexaenoic acid (HDoHE), a major 12/15-LOX-derived product, suppressed IL-33-mediated eosinophilic inflammation in 12/15-LOX-deficient mice. Using bioactive lipid screening, we found that 14(S)-HDoHE and 10(S),17(S)-diHDoHE markedly attenuated ILC2 proliferation and cytokine production at micromolar concentration in vitro. In addition, maresin 1 (MaR1) and resolvin D1 (RvD1), 12/15-LOX-derived specialized proresolving mediators (SPMs), inhibited cytokine production of ILC2s at nanomolar concentration. These findings demonstrate the protective role of endogenous 12/15-LOX-derived lipid mediators in controlling ILC2-mediated eosinophilic airway inflammation and related diseases. Thus, 12/15-LOX-derived lipid mediators may represent a potential therapeutic strategy for ameliorating airway inflammation-associated conditions.

Interleukin-33 regulates metabolic reprogramming of the retinal pigment epithelium in response to immune stressors.

It remains unresolved how retinal pigment epithelial cell metabolism is regulated following immune activation to maintain retinal homeostasis and retinal function. We exposed retinal pigment epithelium (RPE) to several stress signals, particularly Toll-like receptor stimulation, and uncovered an ability of RPE to adapt their metabolic preference on aerobic glycolysis or oxidative glucose metabolism in response to different immune stimuli. We have identified interleukin-33 (IL-33) as a key metabolic checkpoint that antagonizes the Warburg effect to ensure the functional stability of the RPE. The identification of IL-33 as a key regulator of mitochondrial metabolism suggests roles for the cytokine that go beyond its extracellular "alarmin" activities. IL-33 exerts control over mitochondrial respiration in RPE by facilitating oxidative pyruvate catabolism. We have also revealed that in the absence of IL-33, mitochondrial function declined and resultant bioenergetic switching was aligned with altered mitochondrial morphology. Our data not only shed new light on the molecular pathway of activation of mitochondrial respiration in RPE in response to immune stressors but also uncover a potentially novel role of nuclear intrinsic IL-33 as a metabolic checkpoint regulator.

Cannabidiol Ameliorates Cognitive Function via Regulation of IL-33 and TREM2 Upregulation in a Murine Model of Alzheimer's Disease.

There is a dire need for due innovative therapeutic modalities to improve outcomes of AD patients. In this study, we tested whether cannabidiol (CBD) improves outcomes in a translational model of familial AD and to investigate if CBD regulates interleukin (IL)-33 and triggering receptor expressed on myeloid cells 2 (TREM2), which are associated with improved cognitive function. CBD was administered to 5xFAD mice, which recapitulate early onset, familial AD. Behavioral tests and immunoassays were used to evaluate cognitive and motor outcomes. Our findings suggest that CBD treatment enhanced IL-33 and TREM2 expression, ameliorated the symptoms of AD, and retarded cognitive decline.

The therapeutic effect of anti-CD52 treatment in murine experimental autoimmune encephalomyelitis is associated with altered IL-33 and ST2 expression levels.

Experimental autoimmune encephalomyelitis (EAE) mice were administered with murine anti-CD52 antibody to investigate its therapeutic effect and whether the treatment modulates IL-33 and ST2 expression. EAE severity and central nervous system (CNS) inflammation were reduced following the treatment, which was accompanied by peripheral T and B lymphocyte depletion and reduced production of various cytokines including IL-33, while sST2 was increased. In spinal cords of EAE mice, while the number of IL-33+ cells remained unchanged, the extracellular level of IL-33 protein was significantly reduced in anti-CD52 antibody treated mice compared with controls. Furthermore the number of ST2+ cells in the spinal cord of treated EAE mice was downregulated due to decreased inflammation and immune cell infiltration in the CNS. These results suggest that treatment with anti-CD52 antibody differentially alters expression of IL-33 and ST2, both systemically and within the CNS, which may indicate IL-33/ST2 axis is involved in the action of the antibody in inhibiting EAE.

Effects of Quercetin Treatment on Epithelium-derived Cytokines and Epithelial Cell Apoptosis in Allergic Airway Inflammation Mice Model.

Quercetin is a dietary flavonoid which has anti-inflammatory effects. This study aimed to evaluate the influence of quercetin on histopathological aspects and airway epithelium in  allergic airway  inflammation mice model. Twenty-eight BALB/c mice were randomly divided into four groups: Group I (control), Group II (untreated mice with allergic airway inflammation), Group III (allergic airway inflammation quercetin-treated [16mg/kg/day]), Group IV (allergic airway inflammation dexamethasone-treated [1mg/kg/day]). Ovalbumin was administered intraperitoneally and via inhalation to achieve allergic airway inflammation mice model and treatments were also given intraperitoneally. Epithelium thickness, subepithelial smooth muscle thickness, number of mast and goblet cells, and basement membrane thickness were examined on samples isolated from lung. Immunohistochemical evaluationof lung tissues was performed using  IL-25, IL-33, thymic stromal lymphopoietin (TSLP), terminal deoxynucleotidyl transferase-mediated dUTP nick endlabeling (TUNEL) and cysteine-dependent aspartate-specific proteases(caspase)-3 antibodies. IL-4, IL-25, IL-33, TSLP were quantified in bronchoalveolar lavage (BAL) and OVAspecific IgE levels was measured in serum by standard ELISA protocols. IL-25, IL-33, thymic stromal lymphopoietin (TSLP) and cysteine-dependent aspartate-specific proteases (caspase)-3. Quercetin treatment led to lower epithelial thickness, subepithelial smooth muscle thickness, goblet and mast cell numbers compared to untreated  mice with allergic airway inflammation (p<0.05). However, quercetin treatment was not effective on improving basal membane thickness. Immunohistochemical scores of IL-25, IL-33, TSLP, caspase-3 and TUNEL were lower in quercetin-treated mice  t compared to untreated mice with allergic airway inflammation (p<0.05). IL-4, IL-25, IL-33, TSLP levels in BAL and OVA-specific IgE in serum were lower in quercetin treated mice compared to untreated mice (p<0.05). These findings suggest that quercetin improves chronic histopathological changes except basal membrane thickness in lung tissue and its beneficial effects on inflammation might be related to modulating epithelium derived cytokines and epithelial apoptosis.

Protective effects of tranilast on oxazolone-induced rat colitis through a mast cell-dependent pathway.

BACKGROUND: Mast cells in the gut play an important role in the innate and adaptive immune responses that are relevant to human inflammatory bowel disease. However, the contribution of mast cells to the development of inflammatory bowel disease is not well understood. This study aimed to determine the role of mast cells in oxazolone-induced colitis and to explore whether the mast cell membrane stabiliser tranilast could ameliorate colonic inflammation. METHODS: Wild-type rats and mast cell-deficient rats were sensitised and challenged with oxazolone, then treated with tranilast after challenge. Controls were treated with saline. RESULTS: Mast cell-deficient rats presented a weak response to oxazolone, while wild-type rats showed severe ulcerative colitis after stimulation with oxazolone. The mast cell-deficient rats model had a significantly lower disease activity index score than wild-type rats model (1.8±1.64 vs. 8.3±0.58 respectively; P<0.01). Tranilast could reduce the secretion of cytokines, immunoglobulins and myeloperoxidase activity in tranilast treatment groups compared with the model group. The number of mast cells in the wild-type model was higher than in the other groups. There was no significant change in mast cell-deficient rats. CONCLUSION: Mast cells play an important role in oxazolone-induced colitis. The mast cell membrane stabiliser tranilast can ameliorate oxazolone-induced colitis via a mast cell-dependent pathway.

Bone-Conditioned Medium Changes Gene Expression in Bone-Derived Fibroblasts.

PURPOSE: Autologous bone is used for augmentation in the course of oral implant placement. Bone grafts release paracrine signals that can modulate mesenchymal cell differentiation in vitro. The detailed genetic response of the bone-derived fibroblasts to these paracrine signals has remained elusive. Paracrine signals accumulate in bone-conditioned medium (BCM) prepared from porcine cortical bone chips. MATERIALS AND METHODS: In this study, bone-derived fibroblasts were exposed to BCM followed by a whole genome expression profiling and downstream quantitative reverse transciptase polymerase chain reaction of the most strongly regulated genes. RESULTS: The data show that ADM, IL11, IL33, NOX4, PRG4, and PTX3 were differentially expressed in response to BCM in bone-derived fibroblasts. The transforming growth factor beta (TGF-ß) receptor 1 antagonist SB431542 blocked the effect of BCM on the expression of the gene panel, except for IL33. CONCLUSION: These in vitro results extend existing evidence that cortical bone chips release paracrine signals that provoke a robust genetic response in mesenchymal cells that is not exclusively mediated via the TGF-ß receptor. The present data provide further insights into the process of graft consolidation.