C34-09 Loss of Rev-erbα Amplifies IL-33-induced Type 2 Inflammation and Immune Cell Recruitment in the Lung

Abstract Rationale Asthma is a chronic inflammatory disease characterized by an exaggerated immune response to environmental stimuli. Airborne allergens disrupt the lung epithelial barrier, leading to the release of cytokine alarmins such as IL-33, IL-25, and TSLP, which promote immune cell activation and infiltration. IL-33, released from damaged epithelial cells, binds to its receptor ST2 (IL1RL1) expressed on mast cells, eosinophils, Th2 cells, and type 2 innate lymphoid cells (ILC2s), stimulating the secretion of Th2 cytokines (IL-5, IL-13). This cascade contributes to airway eosinophilia, mucus hypersecretion, and airway hyperresponsiveness, hallmarks of allergic asthma. Elevated IL-33 and ST2 levels correlate with asthma severity and exacerbations, positioning the IL-33/ST2 signaling axis as a promising therapeutic target. Circadian clock components are increasingly recognized as key regulators of immune responses. The core clock protein CLOCK temporally gates IL-33-mediated ST2 activation in mast cells, influencing allergic inflammation. However, whether the circadian repressor REV-ERBα modulates IL-33-driven immune responses in asthma remains unclear. We hypothesize that REV-ERBα regulates IL-33-induced inflammation in preclinical models of allergic asthma. Methods Adult C57BL/6 wild-type (WT) and global Rev-erbα knockout (KO) mice (2-3 months old) were intratracheally administered recombinant IL-33 (250 ng) daily for four consecutive days at ZT12 (6:00 p.m.). Twenty-four hours after the final exposure, bronchoalveolar lavage fluid (BALF) was collected to assess IL-33-induced immune infiltration. Myeloid and innate lymphoid cell (ILC) populations were quantified by flow cytometry. Ongoing studies will assess BALF cytokines/chemokines and expression of inflammatory, circadian, and epithelial barrier markers in lung tissues from WT and KO mice. Results IL-33 exposure increased granulocytic and lymphoid cell recruitment in both WT and Rev-erbα KO mice. Compared with WT mice, KO mice exhibited significantly elevated total leukocytes, neutrophils, GR1+ eosinophils, resident eosinophils, and inflammatory eosinophils. In contrast, dendritic cells and macrophage (alveolar and interstitial) populations were markedly reduced in KO mice. Furthermore, IL-33-treated KO mice displayed increased ILC1, ILC2, ILC3, and Th2 cell populations, with reduced Th1 and Th17 cells, indicating enhanced type 2 inflammation. Conclusions These findings demonstrate that REV-ERBα plays a pivotal role in regulating IL-33-mediated immune and inflammatory responses in the lung. Loss of REV-ERBα amplifies IL-33-induced eosinophilic and Th2 inflammation. Ongoing studies will elucidate the underlying mechanisms and evaluate REV-ERBα-targeted chronotherapeutic strategies to mitigate asthma pathogenesis. This abstract is funded by: NIH R01 HL142543