Guttenberg, M. A. | bioRxiv Science

bioRxiv2024

Withaferin A reduces pulmonary eosinophilia and IL-25 production in a mouse model of allergic airways disease

Several studies report that ashwagandha, a traditional Ayurvedic supplement, has anti-inflammatory properties. Type 2 (T2) asthma is characterized by eosinophilic airway inflammation. We hypothesized that allergen-induced eosinophilic airway inflammation in mice would be reduced following administration of Withaferin A (WFA), the primary active phytochemical in Ashwagandha. C57BL/6J mice were given 10 total intra-peritoneal injections of 2 mg/kg WFA or vehicle control, concurrent with 6 total intranasal administrations of 50 {micro}g house dust mite extract (HDM) or saline control over 2 weeks. We observed that treatment with WFA reduced allergen-induced peribronchial inflammation and airway eosinophil counts compared to mice treated with controls. In addition, we observed that treatment with WFA reduced lung levels of interleukin-25 (IL-25) but increased lung gene expression levels of its co-receptor, Il17ra, in HDM-challenged mice compared to HDM-challenged mice that received the vehicle control. This study pinpoints a potential mechanism by which WFA modulates allergen-induced airway eosinophilia via the IL-25 signaling pathway. Future studies will investigate the effects of WFA administration on lung eosinophilia and IL-25 signaling in the context of chronic allergen-challenge.

immunology↗

bioRxiv2023

Tissue-resident alveolar macrophages reduce O3-induced inflammation via MerTK mediated efferocytosis

Lung inflammation, caused by acute exposure to ozone (O3) - one of the six criteria air pollutants - is a significant source of morbidity in susceptible individuals. Alveolar macrophages (AMOs) are the most abundant immune cells in the normal lung and their number increases following O3 exposure. However, the role of AMOs in promoting or limiting O3-induced lung inflammation has not been clearly defined. Here, we used a mouse model of acute O3 exposure, lineage tracing, genetic knockouts, and data from O3-exposed human volunteers to define the role and ontogeny of AMOs during acute O3 exposure. Lineage tracing experiments showed that 12, 24, and 72 h after exposure to O3 (2 ppm) for 3h all AMOs were tissue-resident origin. Similarly, in humans exposed to FA and O3 (200 ppb) for 135 minutes, we did not observe [~]21h post-exposure an increase in monocyte-derived AMOs by flow cytometry. Highlighting a role for tissue-resident AMOs, we demonstrate that depletion of tissue-resident AMOs with clodronate-loaded liposomes led to persistence of neutrophils in the alveolar space after O3 exposure, suggesting that impaired neutrophil clearance (i.e., efferocytosis) leads to prolonged lung inflammation. Moreover, depletion of tissue-resident AMO demonstrated reduced clearance of intratracheally instilled apoptotic Jurkat cells, consistent with reduced efferocytosis. Genetic ablation of MerTK - a key receptor involved in efferocytosis - also resulted in impaired clearance of apoptotic neutrophils followed O3 exposure. Overall, these findings underscore the pivotal role of tissue-resident AMOs in resolving O3-induced inflammation via MerTK-mediated efferocytosis.

immunology↗