Abstract
Allergic asthma is a chronical pulmonary disease with high prevalence. It manifests as a maladaptive immune response to common airborne allergens and is characterized by airway hyperresponsiveness, eosinophilia, type 2 cytokine-associated inflammation, and mucus overproduction. Alveolar macrophages (AMs), although contributing to lung homeostasis and tolerance to allergens at steady state, have attracted less attention compared to professional antigen-presenting and adaptive immune cells in their contributions. Using an acute model of house dust mite-driven allergic asthma in mice, we showed that a fraction of resident tissue-associated AMs, while polarizing to the alternatively activated M2 phenotype, exhibited signs of polynucleation and polyploidy. Mechanistically, in vitro assays showed that only Granulocyte-Macrophage Colony Stimulating Factor and interleukins IL-13 and IL-33, but not IL-4 or IL-5, participate in the establishment of this phenotype, which resulted from division defects and not cell-cell fusion as shown by microscopy. Intriguingly, mRNA analysis of AMs isolated from allergic asthmatic lungs failed to show changes in the expression of genes involved in DNA damage control except for MafB. Altogether, our data support the idea that upon allergic inflammation, AMs undergo DNA damage-induced stresses, which may provide new unconventional therapeutical approaches to treat allergic asthma.
Highlights
Asthma is a widespread disease affecting 300 million people around the world and estimations predict that 100 million more will be affected by 2050 [1]
Activation of alveolar macrophages is associated with allergic asthma-driven inflammation
To further evaluate the characteristics of MHCII+ versus MHCII- populations, we examined the expression of additional specific macrophage markers
Summary
Asthma is a widespread disease affecting 300 million people around the world and estimations predict that 100 million more will be affected by 2050 [1]. It is characterized by airway hyper-responsiveness, narrowing of the airways, inflammatory cell recruitment, and increased mucus production [2]. By suppressing inflammatory responses through the secretion of anti-inflammatory cytokines such as IL-10 and IL-12, Alveolar macrophages (AMs) are associated, at steady state, with the maintenance of immunological homeostasis of the lungs [3]. Macrophages derived from peripheral blood-recruited monocytes infiltrate the lungs where they secrete additional pro-inflammatory mediators [3]. As the inflammatory response matures, resident AMs develop an anti-inflammatory phenotype, which tames and resolves the inflammation and assists in tissue remodeling [4]
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