Estrogen contributes to sex differences in M2a macrophages during multi‐walled carbon nanotube‐induced respiratory inflammation

• Published in: The FASEB journal 2024-01, Vol.38 (1), p.e23350-n/a
• Main Authors: Ray, Jessica L., Postma, Britten, Kendall, Rebekah L., Ngo, Minh Dao, Foo, Cheng Xiang, Saunders, Brett, Ronacher, Katharina, Gowdy, Kymberly M., Holian, Andrij
• Format: Article
• Language: English
• Subjects: Animals; carbon nanotubes; cholesterol; Cholesterol - metabolism; estrogen; Female; Fulvestrant; Humans; inflammation; Inflammation - chemically induced; Inflammation - metabolism; Interleukin-33 - metabolism; lung; Lung - metabolism; macrophage; Macrophages - metabolism; Male; Mice; Mice, Inbred C57BL; Nanotubes, Carbon - toxicity; oxysterol; respiratory; sex; Sex Characteristics
• ISSN: 0892-6638; 1530-6860; 1530-6860
• DOI: 10.1096/fj.202301571RR

Lung diseases characterized by type 2 inflammation are reported to occur with a female bias in prevalence/severity in both humans and mice. This includes previous work examining multi‐walled carbon nanotube (MWCNT)‐induced eosinophilic inflammation, in which a more exaggerated M2a phenotype was observed in female alveolar macrophages (AMs) compared to males. The mechanisms responsible for this sex difference in AM phenotype are still unclear, but estrogen receptor (ER) signaling is a likely contributor. Accordingly, male AMs downregulated ERα expression after MWCNT exposure while female AMs did not. Thus, ER antagonist Fulvestrant was administered prior to MWCNT instillation. In females, Fulvestrant significantly attenuated MWCNT‐induced M2a gene expression and eosinophilia without affecting IL‐33. In males, Fulvestrant did not affect eosinophil recruitment but reduced IL‐33 and M2a genes compared to controls. Regulation of cholesterol efflux and oxysterol synthesis is a potential mechanism through which estrogen promotes the M2a phenotype. Levels of oxysterols 25‐OHC and 7α,25‐OHC were higher in the airways of MWCNT‐exposed males compared to MWCNT‐females, which corresponds with the lower IL‐1β production and greater macrophage recruitment previously observed in males. Sex‐based changes in cholesterol efflux transporters Abca1 and Abcg1 were also observed after MWCNT exposure with or without Fulvestrant. In vitro culture with estrogen decreased cellular cholesterol and increased the M2a response in female AMs, but did not affect cholesterol content in male AMs and reduced M2a polarization. These results reveal the modulation of (oxy)sterols as a potential mechanism through which estrogen signaling may regulate AM phenotype resulting in sex differences in downstream respiratory inflammation. This study demonstrates that Estrogen Receptor (ER) signaling is a critical mediator of sex differences in multi‐walled carbon nanotube (MWCNT)‐induced type 2 respiratory inflammation. Fulvestrant (nuclear ER antagonist) prevented MWCNT‐induced eosinophil recruitment in females and the development of the M2a macrophage phenotype in both sexes. Estrogen also influenced cholesterol efflux in alveolar macrophages, a process that is involved in M2a phenotype development, suggesting a novel pathway by which hormone signaling can modulate immune cell function in the lungs. Created with BioRender.com.