Sex Modifies Acute Ozone-Mediated Airway Physiologic Responses

Abstract

Sex differences clearly exist in incidence, susceptibility, and severity of airway disease and in pulmonary responses to air pollutants such as ozone (O3). Prior rodent O3 exposure studies demonstrate sex-related differences in the expression of lung inflammatory mediators and signaling. However, whether or not sex modifies O3-induced airway physiologic responses remains less explored. To address this, we exposed 8- to 10-week-old male and female C57BL/6 mice to either 1 or 2 ppm O3 or filtered air (FA) for 3 h. At 12, 24, 48, and 72 h following exposure, we assessed airway hyperresponsiveness to methacholine (MCh), bronchoalveolar lavage fluid cellularity, cytokines and total protein/albumin, serum progesterone, and whole lung immune cells by flow cytometry. Male mice generated consistent airway hyperresponsiveness to MCh at all time points following exposure. Alternatively, females had less consistent airway physiologic responses to MCh, which were more variable between individual experiments and did not correlate with serum progesterone levels. Bronchoalveolar lavage fluid total cells peaked at 12 h and were persistently elevated through 72 h. At 48 h, bronchoalveolar lavage cells were greater in females versus males. Bronchoalveolar lavage fluid cytokines and total protein/albumin increased following O3 exposure without sex differences. Flow cytometry of whole lung tissue identified dynamic O3-induced immune cell changes also independent of sex. Our results indicate sex differences in acute O3-induced airway physiology responses and airspace influx without significant difference in other injury and inflammation measures. This study highlights the importance of considering sex as a biological variable in acute O3-induced airway physiology responses.

Androgens augment pulmonary responses to ozone in mice

“…In allergen sensitized and challenged mice, allergen‐induced AHR and allergen‐induced inflammation are greater in females than in males and castration augments rather than attenuates these effects of allergen (Fuseini et al, ). In contrast, we and others have reported that O 3 ‐induced AHR is greater in male than female mice (Cho et al, ; Birukova et al, ) and we now report that castration attenuates rather than augments responses to O 3 (Fig. ).…”

“…There is increasing evidence demonstrating the importance of considering sex as a biologic variable. Our data indicate that androgens augment O 3 -induced AHR and likely contribute to the augmented responses to O 3 observed in male versus female mice (Cho et al, 2018a;Birukova et al, 2019). Better understanding of the mechanistic basis for this effect of androgens may ultimately lead to improved treatment of air pollutant exacerbated lung diseases such as asthma.…”

“…In female mice, the stage of the estrous cycle influences O 3 ‐induced AHR: compared to mice in the luteal stage, mice in the follicular stage of the estrous cycle, when estradiol and luteinizing hormone are elevated, have increased O 3 ‐induced AHR (Fuentes et al, ). In contrast, progesterone, which is elevated in the luteal stage of the estrous cycle, does not associate with induced AHR (Birukova et al, ). These data indicate a role for female sex hormones in the response to O 3 .…”

Early life microbiome perturbation alters pulmonary responses to ozone in male mice

“…Exposure to ozone increases BAL concentrations of many cytokines and chemokines that contribute to the neutrophil recruitment and AHR caused by O 3 (Birukova et al, ; Cho, Abu‐Ali, et al, ; Cho et al, ; Kasahara et al, ; Mathews et al, , ; Tashiro et al, ). To determine whether there were vendor‐ and/or housing‐related differences in the production of these inflammatory moieties following O 3 exposure, we performed a multiplex assay (Figure ).…”

“…In male mice, the magnitude of AHR induced by ozone exposure is decreased by both antibiotic treatment and GF conditions (Cho et al, ). The magnitude of ozone‐induced AHR is greater in male than in female mice (Birukova et al, ; Cho, Abu‐Ali, et al, ; Kasahara et al, ), and this sex difference is abolished when mice are treated with antibiotics (Cho, Abu‐Ali, et al, ). Furthermore, when weanling female pups are housed in cages conditioned by adult male mice, they develop greater ozone‐induced AHR than weanling female pups raised in cages conditioned by adult females (Cho, Abu‐Ali, et al, ).…”