Sex-specific IL-6-associated signaling activation in ozone-induced lung inflammation

Acute ozone (O3) exposure has known deleterious effects on the respiratory system and has been linked with respiratory disease and infection. Inflammatory lung disease induced by air pollution has demonstrated greater severity and poorer prognosis in women vs. men. Both severe damage to the bronchial-alveolar epithelium and malfunctioning of bronchial-blood barrier have been largely attributed to the pathobiology of O3-induced inflammatory response, but the associated mechanisms in the male and female lung remain unknown.

Here, we investigated sex-based differential regulation of lung interleukin-6 (IL-6) and its downstream signaling pathways JAK2/STAT3 and AKT1/NF-κB in response to O3 exposure in a mouse model. We exposed male and female mice (in different stages of the estrous cycle) to 2 ppm of O3 or filtered air (FA) for 3 h, and we harvested lung tissue for protein expression analysis by Western blot.

We found significant up-regulation of IL-6 and IL-6R in females and IL-6 in males in response to O3 vs. FA. Ozone exposure induced a significant increase in STAT3-Y705 phosphorylation in both females and males. Males exposed to O3 had decreased levels of JAK2, but increased JAK2 (Y1007+Y1008) phosphorylation, while females exposed to O3 showed significant up-regulation of both proteins. Both NF-κB (p105/p50) and AKT1 protein levels were significantly increased only in females exposed to O3. In addition, females exposed to O3 during proestrus displayed increased expression of selected genes when compared to females exposed to O3 in other estrous cycle stages.

Together, our observations indicate a sex-based and estrous cycle-dependent differential lung inflammatory response to O3 and involvement of two converging JAK2/STAT3 and AKT1/NF-κB pathways. To our knowledge, this is the first study specifically addressing the impact of the estrous cycle in O3-associated lung inflammatory pathways.