BackgroundHuman innate host defense molecules, surfactant protein A1 (SP-A1), and SP-A2 differentially affect the function and proteome of the alveolar macrophage (AM). We hypothesized that SP-A genes differentially regulate the AM miRNome.MethodsHumanized transgenic mice expressing SP-A1 and SP-A2 were subjected to O3-induced oxidative stress (OxS) or filtered air (FA), AMs were isolated, and miRNA levels were measured.ResultsIn SP-A2 males, we found significant changes in miRNome in terms of sex and sex-OxS effects, with 11 miRNAs differentially expressed under OxS. Their mRNA targets included BCL2, CAT, FOXO1, IL6, NF-kB, SOD2, and STAT3. We followed the expression of these transcripts as well as key cytokines, and we found that (a) the STAT3 mRNA significantly increased at 4 h post OxS and returned to baseline at 18 h post OxS. (b) The anti-oxidant protein SOD2 level significantly increased, but the CAT level did not change after 4 h post OxS compared to control. (c) The anti-apoptotic BCL2 mRNA increased significantly (18 h post OxS), but the levels of the other transcripts were decreased. The presence of the SP-A2 gene had a protective role in apoptosis of AMs under OxS compared to mice lacking SP-A (knockout, KO). (d) Pro-inflammatory cytokine IL-6 protein levels were significantly increased in SP-A2 mice compared to KO (4 and 18 h post OxS), which signifies the role of SP-A2 in pro-inflammatory protein expression. (e) SOD2 and CAT mRNAs changed significantly in OxS indicating a plausible role of SP-A2 in the homeostasis of reactive oxygen species. (f) Gonadectomy of transgenic mice showed that sex hormones contribute to significant changes of the miRNome expression.ConclusionsWe conclude that SP-A2 influences the miRNA-mediated sex-specific differences in response to OxS. In males, these differences pertain to inflammatory, anti-apoptotic, and anti-oxidant pathways.Electronic supplementary materialThe online version of this article (10.1186/s13293-017-0158-2) contains supplementary material, which is available to authorized users.

Background Survival of mice after K. pneumoniae infection and phagocytosis by alveolar macrophages (AMs), in the presence or absence of ozone (O3) exposure prior to infection is sex dependent. Objectives Study the role of gonadal hormones, 5α-dihydrotestosterone (DHT) and 17β-estradiol (E2) on mouse survival after filtered air (FA) or O3 exposure. Methods Gonadectomized female (GxF) and male (GxM) mice implanted with control or hormone pellets (DHT in GxF, or E2 in GxM), exposed to O3 (2 ppm, 3h) or FA and K. pneumoniae-infected were monitored for survival. Results Survival in GxF was identical after FA or O3 exposure; in GxM O3-exposure resulted in lower survival vs. FA. In O3-exposed females gonadectomy resulted in increased survival compared to intact females or to GxM+E2. A similar effect was observed in GxF+DHT. The combined negative effect of oxidative stress and hormone on survival was higher for E2. Conclusions Gonadectomy eliminated (females) or minimized (males) the previously observed sex-differences in survival in response to oxidative stress, and hormone treatment restored them. These findings indicate that gonadal hormones and/or oxidative stress have a significant effect on mouse survival.

Female mice exhibited higher survival rate than males after pneumonia, with a reversal of this pattern following ozone exposure. Surfactant protein A (SP-A) plays an important role in innate immunity and SP-A (−/−) mice were more susceptible to pneumonia than wild type mice. Here, we investigated underlying mechanisms of the differential susceptibility of mice to pneumonia. Wild type and SP-A (−/−) C57BL/6J male and female mice were exposed to ozone or filtered air (FA) and then infected intratracheally with Klebsiella pneumoniae. Blood, spleen, and lung were analyzed for bacterial counts, lung and spleen weights, and sex hormone and cortisol levels were measured in plasma within two days post-infection. We found: 1) in the absence of ozone-induced oxidative stress, males had higher level of bacterial dissemination compared to females; ozone exposure decreased pulmonary clearance in both sexes and ozone-exposed females were more affected than males; 2) ozone exposure increased lung weight, but decreased spleen weight in both sexes, and in both cases ozone-exposed females were affected the most; 3) plasma cortisol levels in infected mice changed: ozone-exposed > FA-exposed, females > males, and infected > non-infected; 4) no major sex hormone differences were observed in the studied conditions; 5) differences between wild type and SP-A (−/−) mice were observed in some of the studied conditions. We concluded that reduced pulmonary clearance, compromised spleen response to infection, and increased cortisol levels in ozone-exposed females, and the higher level of lung bacterial dissemination in FA-exposed males, contribute to the previously observed survival outcomes.