Department of Physiology, University of Arizona, Tucson, Arizona, United States of America.
Department of Medicine, Duke University, Durham, North Carolina, United States of America.
PLoS One. 2021 Feb 22;16(2):e0247504. doi: 10.1371/journal.pone.0247504. eCollection 2021.
Increased exposure to Ozone (O3) is associated with adverse health effects in individuals afflicted with respiratory diseases. Surfactant protein-A (SP-A), encoded by SP-A1 and SP-A2, is the largest protein component in pulmonary surfactant and is functionally impaired by O3-oxidation.
We used humanized SP-A2 transgenic mice with allelic variation corresponding to a glutamine (Q) to lysine (K) amino acid substitution at position 223 in the lectin domain to determine the impact of this genetic variation in regards to O3 exposure.
Mice were exposed to 2ppm O3 or Filtered Air (FA) for 3 hours and 24 hrs post-challenge pulmonary function tests and other parameters associated with inflammation were assessed in the bronchoalveolar lavage (BAL) fluid and lung tissue. Additionally, mouse tracheal epithelial cells were cultured and TEER measurements recorded for each genotype to determine baseline epithelial integrity.
Compared to FA, O3 exposure led to significantly increased sensitivity to methacholine challenge in all groups of mice. SP-A2 223Q variant mice were significantly protected from O3-induced AHR compared to SP-A-/- and SP-A2 223K mice. Neutrophilia was observed in all genotypes of mice post O3-exposure, however, SP-A2 223Q mice had a significantly lower percentage of neutrophils compared to SP-A-/- mice. Albumin levels in BAL were unchanged in O3-exposed SP-A2 223Q mice compared to their FA controls, while levels were significantly increased in all other genotypes of O3-exposed mice. SP-A 223Q MTECS has significant higher TEER values than all other genotypes, and WT MTECS has significantly higher TEER than the SP-A KO and SP-A 223K MTECS.
Taken together, our study suggests that expression of a glutamine (Q) as position 223 in SP-A2, as opposed to expression of lysine (K), is more protective in acute exposures to ozone and results in attenuated O3-induced AHR, neutrophilia, and vascular permeability.
暴露在臭氧（O3）中与患有呼吸道疾病的个体的健康不良影响有关。表面活性蛋白-A（SP-A）由 SP-A1 和 SP-A2 编码，是肺表面活性物质中最大的蛋白质成分，其功能因 O3 氧化而受损。
我们使用具有等位基因变异的人源化 SP-A2 转基因小鼠，该变异对应于凝集素结构域中第 223 位的谷氨酰胺（Q）到赖氨酸（K）氨基酸取代，以确定这种遗传变异对 O3 暴露的影响。
将小鼠暴露于 2ppm O3 或过滤空气（FA）中 3 小时和 24 小时后，评估支气管肺泡灌洗液（BAL）和肺组织中与炎症相关的其他参数。此外，培养小鼠气管上皮细胞并记录每个基因型的 TEER 测量值，以确定上皮完整性的基线。
与 FA 相比，O3 暴露导致所有小鼠组对乙酰甲胆碱挑战的敏感性显著增加。与 SP-A-/-和 SP-A2 223K 小鼠相比，SP-A2 223Q 变体小鼠对 O3 诱导的 AHR 有显著保护作用。所有基因型的小鼠在 O3 暴露后均观察到中性粒细胞增多，但 SP-A2 223Q 小鼠的中性粒细胞百分比明显低于 SP-A-/-小鼠。与 FA 对照组相比，O3 暴露的 SP-A2 223Q 小鼠的 BAL 中白蛋白水平无变化，而所有其他 O3 暴露基因型的小鼠的白蛋白水平均显著增加。SP-A2 223Q MTECS 的 TEER 值明显高于所有其他基因型，WT MTECS 的 TEER 值明显高于 SP-A KO 和 SP-A2 223K MTECS。
综上所述，我们的研究表明，SP-A2 中第 223 位的谷氨酰胺（Q）表达，而不是赖氨酸（K）表达，在急性臭氧暴露中更具保护作用，导致 O3 诱导的 AHR、中性粒细胞增多和血管通透性减弱。
