Analysis of Stratifin Expression and Proteome Variation in a Rat Model of Acute Lung Injury

Diffuse alveolar damage (DAD) is a pathological hallmark
of severe
interstitial lung diseases, such as acute respiratory distress syndrome
(ARDS), and is linked to poor prognosis. Previously, we identified
14–3–3σ/stratifin (SFN) as a serum biomarker candidate
for diagnosing DAD. To clarify the time-dependent relationship between
SFN expression and DAD, we here investigated pathological and molecular
changes in serum, bronchoalveolar lavage fluid (BALF), and lung tissue
in an oleic acid (OA)-induced ARDS rat model. Acute alveolar edema
was observed after OA administration, followed by alveolar epithelial
cell proliferation and increased BALF and serum SFN levels. Proteomic
analysis of lung tissue extracts revealed that proteins related to
“inflammatory response” and “HIF-1 signaling,”
including plasminogen activator inhibitor-1, were markedly increased
3 h after acute lung injury, followed by a gradual decrease. Conversely,
proteins associated with “cell cycle” and “p53
pathway,” including SFN, showed a persistent increase starting
at 3 h and peaking at 48 h. Western blotting and immunohistochemistry
confirmed that SFN was expressed in a part of proliferated alveolar
type-II cells, accompanied by p53 activation, an important event for
differentiation into type-I cells. SFN may be a biomarker closely
related to alveolar remodeling during the repair process after lung
injury.

弥漫性肺泡损伤（Diffuse alveolar damage, DAD）是重症间质性肺疾病的病理标志性特征，例如急性呼吸窘迫综合征（acute respiratory distress syndrome, ARDS），且与不良预后密切相关。既往研究中，我们将14-3-3σ/Stratifin（SFN）鉴定为用于诊断DAD的血清生物标志物候选物。为明确SFN表达与DAD之间的时间依赖性关联，本研究针对油酸（oleic acid, OA）诱导的ARDS大鼠模型，对血清、支气管肺泡灌洗液（bronchoalveolar lavage fluid, BALF）及肺组织中的病理与分子变化展开了探究。油酸给药后可观察到急性肺泡水肿，随后出现肺泡上皮细胞增殖，且支气管肺泡灌洗液与血清中的SFN水平升高。对肺组织提取物的蛋白质组学分析显示，与“炎症反应”及“HIF-1信号通路”相关的蛋白（包括纤溶酶原激活物抑制剂-1）在急性肺损伤后3小时即显著升高，随后逐渐下降。反之，与“细胞周期”及“p53通路”相关的蛋白（包括SFN）则呈现持续升高的趋势，自3小时起开始上升，并于48小时达到峰值。蛋白质印迹法（Western blotting）与免疫组织化学（immunohistochemistry）实验证实，SFN在部分增殖的II型肺泡细胞中表达，同时伴随p53激活——这是向I型肺泡细胞分化的关键事件。SFN或可成为肺损伤后修复过程中与肺泡重塑密切相关的生物标志物。