Surfactant protein-A plays an important role in lung surfactant clearance: evidence using the surfactant protein-A gene-targeted mouse
Surfactant protein-A plays an important role in lung surfactant clearance: evidence using the surfactant protein-A gene-targeted mouse
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DOI：
10.1152/ajplung.00341.2007
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发表时间：
2008-02-01
影响因子：
4.9
通讯作者：
Fisher, Aron B.
中科院分区：
文献类型：
--
作者：
Bates, Sandra R.;Dodia, Chandra;Fisher, Aron B.
先前对离体灌注大鼠肺的研究表明，网格蛋白介导和肌动蛋白介导的途径都与完整肺中颗粒状肺细胞内吞双棕榈酰磷脂酰胆碱（DPPC）标记脂质体有关。使用表面活性剂蛋白a （SP-A）基因靶向小鼠，我们检测了在基础和分泌刺激条件下分离的小鼠肺对[H-3] DPPC脂质体的摄取。将[h -3] DPPC：磷脂酰胆碱：胆固醇：卵磷脂酰甘油（10:5:3:2 mol分数）组成的单层脂质体灌注麻醉小鼠气管，肺灌注2 h。摄取以灌洗后肺内每分钟灌注崩解物的百分比计算。金刚烷胺是一种网格蛋白抑制剂，因此，通过网格蛋白包被的小窝进行受体介导的内吞作用，在SP-A +/+中降低了70%的基础[H-3] DPPC摄取，但在SP-A -/-肺中仅降低了20%，数据与SP-A/受体调节的SP-A +/+小鼠的脂质清除途径相一致。非网格蛋白，肌动蛋白依赖性过程在SP-A +/+肺中较低，但在SP-A -/-小鼠中占脂质体内吞的55%。在促分泌剂（8-溴腺苷3′，5′-环单磷酸腺苷）治疗下，SP-A +/+肺中网格蛋白和肌动蛋白依赖的脂质清除率均升高，而SP-A -/-肺中两种途径均无反应。碘化SP-A与从两种基因型小鼠分离的II型细胞的结合相似，表明SP-A -/-肺中SP-A受体状态正常。通过重建分泌依赖性脂质体摄取增强，将SP-A灌注到脂质体中以“拯救”SP-A -/-肺。这些数据与受体介导的DPPC颗粒肺细胞内吞作用的主要作用相一致，这一过程严重依赖于SP- a。
Previous studies with the isolated perfused rat lung showed that both clathrin- and actin-mediated pathways are responsible for endocytosis of dipalmitoyl-phosphatidylcholine (DPPC)-labeled liposomes by granular pneumocytes in the intact lung. Using surfactant protein-A (SP-A) gene-targeted mice, we examined the uptake of [H-3] DPPC liposomes by isolated mouse lungs under basal and secretagogue-stimulated conditions. Unilamellar liposomes composed of [H-3] DPPC: phosphatidylcholine: cholesterol: egg phosphatidylglycerol ( 10: 5: 3: 2 mol fraction) were instilled into the trachea of anesthetized mice, and the lungs were perfused ( 2 h). Uptake was calculated as percentage of instilled disintegrations per minute in the postlavaged lung. Amantadine, an inhibitor of clathrin and, thus, receptor-mediated endocytosis via clathrin- coated pits, decreased basal [H-3] DPPC uptake by 70% in SP-A +/+ but only by 20% in SP-A -/- lung, data compatible with an SP-A/receptor-regulated lipid clearance pathway in the SP-A +/+ mice. The nonclathrin, actin-dependent process was low in the SP-A +/+ lung but accounted for 55% of liposome endocytosis in the SP-A -/- mouse. With secretagogue (8-bromoadenosine 3', 5'-cyclic monophosphate) treatment, both clathrin- and actin-dependent lipid clearance were elevated in the SP-A +/+ lungs while neither pathway responded in the SP-A -/- lungs. Binding of iodinated SP-A to type II cells isolated from both genotypes of mice was similar indicating a normal SP-A receptor status in the SP-A -/- lung. Inclusion of SP-A with instilled liposomes served to "rescue" the SP-A -/- lungs by reestablishing secretagogue-dependent enhancement of liposome uptake. These data are compatible with a major role for receptor-mediated endocytosis of DPPC by granular pneumocytes, a process critically dependent on SP- A.