【作者】 练雪梅；

【导师】 李廷玉； 严聪；

【作者基本信息】 重庆医科大学 ， 儿科学， 2005， 博士

【摘要】 由肺泡II型上皮细胞分泌的肺表面活性物质主要由5%-10%的表面活性蛋白、80%-90%的磷脂以及 5%-10%的中性脂构成。有关表面活性物质中表面活性蛋白和磷脂在降低肺表面张力,维持肺的顺应性以及机体防御等方面作用的研究较多,但其中中性脂所发挥的作用尚不明了,而且国内外的研究很少。 溶酶体酸性脂肪酶是胆固醇酯和甘油三酯等中性脂在细胞内代谢所必需的水解酶,本研究以溶酶体酸性脂肪酶基因敲除小鼠(lal-/-)为模型,采用免疫组织化学的方法观察中性脂代谢被阻断的情况下,小鼠肺组织的病理变化;进而采用基因芯片技术筛选 lal-/-小鼠与野生型小鼠肺组织差异表达的基因,探讨中性脂代谢被阻断后 lal-/-小鼠肺病理变化可能的发生机制。由于中性脂的代谢产物常常作为配体依赖性核受体家族成员:过氧化物酶增殖体激活受体γ(PPARγ)所必需的配体,在机体防御等方面发挥重要作用;因此研究进一步采用PPARγ配体补充治疗的方法,观察人工补充 PPARγ配体对 lal-/-小鼠肺病理变化的改善作用,从而探讨 PPARγ配体缺乏在 lal-/-小鼠病理变化中可能发生的作用。 研究结果表明:1. lal-/-小鼠存在明显的随年龄增长而逐渐加剧的慢性肺部炎症表现:肺泡 II 型上皮细胞和巨嗜细胞中性脂蓄积;肺泡区域中性粒细胞浸润;巨嗜细胞增生,泡沫样改变;区域性肺气肿和区域性肺组织细胞增生、组织重建并存,以及气道 Clara 细胞反应更多还原

【Abstract】 Pulmonary surfactant deficiency/malfunction is the main cause of neonatal respiratory distress syndrome. Secreted by alveolar type II epithelial cells, pulmonary surfactant consists of 5%-10% surfactant proteins and 80%-90% phospholipids, which are essential for protecting the lung from the collapse by lowering tension at the air-liquid interface, and for maintaining normal lung function in various physiological conditions and host defenses. Still, pulmonary surfactant consists of 5%-10% neutral lipids, the functional roles of which are poorly understood in the lung. Lysosomal acid lipase (LAL) is one of the lysosomal hydrolases which hydrolyze most important components in neutral lipids, such as cholesteryl ester and triglycerides. In the present study, one LAL gene knock out mice model (lal-/-) was utilized to assess physiological consequences after the neutral lipids metabolic pathways in the lung were blocked; Affymetrix GeneChip microarray analysis was conducted to elucidate the mechanism underlining these pathogenesis. Since many neutral lipid metabolites serve as ligands for nuclear receptors, such as peroxisome proliferator activated receptor (PPARγ), intranasal treatment of lal-/- mice with natural occurring and synthetic PPARγ ligands was conducted to observe the potential role of this pathway. The results demonstrated that blocking neutral lipids metabolism in the lal-/- mice resulted in severe age dependent chronic respiratory inflammation: massive neutrophil infiltration; foamy macrophage accumulation; unwanted remodeling of the alveolar structure, pulmonary emphysema, and Clara cell hypertrophy and hyperplasia. Consisted with these pathogenic phenotypes, Affymetrix GeneChip microarray analysis of 1, 3 and 6 month old mice identified aberrant gene expression with age progression. Among them are proinflammatory cytokines/chemokines, matrix metalloproteinase 8, 9 and 12, apoptosis inhibitor 6, erythroblast transformation-specific domain (ETS) transcription factor family member SpiC and oncogene MafB. Treatment of 9-hydroxyoctadecanoic acids (9-HODE) and ciglitazone significantly rescued lal-/- pulmonary inflammation and aberrant gene expression. These studies support the concept that neutral lipids in the pulmonary surfactant play essential roles in pulmonary homeostasis and host defense. The pathological consequences after blocking the neutral lipids metabolism are partially caused by inactivation of PPARγ pathway.更多还原