Buckley S, Barsky L, Driscoll B, Weinberg K, Anderson K D, Warburton D
Pediatric Surgery Program, Childrens Hospital Los Angeles Research Institute 90027, USA.
Am J Physiol. 1998 May;274(5):L714-20. doi: 10.1152/ajplung.1998.274.5.L714.
Apoptosis is a genetically controlled cellular response to developmental stimuli and environmental insult that culminates in cell death. Sublethal hyperoxic injury in rodents is characterized by a complex but reproducible pattern of lung injury and repair during which the alveolar surface is damaged, denuded, and finally repopulated by type 2 alveolar epithelial cells (AEC2). Postulating that apoptosis might occur in AEC2 after hyperoxic injury, we looked for the hallmarks of apoptosis in AEC2 from hyperoxic rats. A pattern of increased DNA end labeling, DNA laddering, and induction of p53, p21, and Bax proteins, strongly suggestive of apoptosis, was seen in AEC2 cultured from hyperoxic rats when compared with control AEC2. In contrast, significant apoptosis was not detected in freshly isolated AEC2 from oxygen-treated rats. Thus the basal culture conditions appeared to be insufficient to ensure the ex vivo survival of AEC2 damaged in vivo. The oxygen-induced DNA strand breaks were blocked by the addition of 20 ng/ml of keratinocyte growth factor (KGF) to the culture medium from the time of plating and were partly inhibited by Matrigel or a soluble extract of Matrigel. KGF treatment resulted in a partial reduction in the expression of the p21, p53, and Bax proteins but had no effect on DNA laddering. We conclude that sublethal doses of oxygen in vivo cause damage to AEC2, resulting in apoptosis in ex vivo culture, and that KGF can reduce the oxygen-induced DNA damage. We speculate that KGF plays a role as a survival factor in AEC2 by limiting apoptosis in the lung after acute hyperoxic injury.
细胞凋亡是一种由基因控制的细胞对发育刺激和环境损伤的反应，最终导致细胞死亡。啮齿动物的亚致死性高氧损伤的特征是肺损伤和修复的模式复杂但可重复，在此过程中肺泡表面受损、剥脱，最终由2型肺泡上皮细胞（AEC2）重新填充。假设高氧损伤后AEC2可能发生凋亡，我们在高氧大鼠的AEC2中寻找凋亡的标志。与对照AEC2相比，在高氧大鼠培养的AEC2中观察到DNA末端标记增加、DNA梯带形成以及p53、p21和Bax蛋白诱导的模式，强烈提示细胞凋亡。相比之下，在氧处理大鼠新鲜分离的AEC2中未检测到明显的细胞凋亡。因此，基础培养条件似乎不足以确保体内受损的AEC2在体外存活。从接种时起，向培养基中添加20 ng/ml的角质形成细胞生长因子（KGF）可阻断氧诱导的DNA链断裂，基质胶或基质胶的可溶性提取物可部分抑制该断裂。KGF处理导致p21、p53和Bax蛋白的表达部分降低，但对DNA梯带形成无影响。我们得出结论，体内亚致死剂量的氧会导致AEC2损伤，导致体外培养中的细胞凋亡，并且KGF可以减少氧诱导的DNA损伤。我们推测，KGF通过限制急性高氧损伤后肺中的细胞凋亡，在AEC2中作为一种存活因子发挥作用。
