Bui K C, Buckley S, Wu F, Uhal B, Joshi I, Liu J, Hussain M, Makhoul I, Warburton D
Division of Neonatology and Pediatric Pulmonology, Children's Hospital of Los Angeles, California 90027, USA.
Am J Physiol. 1995 Apr;268(4 Pt 1):L625-35. doi: 10.1152/ajplung.1995.268.4.L625.
Hyperoxia causes a reproducible pattern of lung injury and repair in rodents, in which proliferation of alveolar epithelial cells (AEC) and fibroblasts is observed during recovery. We postulated that if quiescent cells are stimulated to reenter the cell cycle, then cyclin expression and cyclin-dependent protein kinase activity would be reactivated in AEC during the repair process after hyperoxic lung injury. To test this hypothesis, we exposed adult rats to short-term hyperoxia, followed by recovery for various times in room air. Cellular proliferation in vivo was confirmed by 1) flow cytometric analysis of DNA content (FACS) of freshly isolated AEC and 2) immunohistochemistry of proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine (BrdU) incorporation into DNA on lung sections. The percentage of freshly isolated AEC in S phase and G2/M phase on FACS analysis increased twofold to a maximum of 16.5%, after 48 h in 100% oxygen and 48 h recovery in air. Cyclins A and D and p34cdc2 protein expression were also increased during the recovery period; while p33cdk2 and p34cdk4 increased only slightly. p34cdc2 histone H1 kinase activity, both in whole lung and in AEC, decreased initially after 48 h in oxygen. However, a marked increase in p34cdc2 kinase activity was observed at 48 h recovery in whole lung and returned to baseline by 72 h. In isolated and cultured AEC, p34cdc2 kinase activity was maximal at 24 h of recovery in air. We conclude that cyclins A and D and p34cdc2 protein expression and p34cdc2 kinase activity are increased in vivo during recovery from hyperoxic lung injury in both adult rat lungs and in AEC isolated from these lungs. We speculate that the induction of cyclin-dependent protein kinase activity is a key event in mediating the proliferative cellular repair response to lung injury.
高氧可在啮齿动物中引发可重复的肺损伤和修复模式，在恢复过程中可观察到肺泡上皮细胞（AEC）和成纤维细胞的增殖。我们推测，如果静止细胞被刺激重新进入细胞周期，那么在高氧性肺损伤后的修复过程中，AEC中的细胞周期蛋白表达和细胞周期蛋白依赖性蛋白激酶活性将被重新激活。为了验证这一假设，我们将成年大鼠暴露于短期高氧环境，随后在室内空气中恢复不同时间。通过以下方法证实体内细胞增殖：1）对新鲜分离的AEC进行DNA含量的流式细胞术分析（FACS），以及2）对肺切片上增殖细胞核抗原（PCNA）和掺入DNA的溴脱氧尿苷（BrdU）进行免疫组织化学分析。在100%氧气中暴露48小时并在空气中恢复48小时后，FACS分析显示新鲜分离的AEC处于S期和G2/M期的百分比增加了两倍，最高达到16.5%。细胞周期蛋白A和D以及p34cdc2蛋白表达在恢复期间也增加；而p33cdk2和p34cdk4仅略有增加。在氧气中暴露48小时后，全肺和AEC中的p34cdc2组蛋白H1激酶活性最初均下降。然而，在恢复48小时时，全肺中观察到p34cdc2激酶活性显著增加，并在72小时时恢复到基线水平。在分离培养的AEC中，p34cdc2激酶活性在空气中恢复24小时时达到最大值。我们得出结论，在成年大鼠肺以及从这些肺中分离的AEC从高氧性肺损伤恢复过程中，细胞周期蛋白A和D以及p34cdc2蛋白表达和p34cdc2激酶活性在体内增加。我们推测细胞周期蛋白依赖性蛋白激酶活性的诱导是介导对肺损伤的增殖性细胞修复反应的关键事件。
