Hazinski T A, Noisin E, Hamon I, DeMatteo A
Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-2586, USA.
J Clin Invest. 1995 Oct;96(4):2083-9. doi: 10.1172/JCI118257.
Lung cytochrome P450 activity has been linked to neoplasia and may produce reactive oxidant species and potent arachidonic acid metabolites. In lamb lung, oxygen breathing increases lung P450 activity, and inhibition of lung cytochrome P450 activity reduces oxygen-induced lung injury. The P4501A1 (CYP1A1) isozyme is present in many lung cells, including endothelial cells, and may therefore be involved in the pathogenesis of hyperoxic injury to microvascular endothelium. Therefore, to test the hypothesis that oxygen regulates P4501A1 gene expression in the lung, we cloned the sheep P4501A1 cDNA, and examined its regulation by oxygen breathing significantly increased lung P4501A1 RNA levels and that this increase preceded the increase in isozyme activity. Oxygen exposure also promptly increased P4501A1 RNA levels in cultured lamb lung microvascular endothelial cells but not in endothelial cells isolated from the main pulmonary artery or in lung smooth muscle cells. The oxygen-stimulated increase in P4501A1 RNA levels was not serum dependent, was unaffected by cycloheximide treatment, and could not be mimicked by treatment of the cells with oxygenated medium, conditioned medium, or by chemical oxidants. By nuclear run-on assay in cultured lung endothelial cells, oxygen increased the transcription rate of P4501A1 by almost fourfold after 90 min of oxygen exposure but had no significant effect on P4501A1 RNA stability. We conclude that oxygen tension, but not chemical oxidants, increases P4501A1 gene expression pretranslationally in lung microvascular endothelial cells. We speculate that oxygen induction of P450 activity in these cells may contribute to microvascular injury during oxygen breathing.
肺细胞色素P450活性与肿瘤形成有关，可能产生活性氧物质和强效花生四烯酸代谢产物。在羔羊肺中，吸氧会增加肺P450活性，而抑制肺细胞色素P450活性可减轻氧诱导的肺损伤。P4501A1（CYP1A1）同工酶存在于包括内皮细胞在内的许多肺细胞中，因此可能参与微血管内皮细胞高氧损伤的发病机制。因此，为了验证氧调节肺中P4501A1基因表达的假说，我们克隆了绵羊P4501A1 cDNA，并检测其受吸氧的调节情况。结果显示，吸氧显著增加了肺P4501A1 RNA水平，且这种增加先于同工酶活性的增加。氧暴露也迅速增加了培养的羔羊肺微血管内皮细胞中P4501A1 RNA水平，但在从主肺动脉分离的内皮细胞或肺平滑肌细胞中未观察到这种增加。氧刺激引起的P4501A1 RNA水平升高不依赖于血清，不受环己酰亚胺处理的影响，且用充氧培养基、条件培养基或化学氧化剂处理细胞均无法模拟这种升高。通过对培养的肺内皮细胞进行核转录分析，发现氧暴露90分钟后，P4501A1的转录速率增加了近四倍，但对P4501A1 RNA稳定性无显著影响。我们得出结论，氧张力而非化学氧化剂在翻译前增加了肺微血管内皮细胞中P4501A1基因的表达。我们推测，这些细胞中氧诱导的P450活性可能导致吸氧过程中的微血管损伤。
