Jyonouchi H, Sun S, Iijima K, Wang M, Hecht S S
Department of Pediatrics, University of Minnesota, School of Medicine, UMHC, Minneapolis 55455, USA.
Carcinogenesis. 1999 Jan;20(1):139-45. doi: 10.1093/carcin/20.1.139.
Benzo[a]pyrene (B[a]P), a tobacco-derived carcinogen, induces lung tumors in rodents through its carcinogenic metabolite, anti-7,8-dihydroxy-9,10-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]PDE). Tumorigenesis is inhibited by dietary myo-inositol in the post-initiation phase. However, little is known about how B[a]PDE and myo-inositol affect normal human lung cells. We addressed this question using untransformed human small airway epithelial (SAE) cells. SAE cell viability decreased <50% in parallel to an increase of apoptotic cells (>20%) 2 days after the cells were treated for 1 h with B[a]PDE (>100 nM). In contrast, the cell number and viability were not altered in A549 human lung cancer cells by B[a]PDE treatment up to 10 microM with <5% apoptotic cells and <10 U/l LDH in the medium. SAE cells retain the features of basal cells in serum-free, low Ca2+ (4 nM) medium up to 4-5 passages, but in serum-supplemented or serum-free, high Ca2+ (1 mM) cultures, they differentiate into non-ciliated epithelial cells expressing Clara cell secretory protein (CCSP). A non-toxic, physiologically relevant dose of B[a]PDE (1 nM) partially inhibited serum and Ca2+-induced SAE cell differentiation. This effect was abolished by wortmannin, a phosphatidylinositol-3 kinase (PI-3K) inhibitor, and PD98059, a mitogen activated protein kinase (MAPK) kinase-1 (MEK1) inhibitor, but not by SB202190, a p38 MAPK inhibitor, or melittin, a protein kinase C inhibitor. Myo-inositol (10-100 microM) did not alter growth or differentiation of untreated SAE or A549 cells, but reversed the inhibitory effect of B[a]PDE on serum and Ca2+-induced SAE cell differentiation when supplemented to the culture after B[a]PDE treatment. This myo-inositol action was not altered by PD98059, wortmannin or melittin, but was partially suppressed by SB202190. Collectively, these results indicate that B[a]PDE inhibits serum-induced SAE cell differentiation, possibly involving activating signals through a PI-3K/MEK1 mediated MAPK pathway, whereas myo-inositol protects SAE cells against this inhibitory effect of B[a]PDE perhaps through both PI-3K/MEK1 and p38 MAPK pathways.
苯并[a]芘（B[a]P）是一种烟草衍生的致癌物，通过其致癌代谢产物反式-7,8-二羟基-9,10-环氧-7,8,9,10-四氢苯并[a]芘（B[a]PDE）在啮齿动物中诱发肺肿瘤。在启动后阶段，膳食肌醇可抑制肿瘤发生。然而，关于B[a]PDE和肌醇如何影响正常人类肺细胞，人们知之甚少。我们使用未转化的人类小气道上皮（SAE）细胞来解决这个问题。在用B[a]PDE（>100 nM）处理1小时后2天，SAE细胞活力下降<50%，同时凋亡细胞增加（>20%）。相比之下，用高达10 microM的B[a]PDE处理A549人肺癌细胞，培养基中凋亡细胞<5%，乳酸脱氢酶<10 U/L，细胞数量和活力未改变。SAE细胞在无血清、低钙（4 nM）培养基中传代4 - 5次时仍保留基底细胞特征，但在补充血清或无血清、高钙（1 mM）培养条件下，它们会分化为表达克拉拉细胞分泌蛋白（CCSP）的无纤毛上皮细胞。无毒、生理相关剂量的B[a]PDE（1 nM）部分抑制血清和钙诱导的SAE细胞分化。磷脂酰肌醇-3激酶（PI-3K）抑制剂渥曼青霉素和丝裂原活化蛋白激酶（MAPK）激酶-1（MEK1）抑制剂PD98059可消除这种作用，但p38 MAPK抑制剂SB202190或蛋白激酶C抑制剂蜂毒肽则不能。肌醇（10 - 100 microM）不会改变未处理的SAE或A549细胞的生长或分化，但在B[a]PDE处理后添加到培养基中时，可逆转B[a]PDE对血清和钙诱导的SAE细胞分化的抑制作用。这种肌醇作用不受PD98059、渥曼青霉素或蜂毒肽影响，但部分受SB202190抑制。总体而言，这些结果表明，B[a]PDE抑制血清诱导的SAE细胞分化，可能涉及通过PI-3K/MEK1介导的MAPK途径激活信号，而肌醇可能通过PI-3K/MEK1和p38 MAPK途径保护SAE细胞免受B[a]PDE的这种抑制作用。
