Ou X, Weber T J, Chapkin R S, Ramos K S
Department of Veterinary Physiology and Pharmacology, Texas A & M University, College Station 77843, USA.
Arch Biochem Biophys. 1995 Apr 1;318(1):122-30. doi: 10.1006/abbi.1995.1212.
Elucidation of the mechanisms involved in the deregulation of vascular smooth muscle cell (SMC) growth and differentiation during the course of atherogenesis and the putative role of toxic injury in this process have been a subject of considerable interest in recent years. In this regard, we have recently shown that in vitro exposure of vascular (aortic) SMCs to benzo[a]pyrene (BaP), an atherogenic polycyclic aromatic hydrocarbon, initially delays cell cycle progression and inhibits cell proliferation and then causes permanent modulation to a highly proliferative state. To define the molecular basis of this response, we have examined critical components of the protein kinase C (PKC) signal transduction system upon exposure to BaP. Marked inhibition of serum-stimulated inositol phospholipid turnover was observed in growth-arrested SMC cultures challenged with 30 microM BaP for 24 h and then stimulated with 10% fetal bovine serum for 120 or 1800 s. Benzo[a]pyrene inhibited PKC-mediated phosphorylation of exogenous and endogenous proteins in the cytosolic and particulate fraction of cycling, as well as quiescent cultures. The PKC inhibitory response was observed as early as 0.5 h following BaP treatment and maintained for at least 5 days. Exposure of quiescent SMCs to 30 microM BaP inhibited the ability of serum to induce c-fos mRNA expression and decreased AP-1 binding to a 12-O-tetradecanoyl phorbol-13-acetate responsive element. Inhibition of PKC-related signal transduction was not due to generalized interference with cell cycle events since peak expression of the c-myc and c-Ha-ras protooncogenes following serum stimulation of quiescent cultures was unchanged, or slightly enhanced, by 30 microM BaP. Collectively, these data suggest that the ability of BaP to modulate growth and differentiation programs in vascular SMCs involves early interference with PKC-related mitogenic signal transduction.
阐明动脉粥样硬化形成过程中血管平滑肌细胞（SMC）生长和分化失调所涉及的机制以及毒性损伤在此过程中的假定作用，近年来一直是相当受关注的课题。在这方面，我们最近表明，体外将血管（主动脉）SMC暴露于苯并[a]芘（BaP），一种致动脉粥样硬化的多环芳烃，最初会延迟细胞周期进程并抑制细胞增殖，然后导致细胞永久转变为高度增殖状态。为了确定这种反应的分子基础，我们研究了暴露于BaP后蛋白激酶C（PKC）信号转导系统的关键成分。在用30微摩尔BaP处理24小时然后用10%胎牛血清刺激120或1800秒的生长停滞的SMC培养物中，观察到血清刺激的肌醇磷脂周转受到明显抑制。苯并[a]芘抑制了PKC介导的循环以及静止培养物的胞质和颗粒部分中外源和内源蛋白的磷酸化。PKC抑制反应在BaP处理后0.5小时就已观察到，并持续至少5天。将静止的SMC暴露于30微摩尔BaP会抑制血清诱导c-fos mRNA表达以及降低AP-1与12-O-十四烷酰佛波醇-13-乙酸酯反应元件结合的能力。PKC相关信号转导的抑制并非由于对细胞周期事件的普遍干扰，因为在用血清刺激静止培养物后，c-myc和c-Ha-ras原癌基因的峰值表达在30微摩尔BaP作用下未改变，或略有增强。总体而言，这些数据表明BaP调节血管SMC生长和分化程序的能力涉及对PKC相关有丝分裂信号转导的早期干扰。
