Rich G, Yoder E J, Moore S A
Department of Pathology, The University of Iowa, Iowa City 52242-1181, USA.
J Cell Physiol. 1998 Sep;176(3):495-505. doi: 10.1002/(SICI)1097-4652(199809)176:3<495::AID-JCP6>3.0.CO;2-J.
Growth factors may play a role in the formation of prostaglandins (PG) by cerebral blood vessels during development or reaction to injury. In smooth muscle cultures isolated from murine cerebral microvessels PG production was induced with either serum or epidermal growth factor (EGF). Prostaglandin H synthase (PGHS) activity peaked at 6 h after the addition of 10% serum or 50 ng/ml EGF. Increases in expression of PGHS-1 mRNA were small (7- to 10-fold) compared with PGHS-2 (30- to 120-fold), and the induction patterns were different for serum and EGF. An increase in PGHS-2 message was detected by 0.5 h of adding either agent, but peak induction occurred earlier for EGF than for serum, 1 h vs. 3 h, respectively. The response to either stimulus had returned to prestimulation levels by 12 h. The induction of PGHS-2 protein was also transient, but followed a more delayed time course (peak levels at 6 h). Induction of activity, message, and protein by either agent was blocked by 1 microM dexamethasone and attenuated by genistein (100 microM), a nonspecific tyrosine kinase inhibitor. Tyrphostin 47, a more selective EGF receptor tyrosine kinase inhibitor, dose-dependently inhibited EGF-stimulated PGHS activity, completely abolishing PG production at 100 microM. However, this inhibitor had no effect on serum-stimulated PG production. Curiously, 100 microM tyrphostin 47 enhanced EGF-induced PGHS-2 mRNA and protein expression. These data suggest that EGF induces the expression of PGHS-2 in cerebromicrovascular smooth muscle by a mechanism that requires tyrosine kinase activity and that is distinct from serum.
生长因子可能在发育过程中或对损伤的反应中，在脑血管形成前列腺素（PG）的过程中发挥作用。在从小鼠脑微血管分离的平滑肌培养物中，血清或表皮生长因子（EGF）均可诱导PG生成。添加10%血清或50 ng/ml EGF后6小时，前列腺素H合酶（PGHS）活性达到峰值。与PGHS-2（30至120倍）相比，PGHS-1 mRNA表达的增加较小（7至10倍），血清和EGF的诱导模式不同。添加任何一种试剂0.5小时后即可检测到PGHS-2信息增加，但EGF的诱导峰值出现时间早于血清，分别为1小时和3小时。到12小时时，对任何一种刺激的反应均恢复到刺激前水平。PGHS-2蛋白的诱导也是短暂的，但时间进程更为延迟（峰值水平在6小时）。两种试剂对活性、信息和蛋白的诱导均被1 microM地塞米松阻断，并被非特异性酪氨酸激酶抑制剂染料木黄酮（100 microM）减弱。更具选择性的EGF受体酪氨酸激酶抑制剂酪氨酸磷酸化抑制剂47剂量依赖性地抑制EGF刺激的PGHS活性，在100 microM时完全消除PG生成。然而，该抑制剂对血清刺激的PG生成没有影响。奇怪的是，100 microM酪氨酸磷酸化抑制剂47增强了EGF诱导的PGHS-2 mRNA和蛋白表达。这些数据表明，EGF通过一种需要酪氨酸激酶活性且与血清不同的机制诱导脑微血管平滑肌中PGHS-2的表达。
