Zakar T, Mijovic J E, Eyster K M, Bhardwaj D, Olson D M
Perinatal Research Centre, Department of Obstetrics and Gynaecology, University of Alberta, Edmonton, Alberta, Canada.
Biochim Biophys Acta. 1998 Mar 6;1391(1):37-51. doi: 10.1016/s0005-2760(97)00195-1.
Prostaglandin H2 synthase (PGHS)-1 and PGHS-2 expression was examined in primary cultures of human amnion cells, an in vitro model of amnion tissue. Epidermal growth factor (EGF), the protein kinase C (PKC) activating phorbol ester TPA, and the protein phosphatase inhibitor, okadaic acid (OA), stimulated PGHS activity and the level of PGHS-2 mRNA, but did not affect the level of PGHS-1 mRNA. In situ hybridization suggested that the same population of cells responded to EGF, TPA and OA. Okadaic acid promoted PGHS activity independently of PKC. EGF stimulated the activity of extracellular signal-regulated protein kinase (Erk) and N-terminal c-Jun kinase (Jnk). OA increased Jnk activity but had no effect on Erk activity, while TPA had no influence on either Erk or Jnk activity. PD098059, a selective inhibitor of the Erk-activating kinase MEK, blocked the stimulation of PGHS expression by EGF, but did not decrease stimulation in response to OA. Herbimycin A, a tyrosine kinase inhibitor, suppressed the stimulation of PGHS activity and PGHS-2 mRNA abundance by all three stimulants, and blocked signalling via the Erk and Jnk mitogen-activated protein kinase pathways. Thus, growth factor stimulation, PKC activation and protein phosphatase inhibition induced the expression of PGHS-2 in primary amnion cells by distinct regulatory mechanisms involving tyrosine kinase(s). Tyrosine kinase inhibitors may constitute a new category of PGHS-2 inhibitors that act by blocking the expression of the enzyme.
在人羊膜细胞原代培养物（羊膜组织的体外模型）中检测了前列腺素H2合酶（PGHS）-1和PGHS-2的表达。表皮生长因子（EGF）、激活蛋白激酶C（PKC）的佛波酯TPA以及蛋白磷酸酶抑制剂冈田酸（OA）刺激了PGHS活性和PGHS-2 mRNA水平，但不影响PGHS-1 mRNA水平。原位杂交表明同一群细胞对EGF、TPA和OA有反应。冈田酸独立于PKC促进PGHS活性。EGF刺激细胞外信号调节蛋白激酶（Erk）和N端c-Jun激酶（Jnk）的活性。OA增加Jnk活性但对Erk活性无影响，而TPA对Erk或Jnk活性均无影响。Erk激活激酶MEK的选择性抑制剂PD098059阻断了EGF对PGHS表达的刺激，但不降低对OA的刺激反应。酪氨酸激酶抑制剂赫伯霉素A抑制了所有三种刺激物对PGHS活性和PGHS-2 mRNA丰度的刺激，并阻断了通过Erk和Jnk丝裂原活化蛋白激酶途径的信号传导。因此，生长因子刺激、PKC激活和蛋白磷酸酶抑制通过涉及酪氨酸激酶的不同调节机制诱导原代羊膜细胞中PGHS-2的表达。酪氨酸激酶抑制剂可能构成一类新的PGHS-2抑制剂，其作用方式是阻断该酶的表达。
