Miyaura C, Inada M, Suzawa T, Sugimoto Y, Ushikubi F, Ichikawa A, Narumiya S, Suda T
Department of Biochemistry, School of Dentistry, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, Tokyo 142-8555, Japan.
J Biol Chem. 2000 Jun 30;275(26):19819-23. doi: 10.1074/jbc.M002079200.
Prostaglandin E(2) (PGE(2)) acts as a potent stimulator of bone resorption. In this study, we first clarified in normal ddy mice the involvement of protein kinase A and induction of matrix metalloproteinases (MMPs) in PGE(2)-induced bone resorption, and then identified PGE receptor subtype(s) mediating this PGE(2) action using mice lacking each subtype (EP1, EP2, EP3, and EP4) of PGE receptor. In calvarial culture obtained from normal ddy mice, both PGE(2) and dibutyryl cyclic AMP (Bt(2)cAMP) stimulated bone resorption and induced MMPs including MMP-2 and MMP-13. Addition of an inhibitor of protein kinase A, H89, or an inhibitor of MMPs, BB94, significantly suppressed bone-resorbing activity induced by PGE(2.) In calvarial culture from EP1-, EP2-, and EP3-knockout mice, PGE(2) stimulated bone resorption to an extent similar to that found in calvaria from the wild-type mice. On the other hand, a marked reduction in bone resorption to PGE(2) was found in the calvarial culture from EP4-knockout mice. The impaired bone resorption to PGE(2) was also detected in long bone cultures from EP4-knockout mice. Bt(2)cAMP greatly stimulated bone resorption similarly in both wild-type and EP4-knockout mice. Induction of MMP-2 and MMP-13 by PGE(2) was greatly impaired in calvarial culture from EP4-knockout mice, but Bt(2)cAMP stimulated MMPs induction similarly in the wild-type and EP4-knockout mice. These findings suggest that PGE(2) stimulates bone resorption by a cAMP-dependent mechanism via the EP4 receptor.
前列腺素E(2)（PGE(2)）是骨吸收的强效刺激物。在本研究中，我们首先在正常ddy小鼠中阐明了蛋白激酶A的参与以及基质金属蛋白酶（MMPs）在PGE(2)诱导的骨吸收中的诱导作用，然后使用缺乏PGE受体各亚型（EP1、EP2、EP3和EP4）的小鼠鉴定介导这种PGE(2)作用的PGE受体亚型。在从正常ddy小鼠获得的颅骨培养物中，PGE(2)和二丁酰环磷腺苷（Bt(2)cAMP）均刺激骨吸收并诱导包括MMP-2和MMP-13在内的MMPs。添加蛋白激酶A抑制剂H89或MMPs抑制剂BB94可显著抑制PGE(2)诱导的骨吸收活性。在来自EP1、EP2和EP3基因敲除小鼠的颅骨培养物中，PGE(2)刺激骨吸收的程度与野生型小鼠颅骨中的相似。另一方面，在来自EP4基因敲除小鼠的颅骨培养物中发现对PGE(2)的骨吸收明显减少。在来自EP4基因敲除小鼠的长骨培养物中也检测到对PGE(2)的骨吸收受损。Bt(2)cAMP在野生型和EP4基因敲除小鼠中均同样强烈地刺激骨吸收。PGE(2)对MMP-2和MMP-13的诱导在来自EP4基因敲除小鼠的颅骨培养物中大大受损，但Bt(2)cAMP在野生型和EP4基因敲除小鼠中同样刺激MMPs的诱导。这些发现表明，PGE(2)通过依赖cAMP的机制经由EP4受体刺激骨吸收。
