Iwasaki H, Eguchi S, Shichiri M, Marumo F, Hirata Y
Second Department of Internal Medicine, Tokyo Medical and Dental University, Japan.
Endocrinology. 1998 Aug;139(8):3432-41. doi: 10.1210/endo.139.8.6144.
To examine whether adrenomedullin (AM), a novel vasodilator peptide, acts as a growth modulator in the vasculature, the effects of AM on protein tyrosine phosphorylation, mitogen-activated protein kinase (MAPK) activation, protooncogene expression, DNA synthesis, and cell proliferation were studied in cultured rat vascular smooth muscle cells (VSMC). AM and calcitonin gene-related peptide (CGRP), although weaker than AM, stimulated DNA synthesis and cell proliferation of quiescent VSMC, whose effects were inhibited by a CGRP receptor antagonist, CGRP-(8-37). AM induced a rapid increase in MAPK activity, followed by the expression of the immediate early protooncogene c-fos. AM-induced MAPK activation and cell proliferation were completely blocked by protein tyrosine kinase inhibitors (genistein and ST638). Moreover, AM rapidly induced tyrosine phosphorylation of several proteins (approximately 120, approximately 90, and approximately 50 kDa) and transiently increased association of a tyrosine-phosphorylated protein (approximately 120 kDa) and Shc with the glutathione-S-transferase-Grb2 fusion protein. A MAPK kinase inhibitor (PD98059) also reduced the AM-induced MAPK activation, c-fos messenger RNA expression, and cell proliferation. Although AM has been shown to induce vasodilation through cAMP production in VSMC, a cAMP antagonist (Rp-cAMP-thionate) and a protein kinase A inhibitor (KT5720) failed to block AM-induced MAPK activation and DNA synthesis. Moreover, 8-bromo-cAMP and forskolin did not affect the MAPK activity. AM had no effect on either the intracellular Ca2+ concentration or inositol 1,4,5-trisphosphate formation. In addition, a protein kinase C inhibitor (GF109203X) did not inhibit the AM-induced MAPK activation. These data suggest that in addition to its vasodilatory effect through the cAMP-dependent pathway, AM exerts its mitogenic activity via protein tyrosine kinase-mediated MAPK activation in quiescent rat VSMC.
为研究一种新型血管舒张肽肾上腺髓质素（AM）是否作为血管中的生长调节因子发挥作用，我们在培养的大鼠血管平滑肌细胞（VSMC）中研究了AM对蛋白质酪氨酸磷酸化、丝裂原活化蛋白激酶（MAPK）激活、原癌基因表达、DNA合成及细胞增殖的影响。AM和降钙素基因相关肽（CGRP，尽管其作用比AM弱）刺激了静止VSMC的DNA合成及细胞增殖，其作用被CGRP受体拮抗剂CGRP -（8 - 37）抑制。AM诱导MAPK活性迅速增加，随后立即早期原癌基因c - fos表达。AM诱导的MAPK激活及细胞增殖被蛋白质酪氨酸激酶抑制剂（染料木黄酮和ST638）完全阻断。此外，AM迅速诱导几种蛋白质（约120 kDa、约90 kDa和约50 kDa）的酪氨酸磷酸化，并短暂增加一种酪氨酸磷酸化蛋白质（约120 kDa）和Shc与谷胱甘肽 - S - 转移酶 - Grb2融合蛋白的结合。一种MAPK激酶抑制剂（PD98059）也降低了AM诱导的MAPK激活、c - fos信使核糖核酸表达及细胞增殖。尽管已表明AM通过在VSMC中产生cAMP诱导血管舒张，但一种cAMP拮抗剂（Rp - cAMP - 硫代酸盐）和一种蛋白激酶A抑制剂（KT5720）未能阻断AM诱导的MAPK激活及DNA合成。此外，8 - 溴 - cAMP和福斯高林不影响MAPK活性。AM对细胞内Ca2 +浓度或肌醇1,4,5 - 三磷酸形成均无影响。另外，一种蛋白激酶C抑制剂（GF109203X）不抑制AM诱导的MAPK激活。这些数据表明，除了通过cAMP依赖性途径发挥血管舒张作用外，AM在静止的大鼠VSMC中通过蛋白质酪氨酸激酶介导的MAPK激活发挥其促有丝分裂活性。
