Zacharia Lefteris C, Jackson Edwin K, Gillespie Delbert G, Dubey Raghvendra K
Center for Clinical Pharmacology, Department of Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pa, USA.
Hypertension. 2002 Apr;39(4):854-9. doi: 10.1161/01.hyp.0000014502.44988.39.
Methylation of 2-hydroxyestradiol to 2-methoxyestradiol by catechol-O-methyl transferase (COMT) mediates the antimitogenic effects of 2-hydroxyestradiol on vascular smooth muscle cells. Moreover, 2-hydroxyestradiol inhibits growth of glomerular mesangial cells (GMCs). Because catecholamines are substrates for COMT, which is expressed in GMCs, we hypothesize that catecholamines may abrogate the antimitogenic effects of 2-hydroxyestradiol on GMCs by competing for COMT and inhibiting 2-methoxyestradiol formation. To test this hypothesis, we investigated the antimitogenic effects of 2-hydroxyestradiol on rat GMCs in the presence and absence of catecholamines. The capability of GMCs to methylate 2-hydroxyestradiol in the presence and absence of catecholamines was also evaluated. GMCs metabolized 2-hydoxyestradiol in a concentration-dependent manner with a V(max) of 12.03+/-0.32 pmol/10(6) cells/min and an apparent K(m) of 0.23+/-0.04 micromol/L. Norepinephrine (10 micromol/L) and epinephrine (10 micromol/L) significantly inhibited methylation of 0.25 micromol/L 2-hydroxyestradiol. Norepinephrine concentration-dependently abrogated the ability of 2-hydroxyestradiol to inhibit 3H-thymidine incorporation (index of DNA synthesis). In the presence of 5, 10, and 40 micromol/L norepinephrine, the inhibitory effect of 0.1 micromol/L 2-hydroxyestradiol on 3H-thymidine incorporation was reduced from 51+/-0.7% to 46+/-0.4%, 39+/-0.3%, and 25+/-0.7%, respectively. Similar to DNA synthesis, the inhibitory effects of 2-hydroxyestradiol on cell number and 3H-proline incorporation (index of collagen synthesis) on GMCs were abrogated by catecholamines. Our findings provide evidence that methylation of 2-hydroxyestradiol inhibits GMC proliferation and extracellular matrix synthesis and may in part protect against renal proliferative diseases. Moreover, catecholamines may abrogate the renoprotective effects of 2-hydroxyestradiol in the glomeruli by inhibiting COMT and 2-methoxyestradiol formation.
儿茶酚-O-甲基转移酶（COMT）将2-羟基雌二醇甲基化为2-甲氧基雌二醇，介导了2-羟基雌二醇对血管平滑肌细胞的抗增殖作用。此外，2-羟基雌二醇可抑制肾小球系膜细胞（GMCs）的生长。由于儿茶酚胺是COMT的底物，且COMT在GMCs中表达，我们推测儿茶酚胺可能通过竞争COMT并抑制2-甲氧基雌二醇的形成，从而消除2-羟基雌二醇对GMCs的抗增殖作用。为验证这一假设，我们研究了在有或无儿茶酚胺存在的情况下，2-羟基雌二醇对大鼠GMCs的抗增殖作用。同时还评估了在有或无儿茶酚胺存在的情况下，GMCs将2-羟基雌二醇甲基化的能力。GMCs以浓度依赖的方式代谢2-羟基雌二醇，V(max)为12.03±0.32 pmol/10(6)细胞/分钟，表观K(m)为0.23±0.04 μmol/L。去甲肾上腺素（10 μmol/L）和肾上腺素（10 μmol/L）显著抑制0.25 μmol/L 2-羟基雌二醇的甲基化。去甲肾上腺素浓度依赖性地消除了2-羟基雌二醇抑制3H-胸腺嘧啶核苷掺入（DNA合成指标）的能力。在存在5、10和40 μmol/L去甲肾上腺素的情况下，0.1 μmol/L 2-羟基雌二醇对3H-胸腺嘧啶核苷掺入的抑制作用分别从51±0.7%降至46±0.4%、39±0.3%和25±0.7%。与DNA合成情况类似，儿茶酚胺消除了2-羟基雌二醇对GMCs细胞数量和3H-脯氨酸掺入（胶原蛋白合成指标）的抑制作用。我们的研究结果表明，2-羟基雌二醇的甲基化抑制GMCs增殖和细胞外基质合成，可能在一定程度上预防肾脏增殖性疾病。此外，儿茶酚胺可能通过抑制COMT和2-甲氧基雌二醇的形成，消除2-羟基雌二醇在肾小球中的肾脏保护作用。
