Catecholamines block 2-hydroxyestradiol-induced antimitogenesis in mesangial cells

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 a glomerular mesangial cells (GMCs). Because catecholamines are substrates for COMT, which is expressed growth of 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 mumol/L. Norepinephrine (10 mumol/L) and epinephrine (10 mumol/L) significantly inhibited methylation of 0.25 mumol/L 2-hydroxyestradiol. Norepinephrine concentration-dependently abrogated the ability of 2-hydroxyestradiol to inhibit H-3-thymidine incorporation (index of DNA synthesis). In the presence of 5, 10, and 40 mumol/L norepinephrine, the inhibitory effect of 0.1 mumol/L 2-hydroxyestradiol on H-3-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 H-3-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.