Indomethacin enhances endothelial NO release--evidence for a role of PGI2 in the autocrine control of calcium-dependent autacoid production.
OBJECTIVE
We studied whether NO or prostacyclin (PGI2), which are continuously released by endothelial cells, have autocrine/paracrine effects on the calcium-dependent autacoid production by modulating the intracellular Ca2+ concentration ([Ca2+]i).


METHODS
Histamine(His)-induced [Ca2+]i increases (Fura 2-method) and NO-dependent cGMP increase were measured in human umbilical vein endothelial cell (HUVECs) before and after cyclooxygenase inhibition or application of cAMP- and cGMP-elevating drugs.


RESULTS
0.3 microM His increased endothelial [Ca2+]i from 77 +/- 2 nM to 418 +/- 59 nM. The His-induced [Ca2+]i increases were significantly attenuated following treatment with PGI2 (by 23%) and forskolin (by 33%), both increasing the cAMP release from HUVECs (by 49% and 66%). The His-induced [Ca2+]i increases were inhibited by the protein kinase A-activator cBIMPS (by 61%) which also abolished the His-induced PGI2 release. Conversely, inhibition of the PGI2 production with indomethacin significantly augmented the His-induced [Ca2+]i increases (by 32%), resulting in a significantly augmented NO production as indicated by an enhanced LNNA-sensitive cGMP increase in HUVECs. In contrast, neither increases of cGMP (basal 0.4 +/- 0.1 pmol/mg) elicited by 10 microM SNP (21 +/- 2 pmol/mg) or 10 microM C-type natriuretic peptide (CNP, 4.6 +/- 1.6 pmol/mg) nor its reduction by 30 microM LNNA had any effect on the His-induced [Ca2+]i increases.


CONCLUSIONS
PGI2 attenuates agonist-induced [Ca2+]i increases by a cAMP-dependent mechanism, thereby modulating not only its own synthesis via a negative feedback but also that of NO. Consequently, reduced PGI2 levels result in an increased NO production. NO which does not cause a negative feedback control by cGMP might therefore compensate for the lack of PGI2.
Bolz
S S
SS
Institute of Physiology and Pathophysiology, Johannes-Gutenberg-University Mainz, Germany. bolz@mzdmza.zdv.uni-mainz.de
Pohl
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D019898:Autocrine Communication; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D011464:Epoprostenol / Q000378:metabolism / Q000494:pharmacology; D005246:Feedback; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism*; D014471:Umbilical Veins
D016861:Cyclooxygenase Inhibitors; D005576:Colforsin; D009569:Nitric Oxide; D006632:Histamine; D011464:Epoprostenol; D000242:Cyclic AMP; D006152:Cyclic GMP; D002118:Calcium; D007213:Indomethacin