title: Ethyl isopropyl amiloride inhibits smooth muscle cell proliferation and migration by inducing apoptosis and antagonizing urokinase plasminogen activator activity.
abstract: Amiloride inhibits activation of the Na(+)-H+ exchanger (NHE), a critical step in smooth muscle cell (SMC) growth. While amiloride treatment reduces SMC proliferation and migration, as well as experimental lesion formation, these effects are not exclusively due to NHE inhibition and remain incompletely understood. The purpose of this study was to examine the mechanisms involved in amiloride-induced attenuation of SMC proliferation and migration, looking specifically at the potential role of apoptosis and urokinase plasminogen activator (uPA) activity in these processes. Rabbit SMCs in tissue culture were exposed to 10-80 microM of the amiloride analogue ethyl isopropyl amiloride (EIPA). Compared with controls, EIPA reduced DNA synthesis, cell number, and mitochondrial respiration, but without toxic effects on quiescent or proliferating cells. In a Boyden chamber assay, EIPA reduced uPA-induced SMC migration. Moreover, in a SMC scratch assay EIPA treatment resulted in a 66% reduction in the number of repopulating cells, a 92% decrease in the number of proliferating cells, and a 37-fold increase in the number of apoptotic cells. SMC apoptosis was frequently localized to the scratch edges, where cell proliferation and bcl-2 expression were absent. Finally, uPA enzymatic activity in the cell culture media was lower for EIPA-treated versus control SMCs. Therefore, EIPA inhibits both SMC proliferation and migration by inducing apoptosis and antagonizing uPA activity, respectively, and requires further study as an agent for reducing vascular lesion formation.
authors.affiliation: Vascular Biology Laboratory, Division of Cardiology, University of Ottawa Heart Institute, ON K17 4W7, Canada.
authors.forename: Yong-Xiang
authors.initials: YX
authors.lastname: Chen
authors.forename: E R
authors.initials: ER
authors.lastname: O'Brien
mesh_terms: D000584:Amiloride / Q000031:analogs & derivatives* / Q000494:pharmacology*; D000818:Animals; D001012:Aorta, Abdominal / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D002465:Cell Movement / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006131:Growth Inhibitors / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D011817:Rabbits; D014568:Urokinase-Type Plasminogen Activator / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D006131:Growth Inhibitors; D000584:Amiloride; D014568:Urokinase-Type Plasminogen Activator; C039614:ethylisopropylamiloride