Radical scavengers of indapamide in prostacyclin synthesis in rat smooth muscle cell.

Abstract

Indapamide, a nonthiazide diuretic, exhibits direct vasodilator action as well as natriuretic and diuretic effects. Although calcium antagonist-like activity has been addressed so far, the mechanisms for vasodilator effect are still uncertain. To understand the wide range of indapamide actions, we examined the effects of indapamide on the vascular eicosanoid generation and investigated its mechanisms by using rat vascular smooth muscle cells in culture. Indapamide uniquely increased the prostacyclin generation in the vascular smooth muscle cells in a dose-dependent manner, whereas it did not affect the vasoconstrictor thromboxane A 2 . Thiazide diuretics lowered the prostacyclin generation, while nonthiazide derivatives did not affect the biosynthesis. Enzymatic analysis revealed that indapamide affected neither [ A n o-chlorobenzenesulfonamide molecule is a prototype of various diuretics including thiazide and nonthiazide diuretics (Figure 1). Although natriuretic and diuretic effects are mainly due to the common structure of o-chlorobenzenesulfonamide, varied side chains give the diuretics characteristic properties. In this context, indapamide diuretic comprises an indoline molecule and uniquely exhibits a direct vasodilator action as well as a natriuretic effect on the cortical collecting duct in the kidney. -4 The vasodilator effect is assumed to be caused by its calcium channel blocker-like activity 5 or endothelium-derived relaxing factor-mediated From the Second Department of Medicine (Y.U., T.N., T.I., H.M., T.S.), University of Tokyo, Tokyo, Japan, and Kyoto Pharmaceutical Industries, Ltd (H.S., S.M., S.O.), Kyoto, Japan.Supported in part by a Grant-in-Aid from the Ministry of Education, Science, and Culture of Japan (No. 62570384 and 01570469).Address for correspondence: Yoshio Uehara, MD, The Second Department of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan.Received December 21, 1988; accepted in revised form September 12, 1989. mechanism.6 However, the exact mechanism is not fully understood.On the other hand, the biosynthetic system for eicosanoid (prostaglandins and thromboxanes) is well demonstrated in the vascular smooth muscle cells (VSMC) of rats. 7 -8 Prostacyclin (PGI 2 ), a major product of arachidonate metabolism in VSMC, has a powerful vasodilator action and attenuates the vasoconstrictor response to vasoactive substances. 9 The eicosanoid metabolism is a major component participating in the regulation of the constriction-relaxation mechanism of VSMC.To understand the wide range of indapamide effects, it seems important to disclose the relevance of the eicosanoid system in the vascular wall to the extrarenal indapamide effects. Thus in this study, we investigated the influences of indapamide on the eicosanoid generation in VSMC by using cultured VSMC of rats and attempted to define the mechanisms for its alteration. Methods Vascular Smooth Muscle Cell CultureVSMC were isolated from the thoracic aortas of 7-week-old Wistar rats according to the method of

Effect of Indapamide on the Proliferation of Balb/C 3T3 Cells Induced by Platelet-Derived Growth Factor.

“…Indapamide in single and repeated oral applications lowers blood pressure in humans (1) and normotensive, DOCA-salt hyperten sive and spontaneously hypertensive rats. In addition to its diuretic action, indapamide has vasorelaxing (2), antiplatelet (3), antioxidant (4) and prostacyclin generation enhancing (5) activities.…”

A Novel Series of Thromboxane A2 Synthetase Inhibitors with Free Radical Scavenging and Anti-peroxidative Activities.

“…Anti-peroxidative activity was examined using rat brain homogenate. 8) Known TXA 2 synthetase inhibitors have two moieties bearing a heterocycle (imidazole, thiazole, pyridine etc.) and a carboxylic acid, attached to an aromatic ring such as benzene, benzofuran, benzothiophene, indole or indane.…”

“…Free Radical Scavenging DPPH, a stable free radical was dissolved at 10 Ϫ4 M in ethanol and incubated at 25°C for 20 min in the absence or presence of the synthesized compounds (10 Ϫ4 M) according to the method previously reported. 8) Remaining DPPH in the absence and presence of the test compounds was determined spectrophotometrically at a wavelength of 517 nm and % reduction by the compounds was calculated.…”

“…Lipid Peroxidation in Rat Brain Homogenate Production of lipidperoxide was determined as malondialdehyde (MDA) in the rat brain homogenate as reported previously 8) . Briefly, the cerebral cortex isolated from male SD rats (6-week old) was homogenized in ice-cold 50 mM phosphatebuffered saline (pH.7.4).…”

“…We reported previously that indapamide, a non-thiazide diuretic, has free radical scavenging activity, which is due to its indoline moiety, and protects PGI 2 synthetase from free radicals in vascular smooth muscle cells. 8) Known TXA 2 synthetase inhibitors have an aromatic ring, such as a benzene, a benzofuran or a benzothiophen, which bears two side chains with a carboxylic acid and a heterocycle, respectively ( Fig. 1).…”