Candesartan and amlodipine combination therapy provides powerful vascular protection in stroke-prone spontaneously hypertensive rats

Abstract

The vascular protective effects of placebo, candesartan (1 mg kg À1 per day) monotherapy, candesartan (1 mg kg À1 per day) and amlodipine (1 mg kg À1 per day) combination therapy, and candesartan (1 mg kg À1 per day) and hydrochlorothiazide (HCTZ) (10 mg kg À1 per day) combination therapy for 2 weeks were compared in stroke-prone, spontaneously hypertensive rats. Candesartan monotherapy significantly reduced blood pressure, and both combination therapies were equally and significantly lower than the monotherapy. Acetylcholine-induced vascular relaxation was significantly stronger in all therapeutic groups than in the placebo-treated group. Furthermore, the relaxation was significantly stronger in the candesartan plus amlodipine-treated group than in the candesartan-treated group; however, there was no significant difference between the candesartan-and candesartan plus HCTZ-treated groups. Vascular gene expressions of the NADPH oxidase subunits p22 phox , gp91 phox , NOX1 and NOX4 were significantly attenuated in all therapeutic groups compared with the placebo-treated group, and there were no significant differences among those groups. However, a significant augmentation of vascular superoxide dismutase activity was observed in the candesartan plus amlodipine-treated group, but not in other groups. Malondialdehyde levels in the vascular tissues were significantly attenuated in all therapeutic groups. Compared with the candesartan-treated group, significant attenuation was observed in the candesartan plus amlodipine-treated group, but not in the candesartan plus HCTZ-treated group. Immunohistological analysis showed that areas positive for 4-hydroxy-2-nonenal were significantly reduced in all therapeutic groups, but this reduction was significantly greater for the candesartan plus amlodipine-treated group than for the candesartantreated group. Thus, candesartan and amlodipine combination therapy could have a powerful protective effect in vascular tissues via the reduction of oxidative stress.

The NADPH Oxidase Family and its Inhibitors

“…In primary hypertension, Nox-derived superoxide decreases vascular NO-released from the endothelium resulting in peroxynitrite formation (Dai and Dai 2010). Moreover, vascular gene expression of the NADPH oxidase subunits p22phox, g p91phox, Nox1 and Nox4 are significantly attenuated during hypertension (Takai et al 2011). A recent study also highlights the role played by three single-nucleotide polymorphisms (-930A/G, A640G and C242T) of the p22phox subunit in hypertension (Xaplanteris et al 2010); it was found that the -930A/G, but not the A640G and C242T polymorphism of p22phox is a determinant of peripheral and central pressures in normotensive individuals (Xaplanteris et al 2010).…”

Significance of Vascular Dipeptidyl Peptidase-4 Inhibition on Vascular Protection in Zucker Diabetic Fatty Rats

“…The levels of MDA, which is a product of lipid peroxidation in tissue extracts, were measured by incubating vascular extracts for 1 h at 60°C with 20 mM thiobarbituric acid in 0.3 mM phosphoric acid (15). The reaction was terminated by cooling on ice, and the mixture was subsequently centrifuged at 15,000 × g for 5 min at 4°C.…”

“…Isolated rat carotid arteries were cut into 10 × 1.0 mm helical strips and mounted on a myograph under a resting tension of 1.0 g in Tyrode's solution (137 mM NaCl, 2.7 mM KCl, 1.8 mM CaCl 2 , 1.1 mM MgCl 2 , 0.42 mM NaH 2 PO 4 , 12 mM NaHCO 3 , and 5.7 mM glucose, pH 7.4) at 37°C and continuously bubbled with 5% CO 2 / 95% O 2 (15). The strips were initially vasoconstricted with 50 mM KCl, followed by a wash-out of the bathing medium.…”

“…Aortic total RNA (1 mg) was transcribed into cDNA using Superscript III reverse transcriptase and random hexamers (Invitrogen, Carlsbad, CA, USA) (15). The mRNA levels of p22 phox , a subunit of NADPH oxidase, monocyte chemoattractant protein (MCP)-1, and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) were mea-sured by real-time RT-PCR on a LightCycler with specialized software (Roche Diagnostics, Tokyo) using TaqMan fluorogenic probes.…”

Significance of the Vascular Concentration of Angiotensin II–Receptor Blockers on the Mechanism of Lowering Blood Pressure in Spontaneously Hypertensive Rats

“…Serum ACE activity was measured by incubating plasma for 30 min at 37°C with 5 mM of the substrate hippuryl-His-Leu (Peptide Institute Inc., Osaka) 100 mM phosphate buffer (pH 8.3) containing 300 mM NaCl (18). The reaction was terminated by addition of 3% metaphosphoric acid, and the mixture was subsequently centrifuged at 8,000 × g for 5 min at 4°C.…”