The aim of this study was to determine the effects of
carbon monoxide (CO) at a nontoxic low concentration on the cardiac and vascular hypertrophic response and
reactive oxygen species generation, compared with the action of a
vasodilator,
hydralazine. Twelve- to 16-week-old
low-density lipoprotein receptor knockout mice were subjected to
angiotensin II (Ang II) infusion using osmotic minipumps (Ang II group; n=11) for 2 weeks. Controls were administered saline (n=10). Animals were exposed to CO in a chamber at 60 ppm for 2 hours per day with or without Ang II infusion (Ang II+CO group, n=10; CO group, n=9).
Hydralazine was administered with Ang II infusion (n=10). Animals exhibited elevated arterial
carboxyhemoglobin after CO exposure. Although the CO exposure did not affect systolic blood pressure without Ang II infusion, the hypertensive response after Ang II infusion was significantly attenuated by CO. Accordingly, the mice in the Ang II+CO group showed lesser
left ventricular hypertrophy compared with those in the Ang II group. CO treatment also attenuated aortic
hypertrophy. Interestingly, these changes were accompanied by the reduction of
reactive oxygen species production, p47(
phox) and p67(
phox) subunit expressions of reduced
nicotinamide-adenine dinucleotide phosphate oxidase, and Akt phosphorylation. Although
hydralazine showed stronger
antihypertensive action, superior inhibition on
cardiac hypertrophy was obtained by CO (P<0.05). Furthermore, Ang II-dependent myocardial
reactive oxygen species generation was more effectively suppressed by CO. Low-dose exogenous CO treatment attenuates Ang II-dependent
reactive oxygen species generation, suggesting that appropriate CO administration alleviates
hypertension and reduces organ
hypertrophy mediated by Ang II.