Objective: We demonstrated previously that an NAD(P)H oxidase plays an important role in blood pressure (BP) elevation, cardiovascular hypertrophy, and fibrosis in aldosterone-salt rats. The functional role of the different subunits of the enzyme to target organ damage is still not understood. We evaluated whether the p47phox is implicated in cardiovascular damage in aldosterone-infused rats.
Method: Rats was infused with aldosterone (0.75㎍/h per day for 6 weeks) via a mini-osmotic pump and were given 0.9 % NaCl in the drinking water +/- an aldosterone receptor antagonist, spironolactone (200㎎/㎏ per day) or of NADPH oxidase inhibitor, apocynin (30mg/kg per day) for 6 weeks. Systolic BP (SBP) was measured by tail-cuff method. O2- production in kidney was determined by in situ dihydroethidium (10μmol/L) staining visualized by confocal microscopy. The NADPH oxidase subunit, p47phox expression in kidney and aorta of aldosterone-infused rats was quantified by real-time polymerase chain reaction (PCR) and by immunohistochemistry.
Results: Aldosterone infusion significantly increased SBP to 222±14mmHg compared with control (122±9mmHg). Aldosterone receptor antagonist, spironolactone normalized (103±21mmHg) and the NADPH oxidase inhibitor, apocynin decreased modestly to 189±20mmHg after 6 weeks. Cardiac and renal hypertrophy by aldosterone infusion was reversed by spironolactone and apocynin. Kidney from aldosterone-treated rats showed a marked increase of fluorescence. However, no increase in dihydroethidium (DHE)-detectable O2- production was found by spironolactone and apocynin treatment. mRNA expression of p47phox measured by real-time PCR, was increased in kidney cortex and aorta of aldosterone-infused rats by 2.8- and 6.3-fold, respectively, compared with those of controls. Spironolactone and apocynin significantly decreased p47phox mRNA expression. After 6 weeks of aldosterone infusion, spironolactone or apocynin prevented the expression of the p47phox subunit of NADPH oxidase in kidney and aorta by immunohistochemistry.
Conclusion: There results suggest a pivotal role of the NADPH oxidase subunit, p47phox, in cardiovascular and renal damage in aldosterone-salt hypertension.
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