Reduction of pressor response to vasoconstrictor agents by overexpression of catalase in mice

Background: Hydrogen peroxide (H2O2) has been shown to induce vascular smooth muscle cell contraction in vitro. In this study, the effect of endogenously produced H2O2 on blood pressure (BP) was examined using a transgenic mouse model (hCatTg(+/0)) in which catalase is overexpressed. Methods: The hCatTg(+/0) and wild-type mice received a bolus injection of norepinephrine (NE; 1 mug/g) or angiotensin II (Ang II 0.5 mug/g), or an osmotic minipump infusion of NE (2.5 mug/g/day) or Ang II (0.5 mug/g/day) for 7 days. Systolic BP (SBP) was measured using a tail-cuff apparatus. H2O2 release from mouse aortas was measured using an H2O2 assay kit. Results: The hCatTg(+/0) and wild-type mice showed similar basal levels of systolic BP (SBP) and H2O2 release from the aorta. A bolus injection of NE or Ang II increased SBP 31 +/- 5 and 37 +/- 6 mm Hg, respectively, in wild-type mice. In contrast, same doses of NE and Ang II increased SBP only 15 +/- 3 and 17 +/- 4 min Hg, respectively, in hCatTg(+/0) mice. Osmotic minipump infusion of NE or Ang II increased SBP by approximately 30 mm Hg in wild-type mice, but only by about 10 mm Hg in hCatTg(+/0) mice. The addition of NE or Ang II to the incubation media significantly increased H2O2 release from the aortic segment of wild-type mice but did not alter H2O2 release from the aortic segment of hCatTg(+/0) mice. Conclusion: Overexpression of catalase diminishes the pressor response to NE and Ang II by reducing H2O2 production in the arterial wall.