Endothelium dysfunction in LDL receptor knockout mice: a role for H2O2

Area of Science:

• Vascular Biology
• Cardiovascular Research
• Biochemistry

Background:

• Endothelium-dependent vasodilation is crucial for cardiovascular health.
• Hydrogen peroxide (H2O2) has been proposed as a signaling molecule in vascular function.
• Dysfunctional vasodilation is a hallmark of atherosclerosis.

Purpose of the Study:

• To investigate the role of endogenous hydrogen peroxide (H2O2) in endothelium-dependent relaxation.
• To compare H2O2-mediated vasodilation in control mice and LDL receptor-deficient (LDLR(-/-)) mice.

Main Methods:

• Vessel-based assays using aortic rings from C57BL/6J and LDLR(-/-) mice.
• Pharmacological manipulation with nitric oxide synthase inhibitors (L-NNA, L-NAME), catalase, and superoxide dismutase.
• Assessment of relaxation responses to acetylcholine (ACh) and exogenous H2O2.

Main Results:

• LDLR(-/-) mice exhibited impaired endothelium-dependent relaxation to ACh and A23187 compared to controls.
• Nitric oxide synthase inhibition reduced, but did not abolish, ACh-induced relaxation in control aortas.
• Catalase treatment impaired ACh-induced relaxation in control aortas, but not in LDLR(-/-) aortas, indicating H2O2's role.
• Exogenous H2O2 induced relaxation similarly in both strains.

Conclusions:

• Endogenous H2O2 is a significant contributor to acetylcholine-induced vasodilation in mouse aortas.
• Endothelial dysfunction in LDLR(-/-) mice is associated with impaired H2O2-mediated relaxation.
• Reduced H2O2 biosynthesis or enhanced inactivation may underlie endothelial dysfunction in atherosclerosis-susceptible models.