2A-Adrenoceptors Modulate Renal Sympathetic Neurotransmission and Protect against Hypertensive Kidney Disease.

BACKGROUND

Increased nerve activity causes hypertension and kidney disease. Recent studies suggest that renal denervation reduces BP in patients with hypertension. Renal NE release is regulated by prejunctional 2A-adrenoceptors on sympathetic nerves, and 2A-adrenoceptors act as autoreceptors by binding endogenous NE to inhibit its own release. However, the role of 2A-adrenoceptors in the pathogenesis of hypertensive kidney disease is unknown.

METHODS

We investigated effects of 2A-adrenoceptor-regulated renal NE release on the development of angiotensin II-dependent hypertension and kidney disease. In uninephrectomized wild-type and 2A-adrenoceptor-knockout mice, we induced hypertensive kidney disease by infusing AngII for 28 days.

RESULTS

Urinary NE excretion and BP did not differ between normotensive 2A-adrenoceptor-knockout mice and wild-type mice at baseline. However, NE excretion increased during AngII treatment, with the knockout mice displaying NE levels that were significantly higher than those of wild-type mice. Accordingly, the 2A-adrenoceptor-knockout mice exhibited a systolic BP increase, which was about 40 mm Hg higher than that found in wild-type mice, and more extensive kidney damage. In isolated kidneys, AngII-enhanced renal nerve stimulation induced NE release and pressor responses to a greater extent in kidneys from 2A-adrenoceptor-knockout mice. Activation of specific sodium transporters accompanied the exaggerated hypertensive BP response in 2A-adrenoceptor-deficient kidneys. These effects depend on renal nerves, as demonstrated by reduced severity of AngII-mediated hypertension and improved kidney function observed in 2A-adrenoceptor-knockout mice after renal denervation.

CONCLUSIONS

Our findings reveal a protective role of prejunctional inhibitory 2A-adrenoceptors in pathophysiologic conditions with an activated renin-angiotensin system, such as hypertensive kidney disease, and support the concept of sympatholytic therapy as a treatment.