Impact of Renal Denervation on Circadian Variations of Blood Pressure and Clock Gene Expression in Spontaneously Hypertensive Rats

Hypertension is often associated with elevated nighttime blood pressure (BP), a significant risk factor for cardiovascular and cerebrovascular diseases. This study explores the effects of renal denervation (RDN) on circadian BP rhythms and clock gene expression in spontaneously hypertensive rats (SHR). Ten-week-old SHR were randomized into RDN and sham surgery (Sham) groups, with Wistar-Kyoto rats (WKY) as controls. BP was measured at rest (14:00) and during activity (02:00) biweekly, and BP variability was analyzed. RDN significantly reduced BP, particularly during the resting phase, thereby enhancing circadian BP variation. The Sham group displayed minimal circadian variation in plasma and renal norepinephrine levels, whereas the RDN group exhibited an overall reduction in norepinephrine, with lower levels during rest than during activity. Furthermore, the Sham group showed no significant circadian variation in the renin-angiotensin-aldosterone system (RAS), RDN restored circadian rhythms in ACE1, Ang II, ACE2, and Ang1-7. Additionally, the Sham group demonstrated consistently high renal BMAL1 protein expression, whereas RDN exhibited reduced BMAL1 expression during the resting phase, indicating restored circadian variation. These findings suggest that RDN not only lowers BP but also improves its circadian rhythm, likely through modulation of sympathetic nervous activity, the RAS system, and the circadian clock gene BMAL1.