Increased Vascular Contractility in Hypertension Results From Impaired Endothelial Calcium Signaling

Area of Science:

• Cardiovascular Biology
• Endothelial Cell Physiology
• Hypertension Research

Background:

• Endothelial cells regulate vascular tone via vasoactive factors.
• Hypertension disrupts endothelial function, increasing vascular tone.
• Calcium (Ca²⁺) signaling is crucial for endothelial-derived vasodilators, but its alteration in hypertension is poorly understood.

Purpose of the Study:

• To investigate alterations in endothelial Ca²⁺ signaling at myoendothelial projections in hypertension.
• To determine the impact of these Ca²⁺ signaling changes on vascular tone regulation.

Main Methods:

• Comparison of vascular reactivity to phenylephrine in hypertensive (spontaneously hypertensive rat) and normotensive (Wistar Kyoto) rats.
• Assessment of basal endothelial Ca²⁺ activity and its buffering effects.
• Analysis of local endothelial inositol trisphosphate (IP₃)-mediated Ca²⁺ signals, including amplitude, duration, frequency, site of origin, and spatial distribution relative to myoendothelial projections.

Main Results:

• Hypertensive rats exhibit increased vascular reactivity to phenylephrine compared to normotensive rats.
• Impaired Ca²⁺-dependent endothelial control limits basal vascular contraction in hypertension.
• Buffering endothelial Ca²⁺ changes normalizes phenylephrine-induced contraction in both groups.
• Hypertension is associated with smaller, shorter, less frequent, and spatially disorganized local endothelial IP₃-mediated Ca²⁺ signals near myoendothelial projections.

Conclusions:

• The organization of localized Ca²⁺ signaling circuits at myoendothelial projections is disrupted in hypertension.
• This disruption of endothelial Ca²⁺ signaling contributes to the increased contractile responses observed in hypertension.