Aging attenuates spontaneous endothelial Ca²⁺ events with altered perivascular nerve function in mouse mesenteric arteries in vivo

Abstract

Perivascular nerve activity has been linked to local endothelial cell (EC) Ca2+ events through α1‐adrenoreceptor (AR) activation, but the effects of aging on perivascular nerves and EC Ca2+ are unclear. We tested the hypothesis that aging alters local EC Ca2+ signals in vivo. Superfused (pH, 7.4; 36°C) mesenteric arteries (MAs) of anesthetized Young (3–6 month; n=9) and Old (24–26 month; n=5) Cx40BAC‐GCaMP2 mice were imaged (30 frames/s) using spinning disk confocal intravital microscopy. In Young, ECs exhibited spontaneous Ca2+ events [0.31 ± 0.03 Hz; amplitude (F/Fo): 1.31 ± 0.012; duration: 0.11 ± 0.004 s]. In Old, Ca2+ events were nearly absent. Electrical field stimulation (EFS) produced frequency‐dependent MA constriction with Old >; Young by ~20%. Blocking sensory nerves (capsaicin, 10 μM) enhanced MA constriction during EFS by ~20% in Young (P < 0.05) but not Old indicating loss of sensory inhibition of sympathetic vasoconstriction in Old. Cumulative activation (1 nM to 10 μM) of α1ARs (phenylephrine) but not α2ARs (UK14304) exhibited reduced sensitivity (P<0.05) in Old vs. Young. Immunolabeling confirmed sympathetic and sensory nerves were maintained in Old thus functional changes were not due to loss of perivascular innervation. The loss of local EC Ca2+ signals in Old may reflect α1AR desensitization and thereby reduce EC feedback in regulating smooth muscle tone. (NIH R01HL086483, R37HL041026).