Advanced age protects microvascular endothelium from aberrant Ca²⁺ influx and cell death induced by hydrogen peroxide

Abstract

Key pointsr Calcium signalling in endothelial cells of resistance arteries is integral to blood flow regulation.Oxidative stress and endothelial dysfunction can prevail during advanced age and we questioned how calcium signalling may be affected.r Intact endothelium was freshly isolated from superior epigastric arteries of Young (ß4 months) and Old (ß24 months) male C57BL/6 mice. Under resting conditions, with no difference in intracellular calcium levels, hydrogen peroxide (H 2 O 2 ) availability was ß1/3 greater in endothelium of Old mice while vascular catalase activity was reduced by nearly half. r Microvascular adaptation to advanced age may protect endothelial cells during elevated oxidative stress to preserve functional viability of the intima. Abstract Endothelial cell Ca2+ signalling is integral to blood flow control in the resistance vasculature yet little is known of how its regulation may be affected by advancing age. We tested the hypothesis that advanced age protects microvascular endothelium by attenuating aberrant Ca 2+ signalling during oxidative stress. Intact endothelial tubes (width, ß60 μm; length, ß1000 μm) were isolated from superior epigastric arteries of Young (3-4 months) and Old (24-26 months) male C57BL/6 mice and loaded with Fura-2 dye to monitor [Ca 2+ ] i . At rest there was no difference in [Ca 2+ ] i between age groups. Compared to Young, the [Ca 2+ ] i response to maximal stimulation with acetylcholine (3 μM, 2 min) was ß25% greater in Old, confirming signalling integrity with advanced age. Basal H 2 O 2 availability was ß33% greater in Old while vascular catalase activity was reduced by half. Transient exposure to elevated H 2 O 2 (200 μM, 20 min) progressively increased [Ca 2+ ] i to ß4-fold greater levels in endothelium of Young versus Old. With no difference between age groups at rest, Mn 2+ quench of Fura-2 fluorescence revealed 2-fold greater Ca 2+ influx in Young during elevated H 2 O 2 ; this effect was attenuated by ß75% using ruthenium red (5 μM) as a broad-spectrum inhibitor of transient receptor potential channels. Prolonged exposure to H 2 O 2 (200 μM, 60 min) induced ß7-fold greater cell death in endothelium of Young versus Old. Thus, microvascular endothelium can adapt to advanced age by reducing Ca 2+ influx during elevated oxidative stress. Protection from cell death during oxidative stress will sustain endothelial integrity during ageing.

Depressed perivascular sensory innervation of mouse mesenteric arteries with advanced age

“…; Sinkler & Segal, ; Socha et al . ) and the functional experiments performed here encompassed both nerve stimulation and the application of exogenous CGRP. With both approaches, the present findings confirm dysfunctional sensory neuroeffector signalling for MAs of Old mice when compared to MAs of Young mice.…”

Calcium and electrical signaling in arterial endothelial tubes: New insights into cellular physiology and cardiovascular function

“…Please note that NS309 responses are not significantly dependent on [Ca 2+ ] i increases (91). A robust increase of [Ca 2+ ] i underlies hyperpolarization in response to H 2 O 2 (142). Hyperpolarization via H 2 O 2 treatment is sensitive to SK Ca /IK Ca channel block by apamin and charybdotoxin (71).…”

“…Finally, conclusions between studies can differ based on a lack of awareness for structural changes of the vasculature (e.g., arterial stiffening, smooth muscle hypertrophy) that occur alongside ion channel activity during aging (15-17, 131). At least in skeletal muscle feed arteries, the underlying components of EDH signaling (i.e., increased [Ca 2+ ] i and SK Ca /IK Ca channel function) are enhanced during old age (≥ 24 months) due to increased levels and activity of H 2 O 2 (71, 142). This increase in EDH signaling in old age may be viewed as a compensatory mechanism (67) in response to a decreased NO bioavailability for vasodilation (67, 75).…”

Gene expression profiles of ion channels and receptors in mouse resistance arteries: Effects of cell type, vascular bed, and age

“…Mesenteric and superior epigastric arteries were chosen for two reasons. First, these vessels have been the subject of physiological studies in young and old mice; thus, analyses of gene expression profiles provide a novel context to identify directions for future research in aging. Second, inclusion of vessels from functionally distinct areas of the body enables comparison of expression profiles in tissues that differ in embryonic origin and function.…”