Proceedings of The Physiological Society

Physiology 2016 (Dublin, Ireland) (2016) Proc Physiol Soc 37, PCB302

Poster Communications

AMPK-activated protein kinase α1 controls cytosolic calcium concentration and induces calcium sensitization in resistance arteries

T. Metzinger1,2, C. Dufeys2, C. Dessy1, S. Horman2

1. Institute of Clinical and Experimental Research (IREC), Pole of Pharmacology (FATH), Université Catholique de Louvain, Brussels, Belgium. 2. Institute of Clinical and Experimental Research (IREC), Division of Cardiology (CARD), Université Catholique de Louvain, Brussels, Belgium.

AMP-activated protein kinase (AMPK) is an important sensor and regulator of cellular energy state activated by physiological or pathological stimuli. Our previous work has shown that in large conductance vessels, AMPK also regulates vascular contractility through phosphorylation and inhibition of smooth muscle myosin light chain kinase. Its implication in the control of vascular tone in resistance arteries has never been studied and constitutes the aim of the present work. Vascular tone was assessed ex vivo by pressure myography in small mesenteric resistance arteries (SMRA) and cytosolic calcium concentration measured using FURA2. The role of AMPK was assessed by the use of mice genetically deficient for the α1 isoform of the protein (AMPK-KO) and their littermate controls (AMPK-WT). Results are expressed as means ± S.E.M. .SMRA of AMPK-KO mice showed increased cytosolic calcium concentrations at basal state (t-test; 104.2±12.65 vs 60.3±9.66nM in AMPK-WT, p=0.016, n=6/8) and after contraction induced by depolarization (t-test; 183.3±14.2 vs 104.3±16.5nM in AMPK-WT, p=0.005, n=6/8) or with phenylephrine 1µM (t-test; 241.5±27.2 vs 104.2±16.5nM in AMPK-WT, p=0.001, n=5/7). Contractile tone was modified neither by depolarization (t-test; 29.6±7.9 vs 33.4±3.7% AMPK-WT, p=0.631, n=5/9), nor by the use of 1µM of phenylephrine (t-test; 17.0±2.3 vs 17.4±1.4% AMPK-WT, p=0.833, n=5/8). In consequence contraction/calcium ratios were significantly reduced in the absence of AMPK, both in response to 1µM of phenylephrine (t-test; 0.3±0.2 vs 1.8±1.1µm/nM in AMPK-WT, p=0.03, n=5/6) and to depolarization (t-test; 0.9±0.3 vs 2.3±0.4µm/nM AMPK-WT, p=0.02, n=6/8). Thus, our data first demonstrate that AMPK is involved in the regulation of basal cytosolic calcium concentration in SMRA. Whether this relates to an increased calcium intracellular uptake by SERCA pump (through phosphorylation of phospholamban) is currently investigated. The discovery that AMPK induces a calcium sensitisation in SMRA shows for the first time that this protein could differentially modulate vascular tone in conductance versus resistance vessels.

Where applicable, experiments conform with Society ethical requirements