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2017 ; 8
(ä): 756
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gab.com Text
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English Wikipedia
The AMP-Dependent Protein Kinase (AMPK) Activator A-769662 Causes Arterial
Relaxation by Reducing Cytosolic Free Calcium Independently of an Increase in
AMPK Phosphorylation
#MMPMID29093683
Huang Y
; Smith CA
; Chen G
; Sharma B
; Miner AS
; Barbee RW
; Ratz PH
Front Pharmacol
2017[]; 8
(ä): 756
PMID29093683
show ga
Although recent studies reveal that activation of the metabolic and Ca(2+) sensor
AMPK strongly inhibits smooth muscle contraction, there is a paucity of
information about the potential linkage between pharmacological AMPK activation
and vascular smooth muscle (VSM) contraction regulation. Our aim was to test the
general hypothesis that the allosteric AMPK activator A-769662 causes VSM
relaxation via inhibition of contractile protein activation, and to specifically
determine which activation mechanism(s) is(are) affected. The ability of A-769662
to cause endothelium-independent relaxation of contractions induced by several
contractile stimuli was examined in large and small musculocutaneous and visceral
rabbit arteries. For comparison, the structurally dissimilar AMPK activators MET,
SIM, and BBR were assessed. A-769662 displayed artery- and agonist-dependent
differential inhibitory activities that depended on artery size and location.
A-769662 did not increase AMPK-pT172 levels, but did increase phosphorylation of
the downstream AMPK substrate, acetyl-CoA carboxylase (ACC). A-769662 did not
inhibit basal phosphorylation levels of several contractile protein regulatory
proteins, and did not alter the activation state of rhoA. A-769662 did not
inhibit Ca(2+)- and GTP?S-induced contractions in ?-escin-permeabilized muscle,
suggesting that A-769662 must act by inhibiting Ca(2+) signaling. In intact
artery, A-769662 immediately reduced basal intracellular free calcium
([Ca(2+)](i)), inhibited a stimulus-induced increase in [Ca(2+)](i), and
inhibited a cyclopiazonic acid (CPA)-induced contraction. MET increased
AMPK-pT172, and caused neither inhibition of contraction nor inhibition of
[Ca(2+)](i). Together, these data support the hypothesis that the differential
inhibition of stimulus-induced arterial contractions by A-769662 was due to
selective inhibition of a Ca(2+) mobilization pathway, possibly involving
CPA-dependent Ca(2+) entry via an AMPK-independent pathway. That MET activated
AMPK without causing arterial relaxation suggests that AMPK activation does not
necessarily cause VSM relaxation.