Article

Involvement of FrzA/sFRP-1 and the Wnt/frizzled pathway in ischemic preconditioning.

Department of Cardiovascular Surgery, Hôpital Haut Lévêque, Pessac, France.
Circulation Research (impact factor: 9.49). 07/2005; 96(12):1299-306. DOI:10.1161/01.RES.0000171895.06914.2c pp.1299-306
Source: PubMed

ABSTRACT Phosphorylation and subsequent inactivation of glycogen synthase kinase (GSK)-3beta via the Akt/PI3-Kinase pathway during ischemic preconditioning (PC) has been shown to be cardioprotective. As FrzA/sFRP-1, a secreted antagonist of the Wnt/Frizzled pathway, is expressed in the heart and is able to decrease the phosphorylation of GSK-3beta in vitro on vascular cells, we examined its effect during PC using transgenic mouse overexpressing FrzA in cardiomyocytes (alpha-MHC promoter) under a conditional transgene expression approach (tet-off system). Overexpression of FrzA inhibited the increase in GSK-3beta phosphorylation as well as protein kinase C (PKC) epsilon activation in transgenic mice after PC as compared with littermates. Phospho-Akt (P-Akt), phospho-JNK, or the cytoplasmic beta-catenin levels were not modified, phospho-p38 (P-p38) was slightly increased in transgenic mice after PC as compared with littermates. FrzA transgenic mice displayed a larger infarct size and a greater worsening of cardiac function compared with littermates. All these differences were reversed by the addition of doxycycline. This study demonstrates for the first time that disruption of a beta-catenin independent Wnt/Frizzled pathway induces the activation of GSK-3beta and reverses the benefit of preconditioning.

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Keywords

Akt/PI3-Kinase pathway
 
beta-catenin independent Wnt/Frizzled pathway induces
 
cardiac function
 
conditional transgene expression approach
 
cytoplasmic beta-catenin levels
 
FrzA transgenic mice
 
FrzA/sFRP-1
 
glycogen synthase kinase
 
greater
 
GSK-3beta phosphorylation
 
ischemic preconditioning
 
larger infarct size
 
littermates
 
protein kinase C
 
subsequent inactivation
 
tet-off system
 
transgenic mice
 
transgenic mouse overexpressing FrzA
 
vascular cells
 
Wnt/Frizzled pathway