Low density lipoprotein receptor related protein 6 (LRP6) protects heart against oxidative stress by the crosstalk of HSF1 and GSK3β

Abstract

Low density lipoprotein receptor-related protein 6 (LRP6), a Wnt co-receptor, induces multiple functions in various organs. We recently reported cardiac specific LRP6 deficiency caused cardiac dysfunction in mice. Whether cardiomyocyte-expressed LRP6 protects hearts against ischemic stress is largely unknown. Here, we investigated the effects of cardiac LRP6 in response to ischemic reperfusion (I/R) injury. Tamoxifen inducible cardiac specific LRP6 overexpression mice were generated to build I/R model by occlusion of the left anterior descending (LAD) coronary artery for 40 min and subsequent release of specific time. Cardiac specific LRP6 overexpression significantly ameliorated myocardial I/R injury as characterized by the improved cardiac function, strain pattern and infarct area at 24 h after reperfusion. I/R induced-apoptosis and endoplasmic reticulum (ER) stress were greatly inhibited by LRP6 overexpression in cardiomyocytes. LRP6 overexpression enhanced the expression of heat shock transcription factor-1(HSF1) and heat shock proteins (HSPs), the level of p-glycogen synthase kinase 3β(GSK3β)(S9) and p-AMPK under I/R. HSF1 inhibitor deteriorated the apoptosis and decreased p-GSK3β(S9) level in LRP6 overexpressed –cardiomyocytes treated with H 2 O 2 . Si-HSF1 or overexpression of active GSK3β significantly attenuated the increased expression of HSF1 and p-AMPK, and the inhibition of apoptosis and ER stress induced by LRP6 overexpression in H 2 O 2 -treated cardiomyocytes. AMPK inhibitor suppressed the increase in p-GSK3β (S9) level but didn’t alter HSF1 nucleus expression in LRP6 overexpressed-cardiomyocytes treated with H 2 O 2 . Active GSK3β, but not AMPK inhibitor, attenuated the inhibition of ubiquitination of HSF1 induced by LRP6-overexpressed-cardiomyocytes treated with H 2 O 2 . LRP6 overexpression increased interaction of HSF1 and GSK3β which may be involved in the reciprocal regulation under oxidative stress. In conclusion, cardiac LRP6 overexpression significantly inhibits cardiomyocyte apoptosis and ameliorates myocardial I/R injury by the crosstalk of HSF1 and GSK3β signaling.

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“…Those three proteins then migrate from the ER to the nucleus to interrupt protein transcription more broadly [59]. However, excessive ER stress promotes activation of stress-related proteins such as caspase-12, which is involved in the initiation of cell apoptosis [60]. The relationship between ER stress and endothelial dysfunction has been described in detail in previous studies.…”

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“…Its molecular mechanism involves a variety of biological processes, including cancer development, immune response, or cellular metabolism [ 36 , 37 ]. A study by Wang et al indicated that LRP6 could improve myocardial ischemia after refocusing injury through antioxidant and antiapoptotic effects [ 8 , 38 ]. In recent years, the role of LRP6 in neurological diseases has also been gradually investigated.…”

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“…Sirt1 reportedly improves mitochondrial function and attenuates brain injury by increasing PGC-1 α levels [ 21 ]. Sirt1 interacts with GSK3 β , and Koga et al similarly found that Sirt1 upregulation can be mediated by GSK3 β [ 22 , 23 ] Under oxidative stress, LRP6 overexpression promoted the increased phosphorylation of GSK3 β in cardiomyocytes [ 8 ].…”