CREG1 ameliorates myocardial fibrosis associated with autophagy activation and Rab7 expression

In cardiomyocytes subjected to stress, autophagy activation is a critical survival mechanism that preserves cellular energy status while degrading damaged proteins and organelles. However, little is known about the mechanisms that govern this autophagic response. Cellular repressor of El A genes (CREG1) is an evolutionarily conserved lysosomal protein, and an important new factor in regulating tissue homeostasis that has been shown to antagonize injury of tissues or cells. In the present study, we aimed to investigate the regulatory role of CREG1 in cardiac autophagy, and to clarify autophagy activation mechanisms. First, we generated a CREG1 haploinsufficiency (Cregl(+/-)) mouse model, and identified that CREG1 deficiency aggravates myocardial fibrosis in response to aging or angiotensin II (Ang II). Conversely, exogenous infusion of recombinant CREG1 protein completely reversed cardiac damage. CREG1 deficiency in Creg1(+/-) mouse heart showed a marked accumulation of autophagosome that acquired LC3II and bedin-1, and a decrease in autophagic flux clearance as indicated by upregulating the level of p62. Inversely, restoration of CREG1 activates cardiac autophagy. Furthermore, chloroquine, an inhibitor of lysosomal acidification, was used to confirm that CREG1 protected the heart tissue against Ang II-induced fibrosis by activating autophagy. Using adenoviral infection of primary cardiomyocytes, overexpression of CREG1 with concurrent resveratrol treatment significantly increased autophagy, while silencing CREG1 blocked the resveratrol-induced autophagy. These results suggest that CREG1-induced autophagy is required to maintain heart function in the face of stress-induced myocardiac damage. Both in vitro and in vivo studies identified that CREG1 deficiency influenced the maturation of lysosomes and reduced the expression of Rab7, which might be involved in CREG1-induced cardiomyocyte autophagy. These findings suggest that autophagy activation via CREG1 may be a viable therapeutic strategy for improving cardiac performance under pathologic conditions. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases. (C) 2014 Elsevier B.V. All rights reserved.