Cardiac-specific disruption of the c-raf-1 gene induces cardiac dysfunction and apoptosis
Osamu Yamaguchi, … , Masatsugu Hori, Kinya Otsu
Osamu Yamaguchi, … , Masatsugu Hori, Kinya Otsu
Published October 1, 2004
Citation Information: J Clin Invest. 2004;114(7):937-943. https://doi.org/10.1172/JCI20317.
View: Text | PDF
Article Cardiology

Cardiac-specific disruption of the c-raf-1 gene induces cardiac dysfunction and apoptosis

Abstract

The Raf/MEK/extracellular signal–regulated kinase (ERK) signaling pathway regulates diverse cellular processes such as proliferation, differentiation, and apoptosis and is implicated as an important contributor to the pathogenesis of cardiac hypertrophy and heart failure. To examine the in vivo role of Raf-1 in the heart, we generated cardiac muscle–specific Raf-1–knockout (Raf CKO) mice with Cre-loxP–mediated recombination. The mice demonstrated left ventricular systolic dysfunction and heart dilatation without cardiac hypertrophy or lethality. The Raf CKO mice showed a significant increase in the number of apoptotic cardiomyocytes. The expression level and activation of MEK1/2 or ERK showed no difference, but the kinase activity of apoptosis signal–regulating kinase 1 (ASK1), JNK, or p38 increased significantly compared with that in controls. The ablation of ASK1 rescued heart dysfunction and dilatation as well as cardiac fibrosis. These results indicate that Raf-1 promotes cardiomyocyte survival through a MEK/ERK–independent mechanism.

Authors

Osamu Yamaguchi, Tetsuya Watanabe, Kazuhiko Nishida, Kazunori Kashiwase, Yoshiharu Higuchi, Toshihiro Takeda, Shungo Hikoso, Shinichi Hirotani, Michio Asahi, Masayuki Taniike, Atsuko Nakai, Ikuko Tsujimoto, Yasushi Matsumura, Jun-ichi Miyazaki, Kenneth R. Chien, Atsushi Matsuzawa, Chiharu Sadamitsu, Hidenori Ichijo, Manuela Baccarini, Masatsugu Hori, Kinya Otsu

×

Figure 6

Options: View larger image (or click on image) Download as PowerPoint
Prevention of cardiac dysfunction in Raf-1/ASK1 double-knockout mice. (A...
Prevention of cardiac dysfunction in Raf-1/ASK1 double-knockout mice. (A) Photographs of hearts removed from c-raf-1flox/flox:α-MHCCre(+):ASK+/+ (Raf CKO:ASK+/+) and Raf-1/ASK1 double-knockout, c-raf-1flox/flox:α-MHCCre(+):ASK–/– (Raf CKO:ASK–/–) mice at 10 weeks of age. (B) Western blot analysis of Raf-1 in the hearts of CTLs, Raf CKO:ASK+/+, and Raf CKO:ASK–/– mice. (C and D) Echocardiographical analysis of hearts at 10 weeks of age. (C) Transthoracic M-mode echocardiographic tracings. (D) FS and diastolic left ventricle internal dimension (LVDd) in Raf CKO:ASK+/+ mice (n = 8) and Raf CKO:ASK–/– mice (n = 7). The parameters in c-raf-1flox/flox:α-MHCCre(–):ASK+/+ (CTL:ASK+/+) mice (n = 6) and c-raf-1flox/flox:α-MHCCre(–):ASK–/– (CTL:ASK–/–) mice (n = 6) are also shown as reference. *P < 0.05 versus each group. (E) Cardiac histological analysis of the Raf-1/ASK1 double-knockout mice. Microscopic H&E-stained and Masson trichrome_stained sections of hearts from Raf CKO:ASK+/+ and Raf CKO:ASK–/– mice. (F) The phosphorylation level of JNK or p38 was assessed by immunoblotting with anti-phosphospecific antibody in Raf CKO:ASK–/– and Raf CKO:ASK+/+ hearts at 3 and 4 weeks of age. (G) The number of TUNEL-positive cells in Raf CKO:ASK–/– and Raf CKO:ASK+/+ hearts at 4 and 10 weeks of age. *P < 0.05 versus Raf CKO:ASK+/+ at the same age. Scale bar: 10 mm (A), 100 μm (E).