CVR-2008-1173 R 4 S 1 P 3-mediated cardiac fibrosis in sphingosine kinase 1 transgenic mice involves reactive oxygen species

S1P3-mediated cardiac fibrosis in sphingosine kinase 1 transgenic mice involves reactive oxygen species Noriko Takuwa, Sei-Ichiro Ohkura, Shin-Ichiro Takashima, Keisuke Ohtani, Yasuo Okamoto, Tamotsu Tanaka, Kaoru Hirano, Soichiro Usui, Fei Wang, Wa Du, Kazuaki Yoshioka, Yoshiko Banno, Motoko Sasaki, Ikuyo Ichi, Miwa Okamura, Naotoshi Sugimoto, Kiyomi Mizugishi, Yasuni Nakanuma, Isao Ishii, Masayuki Takamura, Shuichi Kaneko, Shosuke Kojo, Kiyoshi Satouchi, Kunitoshi Mitumori, Jerold Chun, and Yoh Takuwa Aim: Sphingosine kinase 1 (SPHK1), its product sphingosine-1-phosphate (S1P) and S1P receptor subtypes have been suggested to play protective roles for cardiomyocytes in animal models of ischemic preconditioning and cardiac ischemia/reperfusion injury. To get more insight into roles for SPHK1 in vivo, we have generated SPHK1-transgenic (TG) mice and analyzed cardiac phenotype. Methods and Results: SPHK1-TG mice overexpressed SPHK1 in diverse tissues, with a nearly twenty-fold increase in enzymatic activity. The TG mice grew normally with normal blood chemistries, cell counts, heart rate and blood pressure. Unexpectedly, TG mice with high but not low expression levels of SPHK1 developed progressive myocardial degeneration and fibrosis, with upregulation of embryonic genes, elevated RhoA and Rac1 activity, stimulation of Smad3 phosphorylation and increased levels of oxidative stress markers. Treatment of juvenile TG mice with pitavastatin, an established inhibitor of the Rho family G proteins, or deletion of S1P3, a major myocardial S1P receptor subtype that couples to Rho GTPases and transactivates Smad signaling, both inhibited cardiac fibrosis with concomitant inhibition of SPHK1-dependent Smad-3 phosphorylation. In addition, the anti-oxidant N-2-mercaptopropyonylglycine, that reduces reactive oxygen species (ROS), also inhibited cardiac fibrosis. In in vivo ischemia/reperfusion injury, the size of myocardial infract was 30% decreased in SPHK1-TG mice compared with wild-type mice. Conclusion: These results suggest that chronic activation of the SPHK1-S1P signaling results in both the pathological cardiac remodeling through ROS mediated by S1P3 and favorable cardio-protective effect.