S1P3-mediated cardiac fibrosis in sphingosine kinase 1 transgenic mice involves reactive oxygen species.
OBJECTIVE
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 ischaemic preconditioning and cardiac ischaemia/reperfusion injury. To get more insight into roles for SPHK1 in vivo, we have generated SPHK1-transgenic (TG) mice and analysed the cardiac phenotype.


RESULTS
SPHK1-TG mice overexpressed SPHK1 in diverse tissues, with a nearly 20-fold increase in enzymatic activity. The TG mice grew normally with normal blood chemistry, 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 signalling, both inhibited cardiac fibrosis with concomitant inhibition of SPHK1-dependent Smad-3 phosphorylation. In addition, the anti-oxidant N-2-mercaptopropyonylglycine, which reduces reactive oxygen species (ROS), also inhibited cardiac fibrosis. In in vivo ischaemia/reperfusion injury, the size of myocardial infarct was 30% decreased in SPHK1-TG mice compared with wild-type mice.


CONCLUSIONS
These results suggest that chronic activation of SPHK1-S1P signalling results in both pathological cardiac remodelling through ROS mediated by S1P3 and favourable cardioprotective effects.
Takuwa
Noriko
N
Department of Physiology, Kanazawa University Graduate School of Medicine, 13-1 Takara-machi, Kanazawa, Ishikawa 920-8640, Japan.
Ohkura
Sei-Ichiro
S
Takashima
Shin-Ichiro
S
Ohtani
Keisuke
K
Okamoto
Yasuo
Y
Tanaka
Tamotsu
T
Hirano
Kaoru
K
Usui
Soichiro
S
Wang
Fei
F
Du
Wa
W
Yoshioka
Kazuaki
K
Banno
Yoshiko
Y
Sasaki
Motoko
M
Ichi
Ikuyo
I
Okamura
Miwa
M
Sugimoto
Naotoshi
N
Mizugishi
Kiyomi
K
Nakanuma
Yasuni
Y
Ishii
Isao
I
Takamura
Masayuki
M
Kaneko
Shuichi
S
Kojo
Shosuke
S
Satouchi
Kiyoshi
K
Mitumori
Kunitoshi
K
Chun
Jerold
J
Takuwa
Yoh
Y
D000818:Animals; D005355:Fibrosis; D005455:Fluorescent Antibody Technique; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D015428:Myocardial Reperfusion Injury / Q000517:prevention & control; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D009479:Neuropeptides / Q000096:biosynthesis; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000502:physiology*; D011804:Quinolines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D049349:Receptors, Lysosphingolipid / Q000032:analysis / Q000502:physiology*; D000081025:Sphingosine-1-Phosphate Receptors; D020744:rac GTP-Binding Proteins / Q000096:biosynthesis; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins / Q000096:biosynthesis; D020742:rhoA GTP-Binding Protein; D000099157:Sphingosine Kinase
D009479:Neuropeptides; D017853:Phosphotransferases (Alcohol Group Acceptor); D011804:Quinolines; D017382:Reactive Oxygen Species; D049349:Receptors, Lysosphingolipid; D000081025:Sphingosine-1-Phosphate Receptors; D020744:rac GTP-Binding Proteins; D020830:rac1 GTP-Binding Protein; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein; D000099157:Sphingosine Kinase; C484602:Rac1 protein, mouse; C501285:S1pr3 protein, mouse; C526380:RhoA protein, mouse; C108475:pitavastatin