Cardiovascular Research Advance Access [Accepted Manuscript] published online on March 7, 2008
Cardiovascular Research, doi:10.1093/cvr/cvn063
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Imatinib mesylate attenuates fibrosis in coxsackievirus B3 (CVB3)- induced chronic myocarditis
1 Institute of Virology, and Institute of Animal Research, Friedrich Schiller University, Jena, Germany
2 Clinic of Internal Medicine III, Friedrich Schiller University, Jena, Germany
3 Novartis Pharma AG, Basel, Switzerland
4 Istituto Nazionale per la Ricerca sul Cancro, 16132 Genoa, Italy, Institute of Pathology
5 HELIOS-Klinikum, 99012 Erfurt, Germany
6 Institute of Pathology, Friedrich Schiller University, Jena, Germany
7 Institute of Molecular Cell Biology, and Friedrich Schiller University, Jena, Germany
8 Institute for Clinical Chemistry and Laboratory Diagnostics, Medical Faculty, Friedrich Schiller University, Jena, Germany
* To whom correspondence should be addressed: F.-D. Böhmer, Institute of Molecular Cell Biology, Medical Faculty, Friedrich Schiller University, Drackendorfer Str. 1, D-07747 Jena, Germany, Tel. +49-3641-9325660, Fax +49-3641-9325652; e-mail i5frbo{at}rz.uni-jena.de
Aim: Coxsackievirus B3 (CVB3)-induced chronic myocarditis in mice is accompanied by severe fibrosis and by sustained elevation of platelet-derived growth factor (PDGF)-A, -B, and -C levels in the cardiac tissue. To test if PDGF stimulation of resident fibroblasts causally contributes to fibrosis, we employed inhibition of PDGF receptor signalling with the orally available kinase inhibitor Imatinib.
Methods: Chronic myocarditis was induced by CVB3 infection of major histocompatibility complex (MHC) class II knockout (B6Aa0/Aa0) mice. The mice were treated with 100 mg/kg Imatinib or vehicle, respectively, twice daily for 34 days. Expression of PDGF-C and of inflammatory cytokines were analysed by semi-quantitative RT-PCR. PDGF
receptor phosphorylation was detected by immunoblotting of cardiac tissue extracts and in situ by immunohistochemistry. Fibrosis formation was analysed by Sirius Red staining and hydroxyproline determination and by detecting fibronectin, and tenascin expression was assessed by RT-PCR and immunohistochemistry. Matrix metalloproteinase (MMP) activity was assessed with collagen, synthetic peptides, and gelatine as substrates.
Results: Imatinib significantly inhibited the myocarditis-related PDGF receptor activation in the heart tissue. The virus titres in the hearts, inflammatory infiltrations, and elevated PDGF levels were unaffected by the Imatinib treatment. A significant attenuation of fibrosis occurred in Imatinib-treated animals. The Sirius Red-stained fibrotic area was reduced from 5.30±0.50% to 3.21±0.35%, and the hydroxyproline content was reduced from 362±43 to 238±32 µMol/10 mg dry weight versus 190±27 in uninfected controls. The expression of fibronectin, EIIIA+ fibronectin, and tenascin C were likewise reduced. The diminished matrix protein deposition was not caused by elevated MMP activity, since MMP activity was not changed or even reduced under Imatinib.
Conclusions: The data suggest a causal role for elevated PDGF expression and PDGF receptor activity in the pathogenesis of cardiac fibrosis.
KEYWORDS Chronic myocarditis; coxsackievirus B3 (CVB3); platelet derived growth factor (PDGF); STI571/Imatinib mesylate; fibrosis
Time for primary review: 22 days