Imatinib mesylate attenuates fibrosis in coxsackievirus b3-induced chronic myocarditis.
OBJECTIVE
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.


RESULTS
Chronic myocarditis was induced by CVB3 infection of major histocompatibility complex (MHC) class II knockout (B6Aa(0)/Aa(0)) 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. PDGFalpha 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 (HP) determination. Fibronectin, and tenascin expression was analysed by RT-PCR and immunohistochemistry. Matrix metalloproteinase (MMP) activity was assessed with collagen, synthetic peptides, and gelatine as substrates. Imatinib significantly inhibited the myocarditis-related PDGFalpha 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 HP content was reduced from 362 +/- 43 to 238 +/- 32 microMol/10 mg dry weight vs. 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.
Leipner
Carola
C
Institute of Virology, Medical Faculty, Friedrich Schiller University, Jena, Germany.
Grün
Katja
K
Müller
Andreas
A
Buchdunger
Elisabeth
E
Borsi
Laura
L
Kosmehl
Hartwig
H
Berndt
Alexander
A
Janik
Tobias
T
Uecker
Andrea
A
Kiehntopf
Michael
M
Böhmer
Frank-D
FD
D000818:Animals; D001549:Benzamides; D003384:Coxsackievirus Infections / Q000150:complications*; D004195:Disease Models, Animal; D029822:Enterovirus B, Human; D005355:Fibrosis; D006321:Heart / Q000187:drug effects / Q000821:virology; D000068877:Imatinib Mesylate; D008222:Lymphokines / Q000378:metabolism; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009205:Myocarditis / Q000188:drug therapy* / Q000473:pathology / Q000821:virology*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D010879:Piperazines / Q000494:pharmacology*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology*; D017479:Receptors, Platelet-Derived Growth Factor / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects
D001549:Benzamides; D008222:Lymphokines; D010879:Piperazines; D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D020574:Proto-Oncogene Proteins c-sis; D011743:Pyrimidines; C075278:platelet-derived growth factor A; C411423:platelet-derived growth factor C; D000068877:Imatinib Mesylate; D017479:Receptors, Platelet-Derived Growth Factor