Myeloid differentiation factor-88 contributes to TLR9-mediated modulation of acute coxsackievirus B3-induced myocarditis in vivo.
Toll-like receptor 9 (TLR9) is a member of the innate immune system and has been shown to influence myocardial function, but its role in myocarditis is hitherto unknown. We therefore investigated whether or not TLR9 plays a role in this disease in coxsackievirus B3 (CVB3)-induced myocarditis in mice. Left ventricular (LV) function, cardiac immune cell infiltration, virus mRNA, and components of the TLR9 downstream pathway were investigated in TLR9-deficient [knockout (KO)] and wild-type (WT) mice after infection with CVB3. Murine cardiac TLR9 expression was significantly increased in WT mice with acute CVB3 infection but not in WT mice with chronic myocarditis. Furthermore, in the acute phase of CVB3-induced myocarditis, CVB3-infected KO mice displayed improved LV function associated with reduced cardiac inflammation indexed by reduced amounts of immune cells compared with CVB3-infected WT mice. In contrast, in the chronic phase, LV function and inflammation were not seen to differ among the infected groups. The cardioprotective effects due to TLR9 deficiency were associated with suppression of the TLR9 downstream pathway as indexed by reduced cardiac levels of the adapter protein myeloid differentiation factor (MyD)-88 and the proinflammatory cytokine TNF-alpha. In addition, TLR9 deficiency led to an activation of the antiviral cytokine interferon-beta in the heart as a result from viral infection. In conclusion, the MyD88/TNF-alpha axis due to TLR9 activation in the heart contributes the development of acute myocarditis but not of chronic myocarditis.
Dept. of Cardiology, Campus Benjamin Franklin, Charité-Universitätsmedizin Berlin, Hindenburgdamm 30, Berlin 12203, Germany. alexanderriad@web.de
Alexander
A
Riad
Dirk
D
Westermann
Felicitas
F
Escher
Peter M
PM
Becher
Konstantinos
K
Savvatis
Olga
O
Lettau
Markus M
MM
Heimesaat
Stefan
S
Bereswill
Hans D
HD
Volk
Heinz P
HP
Schultheiss
Carsten
C
Tschöpe
D000208:Acute Disease; D000818:Animals; D004195:Disease Models, Animal; D029822:Enterovirus B, Human; D007113:Immunity, Innate / Q000502:physiology; D016899:Interferon-beta / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D053594:Myeloid Differentiation Factor 88 / Q000378:metabolism*; D009205:Myocarditis / Q000378:metabolism* / Q000503:physiopathology / Q000821:virology*; D051217:Toll-Like Receptor 9 / Q000235:genetics / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D016277:Ventricular Function, Left / Q000502:physiology
D053594:Myeloid Differentiation Factor 88; C495370:Tlr9 protein, mouse; D051217:Toll-Like Receptor 9; D014409:Tumor Necrosis Factor-alpha; D016899:Interferon-beta