Inhibition of Transforming Growth Factor β Worsens Elastin Degradation in a Murine Model of Kawasaki Disease

Kawasaki disease (KD) is an acute inflammatory illness marked by coronary arteritis. However, the factors increasing susceptibility to coronary artery lesions are unknown. Because transforming growth factor (TGF) beta increases elastin synthesis and suppresses proteolysis, we hypothesized that, in contrast to the benefit observed in aneurysms forming in those with Marfan syndrome, inhibition of TGF-beta would worsen inflammatory-induced coronary artery lesions. By using a murine model of KD in which injection of Lactobacillus casei wall extract (LCWE) induces coronary arteritis, we show that LCWE increased TGF-beta signaling in the coronary smooth muscle cells beginning at 2 days and continuing through 14 days, the point of peak coronary inflammation. By 42 days, LCWE caused fragmentation of the internal and external elastic lamina. Blocking TGF-beta by administration of a neutralizing antibody accentuated the LCWE-mediated fragmentation of elastin and induced an overall loss of medial elastin without increasing the inflammatory response. We attributed these increased pathological characteristics to a reduction in the proteolytic inhibitor, plasminogen activator inhibitor-1, and an associated threefold increase in matrix metalloproteinase 9 activity compared with LCWE alone. Therefore, our data demonstrate that in the coronary arteritis associated with KD, TGF-beta suppresses elastin degradation by inhibiting plasmin-mediated matrix metalloproteinase 9 activation. Thus, strategies to block TGF-beta, used in those with Marfan syndrome, are unlikely to be beneficial and could be detrimental. (Am J Pathol 2011, 178:1210-1220; DOI. 10.1016/j.ajpath.2010.11.054)