Abstract 14663: Silencing TRAF3IP2 by a Modified 27-mer siRNA Attenuates Pressure-Overload Induced Myocardial Hypertrophy and Fibrosis
The adapter molecule TRAF3IP2 (CIKS/Act1) activates both IKK/NF-κB and JNK/AP-1 pathways that induce inflammatory genes, and mediate myocardial hypertrophy, fibrosis and failure. We investigated if silencing TRAF3IP2 will blunt pressure overload-induced myocardial hypertrophy and fibrosis in vivo, and attenuate IL-18-induced cardiac fibroblast differentiation and migration in vitro.
Methods: WT adult male C57Bl/6 mice (35 g) underwent transaortic constriction (TAC) or sham surgery, and one day later, were administered with phosphorothioated 2’O-methyl modified cholesterol-tagged TRAF3IP2 27-mer siRNA (M.siRNA), or scrambled control (M.Scram) at 10 mg/kg body weight via tail vein for three consecutive days. On day 10, myocardial function was analyzed by echocardiography, and hearts analyzed for histological/biochemical changes. TRAF3IP2-null mice (C57Bl/6) underwent TAC or sham surgery for a similar period of time. In addition, WT adult mouse cardiac fibroblasts (CF) were transfected with TRAF3IP2 siRNA or scrambled control, treated with IL-18, and analyzed for differentiation, migration and proliferation.
Results: TAC induced significant hypertrophy (heart wt/tibial length) in the M.Scram treated animals. Fractional shortening was reduced, and ANF mRNA expression, IKK and JNK activation, and IL-18 protein were induced, together with increased collagen deposition. TRAF3IP2 M.siRNA blunted all of these effects. Consistent with this, TRAF3IP2-null mice exhibited reduced TAC-induced IL-18 expression, hypertrophy and fibrosis. Silencing TRAF3IP2 in CF in vitro attenuated IL-18 induced IKK/NF-κB and JNK/AP-1 activation, αSMA expression, collagen types I and III mRNA levels, and soluble collagen secretion. Silencing TRAF3IP2 also attenuated IL-18-induced CF migration and proliferation.
Conclusions: TRAF3IP2 plays a causal role in pressure overload-induced myocardial hypertrophy and fibrosis in vivo, and is a critical intermediate in IL-18-induced CF differentiation, migration, and proliferation in vitro. Thus TRAF3IP2 represents a novel potential therapeutic target in pressure overload-induced myocardial hypertrophy and adverse remodeling.
- © 2013 by American Heart Association, Inc.