Activation of cardiac fibroblasts is a key event in the progression of cardiac fibrosis that leads to heart failure. However, the molecular mechanisms underlying mechanical stress-induced cardiac fibroblast activation are complex and poorly understood. This study demonstrates that Pellino1, an E3 ubiquitin ligase, was activated in vivo in pressure overloaded rat hearts and in cultured neonatal rat cardiac fibroblasts (NRCFs) exposed to mechanical stretch in vitro. Suppression of the expression and activity of Pellino1 by adenovirus-mediated delivery of shPellino1 (adv-shpeli1) attenuated pressure overload-induced cardiac dysfunction and cardiac hypertrophy and decreased cardiac fibrosis in rat hearts. Transfection of adv-shpeli1 also significantly attenuated mechanical stress-induced proliferation, differentiation and collagen synthesis in NRCFs. Pellino1 silencing also abrogated mechanical stretch-induced polyubiquitination of tumor necrosis factor-alpha receptor association factor-6 (TRAF6) and receptor-interacting protein 1 (RIP1) and consequently decreased the DNA binding activity of nuclear factor-kappa B (NF-κB) in NRCFs. In addition, Pellino1 silencing prevented stretch-induced activation of p38 and activator protein 1 (AP-1) binding activity in NRCFs. Chromatin Immunoprecipitation (ChIP) and luciferase reporter assays showed that Pellino1 silencing prevented the binding of NF-κB and AP-1 to the promoter region of transforming growth factor-β1 (TGF-β1) thus dampening TGF-β1 transactivation. Our data reveal a previously unrecognized role of Pellino1 in extracellular matrix deposition and cardiac fibroblast activation in response to mechanical stress and provides a novel target for treatment of cardiac fibrosis and heart failure.

AimsPellino1 is an evolutionally conserved immune regulator and participates in the regulation of Toll-like receptor/interleukin-1 receptor (TLR/IL-1R)-mediated signalling. Recent studies have shown that TLR/IL-1R contributes to the left ventricular (LV) remodelling after myocardial infarction (MI). However, the role of Pellino1 in LV remodelling following MI has not been investigated. This study examined the effect of Pellino1 silencing on cardiac function and LV remodelling after MI.Methods and resultsMale C57BL/6 mice were subjected to permanent ligation of left anterior descending coronary artery (LAD) to induce MI. The levels of Pellino1 were significantly increased in the myocardium 3 days and sustained for 4 weeks after MI, when compared with the sham control. Hypoxia increased Pellino1 expression in cultured cardiomyocytes and fibroblasts. To examine whether Pellino1 plays a role in MI-induced cardiac dysfunction and the LV remodelling, we suppressed the expression of Pellino1 either by intramyocardial delivery of adenovirus expressing siRNA for Pellino1 (AdsiPeli1) or by Cre-LoxP-mediated conditional deletion of Pellino1 from the myocardium. In both models, silencing of Pellino1 significantly attenuated MI-induced cardiac dysfunction, decreased scar size, and reduced collagen deposition, when compared with the control groups. Pellino1 silencing in mice also attenuated MI-induced Pellino1 E3 ligase activity, receptor-interacting protein 1 and tumor necrosis factor receptor associated factor 6 (TRAF6) ubiquitination, nuclear factor Kappa B (NF-κB) activity, cytokine production, and inflammatory cell infiltration into the myocardium when compared with the MI group.ConclusionsOur data demonstrate that Pellino1 plays an important role in the pathogenesis of MI. Targeting Pellino1 may ameliorate cardiac dysfunction and remodelling following MI.