The Tir/Bb-Loop Mimetic As-1 Attenuates Mechanical Stress-Induced Cardiac Fibroblast Activation and Paracrine Secretion Via Modulation of Large Tumor Suppressor Kinase 1

The TIR/BB-loop mimetic AS-1 has been reported to prevent cardiac hypertrophy by inhibiting interleukin-1 receptor (IL-1R)-mediated myeloid differentiation primary response gene 88 (MyD88)-dependent signaling. To date, it remains unknown whether and if so how AS-1 contributes to mechanical stress (MS)-induced cardiac fibroblast activation, a key process in pressure overload-induced cardiac remodeling and heart failure. Here, we show that phosphorylation and expression of large tumor suppressor kinase 1 (LATS1), a key molecule in the Hippo-Yes associated protein (YAP) signaling pathway, were down-regulated in primary neonatal rat cardiac fibroblasts (NRCFs) in response to MS and in the hearts of mice subjected to transverse aortic constriction (TAC) procedure; AS-1 treatment was able to restore LATS1 phosphorylation and expression both in vitro and in vivo. AS-1 treatment suppressed the induction of proliferation, differentiation and collagen synthesis in response to MS in NRCFs. AS-1 also ameliorated cardiomyocyte hypertrophy and apoptosis through dampening paracrine secretion of stretched cardiac fibroblasts. In mice, AS-1 treatment could protect against TAC-induced cardiac hypertrophy, myocardial fibrosis and heart failure. Of note, LATS1 depletion using siRNA completely abrogated the inhibitory effects of AS-1 on NRCFs under MS including accelerated proliferation, differentiation, enhanced ability to produce collagen and augmented paracrine secretion of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) to induce cardiomyocyte hypertrophy. Therefore, our results delineate a previously unrecognized role for LATS1 in cardiac fibroblast to mediate the beneficial effects of AS-1 in preventing pressure overload-induced cardiac remodeling and heart failure.