PU.1 inhibition attenuates atrial fibrosis and atrial fibrillation vulnerability induced by angiotensin-II by reducing TGF-β1/Smads pathway activation.

Fibrosis serves a critical role in driving atrial remodelling-mediated atrial fibrillation (AF). Abnormal levels of the transcription factor PU.1, a key regulator of fibrosis, are associated with cardiac injury and dysfunction following acute viral myocarditis. However, the role of PU.1 in atrial fibrosis and vulnerability to AF remain unclear. Here, an in vivo atrial fibrosis model was developed by the continuous infusion of C57 mice with subcutaneous Ang-II, while the in vitro model comprised atrial fibroblasts that were isolated and cultured. The expression of PU.1 was significantly up-regulated in the Ang-II-induced group compared with the sham/control group in vivo and in vitro. Moreover, protein expression along the TGF-β1/Smads pathway and the proliferation and differentiation of atrial fibroblasts induced by Ang-II were significantly higher in the Ang-II-induced group than in the sham/control group. These effects were attenuated by exposure to DB1976, a PU.1 inhibitor, both in vivo and in vitro. Importantly, in vitro treatment with small interfering RNA against Smad3 (key protein of TGF-β1/Smads signalling pathway) diminished these Ang-II-mediated effects, and the si-Smad3-mediated effects were, in turn, antagonized by the addition of a PU.1-overexpression adenoviral vector. Finally, PU.1 inhibition reduced the atrial fibrosis induced by Ang-II and attenuated vulnerability to AF, at least in part through the TGF-β1/Smads pathway. Overall, the study implicates PU.1 as a potential therapeutic target to inhibit Ang-II-induced atrial fibrosis and vulnerability to AF.

Hu J ，Zhang JJ ，Li L ，Wang SL ，Yang HT ，Fan XW ，Zhang LM ，Hu GL ，Fu HX ，Song WF ，Yan LJ ，Liu JJ ，Wu JT ，Kong B ... -  《-》

SIRT3 sulfhydration using hydrogen sulfide inhibited angiotensin II-induced atrial fibrosis and vulnerability to atrial fibrillation via suppression of the TGF-β1/smad2/3 signalling pathway.

Atrial fibrosis is associated with the occurrence of atrial fibrillation (AF) and regulated by the transforming growth factor-β1 (TGF-β1)/Smad2/3 signalling pathway. Unfortunately, the mechanisms of regulation of TGF-β1/Smad2/3-induced atrial fibrosis and vulnerability to AF remain still unknown. Previous studies have shown that sirtuin3 (SIRT3) sulfhydration has strong anti-fibrotic effects. We hypothesised that SIRT3 sulfhydration inhibits angiotensin II (Ang-II)-induced atrial fibrosis via blocking the TGF-β1/Smad2/3 signalling pathway. In this study, we found that SIRT3 expression was decreased in the left atrium of patients with AF compared to that in those with sinus rhythm (SR). In vitro, SIRT3 knockdown by small interfering RNA significantly expanded Ang-II-induced atrial fibrosis and TGF-β1/Smad2/3 signalling pathway activation, whereas supplementation with Sodium Hydrosulfide (NaHS, exogenous hydrogen sulfide donor and sulfhydration agonist) and SIRT3 overexpression using adenovirus ameliorated Ang-II-induced atrial fibrosis. Moreover, we observed suppression of the TGF-β1/Smad2/3 pathway when Ang-II was combined with NaHS treatment, and the effect of this co-treatment was consistent with that of Ang-II combined with LY3200882 (Smad pathway inhibitor) on reducing atrial fibroblast proliferation and cell migration in vitro. Supplementation with dithiothreitol (DTT, a sulfhydration inhibitor) and adenovirus SIRT3 shRNA blocked the ameliorating effect of NaHS and AngII co-treatment on atrial fibrosis in vitro. Finally, continued treatment with NaHS in rats ameliorated atrial fibrosis and remodelling, and further improved AF vulnerability induced by Ang-II, which was reversed by DTT and adenovirus SIRT3 shRNA, suggesting that SIRT3 sulfhydration might be a potential therapeutic target in atrial fibrosis and AF.

Hu HJ ，Wang XH ，Zhang ZZ ，Ou Y ，Ning ZH ，Yang JY ，Huang H ，Tang HF ，Jiang ZS ... -  《-》

MFGE8 attenuates Ang-II-induced atrial fibrosis and vulnerability to atrial fibrillation through inhibition of TGF-β1/Smad2/3 pathway.

Atrial fibrillation (AF) is characterized by potentiated growth of atrial fibroblasts and excessive deposition of the extracellular matrix. Atrial fibrosis has emerged as a hallmark of atrial structural remodeling linked to AF. Nonetheless, the specific mechanism underlying the progression of atrial fibrosis to AF is still largely unknown. MFGE8 (milk fat globule-EGF factor 8) is a soluble glycoprotein associated with many human diseases. Recently, a number of studies revealed that MFGE8 plays a crucial role in heart disease. Yet, MFGE8 regulation and function in the process of atrial fibrosis and vulnerability to AF remain unexplored. In this study, we found that the expression of MFGE8 was downregulated in the atriums of patients with AF compared with individuals without AF. In addition, the expression of MFGE8 was lower in atriums of angiotensin II (Ang-II)-stimulated rats as compared with the sham group. In vitro, silencing of MFGE8 by small interfering RNA significantly increased Ang-II-induced atrial fibrosis, whereas administration of recombinant human MFGE8 (rhMFGE8) attenuated the atrial fibrosis. Moreover, we found that the activated TGF-β1/Smad2/3 pathway after Ang-II treatment was significantly potentiated by the MFGE8 knockdown but inhibited by rhMFGE8 in vitro. Inhibition of integrin β3 which is the receptor for MFGE8, suppressed the TGF-β1/Smad2/3 activating effects of the MFGE8 knockdown in Ang-II-treated rat atrial fibroblasts. Finally, we administered rhMFGE8 to rats; it attenuated atrial fibrosis and remodeling and further reduced AF vulnerability induced by Ang-II, indicating that MFGE8 might have the potential both as a novel biomarker and as a therapeutic target in atrial fibrosis and AF.

Ge Z ，Chen Y ，Wang B ，Zhang X ，Yan Y ，Zhou L ，Zhang Y ，Xie Y ... -  《-》

Atrial fibrillation induces myocardial fibrosis through angiotensin II type 1 receptor-specific Arkadia-mediated downregulation of Smad7.

He X ，Gao X ，Peng L ，Wang S ，Zhu Y ，Ma H ，Lin J ，Duan DD ... -  《-》

Circ_0079480 facilitates proliferation, migration and fibrosis of atrial fibroblasts in atrial fibrillation by sponing miR-338-3p to activate the THBS1/TGF-β1/Smad3 signaling.

Atrial fibrosis is associated with the pathogenesis of atrial fibrillation (AF). This study aims to discuss the function of circ_0079480 in atrial fibrosis and its underlying mechanism. In vitro and in vivo models of atrial fibrosis were established by using angiotensin II (Ang II) to treat human atrial fibroblasts (HAFs) and C57/B6J mice. qRT-PCR and western blot were used to examine the mRNA and protein expression levels. CCK-8, EdU, cell strach, and transwell assays were performed to determine the proliferation and migration of HAFs. Dual-luciferase reporter and RIP/RNA pull-down assays were explored to identify the interaction of miR-338-3p and circ_0079480/THBS1. HE and Masson's trichrome staining experiments were performed to analyze the histopathological change in mice atrial tissues. Circ_0079480 expression was increased in AF patients' atrial tissues and Ang II-treated HAFs. Silencing circ_0079480 inhibited cell proliferation and migration and reduced fibrosis-associated gene expression in Ang II-treated HAFs. Circ_0079480 could target miR-338-3p to repress its expression. MiR-338-3p inhibitor blocked the inhibitory effects of circ_0079480 knockdown on HAFs proliferation, migration, and fibrosis. Thrombospondin-1 (THBS1) was confirmed as a downstream target of miR-338-3p, and circ_0079480 could sponge miR-338-3p to upregulate THBS1 expression. Moreover, silencing THBS1 suppressed Ang II-induced proliferation, migration, and fibrosis in HAFs. More importantly, depletion of circ_0079480 inactivated the THBS1/TGF-β1/Smad3 signaling by upregulating miR-338-3p. Mice experiments also confirmed the suppression of circ_0079480 knockdown on atrial fibrosis. Circ_0079480 acts as a sponge of miR-338-3p to upregulate THBS1 expression and activate the TGF-β1/Smad3 signaling, finally promoting Ang II-induced atrial fibrosis.

Wei Z ，Lu Y ，Qian C ，Li J ，Li X ... -  《-》