GAS6-mediated dialogue between decidual stromal cells and macrophages is essential for early pregnancy maintenance by inducing M2-like polarization and cell proliferation of decidual macrophages.

Maternal immunotolerance towards the semi-allogeneic foetus is critical for normal pregnancy (NP). As a secretory protein, growth arrest-specific factor 6 (GAS6) promotes cancer progression by inducing the conversion of tumour-associated macrophages to an immunosuppressive M2-like phenotype. However, little is known about whether GAS6 regulates decidual macrophages (dMφs) in the early maternal-foetal interface. In this study, first-trimester decidual tissues were obtained from normal pregnant women undergoing elective terminations and patients with miscarriages. The expression of GAS6 and its receptors (AXL, TYRO3 and MERTK) in decidua and GAS6 secretion by decidual stromal cells (DSCs) was measured. Then, we investigated the effect of recombinant human GAS6 (rhGAS6) on dMφs isolated from NP and THP-1 cells, and revealed the underlying mechanism. Both the expression of GAS6 in DSCs and MERTK in dMφs, in addition to GAS6 secretion by DSCs, was found to be significantly decreased in miscarriage patients compared to that in NPs. Additionally, we observed that rhGAS6 polarized dMφs and THP-1 cells towards an M2-like phenotype, as evidenced by the up-regulated CD163 expression. Moreover, rhGAS6 enhanced the clearance of toxic cell-free haemoglobin by dMφs by up-regulating CD163 expression, and rhGAS6 also boosted cell proliferation of dMφs and THP-1 cells. Finally, we demonstrated that rhGAS6 stimulated CD163 expression and cell proliferation by activating the PI3K/Akt signalling pathway. Collectively, these findings suggest that GAS6-mediated dialogue between DSCs and dMφs is crucial for the establishment and maintenance of maternal-foetal immunotolerance, and decreased GAS6 secretion by DSCs may lead to the occurrence of miscarriage in the first trimester.

SIRT3 sulfhydration using hydrogen sulfide inhibited angiotensin II-induced atrial fibrosis and vulnerability to atrial fibrillation via suppression of the TGF-ß1/smad2/3 signalling pathway.

Atrial fibrosis is associated with the occurrence of atrial fibrillation (AF) and regulated by the transforming growth factor-ß1 (TGF-ß1)/Smad2/3 signalling pathway. Unfortunately, the mechanisms of regulation of TGF-ß1/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-ß1/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-ß1/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-ß1/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.