Dual roles of chromatin remodeling protein BRG1 in angiotensin II-induced endothelial-mesenchymal transition.

Endothelial-mesenchymal transition (EndMT) is considered one of the processes underlying tissue fibrosis by contributing to the pool of myofibroblasts. In the present study, we investigated the epigenetic mechanism whereby angiotensin II (Ang II) regulates EndMT to promote cardiac fibrosis focusing on the role of chromatin remodeling protein BRG1. BRG1 knockdown or inhibition attenuated Ang II-induced EndMT, as evidenced by down-regulation of CDH5, an endothelial marker, and up-regulation of COL1A2, a mesenchymal marker, in cultured vascular endothelial cells. On the one hand, BRG1 interacted with and was recruited by Sp1 to the SNAI2 (encoding SLUG) promoter to activate SNAI2 transcription in response to Ang II stimulation. Once activated, SLUG bound to the CDH5 promoter to repress CDH5 transcription. On the other hand, BRG1 interacted with and was recruited by SRF to the COL1A2 promoter to activate COL1A2 transcription. Mechanistically, BRG1 evicted histones from the target promoters to facilitate the bindings of Sp1 and SRF. Finally, endothelial conditional BRG1 knockout mice (CKO) exhibited a reduction in cardiac fibrosis, compared to the wild type (WT) littermates, in response to chronic Ang II infusion. In conclusion, our data demonstrate that BRG1 is a key transcriptional coordinator programming Ang II-induced EndMT to contribute to cardiac fibrosis.

Interleukin (IL)-13, Prostaglandin E2 (PGE2), and Prostacyclin 2 (PGI2) Activate Hepatic Stellate Cells via Protein kinase C (PKC) Pathway in Hepatic Fibrosis.

BACKGROUND Protein kinase C (PKC), interleukin (IL)-13, prostaglandin E2 (PGE2), and prostacyclin 2 (PGI2) can all play crucial roles in pulmonary fibrosis. However, their functions remain unclear in hepatic fibrosis mediated by hepatic stellate cells (HSCs), which has been demonstrated to be related to transforming growth factor-ß (TGF-ß) and platelet-derived growth factor (PDGF). MATERIAL AND METHODS All the experiments were based on LX-2 Hepatic stellate cells. The expression of TGF-ß1 and PDGF were assessed by ELISA, RT-PCR, and Western blotting in human HSCs treated by IL-13, PGE2, and PGI2, respectively. At the same time, bridge assay and CCK8 assay were used to detect the cell proliferation and activity, PKC activity assay was used to test the activity of PKC, and PKC agonist and antagonist were used to verify the results obtained previously. RESULTS We found that IL-13, PGE2, and PGI2 significantly enhanced the expression of TGF-ß1 and PDGF in human HSCs, which also clearly improved the proliferation and cell activity of HSCs. Moreover, PKC activity was significantly increased following IL-13, PGE2, and PGI2 treatments. We also found that the expression of TGF-ß1 and PDGF, as well as the proliferation and cell activity of HSCs, were significantly enhanced by the PKC agonist phorbol 12-myristate 13-acetate (PMA), but suppressed by the PKC antagonist calphostin C. CONCLUSIONS We found that IL-13, PGE2, and PGI2 stimulated HSCs proliferation and secretion of TGF-ß1 and PDGF by activating PKC, which predicted their potential roles in hepatic fibrosis.