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Tumor necrosis factor alpha (TNF-α) is a prototypical proinflammatory cytokine that can elicit strong inflammation in macrophages by activating NF-κB. The underlying epigenetic mechanism is obscure. We show here that megakaryocytic leukemia 1 (MKL1) is an epigenetic mediator of TNF-α-induced proinflammatory transcription. Overexpression of a dominant negative form of MKL1 abrogates TNF-α-induced transactivation of proinflammatory genes. Proteomic analysis identifies the histone H3K4 trimethyltransferase ASH2 as a potential cofactor for MKL1. In response to TNF-α stimulation, ASH2 is recruited by MKL1 and interacts with MKL1 to catalyze H3K4 di- and trimethylation. ASH2 modulates proinflammatory transcription at least in part by altering the affinity of p65 for target promoters. Together, our data support an interplay between MKL1 and ASH2 to promote TNF-α-induced proinflammatory transcription in macrophages.

Endothelial dysfunction plays an important role in promoting the progression of disease genesis such as atherosclerosis and abdominal aortic aneurysm (AAA). The physiological unbalance of endothelial cells is a major pathological basis. In this present study, we investigated Brahma-related gene 1 (BRG1), a chromatin remodeling protein, was in mouse models of diabetic atherosclerosis and AAA, focusing on its role in endothelial dysfunction. We report that compared with their wild-type (WT, ApoE–/–; BRG1fl/fl) littermates, endothelium conditional BRG1 knockout mice (CKO, ApoE–/–; BRG1fl/fl; CDH5-cre) exhibited an alleviated phenotype of diabetic atherosclerosis. Immunohistochemically staining and real-time PCR analysis demonstrated fewer macrophages recruitment with a reduction of vascular inflammatory in CKO mice compared with WT mice. Further research in the Ang-II induced AAA model revealed that BRG1 deficiency had the protective effects on endothelium conditional BRG1 deletion, evidenced by the downregulation of pro-inflammatory mediators [interleukin (IL)-1β and IL-6, not tumor necrosis factor-α (TNF-α)] in the vessels of CKO mice compared with WT mice. In Ea.hy926 cell lines, anti-BRG1 small interfering RNA and PFI-3 treatment obviously alleviated tumor necrosis factor-α-induced IL-6 and CCL2 expression, and further research demonstrated that the BRG1 inhibition in endothelial cells not only decreased c-Fos expression but also blocked the c-Fos translocation into nuclei. In conclusion, our results suggest that endothelial BRG1 deficiency may protect the mice from diabetic atherosclerosis and AAA via inhibiting inflammatory response in vessels.

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