Previously, we have shown that CCR5 transcription is regulated by CREB-1. However, the ubiquitous pattern of CREB-1 expression suggests the involvement of an additional level of transcriptional... Show morePreviously, we have shown that CCR5 transcription is regulated by CREB-1. However, the ubiquitous pattern of CREB-1 expression suggests the involvement of an additional level of transcriptional control in the cell type-specific expression of CCR5. In this study we show that epigenetic changes (i.e. DNA methylation and histone modifications) within the context of the CCR5 P1 promoter region correlate with transcript levels of CCR5 in healthy and in malignant CD4(+) T lymphocytes as well as in CD14(+) monocytes. In normal naïve T cells and CD14(+) monocytes the CCR5 P1 promoter resembles a bivalent chromatin state, with both repressive and permissive histone methylation and acetylation marks. The CCR5 expressing CD14(+) monocytes however show much higher levels of acetylated histone H3 (AcH3) compared to the non-CCR5-expressing naïve T cells. Combined with a highly methylated promoter in CD14(+) monocytes, this indicates a dominant role for AcH3 in CCR5 transcription. We also show that pharmacological interference in the epigenetic repressive mechanisms that account for the lack of CCR5 transcription in T leukemic cell lines results in an increase in CREB-1 association with the CCR5 P1 chromatin. Furthermore RNA polymerase II was also recruited into CCR5 P1 chromatin resulting in CCR5 re-expression. Together, these data indicate that epigenetic modifications of DNA, and of histones, contribute to the control of CCR5 transcription in immune effector cells. Show less
AIM Monocytes play a significant role in neovascularisation. The stimuli that differentiate monocytes along a pro-angio-/arteriogenic-supporting pathway are currently unclear. We investigated... Show moreAIM Monocytes play a significant role in neovascularisation. The stimuli that differentiate monocytes along a pro-angio-/arteriogenic-supporting pathway are currently unclear. We investigated whether pre-stimulation of human monocytes with soluble T-cell-derived factors improves revascularisation in murine hind limb ischaemia as a new option for therapeutic angio- and arteriogenesis. DESIGN Human monocytes were cultured with or without soluble T-cell-derived factors. Unstimulated and pre-stimulated monocytes were transfused after induction of hind limb ischaemia in nude mice. METHODS Blood flow was measured with laser Doppler perfusion imaging. Collaterals were visualised by immunohistochemistry and angiography. Monocytes were characterised by flowcytometry and Bio-Plex assays. RESULTS Transfusion of T-cell-pre-stimulated monocytes significantly improved blood flow recovery after hind limb ischaemia and increased collateral size and collateral and capillary number in the post-ischaemic paw. Pre-stimulated monocytes produced a wide variety of factors that support neovascularisation such as platelet-derived growth factor-BB, vascular-endothelial growth factor, interleukin-4 and tumour necrosis factor-α. Few transfused human cells were detected in the muscle tissue, suggesting that paracrine rather than direct effects appear responsible for the enhanced recovery of blood flow observed. CONCLUSION These results show a beneficial role for T-cell-pre-stimulated monocytes in neovascularisation, rendering the monocyte a potential candidate for regenerative cell therapy that promotes revascularisation in peripheral arterial disease patients. Show less
Introduction Epigenetics explained Epigenetic alterations are reversible Atherosclerosis Epigenetics and association with atherosclerosis Epigenetic regulation of cell activity T cells Monocytes... Show moreIntroduction Epigenetics explained Epigenetic alterations are reversible Atherosclerosis Epigenetics and association with atherosclerosis Epigenetic regulation of cell activity T cells Monocytes Endothelial cells Smooth muscle cells Chemokines, their receptors and other genes involved in inflammation eNOS iNOS CCL11 (eotaxin) CCR5 Epigenetics in (vascular) inflammation KDM6B Oestrogen receptor COX2 Transcriptional regulation of MHC molecules - the role of CIITA Non-histone targets MicroRNAs Conclusions Atherosclerosis is a multifactorial disease with a severe burden on western society. Recent insights into the pathogenesis of atherosclerosis underscore the importance of chronic inflammation in both the initiation and progression of vascular remodelling. Expression of immunoregulatory molecules by vascular wall components within the atherosclerotic lesions is accordingly thought to contribute to the ongoing inflammatory process. Besides gene regulatory proteins (transcription factors), epigenetic mechanisms also play an essential and fundamental role in the transcriptional control of gene expression. These epigenetic mechanisms change the accessibility of chromatin by DNA methylation and histone modifications. Epigenetic modulators are thus critically involved in the regulation of vascular, immune and tissue-specific gene expression within the atherosclerotic lesion. Importantly, epigenetic processes are reversible and may provide an excellent therapeutic target. The concept of epigenetic regulation is gradually being recognized as an important factor in the pathogenesis of atherosclerosis. Recent research provides an essential link between inflammation and reprogramming of the epigenome. In this review we therefore discuss the basis of epigenetic regulation - and the contribution thereof in the regulation of inflammatory processes in general and during atherosclerosis in particular. Moreover we highlight potential therapeutic interventions based on epigenetic mechanisms. Show less