Background Chloride intracellular channel 4 (CLIC4) is highly expressed in the endothelium of remodelled pulmonary vessels and plexiform lesions of patients with pulmonary arterial hypertension (PAH). CLIC4 regulates vasculogenesis through endothelial tube formation. Aberrant CLIC4 expression may contribute to the vascular pathology of PAH. Methods and Results CLIC4 protein expression was increased in plasma and blood-derived endothelial cells from patients with idiopathic PAH (IPAH) and in the pulmonary vascular endothelium of 3 rat models of pulmonary hypertension. CLIC4 gene deletion markedly attenuated the development of chronic hypoxia-induced pulmonary hypertension in mice. Adenoviral overexpression of CLIC4 in cultured human pulmonary artery endothelial cells compromised pulmonary endothelial barrier function and enhanced their survival and angiogenic capacity, while CLIC4 shRNA had an inhibitory effect. Similarly, inhibition of CLIC4 expression in blood-derived endothelial cells from patients with IPAH attenuated the abnormal angiogenic behaviour that characterises these cells. The mechanism of CLIC4 effects involves p65-mediated activation of nuclear factor-κB, followed by stabilisation of hypoxia-inducible factor-1α and increased downstream production of vascular endothelial growth factor and endothelin-1. Conclusions Increased CLIC4 expression is an early manifestation and mediator of endothelial dysfunction in pulmonary hypertension.

Based on the current progress in the research field, it is worthy to explore the contributions of cell transformation to the pathogenesis of atherosclerosis to understand the mechanisms on how they are regulated in order to develop novel therapeutic application targeting these processes to reverse the disease progression.

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ESCs, pluripotent cells derived from the fetal blastula, showed early promise for potential therapeutic use and study of vessel development, because of their comparatively easy isolation from embryos and their rapid expansion. Because these cells can potentially commit to any cell line in order for them to be

Circulating levels of asymmetric dimethylarginine (ADMA), a nitric oxide synthase inhibitor, are increased in patients with idiopathic pulmonary hypertension (IPAH). We hypothesized that ADMA abrogates gap junctional communication, required for the coordinated regulation of endothelial barrier function and angiogenesis, and so contributes to pulmonary endothelial dysfunction. The effects of ADMA on expression and function of gap junctional proteins were studied in human pulmonary artery endothelial cells; pulmonary endothelial microvascular cells from mice deficient in an enzyme metabolizing ADMA, dimethylarginine dimethylaminohydrolase I (DDAHI); and blood-derived endothelial-like cells from patients with IPAH. Exogenous and endogenous ADMA inhibited protein expression and membrane localization of connexin 43 (Cx43) in a nitric oxide/ soluble guanosine monophosphate/c-jun-dependent manner in pulmonary endothelial cells, resulting in the inhibition of gap junctional communication, increased permeability, and decreased angiogenesis. The effects of ADMA were prevented by overexpression of DDAHI or Cx43 and by treatment with rotigaptide. Blood-derived endothelial-like cells from IPAH patients displayed a distinct disease-related phenotype compared to cells from healthy controls, characterized by reduced DDAHI expression, increased ADMA production, and abnormal angiogenesis. In summary, we show that ADMA induces pulmonary endothelial dysfunction via changes in expression and activity of Cx43. Cells from IPAH patients exhibit abnormal DDAHI/Cx43 signaling as well as differences in gap junctional communication, barrier function, and angiogenesis. Strategies that promote DDAHI/Cx43 signaling may have an endothelium-protective effect and be beneficial in pulmonary vascular disease.

Histone deacetylase 7 (HDAC7) plays a pivotal role in the maintenance of the endothelium integrity. In this study, we demonstrated that the intron‐containing Hdac7 mRNA existed in the cytosol and that ribosomes bound to a short open reading frame (sORF) within the 5′‐terminal noncoding area of this Hdac7 mRNA in response to vascular endothelial growth factor (VEGF) stimulation in the isolated stem cell antigen‐1 positive (Sca1+) vascular progenitor cells (VPCs). A 7‐amino acid (7A) peptide has been demonstrated to be translated from the sORF in Sca1+‐VPCs in vitro and in vivo. The 7A peptide was shown to receive phosphate group from the activated mitogen‐activated protein kinase MEKK1 and transfer it to 14‐3‐3 gamma protein, forming an MEKK1‐7A‐14‐3‐3γ signal pathway downstream VEGF. The exogenous synthetic 7A peptide could increase Sca1+‐VPCs cell migration, re‐endothelialization in the femoral artery injury, and angiogenesis in hind limb ischemia. A Hd7‐7sFLAG transgenic mice line was generated as the loss‐of‐function model, in which the 7A peptide was replaced by a FLAG‐tagged scrabbled peptide. Loss of the endogenous 7A impaired Sca1+‐VPCs cell migration, re‐endothelialization of the injured femoral artery, and angiogenesis in ischemic tissues, which could be partially rescued by the addition of the exogenous 7A/7Ap peptide. This study provides evidence that sORFs can be alternatively translated and the derived peptides may play an important role in physiological processes including vascular remodeling.

Cardiovascular diseases (CVD) continue to be the leading cause of death in the world despite recent therapeutic advances. Although many CVDs remain incurable, enormous eforts have been placed in harnessing angiogenesis as therapeutics for these diseases. Epigenetics, the modiication of gene expression post-transcriptionally and post-translationally, are important in regulating many biological processes. One of the main post-translational epigenetic modiications, modiication of chromatin structure by the acetylation of histone tails within the chromatin by either histone deacetylases (HDACs) or histone acetyltransferases (HATs), is important in modulating gene transcription and has emerged as an important regulatory player from pathogenesis to therapeutics in CVDs. Particularly, HDACs, which are largely involved in promoting chromatin compaction and hence inhibitions of gene transcription, have been implicated in the pathogenic signalling underlying many aspects of CVDs. Recently, histone modiications have been demonstrated to play important roles in the angiogenesis process. Pharmacological inhibitions of HDACs have displayed promising therapeutic potentials in several pre-clinical models of CVDs where angiogenesis is of paramount importance. There are many evidences proving that pro-and anti-angiogenic therapies-and the impact of epigenetics in these processes-can help to artiicially reconstruct the vasculature in patients with cardiovascular diseases. Conversely, utilising knowledge of HDACs in angiogenesis might help to develop anti-angiogenic therapies in tackling diseases that are characterised with excessive pathological angiogenesis, including cancer and age-related macular degeneration. Understanding the molecular mechanisms underlying HDACs in modulating angiogenesis will undoubtedly beneit future therapeutics development. This chapter focuses on the emerging role of HDACs in angiogenesis and discuss their potentials and challenges in utilising HDAC inhibitors as therapeutics in several major cardiovascular diseases.

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