Exploring the Role of Novel Targets CREBRF and TRIM2 in the Regulation of Angiogenesis

Abstract

Angiogenesis, the formation of new blood vessels from pre-existing vessels, is critical in the pathophysiology of chronic conditions, such as atherosclerotic vascular diseases. While angiogenesis is a key physiological response to ischaemia and wound healing, it is pathological when excessive and driven by inflammation. No current therapies adequately promote hypoxia-driven angiogenesis while inhibiting inflammation-induced angiogenesis. Our group found that high-density lipoproteins (HDL) modulates vessel growth in a contextual manner via classical signalling pathways. Whether novel mediators are involved that would be more amenable as therapeutic targets remains unknown. CREBRF and TRIM2 are two genes with no known roles in vascular biology, identified from a microarray to be upregulated by reconstituted (r)HDL in human endothelial cells (ECs). This thesis hypothesised a novel angiogenic role for these genes and aimed to assess their functional importance via in vitro and in vivo models of hypoxia- and inflammation-driven angiogenesis. CREBRF and TRIM2 were confirmed to be transcriptionally upregulated by rHDL, mainly via its phospholipid component. Lentiviral shRNA knockdown of CREBRF and TRIM2 impaired EC migration, proliferation and tubule-forming capacity in response to hypoxic or inflammatory stimulation in vitro. TRIM2 was also found to mediate the pro-angiogenic actions of rHDL in hypoxia. Mechanistically, TRIM2 knockdown attenuated the induction of key angiogenic mediators in inflammation, including nuclear HIF-1α, NF-κB p65, VEGFA and downstream effectors VEGFR2, p38 MAPK and eNOS. In Trim2–/– mice, the physiological angiogenic response to hindlimb ischaemia was not different to wild-type, however the activation of inflammatory responses to periarterial cuff injury was inhibited. In conclusion, TRIM2 may be a novel regulator of inflammation-induced angiogenesis; and could prove useful as a therapeutic target for diseases driven by pathological vessel growth.