Apolipoprotein A-I Binding Protein Inhibits the Formation of Infantile Hemangioma through Cholesterol-Regulated Hypoxia-Inducible Factor 1α Activation.

Infantile hemangioma (IH) is the most frequent vascular tumor of infancy with unclear pathogenesis; disordered angiogenesis is considered to be involved in its formation. Apolipoprotein A-I binding protein (AIBP)-also known as NAXE (NAD [P]HX epimerase)-a regulator of cholesterol metabolism, plays a critical role in the pathological angiogenesis of mammals. In this study, we found that AIBP had much lower expression levels in both tissues from patients with IH and hemangioma endothelial cells (HemECs) than in adjacent normal tissues and human dermal vascular endothelial cells, respectively. Knockout of NAXE by CRISPR-Cas9 in HemECs enhanced tube formation and migration, and NAXE overexpression impaired tube formation and migration of HemECs. Interestingly, AIBP suppressed the proliferation of HemECs in hypoxia. We then found that reduced expression of AIBP correlated with increased hypoxia-inducible factor 1α levels in tissues from patients with IH and HemECs. Further mechanistic investigation demonstrated that AIBP disrupted hypoxia-inducible factor 1α signaling through cholesterol metabolism under hypoxia. Notably, AIBP significantly inhibited the development of IH in immunodeficient mice. Furthermore, using the validated mouse endothelial cell (ie, EOMA cells) and Naxe-/- mouse models, we demonstrated that both endogenous AIBP from tumors and AIBP in the tumor microenvironment limit the formation of hemangioma. These findings suggested that AIBP was a player in the pathogenesis of IH and could be a potential pharmacological target for treating IH.

1,6-Hexanediol regulates angiogenesis via suppression of cyclin A1-mediated endothelial function.

BACKGROUND: Angiogenesis plays important roles in physiological and pathologic conditions, but the mechanisms underlying this complex process often remain to be elucidated. In recent years, liquid-liquid phase separation (LLPS) has emerged as a new concept to explain many cellular functions and diseases. However, whether LLPS is involved in angiogenesis has not been studied until now. Here, we investigated the potential role of LLPS in angiogenesis and endothelial function. RESULTS: We found 1,6-hexanediol (1,6-HD), an inhibitor of LLPS, but not 2,5-hexanediol (2,5-HD) dramatically decreases neovascularization of Matrigel plug and angiogenesis response of murine corneal in vivo. Moreover, 1,6-HD but not 2,5-HD inhibits microvessel outgrowth of aortic ring and endothelial network formation. The endothelial function of migration, proliferation, and cell growth is suppressed by 1,6-HD. Global transcriptional analysis by RNA-sequencing reveals that 1,6-HD specifically blocks cell cycle and downregulates cell cycle-related genes including cyclin A1. Further experimental data show that 1,6-HD treatment greatly reduces the expression of cyclin A1 but with minimal effect on cyclin D1, cyclin E1, CDK2, and CDK4. The inhibitory effect of 1,6-HD on cyclin A1 is mainly through transcriptional regulation because proteasome inhibitors fail to rescue its expression. Furthermore, overexpression of cyclin A1 in HUVECs largely rescues the dysregulated tube formation upon 1,6-HD treatment. CONCLUSIONS: Our data reveal a critical role of LLPS inhibitor 1,6-HD in angiogenesis and endothelial function, which specifically affects endothelial G1/S transition through transcriptional suppression of CCNA1, implying LLPS as a possible novel player to modulate angiogenesis, and thus, it might represent an interesting therapeutic target to be investigated in clinic angiogenesis-related diseases in future.

Inhibition of BETs prevents heat shock-induced cell death via upregulating HSPs in SV40 large T antigen transfected cells.

BACKGROUND: Heat shock response is a protected mechanism against environmental changes for the organism, which must be tightly regulated. Bromodomain and extra terminal-containing protein family (BETs) regulate numerous gene expression in many physiological and pathological conditions, including viral infection. SV40 is considered as a highly human disease-associated virus. OBJECTIVE: We aimed to explore whether BETs play a role in heat shock in SV40 large T antigen transfected cells. METHODS: SV40LTA was transfected in HeLa cells using the Lipofectamine 8000. BETs inhibitor JQ1 and I-BET-762 was employed to treat transfected cells and HEK-293 T cells. Heat shock treatment was performed to determine the effect of JQ1 and I-BET-762 on these cells. Western blot and quantitative RT-PCR were carried out to assess the expression of HSP70 and other HSPs. RESULTS: We found that inhibition of BETs by JQ1 and I-BET-762 protects cells from heat shock-induced death in HEK293T cells. Both JQ1 and I-BET-762 induce the expression of HSPs and HSF1 in HEK-293 T cells. However, neither JQ1 nor I-BET-762 fail to induce the expression of HSPs in either HeLa or HBL-1 cells. When SV40 large T antigen was transfected into HeLa cells, the induction of HSP70 expressing and the protection of heat shock-induced cell death are reproduced by JQ1 and IBET treatment in these transfected cells. CONCLUSIONS: Inhibition of BETs by JQ1 and I-BET-762 prevents heat shock-induced cell death via upregulating HSPs in SV40 large T antigen transfected cells. Our data indicate a novel function of BETs in SV40 large T antigen transformed cells, affecting HSPs and HSF1 as well as its function on heat shock response.