Ultrafine Particles Exposure Reveals the Importance of FOXO1/Notch Activation Complex for Vascular Regeneration

AIMS: Redox active ultrafine particles (UFP, d < 0.2 µm) promote vascular oxidative stress and atherosclerosis. Notch signaling is intimately involved in vascular homeostasis, in which FOXO1 acts a co-activator of the Notch activation complex. We elucidated the importance of FOXO1/Notch transcriptional activation complex to restore vascular regeneration following UFP exposure. RESULTS: In a zebrafish model of tail injury and repair, transgenic Tg(fli1:GFP) embryos developed vascular regeneration at 3 days post tail amputation, whereas UFP exposure impaired regeneration (P < 0.05, n = 20 for control, n = 28 for UFP). UFP dose-dependently reduced Notch reporter activity and Notch signaling-related genes (Dll4, JAG1, JAG2, Notch1b, Hey2, Hes1) (P < 0.05, n = 3). In the transgenic Tg(tp1:GFP; flk1:mCherry) embryos, UFP attenuated endothelial Notch activity at the amputation site (P < 0.05, n = 20). ADAM10 inhibitor or dominant negative (DN)-Notch1b mRNA disrupted, whereas Notch Intracellular Cytoplasmic Domain (NICD) mRNA restored vascular network (P < 0.05, n = 20). UFP reduced FOXO1 expression, but not Master-mind like 1 (MAML1) or NICD (P < 0.05, n = 3). Immunoprecipitation and immunofluorescence demonstrated that UFP attenuated FOXO1-mediated NICD pull-down and FOXO1/NICD co-localization, respectively (P < 0.05, n = 3). While FOXO1 morpholino oligonucleotides attenuated Notch activity, FOXO1 mRNA reversed UFP-mediated reduction in Notch activity to restore vascular regeneration and blood flow (P < 0.05 , n = 5). Innovation and Conclusion: Our findings indicate the importance of FOXO1/Notch activation complex to restore vascular regeneration following exposure to the redox active UFP.