title: Beta3-adrenergic receptors modulate vascular endothelial growth factor release in response to hypoxia through the nitric oxide pathway in mouse retinal explants.
abstract: Beta-adrenergic receptors (β-ARs) play a role in angiogenic processes that characterize neovascularization-associated retinal diseases, but the role of β3-ARs has not been disclosed yet. We used ex vivo retinal explants to investigate the role of β3-ARs in regulating vascular endothelial growth factor (VEGF) release associated with hypoxia. Whether nitric oxide (NO) mediates β3-AR regulation of VEGF release was also investigated. β3-AR activation was obtained using BRL 37344, whereas SR59230A, L-748,337, or specific siRNAs were used to block β3-ARs. Pharmacological approaches were used to interfere with the NO pathway. Western blot was used to determine β-AR levels. Enzyme-linked immunosorbent assay was used to measure VEGF release. NO production was assessed by a colorimetric assay. We found that hypoxia upregulates β3-ARs. In addition, we observed that β3-AR activation with BRL 37344 increases VEGF release in response to hypoxia. Either β3-AR blocker or β3-AR silencing downregulates drastically hypoxic levels of VEGF. With experiments using NO synthase (NOS) blockade with L-NAME, NOS activation with fluvastatin or NO supplementation with SNAP, we demonstrated that β3-ARs and VEGF are functionally coupled via the NO pathway. In summary, the data presented here support the assumption that β3-ARs are involved in the regulation of angiogenic responses to hypoxia through the NO signalling, a key pathway in hypoxic/ischemic diseases. Although extrapolation of these data to the human situation is difficult, these findings may help to explore the possible role of β3-ARs in vascularization-associated disorders.
authors.affiliation: Department of Biology, University of Pisa, Via San Zeno 31, Pisa, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Dal Monte
authors.forename: Luca
authors.initials: L
authors.lastname: Filippi
authors.forename: Paola
authors.initials: P
authors.lastname: Bagnoli
mesh_terms: D000818:Animals; D000860:Hypoxia / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009569:Nitric Oxide / Q000378:metabolism; D022702:Receptors, Adrenergic, beta-3 / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D022702:Receptors, Adrenergic, beta-3; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; D009569:Nitric Oxide