Increased Pituitary Vascular Endothelial Growth Factor-A in Dopaminergic D2 Receptor Knockout Female Mice

Abstract

Vascular endothelial growth factor (VEGF)-A is an important angiogenic cytokine in cancer and pathological angiogenesis and has been related to the antiangiogenic activity of dopamine in endothelial cells. We investigated VEGF expression, localization, and function in pituitary hyperplasia of dopamine D2 receptor (D2R)-knockout female mice. Pituitaries from knockout mice showed increased protein and mRNA VEGF-A expression when compared with wild-type mice. In wild-type mice, prolonged treatment with the D2R antagonist, haloperidol, enhanced pituitary VEGF expression and prolactin release, suggesting that dopamine inhibits pituitary VEGF expression. VEGF expression was also increased in pituitary cells from knockout mice, even though these cells proliferated less in vitro when compared with wild-type cells, as determined by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium proliferation assay, proliferating cell nuclear antigen expression, and [(3)H]thymidine incorporation. In contrast to other animal models, estrogen did not increase pituitary VEGF protein and mRNA expression and lowered serum prolactin secretion in vivo and in vitro in both genotypes. VEGF (10 and 30 ng/ml) did not modify pituitary cell proliferation in either genotype and increased prolactin secretion in vitro in estrogen-pretreated cells of both genotypes. But conditioned media from D2R(-/-) cells enhanced human umbilical vein cell proliferation, and this effect could be partially inhibited by an anti-VEGF antiserum. Finally, using dual-labeling immunofluorescence and confocal laser microscopy, we found that in the hyperplastic pituitaries, VEGF-A was mostly present in follicle-stellate cells. In conclusion, pituitary VEGF expression is under dopaminergic control, and even though VEGF does not promote pituitary cellular proliferation in vitro, it may be critical for pituitary angiogenesis through paracrine actions in the D2R knockout female mice.

Localization of vascular endothelial growth factor (VEGF) receptors in normal and adenomatous pituitaries: detection of a non-endothelial function of VEGF in pituitary tumours

“…All the six normal pituitaries expressed VEGF-A to a similar extent in 31-60% of all cells, confirming previous reports that not only FS cells (5-10% of all pituitary cells), but also endocrine cells produce VEGF-A ( Jabbour et al 1997, Fan & Iseki 1998, Cristina et al 2005. In pituitary adenomas, VEGF-A was not detectable in 5 out of 39 cases (13%), which is in agreement with a previous study in which 8% of the adenomas studied did not secrete VEGF-A in vitro (Lohrer et al 2001; Table 1).…”

“…In normal pituitary, both folliculostellate (FS) cells and endocrine cells were identified as sources of VEGF (Gospodarowicz et al 1989, Jabbour et al 1997, Fan & Iseki 1998, Gloddek et al 1999, Renner et al 2002, Cristina et al 2005, Nakakura et al 2006. In human pituitary adenomas, tumour cells synthesize and release VEGF-A (Lloyd et al 1999, Iuchi et al 2000, Lohrer et al 2001, McCabe et al 2002, Fukui et al 2003, Viacava et al 2003, Onofri et al 2004.…”

Differential Involvement of D1 and D2 Dopamine Receptors in L-DOPA-Induced Angiogenic Activity in a Rat Model of Parkinson's Disease

“…This effect is strongly correlated to angiogenesis (Lu et al, 2008;Ristori et al, 2008). The anti-mitotic action of D2 receptors on endothelial cells (Basu et al, 2001;Cristina et al, 2005) may explain the potentiating effect of low-dose eticlopride on L-DOPAinduced angiogenesis in this study. High-dose eticlopride did not, however, produce a more marked potentiation.…”

“…Indeed, DA inhibits endothelial proliferation and vessel growth through activation of D2 receptors (Basu et al, 2001;Cristina et al, 2005;Gomez et al, 2006;Sarkar et al, 2004). By contrast, in vitro and in vivo studies have shown that D1 receptor activation stimulates adenylate cyclase and cyclic AMP (cAMP) production in endothelial cells (Bacic et al, 1991).…”

The effects of ergot and non-ergot-derived dopamine agonists in an experimental mouse model of endometriosis

“…On the contrary, we believe that DRD2 is expressed by cells of an immune origin -perhaps macrophages -and that these cells are probably responsible for inducing, in an autocrine and/or paracrine fashion, a decreased expression of VEGF when activated by DRD2-A. In this context, previous work by our group (Ferrero et al 2010) and other authors (Cristina et al 2005) has shown that cell populations expressing DRD2 (granulosa or pituitary cells) inhibit the secretion of VEGF in either an autocrine or a paracrine fashion. In this regard, it is known that most immune cell subtypes express DRD2 (McKenna et al 2002), and among them, macrophages are known to express large amounts of VEGF (Nap et al 2004).…”