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Basal and apical regulation of VEGF-A and placenta growth factor in the RPE/choroid and primary RPE.

Klettner A, Kaya L, Flach J, Lassen J, Treumer F, Roider J - Mol. Vis. (2015)

Bottom Line: In the RPE/choroid, VEGF-A can initially be found on the apical and basal sides with significantly more pronounced secretion on the basal side.In the RPE cell culture, similar effects were found, with inhibition of NF-κB or SP-1 displaying a strong decrease in VEGF-A on both sides, and p38 inhibition displaying only an inhibitory effect on the basal side.In contrast, an apical effect of VEGFR-2 inhibition was not found.

View Article: PubMed Central - PubMed

Affiliation: University of Kiel, University Medical Center, Department of Ophthalmology, Kiel, Germany.

ABSTRACT

Purpose: Members of the vascular endothelial growth factor (VEGF) family are strongly involved in pathological processes in the retina, such as age-related macular degeneration and diabetic retinopathy. Cells of the retinal pigment epithelium (RPE) constitutively secrete VEGF-A, and the secretion of placental growth factor (PlGF) has also been described. RPE cells are strongly polarized cells with different secretome at the apical and basal side. In this study, we evaluated the basal and apical regulation of VEGF-A and PlGF secretion in RPE/choroid explants and primary RPE cells.

Methods: RPE/choroid tissue explants were prepared from porcine eyes and cultivated in modified Ussing chambers, separating apical (RPE) and basal (choroid) supernatant. Primary RPE cells were also prepared from porcine eyes and cultivated on Transwell plates. Explants and cells were treated with inhibitors for VEGFR-2 (SU1498), p38 (SB203580), and the transcription factors nuclear factor-kappa B (NF-κB) and SP-1 (mithramycin), respectively. VEGF-A and PlGF content was evaluated with enzyme-linked immunosorbent assay (ELISA). In addition, western blots were performed.

Results: In the RPE/choroid, VEGF-A can initially be found on the apical and basal sides with significantly more pronounced secretion on the basal side. VEGF-A secretion is differentially regulated on the apical and basal sides, with the inhibition of SP-1 and NF-κB showing strong effects apically and basally after 24 h and 48 h, the inhibition of p38 displaying its effect mainly on the basal side with some effect apically after 48 h, and the inhibition of VEGFR-2 reducing the secretion of VEGF only on the apical side at 24 h and 48 h. In the RPE cell culture, similar effects were found, with inhibition of NF-κB or SP-1 displaying a strong decrease in VEGF-A on both sides, and p38 inhibition displaying only an inhibitory effect on the basal side. In contrast, an apical effect of VEGFR-2 inhibition was not found. However, the western blot experiments exhibited a significant decrease in the VEGF-A protein under SU1498 treatment. In the RPE/choroid organ cultures, PlGF was initially found mainly on the basal site with only minute amounts of PlGF found apically. NF-κB and SP-1 were strongly involved in PlGF regulation apically and basally, while VEGFR2 and to a lesser degree p38 displayed some regulation at the basal site. In the primary RPE cell culture, PlGF was not found on the apical or basal side.

Conclusions: VEGF-A and PlGF were constitutively secreted and regulated by the RPE/choroid complex, with PlGF secreted mainly by the choroid. Although the transcription factors NF-κB and SP-1 were involved in apical and basal regulation of both growth factors, VEGFR-2 displayed a strong polarity, with regulation of apical VEGF-A and basal PlGF secretion.

No MeSH data available.


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Calcein stains of organ cultures after treatment with the indicated inhibitor.
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f2: Calcein stains of organ cultures after treatment with the indicated inhibitor.

Mentions: We have previously shown that the transcription factors NF-κB and SP-1 are involved in the regulation of constitutive VEGF-A secretion in the RPE/choroid. Moreover, autocrine VEGFR-2 regulation was found, in addition to the involvement of p38 that was shown to be independent of NF-κB [9,12]. We investigated the effect of the inhibition of the respective factor on the apical and basal secretion of VEGF-A. The inhibitors were previously shown to not exert toxicity on RPE cells or RPE organ explants in a perfusion culture [12]. Correspondingly, none of the tested inhibitors showed toxicity on the organ cultures cultivated in the Ussing chambers (Figure 2).


Basal and apical regulation of VEGF-A and placenta growth factor in the RPE/choroid and primary RPE.

Klettner A, Kaya L, Flach J, Lassen J, Treumer F, Roider J - Mol. Vis. (2015)

Calcein stains of organ cultures after treatment with the indicated inhibitor.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4499472&req=5

f2: Calcein stains of organ cultures after treatment with the indicated inhibitor.
Mentions: We have previously shown that the transcription factors NF-κB and SP-1 are involved in the regulation of constitutive VEGF-A secretion in the RPE/choroid. Moreover, autocrine VEGFR-2 regulation was found, in addition to the involvement of p38 that was shown to be independent of NF-κB [9,12]. We investigated the effect of the inhibition of the respective factor on the apical and basal secretion of VEGF-A. The inhibitors were previously shown to not exert toxicity on RPE cells or RPE organ explants in a perfusion culture [12]. Correspondingly, none of the tested inhibitors showed toxicity on the organ cultures cultivated in the Ussing chambers (Figure 2).

Bottom Line: In the RPE/choroid, VEGF-A can initially be found on the apical and basal sides with significantly more pronounced secretion on the basal side.In the RPE cell culture, similar effects were found, with inhibition of NF-κB or SP-1 displaying a strong decrease in VEGF-A on both sides, and p38 inhibition displaying only an inhibitory effect on the basal side.In contrast, an apical effect of VEGFR-2 inhibition was not found.

View Article: PubMed Central - PubMed

Affiliation: University of Kiel, University Medical Center, Department of Ophthalmology, Kiel, Germany.

ABSTRACT

Purpose: Members of the vascular endothelial growth factor (VEGF) family are strongly involved in pathological processes in the retina, such as age-related macular degeneration and diabetic retinopathy. Cells of the retinal pigment epithelium (RPE) constitutively secrete VEGF-A, and the secretion of placental growth factor (PlGF) has also been described. RPE cells are strongly polarized cells with different secretome at the apical and basal side. In this study, we evaluated the basal and apical regulation of VEGF-A and PlGF secretion in RPE/choroid explants and primary RPE cells.

Methods: RPE/choroid tissue explants were prepared from porcine eyes and cultivated in modified Ussing chambers, separating apical (RPE) and basal (choroid) supernatant. Primary RPE cells were also prepared from porcine eyes and cultivated on Transwell plates. Explants and cells were treated with inhibitors for VEGFR-2 (SU1498), p38 (SB203580), and the transcription factors nuclear factor-kappa B (NF-κB) and SP-1 (mithramycin), respectively. VEGF-A and PlGF content was evaluated with enzyme-linked immunosorbent assay (ELISA). In addition, western blots were performed.

Results: In the RPE/choroid, VEGF-A can initially be found on the apical and basal sides with significantly more pronounced secretion on the basal side. VEGF-A secretion is differentially regulated on the apical and basal sides, with the inhibition of SP-1 and NF-κB showing strong effects apically and basally after 24 h and 48 h, the inhibition of p38 displaying its effect mainly on the basal side with some effect apically after 48 h, and the inhibition of VEGFR-2 reducing the secretion of VEGF only on the apical side at 24 h and 48 h. In the RPE cell culture, similar effects were found, with inhibition of NF-κB or SP-1 displaying a strong decrease in VEGF-A on both sides, and p38 inhibition displaying only an inhibitory effect on the basal side. In contrast, an apical effect of VEGFR-2 inhibition was not found. However, the western blot experiments exhibited a significant decrease in the VEGF-A protein under SU1498 treatment. In the RPE/choroid organ cultures, PlGF was initially found mainly on the basal site with only minute amounts of PlGF found apically. NF-κB and SP-1 were strongly involved in PlGF regulation apically and basally, while VEGFR2 and to a lesser degree p38 displayed some regulation at the basal site. In the primary RPE cell culture, PlGF was not found on the apical or basal side.

Conclusions: VEGF-A and PlGF were constitutively secreted and regulated by the RPE/choroid complex, with PlGF secreted mainly by the choroid. Although the transcription factors NF-κB and SP-1 were involved in apical and basal regulation of both growth factors, VEGFR-2 displayed a strong polarity, with regulation of apical VEGF-A and basal PlGF secretion.

No MeSH data available.


Related in: MedlinePlus