Prolactin contributes to the regulation of retinal pigment epithelial cell survival and monolayer resistance

Abstract

Purpose: We recently showed that the hormone prolactin (PRL) acts as an endogenous retinal trophic factor able to limit retinal degeneration. In addition to regulating glial-neuronal cell interactions in the retina, we postulated thatPRL targets retinal pigment epithelial (RPE) cells.

Methods: The presence of PRL receptor in the RPE of male albino rats was determined by in situ hybridization and immunochemistry, and in human ARPE-19 cell cultures by Western blot. The viability of ARPE-19 cell cultures was examined by MTT assay, and ARPE-19 cell monolayers were evaluated for transepithelial electrical resistance. A competitive PRL receptor antagonist was used to ensure the specificity of recombinant human PRL actions.

Results: RPE in transverse sections of rat retinas was positive for PRL receptor mRNA and protein. PRL receptor was also detected in flat mounts of rat RPE and in ARPE-19 cell monolayers. A 48-hour PRL treatment increased the viability of ARPE-19 cell cultures in a dose-dependent manner, with a maximal effect dose of 100 pM (2.3 ng/ml). The PRL receptor antagonist increasingly reduced ARPE-19 cell viability at 10 nM, 100 nM and 1 µM. The effect of 10 nM PRL receptor antagonist was prevented by adding 100 pM rhPRL. Moreover, PRL induced a transient increase in the resistance of ARPE-19 monolayers that peaked at 30 minutes.

Conclusions: These findings show that the PRL receptor is present in the RPE, and that the stimulation of PRL signaling may help to regulate RPE permeability and survival.

Keywords: 449 cell survival • 543 growth factors/growth factor receptors • 715 signal transduction: pharmacology/physiology