Prolactin Protects Photoreceptors From Light Damage in vivo

Abstract

Purpose:: Prolactin (PRL) is a survival factor for various cell types, and both PRL and the PRL receptor (PRLR) are expressed in retinal tissue. Here, we determined whether PRL exhibits neuroprotective activity in vivo for photoreceptor cells.

Methods:: Wistar rats were injected intravitreally with 1 µg of PRL in 2 µl of phosphate-buffered saline (PBS) or subjected to endogenous hyperprolactinemia induced by pituitary grafts placed under the kidney capsule for 15 days. Animals were then exposed to white light (1200 lux) for 48 hours. DNA fragmentation evaluated by the TUNEL and the ELISA methods measured apoptosis of photoreceptors.

Results:: Intravitreal injection of PRL or chronic exposure to increased circulating levels of PRL (18.4 ± 0.8 vs. 12.9 ± 1.0 ng/ml for the grafted and control rats, respectively) resulted in a 6- and 3-fold inhibition of photoreceptor cell apoptosis in the retina of light-damaged rats as determined by TUNEL and ELISA, respectively.

Conclusions:: Intraocular and systemic PRL significantly increase photoreceptor cell survival following excessive light exposure. The mechanism(s) underlying this protection are under current investigation and may lead to the development of therapeutic strategies to prevent and treat degenerative diseases of the retina

Keywords: apoptosis/cell death • neuroprotection • photoreceptors