Circadian variations in the expression of estrogen receptor alfa in retina of viscacha

Abstract

In some species the presence of estrogen receptors α (ERα) has been demonstrated in retina. ERα are involved in neuroprotectivefunctions through their ability to regulate apoptosis, autophagy and antioxidant processes. Morphological variations in the retinallayers of viscacha have been demonstrated in response to changes in ambiental lighting. The objective of our work was to study theexpression of ERα in retina according to the morphological variations described previously. Retinas of adult male viscachas(Lagostomus maximus maximus) were obtained at 08:00, 16:00, and 24:00 h (n = 4 for each group). They were processed for lightmicroscopy and histological sections were made for the immunohistochemistry with the primary antibody anti-ERα (MC20): sc-542.The visualization of reaction was performed using an amplified biotin-streptavidin system (DAB chromogen). The immunoreactive (-ir) cells were quantified by image analysis and the number cell was expressed by microscopic field (cell/field). The data wasstatistically analyzed. In retinas from viscachas sacrificed at 08:00 h, intense nuclear immunostaining was observed in cells of theinner nuclear layer (INL) and in retinal ganglion cells (RGC). At 16:00 h, the ERα were not expressed in the retinal layers. However,in samples obtained at 24:00 h was observed nuclear labeling less intense in the INL and RGC. The morphometrical study revealedthat the number ERα-ir cells in the INL was significantly increased at 08:00 h (15.52 ± 2.90 cell/field) compared to the correspondingvalues at 24:00 h (4.45 ± 0.92 cell/field, p < 0.05). In addition, the number of RGC that express ERα were higher at 8:00 h (0.96 ±0.25 cell/field) compared to those obtained at 24:00 h (0.20 ± 0.05 cell/field, p < 0.05). These results show that the expression of ERαis detected at 24:00 h when the photoreceptor layer (PL) thickness was maximal. The expression of ERα reaches a maximum at 8:00h when the thickness of the PL began to decrease and they are absent when the thickness of the PL was minimal. This suggests thatERα expressed in INL and RGC might be involved in processes that regulate autophagy and the daily photoreceptor renewal cyclethrough the specific connections established into the retinal layers. However, future studies will be necessary to elucidate the role ofERα in viscacha retina.