کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
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6263297 | 1613854 | 2014 | 17 صفحه PDF | دانلود رایگان |
- ER-stress induced in retinas conventionally cultured in darkness.
- ER-stress markers increase following dim light illumination for 8Â h/day.
- Cyclic illumination induces autophagic processes as measured by LC3B-II increases.
- Cyclic illumination resulted in altered protein expression for autophagy inducers.
- Photoreceptors degenerate mainly by autophagy and ER-stress in illuminated explants.
The aim of this study was to investigate rod and cone photoreceptor degeneration in organotypic cultures of adult porcine retina. Our hypothesis was that the photoreceptors accumulate opsins, which, together with exposure to cyclic dim light illumination, induce autophagy and endoplasmic reticulum stress (ER-stress) to overcome damaging protein overload. For this purpose, retinas were cultured for 48Â h and 72Â h during which they were illuminated with dim light for 8Â h/day; specimens were analyzed by means of immunohistochemistry, Western blot, real-time polymerase chain reaction (PCR) and transmission electron microscopy. ER-stress and photoreceptor degeneration was observed in conventionally cultured retinas. The additional stress in the form of dim light illumination for 8Â h/day resulted in increased levels of the ER-stress markers GRP78/BiP and CHOP, as well as increased level of active caspase-12. Increased autophagic processes in cone and rod photoreceptors were detected by LC3B-II increases and occurrence of autophagosomes at the ultrastructural level. Illumination also resulted in altered protein expression for autophagy inducers such as p62 and Beclin-1. Moreover, there was a decrease in phosphorylated mammalian target of rapamycin (mTOR), which further indicate an increase of autophagy. Rod and cone photoreceptors in retinas from a diurnal animal that were exposed to dim light illumination in vitro displayed autophagy and ER-stress processes. As no alteration of rhodopsin mRNA was observed, autophagy and ER-stress are suggested to decrease rhodopsin protein at the posttranscriptional level.
Journal: Brain Research - Volume 1585, 17 October 2014, Pages 167-183