Abstract
Purpose :
Photoreceptor cell death due to extensive light exposure and induced oxidative-stress are associated with retinal degenerations. An associated dysregulation of the complement system amplifies the damaging effects, but the local and time-dependent progression of this mechanism is incompletely understood.
Methods :
To test complement involvement in light-induced photoreceptor degeneration (LD), Balb/c mice were treated with cool white light at an intensity of 5000 lux or 1000 lux, respectively. Protein expression levels and mRNA analyses of complement factors (CF) C3, C1s, CFB, MBL-A, MASP1, C4, C9 and CFP were determined 1-4 days (d) after light exposure. Histological analyses visualized apoptosis, microglia migration and deposition of the terminal complement complex. Systemic anaphylatoxin concentrations were determined using an ELISA.
Results :
LD was characterized by TUNEL-positive cells and microglia migration in the outer nuclear layer. Local CF expression revealed an early upregulation of mRNA at d 1-2 post treatment for C3, C1s, CFB, MASP1, C4, and C9 in the RPE/choroid. Intra-retinal mRNA expression for C3, C1s, CFB, MASP1 and C4 was increased at d 2-3 post LD. However, retinal mRNA for C9 and CFP was decreased following LD. This time-delayed pattern for CF mRNA expression in the retina and RPE/choroid after LD, was not observable on protein level. Western blots detected all tested CF in the RPE/choroid, whereas CFB and C4 were missing in the retina. A local regulation on protein level in the retina following LD was only observed for C3, which was early upregulated at d 1-3, but reduced at d 3-4 in the RPE/choroid. This correlated with C4 and C9 protein detection in the RPE/choroid, which showed also decreased signals. In contrast, C1s protein expression was increased after LD in the RPE/choroid. We did not observe a correlated change in systemic complement activation.
Conclusions :
LD in mice eyes is associated with local complement activity. We determined the time-dependent and local progression of complement regulation on mRNA and protein levels following LD. Knowing the relative time courses of local complement expression can help to elucidate novel therapeutic options in retinal degeneration indicating when the complement system has to be rebalanced.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.