Glucocorticoids induce retinal toxicity through mechanismsmainly associated with paraptosis

[摘要] Purpose: Corticosteroids have recorded beneficial clinicaleffects and are widely used in medicine. In ophthalmology, besides theirtreatment benefits, side effects, including ocular toxicity have beenobserved especially when intraocular delivery is used. The mechanism ofthese toxic events remains, however, poorly understood. In our presentstudy, we investigated the mechanisms and potential pathways ofcorticosteroid-induced retinal cell death.Methods: Rats were sacrificed 24 h and 8 days after anintravitreous injection of 1 μl (40 μg) of Kenacort Retard®.The eyes were processed for ultra structure analysis and detection ofactivated caspase-3, cytochrome-C, apoptosis-inducing factor (AIF),LEI-L-Dnase II, terminal transferase dUTP nick end labeling (TUNEL), andmicrotubule-associated protein 1-light chain 3 (MAP-LC3). In vitro, ratretinal pigment epithelial cells (RPE), retinal Müller glial cells(RMG) and human ARPE-19 cells were treated with triamcinolone acetonide(TA) or other glucocorticoids. Cell viability was quantified by3-(4,5-dimethylthiazol-2-yl)-2,5 phenyltetrazolium bromide test (MTT)assay and cell counts. Nuclei staining, TUNEL assay, annexin-V binding,activated caspase-3 and lactate dehydrogenase (LDH) productioncharacterized cell death. Localization of cytochrome-C, AIF, LEI-andL-Dnase II, and staining with MAP-LC3 or monodansylcadaverine were alsocarried out. Finally, ARPE-19 cells transfected with AIP-1/Alix wereexposed to TA.Results: In vitro incubation of retinal cell in the presenceof corticosteroids induced a specific and dose-dependent reduction ofcell viability. These toxic events were not associated with theanti-inflammatory activity of these compounds but depended on the hydrosolubility of their formulation. Before cell death, extensivecytoplasmic vacuolization was observed in the retinal pigment epithelial(RPE) cells in vivo and in vitro. The cells however, did not show knowncaspase-dependent or caspase-independent apoptotic reactions. Theseintracellular vacuoles were negative for MAP-LC3 but some stainedpositive for monodansylcadaverine. Furthermore, over expression ofAIP-1/Alix inhibited RPE cell death.Conclusions: These observations suggest thatcorticosteroid-induced retinal cell death may be carried out mainlythrough a paraptosis pathway.

[学科分类] 生物化学/生物物理