Reactive oxygen species-dependent mitochondrial dynamics and autophagy confer protective effects in retinal pigment epithelial cells against sodium iodate-induced cell death

Abstract

Background Oxidative stress is a major factor in retinal pigment epithelium (RPE) cells injury that contributes to age-related macular degeneration (AMD). NaIO3 is an oxidative toxic agent and its selective RPE cell damage makes it as a reproducible model of AMD. Although NaIO3 is an oxidative stress inducer, the roles of ROS in NaIO3-elicited signaling pathways and cell viability have not been elucidated, and the effect of NaIO3 on autophagy in RPE cells remains elusive. Methods In human ARPE-19 cells, we used Annexin V/PI staining to determine cell viability, immunoblotting to determine protein expression and signaling cascades, confocal microscopy to determine mitochondrial dynamics and mitophagy, and Seahorse analysis to determine mitochondrial oxidative phosphorylation. Results We found that NaIO3 can dramatically induce cytosolic but not mitochondrial ROS production. NaIO3 can also activate ERK, p38, JNK and Akt, increase LC3II expression, induce Drp-1 phosphorylation and mitochondrial fission, but inhibit mitochondrial respiration. Confocal microscopic data indicated a synergism of NaIO3 and bafilomycin A1 on LC3 punctate formation, indicating the induction of autophagy. Using cytosolic ROS antioxidant NAC, we found that p38 and JNK are downstream signals of ROS and involve in NaIO3-induced cytotoxicity but not in mitochondrial dynamics, while ROS is also involved in LC3II expression. Unexpectedly NAC treatment upon NaIO3 stimulation leads to an enhancement of mitochondrial fragmentation and cell death. Moreover, inhibition of autophagy and Akt further enhances cell susceptibility to NaIO3. Conclusions We conclude that NaIO3-induced oxidative stress and cytosolic ROS production exert multiple signaling pathways that coordinate to control cell death in RPE cells. ROS-dependent p38 and JNK activation lead to cytotoxicity, while ROS-mediated autophagy and mitochondrial dynamic balance counteract the cell death mechanisms induced by NaIO3 in RPE cells.

Antioxidative Effects of Chrysoeriol via Activation of the Nrf2 Signaling Pathway and Modulation of Mitochondrial Function

“…The p38 mitogen-activated protein kinase (MAPK) activation is related to redox signaling transduction via stimulation of stress responses, including mitochondrial dysfunction [ 27 , 28 , 29 , 30 , 31 ]. Therefore, the protective antioxidant effect of chrysoeriol on the p38 MAPK pathway was determined in ARPE-19 cells.…”

Oxidative Stress-Induced Pentraxin 3 Expression Human Retinal Pigment Epithelial Cells Is Involved in the Pathogenesis of Age-Related Macular Degeneration

“…However, we have observed different expression levels of inflammatory cytokines, IL-6, IL-1β, and TNF-α, in the presence of NaIO 3 in PTX3 shRNA expressing ARPE-19 cells compared with control shRNA expressing ARPE-19 cells (Figure S3). In a recent study, they found that NaIO 3 can induce cytosolic ROS but not mitochondrial ROS production and activate ERK, p38, JNK, and Akt signaling pathway [26]. Especially, they described that cytosolic ROS-dependent p38 and JNK activation lead to cell death in NaIO 3 -treated ARPE-19 cells.…”

The Relevance of Oxidative Stress in the Pathogenesis and Therapy of Retinal Dystrophies

“…Autophagy is involved in a number of different processes in the retina participating in development and tissue remodeling and it is also implicated in photoreceptor cell death in response to calcium cytotoxicity, structural damage, and oxidative stress [35,47]. On the other hand, the aged retina is characterized by increased levels of reactive oxygen species (ROS), impaired autophagy, excessive energy consumption, and DNA damage, all of which contribute to the degeneration of RPE cells and link to AMD pathogenesis [48,49]. Besides, autophagy is not only linked to AMD but also to glaucoma, since dysregulation of autophagy can harm the outflow path of the trabecular meshwork, whereas promotion of autophagy via rapamycin treatment may have a cytoprotective effect upon oxidative stress [50].…”