Purpose. Dysfunction of the mitochondria and cellular antioxidant systems are linked to aging and neurodegenerative diseases. In the eye, the RPE is exposed to a highly oxidative environment, partly due to elevated oxygen partial pressure from the choriocapillaris and to digestion of polyunsaturated fatty acid laden photoreceptor outer segments. Here we examined that PEDF protects mitochondrial function of RPE cells in the oxidative stress environment. 

Methods.  Primary cultured RPE cells were grown to confluence and treated with PEDF and H₂O₂ for phase-contrast microscopy, electron microscopy, immunocytochemistry, LDH assay, RT- and real-time PCR. ROS, cytoplasmic Ca²⁺ [Ca²⁺]_c and mitochondrial Ca²⁺ [Ca²⁺]_m levels were also measured using H₂-DCF-DA, fluo-3/AM and Rhod-2/AM, respectively, ATP levels by a luciferin/luciferase-based assay, and mitochondrial membrane potential (ΔΨm) by JC-1 fluorescence.

Results. We observed decaying features in the mitochondria of RPE cells including matrix abnormalities, elongation, loss of cristae and disruptions in membrane integrity after H₂O₂ treatment. There was also further lower levels of ATP and [Ca²⁺]_c, higher ROS and [Ca²⁺]_m, decreased ΔΨm after H₂O₂ treatment, and greater susceptibility to H₂O₂ toxicity in aged RPE cells. PEDF can protect the cristae and the integrity of mitochondrial membrane, increase levels of ATP and ΔΨm, lower ROS, [Ca²⁺]_c  and [Ca²⁺]_m in RPE cells induced by H₂O₂. In addition there was increased expression of mitochondrial fission genes, Fis1, MTP18 and decreased expression of mitochondrial fusion genes, Mfn1 and Mfn2 in RPE cells after PEDF treatment.