Expression and production of pigment epithelium-derived factor (PEDF) and PEDF receptor variants from mammalian and bacterial cells

Rabbit model of oxidative stress-induced retinal degeneration

Retinitis pigmentosa (RP) is a disorder that results in the death of rod photoreceptors in the retina, caused by several different mutations. As rods are 95 % of the photoreceptors in the eye and consume the most oxygen, their death causes tissue hyperoxia resulting in oxidative stress in the retina. Oxidative stress is implicated in the pathogenesis of photoreceptor death in RP. Therefore, oxidative stress models are very relevant to identifying drugs to prevent photoreceptor death in RP. Rabbits are an excellent model to study retinal degeneration due to their large eyes and therefore larger subretinal and vitreous space, makes it easier for surgical and drug interventions techniques. Herein, we have created a rabbit model of oxidative stress-induced retinal degeneration using paraquat (PQ), a known oxidant. PQ causes oxidative stress in the retina, that results in functional and structural loss of photoreceptors. We also show that using an antioxidant PEDF[H105A], we were able to blunt the damage to photoreceptors caused by PQ. Therefore, this rabbit model of oxidative stress-induced retinal degeneration will serve as an excellent model to test a wide array of surgical and drug interventions techniques.

Pigment epithelium-derived factor is an interleukin-6 antagonist in the RPE: Insight of structure-function relationships

Retinal and choroidal inflammatory lesions increase the levels of the pro-inflammatory cytokine interleukin-6 (IL-6). Pigment epithelium-derived factor (PEDF) has anti-inflammatory properties, but it is not known if it can prevent the production of IL-6 by the retinal pigment epithelium. To investigate the anti-inflammatory effects of PEDF in the RPE, we used human ARPE-19 cells stimulated with human recombinant tumor necrosis factor-alpha (TNF-α) to induce overexpression of the IL6 gene. We found that the viability of ARPE-19 cells decreased by 22% with TNF-α at 10 ng/ml, being drastically decreased at ≥50 ng/ml. TNF-α at 5-100 ng/ml elevated the production and secretion of IL-6 protein, as measured by ELISA. To challenge the TNF-α-mediated stimulation of IL-6, we used recombinant human PEDF protein. PEDF at 100 nM recovered the TNF-α-mediated loss of cell viability and repressed IL-6 gene expression as determined by RT-PCR. PEDF at 10-100 nM attenuated the IL-6 protein secretion in a dose dependent fashion (IC50 = 65 nM), being abolished with 100 nM PEDF. To map the region that confers the IL-6 blocking effect to the PEDF polypeptide, we used chemically synthesized peptides designed from its biologically active domains, pro-death 34-mer, and pro-survival 44-mer and 17-mer (H105A), to challenge the IL-6 overproduction. The pro-survival peptides recovered the TNF-α-mediated cell viability loss, and inhibited IL-6 secretion, while the 34-mer did not have an effect, suggesting a role for the pro-survival domain in blocking TNF-α-mediated cell death and IL-6 stimulation. Our findings position PEDF as a novel antagonistic agent of IL-6 production in RPE cells, underscoring its use for the management of retinal disease-related inflammation.