Abstract
BackgroundcGMP-degrading phosphodiesterase 6 (PDE6) mutations cause around 4 to 5% of retinitis pigmentosa (RP), a rare form of retinal dystrophy. Growing evidence suggests that inflammation is involved in the progression of RP. The aims of this study were to corroborate the presence of high TNFα concentration in the eyes of RP patients and to evaluate whether the blockade of TNFα with Infliximab, a monoclonal anti-TNFα antibody, prevented retinal degeneration induced by PDE6 inhibition in cultures of porcine retina.MethodsAqueous humor from 30 patients with RP and 13 healthy controls were used to quantify the inflammatory mediators IL-6, TNFα, IL-1β, IL-10 by a multiplex enzyme-linked immunosorbent assay (ELISA) system. Retinal explants from pig were exposed to Zaprinast, a PDE6 inhibitor, for 24 hours in the absence or the presence of Infliximab. Cell death was evaluated by TUNEL assay. The number and distribution of caspase-3 positive cells, indirect poly(ADP)ribose polymerase (PARP) activation and glial fibrillary acidic protein (GFAP) content were visualized by immunolabeling. Antioxidant total capacity, nitrites and thiobarbituric acid reactive substances (TBARS) formation were determined to evaluate antioxidant-oxidant status.ResultsIL-6 and TNFα concentrations were higher in the aqueous humor of RP patients than in controls. Infliximab prevented retinal degeneration, as judging by the reduced presence of TUNEL-positive cells, the reduction of caspase-3 activation and also reduction of glial activation, in an ex vivo model of porcine retina. Additionally, Infliximab partially reduced oxidative stress in retinal explants exposed to Zaprinast.ConclusionsInflammatory mediators IL-6 and TNFα were elevated in the aqueous humor of RP patients corroborating previous studies suggesting sustained chronic inflammation. Our study suggests that TNFα is playing an important role in cell death in an ex vivo model of retinal degeneration by activating different cell pathways at different cell layers of the retina that should be further studied.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-014-0172-9) contains supplementary material, which is available to authorized users.
Highlights
CGMP-degrading phosphodiesterase 6 (PDE6) mutations cause around 4 to 5% of retinitis pigmentosa (RP), a rare form of retinal dystrophy
Increased levels of tumor necrosis factor alpha (TNFα) and IL-6 in aqueous humor of RP patients We performed a multiplex enzyme-linked immunosorbent assay (ELISA) to determine the concentration of TNFα, IL-6, IL-1β and IL-10 in aqueous humor of RP patients
We performed a Multivariate analysis of covariance (MANCOVA) with the results of TNFα and IL-6 as dependent variables while disease, age and gender were taken as predictive variables
Summary
CGMP-degrading phosphodiesterase 6 (PDE6) mutations cause around 4 to 5% of retinitis pigmentosa (RP), a rare form of retinal dystrophy. RP is a genetic disease, increasing evidence in patients and animal models suggests that oxidative stress and inflammation, especially TNFα, contribute to its pathogenesis, independently of the genes mutated [8,9,10]. TNFα mediates a broad range of cellular activities, including proliferation, survival, differentiation, inflammation and cell death. TNFα binding to cell surface receptors such as TNFR1 mediates activation of initiator caspases (caspase-8, caspase-10) and triggers cleavage of effector caspases (extrinsic pathway of cell death) [21]. The poly(ADP-ribose) polymerase (PARP) pathway can activate this mode of programmed necrosis. PARP-1 activation in response to excessive DNA damage results in the massive synthesis of poly(ADP-ribose) polymers (PAR), NAD+ depletion and subsequent release of apoptosis inducing factor (AIF) from mitochondria, which translocates to the nucleus where it forms an active DNA-degrading complex (caspase-independent pathway). The PARP pathway has been considered as an integral part of TNF-induced necroptosis; it has been recently described that both pathways represent distinct and independent routes to programmed necrosis [22]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
