Inflammatory Cytokines Protect Retinal Pigment Epithelial Cells from Oxidative Stress-Induced Death

Abstract

PurposeTo investigate the effects of inflammatory factors and oxidative stress on cell survival of the human retinal pigment epithelial (RPE) cell line, ARPE-19.MethodsConfluent RPE cells were treated with peripheral blood mononuclear cells-conditioned medium (PCM), H2O2, NaIO3, interferon (IFN)-γ, tumor necrosis factor (TNF)-α, or combinations of these. Cell viability was determined by viability assays and by light microscopy. Effector molecules of cell death were investigated by immunofluorescence microscopy and flow cytometry. Microarrays were performed to screen for differential expression of anti-oxidative enzymes, and protein expression was validated by immunoblotting.ResultsViability of RPE cells was reduced by exposure to inflammatory agents (PCM, IFNγ+/-TNFα) or to oxidative agents (H2O2 or NaIO3). Unexpectedly, cells treated with either H2O2 or NaIO3 were partially protected from cell death by the addition of PCM. This protection was conferred, at least in part, by IFNγ and TNFα. Cell death induced by H2O2 or NaIO3 was preceded by mitochondrial dysfunction and by p62 upregulation, both of which were attenuated by PCM and/or by IFNγ+TNFα. RPE cells co-cultured with activated T cells, or treated with cytokines showed increased expression of anti-oxidative genes, with upregulation of superoxide dismutase 2 protein following PCM treatment.ConclusionOxidative stress-induced cell death was reduced by concomitant inflammatory stress. This is likely due to the cytokine-mediated induction of the anti-oxidative stress response, upregulating protective anti-oxidant pathway(s). These findings suggest caution for the clinical use of anti-inflammatory agents in the management of immune-associated eye diseases such as age-related macular degeneration.

Anti-Vascular Endothelial Growth Factors Protect Retinal Pigment Epithelium Cells Against Oxidation by Modulating Nitric Oxide Release and Autophagy

“…Hence, previous data have shown a clear association between RPE health and compromised mitochondrial function. High numbers of mitochondria are present in metabolically active cells like the RPE while their number decreases with age, particularly in AMD [33-35]. Experimental findings have also shown a link between mitochondrial impairment and RPE degeneration, which would arise as a consequence of an in-balance of the cellular redox system.…”

Continuous exposure to non-lethal doses of sodium iodate induces retinal pigment epithelial cell dysfunction

“…Moreover, the increased expressions of inflammation-related proteins (complement factor C3 and calcium-independent phospholipase A2)252627, pro-angiogenic factor (IL-8)14, chemoattractant (stromal cell-derived factor-1)25, oxidative stress-related gene (heme oxygenase)26 as well as apoptotic marker (caspase-3)28 have been reported. Apart from induction of RPE cell death, sodium iodate would also cause mitochondrial dysfunction and impairment of glycolysis1629. In addition, disruption of blood-retina barrier has been indicated in sodium iodate-treated mice3031.…”

“…Besides, sodium iodate induces necrosis in primary mouse RPE cells with decreased expression of necrostatin-1 (Nec-1)15. In addition, acute sodium iodate-induced ARPE-19 cell death is associated with mitochondrial dysfunction and p62 upregulation16. While the acute effects of sodium iodate treatment on RPE cells are extensively studied, the effects of a prolonged exposure and the dosage effect of sodium iodate on culture of RPE cells have not been investigated yet.…”

A novel protective role for the innate immunity Toll-Like Receptor 3 (TLR3) in the retina via Stat3

“…A recent study demonstrated that inflammatory cytokines protect against oxidative stress induced degeneration of the RPE (Chen et al, 2013; Juel et al, 2013). TLR3 signaling within astrocytes leads to secretion of neuroprotective mediators and promotes tissue repair responses (Bsibsi et al, 2006).…”