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Jiangyuan Gao, Aikun Wang, Jing Cui, Catherine Tsilfidis, Joanne Matsubara; XIAP Protects RPE Cells from Oligomeric Aβ1-40 Induced Cell Death. Invest. Ophthalmol. Vis. Sci. 2013;54(15):160.
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© ARVO (1962-2015); The Authors (2016-present)
Oligomeric Aβ1-40 (oAβ40) is a pathological drusen component that causes RPE dysfunction associated with AMD pathogenesis. Previously, we have reported that 0.3μM oAβ40 induced 43% cell loss in cultured RPE cells after 24 hour incubation. Since RPE cell death is the direct cause of geographic atrophy, it is crucial to find agents that can rescue RPE cells when threatened by endogenous pathological stimuli, for instance, oAβ40. The purpose of this study is to elucidate the role of X-linked inhibitor of apoptosis (XIAP), previously used to rescue photoreceptor cells, as a RPE cell survival factor when challenged by oAβ40 in vitro.
The full length, open-reading frame of human XIAP was cloned into a pcDNA3.1 vector. ARPE-19 cells transfected with either the XIAP or the control construct were subsequently stressed with oligomer solutions. The transfection efficiency was assured by qRT-PCR and western blot. The ARPE-19 cell viability at several oligomer concentrations and timepoints was measured by MTT assays. Paraffin sections from AMD and normal post-mortem donor eyes were probed with an XIAP antibody to evaluate changes of XIAP expression in AMD progression.
Preliminary findings suggest XIAP immunoreactivity was observed in RPE of AMD eyes and in young normal eyes without drusen deposits. The old normal eyes demonstrated less XIAP immunoreactivity than the other groups. In vitro, qRT-PCR showed a 371 fold increase of XIAP mRNA in XIAP-transfected cells, compared to cells transfected with the control plasmid and cells without transfection (p<0.001). Protein levels of XIAP were confirmed by western blot. Next, we challenged the three groups of cells with 0.03μM oAβ40, and demonstrated that the XIAP transfected ARPE-19 cells exhibited higher cell viability than control plasmid transfected cells at both 6 hours and 24 hours.
The current study reveals an intriguing facet of XIAP’s capacity against oAβ40’s cellular stressor effects on RPE cells. The increased level of XIAP renders the XIAP-transfected cells more resistant to oAβ40. Given oAβ40’s presence in drusen, it is possible that an anti-apoptotic mechanism, such as known for XIAP, may protect RPE from cellular insults in vivo. The merit of using XIAP as a therapeutic agent for AMD warrants further investigation.
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