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Chieh-Lin (Stanley) Wu, V. Adrian Cioanca, Ling Zhu, Yingying Chen, Riccardo Carlo Natoli, R. Max Conway, Michele C Madigan; Does bright light exposure affect in vitro choroid melanoma viability and secretion of pro-inflammatory chemokines?. Invest. Ophthalmol. Vis. Sci. 2021;62(8):2865.
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Cumulative UV exposure is significant in skin melanoma, and implicated in primary iris melanoma. UV, absorbed by the cornea, iris, lens, and vitreous, does not reach the posterior eye however visible (white) light radiates the retina, underlying retinal pigmented epithelium (RPE), and choroid. The effects of visible light exposure on the choroidal microenvironment and potential roles in choroidal melanoma progression are unknown. This preliminary study investigated if acute light exposure affected viability and secretion of pro-inflammatory CCL2 and IL8 (involved in macrophage and neutrophil migration) in human choroidal melanoma cells.
Choroidal melanoma cells were grown in RPMI with FBS, L-glutamine and sodium pyruvate (MP38 and MP46: RPMI+20% FBS; 92.1: RPMI+10% FBS). ARPE19 cells (DMEM+10% FBS, L-glutamine, and +/- pyruvate) were used as controls; RPE cells in vivo normally absorb abundant visible light. Cells were grown in 96 well black plates (8000 cells/well) (n=5 per cell line; in triplicate) for 18hrs, then fresh medium (with 1% FBS) for 16 hours. Cells were then exposed to 32,000 lux light (LED, λ: 400-700nm) for 4 hours (37°C); unexposed control cells were grown in parallel conditions. Viability of light-exposed and control cells was measured with alamarBlue. Conditioned medium (light-exposed and control) was assessed with ELISA for pro-inflammatory cytokines, CCL2 and IL8.
Viability was reduced 10% to 15% immediately after light exposure for 92.1 and MP46 cells (p<0.05; t-test) but not MP38 cells (p>0.05). Surprisingly, ARPE19 cells showed dramatic cell death (~100%) after light exposure, that was mitigated by sodium pyruvate (110mg/ml). Secretion of CCL2 and IL8 was not induced following light exposure for any cell lines (light and control: ~20-100 pg/ml).
Acute light exposure reduced viability of MP46 and 92.1 melanoma cells but not MP38 cells, possibly due to melanin levels (MP38>MP46 and 92.1). No increase in CCL2 and IL8 secretion was noted following light exposure for melanoma cells, however, cumulative effects of light exposure, resembling real-life, remain to be clarified. Incidental light-induced ARPE19 cell death, ameliorated with sodium pyruvate, indicates effects on metabolism and reduced oxidative stress, and will be studied further.
This is a 2021 ARVO Annual Meeting abstract.
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