TNF-α plays a critical role in cigarette smoke-induced epithelial-mesenchymal transition of retinal pigment epithelial cells in proliferative vitreoretinopathy

Abstract

Purpose : Proliferative vitreoretinopathy (PVR) is characterized by the growth and contraction of cellular membranes within the vitreous cavity and both surfaces of the retina. Two pathologic processes implicated in PVR are epithelial-mesenchymal transition (EMT) of retinal pigment epithelial cells (RPE) and inflammation. Cigarette smoke has been associated with higher rates of PVR and is the only modifiable risk factor, although the mechanism is currently unclear. The purpose of this study was to investigate the role of EMT and inflammation pathways in RPE cells exposed to cigarette smoke in vitro and in a mouse model of PVR.

Methods : Human ARPE-19 cells were treated with varying concentrations of cigarette smoke extract (CSE) ranging from 0% to 1%. Cells were harvested after 4 and 24hrs and analyzed by quantitative PCR (qPCR) and Western blotting for known markers of EMT and inflammation. All experiments were replicated 2-3 times, with similar findings. For in vivo studies, we intravitreously injected ARPE-19 cells exposed to 0% and 0.5% CSE and PVR development was monitored over time by optical imaging (n=17). T test and Chi-Squared analyses were performed for in vitro and in vivo, respectively.

Results : ARPE-19 cells treated with 0.5% CSE for 4h showed significant increase in expression of the inflammation marker TNF-α and early EMT marker, Snail, expression by qPCR analysis (9-fold; p<0.01 and 4-fold; p<0.01, respectively). By 24h, both TNF-α and downstream inflammatory marker IL-8 were significantly upregulated (7-fold; p<0.05 and 9–fold; p<0.01 respectively), and Snail was significantly increased (50-fold; p<0.01). Western blot analysis was consistent with qPCR results, showing elevated EMT markers, Snail and α-SMA, in the 0.5% CSE treated cells (7-fold and 5-fold, respectively) by 24 hours.

In our in vivo studies, 7/8 mice that received an injection with CSE-exposed RPE cells developed Grade 5 PVR or worse at 3 weeks, compared to control mice (2/9 mice) (p<0.05).

Conclusions : We demonstrate that RPE cells exposed to CSE exhibit an acute upregulation of the inflammatory marker TNF-α as well as subsequent activation of pro-inflammatory cytokines and early EMT markers, suggesting that TNF-α may play a crucial role in cigarette smoke-induced EMT of RPE cells in PVR.

This is a 2020 ARVO Annual Meeting abstract.