Abstract
Purpose :
Orbital tissues have a proclivity to inflame, particularly in the context of systemic inflammation, with severe consequences that can include blindness. Building on embryological research (1), we hypothesized that retinoids, transcriptional regulators uniquely enriched in orbital tissues (2), may play an important role in the pro-inflammatory milieu. We tested whether retinoids can regulate cytokine expression de novo, focusing on IL-1B and CCL2/MCP1 because of their known roles in thyroid eye disease and other orbital inflammatory conditions.
1. Bohnsack et al., Dev Biol, 2013
2. Sires et al., Arch Oph, 2001
Methods :
Fibroblasts obtained from patients undergoing either orbital decompression (“thyroid eye disease”) or blepharoplasty (“normal”) were grown to confluence in primary tissue culture and then treated with combinations of all trans retinoic acid (ATRA) and 9-cis-RA (9CRA) at different concentrations. qRT-PCR was used to quantify expression of the cytokines CCL2 and IL-1B relative to the marker gene rps13.
Results :
Treatment with 1.0M ATRA resulted in a higher mean relative expression (vs. DMSO control treatment) for CCL2 (n=33, 4.98 vs. 1.01, p<0.0001), IL-1B (n=28, 8.01 vs. 1.03, p<0.0001). Treatment with 9CRA resulted in a dose-dependent increase in mean relative expression of CCL2 (n=8, 1.0M=2.76, 0.3M=3.86, 0.1M=3.08, 0.03M=1.54), IL-1B (n-8, 1.0M=3.02, 0.3M=3.26, 0.1M=1.86, 0.03M=1.42), with 0.3M 9CRA inducing the highest relative expression for each cytokine. Treatment with a combination of 1.0M ATRA and four concentrations of 9CRA resulted in a higher mean relative expression than 9CRA alone for CCL2 (n=8, 1M 9CRA=6.17, 0.3M 9CRA=5.79, 0.1M 9CRA=4.43, 0.03M 9CRA=6.52) and IL-1B (n=8, 1M 9CRA =5.46, 0.3M 9CRA =5.12, 0.1M 9CRA =3.68, 0.03M 9CRA=6.94).
Conclusions :
Our results reveal that the two retinoids tested are capable of inducing cytokine expression de novo, providing a preliminary explanation for the proclivity of orbital tissues to inflame. Importantly, the response to 9CRA was highly dose-dependent, with greater sensitivity in tissues from thyroid patients. The data suggest that there may be a synergistic effect of ATRA and 9CRA in inducing the expression of pro-inflammatory cytokines.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.