Inhibition of Sodium Iodate-Induced Apoptosis in Human RPE by the Stearoyl Coenzyme A Desaturase Inhibitor Sterculic acid

Abstract

Purpose : Retinal pigment epithelium (RPE) cell loss or dysfunction caused by a variety of stressors is a factor in the onset of age-related macular degeneration (AMD). Sodium iodate (NaIO₃), an oxidizing agent causing selective RPE cell damage, is used in pre-clinical models of RPE damage. NaIO₃ damage to RPE mimics features of AMD and geographic atrophy, due to reactive oxygen species (ROS) generation by NaIO₃. We have found that fenretinide-induced apoptosis in ARPE-19 cells decreases stearoyl-CoA desaturase (SCD), important in regulating cellular functions by maintaining saturated/unsaturated fatty acid equilibrium. Here, we investigate the effect of the SCD inhibitor sterculic acid (SA) on NaIO₃-induced apoptosis in RPE cells.

Methods : Human RPE cells (ARPE-19) grown on tissue culture plates in MEM alpha medium with 1% FBS and antibiotic were differentiated for 4 weeks; media exchange was performed twice a week. Differentiated cells were treated with 5 mM NaIO₃ in the presence or absence of 10 mM SA in a serum-free medium for 20 h. The progression of apoptosis was followed by the extracellular release of LDH. Total RNA fractions were used to analyze mRNA and lncRNA expression using cell death pathway finder, inflammatory response, and autoimmunity PCR arrays by real-time RT-PCR.

Results : NaIO₃ induced apoptosis in ARPE-19 cells in a dose- and time-dependent manner as indicated by LDH release in the medium. Treatment with 10 mM SA blocked NaIO₃-induced apoptosis by ~90%. Of 98 lncRNAs assayed, 12 lncRNAs were upregulated, and 28 were downregulated, while out of 98 mRNAs assayed, 10 mRNAs were upregulated and 48 were downregulated, with a fold change of 2 or more, in cells treated with NaIO₃. NaIO₃ treatment increased GADD45a mRNA and SLC7A11-AS1 lncRNA expression by ~22- and ~34-fold, respectively. This increase was blocked by SA. Increase in expression, in response to NaIO₃ treatment, of HO-1, a stress response protein, and BCL2L11, a regulator of apoptosis via the intrinsic mitochondrial pathway, were also blocked by SA treatment.

Conclusions : Our results show that SA treatment effectively blocked NaIO₃-induced apoptosis in human RPE cells. The mode of action of this SCD inhibitor appears to be at the level of ROS generation. Thus, SA may be an effective agent in regulating the response of RPE to oxidative stress.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.