Figure 8. The anti-inflammatory effects of OTC are not solely dependent upon GPR109A. Mouse primary retinal pigment epithelial (mRPE) cells were prepared from Gpr109a^+/+ (wild-type, WT) and Gpr109a^-/- mouse retinas and exposed to tumor necrosis factor-α (TNF-α; 10 ng/ml; 24 h incubation) in the presence or absence of L-2-oxothiazolidine-4-carboxylic acid (OTC; 0.5 mM) or nicotinic acid (NA; 1 mM; positive control). Quantitative polymerase chain reaction (qPCR) analysis of (A) interleukin-6 (IL-6) and (B) chemokine (C-C) motif ligand 2 (Ccl2) mRNA expression. Cell culture medium was then collected and used for enzyme-linked immunosorbent assay (ELISA) analysis of (C) interleukin-6 (IL-6) and (D) Ccl2 protein. *p<0.01 compared to respective WT or Gpr109a^−/− untreated, control cells; **p<0.01 compared to respective TNF-α-treated WT or Gpr109a^−/− cells.