Fig. 7: Effect of palmitic acid on human macrophages.

a, Lipidomic analysis of conditioned media from PC3 prostate cancer cells. Results are expressed as the percentage of each fatty acid relative to the total fatty acids detected (n = 4). b,c, Luciferase reporter gene assay. Experimental scheme (b). Cells were transfected with 20 ng per well of plasmids encoding an olfactory receptor, 5 ng per well of RTP1S, 10 ng per well of CRE–luciferase and 5 ng per well of pRL-SV40. Twenty-four hours later, cells were stimulated by incubation with 50 μM palmitic acid, sodium acetate or sodium propionate. Four hours after stimulation, luminescence was measured. Bar plot showing all luminescence values divided by Renilla luciferase activity to control for transfection efficiency in a given well (c). Each comparison was performed in three technical triplicates (n = 6). d–f, Ca²⁺ flux in primary macrophages in the absence or presence of partial genetic deletion of OR51E2-KO treated with palmitic acid (100 μM) (Ctrl n = 5, siRNA n = 6) (d), acetate (Ctrl n = 5, siRNA n = 7) (e) or propionate (Ctrl n = 4, siRNA n = 4) (f). g, Immunofluorescence showing palmitic acid (green) and OR51E2 (red) on primary macrophages in the presence or absence of RNA KO of OR51E2. Palmitic acid was administered to the cells for 10 min or 1 h before quantification. h, Results are expressed as fluorescence intensity per cell (Ctrl n = 5, siRNA 10 min n = 6, siRNA 1 h n = 5). i, Expression of CD206 and HLA-DR by FACS on wild-type or OR52E1-KO THP1 cells. Cells were conditioned with either PC3-conditioned media or palmitic acid (100 µM) (CD206: Untr. or siRNA n = 3, CM-tr. or siRNA + CM-tr. n = 3; palmitic-tr. or siRNA + palmitic-tr. n = 4 or 6; HLA-DR: Untr. or siRNA n = 3, CM-tr. or siRNA + CM-tr. n = 3; palmitic-tr. or siRNA + palmitic-tr. n = 4). Statistical analyses were performed using two-tailed unpaired Student’s t-test. Values are presented as the mean ± s.e.m. Schematic in b created using BioRender.com.