Ethylamine increases intracellular protein levels of CCL3L1 in THP‐1 cells

Abstract

Leukocytes secrete chemokine ligand 3‐like‐1 (CCL3L1) upon stimulation. CCL3L1 is a non‐allelic isoform of CCL3, and the most potent ligand of the macrophage receptor, CCR5. Since CCR5 is the primary co‐receptor for macrophage‐tropic HIV‐1, higher levels of CCL3L1 are associated with decreased susceptibility to M‐tropic HIV‐1. In a previous study, we showed an increase in CCL3L1 mRNA in PBMCs stimulated with ethylamine that were obtained from subjects that consumed L‐theanine for 12wk. The goal of this study was to determine if ethylamine (formed by kidney hydrolysis of L‐theanine) caused an increased expression in the protein CCL3L1 and/or a decrease in CCR5 expression. THP‐1 cells (6 × 10^5 cells/mL) were treated with 2 mM ethylamine for 48 hours. They were then stimulated with LPS (1 ug/mL) for 1 hour. Protein levels of CCL3L1 in the culture medium and cell pellet were measured by ELISA. Flow cytometry was used for CCR5 expression using a FITC‐conjugated, anti‐CCR5 antibody. Results showed significantly higher CCL3L1 protein levels in the cell pellets that received ethylamine treatment compared to vehicle‐treated cells. There was no significant difference in CCL3L1 in the culture medium. This suggests that the THP‐1 cell synthesizes CCL3L1 in response to ethylamine, but does not secrete it under these culture conditions. Funded by UF/IFAS Agricultural Experiment Station