The effect of differentiation, polarization and MOX-LDL treatment on the expression level of RPS15A and RPL13A in THP-1 MONOCYTES and macrophages

Abstract

Background: Atherosclerosis is a chronic disease, serving as the primary cause behind cardiovascular diseases (CVDs). Monocytes are the first cells to reach the site of inflammation in atherosclerosis. Subsequently, they differentiate into M0 macrophages via macrophage colony stimulating factor (M-CSF). These macrophages can polarize into either the M1 pro-inflammatory or the M2 anti-inflammatory phenotype. Both phenotypes play critical roles in disease pathogenesis and have the ability to transform into foam cells once they engulf the modified LDL particles. Meanwhile, it was recently reported that some ribosomal proteins exhibit extra ribosomal functions and may be implicated in the pathogenesis of various diseases including CVDs. Aim: Our project aimed at investigating the effect of monocyte differentiation and polarization on the expression of RPS15A and RPL13A, as well as the impact of Mox-LDL on these proteins in THP-1 monocytes and M0, M1, and M2 macrophages. Methods: Using the THP-1 cell model, monocytes were differentiated into M0 macrophages, which were then polarized into M1 and M2 macrophages. Monocytes were treated with PMA (100 µM) for 48 hours to differentiate them into M0 macrophages. Following differentiation, we polarized M0 macrophages to the M1 phenotype by treating them with IFN-γ (20 ng/ml) and LPS (100 ng/ml) and into the M2 phenotype by treating them with IL-13 (20 ng/ml) and IL-4 (20 ng/ml), both for 24 hours. To study oxidized LDL effects, the latter sets of cells were subjected to Mox-LDL (50 µg/ml) for 24 hours. Then, proteins were extracted from monocytes and all macrophage subsets, and their expression levels were assessed using western blot analysis. Results: RPS15A expression was significantly 0.384-fold lower in M0 macrophages than in monocytes and 0.289-fold and 0.189-fold lower in M1 and M2 macrophages respectively, compared to monocytes. Whereas RPL13A expression showed no significant difference among monocytes and all macrophage subsets. Additionally, no significant difference in RPS15A or RPL13A expression was observed between Mox-LDL treated and control groups in either monocytes or macrophages. Conclusion: In our model, monocyte differentiation and polarization appear to downregulate RPS15A expression, suggesting that RPS15A may play a role in macrophage-related inflammatory pathways. This project may have promising prospects for linking the latter ribosomal protein to atherogenic mechanisms that are mediated by macrophages during disease progression, paving the way for effective therapeutic approaches targeting atherosclerosis.