Reduced CARS2 expression elicits a low-grade pro-inflammatory signature in THP-1 macrophages

Genome-wide association studies have linked CARS2 locus, encoding the mitochondrial cysteinyl aminoacyl-tRNA synthetase CARS2, to coronary artery disease. Moreover, we previously demonstrated that CARS2 suppression was associated with a pro-inflammatory expression profile in cell models. However, the mechanisms were largely unexplored. Here, we further examine the changes associated with CARS2 suppression through bioinformatic and experimental approaches. Analysis of transcriptomic data from CARS2-suppressed cells revealed the prominent establishment of an interferon-like response in unpolarized THP-1 macrophages, as well as possible NF-ΚB activation. This was not accompanied by significant activation of STAT1 or NF-ΚB phosphorylation, indicative of interferon pathway activation and NF-ΚB activity, respectively. Rather, an NF-ΚB activity reporter THP-1 model revealed that NF-ΚB activation was modestly diminished in CARS2-suppressed cells. Furthermore, suppression of CARS2, or a YARS2 control, similarly reduced radical oxygen species levels without affecting mitochondrial content or membrane potential. However, YARS2 suppression was not pro-inflammatory, suggesting that reduced ROS levels are insufficient to explain the CARS2 effect. Finally, reduced CARS2 levels did not alter the abundance of respiratory complexes or mitochondrial function. These results argue for an anti-inflammatory contribution of CARS2 in THP-1-derived macrophages, which extends beyond its canonical mitochondrial role.