Extracellular peroxiredoxin 5 exacerbates atherosclerosis via the TLR4/MyD88 pathway

Peroxiredoxin 5 (PRDX5), an atypical 2-Cys peroxiredoxin (PRDX), is known to regulate global oxidative stresses and inflammatory responses. Inflammation and oxidative stress are pivotal factors in the development of atherosclerosis, especially in the context of vascular endothelial dysfunction. However, effects of PRDX5 on atherosclerosis remain unclear. This study aimed to elucidate the role of PRDX5 in the pathogenesis of atherosclerosis.

For in vivo analysis, normal chow diet 60-week old Apolipoprotein E knockout (ApoE^-/-) and Prdx5^-/-; ApoE^-/- mice were used for the experiments. For in vitro analysis, human umbilical vein endothelial cells (HUVECs) were stimulated with oxidized LDL (oxLDL; 50 ng/ml) for 24hrs, following serum starvation by incubation with serum-free Endothelial Cell Growth Medium-2 (EGM-2) for 1hr.

We observed elevated PRDX5 expression under atherosclerotic conditions in both humans and mice. Unexpectedly, Prdx5^-/-; ApoE^-/- mice exhibited reduced plaque formation, with no discernible difference in aortic hydrogen peroxide (H₂O₂) levels compared to ApoE^-/- mice. Additionally, there was a notable decrease in macrophage accumulation and vascular inflammation in the atherosclerotic aorta of Prdx5^-/-; ApoE^-/-. In vitro, HUVECs stimulated with oxLDL showed upregulated PRDX5 expression in both lysate and culture medium. Moreover, PRDX5 knockdown in oxLDL-stimulated (oxLDL-siPRDX5) HUVECs significantly reduced the migration and adhesion of human monocytic cells (THP-1) to HUVECs, indicating diminished vascular immune responses. Mechanistically, both in vivo and in vitro, PRDX5 deficiency inhibited the Toll-like receptor 4 (TLR4)/Myeloid differentiation primary response 88 (MyD88) signaling pathway, resulting in reduced nuclear factor kappa B (NF-κB) and P38 phosphorylation. Furthermore, treatment with recombinant PRDX5 (rPRDX5) protein restored TLR4/MyD88 signaling in oxLDL-siPRDX5 HUVECs.

These data demonstrate that extracellular PRDX5 contributes to endothelial inflammation, promoting macrophage accumulation in the atherosclerotic aorta through activation of TLR4/MyD88/NF-κB and P38 signaling pathways, thereby exacerbating the progression of atherosclerosis.