Genetic Deletion of Interleukin-19 Exacerbates Atherogenesis in Double Knockout Mice by Modulation of mRNA Stability Protein HuR

Abstract

Objective: To test the hypothesis that loss of IL-19 exacerbates atherosclerosis. Approach and Results: Il19-/- mice were crossed into Ldlr-/- mice. Double knockout (dKO) mice had increased plaque burden in aortic arch and root compared to Ldlr-/- controls after 14 weeks of high fat diet (HFD). In a rescue study, dKO mice injected i.p. with 10ng/g/day of IL-19 had significantly less plaque burden compared to saline controls. Quantitative RT-PCR and western blot analysis revealed dKO mice had increased global and intraplaque polarization of T cells and macrophages to pro-inflammatory phenotypes, and also significantly increased TNFa expression in spleen and aortic arch compared to Ldlr-/- controls. Results from bone marrow transplantation experiments suggest immune cells participate in IL-19 mediated atheroprotection. Bone marrow derived macrophages (BMDMs) and vascular smooth muscle cells (VSMCs) isolated from dKO mice had significantly greater expression of TNFa mRNA and protein compared to controls. Importantly from a mechanistic standpoint, spleen and aortic arch from dKO mice had significantly increased expression of the mRNA stability protein Human antigen R (HuR). BMDMs and VSMCs isolated from dKO mice also had greater HuR abundance. HuR stabilizes pro-inflammatory transcripts by binding AU-rich elements (AREs) in the 3’ untranslated region (UTR). Cytokine and HuR mRNA stability were increased in dKO BMDMs and VSMCs compared to controls, which was rescued by addition of IL-19 to these cells. IL-19 induces expression of miR133a, which targets and reduces HuR abundance; miR133a levels were lower in dKO mice compared to controls. Conclusions: These data indicate that IL-19 is an atheroprotective cytokine that decreases abundance of HuR, leading to reduced inflammatory mRNA stability.