ADP-ribosylation in a mouse model of atherosclerosis: A potential novel link between dyslipidemia and inflammation in cardiovascular disease

Introduction

Inflammation and lipid accumulation are major features of atherosclerosis, a leading cause of death and morbidity worldwide. Our previous study recognized ADP-ribosylation, a post-translational modification, as a novel regulator of macrophage activation. We also have established mass spectrometry-based ADP-ribosylation proteomics. Using this technology, we evaluated the completely uncharacterized role of ADP-ribosylation in atherogenesis.

Objectif We hypothesized that ADP-ribosylated proteins circulate from liver, accumulate in aorta and promote atherogenesis.

Method

We harvested the aorta, liver, and plasma of LDL receptor-deficient (Ldlr-/-) mice that were on a regular chow or high-fat diet for 3 or 6 months (n = 40/condition).

Results

To increase ADP-ribosyl peptide signals in the aorta, we applied our novel recently optimized ion mobility mass spectrometry strategy to generate ADP-ribosylation proteomics data. We analyzed 160 mice aortas and identified 3 APOA1 and 3 APOE ADP-ribosylated peptides in both the aorta and the liver (Fig. 1 A). In addition, these peptides were differentially abundant in the aorta of HFD-fed mice, compared to controls (i.e, APOA1 ARPALEDLR peptide relative abundance [Fig. 1 B]). Using the same mouse plasma, we then validated the presence of ADP-ribosylated APOA1 and ADP-ribosylated APOE in HDL and chylomicron/VLDL/LDL fractions (Western blot), respectively. This finding indicates that classical apolipoproteins circulate as ADP-ribosylated forms, representing a completely novel class of modified apolipoproteins. Immunohistochemistry confirmed the enrichment of aortic lesions in macrophages and ADP-ribosylation signal (5-fold increase, P = 0.0006).

Conclusion

This work provides the first in vivo evidence that ADP-ribosylation occurs in atherosclerotic lesions, which may originate from the liver via circulating blood (Fig. 1C). Future studies will examine whether ADP-ribosylation of apolipoproteins, specifically APOA1, alters anti-atherogenic functions of HDL.