Deficiency of Nucleotide-binding oligomerization domain-containing proteins (NOD) 1 and 2 reduces atherosclerosis

Ann-Kathrin Vlacil,Volker Ruppert,Jutta Schuett,Bernhard Schieffer,Kinan Shahin,Raghav Oberoi,Christian Wächter,Harald Schuett,Yu Lei,Thomas Tschernig,Fan Liu,Karsten Grote,Muhidien Soufi,Uwe J F Tietge

doi:10.1007/s00395-020-0806-2

Abstract

Atherosclerosis is crucially fueled by inflammatory pathways including pattern recognition receptor (PRR)-related signaling of the innate immune system. Currently, the impact of the cytoplasmic PRRs nucleotide-binding oligomerization domain-containing protein (NOD) 1 and 2 is incompletely characterized. We, therefore, generated Nod1/Nod2 double knockout mice on a low-density lipoprotein receptor (Ldlr)-deficient background (= Ldlr−/−Nod1/2−/−) which were subsequently analyzed regarding experimental atherosclerosis, lipid metabolism, insulin resistance and gut microbiota composition. Compared to Ldlr−/− mice, Ldlr−/−Nod1/2−/− mice showed reduced plasma lipids and increased hepatic expression of the scavenger receptor LDL receptor-related protein 1 after feeding a high-fat diet for 12 weeks. Furthermore, intestinal cholesterol and its bacterial degradation product coprostanol were elevated in Ldlr−/−Nod1/2−/− mice, correlating with the increased abundance of Eubacterium coprostanoligenes as assessed by 3rd generation sequencing of the gut microbiota. Atherosclerotic plaques of Ldlr−/−Nod1/2−/− mice exhibited less lipid deposition and macrophage accumulation. Moreover, macrophages from Ldlr−/−Nod1/2−/− mice showed higher expression of the cholesterol efflux transporters Abca1 and Abcg1 and accordingly reduced foam cell formation. Deficiency of Nod1 and Nod2 led to reduced plaque lipid deposition and inflammatory cell infiltration in atherosclerotic plaques. This might be explained by diminished plasma lipid levels and foam cell formation due to altered expression of key regulators of the hepatic cholesterol pathway as well as differential intestinal cholesterol metabolism and microbiota composition.

Highlights

Elevated levels of blood cholesterol and vascular inflammation are considered as the primary triggers of cardiovascular disease due to atherosclerosis, a chronic disease of arteries [15]
We observed a comparable induction of inflammatory genes in bone marrow-derived macrophages (BMDM) such as tumor necrosis factor-α (Tnf-α) and interleukin-1β (Il-1β) by the NOD1 ligand l-Ala-γ-d-Glu-meso-diaminopimelic acid (Tri-DAP) and the NOD2 ligand muramyl dipeptide (MDP, Fig. 1a)
Subsequent sequential ultracentrifugation analysis revealed that low-density lipoprotein receptor (Ldlr)−/−Nod1/2−/− mice had significantly lower proatherogenic very-low-density lipoprotein (VLDL) cholesterol levels, whereas low-density lipoprotein (LDL), high-density lipoprotein (HDL) and triglyceride (TG) levels were unchanged (Fig. 2a, Online Table 1)

Summary

Introduction

Elevated levels of blood cholesterol and vascular inflammation are considered as the primary triggers of cardiovascular disease due to atherosclerosis, a chronic disease of arteries [15]. There is an ongoing debate on the weighting of trigger mechanisms or whether they contribute to the initiation and progression of atherosclerosis. In this regard, cholesterol-lowering strategies, such as statins, are widely used as primary as well as secondary prevention in patients with imminent or apparent atherosclerotic cardiovascular disease since the 90s of the past century [1]. The inflammatory nature of atherosclerosis is known for quite some time, the first successful anti-inflammatory therapy for atherosclerotic disease using a monoclonal antibody targeting interleukin (IL)-1β has been reported just in 2017 [27]

Methods

Results

Conclusion