Christoph J. Binder (Austria)
Medical University of Vienna Laboratory MedicineAuthor Of 7 Presentations
Introduction to first session of the day (ID 1604)
Humoral immune responses in the artery wall. (ID 1307)
Live Q&A (ID 1378)
Live Q&A (ID 1434)
Introduction (ID 1587)
O026 - Histone methyltransferase DOT1L regulates macrophage inflammatory responses and lipid metabolism (ID 489)
Abstract
Background and Aims
DOT1L is the only histone methyltransferase for H3K79 and has recently emerged as a central player in the immune system.
Methods
Here we investigate the role of DOT1L in macrophages by application of a selective DOT1L inhibitor on either mouse or human macrophages and using myeloid-specific Dot1l deleted mice. Furthermore, we investigated myeloid Dot1l in vivo in a mouse model for atherosclerosis including scRNAseq on atherosclerotic plaques.
Results
Using RNA-seq and in vitro assays, we found that Dot1l represses macrophage activation and impacts cellular lipid metabolism. ChIP-seq for H3K79me revealed that DOT1L regulates H3K79 methylation of RXRα in macrophages, leading to reduced RXRα mRNA and protein expression, both upon Dot1l deletion as well as DOT1L inhibition. Given the established role for RXRα in controlling macrophage activation and lipid homeostasis, the phenotype we observe can thus be at least partly explained by impaired RXRα signaling. Moreover, we could induce a similar suppressed lipid phenotype using an RXRα antagonist in wild-type macrophages.
In vivo, we confirmed that myeloid Dot1l deletion increases the activation of plaque macrophages. Moreover, although plaque area was not affected, Dot1l deficiency led to enhanced necrosis, indicating potential plaque destabilization. Apart from these direct effects, we found that myeloid Dot1l also affects other immune cell subsets illustrated by reduced production of IgG and IgM antibodies targeting atherosclerosis-related antigens.
Conclusions
Our data show that myeloid DOT1L is a critical regulator of macrophage inflammatory responses and lipid homeostasis and that it impacts in vivo immune responses and atherosclerosis development.
O035 - Phosphorylcholine-targeting vaccination reduces experimental atherosclerosis progression by expanding the B1-like specific B cell pool (ID 726)
Abstract
Background and Aims
Vaccination with phosphorylcholine (PC) reduces experimental atherosclerosis by raising the titer of PC-specific IgM in Apolipoprotein E knockout (ApoEKO) mice.
The epitope of the antibodies elicited by the PC-Vaccine coincides with that of 'natural' anti-pneumococcal antibodies and strikingly similar results can be obtained by vaccination with Prevenar®.
The aim of the present study was therefore to assess whether the atheroprotective effects carried by PC-Vaccine and Prevenar@ are linked to the activation of the germline encoded B cell pool, which is responsible for the production of natural antibodies.
Methods
AID Cre mice were crossed with ApoEKO mice and double transgenic mice were immunized with PC-Vaccine or with Prevenar® as previously reported (DOI:10.1016/j.atherosclerosis.2018.06.903). Three months later, atherosclerotic lesions and natural anti-PC IgM antibodies values were compared to the AID+ (affinity maturated) IgM+ (B1-like) cell pool in the peritoneal cavity and draining lymph nodes.
Results
Discriminant analysis showed that the rise of natural anti-PC IgM antibodies (AB1-2 IgM), the proportion of affinity matured (AID+) B1-like cells (CD19+ CD5+ CD43+ CD1d+ IgM+) having migrated from the draining lymph node to the peritoneal cavity and the lesion size (AUC) were interdependent from each other and that atheroprotection in both PC-Vaccine and Prevenar® mouse groups was proportional to the fraction of affinity matured B1-like cells in the peritoneal cavity and the rise of natural anti-PC IgM antibody production (individual data and bivariate plots are displayed in the figure).
Conclusions
Phosphorylcholine-targeting vaccination boosts affinity maturation of B lymphocytes involved in the production of natural antibodies and prevents experimental atherosclerosis progression.