New therapeutic approaches in clonal hematopoiesis and atherosclerosis

PROJECT SUMMARY Despite the success of LDL lowering treatments, atherosclerotic cardiovascular disease remains the major cause of death in the US. Recent clinical trials employing anti-inflammatory therapies have shown a reduction in CVD but led to increased infections. This indicates an urgent need for more precise targeting of anti-inflammatory treatments to patients with higher inflammatory risk. Clonal hematopoiesis (CH) arises from somatic mutations such as in JAK2 or TET2 that provide a fitness advantage to hematopoietic stem cells and outgrowth of clones of blood cells. CH, which increases in frequency with aging, has emerged as a major independent risk factor for CVD. Studies in Tet2-/- and Jak2VF mouse models indicate a central role of macrophage inflammasome activation. We have shown increased atherosclerosis, defective efferocytosis, increased necrosis and inflammatory myeloid cell populations in mice expressing Jak2VF in hematopoietic cells and in CH models. Inhibition of the inflammasome product lL-1β improved features of plaques stabilization including increased fibrous caps and decreased necrotic cores. We propose to investigate the mechanisms linking CH, inflammasomes and pathways acting downstream of lL-1β to atherosclerotic plaque stability. Low frequency Jak2VF alleles are found in 3-4% of general populations and increase CVD risk. Our recent findings indicate that transplantation of only 1.5% Jak2VF cells leads to increased lesions with impaired efferocytosis and increased necrosis. This suggests a new hypothesis that inflammatory crosstalk from Jak2VF Μφs to bystander WT Μφs or stromal cells, promotes plaque destabilization. In Aim 1 we will assess the impact of CH on bystander cells in lesions focusing on Jak2VF -WT Μφ crosstalk. We will evaluate the hypothesis that inflammatory signals from Jak2VF to WT macrophages, such as inflammasome-derived IL-1, increase inflammatory macrophages and decrease Trem2Hi non-inflammatory macrophages, leading to impaired efferocytosis and increased inflammation in mice with low allele burden Jak2VF CH. In Aim2 we will assess the impact of CH on stromal cells in Jak2VF or Tet2-/- CH mice, building on preliminary studies showing that IL-1b antagonism increases fibroblasts in the cap of atherosclerotic lesions. We will also employ a novel Dre-Cre mouse model that allows Jak2VF to be inactivated during lesion regression to test the hypothesis that this increases fibrogenic Trem2Hi macrophages and fibroblasts in lesion caps. In Aim 3 we will collaborate with the Munich Vascular Biobank to assess the impact of CH on human carotid plaque inflammation. Proposed studies may reveal novel genes and pathways acting downstream of inflammasome activation in clonal hematopoiesis to destabilize plaques, and point to new and more precisely targeted therapeutic approaches that are less immunosuppressive than global inhibition of IL-1β or inflammasomes.