Clonal hematopoiesis, inflammasomes and atherosclerosis

Project Summary Clonal hematopoiesis (CH) has emerged as an independent risk factor for atherosclerotic cardiovascular disease (CVD). CH commonly arises from mutations that cause a loss of function in epigenetic modifiers such as TET2 or that increase hematopoietic cytokine signaling (JAK2VF). These variants promote hematopoietic stem cell (HSC) expansion, myelopoiesis and inflammatory responses in myeloid cells. We have shown a novel role of the AIM2 inflammasome in atherosclerosis promoted by the Jak2VF mutation, and provided evidence for involvement of AIM2 in increased CVD in humans with JAK2VF and other forms of CH. In contrast, the NLRP3 inflammasome has been implicated in accelerated atherosclerosis in Tet2 CH. The mechanisms linking inflammasomes to atherosclerosis remain poorly understood and related therapies not well developed. The overall goal is to explore mechanisms and novel treatments of inflammatory responses in CH. We will focus on atherosclerosis in Tet2 and Jak2VF CH, which have the strongest associations with human CVD and feature prominent inflammasome activation, in mouse models and human cells. We recently developed a mouse model of Jak2VF CH in which a very small number of mutant cells promotes atherosclerosis. In Aim 1 we will test the hypothesis that in Jak2VF or Tet2 mutant cells inflammasome activation and secretion of IL-1b seeds Nlrp3 inflammasome activation in bystander wild type macrophages in plaque. This inflammatory seeding may involve signaling through IKK2 and Jak1/Stat signaling pathways macrophages. In Aim 2 we propose to investigate anti-atherogenic effects of Jak1 deficiency in hematopoietic and myeloid cells in Tet2 deficiency, including studies in human iPS-cell derived macrophages. Inflammasome activation leads to cell death by pyroptosis, leading to plasma membrane rupture and release of DAMPs. In Aim 3 the impact of a novel inflammasome-activated mediator of plasma membrane rupture (PMR), Ninjurin-1 (Ninj1) on macrophages subpopulations and atherosclerosis will be investigated. Proposed studies have the potential to support the precision targeting of new anti-inflammatory treatment to specific groups of patients with CH.