Abstract 14692: Clonal Hematopoiesis Driver Mutations Have Disparate Effects on Macrophage Cytokine Profiles and Only Modestly Drive Atherogenesis at Pathophysiological Levels

Background: Clonal hematopoiesis (CH) is characterized by expansion of hematopoietic stem cells due to somatic mutations in leukemia-associated genes. CH is associated with increased mortality, attributed to cardiovascular disease (CVD) driven by increased IL-1β from clonal macrophages. However, different CH-driver mutations perturb diverse genes with distinct functions and reports of IL-1β release from mutant macrophages are discordant. Furthermore, directionality of the association between CH and CVD is not established.

Hypothesis: We hypothesized that mutations of common CH-driver genes have disparate effects on macrophage cytokine profiles and atherogenesis. We also hypothesized that atherosclerosis-driven systemic inflammation promotes clonal expansion.

Methods/Results: We characterised cytokine expression in LPS-treated murine bone marrow-derived macrophages (BMDMs) harboring CH-driver mutations ( Tet2 , Dnmt3a , or Jak2 ). Transcript level of Il1a , Il1b and Il6 was increased ~3-5 fold in Tet2 ^-/- and Dnmt3a ^-/- BMDMs, but only ~1.5-2 fold with heterozygotic loss, which mimics more closely patients with CH. Notably, Tet2 ^-/- BMDMs (but not Dnmt3a or Jak2 ) release more IL-1α/β, accompanied by increased Asc specks and caspase-1 activity, implying heightened NLRP3 inflammasome activation.

In murine chimera models of CH, Tet2 ^-/- and Tet2 ^+/- cells (but not Dnmt3a or Jak2 ), expand under the steady state. Clonal dynamics were unaffected by systemic inflammation via exogenous IL-1α, or high fat diet-induced atherogenesis in Ldlr ^-/- recipients.

Atherosclerotic plaques in murine CH models at 12 weeks are only mildly increased with heterozygotic Tet2, Dnmt3a, or Jak2 mutations (10-20%). Observational and Mendelian randomisation analyses of UK BioBank did not reveal bidirectional associations between CH and atherosclerosis.

Conclusions: We demonstrate augmented NLRP3 inflammasome activation in Tet2 ^-/- BMDMs and disparate effects of different CH mutations on cytokine profiles. We find no evidence for atherosclerosis or systemic inflammation driving clonal expansion. Thus, the pathogenesis of CH-driven disease should be treated as different entities for each mutation and likely involves overlapping or distinct mediators.