Sleep and exercise modulate mutant cell expansion, inflammasome activation and atherosclerosis in clonal hematopoiesis

Background: Clonal hematopoiesis (CH) is a disproportional outgrowth of hematopoietic stem cells (HSC) in the bone marrow (BM) caused by acquired somatic DNA mutations. In humans and mice, CH exacerbates atherosclerosis and accelerates heart disease. Among the common mutations that cause CH are a gain-of-function mutation in the cell signal regulator JAK2, JAK2^V617F, and loss-of-function mutations in the epigenetic regulator Tet2 (Tet2^-/-) and the DNA-damage repair gene p53 (p53^-/-). These mutations have been shown to aggravate atherosclerosis by increasing proliferation and overactivating inflammatory pathways in mutant plaque macrophages.

Adopting healthy lifestyle behaviors, including sufficient sleep and regular exercise, is highly effective in reducing cardiovascular risk. Both have been shown to induce quantitative and qualitative changes in hematopoiesis and the ensuing output of inflammatory leukocytes into the circulation. However, it is unknown whether lifestyle interacts with host genetics to modulate the expansion of CH mutant HSCs and alter the function of mutant aortic myeloid cells to influence atherosclerosis in the context of CH.

Here, we hypothesize that exercise and sleep modify the expansion dynamics of CH clones in a mutation-specific manner. We further hypothesize that lifestyle modifies CH-associated cardiovascular risk by altering proliferation rates of HSCs in the BM and shaping the inflammatory signature of mutant myeloid cells in atherosclerotic lesions.

Methods:  We used Mx1-driven Cre recombinase to generate mice with inducible JAK2^V617F or Tet2^-/- or p53^-/-  (CH-Mx1Cre). To study CH in the context of atherosclerosis, we generated ldlr^−/− BM-chimeric mice with a mixture of BM from CD45.2 CH-Mx1-Cre mice (10%) or CD45.2 CH^WTMx1-Cre and CD45.1 wild-type mice (90%) and fed them a high-fat diet for 12 weeks. During this time, mice remained sedentary, or were subjected to tactile sleep fragmentation (SF) or exposed to voluntary exercise. 

Results: We discovered that in ldlr^-/- mice with JAK2^V617F or Tet2^-/-  CH, SF accelerated, while exercise slowed CH clone expansion including the proportion of mutant (CD45.2) myeloid cells in the blood, and mutant HSC proliferation and abundance in the BM. In the aortic root of Ldlr^-/- mice with JAK2^V617F or Tet2^-/-  CH, SF enlarged while exercise diminished mutant macrophage abundance, CH-driven atherosclerotic plaque size, and relative necrotic core area. Mechanistically, SF and exercise influenced CH-accelerated atherosclerosis by modifying IL-1β levels in plasma and BM, and the activation of the NLRP3 and AIM2 inflammasomes in mutant macrophages within atherosclerotic plaques. Single cell sequencing revealed sleep and exercise-specific signatures of mutant plaque macrophages, indicating profound qualitative and cell functional effects of lifestyle on mutant myeloid cells in the aorta. Strikingly, sleep and exercise did not alter clone dynamics or plaque size in ldlr^-/- mice with p53^-/- CH. Together, our data demonstrate that lifestyle influences the clonal dynamics of CH and the inflammatory functionality of CH mutant myeloid cells in atherosclerotic plaques in a mutation-specific manner.

Conclusions: Our data reveal that healthy sleep and exercise can slow clonal expansion and protect from CH-associated vascular inflammation and atherosclerosis, suggesting that lifestyle acts as a rheostat critically influencing genetically determined cardiovascular risk.