Hematopoietic JAK2^V617F Mutation Increases Risk for Atrial Fibrillation

Clonal hematopoiesis of indeterminate potential (CHIP), a common age-associated phenomenon, is associated with increased risk of both hematological malignancies and cardiovascular diseases (Schuermans A, et al. Eur Heart J, 2024). TET2, ASXL1, DNMT3Aand JAK2 are the commonest genes implicated in CHIP. JAK2^V617F, as the most common site for JAK2 mutation, is an important driver mutation for myeloproliferative neoplasm (MPN). Atrial fibrillation (AF) is the most common arrhythmia observed in clinical practice, with a similar age of onset to MPN, and is associated with elevated risks of thromboembolism and death (Herbreteau L, et al. Thromb Res, 2023). JAK2^V617F has emerged as an unexpected and important risk factor for cardiovascular disease (CVD). However, the etiological link between hematopoietic JAK2^V617F and arrhythmias, specifically AF has not fully been elucidated.

In this study, we analyzed the occurrence, clinical profiles, cytokine levels, gene mutation characteristics of 906 patients (age 61 (7-100) years; 51.2% male) with myeloid neoplasms in our hospital. AF occurred in 54 (5.9%) patients. Next generation gene sequencing showed that the most commonly mutated genes were JAK2^V617F(37.4%), TET2(16%), ASXL1(15.9%) and DNMT3A(9.7%). In Cox proportion hazard models adjusted for age, sex, body mass index, type 2 diabetes, hypertension, the presence of JAK2^V617F significantly associated with incidence of AF. Concentrations of 14 plasma cytokines from peripheral blood were analyzed. The levels of interleukin (IL)-1β, IL-6, IL-8 and tumor necrosis factor (TNF)-β in AF group were higher than those in no-AF group. Additionally, a significant positive correlation between V617F% and IL-1β level or IL-17F level was found in the AF group. We identified a modest association between JAK2^V617F and incidence of AF in the patients with myeloid neoplasms.

In order to clarify whether or not hematopoietic JAK2^V617F mutation could indeed play a role in the development of AF, we used JAK2^V617F transgenic mouse model (JAK2^V617F mice) which used Vav-1 promoter to drive the expression of JAK2^V617F transgene in the hematopoietic system. JAK2^V617F transgenic mice displayed the typical phenotypes with increased levels of monocytes and splenomegaly. To further study the impact of JAK2^V617F on AF, we next examine the atrial electrophysiological condition in mice, and found an increase in AF induction in JAK2^V617F mice (7/10) relative to WT controls (2/9) (p<0.05). Atrial fibrosis serves as a crucial indicator for atrial remodeling. The increased atrial collagen deposition was observed in JAK2^V617F mice, while WT mice displayed less atrial fibrosis through Masson staining observation. Correspondingly, JAK2^V617F mice exhibited elevated levels of fibrosis-related proteins including Collagen3 (Col3) and Smooth muscle actin-α (α-SMA). Echocardiography to assess cardiac structure showed significant atrial dilation in JAK2^V617F mice when compared with WT mice. Taken together, JAK2^V617F mutation promotes atrial fibrosis and AF.

Inflammation contributes to AF and the study in vivo has established a role for aberrant cardiac inflammasome responses in AF (Lin AE, et al. Circulation, 2024). To explore the role of Nlrp3 inflammasome in AF in our model, Western blotting from the left atrial (LA) of JAK2^V617F mice showed higher level of Nlrp3, IL-6, IL-1β when compared with WT controls. Immunohistochemical analysis showed that there were significant increases in CD45⁺ leukocytes, CD68⁺ macrophages in the LA of the JAK2^V617F mice when compared to WT mice, verified by flow cytometry analysis of CD45⁺CD68⁺ cells. Immunofluorescence confocal microscopy of NLRP3⁺CD68⁺ macrophages showed a significantly increased in NLRP3 expressing in JAK2^V617F mice LA in comparison with the control samples (10.7 vs 3.1 cells/mm³, p<0.05). These data indicate that increased NLRP3 inflammasome activation occurs in macrophages of JAK2^V617F mice LA.

In summary, our clinical study established that JAK2^V617F have increased risk of developing AF. Furthermore, our in vivo studies revealed that hematopoietic JAK2^V617F mutation enhanced macrophages inflammasome activity that may underlie the associated AF pathogenesis. Thus, our results in this study may have important potential implications for the development of targeted therapies in AF patients.

No relevant conflicts of interest to declare.