Jak2 V617F clonal hematopoiesis promotes arterial thrombosis via platelet activation and cross talk.

ABSTRACT: JAK2 V617F (JAK2VF) clonal hematopoiesis (CH) has been associated with atherothrombotic cardiovascular disease (CVD). We assessed the impact of Jak2VF CH on arterial thrombosis and explored the underlying mechanisms. A meta-analysis of 3 large cohort studies confirmed the association of JAK2VF with CVD and with platelet counts and adjusted mean platelet volume (MPV). In mice, 20% or 1.5% Jak2VF CH accelerated arterial thrombosis and increased platelet activation. Megakaryocytes in Jak2VF CH showed elevated proplatelet formation and release, increasing prothrombogenic reticulated platelet counts. Gp1ba-Cre-mediated expression of Jak2VF in platelets (VFGp1ba) increased platelet counts to a similar level as in 20% Jak2VF CH mice while having no effect on leukocyte counts. Like Jak2VF CH mice, VFGp1ba mice showed enhanced platelet activation and accelerated arterial thrombosis. In Jak2VF CH, both Jak2VF and wild-type (WT) platelets showed increased activation, suggesting cross talk between mutant and WT platelets. Jak2VF platelets showed twofold to threefold upregulation of COX-1 and COX-2, particularly in young platelets, with elevated cPLA2 activation and thromboxane A2 production. Compared with controls, conditioned media from activated Jak2VF platelets induced greater activation of WT platelets that was reversed by a thromboxane receptor antagonist. Low-dose aspirin ameliorated carotid artery thrombosis in VFGp1ba and Jak2VF CH mice but not in WT control mice. This study shows accelerated arterial thrombosis and platelet activation in Jak2VF CH with a major role of increased reticulated Jak2VF platelets, which mediate thromboxane cross talk with WT platelets and suggests a potential beneficial effect of aspirin in JAK2VF CH.

The AIM2 inflammasome exacerbates atherosclerosis in clonal haematopoiesis.

Clonal haematopoiesis, which is highly prevalent in older individuals, arises from somatic mutations that endow a proliferative advantage to haematopoietic cells. Clonal haematopoiesis increases the risk of myocardial infarction and stroke independently of traditional risk factors1. Among the common genetic variants that give rise to clonal haematopoiesis, the JAK2V617F (JAK2VF) mutation, which increases JAK-STAT signalling, occurs at a younger age and imparts the strongest risk of premature coronary heart disease1,2. Here we show increased proliferation of macrophages and prominent formation of necrotic cores in atherosclerotic lesions in mice that express Jak2VF selectively in macrophages, and in chimeric mice that model clonal haematopoiesis. Deletion of the essential inflammasome components caspase 1 and 11, or of the pyroptosis executioner gasdermin D, reversed these adverse changes. Jak2VF lesions showed increased expression of AIM2, oxidative DNA damage and DNA replication stress, and Aim2 deficiency reduced atherosclerosis. Single-cell RNA sequencing analysis of Jak2VF lesions revealed a landscape that was enriched for inflammatory myeloid cells, which were suppressed by deletion of Gsdmd. Inhibition of the inflammasome product interleukin-1ß reduced macrophage proliferation and necrotic formation while increasing the thickness of fibrous caps, indicating that it stabilized plaques. Our findings suggest that increased proliferation and glycolytic metabolism in Jak2VF macrophages lead to DNA replication stress and activation of the AIM2 inflammasome, thereby aggravating atherosclerosis. Precise application of therapies that target interleukin-1ß or specific inflammasomes according to clonal haematopoiesis status could substantially reduce cardiovascular risk.

Molecular imaging of cardiac CXCR4 expression in a mouse model of acute myocardial infarction using a novel 68Ga-mCXCL12 PET tracer.

BACKGROUND: The chemokine receptor CXCR4 and its ligand CXCL12 have been shown to be a possible imaging and therapeutic target after myocardial infarction (MI). The murine-based and mouse-specific 68Ga-mCXCL12 PET tracer could be suitable for serial in vivo quantification of cardiac CXCR4 expression in a murine model of MI. METHODS AND RESULTS: At days 1-6 after MI, mice were intravenously injected with 68Ga-mCXCL12. Autoradiography was performed and the infarct-to-remote ratio (I/R) was determined. In vivo PET imaging with 68Ga-mCXCL12 was conducted on days 1-6 after MI and the percentage of the injected dose (%ID/g) of the tracer uptake in the infarct area was calculated. 18F-FDG-PET was performed for anatomical landmarking. Ex vivo autoradiography identified CXCR4 upregulation in the infarct region with an increasing I/R after 12 hours (1.4 ± 0.3), showing a significant increase until day 2 (4.5 ± 0.6), followed by a plateau phase (day 4) and decrease after 10 days (1.3 ± 1.0). In vivo PET imaging identified similar CXCR4 upregulation in the infarct region which peaked around day 3 post MI (9.7 ± 5.0 %ID/g) and then subsequently decreased by day 6 (2.8 ± 1.0 %ID/g). CONCLUSION: Noninvasive molecular imaging of cardiac CXCR4 expression using a novel, murine-based, and specific 68Ga-mCXCL12 tracer is feasible both ex vivo and in vivo.

Optimum cutoff values of anthropometric indices of obesity for predicting hypertension: more than one decades of follow-up in an Iranian population.

We determined cutoff points of body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR), for predicting hypertension in an Iranian population. Study sample included 6359 (3678 female) participants aged ≥20 and <60 years of a prospective cohort. The sex stratified multivariate hazard ratios (HRs) for all indices were estimated using Cox regression in two age groups (20-39 and 40-59 years). Receiver operating characteristic (ROC) was used to evaluate the predictive ability and determine the optimal cut-off values of the indices. In both genders and two age groups, the confounders adjusted HRs were significant for general and central obesity measures indices. AUCs of the indices were similar in men; however, among women 40-59 years, WC and WHtR had significantly higher AUC compared to BMI. Generally, the optimal cut-off values were higher in the 40-59 year age group. Optimal BMI, WC and WHR and WHtR cut-off values were 24.15 kg/m2, 90.5 cm, 0.90 and 0.49 among men, aged 20-39 years; the corresponding values were 28.41 kg/m2, 86.5 cm, 0.96 and 0.50 in men aged 40-59 years, respectively. In women, the aforementioned values were 26.38 kg/m2, 83.5 cm, 0.79 and 0.51 in the age group of 20-39 years, and 29.57 kg/m2, 90.5 cm, 0.88 and 0.59 in the 40-59 year age group, respectively. Our results suggest that gender and age differences in the association between anthropometric indices and hypertension should be considered.

Different glucose tolerance status and incident cardiovascular disease and all-cause mortality among elderly Iranians.

AIMS: To determine the effect of different glucose categories on incident cardiovascular disease (CVD) and all-cause mortality in a population-based cohort. METHODS: A total of 834 individuals aged 65 years and older without a history of CVD at baseline were stratified according to 2-h post-load glucose fasting glucose test into six categories including: (i) normal fasting glucose/normal glucose tolerance; (ii) prediabetes, (iii) isolated fasting hyperglycemia (IFH); (iv) isolated post-challenge hyperglycemia (IPH); (v) IPH and IFH; and (vi) known diabetes mellitus. The prognostic significance of these groups on CVD and total mortality were examined by Cox proportional hazard ratios in a multivariate adjusted model. RESULTS: Over 9 years of follow up, 186 incidents of CVD and 218 deaths occurred (72 CVD mortality).Of the population, 45.2%, 30.7%, 1.2%, 6.1% 4.7%, and 11.9% were normal fasting glucose/normal glucose tolerance, prediabetes IFH, IPH, IFH and IPH, and known diabetes mellitus, respectively. Multivariate adjusted hazard ratios for CVD were 1.13 (95% CI 0.78-1.64), 1.03 (95% CI 0.25-4.22), 1.17 (95% CI 0.65-2.11), 2.52 (95% CI 1.43-4.42) and 2.39 (95% CI 1.55-3.69), and for CVD mortality were 0.59 (95% CI 0.27-1.30), 2.02 (95% CI 0.27-15.15), 1.26 (95% CI 0.51-3.16), 3.57 (95% CI 1.64-7.75), and 4.70 (95% CI 2.54-8.69) for prediabetes, IFH, IPH, IFH and IPH, and known diabetes mellitus phenotypes, respectively. Corresponding hazard ratios for all-cause mortality in multivariate model adjusted for prevalent CVD were 1.07 (95% CI 0.73-1.57), 0.59 (95% CI 0.08-4.30), 0.92 (95% CI 0.5-1.70), 2.31 (95% CI 1.33-4.01) and 3.88 (95% CI 2.70-5.55), respectively. CONCLUSION: Among the elderly population with newly diagnosed diabetes, only the combined IFH and IPH phenotype, but not IFH or IPH alone, was a significant predictor of CVD and mortality events. Prediabetes was not associated with any risk. Geriatr Gerontol Int 2016; 16: 1263-1271.