The maturation of a 'neural-hematopoietic' inflammatory axis in cardiovascular disease

Neighborhood socioeconomic deprivation and individual-level socioeconomic status are associated with dopamine-mediated changes to monocyte subset CCR2 expression via a cAMP-dependent pathway

Social determinants of health (SDoH) include socioeconomic, environmental, and psychological factors that impact health. Neighborhood socioeconomic deprivation (NSD) and low individual-level socioeconomic status (SES) are SDoH that associate with incident heart failure, stroke, and cardiovascular mortality, but the underlying biological mechanisms are not well understood. Previous research has demonstrated an association between NSD, in particular, and key components of the neural-hematopoietic-axis including amygdala activity as a marker of chronic stress, bone marrow activity, and arterial inflammation. Our study further characterizes the role of NSD and SES as potential sources of chronic stress related to downstream immunological factors in this stress-associated biologic pathway. We investigated how NSD, SES, and catecholamine levels (as proxy for sympathetic nervous system activation) may influence monocytes which are known to play a significant role in atherogenesis. First, in an ex vivo approach, we treated healthy donor monocytes with biobanked serum from a community cohort of African Americans at risk for CVD. Subsequently, the treated monocytes were subjected to flow cytometry for characterization of monocyte subsets and receptor expression. We determined that NSD and serum catecholamines (namely dopamine [DA] and norepinephrine [NE]) associated with monocyte C-C chemokine receptor type 2 (CCR2) expression (p < 0.05), a receptor known to facilitate recruitment of monocytes towards arterial plaques. Additionally, NSD associated with catecholamine levels, especially DA in individuals of low SES. To further explore the potential role of NSD and the effects of catecholamines on monocytes, monocytes were treated in vitro with epinephrine [EPI], NE, or DA. Only DA increased CCR2 expression in a dose-dependent manner (p < 0.01), especially on non-classical monocytes (NCM). Furthermore, linear regression analysis between D2-like receptor surface expression and surface CCR2 expression suggested D2-like receptor signaling in NCM. Indicative of D2-signaling, cAMP levels were found to be lower in DA-treated monocytes compared to untreated controls (control 29.78 pmol/ml vs DA 22.97 pmol/ml; p = 0.038) and the impact of DA on NCM CCR2 expression was abrogated by co-treatment with 8-CPT, a cAMP analog. Furthermore, Filamin A (FLNA), a prominent actin-crosslinking protein, that is known to regulate CCR2 recycling, significantly decreased in DA-treated NCM (p < 0.05), indicating a reduction of CCR2 recycling. Overall, we provide a novel immunological mechanism, driven by DA signaling and CCR2, for how NSD may contribute to atherogenesis. Future studies should investigate the importance of DA in CVD development and progression in populations disproportionately experiencing chronic stress due to SDoH.

Associations of Cumulative Perceived Stress with Cardiovascular Risk Factors and Outcomes: Findings from The Dallas Heart Study

Background

Data remain sparse regarding the impact of chronic stress on cardiovascular disease (CVD) risk factors and outcomes. Prior work has been limited by incomplete assessments of perceived stress and focus on single stress domains. We evaluated the association between a composite measure of perceived stress and CVD risk factors and outcomes.

Methods

Participants from the Dallas Heart Study phase 2 (2007-2009) without prevalent CVD who completed questionnaire assessments of perceived stress were included (n=2685). Individual perceived stress subcomponents (generalized stress, psychosocial, financial, and neighborhood stress) were standardized and integrated into a single cumulative stress score (CSS) with equal weighting for each component. Associations between CSS and demographics, psychosocial variables and cardiac risk factors were assessed in univariable and multivariable analyses. Cox proportional hazards models were used to determine associations of the CSS with atherosclerotic CVD (ASCVD) and Global CVD (ASCVD, heart failure, and atrial fibrillation) after adjustment for demographics and traditional risk factors.

Results

Median age of the study population was 48 years, 55% were female, 49% Black and 15% Hispanic/Latinx. CSS was higher among participants who were younger, female, Black or Hispanic, and those with lower income and educational attainment (p<.0001 for each). Higher CSS was associated with self-report of racial/ethnic discrimination, lack of health insurance and last medical contact > one year previously (p<.0001 for each). In multivariable regression models adjusting for age, gender, race/ethnicity, income and education, higher CSS associated with hypertension, smoking, and higher body mass index, waist circumference Hemoglobin A1C, hs-CRP and sedentary time (p< 0.01 for each). Over a median follow-up of 12.4 years, higher CSS associated with ASCVD (adjusted HR 1.22 per SD, 95% CI 1.01-1.47) and Global CVD (HR 1.20, 95% CI 1.03-1.40). No interactions were seen between CSS, demographic factors, and outcomes.

Conclusion

Composite multidimensional assessments of perceived stress may help to identify individuals at risk for CVD who may be targeted for stress mitigation or enhanced prevention strategies. These approaches may be best focused on vulnerable populations, given the higher burden of stress in women, Black and Hispanic individuals, and those with lower income and education.

WHAT IS NEW?

A novel measure of cumulative stress was created that integrates generalized, psychosocial, financial, and neighborhood perceived stress.Cumulative stress was higher among women, Black and Hispanic participants, younger individuals and persons with lower income and educational attainment and was associated with adverse health behaviors and increased burden of cardiovascular disease (CVD) risk factors.In a diverse cohort, higher cumulative stress associated with incident CVD after adjustment for demographics and traditional risk factors. No interactions were seen based on demographic factors.

CLINICAL IMPLICATIONS

Although associations of chronic stress with CVD were similar across demographic subgroups, the higher burden of stress among younger individuals, women, Black and Hispanic participants, and those with lower SES suggests that CVD risk associated with higher stress affects marginalized groups disproportionately.Cumulative Stress is associated with modifiable risk factors and health behaviors. Future studies should explore targeting behavioral modification and risk factor reduction programs, as well as stress reduction strategies, to individuals with high cumulative stress.Additional research is needed to uncover mechanisms that underly the association between chronic stress and cardiovascular disease.

PET-Based Imaging with 18F-FDG and 18F-NaF to Assess Inflammation and Microcalcification in Atherosclerosis and Other Vascular and Thrombotic Disorders

Positron emission tomography (PET) imaging with ¹⁸F-fluorodeoxyglucose (FDG) represents a method of detecting and characterizing arterial wall inflammation, with potential applications in the early assessment of vascular disorders such as atherosclerosis. By portraying early-stage molecular changes, FDG-PET findings have previously been shown to correlate with atherosclerosis progression. In addition, recent studies have suggested that microcalcification revealed by ¹⁸F-sodium fluoride (NaF) may be more sensitive at detecting atherogenic changes compared to FDG-PET. In this review, we summarize the roles of FDG and NaF in the assessment of atherosclerosis and discuss the role of global assessment in quantification of the vascular disease burden. Furthermore, we will review the emerging applications of FDG-PET in various vascular disorders, including pulmonary embolism, as well as inflammatory and infectious vascular diseases.

Chronic Stress-Related Neural Activity Associates With Subclinical Cardiovascular Disease in a Community-Based Cohort: Data From the Washington, D.C. Cardiovascular Health and Needs Assessment

Background: Psychosocial stress correlates with cardiovascular (CV) events; however, associations between physiologic measures of stressors and CVD remain incompletely understood, especially in racial/ethnic minority populations in resource-limited neighborhoods. We examined associations between chronic stress-related neural activity, measured by amygdalar ¹⁸Fluorodeoxyglucose (¹⁸FDG) uptake, and aortic vascular FDG uptake (arterial inflammation measure) in a community-based cohort.

Methods: Forty participants from the Washington, DC CV Health and Needs Assessment (DC-CHNA), a study of a predominantly African-American population in resource-limited urban areas and 25 healthy volunteers underwent detailed phenotyping, including ¹⁸FDG PET/CT for assessing amygdalar activity (AmygA), vascular FDG uptake, and hematopoietic (leukopoietic) tissue activity. Mediation analysis was used to test whether the link between AmygA and vascular FDG uptake was mediated by hematopoietic activity.

Results: AmygA (1.11 ± 0.09 vs. 1.05 ± 0.09, p = 0.004) and vascular FDG uptake (1.63 ± 0.22 vs. 1.55 ± 0.17, p = 0.05) were greater in the DC-CHNA cohort compared to volunteers. Within the DC-CHNA cohort, AmygA associated with vascular FDG uptake after adjustment for Framingham score and body mass index (β = 0.41, p = 0.015). The AmygA and aortic vascular FDG uptake relationship was in part mediated by splenic (20.2%) and bone marrow (11.8%) activity.

Conclusions: AmygA, or chronic stress-related neural activity, associates with subclinical CVD risk in a community-based cohort. This may in part be mediated by the hematopoietic system. Our findings of this hypothesis-generating study are suggestive of a potential relationship between chronic stress-related neural activity and subclinical CVD in an African American community-based population. Taken together, these findings suggest a potential mechanism by which chronic psychosocial stress, such as stressors that can be experienced in adverse social conditions, promotes greater cardiovascular risk amongst resource-limited, community-based populations most impacted by cardiovascular health disparities. However, larger prospective studies examining these findings in other racially and ethnically diverse populations are necessary to confirm and extend these findings.

Granulopoiesis and Neutrophil Homeostasis: A Metabolic, Daily Balancing Act

Granulopoiesis is part of the hematopoietic hierarchic architecture, where hematopoietic stem cells give rise to highly proliferative multipotent and lineage-committed granulocytic progenitor cells that differentiate into unipotent neutrophil progenitors. Given their short lifespan, neutrophils are rapidly cleared from circulation through specialized efferocytic macrophages. Together with an intrinsic clock, these processes contribute to circadian fluctuations, preserving self-tolerance and protection against invading pathogens. However, metabolic perturbation of granulopoiesis and neutrophil homeostasis can result in low-grade chronic inflammation, as observed with aging. During acute pathogenic infections, hematopoiesis can also be switched into emergency mode, which has been recently associated with significant neutrophil functional heterogeneity. This review focuses on a new reassessment of regulatory mechanisms governing neutrophil production, life-cycle, and diversity in health and disease.

Chronic sympathetic driven hypertension promotes atherosclerosis by enhancing hematopoiesis

Hypertension is a major, independent risk factor for atherosclerotic cardiovascular disease. However, this pathology can arise through multiple pathways, which could influence vascular disease through distinct mechanisms. An overactive sympathetic nervous system is a dominant pathway that can precipitate in elevated blood pressure. We aimed to determine how the sympathetic nervous system directly promotes atherosclerosis in the setting of hypertension. We used a mouse model of sympathetic nervous system-driven hypertension on the atherosclerotic-prone apolipoprotein E-deficient background. When mice were placed on a western type diet for 16 weeks, we showed the evolution of unstable atherosclerotic lesions. Fortuitously, the changes in lesion composition were independent of endothelial dysfunction, allowing for the discovery of alternative mechanisms. With the use of flow cytometry and bone marrow imaging, we found that sympathetic activation caused deterioration of the hematopoietic stem and progenitor cell niche in the bone marrow, promoting the liberation of these cells into the circulation and extramedullary hematopoiesis in the spleen. Specifically, sympathetic activation reduced the abundance of key hematopoietic stem and progenitor cell niche cells, sinusoidal endothelial cells and osteoblasts. Additionally, sympathetic bone marrow activity prompted neutrophils to secrete proteases to cleave the hematopoietic stem and progenitor cell surface receptor CXCR4. All these effects could be reversed using the β-blocker propranolol during the feeding period. These findings suggest that elevated blood pressure driven by the sympathetic nervous system can influence mechanisms that modulate the hematopoietic system to promote atherosclerosis and contribute to cardiovascular events.

Prolonged hematopoietic and myeloid cellular response in patients after an acute coronary syndrome measured with 18F-DPA-714 PET/CT

Purpose

An acute coronary syndrome (ACS) is characterized by a multi-level inflammatory response, comprising activation of bone marrow and spleen accompanied by augmented release of leukocytes into the circulation. The duration of this response after an ACS remains unclear. Here, we assessed the effect of an ACS on the multi-level inflammatory response in patients both acutely and after 3 months.

Methods

We performed ¹⁸F-DPA-714 PET/CT acutely and 3 months post-ACS in eight patients and eight matched healthy controls. DPA-714, a PET tracer binding the TSPO receptor and highly expressed in myeloid cells, was used to assess hematopoietic activity. We also characterized circulating monocytes and hematopoietic stem and progenitor cells (HSPCs) by flow cytometry in 20 patients acutely and 3 months post-ACS and in 19 healthy controls.

Results

In the acute phase, patients displayed a 1.4-fold and 1.3-fold higher ¹⁸F-DPA-714 uptake in, respectively, bone marrow (p = 0.012) and spleen (p = 0.039) compared with healthy controls. This coincided with a 2.4-fold higher number of circulating HSPCs (p = 0.001). Three months post-ACS, ¹⁸F-DPA-714 uptake in bone marrow decreased significantly (p = 0.002), but no decrease was observed for ¹⁸F-DPA-714 uptake in the spleen (p = 0.67) nor for the number of circulating HSPCs (p = 0.75).

Conclusions

¹⁸F-DPA-714 PET/CT reveals an ACS- triggered hematopoietic organ activation as initiator of a prolonged cellular inflammatory response beyond 3 months, characterized by a higher number of circulating leukocytes and their precursors. This multi-level inflammatory response may provide an attractive target for novel treatment options aimed at reducing the high recurrence rate post-ACS.

Electronic supplementary material

The online version of this article (10.1007/s00259-018-4038-8) contains supplementary material, which is available to authorized users.