Social Determinants of Cardiovascular Disease.

Social determinants of health (SDoH), which encompass the economic, social, environmental, and psychosocial factors that influence health, play a significant role in the development of cardiovascular disease (CVD) risk factors as well as CVD morbidity and mortality. The COVID-19 pandemic and the current social justice movement sparked by the death of George Floyd have laid bare long-existing health inequities in our society driven by SDoH. Despite a recent focus on these structural drivers of health disparities, the impact of SDoH on cardiovascular health and CVD outcomes remains understudied and incompletely understood. To further investigate the mechanisms connecting SDoH and CVD, and ultimately design targeted and effective interventions, it is important to foster interdisciplinary efforts that incorporate translational, epidemiological, and clinical research in examining SDoH-CVD relationships. This review aims to facilitate research coordination and intervention development by providing an evidence-based framework for SDoH rooted in the lived experiences of marginalized populations. Our framework highlights critical structural/socioeconomic, environmental, and psychosocial factors most strongly associated with CVD and explores several of the underlying biologic mechanisms connecting SDoH to CVD pathogenesis, including excess stress hormones, inflammation, immune cell function, and cellular aging. We present landmark studies and recent findings about SDoH in our framework, with careful consideration of the constructs and measures utilized. Finally, we provide a roadmap for future SDoH research focused on individual, clinical, and policy approaches directed towards developing multilevel community-engaged interventions to promote cardiovascular health.

By what molecular mechanisms do social determinants impact cardiometabolic risk?

While it is well known from numerous epidemiologic investigations that social determinants (socioeconomic, environmental, and psychosocial factors exposed to over the life-course) can dramatically impact cardiovascular health, the molecular mechanisms by which social determinants lead to poor cardiometabolic outcomes are not well understood. This review comprehensively summarizes a variety of current topics surrounding the biological effects of adverse social determinants (i.e., the biology of adversity), linking translational and laboratory studies with epidemiologic findings. With a strong focus on the biological effects of chronic stress, we highlight an array of studies on molecular and immunological signaling in the context of social determinants of health (SDoH). The main topics covered include biomarkers of sympathetic nervous system and hypothalamic-pituitary-adrenal axis activation, and the role of inflammation in the biology of adversity focusing on glucocorticoid resistance and key inflammatory cytokines linked to psychosocial and environmental stressors (PSES). We then further discuss the effect of SDoH on immune cell distribution and characterization by subset, receptor expression, and function. Lastly, we describe epigenetic regulation of the chronic stress response and effects of SDoH on telomere length and aging. Ultimately, we highlight critical knowledge gaps for future research as we strive to develop more targeted interventions that account for SDoH to improve cardiometabolic health for at-risk, vulnerable populations.

Inflammation-induced iron transport and metabolism by brain microglia.

Microglia are immune cells of the central nervous system and are implicated in brain inflammation. However, how brain microglia modulate transport and metabolism of the essential metal iron in response to pro- and anti-inflammatory environmental cues is unclear. Here, we characterized uptake of transferrin (Tf)-bound iron (TBI) and non-Tf-bound iron (NTBI) by immortalized microglial (IMG) cells. We found that these cells preferentially take up NTBI in response to the proinflammatory stimulus lipopolysaccharide (LPS) or ß-amyloid (Aß). In contrast, the anti-inflammatory cytokine interleukin 4 (IL-4) promoted TBI uptake. Concordant with these functional data, levels of the Tf receptor (TfR) in IMG cells were up-regulated in response to IL-4, whereas divalent metal transporter-1 (DMT1) and ferritin levels increased in response to LPS or Aß. Similar changes in expression were confirmed in isolated primary adult mouse microglia treated with pro- or anti-inflammatory inducers. LPS-induced changes in IMG cell iron metabolism were accompanied by notable metabolic changes, including increased glycolysis and decreased oxidative respiration. Under these conditions, the extracellular acidification rate was increased, compatible with changes in the cellular microenvironment that would support the pH-dependent function of DMT1. Moreover, LPS increased heme oxygenase-1 (HO1) expression in IMG cells, and iron released because of HO1 activity increased the intracellular labile free-iron pool. Together, this evidence indicates that brain microglia preferentially acquire iron from Tf or from non-Tf sources, depending on their polarization state; that NTBI uptake is enhanced by the proinflammatory response; and that under these conditions microglia sequester both extra- and intracellular iron.

Social determinants of health, health disparities, and adiposity.

Social determinants of health (SDoH), or the socioeconomic, environmental, and psychosocial conditions in which individuals spend their daily lives, substantially influence obesity as a cardiovascular disease (CVD) risk factor. The coronavirus disease 2019 (COVID-19) pandemic highlighted the converging epidemics of obesity, CVD, and social inequities globally. Obesity and CVD serve as independent risk factors for COVID-19 severity and lower-resourced populations most impacted by adverse SDoH have the highest COVID-19 mortality rates. Better understanding the interplay between social and biologic factors that contribute to obesity-related CVD disparities are important to equitably address obesity across populations. Despite efforts to investigate SDoH and their biologic effects as drivers of health disparities, the connections between SDoH and obesity remain incompletely understood. This review aims to highlight the relationships between socioeconomic, environmental, and psychosocial factors and obesity. We also present potential biologic factors that may play a role in the biology of adversity, or link SDoH to adiposity and poor adipo-cardiology outcomes. Finally, we provide evidence for multi-level obesity interventions targeting multiple aspects of SDoH. Throughout, we emphasize areas for future research to tailor health equity-promoting interventions across populations to reduce obesity and obesity-related CVD disparities.

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 between neighborhood socioeconomic deprivation, IFNγ, and high-density lipoprotein particle size: Data from the Washington, D.C. cardiovascular health and needs assessment.

INTRODUCTION: Neighborhood socioeconomic deprivation is associated with increased cardiovascular risk factors, including inflammation. Inflammation plays an important role in modifying the cardioprotective function of high-density lipoprotein (HDL). Moreover, recent studies suggest that very high HDL is associated with adverse cardiovascular disease (CVD) outcomes. Thus, we sought to explore the relationships between neighborhood socioeconomic deprivation as a marker of chronic stress, inflammation, proprotein convertase subtilisin/kexin type 9 (PCSK9) (a core component of the HDL proteome), HDL characterisitcs, and biological aging as a predictor of CVD and all-cause mortality. METHODS: Sixty African American subjects were recruited to the NIH Clinical Center as part of a community-based participatory research-designed observational study. Neighborhood deprivation index (NDI), a marker of neighborhood socioeconomic deprivation, was measured using US Census data. HDL characteristics (cholesterol, particle number, size, subspecies) were determined from NMR lipoprotein profiling, and plasma cytokines (IL-1ß, IL-6, IL-8, TNFα, IFNγ) were measured using an ELISA-based multiplex technique. Epigenetic clock biomarkers of aging were measured using DNA methylation data obtained from participants' buffy coat samples. We used linear regression modeling adjusted for atherosclerotic cardiovascular disease (ASCVD) risk score, body mass index (BMI), and lipid-lowering medication use to investigate relationships of interest. RESULTS: NDI directly associated with large HDL particle count (H7P) and IFNγ and trended toward significance with HDL-C and PCSK9. IFNγ and PCSK9 then directly associated with H7P. H7P also directly associated with higher DNA methylation phenotypic age (PhenoAge). CONCLUSION: We highlight associations between neighborhood socioeconomic deprivation, IFNγ, PCSK9, HDL subspecies, and epigenetic biomarkers of aging. Taken together, our findings suggest indirect pathways linking neighborhood deprivation-related stress and inflammation to HDL and immune epigenetic changes. Moreover, these results add to recent work showing the pathogenicity of high HDL levels and underscore the need to understand how chronic stress-related inflammation and lipoprotein subspecies relate to CVD risk across diverse populations.

Social Determinants modulate NK cell activity via obesity, LDL, and DUSP1 signaling.

Adverse social determinants of health (aSDoH) are associated with obesity and related comorbidities like diabetes, cardiovascular disease, and cancer. Obesity is also associated with natural killer cell (NK) dysregulation, suggesting a potential mechanistic link. Therefore, we measured NK phenotypes and function in a cohort of African-American (AA) women from resource-limited neighborhoods. Obesity was associated with reduced NK cytotoxicity and a shift towards a regulatory phenotype. In vitro, LDL promoted NK dysfunction, implicating hyperlipidemia as a mediator of obesity-related immune dysregulation. Dual specific phosphatase 1 (DUSP1) was induced by LDL and was upregulated in NK cells from subjects with obesity, implicating DUSP1 in obesity-mediated NK dysfunction. In vitro, DUSP1 repressed LAMP1/CD107a, depleting NK cells of functional lysosomes to prevent degranulation and cytokine secretion. Together, these data provide novel mechanistic links between aSDoH, obesity, and immune dysregulation that could be leveraged to improve outcomes in marginalized populations.