Dopamine D2‐Like Receptor Signaling and Downregulation of Filamin‐A May Drive the Association Between Neighborhood Socioeconomic Status and CCR2 Expression on Monocytes

Abstract

Social determinants of health (SDoH) include socioeconomic, environmental, and psychological factors that impact health. Low neighborhood socioeconomic status (nSES) is a SDoH that associates with cardiovascular mortality in longitudinal studies. While nSES as a chronic stress contributes to adverse health outcomes, the molecular mechanisms and pathogenesis are poorly understood. Previously, we found that residing in lower nSES areas may alter monocyte expression of C‐C chemokine receptor type 2 (CCR2), a regulator of monocyte recruitment during atherogenesis. To explore the effects of nSES as a chronic stress on monocyte CCR2 expression, we treated monocytes in vitro for 4 hours with catecholamines (epinephrine [Epi], norepinephrine [NE], or dopamine [DA]) used as stress biomarkers. Only DA increased CCR2 expression in a dose‐dependent manner (p<0.01), especially on non‐classical monocytes (NCM). In our current study, we investigated DA receptor signaling to learn which pathways may contribute to increases in CCR2 expression. Dopamine acts on five known receptors, the D1‐like receptors (D1 and D5) and D2‐like receptors (D2, D3, and D4). First, we performed flow cytometry on untreated monocytes and found D2 receptors were most abundant on the surface of all monocyte subsets (ie., classical monocytes [CM], intermediate monocytes [IM], and NCM as determined by CD14/CD16 expression). Furthermore, spearman correlation between D2‐like receptor surface expression and surface CCR2 expression in NCM suggested D2‐like receptor signaling (R2=0.79, p=0.04). Because the D2‐like receptor response is known to decrease cAMP levels compared to a D1‐like receptor response, a cAMP assay was performed on monocytes with DA treatment. Indicative of D2‐signaling, cAMP levels were found to be lower in DA‐treated monocytes compared to untreated controls (ctr 29.78pmol/ml vs DA 22.97 pmol/ml; p=0.038). We then investigated downstream mechanisms following DA signaling that could result in increased CCR2 expression. Filamin A (FlnA), a prominent actin‐cross‐linking protein, is known to regulate CCR2 recycling. We examined the expression of FlnA by flow cytometry and RT‐qPCR on flow sorted monocytes with and without DA treatment. There was a significant decrease in FlnA expression in NCM (p < 0.05), indicating a slowing of CCR2 recycling. Expression of an associated scaffold protein mRNA, b‐arrestin 1, was decreased by 66% in NCM (p= 0.008). Overall, we provide a novel immunological mechanism, driven by DA signaling and CCR2, for how nSES 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.