Vitamin D receptor is expressed within human carotid plaques and correlates with pro-inflammatory M1 macrophages

The role of Vitamin D system in cardiovascular diseases remains controversial. Here, we investigated whether intraplaque levels of vitamin D receptor (VDR) predicted major adverse cardiovascular events (MACEs) at 18month-follow-up and correlated with macrophage subsets in 164 patients undergoing endarterectomy for carotid stenosis. In human carotid plaque portions upstream and downstream the blood flow, VDR, lipid, collagen, as well as macrophage subsets were determined. Human primary monocytes were then differentiated in vitro to M1 and M2 macrophages and treated with 1,25(OH)2D3. Intraplaque VDR positively correlated with total and M1 macrophages. According to the result of ROC curve analysis, downstream portions of plaques having high VDR expression were characterized by increased M1 macrophages. Kaplan-Meier analysis showed that the risk of MACEs was greater in patients having low downstream VDR levels (8.2% vs. 1.3%; p=0.005). Cox proportional hazard regression analyses confirmed that MACE risk decreased with increasing downstream VDR (adjusted HR 0.78 [95% CI 0.62-0.98]; p=0.032). In vitro, VDR expression was prevalent in M1, but not M2. Incubation of M1 macrophages with 1,25(OH)2D3, increased VDR expression and suppressed toll-like receptor 4 expression. These results suggest that low intraplaque VDR expression predict MACEs in patients with carotid stenosis potentially involving M1 macrophages.