Over the past two decades, the inflammatory hypothesis of atherothrombosis has gained an increasingly strong footing through multiple lines of supportive evidence. Overall, an increased systemic burden of inflammation prompts a higher CVD incidence, as is the case in chronic inflammatory conditions such as rheumatic arthritis [
8] and systemic lupus erythematosus [
9]. Various soluble mediators of the inflammatory response have been found to predict future cardiovascular risk in atherosclerotic patients (well-described in [
10]). High-sensitivity C-reactive protein (hsCRP) has formed a focus point in this respect, as systemic concentrations of this acute-phase protein compared favorably with LDL cholesterol and blood pressure as CVD risk factors [
11], and were specifically associated to plaque vulnerability [
12,
13]. Building on post hoc analyses from several other large-scale studies (eg, CARE, PROVE-IT TIMI 22, AFCAPS/TexCAPS trials [
14‐
16]), the JUPITER trial prospectively consolidated the correlation of hsCRP and cardiovascular outcome in a primary prevention setting [
17]. Researchers observed that the clinical benefits of statin therapy were greatest when both LDL and hsCRP values were reduced, thus connecting both dyslipidemia and inflammation at the interface of CVD pathogenesis. Intriguingly, even with pre-existent LDL levels below the clinical cut-off point for treatment, persistent inflammation as measured by increased hsCRP levels puts patients at a higher than anticipated risk of CVD. In the AFCAPS/TexCAPS trial, these subjects responded strongly to treatment [
16], indicating LDL burden is not a prerequisite to successful therapy. Apart from providing clinicians with valuable information for risk assessment, this finding proposes that an enhanced inflammatory state might in itself justify targeted therapy. Indeed, US and Canadian prevention guidelines have since embraced hsCRP measurements in the considerations for patients at intermediate risk. Moreover, a number of new trials, using either low-dose methotrexate (CIRT) or anti-IL-1β monoclonal antibodies (CANTOS) as anti-inflammatory treatment, are underway to address and possibly validate the hypothesis of inflammatory causality [
18•,
19•]. These translational efforts could provide a major argument towards a more systematic implementation of anti-inflammatory therapy in our continuing battle to diminish residual cardiovascular risk.
Substantial experimental evidence complements the broad clinical involvement of inflammation in CVD outlined above. Now most agree that systemic risk factors interact with many cell types (both those intrinsic to the vasculature and immune cells attracted from the circulation) to drive plaque development. Particularly, monocyte-derived macrophages are considered critical participants in the atherogenic process, as they secrete pro-inflammatory cytokines and other mediators that affect lesion progression and stability. Consequently, many experimental studies have successfully targeted the abundance of monocytes/macrophages and their soluble repertoire in atherosclerosis as a means of prevention. For instance, atherosclerotic plaque formation was virtually abolished in hyperlipidemic mice lacking the macrophage-colony stimulating factor (M-CSF) gene, which exhibit impaired monocyte development and subsequent differentiation to macrophages [
20,
21]. Other scientific efforts involved the abrogation of chemokine-dependent monocyte recruitment to the plaque [
22], in addition to a wealth of studies addressing the various cytokines produced by macrophages and other cells (reviewed in [
23]). Although not cell-specific, these data still offer valuable insight into how macrophages contribute to nascent lesions. Macrophage apoptosis is another important feature seen during atherosclerosis development. In early lesions, macrophage apoptosis and plaque size exist in an inverse relationship [
24], whereas in later stages this process contributes to the plaque’s lipid core [
25]. This ambiguity appears to be mediated by a process termed “efferocytosis” [
26]. Combined with proof linking plaque macrophages to matrix metalloproteinase (MMP)-dependent collagen breakdown [
27,
28], it is evident that these cells modulate inflammatory mechanisms to determine plaque susceptibility to rupture and clinical atherothrombosis. Associative imaging studies lend weight to this notion by demonstrating that vascular uptake of fluorodeoxyglucose (
18F-FDG) correlates to plaque macrophage load and general inflammatory burden and can thereby assist in the prediction of cardiovascular events [
29,
30].