Background— Given the central importance of nitric oxide (NO) in the development and clinical course of cardiovascular diseases, we sought to determine whether the powerful predictive value of C-reactive protein (CRP) might be explained through an effect on NO production. Methods and Results— Endothelial cells (ECs) were incubated with recombinant CRP (0 to 100 μg/mL, 24 hours), and NO and cyclic guanosine monophosphate (cGMP) production was assessed. The effects of CRP on endothelial NO synthase (eNOS) protein, mRNA expression, and mRNA stability were also examined. In a separate study, the effects of CRP (25 μg/mL) on EC cell survival, apoptosis, and in vitro angiogenesis were evaluated. Incubation of ECs with CRP resulted in a significant inhibition of basal and stimulated NO release, with concomitant reductions in cGMP production. CRP caused a marked downregulation of eNOS mRNA and protein expression. Actinomycin D studies suggested that eNOS downregulation was related to decreased mRNA stability. In conjunction with a decrease in NO production, CRP inhibited both basal and vascular endothelial growth factor–stimulated angiogenesis as assessed by EC migration and capillary-like tube formation. CRP did not induce EC survival but did, however, promote apoptosis in a NO-dependent fashion. Conclusions— CRP, at concentrations known to predict adverse vascular events, directly quenches the production of the NO, in part, through posttranscriptional effect on eNOS mRNA stability. Diminished NO bioactivity, in turn, inhibits angiogenesis, an important compensatory mechanism in chronic ischemia. Through decreasing NO synthesis, CRP may facilitate the development of diverse cardiovascular diseases. Risk reduction strategies designed to lower plasma CRP may be effective by improving NO bioavailability.

Atherosclerotic disease remains the leading cause of death in industrialized nations despite major advances in its diagnosis, treatment, and prevention. The increasing epidemic of obesity, insulin resistance, and diabetes will likely add to this burden. Increasingly, it is becoming apparent that adipose tissue is an active endocrine and paracrine organ that releases several bioactive mediators that influence not only body weight homeostasis but also inflammation, coagulation, fibrinolysis, insulin resistance, diabetes, and atherosclerosis. The cellular mechanisms linking obesity and atherosclerosis are complex and have not been fully elucidated. This review summarizes the experimental and clinical evidence on how excess body fat influences cardiovascular health through multiple yet converging pathways. The role of adipose tissue in the development of obesity-linked insulin resistance, metabolic syndrome, and diabetes will be reviewed, including an examination of the molecular links between obesity and atherosclerosis, namely, the effects of fat-derived adipokines. Finally, we will discuss how these new insights may provide us with innovative therapeutic strategies to improve cardiovascular health.

Background— Adipocyte-derived hormones may represent a mechanism linking insulin resistance to cardiovascular disease. In the present study, we evaluated the direct effects of resistin, a novel adipocyte-derived hormone, on endothelial activation. Methods and Results— Endothelial cells (ECs) were incubated with human recombinant resistin (10 to 100 ng/ML, 24 hours), and endothelin-1 (ET-1) release, ET-1 mRNA expression, and nitric oxide (NO) production were assessed. Transient transfection assays were used to evaluate the effects of resistin on transcription of human ET-1 gene promoter. Furthermore, the effects of resistin on AP-1–mutated ET-1 promoter were evaluated. The effects of resistin on expression of vascular cell adhesion molecule (VCAM-1) and monocyte chemoattractant chemokine (MCP-1) were studied in addition to CD40 receptor, CD40 ligand–induced MCP-1 expression, and tumor necrosis factor receptor–associated factor-3 (TRAF3), an inhibitor of CD40 signaling. Incubation of ECs with resistin resulted in an increase in ET-1 release and ET-1 mRNA expression, with no change in NO production. Whereas treatment with resistin resulted in an increase in ET-1 promoter activity, the AP-1–mutated promoter was inactive after resistin stimulation. Additionally, resistin-treated cells showed increased expression of VCAM-1 and MCP-1, with concomitant reductions in TRAF-3 expression. Resistin did not alter CD40 receptor expression; however, increased CD40 ligand induced MCP-1 production. Conclusions— The novel adipokine resistin exerts direct effects to promote EC activation by promoting ET-1 release, in part by inducing ET-1 promoter activity via the AP-1 site. Furthermore, resistin upregulates adhesion molecules and chemokines and downregulates TRAF-3, an inhibitor of CD40 ligand signaling. In this fashion, resistin may be mechanistically linked to cardiovascular disease in the metabolic syndrome.

Background — C-reactive protein (CRP) has been suggested to actively participate in the development of atherosclerosis. In the present study, we examined the role of the potent endothelium-derived vasoactive factor endothelin-1 (ET-1) and the inflammatory cytokine interleukin-6 (IL-6) as mediators of CRP-induced proatherogenic processes. Methods and Results — Saphenous vein endothelial cells (HSVECs) were incubated with human recombinant CRP (25 μg/mL, 24 hours) and the expression of vascular cell adhesion molecule (VCAM-1), intracellular adhesion molecule (ICAM-1), and monocyte chemoattractant chemokine-1 was determined. The effects of CRP on LDL uptake were assessed in macrophages using immunofluorescent labeling of CD32 and CD14. In each study, the effect of endothelin antagonism (bosentan) and IL-6 inhibition (monoclonal anti-IL-6 antibodies) was examined. The effects of CRP on the secretion of ET-1 and IL-6 from HSVECs were also evaluated. Incubation of HSVECs with recombinant human CRP resulted in a marked increase in ICAM-1 and VCAM-1 expression ( P <0.001). Likewise, CRP caused a significant increase in monocyte chemoattractant chemokine-1 production, a key mediator of leukocyte transmigration ( P <0.001). CRP caused a marked and sustained increase in native LDL uptake by macrophages ( P <0.05). These proatherosclerotic effects of CRP were mediated, in part, via increased secretion of ET-1 and IL-6 ( P <0.01) and were attenuated by both bosentan and IL-6 antagonism ( P <0.01). Conclusions — CRP actively promotes a proatherosclerotic and proinflammatory phenotype. These effects are mediated, in part, via the production of ET-1 and IL-6 and are attenuated by mixed ET _A/B receptor antagonism and IL-6 inhibition. Bosentan may be useful in decreasing CRP-mediated vascular disease.

Background— Myocardial ischemia provides a potent stimulus to angiogenesis, and the mobilization and differentiation of endothelial progenitor cells (EPCs) has been shown to be important in this process. An elevated level of C-reactive protein (CRP) has emerged as one of the most powerful predictors of cardiovascular disease. However, the impact of CRP on EPC biology is unknown. Methods and Results— EPCs were isolated from the peripheral venous blood of healthy male volunteers. Cells were cultured in endothelial cell basal medium-2 in the absence and presence of CRP (5 to 20 μg/mL), rosiglitazone (1 μmol/L), and/or vascular endothelial growth factor. EPC differentiation, survival, and function were assayed. CRP at concentrations ≥15 μg/mL significantly reduced EPC cell number, inhibited the expression of the endothelial cell–specific markers Tie-2, EC-lectin, and VE-cadherin, significantly increased EPC apoptosis, and impaired EPC-induced angiogenesis. EPC-induced angiogenesis was dependent on the presence of nitric oxide, and CRP treatment caused a decrease in endothelial nitric oxide synthase mRNA expression by EPCs. However, all of these detrimental CRP-mediated effects on EPCs were attenuated by pretreatment with rosiglitazone, a peroxisome proliferator–activated receptor-γ (PPARγ) agonist. Conclusions— Human recombinant CRP, at concentrations known to predict adverse vascular outcomes, directly inhibits EPC differentiation, survival, and function, key components of angiogenesis and the response to chronic ischemia. This occurs in part via an effect of CRP to reduce EPC eNOS expression. The PPARγ agonist rosiglitazone inhibits the negative effects of CRP on EPC biology. The ability of CRP to inhibit EPC differentiation and survival may represent an important mechanism that further links inflammation to cardiovascular disease.