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 g/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 (PϽ0.001). Likewise, CRP caused a significant increase in monocyte chemoattractant chemokine-1 production, a key mediator of leukocyte transmigration (PϽ0.001). CRP caused a marked and sustained increase in native LDL uptake by macrophages (PϽ0.05). These proatherosclerotic effects of CRP were mediated, in part, via increased secretion of ET-1 and IL-6 (PϽ0.01) and were attenuated by both bosentan and IL-6 antagonism (PϽ0.01). 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.

Clinical trials of bone marrow stem/progenitor cell therapy after myocardial infarction (MI) have shown promising results, but the mechanism of benefit is unclear. We examined the nature of endogenous myocardial repair that is dependent on the function of the c-kit receptor, which is expressed on bone marrow stem/ progenitor cells and on recently identified cardiac stem cells. MI increased the number of c-kit + cells in the heart. These cells were traced back to a bone marrow origin, using genetic tagging in bone marrow chimeric mice. The recruited c-kit + cells established a proangiogenic milieu in the infarct border zone by increasing VEGF and by reversing the cardiac ratio of angiopoietin-1 to angiopoietin-2. These oscillations potentiated endothelial mitogenesis and were associated with the establishment of an extensive myofibroblast-rich repair tissue. Mutations in the c-kit receptor interfered with the mobilization of the cells to the heart, prevented angiogenesis, diminished myofibroblast-rich repair tissue formation, and led to precipitous cardiac failure and death. Replacement of the mutant bone marrow with wild-type cells rescued the cardiomyopathic phenotype. We conclude that, consistent with their documented role in tumorigenesis, bone marrow c-kit + cells act as key regulators of the angiogenic switch in infarcted myocardium, thereby driving efficient cardiac repair.

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 g/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 g/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. (Circulation. 2002;106:913-919.)