Publications

BACKGROUND

Patients with acute coronary syndromes have elevated plasma levels of the proinflammatory, prothrombotic cytokine CD40 ligand (sCD40L). Statins inhibit CD40L signaling in vitro, but there are no prospective studies of statins and sCD40L in acute coronary syndromes.

METHODS AND RESULTS

We measured sCD40L in subjects with an acute coronary syndrome enrolled in the Myocardial Ischemia Reduction with Aggressive Cholesterol Lowering (MIRACL) study. Subjects were randomized in this double-blind trial to atorvastatin 80 mg/d or placebo for 16 weeks. Plasma CD40L was measured from 2908 (94%) of 3086 subjects at baseline and 2352 (76%) at 16 weeks. Odds ratios (ORs) and 95% CIs from logistic regression models assessed the risk of recurrent cardiovascular events over 16 weeks (death, nonfatal myocardial infarction, cardiac arrest, and worsening angina requiring rehospitalization) in the placebo group from baseline sCD40L and the effect of atorvastatin on the risk associated with CD40L in all subjects. The effects of atorvastatin on plasma concentrations of CD40L were assessed by Wilcoxon tests. There was a threshold effect, with only high sCD40L (>90th centile) being a risk factor for a recurrent cardiovascular event (OR 1.86, 95% CI 1.25 to 2.77). This risk was abolished by atorvastatin (OR 1.09, 95% CI 0.69 to 1.76), which reduced the risk by 48%. Atorvastatin had only a modest effect on sCD40L (P=0.08).

CONCLUSIONS

In patients with acute coronary syndromes, atorvastatin abrogated the risk of recurrent cardiovascular events associated with high sCD40L. Early statin therapy after acute coronary syndromes counters the risk associated with elevated sCD40L.

The type B natriuretic peptide receptor (NPR-B) is the cognate receptor for the C-type natriuretic peptide and, as such, is responsible for signaling growth-suppressant activity in vascular smooth muscle cells. Here we report the isolation and characterization of the human (h) NPR-B gene promoter. Using 5' rapid amplification of cDNA ends analysis, we have identified the 5' terminus of the hNPR-B gene transcript approximately 732 base pairs upstream from the presumed translation start site of the protein. We generated a series of 5' deletion mutants linked to a luciferase reporter and introduced these constructs into rat aortic smooth muscle cells or neonatal rat cardiac fibroblasts. Maximal expression was seen with a construct harboring 441 base pairs of 5' flanking sequence. Site-directed mutagenesis of the proximal promoter revealed a series of GC-rich sequences, 5 of which contributed modestly (approximately 25%) to basal hNPR-B promoter activity. Mutation of a sixth GC-rich sequence led to a >90% reduction in promoter activity. This sequence was shown to associate with Sp1 and Sp3 in vitro. The same mutation that resulted in loss of functional activity also resulted in loss of binding activity in vitro. Overexpression of Sp1 or Sp3 in Drosophila Schneider cells resulted in an increase in hNPR-B promoter activity that was completely nullified with the Sp1 binding site mutation described above. These studies provide the first description and characterization of the NPR-B gene promoter and suggest that this promoter's activity is dominated by a single cluster of Sp1-binding elements in the proximal 5' flanking sequence of the gene.