Up-regulation of a hydrogen peroxide–responsive pre-mRNA binding protein in atherosclerosis and intimal hyperplasia

BackgroundMultiple lines of investigation have implicated hydrogen peroxide (H2O2) as an important endogenous mediator of cell proliferation in the vessel wall. Heterogeneous nuclear ribonucleoprotein C (hnRNP-C), a nuclear pre-mRNA binding protein that plays roles in vertebrate cell proliferation and differentiation, has been identified as a component of a vascular cell signaling pathway activated by low physiologic levels of H2O2. The expression of hnRNP-C in human arteries has not previously been assessed.MethodsSegments of human proximal internal carotid arteries were evaluated for the expression of hnRNP-C by immunohistochemistry.ResultsIn normal proximal internal carotid arteries, hnRNP-C is expressed predominantly by the endothelium, with significantly lower expression by medial smooth muscle. In preatherosclerotic intimal hyperplasia, hnRNP-C is up-regulated in the artery wall, due to the robust expression by the intimal smooth muscle cells, without up-regulation in the medial smooth muscle cells. In arteries with atherosclerotic lesions, there is strong expression of hnRNP-C not only by intimal cells but also by medial smooth muscle cells.ConclusionsThe H2O2 responsive pre-mRNA binding protein hnRNP-C is up-regulated in atherosclerosis and in preatherosclerotic intimal hyperplasia in humans, supporting the hypothesis that H2O2 is a regulator of vascular cell proliferation in these conditions. These data also suggest that hnRNP-C may be useful as a marker of vascular cell activation.