The expression of monocyte chemotactic protein (MCP-1) in human vascular endothelium in vitro and in vivo

A monocyte chemotactic protein (MCP-1) is thought to play a major role in recruiting monocytes to the vascular endothelium where the adherence of monocytes is one of the earliest events in atherogenesis. We cloned MCP-1 cDNA from a λgt 11 cDNA library constructed from human aortic endothelial mRNA to test whether MCP-1 expressed in arterial endothelium is identical to those from other sources. A ∼ 670 bp MCP-1 cDNA clone was identified and showed the identical sequence with the ones from other cell lines. Northern blot analysis using this cloned MCP-1 cDNA as probe revealed two hybridizing bands of RNA at 0.68 and 0.77 kb in human aortic, human pulmonary arterial, and human umbilical vein endothelial cell cultures. Primer extension analysis showed that the difference in size (∼ 90 bp) between the two transcripts is not due to a difference at the 5′-noncoding region. The amount of MCP-1 transcripts increased dramatically in aortic endothelial cells when stimulated with recombinant IL-1α (100 units/ml), IL-1β (100 units/ml), or TNF-α (200 ng/ml). Northern blot and slot blot analysis of RNA isolated from both the endothelium and the underlying vessel wall of freshly removed human arteries and veins showed MCP-1 transcripts. This observation demonstrates for the first time that MCP-1 is expressed not only in atherosclerotic human arteries but also in symptom free arteries and veins in vivo.