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Abstract
Interleukin 6 (IL-6) and interleukin 8 (IL-8) are present in the human arterial atherosclerotic
wall as cellular and extracellular deposits in the connective tissue matrix. Quantitative
determinations of IL-6 by ELISA showed mean values of 27.6 +/- 3.3 ng/100 mg protein
in normal intima, 37.3 +/- 2.1 ng/100 mg protein in fibrous plaque and 25.7 +/- 4.3
ng/100 mg total extracted protein in media. IL-8 levels were 3.5 +/- 0.6 ng/100 mg
protein in normal intima, 11.3 +/- 2.1 ng/100 mg protein in fibrous plaque and 8.5
+/- 1.4 ng/100 mg total extracted protein in media. Fibrous plaques presented statistically
significant higher levels of both IL-6 and IL-8. IL-6 and IL-8 gene transcripts were
present in human iliac fibrous plaque and media prelevated at surgery indicating that
a local production by the cells of the arterial wall participate to their accumulation.
We also tested the role of complement activation in induction of IL-6 and IL-8 protein
synthesis as well as the subsequent activation of endothelial cells. Only IL-8 was
induced by complement activation and this may contribute to increased IL-8 levels
found in the atherosclerotic wall. When exposed to terminal complement complexes,
endothelial cells in culture also showed an increase of both DNA-synthesis and p70
S6 kinase activity indicating that complement is able to induce not only IL-8 synthesis
but also cell activation. The presence of IL-6 and IL-8 in the arterial wall where
complement activation also occurred, clearly show the involvement of inflammatory
events in initiation and progression of atherosclerosis.