Selective absorption of ultraviolet laser energy by human atherosclerotic plaque treated with tetracycline

Abstract

Tetracycline is an antibiotic that absorbs ultraviolet light at 355 nm and preferentially binds to atherosclerotic plaque both in vitro and in vivo. Tetracycline-treated human cadaveric aorta was compared with untreated aorta using several techniques: absorptive spectrophotometry, which demonstrated a distinct absorptive peak at 355 nm in tetracycline-treated plaque that was absent in treated normal vessel; ultraviolet microscopy, which showed that treated atheroma acquired the characteristic fluorescence of tetracycline under ultraviolet light; and tissue uptake of radiolabeled tetracycline, which showed 4-fold greater uptake by atheroma than by normal vessel. In addition, intravenous tetracycline administered to patients undergoing vascular surgery demonstrated characteristic fluorescence in surgically excised diseased arteries. Because of tetracycline's unique properties, we exposed tetracycline-treated and untreated aorta to ultraviolet laser radiation at a wavelength of 355 nm. We found enhanced ablation of tetracycline-treated atheroma compared with untreated atheroma. The plaque ablation caused by ultraviolet laser radiation was twice as extensive in tetracycline-treated vs nontreated plaque (2.2 ± 0.25 mm vs 1.3 ± 0.55 mm, p < 0.017). This study demonstrates the potential of tetracycline plaque enhancement for the selective destruction of atheroma by ultraviolet laser radiation.