Change in chemical composition of lipids accumulated in atheromas of rabbits following photodynamic therapy.
OBJECTIVE
Mono-L-aspartyl chlorin e6 (NPe6) has been used in the photodynamic therapy of neoplasms. This substance has been shown to accumulate in atheroma of rabbits. We evaluated the change in the lipid components of atheromas after photodynamic therapy with NPe6 using Fourier transform infrared (FTIR) microspectroscopy.


METHODS
Rabbits were fed a cholesterol-rich diet for 20 weeks. Six hours after they were administered NPe6 (2 mg/kg), the atheroma present on the abdominal aorta was irradiated with a diode laser with 100 J/cm2 or 200 J/ cm2 of the tissue fluence. Tissue samples were prepared for FTIR and histological analysis.


RESULTS
Specimens of atheroma from the untreated animals appeared as fatty streaks whose infrared spectra exhibited characteristic peaks at 1,738(-1) cm-1, 1,468 cm-1, 1,380 cm-1, and 1,174 cm-1, indicating the accumulation of cholesterol ester. Seven days after photodynamic therapy, FTIR microspectroscopic analysis showed a marked decrease in the peak intensity in the treated atheroma related to the =C=O ester bond at 1738 cm-1 with no concomitant increase in the intensity of the peaks related to free cholesterol.


CONCLUSIONS
Findings suggest a dissociation of ester bonds and the depletion of cholesterol esters in the atheromas after photodynamic therapy with NPe6. The lipids accumulated in the atheroma were perhaps decreased or destroyed following such treatment.
Hayashi
J
J
Department of Medicine & Gerontology, School of Medicine, Kyorin University, Tokyo, Japan.
Saito
T
T
Aizawa
K
K
D000818:Animals; D001012:Aorta, Abdominal / Q000473:pathology; D001161:Arteriosclerosis / Q000473:pathology*; D002788:Cholesterol Esters / Q000737:chemistry / Q000378:metabolism; D004036:Diet, Atherogenic; D050356:Lipid Metabolism; D008055:Lipids / Q000737:chemistry; D010778:Photochemotherapy; D011817:Rabbits; D017550:Spectroscopy, Fourier Transform Infrared; D013329:Structure-Activity Relationship
D002788:Cholesterol Esters; D008055:Lipids