Induction of 15-lipoxygenase mRNA and protein in early atherosclerotic lesions.
BACKGROUND
15-Lipoxygenase (15-LO) may be involved in atherogenesis and in oxidative modification of LDL. In this study, we investigated 15-LO expression in developing atherosclerotic lesions and verified the exact type of the atherosclerosis-associated LO at the nucleotide level.


RESULTS
Quantitative reverse transcription-polymerase chain reaction, in situ hybridization, and immunocytochemistry were used in two models of experimental atherosclerosis. New Zealand White rabbits were given a 1% cholesterol diet for 0 (control group), 3, 6, or 14 weeks. 15-LO mRNA was undetectable in the aortic intima-medias of the control group, whereas it was clearly induced as early as after 3 weeks. 15-LO expression increased further in the 6- and 14-week groups. According to in situ hybridization and immunocytochemical studies, 15-LO was localized to macrophagerich areas. In Watanabe heritable hyperlipidemic rabbits, 15-LO mRNA was undetectable in normal aortic intima-medias. 15-LO mRNA was markedly induced in fatty streaks but less so in more advanced lesions. Identification of the induced LO as reticulocyte-type 15-LO was done by cloning and sequencing. We also observed a distinct basal expression of copper-zinc and extracellular superoxide dismutases in normal aortic intima-medias, but no clear induction of these mRNAs was detected in atherosclerotic aortas.


CONCLUSIONS
The results show that, in contrast to copper-zinc and extracellular superoxide dismutases, the expression of reticulocyte-type 15-LO is markedly induced in rabbit fatty streaks. This may lead to an increase in the oxidative potential during the early phase of atherogenesis and contribute to the development of atherosclerotic lesions.
Hiltunen
T
T
Department of Medical Biochemistry, Medical School, University of Tampere, Finland.
Luoma
J
J
Nikkari
T
T
Ylä-Herttuala
S
S
D000199:Actins / Q000096:biosynthesis; D000818:Animals; D001013:Aorta, Thoracic / Q000201:enzymology; D001093:Arachidonate 15-Lipoxygenase / Q000096:biosynthesis* / Q000737:chemistry; D001161:Arteriosclerosis / Q000201:enzymology*; D002791:Cholesterol, Dietary / Q000008:administration & dosage; D015870:Gene Expression; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000096:biosynthesis; D017403:In Situ Hybridization; D008264:Macrophages / Q000201:enzymology; D008297:Male; D016133:Polymerase Chain Reaction / Q000379:methods; D012333:RNA, Messenger / Q000235:genetics; D011817:Rabbits; D013482:Superoxide Dismutase / Q000096:biosynthesis; D013997:Time Factors; D017539:Tunica Intima / Q000201:enzymology; D017540:Tunica Media / Q000201:enzymology
D000199:Actins; D002791:Cholesterol, Dietary; D012333:RNA, Messenger; D001093:Arachidonate 15-Lipoxygenase; D013482:Superoxide Dismutase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases