出版社：American Society for Biochemistry and Molecular Biology
摘要：Sphingomyelin synthase 1 (SMS1) and SMS2 are two isoforms ofSMS, the last enzyme for sphingomyelin (SM) biosynthesis. Toevaluate the role of SMS in vivo in terms of plasma lipoproteinmetabolism, we generated recombinant adenovirus vectors containinghuman SMS1 cDNA (AdV-SMS1), SMS2 cDNA (AdV-SMS2), or the reporterLacZ cDNA (AdV-LacZ) as a control. On day 7 after intravenousinfusion of 2 x 1011 particles of both AdV-SMS1 and AdV-SMS2into mice, liver SMS1 and SMS2 mRNA levels as well as SMS activitywere significantly increased (2.5-, 2.7-, 2.1-, and 2.3-fold,respectively; P < 0.001). Lipoprotein analysis indicatedthat AdV-SMS1 and AdV-SMS2 treatment caused no changes of totalSM and cholesterol levels but significantly decreased HDL-SMand HDL-cholesterol (42% and 38%, and 27% and 25%, respectively;P < 0.05). It also significantly increased non-HDL-SM andnon-HDL-cholesterol levels (50% and 35%, and 64% and 61%, respectively;P < 0.05) compared with AdV-LacZ controls. SDS-PAGE showeda significant increase in apolipoprotein B (apoB; P < 0.01)but no changes in apoA-I levels. Moreover, we found that non-HDLfrom both AdV-SMS1- and AdV-SMS2-treated mice was significantlyaggregated after treatment with a mammalian sphingomyelinase,whereas lipoproteins from control animals did not aggregate.To investigate the mechanism of HDL changes, we measured liverscavenger receptor class B type I (SR-BI) levels by Westernblot. We found that AdV-SMS1 and AdV-SMS2 mouse liver homogenatescontained 50% and 55% higher SR-BI levels than in controls,whereas no change was observed in hepatic ABCA1 levels. An HDLturnover study revealed an increase of plasma clearance ratesfor [3H]cholesteryl oleyl ether-HDL but not for [125I]HDL inboth AdV-SMS1 and AdV-SMS2 mice compared with controls. In conclusion,adenovirus-mediated SMS1 and SMS2 overexpression increased lipoproteinatherogenic potential. Such an effect may contribute to theincreased plasma SM levels observed in animal models of atherosclerosisand in human patients with coronary artery disease.Supplementary key words lipoprotein • atherosclerosis • sphingolipid
