S-homocysteinylated LDL apolipoprotein B adversely affects human endothelial cells in vitro.
OBJECTIVE
In recent years elevated homocysteine (Hcy) levels have been widely recognized as a risk factor for cardiovascular diseases (CVDs) and a connection between hyperhomocysteinemia and lipid metabolism has been suggested to have a possible role in endothelial vascular damage as lipoprotein fractions contain higher Hcy levels in hypercholesterolemia, compared to normolipidemic individuals. However, the biochemical events underlying the interaction between Hcy and LDL are still poorly understood.


RESULTS
Herein we have investigated the interaction of LDL with Hcy by measuring thiols S-linked to apoprotein using capillary electrophoresis and have evaluated the effect of S-homocysteinylated LDL on human endothelial cells (HECs). We found that Hcy binds to LDL in a dose dependent manner and the saturation binding is achieved at 100 micromol/L Hcy in about 5h. Addition of Hcy resulted in a rapid displacement of other thiols bound to apoprotein and this was dependent on the concentration of Hcy added. For the first time we also demonstrated that treatment of HECs with homocysteine-S-LDL (Hcy-S-LDL) resulted in the induction of significantly higher levels of reactive oxygen species (ROS) compared to N-LDL (native LDL). Furthermore, the Hcy-S-LDL-induced a rise in intracellular ROS production was followed by a marked reduction of HECs proliferation and viability.


CONCLUSIONS
Although the mechanism by which Hcy-S-LDL elicits the current cellular effects needs further investigation, our data suggest that intracellular ROS production induced by Hcy-S-LDL might be responsible for the observed HECs damage and indicate that Hcy-S-LDL may have some role in CVD.
Zinellu
Angelo
A
Department of Biomedical Sciences, University of Sassari, Viale San Pietro 43/B, Sassari, Italy. angelozinellu@libero.it
Sotgia
Salvatore
S
Scanu
Bastianina
B
Pintus
Gianfranco
G
Posadino
Anna Maria
AM
Cossu
Annalisa
A
Deiana
Luca
L
Sengupta
Shantanu
S
Carru
Ciriaco
C
D001055:Apolipoproteins B / Q000378:metabolism / Q000633:toxicity*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006710:Homocysteine / Q000378:metabolism; D006801:Humans; D017382:Reactive Oxygen Species / Q000378:metabolism
D001055:Apolipoproteins B; D017382:Reactive Oxygen Species; D006710:Homocysteine