Homocysteine from endothelial cells promotes LDL nitration and scavenger receptor uptake.
We recently reported that methionine-loaded human umbilical vein endothelial cells (HUVECs) exported homocysteine (Hcy) and were associated with hydroxyl radical generation and oxidation of lipids in LDL. Herein we have analysed the Hcy-induced posttranslational modifications (PTMs) of LDL protein. PTMs have been characterised using electrophoretic mobility shift, protein carbonyl ELISA, HPLC with electrochemical detection and Western blotting of 3-nitrotyrosine, and LDL uptake by scavenger receptors on monocyte/macrophages. We have also analysed PTMs in LDL isolated from rheumatoid (RA) and osteo-(OA) arthritis patients with cardiovascular disease (CVD). While reagent Hcy (< 50 microM) promoted copper-catalysed LDL protein oxidation, Hcy released from methionine-loaded HUVECs promoted LDL protein nitration. In addition, LDL nitration was associated with enhanced monocyte/macrophage uptake when compared with LDL oxidation. LDL protein nitration and uptake by monocytes, but not carbonyl formation, was elevated in both RA and OA patients with CVD compared with disease-matched patients that had no evidence of CVD. Moreover, a direct correlation between plasma total Hcy (tHcy) and LDL uptake was observed. The present studies suggest that elevated plasma tHcy may promote LDL nitration and increased scavenger receptor uptake, providing a molecular mechanism that may contribute to the clinical link between CVD and elevated plasma tHcy.
Griffiths
Helen R
HR
Life and Health Sciences, Aston University, Birmingham B4 7ET, UK. h.r.griffiths@aston.ac.uk
Aldred
Sarah
S
Dale
Chloe
C
Nakano
Emi
E
Kitas
George D
GD
Grant
Melissa G
MG
Nugent
Desmond
D
Taiwo
Fatai A
FA
Li
Li
L
Powers
Hilary J
HJ
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000378:metabolism / Q000473:pathology; D015153:Blotting, Western; D002318:Cardiovascular Diseases; D016022:Case-Control Studies; D002478:Cells, Cultured; D002851:Chromatography, High Pressure Liquid; D003300:Copper / Q000494:pharmacology; D024202:Electrophoretic Mobility Shift Assay; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D008077:Lipoproteins, LDL / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008715:Methionine / Q000378:metabolism; D008875:Middle Aged; D009573:Nitrites / Q000378:metabolism*; D010003:Osteoarthritis / Q000378:metabolism / Q000473:pathology; D051116:Receptors, Scavenger / Q000378:metabolism*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D014471:Umbilical Veins / Q000166:cytology / Q000378:metabolism
D008077:Lipoproteins, LDL; D009573:Nitrites; D051116:Receptors, Scavenger; D006710:Homocysteine; C002744:3-nitrotyrosine; D014443:Tyrosine; D003300:Copper; D008715:Methionine