Effects of homocysteine on murine splenic B lymphocyte proliferation and its signal transduction mechanism.
OBJECTIVE
Elevated plasma homocysteine (Hcy) levels have been defined as an increased risk of atherosclerosis. However, the mechanisms that Hcy induces the development of atherosclerosis are not fully understood. Therefore, effect of Hcy on B lymphocyte proliferation and its cellular mechanism were examined in normal and hyperhomocysteinemia ApoE-knockout mice.


METHODS
Mouse B lymphocytes were incubated with Hcy, related compounds and/or antioxidants and/or inhibitors of PKC, p38 MAPK, NF-kappaB in the presence or absence of lipopolysaccharide. DNA synthesis, production of reactive oxygen species was measured.


RESULTS
Hcy (0.1-3.0 mM) and other compounds with thiol (-SH), such as cysteine and glutathione significantly increased resting and lipopolysaccharide-induced B lymphocyte proliferation. ApoE-knockout mice with hypercysteinemia (plasma Hcy levels were 20.3+/-2.9 vs. 2.6+/-0.6 microM in control, P<0.05) had a significant promotion of B cell proliferation in response to lipopolysaccharide. Hcy also increased intracellular reactive oxygen species production. Radical scavengers reduced Hcy-induced B lymphocyte proliferation. The promotion of Hcy was significantly inhibited by inhibitors of PKC (calphostin C and RO-31-8220), p38 MAPK (SB 202190 and PD 169316) and NF-kappaB (pyrrolidine dithiocarbamate).


CONCLUSIONS
The reactive oxygen species generated by thiol (-SH) auto-oxidation of Hcy are essential, and PKC, p38 MAPK and NF-kappaB are involved in the Hcy-induced B lymphocyte proliferation. Hyperhomocysteinemia may increase B lymphocyte susceptibility to inflammatory progression of atherosclerotic lesions.
Zhang
Q
Q
Institute of Vascular Medicine, Third Hospital, 100083, Beijing, People's Republic of China.
Zeng
X
X
Guo
J
J
Wang
X
X
D000704:Analysis of Variance; D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics; D001161:Arteriosclerosis / Q000201:enzymology / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D002374:Catalase / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003545:Cysteine / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D006710:Homocysteine / Q000097:blood / Q000494:pharmacology*; D007093:Imidazoles / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018345:Mice, Knockout; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors; D016328:NF-kappa B / Q000037:antagonists & inhibitors; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011725:Pyridines / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D013154:Spleen / Q000276:immunology*; D013268:Stimulation, Chemical; D013438:Sulfhydryl Compounds / Q000378:metabolism; D013482:Superoxide Dismutase / Q000494:pharmacology; D013859:Thiocarbamates / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases
D001057:Apolipoproteins E; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; D007093:Imidazoles; D007211:Indoles; D008070:Lipopolysaccharides; D016328:NF-kappa B; D009281:Naphthalenes; D011725:Pyridines; D011759:Pyrrolidines; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D013859:Thiocarbamates; D006710:Homocysteine; C020972:pyrrolidine dithiocarbamic acid; D007770:L-Lactate Dehydrogenase; D002374:Catalase; D013482:Superoxide Dismutase; D011493:Protein Kinase C; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D005978:Glutathione; C408604:2-(4-nitrophenyl)-4-(4-fluorophenyl)-5-(4-pyridinyl)-1H-imidazole; C058819:calphostin C; D003545:Cysteine; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C064758:Ro 31-8220; D004121:Dimethyl Sulfoxide