concanavalin-a and Hyperhomocysteinemia

Moderate hyperhomocysteinaemia is established as an independent risk factor for atherosclerosis, thrombosis, stroke and dementia. Hyperhomocysteinaemia is mostly caused by the deficiency of B-vitamins folate and vitamin B12, which are essential cofactors in the remethylation of homocysteine to methionine. Interestingly, moderate hyperhomocysteinaemia is also often observed in chronic diseases, in which also elevated immune activation markers such as neopterin or sTNFR-II are found. In order to simulate immune activation in vitro, human peripheral blood mononuclear cells (PBMC) were stimulated with mitogens. Stimulation significantly increased homocysteine production in comparison with unstimulated PBMC; in parallel also neopterin formation was induced. Homocysteine formation was due to cell proliferation, proliferating T lymphocytes, and also the myelomonocytic cell line U-937 produced homocysteine. Treatment with the anti-inflammatory drug aspirin dose-dependently inhibited homocysteine production and also neopterin formation in human PBMC. Treatment with salicylic acid showed similar effects as aspirin; FACS analysis showed that both compounds inhibited cell proliferation by arresting cells in the G0/G1-phase. In U-937, both compounds also slightly induced apoptosis at 5 mm. Proliferation-induced homocysteine formation and in parallel also monocyte activation can be suppressed effectively by aspirin and salicylic acid in vitro, suggesting that also in vivo aspirin may downregulate not only inflammation but also formation of homocysteine.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Aspirin; Concanavalin A; Down-Regulation; Flow Cytometry; Homocysteine; Humans; Hyperhomocysteinemia; Leukocytes, Mononuclear; Lymphocyte Activation; Neopterin; Phytohemagglutinins; Pokeweed Mitogens; U937 Cells

An elevated plasma homocysteine (Hcy) level is considered an independent risk factor for atherosclerosis. However, the mechanisms by which hyperhomocysteinemia induces atherosclerosis are only partially understood. The effect of Hcy on T lymphocyte proliferation and its mechanisms were examined in normal and hyperhomocysteinemia ApoE-knockout mice.. The mouse splenic T-cells were treated with Hcy, related compounds and/or antioxidants in the presence or absence of Concanavalin A (Con A). DNA synthesis, cell apoptosis, interleukin-2 level and production of reactive oxygen species (ROS) were measured.. Hcy (0.3-3.0 mM) and related compounds with thiol (-SH), such as cysteine and glutathione significantly potentiated Con A-induced proliferation and partially inhibited apoptosis in T lymphocytes, but it had no direct effect on resting T lymphocyte. ApoE-knockout mice with hyperhomocysteinemia (the level of plasma Hcy was 20.3+/-2.9 vs. 2.6+/-0.6 microM in control group, P<0.05) had a significant promotion of T-cell proliferation in response to Con A. Hcy (0.3-3.0 mM) also increased the intracellular ROS. Radical scavengers reduced Hcy effect.. These data indicate that ROS generated by thiol (-SH) of Hcy auto-oxidation are involved in Hcy effect on Con A-induced T lymphocyte proliferation. These findings suggest a novel mechanism may be involved in chronic inflammatory progression of atherosclerosis with hyperhomocysteinemia.

Topics: Animals; Antioxidants; Apolipoproteins E; Apoptosis; Cell Division; Cells, Cultured; Concanavalin A; Dose-Response Relationship, Immunologic; Homocysteine; Hyperhomocysteinemia; Interleukin-2; L-Lactate Dehydrogenase; Male; Mice; Mice, Inbred BALB C; Mice, Knockout; Oxidative Stress; Reactive Oxygen Species; Spleen; Sulfhydryl Compounds; T-Lymphocytes