Effects of thiol compounds on methotrexate uptake by murine lymphocytes from thymus and thymic lymphosarcoma

Human galectin-1, -2, and -4 induce surface exposure of phosphatidylserine in activated human neutrophils but not in activated T cells

Cellular turnover is associated with exposure of surface phosphatidylserine (PS) in apoptotic cells, leading to their phagocytic recognition and removal. But recent studies indicate that surface PS exposure is not always associated with apoptosis. Here we show that several members of the human galectin family of glycan binding proteins (galectins-1, -2, and -4) induce PS exposure in a carbohydrate-dependent fashion in activated, but not resting, human neutrophils and in several leukocyte cell lines. PS exposure is not associated with apoptosis in activated neutrophils. The exposure of PS in cell lines treated with these galectins is sustained and does not affect cell viability. Unexpectedly, these galectins bind well to activated T lymphocytes, but do not induce either PS exposure or apoptosis, indicating that galectin's effects are cell specific. These results suggest novel immunoregulatory contribution of galectins in regulating leukocyte turnover independently of apoptosis.

Effect of 5-fluorouracil on methotrexate transport and cytotoxicity in HT29 colon adenocarcinoma cells

Exposure of the human colon adenocarcinoma HT29 cells to different concentrations of 5-fluorouracil (5FU) for 24 h resulted in a dose-dependent increase in the cellular glutathione (GSH) level which remained elevated up to 72 h following 5FU treatment. Pretreatment of HT29 cells with 5FU was found to enhance the uptake of methotrexate (MTX) as compared to control cells. Administration of MTX 24 h after 5FU was found to be synergistic, whereas administration of MTX 24 h before 5FU or together with 5FU was not found to be synergistic. The results of this study suggest that the increase in cellular GSH level as a result of 5FU pretreatment may play a role in the enhancement of MTX uptake and the cytotoxicity of both drugs in HT29 cells.