The Effects of Carcinogenic Methylcholanthrene on Carbohydrate Residues of Nk Cells

Abstract

The present study examines the effect of methylcholanthrene (MCA), a carcinogenic polycylic hydrocarbon, on the carbohydrate receptor determinants (RD) on natural killer (NK) cell surface using the bead-coupled lectin assay. Murine NK cells exhibited different degrees of preferential binding to the specific lectins tested. Of the ten lectins tested, five exhibited a positive binding affinity while the remaining five exhibited no or insignificant binding. NK cells bind to beads derivatized with mannose specific lectins: Concanavalin A (Con A), Lens culinaris, and Pisum sativum. NK cells also bind to other lectin beads such as Triticum vulgaris (GalNac) and Vicia villosa (D-G1cNAc). All these lectin beads exhibited greater than 90% adhesion. The underivatized control beads exhibited no NK binding. The NK cells that were exposed to MCA for 2 h demonstrated a significant decrease in lectin bead-cell coupling in a dose dependent manner. MCA (10μg/mL) caused a 17.8%, 40% and 4.7% decrease in binding affinity when introduced to the mannose specific lectins; Con A, L. culinaris and P. sativum beads, respectively. The binding of T. vulgaris and V. villosa to NK cells was inhibited (23.4% and 28%) by MCA treatment. An increase in the dose to 20μg/mL resulted in a greater inhibition in binding affinity towards lectin beads, Con A, 35.3%, L. culinaris, 62.6%, P. sativum, 30.9%, T. vulgaris, 44.2% and V. villosa, 46.2%. The effect of MCA on the synthesis of NK polyphosphoinositides such as phosphatidylinositol 4-phosphate (PIP), phosphotidylinositol 4, 5- biphosphate (PIP2) was examined. The results showed lower phosphate 32 (32P)-labeling of PIP and PIP2 of MCA-treated NK cells as compared to untreated cells. Both of these MCA-induced cellular events (carbohydrate RD, PIP, and PIP2) may be interrelated at the level of transmembrane signal transduction, and may represent important steps in the inhibition of NK mediated cytotoxicity by this carcinogen.