Downregulation of Oxytocin Receptor Decreases the Length of Projections Stimulated by Retinoic Acid in the U-87MG Cells.

Oxytocin is a neuropeptide widely expressed in the brain. Oxytocin plays a role in both proliferation and differentiation of various cells. Previous studies have suggested that oxytocin could affect the morphology of neuronal cells, therefore the objective of the present study was to test whether (1) oxytocin receptor stimulation/inhibition by specific ligands may change cell morphology and gene expression of selected cytoskeletal proteins (2) oxytocin receptor silencing/knockdown may decrease the length of cell projections (3) oxytocin receptor knockdown may affect human glioblastoma U-87MG cell survival. We confirmed the stimulatory effect of retinoic acid (10 µM) and oxytocin (1 µM) on projection growth. The combination of retinoic acid (10 µM) and oxytocin receptor antagonist (L-371,257, 1 µM) decreased projections length. Contrary to our assumptions, oxytocin receptor silencing did not prevent stimulation of length of projection by retinoic acid. Retinoic acid's and oxytocin's stimulation of projections length was significantly blunted in U-87MG cells with oxytocin receptor knockdown. Cell viability was significantly decreased in U-87MG cells with oxytocin receptor knockdown. Significantly higher levels of mRNA for cytoskeletal proteins drebrin and vimentin were observed in response to oxytocin incubation for 48 h. The data obtained in the present study clearly show that oxytocin induces formation and elongation of cell projections in astrocyte-like U-87MG cells. The effect is mediated by oxytocin receptors and it is accompanied by an increase in gene expression of drebrin and vimentin. Thus, oxytocin receptor signaling, particularly in the glial cells, may play an important role in native cell life, differentiation processes, and tumor progression, as well.