Cooperation of Hepatocytes in vitro in the Rhythm of Protein Synthesis is Promoted by the GM1 Ganglioside Contained in Vesicles and Liposomes

Abstract

The medium conditioned by dense, self-synchronized hepatocyte cultures was centrifuged at 150 000 g to obtain two fractions. The light fraction (supernatant fluid) contained ganglioside monomers and micelles, and the heavy fraction (pellet) contained gangliosides in the vesicles shed from the cell membrane. In the test populations of hepatocytes, the rhythm of protein synthesis was used as an indicator of cell synchronization resulting from their cooperative activity. Diluted hepatocyte cultures with asynchronous fluctuations of protein synthesis proved to be synchronized by both the initial conditioned medium and its vesicular fraction. Our previous studies have shown that this occurs under the effect of GM1 monosialoganglioside, which is released from cultured cells and accumulated in the conditioned medium. Liposomes consisting of GM1 and phosphatidylcholine from egg yolk (1 : 19 mol%), compared to free exogenous GM1, synchronized the rhythm of protein synthesis more effectively: synchronization was observed at a GM1 concentration in liposome suspension of only 0.0003 μM, compared to 0.06 μM and higher in the case of free GM1. Thus, GM1 as a component of membranes and monolayer lipid structures proved to be much more effective than free GM1 in promoting hepatocyte cooperation with respect to the rhythm of protein synthesis.