a1 Department of Medicine, University of Alberta, Edmonton, Alberta, Canada
a2 Alberta Institute for Human Nutrition, University of Alberta, Edmonton, Alberta, Canada
Gangliosides are glycosphingolipids found in cell membranes and human milk with important roles in cell proliferation, differentiation, growth, adhesion, migration, signalling and apoptosis. Similar changes in ganglioside composition occur during embryonic development, lactation and cancer cell differentiation. It is not known, however, whether ganglioside compositional changes that occur in differentiating colon cancer cells reflect changes that occur during intestinal development. The Caco-2 cell line is commonly used to study physiological and pathophysiological processes in the small intestine and colon. Therefore, to examine this question, undifferentiated and differentiated Caco-2 cells were grown and total lipid was extracted from cell supernatant fractions using the Folch method. The upper aqueous phase containing gangliosides was collected and purified. Total gangliosides were measured as ganglioside-bound N-acetyl neuraminic acid, while individual ganglioside content was quantified via a colorimetric assay for sialic acid and scanning densitometry. The total ganglioside content of differentiated Caco-2 cells was 2·5 times higher compared with undifferentiated cells. Differentiated Caco-2 cells had significantly more (N-acetylneuraminyl) 2-galactosylglucosyl ceramide (GD3) and polar gangliosides, and a lower N-acetylneuraminylgalactosylglucosylceramide (GM3):GD3 ratio than undifferentiated cells. The present study demonstrates that the total ganglioside content and individual ganglioside composition of differentiated Caco-2 cells are similar to those of human colostrum and neonatal rat intestine. Differentiated Caco-2 cells may therefore be an alternative model for studying physiological and pathological processes in the small intestine and colon, and may help to elucidate possible functions for specific gangliosides in development and differentiation. Further research using more sensitive techniques of ganglioside analysis is needed to confirm these findings.
(Received October 19 2007)
(Revised May 23 2008)
(Accepted June 17 2008)
(Online publication August 20 2008)
Abbreviations: EMEM, Earle's minimum essential medium; GD3, (N-acetylneuraminyl) 2-galactosylglucosyl ceramide; GM2, N-acetylgalactosaminyl-galactosyl-(n-acetylneuraminyl)-glucosylceramide; GM3, N-acetylneuraminylgalactosylglucosylceramide; NANA, N-acetyl neuraminic acid; SAT, sialyltransferase; Tris, 2-amino-2-hydroxymethyl-propane-1,3-diol