Membrane lipids in bromodeoxyuridine-differentiated astroglial cells in culture

Effects of differentiation on the phospholipid and phospholipid fatty acid composition of N1E-115 neuroblastoma cells

The effects of differentiation on the phospholipid and phospholipid fatty acid composition of N1E-115 neuroblastoma cells were determined. The cellular lipids were extracted on days 0, 3 and 7, following the addition of 1.2% dimethylsulfoxide to induce cellular differentiation. Proportions of ethanolamine glycerophospholipids (EtnGpl), phosphatidylinositol (PtdIns) and sphingomyelin (CerPCho) were significantly elevated following differentiation. The mole percentage of choline glycerophospholipids (ChoGpl) decreased with differentiation. The plasmalogens, both choline and ethanolamine, increased by 1.3- and 2.3-fold, respectively, during differentiation. The fatty acid composition of the phospholipid classes was also altered. PtdIns and ChoGpl had decreased proportions of polyenoic fatty acids, while these proportions were increased in EtnGpl. Both ChoGpl and EtnGpl had increased n-3/n-6 series fatty acid ratios, but this ratio was decreased in PtdIns. The mole percentage of arachidonic acid was significantly decreased in both PtdIns and ChoGpl, but elevated in EtnGpl and may be a result of the increase in ethanolamine plasmalogen. Thus, differentiation did not increase the overall mole percentage of polyenoic FA in the cells nor increase the n-6 series fatty acid proportions. We speculate plasmalogens may have a role in the differentiation process or in maintaining the cell in the differentiated state.

Differential effect of butyrate on lipids of human colon cancer cells

Recently, we demonstrated that treatment of LS174T cells with 2 mM butyrate for one day had a significant effect on the composition of cellular fatty acids. In an attempt to further explore this phenomenon, we investigated the effect of long-term butyrate treatment in the presence of different fatty acids in the medium on cellular phospholipids (PLs) and triacylglycerol (TG). Cells were supplemented with 100 microM sodium salts of 18:2 (n-6), 20:4 (n-6), 20:5 (n-3), or 22:6 (n-3) as a fatty acid-free-albumin complex. The molar ratio of the albumin and these long-chain fatty acids (LCFAs) was 3:1. One-half of these cultures were supplied with 2 mM butyrate, and the pH was adjusted to 7.4. The supplementation of the LCFAs and butyrate was maintained for eight days. The present study indicates that butyrate had a differential effect on the fatty acid composition of PLs and TG of LS174T cells. This includes an increase in monounsaturates and elongation of the supplemented LCFA, and this effect was more pronounced on TG than PL fatty acids. Butyrate resulted in a significant reduction in polyunsaturated fatty acid concentration only in PLs. In general, butyrate decreased the unsaturation index (UI) of the PLs but increased that of TG. The present study also confirmed our previous observation regarding the effect of LCFAs on cellular lipids. PL and TG fatty acid chain lengths reflect those of supplemented fatty acids. The UI of these two lipid fractions increased more with supplementation of n-3 than n-6 fatty acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Soluble galactoside-binding vertebrate lectins: a protein family with common properties

1. Soluble galactoside-binding lectins could play a key role in vertebrates by specifical binding to complementary glycoconjugates. 2. Their expression and localization are developmentally regulated. 3. They constitute a large family of structurally related proteins which contain a series of conserved aminoacids. 4. Their functional role could vary from an organ to another, and the same lectin may probably mediate several biological activities.

Incorporation and turnover of phospholipid precursors in normal and tumoral glial cells in culture

The incorporation and turnover of phospholipid precursors in cultured normal and tumoral glial cells was investigated during the plateau phase of growth. Glycerol was incorporated similarly by all cell types, and was renewed with a half-life of 19-37 hr. Acetate had a much longer half-life in primary cultures (50-75 hr) than in proliferative tumor cells (20-40 hr). Phosphate had a more rapid turnover rate in primary cultures (25 hr) than in proliferative tumor cells (50 hr). For all precursors, inositol- and choline phosphoglycerides had a faster turnover rate than other phospholipids.

Incorporation and metabolism of exogenous fatty acids by cultured normal and tumoral glial cells

We have investigated the transformation of exogenous radioactive free fatty acids by cultured glial cells and their incorporation into complex lipids. The cells were either tumor lines (C6 and NN) or primary cultures from newborn rat hemispheres. The tumor lines could undergo morphological differentiation with dibutyryl cyclic AMP or bromodeoxyuridine. The fatty acid precursors used were palmitic, stearic, oleic, linoleic and linolenic acids. Tumor cells presented a higher incorporation of the precursors in the cell lipid acyl groups than did normal cells. Tumor cells desaturated and/or elongated palmitic, stearic and oleic acid to a higher extent than did normal cells. In contrast, tumor cells transformed linoleic and linolenic acids to their polyunsaturated derivatives to a lower extent than did normal cells. In differentiated tumor cells, these patterns of metabolism were shifted toward the patterns of normal cells. Tumor cells did not exhibit delta 4-desaturase activity, but such activity was restored in the C6 line upon dibutyryl cyclic AMP-induced differentiation. Transformation of linoleic and linolenic acid is likely to proceed through initial delta 6 desaturation. Phospholipids were preferentially labelled with the radioactive fatty acids, and only a little radioactivity was found in the neutral lipid fraction, mainly in diacylglycerols. Each fatty acid precursor label was incorporated in individual phospholipids to a proportion which reflected the typical acyl group composition of glycerophospholipids; we observed high levels of incorporation of palmitic acid and its derivatives into choline glycerophospholipids, and high levels of incorporation of linolenic acid and its derivatives into ethanolamine glycerophospholipids. This pattern was more marked in tumor cells than in normal cells, and the differentiation of tumor cells partially restored the normal pattern, mainly in bromodeoxyuridine-treated NN cells. Both types of differentiation of glial cell lines can be useful as models for the understanding of membrane physiology in normal and tumor cells.

Phospholipid acyl group composition in normal and tumoral nerve cells in culture

We have studied the fatty acid composition of total phosphoglycerides from various types of nerve cells in culture. Primary cell cultures were compared with tumoral cell strains. Glial cells exhibited no characteristic pattern when compared to neurons. Tumoral cell phosphoglycerides contained much higher levels of octadecenoic acid and lower levels of C-20 to C-22 polyunsaturated fatty acids than normal cell phosphoglycerides. This observation seems to be a general feature in tumoral cell membranes. It could be of interest in respect to the membrane fluidity of cancer cells.