Membrane fatty acid changes during the cell cycle of CV-1 cells

The highly unnatural fatty acid profile of cells in culture

The fatty acid profile of cells in culture are unlike those of natural cells with twice the monounsaturated (MUFA) and half the polyunsaturated fatty acids (PUFA) level (Mol%). This is not due to cell lines primarily being derived from cancers but is due to limited access to lipid and an inability to make PUFA de novo as vertebrate cells. Classic culture methods use media with 10% serum (the only exogenous source of lipid). Fetal bovine serum (FBS), the serum of choice has a low level of lipid and cholesterol compared to other sera and at 10% of media provides 2-3% of the fatty acid and cholesterol, 1% of the PUFA and 0.3% of the essential fatty acid linoleic acid (18:2n-6) available to cells in the body. Since vertebrate cell lines cannot make PUFA they synthesise MUFA, offsetting their PUFA deficit and reducing their fatty acid diversity. Stem and primary cells in culture appear to be similarly affected, with a rapid loss of their natural fatty acid compositions. The unnatural lipid composition of cells in culture has substantial implications for examining natural stems cell in culture, and for investigations of cellular mechanisms using cell lines based on the pervasive influence of fats.

Shear-induced changes in membrane fluidity during culture of a fragile dinoflagellate microalga

The commonly used shear protective agent Pluronic F68 (PF68) was toxic to the marine dinoflagellate microalga Protoceratium reticulatum, but had a shear-protective effect on it at concentrations of ≤ 0.5 g L(-1) . Supplementation of P. reticulatum cultures with PF68 actually increased the fluidity of the cell membrane; therefore, the shear protective effect of PF68 could not be ascribed to reduced membrane fluidity, an explanation that has been commonly used in relation to its shear protective effect on animal cells. Data are reported on the membrane fluidity of P. reticulatum and its response to the presence of PF68 under sublethal and lethal turbulence regimens. The membrane fluidity was found to depend strongly on the level of lipoperoxides in the cells produced under lethal agitation.

Cell cycle-dependent transduction of cell-permeant Cre recombinase proteins

Protein transduction has been widely used to analyze biochemical processes in living cells quantitatively and under non-steady-state conditions. The present study analyzed the effects of cell cycle on the uptake and activity of cell-permeant Cre recombinase proteins. Previous studies had suggested that the efficiency of recombination and/or protein transduction varied among individual cells, even within a clonal population. We report here that cells in the G1 phase of the cell cycle undergo recombination at a lower rate than cells at other phases of the cell cycle, and that this variation results largely from differences in protein uptake, associated with differences in cell size. These results have implications regarding the mechanism of protein transduction and identify a source of heterogeneity that can influence the response of individual cells to cell-permeant proteins.

Cell cycle arrest and induction of apoptosis in pancreatic cancer cells exposed to eicosapentaenoic acid in vitro

Eicosapentaenoic acid (EPA) has been shown to have an inhibitory effect on the growth of several pancreatic cancer cell lines in vitro. This study investigates the mechanism of growth inhibition and cytotoxicity of EPA on the pancreatic cancer cell line MIA PaCa-2. Cells were analysed for cell count, viability, cell cycle distribution and ultrastructural changes. There was a time- and dose-dependent decrease in cell count and viability in cultures of pancreatic cancer cells supplemented with EPA. Flow cytometric DNA analysis of MIA PaCa-2 cells incubated with EPA demonstrated the presence of sub G1 populations corresponding to the presence of apoptotic cells and the blockade of cell cycle progression in S-phase and G2/M-phase. The presence of apoptosis in EPA-supplemented cultures was further confirmed by DNA fragmentation and ultrastructural changes associated with apoptosis. Therefore, we conclude that EPA mediates its effect on the pancreatic cancer cell line MIA PaCa-2, at least in part, via cell cycle arrest and the induction of apoptosis.

Long-term effect of tetradecylthioacetic acid: a study on plasma lipid profile and fatty acid composition and oxidation in different rat organs

Administration of tetradecylthioacetic acid (a 3-thia fatty acid) increases mitochondrial and peroxisomal beta-oxidative capacity and carnitine palmitoyltransferase activity, but reduces free fatty acid and triacylglycerol levels in plasma compared to palmitic acid-treated rats and controls. The decrease in plasma triacylglycerol was accompanied by a reduction (56%) in VLDL-triacylglycerol. Prolonged supplementation of tetradecylthioacetic acid caused a significant increase in lipogenic enzyme activities (ATP-citrate lyase and acetyl-CoA carboxylase) and diacylglycerol acyltansferase, but did not affect phosphatidate phosphohydrolase. Plasma cholesterol, LDL- and HDL-cholesterol levels were reduced. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase activity was, however, stimulated in 3-thia fatty acid-treated rats compared to controls. In addition. the mRNAs of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and LDL-receptor were increased. Tetradecylthioacetic acid administration affected the fatty acid composition in plasma and liver by increasing the amount of monoenes, especially 18:1(n-9), mostly at the expense of omega-3 fatty acids. Compared to liver a large amount of tetradecylthioacetic acid accumulated in the heart, and this accumulation was accompanied by an increase in omega-3 fatty acids, particularly 22:6(n-3) and a decrease in omega-6 fatty acids, mainly 20:4(n-6). The results show that the hypolipidemic effect of tetradecylthioacetic acid is sustained after prolonged administration and may, at least in part, be due to increased fatty acid oxidation and upregulated LDL-receptor gene expression. The increase in lipogenic enzyme activities as well as increased 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity, may be compensatory mechanisms to maintain cellular integrity. Decreased level of 20:4(n-6) combined with increased omega-3/omega-6 ratio in cardiac tissue after tetradecylthioacetic acid treatment may have influence on membrane dynamics and function.

Variation in heat sensitivity through the cell cycle of M10 and Burkitt P3HR-1 cells

The cell-cycle age response to 44 or 45 degrees C hyperthermic treatment was studied in M10, a mutant of mouse L5178Y cells, and human Burkitt P3HR-1 cells synchronized by centrifugal elutriation. Survival response to 44 degrees C hyperthermia or radiation showed that Burkitt cells were relatively hyperthermic resistant and average in radiosensitivity, while M10 cells were relatively hyperthermic sensitive and substantially radiosensitive. A typical age-response to hyperthermia through the cell-cycle was observed in M10 cells, although no significant variation in the response to hyperthermia was demonstrated in Burkitt P3HR-1 cells. Combined effect of procaine with 44 degrees C 20-min treatment for Burkitt P3HR-1 cells showed a substantial enhancement of cytotoxicity in S phase cells. The probable implication of membrane composition, membrane changes due to heat and its modifying agents are discussed. Furthermore, when hyperthermia was combined with radiation in Burkitt P3HR-1 cells, cytotoxic enhancement was observed in G1/S boundary phase, not in S phase.

Activation of an alpha-fetoprotein (AFP)/receptor autocrine loop in HT-29 human colon carcinoma cells

Immunological and morphological approaches have been used to demonstrate, respectively, alpha-fetoprotein (AFP) synthesis and receptor expression in the HT-29 human colon carcinoma parental cell line. HT-29 cells cultivated in the presence of glucose synthesized and secreted AFP in the medium from 48 to 96 hr after seeding, as revealed by monoclonal antibodies (MAbs) to human AFP. Light microscopic observations of cells incubated with fluoresceinated AFP showed that the protein was specifically bound to the cell surface at 4 degrees C, and was internalized in the cytoplasm at 37 degrees C. At the ultrastructural level, horseradish peroxidase (HRP)-conjugated AFP, as well as HRP-transferrin (Tf) (used as a control), appeared to be internalized via coated pits and vesicles before being delivered to endosomes, from which they were apparently recycled back to the cell surface via small vesicles. Our results suggest that a AFP/receptor autocrine pathway might operate in these cells, be preferentially active at the beginning of the exponential phase of cell culture growth, and contribute to cell proliferation.