A bead-based multiplex immunoassay for cancer autoantibody biomarker discovery

Accurate, reliable and affordable blood tests are needed for early detection of cancer. Here we show data for the development and validation of a sensitive Luminex® bead-based multiplex immunoassay for detecting cancer autoantibodies in multiple cancer types. The cancer autoantibody biomarkers in this new multiplex panel include: CTAG1B/NY-ESO-1, Cyclin B/CCNB1, ENO1, Galectin-1, Galectin-3, Her2, HIF1α, HSP60, IMP2/IGF2BP2/p62, IMP3/IGF2BP3/KOC, MUC1, p16-INK4a, p53, SOX2, and Survivin/BIRC5. This multiplex immunoassay is sensitive and robust. In a 96-well plate, a mixture of recombinant protein-immobilized magnetic bead sets was incubated with serum samples for 2 hours with gentle shaking; after washing, the beads were incubated with detection antibody phycoerythrin (PE)-labeled anti-human IgG for 1.5 hours. After the final wash, the beads were resuspended in sheath fluid and the median fluorescent intensity (MFI) data of 50 beads per bead set were analyzed on a Luminex® reader. The performance of this panel was demonstrated using a set of serum samples from 78 cancer cases and 18 healthy controls. Elevated cancer autoantibodies were detected in serum from patients with various cancer types, as compared to healthy controls. In conclusion, this cancer autoantibody multiplex immunoassay has potential application as a non-invasive tool for studying early detection, diagnosis or monitoring of cancer.

Profiling of soluble immune checkpoint proteins as potential non-invasive biomarkers in colorectal cancer and sepsis

In recent years, targeting immune checkpoint proteins has been shown to be an innovation for treatment of cancer and immune-related adverse events. Many checkpoint molecules have been identified on immune cells and/or tumor cells as activating receptors or inhibitory receptors. Many immune checkpoint proteins are also expressed as soluble forms in circulation, easily accessible as potential biomarker candidates. Here we report the development of a bead-based Luminex® multiplex assay for the quantitative profiling of a panel of co-inhibitory and co-stimulating immune checkpoint proteins: BTLA, CD27, CD28, CD40, CD80/B7-1, CD86/B7-2, CTLA-4, GITR, GITRL, HVEM, ICOS, LAG-3, PD-1, PD-L1, TIM-3, and TLR-2. The aim of this study was to investigate a potential role for serum circulating immune-checkpoint proteins as putative biomarkers in colorectal cancer (CRC) and sepsis patients. We have used this novel 16-plex multiplex assay to measure multiple checkpoint protein expression levels in serum samples from CRC patients (n=20), sepsis patients (n=20), and a corresponding set of normal serum samples (n=20). Analysis of the soluble checkpoint protein signatures generated from this multiplex approach revealed differential expression of 9 soluble form of proteins, sBTLA, sCD27, sTIM-3, sHVEM, sCD40, sPD-1, sPD-L1, sCD86, and sTLR-2, in the CRC or sepsis serum samples, compared to the healthy serum controls. In summary, our results demonstrate that the multiplex immunoassay we developed is a useful research tool for the simultaneous quantitation of circulating immune checkpoint proteins, as well as its potential application in biomarker discovery and translational research.

Multiplex immunoassay detection of autoimmune disease autoantibodies in serum and plasma

Autoantibody formation is principal to the pathogenesis of a variety of autoimmune diseases. Dysregulated apoptosis and the subsequent defective clearance of cellular debris leads to the exposure of autoantigens and the generation of autoantibodies. The presence of autoantibodies may indicate disease activity, prognosis, and clinical associations related to a variety of autoimmune diseases, including systemic lupus erythematosus (SLE), Sjögren’s Syndrome, Scleroderma, Polymyositis/Dermatomyositis, and various overlap syndromes of these diseases. Here we report the development of a multiplex immunoassay to monitor 20 autoantibodies present in blood that are involved in a variety of autoimmune diseases: SSA/Ro60, SSA/Ro52, SSB/La, RNP, RNP/Sm, Sm, Ribosomal P, Proteinase 3, Myeloperoxidase, PCNA, β 2-Glycoprotein, CENP-A, CENP-B, Scl-70, Jo-1, C1q, PM/Scl-100, Ku, Mi-2, and PL-12. Using the 20-plex immunoassay, we measured expression of autoantibodies in serum and plasma from SLE patients with various disease manifestations and overlap syndromes, healthy controls, and CDC reference samples available for 11 autoantibodies. Additionally, control beads were included in the immunoassay. Levels of SSA/Ro60, SSA/Ro52, SSB/La, RNP, RNP/Sm, and Sm matched clinical laboratory features noted at the time of SLE sample collection. Additionally, anti-C1q antibody levels were associated with lupus nephritis. The CDC controls exhibited elevated MFI for the autoantibodies for which they were expected to react strongly. This study demonstrates the value of using multiplex technology to evaluate multiple autoantibodies, allowing for an extensive autoantibody profile to evaluate patients with various autoimmune diseases.

Drinking water and cardiovascular disease

A link between cardiovascular disease (CVD) mortality and the hardness of drinking water (DW) is suggested by about 30 epidemiological studies performed worldwide in the general population since 1957. This review examines the main ecological studies, case-control studies and cohort studies, published between 1960 and 2000. Attention is paid to the problem of interpretation of this typical result of environmental epidemiology. Some studies focused on the role played by inorganic elements known as DW contaminants (mainly, As, Pb) and above all on the role of the magnesium content of DW and its cardioprotective effects. To date, it would be impossible to understand this environmental findings without large intervention studies performed in well-controlled public health programs.

Basal production of pentane in expired gas from healthy humans

BACKGROUND

Pentane in exhaled gas is often used as an index of lipoperoxidation, but today, there is no standardization for its measurement. In this study, with our technical experience, we determined basal production of pentane in healthy subjects, and we evaluated variability of pentane flow 1 month later.

METHODS

18 subjects inhaled hydrocarbon-free air (HCFA) in order to realize a lung washout. Ambient air and three samples (at T0, T10, T30 min) of expired gas were concentrated using a "trap-and-purge" procedure. For the analysis of pentane, an Al(2)O(3)/KCl plot column contained in a gas chromatograph equipped with a flame ionization detector was used.

RESULTS

After 10 min of washout, mean (+/-SD) exhalation rate of pentane was 1+/-0.6 pmol min(-1) kg(-1). After 30 min of washout, mean (+/-SD) exhalation rate of pentane was 0.7+/-0.5 pmol min(-1) kg(-1). No significant difference in pentane flow was shown 1 month later for eight subjects who repeated the protocol.

CONCLUSION

With our results and data of the literature, exhalation rates of pentane from healthy adults appear to range between 0.3 and 2 pmol min(-1) kg(-1). The variability of pentane flow 1 month later seems not very important.

Oxygen toxicity: simultaneous measure of pentane and malondialdehyde in humans exposed to hyperoxia

In order to estimate cell damage caused by free radicals during oxygenotherapy, we investigated the time course of two markers of lipoperoxidation: pentane in breath and malondialdehyde (MDA) in blood during brief normobaric hyperoxia. Nine healthy subjects inhaled hydrocarbon-free air (HCFA) for 30 minutes, hydrocarbon-free 100% O2 (HCFO2) for 125 minutes and then HCFA for 70 minutes. After 15 minutes of washout with HCFA, ambient pentane was eliminated. After HCFO2, at T175 versus T30 (i.e., 145 min from the start of 100% HCFO2), pentane production increased (P< 0.05). MDA rose significantly at T155 min (i.e., 125 min from the start of HCFO2), versus T30 (P< 0.01). These results suggest that acute hyperoxia causes a moderate increase in lipid peroxidation in healthy subjects. The increase of pentane and MDA confirms that acute hyperoxia induces lipid peroxidation in healthy subjects.

Geographic variation of the mortality from cardiovascular disease and drinking water in a French small area (Puy de Dome)

Cardiovascular disease (CVD) has been the first cause of mortality in the population of Puy de Dôme (PDD) (France) between 1988 and 1992. The mortality rates are significantly higher than those observed in the whole population of France (for the female population, 354.8 versus 327.3 per 100,000 persons/year and for the male population, 335.7 versus 287.9 per 100,000 persons/year). Moreover, an ecological study, which used the Standardized Mortality Ratios (SMR) and performed at the canton level, has allowed a special variation of mortality from CVD in PDD to be described. A decreased gradient of mortality (especially, "Ischemic Heart diseases" [ICM-9, codes 410-414] and "Cerebro-vascular Diseases" [ICM-9, codes 430-438]) has been observed from the periphery (rural area) to the middle (urban area) of PDD. Moreover, a statistically significant negative relationship has been observed between the hardness of the drinking water supplies in PDD and the CVD mortality data (i.e., the lower the hardness of drinking water, the higher the SMR). Although, the low hardness of drinking water can contribute to the high CVD mortality observed among the PDD population, the role of other risk factors (i.e., biological, nutritional) must also be taken into consideration in further prospective studies.

Effects of humic substances and phenolic compounds on the in vitro toxicity of aluminium

The effects of natural chelators [humic acids (HA), caffeic acid (CFA), p-coumaric acid (PCA), protocatechuic acid (PA), vanillic acid (VA), salicylic acid (SA), and 4-hydroxyacetophenone (HY)] and effects of well-known chelators [EDTA and citric acid (CA)] on the in vitro toxicity of aluminium (Al) were investigated with the L-929 murine, Vero simian, and MRC-5 human cell lines. Moderate in vitro cytotoxic effects were induced by Al on the three cell lines (IC(50) values ranking from 5.6 to 7.6 mM). Furthermore, an increased toxicity was observed when Al was concurrently administered with CA, SA, VA, PCA, and HY. Inversely, significant cytoprotective effects were noted with EDTA, HA, CFA, and PA. The role of chelators, and especially the position and the number of reactive moieties of the phenolic compounds tested, can be highlighted to explain the different toxicological Al behavior observed.

Tetrahymena pyriformis: a tool for toxicological studies. A review

Among protozoa, Tetrahymena pyriformis is the most commonly ciliated model used for laboratory research. After a brief description of the morphology and biology of Tetrahymena pyriformis, this article focuses on the most important and recent investigations performed with this species in toxicology and ecotoxicology. The methodological features of its culture, and main tests, based on cell growth rate, biochemical markers, behavioral changes and motility, are discussed. Examples of xenobiotics (organic and inorganic substances, pharmaceutical drugs, water pollutants) tested with Tetrahymena pyriformis are also given.

Detection of BCR-ABL transcripts in acute lymphoblastic leukemia in Indian patients

Thirty-three patients with acute lymphoblastic leukemia (ALL) from India were studied for the presence of BCR-ABL chimeric transcripts, by a seminested cDNA-PCR. We report the presence of BCR-ABL chimeric transcripts in 4/17 (24%) children (under 15 years) and 3/16 (19%) adults (15-50 years). This is in sharp contrast to the published literature from the West where the presence of BCR-ABL has been reported in only 2-5% children and 35% adults. Whether the presence of BCR-ABL fusion mRNA, which is generally an attribute of ALL in adults and of poorer prognosis, may contribute to chemo-incurability in young Indian patients, remains to be seen, as a larger number of patients are studied for treatment outcome and survival on uniform therapy protocols.

Toxicity assessment of 16 inorganic environmental pollutants by six bioassays

The relative toxicity of 16 environmental pollutants, such as inorganic elements (Ba, Cd, Co, Cr, Cu, Fe, Ge, Hg, Mn, Nb, Pb, Sb, Sn, Ti, V, and Zn), is evaluated on the L-929 established cell line of murine fibroblasts, with five bioassays [RNA synthesis rate assay (RNA), MTT reduction assay (MTT), neutral red incorporation assay (NRI), Coomassie blue assay, and cellular growth rate assay], and on the ciliated protozoa Tetrahymena pyriformis GL [doubling time of T. pyriformis GL population assay (DTP)]. For each inorganic substance, the six bioassays allowed the toxicological index IC50 ("inhibitory concentration 50%") to be calculated. The IC50 values are useful to rank the tested elements and to compare the features of the six bioassays. The most sensitive assays were the RNA, MTT, NRI, and DTP assays. Moreover, the in vitro IC50 values correlated with the in vivo LD50 values; these results were close to those obtained with established lines of human, murine, or fish cells. The sensitivity and the complementarity of these bioassays would be in favor of their incorporation in a "battery" of tests used for toxicological screening studies of xenobiotics.

Study of magnesium bioavailability using stable isotopes and the inductively-coupled plasma mass spectrometry technique in the rat: single and double labelling approaches

The present work aimed to investigate the feasibility of using stable isotopes and inductively-coupled plasma mass spectrometry (ICP/MS) to study Mg absorption in rats. Male Wistar rats, aged 7 weeks and weighing 180 g, were used. They were fed on a semi-purified diet containing 1070 mg Mg/kg, and had free access to feed and distilled water. In the first experiment, after a 16 d adaptation period, two doses of enriched 25Mg (6 and 12 mg) were administered by oral intubation, faeces and urine were collected daily and blood was sampled. Isotope ratios were determined by ICP/MS. 'True' absorption values, using the faecal isotope data, were 0.63 and 0.56 in rats receiving 6 and 12 mg 25Mg respectively, while apparent absorption was 0.50 for two successive periods of metabolic balance studies. Moreover, the oral isotope administration resulted in a measurable isotopic enrichment in plasma within hours which was still detectable on the third day following the isotope administration. In the second experiment, investigating the double labelling technique, similar rats were dosed simultaneously with 5 mg 26Mg orally (premixed with diet) and 0.29 mg 25Mg intravenously. The calculated Mg true absorption values were very similar when calculated from blood or urine data (0.38) but were lower than that obtained from faecal data (0.50). The possible causes of such an unexpected difference and limits of the double labelling technique for Mg absorption are discussed here. Together these results indicate that although 25Mg and 26Mg isotopes have high natural abundance, the described methodology permits meaningful investigations of Mg bioavailability and metabolism.

Microplate technique for screening and assessing cytotoxicity of xenobiotics with Tetrahymena pyriformis

The microplate technique (MT) is developed and compared to the usual flask technique (FT) of Tetrahymena pyriformis GL cultures for assessing toxic effects of organic and inorganic substances on this ciliated protozoa model. Applied to the IC50 determination of 29 xenobiotics, the MT demonstrated good correlation with the FT (Y = 0.991X + 0.012, r = 0.94, P < 0.0001). The MT is rapid, easy-to-handle, inexpensive, and statistically reliable and, so, may be helpful for screening investigations of water-soluble xenobiotics.

Chemical and in vitro toxicological evaluations of water packaged in polyvinyl chloride and polyethylene terephthalate bottles

This study proposed a new strategy assessing the health risks of mineral water packaging and compared the chemical analytical techniques and some in vitro cytotoxicological assays for the study of PVC and PET materials at the main stages of the manufacturing process of bottles. These evaluations were carried out with food simulant (deionized-endotoxin-tested water) and with natural mineral water in real conditions of packaging and storage (from 0 to 24 months). The complementarity of these two approaches is discussed. Some analytical and cytotoxic abnormalities were detected in the food simulant after contact with the batches of powdered PVC compound, PET resin and their intermediate steps of transformation (PVC-'paraison', PET-'perform'). But these results did not reflect the actual behaviour of the finished PVC and PET bottles, for which no major abnormality was detected in the natural mineral water.

Comparative study of two in vitro models (L-929 fibroblasts and Tetrahymena pyriformis GL) for the cytotoxicological evaluation of packaged water

The preservation of 234 samples of water packaged in polychloride vinyl (PVC), polyethylene terephthalate (PET) and glass-bottles was concurrently evaluated using both classical chemical analysis oriented to finding organic and inorganic substances which could have been leached by the packaging and in vitro toxicological bioassays using two models: the L-929 established cell line of fibroblasts and the ciliated protozoa Tetrahymena pyriformis GL. Although no significant abnormality was detected with the chemical analysis, cytotoxicity was detected with both models in some samples of water bottled for > 18 months, for either PVC, PET or glass-packaging. However, statistical analysis did not allow a mathematical relationship between the cytotoxic effects, the length of storage and the packaging to be demonstrated.

Analysis of BCR/ABL transcripts in chronic myeloid patients by nested PCR using an immunoassay-like detection format

We describe an 'immunoassay-like' detection format, based on the AMPLICIS technique for the routine detection of BCR/ABL transcripts in leukaemic patients. The AMPLICIS technique is characterized as a nested PCR coupled to solid phase isotopic or non-isotopic detection of PCR products. Comparison between this assay and a conventional PCR technique using Southern-blot analysis provided a good correlation between the two procedures. The assay, easier and faster than the conventional one, gives access to automation and therefore appears well suited for the routine screening of BCR/ABL chimaeric mRNAs.

Effect of simvastatin on the synthesis and secretion of lipoproteins in relation to the metabolism of cholesterol in cultured hepatocytes

In primary culture of rat hepatocytes, simvastatin, a powerful HMGCoA reductase inhibitor, inhibited acetate incorporation into cellular and secreted cholesterol and cholesteryl-esters, without any significant effect on triacylglycerol synthesis and secretion. When applied to the culture for 24 h at 10(-7) M, a concentration shown to inhibit cholesterol synthesis by 61%, simvastatin increased apolipoprotein BH and BL synthesis and secretion and strongly decreased apolipoprotein AI synthesis and secretion whereas apolipoprotein AIV remained unaffected. The synthesis and secretion of apolipoprotein E was only slightly affected in contrast with other situations where cholesterol synthesis decreased. All of these modifications occurred at a post-transcriptional level, as the corresponding messenger RNAs of the apolipoproteins did not vary. These results suggest that either the drug itself or variations in cholesterol synthesis might be involved in apo B and apo AI synthesis and secretion.

Partial apolipoprotein E-beta-galactosidase fusion protein expressed in Escherichia coli retains binding activity to the LDL(B/E) receptor

A partial rat apo E-beta-galactosidase fusion protein was produced in Escherichia coli Y1089 infected with recombinant lambda GT11 obtained by immunoscreening of a rat liver cDNA library with an anti-rat LDL antiserum. Partial cDNA overlapped the apo E mRNA sequence coding for apo E binding domain towards the LDL(B/E) receptor up to codon for Arg-139. Fusion protein specifically bound to human fibroblasts. The high-affinity component exhibited a Kd of 5 x 10(-8) M and 4.1 x 10(5) sites per cell. Fusion protein binding to fibroblasts was mediated by their apo E moiety and not by beta-galactosidase since: (1) specific binding of fusion protein was competed out by human LDL; (2) beta-galactosidase did not compete with fusion protein binding; and (3) human fibroblasts from a patient with familial hypercholesterolemia, deficient in LDL(B/E) receptor, bound fusion protein 10-times lower than control fibroblasts. It was demonstrated that partial fusion protein retained the functional activity of the native apo E. However, compared to full-length native or engineered apo E, fusion protein was able to bind fibroblasts without being complexed with phospholipids. Fusion proteins might be a useful tool for studying the functional efficiency of the LDL(B/E) receptor and for mapping residues and domains involved in the binding process.

Eicosanoid synthesis in children with cholestatic disease

The possibility of malabsorption of triglycerides contained in the diets of children with cholestasis suggests a deficiency of essential fatty acids and, therefore, probable effects on eicosanoid metabolism. Children with either biliary atresia (BA) or syndromatic paucity of interlobular bile ducts (PILBD) were evaluated as to plasma and platelet total lipid fatty acid composition and synthesis of prostaglandins (PG) E1, PGE2, PGI2, PGF2, and thromboxane (TXB2) by whole blood incubated at 37 degrees C for 10 min. In both diseases linoleate deficiency was present as shown by low 18:2 fatty acids in plasma lipids. The children with BA had lower plasma arachidonate than controls but normal eicosanoid synthesis except for excess PGI2. Those with PILBD had low platelet arachidonate and were severely deficient in TXB2 synthesis (less than 10% of controls). Three children with PILBD were fed a supplement of structured triglyceride (Captex 810) intended to provide as much as 10% of energy as linoleate for 2-3 months. Results for these three cases suggested that insufficient linoleate was absorbed to increase plasma linoleate and differences in eicosanoids could not be attributed to linoleate supplementation.

Fate of fatty acids taken up as cholesteryl ester by rat hepatocytes in primary culture from high-density lipoprotein

Primary cultures of rat hepatocytes were incubated in the presence of high-density lipoproteins (HDL) labelled with [1-14C]oleyl or [1-14C]linoleyl cholesteryl ester. Labelled HDL were prepared by selective delipidation with heptane, relipidation and sequential ultracentrifugations. Hepatocytes took up cholesteryl esters and cholesteryl ether their non-hydrolizable analog, at the same rate. The uptake increased with time, the cholesteryl ester/protein ratio and the amount of added HDL. It was not dependent on the nature of acyl chain or on the nature of the bond. The uptake did not depend on a specific interaction between HDL and cell membranes, since cholesteryl ester was taken up from HDL to the same extent as from albumin complexes. Linoleic and oleic acids released from cholesteryl esters taken up by hepatocytes were mainly reesterified into phosphatidylcholine and triacylglycerols. Linoleic acid was preferentially channelled into PC. A portion of these lipids were secreted by hepatocytes during a 24-h reincubation in a medium devoid of lipoprotein. Nearly the same amount of radioactivity was recovered in secreted phospholipids as in secreted triacylglycerols, in contrast with hepatocytes labelled with free fatty acids which secreted very little radioactivity as phospholipids. From these results and the high content in polyunsaturated fatty acids of cholesteryl esters, one can hypothesize that hepatic cholesteryl ester uptake may contribute to biliary phosphatidylcholine production, and therefore to polyunsaturated fatty acid sparing.

Arachidonate cannot be released directly from diacyl-sn-glycero-3-phosphocholine in thrombin-stimulated platelets

The origin of the arachidonate released from platelets on stimulation with thrombin was investigated by comparing the specific activities of released arachidonate and of arachidonoyl-containing phospholipids using rat platelets prelabelled with arachidonate. Quantification of the released arachidonate was determined in the presence of BW 755 C, a dual cyclo-oxygenase/lipoxygenase inhibitor, which was found not to modify the arachidonate mobilization between the platelet phospholipids. The phospholipid molecular species were analysed by h.p.l.c. of diradylglycerol benzoate derivatives of diacyl, alkylacyl and alkenylacyl classes. The labelled/unlabelled arachidonate ratio varied greatly in the phospholipids depending on whether an ether or acyl bond was present in sn-1 position of the glycerol, on the length and degree of unsaturation of this fatty chain and on the polar head group. Between 15 s and 5 min of stimulation by thrombin, the released arachidonate kept a constant specific activity which was considerably lower than the specific activity of diacyl-GPC. The specific activity of the released arachidonate was intermediate between the specific activities of the 16:0-20:4 and 18:0-20:4 species of diacyl-GPI and diacyl-GPE, and corresponded to the mean specific activity of alkylacyl-GPC. The data indicate that the released arachidonate cannot come directly from diacyl-GPC, and that two phospholipids in particular can act as direct precursors of the released arachidonate. These are (1) the alkylacyl-GPC and (2) the diacyl-GPE whose hydrolysis would induce an arachidonate transfer from diacyl-GPC.

Selective channelling of arachidonic and linoleic acids into glycerolipids of rat hepatocytes in primary culture

Rat hepatocytes in primary culture were incubated with a mixture of linoleic and arachidonic acid at various total fatty acid/serum albumin molar ratios. Mixed fatty acids were taken up at the same rate and distributed with the same pattern as fatty acids added separately. The rates of total uptake, incorporation into hepatocyte and secreted triacylglycerols and beta-oxidation were linearly related to the fatty acid/albumin ratios, whereas the rate of incorporation into phospholipids was saturable. Neither the uptake rate nor the distribution of both fatty acids considered together varied with the arachidonic acid/linoleic acid molar ratio. Changes in this ratio and in the uptake rate led to significant variations in the respective fate of the fatty acids. The preferential channelling of arachidonic acid versus linoleic acid into beta-oxidation and phosphatidylinositol was greatest at a low uptake rate and then decreased as the uptake rose. Conversely, the preferential channelling of arachidonic acid versus linoleic acid into phosphatidylcholine, but not phosphatidylethanolamine, increased with the uptake rate. Moreover, both arachidonic acid and linoleic acid were preferentially incorporated into the 1-palmitoyl molecular species of phosphatidylcholine and phosphatidylethanolamine at a low uptake rate, and of phosphatidylcholine at a high uptake rate. This could be related to the synthesis of biliary phosphatidylcholine, of which 1-palmitoyl-2-linoleoyl and 1-palmitoyl-2-arachidonoyl are the main molecular species. Linoleic and arachidonic acid were selectively distributed into distinct metabolic pools of triacylglycerol, the intrahepatocyte pool which preferentially incorporated linoleic acid at a low uptake rate and the secreted pool in which the relative enrichment of arachidonic acid increased with the uptake rate. This strengthens the central role of hepatic secretion in the supply of arachidonic acid to peripheral tissues.

Essential fatty acid pattern of glycerolipids in rat hepatocytes in primary culture and in coculture with rat liver epithelial cells

The linoleic acid content of phosphatidylethanolamine (PE), phosphatidylcholine (PC) and triglyceride (TG) rapidly fell in rat hepatocytes in primary culture up to four days and in coculture with liver epithelial cells up to eight days. At the same time, the level of polyunsaturated fatty acids (PUFA), especially arachidonic acid, remained constant in PE, slightly decreased in PC and dropped in TG. There was no variation of the nonessential PUFA, 20:3n-9. Linoleic acid supplementation of cultures 24 hr before the harvest induced a rise in the linoleic acid level of the three lipid classes. Arachidonic acid remained constant in TG and only slightly decreased in PE and PC at day 4 of primary culture and day 8 of coculture. The level of 20:3n-9 increased in PE and PC and much more in TG. This net increase in the arachidonic acid and 20:3n-9 levels in TG could not be explained only by a transfer from the phospholipid pools of PUFA because the phospholipid content of hepatocytes and PUFA levels of phospholipids did not vary under linoleic supplementation. The low percentage of arachidonic acid in epithelial cells rules out any participation of these cells in the increase of arachidonic acid in supplemented cocultures. Triglycerides may act as a storage pool for plasma PUFA up to four days of primary culture and eight days of coculture. Besides, coculture seems more potent than primary culture to maintain the phospholipid level, to spare the essential PUFA in PE and to increase the TG synthesis in response to linoleic acid supplementation.

Antigenic relatedness between phospholipases A2 from Naja naja venom and from mammalian cells

Polyclonal antiserum was prepared against phospholipase A2 from Naja naja and used to prepare a purified antibody. It cross-reacted with the antigen, and with intracellular mammalian PLA2. This antibody was immunoreactive and inhibited the PLA2 activity of Naja naja and of guinea pig alveolar macrophages or rat lymphocytes. By immunoblotting, this antiserum revealed one band of PLA2 from Naja naja (14 kDa) and 3 bands for guinea pig alveolar macrophages and rat lymphocytes (30, 45 kDa and a minor band of 14 kDa). These results show an antigenic relatedness between an extracellular PLA2 and membrane-bound PLA2 from two different mammalian species and cell types.

Essential fatty acid uptake and esterification in primary culture of rat hepatocytes

Primary cultures of adult rat hepatocytes were used to compare the uptake and esterification of essential polyunsaturated fatty acids (18:2, 20:3 and 20:4 of the n-6 series) with those of palmitic and oleic acids. The uptake of unesterified fatty acids was linearly related to the free fatty acid/albumin molar ratio for 14 h and did not depend on the unbound free fatty acid level. Whatever the initial free fatty acid/albumin molar ratio, it dropped to 0.5 +/- 0.1 mM after 14 h, thus showing that hepatocytes have a high capacity for clearing free fatty acids from the medium at high free fatty acid/albumin molar ratios. The free fatty acid uptake become saturable when the free fatty acid and albumin concentrations were raised and the free fatty acid/albumin ratio remained constant. This strongly suggests that albumin-hepatocyte interaction mediates free fatty acid uptake. This uptake was identical whatever the fatty acid tested and did not depend on the relative amounts of fatty acids when they were added simultaneously. Triacylglycerol accumulation and synthesis, monitored by labelled fatty acids, were related to the free fatty acid/albumin molar ratio and exhibited no specificity for the series of fatty acids tested. Triacylglycerols were enriched in all the fatty acids tested by up to 60%, and fatty acid incorporation into diacylglycerols and triacylglycerols reflected the free fatty acid composition of the medium. By contrast, neither the level nor the synthesis of phospholipids varied with free fatty acid/albumin, but the rate of phospholipid turnover depended on the fatty acids tested. Accumulation of these acids was smaller in phospholipids than in triacylglycerols. When linoleic and arachidonic acids were added together, phospholipids (especially phosphatidylethanolamine and phosphatidylinositol) were more enriched in arachidonic acid than triacylglycerols. This might be due to the specificity for fatty acid of the enzymes involved in phospholipid metabolism.

Plasma and erythrocyte essential fatty acids during total parenteral nutrition in infants: effects of a cutaneous supply

In order to prevent essential fatty acid (EFA) deficiency induced by fat-free total parenteral nutrition (TPN), 10 infants on TPN were rubbed three times daily for 20 days using oenethera oil (80% EFA). Total EFA amount provided cutaneously was 1900 mg/kg/d. Plasma and red blood cells phospholipids were determined on days 1 and 20 in these 10 treated and six untreated infants on TPN and compared with those of normal control infants. On day 1, plasma nonessential FA including 20:3 n-9(p less than 0.01) were increased in both TPN groups while 18:2 n-6 and 18:3 n-3 (p less than 0.001 and p less than 0.01) were decreased. On the 20th day, EFA deficiency had worsened with a decrease in plasma level of 20:4 n-6 (p less than 0.02) and a higher than normal triene/tetraene ratio : 3.4 +/- 1.1 and 2.3 +/- 0.6 vs 0.1 +/- 0.1 (p less than 0.02). As for red blood cells phospholipids, 16:0 was increased and 18:2 n-6 and 20:3 n-6 were decreased (p less than 0.05) on day 1. On day 20, these FA were more abnormal while 20:3 n-9 became significantly increased (p less than 0.05). No difference was observed between the TPN groups at any time. These results show that cutaneous application of large amounts of EFA-rich oil is unable to prevent or cure TPN induced EFA deficiency.

Essential fatty acid interconversion during gestation in the rat

The synthesis of arachidonic acid has been investigated in fetal and pregnant rat liver microsomes in the course of the gestation. The delta 5-desaturase activity decreased 2-3 times in rat liver between the 19th and 22nd day of the pregnancy. During this period the delta 5-desaturate activity increased 3-fold in the fetal liver, exceeding the activity of the maternal liver. In contrast, the activity of the fetal delta 6-desaturase was in the same range as in pregnant rat liver and the liver of control animals and did not change between these two stages of the gestation. The elongation rate of linoleic acid in fetal liver was 2-3 times lower than in maternal liver but this increased during the pregnancy. The fatty acid activate rate was always higher than the activity of the desaturases. At the 19th day, the activity of the delta 5-desaturase was apparently the rate limiting step of arachidonic acid synthesis in fetal liver. We did not find any delta 5- and delta 6-desaturase activities or linoleic acid elongation in the placenta microsomes.

Essential fatty acids interconversion in the human fetal liver

In order to study the role played by the fetoplacental unit in providing the human fetus with arachidonic acid, delta 5- and delta 6-desaturase activities were studied in microsomes from human fetal liver and placenta after 18 and 22 weeks of gestation. We evidenced for the first time delta 5- and delta 6-desaturase activities in fetal liver microsomes. As in adult liver, delta 6-desaturation is the rate-limiting step of arachidonic acid synthesis. No activity was found in the placenta. Arachidonic acid concentrations were higher in fetal serum than in maternal serum while the opposite was observed for linoleic acid. The fetal liver microsomal content in arachidonic acid was low. Taken together the data suggest that arachidonic acid is supplied to the fetus through a preferential transfer across the placenta.

Protein-stimulated enrichment of human platelet membranes in linoleylphosphatidylcholines. Effect upon adenylate cyclase and fluidity

In order to study the effect of linoleyl enrichment of platelet membranes upon adenylate cyclase activity and membrane fluidity, manipulations of platelet phospholipids are carried out with phosphatidylcholine-loaded high-density lipoproteins (HDL) or phospholipid-exchange protein and phospholipid-cholesterol mixed vesicles. Incubation with HDL does not appear to be valuable for this purpose. On the other hand, phospholipid-exchange protein and mixed vesicles can be used successfully. Phospholipid-exchange protein stimulated 3-fold the spontaneous exchange of 2-linoleylphosphatidylcholine between the vesicles and the platelets. Linoleyl enrichment of platelets by dilinoleylphosphatidylcholine is about 25% and by 2-linoleylphosphatidylcholine is about 45-50%. The unsaturation index remains constant when the enrichment is performed using dilinoleylphosphatidylcholine but it increases with 2-linoleylphosphatidylcholine. Basal and prostaglandin E1-stimulated adenylate cyclase activities are not modified by dilinoleylphosphatidylcholine, while they increase significantly in the case of 2-linoleylphosphatidylcholine. There is no significant variation in diphenyl hexatriene fluorescence polarization parameters, either with dilinoleylphosphatidylcholine or with 2-linoleylphosphatidylcholine.

[Platelet arachidonic acid and central retinal vein obstruction (author's transl)]

Study of 25 cases of obstruction of the central retinal vein. In the 4 first days it is a low level of arachidonic acid of platelet membrane. This fall of level is the one anomaly of fatty acid from platelet and plasma. We have obtained no correlation between the level of platelet AA and age or lipids level of the blood. Study of platelet agregation was performed in only some cases and no conclusion is possible.

[Plasma bile acids fractionnation by gas-liquid chromatography : application to hepatocellular deficiency investigation (author's transl)]

The level of the four major bile acids was measured in the plasma using gas liquid chromatography. The enhancement of the level of the primary bile acids was well known during bile duct obstruction. In the case of hepatic diseases, the chenodesoxycholiccholic acid concentration ratio (CDC/C) was equal or lower than unity when cholestasis occurred rather than hepatic deficiency. When hepatic deficiency developed, the ratio CDC/C was higher than unity. Plasma bile acid fractionnation exhibits also a prognostic value. When the ratio CDC/C is very high, it is significant of progressive hepatic deficiency. A high level of lithocholic acid is also a sign of unfavourable prognosis.