Ranking the toxicity of fatty acids on Jurkat and Raji cells by flow cytometric analysis

Modulatory effect of fatty acids on fungicidal activity, respiratory burst and TNF-α and IL-6 production in J774 murine macrophages

The reported effects of different families of fatty acids (FA; SFA, MUFA, n-3 and n-6 PUFA) on human health and the importance of macrophage respiratory burst and cytokine release to immune defence led us to examine the influence of palmitic acid (PA), oleic acid (OA), linoleic acid, arachidonic acid, EPA and DHA on macrophage function. We determined fungicidal activity, reactive oxygen species (ROS) and cytokine production after the treatment of J774 cells with non-toxic concentrations of the FA. PA had a late and discrete stimulating effect on ROS production, which may be associated with the reduced fungicidal activity of the cells after treatment with this FA. OA presented a sustained stimulatory effect on ROS production and increased fungicidal activity of the cells, suggesting that enrichment of diets with OA may be beneficial for pathogen elimination. The effects of PUFA on ROS production were time- and dose-dependently regulated, with no evident differences between n-3 and n-6 PUFA. It was worth noting that most changes induced after stimulation of the cells with lipopolysaccharide were suppressed by the FA. The present results suggest that supplementation of the diet with specific FA, not classes of FA, might enable an improvement in host defence mechanisms or a reduction in adverse immunological reactions.

Lipid-dependent cytotoxicity by the lipase PLRP2 and by PLRP2-positive cytotoxic T lymphocytes (CTLs)

IL-4 induces a lipase, pancreatic lipase related protein 2 (PLRP2), in cytotoxic T lymphocytes (CTLs). Because PLRP2 in semen can mediate lipid-dependent toxicity to sperm, we questioned whether CTL-derived PLRP2 could support similar cytotoxicity toward tumor cells. Recombinant PLRP2 was toxic to P815 tumor cells in 48 h when lipid and another protein, colipase, were present. However, PLRP2-positive CTLs (induced with many lots of IL-4) were unable to mediate lipid-dependent cytotoxicity. Notably, CTLs induced with only one lot of IL-4 had lipid-dependent cytotoxicity. The exceptional lot of IL-4 was effective in multiple experiments at inducing lipid-dependent cytotoxicity. The lipid-dependent cytotoxicity it induced was determined to be perforin-independent. CTLs induced with IL-4 that was unable to induce lipid-dependent cytotoxicity had mRNA for PLRP2 but not mRNA for colipase. Therefore, we added exogenous colipase to the CTL assays but still cytotoxicity was unchanged. We conclude (1) that lipid-dependent cytotoxicity, promoted by the lipase PLRP2 and colipase, will kill tumor cells and (2) that more than PLRP2 alone is required for lipid-dependent cytotoxicity mediated by CTLs.

Effect of rapeseed peptide on DNA damage and apoptosis in Hela cells

Rapeseed peptide (RSP), obtained by hydrolyzing rapeseed protein, has anticancer activity. In this study, the effects of RSP on proliferation rate, morphological changes, DNA damage, cell cycle distribution and apoptosis in human cervical carcinoma (Hela) cells were investigated. RSP treatment at a concentration of 640 mg/L for 4 days inhibited Hela cell proliferation significantly, as determined by the MTT assay. We observed a dose-dependent increase in cytotoxicity induced by RSP at 20-640 mg/L. After 4 days of 320 mg/L RSP treatment, typical apoptotic changes were observed by transmission electron microscopy (TEM). Using the comet assay, we found dramatic comet tails, indicating DNA damage by RSP (20-640 mg/L). Moreover, RSP treatment caused inhibition of Hela cell growth, with cycle arrest in the S phase and apoptosis induction. Taken together, the results suggested that rapeseed peptide could be a potential antitumor compound with an apoptotic mode of action.

Enhancement of docetaxel solubility via conjugation of formulation-compatible moieties

Computer-based theoretical calculations were employed to direct the design of docetaxel conjugates with enhanced solubility in the internal phase of a nano-emulsion formulation. The theoretically-identified optimal docetaxel conjugates were synthesized by direct attachment of lauroyl moieties through an ester linkage to docetaxel. In comparison to docetaxel, the conjugates exhibited significantly improved solubility in oil, as predicted by our theoretical calculations. This contributed to high drug entrapment efficiencies (up to 97%) and a high drug loading capacity (5.7% w/w) for the docetaxel conjugates. The mono-substitution of an acyl group at C-2' of docetaxel resulted in a conjugate with 37- to 46-fold lower cytotoxicity than that of the parent drug in two human cancer cell lines. Importantly, the activity exerted by the mono-substituted docetaxel on the cancer cells was due in part to the cytotoxicity of the parent drug that was released via hydrolysis of the ester bond between the lauroyl moiety and the drug under biologically relevant conditions. In contrast, di- and tri-substitution of acyl groups at C-2', C-7 and/or C-10 of docetaxel resulted in non-hydrolysable conjugates that were found to be inactive. Overall, our results show that computer-based theoretical calculation is a promising strategy for guiding the enhancement of material-drug compatibility in formulation development. Also, these studies confirm that chemical modification of docetaxel for enhancement of material-drug compatibility should be limited to mono-substitution at C-2' and result in a prodrug that is hydrolysable at a moderate rate under biologically relevant conditions.

Effects of cholesterol and docosahexaenoic acid on cell viability and (Ca(2+))(i) levels in acutely isolated mouse thymocytes

We investigated the effects of lipids on thymocyte function. The effects of application of cholesterol or docosahexaenoic acid (DHA), a C22, omega-3 (n-3) polyunsaturated fatty acid (PUFA), on viability and intracellular calcium concentrations of acutely isolated mouse thymocytes were investigated using flow cytometry. Cholesterol (100 microM) caused significant cell death after 30-60 min whether or not calcium was present in the medium. Cell death was associated with an elevation of intracellular calcium whether or not calcium was present in the extracellular medium. However, the elevation of calcium concentration was not responsible for the cell death since calcium levels in the presence of ionomycin rose higher without significant cell death. DHA had similar actions but was more potent, causing significant cell death and elevation of calcium concentration within 5 min at 1 microM. In the absence of extracellular calcium 1 microM DHA caused 100% cell death within 15 min. Linolenic acid, a C18 omega-3 fatty acid also caused cytotoxicity at low concentrations whether or not albumin was present, but omega-6 or saturated C22 fatty acids were much less effective. These observations demonstrate that thymocyte viability is very sensitive to acute exposure to low concentrations of omega-3 fatty acids.

Hydrolysis of tumor cell lipids after CTL-mediated death

Contributions of lipases to CTL function have been debated, including if T cell lipases damage target cells. Expression of the lipase pancreatic lipase-related protein 2 (PLRP2) was previously found in IL-4 cultured lymphocyte cell lines but absent from IL-2 cultured lymphocytes. Here, we evaluated IL-2 and IL-4 induced CTLs for hydrolysis of target cell lipids and killing. Using anti-CD3 redirected lysis of [(3)H]-oleic acid-labeled P815 tumor cells, we detected the release of the radioactive fatty acid (FA). When PLRP2(+/+) and PLRP2(-/-) CTLs were compared, there was more killing by the PLRP2(+/+) CTLs. However, [(3)H]-oleic acid release was similar per dead P815, suggesting that lipid hydrolysis was produced by the dead P815s rather than by PLRP2. The FA release and death were completely dependent on perforin and also occurred when P815s were killed by perforin-containing T cell granule extracts that lacked lipase activity. Death by the cytotoxic granules extracts was unaffected by the addition of lipases. A lipase inhibitor, tetrahydrolipstatin, blocked FA release without affecting CTL-mediated cytotoxicity. Also, CTL-mediated death caused as much FA release as death by disruption of cells by freeze-thawing. The released oleic acid may be sufficient to promote secondary apoptotic responses after CTL-induced trauma.

Dietary stearate reduces human breast cancer metastasis burden in athymic nude mice

Stearate is an 18-carbon saturated fatty acid found in many foods in the western diet, including beef and chocolate. Stearate has been shown to have anti-cancer properties during early stages of neoplastic progression. However, previous studies have not investigated the effect of dietary stearate on breast cancer metastasis. In this study, we present evidence that exogenously supplied dietary stearate dramatically reduces the size of tumors that formed from injected human breast cancer cells within the mammary fat pads of athymic nude mice by approximately 50% and partially inhibits breast cancer cell metastasis burden in the lungs in this mouse model system. This metastatic inhibition appears to be independent of primary tumor size, as stearate fed animals that had primary tumors comparable in size to littermates fed either a safflower oil enriched diet or a low fat diet had reduced lung metastasis. Also stearate fed mice sub-groups had different primary tumor sizes but no difference in metastasis. This anti-metastasis effect may be due, at least in part, to the ability of stearate to induce apoptosis in these human breast cancer cells. Overall, this study suggests the possibility of dietary manipulation with selected long-chain saturated fatty acids such as stearate as a potential adjuvant therapeutic strategy for breast cancer patients wishing to maximize the suppression of metastatic disease.

Chronic nickel-induced DNA damage and cell death: the protection role of ascorbic acid

High consumption of nickel-containing products leads to more exposure of humans to nickel and its by-products. Except the lethal effect of acute nickel poison, chronic nickel exposure is also harmful to humans, but the mechanism of chronic nickel-induced cytotoxicity remains unclear. Here, we found that long-term exposure of Ni(2+) led to significant DNA fragmentation, cell death, and reactive oxygen species (ROS) generation in human leukemia HL-60 cells. Induction of Ni(2+) on DNA fragmentation and cell death could be prevented by the antioxidants ascorbic acid (ASA) or N-acetyl-cysteine (NAC), or enhanced by H(2)O(2), indicating the involvement of ROS generation in the chronic nickel cytotoxicity in cells. Long-term exposure of mice to low Ni(2+) also led to a significant increase in both the ROS generation in the serum and the DNA fragmentation in the peripheral blood mononuclear cells (PBMC), while coadministration of ASA with Ni(2+) together significantly decreased both the DNA fragmentation and the ROS generation. Collectively, these results proved that ROS generation is at least one mechanism of the cytotoxicity of chronic nickel exposure, while ASA is probably useful for people to prevent the chronic nickel cytotoxicity, especially for those who work or live near a mining area or a factory related with nickel.

The intestine as source of cytotoxic mediators in shock: free fatty acids and degradation of lipid-binding proteins

Shock and multiple organ failure remain primary causes of late-stage morbidity and mortality in victims of trauma. During shock, the intestine is subject to extensive cell death and is the source of inflammatory factors that cause multiorgan failure. We (34) showed previously that ischemic, but not nonischemic, small intestines and pancreatic protease digested homogenates of normal small intestine can generate cytotoxic factors capable of killing naive cells within minutes. Using chloroform/methanol separation of rat small intestine homogenates into lipid fractions and aqueous and sedimented protein fractions and measuring cell death caused by those fractions, we found that the cytotoxic factors are lipid in nature. Recombining the lipid fraction with protein fractions prevented cell death, except when homogenates were protease digested. Using a fluorescent substrate, we found high levels of lipase activity in intestinal homogenates and cytotoxic levels of free fatty acids. Addition of albumin, a lipid binding protein, prevented cell death, unless the albumin was previously digested with protease. Homogenization of intestinal wall in the presence of the lipase inhibitor orlistat prevented cell death after protease digestion. In vivo, orlistat plus the protease inhibitor aprotinin, administered to the intestinal lumen, significantly improved survival time compared with saline in a splanchnic arterial occlusion model of shock. These results indicate that major cytotoxic mediators derived from an intestine under in vitro conditions are free fatty acids. Breakdown of free fatty acid binding proteins by proteases causes release of free fatty acids to act as powerful cytotoxic mediators.

Experimental and computational studies investigating trehalose protection of HepG2 cells from palmitate-induced toxicity

Understanding the mechanism of saturated fatty acid-induced hepatocyte toxicity may provide insight into cures for diseases such as obesity-associated cirrhosis. Trehalose, a nonreducing disaccharide shown to protect proteins and cellular membranes from inactivation or denaturation caused by different stress conditions, also protects hepatocytes from palmitate-induced toxicity. Our results suggest that trehalose serves as a free radical scavenger and alleviates damage from hydrogen peroxide secreted by the compromised cells. We also observe that trehalose protects HepG2 cells by interacting with the plasma membrane to counteract the changes in membrane fluidity induced by palmitate. The experimental results are supported by molecular dynamics simulations of model cell membranes that closely reflect the experimental conditions. Simulations were performed to understand the specific interactions between lipid bilayers, palmitate, and trehalose. The simulations results reveal the early stages of how palmitate induces biophysical changes to the cellular membrane and the role of trehalose in protecting the membrane structure.

Effect of Rhaphidophora korthalsii methanol extract on human peripheral blood mononuclear cell (PBMC) proliferation and cytolytic activity toward HepG2

The study of bioactivity of natural product is one of the major researches for drug discovery. The aim of this finding was to study the proliferation effect of Rhaphidophora korthalsii methanol extract on human PBMC and subsequently the cytotoxic effect of activated PBMC toward HepG2 human hepatocellular carcinoma. In this present study, MTT assay, cell cycle study and Annexin 5 binding assay were used to study the immunomodulatory and cytotoxic effects. In vitro cytotoxic screening of Rhaphidophora korthalsii methanol extract showed that the extract was non-toxic against hepatocellular carcinoma (HepG2). In contrast, the extract was able to stimulate the proliferation of human PBMC at 48 h and 72 h in MTT assay and cell cycle progress study. The application of immunomodulator in tumor research was studied by using MTT microcytotoxicity assay and flow cytometric Annexin V. Results indicated that pre-treated PBMC with Rhaphidophora korthalsii methanol extract induced the highest cytotoxicity (44.87+/-6.06% for MTT microcytotoxicity assay and 51.51+/-3.85% for Annexin V) toward HepG2. This finding demonstrates that Rhaphidophora korthalsii methanol extract are potent to stimulate the cytotoxic effect of immune cells toward HepG2.

Docosahexaenoic acid enhances the toxic effect of imatinib on Bcr-Abl expressing HL-60 cells

The effect of docosahexaenoic acid (DHA) on the killing efficacy of imatinib on HL-60 cells expressing the Bcr-Abl protein was investigated. Imatinib is an Abl tyrosine kinase inhibitor used in the treatment of patients with chronic myeloid leukemia. The pre-treatment with DHA for 24 h raised the effect of imatinib at 100 microM concentration only. On the other hand, after 72 h pre-treatment, all concentrations of DHA tested (25, 50 and 100 microM) enhanced the toxic effect of imatinib. These results indicate that long-term pre-treatment with DHA makes Bcr-Abl HL-60 cells more susceptible to the toxic effect of imatinib.

Regulation of human lymphocyte proliferation by fatty acids

In the present study, the effect of increasing concentrations of palmitic (PA, C16:0), stearic (SA, C18:0), oleic (OA, C18:1, n-9), linoleic (LA, C18:2n-6), docosahexaenoic (DHA, C22:6 n-3) and eicosapentaenoic (EPA, C20:5 n-3) acids on lymphocyte proliferation was investigated. The maximal non-toxic concentrations of these fatty acids for human lymphocytes in vitro were determined. It was also evaluated whether these fatty acids at non-toxic concentrations affect IL-2 induced lymphocyte proliferation and cell cycle progression. OA and LA at 25 microM increased lymphocyte proliferation and at higher concentrations (75 microM and 100 microM) inhibited it. Both fatty acids promoted cell death at 200 microM concentration. PA and SA decreased lymphocyte proliferation at 50 microM and promoted cell death at concentrations of 100 microM and above. EPA and DHA decreased lymphocyte proliferation at 25 and 50 microM being toxic at 50 and 100 microM, respectively. PA, SA, DHA and EPA decreased the stimulatory effect of IL-2 on lymphocyte proliferation, increasing the percentage of cells in G1 phase and decreasing the proportion of cells in S and G2/M phases. OA and LA caused an even greater pronounced effect. The treatment with all fatty acids increased neutral lipid accumulation in the cells but the effect was more pronounced with PA and DHA. In conclusion, PA, SA, DHA and EPA decreased lymphocyte proliferation, whereas OA and LA stimulated it at non-toxic concentrations.

Propaedeutic study for the delivery of nucleic acid-based molecules from PLGA microparticles and stearic acid nanoparticles

We studied the mechanism governing the delivery of nucleic acid-based drugs (NABD) from microparticles and nanoparticles in zero shear conditions, a situation occurring in applications such as in situ delivery to organ parenchyma. The delivery of a NABD molecule from poly(DL-lactide-co-glycolide) (PLGA) microparticles and stearic acid (SA) nanoparticles was studied using an experimental apparatus comprising a donor chamber separated from the receiver chamber by a synthetic membrane. A possible toxic effect on cell biology, as evaluated by studying cell proliferation, was also conducted forjust PLGA microparticles. A mathematical model based on the hypothesis that NABD release from particles is due to particle erosion was used to interpret experimental release data. Despite zero shear conditions imposed in the donor chamber, particle erosion was the leading mechanism for NABD release from both PLGA microparticles and SA nanoparticles. PLGA microparticle erosion speed is one order of magnitude higher than that of competing SA nanoparticles. Finally, no deleterious effects of PLGA microparticles on cell proliferation were detected. Thus, the data here reported can help optimize the delivery systems aimed at release of NABD from micro- and nanoparticles.

Neutrophil fatty acid composition: effect of a single session of exercise and glutamine supplementation

The fatty acid composition of immune cells appears to contribute to variations of cell function. The independent and combined effects of a single session of exercise (SSE) and glutamine supplementation (GS) on neutrophil fatty acid composition were investigated. Compared to control (no treatment given--i.e. neither SSE or GS), single session of exercise decreased myristic, palmitic and eicosapentaenoic (EPA) acids, and increased lauric, oleic, linoleic, arachidonic (AA) and docosahexaenoic (DHA) acids whereas glutamine supplementation combined with SSE (GS+SSE) increased oleic acid. Polyunsaturated/saturated fatty acid ratio and Unsaturation index were higher in neutrophils from the SSE and GS groups as compared with control. These findings support the proposition that SSE and GS may modulate neutrophil function through alterations in fatty acid composition.

Mechanisms by which fatty acids regulate leucocyte function

Fatty acids (FAs) have been shown to alter leucocyte function and thus to modulate inflammatory and immune responses. In this review, the effects of FAs on several aspects of lymphocyte, neutrophil and macrophage function are discussed. The mechanisms by which FAs modulate the production of lipid mediators, activity of intracellular signalling pathways, activity of lipid-raft-associated proteins, binding to TLRs (Toll-like receptors), control of gene expression, activation of transcription factors, induction of cell death and production of reactive oxygen and nitrogen species are described in this review. The rationale for the use of specific FAs to treat patients with impaired immune function is explained. Substantial improvement in the therapeutic usage of FAs or FA derivatives may be possible based on an improvement in the understanding of the precise molecular mechanisms of action with respect to the different leucocyte types and outcome with respect to the inflammatory responses.

Comparative toxicity of fatty acids on a macrophage cell line (J774)

In the present study, the cytotoxicity of palmitic, stearic, oleic, linoleic, arachidonic, docosahexaenoic and eicosapentaenoic acids on a macrophage cell line (J774) was investigated. The induction of toxicity was investigated by changes in cell size, granularity, membrane integrity, DNA fragmentation and phosphatidylserine externalization by using flow cytometry. Fluorescence microscopy was used to determine the type of cell death (Acridine Orange/ethidium bromide assay). The possible mechanisms involved were examined by measuring mitochondrial depolarization, lipid accumulation and PPARgamma (peroxisome-proliferator-activated receptor gamma) activation. The results demonstrate that fatty acids induce apoptosis and necrosis of J774 cells. At high concentrations, fatty acids cause macrophage death mainly by necrosis. The cytotoxicity of the fatty acids was not strictly related to the number of double bonds in the molecules: palmitic acid>docosahexaenoic acid>stearic acid=eicosapentaenoic acid=arachidonic acid>oleic acid>linoleic acid. The induction of cell death did not involve PPARgamma activation. The mechanisms of fatty acids to induce cell death involved changes in mitochondrial transmembrane potential and intracellular neutral lipid accumulation. Fatty acids poorly incorporated into triacylglycerol had the highest toxicity.

Mechanisms involved in Jurkat cell death induced by oleic and linoleic acids

BACKGROUND & AIMS

Previous study from our laboratory showed the toxicity of oleic (OA) and linoleic acids (LA) on Jurkat and Raji cells and human lymphocytes in vitro. The mechanisms involved in the toxicity induced by OA and LA on Jurkat cells were determined in vitro.

METHODS

Jurkat cells were treated in the presence of OA and LA (25, 50, 100 and 200muM). The parameters investigated were: triglycerides and cholesterol ester concentrations determined by enzymatic assay, activation of peroxisome proliferator activated receptor (PPAR) by electrophoretic mobility shift assay, caspase 3, 6 and 8 activities by spectrofluorometric assay, tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma production by enzyme linked absorbent assay (ELISA), expression of pro- (Bax) and anti- (Bcl-2) apoptotic genes by real time polymerase chain reaction and expression of pleiotropic genes by macroarray technique

RESULTS

Evidence is presented herein that the increase in triglycerides concentrations induced by OA is more pronounced than that caused by LA in Jurkat cells. Importantly, triglycerides accumulation may be a mechanism to protect lymphocytes against the toxicity induced by fatty acids. Both fatty acids raised PPAR activation, caspase 3 and 6 activities and TNF-alpha production. LA in toxic concentrations modulated the expression of genes related to cell cycle, apoptosis, proliferation, oxidative stress, and cytokine receptors.

CONCLUSION

The findings reported herein support the cell death induced by OA and LA involved triglycerides accumulation, PPAR activation, caspase 3 and 6 activities and TNF-alpha production.

Effect of rhodoxanthin from Potamogeton crispus L. on cell apoptosis in Hela cells

Carotenoid, a natural functional pigment, is known to have anti-carcinogenic activity. To verify the anti-cancer effects of rhodoxanthin which is a kind of carotenoids, we investigated the effects of rhodoxanthin from Potamogeton crispus L. on the proliferation rate, cell cycle distribution, apoptosis and the change in mitochondrial membrane potential in Hela cell line. The effects of rhodoxanthin were also tested on the concentration of Ca(2+) in cells. Rhodoxanthin inhibited cell proliferation in Hela cells in a dose and time-dependent manner. Rhodoxanthin induced an accumulation of cells in the S phase of the cell cycle, reduced the mitochondria transmembrane potential and increased the concentration of intracellular Ca(2+). In summary, our results suggested that rhodoxanthin-induced apoptosis in Hela cells occurred via these pathways.

Fatty acid-induced toxicity and neutral lipid accumulation in insulin-producing RINm5F cells

Fatty acids have been shown to cause death of rat and human primary pancreatic beta cells and of insulin-producing cell lines. These studies focused mainly on saturated and monounsaturated FA such as palmitic, stearic and oleic acids. In this study, we have performed a comparison of the toxicity of a wider range of FA. The toxicity of different FA to insulin-producing RINm5F cells was assessed by flow cytometry measuring loss of plasma membrane integrity and increase in DNA fragmentation. Additionally, the FA induced neutral lipid accumulation and the FA composition were determined. Palmitic, linoleic, gamma-linolenic, oleic, stearic, and eicosapentaenoic acid caused DNA fragmentation of insulin-producing RINm5F cells. Loss of membrane integrity was mainly caused by linoleic and gamma-linolenic acid. There was no correlation between cytotoxicity and the abundance of the FA in the cells as determined by HPLC analysis. Taken as whole, the toxic effect of the FA on insulin-producing RINm5F cells varied irrespective of the chain length and the degree of unsaturation. In these cells PA and LA exhibited the highest toxicity, whereas AA was not toxic. In addition, the toxicity of most tested FA was inversely related to low NLA, except for AA and EPA. The results of this study contribute to the understanding of the role of FA in the impairment of pancreatic beta cell function that occurs in type 2 diabetes and obesity.

Synthesis of a novel series of 2-methylsulfanyl fatty acids and their toxicity on the human K-562 and U-937 leukemia cell lines

The hitherto unknown 2-methylsulfanyldecanoic acid and 2-methylsulfanyldodecanoic acid were synthesized from methyl decanoate and methyl dodecanoate, respectively, through the reaction of lithium diisopropylamide and dimethyldisulfide in THF followed by saponification with potassium hydroxide in ethanol. Both alpha-methylsulfanylated FA were cytotoxic to the human chronic myelogenous leukemia K-562 and the human histiocytic lymphoma U-937 cell lines with EC50 values in the 200-300 microM range, which makes them more cytotoxic to these cell lines than decanoic and/or dodecanoic acid. The cytotoxicity of the studied FA toward K-562 followed the order 2-SCH3-12:0 > 2-SCH3-10:0 > 10:0 > 12:0 > 2-OCH3-12:0, whereas toward U-937 the cytotoxicity was 2-SCH3-10:0 > 2-SCH3-12:0 > 12:0 > 10:0 > 2-OCH3-12:0. These results indicate that the alpha-methylsulfanyl substitution increases the cytotoxicity of the C10 and C12 FA toward the studied leukemia cell lines.

Comparative toxicity of oleic and linoleic acid on human lymphocytes

Commercially available lipid emulsions for parenteral nutrition are mainly composed by long chain triacylglycerol containing a high proportion of linoleic acid (LA) or oleic acid (OA). The immunological impact of such therapy is particularly important because parenteral diets are often administered to critically ill patients as a mechanism to supply adequate nutrition during catabolic stress conditions. The comparative toxicity of OA and LA on human lymphocytes and the type of cell death induced by these fatty acids were determined in vitro. Parameters of cell death were investigated by flow cytometry-cell viability, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, neutral lipid accumulation and production of reactive oxygen species-and by fluorescence microscopy-chromatin condensation. Additionally a spectrofluorometric assay was employed to determine the activities of caspase--3, 6 and 8. Evidence is presented herein that OA is less toxic to human lymphocytes than LA. However, both fatty acids promoted apoptosis and necrosis of these cells. The mechanism of cell death induced by OA involved activation of caspase 3 while the mechanism of death induced by LA involved mitochondrial depolarization and ROS production. Importantly, neutral lipid accumulation may be a mechanism to protect lymphocytes against the toxicity induced by OA. OA may offer an immunological less problematic alternative to LA with respect to fatty acid composition of parenteral nutritional emulsions.

Comparative toxicity of oleic acid and linoleic acid on Raji cells

OBJECTIVE

Parenteral diets are often administered to critically ill patients. To study one of the effects of commercially available parenteral lipid diets, rich in triacylglycerol esters of omega-6 polyunsaturated fatty acids or omega-9 monounsaturated fatty acids, on the immune system of such patients, we evaluated the cytotoxicity of oleic and linoleic acids on Raji cells that had been derived from human B-lymphocytes.

METHODS

Cell death intensity and type were investigated by flow cytometry by quantitation of cell volume, granularity, DNA fragmentation, mitochondrial depolarization, and lipid accumulation. Fluorescence microscopy was used to determine chromatin condensation and type of cell death (acridine orange/ethidium bromide assay). Gene expression of BCL-XL, BCL-XS, C-MYC, and P53 was studied by reverse transcriptase polymerase chain reaction.

RESULTS

Oleic acid was less toxic than linoleic acid to Raji cells. Both fatty acids promote apoptosis and necrosis of these cells. The mechanism of cell death induced by these fatty acids seemed to involve mitochondrial depolarization, lipid accumulation, and overexpression of C-MYC and P53.

CONCLUSION

Oleic acid may offer a less harmful alternative to linoleic acid in parenteral diets with respect to patient B-lymphocyte-mediated immunologic activity.

Toxicity of a mixture of fatty acids on human blood lymphocytes and leukaemia cell lines

The effect of a mixture of fatty acids upon lymphocyte and leukaemia cell death was examined. Peripheral lymphocytes from healthy subjects and two human leukaemia cell lines-Jurkat (T lymphocyte) and Raji (B lymphocyte) cells-were treated with increasing concentrations (0.1-0.4 mM) of a fatty acid mixture in a proportion mimicking that of the free fatty acids in plasma. Features of cell death were then evaluated. Phosphatidylserine externalization, and DNA fragmentation (apoptosis), and loss of cell membrane integrity (necrosis) and mitochondrial depolarization (common feature of cell death) were observed in leukaemia cells after the fatty acid treatment for up to 48 h. Human lymphocytes, however, when submitted to the same treatment presented apoptotic feature only. These findings indicate that a free fatty acid mixture (mimicking the proportion found in plasma) triggers apoptosis of leukaemia cell lines followed by loss of cell membrane integrity, whereas in human circulating lymphocytes the same treatment causes apoptosis only. Evidence is presented herein that mitochondria from leukaemic cells are more susceptible to the toxicity of the fatty acids than mitochondria from human circulating lymphocytes.

Toxicity of fatty acids on murine and human melanoma cell lines

High concentrations of certain fatty acids can cause cell death via apoptosis or necrosis. The aim of this study was to investigate the toxicity of saturated and unsaturated fatty acids on melanoma cell lines, which was evaluated by either loss of membrane integrity and/or DNA fragmentation using flow cytometric analysis. Evidence is presented that saturated and unsaturated fatty acids exert toxic effects on melanoma cells through loss of membrane integrity and/or DNA fragmentation. Arachidonic and linoleic acids were the most effective in decreasing the number of viable S91 murine melanoma cells, causing loss of membrane integrity and DNA fragmentation at 100 microM concentration already after 24 h in culture. In B16F10 murine melanoma cells, palmitic acid was the most toxic, inducing cell death by both apoptosis and necrosis. The human melanoma cell lines were more resistant to the toxic effect of fatty acids. In SK-Mel 23 cells, indications of cytotoxicity were detected only after 48 h treatment with arachidonic, linoleic, palmitic and palmitoleic acids at 200 microM concentration. Linoleic acid was the most toxic for this cell line. In SK-Mel 28 human cells, only palmitic acid caused a significant decrease of the number of viable cells, inducing DNA fragmentation after 24 and 48 h treatments at 200 microM concentration.

Regulation of reactive oxygen species (ROS) production by C18 fatty acids in Jurkat and Raji cells

In the present study, the effects of C18 fatty acids with different numbers of double bonds, SA (stearic acid; C18:0), OA (oleic acid; C18:1), LA (linoleic acid; C18:2) and gamma-LNA (gamma-linolenic acid; C18:3), on ROS (reactive oxygen species) production by Jurkat (a human T-lymphocyte-derived cell line) and Raji (a human B-lymphocyte-derived cell line) cells were investigated. ROS production was determined by NBT (Nitro Blue Tetrazolium) reduction (intracellular and extracellular ROS production) and by dihydroethidium oxidation using flow cytometry (intracellular ROS production). The effectiveness on ROS production was gamma-LNA<SA<OA<LA in Jurkat cells and SA<gamma-LNA<OA<LA in Raji cells. LA (found in corn, soya bean and sunflower oils) was more potent than OA (found in olive oil) in stimulating ROS production in both Raji and Jurkat cells. The lower ROS production by OA compared with LA may be one of the benefits of olive oil consumption. As SA and gamma-LNA acids had little or no effect, further studies on the site of ROS production in these cells were carried out with OA and LA only. Activation of NADPH oxidase via PKC (protein kinase C) was found to be the major mechanism of ROS production induced by OA and LA in Jurkat and Raji cells.

Comparative toxicity of oleic acid and linoleic acid on Jurkat cells

BACKGROUND

Lipid emulsions for parenteral nutrition commercially available are mainly composed of long-chain triacylglycerol containing a high proportion of alpha-6 polyunsaturated fatty acids or alpha-9 monounsaturated fatty acids. The immunological impact of such therapy is particularly important because parenteral and enteral diets are often administered to critical ill patients. The comparative toxicity of oleic acid and linoleic acid on Jurkat cells, a human T lymphocyte cell line, and the type of cell death induced by these fatty acids were determined.

METHODS

Cell death was investigated by cytometry: decrease in cell volume, increase of granularity, DNA fragmentation, phosphatidylserine externalization, mitochondrial depolarization, lipid accumulation; by fluorescence microscopy: chromatin condensation and acridine orange/ethidium bromide assay; and by RT-PCR: mRNA expression of apoptotic genes.

RESULTS

Evidence is presented herein that oleic acid is much less toxic to Jurkat cells than linoleic acid. Both fatty acids promote apoptosis and necrosis of these cells. The mechanism of cell death induced by these fatty acids seem to involve with mitochondrial depolarization, lipid accumulation and the levels of C-MYC and P53 mRNA expression.

CONCLUSION

Therefore, oleic acid may offer an immunological less harmful alternative to linoleic acid for parenteral and enteral diets preparation.

Antioxidants and trichostatin A synergistically protect against in vitro cytotoxicity of Ni2+ in human hepatoma cells

The objective of this study was to investigate the separate and combined effects of antioxidants, trichostatin A (TSA) and their combination on the in vitro cytotoxicity of Ni2+ in human hepatoma cells. Cell viability, lactate dehydrogenase (LDH) release, and DNA fragmentation were measured as indicators of cell damage. Reactive oxygen species (ROS) generation and histone acetylation were also measured. The cytotoxicity of Ni2+ increased in a time- and dose-dependent manner. In the presence of 2 mM Ni2+, ROS generation increased 365% (p<0.05), while histone acetylation decreased 37% (p<0.05). Although antioxidants, ascorbic acid (AA, 0.5 or 1 mM), reduced glutathione (GSH, 100 or 200 microM) and N-acetyl-cysteine (NAC, 0.5 or 1 mM) strongly inhibited ROS generation, their effect on Ni2+-caused histone hypoacetylation was not so obvious. On the contrary, TSA (100 nM) showed no inhibition on ROS generation but significantly increased histone acetylation in both control and Ni2+-exposed cells. As expected, the combination of antioxidants and TSA possessed the activity of both diminishing ROS generation and increasing histone hypoacetylation caused by Ni2+. Further studies found that both antioxidants and TSA could diminish the cytotoxicity of Ni2+, and their combined effects obviously improved each of their protection roles, indicating that both ROS generation and histone hypoacetylation are involved in the cytotoxicity of Ni2+, and the combination of antioxidants and TSA may act as a useful strategy to protect against this cytotoxicity.

Butterfat fatty acids differentially regulate growth and differentiation in Jurkat T-cells

Synthetic Conjugated Linoleic Acid mixture (CLA; c9,t11; t10,c12-18:2) has been previously shown to inhibit growth, and enhance apoptosis and IL-2 mRNA synthesis in human lymphoblastic Jurkat T-cells. In this study, two different butterfat types were evaluated and compared for their effects on Jurkat cell viability, oxidative stress, pro-apoptotic activity, and cytokine synthesis: the conventionally produced butterfat (CBF), and organic butterfat (OBF) containing significantly higher amounts of c9,t11 (Rumenic Acid, RA), trans-vaccenic acid (VA; t11-18:1), alpha-linolenic acid (ALA), and lower levels of linoleic acid (LA). Results from cell treatment with both butterfat mixtures showed comparable oxidative stress (superoxide production, intracellular GSH depletion,and lipid peroxides yield), NADPH oxidase activation, cytotoxicity (LDH release), and IL-2 transcript level, whereas the effects of enhanced growth-inhibitory and pro-apoptotic activities were associated with OBF treatment. To then investigate each butterfat-induced effect caused by RA, VA, LA, and ALA, cells were exposed to synthetic FA concentrations similar to those from the different butterfats. Higher oxidative stress (superoxide production, intracellular GSH depletion) was induced by alpha-linolenic (ALA) and linoleic (LA) incubation (P<0.01) and superoxide production was suppressed by specific PKCalpha inhibitor (Gö 6976) and linked to increased toxicity and IL-2 synthesis inhibition. By contrast, cell treatment with RA increased apoptosis and IL-2 synthesis. These results suggest that a supply of ALA and LA is responsible for BF-induced oxidative stress via PKCalpha-NADPH oxidase pathway, and that enhanced antiproliferative effects in OBF treated cells is essentially determined by RA-induced pro-apoptotic activity.

Modulation of lymphocyte proliferation by macrophages and macrophages loaded with arachidonic acid

Arachidonic acid (AA) is incorporated and exported by macrophages. This fatty acid is also transferred from macrophages (Mphi) to lymphocytes (LY) in co-culture. This observation led us to investigate the effect of macrophages pre-loaded with AA on concanavalin A (Con A)-stimulated lymphocyte proliferation. The experiments were performed in co-culture. This condition reproduces the in vivo microenvironment in which the modulation of lymphocyte proliferation is dependent on the interaction with macrophages. Lymphocytes obtained from untreated rats or from intraperitoneally thioglycolate-injected rats (THIO-treated) were co-cultured with macrophages from the same rats. Firstly, macrophages were co-cultured for 48 h with Con A-stimulated lymphocytes in different proportions: 0.5, 1, 2.5, 5, 10, 20 and 30% of 5 x 10(5) lymphocytes per well. At 1% proportion, macrophages caused maximum stimulation of lymphocyte proliferation; a four- to five-fold increase, for cells from both thioglycolate-treated and untreated rats, respectively, whereas at 20% it caused maximum inhibition. In addition, 1 or 20% macrophages were pre-loaded with several AA concentrations during a period of 6 h and co-cultured with lymphocytes. At 180 microM AA and 1% macrophages, lymphocyte proliferation was inhibited (by 25%), whereas at 20% macrophages, proliferation was increased, by 25- and three-fold, respectively, for cells from untreated and THIO-treated rats. AA added directly to the medium reduced lymphocyte proliferation, also being toxic to these cells at 100 microM. No toxic effects of AA were observed on macrophages. Additional evidence suggests that nitric oxide production is involved in the modulation of lymphocyte proliferation by AA-pre-loaded macrophages. These findings support the proposition that AA can directly modulate lymphocyte proliferation and the interaction between macrophages and lymphocytes.

Effect of Cysticercus cellulosae on neutrophil function and death

Neutrophils, eosinophils and macrophages interact with invading parasites and naive hosts. The initial reaction of leukocytes is the generation of reactive oxygen species (ROS). The cytotoxic effects of extracts derived from intact Cysticercus cellulosae and from the scolex or membrane fractions on neutrophils were examined. DNA fragmentation of neutrophils was observed when cells were incubated with an extract from the intact metacestode; however, the addition of antioxidant enzymes to the incubation medium had a protective effect. The scolex and membrane extracts did not affect DNA fragmentation of neutrophils. Hydrogen peroxide production of neutrophils incubated with metacestode fractions from C. cellulosae increased by 190% (total extract), 120% (scolex) or 44% (membrane). An increase in antioxidant catalase activity (28%) concomitant with the increased production of ROS was observed in neutrophils incubated with metacestode fractions, which could be an attempt at self-protection. ROS production by neutrophils in the presence of the intact cysticerci extract did not alter phagocytosis. In contrast, the scolex and membrane fractions increased the phagocytic capacity of neutrophils by 44 and 28%, respectively. The results showed that the extract from intact C. cellulosae was toxic for neutrophils via ROS production, leading to DNA fragmentation and inhibition of phagocytic capacity, but neutrophils are able to protect themselves against oxidative stress by via catalase activity.

Identification of genes regulated by oleic acid in Jurkat cells by suppressive subtractive hybridization analysis

In this study, the effect of oleic acid (50 microM) on gene expression of Jurkat cells (human T lymphocytes cell line) was examined using the suppressive subtractive hybridization approach. This technique allowed us to identify genes with higher or lower expression after cell treatment with oleic acid as compared to untreated cells. Oleic acid upregulated the expression of the translation elongation factor alpha 1 and ATP synthase 8 and downregulated gp96 (human tumor rejection antigen gp96), heat-shock protein 60 and subtilisin-like protein 4. These results suggest that oleic acid, at plasma physiological concentration, can regulate the expression of important genes to maintain the machinery that ensures cell functioning.

Topical delivery of retinyl ascorbate co-drug

A novel synthetic technique was used to synthesise the co-drug retinyl ascorbate (RA-AsA) ester from all-trans-retinyl chloride (RA) and L-ascorbic acid (AsA) suspended in ethanol at low temperature. Its log P, solubility in a Me:PBS, 50/50 at pH 4.8 and degradation constant were determined. The flux and permeation coefficient were determined using heat separated human skin membrane, and skin penetration was determined by tape stripping using full thickness human. All experiments were performed in parallel with retinyl palmitate (Rol-Pal) and ascorbyl palmitate (AsA-Pal), which are used in commercial topical formulations. RA-AsA exhibited favourable log P (2.2), with stability much greater than RA and AsA, but similar stability to Rol-Pal and AsA-Pal. The flux of RA-AsA was lower than for Rol-Pal and AsA-Pal. RA-AsA also demonstrated higher skin retention than the other two esters, but delivered more RA and AsA to the viable epidermis than retinol from Rol-Pal and ascorbic acid from AsA-Pal. Overall, the data suggest the potential value of RA-AsA co-drug for the purpose of treating damage to skin resulting from UV-induced production of free radicals.

Effects of conjugated linoleic acid on growth and cytokine expression in Jurkat T cells

Conjugated linoleic acid (CLA) has shown beneficial properties in animal models including anti-cancer, anti-atherogenic and anti-diabetic effects, while contrasting immunological effects were reported. While its anti-inflammatory activity has been associated to inhibition of arachidonic acid biosynthesis and to peroxisome proliferator-activated receptors (PPARs) activity, the molecular pathways underlying its immunoenhancing activity are essentially unknown. The aim of our study was to examine whether CLA showed specific effects in vitro on a T cell model, represented by the Jurkat cell line. CLA was found non toxic for Jurkat in the range 50-200 microM, as assessed by LDH release; however, incubation with 50 microM CLA was associated to a significant inhibitory effect on cell proliferation. The analysis of IL-2 and IFN-gamma transcript levels, produced in stimulated Jurkat cells, showed an increased expression of both cytokines in CLA-treated cells. Interestingly, the increased induction of IL-2 but not of IFN-gamma mRNA, could be suppressed by co-incubation with Gö 6976, a protein kinase C (PKC) inhibitor. Co-incubation with superoxide dismutase (SOD) or N-acetyl-L-cysteine (NAC) restored the basal levels of RNA synthesis for both cytokines. Taken together, these results suggest a specific role for dietary CLA in the modulation of the immune response in a T cell line model that is mediated, at least in part, by PKC and through the production of oxidative molecules.