Sara R. Alonso-Torre

Role of oleic acid in immune system; mechanism of action: a review

INTRODUCTION Although n-3 polyunsaturated fatty acids have been widely described as anti-inflammatory fats, little is known about the role of oleic acid in immune system. AIM The aim of the present review is to join all the reports available in order to analyze where exactly the knowledge concerning this topic is and what the causes of the controversial data could be. METHODS We searched electronic databases and bibliographies of selected articles were inspected for further reference. RESULTS Diets rich in oleic acid have beneficial effects in inflammatory-related diseases. In addition, a wide range of studies evaluate the effect of oleic acid in different cellular functions thus reporting a potential mechanism for the biological effect of such a fat. However, some controversial data can be found in literature, maybe related to the kind of study or even the dose of the reagent added. CONCLUSION In conclusion, oleic acid could be reported as an anti-inflammatory fatty acid playing a role in the activation of different pathways of immune competent cells.

Antitumor effect of oleic acid; mechanisms of action: A review

INTRODUCTION The beneficial effects of oleic acid in cancer processes can no longer be doubted, but little is known about the mechanisms of action behind this phenomenon. AIM The aim of the present review is to clarify whether oleic acid has an effect on important mechanisms related to the carcinogenic processes. METHODS We searched electronic databases and bibliographies of selected articles were inspected for further reference. We focused our research on two cellular transformations characterizing cancer development: proliferation and cell death or apoptosis. RESULTS Numerous studies have reported an inhibition in cell proliferation induced by oleic acid in different tumor cell lines. Herein, oleic acid could suppress the over-expression of HER2 (erbB-2), a well-characterized oncogene which plays a key role in the etiology, invasive progression and metastasis in several human cancers. In addition, oleic acid could play a role in intracellular calcium signaling pathways linked to the proliferation event. Regarding cell death, oleic acid has been shown to induce apoptosis in carcinoma cells. The mechanisms behind the apoptotic event induced by oleic acid could be related to an increase in intracellular ROS production or caspase 3 activity. Several unsaturated fatty acids have been reported to induce apoptosis through a release of calcium from intracellular stores. However, evidence regarding such a role in oleic acid is lacking. CONCLUSIONS Oleic acid plays a role in the activation of different intracellular pathways involved in carcinoma cell development. Such a role could be the root of its antitumoral effects reported in clinical studies.

Activation of Human Neutrophils by Oleic Acid Involves the Production of Reactive Oxygen Species and a Rise in Cytosolic Calcium Concentration: a Comparison with N-6 Polyunsaturated Fatty Acids

Background: There is a growing body of evidence showing that dietary constituents and lipids in particular, influence the function of the human immune system. However, although the beneficial effects of oleic acid (OA) are clear, its mechanism of action at the molecular level is poorly understood. Aims: To evaluate neutrophil activation under the influence of OA and compare this with several n-6 PUFAs. Methods: Two key aspects of neutrophil activation were investigated: oxygen radical (ROS) production and intracellular Ca2+ signaling. Results: OA and the n-6 PUFA arachidonic acid (AA) both induced ROS production in a dose-dependent manner, although AA was the more potent stimulus. When looking for the mechanisms behind these effects, we found that both FA induce increases in cytosolic calcium concentration [Ca2+]i), but whereas OA-induced ROS production is totally mediated through Ca2+ signaling, this is not the case for AA since ROS generation by AA is only partly inhibited in BAPTA-treated cells. We also found evidence for the involvement of protein kinase C (PKC) in the OA-induced ROS generation; by contrast, other enzymes apart from PKC seem to be implicated in n-6 PUFA-induced ROS production. In addition, our results argue against the involvement of a pertussis toxin-sensitive receptor activated by OA. Conclusions: OA differs from the n-6 PUFA AA in the activation of human neutrophils and these differences may be related to their distinct inmunomodulatory properties.

Diacylglycerol-containing oleic acid induces increases in [Ca(2+)](i) via TRPC3/6 channels in human T-cells.

Though most of the studies have focused on the effects of free fatty acids on T-cell activation, fatty acids incorporated into plasma membrane phospholipids may also affect cell signaling via diacylglycerol (DAG), generally produced by phospholipid hydrolysis. In the present study, we have synthesized a DAG-containing oleic acid and studied its implication in the modulation of calcium signaling in human Jurkat T-cells. 1-palmitoyl-2-oleoyl-sn-glycerol (POG) induced a dose-dependent increase in [Ca(2+)](i). This effect was due to the presence of oleic acid at the sn-2 position as no differences were observed between POG and 1-stearoly-2-oleoyl-sn-glycerol (SOG). However, the substitution of oleic acid with arachidonic acid at the sn-2 position of the DAG moiety exerted a different response on the increases in [Ca(2+)](i) in these cells. POG-evoked increases in [Ca(2+)](i) were not due to its metabolites. Furthermore, POG-induced increases in [Ca(2+)](i) were due to the opening of TRPC3/TRPC6 channels as silencing of TRPC3 and TRPC6 genes by shRNA abolished calcium entry. Moreover, disruption of lipid rafts with methyl-β-cyclodextrin completely abolished POG-evoked increases in [Ca(2+)](i). In conclusion, our results demonstrate that oleic acid can influence T-lymphocyte functions, in the conjugated form of DAG, via opening TRPC3/6 channels.

Oleic acid inhibits store-operated calcium entry in human colorectal adenocarcinoma cells

AimsMuch evidence indicates the association between dietary fat and colorectal cancer risk. However, most of the studies focus on polyunsaturated fatty acids, and little is known about the role of monounsaturated ones and their precise mechanism of action. Being store-operated Ca2+ entry (SOCE) a Ca2+ influx pathway involved in the control of multiple cellular and physiological processes including cell proliferation, we studied the effect of oleic acid in Ca2+ signals of colorectal cancer cells, paying particular attention to SOCE.MethodsCarbachol was used to induce SOCE in Fura 2-loaded HT29 cells. We tested a saturated fatty acid to compare the physiological relevance of our results.ResultsWe show that oleic acid is a potent inhibitor of SOCE. By contrast, stearic acid failed to have a SOCE-inhibitory effect. The SOCE-inhibition induced by oleic acid was protein kinase C-independent and restored by albumin. We also demonstrated that oleic acid induced increases in [Ca2+]i. The novelty of our report is that little variability in the concentration could end in a large different physiological effect.ConclusionsIn conclusion, we suggest a physiological pathway for the beneficial effect of oleic acid in colon carcinoma cells.

High-pressure liquid chromatographic determination of ascorbic acid in cooked sausages.

The purpose of this paper was to study and optimize both extraction and high-pressure liquid chromatography (HPLC)-UV detection procedures to develop a proper method for the determination of ascorbic acid content in cooked sausages. A simple and sensitive reversed-phase HPLC method for the NH2-bonded phase has been described for the determination of ascorbic acid content in cooked sausages. Various extracting agents were tested to solubilize the vitamin, with 5% (wt/vol) metaphosphoric acid giving the best results. Samples were chromatographed with UV detection at 248 nm on a 25-cm Spherisorb NH2 cartridge with a 0.4-cm inside diameter with a mixture of 0.02 M potassium phosphate buffer solution (pH 3.6) and acetonitrile (40:60, vol/vol) for the mobile phase. The methods precision within a day was 1.2%, and its precision between days was 3.8%. The detection limit was 1.6 mg/100 g. Recovery ranged from 91.4 to 96.2% for ascorbic acid added to meat samples. Twenty samples of six different products were analyzed in duplicate. For the samples analyzed, the mean value for ascorbic acid ranged between 21.555 and 24.899 mg/100 g of fresh weight.

Oleic acid versus linoleic and α-linolenic acid. different effects on Ca2+ signaling in rat thymocytes.

Background: Oleic acid is the principal fatty acid of olive oil composition and is reported to play a crucial role in its healthy aspects. However, the detailed mechanism of action is poorly understood. Aims: This study aims to elucidate the role of oleic acid in calcium signaling in rat thymocytes, in comparison to linoleic and linolenic acid. Methods: Fatty acids were applied to thymocytes isolated from wistar rats and loaded with Fura-2 to measure calcium signals. Results: The main results showed a concentration-dependent increase in [Ca2+]i induced by the 3 fatty acids. Raising the number of unsaturations resulted in greater increases. Two different pathways contributed to the increase induced by the polyunsaturated fatty acids: an IP3- independent release from the thapsigargin-sensitive stores and an extracellular calcium entry by econazole and nifedipine-insensitive channels. However, the OA-induced increases in [Ca2+]i seemed to be due mostly to the Ca2+ recruited from the intracellular stores. Conclusion: This study demonstrates that the fatty acids tested induce increases in [Ca2+]i in rat thymocytes, with differences in close relation to the degree of unsaturation. Such differences could be responsible for their different physiological action.

GLOBAL ANTIOXIDANT RESPONSE OF MEAT

BACKGROUND The global antioxidant response (GAR) method uses an enzymatic digestion to release antioxidants from foods. Owing to the importance of digestion for protein breakdown and subsequent release of bioactive compounds, the aim of the present study was to compare the GAR method for meat with the existing methodologies: the extraction-based method and QUENCHER. Seven fresh meats were analyzed using ABTS and FRAP assays. RESULTS Our results indicated that the GAR of meat was higher than the total antioxidant capacity (TAC) assessed with the traditional extraction-based method. When evaluated with GAR, the thermal treatment led to an increase in the TAC of the soluble fraction, contrasting with a decreased TAC after cooking measured using the extraction-based method. The effect of thermal treatment on the TAC assessed by the QUENCHER method seemed to be dependent on the assay applied, since results from ABTS differed from FRAP. CONCLUSION Our results allow us to hypothesize that the activation of latent bioactive peptides along the gastrointestinal tract should be taken into consideration when evaluating the TAC of meat. Therefore, we conclude that the GAR method may be more appropriate for assessing the TAC of meat than the existing, most commonly used methods.

Effect of oleic acid on store-operated calcium entry in immune-competent cells

PurposeTo study the mechanism by which oleic acid (OA) (C18:1) exerts its beneficial effects on immune-competent cells. Since store-operated Ca2+ entry (SOCE) is a Ca2+ influx pathway involved in the control of multiple physiological processes including cell proliferation, we studied the effect of OA in Ca2+ signals of Jurkat T cells and THP-1 monocytes, paying particular attention to SOCE.MethodsChanges in [Ca2+]i were measured using the Fura-2 fluorescence dye. Mn2+ uptake was monitored as a rate of quenching of Fura-2 fluorescence measured at the Ca2+-insensitive wavelengths. Thapsigargin was used to induce SOCE in Fura-2-loaded cells.ResultsWe showed a clear dose-dependent SOCE-inhibitory effect of OA in both cell lines. Such an inhibitory effect was PKC independent and totally restored by albumin, suggesting that OA exerts its effect somewhere in the membrane. We also demonstrated that OA induces increases in [Ca2+]i partly mediated by an extracellular Ca2+ influx through econazole-insensitive channels. Finally, we compared the effect of OA with stearic acid (C18:0), assuming the emerged evidence concerning the link between saturated fats and inflammation disorders. Stearic acid failed to inhibit SOCE, independently on the concentration tested, thus intensifying the physiological relevance of our findings.ConclusionWe suggest a physiological pathway for the beneficial effects of OA in inflammation.

Antioxidant Capacity of Beetroot: Traditional vs Novel Approaches

Red beetroot has been ranked among the 10 most potent antioxidant vegetables, although only extraction-based methods have been used to evaluate its total antioxidant capacity. Therefore, the present study aims at comparing the traditional extraction-based method with two more recent approaches (QUENCHER -QUick, Easy, New, CHEap and Reproducible- and GAR -global antioxidant response method), in order to establish their suitability in the case of beetroot. Our results indicate that the total antioxidant capacity of beetroot would be underestimated when using extraction-based procedures, since both QUENCHER and GAR methods resulted in a higher total antioxidant capacity. The effect of a thermal treatment on the total antioxidant capacity of beetroot varies among the methods evaluated and our findings suggest different compounds responsible for the total antioxidant capacity detected in each pre-processing method. Remarkably, the present study demonstrates that the traditional extraction-based method seems useful to screen for (changes in) the “bioavailable” antioxidant potential of the root.