p-Aminobenzoic acid, but not its metabolite p-acetamidobenzoic acid, inhibits thrombin induced thromboxane formation in human platelets in a non NSAID like manner

New hypotheses for the health-protective mechanisms of whole-grain cereals: what is beyond fibre?

Epidemiological studies have clearly shown that whole-grain cereals can protect against obesity, diabetes, CVD and cancers. The specific effects of food structure (increased satiety, reduced transit time and glycaemic response), fibre (improved faecal bulking and satiety, viscosity and SCFA production, and/or reduced glycaemic response) and Mg (better glycaemic homeostasis through increased insulin secretion), together with the antioxidant and anti-carcinogenic properties of numerous bioactive compounds, especially those in the bran and germ (minerals, trace elements, vitamins, carotenoids, polyphenols and alkylresorcinols), are today well-recognised mechanisms in this protection. Recent findings, the exhaustive listing of bioactive compounds found in whole-grain wheat, their content in whole-grain, bran and germ fractions and their estimated bioavailability, have led to new hypotheses. The involvement of polyphenols in cell signalling and gene regulation, and of sulfur compounds, lignin and phytic acid should be considered in antioxidant protection. Whole-grain wheat is also a rich source of methyl donors and lipotropes (methionine, betaine, choline, inositol and folates) that may be involved in cardiovascular and/or hepatic protection, lipid metabolism and DNA methylation. Potential protective effects of bound phenolic acids within the colon, of the B-complex vitamins on the nervous system and mental health, of oligosaccharides as prebiotics, of compounds associated with skeleton health, and of other compounds such as alpha-linolenic acid, policosanol, melatonin, phytosterols and para-aminobenzoic acid also deserve to be studied in more depth. Finally, benefits of nutrigenomics to study complex physiological effects of the 'whole-grain package', and the most promising ways for improving the nutritional quality of cereal products are discussed.

Influence of liposomal local anesthetics on platelet aggregation in vitro

We assessed the effect of local anesthetics (LA) from different families such as esters (benzocaine), linear aminoamides (lidocaine) and cyclic aminoamides (bupivacaine) on the platelet aggregation induced by ADP. Liposomal formulations of the three LA, prepared with egg phosphatidylcholine:cholesterol alpha-tocopherol, were also tested. The three LA were able to inhibit platelet aggregation induced by ADP, in the following order: bupivacaine > lidocaine > benzocaine. After encapsulation into liposomes the inhibitory effect increased for all anesthetics studied, showing that aggregation tests could be used to assess the toxicity of new drug formulations.

p-Aminobenzoic acid and its metabolite p-acetamidobenzoic acid inhibit agonist-induced aggregation and arachidonic acid-induced [Ca2+]i transients in human platelets

We have previously found that the naturally occurring amine p-aminobenzoic acid (PABA) inhibits the thrombin-induced thromboxane B2 production in human platelets. In this report we show that PABA and its acetylated metabolite p-acetamidobenzoic acid (PACBA) inhibit platelet aggregation induced by agonists such as adenosine diphosphate (ADP) and arachidonic acid (AA). Both substances were equipotent to acetylsalicylic acid regarding inhibition of ADP-induced aggregation and approximately 50% as potent as acetylsalicylic acid regarding arachidonic acid-induced aggregation. Although not significantly inhibiting collagen aggregation, PABA and PACBA reduced the concomitant adenosine triphosphate (ATP) secretion by approximately 30 and 20%, respectively. The antiaggregatory effect does not seem to be mediated through cyclic adenosine monophosphate (cAMP) increase because in our experiments PABA and PACBA did not significantly affect cAMP levels. However, we have found that PABA and PACBA inhibit the intracellular aequorin indicated Ca2+ transient upon arachidonic acid stimulation. Our results describe a hitherto unknown effect of PABA and PACBA on platelet aggregation.

Lipoxygenase inhibitors counteract protein kinase C mediated events in human T lymphocyte proliferation

Four structurally unrelated inhibitors of lipoxygenase (LO), i.e. nordihydroguaiaretic acid (NDGA), Esculetin, AA861 and 5,8,11,14-eicosatetraynoic acid (ETYA) suppressed mitogen induced proliferation of human peripheral blood lymphocytes in a dose-dependent manner. The degree of suppression was influenced by the type of the mitogenic stimulus. Receptor mediated stimulation, i.e. through phytohemagglutinin or the anti-CD3 antibody OKT3, was overall less susceptible, whereas proliferation initiated by direct activation of protein kinase C (PKC), i.e. through phorbol myristate acetate or indolactam V, was profoundly suppressed (up to 90%). The effect of the LO inhibitors was not due to non-specific interference with intracellular radical intermediates, because AA861 and ETYA showed no radical scavenging activity. Two PKC inhibitors, H-7 and H-8, similarly suppressed lymphocyte proliferation and showed essentially the same suppressive pattern as LO inhibitors. The results clearly indicate that LO product(s) participate in signal transduction mechanisms in T lymphocytes, possibly via stimulation of PKC activity and cell proliferation.