Identification of phosphatidyl-1-aminopropane-2-ol in rat liver after administration of 1-aminopropane-2-ol

3: Final Report on the Safety Assessment of Diisopropanolamine, Triisopropanolamine, Isopropanolamine, and Mixed Isopropanolamine

Diisopropanolamine, Triisopropanolamine, Isopropanolamine, and Mixed Isopropanolamine are used as water-soluble emulsifiers and neutralizers in cosmetic products at concentrations up to 1%. In animal studies these ingredients were slightly toxic to practically nontoxic to rats and guinea pigs via acute oral administration. Triisopropanolamine was relatively nontoxic to rats in the two subchronic oral studies. These ingredients were moderate skin irritants for rabbits. All four ingredients, when tested at 100% concentrations, were severe ocular irritants in rabbits. Products containing small amounts (-1%) of Diisopropanolamine or Triisopropanolamine were not ocular irritants in rabbits. The Triisopropanolamine salt was not mutagenic in Aspergillus nidulans. Diisopropanolamine and Isopropanolamine at concentrations of 2% did not induce allergic contact dermatitis or photoallergic dermatitis in humans. Clinical studies on cosmetic products containing no more than 1% Diisopropanolamine or 1.1% Triisopropanolamine were minimal skin irritant and contact sensitizers. It is concluded that Diisopropanolamine, Triisopropanolamine, Isopropanolamine, and Mixed Isopropanolamine are safe as cosmetic ingredients in the present practices of use and concentration. The Isopropanolamines should not be used in products containing N-nitrosating agents.

Metabolome analysis revealed increase in S-methylcysteine and phosphatidylisopropanolamine synthesis upon L-cysteine deprivation in the anaerobic protozoan parasite Entamoeba histolytica

L-cysteine is ubiquitous in all living organisms and is involved in a variety of functions, including the synthesis of iron-sulfur clusters and glutathione and the regulation of the structure, stability, and catalysis of proteins. In the protozoan parasite Entamoeba histolytica, the causative agent of amebiasis, L-cysteine plays an essential role in proliferation, adherence, and defense against oxidative stress; however, the essentiality of this amino acid in the pathways it regulates is not well understood. In the present study, we applied capillary electrophoresis time-of-flight mass spectrometry to quantitate charged metabolites modulated in response to L-cysteine deprivation in E. histolytica, which was selected as a model for examining the biological roles of L-cysteine. L-cysteine deprivation had profound effects on glycolysis, amino acid, and phospholipid metabolism, with sharp decreases in the levels of L-cysteine, L-cystine, and S-adenosylmethionine and a dramatic accumulation of O-acetylserine and S-methylcysteine. We further demonstrated that S-methylcysteine is synthesized from methanethiol and O-acetylserine by cysteine synthase, which was previously considered to be involved in sulfur-assimilatory L-cysteine biosynthesis. In addition, L-cysteine depletion repressed glycolysis and energy generation, as it reduced acetyl-CoA, ethanol, and the major nucleotide di- and triphosphates, and led to the accumulation of glycolytic intermediates. Interestingly, L-cysteine depletion increased the synthesis of isopropanolamine and phosphatidylisopropanolamine, and it was confirmed that their increment was not a result of oxidative stress but was a specific response to L-cysteine depletion. We also identified a pathway in which isopropanolamine is synthesized from methylglyoxal via aminoacetone. To date, this study represents the first case where L-cysteine deprivation leads to drastic changes in core metabolic pathways, including energy, amino acid, and phospholipid metabolism.

Influence of a beta-adrenergic agonist on septic shock-induced alterations of phosphatidylcholine metabolism in rat lung

Changes in surfactant function play an important part in the pathogenesis of adult respiratory distress syndrome (ARDS). Since beta-adrenergic agonists have been shown to exert a decisive influence on surfactant secretion, we studied the effect of fenoterol on lung phospholipid metabolism under conditions of experimental sepsis. Fenoterol administered to live rats increased the incorporation of choline into lung tissue by 80% in normal, by 35% in septic animals. It had no comparable effect on palmitate incorporation. It increased the activity of choline kinase in control animals, but had no additional effect on animals with increased values due to sepsis. Phosphotransferase activity diminished during sepsis was stimulated, and phospholipase activity reduced. Fenoterol restored phosphatidylcholine to normal levels in lung tissue and bronchoalveolar lavage and prevented lysophosphatidylcholine generation. Fenoterol also increased the amount of palmitate in phosphatidylcholine from bronchoalveolar lavage in septic animals. The results imply that a beta-adrenergic agonist influences the conditions of lung phospholipid metabolism altered by sepsis towards normal.

Phospholipid metabolism as a new target for malaria chemotherapy. Mechanism of action of D-2-amino-1-butanol

A number of choline and ethanolamine analogs were evaluated as inhibitors of P. falciparum growth in vitro. 1-Aziridineethanol, DL-2-amino-1,3-propranediol and D- or L-2-amino-1-butanol were the most efficient inhibitors of parasite multiplication, with an IC50 of 50-80 microM, whereas numerous other analogs were less active. The effect of D-2-amino-1-butanol on various metabolisms of P. knowlesi-infected simian erythrocytes was studied by incubating these cells with different labeled precursors of phospholipids, nucleic acids, proteins, and with radioactive glucose. In the presence of radioactive glycerol, oleate or lysophosphatidylcholine, the appearance of radioactivity in an unnatural phospholipid indicated that 2-aminobutanol was incorporated into a new PL which accounted for up to 30-40% of the total biosynthesized lipids. This new phospholipid accumulated primarily at the expense of PE biosynthesis and decreased the decarboxylation of phosphatidylserine. These effects were not accompanied, over a large range of concentrations, by any parallel change in nucleic or protein synthesis, nor in glucose metabolism. These data demonstrate that the incorporation of analogs, instead of the natural polar head groups, into cellular phospholipids, and/or modification of phospholipid composition have a deleterious impact on the growth of Plasmodium. It follows that PL metabolism is a crucial process for Plasmodium growth and may constitute a potentially fruitful chemotherapeutic approach to malaria.

Influence of septic shock upon phosphatidylcholine remodeling mechanism in rat lung

Septic shock in rats lead to pulmonary disorders associated with alterations of phospholipid metabolism. The ratio between phosphatidylcholine and lysophosphatidylcholine is lowered both in lung tissue and in pulmonary surfactant because enzymes of phosphatidylcholine remodeling mechanism are distinctly affected by septic shock. Specific activity of phospholipase A2 is enhanced 5-fold while specific activities of lysolecithin acyltransferase and lysolecithin : lysolecithin acyltransferase are only slightly increased or remain unchanged. Beyond that, palmitic acid content of lung tissue phosphatidylcholine is significantly reduced and replaced mainly by arachidonic acid. The release of this fatty acid by action of phospholipase A2 may lead via intermediates to the generation of potent mediators such as prostaglandins, thromboxane or slow-reacting substance.