High toxicity and specificity of the saponin 3-GlcA-28-AraRhaxyl-medicagenate, from Medicago truncatula seeds, for Sitophilus oryzae

<p>Abstract</p> <p>Background</p> <p>Because of the increasingly concern of consumers and public policy about problems for environment and for public health due to chemical pesticides, the search for molecules more safe is currently of great importance. Particularly, plants are able to fight the pathogens as insects, bacteria or fungi; so that plants could represent a valuable source of new molecules.</p> <p>Results</p> <p>It was observed that <it>Medicago truncatul</it>a seed flour displayed a strong toxic activity towards the adults of the rice weevil <it>Sitophilus oryzae</it> (Coleoptera), a major pest of stored cereals. The molecule responsible for toxicity was purified, by solvent extraction and HPLC, and identified as a saponin, namely 3-GlcA-28-AraRhaxyl-medicagenate. Saponins are detergents, and the CMC of this molecule was found to be 0.65 mg per mL. Neither the worm <it>Caenorhabditis elegans</it> nor the bacteria <it>E. coli</it> were found to be sensitive to this saponin, but growth of the yeast <it>Saccharomyces cerevisiae</it> was inhibited at concentrations higher than 100 μg per mL. The purified molecule is toxic for the adults of the rice weevils at concentrations down to 100 μg per g of food, but this does not apply to the others insects tested, including the coleopteran <it>Tribolium castaneum</it> and the Sf9 insect cultured cells.</p> <p>Conclusions</p> <p>This specificity for the weevil led us to investigate this saponin potential for pest control and to propose the hypothesis that this saponin has a specific mode of action, rather than acting <it>via</it> its non-specific detergent properties.</p

Acute liver injury induces nucleocytoplasmic redistribution of hepatic methionine metabolism enzymes

[Aims]: The discovery of methionine metabolism enzymes in the cell nucleus, together with their association with key nuclear processes, suggested a putative relationship between alterations in their subcellular distribution and disease. [Results]: Using the rat model of D-galactosamine intoxication severe changes in hepatic steady-state mRNA levels were found; the largest decreases corresponded to enzymes exhibiting the highest expression in normal tissue. Cytoplasmic protein levels, activities and metabolite concentrations suffered more moderate changes following a similar trend. Interestingly, galactosamine-treatment induced hepatic nuclear accumulation of MATα1 and S-adenosylhomocysteine hydrolase tetramers, their active assemblies. In fact, galactosamine-treated livers showed enhanced nuclear methionine adenosyltransferase activity. Acetaminophen intoxication mimicked most galactosamine effects on hepatic MATα1, including accumulation of nuclear tetramers. H35 cells overexpressing tagged-MATα1 reproduced the subcellular distribution observed in liver, and the changes induced by galactosamine and acetaminophen that were also observed upon glutathione depletion by buthionine sulfoximine. The H35 nuclear accumulation of tagged-MATα1 induced by these agents correlated with decreased GSH/GSSG ratios and was prevented by N-acetylcysteine and glutathione ethyl ester. However, the changes in epigenetic modifications associated with tagged-MATα1 nuclear accumulation were only prevented by N-acetylcysteine in galactosamine-treated cells. [Innovation]: Cytoplasmic and nuclear changes in proteins regulating the methylation index follow opposite trends in acute liver injury, their nuclear accumulation showing potential as disease marker. [Conclusion]: Altogether these results demonstrate galactosamine- and acetaminophen-induced nuclear accumulation of methionine metabolism enzymes as active oligomers and unveil the implication of redox-dependent mechanisms in the control of MATα1 subcellular distribution.This work was supported by grants of the Ministerio de Economía y Competitividad (BFU2005-00050, BFU2008- 00666, and BFU2009-08977 to M.A.P.; SAF2009-11642 and SAF2012-36519 to D.P.-S.; and PS09/01762 to J.P.-M.) and the Instituto de Salud Carlos III (RCMN C03/08 and PI05/0563 to M.A.P.; RD07/0064/0007 and RD12/0013/0008 to D.P.-S.). M.D. was supported by fellowships of RCMN C03/08 and PI05/0563 and M.P. by BFU2009-08977.Peer reviewe

Homocysteine and DNA methylation: a review of animal and human literature

Homocysteine (Hcy) is a sulfur-containing non-protein forming amino acid, which is synthesized from methionine as an important intermediate in the one-carbon pathway. High concentrations of Hcy in a condition called hyperhomocysteinemia (HHcy) are an independent risk factor for several disorders including cardiovascular diseases and osteoporotic fractures. Since Hcy is produced as a byproduct of the methyltransferase reaction, alteration in DNA methylation is studied as one of the underlying mechanisms of HHcy-associated disorders. In animal models, elevated Hcy concentrations are induced either by diet (high methionine, low B-vitamins, or both), gene knockouts (Mthfr, Cbs, Mtrr or Mtr) or combination of both to investigate their effects on DNA methylation or its markers. In humans, most of the literature involves case-control studies concerning patients. The focus of this review is to study existing literature on HHcy and its role in relation to DNA methylation. Apart from this, a few studies investigated the effect of Hcy-lowering trials on restoring DNA methylation patterns, by giving a folic acid or B-vitamin supplemented diet. These studies which were conducted in animal models as well as humans were included in this review