Electron affinity of tricyclic, bicyclic, and monocyclic compounds containing cyanoenones correlates with their potency as inducers of a cytoprotective enzyme.

Tricyclic, bicyclic, and monocyclic compounds containing cyanoenones induce various anti-inflammatory and cytoprotective enzymes through activation of the Keap1/Nrf2/ARE (antioxidant response element) pathway. The potency of these compounds as Nrf2 activators was determined using a prototypic cytoprotective enzyme quinone oxidoreductase 1 (NQO1) in Hepa1c1c7 murine hepatoma cells. The electron affinity (EA) of the compounds, expressed as the energy of their lowest unoccupied molecular orbital [E (LUMO)], was evaluated using two types of quantum mechanical calculations: the semiempirical (AM1) and the density functional theory (DFT) methods. We observed striking linear correlations [r=0.897 (AM1) and 0.936 (DFT)] between NQO1 inducer potency of these compounds and their E (LUMO) regardless of the molecule size. Importantly and interestingly, this finding demonstrates that the EA is the essentially important factor that determines the reactivity of the cyanoenones with Keap1

Chronic hyperglycaemia increases the vulnerability of the hippocampus to oxidative damage induced during post-hypoglycaemic hyperglycaemia in a mouse model of chemically induced type 1 diabetes

Aims/hypothesis Chronic hyperglycaemia and recurrent hypoglycaemia are independently associated with accelerated cognitive decline in type 1 diabetes. Recurrent hypoglycaemia in rodent models of chemically induced (streptozotocin [STZ]) diabetes leads to cognitive impairment in memory-related tasks associated with hippocampal oxidative damage. This study examined the hypothesis that post-hypoglycaemic hyperglycaemia in STZ-diabetes exacerbates hippocampal oxidative stress and explored potential contributory mechanisms.Methods The hyperinsulinaemic glucose clamp technique was used to induce equivalent hypoglycaemia and to control post-hypoglycaemic glucose levels in mice with and without STZ-diabetes and Nrf2(-/-) mice (lacking Nrf2 [also known as Nfe2l2]). Subsequently, quantitative proteomics based on stable isotope labelling by amino acids in cell culture and biochemical approaches were used to assess oxidative damage and explore contributory pathways.Results Evidence of hippocampal oxidative damage was most marked in mice with STZ-diabetes exposed to post-hypoglycaemic hyperglycaemia; these mice also showed induction of Nrf2 and the Nrf2 transcriptional targets Sod2 and Hmox-1. In this group, hypoglycaemia induced a significant upregulation of proteins involved in alternative fuel provision, reductive biosynthesis and degradation of damaged proteins, and a significant downregulation of proteins mediating the stress response. Key differences emerged between mice with and without STZ-diabetes following recovery from hypoglycaemia in proteins mediating the stress response and reductive biosynthesis.Conclusions/interpretation There is a disruption of the cellular response to a hypoglycaemic challenge in mice with STZ-induced diabetes that is not seen in wild-type non-diabetic animals. The chronic hyperglycaemia of diabetes and post-hypoglycaemic hyperglycaemia act synergistically to induce oxidative stress and damage in the hippocampus, possibly leading to irreversible damage/modification to proteins or synapses between cells. In conclusion, recurrent hypoglycaemia in sub-optimally controlled diabetes may contribute, at least in part, to accelerated cognitive decline through amplifying oxidative damage in key brain regions, such as the hippocampus.Data availability The datasets generated during and/or analysed during the current study are available in ProteomeXchange, accession no. 1-20220824-173727 (www.proteomexchange.org). Additional datasets generated during and/or analysed during the present study are available from the corresponding author upon reasonable request

Biosynthesis of secondary metabolites in sugarcane

A set of genes related to secondary metabolism was extracted from the sugarcane expressed sequence tag (SUCEST) database and was used to investigate both the gene expression pattern of key enzymes regulating the main biosynthetic secondary metabolism pathways and the major classes of metabolites involved in the response of sugarcane to environmental and developmental cues. The SUCEST database was constructed with tissues in different physiological conditions which had been collected under varied situation of environmental stress. This database allows researchers to identify and characterize the expressed genes of a wide range of putative enzymes able to catalyze steps in the phenylpropanoid, isoprenoid and other pathways of the special metabolic mechanisms involved in the response of sugarcane to environmental changes. Our results show that sugarcane cDNAs encoded putative ultra-violet induced sesquiterpene cyclases (SC); chalcone synthase (CHS), the first enzyme in the pathway branch for flavonoid biosynthesis; isoflavone synthase (IFS), involved in plant defense and root nodulation; isoflavone reductase (IFR), a key enzyme in phenylpropanoid phytoalexin biosynthesis; and caffeic acid-O-methyltransferase, a key enzyme in the biosynthesis of lignin cell wall precursors. High levels of CHS transcripts from plantlets infected with Herbaspirillum rubri or Gluconacetobacter diazotroficans suggests that agents of biotic stress can elicit flavonoid biosynthesis in sugarcane. From this data we have predicted the profile of isoprenoid and phenylpropanoid metabolism in sugarcane and pointed the branches of secondary metabolism activated during tissue-specific stages of development and the adaptive response of sugarcane to agents of biotic and abiotic stress, although our assignment of enzyme function should be confirmed by careful biochemical and genetic supporting evidence.<br>Este trabalho foi realizado com os objetivos de gerar uma coleção de genes relacionados ao metabolismo secundário da cana de açúcar e investigar o padrão de expressão gênica de enzimas chaves reguladoras das principais vias biossintéticas ativas nos diferentes tipos de tecidos e situações de estresse físico-químico e biológico a que estão submetidas plantas cultivadas em casas de vegetação, campo ou in vitro. A estratégia de mineração dos dados da database de sequências expressas de cana de açúcar, SUCEST, usando ferramentas de bioinformática, focalizou classes de compostos como isoprenóides e fenilpropanóides que comprovadamente desempenham um papel na resposta de plantas a variações ambientais. Foram identificados e caracterizados genes que codificam enzimas chaves para a síntese de terpenóides, como a sesquiterpeno ciclase (SC); (CHS) para síntese de flavonóides; isoflavona sintase (IFS) envolvida na biossíntese de isoflavonóides que desempenharm importante papel na defesa de plantas e nodulação de raízes; isoflavona redutases (IFR) enzimas chaves para a síntese de fenilpropanóide fitoalexinas, bem como enzimas relacionadas à síntese de precursores de lignina, como a enzima ácido caféico- O- metiltransferase. O efeito do estresse causado por bactérias como Herbaspirillum rubri e Gluconacetobacter diazotroficans também foi avaliado tendo sido constatada a indução da expressão de chalcona sintase (CHS) em plântulas infectadas com esses agentes, sugerindo a ativação da via de flavonóides em resposta a este estresse biológico. Esses resultados apontam para o fato de que as vias do metabolismo de isopropanóides e de fenilpropanóides em cana de açúcar são ativadas de acordo com o estágio de desenvolvimento, especificidade de tecidos e em resposta a situações de estresse. Essas observações deverão ser confirmadas por meio de experimentação genética e bioquímica