N-Acylethanolamines in seeds. Quantification Of molecular species and their degradation upon imbibition

Drought and heat stress mediated activation of lipid signaling in plants: a critical review

Lipids are a principal component of plasma membrane, acting as a protective barrier between the cell and its surroundings. Abiotic stresses such as drought and temperature induce various lipid-dependent signaling responses, and the membrane lipids respond differently to environmental challenges. Recent studies have revealed that lipids serve as signal mediators forreducing stress responses in plant cells and activating defense systems. Signaling lipids, such as phosphatidic acid, phosphoinositides, sphingolipids, lysophospholipids, oxylipins, and N-acylethanolamines, are generated in response to stress. Membrane lipids are essential for maintaining the lamellar stack of chloroplasts and stabilizing chloroplast membranes under stress. However, the effects of lipid signaling targets in plants are not fully understood. This review focuses on the synthesis of various signaling lipids and their roles in abiotic stress tolerance responses, providing an essential perspective for further investigation into the interactions between plant lipids and abiotic stress.

Determination of endocannabinoids in fermented foods of animal and plant origin by liquid chromatography tandem mass spectrometry

An analytical method was developed for the determination of endocannabinoids and endocannabinoid-like compounds using ultra high performance liquid chromatography tandem mass spectrometry in fermented food products. Extraction optimization and method validation were carried out to detect 36 endocannabinoids and endocannabinoid-like compounds including N-acylethanolamines, N-acylamino acids, N-acylneurotransmitters, monoacylglycerols and primary fatty acid amides using 7 isotope labelled internal standards in foods. The method was able to detect precisely these compounds with good linearity (R2 > 0.982), reproducibility (0.1-14.4%), repeatability (0.3-18.4%), recovery (>67%) and high sensitivity. The limit of detection ranged between 0.01 and 4.30 ng/mL, and of quantitation between 0.02 and 14.2 ng/mL. Fermented sausage and cheese as animal-origin fermented foods and cocoa powder as plant-origin fermented foods were found to be rich in endocannabinoids and endocannabinoid-like compounds. N-Acylamino acids and N-acylneurotransmitters detected for the first time in fermented foods will provide important preliminary information for future studies.

Plants and Small Molecules: An Up-and-Coming Synergy

The emergence of Arabidopsis thaliana as a model system has led to a rapid and wide improvement in molecular genetics techniques for studying gene function and regulation. However, there are still several drawbacks that cannot be easily solved with molecular genetic approaches, such as the study of unfriendly species, which are of increasing agronomic interest but are not easily transformed, thus are not prone to many molecular techniques. Chemical genetics represents a methodology able to fill this gap. Chemical genetics lies between chemistry and biology and relies on small molecules to phenocopy genetic mutations addressing specific targets. Advances in recent decades have greatly improved both target specificity and activity, expanding the application of this approach to any biological process. As for classical genetics, chemical genetics also proceeds with a forward or reverse approach depending on the nature of the study. In this review, we addressed this topic in the study of plant photomorphogenesis, stress responses and epigenetic processes. We have dealt with some cases of repurposing compounds whose activity has been previously proven in human cells and, conversely, studies where plants have been a tool for the characterization of small molecules. In addition, we delved into the chemical synthesis and improvement of some of the compounds described.

Fatty acid amide hydrolase and 9-lipoxygenase modulate cotton seedling growth by ethanolamide oxylipin levels

Polyunsaturated N-acylethanolamines (NAEs) can be hydrolyzed by fatty acid amide hydrolase (FAAH) or oxidized by lipoxygenase (LOX). In Arabidopsis (Arabidopsis thaliana), the 9-LOX product of linoleoylethanolamide, namely, 9-hydroxy linoleoylethanolamide (9-NAE-HOD), is reported to negatively regulate seedling development during secondary dormancy. In upland cotton (Gossypium hirsutum L.), six putative FAAH genes (from two diverged groups) and six potential 9-LOX genes are present; however, their involvement in 9-NAE-HOD metabolism and its regulation of seedling development remain unexplored. Here, we report that in cotton plants, two specific FAAH isoforms (GhFAAH Ib and GhFAAH IIb) are needed for hydrolysis of certain endogenous NAEs. Virus-induced gene silencing (VIGS) of either or both FAAHs led to reduced seedling growth and this coincided with reduced amidohydrolase activities and elevated quantities of endogenous 9-NAE-HOD. Transcripts of GhLOX21 were consistently elevated in FAAH-silenced tissues, and co-silencing of GhLOX21 and GhFAAH (Ib and/or IIb) led to reversal of seedling growth to normal levels (comparable with no silencing). This was concomitant with reductions in the levels of 9-NAE-HOD, but not of 13-NAE-HOD. Pharmacological experiments corroborated the genetic and biochemical evidence, demonstrating that direct application of 9-NAE-HOD, but not 13-NAE-HOD or their corresponding free fatty acid oxylipins, inhibited the growth of cotton seedlings. Additionally, VIGS of GhLOX21 in cotton lines overexpressing AtFAAH exhibited enhanced growth and no detectable 9-NAE-HOD. Altogether, we conclude that the growth of cotton seedlings involves fine-tuning of 9-NAE-HOD levels via FAAH-mediated hydrolysis and LOX-mediated production, expanding the mechanistic understanding of plant growth modulation by NAE oxylipins to a perennial crop species.

Fatty Acid-Derived N-acylethanolamines Dietary Supplementation Attenuates Neuroinflammation and Cognitive Impairment in LPS Murine Model

Neuroinflammation plays a critical role in the pathogenesis of most neurological and neurodegenerative diseases and therefore represents a potential therapeutic target. In this regard, accelerating the resolution process in chronic neuroinflammation may be an effective strategy to deal with the cognitive consequences of neuropathology and generalized inflammatory processes. N-acylethanolamine (NAE) derivatives of fatty acids, being highly active lipid mediators, possess pro-resolving activity in inflammatory processes and are promising agents for the suppression of neuroinflammation and its consequences. This paper is devoted to a study of the effects played by dietary supplement (DS), containing a composition of fatty acid-derived NAEs, obtained from squid Berryteuthis magister, on the hippocampal neuroinflammatory and memory processes. By detecting the production of pro-inflammatory cytokines and glial markers, a pronounced anti-inflammatory activity of DS was demonstrated both in vitro and in vivo. DS administration reversed the LPS-induced reduction in hippocampal neurogenesis and memory deterioration. LC-MS analysis revealed an increase in the production of a range of NAEs with well-documented anti-inflammatory activity in response to the administered lipid composition. To conclude, we found that tested DS suppresses the neuroinflammatory response by reducing glial activation, positively regulates neural progenitor proliferation, and attenuates hippocampal-dependent memory impairment.

Enhanced seedling growth by 3-n-pentadecylphenolethanolamide is mediated by fatty acid amide hydrolases in upland cotton (Gossypium hirsutum L.)

Fatty acid amide hydrolase (FAAH) is a conserved amidase that is known to modulate the levels of endogenous N-acylethanolamines (NAEs) in both plants and animals. The activity of FAAH is enhanced in vitro by synthetic phenoxyacylethanolamides resulting in greater hydrolysis of NAEs. Previously, 3-n-pentadecylphenolethanolamide (PDP-EA) was shown to exert positive effects on the development of Arabidopsis seedlings by enhancing Arabidopsis FAAH (AtFAAH) activity. However, there is little information regarding FAAH activity and the impact of PDP-EA in the development of seedlings of other plant species. Here, we examined the effects of PDP-EA on growth of upland cotton (Gossypium hirsutum L. cv Coker 312) seedlings including two lines of transgenic seedlings overexpressing AtFAAH. Independent transgenic events showed accelerated true-leaf emergence compared with non-transgenic controls. Exogenous applications of PDP-EA led to increases in overall seedling growth in AtFAAH transgenic lines. These enhanced-growth phenotypes coincided with elevated FAAH activities toward NAEs and NAE oxylipins. Conversely, the endogenous contents of NAEs and NAE-oxylipin species, especially linoleoylethanolamide and 9-hydroxy linoleoylethanolamide, were lower in PDP-EA treated seedlings than in controls. Further, transcripts for endogenous cotton FAAH genes were increased following PDP-EA exposure. Collectively, our data corroborate that the enhancement of FAAH enzyme activity by PDP-EA stimulates NAE-hydrolysis and that this results in enhanced growth in seedlings of a perennial crop species, extending the role of NAE metabolism in seedling development beyond the model annual plant species, Arabidopsis thaliana.

Nonpharmacological Treatment Strategies for the Management of Canine Chronic Inflammatory Enteropathy—A Narrative Review

Chronic inflammatory enteropathy (CIE) refers to a heterogeneous group of idiopathic diseases of the dog characterised by persistent gastrointestinal (GI) clinical signs. If conventional dietary treatment alone would be unsuccessful, management of CIE is traditionally attained by the use of pharmaceuticals, such as antibiotics and immunosuppressive drugs. While being rather effective, however, these drugs are endowed with side effects, which may impact negatively on the animal’s quality of life. Therefore, novel, safe and effective therapies for CIE are highly sought after. As gut microbiota imbalances are often associated with GI disorders, a compelling rationale exists for the use of nonpharmacological methods of microbial manipulation in CIE, such as faecal microbiota transplantation and administration of pre-, pro-, syn- and postbiotics. In addition to providing direct health benefits to the host via a gentle modulation of the intestinal microbiota composition and function, these treatments may also possess immunomodulatory and epithelial barrier-enhancing actions. Likewise, intestinal barrier integrity, along with mucosal inflammation, are deemed to be two chief therapeutic targets of mesenchymal stem cells and selected vegetable-derived bioactive compounds. Although pioneering studies have revealed encouraging findings regarding the use of novel treatment agents in CIE, a larger body of research is needed to address fully their mode of action, efficacy and safety.

Beyond the Usual Suspects: Physiological Roles of the Arabidopsis Amidase Signature (AS) Superfamily Members in Plant Growth Processes and Stress Responses

The diversification of land plants largely relies on their ability to cope with constant environmental fluctuations, which negatively impact their reproductive fitness and trigger adaptive responses to biotic and abiotic stresses. In this limiting landscape, cumulative research attention has centred on deepening the roles of major phytohormones, mostly auxins, together with brassinosteroids, jasmonates, and abscisic acid, despite the signaling networks orchestrating the crosstalk among them are so far only poorly understood. Accordingly, this review focuses on the Arabidopsis Amidase Signature (AS) superfamily members, with the aim of highlighting the hitherto relatively underappreciated functions of AMIDASE1 (AMI1) and FATTY ACID AMIDE HYDROLASE (FAAH), as comparable coordinators of the growth-defense trade-off, by balancing auxin and ABA homeostasis through the conversion of their likely bioactive substrates, indole-3-acetamide and N-acylethanolamine.

The Nutraceutical N-Palmitoylethanolamide (PEA) Reveals Widespread Molecular Effects Unmasking New Therapeutic Targets in Murine Varicocele

Varicocele is an age-related disease with no current medical treatments positively impacting infertility. Toll-like receptor 4 (TLR4) expression is present in normal testis with an involvement in the immunological reactions. The role of peroxisome proliferator-activated receptor-α (PPAR-α), a nuclear receptor, in fertility is still unclear. N-Palmitoylethanolamide (PEA), an emerging nutraceutical compound present in plants and animal foods, is an endogenous PPAR-α agonist with well-demonstrated anti-inflammatory and analgesics characteristics. In this model of mice varicocele, PPAR-α and TLR4 receptors’ roles were investigated through the administration of ultra-micronized PEA (PEA-um). Male wild-type (WT), PPAR-α knockout (KO), and TLR4 KO mice were used. A group underwent sham operation and administration of vehicle or PEA-um (10 mg/kg i.p.) for 21 days. Another group (WT, PPAR-α KO, and TLR4 KO) underwent surgical varicocele and was treated with vehicle or PEA-um (10 mg/kg i.p.) for 21 days. At the end of treatments, all animals were euthanized. Both operated and contralateral testes were processed for histological and morphometric assessment, for PPAR-α, TLR4, occludin, and claudin-11 immunohistochemistry and for PPAR-α, TLR4, transforming growth factor-beta3 (TGF-β3), phospho-extracellular signal-Regulated-Kinase (p-ERK) 1/2, and nucleotide-binding oligomerization domain-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) Western blot analysis. Collectively, our data showed that administration of PEA-um revealed a key role of PPAR-α and TLR4 in varicocele pathophysiology, unmasking new nutraceutical therapeutic targets for future varicocele research and supporting surgical management of male infertility.

Regiochemical Assignment of N-Acylphosphatidylethanolamines (NAPE) by Liquid Chromatography/Electrospray Ionization with Multistage Mass Spectrometry and Its Application to Extracts of Lupin Seeds

1,2-Diacyl-sn-glycero-3-phospho-N-acyl-ethanolamines (NAPE) are low abundance phospholipids but important constituents of intracellular membranes of plant tissues, responsible for generating bioactive N-acylethanolamine (NAE), which participates in several physiological processes such as regulation of seed germination and protection against pathogenic attacks. From an analytical point of view, the critical aspect of these bioactive lipids lies in the determination of fatty acyl chains located in sn-1/sn-2 position on the glycerol backbone (O-linked), along with the amide-bound (N-linked) fatty acyl chain. Here, the identity and occurrence of NAPE in lipid extracts of lupin seeds (Lupinus luteus L.) was assessed by electrospray ionization in negative ion mode upon reversed-phase liquid chromatography (RPLC-ESI) coupled to mass spectrometry (MS) either at high- (i.e., Orbitrap FTMS) or low- (linear ion trap, LIT) resolution/accuracy. Collisional induced dissociation (CID)-tandem MS and MS³ acquisitions of chemically prepared NAPE allowed to unequivocally recognize the N-linked fatty acyl chain and to establish the diagnostic product ions that were successfully applied to identify NAPE in lipid extracts of yellow lupin seeds. The most abundant NAPE species were those containing N-acyl groups C18:1, C18:2; a minor prevalence was found for C16:0, C18:0, and C18:3, and almost the same acyl chains O-linked on the glycerol backbone in several sn-1/sn-2 combinations were observed. The positional isomers of NAPE species were identified as deprotonated molecules ([M-H]^-) at m/z 978.7541 (three isomers 52:3), m/z 980.7694 (two isomers 52:2), m/z 1002.7535 (four isomers 54:5), m/z 1004.7686 (two isomers 54:4), m/z 1006.7837 (two isomers 54:3), and m/z 1008.8026 (single isomer 54:2). The total amount of NAPE in lupin seeds ranged in the interval of 2.00 ± 0.13 mg/g dw, in agreement with other edible legumes. We anticipate our approach to be a robust assessment method potentially applicable to biological extracts containing NAPE species and can provide comprehensive profiles and contents.

Seedling Chloroplast Responses Induced by N-Linolenoylethanolamine Require Intact G-Protein Complexes

In animals, several long-chain N-acylethanolamines (NAEs) have been identified as endocannabinoids and are autocrine signals that operate through cell surface G-protein-coupled cannabinoid receptors. Despite the occurrence of NAEs in land plants, including nonvascular plants, their precise signaling properties and molecular targets are not well defined. Here we show that the activity of N-linolenoylethanolamine (NAE 18:3) requires an intact G-protein complex. Specifically, genetic ablation of the Gβγ dimer or loss of the full set of atypical Gα subunits strongly attenuates an NAE-18:3-induced degreening of cotyledons in Arabidopsis (Arabidopsis thaliana) seedlings. This effect involves, at least in part, transcriptional regulation of chlorophyll biosynthesis and catabolism genes. In addition, there is feedforward transcriptional control of G-protein signaling components and G-protein interactors. These results are consistent with NAE 18:3 being a lipid signaling molecule in plants with a requirement for G-proteins to mediate signal transduction, a situation similar, but not identical, to the action of NAE endocannabinoids in animal systems.

Therapeutic Efficacy of Palmitoylethanolamide and Its New Formulations in Synergy with Different Antioxidant Molecules Present in Diets

The use of a complete nutritional approach seems increasingly promising to combat chronic inflammation. The choice of healthy sources of carbohydrates, fats, and proteins, associated with regular physical activity and avoidance of smoking is essential to fight the war against chronic diseases. At the base of the analgesic, anti-inflammatory, or antioxidant action of the diets, there are numerous molecules, among which some of a lipidic nature very active in the inflammatory pathway. One class of molecules found in diets with anti-inflammatory actions are ALIAmides. Among all, one is particularly known for its ability to counteract the inflammatory cascade, the Palmitoylethanolamide (PEA). PEA is a molecular that is present in nature, in numerous foods, and is endogenously produced by our body, which acts as a balancer of inflammatory processes, also known as endocannabionoid-like. PEA is often used in the treatment of both acute and chronic inflammatory pathologies, either alone or in association with other molecules with properties, such as antioxidants or analgesics. This review aims to illustrate an overview of the different diets that are involved in the process of opposition to the inflammatory cascade, focusing on capacity of PEA and new formulations in synergy with other molecules.

Food database of N-acyl-phosphatidylethanolamines, N-acylethanolamines and endocannabinoids and daily intake from a Western, a Mediterranean and a vegetarian diet

The contents of N-acylphosphatidylethanolamines (NAPEs), N-acylethanolamines (NAEs) and endocannabinoids (ECs) in 43 food products were assessed and daily intakes, based on consumption of Mediterranean, vegetarian and Western diets, were simulated. NAPEs and NAEs were more abundant in plant-based foods than in animal food products; NAPEs were in the ranges 0-4032 vs 4-398 µg/g dw and NAEs were in the ranges 0-35 vs 0.1-0.7 µg/g dw, respectively while ECs were in the range 0-0.1 vs 0-34 µg/g dw. Daily intakes of NAPEs and NAEs were higher from Mediterranean (263 and 0.25 mg/day) and vegetarian (242 and 0.28 mg/day) diets than the Western diet (163 and 0.08 mg/day). Conversely, ECs intakes were higher from Western and Mediterranean diets (0.17 mg/day) than the vegetarian diet (0.01 mg/day). Future studies will evaluate the physiological role of dietary NAPEs, NAEs and ECs in humans.

Population genomics demystifies the defoliation phenotype in the plant pathogen Verticillium dahliae

Verticillium dahliae is a broad host-range pathogen that causes vascular wilts in plants. Interactions between three hosts and specific V. dahliae genotypes result in severe defoliation. The underlying mechanisms of defoliation are unresolved. Genome resequencing, gene deletion and complementation, gene expression analysis, sequence divergence, defoliating phenotype identification, virulence analysis, and quantification of V. dahliae secondary metabolites were performed. Population genomics previously revealed that G-LSR2 was horizontally transferred from the fungus Fusarium oxysporum f. sp. vasinfectum to V. dahliae and is exclusively found in the genomes of defoliating (D) strains. Deletion of seven genes within G-LSR2, designated as VdDf genes, produced the nondefoliation phenotype on cotton, olive, and okra but complementation of two genes restored the defoliation phenotype. Genes VdDf5 and VdDf6 associated with defoliation shared homology with polyketide synthases involved in secondary metabolism, whereas VdDf7 shared homology with proteins involved in the biosynthesis of N-lauroylethanolamine (N-acylethanolamine (NAE) 12:0), a compound that induces defoliation. NAE overbiosynthesis by D strains also appears to disrupt NAE metabolism in cotton by inducing overexpression of fatty acid amide hydrolase. The VdDfs modulate the synthesis and overproduction of secondary metabolites, such as NAE 12:0, that cause defoliation either by altering abscisic acid sensitivity, hormone disruption, or sensitivity to the pathogen.

Lipid signalling in plant responses to abiotic stress

Lipids are one of the major components of biological membranes including the plasma membrane, which is the interface between the cell and the environment. It has become clear that membrane lipids also serve as substrates for the generation of numerous signalling lipids such as phosphatidic acid, phosphoinositides, sphingolipids, lysophospholipids, oxylipins, N-acylethanolamines, free fatty acids and others. The enzymatic production and metabolism of these signalling molecules are tightly regulated and can rapidly be activated upon abiotic stress signals. Abiotic stress like water deficit and temperature stress triggers lipid-dependent signalling cascades, which control the expression of gene clusters and activate plant adaptation processes. Signalling lipids are able to recruit protein targets transiently to the membrane and thus affect conformation and activity of intracellular proteins and metabolites. In plants, knowledge is still scarce of lipid signalling targets and their physiological consequences. This review focuses on the generation of signalling lipids and their involvement in response to abiotic stress. We describe lipid-binding proteins in the context of changing environmental conditions and compare different approaches to determine lipid-protein interactions, crucial for deciphering the signalling cascades.

2-pentadecyl-2-oxazoline: Identification in coffee, synthesis and activity in a rat model of carrageenan-induced hindpaw inflammation

N-acylethanolamines (NAEs) comprise a family of bioactive lipid molecules present in animal and plant tissues, with N-palmitoylethanolamine (PEA) having received much attention owing to its anti-inflammatory, analgesic and neuroprotective activities. 2-Pentadecyl-2-oxazoline (PEA-OXA), the oxazoline of PEA, reportedly modulates activity of N-acylethanolamine-hydrolyzing acid amidase (NAAA), which catabolizes PEA. Because PEA is produced on demand and exerts pleiotropic effects on non-neuronal cells implicated in neuroinflammation, modulating the specific amidases for NAEs (NAAA in particular) could be a way to preserve PEA role in maintaining cellular homeostasis through its rapid on-demand synthesis and equally rapid degradation. This study provides the first description of PEA-OXA in both green and roasted coffee beans and Moka infusions, and its synthesis. In an established model of carrageenan (CAR)-induced rat paw inflammation, PEA-OXA was orally active in limiting histological damage and thermal hyperalgesia 6h after CAR intraplantar injection in the right hindpaw and the accumulation of infiltrating inflammatory cells. PEA-OXA appeared to be more potent compared to ultramicronized PEA given orally at the same dose (10mg/kg). PEA-OXA markedly reduced also the increase in hindpaw myeloperoxidase activity, an index of polymorphonuclear cell accumulation in inflammatory tissues. NAAA modulators like PEA-OXA may serve to maximize availability of NAEs (e.g. PEA) while providing for recycling of the NAE components for further resynthesis.

Effects of synthetic alkamides on Arabidopsis fatty acid amide hydrolase activity and plant development

Alkamides and N-acylethanolamines (NAEs) are bioactive, amide-linked lipids that influence plant development. Alkamides are restricted to several families of higher plants and some fungi, whereas NAEs are widespread signaling molecules in both plants and animals. Fatty acid amide hydrolase (FAAH) has been described as a key contributor to NAE hydrolysis; however, no enzyme has been associated with alkamide degradation in plants. Herein reported is synthesis of 12 compounds structurally similar to a naturally occurring alkamide (N-isobutyl-(2E,6Z,8E)decatrienamide or affinin) with different acyl compositions more similar to plant NAEs and various amino alkyl head groups. These "hybrid" synthetic alkamides were tested for activity toward recombinant Arabidopsis FAAH and for their effects on plant development (i.e., cotyledon expansion and primary root length). A substantial increase in FAAH activity was discovered toward NAEs in vitro in the presence of some of these synthetic alkamides, such as N-ethyllauroylamide (4). This "enhancement" effect was found to be due, at least in part, to relief from product inhibition of FAAH by ethanolamine, and not due to an alteration in the oligomerization state of the FAAH enzyme. For several of these alkamides, an inhibition of seedling growth was observed with greater results in FAAH knockouts and less in FAAH over-expressing plants, suggesting that these alkamides could be hydrolyzed by FAAH in planta. The tight regulation of NAE levels in vivo appears to be important for proper seedling establishment, and as such, some of these synthetic alkamides may be useful pharmacological tools to manipulate the effects of NAEs in situ.

N-Acylethanolamines: lipid metabolites with functions in plant growth and development

Twenty years ago, N-acylethanolamines (NAEs) were considered by many lipid chemists to be biological 'artifacts' of tissue damage, and were, at best, thought to be minor lipohilic constituents of various organisms. However, that changed dramatically in 1993, when anandamide, an NAE of arachidonic acid (N-arachidonylethanolamine), was shown to bind to the human cannabinoid receptor (CB1) and activate intracellular signal cascades in mammalian neurons. Now NAEs of various types have been identified in diverse multicellular organisms, in which they display profound biological effects. Although targets of NAEs are still being uncovered, and probably vary among eukaryotic species, there appears to be remarkable conservation of the machinery that metabolizes these bioactive fatty acid conjugates of ethanolamine. This review focuses on the metabolism and functions of NAEs in higher plants, with specific reference to the formation, hydrolysis and oxidation of these potent lipid mediators. The discussion centers mostly on early seedling growth and development, for which NAE metabolism has received the most attention, but also considers other areas of plant development in which NAE metabolism has been implicated. Where appropriate, we indicate cross-kingdom conservation in NAE metabolic pathways and metabolites, and suggest areas where opportunities for further investigation appear most pressing.

Ethanolamide oxylipins of linolenic acid can negatively regulate Arabidopsis seedling development

N-Acylethanolamines (NAEs) are fatty-acid derivatives with potent biological activities in a wide range of eukaryotic organisms. Polyunsaturated NAEs are among the most abundant NAE types in seeds of Arabidopsis thaliana, and they can be metabolized by either fatty acid amide hydrolase (FAAH) or by lipoxygenase (LOX) to low levels during seedling establishment. Here, we identify and quantify endogenous oxylipin metabolites of N-linolenoylethanolamine (NAE 18:3) in Arabidopsis seedlings and show that their levels were higher in faah knockout seedlings. Quantification of oxylipin metabolites in lox mutants demonstrated altered partitioning of NAE 18:3 into 9- or 13-LOX pathways, and this was especially exaggerated when exogenous NAE was added to seedlings. When maintained at micromolar concentrations, NAE 18:3 specifically induced cotyledon bleaching of light-grown seedlings within a restricted stage of development. Comprehensive oxylipin profiling together with genetic and pharmacological interference with LOX activity suggested that both 9-hydroxy and 13-hydroxy linolenoylethanolamides, but not corresponding free fatty-acid metabolites, contributed to the reversible disruption of thylakoid membranes in chloroplasts of seedling cotyledons. We suggest that NAE oxylipins of linolenic acid represent a newly identified, endogenous set of bioactive compounds that may act in opposition to progression of normal seedling development and must be depleted for successful establishment.

Identification of N-acylethanolamines in Dictyostelium discoideum and confirmation of their hydrolysis by fatty acid amide hydrolase

N-acylethanolamines (NAEs) are endogenous lipid-based signaling molecules best known for their role in the endocannabinoid system in mammals, but they are also known to play roles in signaling pathways in plants. The regulation of NAEs in vivo is partly accomplished by the enzyme fatty acid amide hydrolase (FAAH), which hydrolyses NAEs to ethanolamine and their corresponding fatty acid. Inhibition of FAAH has been shown to increase the levels of NAEs in vivo and to produce desirable phenotypes. This has led to the development of pharmaceutical-based therapies for a variety of conditions targeting FAAH. Recently, our group identified a functional FAAH homolog in Dictyostelium discoideum, leading to our hypothesis that D. discoideum also possesses NAEs. In this study, we provide a further characterization of FAAH and identify NAEs in D. discoideum for the first time. We also demonstrate the ability to modulate their levels in vivo through the use of a semispecific FAAH inhibitor and confirm that these NAEs are FAAH substrates through in vitro studies. We believe the demonstration of the in vivo modulation of NAE levels suggests that D. discoideum could be a good simple model organism in which to study NAE-mediated signaling.

Analysis of fatty acid amide hydrolase activity in plants

N-Acylethanolamines (NAEs) are fatty acid derivatives amide-linked to ethanolamine. NAEs vary in chain lengths and numbers of double bonds and generally reflect the fatty acids found in membrane lipids in the tissues in which they reside. NAEs are present naturally in trace amounts and occur in a wide range of organisms including plants, animals, and microbes. Some NAE types are known to be involved in the endocannabinoid signaling system of vertebrates, and in plants they may play important regulatory roles in several physiological processes, such as root growth, seedling development, stress responses, and pathogen interactions. The biological effects of NAEs are terminated through their hydrolysis into the ethanolamine and free fatty acid by a membrane enzyme known as the fatty acid amide hydrolase (FAAH). Thus, FAAH represents an important target to better understand the function of these lipid mediators in numerous cellular processes. FAAH has been extensively characterized in mammalian and plant systems, and they share a conserved Ser-Ser-Lys catalytic mechanism. Here we describe procedures and experimental conditions to assay and characterize recombinant and endogenous FAAH enzymatic activity derived from plant tissues.

N-Acylethanolamines and related compounds: aspects of metabolism and functions

N-Acylethanolamines (NAE) are fatty acid derivates that are linked with an ethanolamine group via an amide bond. NAE can be characterized as lipid mediators in the plant and animal kingdoms owing to the diverse functions throughout the eukaryotic domain. The functions of NAE have been widely investigated in animal tissues in part due to their abilities to interact with the cannabinoid receptors, vanilloid receptors or peroxisome proliferator activated receptors. However, the interest of studying the functions of these lipids in plants is progressively becoming more apparent. The number of publications about the functions related to NAE and to structural analogs (homoserine lactone and alkamides) is greatly increasing, showing the importance of these lipids in various plant physiological processes. This review sheds light on their role in different processes such as seedling development, plant pathogen interaction, phospholipase D alpha inhibition and senescence of cut flowers, and underlines the interaction between NAE and NAE-related molecules with plant hormone signaling. The different metabolic pathways promoting the synthesis and degradation of NAE are also discussed, in particular the oxygenation of polyunsaturated N-acylethanolamines, which leads to NAE-oxylipins, a new family of bioactive lipids.

Alkamides activate jasmonic acid biosynthesis and signaling pathways and confer resistance to Botrytis cinerea in Arabidopsis thaliana

Alkamides are fatty acid amides of wide distribution in plants, structurally related to N-acyl-L-homoserine lactones (AHLs) from Gram-negative bacteria and to N- acylethanolamines (NAEs) from plants and mammals. Global analysis of gene expression changes in Arabidopsis thaliana in response to N-isobutyl decanamide, the most highly active alkamide identified to date, revealed an overrepresentation of defense-responsive transcriptional networks. In particular, genes encoding enzymes for jasmonic acid (JA) biosynthesis increased their expression, which occurred in parallel with JA, nitric oxide (NO) and H₂O₂ accumulation. The activity of the alkamide to confer resistance against the necrotizing fungus Botrytis cinerea was tested by inoculating Arabidopsis detached leaves with conidiospores and evaluating disease symptoms and fungal proliferation. N-isobutyl decanamide application significantly reduced necrosis caused by the pathogen and inhibited fungal proliferation. Arabidopsis mutants jar1 and coi1 altered in JA signaling and a MAP kinase mutant (mpk6), unlike salicylic acid- (SA) related mutant eds16/sid2-1, were unable to defend from fungal attack even when N-isobutyl decanamide was supplied, indicating that alkamides could modulate some necrotrophic-associated defense responses through JA-dependent and MPK6-regulated signaling pathways. Our results suggest a role of alkamides in plant immunity induction.

N-acylethanolamine (NAE) inhibits growth in Arabidopsis thaliana seedlings via ABI3-dependent and -independent pathways

N-acylethanolamines (NAEs) are lipid metabolites derived from the hydrolysis of the membrane phospholipid N-acylphosphatidylethanolamine (NAPE). Recent work in Arabidopsis thaliana seedlings showed that combined treatments of NAE 12:0 and ABA inhibited seedling growth synergistically, suggesting low levels of NAE could potentiate the action of ABA. Here we examined the interplay between compound concentrations, growth inhibition and mutant genotypes with impaired sensitivities to these regulators. NAE 12:0 and ABA both induced dose-dependent increases in transcript levels of ABI3, and two ABI3 responsive genes, AtHVA22B and RD29B. Interestingly, even in the absence of growth inhibition, RD29B transcripts were elevated by ABA but not NAE treatment outside the sensitive window for ABA/NAE treatment, indicating some differences in the regulation of growth and the modulation of gene expression by these two compounds. Also noteworthy, the growth of ABA insensitive mutant (abi 3-1) seedlings was inhibited at higher concentrations of NAE 12:0 but not ABA, suggesting that NAE may act to inhibit early seedling establishment by both ABI3-dependent and ABI3-independent pathways. Collectively our results reinforce the concept that NAE12:0 interacts with ABA signaling in seedling establishment, but also points to a complexity in this interaction that modulates the sensitivity of young seedlings to phytohormone-mediated growth arrest.

Lipoxygenase-mediated oxidation of polyunsaturated N-acylethanolamines in Arabidopsis

N-acylethanolamines (NAEs) are bioactive fatty acid derivatives that occur in all eukaryotes. In plants, NAEs have potent negative growth-regulating properties, and fatty acid amide hydrolase (FAAH)-mediated hydrolysis is a primary catabolic pathway that operates during seedling establishment to deplete these compounds. Alternatively, polyunsaturated (PU)-NAEs may serve as substrates for lipid oxidation. In Arabidopsis, PU-NAEs (NAE 18:2 and NAE 18:3) were the most abundant NAE species in seeds, and their levels were depleted during seedling growth even in FAAH tDNA knock-out plants. Therefore, we hypothesized that lipoxygenase (LOX) participated in the metabolism of PU-NAEs through the formation of NAE-oxylipins. Comprehensive chromatographic and mass spectrometric methods were developed to identify NAE hydroperoxides and -hydroxides. Recombinant Arabidopsis LOX enzymes expressed in Escherichia coli utilized NAE 18:2 and NAE 18:3 as substrates with AtLOX1 and AtLOX5 exhibiting 9-LOX activity and AtLOX2, AtLOX3, AtLOX4, and AtLOX6 showing predominantly 13-LOX activity. Feeding experiments with exogenous PU-NAEs showed they were converted to hydroxide metabolites indicating that indeed Arabidopsis seedlings had the capacity for LOX-mediated metabolism of PU-NAEs in planta. Detectable levels of endogenous NAE-oxylipin metabolites were identified in FAAH fatty acid amide hydrolase seedlings but not in wild-type or FAAH overexpressors, suggesting that NAE hydroxide pools normally do not accumulate unless flux through hydrolysis is substantially reduced. These data suggest that Arabidopsis LOXs indeed compete with FAAH to metabolize PU-NAEs during seedling establishment. Identification of endogenous amide-conjugated oxylipins suggests potential significance of these metabolites in vivo, and FAAH mutants may offer opportunities to address this in the future.

Discovery and characterization of an Arabidopsis thaliana N-acylphosphatidylethanolamine synthase

N-Acylethanolamines (NAEs) are lipids involved in several physiological processes in animal and plant cells. In brain, NAEs are ligands of endocannabinoid receptors, which modulate various signaling pathways. In plant, NAEs regulate seed germination and root development, and they are involved in plant defense against pathogen attack. This signaling activity is started by an enzyme called N-acylphosphatidylethanolamine (NAPE) synthase. This catalyzes the N-acylation of phosphatidylethanolamine to form NAPE, which is most likely hydrolyzed by phospholipase D beta/gamma isoforms to generate NAE. This compound is further catabolized by fatty amide hydrolase. The genes encoding the enzymes involved in NAE metabolism are well characterized except for the NAPE synthase gene(s). By heterologous expression in Escherichia coli and overexpression in plants, we characterized an acyltransferase from Arabidopsis thaliana (At1g78690p) catalyzing the synthesis of lipids identified as NAPEs (two-dimensional TLC, phospholipase D hydrolysis assay, and electrospray ionization-tandem mass spectrometry analyses). The ability of free fatty acid and acyl-CoA to be used as acyl donor was compared in vitro with E. coli membranes and purified enzyme (obtained by immobilized metal ion affinity chromatography). In both cases, NAPE was synthesized only in the presence of acyl-CoA. beta-Glucuronidase promoter experiments revealed a strong expression in roots and young tissues of plants. Using yellow fluorescent protein fusion, we showed that the NAPE synthase is located in the plasmalemma of plant cells.

Cytokinin receptors are involved in alkamide regulation of root and shoot development in Arabidopsis

Alkamides and N-acilethanolamides are a class of lipid compounds related to animal endocannabinoids of wide distribution in plants. We investigated the structural features required for alkamides to regulate plant development by comparing the root responses of Arabidopsis (Arabidopsis thaliana) seedlings to a range of natural and synthetic compounds. The length of the acyl chain and the amide moiety were found to play a crucial role in their biological activity. From the different compounds tested, N-isobutyl decanamide, a small saturated alkamide, was found to be the most active in regulating primary root growth and lateral root formation. Proliferative-promoting activity of alkamide treatment was evidenced by formation of callus-like structures in primary roots, ectopic blades along petioles of rosette leaves, and disorganized tumorous tissue originating from the leaf lamina. Ectopic organ formation by N-isobutyl decanamide treatment was related to altered expression of the cell division marker CycB1:uidA and an enhanced expression of the cytokinin-inducible marker ARR5:uidA both in roots and in shoots. The involvement of cytokinins in mediating the observed activity of alkamides was tested using Arabidopsis mutants lacking one, two, or three of the putative cytokinin receptors CRE1, AHK2, and AHK3. The triple cytokinin receptor mutant was insensitive to N-isobutyl decanamide treatment, showing absence of callus-like structures in roots, the lack of lateral root proliferation, and absence of ectopic outgrowths in leaves under elevated levels of this alkamide. Taken together our results suggest that alkamides and N-acylethanolamides may belong to a class of endogenous signaling compounds that interact with a cytokinin-signaling pathway to control meristematic activity and differentiation processes during plant development.

TheN-Acylethanolamine-Mediated Regulatory Pathway in Plants

While cannabinoids are secondary metabolites synthesized by just a few plant species, N-acylethanolamines (NAEs) are distributed widely in the plant kingdom, and are recovered in measurable, bioactive quantities in many plant-derived products. NAEs in higher plants are ethanolamides of fatty acids with acyl-chain lenghts of C12-C(18) and zero to three C=C bonds. Generally, the most-abundant NAEs found in plants and vertebrates are similar, including NAE 16 : 0, 18 : 1, 18 : 2, and 18 : 3. Like in animal systems, NAEs are formed in plants from N-acylphosphatidylethanolamines (NAPEs), and they are hydrolyzed by an amidase to yield ethanolamine and free fatty acids (FFA). Recently, a homologue of the mammalian fatty acid amide hydrolase (FAAH-1) was identified in Arabidopsis thaliana and several other plant species. Overexpression of Arabidopsis FAAH (AtFAAH) resulted in plants that grew faster, but were more sensitive to biotic and abiotic insults, suggesting that the metabolism of NAEs in plants resides at the balance between growth and responses to environmental stresses. Similar to animal systems, exogenously applied NAEs have potent and varied effects on plant cells. Recent pharmacological approaches combined with molecular-genetic experiments revealed that NAEs may act in certain plant tissues via specific membrane-associated proteins or by interacting with phospholipase D-alpha, although other, direct targets for NAE action in plants are likely to be discovered. Polyunsaturated NAEs can be oxidized via the lipoxygenase pathway in plants, producing an array of oxylipin products that have received little attention so far. Overall, the conservation of NAE occurrence and metabolic machinery in plants, coupled with the profound physiological effects of elevating NAE content or perturbing endogenous NAE metabolism, suggest that an NAE-mediated regulatory pathway, sharing similarities with the mammalian endocannabinoid pathway, indeed exists.

N-Acylethanolamine metabolism interacts with abscisic acid signaling in Arabidopsis thaliana seedlings

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. In plants, NAEs are generally elevated in desiccated seeds, suggesting that they may play a role in seed physiology. NAE and abscisic acid (ABA) levels were depleted during seed germination, and both metabolites inhibited the growth of Arabidopsis thaliana seedlings within a similar developmental window. Combined application of low levels of ABA and NAE produced a more dramatic reduction in germination and growth than either compound alone. Transcript profiling and gene expression studies in NAE-treated seedlings revealed elevated transcripts for a number of ABA-responsive genes and genes typically enriched in desiccated seeds. The levels of ABI3 transcripts were inversely associated with NAE-modulated growth. Overexpression of the Arabidopsis NAE degrading enzyme fatty acid amide hydrolase resulted in seedlings that were hypersensitive to ABA, whereas the ABA-insensitive mutants, abi1-1, abi2-1, and abi3-1, exhibited reduced sensitivity to NAE. Collectively, our data indicate that an intact ABA signaling pathway is required for NAE action and that NAE may intersect the ABA pathway downstream from ABA. We propose that NAE metabolism interacts with ABA in the negative regulation of seedling development and that normal seedling establishment depends on the reduction of the endogenous levels of both metabolites.

Synthesis of new plant growth regulator: N-(fatty acid) O-aryloxyacetyl ethanolamine

N-(fatty acyl) O-aryloxyacetyl ethanolamines, prepared from N-acylethanolamine (NAE) and aryloxyacetic acid, were tested for plant growth regulating activity. Compared with N-stearoylethanolamine, most compounds exhibit improved plant growth stimulating activity. In particular, those with chlorine on aryl ring show better activity than 2,4-dichlorophenyloxyacetic acid in stimulating hypocotyls elongation of rape which indicates that chlorine on aryl ring appears significant. Moreover, these derivatives display improved solubility.

New natural noncannabinoid ligands for cannabinoid type-2 (CB2) receptors

Since the discovery that Delta 9-tetrahydrocannabinol and related cannabinoids from Cannabis sativa L. act on specific physiological receptors in the human body and the subsequent elucidation of the mammalian endogenous cannabinoid system, no other natural product class has been reported to mimic the effects of cannabinoids. We recently found that N-alkyl amides from purple coneflower (Echinacea spp.) constitute a new class of cannabinomimetics, which specifically engage and activate the cannabinoid type-2 (CB2) receptors. Cannabinoid type-1 (CB1) and CB2 receptors belong to the family of G protein-coupled receptors and are the primary targets of the endogenous cannabinoids N-arachidonoyl ethanolamine and 2-arachidonoyl glyerol. CB2 receptors are believed to play an important role in distinct pathophysiological processes, including metabolic dysregulation, inflammation, pain, and bone loss. CB2 receptors have, therefore, become of interest as new targets in drug discovery. This review focuses on N-alkyl amide secondary metabolites from plants and underscores that this group of compounds may provide novel lead structures for the development of CB2-directed drugs.

Manipulation of Arabidopsis fatty acid amide hydrolase expression modifies plant growth and sensitivity to N-acylethanolamines

In vertebrates, the endocannabinoid signaling pathway is an important lipid regulatory pathway that modulates a variety of physiological and behavioral processes. N-Acylethanolamines (NAEs) comprise a group of fatty acid derivatives that function within this pathway, and their signaling activity is terminated by an enzyme called fatty acid amide hydrolase (FAAH), which hydrolyzes NAEs to ethanolamine and their corresponding free fatty acids. Bioinformatic approaches led to the identification of plant homologues of FAAH that are capable of hydrolyzing NAEs in vitro. To better understand the role of NAEs in plants, we identified T-DNA knockouts to Arabidopsis FAAH (AtFAAH; At5g64440) and generated plants overexpressing AtFAAH. Here we show that seeds of AtFAAH knockouts had elevated levels of endogenous NAEs, and seedling growth was hypersensitive to exogenously applied NAE. On the other hand, seeds and seedlings of AtFAAH overexpressors had lower endogenous NAE content, and seedlings were less sensitive to exogenous NAE. Moreover, AtFAAH overexpressors displayed enhanced seedling growth and increased cell size. AtFAAH expression and FAAH catalytic activity increased during seed germination and seedling growth, consistent with the timing of NAE depletion during seedling establishment. Collectively, our results show that AtFAAH is one, but not the only, modulator of endogenous NAE levels in plants, and that NAE depletion likely participates in the regulation of plant growth.

Metabolic engineering of proanthocyanidins by ectopic expression of transcription factors in Arabidopsis thaliana

Genetic transformation of Arabidopsis thaliana with the Arabidopsis TT2 MYB transcription factor resulted in ectopic expression of the BANYULS gene, encoding anthocyanidin reductase, AHA10 encoding a P-type proton-pump and TT12 encoding a transporter involved in proanthocyanidin biosynthesis. When coupled with constitutive expression of PAP1, a positive regulator of anthocyanin biosynthesis, TT2 expression in Arabidopsis led to accumulation of proanthocyanidins, but only in a subset of cells in which the BANYULS promoter is naturally expressed. Ectopic expression of the maize Lc MYC transcription factor weakly induced AHA10 but did not induce BANYULS, TT12 or accumulation of proanthocyanidins. However, high-level combined expression of TT2, PAP1 and Lc resulted in proanthocyanidin synthesis throughout young leaves and cotyledons, followed by death of the plants 1 to 2 weeks after germination. We discuss these results in relation to engineering proanthocyanidins to improve the quality of food and forage plants.

N-acylethanolamines in seeds of selected legumes

Seven molecular species of N-acylethanolamines were quantified in seeds from selected members of the legume family. Total concentrations for the 14 taxa studied ranged over approximately three orders of magnitude with no consistent overall relationship to phylogeny. Elevated concentrations observed in some species make them good candidates for natural sources of these compounds which are of increasing therapeutic interest in the modulation of the mammalian endocannabinoid system.

Occurrence, metabolism, and prospective functions of N-acylethanolamines in plants

N-Acylethanolamines (NAEs) are fatty acid amides that are derived from an N-acylated phoshatidylethanolamine presursor, a minor membrane lipid constituent of plant and animal cells. Historically, the formation of N-acylethanolamines was associated with cellular stress and tissue damage in mammals, but more recently has been shown to be part of the endocannabinoid signaling system that regulates a variety of normal physiological functions, including neurotransmission, immune responses, vasodilation, embryo development and implantation, feeding behavior, cell proliferation, etc. The widespread regulation of vertebrate physiology by this class of lipid mediators and the conservation of the mechanisms for NAE formation, perception and degradation in higher plants raises the possibility that the metabolism of NAEs represents an evolutionarily conserved lipid signaling pathway that regulates an array of physiological processes in multicellular eukaryotes. Here the recent information on NAEs in plants is reviewed in the context of the occurrence, metabolism and functions of this bioactive class of lipid mediators.

Molecular identification of a functional homologue of the mammalian fatty acid amide hydrolase in Arabidopsis thaliana

N-Acylethanolamines (NAEs) are endogenous constituents of plant and animal tissues, and in vertebrates their hydrolysis terminates their participation as lipid mediators in the endocannabinoid signaling system. The membrane-bound enzyme responsible for NAE hydrolysis in mammals has been identified at the molecular level (designated fatty acid amide hydrolase, FAAH), and although an analogous enzyme activity was identified in microsomes of cotton seedlings, no molecular information is available for this enzyme in plants. Here we report the identification, the heterologous expression (in Escherichia coli), and the biochemical characterization of an Arabidopsis thaliana FAAH homologue. Candidate Arabidopsis DNA sequences containing a characteristic amidase signature sequence (PS00571) were identified in plant genome data bases, and a cDNA was isolated by reverse transcriptase-PCR using Arabidopsis genome sequences to develop appropriate oligonucleotide primers. The cDNA was sequenced and predicted to encode a protein of 607 amino acids with 37% identity to rat FAAH within the amidase signature domain (18% over the entire length). Residues determined to be important for FAAH catalysis were conserved between the Arabidopsis and rat protein sequences. In addition, a single transmembrane domain near the N terminus was predicted in the Arabidopsis protein sequence, similar to that of the rat FAAH protein. The putative plant FAAH cDNA was expressed as an epitope/His-tagged fusion protein in E. coli and solubilized from cell lysates in the nonionic detergent, dodecyl maltoside. Affinity-purified recombinant protein was indeed active in hydrolyzing a variety of naturally occurring N-acylethanolamine types. Kinetic parameters and inhibition data for the recombinant Arabidopsis protein were consistent with these properties of the enzyme activity characterized previously in plant and animal systems. Collectively these data now provide support at the molecular level for a conserved mechanism between plants and animals for the metabolism of NAEs.

Elevated levels of N-lauroylethanolamine, an endogenous constituent of desiccated seeds, disrupt normal root development in Arabidopsis thaliana seedlings

N-Acylethanolamines (NAEs) are prevalent in desiccated seeds of various plant species, and their levels decline substantially during seed imbibition and germination. Here, seeds of Arabidopsis thaliana (L.) Heynh. were germinated in, and seedlings maintained on, micromolar concentrations of N-lauroylethanolamine (NAE 12:0). NAE 12:0 inhibited root elongation, increased radial swelling of root tips, and reduced root hair numbers in a highly selective and concentration-dependent manner. These effects were reversible when seedlings were transferred to NAE-free medium. Older seedlings (14 days old) acclimated to exogenous NAE by increased formation of lateral roots, and generally, these lateral roots did not exhibit the severe symptoms observed in primary roots. Cells of NAE-treated primary roots were swollen and irregular in shape, and in many cases showed evidence, at the light- and electron-microscope levels, of improper cell wall formation. Microtubule arrangement was disrupted in severely distorted cells close to the root tip, and endoplasmic reticulum (ER)-localized green fluorescent protein (mGFP5-ER) was more abundant, aggregated and distributed differently in NAE-treated root cells, suggesting disruption of proper cell division, endomembrane organization and vesicle trafficking. These results suggest that NAE 12:0 likely influences normal cell expansion in roots by interfering with intracellular membrane trafficking to and/or from the cell surface. The rapid metabolism of NAEs during seed imbibition/germination may be a mechanism to remove this endogenous class of lipid mediators to allow for synchronized membrane reorganization associated with cell expansion.

N-acylethanolamine signaling in tobacco is mediated by a membrane-associated, high-affinity binding protein

N-Acylethanolamines (NAEs) are fatty acid derivatives found as minor constituents of animal and plant tissues, and their levels increase 10- to 50-fold in tobacco (Nicotiana tabacum) leaves treated with fungal elicitors. Infiltration of tobacco leaves with submicromolar to micromolar concentrations of N-myristoylethanolamine (NAE 14:0) resulted in an increase in relative phenylalanine ammonia-lyase (PAL) transcript abundance within 8 h after infiltration, and this PAL activation was reduced after co-infiltration with cannabinoid receptor antagonists (AM 281 and SR 144528). A saturable, high-affinity specific binding activity for [(3)H]NAE 14:0 was identified in suspension-cultured tobacco cells and in microsomes from tobacco leaves (apparent K(d) of 74 and 35 nM, respectively); cannabinoid receptor antagonists reduced or eliminated specific [(3)H]NAE 14:0 binding, consistent with the physiological response. N-Oleoylethanolamine activated PAL2 expression in leaves and diminished [(3)H]NAE 14:0 binding in microsomes, whereas N-linoleoylethanolamine did not activate PAL2 expression in leaves, and did not affect [(3)H]NAE 14:0 binding in microsomes. The nonionic detergent dodecylmaltoside solubilized functional [(3)H]NAE 14:0-binding activity from tobacco microsomal membranes. The dodecylmaltoside-solubilized NAE-binding activity retained similar, but not identical, binding properties to the NAE-binding protein(s) in intact tobacco microsomes. Additionally, high-affinity saturable NAE-binding proteins were identified in microsomes isolated from Arabidopsis and Medicago truncatula tissues, indicating the general prevalence of these binding proteins in plant membranes. We propose that plants possess an NAE-signaling pathway with functional similarities to the "endocannabinoid" pathway of animal systems and that this pathway, in part, participates in xylanase elicitor perception in tobacco.

N-Myristoylethanolamine-cholesterol (1:1) complex: first evidence from differential scanning calorimetry, fast-atom-bombardment mass spectrometry and computational modelling

The interaction of N-myristoylethanolamine (NMEA) with cholesterol is investigated by differential scanning calorimetry (DSC), fast-atom-bombardment mass spectrometry (FAB-MS) and computational modelling. Addition of cholesterol to NMEA leads to a new phase transition at 55 degrees C besides the chain-melting transition of NMEA at 72.5 degrees C. The enthalpy of the new transition increases with cholesterol content up to 50 mol%, but decreases thereafter, vanishing at 80 mol%. The enthalpy of the chain-melting transition of NMEA decreases with an increase in cholesterol; the transition disappears at 50 mol%. FAB-MS spectra of mixtures of NMEA and cholesterol provide clear signatures of the formation of ([NMEA+cholesterol]+) ([NMEA+cholesterol+Na]+). These results are consistent with the formation of a 1:1 complex between NMEA and cholesterol. Molecular modelling studies support this experimental finding and provide a plausible structural model for the complex, which highlights multiple H-bond interactions between the hydroxy group of cholesterol and the hydroxy and carbonyl groups of NMEA besides appreciable dispersion interaction between the hydrocarbon domains of the two molecules.

N-acylethanolamines are metabolized by lipoxygenase and amidohydrolase in competing pathways during cottonseed imbibition

Saturated and unsaturated N-acylethanolamines (NAEs) occur in desiccated seeds primarily as 16C and 18C species with N-palmitoylethanolamine and N-linoleoylethanolamine (NAE 18:2) being most abundant. Here, we examined the metabolic fate of NAEs in vitro and in vivo in imbibed cotton (Gossypium hirsutum) seeds. When synthetic [1-(14)C]N-palmitoylethanolamine was used as a substrate, free fatty acids (FFA) were produced by extracts of imbibed cottonseeds. When synthetic [1-(14)C]NAE 18:2 was used as a substrate, FFA and an additional lipid product(s) were formed. On the basis of polarity, we presumed that the unidentified lipid was a product of the lipoxygenase (LOX) pathway and that inclusion of the characteristic LOX inhibitors nordihydroguaiaretic acid and eicosatetraynoic acid reduced its formation in vitro and in vivo. The conversion of NAE 18:2 in imbibed cottonseed extracts to 12-oxo-13-hydroxy-N-(9Z)-octadecanoylethanolamine was confirmed by gas chromatography-mass spectrometry, indicating the presence of 13-LOX and 13-allene oxide synthase, which metabolized NAE 18:2. Cell fractionation studies showed that the NAE amidohydrolase, responsible for FFA production, was associated mostly with microsomes, whereas LOX, responsible for NAE 18:2-oxylipin production, was distributed in cytosol-enriched fractions and microsomes. The highest activity toward NAE by amidohydrolase was observed 4 to 8 h after imbibition and by LOX 8 h after imbibition. Our results collectively indicate that two pathways exist for NAE metabolism during seed imbibition: one to hydrolyze NAEs in a manner similar to the inactivation of endocannabinoid mediators in animal systems and the other to form novel NAE-derived oxylipins. The rapid depletion of NAEs by these pathways continues to point to a role for NAE metabolites in seed germination.

Inhibition of phospholipase D alpha by N-acylethanolamines

N-Acylethanolamines (NAEs) are endogenous lipids in plants produced from the phospholipid precursor, N-acylphosphatidylethanolamine, by phospholipase D (PLD). Here, we show that seven types of plant NAEs differing in acyl chain length and degree of unsaturation were potent inhibitors of the well-characterized, plant-specific isoform of PLD-PLD alpha. It is notable that PLD alpha, unlike other PLD isoforms, has been shown not to catalyze the formation of NAEs from N-acylphosphatidylethanolamine. In general, inhibition of PLD alpha activity by NAEs increased with decreasing acyl chain length and decreasing degree of unsaturation, such that N-lauroylethanolamine and N-myristoylethanolamine were most potent with IC(50)s at submicromolar concentrations for the recombinant castor bean (Ricinus communis) PLD alpha expressed in Escherichia coli and for partially purified cabbage (Brassica oleracea) PLD alpha. NAEs did not inhibit PLD from Streptomyces chromofuscus, and exhibited only moderate, mixed effects for two other recombinant plant PLD isoforms. Consistent with the inhibitory biochemical effects on PLD alpha in vitro, N-lauroylethanolamine, but not lauric acid, selectively inhibited abscisic acid-induced closure of stomata in epidermal peels of tobacco (Nicotiana tabacum cv Xanthi) and Commelina communis at low micromolar concentrations. Together, these results provide a new class of biochemical inhibitors to assist in the evaluation of PLD alpha physiological function(s), and they suggest a novel, lipid mediator role for endogenously produced NAEs in plant cells.

N-Acylphosphatidylethanolamine accumulation in potato cells upon energy shortage caused by anoxia or respiratory inhibitors

A minor phospholipid was isolated from potato (Solanum tuberosum L. cv Bintje) cells, chromatographically purified, and identified by electrospray ionization mass spectrometry as N-acylphosphatidylethanolamine (NAPE). The NAPE level was low in unstressed cells (13 +/- 4 nmol g fresh weight(-1)). According to acyl chain length, only 16/18/18 species (group II) and 18/18/18 species (group III) were present. NAPE increased up to 13-fold in anoxia-stressed cells, but only when free fatty acids (FFAs) started being released, after about 10 h of treatment. The level of groups II and III was increased by unspecific N-acylation of phosphatidylethanolamine, and new 16/16/18 species (group I) appeared via N-palmitoylation. NAPE also accumulated in aerated cells treated with NaN(3) plus salicylhydroxamate. N-acyl patterns of NAPE were dominated by 18:1, 18:2, and 16:0, but never reflected the FFA composition. Moreover, they did not change greatly after the treatments, in contrast with O-acyl patterns. Anoxia-induced NAPE accumulation is rooted in the metabolic homeostasis failure due to energy deprivation, but not in the absence of O(2), and is part of an oncotic death process. The acyl composition of basal and stress-induced NAPE suggests the existence of spatially distinct FFA and phosphatidylethanolamine pools. It reflects the specificity of NAPE synthase, the acyl composition, localization and availability of substrates, which are intrinsic cell properties, but has no predictive value as to the type of stress imposed. Whether NAPE has a physiological role depends on the cell being still alive and its compartmentation maintained during the stress period.

Two unusual glycerophospholipids from a filamentous fungus, Absidia corymbifera

The chloroform-methanol extractable lipids of the soil filamentous fungus Absidia corymbifera VKMF-965 account for about 20% by weight of dry cells and are composed of low-polarity constituents (about 75% of the total lipids), such as triacylglycerols (mainly), diacylglycerols, sterols and free fatty acids, as well as of glycolipids (about 3%) and phospholipids. The last consist largely of components common to the fungal lipids, namely, phosphatidylethanolamine (38% of the total phospholipids), phosphatidyl-myo-inositol (16%), diphosphatidylglycerol (12%), phosphatidylcholine (7%), phosphatidic acid (6%) and phosphatidylglycerol (3%), and two unusual phospholipids, PL1 (6%) and PL2 (9%). Based on the infrared (IR), (1)H-nuclear magnetic resonance (NMR), (13)C-NMR and mass spectra along with the results of degradation experiment, these two phospholipids have been established to be 1,2-diacyl-sn-glycero-3-phospho(N-acetylethanolamine), or N-acetyl phosphatidylethanolamine, and 1,2-diacyl-sn-glycero-3-phospho(N-ethoxycarbonyl-ethanolamine), respectively. These structures have been confirmed by preparing similar phospholipids from the phosphatidylethanolamine isolated from the same fungus and correlating their chromatographic behaviour, IR and (1)H-NMR spectra with those of PL1 and PL2. So far N-acetyl phosphatidylethanolamine has been detected only in cattle and human brains and a human placenta but its structure was not rigorously proved. PL2 is a novel lipid; to our knowledge no natural phospholipid with an urethane group has yet been found. The main fatty acids of both the phospholipids are n-hexadecanoic, octadecanoic and octadecadienoic ones; PL2 contains in addition a considerable amount of octadecatrienoic acid with its greater portion located at the sn-1 position.

Characterization of N-acylphosphatidylethanolamine and acylphosphatidylglycerol in oats

Two polar lipid classes, both with three acyl groups, were isolated from an extract of oats and characterized by nuclear magnetic resonance spectroscopy, electrospray mass spectrometry (MS), and electron ionization MS (EIMS). Distortionless enhancement by polarization transfer (DEPT) and the two-dimensional correlation experiments 1H-detected heteronuclear multiple quantum coherence spectroscopy, heteronuclear multiple bond correlation spectroscopy, double quantum filtered correlation spectroscopy, and total correlation spectroscopy provided sufficient information for determination of the structure of the two lipid classes. The polar lipid classes were found to be N-acylphosphatidylethanolamine [1,2-diacyl-sn-glycero-3-phospho-(N-acyl)-1'-ethanolamine; N-acyl-PE] and acylphosphatidylglycerol [1,2-diacyl-sn-glycero-3-phospho-(3'-acyl)-1'-sn-glycerol]. High-performance liquid chromatography with electrospray ionization MS (HPLC-ESMS) and with electrospray ionization tandem MS (HPLC-MS/MS) were utilized for the separation and subsequent determination of molecular species. With HPLC-ESMS, ions of deprotonated molecules were obtained and with HPLC-MS/MS carboxylate ions (representing acyl groups) were obtained as well as other structurally significant ions. Fifty molecular species of N-acylphosphatidylethanolamine and 24 molecular species of acylphosphatidylglycerol were found, with a molecular mass range of 924-1032 Da and 959-1035 Da, respectively. Identification of the fatty acid isomers, as picolinyl ester derivatives, was done with gas chromatography with EIMS. Three isomers of 16:1 fatty acids were found in N-acyl-PE, and their double bond positions were determined to 6, 9, and 11 with a relative abundance of 4:10:1.

Emerging physiological roles for N-acylphosphatidylethanolamine metabolism in plants: signal transduction and membrane protection

The activation of N-acylphosphatidylethanolamine (NAPE) metabolism in plants appears to be associated mostly with cellular stresses. In response to pathogen elicitors, NAPE is hydrolzyed by phospholipase-D (PLD), and corresponding medium-chain, saturated N-acylethanolamines (NAEs) are released by plant cells where they act as lipid mediators to modulate ion flux and activate defense gene expression. In desiccated seeds of higher plants, long-chain, saturated and unsaturated NAEs are prevalent, but are rapidly metabolized during the first few hours of imbibition, a period of substantial osmotic stress. NAPE synthesis is increased in seeds during this same period of rapid rehydration. A membrane-bound enzyme designated NAPE synthase has been purified from imbibed cottonseeds and its unusual biochemical properties suggest that it may scavenge free fatty acids in vivo. This feature of NAPE metabolism may be unique to higher plants a may be a mechanism for the rapid recycling of fatty acids back into membrane-associated NAPE. Altogether, increasing evidence indicates that NAPE metabolism in plants shares functional similarities with NAPE metabolism in animal systems, including signal transduction and cellular protection. In particular, the emerging role of released NAEs as lipid mediators in plant defense signaling represents an intriguing parallel to 'endocannabinoid signaling' in several mammalian cell types.