Fluorescence-Based NAPE-PLD Activity Assay

N-Acylphosphatidylethanolamine phospholipase D (NAPE-PLD) is regarded as the principal enzyme that generates N-acylethanolamines (NAEs), a family of signaling lipids that includes the endocannabinoid anandamide. To investigate the biological function and biosynthesis of NAEs, we sought to develop potent NAPE-PLD inhibitors. To this aim, we utilized a high-throughput screening-compatible NAPE-PLD activity assay, which uses the fluorescence-quenched substrate PED6. This assay conveniently uses membrane fractions of NAPE-PLD overexpressing HEK293T cell lysates, thus avoiding the need for protein purification. Here, we give a detailed description of the NAPE-PLD PED6 fluorescence activity assay, which has increased throughput compared to previous radioactivity- or mass-spectrometry-based assays.

Levels of bioactive endogenous lipids and health-related quality of life in Chronic Idiopathic Axonal Polyneuropathy

Background

Although neuropathic pain is a significant problem in polyneuropathy, the underlying molecular mechanisms are poorly understood. The endogenous bioactive lipids 2-arachidonoyl-glycerol (2-AG), oleoylethanolamide (OEA), palmitoylethanolamide (PEA), and stearoylethanolamide (SEA) are known to influence pain and inflammation in the peripheral nervous system. The aim of this study was to explore the plasma levels of endocannabinoids and related lipids and health-related quality of life in patients with polyneuropathy with and without pain.

Methods

Patients (n = 48) with Chronic Idiopathic Axonal Neuropathy were included. Clinical data were retrieved from medical files. All patients filled out the SF-36 and EQ-5D questionnaires. In addition, blood samples were analyzed for 2-AG, OEA, PEA, and SEA.

Results

Neuropathic pain was reported in 21 of the patients. There were significantly lower levels of 2-AG in patients with neuropathic pain (P = 0.03), but there were no significant differences in OEA (P = 0.61), PEA (P = 0.95), or SEA (P = 0.97) levels. The patients reporting pain in the hands had significantly lower SEA levels, 10.0 versus 15.0 (P = 0.03). The levels of 2-AG were significantly higher among patients reporting paresthesia in their feet (80.1 vs. 56.3; P = 0.02). Levels of PEA, SEA, and 2-AG were decreased in patients with loss of vibration. PEA and SEA were decreased in patients with loss of pain and temperature, and SEA decreased in patients with loss of sense of touch. However, the differences in the levels of bioactive endogenous lipids were not statistically significant when corrected for multiple comparisons.

Conclusion

Alterations of 2-AG levels between polyneuropathy patients with and without neurogenic pain indicate that it could play an essential role. Further studies are warranted.

Chemical Genetics to Uncover Mechanisms Underlying Lipid-Mediated Signaling Events in Plants

Like animals, plants use various lipids as signaling molecules to guide their growth and development. The focus of our work is on the N-acylethanolamine (NAE) group of lipid mediators, which have been shown to play important physiological roles in plants. However, mechanisms by which NAEs modulate plant function remain elusive. Chemical genetics has emerged as a potent tool to elucidate signaling pathways in plants, particularly those orchestrated by plant hormones. Like plant hormones, exogenous application of NAEs elicits distinct plant growth phenotypes that can serve as biological readouts for chemical genetic screens. For example, N-lauroylethanolamide (NAE 12:0) inhibits seedling development in the model plant Arabidopsis thaliana. Thus, a library of small synthetic chemical compounds can be rapidly screened for their ability to reverse the inhibitory effect of NAE 12:0 on seedling development. Chemicals identified through such screens could be potential agonists/antagonists of NAE receptors or signaling pathways and therefore serve as additional tools for understanding NAE function in plants. In this chapter, we describe general protocols for NAE 12:0-based chemical genetic screens in Arabidopsis. Although such screens were designed primarily for NAE 12:0, they could potentially be applied for similar work with other NAE species or plant lipid mediators.

Targeted lipidomics and metabolomics evaluations of cortical neuronal stress in schizophrenia

BACKGROUND

Cortical neuronal dysfunction has been proposed to underlie the psychopathology and cognitive dysfunction of schizophrenia. Previously we have reported altered sphingolipid and N-acylphosphatidylserine (NAPS) metabolism in the frontal cortex in schizophrenia. We continue to expand these investigations to define the biochemical basis for these critical neuropathologies.

METHODS

We undertook a targeted high resolution mass spectrometric analysis to validate our previous reports of elevated sphingolipids and NAPS in the frontal cortex of a new cohort of schizophrenia subjects. Furthermore we expanded these analyses to include ceramides, N-acylphosphatidylethanolamines (NAPE), and N-acylethanolamines (NAE). In the same tissue samples we examined N-acetylaspartylglutamate (NAAG), a modulator of excitatory amino acid transmission, hypothesized to be involved in the pathology of schizophrenia.

RESULTS

We repeated our observations of elevated sulfatides in the frontal cortex in schizophrenia. An in-depth analysis of other sphingolipids revealed decrements in ceramide levels and increased levels of lactosylceramides. NAPS also were found to be augmented in schizophrenia as we previously reported. In addition, levels of NAPES, established biomarkers of neuronal stress, were elevated while their metabolites, NAEs were decreased. With regard to excitatory amino acid neurotransmission, NAAG levels were decreased by 50% while the metabolic precursor, N-acetylaspartate was unaltered.

CONCLUSIONS

Our data support the concept of cortical neuronal dysfunction in schizophrenia as indicated by altered metabolism of structural sphingolipids and NAAG, a modulator of excitatory amino acid neurotransmission.

Phospholipase D antagonist 1-butanol inhibited the mobilization of triacylglycerol during seed germination in Arabidopsis

Storage oil breakdown plays an important role in the life cycle of many plants by providing the carbon skeletons that support seedling growth immediately following germination. 1-Butanol, a specific inhibitor of phospholipase D (PLD)-dependent production of the signalling molecule phosphatidic acid (PA), inhibited Arabidopsis seed germination. N-Acylethanolamines (NAEs), which have been shown to inhibits PLDα1 activity, have no effect on seed germination. However, mobilization profile of triacylglycerols (TAG) that induced by each compound has not been reported. To gain deeper insights into the mode of mobilization of TAG during NAE 12:0 or 1-butanol treatment, we conducted a detailed comparative analysis of the effect of NAE 12:0, DMSO, 1-butanol and tert-butanol on Arabidopsis seed germination and fatty acid composition, tert-butanol and DMSO served as the corresponding controls treatment respectively. Our data show that 1-butanol, but not the inactive tert-butanol isomer, inhibited Arabidopsis seed germination, which is accompanied by a with retardation of the mobilization of triacylglycerols (TAG). In contrast, NAE 12:0 did not affect mobilization of TAG, nor did it significantly delay seed germination as monitored by radicle and cotyledon emergence. 1-Butanol induced RNA degradation in seeds and seedlings. We speculate that the large-scale degradation of RNA under the induction of 1-butanol may lead to abnormal gene expression in genes necessary for seed germination, including the genes needed for the mobilization of oil bodies, and thus cause a delay of seed germination. To the best of our knowledge, we report for the first time that 1-butanol delays the mobilization of TAG.

N-Stearoylethanolamine suppresses the pro-inflammatory cytokines production by inhibition of NF-κB translocation

N-Stearoylethanolamine (NSE) is a minor lipid that belongs to the N-Acylethanolamines family that mediates a wide range of biological processes. This study investigates the mechanisms of anti-inflammatory action of NSE on different model systems. Namely, we estimated the effect of NSE on inflammatory cytokines mRNA level (leukemia cells L1210), cytokines content (serum and LPS-stimulated macrophages) and nuclear translocation of NF-κB (peritoneal macrophages LPS-stimulated and isolated from rats with obesity-induced insulin resistance). The results indicated that NSE dose-dependently inhibits the IL-1 and IL-6 mRNA level in L1210 cells. Furthermore, the NSE treatment triggered a normalization of serum TNF-α level in insulin resistant rats and a reduction of medium IL-1 level in LPS-activated peritoneal macrophages. These NSE's effects were associated with the inhibition of nuclear NF-κB translocation in rat peritoneal macrophages.

Effects of two different specific neck exercise interventions on palmitoylethanolamide and stearoylethanolamide concentrations in the interstitium of the trapezius muscle in women with chronic neck shoulder pain

PURPOSE

Chronic neck/shoulder pain (CNSP) is one of the most common pain conditions. The understanding of mechanisms, including the peripheral balance between nociceptive and antinociceptive processes, is incomplete. N-acylethanolamines (NAEs) are a class of endogenous compounds that regulate inflammation and pain. The aim of this study was to investigate the levels of two NAEs: the peroxisome proliferator-activated receptor type-α ligand palmitoylethanolamide (PEA) and stearoylethanolamide (SEA) in the muscle interstitium of the trapezius muscle in women with CNSP randomized to two different neck specific training programs and in a healthy pain-free control group (CON).

MATERIALS AND METHODS

Fifty-seven women with CNSP were randomized to strength + stretch or stretch alone exercise programs. Twenty-nine subjects underwent microdialysis procedure before and after 4-6 months of exercise. Twenty-four CON subjects underwent microdialysis procedure before and after 4-6 months without any intervention in between. Microdialysate samples were collected from the trapezius muscle and analyzed by mass spectrometry for PEA and SEA levels.

RESULTS

PEA and SEA levels were significantly higher in CNSP patients compared with CON. PEA was significantly higher in CNSP than in CON after both training programs. SEA was significantly higher in CNSP than in CON after stretch alone but not after strength + stretch training. A significant positive correlation was found between changes in pain intensity and in SEA levels in the strength + stretch group, but not in the stretch alone group.

CONCLUSION

Our results indicate that exercise interventions differentially affect the levels of the bioactive lipids PEA and SEA in the interstitium of the trapezius muscle in women with CNSP.

Synthesis of phenoxyacyl-ethanolamides and their effects on fatty acid amide hydrolase activity

N-Acylethanolamines (NAEs) are involved in numerous biological activities in plant and animal systems. The metabolism of these lipids by fatty acid amide hydrolase (FAAH) is a key regulatory point in NAE signaling activity. Several active site-directed inhibitors of FAAH have been identified, but few compounds have been described that enhance FAAH activity. Here we synthesized two sets of phenoxyacyl-ethanolamides from natural products, 3-n-pentadecylphenolethanolamide and cardanolethanolamide, with structural similarity to NAEs and characterized their effects on the hydrolytic activity of FAAH. Both compounds increased the apparent Vmax of recombinant FAAH proteins from both plant (Arabidopsis) and mammalian (Rattus) sources. These NAE-like compounds appeared to act by reducing the negative feedback regulation of FAAH activity by free ethanolamine. Both compounds added to seedlings relieved, in part, the negative growth effects of exogenous NAE12:0. Cardanolethanolamide reduced neuronal viability and exacerbated oxidative stress-mediated cell death in primary cultured neurons at nanomolar concentrations. This was reversed by FAAH inhibitors or exogenous NAE substrate. Collectively, our data suggest that these phenoxyacyl-ethanolamides act to enhance the activity of FAAH and may stimulate the turnover of NAEs in vivo. Hence, these compounds might be useful pharmacological tools for manipulating FAAH-mediated regulation of NAE signaling in plants or animals.

Palmitoylethanolamide and stearoylethanolamide levels in the interstitium of the trapezius muscle of women with chronic widespread pain and chronic neck-shoulder pain correlate with pain intensity and sensitivity

Chronic widespread pain (CWP) is a complex condition characterized by central hyperexcitability and altered descending control of nociception. However, nociceptive input from deep tissues is suggested to be an important drive. N-Acylethanolamines (NAEs) are endogenous lipid mediators involved in regulation of inflammation and pain. Previously we have reported elevated levels of the 2 NAEs, the peroxisome proliferator-activated receptor type-α ligand N-palmitoylethanolamine (PEA) and N-stearoylethanolamine (SEA) in chronic neck/shoulder pain (CNSP). In the present study, the levels of PEA and SEA in women with CWP (n=18), CNSP (n=34) and healthy controls (CON, n=24) were investigated. All subjects went through clinical examination, pressure pain threshold measurements and induction of experimental pain in the tibialis anterior muscle. Microdialysis dialysate of the trapezius was collected before and after subjects performed a repetitive low-force exercise and analyzed by mass spectrometry. The levels of PEA and SEA in CNSP were significantly higher post exercise compared with CWP, and both pre and post exercise compared with CON. Levels of both NAEs decreased significantly pre to post exercise in CWP. Intercorrelations existed between aspects of pain intensity and sensitivity and the level of the 2 NAEs in CWP and CNSP. This is the first study demonstrating that CNSP and CWP differ in levels of NAEs in response to a low-force exercise which induces pain. Increases in pain intensity as a consequence of low-force exercise were associated with low levels of PEA and SEA in CNSP and CWP. These results indicate that PEA and SEA have antinociceptive roles in humans.