Anandamide and its congeners inhibit human plasma butyrylcholinesterase. Possible new roles for these endocannabinoids?

Butyrylcholinesterase (BChE), a serine hydrolase biochemically related to the cholinergic enzyme Acetylcholinesterase (AChE), is found in many mammalian tissues, such as serum and central nervous system, but its physiological role is still unclear. BChE is an important human plasma esterase, where it has detoxifying roles. Furthermore, recent studies suggest that brain BChE can have a role in Alzheimer's disease (AD). The endocannabinoid arachidonoylethanolamide (anandamide) and other acylethanolamides (NAEs) are almost ubiquitary molecules and are physiologically present in many tissues, including blood and brain, where they show neuroprotective and anti-inflammatory properties. This paper demonstrates that they are uncompetitive (oleoylethanolamide and palmitoylethanolamide) or non competitive (anandamide) inhibitors of BChE (Ki in the range 1.32-7.48 nM). On the contrary, NAEs are ineffective on AChE kinetic features. On the basis of the X-ray crystallographic structure of human BChE, and by using flexible docking procedures, an hypothesis on the NAE-BChE interaction is formulated by molecular modeling studies. Our results suggest that anandamide and the other acylethanolamides studied could have a role in the modulation of the physiological actions of BChE.

Effect of acylethanolamides on lipid peroxidation and paraoxonase activity.

N-acylethanolamides (NAEs) are hydrophobic molecules synthesized in many tissues. An increase in the plasma levels of NAEs has been observed in human diseases. Previous studies have suggested that NAEs could exert a protective effect against oxidative stress. Aim of the study was to investigate whether NAEs (oleoylethanolamide, palmitoylethanolamide and anandamide), differing for acyl chain length and unsaturation, exert a protective role against plasma lipid peroxidation triggered by incubation with Cu2+2 or AAPH (2,2'-azobis(2-amidinopropane) dihydrochloride). Moreover, we investigated the effect of NAEs on the activity of HDL-associated paraoxonase (PON1), an enzyme involved in the antioxidant end anti-inflammatory role of human high density lipoproteins (HDL). The results demonstrated that the NAEs protect plasma lipids and PON1 activity against AAPH and/or copper-induced oxidation.

Oleoylethanolamide protects human sperm cells from oxidation stress: studies on cases of idiopathic infertility.

N-acylethanolamides are naturally occurring hydrophobic molecules usually present in a very small amount in many mammalian tissues and cells. The presence of N-acylethanolamides has also been demonstrated in human reproductive tracts and fluids, although their biological effects and molecular mechanisms of action are not yet completely elucidated. It is known that some N-acylethanolamides, such as oleoylethanolamide, have antioxidative properties. The aim of this study was to test whether oleoylethanolamide could protect sperm cells from reactive oxygen species-induced oxidative damage in cases of idiopathic infertility, because the excessive generation of these radicals was associated with this pathology. Our results show that 2.5 nM oleoylethanolamide in vitro supplementation significantly reduces DNA strand breaks both in fertile and infertile subjects. Moreover, oleoylethanolamide increases kinematic parameters, such as curvilinear velocity and amplitude of lateral head displacement and hyperactivation, both in the presence and in the absence of oxidative stress. Results of this study support the hypothesis of a possible protective action of oleoylethanolamide against reactive oxygen species, which could explain its beneficial effects on in vitro capacitated spermatozoa.

Temperature-induced molten globule-like state in human alpha1-acid glycoprotein: an infrared spectroscopic study.

Despite extensive investigations on thermal denaturation of alpha(1)-acid glycoprotein (AGP) using a variety of techniques, structural features of the folded-unfolded state in terms of residual secondary structures and the structural transitions involved in this process have not been fully characterized. In this study we employed FT-IR spectroscopy to investigate the thermal unfolding and reversibility of temperature-induced changes in AGP. The data revealed a fully reversible beta-sheet-rich protein which exhibits a molten globule-like state, an important protein folding intermediate. 2D-IR COS revealed the sequence of the conformational changes occurring before denaturation and confirmed the formation of this intermediate which was further supported by CD spectroscopy. On account of the similarities in the FT-IR spectra of AGP with those of porcine odorant-binding protein (OBP), homology modeling of AGP using OBP as template was performed. The resemblance of AGP and OBP 3D structures confirmed the similarities of data obtained using FT-IR spectroscopy. Overall, FT-IR spectroscopy appears to be useful for investigating the structural characteristics and stability of proteins whose 3D structures are unavailable and for assessing the molten globule-like state in small beta-sheet-rich proteins.

Increased plasma concentrations of palmitoylethanolamide, an endogenous fatty acid amide, affect oxidative damage of human low-density lipoproteins: an in vitro study.

Fatty acid ethanolamides (NAEs) are naturally occurring hydrophobic molecules usually present in a very small amount in many mammalian tissues and cells. Moreover, these compounds have been isolated in mammalian biological fluids, such as blood. Palmitoylethanolamide (C16:0) (PEA) is a fully saturated NAE, which presents some possible pharmaceutical activities, such as anti-inflammatory and antinociceptive effects. PEA is physiologically present in the mammalian blood at concentrations ranging from 9.4 to 16.7 pmol/ml. Since increasing evidence indicates that oxidative modification of low-density lipoproteins (LDL) is an important determinant in atherogenesis, the aim of this study was to evaluate the effect of physiologically relevant concentrations of PEA on Cu2+-induced LDL oxidation (measured as conjugated dienes formation). Our experiments indicate both anti-oxidative and slightly pro-oxidative effects of PEA. The anti-oxidative effect is obtained at low PEA concentrations (0.01 and 0.1 microM), while the pro-oxidative effect is obtained at a higher PEA concentration (1 microM). Fluorescence and circular dichroism data indicate that the effect of PEA occurs mainly by affecting the conformational features of ApoB-100.

Idiopathic infertility: effect of palmitoylethanolamide (a homologue of anandamide) on hyperactivated sperm cell motility and Ca2+ influx.

The goal of this study was to examine the effect of palmitoylethanolamide (PEA) on the capacitation process and hyperactivated motility (HA) in idiopathic infertile men. Our data show the effect of PEA on the kinematic parameters of sperm cells from idiopathic infertile men during the capacitation of spermatozoa in vitro, both in the presence and absence of 2.5 nM PEA, a molecule physiologically present in human reproductive tracts. Two groups of sperm cells were identified. In group I (36 +/- 14 x 10(6) cells/mL), PEA significantly increased some motility parameters and HA during capacitation. In group II (58 +/- 18 x 10(6) cells/mL), PEA did not significantly modify motility parameters and HA. Fura 2 AM (acetoxymethyl ester derivative of fura 2) measurements demonstrated that PEA increased external Ca2+ influx (which modulates HA) in group I, while no change was measured in group II. In conclusion, our data indicated that PEA modulated certain physiological sperm functions that are involved in fertilization; in particular, we showed that PEA modulated for HA in men with low sperm kinematic parameters.

Correlation between functional and structural changes of reduced and oxidized trout hemoglobins I and IV at different pHs. A circular dichroism study.

Circular dichroism (CD) spectra of two major hemoglobin components (Hb), HbI and HbIV, from Oncorhyncus mykiss (formerly Salmo irideus) trout were evaluated in the range 250-600 nm. HbI is characterized by a complete insensitivity to pH changes, while HbIV presents the Root effect. Both reduced [iron(II) or oxy] and oxidized (met) forms of the two proteins were studied at different pHs, 7.8 and 6.0, to obtain information about the pH effects on the structural features of these hemoglobins. Data obtained show that oxy and met-HbI are almost insensitive to pH decrease, remaining in the R conformational state also at low pH. On the contrary, the pH decrease induces similar structural changes, characteristics of ligand dissociation and R-->T transition, both in the reduced and in the oxidized HbIV. The structural changes, monitored by CD, are compared with the peroxidative activity of iron(II)-Hb and met-Hb forms and with the superoxide anion scavenger capacity of the proteins.

Different modulation of phospholipase A2 activity by saturated and monounsaturated N-acylethanolamines.

The physiological functions of N-acylethanolamines (NAEs) are poorly understood, although many functions were suggested for these naturally occurring membrane components of plants and animals. The binding with cannabinoid receptors CB1 and CB2 was demonstrated for some NAEs, such as anandamide. However, the chemical nature of these molecules suggests that some of their biological effects on biomembranes could be related, at least partially, to physical interactions with the lipid bilayer. The present work studies the effect of saturated and monounsaturated NAEs on phospholipase A2 (PLA2) activity, which is dependent on lipid bilayer features. The present study, performed by 2-dimethylamino-(6-lauroyl)-naphthalene (Laurdan) fluorescence, demonstrates that the acyl chain length and the presence of a single double bond are crucial for the enzymatic activity modulation by NAEs. In fact, saturated NAEs with 10 carbon atoms don't affect the PLA2 activity, while NAEs with 12 and 16 carbon atoms largely activate the enzyme. On the other hand, an acyl chain length of 18 carbon atoms, with or without the presence of a double bond, only slightly affects the enzymatic activity. A structural model for NAE-lipid interactions is proposed in order to explain the differences in PLA2 activity modulation by these fatty acid derivatives.