International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid receptors and their ligands: beyond CB1 and CB2.

There are at least two types of cannabinoid receptors (CB(1) and CB(2)). Ligands activating these G protein-coupled receptors (GPCRs) include the phytocannabinoid Δ(9)-tetrahydrocannabinol, numerous synthetic compounds, and endogenous compounds known as endocannabinoids. Cannabinoid receptor antagonists have also been developed. Some of these ligands activate or block one type of cannabinoid receptor more potently than the other type. This review summarizes current data indicating the extent to which cannabinoid receptor ligands undergo orthosteric or allosteric interactions with non-CB(1), non-CB(2) established GPCRs, deorphanized receptors such as GPR55, ligand-gated ion channels, transient receptor potential (TRP) channels, and other ion channels or peroxisome proliferator-activated nuclear receptors. From these data, it is clear that some ligands that interact similarly with CB(1) and/or CB(2) receptors are likely to display significantly different pharmacological profiles. The review also lists some criteria that any novel "CB(3)" cannabinoid receptor or channel should fulfil and concludes that these criteria are not currently met by any non-CB(1), non-CB(2) pharmacological receptor or channel. However, it does identify certain pharmacological targets that should be investigated further as potential CB(3) receptors or channels. These include TRP vanilloid 1, which possibly functions as an ionotropic cannabinoid receptor under physiological and/or pathological conditions, and some deorphanized GPCRs. Also discussed are 1) the ability of CB(1) receptors to form heteromeric complexes with certain other GPCRs, 2) phylogenetic relationships that exist between CB(1)/CB(2) receptors and other GPCRs, 3) evidence for the existence of several as-yet-uncharacterized non-CB(1), non-CB(2) cannabinoid receptors; and 4) current cannabinoid receptor nomenclature.

Investigations of the human endocannabinoid system in two subcutaneous adipose tissue depots in lean subjects and in obese subjects before and after weight loss.

CONTEXT: Endocannabinoids (ECs) have a role in obesity by affecting appetite and through peripheral effects. Obesity is associated with a dysregulation of the endocannabinoid system (ECS). OBJECTIVE: We aimed to determine the ECS in subcutaneous adipose tissue (AT) in obese subject and investigate the influence of diet-induced weight loss on this system. DESIGN: The obese study participants underwent a 12 weeks diet regimen resulting in 10-12% weight loss. All study participants underwent fasting blood samples and AT biopsies from abdomen and gluteal region, the obese subjects both before and after weight loss. SETTING AND PARTICIPANTS: A total of 21 healthy obese individuals (10 men/11 women, age 39.5 ± 1.6 years, body mass index (BMI): 37.5 ± 0.8 kg m(-2)) and 21 age- and gender-matched lean subjects (BMI: 23.8 ± 0.4 kg m(-2)) were studied. MAIN OUTCOME MEASURES: The activity of ECS in AT was determined by measuring arachidonoyl glycerol (2-AG) and N-arachidonoylethanolamine/anandamide in AT by mass spectrometry and gene expressions of enzymes and receptors involved in the ECS. RESULTS: The EC, 2-AG was reduced in obese individuals in the gluteal AT depot (P<0.01). Moreover, 2-AG increased in both depots in the obese subjects following weight loss (P<0.05). The gene expression of the CB1 was either not affected by the obese state (in the gluteal AT depot) or reduced (in the abdominal depot, P<0.05) and significantly affected by weight loss. The expression of the degrading enzymes FAAH, FAAH2, MGL and MGL2 was differently affected by obesity, AT depot and weight loss. CONCLUSION: We found reduced levels of 2-AG in subcutaneous AT in obesity, which increased after weight loss. In abdominal AT, the low CB1 expression was normalised after weight loss, whereas in gluteal AT the CB1 expression was reduced after weight loss. These findings support the concept of a dysregulated ECS in AT in association with obesity.

Pentraxin 3 in primary percutaneous coronary intervention for ST elevation myocardial infarction is associated with early irreversible myocardial damage : Kinetic profile, relationship to interleukin 6 and infarct size.

BACKGROUND: The inflammatory marker long pentraxin 3 (PTX3) has been shown to be a strong predictor of 30-day and one-year mortality after acute myocardial infarction. The aim of this study was to evaluate the kinetic profile of PTX3 and its relationship with interleukin 6 (IL-6), high-sensitive C-reactive protein (hs-CRP) and infarct size. METHODS: PTX3, IL-6 and hs-CRP were measured at predefined time points, at baseline (before percutaneous coronary intervention (PCI)), at 12 and 72 hours after PCI in 161 patients with first-time ST elevation myocardial infarction (STEMI). RESULTS: PTX3 and IL-6 levels increased in the early phase, followed by a gradual decrease between 12 and 72 hours. There were statistically significant correlations between PTX3 and IL-6 in general, for all time points and for changes over time (0-72 hours). In a linear mixed model, PTX3 predicted IL-6 (p < 0.001). PTX3 is also correlated with hs-CRP in general, and at each time point post PCI, except at baseline. PTX3, IL-6 and hs-CRP were all significantly correlated with infarct size in general, and at the peak time point for maximum troponin I. In addition, there was a modest correlation between IL-6 levels at baseline and infarct size at 72 hours after PCI (ρ = 0.23, p = 0.006). CONCLUSIONS: PTX3 had a similar kinetic profile to IL-6, with an early increase and decline, and was statistically significantly correlated with markers of infarct size in STEMI patients post primary PCI. Baseline levels of IL-6 only predicted infarct size at 72 hours post PCI.

High-sensitive C-reactive protein is associated with reduced lung function in young adults.

Systemic inflammation has been associated with reduced lung function. However, data on the interrelationships between lung function and inflammation are sparse, and it is not clear if low-grade inflammation leads to reduced lung function. Associations between high-sensitive C-reactive protein (CRP) and spirometric lung function were assessed in a population-based cohort of approximately 1,000 Danes aged 20 yrs. In males, the average decline in forced expiratory volume in one second (FEV(1)) in the highest CRP quintile was 23 mL.yr(-1) versus 1.6 mL.yr(-1) in the lowest quintile. In females, the average decline was 6.2 mL.yr(-1) in the highest CRP quintile versus an increase of 1.8 mL.yr(-1) in the lowest CRP quintile. In a multiple regression analysis adjusted for sex, body mass index, cardiorespiratory fitness, smoking, asthma, airway hyperresponsiveness and serum eosinophil cationic protein, higher levels of CRP at age 20 yrs were associated with a greater reduction in both FEV(1) and forced vital capacity between ages 20 and 29 yrs. The findings show that higher levels of C-reactive protein in young adults are associated with subsequent decline in lung function, suggesting that low-grade systemic inflammation in young adulthood may lead to impaired lung function independently of the effects of smoking, obesity, cardiorespiratory fitness, asthma and eosinophilic inflammation.

Dynamic changes of the endogenous cannabinoid and opioid mesocorticolimbic systems during adolescence: THC effects.

Adolescence is a critical phase of active brain development often characterized by the initiation of marijuana (Cannabis sativa) use. Limited information is known regarding the endogenous cannabinoid system of the adolescent brain as well as related neurotransmitters that appear sensitive to cannabis exposure. We recently observed that adult rats pre-exposed to Delta-9-tetrahydrocannabinol (THC) during adolescence self-administered higher amounts of heroin and had selective impairments of the enkephalin opioid system within the nucleus accumbens (NAc) implicated in reward-related behavior. To explore the ontogeny of the cannabinoid and opioid neuronal systems in association with adolescence THC exposure, rats were examined at different adolescent stages during an intermittent THC paradigm (1.5 mg/kg i.p. every third day) from postnatal days (PNDs) 28-49. Rat brains were examined 24 h after injection at PND 29 (early adolescence), PND 38 (mid adolescence) and PND 50 (late adolescence) and analyzed for endocannabinoids (anandamide and 2-arachidonoylglycerol), Met-enkephalin, cannabinoid CB(1) receptors and micro opioid receptors (microOR) in the NAc, caudate-putamen and prefrontal cortex (PFC). Of the markers studied, the endocannabinoid levels had the most robust alterations throughout adolescence and were specific to the PFC and NAc. Normal correlations between anandamide and 2-arachidonoylglycerol concentrations in the NAc (positive) and PFC (negative) were reversed by THC. Other significant THC-induced effects were confined to the NAc - increased anandamide, decreased Met-enkephalin and decreased microORs. These findings emphasize the dynamic nature of the mesocorticolimbic endocannabinoid system during adolescence and the selective mesocorticolimbic disturbance as a consequence of adolescent cannabis exposure.

No morphine sparing effect of ketamine added to morphine for patient-controlled intravenous analgesia after uterine artery embolization.

BACKGROUND: Pain following embolization of the uterine arteries (UAEs) is variable and may be very severe requiring large doses of parenteral opioids for relief. The present study tested the hypothesis that the addition of ketamine to i.v. patient-controlled morphine reduces the amount of morphine required for pain-control during the first 24 h after UAE embolization. METHODS: Fifty-six patients undergoing UAE embolization for treatment of symptomatic uterine leiomyomata were randomized to receive either 2 mg/ml of morphine (Control group, n=30) or 2 mg/ml of both morphine and ketamine (Ketamine group, n=26) by i.v. patient-controlled analgesia (IV-PCA). Pump settings were bolus dose 1 ml, lockout 10 min, no background infusion. In addition, all patients received diclofenac and acetaminophen for pain relief. Pain scores, morphine consumption and adverse events like nausea, vomiting, itching, visual disturbances, anxiety, dreaming and hallucinations, if any, were recorded for 24 h after embolization. RESULTS: The mean +/- SD 24-h consumption of patient-controlled morphine was 38.3 +/- 21.0 mg in the Ketamine group vs. 33.3 +/- 18.3 mg in the Control group (NS). The difference between the means was 5.0 mg (95% confidence interval: -5.7; 15.6). One patient in the Ketamine group vs. none in the Control group experienced auditory hallucinations. CONCLUSION: Studying an unselected group of patients undergoing embolization of the UAEs for treatment of symptomatic uterine leiomyomata under conditions of basal analgesia with acetaminophen and diclofenac, we failed to demonstrate any morphine-sparing effect of IV-PCA ketamine and morphine compared with IV-PCA morphine alone.

Effects of sucking acidic candies on saliva in unilaterally irradiated pharyngeal cancer patients.

Patients who have received radiation therapy on the head and neck area often use acidic candies to relieve symptoms of dry mouth. Therefore, the aim of this study was to determine the erosive potential in relation to teeth of an acidic candy in 10 such patients. The patients sucked the candy while their whole saliva was collected into a closed system at different times: baseline, candy-stimulated, and post-stimulated. The erosive potential of the candy was evaluated from candy-induced changes in saliva degree of saturation with respect to hydroxyapatite (HAp). Previously published normative values were used for comparison. The results showed that saliva became significantly more undersaturated with respect to HAp in irradiated patients, and failed to return to baseline values during the post-stimulatory period, which it normally does in healthy individuals. Thus, prevention of dental breakdown in these patients should involve counseling regarding choice of stimulant for dry mouth relief.

Oral 2-oleyl glyceryl ether improves glucose tolerance in mice through the GPR119 receptor.

The intestinal G protein-coupled receptor GPR119 is a novel metabolic target involving glucagon-like peptide-1 (GLP-1)-derived insulin-regulated glucose homeostasis. Endogenous and diet-derived lipids, including N-acylethanolamines and 2-monoacylglycerols (2-MAG) activate GPR119. The purpose of this work is to evaluate whether 2-oleoyl glycerol (2-OG) improves glucose tolerance through GPR119, using wild type (WT) and GPR 119 knock out (KO) mice. We here show that GPR119 is essential for 2-OG-mediated release of GLP-1 and CCK from GLUTag cells, since a GPR119 specific antagonist completely abolished the hormone release. Similarly, in isolated primary colonic crypt cultures from WT mice, GPR119 was required for 2-OG-stimulated GLP-1 release while there was no response in crypts from KO mice. In vivo, gavage with 2-oleyl glyceryl ether ((2-OG ether), a stable 2-OG analog with a potency of 5.3 µM for GPR119 with respect to cAMP formation as compared to 2.3 µM for 2-OG), significantly (P < 0.05) improved glucose clearance in WT littermates, but not in GPR119 KO mice. Finally, deletion of GPR119 in mice resulted in lower glucagon levels, whereas the levels of insulin and GIP were unchanged. In the present study we show that 2-OG stimulates GLP-1 secretion through GPR119 activation in vitro, and that fat-derived 2-MAGs are potent candidates for mediating fat-induced GLP-1 release through GPR119 in vivo. © 2016 BioFactors, 42(6):665-673, 2016.

Purification and characterization of a 15-ketoprostaglandin delta 13-reductase from bovine lung.

15-Ketoprostaglandin delta 13-reductase from bovine lung has been purified using affinity chromatography to apparent homogeneity, as judged from polyacrylamide gel electrophoresis with and without sodium dodecyl sulphate. Valine was identified as tne N-terminal aumino acid, and the isoelectric point was estimated at pH 7.8. Molecular weights of 56,000 and 39,500 were found by the use of gel filtration and SDS-polyacrylamide gel electrophoresis, respectively. The enzyme was found to be specific for the 15-keto group, thus 15-ketoprostaglandin E4 (apparent Km = microM) is a substrate, in contrast to prostaglandin E1. The enzyme was active with both NADH (apparent Km = 88--94 microM) and NADH (apparent Km = 5--9 microM) as coenzyme, but the V max with NADH was more than twice that obtained with NADPH. The enzyme did not catalyze the reversed reaction: 13,14-dihydro-15-keto-prostaglandin E1 to 15-ketoprostaglandin E1. The turnover number of the enzyme was determined to be either 60 or 42 min-1. The low value of the turnover number is compensated by a high concentration (96.4 mU/g tissue) of the enzyme in lung tissue, resulting in a high metabolic capacity. Thus, 15-ketoprostaglandin delta 13-reductase together with 15-hydroxyprostaglandin dehydrogenase ensures an irreversible catabolism of prostaglandins.

Characterization and partial purification of phospholipase D from human placenta.

We report the existence in the human placenta of a phosphatidylcholine-hydrolyzing phospholipase D (PLD) activity, which has been characterized and partially purified. Triton X-100 effectively solubilized PLD from the particulate fraction of human placenta in a dose-dependent manner. However, Triton X-100 caused decreasing enzyme activities. Maximum transphosphatidylation was obtained with 2% ethanol. The enzyme was found to have a pH optimum of 7.0-7.5 and an apparent Km of 33 mol% (or 0.8 mM). Ca2+ and Mg2+ was not required for the enzyme activity. Addition of phosphatidyl-4,5-bisphosphate, but not phosphatidylethanolamine, to the substrate mixture gave rise to a pronounced dose-dependent increase in PLD activity (EC50 = 0.3 mol%), suggesting a regulatory role of this phospholipid in PLD action. The enzyme was inhibited by sodium oleate when partly or fully substituting for octylglucoside in the substrate mixture. The PLD activity was enriched 15-fold by solubilization and purification on a DEAE-Sepharose column. N-Ethylmaleimide (10 mM) markedly inhibited the purified enzyme, indicating the presence of free thiol groups on PLD. Sphingosine (20 microM) and (+/-) propranolol (53 microM) had no direct effect on PLD activity. The present results form the basis for further purification of a PLD from human tissue.

Age-related changes in the percentage of oleate in adipose tissue of male and female Fischer rats.

Fischer 344 rats showed sex difference in the percentage of oleate in lipids of the omental adipose tissue (Thorling, E.B. and Overvad, K. (1994) Nutr. Res. 14, 569-576). The development of this difference was studied with respect to time in rats maintained on laboratory chow, from the age of 3 weeks to 20 weeks. From the age of 3 weeks to 5 weeks the percentage of oleate increased slightly in both sexes. From the age of 5 weeks to 13 weeks the percentage (mean +/- S.D., n = 5) increased further in the female rats from 24.8 +/- 0.6% to 27.6 +/- 0.6%, whereas in the male rats it dropped from 22.9 +/- 0.4% to 20.2 +/- 0.6% at the same time points, respectively. In adult rats, age 20 weeks, the percentage of oleate was 28.6 +/- 0.3% and 19.6 +/- 0.5% for females and males, respectively. Castrated males partly maintained their juvenile level, being 21.1 +/- 1.1% fourteen weeks after castration at the age of 6 weeks. Oestrogen injections twice a week to the castrated rats increased their oleate percentage within the same period to 23.4 +/- 0.3%, partly reflecting the increase observed in the female rats. Stearic acid showed similar but less pronounced changes. The ratio oleic acid/stearic acid was constantly higher in the female than in the male rats, and this difference increased with age. The results of the present study suggest that these changes in percentage of oleate in adipose tissue lipids may partly have been caused by an effect of sex steroids on the delta-9-desaturase.

Essential function of linoleic acid esterified in acylglucosylceramide and acylceramide in maintaining the epidermal water permeability barrier. Evidence from feeding studies with oleate, linoleate, arachidonate, columbinate and alpha-linolenate.

Essential fatty acid-deficient rats were supplemented with 300 mg per day of pure fatty acid esters: oleate (O), linoleate (L), arachidonate (A), and columbinate (C) for 10 days. During this period, the rats in groups L, A, and C all showed a decrease in their initially high trans-epidermal water loss, a classical essential fatty acid-deficiency symptom, to a level seen in non-deficient rats (group N). The trans-epidermal water loss in rats of group O was unaffected by the supplementation. Fatty acid composition of two epidermal sphingolipids, acylglucosylceramide and acylceramide, from the skin were determined. The results indicate that re-establishment of a low trans-epidermal water loss was associated with incorporation of linolenate into the two epidermal sphingolipids. Supplementation with columbinate resulted in relatively high amounts of this fatty acid in the investigated epidermal sphingolipids. Analysis of pooled skin specimens from a previous study in which weanling rats were fed a fat-free diet and supplemented orally with pure alpha-linolenate for 13 weeks (Hansen, H.S. and Jensen, B. (1983) Lipids 18, 682-690) revealed very little polyunsaturated fatty acid in the two sphingolipids. These rats showed increased evaporation which was comparable to that of essential fatty acid-deficient rats. We interpret these results as strong evidence for a very specific and essential function of linoleic acid in maintaining the integrity of the epidermal water permeability barrier. This function of linoleate is independent of its role as precursor for arachidonate and icosanoids.

Metabolism of prostaglandin E1 and of glutathione conjugate of prostaglandin A1 (GSH-prostaglandin A1) by prostaglandin 9-ketoreductase from rabbit kidney.

Rabbit kidney prostaglandin 9-ketoreductase was found to metabolize the glutathione conjugate of prostaglandin A1 (GSH-prostaglandin A1). Apparent Km (GSH-prostaglandin A1) 13 microM and apparent Km (prostaglandin E1) 200 microM. The cytosolic preparation was subjected to gelfiltration and isoelectric focusing, which revealed that metabolism of prostaglandin E1 and GSH-prostaglandin A1 occurs by means of the same fractions. Furthermore, prostaglandin E1 and GSH-prostaglandin A1 are competitive inhibitors of the enzyme, when GSH-prostaglandin A1 and prostaglandin E1 are tested as substrates, respectively. It si concluded, that GSH-prostaglandin A1 is a much better substrate for prostaglandin 9-ketoreductase from rabbit kidney than is prostaglandin E1.

15-Hdroxyprostaglandin dehydrogenase activity in vitro in lung and kidney of essential fatty acid-deficient rats.

Weanling rats were fed for 6 months on a diet deficient in essential fatty acids: either fat-free, or with 28% (w/w) partially hydrogenated fish oil. Control rats were fed a diet with 28% (w/w) arachis oil for 6 months. 15-Hydroxyprostaglandin dehydrogenase activity was determined as initial rates of formation of 3H-labelled 15-keto-dihydro-prostaglandin E1 plus 15-keto-prostaglandin E1 in high speed supernatants of lung and kidney from each of the groups of rats. Dehydrogenase activity (expressed as either pmol/min per mg soluble protein, or as nmol/min per g tissue) was decreased 30--40% in the lungs of the two groups on diets deficient in essential fatty acids as compared to the control group. No difference were observed in dehydrogenase activity in the kidneys. The dehydrogenase may be of importance for the regulation of the level of endogenous prostaglandins and, thus, a decrease in activity could result in a slower turnover of prostaglandins.

Elimination of low steady-state concentrations of [5,6-3H2]prostaglandin E1 in the pulmonary and the systemic circulations of anaesthetized rats.

The elimination of [3H]prostaglandin E1 in anaesthetized rats was studied by continuous intravenous or intraarterial infusions, producing steady-state concentrations at the level of endogenous prostaglandin E2 in mixed venous blood. Blood samples (0.5 ml) were collected from the carotid artery or the right atrium, respectively. The levels of [3H]prostaglandin E1 were measured at different infusion time intervals and the 3H-labeled hydrophobic metabolites characterized. Cardiac output was estimated by a modification of the dye injection method, using 125I-labelled albumin as the marker. From the cardiac output and the rate of infusion, the fractional clearance of the lung and the systemic beds in the steady-state situation were estimated to 88.3 +/- 3.2% and 54.1 +/- 15.2% (mean +/- S.D.), RESPECTIVELY. The hydrophobic metabolites were characterized chromatographically on Sephadez LH-20 columns, using synthetically prepared [14C]prostaglandin metabolites as internal standards and markers. The identities of some metabolites were further established by derivative formation to a constant [3H]/[14C] ratio. The major metabolite was 15-keto-13,14-dihydro-[3H]prostaglandin E1, while 15-keto-[3H]prostaglandin E1 and 13,14-dihydro-[3H]prostaglandin E1 could not be demonstrated.

Inhibition of fatty acid synthesis in rat hepatocytes by exogenous polyunsaturated fatty acids is caused by lipid peroxidation.

Rat hepatocyte long-term cultures were utilized to investigate the impact of different polyunsaturated fatty acids (PUFA) on the insulin-induced de novo fatty acid synthesis in vitro. The addition of 0.5 mM albumin-complexed oleic, linoleic, columbinic, arachidonic, eicosapentaenoic or docosahexaenoic acid resulted in a marked suppression of fatty acid synthesis. By evaluation of cell viability (determined as the leakage of lactate dehydrogenase (LDH) it turned out, that the antioxidant used (50 microM alpha-tocopherol phosphate) had a low antioxidant activity, resulting in cytotoxic effects by the peroxidized PUFA. Arachidonic acid and eicosapentaenoic acid showed a dose- and time-dependent cytotoxicity. Two other antioxidants: 50 microM alpha-tocopherol acid succinate and 1 microM N,N'-diphenyl-1,4-phenylenediamine, both proved more efficient than alpha-tocopherol phosphate. There was a significant correlation between LDH-leakage and inhibition of fatty acid synthesis. Lipid peroxidation, measured as thiobarbituric acid-reactive substances, also showed a significant correlation with the degree of inhibition of fatty acid synthesis. Furthermore, PUFA had no inhibitory effect on fatty acid synthesis when peroxidation was minimized by the use of proper antioxidants. These data indicate that PUFA in vitro inhibit the insulin-induced de novo fatty acid synthesis in hepatocytes from starved rats, due to cytotoxic effects caused by lipid peroxidation.

Glutamate stimulates the formation of N-acylphosphatidylethanolamine and N-acylethanolamine in cortical neurons in culture.

The formation of anandamide (N-arachidonoylethanolamine), N-acylethanolamine, and N-acylphosphatidylethanolamine was studied in primary cultures of rat cortical neurons. The cells were incubated for 22 h with [14C]ethanolamine, [U-14C]arachidonic acid, [3H]arachidonic acid, [32P]phosphate, [14C]stearic acid, or [3H]myristic acid. The lipids from the cells and media were separated by thin layer chromatography. [14C]Ethanolamine labelling revealed two compounds (I and II), which on different thin layer chromatography systems migrated as N-acylethanolamine (0.06-0.55% of total radioactivity) and N-acylphosphatidylethanolamine (0.66-6.49% of total radioactivity), respectively. Compound II was also labelled with [32P]phosphate, and radioactive fatty acids. Treatment of compound II with phospholipase D (Streptomyces chromofuscus) resulted in two compounds, one comigrating as phosphatidic acid and the other as N-acylethanolamine. Compound I could be labelled with [14C]stearic acid and [3H]myristic acid, but not with [3H]- or [14C]arachidonic acid. Exogenous [3H]anandamide was metabolised with a t1/2 of 2.6 h. The labelling of the two compounds identified as N-acylethanolamine and N-acylphosphatidylethanolamine were more pronounced the older the culture. The neurotoxic amino acid, glutamate, stimulated within 2 h dose-dependently (ED50 = 40 microM) the formation of both compounds. It is suggested that N-acylethanolamine and N-acylphosphatidylethanolamine are formed in relation to the cytotoxicity induced by glutamate, and that these compounds may be markers of neurotoxicity. We could not detect any formation of anandamide using radioactive arachidonic acid.

Apparent in vivo retroconversion of dietary arachidonic to linoleic acid in essential fatty acid-deficient rats.

Essential fatty acid-deficient rats were fed ethyl [U-14C]arachidonate (308 dpm/nmol) and when a decrease in the transepidermal water loss was seen, the epidermal sphingolipids, acylglucosylceramide and acylceramide were isolated. [14C]Linoleic acid (approx. 130 dpm/nmol) was present in both lipid classes, while the substrate was only detected in the former. These results intimate that in vivo retroconversion of arachidonic to linoleic acid can be induced in the rat.

Arf and RhoA regulate both the cytosolic and the membrane-bound phospholipase D from human placenta.

In this paper we demonstrate for the first time that human placenta contains a cytosolic phospholipase D (PLD) activity. This activity had a pH optimum of 7.0 and was stimulated by PIP2 and inhibited by oleate. Furthermore, cytosolic PLD was stimulated by 30 microM GTP gamma S (6-14-fold) and by the small G proteins 1 microM mArf3 (2-fold) and 0.37 nM RhoA (2-fold). This is the first report to show RhoA activation of a cytosolic PLD. The activation by mArf3 was maintained after partial purification on DEAE Sepharose of the enzyme. We have previously reported the existence of a membrane-bound PLD from human placenta, which is stimulated by PIP2, but not by oleate (Vinggaard, A. M. & Hansen, H. S. (1995) Biochim. Biophys. Acta 1258, 169-176). Here we show that oleic acid and alpha-linolenic acid both dose-dependently inhibited solubilized membrane PLD (65% inhibition at 4 mM), whereas stearic acid (4 mM) had no effect. Thus, the presence of double bonds in the fatty acid is important for the inhibitory effect. Furthermore, placental membrane PLD was activated by 30 microM GTP gamma S (4-fold) and by mArf3 (1 microM) and RhoA (0.37 nM) by a factor of 3 and 2, respectively. The solubilized membrane phospholipase D was partially purified to a basal specific activity of 25-37 nmol/min/mg. This preparation was devoid of endogenous RhoA and Arf and could not be stimulated by GTP gamma S. However, mArf3 (1 microM) still activated this partially purified membrane PLD, whereas RhoA (0.37 nM) was not able to activate this PLD fraction. In conclusion, our results suggest that the human placenta contains a PLD that is located both in the cytosol and the membranes, and that is activated by PIP2, mArf3 and RhoA but inhibited by oleate.