The Interaction of the Endocannabinoid Anandamide and Paracannabinoid Lysophosphatidylinositol during Cell Death Induction in Human Breast Cancer Cells

Endocannabinoid anandamide (AEA) and paracannabinoid lysophosphatidylinositol (LPI) play a significant role in cancer cell proliferation regulation. While anandamide inhibits the proliferation of cancer cells, LPI is known as a cancer stimulant. Despite the known endocannabinoid receptor crosstalk and simultaneous presence in the cancer microenvironment of both molecules, their combined activity has never been studied. We evaluated the effect of LPI on the AEA activity in six human breast cancer cell lines of different carcinogenicity (MCF-10A, MCF-7, BT-474, BT-20, SK-BR-3, MDA-MB-231) using resazurin and LDH tests after a 72 h incubation. AEA exerted both anti-proliferative and cytotoxic activity with EC50 in the range from 31 to 80 µM. LPI did not significantly affect the cell viability. Depending on the cell line, the response to the LPI-AEA combination varied from a decrease in AEA cytotoxicity to an increase in it. Based on the inhibitor analysis of the endocannabinoid receptor panel, we showed that for the former effect, an active GPR18 receptor was required and for the latter, an active CB2 receptor. The data obtained for the first time are important for the understanding the manner by which endocannabinoid receptor ligands acting simultaneously can modulate cancer growth at different stages.

ACTH(6-9)PGP Peptide Protects SH-SY5Y Cells from H2O2, tert-Butyl Hydroperoxide, and Cyanide Cytotoxicity via Stimulation of Proliferation and Induction of Prosurvival-Related Genes

Stabilized melanocortin analog peptide ACTH(6-9)PGP (HFRWPGP) possesses a wide range of neuroprotective activities. However, its mechanism of action remains poorly understood. In this paper, we present a study of the proproliferative and cytoprotective activity of the adrenocorticotropic hormone fragment 6-9 (HFRW) linked with the peptide prolyine-glycyl-proline on the SH-SY5Y cells in the model of oxidative stress-related toxicity. The peptide dose-dependently protected cells from H2O2, tert-butyl hydroperoxide, and KCN and demonstrated proproliferative activity. The mechanism of its action was the modulation of proliferation-related NF-κB genes and stimulation of prosurvival NRF2-gene-related pathway, as well as a decrease in apoptosis.

GPR55 Receptor Activation by the N-Acyl Dopamine Family Lipids Induces Apoptosis in Cancer Cells via the Nitric Oxide Synthase (nNOS) Over-Stimulation

GPR55 is a GPCR of the non-CB1/CB2 cannabinoid receptor family, which is activated by lysophosphatidylinositol (LPI) and stimulates the proliferation of cancer cells. Anandamide, a bioactive lipid endocannabinoid, acts as a biased agonist of GPR55 and induces cancer cell death, but is unstable and psychoactive. We hypothesized that other endocannabinoids and structurally similar compounds, which are more hydrolytically stable, could also induce cancer cell death via GPR55 activation. We chemically synthesized and tested a set of fatty acid amides and esters for cell death induction via GPR55 activation. The most active compounds appeared to be N-acyl dopamines, especially N-docosahexaenoyl dopamine (DHA-DA). Using a panel of cancer cell lines and a set of receptor and intracellular signal transduction machinery inhibitors together with cell viability, Ca2+, NO, ROS (reactive oxygen species) and gene expression measurement, we showed for the first time that for these compounds, the mechanism of cell death induction differed from that published for anandamide and included neuronal nitric oxide synthase (nNOS) overstimulation with concomitant oxidative stress induction. The combination of DHA-DA with LPI, which normally stimulates cancer proliferation and is increased in cancer setting, had an increased cytotoxicity for the cancer cells indicating a therapeutic potential.

N-arachidonoyl dopamine inhibits epithelial-mesenchymal transition of breast cancer cells through ERK signaling and decreasing the cellular cholesterol

N-acyl dopamines (NADAs) are bioactive lipids of the endovanilloid family with known cytotoxicity for the cancer cells; however, the available data on the participation of the endovanilloids in epithelial-mesenchymal transition (EMT) and cancer stemness are controversial. This study unveils the inhibitory role of N-arachidonoyl dopamine (AA-DA), a typical representative of the NADA family, in breast cancer cell migration, EMT, and stemness. AA-DA treatment also led to a decrease in cholesterol biosynthesis gene expressions, and addition of exogenous cholesterol reverted these AA-DA-mediated inhibitory effects. Notably, AA-DA treatment inhibited the key regulatory gene of the cholesterol biosynthesis pathway, sterol regulatory element-binding protein 1 (SREBP1), with concurrent repression of the endoplasmic reticulum kinase 1/2 (ERK1/2) pathway. Furthermore, U0126, an ERK inhibitor, inhibited SREBP1 and decreased cellular cholesterol level, unwinding the molecular mechanism behind AA-DA-mediated anticancer activity. Thus, we, for the first time, revealed that AA-DA counteracts breast cancer EMT via inhibition of ERK signaling and cholesterol content.

In Vivo Targeted Metabolomic Profiling of Prostanit, a Novel Anti-PAD NO-Donating Alprostadil-Based Drug

Prostanit is a novel drug developed for the treatment of peripheral arterial diseases. It consists of a prostaglandin E1 (PGE1) moiety with two nitric oxide (NO) donor fragments, which provide a combined vasodilation effect on smooth muscles and vascular spastic reaction. Prostanit pharmacokinetics, however, remains poorly investigated. Thus, the object of this study was to investigate the pharmacokinetics of Prostanit-related and -affected metabolites in rabbit plasma using the liquid chromatography-mass spectrometry (LC-MS) approach. Besides, NO generation from Prostanit in isolated rat aorta and human smooth muscle cells was studied using the Griess method. In plasma, Prostanit was rapidly metabolized to 1,3-dinitroglycerol (1,3-DNG), PGE1, and 13,14-dihydro-15-keto-PGE1. Simultaneously, the constant growth of amino acid (proline, 4-hydroxyproline, alanine, phenylalanine, etc.), steroid (androsterone and corticosterone), and purine (adenosine, adenosine-5 monophosphate, and guanosine) levels was observed. Glycine, aspartate, cortisol, and testosterone levels were decreased. Ex vivo Prostanit induced both NO synthase-dependent and -independent NO generation. The observed pharmacokinetic properties suggested some novel beneficial activities (i.e., effect prolongation and anti-inflammation). These properties may provide a basis for future research of the effectiveness and safety of Prostanit, as well as for its characterization from a clinical perspective.

The Influence of the Cholesterol Level in Cells on Endovanilloid Cytotoxicity

The influence of the cellular cholesterol content on the cytotoxicity of endovanilloids acyldopamines was studied in MDA-MB-231 and MCF 10A cells. The activity of acyldopamines depends on the cellular cholesterol content, and a decrease in cholesterol content increases the cytotoxicity of acyldopamines.

Novel bexarotene derivatives: Synthesis and cytotoxicity evaluation for glioma cells in 2D and 3D in vitro models

Glioblastoma (GBM) is an aggressive and lethal form of brain cancer with a high invasion capacity and a lack of effective chemotherapeutics. Retinoid bexarotene (BXR) inhibits the neurospheroidal colony formation and migration of primary glioblastoma cells but has side effects. To enhance the BXR glioblastoma selectivity and cytotoxicity, we chemically modified it at the carboxyl group with either nitroethanolamine (NEA) bearing a NO-donating group (a well-known bioactivity enhancer; BXR-NEA) or with a dopamine (DA) moiety (to represent the highly toxic for various tumor cells N-acyldopamine family; BXR-DA). These two novel compounds were tested in the 2D (monolayer culture) and 3D (multicellular tumor spheroids) in vitro models. Both BXR-DA and BXR-NEA were found to be more toxic for rat C6 and human U-87MG glioma cells than the initial BXR. After 24 h incubation of the cells (monolayer culture) with the drugs, the IC₅₀ values were in the range of 28-42, and 122-152 μM for BXR derivatives and BXR, respectively. The cell death occurred via apoptosis according to the annexin staining and caspase activation. The tumor spheroids demonstrated higher resistance to the treatment compared to that one of the monolayer cultures. BXR-DA and BXR-NEA were more specific against tumor cells than the parental drug, in particular the selectivity index was 1.8-2.7 vs. 1.3-1.5, respectively. Moreover, they inhibited cell migration more effectively than parental BXR according to a scratch assay. Cell spreading from the tumor spheroids was also inhibited. Thus, the obtained BXR derivatives could be promising for glioblastoma treatment.

Neuroprotective and Antioxidant Activity of Arachidonoyl Choline, Its Bis-Quaternized Analogues and Other Acylcholines

The antioxidant activity and protective effect in the toxicity model of H₂O₂ were studied for arachidonic (AA-CHOL), docosahexaenoic (DHA-CHOL), linoleic (Ln-CHOL), and oleic (Ol-CHOL) fatty acids, as well as arachidonoyl dicholine (AA-diCHOL) and O-arachidonoyl bistetramethylaminoisopropanol (ABTAP). AA-CHOL, DHA-CHOL and Ln-CHOL provided a 20% increase in cell survival. AA-CHOL, AA-diCHOL, Ol-CHOL, and ABTAP had a radical-scavenging effect in the ABTS test, approximately equal to the activity of a standard radical scavenger Trolox.

5-alkylvinyl-1,2,4-triazole nucleosides: Synthesis and biological evaluation

Some 5-substituted ribavirin analogues have a high antiviral and anticancer activity, but their mechanisms of action are obviously not the same as their parent compound. The SAR studies performed on 3 (5)-substituted 1,2,4-triazole nucleosides have shown a high dependency between the structure of the 3 (5)-substituent and the level of antiviral/anticancer activity. The most active substances of the row contain coplanar with the 1,2,4-triazole ring aromatic substituent which is connected by a rigid ethynyl bond. However, the compounds with the trans-vinyl linker also had antiviral activity. We decided to study the antitumor activity of ribavirin analogues with alkyl/aryl vinyl substituents in the 5th position of the 1,2,4-triazole ring. Protected nucleoside analogues with various 5-alkylvinyl substituents were obtained by Horner-Wadsworth-Emmons reaction from the common precursor and converted to the nucleosides. Arylvinyl nucleosides were synthesised according the reported procedures. All compounds did not show significant antiproliferative activity on several tumour cell lines. Coplanar aromatic motif in the 5-substituent for the anticancer activity manifestation was confirmed.

Arachidonoylcholine and Other Unsaturated Long-Chain Acylcholines Are Endogenous Modulators of the Acetylcholine Signaling System

Cholines acylated with unsaturated fatty acids are a recently discovered family of endogenous lipids. However, the data on the biological activity of acylcholines remain very limited. We hypothesized that acylcholines containing residues of arachidonic (AA-CHOL), oleic (Ol-CHOL), linoleic (Ln-CHOL), and docosahexaenoic (DHA-CHOL) acids act as modulators of the acetylcholine signaling system. In the radioligand binding assay, acylcholines showed inhibition in the micromolar range of both α7 neuronal nAChR overexpressed in GH4C1 cells and muscle type nAChR from Torpedo californica, as well as Lymnaea stagnalis acetylcholine binding protein. Functional response was checked in two cell lines endogenously expressing α7 nAChR. In SH-SY5Y cells, these compounds did not induce Ca2+ rise, but inhibited the acetylcholine-evoked Ca2+ rise with IC50 9 to 12 μM. In the A549 lung cancer cells, where α7 nAChR activation stimulates proliferation, Ol-CHOL, Ln-CHOL, and AA-CHOL dose-dependently decreased cell viability by up to 45%. AA-CHOL inhibited human erythrocyte acetylcholinesterase (AChE) and horse serum butyrylcholinesterase (BChE) by a mixed type mechanism with Ki = 16.7 ± 1.5 μM and αKi = 51.4 ± 4.1 μM for AChE and Ki = 70.5 ± 6.3 μM and αKi = 214 ± 17 μM for BChE, being a weak substrate of the last enzyme only, agrees with molecular docking results. Thus, long-chain unsaturated acylcholines could be viewed as endogenous modulators of the acetylcholine signaling system.

Neuroprotective Action of Amidic Neurolipins in Models of Neurotoxicity on the Culture of Human Neural-Like Cells SH-SY5Y

It was established that in neurodegeneration models in the human neuron-like cell line SH-SY5Y, amide derivatives of arachidonic and docosahexaenoic acids were inactive in experiments with MPP⁺ and CoCl₂ but protected from H₂O₂. The protective activity of neurolipins decreased in the series DHA-DA > AA-SER ≥ AA-GLY > AA-GABA ≥ AA-EA and was manifested starting from a concentration of 0.5 nM.

Synthesis of N-acyl derivatives of Pro-Gly-Pro-Leu peptide: Proteolytic stability in vitro and effects on mouse macrophage cells RAW264.7

Acetyl, oleoyl, arachidonoyl, and docosahexaenoyl derivatives of the Pro-Gly-Pro-Leu peptide with a chemical purity of 99.8% were synthesized. The degradation kinetics of the Pro-Gly-Pro-Leu derivatives under the action of leucine aminopeptidase, nasal mucus, and microsomal fraction of the brain and blood of rats was studied. It was shown that the N-acyl derivatives of Pro-Gly-Pro-Leu proved to be more resistant to the action of leucine aminopeptidase and other enzyme systems. The study of the cytotoxic and anti-inflammatory activity of preparations on the mouse macrophage cell line RAW264.7 showed that acylation with oleic and arachidonic acid makes the peptide cytotoxic with LC50 in the range of 70-15 μM and gives it anti-inflammatory properties with EC50 of 32 and 36 μM, respectively.

N-acyl dopamines induce apoptosis in PC12 cell line via the GPR55 receptor activation

Dopamine amides of arachidonic, docosahexaenoic, and oleic acids were found to induce apoptosis in PC12 cells, which was blocked exclusively by antagonists and preincubation agonists of the receptor GPR55, belonging to the group of non-CB1/CB2 receptors.

N-acyl dopamines induce cell death in PC12 cell line via induction of nitric oxide generation and oxidative stress

It was shown that dopamine amides of arachidonic, oleic, and docosahexaenoic acids exhibit toxicity with respect to PC12 pheochromocytoma cell line. The mechanism of realization of the cytotoxic effect of acyl dopamines is the induction of oxidative stress. This event is preceded by triggering the synthesis of nitric oxide.

[The optimization of the nitric oxide quantitative analysis for its determination in the cultural medium of mammalian cell culture]

The protocol for the quantitative analysis of nitric oxide as nitrite-ion suitable for determination of its production by a mammalian cell culture was developed. The optimal results were obtained using microvolume-adjusted Griess method after the preliminary reduction of NO3- to NO2- with non-activated cadmium. The protocol was verified on a rat glioma C6 cell culture. The developed method may be used for the nitric oxide determination in 96-well and 48-well microplates; the detection limit is 2.1 ± 0.1 μM for NO2- and 2.9 ± 0.1 μM for NO3-.

Cytotoxicity of Endogenous Lipids N-acyl Dopamines and their Possible Metabolic Derivatives for Human Cancer Cell Lines of Different Histological Origin

BACKGROUND/AIM

Dopamine amides of long chain fatty acids are a family of endogenous mammalian lipids with an unknown function; they are anti-proliferative for the C6 glioblastoma cell line. To assess their possible anti-cancer activity we evaluated their cytotoxicity for a set of cancer cell lines.

MATERIALS AND METHODS

Anti-proliferative and cytotoxic actions of these substances were evaluated in HOS, IMR-32, MCF-7, Namalwa, K-562 and HEK 293 cell lines (18 h incubation time) using MTT and lactate dehydrogenase (LDH) tests, accordingly.

RESULTS

All N-acyl dopamines (NADA) induced cell death in all cell lines tested with a 50% lethal dose (LD50) in the range of 0.5-80 μM, except for HEK-293. For HEK-293 only N-arachidonoyl epinephrine demonstrated an LD50 below 100 μM.

CONCLUSION

According to the structure-activity relationship, N-acyl dopamines with an intact catechol group and a non-modified hydrophobic fatty acid residue are cytotoxic to cancer cell lines of various histological origins.

[The influence of docosahexaenoic acid moiety on cytotoxic activity of 1,2,4-thiadiazole derivatives]

Among 3-(2-aminopropyl)-1,2,4-thiadiazole derivatives contatining substitution-ready secondary amino group and exhibiting cytotoxic towards rat C 6 glioma cells three compounds with LD 50 values ranged from 6 to 48 мM were chosen. For these compounds amides with docosahexaenoic acid were synthetised and their cytotoxic activity was studied. It was shown that, although docosahexaenoic acid itself was not toxic for C 6 glioma cells, its addition to the amino derivatives of 1,2,4-thiadiazole increased or decreased resultant cytotoxicity. The effect depended on the structure of 1,2,4-thiadiazole substituents. The obtained data show that the acylation of cytotoxic compounds with docosahexaenoic acid does not necessarily lead to the increase of their activity, but sometimes can inactivate a compound. This fact should be taken into account, especially in the case of anti-cancer drug development.

[A new fluorescent analogue for the investigation of anandamide transport in cell cultures]

For the first time a new fluorescent analogue of anadamide incorporating BODIPY®-FL-fluorophore, attached to arachidonic acid via 2,2'-(ethylenedioxy)-bis(ethylenediamine), was prepared. Using rat glioma C6 cells it was demonstrated that the fluorescent analogue is a substrate of the cellular anandamide uptake system (Km 4.5 ± 0.9 µM, Vmax 20 ± 1 amol/(min x cell)).

[The study of peptide stability during hydrolysis by rat gastroenteric tract fragments]

The hydrolytic stability of therapeutic peptides such as dalargin, stemokin and some others, including cyclic tripeptides modified by ibuprofen and aspirin, was studied. Two experimental systems were used, one containing purified enzymes pepsin, trypsin and chymotrypsin and other based on fragments of rat stomach and ileum. It was found that linear peptides without D-aminoacids are hydrolyzed by fragments of stomach and ileum but resistant to hydrolysis with purified enzymes. The peptides with D-aminoacids and cyclic peptides are stable in all experimental conditions used, however, peptides modified with aspirin lost acetyl moiety of aspirin residue in acidic medium, the process is accelerated in presence of pepsin.

[Docosahexaenoyl dopamine in freshwater hydra: effects on regeneration and metabolic changes]

The effects of docosahexaenoyl dopamine and docosahexaenoic acid on the regeneration of hydra gastric and basal fragments are studied. Docosahexaenoyl dopamine induced morphogenetic abnormalities such as single ectopic tentacles in the gastric region and projections in the gastric and basal regions. Docosahexaenoic acid had no effect on the morphogenesis except for a mild slowing of the regeneration rate. Since no hydrolysis of docosahexaenoyl dopamine was detected in hydra extract, it was assumed that the morphogenetic effect could be associated with the dopamine component of this complex.

Sulfation of N-acyl dopamines in rat tissues

Sulfation of N-acyl dopamines has been shown for the first time in cytosolic fractions of rat liver and nervous system. Sulfation of dopamine amides of docosahexaenoic and oleic acids occurred in all tissues studied, N-arachidonoyl dopamine was sulfated in the liver and spinal cord, and N-stearoyl dopamine was sulfated only in the liver. Depending on the substrate and tissue, the sulfation activity varied from 0.5 to 3.5 nmol/min per mg total protein. Kinetic parameters of N-docosahexaenoyl dopamine sulfation in the brain were determined. The findings characterize the sulfation system as the most productive metabolic pathway of N-acyl dopamines, but the role of this system in the body is unclear because of high K(m) value.

[New aspects of biosynthesis and metabolism of N-acyldopamines in rat tissues]

Possible biosynthetic pathways of N-acyldopamines in rat tissues were compared. It was shown that an insignificant amount of the conjugation products was formed during the incubation of arachidonic acid and dopamine, whereas the substitution of tyrosine for dopamine resulted in the productive biosynthesis of N-arachidonoyldopamine. The biosynthesis presumably involves several closely conjugated enzymatic stages, and free fatty acids rather than their CoA esters served as the starting substrates. The decarboxylation stage probably precedes the stage of catechol system formation, because N-acetyltyramine (a probable intermediate) was easily oxidized by monophenol monooxygenase to N-acyldopamine, whereas N-acyltyrosine is hydrolyzed under these conditions. Biosynthesis of N-acyldopamines in a cell-free medium was accompanied by their methylation. The possibility of oxidative metabolism of N-acyldopamines, which could serve as co-substrates or inhibitors of different oxidoreductases, was shown for the first time.

[N-arachidonoyl dopamine is a possible factor of the rate of tentacle formation in freshwater hydra]

The effect of N-arachidonoyl dopamine, haloperidol, and their mixture on the rate of tentacle formation was studied during regeneration of the gastral and basal fragments of freshwater hydra. Some concentrations of haloperidol inhibited the tentacle formation, which was more pronounced in the basal fragment. N-arachidonoyl dopamine accelerated the tentacle formation in both fragments, particularly, in the basal one (an inversion of the natural difference in the rate of tentacle formation between the gastral and basal fragments). After the exposure to the mixture of these drugs, the effects of each of them were observed. Mass spectrometry assay has demonstrated endogenous N-arachidonoyl dopamine in the intact hydra homogenate. The possible involvement of this acyl-neurotransmitter in the regulation of the rate of tentacle formation in regenerating hydra is discussed.