Effects of Rare Phytocannabinoids on the Endocannabinoid System of Human Keratinocytes.

The decriminalization and legalization of cannabis has paved the way for investigations into the potential of the use of phytocannabinoids (pCBs) as natural therapeutics for the treatment of human diseases. This growing interest has recently focused on rare (less abundant) pCBs that are non-psychotropic compounds, such as cannabigerol (CBG), cannabichromene (CBC), Δ9-tetrahydrocannabivarin (THCV) and cannabigerolic acid (CBGA). Notably, pCBs can act via the endocannabinoid system (ECS), which is involved in the regulation of key pathophysiological processes, and also in the skin. In this study, we used human keratinocytes (HaCaT cells) as an in vitro model that expresses all major ECS elements in order to systematically investigate the effects of CBG, CBC, THCV and CBGA. To this end, we analyzed the gene and protein expression of ECS components (receptors: CB1, CB2, GPR55, TRPV1 and PPARα/γ/δ; enzymes: NAPE-PLD, FAAH, DAGLα/ß and MAGL) using qRT-PCR and Western blotting, along with assessments of their functionality using radioligand binding and activity assays. In addition, we quantified the content of endocannabinoid(-like) compounds (AEA, 2-AG, PEA, etc.) using UHPLC-MS/MS. Our results demonstrated that rare pCBs modulate the gene and protein expression of distinct ECS elements differently, as well as the content of endocannabinoid(-like) compounds. Notably, they all increased CB1/2 binding, TRPV1 channel stimulation and FAAH and MAGL catalytic activity. These unprecedented observations should be considered when exploring the therapeutic potential of cannabis extracts for the treatment of human skin diseases.

The endocannabinoid system is affected by cholesterol dyshomeostasis: Insights from a murine model of Niemann Pick type C disease.

The dyshomeostasis of intracellular cholesterol trafficking is typical of the Niemann-Pick type C (NPC) disease, a fatal inherited lysosomal storage disorder presenting with progressive neurodegeneration and visceral organ involvement. In light of the well-established relevance of cholesterol in regulating the endocannabinoid (eCB) system expression and activity, this study was aimed at elucidating whether NPC disease-related cholesterol dyshomeostasis affects the functional status of the brain eCB system. To this end, we exploited a murine model of NPC deficiency for determining changes in the expression and activity of the major molecular components of the eCB signaling, including cannabinoid type-1 and type-2 (CB1 and CB2) receptors, their ligands, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG), along with their main synthesizing/inactivating enzymes. We found a robust alteration of distinct components of the eCB system in various brain regions, including the cortex, hippocampus, striatum and cerebellum, of Npc1-deficient compared to wild-type pre-symptomatic mice. Changes of the eCB component expression and activity differ from one brain structure to another, although 2-AG and AEA are consistently found to decrease and increase in each structure, respectively. The thorough biochemical characterization of the eCB system was accompanied by a behavioral characterization of Npc1-deficient mice using a number of paradigms evaluating anxiety, locomotor activity, spatial learning/memory abilities, and coping response to stressful experience. Our findings provide the first description of an early and region-specific alteration of the brain eCB system in NPC and suggest that defective eCB signaling could contribute at producing and/or worsening the neurological symptoms of this disorder.

Modulation of Endocannabinoid-Binding Receptors in Human Neuroblastoma Cells by Tunicamycin.

Endocannabinoid (eCB)-binding receptors can be modulated by several ligands and membrane environment, yet the effect of glycosylation remains to be assessed. In this study, we used human neuroblastoma SH-SY5Y cells to interrogate whether expression, cellular localization, and activity of eCB-binding receptors may depend on N-linked glycosylation. Following treatment with tunicamycin (a specific inhibitor of N-linked glycosylation) at the non-cytotoxic dose of 1 µg/mL, mRNA, protein levels and localization of eCB-binding receptors, as well as N-acetylglucosamine (GlcNAc) residues, were evaluated in SH-SY5Y cells by means of quantitative real-time reverse transcriptase-polymerase chain reaction (qRT-PCR), fluorescence-activated cell sorting (FACS), and confocal microscopy, respectively. In addition, the activity of type-1 and type-2 cannabinoid receptors (CB1 and CB2) was assessed by means of rapid binding assays. Significant changes in gene and protein expression were found upon tunicamycin treatment for CB1 and CB2, as well as for GPR55 receptors, but not for transient receptor potential vanilloid 1 (TRPV1). Deglycosylation experiments with N-glycosidase-F and immunoblot of cell membranes derived from SH-SY5Y cells confirmed the presence of one glycosylated form in CB1 (70 kDa), that was reduced by tunicamycin. Morphological studies demonstrated the co-localization of CB1 with GlcNAc residues, and showed that tunicamycin reduced CB1 membrane expression with a marked nuclear localization, as confirmed by immunoblotting. Cleavage of the carbohydrate side chain did not modify CB receptor binding affinity. Overall, these results support N-linked glycosylation as an unprecedented post-translational modification that may modulate eCB-binding receptors' expression and localization, in particular for CB1.

Membrane lipids are key modulators of the endocannabinoid-hydrolase FAAH.

Lipid composition is expected to play an important role in modulating membrane enzyme activity, in particular if the substrates are themselves lipid molecules. A paradigmatic case is FAAH (fatty acid amide hydrolase), an enzyme critical in terminating endocannabinoid signalling and an important therapeutic target. In the present study, using a combined experimental and computational approach, we show that membrane lipids modulate the structure, subcellular localization and activity of FAAH. We report that the FAAH dimer is stabilized by the lipid bilayer and shows a higher membrane-binding affinity and enzymatic activity within membranes containing both cholesterol and the natural FAAH substrate AEA (anandamide). Additionally, co-localization of cholesterol, AEA and FAAH in mouse neuroblastoma cells suggests a mechanism through which cholesterol increases the substrate accessibility of FAAH.

Domain mobility as probed by small-angle X-ray scattering may account for substrate access to the active site of two copper-dependent amine oxidases.

Amine oxidases are a family of dimeric enzymes that contain one copper(II) ion and one 2,4,5-trihydroxyphenyalanine quinone per subunit. Here, the low-resolution structures of two Cu/TPQ amine oxidases from lentil (Lens esculenta) seedlings and from Euphorbia characias latex have been determined in solution by small-angle X-ray scattering. The active site of these enzymes is highly buried and requires a conformational change to allow substrate access. The study suggests that the funnel-shaped cavity located between the D3 and D4 domains is narrower within the crystal structure, whereas in solution the D3 domain could undergo movement resulting in a protein conformational change that is likely to lead to easier substrate access.

Combination of Hydrolysable Tannins and Zinc Oxide on Enterocyte Functionality: In Vitro Insights.

The management of gastrointestinal disease in animals represents a significant challenge in veterinary and zootechnic practice. Traditionally, acute symptoms have been treated with antibiotics and high doses of zinc oxide (ZnO). However, concerns have been raised regarding the potential for microbial resistance and ecological detriment due to the excessive application of this compound. These concerns highlight the urgency of minimizing the use of ZnO and exploring sustainable nutritional solutions. Hydrolysable tannins (HTs), which are known for their role in traditional medicine for acute gastrointestinal issues, have emerged as a promising alternative. This study examined the combined effect of food-grade HTs and subtherapeutic ZnO concentration on relevant biological functions of Caco-2 cells, a widely used model of the intestinal epithelial barrier. We found that, when used together, ZnO and HTs (ZnO/HTs) enhanced tissue repair and improved epithelial barrier function, normalizing the expression and functional organization of tight junction proteins. Finally, the ZnO/HTs combination strengthened enterocytes' defense against oxidative stress induced by inflammation stimuli. In conclusion, combining ZnO and HTs may offer a suitable and practical approach for decreasing ZnO levels in veterinary nutritional applications.

Protective effects of fatty acid amide hydrolase inhibition in UVB-activated microglia.

Neuroinflammation is a hallmark of several neurodegenerative disorders that has been extensively studied in recent years. Microglia, the primary immune cells of the central nervous system (CNS), are key players in this physiological process, demonstrating a remarkable adaptability in responding to various stimuli in the eye and the brain. Within the complex network of neuroinflammatory signals, the fatty acid N-ethanolamines, in particular N-arachidonylethanolamine (anandamide, AEA), emerged as crucial regulators of microglial activity under both physiological and pathological states. In this study, we interrogated for the first time the impact of the signaling of these bioactive lipids on microglial cell responses to a sub-lethal acute UVB radiation, a physical stressor responsible of microglia reactivity in either the retina or the brain. To this end, we developed an in vitro model using mouse microglial BV-2 cells. Upon 24 h of UVB exposure, BV-2 cells showed elevated oxidative stress markers and, cyclooxygenase (COX-2) expression, enhanced phagocytic and chemotactic activities, along with an altered immune profiling. Notably, UVB exposure led to a selective increase in expression and activity of fatty acid amide hydrolase (FAAH), the main enzyme responsible for degradation of fatty acid ethanolamides. Pharmacological FAAH inhibition via URB597 counteracted the effects of UVB exposure, decreasing tumor necrosis factor α (TNF-α) and nitric oxide (NO) release and reverting reactive oxidative species (ROS), interleukin-1ß (IL-1ß), and interleukin-10 (IL-10) levels to the control levels. Our findings support the potential of enhanced fatty acid amide signaling in mitigating UVB-induced cellular damage, paving the way to further exploration of these lipids in light-induced immune responses.

Fluorimetric Assay of FAAH Activity.

Fatty acid amide hydrolase (FAAH) is the enzyme responsible for the degradation of anandamide (N-arachidonoylethanolamine, AEA) to arachidonic acid (AA) and ethanolamine. The method described here measures FAAH activity through the fluorometric arachidonoyl-7-amino-4-methyl-coumarin amide (AAMCA) substrate, which allows a simple and sensitive assay suitable for high-throughput screening tests. FAAH catalyzes the hydrolysis of AAMCA producing AA and the highly fluorescent compound 7-amino-4-methylcoumarin (AMC).

Measuring Endocannabinoid System Interaction with Biomembranes.

Understanding the correct interaction among the different components of the endocannabinoid (eCB) system is fundamental for a proper assessment of the function of eCBs as signaling molecules. The knowledge of how the membrane environment modulates the intracellular trafficking of the eCB system and its interacting proteins holds a huge potential in unraveling new mechanisms of its modulation. This chapter deals with the application of fluorescence resonance energy transfer technique to measure the binding affinity of eCB proteins to model membranes (i.e., large unilamellar vesicles, LUVs). In particular, we describe in detail the paradigmatic example of the interaction of rat recombinant fatty acid amide hydrolase with LUVs constituted of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine.

DNA uptake in swine sperm: effect of plasmid topology and methyl-beta-cyclodextrin-mediated cholesterol depletion.

Sperm-mediated gene transfer (SMGT), the ability of sperm cells to spontaneously incorporate exogenous DNA and to deliver it to oocytes during fertilization, has been proposed as an easy and efficient method for producing transgenic animals. SMGT is still undergoing development and optimization to improve the uptake efficiency of foreign DNA by sperm cells, which is a preliminary, yet critical, step for successful SMGT. Towards this aim, we developed a quantitative, real-time PCR-based assay to assess the absolute number of exogenous plasmids internalized into the spermatozoon. Using this technique, we found that the circular form of the DNA is more efficiently taken up than the linearized form. We also found that DNA internalization into the nucleus of porcine sperm cells is better under specific methyl-ß-cyclodextrin (MCD)-treated conditions, where the plasma membrane properties were altered without significantly compromising sperm physiology. These results provide the first evidence that membrane cholesterol depletion by MCD might represent a novel strategy for enhancing the ability of sperm to take up heterologous DNA.

Cellular Prion Protein Expression in the Brain Tissue from Brucella ceti-Infected Striped Dolphins (Stenella coeruleoalba).

Brucella ceti, a zoonotic pathogen of major concern to cetacean health and conservation, is responsible for severe meningo-encephalitic/myelitic lesions in striped dolphins (Stenella coeruleoalba), often leading to their stranding and death. This study investigated, for the first time, the cellular prion protein (PrPc) expression in the brain tissue from B. ceti-infected, neurobrucellosis-affected striped dolphins. Seven B. ceti-infected, neurobrucellosis-affected striped dolphins, found stranded along the Italian coastline (6) and in the Canary Islands (1), were investigated, along with five B. ceti-uninfected striped dolphins from the coast of Italy, carrying no brain lesions, which served as negative controls. Western Blot (WB) and immunohistochemistry (IHC) with an anti-PrP murine monoclonal antibody were carried out on the brain parenchyma of these dolphins. While PrPc IHC yielded inconclusive results, a clear-cut PrPc expression of different intensity was found by means of WB analyses in the brain tissue of all the seven herein investigated, B. ceti-infected and neurobrucellosis-affected cetacean specimens, with two dolphins stranded along the Italian coastline and one dolphin beached in Canary Islands also exhibiting a statistically significant increase in cerebral PrPc expression as compared to the five Brucella spp.-negative control specimens. The significantly increased PrPc expression found in three out of seven B. ceti-infected, neurobrucellosis-affected striped dolphins does not allow us to draw any firm conclusion(s) about the putative role of PrPc as a host cell receptor for B. ceti. Should this be the case, an upregulation of PrPc mRNA in the brain tissue of neurobrucellosis-affected striped dolphins could be hypothesized during the different stages of B. ceti infection, as previously shown in murine bone marrow cells challenged with Escherichia coli. Noteworthy, the inflammatory infiltrates seen in the brain and in the cervico-thoracic spinal cord segments from the herein investigated, B. ceti-infected and neurobrucellosis-affected striped dolphins were densely populated by macrophage/histiocyte cells, often harboring Brucella spp. antigen in their cytoplasm, similarly to what was reported in macrophages from mice experimentally challenged with B. abortus. Notwithstanding the above, much more work is needed in order to properly assess the role of PrPc, if any, as a host cell receptor for B. ceti in striped dolphins.

A novel role for iron in modulating the activity and membrane-binding ability of a trimmed soybean lipoxygenase-1.

Lipoxygenases (LOXs) are iron-containing enzymes that play critical roles in plants and animals. As yet, metal atom extraction, reconstitution, and substitution have not been successfully applied to soybean LOX-1 [Glycine max (L.) Merrill], a prototype member of the LOX family that is widely used in structural and kinetic studies. Here, tryptic digestion of native LOX-1, used as a control, allowed us to isolate the 60-kDa C-terminal region (termed miniLOX), that retains the catalytically active iron in a more accessible position. Then, iron was removed to obtain an unprecedented apo-miniLOX, which was reconstituted and substituted with different metal ions. These forms of miniLOX were characterized vs. native LOX-1 by kinetic analysis, near UV circular dichroism, steady-state fluorescence, and fluorescence resonance energy transfer. MiniLOX showed a 2-fold increase in the membrane-binding affinity compared with native LOX-1 and a remarkable 4-fold increase compared with apo-miniLOX (K(d)=9.2+/-1.0, 17.9+/-2.0, and 45.4+/-4.3 microM, respectively). Furthermore, miniLOX reconstituted with Fe(II) or Fe(III) partially recovered its membrane-binding ability (K(d)=21.4+/-2.4 and 18.9+/-5.5 microM, respectively), overall supporting a novel noncatalytic role for iron in the LOX family.

The endocannabinoid hydrolase FAAH is an allosteric enzyme.

Fatty acid amide hydrolase (FAAH) is a membrane-bound homodimeric enzyme that in vivo controls content and biological activity of N-arachidonoylethanolamine (AEA) and other relevant bioactive lipids termed endocannabinoids. Parallel orientation of FAAH monomers likely allows both subunits to simultaneously recruit and cleave substrates. Here, we show full inhibition of human and rat FAAH by means of enzyme inhibitors used at a homodimer:inhibitor stoichiometric ratio of 1:1, implying that occupation of only one of the two active sites of FAAH is enough to fully block catalysis. Single W445Y substitution in rat FAAH displayed the same activity as the wild-type, but failed to show full inhibition at the homodimer:inhibitor 1:1 ratio. Instead, F432A mutant exhibited reduced specific activity but was fully inhibited at the homodimer:inhibitor 1:1 ratio. Kinetic analysis of AEA hydrolysis by rat FAAH and its F432A mutant demonstrated a Hill coefficient of ~1.6, that instead was ~1.0 in the W445Y mutant. Of note, also human FAAH catalysed an allosteric hydrolysis of AEA, showing a Hill coefficient of ~1.9. Taken together, this study demonstrates an unprecedented allosterism of FAAH, and represents a case of communication between two enzyme subunits seemingly controlled by a single amino acid (W445) at the dimer interface. In the light of extensive attempts and subsequent failures over the last decade to develop effective drugs for human therapy, these findings pave the way to the rationale design of new molecules that, by acting as positive or negative heterotropic effectors of FAAH, may control more efficiently its activity.

Author Correction: The endocannabinoid hydrolase FAAH is an allosteric enzyme.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Role of Steroids on the Membrane Binding Ability of Fatty Acid Amide Hydrolase.

Background: Fatty acid amide hydrolase (FAAH) is a membrane-bound homodimeric enzyme that gets in contact with a lipophilic substrate in the lipid bilayer, and then cleaves it into water soluble products. FAAH plays a critical role in modulating in vivo content and biological activity of endocannabinoids (eCBs), and its function is affected by membrane lipids. Increasing evidence suggests that also steroids can modulate endocannabinoid signaling, both in the central nervous system and at the periphery. Methods: In this study, we interrogated the effect of six steroids with relevant biological activity (testosterone, hydrocortisone, estradiol, pregnenolone, progesterone, and cortisone) on the membrane binding ability of rat FAAH. The experimental data analysis obtained by Fluorescence Resonance Energy Transfer Spectroscopy was paralleled by computational docking analysis. Results: Our data revealed distinct effects of the different steroids on the interaction of rat FAAH with model membranes. Among them, pregnenolone was found to be the most effective in raising rat FAAH affinity for model membranes. A possible binding pocket for steroid molecules was identified by docking analysis in the membrane-embedded region of the enzyme; such a pocket could account for the observed increase of the membrane affinity in the presence of the tested molecules. Conclusions: Overall, the results point to steroids as new regulators of FAAH interaction with membranes, which may impact the biological activity of eCBs.

The anti-inflammatory agent bindarit acts as a modulator of fatty acid-binding protein 4 in human monocytic cells.

We investigated the cellular and molecular mechanisms by which bindarit, a small indazolic derivative with prominent anti-inflammatory effects, exerts its immunoregulatory activity in lipopolysaccharide (LPS) stimulated human monocytic cells. We found that bindarit differentially regulates the release of interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1), enhancing the release of IL-8 and reducing that of MCP-1. These effects specifically required a functional interaction between bindarit and fatty acid binding protein 4 (FABP4), a lipid chaperone that couples intracellular lipid mediators to their biological targets and signaling pathways. We further demonstrated that bindarit can directly interact with FABP4 by increasing its expression and nuclear localization, thus impacting on peroxisome proliferator-activated receptor γ (PPARγ) and LPS-dependent kinase signaling. Taken together, these findings suggest a potential key-role of FABP4 in the immunomodulatory activity of bindarit, and extend the spectrum of its possible therapeutic applications to FABP4 modulation.

Iron-Dependent Trafficking of 5-Lipoxygenase and Impact on Human Macrophage Activation.

5-lipoxygenase (5-LOX) is a non-heme iron-containing dioxygenase expressed in immune cells that catalyzes the two initial steps in the biosynthesis of leukotrienes. It is well known that 5-LOX activation in innate immunity cells is related to different iron-associated pro-inflammatory disorders, including cancer, neurodegenerative diseases, and atherosclerosis. However, the molecular and cellular mechanism(s) underlying the interplay between iron and 5-LOX activation are largely unexplored. In this study, we investigated whether iron (in the form of Fe3+ and hemin) might modulate 5-LOX influencing its membrane binding, subcellular distribution, and functional activity. We proved by fluorescence resonance energy transfer approach that metal removal from the recombinant human 5-LOX, not only altered the catalytic activity of the enzyme, but also impaired its membrane-binding. To ascertain whether iron can modulate the subcellular distribution of 5-LOX in immune cells, we exposed THP-1 macrophages and human primary macrophages to exogenous iron. Cells exposed to increasing amounts of Fe3+ showed a redistribution (ranging from ~45 to 75%) of the cytosolic 5-LOX to the nuclear fraction. Accordingly, confocal microscopy revealed that acute exposure to extracellular Fe3+, as well as hemin, caused an overt increase in the nuclear fluorescence of 5-LOX, accompanied by a co-localization with the 5-LOX activating protein (FLAP) both in THP-1 macrophages and human macrophages. The functional relevance of iron overloading was demonstrated by a marked induction of the expression of interleukin-6 in iron-treated macrophages. Importantly, pre-treatment of cells with the iron-chelating agent deferoxamine completely abolished the hemin-dependent translocation of 5-LOX to the nuclear fraction, and significantly reverted its effect on interleukin-6 overexpression. These results suggest that exogenous iron modulates the biological activity of 5-LOX in macrophages by increasing its ability to bind to nuclear membranes, further supporting a role for iron in inflammation-based diseases where its homeostasis is altered and suggesting further evidence of risks related to iron overload.

Immunohistochemical investigations on Brucella ceti-infected, neurobrucellosis-affected striped dolphins (Stenella coeruleoalba).

Bacteria of the genus Brucella cause brucellosis, an infectious disease common to humans as well as to terrestrial and aquatic mammals. Since 1994 several cases of Brucella spp. infection have been reported in marine mammals worldwide. While sero-epidemiological data suggest that Brucella spp. infection is widespread globally, detecting Brucella spp.-associated antigens by immunohistochemistry (IHC) in tissues from infected animals is often troublesome. The present study was aimed at investigating, by means of IHC based upon the utilization of an anti-Brucella LPS monoclonal antibody (MAb), the central nervous system (CNS) immunoreactivity shown by B. ceti-infected, neurobrucellosis-affected striped dolphins. The aforementioned MAb, previously characterized by means of ELISA and Western Blotting techniques, was able to immunohistochemically detect smooth brucellae both within the CNS from B. ceti-infected striped dolphins and within a range of tissues from Brucella spp.-infected domestic ruminants. In conclusion, the results of the present study are of relevance both from the B. ceti infection's diagnostic and pathogenetic standpoints.

Structural properties of plant and mammalian lipoxygenases. Temperature-dependent conformational alterations and membrane binding ability.

Lipoxygenases form a heterogeneous family of lipid peroxidizing enzymes, which have been implicated in the synthesis of inflammatory mediators, in cell development and in the pathogenesis of various diseases with major health and political relevance (atherosclerosis, osteoporosis). The crystal structures of various lipoxygenase-isoforms have been reported, and X-ray coordinates for enzyme-ligand complexes are also available. Although the 3D-structures of plant and animal lipoxygenase-isoforms are very similar, recent small-angle X-ray scattering data suggested a higher degree of motional flexibility of mammalian isozymes in aqueous solutions. To explore the molecular basis for these differences we performed dynamic fluorescence measurements that allowed us to study temperature-induced conformational changes arising from three-dimensional fluctuations of the protein matrix. For this purpose, we first investigated the impact of elevated temperature on activity, secondary structure, tertiary structure dynamics and conformational alterations. Applying fluorescence resonance energy transfer we also tested the membrane binding properties of the two lipoxygenase-isoforms, and compared their binding parameters. Taken together, our results indicate that the rabbit 12/15-lipoxygenase is more susceptible to temperature-induced structural alterations than the soybean enzyme. Moreover, the rabbit enzyme exhibits a higher degree of conformational flexibility of the entire protein molecule (global flexibility) and offers the possibility of augmented substrate movement at the catalytic center (local flexibility).

Structural characterization of the ceruloplasmin: lactoferrin complex in solution.

Ceruloplasmin is a copper protein found in vertebrate plasma, which belongs to the family of multicopper oxidases. Like transferrin of the blood plasma, lactoferrin, the iron-containing protein of human milk, saliva, tears, seminal plasma and of neutrophilic leukocytes tightly binds two ferric ions. Human lactoferrin and ceruloplasmin have been previously shown to interact both in vivo and in vitro forming a complex. Here we describe a study of the conformation of the human lactoferrin/ceruloplasmin complex in solution using small angle X-ray scattering. Our ab initio structural analysis shows that the complex has a 1:1 stoichiometry and suggests that complex formation occurs without major conformational rearrangements of either protein. Rigid-body modeling of the mutual arrangement of proteins in the complex essentially yields two families of solutions. Final discrimination is possible when integrating in the modeling process extra information translating into structural constraints on the interaction between the two partners.