Cannabinoid CB1 receptor elevation of intracellular calcium in neuroblastoma SH-SY5Y cells: Interactions with muscarinic and δ-opioid receptors

Isobolographic Analysis of the Cytoprotective Effect of Dapsone and Cannabidiol Alone or Combination upon Oxygen-Glucose Deprivation/Reoxygenation Model in SH-SY5Y Cells

Oxidative stress and apoptosis cell death are critical secondary damage mechanisms that lead to losing neighboring healthy tissue after cerebral ischemia. This study aims to characterize the type of interaction between dapsone (DDS) and cannabidiol (CBD) and its cytoprotective effect in an in vitro model of oxygen and glucose deprivation for 6 h followed by 24 h of reoxygenation (OGD/R), using the SH-SY5Y cell line. For the combined concentrations, an isobolographic study was designed to determine the optimal concentration-response combinations. Cell viability was evaluated by measuring the lactate dehydrogenase (LDH) release and 3-[4, 5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assays. Also, the reactive oxygen species (ROS) and reduced glutathione (GSH) levels were analyzed as oxidative stress markers. Finally, caspase-3 activity was evaluated as a marker cell death by apoptosis. The results showed a decrease in cell viability, an increase in oxidant stress, and the activity of caspase-3 by the effect of OGD/R. Meanwhile, both DDS and CBD demonstrated antioxidant, antiapoptotic, and cytoprotective effects in a concentration-response manner. The isobolographic study indicated that the concentration of 2.5 µM of DDS plus 0.05 µM of CBD presented a synergistic effect so that in treatment, cell death due to OGD/R decreased. The findings indicate that DDS-CBD combined treatment may be a helpful therapy in cerebral ischemia with reperfusion.

M3 Receptor Pathway Stimulates Rapid Transcription of the CB1 Receptor Activation through Calcium Signalling and the CNR1 Gene Promoter

In this study, we have investigated a possible mechanism that enables CB₁/M₃ receptor cross-talk, using SH-SY5Y cells as a model system. Our results show that M₃ receptor activation initiates signaling that rapidly upregulates the CNR1 gene, resulting in a greatly potentiated CB₁ receptor response to agonists. Calcium homeostasis plays an essential intermediary role in this functional CB₁/M₃ receptor cross-talk. We show that M₃ receptor-triggered calcium release greatly increases CB₁ receptor expression via both transcriptional and translational activity, by enhancing CNR1 promoter activity. The co-expression of M₃ and CB₁ receptors in brain areas such as the nucleus accumbens and amygdala support the hypothesis that the altered synaptic plasticity observed after exposure to cannabinoids involves cross-talk with the M₃ receptor subtype. In this context, M₃ receptors and their interaction with the cannabinoid system at the transcriptional level represent a potential pharmacogenomic target not only for the develop of new drugs for addressing addiction and tolerance. but also to understand the mechanisms underpinning response stratification to cannabinoids.

Fluorescence-Based Assay for TRPV1 Channels

The transient receptor potential vanilloid 1 ion channel (TRPV1) is a ligand-gated nonselective calcium-permeant cation channel involved in the detection of a wide variety of chemical and physical noxious stimuli, ranging from exogenous and endogenous ligands to noxious heat (>42 °C) and low pH (pH < 5.2). Due to its central role in pain and hyperalgesia, TRPV1 is considered a relevant therapeutic target for the development of analgesic and anti-inflammatory drugs potentially useful to relieve chronic, neuropathic, and inflammatory pain and to treat disorders such as inflammatory bowel disease. In this view, the availability of in vitro assays for the screening of novel TRPV1 modulators is highly desirable. Since TRPV1 activation leads to an increase in the intracellular calcium (Ca²⁺) levels, the use of Ca²⁺ fluorescent indicators represent a valuable and sensitive tool for monitoring such intracellular changes. In this chapter, we describe methods for recording and monitoring Ca²⁺ signals through the fluorescent indicators Fluo-4 acetoxymethyl (AM) and Fura-2 AM in HEK-293 cells transfected with TRPV1 or other thermoTRP channels.

ML218 HCl Is More Efficient Than Capsaicin in Inhibiting Bacterial Antigen-Induced Cal 27 Oral Cancer Cell Proliferation

The bacterial antigen, lipopolysaccharide (LPS) and disruptions in calcium channels are independently known to influence oral cancer progression. Previously, we found that bacterial antigens, LPS and lipoteichoic acid (LTA) act as confounders during the action of capsaicin on Cal 27 oral cancer proliferation. As calcium channel drugs may affect oral cancer cell proliferation, we investigated the effect of ML218 HCl, a T-type voltage-gated calcium channel blocker, on the proliferation of Cal 27 oral cancer cells. We hypothesized that ML218 HCl could effectively reduce LPS-induced oral cancer cell proliferation. LPS and LTA antigens were added to Cal 27 oral cancer cells either prior to and/or concurrently with ML218 HCl treatment, and the efficacy of the treatment was evaluated by measuring Cal 27 proliferation, cell death and apoptosis. ML218 HCl inhibited oral cancer cell proliferation, increased apoptosis and cell death, but their efficacy was significantly reduced in the presence of bacterial antigens. ML218 HCl proved more effective than capsaicin in reducing bacterial antigen-induced Cal 27 oral cancer cell proliferation. Our results also suggest an interplay of proliferation factors during the bacterial antigens and calcium channel drug interaction in Cal 27. Bacterial antigen reduction of drug efficacy should be considered for developing newer pharmacological agents or testing the efficacy of the existing oral cancer chemotherapeutic agents. Finally, voltage gated calcium channel drugs should be considered for future oral cancer research.

Regulation of Calcium Oscillations in β-Cells by Co-activated Cannabinoid Receptors

Pharmacological treatment of pancreatic β cells targeting cannabinoid receptors 1 and 2 (CB1 and CB2) has been shown to result in significant effects on insulin release, possibly by modulating intracellular calcium levels ([Ca²⁺]_i). It is unclear how the interplay of CB1 and CB2 affects insulin secretion. Here, we demonstrate by the use of highly specific receptor antagonists and the recently developed photo-releasable endocannabinoid 2-arachidonoylglycerol that both receptors have counteracting effects on cytosolic calcium oscillations. We further show that both receptors are juxtaposed in a way that increases [Ca²⁺]_i oscillations in silent β cells but dampens them in active ones. This study highlights a functional role of CB1 and CB2 acting in concert as a compensator/attenuator switch for regulating β cell excitability.

Cannabinoid receptor subtype influence on neuritogenesis in human SH-SY5Y cells

Human SH-SY5Y neuroblastoma cells stably expressing exogenous CB₁ (CB₁XS) or CB₂ (CB₂XS) receptors were developed to investigate endocannabinoid signaling in the extension of neuronal projections. Expression of cannabinoid receptors did not alter proliferation rate, viability, or apoptosis relative to parental SH-SY5Y. Transcripts for endogenous cannabinoid system enzymes (diacylglycerol lipase, monoacylglycerol lipase, α/β-hydrolase domain containing proteins 6 and 12, N-acyl phosphatidylethanolamine-phospholipase D, and fatty acid amide hydrolase) were not altered by CB₁ or CB₂ expression. Endocannabinoid ligands 2-arachidonoylglycerol (2-AG) and anandamide were quantitated in SH-SY5Y cells, and diacylglycerol lipase inhibitor tetrahydrolipstatin decreased 2-AG abundance by 90% but did not alter anandamide abundance. M3 muscarinic agonist oxotremorine M, and inhibitors of monoacylglycerol lipase and α/β hydrolase domain containing proteins 6 &12 increased 2-AG abundance. CB₁ receptor expression increased lengths of short (<30 μm) and long (>30 μm) projections, and this effect was significantly reduced by tetrahydrolipstatin, indicative of stimulation by endogenously produced 2-AG. Pertussis toxin, Gβγ inhibitor gallein, and β-arrestin inhibitor barbadin did not significantly alter long projection length in CB₁XS, but significantly reduced short projections, with gallein having the greatest inhibition. The rho kinase inhibitor Y27632 increased CB₁ receptor-mediated long projection extension, indicative of actin cytoskeleton involvement. CB₁ receptor expression increased GAP43 and ST8SIA2 mRNA and decreased ITGA1 mRNA, whereas CB₂ receptor expression increased NCAM and SYT mRNA. We propose that basal endogenous production of 2-AG provides autocrine stimulation of CB₁ receptor signaling through Gi/o, Gβγ, and β-arrestin mechanisms to promote neuritogenesis, and rho kinase influences process extension.

Gestational exposures to organophosphorus insecticides: From acute poisoning to developmental neurotoxicity

For over three-quarters of a century, organophosphorus (OP) insecticides have been ubiquitously used in agricultural, residential, and commercial settings and in public health programs to mitigate insect-borne diseases. Their broad-spectrum insecticidal effectiveness is accounted for by the irreversible inhibition of acetylcholinesterase (AChE), the enzyme that catalyzes acetylcholine (ACh) hydrolysis, in the nervous system of insects. However, because AChE is evolutionarily conserved, OP insecticides are also toxic to mammals, including humans, and acute OP intoxication remains a major public health concern in countries where OP insecticide usage is poorly regulated. Environmental exposures to OP levels that are generally too low to cause marked inhibition of AChE and to trigger acute signs of intoxication, on the other hand, represent an insidious public health issue worldwide. Gestational exposures to OP insecticides are particularly concerning because of the exquisite sensitivity of the developing brain to these insecticides. The present article overviews and discusses: (i) the health effects and therapeutic management of acute OP poisoning during pregnancy, (ii) epidemiological studies examining associations between environmental OP exposures during gestation and health outcomes of offspring, (iii) preclinical evidence that OP insecticides are developmental neurotoxicants, and (iv) potential mechanisms underlying the developmental neurotoxicity of OP insecticides. Understanding how gestational exposures to different levels of OP insecticides affect pregnancy and childhood development is critical to guiding implementation of preventive measures and direct research aimed at identifying effective therapeutic interventions that can limit the negative impact of these exposures on public health.

Analysis of natural product regulation of cannabinoid receptors in the treatment of human disease

The organized, tightly regulated signaling relays engaged by the cannabinoid receptors (CBs) and their ligands, G proteins and other effectors, together constitute the endocannabinoid system (ECS). This system governs many biological functions including cell proliferation, regulation of ion transport and neuronal messaging. This review will firstly examine the physiology of the ECS, briefly discussing some anomalies in the relay of the ECS signaling as these are consequently linked to maladies of global concern including neurological disorders, cardiovascular disease and cancer. While endogenous ligands are crucial for dispatching messages through the ECS, there are also commonalities in binding affinities with copious exogenous ligands, both natural and synthetic. Therefore, this review provides a comparative analysis of both types of exogenous ligands with emphasis on natural products given their putative safer efficacy and the role of Δ9-tetrahydrocannabinol (Δ9-THC) in uncovering the ECS. Efficacy is congruent to both types of compounds but noteworthy is the effect of a combination therapy to achieve efficacy without unideal side-effects. An example is Sativex that displayed promise in treating Huntington's disease (HD) in preclinical models allowing for its transition to current clinical investigation. Despite the in vitro and preclinical efficacy of Δ9-THC to treat neurodegenerative ailments, its psychotropic effects limit its clinical applicability to treating feeding disorders. We therefore propose further investigation of other compounds and their combinations such as the triterpene, α,β-amyrin that exhibited greater binding affinity to CB₁ than CB₂ and was more potent than Δ9-THC and the N-alkylamides that exhibited CB₂ selective affinity; the latter can be explored towards peripherally exclusive ECS modulation. The synthetic CB₁ antagonist, Rimonabant was pulled from commercial markets for the treatment of diabetes, however its analogue SR144528 maybe an ideal lead molecule towards this end and HU-210 and Org27569 are also promising synthetic small molecules.

Synergistic combinations of the dual enkephalinase inhibitor PL265 given orally with various analgesic compounds acting on different targets, in a murine model of cancer-induced bone pain

BACKGROUND

The first line pharmacological treatment of cancer pain is morphine and surrogates but a significant pain relief and a reduction of the side-effects of these compounds makes it necessary to combine them with other drugs acting on different targets. The aim of this study was to measure the antinociceptive effect on cancer-induced bone pain resulting from the association of the endogenous opioids enkephalin and non-opioid analgesic drugs. For this purpose, PL265 a new orally active single dual inhibitor of the two degrading enkephalins enzymes, neprilysin (NEP) and aminopeptidase N (APN) was used. It strictly increased the levels of enkephalin at their sites of releases. The selected non-opioid compounds are: gabapentin, A-317491 (P2X₃ receptor antagonist), ACEA (CB1 receptor antagonist), AM1241 (CB2 receptor antagonist), JWH-133 (CB2 receptor antagonist), URB937 (FAAH inhibitor), and NAV26 (Nav1.7 channel blocker).

METHODS

Experiments. Experiments were performed in 5-6 weeks old (26-33g weight) C57BL/6 mice. Cell culture and cell inoculation. B16-F10 melanoma cells were cultured and when preconfluent, treated and detached. Finally related cells were resuspended to obtain a concentration of 2×10⁶ cells/100μL. Then 10⁵ cells were injected into the right tibial medullar cavity. Control mice were treated by killed cells by freezing. Behavioural studies. Thermal withdrawal latencies were measured on a unilatered hot plate (UHP) maintained at 49±0.2°C. Mechanical threshold values were obtained by performing the von Frey test using the "up and down" method. To evaluate the nature (additive or synergistic) of the interactions between PL265 and different drugs, an isobolographic analysis following the method described by Tallarida was performed.

RESULTS

The results demonstrate the ability of PL265, a DENKI that prevents the degradation of endogenous ENKs, to counteract cancer-induced bone thermal hyperalgesia in mice, by exclusively stimulating peripheral opioid receptors as demonstrated by used of an opioid antagonist unable to enter the brain. The development of such DENKIs, endowed with druggable pharmacokinetic characteristics, such as good absorption by oral route, can be considered as an important step in the development of much needed novel antihyperalgesic drugs. Furthermore, all the tested combinations resulted in synergistic antihyperalgesic effects. As shown here, the greatest synergistic antinociceptive effect (doses could be lowered by 70%) was produced by the combination of PL265 with the P2X₃ receptor antagonist (A-317491), cannabinoid CB1 receptor agonist (exogenous, ACEA and endogenous URB937-protected-AEA) and Na_v1.7 blocker (NAV26) whose mechanism of action involves the direct activation of the enkephalinergic system.

CONCLUSIONS

These multi-target-based antinociceptive strategies using combinations of non-opioid drugs with dual inhibitors of enkephalin degrading enzymes may bring therapeutic advantages in terms of efficacy and safety by allowing the reduction of doses of one of the compounds or of both, which is of the utmost interest in the chronic treatment of cancer pain.

IMPLICATIONS

This article presents synergistic antinociceptive effect produced by the combination of PL265 with non-opioid analgesic drugs acting via unrelated mechanisms. These multi-target-based antinociceptive strategies may bring therapeutic advantages by allowing the reduction of doses, which is of great interest in the chronic treatment of cancer pain.

Assay of TRPV1 Receptor Signaling

The transient receptor potential vanilloid-1 ion channel (TRPV1) is a non-selective ligand-gated cation channel. It is an integrator of a wide variety of exogenous and endogenous physical and chemical stimuli, including capsaicin, noxious heat (>42 °C), and protons (pH < 5.2). TRPV1 is expressed predominantly in primary sensory neurons involved in pain sensation, but also in other neuronal cell types, in the plasma membrane of different non-neuronal cells such as immune cells, keratinocytes, smooth muscle cells, and in the urothelium. Some of these cell types are involved in inflammation. When activated, TRPV1 leads to the gating of cations, including Ca(2+), thus generating changes in intracellular Ca(2+) concentration. Calcium ions play fundamental roles in many cellular processes, virtually in all cells. The use of Ca(2+) fluorescent indicators is a tool for monitoring intracellular Ca(2+) concentration.In this chapter, we describe a method for recording and monitoring Ca(2+) signals through the single wavelength fluorescent indicator Fluo-4 acetoxymethyl (AM), and the ratiometric fluorescent indicator Fura-2 AM in HEK-293 cells transfected with TRPV1 and other TRP channels. TRPV1 pharmacological modulation may potentially represent a strategy for the control of pain and inflammatory conditions in a variety of diseases and injury states.

Identification of N-arachidonoyl dopamine as a highly biased ligand at cannabinoid CB1 receptors

BACKGROUND AND PURPOSE

N-arachidonyl dopamine (NADA) has been identified as a putative endocannabinoid, but there is little information about which signalling pathways it activates. The purpose of this study was to identify the signalling pathways activated by NADA in vitro.

EXPERIMENTAL APPROACH

Human or rat cannabinoid CB1 receptors were expressed in AtT20, CHO or HEK 293 cells. NADA displacement of radiolabelled cannabinoids, and CB1 receptor mediated activation of K channels or ERK phosphorylation, release of intracellular calcium ([Ca]i ) and modulation of adenylyl cyclase were measured in addition to NADA effects on CB1 receptor trafficking.

KEY RESULTS

At concentrations up to 30 μM, NADA failed to activate any signalling pathways via CB1 receptors, with the exception of mobilization of [Ca]i . The elevations of [Ca]i were insensitive to pertussis toxin, and reduced or abolished by blockers of Gq /11 -dependent processes including U73122, thapsigargin and a peptide antagonist of Gq /11 activation. Prolonged NADA incubation produced modest loss of cell surface CB1 receptors. The prototypical cannabinoid agonist CP55940 signalled as expected in all assays.

CONCLUSIONS AND IMPLICATIONS

NADA is an ineffective agonist at most canonical cannabinoid receptor signalling pathways, but did promote mobilization of [Ca]i via Gq -dependent processes and some CB1 receptor trafficking. This signalling profile is distinct from that of any known cannabinoid, and suggests that NADA may have a unique spectrum of effects in vivo. Our results also indicate that it may be possible to identify highly biased CB1 receptor ligands displaying a subset of the pharmacological or therapeutic effects usually attributed to CB1 ligands.

The role of intracellular calcium for the development and treatment of neuroblastoma

Neuroblastoma is the second most common paediatric cancer. It developsfrom undifferentiated simpatico-adrenal lineage cells and is mostly sporadic; however, theaetiology behind the development of neuroblastoma is still not fully understood. Intracellularcalcium ([Ca2+]i) is a secondary messenger which regulates numerous cellular processesand, therefore, its concentration is tightly regulated. This review focuses on the role of[Ca2+]i in differentiation, apoptosis and proliferation in neuroblastoma. It describes themechanisms by which [Ca2+]i is regulated and how it modulates intracellular pathways.Furthermore, the importance of [Ca2+]i for the function of anti-cancer drugs is illuminatedin this review as [Ca2+]i could be a target to improve the outcome of anti-cancer treatmentin neuroblastoma. Overall, modulations of [Ca2+]i could be a key target to induce apoptosisin cancer cells leading to a more efficient and effective treatment of neuroblastoma.

The endocannabinoid 2-AG controls skeletal muscle cell differentiation via CB1 receptor-dependent inhibition of Kv7 channels

Little is known of the involvement of endocannabinoids and cannabinoid receptors in skeletal muscle cell differentiation. We report that, due to changes in the expression of genes involved in its metabolism, the levels of the endocannabinoid 2-arachidonoylglycerol (2-AG) are decreased both during myotube formation in vitro from murine C2C12 myoblasts and during mouse muscle growth in vivo. The endocannabinoid, as well as the CB1 agonist arachidonoyl-2-chloroethylamide, prevent myotube formation in a manner antagonized by CB1 knockdown and by CB1 antagonists, which, per se, instead stimulate differentiation. Importantly, 2-AG also inhibits differentiation of primary human satellite cells. Muscle fascicles from CB1 knockout embryos contain more muscle fibers, and postnatal mice show muscle fibers of an increased diameter relative to wild-type littermates. Inhibition of Kv7.4 channel activity, which plays a permissive role in myogenesis and depends on phosphatidylinositol 4,5-bisphosphate (PIP2), underlies the effects of 2-AG. We find that CB1 stimulation reduces both total and Kv7.4-bound PIP2 levels in C2C12 cells and inhibits Kv7.4 currents in transfected CHO cells. We suggest that 2-AG is an endogenous repressor of myoblast differentiation via CB1-mediated inhibition of Kv7.4 channels.

Care and feeding of the endocannabinoid system: a systematic review of potential clinical interventions that upregulate the endocannabinoid system

Background

The “classic” endocannabinoid (eCB) system includes the cannabinoid receptors CB₁ and CB₂, the eCB ligands anandamide (AEA) and 2-arachidonoylglycerol (2-AG), and their metabolic enzymes. An emerging literature documents the “eCB deficiency syndrome” as an etiology in migraine, fibromyalgia, irritable bowel syndrome, psychological disorders, and other conditions. We performed a systematic review of clinical interventions that enhance the eCB system—ways to upregulate cannabinoid receptors, increase ligand synthesis, or inhibit ligand degradation.

Methodology/Principal Findings

We searched PubMed for clinical trials, observational studies, and preclinical research. Data synthesis was qualitative. Exclusion criteria limited the results to 184 in vitro studies, 102 in vivo animal studies, and 36 human studies. Evidence indicates that several classes of pharmaceuticals upregulate the eCB system, including analgesics (acetaminophen, non-steroidal anti-inflammatory drugs, opioids, glucocorticoids), antidepressants, antipsychotics, anxiolytics, and anticonvulsants. Clinical interventions characterized as “complementary and alternative medicine” also upregulate the eCB system: massage and manipulation, acupuncture, dietary supplements, and herbal medicines. Lifestyle modification (diet, weight control, exercise, and the use of psychoactive substances—alcohol, tobacco, coffee, cannabis) also modulate the eCB system.

Conclusions/Significance

Few clinical trials have assessed interventions that upregulate the eCB system. Many preclinical studies point to other potential approaches; human trials are needed to explore these promising interventions.

QRFP induces aldosterone production via PKC and T-type calcium channel-mediated pathways in human adrenocortical cells: evidence for a novel role of GPR103

Hormonal regulation of adrenal function occurs primarily through activation of GPCRs. GPCRs are central to many of the body's endocrine and neurotransmitter pathways. Recently, it was shown that activation of GPR103 by its ligand QRFP induced feeding, locomotor activity, and metabolic rate, and QRFP is bioactive in adipose tissue of obese individuals. Given that the adrenal gland is a pivotal organ for energy balance and homeostasis, we hypothesized that GPR103 and QRFP are involved in steroidogenic responses. Using qRT-PCR and immunohistochemistry, we mapped both GPR103 and QRFP in human fetal and adult adrenal gland as well as rat adrenals. Both were primarily localized in the adrenal cortex but not in the medulla. Activation of GPR103 in human adrenocortical H295R cells led to a decrease in forskolin-increased cAMP and an increase of intracellular Ca(2+) levels. In addition, treatment of H295R cells with QRFP induced aldosterone and cortisol secretion as measured by ELISA. These increases were accompanied by increased expression and activity of StAR, CYB11B1, and CYP11B2 as assessed by qRT-PCR and luciferase reporter assay, respectively. Using specific inhibitors, we also demonstrated that aldosterone induction involves MAPK, PKC, and/or T-type Ca(2+) channel-dependent pathways. These novel data demonstrate that QRFP induces adrenal steroidogenesis in vitro by regulating key steroidogenic enzymes involving MAPK/PKC and Ca(2+) signaling pathways.

Signaling cross-talk between cannabinoid and muscarinic systems actives Rho-kinase and increases the contractile responses of the bovine ciliary muscle

The aim of the present study was to evaluate the role of a possible interaction between cannabinoid and muscarinic systems, both widely expressed in the ocular structure and involved in the control of bovine ciliary muscle contractility and intraocular pressure modulation. The ciliary muscle strips isolated by bovine eyes were exposed cumulatively to anandamide in the presence and in the absence of carbachol (5 nM), in a miograph system for isometric recording. The experiments were also conducted in the presence of AM251 (100 nM), 4-DAMP (100 nM), Pertussis toxin (500 ng/ml), U73122 (0.1 and 1 μM), chelerythrine (1 and 10 μM) and Y27632 (1 and 10 μM). Contractile responses were expressed as the percentage of 10 μM carbachol-induced contraction. The anandamide-induced contraction on bovine ciliary muscle strips was enhanced by the previous stimulation of Gq-protein-coupled muscarinic M3 receptors with carbachol. The contractile response to anandamide plus carbachol was affected by different inhibitors such as Pertussis toxin, phospholipase C, protein kinase C and Rho-kinase. The key results of the present study show that sequential activation of muscarinic M3 receptors and cannabinoid CB1 receptors produce synergistic contractile effects of the bovine ciliary muscle by involving the activation of Rho-kinase and protein kinase C.

Neuropeptide FF activates ERK and NF kappa B signal pathways in differentiated SH-SY5Y cells

Neuropeptide FF (NPFF) has been reported to play important roles in regulating diverse biological processes. However, little attention has been focused on the downstream signal transduction pathway of NPFF. Here, we used the differentiated neuroblastoma cell line, dSH-SY5Y, which endogenously expresses hNPFF2 receptor, to investigate the signal transduction downstream of NPFF. In particular we investigated the regulation of the extracellular signal-regulated protein kinase (ERK) and the nuclear factor kappa B (NF-κB) pathways by NPFF in these cells. NPFF rapidly and transiently stimulated ERK. H89, a selective inhibitor of cyclic AMP-dependent protein kinase A (PKA), inhibited the NPFF-activated ERK pathway, indicating the involvement of PKA in the NPFF-induced ERK activation. Down-regulation of nitric oxide synthases also attenuated NPFF-induced ERK activation, suggesting that a nitric oxide synthase-dependent pathway is involved. Moreover, the core upstream components of the NF-κB pathway were also significantly activated in response to NPFF, suggesting that the NF-κB pathway is involved in the signal transduction pathway of NPFF. Collectively, these data demonstrate that nitric oxide synthases are involved in the signal transduction pathway of NPFF, and provide the first evidence for the interaction between NPFF and the NF-κB pathway. These advances in our interpretation of the NPFF pathway mechanism will aid the comprehensive understanding of its function and provide novel molecular insight for further study of the NPFF system.

Modulation of sweet responses of taste receptor cells

Taste receptor cells play a major role in detection of chemical compounds in the oral cavity. Information derived from taste receptor cells, such as sweet, bitter, salty, sour and umami is important for evaluating the quality of food components. Among five basic taste qualities, sweet taste is very attractive for animals and influences food intake. Recent studies have demonstrated that sweet taste sensitivity in taste receptor cells would be affected by leptin and endocannabinoids. Leptin is an anorexigenic mediator that reduces food intake by acting on leptin receptor Ob-Rb in the hypothalamus. Endocannabinoids such as anandamide [N-arachidonoylethanolamine (AEA)] and 2-arachidonoyl glycerol (2-AG) are known as orexigenic mediators that act via cannabinoid receptor 1 (CB1) in the hypothalamus and limbic forebrain to induce appetite and stimulate food intake. At the peripheral gustatory organs, leptin selectively suppresses and endocannabinoids selectively enhance sweet taste sensitivity via Ob-Rb and CB1 expressed in sweet sensitive taste cells. Thus leptin and endocannabinoids not only regulate food intake via central nervous systems but also modulate palatability of foods by altering peripheral sweet taste responses. Such reciprocal modulation of leptin and endocannabinoids on peripheral sweet sensitivity may play an important role in regulating energy homeostasis.

Contrasting protective effects of cannabinoids against oxidative stress and amyloid-β evoked neurotoxicity in vitro

Cannabinoids have been widely reported to have neuroprotective properties in vitro and in vivo. In this study we compared the effects of CB1 and CB2 receptor-selective ligands, the endocannabinoid anandamide and the phytocannabinoid cannabidiol, against oxidative stress and the toxic hallmark Alzheimer's protein, β-amyloid (Aβ) in neuronal cell lines. PC12 or SH-SY5Y cells were selectively exposed to either hydrogen peroxide, tert-butyl hydroperoxide or Aβ, alone or in the presence of the CB1 specific agonist arachidonyl-2'-chloroethylamide (ACEA), CB2 specific agonist JWH-015, anandamide or cannabidiol. Cannabidiol improved cell viability in response to tert-butyl hydroperoxide in PC12 and SH-SY5Y cells, while hydrogen peroxide-mediated toxicity was unaffected by cannabidiol pretreatment. Aβ exposure evoked a loss of cell viability in PC12 cells. Of the cannabinoids tested, only anandamide was able to inhibit Aβ-evoked neurotoxicity. ACEA had no effect on Aβ-evoked neurotoxicity, suggesting a CB1 receptor-independent effect of anandamide. JWH-015 pretreatment was also without protective influence on PC12 cells from either pro-oxidant or Aβ exposure. None of the cannabinoids directly inhibited or disrupted preformed Aβ fibrils and aggregates. In conclusion, the endocannabinoid anandamide protects neuronal cells from Aβ exposure via a pathway unrelated to CB1 or CB2 receptor activation. The protective effect of cannabidiol against oxidative stress does not confer protection against Aβ exposure, suggesting divergent pathways for neuroprotection of these two cannabinoids.

Gut feelings about the endocannabinoid system

Stemming from the centuries-old and well known effects of Cannabis on intestinal motility and secretion, research on the role of the endocannabinoid system in gut function and dysfunction has received ever increasing attention since the discovery of the cannabinoid receptors and their endogenous ligands, the endocannabinoids. In this article, some of the most recent developments in this field are discussed, with particular emphasis on new data, most of which are published in Neurogastroenterology & Motility, on the potential tonic endocannabinoid control of intestinal motility, the function of cannabinoid type-1 (CB1) receptors in gastric function, visceral pain, inflammation and sepsis, the emerging role of cannabinoid type-2 (CB2) receptors in the gut, and the pharmacology of endocannabinoid-related molecules and plant cannabinoids not necessarily acting via cannabinoid CB1 and CB2 receptors. These novel data highlight the multi-faceted aspects of endocannabinoid function in the GI tract, support the feasibility of the future therapeutic exploitation of this signaling system for the treatment of GI disorders, and leave space for some intriguing new hypotheses on the role of endocannabinoids in the gut.

Endogenous opiates and behavior: 2009

This paper is the 32nd consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2009 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Rimonabant inhibits TNF-α-induced endothelial IL-6 secretion via CB1 receptor and cAMP-dependent protein kinase pathway

AIM

To investigate whether rimonabant, a cannabinoid receptor antagonist, had inhibitory effects on inflammatory reactions in human umbilical vein endothelial cells (HUVEC).

METHODS

TNF-α-induced IL-6 production was measured by ELISA and effects on related signaling pathways were investigated by immunoblot analysis. Cellular cAMP level was measured using kinase-coupled luciferase reaction.

RESULTS

Rimonabant at 1 and 10 μmol/L significantly inhibited TNF-α-induced IL-6 production when added 15, 30 and 60 minutes before TNF-α treatment. Rimonabant also inhibited TNF-α-induced phosphorylation of IκB kinase (IKK) α/β and IκB-α degradation. ACEA, a cannabinoid receptor subtype 1 (CB1) agonist, added before rimonabant abolished the former effects of rimonabant. H-89, an inhibitor of cAMP-dependent protein kinase (PKA), abolished the inhibitory effects of rimonabant on TNF-α induced IL-6 production. Rimonabant also increased the phosphorylation of PKA regulatory subunit II (PKA-RII), implying the essential role of PKA activation in the inhibitory effects of rimonabant. Treatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor, wortmannin did not abolish the inhibitory effects of rimonabant on TNF-α induced IL-6 production.

CONCLUSION

Rimonabant had anti-inflammatory effects on endothelial cells and inhibited TNF-α-induced IKKα/β phosphorylation, IκB-α degradation and IL-6 production in HUVEC. This effect was related to CB1 antagonism and PKA activation.