Mitochondrial Localization of CB1 in Progesterone-producing Cells of Ovarian Interstitial Glands of Adult Mice.

Localization of cannabinoid receptor type 1 (CB1) immunoreactivity on mitochondrial membranes, at least their outer membranes distinctly, was detected in progesterone-producing cells characterized by mitochondria having tubular cristae and aggregations of lipid droplets in ovarian interstitial glands in situ of adult mice. Both immunoreactive and immunonegative mitochondria were contained in one and the same cell. Considering that the synthesis of progesterone is processed in mitochondria, the mitochondrial localization of CB1 in the interstitial gland cells suggests the possibility that endocannabinoids modulate the synthetic process of progesterone in the cells through CB1.

Fit-for-purpose based testing and validation of antibodies to amino- and carboxy-terminal domains of cannabinoid receptor 1.

Specific and selective anti-CB1 antibodies are among the most powerful research tools to unravel the complex biological processes mediated by the CB1 receptor in both physiological and pathological conditions. However, low performance of antibodies remains a major source of inconsistency between results from different laboratories. Using a variety of techniques, including some of the most commonly accepted ones for antibody specificity testing, we identified three of five commercial antibodies against different regions of CB1 receptor as the best choice for specific end-use purposes. Specifically, an antibody against a long fragment of the extracellular amino tail of CB1 receptor (but not one against a short sequence of the extreme amino-terminus) detected strong surface staining when applied to live cells, whereas two different antibodies against an identical fragment of the extreme carboxy-terminus of CB1 receptor (but not one against an upstream peptide) showed acceptable performance on all platforms, although they behaved differently in immunohistochemical assays depending on the tissue fixation procedure used and showed different specificity in Western blot assays, which made each of them particularly suitable for one of those techniques. Our results provide a framework to interpret past and future results derived from the use of different anti-CB1 antibodies in the context of current knowledge about the CB1 receptor at the molecular level, and highlight the need for an adequate validation for specific purposes, not only before antibodies are placed on the market, but also before the decision to discontinue them is made.

The Interplay between the Immune and the Endocannabinoid Systems in Cancer.

The therapeutic potential of Cannabis sativa has been recognized since ancient times. Phytocannabinoids, endocannabinoids and synthetic cannabinoids activate two major G protein-coupled receptors, subtype 1 and 2 (CB1 and CB2). Cannabinoids (CBs) modulate several aspects of cancer cells, such as apoptosis, autophagy, proliferation, migration, epithelial-to-mesenchymal transition and stemness. Moreover, agonists of CB1 and CB2 receptors inhibit angiogenesis and lymphangiogenesis in vitro and in vivo. Low-grade inflammation is a hallmark of cancer in the tumor microenvironment (TME), which contains a plethora of innate and adaptive immune cells. These cells play a central role in tumor initiation and growth and the formation of metastasis. CB2 and, to a lesser extent, CB1 receptors are expressed on a variety of immune cells present in TME (e.g., T cells, macrophages, mast cells, neutrophils, NK cells, dendritic cells, monocytes, eosinophils). The activation of CB receptors modulates a variety of biological effects on cells of the adaptive and innate immune system. The expression of CB2 and CB1 on different subsets of immune cells in TME and hence in tumor development is incompletely characterized. The recent characterization of the human cannabinoid receptor CB2-Gi signaling complex will likely aid to design potent and specific CB2/CB1 ligands with therapeutic potential in cancer.

Cannabinoid Receptor Subtype-1 Regulates Allergic Airway Eosinophilia During Lung Helminth Infection.

Introduction: Over 1 billion humans carry infectious helminth parasites that can lead to chronic comorbidities such as anemia and growth retardation in children. Helminths induce a T-helper type 2 (Th2) immune response in the host and can cause severe tissue damage and fibrosis if chronic. We recently reported that mice infected with the soil-transmitted helminth, Nippostrongylus brasiliensis, displayed elevated levels of endocannabinoids (eCBs) in the lung and intestine. eCBs are lipid-signaling molecules that control inflammation; however, their function in infection is not well defined. Materials and Methods: A combination of pharmacological approaches and genetic mouse models was used to investigate roles for the eCB system in inflammatory responses and lung injury in mice during parasitic infection with N. brasiliensis. Results: Hemorrhaging of lung tissue in mice infected with N. brasiliensis was exacerbated by inhibiting peripheral cannabinoid receptor subtype-1 (CB1Rs) with the peripherally restricted CB1R antagonist, AM6545. In addition, these mice exhibited an increase in nonfunctional alveolar space and prolonged airway eosinophilia compared to vehicle-treated infected mice. In contrast to mice treated with AM6545, infected cannabinoid receptor subtype-2-null mice (Cnr2-/-) did not display any changes in these parameters compared to wild-type mice. Conclusions: Roles for the eCB system in Th2 immune responses are not well understood; however, increases in its activity in response to infection suggest an immunomodulatory role. Moreover, these findings suggest a role for eCB signaling at CB1Rs but not cannabinoid receptor subtypes-2 in the resolution of Th2 inflammatory responses, which become host destructive over time.

Anti-inflammatory dopamine- and serotonin-based endocannabinoid epoxides reciprocally regulate cannabinoid receptors and the TRPV1 channel.

The endocannabinoid system is a promising target to mitigate pain as the endocannabinoids are endogenous ligands of the pain-mediating receptors-cannabinoid receptors 1 and 2 (CB1 and CB2) and TRPV1. Herein, we report on a class of lipids formed by the epoxidation of N-arachidonoyl-dopamine (NADA) and N-arachidonoyl-serotonin (NA5HT) by epoxygenases. EpoNADA and epoNA5HT are dual-functional rheostat modulators of the endocannabinoid-TRPV1 axis. EpoNADA and epoNA5HT are stronger modulators of TRPV1 than either NADA or NA5HT, and epoNA5HT displays a significantly stronger inhibition on TRPV1-mediated responses in primary afferent neurons. Moreover, epoNA5HT is a full CB1 agonist. These epoxides reduce the pro-inflammatory biomarkers IL-6, IL-1ß, TNF-α and nitrous oxide and raise anti-inflammatory IL-10 cytokine in activated microglial cells. The epoxides are spontaneously generated by activated microglia cells and their formation is potentiated in the presence of anandamide. Detailed kinetics and molecular dynamics simulation studies provide evidence for this potentiation using the epoxygenase human CYP2J2. Taken together, inflammation leads to an increase in the metabolism of NADA, NA5HT and other eCBs by epoxygenases to form the corresponding epoxides. The epoxide metabolites are bioactive lipids that are potent, multi-faceted molecules, capable of influencing the activity of CB1, CB2 and TRPV1 receptors.

Cannabinoid-Induced Immunomodulation during Viral Infections: A Focus on Mitochondria.

This review examines the impact of cannabinoids on viral infections, as well as its effects on the mitochondria of the nervous and immune system. The paper conveys information about the beneficial and negative impacts of cannabinoids on viral infections, especially HIV-1. These include effects on the inflammatory response as well as neuroprotective effects. We also explore non-apoptotic mitochondrial pathways modulated by the activity of cannabinoids, resulting in modifications to cellular functions. As a large part of the literature derives from studies of the nervous system, we first compile the information related to mitochondrial functions in this system, particularly through the CB1 receptor. Finally, we reflect on how this knowledge could complement what has been demonstrated in the immune system, especially in the context of the CB2 receptor and Ca2+ uptake. The overall conclusion of the review is that cannabinoids have the potential to affect a broad range of cell types through mitochondrial modulation, be it through receptor-specific action or not, and that this pathway has a potential implication in cases of viral infection.

Electroacupuncture increases immunoexpression of CB1 and CB2 receptors in experimental model of inflammatory bone loss.

This study evaluated the participation of CB1 and CB2 receptors in the antiresorptive effect of electroacupuncture (EA) on an experimental model of inflammatory bone loss in rats. 30 rats were divided into five groups: C (control); EP (experimental periodontitis); EA (C+ EA); EP-EA (EP+ EA in the acupoints LI4, LG11, ST36, ST44); EP - EA-sham (EP+ EA in sham acupoints). For the EP groups, a ligature was placed around the right mandibular first molars at day 1. Sessions of EA or EA-sham were assigned every other day. Animals were euthanized at day 11. Histometric analysis was performed to evaluate the percentage of bone area in the furcation area. Immunolabeling patterns in the periodontal tissues and immunofluorescent staining in the trigeminal ganglia and in the trigeminal spinal tract for CB1 and CB2 receptors were performed. It was observed increased bone loss in the furcation in the EP and EP-EA-sham groups, in comparison to the other groups (p < 0.05). Enhanced CB2 immunolabeling was observed in the periodontal tissues in the EP-EA group, when compared to the EP and EP-EA-sham groups (p < 0.05). Increased CB1 immunofluorescent staining was observed in the neural tissues in the EA treated group in comparison with the other groups (p < 0.05), while no expression of CB2 was observed in those regions. Our study showed that in the presence of inflammatory bone disease, EA treatment reduced bone erosion and increased the immunoexpression of CB1 in the neural tissues and CB2 in the periodontal tissues.

The inhibition of CB1 receptor accelerates the onset and development of EAE possibly by regulating microglia/macrophages polarization.

Cannabinoid 1 receptor (CB1R) regulates the neuro-inflammatory and neurodegenerative damages of experimental autoimmune encephalomyelitis (EAE) and of multiple sclerosis (MS). The mechanism by which CB1R inhibition exerts inflammatory effects is still unclear. Here, we explored the cellular and molecular mechanisms of CB1R in the treatment of EAE by using a specific and selective CB1R antagonist SR141716A. Our study demonstrated that SR141716A accelerated the clinical onset and development of EAE, accompanied by body weight loss. SR141716A significantly up-regulated the expression of toll like receptor-4 (TLR-4) and nuclear factor-kappaB/p65 (NF-κB/p65) on microglia/macrophages of EAE mice as well as levels of inflammatory factors (TNF-α, IL-1ß, IL-6) and chemokines (MCP-1, CX3CL1), accompanied by the shifts of cytokines from Th2 (IL-4, IL-10) to Th1 (IFN-γ)/Th17 (IL-17) in the spinal cords of EAE mice. Similar changes happened on splenic mononuclear cells (MNCs) except chemokine CX3CL1. Consistently, SR141716A promoted BV-2 microglia to release inflammatory factors (TNF-α, IL-1ß, IL-6) while inhibited the production of IL-10 and chemokines (MCP-1, CX3CL1). Furthermore, when splenic CD4+ T cells co-cultured with SR141716A-administered BV-2 microglia, the levels of IL-4 and IL-10 were decreased while production of IL-17 and IFN-γ increased significantly. Our research indicated that inhibition of CB1R induced M1 phenotype-Th17 axis changed of microglia/macrophages through TLR-4 and NF-κB/p65 which accelerated the onset and development of EAE. Therefore, CB1R may be a promising target for the treatment of MS/EAE, but its complexity remains to be carefully considered and studied in further clinical application.

Participation of hypothalamic CB1 receptors in reproductive axis disruption during immune challenge.

Immune challenge inhibits reproductive function and endocannabinoids (eCB) modulate sexual hormones. However, no studies have been performed to assess whether the eCB system mediates the inhibition of hormones that control reproduction as a result of immune system activation during systemic infections. For that reason, we evaluated the participation of the hypothalamic cannabinoid receptor CB1 on the hypothalamic-pituitary-gonadal (HPG) axis activity in rats submitted to immune challenge. Male adult rats were treated i.c.v. administration with a CB1 antagonist/inverse agonist (AM251) (500 ng/5 µL), followed by an i.p. injection of lipopolysaccharide (LPS) (5 mg/kg) 15 minutes later. Plasmatic, hypothalamic and adenohypophyseal pro-inflammatory cytokines, hormones and neuropeptides were assessed 90 or 180 minutes post-LPS. The plasma concentration of tumour necrosis factor α and adenohypophyseal mRNA expression of Tnfα and Il1ß increased 90 and 180 minutes post i.p. administration of LPS. However, cytokine mRNA expression in the hypothalamus increased only 180 minutes post-LPS, suggesting an inflammatory delay in this organ. CB1 receptor blockade with AM251 increased LPS inflammatory effects, particularly in the hypothalamus. LPS also inhibited the HPG axis by decreasing gonadotrophin-releasing hormone hypothalamic content and plasma levels of luteinising hormone and testosterone. These disruptor effects were accompanied by decreased hypothalamic Kiss1 mRNA expression and prostaglandin E2 content, as well as by increased gonadotrophin-inhibitory hormone (Rfrp3) mRNA expression. All these disruptive effects were prevented by the presence of AM251. In summary, our results suggest that, in male rats, eCB mediate immune challenge-inhibitory effects on reproductive axis at least partially via hypothalamic CB1 activation. In addition, this receptor also participates in homeostasis recovery by modulating the inflammatory process taking place after LPS administration.

Alteration of SLP2-like immunolabeling in mitochondria signifies early cellular damage in developing and adult mouse brain.

Mitochondria play a critical role in various pathways of regulated cell death. Here we propose a novel method for detection of initial derangement of mitochondria in degenerating and dying neuronal cells. The method is based on our recent finding that antibodies directed against the cannabinoid type 1 receptor (CB1) also bind the mitochondrial stomatin-like protein 2 (SLP2) that belongs to an inner mitochondrial membrane protein complex. It is well established that SLP2 regulates mitochondrial biogenesis and respiratory functions. We now show that anti-CB1 antibodies recognize conformational epitopes but not the linear amino acid sequence of SLP2. In addition we found that anti-CB1 serum mostly labels swollen mitochondria with early or advanced stages of pathology in mouse brain while other proteins of the complex may mask epitopes of SLP2 in the normal mitochondria. Although neurons and endothelial cells in healthy brains contain occasional immunopositive mitochondria detectable with anti-CB1 serum, their numbers increase significantly after hypoxic insults in parallel with signs of cellular damage. Moreover, use of electron microscopy suggests relocation of SLP2 from its normal functional position in the inner mitochondrial membrane into the mitochondrial matrix in pathological cells. Thus, SLP2-like immunolabeling serves as an in situ histochemical target detecting early derangement of mitochondria. Anti-CB1 serum is crucial for this purpose because available anti-SLP2 antibodies do not provide selective labeling of mitochondria in the fixed tissue. This new method of detecting mitochondrial dysfunction can benefit the in vitro research of human diseases and developmental disorders by enabling analysis in live animal models.

The Use of Release-Active Antibody-Based Preparations for Vertigo Prevention in Adults.

The effectiveness of antibody-based release-active preparations Impaza (antibodies to eNOS), Tenoten (antibodies to brain-specific protein S-100), Dietressa (antibodies to type 1 cannabinoid receptor), Brizantin (combined preparation, antibodies to brain-specific protein S-100 and type 1 cannabinoid receptor), and Divaza (combined preparation, antibodies to brain-specific protein S-100 and eNOS) in the prevention of vertigo was studied on the model of intermittent accumulation of Coriolis accelerations (ICCA). Modification of activity of vestibular receptors and signal systems by release-active preparations contributed to an increase in ICCA tolerance time. Combined preparation Impaza possessed the most significant antinaupathic properties. Brizantin was less potent in this respect.

Endocannabinoids and the Immune System in Health and Disease.

Endocannabinoids are bioactive lipids that have the potential to signal through cannabinoid receptors to modulate the functional activities of a variety of immune cells. Their activation of these seven-transmembranal, G protein-coupled receptors sets in motion a series of signal transductional events that converge at the transcriptional level to regulate cell migration and the production of cytokines and chemokines. There is a large body of data that supports a functional relevance for 2-arachidonoylglycerol (2-AG) as acting through the cannabinoid receptor type 2 (CB2R) to inhibit migratory activities for a diverse array of immune cell types. However, unequivocal data that supports a functional linkage of anandamide (AEA) to a cannabinoid receptor in immune modulation remains to be obtained. Endocannabinoids, as typical bioactive lipids, have a short half-life and appear to act in an autocrine and paracrine fashion. Their immediate effective action on immune function may be at localized sites in the periphery and within the central nervous system. It is speculated that endocannabinoids play an important role in maintaining the overall "fine-tuning" of the immune homeostatic balance within the host.

Turning Over a New Leaf: Cannabinoid and Endocannabinoid Modulation of Immune Function.

Cannabis is a complex substance that harbors terpenoid-like compounds referred to as phytocannabinoids. The major psychoactive phytocannabinoid found in cannabis ∆(9)-tetrahydrocannabinol (THC) produces the majority of its pharmacological effects through two cannabinoid receptors, termed CB1 and CB2. The discovery of these receptors as linked functionally to distinct biological effects of THC, and the subsequent development of synthetic cannabinoids, precipitated discovery of the endogenous cannabinoid (or endocannabinoid) system. This system consists of the endogenous lipid ligands N- arachidonoylethanolamine (anandamide; AEA) and 2-arachidonylglycerol (2-AG), their biosynthetic and degradative enzymes, and the CB1 and CB2 receptors that they activate. Endocannabinoids have been identified in immune cells such as monocytes, macrophages, basophils, lymphocytes, and dendritic cells and are believed to be enzymatically produced and released "on demand" in a similar fashion as the eicosanoids. It is now recognized that other phytocannabinoids such as cannabidiol (CBD) and cannabinol (CBN) can alter the functional activities of the immune system. This special edition of the Journal of Neuroimmune Pharmacology (JNIP) presents a collection of cutting edge original research and review articles on the medical implications of phytocannabinoids and the endocannabinoid system. The goal of this special edition is to provide an unbiased assessment of the state of research related to this topic from leading researchers in the field. The potential untoward effects as well as beneficial uses of marijuana, its phytocannabinoid composition, and synthesized cannabinoid analogs are discussed. In addition, the role of the endocannabinoid system and approaches to its manipulation to treat select human disease processes are addressed.

Modulation of HIVGP120 Antigen-Specific Immune Responses In Vivo by Δ9-Tetrahydrocannabinol.

Approximately 25 % of HIV patients use marijuana for its putative therapeutic benefit; however, it is unknown how cannabinoids affect the immune status of HIV patients. Previously, a surrogate in vitro mouse model was established, which induced CD8(+) T cell proliferation and gp120-specific IFNγ production. ∆(9)-Tetrahydrocannabinol (THC), the predominant psychoactive compound in marijuana, suppressed or enhanced the responses depending on the magnitude of cellular activation. The purpose of the current study was to investigate whether THC produced similar effects in vivo and therefore a mouse model to induce HIVgp120-specific immune responses was established. A gp120-expressing plasmid, pVRCgp120, or a vector plasmid, pVRC2000, was injected intramuscularly into mice, which were also dosed with THC orally. The gp120-specific IFNγ and IL-2 responses were detected when splenocytes were restimulated with gp120-derived peptide 81 (IIGDIRQAHCNISRA), which was identified as being immunodominant. Various cellular populations were activated in response to pVRCgp120 stimulation followed by peptide restimulation, as evidenced by increased expression levels of activation markers (e.g., CD69, CD80, and major histocompatibility complex II [MHC II]). The IFNγ response and cellular activation were enhanced by THC in C57Bl/6 wild type (WT) mice but suppressed or not affected by THC in cannabinoid receptor 1 (CB1) and 2 (CB2) knockout (CB1 (-/-)CB2 (-/-)) mice. Furthermore, CB1 (-/-)CB2 (-/-) mice exhibited augmented IFNγ production when compared to WT mice in the absence of THC. Collectively, our findings demonstrate that under certain conditions, THC enhances HIV antigen-specific immune responses, which occurs through CB1/CB2-dependent and -independent mechanisms.

Role of Endocannabinoid Activation of Peripheral CB1 Receptors in the Regulation of Autoimmune Disease.

The impact of the endogenous cannabinoids (AEA, 2-AG, PEA, and virodamine) on the immune cell expressed cannabinoid receptors (CB1, CB2, TRPV-1, and GPR55) and consequent regulation of immune function is an exciting area of research with potential implications in the prevention and treatment of inflammatory and autoimmune diseases. Despite significant advances in understanding the mechanisms through which cannabinoids regulate immune functions, not much is known about the role of endocannabinoids in the pathogenesis or prevention of autoimmune diseases. Inasmuch as CB2 expression on immune cells and its role has been widely reported, the importance of CB1 in immunological disorders has often been overlooked especially because it is not highly expressed on naive immune cells. Therefore, the current review aims at delineating the effect of endocannabinoids on CB1 receptors in T cell driven autoimmune diseases. This review will also highlight some autoimmune diseases in which there is evidence indicating a role for endocannabinoids in the regulation of autoimmune pathogenesis. Overall, based on the evidence presented using the endocannabinoids, specifically AEA, we propose that the peripheral CB1 receptor is involved in the regulation and amelioration of inflammation associated with autoimmune diseases.

Blockade of cannabinoid receptors reduces inflammation, leukocyte accumulation and neovascularization in a model of sponge-induced inflammatory angiogenesis.

OBJECTIVE: Angiogenesis depends on a complex interaction between cellular networks and mediators. The endocannabinoid system and its receptors have been shown to play a role in models of inflammation. Here, we investigated whether blockade of cannabinoid receptors may interfere with inflammatory angiogenesis. MATERIALS AND METHODS: Polyester-polyurethane sponges were implanted in C57Bl/6j mice. Animals received doses (3 and 10 mg/kg/daily, s.c.) of the cannabinoid receptor antagonists SR141716A (CB1) or SR144528 (CB2). Implants were collected at days 7 and 14 for cytokines, hemoglobin, myeloperoxidase, and N-acetylglucosaminidase measurements, as indices of inflammation, angiogenesis, neutrophil and macrophage accumulation, respectively. Histological and morphometric analysis were also performed. RESULTS: Cannabinoid receptors expression in implants was detected from day 4 after implantation. Treatment with CB1 or CB2 receptor antagonists reduced cellular influx into sponges at days 7 and 14 after implantation, although CB1 receptor antagonist were more effective at blocking leukocyte accumulation. There was a reduction in TNF-α, VEGF, CXCL1/KC, CCL2/JE, and CCL3/MIP-1α levels, with increase in CCL5/RANTES. Both treatments reduced neovascularization. Dual blockade of cannabinoid receptors resulted in maximum inhibition of inflammatory angiogenesis. CONCLUSIONS: Blockade of cannabinoid receptors reduced leukocyte accumulation, inflammation and neovascularization, suggesting an important role of endocannabinoids in sponge-induced inflammatory angiogenesis both via CB1 and CB2 receptors.

Antibodies to cannabinoid type 1 receptor co-react with stomatin-like protein 2 in mouse brain mitochondria.

Anti-cannabinoid type 1 receptor (CB1 ) polyclonal antibodies are widely used to detect the presence of CB1 in a variety of brain cells and their organelles, including neuronal mitochondria. Surprisingly, we found that anti-CB1 sera, in parallel with CB1 , also recognize the mitochondrial protein stomatin-like protein 2. In addition, we show that the previously reported effect of synthetic cannabinoid WIN 55,212-2 on mitochondrial complex III respiration is not detectable in purified mitochondrial preparations. Thus, our study indicates that a direct relationship between endocannabinoid signaling and mitochondrial functions in the cerebral cortex seems unlikely, and that caution should be taken interpreting findings obtained using anti-CB1 antibodies.

The role of CB1 in immune modulation by cannabinoids.

There is clear evidence that CB(2), historically referred to as the peripheral cannabinoid receptor, mediates many of the immune modulatory effects of cannabinoids. However, cannabinoid receptors cannot be classified simply as central or peripheral since CB(2) has been shown to play a role in the central nervous system (CNS) and CB(1) mediates many immune system effects. Although Cnr1 mRNA and CB(1) protein expression is lower than Cnr2 mRNA or CB(2) protein expression in cells of the immune system, several studies have shown direct modulation of immune function via CB(1) by endogenous and exogenous cannabinoids in T cells, innate cells, and to a lesser extent, B cells. In addition, indirect, but CB(1)-dependent, mechanisms of immune modulation exist. In fact, the mechanism by which cannabinoids attenuate neuroinflammation via CB(1) is likely a combination of immune suppression and neuroprotection. Although many studies demonstrate that agonists for CB(1) are immune suppressive and anti-inflammatory, CB(1) antagonists also exhibit anti-inflammatory properties. Overall, the data demonstrate that many of the immune modulatory effects of cannabinoids are mediated via CB(1).

Immunity and early pregnancy events: are endocannabinoids the missing link?

The success of pregnancy is dependent on a number of different cell types and signalling pathways, including immune cells which play a vital role in implantation. Immune cells express transcripts for all of the components of the endocannabinoid system, but the role of this system in the function of reproductive tract immune cells is still unclear. In this review, we present the hypothesis that the endocannabinoid signalling system is central to an endocannabinoid-immune-reproductive axis, and that it acts as the link via which immune cells exert their vital influence on implantation and foetal tolerance. Pubmed and Web of Science databases were searched for studies published since 1975 which explore the interaction between the endocannabinoid system and the immune system, the endocannabinoid system in pregnancy as well as the role of immune cells in pregnancy. There is evidence that the endocannabinoid system has established effects in several immune cell lineages including NK cells and T lymphocytes known to be crucial in the development of normal pregnancy. These effects include regulation of cytokine production, chemotaxis and proliferation. The immune system plays a critical role in placental development and foetal tolerance, achieving this through a large number of cytokines and chemokines. We conclude that there are intricate molecular interactions involved in the success of early pregnancy and that the endocannabinoid system, potentially interacting with the immune system, is a key contributor to these events.

Expression and functions of µ-opioid receptors and cannabinoid receptors type 1 in T lymphocytes.

Opioids and cannabinoids modulate T lymphocyte functions. Many effects of the drugs are mediated by µ-opioid receptor and cannabinoid receptor type 1 (CB1), respectively. These two receptors are strikingly similar with respect to their expression in T cells and the mechanisms by which they mediate modulation of T cell activity. Thus, µ-opioid receptors and CB1 not expressed in resting primary human and Jurkat T cells. However, in response to the cytokine IL-4, the epigenetic modifiers 5-aza-2'-deoxycytidine and trichostatin A, and activation of T cells, functional µ-opioid receptors and CB1 are induced. The induced receptors mediate inhibition of T cell signaling and, thereby, IL-2 production, a hallmark of activated T cells. Although coupled to inhibitory G proteins, µ-opioid receptors and CB1 produce a remarkable increase in cAMP levels in T cells stimulated with opioids and cannabinoids, which is a key mechanism for the inhibition of T cell signaling.