1
|
Uthayakumaran K, Sunil M, Ratcliffe EM. Evaluating the Role of the Endocannabinoid System in Axon Guidance: A Literature Review. Cannabis Cannabinoid Res 2024; 9:12-20. [PMID: 38174983 DOI: 10.1089/can.2023.0138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2024] Open
Abstract
Introduction: The endocannabinoid system (ECS) mediates the actions of cannabis and has been implicated in playing critical roles in key developmental events, including axon guidance. Although several recent studies have demonstrated ECS involvement in neurodevelopment, an emphasis on its putative role in axon guidance has not been reviewed comprehensively. Objective: The purpose of this literature review is to evaluate the interrelationships between the ECS and axon guidance. Methodology: This literature review analyzes existing literature demonstrating the normal role of endocannabinoid (eCB) signaling in axon guidance, with evidence from diverse animal models. Studies were obtained from a search strategy involving terms related to the ECS and axon guidance, and cross-checking cited literature to ensure a complete evaluation. Discussion: Cannabinoid receptors, as well as eCB synthesis and degradation machinery, appear necessary for normal axon guidance during neurodevelopment. Genetic and/or pharmacological disruption of eCB signaling results in axon growth and guidance errors, implying high sensitivity to exogenous cannabinoids. Conclusion: Overall, this review highlights the intricate connections between the ECS and axon guidance in normal neurodevelopment. The mechanistic evidence discussed suggests that alterations of the ECS through genetic and pharmacological interference disrupt its normal functioning and by extension its normal role in regulating neural circuitry formation. A comprehensive understanding of this topic will be valuable in potentially uncovering the mechanisms responsible for the neurodevelopmental defects associated with pre-natal cannabis use.
Collapse
Affiliation(s)
- Kavina Uthayakumaran
- Department of Pediatrics, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Farncombe Family Digestive Health Research Institute, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
| | - Maria Sunil
- Department of Pediatrics, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Farncombe Family Digestive Health Research Institute, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Michael G. DeGroote Centre for Medicinal Cannabis Research, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
| | - Elyanne M Ratcliffe
- Farncombe Family Digestive Health Research Institute, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Michael G. DeGroote Centre for Medicinal Cannabis Research, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
- Division of Gastroenterology and Nutrition, Department of Pediatrics, McMaster University, Hamilton, Ontario, Canada
| |
Collapse
|
2
|
Verdikt R, Armstrong AA, Cheng J, Hwang YS, Clark AT, Yang X, Allard P. Metabolic memory of Δ9-tetrahydrocannabinol exposure in pluripotent stem cells and primordial germ cells-like cells. eLife 2023; 12:RP88795. [PMID: 38150302 PMCID: PMC10752584 DOI: 10.7554/elife.88795] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2023] Open
Abstract
Cannabis, the most consumed illicit psychoactive drug in the world, is increasingly used by pregnant women. However, while cannabinoid receptors are expressed in the early embryo, the impact of phytocannabinoids exposure on early embryonic processes is lacking. Here, we leverage a stepwise in vitro differentiation system that captures the early embryonic developmental cascade to investigate the impact of exposure to the most abundant phytocannabinoid, Δ9-tetrahydrocannabinol (Δ9-THC). We demonstrate that Δ9-THC increases the proliferation of naive mouse embryonic stem cells (ESCs) but not of their primed counterpart. Surprisingly, this increased proliferation, dependent on the CB1 receptor binding, is only associated with moderate transcriptomic changes. Instead, Δ9-THC capitalizes on ESCs' metabolic bivalence by increasing their glycolytic rates and anabolic capabilities. A memory of this metabolic rewiring is retained throughout differentiation to Primordial Germ Cell-Like Cells in the absence of direct exposure and is associated with an alteration of their transcriptional profile. These results represent the first in-depth molecular characterization of the impact of Δ9-THC exposure on early stages of germline development.
Collapse
Affiliation(s)
- Roxane Verdikt
- Institute for Society and Genetics, University of California, Los AngelesLos AngelesUnited States
| | - Abigail A Armstrong
- Department of Obstetrics/Gynecology and Reproductive Endocrinology and Infertility, University of California, Los AngelesLos AngelesUnited States
| | - Jenny Cheng
- Molecular, Cellular, and Integrative Physiology Graduate Program, University of California, Los AngelesLos AngelesUnited States
| | - Young Sun Hwang
- Department of Molecular Cell and Developmental Biology, University of California, Los AngelesLos AngelesUnited States
| | - Amander T Clark
- Department of Molecular Cell and Developmental Biology, University of California, Los AngelesLos AngelesUnited States
- Center for Reproductive Science, Health and Education, University of California, Los AngelesLos AngelesUnited States
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los AngelesLos AngelesUnited States
| | - Xia Yang
- Integrative Biology and Physiology Department, University of California, Los AngelesLos AngelesUnited States
- Department of Molecular and Medical Pharmacology, University of California, Los AngelesLos AngelesUnited States
| | - Patrick Allard
- Institute for Society and Genetics, University of California, Los AngelesLos AngelesUnited States
- Molecular Biology Institute, University of California, Los AngelesLos AngelesUnited States
| |
Collapse
|
3
|
Verdikt R, Armstrong AA, Cheng J, Hwang YS, Clark AT, Yang X, Allard P. Metabolic memory of Δ9-tetrahydrocannabinol exposure in pluripotent stem cells and primordial germ cells-like cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.13.531968. [PMID: 36993751 PMCID: PMC10054962 DOI: 10.1101/2023.03.13.531968] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 04/29/2023]
Abstract
Cannabis, the most consumed illicit psychoactive drug in the world, is increasingly used by pregnant women. However, while cannabinoid receptors are expressed in the early embryo, the impact of phytocannabinoids exposure on early embryonic processes is lacking. Here, we leverage a stepwise in vitro differentiation system that captures early embryonic developmental cascade to investigate the impact of exposure to the most abundant phytocannabinoid, Δ9-tetrahydrocannabinol (Δ9-THC). We demonstrate that Δ9-THC increases the proliferation of naïve mouse embryonic stem cells (ESCs) but not of their primed counterpart. Surprisingly, this increased proliferation, dependent on the CB1 receptor binding, is only associated with moderate transcriptomic changes. Instead, Δ9-THC capitalizes on ESCs' metabolic bivalence by increasing their glycolytic rates and anabolic capabilities. A memory of this metabolic rewiring is retained throughout differentiation to Primordial Germ Cell-Like Cells in the absence of direct exposure and is associated with an alteration of their transcriptional profile. These results represent the first in-depth molecular characterization of the impact of Δ9-THC exposure on early stages of germline development.
Collapse
Affiliation(s)
- Roxane Verdikt
- Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Abigail A. Armstrong
- Department of Obstetrics/Gynecology and Reproductive Endocrinology and Infertility, University of California, Los Angeles, CA, USA
| | - Jenny Cheng
- Molecular, Cellular, and Integrative Physiology Graduate Program, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Young Sun Hwang
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Amander T. Clark
- Department of Molecular Cell and Developmental Biology, University of California, Los Angeles, Los Angeles, CA, 90095, USA
- Center for Reproductive Science, Health and Education, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Eli and Edythe Broad Center of Regenerative Medicine and Stem Cell Research, University of California, Los Angeles, Los Angeles, CA, 90095, USA
| | - Xia Yang
- Integrative Biology and Physiology Department, University of California, Los Angeles, CA, 90095, USA
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Patrick Allard
- Institute for Society and Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| |
Collapse
|
4
|
Maciel IDS, de Abreu GH, Johnson CT, Bonday R, Bradshaw HB, Mackie K, Lu HC. Perinatal CBD or THC Exposure Results in Lasting Resistance to Fluoxetine in the Forced Swim Test: Reversal by Fatty Acid Amide Hydrolase Inhibition. Cannabis Cannabinoid Res 2022; 7:318-327. [PMID: 34182795 PMCID: PMC9225394 DOI: 10.1089/can.2021.0015] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Introduction: There is widespread acceptance of cannabis for medical or recreational use across the society, including pregnant women. Concerningly, numerous studies find that the developing central nervous system (CNS) is vulnerable to the detrimental effects of Δ9-tetrahydrocannabinol (THC). In contrast, almost nothing on the consequences of perinatal cannabidiol (CBD) exposure. In this study, we used mice to investigate the adult impact of perinatal cannabinoid exposure (PCE) with THC, CBD, or a 1:1 ratio of THC and CBD on behaviors. Furthermore, the lasting impact of PCE on fluoxetine sensitivity in the forced swim test (FST) was evaluated to probe neurochemical pathways interacting with the endocannabinoid system (ECS). Methods: Pregnant CD1 dams were injected subcutaneously daily with vehicle, 3 mg/kg THC, 3 mg/kg CBD, or 3 mg/kg THC +3 mg/kg CBD from gestational day 5 to postnatal day 10. Mass spectroscopic (MS) analyses were conducted to measure the THC and CBD brain levels in dams and their embryonic progenies. PCE adults were subjected to a battery of behavioral tests: open field arena, sucrose preference test, marble burying test, nestlet shredding test, and FST. Results: MS analysis found substantial levels of THC and CBD in embryonic brains. Our behavioral testing found that PCE females receiving THC or CBD buried significantly more marbles than control mice. Interestingly, PCE males receiving CBD or THC+CBD had significantly increased sucrose preference. While PCE with THC or CBD did not affect FST immobility, PCE with THC or CBD prevented fluoxetine from decreasing immobility in both males and females. Excitingly, fatty acid amide hydrolase (FAAH) inhibition with a dose of URB597 that was behaviorally inactive in the FST rescued fluoxetine efficacy in PCE mice of both sexes. Conclusions: Our data suggest that PCE with either THC, CBD, or THC+CBD alters repetitive and hedonic behaviors in a phytocannabinoid and sex-dependent manner. In addition, PCE with THC or CBD prevents fluoxetine from enhancing coping behavior. The restoration of fluoxetine responsiveness in THC or CBD PCE adults by inhibition of FAAH suggests that PCE causes a lasting reduction of the ECS and that enhancement of anandamide signaling represents a potential treatment for behavioral deficits following PCE.
Collapse
Affiliation(s)
- Izaque de Sousa Maciel
- The Linda and Jack Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana, USA.,Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA
| | - Gabriel H.D. de Abreu
- The Linda and Jack Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Claire T. Johnson
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Rida Bonday
- The Linda and Jack Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana, USA.,Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA
| | - Heather B. Bradshaw
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Ken Mackie
- The Linda and Jack Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana, USA.,Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA
| | - Hui-Chen Lu
- The Linda and Jack Gill Center for Biomolecular Science, Indiana University, Bloomington, Indiana, USA.,Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, USA.,Program in Neuroscience, Indiana University, Bloomington, Indiana, USA.,Address correspondence to: Hui-Chen Lu, PhD, The Linda and Jack Gill Center for Biomolecular Science, Indiana University, 702 N Walnut Grove Ave, IN 47405, USA,
| |
Collapse
|
5
|
Calvigioni D, Hurd YL, Harkany T, Keimpema E. Neuronal substrates and functional consequences of prenatal cannabis exposure. Eur Child Adolesc Psychiatry 2014; 23:931-41. [PMID: 24793873 PMCID: PMC4459494 DOI: 10.1007/s00787-014-0550-y] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Accepted: 04/15/2014] [Indexed: 02/01/2023]
Abstract
Cannabis remains one of the world's most widely used substance of abuse amongst pregnant women. Trends of the last 50 years show an increase in popularity in child-bearing women together with a constant increase in cannabis potency. In addition, potent herbal "legal" highs containing synthetic cannabinoids that mimic the effects of cannabis with unknown pharmacological and toxicological effects have gained rapid popularity amongst young adults. Despite the surge in cannabis use during pregnancy, little is known about the neurobiological and psychological consequences in the exposed offspring. In this review, we emphasize the importance of maternal programming, defined as the intrauterine presentation of maternal stimuli to the foetus, in neurodevelopment. In particular, we focus on cannabis-mediated maternal adverse effects, resulting in direct central nervous system alteration or sensitization to late-onset chronic and neuropsychiatric disorders. We compare clinical and preclinical experimental studies on the effects of foetal cannabis exposure until early adulthood, to stress the importance of animal models that permit the fine control of environmental variables and allow the dissection of cannabis-mediated molecular cascades in the developing central nervous system. In sum, we conclude that preclinical experimental models confirm clinical studies and that cannabis exposure evokes significant molecular modifications to neurodevelopmental programs leading to neurophysiological and behavioural abnormalities.
Collapse
Affiliation(s)
- Daniela Calvigioni
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden. Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Yasmin L. Hurd
- Department of Psychiatry and Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY 10029-6574, USA
| | - Tibor Harkany
- Division of Molecular Neurobiology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, 17177 Stockholm, Sweden. Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| | - Erik Keimpema
- Department of Molecular Neurosciences, Center for Brain Research, Medical University of Vienna, 1090 Vienna, Austria
| |
Collapse
|
6
|
Fatty acid amide hydrolase expression during retinal postnatal development in rats. Neuroscience 2011; 195:145-65. [PMID: 21867744 DOI: 10.1016/j.neuroscience.2011.08.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 07/12/2011] [Accepted: 08/03/2011] [Indexed: 01/01/2023]
Abstract
The endocannabinoid (eCB) system is thought to participate in developmental processes in the CNS. The rodent retina represents a valuable model to study CNS development because it contains well-identified cell types with established developmental timelines. The distribution of cannabinoid receptor type 1 (CB1R) was recently revealed in the developing retina; however, the expression patterns of other elements of this system remain unknown. In this study, we investigated the expression pattern of the degradative enzyme fatty acid amide hydrolase (FAAH), a key regulator of the eCB system, in the rat retina during postnatal development. To identify the cells expressing the enzyme, co-stainings were carried out for FAAH and retinal cell type markers. FAAH was expressed at postnatal day (P) 1 in ganglion and cholinergic amacrine cells. In the course of development, it appeared in cones, horizontal, and bipolar cells. For most cell types (horizontal, cholinergic amacrine cells, and cone bipolar cells), FAAH was transiently expressed, suggesting an important redistribution of the enzyme during postnatal development and thus a potential role of the eCB system in developmental processes. Our results also indicated that, in the adult retina, FAAH is expressed in cones, rod bipolar cells, and some retinal ganglion cells. The presence of FAAH in adult animals supports the hypothesis that the eCB system is involved in retinal functions. Overall these results indicate that, as shown in other structures of the brain, the eCB system could play an instrumental role in the development and function of the retina.
Collapse
|
7
|
Molecular model of cannabis sensitivity in developing neuronal circuits. Trends Pharmacol Sci 2011; 32:551-61. [PMID: 21757242 DOI: 10.1016/j.tips.2011.05.004] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Revised: 04/27/2011] [Accepted: 05/02/2011] [Indexed: 11/21/2022]
Abstract
Prenatal cannabis exposure can complicate in utero development of the nervous system. Cannabis impacts the formation and functions of neuronal circuitries by targeting cannabinoid receptors. Endocannabinoid signaling emerges as a signaling cassette that orchestrates neuronal differentiation programs through the precisely timed interaction of endocannabinoid ligands with their cognate cannabinoid receptors. By indiscriminately prolonging the 'switched-on' period of cannabinoid receptors, cannabis can hijack endocannabinoid signals to evoke molecular rearrangements, leading to the erroneous wiring of neuronal networks. Here, we formulate a hierarchical network design necessary and sufficient to describe the molecular underpinnings of cannabis-induced neural growth defects. We integrate signalosome components, deduced from genome- and proteome-wide arrays and candidate analyses, to propose a mechanistic hypothesis of how cannabis-induced ectopic cannabinoid receptor activity overrides physiological neurodevelopmental endocannabinoid signals, affecting the timely formation of synapses.
Collapse
|
8
|
James A, Hough M, James S, Winmill L, Burge L, Nijhawan S, Matthews PM, Zarei M. Greater white and grey matter changes associated with early cannabis use in adolescent-onset schizophrenia (AOS). Schizophr Res 2011; 128:91-7. [PMID: 21388791 DOI: 10.1016/j.schres.2011.02.014] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 02/15/2011] [Accepted: 02/15/2011] [Indexed: 11/15/2022]
Abstract
BACKGROUND Cannabis use is associated with a higher risk of schizophrenia, however, its specific long-term effect on the structure of the brain of adolescent-onset schizophrenic patients remains unclear. AIMS To study cognitive and structural (grey and white matter) changes in patients with adolescent-onset schizophrenia (AOS) with early cannabis use (CAN+ve) (more than 3 times/week for at least 6 months) and without cannabis use (CAN-ve) versus controls. METHOD An optimised voxel-based morphometry (VBM) and diffusion tensor imaging (DTI) MRI study of 32 adolescents with DSM IV schizophrenia-16 CAN+ve and 16 CAN-ve, and 28 healthy adolescents. RESULTS Compared to CAN-ve subjects, CAN+ve subjects showed GM density loss in temporal fusiform gyrus, parahippocampal gyrus, ventral striatum, right middle temporal gyrus, insular cortex, precuneus, right paracingulate gyrus, dorsolateral prefrontal cortex, left postcentral gyrus, lateral occipital cortex and cerebellum. Similar group comparison showed decreased fractional anisotropy (FA) in particular in brain stem, internal capsule, corona radiata, superior and inferior longitudinal fasciculus in CAN+ve patients. No cognitive differences were apparent between CAN+ve and CAN-ve subjects, and both were impaired relative to controls. CONCLUSION Cannabis use in early adolescence increases WM and GM deficits in AOS, but does not appear to increase the cognitive deficit associated with this illness.
Collapse
Affiliation(s)
- A James
- Highfield Adolescent Unit, Warneford Hospital, Oxford, United Kingdom.
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Zabouri N, Bouchard JF, Casanova C. Cannabinoid receptor type 1 expression during postnatal development of the rat retina. J Comp Neurol 2011; 519:1258-80. [DOI: 10.1002/cne.22534] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
|
10
|
Gómez M, Hernández M, Fernández-Ruiz J. Cannabinoid signaling system: does it play a function in cell proliferation and migration, neuritic elongation and guidance and synaptogenesis during brain ontogenesis? Cell Adh Migr 2008; 2:246-8. [PMID: 19262157 DOI: 10.4161/cam.2.4.6749] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The cannabinoid signaling system is located during brain development in a position concordant with playing a modulatory function in the regulation of neuronal and glial cell proliferation and migration, survival of neural progenitors, axonal elongation and synaptogenesis and differentiation of oligodendrocytes and formation of myelin. This assumption is based on the fact that CB(1) receptors and their ligands emerge early in brain development and are transiently expressed in certain brain regions that play key roles in these processes. We have recently proposed that this modulatory action might be exerted through regulating L1 and other cell adhesion molecules, that are also key elements for those processes. The present commentary will address these two questions trying to summarize all the available evidence and to suggest the future directions for research.
Collapse
Affiliation(s)
- María Gómez
- Departamento de Bioquímica y Biología Molecular and Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | | | | |
Collapse
|
11
|
Gómez M, Hernández ML, Pazos MR, Tolón RM, Romero J, Fernández-Ruiz J. Colocalization of CB1 receptors with L1 and GAP-43 in forebrain white matter regions during fetal rat brain development: evidence for a role of these receptors in axonal growth and guidance. Neuroscience 2008; 153:687-99. [PMID: 18400407 DOI: 10.1016/j.neuroscience.2008.02.038] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2007] [Revised: 01/19/2008] [Accepted: 02/05/2008] [Indexed: 12/13/2022]
Abstract
There is recent evidence supporting the notion that the cannabinoid signaling system plays a modulatory role in the regulation of cell proliferation and migration, survival of neural progenitors, neuritic elongation and guidance, and synaptogenesis. This assumption is based on the fact that cannabinoid 1-type receptors (CB(1) receptors) and their ligands emerge early in brain development and are abundantly expressed in certain brain regions that play key roles in these processes. We have recently presented in vivo evidence showing that this modulatory action might be exerted through regulating the synthesis of the cell adhesion molecule L1 that is also a key element for those processes. To further explore this issue, we conducted here immunohistochemical studies aimed at determining the cellular substrates of CB(1) receptor-L1 interactions in the rat brain during late fetal development. In this period, we previously found that the activation of CB(1) receptors increased L1 synthesis in several forebrain white matter regions but not in gray matter areas. Using double labeling studies, we observed here colocalization of both proteins in fiber tracts including the corpus callosum, the adjacent subcortical white matter, the internal capsule and the anterior commissure. Experiments conducted with cultures of fetal rat cortical nerve cells revealed that L1 is present mainly in neurons but not in glial cells. This fact, together with the results obtained in the double labeling studies, would indicate that L1 and CB(1) receptors should possibly be present in axons elongating through these white matter tracts, or, alternatively, in migrating neurons. Further experiments confirmed the presence of CB(1) receptors in elongating axons, since these receptors colocalized with growth-associated protein 43 (GAP-43), a marker of growth cones, but not with synaptophysin, a marker of active synaptic terminals, in the same forebrain white matter regions. Lastly, using cultured fetal rat cortical neurons, we also observed that the activation of cannabinoid receptors increased the levels of the full-length L1 and altered those of some active proteolytic fragments of this protein whose generation has been associated with specific steps in the process of neuritic elongation in cultured neurons. In summary, we have demonstrated that the effects caused by cannabinoid agonists on L1 are facilitated by the colocalization of this cell adhesion molecule with CB(1) receptors in several forebrain white matter regions during fetal brain development. We have provided strong evidence that this phenomenon occurs in axons elongating through these white matter tracts, and we have explored in vitro how cannabinoid receptors influence L1 levels. Considering the role played by L1 in different events related to neural development, our observations support the occurrence of a physiological mechanism by which the cannabinoid system might regulate the process of axonal growth and guidance through regulating the synthesis and function of L1.
Collapse
Affiliation(s)
- M Gómez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | | | | | | | | | | |
Collapse
|