The CNS endocannabinoid system: synthetic cannabinoids and metabolic enzymes
Publication Date
July 16, 2024
Creator
Abstract
Glioblastoma multiforme (GBM) is a devastating primary tumour of the central nervous system. This tumour arises from glial cells, including astrocytes and oligodendrocytes, which comprise >90% of brain volume. GBM is the most frequent and aggressive malignant brain tumour, with a poor prognosis despite available surgical and radio-/chemotherapy, prompting the necessity for alternative therapies. Recent reports indicate that cannabinoids can inhibit viability of several types of cancer cells in both in vitro and in vivo models. However, the diversity of experimental conditions and of outcomes has hindered definitive conclusions about cannabinoid efficacy. The endocannabinoid system is widely distributed in the body, and its dysregulation is associated with a variety of diseases, including various types of cancer. Anticancer activities of phytocannabinoids are mediated in glioma cells, at least in part, by the endocannabinoid receptors, triggering various cellular signalling pathways. Yet, due to the scarcity of good quality clinical trials, there remains no solid basis for the anticancer therapeutic potential of cannabis compounds.
The initial aim of this project was to study the central nervous system (CNS) endocannabinoid system and its potential involvement in neurotoxicity using cell line models, lab animals, and human brain samples. The first part of this thesis addressed the effects of cannabinoids and inhibitors of the major enzymes involved in endocannabinoid metabolism on the proliferation of the 1321N1 human astrocytoma cell line using a standard colorimetric assay. The modestly CB2-preferring agonist HU210 or CB2-selective agonist JWH015 appeared to increase 1321N1 cell numbers. The selective CB1 inverse agonist AM251 decreased 1321N1 cell viability which could suggest the involvement of the cannabinoid signalling system in the protection of human astrocytoma cells from apoptosis. However, the precise mechanism of action of AM251 was unable to be determined.
Activity-based protein profiling (ABPP) identified distinct patterns of serine hydrolases in the human astrocytoma and neuroblastoma cells. Differentiation of the SH-SY5Y cells changed the activity of multiple enzyme activities. The use of selective inhibitors suggested the presence of endocannabinoid hydrolases (MAGL and possibly ABHD6) in the astrocytoma cells, with FAAH activity in the neuroblastoma. Further characterization of these enzyme activities and their function in the two cells is warranted. ABPP in rat brain soluble and particulate fractions showed distinct profiles of serine hydrolase activities; these were largely consistently expressed across the eight brain regions examined. The use of enzyme inhibitors in the rat brain samples suggested the detection of MAGL and ABHD6, but no clear evidence for FAAH activity, indicating their involvement in brain function pathophysiology. Further work would be needed to corroborate these findings. In the rat spinal system, serine hydrolases could be detected in individual dorsal root ganglia, the pattern of which was distinct from the spinal cord preparations. Analysis of tissue samples from animals treated with monosodium acetate as a model of arthritis showed an elevation in the activities of MAGL and ABHD6 suggesting the role they play in pain transmission. Further research is required for other serine hydrolase enzymes which as CES2 for which the activity increased on the contralateral side, suggesting a potential compensatory role in weight-bearing.
Item Type
ethesis
Thesis Type
PhD
Supervisors
Subjects (LC)
Associated Schools / Departments
School of Life Sciences
eprints ID
78274
UoN Repository URI
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