The effects of phytocannabinoids in stroke and pharmacology of CBD and TMP co-application in cellular models

Maguire, Ryan (2022) The effects of phytocannabinoids in stroke and pharmacology of CBD and TMP co-application in cellular models. PhD thesis, University of Nottingham.

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Abstract

In an ever ageing population, stroke represents a growing burden on society. After the age of 55, the likelihood of experiencing a stroke increases two-fold. People in this age group are also at a substantially higher risk of developing a disability following a stroke. Numerous studies have demonstrated the involvement of the endocannabinoid system in modulating molecular disturbances associated with stroke. Thus phytocannabinoids that modulate the endocannabinoid system may represent a novel strategy for treating a stroke.

A Meta-analysis was conducted to collate the data of relevant studies in the area of cannabidiol (CBD) mediated protection in animal models of stroke. A search of existing literature identified two separate laboratories both using focal ischemic-reperfusion injury (8 articles) induced by middle cerebral artery occlusion, to assess the efficacy of CBD. CBD administered intraperitoneally in male ddY mice (n: control 70, CBD 68) reduced infarct volume by a mean difference of 29.60 mm3 (Cl [34.94, 24.26], p<0.00001) and CBD administered via intracerebroventricular injections in adult male Wistar rats (n: control 81, CBD 81) reduced infarct volume by a mean of 88.62 mm3 (Cl [101.98, 75.26], p<0.0001). Publication bias was evident (p=0.004), and median study quality was 2 (range 0-4/10). Eggers statistic suggested publication bias was evident and negative studies were missing. The results of the meta-analysis indicated more robust evidence was needed to form any meaningful conclusions surrounding the efficacy of CBD in animal models of stroke.

The results from the previous chapter prompted an in vivo investigation into the effects of CBD and cannabidiolic acid (CBDA) in a mouse model of stroke. CBD and CBDA had no significant effect on infarct volume 24 h following permanent middle carotid artery occlusion (pMCAO). An indirect measurement of vasogenic swelling was made, which showed CBD at 1 mg/kg increased brain water content by 7.6% ± 2.6, 95% CI [-5.9, 8.1] (p<0.05) relative to control mice. These results suggest that without adequate reperfusion CBD or CBDA do not reduce infarct volume 24 h following pMCAO. If this is indeed the case, future studies should aim to directly assess whether reperfusion is a necessary perquisite for CBD and CBDA to display efficacy.

Astrocytes are implicated in maintaining neuronal homeostasis and therefore preserving their viability during or following a stroke could represent a novel therapeutic strategy. Using an in vitro model of human astrocytes exposed to oxygen glucose deprivation (OGD), these experiments aimed to identify whether less researched minor phytocannabinoids could influence several endpoints associated with OGD damage, such as; lactate dehydrogenase (LDH) for cellular damage, interleukin-6 (IL-6) for inflammation and mitochondrial complex proteins for impaired energy production. The efficacy of each phytocannabinoid was assessed by being applied before or after OGD injury. These experiments identified that CBD is only effective at protecting against OGD induced damage when applied following the insult. In contrast, CBGV provided the greatest extent of protection, reducing cellular damage when administered before or after OGD, indicating this phytocannabinoid might address molecular disturbances at both the ischemic and reperfusion period. Further studies should look to assess the co-application of these phytocannabinoids and assess their effects in more complex cellular models.

The next set of in vitro experiments aimed to distil the belief held by the non-scientific community that naturally sourced CBD is superior to CBD produced by synthetic means using empirical evidence. To do so, the pharmacological activity of CBD from two different sources (synthetic vs. naturally occurring) was compared in three human cellular models; cancer, stroke and irritable bowel syndrome (IBD). The results from these experiments demonstrated no pharmacological difference exist in the anti-proliferative, anti-inflammatory, or permeability effects of purified natural versus synthetic CBD. Indicating the reliability and formulations of CBD should be considered above the starting source in the development of medicines.

Using two human cellular models of disease, cancer and stroke, a series of in vitro experiments aimed to assess the pharmacological properties of CBD and tetramethylpyrazine (TMP). These experiments would specifically aim to assess whether co-application at a 1:1 ratio produces synergistic, additive, neutral or compromised efficacy. Co-applied CBD and TMP produces an additive effect on anti-proliferative properties, particularly in ovarian cancer cell line SKOV3. The anti-migratory effects of CBD were attenuated when applied alongside TMP in DU145 and SKOV-3 cells. TMP applied alongside CBD in cellular models of OGD/R injury had no effect on or antagonised CBD’s effects. Mechanism of action studies are required to understand why the combination of CBD and TMP produces additive or compromising effects in certain anti-cancer endpoints.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: O'Sullivan, Saoirse
England, Timothy
Keywords: Phytocannabinoids, Stroke, Astrocytes, Pericytes, Cancer, IBD, CBD, CBGV, CBC, CBDV
Subjects: QS-QZ Preclinical sciences (NLM Classification) > QV Pharmacology
Faculties/Schools: UK Campuses > Faculty of Medicine and Health Sciences > School of Medicine
Item ID: 69202
Depositing User: Maguire, Ryan
Date Deposited: 01 Aug 2022 04:40
Last Modified: 01 Aug 2022 04:40
URI: http://eprints.nottingham.ac.uk/id/eprint/69202

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