Pharmacology and Toxicologyhttp://hdl.handle.net/10523/2322024-03-18T17:41:24Z2024-03-18T17:41:24ZRole of P450 and Phase II enzymes in the (A) anticancer effect of various teas (B) metabolism of a novel antitumour drug DACAMaliakal, Piushttp://hdl.handle.net/10523/166182024-03-18T14:40:54Z2024-03-01T02:41:40ZRole of P450 and Phase II enzymes in the (A) anticancer effect of various teas (B) metabolism of a novel antitumour drug DACA
2000-12-09
Maliakal, Pius
The thesis investigates the role of phase I and phase II enzymes in chemoprevention and chemotherapy of cancer. Green, black and herbal teas were chosen to assess the former aspect while a metabolic study of DACA was selected to test the latter. Bioactivation of procarcinogens, detoxification of ultimate carcinogens and biotransformation of chemotherapeutic agents are carried out mainly by drug-metabolizing enzymes. […]
In brief, the present study was able to provide evidence of (a) an association of CYP, UGT and/or GST enzyme activity changes with the anticancer effect of green and herbal teas and (b) mediation of CYP3A in the biotransformation of DACA.
Pages 195 and 226 missing in the original. Some pages out of order in the original, but arranged in proper order for the scan.
2024-03-01T02:41:40ZPharmacokinetic and pharmacodynamic studies of B-blockers and salicylates in the maternal-fetal unitShen, Jingjianhttp://hdl.handle.net/10523/166172024-03-08T14:18:34Z2024-03-01T02:40:58ZPharmacokinetic and pharmacodynamic studies of B-blockers and salicylates in the maternal-fetal unit
1991-12-14
Shen, Jingjian
2024-03-01T02:40:58ZThe delivery of bioactive peptides across the salmonid posterior intestineSchep, Leo Johnhttp://hdl.handle.net/10523/166162024-03-18T14:40:54Z2024-03-01T02:40:32ZThe delivery of bioactive peptides across the salmonid posterior intestine
1999-12-04
Schep, Leo John
The rapid expansion of demand for fish supplies for human consumption has led to the exhaustion of many marine fisheries. Any further increment to satisfy this demand must come from the aquaculture industry. To successfully breed fish in captivity, however, the synchronisation of reproduction must be achieved. Presently, this predominantly involves the parenteral administration of gonadotropin-releasing hormone (GnRH). Because of the recognised disadvantages associated with this route, such as increased stress on fish, oral routes of delivery to fish including salmon are being attempted. However, little is still known of the intestinal barriers to oral peptide delivery in salmon. Therefore, this thesis investigated the physical barriers to oral peptide delivery to salmon and methods to improve such delivery. […]
2024-03-01T02:40:32ZPharmaceutical solid dispersions formed by solvent change co-precipitation : a study of their manufacture and propertiesSertsou, Gabrielhttp://hdl.handle.net/10523/166082024-03-13T02:00:09Z2024-02-28T02:58:16ZPharmaceutical solid dispersions formed by solvent change co-precipitation : a study of their manufacture and properties
2002-12-07
Sertsou, Gabriel
Purpose: Poorly water-soluble drugs often show dissolution rate limited bioavailability. The aim of this study was to investigate the manufacture of pharmaceutical solid dispersions made by solvent change co-precipitation, as a possible method of improving drug dissolution. […]
Conclusions: The work described in this thesis has demonstrated that in-vitro improvement in dissolution of the drug GWX, can be achieved by formulating it as a fairly stable coprecipitate with HPMCP. The advantages with respect to dissolution seen with high HPMCP:drug ratio co-precipitates, may be offset by cost, possible toxicological issues, and mechanical properties less suitable for handling and/or comminution, due to the high polymer loading. Co-precipitation in the manner used, may therefore be more suitable for high potency (low dose) drugs.
2024-02-28T02:58:16ZMolecular pharmacology of synthetic cannabinoid receptor agonists. Exploring potential mechanisms underpinning synthetic cannabinoid receptor agonist toxicity beyond activity at the cannabinoid CB1 receptorPatel, Monicahttp://hdl.handle.net/10523/164272023-12-04T19:28:05Z2023-12-04T19:26:40ZMolecular pharmacology of synthetic cannabinoid receptor agonists. Exploring potential mechanisms underpinning synthetic cannabinoid receptor agonist toxicity beyond activity at the cannabinoid CB1 receptor
2023
Patel, Monica
Synthetic cannabinoid receptor agonists (SCRAs) are a chemically diverse class of compounds originally designed to explore the therapeutic benefits of the endocannabinoid system. The compounds have gained considerable attention owing to their ability to mimic the psychoactive effects of Δ9-tetrahydrocannabinol (THC), the primary bioactive component of cannabis, instigating their diversion to the recreational drug market. However, SCRA use is increasingly associated with incidences of severe toxicity and death worldwide, with limited insight into their pharmacology or toxicology. SCRAs are predicted to mediate their effects primarily through activation of the cannabinoid CB1 receptor (CB1). Yet characterisation of the molecular pharmacology at CB1 has failed to reveal a unique activity profile pertaining to SCRAs, aside from their potent and efficacious activation of the receptor. This thesis aimed to further characterise the molecular pharmacology of SCRAs beyond CB1, focusing on the cannabinoid CB2 receptor (CB2) and potential ‘off-target’ receptors.
Preliminary hypotheses surrounding SCRA toxicity implicated the robust recruitment of β-arrestins, proteins fundamental to the regulation of G protein-coupled receptors (GPCRs), such as the cannabinoid receptors. In this thesis, G protein-coupled receptor kinases (GRKs), enzymes considered crucial to facilitating receptor interactions with β-arrestins, were dispensable in the translocation of β-arrestins to CB2, contrary to the classical paradigm proposed for GPCRs. Subsequent characterisation of several signalling and regulatory pathways revealed SCRAs induced robust activation of CB2, contrasting with the activity profile of THC, most notably in the translocation of β-arrestins – congruent with findings at CB1. Finally, investigation into the activation of non-cannabinoid GPCRs failed to support the proposition that off-target activity partly mediates the complex and extensive physiological effects of SCRAs.
The findings in this thesis corroborated that SCRAs induce robust activation of the cannabinoid receptors, with limited off-target activity. However, this thesis fails to identify a molecular mechanism underlying SCRA-mediated toxicity. Further research is required to elucidate whether the activation of CB2 contributes to the physiological effects of SCRAs. Advancing our understanding of the pharmacology of this diverse class of compounds remains vital to identifying potential links to toxicity and predicting harm in humans.
2023-12-04T19:26:40ZInhibitory Action of a Novel Carbon Monoxide-Releasing Molecule on Hepatic Microsomal CYP3ASewell, Katya Annalisehttp://hdl.handle.net/10523/163982024-01-15T18:52:49Z2023-11-21T20:38:03ZInhibitory Action of a Novel Carbon Monoxide-Releasing Molecule on Hepatic Microsomal CYP3A
2023
Sewell, Katya Annalise
Carbon monoxide (CO), notorious for its toxicity, is endogenously produced by heme oxygenase and plays a role in diverse signalling pathways with wide-ranging physiological effects. Consequently, CO delivery has been explored as a potential therapy for conditions such as cardiovascular diseases. To address this need, CO-releasing pro-drugs have been developed, offering diverse release kinetics and potencies, making them potentially valuable candidates for clinical application. This research direction led to the development of novel and organic pH-dependent carbon monoxide-releasing molecules (oCOms) which have been demonstrated to exert a wide range of cardioprotective effects at low micromolar concentrations with minimal cardiotoxic injury.
The strong binding of CO to heme-containing proteins suggests the strong possibility that oCOms may inhibit the activity of cytochromes P450 (CYP450), key enzymes in xenobiotic metabolism. This study examines the concentration-dependent inhibitory effects of the fast-releasing CO-donor oCOm-21, with a half-life of 20 mins against that of a non-active debromo oCOm-21 (DB-21) and of a CO-depleted oCOm-21 by-product (BP-21) on in vitro microsomal CYP activity. Rat liver microsomes (RLM) were isolated from male Sprague Dawley rats and incubated with 0.3 - 10 µM of the CO-releasing oCOm-21 and the non-CO-releasing compounds DB-21 and BP-21. The enzymatic activity of hepatic rat microsomal CYP3A was assessed by measuring the formation of formaldehyde as the product of an erythromycin N-demethylation assay.
The results showed that both oCOm-21 and DB-21 significantly inhibited CYP3A activity, whereas BP-21 had no effect. This finding confirms that oCOm-21-derived CO produces a concentration-dependent inhibition of CYP3A activity and suggests that oCOm-21 CO release may be additionally activated by CYP450 oxidation mechanisms apart from the established mechanism of pH-triggered CO release. Furthermore, as hypothesised, the CO-depleted BP-21 had far less effect on CYP3A activity suggesting that BP-21 is a more suitable control for oCOm-21 than DB-21 in microsomal assays. These findings support further investigation into the pharmacokinetics of oCOm-21 and contribute to the pre-clinical safety information on oCOms. This research advances our understanding of the potential for drug interactions in a polypharmacy setting, where drug metabolism occurs through CYP450 mechanisms.
2023-11-21T20:38:03ZLocalisation of the Calcitonin Receptor and its Ligands in Migraine-Relevant Regions of Male and Female MiceDawson, Angelina Marianhttp://hdl.handle.net/10523/163802023-11-20T22:08:06Z2023-11-20T22:07:33ZLocalisation of the Calcitonin Receptor and its Ligands in Migraine-Relevant Regions of Male and Female Mice
2023
Dawson, Angelina Marian
Migraine is a common and debilitating neurovascular disorder which affects approximately 15% of the population and presents a significant burden on those living with the disease. During a migraine attack, increased levels of the vasoactive neuropeptide calcitonin gene-related peptide (CGRP) are observed. However, the exact mechanisms of migraine remain unknown. The CGRP-responsive amylin 1 (AMY1) receptor, comprised of the calcitonin receptor (CTR) and receptor activity-modifying protein 1 (RAMP1), has recently been implicated as potentially relevant in migraine signalling. While expression data is available for CGRP and these receptor subunits separately, the expression of these proteins have never been explored in conjunction. Investigating the distribution of this expression in migraine-relevant regions which are documented to express CGRP-binding sites may contribute to elucidating migraine mechanisms. Thus, the present study aimed to investigate the spatial distribution of CTR relative to CGRP within migraine-relevant regions, including the lateral medulla, dorsolateral pons, and the amygdala. In three female and three male mice, immunohistochemistry was performed for the detection of CGRP-like and CTR-like immunoreactivity within these regions, with cell markers included to indicate potential immunoreactivity within cell bodies. Findings were visualised using confocal microscopy. Bright and dense CGRP-like immunoreactivity was predominantly observed in pearl-like fibres, particularly within the spinal trigeminal nucleus of the lateral medulla, the external division of the lateral parabrachial nucleus, and the capsular region of the central amygdala. Strong CTR-like immunoreactivity was observed in a combination of fibres and cell bodies, with regions of expression including the area postrema of the lateral medulla, throughout the parabrachial nucleus and locus coeruleus, and in the lateral region of the central amygdala. No visual qualitative difference was apparent in CGRP-like or CTR-like immunoreactivity between male and female mice. Throughout all sections, no co-localisation of CGRP-like and CTR-like immunoreactivity was observed; however, CGRP-like and CTR-like immunoreactivity was consistently found in close proximity to each other.
These findings suggest that in some migraine-relevant brain regions, CGRP may activate CTR (potentially with RAMP1) in a paracrine manner, and therefore supports a potential role of the AMY1 receptor in migraine.
2023-11-20T22:07:33ZThe Role of Gα12/13 in CB1-Mediated β-arrestin RecruitmentSimpson, Steven Alexanderhttp://hdl.handle.net/10523/163152023-11-10T13:02:07Z2023-11-10T00:23:13ZThe Role of Gα12/13 in CB1-Mediated β-arrestin Recruitment
2023
Simpson, Steven Alexander
The main psychoactive ingredient in the plant Cannabis sativa is Δ9-trans-tetrahydrocannabinol, which was found to signal through the cannabinoid CB1 receptor (CB1). CB1 is one of two main G protein-coupled receptors (GPCRs) in the endocannabinoid system. Though CB1 has been shown to preferentially couple to Gαi/o proteins, there has been evidence for promiscuous coupling to other classes. Gα12/13 proteins are one of the four main families of G proteins and act through Rho-guanine nucleotide exchange factors to stimulate RhoA. This leads to the activation of Rho-associated kinase and regulation of the actomyosin cytoskeleton. To modulate the signalling of GPCRs, arrestins have been demonstrated to have a key role in governing the processes of internalisation and desensitisation. Here, this research aimed to investigate the role of Gα12/13 proteins in the modulation of CB1-mediated β-arrestin recruitment. In HEK293A wild type (WT) cells, CB1 activated both Gα12 and Gα13 proteins in a concentration-dependent manner in TRUPATH G protein dissociation bioluminescence resonance energy transfer (BRET) assays. CB1-mediated β-arrestin 2 recruitment was enhanced in a concentration-dependent manner in HEK293A Gα12/13 protein knock-out (ΔGα12/13) cells, compared to WT cells in BRET β-arrestin translocation assays. β-arrestin 2 recruitment was almost abolished with the reintroduction of Gα12/13 proteins. Phosphorylation of extracellular-signal regulated kinase was assessed using a BRET biosensor assay, showing attenuated levels in ΔGα12/13 cells compared to WT cells, which was not restored when adding back Gα12/13 proteins. Receptor trafficking revealed no differences in cell surface half-life of CB1 between WT and ΔGα12/13 cells, though the addition of β-arrestin reduced half-life in both cell lines. Interestingly, the morphology of ΔGα12/13 cells appeared to have more cytoskeletal outgrowths than WT cells, which was reversed when Gα12/13 proteins were reintroduced. Overall, we demonstrate that ΔGα12/13 proteins are activated at CB1, though their modulatory role on CB1-mediated β-arrestin recruitment requires further study.
2023-11-10T00:23:13Z