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Wong, Sara Wei Ting (2022) Modulating oxytocin brain penetration via intranasal delivery and a novel conjugate peptide (OT-GET). PhD thesis, University of Nottingham.

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Abstract

Oxytocin (OT), an endogenous hormone and neuropeptide has been highlighted for its therapeutic potential to modulate socio-behavioural deficits. However, OT’s high molecular weight and hydrophilicity limits the extent of central nervous system (CNS) brain penetration, highlighting a need to improve OT brain delivery. An alternative popular route of drug delivery is intranasal administration, which allows small peptides to bypass the blood brain barrier (BBB) and access the brain more directly. Yet, the degree of OT brain penetration remains controversial and requires further improvement. As such, this thesis examined the modulation of CNS OT penetration by use of intranasal OT alone and when conjugated to a novel cell penetrating peptide: glycosaminoglycan (GAG)-binding enhanced transduction (GET; P21-LK15- 8R), producing OT-GET, and its ability to affect locomotor activity and social behaviour in rats.

In vitro assays were established to determine OT-GET’s bioactivity, ability to improve OT transduction across a nasal epithelial cell monolayer and potential cytotoxicity. Using a calcium fluorimetry assay, OT-GET induced robust [Ca2+]i transients in OTR expressing Hs 578t breast cancer cells. Subsequent examination of OT-GET in a cell permeability assay using immortalised nasal epithelial cells RPMI 2650 saw an increased rate of OT delivery across the monolayer compared to OT alone. Only the highest GET concentration produced cytotoxicity (on cell viability) effects, which emphasised the need to identify an ideal peptide conjugation ratio in order to achieve desired effects without concomitant toxicity.

In rats, subcutaneous OT (0.1mg/kg) reversed phencyclidine (PCP)-induced hyperactivity. Intranasal OT (100μg) showed slight effect, where cumulative ambulatory counts in the 30 minutes post-PCP was not significantly different to rats pre-treated with subcutaneous OT, although counts remained higher than saline treated animals. The same dose of intranasal OT increased the time spent by weight-matched rat pairs in prosocial body sniffing. Interestingly, a separate quantification of OT levels in the olfactory bulb revealed that OT-GET treated animals had a significant increase in OT compared to OT treated animals.

Overall, OT-GET improved OT permeation across a nasal cell monolayer in vitro and improved brain penetration (olfactory bulb) in vivo compared to OT alone. Intranasal OT-GET did not produce changes in rats’ social behaviour, which may be due to OT receptor (OTR) desensitisation.

Item Type:	Thesis (University of Nottingham only) (PhD)
Supervisors:	Fone, Kevin C.F. King, Madeleine V.
Keywords:	Oxytocin, Intranasal deliver, Novel conjugate peptide, OT-GET
Subjects:	R Medicine > RM Therapeutics. Pharmacology
Faculties/Schools:	UK Campuses > Faculty of Medicine and Health Sciences > School of Life Sciences
Item ID:	67435
Depositing User:	Wong, Sara
Date Deposited:	31 Jul 2022 04:40
Last Modified:	31 Jul 2022 04:40
URI:	https://eprints.nottingham.ac.uk/id/eprint/67435

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