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Title: Interactions of nerve growth factor and tumour necrosis factor alpha signalling in pain relevant cell types
Author: Hammett, Kessia May
ISNI:       0000 0004 7970 0383
Awarding Body: King's College London
Current Institution: King's College London (University of London)
Date of Award: 2019
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Chronic pain occurs due to a maladaptive response of the nociceptive system. As a global health issue, the discovery of novel pain treatments is key to reducing the substantial economic burden associated with this condition, as well as the myriad of co-morbid diseases. Data from pre-clinical mouse models of chronic pain have shown a superior analgesic effect when using a bispecific blocker directed against both nerve growth factor (NGF) and tumour necrosis factor (TNFα) compared to targeting either one alone. Here, we tested the hypothesis that synergistic interactions exist between these two pain-relevant mediators. In primary neuronal cultures and a novel co-culture system, comprising mouse adult dorsal root ganglia (DRG) neurones with bone-marrow derived macrophages (BMDM), we quantified gene expression and functional cellular responses to NGF, TNFα or a combination of the two, assaying for additive or synergistic actions of these two mediators. We demonstrate robust responses of highly purified DRG neuronal cultures to NGF but fail to detect TNFα responsiveness. However, using our novel adult DRG neurone-macrophage co-culture system we highlight a role for NGF and TNFα in sensitising primary afferent CGRP release. We show a critical role for macrophages in delivering TNFα-driven sensitisation, which appears to summate with the direct NGF sensitisation of DRG neurones. In a mouse models of inflammatory chronic pain, we detect an increase in Cd14 and Itgam mRNA within pain-relevant tissue (DRG and knee fat pad), indicative of myeloid cells (most likely macrophage) infiltration. Combined individual antagonism of NGF and TNFα does not prevent these increases in mRNA levels from occurring post intra-articular CFA (Complete Freund's Adjuvant) administration. We show that conditioned medium derived from TNFα-stimulated BMDM enhances the expression of several pain-relevant transcripts in purified DRG cultures. These data suggest that the mechanism(s) by which the dual blockade (of NGF and TNFα) regulates analgesia is not simply by an inhibition of non-neuronal cell type infiltration into pain-relevant tissue types, but more likely to be dependent on a combined dampening of neuronal sensitisation evoked by the TNFα-induced macrophage secretome and the direct activity of NGF at nociceptors.
Supervisor: McMahon, Stephen Brendan Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available