Characterising the transcriptional, spatial and behavioural consequences of TLR7-driven neuroinflammation

Gardner-Stephen, Kirstyn (2025) Characterising the transcriptional, spatial and behavioural consequences of TLR7-driven neuroinflammation. PhD thesis, University of Glasgow.

Abstract

Neuropsychiatric conditions, such as depression and anxiety, are a burden for both the people living with them and from a socioeconomic viewpoint. Traditional pharmacological interventions for these syndromes primarily focus on altering levels of monoamine neurotransmitter availability within the brain. From this patient group, a non-responsive fraction to these monoamine treatments has emerged. This calls for better understanding of alternative pathophysiology that can lead to these clinical conditions. From this search for different causative pathways of neuropsychiatric conditions, an inflammation-driven theory emerged. This neuroinflammation-focused pathophysiology proposes that raised intracerebral pro-inflammatory cytokines can alter neural circuits and ultimately result in behavioural changes.

The molecular and cellular mechanisms underpinning neuroinflammation are relatively poorly understood. To further understand these neural changes, this work uses the Aldara model of non-invasive toll-like receptor (TLR)-7-driven neuroinflammation. The Aldara model involves topically applied cream containing imiquimod (IMQ), which is a TLR7 agonist. This has been found to trigger both a peripheral dermal psoriasis-like response and cross the blood brain barrier (BBB) to directly activate TLR7-expressing CNS-resident cells. This thesis focuses on characterising the transcriptional global and region-specific TLR7-driven neuroinflammation. Both brain-resident microglia and peripheral T cell populations will be explored in respect to their cytokine production and reactive status. To characterise the interplay between microglia and mature lymphocytes, RAG2KO mice which lack B and T cells were used. Spatial transcriptomics was used to evaluate the immune cell response within the Aldara model and transcriptionally investigate brain regions linked to reward behaviours. To further characterise inflammation-driven behavioural changes, a battery of behavioural tests have been implemented to characterise anxiety-like and anhedonia-like behaviours.

This data presents a transcriptionally-validated global neuroinflammation response within the Aldara model. Both microglia and T cells are found to actively produce cytokines in the TLR7-driven neuroinflammation. Spatial transcriptomics identified 5 potential subclusters of immune cells within the CNS. These had a primary pro-inflammatory transcriptional signature with suggestions of a potential anti-inflammatory response. Immune-rich neighbourhoods in the brain were found uniquely in Aldara-treated mice via spatial transcriptomics. RAG2KO Aldara-treated mice still displayed heightened microglial reactivity via Iba1+ staining. Brain regions associated with reward circuity were found to upregulate pro-inflammatory transcriptional responses and downregulate synaptic signalling-related genes. Behavioural tests documented an anhedonia-like phenotype within Aldara-treated mice. This work presents the Aldara model as a useful non-invasive tool to study neuroinflammation.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: Q Science > QR Microbiology > QR180 Immunology; R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Supervisor's Name: McGonigal, Dr. Rhona and Cavanagh, Professor Jonathan
• Date of Award: 2025
• Depositing User: Theses Team
• Unique ID: glathesis:2025-85509
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 08 Oct 2025 08:59
• Last Modified: 09 Oct 2025 09:00
• Thesis DOI: 10.5525/gla.thesis.85509
• URI: https://theses.gla.ac.uk/id/eprint/85509