Thesis

Does protease-activated receptor 2 (PAR2) modulate human astrocyte reactivity?

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Awarding institution
  • University of Strathclyde
Date of award
  • 2026
Thesis identifier
  • T18141
Person Identifier (Local)
  • 202270878
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Abstract
  • Introduction: Astrocytes are the most abundant glial cells in the central nervous system, playing critical roles in maintaining normal function as well as contributing to disease processes. In many neurodegenerative diseases, astrocytes undergo activation and transition into a reactive phenotype, which is proposed to exacerbate disease progression. Hence, these findings have fuelled investigations into whether reducing astrocytic reactivity is a novel pathway to develop therapies for diseases like Alzheimer’s. In a 5X FAD, mouse model of amyloid pathology, we have confirmed that astrocytic reactivity is increased and following protease-activated receptor 2 (PAR2) activation, astrocytic reactivity is significantly reduced leading to reduced amyloid pathology. However, whether modulation of astrocytic reactivity occurs in human astrocytes remains unknown. Hence, in the present study, we hypothesise that PAR2 activation will impair astrocytic reactivity when examined in commercially available human astrocytes. Methods: Ca2+ imaging and western blotting were undertaken in commercially available human astrocytes (cHAs) to examine the consequence of PAR2 activation in naïve cHAs. Astrocytic reactivity was assessed using immunocytochemistry using markers for reactivity, including GFAP, C3 and Gbp2.Results: PAR1 and PAR2 activation resulted in significant increases in intracellular Ca2+ levels in cHAs, which were inhibited by the PLC inhibitor U73122. However, in contrast to previous studies, PAR1 or PAR2 activation did not affect MAPK signalling in cHAs. Similarly, no differences in astrocytic reactivity were observed in cHAs, quantified using astrocytic reactivity markers, when cultured in either serum or serum-free media, as has been reported previously. In addition, PAR1 and PAR2 activation did not alter astrocytic reactivity in cHAs under either media condition. Moreover, these experiments were repeated in human iPSC-derived astrocytes to make a direct comparison with cHAs and determine whether the type of human astrocytes markedly alters their reactivity and potential modulation. TIC stimulation did not induce reactivity in iPSC-derived astrocytes although increased reactive marker transcripts levels were observed from transcriptomic analysis. However, TIC stimulated iPSC-derived astrocytes exhibited increased phagocytic function. In contrast, phagocytosis was unchanged in cHAs upon TIC stimulation. Conclusion: These findings confirm, for the first time, the presence of functional PARs in human astrocytes. However, neither serum-containing nor serum-free media, nor PAR activation, altered the reactivity or phagocytic activity of cHAs, underscoring the complex and heterogeneous nature of astrocytic reactivity.
Advisor / supervisor
  • Bushell, Trevor John
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