Abstract/Summary

The average age of our population continues to grow as a result of increasing longevity. Indeed, according to WHO, by the year 2100, nearly one third of the global population will be 60+ years old. However, the key factors and signalling pathways involved in cellular ageing remain largely unknown. Our hypothesis is that oxidative stress generated by the activation of a Nox2-containing NADPH oxidase plays a key role in ageing-related vascular and neuro-degenerative disorder. Therefore, the overall aim of this PhD research project is to investigate the role of Nox2 activation in ageing-related brain oxidative stress and cerebral endothelial damage using littermates of age-matched wild-type (WT) and Nox2 knockout (KO) mice (C57BL/6J background) at young (3-4 months, similar to human ~20-30 years old) and old age (21-22 months, similar to human ~70-80 years old). I have found a significant increase in the levels of reactive oxygen species (ROS) production in multiple organs of WT ageing mice in comparison with WT young mice, and this can be significantly inhibited by knockout of Nox2. There was a significant reduction of locomotor function in WT ageing mice but not in Nox2 KO ageing mice. Increased ROS production in the WT ageing brain was accompanied by (1) significant decreases in brain endothelia cells and neurons; (2) significant increases in microglial cells and brain Nox2 expression; and (3) an activation of stress signalling pathways such as ERK1/2. Once again, these ageing-related changes were inhibited significantly by knockout of Nox2. The crucial role of ageing related Nox2 activation in oxidative damage of endothelial function was further investigated in vitro using coronary microvascular endothelial cells isolated from WT versus Nox2KO mice stimulated with high glucose plus insulin, and this was further confirmed using brain tissues of endothelial specific Nox2 overexpression mice at young and old ages. Furthermore, ageing-associated increases in brain ROS production and Nox2 activation was confirmed using human post-mortem brain tissues. In conclusion, Nox2-derived oxidative stress plays an important role in ageing-associated systemic oxidative stress, cerebral endothelial damage, neurodegeneration and loss of locomotor function. Targeting Nox2 represents a valuable therapeutic strategy to treat these ageing-related diseases.