Neuroinflammation is linked to the progression of neurodegenerative disorders. Activated inflammatory cells of the myeloid lineage, in particular microglia, play a key role in the pathogenesis of these chronic disorders. Activated microglial cells enhance the production of inflammatory cytokines and chemokines like interleukin-1, interleukin-6, tumor necrosis factor α and make microglia more susceptible to secondary stimuli, promoting microglial activation.
In the described assays a common used bacterial endotoxin (lipopolysaccharide, LPS) is used as a proinflammatory stimulus for microglia cells.
The in-vitro screening assay described uses cortical glial or pure microglial cultures. LPS induces inflammatory reactions in glial cells after 24 hour exposure time. It is possible to determine inflammatory cytokines from the culture medium or cell lysate.
The first in-vivo assay described is the use of microdialysis to continuously sample interstitial fluid (ISF) for example in the hippocampus or the prefrontal cortex to determine cytokine levels after microglia activation by priming with LPS.
The second in-vivo assay is PET imaging to measure neurological changes in various pathological states. However, quantification of PET tracers where reference tissue models cannot be applied, has been challenging in rodents. The method used here is to obtain metabolite corrected arterial input function (AIF) from rats, which allows longitudinal PET scanning individuals and weekly follow-up of neuroinflammation.
The combination of existing in-vitro and in-vivo assays gives us the ability to delineate the underlying molecular mechanisms, thus reinforcing the development of new treatment strategies and biomarkers for neurodegenerative disorders beyond the existing conventional approaches.