Neurology Central

Novel imaging technique uncovers minutiae of neuroinflammation process

Neuroinflammation caused by an immune response in the brain could be a triggering factor of the neurodegeneration present in certain dementias, multiple sclerosis and other conditions of the CNS. At the core of this reactive immune response are immune cells termed microglia, the activation of which may be measurable with a novel PET imaging technique. Details of the technique were presented recently at the 2015 Annual Meeting of the Society of Nuclear Medicine and Molecular Imaging (11–15 June, CA, USA) and could in future offer guidance on how best to treat neurodegenerative conditions associated with inflammation.

“The imaging technique could shed light on the immune dysfunction that underpins a broad range of neuroinflammatory diseases, such as Alzheimer’s disease, depression, post-traumatic stress disorder and addiction,” commented lead author Christine Sandiego from Yale School of Medicine (CT, USA). “This is the first human study that accurately measures this immune response in the brain. The discoveries made with this technique could contribute to promising new drug treatments.”

In the study, the team were able to measure microglia activation and thus immune response in the brain via PET scan by utilizing a molecule isolated from E. coli termed lipopolysaccharide (LPS) accompanied by a radiotracer termed C-11 PBR28. When injected, LPS stimulates the immune system and the C-11 PBR28 binds to proteins that are expressed by active microglia. A PET scan is then able to detect the radioactive emissions, highlighting areas of increased microglia activation before and after immune stimulation with LPS.

Specifically, the study involved 8 healthy men all aged approximately 25 years, give or take 6 years. These eight individuals all received the C-11 PBR28 radiotracer followed by two PET scans, one before and one after injection with LPS. The subjects self-reported any adverse symptoms and blood samples were taken to assess peripheral inflammation. The results of the study demonstrated that administering LPS led to a substantial spike in the systemic inflammatory response and levels of reported sickness, and activated microglia in the CNS.

The authors suggest that with further study into how microglia promote neuroinflammation, drug therapies may be developed that can reduce their effect and encourage neuroprotective processes in the brain.

Source: Society of Nuclear Medicine and Molecular Imaging press release