It is important to gain more insight into
neurodegenerative diseases, because these debilitating diseases can not be cured. A common characteristic of many neurological diseases is
neuroinflammation, which is accompanied by the presence of activated microglia cells. In activated microglia cells, an increase in the expression of peripheral
benzodiazepine receptors (PBR) can be found. The PBR was suggested as a target for monitoring
disease progression and
therapy efficacy with positron emission tomograpy (PET). The PET tracer [(11)C]
PK11195 has been widely used for PBR imaging, but the tracer has a high lipophilicity and high non-specific binding which makes it difficult to quantify uptake. Therefore, efforts are being made to develop more sensitive radioligands for the PBR. Animal studies have yielded several promising new tracers for PBR imaging, such as [(11)C]
DAA1106, [(18)F]FEDAA1106, [(11)C]PBR28, [(11)C]DPA713 and [(
11)C]CLINME. However, the potential of these new PBR
ligands is still under investigation and as a consequence [(11)C]
PK11195 is used so far to image activated microglia cells in
neurological disorders. With [(11)C]
PK11195, distinct
neuroinflammation was detected in
multiple sclerosis,
Parkinson's disease,
encephalitis and other neurological diseases. Because
neuroinflammation plays a central role in the progression of
neurodegenerative diseases, anti-inflammatory drugs have been investigated for therapeutic intervention. Especially
minocycline and
cyclooxygenase inhibitors have shown in vivo anti-inflammatory, hence neuroprotective properties, that could be detected by PET imaging of the PBR with [(11)C]
PK11195. The imaging studies published so far showed that the PBR can be an important target for monitoring
disease progression,
therapy response and determining the optimal
drug dose.