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Open Access Research

Evaluation of age-related changes in translocator protein (TSPO) in human brain using 11C-[R]-PK11195 PET

Ajay Kumar125, Otto Muzik125, Varun Shandal125, Diane Chugani1345, Pulak Chakraborty125 and Harry T Chugani125*

Author Affiliations

1 Department of Pediatrics, School of Medicine, Children’s Hospital of Michigan, Detroit Medical Center, Wayne State University, 3901 Beaubien Boulevard, Detroit, MI, USA

2 Department of Neurology, School of Medicine, Children’s Hospital of Michigan, Detroit Medical Center, Wayne State University, Detroit, MI, USA

3 Department of Radiology, School of Medicine, Children’s Hospital of Michigan, Detroit Medical Center, Wayne State University, Detroit, MI, USA

4 Department of Pharmacology, School of Medicine, Children’s Hospital of Michigan, Detroit Medical Center, Wayne State University, Detroit, MI, USA

5 PET Center, School of Medicine, Children’s Hospital of Michigan, Detroit Medical Center, Wayne State University, Detroit, MI, USA

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Journal of Neuroinflammation 2012, 9:232  doi:10.1186/1742-2094-9-232

Published: 4 October 2012

Abstract

Background

We studied the distribution and expression of translocator protein in the human brain using 11C-[R]-PK-11195 positron emission tomography (PK11195 PET) and evaluated age-related changes.

Methods

A dynamic PK11195 PET scan was performed in 15 normal healthy adults (mean age: 29 ±8.5 years (range: 20 to 49); 7 males) and 10 children (mean age: 8.8 ±5.2 years (range: 1.2 to 17); 5 males), who were studied for potential neuroinflammation but showed no focally increased PK11195 binding. The PET images were evaluated by calculating standard uptake values and regional binding potential, based on a simplified reference region model, as well as with a voxel-wise analysis using statistical parametric mapping.

Results

PK11195 uptake in the brain is relatively low, compared with the subcortical structures, and symmetrical. The overall pattern of PK11195 distribution in the brain does not change with age. PK11195 uptake was lowest in the frontal-parietal-temporal cortex and highest in the pituitary gland, midbrain, thalamus, basal ganglia, occipital cortex, hippocampus and cerebellum, in descending order. White matter showed negligible PK11195 uptake. Overall, brain PK11195 uptake increased with age, with midbrain and thalamus showing relatively higher increases with age compared with other brain regions.

Conclusions

The brain shows low PK11195 uptake, which is lower in the cortex and cerebellum compared with subcortical structures, suggesting a low level of translocator protein expression. There is no hemispheric asymmetry in PK11195 uptake and the overall pattern of PK11195 distribution in the brain does not change with age. However, brain PK11195 uptake increases with age, with the thalamus and midbrain showing relatively higher increases compared with other brain regions. This increase in uptake suggests an age-related increase in translocator protein expression or the number of cells expressing these receptors or both.

Keywords:
Adults; Brain; Children; C-[R]-PK-11195 positron emission tomography; Glial cells; Inflammation; Microglia; Neuroinflammation; PBR; Peripheral benzodiazepine receptor; PK11195 PET; Translocator protein; TSPO