Carbon 11-labeled Pittsburgh Compound B and carbon 11-labeled (R)-PK11195 positron emission tomographic imaging in Alzheimer disease.
BACKGROUND
Alzheimer disease (AD) is defined neuropathologically by the presence of neurofibrillary tangles and plaques associated with tau and beta-amyloid protein deposition. The colocalization of microglia and beta-amyloid plaques has been widely reported in pathological examination of AD and suggests that neuroinflammation may play a role in pathogenesis and/or progression. Because postmortem histopathological analyses are limited to single end-stage assessment, the time course and nature of this relationship are not well understood.


OBJECTIVE
To image microglial activation and beta-amyloid deposition in the brains of subjects with and without AD.


METHODS
Using two carbon 11 ([11C])-labeled positron emission tomographic imaging agents, Pittsburgh Compound B (PiB) and (R)-PK11195, we examined the relationship between amyloid deposition and microglial activation in different stages of AD using 5 control subjects, 6 subjects diagnosed with mild cognitive impairment, and 6 patients with mild to moderate AD.


RESULTS
Consistent with prior reports, subjects with a clinical diagnosis of probable AD showed significantly greater levels of [11C]PiB retention than control subjects, whereas patients with mild cognitive impairment spanned a range from control-like to AD-like levels of [11C]PiB retention. Additionally, 2 asymptomatic control subjects also exhibited evidence of elevated PiB retention in regions associated with the early emergence of plaques in AD and may represent prodromal cases of AD. We observed no differences in brain [11C](R)-PK11195 retention when subjects were grouped by clinical diagnosis or the presence or absence of beta-amyloid pathological findings as indicated by analyses of [11C]PiB retention.


CONCLUSIONS
These findings suggest that either microglial activation is limited to later stages of severe AD or [11C](R)-PK11195 is too insensitive to detect the level of microglial activation associated with mild to moderate AD.
Wiley
Clayton A
CA
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15213, USA. wiley1@pitt.edu
Lopresti
Brian J
BJ
Venneti
Sriram
S
Price
Julie
J
Klunk
William E
WE
DeKosky
Steven T
ST
Mathis
Chester A
CA
D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D016229:Amyloid beta-Peptides / Q000032:analysis / Q000378:metabolism; D000814:Aniline Compounds; D000970:Antineoplastic Agents; D001921:Brain / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D002250:Carbon Radioisotopes; D003072:Cognition Disorders / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D018450:Disease Progression; D004660:Encephalitis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D005260:Female; D005911:Gliosis / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D007546:Isoquinolines; D008297:Male; D017628:Microglia / Q000000981:diagnostic imaging / Q000473:pathology; D008875:Middle Aged; D058225:Plaque, Amyloid / Q000000981:diagnostic imaging / Q000473:pathology; D049268:Positron-Emission Tomography / Q000379:methods*; D011237:Predictive Value of Tests; D013844:Thiazoles
C475519:2-(4'-(methylamino)phenyl)-6-hydroxybenzothiazole; D016229:Amyloid beta-Peptides; D000814:Aniline Compounds; D000970:Antineoplastic Agents; D002250:Carbon Radioisotopes; D007546:Isoquinolines; D013844:Thiazoles; C037850:PK 11195