Amyloid, tau, and astrocyte pathology in autosomal-dominant Alzheimer's disease variants : A beta PParc and PSEN1DE9

Autosomal-dominant Alzheimer's disease (ADAD) may be associated with atypical amyloid beta deposits in the brain. In vivo amyloid imaging using(11)C-Pittsburgh compound B (PiB) tracer has shown differences in binding between brains from ADAD and sporadic Alzheimer's disease (sAD) patients. To gain further insight into the various pathological characteristics of these genetic variants, we performed large frozen hemisphere autoradiography and brain homogenate binding assays with(3)H-PiB,H-3-MK6240-H-3-THK5117, and(3)H-deprenyl for detection of amyloid fibrils, tau depositions, and activated astrocytes, respectively, in twoA beta PParcmutation carriers, onePSEN1 Delta E9mutation carrier, and three sAD cases. The results were compared with Abeta 40, Abeta 42, AT8, and GFAP immunostaining, respectively, as well as with Congo red and Bielschowsky. PiB showed a very low binding inA beta PParc. A high binding was observed inPSEN1 Delta E9and in sAD tissues but with different binding patterns. Comparable(3)H-THK5117 and(3)H-deprenyl brain homogenate binding was observed forA beta PParc,PSEN1 Delta E9, and sAD, respectively. Some differences were observed between(3)H-MK6240 and(3)H-THK5117 in ADAD. A positive correlation between(3)H-deprenyl and(3)H-THK5117 binding was observed inA beta PParc, while no such correlation was found inPSEN1 Delta E9and sAD. Our study demonstrates differences in the properties of the amyloid plaques between two genetic variants of AD and sAD. Despite the lack of measurable amyloid fibrils by PiB in theA beta PParccases, high regional tau and astrocyte binding was observed. The lack of correlation between(3)H-deprenyl and(3)H-THK5117 binding inPSEN1 Delta E9and sAD in contrast of the positive correlation observed in theA beta PParccases suggest differences in the pathological cascade between variants of AD that warrant further exploration in vivo