The 2,6-disubstituted naphthalene derivative FDDNP labeling reliably predicts Congo red birefringence of protein deposits in brain sections of selected human neurodegenerative diseases

Abstract

Deposition of conformationally altered proteins prominently characterizes pathogenesis and pathomorphology of a number of neurodegenerative disorders. 2-(1-{6-[(2-[F-18]fluoroethyl) (methyl)amino]-2-naphthyl} ethylidene) malononitrile ([F-18]FDDNP), a hydrophobic, viscosity-sensitive, solvent-sensitive, fluorescent imaging probe has been used with positron emission tomography to visualize brain pathology in the living brain of Alzheimer disease (AD) patients. Its non-radiofluorinated analog FDDNP was shown to label senile plaques and neurofibrillary tangles (NFTs) in brain tissue sections. This work aimed at evaluating FDDNP labeling of various protein deposits in fixed, paraffin-embedded brain tissue sections of selected neurodegenerative disorders: AD, cerebral amyloid angiopathy (CAA), transmissible spongiform encephalopathies, progressive supranuclear palsy (PSP), Pick disease (PiD), Parkinson disease, dementia with Lewy bodies, multiple system atrophy (MSA). Cerebral hypertensive vascular hyalinosis (HVH) was used as negative control. Significant agreement between amyloid histochemical properties and FDDNP labeling of the deposits was established. FDDNP labeling showed high positive predictive value for birefringence in senile plaques and NFTs in AD, prion plaques and amyloid deposits in CAA. No FDDNP labeled structures were observed in HVH, PSP, PiD or MSA tissue sections. Our findings may be of significant value for the detection of neuropathological aggregates with [F-18]FDDNP in some of these disorders in the living brain of human subjects.

Figures

Figure 1

Cerebral amyloid angiopathy tissue section labeling sequence (A–E), and hypertensive vascular hyalinosis (HVH, F, G). Blood vessels with marked Aβ deposition, shown in haematoxylin and eosin (A), labeled with FDDNP (B, FDDNP is also labeling less dense Aβ deposit spreading from vascular wall, arrowheads), Congo red in light (C) and cross‐polarized light microscopy (D), and anti‐Aβ immunohistochemistry (E). Vascular hyaline in HVH (shown in haematoxylin and eosin, F) is not labeled with FDDNP (G). Green fluorescent signal in B was pseudocolored yellow. Scale bar: A–E, 50 µm; F, G, 60 µm.

Figure 2

Scatter plot of Congo red birefringence vs. FDDNP labeling of studied types of microscopic structures. Horizontal axis shows the proportion of microscopic structures (identified in haematoxylin and eosin and immunohistochemistry photomicrographs), displaying Congo red birefringence and vertical axis shows the proportion of microscopic structures displaying FDDNP fluorescence. Good agreement between Congo red birefringence and FDDNP fluorescence is observed in all but three structure types analyzed: Lewy bodies (LBs) and cortical Lewy bodies (CLBs) displayed moderate FDDNP fluorescence but very little Congo red birefringence, whereas globose neurofibrillary tangles (GNFT) displayed Congo red birefringence to a high degree but showed no FDDNP fluorescence. Abbreviations: GCI = glial cytoplasmic inclusion; NFT = neurofibrillary tangle; nSP = neuritic senile plaques; PP = prion plaque; PPP = primitive prion plaque; PiB = Pick body; VA = vascular amyloid; VH = vascular hyaline.

Figure 3

Prion plaques in variant Creutzfeldt‐Jakob disease (A–D), labeled with anti‐PrP immunohistochemistry (immunohistochemistry, A), stained with Congo red (B), display birefringence (C) and FDDNP labeling (D). Aβ core of a classic senile plaque in Alzheimer Disease (AD) (E–H) remains unlabeled in anti‐tau immunohistochemistry (E, asterisk), but displays marked congophilia (F), birefringence (G) and FDDNP fluorescence (H). Neurofibrillary tangles in AD are labeled with anti‐tau antibodies (E, arrows), are congophilic (F), display birefringence (G), and are labeled with FDDNP (H). Lewy bodies in Parkinson disease (I–M) are α‐synuclein immunopositive deposits (I), that display congophillia (J) and weak birefringence, which is best seen with 90 degree shift of plane of light polarization (K, L), and display FDDNP fluorescence (M). Green fluorescent signal in D, H, M was pseudocolored yellow. Scale bar: A–H, 50 µm; I, J, M, 30 µm and K, L, 10 µm.

Figure 4

Pick bodies (A–D) and glial cytoplasmic inclusions (I–L), labeled with anti‐tau (A) or anti‐α‐synuclein (I) in immunohistochemistry, display no birefringence (C, K), when stained with Congo red (B, J). Only background fluorescence can be seen with FDDNP staining (D, L). Globose neurofibrillary tangles (E–H) are tau‐immunopositive (E), display congophillia (F) and birefringence (G), yet consistently show no detectable FDDNP fluorescence (L). Green fluorescent signal in D, H, L was pseudocolored yellow. Scale bar: 50 µm.