Figure 4.

Confocal double immunofluorescent images showing LPS induced axonal pathology associated with increased labeling of amyloidogenic proteins. All images are taken from the CA3 area of the hippocampus ipsilateral to the intracerebral injection of PBS ((A)–(C)) or LPS ((E)–(U)). Antibody markers and color channels are as indicated. Panels ((A)–(C)) show double labeling of BACE1 and β-amyloid precursor protein (APP) in ipsilateral CA3 of the control animal, with the former expressed predominantly in the mossy fiber (mf) terminals, and the latter largely in somata of CA3 pyramidal neurons. Note that no abnormal neurites are present in the strum oriens (s.o.). Panels ((E)–(H)) illustrate the occurrence of BACE1/APP double labeled swollen neurites (examples are indicated by arrows) in the s.o. of the ipsilateral hippocampus of the LPS injected rat. Panels (I–L) show that these BACE1 positive neurites are locally associated with increased 4G8 labeling within (pointed by arrows) as well as outside (arrowheads) the swollen terminals in the cortex and CA1. Panels ((M)–(P)) show that a partial coexpression of synaptophysin (SYN) among the BACE1 labeled swollen neurites in the s.o. of the LPS injected ipsilateral hippocampus, which appear in yellow in the merged image (arrows, P). Panels (R-U) show that there is no colocalization of the microtubule associated protein-2 (MAP2) in the BACE1 labeled swollen neurites. MAP2 labeling is distinctly associated with the somata and dendrites of pyramidal neurons in the stratum pyramidale (s.p.). DAPI counterstain is included in panels (L) and (U), showing that the BACE1 labeled elements are not somatic. Scale bar = 200 μm in (A) applying to ((B), (C), (E)–(G) and (R)–(T)), equivalent to 100 μm for (I)–(K), (M)–(O)), 50 μm for ((D), (H), (U)) and 25 μm for ((L), (P)).