Twofold overexpression of human ?-amyloid precursor proteins in transgenic mice does not affect the neuromotor, cognitive, or neurodegenerative sequelae following experimental brain injury

Abstract

By using transgenic mice that overexpress human beta-amyloid precursor proteins (APPs) at levels twofold higher than endogenous APPs, following introduction of the human APP gene in a yeast artificial chromosome (YAC), we examined the effects of controlled cortical impact (CCI) brain injury on neuromotor/cognitive dysfunction and the development of Alzheimer's disease (AD)-like neuropathology. Neuropathological analyses included Nissl-staining and immunohistochemistry to detect APPs, beta-amyloid (Abeta), neurofilament proteins, and glial fibrillary acidic protein, whereas Abeta levels were measured in brain homogenates from mice subjected to CCI and control mice by using a sensitive sandwich enzyme-linked immunosorbent assay. Twenty APP-YAC transgenic mice and 17 wild type (WT) littermate controls were anesthetized and subjected to CCI (velocity, 5 m/second; deformation depth, 1 mm). Sham (anesthetized but uninjured) controls (n = 10 APP-YAC; n = 8 WT) also were studied. Motor function was evaluated by using rotarod, inclined-plane, and forelimb/hindlimb flexion tests. The Morris water maze was used to assess memory. Although CCI induced significant motor dysfunction and cognitive deficits, no differences were observed between brain-injured APP-YAC mice and WT mice at 24 hours and 1 week postinjury. By 1 week postinjury, both cortical and hippocampal CA3 neuron loss as well as extensive astrogliosis were observed in all injured animals, suggesting that overexpression of human APPs exhibited no neuroprotective effects. Although AD-like pathology (including amyloid plaques) was not observed in either sham or brain-inj ured animals, a significant decrease in brain concentrations of only Abeta terminating at amino acid 40 (Abeta x-40) was observed following brain injury in APP-YAC mice (P < 0.05 compared with sham control levels). Our data show that the APP-YAC mice do not develop AD-like neuropathology following traumatic brain injury. This may be because this injury does not induce elevated levels of the more amyloidogenic forms of human Abeta (i.e., Abeta x-42/43) in these mice.

Vitamin E reduces amyloidosis and improves cognitive function in Tg2576 mice following repetitive concussive brain injury

“…Thus, for years the relationship between experimental TBI and brain amyloidosis has been characterized by conflicting results. Reports have shown that following controlled cortical impact (CCI), the APP-YAC mice do not develop plaques when evaluated acutely after injury (Murai et al 1998), and in PD-APP mice, CCI produces a marked ipsilateral hippocampal atrophy, almost complete CA3-CA2 cell loss and diminished Ab deposition during aging (Smith et al 1998;Nakagawa et al 1999Nakagawa et al , 2000. On the contrary, in PD-APP mice subjected to CCI brain injury, amyloid deposition is accelerated only in the presence of APO-E4 while cell loss is not influenced (Hartman et al 2002).…”

“…The brains were removed, post-fixed overnight, sliced into 2-mm-thick coronal slabs, and embedded in paraffin in a frontal to occipital series of blocks, and the blocks were cut in a near serial array of 6-lm thick coronal sections. Paraffin sections were subjected to immunohistochemistry (IHC) as previously described (Murai et al 1998;Nakagawa et al 1999Nakagawa et al , 2000. Ab deposits were visualized by NAB228, Ab monoclonal antibody (mAb; Lee et al 2003).…”

Mild head injury increasing the brain's vulnerability to a second concussive impact

“…66,85,87,88 Briefly, the MWM is a circular pool 1 m in diameter that is painted white inside. 65 The water (16-18˚C) filling the pool is made opaque by adding nontoxic, watersoluble white paint.…”

Nitration of Tau Protein Is Linked to Neurodegeneration in Tauopathies

“…The brains were fixed in 70% ethanol in 150 mmol/L NaCl, pH 7.4, or in 10% neutral buffered formalin and processed for IHC analyses using n847 and a panel of antibodies to other neurodegeneration-related proteins (see Table 2 for details on this antibody panel) as described previously. 35,36 The antibody-probed slides were developed with avidin-biotin complex (ABC) method (Vectastain ABC Kit, Vector Laboratories, Burlingame, CA) using positive and negative controls as described. 35,36 Semiquantitative analysis of n847-IR CA1 neurons was conducted by examining eight photographs of the CA1 region of each section from each case using 20X lens and a Nikon-FXA microscope.…”

“…35,36 The antibody-probed slides were developed with avidin-biotin complex (ABC) method (Vectastain ABC Kit, Vector Laboratories, Burlingame, CA) using positive and negative controls as described. 35,36 Semiquantitative analysis of n847-IR CA1 neurons was conducted by examining eight photographs of the CA1 region of each section from each case using 20X lens and a Nikon-FXA microscope. Neurons with different n847 staining patterns were identified, counted, and statistically analyzed using analysis of variance.…”