Eve H. Barlow

Globular amyloid β-peptide1−42 oligomer − a homogenous and stable neuropathological protein in Alzheimer's disease

Amyloid β‐peptide (Aβ)1−42 oligomers have recently been discussed as intermediate toxic species in Alzheimers disease (AD) pathology. Here we describe a new and highly stable Aβ1−42 oligomer species which can easily be prepared in vitro and is present in the brains of patients with AD and Aβ1−42‐overproducing transgenic mice. Physicochemical characterization reveals a pure, highly water‐soluble globular 60‐kDa oligomer which we named ‘Aβ1−42 globulomer’. Our data indicate that Aβ1−42 globulomer is a persistent structural entity formed independently of the fibrillar aggregation pathway. It is a potent antigen in mice and rabbits eliciting generation of Aβ1−42 globulomer‐specific antibodies that do not cross‐react with amyloid precursor protein, Aβ1−40 and Aβ1−42 monomers and Aβ fibrils. Aβ1−42 globulomer binds specifically to dendritic processes of neurons but not glia in hippocampal cell cultures and completely blocks long‐term potentiation in rat hippocampal slices. Our data suggest that Aβ1−42 globulomer represents a basic pathogenic structural principle also present to a minor extent in previously described oligomer preparations and that its formation is an early pathological event in AD. Selective neutralization of the Aβ globulomer structure epitope is expected to have a high potential for treatment of AD.

Dopamine D4 receptor signaling in the rat paraventricular hypothalamic nucleus: Evidence of natural coupling involving immediate early gene induction and mitogen activated protein kinase phosphorylation

The dopamine D4 receptor has been investigated for its potential role in several CNS disorders, notably schizophrenia and more recently, erectile dysfunction. Whereas studies have investigated dopamine D4 receptor-mediated signaling in vitro, there have been few, if any, attempts to identify dopamine D4 receptor signal transduction pathways in vivo. In the present studies, the selective dopamine D4 agonist PD168077 induces c-Fos expression and extracellular signal regulated kinase (ERK) phosphorylation in the hypothalamic paraventricular nucleus (PVN), a site known to regulate proerectile activity. The selective dopamine D4 receptor antagonist A-381393 blocked both c-Fos expression and ERK1/2 phosphorylation produced by PD168077. In addition, PD168077-induced ERK1/2 phosphorylation was prevented by SL327, an inhibitor of ERK1/2 phosphorylation. Interestingly, treatment with A-381393 alone significantly reduced the amount of Fos immunoreactivity as compared to basal expression observed in vehicle-treated controls. Dopamine D4 receptor and c-Fos coexpression in the PVN was observed using double immunohistochemical labeling, suggesting that PD168077-induced signaling may result from direct dopamine D4 receptor activation. Our results demonstrate functional dopamine D4 receptor expression and natural coupling in the PVN linked to signal transduction pathways that include immediate early gene and MAP kinase activation. Further, the ability of the selective dopamine D4 antagonist A-381393 alone to reduce c-Fos expression below control levels may imply the presence of a tonic dopamine D4 receptor activation under basal conditions in vivo. These findings provide additional evidence that the PVN may be a site of dopamine D4 receptor-mediated proerectile activity.

Blocking Nogo Receptor 1 Promotes Functional Regeneration after Spinal Cord Injury

An insult to the mammalian spinal cord often results in persistent functional deficits. Proteins in CNS myelin are important determinants of this situation as they inhibit neurite growth. Among those proteins Nogo-A, oligodendrocyte myelin glycoprotein (OMgp), and myelin-associated glycoprotein (MAG) all bind to the neuronal Nogo-66 receptor (NgR1) and thereby block neuronal regeneration after injury. Neutralizing the interaction between the inhibitory ligands and NgR1 may alleviate the inhibition and therefore result in increased recovery after injury. Thus, antibodies neutralizing ligand/receptor interaction might have therapeutic value. From a set of 300 monoclonal anti-NgR1 antibodies one anti-NgR1 ligand blocking antibody (mAb50) was selected for in vivo studies. mAb50 binds with high affinity (below 100 pM) to human and rat NgR1, competes for binding of a ligand peptide (derived from Nogo-A: Nogo66) to the isolated NgR1 protein and cellular NgR1, and reduces the inhibitory effects of Nogo66 on neurite outgrowth in differentiated human NTera2 cells and rat dorsal root ganglion neurons. In a rat spinal cord hemisection model mAb50 enhanced functional locomotor recovery. These data suggest that neutralization of NgR1 activity with an antibody may be a valuable strategy to neutralize neurite outgrowth inhibition in the mammalian CNS. Thus anti-NgR1 antibodies are a potential approach for the treatment of spinal cord injury and even neurodegenerative diseases.