Pamela E. Potter

Reduction of cerebrospinal fluid amyloid β after systemic administration of M1 muscarinic agonists

Overproduction of the peptide amyloid beta (A beta) is a critical event in Alzheimers disease (AD). Systemic administration of 3 M1-selective muscarinic agonists, AF102B, AF150S and AF267B, decreased cerebrospinal fluid (CSF) A beta concentrations; levels of CSF secreted beta-APP were not significantly altered. Rabbits treated for 5 days with s.c. injections of each drug (2 mg/kg/day) had levels of CSF A beta which were between 55 and 71% of control for A beta 1-40 and between 59 and 84% of control for A beta 1--42.

Cholinergic deafferentation of the rabbit cortex: a new animal model of Aβ deposition

Brain deposition of the amyloid beta-peptide (Abeta) is a critical step in the pathogenesis of Alzheimers disease (AD) and human cerebral amyloid angiopathy (CAA). A small fraction of AD and CAA cases are caused by gene mutations leading to increased production and deposition of Abeta, but for the majority, there is no known direct genetic cause. We have hypothesized that Abeta deposition in these sporadic cases occurs as a result of cortical cholinergic deafferentation. Here we show that cortical cholinergic deafferentation, induced in rabbits by a selective immunotoxin, leads to Abeta deposition in cerebral blood vessels and perivascular neuropil. Biochemical measurements confirmed that lesioned animals had 2.5- and 8-fold elevations of cortical Abeta40 and Abeta42, respectively. Cholinergic deafferentation may be one factor that can contribute to Abeta deposition.

Cortical Cholinergic Denervation Elicits Vascular Aβ Deposition

Abstract: Selective destruction of the cholinergic nucleus basalis magnocellularis (nbm) in the rabbit by the p75 neurotrophin receptor (NTR) immunoglobulin G (IgG) complexed to the toxin saporin leads to the deposition of amyloid‐beta (Aβ) in and around cerebral blood vessels. In some instances, the perivascular Aβ resemble the diffuse deposits observed in Alzheimers disease (AD). We propose that cortical cholinergic deprivation results, among other perturbations, in the loss of vasodilation mediated by acetylcholine. In addition to a dysfunctional cerebral blood flow, alterations in vascular chemistry affecting endothelial and smooth muscle cells may result in cerebral hypoperfusion and a breached blood‐brain barrier (BBB). The selective removal of the rabbit nbm and Aβ accumulation may serve as an important nontransgenic, and more physiological, model for the testing of pharmacological and immunological agents designed to control the deposition and the deleterious effects of Aβ in AD.

Curcumin: a natural substance with potential efficacy in Alzheimer's disease

Curcumin is a component of turmeric, a spice used in many types of cooking. Epidemiological evidence suggesting that populations that eat food with a substantial amount of curcumin were at lower risk of Alzheimer’s disease (AD) led to the idea that this compound might have a neuroprotective effect. Curcumin has substantial antioxidant and anti-inflammatory effects, and is being used as a potential preventative agent or treatment for many types of cancer. There is evidence to suggest that the addition of curcumin to cultured neuronal cells decreases brain inflammation and protects against β-amyloid-induced neurotoxicity. Curcumin also protects against toxicity when β-amyloid is administered to produce animal models of AD. Curcumin decreases β-amyloid formation from amyloid precursor protein, and also inhibits aggregation of β-amyloid into pleated sheets. Studies in transgenic mice with overproduction of β-amyloid demonstrate a neuroprotective effect of curcumin as well. Cognitive function was also improved in these animal models. Clinical trials of curcumin in AD have not been very promising. It is possible that this is due to poor oral bioavailability of curcumin in humans, and thus several approaches are being developed to improve delivery systems or to create analogs that will mimic the neuroprotective effects and easily reach the brain. The lack of efficacy of curcumin in humans with AD may also result from treating for too short a time or starting treatment too late in the course of the disease, where substantial neuronal death has already occurred and cannot be reversed. Curcumin may be beneficial in protecting against development or progression of AD if taken over the long term and started before symptoms of AD become apparent.

Thiorphan-induced neprilysin inhibition raises amyloid β levels in rabbit cortex and cerebrospinal fluid

Studies on the pathogenesis of Alzheimers disease (AD) suggest overproduction of amyloid beta (Abeta) may not be the only pathogenic route to AD. Decreased degradation of Abeta is another possible disease mechanism. Neprilysin is a neutral endopeptidase that has been proposed to be the major enzyme responsible for Abeta degradation. Studies have reported correlations between Abeta deposition and neprilysin activity in the human brain. This study shows that intracerebroventricular infusion of thiorphan, a neprilysin inhibitor, raises cortical and cerebrospinal fluid (CSF) Abeta concentrations in rabbits. Rabbits treated with thiorphan for 5 days had levels of CSF and cortical Abeta40 that were 147 and 142% of the control group, respectively. Results for Abeta42 showed a similar trend. The results indicate that age-related decreases of neprilysin could lead to increased brain concentrations of Abeta, plaque formation, and AD.

Neuroprotection by a novel Nmdar functional glycine site partial agonist, Glyx-13

GLYX-13 (threonine–proline–proline–threonine–amide) is an amidated di-pyrrolidine that acts as a functional partial agonist at the glycine site on N-methyl-D-aspartate glutamate receptors (NMDARs). GLYX-13 can both increase NMDAR conductance at NR2B-containing receptors, and reduce conductance of non-NR2B-containing receptors. Here, we report that GLYX-13 potently reduces delayed (24 h) death of CA1 pyramidal neurons produced by bilateral carotid occlusion in Mongolian gerbils, when administered up to 5 h post-ischemia. GLYX-13 also reduced delayed (24 h) neuronal death of CA1, CA3, and dentate gyrus principal neurons elicited by oxygen/glucose deprivation in in-vitro hippocampal organotypic slice cultures, when applied up to 2 h post-oxygen/glucose deprivation. The glycine site full agonist D-serine completely occluded neuroprotection, indicating that GLYX-13 acts by modulating activation of this site.

Phenytoin protects against hypoxia-induced death of cultured hippocampal neurons

The neuroprotective actions of the anticonvulsant phenytoin (diphenylhydantoin, PHT) were evaluated using 3 week old primary hippocampal cultures derived from 19 day embryonic rat. When added to the culture medium prior to a hypoxic insult, PHT increased neuronal viability two-fold. Doubling extracellular Mg2+ concentration was similarly neuroprotective. In contrast, PHT was unable to protect against hypoxia-induced death in one week old cultures, nor was PHT protective against N-methyl-D-aspartate (NMDA)-induced neurotoxicity in cultures of either age. These findings suggest that non-NMDA receptor mechanisms are important in hypoxia-induced neuronal death, and may have important implications for the treatment of stroke.

Spinal cord acetylcholine content: the consequence of transection or treatment with the neurotoxin 6-aminonicotinamide.

The distribution of choline (Ch) and acetylcholine (ACh) within the rat spinal cord was found to be rather uniform with values for Ch of about 280 pmol/mg protein and for ACh of about 250 pmol/mg protein. Cord transection at the T10-11 level did not reduce ACh below the lesion but there was about a 30% decrease of ACh in the thoracic region suggesting the presence of cholinergic fibers that ascend and terminate within the cord. Treatment of rats with the neurotoxin 6-aminonicotinamide resulted in spastic hindlimb paralysis and a loss of ACh in the lumbar region of the cord.

IDENTIFICATION OF A WIDE VARIETY OF BACTERIA IN THE BRAIN TISSUE OF INDIVIDUALS WITH EITHER MILD COGNITIVE IMPAIRMENT (MCI) OR ALZHEIMER’S DISEASE

results were compared to those of 20 healthy sex and age matched healthy controls(HC). Mechanisms regulating inflammasome signaling involves the priming signal to upregulate the expression of NLRP3 and signal 2 to activate the functional NLRP3; thus monocytes were either primed with LPS(1mg/ml for 2h) and stimulated with Aß42 AlexaFluor488 (FAM)-labeled (10mg/ml) for 24h or stimulated with Aß42 FAM alone for 24h in the presence/absence of Stavudine (50mM) for 22h. Aß-phagocytosis was analyzed by Imagines–FlowCitometry; caspase1 and cytokines were quantified by ELISA. Results: Results showed that: 1) Caspase1, IL1ß and IL18 production by LPS and Aß42 stimulated monocytes of AD patients was significantly increased compared to HC (for all p<0.05); 2) Aß-phagocytosis was significantly reduced in LPS-primed and Aß42 stimulated cells of AD and HC individuals compared to those stimulated with Aß42 alone (for both p<0.05); 3) Stavudine resulted in a drastic reduction of Caspase1, IL1ß and IL18 production (p<0.05) but did not modify the Aß-phagocytosis capacity of monocytes. Conclusions:NLRP3 inflammasome-driven inflammation reduces monocytes mediated Aß phagocytosis in AD and HC. Stavudine dampens NLRP3 activation and downstream inflammation but does not significantly modify Aß-phagocytosis. These results suggest that, even if Stavudine could be useful in modulating neuroinflammation in AD, AD-associated impairments in Aßphagocytosis are not a consequence of a direct consequence of inflammation.

Cortical Cholinergic Deafferentation Induces Aβ Deposition

There are 4 million Americans with Alzheimer’s disease (AD), and the cost of the disease to the United States is estimated at