Early increases in soluble amyloid-ß levels coincide with cholinergic degeneration in 3xTg-AD mice.

Accumulation of amyloid-ß peptides (Aß) and cholinergic degeneration are hallmarks of Alzheimer's disease (AD). In a triple transgenic mouse model of AD (3xTg-AD), soluble Aß42 levels were detected in the septum by 2 months of age, reaching their highest levels at 3-6 months and decreasing at 12 months. Deficits in the number of septal cholinergic neurons and the length of hippocampal cholinergic axons were observed starting at 4 months in 3xTg-AD mice. Our results show that septal Aß and septohippocampal cholinergic pathology in 3xTg-AD mice occur at an early stage of disease.

Amyloid-beta fibrillogenesis: structural insight and therapeutic intervention.

Structural insight into the conformational changes associated with aggregation and assembly of fibrils has provided a number of targets for therapeutic intervention. Solid-state NMR, hydrogen/deuterium exchange and mutagenesis strategies have been used to probe the secondary and tertiary structure of amyloid fibrils and key intermediates. Rational design of peptide inhibitors directed against key residues important for aggregation and stabilization of fibrils has demonstrated effectiveness at inhibiting fibrillogenesis. Studies on the interaction between Abeta and cell membranes led to the discovery that inositol, the head group of phosphatidylinositol, inhibits fibrillogenesis. As a result, scyllo-inositol is currently in clinical trials for the treatment of AD. Additional small-molecule inhibitors, including polyphenolic compounds such as curcumin, (-)-epigallocatechin gallate (EGCG), and grape seed extract have been shown to attenuate Abeta aggregation through distinct mechanisms, and have shown effectiveness at reducing amyloid levels when administered to transgenic mouse models of AD. Although the results of ongoing clinical trials remain to be seen, these compounds represent the first generation of amyloid-based therapeutics, with the potential to alter the progression of AD and, when used prophylactically, alleviate the deposition of Abeta.

Reduced oligomeric and vascular amyloid-beta following immunization of TgCRND8 mice with an Alzheimer's DNA vaccine.

Immunization with amyloid-beta (Abeta) peptide reduces amyloid load in animal studies and in humans; however clinical trials resulted in the development of a pro-inflammatory cellular response to Abeta. Apoptosis has been employed to stimulate humoral and Th2-biased cellular immune responses. Thus, we sought to investigate whether immunization using a DNA vaccine encoding Abeta in conjunction with an attenuated caspase generates therapeutically effective antibodies. Plasmids encoding Abeta and an attenuated caspase were less effective in reducing amyloid pathology than those encoding Abeta alone. Moreover, use of Abeta with an Arctic mutation (E22G) as an immunogen was less effective than wild-type Abeta in terms of improvements in pathology. Low levels of IgG and IgM were generated in response to immunization with a plasmid encoding wild-type Abeta. These antibodies decreased plaque load by as much as 36+/-8% and insoluble Abeta42 levels by 56+/-3%. Clearance of Abeta was most effective when antibodies were directed against N-terminal epitopes of Abeta. Moreover, immunization reduced CAA by as much as 69+/-12% in TgCRND8 mice. Finally, high-molecular-weight oligomers and Abeta trimers were significantly reduced with immunization. Thus, immunization with a plasmid encoding Abeta alone drives an attenuated immune response that is sufficient to clear amyloid pathology in a mouse model of Alzheimer's disease.

Vaccine development for Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of age-related cognitive decline. Both active and passive immunization paradigms have illustrated the potential to prevent and reverse established AD pathology in transgenic and non-transgenic animal models of AD. Follow-up studies have shown that changes in amyloid burden observed with immunization could rescue cognitive deficits in both young and aged mice. Despite the success of immunotherapy in animal models, clinical trials were halted early. It has become clear that more preclinical work was needed before initiating trials, as most of the adverse events observed in patients could have been predicted using animal models. Despite these setbacks, clinical trials have demonstrated the utility of amyloid-beta (Abeta) vaccination in reducing amyloid pathology and potentially reducing cognitive decline. Several novel approaches to immunotherapy, including modified immunogens, adjuvants and modes of administration have been designed, which hold promise for human testing. Clinical trials using a safer vaccine, which is potent enough to elicit a robust antibody response in the absence of encephalitis may prove effective in mitigating progressive neurodegeneration seen in AD. If so, Abeta vaccination could supplant current symptomatic treatment and represent one of the first therapeutic options for AD based on the amyloid cascade hypothesis.

Refining an Alzheimer's vaccine to avoid an inflammatory response.

The utility of vaccine strategies to treat neurodegenerative diseases such as Alzheimer's disease may still hold promise. Phase IIa clinical trials were halted due to a small but significant occurrence of meningoencephalitis. Knowledge gained from studies on amyloid-beta peptide (Abeta) immunotherapy will allow optimisation of new-generation vaccines, targeting highly specific epitopes while reducing undesired side effects. In harnessing and steering the immune system, an effective response can be generated against Abeta, one that might have attenuated immune responses with robust disease-altering activity.

Regulation of Indian hedgehog mRNA levels in chondrocytic cells by ERK1/2 and p38 mitogen-activated protein kinases.

Indian hedgehog (Ihh) is produced by growth plate pre-hypertrophic chondrocytes, and is an important regulator of endochondral ossification. However, little is known about the regulation of Ihh in chondrocytes. We have examined the role of integrins and mitogen-activated protein (MAP) kinases in Ihh mRNA regulation in CFK-2 chondrocytic cells. Cells incubated with the beta1-integrin blocking antibody had decreased Ihh mRNA levels, which was accompanied by decreases of activated extracellular signal-regulated kinases (ERK1/2) and activated p38 MAPK. Ihh mRNA levels were also inhibited by U0126, a specific MEK1/2 inhibitor, or SB203580, a specific p38 MAPK inhibitor. Cells transfected with constitutively active MEK1 or MKK3 had increased Ihh mRNA levels, which were diminished by dominant-negative MEK1, p38alpha or p38beta. Stimulation of the PTH1R with 10(-8) M rPTH (1-34) resulted in dephosphorylation of ERK1/2 that was evident within 15 min and sustained for 1 h, as well as transient dephosphorylation of p38 MAPK that was maximal after 25 min. PTH stimulation decreased Ihh mRNA levels, and this effect was blocked by transfecting the cells with constitutively active MEK1 but not by MKK3. These studies demonstrated that activation of ERK1/2 or p38 MAPK increased Ihh mRNA levels. Stimulation of the PTH1R or blocking of beta1-integrin resulted in inhibition of ERK1/2 and p38 MAPK and decreased levels of Ihh mRNA. Our data demonstrate the central role of MAPK in the regulation of Ihh in CFK-2 cells.

New therapeutic approaches for Alzheimer's disease.

Extract: By undergoing a slight change in shape the normally innocuous peptide, amyloid-beta (A-beta) self-assembles forming aggregates, which are toxic to cells and induce a myriad of changes in the brain. It is now thought that the generation of these toxic species is an initial and necessary step in the pathogenic process underlying Alzheimer's disease (AD). The amyloid cascade hypothesis has led to the rational design of anti-amyloid therapeutics, which holds promise for the treatment and prevention of AD. One therapy, AD vaccination, has received a great deal of attention from both the scientific and lay community, and will be the topic of this discussion. The signs and symptoms of AD are familiar to most: seemingly innocent absent-mindedness, giving way to progressive memory impairment, disordered cognitive function, and altered behavior and language deficits. Ultimately the patient becomes entirely dependent on others for every aspect of daily living, with death typically occurring within 8 to 12 years of diagnosis. These symptoms are characteristic of a number of illnesses termed dementia, of which AD is the most common. Affecting over 12 million people worldwide, the American Alzheimer's Association estimates that $100 billion a year is spent on caring for individuals with AD.