BackgroundThe 5-lipoxygenase (5LO) enzymatic pathway is widely distributed within the central nervous system. Previous works showed that this protein is up-regulated in Alzheimer's disease (AD), and that its genetic absence results in a reduction of Amyloid beta (Aβ) levels in the Tg2576 mice.Here by employing an adeno-associated viral (AAV) vector system to over-express 5LO in the same mouse model, we examined its contribution to their cognitive impairments and brain AD-like amyloid pathology.ResultsOur results showed that compared with controls, 5LO-targeted gene brain over-expression in Tg2576 mice results in significant memory deficits. On the other hand, brain tissues had a significant elevation in the levels of Aβ peptides and deposition, no change in the steady state levels of amyloid-β precursor protein (APP), BACE-1 or ADAM-10, but a significant increase in PS1, nicastrin, and Pen-2, three major components of the γ-secretase complex. Additional data indicate that the transcription factor CREB was elevated and so were the mRNA levels for PS1, nicastrin and Pen-2.ConclusionsThese data demonstrate that neuronal 5LO plays a functional role in the pathogenesis of AD-like amyloidotic phenotype by modulating the γ-secretase pathway. They support the hypothesis that this enzyme is a novel therapeutic target for the treatment and prevention of AD.

Objective The 5-lipoxygenase (5LO) enzyme is up-regulated in Alzheimer’s disease (AD), and its genetic absence reduces Aβ levels in APP mice. However, its functional role in modulating tau neuropathology remains to be elucidated. Methods To this end, we generated triple transgenic mice (3xTg-AD) over-expressing neuronal 5LO and investigated their phenotype. Results Compared with controls, 3xTg-AD mice over-expressing 5LO manifested an exacerbation of memory deficits, plaques and tangles pathologies. The elevation in Aβ was secondary to an up-regulation of γ-secretase pathway, whereas tau hyperphosphorylation resulted from an activation of the Cdk5 kinase. In vitro study confirmed the involvement of this kinase in the 5-LO-dependent tau phosphorylation, which was independent of the effect on Aβ. Interpretation Our findings highlight the novel functional role that neuronal 5LO plays in exacerbating AD-related tau pathologies. They provide critical preclinical evidence to justify testing selective 5LO inhibitors for AD treatment.

The 5-Lipoxygenase (5LO) is upregulated in Alzheimer’s disease (AD), and in vivo modulates the amyloidotic phenotype of APP transgenic mice. However, no data are available on the effects that 5LO has on synaptic function, integrity and cognition. To address this issue we used a genetic and a pharmacologic approach by generating 3xTg mice deficient for 5LO, and administering 3xTg mice which a 5LO inhibitor. Compared with controls, we found that even before the development of overt neuropathology, both animals manifested significant memory improvement, rescue of their synaptic dysfunction and amelioration of synaptic integrity. In addition, later in life these mice had a significant reduction of Aβ and tau pathology.Our findings support a novel functional role for 5LO in regulating synaptic plasticity and memory. They establish this proetin as a pleiotropic contributor to the development of the full spectrum of the AD phenotype, making it a valid therapeutic target for the treatment of AD.

Background The 5-lipoxygenase (5LO) is a protein widely distributed in the central nervous system where modulates amyloidosis and memory impairments in transgenic mouse models of Alzheimer’s disease. However, no data are available as to whether 5LO is elevated in human tauopathy, or if it directly influences tau pathology in a relevant model of the disease. Methods We assayed 5LO levels in brain samples from tauopathy patients and transgenic tau mice, and evaluated the effect that 5LO pharmacological inhibition has on the phenotype of these mice. Results The 5LO is up-regulated in human tauopathy and transgenic tau mice brains. Pharmacological blockade of 5LO in tau mice results in significant memory improvement, rescue of synaptic integrity and dysfunction, and reduction of tau pathology via a cdk5-dependent mechanism. Conclusions Our results establish 5LO as a key player in the development of the tau pathology phenotype, and a novel viable therapeutic target for the pharmacological treatment of human tauopathy.

SUMMARY Background A major hallmark feature of Alzheimer’s disease (AD) is the accumulation of amyloid β (Aβ), whose formation is regulated by the γ-secretase complex and its activating protein (also known as GSAP). Because GSAP interacts with the γ-secretase without affecting the cleavage of Notch, it is an ideal target for a viable anti-Aβ therapy. However, despite much interest in this protein, the mechanisms involved in its neurobiology are not known. Methods Post-mortem brain tissues from AD patients, transgenic mouse models of AD and neuronal cells were used to investigate the molecular mechanism involved in GSAP formation and subsequent amyloidogenesis. Results We identify a caspase-3 processing domain in the GSAP sequence and provide experimental evidence that this caspase is essential for GSAP activation and biogenesis of Aβ peptides. Furthermore, we demonstrate that caspase-3-dependent GSAP formation occurs in brains of individuals with AD and two different mouse models of AD, and that the process is biologically relevant since its pharmacological blockade reduces Aβ pathology in vivo. Interpretation Our data by identifying caspase-3 as the endogenous modulator of GSAP and Aβ production establish it as a novel, attractive and viable Aβ lowering therapeutic target for AD.

Alzheimer's disease (AD) is a chronic neurodegenerative condition characterized by progressive memory. Mutations in genes involved in the production of amyloid-β (Aβ) are linked to the early-onset variant of AD. However, the most common form, sporadic AD, is considered the result of an interaction between environmental risk factors and various genes. Among them, recent work has highlighted the potential role that the 12/15Lipoxygenase (12/15LO) pathway may play in AD pathogenesis. 12/15LO is widely distributed in the central nervous system, and its levels are up-regulated in patients with AD or mild cognitive impairments. Studies using animal models implicated 12/15LO in the molecular pathology of AD, including the metabolism of Aβ and tau, synaptic integrity and cognitive functions. Here, we will provide an overview of this pathway and its relevance to AD pathogenesis, discuss the mechanism(s) involved, and provide an assessment of how targeting 12/15LO could lead to novel AD therapeutics.

Background 5-lipoxygenase activating protein (FLAP) is abundantly present in the central nervous system. Although its function has been extensively interrogated in the context of peripheral inflammation, novel roles for this protein are emerging in the central nervous system. The objective of our study was to investigate the functional role that FLAP plays in a mouse model of Alzheimer’s disease (AD) with plaques and tangles (i.e., 3×Tg mice). Methods By implementing a genetic knockout of FLAP and pharmacologic inhibition with a FLAP inhibitor (MK-591), we evaluated the effect on the AD-like neuropathology, cognition, and synaptic plasticity in the 3×Tg mice. Results We show that reduction of FLAP leads to amelioration of cognition and memory along with the rescuing of synaptic dysfunction at an early age before the development of overt neuropathology. Genetic knockout and pharmacologic inhibition of FLAP also yielded an improvement in AD pathology through a reduction in Aβ via the γ-secretase pathway and a decrease in tau phosphorylation through the cdk5 pathway. Conclusions Our studies identify a novel functional role for FLAP in regulating memory and synaptic plasticity. They establish this protein at the crossroad of multiple pathways that ultimately contribute to the development of the entire AD-like phenotype, making it a viable therapeutic target with disease-modifying capacity for the treatment of this disease.

Summary 12/15-Lipoxygenase (12/15LO) is a lipid-peroxidizing enzyme widely expressed in the central nervous system where it has been involved in the neurobiology of Alzheimer disease (AD) because it modulates Amyloid beta (Aβ) and APP processing. However, its biological effect on tau protein is unknown. We investigated the effect of 12/15LO on tau levels and metabolism in vivo and in vitro and the mechanism involved by using genetic and pharmacologic approaches. While no significant differences were observed in the levels of total tau for both groups, compared with controls, Tg2576 mice over-expressing 12/15LO had elevated levels of phosphorylated tau at two specific epitopes, Ser 202/Thr 205 and Ser 396. In vitro and in vivo studies show that 12/15LO modulates tau metabolism specifically via the cdk5 kinase pathway. Associated with these changes were biochemical markers of synaptic pathology. Finally, 12/15-LO-dependent alteration of tau metabolism was independent from an effect on Aβ. Our findings reveal a novel pathway by which 12/15LO modulates endogenous tau metabolism making this protein an appealing pharmacologic target for treatment of AD and related tauopathies.