Elevated Tau Level in Aged Rat Cerebrospinal Fluid Reduced by Treatment with a Neurotrophic Compound

Alzheimer's disease (AD) is the single major cause of dementia in middle- to old-age individuals, and, as of yet, no disease-modifying therapeutic drug is available for its treatment. A major obstacle in the successful development of disease-modifying therapeutic drugs has been the lack of suitable animal models of the sporadic form of AD as well as a biomarker that can be used both for therapeutic preclinical studies and for human clinical trials. Previously we showed neurogenesis and neuronal plasticity deficits and cognitive impairment and their rescue with a neurotrophic peptidergic compound, DGGLAG named P021, in aged Fisher rats. Here we show that P021 is blood-brain-barrier-permeable, and chronic oral treatment with this compound can reduce the brain level of total tau in the aged rats. Furthermore, cerebrospinal fluid (CSF) levels of both tau and Aβ/AβPP are elevated in the aged animals, and chronic treatment with P021 can reduce tau but not Aβ/AβPP to that of the levels found in young adult rats. Importantly, P021 does not induce any detectable immune reaction in rats. Collectively, these studies show the therapeutic potential of P021 as a disease-modifying compound and the suitability of the aged Fisher rats as a model of cerebral aging in which the therapeutic efficacy of a tau-reducing compound can be monitored in the CSF.

Chronic depression as a model disease for cerebral aging

Conceptualizations of the underlying neurobiology of major depression have changed their focus from dysfunctions of neurotransmission to dysfunctions of neurogenesis and neuroprotection. The “neurogenesis hypothesis of depression” posits that changes in the rate of neurogenesis are the underlying mechanism in the pathology and treatment of major depression. Stress, neuroinflammation, dysfunctional insulin regulation, oxidative stress, and alterations in neurotrophic factors possibly contribute to the development of depression. The influence of antidepressant therapies, namely pharmacotherapy and neuroprotectants, on cellular plasticity are summarized. A dysfunction of complex neuronal networks as a consequence of neural degeneration in neuropsychiatric diseases has led to the application of deep brain stimulation. We discuss the way depression seen in the light of the neurogenesis hypothesis can be used as a model disease for cerebral aging. A common pathological mechanism in depression and cerebral aging—a dysfunction of neuroprotection and neurogenesis—is discussed. This has implications for new treatment methods.

Artistic creativity, artistic production, and aging

This chapter reviews the changes produced by age on various aspects of artistic painting, particularly creativity and actual production. Aging in trained painters is often accompanied by a decline in creativity, which in turn is due to the cognitive decline related to aging. It has been argued, however, that aging does not cause a decline, but only changes in style and content. The two views are not mutually exclusive, and we present examples illustrating both aspects. We also show that, in addition to cognitive changes, impairment of sensory organs, especially vision, and of the bones and joints, may also produce marked changes in an artist's production and style. We conclude by showing that finding ways to induce creativity in persons who do not consider themselves artists can be a way of stimulating creativity and contribute to successful aging.

S 17092: a prolyl endopeptidase inhibitor as a potential therapeutic drug for memory impairment. Preclinical and clinical studies

Any treatment that could positively modulate central neuropeptides levels would provide a promising therapeutic approach to the treatment of cognitive deficits associated with aging and/or neurodegenerative diseases. Therefore, based on the activity in rodents, S 17092 (2S,3aS,7aS)-1][(R,R)-2-phenylcyclopropyl]carbonyl]-2-[(thiazolidin-3-yl)carbonyl]octahydro-1H-indole) has been selected as a potent inhibitor of cerebral prolyl-endopeptidase (PEP). By retarding the degradation of neuroactive peptides, S 17092 was successfully used in a variety of memory tasks. These tasks explored short-term, long-term, reference and working memory in aged mice, as well as in rodents and monkeys with chemically induced amnesia or spontaneous memory deficits. S 17092 has also been safely administered to humans, and showed a clear peripheral expression of its mechanism of action through its inhibitory effect upon PEP activity in plasma. S 17092 exhibited central effects, as evidenced by EEG recording in healthy volunteers, and could improve a delayed verbal memory task. Collectively, the preclinical and clinical effects of S 17092 have suggested a promising role for this compound as an agent for the treatment of cognitive disorders associated with cerebral aging.