CNS & Neurological Disorders - Drug Targets - Volume 7, Issue 6, 2008

This review discusses new mechanisms for the induction of Alzheimer's disease, involving lipid toxicity and adipokines. Ceramide induces oxidative stress and the formation of amyloidβ. Visfatin induces oxidative stress, damages the blood brain barrier and increases the attraction of monocytes, neutrophils and other white blood cells. A new mechanism for visfatin/NAD (nicotinamide adenine dinucleotide)-induced oxidative stress is presented involving redox cycling catalyzed by xanthine dehydrogenase and NADH oxidase. These mechanisms are discussed in terms of the treatment of Alzheimer's disease.

Alzheimer's disease (AD) clinical drug development and patient care depend on rating instruments, research designs and methods, and translations of clinical trial (CT) results into the clinic without support from standardized protocols able to control (i) random measurement error intrusions into observations, (ii) inaccuracy and bias introduced by clinical evaluators, (iii) conformity of research sites to conditions of research protocols, (iv) the ability of the CT to model for practitioners the most effective use of the drug with individual patients, and (v) other factors able to invalidate research and patient care data. This relaxed attitude with regard to AD methods may be changing now with Alzheimer's Disease Neuroimaging Initiative (ADNI) evidence that carefully standardized protocols are needed to validate biomarkers for use in AD diagnosis, drug development, and patient care. In the fields of psychiatry and AD, recent studies have detected serious inaccuracies, imprecision, biases and compromises of study protocols able to invalidate CT outcome data and conclusions drawn from these data. This limited but troubling evidence reinforces ADNI calls for more detailed methodological protocols. Based on the limits to precision and accuracy associated with rated outcomes in CTs and patient care, we call for priority to be given to the qualification and use of biomarkers as outcome variables in AD drug development and patient care and, to insure effective uses of biomarkers, to development of protocol guided practices being modeled in ADNI research. To meet clinical pharmacology's therapeutic aims we conclude that AD CTs need to set for clinicians the conditions of use of drugs shown efficacious, biomarker surrogate endpoints as drug targets, and not to function merely as tests for efficacy conducted under field conditions determined by current clinical practices.

Growing evidence has shown that the p75 neurotrophin receptor (p75NTR) may play important roles in controlling neuronal survival or cell apoptosis within the central nervous system in development, and in pathological or neural injury. Recent studies have further revealed that p75NTR acts as a “molecular signal switch” that determines cell death or survival by three processes. First, pro-nerve growth factor (proNGF) triggers cell apoptosis by its high affinity binding to p75NTR, while NGF induces neuronal survival with lowaffinity binding. Second, p75NTR mediates cell death by combining with co-receptor sortilin, whereas it promotes neuronal survival through combination with proNGF. Third, release of the intracellular domain chopper or cleavaged “short p75NTR” can independently initiate neuronal apoptosis. We have identified the cell self-destructive proNGF-p75NTR-sortilin signalling apparatus assembled in ventral tier dopamine neurons of the substantia nigra pars compacta, suggesting that p75NTR signalling might be involved in selective cell death mechanisms of substantia nigra neurons or disease progression of Parkinson's disease (PD). In addition, experimental manipulation of p75NTR benefited cell survival of cholinergic or motor neurons and improved disease progression of the neurodegenerative diseases Alzheimer's disease and Amyotrophic lateral sclerosis. The proNGF-p75NTR-sortilin signalling complex may thus provide new target for neuroprotection of substantia nigra neurons and the therapeutic treatment of PD.

Central sensitisation phenomena have been well recognized in the development of migraine attacks and tension type headache. It is also known that headache frequency is related to sensitization. Though some studies have focused on the effects of symptomatic treatment on allodynia, few reports have described the action of preventive agents on the facilitating factors for central sensitisation. In this study we aim to review the factors concurrent with an increase in central sensitisation, in view of the choice of preventive agents for primary headaches. Central sensitisation phenomena are increased in pain syndromes with psycho-pathological co-morbidities. For instance, sleep disorders are a frequent symptom in headache, prevailing in chronic forms and in patients with psychiatric comorbidity. Sleep deprivation is also a factor producing hyperalgesic changes. It is known that symptoms attributable to central sensitization are diffusely pronounced in fibromyalgic (FMS) patients, and that FMS co-morbidity is frequent in primary headaches and associated with higher frequency and poorer quality of life. We report our preliminary experience in a group of 20 chronic migraine patients, treated with duloxetine 60 mg/die vs a self-management program including stretching (relaxation training) and exercise (cervical-dorsal flexion and rotation) to decrease strength and flexibility of muscles of cervical and dorsal spine headache patients. Both the treatments were effective on headache frequency and pericranial tenderness, although FMS comorbidity significantly reduced their efficacy on migraine and quality of life. The whole spectrum of action of pharmacological and non pharmacological treatments on central sensitisation mechanisms, and on their facilitating factors, should be taken into account for the best preventive therapeutic approach of primary headaches.

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease of the central nervous system (CNS) that afflicts over 2 million people worldwide. On the basis of the temporal course of disease, MS can be subdivided into three clinical groups: relapsing remitting MS (RR-MS), secondary progressive MS and primary progressive MS. There is a high degree of clinical diversity within these subgroups. The pathogenesis of MS in most patients is likely to result from autoreactive, activated CD4+ T cells moving from the periphery across the blood brain barrier into the CNS. Most therapeutic agents used in MS (e.g. immunosuppressive and immunomodulatory drugs and cell cycle interruption drugs) are only used for RR-MS. These treatments show some efficiency in lessening the relapse rate in RR-MS and time to progression, but cannot cure MS. Thus, there is a need for new efficient treatments for all types of MS. An increasing number of studies indicate that nuclear factor-κB plays an important role in controlling expression of genes relevant to the pathogenesis of autoimmunity. Genetic factors related to NF-κB may also be determinants of MS susceptibility, as polymorphisms in the molecules involved in regulation of the NF-κB signal transduction pathway differ between RRMS and progressive MS. Herein, the role of NF-κB in MS will be reviewed and its potential as a new therapeutic target in MS will be considered and compared with existing treatments.