Effects of TC-1734 (AZD3480), a selective neuronal nicotinic receptor agonist, on cognitive performance and the EEG of young healthy male volunteers

OBJECTIVES

The aim of this study was to get insight into the central effects of TC-1734 (renamed AZD3480), a selective agonist at the neuronal nicotinic receptor of the alpha4beta2 subtype.

MATERIALS AND METHODS

Electroencephalography (EEG) techniques and computerized cognitive tests were performed in young, healthy male volunteers during two double-blind and placebo-controlled studies: a rising single dose crossover study (from 2 to 320 mg) and a rising repeated dose study with a parallel group design (50, 100, and 200 mg).

RESULTS

In contrast to acute administration, administration of AZD3480 over 10 days produced statistically significant enhancement of several cognitive measures (attention and episodic memory) compared to placebo. Regarding EEG data, AZD3480 showed acceleration of the alpha centroid and of the alpha peak in the single-dose study. This EEG profile of the acceleration type was confirmed in the repeated dose study on both day 1 and day 10, with the greatest effect observed with the highest dose. The EEG pattern shown for AZD3480 was consistent with that previously described with other drugs known to improve attention and vigilance (including nicotine). In addition, subjects dosed with AZD3480 showed a statistically significant increase in mismatch negativity (MMN) amplitude at 50 and 200 mg while reducing MMN latency (200 mg only), suggesting an improvement of pre-attentional mechanisms.

CONCLUSION

These early data in healthy subjects provide encouragement to consider development of AZD3480 as a novel agent for the treatment of cognitive decline in the elderly, including age-associated memory impairment and/or dementia of the Alzheimer's type.

Pharmacokinetics and safety profile of ispronicline (TC-1734), a new brain nicotinic receptor partial agonist, in young healthy male volunteers

Recent research suggests that drugs activating nicotine acetylcholine receptors might be promising therapy in cognitive decline seen in the elderly, including Alzheimer's disease. Ispronicline (TC-1734), a brain-selective alpha4beta2 nicotine acetylcholine receptor partial agonist, has shown memory-enhancing properties in rodents and a good tolerability profile. The safety and the full pharmacokinetic profile of TC-1734 and its N-desalkylated metabolite, TC-1784, were investigated in 2 phase I studies, and results are reported in this article. Study A used a double-blind, placebo-controlled, crossover design with a rising single-dose scheme (2-320 mg). Study B used a double-blind, placebo-controlled, parallel-group design with a rising multiple-dose scheme (doses: 50, 100, and 200 mg, once daily, x 10 days). Cmax of TC-1734 was reached around 1 to 2 hours postdose, and mean terminal half-life (t1/2) ranged from 3 to 5.3 hours (single doses) and from 2.7 to 8.8 hours (repeated doses). No accumulation of TC-1734 was observed after 10 days. Renal clearance appeared to be a minor method of elimination of TC-1734 and TC-1784. A high interindividual variability was noted for all parameters. Across the dose ranges explored, TC-1734 was safe and well tolerated. No changes of clinical significance were seen on laboratory and cardiovascular parameters. Adverse events were generally of mild to moderate intensity, with dizziness and headache being reported most frequently.

Death of motoneurons induced by trophic deprivation or by excitotoxicity is not prevented by overexpression of SMN

The telomeric copy of the survival motor neuron gene (SMN1) is deleted or mutated in all spinal muscular atrophy (SMA) patients and these patients present mainly a loss in spinal motoneurons. Although studies performed in HeLa cells suggest that SMN may be involved in the biogenesis and possibly in recycling of spliceosomal small nuclear ribonucleoproteins (snRNPs), no link has been established between this function and the consequence of the absence of SMN in the specific loss of motoneurons. We attempted to answer the question of whether SMN plays a direct role in motoneuron survival by transducing cultured motoneurons with lentiviral vectors coding either for an antisense Smn mRNA or for full-length or truncated forms of SMN. We studied their effect on survival under different anti- or proapoptotic culture conditions. Our results show that increased levels of SMN are unable to protect motoneurons from death induced by trophic deprivation or by excitotoxicity. These results suggest that SMN is not a survival factor per se for motoneurons. In addition, overexpression of a truncated form of SMN shown to induce a modified subcellular localization and to exert a dominant-negative effect on snRNP biogenesis and RNA splicing in HeLa cells was ineffective in modifying both localization and survival in motoneurons.

Efficient gene transfer and expression of biologically active glial cell line-derived neurotrophic factor in rat motoneurons transduced wit lentiviral vectors

Several studies have shown the ability of human immunodeficiency virus type 1 (HIV1)-based lentiviral vectors to infect nondividing brain and retinal neurons with high efficiency and long-term expression of the transduced gene. We show that purified embryonic motoneurons can be efficiently (>95%) transduced in culture using an HIV1-based lentiviral vector encoding LacZ. Expression of beta-galactosidase was observed for at least 9 days in these conditions. Furthermore, motoneurons transduced with a lentiviral vector expressing glial cell line-derived neurotrophic factor survived in the absence of additional trophic support, showing that the overexpressed protein was biologically active. Our results demonstrate the potential of lentiviral vectors in studying the biological effects of proteins expressed in motoneurons and in the development of future gene therapy for motoneuron diseases.

Subcellular distribution of survival motor neuron (SMN) protein: possible involvement in nucleocytoplasmic and dendritic transport

Spinal muscular atrophy (SMA) is among the most common recessive autosomal diseases and is characterized by the loss of spinal motor neurons. A gene termed 'Survival of Motor Neurons' (SMN) has been identified as the SMA-determining gene. Recent work indicates the involvement of the SMN protein and its associated protein SIP1 in spliceosomal snRNP biogenesis. However, the function of SMN remains unknown. Here, we have studied the subcellular localization of SMN in the rat spinal cord and more generally in the central nervous system (CNS), by light fluorescence and electron microscopy. SMN immunoreactivity (IR) was found in the different regions of the spinal cord but also in various regions of the CNS such as the brainstem, cerebellum, thalamus, cortex and hippocampus. In most neurons, we observed a speckled labelling of the cytoplasm and a discontinuous staining of the nuclear envelope. For some neurons (e.g. brainstem nuclei, dentate gyrus, cortex: layer V) and, in particular in motoneurons, SMN-IR was also present as prominent nuclear dot-like-structures. In these nuclear dots, SMN colocalized with SIP1 and with fibrillarin, a marker of coiled bodies. Ultrastructural studies in the anterior horn of the spinal cord confirmed the presence of SMN in the coiled bodies and also revealed the protein at the external side of nuclear pores complexes, in association with polyribosomes, and in dendrites, associated with microtubules. These localizations suggest that, in addition to its involvement in the spliceosome biogenesis, the SMN protein could also play a part in nucleocytoplasmic and dendritic transport.

Survival motor neuron (SMN) protein in rat is expressed as different molecular forms and is developmentally regulated

Spinal muscular atrophy (SMA) is an autosomal recessive disease characterized by a progressive degeneration of motoneurons in spinal cord and brainstem. The telomeric copy of a duplicated gene termed survival motor neuron (smn), which maps to chromosome 5q13, has been found to be deleted in most patients. The encoded gene product is a novel protein which recently has been shown to accumulate in specific nuclear organelles (gemini of coiled bodies, GEMS), and to play a part in the formation of the spliceosome complex. We have cloned and sequenced the rat smn cDNA. Antibodies generated against an N-terminus peptide recognized a main protein of 32 kDa in immunoblots of rat embryonic tissue extracts. Minor bands of 35 kDa, 45 kDa and, in perinatal muscle, of 24 kDa were also specifically detected, indicating that SMN is expressed as different molecular forms. Subcellular fractionation indicated that the 32 kDa form is mainly soluble, while the 35 kDa and 45 kDa products segregate to the microsomal-mitochondrial fraction. SMN protein is highly regulated during development: expression is high in embryonic tissues (central nervous system, muscle, lung and liver), and then progressively decreases to very low levels in most tissues of the adult. The demonstration of different molecular forms of SMN along with its developmental regulation may help to understand the contribution of this protein in the appearance of SMA phenotype.