Functional convergence of dopaminergic and cholinergic input is critical for hippocampus-dependent working memory.

Although Parkinson's disease is a movement disorder, in many patients cognitive dysfunction is an important clinical sign. It is not yet clear whether this is attributable solely to a decrease in dopamine levels, or whether other neurotransmitter systems might be involved as well. In the present study, the importance of the mesocorticolimbic dopamine pathway and a possible convergence with forebrain cholinergic projections to neocortex and hippocampus in the regulation of learning and memory abilities were investigated by using specific lesion paradigms in one or both systems. Lesioning of dopaminergic neurons in the ventral tegmental area resulted in an impaired performance in the reference memory task, whereas the execution of the working memory tasks appeared to be unaffected in the Morris water maze. Analysis of the swim paths revealed that the dopamine-depleted animals were capable of adapting a search strategy on a given testing day but failed to transfer this information to the next day, suggesting a deficit in information storage and/or recall. In contrast, cholinergic lesions alone were without effect in all test paradigms. However, when both dopamine and acetylcholine were depleted, animals were also impaired in the working memory task, indicating that a functional convergence of the inputs from these systems was critical for acquisition of spatial memory. Interestingly, such an additional acquisition deficit appeared only after hippocampal cholinergic depletion regardless of a concurrent disruption of basalo cortical cholinergic afferents. Thus, further analyses of cholinergic alterations may prove useful in better understanding the cognitive symptoms in Parkinson's disease.

Cells over-expressing EAAT2 protect motoneurons from excitotoxic death in vitro.

Amyotrophic lateral sclerosis is an incurable disease in which cerebral and spinal motoneurons degenerate, causing paralysis and death within 2-5 years. One of the pathogenic factors of motoneuron death is a chronic excess of glutamate, which exceeds its removal by astrocytes, i.e. excitotoxicity. Extra glutamate uptake in the spinal cord may slow down or prevent motoneuron death. We have engineered cells over-expressing the main glutamate transporter and tested their potential to rescue motoneurons exposed to high levels of glutamate in vitro. The engineered cells protected motoneurons in a motoneuron-astrocyte co-culture at glutamate concentrations when astrocytes were no longer capable of removing glutamate. This suggests that engineered cells, introduced into the spinal column, can help remove glutamate, thereby preventing motoneuron death.

A phase I dose-escalation and bioequivalence study of a trastuzumab biosimilar in healthy male volunteers.

BACKGROUND: Trastuzumab (Herceptin(®)) is a humanized monoclonal antibody targeting the human epidermal growth factor receptor 2 (HER2) and is used in the treatment of HER2-overexpressing breast and gastric cancer. FTMB is being developed as a biosimilar of trastuzumab. OBJECTIVE: In this combined dose-escalation and bioequivalence study of parallel design, the pharmacokinetic profile of FTMB was compared with Herceptin(®). METHODS: Healthy male volunteers received single doses of 0.5, 1.5, 3.0 or 6.0 mg/kg FTMB, or placebo, in consecutive dose-escalation cohorts to assess the safety profile. Thereafter, the 6 mg/kg cohort was expanded to establish bioequivalence between FTMB (Test) and Herceptin(®) (Reference) based on an acceptance interval of 80.0-125.0 %. In total, 118 subjects were enrolled in the study. RESULT: The mean area under the concentration-time curve from time zero to infinity (AUC∞) was 1,609 µg·day/mL (Test) and 1,330 µg·day/mL (Reference). The log-transformed geometric mean Test/Reference (T/R) ratio for AUC∞ was 89.6 % (90 % confidence interval [CI] 85.1-94.4), demonstrating bioequivalence. For the secondary endpoint, the maximum concentration observed (Cmax), the geometric mean T/R ratio was 89.4 % (90 % CI 83.4-95.9). Non-linear, target-mediated pharmacokinetics were also observed. Adverse events other than the documented side effects of Herceptin(®) (fever, influenza-like illness, and fatigue) did not occur. No signs of cardiotoxicity were observed. CONCLUSIONS: This bioequivalence study with a trastuzumab biosimilar in healthy male volunteers demonstrated bioequivalence of FTMB with Herceptin(®). FTMB was well tolerated in doses up to 6 mg/kg. Non-linear target elimination was also observed in the pharmacokinetic profile of trastuzumab.

The expression of the chemorepellent Semaphorin 3A is selectively induced in terminal Schwann cells of a subset of neuromuscular synapses that display limited anatomical plasticity and enhanced vulnerability in motor neuron disease.

Neuromuscular synapses differ markedly in their plasticity. Motor nerve terminals innervating slow muscle fibers sprout vigorously following synaptic blockage, while those innervating fast-fatigable muscle fibers fail to exhibit any sprouting. Here, we show that the axon repellent Semaphorin 3A is differentially expressed in terminal Schwann cells (TSCs) on different populations of muscle fibers: postnatal, regenerative and paralysis induced remodeling of neuromuscular connections is accompanied by increased expression of Sema3A selectively in TSCs on fast-fatigable muscle fibers. To our knowledge, this is the first demonstration of a molecular difference between TSCs on neuromuscular junctions of different subtypes of muscle fibers. Interestingly, also in a mouse model for amyotrophic lateral sclerosis (ALS), Sema3A is expressed at NMJs of fast-fatigable muscle fibers. We propose that expression of Sema3A by TSCs not only suppresses nerve terminal plasticity at specific neuromuscular synapses, but may also contribute to their early and selective loss in the motor neuron disease ALS.