Brain-Delivery of Zinc-Ions as Potential Treatment for Neurological Diseases: Mini Review.

Homeostasis of metal ions such as Zn(2+) is essential for proper brain function. Moreover, the list of psychiatric and neurodegenerative disorders involving a dysregulation of brain Zn(2+)-levels is long and steadily growing, including Parkinson's and Alzheimer's disease as well as schizophrenia, attention deficit and hyperactivity disorder, depression, amyotrophic lateral sclerosis, Down's syndrome, multiple sclerosis, Wilson's disease and Pick's disease. Furthermore, alterations in Zn(2+)-levels are seen in transient forebrain ischemia, seizures, traumatic brain injury and alcoholism. Thus, the possibility of altering Zn(2+)-levels within the brain is emerging as a new target for the prevention and treatment of psychiatric and neurological diseases. Although the role of Zn(2+) in the brain has been extensively studied over the past decades, methods for controlled regulation and manipulation of Zn(2+) concentrations within the brain are still in their infancy. Since the use of dietary Zn(2+) supplementation and restriction has major limitations, new methods and alternative approaches are currently under investigation, such as the use of intracranial infusion of Zn(2+) chelators or nanoparticle technologies to elevate or decrease intracellular Zn(2+) levels. Therefore, this review briefly summarizes the role of Zn(2+) in psychiatric and neurodegenerative diseases and highlights key findings and impediments of brain Zn(2+)-level manipulation. Furthermore, some methods and compounds, such as metal ion chelation, redistribution and supplementation that are used to control brain Zn(2+)-levels in order to treat brain disorders are evaluated.

Concerted action of zinc and ProSAP/Shank in synaptogenesis and synapse maturation.

Neuronal morphology and number of synapses is not static, but can change in response to a variety of factors, a process called synaptic plasticity. These structural and molecular changes are believed to represent the basis for learning and memory, thereby underling both the developmental and activity-dependent remodelling of excitatory synapses. Here, we report that Zn(2+) ions, which are highly enriched within the postsynaptic density (PSD), are able to influence the recruitment of ProSAP/Shank proteins to PSDs in a family member-specific manner during the course of synaptogenesis and synapse maturation. Through selectively overexpressing each family member at excitatory postsynapses and comparing this to shRNA-mediated knockdown, we could demonstrate that only the overexpression of zinc-sensitive ProSAP1/Shank2 or ProSAP2/Shank3 leads to increased synapse density, although all of them cause a decrease upon knockdown. Furthermore, depletion of synaptic Zn(2+) along with the knockdown of zinc-insensitive Shank1 causes the rapid disintegration of PSDs and the loss of several postsynaptic molecules including Homer1, PSD-95 and NMDA receptors. These findings lead to the model that the concerted action of ProSAP/Shank and Zn(2+) is essential for the structural integrity of PSDs and moreover that it is an important element of synapse formation, maturation and structural plasticity.

Acute pretreatment with estradiol protects against CA1 cell loss and spatial learning impairments resulting from transient global ischemia.

Estradiol can act to protect against hippocampal damage resulting from transient global ischemia, but little is known about the functional consequences of such neuroprotection. The present study examines whether acute estradiol administered prior to the induction of transient global ischemia protects against hippocampal cell death and deficits in performance on a spatial learning task. Ovariectomized female rats were primed with estradiol benzoate or oil vehicle 48 and 24 h prior to experiencing one of three durations of 4-vessel occlusion (0, 5, or 10 min). Performance on the cued and hidden platform versions of the Morris water maze was assessed 1 week following ischemia. On the cued platform task, neither hormone treatment nor ischemia significantly influenced acquisition. When tested on the hidden platform task, however, oil-treated rats exhibited impairments in spatial learning after either 5 or 10 min of ischemia while estradiol-treated rats showed no impairments after 5 min of ischemia and only mild impairments after 10 min of ischemia. Immediately following behavioral testing, rats were perfused and survival of CA1 pyramidal cells was assessed. Ischemia was associated with the loss of CA1 pyramidal cells but rats that received estradiol prior to ischemia showed less severe damage. Furthermore, the extent of cell loss was correlated with degree of spatial bias expressed on a probe trial following hidden platform training. These findings indicate that acute exposure to estradiol prior to ischemia is both neuroprotective and functionally protective.