An imaging assay to analyze primary neurons for cellular neurotoxicity.

The development of high-content screening technologies including automated immunostaining, automated image acquisition and automated image analysis have enabled higher throughput of cellular imaging-based assays. Here we used high-content imaging to thoroughly characterize the cultures of primary rat cerebellar granule neurons (CGNs). We describe procedures to isolate and cultivate the CGNs in 96-well and 384-well format, as well as a procedure to freeze and thaw the CGNs. These methods allow the use of CGNs in 96-well format analyzing 2500 samples per experiment using freshly isolated cells. Down-scaling to 384-well format and freezing and thawing of the CGNs allow even higher throughput. A cellular assay with rat CGN cultures was established to study the neurotoxicity of compounds in order to filter out toxic compounds at an early phase of drug development. The imaging-based toxicity assay was able to reveal adverse effects of compounds on primary neurons which were not detected in neuroblastoma or other cell lines tested.

In vitro neurotoxicity of magnetic resonance imaging (MRI) contrast agents: influence of the molecular structure and paramagnetic ion.

Interest in contrast agent's (CA) neurotoxicity has greatly increased due to the growing need of new compounds dedicated to brain imaging. Magnetic resonance imaging (MRI) CA have been evaluated by means of different toxicological assays with cultured rat primary neurons (evaluation of neurite specific parameters via immunostaining of the cells and LDH leakage). To determine the potential neurotoxicity of a precise paramagnetic ion in a defined structure (architecture and molecular weight), novel hydrosoluble dendritic Manganese (II) and Gadolinium (III) complexes derived from diethylenetriamine pentaacetic acid (DTPA) have been studied and compared to a linear homologue (same molecular weight) and commercially available low molecular weight MRI CA like Mn-DPDP (Teslascan, GE Healthcare) and Gd-DTPA (Magnevist, Schering). The range of CA concentrations studied was 0.1-10mM, suitable for MRI examinations. This set of experiments allows a toxicity ranking of these reagents as a function of molecular structure and nature of the paramagnetic ion. We could determine that the architecture (linear vs. dendritic) does not play an important role in the in vitro neurotoxicity, whereas the structure of the chelating cage is of greater importance.

Development of a dendritic manganese-enhanced magnetic resonance imaging (MEMRI) contrast agent: synthesis, toxicity (in vitro) and relaxivity (in vitro, in vivo) studies.

A new dendritic manganese(II) chelate 1 has been evaluated by in vivo (relaxivity) and in vitro (toxicity and relaxivity) experiments as a manganese enhanced magnetic resonance imaging (MEMRI) contrast agent. Also, a comparison with its corresponding gadolinium(III) homologue 2 and the commercially available MEMRI agent MnDPDP (Teslascan, Amersham Health) was achieved in order to determine respectively the real influence of the paramagnetic ion in terms of toxicity and relaxivity for this precise treelike structure and the potential of 1 to be a favorable candidate for brain-targeting MRI. Complexes 1 and 2 displayed high hydrosolubility (0.1 M) and revealed no in vitro neuronal toxicity at concentrations as high as 1 mM. Considering manganese(II) complex 1, the in vivo nontoxicity at 20 mM (100% rats survival) is very likely due to a slow diffusion of the compound, meaning a controlled release of the paramagnetic ions. Finally, T(1) relaxivity of 4.2 mM(-1).s(-1) for 2 and T(2) relaxivity of 17.4 mM(-1).s(-1) for 1 at 4.7 T were measured and are higher than that of the commercial MRI contrast agents GdDTPA and MnDPDP, respectively.