Ethoxyquin prevents chemotherapy-induced neurotoxicity via Hsp90 modulation.

OBJECTIVE: Peripheral neurotoxicity is a major dose-limiting side effect of many chemotherapeutic drugs. Currently there are no effective disease-modifying therapies for chemotherapy-induced peripheral neuropathies, but these side effects of chemotherapy are potentially ideal targets for development of neuroprotective therapies, because candidate drugs can be co- or preadministered before the injury to peripheral axons takes place. METHODS: We used a phenotypic drug screening approach to identify ethoxyquin as a potential neuroprotective drug and carried out additional biochemical experiments to identify its mechanism of action. RESULTS: We validated the screening results with ethoxyquin and its derivatives and showed that they prevented paclitaxel-induced peripheral neuropathy without blocking paclitaxel's ability to kill tumor cells. Furthermore, we demonstrated that ethoxyquin acts by modulating the chaperone activity of heat shock protein 90 (Hsp90) and blocking the binding of 2 of its client proteins, ataxin-2 and Sf3b2. Ethoxyquin-induced reduction in levels of both of these proteins resulted in prevention of axonal degeneration caused by paclitaxel. INTERPRETATION: Ethoxyquin and its novel derivatives as well as other classes of small molecules that act as Hsp90 modulators may offer a new opportunity for development of drugs to prevent chemotherapy-induced axonal degeneration.

Immortalization and characterization of a nociceptive dorsal root ganglion sensory neuronal line.

Development of neuroprotective strategies for peripheral neuropathies requires high-throughput drug screening assays with appropriate cell types. Currently, immortalized dorsal root ganglion (DRG) sensory neuronal cell lines that maintain nociceptive sensory neuronal properties are not available. We generated immortalized DRG neuronal lines from embryonic day 14.5 rats. Here, we show that one of the immortalized DRG neuronal lines, 50B11, has the properties of a nociceptive neuron. When differentiated in the presence of forskolin, these cells extend long neurites, express neuronal markers, and generate action potentials. They express receptors and markers of small-diameter sensory neurons and upregulate appropriate receptor populations when grown in the presence of glial cell line-derived neurotrophic factor or nerve growth factor. Furthermore, they express capsaicin receptor transient receptor potential vanilloid family-1 (TRPV-1) and respond to capsaicin with increases in intracellular calcium. In a 96-well plate format, these neurons show a decline in ATP levels when exposed to dideoxycytosine (ddC) in a proper time- and dose-dependent manner. This ddC-induced reduction in ATP levels correlates with axonal degeneration. The immortalized DRG neuronal cell line 50B11 can be used for high-throughput drug screening for neuroprotective agents for axonal degeneration and antinociceptive drugs that block TRPV-1.