Identification of 12/15-lipoxygenase as a regulator of axon degeneration through high-content screening

Axon degeneration is a programed process that takes place during development, in response to neuronal injury, and as a component of neurodegenerative disease pathology, yet the molecular mechanisms that drive this process remain poorly defined. In this study, we have developed a semi-automated, 384-well format axon degeneration assay in rat dorsal root ganglion (DRG) neurons using a trophic factor withdrawal paradigm. Using this setup, we have screened a library of known drugs and bioactives to identify several previously unappreciated regulators of axon degeneration, including lipoxygenases. Multiple structurally distinct lipoxygenase inhibitors as well as mouse DRG neurons lacking expression of 12/15-lipoxygenase display protection of axons in this context. Retinal ganglion cell axons from 12/15-lipoxygenase-null mice were similarly protected from degeneration following nerve crush injury. Through additional mechanistic studies, we demonstrate that lipoxygenases act cell autonomously within neurons to regulate degeneration, and are required for mitochondrial permeabilization and caspase activation in the axon. These findings suggest that these enzymes may represent an attractive target for treatment of neuropathies and provide a potential mechanism for the neuroprotection observed in various settings following lipoxygenase inhibitor treatment.