Inhibition of microtubule detyrosination by parthenolide facilitates functional CNS axon regeneration

Abstract

Injured axons in the central nervous system (CNS) usually fail to regenerate, causing permanent disabilities. However, the knockdown of PTEN or treatment of neurons with hyper-IL-6 (hIL-6) transforms neurons into a regenerative state, allowing them to regenerate axons in the injured optic nerve and spinal cord. Transneuronal delivery of hIL-6 to the injured brain stem neurons enables functional recovery after severe spinal cord injury. Here we demonstrate that the beneficial hIL-6 and PTEN knockout effects on axon growth are limited by the induction of tubulin detyrosination in axonal growth cones. Hence, cotreatment with parthenolide, a compound blocking microtubule detyrosination, synergistically accelerates neurite growth of cultured murine and primary RGCs isolated from adult human eyes. Systemic application of the prodrug dimethylamino-parthenolide (DMAPT) enables axon regeneration in the injured optic nerve and spinal cord. Moreover, combinatorial treatment further improves hIL-6-induced axon regeneration and locomotor recovery after severe SCI. Thus, DMAPT facilitates functional CNS regeneration and reduces the limiting effects of pro-regenerative treatments, making it a promising drug candidate for treating CNS injuries. Significance statementInjured axons in the CNS usually fail to regenerate, causing permanent disabilities. No clinically approved drugs are currently available to improve or accelerate axon regeneration. We demonstrate that pro-regenerative treatments induced tubulin detyrosination in axonal growth cones limits axon growth. Hence, cotreatment with parthenolide, a compound blocking detyrosination, synergistically accelerates neurite growth of primary murine and, demonstrated for the first time, human retinal ganglion cells. Furthermore, systemic application of the parthenolides prodrug DMAPT accelerates hIL-6-mediated optic nerve regeneration and locomotor recovery after severe spinal cord injury. Thus, DMAPT facilitates functional CNS regeneration and reduces the limiting effects of pro-regenerative treatments, making it a potential (adjuvant) drug candidate for treating CNS injuries.