Effects of Microtubule Stabilization by Epothilone B Depend on the Type and Age of Neurons

Abstract

Several studies have demonstrated the therapeutic potential of applying microtubule- (MT-) stabilizing agents (MSAs) that cross the blood-brain barrier to promote axon regeneration and prevent axonal dystrophy in rodent models of spinal cord injury and neurodegenerative diseases. Paradoxically, administration of MSAs, which have been widely prescribed to treat malignancies, is well known to cause debilitating peripheral neuropathy and axon degeneration. Despite the growing interest of applying MSAs to treat the injured or degenerating central nervous system (CNS), consequences of MSA exposure to neurons in the central and peripheral nervous system (PNS) have not been thoroughly investigated. Here, we have examined and compared the effects of a brain-penetrant MSA, epothilone B, on cortical and sensory neurons in culture and show that epothilone B exhibits both beneficial and detrimental effects, depending on not only the concentration of drug but also the type and age of a neuron, as seen in clinical settings. Therefore, to exploit MSAs to their full benefit and minimize unwanted side effects, it is important to understand the properties of neuronal MTs and strategies should be devised to deliver minimal effective concentration directly to the site where needed.

Epothilone D alters normal growth, viability and microtubule dependent intracellular functions of cortical neurons in vitro

“…Recently we published data showing EpoD administration in vivo causes increased dendritic spine density in layer 5 pyramidal projection neurons, without pyramidal cell loss, highlighting the capacity for EpoD to alter different cell types and targets 55 . This difference in EpoD concentration required to cause alterations may suggest a differential vulnerability to EpoD between neuronal populations, similar to that of EpoB, as mentioned previously 32,39 . Further, differences in the vulnerability of neuronal compartments to EpoD were identified in the current study, with only dendrite length being affected at sublethal concentrations, whilst lethal concentrations impacted both axon and dendrite readouts.…”

“…Our results suggest that CNS neurons treated with even relative low doses in vivo may be experiencing microtubule dependent dysfunction, particularly when considering organelle transport and general neuronal metabolic activity. Interestingly, treating various types of neurons with EpoB exhibits both beneficial and negative effects depending on neuronal subtype, dosage and the age of the neurons 32 . For example, EpoB was found to decrease cell viability and prevent axonal growth at nanomolar concentrations.…”

Structural and Molecular Basis for Katanin-Mediated Severing of Glutamylated Microtubules

“…Detailed methods are provided in the online version of this paper and include the following: Primary culture and transfection of dorsal root ganglion (DRG) neurons Procedure to dissect and culture neurons from adult DRGs is described in detail elsewhere (Jang et al, 2016). Briefly, DRGs were digested in collagenase A (1 mg ml -1 , 90 min), followed by trypLE (0.05%, 20 min) at 37 C, and then washed three times with MEM containing 10% fetal bovine serum (FBS).…”

Microtubule stabilizer epothilone B as a motor neuron differentiation agent for human endometrial stem cells

“…One of the most important structural elements for axonal regeneration and neuronal morphology are microtubule cytoskeletons, aiding in intracellular movement, division, motility, and secretion (Dent and Baas, 2014; Kapitein and Hoogenraad, 2015). It has been well‐documented that microtubule disorganization and disruption are common features of damaged neurons after an SCI (Erturk et al, 2007; Jang and Sim, 2016). Recent studies have even focused on microtubule disorganization as the primary etiology of neurodegenerative diseases such as Parkinson's and Alzheimer's diseases (Baas et al, 2016; Bonini et al, 2017) with microtubule‐stabilizing agents (MSAs) as a possible treatment modality (Varidaki et al, 2018).…”

“…This class of drug has been shown to prevent microtubule depolymerization and, in fact, binding to specific loci on the tubulin surface to aid in polymerization/stabilization of microtubules. Of particular significance to our study, epothilone B (EpoB), also known as patupilone, is a microtubule stabilizer that can cross the blood‐brain barrier (BBB) and has been reported to promote axon regeneration and axon elongation of damaged neuron, while reducing scar formation after SCI in rodents (Ruschel et al, 2015; Jang and Sim, 2016; Zhao et al, 2017). Axon elongation is also one of the parameters for neuronal differentiation (Ludueña, 1973; Pletto et al, 2018).…”