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

Abstract

Brain penetrant microtubule stabilising agents (MSAs) are being increasingly validated as potential therapeutic strategies for neurodegenerative diseases and traumatic injuries of the nervous system. MSAs are historically used to treat malignancies to great effect. However, this treatment strategy can also cause adverse off-target impacts, such as the generation of debilitating neuropathy and axonal loss. Understanding of the effects that individual MSAs have on neurons of the central nervous system is still incomplete. previous research has revealed that aberrant microtubule stabilisation can perturb many neuronal functions, such as neuronal polarity, neurite outgrowth, microtubule dependant transport and overall neuronal viability. in the current study, we evaluate the dose dependant impact of epothilone D, a brain penetrant MSA, on both immature and relatively mature mouse cortical neurons in vitro. We show that epothilone D reduces the viability, growth and complexity of immature cortical neurons in a dose dependant manner. furthermore, in relatively mature cortical neurons, we demonstrate that while cellularly lethal doses of epothilone D cause cellular demise, low sub lethal doses can also affect mitochondrial transport over time. Our results reveal an underappreciated mitochondrial disruption over a wide range of epothilone D doses and reiterate the importance of understanding the dosage, timing and intended outcome of MSAs, with particular emphasis on brain penetrant MSAs being considered to target neurons in disease and trauma. Historically, the adult neuronal cytoskeleton was considered relatively stable, being involved only in neuroprogenitor cell division during de novo neurogenesis 1,2. With our increased understanding of the neuronal microtubule environment and function, and the adult brains capacity for neuroplasticity 3 , it is now evident that neuronal microtubules, the largest of the three filament components of the cytoskeleton, form a critical dynamic intracellular network 4. In this regard, microtubules consist of both stable and labile domains 5,6 within tubular protofilaments comprised of αand β-tubulin heterodimers. Microtubules display a phenomenon termed "dynamic instability" 7 , which describes the stochastic variations between bouts of growth, pausing and shrinkage of the microtubule population. Microtubules can transition from a growing to a shrinking state, termed catastrophe, which may or may not be rescued back to a growing state. The microtubule protofilament consists of a slow growing "minus end" and a fast growing, highly dynamic "plus end" 8,9 , which plays a critical role in normal neuronal functions including neuronal growth, intracellular transport, establishment and maintenance of cellular polarity, and process remodelling 10-12. Changes to the growth state of microtubules can have downstream consequences for their normal physiological functions, such as the binding of specific motor transport units 13 , and the association of + TIP proteins that facilitate interactions bet...

Investigating Pathogenetic Mechanisms of Alzheimer’s Disease by Systems Biology Approaches for Drug Discovery

“…However, we still believe that further dosage, timing, and their synergistic effect are worth studying for these proposed multiple-molecule drug candidates. For instance, one study has demonstrated that the average transport speed of mitochondria would be affected by the different concentrations of Epothilone D [ 82 ]. The systems biology approach-based analyses in this study might provide a new perspective of finding multitarget-directed drug candidates for the therapeutics of AD.…”

Microtubule Integrity Is Associated with the Functional Activity of Mitochondria in HEK293

“…In a preclinical study, EpD increased the number of microtubules and reduced the number of axons with an abnormal morphology in young and aged Tau-transgenic mice [ 26 ]. In other mouse models of tauopathy, EpD improved cognition and reduced Tau pathology and Tau-related changes in microtubule dynamics [ 15 ]. Among the many microtubule-directed drugs, members of the Taxol family are unique because they stabilize microtubules against depolymerization [ 10 ].…”

“…Bioenergy produced by mitochondria supports assembly of microtubule-associated proteins for microtubule polymerization during cell growth and migration. Microtubule stabilizers such as Taxol and Epothilone D (EpD) play a similar role to microtubule-associated proteins and inhibit microtubule disassembly-dependent chromosome segregation, and thus can be used as anti-cancer therapies [ 15 , 16 , 17 ]. Anti-cancer agents such as microtubule stabilizers regulate mitochondrial structure, movement, and function in cancer cells, and thereby induce apoptosis [ 18 , 19 , 20 ].…”

Tubulin and Tubulin Posttranslational Modifications in Alzheimer’s Disease and Vascular Dementia

“…In a study following treatment with this drug, MT dynamicity decreased, whilst cognition improved, as shown in the Morris Water Maze task (Barten et al, 2012). Another study in cortical neurons put in display the importance of the dose, since it can affect the mitochondrial transport (Clark et al, 2020). Studies have also shown that BM2-241027 reduces axonal dysfunction, neurotoxicity, cognitive deficits, and AD-like pathology in PS19 aged tau transgenic mice (Zhang et al, 2012).…”