Abstract
Nystatin is a pharmacological agent commonly used for the treatment of oral, mucosal and cutaneous fungal infections. Nystatin has also been extensively applied to study the cellular function of cholesterol-enriched structures because of its ability to bind and extract cholesterol from mammalian membranes. In neurons, cholesterol level is tightly regulated, being essential for synapse and dendrite formation, and axonal guidance. However, the action of Nystatin on axon regeneration has been poorly evaluated. Here, we examine the effect of Nystatin on primary cultures of hippocampal neurons, showing how acute dose (minutes) of Nystatin increases the area of growth cones, and chronic treatment (days) enhances axon length, axon branching, and axon regeneration post-axotomy. We describe two alternative signaling pathways responsible for the observed effects and activated at different concentrations of Nystatin. At elevated concentrations, Nystatin promotes growth cone expansion through phosphorylation of Akt; whereas, at low concentrations, Nystatin enhances axon length and regrowth by increasing nitric oxide levels. Together, our findings indicate new signaling pathways of Nystatin and propose this compound as a novel regulator of axon regeneration.
Highlights
Mammalian adult Central Nervous System (CNS) differs from embryonic CNS and Peripheral Nervous System (PNS) by their inherent ability to regenerate lesioned tissues
This study examines the mechanisms through which Nystatin, a drug used normally to treat fungal infections, enhances axonal growth and regeneration using differential dose-dependent mechanism
We demonstrate that only high concentrations of Nystatin increase the size of growth cones through Akt phosphorylation, whereas low concentrations exert the same effect by promoting nitric oxide (NO) production
Summary
Mammalian adult Central Nervous System (CNS) differs from embryonic CNS and Peripheral Nervous System (PNS) by their inherent ability to regenerate lesioned tissues. The first of which consists of the influx of calcium, which increases exocytosis to fuse additional membrane to form a sealing patch to repair the ablated axon (Bradke et al, 2012; Blanquie and Bradke, 2018; Curcio and Bradke, 2018) Following this initial membrane addition, microtubule and actin cytoskeleton is reorganized, multiple signaling cascades are activated and Nystatin Promotes Axon Extension and Regeneration the new membrane is transported to the tip of the growing axon (Bradke et al, 2012; He and Jin, 2016; Curcio and Bradke, 2018). The NO downstream signaling pathway involves the activation of protein kinase G (PKG) and actin-associated proteins such as the Enabled/vasodilatorstimulated phosphoprotein (Ena/VASP), resulting in a strong reorganization of the actin cytoskeleton (Zhou and Zhu, 2009; Forstermann and Sessa, 2012; Cossenza et al, 2014)
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