Paclitaxel-induced epithelial damage and ectopic MMP-13 expression promotes neurotoxicity in zebrafish

Significance

Paclitaxel is a widely used chemotherapeutic agent in the treatment of cancer. Although paclitaxel arrests tumor growth through stabilizing microtubules, it also causes variable peripheral neuropathy in patients. A lack of understanding of the underlying mechanisms hinders therapeutic discovery, and commonly used mammalian models have not provided conclusive evidence about the etiology of this condition. To overcome this, we developed a larval zebrafish model that permits the analysis of paclitaxel neurotoxicity in living animals. This study identifies that keratinocyte damage and ectopic expression of matrix-metalloproteinase 13 (MMP-13) contributes to paclitaxel-induced peripheral neuropathy in zebrafish. We further show that inhibition of MMP-13 improves skin defects and prevents paclitaxel neurotoxicity. Thus, this study offers a previously unidentified avenue for potential therapeutic interventions.

Abstract

Paclitaxel is a microtubule-stabilizing chemotherapeutic agent that is widely used in cancer treatment and in a number of curative and palliative regimens. Despite its beneficial effects on cancer, paclitaxel also damages healthy tissues, most prominently the peripheral sensory nervous system. The mechanisms leading to paclitaxel-induced peripheral neuropathy remain elusive, and therapies that prevent or alleviate this condition are not available. We established a zebrafish in vivo model to study the underlying mechanisms and to identify pharmacological agents that may be developed into therapeutics. Both adult and larval zebrafish displayed signs of paclitaxel neurotoxicity, including sensory axon degeneration and the loss of touch response in the distal caudal fin. Intriguingly, studies in zebrafish larvae showed that paclitaxel rapidly promotes epithelial damage and decreased mechanical stress resistance of the skin before induction of axon degeneration. Moreover, injured paclitaxel-treated zebrafish skin and scratch-wounded human keratinocytes (HEK001) display reduced healing capacity. Epithelial damage correlated with rapid accumulation of fluorescein-conjugated paclitaxel in epidermal basal keratinocytes, but not axons, and up-regulation of matrix-metalloproteinase 13 (MMP-13, collagenase 3) in the skin. Pharmacological inhibition of MMP-13, in contrast, largely rescued paclitaxel-induced epithelial damage and neurotoxicity, whereas MMP-13 overexpression in zebrafish embryos rendered the skin vulnerable to injury under mechanical stress conditions. Thus, our studies provide evidence that the epidermis plays a critical role in this condition, and we provide a previously unidentified candidate for therapeutic interventions.