Role of the mitochondrial dynamics in the neuropathy induced by Paclitaxel

• Grant number: 21/14831-8
• Support Opportunities: Regular Research Grants
• Duration: August 01, 2022 - July 31, 2024
• Field of knowledge: Biological Sciences - Pharmacology - Biochemical and Molecular Pharmacology
• Principal Investigator: Vanessa Olzon Zambelli
• Grantee: Vanessa Olzon Zambelli
• Host Institution: Fundação Butantan. Secretaria da Saúde (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

Paclitaxel is a chemotherapy drug widely used to eliminate breast and ovarian cancer. Despite being effective against cancer cells, this chemotherapy induces neuropathy in about 70% of the patients. So far, little is known about the mechanisms involved in paclitaxel-induced neuropathy and the treatment is often ineffective or non-existent. Mitochondria are critical organelles to supply the cellular energy demand and continuously undergo fusion and fission processes. These opposing processes work together to maintain the shape, size and number of mitochondria. GTPases such as mitofusin 2 and dynamin-related protein (Mfn2, important in mitochondrial fusion and Drp1, important in mitochondrial fission) are important for the regulation of mitochondrial plasticity. Studies demonstrate a causal correlation between impaired bioenergetic metabolism and the development of neuropathies. However, it is unknown whether mitochondrial fusion-fission processes are important for the bioenergetic metabolism in nociceptors and, consequently, for pain development. Considering that neurons have a high metabolic demand and a large amount of mitochondria, and that chemotherapy-induced neuropathy is often accompanied by mitochondrial dysfunction, we sought to investigate the role of mitochondrial plasticity (ability to reorganize its morphology and number under stress) in nociceptors. We hypothesize that the absence of the Mfn2 protein in nociceptors will result in the sustained accumulation of fragmented and dysfunctional mitochondria, contributing to the amplification of neuronal damage. On the other hand, the Drp1 deletion will result in a protective effect in this model. Thus, the aim of this project is to investigate the role of mitochondrial dynamics in the spinal cord dorsal ganglion (DRG or nociceptors) of animals submitted to paclitaxel-induced neuropathy. The specific objectives are: 1. to characterize the mitochondrial morphology and the paclitaxel-induced fragmentation profile, using DRG electron microscopy; 2. characterize the mitochondrial dynamics by quantifying the levels of proteins involved in mitochondrial fusion (Mfn1, Mfn2, Opa1) and fission (Drp1, Fis1); 3. characterize the bioenergetics and mitochondrial function, through functional assays, evaluating: ATP content, mitochondrial oxygen consumption, mitochondrial Ca2+ uptake and H2O2 release; 4. Evaluate the role of mitochondrial fusion and fission in sensory neurons of animals submitted to paclitaxel-induced neuropathy. For that, we will use mice with nociceptor-specific deletion of Drp1 and/or Mfn2 (Drp1flox/Nav1.8Cre, Mfn2flox/Nav1.8Cre), evaluating the nociceptive threshold, morphology and mitochondrial function, as described above. A better understanding of this process may contribute to the development and use of new strategies to minimize the risks caused by chemotherapy-induced peripheral neuropathy and elucidate the mechanisms involved in mitochondrial homeostasis. (AU)