(PQ9) A Redox-Mediated Mechanism of Chemotherapy-Induced Cognitive Impairment

This application addresses the provocative question "What are the molecular and/or cellular mechanisms that underlie the development of cancer therapy-induced severe adverse sequelae?" focusing on therapy-induced neurocognitive impairments. Chemotherapy-induced cognitive impairment (CICI) is a threat to the quality of life. CICI is now a recognized toxicity syndrome that includes loss of executive function (confusion; memory issues), inability to multitask, and impaired intellectual reasoning. While CICI caused by central nervous system (CNS)-directed therapies (such as radiation and intrathecal chemotherapy) is readily understood, the mechanisms underlying a critical and shared toxicity of chemotherapy that occurs after systemic cancer treatment with drugs that did not direct at the brain, are unclear. The number of patients at risk for CICI from systemic therapy far exceeds the number of patients exposed to CNS therapy, but little is known about the mechanisms mediating the effect of systemic therapy on CICI, and there is no clear vision of how to prevent this condition. We have previously shown that generation of reactive oxygen species (ROS) by cytotoxic chemotherapeutic drugs exemplified by Doxorubicin (Dox) is an essential mediator of brain injury even though the drug itself did not get into the brain. It is also imperative to note that anticancer medications, designed specifically to target cancer cells with specialized features, such as the family of Bcl2 inhibitors, also generate ROS. However, the effect of targeted therapy has never been addressed, and, consequently, their mechanisms of action are entirely unknown. The goal of this proposal is to test the overall hypothesis that therapy-induced ROS production in the target tissues leads to increased circulating TNFá through extracellular vesicles (EVs)-mediated reactions, and this pro-inflammatory cytokine crosses the blood brain barrier to elicit mitochondrial dysfunction and consequent neuronal injury leading to CICI. The following specific aims are designed to test the ROS hypothesis, gain an understanding of the EVs-mediated mechanisms, and test the proof-of-concept in an experimental cancer therapy setting using two prototype chemotherapy agents (Dox and Venetoclax) that represent standard cytotoxic and experimental targeted drugs in a lymphoma model. Aim 1 will investigate the fundamental role of TNFá in therapy-induced neuronal injury to gain insight into mechanisms of CICI in the brain and demonstrates efficacy of chemotherapy in the presence of redox-active antioxidants. Aim 2 will determine the mechanistic links between circulating extracellular vesicles and therapy-induced CICI. Aim 3 will define the cell(s) of origin of TNFá produced during chemotherapy that leads to cognitive impairment. These aims will be accomplished in vitro and in vivo using state-of-the-art technologies, including magnetic resonance spectroscopic, redox proteomics, unique animal models, and novel mitochondria targeting anti-oxidant, MnP, to ameliorate CICI without reducing the efficacy of the anti-cancer drugs. Impact: Overall, this is a highly integrated, unique project that brings together various expertises of senior investigators in the fields of neurobiology, cancer biology, redox systems and immunology to address a highly significant problem of CICI faced by cancer patients treated with traditional and targeted drugs. The proposed studies will lead to the understanding of the role of TNFá in CICI and to the identification of small molecules that can mitigate CICI and be translated into human patients. The focus on redox systems, EVs, and immune cells enable interaction across several fields to bring an integrated approach to address a profound practical problem presented by modern therapies. The studies from this project will lay important groundwork for future clinical trials to improve the quality of lives of cancer patients exposed to cytotoxic or targeted therapies.