Single-Nucleus RNA Sequencing of HDAC6 Inhibition in Resolving Doxorubicin-Induced Cognitive Impairment

Breast cancer is the most common cancer worldwide, accounting for 12.5% of all new cases. Doxorubicin, an effective treatment for breast cancer, is associated with chemotherapy-induced cognitive impairment (CICI), which affects up to 82% of survivors. Currently, no interventions for CICI have been approved by the US Food and Drug Administration. Histone deacetylase 6 (HDAC6) inhibition has been shown to improve cognitive function in neurodegenerative disease models, and we previously reported that the HDAC6 inhibitor ACY-1083 restored CICI-related cognitive dysfunction. Here, we used behavioral testing and single-nucleus transcriptomic analysis of the hippocampi of female mice to evaluate the efficacy of ACY-1083 in reversing doxorubicin-induced CICI. Our results from cognitive testing (the novel object placement recognition task as a test for working memory; the puzzle box test as a measure executive functioning) suggest that HDAC6 inhibition successfully reverses CICI. We also identified specific cell populations and gene expression patterns in oligodendrocytes, astrocytes, microglia, and dentate gyrus granule cells from the hippocampus. Doxorubicin treatment upregulated genes related to neurodegeneration, impaired synaptic function, and oxidative stress. Treatment with ACY-1083 reversed some of the doxorubicin-induced changes in gene expression and created a unique transcriptomic phenotype in treated mice that was not present in untreated control mice. This unique phenotype was characterized by increased expression of genes related to neurodevelopment, neurite outgrowth, and mitochondrial function. Therefore, HDAC6 inhibition may not only reverse gene expression caused by doxorubicin treatment but may also induce a unique gene expression that contributes to cognitive function restoration via homeostatic mechanisms. Because HDAC6 inhibitors have been used successfully in clinical trials focusing on tolerability and safety, we suggest that HDAC6 inhibition may be a realistic and effective intervention for reversing CICI in cancer survivors.