The Role of Keratinocytes and TRPM3 in CIPN Pain

Project Summary Individuals on chemotherapy often face debilitating side effects, including chemotherapy induced peripheral neuropathy (CIPN). Up to 60-90% of patients with cancer on paclitaxel (PTX), report signs of CIPN; these symptoms include both mechanically evoked and spontaneous, ongoing pain. Although much of the previous literature on CIPN has focused on the dorsal root ganglion (DRG) neurons we have recently shown that non- neuronal cells of the skin epidermis, keratinocytes, also contribute to CIPN-induced mechanical pain. Compared to mechanical pain, almost nothing is known about the causes of ongoing pain, and nothing is known about the contribution of keratinocytes to non-evoked, ongoing pain. My preliminary data suggests that after PTX administration, mice display non-evoked pain behaviors. Additionally, my analysis of single cell sequencing of mouse hind paws following PTX treatment revealed a potential role of TRPM3. Here, I propose to investigate the role of keratinocytes, and TRPM3, in pain behaviors using a mouse model of CIPN. In Aim 1, I hypothesize that keratinocytes contribute to ongoing pain behaviors in CIPN mice. I plan to test this hypothesis by observing ongoing pain behaviors in mice after inhibition of keratinocytes (1A). Then I plan to utilize a method to measure spontaneous activity of DRG neuron afferents of CIPN mice ex vivo following keratinocyte inhibition using teased fiber recordings (1B). In 1C, I will use a coculture of keratinocytes and DRG neurons to measure electrophysiological properties of DRG neurons following PTX exposure using patch clamp recording. In Aim 2, I hypothesize that the TRPM3 channel contributes to pain behaviors in CIPN. I will test this hypothesis by exposing Trpm3-/- knockout mice to PTX and use a battery of behavioral assays to assess pain-like behaviors (2A). I will use calcium imaging to determine if TRPM3 is sensitized in DRG neurons and in keratinocytes (2B). Finally, I will test whether Trpm3-/- knockout mice DRG neurons display spontaneous activity following CIPN using patch clamp electrophysiology (2C). These aims will provide insights into the mechanisms of ongoing pain and will interrogate a potential target to alleviate paclitaxel induced CIPN pain.