This project is designed to study the specific function of TRPV3 in generating peripheral itch and pain sensations and determine whether targeted delivery of impermeant ion channel blockers can reduce or block these unpleasant sensations. The strategy is based on the success by our collaborators of delivering the charged sodium channel blocker, QX-314, via TRPVl into pain sensing C fibers. TRPV3, like TRPVl, is a large pore channel that is permeant to large molecules. TRPV3 is unique in that it opens at temperatures near skin temperatures (31 oC) and continues to conduct ions well above core body temperatures into the noxious temperature range. Even more surprisingly, TRPV3 continues to increase with repeated stimulation (sensitizes) unlike all other TRP ion channels, which desensitize to repeated stimuli. One ofthe striking properties of TRPV3 is its abundance in skin cells (keratinocytes) where it is much more common than other TRP channels. Recent work with a constitutively active TRPV3 channel in transgenic mice suggests that TRPV3 induces profound itch. TRPV3 is also present in peripheral sensory neurons, but its function in such neurons is not understood. Phannaceutical companies have also presented evidence that TRPV3 blockers are effective in reducing painful stimuli. We will start by defining the detailed distributions of TRPV3 in skin and neurons innervating skin, and determining whether keratinocyte TRPV3 activation produces nociceptive or pruritic mediators, such as ATP and interieukins. Using genetically modified mice, which lack all TRPV3, lack TRPV3 only in keratinocytes, or lack TRPV3 only in dorsal root ganglion neurons, we will tease apart the contributions of keratinocyte and DRG TRPV3 to pain and itch behaviors in mice. Finally, we will collaborate with the other project investigators to use the genetic, pharmacological, and channel blocking agents to selectively eliminate signals from TRPV3-expressing keratinocytes and neurons. This will be accomplished by using the large pore properties of TRPV3 to introduce blocking compounds into these cells. The overall goals are to define the peripheral circuitry of pain and itch, but also to investigate a new and exciting method of drug delivery into specific cell types that will alleviate painful and pruritic sensation.
Pain is familiar to all of us as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. Pain can be beneficial in that it helps us avoid harmful stimuli, but can also be debilitating, significantiy interfering with a person's quality of life and function. Here we propose new targets for the treatment of pain and itch, and novel ways to silence them when they become debilitating.
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