Chronic therapy-refractory trigeminal pain is a major medical problem, with temporo-mandibular-joint (TMJ) pain the most prevalent form of head-face pain. One of the obstacles to development of rationally targeted therapies lies in the shortcomings of available animal models for TMJD. Another roadblock is the lack of clear understanding of molecular, cellular and neural-circuit mechanisms that underlie TMJ pain and dysfunction. We have recently adapted bite-force measurements as read-out of TMJ inflammatory pain in mice, and applied this novel methodology to Trpv4-/- mice. The """"""""osmo-mechano""""""""-TRP, TRPV4, expressed in TMJ-innervating trigeminal ganglion (TG) neurons, is critical for bite-force reduction after TMJ-inflammation. Also, the expression of other pain-relate TRP channels (""""""""pain TRPs""""""""), and activation of extracellular signal-regulated protein kinase (ERK) in the TG after TMJ inflammation are regulated by TRPV4. Based on these mechanistic findings, our first aim is to investigate whether TRPV4 regulates other pain-related TRP channels through ERK in TG neurons. For this aim, we propose (1) to ascertain whether TRPV4- dependent """"""""pain TRP"""""""" expression in the TG in TMJ-inflammation is neuronal, and co-localizes with TRPV4 expression;(2) to test the role of TRPV4 in regulating """"""""pain-TRPs"""""""" in TG neurons by using Trpv4 sensory neuron-specific knockout mice;(3) to better define the role of ERK in regulating """"""""pain TRPs"""""""" in TG neurons by using mice expressing neuron-specific dominant negative mitogen activated protein kinase-kinase (dnMEK). Considering the chronicity of TMJD pain in clinical patients, in addition, we propose to develop a longer-lasting TMJ inflammation by injecting chemical irritant loaded onto carbon nanoparticles, so that a slow-release"""""""" formulation results. By development of a longer-lasting arthritogenic irritant, our mouse model will more accurately reflect patients'cardinal complaints of chronic pain. We will verify th critical role of Trpv4 in a more chronic model. This research plan will elucidate the distinct roleof """"""""pain-TRP"""""""" channels in TMJ pain. Amongst those, TRPV4 could possibly function as a significant regulator of pro-nociceptive signaling in TG sensory neurons that innervate the TMJ. Moreover, research as proposed will advance our understanding of the mechanisms of the persistent nature of TMJ pain and lead to more rational and effective treatments. The research agenda is embedded in a training plan that takes full advantage of rich and diverse institutional resources available at Duke University and UNC-Chapel Hill, so that the applicant will be positioned well to develop an independent career in TMJ pain research.
Temporomandibular joint disorder (TMJD) constitutes a highly significant healthcare problem in the US because of its prevalence, relative therapy-refractoriness and chronic course, yet it is ineffectively treated because of a lack of fundamental understanding, which in turn is rooted in the shortcomings of available animal models for TMJD. This project will use a mouse model to investigate molecular and cellular mechanisms in trigeminal ganglion sensory neurons that are critical for pathological TMJ pain and develop a more long-term TMJD model, which is more representative of pain chronicity. This application, through its research plan with focus on the TRPV4 ion channel, previously shown to be critical for inflammatory TMJ pain by the applicant, will advance our understanding of the mechanisms of persistent TMJ pain and lead to more rational and effective treatments, while at the same time providing a training opportunity for the applicant to become a fully independent investigator in TMJ research.
|Chen, Yong; Fang, Quan; Wang, Zilong et al. (2016) Transient Receptor Potential Vanilloid 4 Ion Channel Functions as a Pruriceptor in Epidermal Keratinocytes to Evoke Histaminergic Itch. J Biol Chem 291:10252-62|
|Kanju, Patrick; Chen, Yong; Lee, Whasil et al. (2016) Small molecule dual-inhibitors of TRPV4 and TRPA1 for attenuation of inflammation and pain. Sci Rep 6:26894|
|McNulty, Amy L; Leddy, Holly A; Liedtke, Wolfgang et al. (2015) TRPV4 as a therapeutic target for joint diseases. Naunyn Schmiedebergs Arch Pharmacol 388:437-50|
|Zhang, Yi; Chen, Yong; Liedtke, Wolfgang et al. (2015) Lack of evidence for ectopic sprouting of genetically labeled AÎ² touch afferents in inflammatory and neuropathic trigeminal pain. Mol Pain 11:18|
|Chen, Yong; Kanju, Patrick; Fang, Quan et al. (2014) TRPV4 is necessary for trigeminal irritant pain and functions as a cellular formalin receptor. Pain 155:2662-72|