Seminal studies suggested that the heightened sensitivity associated with inflammation may, in part, result from nerve growth factor (NGF) activation of nociceptive sensory neurons. My laboratory demonstrated that NGF/BDNF can rapidly increase the ability of sensory neurons to fire action potentials (APs) via p75 neurotrophin receptor (p75NTR) activation of the sphingolipid signaling cascade. The cellular mechanisms and downstream signaling pathways resulting from p75NTR activation are poorly understood. Our results demonstrate that p75NTR/ceramide activation of the novel atypical PKC, PKM? plays a key role in augmenting excitability and suggest that PKM? may have a critical role in the transition of acute to persistent sensitization as a result of PKM? becoming constitutively active. Proposed studies will use sensory neurons isolated from DRG of adult rats as a model system to explore the functional impact of p75NTR activation on membrane excitability. Knowledge gained from isolated neurons will be extended to studies exploring the role of these effector molecules in regulating nociceptive behavioral responses. These studies will be done in collaboration with Dr. Gary Strichartz at Harvard University.
The specific aims are:
Aim 1 will establish the role of p75NTR and its synthesis/activation of PKM?. Also, p75NTR interaction with scaffolding proteins will determine their ability to regulate the activity of PKM? This work will focus on PKM?-induced modulation of ion channels and their regulation of neuronal excitability. In collaboration with Dr. Gary Strichartz Aim 2 will establish the role of p75NTR-PKM? signaling cascades in the regulation of nociceptive behaviors in the intact animal. The strength of this multi-dimensional approach is that biochemical and molecular techniques will establish novel protein-protein associations and electrophysiology will establish the functional outcomes of those associations. These findings will be extended to studies in the intact animal to provide an understanding of the mechanisms whereby activation of p75NTR leads to heightened neuronal sensitivity. A fundamental understanding of these events is necessary so that better compounds and therapies can be designed to facilitate treatment of chronic inflammatory conditions.
Tissue injury and inflammation cause release of chemicals from a variety of cells near the injury site that results in increased sensitivity to painful stimulation. One of those key chemicals is nerve growth factor. Studies proposed in this application seek to understand how intracellular signaling pathways activated by nerve growth factor increase nerve sensitivity and thus lead to the increased pain responses.
|Khodorova, A; Nicol, G D; Strichartz, G (2013) The p75NTR signaling cascade mediates mechanical hyperalgesia induced by nerve growth factor injected into the rat hind paw. Neuroscience 254:312-23|