Neuropathic pain resulting from chronic inflammation and injury to the nervous system is particularly difficult to treat with the currently available drug armamentarium. Annual excess financial cost to the society resulting from neuropathic pain-related treatment is estimated to be $16 billion with much more in terms of lost revenue and associated immeasurable human suffering. A novel mechanism-based treatment for neuropathic pain is clearly needed. Mitogen activated protein kinases (MAPK) are intracellular signal transducing molecules that play a critical role in transducing extracellular events to cellular responses. ERK1/2 and its upstream MAPK kinases (MEK1/2) in the dorsal root ganglion (DRG) have been reported to play a role in the signaling cascade mediating injury to neuropathic pain. We wish to test the working hypothesis that: Selective inhibition of MEK1/2 in the dorsal root ganglion will suppress neuropathic pain. Through 3 specific aims, we propose to investigate inhibition of MEK1/2 by small molecules and a viral vector expressing a dominant-negative MEK1 as a mechanism-based treatment for neuropathic pain. The study involves assessment of anti-nociceptive effects of quercetin, a small molecule flavonol compound found to inhibit MEK1/2 by binding to a region of MEK overlapping the ATP- binding pocket, further high throughput search for other novel small molecule MEK1/2 inhibitor with anti-nociceptive properties, modification of the small molecule through in silico docking-guided rational chemistry, and the use of AAV2/8-DN-MEK1 to selectively inhibit this signaling in the DRG. We employ state of art behavioral methods for in vivo analysis of effectiveness against three rodent pain models with a strong inflammatory (paw pad formalin injection), neuropathic (spared nerve injury), or mixed (chronic constriction injury) etiology. Traditional assessment of pain (thermal hyperalgesia and mechanical allodynia) as well as behavioral assays for spontaneous pain (weight bearing test and conditional place preference) will be employed. Rational chemical modification of a lead flavonol molecule with extensive use of in silico docking of ligands to MEK guided by the free-energy of binding as a measure of ligand affinity is proposed. The research team consists of senior investigators with expertise in neuroscience/pain research, behavior assay of pain, and chemical synthesis, together providing all the necessary skills to execute this project.
Neuropathic pain is a painful condition that persists long after the initial injury is healed Annual excess financial cost to the society resulting from neuropathic pain-related treatment is estimated to be $16 billion with much more in terms of lost revenue and associated immeasurable human suffering (Taylor, 2006). Many mechanisms mediating the initial injury resulting in neuropathic pain have been proposed but little has translated into a novel mechanism-based therapy. We focus on the intracellular signaling molecule ERK1/2 implicated in the pathogenesis of neuropathic pain and propose a study that explores the potential for flavonoids, a class of naturally occurring compounds abundantly found in plants, as novel small molecule drug for treating neuropathic pain. Engineered virus designed to inhibit this biochemical pathway will be investigated as a long-lasting mechanism-based anti- nociceptive treatment. The project will use biochemical methods to study the ERK1/2 inhibitory effect of flavonoids, pain models in rats to assess the anti-nociceptive effects using traditional and complex behavioral assays, high throughput screening of natural flavonoids to identify potent novel anti-nociceptive drugs, and rational small molecule engineering based on ligand-receptor docking to refine the chemical structure to identify and develop effective treatments for neuropathic pain, and gene therapy techniques to provide long lasting relief for this very difficul to treat painful condition.