Summary Adequate management of pain is an unmet medical need. Opioids remain an important class of pain medications but their use in chronic, non-malignant pain has contributed to what is now referred to as the “opioid epidemic”. There is clearly an urgent need to identify and validate novel targets allowing development of novel non-opioid analgesics that are effective and safe. This proposal focuses on a new molecule, Astrocyte elevated gene-1 (AEG-1), as a possible target for pain. AEG-1, also known as metadherin (MTDH), is a scaffold protein which mediates its function by protein-protein interaction. AEG-1 functions as a scaffold protein in multiple intermediary signaling complexes in NF-kB signaling pathway, thereby functioning as a fundamental molecule in NF-kB activation. NF-kB is a key transcription factor regulating pro-inflammatory cytokines and AEG-1 is a major regulator of inflammation. AEG-1 KO mice show a profound inhibition of inflammation and AEG-1 KO macrophages show profound inhibition of lipopolysaccharide (LPS)-induced NF-kB activity and inflammatory gene expression. NF-kB plays a major regulatory role in chronic inflammatory pain. Since AEG-1 regulates NF-kB it may be hypothesized that AEG-1 might function as a key molecule regulating pain mechanisms. Our preliminary studies demonstrate that nociceptive behaviors and inflammation in both the complete Freund adjuvant (CFA) chronic inflammatory pain were significantly reduced in AEG-1 KO mice compared to AEG-1 WT mice, without affecting motor activity and coordination of the animals. These findings identify a key role of AEG-1 in regulating chronic pain and a potential target for ameliorating chronic pain. We hypothesize that AEG-1 is a valid target regulating pain behaviors and AEG-1 inhibition might be developed as a potential strategy for developing new analgesics for chronic pain. We will test our hypothesis in Aim 1 by analyzing pain behaviors in two chronic neuropathic pain models in AEG-1 KO and WT mice. Aim 2 will investigate the role of macrophage/microglia AEG-1 cells by using myeloid cell-specific conditional AEG-1 KO mouse. In Aim 3 we will evaluate efficacy of macrophage-targeted nanoparticles delivering AEG-1 siRNA to ameliorate chronic inflammatory pain. Our studies will identify AEG- 1 as a novel and crucial regulatory molecule modulating pain response and will pave the way for developing RNAi strategy for pain. Multiple clinical trials are ongoing to test siRNAs targeting diverse genes in a variety of diseases thereby establishing potential application of this strategy to manage pain in the clinics.

Narrative In the scenario of ‘opioid epidemic’ there is an urgent need to identify and validate novel targets allowing development of novel non-opioid analgesics that are effective and safe. The proposal focuses on the initial development of Astrocyte elevated gene-1 (AEG-1) as a novel regulator of chronic inflammatory pain and evaluating AEG-1 inhibition as a potential pain remedy strategy.