Anti-PAK1 (aa 1-447) polyclonal antibody

Painful burn injuries are among the most debilitating form of trauma, globally ranking in the top 15 leading causes of chronic disease burden. Despite its prevalence, however, chronic pain after burn injury is under-studied. We previously demonstrated the contribution of the Rac1-signaling pathway in several models of neuropathic pain, including burn injury. However, Rac1 belongs to a class of GTPases with low therapeutic utility due to their complex intracellular dynamics. To further understand the mechanistic underpinnings of burn-induced neuropathic pain, we performed a longitudinal study to address the hypothesis that inhibition of the downstream effector of Rac1, Pak1, will improve pain outcome following a second-degree burn injury. Substantial evidence has identified Pak1 as promising a clinical target in cognitive dysfunction and is required for dendritic spine dysgenesis associated with many neurological diseases. In our burn injury model, mice exhibited significant tactile allodynia and heat hyperalgesia and dendritic spine dysgenesis in the dorsal horn. Activity-dependent expression of c-fos also increased in dorsal horn neurons, an indicator of elevated central nociceptive activity. To inhibit Pak1, we repurposed an FDA-approved inhibitor, romidepsin. Treatment with romidepsin decreased dendritic spine dysgenesis, reduced c-fos expression, and rescued pain thresholds. Drug discontinuation resulted in a relapse of cellular correlates of pain and in lower pain thresholds in behavioral tests. Taken together, our findings identify Pak1 signaling as a potential molecular target for therapeutic intervention in traumatic burn-induced neuropathic pain.

15 K is 1,2, 3-triazolyl ester of ketorolac, an old pain-killer, that blocks PAK1 by its R-form and inhibits COX-2 by its S-form. Mainly due to a robust increase in cell-permeability, 15K is over 500 times more potent than ketorolac in both anti-cancer and anti-PAK1 activities in cell culture with IC50 around 24 nM. However, 15K has no anti-AKT activity. Angiogenesis requires at least the kinase PAK1, and perhaps the kinase AKT as well, and is essential for a robust growth of solid tumors. Thus, in this study, we examined the potential antiangiogenic activity of 15K both in ovo and cell culture, prior to its in vivo (xenograft) anti-cancer activity test. The IC50 of 15K against the embryonic angiogenesis in ovo in CAM (chorioallantoic membrane) assay is around 1 nmol/egg. Surprizingly, however, 15K failed to inhibit the tube formation of HUVECs (human umbilical vein endothelial cells) in cell culture even at high as 150 mu M. In an attempt to solve this mystery, we tested both in ovo as well as HUVECs-based anti-angiogenic activity of a potent survivin-suppressor called YM155, which blocks PAK1, in addition to AKT. YM155 is slightly more potent than 15K in CAM assay with IC50 around 0.5 nmol/egg, and apparenty inhibits the tube formation of HUVECs with IC50 around 18 nM. According to a few previous findings with the direct PAK1-inhibitor frondoside A (FRA), the tube formation of HUVECs depends solely on PAK1. Thus, the failure of 15K to affect their tube formation is most likely due to their drug (15K)-resistance. Furthermore, unlike FRA, YM155 killed HUVECs with IC50 around 18 nM, clearly indicating that AKT is essential for survival of HUVECs, instead of their tube formation.