Mitogen Activated Protein Kinase Phosphatase-1 Prevents the Development of Tactile Sensitivity in a Rodent Model of Neuropathic Pain

Abstract

BackgroundNeuropathic pain due to nerve injury is one of the most difficult types of pain to treat. Following peripheral nerve injury, neuronal and glial plastic changes contribute to central sensitization and perpetuation of mechanical hypersensitivity in rodents. The mitogen activated protein kinase (MAPK) family is pivotal in this spinal cord plasticity. MAPK phosphatases (MKPs) limit inflammatory processes by dephosphorylating MAPKs. For example, MKP-1 preferentially dephosphorylates p-p38. Since spinal p-p38 is pivotal for the development of chronic hypersensitivity in rodent models of pain, and p-p38 inhibitors have shown clinical potential in acute and chronic pain patients, we hypothesize that induction of spinal MKP-1 will prevent the development of peripheral nerve-injury-induced hypersensitivity and p-p38 overexpression.ResultsWe cloned rat spinal cord MKP-1 and optimize MKP-1 cDNA in vitro using transfections to BV-2 cells. We observed that in vitro overexpression of MKP-1 blocked lipopolysaccharide-induced phosphorylation of p38 (and other MAPKs) as well as release of pro-algesic effectors (i.e., cytokines, chemokines, nitric oxide). Using this cDNA MKP-1 and a non-viral, in vivo nanoparticle transfection approach, we found that spinal cord overexpression of MKP-1 prevented development of peripheral nerve-injury-induced tactile hypersensitivity and reduced pro-inflammatory cytokines and chemokines and the phosphorylated form of p38.ConclusionsOur results indicate that MKP-1, the natural regulator of p-p38, mediates resolution of the spinal cord pro-inflammatory milieu induced by peripheral nerve injury, resulting in prevention of chronic mechanical hypersensitivity. We propose that MKP-1 is a potential therapeutic target for pain treatment or prevention.

Evaluation of a nanotechnology-based approach to induce gene-expression in human THP-1 macrophages under inflammatory conditions

“…Moreover, they demonstrated that luciferase expression using in vivo PEI transfection in chicken embryonic neurons was similar to that obtained in primary brain cells in vitro at the optimal N/P ratio of 9. These data are also in accordance with previous data from our laboratory in which in vivo gene induction using PEI was demonstrated in rat spinal cord in a model of neuropathic pain (Ndong et al, 2012).…”

“…Levels of mRNA were determined as described previously (Ndong et al, 2012). Briefly, 1 g of total RNA from each sample was reverse transcribed into cDNA using the ScriptTM Reverse Transcription Supermix (BioRad, Hercules, CA) in the following conditions: 5 min at 25 • C, 30 min at 42 • C and 5 min at 85 • C. We quantified the expression of TNF-␣ (59 • C), IL-6 (60 • C), IL-10 (59 • C), CD14 (57 • C), CD68 (58 • C), GFP (60 • C) and ␤-actin (57 • C) using the SsoAdvancedTM Universal SYBR Green Supermix (BioRad, Hercules, CA) in the following conditions: 1 cycle of 98 • C for 30 s, 45 cycles of 98 • C for 15 s followed by 30 s of the primerspecific annealing temperature.…”

Macrophage-specific nanotechnology-driven CD163 overexpression in human macrophages results in an M2 phenotype under inflammatory conditions

“…The RNA was isolated from THP-1 macrophages and primary macrophages using ReliaprepTM RNA Cell Miniprep System (Promega, Madison, WI), according to the manufacturer’s protocols. Levels of mRNA were determined as described previously (Ndong, et al, 2012). Complementary DNA (cDNA) was synthesized from 1 μg of total RNA from each sample using Script Reverse Transcription Supermix (BioRad, Hercules, CA) under the following conditions: 5 min at 25°C, 30 min at 42°C, and 5 min at 85°C.…”

Lost but making progress—Where will new analgesic drugs come from?

“…Possible reasons for resistance to the development of chronic pain in genetically similar animals (92–94) are currently being explored. Combined with strategies aimed at understanding endogenous factors (95, 96) associated with the natural resolution of pain, as observed in many chronic neuropathic pain patients over time (97), such studies could point to genetic and epigenetic clues to identify those patients who are most at risk to develop (98) or limit chronic pain, thereby linking the laboratory to the reality of the clinical world. Indeed, resolution from injury may be an active process that engages signaling molecules such as the resolvins and the protectins (95, 99).…”