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Wigerblad G, Huie JR, Yin HZ, Leinders M, Pritchard RA, Koehrn FJ, Xiao WH, Bennett GJ, Huganir RL, Ferguson AR, Weiss JH, Svensson CI, Sorkin LS. Inflammation-induced GluA1 trafficking and membrane insertion of Ca 2+ permeable AMPA receptors in dorsal horn neurons is dependent on spinal tumor necrosis factor, PI3 kinase and protein kinase A. Exp Neurol 2017; 293:144-158. [PMID: 28412220 DOI: 10.1016/j.expneurol.2017.04.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 04/06/2017] [Accepted: 04/10/2017] [Indexed: 11/28/2022]
Abstract
Peripheral inflammation induces sensitization of nociceptive spinal cord neurons. Both spinal tumor necrosis factor (TNF) and neuronal membrane insertion of Ca2+ permeable AMPA receptor (AMPAr) contribute to spinal sensitization and resultant pain behavior, molecular mechanisms connecting these two events have not been studied in detail. Intrathecal (i.t.) injection of TNF-blockers attenuated paw carrageenan-induced mechanical and thermal hypersensitivity. Levels of GluA1 and GluA4 from dorsal spinal membrane fractions increased in carrageenan-injected rats compared to controls. In the same tissue, GluA2 levels were not altered. Inflammation-induced increases in membrane GluA1 were prevented by i.t. pre-treatment with antagonists to TNF, PI3K, PKA and NMDA. Interestingly, administration of TNF or PI3K inhibitors followed by carrageenan caused a marked reduction in plasma membrane GluA2 levels, despite the fact that membrane GluA2 levels were stable following inhibitor administration in the absence of carrageenan. TNF pre-incubation induced increased numbers of Co2+ labeled dorsal horn neurons, indicating more neurons with Ca2+ permeable AMPAr. In parallel to Western blot results, this increase was blocked by antagonism of PI3K and PKA. In addition, spinal slices from GluA1 transgenic mice, which had a single alanine replacement at GluA1 ser 845 or ser 831 that prevented phosphorylation, were resistant to TNF-induced increases in Co2+ labeling. However, behavioral responses following intraplantar carrageenan and formalin in the mutant mice were no different from littermate controls, suggesting a more complex regulation of nociception. Co-localization of GluA1, GluA2 and GluA4 with synaptophysin on identified spinoparabrachial neurons and their relative ratios were used to assess inflammation-induced trafficking of AMPAr to synapses. Inflammation induced an increase in synaptic GluA1, but not GluA2. Although total GluA4 also increased with inflammation, co-localization of GluA4 with synaptophysin, fell short of significance. Taken together these data suggest that peripheral inflammation induces a PI3K and PKA dependent TNFR1 activated pathway that culminates with trafficking of calcium permeable AMPAr into synapses of nociceptive dorsal horn projection neurons.
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Affiliation(s)
- G Wigerblad
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - J R Huie
- Department of Neurological Surgery, UC San Francisco, San Francisco, CA, USA
| | - H Z Yin
- Department of Neurology, UC Irvine, Irvine, CA, USA
| | - M Leinders
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA
| | - R A Pritchard
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA
| | - F J Koehrn
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA
| | - W-H Xiao
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA
| | - G J Bennett
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA
| | - R L Huganir
- Department of Neuroscience, Howard Hughes Medical Institute, Johns Hopkins University, Baltimore, MD, USA
| | - A R Ferguson
- Department of Neurological Surgery, UC San Francisco, San Francisco, CA, USA
| | - J H Weiss
- Department of Neurology, UC Irvine, Irvine, CA, USA
| | - C I Svensson
- Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden
| | - L S Sorkin
- Department of Anesthesiology, UC San Diego, La Jolla, CA, USA.
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