title: Targeted overexpression of tumor necrosis factor-α increases cyclin-dependent kinase 5 activity and TRPV1-dependent Ca2+ influx in trigeminal neurons.
abstract: We reported earlier that TNF-α, a proinflammatory cytokine implicated in many inflammatory disorders causing orofacial pain, increases the activity of Cdk5, a key kinase involved in brain development and function and recently found to be involved in pain signaling. To investigate a potential mechanism underlying inflammatory pain in trigeminal ganglia (TGs), we engineered a transgenic mouse model (TNF) that can conditionally overexpresses TNF-α upon genomic recombination by Cre recombinase. TNF mice were bred with Nav1.8-Cre mouse line that expresses the Cre recombinase in sensory neurons to obtain TNF-α:Nav1.8-Cre (TNF-α cTg) mice. Although TNF-α cTg mice appeared normal without any gross phenotype, they displayed a significant increase in TNF-α levels after activation of NFκB signaling in the TG. IL-6 and MCP-1 levels were also increased along with intense immunostaining for Iba1 and GFAP in TG, indicating the presence of infiltrating macrophages and the activation of satellite glial cells. TNF-α cTg mice displayed increased trigeminal Cdk5 activity, and this increase was associated with elevated levels of phospho-T407-TRPV1 and capsaicin-evocated Ca influx in cultured trigeminal neurons. Remarkably, this effect was prevented by roscovitine, an inhibitor of Cdk5, which suggests that TNF-α overexpression induced sensitization of the TRPV1 channel. Furthermore, TNF-α cTg mice displayed more aversive behavior to noxious thermal stimulation (45°C) of the face in an operant pain assessment device as compared with control mice. In summary, TNF-α overexpression in the sensory neurons of TNF-α cTg mice results in inflammatory sensitization and increased Cdk5 activity; therefore, this mouse model would be valuable for investigating the mechanism of TNF-α involved in orofacial pain.
authors.affiliation: Laboratory of Molecular and Cellular Mechanisms of Pain, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile Laboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile Department of Biology, Faculty of Chemistry and Biology, University of Santiago de Chile, Santiago, Chile Functional Genomics Section, Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Pablo
authors.initials: P
authors.lastname: Rozas
authors.forename: Pablo
authors.initials: P
authors.lastname: Lazcano
authors.forename: Ricardo
authors.initials: R
authors.lastname: Piña
authors.forename: Andrew
authors.initials: A
authors.lastname: Cho
authors.forename: Anita
authors.initials: A
authors.lastname: Terse
authors.forename: Maria
authors.initials: M
authors.lastname: Pertusa
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Madrid
authors.forename: Christian
authors.initials: C
authors.lastname: Gonzalez-Billault
authors.forename: Ashok B
authors.initials: AB
authors.lastname: Kulkarni
authors.forename: Elias
authors.initials: E
authors.lastname: Utreras
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D018932:Chemokine CCL2 / Q000378:metabolism; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011984:Sensory Receptor Cells / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*
chemical_list: D018932:Chemokine CCL2; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D051360:Cyclin-Dependent Kinase 5; D002118:Calcium