Targeted overexpression of tumor necrosis factor-α... : PAIN (original) (raw)

Research Paper

Targeted overexpression of tumor necrosis factor-α increases cyclin-dependent kinase 5 activity and TRPV1-dependent Ca2+ influx in trigeminal neurons

Rozas, Pablo; Lazcano, Pablo; Piña, Ricardo; Cho, Andrew; Terse, Anita; Pertusa, Maria; Madrid, Rodolfo; Gonzalez-Billault, Christian; Kulkarni, Ashok B.; Utreras, Elias

aLaboratory of Molecular and Cellular Mechanisms of Pain, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile

bLaboratory of Cellular and Neuronal Dynamics, Department of Biology, Faculty of Sciences, Universidad de Chile, Santiago, Chile

cDepartment of Biology, Faculty of Chemistry and Biology, University of Santiago de Chile, Santiago, Chile

dFunctional Genomics Section, Laboratory of Cell and Developmental Biology, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA

Corresponding author. Address: Department of Biology, Faculty of Sciences, Universidad de Chile, Las Palmeras 3425, Ñuñoa 7800024, Santiago, Chile. Tel.: 562-29787423; fax: 562-22712983. E-mail address: [email protected] (E. Utreras).

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Received July 08, 2015

Received in revised form February 08, 2016

Accepted February 09, 2016

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 (TNFglo) that can conditionally overexpresses TNF-α upon genomic recombination by Cre recombinase. TNFglo 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 Ca2+ 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.