Induction of thermal and mechanical hypersensitivity by parathyroid hormone–related peptide through upregulation of TRPV1 function and trafficking. Issue 9 (September 2015)

• Record Type: Journal Article
• Authors: Mickle, Aaron D.; Shepherd, Andrew J.; Loo, Lipin; Mohapatra, Durga P.
• Is Part Of: Pain. Volume 156:Issue 9(2015)
• Publication Date: 2015-09
• Subjects: TRPV1 -- Parathyroid hormone–related peptide -- Nociceptor sensitization -- Peripheral sensitization -- Thermal hypersensitivity -- Mechanical hypersensitivity -- TRPV1 phosphorylation; Pain -- Periodicals; Douleur -- Périodiques; Anesthésie -- Périodiques; Pain; Electronic journals; Periodicals; Electronic journals; 616.0472
• DOI: 10.1097/j.pain.0000000000000224
• Languages: English
• ISSNs: 0304-3959

Abstract

Abstract : Abstract: The neurobiological mechanisms underlying chronic pain associated with cancers are not well understood. It has been hypothesized that factors specifically elevated in the tumor microenvironment sensitize adjacent nociceptive afferents. We show that parathyroid hormone–related peptide (PTHrP), which is found at elevated levels in the tumor microenvironment of advanced breast and prostate cancers, is a critical modulator of sensory neurons. Intraplantar injection of PTHrP led to the development of thermal and mechanical hypersensitivity in both male and female mice, which were absent in mice lacking functional transient receptor potential vanilloid-1 (TRPV1). The PTHrP treatment of cultured mouse sensory neurons enhanced action potential firing, and increased TRPV1 activation, which was dependent on protein kinase C (PKC) activity. Parathyroid hormone–related peptide induced robust potentiation of TRPV1 activation and enhancement of neuronal firing at mild acidic pH that is relevant to acidic tumor microenvironment. We also observed an increase in plasma membrane TRPV1 protein levels after exposure to PTHrP, leading to upregulation in the proportion of TRPV1-responsive neurons, which was dependent on the activity of PKC and Src kinases. Furthermore, co-injection of PKC or Src inhibitors attenuated PTHrP-induced thermal but not mechanical hypersensitivity. Altogether, our results suggest that PTHrP and mild acidic conditions could induce constitutive pathological activation of sensory neurons through upregulation of TRPV1 function and trafficking, which could serve as a mechanism for peripheral sensitization of nociceptive afferents in the tumor microenvironment. Abstract : Supplemental Digital Content is Available in the Text.Cellular and molecular mechanisms underlying parathyroid hormone–related peptide-induced nociceptor sensitization and induction of thermal and mechanical hypersensitivity through upregulation of transient receptor potential vanilloid-1 function and trafficking.