TNF-α/TNFR1 Signaling is Required for the Full Expression of Acute and Chronic Itch in Mice via Peripheral and Central Mechanisms

Neurosci Bull. 2018 Feb;34(1):42-53. doi: 10.1007/s12264-017-0124-3. Epub 2017 Apr 1.

Abstract

Increasing evidence suggests that cytokines and chemokines play crucial roles in chronic itch. In the present study, we evaluated the roles of tumor necrosis factor-alpha (TNF-α) and its receptors TNF receptor subtype-1 (TNFR1) and TNFR2 in acute and chronic itch in mice. Compared to wild-type (WT) mice, TNFR1-knockout (TNFR1-KO) and TNFR1/R2 double-KO (DKO), but not TNFR2-KO mice, exhibited reduced acute itch induced by compound 48/80 and chloroquine (CQ). Application of the TNF-synthesis inhibitor thalidomide and the TNF-α antagonist etanercept dose-dependently suppressed acute itch. Intradermal injection of TNF-α was not sufficient to evoke scratching, but potentiated itch induced by compound 48/80, but not CQ. In addition, compound 48/80 induced TNF-α mRNA expression in the skin, while CQ induced its expression in the dorsal root ganglia (DRG) and spinal cord. Furthermore, chronic itch induced by dry skin was reduced by administration of thalidomide and etanercept and in TNFR1/R2 DKO mice. Dry skin induced TNF-α expression in the skin, DRG, and spinal cord and TNFR1 expression only in the spinal cord. Thus, our findings suggest that TNF-α/TNFR1 signaling is required for the full expression of acute and chronic itch via peripheral and central mechanisms, and targeting TNFR1 may be beneficial for chronic itch treatment.

Keywords: Central sensitization; Itch; Spinal cord; Tumor necrosis factor; Tumor necrosis factor receptor.

MeSH terms

  • Animals
  • Chloroquine / toxicity
  • Disease Models, Animal
  • Dose-Response Relationship, Drug
  • Etanercept / therapeutic use
  • Ganglia, Spinal / drug effects
  • Ganglia, Spinal / metabolism*
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Pruritus / chemically induced
  • Pruritus / drug therapy
  • Pruritus / metabolism*
  • Pruritus / pathology*
  • RNA, Messenger / metabolism
  • Receptors, Tumor Necrosis Factor, Type I / deficiency*
  • Receptors, Tumor Necrosis Factor, Type I / genetics
  • Receptors, Tumor Necrosis Factor, Type II / deficiency
  • Receptors, Tumor Necrosis Factor, Type II / genetics
  • Signal Transduction / drug effects
  • Skin / drug effects
  • Skin / metabolism*
  • Spinal Cord / drug effects
  • Spinal Cord / metabolism*
  • Thalidomide / therapeutic use
  • Time Factors
  • Tumor Necrosis Factor-alpha / adverse effects
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / metabolism*
  • p-Methoxy-N-methylphenethylamine / toxicity

Substances

  • RNA, Messenger
  • Receptors, Tumor Necrosis Factor, Type I
  • Receptors, Tumor Necrosis Factor, Type II
  • Tumor Necrosis Factor-alpha
  • p-Methoxy-N-methylphenethylamine
  • Thalidomide
  • Chloroquine
  • Etanercept