TRP channels as novel players in the pathogenesis and therapy of itch

Biochim Biophys Acta. 2007 Aug;1772(8):1004-21. doi: 10.1016/j.bbadis.2007.03.002. Epub 2007 Mar 19.

Abstract

Itch (pruritus) is a sensory phenomenon characterized by a (usually) negative affective component and the initiation of a special behavioral act, i.e. scratching. Older studies predominantly have interpreted itch as a type of pain. Recent neurophysiological findings, however, have provided compelling evidence that itch (although it indeed has intimate connections to pain) rather needs to be understood as a separate sensory modality. Therefore, a novel pruriceptive system has been proposed, within which itch-inducing peripheral mediators (pruritogens), itch-selective receptors (pruriceptors), sensory afferents and spinal cord neurons, and defined, itch-processing central nervous system regions display complex, layered responses to itch. In this review, we begin with a current overview on the neurophysiology of pruritus, and distinguish it from that of pain. We then focus on the functional characteristics of the large family of transient receptor potential (TRP) channels in skin-coupled sensory mechanisms, including itch and pain. In particular, we argue that - due to their expression patterns, activation mechanisms, regulatory roles, and pharmacological sensitivities - certain thermosensitive TRP channels are key players in pruritus pathogenesis. We close by proposing a novel, TRP-centered concept of pruritus pathogenesis and sketch important future experimental directions towards the therapeutic targeting of TRP channels in the clinical management of itch.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Animals
  • Cannabinoids / metabolism
  • Capsaicin / metabolism
  • Central Nervous System / physiology
  • Histamine / physiology
  • Humans
  • Inflammation Mediators / physiology
  • Nerve Growth Factors / physiology
  • Neurons / physiology
  • Neurons, Afferent / metabolism
  • Neurons, Afferent / physiology
  • Neuropeptides / physiology
  • Pain / etiology
  • Pain / metabolism
  • Pruritus / classification
  • Pruritus / etiology*
  • Pruritus / physiopathology
  • Pruritus / therapy*
  • Spinal Cord / physiology
  • Substance P / physiology
  • TRPV Cation Channels / metabolism
  • TRPV Cation Channels / physiology
  • Temperature
  • Transient Receptor Potential Channels / physiology*

Substances

  • Cannabinoids
  • Inflammation Mediators
  • Nerve Growth Factors
  • Neuropeptides
  • TRPV Cation Channels
  • Transient Receptor Potential Channels
  • Substance P
  • Histamine
  • Capsaicin