Topical application of a platelet activating factor receptor agonist suppresses phorbol ester-induced acute and chronic inflammation and has cancer chemopreventive activity in mouse skin

PLoS One. 2014 Nov 6;9(11):e111608. doi: 10.1371/journal.pone.0111608. eCollection 2014.

Abstract

Platelet activating factor (PAF) has long been associated with acute edema and inflammatory responses. PAF acts by binding to a specific G-protein coupled receptor (PAF-R, Ptafr). However, the role of chronic PAF-R activation on sustained inflammatory responses has been largely ignored. We recently demonstrated that mice lacking the PAF-R (Ptafr-/- mice) exhibit increased cutaneous tumorigenesis in response to a two-stage chemical carcinogenesis protocol. Ptafr-/- mice also exhibited increased chronic inflammation in response to phorbol ester application. In this present study, we demonstrate that topical application of the non-hydrolysable PAF mimetic (carbamoyl-PAF (CPAF)), exerts a potent, dose-dependent, and short-lived edema response in WT mice, but not Ptafr -/- mice or mice deficient in c-Kit (c-KitW-sh/W-sh mice). Using an ear inflammation model, co-administration of topical CPAF treatment resulted in a paradoxical decrease in both acute ear thickness changes associated with a single PMA application, as well as the sustained inflammation associated with chronic repetitive PMA applications. Moreover, mice treated topically with CPAF also exhibited a significant reduction in chemical carcinogenesis. The ability of CPAF to suppress acute and chronic inflammatory changes in response to PMA application(s) was PAF-R dependent, as CPAF had no effect on basal or PMA-induced inflammation in Ptafr-/- mice. Moreover, c-Kit appears to be necessary for the anti-inflammatory effects of CPAF, as CPAF had no observable effect in c-KitW-sh/W-sh mice. These data provide additional evidence that PAF-R activation exerts complex immunomodulatory effects in a model of chronic inflammation that is relevant to neoplastic development.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • 9,10-Dimethyl-1,2-benzanthracene
  • Administration, Topical
  • Animals
  • Anti-Inflammatory Agents / administration & dosage*
  • Antineoplastic Agents / administration & dosage*
  • Disease Models, Animal
  • Ear
  • Epidermis / drug effects
  • Epidermis / pathology
  • Inflammation / chemically induced*
  • Inflammation / drug therapy*
  • Mice
  • Mice, Inbred C57BL
  • Phorbol Esters / adverse effects
  • Platelet Membrane Glycoproteins / agonists*
  • Platelet Membrane Glycoproteins / genetics
  • Proto-Oncogene Proteins c-kit / genetics
  • Proto-Oncogene Proteins c-kit / metabolism
  • Receptors, G-Protein-Coupled / agonists*
  • Receptors, G-Protein-Coupled / genetics
  • Skin Neoplasms / chemically induced
  • Skin Neoplasms / drug therapy*

Substances

  • Anti-Inflammatory Agents
  • Antineoplastic Agents
  • Phorbol Esters
  • Platelet Membrane Glycoproteins
  • Receptors, G-Protein-Coupled
  • platelet activating factor receptor
  • 9,10-Dimethyl-1,2-benzanthracene
  • Proto-Oncogene Proteins c-kit