title: An essential role for platelet-activating factor in activating mast cell migration following ultraviolet irradiation.
abstract: The UVB (290-320 nm) radiation in sunlight is responsible for inducing skin cancer. Exposure to UV radiation is also immunosuppressive, and the systemic immune suppression induced by UV is a well-recognized risk factor for cancer induction. As UVB radiation is absorbed within the upper layers of the skin, indirect mechanisms must play a role in activating systemic immune suppression. One prominent example is mast cell migration, which from the skin to the draining LN is an essential step in the cascade of events leading to immune suppression. What triggers mast cell migration is not entirely clear. Here, we tested the hypothesis that PAF, a lipid mediator of inflammation produced by the skin in response to UV exposure, is involved. Mast cell-deficient mice (Kit(W-sh/W-sh)) are resistant to the suppressive effect of UV radiation, and reconstituting mast cell-deficient mice with normal bone marrow-derived mast cells restores susceptibility to immunosuppression. However, when mast cells from PAFR-/- mice were used, the reconstituted mice were not susceptible to the suppressive effects of UV. Furthermore, PAFR-/- mice showed impaired UV-induced mast cell migration when compared with WT mice. Finally, injecting PAF into WT mice mimicked the effect of UV irradiation and induced mast cell migration but not in PAFR-/- mice. Our findings indicate that PAFR binding induces mast cells to migrate from the skin to the LNs, where they mediate immune suppression.
authors.affiliation: 1.Unit 902, The University of Texas, MD Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA. sullrich@mdanderson.org.
authors.forename: Rommel
authors.initials: R
authors.lastname: Chacón-Salinas
authors.forename: Limo
authors.initials: L
authors.lastname: Chen
authors.forename: Alma D
authors.initials: AD
authors.lastname: Chávez-Blanco
authors.forename: Alberto Y
authors.initials: AY
authors.lastname: Limón-Flores
authors.forename: Ying
authors.initials: Y
authors.lastname: Ma
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Ullrich
mesh_terms: D000818:Animals; D002633:Chemotaxis / Q000187:drug effects / Q000235:genetics* / Q000276:immunology* / Q000528:radiation effects; D005260:Female; D015870:Gene Expression; D005786:Gene Expression Regulation; D007165:Immunosuppression Therapy; D008407:Mast Cells / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism* / Q000528:radiation effects; D051379:Mice; D018345:Mice, Knockout; D010972:Platelet Activating Factor / Q000235:genetics* / Q000378:metabolism / Q000494:pharmacology; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D010972:Platelet Activating Factor; D019718:Receptors, CXCR4
keywords: UV radiation; cell trafficking; immune suppression; inflammatory mediators