Increased synthesis of the high molecular weight cytosolic
phospholipase a2 mediates early uv- induced prostaglandin e2 in human
skin.
Gresham, Alane, Jaime Masferrer, Xi Chen, Susana Leal-Khouri, and
Alice P Pentland.
Division of Dermatology, Department of Medicine, Department of
Molecular Biology and Pharmacology, Washington University School of
Medicine; Searle Corporation, St. Louis, MO 63110
APStracts 2:0369C, 1995.
Ultraviolet light B (UVB) induced inflammation is characterized by
dramatic increases in prostaglandin E2 (PGE2) synthesis due to
enhanced arachidonate deacylation from the membrane. The effect of UV
on synthesis, mass and distribution of the high molecular weight
phospholipase A2 (cPLA2) in cultured human keratinocytes and human
skin was therefore studied. The 105-kDa cPLA2 was demonstrated to be
the critical enzyme in UV-induced PGE2 synthesis and erythema in the
first 6 hours post-irradiation. Immunoprecipitation of [35S]-labeled
protein showed cPLA2 synthesis increased 3-4 fold 6 hours after
irradiation. Immunoprecipitation of [32P]-labeled cPLA2 demonstrated
phosphorylation of cPLA2 was concurrently induced, suggesting that UV
also activates cPLA2. This increase in cPLA2 synthesis and activation
also closely correlated with increased PGE2 synthesis and [3H]
arachidonic acid release, and was effectively blocked by both a S-
oligonucleotide antisense to cPLA2 and methyl arachidonate
fluorophosphate (MAFP), a specific inhibitor of cPLA2. Biopsy and
histochemical examination of irradiated sites from human volunteers
revealed only erythematous sites expressed increased amounts of
cPLA2, while non-erythematous irradiated sites did not. In contrast,
COX-1 and COX-2 in cultures and skin explants were unaffected 6 hr.
post-UV, and no change in cyclooxygenase activity was observed at
this time point. These results suggest that increased cPLA2 synthesis
occurs only when skin is exposed to UV doses which are sufficient to
cause erythema, and indicate expression of cPLA2 participates in
acute UV inflammation.
Received 24 July 1995; accepted in final form 20 September 1995.
APS Manuscript Number C447-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95