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Abstract
The purpose of this study was to determine whether normal human epidermis could produce
leukotriene B4 (LTB4) from leukotriene A4 (LTA4) ex vivo; and to localize this LTA4-hydrolase activity. Epidermis obtained by suction blister technique incubated with
human polymorphonuclear cells, resulted in a 54% increase in LTB4 formation when compared to polymorphonuclear cells incubated alone. Furthermore,
human epidermis transformed exogenous LTA4 into LTB4, and this reaction obeyed Michaelis-Menten kinetics with an apparent Km of 6 μM. Subcellular fractionation of homogenized epidermis localized the LTA4-hydrolase activity mainly in the 105 000 × g supernatant fraction (cytoplasmic fraction). This activity was inhibited by two inhibitors
of LTA4-hydrolase (bestatin and captopril). Western blot analysis of the 105 000 × g fraction of homogenized epidermis and cultured keratinocytes supported the presence
of a LTA4-hydrolase. Thus, normal human epidermis possesses LTA4-hydrolase activity which can transform exogenous LTA4 and polymorphonuclear cell-derived LTA4 into LTB4. The identification of LTA4-hydrolase in the cytoplasmic fraction of human epidermis indicates that epidermal
cells may play a more active role in the enzymatic process leading to formation of
the proinflammatory compound LTB4 than previously expected.
Keywords
Abbreviations:
AA (arachidonic acid), 5,6-DiHETE (5(S),6(R)-dihydroxy-7,9-trans-11,14-cis-eicosatetraenoic acid), ECL (enhanced chemiluminescence), HETE (hydroxyeicosatetraenoic acid), HSA (human serum albumin), HTAB (hexadecyltrimethylammonium bromide), KCs (keratinocytes), KGM (keratinocyte growth medium), 5-LO (5-lipoxygenase), LT (leukotriene), MeOH (methanol), PBS (phosphate-buffered saline (Ca2+ and Mg2+ free phosphate buffer, pH 7.4)), PMN (polymorphonuclear leukocyte(s)), RIA (radioimmunoassay), RP-HPLC (reversed-phase high performance liquid chromatography)To read this article in full you will need to make a payment
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Article info
Publication history
Accepted:
January 17,
1994
Received in revised form:
December 15,
1993
Received:
September 8,
1993
Identification
Copyright
© 1994 Published by Elsevier Inc.
