X-Message-Number: 12845
Date: Thu, 25 Nov 1999 18:42:01 -0800 (PST)
From: Doug Skrecky <>
Subject: 5-15% cholesterol sulfate can help stabilize membranes

Authors
  Hatfield RM.  Fung LW.
Institution
  Department of Chemistry, Loyola University of Chicago, Illinois 60626, USA.
Title
  A new model system
  for lipid interactions in
  stratum corneum vesicles: effects of lipid composition,
  calcium, and pH.
Source
  Biochemistry.  38(2):784-91, 1999 Jan 12.
Abstract
  We prepared large unilamellar vesicles (LUVs) with three different stratum
  corneum lipid compositions: constant amounts of ceramides
  (55 wt %) and fatty acids (15%) with varying amounts of cholesterol sulfate
  (0-15%) and cholesterol (15-30%). One of the compositions served as a
  model for normal stratum corneum, while the
  second one served as a model for recessive
  X-linked ichthyosis stratum corneum. The third composition consisted of no
  cholesterol sulfate. Intervesicle lipid
  interactions in these LUVs were monitored by fluorescence
  methods for content leakage, and contents mixing at pH 9, in
  the absence and presence of Ca2+, and at pH 6. Since the content leakage and
  contents mixing assays were originally developed for
  phospholipid vesicles, we characterized the probe binding
  and the probe quenching properties for stratum corneum LUV
  systems, and modified the assays slightly accordingly. The
  time-dependent fluorescence intensity changes in the probe-containing LUVs at
  pH 9 and 6 and in response to the addition of calcium were monitored. Our
  results demonstrated that all three types of LUVs were relatively stable at
  pH 9. Addition of Ca2+ or decreasing the pH to 6 activated intervesicle
  lipid mixing followed by vesicle fusion and lysis. We found
  that the LUVs with no cholesterol sulfate and 30% cholesterol exhibited a
  more extensive Ca2+- or low-pH-activated intervesicle lipid
  interaction than LUVs with either 5% cholesterol sulfate and 25% cholesterol
  or 15% cholesterol sulfate and 15% cholesterol. These results suggest that
  fusogenic agents such as Ca2+ and H+ act to neutralize the fatty acids in the
  lipid bilayer of stratum corneum vesicles. The inclusion of
  5-15% cholesterol sulfate helps to prevent the collapse of fused vesicles
  into other structures.

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