The acyl-CoA binding protein is required for normal epidermal barrier function in mice

Maria Bloksgaard,Signe Bek,Ann-Britt Marcher,Ditte Neess,Jonathan Brewer,Hans Kristian Hannibal-Bach,Torben Helledie,Christina Fenger,Marianne Due,Zane Berzina,Reinhard Neubert,John Chemnitz,Bente Finsen,Anders Clemmensen,Johannes Wilbertz,Henrik Saxtorph,Jens Knudsen,Luis Bagatolli,Susanne Mandrup

doi:10.1194/jlr.m029553

Abstract

The acyl-CoA binding protein (ACBP) is a 10 kDa intracellular protein expressed in all eukaryotic species. Mice with targeted disruption of Acbp (ACBP(-/-) mice) are viable and fertile but present a visible skin and fur phenotype characterized by greasy fur and development of alopecia and scaling with age. Morphology and development of skin and appendages are normal in ACBP(-/-) mice; however, the stratum corneum display altered biophysical properties with reduced proton activity and decreased water content. Mass spectrometry analyses of lipids from epidermis and stratum corneum of ACBP(+/+) and ACBP(-/-) mice showed very similar composition, except for a significant and specific decrease in the very long chain free fatty acids (VLC-FFA) in stratum corneum of ACBP(-/-) mice. This finding indicates that ACBP is critically involved in the processes that lead to production of stratum corneum VLC-FFAs via complex phospholipids in the lamellar bodies. Importantly, we show that ACBP(-/-) mice display a ∼50% increased transepidermal water loss compared with ACBP(+/+) mice. Furthermore, skin and fur sebum monoalkyl diacylglycerol (MADAG) levels are significantly increased, suggesting that ACBP limits MADAG synthesis in sebaceous glands. In summary, our study shows that ACBP is required for production of VLC-FFA for stratum corneum and for maintaining normal epidermal barrier function.

Highlights

The acyl-CoA binding protein (ACBP) is a 10 kDa intracellular protein expressed in all eukaryotic species
We show that targeted disruption of ACBP in mice leads to a clearly distinguishable skin and fur phenotype with greasy and matted fur when the mice are approximately 16 days old
Careful histological examinations of skin from 3-week-old and 3-month-old mice show no gross differences in skin morphology, structure of sebaceous glands, or number of hair follicles between ACBPϪ/Ϫ and ACBP+/+ mice

Summary

EXPERIMENTAL PROCEDURES

Standard laboratory chemicals as well as 6-lauroyl-2-(N,Ndimethylamino)naphthalene (LAURDAN), fluorescein, and 2, 7-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) were from Invitrogen (Denmark); DMSO was from Fluka. Mice with targeted disruption of the ACBP gene were generated as described [24, 29]. Ref. 36, using Equation 2, where pKa ‫ف‬7, Ii is the intensity obtained for the ith species and fi is the species fraction (i = BCECF or BCECFH): Two-photon excitation microscopy of excised mouse ear skin – LAURDAN GP studies. LAURDAN generalized polarization (GP) measurements [32] were used to evaluate the organization of the extracellular lipids within stratum corneum, as described by [33]. LAURDAN GP measurements were performed using the microscopy instrumental setup described in Ref. 35. Lifetime of the probe in the stratum corneum was determined to evaluate the local proton activity in the tissue, as described by Ref. 36. An indication of the local proton activity in the skin was estimated from the lifetime images as described by pH pKa

BCECFH f BCECFH

RESULTS

DISCUSSION