Cutaneous water loss and covalently bound lipids of the stratum corneum in nestling house sparrows (<i>Passer domesticus</i> L.) from desert and mesic habitats

Muñoz‐Garcia

Shtayyeh

et al. 2012

Self Cite

SUMMARYIntercellular and covalently bound lipids within the stratum corneum (SC), the outermost layer of the epidermis, are the primary barrier to cutaneous water loss (CWL) in birds. We compared CWL and intercellular SC lipid composition in 20 species of birds from desert and mesic environments. Furthermore, we compared covalently bound lipids with CWL and intercellular lipids in the lark family (Alaudidae). We found that CWL increases in birds from more mesic environments, and this increase was related to changes in intercellular SC lipid composition. The most consistent pattern that emerged was a decrease in the relative amount of cerebrosides as CWL increased, a pattern that is counterintuitive based on studies of mammals with Gaucher disease. Although covalently bound lipids in larks did not correlate with CWL, we found that covalently bound cerebrosides correlated positively with intercellular cerebrosides and intercellular cholesterol ester, and intercellular cerebrosides correlated positively with covalently bound free fatty acids. Our results led us to propose a new model for the organization of lipids in the avian SC, in which the sugar moieties of cerebrosides lie outside of intercellular lipid layers, where they may interdigitate with adjacent intercellular cerebrosides or with covalently bound cerebrosides.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Lipid composition of the stratum corneum and cutaneous water loss in birds along an aridity gradient

Muñoz‐Garcia

Shtayyeh

et al. 2012

Self Cite

“…In another study, adult house sparrows from mesic environments acclimated to different humidity regimes but identical T a showed a reduction of 50% in CWL when acclimated to low humidity (Muñoz-Garcia et al, 2008b). However, changes in CWL were not associated with modifications of the major lipid classes of the SC, either ICLs or CBLs (Muñoz-Garcia et al, 2008b) (Clement et al, 2012). It is unknown whether birds changed other aspects of lipids such as degree of saturation or chain length to modify CWL.…”

Section: Variation In Cwl and The Lipids Of The Sc Across Environmentsmentioning

confidence: 99%

Climate change and cutaneous water loss of birds

Williams

Muñoz‐Garcia

2012

Self Cite

) below the surface of the skin, assumed to be at saturation at skin temperature,  a is absolute humidity above the skin and r v is the total resistance to vapor diffusion. Total resistance is a composite of the resistances of the skin, the boundary layer and the feathers, although the contribution of feathers and boundary layer Summary There is a crucial need to understand how physiological systems of animals will respond to increases in global air temperature. Water conservation may become more important for some species of birds, especially those living in deserts. Lipids of the stratum corneum (SC), the outer layer of the epidermis, create the barrier to water vapor diffusion, and thus control cutaneous water loss (CWL). An appreciation of the ability of birds to change CWL by altering lipids of the skin will be important to predict responses of birds to global warming. The interactions of these lipids are fundamental to the modulation of water loss through skin. Cerebrosides, with their hexose sugar moiety, are a key component of the SC in birds, but how these lipids interact with other lipids of the SC, or how they form hydrogen bonds with water molecules, to form a barrier to water vapor diffusion remains unknown. An understanding of how cerebrosides interact with other lipids of the SC, and of how the hydroxyl groups of cerebrosides interact with water molecules, may be a key to elucidating the control of CWL by the SC.

“…Because of this orientation, the sugar moieties of cerebrosides may slow the rate of CWL by forming strong hydrogen bonds with adjacent water molecules to form a primary solvation shell (Bach et al, 1982). Although these strong hydrogen bonds weaken the hydrogen bonding of water molecules outside the solvation shell (Gallina et al, 2006), the strong hydrogen bonds formed within the solvation shell increase the overall viscosity of the water, which may slow the rate of permeation through the SC (Comesaña et al, 2003;Clement et al, 2012;Champagne et al, 2012). Current models remain speculative and do not address variation in molecular interactions in different layers of the SC, or how this variation affects the rate of CWL.…”

Section: Introductionmentioning

confidence: 99%

Lipid composition and molecular interactions change with depth in the avian stratum corneum to regulate cutaneous water loss

Allen

Williams

2015

Self Cite

The outermost 10-20 µm of the epidermis, the stratum corneum (SC), consists of flat, dead cells embedded in a matrix of intercellular lipids. These lipids regulate cutaneous water loss (CWL), which accounts for over half of total water loss in birds. However, the mechanisms by which lipids are able to regulate CWL and how these mechanisms change with depth in the SC are poorly understood. We used attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) to measure lipid-lipid and lipid-water interactions as a function of depth in the SC of house sparrows (Passer domesticus Linnaeus) in the winter and summer. We then compared these molecular interactions at each depth with lipid composition at the same depth. We found that in both groups, water content increased with depth in the SC, and likely contributed to greater numbers of gauche defects in lipids in deeper levels of the SC. In winter-caught birds, which had lower rates of CWL than summer-caught birds, water exhibited stronger hydrogen bonding in deeper layers of the SC, and these strong hydrogen bonds were associated with greater amounts of polar lipids such as ceramides and cerebrosides. Based on these data, we propose a model by which polar lipids in deep levels of the SC form strong hydrogen bonds with water molecules to increase the viscosity of water and slow the permeation of water through the SC.