A study to determine the effect of tacrolimus on ceramide levels in the stratum corneum of patients with atopic dermatitis

State of the art in Stratum Corneum research: The biophysical properties of ceramides

This review is summarizing an important part of the state of the art in stratum corneum research. A complete overview on discoveries about the general biophysical and physicochemical properties of the known ceramide species' is provided. The ceramides are one of the three major components of the lipid matrix and mainly govern its properties and structure. They are shown to exhibit very little redundancy, despite the minor differences in their chemical structure. The results are discussed, compared to each other as well as the current base of knowledge. New interesting aspects and concepts are concluded or suggested. A novel interpretation of the 3-dimensional structure of the lipid matrix and its influence on the barrier function will be discussed. The most important conclusion is the presentation of a new and up to date theoretical model of the nanostructure of the short periodicity phase. The model suggests three perpendicular layers: The rigid head group region, the rigid chain region and, a liquid-like overlapping middle layer. The general principle of the skin barrier function is highlighted in regard to this structure and the ceramides biophysical and physicochemical properties. As a result of these considerations, the entropy vs. enthalpy principle is introduced, shedding light on the function as well as the effectiveness of the skin barrier. Additionally, general ideas to effectively overcome this barrier principle for dermal and transdermal delivery of actives or how to use it for specific targeting of the stratum corneum are proposed.

Impact of the ceramide subspecies on the nanostructure of stratum corneum lipids using neutron scattering and molecular dynamics simulations. Part I: impact of CER[NS]

For this study mixtures based on the ceramides [NS] (NS = non-hydroxy-sphingosine) and [AP] (AP = α-hydroxy-phytosphingosine) in a 2:1 and 1:2 ratio, together with cholesterol and lignoceric acid, were investigated. These mixtures are modelling the uppermost skin layer, the stratum corneum. Neutron diffraction, utilizing specifically deuterated ceramide molecules, was used to obtain a maximum amount of experimental detail. Highly detailed molecular dynamics simulations were used to generate even more information from the experimental data. It was possible to observe a single lamellar phase for both systems. They had a lamellar repeat distance of 5.43 ± 0.05 nm for the [NS]/[AP] 2:1 and a slightly shorter one of 5.34 ± 0.05 nm for the 1:2 system. The structure and water content was uninfluenced by excess humidity. Both the experimental and simulation data indicated slightly tilted ceramides, with their C24 chains overlapping in the lamellar mid-plane. This arrangement is well comparable to systems investigated before. The structure of both systems, except for the differing repeat distance, looks similar at first. However, on a smaller scale there were various distinct differences, demonstrating only low redundancy between the different ceramide species, despite only minor chemical differences. The mainly ceramide [AP] determined 1:2 system has a slightly smaller repeat distance. This is a result of a tighter arrangement of the lipids chain along the bilayer normal and increased overlapping of the long chains in the lamellar middle. For the CER[NS] some novel features could be shown, despite it being the overall most investigated ceramide. These include the low adaptability to changed lateral interactions, leading to an increased chain opening. This effect could explain its low miscibility with other lipids. The investigated model systems allows it to directly compare results from the literature which have used ceramide [NS] to the most recent studies using the phytosphingosine ceramides such as ceramide [AP].

Investigation of a CER[NP]- and [AP]-Based Stratum Corneum Modeling Membrane System: Using Specifically Deuterated CER Together with a Neutron Diffraction Approach

Neutron diffraction was used as a tool to investigate the lamellar as well as molecular nanostructure of ceramide-[NP]/ceramide-[AP]/cholesterol/lignoceric acid model systems with a nativelike 2:1 ratio and a 1:2 ratio to study the influence of the ceramide-[AP]. By using mixtures together with cholesterol and free fatty acids as well as a humidity and temperature chamber while measuring, natural conditions were simulated as closely as possible. Despite its simplicity, the system simulated the native stratum corneum lipid matrix fairly closely, showing a similar lamellar thickness with a repeat distance of 5.45 ± 0.1 nm and a similar arrangement with overlapping long C24 chains. Furthermore, despite the very minor chemical difference between ceramide-[NP] and ceramide-[AP], which is only a single OH group, it was possible to demonstrate substantial differences between the structural influence of the two ceramides. Ceramide-[AP] could be concluded to be arranged in such a way that its C24 chain in both ratios is somehow shorter than that of ceramide-[NP], not overlapping as much with the opposite lamellar leaflet. Furthermore, in the unnatural 1:2 ratio, the higher ceramide-[AP] content causes an increased tilt of the ceramide acyl chains. This leads to even less overlapping within the lamellar midplane, whereas the repeat distance stays the same as for the ceramide-[NP]-rich system. In this nativelike 2:1 ratio, the chains are arranged mostly straight, and the long C24 chains show a broad overlapping region in the lamellar midplane.

Determination of the influence of C24 D/(2R)- and L/(2S)-isomers of the CER[AP] on the lamellar structure of stratum corneum model systems using neutron diffraction

This study was able to investigate the different influence of the d- and l-ceramide [AP] on the lamellar as well as molecular nanostructure of stratum corneum simulating lipid model mixtures. In this case, neutron diffraction together with specifically deuterated ceramide was used as an effective tool to investigate the lamellar and the molecular nanostructure of the mixtures. It could clearly be demonstrated, that both isomers show distinctly different characteristics, even though the variation between both is only a single differently arranged OH-group. The l-ceramide [AP] promotes a crystalline like phase behaviour even if mixed with ceramide [NP], cholesterol and free fatty acids. The d-ceramide [AP] only shows crystalline-like features if mixed only with cholesterol and free fatty acids but adopts a native-like behaviour if additionally mixed with ceramide [NP]. It furthermore demonstrates that the l-ceramide [AP] should not be used for any applications concerning ceramide substitution. It could however possibly serve its own purpose, if this crystalline like behaviour has some kind of positive influence on the SC or can be utilized for any practical applications. The results obtained in this study demonstrate that the diastereomers of ceramide [AP] are an attractive target for further research because their influence on the lamellar as well as the nanostructure is exceptionally strong. Additionally, the results furthermore show a very strong influence on hydration of the model membrane. With these properties, the d-ceramide [AP] could be effectively used to simulate native like behaviour even in very simple mixtures and could also have a strong impact on the native stratum corneum as well as high relevance for dermal ceramide substitution. The unnatural l-ceramide [AP] on the other hand should be investigated further, to assess its applicability.

Clinical efficacy, safety and tolerance of 0.1% Tacrolimus ointment in the treatment of atopic dermatitis in the moderate and severe forms

Goal: to evaluate the clinical efficacy of 0.1% Protopic ointment in the treatment of atopic dermatitis as a part of a complex therapy. Materials and methods. The study involved a group of 30 patients of both sexes who were diagnosed with atopic dermatitis in the moderate and severe forms at the age of 17—40, who received the 0.1% Tacrolimus ointment (which was applied on the affection foci) as a part of a complex therapy twice a day. The efficacy and safety of this therapy were evaluated based on the SCORAD, Dermatology Life Quality Index (DLQI), indices of personal and situational anxiety, and subjective patient’s feelings. Results. The application of the Protopic ointment resulted in a high total percentage of clinical recovery and significant improvement (86.2%) as well as fast (on Day 7) achievement of a positive effect. Conclusion. The Protopic ointment is characterized by high efficacy and good tolerance when used for the treatment of moderate to severe forms of atopic dermatitis as a part of the complex therapy.

Bicelles: lipid nanostructured platforms with potential dermal applications

Bicelles emerge as promising membrane models, and because of their attractive combination of lipid composition, small size and morphological versatility, they become new targets in skin research. Bicelles are able to modify skin biophysical parameters and modulate the skin's barrier function, acting to enhance drug penetration. Because of their nanostructured assemblies, bicelles have the ability to penetrate through the narrow intercellular spaces of the stratum corneum of the skin to reinforce its lipid lamellae. The bicelle structure also allows for the incorporation of different molecules that can be carried through the skin layers. All of these characteristics can be modulated by varying the lipid composition and experimental conditions. The remarkable versatility of bicelles is their most important characteristic, which makes their use possible in various fields. This system represents a platform for dermal applications. In this review, an overview of the main properties of bicelles and their effects on the skin are presented.

[Atopic dermatitis and tacrolimus in adults]

Topical treatment with tacrolimus is more effective than the placebo and the low potency corticosteroids in the treatment of atopic dermatitis (AD) in both adults and children while it has a similar potency as some topical corticosteroids of medium potency. Since it was put on the market, more evidence has been accumulating to make our previous statements and it has been demonstrated to have greater effectivity than topical pimecrolimus and oral cyclosporine. It is a safe drug and its side effects are of little importance. Specifically no side effects have been demonstrated due to its systemic absorption nor has there been any increase in skin infections. The most frequent side effect is burning sensation or increased pruritus in the area where the product is applied. It is more frequent if the lesions treated are very acute and is generally transitory, not causing the treatment to be discontinued. Furthermore, with the current information, it cannot be associated to an increase of any type of neoplasms.

Are the new moisturizers more effective?

PURPOSE OF REVIEW

The authors discuss the role of moisturizers in the daily skin care regimen of healthy skin and in atopic dermatitis, as well as the efficacy of newer products.

RECENT FINDINGS

Recent findings have shown that the affected skin of atopic individuals is deficient in ceramides, an integral lipid component of the stratum corneum. Several manufacturers have developed topical products with ceramides in an attempt to replace the missing molecules. These products, though more expensive, have shown moderate efficacy improvements over traditional moisturizers.

SUMMARY

Moisturizers are recommended to nearly every atopic patient, and should be part of the daily skin care of these patients, as they have the potential to reduce the quantity of topical steroids necessary to keep disease quiescent. The vast array of choices available to consumers is overwhelming, and most patients would like their physicians to recommend specific products. We attempt to provide a review of the newer products available, with special emphasis on those products that contain ceramides.

The Azerbaijani scrub: a simple method to harvest large amounts of stratum corneum

BACKGROUND

The study of skin barrier constituents may require collection of much stratum corneum. Existing methods are inadequate and/or difficult.

METHODS

A simple and safe method to harvest stratum corneum from glabrous human skin derives from the bathing practices of people in Azerbaijan. The method requires water immersion of the subject for 30 min immediately followed by vigorous scrubbing of skin with a moist rough crepe mitten.

RESULTS

This scrubbing method causes the separation of large amounts of stratum corneum which is easily harvested.

CONCLUSION

The method facilitates study of stratum corneum components, including intercellular lipids.