Ceramides are key components of the skin's permeability barrier. In atopic dermatitis, pathological hydrolysis of ceramide precursors - glucosylceramides and sphingomyelin - into lysosphingolipids, specifically glucosylsphingosine (GS) and sphingosine-phosphorylcholine (SPC), and free fatty acids (FFAs) has been proposed to contribute to impaired skin barrier function. This study investigated whether replacing ceramides with lysosphingolipids and FFAs in skin lipid barrier models would exacerbate barrier dysfunction. When applied topically to human stratum corneum sheets, SPC and GS increased water loss, decreased electrical impedance, and slightly disordered lipid chains. In lipid models containing isolated human stratum corneum ceramides, reducing ceramides by ≥ 30% significantly increased permeability to four markers, likely due to loss of long-periodicity phase (LPP) lamellae and phase separation within the lipid matrix, as revealed by X-ray diffraction and infrared spectroscopy. However, when the missing ceramides were replaced by lysosphingolipids and FFAs, no further increase in permeability was observed. Conversely, these molecules partially mitigated the negative effects of ceramide deficiency, particularly with 5%-10% SPC, which reduced permeability even compared to control with "healthy" lipid composition. These findings suggest that while ceramide deficiency is a key factor in skin barrier dysfunction, the presence of lysosphingolipids and FFAs does not aggravate lipid structural or functional damage, but may provide partial compensation, raising further questions about the behavior of lyso(sphingo)lipids in rigid multilamellar lipid environments, such as the stratum corneum, that warrant further investigation.

• Klíčová slova
• ceramide, fatty acid, glucosylsphingosine, lipid model, lysolipid, permeability, skin barrier, sphingosine-phosphorylcholine,
• MeSH
• ceramidy * metabolismus   nedostatek   MeSH
• fosforylcholin analogy a deriváty   MeSH
• kůže * metabolismus   účinky léků   MeSH
• kyseliny mastné neesterifikované metabolismus   MeSH
• lidé MeSH
• lysofosfolipidy * metabolismus   MeSH
• permeabilita MeSH
• sfingolipidy * metabolismus   MeSH
• sfingosin analogy a deriváty   metabolismus   farmakologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• ceramidy * MeSH
• fosforylcholin MeSH
• kyseliny mastné neesterifikované MeSH
• lysofosfolipidy * MeSH
• sfingolipidy * MeSH
• sfingosin MeSH
• sphingosine phosphorylcholine MeSH Prohlížeč

Lipid membranes play a crucial role in regulating the body's water balance by adjusting their properties in response to hydration. The intercellular lipid matrix of the stratum corneum (SC), the outermost skin layer, serves as the body's primary defense against environmental factors. Osmolytes, including urocanic acid (UCA) and glycerol, are key components of the natural moisturizing factor that help the SC resist osmotic stress from dry environments. This study examines the effects of UCA and glycerol (each at 5 mol %) on isolated human SC lipids. For this, different techniques were employed, offering complementary information of the system's multiscale characteristics, including humidity-scanning quartz crystal microbalance with dissipation monitoring, infrared spectroscopy, x-ray diffraction, electrical impedance spectroscopy, and studies of water loss and permeability. Our results show that UCA increases water sorption and makes lipid films more liquid-like at high relative humidity, without significantly altering the lipid lamellar structure, chain order, or orthorhombic chain packing. Lipid films containing UCA exhibited higher water loss and significantly higher model drug permeability compared to lipid films without UCA. Further, incorporation of UCA resulted in kinetically faster changes in electrical properties upon contact with aqueous solution compared with control lipids. These observations suggest that UCA reduces lipid cohesion in regions other than the acyl chain-rich leaflets, which may impact SC desquamation. In contrast, glycerol did not influence the hydration or permeability of the SC lipid matrix. However, it increased the proportion of orthorhombic domains at high humidities and slowed the kinetics of the hydration process, as evidenced by slower changes in the dielectric properties of the lipid film. These findings suggest that glycerol enhances lipid cohesion rather than increasing water uptake, which is typically the expected function of humectants. Consequently, UCA and glycerol appear to have distinct roles in maintaining epidermal homeostasis.

• MeSH
• glycerol * chemie   farmakologie   MeSH
• kůže metabolismus   MeSH
• kyselina urokanová chemie   farmakologie   metabolismus   MeSH
• lidé MeSH
• lipidy chemie   MeSH
• permeabilita MeSH
• voda * chemie   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• glycerol * MeSH
• kyselina urokanová MeSH
• lipidy MeSH
• voda * MeSH

Ceramides belong to sphingolipids, an important group of cellular and extracellular lipids. Their physiological functions range from cell signaling to participation in the formation of barriers against water evaporation. In the skin, they are essential for the permeability barrier, together with free fatty acids and cholesterol. We examined the periodical structure and permeability of lipid films composed of ceramides (Cer; namely, N-lignoceroyl 6-hydroxysphingosine, CerNH24, and N-lignoceroyl sphingosine, CerNS24), lignoceric acid (LIG; 24:0), and cholesterol (Chol). X-ray diffraction experiments showed that the CerNH24-based samples form either a short lamellar phase (SLP, d ∼ 5.4 nm) or a medium lamellar phase (MLP, d = 10.63-10.78 nm) depending on the annealing conditions. The proposed molecular arrangement of the MLP based on extended Cer molecules also agreed with the relative neutron scattering length density profiles obtained from the neutron diffraction data. The presence of MLP increased the lipid film permeability to the lipophilic model permeant (indomethacin) relative to the CerNS24-based control samples and the samples that had the same lipid composition but formed an SLP. Thus, the arrangement of lipids in various nanostructures is responsive to external conditions during sample preparation. This polymorphic behavior directly affects the barrier properties, which could also be (patho)physiologically relevant.

• Publikační typ
• časopisecké články MeSH

Ceramides (Cer) are essential components of the skin permeability barrier. To probe the role of Cer polar head groups involved in the interfacial hydrogen bonding, the N-lignoceroyl sphingosine polar head was modified by removing the hydroxyls in C-1 (1-deoxy-Cer) or C-3 positions (3-deoxy-Cer) and by N-methylation of amide group (N-Me-Cer). Multilamellar skin lipid models were prepared as equimolar mixtures of Cer, lignoceric acid and cholesterol, with 5 wt% cholesteryl sulfate. In the 1-deoxy-Cer-based models, the lipid species were separated into highly ordered domains (as found by X-ray diffraction and infrared spectroscopy) resulting in similar water loss but 4-5-fold higher permeability to model substances compared to control with natural Cer. In contrast, 3-deoxy-Cer did not change lipid chain order but promoted the formation of a well-organized structure with a 10.8 nm repeat period. Yet both lipid models comprising deoxy-Cer had similar permeabilities to all markers. N-Methylation of Cer decreased lipid chain order, led to phase separation, and improved cholesterol miscibility in the lipid membranes, resulting in 3-fold increased water loss and 10-fold increased permeability to model compounds compared to control. Thus, the C-1 and C-3 hydroxyls and amide group, which are common to all Cer subclasses, considerably affect lipid miscibility and chain order, formation of periodical nanostructures, and permeability of the skin barrier lipid models.

• MeSH
• buněčná membrána metabolismus   MeSH
• ceramidy chemie   metabolismus   MeSH
• kůže metabolismus   MeSH
• membrány umělé * MeSH
• permeabilita MeSH
• voda metabolismus   MeSH
• změna skupenství MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ceramidy MeSH
• membrány umělé * MeSH
• voda MeSH

Membrane models of the stratum corneum (SC) lipid barrier, either healthy or affected by recessive X-linked ichthyosis, constructed from ceramide [Cer; nonhydroxyacyl sphingosine N-tetracosanoyl-d-erythro-sphingosine (CerNS24) alone or with omega-O-acylceramide N-(32-linoleyloxy)dotriacontanoyl-d-erythro-sphingosine (CerEOS)], FFAs(C16-24), cholesterol (Chol), and sodium cholesteryl sulfate (CholS) were investigated. X-ray diffraction (XRD) revealed a previously unreported polymorphism of the membranes. In the absence of CerEOS, the membranes formed a short lamellar phase (SLP; the repeat distance d = 5.3 nm), a medium lamellar phase (MLP; d = 10.6 nm), or very long lamellar phases (VLLP; d = 15.9 and 21.2 nm). An increased CholS-to-Chol ratio modulated the membrane polymorphism, although the CholS phase separated at ≥ 7 weight% (of total lipids). The presence of CerEOS led to the stable long lamellar phase (LLP) with d = 12.2 nm and prevented VLLP formation. Our XRD results agree well with recently published cryo-electron microscopy data for vitreous skin sections, while also revealing new structures. Thus, lamellar phases with long repeat distances (MLP and VLLP) may be formed in the absence of omega-O-acylceramide, whereas these ultralong Cer species likely stabilize the final SC lipid architecture of LLP by riveting the adjacent lipid layers.

• Klíčová slova
• X-ray crystallography, ceramide, cholesterol, cholesteryl sulfate, extracellular matrix, membranes/model, skin, skin barrier,
• MeSH
• biologické modely * MeSH
• elektronová kryomikroskopie MeSH
• ichtyóza vázaná na chromozom X genetika   metabolismus   patologie   MeSH
• kůže chemie   metabolismus   patologie   MeSH
• lidé MeSH
• membránové lipidy chemie   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• membránové lipidy MeSH