Identification and Biochemical Characterization of High Mobility Group Protein 20A as a Novel Ca2+/S100A6 Target

During screening of protein-protein interactions, using human protein arrays carrying 19,676 recombinant glutathione s-transferase (GST)-fused human proteins, we identified the high-mobility protein group 20A (HMG20A) as a novel S100A6 binding partner. We confirmed the Ca²⁺-dependent interaction of HMG20A with S100A6 by the protein array method, biotinylated S100A6 overlay, and GST-pulldown assay in vitro and in transfected COS-7 cells. Co-immunoprecipitation of S100A6 with HMG20A from HeLa cells in a Ca²⁺-dependent manner revealed the physiological relevance of the S100A6/HMG20A interaction. In addition, HMG20A has the ability to interact with S100A1, S100A2, and S100B in a Ca²⁺-dependent manner, but not with S100A4, A11, A12, and calmodulin. S100A6 binding experiments using various HMG20A mutants revealed that Ca²⁺/S100A6 interacts with the C-terminal region (residues 311–342) of HMG20A with stoichiometric binding (HMG20A:S100A6 dimer = 1:1). This was confirmed by the fact that a GST-HMG20A mutant lacking the S100A6 binding region (residues 311–347, HMG20A-ΔC) failed to interact with endogenous S100A6 in transfected COS-7 cells, unlike wild-type HMG20A. Taken together, these results identify, for the first time, HMG20A as a target of Ca²⁺/S100 proteins, and may suggest a novel linkage between Ca²⁺/S100 protein signaling and HMG20A function, including in the regulation of neural differentiation.

Regulation of the tubulin polymerization-promoting protein by Ca2+/S100 proteins

To elucidate S100 protein-mediated signaling pathways, we attempted to identify novel binding partners for S100A2 by screening protein arrays carrying 19,676 recombinant glutathione S-transferase (GST)-fused human proteins with biotinylated S100A2. Among newly discovered putative S100A2 interactants, including TMLHE, TRH, RPL36, MRPS34, CDR2L, OIP5, and MED29, we identified and characterized the tubulin polymerization-promoting protein (TPPP) as a novel S100A2-binding protein. We confirmed the interaction of TPPP with Ca²⁺/S100A2 by multiple independent methods, including the protein array method, S100A2 overlay, and pulldown assay in vitro and in transfected COS-7 cells. Based on the results from the S100A2 overlay assay using various GST-TPPP mutants, the S100A2-binding region was identified in the C-terminal (residues 111-160) of the central core domain of a monomeric form of TPPP that is involved in TPPP dimerization. Chemical cross-linking experiments indicated that S100A2 suppresses dimer formation of His-tagged TPPP in a dose-dependent and a Ca²⁺-dependent manner. In addition to S100A2, TPPP dimerization is disrupted by other multiple S100 proteins, including S100A6 and S100B, in a Ca²⁺-dependent manner but not by S100A4. This is consistent with the fact that S100A6 and S100B, but not S100A4, are capable of interacting with GST-TPPP in the presence of Ca²⁺. Considering these results together, TPPP was identified as a novel target for S100A2, and it is a potential binding target for other multiple S100 proteins, including S100A6 and S100B. Direct binding of the S100 proteins with TPPP may cause disassembly of TPPP dimer formation in response to the increasing concentration of intracellular Ca²⁺, thus resulting in the regulation of the physiological function of TPPP, such as microtubule organization.

Tranexamic acid blocks the thrombin-mediated delay of epidermal permeability barrier recovery induced by the cedar pollen allergen, Cry j1

We previously demonstrated that Cry j1, the major pollen allergen of Cryptomeria japonica (Japanese cedar), transiently increases protease activity and intracellular Ca²⁺ concentration in cultured human keratinocytes, and delays recovery after stratum corneum barrier disruption in human skin ex vivo. Topical application of tranexamic acid or trypsin-type serine protease inhibitors accelerates barrier recovery. We hypothesized that tranexamic acid might prevent the transient protease activity increase and the barrier recovery delay induced by Cry j1. Here, we tested this hypothesis and examined the mechanism involved. In cultured human keratinocytes, knock-down of protease-activated receptor 1 (PAR-1) reduced the transient increase of calcium induced by Cry j1, whereas knock-down of PAR-2 did not. Knock-down of thrombin significantly reduced the transient increases of calcium concentration and protease activity. Tranexamic acid, soybean trypsin inhibitor, or bivalirudin (a thrombin inhibitor) also reduced the calcium elevation induced by Cry j1 and/or thrombin. Co-application of tranexamic acid or bivalirudin with Cry j1 to human skin ex vivo blocked the delay of barrier recovery. These results suggest that thrombin and PAR-1 or PAR-1-like receptor might mediate the adverse effects of Cry j1 on human epidermal keratinocytes, and could open up a new strategy for treating inflammatory skin diseases.

Identification of striated muscle activator of Rho signaling (STARS) as a novel calmodulin target by a newly developed genome-wide screen

To search for novel target(s) of the Ca(2+)-signaling transducer, calmodulin (CaM), we performed a newly developed genome-wide CaM interaction screening of 19,676 GST-fused proteins expressed in human. We identified striated muscle activator of Rho signaling (STARS) as a novel CaM target and characterized its CaM binding ability and found that the Ca(2+)/CaM complex interacted stoichiometrically with the N-terminal region (Ala13-Gln35) of STARS in vitro as well as in living cells. Mutagenesis studies identified Ile20 and Trp33 as the essential hydrophobic residues in CaM anchoring. Furthermore, the CaM binding deficient mutant (Ile20Ala, Trp33Ala) of STARS further enhanced its stimulatory effect on SRF-dependent transcriptional activation. These results suggest a connection between Ca(2+)-signaling via excitation-contraction coupling and the regulation of STARS-mediated gene expression in muscles.

Function of oleic acid on epidermal barrier and calcium influx into keratinocytes is associated with N-methyl D-aspartate-type glutamate receptors

BACKGROUND

Unsaturated fatty acids from sebum affect calcium dynamics in epidermal keratinocytes, disrupt the barrier function and induce abnormal keratinization. However, the mechanisms of these effects have not been clarified.

OBJECTIVES

To investigate the function of unsaturated fatty acids in epidermis.

METHODS

Antagonists of calcium channel receptors were applied to mouse skin together with oleic acid. Measurements were made of transepidermal water loss (TEWL), and hyperproliferation was assessed. The effects of the antagonists on calcium influx into cultured normal human keratinocytes and on cytokine production were also evaluated.

RESULTS

N-methyl-d-aspartate (NMDA) receptor antagonists such as MK801 and D-AP5 specifically inhibited the increase in TEWL caused by oleic acid, and suppressed keratinocyte hyperproliferation. These compounds also inhibited the increase in the intracellular concentration of calcium ions induced by oleic acid. MK801 suppressed the production of interleukin-1alpha by keratinocytes induced by oleic acid.

CONCLUSIONS

Unsaturated fatty acids such as oleic acid might function via NMDA receptors.

Potassium channel openers accelerate epidermal barrier recovery

BACKGROUND

Maintenance of a competent permeability barrier in the face of external and internal stressors requires signals between the stratum corneum interface and the metabolic machinery in the underlying nucleated layers. For example, reductions in the ion gradients for Ca2+ after acute barrier disruption stimulate lamellar body (LB) secretion, a response required to restore barrier homeostasis. Although alterations in external K+ levels also regulate barrier recovery after acute insults, the mechanisms whereby K+ regulates barrier function remain unknown.

OBJECTIVES

To evaluate effects of regulators of K+ channels on barrier homeostasis in hairless mice.

METHODS

We tested a number of chemically different drugs that alter intracellular K+ levels. Results Single applications of either K+ channel openers (i.e. 1-EBIO, minoxidil, diazoxide) or the K+ ionophore, valinomycin, accelerated barrier recovery after acute insults to murine skin, paralleled by a reduction in intracellular K+ levels in cultured human keratinocytes. In contrast, applications of K+ channel blockers (i.e. gilbenclamide, dequalinium) delayed barrier recovery. Alterations in intracellular K+ regulated barrier homeostasis by either stimulating (reduced K+) or inhibiting (elevated K+) LB secretion. Finally, development of epidermal hyperplasia, a downstream consequence of barrier disruption, was also inhibited by agents that reduce intracellular K+ levels.

CONCLUSIONS

These results demonstrate that changes in K+ levels that can be presumed to occur after barrier disruption signal metabolic responses, i.e. LB secretion, which accelerates normalization of barrier function.

Paradoxical effects of beta-estradiol on epidermal permeability barrier homeostasis

BACKGROUND

Previous studies have demonstrated that sex hormones modulate epidermal permeability barrier homeostasis, and when the balance of these hormones is altered at menopause or during the menstrual cycle, skin sensitivity or barrier function is changed.

OBJECTIVES

To observe the direct effects of sex hormones on epidermal homeostasis.

METHODS

We examined the effects of topical application of sex hormones on permeability barrier recovery after tape stripping in the hairless mouse. To avoid the influence of systemic hormonal alteration, we employed male animals.

RESULTS

Application of androgen (testosterone or androsterone) delayed the barrier recovery, and the delay was overcome by co-application of beta-estradiol. Progesterone also delayed the barrier recovery, but in this case the delay was enhanced by beta-estradiol.

CONCLUSIONS

These results suggest that changes in sex hormone balance might be associated with the skin dysfunction that often occurs during menopause, and at certain points during the menstrual cycle.

Topical Application of Ionic Polymers Affects Skin Permeability Barrier Homeostasis

We previously demonstrated that the external electric potential affected skin barrier homeostasis. On the other hand, topical application of an ionic polymer formed a diffusion electric double layer on the surface of the skin. Thus, we evaluated effects of topical application of ionic polymers on the damaged skin barrier. Application of a nonionic polymer did not affect barrier recovery. Application of sodium salts of anionic polymers accelerated barrier recovery, while that of cationic polymers delayed it. Topical application of a sodium-exchange resin accelerated barrier recovery, but application of a calcium-exchange resin had no effect even when the resins had the same structure. Application of a chloride-exchange resin delayed barrier recovery. Topical application of ionic polymers influenced skin barrier homeostasis.

Barium sulphate with a negative zeta potential accelerates skin permeability barrier recovery and prevents epidermal hyperplasia induced by barrier disruption

BACKGROUND

Barium sulphate, a stable inorganic material, has been used in contrast media and cosmetic products because of its stability. As a negative external electric potential accelerates the skin barrier repair after barrier disruption, we hypothesized that topical application of barium sulphate may affect the skin barrier recovery rate depending on its zeta potential.

OBJECTIVES

To investigate whether barium sulphate particles in aqueous solution have different zeta potentials depending on their surface structure, and to investigate the possible relation between zeta potential and skin barrier recovery rate.

METHODS

Mice were subjected to tape stripping to disrupt barrier function, or were treated with acetone and kept in a dry environment to induce epidermal hyperplasia. They were then treated with different forms of barium sulphate, and barrier recovery was monitored by measurements of transepidermal water loss.

RESULTS

There was a significant correlation between the barrier recovery rate and zeta potential of barium sulphate applied topically. Barium sulphate with a negative zeta potential significantly accelerated barrier recovery, but barium sulphate with a positive zeta potential did not accelerate or even delayed barrier repair. Barium sulphate with a negative zeta potential had an X-ray diffraction pattern different from that with a positive potential. The distribution of calcium in the epidermis was also influenced by the polarity of zeta potential.

CONCLUSIONS

These findings suggest a new pharmacological approach towards altering barrier function or epidermal hyperplasia with inorganic particles in healthy and diseased skin.

Dry environment increases mast cell number and histamine content in dermis in hairless mice

BACKGROUND

A variety of skin diseases, such as atopic dermatitis, senile xerosis or psoriasis tends to worsen during the dry winter season. These skin diseases are also characterized by itch sensation.

OBJECTIVES

To evaluate the generation of histamine in the dermis of hairless mice kept under various conditions of environmental humidity.

MATERIALS AND METHODS

We carried out the quantification of mast cell population and evaluated the histamine content in the epidermis, dermis and serum of the mice kept under various conditions of environmental humidity.

RESULTS

Histamine content in the dermis of the mice kept in a low environmental humidity (relative humidity < 10%) for 3 and 5 days was significantly higher than that of the mice kept in a high environmental humidity (relative humidity > 80%) for the same period of time. No significant difference was observed on the histamine content in the epidermis between the two humidity groups. The number of mast cells in the dermis of the mice kept in the low environmental humidity was significantly higher than that of the mice kept in the high environmental humidity. Topical application of petrolatum reduced the level of histamine in the dermis of the mice under the low environmental humidity.

CONCLUSIONS

These results suggest that a low environmental humidity increases mast cell number and dermal histamine content.

Immunoreactivity of VR1 on epidermal keratinocyte of human skin

We demonstrated the immunoreactivity of the receptor proteins, VR1, ion channels associated with pain sensation, on the epidermis of the human skin. Immunohistochemistry using antiserum against VR1 derived peptide showed immunoreactivity on the keratinocytes cell membrane of the human epidermis and cultured keratinocytes. The blocking peptide of the antiserum reduced the immunoreactivity on the epidermis. RT-PCR assay of cultured human keratinocyte also showed expression of VR1 mRNA. These results suggest the existence of VR1-like protein in epidermal keratinocytes of human skin.

Epidermal proliferative response induced by sodium dodecyl sulphate varies with environmental humidity

BACKGROUND

Previous studies have suggested that susceptibility of skin to external agents increases in the dry winter season.

OBJECTIVES

To test the hypothesis that environmental humidity affects skin sensitivity to irritants.

METHODS

The epidermal hyperplasia induced by sodium dodecyl sulphate (SDS) under various humidity conditions was evaluated on the skin of hairless mice.

RESULTS

Mice kept under low humidity for 2 days showed more obvious epidermal proliferation 24 h after topical application of SDS than those kept under high or normal humidity for 2 days. In contrast, mice kept under high humidity for 2 weeks showed more obvious epidermal proliferation 24 h after topical application of SDS than those kept under low or normal humidity. The transepidermal water loss was altered significantly in the animals kept under high humidity for 2 weeks, although it was not altered during the first 7 days under either low or high humidity.

CONCLUSIONS

These results suggest that environmental humidity influences the sensitivity of skin to topical application of SDS and that increased sensitivity is not always associated with alteration of the water impermeability of the stratum corneum.

Skin Surface Electric Potential Induced by Ion-Flux through Epidermal Cell Layers

The skin surface electric potential has been widely used for psychological studies because it is sensitive to emotional conditions. We measured the electric potential on the surface of hairless mice skin in organ culture with several physiological factors. Disruption of mitochondrial function and inhibition of ATPase reduced the skin surface potential 50-70%. Calcium, potassium, and sodium channel blockers also reduced the potential. A calcium-specific and potassium ionophore reduced the potential, but the calcium and magnesium ionophore increased it. EDTA decreased the potential but EGTA had no effect. Skin surface barrier disruption reduced the potential and calcium and potassium channel blockers partially prevented the decrease. Substance P and corticotropin-releasing factor decreased the potential, and antagonists blocked the decreases. These results suggest that the ion flux in the nucleated layer of the epidermis induce the skin surface potential and it is influenced by environmental and neuroendocrinological factors.

A Brassica oleracea gene expressed in a variety-specific manner may encode a novel plant transmembrane receptor

The species Brassica oleracea includes several agricultural varieties characterized by the proliferation of different types of meristems. Using a combination of subtractive hybridization and PCR (polymerase chain reaction) techniques we have identified several genes which are expressed in the reproductive meristems of the cauliflower curd (B. oleracea var. botrytis) but not in the vegetative meristems of Brussels sprouts (B. oleracea var. gemmifera) axillary buds. One of the cloned genes, termed CCE1 (CAULIFLOWER CURD EXPRESSION 1) shows specific expression in the botrytis variety. Preferential expression takes place in this variety in the meristems of the curd and in the stem throughout the vegetative and reproductive stages of plant growth. CCE1 transcripts are not detected in any of the organs of other B. oleracea varieties analyzed. Based on the nucleotide sequence of a cDNA encompassing the complete coding region, we predict that this gene encodes a transmembrane protein, with three transmembrane domains. The deduced amino acid sequence includes motifs conserved in G-protein-coupled receptors (GPCRs) from yeast and animal species. Our results suggest that the cloned gene encodes a protein belonging to a new, so far unidentified, family of transmembrane receptors in plants. The expression pattern of the gene suggests that the receptor may be involved in the control of meristem development/arrest that takes place in cauliflower.

Histamine H1 and H2 receptor antagonists accelerate skin barrier repair and prevent epidermal hyperplasia induced by barrier disruption in a dry environment

Keratinocytes have histamine H1 and H2 receptors, but their functions are poorly understood. To clarify the role of histamine receptors in the epidermis, we examined the effects of histamine receptor antagonists and agonists applied epicutaneously on the recovery of skin barrier function disrupted by tape stripping in hairless mice. Histamine H2 receptor antagonists famotidine and cimetidine accelerated the recovery of skin barrier function, but histamine and histamine H2 receptor agonist dimaprit delayed the barrier repair. Application of compound 48/80, a histamine releaser, also delayed the recovery. Imidazole, an analog of histamine, had no effect. The histamine H1 receptor antagonists diphenhydramine and tripelennamine accelerated the recovery. Histamine H3 receptor agonist Nalpha-methylhistamine and antagonist thioperamide had no effect. In addition, topical application of famotidine or diphenhydramine prevented epidermal hyperplasia in mice with skin barrier disrupted by acetone treatment in a dry environment (humidity < 10%) for 4 d. In conclusion, both the histamine H1 and H2 receptors in the epidermis are involved in skin barrier function and the cutaneous condition of epidermal hyperplasia.

Epidermal interleukin-1 alpha generation is amplified at low humidity: implications for the pathogenesis of inflammatory dermatoses

BACKGROUND

We have previously reported that low humidity amplifies the hyperproliferative and inflammatory response to barrier disruption. Other reports suggest that epidermal interleukin (IL)-1 alpha is stimulated by various factors related to epidermal inflammation and that it may induce other proinflammatory molecules.

OBJECTIVES

To evaluate the generation of IL-1 alpha in the skin of hairless mice kept under various conditions of environmental humidity.

METHODS

We carried out an immunohistochemical study, and evaluated epidermal IL-1 alpha mRNA and protein levels, and release of IL-1 alpha from skin after tape stripping, in hairless mice kept under low or high humidity.

RESULTS

The immunohistochemical study showed that the amount of IL-1 alpha in the epidermis was higher in animals kept in a low-humidity environment than in a high-humidity one. The epidermal IL-1 alpha mRNA and protein levels increased significantly when the animals were kept under low humidity. Moreover, the release of IL-1 alpha from skin immediately after tape stripping was significantly higher in animals kept in a low-humidity environment than in a high-humidity one.

CONCLUSIONS

These results suggest that IL-1 alpha is an important factor in mediating the relationship between environmental humidity and epidermal pathology.

Identification of immature cornified envelopes in the barrier-impaired epidermis by characterization of their hydrophobicity and antigenicities of the components

Cornified envelopes (CEs), rigid and insoluble structures in the stratum corneum, which are assembled by crosslinking of several precursor proteins by transglutaminases, provide a hydrophobic foundation for barrier function; omega-hydroxyceramides are covalently attached to the outer surface of CE components, and onto this hydrophobic assembly, lamellar layers of intercellular lipids are organized. Morphologically irregular, fragile CEs are found in the deep layer of the stratum corneum or in certain disorders, such as psoriasis, whereas most CEs from healthy subjects are rigid and polygonal. We have established a staining method to characterize such fragile CEs as immature and less hydrophobic CEs, and employed it to examine regional differences in the properties of CEs, especially in relation to the barrier function of the skin. CEs from the outermost stratum corneum of the trunk and extremities of healthy subjects were relatively uniform in morphology with larger shape, and were homogeneous in hydrophobicity as judged from the use of an environment-sensitive fluorescent dye, Nile red. However, CEs from the face were strikingly heterogeneous, and consisted of both rigid and fragile CEs. Rigid CEs were Nile red-positive and little stained by anti-involucrin. In contrast, fragile CEs were Nile red-negative but strongly stained with anti-involucrin, as detected by indirect immunofluorescence. Thus, CEs from the face were stained with Nile red or involucrin in a mutually exclusive manner. Fragile CEs were stained with antibodies against other CE components, including loricrin, envoplakin, filaggrin, and isopeptides. Such fragile, involucrin-positive CEs were detected not only in the face, but also in the deep layer of the stratum corneum of the arm. In addition, experimental barrier disruption resulted in the appearance of involucrin-positive CEs in the outermost stratum corneum. These results suggest that involucrin-positive, fragile CEs are immature and less hydrophobic, and that their occurrence is closely related to impairment of the barrier function of the skin.

Influence of dry environment on epidermal function

Recent studies have demonstrated that a dry environment contributes to the exacerbation of cutaneous disorders such as epidermal hyperplasia, mast cell degranulation, and cytokine secretion. The effects of a dry environment on the skin can be prevented by occlusion with water-impermeable material or topical application of a humectant. The stratum corneum, which protects internal organs from the environment, has two functions: a water-impermeable barrier function and a buffer function against a dry environment. Regulation of protease activity or ionic balance in the epidermis can accelerate barrier repair after injury. Improvement of the stratum corneum homeostasis can ameliorate skin damage induced by barrier disruption in a dry environment.

The relationship between pentosidine and hemodialysis-related connective tissue disorders

Dialysis-related amyloidosis (DRA), such as destructive spondyloarthropathy (DSA) and carpal tunnel syndrome (CTS), occurs in the connective tissues of patients on long-term hemodialysis (HD). Recently, it was suggested that advanced glycation end products (AGEs) and beta2-microglobulin (beta2m) modified with AGEs are related to DRA. The aim of this study is to elucidate whether serum levels of pentosidine, which is an AGE, relate to the occurrence of DRA in patients with long-term HD. 127 end-stage renal failure patients, with DSA or CTS and undergoing HD, were examined. Serum pentosidine was measured by the HPLC method with column switching. Beta2m and intact parathyroid hormone (i-PTH) were measured. Pentosidine levels were significantly elevated in the DSA, CTS, and DRA groups (patients in the DRA group had either DSA and/or CTS). There were no significant differences in the beta2m and i-PTH levels between any group. The duration of HD did not correlate with either pentosidine or beta2m levels, but did with i-PTH. Receiver-operating characteristic (ROC) analysis was performed to examine the discriminatory ability of pentosidine, beta2m, and i-PTH for DRA. The area under the ROC curve was the greatest for pentosidine. Serum beta2m levels were not related with the occurrence of DRA. The fact that serum pentosidine was higher in DRA than in non-DRA indicates that it has potential as an indicator of the occurrence of DRA in long-term HD patients.

Water content and thickness of the stratum corneum contribute to skin surface morphology

Skin surface morphology has long been recognized as reflecting skin pathology. In the present study, we evaluated skin surface morphology using hairless mice under contrasting conditions of humidity. The skin surface microrelief was recorded with opaque quick-drying silicone rubber, and examined under a microscope. A binary image was produced by density slicing. Within 3 days of exposure to dry conditions, skin roughness was significantly increased. The skin roughness was partially mitigated by topical application of an aqueous solution of glycerol or hydration by immersion in water. A significant correlation between skin roughness and stratum corneum thickness was also observed. These results suggest that skin surface morphology is associated with both water content and thickness of the stratum corneum.

Visual imaging of ion distribution in human epidermis

The distribution of calcium, magnesium, potassium, sodium, and hydrogen ions in the human epidermis was visualized by blotting to gel containing chemical indicators and the effects of skin barrier disruption were examined. In normal skin, both calcium and magnesium were localized with high concentration in the upper epidermis. EDTA blocked these imaging. The hydrogen ion was also high in the upper epidermis. Sodium did not show obvious gradation in the epidermis. The potassium concentration was the lowest in the upper epidermis. After the barrier disruption, the gradients of calcium, magnesium, and potassium disappeared while the pH gradation was not altered. Observation at a high magnification revealed lower calcium and sodium concentrations in the nucleus. The concentration of magnesium was slightly higher in the nucleus. The novel method of the present study could show the visual image of the ions in frozen tissue without further preparation.

Barrier recovery rate varies time-dependently in human skin

The recovery in cutaneous barrier functions, assessed in terms of transepidermal water loss, 1 h after tape stripping of volar forearm skin in human volunteers, was investigated at different times over the 24 h day. The barrier recovery rate was significantly lower between 20:00 h and 23:00 h than that at other time points. The skin surface temperature and the basal transepidermal water loss reached their highest values at about 03:00 h (33.6 degrees C and 0.30 mg cm-2 h-1), while the cortisol level in the saliva was highest at 09:00 h (7.8 pmol mL-1). These results suggest significant time-dependent variation in cutaneous barrier repair independent of changes in skin temperature and cortisol level.

Odorant inhalation affects skin barrier homeostasis in mice and humans

Previous studies have suggested that psychological stress delays cutaneous barrier recovery following acute barrier disruption, and that sedative drugs block this delay. A sedative effect of some odorants has been reported. In the present study, we demonstrate that odorant inhalation affects cutaneous barrier homeostasis in both mice and humans. Odorants with a sedative effect prevented the delay of skin barrier recovery induced by stress after acute barrier disruption. Other odorants did not show this effect.

Regulation of the cutaneous allergic reaction by humidity

Humidity is 1 of the environmental factors which regulate skin conditions. Effects of humidity on the cutaneous immune reaction were examined. Contact hypersensitivity to 2,4,6-trinitrochlorobenzene was elicited in C57BL/6 mice. The reaction was greater in mice housed under low humidity conditions (about 10%) for 2 days, at either the induction or elicitation phase, than in mice housed under rather high humidity conditions (80%). After housing under controlled humidity for 2 days, the number of I-A positive cells was 16% higher in the epidermis exposed to the dry condition. The increased population of FITC-positive cells were in regional lymph nodes after painting of FITC during housing under lower humidity. Our study demonstrated that the cutaneous immune reaction is regulated by environmental humidity and suggested 2 possible mechanisms, i.e., increase in Langerhans cells and increased penetration of allergen with low humidity.

Stress alters cutaneous permeability barrier homeostasis

Recent studies have shown that psychological stress can influence cutaneous barrier function, suggesting that this form of stress could trigger or aggravate skin disease. In the present study, we demonstrate that transfer of hairless mice to a different cage delays barrier recovery rates. Pretreatment with a phenothiazine sedative, chlorpromazine, before transfer of animals restored the kinetics of barrier recovery toward normal, suggesting that psychological stress is the basis for this alteration in barrier homeostasis. To determine the mechanism linking psychological stress to altered barrier recovery, we first demonstrated that plasma corticosterone levels increase markedly after transfer of animals to new cages and that pretreatment with chlorpromazine blocks this increase. Second, we demonstrated that the systemic administration of corticosterone delays barrier recovery. Finally, we demonstrated that pretreatment with the glucocorticoid receptor antagonist RU-486 blocks the delay in barrier recovery produced by systemic corticosterone, change of cage, or immobilization. These results suggest that psychological stress stimulates increased production of glucocorticoids, which, in turn, adversely affects permeability barrier homeostasis.

Changes in levels of biochemical markers and ultrasound indices of Os calcis across the menopausal transition

The aim of this longitudinal study was to investigate the changes in the levels of biochemical markers and ultrasound indices of os calcis across the menopausal transition. One hundred and ten healthy women (age 35-59 years at the 1992 baseline) participated in this 4-year population-based longitudinal study. Serum intact osteocalcin (IOC), urinary pyridinoline (Pyr), urinary deoxypyridinoline (Dpyr) and ultrasound indices were measured at baseline and after 4 years. The percentage changes in biochemical markers (% delta IOC, % delta Pyr and % delta Dpyr) and the percentage decreases in the ultrasound indices (% delta SOS, % delta BUA and % delta Stiffness) were calculated. The values of % delta IOC and % delta Dpyr in the perimenopausal subgroup (-4 to -3 years since menopause) and the values of % delta SOS and % delta Stiffness in the perimenopausal subgroup (-2 to 0 years since menopause) were significantly higher than those in other groups. Pyr was significantly correlated with % delta SOS (r = -0.467, p < 0.01) and % delta Stiffness (r = -0.330, p < 0.05) and Dpyr was significantly correlated with % delta SOS (r = -0.390, p < 0.05), % delta BUA (r = -0.353, p < 0.05) and % delta Stiffness (r = -0.454, p < 0.05), while % delta IOC was significantly correlated with % delta SOS (r = -0.278, p < 0.05), % delta BUA (r = -0.369, p < 0.01) and % delta Stiffness (r = -0.383, p < 0.01) in the peri- and postmenopausal groups. These results indicate that the increase in bone turnover occurs 4 years before menopause. However, the correlations between biochemical markers and ultrasound indices were too low to allow prediction of bone change in the individual patient.

Some magnesium salts and a mixture of magnesium and calcium salts accelerate skin barrier recovery

The effects of four different magnesium salts on the cutaneous barrier recovery rate after barrier disruption were evaluated. We spread an aqueous solution of each salt on the flank skin of hairless mice, occluded the area with a plastic membrane for 20 min, and then left the skin surface to dry. All of the magnesium salts, except magnesium bis(dihydrogen phosphate), accelerated barrier repair. We next estimated the effects of magnesium chloride aqueous solutions which contained calcium chloride at different molar ratios. When the calcium to magnesium ratio was lower than 1, the mixture accelerated barrier repair. The application of an aqueous solution of 10 mM magnesium chloride and 10 mM calcium chloride was found to hasten the barrier recovery more effectively than a solution of 10 mM magnesium chloride. These results suggest that the effects of these metal ions are different depending on the counter ion and/or the method of application.

Dry condition affects desquamation of stratum corneum in vivo

We examined whether a dry condition actually induces scaly skin in vivo. Hairless mice were kept in a high humidity condition or a low humidity condition and skin changes were examined. Scales appeared on the backs of mice kept for 3 days under the dry condition. The weight of stratum corneum (SC) was increased at this point, and these alterations were not accompanied with hyperproliferation of the nucleated cell layer of the epidermis. A decrease of desmosomal degradation was observed, though, desquamation-related enzyme activity was not altered. The regulation mechanism of desquamation is not yet clear, however, in vitro experiments suggest that the water content in SC is an important factor. The water content of SC was decreased in the dry condition. These results indicate that a dry environment perturbs desmosome degradation in intact SC by decreasing the water content of SC, and the consequent impairment of desquamation in normal skin in vivo may lead to the induction of a scaly skin surface.

Low humidity stimulates epidermal DNA synthesis and amplifies the hyperproliferative response to barrier disruption: implication for seasonal exacerbations of inflammatory dermatoses

Although seasonal changes in humidity are thought to exacerbate various skin diseases, whether these flares can be attributed to prolonged exposure to extremes in environmental humidities has not been studied systematically. We recently showed that prolonged exposure to high versus low humidities induced profound changes in epidermal structure and permeability barrier homeostasis. Therefore, we asked here whether comparable extremes in humidity could initiate not only homeostatic, but also potentially pathophysiologic alterations. We showed first that exposure to low humidity increases epidermal DNA synthesis in normal murine epidermis. Moreover, exposure to a low humidity for 48 h further amplifies the DNA synthetic response to barrier disruption, resulting in marked epidermal hyperplasia. Additionally, exposure to a dry environment for 48 h prior to barrier disruption results in dermal mast cell hypertrophy, degranulation, as well as histologic evidence of inflammation. To demonstrate the role of changes in external moisture on these phenomena, we applied either an occlusive, water-impermeable plastic membrane, Petrolatum, or a nonocclusive humectant, both to nonperturbated and to perturbed skin. All three forms of treatment prevented the epidermal hyperplasia and dermal mast cell hypertrophy and degranulation induced by exposure to low humidity. These studies indicate that (i) exposure to changes in environmental humidity alone induces increased keratinocyte proliferation and markers of inflammation, and (ii) that these changes are attributable to changes in stratum corneum moisture content. Finally, these studies provide evidence that changes in environmental humidity contribute to the seasonal exacerbations/amelioration of cutaneous disorders, such as atopic dermatitis and psoriasis, diseases which are characterized by a defective barrier, epidermal hyperplasia, and inflammation.

Loss of water from the stratum corneum induces epidermal DNA synthesis in hairless mice

Many clinical studies have shown that low humidity has a deleterious effect on skin, but the mechanisms involved are poorly understood. To clarify the changes that occur in skin, we examined epidermal cell proliferation in mice kept in a dry (relative humidity < 10%) or a moist (relative humidity > 90%) environment. In animals exposed to low humidity, epidermal DNA synthesis started to increase within 12 h, reaching twice the original level, and the increased level was maintained for up to 5 days. The transepidermal water loss (TEWL) of mice kept for 12 h in the dry environment was the same as that of mice kept in the moist environment, but the skin conductance was lower. The increase in epidermal DNA synthesis following exposure to the dry environment was inhibited by topical application of petrolatum. It is concluded that loss of water from the stratum corneum induces epidermal cell proliferation within 12 h, and this change occurs in the absence of apparent cutaneous barrier dysfunction.

Recessive x-linked ichthyosis: role of cholesterol-sulfate accumulation in the barrier abnormality

Cholesterol sulfate is a multifunctional sterol metabolite, produced in large amounts in squamous keratinizing epithelia. Because patients with recessive x-linked ichthyosis display not only a 10-fold increase in cholesterol sulfate, but also a 50% reduction in cholesterol, we assessed here whether cholesterol sulfate accumulation and/or cholesterol deficiency produce abnormal barrier function in recessive x-linked ichthyosis. Patients with recessive x-linked ichthyosis display both an abnormal barrier under basal conditions, and a delay in barrier recovery after acute perturbation, which correlate with minor abnormalities in membrane structure and extensive lamellar-phase separation. Moreover, both the functional and the structural abnormalities were corrected by topical cholesterol. Yet, topical cholesterol sulfate produced both a barrier abnormality in intact skin and extracellular abnormalities in isolated stratum corneum, effects largely reversed by coapplications of cholesterol. Together, these results suggest that cholesterol sulfate accumulation rather than cholesterol deficiency is responsible for the barrier abnormality. Despite the apparent importance of cholesterol sulfate-to-cholesterol processing for normal barrier homeostasis, neither steroid sulfatase activity nor mRNA levels are upregulated following acute perturbations. These results demonstrate both a potential role for cholesterol sulfate-to-cholesterol processing in normal permeability barrier homeostasis, and that basal levels of steroid sulfatase are sufficient to accommodate acute insults to the permeability barrier.

Exposure to a dry environment enhances epidermal permeability barrier function

Previous studies have suggested that transepidermal water movement may play an important role in epidermal homeostasis and barrier repair. Here we analyzed cutaneous barrier function, epidermal morphology, and lipid content of the stratum corneum in hairless mice maintained in a high relative humidity (RH > 80%) versus low humidity (RH < 10%) environment for 2 wk. Basal transepidermal water loss was reduced by 31% in animals maintained in a dry versus humid environment. Moreover, the number of lamellar bodies in stratum granulosum cells, the extent of lamellar body exocytosis, and the number of layers of stratum corneum increased in animals kept in a dry environment. Furthermore, the dry weight of the stratum corneum and the thickness of the epidermis also increased in a dry environment. In addition, total stratum corneum lipids increased but lipid analysis revealed no significant differences in lipid distribution. Lastly, barrier recovery following either acetone treatment or tape stripping was accelerated after prolonged prior exposure to a dry environment, while conversely, it was delayed by prior exposure to a humid environment. These studies demonstrate that environmental conditions markedly influence epidermal structure and function, and suggest mechanisms by which the environment could induce or exacerbate various cutaneous disorders.

Modification of LC phenotype and suppression of contact hypersensitivity response by stress

BACKGROUND

Stress is thought to exacerbate a number of diseases, some of which are skin disorders. Epidermal Langerhans' cells play a major role in cutaneous immune reactions.

OBJECTIVE

The effects of two types of stress on the cutaneous immune system were to be assessed in mice.

METHODS

Mice received stress by immobilization or housing at various population densities. Epidermal sheets were stained for I-A molecules (a member of class II major histocompatibility complex) and analyzed with a confocal-laser- scanning microscope. Contact hypersensitivity reaction to 2,4,6-trinitrochlorobenzene was elicited in mouse ears.

RESULTS

The cell density, intensity of I-A expression, and number of dendrites were decreased as the population density increased. Elicitation of contact hypersensitivity was suppressed in mice that received either population or immobilization stress. Increased I-A expression and number of dendrites were observed in adrenalectomized compared to sham-operated mice. The population-dependent suppression of contact hypersensitivity reaction was not observed in adrenalectomized mice. After incubation with serum from mice that received either immobilization stress or population stress, the expression of I-A molecules on a XS52 Langerhans' cell-like cell line was reduced.

CONCLUSION

Stress affected the cutaneous immune system. There were indications that adrenergic hormones played a role in the regulation of the system.

Cholesterol sulfate inhibits proteases that are involved in desquamation of stratum corneum

We previously reported that desmosomes play a key role in the adhesion of corneocytes, and their digestion by two types of serine proteases leads to desquamation. Patients with recessive X-linked ichthyosis show hyperkeratosis attributable to desmosomes, associated with an increased content of cholesterol sulfate (CS) and an increased thickness of stratum corneum. In this study, therefore, we examined the possibility that CS provokes the abnormal desquamation, acting as a protease inhibitor. Scaling was induced on mice after topical application of chymostatin and leupeptin. Visible scale was also observed on mice after topical application of CS. We found that the stratum corneum thickness of CS-treated mice was increased in comparison with that of vehicle-treated mice. The thickness of the epidermis and the labeling index with proliferating cell nuclear antigen from CS-treated mice was almost the same as that from vehicle-treated mice. Moreover, in the stratum corneum of CS-treated mice, the content of desmosomes was higher than that in vehicle-treated mice. CS also inhibited the protease-induced cell dissociation of human stratum corneum sheets. In vitro, CS competitively inhibited both types of serine protease: the Ki for trypsin was 5.5 x 10(-6) M and that for chymotrypsin was 2.1 x 10(-6) M. These results indicate that CS retards desquamation by acting as a protease inhibitor. Thus, accumulation of stratum corneum in recessive X-linked ichthyosis may be a result of the inhibition by excessive CS of proteases involved in the dissolution of desmosomes, required for desquamation of the stratum corneum.

Immobilization-induced and crowded environment-induced stress delay barrier recovery in murine skin

To examine the effect of stress on skin homeostasis, cutaneous barrier recovery was measured in rate exposed to immobilization stress after tape stripping or sodium dodecyl sulphate treatment. The barrier function was evaluated by measuring transepidermal water loss. Barrier recovery was delayed in rats exposed to stress in comparison with untreated controls. This tendency was observed in both male and female animals. The delay in barrier recovery was blocked by application of the sedative drugs diazepam and chlorpromazine. The barrier recovery rate in mice which were kept at a high population density (10 animals per cage) for 2 weeks was slower than that in mice kept at lower population densities (five animals or one animal per cage). These animal models could be useful for objectively quantifying the influence of stress on the cutaneous function.

Characteristics of biochemical markers in patients with metabolic bone disorders

Biochemical markers of bone turnover are expected to have some different characteristics among bone metabolic disorders. We compared bone formation markers: serum total alkaline phosphatase (s-Alp), serum osteocalcin (s-OC) and serum carboxy-terminal propeptide of type I collagen (s-PICP); and bone resorption markers: serum carboxy-terminal telopeptide of type I collagen (s-ICTP), urinary pyridinoline (u-Pyr) and urinary deoxypyridinoline (u-Dpyr) to examine which marker is the most suitable and reliable to evaluate bone turnover in patients with osteoporosis (n = 29), osteomalacia (n = 10), primary hyperparathyroidism (n = 6) and renal osteodystrophy (n = 21). The value of s-Alp in the osteomalacia group was significantly higher than those in the normal control group and the osteoporosis group (p < 0.001), and T-score of s-Alp was significantly higher than those of s-OC and s-PICP in the osteomalacia group. The values of u-Pyr and u-Dpyr in the primary hyperparathyroidism group were significantly higher than those in the other groups (p < 0.001). S-PICP, which are not dependent upon renal function, was much higher in the renal osteodystrophy group than in all other groups. In the osteoporosis group, T-score of s-ICTP was significantly higher than those of s-OC. Thus, s-Alp was a good marker in osteomalacia, u-Pyr and u-Dpyr in primary hyperparathyroidism, s-PICP in renal osteodystrophy, and s-ICTP in osteoporosis.

A new analog of 1,25-(OH)2D3, 19-NOR-1,25-(OH)2D2, suppresses serum PTH and parathyroid gland growth in uremic rats without elevation of intestinal vitamin D receptor content

We have previously reported that 19-nor-1,25-(OH)2D2, a new analog of 1,25-(OH)2D3, suppresses parathyroid hormone (PTH) secretion in uremic rats in the absence of hypercalcemia or hyperphosphatemia. In the current study, we examined the effect of 19-nor-1,25-(OH)2D2 on parathyroid gland growth and intestinal vitamin D receptor (VDR) content. After induction of uremia by 5/6 nephrectomy, rats were divided into five experimental groups and received intraperitoneal injections of vehicle, 1,25-(OH)2D3 (2 or 6 ng/rat), or 19-nor-1,25-(OH)2D2 (25 or 100 ng/rat) three times a week for 8 weeks. Twelve normal rats received vehicle and served as the normal control group. During the course of the study, rats were maintained on a 1.0% calcium and 0.8% phosphorus diet. The higher dose of 1,25-(OH)2D3, 6 ng, significantly decreased PTH from 52.7 +/- 10.2 pg/mL in the uremic control group to 25.7 +/- 6.7 pg/mL (P < 0.01). This dose of 1,25-(OH)2D3, however, increased serum levels of both ionized calcium (4.71 +/- 0.05 to 4.85 +/- 0.06 mg/dL; P < 0.05) and phosphorus (4.34 +/- 0.30 to 6.67 +/- 0.63 mg/dL; P < 0.01). Both doses of 19-nor-1,25-(OH)2D2 decreased serum PTH as effectively as 1,25-(OH)2D3 without changes in serum calcium or phosphorus. The 100-ng dose of 19-nor-1,25-(OH)2D2 decreased PTH to 20.7 +/- 3.1 pg/mL (P < 0.01) and suppressed parathyroid gland growth by more than 50%. Both doses of 19-nor-1,25-(OH)2D2 also decreased endogenous 1,25-(OH)2D3 levels compared with uremic control rats (25 ng:30.4 +/- 2.0, P < 0.05, and 100 ng:27.9 +/- 3.2, P < 0.01, v 48.4 +/- 6.6 pg/mL). The 6-ng dose of 1,25-(OH)2D3 elevated intestinal VDR content (138.5 +/- 20.0 fmol/mg protein) compared with animals receiving both doses of 19-nor-1,25-(OH)2D2 (25 ng:84.0 +/- 11.9, P < 0.05, and 100 ng:78.4 +/- 10.9, P < 0.01). This was probably attributable to the marked decrease in endogenous 1,25-(OH)2D3 levels caused by both doses of 19-nor-1,25-(OH)2D2 because intestinal VDR correlated directly with serum 1,25-(OH)2D3 (r = 0.963; P = 0.008). Thus, 19-nor-1,25-(OH)2D2 appears to exert a selective action on the parathyroid glands compared with the intestine. Its low calcemic and phosphatemic properties may result from the decreased endogenous 1,25-(OH)2D3 levels that lead to a reduction in intestinal VDR. This selectivity makes this analog ideal for the treatment of secondary hyperparathyroidism.

trans-4-(Aminomethyl)cyclohexane carboxylic acid (T-AMCHA), an anti-fibrinolytic agent, accelerates barrier recovery and prevents the epidermal hyperplasia induced by epidermal injury in hairless mice and humans

Because wounding the epidermis increases proteolytic activity and because disorders associated with barrier dysfunction have elevated protease activity, we studied the effect of protease inhibitors on the time course of barrier recovery and on the development of epidermal hyperplasia induced by repeated injury. After injuries to the epidermis produced by tape stripping, acetone treatment, or detergent (SDS) treatment that disrupt the barrier, a single application of 5% tranexamic acid [4-(aminomethyl)cyclohexane carboxylic acid, t-AMCHA], a well known anti-plasmin reagent, accelerated barrier recovery in both hairless mouse and human skin. In contrast, neither aminocaproic acid nor aminobutyric acid, inactive analogs of t-AMCHA, affected the time course of barrier recovery. Several trypsin-like serine protease inhibitors, e.g., leupeptin, TLCK, and PMSF, also accelerated barrier repair. In contrast other types of protease inhibitors, e.g., EDTA, pepstatin, N-ethylmaleimide, chymostatin, and TPCK, did not accelerate barrier recovery. We next evaluated the effects of daily topical application of t-AMCHA on epidermal hyperplasia, induced by repeated tape stripping or acetone treatment for 7 d. The degree of hyperplasia, quantified by the measurement of epidermal thickness, was reduced in both models by repeated applications of t-AMCHA. Finally, proteolytic activity in both human and mouse epidermis increased 1-2 h after epidermal injuries that disrupt the barrier. These results demonstrate that the inhibition of plasmin, a serine protease, accelerates barrier recovery and inhibits the epidermal hyperplasia induced by repeated barrier disruption, perhaps by decreasing the extent of attendant epidermal injury.