Retention of corneodesmosomes and increased expression of protease inhibitors in dandruff

Effects of eczema calming lotion on the stratum corneum in atopic dermatitis: Corneodesmosin and intercellular lipid lamellae

OBJECTIVE

Atopic dermatitis (AD) is characterized by compositional and structural changes to the skin at lesional sites. Alteration to the levels and organization of both protein and lipid components are associated with disease status and lead to impaired barrier and hydration. Corneodesmosin (CDSN) and the arrangement and length of the intercellular lipid lamellae (ICLL) are altered in disrupted skin states. The aim of this research was to profile the distribution of CDSN and the ICLL in the stratum corneum (SC) at lesional and non-lesional sites in AD-prone skin and to investigate the impact of an eczema calming lotion containing petroleum jelly, fatty acids, and colloidal oatmeal.

METHODS

An IRB-approved study was conducted with participants with active AD. From a small subset of participants, tape strips were collected from lesional and non-lesional sites on the arm, prior to and after twice daily application, over 4 weeks of an eczema calming lotion containing petroleum jelly, fatty acids, and colloidal oatmeal. Fluorescent antibody staining was used to investigate the distribution of CDSN. Transmission electron microscopy (TEM) was used to characterize the ICLL.

RESULTS

The distribution/coverage of CDSN was similar between lesional and non-lesional sites at baseline; application of the lotion resulted in a more defined honeycomb/peripheral distribution. Normalized ICLL (nICLL) was lower in baseline samples from lesional sites relative to non-lesional sites. Application of the lotion increased this parameter by the end of the study at all sites.

CONCLUSION

The eczema calming lotion containing petroleum jelly, fatty acids and colloidal oatmeal provided changes in corneodesmosomal proteins distribution and ICLL, consistent with improvements in corneocyte maturation and improved barrier function in the skin of individuals with atopic dermatitis.

Malassezia restricta-mediated Lipoperoxidation: A Novel Trigger in Dandruff

Dandruff is a common scalp disorder with multiple microbial and host-related factors contributing to its aetiology, including alterations in scalp sebum. Despite existing evidence that the yeast Malassezia restricta plays a key role in the onset of dandruff, the interplay of these factors is poorly understood. Recently, squalene monohydroperoxide and malondialdehyde were established as biomarkers of dandruff-afflicted scalp, highlighting the role of sebum lipoperoxidation in the triggering and maintenance of dandruff, although its mechanism of action is unknown. The current study provides evidence that M. restricta mediates sebum peroxidation, leading to production of squalene monohydroperoxide and malondialdehyde. Furthermore, in vitro data show that these lipoperoxidation products act on epidermal cells and alter the skin barrier. These results support the role of Malassezia restricta-induced lipoperoxides as triggers of dandruff, which suggests that blocking their production could be a novel anti-dandruff treatment approach.

Human Tissue Kallikreins-Related Peptidases Are Targets for the Treatment of Skin Desquamation Diseases

Human tissue Kallikrein-related peptidases (hKLKs) are serine proteases distributed in several tissues that are involved in several biological processes. In skin, many are responsible for skin desquamation in the Stratum Corneum (SC) of the epidermis, specially hKLK5, hKLK7, hKLK6, hKLK8, and hKLK14. In SC, hKLKs cleave proteins of corneodesmosomes, an important structure responsible to maintain corneocytes attached. As part of skin desquamation, hKLKs are also involved in skin diseases with abnormal desquamation and inflammation, such as Atopic Dermatitis (AD), psoriasis, and the rare disease Netherton Syndrome (NS). Many studies point to hKLK overexpression or overactive in skin diseases, and they are also part of the natural skin inflammation process, through the PAR2 cleavage pathway. Therefore, the control of hKLK activity may offer successful treatments for skin diseases, improving the quality of life in patients. Diseases like AD, Psoriasis, and NS have an impact on social life, causing pain, itchy and mental disorders. In this review, we address the molecular mechanisms of skin desquamation, emphasizing the roles of human tissue Kallikrein-related peptidases, and the promising therapies targeting the inhibition of hKLKs.

A folliculocentric perspective of dandruff pathogenesis: Could a troublesome condition be caused by changes to a natural secretory mechanism?

Dandruff is a common scalp condition, which frequently causes psychological distress in those affected. Dandruff is considered to be caused by an interplay of several factors. However, the pathogenesis of dandruff remains under-investigated, especially with respect to the contribution of the hair follicle. As the hair follicle exhibits unique immune-modulatory properties, including the creation of an immunoinhibitory, immune-privileged milieu, we propose a novel hypothesis taking into account the role of the hair follicle. We hypothesize that the changes and imbalance of yeast and bacterial species, along with increasing proinflammatory sebum by-products, leads to the activation of immune response and inflammation. Hair follicle keratinocytes may then detect these changes in scalp microbiota resulting in the recruitment of leukocytes to the inflammation site. These changes in the scalp skin immune-microenvironment may impact hair follicle immune privilege status, which opens new avenues into exploring the role of the hair follicle in dandruff pathogenesis. Also see the video abstract here: https://youtu.be/mEZEznCYtNs.

Biophysical characteristics of dandruff-affected scalp categorized on the basis of sebum levels

BACKGROUND

Various sebum levels can be detected in dandruff-affected scalps. However, few studies have compared the biophysical characteristics of dandruff scalps categorized based on sebum levels.

AIMS

To investigate and compare the biophysical characteristics of dandruff-affected scalps categorized based on sebum levels.

METHODS

Fifty-four Korean women with dandruff and 30 healthy Korean women underwent physiological measurements, including evaluation of sebum and hydration levels, pH, and transepidermal water loss (TEWL) in the scalp. The levels of the biomarkers of interleukin-8 (IL-8) and kallikrein 5 (KLK5) and corneodesmosomes were investigated in the stratum corneum (SC) of the scalp.

RESULTS

Dandruff was categorized as dry (low-sebum, n = 25) or oily (high-sebum, n = 29) based on a sebum cutoff level of 97.82 μg/cm² . Both dry and oily dandruff-affected scalps showed significantly decreased hydration levels and increased pH and TEWL compared with healthy subjects, with hydration levels being lower in dry dandruff-affected scalps. IL-8 expression was significantly increased in the oily dandruff-affected scalp. In addition, both dry and oily dandruff-affected scalps showed significantly increased KLK5 levels in the SC, with the levels being higher in oily dandruff-affected scalps. Altered distribution of corneodesmosomes, present on the entire surface area of the corneocytes, was notable in oily dandruff-affected scalps.

CONCLUSION

The biophysical characteristics of the two types of dandruff represent the influence of different characteristics, including hydration levels, expression of IL-8 and KLK5, and corneodesmosome distribution. Thus, strategies to reduce dandruff levels should differ according to sebum levels.

Evaluation of factors triggering sensitive scalp in Korean adult women

BACKGROUND

The scalp care market is growing rapidly and research into the factors associated with sensitive scalp is performed in many countries. However, to the best of our knowledge, no previous study has examined the factors triggering sensitive scalp in Korean women. Thus, the aim of our study was to establish objective standards for sensitive scalp, investigate factors that trigger this condition, and determine the ratio of sensitive scalp in Korean women.

METHODS

A total of 125 Korean adult women participated in the study. The participants answered the questionnaire, had their scalp temperature measured, and the sensitive scalp condition was evaluated and analyzed.

RESULTS

Compared to the non-sensitive scalp (NS) group, the sensitive scalp (SS) group had a significantly higher average temperature and increased heat sensation, dandruff, erythema in the scalp, past history of atopy, history of hair loss, medical history of scalp disease, concern for scalp care, and interest in mild products and frequency of use. The majority of participants in the SS group had a dry scalp, and itching was common.

CONCLUSION

This study may help us to understand the characteristics of the sensitive scalp in Korean females and determine factors associated with triggering a sensitive scalp.

Activography reveals aberrant proteolysis in desquamating diseases of differing backgrounds

The role of epidermal proteolysis in overdesquamation was revealed in Netherton syndrome, a rare ichthyosis due to genetic deficiency of the LEKTI inhibitor of serine proteases. Recently, we developed activography, a new histochemical method, to spatially localize and semiquantitatively assess proteolytic activities using activity-based probes. Activography provides specificity and versatility compared to in situ zymography, the only available method to determine enzymatic activities in tissue biopsies. Here, activography was validated in skin biopsies obtained from an array of distinct disorders and compared with in situ zymography. Activography provides a methodological advancement due to its simplicity and specificity and can be readily adapted as a routine diagnostic assay. Interestingly, the levels of epidermal proteolysis correlated with the degree of desquamation independent of skin pathology. Thus, deregulated epidermal proteolysis likely represents a universal mechanism underlying aberrant desquamation.

iTRAQ-based quantitative proteomics of stratum corneum of dandruff scalp reveals new insights into its aetiology and similarities with atopic dermatitis

The study aimed at detecting differentially expressed proteins in the stratum corneum of dandruff versus non-dandruff scalps to better understand dandruff aetiology. iTRAQ-based quantitative proteomic analysis revealed a total of 68 differentially expressed biomarkers. A detailed analysis of their known physiological functions provided new insights into the affected metabolic pathways of a dandruff scalp. Dandruff scalp showed (1) profound changes in the expression and maturation of structural and epidermal differentiation related proteins, that are responsible for the integrity of the skin, (2) altered relevant factors that regulate skin hydration, and (3) an imbalanced physiological protease-protease inhibitor ratio. Stratum corneum proteins with antimicrobial activity, mainly those derived from sweat and sebaceous glands were also found modified. Comparing our data with those reported for atopic dermatitis revealed that about 50 % of the differentially expressed proteins in the superficial layers of the stratum corneum from dandruff and atopic dermatitis are identical.

'Memory' of the stratum corneum: exploration of the epidermis' past

The stratum corneum (SC) is the final product of the process of epidermal differentiation. Besides its crucial protective role as a physical permeability barrier, this composite structure made of cornified keratinocytes embedded in a layered lipid matrix is also, by nature, a tissue that keeps track of past events occurring in the outermost living layers. In normal human epidermis, formation of the SC is very rapid, and during this cornification process several structures expressed by the last granular layer of keratinocytes become entrapped and immobilized at the cells' periphery. Cell-cell junctions are obvious targets of transglutaminases that cross-link junctions' components within the corneocyte envelopes. Thus, desmosomes and tight junctions (TJs) in living cells become fixed at the corneocyte periphery and cannot be recycled anymore. We have quantified the TJ-like structures residing in the SC of human skin explants subjected to environmental stress and compared these results with fresh skin controls. Significant overexpression of TJ-like cell-cell envelope fusions has been observed in the stressed epidermis and in two different hereditary skin diseases characterized by increased SC cohesion. Quantitation of TJ-like structures has contributed to the interpretation of the diseases' physiopathology. Other examples of information retrieved from the SC concern fluctuating lipid expression in the course of atopic dermatitis and patterns of corneodesmosome breakdown influencing SC desquamation. It is, therefore, possible to analyse and quantify the traces left in the SC and to draw conclusions on the dynamics of living tissue over the past several days.

Epidermal barrier disorders and corneodesmosome defects

Corneodesmosomes are modified desmosomes present in the stratum corneum (SC). They are crucial for SC cohesion and, thus, constitute one of the pivotal elements of the functional protective barrier of human skin. Expression of corneodesmosomes and, notably, the process of their degradation are probably altered during several dermatoses leading to the disruption of the permeability barrier or to abnormal, often compensative, SC accumulation. These different situations are reviewed in the present paper.