The impact of irritant challenge on the skin barrier and myeloid resident immune cells in post-menopausal women is modulated by hormone replacement therapy.

BACKGROUND: Sex hormone changes during menopausal transition contribute to declining skin health. However, how menopause and its treatment by hormone replacement therapy (HRT) impact the skin barrier and immune system is unclear. Therefore, we examined how menopause and HRT affect skin barrier and immune cell composition in post-menopausal women following irritant challenge. METHODS: Two cohorts of post-menopausal women were recruited to the study, one untreated (HRT-; n = 10; mean age 56.5 yrs [range 48-63 yrs]) and the other receiving HRT (n = 8; mean age 54 yrs [range 48-63 yrs]). Skin irritation was induced by applying 1.25% topical Sodium Lauryl Sulfate (SLS) to occluded buttock skin for 48 hours. Clinical assessment was conducted after 24 hours, followed by biopsy of both SLS-challenged and unchallenged skin for analysis of skin barrier proteins and immune cell distribution using immunofluorescence. RESULTS: Clinically, there were no significant differences in skin irritant responses between those taking or not taking HRT (including increased skin redness and blood flow). In response to SLS challenge a significant increase in trans-epidermal water loss (p<0.05), filaggrin deposition and keratin-10-positive cell layers (p<0.01) was observed in individuals receiving HRT compared to the HRT- group. Following SLS challenge in individuals taking HRT, a significant (p<0.01) reduction of CD207+ cells in the epidermis was observed, accompanied by an increase of CD207+ cells in the dermis, indicative of migrating Langerhans' cells (LCs). Significantly fewer migrating LCs were observed in those not receiving HRT (p<0.01). Furthermore, the number of dermal dendritic cells (DCs), macrophages, and CD11c+CD206- and CD68+CD206- subsets were found to be significantly (p<0.05) higher in those taking HRT following SLS challenge. CONCLUSION: Individuals receiving HRT displayed enhanced skin barrier response to SLS challenge with thicker filaggrin and increased keratin-10-positive epidermal cell layers. Following challenge, HRT users exhibited elevated counts of LCs, inflammatory DCs, and macrophages in the dermis. These may render skin both, more prone to inflammation and more capable of resolving it, while also promoting skin repair.

TNF-α‒Mediated Keratinocyte Expression and Release of Matrix Metalloproteinase 9: Putative Mechanism of Pathogenesis in Stevens‒Johnson Syndrome/Toxic Epidermal Necrolysis.

Stevens‒Johnson syndrome and toxic epidermal necrolysis (SJS/TEN) are severe cutaneous adverse drug reactions characterized by widespread keratinocyte cell death and epidermal detachment. At present, there is little understanding of how the detachment occurs or how it is abrogated by the TNF-α inhibitor etanercept, an effective SJS/TEN treatment. RNA sequencing was used to identify upregulated transcripts in formalin-fixed paraffin-embedded SJS/TEN skin biopsies. Epidermal matrix metalloproteinase 9 (MMP9) expression was assessed by immunohistochemistry in skin biopsies and cultured human skin explants exposed to serum from patients with cutaneous adverse drug reactions. TNF-α‒induced MMP9 expression and activity and its abrogation by etanercept were determined using the HaCaT immortalized keratinocyte cell line. Epidermal MMP9 expression was significantly higher in SJS/TEN skin (70.6%) than in healthy control skin (0%) (P = 0.0098) and nonbullous skin reactions (10.7%) (P = 0.0002). SJS/TEN serum induced significant MMP9 expression and collagenase activity in healthy skin explants, which was reduced by etanercept. Etanercept was also able to negate the TNF-α‒induced MMP9 expression in the HaCaT cell line. Data suggest that elevated epidermal MMP9 expression and collagenase activity are a putative pathogenic mechanism in SJS/TEN, which is limited by etanercept. Modulation of MMP9 expression and activity represents, to our knowledge, a previously unreported therapeutic target for the treatment of SJS/TEN.

Remodelling of fibrillin-rich microfibrils by solar-simulated radiation: impact of skin ethnicity.

Fibrillin-rich microfibrils (FRMs) constitute integral components of the dermal elastic fibre network with a distinctive ultrastructural 'beads-on-a-string' appearance that can be visualised using atomic force microscopy and characterised by measurement of their length and inter-bead periodicity. Their deposition within the dermis in photoprotected skin appears to be contingent on skin ethnicity, and influences the ultrastructure of papillary - but not reticular - dermal FRMs. Truncation and depletion of FRMs at the dermal-epidermal junction of skin occurs early in photoageing in people with lightly pigmented skin; a process of accelerated skin ageing that arises due to chronic sun exposure. Accumulation of ultraviolet radiation (UVR)-induced damage, either by the action of enzymes, oxidation or direct photon absorption, results in FRM remodelling and changes to ultrastructure. In the current study, the direct effect of UVR exposure on FRM ultrastructure was assayed by isolating FRMs from the papillary and reticular dermis of photoprotected buttock skin of individuals of either black African or white Northern European ancestry and exposing them to solar-simulated radiation (SSR). Exposure to SSR resulted in significant reduction in inter-bead periodicity for reticular dermis-derived FRMs across both cohorts. In contrast, papillary dermal FRMs exhibited significantly increased inter-bead periodicity, with the magnitude of damage greater for African FRMs, as compared to Northern European FRMs. Our data suggest that FRMs of the dermis should be considered as two distinct populations that differentially accrue damage in response to SSR. Furthermore, papillary dermal FRMs derived from black African subjects show greater change following UVR challenge, when extracted from skin. Future studies should focus on understanding the consequences of UVR exposure in vivo, regardless of skin ethnicity, on the molecular composition of FRMs and how this UVR-induced remodelling may affect the role FRMs play in skin homeostasis.

The systemic influence of chronic smoking on skin structure and mechanical function.

One of the major functions of human skin is to provide protection from the environment. Although we cannot entirely avoid, for example, sun exposure, it is likely that exposure to other environmental factors could affect cutaneous function. A number of studies have identified smoking as one such factor that leads to both facial wrinkle formation and a decline in skin function. In addition to the direct physical effects of tobacco smoke on skin, its inhalation has additional profound systemic effects for the smoker. The adverse effects on the respiratory and cardiovascular systems from smoking are well known. Central to the pathological changes associated with smoking is the elastic fibre, a key component of the extracellular matrices of lungs. In this study we examined the systemic effect of chronic smoking (>40 cigarettes/day; >5 years) on the histology of the cutaneous elastic fibre system, the nanostructure and mechanics of one of its key components, the fibrillin-rich microfibril, and the micromechanical stiffness of the dermis and epidermis. We show that photoprotected skin of chronic smokers exhibits significant remodelling of the elastic fibre network (both elastin and fibrillin-rich microfibrils) as compared to the skin of age- and sex-matched non-smokers. This remodelling is not associated with increased gelatinase activity (as identified by in situ zymography). Histological remodelling is accompanied by significant ultrastructural changes to extracted fibrillin-rich microfibrils. Finally, using scanning acoustic microscopy, we demonstrated that chronic smoking significantly increases the stiffness of both the dermis and the epidermis. Taken together, these data suggest an unappreciated systemic effect of chronic inhalation of tobacco smoke on the cutaneous elastic fibre network. Such changes may in part underlie the skin wrinkling and loss of skin elasticity associated with smoking. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Fractional Sunburn Threshold UVR Doses Generate Equivalent Vitamin D and DNA Damage in Skin Types I-VI but with Epidermal DNA Damage Gradient Correlated to Skin Darkness.

Public health guidance recommends limiting sun exposure to sub-sunburn levels, but it is unknown whether these can gain vitamin D (for musculoskeletal health) while avoiding epidermal DNA damage (initiates skin cancer). Well-characterized healthy humans of all skin types (I-VI, lightest to darkest skin) were exposed to a low-dose series of solar simulated UVR of 20%-80% their individual sunburn threshold dose (minimal erythema dose). Significant UVR dose responses were seen for serum 25-hydroxyvitamin D and whole epidermal cyclobutane pyrimidine dimers (CPDs), with as little as 0.2 minimal erythema dose concurrently producing 25-hydroxyvitamin D and CPD. Fractional MEDs generated equivalent levels of whole epidermal CPD and 25-hydroxyvitamin D across all skin types. Crucially, we showed an epidermal gradient of CPD formation strongly correlated with skin darkness (r = 0.74, P < 0.0001), which reflected melanin content and showed increasing protection across the skin types, ranging from darkest skin, where high CPD levels occurred superficially, with none in the germinative basal layer, to lightest skin, where CPD levels were induced evenly across the epidermal depth. People with darker skin can be encouraged to use sub-sunburn UVR-exposure to enhance their vitamin D. In people with lighter skin, basal cell damage occurs concurrent with vitamin D synthesis at exquisitely low UVR levels, providing an explanation for their high skin cancer incidence; greater caution is required.