In Vitro Disease Models for Understanding Psoriasis and Atopic Dermatitis

Psoriasis (PS) and Atopic Dermatitis (AD) are two of the most prevalent inflammatory skin diseases. Dysregulations in the immune response are believed to play a crucial role in the pathogenesis of these conditions. Various parallels can be drawn between the two disorders, as they are both genetically mediated, and characterised by dry, scaly skin caused by abnormal proliferation of epidermal keratinocytes. The use of in vitro disease models has become an increasingly popular method to study PS and AD due to the high reproducibility and accuracy in recapitulating the pathogenesis of these conditions. However, due to the extensive range of in vitro models available and the majority of these being at early stages of production, areas of development are needed. This review summarises the key features of PS and AD, the different types of in vitro models available to study their pathophysiology and evaluating their efficacy in addition to discussing future research opportunities.

Expression Pattern and Immunoregulatory Roles of Galectin-1 and Galectin-3 in Atopic Dermatitis and Psoriasis

The pathogenesis of atopic dermatitis (AD) and psoriasis (Ps) overlaps, particularly the activation of the immune response and tissue damage. Here, we evaluated galectin (Gal)-1 and Gal-3 levels, which are beta-galactoside-binding proteins with immunomodulatory functions and examined their effects on human keratinocytes stimulated with either interleukin (IL)-4 or IL-17A. Skin biopsies from AD, Ps, and control patients were evaluated using histological and immunohistochemical analyses. Six studies containing publicly available transcriptome data were individually analyzed using the GEO2R tool to detect Gal-1 and Gal-3 mRNA levels. In vitro, IL-4- or IL-17A-stimulated keratinocytes were treated with or without Gal-1 or Gal-3 to evaluate cytokine release and migration. Our findings showed different patterns of expression for Gal-1 and Gal-3 in AD and Ps skins. Densitometric analysis in skin samples showed a marked increase in the protein Gal-1 levels in Ps epidermis and in both AD and Ps dermis compared to controls. Protein and mRNA Gal-3 levels were downregulated in AD and Ps lesional skin compared with the control samples. In vitro, both galectins addition abrogated the release of IL-8 and RANTES in IL-17-stimulated keratinocytes after 24 h, whereas IL-6 release was downregulated by Gal-3 and Gal-1 in IL-4- and IL-17-stimulated cells, respectively. Administration of both galectins also increased the rate of keratinocyte migration under IL-4 or IL-17 stimulation conditions compared with untreated cells. Altogether, the immunoregulatory and migration effects of Gal-1 and Gal-3 on keratinocytes under inflammatory microenvironment make them interesting targets for future therapies in cutaneous diseases.

Bellis perennis extract mitigates UVA-induced keratinocyte damage: Photoprotective and immunomodulatory effects

A need exists for further research elucidating the benefits of environmentally safe photoprotective agents against ultraviolet (UV) exposure, and plant extracts represent a human-friendly alternative formulation. This study was designed to evaluate the potential use of Bellis perennis extract (BPE), from the Asteraceae family, known as the common daisy or the English daisy, in cosmeceuticals as a photoprotective factor, using an in vitro model of UVA-induced keratinocyte damage. Human skin keratinocytes (HaCaT cell line) were incubated with BPE at 0.01, 0.1, or 1% in Dulbecco's Modified Eagle Medium (DMEM), and after 15 min they were submitted to UVA radiation at 5, 10, and 15 J/cm² doses, respectively. For comparative purposes, Polypodium leucotomos extract (PLE), known as the fern, was used as a positive control in assessing the photoprotective effect. After 24 h of UVA exposure, cell viability (MTT and LDH assays), levels of cleaved caspase-3, cyclooxygenase-2, IL-6, reactive oxygen species (ROS) and antioxidant enzyme (catalase, SOD, and glutathione peroxidase) activity were determined. UVA radiation at 5, 10, and 15 J/cm² doses reduced cell viability to 63%, 43%, and 23%, respectively; we selected 10 J/cm² for our purposes. After 24 h of UVA exposure, treatment with 1% BPE and 1% PLE significantly recovered cell viability (p < 0.05). Furthermore, treatment was associated with lower cleaved caspase-3 and ROS levels, higher catalase activity, and lower IL-6 levels in the treated UVA keratinocytes compared with the untreated UVA group (p < 0.01). Our results demonstrate photoprotective and immunomodulatory effects of BPE in skin keratinocytes and support its use as a bioactive agent in cosmetic formulations to prevent skin damage caused by exposure to the UV light.

The Role of Galectin-9 as Mediator of Atopic Dermatitis: Effect on Keratinocytes

Galectin-9 (Gal-9) is a beta-galactoside-binding protein with a variety of biological functions related to immune response. However, in allergic diseases, its mechanism of action is not fully understood. This study evaluates the expression pattern of Gal-9 in patients with atopic dermatitis (AD), in ovalbumin (OVA)-induced experimental atopic dermatitis (AD) in mice, as well as its effect on human keratinocytes. The skin of OVA-immunized BALB/c mice was challenged with drops containing OVA on days 11, 14-18, and 21-24. HaCaT cells were cultured in the following experimental conditions: control (growth medium only) or stimulated with TNF-α/IFN-γ, or IL-4, or IL-17 with or without Gal-9 treatment. AD was characterized by increased levels of Gal-9 in mouse and human skin, especially in the epidermis, and with a marked influx of Gal-9 positive eosinophils and mast cells compared to the control group. Gal-9 showed an immunomodulatory effect on keratinocytes by decreasing the release of IL-6 by IL-4-stimulated keratinocytes or increasing the IL-6 and RANTES levels by IL-17- or TNF-α/IFN-γ-stimulated cells, respectively. Under IL-17, Gal-9 treatment also altered the proliferation rate of cells. Overall, increased levels of Gal-9 in AD skin contribute to the control of inflammatory response and the proliferative process of keratinocytes, suggesting this lectin as a relevant therapeutic target.

Changes in the total ozone content over the period 2006 to 2100 and the effects on the erythemal and vitamin D effective UV doses for South America and Antarctica

Recent studies show that the ozone layer will recover by the middle part of this century. This is a significant result arising from the Montreal Protocol, and highlights the success of this environmental protection agreement. Climate change projections show that Total Ozone Content (TOC) levels will increase significantly by the end of this century, mainly at higher latitudes. This increase may result in a reduction of the adverse effects of UV radiation overexposure. By contrast, reduced UV radiation levels at the surface of the Earth can result in reduced levels of vitamin D synthesis among the inhabitants of these regions. In this study we provide estimates for the UVI, erythemal, and vitamin-D weighted daily doses for ten different locations in South America and Antarctica. Our calculations were based on ozone projections provided by climate models set forth in the last IPCC report. Results show that the increase of TOC levels in middle and high latitude regions may result in decreased UVI and UV doses throughout the century. In high latitudes, erythemal doses and vitamin D synthesis doses may be reduced by up to 22 and 39%, respectively, if anthropogenic emissions continue to rise throughout the century. Furthermore, there may be reductions of up to 9 and 12%, respectively, in mid-latitudes (20°S to 35°S). Significant variations at Equatorial sites were not observed. In most of South America, the attenuation in UVR caused by increases in TOC during the 21^st century is neither enough to promote protective effects from this radiation, nor for the lack of UVR for vitamin D synthesis. The incidence of UVR in tropical and sub-tropical areas of the continent will continue to be a public health risk for the entire 21^st century during all seasons, regardless of the climatic scenarios. Our results can be used as an important tool for health studies focusing on the excess and/or lack of sun exposure.

An overview of the ultraviolet index and the skin cancer cases in Brazil

This study relates regional and seasonal UV index (UVI) variations, number of skin cancer cases and population skin-color distribution in Brazil. UVI calculations were performed using the UV Global Atmospheric Model (UVGAME), whose characteristics and validations are provided in thiis article. Health and racial data sets are based on the health and census data collected by Brazilian governmental agencies in the past. The discussion covers cultural customs and details of health and educational campaigns in Brazil. Despite lower UV levels in the South and Southeast regions, the results show a number of nonmelanoma skin cancer (NMSC) cases regions, where the white population is predominant. In general, in the southern regions about 50 new NMSC cases per 100000 inhabitants have been diagnosed each year. These rates decrease almost 40% in the Central-North regions and more than 80% in Northeast region, where miscegenation is common. In addition, the UVI evaluation is extended to other South American sites with singular characteristics, e.g. populous cities located in high altitudes or those affected by the Antarctic ozone hole in the extreme south of the continent.