Ultraviolet radiation-induced cytokines promote mast cell accumulation and matrix metalloproteinase production: potential role in cutaneous lupus erythematosus

Resident cutaneous memory T cells: a clinical review of their role in chronic inflammatory dermatoses and potential as therapeutic targets

Resident memory T cells (T-RMs) remain in epithelial barrier tissues after antigen exposure and the initial effector phase. These T-RMs provide effective antimicrobial and anticancer immunity; however, pathogenic T-RMs have been shown to mediate various chronic inflammatory disorders in a variety of tissue types. In the skin, T-RMs are referred to as resident cutaneous memory T cells (cT-RMs). Understanding the mechanisms leading to the development and establishment of these cT-RMs populations may allow for targeted treatments that provide durable responses in chronic immune-mediated skin diseases, even after cessation. In this review, we summarize the evidence on cT-RMs as drivers of chronic inflammatory dermatoses, including psoriasis, vitiligo, atopic dermatitis, cutaneous lupus erythematosus and alopecia areata, among others. Data from in vitro, animal model and ex vivo human studies are presented, with a focus on the potential for cT-RMs to trigger acute disease flares, as well as recurrent disease, by establishing an immune 'memory' in the skin. Furthermore, the available data on the potential for existing and novel treatments to affect the development or survival of cT-RMs in the skin are synthesized. The data suggest a dynamic and rapidly growing area in the field of dermatology; however, we also discuss areas in need of greater research to allow for optimal treatment selection for long-term disease control.

Counteracting Interleukin-15 to Elucidate Its Modes of Action in Physiology and Pathology

Interleukin (IL)-15 belongs to the common gamma-dependent cytokine family, along with IL-2, IL-4, IL-7, IL-9, and IL-21. IL-15 is crucial for the homeostasis of Natural Killer (NK) and memory CD8 T cells, and to fight against cancer progression. However, dysregulations of IL-15 expression could occur and participate in the emergence of autoimmune inflammatory diseases as well as hematological malignancies. It is therefore important to understand the different modes of action of IL-15 to decrease its harmful action in pathology without affecting its beneficial effects in the immune system. In this review, we present the different approaches used by researchers to inhibit the action of IL-15, from most broad to the most selective. Indeed, it appears that it is important to selectively target the mode of action of the cytokine rather than the cytokine itself as they are involved in numerous biological processes.

Recent advances in cutaneous lupus

Cutaneous lupus erythematosus (CLE) is an inflammatory and autoimmune skin condition that affects patients with systemic lupus erythematosus (SLE) and exists as an isolated entity without associated SLE. Flares of CLE, often triggered by exposure to ultraviolet (UV) light result in lost productivity and poor quality of life for patients and can be associated with trigger of systemic inflammation. In the past 10 years, the knowledge of CLE etiopathogenesis has grown, leading to promising targets for better therapies. Development of lesions likely begins in a pro-inflammatory epidermis, conditioned by excess type I interferon (IFN) production to undergo increased cell death and inflammatory cytokine production after UV light exposure. The reasons for this inflammatory predisposition are not well-understood, but may be an early event, as ANA + patients without criteria for autoimmune disease exhibit similar (although less robust) findings. Non-lesional skin of SLE patients also exhibits increased innate immune cell infiltration, conditioned by excess IFNs to release pro-inflammatory cytokines, and potentially increase activation of the adaptive immune system. Plasmacytoid dendritic cells are also found in non-lesional skin and may contribute to type I IFN production, although this finding is now being questioned by new data. Once the inflammatory cycle begins, lesional infiltration by numerous other cell populations ensues, including IFN-educated T cells. The heterogeneity amongst lesional CLE subtypes isn't fully understood, but B cells appear to discriminate discoid lupus erythematosus from other subtypes. Continued discovery will provide novel targets for additional therapeutic pursuits. This review will comprehensively discuss the contributions of tissue-specific and immune cell populations to the initiation and propagation of disease.

Modulation of Immune Cells as a Therapy for Cutaneous Lupus Erythematosus

Cutaneous lupus erythematosus (CLE) is an autoimmune disorder like systemic lupus erythematosus (SLE). Both SLE and CLE characterize autoantibody secretion and immune cell recruitment. In particular, CLE can be divided into three more frequent types, varying in the severity of the skin lesions they present. The role of type I IFN was shown to be one of the leading causes of the development of this pathology in the skin. Different treatments have been developed and tested against these different variants of CLE to decrease the increasing levels of CLE in humans. In this article, a literature revision discussing the similarities between SLE and CLE is carried out. In addition, new advances in understanding the development of CLE and the leading treatments being evaluated in animal models and clinical trials are reviewed.

Current concepts of photosensitivity in cutaneous lupus erythematosus

Cutaneous lupus erythematosus (CLE) represents a complex autoimmune disease with a broad phenotypic spectrum ranging from acute to chronic destructive cutaneous lesions. Patients with CLE exhibit high photosensitivity and ultraviolet (UV) irradiation can lead to systemic flares in systemic lupus erythematosus. However, the exact mechanisms how UV irradiation enhances cutaneous inflammation in lupus are not fully understood. Recently, new molecular mechanisms of UV-driven immune responses in CLE were identified, offering potential therapeutic approaches. Especially the induction of type I interferons, central cytokines in lupus pathogenesis which are released by various skin cells, have become the focus of current research. In this review, we describe current pathogenic concepts of photosensitivity in lupus erythematosus, including UV-driven activation of intracellular nucleic acid sensors, cellular cytokine production and immune cell activation. Furthermore, we discuss activated pathways contributing to enhanced apoptosis as well as intracellular translocation of autoantigens thereby promoting CLE upon UV light exposure.

A Systematic Review of Keratinocyte Secretions: A Regenerative Perspective

Cell regenerative therapy is a modern solution for difficult-to-heal wounds. Keratinocytes, the most common cell type in the skin, are difficult to obtain without the creation of another wound. Stem cell differentiation towards keratinocytes is a challenging process, and it is difficult to reproduce in chemically defined media. Nevertheless, a co-culture of keratinocytes with stem cells usually achieves efficient differentiation. This systematic review aims to identify the secretions of normal human keratinocytes reported in the literature and correlate them with the differentiation process. An online search revealed 338 references, of which 100 met the selection criteria. A total of 80 different keratinocyte secretions were reported, which can be grouped mainly into cytokines, growth factors, and antimicrobial peptides. The growth-factor group mostly affects stem cell differentiation into keratinocytes, especially epidermal growth factor and members of the transforming growth factor family. Nevertheless, the reported secretions reflected the nature of the involved studies, as most of them focused on keratinocyte interaction with inflammation. This review highlights the secretory function of keratinocytes, as well as the need for intense investigation to characterize these secretions and evaluate their regenerative capacities.

Bioinformatics analyses of gene expression profile identify key genes and functional pathways involved in cutaneous lupus erythematosus

BACKGROUND

Lupus erythematosus is an autoimmune disease that causes damage to multiple organs ranging from skin lesions to systemic manifestations. Cutaneous lupus erythematosus (CLE) is a common type of lupus erythematosus (LE), but its molecular mechanisms are currently unknown. The study aimed to explore changes in the gene expression profiles and identify key genes involved in CLE, hoping to uncover its molecular mechanism and identify new targets for CLE.

METHOD

We analyzed the microarray dataset (GSE109248) derived from the Gene Expression Omnibus (GEO) database, which was a transcriptome profiling of CLE cutaneous lesions. The differentially expressed genes (DEGs) were identified, and the functional annotation of DEGs was performed with Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Protein-protein interaction (PPI) network was also constructed to identify hub genes involved in CLE.

RESULT

A total of 755 up-regulated DEGs and 405 down-regulated DEGs were identified. GO enrichment analysis showed that defense response to virus, immune response, and type I interferon signaling pathway were the most significant enrichment items in DEGs. The KEGG pathway analysis identified 51 significant enrichment pathways, which mainly included systemic lupus erythematosus, osteoclast differentiation, cytokine-cytokine receptor interaction, and primary immunodeficiency. Based on the PPI network, the study identified the top 10 hub genes involved in CLE, which were CXCL10, CCR7, FPR3, PPARGC1A, MMP9, IRF7, IL2RG, SOCS1, ISG15, and GSTM3. By comparison between subtypes, the results showed that ACLE had the least DEGs, while CCLE showed the most gene and functional changes.

CONCLUSION

The identified hub genes and functional pathways found in this study may expand our understanding on the underlying pathogenesis of CLE and provide new insights into potential biomarkers or targets for the diagnosis and treatment of CLE. Key Points • The bioinformatics analysis based on CLE patients and healthy controls was performed and 1160 DEGs were identified • The 1160 DEGs were mainly enriched in biological processes related to immune responses, including innate immune response, type I interferon signaling pathway, interferon-γ-mediated signaling pathway, positive regulation of T cell proliferation, regulation of immune response, antigen processing, and presentation via MHC class Ib and so on • KEGG pathway enrichment analysis indicated that DEGs were mainly enriched in several immune-related diseases and virus infection, including systemic lupus erythematosus, primary immunodeficiency, herpes simplex infection, measles, influenza A, and so on • The hub genes such as CXCL10, IRF7, MMP9, CCR7, and SOCS1 may become new markers or targets for the diagnosis and treatment of CLE.

Mechanisms of Photosensitivity in Autoimmunity

Aberrant responses to UV light frequently lead to the formation of skin lesions and the activation of systemic inflammation in some autoimmune diseases, especially systemic lupus erythematosus. Whereas the effects of UV light on the skin have been studied for decades, only recently have some of the mechanisms that contribute to abnormal responses to UV light in patients with autoimmune diseases been uncovered. This review will discuss the biology of UV in the epidermis and discuss the abnormal epidermal and inflammatory mechanisms that contribute to photosensitivity. Further research is required to fully understand how to normalize UV-mediated inflammation in patients with autoimmune diseases.

Human and Murine Evidence for Mechanisms Driving Autoimmune Photosensitivity

Ultraviolet (UV) light is an important environmental trigger for systemic lupus erythematosus (SLE) patients, yet the mechanisms by which UV light impacts disease are not fully known. This review covers evidence in both human and murine systems for the impacts of UV light on DNA damage, apoptosis, autoantigen exposure, cytokine production, inflammatory cell recruitment, and systemic flare induction. In addition, the role of the circadian clock is discussed. Evidence is compared in healthy individuals and SLE patients as well as in wild-type and lupus-prone mice. Further research is needed into the effects of UV light on cutaneous and systemic immune responses to understand how to prevent UV-light mediated lupus flares.

Adipochemokines induced by ultraviolet irradiation contribute to impaired fat metabolism in subcutaneous fat cells

BACKGROUND

Adipose tissue is now appreciated as the pivotal regulator of metabolic and endocrine functions. Subcutaneous (SC) fat, in contrast to visceral fat, may protect against metabolic syndrome and systemic inflammation. We demonstrated that chronic as well as acute ultraviolet (UV) irradiation to the skin induces loss of underlying SC fat. UV-irradiated SC fat may produce chemokines or cytokines that modulate lipid homeostasis and secretion of adipokines.

OBJECTIVES

To elucidate UV-induced specific adipochemokines implicated in UV-induced modulation of SC fat.

METHODS

Primary cultured adipocytes were treated with conditioned medium from UV- or sham-irradiated skin cells. Young and older healthy participants provided SC fat from sun-exposed and sun-protected skin. Sun-protected skin from other participants was irradiated with UV. Differentially expressed adipochemokines were screened by cytokine array, and confirmed in vitro and in vivo. The functions of select adipochemokines involved in lipid metabolism were examined via short interfering RNA-mediated knockdown of cognate receptors.

RESULTS

Specific adipochemokines, including C-X-C motif chemokine (CXCL) family members such as CXCL5/ENA-78, and C-C motif chemokine (CCL) family members such as CCL20/MIP-3α and CCL5/RANTES, were greatly induced in SC fat by UV exposure. They could impair triglyceride synthesis via downregulation of lipogenic enzymes and sterol regulatory element-binding protein-1 through their respective cognate receptors, CXC chemokine receptor type (CXC-R)2, C-C chemokine receptor type (CCR)-6, and CCR-5. In addition, UV irradiation induced infiltration of adipose tissue macrophages responsible for the secretion of several chemokines into SC fat.

CONCLUSIONS

These UV-induced adipochemokines may be implicated in the reduction of lipogenesis in SC fat, leading to impairment of fat homeostasis and associated comorbidities such as obesity.

Ultraviolet radiation and skin mast cells: Effects, mechanisms and relevance for skin diseases

Mast cells (MCs) are well known as versatile effector cells in allergic reactions and several other immune responses. Skin MCs and cutaneous MC responses are subject to the effects of environmental factors including ultraviolet radiation (UVR). Numerous studies have assessed the effects of UVR on MCs, in vitro and in vivo. Interestingly, UVR seems to have variable effects on non-activated and activated mast cells. In general, UV therapy is beneficial in the treatment of urticaria and mastocytosis, but the effects are variable depending on treatment regimen and type of UVR. Here, we review and summarise key reports from the older and current literature on the crosstalk of UVR and skin MCs. Specifically, we present the literature and discuss published reports on the effects of UVR on skin MCs in rodents and humans. In addition, we review the role of MCs in UVR-driven skin diseases and the influence of UV light on MC-mediated skin diseases. This summary of our current understanding of the interplay of skin MCs and UVR may help to improve the management of patients with urticaria and other MC disorders, to identify current gaps of knowledge, and to guide further research.

Pathogenesis of cutaneous lupus erythema associated with and without systemic lupus erythema

Cutaneous lupus erythematosus (CLE) can be an individual disease only involving skin, or presents as part of the manifestations of SLE. A small proportion of CLE may progress into SLE, however, the underlying pathogenic mediators remain elusive. By only including researches that clearly described if the subtypes of CLE presented by enrolled subjects was associated with or without SLE, we provided an overview of antibodies, inflammatory cells and inflammatory molecular mediators identified in blood and skin that were possibly involved in lupus skin damages. IgG autoantibodies are crucial for the development of CLE associated with SLE, but the circulating inflammatory cells and molecular mediators require further studies to provide definitive proof for their association with skin damages. Discoid lupus erythematosus (DLE) is the most common subtype of CLE. For DLE without associated with SLE (CDLE), it is lack of evidences if autoantibodies and circulating inflammatory cells are involved in the pathogenesis or not, but is clear that the cutaneous inflammatory infiltrates are dominated by Th1, but not Th17 cells in contrast to the various complex profile in SLE. As the major target cells in skin, keratinocytes may participate the pathophysiological process by increase cell apoptosis and the production of proinflammatory cytokines in SLE and CDLE. Insights into the similarities and differences of the pathogenesis of CLE and CLE associated with SLE will also improve our therapeutic strategies for CLE that is currently adopted from SLE, and prevent the progression of CLE to SLE by providing interventions within an appropriate window of disease development.

Triolein reduces MMP-1 upregulation in dermal fibroblasts generated by ROS production in UVB-irradiated keratinocytes

BACKGROUND

Cytokine production and oxidative stress generated by ultraviolet radiation B (UVB) skin exposure are main factors of skin photoaging. Interleukin-6 (IL-6) produced by irradiated keratinocytes is proposed to have a role in metalloproteinases (MMPs) expression activation in dermal fibroblasts.

OBJECTIVES

We examined the effect of triolein treatment of UVB-irradiated keratinocytes on MMP1 (interstitial collagenase) expression response of dermal fibroblasts. We assayed UVB-irradiated keratinocytes soluble signals, mainly IL-6 and reactive oxygen species (ROS).

METHODS

IL-6 expression and ROS generation were assayed in UVB-irradiated keratinocytes. MMP1 mRNA expression response was assayed in fibroblasts grown in keratinocytes conditioned medium. We evaluated the effect of treating keratinocytes with triolein on IL-6 expression and ROS generation in keratinocytes, and MMP1 expression in fibroblasts.

RESULTS

The irradiation of epidermal cells with sublethal UVB doses increased IL-6 expression and ROS generation. Conditioned culture medium collected from keratinocytes was used to culture dermal fibroblasts. MMP1 mRNA expression increase was observed in fibroblasts cultured in medium collected from UVB-irradiated keratinocytes. Triolein treatment reduced the IL-6 expression and ROS generation in keratinocytes and this effect was reflected in downregulation of MMP1 expression in fibroblasts.

CONCLUSIONS

Triolein reduces both the expression of IL-6 and ROS generation in irradiated keratinocytes. It seems to exert an anti-inflammatory and anti-oxidative stress effect on irradiated keratinocytes that in turn reduces MMP1 expression in dermal fibroblasts. Collectively, these results indicate that triolein could act as a photoprotective agent.

TWEAK/Fn14 Signaling Involvement in the Pathogenesis of Cutaneous Disease in the MRL/lpr Model of Spontaneous Lupus

Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK, TNFSF12) and its sole receptor Fn14, belonging to the TNF ligand and receptor superfamilies respectively, are involved in cell survival and cytokine production. The role of TWEAK/Fn14 interactions in the pathogenesis of cutaneous lupus has not been explored. TWEAK treatment of murine PAM212 keratinocytes stimulated the secretion of RANTES via Fn14 and promoted apoptosis. Parthenolide, but not wortmanin or the MAPK inhibitor PD98059, significantly decreased production of RANTES, indicating that this effect of TWEAK is mediated via NF-κB signaling. UVB irradiation significantly upregulated the expression of Fn14 on keratinocytes in vitro and in vivo and increased RANTES production. MRL/lpr Fn14 knockout (KO) lupus mice were compared with MRL/lpr Fn14 wild-type (WT) mice to evaluate for any possible differences in the severity of cutaneous lesions and the presence of infiltrating immune cells. MRL/lpr Fn14 KO mice had markedly attenuated cutaneous disease as compared with their Fn14 WT littermates, as evidenced by the well-maintained architecture of the skin and significantly decreased skin infiltration of T cells and macrophages. Our data strongly implicate TWEAK/Fn14 signaling in the pathogenesis of the cutaneous manifestations in the MRL/lpr model of spontaneous lupus and suggest a possible target for therapeutic intervention.

[Mucocutaneous diseases and murine models with death of keratinocytes induced by lichenoid tissue reaction/interface dermatitis]

A set of histopathological elements with death of epidermal basal cell layer keratinocytes along with inflammatory cell infiltration distinguishes lichenoid tissue reaction (LTR)/interface dermatitis (IFD) from other inflammatory mucocutaneous diseases. The LTR/IFD can be seen in skin disorders like as lichen planus, acute graft-versus-host disease, lupus erythematosus, dermatomyositis, and toxic epidermal necrolysis/Stevesn-Johnson syndrome. Clinical and basic researches suggested that cytotoxic CD8 T cells producing interferon-γ and FasL are final effector cells to cause apoptosis of keratinocyte. Some murine models of LTR/IFD have been established, for example, LTR/IFD reactions of keratinocyte-specific ovalbumin (OVA)-transgenic mice after OVA-specific T-cell-receptor(+)CD8 T cells. By analysis of the murine model, a new class of immunosuppressant, a JAK inhibitor, has been suggested as a new candidate for treatment of LTR/IFD.

Mast cells as targets for immunotherapy of solid tumors

Mast cells have historically been studied mainly in the context of allergic disease. In recent years, we have come to understand the critical importance of mast cells in tissue remodeling events and their role as sentinel cells in the induction and development of effective immune responses to infection. Studies of the role of mast cells in tumor immunity are more limited. The pro-tumorigenic role of mast cells has been widely reported. However, mast cell infiltration predicts improved prognosis in some cancers, suggesting that their prognostic value may be dependent on other variables. Such factors may include the nature of local mast cell subsets and the various activation stimuli present within the tumor microenvironment. Experimental models have highlighted the importance of mast cells in orchestrating the anti-tumor events that follow immunotherapies that target innate immunity. Mast cells are long-lived tissue resident cells that are abundant around many solid tumors and are radiation resistant making them unique candidates for combined treatment modalities. This review will examine some of the key roles of mast cells in tumor immunity, with a focus on potential immunotherapeutic interventions that harness the sentinel role of mast cells.

Pharmacologically antagonizing the CXCR4-CXCL12 chemokine pathway with AMD3100 inhibits sunlight-induced skin cancer

One way sunlight causes skin cancer is by suppressing anti-tumor immunity. A major mechanism involves altering mast cell migration via the C-X-C motif chemokine receptor 4-C-X-C motif chemokine ligand 12 (CXCR4-CXCL12) chemokine pathway. We have discovered that pharmacologically blocking this pathway with the CXCR4 antagonist AMD3100 prevents both UV radiation-induced immune suppression and skin cancer. The majority of control mice receiving UV-only developed histopathologically confirmed squamous cell carcinomas. In contrast, skin tumor incidence and burden was significantly lower in AMD3100-treated mice. Perhaps most striking was that AMD3100 completely prevented the outgrowth of latent tumors that occurred once UV irradiation ceased. AMD3100 protection from UV immunosuppression and skin cancer was associated with reduced mast cell infiltration into the skin, draining lymph nodes, and the tumor itself. Thus a major target of CXCR4 antagonism was the mast cell. Our results indicate that interfering with UV-induced CXCL12 by antagonizing CXCR4 significantly inhibits skin tumor development by blocking UV-induced effects on mast cells. Hence, the CXCR4-CXCL12 chemokine pathway is a novel therapeutic target in the prevention of UV-induced skin cancer.

MLK3 is a direct target of biochanin A, which plays a role in solar UV-induced COX-2 expression in human keratinocytes

Solar UV (sUV) is an important environmental carcinogen. Recent studies have shown that sUV is associated with numerous human skin disorders, such as wrinkle formation and inflammation. In this study, we found that the isoflavone, biochanin A, inhibited the expression of sUV-induced COX-2, which is a well-characterized sUV-induced enzyme, in both human HaCaT keratinocytes and JB6 P+ mouse skin epidermal cells. Several studies have demonstrated the beneficial effects of biochanin A. However, its direct molecular target is unknown. We found that biochanin A inhibited sUV-induced phosphorylation of MKK4/JNK/c-Jun and MKK3/6/p38/MSK1. Mixed-lineage kinase 3 (MLK3) is an upstream kinase of MKK4 and MKK3/6. Thus, we evaluated the effect of biochanin A on MLK3. We found that sUV-induced MLK3 phosphorylation was not affected, whereas MLK3 kinase activity was significantly suppressed by biochanin A. Furthermore, direct binding of biochanin A in the MLK3 ATP-binding pocket was detected using pull-down assays. Computer modeling supported our observation that MLK3 is a novel target of biochanin A. These results suggest that biochanin A exerts chemopreventive effects by suppressing sUV-induced COX-2 expression mediated through MLK3 inhibition.

Ultraviolet B irradiation of the mouse eye induces pigmentation of the skin more strongly than does stress loading, by increasing the levels of prohormone convertase 2 and α-melanocyte-stimulating hormone

BACKGROUND

In previous studies, we made the unexpected finding that in mice, ultraviolet (UV)B irradiation of the eye increased the concentration of α-melanocyte-stimulating hormone (α-MSH) in plasma, and systemically stimulated epidermal melanocytes.

AIMS

To compare the extent of the pigmentation induced by social and restraint stress (which activate the hippocampus-pituitary system) with that induced by UVB irradiation.

METHODS

DBA/2 and sham-operated or hypophysectomized DBA/2 mice were subjected to local UVB exposure using a sunlamp directed at the eye, and two types of stress (social and restraint) were imposed.

RESULTS

UVB irradiation of the eye or exposure to stress loading both increased the number of Dopa-positive melanocytes in the epidermis, and hypophysectomy strongly inhibited the UVB-induced and stress-induced stimulation of melanocytes. Irradiation of the eye caused a much greater increase in dopamine than did the stress load. Both UVB eye irradiation and stress increased the blood levels of α-MSH and adrenocorticotropic hormone (ACTH). In addition, the increase in plasma α-MSH was greater in animals subjected to UVB eye irradiation than in those subjected to stress loading, whereas the reverse occurred for plasma ACTH. UVB irradiation to the eye and stress loading increased the expression of prohormone convertase (PC)1/3 and PC2 in the pituitary gland. The increase in expression of pituitary PC2 was greater in animals subjected to UVB eye irradiation than to stress, whereas no difference was seen between the two groups for the increase in PC1/3.

CONCLUSIONS

UVB eye irradiation exerts a stronger effect on pigmentation than stress loading, and is related to increased levels of α-MSH and PC2.

Phototherapeutic hardening modulates systemic cytokine levels in patients with polymorphic light eruption

The etiopathogenesis of polymorphic light eruption (PLE) has been linked to impaired UV-immunosuppression, Langerhans cell (LC) retention, and an absence of neutrophil infiltration into UV-exposed PLE skin. We have previously shown that photohardening restores the impaired neutrophil responsiveness to the chemoattractants leucotriene B4 and formyl-methionyl-leucyl-phenylalanin in PLE patients. The aim of this study was to investigate whether photohardening modulates baseline chemokine and cytokine levels which would alter chemoresponsiveness and hence immune function in PLE patients. Sixteen PLE patients received photohardening therapy for 4-9 weeks by 311 nm UVB. Plasma samples were taken both before and within 48 h of the penultimate phototherapeutic exposure. Plasma from these 16 patients, 8 non-irradiated PLE patients, and 14 control subjects was analyzed for IL-1β, CXCL8 (IL-8), IL-10, IL-17, TNF, CCL2 (MCP-1), CCL5 (RANTES), CCL11 (eotaxin), and CCL22 (MDC). These cytokines and chemokines were measured in early spring (March to April) and again in late spring (April to June). PLE patients had a significantly elevated level of CCL11 (p = 0.003) and IL-1β (p = 0.002) in early spring (before phototherapy). In late spring, after phototherapy, PLE patients had significantly elevated CCL2 (p = 0.002) and TNF (p = 0.002) but a trend for lowered plasma levels of CXCL8 (p = 0.021). When comparing the cytokine shifts from early to late spring, while healthy controls and non-UV-irradiated PLE patients showed an increase, PLE patients undergoing photohardening exhibited a trend for decrease in IL-1β (p = 0.012). Taken together, our results indicate that photohardening may alter the complex cytokine milieu in PLE, in particular via IL-1β, helping to normalise the pathophysiologic response to subsequent UV exposure.

Histological study on the effect of electrolyzed reduced water-bathing on UVB radiation-induced skin injury in hairless mice

Electrolyzed reduced water (ERW), functional water, has various beneficial effects via antioxidant mechanism in vivo and in vitro. However there is no study about beneficial effects of ERW bathing. This study aimed to determine the effect of ERW bathing on the UVB-induced skin injury in hairless mice. For this purpose, mice were irradiated with UVB to cause skin injury, followed by individually taken a bath in ERW (ERW-bathing) and tap water (TW-bathing) for 21 d. We examined cytokines profile in acute period, and histological and ultrastructural observation of skin in chronic period. We found that UVB-mediated skin injury of ERW-bathing group was significantly low compared to TW control group in the early stage of experiment. Consistently, epidermal thickening as well as the number of dermal mast cell was significantly lowered in ERW-bathing group. Defection of corneocytes under the scanning electron microscope was less observed in ERW-bathing group than in TW-bathing group. Further, the level of interleukin (IL)-1β, tumor necrosis factor (TNF)-α and IL-12p70 in ERW group decreased whereas those of IL-10 increased. Collectively, our data indicate that ERW-bathing significantly reduces UVB-induced skin damage through influencing pro-/anti-inflammatory cytokine balance in hairless mice. This suggests that ERW-bathing has a positive effect on acute UVB-mediated skin disorders. This is the first report on bathing effects of ERW in UVB-induced skin injury.

Dermal mast cells affect the development of sunlight-induced skin tumours

Ultraviolet (UV) radiation contained in sunlight is considered a major risk in the induction of skin cancer. While mast cells are best known for their role in allergic responses, they have also been shown to play a crucial role in suppressing the anti-tumour immune response following UV exposure. Evidence is now emerging that UV may also trigger mast cell release of cutaneous tissue remodelling and pro-angiogenic factors. In this review, we will focus on the cellular and molecular mechanisms by which UV recruits and then activates mast cells to initiate and promote skin cancer development.

The consequences of UV-induced immunosuppression for human health

Exposure to UV radiation can cause suppression of specific immune responses. The pathways leading to the down-regulation are complex, starting from the absorption of UV photons by chromophores in the skin and ending with local and systemic changes in immune mediators, the generation of T and B regulatory cells and inhibition of effector and memory T cell activation. The consequences for human health are thought to be both beneficial and adverse. The former are illustrated by protection against polymorphic light eruption, and possible protection against T cell-mediated autoimmune diseases and asthma. The latter are illustrated by skin cancer, cutaneous lupus erythematosus and infectious diseases including vaccination. Many outstanding questions remain in this rapidly developing and controversial area, not least what advice to give the general public regarding their sun exposure. While considerable advances have been made in the development of strategies that preserve the health benefits of sunlight exposure and decrease its detrimental effects, further research is required before optimal levels of protection are achieved.