Ultraviolet B radiation suppresses Langerhans cell migration in the dermis by down-regulation of alpha4 integrin

Integrin α5 regulates motility of human monocyte-derived Langerhans cells during immune response

Langerhans cells (LCs) are mainly present in the epidermis and mucosa, and have important roles during skin infection. Migration of LCs to lymph nodes is essential for antigen presentation. However, due to the difficulties in isolating and culturing human LCs, it is not fully understood how LCs move and interact with the extracellular matrix (ECM) through their adhesion molecules such as integrin, during the immune responses. In this study, we aimed to investigate LC motility, cell shape and the role of integrin under inflammatory conditions using monocyte-derived Langerhans cells (moLCs) as a model. As a result, lipopolysaccharide (LPS) stimulation increased adhesion on fibronectin coated substrate and integrin α5 expression in moLCs. Time-lapse imaging of moLCs revealed that stimulation with LPS elongated cell shape, whilst decreasing their motility. Additionally, this decrease in motility was not observed when pre-treated with a neutralising antibody targeting integrin α5. Together, our data suggested that activation of LCs decreases their motility by promoting integrin α5 expression to enhance their affinity to the fibronectin, which may contribute to their migration during inflammation.

The Prospects of Swietenia macrophylla King in Skin Care

The importance of cosmetics in our lives is immeasurable. Covering items from daily personal hygienic products to skincare, it has become essential to consumers that the items that they use are safe and effective. Since natural products are from natural sources, and therefore considered “natural” and “green” in the public’s eyes, the rise in demand for such products is not surprising. Even so, factoring in the need to remain on trend and innovative, cosmetic companies are on a constant search for new ingredients and inventive new formulations. Based on numerous literature, the seed of Swietenia macrophylla has been shown to possess several potential “cosmetic-worthy” bioproperties, such as skin whitening, photoprotective, antioxidant, antimicrobial, etc. These properties are vital in the cosmetic business, as they ultimately contribute to the “ageless” beauty that many consumers yearn for. Therefore, with further refinement and research, these active phytocompounds may be a great contribution to the cosmetic field in the near future.

The Role of the Immune System in Cutaneous Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer. In immunosuppressed populations it is a source of considerable morbidity and mortality due to its enhanced recurrence and metastatic potential. In common with many malignancies, leucocyte populations are both protective against cancer development and also play a role in 'sculpting' the nascent tumor, leading to loss of immunogenicity and tumor progression. UV radiation and chronic viral carriage may represent unique risk factors for cSCC development, and the immune system plays a key role in modulating the response to both. In this review, we discuss the lessons learned from animal and ex vivo human studies of the role of individual leucocyte subpopulations in the development of cutaneous SCC. We then discuss the insights into cSCC immunity gleaned from studies in humans, particularly in populations receiving pharmacological immunosuppression such as transplant recipients. Similar insights in other malignancies have led to exciting and novel immune therapies, which are beginning to emerge into the cSCC clinical arena.

From Early Immunomodulatory Triggers to Immunosuppressive Outcome: Therapeutic Implications of the Complex Interplay Between the Wavebands of Sunlight and the Skin

Phototherapy is an efficient treatment for many cutaneous diseases that involve the activation of inflammatory pathways or the overgrowth of cells with aberrant phenotype. In this review, we discuss recent advances in photoimmunology, focusing on the effects of UV-based therapies currently used in dermatology. We describe the molecular responses to the main forms of photo(chemo)therapy such as UVB, UVA-1, and PUVA that include the triggering of apoptotic or immunosuppressive pathways and help to clear diseased skin. The early molecular response to UV involves DNA photoproducts, the isomerization of urocanic acid, the secretion of biophospholipids such as platelet activating factor (PAF), the activation of aryl hydrocarbon receptor and inflammasome, and vitamin D synthesis. The simultaneous and complex interaction of these events regulates the activity of the immune system both locally and systemically, resulting in apoptosis of neoplastic and/or benign cells, reduction of cellular infiltrate, and regulation of cytokines and chemokines. Regulatory T-cells and Langerhans cells, among other skin-resident cellular populations, are deeply affected by UV exposure and are therefore important players in the mechanisms of immunomodulation and the therapeutic value of UV in all its forms. We weigh the contribution of these cells to the therapeutic application of UV and how they may participate in transferring the direct impact of UV on the skin into local and systemic immunomodulation. Moreover, we review the therapeutic mechanisms revealed by clinical and laboratory animal investigations in the most common cutaneous diseases treated with phototherapy such as psoriasis, atopic dermatitis, vitiligo, and cutaneous T-cell lymphoma. Better understanding of phototherapeutic mechanisms in these diseases will help advance treatment in general and make future therapeutic strategies more precise, targeted, personalized, safe, and efficient.

Human skin explants an in vitro approach for assessing UVB induced damage

Lifestyle changes involving frequent outdoor activities are contributing to higher exposure to harmful ultraviolet light (UVB). The acute effects of UVB irradiation on human skin was evaluated in this study using freshly excised human skin from elective surgery subjected to UVB doses (0-3.76 J/cm²). The assessment of UVB induced cellular and skin damages was undertaken at two time points immediately and 24 h post exposure using in vitro, and immunohistochemical staining techniques. The results indicated no significant loss of skin integrity or significant acute mitochondrial cellular damages in UVB exposed skin sections as measured by the MTS cytotoxicity assay. The other key markers of damage showed significant extracellular LDH membrane leakages and upregulation of inflammatory cytokines such as IL-1β. Skin integrity analysis was also undertaken using H&E, HLADR, and anti-cytokeratin antibodies. The results showed significant epidermal changes, basal cell activation and Langerhans cells depletion. The research proved the usefulness of freshly excised human skin explant model in measuring UVB damage. Furthermore, freshly excised human skin maintains the natural layering and therefore does not pose the same challenges faced by commercially available reconstructed skin in terms of higher costs and accurate mimicking of all the complex interactions observed in human skin.

Disruption of circulating CD4+ T-lymphocyte subpopulations in psoriasis patients is ameliorated by narrow-band UVB therapy

Narrow-band UVB (NB-UVB) therapy is widely used in the treatment of psoriasis; however, its precise mechanism is still unclear. To investigate the circulating CD4(+) T-lymphocyte subpopulations in psoriasis patients before and after NB-UVB, thus providing new insights into the mechanism of NB-UVB in the treatment of psoriasis. We performed NB-UVB treatments for psoriasis patients (n = 30) and used flow cytometry, real-time PCR, and ELISA for the detection of circulating CD4(+) T-lymphocyte subpopulations. The results were compared with healthy controls (n = 20) as well. We found increased circulating T helper 1 (Th1) and Th17 cell levels as well as decreased circulating regulatory T cells (Treg) levels compared to healthy controls. Additionally, there was a positive correlation between the percentage of circulating Th17 cells and Psoriasis Area and Severity Index (PASI) score. Furthermore, the percentage of circulating Th17 cells was negatively correlated with the Treg cells which led to an imbalance of Th17/Treg. NB-UVB therapy significantly reduced circulating Th1and Th17 cell levels while increasing Treg cell levels. These findings indicate that the overexpression of Th1 and Th17 cells together with the imbalance of Th17/Treg cells may play an important role in the pathogenesis of psoriasis. The mechanism of NB-UVB in the treatment of psoriasis may be through the inhibition of Th1 and Th17 cell immune response as well as the promotion of Treg cell immune response, thus ameliorating the disorder of circulating CD4(+) T-lymphocyte subsets.

Grp1-associated scaffold protein regulates skin homeostasis after ultraviolet irradiation

Grp1-associated scaffold protein (Grasp), the product of a retinoic acid-induced gene in P19 embryonal carcinoma cells, is expressed primarily in brain, heart, and lung of the mouse. We report herein that Grasp transcripts are also found in mouse skin in which the Grasp gene is robustly induced following acute ultraviolet-B (UVB) exposure. Grasp(-/-) mice were found to exhibit delayed epidermal proliferation and a blunted apoptotic response after acute UVB exposure. Immunohistochemical analyses revealed that the nuclear residence time of the tumor suppressor protein p53 was reduced in Grasp(-/-) mice after UVB exposure. Taken together, our results suggest that a physiological role of Grasp may be to regulate skin homeostasis after UVB exposure, potentially by influencing p53-mediated apoptotic responses in skin.

Molecular Mechanisms of UV-Induced Apoptosis and Its Effects on Skin Residential Cells: The Implication in UV-Based Phototherapy

The human skin is an integral system that acts as a physical and immunological barrier to outside pathogens, toxicants, and harmful irradiations. Environmental ultraviolet rays (UV) from the sun might potentially play a more active role in regulating several important biological responses in the context of global warming. UV rays first encounter the uppermost epidermal keratinocytes causing apoptosis. The molecular mechanisms of UV-induced apoptosis of keratinocytes include direct DNA damage (intrinsic), clustering of death receptors on the cell surface (extrinsic), and generation of ROS. When apoptotic keratinocytes are processed by adjacent immature Langerhans cells (LCs), the inappropriately activated Langerhans cells could result in immunosuppression. Furthermore, UV can deplete LCs in the epidermis and impair their migratory capacity, leading to their accumulation in the dermis. Intriguingly, receptor activator of NF-κB (RANK) activation of LCs by UV can induce the pro-survival and anti-apoptotic signals due to the upregulation of Bcl-xL, leading to the generation of regulatory T cells. Meanwhile, a physiological dosage of UV can also enhance melanocyte survival and melanogenesis. Analogous to its effect in keratinocytes, a therapeutic dosage of UV can induce cell cycle arrest, activate antioxidant and DNA repair enzymes, and induce apoptosis through translocation of the Bcl-2 family proteins in melanocytes to ensure genomic integrity and survival of melanocytes. Furthermore, UV can elicit the synthesis of vitamin D, an important molecule in calcium homeostasis of various types of skin cells contributing to DNA repair and immunomodulation. Taken together, the above-mentioned effects of UV on apoptosis and its related biological effects such as proliferation inhibition, melanin synthesis, and immunomodulations on skin residential cells have provided an integrated biochemical and molecular biological basis for phototherapy that has been widely used in the treatment of many dermatological diseases.

Adhesive substrates modulate the activation and stimulatory capacity of non-obese diabetic mouse-derived dendritic cells

It is known that adsorbed adhesive proteins on implanted biomaterials modulate inflammatory responses; however, modulation of dendritic cell (DC) responses upon interaction with adhesive proteins has only begun to be characterized. DCs are specialized antigen-presenting cells that modulate both innate and adaptive immune responses. Previously we have shown that the activation and stimulatory capacity of DCs derived from C57BL6/j mice is differentially modulated by adhesive substrates. Here we extend our investigation of adhesive substrate modulation of DC responses to consider the case where the DCs had maturational defects associated with diabetes. Understanding the adhesive responses of DCs in diabetics is potentially important for immunotherapy and tissue engineering applications. In this work we use the non-obese diabetic (NOD) mouse, an established animal model for type 1 diabetes, to generate DCs (NOD-DCs). We demonstrate that NOD-DCs cultured on different adhesive substrates (collagen, fibrinogen, fibronectin, laminin, vitronectin, albumin and serum) respond with substrate-dependent modulation of the surface expression of the stimulatory molecule MHC-II and the co-stimulatory molecules CD80 and CD86 and production of the cytokines IL-12p40 and IL-10. Furthermore, the capacity of NOD-DCs to stimulate CD4(+) T-cell proliferation and cytokine production (IL-4 and IFN-γ) showed substrate-dependent modulation. Specifically, NOD-DCs cultured on vitronectin induced the highest IL-12p40 production, whereas collagen induced the highest IL-10 production. Dendritic cells cultured on collagen, fibrinogen and serum-coated substrates stimulated the highest CD4(+) T-cell proliferation. It was further determined that DCs cultured on vitronectin induced the highest percent population of IL-4-producing T-cells and DCs cultured on a fibronectin-coated substrate induced the highest expression of IFN-γ in T-cells. Pearson's correlation analysis revealed high correlations between T-cell proliferation and DC expression level of CD80 and T-cell production of IL-4 and DC production of IL-10. This demonstration of substrate-based control of NOD-DC activatory and stimulatory capacity, distinct from non-diabetic B6-DC responses, establishes the field of adhesive modulation of immune cell responses and informs the rational design of biomaterials for patients with type 1 diabetes.

Prevention of scattered light-induced asthenopia and fatigue by a polarized filter

BACKGROUND

It has been well documented that a long-time irradiation of the eye by a strong light elicits eyestrain and fatigue. To elucidate the mechanism for the induction of light-induced fatigue and asthenopia, changes in the mouse were analyzed after white light-irradiation to the eye.

METHODS

C57BL/6j male mice were irradiated with white light in a specially designed room equipped with four mirrors covering all areas of its four walls to elicit diffused reflected light, and changes in their plasma levels of cortisol, INF-gamma, interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) were analyzed.

RESULTS

Irradiation of mice with scattered white light significantly decreased the motional activity of animals, suggesting the occurrence of fatigue. Biochemical analysis and enzyme-immunoassay revealed that the irradiation of mice significantly elevated the plasma levels of cortisol, IFN-gamma, IL-10 and TGF-beta. All these changes were not observed with mice irradiated with the light in a similar room not equipped with mirrors. These changes were successfully inhibited by a polarized glass filter but not by a non-polarized filter with a similar absorbance.

CONCLUSIONS

These observations suggest that irradiation of the eye by scattered reflected light stimulated a stress response via hypothalamo-pituitary-adrenal axis to enhance the secretion of cortisol from the adrenal grand and increase the plasma levels of cytokines.

The modulation of dendritic cell integrin binding and activation by RGD-peptide density gradient substrates

Dendritic cells (DCs) are central regulators of the immune system that operate in both innate and adaptive branches of immunity. Activation of DC by numerous factors, such as danger signals, has been well established. However, modulation of DC functions through adhesion-based cues has only begun to be characterized. In this work, DCs were cultured on surfaces presenting a uniform gradient of the integrin-targeting RGD peptide generated using the recently established "universal gradient substrate for click biofunctionalization" methodology. Surface expression of activation markers (costimulatory molecule CD86 and stimulatory molecule MHC-II) and production of cytokines IL-10 and IL-12p40 of adherent DCs was quantified in situ. Additionally, bound alpha(V) integrin was quantified in situ using a biochemical crosslinking/extraction method. Our findings demonstrate that DCs upregulated CD86, MHC-II, IL-10, IL-12p40 and alpha(V) integrin binding as a function of RGD surface density, with production of IL-12p40 being the marker most sensitive to RGD surface density. Surface expression of activation markers demonstrated moderate correlation with alpha(V) integrin binding, while cytokine production was highly correlated with alpha(V) integrin binding. This work demonstrates the utility of the surface density gradient platform as a high-throughput method to investigate RGD density-dependent DC adhesive responses. Furthermore, this quantitative analysis of DC integrin-based activation represents a first of its type, helping to establish the field of adhesion-based modulation of DCs as a general mechanism that has previously not been defined, and informs the rational design of biomimetic biomaterials for immunomodulation.

Identification of genes responsive to solar simulated UV radiation in human monocyte-derived dendritic cells

Ultraviolet (UV) irradiation has profound effects on the skin and the systemic immune system. Several effects of UV radiation on Dendritic cells (DCs) functions have been described. However, gene expression changes induced by UV radiation in DCs have not been addressed before. In this report, we irradiated human monocyte-derived DCs with solar-simulated UVA/UVB and analyzed regulated genes on human whole genome arrays. Results were validated by RT-PCR and further analyzed by Gene Set Enrichment Analysis (GSEA). Solar-simulated UV radiation up-regulated expression of genes involved in cellular stress and inflammation, and down-regulated genes involved in chemotaxis, vesicular transport and RNA processing. Twenty four genes were selected for comparison by RT-PCR with similarly treated human primary keratinocytes and human melanocytes. Several genes involved in the regulation of the immune response were differentially regulated in UVA/UVB irradiated human monocyte-derived DCs, such as protein tyrosine phosphatase, receptor type E (PTPRE), thrombospondin-1 (THBS1), inducible costimulator ligand (ICOSL), galectins, Src-like adapter protein (SLA), IL-10 and CCR7. These results indicate that UV-exposure triggers the regulation of a complex gene repertoire involved in human-DC–mediated immune responses.

Adhesive substrate-modulation of adaptive immune responses

While it is well-known that adsorbed proteins on implanted biomaterials modulate inflammatory responses, modulation of dendritic cells (DCs) via adhesion-dependent signaling has only been begun to be characterized. In this work, we demonstrate that adhesive substrates elicit differential DC maturation and adaptive immune responses. We find that adhesive substrates support similar levels of DC adhesion and expression of stimulatory and co-stimulatory molecules. Conversely, DC morphology and differential production of pro- and anti-inflammatory cytokines (IL-12p40 and IL-10, respectively) is adhesive substrate-dependent. For example, DCs cultured on collagen and vitronectin substrates generate higher levels of IL-12p40, whereas DCs cultured on albumin and serum-coated tissue culture-treated substrates produce the higher levels of IL-10 compared to other substrates. Additionally, our results suggest substrate-dependent trends in DC-mediated allogeneic CD4(+) T-cell proliferation and T-helper cell type responses. Specifically, we show that substrate-dependent modulation of DC IL-12p40 cytokine production correlates with CD4(+) T-cell proliferation and T(h)1 type response in terms of IFN-gamma producing T-helper cells. Furthermore, our results suggest substrate-dependent trends in DC-mediated stimulation of IL-4 producing T-cells, but this T(h)2 type response is not dependent on DC production of IL-10 cytokine. This work has impact in the rational design of biomaterials for diverse applications such as tissue-engineered constructs, synthetic particle-based vaccines and the ex vivo culture of DCs for immunotherapies.

A critical role for the proapoptotic protein bid in ultraviolet-induced immune suppression and cutaneous apoptosis

Apoptosis plays an important role in eliminating UV-damaged keratinocytes, but its role in UV-induced immune suppression is not clear. Langerhans cells (LCs) may function as inducers of immune suppression. We have shown that LCs derived from mice deficient in the proapoptotic Bid (BH3-interacting death domain protein) gene (Bid KO) resist apoptosis and induce amplified immune responses. In this report, we examined responses in Bid KO mice to UVB exposure. Acute UV exposure led Bid KO mice to develop fewer apoptotic cells and retain a greater fraction of LCs in the epidermal layer of skin in comparison to wild-type mice. Bid KO mice were also markedly resistant to local and systemic UV tolerance induction to hapten sensitization and contact hypersensitivity responses. Elicitation responses and inflammation at skin sensitization sites in UV-treated Bid KO mice were equal to or greater than nonsuppressed control responses. In Bid KO mice, LCs accumulated in lymph nodes to greater numbers, demonstrated longer lifespans, and contained fewer DNA-damaged cells. These studies provide evidence that Bid activation is a critical upstream mediator in UV-induced keratinocyte and LC apoptosis and that its absence abrogates UV-induced immune tolerance.