UVB IRRADIATION SUPPRESSES CYTOKINE PRODUCTION AND INNATE CELLULAR IMMUNE FUNCTIONS IN MICE

Effect of immunosuppression by UV-B radiation on components of the innate immune response in skin lesions with Leishmania mexicana: Effect of UVB on the innate immune response in cutaneous infection by L. mexicana

Cutaneous leishmaniasis is the most common form of leishmaniasis in humans, factors such as poverty, poor housing, inadequate domestic hygiene, malnutrition, mobility, and occupational exposure are risk factors associated with the condition, however, there are few studies focused on determining the immune mechanism involved in the resolution of cutaneous leishmaniasis caused by the species Leishmania mexicana, as well as possible environmental factors such as solar radiation, which could contribute to its establishment. through mechanisms immunosuppressants, of which to date is unknown. In this study, the effect of UV-B light was evaluated as a risk factor affecting components of the innate immune response 3 days after infection with L. mexicana. A delayed-type hypersensitivity reaction (DTH) was used to evaluate immunosuppression induced by UV-B light. Through a histological analysis, the skin lesions of the mice (Hematoxylin & Eosin) were evaluated, the presence of mast cells and their level of degranulation (toluidine blue staining), the presence of IL-10⁺ and MOMA2⁺ cells were analyzed by immunohistochemistry and finally, the cytokine profile was evaluated by qPCR in the skin lesions tissue. An alteration in the architecture of the tissue was observed, as well as a greater number of mast cells, both complete and degranulated, as well as an increase in IL-10⁺ and MOMA2⁺ cells in the skin lesions of the mice that were irradiated and subsequently infected, when compared with the lesions of infected mice (P> 0.0001), immunomodulation was also observed in the profile of cytokines expressed between both groups analyzed. This is the first study to demonstrate the effects of UV-B radiation on components of the innate immune response at short times of infection by L. mexicana.

Narrow-band phototherapy in the treatment of atopic dermatitis: mechanisms of action, methodology of implementation

Phototherapy is widely used to treat various chronic skin diseases. One of the most effective methods of treatment is narrow-band medium-wave ultraviolet radiation with a wavelength of 311 nm (UVB-311). UVB-311 is used for such immune-mediated diseases as atopic dermatitis, psoriasis, vitiligo, mycosis fungoides and others. Despite the fact that the method was developed more than 30 years ago, the exact mechanism of its therapeutic action remains insufficiently studied. To date, most of the effects of UVB-311 are explained by its effect on the immune cells of the skin. This review examines data on the effects on the main molecular targets, including T-lymphocytes, keratinocytes, Langerhans cells, cytokine profile, epidermal barrier proteins. Data on the features of the pathogenetic effect of UVB-311 on the immune mechanisms of pathogenesis in atopic dermatitis were obtained. The issues of dosing by determining the minimum erythemic dose (MED) or skin phototype, methodology of procedures are discussed. Prospects for further study of photobiological aspects of UVB-311 action are determined.

Advances in phototherapy for psoriasis and atopic dermatitis

Introduction: Phototherapy has long been used for the treatment of inflammatory skin diseases, such as psoriasis and atopic dermatitis. The most frequent treatment approach utilizes ultraviolet (UV) light, however, recently, different lasers and low-level light therapies (LLLT) emitting wavelengths in the spectrum of the visible light have also been tried for the treatment of inflammatory skin diseases with variable success.Areas covered: This review provides an update on the different forms of phototherapy used for the treatment of psoriasis and atopic dermatitis. The proposed mechanism of action of the different phototherapeutical approaches are covered, including the immunosuppressive effect of UV light, the anti-inflammatory effect of vascular lasers and the LLLT induced photobiomodulation. The clinical efficacy of the different treatment options is also discussed.Expert opinion: Based on the efficacy and safety, NB-UVB represents the gold standard for treating psoriasis and atopic dermatitis. The UVB excimer laser and excimer lamp might be the best option for clearing localized therapy-resistant lesions. Home UV phototherapy systems might promote treatment adherence and better compliance of the patients. Vascular lasers, IPLs and LLLT, however, can not currently be recommended for the treatment of inflammatory skin diseases because of the lack of well-controlled studies.

The acute effects of ultraviolet radiation on the blood transcriptome are independent of plasma 25OHD3

The molecular basis of many health outcomes attributed to solar ultraviolet radiation (UVR) is unknown. We tested the hypothesis that they may originate from transcriptional changes in blood cells. This was determined by assessing the effect of fluorescent solar simulated radiation (FSSR) on the transcriptional profile of peripheral blood pre- and 6h, 24h and 48h post-exposure in nine healthy volunteers. Expression of 20 genes was down-regulated and one was up-regulated at 6h after FSSR. All recovered to baseline expression at 24h or 48h. These genes have been associated with immune regulation, cancer and blood pressure; health effects attributed to vitamin D via solar UVR exposure. Plasma 25-hydroxyvitamin D₃ [25OHD₃] levels increased over time after FSSR and were maximal at 48h. The increase was more pronounced in participants with low basal 25OHD₃ levels. Mediation analyses suggested that changes in gene expression due to FSSR were independent of 25OHD₃ and blood cell subpopulations.

Silibinin inhibits ultraviolet B radiation-induced DNA-damage and apoptosis by enhancing interleukin-12 expression in JB6 cells and SKH-1 hairless mouse skin

Recent studies have demonstrated silibinin efficacy against ultraviolet B (UVB)-induced skin carcinogenesis via different mechanisms in cell lines and animal models; however, its role in regulating interleukin-12 (IL-12), an immunomodulatory cytokine that reduces UVB-induced DNA damage and apoptosis, is not known. Here, we report that UVB irradiation causes caspase 3 and PARP cleavage and apoptosis, and addition of recombinant IL-12 or silibinin immediately after UVB significantly protects UVB-induced apoptosis in JB6 cells. IL-12 antibody-mediated blocking of IL-12 activity compromised the protective effects of both IL-12 and silibinin. Both silibinin and IL-12 also accelerated the repair of UVB-caused cyclobutane-pyrimidine dimers (CPDs) in JB6 cells. Additional studies confirmed that indeed silibinin causes a significant increase in IL-12 levels in UVB-irradiated JB6 cells as well as in mouse skin epidermis, and that similar to cell-culture findings, silibinin topical application immediately after UVB exposure causes a strong protection against UVB-induced TUNEL positive cells in epidermis possibly through a significantly accelerated repair of UVB-caused CPDs. Together, these findings for the first time provide an important insight regarding the pharmacological mechanism wherein silibinin induces endogenous IL-12 in its efficacy against UVB-caused skin damages. In view of the fact that an enhanced endogenous IL-12 level could effectively remove UVB-caused DNA damage and associated skin cancer, our findings suggest that the use of silibinin in UVB-damaged human skin would also be a practical and translational strategy to manage solar radiation-caused skin damages as well as skin cancer.

Ultraviolet B irradiation selectively increases the production of interleukin-8 in human cord blood-derived mast cells

UVB irradiation modulates immune responses in the skin and is a major cause of sunburn, during which neutrophils accumulate in the skin. Because of their abundance in skin and ability to produce a variety of proinflammatory mediators, we propose that mast cells may play a key role in ultraviolet B (UVB)-induced skin inflammation. Cord blood-derived human mast cells were treated in vitro with varying doses of UVB and production of multiple cytokines was measured in culture supernatants. UVB exposure significantly increased the release of interleukin (IL)-8 and modestly increased IL-1alpha production, but cytokines such as IL-2, IL-4, IL-6, IL-10, IL-12, IL-13, tumour necrosis factor (TNF)-alpha and interferon (IFN)-gamma were unaffected. Cycloheximide reduced the UVB-mediated induction of IL-8 by 30-40%, suggesting that new protein synthesis contributed to IL-8 production. In line with this, UVB treatment of mast cells significantly increased IL-8 mRNA. In contrast to its effect on IL-8 production, optimal doses of UVB did not provoke histamine or tryptase release, indicating little effect on degranulation. Our data suggest that mast cells may play a major role during UVB-induced acute inflammation by selectively inducing cytokines involved in neutrophil recruitment.

Adaptation to the UV-induced suppression of phagocytic activity in murine peritoneal macrophages following chronic exposure to solar simulated radiation

Exposure of certain strains of mice to ultraviolet radiation (UVR) is known to suppress both local and systemic immune responses, including a reduction in the phagocytic activity of peritoneal macrophages. However, in many instances, the immunological effects have been observed following a single or a limited number of doses of UVR from sources containing a higher proportion of UVB than that emitted by the sun. The first aim of the present study was to establish whether a single exposure of C3H/HeN mice to solar simulated radiation (SSR) suppressed the ability of the peritoneal macrophages to phagocytose opsonised sheep red blood cells. The mice were irradiated with SSR from Cleo Natural lamps and a single dose of 31.9 J cm(-2) was found to be the minimal dose for significant suppression of macrophage phagocytic activity. Such a dose did not modulate the surface expression of I-A(k), CD11b, CD86 or FcgammaRII/III (CD32/16) on the macrophages. The second aim was to assess whether repeated SSR exposures with a dose below the minimal immunosuppressive dose affected macrophage activity and, if so, to test for photoadaptation by repeated exposures followed by a single, normally immunosuppressive dose of SSR, and then assaying the macrophage activity. Groups of mice were irradiated on each of 2, 10 and 30 days with 14.9 J cm(-2) SSR, followed in some instances by a single additional exposure of 31.9 J cm(-2) on the same day as the last irradiation. The phagocytic activity of the peritoneal macrophages was tested 24 h later. It was reduced by 32%, 18% and 4% respectively after 2, 10 and 30 repeated exposures to SSR, and by 39%, 21% and 7% respectively after 2, 10 and 30 repeated exposures plus the additional higher dose at the end. Thus, although the macrophage activity was initially suppressed by the SSR, photoadaptation of this immune parameter occurred following repeated exposures.

Immunotoxic effects of cis-urocanic acid exposure in C57BL/6N and C3H/HeN mice

Exposure to ultraviolet radiation results in increased levels of intradermal cis-urocanic acid (cUCA) and alters cutaneous immunity by interfering with processing and presentation of antigen by Langerhans cells. Reports on effects of systemic immunotoxicity with 30 day cUCA exposure in laboratory rodents include thymic atrophy, thymic hypocellularity and decreased T-cell-mediated immunity; however, immune effects of single exposure or 5 day cUCA administration, which may better mimic human exposures, are poorly defined. The present study initially evaluated immune effects of single, 5 day, and 4 week cUCA exposure in C57BL/6N mice. Single administration of intradermal cUCA resulted in decreased splenocyte phagocytosis that persisted for 30 days after cUCA exposure. Five day consecutive cUCA exposure decreased numbers of phenotypically mature CD4(+)CD8(-) and CD4(-)CD8(+) (single positive) thymocytes, increased CD4(+)CD8(+) (double positive) immature thymocytes and increased splenocyte proliferation. Prolonged cUCA exposure (4 weeks) caused profound thymic hypocellularity and splenic hypercellularity and increased splenic macrophage chemiluminescence. Because of this apparent sensitivity of C57BL/6N mice to cUCA, thymic hypocellularity was compared between C57BL/6N and C3H/HeN mice dosed with cUCA, and was found to be more pronounced in the C57BL/6N strain. These results are an extension of previous conclusions on immune modulation caused by cUCA in the spleen and thymus. Further, the observed variation in sensitivity between the mouse strains is consistent with known genetic susceptibility of these strains to the immunomodulatory effects of exposure to sunlight.

Dissociation of innate and adaptive immunity by UVB irradiation

Increasing ultraviolet-B irradiation (UVB) resulting from diminution of stratospheric ozone is becoming a serious international problem. UVB irradiation exerts not only carcinogenic effects on animals but also causes them to become vulnerable to infections by modulating their immune responses. UVB irradiation suppresses innate immune functions of cells such as macrophages, neutrophils, Langerhans cells, dendritic cells, and the serum component, complement. UVB irradiation also causes changes in cytokine profiles, represented by the induction of a paradigm switch involving Th1/Th2 phenotypes. According to earlier studies, Th1 responses are suppressed, whereas Th2 activities are augmented by UVB irradiation. These immune modulations are caused by several pathways via cytokines and neuropeptides, and eventually may lead to increasing incidences of infection, allergy, and cancer. We have reviewed reports concerning UVB-irradiation induced immune modulation from the viewpoint of risks for human diseases and, in addition, for ecosystems and immunity of lower animals.

Effects of diesel exhaust particle extracts on Th1 and Th2 immune responses in mice

The present study was undertaken to investigate the effects of extracts of diesel exhaust particles (DEP) on Th1 and Th2 immune responses. In order to separate compounds from DEP different in hydrophobicity, a single DEP sample was consecutively extracted with hexane (HEX-DEP), benzene (BEN-DEP), dichloromethane (DIC-DEP), methanol (MET-DEP), and 1M ammonia (AMM-DEP). The last unextracted residue (UNE-DEP) was also used to test its effect on immune responses. To immunize mice, hen egg lysozyme (HEL) was injected i.p. (day 0). Varying doses of DEP, each DEP extract, and UNE-DEP were intranasally administered every 2 days from days 0 to 18. Anti-HEL IgG2a antibodies in sera and IFN-γ secreted from spleen cells were measured as an indicator of Th1 immune responses, while anti-HEL IgG1 antibodies and IL-4 as that of Th2 responses. The results showed that treatment with DEP and DIC-DEP increased both Th1 and Th2 responses to HEL. UNE-DEP facilitated Th1 but not Th2 responses, while MET- and AMM-DEP administration was followed by enhancement of Th2 but not Th1 responses. Neither HEX- nor BEN-DEP modulated Th1 as well as Th2 responses. These results suggest that DEP contain various compounds different in hydrophobicity which may affect both Th1 and Th2, Th1 but not Th2, and Th2 but not Th1 immune responses.