Comparative immunotoxicology of ultraviolet B exposure I. Effects of in vitro and in situ ultraviolet B exposure on the functional activity and morphology of Langerhans cells in the skin of different species

Plaque-based sub-blistering dosimetry: Reaching PASI-75 after two treatments with 308-nm excimer laser in a generalized psoriasis patient

BACKGROUND

Generalized UVB phototherapy has been established as an effective and safe treatment for chronic plaque-type psoriasis for decades and in recent years, targeted 308-nm excimer laser has emerged as an equally safe and more effective treatment option. While traditional dosimetry for laser has been determined either through minimal erythema dose (MED) or a combination of the patient's Fitzpatrick skin type and the level of plaque induration, we have developed "Plaque-based Sub-blistering Dosimtery" based on observations that administering anywhere from 8 to 16 multiples of MED to psoriatic plaques has resulted in clearance after one treatment with longer remission rates than the traditional dosing protocol.

CASE REPORT

The authors describe a case in which a patient achieved PASI 75 following only two treatments with 308 nm excimer laser using this new protocol. Biopsies taken before and after treatment reveal a dramatic decrease in CD4+T cells as well as TNF-alpha- and IL-2-producing T cells.

CONCLUSION

This case demonstrates using a more aggressive dosing protocol determined by plaque testing is well-tolerated and can lead to excellent clearance with minimal side effects and comorbidity.

Effective narrow-band UVB radiation therapy suppresses the IL-23/IL-17 axis in normalized psoriasis plaques

Narrow-band UVB radiation (NB-UVB) therapy offers a well-established treatment modality for psoriasis. However, despite the common use of this form of treatment, the mechanism of action of NB-UVB is not well understood. We studied a group of 14 patients with moderate-to-severe psoriasis treated with carefully titrated and monitored NB-UVB for 6 weeks. Lesional plaques were classified as normalized (n=8) or nonresponsive (n=6) based on their histological improvement and normalization. We characterized lesional myeloid dendritic cells (DCs) and T cells and their inflammatory mediators using immunohistochemistry and real-time PCR. NB-UVB suppressed multiple parameters of the IL-23/IL-17 pathway in normalized plaques, but not in nonresponsive plaques. NB-UVB decreased the numbers of CD11c(+) DCs, specifically CD1c(-)CD11c(+) "inflammatory" DCs, and their products, IL-20, inducible nitric oxide synthase, IL-12/23p40, and IL-23p19. Furthermore, effective NB-UVB suppressed IL-17 and IL-22 mRNAs, which strongly correlated with lesion resolution. Therefore, in addition to its known role in suppressing IFN-γ production, NB-UVB radiation therapy can also target the IL-17 pathway to resolve psoriatic inflammation.JID JOURNAL CLUB ARTICLE: For questions, answers, and open discussion about this article, please go to http://www.nature.com/jid/journalclub.

Effects of narrowband UV-B on pharmacodynamic markers of response to therapy: an immunohistochemical study over sequential samples

BACKGROUND

To evaluate the effects of narrow-band UV-B (NBUVB) on the immunohistochemical markers of cellular and cytokine activation as well as of abnormal epidermal differentiation and proliferation--pharmacodynamic markers of response to therapy (PMT)--in psoriatic lesions.

METHODS

Clinical assessments and immunohistological staining of formalin-fixed paraffin sections of biopsies from psoriatic skin were done at baseline and at the end of the treatment period.

RESULTS

Ten patients with chronic plaque-type psoriasis were included. After treatment with NBUVB, the total number of CD3+, CD4+ and CD8+ T cells was reduced by an average of 86.6%, 86% and 85% in the epidermis and 70.3%, 70% and 62% in the dermis, respectively. Only the decrease in the number of epidermal CD4+ cells was statistically related with long-lasting remissions. The mean reduction in the expression of keratinocyte proliferation markers after NBUVB was 62%, 68% and 81% for Ki-67, cyclin A and cyclin B, respectively. Expression of suprabasal keratin 16 and filaggrin was almost normalized in most cases. All patients in whom expression of keratin16 remained after finishing UV-B therapy had an early relapse.

CONCLUSIONS

NBUVB is associated with changes in PMT close to those seen after remittive therapies. The normalization of immunohistochemical parameters of differentiation and the reduction/depletion in epidermal CD4+ cells was the most important markers of long-lasting remissions.

Sunburn Cell Formation, Dendritic Cell Migration, and Immunomodulatory Factor Production After Solar-Simulated Irradiation of Sunscreen-Treated Human Skin Explants In Vitro

Using human skin explants, we investigated the effects of two different sunscreen preparations containing a chemical UVB filter alone [sun protection factor (SPF) 5.2] or UVA+UVB filter [SPF 6.2] on sunburn cell formation, dendritic cell (DC) migration, CD86- and CD1a-positive cell number, and tumor necrosis factor alpha (TNFalpha) and interleukin (IL)-1, IL-10, and IL-12 production in the skin after irradiation with different doses of solar-simulated UV radiation. Sunscreen- or placebo-treated skin explants were irradiated with solar-simulated UV radiation at 0.5, 1, and 2 minimal erythematous dose equivalents (MEDE) (as determined in an in vivo human study) multiplied by the SPF of the placebo or sunscreens. After irradiation, skin explants were floated on RMPI medium for 48 h. Cells that had emigrated and the skin explants were histologically analyzed, and the soluble mediators were measured in the supernatants by ELISA. Exposure to UV radiation led to concentration-dependent increases in sunburn cell formation and TNFalpha production but a concentration-dependent decrease in DC migration and CD86- and CD1a-positive cell number in the epidermis. Both chemical sunscreens protected against those alterations. The immunoprotective capacity of the sunscreens correlated with their SPF but was independent of the sunscreens' UVA protection capacity, suggesting that UVA is not a major factor for immunosuppression under the conditions used in the model. UV irradiation did not significantly affect the vitality of emigrated DC; the expression of HLA, CD80, and lag on emigrated cells; the number of CD1a-positive cells in the dermis; or the production of IL-1, IL-10, and IL-12. We conclude that our model may be useful in determining the immunoprotective capacity of sunscreens.

The effects of UV waveband and cis-urocanic acid on tumour outgrowth in mice

Immunogenic murine tumours that are normally rejected upon transplantation into syngeneic hosts grow progressively if the hosts are UV-irradiated prior to tumour implantation. Using three sources of UV we investigated the most effective waveband and dose for increased outgrowth of injected fibrosarcoma (FSA) cells in mice, compared with unirradiated controls. The animals were exposed on their shaved dorsal skin twice a week for 3 weeks to either broad-band (TL12) or narrow-band (TL01) UVB, or UVA-I radiation; FSA cells were then injected subcutaneously into the UV-irradiated skin. Exposure to TL12 at doses higher than 1000 J m(-2), but not TL01 or UVA-I, caused increased outgrowth of the injected tumour cells. The effect of the UV irradiation seemed to be local as injection of the FSA cells into the unirradiated ventral skin of mice irradiated with TL12 on the dorsal surface did not result in increased outgrowth of the tumours. Cis-urocanic acid, a recognised initiator of UV-induced immunosuppression, applied topically or intradermally for 3 weeks prior to FSA cell injection, had no effect on the rate of tumour outgrowth. Similarly, injection of a monoclonal antibody with specificity for cis-urocanic acid, prior to each irradiation with TL12, did not reverse the increased growth of FSA cells injected into the UV-irradiated skin. Thus wavelengths within the broad-band UVB range are the most effective for inducing increased outgrowth of FSA cells; cis-urocanic acid is not an important mediator in this UV-enhanced growth of tumours.

Ultraviolet radiation, resistance to infectious diseases, and vaccination responses

Exposure to ultraviolet (UV) radiation, as in sunlight, can modulate immune responses in animals and humans. This immunomodulation can lead to positive health effects especially with respect to certain autoimmune diseases and allergies. However, UV-induced immunomodulation has also been shown to be deleterious. Experimental animal studies have revealed that UV exposure can impair resistance to many infectious agents, such as bacteria, parasites, viruses, and fungi. Importantly, these effects are not restricted to skin-associated infections, but also concern systemic infections. The real consequences of UV-induced immunomodulation on resistance to infectious diseases are not known for humans. Risk estimations have been performed through extrapolation of animal data, obtained from infection models, to the human situation. This estimation indicated that UV doses relevant to outdoor exposure can impair the human immune system sufficiently to have effects on resistance to infections. To further quantify and validate this risk estimation, data, e.g., from human volunteer studies, are necessary. Infection models in humans are not allowed for ethical reasons. However, vaccination against an infectious disease evokes a similar immune response as the pathogen and thereby provides an opportunity to measure the effect of UV radiation on the immune system and an estimate of the possible consequences of altered resistance to infectious agents. Effects of controlled UVB exposure on immune responses after hepatitis B vaccination have been established in mice and human volunteers. In mice, cellular and Th1-associated humoral immune responses to hepatitis B were significantly impaired, whereas in human volunteers no significant effect of UVB on these responses could be found. Preliminary data indicate that cytokine polymorphisms might be, at least in part, responsible for interindividual differences in immune responses and in susceptibility to UVB-induced immunomodulation. In addition, adaptation to UV exposure needs to be considered as a possible explanation for the difference between mice and humans that was observed in the hepatitis B vaccination model.

Simulated solar UVB exposure inhibits transcutaneous immunization to cholera toxin via an irradiated skin site in cattle

Transcutaneous immunization (TCI) is a new needle-free vaccination technology with the potential to reduce the risk of needle-borne disease transmission and carcass damage within the livestock industries. The principal antigen-presenting cell involved in TCI is thought to be the epidermal Langerhans cell. Langerhans cell function is inhibited by cutaneous ultraviolet-B radiation (UVB) exposure. Such exposure may inhibit TCI through sun exposed skin sites due to the phenomenon of local low dose photoimmunosuppression. TCI of cattle to cholera toxin (CT) resulted in the generation of a serum anti-CT-specific IgG(2) response. However, exposure of cattle to a sub-inflammatory dose of simulated solar UVB (2.43 x 10(3)J/m(2)) significantly (P<0.05) inhibited TCI to CT via irradiated skin sites.

Ultraviolet a radiation suppresses an established immune response: implications for sunscreen design

The ultraviolet radiation present in sunlight is the primary cause of nonmelanoma skin cancer and has been implicated in the development of cutaneous malignant melanoma. In addition, ultraviolet is immune suppressive and the suppression induced by ultraviolet radiation has been identified as a risk factor for skin cancer induction. Ultraviolet also suppresses the immune response to infectious agents. In most experimental models, ultraviolet is applied to immunologically naive animals prior to immunization. Of equal concern, however, is the ability of sunlight to suppress established immune reactions, such as the recall reaction in humans, which protects against microbial infections. Here we demonstrate that solar-simulated ultraviolet radiation, applied after immunization, suppresses immunologic memory and the elicitation of delayed-type hypersensitivity. Further, we found that wavelengths in the ultraviolet A region of the solar spectrum were critical for inducing immune suppression. Ultraviolet A (320-400 nm) radiation was as effective as solar-simulated ultraviolet A + B (290-400 nm) in suppressing the elicitation of an established immune response. Irradiation with ultraviolet AI (340-400 nm) had no effect. Supporting a critical role for ultraviolet A in ultraviolet-induced immune suppression was the observation that applying a sunscreen that contained an ultraviolet B only filter had no protective effect, whereas, a sunscreen containing both ultraviolet A and ultraviolet B filters totally blocked ultraviolet-induced immune suppression. These data suggest that sunlight may depress the protective effect of prior vaccination. In addition, the observation that ultraviolet A is immunosuppressive indicates the need for ultraviolet A protection when designing sun protection strategies.