Effects of ultraviolet irradiation on surface marker expression by epidermal immunocompetent cells and contact sensitization to dinitrofluorobenzene in mice

We studied the effects of ultraviolet (UV) irradiation on murine epidermal Ia-positive Langerhans cells (Ia + LC) and Thy-I-positive dendritic epidermal cells (Thy-I + dEC). We also studied contact hypersensitivity to dinitrofluorobenzene (DNFB) introduced through UV-treated epidermis. C3H/HeN mice were exposed to UVB or 8-methoxypsoralen plus UVA (PUVA). UVB and PUVA treatment led to a dramatic reduction in surface marker expression of both Ia + LC and Thy-I + dEC. High-dose UVB irradiation (360 J/m2) interfered with contact hypersensitivity to DNFB; the density of Ia + LC may thus be related to the sensitizing potential. In contrast, low-dose UVB (120 J/m2) and PUVA treatment had little effect on contact hypersensitivity despite a marked reduction in Ia + LC. The density of Thy-I + dEC appeared not to be associated with contact hypersensitivity. These results suggest that there may be a Langerhans cell density-independent mechanism for the induction of contact hypersensitivity.     

Chronic eczematous dermatitis of the hands: a comparison of PUVA and UVB treatment

The efficacy of PUVA and UVB treatment in chronic eczematous dermatitis of the hands was compared in a randomised controlled study including 35 patients who were randomly allocated to PUVA or UVB treatment. One hand was exposed to light and the other served as an untreated control. The dermatitis cleared on the treated hand in all PUVA patients, but in 9 out of 14 there was a relapse within three months. In the UVB group clearing of the skin lesions was not achieved, but compared with the "untreated" hands a statistically significant improvement was found at 12 weeks of treatment. A statistically significant improvement of "untreated" hands was found in both groups. PUVA and UVB treatments are alternative treatment modalities in patients with recalcitrant chronic eczematous dermatitis of the hands. PUVA is superior to UVB.     

Epidermal Langerhans' cells in patients with pustulosis palmoplantaris treated with etretinate or etretinate + methoxsalen photochemotherapy

Epidermal Langerhans' cells (LC) were studied in patients with pustulosis palmoplantaris (PPP) by utilizing the monoclonal antibodies anti-Leu6 and anti-HLA-DR in combination with an immunoperoxidase technique. In non-pustular areas of the skin lesions in PPP, an increased number of epidermal LC was found compared with control subjects. No change in LC counts was observed following etretinate monotherapy for 2 weeks. Etretinate was then combined with PUVA treatment of one palm/sole with the contralateral side as a non-UVA exposed control. After 6-12 weeks of etretinate + PUVA treatment the PPP had resolved and the number of epidermal dendritic HLA-DR+ and Leu6+ cells had normalized. On the contralateral side, etretinate treatment induced a marked clinical improvement and a reduction of HLA-DR+ cells. The observation of an increased LC population in active PPP and a reduction during clinical improvement indicates a close relationship between LC and the activity of PPP.     

New aspects in uv and photochemotherapy

Recent data show that from a pharmacological point of view topical (cream or bath) PUVA therapy is superior to systemic PUVA. Due to a significant reduction of side effects compared to systemic PUVA, bath PUVA has now started to replace oral PUVA therapy. Narrowband UVB has proved to be superior to broadband UVB in the treatment of psoriasis and is effective for a number of dermatoses such as vitilgo, atopic dermatitis and polymorphic light eruption. UVA1 phototherapy is highly effective in the treatment of moderate to severe atopic dermatitis and sclerosing diseases of the skin. Data dealing with UVA1 phototherapy for other indications are still preliminary. High-dose UVA1 is has been widely replaced by medium-dose UVA1, as a number of studies have shown similar therapeutic efficacy of both dose regimens.     

Differential analysis of experimental hypermelanosis induced by UVB,PUVA, and allergic contact dermatitis using a brownish guinea pig model

Summary In moderately colored guinea-pig skin, UVB, PUVA, and allergic contact dermatitis were shown to induce hyperpigmentation that resembled the pigmentary changes observed in mongoloid human skin. Using this model, we examined the effects of chemical agents, including tyrosinase inhibitors and sunscreen agents, on the color changes induced by UV irradiation. The daily exposure of brownish guinea-pig skin to UVB irradiation at a variety of energies for 3 successive days induced clearly visible black pigmentation on the irradiated rectangular areas of the flank within a few days of irradiation, the maximum being reached about 1 week after irradiation, i.e., similar to the changes that occur in pigmented human skin. Split epidermal sheets prepared from untreated pigmented guinea pigs exhibited 200–400 melanocytes/mm²; 1 week after UV irradiation, the applied areas show an increased number of strongly dopa-positive melanocytes with stout dendrites (800–1,000 cells/mm²). UVA irradiation following an intraperitoneal injection of 8-methoxypsoralen (8-MOP) also produced black pigmentation 1 week after irradiation, and this was paralleled by a marked increase in the number of dopa-positive melanocytes in dopa-reacted split epidermal sheets. Allergic contact dermatitis produced by the application of 1-phenylazo-2-naphtol induced hyperpigmentation after an interval of about 14 days in 10 of the 21 allergy-acquiring animals examined. This induced pigmentation was accompanied by an increase in the number of dopa-positive melanocytes as compared to the number seen in controls. In contrast, allergic contact dermatitis produced by the application of dinitrochlorobenzene failed to induce such a high ratio of postpigmentation, with only 3 of the 21 allergy-acquiring animals showing hyperpigmentation and 5 showing depigmentation; in the latter, there was a slight decrease in the number of dopa-positive melanocytes. To study the preventive effect of tyrosine inhibitors on UVB-induced pigmentation, daily topical applications of these compounds were performed after three daily UVB irradiations. Treatment with 10% hydroquinone for 10 days interrupted UVB-induced pigmentation and resulted in a marked reduction in the number of epidermal melanocytes as compared to the number found in UVB-irradiated, untreated control skin.     

PUVA therapy prevents sensitization to mechlorethamine in patients with psoriasis

Two groups of 20 patients with psoriasis were treated with mechlorethamine applied topically (group A) or with PUVA combined with mechlorethamine (group B). In group B mechlorethamine was started after six PUVA treatments. Results showed a significant decrease of the incidence of contact dermatitis in group B (30%) compared with group A (75%). Allergic dermatitis, demonstrated by a positive patch test to mechlorethamine with an histology of eczema, was observed in 55% of patients in group A and 20% in group B. The incidence of irritant dermatitis was not significantly different in the two groups. Allergic dermatitis was observed later in group B: after an average of 32.2 applications of mechlorethamine compared with 25 applications in group A. Possible mechanisms responsible for these results are reduction of epidermal Langerhans cells by PUVA therapy and induction of antigen-specific suppressor T cells. Patients living far from a specialized centre might be treated initially with PUVA therapy then with mechlorethamine alone, at home. This schedule may reduce the incidence of contact dermatitis to mechlorethamine.     

Effects of ultraviolet radiation on murine epidermal Langerhans cells: doses of ultraviolet radiation that modulate ICAM-1 (CD54) expression and inhibit Langerhans cell function cause delayed cytotoxicity in vitro.

Low doses (100 J/m2) of ultraviolet B (UVB) radiation from sunlamp fluorescent FS20 tubes inhibit the ability of freshly isolated murine epidermal Langerhans cells (LC) to support anti-CD3 MoAb-induced T-cell mitogenesis and selectively inhibit the upregulation of ICAM-1 expression by LC without causing appreciable cytotoxicity in short-term (less than or equal to 24 h) incubations (J Immunol 146:3347-3355, 1991). In the present study, epidermal cells (EC) were exposed to UVB radiation or were sham-irradiated and cultured for 24, 48, or 72 h when LC were recovered, enumerated, and assayed for simultaneous expression of I-A antigens and ICAM-1 by flow cytometry. UVB-irradiated LC that had been cultured for 24 h exhibited levels of I-A antigens comparable to those on unirradiated LC but expressed substantially less ICAM-1. After 48 and 72 h, cultured UVB-irradiated LC expressed somewhat lower levels of I-A antigens and markedly less ICAM-1 than unirradiated controls. Although similar numbers of LC were recovered from cultures initiated with UVB-irradiated and unirradiated epidermal cells after 24 h, far fewer identifiable LC were recovered from cultures seeded with irradiated cells at 48 and 72 h (approximately 50 and approximately 10% of control, respectively). The effect of UVB radiation on the survival of LC in vitro was not reversible with exogenous TNF alpha (125 U/ml) alone or granulocyte/macrophage colony-stimulating factor (5 ng/ml) and IL-1 (50 U/ml) in combination, although these cytokines had modest effects on the expression of I-A antigens and ICAM-1 by cultured UVB-irradiated LC. Results of survival studies performed with enriched LC preparations demonstrated that UVB radiation was clearly cytotoxic for LC and did not merely downregulate surface expression of I-A antigens or alter LC buoyant density. Exposure of LC to radiation from blacklight fluorescent (UVA) tubes (0.25 J/cm2) in the presence of 8-methoxypsoralen (1 micrograms/ml; PUVA) or monochromatic UVC radiation (20 J/m2) also inhibited LC accessory cell function. Results of survival studies performed with EC that had been exposed to PUVA or UVC radiation before culture were similar to those of studies performed with UVB-irradiated cells, although PUVA- and UVC-induced LC cytotoxicity was much more pronounced 48 h after culture initiation than UVB-induced cytotoxicity. UVA radiation alone augmented LC recovery at 24 and 48 h, but did not influence I-A antigen or ICAM-1 expression.(ABSTRACT TRUNCATED AT 400 WORDS)     

In vivo PUVA and UVB sensitivity of various human epidermal Langerhans cell markers (ATPase, HLA-DR and T6)—Dose-response and time-sequence studies

To form a comprehensive view of the UV-sensitivity of human epidermal Langerhans cells (LC), the time-sequence and close response effects of single doses of UVB or 8-methoxypsoralen plus UVA (PUVA) radiation on three different LC surface markers were studied with histochemical and immunohistochemical staining. An increasing PUVA dose from 1 to 10 J/cm² caused an almost linear decrease in the surface enzyme (ATPase) positive LC count, whereas the cell surface antigens (HLA-DR and T6) were rather more resistant, up to a PUVA dose of 5 J/cm². A single dose of 5 J/cm² of PUVA induced an LC depletion that was similar during the 21 days of observation, irrespective of whether the cells were visualized with ATPase staining or with monoclonal antibodies against the cell surface antigens HLA-DR or T6. In each case, the nadir was reached 14 days after irradiation; the average residual LC count was then 57%. The cell counts 21 days after PUVA irradiation were still only approximately 74% of the nontreated skin counts. Langerhans cell depletion induced by an erythemagenic dose of UVB irradiation was swifter and more pronounced than that induced by 5 J/cm² of PUVA but, again, a similar time schedule was recorded with ATPase, HLA-DR and T6 staining.     

Treatment of palmoplantar psoriasis with monochromatic excimer light (308-nm) versus cream PUVA

Palmoplantar psoriasis is a chronic disease, which is very resistant to treatment and often leads to severe disabilities. Photochemotherapy employing psoralens combined with UVA irradiation (PUVA) is a well-accepted therapy for palmoplantar psoriasis. Its topical application (bath PUVA; cream PUVA) avoids the typical side effects of orally applied psoralens. We compared the efficacy of cream PUVA therapy with monochromatic excimer light therapy, a treatment modality employing 308-nm UVB radiation generated by a new kind of light source. Ten patients with psoriasis of the palms and soles were randomly assigned to receive cream PUVA on one side and 308-nm UVB on the contralateral side. Based on the psoriasis area and severity index (PASI) score, clinical assessment was carried out before and 5 weeks after the beginning of the study. At the end of the treatment period both test groups showed a remarkable PASI score reduction (308-nm UVB, 63.57%; cream PUVA, 64.64%). No relevant adverse effects were observed, except for mild irritation in a few patients. After a 12-week follow-up, a relapse of the disease was only observed in one patient. Thus, mono-chromatic excimer light cleared palmoplantar psoriasis as rapidly as cream PUVA. In contrast to cream PUVA, monochromatic excimer light therapy is not associated with prior drug application. This might lead to a lower incidence of adverse reactions and better compliance. Therefore, monochromatic excimer light therapy seems to be a useful new therapeutic option for palmoplantar psoriasis.     

Phototherapy: Theory and practice

Despite the development of highly effective biologics for skin diseases such as psoriasis or atopic dermatitis, UVA and UVB therapy, alone or in combination, are still essential components of various guidelines. Phototherapy is not only a first-line treatment and highly effective for a number of skin diseases, but is also economical and has few side effects. The targeted use of UVA and UVB, if necessary, in combination with the photosensitizer psoralen in the context of PUVA therapy, enables the dermatologist to effectively treat a wide variety of skin diseases. Indications for phototherapy include epidermal diseases such as atopic dermatitis, psoriasis and vitiligo, as well as photodermatoses, mycosis fungoides, graft-versus-host disease and deep dermal diseases such as scleroderma. This article reviews the physical principles, molecular mechanisms, current treatment regimens, and individual indications for phototherapy and photochemotherapy.     

Papular dermatitis (subacute prurigo, “itchy red bump” disease): Pilot study of phototherapy

Background: Some patients with a subacute or chronic pruritic erythematous papular eruption are refractory to treatment. We previously described a number of these patients with papular dermatitis or subacute prurigo. Objective: The purpose of this study was to examine the effectiveness of different types of phototherapy for treatment of papular dermatitis. Methods: We reviewed the medical records of 11 patients who were diagnosed with papular dermatitis and who underwent phototherapy within the last 5 years. Results: Eleven patients had a total of 17 phototherapy courses: psoralen–UVA (PUVA; 9), UVA/UVB light (3), and UVB alone (5). Within the PUVA treatment group, three of nine patients experienced total clearing, and six of nine patients experienced partial improvement. Although patients in all groups relapsed with time, overall the PUVA-treated patients had the best response rate and the best chance of the condition remaining clear after treatment was stopped. Conclusion: PUVA may be an effective treatment for papular dermatitis. The frequency of relapse indicates that maintenance treatments may be necessary for long-term control of the disease. (J Am Acad Dermatol 1998;38:929-33.)     

Quantitative immunohistochemical differences in Langerhans cells in dermatitis due to internal versus external antigen sources

Cutaneous hypersensitivity reactions can develop against antigens delivered through the epidermis (contact dermatitis) or through the blood vessels (e.g., drug eruptions). On routine histology alone, it is not always possible to determine the route of the antigen. Langerhans cells (LC) are the main antigen-presenting cells in contact dermatitis. Dermal dendrocytes (DC) are antigen-presenting cells and may be involved in dermal reactions. We tested the hypothesis that there is a difference between dermatitis due to external and internal antigen sources with regard to the number or function of LC and DC. In 85 cases of dermatitis, numhers of S100 and HLA-DR reactive cells per linear millimetre of epidermis were counted. The amount of epidermal spongiosis was evaluated qualitatively. In 35 cases, the numher of DC per mm² (as defined by Factor XIIIa expression) was evaluated. The patients were then divided into two groups based on whether the final clinical evaluation considered the dermatitis to be secondary to an external (35 cases) or internal antigen (50 cases). Dermatitis due to external antigens had significantly more LC/mm and more frequent HLA-DR expression than dermatitis due to internal antigens, mean ± SEM; 21.2±2.04 vs. 9.1±1.02 (p<0.00001) and 16.3±2.49 vs. 6.0±0.92 (p=0.0001), respectively. Spongiosis was more marked in external antigen cases. DC were more numerous in internal than in external antigen cases, but the differences were not statistically significant. In our model, determination of numbers of LC/mm is the variable with the highest power to discriminate between internal and internal sources. Quantification of HLA-DR+ LC and degree of spongiosis provide little additional discriminatory power.     

Ultraviolet-B phototherapy is successful in Japanese patients with early-stage mycosis fungoides

UVB phototherapy is widely used for the treatment of psoriasis and atopic dermatitis, however, only limited reports evaluate its usefulness in the treatment of mycosis fungoides. We introduced UVB phototherapy to five patients with early-stage mycosis fungoides. All of them were classified as stage IB (erythematous stage), and none had obtained a satisfactory response to other therapies. After initial treatment with UVB phototherapy, all the patients obtained significant improvement in their skin lesions leaving pigmentary changes. After this satisfactory response was achieved, the same dose of UVB was administrated as a maintenance therapy with longer intervals between exposures. Histopathological examination of three patients revealed decreased numbers of inflammatory cells in both the epidermis and the dermis after the treatment. Immunohistochemical study showed that CD1a+/HLA-DR+ dendritic cells were present throughout the lesional epidermis before the treatment. In contrast, after the treatment, the dendritic cells in the epidermis were CD1a+/HLA-DR-. Although it remains unclear why only the expression of HLA-DR antigen was eliminated after treatment, we presume that this loss of HLA-DR antigen expression by epidermal Langerhans cells was, in part, responsible for the improvement of skin lesions. This preliminary study suggests that UVB phototherapy is an effective treatment for patients with early-stage mycosis fungoides.     

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

Background/Purpose: Ultraviolet B (UVB) radiation affects the migration and function of epidermal Langerhans cells (LC) and causes immunosuppression of contact hypersensitivity. It is known that LC leaves the epidermis after exposure to UVB. To know the behavior of LC in the dermis after UVB radiation, we studied the effect of UVB radiation on the expression of integrin families on freshly isolated or cultured murine LC. We also examined whether UVB radiation affects the migration of LC to secondary lymphoid tissue chemokine (SLC/6Ckine).
Methods: Integrin expressions of murine LC cultured in epidermal cell suspension were analyzed using flowcytometry. We used murine LC sorted flowcytometrically for binding assay to extracellular matrix and for migration assay to chemokine. Skin explant assay and immnohistochemical staining for 'cords formation' were performed as previously described.
Results: Twenty and 40 mJ/cm² of UVB radiation down-regulated the expression of α4 integrin on 24 h-cultured LC, but not that of α6, β1, or β4 integrin. The number of cultured LC adhered to fibronectin, a ligand for α4 integrin, was decreased after UVB irradiation, while that to laminin, a ligand for α6 integrin, was not influenced. UVB radiation reduced the number of migrating LC to SLC. Furthermore, skin sheet explant experiments showed that UVB radiation inhibited the 'cords' formation in dermal vessels of the 48 h-cultured skin.
Conclusions: These data suggest that UVB radiation may suppress the migration of LC from the dermis to lymphatic vessels. UVB radiation may downregulate the adherence of LC to dermal fibronectin and migration to SLC, and consequently suppress the migration of LC from the UVB-irradiated dermis to lymphatics.     

Disappearance of epidermal Langerhans cells during PUVA therapy

The numbers and morphological appearance of epidermal Langerhans cells (LCs) were studied in twenty-five patients with psoriasis receiving treatment with 8-methoxypsoralen (8-MOP) and long wavelength UV irradiation (UV-A) (PUVA). After a single exposure, LCs showed loss of fine dendritic processes. Repeated treatments resulted in a reduction of the number of LCs from the mean pretreatment value of 713/mm² to less than 60/mm² after seven treatments. The number of LCs remained low while treatment continued for up to 4 weeks. This finding may explain the impaired contact hypersensitivity observed in patients with psoriasis receiving PUVA therapy.     

Effect of psoralens and ultraviolet radiation on murine dendritic epidermal cells

Monofunctional psoralens produce less phototoxicity than bifunctional psoralens after ultraviolet A (UVA) irradiation. We investigated the effect of repetitive treatments with angelicin (isopsoralen), a monofunctional psoralen, plus UVA radiation (IPUVA) on the number and morphology of dendritic epidermal cells (dEC). This effect was compared with that of 8-methoxypsoralen plus UVA radiation (PUVA), UVA alone, and UVB radiation. C3H/HeN mice were treated topically with the drugs three times/wk for 4 consecutive wk; followed each time by 1 or 2.5 J/cm2 of UVA radiation. Other groups of mice were treated with the drugs alone, UVA alone, or 0.81 J/cm2 of UVB. Epidermal sheets were stained for ATPase, Ia, and Thy-1 markers. Mice treated with PUVA and UVB exhibited severe phototoxicity, whereas no overt phototoxicity was observed in mice treated with IPUVA, UVA alone, or the drugs alone. Early during the PUVA and UVA treatments the ATPase marker was lost from dEC, followed by loss of the Ia marker; the Ia marker was lost before the ATPase marker from dEC in animals treated with IPUVA. At the end of the treatment, however, nearly total depletion of ATPase+, Ia+, and Thy-1+ dEC was observed in mice treated with PUVA and IPUVA. UVB radiation caused rapid depletion of Thy-1+ dEC as well as ATPase+ and Ia+ cells. During treatments with IPUVA, PUVA, UVA, and UVB, the Langerhans cells became rounded and lost their dendrites. These changes were quantitated by image analysis. We conclude that alterations of cutaneous immune cells can occur in the absence of overt phototoxicity, and that monofunctional and bifunctional psoralens plus low dose of UVA radiation may have different effects on dEC markers.     

Efficacy of localized phototherapy and photodynamic therapy for psoriasis: a systematic review and meta‐analysis

Localized phototherapy including topical psoralen plus ultraviolet A (PUVA) and targeted ultraviolet B (UVB), and photodynamic therapy (PDT) have been increasingly used in the treatment of localized psoriasis. Yet, there are no systematic reviews or meta‐analyses that scientifically evaluated the pooled efficacy of these treatments in psoriasis. We searched Medline, Embase, and Cochrane databases during the period of January 1980 to June 2012. Our systematic search resulted in 765 studies, 23 of them were included in the review. The primary outcome was 75% reduction in severity score from baseline. A meta‐analysis using random effect model found topical PUVA to be more effective than non‐laser targeted UVB [odds ratio: 3.48 (95% confidence interval 0.56–21.84), P = 0.183]. The pooled effect estimate of the efficacy (75% reduction in severity score) of topical PUVA, targeted UVB, and PDT were as follows: 77% (topical PUVA), 61% (targeted UVB), and 22% (PDT). Topical PUVA and targeted UVB phototherapy are very effective in the treatment of localized psoriasis. Topical PUVA seems more effective than non‐laser targeted UVB phototherapy. On the other hand, PDT has low efficacy and high percentage of side effects in treating localized psoriasis.     

PUVA treatment of chronic eczematous dermatitis of the palms and soles

Thirty-eight patients were treated with PUVA for chronic eczematous dermatitis of the palms. Twenty (53%) were completely free from lesions when treatment was stopped, and 11 (29%) were improved. Patients who showed healing remained in remission for an average of greater than or equal to 11 months (range 3 weeks to greater than or equal to 36 months). When the rash recurred it was often milder than before PUVA. Sixteen of the 38 patients also had chronic plantar dermatitis; PUVA treatment resulted in complete clearing in 7 (41%), and remission persisted for an average of greater than or equal to 16 months.     

Atopic Dermatitis: Studies of Skin Permeability and Effectiveness of Topical PUVA Treatment

Ultraviolet light is effective treatment for patients with atopic dermatitis that is resistant to conservative therapy, or complicated by adverse effects of extended steroid use. We designed a protocol using topical psoralen chemotherapy with ultraviolet A (PUVA) to treat atopic dermatitis in 114 patients. Clinical results were excellent, with complete clearing in 50% of patients receiving daily treatment. Histologic and immunologic values correlated with the clinical response, including reduced epidermal thickness, and decreased numbers of epidermal Langerhans cells and dermal mast and mononuclear cell infiltrates. The pattern of keratin 14-positive keratinocytes returned toward normal. In addition, the water-holding capacity of the stratum corneum increased to near normal levels. We also studied stratum corneum permeability in lesional and nonlesional skin using the dimethyl sulfoxide whealing test and theophylline absorption studies. Compared with controls, permeability was markedly increased in lesional skin and mildly increased in nonlesional skin in patients with atopic dermatitis. These results suggest that immune abnormalities and barrier dysfunction participate in the pathogenesis of atopic dermatitis.