Treatment of actinic prurigo with PUVA: mechanism of action

Five patients with actinic prurigo were treated twice weekly with PUVA. One area on the back was shielded from UVA throughout the 15-week treatment period. Before PUVA, all patients had increased erythemal sensitivity to UVA and showed abnormal augmentation of UVB erythema by topical indomethacin. After PUVA, all patients were free of photosensitive symptoms and skin that had been exposed to UVA showed normal erythemal responses. By contrast, the areas of skin that had been protected from UVA showed erythemal responses that were unchanged from pre-PUVA values. Augmentation of UVB erythema by topical indomethacin persisted, both on UVA exposed and UVA protected skin. These results show that, although PUVA is an effective treatment in actinic prurigo, it does not alter the underlying mechanism of photosensitivity. The protective effect is local and is due presumably to an increase in melanin pigmentation and epidermal thickness.     

Erythemal and therapeutic response of psoriasis to PUVA using high-dose UVA

In PUVA treatment of psoriasis, clinical observation suggests that uninvolved skin is more susceptible to PUVA erythema than lesions of psoriasis. If this is the case, then the efficacy of PUVA treatment might be increased by using localized high-dose UVA restricted to lesional skin. We have therefore studied the erythemal and therapeutic response of psoriasis to PUVA using high-dose UVA and, for comparison, the erythemal response to UVB. In 14 patients, an area of psoriasis and adjacent uninvolved skin were exposed to a series of UVA doses (350 ± 30 nm, 1–16 J/cm²), using an irradiation monochromator. Six other patients were similarly phototested with a series of UVB doses (300 ± 5 nm, 20–112 mJ/cm²) to both uninvolved and lesional skin. Erythema was judged visually at 72 h for psoralen–UVA, and at 24 h for UVB, and measured using a scanning laser–Doppler velocimeter. In 10 patients, PUVA therapy using high-dose UVA was subsequently given to lesional skin (8–16 J/cm² twice weekly) in addition to conventional whole-body PUVA. For psoralen–UVA, the minimal phototoxic dose within psoriasis was increased by a factor of 4 compared with non-lesional skin (P < 0.01, Wilcoxon signed-rank test). For UVB, the minimal erythema dose within psoriasis was higher than that for non-lesional skin (medians > 112 and 28 respectively, P < 0.05). Laser–Doppler measurements confirmed that the reduced erythemal sensitivity was not due to masking of response by pre-existing increased blood flux within psoriasis. In six patients, the sites subsequently treated twice weekly with PUVA, using high-dose UVA, cleared faster (median number of treatments 3), but with a similar cumulative UVA dose, compared with adjacent lesional skin treated with conventional PUVA (median number of treatments 12). This study demonstrates that psoriasis may clear rapidly, without burning, using high-dose UVA. Availability of a suitable irradiation apparatus would allow rapid and effective PUVA treatment to be used for localized, resistant disease.     

Phototherapie und Karzinogenese

Phototherapy successfully uses the short-term effects of ultraviolet light against inflammation and proliferation. For its long-term effects, however, ultraviolet light was recently classified as a carcinogen. The wave spectrum employed in phototherapy has various carcinogenic effects in experimental systems, most notably DNA mutations in keratinocytes. Clinically, PUVA increases the risk for squamous cell carcinoma of the skin, especially after following 350 or more phototherapy sessions over a lifetime. Melanoma and genital skin cancer are not increased by PUVA alone. Previous UV damage, immunosuppression and other systemic treatments increase cutaneous carcinogenesis through PUVA. In contrast, broad-band UVB, narrow-band UVB and UVA1 have not yet been linked to cutaneous carcinogenesis, but will need careful follow-up in larger studies. Phototherapy remains a safe treatment modality, provided that the indication is well-founded, previous exposure and co-carcinogens are considered, and short and dose-intensive treatment protocols are favored, PUVA is chosen as second-line treatment that should not be used for more than a lifetime total of 250–300 phototherapy sessions.     

The mechanism of the inhibitory effects of antimalarials on UV-induced skin inflammation in mice

In order to elucidate the mechanism of UV-induced skin inflammation, the effects of antimalarials, inhibitors of phospholipase A₂ and membrane phospholipid methylation, on UV-induced ear swelling response (ESR) was examined. Antimalarials inhibited ESR induced by 8-methoxypsoralen (0.5%) plus UVA irradiation (PUVA treatment) or UVB irradiation. However, they did not inhibit ESR induced by the application of arachidonic acid (AA). Although it has been reported that PUVA treatment and UVB irradiation may work through different AA pathways, it seems likely that both PUVA and UVB may affect the initial cellular metabolism of the inflammatory process.     

Cutaneous carcinoma and PUVA lentigines in Thai patients treated with oral PUVA

A total of 113 Thai patients who were treated with oral PUVA from 1979 to 1992 were examined for long-term cutaneous side effects of PUVA. Two psoriatic patients developed PUVA keratosis on non-sun-exposed areas. Both were skin type IV and had had phototherapy with UVB and sunlight previously. The total doses of UVA were 909 J/cm² and 242 J/cm² respectively. One psoriatic patient developed Bowen's disease. He had had a cumulative dose of UVA 2207 J/cm². He also had a past history of arsenic intake and phototherapy with UVB and sunlight. PUVA lentigines were seen in 58 patients (51.4%). It was associated with older age at starting PUVA, higher cumulative UVA dose and greater number of PUVA treatment. This study suggests that previous exposure to other risk factors is important for inducing skin cancer in populations with skin phototype III, IV and V treated with oral PUVA.     

Ultraviolet radiation-induced inflammation and leukocytes.

To evaluate the role of leukocytes in inflammation induced by ultraviolet radiation, the response of guinea pigs make leukopenic with cyclophosphamide was compared with the response of nonleukopenic animals. The response of leukopenic animals to UVB (295 nm) was significantly altered. Leukopenic animals and saline-treated (i.e., nonleukopenic) animals responded similarly to (1) UVC (250 nm), (2) UVA (340 nm) given after 8-methoxypsoralen pretreatment (PUVA), (3) intradermal histamine and (4) a topically applied prostaglandin analogue. These results suggest that leukocytes are important in UVB-induced inflammation but not in the inflammation induced by UVC or PUVA.     

Modulation of endothelin-1 in normal human keratinocytes by UVA1/B radiations, prostaglandin E2 and peptidase inhibitors

In the skin, keratinocytes synthesize and secrete endothelin-(ET-1), a potent vasoconstrictor peptide which acts also as a growth factor for most skin cells. The aim of the study was to test the effects of UVA1 and the associations UVA1/B on the expression of ET-1 in normal human keratinocytes and to determine whether exogenously added prostaglandin E2 (PGE2) regulated ET-1 expression. As ET-1 is susceptible to degradation, we also evaluated whether ET-1 secretion was modulated by peptidase inhibitors. Our results showed that UVA1 (365 nm) did not modify the levels of preproET-1 mRNA and protein. Moreover, the associations UVA1+UVB or UVB+UVA1 down-regulated the overexpression of secreted ET-1 induced by UVB alone. PGE2 at 10(-5) M reduced the expression of ET-1 at the mRNA and protein levels but did not exert any significant modification at lower concentrations from 10(-10) to 10(6) M. Phosphoramidon, an endothelin converting enzyme (ECE) inhibitor, drastically decreased the amount of ET-1 accumulating in the culture medium in basal conditions or after UVB irradiation. Conversely, thiorphan, a specific inhibitor of neutral endopeptidase (NEP), rather increased the levels of ET-1 secretion mainly after UVB irradiation. Taken together, the results showed that normal human keratinocytes secrete and partly degrade ET-1 through ECE and NEP pathways and pointed out a differential regulation of ET-1 by UVB and UVA1 radiations without any noticeable role for PGE2.     

DNA repair elicited by UVB during PUVA therapy for psoriasis

Summary The skin of patients receiving psoralen and UVA (PUVA) therapy for psoriasis is exposed to trace amounts of UVB radiation emitted by PUVA irradiators in addition to UVA. DNA repair activity was measured using autoradiography in the uninvolved skin of PUVA-treated patients in order to determine whether 8-methoxypsoralen (8-MOP) plus UVA elicits repair, inhibits the skin repair response to UVB, or protects epidermal-cell DNA from UVB damage by promoting a tan. Epidermal-DNA repair activity was observed in 27 out of 37 patients following the first PUVA treatment. Phototesting with multiples of the initial UV dose elicited a linear increase in repair activity. Glass-filtered radiation failed to stimulate repair, indicating that the reaction was due to UVB, not to 8-MOP plus UVA. The same amount of repair activity was observed in the skin of patients irradiated either before or after 8-MOP ingestion, demonstrating that the drug did not interfere with the response of the skin to UVB. At clearing, however, the repair activity was never greater than that elicited at the initial treatment and was often undetectable despite a tenfold increase in UV exposure. It is proposed that DNA damage should be measured to determine whether epidermal cells are entirely protected from UVB radiation at the completion of therapy.     

Long-wave ultraviolet light induces phospholipase activation in cultured human epidermal keratinocytes

Long wave ultraviolet radiation (UVA) has been shown to play an important role in the overall response of skin to solar radiation, including sunburn, tanning, premature aging, and non-melanoma skin cancer. UVA induction of inflammation in human skin is thought to be mediated by membrane lipid derived products. In order to investigate the mechanism of this response we examined the effect of UVA on phospholipid metabolism of human epidermal keratinocytes in culture. Keratinocytes were grown in serum free low calcium medium. The cells were prelabeled with [3H] arachidonic acid or [3H] choline and irradiated with UVA (Honle 2002-Hg vapor lamp). Identification and quantitation of specific membrane phospholipid-derived components was achieved using high-performance liquid chromatography, paper chromatography, and radioimmunoassay. UVA resulted in a linear dose dependent release of [3H] arachidonic acid into medium between 1 and 20 joule/cm2. This response was inhibited in an oxygen-reduced environment. The radiolabel released was predominantly free arachidonate and cyclooxygenase metabolites. Cyclooxygenase metabolites prostaglandin E2 and prostacyclin derivative, 6-keto-prostaglandin F1a, were stimulated following UVA irradiation, but the lipoxygenase metabolite, leukotriene B was not detected. Maximal release was measured immediately after irradiation and changed little over 24 h post-irradiation. UVA stimulated an increase of [3H] choline metabolites glycerophosphorylcholine and phosphorylcholine in media extracts suggesting UVA activation of phospholipase C and phospholipase A2 or diacylglyceride lipase.     

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.     

Cumulative UV radiation dose and outcome in clinical practice: effectiveness of trioxsalen bath PUVA with minimal UVA exposure

BACKGROUND: The cumulative artificial ultraviolet (UV) exposure dose of dermatological patients was prospectively monitored in clinical conditions for a total of 2 years (August 1997 - July 1999). We focused on whole body UV treatments, i.e. the trioxsalen (TMP) bath PUVA, the broad-band UVB, and the UVA plus UVB phototherapy. METHODS: Irradiance of the UV devices was calibrated with a spectroradiometer. The cumulative UV doses received by the patients were recorded. A visual analog scale scoring system (VAS) was employed to assess the improvement of various skin conditions at the end of the treatment course. RESULTS: The analysis included 265 patients (141 females and 124 males) and a total of 311 UV treatment courses. Treatments consisted of 86 courses of TMP bath PUVA for psoriasis with a mean cumulative UVA dose of 3.54 J/cm2 and an improvement rate of 89%. For other conditions, 30 courses were needed, with a cumulative UVA dose of 1.47 J/cm2 and an improvement rate of 76%. Altogether, 47 UVB courses were undertaken for psoriasis, and the mean cumulative unweighted UV dose was 2.20 J/cm2, equivalent to 85 standard erythema doses (SED), and an improvement rate of 85%. A total of 25 UVB courses was used for other skin conditions with a mean UV dose of 1.05 J/ cm2, equivalent to 40 SED, and an improvement rate of 71%. A total of 123 courses of UVA plus UVB phototherapy were completed, resulting in a mean cumulative dose of 73.01 J/cm2 for UVA and 0.75 J/cm2 for the unweighted UVB, equivalent to 29 SED. The VAS improvement rate was 85%. CONCLUSION: The exceptionally low mean cumulative UVA dose in the TMP bath PUVA, taken together with the previous report showing no increase in the risk of squamous cell carcinoma or cutaneous malignant melanoma after TMP bath PUVA, suggests that TMP bath PUVA is an effective and safe therapeutic option.     

Inhibition of ultraviolet and phototoxic dermatitis in the mouse.

The effect of inhibitors on the inflammatory oedema elicited by medium-wave ultraviolet radiation (UVB) and long-wave ultraviolet radiation (UVA) in combination with chlorpromazine has been studied in the mouse, by means of a quantitative technique. Inhibition of the UVB reaction was observed with indomethacin, acetylsalicylic acid and betamethasone valerate, whereas the latter compound only was effective in the phototoxic state. No inhibition was obtained with hydrocortisone, phenylbutazone, epsilon-aminocaproic acid, polyphloretin phosphate, clemastin, alpha-tocopherol or ascorbic acid. With indomethacin and betamethasone valerate there was no inhibition at high doses when the compound was administered before UVB irradiation. These results are in accordance with a proposed central role for the prostaglandins in UVB inflammation. It is suggested that the phototoxic reaction to chlorpromazine may not be due to mediator action but rather to the effect of toxic photoproducts.     

Radiation from ultraviolet phototherapy sources results in photodegradation of 12(R) and 12(S)-hydroxy-eicosatetraenoic acid: high-performance liquid chromatography and polymorph migration studies.

The effect of irradiation from Sylvania PUVA lamps (emitting predominantly in the ultraviolet (UVA) region) and broadband Philips TL-12 lamps (peaking in the UVB region) on two inflammatory mediators, 12(R)- and 12(S)-hydroxy-eicosatetraenoic acid (HETE) was studied. A high-performance liquid chromatography study showed significant photodegradation of both enantiomers at a concentration of 5 micrograms/ml in phosphate-buffered saline following irradiation with 10 J.cm-2 UVA or 0.375 J.cm-2 UVB. The in vitro chemokinetic microdroplet migration response of human peripheral polymorphonuclear leukocytes from normal and psoriatic subjects was significantly reduced following irradiation of 12(R)-HETE at a concentration of 1 micrograms/ml in medium with 40 J.cm-2 UVA and 1.5 J.cm-2 UVB respectively. No such effect was seen with 12(S)-HETE. The effect of ultraviolet on skin physiology, and in particular in the successful phototherapy of a range of inflammatory skin disorders, is not fully understood. The photodegradation of inflammatory mediators such as 12-HETE, as shown in this study, provides another factor of possible therapeutic significance.     

Activation of keratinocytes with psoralen plus UVA radiation induces the release of soluble factors that suppress delayed and contact hypersensitivity.

Exposure of mice to psoralen plus ultraviolet A (320-400 nm) radiation or midrange ultraviolet B (280-320 nm) radiation causes a systemic suppression of the immune response. Although the mechanisms involved in the induction of suppression are not entirely clear, recent studies have demonstrated that ultraviolet B--irradiated keratinocytes release soluble factors that depress delayed-type hypersensitivity to alloantigens and activate the suppressor cell pathway. The purpose of this study was to determine whether PUVA-treated keratinocytes could also cause the release of such immunosuppressive factors. Treatment of keratinocytes with psoralen and UVA radiation induced the release of a factor that depressed the delayed-type hypersensitivity reaction to alloantigen. The suppressive factor was released regardless of whether the psoralen formed monofunctional or bifunctional adducts with DNA and regardless of its phototoxicity. In addition, keratinocytes treated with psoralen and lower doses of UVA radiation released a factor that inhibited contact but not delayed-type hypersensitivity, suggesting that more than one immunosuppressive factor is released following treatment of keratinocytes with appropriate doses of psoralen and UVA radiation. Our findings provide evidence that immunosuppressive factors released from keratinocytes may play a role in the induction of systemic immune suppression following PUVA treatment. Moreover, they demonstrate that PUVA treatment, unlike UVB treatment, can cause the release of more than one immunosuppressive factor from keratinocytes.     

Effect of cutaneous hypoxia upon erythema and pigment responses to UVA, UVB, and PUVA (8-MOP + UVA) in human skin

The effect of oxygen deprivation upon UVA-, UVB-, and PUVA-induced pigment and erythema responses in normal human skin was examined. Before exposure, varying degrees of hypoxia in the skin of the forearm were achieved by inflating a sphygmomanometer cuff applied to the upper arm. After the transcutaneously measured pO2 had stabilized, sites on the inner forearm were exposed to UVA, UVB, or 8-MOP + UVA radiation, to determine dose thresholds for the induction of erythema and pigmentation at different cuff pressures. Inflation of the cuff to greater than systolic pressure completely inhibited immediate and delayed pigment responses (IPD, DT) to UVA doses greater than 10 times the normal pigmentation threshold dose. UVA-induced delayed erythema responses were partially inhibited by cuff inflation: 2.7 times the minimal erythema dose of UVA was necessary to cause an erythema response when exposure occurred during vascular occlusion. In contrast, erythema and pigment responses to UVB and PUVA were unaltered by cuff pressures exceeding systolic pressure during exposure. Inhibition of UVA-induced erythema and pigment responses by vascular occlusion were reversed by the transcutaneous diffusion of 100% O2. These findings indicate that the cutaneous responses to UVA and UVB occur by separate pathways differing with respect to O2 dependence. Our findings agree with those of other studies which indicate that PUVA-induced phototoxicity and melanogenesis are not O2-dependent.     

Effect of ultraviolet irradiation on mast cell-deficient W/Wv mice

The effect of UV irradiation on the skin was investigated in (WB-W/+) X (C57BL/6J-Wv/+)F1-W/Wv mice, which are genetically deficient in tissue mast cells. Their congenic littermates (+/+) and normal albino mice (ICR or BALB/c) were used as controls. Mice were irradiated with 500 mJ/cm2 of UVB and the increment of ear thickness was measured before and 6, 12, and 24 h after irradiation. Ear swelling in W/Wv mice at 12 and 24 h after irradiation was significantly smaller than that in +/+ and ICR mice. In contrast, the number of sunburn cells formed 24 h after UVB irradiation (200 or 500 mJ/cm2) was similar in W/Wv, +/+ and ICR mice. On the other hand, when mice were treated with 8-methoxy-psoralen (0.5%) plus UVA irradiation (4 J/cm2) (topical PUVA), ears of W/Wv and BALB/c mice, which were both white in color, were thickened similarly 72 h after treatment, but less swelling was observed in +/+ mice, which were black in skin color. The amount of prostaglandin D2 (PGD2) in ears, determined by radioimmunoassay specific for PGD2, was elevated 3-fold in +/+ and ICR mice at 3 h after irradiation with 500 mJ/cm2 of UVB in comparison with basal level without irradiation. However, such elevation was not observed in W/Wv mice. These results suggest that mast cells play an important role in UVB-induced inflammation, and PGs from mast cells are responsible at least in part for the development of this reaction. However, neither mast cells nor PGs contribute to the sunburn cell formation and ear swelling response by PUVA treatment.     

Anti-inflammatory activity of 2,4, 6-trihydroxy-alpha-p-methoxyphenyl-acetophenone (compound D-58)

BACKGROUND: Active oxygen radicals as well as a variety of cytosolic protein tyrosine kinases play a role in the regulation of prostaglandin E(2) (PGE(2)), a key inflammatory mediator, released by skin cells in response to irradiation with ultraviolet B light (UVB). Identification of chemical compounds that can interrupt such events may provide a basis for the development of potent anti-inflammatory agents. OBJECTIVE: To investigate the effect of a novel genistein analog, 2,4, 6-trihydroxy-alpha-p-methoxyphenylacetophenone, with antioxidant property (compound D-58), on UVB-induced inflammatory responses. METHODS: Epidermal cell cultures were irradiated with UVB both in the presence and absence of compound D-58 and the PGE(2) released in the medium was determined by ELISA. For in vivo studies, skin inflammation was induced in mice either by carrageenan challenge of the air pouch or by an acute exposure of skin to UVB radiation. The resulting inflammatory mediator release, skin edema and the histological changes of the skin were determined both in the presence and absence of compound D-58. RESULTS: Compound D-58 treatment effectively inhibited the development of edema and histological changes in the skin of UVB-irradiated mice as well as the release of PGE(2) in vitro as well as in vivo. CONCLUSION: Compound D-58 (2,4,6-trihydroxy-alpha-p-methoxyphenylacetophenone) has potent anti-inflammatory properties.     

Impact of ultraviolet radiation on the expression of marker proteins of gap and adhesion junctions in human epidermis

Aims/background: We aimed to investigate the impact of ultraviolet B (UVB) as well as UVA1 on the epidermal expression of specific markers of gap and adhesion junctions. Methods: Twelve healthy subjects were enrolled in the study. The back of the subjects was irradiated with three MED‐UVB as well as three MED‐UVA1. Twenty‐four hours later, punch biopsies were taken from irradiated and non‐irradiated skin. Immunohistochemical procedures were used for the detection of connexin 43, E‐cadherin, involucrin, Ki‐67 using specific antibodies. Results: Staining intensity of connexin 43 in UVB‐exposed skin was significantly increased when compared with non‐exposed and UVA1‐exposed sites. By contrast, staining intensity of E‐cadherin in UVB‐exposed skin was significantly decreased when compared with non‐exposed and UVA1‐exposed sites. Involucrin and Ki‐67 staining of keratinocytes was significantly increased in UVB‐exposed sites as compared with non‐exposed and UVA1‐irradiated sites. Conclusions: UVB significantly alters the epidermal expression of gap and adhesion junction proteins possibly indicating a role of these proteins in the regulation of UV‐induced inflammation and development and progression of skin cancer.     

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.