THE EFFECT OF THE ANTIHISTAMINE CIMETIDINE ON ULTRAVIOLET-RADIATION-INDUCED TUMORIGENESIS IN THE HAIRLESS MOUSE

This experiment investigated the effect on ultraviolet (UV) radiation-induced tumorigenesis of feeding the histamine type 2 receptor antagonist, cimetidine, to Skh:HR mice. Cimetidine was fed to one group during a 70 day period of chronic UVR (5 days/week for 10 weeks), to a second group from the end of this period to the end of the experiment at 286 days and a third group was fed a control diet only throughout the experiment. Feeding mice cimetidine during the 70 day period of irradiation protected them against the later development of skin tumours.     

DEVELOPMENT OF AN in vitro SYSTEM FOR THE ANALYSIS OF ULTRAVIOLET RADIATION-INDUCED SUPPRESSION OF NATURAL KILLER CELL ACTIVITY

Previous studies have shown that natural killer (NK) cell activity was suppressed in volunteer subjects exposed to ultraviolet radiation (UVR) from solarium lamps. The present studies were carried out to determine that spectrum of UVR responsible for suppression of NK activity and to develop in vitro methods to analyze the effectivenes of sunscreen agents in prevention of UVR-mediated suppression of NK activity and other aspects of immune function. UVR from a xenon are lamp source was used to irradiate peripheral blood lymphocytes (PBL) in wells of tissue culture flasks, and transmission interference filters were used to eliminate UVR of particular wavelengths. The results indicated that UVR from this source inhibited NK activity of PBL in a dose-dependent manner with a 50% inhibitory dose of 5.5 mJ/cm² when unfiltered and 29.6 mJ/cm² when diluted through cellulose acetate, which gave a UV spectrum similar to that in solar radiation. Equivalent suppression of NK activity was mediated by UV-A (UVR > 315 nm) at dose levels of 4.2 J/cm², which was approximately 140 times greater than the amount of UV-B (UVR > 315 nm) needed to suppress NK activity. Similar dose-response curves were seen for inhibition of mitogenic responses to phytohemagglutinin except that the latter appeared less sensitive than NK to inhibition by UV-A. These studies suggest that whe the greater proportion of UV-A in solar radiation adn its greater penetration into skin is taken into account, UV-A may have equivalent or greater direct immunosuppressive effects than UV-B. The mechanisms of their immunosuppressive effects may, however, differ. The in vitro system described here would appear to provide a simple test system for further analysis of UVR-indued imunosuppression.     

Comparison of action spectra for acute cutaneous responses to ultraviolet radiation: man and albino hairless mouse

Abstract The hairless mouse has been used as an experimental model for photocarcinogenesis for about 20 years. Although the carcinogenesis action spectra for mice and man are not known, acute responses to ultraviolet radiation (UVR) in the biologically active UVB and UVC region (wavelengths below 320 nm) can be compared. Vascular response (predominantly edema) action spectra for monochromatic radiation in the Skh:HR-l (albino hairless) male mouse were determined. These action spectra were found to be very similar to the human erythema action spectrum that had been developed using the same monochromator. The accuracy of this experimentally derived action spectrum was tested with a series of polychromatic source spectra. The mice were exposed to radiation from a long arc Xe lamp filtered by varying thicknesses of Schott WG320 filters, which yielded a wide range of biologically effective spectra. Spectral irradiance measurements, when weighted with the mouse edema and human erythema action spectra and multiplied by the irradiation time required to elicit a threshold response (edema), yielded a constant weighted dose regardless of irradiation spectral quality. The integrated effective dose was approximately 200 J/m² of 297 nm equivalent energy, agreeing with requirements for the monochromatic 297 nm dose in the mice as well as for minimal human erythema. These data suggest a commonality in the UVR chromophores of mice and men as they relate to the acute responses described, and a direct additivity of effectiveness from the UVR components in a polychromatic beam, at least over the portion of the UVR spectrum tested (λ > 295 nm).     

Quercetin Prevents UV-lnduced Local Immunosuppression, but Does Not Affect UV-lnduced Tumor Growth in SKH-1 Hairless Mice

Abstract— Ultraviolet is thought to induce skin tumors by its dual activity as a mutagenic agent and a suppressor of cell-mediated immunity. In the present study the effects of quercetin, a flavonoid-containing compound, on carcinogenesis and immunosuppression were studied in SKH hairless mice exposed to suberythemal doses of UV for up to 17 weeks. It was found that quercetin did not affect the onset or growth of non-melanoma skin tumors resulting from UV exposure. In contrast, it prevented the suppression in contact hypersensitivity (CHS) to picryl chloride induced by UV. The mechanism of this prevention might be explained by the observation that the decreased number of epidermal Langerhans'cells is partly prevented by the quercetin. Quercetin did not alter the effects of UV in increasing numbers of spleen and lymph node cells, only partly in decreasing the CD8-positive cells in spleen cell populations and decreasing the lym-phoproliferative response of spleen cells to the mitogens concanavalin A and phytohemagglutinin. Thus oral quercetin did not prevent UV-induced carcinogenesis although it restored the skin-associated CHS response probably by protecting the antigen-presenting cells in the skin.     

Ultraviolet B but not A radiation activates suppressor B cells in draining lymph nodes

Immunosuppressive doses of solar-simulated UV radiation activate lymph node B cells that can suppress primary immunity by inhibiting the function of dendritic cells. The aim of this study was to determine the waveband responsible for activation of these suppressor B cells. We exposed C57BL/6 mice to various doses of either UVA or UVB radiation and analyzed the number and activation state of lymph node antigen-presenting cells (APC). Immunosuppressive doses of UVB but not UVA activated B cells as assessed by major histocompatibility complex II (MHC II) expression and doubled their numbers in draining lymph nodes. Higher doses of UVA that were not immunosuppressive actually suppressed B cell activation. Our results show that UVA and UVB suppress systemic immunity via different mechanisms. Lymph node B cells are activated in response to immunosuppressive doses of UVB but not UVA. Thus, the activation state of lymph node APC appears to be important for UV immunomodulation.     

Guinea Pig Skin,a Model for Epidermal Cellular and Molecular Changes Induced by UVR in vivo and in vitro: Effects on Mycobacterium bovis Bacillus Calmette–Guérin Vaccination

Previously, we reported that ultraviolet B‐radiation (UVR) suppressed Bacillus Calmette–Guérin (BCG) vaccine‐induced resistance to Mycobacterium tuberculosis in guinea pigs (GP). Herein, we investigated the cellular and molecular changes within the irradiated GP epidermis and the in vivo effect of supernatants from UV‐irradiated (200 J m^?2) epidermal cells (UV‐sup) on M. bovis BCG vaccination. UVR increased the number of nucleated keratinocytes in the skin, but caused a decrease in the proportions of CD25⁺T cells. In the spleen, UVR resulted in a decrease in the proportions of T‐cell subsets including CD25⁺T cells, and major histocompatibility complex (MHC) class II⁺ and CD14⁺ cells. Similarly, significant up‐regulation of several cytokine mRNAs including IL‐10 was also observed. Furthermore, UV‐sup significantly reduced the MHC class II expression in peritoneal cells and reduced T‐cell proliferation to ConA. The proliferation to purified protein derivative (PPD) was restored to normal levels by anti‐IL‐10 antibody. The UV‐sup when injected into BCG‐vaccinated GP significantly diminished the skin test response and T‐cell proliferation to PPD and up‐regulated the expression of IL‐10, IL‐4, IL‐1β and Foxp3 mRNAs in the lymph node or spleen. Thus, whole body UVR induces profound cellular and molecular changes and injection of UV‐sup from epidermal cells mimics the effect of whole body UVR in BCG‐vaccinated GP.     

No adaptation to UV-induced immunosuppression and DNA damage following exposure of mice to chronic UV-exposure

It is well known that ultraviolet (UV) radiation induces erythema, immunosuppression and carcinogenesis. We hypothesized that chronic exposure to solar UV radiation induces adaptation that eventually prevents the suppression of acquired immunity. We studied adaptation for UV-induced immunosuppression after chronic exposure of mice to a suberythemal dose of solar simulated radiation (SSR) with Cleo Natural lamps, and subsequent exposure to an immunosuppressive dose of solar or UVB radiation (TL12). After UV dosing, the mice were sensitized and challenged with either diphenylcyclopropenone (DPCP) or picryl chloride (PCl). To assess the adaptation induced by solar simulated radiation, we measured the proliferative response and cytokine production of skin-draining lymph node cells after immunization to DPCP, the contact hypersensitivity (CHS) response to PCl, and thymine-thymine (T-T) cyclobutane dimers in the skin of mice. After induction of immunosuppression by SSR or by TL12 lamps, the proliferative response of draining lymph node cells after challenge with DPCP, or the CHS after challenge with PCl, showed significant suppression of the immune response. Chronic irradiation from SSR preceding the immunosuppressive dose of UV failed to restore the suppressed immune response. Reduced lipopolysaccharide-triggered cytokine production (of IL-12p40, IFN-gamma, IL-6 and TNF-alpha) by draining lymph node cells of mice sensitized and challenged with DPCP indicated that no adaptation is induced. In addition, the mice were not protected from T-T dimer DNA damage after chronic solar irradiation. Our studies reveal no evidence that chronic exposure to low doses of SSR induces adaptation to UV-induced suppression of acquired immunity.     

Inverse relationship between increased apoptosis and decreased skin cancer in UV-irradiated CD1d-/- mice

We previously demonstrated that CD1d knockout mice were resistant to ultraviolet (UV)-induced immunosuppression. Because immune suppression is a critical factor in the development of UV-induced skin cancers, we investigated the response of wild type (WT) and CD1d-/- mice to UV carcinogenesis. We found that although 100% of WT mice developed skin tumors after 45 weeks of UV irradiation, only 60% of CD1d-/- mice developed skin tumors. To investigate the mechanisms involved in the resistance of CD1d-/- mice to UV-induced carcinogenesis, we determined the time course and kinetics of keratinocyte cell death after UV irradiation. After acute UV exposure, the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL)-positive keratinocytes were eliminated from the skin of WT mice by 72 h post-UV, but they still persisted until 96 h in CD1d-/- mice. The kinetics of p53 protein expression closely followed the kinetics of apoptotic cell death. Chronic UV irradiation resulted in induction of a significantly higher number of apoptotic keratinocytes in CD1d-/- than WT mice. In addition, epidermis and dermis from chronically UV-irradiated CD1d-/- mice harbored significantly fewer p53 mutations than WT mice. These results indicate that the resistance of CD1d-/- mice to UV carcinogenesis may be due to increased cell death and elimination of keratinocytes and fibroblasts containing DNA damage and p53 mutations.     

Antioxidative Responses of Two Marine Microalgae During Acclimation to Static and Fluctuating Natural UV Radiation

Photoacclimation properties were investigated in two marine microalgae exposed to four ambient irradiance conditions: static photosynthetically active radiation (PAR: 400–700 nm), static PAR + UVR (280–700 nm), dynamic PAR and dynamic PAR + UVR. High light acclimated cultures of Thalassiosira weissflogii and Dunaliella tertiolecta were exposed outdoors for a maximum of 7 days. Dynamic irradiance was established by computer controlled vertical movement of 2 L bottles in a water filled basin. Immediate (<24 h), short-term (1–3 days) and long-term (4–7 days) photoacclimation was followed for antioxidants (superoxide dismutase, ascorbate peroxidase and glutathione cycling), growth and pigment pools. Changes in UVR sensitivity during photoacclimation were monitored by measuring UVR-induced inhibition of carbon assimilation under standardized UV conditions using an indoor solar simulator. Both species showed immediate antioxidant responses due to their transfer to the outdoor conditions. Furthermore, upon outdoor exposure, carbon assimilation and growth rates were reduced in both species compared with initial conditions; however, these effects were most pronounced in D. tertiolecta . Outdoor UV exposure did not alter antioxidant levels when compared with PAR-only controls in both species. In contrast, growth was significantly affected in the static UVR cultures, concurrent with significantly enhanced UVR resistance. We conclude that antioxidants play a minor role in the reinforcement of natural UVR resistance in T. weissflogii and D. tertiolecta .     

Analysis of Compact Fluorescent Lights for Use by Patients with Photosensitive Conditions

Ultraviolet radiation (UVR) is hazardous to patients with photosensitive skin disorders, such as lupus erythematosus, xeroderma pigmentosum and skin cancer. As such, these patients are advised to minimize their exposure to UVR. Classically, this is accomplished through careful avoidance of sun exposure and artificial tanning booths. Indoor light bulbs, however, are generally not considered to pose significant UVR hazard. We sought to test this notion by measuring the UV emissions of 19 different compact fluorescent light bulbs. The ability to induce skin damage was assessed with the CIE erythema action spectrum, ANSI S(λ) generalized UV hazard spectrum and the CIE photocarcinogenesis action spectrum. The results indicate that there is a great deal of variation amongst different bulbs, even within the same class. Although the irradiance of any given bulb is low, the possible daily exposure time is rather lengthy. This results in potential daily UVR doses ranging from 0.1 to 625 mJ cm⁻², including a daily UVB (290–320 nm) dose of 0.01 to 15 mJ cm⁻². Because patients are exposed continually over long time frames, this could lead to significant cumulative damage. It would therefore be prudent for patients to use bulbs with the lowest UV irradiance.     

ULTRAVIOLET ENHANCED REACTIVATION OF HERPES SIMPLEX VIRUS INACTIVATED BY DIFFERENT WAVELENGTHS OF UV RADIATION

The degree of ultraviolet enhanced reactivation (UVR) exhibited by mammalian cells when infected with Herpes simplex virus inactivated by different wavelengths of far ultraviolet (UV) radiation was measured. A wavelength dependence for this effect is presented over the wavelength region 238–297 nm. Within the limits of the deviations obtained, the degree of UVR exhibited is similar at each wavelength. This suggests that virus irradiated with different wavelengths of UV radiation received the same type of damage or that cells repaired the different types of viral damage with the same efficiency.     

CARCINOGENIC and MELANOGENIC EFFECTS OF A FILTERED METAL HALIDE UVA SOURCE and A TUBULAR FLUORESCENT UVA TANNING SOURCE WITH OR WITHOUT ADDITIONAL SOLAR-SIMULATED UV RADIATION IN HAIRLESS MICE

Abstract— The carcinogenic and melanogenic effects of a filtered metal halide source (UVASUN) that emits UV radiation in a range from 340 to 400 nm and a bank of Philips TL 09R tubes (TL 09) emitting in a range from 310 to 400 nm were studied in lightly pigmented hairless hr/hr C3H/Tif mice. Both the carcinogenic effect of the two UVA radiation sources alone and in combination with a UV source, consisting of one Philips TL 12 and five Bellarium-S SA-1–12 tubes emitting radiation somewhat similar to the UV part of the solar spectrum (SOLAR UV), were investigated. Finally, the melanogenic effect of exposure to the two UVA sources were studied. The mice were exposed to the UVA sources 30 min/ day, 5 days/week, in equal erythemogenic doses, calculated by using the Commission Internationale de 1'Eclairage human erythema action spectrum. Equal erythemogenic doses of TL 09 and UVASUN induced the same degree of skin pigmentation, but skin tumor development was enhanced in mice exposed to TL 09 compared with UVASUN ( P < 0.0005). For all but one tumor, endpoint pretreatment with TL 09 or UVASUN for 91 days did not influence tumor development during subsequent exposure to SOLAR UV radiation 10 min/day, 4 days/week. Exposure to the two UVA radiation sources after 91 days of SOLAR UV exposure significantly enhanced skin tumor development. Overall, the data on the interaction between exposure to the UVA sources and SOLAR UV indicated that the risk of SOLAR UV-induced carcinogenesis was independent of the type of prior-UVA exposure and post-UVA exposure.     

Protection from inflammation, immunosuppression and carcinogenesis induced by UV radiation in mice by topical Pycnogenol

Pycnogenol is a standardized extract of the bark of the French maritime pine, Pinus pinaster Ait., that has multiple biological effects, including antioxidant, anti-inflammatory and anticarcinogenic properties. This study describes the effect of topical application of lotions containing Pycnogenol to Skh:hr hairless mice undergoing minimally inflammatory daily exposures to solar-simulated UV radiation (SSUV). We report that concentrations of Pycnogenol of 0.05-0.2% applied to the irradiated dorsal skin immediately after exposure resulted in dose-dependent reduction of the inflammatory sunburn reaction, measured as its edema component. When mice received three consecutive daily exposures of minimally edematous SSUV, their ability to raise a contact hypersensitivity (CHS) reaction was suppressed by 54%. Pycnogenol lotions applied postirradiation reduced this immunosuppression to 22% (0.05% Pycnogenol) and 13% (0.1% Pycnogenol). Furthermore, when CHS was suppressed by 71% with exogenous treatment with cis-urocanic acid, the putative epidermal mediator of photoimmunosuppression, 0.2% Pycnogenol lotion reduced the immunosuppression to 18%. Chronic exposure to SSUV on 5 days/week for 10 weeks induced skin tumors from 11 weeks in both control mice and in mice receiving daily applications of 0.05% Pycnogenol, but tumor appearance was significantly delayed until 20 weeks in mice receiving 0.2% Pycnogenol. Furthermore, whereas 100% of control mice had at least one tumor by 30 weeks, and mice treated with 0.05% Pycnogenol by 33 weeks, the maximum tumor prevalence in mice treated with 0.2% Pycnogenol was significantly reduced to 85%, with some mice remaining tumor free. Average tumor multiplicity was also significantly reduced by 0.2% Pycnogenol, from 5.2 in control mice to 3.5 at 35 weeks. Thus, topical Pycnogenol offered significant and dose-dependent protection from SSUV-induced acute inflammation, immunosuppression and carcinogenesis, when applied to the skin after daily irradiation. Pycnogenol, therefore, in addition to its recognized health benefits in other organs, appears to have potential in providing photoprotection for humans in a complementary role with sunscreens, having demonstrable activity when applied to the skin after, rather than before, UV exposure.     

Protein kinase C epsilon signals ultraviolet light-induced cutaneous damage and development of squamous cell carcinoma possibly through Induction of specific cytokines in a paracrine mechanism

Protein kinase C (PKC), a family of phospholipid-dependent serine/threonine kinases, is not only the major intracellular receptor for the mouse skin tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) but also is activated by a variety of stress factors including ultraviolet radiation (UVR). PKCepsilon is among six isoforms (alpha, delta, epsilon, eta, mu and zeta) expressed in the mouse skin. To determine the in vivo functional specificity of PKCepsilon in mouse skin carcinogenesis, we generated PKCepsilon transgenic mouse (FVB/N) lines 224 and 215 that overexpress PKCepsilon protein approximately 8- and 18-fold, respectively, over endogenous levels in the basal epidermal cells and cells of the hair follicle. PKCepsilon transgenic mice were observed to be highly sensitive to the development of papilloma-independent metastatic squamous cell carcinoma (mSCC) elicited either by repeated exposure to UVR or by the 7,12-Dimethylbenzanthracene-TPA tumor promotion protocol. The development of squamous cell carcinoma (SCC) appears to be linked to the PKCepsilon-mediated induction of cytokine tumor necrosis factor-alpha(TNFalpha). Immunohistochemical analysis for the expression of PKCepsilon in the SCC of PKCepsilon transgenic mice revealed that PKCepsilon was not expressed in the tumor itself; however, the uninvolved tissue surrounding the SCC exhibited intense PKCepsilon expression. Also, human SCC, similar to mouse SCC, did not express PKCepsilon in the tumor, whereas the surrounding uninvolved epidermis revealed strong PKCepsilon expression. These findings in both the PKCepsilon mouse model and human SCC indicate that overexpression of PKCepsilon in epidermis may lead to a microenvironment, which is suitable for enhancing the development of mSCC by a paracrine mechanism involving specific cytokines including TNFalpha.     

Decrease in langerhans cells and increase in lymph node dendritic cells following chronic exposure of mice to suberythemal doses of solar simulated radiation

Exposure of certain strains of mice to ultraviolet radiation (UVR) causes suppression of some innate and adaptive immune responses. One such consequence of acute UVB exposure is a reduction in the number of Langerhans cells (LC) in the epidermis and an increase in dendritic cells (DC) in lymph nodes draining the irradiated skin sites. Exposure to chronic UVB irradiation also has effects on the immune system, but it is unknown what effects are caused by repeated doses of solar simulated radiation (SSR). Consequently, the main aims of the present study were to determine whether repeated exposure to low doses of SSR would lead to similar changes in these cell populations and whether chronic doses of SSR activate a protective photoadaptation mechanism. Groups of C3H/HeN mice were irradiated daily with 3.7 J/cm(2) SSR from Cleo Natural lamps for 2, 10, 20, 30 or 60 days. Further groups of mice received an additional dose of 7.4 J/cm(2) SSR on days 2, 10, 30 or 60 to test for photoadaptation. The numbers of LC in the epidermis and DC in the lymph nodes draining irradiated skin sites were counted 24 h after the final irradiation. With the exception of mice irradiated for only 2 days, LC were significantly reduced throughout the chronic irradiation protocol, and no recovery occurred. DC numbers were significantly increased in the draining lymph nodes of mice irradiated for 20 days and 60 days.     

Photo‐co‐carcinogenesis of Topically Applied Retinyl Palmitate in SKH‐1 Hairless Mice

Cosmetic products that contain retinyl palmitate are popular as antiaging skin treatments; however, recent studies suggest a risk for enhanced skin tumor development with topical retinyl palmitate applications and exposure to solar ultraviolet radiation (UVR). In this study, we investigated the potential of retinyl palmitate to enhance UVR‐induced photo‐co‐carcinogenesis. Groups of 36 male and 36 female SKH‐1 hairless mice were exposed to simulated solar light (SSL) and treated with the control cream or creams containing retinyl palmitate, 5 days per week for 40 weeks. Other groups of mice were exposed to SSL and received no cream treatment or received cream treatments and were exposed to ultraviolet‐A or ultraviolet‐B. Mice were monitored for the development of skin tumors, and the incidences and multiplicities of squamous cell neoplasia were determined by histopathology. In both the absence and presence of SSL, mice administered the control cream developed skin tumors earlier and had higher incidences and multiplicities of skin squamous cell neoplasms than mice that received no cream treatment. Compared to the control cream groups, mice exposed to SSL and administered the retinyl palmitate creams demonstrated earlier onsets of skin tumors and had increased incidences and multiplicities of squamous cell skin neoplasms.     

Effect of Ultraviolet Radiation on Acetylcholinesterase Activity in Freshwater Copepods

We analyzed the effects of UV radiation (UVR) effects on acetylcholinesterase (AChE) activity in two calanoid copepods, Boeckella gibbosa and Parabroteas sarsi that inhabit Patagonian shallow lakes. We studied the effect of experimental UVR (UV-B and UV-A) exposure on AChE activity in relation to basal antioxidant capacities of both copepods. Our experiments showed that UVR can effectively depress AChE activity, although with differences between species. In both copepods AChE was affected by UV-B, whereas UV-A only affected AChE in B. gibbosa. Both copepods also differed in body elemental composition (C:N:P), photoprotecting compound content (carotenoids and mycosporine-like amino acids) and enzymatic antioxidant capacity (glutathione S-transferase [GST]). Our results suggest that when exposed to UVR, AChE activity would depend more on the antioxidant capacity (GST) and P availability for enzyme synthesis than on the photoprotective compounds.