UVB-induced Immunosuppression Research Articles

208 Mouse langerhans cells do not express high affinity IgE receptor

Nucleotide excision repair (NER) removes a wide variety of lesions from the genome and is deficient in the genetic disorder, xeroderma pigmentosum (XP). In this paper, an in vitro analysis of the XP group A gene product (XPA protein) is reported. Results of an analysis on the pathogenesis of ultraviolet (UV)-B-induced skin cancer in the XPA gene-knockout mouse are also described: (1) contrary to wild type mice, significant bias of p53 mutations to the transcribed strand and no evident p53 mutational hot spots were detected in the skin tumors of XPA-knockout mice. (2) Skin cancer cell lines from UVB-irradiated XPA-knockout mice had a decreased mismatch repair activity and an abnormal cell cycle checkpoint, suggesting that the downregulation of mismatch repair helps cells escape killing by UVB and that mismatch repair-deficient clones are selected for during the tumorigenic transformation of XPA (−/−) cells. (3) The XPA-knockout mice showed a higher frequency of UVB-induced mutation in the rpsL transgene at a low dose of UVB-irradiation than the wild type mice. CC→TT tandem transition, a hallmark of UV-induced mutation, was detected at higher frequency in the rpsL transgene in the XPA-knockout mice than the wild type mice. This rpsL/XPA mouse system will be useful for further analysing the role of NER in the mutagenesis induced by various carcinogens. (4) The UVB-induced immunosuppression was greatly enhanced in the XPA-knockout mice. It is possible that an enhanced impairment of the immune system by UVB irradiation is involved in the high incidence of skin cancer in XP.

The effect of oral quercetin on UVB-induced tumor growth and local immunosuppression in SKH-1

The effects of quercetin (4%) on UVB-induced carcinogenesis and immunosuppression were studied in hairless SKH-1 mice exposed daily to suberythemal UVB for 12/13 and 16/17 weeks. Macroscopic and microscopic examinations showed that quercetin did not affect the onset and growth of UVB-induced non-melanoma skin tumors. Quercetin prevented the UV-induced suppression of the contact hypersensitivity (CHS) and the reduction of the percentage of CD8-positive cells in spleen and lymph nodes. Other immunological parameters were not affected. Thus, the results indicate that oral intake of a high dose of quercetin does not prevent UVB-induced carcinogenesis, although it restores the skin-associated CHS response.

Molecular aspects of UVB-induced immunosuppression.

Ultraviolet light can affect the immune system locally as well as systemically leading to an impaired resistance to neoplastic cells and/or infections. Prior to the biological effect, UVB must be absorbed by a chromophore in the skin where it will give a signal that can lead to an altered immune response in the skin or elsewhere. These altered immune responses may be constituted by alteration in among others: cytokine profile, growth factors and costimulatory signals. Several hypotheses about the identity of the photoreceptor have been put forward. One photoreceptor in the skin is urocanic acid (UCA), that can isomerize from the trans- to the cis-isomer. The cis-isomer has immunosuppressive properties. Another photoreceptor is DNA that also efficiently absorbs UV wavelengths. After absorption the structure of the DNA molecule is altered. This alteration might lead to gene activation responsible for the immunotoxic outcome (altered gene expression). It has been demonstrated that the formation of DNA photoproducts by UV light is associated with the activation of many genes. Several studies indicate that UV-induced DNA damage, in the form of cyclobutyl pyrimidine dimers plays a role in UV-induced suppression of the immune system locally as well as systemically. In mice that were injected with liposomes containing the excision repair enzyme T4 endonuclease UVB-induced dimers were removed more efficiently as compared to control mice. In these mice UV-induced immunosuppression was prevented. Pilot studies by Kripke et al. indicated that the release of IL-IO and TNF alpha that are both induced by DNA damage might be involved. In preliminary studies with mice that were deficient with respect to DNA repair lower doses of UV were needed for the induction of immunosuppression as compared to their normal littermates. These studies indicate that altered gene expression plays a pivotal role in UVB-induced immunosuppression. In addition to a role for UCA and DNA in UV-induced immunosuppression it is postulated recently that signal transduction (EGF-receptor mediated upregulation of phospholipase A2) and transcription factors (NF kappa B, p91) are involved in UV-induced immunomodulation.

Impaired Immunosuppressive Response to Ultraviolet Radiation in Interleukin-10–Deficient Mice

Exposure to mid-range ultraviolet radiation (UVR) [280-320 nm, ultraviolet B (UVB) radiation] inhibits the acquisition of delayed-type hypersensitivity in mice and contact hypersensitivity in rodents and humans. Intraperitoneal administration of interleukin 10 (IL-10) inhibits the sensitization of mice to alloantigens for a delayed-type hypersensitivity reaction and administration of neutralizing antibodies to IL-10 largely, but not totally, blocks the UVR-mediated suppression of the ability to sensitize mice. This suggests that these inhibitory effects of UVB radiation may be mediated by release of IL-10. To test this hypothesis directly, IL-10 gene-targeted (IL-10T) mice lacking expression of IL-10 were examined for the ability of UVB radiation to suppress induction of delayed-type hypersensitivity to alloantigens. IL-10T mice were completely resistant to UVB-induced immunosuppression in this system. Interestingly, UVB radiation could suppress in IL-10T mice the induction of contact hypersensitivity to a hapten applied to the skin at a site distant of irradiation, supporting the concept that regulation pathways of delayed-type hypersensitivity and contact hypersensitivity responses by UVR differ. These data provide additional understanding of the mechanisms of immunosuppression induced by UVR and suggest that IL-10 release subsequent to UVB radiation may play a role in the growth immunogenic UVB-induced cutaneous malignancies in the primary host.

The protective effect of N-acetylcysteine on UVB-induced immunosuppression by inhibition of the action of cis-urocanic acid.

A recent study has shown that N-acetylcysteine (NAC) not only has sun-protective properties but also inhibits the UVB-induced suppression of contact hypersensitivity (CHS) in mice. Because NAC does not absorb any UVA (320-400 nm radiation) or UVB (290-320 nm radiation) we have studied the underlying mechanism of protection. Irradiation of solutions of plasmid DNA with UVC (200-290 nm radiation) (10 J m-2) resulted in the formation of cyclobutane pyrimidine dimers, but the extent to which this occurred was not affected by the presence of NAC as was determined by an in vitro T4 endonuclease assay. N-acetylcysteine proved not to have any effect on the photoisomerization of trans-urocanic acid (UCA) to its cis-form in vitro; at equilibrium, approximately 55% cis-UCA was formed. The same percentage was also found in vivo on exposure of mice to UVB (15 kJ m-2). Topical application of NAC 30 min prior to irradiation did not have any influence as well on the photoisomerization of trans- to cis-UCA. These in vivo experiments were performed under the same conditions used previously to show the protective effect of NAC against UVB-induced suppression of CHS. We conclude that this protection of NAC is at least partly based on interference in the role of cis-UCA in UVB-induced suppression of CHS. This conclusion is supported by the observation that NAC completely inhibits the suppression of CHS by cis-UCA administered to mice that were always kept in the dark. In the same range of doses as used in the present study, it was shown in our previous study that NAC alone does not affect the CHS response.

Effects of UV light on the immune system: Answers to five basic questions

Since the first clear demonstration in the 1970s of an immunologic linkage between UV-light exposure of laboratory mice and the development of skin cancers in these animals, much progress has been achieved in our understanding of the effects of UV light on the immune system. At the cellular level, two overlapping mechanisms have been expounded to explain UVB-induced immunosuppression: (1) altered cutaneous antigen presentation due to perturbations in Langerhans' cells and/or the recruitment of macrophage-like cells into skin, and (2) the initiated or up-regulated secretion by skin cells (particularly but not limited to keratinocytes) of soluble mediators of immunosuppression (α-melanocyte-stimulating hormone, interleukin 10, tumor necrosis factor α). An end result common to both mechanisms is inhibition of Th1-type immunity in favor of preserved or heightened Th2-type immunity. At the molecular level, two targets of UVB radiation are the subject of intense investigation. Circumstantial evidence has accumulated to implicate a direct effect of UVB on DNA (in antigen-presenting cells and/or cytokine-producing cells) as the triggering cause of UVB-evoked immunosuppression. On the other hand, UVB-triggered changes in cell membrane molecules (epidermal growth factor receptor, intercellular adhesion molecule 1, B7) have been correlated with temporally distal UV effects, including the activation of gene transcription pathways and the down-regulation of antigen presentation independent of DNA damage.

The role of cis-urocanic acid in UVB-induced suppression of contact hypersensitivity

Ultraviolet light B (UVB) is well recognized to suppress the contact hypersensitivity (CHS) response and it has been postulated that cis-urocanic acid (UCA) is a mediator of the immunosuppression. This study was designed to examine the effect of UCA on CHS and to clarify its role in UVB-induced immunosuppression in C57BL/6 mice. Intradermal injection of 0.5–50 μg cis-UCA into the ear 2 h before DNFB sensitization resulted in a 60–70% reduction of CHS assessed by car swelling, whereas trans-UCA did not have a significant effect on CHS except at a high dose (50 μg) which showed a 20–40% suppression. Intraperitoneal injection of anti- cis-UCA antibody before administration of cis-UCA abrogated the suppression. To examine the effect of UCA on UVB-induced immunosuppression, some mice were pre-treated with anti- cis-UCA antibody and then exposed to UVB (960 J/m 2). After 3 days the mice were sensitized either on the irradiated abdominal skin or on the unirradiated dorsal surface of the right ear followed by the challenge on the left ear. The CHS response was significantly suppressed in UVB-irradiated mice both locally (abdominal sensitization, suppression was 45%, P < 0.001) and systemically (ear sensitization, suppression was 53%, P < 0.0025). The CHS response was partially restored in both abdominal sensitized mice and ear sensitized mice by pre-treatment with anti- cis-UCA antibody. These results confirmed the immunosuppressive effects of cis-UCA on CHS and suggest that cis-UCA plays a role in UVB-induced local and systemic immunosuppression.

Keratinocyte-derived cytokines and UVB-induced immunosuppression.

Ultraviolet radiation (UVB) in sunlight is known to have multiple effects on the immune system. Evidence suggests that UVB-induced immunosuppression is mediated in part by immunosuppressive and immunoregulatory cytokines. Our studies have utilized gene-targeted mutant mice to determine key molecular requirements essential for the development of UVB-induced immunosuppression. Preliminary results from our laboratory suggest that TNF-alpha plays a regulatory role in contact hypersensitivity, but is not a crucial factor for UVB-induced immunosuppression, and that multiple factors are involved in the induction of UVB mediated immunosuppression.

Protection against ultraviolet-B radiation-induced local and systemic suppression of contact hypersensitivity and edema responses in C3H/HeN mice by green tea polyphenols.

Exposure of skin to UV radiation can cause diverse biological effects, including induction of inflammation, alteration in cutaneous immune cells and impairment of contact hypersensitivity (CHS) responses. Our laboratory has demonstrated that oral feeding as well as topical application of a polyphenolic fraction isolated from green tea (GTP) affords protection against the carcinogenic effects of UVB (280-320 nm) radiation. In this study, we investigated whether GTP could protect against UVB-induced immunosuppression and cutaneous inflammatory responses in C3H mice. Immunosuppression was assessed by contact sensitization with 2,4-dinitrofluorobenzene applied to UVB-irradiated skin (local suppression) or to a distant site (systemic suppression), while double skin-fold swelling was used as the measure of UVB-induced inflammation. Topical application of GTP (1-6 mg/animal), 30 min prior to or 30 min after exposure to a single dose of UVB (2 kJ/m2) resulted in significant protection against local (25-90%) and systemic suppression (23-95%) of CHS and inflammation in mouse dorsal skin (70-80%). These protective effects were dependent on the dose of GTP employed; increasing the dose (1-6 mg/animal) resulted in an increased protective effect (25-93%). The protective effects were also dependent on the dose of UVB (2-32 kJ/m2). Among the four major epicatechin derivatives present in GTP, (-)-epigallocatechin-3-gallate, the major constituent in GTP, was found to be the most effective in affording protection against UVB-caused CHS and inflammatory responses. Our study suggests that green tea, specifically polyphenols present therein, may be useful against inflammatory dermatoses and immunosuppression caused by solar radiation.

Cis-urocanic acid failed to affect in vitro human Langerhans cell allostimulatory function.

Urocanic acid (UCA) represents the major ultraviolet B (UVB, 290-320 nm)-absorbing component of the skin. Trans-UCA is naturally produced in the stratum corneum and converts to the cis isomer upon UVB irradiation. In this study, we examined the effect of purified cis-UCA (about 99% of cis isomer) on the human Langerhans cell (LC) allostimulatory function by using the mixed epidermal cell-lymphocyte reaction (MELR). We found that addition of increasing amounts (6.5-400 micrograms/mL) of purified cis-UCA or trans-UCA did not modify the T-cell response supported by enriched LC (eLC: 8-25% LC) as well as purified LC (pLC: 70-90% LC) suspensions. Because cis-UCA had no effect on the allostimulatory function of untreated LC, we investigated whether this compound could modify T-cell proliferation induced by UVB-irradiated LC. The UVB exposure of eLC or pLC to 100 J/m2 significantly inhibited the capacity of both suspensions to mount a T-cell response. However, addition of cis-UCA did not potentiate this UVB-induced immunosuppression. The eLC or pLC were then incubated with cis-UCA for 18 h at 37 degrees C and washed before adding to allogeneic T cells. The obtained proliferative response was similar to that induced by control LC incubated in medium alone, demonstrating that pretreatment with cis-UCA did not alter human LC function. In conclusion, these results strongly suggest that cis-UCA has no direct effect on human LC antigen-presenting function.

Do Sunscreens Prevent UVB-Induced Immunosuppression?

Exposure to ultraviolet light in the 280-to-320-nm range (UVB) induces local and systemic immunosuppression in experimental animals and humans. In

Prevention of UVB-induced immunosuppression in humans by a high sun protection factor sunscreen

<h3>Background and Design:</h3> To date, studies of the effectiveness of sunscreens in preventing UVB-induced suppression of contact hypersensitivity in humans have not been published. Several studies in mice of the protection afforded by sunscreens from UVB-induced suppression of contact hypersensitivity and rejection of transplanted skin cancers have yielded dissimilar results, ranging from ''no'' to ''complete'' protection. We sought to determine whether the effect of preapplication of a sun protection factor (SPF) 29 sunscreen (containing octyl methoxycinnamate, oxybenzone, and octyl salicylate) could prevent local UVB-induced suppression of contact hypersensitivity to dinitrochlorobenzene (DNCB). Nineteen subjects received either three minimal erythema doses of UVB daily on three consecutive days (UVB group) or sunscreen followed by this same dose of UVB irradiation (sunscreen plus UVB group) to a 16-cm²area of the buttock. One day after completion of irradiation, DNCB was applied to this buttock site, and 2 weeks later, forearm challenge with four different concentrations of DNCB was performed. A control group of 10 subjects underwent DNCB testing as above, but with no prior exposure to UVB (no-UVB group). <h3>Results:</h3> The UVB group had a reduced response rate to all challenge doses of DNCB (3.125, 6.25, and 8.8 μg), except for the highest dose (12.5 μg) compared with the no-UVB control group (Fisher's Exact test, P≤.008), and compared with the sunscreen plus UVB group (P≤.02). The no-UVB and sunscreen plus UVB groups showed no significant differences in response rates to any of the doses of DNCB tested (P≥.53). <h3>Conclusions:</h3> These results indicate that application of a sunscreen with over ninefold greater protection than that needed to prevent erythema prior to localized UVB radiation prevents localized UVB-induced suppression of contact hypersensitivity. Further studies are needed to determine whether sunscreens providing less protection, yet still preventing erythema, adequately prevent suppression of contact hypersensitivity, a possible surrogate marker for skin cancer tumor antigen recognition and rejection. (Arch Dermatol. 1995;131:1128-1133)

Prevention of UVB-Induced Immunosuppression in Humans by a High Sun Protection Factor Sunscreen

To date, studies of the effectiveness of sunscreens in preventing UVB-induced suppression of contact hypersensitivity in humans have not been published. Several studies in mice of the protection afforded by sunscreens from UVB-induced suppression of contact hypersensitivity and rejection of transplanted skin cancers have yielded dissimilar results, ranging from "no" to "complete" protection. We sought to determine whether the effect of preapplication of a sun protection factor (SPF) 29 sunscreen (containing octyl methoxycinnamate, oxybenzone, and octyl salicylate) could prevent local UVB-induced suppression of contact hypersensitivity to dinitrochlorobenzene (DNCB). Nineteen subjects received either three minimal erythema doses of UVB daily on three consecutive days (UVB group) or sunscreen followed by this same dose of UVB irradiation (sunscreen plus UVB group) to a 16-cm2 area of the buttock. One day after completion of irradiation, DNCB was applied to this buttock site, and 2 weeks later, forearm challenge with four different concentrations of DNCB was performed. A control group of 10 subjects underwent DNCB testing as above, but with no prior exposure to UVB (no-UVB group). The UVB group had a reduced response rate to all challenge doses of DNCB (3.125, 6.25, and 8.8 micrograms), except for the highest dose (12.5 micrograms) compared with the no-UVB control group (Fisher's Exact test, P < or = .008), and compared with the sunscreen plus UVB group (P < or = .02). The no-UVB and sunscreen plus UVB groups showed no significant differences in response rates to any of the doses of DNCB tested (P > or = .53). These results indicate that application of a sunscreen with over ninefold greater protection than that needed to prevent erythema prior to localized UVB radiation prevents localized UVB-induced suppression of contact hypersensitivity. Further studies are needed to determine whether sunscreens providing less protection, yet still preventing erythema, adequately prevent suppression of contact hypersensitivity, a possible surrogate marker for skin cancer tumor antigen recognition and rejection.

In Vitro Effects of Ultraviolet B Radiation on Human Langerhans Cell Antigen-Presenting Function

The effects of ultraviolet B radiation (UVB) on the immune function of human epidermal Langerhans cells (LC) were studied by using the mixed epidermal cell-lymphocyte reaction (MELR). Exposure of both enriched LC suspensions (eLC, 8-20% LC) and purified LC suspensions (pLC, 70-90% LC) to increasing doses of UVB radiation (25 to 200 J/m2) decreased the proliferative T cell response in a very similar dose-dependent way, suggesting that keratinocytes did not play a major role in the UVB-induced inhibition of MELR. Supernatants from irradiated cultured eLC or pLC failed to inhibit T cell proliferation induced by untreated pLC. Furthermore, addition of irradiated eLC to untreated pLC did not affect the allogeneic T cell response. Taken together, these results provide evidence that in vitro UVB-induced immunosuppression was not mediated by inhibitory soluble factors that could affect either LC allostimulatory property or T cell proliferative response. UVB irradiation of human LC inhibited the capacity of these cells to induce CD4+ as well as CD8+ T cell proliferation. UVB-irradiated LC also induced a decreased T cell response to recall antigen or mitogen. Moreover, addition of exogeneous cytokines such as IL-1β, IL-1α, or IL-2 did not reverse the defective function of UVB-irradiated LC in MELR. The inhibitory effect of UVB radiation on human LC was not related to a decreased HLA-DR expression. Because cultured LC appeared to be less sensitive than freshly isolated LC to UVB-induced suppressive effects, the deleterious effects of UVB radiation on human LC allostimulatory properties may be associated with an impaired development of LC accessory function.

Topically applied N-acetylcysteine as a protector against UVB-induced systemic immunosuppression

The potential protective efficacy of N-acetylcysteine against systemic immunosuppression in mice, as a result of UVB exposure, was investigated. The contact hypersensitivity response to trinitrochlorobenzene applied at a distant, non-irradiated site, was used to assess the systemic immunosuppression. Topical application of N-acetylcysteine (0.4–3.2 μmol cm −2), 30 min prior to irradiation (15 kJ m −2), markedly inhibited the UVB-induced immunosuppression. Because N-acetylcysteine does not absorb UVA or UVB radiation, the mechanism of protection must be different from that of sunscreens. The results of this study may have important practical implications in protecting human beings against the deleterious effects of UVB radiation.

Inhibitory effects of ultraviolet B on human Langerhans cell antigen presenting function.

Ultraviolet B (UVB) radiations are known to suppress induction of cutaneous immune responses. Since these radiations are almost completely absorbed within epidermis, epidermal cells were considered as potential targets for their various effects. Among epidermal cells, interest was focused on Langerhans cells (LC) because these cells are the antigen presenting cell of epidermis and play a key role in contact hypersensitivity reactions. In the murine models, UVB-induced immunosuppression has been described to both direct effect on LC function1 and/or to indirect effect through the liberation of keratinocyte-derived factors2. In human being, only few data are available concerning the mechanisms involved in this process. Here, we analysed the effects of narrow-band of UVB radiation (312 nm) on human LC antigen presenting function by using the mixed epidermal cell lymphocyte reaction (MELR).KeywordsAccessory FunctionAntigen Present FunctionUrocanic AcidUnirradiated CellCell Antigen Present FunctionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Mechanisms of local, low-dose UVB-induced immunosuppression in contact hypersensitivity.

Preirradiation of contact sensitizing sites to low-dose ultraviolet B (UVB) renders animals unresponsive to challenge reaction. This unresponsiveness is known as local, low-dose UVB-induced immunosuppression. Although researchers in this area have developed theories, the exact mechanisms of UVB-induced immunosuppression are still a matter of controversy. This article reviewed various scientific data on UVB-induced immunosuppression, categorizing them into individual sequential steps in the whole cascade.

Factors influencing UVB-induced local immunosuppression of contact hypersensitization (CHS)

Factors influencing UVB-induced local immunosuppression of contact hypersensitization (CHS)

Ultraviolet-induced suppressor T cells and factor(s) in murine contact photosensitivity: III. Mode of action of T-cell-suppressor factor(s) and interaction with cytokines

The mode of action of T-cell-suppressor factor (TsF) induced by ultraviolet B (UVB) preirradiation in terms of interaction with several cytokines was studied. Suppression of murine contact photosensitivity (CPS) to 3,3′,4′,5-tetrachlorosalicylanilide (TCSA) by preirradiation of the sensitizing site to low doses of UVB was caused by antigen-specific suppressor T cells (Ts) and was not associated with the generation of efferent limb-acting suppressor cells. TsF released by Ts inhibited the proliferation of immune lymph node (LN) cells in vitro and reduced interleukin (IL)-2 production of these cells in an antigen-specific fashion without affecting the IL-2 receptor (IL-2R) expression. Both rIL-2 and rGM-CSF have the ability to restore CPS responses in the UVB-preirradiated mice when administered after but not before photosensitization. However, rIL-2 but not rGM-CSF counteracted the in vivo inhibitory effect of TsF. rGM-CSF did not affect the density of I-A + epidermal Langerhans cells (LCs). It was suggested that TsF inhibited IL-2-mediated immune T-cell proliferation, while rGM-CSF reconstituted the CPS by enhancing the function of photodamaged LCs. These results indicate multiple steps of the UVB-induced immunosuppression circuit, each of which seems to be controlled by different immunomodulators.

Mechanisms in the suppression of tumor rejection produced in mice by repeated UV irradiation.

Mice exposed repeatedly to UVB (280 to 320 nm) radiation are unable to reject highly antigenic UVB-induced skin cancers, and their lymphoid organs contain T lymphocytes that transfer this inability to nonimmune recipients. We show that the phenotype of the cells capable of transferring suppression of tumor rejection is Lyt-1+2-,Ia-. Removal of the suppressive activity of spleen cells from UVB-irradiated mice through the use of monoclonal anti-Lyt-1 antibodies resulted in a population of cells capable of mediating tumor rejection when injected into lethally x-irradiated recipients. This finding demonstrates that the inability of UVB-irradiated mice to reject skin cancers induced by UVB radiation is not due to clonal deletion, e.g., the absence of lymphocytes that are capable of recognizing and responding to antigens on these tumors, but instead is likely to depend solely on the activity of suppressor lymphocytes. The phenotype of antigen-specific suppressor lymphocytes induced by painting oxazalone on the unirradiated skin of mice exposed once to UVB radiation was Lyt-1+2-, also a finding consistent with the hypothesis that the two forms of UVB-induced immunosuppression occur by means of the same mechanism. The phenotype of suppressor cells induced in mice treated once with 8-methoxypsoralen plus UVA (320 to 400 nm) radiation, followed by painting unexposed skin with oxazalone, was Lyt-1+2+, suggesting that this treatment may activate a different suppressor pathway.