Reference #: SLE-1017-148997
Submit Date: 03/26/2002 07:03:11-0500

Influence of adaptation to UVB on UVB-induced immunosuppression

ABSTRACT:
UVB radiation can modulate immune responses in animal and in man. It has been demonstrated that UVB exposure impairs the resistance against several infectious diseases in animal models. Determination of the effects of controlled UVB exposure on immune responses following hepatitis B vaccination, is a tool to establish the immunomodulating effects of UVB radiation on the human immune system. UVB exposure of two different mouse strains, and subsequent vaccination of these mice to hepatitis B, revealed that UVB exposure impaired cellular and Th-1 associated humoral immune responses. In a human volunteer study, in which volunteers were exposed to UVB prior to hepatitis B vaccination, no significant effects on the immune responses were established. However, the UVB exposure was proven to be immunosuppressive by decreased Natural Killer cell activity and suppressed contact hypersensitivity (CHS) responses. Since humans are exposed to natural sunlight from an early age, and laboratory mice have never seen sunlight during their lifetime, we hypothesized that adaptation to UVB could play a role in these interspecies differences. Therefore we adapted BALB/c mice, three weeks of age, for 6 weeks at a 1/3 minimal edema dose (MED) UVB per day, after which they received an immunosuppressive protocol of 5 consecutive days, at 3/4 MED UVB per day. Subsequently the mice were vaccinated with a hepatitis B vaccine and immune responses were assessed. Preliminary results showed that adaptation to UVB could prevent the UVB-induced immunosuppression of both cellular and humoral immune responses. In addition, since in the human volunteer study the CHS responses were suppressed, we hypothesized whether adaptation to UVB could not prevent the UVB-induced impairment of CHS responses. Therefore BALB/c mice were sensitized to picryl chloride in the same adaptation protocol. Analysis of DTH responses and IFN- in supernatant of spleen cells revealed that adaptation to UVB for 6 weeks with 1/3 MED per day UVB could not prevent the UVB-induced suppression of DTH responses and IFN- levels. In summary, preliminary data show that adaptation to UVB could play a role in UVB-induced impairment of immune responses to hepatitis B, while we did not observe such effects on a contact senzitizer, such as picryl chloride.

Keywords: UVB radiation, adaptation, hepatitis B vaccination, picryl chloride

Reference #: JON-1017-311518
Submit Date: 03/28/2002 03:54:42-0500

Telomerase reactivation and p53 mutation in solar keratosis

ABSTRACT:
In Australia solar keratosis (SK) occur in nearly 100% of Caucasoid Australians over the age of 50. SK vary tremendously in their degree of dysplasia, less than 1% progress to squamous cell carcinoma (SCC) per year and they have a high rate of regression. Previous studies by our group showed that 50% of inflamed SK (ISK) were histologically SCC. Previous phenotypic analysis of this ISK group including p53 immunohistochemistry, suggested that ISKs (histologically still SK) might represent a recently transformed group of SKs. Telomerase reactivation, is thought to be a useful marker of malignant transformation and may be an early event in skin carcinogenesis. We analysed telomerase reactivation using the TRAP assay in 3mm punch biopsy specimens of normal skin, SK, ISK and SCC to determine if the ISKs might represent a distinct group of recently transformed SKs. 30% of normal skin, 40% of SKs, 100% of ISKs and 100% of SCCs were positive for telomerase. In contrast to other reports telomerase activity in normal skin did not correlate with sun exposure. As yet no histological parameters correlate with telomerase activity in the SKs but the ISKs showed increased dysplasia compared to the SK group. In order to determine whether ISKs represented a group of transformed SKs, exons 5 to 9 of the p53 gene were sequenced in a separate group of specimens. On average there were 0.66 and 0 mutations in sunexposed and non-sunexposed skin respectively and 8, 11.33 and 11.25 mutations in each SK, ISK and SCC respectively. Thus ISK showed a similar p53 mutational profile to SCC, whilst clinically and histologically resembling a SK. These results suggest that ISKs in particular, are proliferations of transformed neoplastic keratinocytes and may represent evolving SCC.

Keywords: Solar Keratosis, Telomerase, p53

Reference #: AGA-1017-273307
Submit Date: 03/27/2002 17:28:08-0500

UV fingerprint and oxygen radical mediated genetic damage occur at different depths in the p53 gene of solar keratosis and squamous cell carcinoma of the skin in humans

ABSTRACT:
Whilst ultraviolet radiation is known to play a pivotal role in skin cancer formation most research to date has attributed these effects to the UVB fraction of sunlight. The role of UVA induced Reactive Oxygen Species(ROS) in carcinogenesis is still poorly understood particularly at a molecular level. In contrast to the classic CC-TT fingerprint mutations known to be caused by UVB radiation, the UVA portion of sunlight produces a different mutational profile in DNA (such as T to G transversions). Utilising Laser Capture Microdissection we have for the first time exactly mapped out the nature and pattern of mutational damage in the p53 gene within both Solar Keratosis and Squamous Cell Carcinoma of the skin in humans. Mutational profiles were compared to imunohistochemical analysis of known markers of UVA and UVB damage.We found both C-T and T-G mutations in the p53 DNA demonstrating that both UVB and UVA damage are evident within both lesion groups. While UVB fingerprints were seen in the upper epithelium, the basal layers displayed significantly more oxidative induced damage. This distribution was supported by immunohistochemical analysis of 8OHdG (a marker of UVA damage) & CPD Ab (marker UVB damage) staining within these defined areas. Interestingly SCC displayed a very similar mutational profile when compared to the SK, differing principally only in the significant increase in number of mutations present. We have been the first to successfully microdissect solar keratosis and squamous cell carcinoma of the skin with Laser Capture Microdissection. Utilising this technology we have been able to demonstrate not only the presence of ROS mediated damage in Solar Keratosis and SCCs but also exactly map the regions & pattern of this occurrence. The distinctive basal localisation of ROS mediated changes suggests a greater role for UVA in the formative stem cell region of epithelium than has been previously described. In addition the minimal difference in the spectrum of mutations contrasted to the increased overall number of mutations between the cancerous SCC & precancerous SK groups further supports the theory that it is the accumulation rather than simply the presence of pivotal mutations that gives rise to the malignant phenotype.

Keywords: p53, Solar Keratosis, UVA

Reference #: POE-1017-165001
Submit Date: 03/26/2002 11:34:41-0500

Immune Function in the Hepatocyte Growth Factor/Scatter Factor (HGF/SF) Transgenic Mouse Model of Ultraviolet (UV) Irradiation-induced Melanoma

ABSTRACT:
Although the mechanisms by which solar radiation induces melanoma in the human population are largely unknown, it has been suggested that UV-induced immune suppression plays an important role. Mice overexpressing an HGF/SF transgene and given a single erythemal dose of UV radiation as neonates develop skin tumors within a year that exhibit pathology strikingly similar to cutaneous malignant melanoma (Noonan et al, Nature 413:271, 2001). In order to employ this unique mouse melanoma model in the study of UV-mediated immunosuppression, it was necessary to first evaluate the status of the transgenic immune system for possible effects of HGF/SF expression. A preliminary analysis of thymocyte subsets and splenic and lymph node lymphocyte profiles using flow cytometry was executed. The percentages of the four major thymic subsets as defined by CD4 and CD8 co-receptor expression, CD4^-8^-, CD4⁺8⁺, CD4⁺8^- and CD4^-8⁺, were similar in the HGF/SF transgenic and non-transgenic littermates between the ages of 4 to 6 weeks. Splenic and lymph node T cell to B cell ratios were also comparable in these experimental animals. In addition, immunohistochemical studies in epidermal sheets from 2-week-old HGF/SF transgenic and non-transgenic littermates, using antibodies to the major histocompatibility complex (MHC) class II and to the endocytic receptor DEC-205 molecules, indicated comparable epidermal Langerhans cell development at this stage. In conclusion, these preliminary data indicate that the HGF/SF overexpression does not overtly affect the murine immune system. Therefore, the HGF/SF transgenic murine model of UV-induced melanoma should prove a valuable system to examine the interactions of UV-induced immunosuppression and neonatal tolerance in melanoma-genesis.

Keywords: melanoma, immunosuppression, ultraviolet-irradiation, murine

Reference #: NGH-1017-694195
Submit Date: 04/01/2002 14:17:39-0500

Cis-urocanic acid causes immunosuppression through 5-HT receptor signaling.

ABSTRACT:
It is generally accepted that prolonged exposure to ultraviolet (UV) light plays a critical role in the initiation and promotion of non-melanoma skin cancer. UV also causes antigen-specific, systemic immune suppression. Studies have shown that UV-induced immune suppression is a risk factor for skin cancer induction. It is well known that UV irradiation causes the production and release of serum IL-4 and IL-10. These immunomodulatory cytokines, particularly IL-10, impair systemic antigen presenting cell function to type-1 T cells and ultimately suppress the induction of delayed-type hypersensitivity reactions (DTH). However, the earliest molecular events that occur after UV exposure are not well defined. It is now known that UV induces immune suppression by signaling through the platelet activating factor (PAF) receptor. It is also known that cis-urocanic acid (cis-UCA) is sufficient to induce immunosuppression, yet the mechanism of a receptor-mediated pathway has remained elusive. In order to understand the primary events of the immunosuppressive pathway, we studied the effects of 5-HT and cis-UCA on the DTH response. When C3H mice are exposed to 80 kJ/m² of WG320 filtered solar-simulated radiation, injected with 50 nmol 5-HT, or 5 mol cis-UCA, immune suppression of the DTH reaction was observed. Mice receiving 5 mol trans-UCA generated an immune response equivalent to the positive controls. Mice treated with 500 nmol PCA-4248, a PAF receptor (PAFR) antagonist, or 500 nmol ketanserin, a 5-HT2A receptor antagonist, before receiving UV or 5-HT receptor agonists were protected against immune suppression. Furthermore, injecting mice with 5 g of anti-cis-UCA antibody before receiving 50 nmol 5-HT prevented suppression of the DTH reaction. Therefore, we propose that UV exposure produces 5-HT agonists capable of signaling through the 5-HT receptor. This signal ultimately results in the suppression of cell-mediated immune responses.

Keywords: 5-HT, cis-UCA, UV, immunosuppression

Reference #: WAL-1017-694590
Submit Date: 04/01/2002 14:50:58-0500

Cis-urocanic acid acts as a 5-HT receptor agonist.

ABSTRACT:
This project tests the hypothesis that the systemic immune suppression caused by cis-urocanic acid (cis-UCA) is due to the signaling of 5-HT receptors, presumably on the surface of activated lymphocytes. It is now known that UV-irradiated keratinocytes produce and secrete PGE2 and IL-10 because of platelet-activating factor (PAF) receptor signaling, yet the initial molecular events involving cis-UCA are poorly understood. Earlier, we discovered that ultraviolet light oxidatively degrades phosphatidylcholine to become a platelet-activating factor (PAF) receptor agonist. Since there is a close association between the inflammatory effects of PAF and serotonin (5-hydroxytryptamine or 5-HT), we pursued the hypothesis that cis-UCA and 5-HT are structurally similar and have equivalent biological effects. To prove that cis-UCA binds to the 5-HT receptor, radioisotopically labeled 5-HT was incubated with 5-HT receptor preparations and competitively bound with respect to excess isotopically stable cis-UCA, 5-HT, PCA-4248, or ketanserin, but not trans-UCA. Likewise, radioisotopically labeled cis-UCA competitively bound in the same manner. Since it is known that activated T cells express 5-HT receptors on the cell surface, it may explain how cis-UCA induces activated T-cells to secrete IL-10. We propose that the early events of UV-induced immune suppression entail the release of local stores of 5-HT and isomerization of endogenous trans-UCA. The 5-HT receptor agonists, 5-HT and cis-UCA, are sufficient to elicit a signal through the 5-HT receptor, which initiates the formation of lipid inflammatory mediators and ultimately results in the release of immunosuppressive cytokines.

Keywords: 5-HT, cis-UCA, receptor

Reference #: BEI-1017-419637
Submit Date: 03/29/2002 09:59:40-0500

An integral role of CD80/CD86-CD152 costimulation in murine photocarcinogenesis

ABSTRACT:
UV radiation (UVR) induces skin cancer by its direct mutagenic effects and by suppressing cellular immunity. It has been hypothesized that altered CD80/86 costimulation plays a role in UV-induced immunosuppression. Ligation of CD28 by CD80/86 transduces stimulatory signals to T cells, whereas CD80/86-CD152 interaction inhibits T cell activation. To investigate the CD80/86-CD152 signaling pathway in UV-carcinogenesis we chronically irradiated groups of mice with UVB. In order to block CD80/86-CD152 signaling, one group of mice was treated with an antagonistic anti-CD152 Ab after UVR. Control groups were either injected with an irrelevant IgG Ab or left untreated after UVR. Chronic UVR induced tumor development in all animals of both control groups. In contrast, in the group treated with the anti-CD152 Ab only 9 out of 20 mice developed skin tumors. Moreover, anti-CD152 treatment induced strong protective tumor immunity because UV-induced tumors which grew progressively in control mice were rejected upon transplantation into anti-CD152 treated animals. Since CD152 is able to bind to CD80 and CD86 surface molecules, we next used mice deficient in both CD80 and CD86 for photocarcinogenesis studies. Accordingly, these double-deficient mice showed a significantly reduced probability of UV-induced skin tumor development. To further clarify whether there are differences between the two costimulatory B7 molecules in terms of UV-carcinogenesis, mice deficient in either CD80 or CD86 were chronically UV-exposed. CD80-deficient mice displayed no differences in UV-induced skin tumors compared to the control animals. Interestingly, CD86-deficient mice developed UV-induced skin cancer much earlier than the controls. These data indicate that blocking CD80/CD86-CD152 signaling by anti-CD152 Ab induces immune protection against the development of UV-induced skin tumors. Furthermore, CD86-mediated costimulation appears to play a more critical role in the protection against photocarcinogenesis than CD80.

Keywords: carcinogenesis, mutant mice, photoimmunology

Reference #: BAR-1017-491705
Submit Date: 03/30/2002 06:07:19-0500

Comparing the effects of T4 liposomes, RNA fragments, and photoprotective lotion on UV-induced immune suppression in human subjects.

ABSTRACT:
Solar ultraviolet radiation (UVR) causes immune suppression associated with cutaneous carcinogenesis. Although the complete mechanism is unclear, DNA damage is known to be involved. Sunscreens attenuate the UVR that reaches the epidermis. Once DNA damage ensues, other agents may be useful in the repair process. T4 endonuclease liposomes excise CPDs generated by UVR and have shown efficacy in reducing the incidence of neoplasia among skin cancer-prone individuals. RNA fragments have never been utilized for photoprotection, although previous reports have demonstrated that DNA fragments have photoprotective effects. The benefits of antioxidants against UV-induced damage have likewise been shown. This study aimed to compare the effect of three topical formulations containing either T4 endonuclease liposomes, RNA fragments, or a lotion with multiple photoprotective agents, on the prevention of UV-induced contact hypersensitivity (CHS) suppression in humans. 100 volunteers, FST I-III and MED of 20-50 mJ/cm2 were randomized into 5 groups which received no treatment, vehicle, or one of the above preparations. Products were self-applied on gluteal skin once daily for 6 days. Half of the subjects per group received solar simulated radiation (SSR) at 0.75 MED over the treatment site on day 3 of product application. DNCB sensitization followed 3 days after irradiation (24 hours after the last product application). CHS response was measured by the increase in skin fold thickness over 5 elicitation sites on the arm, 2 weeks after sensitization. Unprotected SSR irradiation resulted in 65% CHS suppression. CHS suppression was reduced to 35% by T4 endonuclease, and 23% by RNA fragments. CHS response was enhanced by 29% in the group treated with photoprotective lotion, which contained sunscreen, antioxidants and RNA. These results introduce RNA fragments as a photoprotective agent with efficacy against UV-induced immunosuppression that is greater than T4 endonuclease alone, but not as great as a multiagent formulation containing RNA fragments.

Keywords: photoprotection, T4 endonuclease liposomes, RNA fragments, CHS suppression

Reference #: 010522
Submit Date:

Photoimmunology in Quebec City– Where are we going today?

ABSTRACT:

Keywords:

Reference #: KRI-1017-770402
Submit Date: 04/02/2002 10:38:40-0500

Photoimmunology--Where have we been? Where are we going?

ABSTRACT:
The field of photoimmunology had its origins in three major, independent lines of investigation: photocarcinogenesis, phototherapy, and cutaneous biology. From studies in these areas, we now know that skin is an organ with multiple immunologic functions and contains many types of cells with immunological and immunoregulatory activities. Because the skin is exposed to the external environment, the immune system is vulnerable to the effects of UV radiation. Over the past 25 years, we have learned that exposing the skin to UV radiation results in many alterations of immune function, the most well studied of which is abrogation of the induction of contact allergy, with the concomitant induction of suppressor T lymphocytes. In addition to suppressing contact allergy responses, exposing the skin to UV radiation can prevent the rejection of UV-induced skin cancers, enhance the growth of melanomas in UV-irradiated skin, prevent both the induction and elicitation of delayed hypersensitivity responses, and modify resistance to a variety of infectious diseases in experimental models. Cellular mechanisms underlying the immunosuppressive effects of UV radiation include alteration of the antigen-presenting activity of epidermal Langerhans cells, the induction of inflammatory cells into the skin, and the release of immunomodulatory cytokines from keratinocytes and other cells in the skin. Molecular mechanisms include direct DNA damage to cells in the skin, isomerization of urocanic acid, and UV-induced activation of signal transduction pathways resulting in gene activation. Although much has been learned in the past few decades, much more remains to be done. Future studies need to continue to unravel the complex mechanisms involved in UV-induced immune suppression, to apply what we have learned so far to photomedicine, and to provide new insights into the significance of photoimmunology for human health and disease. In addition, fundamental questions on the nature of the antigenicity of UV-induced skin cancers and the evolutionary significance of UV-induced immune suppression still remain for the next generation of photoimmunologists to address.

Keywords: photoimmunology