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Abstract
Endogenous photosensitizers play a critical role in both beneficial and harmful light-induced transformations in biological systems. Understanding their mode of action is essential for advancing fields such as photomedicine, photoredox catalysis, environmental science, and the development of sun care products. This review offers a comprehensive analysis of endogenous photosensitizers in human skin, investigating the connections between their electronic excitation and the subsequent activation or damage of organic biomolecules. We gather the physicochemical and photochemical properties of key endogenous photosensitizers and examine the relationships between their chemical reactivity, location within the skin, and the primary biochemical events following solar radiation exposure, along with their influence on skin physiology and pathology. An important take-home message of this review is that photosensitization allows visible light and UV-A radiation to have large effects on skin. The analysis presented here unveils potential causes for the continuous increase in global skin cancer cases and emphasizes the limitations of current sun protection approaches.
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Affiliation(s)
- Erick L Bastos
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Frank H Quina
- Department of Fundamental Chemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
- Department of Chemical Engineering, Polytechnic School, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
| | - Maurício S Baptista
- Department of Biochemistry, Institute of Chemistry, University of São Paulo, 05508-000 São Paulo, São Paulo, Brazil
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Leitch CS, Natafji E, Yu C, Abdul-Ghaffar S, Madarasingha N, Venables ZC, Chu R, Fitch PM, Muinonen-Martin AJ, Campbell LE, McLean WHI, Schwarze J, Howie SEM, Weller RB. Filaggrin-null mutations are associated with increased maturation markers on Langerhans cells. J Allergy Clin Immunol 2016; 138:482-490.e7. [PMID: 26934939 PMCID: PMC5422581 DOI: 10.1016/j.jaci.2015.11.040] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 09/28/2015] [Accepted: 11/10/2015] [Indexed: 12/21/2022]
Abstract
BACKGROUND Mutations in the gene encoding filaggrin (FLG), an epidermal structural protein, are the strongest risk factor identified for the development of atopic dermatitis (AD). Up to 50% of patients with moderate-to-severe AD in European populations have FLG-null alleles compared with a general population frequency of 7% to 10%. OBJECTIVE This study aimed to investigate the relationship between FLG-null mutations and epidermal antigen-presenting cell (APC) maturation in subjects with and without AD. Additionally, we investigated whether the cis isomer of urocanic acid (UCA), a filaggrin breakdown product, exerts immunomodulatory effects on dendritic cells. METHODS Epidermal APCs from nonlesional skin were assessed by using flow cytometry (n = 27) and confocal microscopy (n = 16). Monocyte-derived dendritic cells from healthy volunteers were used to assess the effects of cis- and trans-UCA on dendritic cell phenotype by using flow cytometry (n = 11). RESULTS Epidermal APCs from FLG-null subjects had increased CD11c expression. Confocal microscopy confirmed this and additionally revealed an increased number of epidermal CD83(+) Langerhans cells in FLG-null subjects. In vitro differentiation in the presence of cis-UCA significantly reduced costimulatory molecule expression on monocyte-derived dendritic cells from healthy volunteers and increased their ability to induce a regulatory T-cell phenotype in mixed lymphocyte reactions. CONCLUSIONS We show that subjects with FLG-null mutations have more mature Langerhans cells in nonlesional skin irrespective of whether they have AD. We also demonstrate that cis-UCA reduces maturation of dendritic cells and increases their capacity to induce regulatory T cells, suggesting a novel link between filaggrin deficiency and immune dysregulation.
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Affiliation(s)
- Claire S Leitch
- Department of Dermatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Eenass Natafji
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Cunjing Yu
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Nayani Madarasingha
- Department of Dermatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Zoë C Venables
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Roland Chu
- Department of Dermatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; School of Chemistry, University of Edinburgh, Edinburgh, United Kingdom
| | - Paul M Fitch
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Linda E Campbell
- Centre for Dermatology and Genetic Medicine, University of Dundee, Dundee, United Kingdom
| | - W H Irwin McLean
- Centre for Dermatology and Genetic Medicine, University of Dundee, Dundee, United Kingdom
| | - Jürgen Schwarze
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Sarah E M Howie
- MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Richard B Weller
- Department of Dermatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; MRC Centre for Inflammation Research, University of Edinburgh, Edinburgh, United Kingdom.
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Single-cell mass spectrometry reveals small molecules that affect cell fates in the 16-cell embryo. Proc Natl Acad Sci U S A 2015; 112:6545-50. [PMID: 25941375 DOI: 10.1073/pnas.1423682112] [Citation(s) in RCA: 149] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Spatial and temporal changes in molecular expression are essential to embryonic development, and their characterization is critical to understand mechanisms by which cells acquire different phenotypes. Although technological advances have made it possible to quantify expression of large molecules during embryogenesis, little information is available on metabolites, the ultimate indicator of physiological activity of the cell. Here, we demonstrate that single-cell capillary electrophoresis-electrospray ionization mass spectrometry is able to test whether differential expression of the genome translates to the domain of metabolites between single embryonic cells. Dissection of three different cell types with distinct tissue fates from 16-cell embryos of the South African clawed frog (Xenopus laevis) and microextraction of their metabolomes enabled the identification of 40 metabolites that anchored interconnected central metabolic networks. Relative quantitation revealed that several metabolites were differentially active between the cell types in the wild-type, unperturbed embryos. Altering postfertilization cytoplasmic movements that perturb dorsal development confirmed that these three cells have characteristic small-molecular activity already at cleavage stages as a result of cell type and not differences in pigmentation, yolk content, cell size, or position in the embryo. Changing the metabolite concentration caused changes in cell movements at gastrulation that also altered the tissue fates of these cells, demonstrating that the metabolome affects cell phenotypes in the embryo.
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Horikoshi S, Sato T, Sakamoto K, Abe M, Serpone N. Microwave discharge electrodeless lamps (MDEL). Part VII. Photo-isomerization of trans-urocanic acid in aqueous media driven by UV light from a novel Hg-free Dewar-like microwave discharge thermally-insulated electrodeless lamp (MDTIEL). Performance evaluation. Photochem Photobiol Sci 2011; 10:1239-48. [PMID: 21523270 DOI: 10.1039/c1pp05059a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A novel mercury-free Dewar-like (double-walled structure) microwave discharge thermally-insulated electrodeless lamp (MDTIEL) was fabricated and its performance evaluated using the photo-isomerization of trans-urocanic acid (trans-UA) in aqueous media as a test process driven by the emitted UV light when ignited with microwave radiation. The photo-isomerization processes trans-UA → cis-UA and cis-UA → trans-UA were re-visited using light emitted from a conventional high-pressure Hg light source and examined for the influence of UV light irradiance and solution temperature; the temperature dependence of the trans → cis process displayed a negative activation energy, E(a) = -1.3 cal mol(-1). To control the photo-isomerization of urocanic acid from the heat usually dissipated by a microwave discharge electrodeless lamp (single-walled MDEL), it was necessary to suppress the microwave-initiated heat. For comparison, the gas-fill in the MDEL lamp, which typically consists of a mixture of Hg and Ar, was changed to the more eco-friendly N(2) gas in the novel MDTIEL device. The dynamics of the photo-isomerization of urocanic acid driven by the UV wavelengths of the N(2)-MDTIEL light source were compared to those from the more conventional single-walled N(2)-MDEL and Hg/Ar-MDEL light sources, and with those from the Hg lamp used to irradiate, via a fiber optic, the photoreactor located in the wave-guide of the microwave apparatus. The heating efficiency of a solution with the double-walled N(2)-MDTIEL was compared to the efficiency from the single-walled N(2)-MDEL device. Advantages of N(2)-MDTIEL are described from a comparison of the dynamics of the trans-UA → cis-UA process on the basis of unit surface area of the lamp and unit power consumption. The considerably lower temperature on the external surface of the N(2)-MDTIEL light source should make it attractive in carrying out photochemical reactions that may be heat-sensitive such as the photothermochromic urocanic acid system.
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Affiliation(s)
- Satoshi Horikoshi
- Department of Material & Life Science, Faculty of Science and Technology, Sophia University, 7-1 Kioicho, Chiyodaku, Tokyo 102-8554, Japan.
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Kaneko K, Walker SL, Lai-Cheong J, Matsui MS, Norval M, Young AR. cis-Urocanic acid enhances prostaglandin E2 release and apoptotic cell death via reactive oxygen species in human keratinocytes. J Invest Dermatol 2011; 131:1262-71. [PMID: 21412256 DOI: 10.1038/jid.2011.37] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Urocanic acid (UCA) is a major UVR-absorbing skin molecule that undergoes trans to cis photoisomerization in the epidermis following UVR exposure. Murine studies have established that cis-UCA is an important mediator of UVR-induced immune suppression, but little is known about its signaling pathway. We have previously demonstrated that treatment of normal human epidermal keratinocytes with cis-UCA resulted in increased synthesis of prostaglandin E(2) (PGE(2)) and cell death. Here, using immortalized human keratinocytes, we report that cis-UCA but not trans-UCA generates reactive oxygen species (ROS) in a dose-dependent manner and that the natural antioxidant α-tocopherol can reduce this ROS generation, subsequent PGE(2) release, and apoptotic cell death. Western blot analysis revealed that cis-UCA leads to a transient phosphorylation of EGFR as well as downstream mitogen-activated protein kinases (MAPKs), extracellular signal-regulated kinase (ERK) and p38. Pharmacological inhibition of their activity attenuated PGE(2) release induced by cis-UCA. After transient activation, cis-UCA downregulated EGFR protein expression that corresponded to activation of caspase-3. In addition, pretreatment with α-tocopherol inhibited EGFR downregulation and caspase-3 activation induced by cis-UCA. These results suggest that cis-UCA exerts its effects on human keratinocytes via intracellular ROS generation that modulates EGFR signaling and subsequently induces PGE(2) synthesis and apoptotic cell death.
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Affiliation(s)
- Kazuyo Kaneko
- St John's Institute of Dermatology, King's College London School of Medicine, London, UK
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Protodynamic intracellular acidification by cis-urocanic acid promotes apoptosis of melanoma cells in vitro and in vivo. J Invest Dermatol 2010; 130:2431-9. [PMID: 20520626 DOI: 10.1038/jid.2010.151] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The extracellular tumor microenvironment is acidified, whereas the intracellular pH of tumor and stromal cells is neutral. cis-Urocanic acid (cis-UCA), an endogenous compound of the skin, can acidify the cytosol by transporting protons into the cells. This phenomenon, termed the protodynamic concept, was studied here in human cancer cells. cis-UCA dose-dependently reduced the number of viable human melanoma, cervical carcinoma, and fibrosarcoma cells at weakly acidic extracellular pH. The intracellular pH decreased by up to 0.5 pH units in a concentration-dependent manner with 0.3-30 m cis-UCA at extracellular pH 6.5 but not at pH 7.4. Under the same conditions, 30 mM cis-UCA induced annexin-V binding and activation of caspase-3 in A2058 melanoma cells as signs of apoptotic cell death. Finally, growth of human melanoma xenografts in SCID mice was suppressed by 60% following intratumoral injection of cis-UCA. Accordingly, the percentage of tumor necrosis and active caspase-3-immunopositive cells increased, whereas proliferation activity decreased. These results identify cis-UCA as an anticancer agent inhibiting melanoma growth by immediate intracellular acidification followed by apoptotic cell death in vivo.
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Kaneko K, Smetana-Just U, Matsui M, Young AR, John S, Norval M, Walker SL. cis-Urocanic Acid Initiates Gene Transcription in Primary Human Keratinocytes. THE JOURNAL OF IMMUNOLOGY 2008; 181:217-24. [DOI: 10.4049/jimmunol.181.1.217] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Gibbs NK, Tye J, Norval M. Recent advances in urocanic acid photochemistry, photobiology and photoimmunology. Photochem Photobiol Sci 2008; 7:655-67. [PMID: 18528548 DOI: 10.1039/b717398a] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Urocanic acid (UCA), produced in the upper layers of mammalian skin, is a major absorber of ultraviolet radiation (UVR). Originally thought to be a 'natural sunscreen', studies conducted a quarter of a century ago proposed that UCA may be a chromophore for the immunosuppression that follows exposure to UVR. With its intriguing photochemistry, its role in immunosuppression and skin cancer development, and skin barrier function, UCA continues to be the subject of intense research effort. This review summarises the photochemical, photobiological and photoimmunological findings regarding UCA, published since 1998.
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Affiliation(s)
- Neil K Gibbs
- Dermatological Sciences, University of Manchester Medical School, Stopford Building, Oxford Road, Manchester, UK M13 9PT.
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Walterscheid JP, Nghiem DX, Kazimi N, Nutt LK, McConkey DJ, Norval M, Ullrich SE. Cis-urocanic acid, a sunlight-induced immunosuppressive factor, activates immune suppression via the 5-HT2A receptor. Proc Natl Acad Sci U S A 2006; 103:17420-5. [PMID: 17085585 PMCID: PMC1859944 DOI: 10.1073/pnas.0603119103] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Exposure to UV radiation induces skin cancer and suppresses the immune response. To induce immune suppression, the electromagnetic energy of UV radiation must be absorbed by an epidermal photoreceptor and converted into a biologically recognizable signal. Two photoreceptors have been recognized: DNA and trans-urocanic acid (UCA). Trans-UCA is normally found in the outermost layer of skin and isomerizes to the cis isomer upon exposure to UV radiation. Although UCA was identified as a UV photoreceptor years ago, and many have documented its ability to induce immune suppression, its exact mode of action remains elusive. Particularly vexing has been the identity of the molecular pathway by which cis-UCA mediates immune suppression. Here we provide evidence that cis-UCA binds to the serotonin [5-hydroxytryptamine (5-HT)] receptor with relatively high affinity (Kd = 4.6 nM). Anti-cis-UCA antibody precipitates radiolabeled 5-HT, and the binding is inhibited by excess 5-HT and/or excess cis-UCA. Similarly, anti-5-HT antibody precipitates radiolabeled cis-UCA, and the binding is inhibited by excess 5-HT or excess cis-UCA. Calcium mobilization was activated when a mouse fibroblast line, stably transfected with the human 5-HT2A receptor, was treated with cis-UCA. Cis-UCA-induced calcium mobilization was blocked with a selective 5-HT2A receptor antagonist. UV- and cis-UCA-induced immune suppression was blocked by antiserotonin antibodies or by treating the mice with 5-HT2A receptor antagonists. Our findings identify cis-UCA as a serotonin receptor ligand and indicate that the immunosuppressive effects of cis-UCA and UV radiation are mediated by activation of the 5-HT2A receptor.
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Affiliation(s)
- Jeffrey P. Walterscheid
- *Department of Immunology and Center for Cancer Immunology Research and
- Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030; and
| | - Dat X. Nghiem
- *Department of Immunology and Center for Cancer Immunology Research and
- Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030; and
| | - Nasser Kazimi
- *Department of Immunology and Center for Cancer Immunology Research and
| | - Leta K. Nutt
- Department of Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
- Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030; and
| | - David J. McConkey
- Department of Cancer Biology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
- Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030; and
| | - Mary Norval
- Medical Microbiology, University of Edinburgh Medical School, Edinburgh EH8 9AG, Scotland
| | - Stephen E. Ullrich
- *Department of Immunology and Center for Cancer Immunology Research and
- Graduate School of Biomedical Sciences, University of Texas, Houston, TX 77030; and
- To whom correspondence should be addressed at:
Department of Immunology/Unit 902, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030. E-mail:
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Woodward EA, Prêle CM, Finlay-Jones JJ, Hart PH. The receptor for cis-urocanic acid remains elusive. J Invest Dermatol 2006; 126:1191-3. [PMID: 16528353 DOI: 10.1038/sj.jid.5700249] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Hart PH, Townley SL, Grimbaldeston MA, Khalil Z, Finlay-Jones JJ. Mast cells, neuropeptides, histamine, and prostaglandins in UV-induced systemic immunosuppression. Methods 2002; 28:79-89. [PMID: 12231191 DOI: 10.1016/s1046-2023(02)00201-3] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
There is a direct correlation between dermal mast cell prevalence in dorsal skin of different mouse strains and susceptibility to UVB-induced systemic immunosuppression; highly UV-susceptible C57BL/6 mice have a high dermal mast cell prevalence while BALB/c mice, which require considerable UV radiation for 50% immunosuppression, have a low mast cell prevalence. There is also a functional link between the prevalence of dermal mast cells and susceptibility to UVB- and cis-urocanic acid (UCA)-induced systemic immunosuppression. Mast cell-depleted mice are unresponsive to UVB or cis-UCA for systemic immunosuppression unless they are previously reconstituted at the irradiated or cis-UCA-administered site with bone marrow-derived mast cell precursors. cis-UCA does not stimulate mast cell degranulation directly. Instead, in support of studies showing that neither UVB nor cis-UCA was immunosuppressive in capsaicin-treated, neuropeptide-depleted mice, cis-UCA-stimulated neuropeptide release from sensory c-fibers which, in turn, could efficiently degranulate mast cells. Studies in mice suggested that histamine, and not tumor necrosis factor alpha (TNF-alpha), was the product from mast cells that stimulated downstream immunosuppression. Histamine receptor antagonists reduced by approximately 60% UVB and cis-UCA-induced systemic immunosuppression. Indomethacin administration to mice had a similar effect which was not cumulative with the histamine receptor antagonists. Histamine can stimulate keratinocyte prostanoid production. We propose that both histamine and prostaglandin E(2) are important in downstream immunosuppression; both are regulatory molecules supporting the development of T helper 2 cells and reduced expression of type 1 immune responses such as a contact hypersensitivity reaction.
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Affiliation(s)
- Prue H Hart
- Department of Microbiology and Infectious Diseases, School of Medicine, Flinders University, Adelaide, Australia.
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Haralampus-Grynaviski N, Ransom C, Ye T, Rôzanowska M, Wrona M, Sarna T, Simon JD. Photogeneration and quenching of reactive oxygen species by urocanic acid. J Am Chem Soc 2002; 124:3461-8. [PMID: 11916432 DOI: 10.1021/ja016902x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Urocanic acid, UCA, is characterized by two electronic transitions in the UV-B (280-320 nm) which comprise its broad absorption spectrum and give rise to wavelength-dependent isomerization quantum yields. The absorption spectrum of UCA extends into the UV-A (320-400 nm). Given the UV-A component of sunlight is significantly greater than the UV-B component it is hypothesized even weak UV-A photochemistry of UCA could be important for in vivo responses to UV radiation. Degenerate pump-probe experiments performed on t-UCA at several wavelengths in the UV-A reveal an excited-state absorption that undergoes a rapid, approximately 1 ps decay. Photoacoustic experiments performed on both the cis and trans isomers reveal the formation of a long-lived intermediate following UV-A excitation. The efficiency and action spectra for this latter photoactive process are presented and are similar for both isomers of UCA. Cholesterol hydroperoxide assays designed to investigate the nature of the UV-A photoreactivity of t-UCA confirm the production of reactive oxygen species. The bimolecular rate constant for the quenching of singlet oxygen by t-UCA is determined to be 3.5 x 10(6) M(-1) s(-1). Taking into consideration recent theoretical calculations and jet expansion studies of the electronic structure of gas-phase t-UCA, a model is proposed to explain the isomerization and photoreactivity of t-UCA in solution over the UV-A region.
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Khalil Z, Townley SL, Grimbaldeston MA, Finlay-Jones JJ, Hart PH. cis-Urocanic acid stimulates neuropeptide release from peripheral sensory nerves. J Invest Dermatol 2001; 117:886-91. [PMID: 11676828 DOI: 10.1046/j.0022-202x.2001.01466.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Previous studies using an antibody to cis-urocanic acid and mast-cell-depleted mice implicated both cis-urocanic acid and mast cells in the mechanisms by which ultraviolet B light suppresses systemic contact hypersensitivity responses in mice. In the absence of a direct stimulatory effect of cis-urocanic acid on connective tissue mast cells, an indirect association was investigated. A blister induced in the rat hind footpad was used to examine the effects of slowly perfused cis-urocanic acid on cutaneous blood flow. cis-Urocanic acid but not trans-urocanic acid increased microvascular flow by a mechanism largely dependent on the combined activity of the neuropeptides, substance P and calcitonin gene-related peptide. Perfusion of cis-urocanic acid over the base of blisters induced in sensory-neuropeptide-depleted rats did not have any stimulatory effect above that seen with perfusion of cis-urocanic acid together with neuropeptide receptor antagonists in control rats. There was a small direct effect of cis-urocanic acid on microvascular blood flow. As both substance P and calcitonin gene-related peptide could directly degranulate connective tissue mast cells, this study suggests that cis-urocanic acid indirectly activates mast cells via its effects on peripheral terminals of unmyelinated primary afferent sensory nerves. cis-Urocanic-acid-induced neuropeptides may also contribute to ultraviolet-B-induced cutaneous inflammation and alterations to Langerhans cell activity.
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Affiliation(s)
- Z Khalil
- National Ageing Research Institute, University of Melbourne, Parkville, Victoria, Australia
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Norval M. Effects of solar radiation on the human immune system. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2001; 63:28-40. [PMID: 11684449 DOI: 10.1016/s1011-1344(01)00200-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
On UV irradiation of the skin, a complex cascade of immunological changes results, initiated by cutaneous chromophores and ending in suppression of some local and systemic immune responses. In this review, the stages in this process are outlined first, concentrating on the roles of DNA and urocanic acid as photoreceptors. Evidence indicating UV-induced immunomodulation of delayed hypersensitivity and resistance to infectious diseases in human subjects follows. Aspects of genetic susceptibility to the immunosuppressive effects of UV exposure and extrapolation of the data obtained in animal models to the human situation are included. Finally uncertain and unknown factors relating to the impact of UV on the human immune system are discussed.
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Affiliation(s)
- M Norval
- Department of Medical Microbiology, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, Scotland, UK.
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Effects of solar radiation on the human immune system. COMPREHENSIVE SERIES IN PHOTOSCIENCES 2001. [DOI: 10.1016/s1568-461x(01)80040-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Hart PH, Grimbaldeston MA, Finlay-Jones JJ. Sunlight, immunosuppression and skin cancer: role of histamine and mast cells. Clin Exp Pharmacol Physiol 2001; 28:1-8. [PMID: 11153522 DOI: 10.1046/j.1440-1681.2001.03392.x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
1. The development into tumours of skin cells transformed by ultraviolet (UV) B radiation of wavelengths 290-320 nm is enhanced by the ability of UVB to suppress an immune response that would otherwise destroy them. Ultraviolet B-induced immunomodulation may be by multiple mechanisms, but generally manifests in an antigen-presenting cell defect and an altered cytokine environment in the draining lymph nodes. 2. Immune responses to microbial or self-antigens may be dysfunctional by similar mechanisms following UVB exposure. 3. Earliest-acting intermediates in the initiation of UVB-induced immunosuppression are the UVB absorbers (photoreceptors) of the skin, notably DNA resulting in immunoregulatory cytokine production, and trans-urocanic acid (UCA), which, upon isomerization to its cis isomer, signals downstream immunosuppressive events. 4. In mice, dermal mast cells are critical to UVB-induced systemic immunomodulation. In mice, there is a functional link as well as a linear relationship between the prevalence of histamine-staining dermal mast cells and the log of the dose of UVB required for 50% immunosuppression. Studies with histamine receptor antagonists support histamine as the main' product of mast cells involved. Histamine acts in large part via a prostanoid-dependent pathway. 5. Approximately 50% of humans and greater than 90% of patients with non-melanoma skin cancer are UVB susceptible for suppression of a contact hypersensitivity response. Neither cytokine polymorphisms nor UVB-induced levels of cis-UCA in irradiated skin have been linked to UVB susceptibility. Patients with basal cell carcinomas (BCC) have an increased dermal mast cell prevalence in non-sun-exposed buttock skin. We propose that mast cells function in humans, as in mice, by initiating immunosuppression and, thereby, allowing a permissive environment for BCC development.
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Affiliation(s)
- P H Hart
- Department of Microbiology and Infectious Diseases, School of Medicine, Flinders University, Adelaide, South Australia, Australia.
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van der Molen RG, Out-Luiting C, Driller H, Claas FH, Koerten HK, Mommaas AM. Broad-spectrum sunscreens offer protection against urocanic acid photoisomerization by artificial ultraviolet radiation in human skin. J Invest Dermatol 2000; 115:421-6. [PMID: 10951278 DOI: 10.1046/j.1523-1747.2000.00074.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cis-urocanic acid (UCA) has been indicated as an important mediator of ultraviolet (UV)-induced immunosuppression. In this study we describe a rapid, noninvasive method for the determination of the protective capacity of various sunscreens against the UV-induced isomerization of trans-UCA into its cis form. For this purpose we applied sunscreens prior to in vivo exposure of human volunteers with single or repeated broadband UVB irradiations of 100 mJ per cm2. We found significant but different levels of protection against UCA photoisomerization by all sunscreens that correlated with the sun protection factor. A comparison of various sunscreens with a sun protection factor of 10, showed that the best protection was offered by the sunscreens (containing organic UV filters or TiO2) with broad absorption spectra. The ability to inhibit cis-UCA formation was not influenced by the penetration characteristics of sunscreens, as determined by application of the sunscreen on quartz glass that was placed on the skin, preventing penetration of sunscreen in the skin. In addition ex vivo UV exposure of human skin was employed to permit other tests of immunomodulation, in this case the mixed epidermal cell lymphocyte reaction. The advantage of this ex vivo method is that there is no need to take biopsies from volunteers. Ex vivo irradiation of human skin with a single dose of 200 mJ per cm2 resulted in similar protection by the sunscreens against cis-UCA formation as in the in vivo system. Furthermore, the mixed epidermal cell lymphocyte reaction data correlated with the cis-UCA findings. We conclude that UCA isomerization is an excellent method to determine sunscreen efficacy and that broad-spectrum sunscreens offer good immunoprotection.
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Affiliation(s)
- R G van der Molen
- Center for Electron Microscopy, Departments of Dermatology and Immunohaematology and Bloodbank, Leiden University Medical Center, Leiden, The Netherlands.
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Uusi-Oukari M, Soini SL, Heikkilä J, Koivisto A, Neuvonen K, Pasanen P, Sinkkonen ST, Laihia JK, Jansén CT, Korpi ER. Stereospecific modulation of GABA(A) receptor function by urocanic acid isomers. Eur J Pharmacol 2000; 400:11-7. [PMID: 10913580 DOI: 10.1016/s0014-2999(00)00395-2] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A deamination product of histidine, urocanic acid, accumulates in the skin of mammals as trans-urocanic acid. Ultraviolet (UV) irradition converts it to the cis-isomer that is an important mediator in UV-induced immunosuppression. We have recently shown that urocanic acid interferes with the agonist binding to GABA(A) receptors. We now report that the effects of urocanic acid on binding of a convulsant ligand (t-butylbicyclo[35S]phosphorothionate) to GABA(A) receptors in brain membrane homogenates are dependent on pH of the incubation medium, the agonistic actions being enhanced at the normal pH of the skin (5.5). Using Xenopus laevis oocytes expressing recombinant rat alpha1beta1gamma2S GABA(A) receptors, the low pH potentiated the direct agonistic action of trans-urocanic acid under two-electrode voltage-clamp, whereas cis-urocanic acid retained its low efficacy both at pH 5.5 and 7.4. The results thus indicate clear differences between urocanic acid isomers in functional activity at one putative receptor site of immunosuppression, the GABA(A) receptor, the presence of which in the skin remains to be demonstrated.
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Affiliation(s)
- M Uusi-Oukari
- Department of Pharmacology and Clinical Pharmacology, University of Turku, Kiinamyllynkatu 10, FIN-20520, Turku, Finland
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Hart PH, Grimbaldeston MA, Finlay-Jones JJ. Mast cells in UV-B-induced immunosuppression. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 2000; 55:81-7. [PMID: 10942071 DOI: 10.1016/s1011-1344(00)00032-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Degranulating dermal mast cells in UV-B-irradiated skin have been implicated for many years in the mechanisms of irradiation erythema. There is now considerable evidence that dermal mast cells are important to the processes by which both UV-B radiation and cis-urocanic acid (cis-UCA) suppress immune responses to sensitizing antigens applied to non-irradiated/non-cis-UCA-exposed sites. Mast-cell-depleted mice are resistant to the immunosuppressive effects of UV-B radiation and cis-UCA for 'systemic' immunomodulation. However, these mice gain responsiveness if the dorsal skin is reconstituted six weeks prior to irradiation or cis-UCA administration at that site with cultured bone-marrow-derived mast cells from +/+ mice. The molecular triggers for initiating mast-cell degranulation are being actively sought. Evidence suggests that histamine, and not tumour necrosis factor alpha, is the major mast-cell product that signals altered immune responses to sensitizing antigens applied to non-irradiated, non-cis-UCA-exposed sites. Histamine may have multiple roles, but experiments with indomethacin administered to mice have shown that one process involves induction of prostanoid production.
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Affiliation(s)
- P H Hart
- Department of Microbiology and Infectious Diseases, School of Medicine, Flinders University, Adelaide, Australia.
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Hart PH, Grimbaldeston MA, Swift GJ, Hosszu EK, Finlay-Jones JJ. A Critical Role for Dermal Mast Cells in Cis-Urocanic Acid-induced Systemic Suppression of Contact Hypersensitivity Responses in Mice. Photochem Photobiol 1999. [DOI: 10.1111/j.1751-1097.1999.tb08286.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Hug DH, Dunkerson DD, Hunter JK. The degradation of L-histidine and trans- and cis-urocanic acid by bacteria from skin and the role of bacterial cis-urocanic acid isomerase. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY. B, BIOLOGY 1999; 50:66-73. [PMID: 10443033 DOI: 10.1016/s1011-1344(99)00072-x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
UV-B radiation suppresses cell-mediated immunity. Histidine forms trans-urocanic acid (trans-UCA) enzymatically in the stratum corneum. Photoisomerization of trans-UCA to cis-urocanic acid (cis-UCA) has been proposed for the initiation of an immunosuppressive process. Many microorganisms described in the literature metabolize histidine and/or trans-UCA. Our enrichment cultures of soil and sewage contain organisms that can degrade cis-UCA. We have tested microorganisms for degradation of cis-UCA, trans-UCA, or L-histidine when they are incorporated at 0.2% in nutrient broth. Six out of 10 selected genera isolated by our clinical microbiology laboratory degrade one or more of the imidazole substrates. We have cultured over 60 aerobic isolates from human skin. Of these, 33 degrade one or more of the three imidazole substrates and 12 degrade cis-UCA. Isolates from BALB/c mice are also active on cis-UCA. We have identified a cis-UCA-degrading bacterium as Micrococcus luteus. Four ATCC strains of M. luteus have been tested and three are active on histidine or trans-UCA; two are active on cis-UCA. Micrococci that degrade cis-UCA contain a new enzyme, cis-UCA isomerase, which converts the substrate to the trans-isomer. This enzyme provides access to the classical L-histidine degradation pathway. We hypothesize that an epidermal microflora that degrades L-histidine, trans-UCA, or cis-UCA influences the concentration of urocanic acids on the skin and, thus, affects immune suppression.
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Affiliation(s)
- D H Hug
- Bacteriology Research Laboratory, Department of Veterans Affairs Medical Center, Iowa City 52246, USA
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