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Kasraian Z, Trompezinski S, Cario-André M, Morice-Picard F, Ged C, Jullie ML, Taieb A, Rezvani HR. Pigmentation abnormalities in nucleotide excision repair disorders: Evidence and hypotheses. Pigment Cell Melanoma Res 2018; 32:25-40. [PMID: 29938913 DOI: 10.1111/pcmr.12720] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 05/11/2018] [Accepted: 06/11/2018] [Indexed: 12/12/2022]
Abstract
Skin pigmentation abnormalities are manifested in several disorders associated with deficient DNA repair mechanisms such as nucleotide excision repair (NER) and double-strand break (DSB) diseases, a topic that has not received much attention up to now. Hereditary disorders associated with defective DNA repair are valuable models for understanding mechanisms that lead to hypo- and hyperpigmentation. Owing to the UV-associated nature of abnormal pigmentary manifestations, the outcome of the activated DNA damage response (DDR) network could be the effector signal for alterations in pigmentation, ultimately manifesting as pigmentary abnormalities in repair-deficient disorders. In this review, the role of the DDR network in the manifestation of pigmentary abnormalities in NER and DSB disorders is discussed with a special emphasis on NER disorders.
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Affiliation(s)
- Zeinab Kasraian
- NAOS, Aix en Provence, France.,Univ. Bordeaux, Inserm, BMGIC, UMR 1035, Bordeaux, France
| | | | - Muriel Cario-André
- Univ. Bordeaux, Inserm, BMGIC, UMR 1035, Bordeaux, France.,Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France
| | - Fanny Morice-Picard
- Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France.,Service de Dermatologie Adulte et Pédiatrique, CHU de Bordeaux, Bordeaux, France
| | - Cécile Ged
- Univ. Bordeaux, Inserm, BMGIC, UMR 1035, Bordeaux, France.,Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France
| | | | - Alain Taieb
- Univ. Bordeaux, Inserm, BMGIC, UMR 1035, Bordeaux, France.,Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France.,Service de Dermatologie Adulte et Pédiatrique, CHU de Bordeaux, Bordeaux, France
| | - Hamid Reza Rezvani
- Univ. Bordeaux, Inserm, BMGIC, UMR 1035, Bordeaux, France.,Centre de Référence pour les Maladies Rares de la Peau, CHU de Bordeaux, Bordeaux, France
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2
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Stevens EV, Nishizuka S, Antony S, Reimers M, Varma S, Young L, Munson PJ, Weinstein JN, Kohn EC, Pommier Y. Predicting cisplatin and trabectedin drug sensitivity in ovarian and colon cancers. Mol Cancer Ther 2008; 7:10-8. [PMID: 18187810 DOI: 10.1158/1535-7163.mct-07-0192] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Molecular profiling of markers involved in the activity of chemotherapeutic agents can shed light on the successes and failures of treatment in patients and can also provide a basis for individualization of therapy. Toward those ends, we have used reverse-phase protein lysate microarrays to evaluate expression of protein components of the nucleotide excision repair (NER) pathways. Those pathways strongly influence the anticancer activities of numerous drugs, including those that are the focus here, cisplatin and ecteinascidin 743 (Et-743; Yondelis, Trabectedin). Cisplatin is generally more active in cell types deficient in NER, whereas Et-743 tends to be less active in those cells. We measured protein expression and sensitivity to those drugs in 17 human ovarian and colon cancer cell lines (13 of them from the NCI-60 panel) and five xeroderma pigmentosum (XP) patient cell types, each containing a different NER defect. Of the NER proteins giving reliable signals, XPF and XPG showed the highest correlations of protein expression with drug activity across all three tissue-of-origin groups. When we compared protein expression data with mRNA expression data from Affymetrix U133A chips, we found no consistent correlation between the two across the cell lines studied, which reinforces the conclusion that protein measurements can give more interpretable mechanistic information than can transcript measurements. The work reported here provides motivation for larger proteomic studies with more cell types focused on potential biomarkers in additional pharmacologically pertinent pathways.
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Affiliation(s)
- Ellen V Stevens
- National Cancer Institute, Building 37, Room 5068, Bethesda, MD 20892, USA
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3
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Knezevic D, Zhang W, Rochette PJ, Brash DE. Bcl-2 is the target of a UV-inducible apoptosis switch and a node for UV signaling. Proc Natl Acad Sci U S A 2007; 104:11286-91. [PMID: 17586682 PMCID: PMC2040891 DOI: 10.1073/pnas.0701318104] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Sunlight's UVB radiation triggers cell signaling at multiple sites to induce apoptosis. The integration of these signal entry sites is not understood. Here we show that P53 and E2f1 constitute a UV-inducible apoptosis switch. At low-UV doses, wild-type cells resemble the OFF state of an siP53-treated cell, whereas at high-UV doses, the apoptosis frequency transitions to the fully ON behavior of an siE2f1-treated cell. The switch's target is Bcl-2: Rapid Bcl-2 down-regulation in response to UVB-induced DNA photoproducts is lost in P53-deficient cells, but, as for apoptosis, is restored when both P53 and its inhibited target E2f1 are absent. P53's down-regulation of Bcl-2 is mediated entirely through E2f1. Bcl-2 is also down-regulated by a separate pathway triggered by DNA photoproducts in the absence of P53 and E2f1. Four UV pathways terminating on Bcl-2 contribute to apoptosis after UVB irradiation. The apoptosis lost in p53(-/-) is completely restored by siBcl-2, implying that Bcl-2 is a rate-limiting member of this network. These results identify Bcl-2 as an integrator of several UV-induced proapoptotic signals and show that it, in turn, suppresses a direct UV-apoptosis pathway. UV-induced apoptosis requires both UV activation of the direct pathway and a separate UV disinhibition of this pathway through P53-E2f1-Bcl-2.
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Affiliation(s)
- Dejan Knezevic
- Departments of *Therapeutic Radiology
- Physiology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06525
| | | | | | - Douglas E. Brash
- Departments of *Therapeutic Radiology
- Genetics
- Dermatology, and
- To whom correspondence should be addressed. E-mail:
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4
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Young AR, Orchard GE, Harrison GI, Klock JL. The Detrimental Effects of Daily Sub-Erythemal Exposure on Human Skin In Vivo Can Be Prevented by a Daily-Care Broad-Spectrum Sunscreen. J Invest Dermatol 2007; 127:975-8. [PMID: 17082784 DOI: 10.1038/sj.jid.5700606] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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5
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Reefman E, Limburg PC, Kallenberg CGM, Bijl M. Apoptosis in Human Skin: Role in Pathogenesis of Various Diseases and Relevance for Therapy. Ann N Y Acad Sci 2005; 1051:52-63. [PMID: 16126944 DOI: 10.1196/annals.1361.046] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Cell death by apoptosis is a physiological process that enables the elimination of cells without causing an inflammatory response. In self-renewing tissue like the epidermal layers of the skin, cell numbers are tightly regulated by a delicate balance between proliferation, differentiation, and cell death. Besides cell death by terminal differentiation in normal skin, cell death can also be induced by exposure to sunlight. This paper will review the different forms of cell death in the skin and discuss the role of apoptosis in diseases like skin cancer, psoriasis, and systemic lupus erythematosus.
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Affiliation(s)
- Esther Reefman
- Departments of Rheumatology and Clinical Immunology, University Hospital Groningen, P.O. Box 30.001, 9700 RB Groningen, the Netherlands.
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6
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Martínez A, Brethauer U, Rojas IG, Spencer M, Mucientes F, Borlando J, Rudolph MI. Expression of apoptotic and cell proliferation regulatory proteins in actinic cheilitis. J Oral Pathol Med 2005; 34:257-62. [PMID: 15817067 DOI: 10.1111/j.1600-0714.2004.00299.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Actinic cheilitis (AC) is a pre-malignant lesion caused by ultraviolet (UV) radiation. The apoptotic proteins p53, bax, bcl-2, and the proliferation marker Ki-67, are known to play an important role in UV-exposed skin and carcinomas, therefore, these markers were assessed in AC and compared with normal lip and oral mucosa. METHODS AC (n = 13), normal lip (n = 7) and oral mucosa (n = 6) biopsies were stained immunohistochemically for p53, bax, bcl-2 and Ki-67, to determine their expression and distribution. RESULTS p53 was over-expressed in AC as compared with normal lip and oral mucosa (P < 0.003). Although bcl-2 expression was higher in AC than in oral mucosa (P < 0.002), it was significantly reduced as compared with normal lip (P < 0.04). Bax expression remained unchanged, and Ki-67 was significantly increased in AC and normal lip as compared with oral mucosa (P < 0.05). CONCLUSION The results suggest that DNA-damaged cells by UV radiation in AC are eliminated by apoptosis.
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Affiliation(s)
- A Martínez
- Department of Oral Pathology, College of Dentistry, Universidad de Concepción, Chile.
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7
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Berton TR, Mitchell DL, Guo R, Johnson DG. Regulation of epidermal apoptosis and DNA repair by E2F1 in response to ultraviolet B radiation. Oncogene 2005; 24:2449-60. [PMID: 15735727 DOI: 10.1038/sj.onc.1208462] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The E2F1 transcription factor regulates the expression of genes involved in cell proliferation, apoptosis and DNA repair. Following DNA damage, E2F1 is phosphorylated and stabilized, but the physiological role of E2F1 in the response to DNA damage is unclear. We find that mice lacking E2F1 have increased levels of epidermal apoptosis compared to wild-type mice following exposure to ultraviolet B (UVB) radiation. Moreover, transgenic overexpression of E2F1 in basal layer keratinocytes suppresses apoptosis induced by UVB. Inhibition of UVB-induced apoptosis by E2F1 is unexpected given that most studies have demonstrated a proapoptotic function for E2F1. E2F1-mediated suppression of apoptosis does not involve alterations in mitogen-activated protein kinase activation or Bcl-2 downregulation in response to UVB and is independent of p53. Instead, inhibition of UVB-induced apoptosis by E2F1 correlates with a stimulation of DNA repair. Mice lacking E2F1 are impaired for the removal of DNA photoproducts, while E2F1 transgenic mice repair UVB-induced DNA damage at an accelerated rate compared to wild-type mice. These findings suggest that E2F1 participates in the response to UVB by promoting DNA repair and suppressing apoptosis.
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Affiliation(s)
- Thomas R Berton
- Department of Carcinogenesis, Science Park Research Division, The University of Texas MD Anderson Cancer Center, PO Box 389, 1808 Park Road 1C, Smithville, TX 78957, USA
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8
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Tamura S, Bito T, Ichihashi M, Ueda M. Genistein enhances the cisplatin-induced inhibition of cell growth and apoptosis in human malignant melanoma cells. PIGMENT CELL RESEARCH 2003; 16:470-6. [PMID: 12950722 DOI: 10.1034/j.1600-0749.2003.00068.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Genistein, a naturally occurring isoflavone found chiefly in soybeans, has been reported to be a potent antitumor agent. Genistein is presumed to exert multiple effects related to the inhibition of cancer growth. Metastatic melanoma is a chemotherapy-refractory neoplasm. The present study was designed to explore the possible activity of genistein to inhibit the aberrant proliferation and to induce apoptosis of human malignant melanoma cells in cooperation with cisplatin treatment. Five human melanoma cell lines were utilized for these experiments. Genistein at physiologic concentrations (20 microM) did not induce apoptosis by itself but did enhance cisplatin-induced apoptosis in all five human melanoma cell lines tested. The enhanced susceptibility among the cell lines was diverse. Changes in the expression of two anti-apoptotic proteins, bcl-2 and bcl-xL, and one pro-apoptotic protein, apoptotic protease activating factor-1 (Apaf-1), were examined. Genistein alone or cisplatin alone generally did not alter bcl-2 expression or bcl-xL expression, but slightly increased Apaf-1 in some cell lines. The combined treatment with genistein and cisplatin significantly reduced bcl-2 and bcl-xL protein and increased Apaf-1 protein expression. These data suggest that genistein therapy may enhance the chemosensitivity of melanoma patients.
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Affiliation(s)
- Shingo Tamura
- Division of Dermatology, Department of Clinical Molecular Medicine, Translational Medical Faculty of Medicine, Kobe University Graduate School of Medicine, Kobe, Japan
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9
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Kulms D, Schwarz T. Independent contribution of three different pathways to ultraviolet-B-induced apoptosis. Biochem Pharmacol 2002; 64:837-41. [PMID: 12213577 DOI: 10.1016/s0006-2952(02)01146-2] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Ultraviolet-B radiation (UVB) causes a variety of biological effects which include the induction of apoptosis. UVB-induced apoptosis provides a well controlled scavenging mechanism protecting cells from malignant transformation. To induce programmed cell death, UVB uses a variety of cellular signaling pathways. In this context induction of nuclear DNA damage seems to be the predominant pathway, since experimental reduction of DNA damage was associated with a strong suppression of apoptosis. Additionally, UVB has been shown to target cytoplasmatically located or membrane bound components to induce signal transduction. UVB was found to directly activate cell surface death receptors, thereby triggering the apoptotic machinery. Furthermore, UVB-induced intracellular formation of reactive oxygen species (ROS) accompanied by mitochondrial dysfunction and cytochrome c release was demonstrated to be additionally involved in the apoptotic program. The following review will briefly discuss current aspects of the interplay between the different signaling pathways involved in UVB-induced apoptosis.
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Affiliation(s)
- Dagmar Kulms
- Department of Dermatology, Ludwig Boltzmann Institute for Cell Biology and Immunobiology of the Skin, University of Münster D-48149, Münster, Germany.
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10
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Sheehan JM, Young AR. The sunburn cell revisited: an update on mechanistic aspects. Photochem Photobiol Sci 2002; 1:365-77. [PMID: 12856704 DOI: 10.1039/b108291d] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The sunburn cell (SBC), with its pyknotic nucleus and eosinophilic cytoplasm, is characteristic of mammalian epidermis after exposure to UVC and UVB radiation or UVA radiation in the presence of psoralens. SBC may be regarded as an example of apoptosis: controlled individual cell death. Since the discovery of apoptosis over thirty years ago, there has been a considerable increase in the knowledge of mechanisms involved in this process. DNA damage has been shown to be a major determinant of SBC production both in a p53-dependent and -independent manner. Extranuclear events such as activation of membrane bound death receptors also contribute to SBC formation. The development of new technologies and techniques has resulted in a better understanding of the mechanisms and machinery involved in apoptosis, triggered by various stimuli and in different cell types. Of particular importance has been the elucidation of regulatory molecules such as caspases, inhibitor of apoptosis proteins (IAP) and the role of mitochondria as key to the process of apoptosis and consequent production of SBC. This review attempts to give an update on those mechanisms involved and the occurrence and relevance of SBC in mammalian skin are discussed.
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Affiliation(s)
- John M Sheehan
- Department of Environmental Dermatology, St John's Institute of Dermatology, KCL, University of London, St Thomas' Hospital, Lambeth Palace Road, London, UK SE1 7EH.
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11
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Muotri AR, Marchetto MCN, Suzuki MF, Okazaki K, Lotfi CFP, Brumatti G, Amarante-Mendes GP, Menck CFM. Low amounts of the DNA repair XPA protein are sufficient to recover UV-resistance. Carcinogenesis 2002; 23:1039-46. [PMID: 12082027 DOI: 10.1093/carcin/23.6.1039] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
DNA integrity is threatened by the damaging effects of physical and chemical agents that can affect its function. Nucleotide excision repair (NER) is one of the most known and flexible mechanisms of DNA repair. This mechanism can recognize and remove damages causing DNA double-helix distortion, including the cyclobutane pyrimidine dimers (CPDs) and the pyrimidine-pyrimidone (6-4) photoproducts, promoted by ultraviolet light (UV). The human syndrome xeroderma pigmentosum (XP) is clinically characterized chiefly by the early onset of severe photosensitivity of the exposed regions of the skin, a very high incidence of skin cancers and frequent neurological abnormalities. The xpa gene seems to be involved during UV damage recognition, in both global genome repair (GGR) and transcription-coupled repair (TCR). The modulation of xpa expression may modify the DNA repair rate in the cell genome, providing a valuable contribution to an understanding of the NER process. The controlled expression of the cDNA xpa in XP12RO deficient cells was achieved through the transfection of a muristerone-A inducible vector, pINXA. The INXA15 clone shows good induction of the XPA protein and total complementation of XP12RO cell deficiency. Overexpression of this protein resulted in UV cell survival comparable to normal control human cells. Moreover, low expression of the XPA protein in these cells is sufficient for total complementation in cellular UV sensitivity and DNA repair activity. These data demonstrate that XPA protein concentration is not a limiting factor for DNA repair.
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Affiliation(s)
- Alysson R Muotri
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, SP, Brazil
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12
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Del Carratore R, Della Croce C, Simili M, Taccini E, Scavuzzo M, Sbrana S. Cell cycle and morphological alterations as indicative of apoptosis promoted by UV irradiation in S. cerevisiae. Mutat Res 2002; 513:183-91. [PMID: 11719103 DOI: 10.1016/s1383-5718(01)00310-2] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An apoptotic phenotype induced by oxygen radicals or Bax expression has been observed in Saccharomyces cerevisiae yeast cells by electron and fluorescence microscopy. In this work, we analyzed DNA content and cellular morphology of S. cerevisiae after H(2)O(2) or UV treatment by TdT-mediated dUTP nick end labeling (TUNEL)-test and flow cytofluorimetry. A TUNEL-positive phenotype was observed in both cases, on the same samples a dose-dependent increase in the sub-G(1) population was pointed out by flow cytometry. Sub-G(1) cells were isolated by flow sorting and analyzed by electron microscopy. This population showed condensed chromatin in the nucleus and cell shrinking. This paper reports the first evidence of apoptosis in yeast cells induced by DNA damage after UV irradiation.
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Affiliation(s)
- Renata Del Carratore
- Istitute of Mutagenesis and Differenziation, National Council of Research, Via Svezia 10, 56124 Pisa, Italy.
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Suzuki H, Kalair W, Shivji GM, Wang B, Toto P, Amerio P, Kraemer KH, Sauder DN. Impaired ultraviolet-B-induced cytokine induction in xeroderma pigmentosum fibroblasts. J Invest Dermatol 2001; 117:1151-5. [PMID: 11710926 DOI: 10.1046/j.0022-202x.2001.01525.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Xeroderma pigmentosum is a rare, autosomal recessive disease in which patients develop excessive solar damage at an early age and have a 1000-fold increased risk of developing cutaneous neoplasms. Xeroderma pigmentosum can be classified into seven complementation groups (A-G) with defects in different DNA nucleotide excision repair genes. Xeroderma pigmentosum patients also have impaired immune function including reduced natural killer cell activity and impaired induction of interferon-gamma. We hypothesized that altered cytokine induction may contribute to the immune defect in xeroderma pigmentosum patients. We examined cytokine mRNA expression after ultraviolet B irradiation using reverse transcriptase polymerase chain reaction in fibroblasts derived from five xeroderma pigmentosum patients in complementation groups A, C, and D and in complemented XP-A and XP-D cells. Cytokines interleukin-1beta and interleukin-6 displayed impaired ultraviolet B induction whereas interleukin-8 had normal induction in the xeroderma pigmentosum fibroblasts. Stable complementation of XP-A and XP-D cell lines increased ultraviolet-B-induced interleukin-1beta and interleukin-6 expression. These results demonstrate a deficient response of xeroderma pigmentosum fibroblasts to ultraviolet B in terms of cytokine interleukin-1beta and interleukin-6 induction but normal interleukin-8 induction and exhibit a role for DNA repair in cytokine induction.
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Affiliation(s)
- H Suzuki
- Division of Dermatology, University of Toronto, Sunnybrook and Women's College Health Science Center, Toronto, Ontario, Canada
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Tsuru K, Horikawa T, Budiyanto A, Hikita I, Ueda M, Ichihashi M. Low-dose ultraviolet B radiation synergizes with TNF-alpha to induce apoptosis of keratinocytes. J Dermatol Sci 2001; 26:209-16. [PMID: 11390206 DOI: 10.1016/s0923-1811(01)00090-1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
High-dose ultraviolet B (UVB) irradiation is known to induce apoptosis of keratinocytes, but low-dose UVB dose not. In this paper we present evidence that low-dose UVB can induce TNF-alpha-dependent apoptosis of keratinocytes. In our study, 5 mJ/cm(2) doses of UVB were not sufficient by themselves to induce apoptosis of cultured human keratinocytes, but 20 mJ/cm(2) doses of UVB were. The combination of 5 mJ/cm(2) doses of UVB and exogenous TNF-alpha (15 ng/ml) induced significant apoptosis of keratinocytes, although exogenous TNF-alpha without UVB did not. This phenomenon was accompanied by enhanced clustering of tumor necrosis factor receptor 1 (TNFR1). TNF-alpha's promotion of the induction of apoptosis by low-dose UVB was seen until 30 min after irradiation but not at 1 h. We confirmed this finding using a skin organ culture system. UVB (20 mJ/cm(2)), which did not induce transformation of epidermal keratinocytes into sunburn cells, induced apoptosis when TNF-alpha was added to the culture medium. These results suggest that one of the possible mechanisms of inducing keratinocyte apoptosis by low-dose UVB and TNF-alpha is that low-dose UVB augments ligand-binding-induced TNFR1 clustering, resulting in increased apoptotic cell death.
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Affiliation(s)
- K Tsuru
- Department of Dermatology, Kobe University School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan
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15
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Abstract
Sunburn cell (SBC) formation in the epidermis is a characteristic consequence of ultraviolet radiation (UVR) exposure at doses around or above the minimum erythema dose. SBC have been identified morphologically and biologically as keratinocytes undergoing apoptosis. There is evidence that SBC formation is a protective mechanism to eliminate cells at risk of malignant transformation. The level of DNA photodamage is a major determinant of SBC induction by a process controlled by the tumor suppressor gene p53. However, extra-nuclear events also contribute to SBC formation, such as the activation of death receptors including CD95/Fas. UVR triggers death receptors either by direct activation of these surface molecules or by inducing the release of their ligands such as CD95 ligand or tumor necrosis factor. Oxidative stress also appears to be involved, probably via mitochondrial pathways, resulting in the release of cytochrome C. Pathways which modify SBC formation are now extensively studied given the importance of apoptosis in eliminating irreparably damaged cells. A greater understanding of the mechanisms that induce and prevent UVR-induced apoptosis will contribute to our understanding of mechanisms relevant in genomic integrity.
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Affiliation(s)
- G Murphy
- Department of Dermatology, Beaumont Hospital Dublin, Ireland
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