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Regulation of TNFα production and release in human and mouse keratinocytes and mouse skin after UV‐B irradiation
Author(s) -
Yarosh Daniel,
Both Dawn,
Kibitel Jeannie,
Anderson Cathy,
Elmets Craig,
Brash Douglas,
Brown David
Publication year - 2000
Publication title -
photodermatology, photoimmunology and photomedicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.736
H-Index - 60
eISSN - 1600-0781
pISSN - 0905-4383
DOI - 10.1034/j.1600-0781.2000.160606.x
Subject(s) - tumor necrosis factor alpha , microbiology and biotechnology , cytokine , signal transduction , epidermis (zoology) , keratinocyte , biology , messenger rna , gene expression , cell culture , immunology , gene , biochemistry , genetics , anatomy
TNFα is a primary cytokine responsible for inflammatory and immunosuppressive responses in skin. After UV‐B irradiation of cultured human keratinocytes, we found that TNFα was released into the media, as monitored by ELISA, and was bound to cells, as observed by immunofluorescence microscopy. The release of TNFα into cell culture supernatant during the 24 h after UV‐B irradiation was augmented by the addition of IL‐1α to the cells. Further, we found this secretion was unaffected by rapamycin, and therefore independent of FRAP DNA‐protein kinase mediated signal transduction. However, UV‐B also induced expression of membrane‐bound TNFα, and this was dependent on FRAP signaling. In wild type mice, TNFα bound to skin increased immediately after irradiation, declined at 6 h, and then rose again at 12 h before falling by 24 h. This pattern of induction was confirmed by RT‐PCR of TNFα mRNA message in cultured epidermal cells. Induction of membrane‐bound TNFα was also found in c‐fos gene knockout mice deficient in the AP‐1 transcription factor, suggesting that, although AP‐1 containing c‐fos signaling is required for some UV responses, AP‐1 containing c‐fos is not required for this TNFα activation. However, in homozygous p53 knockout mice the basal level of TNFα bound to the epidermis was greatly elevated without UV irradiation. This level declined and remained constant following irradiation. This implies that p53 directly or indirectly represses TNFα gene expression and that modification of p53 mRNA stability or phosphorylation of p53 protein after UV may be responsible for TNFα induction in the membrane. Overexpression of the immunosuppressive cytokine TNFα in this locale may contribute to the carcinogen‐susceptibility of p53 knockout mice.