Human keratinocytes are a source for tumor necrosis factor alpha: evidence for synthesis and release upon stimulation with endotoxin or ultraviolet light.
Tumor necrosis factor alpha (TNF-alpha), in addition to being cytotoxic for certain tumor cells, has turned out as a multifunctional cytokine that is involved in the regulation of immunity and inflammation. Since human keratinocytes have been demonstrated to be a potent source of various cytokines, it was investigated whether epidermal cells synthesize and release TNF-alpha. Supernatants derived from normal human keratinocytes (HNK) and human epidermoid carcinoma cell lines (KB, A431) were tested both in a TNF-alpha-specific ELISA and a bioassay. In supernatants of untreated epidermal cells, no or minimal TNF-alpha activity was found, while after stimulation with lipopolysaccharide (LPS) or ultraviolet (UV) light, significant amounts were detected. Western blot analysis using an antibody directed against human TNF-alpha revealed a molecular mass of 17 kD for keratinocyte-derived TNF-alpha. These biological and biochemical data were also confirmed by Northern blot analysis revealing mRNA specific for TNF-alpha in LPS- or ultraviolet B (UVB)-treated HNK and KB cells. In addition, increased TNF-alpha levels were detected in the serum obtained from human volunteers 12 and 24 h after a single total body UVB exposure, which caused a severe sunburn reaction. These findings indicate that keratinocytes upon stimulation are able to synthesize and release TNF-alpha, which may gain access to the circulation. Thus, TNF-alpha in concert with other epidermal cell-derived cytokines may mediate local and systemic inflammatory reactions during host defense against injurious events caused by microbial agents or UV irradiation.
Köck
A
A
Department of Dermatology II, University of Vienna, Austria.
Schwarz
T
T
Kirnbauer
R
R
Urbanski
A
A
Perry
P
P
Ansel
J C
JC
Luger
T A
TA
D015152:Blotting, Northern; D002294:Carcinoma, Squamous Cell; D002460:Cell Line; D002478:Cells, Cultured; D006801:Humans; D015603:Keratinocytes / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D007700:Kinetics; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008970:Molecular Weight; D012333:RNA, Messenger / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D014466:Ultraviolet Rays
D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha