Expression and regulation of superoxide dismutase activity in human skin fibroblasts from donors of different ages

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Abstract
We have determined the activities, protein, and mRNA abundances as well as the level of transcriptional activation of two intracellular forms of the free radical metabolizing enzyme superoxide dismutase in 29 human skin fibroblast lines established from donors of different ages. SOD-1 (a copper and zinc containing from of SOD) and SOD-2 (a manganese containing form of the enzyme) activities were both observed to be significantly lower in cell lines derived from fetal skin than in lines established form postnatal skin (ages 17–94 years). The percent of total activity contributed by SOD-1 decreased in an age-associated manner from approximately 50% in the fetal lines to less than 20% in lines established from old tissue donors. All of the cell lines were screened to exclude the possibility that they contained a polymorphism known to influence SOD-2 activity. Northern blot analysis revealed three SOD-1 mRNA transcripts that were 0.5, 0.7, and 1.9 kb in length. Although SOD-1 protein abundance was lower in fetal lines than in lines derived from postnatal donors, SOD-1 mRNA abundance did not differ between fetal cells and cell lines derived from young donors. SOD-2 protein abundance and mRNA abundance were both significantly lower in fetal lines than in postnatal lines. No postnatal age-dependent differences were observed in any of the SOD-2 parameters examined. Nuclear run-on analysis revealed that fetal cell lines exhibited a lower level of transcriptional initiation for SOD-1 than postnatal lines. The transcription of SOD-2 was readily detected in postnatal lines, but undetectable in fetal lines. These results are consisten with multiple levels of control of SOD-1 expression and with a strong transcriptional influence on SOD-2 expression. © 1995 Wiley-Liss Inc.