Comparison of primary human fibroblasts and keratinocytes with immortalized cell lines regarding their sensitivity to sodium dodecyl sulfate in a neutral red uptake cytotoxicity assay.

Cell lines present a valuable tool for in vitro assessment of skin damage caused by application of cosmeticals or pharmaceuticals. They form a reproducible test system under controllable test conditions and, in many cases, can be used as alternatives to animal testing in order to assess the compatibility of drugs or cosmetics and human skin. Yet, it can not necessarily be assumed that the behavior of cultured cells, when treated with different substances, is exactly consistent with the behavior of cells being part of a live organism. Becoming immortal, cells exhibit changes in genotype and/or phenotype, possibly resulting in modified reactions to external influences. Therefore, to obtain results close to in vivo studies, it seems apparent to use primary cells for testing that have not yet undergone any modifications. To compare the properties of primary fibroblasts (Normal Human Dermal Fibroblasts, NHDF) and primary keratinocytes (Normal Human Epidermal Keratinocytes, NHEK) with those of immortal cell lines (3T3 (ACC 173) Swiss albino mouse fibroblasts and HaCaT (human, adult, low calcium, high temperature, human adult skin keratinocytes) cells), their sensitivities in cytotoxicity assays have been assessed. While both fibroblast cell cultures showed similar sensitivities towards sodium dodecyl sulfate (SDS), primary keratinocytes died at SDS concentrations about three times lower than the immortal HaCaT cells.

Lung-specific expression of active Raf kinase results in increased mortality of influenza A virus-infected mice.

Alterations in signalling via the Raf/MEK/ERK pathway interfere with influenza A virus replication in cell culture. While virus yields are reduced in cells expressing dominant-negative Raf or ERK, virus propagation is enhanced upon expression of constitutively active Raf or MEK. To study the impact of active Raf on influenza virus propagation in vivo, we investigated transgenic mice expressing an activated mutant of c-Raf (Raf-BxB) in the main target tissue of influenza virus, the lung. Raf-BxB expression results in multicentric alveolar adenomas. Influenza virus A infection of Raf-BxB mice results in increased disease symptoms and higher mortality rates. The immune response against viral pathogens in transgenic animals did not differ from wild-type mice as determined by the use of a Pseudorabies virus (PRV) as a model for a viral infection not affecting the lung. No significant differences of influenza virus titers in the lung of Raf-BxB and wild-type mice were observed. However, immunohistology revealed increased numbers of influenza NP-positive cells in the alveolar linings of Raf-BxB mice, demonstrating the strong tropism of influenza virus for cells expressing active Raf. These findings disclose the possibility to use modified influenza virus for the therapy of tumors with an activated Ras/Raf signalling pathway.