Biomedical subjects
M Grewe
Publications and source records attributed to M Grewe.
Human epidermal keratinocytes are a source of soluble ICAM-1 molecules.
A soluble form of the usually membrane-bound adhesion molecule ICAM-1 was detected in supernatants derived from human epidermal keratinocytes. Specifically, supernatants harvested from long-term cultured normal human keratinocytes, or from the spontaneously immortalized keratinocyte cell line HaCaT, did not contain significant amounts of sICAM-1, but shedding of sICAM-1 was found to be markedly induced upon stimulation of keratinocytes with rh IFN gamma. In contrast, cells from the two epidermoid carcinoma cell lines, KB and A431, constitutively shed significant amounts of sICAM-1 even without cytokine stimulation, and sICAM-1 contents in supernatants harvested from these cells were further increased upon stimulation of cells with rh IFN gamma. These studies indicate, that in addition to peripheral blood mononuclear cells and human melanoma cells, human epidermal keratinocytes constitute an important cellular source of sICAM-1. By binding to leukocyte LFA-1 molecules, keratinocyte-derived sICAM-1 may influence inflammatory responses in the skin. In addition, constitutive shedding of sICAM-1 by transformed human keratinocytes may represent a possible mechanism by which neoplastic keratinocytes escape from cytotoxicity.
Rat tumor necrosis factor-alpha. Transcription in rat Kupffer cells and in vitro posttranslational processing based on a PCR-derived cDNA.
A DNA fragment with a reading frame of 708 basepairs coding for TNF-alpha from rat liver was cloned by the polymerase chain reaction. Using this species-specific cDNA a biotin-labelled antisense (-)RNA was transcribed. This probe was used for Northern blot analysis of TNF-alpha gene activation. Exposure of rat Kupffer cells to LPS led to a time-dependent change of TNF-alpha-mRNA expression with a maximum between one and two hours after stimulation. In vitro translation was carried out with sense (+)RNA in the presence of microsomes. SDS gel electrophoresis of the immunoprecipitated proteins revealed the formation of polypeptides with estimated molar masses of 26 and 17 kDa. They correspond to the estimated molar masses of a precursor of TNF-alpha encoded by the entire reading frame and of the mature form of TNF-alpha, respectively. A sequence of the cDNA assumed to code for the leader peptide was deleted and the remainder used for the construction of an expression plasmid. Using this construct, biologically active mature TNF-alpha was expressed in E. coli (10(6) units TNF-alpha per liter of culture medium). The propeptide as well as the biologically active TNF-alpha possess a homology of 92 and 76% to mouse and human TNF-alpha, respectively.
Prostaglandin D2 and E2 syntheses in rat Kupffer cells are antagonistically regulated by lipopolysaccharide and phorbol ester.
Prostaglandin-synthesizing activities were demonstrated in cell-free extracts of rat Kupffer cells and characterized. The enzymatic properties of PGH2 synthase were found to be similar to those of synthases present in other organs or cell types. The specific activity of the enzyme was not changed by substances that stimulate prostanoid release by intact Kupffer cells; however, it was reduced by pretreatment of the cells with glucocorticoid hormones. On the other hand, the activities of PGD2 and PGE2 synthase were influenced differently by the kind of cell stimulation. While pretreatment of the intact cells with endotoxin and/or inhibition of protein kinase C led to an enhanced PGE2 formation in cell-free extracts, exposure to agents that enhance protein kinase C-dependent signalling pathways, e.g. phagocytotic stimuli or phorbol ester, suppressed PGE2 synthase activity and, therefore, led to enhanced PGD2 synthesis. It is in line with this observation that in vitro activation of protein kinase C of Kupffer cells resulted in a reduced PGE2 and an enhanced PGD2 synthase activity.
[Nursing care, monitoring and early mobilization of patients with myocardial infarct].
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