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Einleitung: MMP-1 ist ein Mitglied der Matrix Metalloproteinase-Familie (MMP-Familie), das wie die übrigen MMPs entscheidend beim Abbau und der Remodulierung der extrazellulären Matrix beteiligt ist. Die Regulierung dieser Proteinasen ist physiologisch zum einen durch die Aktivierung ihrer[for full text, please go to the a.m. URL], 126. Kongress der Deutschen Gesellschaft für Chirurgie

BACKGROUND: Nitric oxide (NO) has frequently been shown to inhibit leukocyte adherence to activated endothelium thus displaying anti-adhesive and immunosuppressive activities. A molecular mechanism contributing to this effect is described. MATERIALS AND METHODS: Primary murine aortic endothelial cells were activated with interleukin (IL)-1beta to express intercellular adhesion molecule-1 (ICAM-1) mRNA in the presence or absence of the physiological spontaneous NO-donor S-nitrosocysteine. Subsequently, semiquantitative RT-PCR and gel shift assays with nuclear extracts were performed to analyse the effects of NO on ICAM-1 mRNA expression and on the activity of transcription factors involved in ICAM-1 transcription. In addition, luciferase reporter gene activity of cytokine-activated cells transiently transfected with an ICAM-1 promoter-luciferase construct and cultured in the presence of the slow-releasing NO-donor DETA/NO was determined. RESULTS: NO at subtoxic concentrations decreases IL-1beta-induced endothelial ICAM-1 mRNA expression. This inhibition occurs at the transcriptional level, as NO affects IL-1b-induced ICAM-1 promoter activity in transiently transfected cells. Using gel-shift assays and double-stranded oligonucleotide consensus sequences of the known transcription factor binding sites of the ICAM-1 promoter, Sp1 and AP-1 were identified as transcriptional activators of IL-1beta-driven ICAM-1 expression. The DNA binding of both of these transcription factors to specific binding sites of the ICAM-1 promoter was decreased in MAEC exposed to NO. CONCLUSIONS: Our studies indicate that the anti-adhesive effect of NO concentrations equivalent to high-output NO synthesis is mediated, at least in part, by inhibition of ICAM-1 expression via a concerted action of NO on the redox-sensitive transcriptional activators Sp1 and AP-1. This molecular mechanism may contribute to the anti-inflammatory actions of NO synthesized by the inducible NO synthase.

Treatment of L929 cells with TNF alpha initiates apoptosis and subsequent cell death. The authors have visualized sites of DNA damage in situ by using DNA polymerase to synthesize new strands from the DNA strands breaks as starting point. Biotin-dUTP was incorporated into the newly synthesized strand and visualized by immunocytochemistry. DNA strand breaks were first observed 3 to 4 hours after contact with TNF alpha and preceded cell death. Limiting doses of TNF alpha caused DNA strand breaks only in a subpopulation of L929 cells. At a low dose, TNF alpha led to DNA damage without any subsequent loss of cell viability. The new assay also detects DNase-induced single strand breaks and thus is able to visualize apoptotic as well as non-apoptotic types of DNA damage.