C3 synthesis and CRs expression during differentiation of a murine stem cell line

Pentoxifylline Inhibits Tumor Necrosis Factor-Alpha Induced Synthesis of Complement Component C3 in Human Endothelial Cells

Vascular endothelium is a major target for the inflammatory damage that occurs with multiple organ dysfunction associated with sepsis and other trauma. The growing appreciation of endothelium as a target of inflammation has obscured the importance of these cells as a source of inflammatory mediators. In the following study we evaluated the ability of tumor necrosis factor-alpha (TNF) to induce the synthesis of complement component C3 in human umbilical vein endothelial cells (HUVEC) and whether pentoxifylline (PTX) could reduce C3 expression. Confluent monolayers of HUVEC were treated with increasing concentrations of TNF with and without two concentrations of PTX. Concentrations of C3 were determined every 48 h for 144 h in cellular supernatants and C3 mRNA was amplified using RT-PCR. TNF increased C3 release from HUVEC in a concentration dependent manner. PTX added at the same time as TNF significantly reduced C3 release at the 96 h time point. Consistent with data on C3 release PTX inhibited the increased C3 mRNA expression associated with TNF treatment. TNF increases C3 synthesis and release from endothelial cells which were inhibited by clinical concentrations of PTX. This data further supports the potential benefit of PTX in multiple organ dysfunction and other inflammatory processes involving the endothelium by inhibiting one of the major mediators of vascular damage.

Potential involvement of the AML1-MTG8 fusion protein in the granulocytic maturation characteristic of the t(8;21) acute myelogenous leukemia revealed by microarray analysis

The AML1 (RUNX1)-MTG8 (ETO) fusion transcription factor generated by the t(8;21) translocation is believed to deregulate the expression of genes that are crucial for normal differentiation and proliferation of hematopoietic progenitors, resulting in acute myelogenous leukemia. To elucidate the role of AML1-MTG8 in leukemogenesis, we used oligonucleotide microarrays to detect alterations in gene expression caused by ectopic expression of AML1-MTG8 in a murine myeloid progenitor cell line, L-G. Microarray analysis of approximately 6500 genes identified 32 candidate genes under the downstream control of AML1-MTG8. Among the 32 genes, 23 were not known to be regulated by AML1-MTG8. These included many granule protein genes and several cell surface antigen genes. Interestingly, AML1-MTG8 enhanced the expression of several genes that are usually induced during granulocytic differentiation, particularly those encoding azurophil granule proteins, including cathepsin G, myeloperoxidase and lysozyme. This indicates that AML1-MTG8 induces partial differentiation of myeloid progenitor cells into promyelocytes in the absence of the usual differentiation signals, while it inhibits terminal differentiation into mature granulocytes. Thus, AML1-MTG8 itself may play a crucial role in defining a unique cytologic type with abnormal maturation, characteristic of t(8;21) acute myelogenous leukemia.