title: Downregulation of c-kit expression in human endothelial cells by inflammatory stimuli.
abstract: In recent studies we have shown that the expression of stem cell factor (SCF) in human endothelial cells is regulated by inflammatory processes. Gram-negative bacteria, interleukin-1 (IL-1), and lipopolysaccharide were able to upregulate the expression of SCF in human umbilical vein endothelial cells (HUVEC) (Blood 83:2836, 1994). Interestingly enough c-kit, the receptor of SCF, is coexpressed on HUVEC, suggesting an autoregulatory mechanism. To investigate the relation of c-kit and inflammatory processes we stimulated HUVEC with IL-1alpha and we established an in vitro model of inflammation. Binding experiments with 125I-SCF were performed to study the c-kit receptor expression on HUVEC. Scatchard analysis revealed both high-affinity receptors (K(d) approximately 0.36 nmol/L) and low-affinity receptors (K(d) approximately 2.9 nmol/L). Exposure to IL-1alpha led to a significant 50% reduction of c-kit high-affinity receptors, whereas the number of low-affinity receptors was not affected, in comparison to a control group of untreated HUVEC. Furthermore, using Northern blot analysis we studied the regulation c-kit mRNA expression in HUVEC after stimulation with IL-1alpha. Kinetic experiments showed a time-dependent downregulation of c-kit specific transcripts. In addition, we cocultured HUVEC with diverse bacterial strains. Experiments were performed over time with 1 x 10(6) bacteria/mL. Our data showed that, in contrary to the previously reported upregulation of SCF mRNA expression, stimulation with Yersinia enterocolitica or with Neisseria meningitidis led to a significant time-dependent downregulation of c-kit mRNA within 3 hours. These data indicate that inflammatory stimuli such as IL-1 or living bacteria activate a mechanism that downregulates c-kit receptor expression in human endothelial cells during the state of inflammation.
authors.affiliation: Department of Pediatric Hematology and Oncology, Children's Hospital, Medical School Hannover, Germany.
authors.forename: A
authors.initials: A
authors.lastname: König
authors.forename: S
authors.initials: S
authors.lastname: Corbacioglu
authors.forename: M
authors.initials: M
authors.lastname: Ballmaier
authors.forename: K
authors.initials: K
authors.lastname: Welte
mesh_terms: D002478:Cells, Cultured; D015536:Down-Regulation; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000382:microbiology; D006801:Humans; D007249:Inflammation / Q000378:metabolism; D008589:Meningococcal Infections / Q000378:metabolism; D009345:Neisseria meningitidis; D019009:Proto-Oncogene Proteins c-kit / Q000378:metabolism*; D019089:Stem Cell Factor / Q000378:metabolism; D015009:Yersinia Infections / Q000378:metabolism; D015008:Yersinia enterocolitica
chemical_list: D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit