title: Endothelial cells are main producers of interleukin 8 through Toll-like receptor 2 and 4 signaling during bacterial infection in leukopenic cancer patients.
abstract: Cancer patients who are leukopenic due to chemotherapy are susceptible to bacterial infections. Normally, clinical conditions during bacterial infections are caused by pathogen-associated molecular patterns, which are components that bind to Toll-like receptor (TLR) 2 (TLR-2) and TLR-4 on leukocytes, resulting in the production of inflammatory cytokines. The mechanism of this inflammatory response in cancer patients with diminished numbers of leukocytes is not completely clear. The levels of interleukin 1 beta (IL-1 beta) and tumor necrosis factor alpha measured in the circulation of leukopenic cancer patients are lower than those measured in that of nonleukopenic patients during bacterial infections, whereas plasma interleukin 8 (IL-8) levels show distinct identical increases during bacterial infections in both leukopenic and nonleukopenic patients. Normally, these cytokines are mainly secreted by leukocytes. In cancer patients with bacterial infections and a diminished number of leukocytes, other sources of IL-8 production, such as endothelial cells, might be expected. Endothelial cells instead of leukocytes become the most important producers of IL-8 during bacterial infections in patients with chemotherapy-induced leukopenia through TLR-2 and TLR-4 signaling. Whole blood samples from six cancer patients were stimulated with lipopolysaccharide (LPS), and then IL-8 concentrations in supernatants were measured. Further, human umbilical vein endothelial cells (HUVECs) were incubated with sera from leukopenic cancer patients with or without bacterial infections, and then IL-8 concentrations in supernatants were measured (n = 6). In addition, the same HUVEC experiment was performed with the addition of neutralizing antibodies against TLR-2 and TLR-4. During leukopenia (<10(9) cells/liter), LPS stimulation of whole blood did not result in an increase in IL-8 levels. However, when endothelial cells were incubated with sera from leukopenic cancer patients during bacterial infections, a three- to eightfold increase in IL-8 production was found, compared to the IL-8 production found after incubation with sera from patients without signs of infections. This increase did not reflect a higher level of IL-8 already present in the sera. Further, we demonstrated that IL-8 production induced in endothelial cells by sera from patients with documented gram-negative infections could be reduced significantly by up to 40% when the cells were incubated with neutralizing antibodies against TLR-4 (P = 0.028). The addition of TLR-2 antibodies slightly enhanced the reduction of IL-8 production. These results suggest that during bacterial infections in cancer patients with markedly diminished numbers of leukocytes, endothelial cells become important producers of IL-8 through TLR-4 signaling and, to a lesser extent, TLR-2 signaling.
authors.affiliation: Division of Pediatric Oncology, Beatrix Children's Hospital, University Hospital Groningen, Groningen, The Netherlands.
authors.forename: C S M
authors.initials: CS
authors.lastname: Oude Nijhuis
authors.forename: E
authors.initials: E
authors.lastname: Vellenga
authors.forename: S M G J
authors.initials: SM
authors.lastname: Daenen
authors.forename: W A
authors.initials: WA
authors.lastname: Kamps
authors.forename: E S J M
authors.initials: ES
authors.lastname: De Bont
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000009:adverse effects; D001424:Bacterial Infections / Q000209:etiology / Q000378:metabolism*; D001790:Blood Physiological Phenomena; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002648:Child; D003470:Culture Media / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D019337:Hematologic Neoplasms / Q000097:blood / Q000150:complications; D006801:Humans; D016209:Interleukin-8 / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics; D007970:Leukopenia / Q000139:chemically induced / Q000150:complications*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D009369:Neoplasms / Q000097:blood / Q000150:complications*; D011446:Prospective Studies; D011956:Receptors, Cell Surface / Q000037:antagonists & inhibitors / Q000502:physiology*; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha / Q000032:analysis / Q000096:biosynthesis
chemical_list: D000970:Antineoplastic Agents; D003470:Culture Media; D016209:Interleukin-8; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; C495342:TLR2 protein, human; C495345:TLR4 protein, human; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha