Selectivity of endotoxin-induced defect in endothelial calcium mobilization

Jason G. Umans, Debra Salvi, Patrick T. Murray, Mark E. Wylam

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Background. We hypothesized that endotoxin (LPS) would impair bradykinin (BK)-induced calcium (Ca2+) mobilization in aortic endothelial cells, perhaps due to cytotoxicity or via stimulation of nitric oxide (NO) synthesis. As well, we sought to define contributions of LPS-stimulated Ca2+ mobilization to these effects. Methods. LPS- or BK-induced increments of intracellular Ca2+ were assessed by microspectrofluorimetry with fura-2 in passaged bovine aortic endothelial cells. Time- and dose-dependent effects of LPS exposure (± inhibitors of NO or prostaglandin synthesis) on subsequent BK-induced Ca2+ mobilization and on attached cell counts were determined. Results. LPS (0.1 to 1.0 mg/ml) led to rapid increments of Ca2+, while Ca2+ responses were delayed following LPS (1 to 10 μg/ml) and lower doses were without effect. By contrast, LPS more potently (1.0 pg to 1.0 μg/ml) led to dose- and time-dependent impairment of subsequent BK- induced Ca2+ mobilization, with peak effect at four to six hours, persisting for at least 18 hours. This delayed effect on BK-response was unaltered by inhibition of either NO synthase or cyclooxygenase. The effect of LPS on BK-responsivity depended importantly on cell confluence, as it was not observed in subconfluent cells. By contrast, LPS-induced cell detachment, which was observed only at doses ≤ 1.0 μg/ml, did not depend on confluence. Conclusions. Different mechanisms lead to endothelial cytotoxicity and to impaired BK-response following LPS. Only the former effect, occurring at higher doses, might depend on initial LPS-induced Ca2+ mobilization.

Original languageEnglish (US)
Pages (from-to)1063-1069
Number of pages7
JournalKidney international
Volume54
Issue number4
DOIs
StatePublished - Jan 1 1998

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Keywords

  • Bradykinin
  • Endothelial cells
  • Endotoxin
  • Intracellular calcium
  • Sepsis
  • Vascular

ASJC Scopus subject areas

  • Nephrology

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