Key result
Co-administration of 1 mM Spermine NONOate and 0.1 mM H2O2 increased endothelial permeability to 764% of baseline, compared to 298% with H2O2 alone.
Why the study?
Does nitric oxide enhance hydrogen peroxide-mediated endothelial permeability in vitro?
Does nitric oxide enhance hydrogen peroxide-mediated endothelial permeability in vitro?
Absolute Event Rate: 764% vs 298%
Nitric oxide exacerbates H2O2-dependent increases in endothelial permeability via iron-catalyzed formation of reactive oxygen metabolites.
May indicate NO potentiates H2O2-mediated endothelial leak in vitro; hypothesis-generating and should not change practice.
The objective of this study was to evaluate the effects of nitric oxide (NO) on H2O2-mediated endothelial permeability. H2O2 (0.1 mM) increased permeability at 90 min to 298% of baseline. Spermine NONOate (SNO), an NO donor, at 0.1 or 1 mM did not alter permeability. However, 0.1 mM H2O2 + 1 mM SNO increased permeability to 764%, twice that of 0.1 mM H2O2 alone. These treatments were not directly toxic to endothelial cells. This NO effect was concentration dependent, inasmuch as 0.1 mM SNO did not significantly change H2O2-mediated permeability. The NO-enhanced, H2O2-dependent permeability required the simultaneous presence of NO and H2O2, inasmuch as preincubation with SNO for 30 min followed by 0.1 mM H2O2 did not alter permeability. Staining of endothelial junctions showed widening of the intercellular space only in junctions of cells exposed to H2O2 (0.1 mM) + SNO (1 mM). Furthermore, NO did not affect H2O2 metabolism by endothelial cells but significantly depleted intracellular glutathione. This reduction of cell glutathione produced by NO exposure recovered 15-30 min after removal of the NO donor. NO-enhanced permeability was completely blocked by methionine (1 mM), a scavenger of reactive oxygen species, and by the iron chelator desferrioxamine (0.1 mM). These results suggest that NO may exacerbate the effects of H2O2-dependent increase in endothelial monolayer permeability via the iron-catalyzed formation of reactive oxygen metabolites.
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Okayama et al. (1997) studied this question. Nitric oxide (Spermine NONOate) and H2O2 vs. H2O2 alone (0.1 mM) was evaluated on Endothelial permeability. Co-administration of 1 mM Spermine NONOate and 0.1 mM H2O2 increased endothelial permeability to 764% of baseline, compared to 298% with H2O2 alone.
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