Accumulating Mb (
myoglobin) in the kidney following severe
burns promotes oxidative damage and
inflammation, which leads to
acute renal failure. The potential for
haem-
iron to induce oxidative damage has prompted testing of
iron chelators [e.g. DFOB (
desferrioxamine B)] as renal
protective agents. We compared the ability of DFOB and a DFOB-derivative {DFOB-AdAOH [DFOB-N-(3-hydroxyadamant-1-yl)carboxamide]} to protect renal epithelial cells from Mb insult. Loading kidney-tubule epithelial cells with dihydrorhodamine-123 before exposure to 100 μM Mb increased rhodamine-123 fluorescence relative to controls (absence of Mb), indicating increased oxidative stress. Extracellular Mb elicited a reorganization of the
transferrin receptor as assessed by monitoring labelled
transferrin uptake with flow cytometry and inverted fluorescence microscopy. Mb stimulated HO-1 (haem oxygenase-1), TNFα (tumour
necrosis factor α), and both ICAM (
intercellular adhesion molecule) and VCAM (
vascular cell adhesion molecule) gene expression and inhibited epithelial monolayer permeability. Pre-treatment with DFOB or DFOB-AdAOH decreased Mb-mediated rhodamine-123 fluorescence, HO-1, ICAM and TNFα gene expression and restored monolayer permeability. MCP-1 (
monocyte chemotactic protein 1) secretion increased in cells exposed to Mb-insult and this was abrogated by DFOB or DFOB-AdAOH. Cells treated with DFOB or DFOB-AdAOH alone showed no change in permeability, MCP-1 secretion or HO-1, TNFα, ICAM or VCAM gene expression. Similarly to DFOB, incubation of DFOB-AdAOH with Mb plus H2O2 yielded
nitroxide radicals as detected by EPR spectroscopy, indicating a potential
antioxidant activity in addition to
metal chelation; Fe(III)-loaded DFOB-AdAOH showed no
nitroxide radical formation. Overall, the
chelators inhibited Mb-induced oxidative stress and
inflammation and improved epithelial cell function. DFOB-AdAOH showed similar activity to DFOB, indicating that this novel low-toxicity
chelator may protect the kidney after severe
burns.