Nuclear factor kappaB activity determines the sensitivity of kidney epithelial cells to apoptosis: implications for mercury-induced renal failure.
Nuclear factor kappa B (NF-kappaB) is a thiol-dependent transcriptional factor that promotes cell survival and protects cells from apoptotic stimuli. Numerous studies have demonstrated increased sensitivity to apoptosis associated with inhibition of NF-kappaB activation in various cell types. We have previously demonstrated that mercuric ion (Hg(2+)), one of the strongest thiol-binding agents known, impairs NF-kappaB activation and DNA binding at low microM concentrations in kidney epithelial cells. In the present studies we investigated the hypothesis that inhibition of NF-kappaB activation by Hg(2+) and other selective NF-kappaB inhibitors would increase the sensitivity of kidney epithelial (NRK52E) cells to apoptogenic agents to which these cells are normally resistant. Fewer than 10% of untreated cells in culture were found to be apoptotic when evaluated by DNA fragmentation (TUNEL) assay. Treatment of cells with Hg(2+) in concentrations up to 5 microM or with tumor necrosis factor-alpha (TNF) (300 units/ml) did not significantly increase the proportion of apoptotic cells, compared with untreated controls. However, when TNF was given following Hg(2+) pretreatment (0.5 to 5 microM for 30 min), the proportion of cells undergoing apoptosis increased by 2- to 6-fold over that seen in untreated controls. Kidney cells pretreated with specific NF-kappaB inhibitors (Bay11-7082 or SN50) prior to TNF also showed a significant increase in apoptosis. Increased sensitivity to apoptotic cell death following these treatments was significantly attenuated in cells transfected with a p65 expression vector. In studies in vivo, rats pretreated by intraperitoneal injection with Hg(2+) (0.75 mg/kg) 18 h prior to administration of bacterial lipopolysaccharide (LPS) (10 mg/kg) displayed impaired NF-kappaB activation and an increased mitochondrial cytochrome c release in kidney cortical cells. These findings are consistent with the view that prevention of NF-kappaB activity in vitro or in vivo enhances the sensitivity of kidney cells to apoptotic stimuli to which these cells are otherwise resistant. Since apoptosis is known to play a seminal role in the pathogenesis of renal failure caused by toxicant injury to tubular cells, the present findings suggest that inhibition of NF-kappaB activity may define a molecular mechanism underlying the pathogenesis of Hg(2+) toxicity in kidney cells.
Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA.
Francisco J
FJ
Dieguez-Acuña
William W
WW
Polk
Maureen E
ME
Ellis
P Lynne
PL
Simmonds
John V
JV
Kushleika
James S
JS
Woods
D017209:Apoptosis / Q000187:drug effects*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D020287:In Situ Nick-End Labeling; D007274:Injections, Intraperitoneal; D007668:Kidney / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D007672:Kidney Cortex / Q000187:drug effects / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008628:Mercury / Q000008:administration & dosage / Q000633:toxicity*; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D051437:Renal Insufficiency / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D013450:Sulfones / Q000494:pharmacology; D050863:Synaptotagmin I; D050857:Synaptotagmins; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
C434003:3-(4-methylphenylsulfonyl)-2-propenenitrile; D002135:Calcium-Binding Proteins; D004338:Drug Combinations; D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D016328:NF-kappa B; D009419:Nerve Tissue Proteins; D009570:Nitriles; D010455:Peptides; C118258:SN50 peptide; D013450:Sulfones; D050863:Synaptotagmin I; D014409:Tumor Necrosis Factor-alpha; D050857:Synaptotagmins; D008628:Mercury