Phosphate-induced chondrocyte apoptosis is linked to nitric oxide generation.
An elevation in inorganic phosphate (P(i)) concentration activates epiphyseal chondrocyte apoptosis. To determine the mechanism of apoptosis, tibial chondrocytes were treated with P(i), and nitrate/nitrite (NO/NO) levels were determined. P(i) induced a threefold increase in the NO/NO concentration; inhibitors of nitric oxide (NO) synthase activity and P(i) transport significantly reduced NO/NO levels and prevented cell death. Furthermore, a dose-dependent increase in cell death was observed after exposure of chondrocytes to S-nitrosoglutathione. P(i) increased caspase 3 activity 2.7-fold. Both caspase 1 and caspase 3 inhibitors protected chondrocytes from P(i)-induced apoptosis. P(i) caused a significant decrease in the mitochondrial membrane potential, while NO synthase inhibitors maintained mitochondrial function. While P(i) caused thiol depletion, inhibition of P(i) uptake or NO generation served to maintain glutathione levels. The results suggest that NO serves to mediate key metabolic events linked to P(i)-dependent chondrocyte apoptosis.
Teixeira
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Department of Biochemistry, School of Dental Medicine, Philadelphia, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Mansfield
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Hertkorn
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Ischiropoulos
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Shapiro
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D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D020170:Caspase 1 / Q000378:metabolism; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D019902:Chondrocytes / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000031:analogs & derivatives / Q000494:pharmacology; D006132:Growth Plate / Q000166:cytology; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009566:Nitrates / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009573:Nitrites / Q000378:metabolism; D009603:Nitroso Compounds / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D026422:S-Nitrosoglutathione; D019311:Staurosporine / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004791:Enzyme Inhibitors; D009566:Nitrates; D009573:Nitrites; D009603:Nitroso Compounds; D010975:Platelet Aggregation Inhibitors; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D026422:S-Nitrosoglutathione; D019001:Nitric Oxide Synthase; D053148:Caspase 3; D020169:Caspases; D020170:Caspase 1; D005978:Glutathione; D019311:Staurosporine; D019331:NG-Nitroarginine Methyl Ester