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Arachidonic acid release in renal proximal tubule cell injuries and death
R G Schnellmann1, X Yang, J B Carrick
1Department of Physiology and Pharmacology, College of Veterinary Medicine, Athens, GA.
Abstract:
Arachidonic acid release and the effect of phospholipase inhibitors on various types of cell injuries and death to rabbit renal proximal tubule suspensions were determined. Proximal tubules were exposed to the mitochondrial inhibitor antimycin A (0.1 microM), the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone (1 microM FCCP), the oxidant tert-butyl hydroperoxide (0.5 mM TBHP), or the calcium ionophore ionomycin (5 microM) in the absence or presence of the putative phospholipase inhibitors dibucaine, mepacrine, chlorpromazine, or U-26384. The phospholipase inhibitors had no effect on the proximal tubule lactate dehydrogenase (LDH) release (a marker of cell death) produced by FCCP, antimycin A, or ionomycin after 1,2, or 2 hours of exposure, respectively. Only dibucaine and mepacrine decreased LDH release in TBHP-treated proximal tubules without decreasing TBHP-induced lipid peroxidation. Antimycin A and ionomycin did not release arachidonic acid from proximal tubules prelabeled with [1-14C] arachidonic acid. In contrast, TBHP released arachidonic acid from proximal tubules prior to the onset of cell death, and dibucaine and mepacrine decreased the TBHP-induced release. Thus, phospholipase inhibitors were cytoprotective in those injuries that produced arachidonic acid release. These results suggest that arachidonic acid release and phospholipase A2 activation play a contributing role in oxidant-induced renal proximal tubule cell injury and death but not in mitochondrial inhibitor- or calcium ionophore-induced proximal tubule cell injury and death.
Insights
Phospholipase inhibitors protected kidney cells from oxidant injury by reducing arachidonic acid release. However, they did not prevent cell death from mitochondrial inhibitors or calcium ionophores.
Area of Science:
- Nephrology
- Cell Biology
- Biochemistry
Background:
- Renal proximal tubule injury is a significant clinical concern.
- Understanding the mechanisms of cell death is crucial for developing protective strategies.
Purpose of the Study:
- To investigate the role of arachidonic acid release and phospholipase activity in renal proximal tubule cell injury.
- To determine the effect of phospholipase inhibitors on cell death induced by various agents.
Main Methods:
- Rabbit renal proximal tubule suspensions were exposed to mitochondrial inhibitors (antimycin A), a protonophore (FCCP), an oxidant (TBHP), or a calcium ionophore (ionomycin).
- The release of lactate dehydrogenase (LDH) and arachidonic acid was measured.
- The effects of phospholipase inhibitors (dibucaine, mepacrine, chlorpromazine, U-26384) were assessed.
Main Results:
- Phospholipase inhibitors did not affect cell death induced by FCCP, antimycin A, or ionomycin.
- Dibucaine and mepacrine reduced LDH release in TBHP-treated tubules without altering lipid peroxidation.
- TBHP induced arachidonic acid release prior to cell death, which was reduced by dibucaine and mepacrine.
Conclusions:
- Arachidonic acid release and phospholipase A2 activation contribute to oxidant-induced renal proximal tubule cell injury.
- These mechanisms are not involved in cell injury caused by mitochondrial inhibitors or calcium ionophores.