Inhibition of mitochondria prevents cell death in kidney epithelial cells by intra- and extracellular acidification.
BACKGROUND
Nephrotoxic substances like cisplatin or ochratoxin A (OTA) induce cell death in human proximal tubule-derived cells (IHKE cells). Mitochondria play a significant role in apoptosis and loss of their function may influence OTA- or cisplatin-induced apoptosis. Extracellular pH also plays an important role in tumor genesis. Therefore, we investigated the role of mitochondria and intra- and extracellular pH on cell death induction by cisplatin or OTA.


METHODS
IHKE cells were incubated in the presence of OTA or cisplatin, together with inhibitors of the mitochondrial metabolism, and the activity of caspase-3 was measured and DNA laddering was monitored. Adenosine triphosphate (ATP) content of the cells, lactate release into the media, and glucose consumption was determined. In addition, media and cells were acidified or alkalized artificially to investigate the effect of intra- and extracellular pH on cell death induction. Cytochrome C was immunodetected in cellular compartments.


RESULTS
Inhibition of the mitochondrial function reduced OTA- or cisplatin-induced cell death and led to considerable lactic acid production and extracellular acidification. Intra- and extracellular acidification prevented cells from cell death induced by OTA or cisplatin. No cytochrome C release from mitochondria could be detected during 24 hours of exposure to OTA or cisplatin.


CONCLUSIONS
We conclude that OTA- or cisplatin-induced cell death is dependent on functional and intact, ATP-producing mitochondria and that intra- and extracellular pH is crucial for induction of cell death in IHKE cells.
Schwerdt
Gerald
G
Physiologisches Institut, Universität Würzburg, Würzburg, Germany. gerald schwerdt@mail.uni-wuerzburg.de
Freudinger
Ruth
R
Schuster
Claudia
C
Silbernagl
Stefan
S
Gekle
Michael
M
D000138:Acidosis / Q000378:metabolism / Q000473:pathology*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D002021:Buffers; D002273:Carcinogens / Q000494:pharmacology; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002461:Cell Line, Transformed; D002945:Cisplatin / Q000494:pharmacology; D045304:Cytochromes c / Q000378:metabolism; D004247:DNA / Q000032:analysis; D004579:Electron Transport / Q000187:drug effects; D004847:Epithelial Cells / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007687:Kidney Tubules, Proximal / Q000166:cytology*; D019344:Lactic Acid / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects / Q000502:physiology*; D000226:Mitochondrial ADP, ATP Translocases / Q000037:antagonists & inhibitors; D025261:Mitochondrial Proton-Translocating ATPases / Q000037:antagonists & inhibitors; D009793:Ochratoxins / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D000970:Antineoplastic Agents; D002021:Buffers; D002273:Carcinogens; D009793:Ochratoxins; D014475:Uncoupling Agents; C025589:ochratoxin A; D019344:Lactic Acid; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D004247:DNA; D000226:Mitochondrial ADP, ATP Translocases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D025261:Mitochondrial Proton-Translocating ATPases; D005947:Glucose; D002945:Cisplatin