Variable effects of the mitoK(ATP) channel modulators diazoxide and 5-HD in ATP-depleted renal epithelial cells.
The role of mitochondrial K(ATP) (mitoK(ATP)) channels in renal ischemia-reperfusion injury is controversial with studies showing both protective and deleterious effects. In this study, we compared the effects of the putative mitoK(ATP) opener, diazoxide, and the mitoK(ATP) blocker, 5-hydroxydecanoate (5-HD) on cytotoxicity and apoptosis in tubular epithelial cells derived from rat (NRK-52E) and pig (LLC-PK1) following in vitro ischemic injury. Following ATP depletion-recovery, there was a significant increase in cytotoxicity in both NRK cells and LLC-PK1 cells although NRK cells were more sensitive to the injury. Diazoxide treatment attenuated cytotoxicity in both cell types and 5-HD treatment-increased cytotoxicity in the sensitive NRK cells in a superoxide-dependant manner. The protective effect of diazoxide was also reversed in the presence of 5-HD in ATP-depleted NRK cells. The ATP depletion-mediated increase in superoxide was enhanced by both diazoxide and 5-HD with the effect being more pronounced in the cells undergoing 5-HD treatment. Further, ATP depletion-induced activation of caspase-3 was decreased by diazoxide in NRK cells. In order to determine the signaling pathways involved in apoptosis, we examined the activation of Erk and JNK in ATP-depleted NRK cells. Diazoxide-activated Erk in ATP-depleted cells, but did not have any effect on JNK activation. In contrast, 5-HD did not impact Erk levels but increased JNK activation even under controlled conditions. Further, the use of a JNK inhibitor with 5-HD reversed the deleterious effects of 5-HD. This study demonstrates that in cells that are sensitive to ATP depletion-recovery, mitoK(ATP) channels protect against ATP depletion-mediated cytotoxicity and apoptosis through Erk- and JNK-dependant mechanisms.
Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA. vnilakan@mcw.edu
Vani
V
Nilakantan
Huanling
H
Liang
Jordan
J
Mortensen
Erin
E
Taylor
Christopher P
CP
Johnson
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D003652:Decanoic Acids / Q000494:pharmacology*; D003981:Diazoxide / Q000494:pharmacology*; D004847:Epithelial Cells / Q000378:metabolism*; D006880:Hydroxy Acids / Q000494:pharmacology*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D018374:LLC-PK1 Cells; D015221:Potassium Channels / Q000378:metabolism*; D051381:Rats; D015427:Reperfusion Injury / Q000378:metabolism; D013552:Swine
D003652:Decanoic Acids; D006880:Hydroxy Acids; D015221:Potassium Channels; C117780:mitochondrial K(ATP) channel; C052853:5-hydroxydecanoic acid; D000255:Adenosine Triphosphate; D003981:Diazoxide