Abstract
Oxidative stress is a major mechanism of a variety of renal diseases. Tocopherols and tocotrienols are well known antioxidants. This study aimed to determine whether γ-tocotrienol (GT3) protects against mitochondrial dysfunction and renal proximal tubular cell (RPTC) injury caused by oxidants. Primary cultures of RPTCs were injured by using tert-butyl hydroperoxide (TBHP) in the absence and presence of GT3 or α-tocopherol (AT). Reactive oxygen species (ROS) production increased 300% in TBHP-injured RPTCs. State 3 respiration, oligomycin-sensitive respiration, and respiratory control ratio (RCR) decreased 50, 63, and 47%, respectively. The number of RPTCs with polarized mitochondria decreased 54%. F0F1-ATPase activity and ATP content decreased 31 and 65%, respectively. Cell lysis increased from 3% in controls to 26 and 52% at 4 and 24 h, respectively, after TBHP exposure. GT3 blocked ROS production, ameliorated decreases in state 3 and oligomycin-sensitive respirations and F0F1-ATPase activity, and maintained RCR and mitochondrial membrane potential (ΔΨm) in injured RPTCs. GT3 maintained ATP content, blocked RPTC lysis at 4 h, and reduced it to 13% at 24 h after injury. Treatment with equivalent concentrations of AT did not block ROS production and cell lysis and moderately improved mitochondrial respiration and coupling. This is the first report demonstrating the protective effects of GT3 against RPTC injury by: 1) decreasing production of ROS, 2) improving mitochondrial respiration, coupling, ΔΨm, and F0F1-ATPase function, 3) maintaining ATP levels, and 4) preventing RPTC lysis. Our data suggest that GT3 is superior to AT in protecting RPTCs against oxidant injury and may prove therapeutically valuable for preventing renal injury associated with oxidative stress.
Footnotes
This work was supported by the National Institutes of Health National Institute of Diabetes and Digestive and Kidney Diseases [Grant DK059558] (to G.N.) and the National Institutes of Health National Institute of Allergy and Infectious Diseases [Grant AI67798] (to M.H.-J.). The University of Arkansas for Medical Sciences Translational Research Institute, supported by the National Institutes of Health National Center for Research Resources [Grant UL1-RR029884], provided partial funding for the Flow Cytometry Core at the University of Arkansas for Medical Sciences.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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ABBREVIATIONS:
- AT
- α-tocopherol
- GT3
- γ-tocotrienol
- RPTC
- renal proximal tubular cell
- TBHP
- tert-butyl hydroperoxide
- ROS
- reactive oxygen species
- LDH
- lactate dehydrogenase
- RCR
- respiratory control ratio
- carboxy-H2DCFDA
- 5-(and-6)-carboxy-2′,7′-dichlorodihydro-fluorescein diacetate
- ΔΨm
- mitochondrial membrane potential
- MTP
- mitochondrial permeability transition.
- Received August 10, 2011.
- Accepted October 28, 2011.
- U.S. Government work not protected by U.S. copyright
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