Mitochondrial permeability transition as the critical target of N-acetyl perfluorooctane sulfonamide toxicity in vitro.
Perfluorooctanyl compounds with active functional groups have been shown to disrupt mitochondrial bioenergetics by three distinct mechanisms: protonophoric uncoupling of mitochondrial respiration, induction of the mitochondrial permeability transition (MPT), or a nonselective increase in membrane permeability. The purpose of this investigation was to identify the initial target and specific sequence of events associated with the N-acetyl substituted perfluorooctanesulfonamides induced MPT. N-acetyl-perfluorooctanesulfonamide (FOSAA), N-ethyl-N-acetyl-perfluorooctanesulfonamide (N-Et FOSAA), perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), and N-ethyl-N-(2-ethoxy)-perfluorooctanesulfonamide (N-Et FOSE) were added individually to liver mitochondria freshly isolated from Sprague-Dawley rats. Mitochondrial swelling and cytochrome c release were recorded spectrophotometrically, oxygen uptake was monitored with a Clark-type oxygen electrode, and reactive oxygen species (ROS) were monitored by dichlorodihydrofluorescein diacetate (H(2)DCFDA) fluorescence. FOSAA (45 microM) and N-Et FOSAA (7.5 microM) induced calcium-dependent mitochondrial swelling, the release of cytochrome c, inhibition of uncoupled mitochondrial respiration, and ROS generation, all of which were inhibited by cyclosporin-A (CsA). PFOA (200 microM) displayed slight CsA sensitive activity, but neither PFOS (10 microM) nor N-Et FOSE (70 microM) induced the MPT. Results of this investigation demonstrate two important findings: (1) MPT induction is specific to the N-acetyl substituted perfluorooctanesulfonamides and, (2) the sequence of events is initiated by induction of the MPT, which causes the release of cytochrome c as well as other cofactors leading to inhibition of respiration and ROS generation. The toxicity of N-acetyl perfluorooctanyl compounds may therefore reflect the mitochondrial dysfunction, which is compounded by the ensuing oxidative injury.
O'Brien
Timothy M
TM
Department of Biochemistry and Molecular Biology, Toxicology Graduate Program, University of Minnesota School of Medicine, 1035 University Drive, Duluth, MN 55812, USA.
Wallace
Kendall B
KB
D000818:Animals; D002210:Caprylates / Q000737:chemistry / Q000633:toxicity; D045304:Cytochromes c / Q000378:metabolism; D005466:Fluorocarbons / Q000737:chemistry / Q000633:toxicity*; D066298:In Vitro Techniques; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D008933:Mitochondrial Swelling / Q000187:drug effects; D010539:Permeability / Q000187:drug effects; D051381:Rats; D013329:Structure-Activity Relationship; D013449:Sulfonamides / Q000737:chemistry / Q000633:toxicity*
D002210:Caprylates; D005466:Fluorocarbons; D013449:Sulfonamides; C063900:perfluorooctanesulfonamide; D045304:Cytochromes c; C023036:perfluorooctanoic acid