Endotoxin treatment increases lung mitochondrial scavenging of extramitochondrial superoxide in hyperoxia-exposed rats.
Mitochondria scavenge extramitochondrial superoxide anion via a respiration-dependent (i.e., non-enzymatic) mechanism. This study reports that hyperoxia exposure ( > 95 % O2 for 48h) reduced (P < 0.05) lung mitochondrial respiration-dependent superoxide scavenging by 56% compared to lung mitochondria from untreated control rats. In comparison, endotoxin treatment (5 micrograms insufflated intratracheally 24 h earlier) increased (P < 0.05) lung mitochondrial respiration-dependent superoxide scavenging by 57% compared to mitochondria from untreated control rats. Further, lung mitochondria from rats given endotoxin 24 h prior to hyperoxia exposure had more than twice the respiration-dependent superoxide scavenging capacity as compared to mitochondria from untreated rats exposed to hyperoxia (P < 0.05). In contrast, endotoxin treatment did not increase (P < 0.05) lung mitochondrial enzymatic (i.e., superoxide dismutase) scavenging activity when corrected for mitochondrial protein content in either hyperoxia-exposed or air-exposed rats. Therefore, hyperoxia exposure decreased, whereas endotoxin treatment increased, respiration-dependent lung mitochondrial scavenging of extramitochondrial superoxide. This recently identified cellular antioxidant defense appears to be an early target in hyperoxia but its induction provides an important component of endotoxin-induced tolerance to hyperoxic lung damage.
Guidot
D M
DM
Webb-Waring Institute for Research, University of Colorado Health Sciences Center, Denver, USA.
D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D004731:Endotoxins / Q000633:toxicity*; D016166:Free Radical Scavengers / Q000378:metabolism; D018496:Hyperoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D008168:Lung / Q000187:drug effects* / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism*; D018384:Oxidative Stress; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
D000975:Antioxidants; D004731:Endotoxins; D016166:Free Radical Scavengers; D012333:RNA, Messenger; D013481:Superoxides; D013482:Superoxide Dismutase