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Generation of 8‐epi‐prostaglandin F 2α in isolated rat kidney glomeruli by a radical‐independent mechanism
Author(s) -
Klein Thomas,
Neuhaus Katrin,
Reutter Felix,
Nüsing Rolf M
Publication year - 2001
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0704111
Subject(s) - chemistry , isoprostanes , nordihydroguaiaretic acid , prostanoid , isoprostane , prostaglandin , arachidonic acid , butylated hydroxytoluene , lipoxygenase , medicine , biochemistry , endocrinology , lipid peroxidation , enzyme , antioxidant , biology
Isoprostanes comprise a group of free radical‐catalyzed products of arachidonic acid. However, there is recent evidence pointing towards an enzyme‐dependent formation of isoprostanes. With the use of isolated rat glomeruli we addressed the mechanisms of isoprostane generation. Synthesis of prostanoids and isoprostanes, including 8‐epi‐PGF 2α , was studied under conditions favouring radical formation. Cultured glomeruli formed different prostanoids including 8‐epi‐PGF 2α . Upon LPS challenge cyclo‐oxygenase (COX)‐2 expression was enhanced, and this was paralleled by a 2–9‐fold increase in prostanoid formation, including isoprostanes. Addition of COX‐isoform unselective inhibitors (diclofenac, indomethacin) or a selective inhibitor (NS‐398) suppressed the synthesis of prostanoids, 8‐epi‐PGF 2α and total isoprostane fraction; however, inhibition of the latter was less pronounced. Antioxidants such as butylated hydroxytoluene (BHT), nordihydroguaiaretic acid (NDGA), or dimethylurea exhibited an only minimal inhibitory effect on 8‐epi‐PGF 2α synthesis. Moreover, ROS‐generating drugs (menadione, methylviologen) or NADPH‐driven radical formation were unable to cause the generation of significant amounts of 8‐epi‐PGF 2α by rat glomeruli. In contrast, the total isoprostane fraction could be increased by menadione addition. These data provide further evidence for a radical‐independent, but COX‐dependent formation of 8‐epi‐PGF 2α in renal tissue. Regarding the other isoprostanes, both radicals and COX enzymes contribute to their formation. Based on our data we assume that elevated release of vasoactive 8‐epi‐PGF 2α has to be expected under conditions when the prostanoid system in the kidney is stimulated, e.g. under inflammatory conditions. Regarding renal oxidative injuries, the usefulness of 8‐epi‐PGF 2α as a representative marker molecule of oxidative stress has to be questioned.British Journal of Pharmacology (2001) 133 , 643–650; doi: 10.1038/sj.bjp.0704111