Nitration of indoxyl sulfate facilitates its cytotoxicity in human renal proximal tubular cells via expression of heme oxygenase-1.
Peroxynitrite, the reaction product of superoxide [Formula: see text] and nitric oxide (NO), nitrates tyrosine residues, unsaturated fatty acids, cyclic guanosine monophosphate and other phenolics. We report herein that indoxyl sulfate (IS) is also nitrated by peroxynitrite in vitro and forms 2-nitro-IS, as determined from spectral characteristics and (1)H-NMR. IS is one of the very important uremic toxins that accelerate the progression of chronic kidney disease via various mechanisms. However, cell viability experiments with human proximal tubular cells show that the cytotoxicity of 2-nitro-IS is several-fold higher than that of IS. The explanation for this finding seems to be that 2-nitro-IS induces a much more pronounced generation of intracellular reactive oxygen species (ROS) than IS. Results with inhibitors revealed that an organic anion transporter, several intracellular enzymes and nonprotein-bound iron ions are reasons for this finding. Most importantly, however, as detected by immunofluorescence and Western blotting, 2-nitro-IS induces the expression of heme oxygenase-1 and thereby the formation of ROS; most probably through the Fenton reaction. The final result of the increased amounts of ROS is death of the kidney cells. Thus, nitration of uremic toxins by peroxynitrite may help us to understand the initiation and progress of chronic kidney diseases.
Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan; Center for Clinical Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Yu
Y
Ishima
Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Toru
T
Narisoko
Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C, Denmark.
Ulrich
U
Kragh-Hansen
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Shunsuke
S
Kotani
Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan.
Makoto
M
Nakajima
Faculty of Pharmaceutical Sciences, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan; Drug Delivery System Institute, Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
Masaki
M
Otagiri
Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan; Center for Clinical Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto 862-0973, Japan. Electronic address: tomaru@gpo.kumamoto-u.ac.jp.
Toru
T
Maruyama
D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006801:Humans; D007200:Indican / Q000008:administration & dosage* / Q000737:chemistry*; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000187:drug effects / Q000502:physiology*; D009574:Nitro Compounds / Q000008:administration & dosage / Q000138:chemical synthesis; D030421:Peroxynitrous Acid / Q000737:chemistry*
D009574:Nitro Compounds; D030421:Peroxynitrous Acid; D051547:Heme Oxygenase-1; D007200:Indican
Heme oxygenase-1; Indoxyl sulfate; NADPH oxidase; Nitration; Peroxynitrite; Reactive oxygen species