Mechanisms underlying sodium nitroprusside-induced tolerance in the mouse aorta: Role of ROS and cyclooxygenase-derived prostanoids.
OBJECTIVE
To determine the role of reactive oxygen species (ROS) on sodium nitroprusside (SNP)-induced tolerance. Additionally, we evaluated the role of ROS on NF-κB activation and pro-inflammatory cytokines production during SNP-induced tolerance.


METHODS
To induce in vitro tolerance, endothelium-intact or -denuded aortic rings isolated from male Balb-c mice were incubated for 15, 30, 45 or 60min with SNP (10nmol/L).


RESULTS
Tolerance to SNP was observed after incubation of endothelium-denuded, but not endothelium-intact aortas for 60min with this inorganic nitrate. Pre-incubation of denuded rings with tiron (superoxide anion (O2-) scavenger), and the NADPH oxidase inhibitors apocynin and atorvastatin reversed SNP-induced tolerance. l-NAME (non-selective NOS inhibitor) and l-arginine (NOS substrate) also prevented SNP-induced tolerance. Similarly, ibuprofen (non-selective cyclooxygenase (COX) inhibitor), nimesulide (selective COX-2 inhibitor), AH6809 (prostaglandin PGF2α receptor antagonist) or SQ29584 [PGH2/thromboxane TXA2receptor antagonist] reversed SNP-induced tolerance. Increased ROS generation was detected in tolerant arteries and both tiron and atorvastatin reversed this response. Tiron prevented tolerance-induced increase on O2-and hydrogen peroxide (H2O2) levels. The increase onp65/NF-κB expression and TNF-α production in tolerant arteries was prevented by tiron. The major new finding of our study is that SNP-induced tolerance is mediated by NADPH-oxidase derived ROS and vasoconstrictor prostanoids derived from COX-2, which are capable of reducing the vasorelaxation induced by SNP. Additionally, we found that ROS mediate the activation of NF-κB and the production of TNF-α in tolerant arteries.


CONCLUSIONS
These findings identify putative molecular mechanisms whereby SNP induces tolerance in the vasculature.
Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Brazil.
Mariana C
MC
Diniz
Departamento de Fisiologia, ICB, Universidade Federal de Minas Gerais, Brazil.
Vania C
VC
Olivon
Departamento de Microbiologia, ICB, Universidade Federal de Minas Gerais, Brazil.
Lívia D
LD
Tavares
Laboratório de Farmacologia, DEPCH, Escola de Enfermagem de Ribeirão Preto, USP, SP, Brazil.
Janaina A
JA
Simplicio
Laboratório de Farmacologia, DEPCH, Escola de Enfermagem de Ribeirão Preto, USP, SP, Brazil.
Natália A
NA
Gonzaga
Departamento de Microbiologia, ICB, Universidade Federal de Minas Gerais, Brazil.
Daniele G
DG
de Souza
Departamento Física e Química, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, USP, SP, Brazil.
Lusiane M
LM
Bendhack
Laboratório de Farmacologia, DEPCH, Escola de Enfermagem de Ribeirão Preto, USP, SP, Brazil.
Carlos R
CR
Tirapelli
Departamento de Farmacologia, ICB, Universidade Federal de Minas Gerais, Brazil. Electronic address: danibona@icb.ufmg.br.
Daniella
D
Bonaventura
D000818:Animals; D001011:Aorta / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009599:Nitroprusside / Q000494:pharmacology*; D044262:Prostaglandin H2 / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014664:Vasodilation / Q000187:drug effects
D017382:Reactive Oxygen Species; D009599:Nitroprusside; D044262:Prostaglandin H2; C077623:Ptgs2 protein, mouse; D051546:Cyclooxygenase 2
Nitrate tolerance; Prostanoids; Reactive oxygen species; Sodium nitroprusside