Inhibition of iNOS protects endothelial-dependent vasodilation in aged rats

Abstract

Aim: To examine whether iNOS contributes to endothelial dysfunction in aged rats. Methods: Male Sprague Dawley rats were divided into three groups: young rats, aged rats treated with vehicle and aged rats treated with N-[3-(Aminomethyl) benzyl] acetamidine (1400W, 1 mg/kg, ip). Vasorelaxation was measured in isolated thoracic aorta. iNOS expression of thoracic aortic arteries was detected using immunohistochemistry and Western blot. Nitrotyrosine (a marker for peroxynitrite formation) content and expression in thoracic aortic tissue were determined using enzyme linked immunosorbent assay and immunohistochemistry. Results: Maximal relaxation induced by acetylcholine (10 -9 to 10 -5 mol/L) in the aged rats treated with vehicle was significantly decreased (70%±15%, P<0.01), as compared with the young rats (95%±8%). However, the maximal relaxation induced by acidified NaNO2 (an endothelium-independent vasodilator) had no significant difference between the two groups. Moreover, iNOS and nitrotyrosine expression increased in the vessels of the aged rats. In the aged rats treated with 1400W (a highly selective iNOS inhibitor) nitrotyrosine expression was reduced and acetylcholine-induced vasorelaxation was markedly improved (maximal relaxation was increased to 87%±8%, P<0.05), but the acidified NaNO 2 -induced vasorelaxation had no significant change. Conclusion: Our study demonstrated that inhibition of iNOS by 1400W increased endothelium-dependent vasodilation in aged rats. The mechanism was related with attenuation of peroxynitrite formation.Keywords: aging; nitric oxide synthase; endothelium; vasodilation; 1400W Acta Pharmacologica Sinica (2010Sinica ( ) 31: 1324Sinica ( -1328 doi: 10.1038/aps.2010 published online 13 Sep 2010 Original Article * To whom correspondence should be addressed. [17,18] , respectively. Thirty minutes after 1400W treatment [18,19] young and aged rats were sacrificed to obtain vessel tissues (n=7 rats per group) for nitrotyrosine content and immunohistochemical studies of iNOS and nitrotyrosine. Determination of endothelial functionEndothelial function was determined by comparing the vasorelaxation response to acetylcholine (ACh), an endothelium-dependent vasodilator, with that of acidified NaNO 2 , an endothelium-independent vasodilator, as described previously [20] . Briefly, thoracic aortic rings were mounted onto hooks, suspended in organ chambers filled with Krebs buffer (mmol/L: NaCl 118.3, KCl 4.7, CaCl 2 2.5, MgSO 4 1.2, KH 2 PO 4 1.2, NaHCO 3 25.0, glucose 11.0, pH=7.4) [21] and aerated with 95% O 2 and 5% CO 2 at 37 °C, and connected to force transducers to record changes in tension via a Chart 5.3 data acquisition system. After equilibration for 60 min at a preload of 1 g, the rings were precontracted with norepinephrine (NE, 1 μmol/L). Once a stable contraction was achieved, the rings were exposed to cumulative concentrations of ACh (10 -9 to 10 -5 mol/L). After the cumulative response was stabilized, the rings were washed and allowed to equilibrate to baseline. The procedur...

Efficacy of subantimicrobial-dose doxycycline against nitrosative stress in chronic periodontitis

“…There is evidence that a number of less abundant proteins (ie, α1-proteinase inhibitor, cytochrome P450, chemokines, manganese superoxide dismutase, and cyclooxygenase) and peptides have altered functions after protein nitration, which may work as negative feedback in the inflammatory process [20] . However, basal low-level 3NT has been detected under physiological conditions in most tissues and plasma.…”

“…In the study population, the positive correlation between iNOS and 3NT staining in the periodontal tissue at baseline proved that this effect was not attributed to physiological nitration, but rather, it was due to increased iNOS expression. Consequently, it may be an indication of increased nitrosative stress [20] . The significant changes in periodontal iNOS and 3NT suggest that these tests may be useful for the evaluation of the severity of periodontal damage.…”

“…For immunohistochemistry, the sections were incubated with primary monoclonal antibodies against iNOS and 3NT, diluted in 1% phosphate-buffered saline-bovine serum albumin [20] . The secondary antibody (labeled streptavidin biotin) was applied, followed by incubation with diaminobenzidine.…”

Efeitos da inibição da sintase induzida do óxido nítrico na fisiopatologia da pré-eclâmpsia experimental

“…Considerando que o 1400W é um inibidor altamente seletivos da iNOS (Garvey, Oplinger et al, 1997), este também pode reduzir a expressão da iNOS, como retratado aqui e em outros estudos (El-Mas, Fan et al, 2008;Kan, Hsu et al, 2008;Tian, Yan et al, 2010). Esse importante efeito do 1400W pode explicar a atenuação do aumento dos níveis de nitrotirosina induzido no modelo RUPP, o qual, pode refletir na formação ONOO -.…”

“…O aumento da atividade e expressão da iNOS vascular tem sido descrito na hipertensão (Chou, Yen et al, 1998;Hong, Loh et al, 2000) e o uso dos inibidores farmacológicos seletivos da iNOS causaram reduções significativas da pressão arterial e da disfunção endotelial no modelo de ratos espontaneamente hipertensos (SHR) e em ratos Wistar velhos (Chou, Yen et al, 1998;Hong, Loh et al, 2000;Tian, Yan et al, 2010).…”