Nitrite-generated NO circumvents dysregulated arginine/NOS signaling to protect against intimal hyperplasia in Sprague-Dawley rats
Matthew J. Alef, … , Edith Tzeng, Brian S. Zuckerbraun
Matthew J. Alef, … , Edith Tzeng, Brian S. Zuckerbraun
Published March 23, 2011
Citation Information: J Clin Invest. 2011;121(4):1646-1656. https://doi.org/10.1172/JCI44079.
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Nitrite-generated NO circumvents dysregulated arginine/NOS signaling to protect against intimal hyperplasia in Sprague-Dawley rats

Abstract

Vascular disease, a significant cause of morbidity and mortality in the developed world, results from vascular injury. Following vascular injury, damaged or dysfunctional endothelial cells and activated SMCs engage in vasoproliferative remodeling and the formation of flow-limiting intimal hyperplasia (IH). We hypothesized that vascular injury results in decreased bioavailability of NO secondary to dysregulated arginine-dependent NO generation. Furthermore, we postulated that nitrite-dependent NO generation is augmented as an adaptive response to limit vascular injury/proliferation and can be harnessed for its protective effects. Here we report that sodium nitrite (intraperitoneal, inhaled, or oral) limited the development of IH in a rat model of vascular injury. Additionally, nitrite led to the generation of NO in vessels and SMCs, as well as limited SMC proliferation via p21Waf1/Cip1 signaling. These data demonstrate that IH is associated with increased arginase-1 levels, which leads to decreased NO production and bioavailability. Vascular injury also was associated with increased levels of xanthine oxidoreductase (XOR), a known nitrite reductase. Chronic inhibition of XOR and a diet deficient in nitrate/nitrite each exacerbated vascular injury. Moreover, established IH was reversed by dietary supplementation of nitrite. The vasoprotective effects of nitrite were counteracted by inhibition of XOR. These data illustrate the importance of nitrite-generated NO as an endogenous adaptive response and as a pathway that can be harnessed for therapeutic benefit.

Authors

Matthew J. Alef, Raghuveer Vallabhaneni, Evie Carchman, Sidney M. Morris Jr., Sruti Shiva, Yinna Wang, Eric E. Kelley, Margaret M. Tarpey, Mark T. Gladwin, Edith Tzeng, Brian S. Zuckerbraun

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Figure 5

Sodium nitrite–induced NO generation, inhibition of SMC proliferation, and p21 induction are dependent on XOR.

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Sodium nitrite–induced NO generation, inhibition of SMC proliferation, a...
Allopurinol (100 μM) inhibited nitrite-induced (250 μM) NO generation within ex vivo carotid arteries (A; n = 4 independent arteries, each condition measured in triplicate; *P < 0.01 compared with vehicle, #P < 0.05 compared with nitrite-treated, injured vessels) and cultured SMCs (B; each condition measured in triplicate in 3 independent experiments; *P < 0.01 compared with vehicle, control SMCs, #P < 0.05 compared with nitrite-treated, control SMCs). (C) Allopurinol prevented nitrite-induced inhibition of SMC proliferation (*P < 0.01 compared with non-nitrite controls; #P < 0.05 compared with nitrite-treated SMCs). The results are the mean ± SEM of 3 independent experiments, with experiments performed in triplicate for each condition. (D) Western blot analysis demonstrated increased p21 protein levels following nitrite treatment, an effect that was inhibited by the addition of allopurinol (representative blot of 3 independent experiments). (E) Protection against IH formation by oral sodium nitrite pretreatment was inhibited in the presence of allopurinol (100 μM/kg/d; 48 hours prior to injury and 24 hours after injury) (n = 6/group; *P < 0.01 compared with non-nitrite-treated rats; #P < 0.01 compared with nitrite-treated rats). Brief allopurinol treatment alone had no effect on IH in non-nitrite-treated, injured vessels.