Oral nitrite circumvents antiseptic mouthwash-induced disruption of enterosalivary circuit of nitrate and promotes nitrosation and blood pressure lowering effect

Abstract

The nitric oxide (NO) metabolites nitrite and nitrate exert antihypertensive effects by mechanisms that involve gastric formation of S-nitrosothiols. However, while the use of antiseptic mouthwash (AM) is known to attenuate the responses to nitrate by disrupting its enterosalivary cycle, there is little information about whether AM attenuates the effects of orally administered nitrite. We hypothesized that the antihypertensive effects of orally administered nitrite would not be prevented by AM because, in contrast to oral nitrate, oral nitrite could promote S-nitrosothiols formation in the stomach without intereference by AM. Chronic effects of oral nitrite or nitrate were studied in two-kidney, one-clip (2K1C) hypertensive rats (and normotensive controls) treated with AM (or vehicle) once/day. We found that orally administered nitrite exerts antihypertensive effects that were not affected by AM. This finding contrasts with lack of antihypertensive responses to oral nitrate in 2K1C hypertensive rats treated with AM. Nitrite and nitrate treatments increased plasma nitrites, nitrates, and S-nitrosothiols concentrations. However, while treatment with AM attenuated the increases in plasma nitrite concentrations after both nitrite and nitrate treatments, AM attenuated the increases in S-nitrosothiols in nitrate-treated rats, but not in nitrite-treated rats. Moreover, AM attenuated vascular S-nitrosylation (detected by the SNO-RAC method) after nitrate, but not after nitrite treatment. Significant correlations were found between the hypotensive responses and S-nitrosothiols, and vascular S-nitrosylation levels. These results show for the first time that oral nitrite exerts antihypertensive effects notwithstanding the fact that antiseptic mouthwash disrupts the enterosalivary circulation of nitrate. Our results support a major role for S-nitrosothiols formation resulting in vascular S-nitrosylation as a key mechanism for the antihypertensive effects of both oral nitrite and nitrate.

The effect of dietary nitrate supplementation on the spatial heterogeneity of quadriceps deoxygenation during heavy-intensity cycling

“…) or other reactive nitrogen intermediates generated from NO 3 − treatment (Pinheiro et al. ) on augmenting the vascular response following the onset of step exercise. Accordingly, an increased number/volume of RBCs by longitudinal capillary recruitment (increased hematocrit, Poole et al.…”

“…3A). This response in the BR trial may have reflected the effect of an increased plasma [NO 2 À ] per se (Gladwin et al 2000) or other reactive nitrogen intermediates generated from NO 3 À treatment (Pinheiro et al 2016) on augmenting the vascular response following the onset of step exercise. Accordingly, an increased number/ volume of RBCs by longitudinal capillary recruitment (increased hematocrit, Poole et al 2013), hence D m O 2 (Federspiel and Popel 1986;Groebe and Thews 1990), would be expected to have facilitated O 2 release from capillaries, which may explain the increased muscle fractional O 2 extraction reported herein following NO 3 À supplementation.…”

Nitrate decreases xanthine oxidoreductase-mediated nitrite reductase activity and attenuates vascular and blood pressure responses to nitrite

“…Briefly, plasma samples (50 µl) were injected into a solution of acidified tri-iodide (2 g potassium iodide and 1.3 g iodine dissolved in 40 ml water with 140 ml acetic acid), purged with nitrogen in-line with a gas-phase chemiluminescence NO analyzer (Sievers Model 280 NO analyzer, Boulder, CO, USA). Plasma nitrate + nitrite (NO X ) concentrations were measured by using the Griess reaction, as previously described [22]. Briefly, 40 µl of plasma samples and a standard nitrate curve were incubated with the same volume of nitrate reductase buffer (0.1 mol/l potassium phosphate, pH 7.5, containing 1 mmol/l β-nicotinamide adenine dinucleotide phosphate and 2 U/ml of nitrate reductase) in 96-well plates.…”

Efeitos de drogas inibidoras da secreção ácida do estômago sobre as respostas hipotensoras do nitrito de sódio

“…Para a quantificação de espécies nitrosiladas, foi adicionada a amostra sulfanilamida ácida (5% em ácido fosfórico) na proporção de 10% do volume da amostra. Após 5 minutos de reação 500 μl de amostra foram injetados no analisador como descrito acima (Pinheiro et al 2016). …”

“…O tratamento crônico ou agudo com nitrito de sódio reduz a pressão arterial em diversos modelos de hipertensão, incluindo o modelo L-NAME (Pinheiro et al 2012;Montenegro et al 2014). Com a finalidade de avaliar os efeitos do nitrito de sódio na PAM, induzimos hipertensão com o modelo agudo L-NAME, uma vez que o nitrito de sódio 15 mg/kg por gavagem, não induz alterações na PAM em ratos normotensos (Pinheiro et al 2016). No presente estudo, a administração do nitrito de sódio levou a uma queda de aproximadamente 40 mmHg, o que corrobora com valores já apresentados na literatura (Pinheiro et al 2012).…”