Department of Pharmacology, Ribeirao Preto Medical School, University of Sao Paulo, Ribeirao Preto, SP, Brazil.
Department of Pharmacology, Faculty of Medical Sciences, State University of Campinas, Campinas, SP, Brazil.
Chem Biol Interact. 2021 Nov 1;349:109658. doi: 10.1016/j.cbi.2021.109658. Epub 2021 Sep 17.
Nitric oxide (NO) metabolites have physiological and pharmacological importance and increasing their tissue concentrations may result in beneficial effects. Tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) has antioxidant properties that may improve NO bioavailability. Moreover, tempol increases oral nitrite-derived gastric formation of S-nitrosothiols (RSNO). We hypothesized that pretreatment with tempol may further increase tissue concentrations of NO-related species after oral nitrite administration and therefore we carried out a time-dependent analysis of how tempol affects the concentrations of NO metabolites in different tissues after oral nitrite administration to rats. NO metabolites (nitrate, nitrite and RSNO) were assessed by ozone-based reductive chemiluminescence assays in plasma, stomach, aorta, heart and liver samples obtained from anesthetized rats at baseline conditions and 15 min, 30 min, 2 h or 24 h after oral nitrite (15 mg/kg) was administered to rats pretreated with tempol (18 mg/kg) or vehicle 15 min prior to nitrite administration. Aortic protein nitrosation was assessed by resin-assited capture (SNO-RAC) method. We found that pretreatment with tempol transiently enhanced nitrite-induced increases in nitrite, RSNO and nitrate concentrations in the stomach and in the plasma (all P < 0.05), particularly for 15-30 min, without affecting aortic protein nitrosation. Pretreatment with tempol enhanced nitrite-induced increases in nitrite (but not RSNO or nitrate) concentrations in the heart (P < 0.05). In contrast, tempol attenuated nitrite-induced increases in nitrite, RSNO or nitrate concentrations in the liver. These findings show that pretreatment with tempol affects oral nitrite-induced changes in tissue concentrations of NO metabolites depending on tissue type and does not increase nitrite-induced vascular nitrosation. These results may indicate that oral nitrite therapy aiming at achieving increased nitrosation of cardiovascular targets requires appropriate doses of nitrite and is not optimized by tempol.
一氧化氮（NO）代谢物具有生理和药理学意义，增加其组织浓度可能会产生有益的效果。Tempol（4-羟基-2,2,6,6-四甲基哌啶-N-氧自由基）具有抗氧化特性，可提高 NO 的生物利用度。此外，Tempol 增加了口服亚硝酸盐衍生的胃 S-亚硝基硫醇（RSNO）的形成。我们假设，Tempol 预处理可能会在口服亚硝酸盐给药后进一步增加组织中与 NO 相关的物质浓度，因此我们进行了一项时间依赖性分析，以研究 Tempol 如何影响口服亚硝酸盐给药后不同组织中 NO 代谢物的浓度。通过臭氧还原化学发光测定法，在麻醉大鼠的血浆、胃、主动脉、心脏和肝脏样本中评估 NO 代谢物（硝酸盐、亚硝酸盐和 RSNO），这些样本是在口服亚硝酸盐（15mg/kg）给药前 15 分钟、30 分钟、2 小时或 24 小时，以及在 Tempol（18mg/kg）预处理或载体预处理 15 分钟后获得的。采用树脂辅助捕获（SNO-RAC）方法评估主动脉蛋白硝化物。我们发现，Tempol 预处理会短暂增强亚硝酸盐诱导的胃和血浆中亚硝酸盐、RSNO 和硝酸盐浓度的增加（所有 P 值均<0.05），尤其是在 15-30 分钟内，而不影响主动脉蛋白硝化物。Tempol 预处理增强了亚硝酸盐诱导的心脏中亚硝酸盐（但不是 RSNO 或硝酸盐）浓度的增加（P 值<0.05）。相比之下，Tempol 减弱了亚硝酸盐诱导的肝脏中亚硝酸盐、RSNO 或硝酸盐浓度的增加。这些发现表明，Tempol 预处理会根据组织类型影响口服亚硝酸盐诱导的组织中 NO 代谢物浓度的变化，并且不会增加亚硝酸盐诱导的血管硝化物形成。这些结果可能表明，旨在实现心血管靶标增加硝化物形成的口服亚硝酸盐治疗需要适当剂量的亚硝酸盐，并且不能通过 Tempol 来优化。
