Circulating levels of hydrogen sulphide negatively correlate to nitrite levels in gestational hypertensive and preeclamptic pregnant women.

Endothelial dysfunction is a hallmark of preeclampsia and the role of nitric oxide (NO) has been extensively studied in this pregnancy complication. In recent years, hydrogen sulphide (H2 S) has arisen as a new gasotransmitter with an impact on endothelial function. However, the involvement of H2 S in the pathophysiology of preeclampsia is not fully understood, and only a few studies with limited sample size have investigated circulating levels of H2 S in preeclamptic patients. Moreover, H2 S levels have not been previously evaluated in gestational hypertension. Furthermore, the relationship between H2 S and NO in these hypertensive disorders of pregnancy has yet to be determined. We measured H2 S levels in plasma of 120 healthy pregnant women, 88 gestational hypertensive and 62 preeclamptic women. We also measured plasma nitrite in a subset of patients and carried out correlation analysis between plasma H2 S and nitrite in these three groups. We found that plasma H2 S was elevated in preeclampsia and further increased in gestational hypertension compared to healthy pregnancy. Plasma nitrite was reduced in gestational hypertension and preeclampsia, and these levels were negatively correlated with H2 S in both gestational hypertension and preeclampsia, but not in healthy pregnancy. Our results indicate that increases in H2 S may represent a mechanism triggered as an attempt to compensate reduced NO in gestational hypertension and preeclampsia. Future studies are warranted to investigate the mechanisms underlying H2 S/NO interaction on mediating endothelial dysfunction in these hypertensive disorders of pregnancy.

Sodium nitrite attenuates hypertension-in-pregnancy and blunts increases in soluble fms-like tyrosine kinase-1 and in vascular endothelial growth factor.

Preeclampsia is a pregnancy-associated disorder characterized by hypertension with uncertain pathogenesis. Increases in antiangiogenic soluble fms-like tyrosine kinase-1 (sFlt-1) and reductions in nitric oxide (NO) bioavailability have been observed in preeclamptic women. However, the specific mechanisms linking these detrimental changes to the hypertension-in-pregnancy are not clearly understood. In this regard, while recent findings have suggested that nitrite-derived NO formation exerts antihypertensive and antioxidant effects, no previous study has examined these responses to orally administered nitrite in hypertension-in-pregnancy. We then hypothesized restoring NO bioavailability with sodium nitrite in pregnant rats upon NO synthesis inhibition with N(omega)-nitro-l-arginine methyl ester (L-NAME) attenuates hypertension and high circulating levels of sFlt-1. Number and weight of pups and placentae were recorded to assess maternal-fetal interface. Plasma sFlt-1, vascular endothelial growth factor (VEGF) and biochemical determinants of NO formation and of antioxidant function were measured. We found that sodium nitrite blunts the hypertension-in-pregnancy and restores the NO bioavailability, and concomitantly prevents the L-NAME-induced high circulating sFlt-1 and VEGF levels. Also, our results suggest that nitrite-derived NO protected against reductions in litter size and placental weight caused by L-NAME, improving number of viable and resorbed fetuses and antioxidant function. Therefore, the present findings are consistent with the hypothesis that nitrite-derived NO may possibly be the driving force behind the maternal and fetal beneficial effects observed with sodium nitrite during hypertension-in-pregnancy. Certainly further investigations are required in preeclampsia, since counteracting the damages to the mother and fetal sides resulting from hypertension and elevated sFlt-1 levels may provide a great benefit in this gestational hypertensive disease.

Effects of fast versus slow-releasing hydrogen sulfide donors in hypertension in pregnancy and fetoplacental growth restriction.

Hydrogen sulfide (H2S) is a vasorelaxant gas with therapeutic potential in several diseases. However, effects of H2S donors in hypertensive pregnancy complicated by feto-placental growth restriction are unclear. Therefore, we aimed to examine and compare the effects of fast-releasing H2S donor (sodium hydrosulfide-NaHS) and slow-releasing H2S donor (GYY4137) in hypertension-in-pregnancy. Pregnant rats were distributed into four groups: normal pregnancy (Norm-Preg), hypertensive pregnancy (HTN-Preg), hypertensive pregnancy + NaHS (HTN-Preg + NaHS), and hypertensive pregnancy + GYY4137 (HTN-Preg + GYY). Systolic blood pressure, plasma H2S levels, fetal and placental weights, number of viable fetuses, litter size, and endothelium-dependent vasodilation were examined. Also, oxidative stress was assessed in placenta. We found that GYY4137 attenuated hypertension on gestational days 16 and 18, while NaHS presented antihypertensive effect only on gestational day 18. GYY4137, but not NaHS, increased plasma H2S levels. Greater fetal and placental weights were found with GYY4137 than NaHS treatment. Also, HTN-Preg + NaHS presented further reductions in placental weights when compared to HTN-Preg group. Number of viable fetuses and litter size presented no significant changes. GYY4137 reduced placental oxidative stress caused by hypertension, while greater increases in oxidative stress were found in HTN-Preg + NaHS than HTN-Preg group. Hypertensive pregnancy caused impaired endothelium-dependent vasodilation, while GYY4137 and NaHS treatments blunted endothelial dysfunction. Endothelium-dependent vasodilation was completely blocked by the nitric oxide synthase inhibitor. We conclude that slow-releasing H2S donor GYY4137 is advantageous compared with fast-releasing H2S-donor NaHS to attenuate hypertension-in-pregnancy and to protect against feto-placental growth restriction and oxidative stress.

Placental nitric oxide formation and endothelium-dependent vasodilation underlie pravastatin effects against angiogenic imbalance, hypertension in pregnancy and intrauterine growth restriction.

Pre-eclampsia and hypertensive disorders of pregnancy are frequently associated with foeto-placental growth restriction, and that may be triggered by angiogenic imbalance and endothelial dysfunction. Impaired nitric oxide (NO) bioavailability seems to be involved in these pathophysiological changes observed in hypertensive pregnancy. Pravastatin has shown efficacy and to be safe during hypertension in pregnancy. However, NO involvement in pravastatin effects during maternal hypertension and foeto-placental development is unclear. Therefore, we aimed to examine pravastatin effects on placental NO formation, endothelium-dependent vasodilation, systolic blood pressure and foeto-placental development in hypertensive pregnant rats. Biochemical determinants of angiogenesis and oxidative stress were also assessed. Pregnant rats were distributed into four groups: normal pregnancy (Norm-Preg), pregnancy+pravastatin (Preg-Prava), hypertensive pregnancy (HTN-Preg) and hypertensive pregnancy+pravastatin (HTN-Preg+Prava). Our results showed that pravastatin treatment blunts hypertension and foeto-placental growth restriction. Also, increases in placental NO levels were found in the HTN-Preg+Prava group. Pravastatin prevents impaired endothelium-dependent acetylcholine-induced vasodilation, exacerbated contractile response to phenylephrine and increases in oxidative stress in the HTN-Preg+Prava group. Increased soluble fms-like tyrosine kinase-1-to-placental growth factor (sFlt-1/PlGF) ratio is reversed by pravastatin treatment in the HTN-Preg+Prava group. We conclude that NO formation and endothelium-dependent vasodilation underlie pleiotropic effects associated with pravastatin treatment against hypertension in pregnancy, intrauterine growth restriction, vascular dysfunction and angiogenic imbalance.

Maternal hypertension and feto-placental growth restriction is reversed by sildenafil: Evidence of independent effects of circulating nitric oxide levels.

Sildenafil has shown nitric oxide (NO)-independent pleiotropic effects, however the mechanisms involved are unclear. We investigated the protective effects of sildenafil against hypertension in pregnancy and feto-placental growth restriction induced by NO inhibition, and if sodium nitrite-derived NO formation influences sildenafil effects. We evaluated the plasmatic levels of NO metabolites, cyclic guanosine monophosphate (cGMP), oxidative stress and myeloperoxidase, which are involved in endothelial dysfunction during hypertension in pregnancy. Also, we performed in vitro experiments to examine cell viability and NO synthesis in human umbilical vein endothelial cells (HUVECs) cultures incubated with plasma from healthy or hypertensive pregnant rats treated (or not) with both drugs, either alone or in association. Sildenafil blunted hypertension in pregnancy and protected against feto-placental growth restriction induced by NO inhibition and these effects of sildenafil alone were similar to those presented by its association with sodium nitrite. Protective effects of sildenafil were observed even with low plasmatic NO levels and were not followed by increases in cGMP levels. Also, sildenafil, but not sodium nitrite, blunted the increases in myeloperoxidase activity. Both drugs (isolated or in association) presented antioxidant effects. Plasma from hypertensive pregnant rats treated with sildenafil, but not sodium nitrite alone, increased the viability of HUVECs. NO synthesis in HUVECs cultures was increased with plasma from rats treated with both drugs. We conclude that sildenafil effects are not dependent of circulating NO levels in hypertension and feto-placental growth restriction. These findings may reflect a protection against myeloperoxidase and pro-oxidant activation in hypertension in pregnancy.

Clinical and Experimental Evidences of Hydrogen Sulfide Involvement in Lead-Induced Hypertension.

Lead- (Pb-) induced hypertension has been shown in humans and experimental animals and cardiovascular effects of hydrogen sulfide (H2S) have been reported previously. However, no studies examined involvement of H2S in Pb-induced hypertension. We found increases in diastolic blood pressure and mean blood pressure in Pb-intoxicated humans followed by diminished H2S plasmatic levels. In order to expand our findings, male Wistar rats were divided into four groups: Saline, Pb, NaHS, and Pb + NaHS. Pb-intoxicated animals received intraperitoneally (i.p.) 1st dose of 8 µg/100 g of Pb acetate and subsequent doses of 0.1 µg/100 g for seven days and sodium hydrosulfide- (NaHS-) treated animals received i.p. NaHS injections (50 µmol/kg/twice daily) for seven days. NaHS treatment blunted increases in systolic blood pressure, increased H2S plasmatic levels, and diminished whole-blood lead levels. Treatment with NaHS in Pb-induced hypertension seems to induce a protective role in rat aorta which is dependent on endothelium and seems to promote non-NO-mediated relaxation. Pb-intoxication increased oxidative stress in rats, while treatment with NaHS blunted increases in plasmatic MDA levels and increased antioxidant status of plasma. Therefore, H2S pathway may be involved in Pb-induced hypertension and treatment with NaHS exerts antihypertensive effect, promotes non-NO-mediated relaxation, and decreases oxidative stress in rats with Pb-induced hypertension.

Sodium Nitrite Prevents both Reductions in Circulating Nitric Oxide and Hypertension in 7-Day Lead-Treated Rats.

Hypotensive effects of oral sodium nitrite have been reported as alternative sources of nitric oxide (NO) formation in animals and human beings. Reductions in NO bioavailability were observed in lead-induced hypertension. However, no previous study has examined whether a single daily dose of sodium nitrite prevents the reductions in the NO bioavailability in lead-induced hypertension. Then, we expanded previous reports and evaluated the effects of sodium nitrite in 7-day lead-treated rats. Wistar rats were divided into four experimental groups: Pb+sodium nitrite group received intraperitoneally (i.p.) 1st dose 8 µg/100 g of lead acetate and a subsequent dose of 0.1 µg/100 g, and daily treatment with sodium nitrite (45 mg/kg/day) or water (Pb group) by gavage for 7 days; Sodium nitrite group received i.p. 1st dose 8 µg/100 g of sodium acetate and a subsequent dose of 0.1 µg/100 g, and daily treatment with sodium nitrite (45 mg/kg/day) or water (saline group) by gavage for 7 days. Similar and higher whole-blood lead levels (11.5 ± 1.2 and 13.2 ± 0.7 µg/dL) were found in lead-exposed rats treated with either water or sodium nitrite (Pb or Pb+sodium nitrite, respectively; both p < 0.05 versus control groups). We found lower NO markers such as plasma nitrite and nitrite + nitrate (NOx) levels (both p < 0.05 versus controls) in lead-exposed rats compared with normotensive (sodium acetate)-treated controls (Pb group versus saline group; p < 0.05). Lead induced increases in systolic blood pressure (from 130 ± 2 to 164 ± 6 mmHg in Pb group; p < 0.05); however, both lead-induced decreases in NO markers and hypertension (Pb+sodium nitrite group versus Pb group; both p < 0.05) were prevented by a single daily dose of sodium nitrite. In conclusion, these findings are consistent with the idea that impaired NO bioavailability contributes to the maintenance of elevated blood pressure in lead-induced hypertension. Additionally, our results show that sodium nitrite exerts antihypertensive effects in lead-induced hypertension and provide evidence that sodium nitrite prevents the impairment of NO, thus, reaffirming the relevance of nitrite as alternative source of recycling back to NO.

Sodium hydrosulfide prevents hypertension and increases in vascular endothelial growth factor and soluble fms-like tyrosine kinase-1 in hypertensive pregnant rats.

Sodium hydrosulfide (NaHS) has presented antihypertensive and antioxidant effects and may reduce circulating soluble fms-like tyrosine kinase-1 (sFlt-1). We examined whether NaHS prevents maternal and fetal detrimental changes in a model of hypertension in pregnancy induced by N(G)-nitro-L-arginine methyl ester (L-NAME). Forty pregnant rats were divided into four groups (n = 10 per group): Norm-Preg, Preg + NaHS, HTN-Preg, or HTN-Preg + NaHS. Systolic blood pressure (SBP), number of viable fetuses, litter size, pups, and placentae weights were recorded. Circulating plasma sFlt-1, vascular endothelial growth factor (VEGF), myeloperoxidase (MPO), trolox equivalent antioxidant capacity (TEAC) levels, and biochemical determinants of nitric oxide (NO) formation were assessed. SBP values were elevated in the HTN-Preg group on gestational days 16, 18, and 20. However, HTN-Preg + NaHS group presented lower SBP values on days 18 and 20. Lower number of viable fetuses and litter size were found only in HTN-Preg group compared to other. Reductions in placental weight were found in HTN-Preg and HTN-Preg + NaHS groups. Increases in fetal weight were found only in Preg + NaHS group. Increases in circulating sFlt-1 and VEGF levels were observed only in HTN-Preg group compared to other. Higher MPO and lower TEAC plasma levels were found in HTN-Preg + NaHS and HTN-Preg groups. NO was diminished in HTN-Preg animals, and NaHS treatment increased NO levels only in hypertensive pregnant animals. Treatment with NaHS prevents hypertension in pregnancy and concomitantly reduces circulating plasma sFlt-1 and VEGF levels; this correlates with improved litter size with more viable fetuses and increase in NO levels. However, these beneficial effects presented no relation with oxidative stress.

Exposure to fipronil elevates systolic blood pressure and disturbs related biomarkers in plasma of rats.

Recent reports show that fipronil affects non-target organisms, including environmental species populations and potentially humans. We aimed to examine if fipronil exposure affects the systolic blood pressure and related biomarkers. Thus, fipronil was orally administered to rats (30 mg/kg/day) during 15 days (Fipronil group) or physiological solution (Control group). While fipronil increased significantly the systolic blood pressure (158±13 mmHg), no significant changes were observed in Control group (127±3 mmHg). Significantly, higher levels of fipronil in plasma were observed in Fipronil group (0.46±0.09 µg/mL versus 0.17±0.11 µg/mL in Control group). Fipronil group showed lower weight gain compared with Control group. While fipronil resulted in higher concentrations of endothelin-1, reduced antioxidant capacity and lower levels of circulating matrix metalloproteinase 2 (MMP-2) and nitric oxide (NO) metabolites compared to Control group, no alteration was observed in serum biomarkers of renal and hepatic/biliary functional abilities. Therefore, this study suggests that fipronil causes hypertension and endothelin-1 plays a key role. Also, these findings suggest that reductions of both MMP-2 and NO may contribute with the elevation of systolic blood pressure observed with fipronil.

Impacto da exposição pós-natal crônica ao estresse sobre o comportamento ansiogênico de ratos jovens induzidos pela desnutrição in utero / Impact of chronic postnatal exposure to stress on the anxiogenic behavior of young rats induced by undernutrition in utero

Exposure to stress and undernutrition alone are important risk factors in the development of neurobehavioral disorders. However, few studies focus on how chronic postnatal stress affects adaptive behavioral response to undernutrition in utero. OBJECTIVE: to investigate whether chronic postnatal stress exposure constitutes a risk factor in addition to undernutrition in utero to developing neurobehavioral disorders in young rats. METHODS: we evaluated the overall activity in the Open Field, and anxiety in the Elevated Plus Maze of male Wistar rats (35 days) from dams submitted or not to food restriction (50%) throughout pregnancy and exposed or not to restraint stress (single sections 1 h/day, 5 days/week for 2 weeks from weaning). RESULTS: postnatal stress and undernutrition in utero, alone and in combination, did not cause changes to the young rats behavior, except for a decrease of locomotion in the central and middle zone of the Open Field in the offsprings subjected to undernutrition in utero. The postnatal stress, alone and in combination, did not change the activity in Elevated Plus Maze. However, the time spent in the open arms decreased while the time in the closed arms increased in undernourished rats in utero. The anxiety index was decreased by undernutrition in utero. CONCLUSION: the absence of behavioral changes in young rats exposed to undernutrition in utero in association with chronic postnatal stress suggests that the physiological changes that lead to anxiogenic condition induced by undernutrition in utero alone take place mainly during the postnatal development

Exposição ao estresse e desnutrição, isoladamente, são importantes fatores de risco no desenvolvimento de transtornos neurocomportamentais. Entretanto, poucos estudos focam como o estresse pós-natal crônico afeta a resposta comportamental adaptativa à desnutrição in utero. OBJETIVO: investigar se a exposição pós-natal crônica ao estresse constitui-se em fator de risco adicional à desnutrição in utero para o desenvolvimento de transtornos neurocomportamentais em ratos jovens. MÉTODOS: avaliou-se a atividade geral, em Campo Aberto, e a ansiedade, no Labirinto em Cruz Elevado, de ratos machos Wistar (35 dias) provenientes de ratas submetidas ou não à restrição alimentar (50%) durante toda a prenhez, e expostos ou não ao estresse de contenção (seções únicas 1 h/dia, 5 dias/semana, durante 2 semanas a partir do desmame). RESULTADOS: o estresse pós-natal e a desnutrição in utero, isoladamente e em associação, não determinaram alterações no comportamento de ratos jovens, exceto pela diminuição da locomoção na zona central e mediana do Campo Aberto em proles submetidas à desnutrição in utero. O estresse pós-natal, isoladamente e em associação, não alterou a atividade no Labirinto em Cruz Elevado. Entretanto, o tempo de permanência nos braços abertos diminuiu enquanto o tempo nos braços fechados aumentou em ratos desnutridos in utero. O índice de ansiedade foi diminuído pela desnutrição in utero. CONCLUSÃO: a ausência de alterações comportamentais em ratos jovens expostos à desnutrição in utero em associação ao estresse pós-natal crônico sugere que as alterações fisiológicas que levam à condição ansiogênica induzida pela desnutrição in utero, isoladamente, têm lugar principalmente durante o desenvolvimento pós-natal