Circulating microRNA expression profiles in pre-eclampsia: evidence of increased miR-885-5p levels

OBJECTIVE

To validate and to compare the circulating microRNA (miR) expression profiles between pre-eclampsia and healthy pregnant women, to perform correlation analysis of the differently expressed miRs with clinical and biochemical parameters, and to verify the extracellular localisation of miRs in apoptotic bodies, microvesicles, and exosomes.

DESIGN

A case-control study with a replication study.

SETTING

Pregnant women attending maternity hospitals in Southeastern Brazil.

POPULATION

Two obstetric white populations: a case-control study (19 pre-eclampsia and 14 healthy pregnant) and a replication study (eight pre-eclampsia and eight healthy pregnant).

METHODS

PCR-array with 84 different miRs was performed in plasma from five pre-eclampsia and four healthy pregnant women. In the case-control study, differently expressed miRs were validated using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR), and correlated with clinical and biochemical parameters. The plasma was then fractioned to study the extracellular localisation of miRs.

MAIN OUTCOME MEASURES

Gene expression profiles of miRs.

RESULTS

From PCR-array, three miRs (miR-376c-3p, miR-19a-3p, and miR-19b-3p) were found to be down-regulated and the miR-885-5p was found to be up-regulated in pre-eclampsia compared with healthy pregnant women. In the validation step, miR-885-5p was the only significantly different miR (fold-change = 5.0, P < 0.05), which was confirmed in the replication study (fold-change = 4.5, P < 0.05). Moreover, miR-885-5p was significantly correlated with the hepatic enzyme aspartate transaminase (r = 0.66; P = 0.0034) and it was mostly associated with the exosomes (32-fold higher than apoptotic bodies).

CONCLUSIONS

miR-885-5p is increased in plasma from pre-eclampsia compared with healthy pregnant women, and it is released into circulation mainly inside exosomes. TWEETABLE ABSTRACT: miR-885-5p is increased in pre-eclampsia and is released into circulation mainly inside exosomes.

Reduction of blood nitric oxide levels is associated with clinical improvement of the chronic pelvic pain related to endometriosis

The objective of this prospective study was to determine the plasma levels of nitric oxide (NO) in women with chronic pelvic pain secondary to endometriosis (n=24) and abdominal myofascial pain syndrome (n=16). NO levels were measured in plasma collected before and 1 month after treatment. Pretreatment NO levels (μM) were lower in healthy volunteers (47.0±12.7) than in women with myofascial pain (64.2±5.0, P=0.01) or endometriosis (99.5±12.9, P<0.0001). After treatment, plasma NO levels were reduced only in the endometriosis group (99.5±12.9 vs 61.6±5.9, P=0.002). A correlation between reduction of pain intensity and reduction of NO level was observed in the endometriosis group [correlation = 0.67 (95%CI = 0.35 to 0.85), P<0.0001]. Reduction of NO levels was associated with an increase of pain threshold in this group [correlation = -0.53 (-0.78 to -0.14), P<0.0001]. NO levels appeared elevated in women with chronic pelvic pain diagnosed as secondary to endometriosis, and were directly associated with reduction in pain intensity and increase in pain threshold after treatment. Further studies are needed to investigate the role of NO in the pathophysiology of pain in women with endometriosis and its eventual association with central sensitization.

Tissue inhibitor of matrix metalloproteinase-1 polymorphism, plasma TIMP-1 levels, and antihypertensive therapy responsiveness in hypertensive disorders of pregnancy

Tissue inhibitor of metalloproteinase (TIMP)-1 is a major endogenous inhibitor of matrix metalloproteinase (MMP)-9, which may affect the responsiveness to therapy in hypertensive disorders of pregnancy. We examined whether TIMP-1 polymorphism (g.-9830T>G, rs2070584) modifies plasma MMP-9 and TIMP-1 levels and the response to antihypertensive therapy in 596 pregnant: 206 patients with preeclampsia (PE), 183 patients with gestational hypertension (GH) and 207 healthy pregnant controls. We also studied the TIMP-3 polymorphism (g.-1296T>C, rs9619311). Plasma MMP-9 and TIMP-1 levels were measured by ELISA. GH patients with the GG genotype for the TIMP-1 polymorphism had lower MMP-9 levels and MMP-9/TIMP-1 ratios than those with the TT genotype. PE patients with the TG genotype had higher TIMP-1 levels. The G allele and the GG genotype were associated with PE and responsiveness to antihypertensive therapy in PE, but not in GH. Our results suggest that the TIMP-1 g.-9830T>G polymorphism not only promotes PE but also decreases the responses to antihypertensive therapy.

The effects of endothelial nitric oxide synthase tagSNPs on nitrite levels and risk of hypertension and obesity in children and adolescents

Obesity and the nitric oxide synthase 3 (NOS3) gene polymorphisms are associated with nitrite levels and hypertension. However, no study has tested the hypothesis that NOS3 tagSNPs rs3918226, rs3918188, rs743506 and rs7830 affect nitrite levels and are associated with hypertension in childhood obesity. We investigated the association of these NOS3 tagSNPs and the haplotypes formed by them with hypertension and with nitrite levels in children and adolescents with obesity and with obesity plus hypertension. We studied 355 subjects: 174 healthy (controls), 109 normotensive obese, and 72 obese children and adolescents with obesity plus hypertension. Genotypes were determined by Taqman allele discrimination assay and real-time PCR. We compared the distribution of NOS3 tagSNP genotypes, alleles and haplotypes in the three groups of subjects. Nitrite levels were determined by ozone-based chemiluminescence. Nitrite levels were affected by the rs3918226 polymorphism (P<0.05) but not by NOS3 haplotypes. There was no association between the tagSNPs studied and hypertension in children and adolescents. Our findings show that the NOS3 tagSNP rs3918226 is associated with NO production in children and adolescents, and suggest that this polymorphism may have an impact on cardiovascular health. Further studies are needed to better clarify the effects of this polymorphism on cardiovascular risk.

The effects of NAMPT haplotypes and metabolic risk factors on circulating visfatin/NAMPT levels in childhood obesity

OBJECTIVE

Polymorphisms in the NAMPT gene, which encodes the adipocytokine visfatin/nicotinamide phosphorybosil transferase (NAMPT), affect the circulating visfatin/NAMPT levels and are associated with obesity and cardiovascular diseases. However, no study has tested the hypothesis that NAMPT haplotypes could affect visfatin/NAMPT levels in case of childhood obesity. We investigated the effects of traditional metabolic risk factors (MRFs) and NAMPT polymorphisms T/C (rs1319501) and A/G (rs3801266) or haplotypes on visfatin/NAMPT levels in obese children and adolescents, and whether NAMPT polymorphisms and/or haplotypes are associated with susceptibility to childhood obesity.

METHODS

We studied 175 control, 99 obese and 82 obese with ⩾ 3 MRFs children and adolescents. Genotypes were determined by a Taqman allele discrimination assay and real-time PCR. The plasma visfatin/NAMPT level was measured using an enzyme immunoassay.

RESULTS

Obese children and adolescents with ⩾ 3 MRFs had higher plasma visfatin/NAMPT levels in comparison with control children and adolescents (P<0.05). Although positive associations were observed between visfatin/NAMPT and body mass index (rs = 0.157; P = 0.034) as well as visfatin/NAMPT and waist circumference (rs = 0.192; P = 0.011), visfatin/NAMPT and high-density lipoprotein cholesterol were inversely associated (rs = -0.162; P = 0.031). No significant differences in genotype, allele or haplotype frequency distributions for the studied polymorphisms were found when the three groups were compared. However, higher plasma visfatin/NAMPT levels were found in control and obese subjects carrying the GG genotype for the A/G (rs3801266) polymorphism (P<0.05) but not in obese children with ⩾ 3 MRFs. Moreover, control subjects carrying the 'T-G' haplotype showed higher plasma visfatin/NAMPT levels. NAMPT genotypes or haplotypes were not associated with childhood obesity.

CONCLUSIONS

Obesity in children with ⩾ 3 MRFs increases plasma visfatin/NAMPT levels, and this marker was associated with body mass index and waist circumference. The A/G polymorphism and NAMPT haplotypes affect plasma visfatin/NAMPT levels in controls but not in obese children with ⩾ 3 MRFs. These results suggest that obesity and MRFs are more influential than genetic polymorphisms in the determination of visfatin/NAMPT levels in obese children. Further research is necessary to explain why the GG genotype is not associated with increased visfatin/NAMPT levels in obese children with ⩾ 3 MRFs.

Haptoglobin polymorphism affects nitric oxide bioavailability in preeclampsia

Studies showed elevated cell-free hemoglobin (Hb) in preeclampsia (PE), and Hb reacts with nitric oxide (NO), decreasing its bioavailability. Haptoglobin (Hp) is a polymorphic protein (Hp1-1, Hp2-1 and Hp2-2) that binds Hb to form a complex that is removed from circulation, thus preventing Hb-driven oxidative stress and NO scavenging. Hp protein products differ in biochemical and biophysical properties, which reflects on the Hb-Hp complex clearance rate. We hypothesized that Hp phenotypes modulate NO bioavailability by influencing NO consumption in PE. We studied 92 PE subjects and 105 normal pregnant women (NP). Hp genotypes were determined using real-time PCR. To assess NO bioavailability, we measured plasma nitrite using an ozone-based chemiluminescence assay. Plasma Hb and Hp were assessed with commercial immunoassays. A NO consumption assay was used to measure NO consumption. We found no differences in Hp genotype frequencies between PE and NP groups. Hp genotypes had no effects on plasma heme levels, NO consumption and plasma nitrite in NP. However, in PE, Hp2-1 and Hp2-2 were associated with higher plasma heme levels (48 and 55% higher, respectively; P<0.05), increased NO consumption (42 and 44% more, respectively; P<0.05) and lower plasma nitrite (39% less for Hp2-2; P<0.05) compared with Hp1-1. These findings indicate that although Hp genotype does not affect the risk of PE, Hp1-1 genotype may exert a protective role in PE by reducing NO scavenging, whereas Hp2-1 and Hp2-2 further may aggravate PE by reducing NO bioavailability.

Pyrrolidine dithiocarbamate down-regulates vascular matrix metalloproteinases and ameliorates vascular dysfunction and remodelling in renovascular hypertension

BACKGROUND AND PURPOSE

Mounting evidence implicates matrix metalloproteinase (MMP) in the vascular dysfunction and remodelling associated with hypertension. We tested the hypothesis that treatment with pyrrolidine dithiocarbamate (PDTC), which interferes with NF-κB-induced MMPs gene transcription, could exert antihypertensive effects, prevent MMP-2 and MMP-9 up-regulation, and protect against the functional alterations and vascular remodelling of two-kidney, one clip (2K1C) hypertension.

EXPERIMENTAL APPROACH

Sham-operated or hypertensive rats were treated with vehicle or PDTC (100 mg·Kg(-1) ·day(-1)) by gavage for 8 weeks. Systolic blood pressure (SBP) was monitored weekly. Aortic rings were isolated to assess endothelium-dependent relaxations. Quantitative morphometry of structural alterations of the aortic wall was carried out in haematoxylin/eosin sections. Formation of vascular reactive oxygen species (ROS), and inducible (i) NOS and phosphorylated-p65 NF-κB subunit expression were measured in the aortas. MMP-2 and MMP-9 aortic levels and gelatinolytic activity were determined by gelatin and in situ zymography and by immunofluorescence.

KEY RESULTS

Treatment with PDTC attenuated the increases in SBP and prevented the endothelial dysfunction associated with 2K1C hypertension. Moreover, PDTC reversed the vascular aortic remodelling, the increases in aortic ROS levels and in iNOS and phosphorylated-p65 NF-κB expression found in 2K1C rats. These effects were associated with attenuation of 2K1C up-regulation of aortic MMP-2 and MMP-9 levels and gelatinolytic activity.

CONCLUSION AND IMPLICATIONS

These findings suggest that PDTC down-regulates vascular MMPs and ameliorates vascular dysfunction and remodelling in renovascular hypertension, thus providing evidence supporting the suggestion that PDTC is probably a good candidate to be used to treat hypertension.

Maternal iNOS genetic polymorphisms and hypertensive disorders of pregnancy

Increased expression and activity of inducible nitric oxide synthase (iNOS) may contribute to the pathogenesis of pre-eclampsia (PE) and gestational hypertension (GH). However, no previous study has examined whether genetic polymorphisms in the iNOS gene are associated with PE or GH. We examined whether two functional, clinically relevant iNOS genetic polymorphisms (the C(-1026)A polymorphism, rs2779249, in the promoter region, and the G2087A polymorphism, rs2297518, in exon 16) are associated with GH or with PE. We studied 565 pregnant women: 212 healthy pregnant (HP), 166 pregnant with GH and 187 pregnant with PE. Genotypes were determined by real-time PCR, using the Taqman allele discrimination assay. The PHASE 2.1 program was used to estimate haplotype distributions in the three study groups. We found no significant association between the C(-1026)A polymorphism and PE or GH (P>0.05). However, we found the GA genotype and the A allele for the G2087A polymorphism at higher frequency in PE, but not in GH, compared with HP (P<0.05). The haplotype analysis showed no significant intergroup differences (P>0.05). These findings suggest that iNOS genetic variants may affect the susceptibility to PE, but not to GH.

Spironolactone and hydrochlorothiazide exert antioxidant effects and reduce vascular matrix metalloproteinase-2 activity and expression in a model of renovascular hypertension

BACKGROUND AND PURPOSE

Increased oxidative stress and up-regulation of matrix metalloproteinases (MMPs) may cause structural and functional vascular changes in renovascular hypertension. We examined whether treatment with spironolactone (SPRL), hydrochlorothiazide (HCTZ) or both drugs together modified hypertension-induced changes in arterial blood pressure, aortic remodelling, vascular reactivity, oxidative stress and MMP levels and activity, in a model of renovascular hypertension.

EXPERIMENTAL APPROACH

We used the two-kidney,one-clip (2K1C) model of hypertension in Wistar rats. Sham-operated or hypertensive rats were treated with vehicle, SPRL (25 mg.kg(-1).day(-1)), HCTZ (20 mg.kg(-1).day(-1)) or a combination for 8 weeks. Systolic blood pressure was monitored weekly. Aortic rings were isolated to assess endothelium-dependent and -independent relaxations. Morphometry of the vascular wall was carried out in sections of aorta. Aortic NADPH oxidase activity and superoxide production were evaluated. Formation of reactive oxygen species was measured in plasma as thiobarbituric acid-reactive substances. Aortic MMP-2 levels and activity were determined by gelatin and in situ zymography, fluorimetry and immunohistochemistry.

KEY RESULTS

Treatment with SPRL, HCTZ or the combination attenuated 2K1C-induced hypertension, and reversed the endothelial dysfunction in 2K1C rats. Both drugs or the combination reversed vascular aortic remodelling induced by hypertension, attenuated hypertension-induced increases in oxidative stress and reduced MMP-2 levels and activity.

CONCLUSIONS AND IMPLICATIONS

SPRL or HCTZ, alone or combined, exerted antioxidant effects, and decreased renovascular hypertension-induced MMP-2 up-regulation, thus improving the vascular dysfunction and remodelling found in this model of hypertension.

eNOS haplotypes affect the responsiveness to antihypertensive therapy in preeclampsia but not in gestational hypertension

Variations of the endothelial nitric oxide synthase (eNOS) gene have been associated with hypertensive disorders of pregnancy. We examined whether eNOS polymorphisms affect the therapeutic responses of women with gestational hypertension (GH) or preeclampsia (PE). We studied 304 hypertensive pregnant women (152 GH and 152 PE), who were stratified according to clinical and laboratorial parameters of therapeutic responsiveness. We compared the frequencies of three eNOS genetic polymorphisms (T-786C, Glu298Asp and b/a intron 4) in responsive and nonresponsive PE and GH patients. We found no significant differences in genotype or allele distributions when responsive and nonresponsive groups were compared (both PE or GH; all P>0.05). However, the eNOS haplotype distribution differed in PE (but not in GH)-responsive and -nonresponsive groups (P=0.0003). The 'C-Glu-a' and 'T-Asp-a' hapotypes were associated with responsiveness and nonresponsiveness to therapy, respectively (both P<0.001), thus suggesting that eNOS haplotypes affect the responsiveness to antihypertensive therapy in PE.

Aminoguanidine produces beneficial haemodynamic effects in a canine model of acute pulmonary thromboembolism

AIM

Activating the nitric oxide (NO)-cyclic guanosine 3',5'-monophosphate (cGMP) pathway improves haemodynamics following acute pulmonary thromboembolism (APT). However, the role of NO synthase (NOS) isoforms in the responses to APT has not been determined. We examined the effects of selective and non-selective inducible NOS (iNOS) inhibition.

METHODS

Haemodynamic evaluations were performed in non-embolized dogs treated with saline (control group; n = 4), L-NAME (NAME group; n = 3), or aminoguanidine (AG group; n = 3), and in dogs that received the same drugs and were embolized with 5 mL kg(-1) of clots made with autologous blood (Emb group, n = 9; NAME + Emb group, n = 4 and AG + Emb group, n = 7). The lung concentrations of nitrite/nitrate (NOx) and cGMP were determined by chemiluminescence and ELISA respectively.

RESULTS

Acute pulmonary thromboembolism increased mean pulmonary arterial pressure (MPAP) and pulmonary vascular resistance index (PVRI) by 21.4 +/- 1.7 mmHg and by 843 +/- 34 dyn s cm(-5) m(-2), respectively, in Emb group. MPAP and PVRI increased to higher levels in the NAME + Emb group 15 min after APT and all dogs in this group died 15-30 min after APT. Conversely, lower MPAP and PVRI levels were found in the AG + Emb group 2 h after APT compared with the Emb group (both P < 0.05). Higher NOx concentrations were found in the Emb group compared with the other groups (all P < 0.05). Higher cGMP concentrations were found in the Emb and AG + Emb groups compared with the other groups (all P < 0.05).

CONCLUSIONS

These results indicate that endogenous NO protects against APT-induced cardiovascular responses. Moreover, iNOS-derived NO possibly produces unfavourable effects, which are counteracted by aminoguanidine. However, non-NO-related mechanisms may also be involved.

Relationship between systemic nitric oxide metabolites and cyclic GMP in healthy male volunteers

AIM

Nitric oxide (NO) is an endogenous mediator of many physiological processes, many of which are mediated by cyclic guanosine 3',5'-monophosphate (cGMP). Much effort has been made to validate clinical markers of NO production or bioavailability. While the measurement of plasma nitrate, nitrite, and cGMP concentrations have been suggested to reflect endogenous production of NO, there is no study showing whether there is correlation between these three markers. In the present study, we investigate whether there is correlation between the plasma concentrations of nitrate, nitrite, and cGMP in a relatively homogeneous group of 141 healthy subjects.

METHODS

Venous blood samples were collected from healthy male subjects and plasma aliquots were then immediately removed and stored at -70 degrees C until analysed in duplicate for their nitrite and nitrate content using ozone-based chemiluminescence assays. Plasma cGMP levels were determined by using a commercial enzyme immunoassay.

RESULTS

While we found no significant correlation between plasma nitrite and nitrate concentrations (P = 0.747), or between plasma nitrate and cGMP concentrations (P = 0.221), a significant positive correlation was found between plasma cGMP and nitrite concentrations (P = 0.017, r(s) = 0.270).

CONCLUSIONS

The significant correlation we found between plasma nitrite and cGMP concentrations is consistent with the notion that nitrite or cGMP concentrations in plasma may be useful clinical markers of NO formation in healthy subjects.

Pharmacokinetics and QT interval pharmacodynamics of oral haloperidol in poor and extensive metabolizers of CYP2D6

We studied the pharmacokinetics and QT interval pharmacodynamics of a single 10 mg dose of oral haloperidol in a randomized, double-blind, placebo-controlled, crossover trial of healthy poor (PMs) and extensive (EMs) metabolizers of CYP2D6. There was a statistically significant greater mean QT(c) on haloperidol (421.6+/-20.1 ms) than on placebo (408.4+/-18.5 ms, P=0.0053) occurring 10 h post haloperidol/placebo administration. Men and women had similar ranges of QT(c) changes from placebo. Despite a statistically significant greater mean elimination half-life (19.1+/-3.6 vs 12.9+/-4.0 h, P=0.04) and lower mean apparent oral clearance (12.8+/-4.1 vs 27.0+/-11.3 ml/min/kg, P=0.02) of haloperidol in CYP2D6 PMs than in EMs, this exposure change did not translate into marked QT(c) changes from baseline that could be considered clinically important. Although the magnitude of the mean QT(c) prolongation on haloperidol relative to placebo is relatively small, it may assume significance in the presence of other risk factors for QT prolongation.

Effects of ethnicity on the distribution of clinically relevant endothelial nitric oxide variants

Polymorphisms in the endothelial nitric oxide synthase (eNOS) gene have been associated inconsistently with cardiovascular diseases. A maldistribution of eNOS variants among ethnic groups may explain interethnic differences in nitric oxide (NO)-mediated vasodilation and response to drugs. To test this possibility, we examined the distribution of genetic variants of three clinically relevant eNOS polymorphisms (T-786C in the promoter, the variable number of tandem repeats (VNTR) in intron 4, and the Glu298Asp variant in exon 7) in 305 ethnically well-characterized DNA samples (100 Caucasians, 100 African-Americans, and 105 Asians). We estimated the haplotype frequency, and evaluated associations between these variants. The Asp298 variant was more common in Caucasians (34.5%) than in African-Americans (15.5%) or Asians (8.6%)(P < 0.0001). The C-786 variant was also more common in Caucasians (42.0%) than in African-Americans (17.5%) or Asians (13.8%) (P < 0.0001). The 4a variant in intron 4 was more common in African-Americans (26.5%) than in Caucasians (16.0%) or Asians (12.9%) (P < 0.0001). The most common predicted haplotype in the three groups combined only wild-type variants. Asians had the highest frequency of this haplotype (77% in Asians v. 46% in the other groups). In Caucasians, the Asp298 and C-786variants were associated, and this haplotype was predicted to have a frequency of 24%. In African-Americans, the second most common haplotype included the variant 4a and wild-type variants; the Asp298 and 4a variants were associated negatively in this group. The C-786 and 4a variants were associated in Asians (P < 0.0001). The marked interethnic differences that we found in the distribution of eNOS variants, in the estimated haplotype frequency, and in the association between variants may help us to understand how the combination of these genetic variants may influence cardiovascular diseases.

Pravastatin reduces myocardial lesions induced by acute inhibition of nitric oxide biosynthesis in normocholesterolemic rats

Pravastatin is useful in restoring endothelium-dependent relaxation in hypercholesterolemic animals. A single intravenous bolus injection of N(omega)-nitro-L-arginine methyl ester (L-NAME), a non-specific inhibitor of NO synthase, causes myocardial necrosis and reduces coronary flow in rats. Since rats do not develop hypercholesterolemia and atherosclerosis, we have tested the hypothesis that pravastatin protects the heart from myocardial lesions induced by L-NAME in the absence of alterations in cholesterol levels and plaque formation. Male Wistar rats fed standard chow were divided into four groups: CONTROL (n=14) - rats that received tap water alone for 18 days; L-NAME (n=14) -- rats that received L-NAME (15 mg/kg, i.v.) on the 14th day of the study; PRAVASTATIN (n=11) -- rats that received pravastatin (6 mg/kg/day) in their drinking water for 18 days; PRAVASTATIN+L-NAME (n=12) -- rats that received pravastatin (6 mg/kg/day) and L-NAME (15 mg/kg, i.v.) as indicated in the preceding groups. At the end of 18 days, the rats were sacrificed and the hearts removed for stereological analysis by light microscopy. Plasma nitrate/nitrite and thromboxane B(2) concentrations were determined immediately before and after L-NAME administration. Pravastatin prevented the ischemic lesions induced by the acute inhibition of NO biosynthesis (the area of myocardial lesions in the L-NAME group was greater than in the Pravastatin+L-NAME group: 101.6 microm(2) vs. 1.2 microm(2), respectively; P<0.0001) and markedly increased the plasma nitrate/nitrate concentrations, even before L-NAME administration. There were no significant changes in the plasma thromboxane B(2) concentrations.

Cardiovascular effects of transdermal nicotine in mildly hypertensive smokers

Smoking potentiates the enhanced cardiovascular risk of hypertensive patients. Although nicotine replacement therapy is safe when used by healthy individuals to quit smoking, there is no evidence that nicotine replacement therapy is safe in hypertensive smokers. In this crossover, single-blinded, placebo-controlled study, we compared for 4 h the acute effects of transdermal nicotine on the mean arterial pressure (MAP) and heart rate (HR) of mildly hypertensive smokers treated with hydrochlorothiazide with the responses in normotensive smokers and nonsmokers monitored with Finapres and ambulatory blood pressure systems. The plasma concentrations of thromboxane B2 (TXB2, the stable breakdown product of TXA2) were also measured by ELISA to assess whether transdermal nicotine acutely affects TXA2 production. The use of 21-mg nicotine patches increased the MAP and HR in nonsmokers (from 94+/-4 mm Hg and 69+/-3 beats/min to 117+/-7 mm Hg and 83+/-3 beats/min, respectively; P < .05) as well as the MAP in normotensive smokers (from 83+/-4 to 106+/-7 mm Hg; P < .05). However, MAP and HR remained unaltered in hypertensive smokers after transdermal nicotine. Higher basal TXB2 levels were observed in hypertensive smokers compared with normotensive smokers and nonsmokers (2019+/-402 v 670+/-167 and 556+/-68 pg/mL, respectively; P < .05). Transdermal nicotine increased the TXB2 levels only in nonsmokers (P < .05). These data indicate that the use of transdermal nicotine in mildly hypertensive smokers is probably safe. Further studies involving other classes of hypertensive patients are warranted.

Acute administration of nicotine impairs the hypotensive responses to bradykinin in rats

Nicotine may contribute to smoking-induced endothelial dysfunction because of its ability to impair endothelium-dependent vasodilatation. We investigated whether the acute administration of nicotine changes the hypotensive responses to bradykinin in rats. The effects of pre-treatment with losartan or enalapril on the nicotine-induced changes in the responses to bradykinin were also evaluated. In study 1, anesthetized rats were cannulated via carotid artery for the measurement of mean arterial pressure. Dose-response curves to bradykinin (0.1, 0.4, 1.6, 6.4, 25 and 100 microg/kg) were generated before and 10 min after the injection of nicotine (200 microg/kg, i.v.) or saline. The individual dose-response curves were fitted to a four-parameter logistic equation using the ALLFIT program, which provided an estimate of the maximal response (E(max)) and of the dose of bradykinin producing the half-maximal response (ED(50)). In study 2, rats were pre-treated orally with losartan (10 mg/kg/day) or enalapril maleate (25 mg/kg/day) for 2 weeks. Control rats received tap water alone. After pre-treatment, the rats were anesthetized and used as described in study 1. Nicotine decreased the E(max) (from 73.0+/-7.5 to 65.7+/-3.3 mm Hg; P<0.05) but did not affect the ED(50). In study 2, losartan or enalapril did not affect nicotine-induced decrease in responses to bradykinin; E(max) decreased in both groups (from 68.7+/-6.3 to 62.8+/-4.2 mm Hg, and from 53.8+/-13.0 to 43.1+/-7.1 mm Hg, respectively; P<0.05) without significantly changing the ED(50). These results suggest that nicotine impairs the endothelium-dependent hypotensive responses to bradykinin. This effect is not influenced by inhibition of the angiotensin-converting enzyme or by blockade of the angiotensin AT(1) receptors.

Plasma cGMP levels in air embolism-induced acute lung injury

PURPOSE

An impaired generation of cGMP may account for the pulmonary hypertension seen in acute lung injury (ALI). We investigated the hemodynamic changes and the plasma levels of cGMP during air embolism-induced ALI in two different models: venous air infusion (VAI) and massive air embolism (MAE).

MATERIALS AND METHODS

After a baseline hemodynamic evaluation, anesthetized dogs received a VAI (0.2 mL/kg/min, n = 10) or a bolus of air (MAE, 2.5 mL/kg, n = 10) intravenously. A group of control dogs (n = 5) received no further treatment. Hemodynamic evaluation was performed 5 to 60 minutes after the VAI was initiated or after the MAE. Blood samples were drawn for plasma cGMP determinations.

RESULTS

The VAI increased the pulmonary artery pressure (by 181%, P<.05) after 15 minutes of air infusion without changing the cardiac index. The MAE increased the pulmonary artery pressure (by 252%) and decreased the cardiac index (by 31%) 5 minutes after the air injection (both P<.05). These variables returned to baseline 15 to 30 minutes thereafter. The cGMP concentrations remained unaltered during the VAI. In contrast, cGMP levels increased 26% (P<.05) by 15 minutes after the MAE and returned to basal levels thereafter.

CONCLUSION

These findings suggest that a lack of increase in the production of the cGMP may account for the pulmonary hypertension seen in air embolism-induced ALI. Additionally, the small increase in cGMP levels after the MAE may reflect the more severe hemodynamic derangement in this setting.

Transdermal nicotine mimics the smoking-induced endothelial dysfunction

BACKGROUND

Cigarette smoking is a major risk factor for coronary artery disease and causes endothelial dysfunction, perhaps by decreasing the availability of nitric oxide availability in arteries and veins. Nicotine in cigarette smoke may be responsible for this impaired endothelial response.

METHODS

We studied nine healthy nonsmokers and 12 healthy mild to moderate smokers by use of the dorsal hand vein compliance technique. Dose-response curves to bradykinin and sodium nitroprusside were obtained to test the endothelium-dependent and endothelium-independent vasorelaxation before and during the use of a nicotine (21 mg) patch. Mean arterial blood pressure and heart rate were measured beat-to-beat during the 4-hour study and serial blood samples were drawn to assay plasma thromboxane B2 levels.

RESULTS

Transdermal nicotine reduced the venous responsiveness to bradykinin in nonsmokers (Emax = 88.0% +/- 17.9% and 54.3% +/- 14.9%, respectively, before and after the nicotine patch; P < .05); the latter response was similar to that in smokers (Emax = 56.3% +/- 16.6%). Sodium nitroprusside-induced venodilation was unaltered. Mean arterial blood pressure increased in both smokers and nonsmokers. Transdermal nicotine increased the plasma thromboxane B2 concentrations only among nonsmokers.

CONCLUSION

These findings indicate that nicotine can have a major role in the impaired endothelial function in smokers. The results probably also reflect what occurs in arterial beds because the nicotine patches increased the mean arterial blood pressure in both smokers and nonsmokers.

Nonselective endothelin-receptor antagonism attenuates hemodynamic changes after massive pulmonary air embolism in dogs

STUDY OBJECTIVES

To evaluate the effects of nonselective endothelin (ET)-receptor antagonism on the hemodynamic changes and serum thromboxane (TX)-A(2) levels after a massive pulmonary air embolism (PAE) in dogs.

DESIGN

Prospective trial.

SETTING

University laboratory.

INTERVENTIONS

Anesthetized mongrel dogs (ET-receptor antagonist group; n = 6) received a bolus injection of 1 mg of the nonselective ET-A/ET-B-receptor antagonist PD 145065 (Sigma Chemical; St. Louis, MO), and dogs in the control group (n = 6) received saline solution. Hemodynamic data were recorded 5 min after the administration of antagonist or saline solution. Subsequently, each dog received 2.5-mL air/kg via the right femoral vein (the PAE), and the hemodynamic data were recorded for up to 60 min thereafter. Arterial blood samples were drawn at baseline and 15 min after PAE for the determination of plasma TX-A(2), measured by enzyme-linked immunosorbent assay as TX-B(2) (the stable metabolite of TX-A(2)).

RESULTS

PD 145065 alone produced no hemodynamic effects. However, dogs pretreated with PD 145065 had significantly lower increases in mean pulmonary arterial pressure and in pulmonary vascular resistance after the PAE (116% and 165%, respectively) compared to the control dogs (187% and 367%, respectively). The mean arterial pressure (MAP), cardiac index (CI), and plasma TX-B(2) levels were unaltered after PAE in the presence of ET-receptor antagonist, whereas CI and MAP decreased 5 to 10 min after PAE, and TX-B(2) concentrations increased 15 min after PAE in control dogs (p < 0.05 in all cases).

CONCLUSIONS

Nonselective antagonism of ET receptors attenuates the pulmonary hypertension and blunts the TX-A(2) release caused by massive PAE in dogs.

Endothelin-1 attenuates bradykinin-induced hypotension in rats

Endothelin-1 has vasoconstrictor and mitogenic properties and may contribute to the pathogenesis of hypertension by enhancing vasoconstrictor mechanisms. In this study, we investigated the ability of endothelin-1 decrease the hypotensive effects of the vasodilator bradykinin in anesthetized rats. We also studied the effects a two-week oral pre-treatment with losartan (10 mg/kg/day) or enalapril (25 mg/kg/day) on endothelin-1-induced changes in the hypotensive responses to bradykinin. Bradykinin (0.4, 1.6, 6.4, and 25 mcg/kg, i.v.) induced dose-dependent hypotensive responses which were attenuated (P<0.05) by endothelin-1 (2 mcg/kg, i.v.). This effect of endothelin-1 was abolished by the mixed endothelin receptor antagonist N-Acetyl-alpha-[10,11-Dihydro-5H-dibenzo[a, d]cycloheptadien-5-yl]-D-Gly-Leu-Asp-Ile-Ile-Trp (PD145065, 1 mg/kg, i.v.). Endothelin-1 also decreased (P<0.05) the responses to bradykinin in rats pre-treated with losartan, but had no effect in rats pre-treated with enalapril. These results suggest that endothelin-1 may contribute to the development of hypertension by decreasing the responses to bradykinin through a mechanism not involving angiotensin AT(1) receptors, although the inhibition of angiotensin converting enzyme blunted the effect of endothelin-1.

Endothelin ET(A) receptor antagonism attenuates the pressor effects of nicotine in rats

The increased endothelin-1 levels observed after smoking may result from nicotine-stimulated endothelin-1 production by endothelial cells. In this study, we investigated the effects of selective endothelin ET(A) receptors antagonist Cycle D-a-aspartyl-L-prolyl-D-isoleucyl-D-tryptophyl (JKC 301) and of endothelin ET(B) receptors antagonist N-cis-2, 6-dimethylpiperidino-carbonyl-L-gamma-methyl-leucyl-D-L-m ethoxycarbonyl-tryptophanyl-norleucine (BQ 788) on the changes in mean arterial pressure, heart rate, and plasma thromboxane B(2) (the stable product of thromboxane A(2)) levels caused by increasing doses of nicotine (0.6, 2, 6, and 20 micromol/kg) in anesthetised rats. Nicotine (0.6, 2, and 6 micromol/kg) significantly increased the mean arterial pressure in control and BQ 788-pretreated rats, while only a nicotine dose of 2 micromol/kg) increased the mean arterial pressure in JKC 301-pretreated animals. There were no differences in the nicotine-induced changes in heart rate or in the increases in thromboxane B(2) levels among the groups treated with saline, JKC 301 and BQ 788. These results demonstrate that whereas the antagonism of endothelin ET(A) receptors attenuated the increase in blood pressure after nicotine injections, endothelin ET(B) receptor antagonism had no such effect. In addition, the antagonism of endothelin ET(A) or ET(B) receptors did not affect thromboxane A(2) production after nicotine administration. These findings suggest that endothelin-1 may have a role in the acute effects of nicotine.

The hemodynamic effects of endothelin receptor antagonism during a venous air infusion in dogs

Endothelin (ET) is involved in the humoral component of the vasoconstriction during pulmonary embolism. We examined the effects of selective ET receptor antagonists on the hemodynamic and respiratory changes and on serum thromboxane B2 (TXB2) levels, during a continuous venous air infusion (VAI) in anesthetized mongrel dogs. The VAI (0.2 mL x kg(-1) x min(-1)) was initiated 5 min after an injection of saline (controls, n = 7), 1 micromol of the selective ET(A) receptor antagonist JKC-301 (group A, n = 6), or 1 micromol of the selective ET(B) receptor antagonist BQ-788 (group B, n = 6). Hemodynamic evaluation was performed every 15 min of VAI, and blood samples were drawn for blood gas analysis and TXB2 determinations. The increase in pulmonary perfusion pressure after 30 min of VAI was attenuated in Group A compared with the controls and Group B (Group A = 7+/-1 mm Hg; Group B = 16+/-1 mm Hg; controls = 14+/-1 mm Hg; P < 0.05). Pulmonary vascular resistance showed a similar behavior. TXB2 concentrations increased after 60 min of VAI in the controls and in Group B, but not in Group A (controls = 48%; Group B = 104%; Group A = 18%; P < 0.05 for controls and Group B). Similar decreases in Pao2 and Sao2 were observed in the three groups. We conclude that antagonism of ET(A) receptors attenuates the hemodynamic changes and blunts the increase in thromboxane A2 production during a VAI in dogs.

IMPLICATIONS

We evaluated the effects of endothelin receptor antagonists during a venous air infusion in dogs. EndothelinA receptor antagonism attenuated the hemodynamic changes and blunted the increase in thromboxane A2 production in this setting.

The role of heart rate in the modulation of the decreased cardiac output induced by acute nitric oxide synthesis inhibition in anaesthetized dogs

1. The role of the heart rate modulating the decrease in cardiac output induced by the nitric oxide synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) was investigated in anaesthetized dogs. This was achieved in dogs in which a positive pacemaker (PM) cable was located at the right ventricle. 2. The haemodynamic events were evaluated: mean arterial blood pressure (MABP), systemic vascular resistance index (SVRI), stroke volume index (SVI), heart rate (HR) and cardiac index (CI). 3. The infusion of L-NAME (0.01-10 mg kg(-1)) in the animals with the PM off caused a dose-dependent rise in MABP and SVRI, accompanied by significant decreases of HR and SVI. A resulting decrease in CI was observed at all doses of L-NAME used. 4. In the animals with the PM on, HR was maintained stable. Under this condition, the increase in MABP and SVRI as well as the decrease in SVI induced by the L-NAME infusion did not significantly differ from the PM-off animals. However, the resulting decreased CI was markedly attenuated compared to PM-off animals but significant decreases in CI were still observed at higher doses of L-NAME. 5. The results suggest that HR plays an important role in the L-NAME-mediated decreased cardiac output but other factors might also be involved.

Inhaled nitric oxide improves hemodynamics during a venous air infusion (VAI) in dogs

OBJECTIVE

To evaluate the hemodynamic effects of inhaled nitric oxide (NO) during a venous air infusion (VAI) in dogs. We also addressed the question of whether NO therapy changes thromboxane (Tx) A(2) release and nitrate/nitrite production during a VAI.

DESIGN

Prospective trial.

SETTING

University laboratory.

INTERVENTIONS

Anesthetized mongrel dogs received a VAI (0.2 ml x kg(-1)x min(-1)) after the measurement of baseline hemodynamics. Control dogs (n = 8) received no further treatment. After 30 min of VAI, NO 3 ppm inhalation was initiated (n = 7) for 30 min, followed by 30 min without NO inhalation, and then a final 30 min of NO 40 ppm treatment. Hemodynamic variables were registered and arterial and mixed venous blood samples were drawn for gas analysis and for the determinations of serum TxB(2) (by enzyme-linked immunosorbent assay) and nitrate/nitrite (by high-performance liquid chromatography) levels.

RESULTS

The cardiac index increased 24 % and the pulmonary vascular resistance index decreased 30 % during both periods of NO inhalation. Arterial oxygen tension and arterial oxygen saturation were slightly lower after NO therapy. Nitrate/nitrite concentrations were unaltered in the control group and there were no differences between the arterial and mixed venous serum nitrate/nitrite levels. Nitrite concentrations remained below 1 microM in both groups of animals, but the nitrate concentration increased after inhalation of 40 ppm NO. Serum TxB(2) increased after 60 min of VAI in the control group, but there was no increase in NO-treated animals (all p < 0.05)

CONCLUSIONS

Nitrate/nitrite concentrations were unaltered after VAI in dogs. NO therapy attenuated TxA(2) release and improved hemodynamics, but not blood oxygenation, in dogs with a VAI. There were no differences between the responses to 3 ppm and 40 ppm NO.

Small-dose inhaled nitric oxide attenuates hemodynamic changes after pulmonary air embolism in dogs

Inhaled nitric oxide (NO) has been used to treat pulmonary hypertension. Experimental studies have suggested therapeutic effects of NO after pulmonary microembolism. We evaluated the protective effects of NO in dogs during a pulmonary air embolism (PAE). NO (3 ppm) was administered to six anesthetized mongrel dogs (NO group) but not to the seven dogs in the control group. After 20 min, each dog received a venous air injection of 2.5 mL/kg. Hemodynamic evaluation was performed, and blood samples were drawn for blood gas analysis before and after NO inhalation and 5-60 min after the PAE. Both arterial blood pressure and cardiac output were decreased in the control group for >15 min after PAE, whereas NO-treated animals showed only transient hypotension. NO attenuated the pulmonary hypertension after PAE, as demonstrated by small (P < 0.05) increases in pulmonary artery pressure and pulmonary vascular resistance index in NO-treated animals (90% and 135%, respectively) compared with the controls (196% and 282%, respectively). These hemodynamic effects of NO were associated with higher mixed venous O2 tensions and saturations in the NO group compared with the controls. We conclude that small-dose NO (3 ppm) attenuated the hemodynamic changes induced by PAE in dogs. This protective effect of NO on hemodynamics is not accompanied by improvement in pulmonary oxygenation in this setting.

IMPLICATIONS

In this study, we evaluated the protective effects of inhaled nitric oxide in a pulmonary air embolism setting. Nitric oxide attenuated the hemodynamic changes induced by pulmonary air embolism without improving pulmonary oxygenation.