Severity dependent increases in circulating cardiac troponin I and MMP-9 concentrations after experimental acute pulmonary thromboembolism.

BACKGROUND: Making the diagnosis of acute pulmonary thromboembolism (APT) and assessing its severity is very challenging. While cardiac troponin I (cTnI) concentrations are promising in risk stratification, no previous study has examined whether there is a linear relation between cTnI concentrations and the severity of APT. Moreover, matrix metalloproteinases (MMPs) are involved in the pathophysiology of APT. However, it is unknown whether the increases in MMP concentrations after APT reflect the severity of this condition. We examined whether the circulating concentrations of these biomarkers increase in proportion to the severity of experimental APT induced in anesthetized dogs. METHODS: APT was induced with autologous blood clots (saline, 1, 3, or 5 ml/kg) injected into the right atrium. Hemodynamic evaluations were carried out for 120 min. Gelatin zymography of MMP-2 and MMP-9 from plasma samples were performed and serum cTnI concentrations were determined at baseline and 120 min after APT. RESULTS: While no significant increases in pro-MMP-2 concentrations were found after APT, pro-MMP-9 concentrations increased by 80% only after 5 ml/kg of clot embolization. Serum cTnI and plasma pro-MMP-9 concentrations correlated positively with pulmonary vascular resistance (P=0.007 and rs=0.833 for troponin I, and P=0.034 and rs=0.684 for pro-MMP-9) and with pulmonary artery pressure (P=0.005 and rs=0.610 for troponin I, and P=0.022 and rs=0.720 for pro-MMP-9). CONCLUSIONS: Circulating cTnI and pro-MMP-9 increase in proportion to the severity of APT, although the increases in plasma pro-MMP-9 are less clear with less severe APT. These findings may be relevant for clinical APT.

Hemodynamic effects of combined sildenafil and L-arginine during acute pulmonary embolism-induced pulmonary hypertension.

Sildenafil attenuates acute pulmonary embolism-induced pulmonary hypertension. However, the hemodynamic effects of sildenafil in combination with other vasodilators during acute pulmonary embolism have not been examined yet. In the present study, we examined the hemodynamic effects of combined sildenafil (0.25 mg/kg, i.v.) and L-arginine (100, 200, 500, and 1000 mg/kg/h, i.v.) in an anesthetized dog model of acute pulmonary embolism. Plasma nitrite/nitrate (NO(x)) and cGMP concentrations were determined using an ozone-based chemiluminescence assay and a commercial enzyme immunoassay, respectively. We found that L-arginine alone did not attenuate acute pulmonary embolism-induced pulmonary hypertension. However, significant decreases in mean pulmonary artery pressure were observed 30, 45, 60, and 75 min after the administration of sildenafil alone or after the combined administration of sildenafil and L-arginine (all P < 0.05). No significant differences among groups were observed in the respiratory parameters. While L-arginine significantly increased NO(x) concentrations, cGMP concentrations increased only when sildenafil was administered (all P < 0.05). These results suggest that while sildenafil attenuates acute pulmonary embolism-induced pulmonary hypertension, L-arginine does not enhance the beneficial hemodynamic effects of sildenafil. In addition, these findings suggest that stimulation of NO synthesis with L-arginine during acute pulmonary embolism does not produce beneficial effects.

Methodological issues affecting the determination of plasma matrix metalloproteinase (MMP)-2 and MMP-9 activities.

OBJECTIVES: To examine whether a linear relationship exists between the volume of plasma loaded in each gel lane and the gelatinolytic activities of plasma matrix metalloproteinase (pMMP)-2 and pMMP-9, and the influences of plasma storage temperature, fasting, and a variable number of repeated freeze-thaw cycles. DESIGN AND METHODS: Plasma from venous blood collected into EDTA tubes was stored for 1 month at -20 degrees C or at -70 degrees C until assayed for gelatin zymography of pMMP-2 and pMMP-9. The effects of food intake, repeated freeze-thaw cycles, and the gelatinolytic activity produced by serial dilutions of plasma were examined. RESULTS: Storage temperature, fasting, and up to five repeated freeze-thaw cycles had no effect on the activities of pMMPs (all P < 0.05). A linear relationship was found with plasma volumes below 0.75 microL/lane for MMP-2, and from 0.75 microL/lane to 2 microL/lane for MMP-9. CONCLUSIONS: Different volumes of plasma should be studied when pMMP-2 and pMMP-9 activities are studied. Storage temperature, repeated freeze-thaw cycles, and food intake do not affect the activities of pMMPs.

eNOS genotype is without effect on circulating nitrite/nitrate level in healthy male population.

INTRODUCTION: Nitric oxide (NO) plays an important role in the regulation of the cardiovascular system. It is produced by endothelial nitric oxide synthase (eNOS), which exhibits genetic polymorphisms. Although the clinically relevant polymorphism T(+IhI-786)C reduces eNOS-promoter activity, it is not clear whether circulating nitrite/nitrate (NOx) are affected by this polymorphism. MATERIALS AND METHODS: We addressed this issue by studying a homogeneous group of 200 healthy subjects (males, Caucasians, nonsmokers, 18+IBM-56 years of age, and not taking any medication). Genotypes were determined by restriction fragment length polymorphism and circulating NOx were determined by chemiluminescence. RESULTS: We found nonsignificant effects of the T(+IhI-786)C polymorphism on circulating NOx (mean+ALE-S.D.=52.2+ALE-21.4, 49.0+ALE-17.8, and 45.9+ALE-16.8 +A7w-mol/L for genotypes +IBw-TT,+IB0 +IBw-TC,+IB0 and +IBw-CC,+IB0 respectively) and on total plasma cholesterol concentrations (both P>.05). No correlation was found between circulating NOx and total plasma cholesterol concentrations (P>.05). CONCLUSIONS: Our study provides strong evidence that the T(+IhI-786)C polymorphism does not affect plasma NOx concentrations, which are believed to reflect endogenous production of NO. Therefore, our results suggest that this polymorphism does not affect endogenous NO production.

Sildenafil improves the beneficial hemodynamic effects exerted by atorvastatin during acute pulmonary thromboembolism.

We investigated whether atorvastatin has beneficial hemodynamic effects during acute pulmonary thromboembolism (APT) and whether sildenafil improves these effects. We studied the involvement of oxidative stress, matrix metalloproteinases (MMPs), and neutrophil activation. APT was induced with autologous blood clots (500 mg/kg) in anesthetized male lambs pretreated with atorvastatin (10 mg/kg/day, subcutaneously; 1 week) or vehicle (dimethyl sulfoxide 10% subcutaneously). Sildenafil (0.7 mg/kg intravenously) or saline infusions were performed 60 min after APT induction. Non-embolized control animals received saline. APT significantly increased pulmonary vascular resistance index (PVRI) and mean pulmonary artery pressure (MPAP) by approximately 310% and 258% respectively. While atorvastatin pretreatment attenuated these increases (~150% and 153%, respectively; P < 0.05), its combination with sildenafil was associated with lower increases in PVRI and MPAP (~32% and 36%, respectively). Gelatin zymography showed increased MMP-9 and MMP-2 levels in the bronchoalveolar lavage, and increased MMP-9 levels in plasma from embolized animals. Atorvastatin pretreatment attenuated bronchoalveolar lavage MMP-2 increases. The combination of drugs blunted the MMPs increases in bronchoalveolar lavage and plasma (P < 0.05). Neutrophils accumulated in bronchoalveolar lavage after APT, and atorvastatin pretreatment combined with sildenafil (but not atorvastatin alone) attenuated this effect (P < 0.05). APT increased lung lipid peroxidation and total protein concentrations in bronchoalveolar lavage, thus indicating oxidative stress and alveolar-capillary barrier damage, respectively. Both increases were attenuated by atorvastatin pretreatment alone or combined with sildenafil (P < 0.05). We conclude that pretreatment with atorvastatin protects against the pulmonary hypertension associated with APT and that sildenafil improves this response. These findings may reflect antioxidant effects and inhibited neutrophils/MMPs activation.

Increases in circulating matrix metalloproteinase-9 levels following fibrinolysis for acute pulmonary embolism.

INTRODUCTION: Fibrinolyis is one of the first line therapies in high risk pulmonary embolism (PE) according to current guidelines. Previous studies showed that fibrinolytic therapy with tPA (tissue plasminogen activator, or alteplase) upregulates the concentrations of matrix metalloproteinases (MMPs) and contributes to hemorrhagic transformation after cardioembolic stroke. However, no previous study has described the circulating MMPs levels following fibrinolysis for acute PE. MATERIALS AND METHODS: We serially measured the circulating levels of MMPs (MMP-9 and MMP-2) and their endogenous inhibitors, the tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 in alteplase and in streptokinase-treated patients with acute PE by gelatin zymography and by enzyme-linked immunosorbent assays, respectively. RESULTS: We found that therapy of PE streptokinase or with alteplase is associated increased pro-MMP-9, but not MMP-2, concentrations for up to 24hours, whereas no significant changes were found in TIMP-1 or TIMP-2 concentrations. This alteration returned to normal 3 to 5days after thrombolysis. This is the first study reporting on MMPs alterations following fibrinolysis for acute PE. CONCLUSIONS: We found transient increases in circulating pro-MMP-9 levels following fibrinolysis for acute PE. Our findings support the hypothesis that increased MMP-9 levels may underlie the risk of intracerebral hemorrhage or other bleeding complication of thrombolysis for acute PE, and the use of MMP inhibitors may decrease such risk.

Circulating cell-free DNA levels in plasma increase with severity in experimental acute pulmonary thromboembolism.

BACKGROUND: The diagnosis of acute pulmonary thromboembolism (APT) and its severity is challenging. No previous study has examined whether there is a linear relation between plasma DNA concentrations and the severity of APT. We examined this hypothesis in anesthetized dogs. We also examined the changes in plasma DNA concentrations in microspheres lung embolization and whether the therapy of APT with nitrite could modify APT-induced changes in plasma DNA concentrations. In vitro DNA release from blood clots was also studied. METHODS: APT was induced with autologous blood clots (saline, 1, 3, or 5 ml/kg) injected into the right atrium. A group of dogs received 300 microm microspheres into the inferior vena cava to produce similar pulmonary hypertension. Another group of dogs received 6.75 micromol/kg nitrite after APT with blood clots of 5 ml/kg. Hemodynamic evaluations were carried out for 120 min. DNA was extracted from plasma samples using QIAamp DNA Blood Mini Kit and quantified using Quant-iT PicoGreen dsDNA detection kit at baseline and 120 min after APT. RESULTS: APT produced dose-dependent increases in plasma DNA concentrations, which correlated positively with pulmonary vascular resistance (P=0.002, r=0.897) and with mean pulmonary arterial pressure (P=0.006, r=0.856). Conversely, lung embolization with microspheres produced no significant changes in plasma DNA concentrations. While nitrite attenuated APT-induced pulmonary hypertension, it produced no changes in plasma DNA concentrations. Blood clots released dose-dependent amounts of DNA in vitro. CONCLUSIONS: Cell-free DNA concentrations increase in proportion to the severity of APT, probably as a result of increasing amounts of thrombi obstructing the pulmonary vessels.

eNOS genotype-dependent correlation between whole blood lead and plasma nitric oxide products concentrations.

Experimental data indicate that lead exposure decreases nitric oxide (NO) availability. However, no previous study has examined whether lead exposure affects plasma nitrite/nitrate (NO(x)) concentrations in humans. In addition, the T(-786)C polymorphism affects endothelial NO synthase (eNOS) expression and endogenous NO release. Here, we investigated whether there is an association between the circulating concentrations of NO(x) and the concentrations of lead in whole blood (B-Pb) and in plasma (P-Pb) from lead-exposed subjects. In addition, we also evaluated whether eNOS genotype for the T(-786)C polymorphism affects NO(x) concentrations in lead-exposed subjects. We studied 104 subjects exposed to lead who were non-smokers, 18-60 years of age, and not alcohol consumers. Genomic DNA was isolated from blood samples and genotypes for the T(-786)C polymorphism were determined by PCR and restriction fragment length digestion. Circulating NO(x) was determined by chemiluminescence. B-Pb and P-Pb were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. No significant correlations were found between NO(x) and B-Pb and P-Pb measured in the 104 subjects (all P > 0.05). However, while no significant correlation was found in subjects with TT genotype, a negative correlation was found between plasma NO(x) and B-Pb (r = 0.230, P = 0.048) and P-Pb (r = 0.194, P = 0.110) in subjects from TC + CC genotypes group. Our study shows a negative correlation between plasma NO(x) concentrations and B-Pb in carriers of the "C" allele, thus suggesting a possible mechanism possibly involved in lead exposure-induced increase in the susceptibility to cardiovascular diseases.