Influence of antiplatelet drugs in the pathogenesis of experimental periodontitis and periodontal repair in rats

BACKGROUND

Platelets contain an array of biologic mediators that can modulate inflammation and repair processes including proinflammatory mediators and growth factors. Previous studies have shown that periodontitis and periodontal repair are associated with platelet activation. We hypothesized that drug-induced platelet inactivation may interfere in the processes of inflammation and repair in experimental periodontitis in rats by suppressing the release of biologic mediators from platelets to the site of injury.

METHODS

To measure the effects on periodontitis, ligatures were placed around first molars, and aspirin (Asp, 30 mg/kg) or clopidogrel (Clo, 75 mg/kg) was given intragastrically once daily for 15 days. Interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and thromboxane A(2) levels were measured by enzyme-linked immunosorbent assay. To evaluate the effects of antiplatelet drugs on periodontal repair, ligatures were removed after 15 days of periodontitis induction, and Asp or Clo were administered beginning the following day for 15 days. Periodontal repair was assessed by microcomputed tomography.

RESULTS

On periodontitis phase, Asp and Clo significantly reduced levels of TNF-α and Il-6 (P <0.05), but only Asp decreased thromboxane A(2) (P <0.05). Asp and Clo decreased inflammatory infiltration; however, this reduction was more pronounced with Clo treatment (P <0.05). Histometric analysis showed that Asp and Clo impaired alveolar bone resorption. During the repair phase and after removal of the ligatures, microcomputed tomography analysis demonstrated that treatment with Asp and Clo did not impair alveolar bone repair.

CONCLUSION

Systemic administration of Asp and Clo attenuates the inflammation associated with periodontitis without affecting the repair process when stimulus is removed.

Comparative study on antioxidant effects and vascular matrix metalloproteinase-2 downregulation by dihydropyridines in renovascular hypertension

The vascular remodeling associated with hypertension involves oxidative stress and enhanced matrix metalloproteinases (MMPs) expression/activity, especially MMP-2. While previous work showed that lercanidipine, a third-generation dihydropyridine calcium channel blocker (CCB), attenuated the oxidative stress and increased MMP-2 expression/activity in two-kidney, one-clip (2K1C) hypertension, no previous study has examined whether first- or second-generation dihydropyridines produce similar effects. We compared the effects of nifedipine, nimodipine, and amlodipine on 2K1C hypertension-induced changes in systolic blood pressure (SBP), vascular remodeling, oxidative stress, and MMPs levels/activity. Sham-operated and 2K1C rats were treated with water, nifedipine 10 mg/kg/day, nimodipine 15 mg/kg/day, or amlodipine 10 mg/kg/day by gavage, starting 3 weeks after hypertension was induced. SBP was monitored weekly. After 6 weeks of treatment, quantitative morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin-stained sections. Aortic and systemic reactive oxygen species levels were measured by using dihydroethidine and thiobarbituric acid-reactive substances (TBARs), respectively. Aortic MMP-2 levels and activity were determined by gelatin zymography, in situ zymography, and immunofluorescence. Nifedipine, nimodipine, or amlodipine attenuated the increases in SBP in hypertensive rats by approximately 17% (P < 0.05) and prevented vascular hypertrophy (P < 0.05). These CCBs blunted 2K1C-induced increases in vascular oxidative stress and plasma TBARs concentrations (P < 0.05). All dihydropyridines attenuated the increases in aortic MMP-2 levels and activity associated with 2K1C hypertension. These findings suggest lack of superiority of one particular dihydropyridine, at least with respect to antioxidant effects, MMPs downregulation, and inhibition of vascular remodeling in hypertension.

Combining two potential causes of metalloproteinase secretion causes abdominal aortic aneurysms in rats: a new experimental model

Progress in understanding the pathophysiology of abdominal aortic aneurysms (AAA) is dependent in part on the development and application of effective animal models that recapitulate key aspects of the disease. The objective was to produce an experimental model of AAA in rats by combining two potential causes of metalloproteinase (MMP) secretion: inflammation and turbulent blood flow. Male Wistar rats were randomly divided in four groups: Injury, Stenosis, Aneurysm and Control (40/group). The Injury group received a traumatic injury to the external aortic wall. The Stenosis group received an extrinsic stenosis at a corresponding location. The Aneurysm group received both the injury and stenosis simultaneously, and the Control group received a sham operation. Animals were euthanized at days 1, 3, 7 and 15. Aorta and/or aneurysms were collected and the fragments were fixed for morphologic, immunohistochemistry and morphometric analyses or frozen for MMP assays. AAAs had developed by day 3 in 60-70% of the animals, reaching an aortic dilatation ratio of more than 300%, exhibiting intense wall remodelling initiated at the adventitia and characterized by an obvious inflammatory infiltrate, mesenchymal proliferation, neoangiogenesis, elastin degradation and collagen deposition. Immunohistochemistry and zymography studies displayed significantly increased expressions of MMP-2 and MMP-9 in aneurysm walls compared to other groups. The haemo-dynamic alterations caused by the stenosis may have provided additional contribution to the MMPs liberation. This new model illustrated that AAA can be multifactorial and confirmed the key roles of MMP-2 and MMP-9 in this dynamic remodelling process.

Vitamin D receptor haplotypes affect lead levels during pregnancy

Pregnant women are particularly susceptible to toxic effects associated with lead (Pb) exposure. Pb accumulates in bone tissue and is rapidly mobilized from bones during pregnancy, thus resulting in fetal contamination. While vitamin D receptor (VDR) polymorphisms modify bone mineralization and affect Pb biomarkers including blood (Pb-B) and serum (Pb-S) Pb concentrations, and %Pb-S/Pb-B ratio, the effects of these polymorphisms on Pb levels in pregnant women are unknown. This study aimed at examining the effects of three (FokI, BsmI and ApaI) VDR polymorphisms (and VDR haplotypes) on Pb levels in pregnant women. Pb-B and Pb-S were determined by inductively coupled plasma mass spectrometry in samples from 256 healthy pregnant women and their respective umbilical cords. Genotypes for the VDR polymorphisms were determined by PCR and restriction fragment length digestion. While the three VDR polymorphisms had no significant effects on Pb-B, Pb-S or %Pb-S/Pb-B ratio, the haplotype combining the f, a, and b alleles for the FokI, ApaI and BsmI polymorphisms, respectively, was associated with significantly lower Pb-S and %Pb-S/Pb-B (P<0.05). However, maternal VDR haplotypes had no effects on Pb levels in the umbilical cords. To our knowledge, this is the first study showing that a combination of genetic polymorphisms (haplotype) commonly found in the VDR gene affects Pb-S and %Pb-S/Pb-B ratios in pregnant women. These findings may have major implications for Pb toxicity because they may help to predict the existence of a group of subjects that is genetically less prone to Pb toxicity during pregnancy.

A functional matrix metalloproteinase (MMP)-9 polymorphism modifies plasma MMP-9 levels in subjects environmentally exposed to mercury

Mercury (Hg) exposure causes health problems including cardiovascular diseases. Although precise mechanisms have not been precisely defined yet, matrix metalloproteinases (MMPs) may be involved. The gene encoding MMP-9 presents genetic polymorphisms which affect the expression and activity level of this enzyme. Two polymorphisms in the promoter region [C(-1562)T and (CA)(n)] are functionally relevant, and are implicated in several diseases. This study aimed at examining how these polymorphisms affect the circulating MMP-9 levels and its endogenous inhibitor, the tissue inhibitor of metalloproteinase-1 (TIMP-1) in 266 subjects environmentally exposed to Hg. Blood and plasma Hg concentrations were determined by inductively coupled plasma-mass spectrometry (ICP-MS). MMP-9 and TIMP-1 concentrations were measured in plasma samples by gelatin zymography and ELISA, respectively. Genotypes for the C(-1562)T and the microsatellite (CA)(n) polymorphisms were determined. We found a positive association (P<0.05) between plasma Hg concentrations and MMP-9/TIMP-1 ratio (an index of net MMP-9 activity). When the subjects were divided into tertiles with basis on their plasma Hg concentrations, we found that the (CA)(n) polymorphism modified MMP-9 concentrations and MMP-9/TIMP-1 ratio in subjects with the lowest Hg concentrations (first tertile), with the highest MMP-9 levels being found in subjects with genotypes including alleles with 21 or more CA repeats (H alleles) (P<0.05). Conversely, this polymorphism had no effects on subjects with intermediate or high plasma Hg levels (second and third tertiles, respectively). The C(-1562)T polymorphism had no effects on MMP-9 levels. These findings suggest a significant interaction between the (CA)(n) polymorphism and low levels of Hg exposure, possibly increasing the risk of developing diseases in subjects with H alleles.

Should we measure serum or plasma lead concentrations?

PROJECT

Serum samples may not be appropriate to assess lead (Pb) concentrations because they may contain artificially higher Pb concentrations compared with those measured in plasma samples. Here, we compared Pb concentrations in serum versus heparin plasma separated from blood collected with or without vacuum. We have also examined the effects of sample standing time on Pb concentrations measured in serum, heparin plasma, and EDTA plasma.

PROCEDURE

We studied plasma and serum samples from twelve healthy subjects. Blood samples were collected via venous drainage phlebotomy with and without vacuum into trace metal free tubes containing no anticoagulants (serum), or lithium heparin, or EDTA (to obtain plasma). Variable sample standing times (0, 5, and 30 min) prior to centrifugation were allowed. Plasma and serum Pb and iron concentrations were determined by inductively coupled plasma mass spectrometry. Plasma and serum cell-free hemoglobin concentrations were measured.

RESULTS

Pb concentrations in serum and in heparin plasma from blood samples collected with or without vacuum were similar and not associated with significant changes in iron or hemoglobin concentrations. The sample standing time (up to 30 min) did not affect Pb concentrations in serum or in heparin plasma, which were approximately 50% lower than those found in EDTA plasma.

CONCLUSIONS

Serum or heparin plasma separated from blood samples collected via venous phlebotomy with or without vacuum are appropriate medium to assess Pb concentrations, independently of the sample standing time.

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.

Fluoride increases lead concentrations in whole blood and in calcified tissues from lead-exposed rats

Higher blood lead (BPb) levels have been reported in children living in communities that receive fluoride-treated water. Here, we examined whether fluoride co-administered with lead increases BPb and lead concentrations in calcified tissues in Wistar rats exposed to this metal from the beginning of gestation. We exposed female rats and their offspring to control water (Control Group), 100mg/L of fluoride (F Group), 30mg/L of lead (Pb Group), or 100mg/L of fluoride and 30mg/L of lead (F+Pb Group) from 1 week prior to mating until offspring was 81 days old. Blood and calcified tissues (enamel, dentine, and bone) were harvested at day 81 for lead and fluoride analyses. Higher BPb concentrations were found in the F+Pb Group compared with the Pb Group (76.7+/-11.0microg/dL vs. 22.6+/-8.5microg/dL, respectively; p<0.001). Two- to threefold higher lead concentrations were found in the calcified tissues in the F+Pb Group compared with the Pb Group (all p<0.001). Fluoride concentrations were similar in the F and in the F+Pb Groups. These findings show that fluoride consistently increases BPb and calcified tissues Pb concentrations in animals exposed to low levels of lead and suggest that a biological effect not yet recognized may underlie the epidemiological association between increased BPb lead levels in children living in water-fluoridated communities.

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.

Circulating matrix metalloproteinase-8 (MMP-8) and MMP-9 are increased in chronic periodontal disease and decrease after non-surgical periodontal therapy

BACKGROUND

Periodontal disease shares risk factors with cardiovascular diseases and other systemic inflammatory diseases. The present study was designed to assess the circulating matrix metalloproteinases (MMPs) from chronic periodontal disease patients and, subsequently, after periodontal therapy.

METHODS

We compared the plasma concentrations of MMP-2, MMP-3, MMP-8, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2, and total gelatinolytic activity in patients with periodontal disease (n=28) with those of control subjects (n=22) before and 3 months after non-surgical periodontal therapy.

RESULTS

Higher plasma MMP-3, MMP-8, and MMP-9 concentrations were found in periodontal disease patients compared with healthy controls (all P<0.05), whereas MMP-2, TIMP-1, and TIMP-2 levels were not different. Treatment decreased plasma MMP-8 and MMP-9 concentrations by 35% and 39%, respectively (both P<0.02), while no changes were found in controls. MMP-2, MMP-3, TIMP-1, and TIMP-2 remained unaltered in both groups. Plasma gelatinolytic activity was higher in periodontal disease patients compared with controls (P<0.001) and decreased after periodontal therapy (P<0.05).

CONCLUSIONS

This study showed increased circulating MMP-8 and MMP-9 levels and proteolytic activity in periodontal disease patients that decrease after periodontal therapy. The effects of periodontal therapy suggest that it may attenuate inflammatory chronic diseases.

Circulating interleukin-6 and high-sensitivity C-reactive protein decrease after periodontal therapy in otherwise healthy subjects

BACKGROUND

Periodontal disease has been associated with many chronic inflammatory systemic diseases, and a common chronic inflammation pathway has been suggested for these conditions. However, few studies have evaluated whether periodontal disease, in the absence of other known inflammatory conditions and smoking, affects circulating markers of chronic inflammation. This study compared chronic inflammation markers in control individuals and patients with periodontal disease and observed whether non-surgical periodontal therapy affected inflammatory disease markers after 3 months.

METHODS

Plasma and serum of 20 controls and 25 patients with periodontal disease were obtained prior to and 3 months after non-surgical periodontal therapy. All patients were non-smokers, they did not use any medication, and they had no history or detectable signs and symptoms of systemic diseases. Periodontal and systemic parameters included probing depth, bleeding on probing, clinical attachment level, hematologic parameters, as well as the following inflammatory markers: interleukin (IL)-6, high-sensitivity C-reactive protein (hs-CRP), CD40 ligand, monocyte chemoattractant protein (MCP)-1, soluble P-selectin (sP-selectin), soluble vascular adhesion molecule (sVCAM)-1, and soluble intercellular adhesion molecule (sICAM)-1.

RESULTS

There were no differences in the hematologic parameters of the patients in the control and periodontal disease groups. Among the tested inflammatory markers, IL-6 concentrations were higher in the periodontal disease group at baseline compared to the controls (P = 0.006). Therapy was highly effective (P <0.001 for all the analyzed clinical parameters), and a decrease in circulating IL-6 and hs-CRP concentrations was observed 3 months after therapy (P = 0.001 and P = 0.006, respectively). Our results also suggest that the CD40 ligand marker may have been different in the control and periodontal disease groups prior to the therapy (P = 0.009).

CONCLUSIONS

In apparently otherwise healthy patients, periodontal disease is associated with increased circulating concentrations of IL-6 and hs-CRP, which decreased 3 months after non-surgical periodontal therapy. With regard to the CD40 ligand, MCP-1, sP-selectin, sVCAM-1, and sICAM-1, no changes were seen in the periodontal disease group between baseline and 3 months after therapy.

Antioxidant treatment reduces matrix metalloproteinase-2-induced vascular changes in renovascular hypertension

Mounting evidence indicates that structural and functional vascular changes associated with two-kidney, one-clip (2K-1C) hypertension result, at least in part, from altered activity of matrix metalloproteinases (MMPs). Because MMPs are upregulated by increased formation of reactive oxygen species (ROS), we hypothesized that antioxidant approaches could attenuate the increases in MMP-2 expression/activity and the vascular dysfunction and remodeling associated with 2K-1C hypertension. Sham-operated or 2K-1C hypertensive rats were treated with tempol 18 mg/kg/day or apocyanin 25 mg/kg/day (or vehicle). Systolic blood pressure was monitored weekly. After 8 weeks of treatment, aortic rings were isolated to assess endothelium-dependent and -independent relaxation. Quantitative morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin sections. Aortic and systemic ROS levels were measured using dihydroethidine and thiobarbituric acid-reactive substances, respectively. Aortic MMP-2 levels and activity were determined by gelatin and in situ zymography, fluorimetry, and immunohistochemistry. Tempol and apocyanin attenuated 2K-1C hypertension (181+/-20.8 and 192+/-17.6 mm Hg, respectively, versus 213+/-18 mm Hg in hypertensive controls; both p<0.05) and prevented the reduction in endothelium-dependent vasorelaxation found in 2K-1C rats. Tempol, but not apocyanin (p>0.05), prevented the vascular remodeling found in 2K-1C rats (all p<0.01). Tempol was more effective than apocyanin in attenuating hypertension-induced increases in oxidative stress (both p<0.05), MMP-2 levels, and MMP-2 activity in hypertensive rats (all p<0.05). Our results suggest that antioxidant approaches decrease MMP-2 upregulation and attenuate the vascular dysfunction and remodeling during 2K-1C hypertension.

In situ zymography and immunolabeling in fixed and decalcified craniofacial tissues

In situ zymography is a very important technique that shows the proteolytic activity in sections and allows researchers to observe the specific sites of proteolysis in tissues or cells. It is normally performed in non-fixed frozen sections and is not routinely performed in calcified tissues. In this study, we describe a technique that maintains proteolytic activity in fixed and decalcified sections obtained after routine paraffin sectioning in conventional microtome and cryostat sections. We used adult rat hemimandibles, which presented bone, enamel, and dentine matrices; the substrate used was dye-quenched-gelatin. Gelatinolytic activity was colocalized with MMP-2 using fluorescent antibodies. Specific proteolytic activity was observed in all sections, compatible with metalloproteinase activity, particularly in dentine and bone. Furthermore, matrix metalloproteinase-2 was colocalized to the sites of green fluorescence in dentine. In conclusion, the technique presented here will allow in situ zymography reactions in fixed, decalcified, and paraffin-embedded tissues, and we showed that paraformaldehyde-lysine-periodate-fixed cryostat sections are suitable for colocalization of gelatinolytic activity and protein labeling with antibodies.

Inverse relationship between markers of nitric oxide formation and plasma matrix metalloproteinase-9 levels in healthy volunteers

BACKGROUND

Nitric oxide (NO) is a major regulator of cardiovascular homeostasis and has anti-atherogenic properties. Reduced NO formation is associated with endothelial dysfunction and with cardiovascular risk factors. Although NO downregulates the expression and activity of the pro-atherogenic enzyme matrix metalloproteinase-9 (MMP-9), no previous clinical study has examined whether endogenous NO formation is inversely associated with the circulating levels of pro-MMP-9, which are associated with cardiovascular events. We examined this hypothesis in 175 healthy male subjects who were non-smokers.

METHODS

To assess NO bioavailability, the plasma concentrations of nitrite, nitrate, and cGMP were determined using an ozone-based chemiluminescence assay and an enzyme immunoassay. Pro-MMP-9 and pro-MMP-2 levels were measured in plasma samples by gelatin zymography.

RESULTS

We found significant negative correlations between pro-MMP-9 levels and plasma nitrite (P=0.035, rs= -0.159), nitrate (P=0.040, rs= -0.158), and cGMP (P=0.011, rs= -0.189) concentrations. However, no significant correlations were found between pro-MMP-2 levels and the plasma concentrations of markers of NO bioavailability (all P>0.05).

CONCLUSIONS

There is an inverse relationship between markers of NO formation and plasma MMP-9 levels. This finding may shed some light on the possible mechanisms involved in the increased cardiovascular risk of apparently healthy subjects with low NO bioavailability or high circulating levels of pro-MMP-9.

An interethnic comparison of the distribution of vitamin D receptor genotypes and haplotypes

BACKGROUND

The biological actions of vitamin D receptor (VDR) may be affected by genetic variations in the VDR gene. While there are interethnic differences in the frequency of VDR gene variants, there is little haplotype information, especially from admixed populations. We examined the distribution of genetic variants of 3 VDR polymorphisms (BsmI, ApaI and FokI) and haplotypes in black and white Brazilians. We have also compared our results with those from the HapMap project.

METHODS

We studied 120 subjects self-reported as black, and 100 subjects self-reported as white (total N=220; men and women; age range: 19-56 years). Genomic DNA was extracted from venous blood and the genotypes for the VDR gene polymorphisms were determined by PCR followed by restriction fragment length digestion and gel electrophoresis. Haplotypes were inferred with the program PHASE ver. 2.1.

RESULTS

While the distribution of VDR genotypes or alleles for the 3 VDR gene polymorphisms in Brazilians showed no interethnic differences (all P<0.05), significant differences were found for the ApaI and FokI polymorphisms in the HapMap populations (both P<0.05). While no interethnic differences in the distribution of haplotypes were found in Brazilians (P>0.05), significant differences were found in the HapMap populations (P<0.05).

CONCLUSIONS

VDR genotype and haplotype differences between the Brazilian population and the HapMap population gives support to the idea that significant differences in haplotype structures may exist between different populations, especially admixed populations.

Clinical evidence for lead-induced inhibition of nitric oxide formation

Lead exposure has been associated with increased cardiovascular risk, which may result, at least in part, from lead-induced increases in oxidative stress and depressed nitric oxide (NO) availability. However, no previous clinical study has examined whether lead exposure is associated with significant effects on biomarkers of NO activity (plasma nitrites, nitrates, and cyclic guanosine 3',5'-monophosphate; cGMP). We investigated whether there is an association between the circulating concentrations of nitrites, nitrates, and cGMP and the concentrations of lead in whole blood (B-Pb) or plasma (P-Pb) from 62 lead-exposed subjects (30 men and 32 women). P-Pb was determined by inductively coupled plasma mass spectrometry and B-Pb by graphite furnace atomic absorption spectrometry. Plasma nitrite and nitrate concentrations were measured using an ozone-based chemiluminescence assay. Plasma cGMP concentrations were measured using a commercial enzyme immunoassay. We found a negative correlation between plasma nitrite and B-Pb concentrations (r = -0.358; P = 0.004), and between plasma nitrite and P-Pb concentrations (r = -0.264; P = 0.038), thus suggesting increased inhibition of NO formation with increasing B-Pb or P-Pb concentrations. However, no significant correlations were found between plasma nitrate or cGMP and B-Pb or P-Pb concentrations (all P > 0.05). These findings suggest a significant inhibitory effect of lead exposure on NO formation and provide clinical evidence for a biological mechanism possibly involved the association between lead exposure and increased cardiovascular risk.

Haplotypes of vitamin D receptor modulate the circulating levels of lead in exposed subjects

Genetic factors influence whole blood lead (Pb-B) concentrations in lead exposed subjects. This study aimed at examining the combined effects (haplotype analysis) of three polymorphisms (BsmI, ApaI and FokI) in vitamin D receptor (VDR) gene on Pb-B and on the concentrations of lead in plasma (Pb-P), which is more relevant to lead toxicity, in 150 environmentally exposed subjects. Genotypes were determined by RFLP, and Pb-P and Pb-B were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. Subjects with the bb (BsmI polymorphism) or ff (FokI polymorphism) genotypes have lower B-Pb than subjects in the other genotype groups. Subjects with the aa (ApaI polymorphism) or ff genotypes have lower P-Pb than subjects in the other genotype groups. Lower Pb-P, Pb-B, and %Pb-P/Pb-B levels were found in subjects with the haplotype combining the a, b, and f alleles for the ApaI, BsmI, and FokI polymorphisms, respectively, compared with the other haplotype groups, thus suggesting that VDR haplotypes modulate the circulating levels of lead in exposed subjects.

Protective effects of atorvastatin in rat models of acute pulmonary embolism: Involvement of matrix metalloproteinase-9*

OBJECTIVE

Matrix metalloproteinases (MMPs) have been implicated in the pathophysiology of acute pulmonary embolism (APE)-induced pulmonary hypertension. Here, we evaluate the effects of atorvastatin pretreatment on APE-induced pulmonary hypertension, 24-hr mortality rate, and changes in plasma and lung MMP-2 and MMP-9 activities.

DESIGN

Controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Rats received atorvastatin (30 mg/kg/day orally) or tap water for 2 wks. In study 1, we examined whether atorvastatin affected APE-induced pulmonary hypertension by using a rat isolated lung perfusion model of APE. In study 2, we examined whether atorvastatin affects the survival rate after APE, which was induced by rapid intravenous injection of 14 mg/kg of a suspension of microspheres (or saline) into the tail vein.

MEASUREMENTS AND MAIN RESULTS

Plasma nitrite/nitrate concentrations were measured by chemiluminescence. Pretreatment with atorvastatin was associated with 49% higher nitrite/nitrate levels compared with controls (p < .05). In study 1, whereas APE increased mean pulmonary artery pressure (MPAP) by 13.0 +/- 1.6 mm Hg in perfused lungs isolated from rats pretreated with water, pretreatment with atorvastatin attenuated by 27% the increases in MPAP after APE. In study 2, pretreatment with atorvastatin was associated with a significant increase in 24-hr survival rate after APE, which was 48% in embolized rats pretreated with water and 64% in rats pretreated with atorvastatin (p < .05). Gelatin zymography of lung and plasma MMP-2 and MMP-9 was performed. Lungs and plasma from embolized rats showed higher levels of both pro- and activated forms of MMP-9 compared with those from nonembolized animals (all p < .05). However, pretreatment with atorvastatin attenuated by 32% the increases in lung-activated MMP-9 levels after APE (p < .05).

CONCLUSIONS

These results suggest that pretreatment with atorvastatin attenuates APE-induced pulmonary hypertension and increases 24-hr survival rate by mechanisms that result in attenuated increases in lung activated MMP-9 after APE.

A role for matrix metalloproteinase-9 in the hemodynamic changes following acute pulmonary embolism

BACKGROUND

Matrix metalloproteinases (MMPs) modulate vascular contractility and may affect acute pulmonary embolism (APE)-induced pulmonary hypertension. We examined the effects of the administration of doxycycline (a MMP inhibitor) following APE in anesthetized dogs.

METHODS

Sham operated dogs (N=5) received only saline. APE was induced by intravenous injections of microspheres in amounts to increase mean pulmonary artery pressure (MPAP) by 20 mm Hg, and embolized dogs received saline (Emb group, N=8), or doxycycline (10 mg/kg, i.v.) 5 or 30 min of APE (Emb+Doxy 5 and Emb+Doxy 30 groups, N=9 and 8, respectively). Hemodynamic evaluation was performed at baseline and 5-120 after APE. Gelatin zymography of MMP-2 and MMP-9 from plasma samples was performed.

RESULTS

No significant hemodynamic changes were found in Sham animals. Embolization increased MPAP by 218+/-16% and the pulmonary vascular resistance index (PVRI) by 289+/-42% in Emb group (both P<0.05). Doxycyline increased the cardiac index by 24+/-5% and reduced PVRI by 23+/-4% 120 min of APE in Doxy 30+Emb group. In addition, doxycyline reduced MPAP and PVRI 30 min after APE with maximum effects seen 120 min after APE (25+/-4% decrease in MPAP and 33+/-6% decrease in PVRI; both P<0.05) in Doxy+5 group. Plasma pro-MMP-9 and MMP-9 levels increased only in Emb group and MMP-2 remained unaltered.

CONCLUSIONS

Our study shows that doxycycline attenuates APE-induced pulmonary hypertension, and indicates that MMP-9 has a role in APE-induced pulmonary hypertension. MMP-9 may be a pharmacological target in APE.

Rapid separation of serum does not avoid artificially higher matrix metalloproteinase (MMP)-9 levels in serum versus plasma

OBJECTIVES

To examine whether the time between blood drawing and centrifugation (TBDC) affects the levels of matrix metalloproteinase (MMP)-9 and MMP-2 levels in serum and in plasma samples, and to assess whether there is correlation between MMP-9 and MMP-2 levels in serum and plasma samples.

DESIGN AND METHODS

Serum and plasma samples (N=8) were separated from venous blood collected into citrate, heparin, and EDTA tubes, which were either centrifuged immediately or after 5, 10, 20, or 30 min after blood drawing. We assessed the correlation between MMP-9/MMP-2 in serum and citrate, heparin, and plasma samples (N=20), which were assayed for gelatine zymography of MMP-2 and MMP-9.

RESULTS

MMPs are released by platelets or leukocytes during platelet activation or sampling process, thus leading to artificially higher MMP-9 levels in serum compared with citrate, heparin, or EDTA plasma samples, independently of TBDC. Citrate and heparin plasma samples had the lowest Pro-MMP-9 and MMP-9 levels, which correlated with each other. Pro-MMP-9 levels in serum correlated with Pro-MMP-9 levels in EDTA or citrate plasma, but not with heparin plasma. While no significant correlations were found between MMP-9 levels in serum and those found in plasma samples, the total MMP-9 levels (Pro-MMP-9+MMP-9) in serum and in plasma samples correlated with each other. No significant differences were found in pro-MMP-2 levels.

CONCLUSIONS

These results suggest that the circulating levels of MMP-9 should be assessed in citrate or heparin plasma samples, but not in serum samples because of artificially higher MMP-9 levels in serum, independently of TBDC, and because they do not correlate with the MMP-9 levels in plasma samples.

Contrasting effects of age on the plasma/whole blood lead ratio in men and women with a history of lead exposure

We examined the effect of age and sex on the relationship between the concentrations of Pb in blood (Pb-B) and in plasma (Pb-P) in an adult population with a history of lead exposure. Pb-P was determined by inductively coupled plasma mass spectrometry (ICP-MS) and Pb-B by graphite furnace atomic absorption spectrometry (GF AAS). We studied 154 adults (56 men and 98 women) from 18 to 60-year old. Pb-B levels varied from 10.0 to 428.0 microg/L, with a mean of 76 microg/L. Blood lead levels varied from 10.0 to 428.0 microg/L in men (mean, 98.3 microg/L) and from 10.0 to 263.0 microg/L (mean, 62.8 microg/L) in women. Corresponding Pb-Ps were 0.02-2.9 microg/L (mean, 0.66 microg/L) and 0.02-1.5 microg/L (mean, 0.42 microg/L) in men and women, respectively. The relationship between Pb-B and Pb-P was found to be curvilinear (r = 0.757, P < 0.001 Spearman's correlation). The two quantities are related by the line y = 0.0006x(1492) (y = Pb-P, and x = Pb-B). The %Pb-P/Pb-B ratio ranged from 0.03% to 1.85%. A positive association was found between %Pb-P/Pb-B ratio and Pb-B levels. When data were separated by sex, this association was also relevant for men (y = 0.0184x(0.702)) and women (y = 0.0534x(0.5209)) (y = %Pb-P/Pb-B and x = Pb-B). Moreover, we found an interesting positive correlation between Log (Pb-P/Pb-B) and age for women (r = 0.31, P < 0.0001) and a negative correlation for men (r = -0.164, P = 0.07). Taken together, these results suggest contrasting effects of age on the plasma/whole blood lead ratio in men and women with a history of lead exposure. Moreover, sex might play an important role in the metabolism of lead, implying further consideration on the kinetic models constructed of lead toxicity.

Anti-inflammatory effects of atorvastatin: modulation by the T-786C polymorphism in the endothelial nitric oxide synthase gene

Statins produce cholesterol-independent, anti-inflammatory effects, which result at least in part from increased endothelial nitric oxide production. These effects may be modulated by polymorphisms in the endothelial nitric oxide synthase (eNOS) gene. Here, we examined whether the T-786C polymorphism of eNOS gene affects the concentrations of markers of atherosclerosis and inflammation (sCD40L, sVCAM-1, sICAM-1, sP-selectin, MCP-1, high sensitivity (hs)-CRP, MMP-2, MMP-9, and TIMP-1). We also studied whether atorvastatin-induced anti-inflammatory effects are modulated by this polymorphism. Healthy male volunteers (N=200), Caucasians, non-smokers, were genotyped for the T-786C polymorphism by restriction fragment length polymorphism. Subjects with TT or CC genotype received placebo for 14 days followed by 14 days of treatment with atorvastatin, 10mg/day p.o. The concentrations of inflammatory markers were measured with ELISA kits or by gelatin zymography. Serum cholesterol and LDL-cholesterol were significantly reduced after atorvastatin treatment in both genotype groups (P<0.05). No significant differences between genotype groups were found in the concentrations of the inflammatory markers after placebo. However, atorvastatin significantly reduced the concentrations of sCD40L, sVCAM-1, sP-selectin and MMP-9 in subjects with CC (but not TT) genotype (P<0.05). While atorvastatin decreased hs-CRP levels in both genotype groups (P<0.05), no significant effects were found on the concentrations of sICAM-1, MCP-1, pro-MMP-9, pro-MMP-2 and TIMP-1. These results suggest no effects for the T-786C polymorphism on the concentrations of inflammatory markers. However, this polymorphism modulates the anti-inflammatory effects of atorvastatin. These findings may be relevant for the primary prevention of cardiovascular events in subjects with CC genotype, who may be at increased cardiovascular risk and could benefit from treatment with statins.

Matrix Metalloproteinase-9 Activity in Plasma Correlates with Plasma and Whole Blood Lead Concentrations

Matrix metalloproteinases (MMPs) are enzymes involved in the degradation of the extracellular matrix. MMP-2 and MMP-9 have been implicated in a variety of pathological conditions including cardiovascular and neoplastic diseases, and recent studies have shown that circulating concentrations of MMP-9 may be a marker helping in the diagnosis and prognosis of cardiovascular and neoplastic diseases. We investigated whether there is an association between plasma MMP-2 and MMP-9 activities and the concentrations of lead in whole blood (blood Pb) or plasma (plasma Pb) from 40 lead-exposed persons (22 men and 18 women). Plasma Pb was determined by inductively coupled plasma mass spectrometry (ICP-MS) and blood Pb by graphite furnace atomic absorption spectrometry (GF-AAS). Plasma MMP-2 and MMP-9 activities were measured by gelatin zymography. We found a significant correlation between pro-MMP-9 activity in plasma and blood Pb (r=0.454; P=0.003), and between pro-MMP-9 activity in plasma and plasma Pb (r=0.312; P=0.049). No significant correlations were found between blood Pb or plasma Pb and plasma MMP-2. The association between pro-MMP-9 activity in plasma and both blood Pb and plasma Pb concentrations suggests a mechanism through which low lead exposure may increase the susceptibility to cardiovascular and neoplastic diseases. A causal relationship, however, remains to be proved.

Lercanidipine reduces matrix metalloproteinase-9 activity in patients with hypertension

Increased levels of metalloproteinase (MMP)-9 have been shown in hypertensive patients. Lercanidipine is a calcium channel blocker with antioxidant actions. We examined whether lercanidipine produces antioxidant effects and reduces MMP-9 activity in hypertensive patients in a placebo-controlled, crossover, single-blinded design study including 18 healthy volunteers (control group), and 14 hypertensive patients without (N = 7) or with (N = 7) diabetes mellitus. Hypertensive patients were randomized to treatment with placebo (15 days) or lercanidipine 20 mg/d (15 days). Arterial blood pressure was evaluated with ambulatory blood pressure monitoring. Plasma thiobarbituric acid reactive species (TBA-RS) levels were measured to assess oxidative stress, and plasma MMP-2 and MMP-9 were assayed by gel zymography before and after treatment with placebo or lercanidipine. Plasma concentrations of tissue inhibitor of metalloproteinases (TIMP)-1 were measured by ELISA. Lercanidipine reduced mean arterial pressure by 7% in hypertensive patients without diabetes (P < 0.05), but not in hypertensive patients with diabetes. It significantly decreased plasma TBA-RS levels in hypertensive patients without and with diabetes (95% confidence interval [CI], -26 to -46%, P = 0.048, and -22 to -33%, P = 0.036, respectively). In addition, lercanidipine decreased activated MMP-9 in hypertensive patients without and with diabetes (95% CI, -19 to -47%, P = 0.047, and -80 to -96%, P = 0.010, respectively). No effects were seen on MMP-2. No significant differences or changes in plasma TIMP-1 concentrations were found. Therefore, we demonstrate for the first time that lercanidipine consistently decreased MMP-9 activity and reduced oxidative stress in hypertensive patients, thus suggesting a mechanism probably involved in the pleotropic actions of lercanidipine.

Comparison of three methods for enamel protein extraction in different developmental phases of rat lower incisors

Protein extraction methods [urea, trichloroacetic acid (TCA), and acetic acid] were compared for protein recovery from rat incisor developing enamel in the S phase (intermediate/late secretion), M1 phase (early maturation), M2 phase (intermediate maturation), and M3 phase (final maturation). We compared the protein recoveries with the percentage of enamel matrix dry weight burnt off by incineration. Our results indicate that TCA and urea were equally efficient for the extraction of S-stage proteins (85% and 90% recovery, respectively), while urea was the best for M1-stage proteins (92% recovery), and TCA the best for M2-stage (99% recovery) and M3-stage (60% recovery) proteins. The other methods yielded less than 30% recovery in comparison to incineration for M2 and M3 stages. The fact that urea extraction works well in the S and M1 stages and not thereafter is probably related to the changes in the proteins during enamel development and the amount of mineral that needs to be dissolved. TCA is the single method that effectively recovered proteins from all developmental stages of the rat incisor enamel.

Evaluation of the use of salivary lead levels as a surrogate of blood lead or plasma lead levels in lead exposed subjects

We conducted a study to evaluate the use of parotid salivary lead (Pb-saliva) levels as a surrogate of the blood lead (Pb-B) or plasma lead levels (Pb-P) to diagnose lead exposure. The relationship between these biomarkers was assessed in a lead exposed population. Pb-saliva and Pb-P were determined by inductively coupled plasma mass spectrometry, while in whole blood lead was determined by graphite furnace atomic absorption spectrometry. We studied 88 adults (31 men and 57 women) from 18 to 60 years old. Pb-saliva levels varied from 0.05 to 4.4 microg/l, with a mean of 0.85 microg/l. Blood lead levels varied from 32.0 to 428.0 microg/l in men (mean 112.3 microg/l) and from 25.0 to 263.0 microg/l (mean 63.5 microg/l) in women. Corresponding Pb-Ps were 0.02-2.50 microg/l (mean 0.77 microg/l) and 0.03-1.6 microg/l (mean 0.42 microg/l) in men and women, respectively. A weak correlation was found between Log Pb-saliva and Log Pb-B (r=0.277, P<0.008), and between Log Pb-saliva and Log Pb-P (r=0.280, P=0.006). The Pb-saliva/Pb-P ratio ranged from 0.20 to 18.0. Age or gender does not affect Pb-saliva levels or Pb-saliva/Pb-P ratio. Taken together, these results suggest that salivary lead may not be used as a biomarker to diagnose lead exposure nor as a surrogate of plasma lead levels at least for low to moderately lead exposed population.

Ethnicity affects the distribution of delta-aminolevulinic acid dehydratase (ALAD) genetic variants

BACKGROUND

delta-Aminolevulinic acid dehydratase (ALAD) catalyzes the second step of heme synthesis. The ALAD gene shows a polymorphism (G-to-C transversion at position 177) leading to 2 alleles (ALAD1 and ALAD2) and 3 phenotypes (ALAD 1-1, ALAD 1-2 and ALAD 2-2). This polymorphism has been shown to affect lead toxicity and the risk of meningioma. In addition, there is little evidence showing interethnic differences in the distribution this polymorphism, especially in heterogeneous populations such as the present-day Brazilian population. We examined the distribution of genetic variants of the G177C ALAD polymorphism in black and white Brazilians.

METHODS

We studied 115 subjects self-reported as black and 119 subjects as white (total N=234; 135 men and 99 women; age range: 18-60 years). Genomic DNA was extracted from venous blood and the genotypes for the ALAD polymorphism were determined by PCR followed by RFLP digestion and gel electrophoresis.

RESULTS

We found a notable interethnic disparity in the distribution of G177C ALAD genotypes and alleles. The ALAD2 allele was more common in whites (12%) than in blacks (4%) (P<0.05). Correspondingly, the heterozygote (ALAD 1-2) or homozygote variant (ALAD 2-2) genotypes for this polymorphism were more common in whites than in blacks (P<0.05).

CONCLUSIONS

The significant interethnic differences in the distribution of G177C ALAD variants found in the Brazilian population is consistent with differences previously reported in other countries. These findings may help us understand the interethnic disparities in susceptibility to lead toxicity and brain tumors.

L-arginine attenuates acute pulmonary embolism-induced increases in lung matrix metalloproteinase-2 and matrix metalloproteinase-9

STUDY OBJECTIVES

To evaluate the effects of L-arginine on acute pulmonary embolism (APE)-induced pulmonary hypertension and increases in lung matrix metalloproteinase (MMP)-2 and MMP-9 activities.

DESIGN

Prospective trial.

SETTING

University laboratory.

INTERVENTIONS

Using an isolated lung perfusion rat model of APE, we examined whether L-arginine (0, 0.5, 3, and 10 mmol/L; five to seven rats per group) attenuates the pulmonary hypertension induced by the injection of 6.6 mg/kg of 300 microm microspheres into the pulmonary artery. In a second series of experiments (6 to 11 rats per group), we investigated whether nonselective inhibition of nitric oxide (NO) synthases with N(G)-nitro-L-arginine methyl ester (L-NAME; 4 mmol/L) decreases the effects produced by L-arginine. Lung MMP-2 and MMP-9 activities were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis gelatin zymography.

RESULTS

L-arginine at 0.5, 3, and 10 mmol/L attenuated APE-induced pulmonary hypertension by 25 to 42% (all p < 0.05). The protective effect of L-arginine was completely reversed by inhibition of NO synthesis with L-NAME. APE was associated with increased lung MMP-2 and MMP-9 activities (both p < 0.05). While L-arginine at 0.5 mmol/L produced no effect on MMPs, L-arginine 3 at mmol/L and 10 mmol/L attenuated the increases in MMP-2 and MMP-9 activities after APE (both p < 0.05).

CONCLUSIONS

L-arginine attenuates APE-induced pulmonary hypertension through mechanisms involving increased NO synthesis and maybe attenuation of lung MMP-2 and MMP-9 activities.

A polymorphism in the delta-aminolevulinic acid dehydratase gene modifies plasma/whole blood lead ratio

Delta aminolevulinic acid dehydratase (ALAD) plays an important role in lead poisoning. This study was carried out to examine the effects of ALAD gene polymorphism (G177C) on %Pb-P(plasma lead)/Pb-B(whole blood) ratio in 142 subjects environmentally exposed to lead. Genotypes for the ALAD G177C polymorphism were determined by PCR and restriction fragment length digestion. Pb-P and Pb-B were determined by inductively coupled plasma mass spectrometry and by graphite furnace atomic absorption spectrometry, respectively. The allele frequencies for ALAD1 and ALAD2 alleles were 0.897 and 0.103, respectively. We combined both ALAD 1-2 and ALAD 2-2 genotypes together (ALAD 1-2/2-2 group) and compared with the ALAD 1-1 genotype group. While no significant differences were found in Pb-B, subjects from the ALAD 1-2/2-2 genotype group presented significantly higher Pb-P concentrations and %Pb-P/Pb-B ratios (0.89+/-0.07 microg/l, and 1.45+/-0.10%, respectively) when compared with subjects from the ALAD 1-1 genotype group (0.44+/-0.05 microg/l, and 0.48+/-0.02, respectively; both P<0.0001). The higher %Pb-P/Pb-B ratios in carriers of the ALAD-2 allele compared with noncarriers indicate that ALAD 1-2/2-2 subjects are probably at increased health risks associated with lead exposure.

Hemodynamic benefits of matrix metalloproteinase-9 inhibition by doxycycline during experimental acute pulmonary embolism

The authors examined whether acute pulmonary embolism (APE) increases lung matrix metalloproteinase (MMP)-2 and MMP-9 activities and whether inhibition of MMPs with doxycycline attenuates the hemodynamic changes associated with APE. Anesthetized male Wistar rats were monitored for mean arterial blood pressure (MAP) and heart rate (HR). Rats in the control group (n = 5) received only saline IV; rats in the embolism (Emb) group (n = 8) received saline IV followed 10 minutes later by an injection of Sephadex microspheres (9 mg/kg) IV; rats in the doxycycline (Doxy) group (n = 4) received only doxycycline (30 mg/kg) IV, followed 10 minutes later by an injection of saline IV; rats in the Doxy + Emb group (n = 8) received the same dose of doxycycline followed 10 minutes later by the same amount of microspheres described above. Lung samples were homogenized and assayed by SDS-polyacrilamide gel electrophoresis gelatin zymography to evaluate lung MMP-2 and MMP-9 activities. Saline or doxycycline produced no significant changes in MAP, HR, and in MMP-2 and MMP-9 activities. Conversely, lung embolization significantly reduced MAP by > 32 mm Hg and HR by > 90 bpm for more than 60 minutes, and increased MMP-9 activity by 43% (all p < 0.05). No significant differences were observed in MMP-2 activity. However, lung embolization produced only transient hypotension in rats pretreated with doxycycline. In this group, MAP returned to baseline values 5 to 10 minutes after embolization. In addition, pretreatment with doxycycline blunted the increase in lung MMP-9 activity after lung embolization (p < 0.05). This study demonstrates for the first time that MMP-9 inhibition with doxycycline attenuates APE-induced hemodynamic changes in the animal model examined. These findings indicate that MMP-9 activation plays a role in the pathophysiology of APE and suggest that pharmacologic strategies targeting specific MMPs with selective inhibitors may prevent the detrimental acute hemodynamic consequences of APE.

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.

Genetic polymorphism of matrix metalloproteinase (MMP)-9 does not affect plasma MMP-9 activity in healthy subjects

BACKGROUND

Plasma MMP-9 levels have been shown to predict cardiovascular risk, and a functional substitution C to T at position -1562 in the promoter region of the MMP-9 gene has been associated with the severity of cardiovascular diseases. We examined the association between the C(-1562)T polymorphism and MMP-9 activity in healthy subjects.

METHODS

We studied 200 healthy male white volunteers (age range: 20-55 y) who were nonsmokers and were not taking medicines. Genomic DNA was extracted and genotypes for the C(-1562)T polymorphism were determined by PCR and restriction fragment length digestion. Plasma was assayed for pro-MMP-9 and MMP-9 activities by gelatin zymography.

RESULTS

The frequency of the alleles "C" and "T" were 90% and 10%, respectively. Because of the relatively low frequency of the TT genotype, we combined both TT and CT genotypes together (CT+TT group) and compared with the CC genotype group. We found no differences in pro-MM9 and MMP-9 activity levels among the genotype groups (both P>0.05).

CONCLUSIONS

While the present study indicates lack of effect for the C(-1562)T polymorphism on MMP-9 activity in plasma, it is possible that the C(-1562)T polymorphism contributes to an increased cardiovascular risk under conditions of induced MMP-9 expression.

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.

The Effect of Sildenafil on Pulmonary Embolism-Induced Oxidative Stress and Pulmonary Hypertension

Acute pulmonary embolism (APE) is a major cause of pulmonary hypertension and death. We examined the effects of sildenafil on the hemodynamic changes caused by APE in anesthetized dogs. Sham-operated dogs (n = 3) received only saline. APE was induced by stepwise IV injections of 300 mum microspheres in amounts adjusted to increase mean pulmonary artery pressures by 20 mm Hg. Hemodynamic evaluation was performed at baseline, after APE was induced, and then after sildenafil 0.25 mg/kg (n = 8), or sildenafil 1 mg/kg + 0.3 mg . kg(-1) . h(-1) (n = 8) or saline (n = 9) infusions were started. Similar experiments were conducted to examine the effects of sildenafil in rat isolated perfused lung preparation. Plasma thiobarbituric acid reactive species were also determined in both studies to measure oxidative stress. Both doses of sildenafil reduced mean pulmonary artery pressures in dogs by approximately 8 to 16 mm Hg (both P < 0.05) and attenuated the increase in oxidative stress after APE. Mean arterial blood pressure remained unaltered after both doses of sildenafil. Sildenafil produced similar effects after APE in rat isolated perfused lung preparation. These findings indicate that IV sildenafil can selectively attenuate the increases in mean pulmonary artery pressures after APE, possibly through antioxidant mechanisms.

Inhibition of human pulpal gelatinases (MMP-2 and MMP-9) by zinc oxide cements

The interaction between metal ions and the oral environment is a major subject matter in dental research. Matrix metalloproteinases (MMPs) have been implicated in several pathological and physiological processes such as, periodontal tissue destruction, root caries, dentin calcification and pulpal inflammation. The aim of this work was to test the effect of zinc released from zinc oxide-eugenol (ZOE) cements, on the activity of the major pulpal gelatinolytic MMPs. Pulpal explants were cultured overnight in Dulbecco's Modified Eagle Medium and the activity of secreted enzymes was analysed by gelatin zymography in buffer conditioned with diverse ZOE cements. Phenanthroline, a zinc chelator, was used to revert the inhibition of MMPs caused by zinc. The major gelatinolytic proteinases present in the conditioned media were characterized as MMP-2 and MMP-9 by immunoprecipitation. All ZOE cements inhibited MMPs activity, whereas phenanthroline could partially revert the inhibition caused by plain ZOE and Intermediate Restorative Material (IRM).