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-a (TNF-alpha), 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-alpha and II-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. J Periodontol 2011;82:767-777.

Nitric oxide synthase inhibitors improve prepulse inhibition responses of Wistar rats

Introduction: Cognitive and attentional deficits in schizophrenia include impairment of the sensorimotor filter as measured by prepulse inhibition (PPI). In this way, the study of animals that naturally present low PPI responses could be a useful approach for screening new antipsychotic drugs. Several pieces of evidence suggest that dopamine and nitric oxide (NO) can modulate PPI but their role in those animals is unknown. Objectives: The aim of this study was to investigate the role of dopamine and NO in Wistar rats with naturally low PPI response. Methods: Male Wistar rats with low PPI responses received an i.p. injection of the antipsychotics haloperidol (0.1, 0.3 or 1 mg/kg) or clozapine (0.5, 1.5 or 5 mg/kg), the anxiolytic diazepam (1 or 3 mg/kg) or the NO synthase (NOS) inhibitors, N(G)- nitro-L-arginine (L-NOARG; 40 mg/kg, acutely or sub-chronically) or 7-Nitroindazole (7-NI; 3, 10 or 30 mg/kg). All animals were submitted to the PPI test 1 h after injection. Striatal and cortical dopamine, DOPAC, and noradrenaline levels of rats with low PPI responses were compared to rats with normal PPI responses. Results: We found increased levels of catecholamines on the striatum and prefrontal cortex of Wistar rats with low PPI. In these animals, both antipsychotics, typical and atypical, and NOS inhibitors significantly increased PPI. Conclusion: Taken together, our findings suggest that the low PPI phenotype may be driven by an over-active catecholamine system. Additionally, our results corroborate the hypothesis of dopamine and NO interaction on PPI modulation and suggest that Wistar rats with low PPI may represent an interesting non-pharmacological model to evaluate new potential antipsychotics. (C) 2010 Elsevier B.V. All rights reserved.

Metalloproteinase inhibition protects against cardiomyocyte injury during experimental acute pulmonary thromboembolism

Objectives: Up-regulated matrix metalloproteinases may be involved in the development of cardiomyocyte injury and the degradation of troponin associated with acute pulmonary thromboembolism. We examined whether pretreatment with doxycycline (a nonspecific matrix metalloproteinase inhibitor) protects against cardiomyocyte injury associated with acute pulmonary thromboembolism. Design: Controlled animal study. Setting: University research laboratory. Subjects: Mongrel dogs. Interventions: Anesthetized animals received doxycycline (10 mg/kg intravenously) or saline and acute pulmonary thromboembolism was induced with autologous blood clots injected into the right atrium. Control animals received doxycycline (or saline). Measurements and Main Results: Hemodynamic measurements were performed, and acute pulmonary thromboembolism increased baseline mean pulmonary arterial pressure and pulmonary vascular resistance by approximately 160% and 362%, respectively (both p<.05), 120 mins after acute pulmonary thromboembolism. Pretreatment with doxycycline attenuated these increases (to 125% and 232%, respectively; both p<.05). Although acute pulmonary thromboembolism tended to increase the right ventricle maximum rate of isovolumic pressure development and the maximum rate of isovolumic pressure decay, doxycycline produced no effects on these parameters. Gelatin zymograms of right ventricle showed that acute pulmonary thromboembolism marginally increased matrix metalloproteinase-9 (but not matrix metalloproteinase-2) levels in the right ventricle. A fluorometric assay to assess net matrix metalloproteinase activities showed that acute pulmonary thromboembolism increased matrix metalloproteinase activities in the right ventricle by >100% (p<.05), and this finding was confirmed by in situ zymography of the right ventricle. Doxycycline attenuated acute pulmonary thromboembolism-induced increases in right ventricle matrix metalloproteinase activities. Acute pulmonary thromboembolism induced neutrophil accumulation in the right ventricle, as estimated by myeloperoxidase activity, and doxycycline blunted this effect (p<.05). Serum cardiac troponin I concentrations, which reflect cardiomyocyte injury, increased after acute pulmonary thromboembolism, and this increase was attenuated by pretreatment with doxycycline (p<.05). Conclusions: We found evidence supporting the idea that acute pulmonary thromboembolism is associated with increased matrix metalloproteinase activities in the right ventricle, which may lead to degradation of sarcomeric proteins, including cardiac troponin I. Inhibition of matrix metalloproteinases may be an effective therapeutic intervention in the management of acute pulmonary thromboembolism. (Crit Care Med 2011; 39: 349-356)

Central NOS inhibition differentially affects vasopressin gene expression in hypothalamic nuclei in septic rats

Our aim was to investigate the effect of central NOS inhibition on hypothalamic arginine vasopressin (AVP) gene expression, hormone release and on the cardiovascular response during experimental sepsis. Male Wistar rats were intracerebroventricularly injected with the non-selective NO synthase (NOS) inhibitor (L-NAME) or aminoguanidine, a selective inhibitor of the inducible isoform (iNOS). After 30 min. sepsis was induced by cecal ligation and puncture (CLP) causing an increase in heart rate (HR), as well as a reduction in median arterial pressure (MAP) and AVP expression ratio (AVP(R)), mainly in the supraoptic nucleus. AVP plasma levels (AVP(P)) increased in the early but not in the late phase of sepsis. L-NAME pretreatment increased MAP but did not change HR. It also resulted in an increase in AVP(P) at all time points, except 24 h, when it returned to basal levels. AVP(R), however remained reduced in both nuclei. Aminoguanidine pretreatment resulted in increased MAP in the early phase and higher AVP(R) in the supraoptic, but not in the paraventricular nucleus, while AVP(P) remained elevated at all time points. We suggest that increased central NO production, mainly inducible NOS-derived, reduces AVP gene expression differentially in supraoptic and paraventricular nuclei, and that this may contribute to low AVP plasma levels and hypotension in the late phase of sepsis. (c) 2010 Elsevier B.V. All rights reserved.

Nitric oxide modulation of methylphenidate-induced disruption of prepulse inhibition in Swiss mice

Drugs that facilitate dopaminergic neurotransmission induce cognitive and attentional deficits which include inability to filter sensory input measured by prepulse inhibition (PPI) Methylphenidate, an amphetamine analog is used in the treatment of attention deficit hyperactivity disorder Given that nitric oxide (NO) modulates dopamine effect our aim is to analyze the nitric oxide synthase (NOS) and soluble guanylate cyclase (sGC) inhibitors effect on PPI disruption induced by methylphenidate The inhibitors effects were compared to those produced by haloperidol and clozapine Male Swiss mice received a first I p. Injection (one hour before testing), of either saline, or N(G) nitro L-arginine (10, 40 or 90 mg/kg) or 7-Nitroindazole (3, 10, 30 or 60 mg/kg). or oxadiazolo-quinoxalin (5 or 10 mg/kg). or haloperidol (1 mg/kg), or clozapine (5 mg/kg) Thirty min later mice received the second injection of either saline or methylphenidate (20 or 30 mg/kg) or amphetamine (5 or 10 mg/kg). One group of mice received intracerebroventricular 7-Nitroindazole (50 or 100 nM) followed by systemic administration of saline or methylphenidate (30 mg/kg) The results revealed a methylphenidate dose-dependent disruption of PPI comparable to amphetamine. The effect was prevented by either nitric oxide synthase or guanilate cyclase inhibitors or clozapine or haloperidol In conclusion, methylphenidate induced a dose-dependent PPI disruption in Swiss mice modulated by dopamine and NO/sGC. The results corroborate the hypothesis of dopamine and NO interacting to modulate sensorimotor gating through central nervous system. It may be useful to understand methylphenidate and other psychostimulants effects (C) 2009 Elsevier B.V All rights reserved

NITRIC OXIDE SYNTHASE INHIBITION ATTENUATES L-DOPA-INDUCED DYSKINESIAS IN A RODENT MODEL OF PARKINSON`S DISEASE

Chronic L-DOPA pharmacotherapy in Parkinson`s disease is often, accompanied by the development of abnormal and excessive movements known as L-DOPA-induced dyskinesia. Rats with 6-hydroxydopamine lesion of dopaminergic neurons chronically treated with L-DOPA develop a rodent analog of this dyskinesia characterized by severe axial, limb, locomotor and orofacial abnormal involuntary movements. While the mechanisms by which these effects occur are not clear, they may involve the nitric oxide system. In the present study we investigate if nitric oxide synthase inhibitors can prevent dyskinesias induced by repeated administration Of L-DOPA in rats with unilateral 6-hydroxydopamine lesion. Chronic L-DOPA (high fixed dose, 100 mg/kg; low escalating dose, 10-30 mg/kg) treatment induced progressive dyskinesia changes. Two nitric oxide synthase inhibitors, 7-nitroindazole (1-30 mg/kg) and NG-nitro-L-arginine (50 mg/kg), given 30 min before L-DOPA, attenuate dyskinesia. 7-Nitroindazolee also improved motor performance of these animals in the rota-rod test. These results suggest the possibility that nitric oxide synthase inhibitors may be useful to treat L-DOPA.-Induced dyskinesia. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.

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. (C) 2008 Elsevier B.V. All rights reserved.

Study on the potential inhibition of root dentine wear adjacent to fluoride-containing restorations

The purpose of this in vitro study was to determine whether the vicinity of root dentine that had been restored with fluoride-releasing materials was at reduced risk for erosive/abrasive wear compared to root dentine restored with a non-fluoride-containing material. According to a randomized complete block design, standardized cavities prepared on the surface of 150 bovine root dentine slabs were restored with glass-ionomer cement, resin-modified glass ionomer, polyacid-modified resin composite, fluoride-containing or conventional composite. Specimens were coated with two layers of an acid-resistant nail varnish exposing half of the dentine surface and half of the restoration. Subsequently, specimens were either eroded in an acidic drink or left uneroded, then exposed to artificial saliva and abraded in a toothbrushing machine. Wear depth in the vicinity of restorations was quantified by a stylus profilometer, based on the nonabraded areas surrounding the erosion/abrasion region. Two-way ANOVA did not demonstrate significant interaction between restoratives and eroded-uneroded dentine (p = 0.5549) nor significant difference among restorative materials (p = 0.8639). Tukey`s test ascertained that the wear depth was higher for eroded than for uneroded groups. Fluoride-releasing materials seemed to negligibly inhibit wear in the vicinity of restored root dentine subjected to erosive/abrasive challenges.