Periprostatic adipose tissue (PPAT) supernatant from obese mice releases anticontractile substances and increases human prostate epithelial cell proliferation: the role of nitric oxide and adenosine

Background: The prostate gland is surrounded by periprostatic adipose tissue (PPAT) that can release mediators that interfere in prostate function. In this study, we examined the effect of periprostatic adipose tissue supernatant obtained from obese mice on prostate reactivity in vitro and on the viability of human prostatic epithelial cell lines. Methods: Male C57BL/6 mice were fed a standard or high-fat diet after which PPAT was isolated, incubated in Krebs-Henseleit solution for 30 min (without prostate) or 60 min (with prostate), and the supernatant was then collected and screened for biological activity. Total nitrate and nitrite (NOx^-) and adenosine were quantified, and the supernatant was then collected and screened for biological activity. NOx^- and adenosine were quantified. Concentration-response curves to phenylephrine (PE) were obtained in prostatic tissue from lean and obese mice incubated with or without periprostatic adipose tissue. In some experiments, periprostatic adipose tissue was co-incubated with inhibitors of the nitric oxide (NO)-cyclic guanosine monophosphate pathway (L-NAME, 1400W, ODQ), adenylate cyclase (SQ22536) or with adenosine A_2A (ZM241385), and A_2B (MRS1754) receptor antagonists. PNT1-A (normal) and BPH-1 (hyperplasic) human epithelial cells were cultured and incubated with supernatant from periprostatic adipose tissue for 24, 48, or 72 h in the absence or presence of these inhibitors/antagonists, after which cell viability and proliferation were assessed. Results: The levels of NOx^- and adenosine were significantly higher in the periprostatic adipose tissue supernatant (30 min, without prostate) when compared to the vehicle. A trend toward an increase in the levels of NOX was observed after 60 min. PPAT supernatant from obese mice significantly reduced the PE-induced contractions only in prostate from obese mice. The co-incubation of periprostatic adipose tissue with L-NAME, 1400W, ODQ, or ZM241385 attenuated the anticontractile activity of the periprostatic adipose tissue supernatant. Incubation with the supernatant of periprostatic adipose tissue from obese mice significantly increased the viability of PNT1-A cells and attenuated expression of the apoptosis marker protein caspase-3 when compared to cells incubated with periprostatic adipose tissue from lean mice. Hyperplastic cells (BPH-1) incubated with periprostatic adipose tissue from obese mice showed greater proliferation after 24 h, 48 h, and 72 h compared to cells incubated with culture medium alone. BPH-1 cell proliferation in the presence of PPAT supernatant was attenuated by NO-signaling pathway inhibitors and by adenosine receptor antagonists after 72 h. Conclusion: NO and adenosine are involved in the anticontractile and pro-proliferative activities of periprostatic adipose tissue supernatant from obese mice. More studies are needed to determine whether the blockade of NO and/or adenosine derived from periprostatic adipose tissue can improve prostate function.

Effects of Selective Versus Non-Selective COX-2 Inhibition on Experimental Periodontitis

In the present study we compared the effects of the selective COX-2 inhibitor etoricoxib with those of the classical non-selective NSAID diclofenac on the inflammatory process and alveolar bone loss in an experimental model of periodontitis in rats. Ninety male Holtzman rats (250 g) were randomly sorted into four experimental groups: Sham+CMC and Ligature+CMC (control) groups which received 0.5% carboxymethylcellulose sodium (CMC) solution; Ligature+Diclofenac and Ligature+Etoricoxib groups which received Potassium Diclofenac and Etoricoxib, respectively, suspended in 0.5% CMC (10 mg/kg/day). At 7, 14 and 21 days after placing ligatures in the cervical region of both the lower right and left first molars, the animals were euthanized. At the end of each period, the mandibles were collected for radiographic examination of alveolar bone loss. In addition, alveolar bone and periodontal ligament tissue samples were collected for COX-2 expression analysis and gingival tissues were collected for measurement of PGE2 contents. Animals with ligature-induced periodontal disease showed significant increased COX-2 gene expression at days 7, 14 and 21 (p<0.05) on alveolar bone and periodontal ligament. However, both treatments resulted in significantly reduced alveolar bone loss when compared to the untreated Ligature group (p<0.05), with no statistical difference between Etoricoxib and Diclofenac Potassium groups. This study shows that both drugs were able to reduce alveolar bone loss after periodontal disease induction.

Involvement of neuronal nitric oxide synthase in cross-sensitization between chronic unpredictable stress and ethanol in adolescent and adult mice

The peculiar neurochemical profile of the adolescent brain renders it differently susceptible to several stimuli, including stress and/or drug exposure. Among several stress mediators, nitric oxide (NO) has a role in stress responses. We have demonstrated that adolescent mice are less sensitive to ethanol-induced sensitization than adult mice. The present study investigated whether chronic unpredictable stress (CUS) induces behavioral sensitization to ethanol in adolescent and adult Swiss mice, and investigated the influence of Ca²⁺-dependent nitric oxide synthase (NOS) activity in the phenomenon. Adolescent and adult mice were exposed to repeated 1.8 g/kg ethanol or CUS and challenged with saline or ethanol. A neuronal nitric oxide synthase (nNOS) inhibitor, 7-nitroindazole (7NI), was administered along with ethanol and CUS to test its effects on behavioral sensitization. Both adolescent and adult mice displayed cross-sensitization between CUS and ethanol in adult mice, with adolescents showing a lower degree of sensitization than adults. nNOS inhibition by 7NI reduced both ethanol sensitization and cross-sensitization. All age differences in the Ca²⁺-dependent NOS activity in the hippocampus and prefrontal cortex were in the direction of greater activity in adults than in adolescents. Adolescents showed lower sensitivity to cross-sensitization between CUS and ethanol, and the nitric oxide (NO) system seems to have a pivotal role in ethanol-induced behavioral sensitization and cross-sensitization in both adolescent and adult mice.

Protective effects of exogenous and endogenous hydrogen sulfide in mast cell-mediated pruritus and cutaneous acute inflammation in mice

The recently described 'gasomediator' hydrogen sulfide (H₂S) has been involved in pain mechanisms, but its effect on pruritus, a sensory modality that similarly to pain acts as a protective mechanism, is poorly known and controversial. The effects of the slow-releasing (GYY4137) and spontaneous H₂S donors (Na₂S and Lawesson's reagent, LR) were evaluated in histamine and compound 48/80 (C48/80)-dependent dorsal skin pruritus and inflammation in male BALB/c mice. Animals were intradermally (i.d.) injected with C48/80 (3μg/site) or histamine (1μmol/site) alone or co-injected with Na₂S, LR or GYY4137 (within the 0.3-100nmol range). The involvement of endogenous H₂S and K_ATP channel-dependent mechanism were also evaluated. Pruritus was assessed by the number of scratching bouts, whilst skin inflammation was evaluated by the extravascular accumulation of intravenously injected ¹²⁵I-albumin (plasma extravasation) and myeloperoxidase (MPO) activity (neutrophil recruitment). Histamine or C48/80 significantly evoked itching behavior paralleled by plasma extravasation and increased MPO activity. Na₂S and LR significantly ameliorated histamine or C48/80-induced pruritus and inflammation, although these effects were less pronounced or absent with GYY4137. Inhibition of endogenous H₂S synthesis increased both Tyrode and C48/80-induced responses in the skin, whereas the blockade of K_ATP channels by glibenclamide did not. H₂S-releasing donors significantly attenuate C48/80-induced mast cell degranulation either in vivo or in vitro. We provide first evidences that H₂S donors confer protective effect against histamine-mediated acute pruritus and cutaneous inflammation. These effects can be mediated, at least in part, by stabilizing mast cells, known to contain multiple mediators and to be primary initiators of allergic processes, thus making of H₂S donors a potential alternative/complementary therapy for treating inflammatory allergic skin diseases and related pruritus.

Hydrogen sulfide donors alleviate itch secondary to the activation of type-2 protease activated receptors (PAR-2) in mice

Hydrogen sulfide (H₂S) has been highlighted as an endogenous signaling molecule and we have previously found that it can inhibit histamine-mediated itching. Pruritus is the most common symptom of cutaneous diseases and anti-histamines are the usual treatment; however, anti-histamine-resistant pruritus is common in some clinical settings. In this way, the involvement of mediators other than histamine in the context of pruritus requires new therapeutic targets. Considering that the activation of proteinase-activated receptor 2 (PAR-2) is involved in pruritus both in rodents and humans, in this study we investigated the effect of H₂S donors on the acute scratching behavior mediated by PAR-2 activation in mice, as well as some of the possible pharmacological mechanisms involved. The intradermal injection of the PAR-2 peptide agonist SLIGRL-NH₂ (8-80nmol) caused a dose-dependent scratching that was unaffected by intraperitoneal pre-treatment with the histamine H1 antagonist pyrilamine (30mg/kg). Co-injection of SLIGRL-NH₂ (40nmol) with either the slow-release H₂S donor GYY4137 (1 and 3nmol) or the spontaneous donor NaHS (1 and 0.3nmol) significantly reduced pruritus. Co-treatment with the K_ATP channel blocker glibenclamide (200nmol) or the nitric oxide (NO) donor sodium nitroprusside (10nmol) abolished the antipruritic effects of NaHS; however, the specific soluble guanylyl cyclase inhibitor ODQ (30μg) had no significant effects. The transient receptor potential ankyrin type 1 (TRPA1) antagonist HC-030031 (20μg) significantly reduced SLIGRL-NH₂-induced pruritus; however pruritus induced by the TRPA1 agonist AITC (1000nmol) was unaffected by NaHS. Based on these data, we conclude that pruritus secondary to PAR-2 activation can be reduced by H₂S, which acts through K_ATP channel opening and involves NO in a cyclic guanosine monophosphate (cGMP)-independent manner. Furthermore, TRPA1 receptors mediate the pruritus induced by activation of PAR-2, but H₂S does not interfere with this pathway. These results provide additional support for the development of new therapeutical alternatives, mainly intended for treatment of pruritus in patients unresponsive to anti-histamines.

Expression of glyceraldehyde 3-phosphate dehydrogenase is enhanced in Leishmania spp naturally resistant to nitric oxide

Leishmania spp are the causative agents of a spectrum of diseases termed leishmaniasis that affect mammals, including humans and dogs. Although reactive nitrogen species are employed in the control of parasitism by the immune system, it is known that Leishmania can withstand this oxidative stress. As the mechanism by which these species are resistant to nitric oxide (NO) is poorly understood, the main objective of this study was to evaluate the expression of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) in Leishmania amazonensis and Leishmania chagasi promastigotes showing natural resistance to NO. GAPDH transcript levels were quantified by real-time polymerase chain reaction amplification, and GAPDH activity (assessed by levels of NADH oxidation) was measured by spectrophotometry. The level of nitration in total protein was assessed by immunoblotting. The results demonstrated an increase in GAPDH expression in resistant isolates of both species compared to susceptible isolates. The increase in GAPDH expression led to an increase in the activity of GAPDH in L. amazonensis human isolates resistant to NO. The pattern of protein nitration did not differ between sensitive and resistant isolates. Our results suggest that changes in expression of GAPDH may be responsible, at least in part, to natural resistance to NO found in human and canine Leishmania spp.

Intracellular mechanisms of hydroquinone toxicity on endotoxin-activated neutrophils

Circulating neutrophils promptly react to different substances in the blood and orchestrate the beginning of the innate inflammatory response. We have shown that in vivo exposure to hydroquinone (HQ), the most oxidative compound of cigarette smoke and a toxic benzene metabolite, affects circulating neutrophils, making them unresponsive to a subsequent bacterial infection. In order to understand the action of toxic molecular mechanisms on neutrophil functions, in vitro HQ actions on pro-inflammatory mediator secretions evoked by Escherichia coli lipopolysaccharide (LPS) were investigated. Neutrophils from male Wistar rats were cultured with vehicle or HQ (5 or 10 μM; 2 h) and subsequently incubated with LPS (5 μg/ml; 18 h). Hydroquinone treatment impaired LPS-induced nitric oxide (NO), tumour necrosis factor α (TNF-α), interleukin (IL)-1β and IL-6 secretions by neutrophils. The toxic effect was not dependent on cell death, reduced expression of the LPS receptor or toll-like receptor-4 (TLR-4) or cell priming, as HQ did not induce reactive oxygen species generation or β(2)integrin membrane expression. The action of toxic mechanisms on cytokine secretion was dependent on reduced gene synthesis, which may be due to decreased nuclear factor κB (NF-κB) nuclear translocation. Conversely, this intracellular pathway was not involved in impaired NO production because HQ treatments only affected inducible nitric oxide synthase protein expression and activity, suggesting posttranscriptional and/or posttranslational mechanisms of action. Altogether, our data show that HQ alters the action of different LPS-activated pathways on neutrophils, which may contribute to the impaired triggering of the host innate immune reaction detected during in vivo HQ exposure.

Environmental tobacco smoke induces oxidative stress in distinct brain regions of infant mice

Environmental tobacco smoke (ETS) leads to the death of 600,000 nonsmokers annually and is associated with disturbances in antioxidant enzyme capacity in the adult rodent brain. However, little is known regarding the influence of ETS on brain development. The aim of this study was to determine levels of malonaldehyde (MDA) and 3-nitrotyrosine (3-NT), as well as enzymatic antioxidant activities of glutathione peroxidase (GPx), glutathione reductase (GR), glutathione S-transferase (GST), and superoxide dismutase (SOD), in distinct brain structures. BALB/c mice were exposed to ETS twice daily for 1 h from postnatal day 5 through postnatal day 18. Acute exposure was performed for 1 h on postnatal day 18. Mice were euthanized either immediately (0) or 3 h after the last exposure. Immediately after an acute exposure there were higher GR and GST activities and MDA levels in the hippocampus, higher GPx and SOD activities in the prefrontal cortex, and higher GST activity and MDA levels in the striatum and cerebellum. Three hours later there was an increase in SOD activity and MDA levels in the hippocampus and a decrease in the activity of all enzymes in the prefrontal cortex. Immediately after final repeated exposure there were elevated levels of GST and GR activity and decreased GPx activity in the hippocampus. Moreover, a rise was found in GPx and GST activities in the prefrontal cortex and increased GST and GPx activity in the striatum and cerebellum, respectively. After 3 h the prefrontal cortex showed elevated GR and GST activities, and the striatum displayed enhanced GST activity. Data showed that enzymatic antioxidant system in the central nervous system responds to ETS differently in different regions of the brain and that a form of adaptation occurs after several days of exposure.

Nitric oxide modulates lipopolysaccharide-induced endothelial platelet endothelial cell adhesion molecule expression via interleukin-10

We have shown previously that nitric oxide (NO) controls platelet endothelial cell adhesion molecule (PECAM-1) expression on both neutrophils and endothelial cells under physiological conditions. Here, the molecular mechanism by which NO regulates lipopolysaccharide (LPS)-induced endothelial PECAM-1 expression and the role of interleukin (IL)-10 on this control was investigated. For this purpose, N-(G)-nitro-L-arginine methyl ester (L-NAME; 20 mg/kg/day for 14 days dissolved in drinking water) was used to inhibit both constitutive (cNOS) and inducible nitric oxide (iNOS) synthase activities in LPS-stimulated Wistar rats (5 mg/kg, intraperitoneally). This treatment resulted in reduced levels of serum NO. Under this condition, circulating levels of IL-10 was enhanced, secreted mainly by circulating lymphocytes, dependent on transcriptional activation, and endothelial PECAM-1 expression was reduced independently on reduced gene synthesis. The connection between NO, IL-10 and PECAM-1 expression was examined by incubating LPS-stimulated (1 µg/ml) cultured endothelial cells obtained from naive rats with supernatant of LPS-stimulated lymphocytes, which were obtained from blood of control or L-NAME-treated rats. Supernatant of LPS-stimulated lymphocytes obtained from L-NAME-treated rats, which contained higher levels of IL-10, reduced LPS-induced PECAM-1 expression by endothelial cells, and this reduction was reversed by adding the anti-IL-10 monoclonal antibody. Therefore, an association between NO, IL-10 and PECAM-1 was found and may represent a novel mechanism by which NO controls endothelial cell functions.

Differing effects of exogenous and endogenous hydrogen sulphide in carrageenan-induced knee joint synovitis in the rat

BACKGROUND AND PURPOSE

Recent findings suggest that the noxious gas H(2)S is produced endogenously, and that physiological concentrations of H(2)S are able to modulate pain and inflammation in rodents. This study was undertaken to evaluate the ability of endogenous and exogenous H(2)S to modulate carrageenan-induced synovitis in the rat knee.

EXPERIMENTAL APPROACH

Synovitis was induced in Wistar rats by intra-articular injection of carrageenan into the knee joint. Sixty minutes prior to carrageenan injection, the rats were pretreated with indomethacin, an inhibitor of H(2)S formation (DL-propargylglycine) or an H(2)S donor [Lawesson's reagent (LR)].

KEY RESULTS

Injection of carrageenan evoked knee inflammation, pain as characterized by impaired gait, secondary tactile allodynia of the ipsilateral hindpaw, joint swelling, histological changes, inflammatory cell infiltration, increased synovial myeloperoxidase, protein nitrotyrosine residues, inducible NOS (iNOS) activity and NO production. Pretreatment with LR or indomethacin significantly attenuated the pain responses, and all the inflammatory and biochemical changes, except for the increased iNOS activity, NO production and 3-NT. Propargylglycine pretreatment potentiated synovial iNOS activity (and NO production), and enhanced macrophage infiltration, but had no effect on other inflammatory parameters.

CONCLUSIONS AND IMPLICATIONS

Whereas exogenous H(2)S delivered to the knee joint can produce a significant anti-inflammatory and anti-nociceptive effect, locally produced H(2)S exerts little immunomodulatory effect. These data further support the development and use of H(2)S donors as potential alternatives (or complementary therapies) to the available anti-inflammatory compounds used for treatment of joint inflammation or relief of its symptoms.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

BACKGROUND AND OBJECTIVE

Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process.

MATERIAL AND METHODS

Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period.

RESULTS

After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations.

CONCLUSION

Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Lymphatic-borne IL-1beta and the inducible isoform of nitric oxide synthase trigger the bronchial hyporesponsiveness after intestinal ischema/reperfusion in rats

Intestinal I/R (i-I/R) is an insult associated to further adult respiratory distress syndrome and multiple organ failure. This study was designed to evaluate the repercussions of i-I/R on bronchial reactivity to the cholinergic agent methacholine. Anesthetized rats were subjected to superior mesenteric artery occlusion (45 min) and killed after clamp release and defined intestinal reperfusion periods (30 min, 2, 4, or 24 h). Intestinal I/R caused a progressive bronchial hyporesponsiveness (BHR) that was maximal upon 2 h but reverted within 24 h of intestinal reperfusion. The BHR observed at 2-h i-I/R was prevented by NOS inhibitors (N-L-nitroarginine methyl ester and aminoguanidine) or the KATP channel blocker glibenclamide. Moreover, 2-h i-I/R increased the pulmonary iNOS mRNA expression, a fact prevented by lymphatic thoracic duct ligation. The methacholine reactivity of 2-h i-I/R bronchial segments incubated with NOS inhibitors or glibenclamide was similar to that of naive tissues. In vivo blockade of IL-1beta receptors or lymphatic duct ligation before 2-h i-I/R both abolished BHR. Incubation of naive bronchial segments with lymph collected from 2-h i-I/R rats determined BHR, an effect fully preventable by ex vivo blockade of IL-1beta receptors. Incubation of naive bronchial segments with IL-1beta, but not with IL-10 or TNF-alpha, significantly induced BHR that was prevented by N-L-nitroarginine methyl ester. Our data suggest that a gut ischemic insult generates IL-1beta that, upon reperfusion, travels through the lymph into the lungs. In this tissue, IL-1beta would stimulate the generation of NO that orchestrates the ensuing BHR for which the opening of KATP channels seems to play a pivotal role.

Long-term nitric oxide deficiency causes muscarinic supersensitivity and reduces beta(3)-adrenoceptor-mediated relaxation, causing rat detrusor overactivity

BACKGROUND AND PURPOSE

Overactive bladder is a complex and widely prevalent condition, but little is known about its physiopathology. We have carried out morphological, biochemical and functional assays to investigate the effects of long-term nitric oxide (NO) deficiency on muscarinic receptor and beta-adrenoceptor modulation leading to overactivity of rat detrusor muscle.

EXPERIMENTAL APPROACH

Male Wistar rats received N(omega)-nitro-L-arginine methyl ester (L-NAME) in drinking water for 7-30 days. Functional responses to muscarinic and beta-adrenoceptor agonists were measured in detrusor smooth muscle (DSM) strips in Krebs-Henseleit solution. Measurements of [(3)H]inositol phosphate, NO synthase (NOS) activity, [(3)H]quinuclidinyl benzilate ([(3)H]QNB) binding and bladder morphology were also performed.

KEY RESULTS

Long-term L-NAME treatment significantly increased carbachol-induced DSM contractile responses after 15 and 30 days; relaxing responses to the beta(3)-adrenoceptor agonist BRL 37-344 were significantly reduced at 30 days. Constitutive NOS activity in bladder was reduced by 86% after 7 days and maintained up to 30 days of L-NAME treatment. Carbachol increased sixfold the [(3)H]inositol phosphate in bladder tissue from rats treated with L-NAME. [(3)H]QNB was bound with an apparent K(D) twofold higher in bladder membranes after L-NAME treatment compared with that in control. No morphological alterations in DSM were found.

CONCLUSIONS AND IMPLICATIONS

Long-term NO deficiency increased rat DSM contractile responses to a muscarinic agonist, accompanied by significantly enhanced K(D) values for muscarinic receptors and [(3)H]inositol phosphate accumulation in bladder. This supersensitivity for muscarinic agonists along with reductions of beta(3)-adrenoceptor-mediated relaxations indicated that overactive DSM resulted from chronic NO deficiency.

Effect of low-level laser (Ga-Al-As 655 nm) on skeletal muscle fatigue induced by electrical stimulation in rats

We investigated whether low-level laser therapy (LLLT) can reduce muscular fatigue during tetanic contractions in rats. Thirty-two male Wistar rats were divided into four groups receiving either one of three different LLLT doses (0.5, 1.0, and 2.5 J/cm2) or a no-treatment control group. Electrical stimulation was used to induce six tetanic muscle contractions in the tibial anterior muscle. Contractions were stopped when the muscle force fell to 50% of the initial value for each contraction (T50%). There was no significant difference between the 2.5 J/cm2 laser-irradiated group and the control group in mean T50% values. Laser-irradiated groups (0.5 and 1.0 J/cm2) had significantly longer T50% values than the control group. The relative peak force for the sixth contraction in the laser-irradiated groups were significantly higher at 92.2% (SD 12.6) for 0.5 J/cm2, 83.2% (SD 20.5) for 1.0 J/cm2, and 82.9% (SD 18.3) for 2.5 J/cm2 than for the control group [50% (SD 15)]. Laser groups receiving 0.5 and 1.0 J/cm2 showed significant increases in mean performed work compared with both the control group and their first contraction values. Muscle damage was indirectly measured by creatine kinase levels in plasma. A distinct dose-response pattern was found in which 1.0 and 2.5 J/cm2 LLLT groups had significantly lower creatine kinase levels than the 0.5 J/cm2 LLLT group and the control group. We conclude that LLLT doses of 0.5 and 1.0 J/cm2 can prevent development of muscular fatigue in rats during repeated tetanic contractions.

Nitric oxide synthase activity and endogenous inhibitors in rats recovered from allergic encephalomyelitis

We have previously reported that in comparison with normal rats, the presence of experimental allergic encephalomyelitis (EAE) leads to decreased endogenous inhibitory activity (EIA) of Ca2+-dependent nitric oxide synthase (NOS) in both brain and serum, and increased expression of protein 3-nitrotyrosine (NT) in brain. In this work we show that animals recovered from the clinical signs of EAE are not different from controls in terms of either brain NOS activity, EIA of NOS, or NT expression. These results suggest that parallel to the reversal of the disease symptoms, a normalization of the production of nitric oxide and related species occurs.

Effects of amphetamine on immune-mediated lung inflammatory response in rats

OBJECTIVE

The present study analyzed the effects of acute amphetamine (AMPH) treatment on immune-mediated lung inflammatory response in rats.

METHODS

There were four experiments. In the first and second experiments, rats were treated with AMPH (1 mg/kg) or 0.9% NaCl, and locomotor activity (experiment 1) and serum AMPH concentrations (experiment 2) were measured 1 or 12 h after treatment. In the third experiment, rats which were immunized with ovalbumin (OVA) were treated 14 days later with 0.9% NaCl or AMPH (1 mg/kg). Twelve hours after these treatments, all animals were submitted to challenge by 1% OVA inhalation being analyzed afterwards for bronchoalveolar lavage fluid (BAL), peripheral blood and bone marrow cellularity. In the fourth and final experiment, rats were treated and studied as for experiment 3, except that half of the animals within each group were previously treated with metyrapone prior to the OVA challenge.

RESULTS

In the non-immunized rats, AMPH treatment induced an increase in locomotor activity synchronized to high serum AMPH concentrations 1 h after, but not 12 h after treatment. In OVA-challenged rats, AMPH treatment decreased the total number of inflammatory cells, recovered in both BAL and peripheral blood and increased the total number of bone marrow cells. These effects, observed 1 day after OVA challenge, were abrogated by previous metyrapone treatment.

CONCLUSION

AMPH treatment changed HPA-axis responsiveness to the stress condition imposed by the OVA challenge decreasing lung and blood leukocytes cellularity most probably via corticosterone actions on bone marrow activity.

Reduction of inflammation in rats by diazepam: tolerance development

High doses of diazepam (10-20 mg/kg) were shown to reduce the volume of acute carrageenan-induced inflammatory paw edema in rats. This effect was not observed after adrenalectomy or long-term use of similar doses of diazepam. The present experiment was undertaken to analyze the effects of long-term (21 daily injections) treatment with diazepam (10 mg/kg) on both carrageenan-induced paw edema (CIPE) and corticosterone serum levels. For comparison, the effects of a single and acute 10 mg/kg dose of diazepam were also analyzed. Results showed that: 1- long-term diazepam treatment induced no changes in CIPE values and corticosterone serum levels; 2- acute diazepam treatment reduced CIPE values and increased corticosterone serum levels; 3- the plasmatic levels of diazepam measured 1 hour after the single treatment or 1 hour after the last dose of long-term diazepam administration were not different. These results indicate the development of tolerance to diazepam effects on both CIPE and corticosterone serum levels and suggest a relevant role for corticosterone on diazepam-induced inhibition of acute inflammation. Data were discussed in the light of peripheral benzodiazepine receptor site (PBR) activation within adrenal gland cells by diazepam, thereby increasing the serum levels of corticosterone and thus reducing CIPE. Possible actions of diazepam on HPA axis activity and/or on cytokine network were also discussed.

Quantification of nimesulide in human plasma by high-performance liquid chromatography/tandem mass spectrometry. Application to bioequivalence studies

A method based on liquid chromatography with negative ion electrospray ionization and tandem mass spectrometry is described for the determination of nimesulide in human plasma. Liquid-liquid extraction using a mixture of diethyl ether and dichloromethane was employed and celecoxib was used as an internal standard. The chromatographic run time was 4.5 min and the weighted (1/x) calibration curve was linear in the range 10.0-2000 ng x ml(-1). The limit of quantification was 10 ng x ml(-1), the intra-batch precision was 6.3, 2.1 and 2.1% and the intra-batch accuracy was 3.2, 0.3 and 0.1% for 30, 300 and 1200 ng x ml(-1) respectively. The inter-batch precision was 2.3, 2.8 and 2.7% and the accuracy was 3.3, 0.3 and 0.1% for 30, 300 and 1200 ng x ml(-1) respectively. This method was employed in a bioequivalence study of one nimesulide drop formulation (nimesulide 50 mg x ml(-1) drop, Medley S/A Indústria Farmacêutica, Brazil) against one standard nimesulide drop formulation (Nisulid, 50 mg x ml(-1) drop, Astra Médica, Brazil). Twenty-four healthy volunteers (both sexes) took part in the study and received a single oral dose of nimesulide (100 mg, equivalent to 2 ml of either formulation) in an open, randomized, two-period crossover way, with a 2-week washout interval between periods. The 90% confidence interval (CI) for geometric mean ratios between nimesulide and Nisulid were 93.1-109.6% for C(max), 87.7-99.8% for AUC(last) and 88.1-99.7% for AUC(0-infinity). Since the 90% CI for the above-mentioned parameters were included in the 80-125% interval proposed by the US Food and Drug Administration, the two formulations were considered bioequivalent in terms of both rate and extent of absorption.

Selective cyclo-oxygenase-2 inhibitors: cardiovascular and gastrointestinal toxicity

The introduction of selective inhibitors of cyclo-oxygenase-2 to the marketplace has been much anticipated for several years. It would appear that these compounds have lived up to the expectations of having reduced gastrointestinal toxicity and, at least for some indications, of efficacy similar to that of conventional non-steroidal anti-inflammatory drugs. However, there is a growing body of evidence suggesting that cyclo-oxygenase-2 plays a very important role in gastrointestinal mucosal defence, particularly in situations in which the mucosa is damaged or inflamed. Moreover, physiological roles for cyclo-oxygenase-2 both in the renal and cardiovascular systems are becoming better recognized. Inhibition of cyclo-oxygenase-2 can lead to peripheral oedema and hypertension, and may promote thrombosis. Indeed, there is recent evidence of increased rates of myocardial infarction in arthritis patients taking a selective cyclo-oxygenase-2 inhibitor. Use of low-dose aspirin concurrently with use of a selective cyclo-oxygenase-2 inhibitor may provide some degree of protection against the potential cardiovascular toxicity of the latter but both laboratory and clinical studies suggest that the concomitant use of these two types of drugs results in gastrointestinal ulceration comparable to what is seen with conventional non-steroidal anti-inflammatory drugs. These recent results suggest that care must be exercised in the use of selective cyclo-oxygenase-2 inhibitors by individuals who are at increased risk of myocardial infarction and stroke, and the use of low-dose aspirin by these patients may place them at increased risk of gastrointestinal complications.

Bothrops asper and Bothrops jararaca snake venoms trigger microbicidal functions of peritoneal leukocytes in vivo

Venoms from snakes of the genus Bothrops cause pronounced local effects in the victims. These alterations result not only from the direct toxic action of venom components, but also from the prominent inflammatory reaction associated with these envenomations. In this study we investigated the ability of Bothrops asper (BaV) and Bothrops jararaca (BjV) venoms to induce cellular influx and microbicidal functions in leukocytes. BaV and BjV (5 microg/animal) caused a long lasting infiltration of leukocytes (3-48 h) when injected into mouse peritoneal cavity. Both venoms increased phagocytosis and production of hydrogen peroxide (H2O2) by polymorphonuclear (PMN) and mononuclear (MN) peritoneal leukocytes. In addition, nitric oxide (NO) production by macrophages was also enhanced after the venom injections. This effect was inhibited by treating animals with L-NAME and aminoguanidine, thus suggesting the induction of iNOS synthesis by the venoms. Western blot analysis confirmed the expression of iNOS in macrophages. BaV and BjV injection led to increased levels of IFN-gamma at the site of inflammation. Since IFN-gamma is an effective inducer of iNOS expression, an indirect action of the venoms on iNOS expression can be proposed. A marked formation of nitrotyrosine-containing proteins was also observed in macrophage homogenates. Based on these results, we suggest that reactive oxygen and nitrogen-derived species are involved in the pathogenesis of the local tissue damage characteristic of Bothrops sp envenomations.

Antihypertensive properties of a nitric oxide-releasing naproxen derivative in two-kidney, one-clip rats

Nonsteroidal anti-inflammatory drugs have been reported to exacerbate hypertension. In this study, we tested the hypothesis that a nitric oxide-releasing derivative of naproxen would ameliorate hypertension in the rat. Hypertension was induced by partially occluding one renal artery (the "2K,1C" model), and 2 wk later the rats started receiving naproxen, the nitric oxide-releasing derivative HCT-3012, or vehicle each day for 2 wk. Naproxen significantly exacerbated the hypertension. HCT-3012 significantly reduced blood pressure relative to both the naproxen- and vehicle-treated groups. Both naproxen and HCT-3012 markedly suppressed whole blood thromboxane B(2) synthesis. In studies of anesthetized rats, naproxen significantly enhanced the late hypertensive response to endothelin-1 and significantly blunted the early hypotensive response. In contrast, HCT-3102 did not affect either response to endothelin-1. In vitro, HCT-3012 significantly reduced the responsiveness of aortic rings to the contractile effects of phenylephrine. These studies suggest that HCT-3012 reduces blood pressure in hypertensive rats, not simply through the vasodilatory actions of the nitric oxide it releases, but through alterations in the responsiveness of the vasculature to endogenous pressor agents.

Plasma hydroxy-metronidazole/metronidazole ratio can detect early changes in hepatic function in ethanol-induced liver injury

AIMS

To evaluate the usefulness of plasma hydroxy-metronidazole/metronidazole (OH-MET/MET) ratios as a dynamic liver function test in ethanol abusers with or without liver cirrhosis.

METHODS

Metronidazole was administered intravenously for 20 min to healthy volunteers, and to patients with alcohol-induced, non-cirrhotic hepatopathy and liver cirrhosis. Plasma concentrations of metronidazole and hydroxy-metronidazole were measured by high performance liquid chromatography in samples collected 5, 10, 20 and 30 min after the metronidazole infusion.

RESULTS

Patients with non-cirrhotic alcoholic hepatopathy had significantly elevated aminotransferase levels compared to healthy volunteers and Child A patients. Child-Pugh C patients had significantly prolonged prothrombin times when compared to healthy volunteers and patients with non-cirrhotic hepatopathy. Metronidazole metabolism, as measured by the OH-MET/MET ratio following the intravenous administration of 500 mg of the drug, was significantly impaired in all ethanol-abusing individuals, including patients with non-cirrhotic alcoholic hepatopathy.

CONCLUSIONS

Metronidazole metabolism was impaired in ethanol abusers, even in the absence of liver cirrhosis, indicating that ethanol was capable of affecting liver function in the early stages of alcohol-induced liver disease.

Enhanced anti-inflammatory effects of a nitric oxide-releasing derivative of mesalamine in rats

BACKGROUND & AIMS

Nitric oxide (NO)-releasing derivatives of cyclooxygenase inhibitors exhibit enhanced anti-inflammatory activity and greatly reduced gastrointestinal toxicity. We evaluated whether a similar derivatization of mesalamine (5-aminosalicylic acid) would improve its anti-inflammatory activity.

METHODS

Effects of an NO-releasing derivative of mesalamine (NCX-456; NO-mesalamine) were compared with those of mesalamine itself and 2 other NO donors in a rat model of colitis. These drugs were compared for their ability to inhibit leukocyte adherence to the vascular endothelium in vivo, interleukin (IL)-1beta and interferon (IFN)-gamma release in vitro (splenocytes and colon), and messenger RNA expression in the inflamed colon.

RESULTS

NO-mesalamine was significantly more effective than mesalamine in reducing the severity of colitis (damage and granulocyte infiltration). Unlike mesalamine, NO-mesalamine significantly suppressed leukocyte adherence to the vascular endothelium in vivo. NO-mesalamine inhibited IL-1beta and IFN-gamma release and caspase 1 activity in splenocytes; such effects were not found in the inflamed colon.

CONCLUSIONS

These studies show that an NO-releasing derivative of mesalamine has significantly enhanced anti-inflammatory activity, including improved efficacy in a rat model of colitis. The improved efficacy of this derivative is most likely caused by its enhanced ability to suppress leukocyte infiltration and possibly to scavenge peroxynitrite.

Nitric Oxide. V. therapeutic potential of nitric oxide donors and inhibitors

Nitric oxide is a crucial mediator of gastrointestinal mucosal defense, but, paradoxically, it also contributes to mucosal injury in several situations. Inhibitors of nitric oxide synthesis and compounds that release nitric oxide have been useful pharmacological tools for evaluating the role of nitric oxide in gastrointestinal physiology and pathophysiology. Newer inhibitors with selectivity for one of the isoforms of nitric oxide synthase are even more powerful tools and may have utility as therapeutic agents. Also, agents that can scavenge nitric oxide or peroxynitrite are promising as drugs to prevent nitric oxide-associated tissue injury. Compounds that release nitric oxide in small amounts over a prolonged period of time may also be very useful for prevention of gastrointestinal injury associated with shock and with the use of drugs that have ulcerogenic effects. Indeed, the coupling of a nitric oxide-releasing moiety to nonsteroidal anti-inflammatory drugs has proven to be a valid means of substantially reducing the gastrointestinal toxicity of these drugs without decreasing their efficacy.

Nitric oxide-releasing NSAIDs: GI-safe antithrombotics

Aspirin is increasingly being used for long-term prophylaxis of myocardial infarction and stroke, but its use is limited by toxicity in the gastrointestinal tract. Even very low doses of aspirin can markedly increase the risk of gastrointestinal bleeding and ulceration. While proven effective in prophylaxis of stroke and myocardial infarction, the efficacy of aspirin is limited. Addition of a nitric oxide-releasing moiety to several non-steroidal anti-inflammatory drugs results in a profound reduction in their toxicity in the gastrointestinal tract and kidney. A similar derivatization of aspirin has recently been shown to result in a more potent, gastrointestinal-sparing antithrombotic drug. Two such compounds (NCX-4215 and NCX-4016; NicOx SA) have undergone detailed evaluation thus far. In each case, the NO-aspirin has shown improved anti-aggregatory activity while not inducing detectable gastric damage. The compounds have also been shown to exert protective effects in the gastrointestinal tract exposed to other injurious agents. The NO-aspirin derivatives significantly inhibit leukocyte adherence to the vascular endothelium, which may contribute to their anti-thrombotic activity. NO-releasing derivatives of aspirin and naproxen also exhibit beneficial effects in experimental hypertension, which would also contribute to improved anti-thrombotic activity. NO-releasing derivatives of NSAIDs offer great potential as gastrointestinal-sparing anti-thrombotic drugs.

Plasma hydroxy metronidazole/metronidazole ratio in anti-HCV carriers with and without apparent liver disease

AIMS

To evaluate plasma hydroxy-metronidazole/metronidazole ratio as a dynamic liver function test in HCV-infected individuals with/without liver disease, in the absence of liver cirrhosis.

METHODS

Metronidazole was administered intravenously in healthy volunteers, asymptomatic anti-HCV-positive blood donors, and in chronic hepatitis C patients. Serology to HCV was determined by a second generation assay and confirmed by gelatin particle agglutination test using recombinant antigens C22-3 and C200. Plasma concentration of metronidazole and hydroxy-metronidazole was measured by high performance liquid chromatography in samples collected 5, 10, 20 and 30 min following the end of metronidazole infusion.

RESULTS

Chronic hepatitis C patients had abnormal liver enzymes, while healthy volunteers and anti-HCV-positive blood donors had normal liver biochemistry tests. Plasma metronidazole concentration was similar in all groups studied. Plasma hydroxy-metronidazole/metronidazole ratio was significantly reduced in HCV-infected subjects, an effect observed 10 min after the end of drug infusion.

CONCLUSIONS

Metronidazole clearance is impaired in anti-HCV-positive blood donors and chronic hepatitis C patients, indicating that HCV is capable of affecting liver function at early stages of the disease. The metronidazole clearance test can detect impaired liver function in HCV-infected individuals even in the absence of liver cirrhosis.

Effect of a nitric oxide-releasing naproxen derivative on hypertension and gastric damage induced by chronic nitric oxide inhibition in the rat

NSAIDs can elevate blood pressure through mechanisms such as renal vasoconstriction and sodium retention. These effects are particularly evident in hypertensive individuals. Nitric oxide-releasing NSAID derivatives have been shown to have greatly reduced toxicity in the gastrointestinal tract and kidney. We therefore evaluated the effects of a 4 week treatment with either naproxen or its nitric oxide-releasing derivative (NO-naproxen) on systemic arterial blood pressure and gastric damage in rats in which hypertension was induced by L-NAME. Rats received either L-NAME dissolved in the drinking water (400 mg/L) or tap water (control). Vehicle, naproxen (10 mg/kg) or an equimolar dose of NO-naproxen (14.5 mg/kg) were administered orally each day. After 4 weeks, blood pressure was measured, blood samples were taken for measurement of thromboxane synthesis, and gastric damage was evaluated by blind, macroscopic scoring. Both naproxen and NO-naproxen inhibited systemic cyclooxygenase activity by >90%. NO-naproxen-treated rats exhibited no significant gastric damage. The gastric damage produced by L-NAME alone was potentiated by naproxen but prevented by NO-naproxen. L-NAME treatment significantly increased blood pressure. In the absence of L-NAME, the naproxen group had significantly higher blood pressure than both the control and NO-naproxen groups. In rats receiving L-NAME, the same conclusions apply, but the concomitant administration of NO-naproxen was able to significantly reduce the blood pressure compared to L-NAME alone. Based on these results, we conclude that NO-naproxen may represent a safer alternative to standard NSAIDs in the treatment of inflammatory conditions in hypertensive patients.

Effect of Tityus serrulatus scorpion venom on the rabbit isolated corpus cavernosum and the involvement of NANC nitrergic nerve fibres

1. The effect of Tityus serrulatus scorpion venom and its toxin components on the rabbit isolated corpus cavernosum was investigated by use of a bioassay cascade. 2. Tityus serrulatus venom (3-100 microg), acetylcholine (ACh; 0.3-30 nmol) and glyceryl trinitrate (GTN; 0.5-10 nmol) dose-dependently relaxed rabbit isolated corpus cavernosum preparations precontracted with noradrenaline (3 microM). The selective soluble guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3,-alquinoxalin-1-one] (ODQ; 30 microM) increased the basal tone of the rabbit isolated corpus cavernosum and abolished the relaxations induced by the agents mentioned above. Methylene blue (30 microM) also inhibited the relaxations induced by Tityus serrulatus venom but, in contrast to ODQ, the inhibition was irreversible. 3. The non-selective NO synthase (NOS) inhibitors Nomega-nitro-L-arginine methyl ester (L-NAME; 10 microM) and NG-iminoethyl-L-ornithine (L-NIO; 30 microM) also increased the tone of the rabbit isolated corpus cavernosum and markedly reduced both ACh- and Tityus serrulatus venom-induced relaxations without affecting those evoked by GTN. The inhibitory effect was reversed by infusion of L-arginine (300 microM), but not D-arginine (300 microM). The neuronal NOS inhibitor 1-(2-trifluoromethylphenyl) imidazole (TRIM, 100 microM) did not affect either the tone of the rabbit isolated corpus cavernosum or the relaxations induced by ACh, bradykinin (Bk), Tityus serrulatus venom and GTN. TRIM was approximately 1,000 times less potent than L-NAME in inhibiting rabbit cerebellar NOS in vitro, as measured by the conversion of [3H]-L-arginine to [3H]-L-citrulline. 4. The protease inhibitor aprotinin (Trasylol; 10 microg ml[-1]) and the bradykinin B2 receptor antagonist Hoe 140 (D-Arg-[Hyp3,Thi5,D-Tic7, Oic8]-BK; 50 nM) did not affect the rabbit isolated corpus cavernosum relaxations induced by Tityus serrulatus venom. The ATP-dependent K+ channel antagonist glibenclamide (10 microm) and the Ca2+-activated K+ channel antagonists apamin (0.1 microM) and charybdotoxin (0.1 microM) also failed to affect the venom-induced relaxations. Similarly, the K+ channel blocker tetraethylammonium (TEA; 10 microM) had no effect on the venom-induced relaxations. 5. Capsaicin (3 and 10 nmol) relaxed the rabbit isolated corpus cavernosum in a dose-dependent and non-tachyphylactic manner. Ruthenium red (30 microM), an inhibitor of capsaicin-induced responses, markedly reduced the relaxations caused by capsaicin, but failed to affect those induced by Tityus serrulatus venom. L-NAME (10 microM) had no effect on the capsaicin-induced relaxations of the rabbit isolated corpus cavernosum. 6. The sodium channel blocker tetrodotoxin (TTX; 1 microM) abolished the relaxations of the rabbit isolated corpus cavernosum induced by Tityus serrulatus venom without affecting those evoked by capsaicin, ACh and GTN. Tetrodotoxin (1 microM) also promptly reversed the response to the venom when infused during the relaxation phase. 7. The bioassay cascade of the toxin components purified from Tityus serrulatus venom revealed that only fractions X, XI and XII caused dose-dependent relaxations of the rabbit isolated corpus cavernosum and these were markedly reduced by either TTX (1 microM) or L-NAME (10 microM). 8. Our results indicate that Tityus serrulatus scorpion venom (and the active fractions X, XI and XII) relaxes rabbit corpus cavernosum via the release of NO. This release is specifically triggered by the activation of capsaicin-insensitive cavernosal non-adrenergic non-cholinergic (NANC) fibres, that may possibly be nitrergic neurones. Tityus serrulatus venom may therefore provide an important tool for understanding further the mechanism of NANC nitrergic nerve activation.

Comparative bioavailability of two atenolol tablet formulations in healthy male volunteers after a single dose administration

The bioavailability of 2 atenolol tablet formulations (Angipress from Laboratórios Biosintética, and Atenol from Wellcome ICI Laboratory, Brazil) were compared in 18 healthy male volunteers who received a single 50 mg dose of each atenolol formulation. The study was conducted following an open randomized 2-period crossover design with a 14-day washout interval between doses. Plasma samples were obtained over a 24-hour interval and atenolol concentrations were determined by HPLC with fluorimetric detection. From the plasma atenolol concentration vs time curves the following pharmacokinetic parameters were obtained: AUC(zero-24) (area under the concentration vs time curves from 0-24 h), ke (terminal elimination constant), t1/2 (terminal first order elimination half-life), AUC (area under the concentration vs time curves extrapolated to infinity), Cmax (maximum achieved concentration), Tmax (time to achieve Cmax) and Cmax/AUC. All these variables were analyzed using both parametric and nonparametric statistics. Geometric mean Angipress/Atenol individual percent ratios were 99.6% for AUC(zero-24), 99.7% for AUC, 98.0% for Cmax, 102.8% for t1/2, 97.2% for ke and 97.8% for Cmax/AUC, with all their 90% confidence intervals within the bioequivalence range 80-125%, thus showing similar patterns of absorption and disposition. Arithmetic mean for individual Tmax differences was 0.8 h, and the 90% confidence interval did not include the zero value. Based on these results and in accordance with the European Union and the US Food and Drug Administration bioequivalence requirements we conclude that both atenolol formulations are bioequivalent for both the extent and the rate of absorption.

Acute inhibition of nitric oxide synthesis induces anxiolysis in the plus maze test

The involvement of nitric oxide (NO) in anxiety was investigated in rats, using the elevated plus maze test. Acute, but not chronic, systemic treatment with N omega-nitro-L-arginine methyl ester (L-NAME, 10 and 60 mg.kg-1), an inhibitor of NO synthase, increased the time spent by the rats in the open arms. Both the acute and chronic treatments with L-NAME inhibited NO synthase in endothelial cells and in the central nervous system, as shown by the increase in mean arterial pressure and decreased NO synthase activity in brain tissue. Chronic treatment with L-NAME also decreased the serum nitrate levels. The anxiolysis induced by acute L-NAME treatment is unlikely to be due to hypertension, since two-kidney one-clip hypertension in non-L-NAME-treated rats failed to significantly change exploratory behaviour in the elevated plus maze. These results indicate that acute inhibition of NO synthesis decreases anxiety in rats.

Nitric oxide synthase inhibitor influences prostaglandin and interleukin-1 production in experimental arthritic joints

OBJECTIVE

To assess involvement of nitric oxide (NO) in the increase in eicosanoid and interleukin- 1 (IL-1) levels in the synovial fluid during antigen-induced arthritis (AIA) in rabbits treated with a competitive inhibitor of NO synthesis.

SUBJECTS

Thirteen New Zealand White rabbits were sensitized with 5 mg of methylated bovine serum albumin (mBSA). Arthritis was induced in the knee joint by injecting 0.5 ml of a sterile solution of mBSA (2 mg/ml) into the intra-articular cavity.

TREATMENT

Prior to the induction of arthritis, the animals received N-Omega-Nitro-L-Arginine Methyl Ester (LNAME) or N-Omega-Nitro-D-Arginine Methyl Ester (DNAME) for 2 weeks, both at a dose of 20 mg/kg/day mixed with drinking water.

METHODS

Leukocyte efflux (total and differential white cell count), vascular permeability (Evans's blue method), synovial PMN cell infiltrate, and total nitrite (NO2.)/nitrate (NO3.) (HPLC), PGE2, TxB2, LTB4 (radioimmunoassay), and IL-1 beta (ELISA) levels were quantified in the synovial fluid.

RESULTS

LNAME but not DNAME significantly suppressed leukocyte efflux and protein leakage into the articular cavity as well as synovial PMN cell infiltrate. Total NO2./NO3., PGE2 and IL-1 beta levels were significantly reduced in the synovial fluid of LNAME treated animals. TxB2 and LTB4 were not affected by LNAME treatment.

CONCLUSION

These data clearly show NO involvement in the IL-1-induced PGE2 production in the synovial fluid of antigen-induced arthritis in rabbits.

Short-term sucralfate administration alters potassium diclofenac absorption in healthy male volunteers

AIMS

Since patients who regularly take NSAIDS may use sucralfate because of its cytoprotective properties, we examined the influence of this compound on the pharmacokinetics of diclofenac.

METHODS

Potassium diclofenac (105 mg) was administered orally to eighteen healthy male volunteers with or without a 5-day pre-treatment with sucralfate (2000 mg twice daily). Blood samples were collected at intervals post-dose and serum concentrations of diclofenac were determined by reverse-phase h.p.l.c.

RESULTS

Pre-treatment with sucralfate significantly decreased both the AUC(0,8 h) [2265 ng h ml-1 (geometric mean) (range 1815-2827) vs 1821 ng h ml-1 (1295-2562)] and the Cmax [1135 ng ml-1 (geometric mean) (range 898-1436) 701 ng ml-1 (501-981)] with no significant delay in absorption [tmax 1.0 h (median) (range 0.5-2.0) vs 1.0 h (0.5-4.0)].

CONCLUSIONS

The short-term treatment of healthy male volunteers with sucralfate decreases potassium diclofenac bioavailability. These findings suggest that either an appropriate increase in the diclofenac intake or the use of another gastric mucosa protector must be adopted.

In vivo inhibition of nitric oxide synthesis does not depend on renin-angiotensin system activation

The role of the renin-angiotensin system in the haemodynamic changes induced by acute administration of N omega-nitro-L-arginine methyl ester in anaesthetised dogs was investigated. The left femoral artery and vein were cannulated for blood pressure measurement and drug administration, respectively. A Swan-Ganz catheter was introduced through the right femoral vein and advanced to the pulmonary artery. Pulmonary arterial pressure, right atrial pressure and cardiac output were also determined. N omega-Nitro-L-arginine methyl ester (0.01-10.0 mg/kg) was administered alone (control animals, n = 18) or in the presence of the angiotensin-converting enzyme inhibitors, captopril (2 mg/kg, n = 9) or enalapril (2 mg/kg, n = 7) or of the bradykinin B2 receptor antagonist D-[Arg-Hyp3, Thi5, D-Tic7, Oic8]bradykinin (Hoe 140, 0.1 mg/kg, n = 6). Cerebellum nitric oxide synthase and serum angiotensin-converting enzyme activities were also measured. N omega-Nitro-L-arginine methyl ester induced dose-dependent increases in blood pressure and systemic vascular resistance and decreases in heart rate and cardiac output. Nitric oxide synthase activity was inhibited 58% by N omega-nitro-L-arginine methyl ester (from 3.37 +/- 0.30 to 1.40 +/- 0.24 pmol/min per mg protein, P < 0.05, n = 5). Both enalapril and captopril potentiated the cardiovascular changes induced by bradykinin (300 ng/kg, bolus). Moreover, enalapril inhibited angiotensin-converting enzyme activity from 12.8 +/- 1.2 to 1.1 +/- 0.2 nmol/ml per min (P < 0.05, n = 6). Under these conditions, N omega-nitro-L-arginine methyl ester administration elicited the same haemodynamic changes as those observed in non-treated animals, except for preventing the decrease in systolic index. Hoe 140 had no effect on the cardiovascular responses to N omega-nitro-L-arginine methyl ester. These results indicate that the renin-angiotensin system does not modulate these haemodynamic changes.

Simultaneous determination of nitrite and nitrate anions in plasma, urine and cell culture supernatants by high-performance liquid chromatography with post-column reactions

A high-performance liquid chromatographic method for the determination of nitrite and nitrate anions derived from nitric oxide in biological fluids is presented. After separation on a strong anion-exchange column (Spherisorb SAX, 250 x 4.6 mm I.D., 5 microns), two on-line post-column reactions occur. The first involves nitrate reduction to nitrite on a copper-plated cadmium-filled column. In the second, the diazotization-coupling reaction between nitrite and the Griess reagent (0.05% naphtylethylendiamine dihydrochloride plus 0.5% sulphanilamide in 5% phosphoric acid) takes place, and the absorbance of the chromophore is read at 540 nm. This methodology was applied to biological fluids. Before injection into the chromatographic system, the samples were diluted and submitted to suitable clean-up procedures (urine and cell culture supernatant samples are passed through C18 cartridges, and serum samples were deproteinized by ultrafiltration through membranes with a molecular mass cut-off of 3000). The method has a sensitivity of 30 pmol for both anions, as little as 0.05-0.1 ml sample volume is required and linearity is observed up to 60 nmol for each anion.

Short-term sucralfate administration does not alter the absorption of metronidazole in healthy male volunteers

BACKGROUND

An oral triple therapy using sucralfate instead of a bismuth to eradicate Helicobacter pylori has yielded worse results than those obtained with conventional oral triple therapies. To date, the effect of sucralfate on the pharmacokinetics of nitroimidazolic compounds used in triple therapy such as with metronidazole is unknown. The aim of this study was to investigate the effect of a 5-day administration period of sucralfate (2 g b.i.d.) on metronidazole pharmacokinetics.

METHODS

Fourteen healthy male volunteers were selected. The study had an open randomized 2-period crossover design with a 14-day washout period between the phases. The plasma concentration of metronidazole and its hydroxy-metabolite were measured by reverse-phase HPLC with ultraviolet detection.

RESULTS

No statistically significant difference was observed in any of the pharmacokinetic parameters studied in the absence and presence of sucralfate.

CONCLUSION

Our results clearly indicate that short-term treatment with sucralfate in healthy volunteers does not alter the extent or the rate of metronidazole absorption, and does not affect metronidazole clearance.

Bioequivalence study of two enalapril maleate tablet formulations in healthy male volunteers. Pharmacokinetic versus pharmacodynamic approach

OBJECTIVE

Two different conventional release enalapril maleate tablet formulations were evaluated for their relative bioavailability (Eupressin tablets 10 mg, Biosintética as the test formulation vs Renitec tablets 10 mg Merck Sharp & Dhome, as the reference formulation). A single 20 mg oral dose of each preparation was administered to 18 healthy male adult volunteers and their bioequivalence was assessed by comparing the serum enalaprilat and total enalapril (enalaprilat plus enalapril maleate) concentration-time curves. Angiotensin converting enzyme (ACE) activity was also quantified in each serum sample.

RESULTS

The pharmacokinetic parameters obtained for each formation were the area under the time-concentration curve from 0 to 24 h (AUC[0-24]), maximum concentration Cmax and the time at which it occurred (tmax). When serum enalaprilat concentration-time curves were employed to assess bioequivalence, the formulations were bioequivalent in the extent but not in the rate of absorption. However, no difference in either the extent or the rate of absorption were observed when serum total enalapril vs time curves were analysed. ACE activity-time curves were similar for both formulations and showed that ACE was 90% inhibited for 3-5 h after enalapril administration, and till approximately 50% after 24 h. At that time, circulating enalaprilat and total enalapril levels were less than the tenth of Cmax.

CONCLUSION

The results show that complete bioequivalence of the two formulations can be concluded from serum total enalapril concentration data, and that serum ACE activity is not a suitable pharmacodynamic variable for assessing bioequivalence.

Effect of therapy with recombinant human interferon-gamma on the release of nitric oxide by neutrophils and mononuclear cells from patients with chronic granulomatous disease

The aim of this study was to investigate the effect of recombinant human interferon-gamma (rHuIFN-gamma) therapy on the release of nitric oxide (NO) by neutrophils (NEU) and mononuclear cells (MON) from patients with chronic granulomatous disease (CGD). Five patients with this rare disease received rHuIFN-gamma (50 micrograms/m2 of body surface, given by subcutaneous injection three times a week) for 6 months. Clinical and laboratory evaluations were performed before and after 1 and 6 months of rHuIFN-gamma therapy. Nitric oxide release by NEU and MON was assessed by the ability of these cells to inhibit thrombin-induced washed platelet aggregation. The nitrite (NO2-) and nitrate (NO3-) levels in the supernatant of cultured NEU and MON, as well as in plasma and urine (24 h diuresis), were quantified by high-performance liquid chromatography (HPLC). Conventional immunologic tests for assessing phagocyte and lymphocyte functions and humoral immunity were also performed. Therapy with rHuIFN-gamma for 6 months did not enhance NO synthesis by NEU or MON from the patients with CGD. The urinary but not plasma levels of NO2- and NO3- were elevated after rHuIFN-gamma therapy. Phagocyte and lymphocyte functions as well as humoral immunity were not affected by rHuIFN-gamma therapy. Although few patients were available for the study, we conclude that therapy with rHuIFN-gamma for 6 months did not enhance the synthesis of NO by NEU and MON in CGD patients. Whether the increased excretion of NO2- and NO3- in the urine of CGD patients after rHUIFN-gamma therapy reflects an induction of NO-synthase in cells other than leukocytes remains to be investigated.

The release of nitric oxide and superoxide anion by neutrophils and mononuclear cells from patients with sickle cell anaemia

The aim of this work was to investigate the release of nitric oxide and superoxide by neutrophils and mononuclear cells from patients with sickle cell anaemia. Nitric oxide release was assayed by the ability of leucocytes to inhibit thrombin-induced washed platelet aggregation. Superoxide release was assessed by a cytochrome c reduction assay. Neutrophils from sickle cell anaemia patients released nitric oxide in a similar manner to those from healthy controls, because inhibition of platelet aggregation by neutrophils from sickle cell anaemia or from healthy controls was blocked by the inhibitor of nitric oxide synthesis N(omega)-nitro-L-arginine methyl ester (300 microM), but not by N(omega)-nitro-D-arginine methyl ester (300 microM) and was reversed by L-arginine (1 mM). Additionally, a similar number of neutrophils from sickle cell anaemia patients and from healthy controls was required to inhibit platelet aggregation. Mononuclear cells from sickle cell anaemia patients inhibited platelet aggregation only in the presence of superoxide dismutase (60 U ml(-1)). Phorbol 12-myristate 13-acetate (PMA, 30 nM)- or zymosan (100 particles/cell)-induced release of superoxide by mononuclear cells from sickle cell anaemia patients was significantly higher than that observed in mononuclear cells from healthy controls (P<0.001 and P<0.01 respectively, Mann-Whitney test). The levels of superoxide released by neutrophils from sickle cell anaemia patients were similar to those from healthy controls. We conclude that mononuclear cells from sickle cell anaemia patients release more superoxide than those from healthy controls, when stimulated with PMA or zymosan in vitro. Considering that superoxide inactivates nitric oxide, that nitric oxide is an important endogenous vasodilator, and that superoxide produces oxidant damage, this greater production of superoxide by mononuclear cells from sickle cell anaemia patients may represent an additional risk factor for the obstruction of the microcirculation and tissue damage in these patients.

Plasma hydroxy-metronidazole/metronidazole ratio in patients with liver disease and in healthy volunteers

Metronidazole pharmacokinetics were studied in patients with different degrees of liver cirrhosis, classified according to the Child-Pugh algorithm (A, B or C, as liver disease severity increases) and in schistosomic patients. Metronidazole (500 mg) was administered i.v. as a slow infusion over 20 min, and blood samples were collected at set intervals after the end of the infusion. The plasma concentrations of metronidazole and its main metabolite hydroxy-metronidazole were quantified by reversed-phase h.p.l.c. with u.v. detection. The metronidazole and hydroxy-metronidazole areas under the curve from 0 to 24 h (AUC0,24h), the metronidazole terminal elimination half-life (t1/2), the total clearance (CL), the metronidazole volume of distribution (V) values and the hydroxy-metronidazole/metronidazole concentration ratios as a function of time were calculated for each group. Comparison of the metronidazole AUC0,24h, t1/2 and CL values revealed that metronidazole metabolism is progressively impaired as the severity of liver disease increases. There were no variations in these parameters between the schistosomic and Child-Pugh A groups. In addition, there were no differences in the V and hydroxy-metronidazole AUC0,24h among the various groups studied. However, metronidazole metabolism was delayed in patients with hepatic disease, as illustrated by the hydroxy-metronidazole/metronidazole ratio 10 min after the end of metronidazole infusion. These results indicate that the clinical assessment of liver disease is paralleled by an impairment of metronidazole metabolism. Of the studied variables, we propose the hydroxy-metronidazole/metronidazole ratio 10 min after metronidazole infusion as a suitable and practical index for liver function evaluation.

Nifedipine prevents renal injury in rats with chronic nitric oxide inhibition

Chronic nitric oxide inhibition promotes hypertension, renal dysfunction, and renal injury by unclear mechanisms. We examined the effects in this model of concomitant treatment with the calcium channel blocker nifedipine. Six adult male Munich-Wistar rats received 0.025% nifedipine in chow. Six untreated rats served as controls. Fifteen days later, renal function was evaluated in anesthetized rats before and after a bolus injection of the nitric oxide inhibitor N omega-nitro-L-arginine methyl ester at 3 mg/kg IV. Renal vasoconstriction and systemic hypertension induced by the inhibitor were similar in untreated and nifedipine-treated rats. In a second protocol, eight rats received the nitric oxide inhibitor in their drinking water at 2.6 mmol/L. Eight additional rats also received nifedipine as above. At day 15, rats given the nitric oxide inhibitor exhibited systemic hypertension and renal vasoconstriction. Simultaneous nifedipine lowered blood pressure slightly without ameliorating renal hemodynamics. Tail-cuff pressure rose continuously in rats receiving the nitric oxide blocker, reaching 171 +/- 7 mm Hg at 30 days, but remained at 143 +/- 3 mm Hg in rats also given nifedipine. At this stage, rats treated with the nitric oxide inhibitor exhibited extremely variable plasma renin activity, tuft collapse in 10.1 +/- 2.2% of the glomeruli, and renal interstitial fibrosis. Simultaneous nifedipine treatment normalized the dispersion of plasma renin levels, while preventing renal morphological abnormalities. These results suggest that in the chronic nitric oxide inhibition model, sustained operation of voltage-sensitive calcium channels is not essential for renal vasoconstriction but contributes to systemic hypertension and plays a pivotal role in the development of renal structural injury.

Comparative bioavailability of single doses of tablet formulations of cetirizine dihydrochloride in healthy male volunteers

The bioavailability of two tablet formulations of cetirizine (Zetir from Abbott and Zyrtek from UCB) were compared in 14 healthy male volunteers who received a single dose of 10 mg of cetirizine dihydrochloride in an open randomized two-period crossover design with a 7-day washout period between doses. Plasma samples were obtained over a 24 h interval and cetirizine concentrations were determined by HPLC with ultraviolet detection. From the plasma cetirizine concentration vs. time curves, AUC(0-24) (area under the concentration vs. time curves from 0 to 24 h), Cmax (maximum achieved concentration), Tmax (time to achieve Cmax), Ke (terminal first order elimination constant), elimination half-life (t1/2) and AUC(0-infinity) (area under the concentration vs. time curves extrapolated to infinity) were obtained. The two cetirizine dihydrochloride tablet brands did not show statistically significant differences in bioavailability as assessed by analysis of AUC(0-24), AUC(0-infinity), Cmax, Tmax, Ke and t1/2 values. Based on these results and on the U.S. Food and Drug Administration requirements [1985, 1993], we conclude that both formulations are bioequivalent.

Effect of arginine analogues on rat hind paw oedema and mast cell activation in vitro

Nitro-L-arginine methyl ester (0.15 mumol/paw) significantly reduced both bradykinin- and 5-hydroxytryptamine-induced rat paw oedema. At this dose, L-arginine (L-Arg), D-Arg and nitro-D-arginine methyl ester had no effect on the oedematogenic responses induced by these agents. Nitro-L-arginine methyl ester, nitro-D-arginine methyl ester, L-Arg, D-Arg, L-arginine methyl ester and L-arginine ethyl ester, at the dose of 15 mumol/paw, significantly potentiated both bradykinin- and 5-hydroxytryptamine-induced oedema. This potentiation was not observed in animals treated with both mepyramine and methysergide or in animals chronically treated with compound 48/80. Nitro-L-arginine methyl ester (0.3-3 mM) and L-Arg (0.3-3 mM) released small amounts (< 10%) of histamine from rat peritoneal mast cells when compared to compound 48/80-induced degranulation (> 40%). Histamine release was quantified by radioimmunoassay since nitro-L-arginine methyl ester and L-Arg interfere with the fluorometric assay. The potentiation of paw oedema observed with higher doses of all arginine analogues is caused by in vivo mast cell degranulation and is probably due to the cationic charge of these substances.

Measurement of plasma verapamil levels by high-performance liquid chromatography

1. We have developed an alternative procedure for the measurement of verapamil levels in human plasma by reverse-phase high performance liquid chromatography with fluorimetric detection. 2. Prior to assay, plasma is submitted to a double extraction procedure, using first n-heptane in alkaline medium and then an acid phosphate buffer. Flecainide, a compound not related to verapamil, is used as internal standard. Mean recoveries of 70 and 63% were obtained for verapamil and flecainide, respectively. 3. The sensitivity (5 ng/ml), reproducibility (inter-assay %CV = 1.7-8.7; intra-assay %CV = 2-4) and high recovery during sample clean-up make this method useful for the quantitation of verapamil in therapeutic monitoring and pharmacokinetic studies. 4. The method is illustrated with the pharmacokinetic results obtained for 14 healthy male volunteers who received a single 240 mg dose of the commercially available tablets of Dilacoron Retard 240 mg. The mean values for the area under the curve from 0 to 24 h (AUC[0-24]), maximum achieved concentration (Cmax) and time to achieve the maximum concentration (Tmax) were 863 ng h-1 ml-1, 112 ng/ml and 4 h, respectively.

Neutrophils and mononuclear cells from patients with chronic granulomatous disease release nitric oxide

1. Chronic granulomatous disease (CGD) is a group of genetic disorders characterised by recurrent severe suppurative infections due to impaired microbial killing. The principal biochemical defect is an impairment in the production of reactive oxygen intermediates by phagocytes. 2. Nitric oxide (NO) is synthesised from the guanidino nitrogen atom(s) of L-arginine and has recently been proposed to be involved in defence mechanisms. The aim of this study was to investigate the involvement of the oxidative burst in the biosynthesis of NO by neutrophils and mononuclear cells from patients with CGD. 3. NO synthesis was assayed by the ability of neutrophils and mononuclear cells to inhibit thrombin-induced washed platelet aggregation while superoxide anion (O2-) production was measured spectrophotometrically by the superoxide dismutase inhibitable reduction of cytochrome c. 4. Neutrophils and mononuclear cells from patients with CGD released NO. This release was inhibited by nitro-L-arginine methyl ester but could be reversed by L-arginine. Zymosan- and PMA-induced O2- production was less than 10% as compared with healthy controls. 5. These results indicate that O2- production is not essential for NO synthesis in human leucocytes.

Pharmacokinetic profile of two different pharmaceutical forms of theophylline (a slow release tablet and a syrup) after multiple dose administration to healthy human volunteers

Due to the narrow therapeutic range of theophylline, plasma concentrations of this drug are monitored in patients undergoing chronic therapy. Slow-release preparations avoid the fluctuations in plasma levels and improve patient compliance. In this study, we have compared the pharmacokinetic profiles of a theophylline slow-release tablet and a syrup form, when administered in multiple doses to healthy adult volunteers. The classification based upon releasing patterns is confirmed.