Comparison of the in vitro effects of amoxicillin and ampicillin on the polymorphonuclear neutrophil respiratory burst.

OBJECTIVES: The aim was to compare the in vitro effects of amoxicillin and ampicillin on the oxidative metabolism of polymorphonuclear neutrophils (PMNs). METHODS: Superoxide radical anion production by PMNs, stimulated or not by various exogenous stimulants and in contact with increasing antibiotic concentrations, was measured using spectrophotometric methods. RESULTS: Whereas a pro-oxidative action of amoxicillin on PMNs was obtained without exogenous stimulation or with opsonized zymosan (OZ), the O(2)(-) production by PMNs incubated with ampicillin did not increase significantly. CONCLUSIONS: This amoxicillin pro-oxidative effect could be due to the activation of the PMN NADPH oxidase, to its induction by a membrane effect or via the OZ pathway. It probably reinforces amoxicillin intrinsic bactericidal action and might partly explain the severe rashes sometimes occurring with amoxicillin treatment.

Antioxidative effect of Bacteroides thetaiotaomicron extracts: superoxide dismutase identification.

Bacteroides thetaiotaomicron, a bowel anaerobic commensal, seems to release enzymes detoxifying reactive oxygen species according to our recent work. This opportunistic pathogen would be beneficial in the case of an inflammatory process. To explore its role after an oxidative or nutritive stress, six to seven separate experiments were performed. The bacteria were grown on media restricted in growth factors or supplemented with bile. Their viability was checked after surface protein extraction. The extracts underwent 2D electrophoresis. Gel images were statistically analysed to construct "master" gels. Proteins were identified (peptide-mass fingerprinting technique). The effect of each extract on superoxide anions was evaluated (spectrophotometric method). Superoxide dismutase was identified and a major superoxide anion inhibition was shown by extracts obtained after a nutritive and oxidative stress without significant bacterial death. So, a therapeutic antioxidant potential is firmly hoped for. [figure: see text]

Molecular modelling of phthalates - PPARs interactions.

Di(2-ethylhexyl) phthalate (DEHP) is the most widely plasticizer for polyvinyl chloride (PVC) that is used in plastic tubes, in medical and paramedical devices as well as in food storage packaging. The toxicological profile of DEHP has been evaluated in a number of experimental animal models and has been extensively documented. Its toxicity is in part linked to the activation of the peroxisome proliferator-activated receptor alpha (PPAR(alpha)). As a response, an intensive research for a new, biologically inert plasticizer has been initiated. Among the alternative studied, tri(2-ethylhexyl) trimellitate (TEHTM) or trioctyl trimellitate (TOTM) has attracted increasing interest. However, very little information is available on their biological effects. We proceeded to dock TOTM, DEHP and its metabolites in order to identify compounds that are likely to interact with PPAR(alpha) and PPAR(gamma) binding sites. The results obtained hint that TOTM is not able to bind to PPARs and should therefore be safer than DEHP.

Vasoactivity, antioxidant and aphrodisiac properties of Caesalpinia benthamiana roots.

AIMS OF THE STUDY: Caesalpinia benthamiana (=Mezoneuron benthamianum) (Fabaceae) is an African tropical plant whose roots are used in traditional medicine as an aqueous decoction for many purposes, especially for erection impairment but its action mechanism is unknown. The action of Caesalpinia benthamiana on sexual behaviour and some assays on potential modes of action were performed. MATERIALS AND METHODS: The aqueous extract of Caesalpinia benthamiana (AECB) was tested for vasorelaxing properties using isolated rat aortic rings precontracted by phenylephrine. Influence of AECB in the production of endothelial isoform of nitric oxide synthase (eNOS) was measured by quantitative polymerase chain reaction (QPCR) analysis. Scavenging activities versus reactive oxygen species (ROS), such as superoxide anion (O(2).(-)), hydrogen peroxide (H(2)O(2)), and hypochlorous acid (HOCl) were assessed. Action of AECB on the cellular generation of O(2).(-) was also tested in a physiopathology model of oxidative burst using human polymorphonuclear neutrophils stimulated by phorbol myristate acetate. The aphrodisiac properties of AECB administered orally by gavage (50 mg/kg body weight) to male rats were evaluated by observing the sexual behaviour of animals. Finally, a short-term toxicity study was undertaken to establish the therapeutic index of AECB administered orally to rats at high dose (2 g/kg body weight). RESULTS: C. benthamiana roots are rich in phenolic compounds (gallic acid, resveratrol and tannins). The results showed that AECB had significant vasorelaxing properties. The extract also had a strong radical activity against ROS in cell-free and cellular systems and stimulated eNOS mRNA expression. As for the aphrodisiac activity of AECB in male rats, results have shown that sexual parameters are stimulated. Furthermore, after oral administration at high dose, AECB causes no mortality or changes in rats' behaviour. CONCLUSION: AECB enhanced the sexual activity of male rats. This could be partly explained by its vasorelaxant properties, which may be caused by an increase in NO production in vascular bed and a decrease in its destruction.

Vasoactivity and antioxidant properties of Microdesmis keayana roots.

Endothelial isoform of nitric oxide synthase (eNOS) mRNA expression increases in the corpora cavernosum, penile arteries and arterioles during erection. But eNOS expression and nitric oxide (NO), the product of its catalytic action, are inactivated by reactive oxygen species (ROS), especially by superoxide anion. ROS are involved in the impairment of endothelium-dependent relaxation and are responsible for some of the pathologies linked to erectile dysfunction (i.e. hypertension, atherosclerosis, etc.). While investigating Microdesmis keayana J. Léonard (Pandaceae) (syn. Microdesmis puberula Hook.f. ex. Planch.), used in African traditional medicine for erectile dysfunction, the hypotensive and the vasorelaxing properties of the aqueous extract of Microdesmis keayana (AEMK) were, respectively, tested using normotensive rabbits and aorta strips of guinea pigs in an organ bath experience. Interaction of AEMK in endothelial production of eNOS was measured by the quantitative polymerase chain reaction (QPCR) analysis. The scavenging activities versus ROS, such as superoxide anion (O(2)(.-)), hydrogen peroxide (H(2)O(2)), hypochlorous acid (HOCl) and hydroxyl radical (HO.) were evaluated. Action of AEMK on cellular generation of superoxide anion was also tested in a physiopathology model of oxidative burst using human polymorphonuclear neutrophils (PMNs) stimulated by phorbol myristate acetate. The results showed that Microdesmis keayana roots had significant hypotensive and vasorelaxing properties. These properties are due to both antioxidant activities and stimulation of eNOS mRNA expression. Therefore, AEMK stimulated indirectly NO production in the vascular bed.

Effects of a caffeine-free Cola nitida nuts extract on elastase/alpha-1-proteinase inhibitor balance.

In an infection, polymorphonuclear neutrophils (PMN) become activated and they produce oxidizing compounds and elastase in the extracellular medium. Alpha-1-proteinase inhibitor (alpha1PI), a protease inhibitor which is inactivated by oxidants, is the main endogenous inhibitor of elastase helping to limit excessive elastase activity. This study evaluates the ability of a plant extract, Cola nitida nuts, to protect alpha1PI from inactivation by oxidizing compounds as reactive oxygen species. On the one hand, we have evaluated the direct effect of cola nut extract on neutrophil elastase, and on the H(2)O(2) and myeloperoxidase (MPO)-H(2)O(2) system via cell-free systems. Results showed that cola nut extract scavenges H(2)O(2) and therefore protects alpha1PI from HOCl which is produced from the MPO-H(2)O(2) system. Experiments also showed that cola extract has the capacity to limit elastase activity. On the other hand, we have worked on cellular systems including isolated PMN with the aim to study the effect of cola extract on PMN metabolism. PMN were stimulated with PMA, calcium ionophore or fMLP. Each stimulant possesses its own stimulation pathway. According to the inhibitory concentration obtained at 50%, the results on cellular systems led to the conclusion that cola extract can reduce elastase liberation from PMN. It can then be concluded that cola nut extract can protect alpha1PI from inactivation, and has an effect both on elastase liberation and elastase activity. The cola nut extract effect is rather biased towards a reduction in elastase release, thus limiting the injurious effects caused by this enzyme.

In vitro and ex vivo antioxidant activities of labetalol on rabbit neutrophil respiratory burst.

The beta-adrenoreceptor blocker labetalol has demonstrated important antioxidant properties in vitro that inhibit superoxide anion production during normal leukocyte oxidative metabolism. This study investigated the in vitro and ex vivo effects of labetalol on respiratory burst in rabbit neutrophils. The production of superoxide anions was examined in activated purified rabbit neutrophils after intravenous administration of labetalol (4.0 mg/kg of body weight). At a concentration up to 200 mg/L, labetalol did not demonstrate any cytotoxic effects on neutrophils, as determined by enzyme lactate dehydrogenase activity. In the cell-free system, labetalol demonstrated no significant activity, but in formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated rabbit neutrophils, labetalol demonstrated concentration-dependent antioxidant activity. The in vitro 50% inhibitory concentration (IC50) with the fMLP stimulus was 16.5+/-0.21 mg/L in the rabbit neutrophils and 13.2+/-0.16 mg/L in the human neutrophils. In the fMLP-stimulated rabbit polymorphonuclear leukocytes, labetalol demonstrated its peak inhibitory activity (47%) 3 hours after administration. The mechanism by which labetalol acts in the treatment of hypertension may occur from an interaction in the signaling pathway of protein kinase C activation. The antioxidant properties demonstrated in this mechanism contribute to the drug's antihypertensive action and thus, may reduce the risk of injuries inflicted by reactive oxygen species involved in the pathogenesis of hypertension.

Pharmacokinetics and dialysability of naltrexone in patients undergoing hemodialysis.

The disposition of naltrexone (NLT) (REVIA), an opioid antagonist intended for patients with impaired renal function and with severe intractable itching refractory to regular antipruritic therapy, was characterized. Hemodialysis effects on both efficacy and elimination of NLT also were assessed. We developed a simple, sensitive and selective reverse-phase high-performance liquid chromatographic (HPLC) method for measuring NLT plasma concentration in hemodialysis patients treated to relieve pruritus. NLT and the internal standard, naloxone (NLX) were extracted from plasma using a solid-phase extraction method with sep-pack C18 cartridge. The method was employed to determine both naltrexone pharmacokinetics and dialysability parameters during 4-h in dialyzed patients with chronic renal impairment. Thus, seven patients (2 men, 5 women) with end-stage renal disease and pruritus on regular hemodialysis were included. They received one tablet of NLT (Revia, 50 mg) orally prior dialysis session. The Cmax at the inlet and at the outlet the dialyzer were higher (255+/-117 ng/mL and 206+/-137 ng/ml respectively) in comparison with healthy subjects (9 - 44 ng/mL). The decrease hepatic first-pass metabolism of NLT consecutive to end-stage renal disease and the renal impairment could explain the increased levels of the drug in plasma. Tmax before and after dialysis plates remain unchanged as healthy subjects (approximately 1h). With regard to dialysability, a high dialyzer extraction ratio averating 30 % was found with a low dialysis clearance of 58.70+/-17 mL/min. The amount removed by dialysis is only 1.27 mg. We concluded that hemodialysis has little effect on NLT blood levels, and consequently on drug pharmacokinetics, when the drug is delivered to dialyzed patients following oral route. Thus, dosage adjustement is not required in the presence of advanced dialysis-dependant renal failure. In patients with end-stage renal disease, hemodialysis does not result in clinically significant alterations in the disposition of NLT. Post-dialysis supplementation is not required. These data suggest that there is no pharmacokinetic basis for modification of the initial dosage, but in view of NLT plasma concentration levels in the patients, a clinician could determine whether dosage adjustment are necessary and, if so, make the required calculations accurately.

Strong variability of di(2-ethylhexyl)phthalate (DEHP) plasmatic rate in infants and children undergoing 12-hour cyclic parenteral nutrition.

BACKGROUND: Medical devices such as perfusion materials in polyvinyl chloride may contain di(2-ethylhexyl)phthalate (DEHP). Several studies have questioned the harmlessness of phthalates, which have been shown to have toxic effects on the reproductive system and general development. This study was designed to assess DEHP exposure in infants and children benefitting from cyclic parenteral nutrition (PN). The results are compared with those obtained from children used as controls and receiving no PN, to estimate the potential risk to this pediatric population, taking into account exposure levels and already published data. METHODS: Plasmatic concentrations of DEHP were assessed by high-performance liquid chromatography from blood samples taken from 22 children at the start and finish of a 12-hour cyclic PN period and compared with those obtained from 20 control children of comparable age and gender. RESULTS: After a 12-hour cyclic PN period, DEHP migration varied widely among the patients. The concentrations were not quantifiable in 4 children at the start of PN. In 1 child, they were quantifiable neither at the start nor at the end of PN. However, for 17 children, DEHP concentrations were quantifiable at the start of PN and were very variable from one child to another. At the end, DEHP concentrations had significantly but variably increased in these children. No trace of DEHP was found in the blood samples from 20 healthy controls. CONCLUSION: Considering published data on phthalate toxicity, it would appear advisable to encourage the use of medical devices that are either phthalate or DEHP free.

Correlation between exposure to phthalates and concentrations of malondialdehyde in infants and children undergoing cyclic parenteral nutrition.

BACKGROUND: Plasticizers such as di(2-ethylhexyl) phthalate (DEHP) are added to polyvinyl chloride (PVC) to confer flexibility. However, DEHP is associated with reproductive disorders in humans. Because of its noncovalent bond to the PVC matrix, this plasticizer tends to leach easily. Infants and children undergoing cyclic, long-term parenteral nutrition (PN) could be particularly at risk of potential toxicity from DEHP due to regular exposure. Malondialdehyde (MDA) is one of the most commonly used markers of free radical activity. The purpose of this study was to investigate how long-term exposure to phthalate affects the plasmatic rate of MDA. METHODS: Studies were performed on 7 randomized infants and children on regular cyclic, long-term PN, and the results were compared with those of 5 nontreated infants. The circulating concentrations of DEHP in children and infants during the PN therapy were measured by high-performance liquid chromatography. The concentrations were assessed before and after the PN session. In the same way, plasma MDA concentrations were measured. RESULTS: The circulating concentrations of DEHP before and after a 10- to 11-hour cyclic PN treatment in 7 infants and children under regular perfusion ranged widely, showing a significant increase after the treatment among all the patients. The same phenomenon observed with the rate of MDA showed that the 2 events are closely dependent. Therefore, long-term exposure to DEHP during cyclic PN raised plasma MDA levels, indicating increased oxidative stress. CONCLUSION: Long-term exposure to DEHP during PN increased free radical activity in vivo.

Antioxidant effects and anti-elastase activity of the calcium antagonist nicardipine on activated human and rabbit neutrophils--a potential antiatherosclerotic property of calcium antagonists?

Activated neutrophils which produce certain proteases, such as elastase and reactive oxygen species (ROS) are involved in oxidative stress and inflammation. In the present study, we have shown that nicardipine, a calcium channel blocker, affects the release of elastase and superoxide anion radicals (O(2-)) in vitro during human and rabbit neutrophil respiratory bursts. The drug inhibited the release of elastase and O(2-) by fMLP (N-formyl-methionylleucin-phenylalaninin), calcium ionophore (A23187) and PMA (phorbol-myristate-acetate)-stimulated human and rabbit neutrophils. Besides the release of elastase, strongly inhibited in the fMLP and A23187 stimulated systems, nicardipine affected elastase and O(2-) in a dose-dependent manner. The corresponding 50% inhibitory concentration (IC(50)) of nicardipine for elastase, released in PMA-stimulated human and rabbit neutrophils, was 15.95 +/- 0.17 microM and 18.06 +/- 0.08 microM, respectively, whereas for O(2-), the IC(50) of nicardipine in PMA, fMLP and A23187-stimulated human and rabbit neutrophils was 55.41 +/- 0.09 microM and 58.43 +/- 0.03 microM, 45.21 +/- 0.13 microM and 37.19 +/- 0.53 microM, 33.54 +/- 0.09 microM and 30.54 +/- 0.29, respectively. The mechanisms underlying the inhibition of elastase and superoxide anion radicals by nicardipine appear related to an inhibiting effect on the mobilisation of cytosolic calcium and on activation of protein kinase C (PKC). These antioxidant and anti-elastasic activities contribute to the properties of nicardipine, as positive side effects of its antihypertensive activity and may be useful to prevent inflammatory disorders (tissue damage, oxidative injury) involved in the pathogenesis of hypertension.