Inhibition of human neutrophil oxidative burst by pyrazolone derivatives

Evaluation of the accuracy of antioxidant competition assays: incorrect assumptions with major impact

The activity of antioxidants is frequently determined in competition assays. In these assays an antioxidant (A) and a detector molecule (D) compete for the reactive species (R). The competitive inhibitory effect of A on the reaction of D with R is a measure of the antioxidant activity of A. In determining the activity of A, it is in general incorrectly assumed that the concentrations of A and D remain equal to the initial concentration. However, the principle of the assay is that some A and D is consumed and consequently the concentrations of A and D will decrease during a competition assay, resulting in a deviation in the observed antioxidant activity. Computer modeling was used to obtain a graphical tool to estimate the extent of the deviation caused by the incorrect assumption that the concentrations of A and D do not decrease. Several competition assays were evaluated using this graphical tool, demonstrating that frequently inaccurate antioxidant activities have been reported. In general, differences between antioxidants are underestimated and the activity of all antioxidants shifts toward the antioxidant activity of D. A strategy is provided to improve the accuracy of a competition assay. To obtain accurate results in a competition assay, the reaction rate constant of the detector molecule with the reactive species should be comparable to that of the antioxidant. In addition, the concentration of the reactive species should be as low as possible.

Antioxidant activity of methanolic extract of Bombax ceiba

The antioxidant activity of a methanolic extract of Bombax ceiba was evaluated using several antioxidant assays, in terms of its: (i) ability to scavenge DPPH (1,1-diphenyl-2-picryl-hydrazyl) and hydroxyl free radicals; (ii) action against lipid peroxidation (in rat liver microsomes and soy bean phosphatidylcholine liposomes), induced by ascorbyl radicals and peroxynitrite; and (iii) effect on myeloperoxidase activity. The cytotoxicity was monitored through the mitochondrial activity in the Vero cell line. The extract showed antioxidant activity in all assays, the EC(50) (microg/ml) for DPPH was 87 and for lipid peroxidation of microsomes and soy bean liposomes induced by ascorbyl radicals were 141 and 105, respectively, and by peroxynitrite were 115 and 77, respectively. The K(0.5) value for myeloperoxidase activity inhibition by the extract was 264 microg/ml. The extract showed very low toxicity toward Vero cells.

Singlet oxygen scavenging activity of non-steroidal anti-inflammatory drugs

It has long been known that singlet oxygen ((1)O2) is generated during inflammatory processes. Once formed in substantial amounts, (1)O2 may have an important role in mediating the destruction of infectious agents during host defense. On the other hand, (1)O2 is capable of damaging almost all biological molecules and is particularly genotoxic, which gives a special relevance to the scavenging of this ROS throughout anti-inflammatory treatments. Considering that the use of non-steroidal anti-inflammatory drugs (NSAIDs) constitutes a first approach in the treatment of persistent inflammatory processes (due to their ability to inhibit cyclooxygenase), a putative scavenging activity of NSAIDs for (1)O2 would also represent a significant component of their therapeutic effect. The aim of the present study was to evaluate the scavenging activity for (1)O2 by several chemical families of NSAIDs. The results suggested that the pyrazole derivatives (dipyrone and aminopyrine) are, by far, the most potent scavengers of (1)O2 (much more potent compared to the other tested NSAIDs), displaying IC(50)-values in the low micromolar range. There was a lack of activity for most of the arylpropionic acid derivatives tested, with only naproxen and indoprofen displaying residual activities, as for the oxazole derivative, oxaprozin. On the other hand, the pyrrole derivatives (tolmetin and ketorolac), the indolacetic acid derivatives (indomethacin, and etodolac), as well as sulindac and its metabolites (sulindac sulfide and sulindac sulfone) displayed scavenging activity in the high micromolar range. Thus, the scavenging effect observed for dipyrone and aminopyrine will almost certainly contribute to their healing effect in the treatment of prolonged or chronic inflammation, while that of the other studied NSAIDs may have a lower contribution, though these assumptions still require further in vivo validation.

Toxicological evaluation of lactose and chitosan delivered by inhalation

These days, inhalation constitutes a promising administration route for many drugs. However, this route exhibits unique limitations, and formulations aimed at pulmonary delivery should include as few as possible additives in order to maintain lung functionality. The purpose of this work was to investigate the safety of lactose and chitosan to the pulmonary tissue when delivered by inhalation. The study was carried out with 18 Wistar rats divided in three groups receiving distilled water, lactose or chitosan. A solution of each excipient was administered by inhalation at a dose of 20 mg. The lungs were excised and processed to determine several biochemical parameters used as toxicity biomarkers. Protein and carbonyl group content, lipid peroxidation, reduced and oxidized glutathione (GSSG), myeloperoxidase (MPO), cooper/zinc and manganese superoxide dismutase, catalase, glutathione S-transferase and glutathione peroxidase were determined. Results of myeloperoxidase activity and glutathione disulfide lung concentrations showed a relevant decrease for chitosan group compared to control: 4.67 +/- 2.27 versus 15.10 +/- 7.27 (P = 0.011) for MPO and 0.89 +/- 0.68 versus 2.02 +/- 0.22 (P = 0.014) for GSSG. The other parameters did not vary significantly among groups. Lactose and chitosan administered by inhalation failed to show toxic effects to the pulmonary tissue. A protective effect against oxidative stress might even be attributed to chitosan, since some biomarkers had values significantly lower than those observed in the control group when this product was inhaled. Nevertheless, caution must be taken regarding chemical composition and technological processes applied to incorporate these products during drug formulation, in particular for dry powder inhalators.

Isolation and activation of human neutrophils in vitro. The importance of the anticoagulant used during blood collection

OBJECTIVES

To assess the effect of different anticoagulants (EDTA, citrate and heparin) on the isolation procedure of human neutrophils and in the subsequent alterations of calcium levels and respiratory burst induced by phorbol myristate acetate (PMA).

DESIGN AND METHODS

Isolation of human neutrophils from whole blood was performed by the gradient density centrifugation method. PMA-induced neutrophil burst was measured by chemiluminescence. Intracellular calcium ([Ca(2+)](i)) was measured using Fluo-3 AM, a calcium-sensitive dye.

RESULTS

EDTA provided the highest number of isolated neutrophils/mL of blood (1.7x10(6)+/-1.5x10(5)) when compared with citrate (0.46x10(6)+/-0.95x10(5)) and heparin (0.66x10(6)+/-0.15x10(5)). EDTA originated less degree of PMA-induced activation (370+/-30%) relatively to citrate (830+/-98%) and heparin (827+/-77%). [Ca(2+)](i) was lower with EDTA (122+/-11 nM) when compared with citrate and heparin (150+/-13 and 230+/-30 nM).

CONCLUSION

The anticoagulant used during blood collection interfered differently with the yield of isolated neutrophils as well as on their calcium levels and reactivity to PMA.

Inhibition of cyclooxygenases by dipyrone

BACKGROUND AND PURPOSE

Dipyrone is a potent analgesic drug that has been demonstrated to inhibit cyclooxygenase (COX). In contrast to classical COX-inhibitors, such as aspirin-like drugs, dipyrone has no anti-inflammatory effect and a low gastrointestinal toxicity, indicating a different mode of action. Here, we aimed to investigate the effects of dipyrone on COX.

EXPERIMENTAL APPROACH

The four major metabolites of dipyrone, including the two pharmacologically active metabolites, 4-methyl-amino-antipyrine (MAA) and amino-antipyrine (AA), were used to characterise their binding to COX and haem as well as their effects on the biochemical properties of COX. Mass spectrometry, UV and visible photometry were used to study binding and prostaglandin production. Levels of anti-oxidant enzymes were assessed by Western blotting.

KEY RESULTS

The pharmacologically active metabolites of dipyrone, MAA and AA, did not inhibit COX activity in vitro like classical COX inhibitors, but instead redirected the prostaglandin synthesis, ruling out inhibition of COX through binding to its active site. We found that MAA and AA formed stable complexes with haem and reacted with hydrogen peroxide in presence of haem, ferrous ions (Fe(2+)) or COX. Moreover, MAA reduced Fe(3+) to Fe(2+) and accordingly increased lipid peroxidation and the expression of anti-oxidant enzymes in cultured cells and in vivo.

CONCLUSIONS AND IMPLICATIONS

Our data suggest that the pharmacologically active metabolites of dipyrone inhibit COX activity by sequestering radicals which initiate the catalytic activity of this enzyme or through the reduction of the oxidative states of the COX protein.

Automatic in Vitro Determination of Hypochlorous Acid Scavenging Capacity Exploiting Multisyringe Flow Injection Analysis and Chemiluminescence

In the present work, a chemiluminometric automatic flow methodology for the in vitro determination of hypochlorous acid scavenging capacity, under pH and concentration conditions similar to those found in vivo, is proposed. As the pH found in physiological conditions (7.4) and the pH required for the chemiluminescence detection reaction (>10) are different, the multisyringe flow injection analysis features were exploited to perform the in-line reaction of HOCl and the scavenger molecule at physiological pH prior to reaction of the remaining HOCl with luminol at alkaline conditions. These two reactions were carried out in about 3 s, allowing the determination of fast reacting antioxidants, in a time frame closer to in vivo generation of HOCl when compared to previously described methods. The developed method was applied to nonsteroidal antiinflammatory drugs of different chemical families, and positive controls (cysteine, gallic acid, lipoic acid). The HOCl scavenging capacity was evaluated at pH 7.4 and 10.0; different results were found for oxicam derivatives, providing evidence that the pH of in vitro methods should be carefully selected to allow assumptions about putative in vivo effects.

Lgf-YL-9 induces apoptosis in human epidermoid carcinoma KB cells and multidrug resistant KBv200 cells via reactive oxygen species-independent mitochondrial pathway

Pyrazolon derivatives were reported to have cytotoxicity to some tumour cells. In the present study, we investigated the effect of Lgf-YL-9 on cytotoxicity and cell apoptosis in human epidermoid carcinoma drug-sensitive parental KB cells and multidrug resistant (MDR) KBv200 cells. Lgf-YL-9 exhibited potent cytotoxicity not only to KB cells but also to KBv200 cells, and the IC(50) were 3.81 and 3.45 microg/mL in KB cells and KBv200 cells, respectively. Importantly, Lgf-YL-9 effectively inhibited tumour growth of KB cell xenografts in nude mice. Lgf-YL-9-induced cell apoptosis was confirmed by chromatin condensation, DNA fragmentation, Annexin-V and propidium iodide (PI) double-staining assay and poly(ADP-ribose) polymerase (PARP) cleavage. Furthermore, Lgf-YL-9-mediated apoptosis in KB cells and KBv200 cells was accompanied by the loss of mitochondrial membrane potential (DeltaPsi(m)), the release of cytochrome c, and the activation of caspases-3, -7, and -9, but not by intercalating to DNA. Although Lgf-YL-9-induced apoptosis was associated with the decrease of DeltaPsi(m), reactive oxygen species (ROS) reduction was interestingly observed in both cell lines. The data suggest that Lgf-YL-9 has similar cytotoxicity to drug-sensitive parental KB cells and MDR KBv200 cells. Lgf-YL-9-induced apoptosis is involved in a new ROS-independent mitochondrial dysfunction pathway, but not in intercalating to DNA.

Antioxidant activity and inhibition of human neutrophil oxidative burst mediated by arylpropionic acid non-steroidal anti-inflammatory drugs

It has been suggested that the anti-inflammatory activity of some non-steroidal anti-inflammatory drugs (NSAIDs) may be partly due to their ability to scavenge reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as to inhibit the respiratory burst of neutrophils triggered by various activating agents. Therefore, the aim of the present work was to evaluate and compare the potential scavenging activity for an array of ROS (O2*-, H2O2, HO*, ROO* and HOCl) and RNS (*NO and ONOO-) using in vitro non-cellular screening systems as well as a cellular screening system (human neutrophil oxidative burst), mediated by the arylpropionic acid derivatives (APAs) NSAIDs ibuprofen, flurbiprofen, fenoprofen, fenbufen, ketoprofen, naproxen and indoprofen. The results obtained in the present work demonstrate that under the present experimental conditions, many of the studied APA NSAIDs showed O2*- scavenging activity (fenbufen approximately equal to flurbiprofen approximately equal to indoprofen approximately equal to ketoprofen), H2O2 (ketoprofen approximately equal to indoprofen approximately equal to fenbufen>flurbiprofen>naproxen), HO* (fenoprofen approximately equal to ibuprofen>fenbufen approximately equal to flurbiprofen>ketoprofen>indoprofen approximately equal to naproxen), *NO (indoprofen>naproxen), ONOO- (indoprofen>naproxen>fenoprofen approximately equal to flurbiprofen approximately equal to ibuprofen), as well as inhibit myeloperoxidase (MPO) activity (indoprofen) and scavenge human neutrophil derived ROS (ketoprofen>indoprofen>fenbufen>flurbiprofen). The observed effects, if confirmed in vivo, may strongly contribute to the anti-inflammatory therapeutical activity observed with these NSAIDs.

Dipyrone and aminopyrine are effective scavengers of reactive nitrogen species

Reactive nitrogen species (RNS), namely nitric oxide (NO*) and peroxynitrite (ONOO-) are produced in the inflammatory sites and may contribute to the deleterious effects of inflammation. The aim of the present study was to evaluate the putative scavenging effect of a particular group of non-steroidal anti-inflammatory drugs (NSAIDs), the pyrazolone derivatives dipyrone, aminopyrine, isopropylantipyrine, and antipyrine against RNS, using in vitro non-cellular screening systems. The results obtained showed that dipyrone and aminopyrine were highly potent scavengers of NO* and ONOO- while antipyrine exerted little effect and isopropylantipyrine no effect whatsoever against these two RNS and that, in the presence of bicarbonate, the scavenging potencies of both dipyrone and aminopyrine were slightly decreased. It could thus be inferred that the observed scavenging effects may be of therapeutic benefit for patients under anti-inflammatory treatment with dipyrone and aminopyrine in the case of overproduction of RNS. On the other hand, the possible depletion of physiological NO* concentrations, namely at the gastrointestinal tract as well as the formation of reactive derivatives of aminopyrine and/or dipyrone, resulting from their reaction with RNS, may otherwise be harmful for these patients.