Oxidation of diclofenac to reactive intermediates by neutrophils, myeloperoxidase, and hypochlorous acid

Formation of potentially toxic metabolites of drugs in reactions catalyzed by human drug-metabolizing enzymes

Data are presented on the formation of potentially toxic metabolites of drugs that are substrates of human drug metabolizing enzymes. The tabular data lists the formation of potentially toxic/reactive products. The data were obtained from in vitro experiments and showed that the oxidative reactions predominate (with 96% of the total potential toxication reactions). Reductive reactions (e.g., reduction of nitro to amino group and reductive dehalogenation) participate to the extent of 4%. Of the enzymes, cytochrome P450 (P450, CYP) enzymes catalyzed 72% of the reactions, myeloperoxidase (MPO) 7%, flavin-containing monooxygenase (FMO) 3%, aldehyde oxidase (AOX) 4%, sulfotransferase (SULT) 5%, and a group of minor participating enzymes to the extent of 9%. Within the P450 Superfamily, P450 Subfamily 3A (P450 3A4 and 3A5) participates to the extent of 27% and the Subfamily 2C (P450 2C9 and P450 2C19) to the extent of 16%, together catalyzing 43% of the reactions, followed by P450 Subfamily 1A (P450 1A1 and P450 1A2) with 15%. The P450 2D6 enzyme participated in an extent of 8%, P450 2E1 in 10%, and P450 2B6 in 6% of the reactions. All other enzymes participate to the extent of 14%. The data show that, of the human enzymes analyzed, P450 enzymes were dominant in catalyzing potential toxication reactions of drugs and their metabolites, with the major role assigned to the P450 Subfamily 3A and significant participation of the P450 Subfamilies 2C and 1A, plus the 2D6, 2E1 and 2B6 enzymes contributing. Selected examples of drugs that are activated or proposed to form toxic species are discussed.

An integrated approach for the assessment of the electrochemical oxidation of diclofenac: By-product identification, microbiological and eco-genotoxicological evaluation

Diclofenac (DCF), a contaminant of emerging concern, is a non-steroidal anti-inflammatory drug widely detected in water bodies, which demonstrated harmful acute and chronic toxicity toward algae, zooplankton and aquatic invertebrates, therefore its removal from impacted water is necessary. DCF is recalcitrant toward traditional treatment technologies, thus, innovative approaches are required. Among them, electrochemical oxidation (EO) has shown promising results. In this research, an innovative multidisciplinary approach is proposed to assess the electrochemical oxidation (EO) of diclofenac from wastewater by integrating the investigations on the removal efficiency and by-product identification with the disinfection capacity and the assessment of the effect on environmental geno-toxicity of by-products generated through the oxidation. The electrochemical treatment successfully degraded DCF by achieving >98 % removal efficiency, operating with NaCl 0.02 M at 50 A m-2. By-product identification analyses showed the formation of five DCF parental compounds generated by decarboxylic and CN cleavage reactions. The disinfection capacity of the EO technique was evaluated by carrying out microbiological tests on pathogens generally found in aquatic environments, including two rod-shaped Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli), one rod-shaped Gram-positive bacterium (Bacillus atrophaeus), and one Gram-positive coccus (Enterococcus hirae). Eco-toxicity was evaluated in freshwater organisms (algae, rotifers and crustaceans) belonging to two trophic levels through acute and chronic tests. Genotoxicity tests were carried out by Comet assay, and relative expression levels of catalase, manganese and copper superoxide dismutase genes in crustaceans. Results highlight the effectiveness of EO for the degradation of diclofenac and the inactivation of pathogens; however, the downstream mixture results in being harmful to the aquatic ecosystem.

Enhanced chlorination of diclofenac using ABTS as electron shuttle: Performance, mechanism and applicability

Chlorination, one of the most common oxidation strategies, performed limited degradation capacity towards many emerging organic contaminants under neutral pH conditions. In this study, 2,2'-azinobis(3-ethylbenzothiazoline)-6-sulfonate (ABTS) was discovered to possess an outstanding activation property towards free available chlorine (FAC) during the chlorination of diclofenac (DCF) among pH 6.0-9.5. ABTS radical (ABTS•+) primarily accounted for the elimination of DCF in the ABTS/FAC system, although hydroxyl radicals, reactive chlorine species, and singlet oxygen were also generated via the self-decomposition of FAC. ABTS acted as the electron shuttle to degrade DCF in the ABTS/FAC system, where ABTS was firstly oxidized by FAC to ABTS•+ via single electron transfer, and followed by the elimination of DCF with the generated ABTS•+. Eight DCF degradation intermediates were identified by LC/Q-TOF/MS, and four DCF degradation pathways were proposed. Real water bodies, humic acid, and the coexistent anions of Cl-, HCO3-, NO3-, and SO42- performed negligible influence on DCF removal in ABTS/FAC system. ABTS/FAC system was much superior to sole chlorination in terms of toxicity reduction and anti-interference capacity. Overall, this study innovatively introduced ABTS as the electron shuttle to enhance the oxidative capacity of FAC under neutral pH conditions and provided a new insight that the ABTS-like organic/synthetic components might play an important role in degrading emerging organic contaminants by chlorination in water treatment.

Comparison of the degradation mechanisms of diclofenac in the presence of iron octacarboxyphthalocyanine and myeloperoxidase

The degradation process of diclofenac (DCF) by hematoprotein myeloperoxidase (MPO) and iron octacarboxyphthalocyanine (FePcOC) in the presence of hydrogen peroxide was compared. During the oxidation of diclofenac, in the presence of iron octacarboxyphthalocyanine (FePcOC) and hydroxyl radicals (HO^•) (from H₂O₂), an intermediate product (dimer with an m/z value of 587) with the characteristic yellow colouration and an intense band at λ_max = 451 nm is formed. Iron octacarboxyphthalocyanine oxidises in the presence of hydrogen peroxide, following the first-order reaction kinetics for FePcOC and H₂O₂. The concentration of diclofenac does not affect the initial reaction rate. For comparison, the oxidation of DCF in the presence of myeloperoxidase and hydrogen peroxide also provided yellow-coloured solutions with an absorption maximum at λ_max = 451 nm. However, LC-MS/MS analysis indicates the presence of at least seven main products of the diclofenac oxidation process in the final reaction mixture, including two dimers with the ion mass [M-H]^¯ = 587.01. The mechanism of the diclofenac degradation with hematoprotein myeloperoxidase is more complex than with iron octacarboxyphthalocyanine. Furthermore, the biological activity of diclofenac and DCF dimer (iron octacarboxyphthalocyanine and hydroxyl radicals degradation product) was tested. In this case, the long-term assayed in vitro against E. coli, colorectal HCT116 and melanoma Me45 cancer cells were performed.

Diclofenac Disrupts the Circadian Clock and through Complex Cross-Talks Aggravates Immune-Mediated Liver Injury-A Repeated Dose Study in Minipigs for 28 Days

Diclofenac effectively reduces pain and inflammation; however, its use is associated with hepato- and nephrotoxicity. To delineate mechanisms of injury, we investigated a clinically relevant (3 mg/kg) and high-dose (15 mg/kg) in minipigs for 4 weeks. Initially, serum biochemistries and blood-smears indicated an inflammatory response but returned to normal after 4 weeks of treatment. Notwithstanding, histopathology revealed drug-induced hepatitis, marked glycogen depletion, necrosis and steatosis. Strikingly, the genomic study revealed diclofenac to desynchronize the liver clock with manifest inductions of its components CLOCK, NPAS2 and BMAL1. The > 4-fold induced CRY1 expression underscored an activated core-loop, and the dose dependent > 60% reduction in PER2mRNA repressed the negative feedback loop; however, it exacerbated hepatotoxicity. Bioinformatics enabled the construction of gene-regulatory networks, and we linked the disruption of the liver-clock to impaired glycogenesis, lipid metabolism and the control of immune responses, as shown by the 3-, 6- and 8-fold induced expression of pro-inflammatory CXCL2, lysozyme and ß-defensin. Additionally, diclofenac treatment caused adrenocortical hypertrophy and thymic atrophy, and we evidenced induced glucocorticoid receptor (GR) activity by immunohistochemistry. Given that REV-ERB connects the circadian clock with hepatic GR, its > 80% repression alleviated immune responses as manifested by repressed expressions of CXCL9(90%), CCL8(60%) and RSAD2(70%). Together, we propose a circuitry, whereby diclofenac desynchronizes the liver clock in the control of the hepatic metabolism and immune response.

A Near-Infrared Fluorescent Probe for Recognition of Hypochlorite Anions Based on Dicyanoisophorone Skeleton

A novel near-infrared (NIR) fluorescent probe (SWJT-9) was designed and synthesized for the detection of hypochlorite anion (ClO^-) using a diaminomaleonitrile group as the recognition site. SWJT-9 had large Stokes shift (237 nm) and showed an excellent NIR fluorescence response to ClO^- with the color change under the visible light. It showed a low detection limit (24.7 nM), high selectivity, and rapid detection (within 2 min) for ClO^-. The new detection mechanism of SWJT-9 on ClO^- was confirmed by ¹H NMR, MS spectrum, and the density functional theory (DFT) calculations. In addition, the probe was successfully used to detect ClO^- in HeLa cells.

Idiosyncratic Drug Reactions: A 35-Year Chemical Research in Toxicology Perspective

When Larry Marnett founded Chemical Research in Toxicology, the study of idiosyncratic drug reactions (IDRs) was in its infancy. There was evidence that IDRs involve chemically reactive metabolites, and many of the papers in Chemical Research in Toxicology investigated the bioactivation of drugs. However, it became clear that not all drugs that form reactive metabolites are associated with a high risk of IDRs, and some drugs that do not appear to form reactive metabolites do cause IDRs. Some of the early Chemical Research in Toxicology papers investigated involvement of the adaptive immune system in the mechanism of IDRs, and HLA associations provided strong evidence for an immune mechanism of IDRs. This led to the question of how reactive metabolites might induce an immune response. The classic hapten hypothesis provided an obvious explanation, but a new hypothesis the danger hypothesis, added another dimension. Although there are common features to IDRs, it is becoming increasingly clear that there are also many differences in the mechanisms caused by different drugs. Other pharmacological effects of drugs may also play a role in the mechanism, and that is obviously true of IDRs caused by biological agents. The requirement for specific HLA and T-cell receptors is presumably the major factor that makes IDRs idiosyncratic. However, an innate immune response is required to prime the adaptive immune response. In contrast to the adaptive immune response, the innate immune response is unlikely to be idiosyncratic, and studies of the innate immune response to drugs may provide a much more accurate way to screen drugs for their potential to cause IDRs. For essential drugs that are known to cause IDRs, it may be possible to markedly decrease risk by a slow dose titration to induce immune tolerance. Significant progress has been made in the study of IDRs, but there is still a long way to go.

Oxidation of diclofenac in the presence of iron(II) octacarboxyphthalocyanine

This paper presents the results of the research on the influence of catalytic activity of iron(II) octacarboxyphthalocyanines (FePcOC) on the transformation of diclofenac (DCF) which is the most popular anti-inflammatory analgesic. Diclofenac poses a serious threat to the natural environment. The paper demonstrates that diclofenac, in the presence a monomeric form of iron octacarboxyphthalocyanine and hydroxyl radicals (HO^•) (from H₂O₂), undergoes a transformation into diclofenac-2,5-iminoquinone (DCF-2,5-IQ), causing distinct changes in the UV-Vis absorption spectrum. In the presence of iron octacarboxyphthalocyanine and H₂O₂, the previously colourless diclofenac solution becomes intense orange. As a result, a new band at approx. 450 nm appears in the absorption spectrum. HPLC analysis has shown that the concentration of diclofenac decreases with time. TD-DFT calculations using the CAM-B3LYP/6-31+G (d, p) method have been conducted to confirm experimental data concerning the formation of a new band at λ_max = 450 nm.

Oxidation of diclofenac by birnessite: Identification of products and proposed transformation pathway

Diclofenac (DCF), a widely used non-steroidal anti-inflammatory, reacted readily with birnessite under mild conditions, and the pseudo first order kinetic constants achieved 8.84 × 10^-2 hr^-1. Five products of DCF including an iminoquinone product (2,5-iminoquinone-diclofenac) and four dimer products were observed and identified by tandem mass spectrometry during the reaction. Meanwhile, 2,5-iminoquinone-diclofenac was identified to be the major product, accounting for 83.09% of the transformed DCF. According to the results of spectroscopic Mn(III) trapping experiments and X-ray Photoelectron Spectroscopy, Mn(IV) contained in birnessite solid was consumed and mainly converted into Mn(III) during reaction process, which proved that the removal of DCF by birnessite was through oxidation. Based on the identified products of DCF and the changes of Mn valence state in birnessite solid, a tentative transformation pathway of DCF was proposed.

Oxidation of diclofenac in water by sodium hypochlorite: Identification of new degradation by-products and their ecotoxicological evaluation

Diclofenac (DCF) is the most widely prescribed non-steroidal anti-inflammatory drug in the world and it has been detected in drinking and surface waters. In this paper, the effect of chlorination process on DCF in aqueous solutions was investigated and the structures of 14 isolated degradation by-products (DPs), of which nine are new, have been determined from combining mass spectrometry and nuclear magnetic resonance data and justified by a proposed mechanism of formation beginning from the parent drug. Some degradation by-products show only one phenyl, others are dimers or trimers of the parental compound, which has undergone oxidative decarboxylation of the side chain and/or chlorination of this or one or both aromatic rings. Ecotoxicological bioassays evidenced the following sensitivities D. magna < R. subcapitata < A. fischeri. The isolated DPs (DP1-8, except for DP9) exhibited effects ≥ 50 % in the exposed microalgae and crustaceans showing toxicities mainly ranked from slight to acute.

Bioactivation of diclofenac in human hepatocytes and the proposed human hepatic proteins modified by reactive metabolites

To reveal putative bioactivation pathways of diclofenac, in vitro human liver materials such as microsomal fractions and hepatocytes were used to confirm metabolic activation of diclofenac by ³⁵S-cysteine trapping assay and covalent binding assay. Candidate human liver proteins possibly targeted by ¹⁴C-diclofenac via bioactivation were investigated using two-dimensional gel electrophoresis followed by detection of remaining radioactivity on the modified proteins with bio-imaging analyzer.In the ³⁵S-cysteine trapping assay, three and two adducts with ³⁵S-cysteine were observed in NADPH-fortified and UDPGA-fortified human liver microsomes, respectively. In the covalent binding assay using ¹⁴C-diclofenac in human hepatocytes, the extent of covalent binding of diclofenac to human hepatic proteins increased time-dependently. Addition of glutathione attenuated the extent of covalent binding of ¹⁴C-diclofenac to human liver microsomal proteins.Fifty-nine proteins from human hepatocytes were proposed as the candidate proteins targeted by reactive metabolites of diclofenac. Proteins modified by cytochrome P450-mediated reactive metabolites were identified by using a cytochrome P450 inhibitor, 1-aminobenzyltriazole and seven of the nine radioactive protein spots were removed by 1-aminobenzyltriazole treatment.In contrast, the remaining two radioactive protein spots, mainly containing human serum albumin and heat shock proteins, were not affected by the addition of 1-aminobenzyltriazole, which suggested the involvement of the acyl glucuronide of diclofenac, formed via uridine diphosphate-glucuronosyl transferases, in the covalent modifications induced by diclofenac.

Simultaneous aqueous chlorination of amine-containing pharmaceuticals

Amine-containing pharmaceuticals such as acetaminophen, diclofenac, and sulfamethoxazole are the most often detected pharmaceuticals in wastewater and other aquatic environments. Amine-containing pharmaceuticals can be effectively removed by chlorination. These drugs, however, may coexist in wastewater. Thus, they may compete with each other, and their chlorinated products may react with each other to form new products. In this study, competitive effects of the above three amine-containing pharmaceuticals by chlorination and their products were investigated. The priority of chlorination of these compounds was dependent upon the pH of the solution, due to the dissociation of the compounds and hypochlorite. It followed the order of sulfamethoxazole > diclofenac > acetaminophen in an acidic condition, the order of sulfamethoxazole > acetaminophen > diclofenac in a neutral condition, and the order of sulfamethoxazole ≈ acetaminophen > diclofenac in an alkaline condition. Some of the chlorinated products in single- and multiple-compound systems were the same. Dimers of sulfamethoxazole and its chlorinated products, however, were not found, but dimers of sulfamethoxazole and acetaminophen or diclofenac were found in multiple-compound systems. This finding is important because it means that new products may be produced if different amine-containing pharmaceuticals react with free chlorine simultaneously.

Direct and indirect electrochemical oxidation of amine-containing pharmaceuticals using graphite electrodes

This study investigated the direct and indirect electro-oxidation of amine-containing pharmaceuticals (acetaminophen (ACT), diclofenac (DIC), and sulfamethoxazole (SMX)) by using graphite electrodes, and to compare the influence by using different electrolytes (Na₂SO₄ and NaCl). Under the optimum conditions of current (I) at 0.5 A, in direct system, 74.3%, 90.0%, 81.6% of ACT, DIC, and SMX were respectively removed after 60 min (k = 0.023, 0.037, 0.027 min^-1), 48.9%, 85.9%, 68.2% of TOC respectively removed after reaction time. In contrast, at the same current intensity, in indirect system, ACT, DIC, and SMX were eliminated within 30 min (k = 0.117, 0.307, 0.170 min^-1), 89.6%, 92.6%, 99.6% of TOC respectively removed after reaction time. The results indicated that the dissociated compounds were attracted to the anode due to electrostatic forces and had higher mass transformation rates in the direct electro-oxidation process. According to the cyclic voltammogram, indirect oxidation occurred when active chlorine species were generated from chloride ions anodically to destroy pollutants. Based on intermediates detected during electro-oxidation treatment by ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), only oxidized intermediates were found in the direct oxidation system, while both oxidized and chlorinated intermediates were found in the indirect oxidation system.

Formation of a Toxic Quinoneimine Metabolite from Diclofenac: A Quantum Chemical Study

BACKGROUND

Diclofenac is a non-steroidal antiinflammatory drug. It is predominantly metabolized by CYP2C9. 4'-hydroxydiclofenac and its quinoneimine are the metabolites of diclofenac. However, few numbers of serious cases of idiosyncratic hepatotoxicity due to diclofenac metabolism were reported. The formation of the quinoneimine metabolite was found to be responsible for this idiosyncratic toxicity. Quinoneimine is an over-oxidized metabolite of diclofenac.

METHOD

In this work, computational studies were conducted to detail the formation of a quinoneimine metabolite from diclofenac. Further, the idiosyncratic toxicity of quinoneimine due to its reactivity was also investigated by quantum chemical analysis.

RESULTS & CONCLUSION

The results demonstrate the possibility of formation of quinoneimine metabolite due to various factors that are involved in the metabolism of diclofenac. The present study may provide the structural in-sights during the drug development processes to avoid the metabolism directed idiosyncratic toxicity.

A new diclofenac molecularly imprinted electrochemical sensor based upon a polyaniline/reduced graphene oxide nano-composite

A diclofenac (DCF)-imprinted polymer, composed of polyaniline, reduced graphene oxide (rGO) and triphenylamine, as cross linker, was synthetized. This composite was identified by using SEM and FT-IR techniques. The prepared DCF-imprinted polymer (MIP) was used for modification of carbon paste electrodes (CPEs) to fabricate a selective DCF electrochemical sensor. Electrochemical behavior of DCF on the investigated sensor and the optimization of the parameters affecting the DCF determination were screened by cyclic voltammetry (CV). The cyclic voltammogram of DCF showed an anodic peak current at about 0.5 V (vs. SCE). The calibration curve for DCF determination was obtained by applying the investigated sensor as working electrode in differential pulse voltammetry (DPV). A linear increase in the anodic peak current was observed in the range 5-80 mg L^-1 of DCF. The corresponding limit of detection was calculated to be 1.1 mg L^-1. The relative standard deviations of the inter- and intra-day analysis of DCF presented by the method were found to be as 2.43% and 2.47%, respectively. The selectivity of the investigated sensor was evaluated by its use for determination of DCF in the binary solutions containing DCF/glucose, DCF/urea and DCF/ascorbic acid. It was shown that the fabricated electrode can be successfully used for analysis of DCF in pharmaceutical and urine samples.

An evaluation of myeloperoxidase-mediated bio-activation of NSAIDs in promyelocytic leukemia (HL-60) cells for potential cytotoxic selectivity

Several lines of evidence have pointed towards the potential therapeutic benefit of NSAIDs in cancer therapy. In this study, we have investigated the acute bio-activation of NSAIDs and their metabolites via myeloperoxidase (MPO), a highly-expressed peroxidase enzyme in acute myeloid leukemia. As bio-activation involves the formation of reactive metabolites, we hypothesized that NSAIDs which produced reactive metabolites would be correlated with leukemia cell toxicity. We tested the enzymatic peroxidation of three NSAIDs, namely diclofenac, indomethacin, and naproxen in comparison with their hepatic metabolites, 4'- hydroxydiclofenac (4'-OHD), 5-hydroxydiclofenac (5-OHD), O-desmethyl-N-deschlorobenzoylindomethacin (DMBI), O-desmethylindomethacin (DMI) and O-desmethylnaproxen (ODN). Firstly, we used purified peroxidases in kinetic UV-vis kinetic spectrophotometry, and electron paramagnetic resonance (EPR) experiments to determine oxidation of ascorbic acid and glutathione (GSH), respectively. We then used HL-60 cells, as a model of acute myelogenous leukemia to carry out trypan blue exclusion, cellular ATP analysis, mitochondrial membrane potential (MMP) and cytofluorometric GSH assays. Our results present evidence that diclofenac, 4'-OHD, 5-OHD, DMBI and DMI demonstrated significant cytotoxic effect in the leukemic cells through oxidation by intracellular MPO. In the same vein, only diclofenac and its two metabolites caused a significant drop in the MMP and cellular ATP level; however, the cell death induced by indomethacin metabolites reflected a subtle effect on MMP or GSH content. Interestingly, only diclofenac and 4'-OHD (and not 5- OHD) caused a significant drop in HL-60 cells' GSH content. Among diclofenac compounds, only 4'-OHD also generated GS radical and caused a significant increase in ascorbate co-oxidation rate. Lastly, even though ODN also generated GS radical and potently cooxidized ascorbate, it showed no significant cytotoxicity. These results provide evidence of a correlation between acute cytotoxicity and MPO-bioactivated NSAIDs, though this was not correlated for all compounds (e.g., ODN). Further studies are required to determine both the MPO-dependent and MPO-independent mechanisms of cytotoxicity.

In vitro and in vivo anti-inflammatory active copper(II)-lawsone complexes

We report in vitro and in vivo anti-inflammatory activities of a series of copper(II)-lawsone complexes of the general composition [Cu(Law)₂(L_N)_x(H₂O)_(2-x)]·yH₂O; where HLaw = 2-hydroxy-1,4-naphthoquinone, x = 1 when L_N = pyridine (1) and 2-aminopyridine (3) and x = 2 when L_N = imidazole (2), 3-aminopyridine (4), 4-aminopyridine (5), 3-hydroxypyridine (6), and 3,5-dimethylpyrazole (7). The compounds were thoroughly characterized by physical techniques, including single crystal X-ray analysis of complex 2. Some of the complexes showed the ability to suppress significantly the activation of nuclear factor κB (NF-κB) both by lipopolysaccharide (LPS) and TNF-alpha (complexes 3–7 at 100 nM level) in the similar manner as the reference drug prednisone (at 1 μM level). On the other hand, all the complexes 1–7 decreased significantly the levels of the secreted TNF-alpha after the LPS activation of THP-1 cells, thus showing the anti-inflammatory potential via both NF-κB moderation and by other mechanisms, such as influence on TNF-alpha transcription and/or translation and/or secretion. In addition, a strong intracellular pro-oxidative effect of all the complexes has been found at 100 nM dose in vitro. The ability to suppress the inflammatory response, caused by the subcutaneous application of λ-carrageenan, has been determined by in vivo testing in hind-paw edema model on rats. The most active complexes 1–3 (applied in a dose corresponding to 40 μmol Cu/kg), diminished the formation of edema simalarly as the reference drug indomethacine (applied in 10 mg/kg dose). The overall effect of the complexes, dominantly 1–3, shows similarity to anti-inflammatory drug benoxaprofen, known to induce intracellular pro-oxidative effects.

Emerging pollutants and plants--Metabolic activation of diclofenac by peroxidases

Human pharmaceuticals and their residues are constantly detected in our waterbodies, due to poor elimination rates, even in the most advanced waste water treatment plants. Their impact on the environment and human health still remains unclear. When phytoremediation is applied to aid water treatment, plants may transform and degrade xenobiotic contaminants through phase I and phase II metabolism to more water soluble and less toxic intermediates. In this context, peroxidases play a major role in activating compounds during phase I via oxidation. In the present work, the ability of a plant peroxidase to oxidize the human painkiller diclofenac was confirmed using stopped flow spectroscopy in combination with LC-MS analysis. Analysis of an orange colored product revealed the structure of the highly reactive Diclofenac-2,5-Iminoquinone, which may be the precursor of several biological conjugates and breakdown products in planta.

Permanganate oxidation of diclofenac: The pH-dependent reaction kinetics and a ring-opening mechanism

In this work, the fate of diclofenac (DCF) during permanganate (Mn(VII)) oxidation was investigated at environmentally relevant pH conditions (from 5 to 9). The batch experiments showed that the kinetics of the Mn(VII)/DCF reaction follows a second-order rate law with an apparent rate constant of 1.57±0.02 M(-1) s(-1) at pH 7 and 20 °C. The half-value of DCF was calculated to be 37.5 min, when the concentration of Mn(VII) (0.4 mM) was 20-fold excess of DCF. The pH-dependence of the reaction kinetics was investigated, and the DCF reactivity with Mn(VII) was found to decrease with increasing pH. The second-order rate constants were then quantitatively described by incorporating the species distribution of DCF. A lower reactivity of the anionic DCF (DCF(-)) in comparison with its neutral counterpart (DCF(0)) was most likely attributable to the interaction between the ionized carboxylate group and amine nitrogen position, which can reduce the nucleophilicity of amine nitrogen by inductive and resonance effects. Moreover, a range of degradation products and the corresponding structures were proposed on the basis of the LC-Q-TOF-MS analysis. A detailed ring-opening reaction mechanism was proposed as follows: Mn(VII) acts as an electrophile to attack the amine moiety, leading to the formation of the primary intermediate products 2,6-dichloroaniline and 5-hydroxy-diclofenac, which can be further transformed. The further degradation proceeded through a multistep process including ring-opening, decarboxylation, hydroxylation, and cyclation reactions.

Phototransformation of mefenamic acid induced by nitrite ions in water: mechanism, toxicity, and degradation pathways

Here, we evidenced the photo-induced degradation of mefenamic acid, a nonsteroidal anti-inflammatory drug, through the 254-nm light excitation of nitrite. The results demonstrated that the photodegradation of mefenamic acid was enhanced, and the mefenamic acid photodegradation rate significantly increased, from 0.00627 to 0.0350 min(-1) as the nitrite was increased from 0 to 0.5 mmol L(-1). The photodegradation rate increased from 0.0287 to 0.0512 min(-1) as the pH was elevated, from 5.0 to 10.0. The actual second-order rate constant for the reaction of mefenamic acid with ·OH was investigated to 1.079 × 10(10) M(-1) s(-1) according to steady-state ·OH concentration of 3.5 × 10(-14) mmol L(-1) and the contribution to the rate of ·OH of 67.1%. The photoproducts were identified using HPLC/MS/MS, and possible nitrite-induced photodegradation pathways were proposed by hydroxylation, dehydrogenation, hydration, nitrosylation, and ketonized reactions. The toxicity of the phototransformation products was evaluated using the Microtox test, which revealed that the photoproducts were more toxic than mefenamic acid for the generation of nitrosation aromatic compounds.

The Relationship of Bone Mineral Density to Oxidant/Antioxidant Status and Inflammatory and Bone Turnover Markers in a Multicenter Cross-Sectional Study of Young Men with Ankylosing Spondylitis

Low bone mineral density (BMD) is an important complication of ankylosing spondylitis (AS) that seriously affects men and their quality of life, even in young patients. However, the relationships among redox; levels of bone turnover markers (BTMs), inflammatory markers and disease activity; and low BMD in AS require clarification. We recruited 102 men aged 30-39 year with AS and 102 healthy, sex- and age-matched controls for this cross-sectional study. The subjects were analyzed for lumbar spine and femoral neck BMD by dual-energy X-ray absorptiometry. Significantly lower BMD and corresponding T-scores were observed in the AS patients compared with the controls (P < 0.05). The oxidant biomarker and antioxidant levels were significantly (P < 0.05) higher and lower, respectively, in the AS subjects compared with the controls, and the bone resorption and inflammatory marker levels were higher (P < 0.05). In subgroup analyses, the patients with osteoporosis or active disease had the highest levels of oxidant biomarkers (P < 0.05). Furthermore, the BMD T-scores in AS were found to be negatively correlated with oxidative status (P < 0.05). Multivariate binary logistic analysis showed that low BMD in the AS patients was associated with higher levels of advanced oxidation protein products, malondialdehyde and C-terminal telopeptide of type I collagen; lower levels of glutathione peroxidase; and higher scores of a bath ankylosing spondylitis metrology index. In conclusion, imbalanced redox was independently associated with low BMD in young men with AS and may play an important role in the pathogenesis of AS-related low BMD.

Role of drug-independent stress factors in liver injury associated with diclofenac intake

Although a basic understanding of the chemical and biological events leading to idiosyncratic drug toxicity is still lacking, it appears that drug-independent risk factors that increase reactive metabolite formation or alter cellular stress and immune response may be critical determinants in the response to an otherwise non-toxic drug. Thus, we were interested to determine the impact of various drug-independent stress factors - lipopolysaccharide (LPS), poly I:C (PIC) or glutathione depletion via buthionine sulfoximine (BSO) - on the toxicity of diclofenac (Dcl), a model drug associated with rare but significant cases of serious hepatotoxicity, and to understand if enhanced toxicity occurs through alterations of drug metabolism and/or modulation of stress response pathways. Co-treatment of rats repeatedly given therapeutic doses of Dcl for 7 days with a single dose of LPS 2h before the last Dcl dose resulted in severe liver toxicity. Neither LPS nor diclofenac alone or in combination with PIC or BSO had such an effect. While it is thought that bioactivation to reactive Dcl acyl glucuronides (AG) and subsequent protein adduct formation contribute to Dcl induced liver injury, LC-MS/MS analyses did not reveal increased formation of 4'- and 5-hydroxy-Dcl, Dcl-AG or Dcl-AG dependent protein adducts in animals treated with LPS/Dcl. Hepatic gene expression analysis suggested enhanced activation of NFκB and MAPK pathways and up-regulation of co-stimulatory molecules (IL-1β, TNF-α, CINC-1) by LPS/Dcl and PIC/Dcl, while protective factors (HSPs, SOD2) were down-regulated. LPS/Dcl led to extensive release of pro-inflammatory cytokines (IL-1β, IL-6, IFN-γ, TNF-α) and factors thought to constitute danger signals (HMGB1, CINC-1) into plasma. Taken together, our results show that Dcl enhanced the inflammatory response induced by LPS - and to a lesser extent by PIC - through up-regulation of pro-inflammatory molecules and down-regulation of protective factors. This suggests sensitization of cells to cellular stress mediated by non-drug-related risk factors by therapeutic doses of Dcl, rather than potentiation of Dcl toxicity by the stress factors.

Removal of diclofenac by conventional drinking water treatment processes and granular activated carbon filtration

This study was carried out to evaluate the efficiency of conventional drinking water treatment processes with and without pre-oxidation with chlorine and chlorine dioxide and the use of granular activated carbon (GAC) filtration for the removal of diclofenac (DCF). Water treatment was performed using the Jar test with filters on a lab scale, employing nonchlorinated artesian well water prepared with aquatic humic substances to yield 20HU true color, kaolin turbidity of 70 NTU and 1mgL(-1) DCF. For the quantification of DCF in water samples, solid phase extraction and HPLC-DAD methods were developed and validated. There was no removal of DCF in coagulation with aluminum sulfate (3.47mgAlL(-1) and pH=6.5), flocculation, sedimentation and sand filtration. In the treatment with pre-oxidation and disinfection, DCF was partially removed, but the concentration of dissolved organic carbon (DOC) was unchanged and byproducts of DCF were observed. Chlorine dioxide was more effective than chorine in oxidizing DCF. In conclusion, the identification of DCF and DOC in finished water indicated the incomplete elimination of DCF through conventional treatments. Nevertheless, conventional drinking water treatment followed by GAC filtration was effective in removing DCF (⩾99.7%). In the oxidation with chlorine, three byproducts were tentatively identified, corresponding to a hydroxylation, aromatic substitution of one hydrogen by chlorine and a decarboxylation/hydroxylation. Oxidation with chlorine dioxide resulted in only one byproduct (hydroxylation).

The effects of diclofenac on early life stages of common carp (Cyprinus carpio)

Diclofenac residues have been found in surface water, and thus could present a potential risk to aquatic species. The aim of this study was to assess the impact of diclofenac on the mortality, growth, and development of fish, as well as the impact of the drug on histological changes and selected parameters of oxidative stress in the fish. Subchronic toxic effects of diclofenac at concentrations of 0.015, 0.03, 1, and 3mg/L on embryos and larvae of common carp (Cyprinus carpio) were investigated during a 30-day toxicity test under experimental conditions. Exposure to diclofenac at 3mg/L was associated with increased mortality, increased activity of glutathione S-transferase, and decreased activity of glutathione reductase. Decreases in the levels of thiobarbituric-acid-reactive substances were associated with concentrations ≥ 0.03 mg/L. Based on these results a no observed effect concentration (NOEC)=0.015 mg/L and lowest observed effect concentration (LOEC)=0.03 mg/L were generated.

Aqueous chlorination of diclofenac: kinetic study and transformation products identification

Diclofenac reactivity and fate during water chlorination was investigated in this work. In the first step, chlorination kinetic of diclofenac (DCF) was studied in the pH range of 4-10 at 20 ± 2 °C and in the presence of an excess of total chlorine. A second-order reaction (first-order relative to DCF concentration and first-order relative to free chlorine concentration) was shown with rate constant about 3.89 ± 1.17 M(-1) s(-1) at pH 7. The elementary reactions (i.e. reactions of hypochlorous acid (HOCl) with neutral and ionized forms of DCF, and acid-catalysed reaction of HOCl with neutral and ionized forms of DCF) were proposed to explain the pH-dependence of the rate constants and intrinsic constant of each of them were calculated. In the second step, several degradation products formed during chlorination of DCF were identified. These compounds could come from an initial chlorine electrophilic attack on aromatic ring or amine function of DCF. Some of these chlorinated derivatives seem to accumulate in solution in the presence of an excess of chlorine.

Metabolic activation in drug-induced liver injury

It is generally believed that metabolic bioactivation of drug molecules to form reactive metabolites, followed by their covalent binding to endogenous macromolecules, is one of the mechanisms that can lead to hepatotoxicity or idiosyncratic adverse drug reactions (IADRs). Although the role of bioactivation in drug-induced liver injury has been reasonably well established and accepted, and methodologies (e.g., structural alerts, reactive metabolite trapping, and covalent binding) continue to emerge in an attempt to detect the occurrence of bioactivation, the challenge remains to accurately predict the likelihood for idiosyncratic liver toxicity. Recent advances in risk-assessment methodologies, such as by the estimate of total body burden of covalent binding or by zone classification, taking the clinical dose into consideration, are positive steps toward improving risk assessment. The ability to better predict the potential of a drug candidate to cause IADRs will further be dependent upon a better understanding of the pathophysiological mechanisms of such reactions. Until a thorough understanding of the relationship between liver toxicity and the formation of reactive metabolites is achieved, it appears, at present, that the most practical strategy in drug discovery and development to reduce the likelihood of idiosyncratic liver toxicity via metabolic activation is to minimize or eliminate the occurrence of bioactivation and, at the same time, to maximize the pharmacological potency (to minimze the clinical dose) of the drug of interest.

Potential carcinogenic hazards of non-regulated disinfection by-products: haloquinones, halo-cyclopentene and cyclohexene derivatives, N-halamines, halonitriles, and heterocyclic amines

Drinking water disinfectants react with natural organic material (NOM) present in source waters used for drinking water to produce a wide variety of by-products. Several hundred disinfections by-products (DBPs) have been identified, but none have been identified with sufficient carcinogenic potency to account for the cancer risks projected from epidemiological studies. In a search for DBPs that might fill this risk gap, the present study projected reactions of chlorine and chloramine that could occur with substructures present in NOM to produce novel by-products. A review of toxicological data on related compounds, supplemented by use of a quantitative structure toxicity relationship (QSTR) program TOPKAT®) identified chemicals with a high probability of being chronically toxic and/or carcinogenic among 489 established and novel DBPs. Classes of DBPs that were specifically examined were haloquinones (HQs), related halo-cyclopentene and cyclohexene (HCP&H) derivatives, halonitriles (HNs), organic N-chloramines (NCls), haloacetamides (HAMs), and nitrosamines (NAs). A review of toxicological data available for quinones suggested that HQs and HCP&H derivatives appeared likely to be of health concern and were predicted to have chronic lowest observed adverse effect levels (LOAELs) in the low μg/kg day range. Several HQs were predicted to be carcinogenic. Some have now been identified in drinking water. The broader class of HNs was explored by considering current toxicological data on haloacetonitriles and extending this to halopropionitriles. 2,2-dichloropropionitrile has been identified in drinking water at low concentrations, as well as the more widely recognized haloacetonitriles. The occurrence of HAMs has been previously documented. The very limited toxicological data on HAMs suggests that this class would have toxicological potencies similar to the dihaloacetic acids. Organic N-halamines are also known to be produced in drinking water treatment and have biological properties of concern, but no member has ever been characterized toxicologically beyond bacterial or in vitro studies of genotoxicity. The documented formation of several nitrosamines from secondary amines from both natural and industrial sources prompted exploration of the formation of additional nitrosamines. N-diphenylnitrosamine was identified in drinking waters. Of more interest, however, was the formation of phenazine (and subsequently N-chorophenazine) in a competing reaction. These are the first heterocyclic amines that have been identified as chlorination by-products. Consideration of the amounts detected of members of these by-product classes and their probable toxicological potency suggest a prioritization for obtaining more detailed toxicological data of HQs>HCP&H derivatives>NCls>HNs. Based upon a ubiquitous occurrence and virtual lack of in vivo toxicological data, NCls are the most difficult group to assign a priority as potential carcinogenic risks. This analysis indicates that research on the general problem of DBPs requires a more systematic approach than has been pursued in the past. Utilization of predictive chemical tools to guide further research can help bring resolution to the DBP issue by identifying likely DBPs with high toxicological potency.

Identification of quinone imine containing glutathione conjugates of diclofenac in rat bile

High-resolution accurate MS with an LTQ-Orbitrap was used to identify quinone imine metabolites derived from the 5-hydroxy (5-OH) and 4 prime-hydroxy (4'-OH) glutathione conjugates of diclofenac in rat bile. The initial quinone imine metabolites formed by oxidation of diclofenac have been postulated to be reactive intermediates potentially involved in diclofenac-mediated hepatotoxicity; while these metabolites could be formed using in vitro systems, they have never been detected in vivo. This report describes the identification of secondary quinone imine metabolites derived from 5-OH and 4'-OH diclofenac glutathione conjugates in rat bile. To verify the proposed structures, the diclofenac quinone imine GSH conjugate standards were prepared synthetically and enzymatically. The novel metabolite peaks displayed the identical retention times, accurate mass MS/MS spectra, and the fragmentation patterns as the corresponding authentic standards. The formation of these secondary quinone metabolites occurs only under conditions where bile salt homeostasis was experimentally altered. Standard practice in biliary excretion experiments using bile duct-cannulated rats includes infusion of taurocholic acid and/or other bile acids to replace those lost due to continuous collection of bile; for this experiment, the rats received no replacement bile acid infusion. High-resolution accurate mass spectrometry data and comparison with chemically and enzymatically prepared quinone imines of diclofenac glutathione conjugates support the identification of these metabolites. A mechanism for the formation of these reactive quinone imine containing glutathione conjugates of diclofenac is proposed.

Diclofenac oxidation by biogenic manganese oxides

Diclofenac, a nonsteroidal anti-inflammatory drug, is one of the most commonly detected pharmaceuticals in sewage treatment plant (STP) effluents. In this work, biologically produced manganese oxides (BioMnOx) were investigated to remove diclofenac. At neutral pH, the diclofenac oxidation with BioMnOx was 10-fold faster than with chemically produced MnO(2). The main advantage of BioMnOx over chemical MnO(2) is the ability of the bacteria to reoxidize the formed Mn(2+), which inhibits the oxidation of diclofenac. Diclofenac-2,5-iminoquinone was identified as a major transformation product, accounting for 5-10% of the transformed diclofenac. Except for 5-hydroxydiclofenac, which was identified as an intermediate, no other oxidation products were detected. Diclofenac oxidation was proportional to the amount of BioMnOx dosed, and the pseudo first order rate constant k was 6-fold higher when pH was decreased from 6.8 to 6.2. The Mn(2+) levels remained below the drinking water limit (0.05 mg L(-1)), thus indicating the efficient in situ microbiological regeneration of the oxidant. These results combined with previous studies suggest the potential of BioMnOx for STP effluent polishing.

Inflammatory stress and idiosyncratic hepatotoxicity: hints from animal models

Adverse drug reactions (ADRs) present a serious human health problem. They are major contributors to hospitalization and mortality throughout the world (Lazarou et al., 1998; Pirmohamed et al., 2004). A small fraction (less than 5%) of ADRs can be classified as "idiosyncratic." Idiosyncratic ADRs (IADRs) are caused by drugs with diverse pharmacological effects and occur at various times during drug therapy. Although IADRs affect a number of organs, liver toxicity occurs frequently and is the primary focus of this review. Because of the inconsistency of clinical data and the lack of experimental animal models, how IADRs arise is largely undefined. Generation of toxic drug metabolites and induction of specific immunity are frequently cited as causes of IADRs, but definitive evidence supporting either mechanism is lacking for most drugs. Among the more recent hypotheses for causation of IADRs is that inflammatory stress induced by exogenous or endogenous inflammagens is a susceptibility factor. In this review, we give a brief overview of idiosyncratic hepatotoxicity and the inflammatory response induced by bacterial lipopolysaccharide. We discuss the inflammatory stress hypothesis and use as examples two drugs that have caused IADRs in human patients: ranitidine and diclofenac. The review focuses on experimental animal models that support the inflammatory stress hypothesis and on the mechanisms of hepatotoxic response in these models. The need for design of epidemiological studies and the potential for implementation of inflammation interaction studies in preclinical toxicity screening are also discussed briefly.

Investigating the chlorination of acidic pharmaceuticals and by-product formation aided by an experimental design methodology

The degradation of seven acidic drugs and two metabolites during chlorination was investigated by liquid chromatography-mass spectrometry (LC-MS). A triple-quadrupole (QqQ) system was used to follow the time course of the pharmaceuticals and by-products, while a quadrupole time-of-flight (Q-TOF) system was also used for the identification of the by-products. Under strong chlorination conditions (10mg/L Cl(2), 24h), only four of the target compounds were significantly degraded: salicylic acid, naproxen, diclofenac and indomethacine. The degradation kinetics of these four compounds were investigated at different concentrations of chlorine, bromide and pH by means of a Box-Behnken experimental design. Depending on these factors, measured pseudo-first order half-lives were in the ranges: 23-573h for salicylic acid, 13-446min for naproxen, 5-328min for diclofenac and 0.4-13.4min for indomethacine. Also, it was observed that chlorine concentration was the overall most significant factor, followed by the bromide concentration (except for indomethacine), resulting in increased degradation kinetics as they are increased. The degradation path of salicylic acid, naproxen and diclofenac consisted of aromatic substitution of one or two hydrogens by chlorine and/or bromide. Moreover, for diclofenac, two other by-products corresponding to a decarboxylation/hydroxylation pathway from the monohalogenated products were also identified. On the other hand, indomethacine degradation did not lead to halogenation products but to oxidation ones. The investigation of these by-products in real samples by LC-MS/MS (QqQ) showed that the halogenated derivates of salicylic acid occurred in all the drinking water and wastewater samples analysed.

Oxidation of diclofenac with ozone in aqueous solution

Ozonation of diclofenac in aqueous solution in the presence and absence of an *OH scavenger, tertiary butanol (t-BuOH), was studied, and the most important reaction intermediates and products were identified. The second-order O3 rate constantwas determined by competition with buten-3-ol and was found to be 6.8 x 10(5) M(-1) s(-1) at 20 degrees C. From this high rate constant, it has been concluded that O3 must initially add on the amino nitrogen. Decomposition of the adduct results in the formation of O3*- (--> *OH) and aminyl radical precursors. A free *OH yield of 30% was estimated based on the HCHO yields generated upon reaction of *OH with 0.01 M t-BuOH. Almost all diclofenac reacted when the molar ratio of O3/diclofenac was approximately 5:1 in the presence of t-BuOH and approximately 8:1 in its absence. As primary reaction products (maximum yield), diclofenac-2,5-iminoquinone (32%), 5-hydroxydiclofenac (7%), and 2,6-dichloroaniline (19%) were detected with respect to reacted diclofenac in the presence of t-BuOH. These primary products degraded into secondary ones when the O3 dose was increased. In the *OH-mediated reaction (absence of t-BuOH) small yields of 5-hydroxydiclofenac (4.5%), diclofenac-2,5-iminoquinone (2.7%), and 2,6-dichloroaniline (6%) resulted. Practically all Cl- (95%) was released in the absence of t-BuOH but only about 45% in the presence of t-BuOH at an O3/diclofenac molar ratio of 10: 1. Based on the reaction products, mechanisms that may account for the high O3 consumption during ozonation of diclofenac are suggested. For technical applications, adequate supply of O3 is needed not only to eliminate diclofenac, but also for the degradation of its potentially toxic products like diclofenac-2,5-iminoquinone and 5-hydroxydiclofenac.

Inhibition of the myeloperoxidase chlorinating activity by non-steroidal anti-inflammatory drugs: Flufenamic acid and its 5-chloro-derivative directly interact with a recombinant human myeloperoxidase to inhibit the synthesis of hypochlorous acid

The present in vitro study was designed to assess the inhibition of the myeloperoxidase (MPO)/H(2)O(2)/Cl(-) system by several non steroidal anti-inflammatory drugs (NSAIDs) of the oxicam family and of nimesulide and to compare their effect with flufenamic acid in order to investigate their influence on the chlorinating activity of MPO as a protective mechanism during chronic inflammatory syndromes. The inhibition of the system was assessed by measurement of the taurine chlorination while the accumulation of compound II was used to investigate the mechanism of inhibition. The oxidation products of NSAIDs by the MPO/H(2)O(2)/Cl(-) system were identified and flufenamic acid and derivatives were also assessed in the inhibition of LDL oxidation in two models. Flufenamic acid (IC(50) = 1.1+/-0.3 microM) is the most efficient inhibitor of the MPO/H(2)O(2)/Cl(-) system and nimesulide (IC(50) = 2.1+/-0.3 microM) is more active than the other NSAIDs of the oxicam family (IC(50) = 8-12 microM). The accumulation of compound II revealed that flufenamic acid acts as an electron donor while the other NSAIDs are antagonists of chloride anions. The identification of the oxidation products confirms that flufenamic behaves like an electron donor and is directly oxidized in the 5-hydroxy-derivative but gives also the 5-chloro-derivative which similarly inhibits the MPO/H(2)O(2)/Cl(-) system. Flufenamic acid has the best inhibiting activity towards the MPO/H(2)O(2)/Cl(-) system. However, in models that assess the LDL oxidation, flufenamic acid and its derivatives were unable to properly inhibit MPO activity as the enzyme is adsorbed on macrostructures such as LDL molecules.

Myeloperoxidase: a target for new drug development?

Myeloperoxidase (MPO), a member of the haem peroxidase-cyclooxygenase superfamily, is abundantly expressed in neutrophils and to a lesser extent in monocytes and certain type of macrophages. MPO participates in innate immune defence mechanism through formation of microbicidal reactive oxidants and diffusible radical species. A unique activity of MPO is its ability to use chloride as a cosubstrate with hydrogen peroxide to generate chlorinating oxidants such as hypochlorous acid, a potent antimicrobial agent. However, evidence has emerged that MPO-derived oxidants contribute to tissue damage and the initiation and propagation of acute and chronic vascular inflammatory disease. The fact that circulating levels of MPO have been shown to predict risks for major adverse cardiac events and that levels of MPO-derived chlorinated compounds are specific biomarkers for disease progression, has attracted considerable interest in the development of therapeutically useful MPO inhibitors. Today, detailed information on the structure of ferric MPO and its complexes with low- and high-spin ligands is available. This, together with a thorough understanding of reaction mechanisms including redox properties of intermediates, enables a rationale attempt in developing specific MPO inhibitors that still maintain MPO activity during host defence and bacterial killing but interfere with pathophysiologically persistent activation of MPO. The various approaches to inhibit enzyme activity of MPO and to ameliorate adverse effects of MPO-derived oxidants will be discussed. Emphasis will be put on mechanism-based inhibitors and high-throughput screening of compounds as well as the discussion of physiologically useful HOCl scavengers.

The effects of non-steroidal anti-inflammatory drug application on incisional wound healing in rats

OBJECTIVE

There is evidence that non-steroidal anti-inflammatory drugs (NSAIDs) delay both epithelialisation and angiogenesis in the early phases of wound healing because of an antiproliferative effect. We investigated the influence of diclofenac, a non-selective NSAID, on incisional wound healing.

METHOD

Ten male Wistar rats were given 5 mg diclofenac per kg bodyweight per day; 10 rats were given placebo pellets. After 10 days, unimpaired healing occurred independently of drug treatment both macroscopically and microscopically. Histomorphometry revealed a significant reduction (p = 0.006) in fibroblasts after diclofenac application (median 3 166 cells per mm2) compared with the placebo group (median 3940 cells per mm2). Epidermal thickness was not statistically different between the two groups.

RESULTS

Diclofenac diminished the amount of fibroblasts in connective tissue, reflecting the known antiproliferative effect of NSAIDs on fibroblasts. Clinical healing was not affected.

CONCLUSION

We recommend short-term diclofenac application for post-surgical and post-traumatic patients with wounds who would benefit from its antiphlogistic and analgesic effect. However, if wound healing is disturbed, the negative effect of diclofenac on fibroblasts should be considered. This is particularly relevant for patients with chronic wounds or conditions such as diabetes which can delay wound healing.