NADPH oxidase inhibition prevents beta cell dysfunction induced by prolonged elevation of oleate in rodents.

AIMS/HYPOTHESIS: The activation of NADPH oxidase has been implicated in NEFA-induced beta cell dysfunction. However, the causal role of this activation in vivo remains unclear. Here, using rodents, we investigated whether pharmacological or genetic inhibition of NADPH oxidase could prevent NEFA-induced beta cell dysfunction in vivo. METHODS: Normal rats were infused for 48 h with saline or oleate with or without the NADPH oxidase inhibitor apocynin. In addition, NADPH oxidase subunit p47(phox)-null mice and wild-type littermate controls were infused with saline or oleate for 48 h. This was followed by measurement of NADPH oxidase activity, reactive oxygen species (ROS) and superoxide imaging and assessment of beta cell function in isolated islets and hyperglycaemic clamps. RESULTS: Oleate infusion in rats increased NADPH oxidase activity, consistent with increased total but not mitochondrial superoxide in islets and impaired beta cell function in isolated islets and during hyperglycaemic clamps. Co-infusion of apocynin with oleate normalised NADPH oxidase activity and total superoxide levels and prevented beta cell dysfunction. Similarly, 48 h NEFA elevation in wild-type mice increased total but not mitochondrial superoxide and impaired beta cell function in isolated islets. p47(phox)-null mice were protected against these effects when subjected to 48 h oleate infusion. Finally, oleate increased the levels of total ROS, in both models, whereas inhibition of NADPH oxidase prevented this increase, suggesting that NADPH oxidase is the main source of ROS in this model. CONCLUSIONS/INTERPRETATION: These data show that NADPH-oxidase-derived cytosolic superoxide is increased in islets upon oleate infusion in vivo; and whole-body NADPH-oxidase inhibition decreases superoxide in concert with restoration of islet function.

Diffuse interstitial pneumonia and pulmonary hypertension: a novel manifestation of chronic granulomatous disease.

The present authors report the case of an adult with chronic granulomatous disease who developed an unusual lung fibrosis associated with severe pulmonary hypertension. Histological analysis of a lung biopsy showed a diffuse infiltration with pigmented macrophages without granulomas, which particularly involved the pulmonary arterial and venular walls. Clinical and histological findings were suggestive of pulmonary veno-occlusive disease. Such a clinical association has not been previously described in the literature and might be due to the persistent expression of gp91phox at a very low level. In conclusion, the present case report illustrates a novel manifestation of chronic granulomatous disease.

Potential role of the "NADPH oxidases" (NOX/DUOX) family in cystic fibrosis.

Cystic fibrosis (CF), is the most common life-shortening autosomal recessive disorder in Caucasians. It is caused by mutations in a single gene on the long arm of chromosome 7 that encodes the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CF is characterized by abnormal Na+ and Cl- ion transport in several tissues, including the lungs, pancreas, gastrointestinal tract, liver, sweat glands, and male reproductive system. Progressive pulmonary disease is the dominant clinical feature of CF and accounts for morbidity and mortality. The inflammation characterized by an overabundance of activated neutrophils and macrophages on the respiratory epithelial surface is associated to a high production of reactive oxygen species (ROS) which contribute to the pathogenesis of cystic fibrosis. ROS could have different origins but the role of the NADPH oxidase system is essential. The "NADPH oxidases" (NOX/DUOX) family is an enzymatic complex formed by cytosolic and membrane subunits. Until now several homologues of the phagocytic NADPH oxidase have been identified in different tissues and it has been shown that the lungs preferentially expressed DUOX1-2. Thus, DUOX1-2 could be implicated in the anti-infectious defense system. The role of DUOX enzymes as a source of ROS in cystic fibrosis is examined as they could contribute to a better understanding of molecular mechanisms in CF. Moreover they could be a potential target for a new therapeutic approach.

The phosphorylation targets of p47phox, a subunit of the respiratory burst oxidase. Functions of the individual target serines as evaluated by site-directed mutagenesis.

The respiratory burst oxidase of phagocytes and B lymphocytes catalyzes the reduction of oxygen to O2- at the expense of NADPH. Dormant in resting cells, the oxidase is activated by exposing the cells to appropriate stimuli. During activation, p47phox, a cytosolic oxidase subunit, becomes extensively phosphorylated on a number of serines located between S303 and S379. To determine whether this phosphorylation is necessary for oxidase activation, we examined phorbol-elicited oxidase activity in EBV-transformed B lymphoblasts deficient in p47phox after transfection with plasmids expressing various S-->A mutants of p47phox. The mutant containing S-->A mutations involving all serines between S303 and S379 [S(303-379)A] was not phosphorylated, did not translocate to plasma membrane during activation and was almost devoid of function. As to individual serines, S379 was of special interest because (a) p47 phox S379 was phosphorylated in phorbol-activated lymphoblasts expressing wild-type p47phox, and (b) p47phox S379A failed to translocate to the membrane, and was as functionless as p47phox S(303-379)A; other single S-->A mutations had little effect on oxidase activity. These findings suggest that the phosphorylation of S379 may be important for oxidase activation in whole cells.

Vasoactive intestinal peptide dampens formyl-peptide-induced ROS production and inflammation by targeting a MAPK-p47phox phosphorylation pathway in monocytes.

Reactive oxygen species (ROS) produced by the phagocyte NADPH oxidase (NOX2) are required for microbial clearance; however, when produced in excess they exacerbate inflammatory response and injure surrounding tissues. NOX2 is a multicomponent enzyme composed of membrane-associated cytochrome b588 and cytosolic components p47phox, p67phox, p40phox, and rac1/2. We investigated whether vasoactive intestinal peptide (VIP), an endogenous immune-modulatory peptide, could affect ROS production by NOX2 in primary human phagocytes. VIP did not modulate basal ROS production by phagocytes, but it inhibited monocyte and not neutrophil ROS production in response to the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). The action of VIP was essentially mediated by high-affinity G-protein coupled receptors VPAC1 as its specific agonist, [ALA11,22,28]VIP, mimicked VIP-inhibitory effect, whereas the specific VPAC1 antagonist, PG97-269, blunted VIP action. Further, we showed that VIP inhibited fMLF-induced phosphorylation of ERK1/2 (extracellular signal-regulated kinase 1/2), p38MAPK (p38 mitogen-activated protein kinase) pathways, and phosphorylation of p47phox on Ser345 residue. Also, VIP exerted an anti-inflammatory effect in a model of carrageenan-induced inflammation in rats. We thus found that VIP exerts anti-inflammatory effects by inhibiting the "MAPK-p47phox phosphorylation-NOX2 activation" axis. These data suggest that VIP acts as a natural anti-inflammatory agent of the mucosal system and its analogs could be novel anti-inflammatory molecules.

Resolution of major protein kinase substrates in neutrophil cytosol in response to DAG/PS and arachidonic acid stimulation and the selective action of various protein kinase inhibitors.

Stimulation of human neutrophils induces phosphorylation of several cellular proteins. Human neutrophils possess calcium-dependent protein kinase C (PKC) alpha and beta isoforms and calcium-independent n isoforms. Little is known, however, of the physiological substrates of each isoform. In this study, we characterized the substrates of calcium-dependent and -independent PKC isoforms and the substrate of PKC activated by arachidonic acid. Furthermore, we found that the PKC inhibitor H-7 failed to inhibit phosphorylation of endogenous substrates of calcium-independent PKC activity. These results may help to understand the role of PKC in neutrophil activation and shed light on the different responses elicited by H-7 in intact cells.

P40phox associates with the neutrophil Triton X-100-insoluble cytoskeletal fraction and PMA-activated membrane skeleton: a comparative study with P67phox and P47phox.

NADPH oxidase is an O2*- -generating enzyme found in phagocytes such as neutrophils. It is composed of a membrane-bound cytochrome b, the cytosolic proteins p67phox, p47phox, p40phox, and the G-protein p21rac. The system is dormant in resting cells but acquires catalytic activity on exposure to appropriate stimuli. Cytochrome b, p67phox, p47phox, and rac2 associate with the cytoskeleton and membrane skeleton of activated neutrophils. It is not known whether p40phox associates with the cytoskeleton. The purpose of this study was to analyze the subcellular distribution of p40phox. When resting neutrophils were lysed in Triton X-100 or octyl glucoside buffer and separated into detergent-soluble and detergent-insoluble fractions, p40phox and p67phox were mainly associated with the detergent-insoluble fraction (defined as the cytoskeleton), whereas p47phox was mainly found in the soluble fraction. Neutrophil activation by phorbol myristate acetate (PMA) induced p47phox translocation to the cytoskeleton but did not affect the distribution of p40phox or p67phox. Using immunofluorescence confocal microscopy, we found that p40phox colocalized with filamentous actin. In neutrophils from a p67phox-deficient patient with detectable p40phox, p40phox associated with the cytoskeleton only after activation by PMA. A complex containing the three proteins was isolated from the cytoskeleton of activated neutrophils. When activated membranes were treated with Triton X-100 buffer, p40phox, p47phox, and p67phox were found in the membrane skeleton enriched in NADPH-oxidase activity; some p40phox and p47phox was found in the soluble membrane fraction, but no p67phox was detected. These findings show that p40phox, like p67phox and p47phox, binds to the cytoskeleton and membrane skeleton. In addition, p40phox can dissociate from p67phox in activated membranes.

Characterization of 11 novel mutations in the X-linked chronic granulomatous disease (CYBB gene).

The most frequent form of chronic granulomatous disease (CGD) is caused by inactivation of the CYBB gene, which encodes the gp91-phox subunit of phagocyte NADPH oxidase. This defect prevents phagocytes from producing reactive oxygen species and thus from eradicating bacterial and fungal infections. We investigated 16 unrelated male patients with suspected X-linked CGD and gp91-phox deficiency. A mutation was found in the CYBB gene of all 16 patients, and 11 of these mutations were novel. Eleven patients (69%) had a point mutation (84G>A in two unrelated patients, and 177C>G, 217C>T, 388C>T, 676C>T, 691C>T, 868C>T, 919A>C, 1384G>T and T1514G in one case each, yielding W28X, C59W, R73X, R130X, R226X, Q231X, R290X, T307P, E462X, L505R gp-91phox). One patient had an in-frame deletion removing two amino acids (R54 and A55). Finally, insertions or duplications were found in four patients (from +1 to +31 bases). Overall, 12 (75%) of the mutations led to the production of a truncated protein. No clear correlation was found between clinical manifestations and genomic/biochemical alterations. Thirteen mothers could be tested, and all were carriers. Hum Mutat 18:163, 2001.

Inhibition of human neutrophil protein kinase C activity by the antimalarial drug mefloquine.

Mefloquine (alpha-(2-piperidyl)-2,8-bis(trifluoromethyl)-4-quinolinemethanol) , an antimalarial drug, has been shown to inhibit human neutrophil functions, particularly oxygen-dependent bactericidal activity. Since calcium- and phospholipid-dependent protein kinase C (PKC) has a central role in the regulation of this function, we hypothesized that its activity might be altered by mefloquine. We found that mefloquine directly inhibited PKC in a dose-dependent manner, with an IC50 of 45 microM. This inhibition appeared to be non-competitive with respect to ATP, histone and phosphatidylserine. In addition, mefloquine inhibited the binding of [3H]phorbol 12,13 dibutyrate to PKC, indicating that it interacts with the regulatory domain of PKC. By contrast, mefloquine had little or no effect on neutrophil cAMP-dependent protein kinase or its catalytic subunit. Phorbol myristate acetate-induced protein phosphorylation in intact neutrophils was also inhibited by preincubation with mefloquine at concentrations similar to those inhibiting superoxide anion production. These data suggest that inhibition of neutrophil functions by mefloquine may be due to the inhibition of cellular PKC and that mefloquine could have further biological effects in situations in which PKC is involved.

Phosphoinositide 3-kinase couples NMDA receptors to superoxide release in excitotoxic neuronal death.

Sustained activation of neuronal N-methly D-aspartate (NMDA)-type glutamate receptors leads to excitotoxic cell death in stroke, trauma, and neurodegenerative disorders. Excitotoxic neuronal death results in part from superoxide produced by neuronal NADPH oxidase (NOX2), but how NMDA receptors are coupled to neuronal NOX2 activation is not well understood. Here, we identify a signaling pathway coupling NMDA receptor activation to NOX2 activation in primary neuron cultures. Calcium influx through the NR2B subunit of NMDA receptors leads to the activation of phosphoinositide 3-kinase (PI3K). Formation of phosphatidylinositol (3,4,5)-triphosphate (PI(3,4,5)P3) by PI3K activates the atypical protein kinase C, PKC zeta (PKCζ), which in turn phosphorylates the p47(phox) organizing subunit of neuronal NOX2. Calcium influx through NR2B-containing NMDA receptors triggered mitochondrial depolarization, NOX2 activation, superoxide formation, and cell death. However, equivalent magnitude calcium elevations induced by ionomycin did not induce NOX2 activation or neuronal death, despite causing mitochondrial depolarization. The PI3K inhibitor wortmannin prevented NMDA-induced NOX2 activation and cell death, without preventing cell swelling, calcium elevation, or mitochondrial depolarization. The effects of wortmannin were circumvented by exogenous supply of the PI3K product, PI(3,4,5)P3, and by transfection with protein kinase M, a constitutively active form of PKCζ. These findings demonstrate that superoxide formation and excitotoxic neuronal death can be dissociated from mitochondrial depolarization, and identify a novel role for PI3K in this cell death pathway. Perturbations in this pathway may either increase or decrease superoxide production in response to NMDA receptor activation, and may thereby impact neurological disorders, in which excitotoxicity is a contributing factor.

ATP-gated P2X1 ion channels protect against endotoxemia by dampening neutrophil activation.

BACKGROUND: In sepsis, extracellular ATP, secreted by activated platelets and leukocytes, may contribute to the crosstalk between hemostasis and inflammation. Previously, we showed that, in addition to their role in platelet activation, ATP-gated P2X(1) ion channels are involved in promoting neutrophil chemotaxis. OBJECTIVES: To elucidate the contribution of P2X(1) ion channels to sepsis and the associated disturbance of hemostasis. METHODS: We used P2X(1) (-/-) mice in a model of lipopolysaccharide (LPS)-induced sepsis. Hemostasis and inflammation parameters were analyzed together with outcome. Mechanisms were further studied ex vivo with mouse and human blood or isolated neutrophils and monocytes. RESULTS: P2X(1) (-/-) mice were more susceptible to LPS-induced shock than wild-type mice, despite normal cytokine production. Plasma levels of thrombin-antithrombin complexes were higher, thrombocytopenia was worsened, and whole blood coagulation time was markedly reduced, pointing to aggravated hemostasis disturbance in the absence of P2X(1). However, whole blood platelet aggregation occurred normally, and P2X(1) (-/-) macrophages displayed normal levels of total tissue factor activity. We found that P2X(1) (-/-) neutrophils produced higher amounts of reactive oxygen species. Increased amounts of myeloperoxidase were released in the blood of LPS-treated P2X(1) (-/-) mice, and circulating neutrophils and monocytes expressed higher levels of CD11b. Neutrophil accumulation in the lungs was also significantly augmented, as was lipid peroxidation in the liver. Desensitization of P2X(1) ion channels led to increased activation of human neutrophils and enhanced formation of platelet-leukocyte aggregates. CONCLUSIONS: P2X(1) ion channels play a protective role in endotoxemia by negatively regulating systemic neutrophil activation, thereby limiting the oxidative response, coagulation, and organ damage.

[Synergism of josamycin and oxidation against Staphylococcus aureus]. / Synergie entre la josamycine et un stress oxydant pour la bactéricidie de Staphylococcus aureus.

We have previously reported that josamycin (JM) displayed a bactericidal synergy with human neutrophils (PMN) in vitro without altering significantly various cell functions (Labro et al., Path. Biol., 1989, 37, 329-334). Since JM may concentrate into phagocytes, and partly at least into lysosomes, it was of interest to analyze if the presence of this molecule could enhance the bactericidal activity of some acellular systems mimicking those acting inside the phagolysosome, using Staphylococcus aureus as the bacterial target. Erythromycin (EM) was assessed comparatively. While none of the macrolides increased the lethal effect of a crude PMN extract (02-independent system), an enhancement of the bacterial killing by an oxidant stress was observed in the presence of the 2 molecules. However, the effect of JM was strongest that the one induced by EM: S. aureus survival after exposure to xanthine + xanthine oxidase was 38 +/- 17.2% and it was reduced to 11 +/- 5.0 and 23 +/- 15.6 with JM (30 and 3 mg/l) and 22 +/- 13.1 and 23 +/- 9.7 with EM (30 and 3 mg/l). On the other hand, S. aureus survival after exposure to H2 O2 was reduced only by JM (16 +/- 9.4 and 32 +/- 6.9% versus 43 +/- 11.2% for controls). Pretreatment of S. aureus for 60 min by JM or EM did not alter the sensitivity of the bacteria either to PMN or to acellular systems. These data suggest that JM (and at a lesser degree EM) could be transformed by reactive oxygen species generated inside the phagolysosome to become more toxic for the bacteria.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of quinine and cinchonine on human neutrophils functions in vitro.

We have compared the in-vitro interactions of quinine and cinchonine, two alkaloids from cinchona bark, with human neutrophil functions. Although these molecules are structurally similar, they induced a quantitatively different depressive effect on neutrophil chemotaxis and oxidative response. Quinine produced the strongest effect at concentrations as low as 10 mg/l, which may be achievable in serum during therapeutic use of this compound. The depression induced by cinchonine was noticeable only at 100 mg/l. Chemotaxis was decreased by about 25% (formyl-methionyl-leucyl-phenylalanine) or 39% (serum) for quinine (100 mg/l) only if a constant concentration of the drug was maintained during the assay while cinchonine had no effect on this PMN function. The greatest impairment was observed for the PMN oxidative burst: this was dose-dependent whatever the stimulus used (phorbol-myristate-acetate or opsonized zymosan). After 30 min incubation in the presence of the drugs, the zymosan-induced chemiluminescence response was decreased by 96% and by 67% with quinine, 100 and 10 mg/l, respectively, and by 62% with cinchonine 100 mg/l. The myeloperoxidase-mediated iodination of PMN was reduced by 100% and 46% with quinine, 100 and 10 mg/l, respectively, whereas cinchonine decreased this function by about 95% at 100 mg/l and 14% at 10 mg/l. Superoxide anion generation was impaired by 94% (quinine 100 mg/l) or 45% (cinchonine 100 mg/l). The relevance to the clinical situation and the possible mechanisms of such effects are discussed.

Effects of anti-infectious agents on polymorphonuclear neutrophils.

Polymorphonuclear neutrophils play a crucial role in host defences against infectious diseases. New trends in anti-infectious therapy require knowledge of the possible interactions between the drugs and the natural defence system. This overview summarizes some of the in vitro data on the effects of anti-infectious agents on neutrophils. The relevance for the clinical situation is discussed.

Synergistic bactericidal interaction of josamycin with human neutrophils in vitro.

Josamycin and erythromycin have been compared for their in-vitro interaction with bactericidal killing by human neutrophils. The mechanism of this interaction was studied in two ways. First, the target organisms (Staphylococcus aureus and Pseudomonas aeruginosa) were incubated for 60 min with josamycin, erythromycin or control buffer prior to use in a human polymorphonuclear neutrophil (PMN) killing assay. Second the macrolides were added directly to acellular killing systems mimicking those acting inside the phagolysosome; oxygen-independent systems were obtained from a crude granule extract of PMN and oxygen-dependent systems consisted either of a mixture of xanthine plus xanthine oxidase or of a solution of H2O2. Whereas josamycin-pretreated P. aeruginosa were twice as sensitive to killing by PMN than were control cells, this was not the case for S. aureus. Both oxidant generating systems were more effective in destroying S. aureus in the presence of josamycin (3 and 30 mg/l). Erythromycin showed a similar synergy but only with the xanthine plus xanthine oxidase system. This synergy was observed with neither of the O2-independent systems for S. aureus, nor with any acellular system for P. aeruginosa. These data suggest that at least two kinds of mechanism may explain the bactericidal synergy observed between macrolides and PMN. The first (for macrolide-resistant species such as P. aeruginosa) could be due to alterations in the bacteria by the antibiotics, while the second (for macrolide-sensitive species such as S. aureus) could be based upon an as yet unexplained transformation of the molecules by reactive oxygen species into more "toxic" forms. These differences between josamycin and erythromycin could arise from differences in their chemical structure.

Effect of monodesethyl amodiaquine on human polymorphonuclear neutrophil functions in vitro.

We have previously observed that the antimalarial drug amodiaquine impairs the human polymorphonuclear neutrophil (PMN) oxidative burst in vitro. However, the drug acted at a concentration of 100 micrograms/ml, far higher than that which is achievable therapeutically. Since amodiaquine is extensively metabolized into monodesethyl amodiaquine, we investigated whether the metabolite modified PMN functions at lower concentrations than amodiaquine does. Monodesethyl amodiaquine strongly depressed PMN chemotaxis and phagocytosis at concentrations as low as 10 micrograms/ml. This inhibition was reversed by washing out the drug. The PMN oxidative burst was markedly depressed by monodesethyl amodiaquine, whatever the assay technique (luminol-amplified chemiluminescence, lucigenin-amplified chemiluminescence, myeloperoxidase activity) or stimulus used (opsonized zymosan, phorbol myristate acetate, formylmethionyl leucyl phenylalanine). There were extreme interindividual variations in sensitivity to the depressive effect of monodesethyl amodiaquine when the PMN oxidative burst was assayed in terms of luminol-amplified chemiluminescence or lucigenin-amplified chemiluminescence. PMN samples were divided into two groups on the basis of the MIC of the drug: 60% of the samples were "highly sensitive," being strongly inhibited at concentrations as low as 0.1 micrograms/ml (obtained during therapy), whereas the "moderately sensitive" samples were inhibited at concentrations of 10 micrograms/ml and above. The difference between the two groups was highly significant. This PMN sensitivity to the inhibitory effect of the drug was not related to intrinsic oxidative metabolism. Our data indicate that monodesethyl amodiaquine, the main metabolite of amodiaquine, has a far stronger inhibitory effect on various PMN functions in vitro than the parent drug, warranting relevant in vivo studies.

Comparison of cefodizime with various cephalosporins for their indirect effect on the human neutrophil oxidative burst in vitro.

Cefodizime, a 2-amino-thiazolyl cephalosporin, is reported to display in-vitro, ex-vivo and in-vivo immunomodulatory properties; in particular, it enhances the survival of mice infected with cefodizime-resistant pathogens. We have used an in-vitro model to assess the indirect effect of this drug (compared with other cephalosporins) on the neutrophil (PMN) oxidative response. Pseudomonas aeruginosa was employed as the bacterial target for cefodizime and cefotaxime (MICs greater than 128 mg/l), cefsulodin (MIC 16 mg/l) and ceftazidime (MIC 32 mg/l). After overnight growth in the presence of subinhibitory concentrations of each drug (10 mg/l), the altered filamentous P. aeruginosa induced a stronger oxidative response of PMN than untreated control bacteria. For all cephalosporins this was related to alterations of bacterial structure leading to increased deposits of antibodies and/or complement. Furthermore, increased non-opsonin dependent stimulation of the PMN oxidative burst was obtained; the strongest response was observed with cefodizime-treated P. aeruginosa in the case of low responder PMN, which displayed a deficient response after stimulation by control bacteria. The possibility that cefodizime could enhance this PMN function in opsonin-deficient patients requires further investigation.

Comparison of the in-vitro effect of several macrolides on the oxidative burst of human neutrophils.

We have compared the in-vitro interaction of five macrolides (roxithromycin, erythromycin, spiramycin, oleandomycin and josamycin) with human neutrophils (PMN). Only roxithromycin strongly impaired the oxidative burst of PMN assessed by luminol amplified chemiluminescence, superoxide anion generation, and myeloperoxidase-mediated iodination of proteins. This effect was observed only for high concentrations of this drug (100 and 50 mg/l). Furthermore, the sensitivity of PMN to the depressive effect of roxithromycin permitted the definition of two kinds of PMN: in Highly Sensitive (HS)-PMN, the oxidative response was completely abolished while in Moderately Sensitive (MS)-PMN, a decreased, but yet measurable (20-50% of the control), response was obtained. The roxithromycin-induced depression of PMN was time-dependent and partly reversed by washing. Chemotaxis was also impaired by roxithromycin (100 mg/l) but phagocytosis of Klebsiella pneumoniae was unaltered even at high concentrations of the drug. Since roxithromycin displays the highest intracellular uptake, compared with the other macrolides assessed in this study, this could explain the results observed here. The relevance to the clinical situation needs further study. This effect of roxithromycin could be useful to control the inflammatory process associated in certain infectious diseases, in particular if high concentrations of the drug are obtained in tissues.

[Alteration of bacteria induced by subinhibitory concentrations of cefixime: consequences on bactericidal activity of human polynuclear neutrophils]. / Modification des bactéries induites par le céfixime à concentrations subinhibitrices: conséquences sur l'activité bactéricide des polynucléaires neutrophiles humains.

Subinhibitory concentrations of most parenteral cephalosporins have been reported to alter bacterial infectivity and, in particular, to increase the susceptibility of altered bacteria to the killing effects of polymorphonuclear neutrophils (PMN). Few data on this issue are available for oral cephalosporins. This study investigated the effects of sub-MIC concentrations of the new oral cephalosporin cefixime on two bacterial targets, i.e., S. aureus 209P (MIC 20 mg/l) and E. coli K12 (MIC 0.15 mg/l). After overnight incubation (18 hours) with 10 or 5 mg/l cefixime, susceptibility of S. aureus to the killing effects of PMNs was increased two-fold as compared with control organisms and susceptibility to the O2-independent PMN bactericidal system (PMN extract) was also increased. In contrast, the susceptibility of E. coli to PMN and to cell-free bactericidal systems was identical for cefixime-exposed strains (0.1 and 0.05 mg/l) and for unexposed controls. However, cefixime-exposed E. coli were filamentous, suggesting that bactericidal efficacy in terms of the bacterial mass eliminated was enhanced in exposed strains. These data show that low levels of cefixime are capable of producing major alterations in susceptible and resistant bacteria and of increasing their susceptibility to PMN. These effects may be relevant in vivo, in particular when low concentrations of antibiotics persist over long periods in infected sites.