Superoxide scavenging activity of erythromycin-iron complex

Diffuse Panbronchiolitis

Diffuse panbronchiolitis (DPB) is characterized by chronic sinobronchial infection and diffuse bilateral micronodular pulmonary lesions consisting of inflammatory cells. Studies on disease etiology point to a genetic predisposition unique to Asians. Early therapy for DPB was largely symptomatic. The advent of macrolide antibiotics, including erythromycin, roxithromycin and clarithromycin, has strikingly changed disease prognosis. Low-dose, long-term macrolide therapy for DPB originated from detailed observations of response to therapy in a single patient. The bactericidal activity of macrolides, particularly erythromycin, is not a significant factor for their clinical efficacy in DPB. Firstly, irrespective of bacterial clearance, clinical improvement is observed in patients treated with erythromycin. Secondly, even in cases with bacterial superinfection with Pseudomonas aeruginosa resistant to macrolides, treatment has proved effective. Thirdly, the recommended dosage of macrolides produces peak levels in tissue that are below the minimum inhibitory concentrations for major pathogenic bacteria that colonize the airway. In the last two decades, the possible mechanism underlying the effectiveness of macrolide therapy has been extensively studied. The proposed mechanism of action includes inhibition of excessive mucus and water secretion from the airway epithelium, inhibition of neutrophil accumulation in the large airway, inhibition of lymphocyte and macrophage accumulation around the small airway, and modulation of bacterial virulence. The great success of macrolide therapy in diffuse panbronchiolitis may extend its application to the treatment of other chronic inflammatory disorders. If the anti-inflammatory activity of macrolides is independent of their bactericidal effect, new anti-inflammatory macrolides without antimicrobial activity should be developed to minimize emergence of macrolide-resistant micro-organisms.

Suppression of nitric oxide production from nasal fibroblasts by metabolized clarithromycin in vitro

Background

Low-dose and long-term administration of 14-membered macrolide antibiotics, so called macrolide therapy, has been reported to favorably modify the clinical conditions of chronic airway diseases. Since there is growing evidence that macrolide antibiotic-resistant bacteria's spreaders in the populations received macrolide therapy, it is strongly desired to develop macrolide antibiotics, which showed only anti-inflammatory action. The present study was designed to examine the influence of clarithromycin (CAM) and its metabolized materials, M-1, M-4 and M-5, on free radical generation from nasal polyp fibroblasts (NPFs) through the choice of nitric oxide (NO), which is one of important effector molecule in the development of airway inflammatory disease in vitro.

Methods

NPFs (5 × 10⁵ cells/ml) were stimulated with 1.0 μg/ml lipopolysaccharide (LPS) in the presence of agents for 24 hours. NO levels in culture supernatants were examined by the Griess method. We also examined the influence of agents on the phosphorylation of MAPKs, NF-κB activation, iNOS mRNA expression and iNOS production in NPFs cultured for 2, 4, 8, and 12 hours, respectively.

Results

The addition of CAM (> 0.4 μg/ml) and M-4 (> 0.04 μg/ml) could suppress NO production from NPFs after LPS stimulation through the suppression of iNOS mRNA expression and NF-κB activation. CAM and M-4 also suppressed phosphorylation of MAPKs, ERK and p38 MAPK, but not JNK, which are increased LPS stimulation. On the other hand, M-1 and M-5 could not inhibit the NO generation, even when 0.1 μg/ml of the agent was added to cell cultures.

Conclusion

The present results may suggest that M-4 will be a good candidate for the agent in the treatment of chronic airway inflammatory diseases, since M-4 did not have antimicribiological effects on gram positive and negative bacteria.

Therapeutic effect of lecithinized superoxide dismutase against colitis

Ulcerative colitis (UC) involves intestinal mucosal damage induced by reactive oxygen species (ROS), in particular, superoxide anion. Superoxide dismutase (SOD) catalyzes dismutation of superoxide anion to hydrogen peroxide, which is subsequently detoxified by catalase. Lecithinized SOD (PC-SOD) is a new modified form of SOD that has overcome previous clinical limitations of SOD. In this study, we examined the action of PC-SOD using an animal model of UC, dextran sulfate sodium (DSS)-induced colitis. DSS-induced colitis was ameliorated by daily intravenous administration of PC-SOD. Unmodified SOD produced a similar effect but only at more than 30 times the concentration of PC-SOD. In vivo electron spin resonance analysis confirmed that the increase in the colonic level of ROS associated with development of colitis was suppressed by PC-SOD administration. The dose-response profile of PC-SOD was bell-shaped, but simultaneous administration of catalase restored the ameliorative effect at high doses of PC-SOD. Accumulation of hydrogen peroxide was observed with the administration of high doses of PC-SOD, an effect that was suppressed by the simultaneous administration of catalase. We also found that either a weekly intravenous administration or daily oral administration of PC-SOD conferred protection. These results suggest that PC-SOD achieves its ameliorative effect against colitis through decreasing the colonic level of ROS and that its ineffectiveness at higher doses is because of the accumulation of hydrogen peroxide. Furthermore, we consider that intermittent or oral administration of PC-SOD can be applied clinically to improve the quality of life of UC patients.

Suppressive activity of macrolide antibiotics on nitric oxide production by lipopolysaccharide stimulation in mice

BACKGROUND: Low-dose and long-term administration of macrolide antibiotics into patients with chronic airway inflammatory diseases could favorably modify their clinical conditions. However, the therapeutic mode of action of macrolides is not well understood. Free oxygen radicals, including nitric oxide (NO), are well recognized as the important final effector molecules in the development and the maintenance of inflammatory diseases. PURPOSE: The influence of macrolide antibiotics on NO generation was examined in vivo. METHODS: Male ICR mice, 5 weeks of age, were orally administered with either roxithromycin, clarithromycin, azithromycin or josamycin once a day for 2-4 weeks. The mice were then injected intraperitoneally with 5.0 mg/kg lipopolysaccharide (LPS) and the plasma NO level was examined 6 h later. RESULTS: Although pre-treatment of mice with macrolide antibiotics for 2 weeks scarcely affected NO generation by LPS injection, the administration of macrolide antibiotics, except for josamycin, for 4 weeks significantly inhibited LPS-induced NO generation. The data in the present study also showed that pre-treatment of mice with macrolide antibiotics for 4 weeks significantly suppresses not only production of pro-inflammatory cytokines interleukin-1beta, interleukin-6, and tumor necrosis factor-alpha, but also inducible nitric oxide synthase mRNA expressions, which are enhanced by LPS injection. CONCLUSION: These results strongly suggest that suppressive activity of macrolide antibiotics on NO generation in response to LPS stimulation in vivo may, in part, account for the clinical efficacy of macrolides on chronic inflammatory diseases.

Reactive Oxygen Species (ROS) Generation Inhibited by Aporphine and Phenanthrene Alkaloids Semi-Synthesized from Natural Boldine

Four phenanthrene and one aporphine alkaloids semi-synthesized from boldine were evaluated for their inhibitory effect on reactive oxygen species (ROS) generation. ROS generation by neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine was inhibited in a concentration dependent manner. Alkaloids exerted similar inhibitory effect in the hypoxanthine-xanthine oxidase system than in stimulated neutrophils, which could be attributed to a direct ROS scavenging activity. None of the alkaloids assayed had any effect on xanthine oxidase activity. Therefore the synthesized alkaloids might constitute an alternative therapy in inflammation disorders in which ROS generation is involved.

Suppressive activity of macrolide antibiotics on nitric oxide production from nasal polyp fibroblasts in vitro

The influence of macrolide antibiotics on nitric oxide (NO) generation was examined using human nasal polyp fibroblasts (NPFs) in vitro. Addition of roxithromycin (RXM) at a concentration of > 7.5 microg/ml to cell cultures was shown to suppress NO production in response to stimulation with 25.0 ng/ml tumor necrosis factor (TNF)-alpha. However, jyosamycin (JM) did not suppress NO production from NPFs induced by TNF-alpha stimulation in vitro, even when added to cell cultures at a concentration of 20.0 microg/ml. We then examined the influence of RXM on inducible nitric oxide synthase (iNOS) mRNA expression in NPFs. Addition of RXM at a dose of 7.5 microg/ml to cell cultures caused reduction of iNOS mRNA expression, which was enhanced by TNF-alpha stimulation in vitro.

Structure and function of "metalloantibiotics"

Although most antibiotics do not need metal ions for their biological activities, there are a number of antibiotics that require metal ions to function properly, such as bleomycin (BLM), streptonigrin (SN), and bacitracin. The coordinated metal ions in these antibiotics play an important role in maintaining proper structure and/or function of these antibiotics. Removal of the metal ions from these antibiotics can cause changes in structure and/or function of these antibiotics. Similar to the case of "metalloproteins," these antibiotics are dubbed "metalloantibiotics" which are the title subjects of this review. Metalloantibiotics can interact with several different kinds of biomolecules, including DNA, RNA, proteins, receptors, and lipids, rendering their unique and specific bioactivities. In addition to the microbial-originated metalloantibiotics, many metalloantibiotic derivatives and metal complexes of synthetic ligands also show antibacterial, antiviral, and anti-neoplastic activities which are also briefly discussed to provide a broad sense of the term "metalloantibiotics."

Killing of bacillus spores by aqueous dissolved oxygen, ascorbic acid, and copper ions

An approach to decontamination of biological endospores is discussed. Specifically, the performance of an aqueous modified Fenton reagent is examined. A modified Fenton reagent formulation of cupric chloride, ascorbic acid, and sodium chloride is shown to be an effective sporicide under aerobic conditions. The traditional Fenton reaction involves the conversion of hydrogen peroxide to hydroxyl radical by aqueous ionic catalysts such as the transition metal ions. Our modified Fenton reaction involves the conversion of aqueous dissolved oxygen to hydrogen peroxide by an ionic catalyst (Cu(2+)) and then subsequent conversion to hydroxyl radicals. Results are given for the modified Fenton reagent deactivating spores of Bacillus globigii. A biocidal mechanism is proposed that is consistent with our experimental results and independently derived information found in the literature. This mechanism requires diffusion of relatively benign species into the interior of the spore, where dissolved O(2) is then converted through a series of reactions which ultimately produce hydroxyl radicals that perform the killing action.