A newly developed fluoroquinoline, Q-35 (8-OCH3), in which a methoxy group was substituted at the 8 position of the quinoline nucleus, was very stable under irradiation with long-wave UV light (UVA). Derivatives, a fluoroquinolone with no substitution (the 8-H analog) and one in which a fluorine was substituted (the 8-F analog), were degraded in their solutions by the UVA irradiation. The phototoxic inducibility by these derivatives was further studied in a murine model. When mice were dosed orally with 800 mg of Q-35 (8-OCH3) per kg of body weight, the maximum dose given, and exposed to the UVA light, no inflammatory lesions were observed in their ears. Ear redness was marked in mice given more than 12.5 mg of the 8-F analog or 200 mg of the 8-H analog per kg. Histopathological changes, edema, and infiltration of neutrophils were also observed microscopically in groups receiving the 8-H or 8-F analog but not in groups receiving Q-35 (8-OCH3). Similar inflammatory reactions were observed to occur in a dose-dependent manner with other available fluoroquinolone antibacterial agents such as lomefloxacin, enoxacin, norfloxacin, ciprofloxacin and ofloxacin. These results suggest that the introduction of a methoxy group at the 8 position of the quinolone nucleus is important for the reduction of phototoxicity.
Q-35 [1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-7-(3-methylaminopiperidine-1-yl)-4-oxoquinoline-3-carboxylic acid], a fluoroquinolone, has absorbance peaks at 333 and 286 nm. No spectral change was observed even when this aqueous solution was irradiated with 3 J of long-wavelength UV light (UVA) per cm2. On the other hand, its derivatives, which are unsubstituted (8-H analog) or which are substituted with fluorine at the 8 position (8-F analog), were found to have decreased antibacterial activities with a simultaneous increase in their cytotoxicities when they were degraded in a dose-dependent manner with respect to UVA irradiation. Similar results were observed with the other available fluoroquinolones. Enoxacin and lomefloxacin exposed to 0.3 J of irradiation per cm2 and norfloxacin, ofloxacin, and ciprofloxacin exposed to 1 J of irradiation per cm2 underwent absorption spectrum changes, an accompanying decrease in antibacterial activity, and an increase in cytotoxic activity. These results suggest that the introduction of a methoxy group into the 8 position of quinolones plays an important role in the stability of fluoroquinolones against irradiation by UV light.
A purified human granulocyte colony-stimulating factor (hG-CSF) was studied for its protective effect on the induction of neutropenia and enhanced susceptibility to microbial infections in mice receiving cyclophosphamide (CPA). A severe reduction in peripheral blood nteutrophils was induced 4 days after injection with 200 mg of CPA per kg although the level normalized rapidly thereafter. When mice were injected subcutaneously once a day with 2.5 ,ug of hG-CSF beginning on the day after CPA injection, the reduction was prevented markedly, even 4 days later. On the other hand, in mice receiving CPA 4 days prior to infection, a weakened resistance to intraperitoneal challenge with a strain of Pseudomonas aeruginosa was induced. This weakened resistance was dose-dependently restored to normal by four daily injections with hG-CSF. A daily dose of 1.0 ,ug was required for complete restoration, although hG-CSF did not directly inhibit bacterial growth in vitro. In hG-CSF-treated mice, morphologically mature neutrophils migrated rapidly into the peritoneal cavities where bacteria were inoculated, followed by a rapid elimination of bacteria from the locality as compared with controls. In addition, the same treatment with hG-CSF was able to protect significantly against systemic infections caused by Serratia marcescens, Escherichia coli, Staphylococcus aureus, and Candida albicans. These data show the possibility that prophylactic therapy with hG-CSF may augment the resistance of immunocompromised patients to infections.
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