Distribution characteristics of orally administered olamufloxacin, a newly synthesized fluoroquinolone antibacterial, in lung epithelial lining fluid and alveolar macrophage in rats.

This study described distribution characteristics of olamufloxacin (HSR-903) in lung epithelial lining fluid (ELF) and alveolar macrophage (AM) in rats, two important representative infectious sites in lower respiratory tract infections. The rats were orally administered at a dose of 10mg/kg. At each designated time, rats were sacrificed, and blood samples were collected from the superior vena cava, and ELF and AM samples were gathered by the bronchoalveolar lavage method. The AUC ratios of ELF/plasma and AM/plasma of HSR-903 were 3.03+/-0.54 and 97.5+/-24.2, respectively, notably higher than those of ciprofloxacin (CPFX). Kinetic analyses of concentration-time profiles of HSR-903 in ELF and AM indicated that the influx clearance from plasma to ELF across the alveolar barrier was 5.8-fold higher than the efflux clearance from ELF. Furthermore, the permeability of HSR-903 across the cultured AM plasma membrane was 5.5 and 14.5 times greater than those of CPFX and pipemidic acid (PPA), respectively. A significant correlation (r2 = 0.995) was achieved between permeability across AM plasma membrane and hydrophobicity, implying that passage through AM membrane was principally involved in the passive diffusion. The extent of AM intracellular binding was the greatest for grepafloxacin, followed by HSR-903, CPFX, levofloxacin and PPA. In conclusion, HSR-903 distributed more efficiently in ELF and AM than CPFX, and the high accumulation of HSR-903 by AM cells may be accounted for by both the high transferability across the AM membrane and avid binding to the membrane phospholipids.     

Lung tissue distribution after intravenous administration of grepafloxacin: comparative study with levofloxacin

The aim of the present study is to study the pharmacokinetics in plasma, lung lymph and bronchial washing fluid after intravenous infusion of grepafloxacin (GPFX), in comparison with those of levofloxacin (LVFX). Four conscious sheep with chronically instrumented lung lymph fistulas and tracheotomy were prepared. GPFX and LVFX concentrations in plasma and lung lymph after intravenous infusion of the drugs (10 mg/kg) for over 10 min were measured. In addition serial bronchial washing with 50 mL normal saline was performed to obtain epithelial lining fluid (ELF) at 2, 4, 6, 8, 12, 24 h after the intravenous administration. The time courses of lung lymph concentration were almost identical to those of the concomitant levels of both GPFX and LVFX in plasma, suggesting that both GPFX and LVFX could be easily moved from plasma to pulmonary interstitium and/or lung lymph circulation. However, GPFX concentrations of ELF were significantly higher than LVFX concentrations over time after the administration. In addition, intracellular concentrations in ELF of GPFX were also extremely high compared with those of LVFX. These results demonstrated that penetration of GPFX in bronchial wall, bronchial epithelium and/or phagocytic cells was superior to that of LVFX. These observations suggest that the pharmacokinetic characteristics of GPFX in the lung may provide a new insight into the strategy for clinical treatment of various pulmonary infections, especially cytotropic bacterial infections.     

The inhibitory effects of fluoroquinolones on L-carnitine transport in placental cell line BeWo

L-Carnitine plays an important role in lipid metabolism by facilitating the transport of long-chain fatty acids across the mitochondrial inner membrane followed by fatty acid beta-oxidation. It is known that members of the OCTN family play an important role in L-carnitine transport in the placenta. Investigation of drug-drug or drug-nutrient interaction in the placenta is important for establishment of safety drug medication during pregnancy. The aim of this study was to determine the effects of fluoroquinolones, inhibitors of OCTN2, on L-carnitine transport in the placenta which is known to have a high expression level of OCTN2. We investigated the inhibitory effect of five fluoroquinolones, ciprofloxacin (CPFX), gatifloxacin (GFLX), ofloxacin (OFLX), levofloxacin (LVFX) and grepafloxacin (GPFX), on L-carnitine transport mediated by OCTN2 in placental cell line BeWo cells. We found that all of the fluoroquinolones inhibited L-carnitine transport, GPFX being the strongest inhibitor. We also found that the inhibitory effects of LVFX and GPFX depended on their existence ratio of zwitterionic forms as, we reported previously. Furthermore, we elucidated the LVFX transport mechanism in BeWo cells. LVFX was transported actively by transporters. However, we found that LVFX transport was Na+-independent and l-carnitine had no inhibitory effect on LVFX transport, suggesting that LVFX acts as inhibitor of OCTN2, not as a substrate for OCTN2.     

Differences in the hepatobiliary transport of two quinolone antibiotics, grepafloxacin and lomefloxacin, in the rat

The biliary excretion of grepafloxacin (GPFX) was compared with that of lomefloxacin (LFLX) in rats. The biliary clearances (Cl(plasma)(bile)) of GPFX was 2.9 times greater than LFLX based on the plasma concentration reached during constant intravenous (i.v.) infusion. The liver-plasma unbound concentration ratio, K(pu), of GPFX (1.7) was also higher than that of LFLX (0.7). The hepatic uptake clearance, assessed from an integration plot analysis, of GPFX was comparable with the hepatic blood flow rate, and 1.5 times that of LFLX, indicating that membrane transport in the uptake process is more efficient for GPFX. This was also supported by the difference between the uptake clearance of GPFX and LFLX in isolated rat hepatocytes. The bile-liver unbound concentration ratio of GPFX and LFLX was approximately 6 and 3, respectively, and the biliary clearance based on the unbound liver concentration of GPFX was 1.8 times that of LFLX. These results suggest that the concentrative transport of GPFX also across the canalicular membrane was more efficient than that of LFLX. Thus, the membrane transport activity via both sinusoidal and canalicular membranes determines the net excretion of each compound.     

Determination of lipophilicity of two quinolone antibacterials, ciprofloxacin and grepafloxacin, in the protonation equilibrium.

The objective of this study was to compare protonation equilibrium and lipophilicity of two quinolone antibacterials, grepafloxacin (GPFX) and ciprofloxacin (CPFX), in order to give an insight into effects on the physicochemical properties by slight structural motifs. The protonation equilibrium was investigated by a spectrophotometry. Macro- and micro-dissociation constants were simultaneously determined, based on nonlinear regression analysis using the MULTI program, and then microspecies distribution could be described accordingly. Zwitterionic microspecies predominated at isoelectrical point (pI) for both drugs, and the concentration ratio of neutral to zwitterionic forms was near 4-fold greater for GPFX than that for CPFX. The apparent partition coefficient (D(O/B,pH)) versus pH profiles had the shape of a parabolic curve in an n-octanol/buffer system, and reached the maximum around pI for both, respectively. Moreover, two introduced methyl groups in GPFX increased not only intrinsic lipophilicity but also neutral microspecies fraction relative to CPFX, and D(O/B,pH) of GPFX was consequently far higher than that of CPFX. The results emphasized that there were significant differences in protonation equilibrium and lipophilicity between GPFX and CPFX, which conduced to explaining their different behavior in terms of antibacterial activities and pharmacokinetics.     

Pharmacokinetic and pharmacodynamic efficacy of intrapulmonary administration of ciprofloxacin for the treatment of respiratory infections

The pharmacokinetic and pharmacodynamic efficacy of intrapulmonary administration of ciprofloxacin (CPFX) for the treatment of respiratory infections caused by pathogenic microorganisms resisting sterilization systems of alveolar macrophages (AMs) was evaluated by comparison with an oral administration. The time-courses of the concentration of CPFX in AMs and lung epithelial lining fluid (ELF) following intrapulmonary administration of CPFX solution to rats (200 microg/kg) were markedly higher than that following oral administration (10 mg/kg). The time-course of the concentrations of CPFX in plasma following intrapulmonary administration was markedly lower than that in AMs and ELF. These results indicate that intrapulmonary administration is more effective in delivering CPFX to AMs and ELF, compared with oral administration, in spite of a low dose and it avoids distribution of CPFX to the blood. In addition, the antibacterial effects of CPFX in AMs and ELF following intrapulmonary administration were evaluated by pharmacokinetics/pharmacodynamics analysis. The concentration of CPFX in AMs and ELF-time curve (AUC)/minimum inhibitory concentration of CPFX (MIC) ratio and the maximum concentration of CPFX in AMs and ELF (Cmax)/MIC ratio were markedly higher than the effective values. The present study indicates that intrapulmonary administration of CPFX is an effective technique for the treatment of respiratory infections.     

Acyl glucuronidation of fluoroquinolone antibiotics by the UDP-glucuronosyltransferase 1A subfamily in human liver microsomes.

Acyl glucuronidation is an important metabolic pathway for fluoroquinolone antibiotics. However, it is unclear which human UDP-glucuronosyltransferase (UGT) enzymes are involved in the glucuronidation of the fluoroquinolones. The in vitro formation of levofloxacin (LVFX), grepafloxacin (GPFX), moxifloxacin (MFLX), and sitafloxacin (STFX) glucuronides was investigated in human liver microsomes and cDNA-expressed recombinant human UGT enzymes. The apparent Km values for human liver microsomes ranged from 1.9 to 10.0 mM, and the intrinsic clearance values (calculated as Vmax/Km) had a rank order of MFLX > GPFX > STFX > > LVFX. In a bank of human liver microsomes (n = 14), the glucuronidation activities of LVFX, MFLX, and STFX correlated highly with UGT1A1-selective beta-estradiol 3-glucuronidation activity, whereas the glucuronidation activity of GPFX correlated highly with UGT1A9-selective propofol glucuronidation activity. Among 12 recombinant UGT enzymes, UGT1A1, 1A3, 1A7, and 1A9 catalyzed the glucuronidation of these fluoroquinolones. Results of enzyme kinetics studies using the recombinant UGT enzymes indicated that UGT1A1 most efficiently glucuronidates MFLX, and UGT1A9 most efficiently glucuronidates GPFX. In addition, the glucuronidation activities of MFLX and STFX in human liver microsomes were potently inhibited by bilirubin with IC50 values of 4.9 microM and 4.7 microM, respectively; in contrast, the glucuronidation activity of GPFX was inhibited by mefenamic acid with an IC50 value of 9.8 microM. These results demonstrate that UGT1A1, 1A3, and 1A9 enzymes are involved in the glucuronidation of LVFX, GPFX, MFLX, and STFX in human liver microsomes, and that MFLX and STFX are predominantly glucuronidated by UGT1A1, whereas GPFX is mainly glucuronidated by UGT1A9.     

In vitro activities of levofloxacin and other antibiotics against fresh clinical isolates

In this study, the in vitro activity of levofloxacin (LVFX) against 1,020 fresh bacterial clinical isolates was compared with the activities of a range of ofloxacin, ciprofloxacin (CPFX), ampicillin (ABPC), cefaclor, cefpodoxime, methicillin and benzylpenicillin. The clinical isolates except Vibrio cholerae were collected in Japan during 1998 from patients with infectious diseases. MICs were determined using the agar dilution method according to the recommendations by the Japan Society of Chemotherapy. Some isolates of methicillin resistant Staphylococcus aureus (MRSA) and coagulase negative Staphylococcus were resistant to fluoroquinolones, but the MIC50 of LVFX against MRSA was 6.25 micrograms/ml. LVFX was the most active against MRSA among the antibiotics tested. Most of Staphylococcus epidermidis strains were susceptible to the fluoroquinolones. LVFX showed greater activity against all streptococci strains compared with fluoroquinolones tested. In particular, all Streptococcus pneumoniae strains including PRSP were susceptible to LVFX at < or = 1.56 micrograms/ml. Among Enterococcus, ABPC showed superior activity against Enterococcus faecalis but many isolates of Enterococcus species were resistant to ABPC. LVFX was more active against to these Enterococcus species compared with other fluoroquinolones. On the other hand, LVFX and CPFX showed similar activity against isolates of Enterobacteriaceae. CPFX had an MIC50/90 of 0.20, 0.39 microgram/ml and LVFX showed an MIC50/90 of 0.78, 1.56 micrograms/ml against Pseudomonas aeruginosa. LVFX (MIC50/90 0.10, 0.20 microgram/ml) was more active against Acinetobacter species than CPFX (MIC50/90 0.10, 0.39 microgram/ml). Haemophilus influenzae, Branhamella (Moraxella) catarrhalis and V. cholerae were inhibited by low concentration of the fluoroquinolones tested. The MIC90 of LVFX and CPFX were < or = 0.10 microgram/ml against above three species. Some isolates of Neisseria gonorrhoeae and Campylobacter species were moderately resistant to the fluoroquinolones tested but the MIC50 of LVFX and CPFX were < or = 0.39 microgram/ml. Among anaerobes, Propionibacterium acnes was more susceptible than Peptostreptococcus species, and the MIC90 of beta-lactams and fluoroquinolones tested were < or = 0.78 microgram/ml. In conclusion, this study, performed on large number of strains, confirmed an excellent and wide spectrum antibacterial activity of LVFX compared with the fluoroquinolones and beta-lactams tested. And our results suggest that LVFX may be useful in the treatment of various bacterial infections.     

Stereoselective permeation of new fluorinated quinolone derivatives across LLC-PK1 cell monolayers.

We examined the stereoselective membrane permeation of new fluorinated quinolone derivatives (NQs) across LLC-PK1 cell monolayers, using levofloxacin (LVFX) and its R-(+) isomer. LVFX permeation was 1.6-fold greater in the basal-to-apical direction than that in the apical-to-basal direction, suggesting that LVFX permeated LLC-PK1 cell monolayers in a secretory-oriented manner. In contrast to LVFX, the permeation of the R-(+) isomer was almost identical in both directions. LVFX permeation in the basal-to-apical direction was significantly reduced in the presence of guanidine, enoxacin, and L-arginine, whereas tetraethylammonium, D-arginine, D- and L-lysine had no effect on the basal-to-apical permeation of LVFX. Basal-to-apical permeation of the R-(+) isomer was not affected by these compounds. Cellular accumulation of LVFX was inversely increased when guanidine suppressed the appearance of LVFX in the apical medium in a concentration-dependent manner. These results imply that the inhibitory effect of guanidine on the basal-to-apical permeation of LVFX involves the permeation process across the apical membrane. Guanidine trans-stimulated the efflux of LVFX from LLC-PK1 cells but did not affect cimetidine efflux. These results suggest that some NQs, like LVFX and its R-(+) isomer, are stereoselectively secreted across LLC-PK1 cell monolayers and that an organic cation transport system, which favors guanidine as a typical substrate, may be involved in the secretory-oriented permeation of some NQs.     

Mechanism for the tissue distribution of grepafloxacin, a fluoroquinolone antibiotic, in rats.

This study was carried out to investigate the most important factor(s) governing the tissue distribution of grepafloxacin (GPFX), a fluoroquinolone antibiotic, in rats. The tissue-to-blood concentration ratio (K(p)) of GPFX at steady state during constant infusion was highest in the lung, followed by the pancreas, kidney, and spleen. After bolus injection, GPFX was efficiently taken up by most of the organs examined, the uptake clearance other than the lung being almost blood flow-limited. Approximately 10% of the intravenously injected dose was rapidly trapped by the lung, but GPFX distribution rapidly decreased within 30 s due to the washout by the plasma flow. Thus, the higher distribution of GPFX to the lung compared with the other organs cannot be accounted for by a difference in its uptake or efflux. Subcellular fractionation after the infusion indicated that GPFX is primarily distributed to the organelle fractions in most organs, 60% of lung-associated GPFX being recovered in the nucleus and plasma membrane fraction. Such subcellular distribution in the lung was proportional to the phosphatidylserine (PhS) content of each fraction. The steady-state K(p) value in each tissue in vivo also correlated with the tissue content of PhS. GPFX preferentially binds to PhS, compared with other phospholipids, and this binding was inhibited by weakly basic drugs, such as quinidine, imipramine, and propranolol, that have also been reported to bind to PhS. The association of GPFX with PhS synthase transformants of Chinese hamster ovary (CHO-K1) cells depends on the PhS content of each cell line, this association being also inhibited by basic drugs. These results suggest that binding of GPFX to PhS is the major determinant of the high distribution of GPFX to the lung.     

In vitro short-term bactericidal activity and accumulation of NM394, the active metabolite of prulifloxacin,for Staphylococcus aureus,Escherichia coli and Pseudomonas aeruginosa: comparison with ciprofloxacin,levofloxacin, and gatifloxacin

The in vitro short-term bactericidal activity and accumulation of NM394, the active metabolite of prulifloxacin, was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX), using Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa. Of the 4 fluoroquinolones examined, NM394 accumulated to the highest concentration in all three strains. The order of concentration of the fluoroquinolones accumurated in S. aureus 209P JC-1, E. coli NIHJ JC-2 and P. aeruginosa PAO1 were NM394 > CPFX > GFLX > or = LVFX. The accumulation of fluoroquinolones into bacterial cells correlated with their MICs of the drugs for E. coli and P. aeruginosa, whereas there was no correlation between the accumulation and MICs of the drugs for S. aureus. We also studied the reduction of viable cells after addition of each fluoroquinolones to clarify relationship between the short-term bactericidal activity and the accumulation of the quinolones. The short-term bactericidal activity of NM394 against S. aureus 209P JC-1, E. coli NIHJ JC-2 and P. aeruginosa PAO1 were stronger than those of CPFX, LVFX and GFLX when compared at the same concentration. In conclusion, the strong short-term bactericidal activity of NM394 may be attributed to its high accumulation in bacterial cells.     

In vitro antibacterial activity of prulifloxacin,a new oral fluoroquinolone

We compared antibacterial activity of NM394, which is the active metabolite of a prodrug of new fluoroquinolone prulifloxacin (PUFX), against clinical isolates of bacteria with those of ciprofloxacin (CPFX), levofloxacin (LVFX), gatifloxacin (GFLX), tosufloxacin (TFLX) and fleroxacin (FLRX). 1. NM394 showed a broad-spectrum antibacterial activity against both Gram-positive and Gram-negative bacteria. 2. MIC80 of NM394 for methicillin-sensitive Staphylococcus aureus, Streptococcus pneumoniae and Enterococcus faecalis were 0.5 microgram/ml, 2 micrograms/ml and 4 micrograms/ml, respectively. MIC80 of NM394 for Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae was lower than 0.06 microgram/ml. MIC80 of NM394 for Serratia marcescens and Pseudomonas aeruginosa were 0.25 microgram/ml and 2 micrograms/ml, respectively. 3. Short-time bactericidal activity of NM394 against P. aeruginosa was stronger than those of CPFX, GFLX, LVFX and TFLX. 4. Short-time bactericidal activity of NM394 at Cmax concentration against 12 strains of P. aeruginosa was stronger than those of CPFX, LVFX, GFLX and TFLX.     

Laboratory and clinical studies on levofloxacin]

A newly developed broad-spectrum fluoroquinolone, levofloxacin (LVFX, DR-3355), was evaluated in vitro and in vivo in comparison with ciprofloxacin (CPFX), ofloxacin (OFLX) and norfloxacin (NFLX). The results were as follows. 1. Antimicrobial activity Minimal inhibitory concentrations (MICs) against 480 clinical isolates including 16 different species were determined using the microbroth dilution method. LVFX showed excellent antimicrobial activities against Gram-positive and -negative bacteria. The MIC values of LVFX for Gram-positive bacteria were superior to those of the other quinolones tested. The MIC values of LVFX for Gram-negative bacteria were comparable to those of CPFX and superior to those of OFLX and NFLX. 2. LVFX concentrations in serum and sputum LVFX was orally administered in a single dose of 200 mg to 2 patients with chronic lower respiratory tract infections, and its concentrations in serum and sputum were measured at intervals using bioassay. The peak concentrations of LVFX in serum were 1.52 and 1.24 micrograms/ml, and 84-95% of serum level were detected in sputum. From these data, it appeared that LVFX penetrate well into the lung. 3. Clinical efficacy and adverse reactions Fifteen patients with respiratory tract infections were treated with LVFX, and the overall efficacy rate was 78.6% (excellent in 3 cases, good in 8, fair in 3, poor in 0). As adverse reactions, anorexia was observed in 2 cases, diarrhea in 1 case and tremor of finger in 1 case. Although an elevation of total bilirubin in serum was observed in a case as an abnormal laboratory finding, it was mild, transient and improved rapidly after the completion of LVFX treatment.     

Effect of sex and AIDS status on the plasma and intrapulmonary pharmacokinetics of rifampicin

OBJECTIVE: To compare the steady-state plasma and intrapulmonary concentrations of oral rifampicin (rifampin) in men and women with and without AIDS. DESIGN: Prospective nonblinded pharmacokinetic study. PARTICIPANTS: Ten men with AIDS, ten men without AIDS, ten women with AIDS, and ten women without AIDS. METHODS: Rifampicin 600 mg was administered orally once daily for 5 days to 40 adult volunteers. Blood was obtained 2 hours after the last dose and at the time of bronchoalveolar lavage (BAL) performed 4 hours after the last dose. Rifampicin was measured in plasma, epithelial lining fluid (ELF) and alveolar cells. Standardised BAL was performed without systemic sedation. The volume of ELF was calculated by the urea dilution method, and alveolar cells were recovered by a standardised centrifugation technique. The volume of alveolar cells was calculated from the cell count and differential performed on the BAL fluid. Rifampicin was measured by high-performance liquid chromatography. RESULTS: Sex or AIDS status had no effect on plasma concentrations of rifampicin at 2 hours, 4 hours, or in ELF. Plasma concentrations (mean +/- SD) of rifampicin at 2 hours (9.15 +/- 5.4 mg/L) were not significantly different (p > 0.05) from those at 4 hours (9.10 +/- 5.6 mg/L) following the last dose. The ELF concentration was 2.0 +/- 1.6 mg/L with a range of 0-7.3 mg/L and the ELF/plasma ratio at 4 hours was 0.2 +/- 0.2. Rifampicin was not detectable in ELF in eight subjects (three with AIDS and five without AIDS) or in alveolar cells in three subjects without AIDS. There was no significant effect of AIDS on alveolar cell concentrations of rifampicin. Alveolar cell concentrations of rifampicin were significantly greater in women (13.9 +/- 6.7 mg/L) than in men (6.6 +/- 4.1 mg/L) [p = 0.0003]. Alveolar cell rifampicin concentrations were 78% greater in smoking women (17.8 +/- 7.0 mg/L) than in nonsmoking women (10.0 +/- 2.4 mg/L), but the difference was not significant (p > 0.05). CD4+ cell counts in the AIDS subjects were not correlated with the concentrations of rifampicin in plasma, ELF or alveolar cells. CONCLUSIONS: The absorption of oral rifampicin was not affected by sex or AIDS. Plasma and alveolar cell concentrations were not significantly different, were both greater than ELF concentrations, and were adequate to inhibit Mycobacterium tuberculosis. Considerable interpatient variability was detected despite witnessed drug administration. The clinical significance of these findings is unknown but merits further investigation.     

Inhibitory activity of NM394, the active form of prodrug prulifloxacin against type II topoisomerase from Pseudomonas aeruginosa

The inhibitory activity of NM394, the active form of the prodrug prulifloxacin, against type II topoisomerase from Pseudomonas aeruginosa was compared with those of ciprofloxacin (CPFX), levofloxacin (LVFX) and gatifloxacin (GFLX). The 50% inhibitory concentrations (IC50S) of NM394 for supercoiling activity of DNA gyrase and the decatenation activity of topoisomerase IV were 1.21 and 21.1 micrograms/ml, respectively. The IC50 of NM394 was equal to that of CPFX and lower than those of LVFX and GFLX. The inhibitory activity of the four drugs for DNA gyrase was also corresponding to the antimicrobial activity of the drugs for P. aeruginosa PAO1. The IC50S of the drugs tested for the decatenation activity of topoisomerase IV were from 17.4 to 24.2 times higher than those for the supercoiling activities of DNA gyrase. These results show that DNA gyrase is more sensitive to quinolones than is topoisomerase IV and may be a primary target of quinolones in P. aeruginosa. We concluded that NM394 exerts the potent antimicrobial activity through its strong inhibitory activity for DNA gyrase.     

Physiologically-based pharmacokinetic analysis of grepafloxacin

Grepafloxacin (GPFX) is a synthetic new quinolone antimicrobial agent that possesses an extensive tissue distribution and exhibits a strong antibacterial activity in vivo. In this study, the tissue distribution characteristics of GPFX were examined using tissue concentration-time profiles following intravenous administration to rats. Subsequently, the pharmacokinetics of GPFX were analyzed based on the physiological pharmacokinetic model. The tissue-to-plasma partition coefficients (Kp) of GPFX in rats were high in all tissues except brain. A pharmacokinetic model for rabbits, monkeys and dogs was constructed using the tissue-to-plasma free concentration ratio (Kp,f) of GPFX in rats to simulate the GPFX concentration-time profile in plasma following intravenous administration of GPFX to each animal. The calculation-derived concentrations correlated well with the experimentally-derived data, suggesting that there are no interspecies differences in the high tissue distribution characteristics of GPFX. The clearance rates of GPFX in humans were predicted from the pharmacokinetic parameters of rats, rabbits, monkeys and dogs by an animal scale-up method and a pharmacokinetic model for humans was constructed. The GPFX concentration-time profiles in plasma, following oral administration of GPFX to humans, were predicted within 0.5-1.0 h of mean absorption time and the calculation-derived results were in good agreement with the experimental data. Thus, it is suggested that the concentration-time profile in plasma and all human organs can be predicted from the pharmacokinetic data of animals.     

Proposal of membrane transport mechanism of protein-unbound ulifloxacin into epithelial lining fluid determined by improved microdialysis

Microdialysis method (MD) is useful for sampling protein-unbound substances in vivo. Generally in the MD, a reference compound is used to correct differences in drug permeation clearance through a dialysis membrane in vivo and in vitro. No reference compound was, however, used for determination of a protein-unbound drug concentration in the epithelial lining fluid (ELF). In this study, we firstly examined the propriety of endogenous urea as a reference compound to determine the protein-unbound ulifloxacin concentrations in rat ELF by MD. Endogenous urea was used to correct differences in the permeation clearance in vivo and in vitro which reflect the differences in the extent of contact between a tip probe and ELF in vivo and in vitro. The results showed that our MD is applicable to determine the various concentrations of ulifloxacin and urea, and that we can use endogenous urea as a reference compound even if the extent of the contact between a tip of the probe and the ELF is small. In addition, use of urea concentrations does not affect drug distribution from plasma to ELF because we used endogenous urea. These results support usefulness of endogenous urea as a reference compound to determine protein-unbound drug concentration in ELF by MD. In addition, our results also suggest the existence of certain distribution mechanisms which cause the high penetration ulifloxacin into ELF. Our MD can help progress in pharmacokinetic-pharmacodynamic analysis of various antibiotics in the case where the concentrations in ELF are not equal to that in plasma.     

Distribution characteristics of clarithromycin and azithromycin, macrolide antimicrobial agents used for treatment of respiratory infections, in lung epithelial lining fluid and alveolar macrophages

The distribution characteristics of clarithromycin (CAM) and azithromycin (AZM), macrolide antimicrobial agents, in lung epithelial lining fluid (ELF) and alveolar macrophages (AMs) were evaluated. In the in vivo animal experiments, the time‐courses of the concentrations of CAM and AZM in ELF and AMs following oral administration (50 mg/kg) to rats were markedly higher than those in plasma, and the area under the drug concentration–time curve (AUC) ratios of ELF/plasma of CAM and AZM were 12 and 2.2, and the AUC ratios of AMs/ELF were 37 and 291, respectively. In the in vitro transport experiments, the basolateral‐to‐apical transport of CAM and AZM through model lung epithelial cell (Calu‐3) monolayers were greater than the apical‐to‐basolateral transport. MDR1 substrates reduced the basolateral‐to‐apical transport of CAM and AZM. In the in vitro uptake experiments, the intracellular concentrations of CAM and AZM in cultured AMs (NR8383) were greater than the extracellular concentrations. The uptake of CAM and AZM by NR8383 was inhibited by ATP depletors. These data suggest that the high distribution of CAM and AZM to AMs is due to the sustained distribution to ELF via MDR1 as well as the high uptake by the AMs themselves via active transport mechanisms. Copyright © 2011 John Wiley & Sons, Ltd.     

HEALTH EFFECTS OF SULFUR-RELATED ENVIRONMENTAL AIR POLLUTION. III. Nonspecific Respiratory Defense Capacities

Recently concern has been raised about health effects related to environmental sulfur and/or acidic aerosols. To assess long-term effects on respiratory lung function, 8 beagle dogs were exposed over a period of 13 mo for 16.5 h/day to 1.0 mum neutral sulfite aerosol with a particle associated sulfur (IV) concentration of 0.32 mg m-3 and for 6 h/ day to 1.1 mum acidic sulfate aerosol providing an hydrogen ion concentration of 15.2 mumol m-3 for inhalation. Prior to exposure the dogs were kept under clean air conditions for 16 mo to establish physiological baseline values for each dog. A second group of eight dogs (control) was kept for the entire study under clean air conditions. Nonspecific defense mechanisms in the airways and in the peripheral lung were studied during chronic exposure of the combination of neutral sulfur(IV) and acidic sulfur(VI) aerosols. No functional changes of tracheal mucus velocity were found, in agreement with unchanged morphometry of the airways. However, the exposure resulted in changes of several alveolar macrophage (AM) mediated particle clearance mechanisms: (1) Based on in vivo clearance analysis and cultured AM studies using moderately soluble cobalt oxide particles, intracellular particle dissolution was significantly reduced since phagolysosomal proton concentration was decreased. We deduce exposure-related malfunction of proton pumps bound to the phagolysosomal membrane as a result of an increase of cytosolic proton concentration. (2) Based on in vivo clearance analysis using insoluble polystyrene particles, AM-mediated particle transport from the lung periphery toward ciliated terminal bronchioli and further to the larynx was significantly reduced. Activation of epithelial type II cells at the entrance of alveoli was inferred from observed type II cell proliferation at those alveolar ridges and enhanced secretion of alkaline phosphatase in the fluid of bronchoalveolar lavages. As a result, hypersecretion of chemotactic mediators by activated type II cells at these loci led to the observed decrease of particle transport toward ciliated bronchioli. (3) Based on in vivo clearance analysis using insoluble polystyrene particles, particle transport from the alveolar epithelium into interstitial tissues was increased and (4) particle transport to the tracheobronchial lymph nodes was significantly enhanced. Particle transport into interstitial tissues is the most prominant clearance pathway from the canine alveolar epithelium. We conclude that the deteriorated particle transport toward ciliated terminal bronchioli resulted in an enhanced particle transport across the epithelial membrane into interstitial tissues and the lymphatic drainage. The observed alterations in alveolar macrophage-mediated clearance mechanisms during chronic exposure of these air pollutants indicate an increased risk of health.     

Effects of blowing sand fine particles on plasma membrane permeability and fluidity, and intracellular calcium levels of rat alveolar macrophages

Ambient fine particulate matter (PM2.5, particulates with an aerodynamic diameter < or = 2.5 microm) can suppress alveolar macrophage (AM) functions, but the data concerning the effects of blowing sand PM2.5 on AMs remain limited. The aim of the present study is to investigate the influences of blowing sand PM2.5 on AM plasma membranes and intracellular calcium ion concentration ([Ca2+]i), and explore the mechanisms of the observed toxicological effects. The samples of normal PM2.5 (collected on sunshiny and non-blowing sand days) and blowing sand PM2.5 were collected in Wuwei city, Gansu Province, China. After AMs from rat bronchoalveolar lavage fluid (BALF) were treated in vitro for 4 h with the suspensions of these samples, the cell viability, plasma membrane permeability and fluidity, cytosolic free Ca2+ levels, and oxidative stress were examined. It was observed a dose-dependent decrease in cell viability, plasma membrane Ca2+Mg2+-dependent adenosinetriphosphatase (Ca2+Mg2+-ATPase) and Na+K+-dependent adenosinetriphosphatase (Na+K+-ATPase) activities, cellular glutathione (GSH) levels, fluorescence intensities of lipid probe 8-anilino-1-naphthalene-sulfonic acid (ANS) and fluorescence polarization of lipid probe 1,6-diphenyl-1,3,5-hexatriene (DPH) combined with cell membranes in the treatment groups of normal and blowing sand PM2.5 as compared to the control (saline group); and also observed a dose-dependent increase in the leakage of lactate dehydrogenase (LDH) and acid phosphatase (ACP), and intracellular [Ca2+]i and malondialdehyde (MDA) levels. These observations indicate blowing sand PM2.5, as similar to urban normal ones, could induce oxidative stress on AMs, enlarge plasma membrane permeability and membrane lipid fluidity, and elevate intracellular [Ca2+]i levels, resulting in cytotoxicity. A two-way ANOVA showed the toxic effects of normal and blowing sand PM2.5 on AMs were only relative to treatment dosages but not to dust types, suggesting the blowing sand PM2.5 whose airborne mass concentrations were much higher should be more harmful.