Comparison of In Vivo Transportability of Anti-Methicillin-Resistant Staphylococcus aureus (MRSA) Agents Into Intracellular and Extracellular Tissue Spaces in Rats

The pathogenic bacterium Staphylococcus aureus can penetrate host cells. However, intracellular S. aureus is not considered during antimicrobial agent selection in clinical chemotherapy because of the lack of information about drug transportability into cells in vivo. We focused on agents used to treat methicillin-resistant S. aureus (MRSA) (vancomycin, arbekacin, linezolid, and daptomycin) and indirectly assessed the drug levels in intracellular compartment using plasma, tissue homogenates, and interstitial fluid (ISF) samples from the skin of rats using the microneedle array technique. Lower drug levels were observed in the ISF than in the plasma for daptomycin but extracellular and intracellular drug levels were comparable. In contrast, vancomycin, arbekacin, and linezolid showed higher concentrations in the ISF than in the plasma. Intracellular transport was estimated only for arbekacin. Stasis of vancomycin in the ISF was also observed. These results suggest that both low vancomycin exposure against intracellular S. aureus infection and long-term subinhibitory drug levels in the ISF contribute to the failure of treatment and emergence of antibiotic resistance. Based on its pharmacokinetic characteristics in niche extravascular tissue spaces, arbekacin may be suitable for achieving sufficient clinical outcomes for MRSA infection because the drug is widely distributed in extracellular and intracellular compartments.     

Proapoptotic effect of a dietary supplement: water soluble chitosan activates caspase-8 and modulating death receptor expression

The effect of water-soluble chitosan, a natural polymer used as a dietary supplement, on human bladder-tumor cells was investigated. Apoptotic morphological change was demonstrated by nuclear staining. Chitosan-treated cells showed elevation of caspase-8-like activity, but no significant elevation of caspase-9-like activity, which suggest that proapoptotic effect of chitosan is attributable to death receptor activation and not to activation of the mitochondria-cytochrome c pathway. Chitosan increased expression of TNF-R1, but decreased Fas expression. Use of monoclonal antibodies to inhibit death-receptor signal transduction did not attenuate the proapoptotic activity of chitosan. Examination of death-ligands revealed that TNFalpha mRNA expression was markedly increased by chitosan treatment while FasL mRNA was not affected. Although the direct interaction of chitosan with death receptors remains unidentified, the results suggest that its proapoptotic effect might be related to interaction with TNFalpha or TNF-R1.     

Biodistribution and pharmacokinetics of O-palmitoyl tilisolol,a lipophilic prodrug of tilisolol,after intravenous administration in rats

The purpose of this study was to modify the biodistribution and pharmacokinetics of tilisolol, a beta-blocker, using the palmitoyl prodrug approach. After intravenous administration of tilisolol and O-palmitoyl tilisolol in rats, drug concentrations were determined in blood, bile, urine, and several tissues. The concentration-time profiles of tilisolol and O-palmitoyl tilisolol were analyzed pharmacokinetically. The blood concentrations of O-palmitoyl tilisolol after intravenous administration of O-palmitoyl tilisolol were about 10-fold higher than those of tilisolol after intravenous administration of tilisolol. The biliary excretion rates of O-palmitoyl tilisolol and tilisolol after intravenous administration of O-palmitoyl tilisolol were about 10- to 100-fold larger than those of tilisolol after intravenous administration of tilisolol. In addition, the hepatic uptake clearance of O-palmitoyl tilisolol after intravenous administration of O-palmitoyl tilisolol was 3.6-fold higher than that of tilisolol after the intravenous administration of tilisolol. In the in vitro experiments, it was demonstrated that the distribution ratios between blood cells and plasma (blood/plasma) of O-palmitoyl tilisolol and tilisolol was 95.7 and 55.5%, respectively. These findings suggest that O-palmitoyl tilisolol exists as a binding form with biological components, especially blood cells, in systemic circulation. In conclusion, the palmitoyl prodrug approach is useful as a drug delivery system to deliver the parent drug to the liver.     

MDR1 Genotype-Related Duodenal Absorption Rate of Digoxin in Healthy Japanese Subjects

Purpose. Recent clinical studies suggest the importance of the MDR1 genotype at position 3435 (C3435T) in terms of pharmacokinetics, but there is still no consensus in reports on the relationship between the genotype and plasma/serum concentration-time profiles of drugs after conventional oral administration. This study was performed to elucidate the effects of C3435T on the rate of duodenal absorption of digoxin in healthy Japanese subjects. Methods. Digoxin solution was sprinkled directly over the surface of the duodenum using an endoscope, and its absorption rate was evaluated by serial monitoring of the serum concentration and by analysis of its initial 15-min increasing phase. Results. The duodenal absorption rates of digoxin were 911 ± 91 ng/min and 506 ± 76 ng/min for C/C and T/T, respectively (±SE, p = 0.007). Conclusions. The C3435T mutation of the MDR1 gene is associated with suppression of duodenal absorption of digoxin.     

Effects of reactive oxygen species on cell proliferation and death in HeLa cells and its MDR1-overexpressing derivative cell line

In this paper, the effects of H2O2, a typical reactive oxygen species (ROS), on cell proliferation or death were examined using the human cervical carcinoma cell line HeLa and its MDR1-overexpressing subline, Hvr100-6, which was established by stepwise exposure to vinblastine. It was confirmed that the growth of HeLa cells was enhanced by H2O2 at relatively low concentrations in a concentration-dependent manner, and the growth enhancement was suppressed by antioxidants. Doxorubicin and daunorubicin also enhanced the growth of HeLa cells at concentrations lower than IC50 values, and the antioxidants suppressed this effect, being consistent with the fact that both anticancer drugs generate ROS. The growth enhancement by H2O2 or doxorubicin and daunorubicin was not observed in Hvr100-6 cells. In addition, it was suggested that antioxidants had no effect on MDR1 mRNA expression in HeLa and Hvr100-6 cells, and thereby hardly reverse multidrug resistance in tumor cells.     

VEGF G-1154A is predictive of severe acute toxicities during chemoradiotherapy for esophageal squamous cell carcinoma in Japanese patients

This study was conducted to evaluate the association between systemic exposure to 5-fluorouracil (5-FU) and genetic polymorphisms of vascular endothelial growth factor (VEGF) with clinical outcomes to a 5-FU/cisplatin-based chemoradiotherapy in Japanese patients with esophageal squamous cell carcinoma (ESCC). Forty-nine patients with ESCC (I/II/III/IVa = 11/9/17/7, with 5 postoperative recurrences) were enrolled into this study. One course of treatment consisted of protracted venous infusions of 5-FU (400 mg/m2/24 hr for day 1-5 and 8-12) and cisplatin (40 mg/m2/3 hr on day 1 and 8), and radiation (2 Gy/day on day 1-5, 8-12, and 15-19); a second course was repeated after a 2 week interval. A total of eight measurements of the plasma concentration of 5-FU were made per patient to evaluate its systemic exposure as area under the concentration time curve for 480 hours (AUC480h), and VEGF genotypes of T-1498C, G-1154A, C-634G, C-7T, C936T, and G1612A were evaluated. The mean value of AUC480h in the patients with a complete response was 58.7 +/- 16.8 mg*h/L, which was higher than that in the others, 49.0 +/- 10.9 mg*h/L (P = 0.029), whereas no such association was found for severe acute toxicities. VEGF genotype was not associated with the clinical response, whereas VEGF G-1154A resulted in severe acute leukopenia (P = 0.042) and severe acute cheilitis (P = 0.025). In conclusion, VEGF G-1154A was a predictor of severe acute toxicities during 5-FU/cisplatin-based chemoradiotherapy in Japanese ESCC patients, whereas the AUC480h value of 5-FU was predictive of the clinical response.     

Serum Lactate Dehydrogenase Levels as a Predictive Marker of Oxaliplatin-Induced Hypersensitivity Reactions in Japanese Patients with Advanced Colorectal Cancer

Objective: Clinical laboratory test data obtained prior to treatments were previously analyzed from the standpoint of susceptibility to hypersensitivity reactions in patients treated with the platimun anticancer agent, oxaliplatin (L-OHP). In the present study, the time course from the first to last cycle of the treatment was additionally analyzed to determine a better predictor of these reactions.Methods: A total of 20 laboratory test data were obtained from 108 Japanese patients with advanced colorectal cancer who were treated with the L-OHP-containing regimens, FOLFOX4 and/or mFOLFOX6. The averages and variation coefficients (CV%) of the data until the last cycle of the treatment were compared between patients with hypersensitivity reactions and those without.Results: The average serum lactate dehydrogenase (LDH) level was lower in patients with grade 1/2 reactions (P=0.016), whereas its CV% value was higher in patients with grade 3/4 reactions (P=0.005) than in those without reactions. An increase in serum LDH levels was observed in some patients with grade 3/4 reactions as the cycle number increased, and thereafter hypersensitivity reactions occurred. This phenomenon was not always observed, but was never detected in patients with grade 1/2 reactions.Conclusions: Serum LDH levels may be a predictive marker of hypersensitivity reactions in patients treated with L-OHP. Further extensive examinations with a larger number of patients are needed to establish a patient management strategy.     

Effects of bolus injection of 5-fluorouracil on steady-state plasma concentrations of 5-fluorouracil in Japanese patients with advanced colorectal cancer

Objectives: The irinotecan (CPT-11) + 5-fluorouracil (5-FU)/leucovorin (LV) + UFT/LV chemotherapy, in which repetitive oral administration of UFT/LV replaces the infusion of 5-FU/LV in the FOLFIRI regimen, has been proposed previously. In this study, five of 10 patients were injected with a bolus of 5-FU and the other were not injected with it in order to examine the effect of omitting it in terms of pharmacokinetics of 5-FU.Methods: The treatment consisted of the intravenous infusions of CPT-11 at 100 mg/m² and l-LV at 15 mg/m², and the injection of a bolus of 5-FU at 500 mg/m² on day 1, and the repetitive oral administration of UFT/LV (300 mg/m²/day as tegafur + 75 mg/day of LV) on days 1-5. A total of 13 measurements of the plasma concentrations of uracil, 5-FU and tegafur were made per patient within 48 hr after the start of chemotherapy and the value of area under the concentration-time curve (AUC_0-48) was evaluated. The plasma concentration was also determined at 2 weeks to assess long-term exposure to 5-FU.Results: The plasma concentrations of 5-FU at 24 hr after the start of treatment were 27.4 ng/mL and 9.4 ng/mL in the patients with and without the bolus injection, respectively. At 48 hr, they were 31.3 ng/mL and 10.4 ng/mL with the AUC_0-48 values of 22.16 mg*h/L and 0.65 mg*h/L, respectively. The 5-FU was detected in the plasma at 226 hr after the last administration of UFT/LV for the patients with the bolus injection, but not for those without.Conclusion: A bolus of 5-FU on day 1 provided long-term exposure to 5-FU.     

Change in pharmacokinetics of model compounds with different elimination processes in rats during hypothermia

We compared the pharmacokinetics of model compounds with different elimination processes between hypothermic and normothermic rats, to obtain basic information concerning drug therapy during hypothermia. Male Wistar rats were anesthetized with sodium pentobarbital and kept at temperatures of 37 degrees C (normothermic group) by heat lamp, and 32 degrees C or 28 degrees C (hypothermic group) by external cooling. We chose phenolsulfonphthalein (PSP), indocyanine green (ICG) and fluorescein isothiocyanate (FITC)-dextran (FD-4, Mw 4400) as model compounds to determine changes in clearance pathways during hypothermia therapy. The plasma concentrations of PSP as biliary, urinary and metabolic elimination type were increased significantly in the hypothermic group (32 degrees C, 28 degrees C) after i.v. administration at a dose of 1 mg, compared to the normothermic group (37 degrees C). Each PSP clearance (bile, urine and metabolites) in the hypothermic group was decreased, suggesting an influence of hypothermia on the active elimination process. The decreasing tendency was marked at a temperature of 28 degrees C. Moreover, the plasma concentrations of ICG as the biliary excretion type after i.v. administration to the hypothermic rats at a dose of 1 mg were higher with more than 50% decrease in the total body clearance compared to normothermic rats. On the other hand, there was almost no difference in the i.v. pharmacokinetics of FD-4 as the urinary excretion type between 37 degrees C and 32 degrees C. However, renal clearance of FD-4 was significantly decreased at a temperature of 28 degrees C. Accordingly, the change in pharmacokinetics of a drug in the hypothermic group could differ with the elimination processes.     

Association of cumulative cyclosporine dose with its irreversible nephrotoxicity in Japanese patients with pediatric-onset autoimmune diseases

Cyclosporine (CsA)-induced nephrotoxicity can become a major obstacle to continuous use. The aim of this study was to optimize CsA dose to avoid its irreversible nephrotoxicity. Twenty-three Japanese patients with pediatric-onset systemic lupus erythematosus or idiopathic nephrotic syndrome, who were maintained in a stable condition by oral dosing of CsA microemulsion, were enrolled in this study. The patients were stratified into 3 groups; those with no, reversible, and irreversible nephrotoxicity, according to periodically performed renal pathohistological examinations. A higher concentration of CsA in blood (p=0.002-0.011) and a longer duration of CsA treatment (p=0.002) were risk factors for irreversible nephrotoxicity, and the cumulative CsA dose, the product of the maintenance dose and duration of CsA treatment, was predictive of nephrotoxicity (p=0.036). The maximum target blood concentration at 2 h post-dose, C(2), to avoid CsA-induced irreversible nephrotoxicity was 700 ng/ml, although the cumulative CsA dose of 4850 mg/kg would result in a 50% probability of nephrotoxicity.