Takafumi Kuzuya

Pharmacokinetic Characteristics of 5‐Fluorouracil and Mitomycin C in Intraperitoneal Chemotherapy

Abstract— Eight patients with malignancies confined to the peritoneal space participated in this study. Five hundred milligrams 5‐fluorouracil or 10 mg mitomycin C was diluted in 1 L saline. The mixed solution was injected intraperitoneally through the semi‐permanent peritoneal catheter. Blood and peritoneal fluid were collected after injection. 5‐Fluorouracil concentrations in the peritoneal fluid were 1000 times those in serum, while mitomycin C concentrations were 100 times those in serum. Areas under the concentration vs time curve (AUC) were calculated by the trapezoidal method with extrapolation to infinity. The ratio of peritoneal fluid AUC to serum AUC was about 1400 for 5‐fluorouracil and 80 for mitomycin C. Patterns for the absorption and elimination from systemic circulation were similar for both compounds. Drug concentrations in the peritoneal fluid and serum were analysed according to the compartment model. The half‐life in the peritoneal fluid (t½p) and the rate constant from the peritoneal fluid to the systemic circulation (ka) were nearly equal for both 5‐fluorouracil and mitomycin C (t½p, 1·0 h for 5‐fluorouracil and 1·3 h for mitomycin C; ka 0·71 h−1 for 5‐fluorouracil and 0·68 h−1 for mitomycin C), although the apparent volume of distribution (Vds/F) and clearance in the peritoneal cavity (CLp) for mitomycin C (78 Lm−2 and 1.8 L h−1 m−2) were about twice the values for 5‐fluorouracil (149 L m−2 and 0·8 L h−1 m−2).

Amlodipine, but not MDR1 polymorphisms, alters the pharmacokinetics of cyclosporine A in Japanese kidney transplant recipients

Background. Cyclosporine A (CsA) is a critical immunosuppressive drug with a narrow therapeutic range and wide interindividual variation in its pharmacokinetics. Many factors, including P-glycoprotein (PGP), influence the oral bioavailability and interpatient variability of CsA. A number of polymorphisms have been identified in the human MDR1 gene, and some of them have been found to be associated with an altered expression of PGP. We have investigated the role of these polymorphisms in CsA absorption from kidney transplant recipients. In addition, we also investigated the effect of amlodipine on CsA absorption. Methods. The area under the time-concentration curve from 0 to 2 hr (AUC0–2) estimated by the trapezoidal rule was used for the evaluation of extent of CsA absorption. The genotypes were identified by a polymerase chain reaction, restriction fragment length polymorphism analysis. Results. No association was found between polymorphisms in the MDR1 and CsA AUC0–2/dose/kg. In contrast, the combination of amlodipine significantly increased CsA AUC0–2/dose/kg (706.2 &mgr;g·hr/L to 819.2 &mgr;g·hr/L, P <0.05). Furthermore, we attempted to compare MDR1 polymorphisms and the absorption of CsA again without patients receiving amlodipine, but there was still no significant difference. Conclusions. There is no relationship between polymorphisms for MDR1 and CsA absorption, suggesting polymorphisms for MDR1 cannot account for the interpatient variability of CsA. Amlodipine, which is the substrate of PGP, significantly increased CsA absorption. These results indicate that PGP plays a significant role in CsA absorption, but its polymorphisms could not influence the CsA absorption.

Clinical significance of regulatory T-cell-related gene expression in peripheral blood after renal transplantation.

Background. Regulatory T cells (Tregs) have been suggested to be deeply associated with immune tolerance and long-term graft survival in transplantation. Some recipients with stable graft function (ST) could possibly minimize immunosuppression during the maintenance period. However, effective assays for assessing the suitability of patients have yet to be established. The purpose of this study was to elucidate the clinical relevance of Treg-related gene expression such as forkhead box P3 (Foxp3) in peripheral blood after renal transplantation. Methods. Several key molecules related to the function of immune cells such as Treg, including Foxp3, transforming growth factor-&bgr;, cytotoxic T-lymphocyte antigen-4, chemokine receptor 7, toll-like receptor 4, granzyme B, T-bet, GATA3, RORC, &agr;1,2-mannosidase, and proteasome subunit &bgr; 10 were examined in the peripheral blood of 272 renal transplant recipients by quantitative real-time reverse-transcriptase polymerase chain reaction. The expression levels were compared between recipients with chronic rejection and ST. Results. Foxp3 messenger RNA (mRNA) levels were reduced immediately after transplantation and gradually recovered. Pretransplantation levels were closely correlated with 1 year posttransplantation levels. Recipients with chronic rejection had significantly lower levels of Foxp3, chemokine receptor 7, and granzyme B mRNA, and higher levels of toll-like receptor 4 and proteasome subunit &bgr; 10 mRNA compared with those with ST, although Foxp3 was the most relevant marker. Conclusion. There is a possibility that monitoring mRNA expression levels of Treg-related molecules in peripheral blood might offer useful information on patient selection and early detection of rejection when immunosuppression minimization strategy is implemented in renal transplantation.

Interference of hematocrit in the tacrolimus II microparticle enzyme immunoassay.

The authors studied the effect of hematocrit, bilirubin, and alkaline phosphatase on microparticle enzyme immunoassay for tacrolimus II (MEIA II) using specimens of whole blood obtained from 33 patients undergoing cyclosporine treatment. Tacrolimus was added to these samples at a final concentration of 7.5 &mgr;g/L and 15 &mgr;g/L. Both coefficients of variation were over 20% (21% at 7.5 &mgr;g/L of tacrolimus and 22% at 15 &mgr;g/L of tacrolimus). No correlation was found between bilirubin and tacrolimus concentrations or between alkaline phosphatase and tacrolimus concentrations. On the other hand, negative correlations were found between hematocrit values and tacrolimus concentrations (r2 = 0.47;P < 0.0001 at 7.5 &mgr;g/L tacrolimus, r2 = 0.54;P < 0.0001 at 15 &mgr;g/L tacrolimus). Negative correlations were also found between hematocrit and the tacrolimus concentration using normal human red blood cells diluted with physiological saline solution (r2 = 0.93;P < 0.0001 at 7.5 &mgr;g/L tacrolimus, r2 = 0.91;P < 0.0001 at 15 &mgr;g/L tacrolimus). The results showed that the hematocrit interferes with the MEIA II for tacrolimus, and the magnitude of the interference is clinically significant. Beyond the normal range of hematocrit values, caution should be exercised in interpreting results as one may need to compensate for the levels of tacrolimus.

Comparative study on signal transduction in endothelial cells after anti-a/b and human leukocyte antigen antibody reaction: implication of accommodation.

Background. Recent development of immunosuppressive therapy has provided a platform for clinical human leukocyte antigen (HLA)- and ABO-incompatible kidney transplantation. However, the prognosis seems to be different between the two. Accommodation, the condition of no injury even in the presence of antidonor antibody, is one of the key factors for successful transplantation with antidonor antibody. The purpose of this study was to compare signal transduction between anti-A/B and anti-HLA antibody reaction and to elucidate the mechanisms underlying accommodation. Methods. Blood type A- or B-transferase gene was transfected into human EA.hy926 endothelial cells. After cell sorting, A- or B-expressing cells at high levels were obtained. The effects of anti-HLA and anti-A/B antibody binding on complement-mediated cytotoxicity and signal transduction were examined. Results. Preincubation with anti-HLA antibodies only at low levels (<10% of saturation level) or anti-A/B antibodies at high levels (even at near saturation levels) for 24 hr resulted in resistance to complement-mediated cytotoxicity. Anti-A/B antibody ligation inactivated ERK1/2 pathway and increased complement regulatory proteins such as CD55 and CD59, whereas anti-HLA ligation activated PI3K/AKT pathway and increased cytoprotective genes such as hemeoxygenase-1 and ferritin H. Conclusion. Complement inhibition by upregulation of CD55 and CD59 through ERK1/2 inactivation might play a substantial role in accommodation after ABO-incompatible transplantation, which could also explain the intriguing finding of C4d deposition in the graft without rejection.

Population pharmacokinetic analysis of vancomycin in patients with gram‐positive infections and the influence of infectious disease type

Objective:  To describe the population pharmacokinetics of vancomycin in patients with gram‐positive infections and to investigate the influence of type of infectious disease.

Comparative analysis of drug action on B-cell proliferation and differentiation for mycophenolic acid, everolimus, and prednisolone.

Background Although more attention has been paid recently to B-cell immunity, assay for B-cell analysis has yet to be clinically applicable because, unlike T cell, a B-cell culture system has not been well established. Methods We attempted to develop an in vitro culture system for the proliferation and differentiation of peripheral B cells into plasma cells, and to analyze the action of everolimus (EVR), mycophenolic acid (MPA), and prednisolone (PRD). Results Using a three-step culture system, peripheral CD19+ B cells could differentiate into plasma cells and produce IgG antibody. Activated B cells (CD19(hi)CD38(lo)IgD(−)), plasmablasts (CD19(hi)CD38(hi)IgD(−)), and plasma cells (CD19(lo/−)CD38(hi)IgD(−)) were observed as a main cell subset in step 1 (day 0–4), 2 (day 4–7), and 3 (day 7–10), respectively. IgG production on day 10 was significantly suppressed by EVR, MPA, and PRD, but not cyclosporine. Although both EVR and MPA inhibited B-cell proliferation and differentiation in step 1, EVR suppressed B-cell differentiation in step 2. Only a high concentration of PRD significantly inhibited B-cell proliferation, differentiation, and IgG production in step 3. Conclusions Although both MPA and EVR efficiently suppressed cell proliferation during the early phase of B-cell immune reaction, EVR could act in a later phase than MPA. PRD at a high concentration worked even in the last phase. An in vitro B-cell culture system would clarify the mode of drug action during B-cell differentiation and provide useful information on the effective selection or combination of immunosuppressive agents.

The Possible Mechanism of Interaction between Xanthines and Quinolone

Abstract— To clarify the mechanism of interaction between theophylline and enoxacin, the effects of enoxacin and its metabolite, 4‐oxo‐enoxacin, on the disposition of new xanthine derivatives, 1‐methyl‐3‐propylxanthine (MPX) and 3‐propylxanthine (enprofylline), as models of theophylline have been investigated in rats. Pretreatment with enoxacin significantly delayed the elimination of MPX from plasma. No significant change in the volume of distribution of MPX was observed in the presence of enoxacin, but the total body clearance of MPX was significantly decreased by approximately 60 and 80% after pretreatment with 25 and 100 mg kg−1 of enoxacin, respectively. The amount of the decrease in total body clearance depended on the dose of enoxacin. 4‐Oxo‐enoxacin had little or no effect on MPX disposition. A newly developed quinolone, NY‐198, which does not affect the disposition of theophylline, also did not affect the disposition of MPX. Enoxacin also had no effect on the disposition of enprofylline. These results indicate that the mechanism for decrease in theophylline clearance induced by enoxacin may not be due to its metabolite, 4‐oxo‐enoxacin, but to enoxacin itself, and that enoxacin does not inhibit solely the elimination process depending on cytochrome P450 isoenzyme for N‐demethylation. It is likely that enoxacin has no influence on the renal excretion of xanthines.

Methylprednisolone reduces postoperative nausea in total knee and hip arthroplasty.

What is known and objective:  Total knee and hip joint replacement has a high risk of postoperative nausea and vomiting (PONV), and steroid cover is used for cases associated with autoimmune diseases. Our aim is to evaluate the antiemetic efficacy of methylprednisolone as steroid cover in patients undergoing the surgery.

Production of cloned pigs expressing human thrombomodulin in endothelial cells.

Yazaki S, Iwamoto M, Onishi A, Miwa Y, Hashimoto M, Oishi T, Suzuki S, Fuchimoto D‐I, Sembon S, Furusawa T, Liu DG, Nagasaka T, Kuzuya T, Ogawa H, Yamamoto K, Iwasaki K, Haneda M, Maruyama S, Kobayashi T. Production of cloned pigs expressing human thrombomodulin in endothelial cells. Xenotransplantation 2012; 19: 82–91.