Effect of low dose cyclosporine and sirolimus on hepatic drug metabolism in the rat1.

BACKGROUND: We examined the effect cyclosporine (CsA) and sirolimus (SRL) alone and in combination on hepatic cytochrome P450-mediated metabolism in rats. METHODS: Rats were given 1 mg/kg of CsA or 0.4 mg/kg of SRL alone or in combination via constant intravenous infusion. Renal function was evaluated at the end of treatment. Blood samples were obtained to estimate CsA and SRL concentrations. Hepatic microsomes were prepared for immunoblotting and catalytic assays. RESULTS: CsA alone did not alter serum creatinine levels. SRL given alone or in combination with CsA produced a significant increase in urine output without changes in fluid balance. Although CsA and SRL administered alone caused damage to renal proximal tubules, the two-drug combination dramatically increased the renal structural damage. CsA alone suppressed cytochrome P450 (CYP) 3A2 protein levels by 39% (P=0.012) and catalytic activity by 30% (P=0.042). SRL alone reduced catalytic activity by 38% (P=0.012). Combination therapy reduced both CYP3A2 levels by 55% (P<0.001) and catalytic activity by 55% (P=0.001). CYP2C11 protein expression or catalytic activity were not changed in any group. CYP2A1 protein expression and catalytic activity were both significantly reduced in rats given CsA or/and SRL. Steady-state CsA levels were increased during concurrent SRL dosing, however, SRL concentrations were not changed by CsA coadministration. CONCLUSIONS: Concurrent SRL dosing increases CsA concentrations due to inhibition of hepatic CYP3A2 protein expression. Nephrotoxicity caused by combination therapy is due to CsA elevating levels of SRL or by SRL itself. Concurrent administration of CsA and SRL in transplant patients should be performed with caution.     

Sirolimus increases transforming growth factor-beta1 expression and potentiates chronic cyclosporine nephrotoxicity

BACKGROUND: Sirolimus (SRL) is increasingly being used to decrease cyclosporine (CsA) exposure. SRL is not known to be nephrotoxic and has a mechanism of action distinct from CsA. We investigated the effect of combining CsA and SRL on renal structure and function and on transforming growth factor-beta1 (TGF-beta1) and extracellular matrix (ECM) proteins in a model of chronic CsA nephrotoxicity. METHODS: Rats treated with vehicle, SRL 0.3 mg/kg/day, CsA 5 or 10 mg/kg/day, or CsA5+SRL were sacrificed at 7 or 28 days. Physiologic and histologic changes were studied in addition to TGF-beta1 mRNA and protein expressions, and mRNA expression of plasminogen activator inhibitor-1 (PAI-1) and ECM proteins biglycan and types I and IV collagen. RESULTS: While SRL alone did not alter renal function and structure, it potentiated the nephrotoxic actions of CsA when used in combination with low-dose CsA5 and resulted in significant changes similar to high-dose CsA10. In addition, SRL alone increased TGF-beta1 by 44% to 49% (P < 0.05 vs. VH). When used in combination with low-dose CsA5, SRL potentiated TGF-beta1 mRNA and protein by 121% and 176%, respectively (P < 0.05 vs. VH and CsA5), to levels achieved with high-dose CsA10. The expression of the ECM proteins followed that of TGF-beta1; a similar effect was observed with PAI-1, suggesting a decrease in ECM degradation. CONCLUSION: Because SRL augments nephrotoxicity, caution should be exercised when it is used in combination with CsA. More studies are needed to determine the long-term clinical impact of SRL on nephrotoxicity and allograft function.     

Synergistic effects of sirolimus with cyclosporine and tacrolimus: analysis of immunosuppression on lymphocyte proliferation and activation in rat whole blood

BACKGROUND: Whole-blood analysis of lymphocyte function was used to investigate the pharmacodynamic (PD) interaction of sirolimus (SRL) with cyclosporine (CsA) or tacrolimus (TRL) in vitro and to determine the relation between PD and pharmacokinetics (PK) of SRL in an in vivo rat model. METHODS: In vitro, experiments involved incubation of increasing concentrations (0.25-25 [corrected] nM) of SRL with either CsA or TRL in rat whole blood. For the in vivo study, rats were orally treated with different doses of SRL alone (1, 3, 5, or 8 mg/kg) or with a combination of 3 mg/kg SRL plus 2.5 or 5 mg/kg CsA. Blood was obtained before and at different times after dosing. Inhibition of lymphocyte proliferation (proliferating cell nuclear antigen [PCNA]) and activation (CD25, CD71, CD11a, CD134) in mitogen-stimulated blood was determined using fluorescence-activated cell sorter analysis. SRL and CsA blood concentrations were determined at the same time points by light chromatography tandem mass spectrometry (LC-MS). RESULTS: In vitro, concentrations of SRL between 0.25-25 [corrected] nM acted synergistically in combination with CsA or TRL at concentrations between 0.25-1.0 [corrected] nM. Higher SRL concentrations did not further increase inhibition of lymphocyte function in these combinations. In vivo, good correlations (r=0.68-0.94) were observed between PD parameters of lymphocyte function and SRL-PK and dose. Increasing SRL doses produced higher blood concentrations, but SRL doses of 8 mg/kg did not further increase inhibition of lymphocyte function. PD effects on lymphocyte function were prolonged, but maximal inhibition was not increased when SRL was applied in combination with CsA as compared to SRL mono therapy. CONCLUSIONS: The results suggest that analysis of lymphocyte function in whole blood may be useful to optimize dosing of SRL in combination with CsA or TRL and that PD monitoring of immunosuppressive drugs will enhance the value of PK monitoring.     

Human allograft arterial injury is ameliorated by sirolimus and cyclosporine and correlates with suppression of interferon-gamma

BACKGROUND: Chronic allograft dysfunction may result from arterial injury, manifest as transplant arteriosclerosis (TA). This represents an important factor limiting long-term outcomes after heart and kidney transplantation; a relationship between acute allograft arterial injury and TA has been suggested. We have used SCID/bg mice bearing transplanted human artery, inoculated with allogeneic human PBMC to study arteriopathy in human vessels. Earlier work demonstrated arteriopathy similar to that observed clinically, and identified interferon-gamma as a mediator of the process. This study evaluated whether sirolimus (SRL), with cyclosporine A (CsA) or alone, affects TA, and examined possible mechanisms of action. METHODS: CB17/SCID/bg mice were transplanted with human arteries replacing the abdominal aorta; reconstituted with allogeneic human PBMC. Controls received vehicle alone for comparison with mice given CsA (5 mg/kg/d), SRL (0.1 or 0.5 mg/kg/d), or CsA (5 mg/kg/d) plus SRL (0.1 mg/kg/d). Transplant arteries were examined 28 days later by histology and immunohistochemistry; circulating human interferon-gamma was evaluated by ELISA, and intragraft interferon-gamma mRNA by qRT-PCR. RESULTS: The characteristic TA was modestly reduced by CsA or low-dose SRL, but eliminated by combination CsA plus SRL or higher dose SRL alone. Circulating interferon-gamma was reduced by CsA, but inhibition was dramatic with SRL alone or combined with CsA. Intragraft interferon-gamma and HLA-DR expression were moderately reduced by CsA or SRL, and eliminated with combined CsA plus SRL. CONCLUSIONS: SRL plus CsA prevented allograft arteriopathy, correlating with suppression of intragraft interferon-gamma, suggesting that SRL effects may result from anti-inflammatory consequences from inhibiting interferon-gamma.     

P-glycoprotein inhibitors stimulate renal phosphate reabsorption in rats

BACKGROUND: Dipyridamole (Dip) was previously shown to increase renal phosphate (Pi) reabsorption in humans. However, the mechanism(s) underlying this renal tubular effect is not fully elucidated. It is known that Dip inhibits the activity of the P-glycoprotein (Pgp) multidrug resistance protein 1 (MDR1) expressed on the apical membrane of renal proximal tubular cells where the Na-Pi cotransporter (NPT2) is also expressed. We hypothesized that Dip could increase renal Pi reabsorption by inhibiting Pgp activity. METHODS: To test this hypothesis, the effects of Dip, verapamil (Ver), and cyclosporine A (CsA), three unrelated Pgp inhibitors, were studied on the renal Pi reabsorption in rats. RESULTS: All three drugs decreased the fractional excretion of Pi (FE(Pi)) in a dose-dependent manner within one hour after beginning the drug infusion, without altering the glomerular filtration rate or serum parathyroid hormone concentration. Sodium-dependent Pi uptake but not Na-glucose transport was increased in brush-border membrane vesicles (BBMVs) when comparing treated with untreated rats. Western blot analysis showed that NPT2 protein was increased in BBMVs from treated rats. Dip and Ver had no effect when applied directly to BBMVs prepared from untreated rats. Pretreatment of rats with colchicine prevented the effects of Dip on the FE(Pi) and NPT2 expression in brush-border membranes. CONCLUSIONS: Our results suggest that inhibition of Pgp in the proximal tubule increases Pi uptake and NPT2 translocation to the apical membrane.     

Correlation between cyclosporine-induced nephrotoxicity in reduced nephron mass and expression of kidney injury molecule-1 and aquaporin-2 gene

Sirolimus (SRL) has been shown to exacerbate cyclosporine (CsA)-induced nephrotoxicity. The expression of the kidney injury molecule-1 (KIM-1) is markedly upregulated in the postischemic rat kidney. We sought to correlate drug-induced nephrotoxicity and the expression of KIM-1 and aquaporin-2 (AQP-2) in male PVG rats with 2 kidneys (2K), 1 kidney (1K), and half a kidney (1/2K) treated with SRL alone, CsA alone, or a combination of both (SRL-CsA). After 7 days of treatment, the 2K group treated with SRL-CsA showed a significant decrease in creatinine clearance compared with the 2K SRL alone and 2K CsA alone groups (1.2 vs 2.47 vs 2.46 mL/min; P < .001). There was a trend toward deterioration of creatinine clearance in the 1K and 1/2K groups treated with SRL-CsA. The KIM-1 expression in the 2K SRL-CsA group was significantly upregulated compared with that in the 2K SRL alone and 2K CsA alone groups (P = .02). The AQP-2 expression was comparable in the 3 groups. After 1 week of treatment washout, the 2K, 1K, and 1/2K groups treated with SRL alone demonstrated a significantly higher creatinine clearance rate than did the groups treated with SRL-CsA (P = .04, P = .02, and P = .004). The expression of KIM-1 and AQP-2 was similar among the treatment groups. SRL-CsA-induced nephrotoxicity resulted in overexpression of KIM-1, suggesting injury to the proximal tubule. Treatment with SRL alone may enable earlier reversal of tubular injury.     

Influence of Sirolimus on Cyclosporine-Induced Pancreas Islet Dysfunction in Rats

This study was performed to investigate the effect of sirolimus (SRL) on cyclosporine (CsA)-induced pancreatic islet dysfunction in rats. Three separate studies were performed. First, diabetogenic effect of SRL was evaluated with three different doses (0.15, 0.3 and 0.6 mg/kg). Second, rats were treated with SRL (0.3 mg/kg) with or without CsA (15 mg/kg) for 4 weeks. Third, rats were treated with CsA for 4 weeks, and then switched to SRL for 4 weeks. The effect of SRL on CsA-induced pancreatic islet dysfunction was evaluated by an intraperitoneal glucose tolerance test, plasma insulin concentration, HbA1c level, HOMA-R index, immunohistochemistry of insulin and pancreatic beta islet cell mass. The SRL treatment increased blood glucose concentration in a dose-dependent manner. The combined treatment with SRL and CsA increased blood glucose concentration, Hemoglobin A1c (HbA1c) level, HOMA-R [fasting insulin (mU/mL) x fasting glucose (mmol/L)]/22.5] index and decreased plasma insulin concentration, immunoreactivity of insulin and pancreatic beta islet cell mass compared with rats treated with CsA. CsA withdrawal for 4 weeks improved pancreatic beta-cell function and structure. However, conversion from CsA to SRL further increased blood glucose levels compared with the rats converted from vehicle to SRL. The results of our study demonstrate that SRL is diabetogenic and aggravates CsA-induced pancreatic islet dysfunction.     

Immunosuppressant use without bone loss--implications for bone loss after transplantation.

Cyclosporine A (CsA) is associated with posttransplantation bone disease. Immunosuppressant drugs such as sirolimus (SRL), which are more potent and less deleterious than CsA, are being developed. Previous experiments have shown that SRL although immunosuppressive, is relatively bone sparing. The use of low doses of CsA and SRL in combination has displayed in vivo synergism. This study was initiated to examine the effect of low-dose CsA and SRL on bone metabolism, thereby hopefully providing a bone sparing immunosuppressive regimen for transplant recipients. One hundred and nineteen rats were divided into groups: basal, vehicle, CsA high dose, CsA low dose, SRL low dose, and combination low-dose CsA and SRL. The basal group was killed on day 0 for histomorphometry. The experimental groups were weighed and bled on days 0, 28, 56, and 84 and were killed on day 84 for histomorphometry. Serial assays for blood urea nitrogen (BUN), creatinine, and osteocalcin were performed. Osteocalcin was raised on days 28 and 56 in the high dose CsA group. Histomorphometry showed osteopenia with high-dose CsA. Low-dose CsA was relatively bone sparing, while low-dose SRL and combined low-dose CsA did not cause bone loss. In conclusion, the synergistic combination of low-dose CsA and SRL has the potential of providing both bone sparing and immunosuppressive benefits.     

Kidney function and morphology after short-term combination therapy with cyclosporine A, tacrolimus and sirolimus in the rat.

BACKGROUND: Sirolimus (SRL) may supplement calcineurin inhibitors in clinical organ transplantation. These are nephrotoxic, but SRL seems to act differently displaying only minor nephrotoxic effects, although this question is still open. In a number of treatment protocols where SRL was combined with a calcineurin inhibitor indications of a synergistic nephrotoxic effect were described. The aim of this study was to examine further the renal function, including morphological analysis of the kidneys of male Sprague-Dawley rats treated with either cyclosporine A (CsA), tacrolimus (FK506) or SRL as monotherapies or in different combinations. METHODS: For a period of 2 weeks, CsA 15 mg/kg/day (given orally), FK506 3.0 mg/kg/day (given orally) or SRL 0.4 mg/kg/day (given intraperitoneally) was administered once a day as these doses have earlier been found to achieve a significant immunosuppressive effect in Sprague-Dawley rats. In the 'conscious catheterized rat' model, the glomerular filtration rate (GFR) was measured as the clearance of Cr(EDTA). The morphological analysis of the kidneys included a semi-quantitative scoring system analysing the degree of striped fibrosis, subcapsular fibrosis and the number of basophilic tubules, plus an additional stereological analysis of the total grade of fibrosis in the cortex stained with Sirius Red. RESULTS: CsA, FK506 and SRL all significantly decreased the GFR. A further deterioration was seen when CsA was combined with either FK506 or SRL, whereas the GFR remained unchanged in the group treated with FK506 plus SRL when compared with treatment with any of the single substances. The morphological changes presented a similar pattern. The semi-quantitative scoring was significantly worst in the group treated with CsA plus SRL (P<0.001 compared with controls) and the analysis of the total grade of fibrosis also showed the highest proportion in the same group and was significantly different from controls (P<0.02). The FK506 plus SRL combination showed only a marginally higher degree of fibrosis as compared with controls (P=0.05). CONCLUSION: This rat study demonstrated a synergistic nephrotoxic effect of CsA plus SRL, whereas FK506 plus SRL was better tolerated.     

Incidence of posttransplant diabetes mellitus in kidney transplant recipients immunosuppressed with sirolimus in combination with cyclosporine

Sirolimus (SRL) in combination with Cyclosporine A (CsA) and steroids has been shown to lower the incidence of acute renal allograft rejection episodes, allowing CsA sparing. We retrospectively compared the incidence of posttransplant diabetes mellitus (PTDM) among kidney transplant recipients (KTx) immunosuppressed with SRL + CsA versus CsA alone. Patients were divided into two groups: SRL + CsA (n = 38) versus CsA (n = 48). Mean follow-up was 53.9 +/- 17.1 months. Seventeen/86 subjects (19.8%) developed diabetes after transplantation (7 IFG, 8.1%; 10 PTDM, 11.6%). The incidence was significantly higher in SRL + CsA (12/38 patients, 31.6%) compared with CsA (5/43 patients, 10.4%) (P = .0144, odds ratio 3.97). More patients required treatment in the SRL + CsA compared to CsA alone cohort (13.2% vs 2.1%, P = .051): 4 pts (10.5%) became insulin- dependent among SRL+CsA, vs none in the CsA group. Use of OHD was similar in both groups (2.6% SRL + CsA vs 2.1% CsA). There were no significant differences between the two groups in terms of age, sex distribution, BMI, or serum creatinine at 1 to 3 and 5 years from transplantation. All PTDM patients are alive at follow-up, while two grafts were lost due to chronic renal allograft dysfunction. Within the limits of a small retrospective study, we observed that SRL in combination with CsA increased the diabetogenic potential of CsA. A possible explanation of our findings is that higher CsA doses were used in the early experience with SRL + CsA; therefore the higher incidence of PTDM that we observed in the SRL + CsA combination may be a sign of toxicity. Careful monitoring of blood levels is mandatory in the SRL + CsA combination to avoid pleiotropic toxicity.     

Effect of cyclosporine and sirolimus on the expression of connective tissue growth factor in rat experimental chronic nephrotoxicity

BACKGROUND/AIMS: Connective tissue growth factor (CTGF) is a pro-fibrotic growth factor that acts downstream of transforming growth factor (TGF)-beta. However, CTGF regulation remains unknown. We tried to determine the effect of two commonly used immunosuppressants, cyclosporine (CsA) and sirolimus (SRL), on CTGF expression in a model of chronic nephrotoxicity. METHODS: Adult Sprague-Dawley rats kept on a low-salt diet were treated daily for 4 weeks with vehicle (VH), SRL (0.3 mg/kg), CsA5 (5 mg/kg), CsA10 (10 mg/kg) or both CsA5 and SRL. CTGF and TGF-beta1 expressions were evaluated by Northern blot. Functional and histologic parameters in addition to number of apoptotic cells were determined. RESULTS: At 28 days, both CsA doses were capable of inhibiting CTGF mRNA expression to levels similar to control. On the other hand, SRL increased CTGF expression by 3.5-fold. However, addition of CsA to SRL completely reversed that trend and returned levels to control. The results were different for TGF-beta1, which was increased by both CsA and SRL and to a greater extent by the drug combination. CONCLUSION: Unlike TGF-beta, CTGF does not seem to play an important role in CsA-induced chronic nephrotoxicity. In addition, calcineurin-dependent pathways are likely involved in CTGF regulation.     

Sirolimus reduces the incidence of acute rejection episodes despite lower cyclosporine doses in caucasian recipients of mismatched primary renal allografts: a phase II trial. Rapamune Study Group

BACKGROUND: The novel agent sirolimus (SRL; Rapamune; rapamycin) inhibits the immune response by a mechanism distinct from those of calcineurin antagonists or antimetabolites. This randomized, controlled, multicenter, single blind, phase II trial examined the combination of SRL, steroids, and full versus reduced doses of cyclosporine (CsA) for prophylaxis of acute renal allograft rejection. METHODS: A total of 149 recipients of mismatched cadaveric- or living-donor primary renal allografts were randomized into six groups. Three groups received placebo or 1 or 3 mg/m2/day SRL, as well as steroids and full-dose CsA (Sandimmune). Three groups received steroids, reduced-dose CsA (target trough level 50% of full-dose range), and 1, 3, or 5 mg/m2/day SRL. RESULTS: The incidence of biopsy-proven acute rejection episodes within the first 6 months after transplant was reduced from 32.0% in the control group to 8.5% in patients receiving SRL (1 or 3 mg/m2/day) and full-dose Sandimmune CsA (P=0.018). Similar low rates of acute rejection episodes were observed among non-African-Americans, but not African-Americans, treated with SRL and reduced-dose Sandimmune CsA. Despite the augmented immunosuppression, 1-year patient and graft survival rates did not differ significantly across groups. Adverse effects attributable to CsA, including hypertension and new-onset diabetes mellitus, were not exacerbated by SRL. Except for an increased incidence of pneumonia among patients receiving full-dose CsA and 3 mg/m2/day SRL, the incidences of opportunistic infections were similar in all treatment groups. Although SRL produced more frequent, but reversible, hematological and lipid abnormalities, it had no apparent nephrotoxic effects to exacerbate CsA-induced renal dysfunction. CONCLUSIONS: SRL in combination with CsA and steroids not only lowers the incidence of biopsy-proven acute renal allograft rejection episodes, but also may permit CsA sparing, at least among Caucasian patients, without an increased risk of rejection.     

Health-related quality-of-life outcomes of sirolimus-treated kidney transplant patients after elimination of cyclosporine A: results of a 2-year randomized clinical trial

BACKGROUND: This study compared 2-year health-related quality-of-life (HRQL) outcomes of sirolimus (SRL)-treated kidney transplant patients after elimination of cyclosporine A (CsA) to patients continuing on a combined CsA and SRL regimen. METHODS: A randomized, open-label, clinical trial was performed in Europe, Australia, and Canada. Four hundred thirty kidney transplant patients were randomly assigned to sirolimus plus steroids (ST) (n=215) or SRL and CsA+ST (n=215) therapy after 3 months of combined SRL+CsA+ST treatment. HRQL was measured using the Kidney Transplant Questionnaire (KTQ) and the SF-36 Health Survey at month 3 (time of randomization) and months 12 and 24 after transplantation. Repeated-measures analysis of covariance was used to evaluate treatment differences in HRQL scores over the 2-year period. RESULTS: HRQL scores were available for 361 (86%) eligible study patients. Statistically significant treatment-by-assessment time interactions, favoring SRL+ST, were found on KTQ Fatigue (P=0.0158) and Appearance scores (P=0.0007). No treatment differences were observed in KTQ Physical Symptom, Uncertainty-Fear, and Emotion scores. Statistically significant treatment-by-assessment time interactions were observed for SF-36 Vitality scores (P=0.0203) but not other SF-36 scores (P>0.05). For Vitality scores, the SRL+ST group remained stable (mean, 0.4-point change) from month 3 to month 24 compared with decreases in the SRL+CsA+ST group (mean, -6.5-point change). CONCLUSIONS: SRL-based therapy with early elimination of CsA results in fewer appearance-related problems, less fatigue, and better vitality compared with continuous treatment with SRL, CsA, and ST.     

Pharmacokinetics of mycophenolic acid in kidney transplant patients receiving sirolimus versus cyclosporine

INTRODUCTION: Mycophenolic acid (MPA) pharmacokinetics exhibit large variability in transplant recipients and may be altered due to concurrent immunosuppressants. Little is known about the influence of sirolimus (SRL) on MPA pharmacokinetics in kidney transplant patients. METHODS: We studied the areas under concentration-time curves (AUC) for MPA in 15 patients receiving immunosuppression combining SRL with mycophenolate mofetil (MMF). The pharmacokinetic measurements were performed in all patients using three MMF dosing regimens (0.5 g twice a day, 0.75 g twice a day, 1 g twice a day). Similar blood AUC profiles were also sampled from 12 patients treated with a fixed dose of MMF 1 g twice a day and cyclosporine (CsA). MPA was measured using HPLC; the AUC0-12 of MPA was determined by the trapezoidal method using four sampling time points: C0, C1, C3, C5. RESULTS: While patients on SRL were receiving 0.75 g MMF twice a day, mean AUC0-12 and C0 values of MPA were comparable to those of patients receiving CsA and 1 g MMF twice a day (54.1 +/- 17.6 and 3 +/- 1.87 vs 51.7 +/- 16.7 mg.h/L and 2.76 +/- 1.57 mg/L, respectively). On the other hand, 0.5 g MMF twice a day with SRL therapy resulted in AUC0-12 and C0 values of MPA of 32.3 +/- 12.6 mg.h/L and 2.32 +/- 1.72 mg/L, respectively, whereas, 1 g MMF twice a day with SRL resulted in AUC0-12 and C0 values of MPA of 70.9 +/- 19.3 mg.h/L and 4.7 +/- 2.44 mg/L, respectively. CONCLUSIONS: These findings demonstrate that MPA exposure in the presence of SRL is higher than that with CsA. It appears that the MMF dose should be reduced to 0.75 g twice a day in patients receiving SRL to obtain AUC0-12 of MPA levels comparable to that in patients treated with CsA and MMF 1 g twice a day.     

抗P-糖蛋白单克隆抗体JSB-1和环孢素A协同逆转人膀胱癌MDR的研究

为了证实抗Ｐ糖蛋白（Ｐｇｐ）单克隆抗体协同环孢素Ａ（ＣｓＡ）逆转人膀胱癌耐药细胞亚株的抗药性以及建立能有效地克服ＭＤＲ的治疗方案，对人膀胱移行细胞癌ＢＩＵ８７细胞系和ＢＩＵ８７／ＡＤＭ耐药细胞亚株经柔红霉素（ＤＮＲ）与抗Ｐｇｐ单克隆抗体ＪＳＢ１和单独或联合ＣｓＡ；ＪＳＢ１和单独或联合异搏定（Ｖｅｒ）处理后，采用ＭＴＴ法评价细胞毒作用，荧光分光光度计检测细胞内ＤＮＲ的聚集量。结果：ＪＳＢ１和ＣｓＡ能协同增加ＤＮＲ对ＢＩＵ８７／ＡＤＭ的抗肿瘤作用，但ＪＳＢ１和Ｖｅｒ联合应用却不存在这种协同效应。结果显示：ＪＳＢ１和ＣｓＡ联合应用能增加细胞毒剂对具有Ｐｇｐ表达的ＭＤＲ肿瘤的抗肿瘤效应，是适合于临床应用的多药抗性逆转方案。     

Addition of sirolimus to cyclosporine in long-term kidney transplant recipients to withdraw steroid

The aim of this study was to evaluate the feasibility of a steroid-free maintenance immunosuppression regimen in long-term renal transplant (KTx) recipients after addition of sirolimus (SRL) to cyclosporine (CsA)-based immunosuppression. A multicenter, prospective pilot study of steroid withdrawal (SW) was initiated for KTx patients. SW was divided into three phases: (A) conversion to a SRL + CsA + steroid regimen; (B) steroid tapering and withdrawal; and (C) maintenance with SRL + CsA. Primary endpoints of the study were incidence of acute biopsy-proven rejection (AR) and safety. In the A and B phases of the study 42 KTx patients (132 +/- 75 months post-Tx) were entered into the study, 18 of 42 (43%) with severe, acute side effects due to the CsA + SRL combination. These side effects were reversible with reduction of CsA or with suspension of the SRL/CsA combination. An amendment was introduced in the protocol to drastically reduce the CsA exposure to <50 ng/mL (trough) at the time of SRL addition. After this amendment, 39 other KTx patients entered the study and only 3 of 39 (8%) were discontinued because of toxic side effects. In the overall cohort of 81 KTx patients, the incidence of AR after SW was low (n = 5, 6.1%), all occurring within the first 3 months after SW. These findings indicate: (1) addition of SRL to very low-maintenance CyA exposure allows safe SW in KTx; (2) with the SRL + CsA combination, the incidence of AR after SW is low in long-term KTx patients; and (3) in the first 3 months after SW strict monitoring for early diagnosis and treatment of AR is mandatory.     

Modulation of multidrug resistance with antisense oligodeoxynucleotide to mdr1 mRNA

Background: P-glycoprotein (Pgp), a 170-kDa adenosine triphosphate-dependent membrane drug-efflux pump encoded by themdr1 gene, mediates cross-resistance in tumor cells to structurally unrelated cancer drugs. We investigated the capacity for modulating multidrug resistance by selectively inhibiting synthesis of Pgp using an antisense oligodeoxynucleotide complementary to the initiation codon ofmdr1 messenger RNA. Methods: By continuous culture of K562 in 100 nM vincristine, a resistant cell line, K562/VCR₁₀₀, was derived with high expression of Pgp (95.9% of cells) and an IC₅₀ 40-fold greater than that of the parental cell line. The K562/VCR₁₀₀ cells were treated with 10 μM of 15-mer antisense and sense phosphorothioate oligodeoxynucleotides. Modulation of multidrug resistance was analyzed using a daunorubicin/tritiated thymidine incorporation assay and flow cytometric assessment of cellular rhodamine 123 accumulation. Results: Treatment of K562/VCR₁₀₀ with the antisense oligodeoxynucleotide led to a doubling in daunorubicin growth inhibition at 1 μg/ml and a tripling of growth inhibition at 0.6 μg/ml (p<0.0023); a 58% reduction in the daunorubicin IC₅₀ (p<0.02); and an increased rate of rhodamine-123 accumulation (p=0.02) compared with treatment with sense oligodeoxynucleotide or media controls. Conclusions: These results suggest that antisense oligodeoxynucleotides may serve as a useful adjunct in the treatment and prevention of multidrug resistance during cancer chamotherapy.     

Effect of Cyclosporine and Sirolimus on Fatty Acid Desaturase Activities in Cultured HEPG2 Cells

The aim of the present work was to evaluate the influence of cyclosporine (CsA) and sirolimus (SRL) on fatty acid (FA) desaturase activities. These enzymes (named Δ9, Δ6, and Δ5 desaturases) catalyze reactions leading to the biosynthesis of n-9, n-6, and n-3 FA families. n-3 FA family, derived from alpha-linolenic acid, is involved in the prevention of vascular events, which appear after successful kidney transplantation. Five groups of HepG₂ cells in culture were treated with either CsA (1 μg/μL and 2 μg/μL) or SRL (10 ng/mL and 20 ng/mL) for 3 days, including a control group without immunosuppressive treatment. We studied the incorporation and metabolic conversion of radioactive [1-¹⁴C]palmitic, linoleic, and eicosatrienoic acids. We also analyzed fatty acid composition. The distribution of radioactive metabolic products after incubation of these cells with [1-¹⁴C]palmitic acid revealed a decrease in Δ9 desaturase activity in the presence of each immunosuppressive drug: CsA = 0.61 ± 0.01; SRL = 0.59 ± 0.04 versus control = 0.79 ± 0.05 (P < .01). We observed a significant increase in Δ6 and Δ5 desaturase activities under the influence of the immunosuppressive drugs: radiolabeled linoleic acid (CsA: 0.93 ± 0.04; SRL: 1.02 ± 0.03 vs control 0.60 ± 0.03; P < .01) and eicosatrienoic acid (CsA: 1.12 ± 0.02; SRL: 1.07 ± 0.01 vs control 0.75 ± 0.01; P < .01). In conclusion, CsA and SRL modulated the biosynthesis of polyunsaturated FAs, decreasing Δ9 desaturase and increasing Δ6 and Δ5 desaturase activities.