Protopic
Protective effects of ex vivo graft radiation and tacrolimus on syngeneic transplanted rat small bowel motility.

Schwarz NT, Nakao A, Nalesnik MA, Kalff JC, Murase N, Bauer AJ.

Department of Surgery, University of Pittsburgh Medical Center, 3550 Terrace Street, Pittsburgh, PA 15261, USA.

BACKGROUND: Intestinal transplantation is unduly complicated by the nontolerogenic properties of the gut-associated lymphoid tissue. Because simultaneous graft irradiation and bone marrow infusion significantly prolong the survival of the small bowel transplanted animal, our objective was to determine the functional motility effects of the immune modulating, graft irradiation procedure in the presence and absence of tacrolimus immunosuppression. METHODS: Four groups of syngeneic orthotopic small bowel transplanted animals were studied 48 hours after operations (untreated, tacrolimus, ex vivo graft irradiation, and tacrolimus + irradiation) and compared with controls. Histologic analysis was performed for mucosal apoptosis and neutrophilic infiltration into the muscularis externa. Gastrointestinal in vivo transit and in vitro circular muscle strip contractions were quantified in response to bethanechol (0.3-300 micromol/L). RESULTS: Graft irradiation ex vivo alone or in the presence of tacrolimus significantly increases (> 10-fold) the number of apoptotic mucosal cells after transplantation. Functional measurements showed that transplantation resulted in a significant delay in gastrointestinal transit and a decrease in muscle strip contractility. Tacrolimus and graft irradiation significantly ameliorated the transplant-induced dysfunction. CONCLUSIONS: Given the endowed propensity of mucosal regeneration, the immunologic and functional benefits of ex vivo graft irradiation appear to outweigh the detrimental effects to the mucosa.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11935132&dopt=Abstract tacrolimus Protopic



Protopic
Combination therapy with low dose sirolimus and tacrolimus is synergistic in preventing spontaneous and recurrent autoimmune diabetes in non-obese diabetic mice.

Shapiro AM, Suarez-Pinzon WL, Power R, Rabinovitch A.

Department of Surgery, University of Alberta, Edmonton, Canada.

AIMS/HYPOTHESIS: Sirolimus and tacrolimus are immunosuppressive drugs that prevent rejection of pancreatic islet allografts transplanted into patients with Type I (insulin-dependent) diabetes mellitus. This study aimed to determine whether sirolimus and tacrolimus can prevent autoimmune beta-cell destruction, and if so, what the mechanisms of action are. METHODS: Sirolimus and tacrolimus were given separately and together to female non-obese diabetic (NOD) mice from age 12 to 35 weeks. Diabetes incidence was determined and pancreatic insulitis and insulin content were measured. Sirolimus and tacrolimus were also given separately and together to diabetic NOD mice from the time of syngeneic islet transplantation until the reappearance of hyperglycaemia. Islet grafts were examined by RT-PCR assay for expression of interferon (IFN)- gamma, interleukin (IL)-2, IL-4, IL-10 and transforming growth factor (TGF)- beta1. RESULTS: Low doses of sirolimus (0.1 mg/kg) and tacrolimus (0.1 mg/kg) were synergistic in reducing insulitis, preserving pancreatic insulin content and preventing diabetes in female NOD mice (8 % diabetes incidence at 35 weeks vs 66 % in vehicle-treated mice). Also, the combination of sirolimus and tacrolimus prolonged syngeneic islet graft survival (median 34 days vs 13 days for vehicle-treated mice). Islet grafts from sirolimus plus tacrolimus-treated mice expressed significantly decreased mRNA contents of Th1-type cytokines (IFN- gamma and IL-2) and the highest ratio of TGF- beta1/IFN- gamma mRNA. CONCLUSION/INTERPRETATION: These findings suggest that combination therapy with sirolimus and tacrolimus prevent autoimmune beta-cell destruction by upregulating expression of the immunoregulatory cytokine, TGF- beta1 and reducing Th1 cytokines (IFN- gamma and IL-2) expressed in the islets. Low-dose sirolimus and tacrolimus combination therapy could warrant consideration for prevention or early treatment of human Type I diabetes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11935154&dopt=Abstract tacrolimus Protopic



Protopic
Tacrolimus and low-dose steroid immunosuppression preserves bone mass after renal transplantation.

Goffin E, Devogelaer JP, Lalaoui A, Depresseux G, De Naeyer P, Squifflet JP, Pirson Y, van Ypersele de Strihou C.

Department of Nephrology, Hopital Saint-Luc, Universite Catholique de Louvain, 10 Ave. Hippocrate, 1200 Brussels, Belgium. goffin nefr.ucl.ac.be

Bone loss, a recognized complication of renal transplantation (TP), is mainly attributed to steroids. The effect of other immunosuppressive agents on patients' bone mass is difficult to distinguish from that of steroids. In this study, we evaluate the evolution of bone mass density over the first 12 months following renal TP in two groups of patients given either low-dose steroids with tacrolimus ( n=7) or normal-dose steroids and cyclosporine ( n=19). Bone mineral density (BMD) of the lumbar spine, total hip, and hip subregions and total-body bone mineral content (BMC) were measured by dual-energy X-ray absorptiometry within the first 15 days, and 1 year after TP. Biological markers of bone turnover (serum calcium, phosphate, total alkaline phosphatase activity, intact parathyroid hormone, bone-specific alkaline phosphatase, calcitriol, and urinary pyridinolines) were regularly measured during follow-up. After TP, renal function improved rapidly in all patients. One year after TP, bone mass had decreased significantly in the cyclosporine group in all investigated sites. By contrast it had increased in the tacrolimus group. In order to compare the evolution of bone mass in patients given similar amounts of steroids, the cyclosporine group was subdivided in tertiles according to the 1-year cumulative oral intake of prednisolone. A significant bone loss was still observed in the low-steroid cyclosporine subgroup but not in the tacrolimus group, despite the similar steroids intake (3.5+/-0.5 g and 2.7+/-1 g, respectively). Bone gain in the tacrolimus group occurred despite a previous longer dialysis duration and a higher number of postmenopausal women who were not receiving hormone substitutes. Long-term evaluation of bone density (3-5 years post-TP) confirmed the bone gain in the tacrolimus patients. Interestingly, the profile of the biological markers of bone turnover appeared better in patients prescribed tacrolimus than in those given cyclosporine, though the differences did not reach statistical significance. Weconclude that tacrolimus associated with low-dose steroids might better preserve bone mass after renal TP than cyclosporine and normal doses of steroids.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11935163&dopt=Abstract tacrolimus Protopic



Protopic
Sampling times for monitoring tacrolimus in stable adult liver transplant recipients.

Dansirikul C, Staatz CE, Duffull SB, Taylor PJ, Lynch SV, Tett SE.

School of Pharmacy, University of Queensland, Queensland 4072, Australia. joy pharmacy.uq.edu.au

The aim of this study was to determine the most informative sampling time(s) providing a precise prediction of tacrolimus area under the concentration-time curve (AUC). Fifty-four concentration-time profiles of tacrolimus from 31 adult liver transplant recipients were analyzed. Each profile contained 5 tacrolimus whole-blood concentrations (predose and 1, 2, 4, and 6 or 8 hours postdose), measured using liquid chromatography-tandem mass spectrometry. The concentration at 6 hours was interpolated for each profile, and 54 values of AUC(0-6) were calculated using the trapezoidal rule. The best sampling times were then determined using limited sampling strategies and sensitivity analysis. Linear mixed-effects modeling was performed to estimate regression coefficients of equations incorporating each concentration-time point (C0, C1, C2, C4, interpolated C5, and interpolated C6) as a predictor of AUC(0-6). Predictive performance was evaluated by assessment of the mean error (ME) and root mean square error (RMSE). Limited sampling strategy (LSS) equations with C2, C4, and C5 provided similar results for prediction of AUC(0-6) (R2 = 0.869, 0.844, and 0.832, respectively). These 3 time points were superior to C0 in the prediction of AUC. The ME was similar for all time points; the RMSE was smallest for C2, C4, and C5. The highest sensitivity index was determined to be 4.9 hours postdose at steady state, suggesting that this time point provides the most information about the AUC(0-12). The results from limited sampling strategies and sensitivity analysis supported the use of a single blood sample at 5 hours postdose as a predictor of both AUC(0-6) and AUC(0-12). A jackknife procedure was used to evaluate the predictive performance of the model, and this demonstrated that collecting a sample at 5 hours after dosing could be considered as the optimal sampling time for predicting AUC(0-6).

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Protopic
Ocular toxicity of intravitreal tacrolimus.

Passos E, Genaidy MM, Peyman GA.

Department of Ophthalmology, Tulane University Health Sciences Center, New Orleans, Louisiana, USA.

BACKGROUND AND OBJECTIVE: To investigate the ocular toxicity of intravitreally administered tacrolimus, a drug with potent immunosuppressive activity. METHODS: To evaluate toxicity, tacrolimus was injected into the midvitreous cavity of 20 eyes of New Zealand pigmented rabbits at concentrations of 10, 50, 100, 250, 500, and 1000 microg. Control eyes received balanced salt solution. Eyes receiving 1000 microg were given injections of 0.2 mL solution; all others, including controls, received 0.1 mL. Rabbits were examined before the injections by slit-lamp biomicroscopy, indirect ophthalmoscopy, and an electroretinography test (ERG) was performed. The animals were followed up to 14 days postinjection by clinical examination and ERG. The animals were killed and the eyes were enucleated and processed for light microscopy. RESULTS: No evidence of a retinal toxic reaction was seen in the eyes receiving 10 or 50 microg of tacrolimus. One out of 4 eyes that received 100 microg of the drug developed a vitreous reaction. All eyes treated with 250 microg or more developed vitreous reaction. One eye injected with 1000 microg of the drug developed occlusion of the temporal retinal vessels. Electroretinography showed decreasing b-wave amplitude with both dark- and light-adapted stimulus in the 500 and 1000 microg groups, and it was normal in the other groups. Histopathologic sections showed mild disorganization of the retina only at the 500 and 1000 microg dosage. CONCLUSIONS: Doses of 10 and 50 microg of tacrolimus are nontoxic to rabbit eyes. Only transient vitreous opacities were observed in the groups that received 100 and 250 microg. Intravitreal doses of 500 and 1000 microg of tacrolimus proved to be toxic to the retina.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11942546&dopt=Abstract tacrolimus Protopic



Protopic
Contractile effects of tacrolimus in human and rat isolated renal arteries.

Schwertfeger E, Wehrens J, Oberhauser V, Katzenwadel A, Rump LC.

Department of Internal Medicine, University of Freiburg, Hugstetter Str. 55, D-79106 Freiburg, Germany.

1. We tested the vasoactive properties of the immunosuppressive drug FK 506 (tacrolimus) in preconstricted rat and human isolated renal arteries in vitro. 2. In rat renal arteries, tacrolimus (3, 10 microM) showed a direct and dose-dependent contractile effect by maximally 23 microm (10% of the noradrenaline effect), which was only observed in the presence of intact endothelium. Moreover, a lower concentration of tacrolimus (1 microM) potentiated pressor responses to the sympathetic neurotransmitter noradrenaline but not to ATP in this species. ATP- (0.01-10 microM) induced vasodilation was not affected by tacrolimus (1 microM). 3. In contrast, in human interlobar arteries, tacrolimus failed to induce direct vasoconstriction and did not significantly potentiate constrictor responses to noradrenaline. Acetylcholine-(1 microM) induced vasodilation was much smaller in human than in rat renal arteries suggesting the lack of functional endothelium in the human preparation. 4. The findings suggest that tacrolimus releases an endothelium-derived constricting factor in rat renal arteries to increase vascular tone and to potentiate pressor responses to noradrenaline. In human interlobar arteries, this effect of tacrolimus is not observed probably because of the absence of functional endothelium or the necessary mediator mechanism.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11952876&dopt=Abstract tacrolimus Protopic



Protopic
Pharmacokinetic changes of intravenous tacrolimus in rats with uranyl nitrate-induced acute renal failure.

Son IJ, Moon YJ, Lee MG, Sohn YT.

Department of Pharmacy, College of Pharmacy, Duksung Women's University Tobong-Gu, Seoul, South Korea.

Because the physiological changes that occur in patients with acute renal failure could alter the pharmacokinetics of the drugs, the pharmacokinetics of tacrolimus were investigated after 1-min intravenous administration of the drug (1 mg kg(-1)) to control rats and rats with uranyl nitrate-induced acute renal failure (rats with U-ARF). The impaired kidney and hepatic functions were observed in rats with U-ARF on the basis of physiological parameters and by microscopy of the tissues. After intravenous infusion of tacrolimus, the total area under the blood concentration-time curve from time zero to time infinity was significantly greater in rats with U-ARF than that in control rats (35.8 versus 29.2 microg min mL(-1)) due to significantly slower total body clearance of tacrolimus (27.9 versus 34.3 mL min(-1) kg(-1)), and this could be due to significantly slower nonrenal clearance (because of impaired hepatic function). The urinary excretion of unchanged tacrolimus was almost negligible for both groups of rats, therefore, effects of kidney impairment on the pharmacokinetics of tacrolimus seemed to be minor.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11958289&dopt=Abstract tacrolimus Protopic