FK506 in solid organ transplantation

Immunosuppression in solid organ-transplant recipients and impact on nutrition support

A key component to nutrition support is to consider immunosuppressive agents, the interaction with nutrients, and how the side effects of the medications influence nutrition support. The immunosuppression of the solid organ-transplant recipient involves the individualized titration of multiple therapeutic agents to prevent allorecognition and, thus, rejection of the transplanted organ. Induction immunosuppression includes the agents used at the time of transplant to prevent early rejection. Maintenance immunosuppression typically consists of oral medications taken for life. Regular therapeutic monitoring of immunosuppression is necessary to balance the risk of rejection with that of infections and malignancy. In the acute-care setting, multidisciplinary collaboration, including pharmacy and nutrition, is needed to optimize the route of administration, titration, and side effects of immunosuppression. Long-term nutrition management after transplant is also vital to prevent exacerbating adverse effects of immunosuppressive therapies, including diabetes mellitus, hypertension, dyslipidemia, obesity, and bone loss. This review summarizes common immunosuppressive agents currently utilized in solid organ-transplant recipients and factors that may influence decisions on nutrition support.

Peripheral nerve repair is associated with augmented cross-tissue inflammation following vascularized composite allotransplantation

Introduction

Vascularized composite allotransplantation (VCA), with nerve repair/coaptation (NR) and tacrolimus (TAC) immunosuppressive therapy, is used to repair devastating traumatic injuries but is often complicated by inflammation spanning multiple tissues. We identified the parallel upregulation of transcriptional pathways involving chemokine signaling, T-cell receptor signaling, Th17, Th1, and Th2 pathways in skin and nerve tissue in complete VCA rejection compared to baseline in 7 human hand transplants and defined increasing complexity of protein-level dynamic networks involving chemokine, Th1, and Th17 pathways as a function of rejection severity in 5 of these patients. We next hypothesized that neural mechanisms may regulate the complex spatiotemporal evolution of rejection-associated inflammation post-VCA.

Methods

For mechanistic and ethical reasons, protein-level inflammatory mediators in tissues from Lewis rats (8 per group) receiving either syngeneic (Lewis) or allogeneic (Brown-Norway) orthotopic hind limb transplants in combination with TAC, with and without sciatic NR, were compared to human hand transplant samples using computational methods.

Results

In cross-correlation analyses of these mediators, VCA tissues from human hand transplants (which included NR) were most similar to those from rats undergoing VCA + NR. Based on dynamic hypergraph analyses, NR following either syngeneic or allogeneic transplantation in rats was associated with greater trans-compartmental localization of early inflammatory mediators vs. no-NR, and impaired downregulation of mediators including IL-17A at later times.

Discussion

Thus, NR, while considered necessary for restoring graft function, may also result in dysregulated and mis-compartmentalized inflammation post-VCA and therefore necessitate mitigation strategies. Our novel computational pipeline may also yield translational, spatiotemporal insights in other contexts.

In memoriam of Thomas Earl Starzl, the pioneer of liver transplantation

Starzl’s nearly 3000 publications that contribute to the science of transplantation in every field have been the most important resources for every scientist working in this field. For those of us who work in the liver transplant field, his contributions throughout his life have shaped our career and passion, even for those who have never met, spoken to, or worked with him. If we are able to help patients with liver failure today by offering them the chance of transplantation, it is because of Starzl’s passionate work and efforts. Thanks to Starzl’s scientific legacy, hundreds of scientists serve humanity and thousands of patients can hold on to life. It has been an honor for us to write this article about Professor Starzl.

Immunosuppression trends in solid organ transplantation: The future of individualization, monitoring, and management

Immunosuppression regimens used in solid organ transplant have evolved significantly over the past 70 years in the United States. Early immunosuppression and targets for allograft success were measured by incidence and severity of allograft rejection and 1-year patient survival. The limited number of agents, infancy of human leukocyte antigen (HLA) matching techniques and lack of understanding of immunoreactivity limited the early development of effective regimens. The 1980s and 1990s saw incredible advancements in these areas, with acute rejection rates halving in a short span of time. However, the constant struggle to achieve the optimal balance between under- and overimmunosuppression is weaved throughout the history of transplant immunosuppression. The aim of this paper is to discuss the different eras of immunosuppression and highlight the important milestones that were achieved while also discussing this in the context of rational agent selection and regimen design. This discussion sets the stage for how we can achieve optimal long-term outcomes during the next era of immunosuppression, which will move from universal protocols to patient-specific optimization.

Adult liver transplantation using pediatric donor livers after cardiac or brain death: A report of three cases

The present study reports on the experience at Jiangxi Provincial People's Hospital (Nanchang, China) with liver transplantation in adults using pediatric donor livers, including indications, technique and results. A total of three cases of liver transplantation performed between April 2008 and May 2016 were retrospectively reviewed. Liver procurement and trimming, recipient selection, surgical tips, prevention and treatment of small-for-size syndrome, selection of immunosuppressive regimens, prevention and treatment of vascular complications and anticoagulant therapy were discussed. The three pediatric donors were 8, 8 and 10 years old. The three recipients were confirmed to have primary liver cancer. In recipient 1 (female; age, 39 years), jaundice persisted in the recipient after the liver transplantation. A reduced dose of FK506 was then given to gradually decrease the total bilirubin level to the normal range. Recipient 1 recovered and was discharged from hospital; however, the patient died of liver cancer recurrence and bone metastasis 6 years post-transplantation. In recipient 2 (male; age, 56 years), the recipient experienced sudden abdominal distension on postoperative day 7. The patient's clotting time was prolonged and the transaminase level was sharply increased, peaking on day 9. The patient was suspected of having small-for-size syndrome and was treated symptomatically. The patient experienced a significant improvement in symptoms on postoperative day 13 and regular postoperative follow-ups were performed until now and the patient is now in remission. In recipient 3 (male; age, 48 years), the recipient recovered well and the liver function returned to normal on postoperative day 3. The patient was discharged from hospital and has been in remission thus far. Adult liver transplantations from pediatric donors are feasible treatments. Systematic donor and recipient assessments, sound surgical skills and optimal postoperative treatments are essential for success in the transplantation of livers from pediatric donors into adult recipients. Considering the condition of the donor liver, the selection of recipients and appropriate surgical methods are particularly important in these cases.

Costimulation Blockade in Vascularized Composite Allotransplantation

Vascular composite allotransplantation (VCA) is a field under research and has emerged as an alternative option for the repair of severe disfiguring defects that result from infections or traumatic amputation in a selected group of patients. VCA is performed in centers with appropriate expertise, experience and adequate resources to effectively manage the complexity and complications of this treatment. Lifelong immunosuppressive therapy, immunosuppression associated complications, and the effects of the host immune response in the graft are major concerns in VCA. VCA is considered a quality of life transplant and the risk-benefit ratio is dissimilar to life saving transplants. Belatacept seems a promising drug that prolongs patient and graft survival in kidney transplantation and it could also be an alternative approach to VCA immunosuppression. In this review, we are summarizing current literature about the role of costimulation blockade, with a focus on belatacept in VCA.

Expression and characterization of functional domains of FK506-binding protein 35 from Plasmodium knowlesi

The FK506-binding protein of Plasmodium knowlesi (Pk-FKBP35) is considerably a viable antimalarial drug target, which belongs to the peptidyl-prolyl cis-trans isomerase (PPIase) protein family member. Structurally, this protein consists of an N-terminal FK506-binding domain (FKBD) and a C-terminal tetratricopeptide repeat domain (TPRD). This study aims to decipher functional properties of these domains as a platform for development of novel antimalarial drugs. Accordingly, full-length Pk-FKBP35 as well as its isolated domains, Pk-FKBD and Pk-TPRD were overexpressed, purified, and characterized. The results showed that catalytic PPIase activity was confined to the full-length Pk-FKBP35 and Pk-FKBD, suggesting that the catalytic activity is structurally regulated by the FKBD. Meanwhile, oligomerization analysis revealed that Pk-TPRD is essential for dimerization. Asp55, Arg60, Trp77 and Phe117 in the Pk-FKBD were considerably important for catalysis as underlined by significant reduction of PPIase activity upon mutations at these residues. Further, inhibition activity of Pk-FKBP35 towards calcineurin phosphatase activity revealed that the presence of FKBD is essential for the inhibitory property, while TPRD may be important for efficient binding to calcineurin. We then discussed possible roles of FKBP35 in Plasmodium cells and proposed mechanisms by which the immunosuppressive drug, FK506, interacts with the protein.

Tacrolimus induces fibroblasts apoptosis and reduces epidural fibrosis by regulating miR-429 and its target of RhoE

Tacrolimus (FK506) has been demonstrated to reduce epidural fibrosis. However, the detailed mechanism of action has not been elucidated. Aberrant miR-429 is involved in many diseases. The aim of this study was to describe the exact mechanism of FK506 induced apoptosis in fibroblasts and the prevention of epidural fibrosis. FK506 induced fibroblast apoptosis was evaluated using CCK-8 assays, flow cytometry, and western blotting. The expression of miR-429 in fibroblasts treated with FK506 was determined by RT-qPCR. Additionally, luciferase activity assays were used to determine the target relationship between miR-429 and RhoE. Flow cytometry and western blot analysis were used to determine the effects of FK506 and miR-429 on fibroblast apoptosis. The effects of FK506 and RhoE on fibroblast apoptosis were determined by CCK-8 assay, flow cytometry, and western blotting. We also evaluate the effects of FK506 and miR-429 on epidural fibrosis in rats by using histological analysis and TUNEL-staining. The results revealed FK506 induces fibroblast apoptosis and significantly downregulates miR-429 expression in fibroblasts. Additionally, miR-429 downregulation caused the apoptosis of fibroblasts. The luciferase activity assay confirmed that RhoE is a direct target of miR-429 and RhoE promotes fibroblast apoptosis. The rat model demonstrated miR-429 inhibition promotes fibroblast apoptosis and epidural fibrosis, which is consistent with the results of FK506 treatment. Our study demonstrates that FK506 induces fibroblast apoptosis and reduces epidural fibrosis by regulating miR-429 expression and its target of RhoE.

Topical tacrolimus, triamcinolone acetonide, and placebo in oral lichen planus: a pilot randomized controlled trial

OBJECTIVE

To carry out a double-blind randomized controlled trial (RCT) to compare the effectiveness of topical tacrolimus (TAC), triamcinolone acetonide (TRI), and placebo (PLA) in symptomatic oral lichen planus (OLP).

SUBJECTS AND METHODS

A clinical score (CS, range 0-130) was developed to measure the clinical signs and symptoms of OLP. Twenty-seven OLP patients with a CS of ≥20 were randomly allocated to receive 0.1% TAC ointment (n = 11), 0.1% TRI paste (n = 7), or Orabase^® paste as PLA (n = 9) for 3 weeks. If the CS dropped ≥20% (interpreted as response), the patients continued the same medication for another 3 weeks. If the CS dropped <20% or increased (non-response), the patients were switched to TAC for 6 weeks. A 6-month follow-up period ensued. The primary outcome variable was the change in CS from baseline to week 3. In primary outcome analysis, CS values between the treatment arms were compared.

RESULTS

Tacrolimus and TRI were more effective (P = 0.012 and 0.031, respectively) than PLA in reducing the CS at week 3. No difference in the efficacy was noted between TAC and TRI (P = 0.997).

CONCLUSIONS

This pilot RCT provides evidence for the effectiveness of TAC and TRI over PLA in the management of OLP.

Hypomagnesemia and increased risk of new-onset diabetes mellitus after transplantation in pediatric renal transplant recipients

BACKGROUND

New-onset diabetes after transplantation (NODAT) is a significant co-morbidity following kidney transplantation. Lower post-transplant serum magnesium levels have been found to be an independent risk factor for NODAT in adult kidney transplant recipients.

METHODS

We undertook a retrospective analysis of risk factors for NODAT in pediatric renal transplant recipients at our institution with the aim of determining if hypomagnesemia confers a significant risk of developing NODAT in this patient population.

RESULTS

A total of 173 children with a median age at transplantation of 7.0 (range 1.3-17.5) years were included. Hypomagnesemia was found to be a significant independent risk factor for NODAT (p = 0.01). High trough tacrolimus levels were also independently associated with NODAT (p < 0.001). There was no significant association between NODAT and body mass index at the time of transplantation, monthly cumulative steroid dose or post-transplant cytomegalovirus viremia (p = 0.9, 0.6 and 0.7, respectively).

CONCLUSIONS

This study identifies hypomagnesemia as a significant independent risk factor for the development of NODAT in pediatric renal transplant recipients. Given the clear association between hypomagnesemia and NODAT in both adults and children following renal transplantation, further studies are merited to clarify the etiology of this association and to examine the effect of magnesium supplementation on NODAT.

Targeting Kv1.3 channels to reduce white matter pathology after traumatic brain injury

Axonal injury is present in essentially all clinically significant cases of traumatic brain injury (TBI). While no effective treatment has been identified to date, experimental TBI models have shown promising axonal protection using immunosuppressants FK506 and Cyclosporine-A, with treatment benefits attributed to calcineurin inhibition or protection of mitochondrial function. However, growing evidence suggests neuroprotective efficacy of these compounds may also involve direct modulation of ion channels, and in particular Kv1.3. The present study tested whether blockade of Kv1.3 channels, using Clofazimine (CFZ), would alleviate TBI-induced white matter pathology in rodents. Postinjury CFZ administration prevented suppression of compound action potential (CAP) amplitude in the corpus callosum of adult rats following midline fluid percussion TBI, with injury and treatment effects primarily expressed in unmyelinated CAPs. Kv1.3 protein levels in callosal tissue extracts were significantly reduced postinjury, but this loss was prevented by CFZ treatment. In parallel, CFZ also attenuated the injury-induced elevation in pro-inflammatory cytokine IL1-β. The effects of CFZ on glial function were further studied using mixed microglia/astrocyte cell cultures derived from P3-5 mouse corpus callosum. Cultures of callosal glia challenged with lipopolysaccharide exhibited a dramatic increase in IL1-β levels, accompanied by reactive morphological changes in microglia, both of which were attenuated by CFZ treatment. These results support a cell specific role for Kv1.3 signaling in white matter pathology after TBI, and suggest a treatment approach based on the blockade of these channels. This therapeutic strategy may be especially efficacious for normalizing neuro-glial interactions affecting unmyelinated axons after TBI.

A population pharmacokinetic study of tacrolimus in healthy Chinese volunteers and liver transplant patients

AIM

To develop a population pharmacokinetic (PopPK) model of tacrolimus in healthy Chinese volunteers and liver transplant recipients for investigating the difference between the populations, and for potential individualized medication.

METHODS

A set of 1100 sparse trough concentration data points from 112 orthotopic liver transplant recipients, as well as 851 dense data points from 40 healthy volunteers receiving a single dose of tacrolimus (2 mg, p.o.) were collected. PopPK model of tacrolimus was constructed using the program NONMEM. Related covariates such as age, hepatic and renal functions that were potentially associated with tacrolimus disposition were evaluated. The final model was validated using bootstrapping and a visual predictive check.

RESULTS

A two-compartment model of tacrolimus could best describe the data from the two populations. The final model including two covariates, population (liver transplant recipients or volunteers) and serum ALT (alanine aminotransferase) level, was verified and adequately described the pharmacokinetic characteristics of tacrolimus. The estimates of V2/F, Q/F and V3/F were 22.7 L, 76.3 L/h and 916 L, respectively. The estimated CL/F in the volunteers and liver transplant recipients was 32.8 and 18.4 L/h, respectively. Serum ALT level was inversely related to CL/F, whereas age did not influence CL/F. Thus, the elderly (≥65 years) and adult (<65 years) groups in the liver transplant recipients showed no significant difference in the clearance of tacrolimus.

CONCLUSION

Compared with using the sparse data only, the integrating modeling technique combining sparse data from the patients and dense data from the healthy volunteers improved the PopPK analysis of tacrolimus.

Classical force field parameters for two high-affinity ligands of FKBP12

FKBP12 is an important target in the treatment of transplant rejection and is also a promising target for cancer and neurodegenerative diseases. We determined for two ligands of nanomolar affinity the set of parameters in the CHARMM force field. The fitting procedure was based on reproducing the quantum chemistry data (distances, angles, and energies). Since the dynamical behavior of such ligands strongly depends on the dihedral angles, care was taken to derive the corresponding parameters. Moreover, since each of the central core region of these two ligands is similar to other known ligands or drugs of other proteins, part at least of these parameters could also be useful for these other ligands.

Minimization and withdrawal of steroids in pancreas and islet transplantation

For reducing the corticosteroid (CS)-related side-effects, especially cardiovascular events, CS-sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho-depleting induction antibodies, such as rabbit anti-thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS-sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low-risk patients, therefore the grade of evidence is limited. Large-scale prospective studies with long-term follow up are necessary to assess risks and benefits of CS-sparing regimens in PT before recommending such strategies as standard practice. Islet allo-transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high-dose CNI, prevented satisfactory results (10% insulin-independence at 1-year post-transplant). Since 2000, CS-free and CNI-reducing protocols, including more potent induction [daclizumab, OKT3gamma1(ala-ala) anti-CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short-term outcomes whereas long-term are still inadequate (from 80% to 20% insulin-independence from 1- to 5-year post-transplant). Main limitations are allo- and autoimmunity, immunosuppression-related islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.

Affinity maturation of tacrolimus antibody for improved immunoassay performance

BACKGROUND

Organic solvents used for extraction of tacrolimus from whole blood samples lower the apparent affinity of the antibody used in a diagnostic immunoassay, thereby affecting the detection limit.

METHODS

We used in vitro recombinant antibody engineering to screen and isolate clones from diverse libraries with mutagenic complementarity regions (CDRs) from tacrolimus 1-60-46 hybridoma cell line, with improved binding to tacrolimus in the presence of 10% methanol organic solvent solution.

RESULTS

We isolated a number of clones with mutations in variable heavy (VH) CDR 2, variable light (VL) CDR 1, and VL CDR 3 with improved binding. Various combinatorial pairings constructed from these individual mutations contained >10-fold improvements in both the dissociation rate and overall equilibrium affinity constants. Selected clones produced as IgG have increased functional sensitivity, with a 3- to 6-fold reduction in the limit of detection relative to the parental tacrolimus 1-60-46 monoclonal antibody in the Architect Tacrolimus immunodiagnostic assay.

CONCLUSIONS

The recent advent of recombinant in vitro antibody display technologies in general, and yeast surface display in particular, allows the flexibility to engineer new or augment specific analytical characteristics, such as affinity, specificity, or stability, into previously isolated and otherwise desirable antibodies to enhance assay performance. These in vitro selections can also be performed under conditions meant to mimic the assay in which the reagent will ultimately be used, to increase the likelihood of successful assay development.

Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property

The interaction of FK-506 with KV1.3, stably expressed in Chinese hamster ovary cells, was investigated with the whole cell patch-clamp technique. FK-506 inhibited KV1.3 in a reversible, concentration-dependent manner with an IC50of 5.6 μM. Rapamycin, another immunosuppressant, produced effects that were similar to those of FK-506 (IC50= 6.7 μM). Other calcineurin inhibitors (cypermethrin or calcineurin autoinhibitory peptide) alone had no effect on the amplitude or kinetics of KV1.3. In addition, the inhibitory action of FK-506 continued, even after the inhibition of calcineurin activity. The inhibition produced by FK-506 was voltage dependent, increasing in the voltage range for channel activation. At potentials positive to 0 mV (where maximal conductance is reached), however, no voltage-dependent inhibition was found. FK-506 exhibited a strong use-dependent inhibition of KV1.3. FK-506 shifted the steady-state inactivation curves of KV1.3 in the hyperpolarizing direction in a concentration-dependent manner. The apparent dissociation constant for FK-506 to inhibit KV1.3 in the inactivated state was estimated from the concentration-dependent shift in the steady-state inactivation curve and was calculated to be 0.37 μM. Moreover, the rate of recovery from inactivation of KV1.3 was decreased. In inside-out patches, FK-506 not only reduced the current amplitude but also accelerated the rate of inactivation during depolarization. FK-506 also inhibited KV1.5 and KV4.3 in a concentration-dependent manner with IC50of 4.6 and 53.9 μM, respectively. The present results indicate that FK-506 inhibits KV1.3 directly and that this effect is not mediated via the inhibition of the phosphatase activity of calcineurin.

Peripheral nerve regeneration through allografts compared with autografts in FK506-treated monkeys

Object

The clinical use of nerve allografts combined with immunosuppressant therapy has become a genuine possibility that could supersede the classic use of autografts. However, contradictory data have been reported on whether immunosuppressant therapy should be temporarily administered. The purpose of this study was to compare the nerve regeneration obtained using ulnar nerve allografts in nonhuman primates temporarily treated with FK506 (tacrolimus) with that obtained using nerve autografts.

Methods

Four-centimeter nerve autografts or allografts were placed in the distal ulnar motor nerve of eight monkeys. The FK506 was temporarily administered to the animals of the allograft group for 2 months. At periods of 3, 5, and 8 months postsurgery, quantitative electrophysiological recordings were obtained to estimate muscle response. A quantitative analysis of ulnar motor neurons in the spinal cord was performed and axons were counted stereologically.

No statistically significant differences were found in the neuronal and axonal counts between autograft and allograft groups at 8 months. The electrophysiological studies showed no differences relative to the amplitude, but the autograft group presented with a greater nerve conduction velocity (NCV). However, no statistically significant differences were found between the number of neurons and distal axonal counts in the two groups.

Conclusions

Nerve regeneration through cold-preserved allografts in a primate model temporarily treated with FK506 was similar to that obtained using nerve autografts, in terms of neuronal and axonal counts. Nevertheless, temporary immunosuppression produced lower NCV when allografts were used, with less maturation of the myelinated fibers, which indicated that a partial rejection had taken place.

Neuroregeneration in Composite Tissue Allografts: Effect of Low-Dose FK506 and Mycophenolate Mofetil Immunotherapy

BACKGROUND

The immunosuppressant FK506 has been reported to increase the rate of peripheral nerve regeneration in nerve crush injury and nerve allograft models. The purpose of this study was to determine whether low doses of FK506 and mycophenolate mofetil had a neuroregenerative effect in revascularized peripheral nerve allografts in a rat hind limb transplantation model.

METHODS

Wistar Furth rat recipients received limbs from syngeneic Wistar Furth donors (group 1, n = 4) or from allogeneic August X Copenhagen Irish rat donors (group 2, n = 6). Wistar Furth recipients received limbs from August X Copenhagen Irish donors and were treated with FK506/mycophenolate mofetil for 5 months (group 3, n = 7). At the end of the follow-up period, histomorphometric analysis of sciatic and tibial nerves from transplanted and intact hind limbs was conducted. Sciatic and tibial nerves were examined at the level of coaptation and near the neuromuscular junction, respectively.

RESULTS

Transplanted limbs in groups 1 and 3 completed the study without rejection, while the limbs in group 2 were rejected within a few days. Sciatic and tibial nerve analysis in groups 1 and 3 limbs showed myelinated axons of various diameters but in significantly fewer numbers than in nontransplanted contralateral nerves. The number and size of myelinated axons of transplanted nerves at corresponding levels were not significantly different between syngeneic and allogeneic (FK506/mycophenolate mofetil-treated) transplants.

CONCLUSIONS

The authors conclude that long-term neuroregeneration of revascularized peripheral nerves using low-dose FK506/mycophenolate mofetil was similar to that of syngeneic transplants. The occurrence of acute rejection episodes with low-dose FK506/mycophenolate mofetil did not appear to benefit nor impair neuroregeneration.

Survival after liver transplantation in the United States: a disease-specific analysis of the UNOS database

Our goal was to describe disease-specific survival and the clinical variables that predict survival in a large national cohort of adult liver transplant recipients. Data on 17,044 adult patients who received an initial orthotopic liver transplant between 1990 and 1996 with follow-up through 1999 was obtained from the United Network for Organ Sharing (UNOS). Disease-specific Kaplan-Meier survival plots and Cox Proportional Hazards models were estimated, and differences in the clinical characteristics of patients at the time of transplantation by disease were examined. Overall posttransplant survival currently exceeds 85% in the first year and is approaching 75% at 5 years. Unadjusted Kaplan-Meier survival is improved for recipients who are younger, female, and in better clinical condition. Survival is a function of disease and level of illness: cancer, fulminant liver failure, alcoholic liver disease, and the hepatitidies have the poorest prognosis, while primary billiary cirrohsis and sclerosing cholangitis have the best. Recipients who were outpatients before transplantation have longer survival than those transplanted from the hospital or intensive care unit. Although the model for end-stage liver disease (MELD) score was designed to predict pretransplant survival, patients with higher MELD scores have poorer posttransplant survival, but the MELD score is less predictive than the specific disease. Differences in disease-specific survival are partially explained by differences in disease severity at the time of transplantation. In conclusion, Disease-specific survival models indicate that there remains tremendous variability in survival as a function of underlying liver disease. However, a significant portion of the difference in survival between diseases arises from differences in clinical characteristics at the time of transplantation.

A Method to Identify p62's UBA Domain Interacting Proteins

The UBA domain is a conserved sequence motif among polyubiquitin binding proteins. For the first time, we demonstrate a systematic, high throughput approach to identification of UBA domain-interacting proteins from a proteome-wide perspective. Using the rabbit reticulocyte lysate in vitro expression cloning system, we have successfully identified eleven proteins that interact with p62’s UBA domain, and the majority of the eleven proteins are associated with neurodegenerative disorders, such as Alzheimer’s disease. Therefore, p62 may play a novel regulatory role through its UBA domain. Our approach provides an easy route to the characterization of UBA domain interacting proteins and its application will unfold the important roles that the UBA domain plays.

Liver transplantation in the UK

INTRODUCTION

This paper provides a review of the practice of liver transplantation with the main emphasis on UK practice and indications for transplantation.

REFERRAL AND ASSESSMENT

This section reviews the process of referral and assessment of patients with liver disease with reference to UK practice.

DONOR ORGANS

The practice of brainstem death and cadaveric organ donation is peculiar to individual countries and rates of donation and potential areas of improvement are addressed.

OPERATIVE TECHNIQUE

The technical innovations that have led to liver transplantation becoming a semi-elective procedure are reviewed. Specific emphasis is made to the role of liver reduction and splitting and living related liver transplantation and how this impacts on UK practice are reviewed. The complications of liver transplan-tation are also reviewed with reference to our own unit. Immunosuppression:The evolution of immunosuppression and its impact on liver transplantation are reviewed with some reference to future protocols.

RETRANSPLANTATION

The role of retransplantation is reviewed.

OUTCOME AND SURVIVAL

The results of liver transplantation are reviewed with specific emphasis on our own experience.

FUTURE

The future of liver transplantation is addressed.

Cyclosporine microemulsion and tacrolimus are associated with decreased chronic allograft failure and improved long-term graft survival as compared with sandimmune

Tacrolimus and cyclosporine in the microemulsion formulation Neoral have demonstrated improvements in acute rejection rates after renal transplantation compared with conventional cyclosporine formulation, Sandimmune. To evaluate whether these drugs are also associated with improvements in chronic allograft failure (CAF) rates, we retrospectively analyzed 32,040 primary renal allograft recipients reported to the United States Renal Data System (USRDS) between 1994 and 1997. Graft loss secondary to CAF was defined as graft loss beyond 6 months post-transplant, censored for death, acute rejection, thrombosis, infections and noncompliance. A Cox proportional hazard model was used to investigate the relationship between graft loss secondary to CAF and the use of conventional cyclosporine formulation, as opposed to cyclosporine microemulsion and tacrolimus (Prograf). The analysis was corrected for confounding variables, such as acute rejection, sex, race, human leukocyte antigen (HLA) mismatch, % panel reactive antibodies (PRA), delayed graft function (DGF), cold ischemia time, induction therapy, dialysis time, etiology of end-stage renal disease, cytomegalovirus (CMV) risk group, donor source, era effect, and mycophenolate mofetil (MMF) use. Cyclosporine microemulsion use was associated with a significantly lower relative risk (RR = 0.6, Cl = 0.5-0.7) for CAF as opposed to conventional cyclosporine formulation. Likewise tacrolimus as compared with conventional cyclosporine formulation was associated with a significantly lower relative risk (RR = 0.7, CI = 0.6-0.8) for CAF. Conventional cyclosporine formulation treatment was associated with a 87.6% adjusted CAF-free survival rate at 4 years. Both tacrolimus and cyclosporine microemulsion were associated with a significantly better adjusted CAF-free survival at 4years (91.4 and 92.4%, respectively). Both cyclosporine microemulsion and tacrolimus are associated with improved graft survival and a decreased relative risk for CAF when compared with the older conventional cyclosporine formulation. This association is independent of the use of MMF or changes in era.

Liver transplantation in the UK

INTRODUCTION

This paper provides a review of the practice of liver transplantation with the main emphasis on UK practice and indications for transplantation.

REFERRAL AND ASSESSMENT

This section reviews the process of referral and assessment of patients with liver disease with reference to UK practice.

DONOR ORGANS

The practice of brainstem death and cadaveric organ donation is peculiar to individual countries and rates of donation and potential areas of improvement are addressed.

OPERATIVE TECHNIQUE

The technical innovations that have led to liver transplantation becoming a semi-elective procedure are reviewed. Specific emphasis is made to the role of liver reduction and splitting and living related liver transplantation and how this impacts on UK practice are reviewed. The complications of liver transplan-tation are also reviewed with reference to our own unit. Immunosuppression:The evolution of immunosuppression and its impact on liver transplantation are reviewed with some reference to future protocols.

RETRANSPLANTATION

The role of retransplantation is reviewed.

OUTCOME AND SURVIVAL

The results of liver transplantation are reviewed with specific emphasis on our own experience.

FUTURE

The future of liver transplantation is addressed.

Immunophilins: switched on protein binding domains?

Peptidylprolyl isomerases (PPIases) are a group of cytosolic enzymes first characterized by their ability to catalyze the cis-trans isomerization of cis-peptidylprolyl bonds. Subsequently, some PPIases were also identified as the initial targets of the immunosuppressant drugs-cyclosporin A (CsA), FK506, and rapamycin-have been called immunophilins. Immunophilins have been found to be both widely distributed and abundantly expressed leading to suggestions that they may play a general role in cellular biochemistry. However, the nature of this role has been difficult to elucidate and is still controversial in vivo. A number of roles for these enzymes have been identified in vitro including the ability to catalyze the refolding of partly denatured proteins and stabilize multiprotein complexes such as Ca(2+) channels, inactive steroid receptor complexes, and receptor protein tyrosine kinases. Generally, these effects appear to depend on the ability of immunophilins to selectively bind to other proteins. This review will examine in detail experimental and structural investigations of the mechanism of PPIase activity for both FKBPs and cyclophilins and suggest a mechanism for these enzymes, which depends on their ability to recognize a specific peptide conformation rather than sequence. Examination of structures of immunophilin-protein complexes will then be used to further suggest that the ability of these enzymes to recognize specific peptide conformations is central to the formation of these complexes and may constitute a general function of immunophilin enzymes. The binding of ligand to immunophilins will also be shown to stabilize specific conformations in surface loops of these proteins that are observed to play a critical role in a number of immunophilin-protein complexes suggesting that the immunophilins may constitute a class of ligand-triggered selective protein binders.

Treatment of tacrolimus-related adverse effects by conversion to cyclosporine in liver transplant recipients

When tacrolimus side effects persist despite dose reduction, conversion to cyclosporine-based immunosuppression (CyA) is necessary. We characterized tacrolimus side effects that warranted discontinuation of the drug, and outcomes after conversion. Of 388 liver recipients who received tacrolimus as primary immunosuppression, 70 required conversion to CyA. We recorded indication for conversion, whether conversion was early or late after transplantation, tacrolimus dose and trough blood level at conversion, and incidence of rejection after conversion. Conversion was early in 29 patients (41.4%) and late in 41 (58.6%). Indications for early conversion were neurotoxicity (20), (insulin-dependent) diabetes mellitus (IDDM) (5), nephrotoxicity (3), gastrointestinal (GI) toxicity (6), and cardiomyopathy (1), and for late conversion were neurotoxicity (15), IDDM (12), nephrotoxicity (3), GI toxicity (5), hepatotoxicity (6), post-transplant lmphoproliferate disease (PTLD) (2), cardiomyopathy (1), hemolytic anemia (1), and pruritus (1). All early-conversion patients showed improvement/resolution of symptoms. Among late-conversion patients, 37 (90.2%) had improvement/resolution; in 4 (9.8%), adverse effects persisted. The overall rejection rate was 30%. Sixty-two patients (88.6%) are alive with functioning grafts 686 +/- 362 days (range, 154-1433 days) after conversion. When tacrolimus side effects are unresponsive to dose reduction, conversion to CyA can be accomplished safely, with no increased risk of rejection and excellent long-term outcome.

Long-term results of pancreas transplantation under tacrolius immunosuppression

BACKGROUND

The long-term safety and efficacy of tacrolimus in pancreas transplantation has not yet been demonstrated. The observation of prolonged pancreatic graft function under tacrolimus would indicate that any potential islet toxicity is short-lived and clinically insignificant. We report herein the results of pancreas transplantation in patients receiving primary tacrolimus immunosuppression for a minimum of 2 years.

METHODS

From July 4, 1994 until April 18, 1996, 60 patients received either simultaneous pancreas-kidney transplant (n=55), pancreas transplant only (n=4), or pancreas after kidney transplantation (n=1). Baseline immunosuppression consisted of tacrolimus and steroids without antilymphocyte induction. Azathioprine was used as a third agent in 51 patients and mycophenolate mofetil in 9. Rejection episodes within the first 6 months occurred in 48 (80%) patients and were treated with high-dose corticosteroids. Antilymphocyte antibody was required in eight (13%) patients with steroid-resistant rejection.

RESULTS

With a mean follow-up of 35.1+/-5.9 months (range: 24.3-45.7 months), 6-month and 1-, 2-, and 33-year graft survival is 88%, 82%, 80%, and 80% (pancreas) and 98%, 96%, 93%, and 91% (kidney), respectively. Six-month and 1-, 2-, and 3-year patient survival is 100%, 98%, 98%, and 96.5%. Mean fasting glucose is 91.6+/-13.8 mg/dl, and mean glycosylated hemoglobin is 5.1+/-0.7% (normal range: 4.3-6.1%). Mean tacrolimus dose is 6.5+/-2.6 mg/day and mean prednisone dose 2.0+/-2.9 mg/day at follow-up. Complete steroid withdrawal was possible in 31 (65%) of the 48 patients with functioning pancreases.

CONCLUSIONS

These data show for the first time that tacrolimus is a safe and effective long-term primary agent in pancreas transplantation and provides excellent long-term islet function without evidence of toxicity while permitting steroid withdrawal in the majority of patients.

Therapeutic drug monitoring of tacrolimus in liver transplantation, phase III FK506 multicenter Spanish Study Group: a two-year follow-up

The aim of the Multicentric Liver Transplant Spanish Study was to evaluate tacrolimus therapy at the reduced, initial oral dose of 0.1 mg/kg per day to maintain the immunosuppressive potency of the drug and to avoid toxicity. The dosage of tacrolimus (D), the trough blood concentrations (C), and the evolution of the ratio (D/C) were followed up for 2 years after transplantation in 50 adult patients (38 men, 12 women) undergoing liver allograft transplantation. A total of 1732 samples were analyzed using the IMx tacrolimus method. The overall mean+/-SD concentrations were 10.84 ng/ml+/-5.32 ng/ml. During the first month, the median of the tacrolimus levels was 8.40 ng/ml, and 73.1% of the analyzed samples were within the established therapeutic range. The median oral tacrolimus dose was progressively reduced from 0.12 mg/kg per day during the first month to 0.058 mg/kg per day at the end of study period. A significant negative association was observed between the ratio of D/C and the post-transplantation period (r=-0.3624; p < 0.001). The median D/C ratio ranged from 0.0144 at the end of the first month to 0.0053 at 1 year. Significant declines in D/C were observed after the first and the third months after transplantation. The decrease in corticosteroid doses and the increase in serum albumin may explain the reduction in clearance with time.

Therapeutic monitoring of tacrolimus (FK506) with the first- and second-generation microparticle enzyme immunoassays: performance and results in four patient populations

The performance of the first- and second-generation microparticle enzyme immunoassays for tacrolimus (Tacrolimus I and Tacrolimus II, respectively) was compared during 8 months routine drug monitoring. The minimum detection limit of the Tacrolimus II assay was lower: 1.4 versus 4.0 microg tacrolimus/l. There was also no overlap between results using 10 samples containing 0 and 1 microg tacrolimus/l in the Tacrolimus II assay (p < 0.001), with a corresponding significant difference achieved for the Tacrolimus I assay only at 0 and 4 microg/l. For control specimens, within-assay precision was superior for Tacrolimus II at 5 microg/l (7.3% vs. 31.5%), similar at 10 and 15 microg/l (6.3% versus 6.6% and 4.4% vs. 4.6%, respectively) but worse than Tacrolimus I at 25 microg/l (8.0% vs. 4.0%). Using three pools of blood samples from recipients of liver transplants (containing approximately 4, 10, and 20 microg tacrolimus/l) interassay precision (n > 20) was 14.2%, 10.4%, and 8.0% for Tacrolimus II and 42.4%, 13.8%, and 7.1%, for Tacrolimus I. The analytical times and stability of the calibration curves were similar for the two assays. Tacrolimus I and Tacrolimus II results were closely correlated using patients' blood samples (r approximately equal to 0.8 in 249 adult and 168 pediatric liver transplant samples, 161 renal transplant samples, and 61 samples from patients with autoimmune diseases). However, Tacrolimus II assay results were consistently lower (by a mean of 1.02 to 2.05 microg/l). The authors conclude that the Tacrolimus II assay retains the speed, accuracy, and precision of its predecessor and demonstrates an improved sensitivity, which should facilitate monitoring at less than 5 microg tacrolimus/l.

Cyclosporine and tacrolimus: the mainstay of immunosuppressive therapy for solid organ transplantation

Orthotopic liver transplant is the only cure for end stage liver disease. Enormous progress has been made in the fields of graft and patient survival since the introduction of cyclosporine and tacrolimus. Scientists involved in basic and clinical research have dedicated their efforts to understanding the mechanisms of action and the side effects of these medications with the goal of finding the perfect balance between the well-being of the patient and the avoidance of rejection. A great deal of work has been done and now we can propose a variety of treatments suitable to different clinical scenarios. The introduction of new medications will offer even more options for the treatment of rejection in liver transplant patients.