FK-506 and cyclosporin A: immunosuppressive mechanism of action and beyond

Bone Loss after Solid Organ Transplantation: A Review of Organ-Specific Considerations

This review article investigates solid organ transplantation-induced osteoporosis, a critical yet often overlooked issue, emphasizing its significance in post-transplant care. The initial sections provide a comprehensive understanding of the prevalence and multifactorial pathogenesis of transplantation osteoporosis, including factors such as deteriorating post-transplantation health, hormonal changes, and the impact of immunosuppressive medications. Furthermore, the review is dedicated to organ-specific considerations in transplantation osteoporosis, with separate analyses for kidney, liver, heart, and lung transplantations. Each section elucidates the unique challenges and management strategies pertinent to transplantation osteoporosis in relation to each organ type, highlighting the necessity of an organ-specific approach to fully understand the diverse manifestations and implications of transplantation osteoporosis. This review underscores the importance of this topic in transplant medicine, aiming to enhance awareness and knowledge among clinicians and researchers. By comprehensively examining transplantation osteoporosis, this study contributes to the development of improved management and care strategies, ultimately leading to improved patient outcomes in this vulnerable group. This detailed review serves as an essential resource for those involved in the complex multidisciplinary care of transplant recipients.

Calcineurin inhibitors in the treatment of systemic lupus erythematosus during pregnancy: A narrative review with emphasis on efficacy and safety

Systemic lupus erythematosus (SLE) predominantly affects child-bearing women, leading to an elevated risk of maternal and fetal complications and adverse pregnancy outcomes. Since some medications can cross the placental barrier that persist a threat to both mother and fetus, the risk-benefit ratio of SLE medications should be taken into consideration during pregnancy. Calcineurin inhibitor (CNI), mainly including cyclosporin A, tacrolimus, and voclosporin, is a category of immunosuppressive agents that inhibit calcium/calmodulin-dependent phosphatase calcineurin to block T cell activation. Based on the current clinical evidence, CNI is an alternative in pregnant SLE patients with persistent disease activity (especially lupus nephritis patients) and non-responders to azathioprine. However, there is no comprehensive review that summarizes the efficacy and safety profile of CNI for SLE management during pregnancy. This review presents a summary on the utilization of CNI for SLE management during pregnancy, including the mechanism of action, gestational amelioration of lupus flare, and the balance of maternal benefit-fetal risk, which may provide more references for the management of SLE pregnancies.

Comparison between mono-tacrolimus and mono-glucocorticoid in the treatment of myasthenia gravis

OBJECTIVE

Use of tacrolimus in mild to moderate myasthenia gravis (MG) is generally limited to glucocorticoid-refractory cases; the advantage of mono-tacrolimus over mono-glucocorticoids is unknown.

METHODS

We included mild to moderate MG patients treated with mono-tacrolimus (mono-TAC) or mono-glucocorticoids (mono-GC). The correlation between the immunotherapy options and the treatment efficacy and side effects were examined in 1:1 propensity-score matching. The main outcome was time to minimal manifestations status or better (MMS or better). Secondary outcomes include time to relapse, the mean changes in Myasthenia Gravis-specific Activities of Daily Living (MG-ADL) scores and the rate of adverse events.

RESULTS

Baseline characteristics showed no difference between matched groups (49 matched pairs). There were no differences in median time to MMS or better between the mono-TAC group and mono-GC group (5.1 vs. 2.8 months: unadjusted hazard ratio [HR], 0.73; 95% CI, 0.46-1.16; p = 0.180), as well as in median time to relapse (data unavailable for the mono-TAC group since 44 of 49 [89.8%] participants remained in MMS or better; 39.7 months in mono-GC group: unadjusted HR, 0.67; 95% CI, 0.23-1.97; p = 0.464). Changes in MG-ADL scores between the two groups were similar (mean differences, 0.3; 95% CI, -0.4 to 1.0; p = 0.462). The rate of adverse events was lower in the mono-TAC group compared to the mono-GC group (24.5% vs. 55.1%, p = 0.002).

INTERPRETATION

Mono-tacrolimus performs superior tolerability with non-inferior efficacy compared to mono-glucocorticoids in mild to moderate myasthenia gravis patients who refuse or have a contraindication to glucocorticoids.

Cyclophilin A accelerates SiO2-induced macrophage foaming

Silicosis is a common occupational disease characterized by lung inflammation, fibrosis and pulmonary dysfunction caused by long-term inhalation of free SiO₂. Cell foaming and the change of CyPA have been observed in SiO₂-induced macrophages, but the specific mechanism of CyPA in SiO₂-induced foam cells remains poorly understood. The purpose of this study is to explore the mechanism of CyPA in SiO₂-induced macrophage foaming and its effect on silicosis. We found that overexpression of CyPA promoted the macrophage foaming and the expression of COL I and α-SMA, while silencing CyPA inhibites the macrophage foaming and the expression of COL I and α-SMA. After blocking the expression of CD36 on the basis of overexpression CyPA, we found it inhibites the macrophage foaming. In conclusion, CyPA can affect the foaming of macrophages and may participate in silicosis fibrosis.

Diagnosis and Treatment of Subcutaneous Panniculitis-like T-cell Lymphoma: A Systematic Literature Review

OBJECTIVES

The aim of this systematic review is to investigate different diagnostic methods and the available treatment options for subcutaneous panniculitis-like T-cell lymphoma (SPTCL).

METHODS

We searched PubMed, Web of Science, SCOPUS, EBSCO, and CINAHL Plus for published case reports of SPTCL. From each record, we extracted data of the diagnostic methods, immunohistochemical profile, clinical characteristics, and the treatment approaches provided. Data were summarized and narratively synthesized to highlight the various diagnostic methods and treatment options of SPTCL.

RESULTS

Our literature search yielded 1293 unique citations. Following screening, nine articles reporting a total of 15 cases were included in this systematic review. All patients presented with subcutaneous nodules. Three of the 15 cases were initially misdiagnosed. The atypical lymphoid cells were positive for CD2, CD3, granzyme B, and TIA-1 and negative for CD1a, EBER, and CD20 in all the reported cases. The atypical lymphoid cells were positive for CD45RO in four out of seven cases, positive for CD56 in three out of 12 cases tested, while positive for CD5 and CD8 in the majority of cases. Therapy ranged from topical agents to immunosuppressive agents all the way to multiagent chemotherapy.

CONCLUSION

SPTCL is a rare lymphoma. Diagnosis is highly dependent on the immunohistochemical stains added to histopathologic and radiologic findings. Therapy is dependent on the pace of the disease, with encouraging results obtained with single-agent cyclosporine.

Beta-Cell Dysfunction Induced by Tacrolimus: A Way to Explain Type 2 Diabetes?

The combination of insulin resistance and β-cells dysfunction leads to the onset of type-2 diabetes mellitus (T2DM). This process can last for decades, as β-cells are able to compensate the demand for insulin and maintain normoglycemia. Understanding the adaptive capacity of β-cells during this process and the causes of its failure is essential to the limit onset of diabetes. Post-transplant diabetes mellitus (PTDM) is a common and serious disease that affects 30% of renal transplant recipients. With the exception of immunosuppressive therapy, the risk factors for T2D are the same as for PTDM: obesity, dyslipidaemia, insulin resistance and metabolic syndrome. Tacrolimus (TAC) is the immunosuppressant of choice after renal transplantation but it has the highest rates of PTDM. Our group has shown that insulin resistance and glucolipotoxicity, without favouring the appearance of apoptosis, modify key nuclear factors for the maintenance of identity and functionality of β-cells. In this context, TAC accelerates or enhances these changes. Our hypothesis is that the pathways that are affected in the progression from pre-diabetes to diabetes in the general population are the same pathways that are affected by TAC. So, TAC can be considered a tool to study the pathogenesis of T2DM. Here, we review the common pathways of β-cells dysfunction on T2DM and TAC-induced diabetes.

Combination Therapy to Treat Fungal Biofilm-Based Infections

An increasing number of people is affected by fungal biofilm-based infections, which are resistant to the majority of currently-used antifungal drugs. Such infections are often caused by species from the genera Candida, Aspergillus or Cryptococcus. Only a few antifungal drugs, including echinocandins and liposomal formulations of amphotericin B, are available to treat such biofilm-based fungal infections. This review discusses combination therapy as a novel antibiofilm strategy. More specifically, in vitro methods to discover new antibiofilm combinations will be discussed. Furthermore, an overview of the main modes of action of promising antibiofilm combination treatments will be provided as this knowledge may facilitate the optimization of existing antibiofilm combinations or the development of new ones with a similar mode of action.

The role of immunosuppressive agents in the management of severe and refractory immune-related adverse events

The advent of immune checkpoint inhibitors has improved survival in some types of cancer and brought promising prospects to cancer immunotherapy. Despite their clinical benefits, significant off-target toxicities resulting from the immune system activation have been observed, namely immune-related adverse events (irAEs), which pose to clinicians a new challenge of optimal management. With steroids being the mainstay of current management of irAEs, immunosuppressive agents are especially indicated for severe or steroid-refractory cases, based on current immunopathophysiological knowledge and on extrapolations of treatment options for primary autoimmune disorders. This review focuses on the status and recent clinical progress of immunosuppressive agents in the management of severe and steroid-refractory irAEs.

Observation of topical tacrolimus on high-risk penetrating keratoplasty patients: a randomized clinical trial study

Background/Objectives

To evaluate the clinical efficacy of topical tacrolimus 0.1% and cyclosporine 1% on high-risk penetrating keratoplasty (PKP) patients.

Subjects/Methods

A series of 49 high-risk PKP patients (49 eyes), 20 males, 29 females from the age of 4 months to 74 years of age with the mean of 32.5 from 2012 to 2017 were recruited in this study. The patients were randomly divided into two groups by receiving either topical tacrolimus 0.1% or cyclosporine 1% respectively. Twenty five patients were treated with topical tacrolimus 0.1% and 24 patients with topical cyclosporine 1%. The traditional baseline management on these two groups were Tobramycin and Dexamethasone eye drops in the first 3 weeks and then tapered off. Clinical procedures and postoperative follow-up were documented.

Results

After 6–54 months follow-up, with the average of 24 months, 11 of 24 high-risk patients (11 eyes) had graft rejection, the rejection rate was 45.8% in topical cyclosporine 1% group. The rejections occurred from 35 days to 20 months after PKP. Three patients had irreversible rejection. On topical tacrolimus 0.1% group, the rejection occurred in four patients (four eyes) with rejection rate of 16%, and no irreversible rejection was observed. The graft rejection episodes were documented between 23 days and 24 months. As compared with the topical cyclosporine 1%, topical tacrolimus 0.1%, a key immunosuppressant, significantly decreased corneal graft rejection rate (p = 0.02).

Conclusions

Topical tacrolimus 01% on high-risk PKP patients significantly prevented corneal graft rejection, and it had less adverse effects and was very safe to high-risk patients as to topical cyclosporine 1%. Further case controlled randomized clinical trial studies are needed to establish the best management option for these high-risk patients.

Microglial Calcium Release-Activated Calcium Channel Inhibition Improves Outcome from Experimental Traumatic Brain Injury and Microglia-Induced Neuronal Death

Store-operated Ca²⁺ entry (SOCE) mediated by calcium release-activated calcium (CRAC) channels contributes to calcium signaling. The resulting intracellular calcium increases activate calcineurin, which in turn activates immune transcription factor nuclear factor of activated T cells (NFAT). Microglia contain CRAC channels, but little is known whether these channels play a role in acute brain insults. We studied a novel CRAC channel inhibitor to explore the therapeutic potential of this compound in microglia-mediated injury. Cultured microglial BV2 cells were activated by Toll-like receptor agonists or IFNγ. Some cultures were treated with a novel CRAC channel inhibitor (CM-EX-137). Western blots revealed the presence of CRAC channel proteins STIM1 and Orai1 in BV2 cells. CM-EX-137 decreased nitric oxide (NO) release and inducible nitric oxide synthase (iNOS) expression in activated microglia and reduced agonist-induced intracellular calcium accumulation in microglia, while suppressing inflammatory transcription factors nuclear factor kappa B (NF-κB) and nuclear factor of activated T cells (NFAT). Male C57/BL6 mice exposed to experimental brain trauma and treated with CM-EX-137 had decreased lesion size, brain hemorrhage, and improved neurological deficits with decreased microglial activation, iNOS and Orai1 and STIM1 levels. We suggest a novel anti-inflammatory approach for managing acute brain injury. Our observations also shed light on new calcium signaling pathways not described previously in brain injury models.

The ARE-binding protein Tristetraprolin (TTP) is a novel target and mediator of calcineurin tumor suppressing function in the skin

An increased incidence of skin inflammatory diseases is frequently observed in organtransplanted patients being treated with calcineurin inhibitor-based immunosuppressive agents. The mechanism of increased skin inflammation in this context has however not yet been clarified. Here we report an increased inflammation following inhibition of calcineurin signaling seen in both chemically induced mouse skin tumors and in tumors grafted from H-rasV12 expressing primary human keratinocytes (HKCs). Following UVB or TPA treatment, we specifically found that deletion of the calcineurin gene in mouse keratinocytes (MKCs) resulted in increased inflammation, and this was accompanied by the enhanced production of pro-inflammatory cytokines, such as TNFα, IL-8 and CXCL1. Furthermore, expression of the RNA-binding protein, tristetraprolin (TTP) was down-regulated in response to calcineurin inhibition, wherein TTP was shown to negatively regulate the production of pro-inflammatory cytokines in keratinocytes. The induction of TTP following TPA or UVB treatment was attenuated by calcineurin inhibition in keratinocytes, and correspondingly, disruption of calcineurin signaling down-regulated the amounts of TTP in both clinical and H-rasV12-transformed keratinocyte tumor models. Our results further demonstrated that calcineurin positively controls the stabilization of TTP in keratinocytes through a proteasome-dependent mechanism. Reducing the expression of TTP functionally promoted tumor growth of H-rasV12 expressing HKCs, while stabilizing TTP expression counteracted the tumor-promoting effects of calcineurin inhibition. Collectively these results suggest that calcineurin signaling, acting through TTP protein level stabilization, suppresses keratinocyte tumors by downregulating skin inflammation.

Had1 Is Required for Cell Wall Integrity and Fungal Virulence in Cryptococcus neoformans

Calcineurin modulates environmental stress survival and virulence of the human fungal pathogen Cryptococcus neoformans Previously, we identified 44 putative calcineurin substrates, and proposed that the calcineurin pathway is branched to regulate targets including Crz1, Pbp1, and Puf4 in C. neoformans In this study, we characterized Had1, which is one of the putative calcineurin substrates belonging to the ubiquitously conserved haloacid dehalogenase β-phosphoglucomutase protein superfamily. Growth of the had1∆ mutant was found to be compromised at 38° or higher. In addition, the had1∆ mutant exhibited increased sensitivity to cell wall perturbing agents, including Congo Red and Calcofluor White, and to an endoplasmic reticulum stress inducer dithiothreitol. Virulence studies revealed that the had1 mutation results in attenuated virulence compared to the wild-type strain in a murine inhalation infection model. Genetic epistasis analysis revealed that Had1 and the zinc finger transcription factor Crz1 play roles in parallel pathways that orchestrate stress survival and fungal virulence. Overall, our results demonstrate that Had1 is a key regulator of thermotolerance, cell wall integrity, and virulence of C. neoformans.

A calcineurin antifungal strategy with analogs of FK506

A novel antifungal strategy targeting the inhibition of calcineurin is described. To develop a calcineurin based inhibitor of pathogenic fungi, analogs of FK506 were synthesized that were able to permeate mammalian but not fungal cells. Antagonists in combination with FK506 were not immunosuppressive and retained antifungal activity in A. fumigatus. To reduce the dosage burden of the antagonist, murine oral PK was improved an order of magnitude relative to previous FK506 antagonists.

Feeding an army: The metabolism of T cells in activation, anergy, and exhaustion

Through the direct control of infection or by providing cytokine signals to other cellular players, T cells play a central role in the orchestration of the immune response. However, in many disease states, T cells are rendered dysfunctional, unable to carry out their effector functions. As T cell activation is bioenergetically demanding, some T cell dysfunction can have metabolic underpinnings. In this review, we will discuss how T cells are programmed to fuel their effector response, and how programmed or pathologic changes can disrupt their ability to generate the energy needed to proliferate and carry out their critical functions.

Efficacy and safety of systemic tacrolimus in high-risk penetrating keratoplasty after graft failure with systemic cyclosporine

PURPOSE

The aim of this study was to investigate the efficacy and safety of systemic tacrolimus for the treatment of eyes that developed graft failure despite treatment with cyclosporine (CsA).

METHODS

Ten eyes of 10 patients who underwent high-risk penetrating keratoplasty (PKP) and developed graft failure despite treatment with systemic CsA were included in this study. The patients underwent PKP and were treated with systemic tacrolimus according to the standardized protocol.

RESULTS

Treatment with tacrolimus was continued for 18.1 ± 13.9 months. The median duration of corneal graft clarity was 34.5 months. Graft rejection occurred in 2 of 10 eyes during a mean follow-up period of 48.9 ± 22.9 months. Kaplan-Meier survival plots showed significantly fewer graft rejection episodes (P = 0.033) and longer graft survival (P = 0.042) after treatment with tacrolimus compared those with CsA. Tacrolimus was discontinued in 2 patients; 1 had renal dysfunction and the other had muscle pain and fatigue. These side effects subsided after discontinuation of tacrolimus.

CONCLUSIONS

Treatment with systemic tacrolimus is possibly safe and effective in reducing graft rejection and prolonging graft survival in patients with high-risk PKP after graft failure with systemic CsA.

Review of the early diagnoses and assessment of rejection in vascularized composite allotransplantation

The emerging field of vascular composite allotransplantation (VCA) has become a clinical reality. Building upon cutting edge understandings of transplant surgery and immunology, complex grafts such as hands and faces can now be transplanted with success. Many of the challenges that have historically been limiting factors in transplantation, such as rejection and the morbidity of immunosuppression, remain challenges in VCA. Because of the accessibility of most VCA grafts, and the highly immunogenic nature of the skin in particular, VCA has become the focal point for cross-disciplinary approaches to developing novel approaches for some of the most challenging immunological problems in transplantation, particularly the early diagnoses and assessment of rejection. This paper provides a historically oriented introduction to the field of organ transplantation and the evolution of VCA.

Design and physicochemical characterization of advanced spray-dried tacrolimus multifunctional particles for inhalation

The aim of this study was to design, develop, and optimize respirable tacrolimus microparticles and nanoparticles and multifunctional tacrolimus lung surfactant mimic particles for targeted dry powder inhalation delivery as a pulmonary nanomedicine. Particles were rationally designed and produced at different pump rates by advanced spray-drying particle engineering design from organic solution in closed mode. In addition, multifunctional tacrolimus lung surfactant mimic dry powder particles were prepared by co-dissolving tacrolimus and lung surfactant mimic phospholipids in methanol, followed by advanced co-spray-drying particle engineering design technology in closed mode. The lung surfactant mimic phospholipids were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-[phosphor-rac-1-glycerol]. Laser diffraction particle sizing indicated that the particle size distributions were suitable for pulmonary delivery, whereas scanning electron microscopy imaging indicated that these particles had both optimal particle morphology and surface morphology. Increasing the pump rate percent of tacrolimus solution resulted in a larger particle size. X-ray powder diffraction patterns and differential scanning calorimetry thermograms indicated that spray drying produced particles with higher amounts of amorphous phase. X-ray powder diffraction and differential scanning calorimetry also confirmed the preservation of the phospholipid bilayer structure in the solid state for all engineered respirable particles. Furthermore, it was observed in hot-stage micrographs that raw tacrolimus displayed a liquid crystal transition following the main phase transition, which is consistent with its interfacial properties. Water vapor uptake and lyotropic phase transitions in the solid state at varying levels of relative humidity were determined by gravimetric vapor sorption technique. Water content in the various powders was very low and well within the levels necessary for dry powder inhalation, as quantified by Karl Fisher coulometric titration. Conclusively, advanced spray-drying particle engineering design from organic solution in closed mode was successfully used to design and optimize solid-state particles in the respirable size range necessary for targeted pulmonary delivery, particularly for the deep lung. These particles were dry, stable, and had optimal properties for dry powder inhalation as a novel pulmonary nanomedicine.

Outcomes and adverse events in children and young adults undergoing tacrolimus therapy for steroid-refractory colitis

BACKGROUND

Children with severe corticosteroid-resistant ulcerative colitis either need to undergo surgery or be treated with more intensive immunosuppression. Our aim was to characterize the short- and long-term outcomes and adverse events associated with the use of tacrolimus in a steroid-refractory pediatric population.

METHODS

We retrospectively reviewed the medical records of 46 children with steroid-refractory colitis treated with tacrolimus at Children's Hospital Boston between 1994 and 2008. Oral tacrolimus was initiated at a dose of 0.1 mg/kg twice a day and titrated to yield trough levels of 10-15 ng/mL for induction, and 5-10 ng/mL once in remission. The Pediatric Ulcerative Colitis Activity Index (PUCAI) and other measures of disease activity, adverse events, and long-term outcomes were assessed. Statistical analysis of outcomes was performed using SAS statistical software.

RESULTS

Ninety-three percent of patients were discharged without undergoing surgery. The median length of stay after starting tacrolimus was 10 days (range 4-37 days). The mean PUCAI score was 68 ± 13 prior to initiating tacrolimus, and 27 ± 18 at the time of hospital discharge. The probability of avoiding colectomy after starting tacrolimus was 40% at 26 months. The most common adverse events included hypertension (52%) and tremor (44%). There was one seizure and no deaths.

CONCLUSIONS

Tacrolimus is useful as induction therapy in pediatric patients with corticosteroid-refractory colitis and side effects are generally mild and reversible. Despite these findings, many patients develop exacerbations of colitis upon transition to maintenance therapies. The long-term colectomy rate in this challenging population remains ≈60% over time.

[Progress of CypA and lung cancer-related research]

亲环素A（cyclophilin A, CypA）作为亲环素家族中最重要的一员，在自然界中广泛表达，发挥着肽基脯氨酰顺反异构酶（peptidyl-prolyl cis-trans isomeras, PPⅠase）活性和分子伴侣效应，辅助细胞内蛋白质的正确折叠，参与免疫抑制，介导炎性反应，平衡细胞内外胆固醇。随着对CypA认识的加深，人们逐渐意识到它与恶性肿瘤之间的密切联系。CypA最先被发现在肺癌中高表达，具有促进肺癌细胞生长、抑制凋亡、介导侵袭转移等作用，可能成为一个肺癌的早期诊断和治疗的新靶点。

Single center prospective study of tacrolimus efficacy and safety in the treatment of various manifestations in systemic lupus erythematosus

The aim of this study was to prospectively evaluate the efficacy and safety of tacrolimus (TAC) in various manifestations of systemic lupus erythematosus (SLE) patients in daily clinical practice. Each of the 21 TAC-treated patients with SLE in our care over 2 years was enrolled in this open-label trial. Patients were administered TAC at a dosage of 1-6 mg once daily, followed up for 24 weeks. Efficacy and safety were evaluated utilizing clinical and laboratory findings. As treatment targets, TAC was preferentially used with oral corticosteroid administration for mild active manifestations such as arthritis, skin eruptions, or asymptomatic nephritis. In efficacy, the mean value of the SLE disease activity index was significantly reduced to 4.1, 2.7, 1.8, and 1.2 (N=21, 20, 16 and 13) at 0, 4, 12, and 24 weeks, respectively. In eight cases, treatment was discontinued within 24 weeks due to insufficient effects (6 cases) and side effects (2 cases). Non-serious side effects were observed in only five cases (23.8%) over 24 weeks. TAC can be considered both effective and safe for the treatment of various manifestations of SLE.

Post-surgical irradiation causes cellular immune suppression in patients with breast cancer

According to several studies, even the locoregional irradiation of patients with carcinoma can cause a severe and rather alarming cellular immune defect. We thus designed a prospective research in order to study the effect of post-operative irradiation on cellular immunity in patients suffering from breast cancer. In 35 patients with breast cancer who required post-operative irradiation, four blood samples were taken at indicated point times. Nineteen out of 35 patients received post-surgical chemotherapy before irradiation. The total lymphocytes as well as CD4 and CD8 subpopulations were measured by using flow cytometry analysis. The mean T-lymphocyte (Tol) count dropped from 1487.77 to 1227.91 (P = 0.0013) and the CD4+ count from 674.17 to 580.91 (P = 0.0189). The mean value of CD8+ dropped from 421.31 to 314.00 (P = 0.0003). Moreover, a statistically significant difference regarding the pattern of temporal change was observed between a group of patients that received irradiation only and a group that received radiation therapy (RT) with chemotherapy (P-values 0.0015, 0.01 and 0.092 for Tol, CD4+ and CD8+ respectively). The group of patients that received RT only presented a more rapid decrease of Tol concerning the decrease observed in the group that underwent chemotherapy and RT.

Single center prospective study of tacrolimus efficacy and safety in treatment of rheumatoid arthritis

The aim of this study was to prospectively evaluate the efficacy and safety of tacrolimus for treating rheumatoid arthritis (RA) patients in clinical practice. Fifty-five active RA patients who had been resistant or intolerant to other disease-modifying antirheumatic drugs were enrolled in this open-label trial. Patients were administered tacrolimus at a dosage of 1, 2 or 3 mg once daily, and followed up for 24 weeks. They were divided into three groups according to their dosage. Efficacy and safety were evaluated utilizing clinical and laboratory findings. Eighty percent of the patients had moderate or high disease activity; 55% were elderly and 53% had complications; 65% of the patients were started on tacrolimus as a monotherapy. Moderate or good response rates were achieved as follows: 38.2% (4 weeks); 41.8% (12 weeks); and 45.6% (24 weeks). Adverse events were observed in seven cases (12.7%). Only one case required hospitalization due to severe hyperglycemia caused by a high tacrolimus concentration (24.2 ng/ml); we suspected a drug interaction in this subject. Mean concentrations were dose-dependent in the 1, 2, and 3 mg/day groups (2.96, 4.29, and 8.32 ng/ml, respectively). Four cases of high concentration (over 10 ng/ml), without any signs or symptoms, were observed in the 3 mg/day group; in these cases, doses were decreased and no severe adverse events occurred. Tacrolimus was found to be both effective and safe in treating active RA patients with complicated backgrounds in clinical practice. Blood concentration measurements and dose adjustments should be performed to prevent severe adverse events in a 3 mg/day group.

Effects of ciclosporin A, tacrolimus and sirolimus on cytokine production in neonatal immune cells

BACKGROUND

It was the aim of this study to evaluate the effects of the well-known immunosuppressive drugs ciclosporin A (CsA), tacrolimus and sirolimus on the intracytoplasmic cytokine expression of neonatal immune cells.

METHODS

Immunosuppressive drugs were added to whole blood cultures of neonatal cord blood samples (n = 17) and peripheral blood samples of adults (n = 17) in vitro prior to stimulation of lymphocytes with phorbol 12-myristate 13-acetate (PMA)/ionomycin or monocytes.

RESULTS

Upon exposure to ciclosporin A (500 ng/mL) or tacrolimus (25 ng/mL) the number of cytokine expressing T cells was almost completely blocked in neonatal T cells while sirolimus (10 ng/mL) only inhibited intracytoplasmatic tumour necrosis factor alpha (TNF-alpha) expression (mean% positive cells; 4.0 +/- 2.1% vs. 1.09 +/- 0.6%, p = 0.003), but mildly stimulated the intracellular expression of interleukin (IL)-2 (24.4 +/- 6.5% vs. 28.1 +/- 7.1%, p = 0.041). In cord blood lymphocytes, the inhibitory effect of ciclosporin A and tacrolimus was dose-dependent (e.g. IL-2: control, 12.3 +/- 5.33%, ciclosporin A 5 ng/mL, 10.1 +/- 5.5%; 50 ng/mL, 7.1 +/- 4.7%; 500 ng/mL, 1.2 +/- 0.3%; tacrolimus 0.25 ng/mL, 9.3 +/- 4.9%; 2.5 ng/mL, 6.1 +/- 3.3%; 25 ng/mL, 1.0 +/- 0.6%), while the function of adult lymphocytes was only impaired at high doses of both compounds. In contrast, the number of cytokine expressing monocytes was not influenced by ciclosporin A and tacrolimus except for a minor decrease of TNF-alpha producing neonatal monocytes after addition of tacrolimus (17.9% vs. 13.9%, p = 0.031). Interestingly, sirolimus was shown to inhibit intracellular IL-6 production in adults (63.1 +/- 12.7% vs. 52.0 +/- 16.0%, p = 0.005), but in neonatal monocytes intracellular IL-6 expression was stimulated (53.5 +/- 22.0% vs. 64.7 +/- 19.1%, p = 0.041).

CONCLUSIONS

The potent dose-dependent inhibitory effect of ciclosporin A and tacrolimus in cord blood lymphocytes provides the basis for further studies on functional immaturity of the neonatal immune system and for future strategies to optimize umbilical cord blood transplantion. Sirolimus was demonstrated to have a distinct effect on neonatal immune cells as shown by increased expression of IL-2 in lymphocytes and IL-6 in monocytes, while only lymphocytic TNF-alpha expression was inhibited.

Cyclosporin versus tacrolimus for liver transplanted patients

BACKGROUND

Most liver transplant recipients receive either cyclosporin or tacrolimus to prevent rejection. Both drugs inhibit calcineurin phosphatase which is thought to be the mechanism of their anti-rejection effect and principle toxicities. The drugs have different pharmacokinetic profiles and potencies. Several randomised clinical trials have compared cyclosporin and tacrolimus in liver transplant recipients, but it remains unclear which is superior.

OBJECTIVES

To evaluate the beneficial and harmful effects of immunosuppression with cyclosporin versus tacrolimus for liver transplanted patients.

SEARCH STRATEGY

The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded, and conference proceedings were searched (August 2005) to identify relevant randomised clinical trials. Our search included scanning of reference lists in relevant articles and correspondence with investigators and pharmaceutical companies.

SELECTION CRITERIA

All randomised clinical trials where tacrolimus was compared with cyclosporin for the initial treatment of first-time liver transplant recipients. We included randomised trials irrespective of blinding, language, and publication status.

DATA COLLECTION AND ANALYSIS

The primary outcome measure was all-cause mortality. Data were synthesised (fixed-effect model) and results expressed as relative risk (RR), values less than 1.0 favouring tacrolimus, with 95% confidence intervals (CI). Two authors assessed trials for eligibility, quality, and extracted data independently.

MAIN RESULTS

We included 16 randomised trials. The number of deaths was 254 in the tacrolimus group (1899 patients) and 302 in the cyclosporin group (1914 patients). At one year, mortality (RR 0.85, 95% CI 0.73 to 0.99) and graft loss (RR 0.73, 95% CI 0.61 to 0.86) were significantly reduced in tacrolimus-treated recipients. Tacrolimus reduced the number of recipients with acute rejection (RR 0.81, 95% CI 0.75 to 0.88), and steroid-resistant rejection (RR 0.54, 95% CI 0.47 to 0.74) in the first year. Differences were not seen with respect to lymphoproliferative disorder or de-novo dialysis rates, but more de-novo insulin-requiring diabetes mellitus (RR 1.38, 95% CI 1.01 to 1.86) occurred in the tacrolimus group. More patients were withdrawn from cyclosporin therapy than from tacrolimus (RR 0.57, 95% CI 0.49 to 0.66).

AUTHORS' CONCLUSIONS

Tacrolimus is superior to cyclosporin in improving survival (patient and graft) and preventing acute rejection after liver transplantation, but it increases the risk of post-transplant diabetes. Treating 100 recipients with tacrolimus instead of cyclosporin would avoid acute rejection and steroid-resistant rejection in nine and seven patients, respectively, and graft loss and death in five and two patients, respectively, but four additional patients would develop diabetes after liver transplantation.

Cyclosporin versus tacrolimus for liver transplanted patients

BACKGROUND

Most liver transplant recipients receive either cyclosporin or tacrolimus to prevent rejection. Both drugs inhibit calcineurin phosphatase which is thought to be the mechanism of their anti-rejection effect and principle toxicities. The drugs have different pharmacokinetic profiles and potencies. Several randomised clinical trials have compared cyclosporin and tacrolimus in liver transplant recipients, but it remains unclear which is superior.

OBJECTIVES

To evaluate the beneficial and harmful effects of immunosuppression with cyclosporin versus tacrolimus for liver transplanted patients.

SEARCH STRATEGY

The Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded, and conference proceedings were searched (August 2005) to identify relevant randomised clinical trials. Our search included scanning of reference lists in relevant articles and correspondence with investigators and pharmaceutical companies.

SELECTION CRITERIA

All randomised clinical trials where tacrolimus was compared with cyclosporin for the initial treatment of first-time liver transplant recipients. We included randomised trials irrespective of blinding, language, and publication status.

DATA COLLECTION AND ANALYSIS

The primary outcome measure was all-cause mortality. Data were synthesised (fixed-effect model) and results expressed as relative risk (RR), values less than 1.0 favouring tacrolimus, with 95% confidence intervals (CI). Two authors assessed trials for eligibility, quality, and extracted data independently.

MAIN RESULTS

We included 16 randomised trials. The number of deaths was 254 in the tacrolimus group (1899 patients) and 302 in the cyclosporin group (1914 patients). At one year, mortality (RR 0.85, 95% CI 0.73 to 0.99) and graft loss (RR 0.73, 95% CI 0.61 to 0.86) were significantly reduced in tacrolimus-treated recipients. Tacrolimus reduced the number of recipients with acute rejection (RR 0.81, 95% CI 0.75 to 0.88), and steroid-resistant rejection (RR 0.54, 95% CI 0.47 to 0.74) in the first year. Differences were not seen with respect to lymphoproliferative disorder or de-novo dialysis rates, but more de-novo insulin-requiring diabetes mellitus (RR 1.38, 95% CI 1.01 to 1.86) occurred in the tacrolimus group. More patients were withdrawn from cyclosporin therapy than from tacrolimus (RR 0.57, 95% CI 0.49 to 0.66).

AUTHORS' CONCLUSIONS

Tacrolimus is superior to cyclosporin in improving survival (patient and graft) and preventing acute rejection after liver transplantation, but it increases the risk of post-transplant diabetes. Treating 100 recipients with tacrolimus instead of cyclosporin would avoid acute rejection and steroid-resistant rejection in nine and seven patients, respectively, and graft loss and death in five and two patients, respectively, but four additional patients would develop diabetes after liver transplantation.

Nonsteroid immune modulators and bone disease

Glucocorticoids have been the main agents for preventing organ rejection,but unfortunately they possess serious side effects. Newer immunosuppressive agents have therefore been introduced to overcome these effects and have had a dramatic impact on reducing the incidence of organ rejection, enhancing donor organ acceptance, and hence patient survival posttransplantation. However, calcineurin inhibitors (CIs), such as cyclosporine and tacrolimus, also have serious effects causing rapid and severe bone loss in animal models and humans. The mechanism accounting for this action is unclear at present, but the role of T lymphocyte action via RANKL seems to be of essence in triggering bone loss. The mechanism is complex and in vitro studies often produce results that are opposite to those seen in vivo. In addition to acute, rapid, and severe bone loss (ARSBL), the clinical picture shows an extremely high incidence of fractures at all sites, and depends upon the organ transplanted, preexisting bone disease, interval before transplantation, and the dose and duration of multiple immunosuppressive drugs. Other immune-modifying drugs, such as azathioprine, mycophenolate mofetil, and sirolimus, which are used in conjunction with glucocorticoids and CIs have not been shown to promote bone loss experimentally or clinically. With the exception of glucocorticoids, all of the agents discussed here demand further investigation with regard to their effects on bone health in the clinical setting.

Cyclosporin versus tacrolimus as primary immunosuppressant after liver transplantation: a meta-analysis

A systematic review of randomized clinical trials (RCT) was undertaken to evaluate the beneficial and harmful effects of immunosuppression with cyclosporin versus tacrolimus for liver transplanted patients. MEDLINE, EMBASE, Cochrane Central and Hepato-Biliary Group Controlled Trials Registers were searched. Using fixed and random effects model, relative risk (RR), values <1 favoring tacrolimus, with 95% confidence intervals (CI) were calculated. Of 717 potentially relevant references, 16 RCTs were eligible for inclusion. Mortality and graft loss at 1 year were significantly reduced in tacrolimus-treated recipients (Death: RR 0.85, 95% CI 0.73-0.99; graft loss: RR 0.73, 95% CI 0.61-0.86). Tacrolimus reduced the number of recipients with acute rejection (RR 0.81, 95% CI 0.75-0.88) and steroid-resistant rejection (RR 0.54, 95% CI 0.47-0.74) in the first year. Lymphoproliferative disorder or dialysis rates were not different but more de novo diabetes (RR 1.38, 95% CI 1.01-1.86) occurred with tacrolimus. More patients stopped cyclosporin than tacrolimus (RR 0.57, 95% CI 0.49-0.66). Treating 100 recipients with tacrolimus instead of cyclosporin would avoid rejection and steroid-resistant rejection in nine and seven patients respectively, graft loss and death in five and two patients respectively, but four additional patients would develop diabetes after liver transplantation.

Bifurcated converging pathways for high Ca2+- and TGFbeta-induced inhibition of growth of normal human keratinocytes

Growth suppression of normal human keratinocytes by high Ca2+ or TGFbeta was shown to be mediated by p21WAF1/CIP1 and Sp1 [Pardali, K., et al. (2000) J. Biol. Chem. 275, 29244-29256; Santini, M. P., Talora, C., Seki, T., Bolgan, L. & Dotto, G. P. (2001) Proc. Nat. Acad. Sci. USA 98, 9575-9580; Al-Daraji, W. I., Grant, K. R., Ryan, K., Saxton, A., & Reynolds, N. J. (2002) J. Invest. Dermatol. 118, 779-788]. We previously demonstrated that S100C/A11 is a key mediator for growth inhibition of normal human epidermal keratinocytes (NHK) triggered by high Ca2+ or TGFbeta [Sakaguchi, M., et al. (2003) J. Cell Biol. 163, 825-835; Sakaguchi, M., et al. (2004) 164, 979-984]. On exposure of NHK cells to either agent, S100C/A11 is transferred to nuclei, where it induces p21WAF1/CIP1 through activation of Sp1/Sp3. In the present study, we found that high Ca2+ activated NFAT1 through calcineurin-dependent dephosphorylation. In growing NHK cells, Krueppel-like factor (KLF)16, a member of the Sp/KLF family, bound to the p21WAF1/CIP1 promoter and, thereby, inhibited the transcription of p21(WAF1/CIP1). Sp1 complexed with NFAT1 in high Ca2+-treated cells or with Smad3 in TGFbeta1-treated cells, but not Sp1 alone, replaced KLF16 from the p21WAF1/CIP1 promoter and transcriptionally activated the p21WAF1/CIP1 gene. Thus, high Ca2+ and TGFbeta1 have a common S100C/A11-mediated pathway in addition to a unique pathway (NFAT1-mediated pathway for high Ca2+ and Smad-mediated pathway for TGFbeta1) for exhibiting a growth inhibitory effect on NHK cells, and both pathways were shown to be indispensable for growth inhibition.

EBV-specific memory CD8+ T cell phenotype and function in stable solid organ transplant patients

Immune responses to EBV in immunosuppressed (IS) solid organ transplant (SOTx) recipients have not been well characterized. Here we evaluate the phenotype and function of EBV-specific CD8+ T cells in peripheral blood isolated from "stable" IS SOTx recipients. The EBV-specific CD8+ T cell memory subset distribution in the peripheral blood of patients was examined by flow cytometric analysis using HLA-A2 tetramers incorporating BMLF1 (lytic), and LMP2 and EBNA3A (latent)-derived peptides, in conjunction with mAbs against the CD45RO, CD45RA, and CD62L markers. The ability of CD8+ T cells to produce IFN-gamma in response to the same EBV-derived peptides was measured by ELISPOT assay. Patients and healthy normal donors exhibited similar anti-EBV CD8+ T cell frequencies and specificities against the EBV epitopes evaluated. When compared to healthy normal donors, an overall significant expansion of the CD8+ T cell "effector memory" (CD45RO+/CD62L-) pool, including that of EBV "latent" (LMP2 and EBNA3A)-specific CD8+ T cells was detected in IS SOTx patients. However, the patients' EBV-specific CD8+ T cells showed decreased IFN-gamma production to the EBV-peptide stimulation. These results indicate that the impairment of EBV-specific CD8+ T cell activity is not due to clonal depletion, but is mainly due to impaired functional activation.

A role for schwann cells in the neuroregenerative effects of a non-immunosuppressive fk506 derivative, jnj460

FK506 and its non-immunosuppressive derivatives represent a class of pharmacological agents referred to as immunophilin ligands that have been reported to promote neuroregeneration and survival in several experimental models; however their cellular and molecular mechanisms of action have not been well established. Here we characterize a new immunophilin ligand that interacts with both FK506 binding protein 12 (FKBP12) and FKBP52, and demonstrate that JNJ460 induces neurite outgrowth from freshly explanted dorsal root ganglia (DRG) in a Schwann cell-dependent manner. Purified cultures of neurons fail to respond to these drugs, but cultures containing Schwann cells and neurons respond with neurite outgrowth, as do neurons grown in conditioned medium from JNJ460-treated Schwann cells. Using microarray analysis and a transcription reporter assay, we show that JNJ460 induces a series of transcriptional changes that occur in a temporal cascade. Among the Schwann cell-expressed genes upregulated following JNJ460 treatment is the POU transcription factor SCIP, which has been shown to regulate Schwann cell gene transcription and differentiation. JNJ460 potentiated transforming growth factor beta (TGF-beta)-induced transcriptional activation and SCIP induction in Schwann cells, by altering the interaction between FKBP12 and the TGF-beta type I receptor, TbetaR1. Finally, to test whether JNJ460 enhances neurite regeneration in vivo, we treated animals with JNJ460 for 30 days following mechanical transection of the sciatic nerve and demonstrated myelin and axonal hypertrophy at the ultrastructural level. Collectively, these data suggest that Schwann cells play an important role in the biological effects of immunophilin ligands by affecting neuron-glial signaling during regeneration.

SUMMARY

The cellular and molecular mechanisms responsible for the regenerative effects of immunophilin ligands are not well understood. Here we show that the neuritogenic effects of JNJ460 in a DRG model depend on interactions between neurons and Schwann cells. Treatment of purified Schwann cells with JNJ460 alters Schwann cell gene expression, and promotes the generation of factors that act on neurons. These data indicate that Schwann cells play an important role in the actions of immunophilin ligands.

Disorders associated with acute rapid and severe bone loss

We describe a constellation of bone diseases characterized by the common feature of acute, rapid, and severe bone loss accompanied by dramatic fracture rates. These disorders are poorly recognized, resulting mainly from systemic diseases, frailty, immobilization, and immunosuppressive drugs, such as glucocorticoids and the calcineurin inhibitors. The opportunity to prevent or treat fractures is commonly missed because they are often not detected. Ideally, patients need to be identified early and preventative therapy initiated promptly to avoid the rapid bone loss and fractures. The most effective therapy at present seems to be the bisphosphonates, particularly when bone resorption is predominant. However, more severe forms of bone loss that result from an osteoblastic defect and reduced bone formation may benefit potentially more from newer anabolic agents, such as recombinant human parathyroid hormone (rhPTH).

Tacrolimus enhances transforming growth factor-beta1 expression and promotes tumor progression

BACKGROUND

Immunosuppressive therapy is a risk factor for the increased incidence and metastatic progression of malignancies in organ graft recipients. Transforming growth factor (TGF)-beta(1) has been associated with tumor invasion and metastasis, and we have implicated cyclosporine-associated TGF-beta(1) hyperexpression in tumor progression in mice.

METHODS

BALB/c mice or severe combined immunodeficient-beige mice were treated with 2 or 4 mg/kg of tacrolimus, and the effect of treatment on mouse renal cancer cell pulmonary metastasis was investigated. We also determined whether tacrolimus induces TGF-beta(1) expression. Spleens from tacrolimus-treated mice were analyzed for level of expression of TGF-beta(1) mRNA with the use of competitive-quantitative polymerase chain reaction assay, and circulating levels of TGF-beta(1) protein were measured with the use of an enzyme-linked immunosorbent assay.

RESULTS

Treatment with tacrolimus resulted in a dose-dependent increase in the number of pulmonary metastases in the BALB/c mice (197+/-16 in untreated mice, 281+/-26 in mice treated with 2 mg/kg of tacrolimus, and 339+/-25 in mice treated with 4 mg/kg of tacrolimus; no treatment vs. 4 mg/kg tacrolimus, Bonferroni's P<0.001) and in the severe combined immunodeficient-beige mice (117+/-18 in untreated mice, 137+/-19 in mice treated with 2 mg/kg of tacrolimus, and 216+/-29 in mice treated with 4 mg/kg of tacrolimus; no treatment vs. 4 mg/kg tacrolimus, P<0.05). Treatment with 4 mg/kg but not 2 mg/kg of tacrolimus resulted in a significant increase in the levels of expression of TGF-beta(1) mRNA and circulating levels of TGF-beta(1) protein.

CONCLUSIONS

Tacrolimus has a dose-dependent effect on tumor progression and TGF-beta(1) expression, and tacrolimus-induced TGF-beta(1) overexpression may be a pathogenetic mechanism in tumor progression.

TH1 and TH2 cytokine inhibition by 3,5-bis(trifluoromethyl)pyrazoles, a novel class of immunomodulators

In order to discover novel immunomodulators for application in treating autoimmune diseases, a stable Jurkat transfectant was constructed in which luciferase reporter gene is driven by a full-length IL-2 promotor. A chemical library was screened to identify compounds that inhibited luciferase expression in Jurkat transfectants stimulated with PMA and ionomycin. A class of compounds (bis-trifluoromethyl pyrazole, BTPs) was identified from this screen. BTPs were shown to inhibit anti-CD3 and anti-CD28 antibody-induced IL-2 secretion, mixed lymphocyte reaction, and Con A-induced T cell proliferation in normal human peripheral blood T cells. In addition, mRNA levels of IL-4, IL-5, IL-9, IL-10, IL-13, IL-15, and IFN-gamma were markedly inhibited by BTPs in peripheral blood mononuclear cells stimulated by Con A as determined by multi-probe RNA protection assay. Furthermore, IL-2, IL-4, IL-5, and IFN-gamma secretion by Hut 78 cells or CD3(+) T cells stimulated with PMA plus ionomycin or anti-CD3 antibody plus PMA were inhibited in a concentration-dependent manner by BTPs. Therefore, BTPs inhibit a wide spectrum of cytokine production including TH1 and TH2 type cytokines. Taken together, these compounds may be useful for treating autoimmune diseases and organ transplant rejection.

Conventional immunosuppression and co-stimulation blockade

Organ transplantation has become an accepted and successful therapeutic intervention for many patients with end-stage organ disease. Current conventional immunosuppressive regimens achieve very good short-term allograft survival but long-term outcomes are less than adequate. Furthermore, non-specific immunosuppression has its attendant side-effects including increased risks of malignancy and infection as well as drug-specific sequellae. With recent advances in the field of immunology, promising new therapies have arisen that could potentially eliminate lifelong drug therapy and promote indefinite acceptance of the donor tissue. Identification of co-stimulatory signals essential for T-cell activation has provided exciting new possibilities for controlling the alloimmune response. The compatibility of these new agents with proven conventional therapeutics has yielded mixed results. When used in combination, their immunosuppressive properties appear synergistic. However, if the goal of therapy is sustained, specific T-cell hyporesponsiveness, many conventional agents antagonize the effects of co-stimulatory blockade in several immune tolerance models.

Cross talk among calcineurin, Sp1/Sp3, and NFAT in control of p21(WAF1/CIP1) expression in keratinocyte differentiation

Calcium functions as a trigger for the switch between epithelial cell growth and differentiation. We report here that the calcium/calmodulin-dependent phosphatase calcineurin is involved in this process. Treatment of primary mouse keratinocytes with cyclosporin A, an inhibitor of calcineurin activity, suppresses the expression of terminal differentiation markers and of p21(WAF1/Cip1) and p27(KIP1), two cyclin-dependent kinase inhibitors that are usually induced with differentiation. In parallel with down-modulation of the endogenous genes, suppression of calcineurin function blocks induction of the promoters for the p21(WAF1/Cip1) and loricrin differentiation marker genes, whereas activity of these promoters is enhanced by calcineurin overexpression. The calcineurin- responsive region of the p21 promoter maps to a 78-bp Sp1/Sp3-binding sequence next to the TATA box, and calcineurin induces activity of the p21 promoter through Sp1/Sp3-dependent transcription. We find that the endogenous NFAT-1 and -2 transcription factors, major downstream targets of calcineurin, associate with Sp1 in keratinocytes in a calcineurin-dependent manner, and calcineurin up-regulates Sp1/Sp3-dependent transcription and p21 promoter activity in synergism with NFAT1/2. Thus, our study reveals an important role for calcineurin in control of keratinocyte differentiation and p21 expression, and points to a so-far-unsuspected interconnection among this phosphatase, NFATs, and Sp1/Sp3-dependent transcription.

Tacrolimus suppressed the production of cytokines involved in atopic dermatitis by direct stimulation of human PBMC system. (Comparison with steroids)

Tacrolimus (FK506) ointment showed remarkable efficacy against atopic dermatitis in animal models and clinical trials. The suppressive effect of tacrolimus on the production of the cytokines involved in atopic dermatitis (IL-2, IL-3, IL-4, IL-5, IFN-gamma and GM-CSF) from human peripheral blood mononuclear cells (PBMC) was investigated. We constructed a new cytokine production system in which T cells are activated by direct stimulation in vitro with anti-CD3/CD2 or anti-CD3/CD28 antibody combination. Tacrolimus inhibited the production of these cytokines by both stimulations. In a comparative study with steroids (alclometasone dipropionate and betamethason valerate) in anti-CD3/CD2 system, tacrolimus and both steroids inhibited Th1 cytokines (IL-2, IFN-gamma), Th2 cytokines (IL-4, IL-5) and IL-3, GM-CSF (produced by both Th1 and Th2). The suppressive effect of tacrolimus on cytokine production was stronger than that of alclometasone dipropionate and equal to or stronger than that of betamethason valerate. The effective dose of tacrolimus (IC50, 0.02-0.11 ng/ml) is almost the same as for Th1 and Th2 cytokines, and 1 ng/ml of tacrolimus suppressed all cytokines completely. These results suggest that tacrolimus suppresses the allergic cytokines from T cells, and that tacrolimus ointment is effective against atopic dermatitis through the inhibition of cytokine production.

Calcineurin: form and function

Calcineurin is a eukaryotic Ca(2+)- and calmodulin-dependent serine/threonine protein phosphatase. It is a heterodimeric protein consisting of a catalytic subunit calcineurin A, which contains an active site dinuclear metal center, and a tightly associated, myristoylated, Ca(2+)-binding subunit, calcineurin B. The primary sequence of both subunits and heterodimeric quaternary structure is highly conserved from yeast to mammals. As a serine/threonine protein phosphatase, calcineurin participates in a number of cellular processes and Ca(2+)-dependent signal transduction pathways. Calcineurin is potently inhibited by immunosuppressant drugs, cyclosporin A and FK506, in the presence of their respective cytoplasmic immunophilin proteins, cyclophilin and FK506-binding protein. Many studies have used these immunosuppressant drugs and/or modern genetic techniques to disrupt calcineurin in model organisms such as yeast, filamentous fungi, plants, vertebrates, and mammals to explore its biological function. Recent advances regarding calcineurin structure include the determination of its three-dimensional structure. In addition, biochemical and spectroscopic studies are beginning to unravel aspects of the mechanism of phosphate ester hydrolysis including the importance of the dinuclear metal ion cofactor and metal ion redox chemistry, studies which may lead to new calcineurin inhibitors. This review provides a comprehensive examination of the biological roles of calcineurin and reviews aspects related to its structure and catalytic mechanism.

Structural basis for selective inhibition of Src family kinases by PP1

BACKGROUND

Small-molecule inhibitors that can target individual kinases are powerful tools for use in signal transduction research. It is difficult to find such compounds because of the enormous number of protein kinases and the highly conserved nature of their catalytic domains. Recently, a novel, potent, Src family selective tyrosine kinase inhibitor was reported (PP1). Here, we study the structural basis for this inhibitor's specificity for Src family kinases.

RESULTS

A single residue corresponding to Ile338 (v-Src numbering; Thr338 in c-Src) in Src family tyrosine kinases largely controls PP1's ability to inhibit protein kinases. Mutation of Ile338 to a larger residue such as methionine or phenylalanine in v-Src makes this inhibitor less potent. Conversely, mutation of Ile338 to alanine or glycine increases PP1's potency. PP1 can inhibit Ser/Thr kinases if the residue corresponding to Ile338 in v-Src is mutated to glycine. We have accurately predicted several non-Src family kinases that are moderately (IC(50) approximately 1 microM) inhibited by PP1, including c-Abl and the MAP kinase p38.

CONCLUSIONS

Our mutagenesis studies of the ATP-binding site in both tyrosine kinases and Ser/Thr kinases explain why PP1 is a specific inhibitor of Src family tyrosine kinases. Determination of the structural basis of inhibitor specificity will aid in the design of more potent and more selective protein kinase inhibitors. The ability to desensitize a particular kinase to PP1 inhibition of residue 338 or conversely to sensitize a kinase to PP1 inhibition by mutation should provide a useful basis for chemical genetic studies of kinase signal transduction.

Effects of FK506 in rat and human resistance arteries

BACKGROUND

FK506 is widely used in organ transplantation and causes hypertension. However, little is known about the impact of the drug on the cardiovascular system.

METHODS

We therefore investigated the effect of FK506 on resistance artery and blood pressure responsiveness to vasoconstrictors and vasodilators. Studies were conducted in vitro using human and murine resistance artery, ex vivo in resistance artery isolated from rats treated with FK506 (6 mg/kg/day), and in vivo in conscious, treated animals.

RESULTS

In vitro exposure (24 hr) of human and rat resistance artery to FK506 (1000 ng/ml) increased the sensitivity to norepinephrine (NE) and impaired the response to acetylcholine (Ach) and sodium nitroprusside (SNp). In contrast, arteries isolated from rats given FK506 for eight days showed a reduced sensitivity to NE (P < 0.05) and a normal endothelium-dependent relaxation. Their incubation with L-arginine caused a significant reduction in Ach sensitivity in the FK506 group (P < 0.05) but not in controls, suggesting enhancement of nitric oxide production by the drug. The sensitivity to SNp was reduced, as in the in vitro experiments (P < 0.05). Rats given FK506 for eight days presented blood pressure similar to that in controls but also presented signs of a compensatory response to excess vasodilation: tachycardia (P < 0.01), reduced blood pressure sensitivity to NE and Ach, blunted heart rate response to both agonists, and exaggerated hypotension at high doses of Ach. After 21 days of treatment, blood pressure remained similar to that in controls, but resistance artery showed further functional deterioration, with significant impairment of the maximum responses to Ach and to SNp.

CONCLUSION

FK506 presents significant vascular toxicity affecting mainly smooth muscle relaxation and alters vascular hemodynamics. The data suggest that similar cardiovascular changes may occur in transplant patients and represent the forerunner of hypertension often seen with more prolonged use of the drug.

Ex vivo assessment of immunosuppression in undiluted whole blood from pigs dosed with tacrolimus (FK506)

To assess the duration of immunosuppression in FK506-dosed pigs, an undiluted whole blood assay was established to measure reactivities of T cells in their physiological milieu. PMA and ionomycin were shown to induce IL-2 production in swine blood. The IC50 of FK506 in inhibiting IL-2 production in whole blood and isolated PBMC stimulated with PMA and ionomycin measured 1.2 and 0.04 nM, respectively. These data underscore the influence of red blood cells and plasma proteins on drug potency. IL-2 levels were determined in blood drawn immediately before and 1, 24, 48, and 72 h after iv dosing. For pigs dosed with 0.05 mg/kg, 50% recovery of IL-2 production was observed at 16 h and 100% at 35 h after dosing. For pigs dosed with 0.15 mg/kg, 50% recovery was observed at 38 h and 100% at 72 h. Blood concentrations of FK506 at 50 and 100% recovery of IL-2 production measured 10.8 and 2.2 nM for pigs dosed with 0.05 mg/kg and 6.1 and 1.1 nM for pigs dosed with 0.15 mg/kg, respectively. These concentrations are severalfold higher than predicted from the IC50 of FK506 for inhibiting IL-2 production in the whole blood assay. These data suggest that the true potency of FK506 in blood after dosing is influenced by additional factors, which could include plasma protein binding, the presence of active or interfering metabolites, serum interfering factors, and sequestration of drug in blood cells. Our results demonstrate the utility of an undiluted whole blood assay for assessing the duration of immunosuppression in drug-dosed animals and emphasize the importance of assessing drug potency in the whole blood environment ex vivo.

Cellular immune defect caused by postsurgical radiation therapy in patients with head and neck cancer

The effects of locoregional postoperative radiation therapy (60 Gy on average) on cellular immunity were investigated in 11 patients with squamocellular carcinomas of the oral cavity, pharynx, or larynx. During radiation treatment, the total lymphocyte counts, CD8+ T-lymphocyte count, and especially CD4+ T-lymphocyte count decreased significantly. The mean CD4+ T-lymphocyte counts dropped from an average of 739/microl to 183/microl (p <0.001), and the CD4+/CD8+ quotient also decreased significantly. Not only the lymphocyte counts but also the in vitro lymphocyte stimulation responses to several mitogens decreased, with reductions averaging 10% to 50% of normal responses by the end of radiation therapy. Within 3 to 4 weeks after radiation therapy, the CD4+ T-lymphocyte counts and the in vitro lymphocyte stimulation responses showed a tendency toward normalization. This study shows that postoperative locoregional radiation therapy in patients with head and neck cancer induces a severe generalized impairment of cellular immunity.