Immunosuppressive agents: recent developments in molecular action and clinical application

Modified tectonic corneoscleral graft technique for treating devastating corneoscleral infections

BACKGROUND

This study aims to evaluate the clinical outcomes and efficacy of a modified tectonic corneoscleral graft (TCG) in patients suffering from devastating corneoscleral infections.

METHODS

Thirty-eight eyes from 38 patients who underwent the modified TCG were included in this study. The outcomes measured were recurrence rates, best-corrected visual acuity (BCVA), ocular surface stability, postoperative complications, and graft survival.

RESULTS

Among the 38 patients, 23 had fungal infections, 9 had bacterial infections and 6 had Pythium insidiosum infections. At the final follow-up, with an average duration of 25.1 ± 8.6 months, the rate of monocular blindness decreased from 100 to 58%. Significant improvements in LogMAR BCVA were observed from preoperative to postoperative measurements (P < 0.001). Thirty-two eyes (84.2%) maintained a stable ocular surface. The survival rate of ocular surface stability was 84.2%±5.9% at one year and 57.7%±9.7% at three years post-surgery. Twenty eyes (52.6%) retained a clear graft, with a survival rate for graft clarity was 81.6%±6.3% at one year and 36.0%±10.8% at three years post-surgery. The incidence of immune rejection was 36.8%. Corneal epithelial defects were observed in ten patients, and choroidal detachment occurred in four patients. No cases of elevated intraocular pressure were detected.

CONCLUSIONS

The modified TCG is effective in eradicating infections, preserving the eyeball, and maintaining useful vision in cases of devastating corneoscleral infections. Regular use of tacrolimus, timely administration of glucocorticoids, and good patient compliance can help mitigate postoperative challenges.

Systemic immunosuppressive therapies for uveitis in developing countries

There are multiple approaches to inhibit inflammatory molecules and pathways in noninfectious uveitis. The cornerstone of local and systemic anti-inflammatory treatment is corticosteroid therapy. Corticosteroids remain the most potent and efficacious drugs for treating intraocular inflammation. However, their long-term use is limited by their medium- and long-term side effects, which are a major concern. The approach taken to limit corticosteroid side effects is to introduce steroid-sparing agents that suppress the inflammatory pathways and immune response differently than corticosteroids. There are several classes of such drugs that are affordable, effective, and generally well-tolerated. Relatively recently, an increasing range of biologic agents has become available to treat intraocular inflammation. However, the relatively expensive cost of these therapies limits their use in the developing world. This systemic review aimst to discuss the use of corticosteroids and different immunosuppressive regimens in the management of various uveitides.

The Effective Treatment with Cyclosporine of a Ulcerative Colitis Patient with Concurrent Idiopathic Thrombocytopenic Purpura Who Subsequently Developed Spontaneous Pneumomediastinum

Although extraintestinal manifestations of inflammatory bowel diseases are not uncommon, few reports have described concurrent idiopathic thrombocytopenic purpura (ITP). Spontaneous pneumomediastinum is also a rare complication of ulcerative colitis (UC). This report describes the case of a 14-year-old boy who experienced recurrent ulcerative colitis 3 months after temporary improvement following treatment with prednisolone (20 mg/day) and granulocyte/monocyte adsorption apheresis. His platelet counts decreased, suggesting ITP. The dosage of prednisolone was increased to 60 mg/day; however, his thrombocytopenia did not improve and he suddenly developed pneumomediastinum. A continuous infusion of cyclosporine increased his platelet counts and improved his ulcerative colitis. Cyclosporine should be considered when steroid-resistant ITP accompanies UC.

Biosynthesis, regulation, and engineering of a linear polyketide tautomycetin: a novel immunosuppressant in Streptomyces sp. CK4412

Tautomycetin (TMC) is a natural product with a linear structure that includes an ester bond connecting a dialkylmaleic moiety to a type I polyketide chain. Although TMC was originally identified as an antifungal antibiotic in the late 1980s, follow-up studies revealed its novel immunosuppressant activity. Specifically, TMC exhibited a mechanistically unique immunosuppressant activity about 100 times higher than that of cyclosporine A, a widely used immunosuppressant drug. Interestingly, a structurally close relative, tautomycin (TTM), was reported to not possess TMC-like immunosuppressant activity, suggesting that a distinctive polyketide moiety of TMC plays a critical role in immunosuppressant activity. Cloning and engineering of a TMC polyketide biosynthetic gene cluster generated several derivatives showing different biological activities. TMC was also found to be biosynthesized as a linear structure without forming a lactone ring, unlike the most polyketide-based compounds, implying the presence of a unique polyketide thioesterase in the cluster. Although TMC biosynthesis was limited due to its tight regulation by two pathway-specific regulatory genes located in the cluster, its production was significantly stimulated through homologous and heterologous expression of its entire biosynthetic gene cluster using a Streptomyces artificial chromosome vector system. In this mini-review, we summarize recent advances in the biosynthesis, regulation, and pathway engineering of a linear polyketide, TMC, in Streptomyces sp. CK4412.

Steroid-resistant protein-losing gastroenteropathy complicated with Sjögren's syndrome successfully treated with mizoribine

A 64-year-old woman with leg edema was diagnosed with protein-losing gastroenteropathy and Sjögren's syndrome. Central venous nutrition led to infection of her catheter, ascites, and deep vein thrombosis. Following successful treatment of these conditions with antibiotics and anticoagulants, she was treated unsuccessfully with prednisolone and steroid pulse therapy. Mizoribine add-on markedly reduced edema and normalized serum albumin. This is the first report of a steroid-resistant protein-losing gastroenteropathy patient with Sjögren's syndrome successfully treated with mizoribine.

Synergistic Inhibition of Tumor Necrosis Factor-Alpha-Stimulated Pro-Inflammatory Cytokine Expression in HaCaT Cells by a Combination of Rapamycin and Mycophenolic Acid

Background

Keratinocytes release various pro-inflammatory cytokines, chemokines, and adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1) in response to cytokines such as tumor necrosis factor (TNF)-α and interferon (IFN)-γ. Rapamycin and mycophenolic acid (MPA) have potent immunosuppressive activity because they inhibit lymphocyte proliferation.

Objective

We investigated the effects of rapamycin and MPA on the expression of inflammation-related factors such as ICAM-1 and inducible nitric oxide synthase (iNOS), pro-inflammatory cytokines and chemokines, and related signaling pathways in TNF-α-stimulated HaCaT cells.

Methods

The viability of HaCaT cells treated with rapamycin and MPA was confirmed using MTT assay. The expression of various cytokines such as interleukin (IL)-1β, IL-6, and IL-8; inflammation-related factors such as ICAM-1 and iNOS; and the activation of mitogen activated protein kinase (MAPK) signaling pathways mediated by extracellular signal-related kinases (ERK), p38, and c-Jun N-terminal kinases (JNK) in TNF-α-stimulated HaCaT cells were confirmed using reverse transcription-polymerase chain reaction and western blotting.

Results

Combined treatment of TNF-α-induced HaCaT cells with rapamycin and MPA decreased ICAM-1 and iNOS expression and ERK and p38 activation more than treatment with either drug alone. The most significant decrease was observed with a combination of rapamycin (80 nM) and MPA (20 nM). These results show that co-treatment with these agents has a synergistic anti-inflammatory effect by blocking the activation of the ERK/p38 MAPK signaling pathway and thus suppressing the TNF-α-induced expression of ICAM-1 and iNOS.

Conclusion

The combination of rapamycin and MPA could potentially be used as a therapeutic approach in inflammatory skin diseases.

Prodigiosin alkaloids: recent advancements in total synthesis and their biological potential

The present review article is focused on the medicinal potential and total synthesis of prodigiosins witnessed in the last decade. The aim will be to provide an inspiration to the marvels and pit falls of constructing the polypyrrole heterocycles with in the complex systems.

Systemic treatments for noninfectious vitreous inflammation

Vitreous inflammation, or vitritis, may result from many causes, including both infectious and noninfectious, including rheumatologic and autoimmune processes. Vitritis is commonly vision threatening and has serious sequelae. Treatment is frequently challenging, but, today, there are multiple methods of systemic treatment for vitritis. These categories include corticosteroids, antimetabolites, alkylating agents, T-cell inhibitors/calcineurin inhibitors, and biologic agents. These treatment categories were reviewed last year, but, even over the course of just a year, many therapies have made progress, as we have learned more about their indications and efficacy. We discuss here discoveries made over the past year on both existing and new drugs, as well as reviewing mechanisms of action, clinical dosages, specific conditions that are treated, adverse effects, and usual course of treatment for each class of therapy.

Mizoribine as a safe and effective combined maintenance therapy with prednisolone for anti-neutrophil cytoplasmic antibody-associated vasculitis in a hemodialysis patient

A 77-year-old man developed severe renal insufficiency due to proteinase 3 anti-neutrophil cytoplasmic antibody (PR3-ANCA)-associated vasculitis, and was started on hemodialysis (HD). Because his renal insufficiency appeared to be irreversible, he was maintained on oral prednisolone (PSL) at 5 mg/day. However, a disease flare-up with alveolar hemorrhage occurred. Serology revealed elevated levels of PR3-ANCA and C-reactive protein (CRP). The patient was given pulse therapy with a quarter dose of methylprednisolone (m-PSL) (250 mg, 3 days), followed by oral PSL at 15 mg/day. As a supplemental treatment, he was given 25 mg of mizoribine (MZR) immediately after each HD session. Subsequently, the levels of PR3-ANCA and CRP decreased, and the alveolar hemorrhage resolved. The dose of MZR to be given was determined by measuring the patient's serum concentrations of MZR at various time points after the HD session. The maintenance dose of MZR was finally set at 50 mg. At present, the oral PSL dosage has been tapered to 10 mg/day, and the patient has achieved a state of remission without any side effects.

Predictive value of the Pediatric Ulcerative Colitis Activity Index in the surgical management of ulcerative colitis

PURPOSE

The primary purpose of this study was to investigate the relationship between Pediatric Ulcerative Colitis Activity Index (PUCAI) and operative management. We also specifically evaluated those patients receiving tacrolimus for their disease.

METHODS

A retrospective review (1/06-1/11) identified ulcerative colitis patients (≤21 years old) undergoing restorative proctocolectomy with rectal mucosectomy and ileal pouch-anal anastomosis. Main outcomes included pre-operative PUCAI, combined versus staged procedure, and postoperative complications. Patients receiving tacrolimus within 3 months of surgical intervention were identified. PUCAI at tacrolimus induction and medication side effects were also noted.

RESULTS

Sixty patients were identified. Forty-two (70%) underwent combined and 18 (30%) had staged procedures. Pre-operative PUCAI was lower for combined versus staged patients (p = < 0.001). Furthermore, a higher pre-operative PUCAI strongly correlated with the likelihood of undergoing a staged procedure (p < 0.001). Forty-four patients (73%) received tacrolimus. Significant improvement in their PUCAI was noted from induction to pre-operative evaluation (p < 0.001). Minor and reversible side effects occurred in 46% of patients receiving tacrolimus, but complication rates were not significantly different.

CONCLUSIONS

There is a very strong correlation between the PUCAI and the likelihood of undergoing a staged procedure. A significant improvement in PUCAI occurs following preoperative tacrolimus therapy.

Pharmacogenetics of drugs used in the treatment of ocular inflammatory diseases

INTRODUCTION

Ocular inflammatory diseases comprise uveitis, scleritis, and inflammation of adjacent structures of the eye. Therapy may be challenging and often involves corticosteroids and immunomodulatory agents.

AREAS COVERED

This review describes the genes involved in noninfectious ocular inflammatory diseases and focuses on pharmacogenetic studies regarding different classes of anti-inflammatory drugs used in the management of uveitis, including corticosteroids, antimetabolites, calcineurin inhibitors, alkylating agents, and biological agents.

EXPERT OPINION

Pharmacogenetics holds the promise of a personalized medicine with potential to customize treatment that can achieve the best clinical response and avoid toxicity. Several polymorphisms in various genes involved in the metabolism of drugs commonly utilized in the treatment of ocular inflammatory diseases have been described. Most promising is the polymorphism in thiopurinemethyltransferase gene for which a genotype analysis can reveal slow metabolizers of azathioprine and help avoid serious drug toxicity. Although pharmacogenetic studies with specific focus on ocular inflammatory diseases are lacking, knowledge from studies in rheumatologic diseases and transplant medicine can provide a platform for future research. Prospective clinical studies are needed to determine the clinical significance of such polymorphisms and their true effect on drug metabolism and side effects.

Pharmacotherapy of scleritis: current paradigms and future directions

INTRODUCTION

Scleritis is an inflammatory condition affecting the eye wall that may be associated with a number of systemic inflammatory diseases. Because scleritis can be refractory to standard treatment, knowledge of the body of available and emerging therapies is paramount and is reviewed here.

AREAS COVERED

This review focuses on both traditional and emerging therapies for noninfectious scleritis. The authors cover the mechanisms of action and potential adverse effects of each of the treatment modalities. In addition, a summary of the significant MEDLINE indexed literature under the subject heading 'scleritis', 'treatment', 'immunomodulator' will be provided on each therapy, including commentary on appropriate use and relative contraindications. Novel treatments and potential drug candidates that are currently being evaluated in clinical trials with therapeutic potential will also be reviewed.

EXPERT OPINION

While oral nonsteroidal anti-inflammatory drugs and oral corticosteroids are widely used, effective, first-line agents for inflammatory scleritis, refractory cases require antimetabolites, T-cell inhibitors, or biologic response modifiers. In particular, there is emerging evidence for the use of targeted biologic response modifiers, and potentially, for local drug delivery.

Systemic treatment of vitreous inflammation

Non infectious vitreous inflammation is often vision threatening and can be associated with potentially life-threatening systemic conditions. Treatment is often challenging as it involves systemic medications that can be associated with adverse effects. The classes of drugs are ever expanding and include corticosteroids, antimetabolites, alkylating agents, T-cell and calcineurin agents, biologic agents, and interferons. Each class of systemic therapy for non-infectious vitreous inflammation is reviewed. We discuss the mechanisms of action, usual clinical dosages, the specific conditions that are treated, the adverse effects, and usual course of treatment for each class of therapy.

Effects of immunosuppressive therapy on wound healing

Immunosuppressive therapy is increasingly being used in clinical practice and has been shown to affect wound healing to varying degrees. This article looks at the effects of the newer immunosuppressive agents on wound healing. It is shown that wound healing is impaired via different mechanisms. Some of the animal and human studies are reviewed in more detail. It is shown that some of the newer agents affect wound healing to such an extent that reduction or avoidance of these drugs until complete wound healing is achieved is advocated. More research is required for these newer agents to determine the most appropriate time to introduce them.

SHP2 is a target of the immunosuppressant tautomycetin

SHP2 phosphatase is a positive transducer of growth factor and cytokine signaling. SHP2 is also a bona fide oncogene; gain-of-function SHP2 mutations leading to increased phosphatase activity cause Noonan syndrome, as well as multiple forms of leukemia and solid tumors. We report that tautomycetin (TTN), an immunosuppressor in organ transplantation, and its engineered analog TTN D-1 are potent SHP2 inhibitors. TTN and TTN D-1 block T cell receptor-mediated tyrosine phosphorylation and ERK activation and gain-of-function mutant SHP2-induced hematopoietic progenitor hyperproliferation and monocytic differentiation. Crystal structure of the SHP2⋅TTN D-1 complex reveals that TTN D-1 occupies the SHP2 active site in a manner similar to that of a peptide substrate. Collectively, the data support the notion that SHP2 is a cellular target for TTN and provide a potential mechanism for the immunosuppressive activity of TTN. Moreover, the structure furnishes molecular insights upon which therapeutics targeting SHP2 can be developed on the basis of the TTN scaffold.

Cryopreservation and the age of the allotransplant

For centuries, reconstructive surgeons have restored form and function with autografts. These techniques are highly effective, but they are associated invariably with donor site morbidity. To avoid this, surgeons have long dreamed of using cadaveric sources for reconstructive material. However, allografts have two major limitations: rejection and limited donor tissue. In order to limit rejection, the allograft must be rendered more tolerable to the host or the host must be rendered more tolerant of the allograft. Both strategies have been used with considerable success in recent years. As understanding of the human immune response increases, clinical immunosuppressive regimens will undoubtedly become less morbid, and the indications for allotransplantation will broaden. This will place an even greater burden on the already small donor pool. One way to relieve this burden would be through the development of strategies for the long-term preservation of donated tissues and organs. Cryopreservation has been used clinically for decades, and recent advances in the field have allowed the preservation of an ever widening array of tissues and organs. As cold storage has been shown to reduce the antigenicity of parts, cryopreservation may actually serve to improve the survival rate of transplanted parts, as well as increase their availability. As the era of autotransplantation gives way to the age of allotransplantation, cryopreservation will play an increasingly important role.

[Hepatotoxicity induced by new immunosuppressants]

Immunosuppressants are among the pharmacological agents with the greatest potential to cause adverse reactions, although induction of hepatotoxicity is paradoxical from the pathogenic point of view, since the response of the innate and acquired immune system is a key element in the chain of events leading to chemical liver damage. Hepatotoxicity induced by immunosuppressants is difficult to evaluate since these drugs are sometimes used to treat liver diseases, or in combination with other drugs that can also cause hepatotoxicity, or in the context of liver transplantation, in which rejection or biliary complications can act as confounding factors. In addition, immunosuppressant therapy can favor the development of infections, which by themselves can cause liver damage, or reactivate latent chronic viral hepatitis. Corticosteroids and calcineurin inhibitors only exceptionally cause hepatotoxicity. Methotrexate at high doses and in patients with risk factors can induce advanced fibrosis and cirrhosis. Thiopurine agents can cause a spectrum of hepatic lesions, including hepatocellular of cholestatic lesions, and hepatic vascular alterations. Leflunomide has high hepatotoxic potential, especially when combined with methotrexate. Anti-tumor necrosis factor-alpha agents have rarely been associated with hepatotoxicity, often with detectable autoantibodies, and most of the reactions - some severe - have been linked to infliximab, especially when used in patients with rheumatological diseases.

Neuropilin-1 expression on regulatory T cells enhances their interactions with dendritic cells during antigen recognition

The interaction of T cells with dendritic cells (DCs) determines whether an immune response is launched or not. Recognition of antigen leads to formation of immunological synapses at the interface between the cells. The length of interaction is likely to determine the functional outcome, because it limits the number of MHC class II-peptide complexes that can be recruited into the synapse. Here, we show that regulatory T (Treg) cells and naive helper T (Th) cells interact differently with DCs in the absence of proinflammatory stimuli. Although differences in T cell receptor repertoire might contribute, Foxp3-induced phenotypic differences play a major role. We found that Neuropilin-1 (Nrp-1), which is expressed by most Treg cells but not naive Th cells, promoted prolonged interactions with immature DCs (iDCs), resulting in higher sensitivity to limiting amounts of antigen. This is likely to give Treg cells an advantage over naive Th cells, with the same specificity leading to a "default" suppression of immune responses in the absence of "danger signals."

Basics of immune responses in transplantation in preparation for application of composite tissue allografts in plastic and reconstructive surgery: part I

Currently, composite tissue allografts are applied only occasionally as a reconstructive option in the field of plastic and reconstructive surgery. Composite tissue allografts offer a unique potential for coverage of large multitissue defects. However, compared with the relatively homogenous tissue of solid organ transplants, the heterogenicity of tissue components of composite tissue allografts may generate high immunologic responses. Modern immunosuppressive agents significantly improve successful allograft acceptance. However, chronic allograft rejection and immunosuppressive drug toxicity are still major problems in the clinical practice of transplantation. The major goals of transplantation immunology are (1) to develop tolerance to allograft transplants and (2) long-term drug-free survival. A number of experimental protocols were designed to develop tolerance; however, none of them has been proven to induce tolerance in clinical transplantation. In this article, the authors outline the mechanisms of allograft acceptance and rejection and barriers to transplantation tolerance. Novel immunosuppressive protocols are discussed in this review. This basic immunologic knowledge of allograft acceptance and rejection will allow plastic surgeons to apply composite tissue allograft transplants to plastic and reconstructive surgery.

Pouch outcomes among children with ulcerative colitis treated with calcineurin inhibitors before ileal pouch anal anastomosis surgery

PURPOSE

The purpose of this article is to describe the outcomes of the pouches of 14 children with ulcerative colitis (UC) who were pretreated with calcineurin inhibitors before they underwent their ileal pouch anal anastomosis (IPAA) surgery.

METHODS

An institutional review board-approved retrospective review of the charts of consecutive patients with UC treated with calcineurin inhibitors before undergoing IPAA surgery at a tertiary pediatric center between 1998 and 2003 was performed. The primary endpoint was pouch outcome after at least 2 years of follow-up (healthy pouch, acute pouchitis, chronic refractory pouchitis, or pouch failure); the secondary endpoints were early postoperative complications, number of stages, and time between stages.

RESULTS

Fourteen of 53 consecutive patients who underwent IPAA for UC were treated with calcineurin inhibitors before their surgery (26%; 6 with cyclosporine and 8 with tacrolimus). All 14 patients were concomitantly treated with systemic steroids. Ten patients (71%) were also taking 6-mercaptopurine or azathioprine, and 9 (64%) were also taking mesalamine. Three patients (21%) had healthy pouches with no clinical evidence of pouchitis, 6 (43%) had at least one episode of acute pouchitis (average of 2 episodes per year), 3 (21%) had chronic relapsing pouchitis, and 2 (14%) were later determined to have Crohn's disease. There was no pouch failure. Two patients (14%) had an early postoperative complication (intraabdominal abscess, anastomotic stricture). Five patients (36%) had a 2-staged procedure, and 8 (64%) had a 3-staged procedure. For the 2-staged procedures, the mean time between the first and second stages was 3.14 months (range, 3-4 months). For the 3-staged procedures, the mean time between the first and second stages was 4.25 months (range, 2-6 months) and that between the second and third stages was 4 months (range, 2.5-6 months).

CONCLUSIONS

In this series, chronic pouchitis was an infrequent complication among children who were pretreated with calcineurin inhibitors. Calcineurin inhibitor use did not lead to or portend increased early postoperative complications or affect the number or duration of surgical stages. Further studies are required to determine if preoperative calcineurin inhibitors improve pouch outcomes or facilitate the performance of 2-staged procedures.

Marked erythrocyte microcytosis under primary immunosuppression with sirolimus

The preliminary observation of marked erythrocyte microcytosis in patients treated with sirolimus (SRL) and mycophenolate mofetil (MMF) has been evaluated as part of a prospective study comparing SRL and cyclosporin A (CsA) as a primary immunosuppressant. Normal risk de novo kidney recipients were randomized either to SRL or to CsA. Additional immunosuppressants consisted of MMF and prednisone. In patients with erythrocyte microcytosis, iron deficiency was excluded by measuring serum ferritin and transferrin saturation rate. Fifty-nine patients (30 in SRL and 29 in CsA) were included. Mean corpuscular volume (MCV) (fl) on day 7 was 91.7 +/- 4.8 in SRL group versus 91.4 +/- 4.2 in CsA group (P = 0.77), whereas mean MCV on day 183 post-transplant was 78.5 +/- 3.8 in SRL group versus 88.4 +/- 3.4 in CsA group (P < 0.0001). Hemoglobin concentration (g/dl) was not significantly different. Only two patients in SRL group presented decreased transferrin saturation rate. Marked erythrocyte microcytosis without persistent anemia was observed in patients treated with SRL and MMF.

Review article: practical management of inflammatory bowel disease patients taking immunomodulators

Azathioprine, mercaptopurine, methotrexate, ciclosporin and tacrolimus all have their respective niches in the treatment of inflammatory bowel disease. These immunomodulators are potent and effective medications; however, they potentially have serious toxicity. To maximize benefit and minimize risk, clinicians must understand the mechanism of action, appropriate indications, range of toxicity and proper dosing of these medications. Furthermore, once initiating therapy, patients need to be monitored appropriately for evidence of efficacy and toxicity. This review includes the rationale behind recommendations for the management and monitoring of patients using immunomodulators. For the purine antagonists--azathioprine and mercaptopurine--the evidence for utility of thiopurine methyltransferase testing and mercaptopurine metabolite monitoring is addressed. The roles of liver biopsy and screening for methylenetetrahydrofolate reductase mutations in patients taking methotrexate are reviewed. With appropriate monitoring, the calcineurin inhibitors--ciclosporin and tacrolimus--can be used safely and effectively. Immunomodulators are important agents for the treatment of Crohn's disease and ulcerative colitis, and prescribing clinicians should be comfortable recognizing both their value and their limitations.

Application of real-time PCR for testing antiviral compounds against Lassa virus, SARS coronavirus and Ebola virus in vitro

This report describes the application of real-time PCR for testing antivirals against highly pathogenic viruses such as Lassa virus, SARS coronavirus and Ebola virus. The test combines classical cell culture with a quantitative real-time PCR read-out. The assay for Lassa virus was validated with ribavirin, which showed an IC(50) of 9 micrograms/ml. Small-scale screening identified a class of imidazole nucleoside/nucleotide analogues with antiviral activity against Lassa virus. The analogues contained either dinitrile or diester groups at the imidazole 4,5-positions, and many of which possessed an acyclic sugar or sugar phosphonate moiety at the imidazole 1-position. The IC(50) values of the most active compounds ranged from 5 to 21 micrograms/ml. The compounds also inhibited replication of SARS coronavirus and Ebola virus in analogous assays, although to a lesser extent than Lassa virus.

Regulation of T Lymphocyte Metabolism

Upon stimulation, lymphocytes develop from small resting cells into highly proliferative and secretory cells. Although a great deal of study has focused on the genetic program induced by Ag receptor signals, lymphocytes must also regulate their metabolic function to meet the energetic demands of activation. In this review, we discuss the changes in cellular metabolism that accompany lymphocyte activation, with a particular emphasis on glucose metabolism, a major source of both energy and biosynthetic building blocks. We will also cover the signaling pathways that positively and negatively regulate these changes to maintain metabolic homeostasis in cells that are rapidly growing, dividing, and differentiating.

Effect of conversion from cyclosporine A to mizoribine on transplant arteriosclerosis in rat aortic allograft models

Recent studies suggested that conversion from cyclosporine A (CsA) to antimetabolic agents protects allograft vasculopathy. However, the mechanism of this beneficial effect by the conversion therapy is not fully understood. In the present study, we investigated the effects of conversion from CsA to antimetabolic agent mizoribine (MZR) on the formation of transplant arteriosclerosis in rat aortic allografts. Conversion from CsA to MZR significantly prevented intimal hyperplasia and perivascular inflammatory cell infiltration at 28 days after aortic transplantation. These findings suggest that conversion therapy from CsA to antimetabolic agents might have therapeutic potential in transplant patients with chronic vascular rejection.

Randomized, double-blind comparison of 4 mg/kg versus 2 mg/kg intravenous cyclosporine in severe ulcerative colitis

BACKGROUND AND AIMS

Cyclosporine A is highly effective in severe attacks of ulcerative colitis (UC) but is associated with important adverse effects that are mainly dose dependent. Our single center, randomized, double-blind, controlled trial aimed to evaluate the additional clinical benefit of 4 mg/kg over 2 mg/kg IV cyclosporine in the acute treatment of severe UC.

METHODS

Primary end point was the proportion of patients with a clinical response. Secondary end points included time to response, colectomy rate, and adverse effects.

RESULTS

Seventy-three patients were included. Day-8 response rates were 84.2% (32 of 38, 4 mg/kg) and 85.7% (32 of 35, 2 mg/kg) after a median of 4 days in both groups. Short-term colectomy rates were 13.1% (4 mg/kg) and 8.6% (2 mg/kg). Mean cyclosporine blood levels were 237 +/- 33 in the 2-mg/kg group and 332 +/- 43 ng/mL in the 4-mg/kg group. Active smoking was inversely correlated with clinical response (odds ratio, 0.06), but concomitant azathioprine or steroids were not predictive. A trend toward a higher incidence of hypertension was observed in the 4-mg/kg group (23.7% vs. 8.6%, 2 mg/kg, P < 0.08).

CONCLUSIONS

High-dose IV cyclosporine has no additional clinical benefit over low dose in the treatment of severe UC. Although we did not observe differences in adverse effects on the short term, the use of 2 mg/kg IV cyclosporine should provide an improved toxicity profile for medical treatment of severe UC.

A pilot study on the use of the humanized anti-interleukin-2 receptor antibody daclizumab in active ulcerative colitis

OBJECTIVES

Medical therapy of refractory ulcerative colitis (UC) is associated with long-term side effects of cyclosporine and steroids. Because cyclosporine acts by inhibiting interleukin-2 (IL-2) production, we studied the efficacy and safety of humanized anti-IL2 receptor (CD25) antibodies daclizumab for refractory UC in an open label pilot study.

METHODS

Ten patients with chronically active UC received daclizumab, 1 mg/kg i.v. twice with a 4-wk interval. Clinical, endoscopic, and histological evaluation was scored at regular intervals. CD25 immunohistochemistry was followed in mucosal biopsies. The primary study endpoint was clinical improvement at wk 8.

RESULTS

Nine of 10 patients completed the study. The median clinical activity score decreased from a median of 8 (95% CI = 7.2-9.2) at baseline to 3.5 (95% CI = 1.4-4.9) at wk 8 (p < 0.005). Endoscopic scores were significantly decreased at wk 8 (wk 0: 8, 95% CI = 6.3-8.5; wk 8: 5.0, 95% CI = 2.6-6.3; p < 0.01). Mucosal biopsies showed a significant decrease in CD25+ cells, and there was a trend toward lower histology scores at wk 8. Quality of life as assessed by the Inflammatory Bowel Disease Questionnaire increased after therapy (baseline: 131, 95% CI = 119-178; wk 8: 169; 95% CI = 124-216, p < 0.05). Nausea was most frequently reported as an adverse event, but always in patients that were concomitantly started on azathioprine.

CONCLUSIONS

The anti-IL-2R antibody daclizumab was safe and well tolerated in acute UC. Patients experienced clinical benefit along with signs of endoscopic improvement, but further controlled trials are needed to determine the therapeutic benefit of this compound.

Immunosuppressive effects of tautomycetin in vivo and in vitro via T cell-specific apoptosis induction

Tautomycetin (TMC) was identified as an immunosuppressor of activated T cells. Inhibition of T cell proliferation with TMC was observed at concentrations 100-fold lower than those needed to achieve maximal inhibition with cyclosporin A (CsA). TMC specifically blocked tyrosine phosphorylation of intracellular signal mediators downstream of Src tyrosine kinases in a T cell-specific manner, leading to apoptosis due to cleavage of Bcl-2, caspase-9, caspase-3, and poly(ADP-ribose) polymerase, but not caspase-1. In TMC-treated rats that received a heterotopic cardiac allograft, the graft survived more than 160 days, comparable to graft survival in allografted rats treated with CsA. Thus, TMC, whose mechanism of action is different from that of CsA or FK506, can be used as a potent T cell-specific immunosuppressor.

New approaches to immunosuppression in liver transplantation

With the continued improvements in outcome following liver transplantation, the drawbacks associated with conventional immunosuppression regimens become increasingly apparent. Although up to 70% of patients develop a histological infiltrate of the graft (acute rejection), many of these will resolve spontaneously, and chronic rejection is rare. If a robust form of allograft acceptance or tolerance can be established, then immunosuppression can be withdrawn along with all the accompanying risks. The liver is already known to be associated with downregulated immune responses; the mechanism for this is unclear, but may be related to a number of mechanisms known to be involved in peripheral tolerance. There are many strategies being studied for achieving allograft tolerance, including the use of modern immunosuppressants, antibodies that target key molecules in the immune response, and recruitment of leukocytes to allografts. In the interim, it is necessary to look for safe protocols that allow trials of tolerance strategies without putting patients at increased risk.

Developments in the treatment of uveitis

Uveitis remains a challenging field to the ophthalmologist as the disease causes significant morbidity and the use of traditional forms of treatment is restricted by limited effectiveness and considerable side effects. This article explores new agents used in the treatment of uveitis as well as the potential of agents used successfully in experimental uveitis. This paper also reviews agents in use for a long time but now used in novel ways.

Effects of immunoregulatory drugs on human peripheral blood T lymphocytes function in vitro

BACKGROUND: The purpose of the study was to evaluate the mode of action of different immunoregulatory drugs in lymphocyte proliferation and activation METHODS: The drugs studied were prednisolone (PRED), cyclosporin A (CsA) the recombination of PRED and CsA, L-asparaginase and cytosine-arabinose (ara-C). Peripheral blood lymphocytes from normal blood donors were stimulated by phytohemagglutinin (PHA). Lymphocytes proliferation and activation were determined by tritiated thymidine ([3H]TdR) incorporation secretion of interleukin-2, level of soluble interleukin-2 receptors in the supernatant of the culture medium, and immunophenotyping analysis of T lymphocyte subsets. RESULTS: Among PRED CsA and their combination, the strongest inhibition of cell proliferation was induced by PRED while L-asparaginase and ara-C inhibited PHA stimulated T cells proliferation in concentration and time dependent manner. Among PRED, CsA and their combination, CsA induced the greatest inhibition of IL-2 production. All the immunoregulatory drugs inhibited lymphocyte proliferation and expression of activation antigens. CONCLUSION: The immunoregulatory drugs inhibit both lymphocyte proliferation and activation but in a different way.

Acyclic nucleoside/nucleotide analogues with an imidazole ring skeleton

Syntheses of a few acyclic nucleoside and acyclic nucleoside phosphonate analogues containing an imidazole ring have been reported. These analogues include methyl 1-(2-hydroxyethoxymethyl)imidazole-4, 5-dicarbo-xylate (1), 4,5-dicarbamoyl-1-(2-hydroxyethoxymethyl)imidazole (2), 4,5-dicyano-1-(2-hydroxyethoxymethyl)imidazole (4), Methyl 1-(2-bromoethoxymethyl)imidazole-4,5-dicarboxylate (7), 4,5-dicyano-(2-bromoethoxymethyl)imidazole (8), and Methyl 1-(2-phosphonomethoxyethyl)imidazole (10). Also reported are a few potential prodrugs of the above compounds, including the acetyl derivatives 5 and 6 (of 1 and 4, respectively), and the diethyl phosphonate ester 9 (of 10). In addition, the corresponding benzyl-protected precursors 11 and 12 (of 1 and 4, respectively), along with their common hydrolysis product, 1-(2-benzyloxy-ethoxymethyl)-4,5-imidazoledicarboxylic acid (3), are reported. Another potential prodrug included in the list is 1-(2-acetoxyethyl)-4,5-dicyanoimidazole (15). The compounds were screened for in vitro antiviral activity against a wide variety of herpes and respiratory viruses. The most active compound was the phosphonate analogue 9 which exhibited an anti-measles virus activity with an EC50 of <2.5 microg/mL and an SI value of > 176.

Sanglifehrin A, a novel cyclophilin-binding immunosuppressant, inhibits IL-2-dependent T cell proliferation at the G1 phase of the cell cycle

Sanglifehrin A (SFA) is a novel immunosuppressive natural product that binds to cyclophilin but is structurally distinct from cyclosporin A (CsA). We have investigated the cellular and molecular mechanisms of the action of SFA in T lymphocytes. We show that SFA inhibits T cell proliferation induced by IL-2 with an IC(50) of 200 nM. Distinct from CsA, which also binds to cyclophilin, SFA does not affect calcium-dependent IL-2 production, although SFA enhanced IL-2 gene transcription in the same cells. SFA blocks T cell proliferation induced by IL-2 in G(1) with no appreciable effect on IL-2 receptor expression in a manner similar to that of the immunosuppressant rapamycin. Unlike rapamycin, however, SFA has no effect on the phosphorylation or enzymatic activity of p70(s6k) kinase, distinguishing SFA from rapamycin in their mode of action. SFA inhibits hyperphosphorylation of Rb and the activity of cyclin E-cyclin-dependent kinase 2 on IL-2 signaling. These results suggest that SFA has a novel mode of action in comparison with CsA, FK506, and rapamycin, and that its use as a molecular probe may lead to the discovery of a novel target involved in T cell activation.

Transcending conventional therapies: the role of biologic and other novel therapies

Biologic and other novel therapies targeted to specific pathogenic processes offer the potential for improved treatment outcomes in patients with Crohn's disease and alteration of the course of the disease. Therapies targeted to tumor necrosis factor alpha (TNF-alpha) include anti-TNF-alpha monoclonal antibodies (infliximab and CDP-571), TNF-binding neutralizing fusion proteins (etanercept), and TNF-alpha production inhibitors (thalidomide). In placebo-controlled trials, infliximab has rapidly induced clinical response and remission in patients with moderately to severely active Crohn's disease refractory to conventional therapy and patients with fistulizing Crohn's disease, with minimal toxicity; retreatment with infliximab in patients who experienced an initial response maintained their clinical improvement. Clinical experience suggests that infliximab may also be effective when administered as corticosteroid-sparing therapy. Infliximab is the only anti-TNF-alpha therapy currently available in clinical practice for the treatment of active Crohn's disease. Controlled trials of the investigational anti-TNF-alpha agent CDP-571 show benefit for induction of clinical improvement and steroid-sparing, but further investigation is needed. A pilot study of etanercept suggested a beneficial effect, but its efficacy was not confirmed in a controlled trial. In open-label trials, thalidomide has demonstrated efficacy in patients with refractory Crohn's disease; however, the therapeutic potential of thalidomide may be severely limited by the high incidence of drug-induced side effects. Other novel agents, including anti-alpha4 integrin antibodies, interleukin (IL)-10 and IL-11, and the immunomodulators tacrolimus and mycophenolate mofetil have been evaluated as treatment in patients with severely active or fistulizing Crohn's disease in open-label and controlled trials, with varied results reported to date. The development of these new therapies is an exciting advance that promises to improve the management of Crohn's disease and expand current knowledge of underlying pathophysiologic mechanisms.

Different mechanisms mediate the rejection of porcine neurons and endothelial cells transplanted into the rat brain

In order to investigate the early cellular responses mediating xenograft rejection in the brain, porcine aortic endothelial cells (PAEC) or porcine fetal mesencephalic neurons (PNEU) were transplanted into the striatum of LEW.1A rats. PAEC were detected with a specific anti-beta1 integrin antibody, and PNEU with an anti-porcine neurofilament antibody, or an antibody recognizing the NeuN antigen. PAEC grafts were massively infiltrated within 24 h by OX42-positive cells, which may correspond to polymorphonuclear (PMN) cells or macrophages. At that moment, the graft contained numerous cells expressing the inducible isoform of NO-synthase (iNOS). Infiltration by ED1-positive macrophages was effective after three days. The beta1-integrin labeling decreased from that time-point to day 7 post-implantation, and vanished after 11 days. Although some OX8-positive cells were present around the graft as soon as 3 days after transplantation, cells expressing the T-cell receptor (TCR)-beta chain infiltrated the graft after 7 days and their number remained low. A strong, diffuse OX8-and ED1-positive immunoreactive material remained in the scar up to the third week. In striking contrast, PNEU grafts remained poorly infiltrated by OX42- or ED1-positive cells during the first two weeks. A massive infiltration by macrophages and TCRbeta-positive lymphocytes occurred after 3 weeks. Natural killer (NK) cells were more scarce. The inflammation territory enlarged, and blood vessels were overloaded with macrophages or lymphocytes. Nevertheless, the graft contained NeuN-positive nuclei and neurites harbouring the porcine neurofilament protein. Hence, rejection was not completed at this time-point. These results suggest that the rapid rejection of PAEC is mainly driven by macrophages and possibly PMN cells, unlike PNEU, whose rejection is delayed and also involves lymphocytes. Differences in immunogenicity of grafted cells and/or patterns of production of pro-inflammatory cytokines may account for these contrasted rejection kinetics.

Cell-surface trafficking and release of flt3 ligand from T lymphocytes is induced by common cytokine receptor gamma-chain signaling and inhibited by cyclosporin A

The flt3 ligand (FL) is a growth and differentiation factor for primitive hematopoietic precursors, dendritic cells, and natural killer cells. Human T lymphocytes express FL constitutively, but the cytokine is retained intracellularly within the Golgi complex. FL is mobilized from the cytoplasmic stores and its serum levels are massively increased during the period of bone marrow aplasia after stem cell transplantation (SCT). Signals that trigger the release of FL by T cells remain unknown. This study shows that interleukin (IL)-2, IL-4, IL-7, and IL-15, acting through a common receptor gamma chain (gammac), but not cytokines interacting with other receptor families, are efficient inducers of cell surface expression of membrane-bound FL (mFL) and secretion of soluble FL (sFL) by human peripheral blood T lymphocytes. The gammac-mediated signaling up-regulated FL in a T-cell receptor-independent manner. IL-2 and IL-7 stimulated both FL messenger RNA (mRNA) expression and translocation of FL protein to the cell surface. Cyclosporin A (CsA) inhibited gammac-mediated trafficking of FL at the level of transition from the Golgi to the trans-Golgi network. Accordingly, serum levels of sFL and expression of mFL by T cells of CsA-treated recipients of stem cell allografts were reduced approximately 2-fold (P <.01) compared to patients receiving autologous grafts. The conclusion is that FL expression is controlled by gammac receptor signaling and that CsA interferes with FL release by T cells. The link between gammac-dependent T-cell activation and FL expression might be important for T-cell effector functions in graft acceptance and antitumor immunity after SCT.

Recent advances in inflammatory bowel disease

The last decade has seen tremendous advances in our knowledge, which has led to genuine improvements in our understanding of the pathogenesis and management of inflammatory bowel disease (IBD). The combined power of cellular and molecular biology has begun to unveil the enigmas of IBD, and, consequently, substantial gains have been made in the treatment of IBD. Refinements in drug formulation have provided the ability to target distinct sites of delivery, while enhancing the safety and efficacy of older agents. Simultaneous progress in biotechnology has fostered the development of new agents that strategically target pivotal processes in disease pathogenesis. This article addresses our current understanding of the pathogenesis of IBD, including the latest developments in animal models and covers agents currently used in the treatment of IBD as well as emerging therapies.

Update in medical treatment of Crohn's disease

Crohn's disease is an inflammatory bowel disorder that has no known cause. The goal of medical treatment is to control active disease, induce and maintain clinical remission, and treat complications. Anti-inflammatory medications and immunomodulatory therapies are the primary treatment modalities for Crohn's disease. The categories of standard treatment include the 5-aminosalicylic acid compounds, corticosteroids, antibiotics, and immunomodulators. New biologic therapy has been developed to better target the immune mediators that are active in Crohn's disease. Infliximab is the first of the biologic agents approved for the treatment of fistulizing and active Crohn's disease. Despite medical advances in treatment, there is still no cure for Crohn's disease.

Guidelines for the use of immunosuppressive drugs in patients with ocular inflammatory disorders: recommendations of an expert panel

PURPOSE

To provide recommendations for the use of immunosuppressive drugs in the treatment of patients with ocular inflammatory disorders.

PARTICIPANTS

A 12-person panel of physicians with expertise in ophthalmologic, pediatric, and rheumatologic disease, in research, and in the use of immunosuppressive drugs in patient care.

EVIDENCE

Published clinical study results. Recommendations were rated according to the quality and strength of available evidence.

PROCESS

The panel was convened in September of 1999 and met regularly through May 2000. Subgroups of the panel summarized and presented available information on specific topics to the full panel; recommendations and ratings were determined by group consensus.

CONCLUSIONS

Although corticosteroids represent one of the mainstays in the management of patients with ocular inflammation, in many patients, the severity of the disease, the presence of corticosteroid side effects, or the requirement for doses of systemic corticosteroids highly likely to result in corticosteroid complications supports the rationale for immunosuppressive drugs (for example, antimetabolites, T-cell inhibitors, and alkylating agents) being used in the management of these patients. Because of the potential for side effects, treatment must be individualized and regular monitoring performed. With careful use of immunosuppressive drugs for treatment of ocular inflammatory disorders, many patients will benefit from them either with better control of the ocular inflammation or with a decrease in corticosteroid side effects.

A multicenter trial of mizoribine compared with placebo in children with frequently relapsing nephrotic syndrome

BACKGROUND

The use of corticosteroids or cytotoxic/immunosuppressive agents such as cyclophosphamide, chlorambucil, and cyclosporine for the treatment of frequently relapsing nephrotic syndrome (FRNS) is limited because of their adverse effects. This study was conducted to evaluate the efficacy and safety of mizoribine, a relatively new immunosuppressive drug developed in Japan, in children with FRNS.

METHODS

A double-blind, placebo-controlled, multicenter trial was carried out in children, from 2 to 19 years old, with FRNS. At relapse, patients were treated with prednisolone. According to a dynamic allocation, mizoribine or a placebo was concurrently administered to each patient. Prednisolone was gradually tapered and discontinued within 12 weeks. The test drug was maintained for 48 weeks. The primary end point was the relapse rate (the total number of relapses/the total treatment days for all patients). Analyses were performed according to the intention-to-treat principle.

RESULTS

The primary analysis was conducted on 99 mizoribine- and 98 placebo-treated patients. The relapse rate was lower in the mizoribine group than in the placebo group (0.0055 vs. 0.0067; ratio 0.81, 95% CI, 0.61 to 1.05, P = 0.12). The hazard ratio of the cumulative remission rate between the two groups was 0.79 (95% CI, 0. 57 to 1.08). In the subgroups consisting of patients 10 years old or younger, the relapse rate ratio between the mizoribine subgroup (54 patients) and the placebo subgroup (57 patients) was 0.66 (95% CI, 0. 44 to 0.94, P = 0.017). The hazard ratio of the cumulative remission rate between the two subgroups was 0.56 (95% CI, 0.37 to 0.85, P = 0. 007). Hyperuricemia was the most common adverse event with mizoribine (16%), but was transient.

CONCLUSIONS

Compared with the placebo, mizoribine significantly decreased the relapse rate and prolonged the remission period in the subgroup consisting of patients 10 years old or younger. This drug may be useful in young children with FRNS who generally relapse more frequently than older children.

Synthesis and immunosuppressive activity of novel prodigiosin derivatives

Prodigiosins (Ps) represent a family of naturally occurring red pigments characterized by a common pyrrolylpyrromethene skeleton. Some members of this family have been shown to possess interesting immunosuppressive properties exerted with a novel mechanism of action, different from that of currently used drugs. In fact, Ps inhibit phosphorylation and activation of JAK-3, a cytoplasmic tyrosine kinase associated with a cell surface receptor component called common gamma-chain, which is exclusive of all IL-2 cytokine family receptors. Blocking common gamma-chain transduction activity results in a potent and specific immunosuppressive activity. With respect to the interesting and unexploited immunomodulating properties of this family of compounds we initiated a medicinal chemistry program aimed at finding novel prodigiosin derivatives with improved immunosuppressive activity and lower toxicity. Utilizing an unprecedented and flexible way of assembling the prodigiosin frame, a number of new derivatives have been prepared and tested leading to the choice of 4-benzyloxy-5-[(5-undecyl-2H-pyrrol-2-ylidene)methyl]-2, 2'-bi-1H-pyrrole (PNU-156804, 16) as a lead immunosuppressant.

Identification and immune regulation of 25-hydroxyvitamin D-1-alpha-hydroxylase in murine macrophages

Receptors for 1,25(OH)2vitaminD3 are found in most immune cells and important immunological effects have been described in vitro, reflected by its capacity to prevent autoimmunity and to prolong graft survival. The aim of this study was to examine the presence and nature of the enzyme responsible for final activation of the molecule, 1-alpha-hydroxylase, in murine macrophages and to analyse its regulation and possible role in the immune system. Peritoneal macrophages from C57Bl/6 mice were incubated with lipopolysaccharide (LPS; 100 microg/ml), interferon-gamma (IFN-gamma; 500 U/ml) or a combination of both. By quantitative reverse transcriptase-polymerase chain reaction, using primers based on the murine renal cDNA sequence, low levels of 1-alpha-hydroxylase mRNA were detected in freshly isolated cells (18 +/- 7 x 10-6 copies/beta-actin copies). Analysis of the cDNA sequence of the gene revealed identical coding sequences for the macrophage and renal enzymes. mRNA levels rose three-fold with LPS (NS), but a six-fold increase was seen after IFN-gamma stimulation (P < 0.05). Combining LPS and IFN-gamma did not result in a major additional increase, but addition of cyclosporin A further increased levels 2.5-fold both in IFN-gamma- and combination-stimulated cells (P < 0.05). Time course analysis revealed that up-regulation of 1-alpha-hydroxylase was a late phenomenon, preceded by the up-regulation of activating macrophage products such as IL-1 and tumour necrosis factor-alpha. Finally, a defect in 1-alpha-hydroxylase up-regulation by immune stimuli was found in autoimmune non-obese diabetic mice. In conclusion, we propose that the up-regulation of 1-alpha-hydroxylase in activated macrophages, resulting in the synthesis of 1,25(OH)2D3, might be a negative feedback loop in inflammation. A defect in this system might be an additional element in tipping the balance towards autoimmunity.

Therapy of inflammatory bowel disease

In the last decade, substantial gains have been made in the treatment of inflammatory bowel disease (IBD). Refinements in drug formulation have provided the ability to target distinct sites of delivery, enhancing the safety and efficacy of older agents. Immunosuppressive agents beyond corticosteroids have assumed a routine part in the care of patients with IBD. Moreover, as the century closes, we stand at the threshold of unprecedented advances in knowledge of the pathogenesis of ulcerative colitis and Crohn's disease. Simultaneous progress in biotechnology has fostered the development of new agents that strategically target pivotal processes in disease pathogenesis. This review covers agents currently used in the treatment of IBD and seeks to provide an overview of emerging therapies.

Immunosuppressive therapy using FTY720 combined with tacrolimus in rat liver transplantation

BACKGROUND

FTY720 (FTY) exerts its effects through a reduction of peripheral lymphocytes. This unique mechanism allows for a possible combination effect with other immunosuppressants. We investigated therapy with FTY combined with tacrolimus (FK) in rat liver transplantation.

METHODS

Different doses of FK, FTY, or both were orally administered to the recipients for 15 days. Expression of cytokine mRNAs using RT-PCR and appearance of lymphocyte apoptosis by immunohistologic staining were studied in the allografts.

RESULTS

Recipients treated with a low dose of FK (0.3 mg/kg) or FTY (0.03 mg/kg) showed a slightly prolonged survival time, although combination therapy with these drugs prolonged survival time similar to the duration obtained by an optimal dose of each drug alone. A marked suppression of lymphocyte infiltration and decreased levels of mRNAs for IL-2, IFN-gamma, and granzyme B were seen in the grafts with combination therapy. Grafts with combination therapy showed an increased number of cells double-stained with TUNEL and CD2 in infiltrated lymphocytes.

CONCLUSIONS

Allografts that underwent combination therapy demonstrated markedly reduced lymphocyte infiltration; a number of cells had induced apoptosis and an inhibition of IL-2, IFN-gamma, and granzyme B mRNA transcription, but not IL-4 and IL-10 transcripts, accounting for powerful mutual effect of FTY and FK.

Transport of monoglucuronosyl and bisglucuronosyl bilirubin by recombinant human and rat multidrug resistance protein 2

The secretion of bilirubin conjugates from hepatocytes into bile represents a decisive step in the prevention of hyperbilirubinemia. The bilirubin conjugates, monoglucuronosyl bilirubin (MGB) and bisglucuronosyl bilirubin (BGB), were previously suggested to be endogenous substrates for the apical multidrug resistance protein (MRP2), a member of the adenosine triphosphate (ATP)-binding cassette family of transporters (symbol ABCC2), also termed canalicular multispecific organic anion transporter. We have characterized this ATP-dependent transport using membrane vesicles from human embryonic kidney (HEK) cells expressing recombinant rat as well as human MRP2. MGB and BGB, (3)H-labeled in the glucuronosyl moiety, were synthesized enzymatically with recombinant UDP-glucuronosyltransferase 1A1, and stabilized with ascorbate. Rates for ATP-dependent transport of MGB and BGB (0.5 micromol/L each) by human MRP2 were 183 and 104 pmol x mg protein(-1) x min(-1), respectively. K(m) values were 0.7 and 0.9 micromol/L for human MRP2, and 0.8 and 0.5 micromol/L for rat MRP2, with MGB and BGB as substrates, respectively. Leukotriene C(4) and 17beta-glucuronosyl estradiol, which are both known high-affinity substrates for human MRP2, inhibited [(3)H]MGB transport with IC(50) values of 2.3 and 30 micromol/L, respectively. Cyclosporin A competitively inhibited human and rat MRP2-mediated transport of [(3)H]MGB, with K(i) values of 21 and 10 micromol/L, respectively. Our results provide direct evidence that recombinant MRP2, cloned from rat as well as human liver, mediates the primary-active ATP-dependent transport of the bilirubin conjugates MGB and BGB.

Novel therapies for inflammatory bowel disease

Looking back at successes and failures in newer approaches to treating IBD, it is tempting--although still difficult--to draw conclusions about pathogenesis. When a therapy proves effective, do clinicians truly know how it works? Even with a therapy as specific as anti-TNF antibody, it is not clear if the benefit is attributable to simple binding and clearance of TNF-alpha or to binding on the cell surface and subsequent deletion of the activated macrophage. When a drug appears to be less effective than preclinical models suggest, can failures in effectiveness from delivery or dosing be differentiated? The disappointing results of clinical trials with IL-10--so at odds with the prediction of benefit from animal models--bring into question the validity of those models as well as the soundness of design of the clinical trials on which efficacy of IL-10 is judged. The variability of response even to the most narrowly targeted agents suggests that these diseases are far more heterogeneous in humans than in their murine counterparts. Clinicians are only just beginning to recognize subclinical markers of response, and it may soon be possible to predict response on the basis of genetic composition. For the moment, however, the field of pharmacogenetics is embryonic. Challenges in developing new therapeutic strategies include not only identifying novel agents, but also improving the definitions of clinical endpoints and defining efficacy at the biologic level. Only through considered evaluation of clinical evidence may clinicians determine which therapies should remain novelties and which should become an accepted part of the armamentarium.