Rescue therapy: a role for sirolimus in lung and heart transplant recipients

Macrophage phenotypes in atherosclerosis

Initiation and progression of atherosclerosis depend on local inflammation and accumulation of lipids in the vascular wall. Although many cells are involved in the development and progression of atherosclerosis, macrophages are fundamental contributors. For nearly a decade, the phenotypic heterogeneity and plasticity of macrophages has been studied. In atherosclerotic lesions, macrophages are submitted to a large variety of micro-environmental signals, such as oxidized lipids and cytokines, which influence the phenotypic polarization and activation of macrophages resulting in a dynamic plasticity. The macrophage phenotype spectrum is characterized, at the extremes, by the classical M1 macrophages induced by T-helper 1 (Th-1) cytokines and by the alternative M2 macrophages induced by Th-2 cytokines. M2 macrophages can be further classified into M2a, M2b, M2c, and M2d subtypes. More recently, additional plaque-specific macrophage phenotypes have been identified, termed as Mox, Mhem, and M4. Understanding the mechanisms and functional consequences of the phenotypic heterogeneity of macrophages will contribute to determine their potential role in lesion development and plaque stability. Furthermore, research on macrophage plasticity could lead to novel therapeutic approaches to counteract cardiovascular diseases such as atherosclerosis. The present review summarizes our current knowledge on macrophage subsets in atherosclerotic plaques and mechanism behind the modulation of the macrophage phenotype.

Rapamycin unbalances the polarization of human macrophages to M1

Plasticity is a hallmark of macrophages, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic (M1) and alternative (M2). Rapamycin (RAPA) is crucial for survival and functions of myeloid phagocytes, but its effects on macrophage polarization are not yet studied. To address this issue, human macrophages obtained from six normal blood donors were polarized to M1 or M2 in vitro by lipopolysaccharide plus interferon-γ or interleukin-4 (IL-4), respectively. The presence of RAPA (10 ng/ml) induced macrophage apoptosis in M2 but not in M1. Beyond the impact on survival in M2, RAPA reduced CXCR4, CD206 and CD209 expression and stem cell growth factor-β, CCL18 and CCL13 release. In contrast, in M1 RAPA increased CD86 and CCR7 expression and IL-6, tumour necrosis factor-α and IL-1β release but reduced CD206 and CD209 expression and IL-10, vascular endothelial growth factor and CCL18 release. In view of the in vitro data, we examined the in vivo effect of RAPA monotherapy (0·1 mg/kg/day) in 12 patients who were treated for at least 1 month before islet transplant. Cytokine release by Toll-like receptor 4-stimulated peripheral blood mononuclear cells showed a clear shift to an M1-like profile. Moreover, macrophage polarization 21 days after treatment showed a significant quantitative shift to M1. These results suggest a role of mammalian target of rapamycin (mTOR) into the molecular mechanisms of macrophage polarization and propose new therapeutic strategies for human M2-related diseases through mTOR inhibitor treatment.

Clinical recommendations for the use of everolimus in heart transplantation

Proliferation signal inhibitors (PSIs), everolimus (EVL), and sirolimus are a group of immunosuppressor agents indicated for the prevention of acute rejection in adult heart transplant recipients. Proliferation signal inhibitors have a mechanism of action with both immunosuppressive and antiproliferative effects, representing an especially interesting treatment option for the prevention and management of some specific conditions in heart transplant population, such as graft vasculopathy or malignancies. Proliferation signal inhibitors have been observed to work synergistically with calcineurin inhibitors (CNIs). Data from clinical trials and from the growing clinical experience show that when administered concomitantly with CNIs, PSIs allow significant dose reductions of the latter without loss of efficacy, a fact that has been associated with stabilization or significant improvement in renal function in patients with CNI-induced nephrotoxicity. The purpose of this article was to review the current knowledge of the role of PSIs in heart transplantation to provide recommendations for the proper use of EVL in cardiac transplant recipients, including indications, treatment regimens, monitoring, and management of the adverse events.

Everolimus: an update on the mechanism of action, pharmacokinetics and recent clinical trials

BACKGROUND

A growing body of evidence suggests that everolimus might offer effective immunosuppressive activity together with antiproliferative effects that may address some of the unmet needs in the long-term therapeutic management of the post-transplant patient.

OBJECTIVE

To summarize the emerging evidence for employing everolimus-based immunosuppression.

METHODS

A systematic review was conducted of the Medline, Embase and Renal Health Library (Cochrane Collaboration) databases, and of the summary publications from international transplant meetings and congresses during 2000-2008.

RESULTS

This article summarizes this analysis, with special focus on the pharmacokinetic characteristics of everolimus and on the results of its use in renal transplantation. Some data has also been included about the efficacy of the drug in other solid organ transplantation and in tumours.

CONCLUSIONS

Everolimus is an immunosuppressant drug with proven efficacy in transplantation. When used in combination with cyclosporin, better results are obtained in renal function with low cyclosporin doses. Adverse events related to this drug are frequent and lead to moderate dropout rates.

Proliferation signal inhibitors in cardiac transplantation

PURPOSE OF REVIEW

Standard immunosuppression after cardiac transplantation includes a calcineurin inhibitor in combination with mycophenolate mofetil or azathioprine and corticosteroids. These agents have led to excellent outcomes but have shortcomings in terms of efficacy and toxicity. A new class of immunosuppressants, proliferation signal inhibitors, may meet some of these shortcomings.

RECENT FINDINGS

The efficacy of the available proliferation signal inhibitors - sirolimus and its derivative everolimus - has been compared with azathioprine in three randomized clinical trials. Sirolimus or everolimus use was associated with lower rates of acute rejection and reduced development of chronic allograft vasculopathy. Sirolimus was not found to be superior to mycophenolate mofetil in a randomized trial. Proliferation signal inhibitors have been reported to be effective in refractory recurrent acute rejection. Nonrandomized studies have demonstrated that proliferation signal inhibitor-based immunosuppression enables recovery from renal dysfunction secondary to calcineurin inhibitor treatment. Proliferation signal inhibitor-based treatment is associated with a lower risk of malignancy than calcineurin inhibitor-based regimens. Proliferation signal inhibitors have significant adverse effects that may limit widespread use.

SUMMARY

Proliferation signal inhibitors are important new immunosuppressive agents that have added considerably to the armamentarium allowing further tailored immunosuppression to individualize patient care after heart transplantation.

Microsatellite polymorphism in the heme oxygenase-1 gene promoter and cardiac allograft vasculopathy

BACKGROUND

The heme oxygenase-1 (HO-1) isoenzyme has recently been suggested to protect transplants from ischemia-reperfusion and immunologic injury. Inducibility of this enzyme is modulated by a (GT)n dinucleotide length polymorphism in the HO-1 gene promoter. Short (class S) repeats are associated with greater up-regulation of HO-1 than are long repeats. In the present study, we investigated the impact of the promoter polymorphism on the development of cardiac allograft vasculopathy (CAV) in human heart transplants.

METHODS

We enrolled 152 recipients of a heart allograft with at least 1 year survival post-transplantation in this retrospective study. The HO-1 genotype was assessed using genomic DNA isolated from paraffin-embedded allograft biopsy specimens. Patients were followed angiographically for CAV. Angiographic vessel-wall abnormalities were defined as CAV, and a stenosis of more than 50% in at least 1 vessel area was defined as severe CAV.

RESULTS

Eighty-seven patients (57%) had received a heart from a donor with at least 1 class S allele. Within the mean follow-up period of 9 years, 95 patients (63%) showed signs of CAV, among which 60 patients (40%) developed severe CAV. The frequency of CAV and severe CAV was not significantly different between class S allele recipients and non-recipients (CAV, 57/87 vs 38/65, p = 0.12; severe CAV, 35/87 vs 25/65, p = 0.30).

CONCLUSION

In contrast to recent findings in renal allografts and vascular injury, the HO-1 gene promoter polymorphism does not show an association with the development of CAV in heart transplants.

Rapamycin induces a caspase-independent cell death in human monocytes

The immunosuppressive activity of rapamycin (RAPA) and its efficacy as an anti-rejection agent in organ transplantation have been ascribed principally to its anti-proliferative effects on T cells, while the activity on monocytes is partially unknown. In vitro, RAPA reduced monocyte survival by inducing a caspase-independent cell death. RAPA-induced monocyte cell death (RAPA-CD) was impeded by activation of granulocyte macrophage-colony stimulating factor family receptors or toll-like receptor 4, and by exposure to inflammatory cytokines. In vivo, in patients who received RAPA monotherapy as part of pre-conditioning for islet transplantation, RAPA affected survival of myeloid lineage cells. In the peripheral blood, CD33(+) and CD14(+) cells decreased, whereas lymphocytes appeared unaffected. In the bone marrow, myeloid precursors such as CD15(+) and CD15(+)/CD16(+) were selectively and significantly decreased, but no major cytotoxic effects were observed. The RAPA-CD suggests a dependence of monocytes on mammalian target of RAPA pathways for nutrient usage, and this feature implies that RAPA could be selectively useful as a treatment to reduce monocytes or myeloid cells in conditions where these cells negatively affect patient, suggesting a potential anti-inflammatory action of this drug.

Wound healing complications with de novo sirolimus versus mycophenolate mofetil-based regimen in cardiac transplant recipients

Sirolimus was introduced in de novo immunosuppression at Stanford University in view of its favorable effects on reduced rejection and cardiac allograft vasculopathy. After an apparent increase in the incidence of post-surgical wound complications as well as symptomatic pleural and pericardial effusions, we reverted to a mycophenolate mofetil (MMF)-based regimen. This retrospective study compared the outcome in heart transplant recipients on sirolimus (48 patients) with those on MMF (46 patients) in de novo immunosuppressive regimen. The incidence of any post-surgical wound complication (52% vs. 28%, p=0.019) and deep surgical wound complication (35% vs. 13%, p=0.012) was significantly higher in patients on sirolimus than on MMF. More patients on sirolimus also had symptomatic pleural (p=0.035) and large pericardial effusions (p=0.033) requiring intervention. Logistic regression analysis showed sirolimus (p=0.027) and longer cardiac bypass time (OR=1.011; p=0.048) as risk factors for any wound complication. Sirolimus in de novo immunosuppression after cardiac transplantation was associated with a significant increase in the incidence of post-surgical wound healing complications as well as symptomatic pleural and pericardial effusions.

Rapamycin in lung transplantation

INTRODUCTION

Rapamycin (RAPA) is a powerful immunosuppressant that also acts as an antiproliferative, which, therefore, could be useful in the treatment and prevention of bronchiolitis obliterans (BOS) in lung transplant recipients. We sought to report our experiences with RAPA in lung transplant patients with BOS that has not responded to the administration of other drugs.

MATERIALS AND METHODS

We performed a retrospective analysis of the clinical characteristics, pulmonary function, and complications among patients with BOS who received RAPA.

RESULTS

RAPA was administered to 11 patients, three single-lung transplant and eight bilateral lung transplant recipients, of whom five were women and six men, of mean age 48 years (26 to 65). The median posttransplant time to the initiation of RAPA for progressive BOS was 32 months (4 to 69) with a posttreatment follow-up of 15 months (3 to 34). RAPA was administered to all patients in association with a calcineurin inhibitor (tacrolimus in seven cases, and cyclosporine in four and steroids. Eight of the 11 patients (72%) with progressive deterioration of pulmonary function showed improved and/or stabilized FEV1 figures after introduction of RAPA. Eight patients developed adverse effects, which were possibly related to RAPA, leading to treatment withdrawal in two cases. The most frequent adverse effects were infections among 6 of the 12 cases, and myelosuppression in three.

CONCLUSIONS

RAPA may be useful to stabilize or improve pulmonary function in patients with BOS. Nevertheless, it was necessary for patients to be closely monitored so that possible adverse effects, and especially infections, may be detected early.

Total lymphoid irradiation: new therapeutic option for refractory giant cell myocarditis

Idiopathic giant cell myocarditis (GCM) is believed to be a T-lymphocyte-mediated autoimmune disease. Some patients with GCM have a dramatic clinical response to anti-T-cell immunosuppression. However, this response is not uniform and patients often deteriorate rapidly and need a cardiac transplantation within months of diagnosis. Following cardiac transplantation, GCM may recur in the graft but is usually mild and responds to augmentation of immunosuppression. This report is the first description of total lymphoid irradiation (TLI) for the treatment of GCM, which was used in a patient who developed an exceptionally early and severe recurrence of GCM in the cardiac graft that remained refractory to heightened immunosuppression for 4 months. Clinical and histologic remission followed a course of TLI and was maintained for 1 year despite a gradual decrease in immunosuppression. This novel treatment should be considered in all patients with GCM who do not have histologic remission with the currently employed anti-T-cell immunosuppression.

Recovery of Chronic Renal Impairment With Sirolimus After Lung Transplantation

BACKGROUND

Standard immunosuppression after lung transplantation includes calcineurin inhibitors, azathioprine, and steroids. Calcineurin inhibitor administration is associated with an increased renal impairment. Sirolimus shows no renal toxicity and could be used in selected patients.

METHODS

We have prospectively administered sirolimus as an alternative to calcineurin inhibitors in 15 lung transplantation recipients with persistent drug nephrotoxicity. Eight patients had also bronchiolitis obliterans syndrome. The mean serum creatinine and azotemia were 2.7 +/- 1.1 mg/dL and 111 +/- 39 mg/dL. After starting sirolimus, azathioprine was reduced to 50%-25% of baseline, calcineurin inhibitors were gradually reduced and eventually stopped, and steroids were maintained stable. Patients started sirolimus with 2 to 5 mg/d orally; adjustments were made according to trough levels (4 to 12 ng/mL for combined sirolimus + calcineurin inhibitors; 12 to 20 ng/mL as monotherapy), toxicity, and perceived efficacy. Patients were monitored for renal and graft function and clinical status.

RESULTS

A significant creatinine decrease was observed after 6 months of treatment (p < 0.02); azotemia decreased after 1 month and remained stable (p < 0.01). Pulmonary function tests did not show any significant modification from before sirolimus baseline in patients without bronchiolitis obliterans syndrome. There were eight infectious complications and 10 episodes of toxicity (4 dermatitis, 2 epistaxis, 1 headache, 1 diarrhea, 1 nausea, 1 laryngeal cancer). Moderate leukocytopenia (n = 3) and hypertriglyceridemia (n = 6) responded to dose reduction. One patient was lost to follow-up. Three patients died of complications related to bronchiolitis obliterans. One patient underwent transplantation again.

CONCLUSIONS

Sirolimus administration allows amelioration of renal function with a relatively low morbidity and is useful for chronic renal impairment rescue after lung transplantation.

Critical care aspects of lung transplantation

Lung transplantation currently is the preferred treatment option for a variety of end-stage pulmonary diseases. Remarkable progress has occurred through refinements in technique and improved understanding of transplant immunology and microbiology. As a result, recipients are surviving longer after their transplant. Despite improvements in short- and intermediate-term survival, long-term success with lung transplantation remains limited by chronic allograft rejection, also known as bronchiolitis obliterans syndrome. Despite its long-term limitations, lung transplantation remains the only hope for many with end-stage pulmonary disease, and during the past 20 years, it has become increasingly accepted and used. As a result, clinicians working in an intensive care unit (ICU) are more likely to be exposed to these patients both in the immediate postoperative period as well as throughout their remaining lives. It is thus important that the ICU team have a working knowledge of the common complications, when these complications are most likely to occur, and how best to treat them when they do arise. The main focus of this review is to address the variety of potential graft and life-threatening problems that may occur in lung transplant recipients. Because the ICU is also the most common setting where a potential donor is identified, donor issues will briefly be addressed.

Heart transplantation

Heart transplantation remains the best treatment option for end-stage heart failure. For patients who are not candidates for transplantation, better medical management and surgical options in heart failure can improve both the length and quality of a patient's life. Continuing research on xenotransplantation and the total artificial heart may decrease the need for human transplantation in years to come and may allow others with severe heart failure to have a chance at living longer.

Rapamycin has a deleterious effect on MIN-6 cells and rat and human islets

Rapamycin (sirolimus) is a macrolide fungicide with immunosuppressant properties that is used in human islet transplantation. Little is known about the effects of rapamycin on MIN-6 cells and islets. Rapamycin had a dose-dependent, time-dependent, and glucose-independent deleterious effect on MIN-6 cell viability. At day 1, using the MTT method, 0.01 nmol/l rapamycin reduced cell viability to 83 +/- 6% of control (P < 0.05). Using the calcein AM method, at day 2, 10 nmol/l rapamycin caused a reduction in cell viability to 73 +/- 5% of control (P < 0.001). Furthermore, 10 and 100 nmol/l rapamycin caused apoptosis in MIN-6 cells as assessed by the transferase-mediated dUTP nick-end labeling assay. Compared with control, there was a 3.1 +/- 0.6-fold increase (P < 0.01) in apoptosis in MIN-6 cells treated with 10 nmol/l rapamycin. A supra-therapeutic rapamycin concentration of 100 nmol/l significantly impaired glucose- and carbachol-stimulated insulin secretion in rat islets and had a deleterious effect on the viability of rat and human islets, causing apoptosis of both alpha- and beta-cells.

Sirolimus in heart transplantation: a single center initial experience

Sirolimus (SRL) is a potent non-nephrotoxic immunosuppressant. In our unit, SRL was administered to 17 heart transplant (HT) recipients at 1770+/-1234 days' posttransplant surgery, for the following reasons: (1) calcineurin inhibitor (CI) withdrawal due to renal insufficiency (RI; n=6); (2) neurotoxicity (n=1) and pancytopenia (n=1); (3) vascular graft disease (VGD) treatment (n=5); (4) immunosuppression optimization due to lung cancer (n=2); (5) CI use was delayed due to postsurgery RI (n=2). The mean follow-up was 190+/-165 days. Mean SRL doses (mg)/concentrations (ng/mL) at 7 (n=17), 30 (n=14), and 180 (n=8) days were: 1.2+/-0.6/5.9+/-6; 1.6+/-0.8/4.8+/-3.1; and 1.7+/-1.0/5.2+/-3.7. Among group 1, CI patients were discontinued without favorable functional impact. Neurotoxicity and pancytopenia improved, but there were no major clinical events in the VGD group. One "bridge" to CI was successfully performed (postsurgery RI). Total leukocyte count fell while hemoglobin, platelet, and cholesterol profiles were not affected. Ten of 15 patients (67%) were discontinued from CI without rejection and with a dose reduction of mycophenolate mofetil. There were 8 episodes (47%) of SRL-related toxicity, leading to 4 discontinuations (23%); 8 patients (47%) have died during follow-up. This retrospective analysis of outcomes in the context of severe complicated patients suggests that more premature introduction SRL is preferable, particularly in a large patient cohort.

Rapamycin in lung transplantation: preliminary results

INTRODUCTION

Rapamycin is a potent immunosuppressive agent with a different mechanism of action and different adverse effects from those of calcineurin inhibitors (CNIs).

OBJECTIVE

To analyze our experience with rapamycin in patients undergoing lung transplantation and heart-lung transplantation in our center.

PATIENTS AND METHODS

Patients were treated with rapamycin when showing chronic rejection and/or toxicity associated with the CNI after lung transplantation or heartlung transplantation. Patients with chronic rejection were administered rapamycin in combination with CNIs, whereas the CNIs were eliminated in patients with toxicity.

RESULTS

Since October 2001, 7 patients (4 women), of mean age 45+/-15 years, received treatment with rapamycin (heart-lung transplantation, 2 cases; lung transplantation, 5 cases). The indications were chronic rejection in 4 patients and CMIs toxicity in 3 patients (kidney failure in 2 cases and optic neuropathy in 1 case). Pulmonary function stabilization was observed in 3 of 4 patients receiving rapamycin for chronic rejection. In the 3 patients with CNIs toxicity elimination of these drugs did not result in pulmonary functional deterioration. Patients with kidney failure showed an improvement in creatinine levels; visual acuity improved in the patient with optic neuropathy. We observed 2 infectious complications (pneumococcal pneumonia and pulmonary aspergillosis), which resolved with treatment.

CONCLUSION

Rapamycin is an alternative for lung-transplant recipients who develop chronic rejection and/or CNIs toxicity.

Acute allograft rejection after lung transplantation: diagnosis and therapy

Acute rejection remains a significant problem after lung transplantation. While it generally is a treatable condition, significant resources and therapies are directed toward its prevention and resolution. Its larger significance undoubtedly rests in its contribution to the pathogenesis of BOS. Significant questions regarding the origins of AR, the role of LBB, alternative histologic appearances of acute allograft injury, and optimal therapy remain. Controversy regarding the utility of surveillance bronchoscopy and preemptive treatment of occult AR persists because of lack of conclusive evidence. Future investigations might resolve these matters and provide more efficacious and less toxic therapies that will hopefully reduce the impact of chronic rejection and improve long-term outcomes.

Sirolimus therapy in cardiac transplantation

Rapamycin powerfully inhibits the progression of antigen-activated T cells through the cell cycle. In animal heart transplantation models, rapamycin therapy has been associated with profound immunosuppressive effects on host humoral and cellular responses. In consequence, further studies have been conducted to evaluate the efficiency of rapamycin in preventing acute heart allograft rejection, treating refractory acute heart allograft rejection, inducing transplantation tolerance, and preventing and treating transplant coronary artery disease. The results of these studies indicated that rapamycin can effectively prevent acute graft rejection and inhibit refractory acute graft rejection in heart transplant recipients by exerting potent immunosuppressive and antiproliferative effects without adversely affecting renal function. This supports the use of rapamycin therapy in heart transplant recipients, especially in those with renal dysfunction, for whom treatment with calcineurin inhibitors is contraindicated. Rapamycin may also halt and even reverse the progression of cardiac allograft vasculopathy, which warrants further clinical trials in humans. Finally, rapamycin may be able to induce transplantation tolerance, thus making it one of the most promising modalities for improving the long-term survival of heart transplant recipients.

Interstitial pneumonitis associated with sirolimus: a dilemma for lung transplantation

Rapamycin/sirolimus (SR), trade named Rapammune (Wyeth-Ayerst, Sydney, Australia), is a potent immunosuppressive drug associated with myelosuppression, hypertension, hyperlipidemia, and infection. Rapamycin/sirolimus-induced pneumonitis has been described previously in renal transplant recipients, and this report describes a stable heart-lung transplant recipient who developed a pulmonary infiltrate that reversed after ceasing SR therapy. We believe that immunosuppression-induced pneumonitis in a lung allograft is a serious dilemma for lung transplant physicians

Current practices: immunosuppression induction, maintenance, and rejection regimens in contemporary post-heart transplant patient treatment

Cardiac transplantation is the definitive treatment for eligible patients with end-stage cardiomyopathy. Survival rates have improved dramatically during the last 10 years, especially since the advent of cyclosporine-A. Cardiac allograft rejection, previously considered a major cause of early mortality after transplantation, is no longer the limiting factor for early survival, with the use of newer and more specific immunosuppression regimens. Very few randomized, prospective trials, including comparisons between immunosuppression regimens, have been conducted in this area. Therefore, practices vary with physician and institutional experience. Most centers use a multipronged approach to immunosuppression, targeting multiple sites in the immune cascade that lead to allograft rejection. Multiple new agents in development are reviewed. Drugs such as sirolimus and its derivative, everolimus, act on specific intracellular receptors within lymphocytes, whereas other medications such as Daclizumab (Roche Laboratories, Nutley, NJ) block the interleukin-2 receptor on the surface of activated T cells. The immune response to foreign antigens is complex, with multiple redundant levels. Immunosuppression regimens continue to seek a fine balance between overimmunosuppression and insufficient protection, which may lead to allograft rejection or loss.

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.