Cyclosporine A enhances platelet aggregation

Quantitative Analysis of Drugs in a Mimetic Tissue Model Using Nano-DESI on a Triple Quadrupole Mass Spectrometer

Mass spectrometry is a powerful analytical technique used at every stage of the pharmaceutical research process. A specialized branch of this method, mass spectrometry imaging (MSI), has emerged as an important tool for determining the spatial distribution of drugs in biological samples. Despite the importance of MSI, its quantitative capabilities are still limited due to the complexity of biological samples and the lack of separation prior to analysis. This makes the simultaneous quantification and visualization of analytes challenging. Several techniques have been developed to address this challenge and enable quantitative MSI. One such approach is the mimetic tissue model, which involves the incorporation of an analyte of interest into tissue homogenates at several concentrations. A calibration curve that accounts for signal suppression by the complex biological matrix is then created by measuring the signal of the analyte in the series of tissue homogenates. Herein, we use the mimetic tissue model on a triple quadrupole mass spectrometer (QqQ) in multiple reaction monitoring mode to demonstrate the quantitative abilities of nanospray desorption electrospray ionization (nano-DESI) and compare these results with those obtained using atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI). For the tested compounds, our findings indicate that nano-DESI achieves lower standard deviations than AP-MALDI, resulting in superior limits of detection for the studied analytes. Additionally, we discuss the limitations of the mimetic tissue model in the quantification of certain analytes and the challenges involved with the implementation of the model.

Small-Molecule Cyclophilin Inhibitors Potently Reduce Platelet Procoagulant Activity

Procoagulant platelets are associated with an increased risk for thrombosis. Procoagulant platelet formation is mediated via Cyclophilin D (CypD) mediated opening of the mitochondrial permeability transition pore. Inhibiting CypD activity could therefore be an interesting approach to limiting thrombosis. In this study, we investigated the potential of two novel, non-immunosuppressive, non-peptidic small-molecule cyclophilin inhibitors (SMCypIs) to limit thrombosis in vitro, in comparison with the cyclophilin inhibitor and immunosuppressant Cyclosporin A (CsA). Both cyclophilin inhibitors significantly decreased procoagulant platelet formation upon dual-agonist stimulation, shown by a decreased phosphatidylserine (PS) exposure, as well as a reduction in the loss of mitochondrial membrane potential. Furthermore, the SMCypIs potently reduced procoagulant platelet-dependent clotting time, as well as fibrin formation under flow, comparable to CsA. No effect was observed on agonist-induced platelet activation measured by P-selectin expression, as well as CypA-mediated integrin α_IIbβ₃ activation. Importantly, whereas CsA increased Adenosine 5'-diphosphate (ADP)-induced platelet aggregation, this was unaffected in the presence of the SMCypIs. We here demonstrate specific cyclophilin inhibition does not affect normal platelet function, while a clear reduction in procoagulant platelets is observed. Reducing platelet procoagulant activity by inhibiting cyclophilins with SMCypIs forms a promising strategy to limit thrombosis.

Inhibition of transcription factor NFAT activity in activated platelets enhances their aggregation and exacerbates gram-negative bacterial septicemia

During gram-negative septicemia, interactions between platelets and neutrophils initiate a detrimental feedback loop that sustains neutrophil extracellular trap (NET) induction, disseminated intravascular coagulation, and inflammation. Understanding intracellular pathways that control platelet-neutrophil interactions is essential for identifying new therapeutic targets. Here, we found that thrombin signaling induced activation of the transcription factor NFAT in platelets. Using genetic and pharmacologic approaches, as well as iNFATuation, a newly developed mouse model in which NFAT activation can be abrogated in a cell-specific manner, we demonstrated that NFAT inhibition in activated murine and human platelets enhanced their activation and aggregation, as well as their interactions with neutrophils and NET induction. During gram-negative septicemia, NFAT inhibition in platelets promoted disease severity by increasing disseminated coagulation and NETosis. NFAT inhibition also partially restored coagulation ex vivo in patients with hypoactive platelets. Our results define non-transcriptional roles for NFAT that could be harnessed to address pressing clinical needs.

In Silico Evaluation of Cyclophilin Inhibitors as Potential Treatment for SARS-CoV-2

BACKGROUND

The advent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) provoked researchers to propose multiple antiviral strategies to improve patients' outcomes. Studies provide evidence that cyclosporine A (CsA) decreases SARS-CoV-2 replication in vitro and decreases mortality rates of coronavirus disease 2019 (COVID-19) patients. CsA binds cyclophilins, which isomerize prolines, affecting viral protein activity.

METHODS

We investigated the proline composition from various coronavirus proteomes to identify proteins that may critically rely on cyclophilin's peptidyl-proline isomerase activity and found that the nucleocapsid (N) protein significantly depends on cyclophilin A (CyPA). We modeled CyPA and N protein interactions to demonstrate the N protein as a potential indirect therapeutic target of CsA, which we propose may impede coronavirus replication by obstructing nucleocapsid folding.

RESULTS

Finally, we analyzed the literature and protein-protein interactions, finding evidence that, by inhibiting CyPA, CsA may impact coagulation proteins and hemostasis.

CONCLUSIONS

Despite CsA's promising antiviral characteristics, the interactions between cyclophilins and coagulation factors emphasize risk stratification for COVID patients with thrombosis dispositions.

Association of Aspirin Treatment With Cardiac Allograft Vasculopathy Progression and Adverse Outcomes After Heart Transplantation

BACKGROUND

Enhanced platelet reactivity may play a role in cardiac allograft vasculopathy (CAV) progression. The use of antiplatelet agents after heart transplantation (HT) has been inconsistent and although aspirin (ASA) is often a part of the medication regimen after HT, limited evidence is available on its benefit.

METHODS AND RESULTS

CAV progression was assessed by measuring the difference in plaque volume and plaque index between the last follow-up and the baseline coronary intravascular ultrasound examination. Overall, 529 HT recipients were retrospectively analyzed (337 had ≥2 intravascular ultrasound studies). The progression in plaque volume (P = .007) and plaque index (P = .002) was significantly attenuated among patients treated with early ASA (within the first year after HT). Over a 6.7-year follow-up, all-cause mortality was lower with early ASA compared with late or no ASA use (P < .001). No cardiac deaths were observed in the early ASA group, and the risk of CAV-related graft dysfunction was significantly lower in this group (P = .03). However, the composite of all CAV-related events (cardiac death, CAV-related graft dysfunction, or coronary angioplasty) was not significantly different between the groups (P = .16).

CONCLUSIONS

Early ASA use after HT may delay CAV progression and decrease mortality and CAV-related graft dysfunction, but does not seem to affect overall CAV-associated events.

Effects of immunosuppressive agents on the hemostatic system in normal dogs

Background

In dogs, the effects of immunosuppressive medications on hemostasis are not well known.

Hypothesis/Objectives

The objective was to determine the effects of immunosuppressive medications on primary and secondary hemostasis. Our hypothesis was that cyclosporine and prednisone would increase markers of hypercoagulability and thromboxane synthesis, while azathioprine, mycophenolate mofetil, and leflunomide would have minimal effects on hemostasis.

Animals

Eight healthy dogs.

Methods

A randomized, cross‐over study used aggregometry, the PFA‐100 platelet function analyzer, viscoelastometry, platelet count, and prothrombin and activated partial thromboplastin times to evaluate hemostasis during the administration of prednisone, azathioprine, cyclosporine, mycophenolate mofetil, and leflunomide for 1 week each at standard oral doses. Urine 11‐dehydro‐thromboxane‐B₂ (11‐dTXB₂) and 6‐keto‐prostaglandin‐F_1α (6‐keto‐PGF_1α) concentrations, normalized to urine creatinine concentration, were measured.

Results

The aggregometry amplitude decreased from 51 ± 21 to 27 ± 14 (P = .002) during leflunomide treatment (ADP activation), but there were no differences in amplitude (P = .240) for any medications when platelets were activated with collagen. For all medications, there were no significant differences in viscoelastometry indices (ACT, P = .666; ClotRate, P = .340; and platelet function, P = .411) and platelet count (P = .552). Compared with pretreatment values, urinary 11‐dTXB₂‐to‐creatinine ratio increased (P = .001) after drug administration (from 3.7 ± 0.6 to 5.6 ± 1.1). Cyclosporine was associated with an increase (P < .001) in the 6‐keto‐PGF_1α‐to‐creatinine ratio (from 10.3 ± 4.6 to 22.1 ± 5.3).

Conclusions and Clinical Importance

Most immunosuppressive drugs do not enhance platelet function or coagulation in healthy dogs, suggesting that these medications might not predispose hypercoagulable dogs to thromboembolism. The results of our study need to be correlated with the clinical outcomes of hypercoagulable dogs.

Functional cyclophilin D moderates platelet adhesion, but enhances the lytic resistance of fibrin

In the course of thrombosis, platelets are exposed to a variety of activating stimuli classified as 'strong' (e.g. thrombin and collagen) or 'mild' (e.g. ADP). In response, activated platelets adhere to injured vasculature, aggregate, and stabilise the three-dimensional fibrin scaffold of the expanding thrombus. Since 'strong' stimuli also induce opening of the mitochondrial permeability transition pore (MPTP) in platelets, the MPTP-enhancer Cyclophilin D (CypD) has been suggested as a critical pharmacological target to influence thrombosis. However, it is poorly understood what role CypD plays in the platelet response to 'mild' stimuli which act independently of MPTP. Furthermore, it is unknown how CypD influences platelet-driven clot stabilisation against enzymatic breakdown (fibrinolysis). Here we show that treatment of human platelets with Cyclosporine A (a cyclophilin-inhibitor) boosts ADP-induced adhesion and aggregation, while genetic ablation of CypD in murine platelets enhances adhesion but not aggregation. We also report that platelets lacking CypD preserve their integrity in a fibrin environment, and lose their ability to render clots resistant against fibrinolysis. Our results indicate that CypD has opposing haemostatic roles depending on the stimulus and stage of platelet activation, warranting a careful design of any antithrombotic strategy targeting CypD.

Blood Coagulation, Fibrinolytic and Inhibitory Profiles in Renal Transplant Recipients: Comparison of Cyclosporine and Azathioprine

Renal transplant recipients treated with cyclosporine (CS) have been reported to be at increased risk of thrombotic complications. The present study was intended to examine the blood coagulation, fibrinolytic, and inhibitory systems in such patients. Eight transplant recipients on maintenance immunosuppression with CS and prednisone were studied. Five transplant recipients maintained on azathioprine (AZA) and prednisone and 32 normal volunteers served as controls. Plasma antigen concentrations and/or activities of various proteins in the above pathways were measured. Both the CS and AZA groups exhibited significant elevations of factor IX activity, von Willebrand factor (vWF), D-dimer, protein C and tissue type plasminogen activator (t-PA) levels when compared with the normal controls. In addition, CS group showed a significant elevation of α2-macroglobulin activity and AZA group showed a significant reduction in factor XII activity when compared with the normal controls. Comparison of data from CS and AZA groups revealed higher factor XII activity and vWF concentration in the former group. In conclusion, transplant recipients treated with long-term cyclosporine and prednisone exhibited significant elevation of plasma vWF, D-dimer and protein C concentrations. In addition, both CS and AZA-treated transplant recipients showed increased plasma concentrations of D-dimer and t-PA. The latter observations suggest in vivo thrombin generation, fibrin formation and degradation.

Acute vision loss in systemic lupus erythematosus: bilateral combined retinal artery and vein occlusion as a catastrophic form of clinical flare

Presentation of a combination of branch retinal artery occlusion (BRAO)/central retinal artery occlusion (CRAO) and central retinal vein occlusion (CRVO) in systemic lupus erythematosus (SLE) is extremely rare. Herein, we have presented the case of a 29-year-old female with SLE, who simultaneously developed bilateral CRVO and BRAO/CRAO in the absence of antiphospholipid syndrome (APS) as a catastrophic form of clinical flare. A combinatorial diagnosis of CRVO and BRAO/CRAO should be considered during clinical flare-up in a patient with SLE who presents with rapidly progressive visual loss.

The Effects of Cyclosporine and Aspirin on Platelet Function in Normal Dogs

Background

Cyclosporine increases thromboxane synthesis in dogs, potentially increasing the thrombogenic properties of platelets.

Hypothesis/Objectives

Our hypothesis was that the concurrent administration of low‐dose aspirin and cyclosporine would inhibit cyclosporine‐associated thromboxane synthesis without altering the antiplatelet effects of aspirin. The objective was to determine the effects of cyclosporine and aspirin on primary hemostasis.

Animals

Seven healthy dogs.

Methods

A randomized, crossover study utilized turbidimetric aggregometry and a platelet function analyzer to evaluate platelet function during the administration of low‐dose aspirin (1 mg/kg PO q24h), high‐dose aspirin (10 mg/kg PO q12h), cyclosporine (10 mg/kg PO q12h), and combined low‐dose aspirin and cyclosporine. The urine 11‐dehydro‐thromboxane‐B₂ (11‐dTXB₂)‐to‐creatinine ratio also was determined.

Results

On days 3 and 7 of administration, there was no difference in the aggregometry amplitude or the platelet function analyzer closure time between the low‐dose aspirin group and the combined low‐dose aspirin and cyclosporine group. On day 7, there was a significant difference in amplitude and closure time between the cyclosporine group and the combined low‐dose aspirin and cyclosporine group. High‐dose aspirin consistently inhibited platelet function. On both days, there was a significant difference in the urinary 11‐dTXB₂‐to‐creatinine ratio between the cyclosporine group and the combined low‐dose aspirin and cyclosporine group. There was no difference in the urinary 11‐dTXB₂‐to‐creatinine ratio among the low‐dose aspirin, high‐dose aspirin, and combined low‐dose aspirin and cyclosporine groups.

Conclusions and Clinical Importance

Low‐dose aspirin inhibits cyclosporine‐induced thromboxane synthesis, and concurrent use of these medications does not alter the antiplatelet effects of aspirin.

The β isoform of the catalytic subunit of protein phosphatase 2B restrains platelet function by suppressing outside-in αII b β3 integrin signaling

BACKGROUND

Calcium-dependent signaling mechanisms play a critical role in platelet activation. Unlike calcium-activated protease and kinase, the contribution of calcium-activated protein serine/threonine phosphatase in platelet activation is poorly understood.

OBJECTIVE

To assess the role of catalytic subunit of protein phosphatase 2B (PP2B) or calcineurin in platelet function.

RESULTS

Here, we showed that an increase in PP2B activity was associated with agonist-induced activation of human and murine platelets. Pharmacological inhibitors of the catalytic subunit of protein phosphatase 2B (PP2B-A) such as cyclosporine A or tacrolimus (FK506) potentiated aggregation of human platelets. Murine platelets lacking the β isoform of PP2B-A (PP2B-Aβ(-/-) ) displayed increased aggregation with low doses of agonist concentrations. Loss of PP2B-Aβ did not affect agonist-induced integrin αII b β3 inside-out signaling, but increased basal Src activation and outside-in αII b β3 signaling to p38 mitogen-activated protein kinase (MAPK), with a concomitant enhancement in platelet spreading on immobilized fibrinogen and greater fibrin clot retraction. Fibrinogen-induced increased p38 activation in PP2B-Aβ(-/-) platelets were blocked by Src inhibitor. Both PP2B-Aβ(-/-) platelets and PP2B-Aβ-depleted human embryonal kidney 293 αII b β3 cells displayed increased adhesion to immobilized fibrinogen. Filamin A, an actin crosslinking phosphoprotein that is known to associate with β3 , was dephosphorylated on Ser(2152) in fibrinogen-adhered wild-type but not in PP2B-Aβ(-/-) platelets. In a FeCl3 injury thrombosis model, PP2B-Aβ(-/-) mice showed decreased time to occlusion in the carotid artery.

CONCLUSION

These observations indicate that PP2B-Aβ by suppressing outside-in αII b β3 integrin signaling limits platelet response to vascular injury.

[Thrombotic microangiopathy]

Thrombotic microangiopathy should be suspected every time the combination of microangiopathic hemolytic anemia without a coexisting cause, thrombocytopenia as well as renal and/or neurologic abnormalities occurs. The general term thrombotic microangiopathy includes different subtypes of the disease leading to abnormalities in multiple organ systems by endothelial injury and formation of platelet-rich thrombi in small vessels. The main types include thrombotic thrombocytopenic purpura in case of dominant neurologic abnormalities and the hemolytic uremic syndrome in case of acute kidney injury, respectively. Although these syndromes differ in their etiologies, clinical features, response to treatment, and prognosis, an early initiation of a direct therapeutic intervention frequently determines the clinical course of the patient. Irrespectively of the underlying etiology, plasma exchange is an essential component of acute therapeutic intervention while ongoing diagnostics are used to identify the definite treatment.

Aortic arterial stiffness is a moderate predictor of cardiovascular disease in patients with psoriasis vulgaris

Psoriasis is associated with an increased risk of atherosclerosis. Endothelial dysfunction is the critical early step in the process of atherogenesis, and it is commonly investigated by measuring arterial stiffness. We aimed to investigate the relationship between arterial stiffness and high-sensitivity C-reactive protein (hsCRP) in patients with psoriasis. A total of 32 patients with psoriasis and 35 patients with other skin diseases were included in the study. The hsCRP levels and arterial stiffness measurements were compared. Arterial stiffness was significantly different between the 2 groups (P = .01). Arterial stiffness was not associated with the duration of the disease or the disease activity (P = .34 and .64, respectively). In patients with psoriasis, arterial stiffness correlated positively with age, sex, body mass index, diastolic blood pressure, and hsCRP level (P < .05). These findings provide further evidence of a link between inflammation, premature atherosclerosis, and psoriasis.

Catheter fragmentation and local lysis in two lung transplant patients with pulmonary embolism

In conjunction with the rising number of lung transplant operations in the past decade, an increased predisposition to venous thrombosis (VT), particularly within the first year posttransplantation has been observed. Previous studies have revealed that between 8.6% and 12% of patients develop VT, which can ultimately result in pulmonary emboli (PE).Transplanted lungs pose a much greater infarction risk due to their lack of collateral vascularisation, relying entirely on the vasa publica--the pulmonary artery--in the absence of vasa privata. Such losses in viable lung parenchyma are always serious, but carry still greater risks for single-lung transplant recipients, an early diagnosis and treatment remain critical. Here we report on two cases of PE after lung transplantation, both of whom were managed with catheter fragmentation and local thrombolysis. In our opinion, this approach represents a viable treatment for symptomatic PE in lung transplant recipients. The benefits and risks of the alternative treatment options in these special cases will be reviewed and the definitive therapy was described. In the patients treated, catheter fragmentation with localized thrombolysis resulted in short term improvements in graft function, but could not prevent later lung infarction in one case.

A kidney transplant patient on cyclosporine therapy presenting with dural venous sinus thrombosis: a case report

Dural vein thrombosis is an important but rare cause of headache. Therapy with cyclosporine has been reported to result in thrombotic events. We report an unusual case of superior sagittal and transverse sinus thrombosis associated with cyclosporine therapy in a kidney transplant patient.

Effects of immunosuppressive drugs on platelet aggregation and soluble P-selectin levels in renal transplant patients

BACKGROUND/AIM

Post-transplant cardiovascular events are associated with increased morbidity and mortality after renal transplantation. Though renal transplantation eliminates cardiovascular disease risk factors by restoring renal function, it introduces new cardiovascular risks derived partly from immunosuppressive medications. In this study, to assess the effects of various immunosuppressive drugs on platelet function of renal transplant patients, we measured soluble P selectin levels (sP-selectin) and performed platelet aggregation studies in patients who have undergone renal transplantation.

METHODS

sP-selectin levels and platelet aggregation induced by 5 microM adenosine diphosphate (ADP), 5 microM epinephrine, 1.25 mg/mL ristocetin, and 2 microg/mL collagen were studied by whole blood platelet lumi-aggregometer in 40 renal transplant patients. Patients in group 1 (n = 24) were treated with cyclosporine/mycophenolate mofetil/methylprednisolone, and group 2 (n = 16) were treated with tacrolimus/mycophenolate mofetil/methylprednisolone. Effects were compared with those in control groups of hypertensive subjects and healthy subjects.

RESULTS

Platelet aggregation values induced by ADP, epinephrine, ristocetin, and collagen were lower in cyclosporine-treated patients than tacrolimus-treated patients, hypertensive subjects, and healthy subjects, though the difference was not statistically significant (p > 0.05). sP-selectin levels were appreciably higher in cyclosporine-treated patients, and statistically significant differences were observed compared with those of tacrolimus-treated patients (p < 0.05), hypertensive subjects (p < 0.01), and healthy subjects (p < 0.05).

CONCLUSION

We conclude that cyclosporine-treated renal transplant patients show enhanced platelet activation in which anti-platelet therapy should be considered, in addition to management of other conventional cardiovascular risk factors, to decrease the cardiovascular morbidity and mortality in this high risk population.

[Orthotopic renal transplant: our experience]

Orthotopic renal transplant (ORT) is useful in cases of severe atherosclerosis, heterotopic bilateral transplant, unsuitable pelvic vessels and in aortic thrombosis, but it is not available in all the institutions and it is only realized of exceptional form.

AIM

To review the indication, surgical technique and outcome of the ORT at our hospital.

MATERIAL AND METHODS

The studied included five cases between January 1990 and December 2005. We analyzed several variables: demographic characteristics, characteristics of the donor, ischemia times, evolution of renal function and morbi-mortality associated.

RESULTS

Left ORT was performed in three men and two women. Mean patient age was 52+/-5 years, all the patients received kidneys from cadaveric donors. Mean creatinine and urea one month postoperative were 2.2+/-0.72 mg/dl and 103+/-17.2 mg/dl and at 6 months postoperative were 1.8+/-0.59 mg/dl and 78+/-14 mg/dl respectively. Immediately all patients received prophylaxis with low molecular weight heparin but it was indicated antiaggregation to two patients when they left the hospital, anticoagulation to two patients and to one of them was decided to anticoagulation nor antiagregation for history of bled digestive. A patient died for bleeding episode at level of the renal graft six months after the transplant, she was in treatment with dicumarinics, they were indicated by venous deep thrombosis in right leg. The survival a year is 80 % of the graft and the patient. Only two patients returned to hospital later, one of them for presenting an episode of diverticulitis and the other one for renal obstructive failure that needed laying of catheter pig-tail. Four patients presented stenosis of renal native vassels detected in control magnetic nuclear resonance, not symptomatic. There are two patients who take more than three years transplanted with renal stable function (creatinina 1.3 mg/dl and 1.4 mg/dl respectively).

CONCLUSION

ORT is an excellent option in patients with co-morbidity increased for atherosclerosis and that cannot be placed in the iliac fossaes.

Critical care perspective on immunotherapy in lung transplantation

Lung transplantation is now a viable therapeutic option in the care of patients with advanced pulmonary parenchymal or pulmonary vascular disease. Lung transplantation, however, with chronic posttransplant immunosuppression, creates a uniquely vulnerable population of patients likely to experience significant life-threatening complications requiring intensive care. The introduction of several novel immunosuppressive agents, such as sirolimus and mycophenolate mofetil, in conjunction with more established agents such as cyclosporine and tacrolimus, has greatly increased treatment options for lung transplant recipients and likely contributed to improved short-term transplant outcomes. Modern transplant immunosuppression, however, is associated with a host of complications such as opportunistic infections, renal failure, and thrombotic thrombocytopenic purpura. The main focus of this review is to provide a comprehensive summary of modern immunotherapy in lung transplantation and to increase awareness of the serious and potentially life-threatening complications of these medications.

Decreased risk of renal allograft thrombosis associated with interleukin-2 receptor antagonists: a report of the NAPRTCS

Graft thrombosis is the most common cause of first year graft failure in pediatric renal transplantation. The North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database was analyzed for cases of graft failure due to thrombosis among patients transplanted from 1998 to 2004. The impact of interleukin-2 (IL-2) receptor antagonists as induction therapy was determined. There were a total of 51 graft failures due to thrombosis among the 2750 reported renal transplants (1.85%) (95% CI (1.39%, 2.41%)). This represents the most common cause of graft loss during the first year post-transplant accounting for 35% of first year losses and 18% of all graft losses. The incidence of thrombosis among patients who received IL-2 receptor antibodies was 1.07% (12/1126) compared to 2.40% (39/1624) among patients who did not (OR 0.44, 95% CI 0.23, 0.84, p = 0.014). Use of IL-2 receptor blockade was the only significant prognostic factor in a multivariate model with previously identified risk factors. Analysis of NAPRTCS data found that the use of IL-2 receptor antibodies as induction therapy is associated with a significantly decreased risk of graft failure due to thrombosis. This provocative finding requires further investigation to determine whether thrombotic failure can be decreased by this therapeutic strategy.

Calcineurin inhibitor-free immunosuppression in renal allograft recipients with thrombotic microangiopathy/hemolytic uremic syndrome

Thrombotic microangiopathy (TMA) and hemolytic uremic syndrome (HUS) represent serious threats to kidney allograft recipients. During a 4-year period, among 850 kidney transplantations, seven recipients with primary HUS and seven recipients (eight transplants) with previous or de novo TMA/HUS were identified and given calcineurin inhibitor (CNI)-free immunosuppression by sirolimus (SRL), mycophenolate mofetil and steroids. Thirteen out of 15 transplantations were successful in the long term; resulting in a mean creatinine of 101 mumol/L (16.4 months follow-up). In patients maintained on CNI-free regimen, no TMA/HUS recurrences were observed. A high rate of acute rejections (53%) may indicate insufficient immunosuppressive power and/or a causative relationship between TMA/HUS and rejection. Wound-related complications were abundant (60%), and call for surgical/immunosuppressive countermeasures. Our experience supports the idea that CNI's are major offenders in TMA/HUS induction. Total CNI elimination seems essential, as the nephrotoxic combination CNI + SRL may promote TMA. Features of TMA/HUS should be carefully explored in recurrent 'high responders'.

Platelet surface receptor activation in patients with chronic renal failure on hemodialysis, peritoneal dialysis and those with successful kidney transplantation

Hemostatic disorders associated with chronic renal failure (CRF) include hemorrhagic and/or thrombotic manifestations, which were ascribed, in part, to uremic platelet dysfunction including abnormalities of expression of platelet glycoprotein receptors. There is, however, still no general agreement on the exact characterization of these platelet abnormalities. This study aims at characterizing the platelet glycoprotein abnormalities associated with CRF, by recording the effect of the three renal replacement therapies, hemodialysis (HD), chronic ambulatory peritoneal dialysis (CAPD), and renal transplantation, on these receptors. The study, which was mainly cross-sectional, included two groups: (i) Patient groups (n = 50): HD patients (n = 20), CAPD patients (n = 10) and successful renal transplant patients (n = 20); (ii) Healthy Controls (n = 34): 23 were men and 11 were women who were age- and sex-matched with the patients. Flow cytometric quantitation of CD41, CD42a, CD42b and CD61 was carried out using a Becton-Dickinson FACScan. The expression of CD41 levels showed a highly significant increase in HD and CAPD patients when compared with the normal control levels. However, levels in transplant patients were comparable to the normal control levels. On the other hand, the expression of CD42a, CD42b, and CD61 showed no significant change in HD and CAPD patients when compared with normal control levels, but there was a significant decrease in transplant patients when compared to the normal control levels. In conclusion, there was evidence of increased expression of one glycoprotein receptor (GpIIb-IIIa) pre-dialysis whether HD or CAPD. In transplant patients, no evidence of platelet activation could be demonstrated.

Some aspects of hemostasis in kidney transplant recipients maintained on cyclosporine, azathioprine, and prednisone in comparison to patients treated with cyclosporine and prednisone

Cyclosporine (CyA) has been implicated to increase cardiovascular morbidity and mortality after renal transplantation. Impairment of the fibrinolytic system is one factor involved in the development of thrombotic complications. The aim of this study was to compare hematological and hemostatic parameters among patients on CyA, azathioprine, and prednisone (n = 31) versus CyA and steroids (n = 14). Using commercially available kits we evaluated thrombin activity as thrombin-antithrombin complexes (TAT), prothrombin fragments (1 + 2), thrombin activatable fibrinolysis inhibitor-(TAFI), TAFI activator, thrombomodulin (TM)-a marker for endothelial cell injury,-plasmin generation (plasmin-antiplasmin complex PAP), a glycoprotein linking coagulation and fibrinolysis. We observed that patients not treated with azathioprine displayed longer prothrombin times and activated partial thromboplastin times; higher fibrinogen, platelet counts and fibrinolytic activity index (FAI); shorter euglobulin clot lysis time; as well as lower thrombin generation markers namely, prothrombin fragments 1 + 2 and thrombin-antithrombin complexes. Although patients in the non-AZA group tended to have been engrafted for a longer time (P =.086), the groups did not differ with regard to age, BMI, erythrocyte count, hematocrit, leukocyte count, creatinine clearance, alanine and asparagine aminotransferase activities mean arterial blood pressure, fibrinogen, TAFI, thrombomodulin, or plasmin-antiplasmin complexes. These findings suggest that kidney transplant recipients on triple therapy are at greater risk of cardiovascular disease than those without azathioprine treatment, despite the lower fibrinolytic activity.

Posttransplantation thrombotic thrombocytopenic purpura: a single-center experience and a contemporary review

OBJECTIVE

To assess the activity of von Willebrand factor-cleaving protease (vWF-CP) in patients with thrombotic thrombocytopenic purpura (TTP) complicating bone marrow transplantation (BMT) and peripheral blood stem cell transplantation (PBSCT).

PATIENTS AND METHODS

From March 1, 1999, to June 30, 2001, allogeneic and autologous hematopoietic stem cell transplantation was performed in 118 and 400 patients, respectively. We reviewed risk factors for development of posttransplantation TTP and measured vWF-CP activity during active TTP in 10 recipients.

RESULTS

The incidence of TTP after allogeneic and autologous transplantation was 6.8% (8/118) and 0.25% (1/400), respectively. Among the allogeneic transplant recipients, the incidence of TTP after nonmyeloablative (NMA) PBSCT, matched unrelated donor BMT, and sibling BMT or PBSCT was 15.4% (2/13), 11.8% (2/17), and 4.5% (4/88), respectively. Of the 10 patients with TTP, 9 (90%) had received extensive prior therapy, including autologous transplantation in both NMA recipients. Acute graft-vs-host disease (GVHD) prophylaxis consisted of cyclosporine and methotrexate in most affected patients. The vWF antigen level was elevated in all patients, and no patients showed evidence of vWF-CP deficiency. During active TTP, 6 patients had grade II-IV acute GVHD, 1 had extensive chronic GVHD, and 4 had cytomegalovirus viremia. Risk factor analysis for development of TTP showed that transplant type (NMA and matched unrelated donor) and source of stem cells (bone marrow vs peripheral blood stem cell) were significant.

CONCLUSIONS

Posttransplantation TTP was not found to be associated with severe vWF-CP deficiency. The elevated levels of vWF antigen are consistent with diffuse endothelial injury likely because of multiple interacting factors such as extensive prior therapy, GVHD, cyclosporine, and reactivation of cytomegalovirus. The disorder appears to be more frequent among patients with, or at risk for, acute GVHD, suggesting a possible role in the pathogenesis. Nonmyeloablative transplantation does not appear to confer a lesser risk, possibly for these reasons.

Thrombotic thrombocytopenic purpura following stem cell transplantation

Thrombotic thrombocytopenic purpura (TTP) occurring after stem cell transplantation is poorly understood. The literature is scant and heterogeneous; little is known about the condition's pathogenesis except that it appears to differ from that of classical or de novo TTP. There are no widely agreed diagnostic criteria hence, it is difficult to compare the major findings of the relatively small, single centre series that have been reported. The true incidence is disputed and risk factors have only recently been evaluated. Plasma exchange is commonly employed for the therapy of severe post-transplant TTP but there are no data that support its use. This review summarises the state of knowledge of post-transplant TTP in 2002, addressing all the aforementioned issues and aims to provide the basis for further systematic study of this problematic complication of transplant.

Thrombotic thrombocytopenic purpura after allogeneic stem cell transplantation: a survey of the European Group for Blood and Marrow Transplantation (EBMT)

A survey was carried out among the European Group for Blood and Marrow Transplantation (EBMT) centres to determine the incidence, risk factors, treatment and outcome of thrombotic thrombocytopenic purpura (TTP) following allogeneic haematopoietic stem cell transplantation. TTP was defined as the simultaneous occurrence of red cell fragmentation, laboratory findings of haemolysis, red cell transfusion requirement and de novo or persistent thrombocytopenia caused by consumption, in the absence of disseminated intravascular coagulation. Forty-five centres reported all patients (n = 406) transplanted between July and December 1996. Twenty-three patients developed TTP; the risk of developing TTP was 6.7% at 2 years (95% CI: 4.1% to 9.3%). The median time of onset was 44 d (range 13-319) post transplantation. Significant risk factors for the development of TTP were female gender (P = 0.005) and an unrelated donor (P = 0.046). To treat TTP, cyclosporin administration was discontinued in 10 cases, plasma exchanges were performed in five cases and 12 patients received plasma infusions without plasma exchange. TTP resolved in 13 of the 23 patients (57%). The only factor predictive of resolution of TTP was the absence of nephropathy. Seven patients (30%) were alive at follow-up of 38-45 months from the onset of TTP. Sixteen patients died; the causes were multiple, only three patients had TTP as a central factor. The median time to death was 41 d (range 1-762 d) from the onset of TTP. TTP is a relatively frequent complication of allogeneic stem cell transplantation and it is associated with high mortality, though death is usually caused by multiple factors.

Enhancement by cyclosporine A and tacrolimus of serotonin-induced formation of small platelet aggregation

Cyclosporine A (CsA) may increase the incidence of thrombotic events, but whether tacrolimus (Tc) has such effects is still unclear. The serotonergic system has been linked to the thrombotic effects of CsA, but a direct effect of CsA on serotonin-induced platelet aggregation has not been demonstrated because of methodological difficulties. We measured the effects of CsA and Tc on serotonin-induced platelet aggregate formation by particle counting using light scattering. CsA and Tc both enhanced serotonin-induced formation of small platelet aggregates, however, neither CsA nor Tc affected aggregation induced by high or low concentrations of ADP, with or without addition of a serotonin receptor antagonist. Both CsA and Tc enhance platelet aggregation induced via the serotonin pathway.

Determinants of enhanced thromboxane biosynthesis in renal transplantation

BACKGROUND

Despite great improvement in patient and graft survival, the long-term morbidity and mortality in renal transplant recipients (RTRs) are still significant, with a high incidence of cardiovascular disease-related deaths.

METHODS

We investigated thromboxane (TXA2) biosynthesis and endothelial and coagulative activation in 65 patients who received a renal transplant.

RESULTS

The rate of TXA2 biosynthesis (urinary 11-dehydro-TXB2 excretion largely reflects platelet TXA2 production in vivo) was significantly (P < 0.0001) higher in RTRs than in healthy subjects. Plasma von Willebrand factor (vWF) and thrombin-antithrombin (TAT) complexes were significantly higher (P < 0.001) in RTRs compared with controls. Urinary 11-dehydro-TXB2 directly correlated with plasma vWF and cholesterol. We next examined the relative influence of cyclosporine A (CsA) on TXA2 biosynthesis and endothelial activation, comparing a group of RTRs not receiving CsA with an age- and sex-matched group of patients treated with CsA. Urinary excretion of 11-dehydro-TXB2 and plasma levels of vWF were significantly increased in RTRs who received CsA compared with those who did not. After an overall follow-up of 120 months, RTRs who experienced cardiovascular events had a higher frequency of abnormal plasma levels of vWF than patients who remained event free.

CONCLUSION

Renal transplantation is associated with in vivo platelet activation highly related to endothelial activation. This is particularly evident in CsA-treated patients. Administration of drugs that are able to reduce or eliminate thromboxane-dependent platelet activation in vivo may be beneficial to reduce the risk of cardiovascular events in RTRs.

Pretreatment with FK506 improves survival rate and gas exchange in canine model of acute lung injury

The novel effects of FK506 on shock induced by lipopolysaccharide and phorbol myristate acetate (LPS/PMA) were studied using beagles. Five groups were studied: endotoxin shock control group (both 0.5 mg/kg of LPS and 30 microg/kg of PMA, n = 6); methylprednisolone-treated endotoxin shock group (n = 5); FK506-treated endotoxin shock groups in which intravenous infusions of FK506 at 2.5 microg/kg/h (low dose, n = 5), 8 microg/kg/h (medium dose, n = 5), and 25 microg/kg/h (high dose, n = 5) were administered. In the control group, the survival rate was 33%. Also, arterial hypoxemia, systemic hypotension, and marked increases in pulmonary vascular resistance (PVR) and wet-to-dry weight ratio (W/D) were observed. FK506 treatment at both medium and high doses significantly attenuated these LPS/PMA-induced physiological changes, and the survival rates were 80 and 100%, respectively. On the other hand, in the methylprednisolone group, no obvious effects were observed. The present study suggests that FK506 could have prophylactic potential against acute lung injury in endotoxin shock.

Changes in surface expression of platelet membrane glycoproteins and progression of heart transplant vasculopathy

BACKGROUND

Transplant vasculopathy is the main limiting factor of the long-term success of heart transplantation. We sought to establish the role of platelets in the development and progression of transplant vasculopathy.

METHODS AND RESULTS

Platelet analysis and intracoronary ultrasound examination were performed in 78 heart transplant recipients. Quantitative intracoronary ultrasound was used to define the severity of disease at baseline (48.8+/-4.5 months after transplantation) and at 1-year follow-up. Platelet activation was assessed with the use of immunological surface markers of activation (ligand-induced binding site 1 [LIBS-1], P-selectin, GPIIb-IIIa) and flow cytometry. We found that LIBS-1 immunoreactivity was significantly increased in patients with diffuse disease when compared with focal transplant disease (median [quartile], 27[14, 64] versus 18[7.9, 47], P=0.04). In a logistic regression model, we found that LIBS-1 was an independent predictor for the presence and progression of diffuse transplant vasculopathy (P=0.04). Patients with enhanced LIBS-1 levels (>75% quartile) had a 3.3-fold increased relative risk (95% CI 1.8 and 18.9, P=0.002) for the presence of diffuse transplant vasculopathy. When a cutoff value of 16.5 for the level of LIBS-1 was used, patients had a 4.8-fold increased relative risk (95% CI 1.9 and 12.5, P<0.01) for the progression of transplant vasculopathy.

CONCLUSIONS

Enhanced platelet activation is strongly associated with the development and progression of transplant vasculopathy. Understanding the underlying pathophysiological mechanisms might contribute to the development of treatment strategies to prevent transplant vasculopathy.

Therapeutic apheresis for cancer related hemolytic uremic syndrome

Hemolytic uremic syndrome (HUS) can be seen as a result of disseminated cancer, as a consequence of chemotherapy, or in association with bone marrow transplantation (BMT). Further distinction can be made when the clinical presentation is that of an acute, fulminant course with rapidly progressive renal failure or that of a sub-acute form with a slow progression of renal involvement. Each of the different etiologies (cancer, chemotherapy, or BMT) and each of the two basic clinical presentations has its own prognosis. There are no randomized, controlled studies to elucidate the role of therapeutic apheresis for cancer-related HUS. Hemolytic uremic syndrome related to disseminated cancer is most often a terminal event and is not commonly treated with apheresis procedures, although there are anecdotal reports that plasma exchange may be beneficial. Chemotherapy and drug-related HUS have a prognosis that is strongly dependent on the severity of the presentation, but even in the most severe cases may respond to either immunoadsorption or plasma exchange with fresh frozen plasma (FFP). Finally, BMT-related HUS has a poor prognosis but may respond to immunoadsorption, plasma exchange, or a combination of the two.

Docosahexaenoic acid reverses cyclosporin A-induced changes in membrane structure and function

The use of a fish oil vehicle for cyclosporin A (CsA) can decrease the toxic effects of CsA but the mechanism is unclear. Here we examine the mechanism by which docosahexaenoic acid (DHA), a fish oil-derived polyunsaturated fatty acid, can alter the toxic effects of CsA on mouse organ function, endothelial macromolecular permeability, and membrane bilayer function. Mice given CsA and fish oil showed increased liver toxicity, kidney toxicity, incorporation of DHA, and evidence of oxidized fatty acids compared to control animals. We hypothesized that the toxic effects of CsA were primarily a result of membrane perturbation, which could be decreased if DHA were not oxidized. The presence of CsA (10 mol%) alone increased dipalmitoylphosphatidylcholine membrane permeability by seven fold over control (no CsA, no DHA). However, if non-oxidized DHA (15 mol%) and CsA were added to the membrane, the permeability returned to control levels. Interestingly, if the DHA was oxidized, the antagonistic effect of DHA on CsA was completely lost. While CsA alone increased endothelial permeability to albumin, the combination of non-oxidized DHA and CsA had no effect on endothelial macromolecular permeability. However the combination of oxidized DHA and CsA was no different than the effects of CsA only. CsA increased the fluorescence anisotropy of DPH in the liquid crystalline state of DPPC, while DHA decreased fluorescence anisotropy. However the combination of CsA and DHA was no different than DHA alone. We conclude that non-oxidized DHA can reverse the membrane perturbing effects of CsA, and the increases in endothelial macromolecular permeability, which may explain how fish oil is capable of decreasing the toxicity of CsA.

Nephrotoxicity of immunosuppressive drugs: long-term consequences and challenges for the future

The calcineurin inhibitors cyclosporin A (CsA) and tacrolimus (FK506) are associated with dose- and efficacy-limiting adverse events, including nephrotoxicity, which may diminish their overall benefits for long-term graft survival. Nephrotoxicity is difficult to distinguish from chronic allograft rejection and is a particular problem in the setting of renal transplantation. Minimizing immunosuppressant-induced nephrotoxicity could improve long-term renal allograft survival. However, to obtain significant long-term improvement in renal allograft outcomes, it may be necessary to adopt new immunosuppressive regimens that rely less on calcineurin inhibitors. Recipients of other transplanted organs, as well as patients with autoimmune diseases who require immunosuppressant therapy, could also benefit from this change in immunosuppressive drug strategy because their healthy, native kidneys are particularly susceptible to the nephrotoxic effects of CsA and FK506. CsA- and FK506-sparing regimens, which use reduced doses of CsA and FK506 in combination with other nonnephrotoxic immunosuppressants, may be the best current option for reducing nephrotoxicity. The chemical immunosuppressant mycophenolate mofetil (MMF) has been used as part of CsA- and FK506-sparing regimens that provide improved renal function while maintaining adequate immunosuppression. Such regimens should reduce patient morbidity and mortality. Also, because immunosuppressant-induced nephrotoxicity has been associated with significant financial costs, CsA- and FK506-sparing regimens should result in substantial savings in health care costs.

The peripheral serotonergic system and platelet aggregation in cyclosporin A-induced hypertensive rats

Cyclosporin A plays an important role in preventing rejection in allograft transplant recipients. However, the therapeutic use of cyclosporin A is associated with increased incidence of thromboembolic complications and drug-related hypertension. In order to study the mechanisms by which cyclosporin A induces these abnormal pathophysiological situations, we have assessed the platelet serotonin contents and whole blood platelet aggregation in control rats as well as in rats treated (orally) with 30 and 5 mg/kg/day of cyclosporin A, after 2 and 7 weeks of treatment. These doses correspond respectively to CsA "peak" and "trough" concentrations achieved in human blood in clinical practice (immediately following an intake of a daily dose of CsA and when the blood concentration stabilizes, respectively). Both trough and peak doses caused an increase in blood pressure after 2 and 7 weeks. Platelet serotonin content decreased in the cyclosporin-treated groups, in contrast with the control. Collagen-induced whole blood platelet aggregation increased drastically for the peak concentration-treated group, while adenosine 5'-diphosphate-induced platelet aggregation did not reach statistical significance. Finally, in vitro platelet thromboxane A2 generation increased in cyclosporin A concentrations when platelets were stimulated with either collagen or adenosine 5'-diphosphate. In conclusion, both tested cyclosporin A concentrations induced important changes in platelet serotonin and thromboxane content and aggregation, factors which may play a decisive role in the development and/or maintenance of hypertension and thrombotic complications.