Inhibition of the mTORC pathway in the antiphospholipid syndrome

Thrombosis and Anti-phospholipid Syndrome: a 5-Year Update on Treatment

PURPOSE OF REVIEW

The aim of this review is to provide an update of the therapeutic tools for thrombotic anti-phospholipid syndrome (APS), focusing on the last 5 years.

RECENT FINDINGS

Early studies appointed anticoagulation at moderate intensity as the mainstay of treatment of thrombotic APS; in the last 5 years, the strategy has not much mutated. Some uncertainties regarding the role of direct oral anticoagulants and the optimal regimen for arterial thrombotic APS still persist: high-intensity anticoagulation, anticoagulation plus anti-platelet agent, and double anti-platelet agents being the possible alternatives. Several drugs have been proposed as effective additional tools for the management of thrombotic APS: hydroxychloroquine, statins, vitamin D, and sirolimus might be beneficial when added on the top of anticoagulation. Pregnant women with thrombotic APS should be switched to low-dose aspirin plus low molecular weight heparin at therapeutic dose. Despite adequate treatment, APS patients display a significant rate of recurrences; rituximab, eculizumab, and intravenous immunoglobulins are among the options to be considered for these patients. From 2013 to date, the kaleidoscope of therapeutic options in thrombotic APS has been enriched, but tangible improvements in the management of patients are still awaited.

An unusual case of heart attack

We reported a patient with antiphospholipid syndrome (APS) secondary to systemic lupus erythematosus (SLE) who suffered from myocardial infarction and graft occlusion after coronary artery bypass surgery. Our patient illustrates the impact of accelerated atherosclerosis in patients with SLE and APS and the importance of early institution of antithrombotic therapies. In this article, the treatment of APS is summarized. Although the main stay of treatment is anticoagulation, there is emerging evidence to support rituximab as an option for “refractory” cases of APS.

Renal Involvement in Antiphospholipid Syndrome

Antiphospholipid syndrome is a complex autoimmune disease, characterized by the presence of vascular thrombosis, obstetric, hematologic, cutaneous, and cardiac manifestations. Renal disease in patients with antiphospholipid syndrome was not recognized in the first descriptions of the disease, but later on, the renal manifestations of the syndrome have been investigated widely. Renal manifestations of antiphospholipid syndrome conform a wide spectrum of diverse renal syndromes. Hypertension is one of the most frequent, but less commonly recognized renal alteration. It can be difficult to control as its origin is renovascular. Renal vascular thrombosis can be arterial or venous. Other alterations are renal infarction and vascular thrombosis in arterial territories. Venous thrombosis can be present in primary and secondary antiphospholipid syndrome; it presents with worsening of previous proteinuria or de novo nephrotic syndrome, hypertension and renal failure. Antiphospholipid syndrome nephropathy is a vascular disease that affects glomerular tuft, interstitial vessels, and peritubular vessels; histopathology characterizes the renal lesions as acute or chronic, the classic finding is thrombotic microangiopathy, that leads to fibrosis, tubule thyroidization, focal cortical atrophy, and glomerular sclerosis. Antiphospholipid syndrome nephropathy can also complicate patients with systemic lupus erythematosus, and there is vast information supporting the worse renal prognosis in this group of patients with the classic histopathologic lesions. Treatment consists of anticoagulation, as for other thrombotic manifestations of antiphospholipid syndrome. There is some evidence of glomerulonephritis as an isolated lesion in patients with antiphospholipid syndrome. The most frequently reported glomerulonephritis is membranous; with some reports suggesting that immunosuppressive treatment may be effective. Patients with end stage renal disease commonly are positive for antiphospholipid antibodies, but it is not clear what is the role of aPL in this setting. Patients with vascular access may have complications in the presence of antibodies so that anticoagulation is recommended. Patients ongoing renal transplant with persistent antiphospholipid antibody positivity may have early and late graft failure.

Cellular and Molecular Mechanisms of Anti-Phospholipid Syndrome

The primary anti-phospholipid syndrome (APS) is characterized by the production of antibodies that bind the phospholipid-binding protein β2 glycoprotein I (β2GPI) or that directly recognize negatively charged membrane phospholipids in a manner that may contribute to arterial or venous thrombosis. Clinically, the binding of antibodies to β2GPI could contribute to pathogenesis by formation of immune complexes or modification of coagulation steps that operate along cell surfaces. However, additional events are likely to play a role in pathogenesis, including platelet and endothelial cell activation. Recent studies focus on neutrophil release of chromatin in the form of neutrophil extracellular traps as an important disease contributor. Jointly, the participation of both the innate and adaptive arms of the immune system in aspects of the APS make the complete understanding of crucial steps in pathogenesis extremely difficult. Only coordinated and comprehensive analyses, carried out in different clinical and research settings, are likely to advance the understanding of this complex disease condition.

Renal involvement in antiphospholipid syndrome

This is a review of scientific publications on renal involvement in antiphospholipid syndrome (APS), with focus on clinical and histopathological findings and treatment. A search for English-language articles on renal involvement in APS covering the period 1980-2017 was conducted in Medline/PubMed and Scopus databases using the MeSH terms "antiphospholipid syndrome", "antiphospholipid antibodies", "glomerulonephritis" and "thrombotic microangiopathy" (TMA). APS nephropathy is primarily the result of thromboses in renal arteries or veins, intraparenchymatous arteries and glomerular capillaries. On histology, APS nephropathy is characterized by TMA, but chronic vaso-occlusive lesions are also commonly observed (fibrous intimal hyperplasia, focal cortical atrophy, fibrous occlusions of arteries). Anticardiolipin and lupus anticoagulant are the most prevalent antibodies in patients with APS nephropathy. The spectrum of renal manifestations includes renal vein thrombosis, renal artery thrombosis/stenosis, TMA, increased allograft vascular thrombosis and malignant hypertension. Anticoagulation is the standard treatment of thrombotic events. In systemic lupus erythematosus (SLE) patients with antiphospholipid antibodies (aPL), kidney failure due to SLE nephritis (immune-complex disease) should be clearly distinguished from kidney failure due to APS-related TMA. In such cases, renal biopsy is mandatory. SLE nephritis requires immunosuppressive therapy, whereas APS nephropathy is usually treated with anticoagulants. Recently, eculizumab and sirolimus have been proposed as a rescue therapy. Based on our review, APS nephropathy appears to be a distinct clinical condition. TMA is a characteristic histopathological finding in APS and is strongly associated with the presence of aPL. This has important therapeutic implications and allows distinguishing APS nephropathy from lupus nephritis.

Targeting Regulatory T Cells to Treat Patients With Systemic Lupus Erythematosus

Regulatory T cells (Tregs) are central in integration and maintenance of immune homeostasis. Since breakdown of self-tolerance is a major culprit in the pathogenesis of systemic lupus erythematosus (SLE), restoration of the immune tolerance through the manipulation of Tregs can be exploited to treat patients with SLE. New information has revealed that Tregs besides their role in suppressing the immune response are important in tissue protection and regeneration. Expansion of Tregs with low-dose IL-2 represents an approach to control the autoimmune response. Moreover, control of Treg metabolism can be exploited to restore or improve their function. Here, we summarize the function and diversity of Tregs and recent strategies to improve their function in patients with SLE.

Sirolimus in patients with clinically active systemic lupus erythematosus resistant to, or intolerant of, conventional medications: a single-arm, open-label, phase 1/2 trial

BACKGROUND

Patients with systemic lupus erythematosus have T-cell dysfunction that has been attributed to the activation of the mammalian target of rapamycin (mTOR). Rapamycin inhibits antigen-induced T-cell proliferation and has been developed as a medication under the generic designation of sirolimus. We assessed safety, tolerance, and efficacy of sirolimus in a prospective, biomarker-driven, open-label clinical trial.

METHODS

We did a single-arm, open-label, phase 1/2 trial of sirolimus in patients with active systemic lupus erythematosus disease unresponsive to, or intolerant of, conventional medications at the State University of New York Upstate Medical University (Syracuse, NY, USA). Eligible participants (aged ≥18 years) had active systemic lupus erythematosus fulfilling four or more of 11 diagnostic criteria defined by the American College of Rheumatology. We excluded patients with allergy or intolerance to sirolimus, patients with life-threatening manifestations of systemic lupus erythematosus, proteinuria, a urine protein to creatinine ratio higher than 0·5, anaemia, leucopenia, or thrombocytopenia. Patients received oral sirolimus at a starting dose of 2 mg per day, with dose adjusted according to tolerance and to maintain a therapeutic range of 6-15 ng/mL. Patients were treated with sirolimus for 12 months. Safety outcomes included tolerance as assessed by the occurrence of common side-effects. The primary efficacy endpoint was decrease in disease activity, assessed using the British Isles Lupus Assessment Group (BILAG) index and the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Blood samples of 56 matched healthy individuals were obtained as controls for immunobiological outcomes monitored at each visit. The primary efficacy endpoint was assessed in all patients who completed 12 months of treatment, and all patients who received at least one dose of treatment were included in the safety analyses. This trial is registered with ClinicalTrials.gov, number NCT00779194.

FINDINGS

Between March 9, 2009, and Dec 8, 2014, 43 patients were enrolled, three of whom did not meet eligibility criteria. 11 of the 40 eligible patients discontinued study treatment because of intolerance (n=2) or non-compliance (n=9). SLEDAI and BILAG disease activity scores were reduced during 12 months of treatment in 16 (55%) of 29 patients who completed treatment. Mean SLEDAI score decreased from 10·2 (SD 5·6) at enrolment to 4·8 (4·5) after 12 months of treatment (p<0·001) and the mean total BILAG index score decreased from 28·4 (12·4) at enrolment to 17·4 (10·7) after 12 months of treatment (p<0·001). The mean daily dose of prednisone required to control disease activity decreased from 23·7 mg (SD 9·6) to 7·2 mg (2·3; p<0·001) after 12 months of treatment. Sirolimus expanded CD4+CD25+FoxP3+ regulatory T cells and CD8+ memory T-cell populations and inhibited interleukin-4 and interleukin-17 production by CD4+ and CD4-CD8- double-negative T cells after 12 months. CD8+ memory T cells were selectively expanded in SRI-responders. Patient liver function and lymphocyte counts were unchanged. Although HDL-cholesterol (Z=-2·50, p=0·012), neutrophil counts (Z=-1·92, p=0·054), and haemoglobin (Z=-2·83, p=0·005) were moderately reduced during treatment, all changes occurred within a range that was considered safe. Platelet counts were slightly elevated during treatment (Z=2·06, p=0·0400).

INTERPRETATION

These data show that a progressive improvement in disease activity is associated with correction of pro-inflammatory T-cell lineage specification in patients with active systemic lupus erythematosus during 12 months of sirolimus treatment. Follow-up placebo-controlled clinical trials in diverse patient populations are warranted to further define the role of mTOR blockade in treatment of systemic lupus erythematosus.

FUNDING

Pfizer, the National Institutes of Health, and the Central New York Community Foundation.

Pretransplant IgA-Anti-Beta 2 Glycoprotein I Antibodies As a Predictor of Early Graft Thrombosis after Renal Transplantation in the Clinical Practice: A Multicenter and Prospective Study

Background

Graft thrombosis is a devastating complication after renal transplantation. We recently described the association of anti-beta-2-glycoprotein-I (IgA-ab2GP1) antibodies with early graft loss mainly caused by thrombosis in a monocenter study.

Methods

Multicenter prospective observational cohort study.

Setting and participants

Seven hundred forty patients from five hospitals of the Spanish Forum Renal Group transplanted from 2000 to 2002 were prospectively followed-up for 10 years.

Outcomes

Early graft loss and graft loss by thrombosis.

Measurements

The presence of IgA anti-B2GP1 antibodies in pretransplant serum was examined using the same methodology in all the patients.

Results

At transplantation, 288 patients were positive for IgA-B2GP1 (39%, Group-1) and the remaining were negative (Group-2). Graft loss at 6 months was higher in Group-1 (12.5 vs. 4.2% p < 0.001), vessel thrombosis being the most frequent cause of early graft loss, especially in Group-1 (6.9 vs. 0.4% p < 0.001). IgA-aB2GP1 was the most important independent risk factor for graft thrombosis (hazard ratio: 13.83; 95% CI: 3.17-60.27, p < 0.001). Furthermore, the, presence of IgA-aB2GP1 was associated with early graft loss and delayed graft function. At 10 years, survival figures were also lower in Group-1: graft survival was lower compared with Group-2 (60.4 vs. 76.8%, p < 0.001). Mortality was significantly higher in Group-1 (19.8 vs. 12.2%, p = 0.005).

Limitations

Patients were obtained during a 3-year period (1 January 2000-31 December 2002) and kidneys were only transplanted from brain-dead donors. Nowadays, the patients are older and the percentage of sensitized and retransplants is high.

Conclusion

In a prospective observational multicenter study, we were able to corroborate that pretransplant presence of IgA-aB2GP1 was the main risk factor for graft thrombosis and early graft loss. Therefore, a prospective study is needed to evaluate the efficacy and safety of prophylactic anticoagulation to avoid this severe complication.

Treatment of antiphospholipid syndrome beyond anticoagulation

Antiphospholipid syndrome (APS) is a systemic autoimmune disorder marked by thrombosis and/or pregnancy morbidity in the presence of antiphospholipid antibodies (aPL). At the present time, treatment is primarily focused on anticoagulation. However, there is increasing awareness of the mechanisms involved in APS pathogenesis, which has led to the trial of novel therapies targeting those mechanisms. Following a brief review of the etiopathogenesis of and current management strategies in APS, this paper focuses on the evidence for these potential, targeted APS treatments, e.g., hydroxychloroquine, statins, rituximab, belimumab, eculizumab, defibrotide, sirolimus, and peptide therapy.

Antiphospholipid syndrome, "the best prophet of the future"

The antiphospholipid syndrome (APS) is an autoimmune disorder characterized by the occurrence of venous and arterial thromboses, often multiple, and obstetric-related adverse events in the presence of antiphospholipid antibodies (aPL). APS, first described in 1983, as thrombosis, abortion and cerebral disease, is nowadays recognised as a systemic disease with a wide constellation of clinical manifestations related to acute and chronic vascular lesions. The presence of aPL is the serological hallmark of APS representing a heterogeneous population of autoantibodies with many antigenic specificities directed to phospholipid-binding proteins, either alone or in combination with phospholipids. Many assays have been developed for aPL detection. Particularly, anticardiolipin antibodies, anti-β2-glycoprotein I antibodies and lupus anticoagulant are essential tools for APS diagnosis. The cumulative evidence indicates that aPL are pathogenic autoantibodies binding to target cells and promoting thrombosis and pregnancy complications through a wide range of pathological mechanisms not yet fully understood. Finally, the recognition of the important role of aPL to assess the individual risk of thrombosis or pregnancy complications has expanded the concept of aPL, and currently aPL profile is regarded as a major risk factor for clinical thrombotic events.

The Potential Role of Trained Immunity in Autoimmune and Autoinflammatory Disorders

During induction of trained immunity, monocytes and macrophages undergo a functional and transcriptional reprogramming toward increased activation. Important rewiring of cellular metabolism of the myeloid cells takes place during induction of trained immunity, including a shift toward glycolysis induced through the mTOR pathway, as well as glutaminolysis and cholesterol synthesis. Subsequently, this leads to modulation of the function of epigenetic enzymes, resulting in important changes in chromatin architecture that enables increased gene transcription. However, in addition to the beneficial effects of trained immunity as a host defense mechanism, we hypothesize that trained immunity also plays a deleterious role in the induction and/or maintenance of autoimmune and autoinflammatory diseases if inappropriately activated.

Early Renin-angiotensin System Blockade Improved Short-term and Longterm Renal Outcomes in Systemic Lupus Erythematosus Patients with Antiphospholipid-associated Nephropathy

Objective.

To investigate the renal protective effects of early renin-angiotensin-aldosterone system (RAAS) blockade with renin-angiotensin system inhibitors (RASI) in systemic lupus erythematosus (SLE) patients with antiphospholipid-associated nephropathy (aPLN).

Methods.

Medical data of 57 SLE patients with biopsy-proven aPLN were analyzed. Early RAAS blockade was defined as administration of RASI within 3 months after kidney biopsy and continued for ≥ 12 months.

Results.

There was no significant difference in demographic data, laboratory findings, and renal histology by the time of kidney biopsy, except that the RASI group had higher proteinuria levels vs the non-RASI group [5.2 (2.8–8.8) vs 1.9 (0.6–2.8) g/d, p = 0.005, respectively] and higher prevalence of hypertension (75% vs 29%, p = 0.001, respectively). No significant difference between the 2 groups was observed in estimated glomerular filtration rate (eGFR), mean arterial pressure, and proteinuria level at 12 months after kidney biopsy. The improvement ratio of eGFR at 12 months was significantly higher in the RASI group versus the non-RASI group [26% (−5 to 86) vs −2% (−20 to 20), p = 0.028, respectively], and the rate of change in eGFR beyond 12 months was similar between the 2 groups. During a mean followup of 80 months, 4 (23%) patients in the non-RASI group and 3 (8%) patients in the RASI group developed kidney disease progression. Early RAAS blockade significantly decreased the risk of kidney disease progression [HR = 0.11 (0.02–0.59); p = 0.010]. Proteinuria and hypertension controls were similar between the 2 groups.

Conclusion.

Early RAAS blockade improved the short-term and longterm renal outcomes in SLE patients with aPLN. The renal protective effect of RASI was independent of its antihypertensive and antiproteinuric effects.

The treatment of anti-phospholipid syndrome: A comprehensive clinical approach

Anti-phospholipid syndrome (APS) is an acquired pro-thrombotic autoimmune disease that predisposes to thrombotic events and/or obstetric complications, in the persistent presence of anti-phospholipid antibodies (aPL). Life long moderate-intensity anticoagulation is the option of choice for aPL-positive patients with a previous thrombosis; critical issues concern the management of those with a history of arterial event due to the high rate of recurrence. Alternatives comprise anti-platelet agents and high-intensity anticoagulation. Low dose aspirin (LDASA) and low molecular weight heparin provide the mainstay of the treatment of obstetric APS, allowing a birth rate in 70% of cases. The management of refractory APS, thrombotic as well as obstetric, is highly debated, but an increasing burden of evidence points towards the beneficial effects of multiple treatments. Similarly, a management envisaging multiple drugs (anticoagulation, steroids, plasma exchange and/or intravenous immunoglobulins) is the most effective approach in catastrophic APS. Asymptomatic aPL carriers are at higher risk of thrombotic and obstetric complications compared to the general population, thus potentially benefitting of a pharmacological intervention. LDASA and hydroxychloroquine can be considered as options, in particular in case of high risk aPL profile, concomitant cardiovascular risk factors or associated autoimmune disease. APS is apparently a simple condition, but its multifaceted nature requires a complex and tailored treatment.

Catastrophic antiphospholipid syndrome and pregnancy

Catastrophic antiphospholipid syndrome (CAPS) is a rare but life-threatening condition that may be precipitated by pregnancy. The condition can be hard to diagnose since it mimics other thrombotic microangiopathies that are associated with pregnancy. Accurate and timely diagnosis is critical for effective treatment. In this review, we highlight pertinent clinical features of CAPS so that obstetricians will be able to recognize and treat the condition.

Blockade of Treg Cell Differentiation and Function by the Interleukin-21-Mechanistic Target of Rapamycin Axis Via Suppression of Autophagy in Patients With Systemic Lupus Erythematosus

OBJECTIVE

The mechanistic target of rapamycin (mTOR) has become a therapeutic target in systemic lupus erythematosus (SLE). In T cells, mTOR plays a central role in lineage specification, including development of regulatory cells (Treg cells). This study sought to investigate whether mTOR is activated within Treg cells and whether this contributes to the depletion and dysfunction of Treg cells in patients with SLE.

METHODS

Activities of mTOR complexes 1 (mTORC1) and 2 (mTORC2) were examined by quantifying phosphorylation of translation initiation factor 4E-binding protein 1, S6 kinase, and Akt in SLE patients relative to age- and sex-matched female healthy control subjects. Polarization of Treg cells from naive CD4+ T cells was assessed in the presence of interleukin-6 (IL-6), IL-17, and IL-21. The suppressor function of sorted CD4+CD25+ Treg cells was measured by determining their impact on the proliferation of autologous CD4+CD25- responder T cells. Treg cell expression of FoxP3, GATA-3, and CTLA-4 was monitored by flow cytometry. Autophagy was assessed using immunoblotting of light chain 3 lipidation. The effect of mTOR blockade was evaluated by testing the impact of rapamycin treatment on Treg cell function.

RESULTS

SLE Treg cells exhibited increased activities of mTORC1 and mTORC2, whereas autophagy, the expression of GATA-3 and CTLA-4, and the suppressor function of Treg cells were diminished. IL-21, but not IL-6 or IL-17, blocked the development of Treg cells. IL-21 stimulated mTORC1 and mTORC2, and it abrogated the autophagy, differentiation, and function of Treg cells. Moreover, IL-21 constrained the expression of GATA-3 and CTLA-4 selectively in Treg cells. In turn, blockade of mTORC1 by 3-day rapamycin treatment enhanced transforming growth factor β production, while dual blockade of mTORC1 and mTORC2 by 4-week rapamycin treatment induced autophagy, restored the expression of GATA-3 and CTLA-4, and corrected Treg cell function.

CONCLUSION

IL-21-driven mTOR activation is a pharmacologically targetable checkpoint of the deficient autophagy that underlies Treg cell dysfunction in SLE.

Arterial stenosis in antiphospholipid syndrome: Update on the unrevealed mechanisms of an endothelial disease

First described in 1983, antiphospholipid syndrome (APS) is an autoimmune condition characterized by the occurrence of recurrent arterial and/or venous thrombosis, and/or pregnancy morbidity, in the setting of persistent presence of antiphospholipid antibodies (aPL). While thrombosis is the most well-known pathogenic mechanism in this disorder, the relevance of some other mechanisms such as arterial stenosis is being increasingly recognized. Arterial stenosis has been first described in the renal arteries in patients with APS, however intracranial and coeliac arteries can also be involved with various and treatable clinical manifestations. The underlying pathophysiology of this stenotic arterial vasculopathy is not fully understood but some recent studies revealed new insights into the molecular mechanism behind this endothelial cell activation in APS. In this review, we discuss these newly discovered mechanisms and highlight the diagnostic and therapeutic modalities of the APS related arterial stenosis.

Catastrophic Antiphospholipid Syndrome: Candidate Therapies for a Potentially Lethal Disease

Catastrophic antiphospholipid syndrome (CAPS) is a potentially lethal disease that presents with rapidly progressive multiple organ thromboses. Anticoagulation, corticosteroids, intravenous immunoglobulin, and plasma exchange are the most commonly used treatments for CAPS patients. However, the high mortality despite these medications necessitates new treatment strategies. Following a brief review of current diagnostic and management strategies, we discuss the candidate therapies, i.e., hydroxychloroquine, rituximab, eculizumab, sirolimus, and defibrotide, that can be considered in CAPS patients refractory to traditional treatment.

IgA anti-β2 glycoprotein I antibodies: Experience from a large center

OBJECTIVE

IgG and IgM antibodies directed at β2-glycoprotein I are included in the classification criteria for the antiphospholipid syndrome (APS) while the IgA antibodies against β2-glycoprotein I (IgA aβ2GPI) are not. Conflicting data about the significance of IgA aβ2GPI and APS manifestation can be found and more studies are necessary in order to define the diagnostic value of IgA aβ2GPI. In the present article, we investigated the possible role of IgA aβ2GPI as marker of APS.

METHODS

A cohort of 314 patients with APS and systemic autoimmune disease was investigated for the presence of IgA aβ2GPI and its association with clinical manifestation of APS.

RESULTS

Eighty-nine patients presented IgA aβ2GPI, 68 cases associated with others antiphospholipid antibodies (aPL) and in 21 cases being the only aPL present. In primary APS IgA aβ2GPI are highly coincidental with other aPL (92,2%) while most of the isolated IgA aβ2GPI were present in the SLE group (16/21). No association between IgA aβ2GPI and APS manifestations: thrombosis and pregnancy morbidity was found, while a positive association between IgA aβ2GPI and the presence of anti-nDNA, anti-RNP, anti-Sm, anti-SSA, anti-SSB antibodies was encountered.

CONCLUSION

Our study does not show association between IgA aβ2GPI and APS manifestations and does not support the inclusion of IgA aβ2GPI as a classification criteria for APS.

Antiphospholipid antibody-induced cellular responses depend on epitope specificity : implications for treatment of antiphospholipid syndrome

Essentials Antiphospholipid antibodies (aPL) are heterogeneous and induce different cellular responses. We analyzed signaling events induced by different monoclonal and patient aPL in monocytes. Two major signaling pathways involving either NADPH-oxidase or LRP8 were identified. Our data suggest that these two pathways mediate the majority of aPL effects on monocytes.

SUMMARY

Background Antiphospholipid antibodies (aPLs) contribute to the pathogenesis of the antiphospholipid syndrome (APS) by induction of an inflammatory and procoagulant state in different cell types, and several signaling pathways have been described. Objectives To investigate whether signaling depends on the epitope specificity of aPLs. Methods Cellular effects of three human monoclonal aPLs with distinctly different epitope specificities were analyzed in vitro. Expression of tumor necrosis factor-α mRNA by mouse and human monocytes was the major readout. Analysis included cells from genetically modified mice, and the use of specific inhibitors in human monocytes. Data were validated with IgG isolated from 20 APS patients. Results Cofactor-independent anticardiolipin aPLs activated monocytes by induction of endosomal NADPH oxidase. Activation could be blocked by hydroxychloroquine (HCQ). Anti-β2 -glycoprotein I aPL activated monocytes by interacting with LDL receptor-related protein 8 (LRP8). This could be blocked by rapamycin. Analysis of 20 APS patients' IgG showed that all IgG fractions activated the same two pathways as the monoclonal aPL, depending on their epitope patterns as determined by ELISA. Monocyte activation by APS IgG could be blocked completely by HCQ and/or rapamycin, suggesting that in most, if not all, APS patients there is no other relevant signaling pathway. Conclusions aPLs activate two major proinflammatory signal transduction pathways, depending on their epitope specificity. HCQ and rapamycin, either alone or in combination, completely suppress signaling by APS IgG. These observations may provide a rationale for specific treatment of APS patients according to their aPL profile.

Endosomal Redox Signaling in the Antiphospholipid Syndrome

PURPOSE OF REVIEW

It is well established that the antiphospholipid syndrome (APS) is caused by antiphospholipid antibodies (aPL). While several underlying mechanisms have been described in the past, many open questions remain. Here, we will review data on endosomal signaling and, in particular, redox signaling in APS.

RECENT FINDINGS

Endosomal redox signaling has been implicated in several cellular processes including signaling of proinflammatory cytokines. We have shown that certain aPL can activate endosomal NADPH-oxidase (NOX) in several cell types followed by induction of proinflammatory and procoagulant cellular responses in vitro. Involvement of endosomes in aPL signaling has also been reported by others. In wild-type mice but not in NOX-deficient mice, aPL accelerate venous thrombus formation underscoring the relevance of endosomal NOX. Furthermore, hydroxychloroquine (HCQ) inhibits activation of endosomal NOX and prevents thrombus formation in aPL-treated mice. Endosomal redox signaling is an important novel mechanism involved in APS pathogenesis. This makes endosomes a potential target for future treatment approaches of APS.

Complement C5-inhibiting therapy for the thrombotic microangiopathies: accumulating evidence, but not a panacea

Thrombotic microangiopathy (TMA), characterized by organ injury occurring consequent to severe endothelial damage, can manifest in a diverse range of diseases. In complement-mediated atypical haemolytic uraemic syndrome (aHUS) a primary defect in complement, such as a mutation or autoantibody leading to over activation of the alternative pathway, predisposes to the development of disease, usually following exposure to an environmental trigger. The elucidation of the pathogenesis of aHUS resulted in the successful introduction of the complement inhibitor eculizumab into clinical practice. In other TMAs, although complement activation may be seen, its role in the pathogenesis remains to be confirmed by an interventional trial. Although many case reports in TMAs other than complement-mediated aHUS hint at efficacy, publication bias, concurrent therapies and in some cases the self-limiting nature of disease make broader interpretation difficult. In this article, we will review the evidence for the role of complement inhibition in complement-mediated aHUS and other TMAs.

Vascular Manifestations in Antiphospholipid Syndrome (APS): Is APS a Thrombophilia or a Vasculopathy?

PURPOSE OF REVIEW

Antiphospholipid antibody syndrome (APS) is characterized primarily by thrombosis and pregnancy morbidity. Chronic vascular lesions can also occur. While the underlying mechanisms of these vascular lesions are not entirely known, there have been multiple theories describing the potential process of vasculopathy in APS and the various clinical manifestations associated with it.

RECENT FINDINGS

Recently, it has been demonstrated that endothelial proliferation in kidneys can be explained by the activation of the mammalian target of rapamycin complex (mTORC) pathway by antiphospholipid antibodies (aPL). These data support the existence of an APS-related vasculopathy in different locations which can explain-in part-the different manifestations of APS. This review focuses on the various manifestations of APS as a result of APS-related vasculopathy, as well as pathophysiology, current screening, and treatment options for clinicians to be aware of.

Diagnosing antiphospholipid syndrome: 'extra-criteria' manifestations and technical advances

First described in the early 1980s, antiphospholipid syndrome (APS) is a unique form of acquired autoimmune thrombophilia in which patients present with clinical features of recurrent thrombosis and pregnancy morbidity and persistently test positive for the presence of antiphospholipid antibodies (aPL). At least one clinical (vascular thrombosis or pregnancy morbidity) and one lab-based (positive test result for lupus anticoagulant, anticardiolipin antibodies and/or anti-β2-glycoprotein 1 antibodies) criterion have to be met for a patient to be classified as having APS. However, the clinical spectrum of APS encompasses additional manifestations that can affect many organs and cannot be explained exclusively by patients being in a prothrombotic state; clinical manifestations not listed in the classification criteria (known as extra-criteria manifestations) include neurologic manifestations (chorea, myelitis and migraine), haematologic manifestations (thrombocytopenia and haemolytic anaemia), livedo reticularis, nephropathy and valvular heart disease. Increasingly, research interest has focused on the development of novel assays that might be more specific for APS than the current aPL tests. This Review focuses on the current classification criteria for APS, presenting the role of extra-criteria manifestations and lab-based tests. Diagnostic approaches to difficult cases, including so-called seronegative APS, are also discussed.

Association of Lupus Anticoagulant With Long-Term Damage Accrual in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

OBJECTIVE

Antiphospholipid antibodies (aPL) are frequently present in antineutrophil cytoplasmic antibody-associated vasculitis (AAV) patients; however, the prognostic impact of aPL in such patients has not been elucidated. The objective of this study was to determine whether persistent aPL positivity in AAV patients was associated with increased long-term damage accrual.

METHODS

Clinical data were retrospectively collected on all AAV patients who attended the vasculitis clinic at our center over a 4-year period. Data collection included presence of lupus anticoagulant (LAC) and IgG and IgM anticardiolipin (aCL) antibody titers, along with concurrent diagnosis of antiphospholipid syndrome (APS). Accumulation of long-term damage was quantified using the Vasculitis Damage Index (VDI).

RESULTS

Data from 116 AAV patients were analyzed. A total of 34% (n = 40) had persistently positive aCL or LAC or a concurrent diagnosis of APS and were classified as AAV/aPL. A total of 76 patients (66%) were classified as AAV alone. LAC was present in a statistically higher proportion of AAV/aPL patients than those in the AAV-alone group (P < 0.0001). Mean VDI score was significantly higher in the AAV/aPL group at mean ± SD 3.54 ± 1.36 as compared to 1.96 ± 1.42 in the AAV-alone group (P < 0.0001). Major vascular damage scores were significantly higher in the AAV/aPL group, with mean ± SD 0.32 ± 0.59 as compared to 0.07 ± 0.26 in the AAV-alone group (P < 0.007).

CONCLUSION

Persistently positive occurrence of aPL, in particular LAC, is present in a significant proportion of AAV patients and is associated with a higher VDI score. Clinicians should consider screening AAV patients for aPL.

Antiphospholipid Syndrome: Role of Vascular Endothelial Cells and Implications for Risk Stratification and Targeted Therapeutics

Antiphospholipid syndrome (APS) is an autoimmune disease characterized by venous thromboembolism, arterial thrombosis, and obstetric morbidities in the setting of persistently positive levels of antiphospholipid antibodies measured on 2 different occasions 12 weeks apart. Patients with APS are at increased risk for accelerated atherosclerosis, myocardial infarction, stroke, and valvular heart disease. Vascular endothelial cell dysfunction mediated by antiphospholipid antibodies and subsequent complement system activation play a cardinal role in APS pathogenesis. Improved understanding of their pathogenic function could help in the risk stratification of patients with APS and provide new molecular therapeutic targets.

Kidney disease in primary anti-phospholipid antibody syndrome

APS is an autoimmune disease defined by the presence of arterial or venous thrombotic events and/or pregnancy morbidity in patients who test positive for aPL. APS can be isolated (primary APS) or associated with other autoimmune diseases. The kidney is a major target organ in APS, and renal thrombosis can occur at any level within the vasculature of the kidney (renal arteries, intrarenal vasculature and renal veins). Histological findings vary widely, including ischaemic glomeruli and thrombotic lesions without glomerular or arterial immune deposits on immunofluorescence. Renal involvement in patients with definite APS is treated with long-term anticoagulants as warfarin, but new treatments are being tried. The aim of this article is to review the links between primary APS and kidney disease.

A importância de reconhecer a síndrome antifosfolípide na medicina vascular

A síndrome antifosfolipíde (SAF) é uma doença autoimune sistêmica caracterizada por trombose arterial ou venosa recorrente e/ou morbidade gestacional e pela presença dos anticorpos antifosfolipídeos, podendo apresentar outras manifestações vasculares, como microangiopatia, arteriopatia crônica e SAF catastrófica. Determinados testes laboratoriais para a síndrome (por exemplo, o anticoagulante lúpico) podem sofrer interferência do uso de medicações anticoagulantes, dificultando o diagnóstico. A fisiopatologia da SAF é complexa, sendo enumerados no texto diversos mecanismos patogênicos relacionados à coagulação, ao endotélio e às plaquetas. Por fim, discutimos o tratamento da SAF de acordo com a presença e o tipo de manifestações clínicas, o uso dos anticoagulantes orais diretos e o manejo perioperatório de pacientes com SAF.

Pharmacologic Complement Inhibition in Clinical Transplantation

Purpose of Review

Over the past two decades, significant strides made in our understanding of the etiology of antibody-mediated rejection (AMR) in transplantation have put the complement system in the spotlight. Here, we review recent progress made in the field of pharmacologic complement inhibition in clinical transplantation and aim to understand the impact of this therapeutic approach on outcomes in transplant recipients.

Recent Findings

Encouraged by the success of agents targeting the complement cascade in disorders of unrestrained complement activation like paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS), investigators are testing the safety and efficacy of pharmacologic complement blockade in mitigating allograft injury in conditions ranging from AMR to recurrent post-transplant aHUS, C3 glomerulopathies and antiphospholipid anti-body syndrome (APS). A recent prospective study demonstrated the efficacy of terminal complement inhibition with eculizumab in the prevention of acute AMR in human leukocyte antigen (HLA)-incompatible living donor renal transplant recipients. C1 esterase inhibitor (C1-INH) was well tolerated in two recent studies in the treatment of AMR and was associated with improved renal allograft function.

Summary

Pharmacologic complement inhibition is emerging as valuable therapeutic tool, especially in the management of highly sensitized renal transplant recipients. Novel and promising agents that target various elements in the complement cascade are in development. Graphical Abstractᅟ.

Pathogenesis and management of antiphospholipid syndrome

Antiphospholipid antibodies are a heterogeneous group of autoantibodies that have clear associations with thrombosis and pregnancy morbidity, and which together constitute the 'antiphospholipid syndrome' (APS). However, the pathophysiology of these complications is not well understood and their heterogeneity suggests that more than one pathogenic process may be involved. Diagnosis remains a combination of laboratory analysis and clinical observation but there have been significant advances in identifying specific pathogenic features, such as domain I-specific anti-β2-glycoprotein-I antibodies. This in turn has pointed to endothelial and complement activation as important factors in the pathogenesis of APS. Consequently, although anticoagulation remains the standard treatment for thrombotic APS and during pregnancy, the realisation that these additional pathways are involved in the pathogenesis of APS has significant implications for treatment: agents acting outside the coagulation system, such as hydroxychloroquine for pregnancy complications and sirolimus as an inhibitor of the mammalian target of rapamycin (mTOR) pathway, are now under evaluation and represent a radical change in thinking for haematologists. Conventional anticoagulation is also under challenge from new, direct acting anticoagulants. This review will provide a comprehensive overview of the evolving understanding of APS pathogenesis and how this and novel therapeutics will alter diagnosis and management.

Activation of the mTOR dependent signaling pathway underlies ketamine-induced uropathy

AIMS

To investigate the pathogenic role of activation of the mammalian target of the rapamycin (mTOR) in the ketamine induced microvascular injury.

METHODS

Twenty-three patients with ketamine-induced cystitis (KC) and 16 control volunteers were recruited. Bladder tissues were obtained from both groups by cystoscopic biopsies. Phospho-S6 ribosomal protein (p-S6RP), an end product of the mTOR pathway, was stained in the urinary bladder from both groups. Endothelial cells of the urinary bladder (HBdMECs) were examined to investigate the in vitro activation of the mTOR pathway and the co-expression of the endothelial marker (cluster of differentiation 31 [CD31]) and the mesenchymal marker (fibroblast-specific protein 1 [FSP-1]).

RESULTS

Expression of p-S6RP increased significantly after ketamine exposure, especially in the vesical microvessels of KC patients. In HBdMECs treated with 100 µM Ketamine, time-dependent activation of the mTOR pathway occurred, with significantly increased levels of the phosphorylated forms of mTOR at 30 min and of S6RP and p70S6 kinase (p70S6K) at 6 h. The increased level of p-S6RP returned to baseline within 2 days after ketamine exposure. The co-expression of CD31 and FSP-1 implied that EndMT was present in HBdMECs at 7 days after ketamine treatment, while TGF-β1 facilitated significant up-regulation of FSP-1 at 1 day after treatment. Furthermore, when the mTOR inhibitor rapamycin was administered with ketamine to the HBdMECs, the expression of FSP-1 decreased significantly.

CONCLUSIONS

Ketamine induces activation of the mTOR pathway and subsequent mesenchymal phenotypic expression (FSP1) in HBdMECs.

The Role of Complement Inhibition in Thrombotic Angiopathies and Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is characterized by thrombosis (arterial, venous, small vessel) and/or pregnancy morbidity occurring in patients with persistently positive antiphospholipid antibodies (aPL). Catastrophic APS is the most severe form of the disease, characterized by multiple organ thromboses occurring in a short period and commonly associated with thrombotic microangiopathy (TMA). Similar to patients with complement regulatory gene mutations developing TMA, increased complement activation on endothelial cells plays a role in hypercoagulability in aPL-positive patients. In mouse models of APS, activation of the complement is required and interaction of complement (C) 5a with its receptor C5aR leads to aPL-induced inflammation, placental insufficiency, and thrombosis. Anti-C5 antibody and C5aR antagonist peptides prevent aPL-mediated pregnancy loss and thrombosis in these experimental models. Clinical studies of anti-C5 monoclonal antibody in aPL-positive patients are limited to a small number of case reports. Ongoing and future clinical studies of complement inhibitors will help determine the role of complement inhibition in the management of aPL-positive patients.

Recent advances in understanding antiphospholipid syndrome

Antiphospholipid syndrome (APS), also known as Hughes Syndrome, is a systemic autoimmune disease characterized by thrombosis and/or pregnancy morbidity in the presence of persistently positive antiphospholipid antibodies. A patient with APS must meet at least one of two clinical criteria (vascular thrombosis or complications of pregnancy) and at least one of two laboratory criteria including the persistent presence of lupus anticoagulant (LA), anticardiolipin antibodies (aCL), and/or anti-b2 glycoprotein I (anti-b2GPI) antibodies of IgG or IgM isotype at medium to high titres in patient’s plasma. However, several other autoantibodies targeting other coagulation cascade proteins (i.e. prothrombin) or their complex with phospholipids (i.e. phosphatidylserine/prothrombin complex), or to some domains of β2GPI, have been proposed to be also relevant to APS. In fact, the value of testing for new aPL specificities in the identification of APS in thrombosis and/or pregnancy morbidity patients is currently being investigated.

Emerging Therapies in Antiphospholipid Syndrome

Antiphospholipid syndrome (APS) is a hypercoagulable state characterized by arterial and venous thromboses and pregnancy morbidity in the presence of antiphospholipid antibodies. Although warfarin remains the main therapeutic choice in APS, there is still concern about its efficacy, safety, and patient compliance. Patients with refractory APS to conventional therapy as well as patients with non-classical manifestations of APS may have alternative treatment approaches. APS pathogenesis has been further elucidated over the past years identifying new molecules as potential new treatment targets. This review summarizes available data from in vitro and animal models and clinical studies on the role of new potential treatment approaches including new oral anticoagulants and immunoregulatory agents: direct thrombin or factor Xa inhibitors, hydroxychloroquine, statins, B cell inhibition, complement inhibition, peptide therapy, nuclear factor κB and p38 mitogen-activated kinase inhibitors, defibrotide, abciximab, mTOR inhibitor, and other potential targets. Large multicenter prospective studies of well-characterized APS patients are needed to assess the efficacy and safety profile of these potential treatment alternatives.

A 3-year follow-up of a patient with acute renal failure caused by thrombotic microangiopathy related to antiphospholipid syndrome: case report

Background Microvascular manifestations of antiphospholipid antibody syndrome in the kidneys include acute renal failure, thrombotic microangiopathy and hypertension. Therapy has been largely empiric. Case report A 49-year-old Chinese man presented with anuric acute renal failure without abundant proteinuria and heavy haematuria, but markedly low levels of urinary sodium, potassium and chlorine upon admission. On day 1 of hospitalization, his thrombocytopenia, anaemia and renal failure showed rapid progression. The presence of lupus anticoagulant and vascular ischaemia of the small vessels in renal arteriography were also observed. Anticoagulants, continuous renal replacement therapy, glucocorticoids and six sessions of plasma exchange were started. After the fourth plasma exchange (on day 20), his urine output increased and began to normalize. On day 25, haemodialysis was stopped and his general condition gradually improved. A renal biopsy was subsequently performed, and the histopathological diagnosis was thrombotic microangiopathy due to antiphospholipid antibody syndrome. A further 3-year follow-up showed that his haemoglobin level, platelet count and serum creatinine were within the normal range, with stable blood pressure. Conclusion Treatment modalities such as anticoagulation, immunosuppression and plasma exchange are likely to be necessary when severe acute renal failure combined with thrombotic microangiopathy present in nephropathy of antiphospholipid antibody syndrome.

Kidney retransplantation in children following rejection and recurrent disease

Retransplantation accounts for approximately 15 % of the annual transplants performed in the USA, and in the recent International Collaborative Transplant Study report on pediatric patients 15.2 % of the 9209 patients included in the report were retransplant recipients. Although the significant advances in clinical management and newer immunosuppressive agents have had a significant impact on improving short-term allograft function, it is apparent that long-term allograft function remains suboptimal. Therefore, it is likely that the majority of pediatric renal allograft recipients will require one or more retransplants during their lifetime. Unfortunately, a second or subsequent graft in pediatric recipients has inferior long-term graft survival rates compared to initial grafts, with decreasing rates with each subsequent graft. Multiple issues influence the outcome of retransplantation, with the most significant being the cause of the prior transplant failure. Non-adherence-associated graft loss poses unresolved ethical issues that may impact access to retransplantation. Graft nephrectomy prior to retransplantation may benefit selected patients, but the impact of an in situ failed graft on the development of panel-reactive antibodies remains to be definitively determined. It is important that these and other factors discussed in this review be taken into consideration during the counseling of families on the optimal approach for their child who requires a retransplant.

Activation of the Mechanistic Target of Rapamycin in SLE: Explosion of Evidence in the Last Five Years

The mechanistic target of rapamycin (mTOR) is a central regulator in cell growth, activation, proliferation, and survival. Activation of the mTOR pathway underlies the pathogenesis of systemic lupus erythematosus (SLE). While mTOR activation and its therapeutic reversal were originally discovered in T cells, recent investigations have also uncovered roles in other cell subsets including B cells, macrophages, and "non-immune" organs such as the liver and the kidney. Activation of mTOR complex 1 (mTORC1) precedes the onset of SLE and associated co-morbidities, such as anti-phospholipid syndrome (APS), and may act as an early marker of disease pathogenesis. Six case reports have now been published that document the development of SLE in patients with genetic activation of mTORC1. Targeting mTORC1 over-activation with N-acetylcysteine, rapamycin, and rapalogs provides an opportunity to supplant current therapies with severe side effect profiles such as prednisone or cyclophosphamide. In the present review, we will discuss the recent explosion of findings in support for a central role for mTOR activation in SLE.