Antiphospholipid antibodies as a risk factor for atherosclerotic events in renal transplant recipients

The Role of Cardiolipin and Mitochondrial Damage in Kidney Transplant

Chronic kidney disease (CKD) is highly incident and prevalent in the world. The death of patients with CKD is primarily due to cardiovascular disease. Renal transplantation (RT) emerges as the best management alternative for patients with CKD. However, the incidence of acute renal graft dysfunction is 11.8% of the related living donor and 17.4% of the cadaveric donor. Anticardiolipin antibodies (ACAs) or antiphospholipid antibodies (APAs) are important risk factors for acute renal graft dysfunction. The determination of ACA or APA to candidates for RT could serve as prognostic markers of early graft failure and would indicate which patients could benefit from anticoagulant therapy. Cardiolipin is a fundamental molecule that plays an important role in the adequate conformation of the mitochondrial cristae and the correct assembly of the mitochondrial respiratory supercomplexes and other proteins essential for proper mitochondrial function. Cardiolipin undergoes a nonrandom oxidation process by having pronounced specificity unrelated to the polyunsaturation pattern of its acyl groups. Accumulation of hydroxyl derivatives and cardiolipin hydroperoxides has been observed in the affected tissues, and recent studies showed that oxidation of cardiolipin is carried out by a cardiolipin-specific peroxidase activity of cardiolipin-bound cytochrome c. Cardiolipin could be responsible for the proapoptotic production of death signals. Cardiolipin modulates the production of energy and participates in inflammation, mitophagy, and cellular apoptosis. The determination of cardiolipin or its antibodies is an attractive therapeutic, diagnostic target in RT and kidney diseases.

Atrial fibrillation in kidney transplant recipients: is there a place for the novel drugs?

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia of high clinical importance, occurring in 2% of the general population and in 19-24% in patients with chronic kidney disease. It is a well-known risk factor for cardiovascular morbidity and mortality. Kidney transplant recipients with a history of AF were associated with significantly higher rate of ischaemic strokes, graft failure and post-transplant mortality. AF occurs in over 7% of kidney transplant recipients in the first 3 years after transplantation and is associated with reduced graft and patient survival. The incidence of stroke in patients after kidney transplantation (KTx) is higher than the general population, but markedly lower than those on dialysis. Oral anticoagulation (OAC) therapy is recommended in AF patients at high risk of stroke. There are no randomized studies assessing OAC in patients after KTx and there are no specific recommendations and guidelines on therapeutic strategies in these patients. KTx recipients are a vulnerable population, exposed to variations in renal function, being at higher risk of bleeding and thrombotic complications, with possible interactions with immunosuppression. Surely, there is a place for novel oral anticoagulants (NOACs) in this group of patients as long as the summary of product characteristics is followed, as they are a valuable anticoagulation therapy. On one hand, they are at least as effective as warfarin; on the other hand NOACs are safer, especially when it comes to intracranial haemorrhages. However, NOACs seem to be underused in this population as they are excreted via kidney, may interact with immunosuppressive therapy and physicians need more experience and confidence in their administration. Percutaneous left atrial appendage occlusion procedure may also be considered as an opportunity for this group of patients, in particular in the presence of contraindications to anticoagulation.

Effects of body weight variation in obese kidney recipients: a retrospective cohort study

Background

Obese kidney allograft recipients have worse results in kidney transplantation (KT). However, there is lack of information regarding the effect of body mass index (BMI) variation after KT. The objective of the study was to evaluate the effects of body weight changes in obese kidney transplant recipients.

Methods

In this study we used data from the Catalan Renal Registry that included KT recipients from 1990 to 2011 (n = 5607). The annual change in post-transplantation BMI was calculated. The main outcome variables were delayed graft function (DGF), estimated glomerular filtration rate (eGFR) and patient and graft survival.

Results

Obesity was observed in 609 patients (10.9%) at the time of transplantation. The incidence of DGF was significantly higher in obese patients (40.4% versus 28.3%; P < 0.001). Baseline obesity was significantly associated with worse short- and long-term graft survival (P < 0.05) and worse graft function during the follow-up (P < 0.005). BMI variations in obese patients did not improve eGFR or graft or patient survival.

Conclusions

Our conclusion is that in obese patients, decreasing body weight after KT does not improve either short-term graft outcomes or long-term renal function.

Antiphospholipid Syndrome and Kidney Involvement: New Insights

Antiphospholipid syndrome is an autoimmune disorder characterized by vascular thromboses and pregnancy morbidity associated with antiphospholipid antibodies: lupus anticoagulant, IgG or IgM anticardiolipin or anti-beta 2-glycoprotein I. The kidney is one of the major target organs in antiphospholipid syndrome (APS). However, beyond the known involvement of the kidney in primary and associated APS, we may be observing a new form of APS within the context of renal failure. This review describes the classical kidney manifestations of APS and provides new considerations to be taken into account.

Systemic lupus erythematosus and cardiovascular disease: prediction and potential for therapeutic intervention

Patients with systemic lupus erythematosus have a significantly increased risk of cardiovascular events due to atherosclerosis. Traditional cardiac risk factors cannot fully explain this increased risk. Recent evidence strongly suggests that atherosclerotic plaque is largely driven by inflammation and an active immunological response, in contrast to the long-held belief that plaque is a passive accumulation of lipids in the arterial wall. Current approaches to the prevention of atherosclerosis in systemic lupus erythematosus involve targeting modifiable cardiac risk factors. Future preventive strategies may include therapies that counteract the immunologic responses that lead to plaque formation.

Chronic humoral rejection of human kidney allografts associates with broad autoantibody responses

BACKGROUND

Chronic humoral rejection (CHR) is a major complication after kidney transplantation. The cause of CHR is currently unknown. Autoantibodies have often been reported in kidney transplant recipients alongside antidonor human leukocyte antigen antibodies. Yet, the lack of comprehensive studies has limited our understanding of this autoimmune component in the pathophysiology of CHR.

METHODS

By using a series of ELISA and immunocytochemistry assays, we assessed the development of autoantibodies in 25 kidney transplant recipients with CHR and 25 patients with stable graft function. We also compared the reactivity of five CHR and five non-CHR patient sera with 8027 recombinant human proteins using protein microarrays.

RESULTS

We observed that a majority of CHR patients, but not non-CHR control patients, had developed antibody responses to one or several autoantigens at the time of rejection. Protein microarray assays revealed a burst of autoimmunity at the time of CHR. Remarkably, microarray analysis showed minimal overlap between profiles, indicating that each CHR patient had developed autoantibodies to a unique set of antigenic targets.

CONCLUSION

The breadth of autoantibody responses, together with the absence of consensual targets, suggests that these antibody responses result from systemic B-cell deregulation.

Thrombophilic factors do not predict outcomes in renal transplant recipients under prophylactic acetylsalicylic acid

A cohort of recipients of renal transplant after 2000 (N=310) was prospectively screened on the day of transplantation and 1 month later for a panel of 11 thrombophilic factors to assess their effect on posttransplant outcomes. All patients received prophylactic acetylsalicylic acid, started before transplantation. The rate of thromboembolic events or acute rejection episodes during the first posttransplant year (primary composite endpoint) was 16.7% among patients free of thrombophilic factor (N=60) and 17.2% in those with >or=1 thrombophilic factor (N=250) (p>0.99). The incidence of the primary endpoint was similar among patients free of thrombophilic factors and those with >or=2 (N=135), or >or=3 (N=53) factors (16.3% and 15.1% respectively; p=1) and in patients who remained thrombophilic at 1 month (15.7%; p=0.84). None of the individual thrombophilic factor present at the day of transplantation was associated with the primary endpoint. The incidence of cardiovascular events at 1-year, serum creatinine at 1-year, 4-year actuarial graft and patient survival were not influenced by the presence of >or=1 thrombophilic factor at baseline (p=NS). In conclusion, the presence of thrombophilic factors does not influence thromboembolic events, acute rejection, graft or patient survival in patients transplanted after 2000 and receiving prophylactic acetylsalicylic acid.

Effects of pioglitazone on subclinical atherosclerosis and insulin resistance in nondiabetic renal allograft recipients

BACKGROUND

The aim of this study was to evaluate the effect of pioglitazone treatment on the progression of subclinical atherosclerosis and insulin resistance in renal allograft recipients with no preoperative history of diabetes.

METHODS

Eighty-three patients without diabetes were randomly assigned to either the pioglitazone group or the control group. Carotid intima-media thickness (IMT), serum adiponectin level and lipid profile were assessed before transplantation and at 12 months after transplantation. Insulin secretory function and insulin resistance were evaluated by the oral glucose tolerance test.

RESULTS

The pioglitazone group showed a significant reduction in the mean and maximum carotid IMT compared with the control group after 12 months (mean carotid IMT, 0.05 +/- 0.04 vs -0.03 +/- 0.07 mm, P < 0.001; maximum carotid IMT, 0.08 +/- 0.05 vs -0.05 +/- 0.09 mm, P < 0.001). Pioglitazone increased the adiponectin level, and the change in adiponectin was negatively correlated with carotid IMT changes. Pioglitazone treatment increased the insulin sensitivity index compared with the control group (-0.8 +/- 3.1x10(-)(2) vs +1.1 +/- 3.7x10(-)(2), P = 0.036).

CONCLUSIONS

These results suggest that pioglitazone treatment reduces the progression of carotid IMT and improves insulin resistance in renal allograft recipients without a history of diabetes. Trial Registration. Clinicaltrials.gov Identifier: NCT00598013.

B-cell immunity in the context of T-cell tolerance after combined kidney and bone marrow transplantation in humans

Five patients with end-stage kidney disease received combined kidney and bone marrow transplants from HLA haploidentical donors following nonmyeloablative conditioning to induce renal allograft tolerance. Immunosuppressive therapy was successfully discontinued in four patients with subsequent follow-up of 3 to more than 6 years. This allograft acceptance was accompanied by specific T-cell unresponsiveness to donor antigens. However, two of these four patients showed evidence of de novo antibodies reactive to donor antigens between 1 and 2 years posttransplant. These humoral responses were characterized by the presence of donor HLA-specific antibodies in the serum with or without the deposition of the complement molecule C4d in the graft. Immunofluorescence staining, ELISA assays and antibody profiling using protein microarrays demonstrated the co-development of auto- and alloantibodies in these two patients. These responses were preceded by elevated serum BAFF levels and coincided with B-cell reconstitution as revealed by a high frequency of transitional B cells in the periphery. To date, these B cell responses have not been associated with evidence of humoral rejection and their clinical significance is still unclear. Overall, our findings showed the development of B-cell allo- and autoimmunity in patients with T-cell tolerance to the donor graft.

Antiphospholipid antibodies after renal transplantation and cardiovascular disease

BACKGROUND

The aim was to assess the presence of pre- or post-transplant serum antiphospholipid antibodies (APA) and its association with the development of cardiovascular disease (CVD) in renal transplantation.

METHODS

We studied 138 patients transplanted with a cadaver kidney graft between 1990 and 1998 and with a graft functioning for longer than one yr. One pre-transplant sample and another obtained after transplantation from our serum bank were analyzed. The ELISA used were set up in our laboratory, following established international guidelines, and results were confirmed in three different runs.

RESULTS

23.9% and 31.2% of patients had pre- and post-transplant positive titers of APA, respectively. 16% developed those antibodies de novo after transplantation. Post-transplant CVD was observed in 20.3% of patients but they were not associated with the production of APA in the whole population studied. However, multivariate analysis demonstrated an increased risk (RR 2.27; p = 0.02) for CVD when APA were produced after acute rejection.

CONCLUSIONS

The presence of serum APA alone was not an independent risk factor for CVD after kidney transplantation. Nonetheless, in kidney recipients who produced APA de novo after acute rejection, the control of cardiovascular risk factors must be intensified.

Cardiovascular complications after renal transplantation and their prevention

By the time of renal transplantation, end-stage renal disease patients have a huge burden of cardiovascular disease (CVD) and are heavily saturated with atherosclerotic risk factors. Worsening of preexisting risk factors or new CVD risk factors may develop in the posttransplant period consequent in part to the diabetogenic and atherogenic potential of immunosuppressive drugs. The annual risk of a fatal or non-fatal CVD event of 3.5 to 5% in kidney transplant recipients is 50-fold higher than the general population. Renal allograft dysfunction, proteinuria, anemia, moderate hyperhomocysteinemia and elevated serum C-reactive protein concentrations, each dependently confer greater risk of CVD morbidity and mortality in the posttransplant period. Long-term care of renal transplant recipients should programmatically incorporate the recommendations of the National Kidney Foundation Working Groups and European Best Practice Guidelines Expert Group on Renal Transplantations into the management of hypertension, dyslipidemia, smoking, and posttransplant diabetes mellitus. Timely utilization of coronary revascularization procedures should be undertaken as these treatments are equally effective in the kidney transplant population.

Clinical significance of antiphospholipid antibodies on allograft and patient outcome after kidney transplantation

INTRODUCTION

Antiphospholipid antibodies (APA) have acquired great relevance as atherogenic factors. Kidney graft recipients have a higher prevalence of cardiovascular disease (CVD) than the general population, which is not fully explained by the classical vascular risk factors. The aim of this study was to assess the influence of APA on kidney graft and patient outcomes with special focus on CVD.

MATERIALS AND METHODS

One hundred ninety seven cadaveric kidney graft recipients with functioning grafts for more than 1 year underwent determination of serum APA titres (anti-cardiolipin and anti-beta-2 glycoprotein I IgG and IgM antibodies) in one pretransplant serum and in second one obtained at least 1 year after transplantation. In the case of postransplant CVD, the postransplant serum was always chosen before the cardiovascular event. The enzyme linked immunosorbent assay (ELISA) for anti-cardiolipin antibodies was performed in the presence of cofactor.

RESULTS

Twenty-seven percent of patients had pretransplant APA, whereas 15.7% developed postransplant APA de novo. The presence of pretransplant serum APA was not associated with a higher risk of postransplant CVD. The development of postransplant APA de novo showed a relationship to an acute rejection episode (ARE): the frequency of patients who had APA de novo was higher among patients who suffered ARE (18.8% vs 7%, P = .01). In addition, in patients who suffered any ARE, the production of postransplant APA was associated with a higher frequency of postransplant CVD.

CONCLUSIONS

The detection of APA is not an independent risk factor for CVD after kidney transplantation. The inflammatory phenomena secondary to an ARE may be responsible for the de novo production of postransplant APA, which may be associated with the development of postransplant CVD. The control of cardiovascular risk factors should be intensified in this special group of patients.