Apolipoprotein C3 induces inflammation and organ damage by alternative inflammasome activation.

NLRP3-inflammasome-driven inflammation is involved in the pathogenesis of a variety of diseases. Identification of endogenous inflammasome activators is essential for the development of new anti-inflammatory treatment strategies. Here, we identified that apolipoprotein C3 (ApoC3) activates the NLRP3 inflammasome in human monocytes by inducing an alternative NLRP3 inflammasome via caspase-8 and dimerization of Toll-like receptors 2 and 4. Alternative inflammasome activation in human monocytes is mediated by the Toll-like receptor adapter protein SCIMP. This triggers Lyn/Syk-dependent calcium entry and the production of reactive oxygen species, leading to activation of caspase-8. In humanized mouse models, ApoC3 activated human monocytes in vivo to impede endothelial regeneration and promote kidney injury in an NLRP3- and caspase-8-dependent manner. These data provide new insights into the regulation of the NLRP3 inflammasome and the pathophysiological role of triglyceride-rich lipoproteins containing ApoC3. Targeting ApoC3 might prevent organ damage and provide an anti-inflammatory treatment for vascular and kidney diseases.

Loss of Y Chromosome and Cardiovascular Events in Chronic Kidney Disease.

BACKGROUND: Chronic kidney disease represents one of the strongest risk factors for cardiovascular diseases, and particularly for heart failure. Despite improved pharmaceutical treatments, mortality remains high. Recently, experimental studies demonstrated that mosaic loss of Y chromosome (LOY) associates with cardiac fibrosis in male mice. Since diffuse cardiac fibrosis is the common denominator for progression of all forms of heart failure, we determined the association of LOY on mortality and cardiovascular disease outcomes in patients with chronic kidney disease. METHODS: LOY was quantified in men with stable chronic kidney disease (CARE for HOMe study [XXX], n=279) and dialysis patients (4D study, n=544). The association between LOY and mortality, combined cardiovascular and heart failure-specific end points, and echocardiographic measures was assessed. RESULTS: In CARE for HOMe, the frequency of LOY increased with age. LOY >17% was associated with increased mortality (heart rate, 2.58 [95% CI, 1.33-5.03]) and risk for cardiac decompensation or death (heart rate, 2.30 [95% CI, 1.23-4.27]). Patients with LOY >17% showed a significant decline of ejection fraction and an increase of E/E' within 5 years. Consistently, in the 4D study, LOY >17% was significantly associated with increased mortality (heart rate, 2.76 [95% CI, 1.83-4.16]), higher risk of death due to heart failure and sudden cardiac death (heart rate, 4.11 [95% CI, 2.09-8.08]), but not atherosclerotic events. Patients with LOY >17% showed significantly higher plasma levels of soluble interleukin 1 receptor-like 1, a biomarker for myocardial fibrosis. Mechanistically, intermediate monocytes from patients with LOY >17% showed significantly higher C-C chemokine receptor type 2 expression and higher plasma levels of the C-C chemokine receptor type 2 chemokine (C-C motif) ligand 2, which may have contributed to increased heart failure events. CONCLUSIONS: LOY identifies male patients with chronic kidney disease at high risk for mortality and heart failure events.

Interleukin-1α Is a Central Regulator of Leukocyte-Endothelial Adhesion in Myocardial Infarction and in Chronic Kidney Disease.

BACKGROUND: Cardiovascular diseases and chronic kidney disease (CKD) are highly prevalent, aggravate each other, and account for substantial mortality. Both conditions are characterized by activation of the innate immune system. The alarmin interleukin-1α (IL-1α) is expressed in a variety of cell types promoting (sterile) systemic inflammation. The aim of the present study was to examine the role of IL-1α in mediating inflammation in the setting of acute myocardial infarction (AMI) and CKD. METHODS: We assessed the expression of IL-1α on the surface of monocytes from patients with AMI and patients with CKD and determined its association with atherosclerotic cardiovascular disease events during follow-up in an explorative clinical study. Furthermore, we assessed the inflammatory effects of IL-1α in several organ injury models in Il1a-/- and Il1b-/- mice and investigated the underlying mechanisms in vitro in monocytes and endothelial cells. RESULTS: IL-1α is strongly expressed on the surface of monocytes from patients with AMI and CKD compared with healthy controls. Higher IL-1α surface expression on monocytes from patients with AMI and CKD was associated with a higher risk for atherosclerotic cardiovascular disease events, which underlines the clinical relevance of IL-1α. In mice, IL-1α, but not IL-1ß, mediates leukocyte-endothelial adhesion as determined by intravital microscopy. IL-1α promotes accumulation of macrophages and neutrophils in inflamed tissue in vivo. Furthermore, IL-1α on monocytes stimulates their homing at sites of vascular injury. A variety of stimuli such as free fatty acids or oxalate crystals induce IL-1α surface expression and release by monocytes, which then mediates their adhesion to the endothelium via IL-1 receptor-1. IL-1α also promotes expression of the VCAM-1 (vascular cell adhesion molecule-1) on endothelial cells, thereby fostering the adhesion of circulating leukocytes. IL-1α induces inflammatory injury after experimental AMI, and abrogation of IL-1α prevents the development of CKD in oxalate or adenine-fed mice. CONCLUSIONS: IL-1α represents a key mediator of leukocyte-endothelial adhesion and inflammation in AMI and CKD. Inhibition of IL-1α may serve as a novel anti-inflammatory treatment strategy.

Abnormal high-density lipoprotein induces endothelial dysfunction via activation of Toll-like receptor-2.

Endothelial injury and dysfunction (ED) represent a link between cardiovascular risk factors promoting hypertension and atherosclerosis, the leading cause of death in Western populations. High-density lipoprotein (HDL) is considered antiatherogenic and known to prevent ED. Using HDL from children and adults with chronic kidney dysfunction (HDL(CKD)), a population with high cardiovascular risk, we have demonstrated that HDL(CKD) in contrast to HDL(Healthy) promoted endothelial superoxide production, substantially reduced nitric oxide (NO) bioavailability, and subsequently increased arterial blood pressure (ABP). We have identified symmetric dimethylarginine (SDMA) in HDL(CKD) that causes transformation from physiological HDL into an abnormal lipoprotein inducing ED. Furthermore, we report that HDL(CKD) reduced endothelial NO availability via toll-like receptor-2 (TLR-2), leading to impaired endothelial repair, increased proinflammatory activation, and ABP. These data demonstrate how SDMA can modify the HDL particle to mimic a damage-associated molecular pattern that activates TLR-2 via a TLR-1- or TLR-6-coreceptor-independent pathway, linking abnormal HDL to innate immunity, ED, and hypertension.

Guanidinylated Apolipoprotein C3 (ApoC3) Associates with Kidney and Vascular Injury.

BACKGROUND: Coexistent CKD and cardiovascular diseases are highly prevalent in Western populations and account for substantial mortality. We recently found that apolipoprotein C-3 (ApoC3), a major constituent of triglyceride-rich lipoproteins, induces sterile systemic inflammation by activating the NOD-like receptor protein-3 (NLRP3) inflammasome in human monocytes via an alternative pathway. METHODS: To identify posttranslational modifications of ApoC3 in patients with CKD, we used mass spectrometry to analyze ApoC3 from such patients and from healthy individuals. We determined the effects of posttranslationally modified ApoC3 on monocyte inflammatory response in vitro, as well as in humanized mice subjected to unilateral ureter ligation (a kidney fibrosis model) and in a humanized mouse model for vascular injury and regeneration. Finally, we conducted a prospective observational trial of 543 patients with CKD to explore the association of posttranslationally modified ApoC3 with renal and cardiovascular events in such patients. RESULTS: We identified significant posttranslational guanidinylation of ApoC3 (gApoC3) in patients with CKD. We also found that mechanistically, guanidine and urea induce guanidinylation of ApoC3. A 2D-proteomic analysis revealed that gApoC3 accumulated in kidneys and plasma in a CKD mouse model (mice fed an adenine-rich diet). In addition, gApoC3 augmented the proinflammatory effects of ApoC3 in monocytes in vitro . In humanized mice, gApoC3 promoted kidney tissue fibrosis and impeded vascular regeneration. In CKD patients, higher gApoC3 plasma levels (as determined by mass spectrometry) were associated with increased mortality as well as with renal and cardiovascular events. CONCLUSIONS: Guanidinylation of ApoC3 represents a novel pathogenic mechanism in CKD and CKD-associated vascular injury, pointing to gApoC3 as a potential therapeutic target.

Genetically determined NLRP3 inflammasome activation associates with systemic inflammation and cardiovascular mortality.

AIMS: Inflammation plays an important role in cardiovascular disease (CVD) development. The NOD-like receptor protein-3 (NLRP3) inflammasome contributes to the development of atherosclerosis in animal models. Components of the NLRP3 inflammasome pathway such as interleukin-1ß can therapeutically be targeted. Associations of genetically determined inflammasome-mediated systemic inflammation with CVD and mortality in humans are unknown. METHODS AND RESULTS: We explored the association of genetic NLRP3 variants with prevalent CVD and cardiovascular mortality in 538 167 subjects on the individual participant level in an explorative gene-centric approach without performing multiple testing. Functional relevance of single-nucleotide polymorphisms on NLRP3 inflammasome activation has been evaluated in monocyte-enriched peripheral blood mononuclear cells (PBMCs). Genetic analyses identified the highly prevalent (minor allele frequency 39.9%) intronic NLRP3 variant rs10754555 to affect NLRP3 gene expression. rs10754555 carriers showed significantly higher C-reactive protein and serum amyloid A plasma levels. Carriers of the G allele showed higher NLRP3 inflammasome activation in isolated human PBMCs. In carriers of the rs10754555 variant, the prevalence of coronary artery disease was significantly higher as compared to non-carriers with a significant interaction between rs10754555 and age. Importantly, rs10754555 carriers had significantly higher risk for cardiovascular mortality during follow-up. Inflammasome inducers (e.g. urate, triglycerides, apolipoprotein C3) modulated the association between rs10754555 and mortality. CONCLUSION: The NLRP3 intronic variant rs10754555 is associated with increased systemic inflammation, inflammasome activation, prevalent coronary artery disease, and mortality. This study provides evidence for a substantial role of genetically driven systemic inflammation in CVD and highlights the NLRP3 inflammasome as a therapeutic target.

Measurement of urinary Dickkopf-3 uncovered silent progressive kidney injury in patients with chronic obstructive pulmonary disease.

Chronic kidney disease (CKD) represents a global public health problem with high disease related morbidity and mortality. Since CKD etiology is heterogeneous, early recognition of patients at risk for progressive kidney injury is important. Here, we evaluated the tubular epithelial derived glycoprotein dickkopf-3 (DKK3) as a urinary marker for the identification of progressive kidney injury in a non-CKD cohort of patients with chronic obstructive pulmonary disease (COPD) and in an experimental model. In COSYCONET, a prospective multicenter trial comprising 2,314 patients with stable COPD (follow-up 37.1 months), baseline urinary DKK3, proteinuria and estimated glomerular filtration rate (eGFR) were tested for their association with the risk of declining eGFR and the COPD marker, forced expiratory volume in one second. Baseline urinary DKK3 but not proteinuria or eGFR identified patients with a significantly higher risk for over a 10% (odds ratio: 1.54, 95% confidence interval: 1.13-2.08) and over a 20% (2.59: 1.28-5.25) decline of eGFR during follow-up. In particular, DKK3 was associated with a significantly higher risk for declining eGFR in patients with eGFR over 90 ml/min/1.73m2 and proteinuria under 30 mg/g. DKK3 was also associated with declining COPD marker (2.90: 1.70-4.68). The impact of DKK3 was further explored in wild-type and Dkk3-/- mice subjected to cigarette smoke-induced lung injury combined with a CKD model. In this model, genetic abrogation of DKK3 resulted in reduced pulmonary inflammation and preserved kidney function. Thus, our data highlight urinary DKK3 as a possible marker for early identification of patients with silent progressive CKD and for adverse outcomes in patients with COPD.

Association between urinary dickkopf-3, acute kidney injury, and subsequent loss of kidney function in patients undergoing cardiac surgery: an observational cohort study.

BACKGROUND: Cardiac surgery is associated with a high risk of postoperative acute kidney injury (AKI) and subsequent loss of kidney function. We explored the clinical utility of urinary dickkopf-3 (DKK3), a renal tubular stress marker, for preoperative identification of patients at risk for AKI and subsequent kidney function loss. METHODS: This observational cohort study included patients who had cardiac surgery in a derivation cohort and those who had cardiac surgery in a validation cohort (RenalRIP trial). The study comprised consecutive patients who had elective cardiac surgery at the Saarland University Medical Centre (Homburg, Germany; derivation cohort) and those undergoing elective cardiac surgery (selected on the basis of a Cleveland Clinical Foundation score of 6 or higher) who were enrolled in the prospective RenalRIP multicentre trial (validation cohort) and who were randomly assigned to remote ischaemic preconditioning or a sham procedure. The association between the ratio of preoperative urinary concentrations of DKK3 to creatinine (DKK3:creatinine) and postoperative AKI, defined according to the Kidney Disease Improving Global Outcomes criteria, and subsequent kidney function loss, as determined by estimated glomerular filtration rate, was assessed. FINDINGS: In the 733 patient in the derivation cohort, urinary concentrations of DKK3 to creatinine that were higher than 471 pg/mg were associated with significantly increased risk for AKI (odds ratio [OR] 1·65, 95% CI 1·10-2·47, p=0·015), independent of baseline kidney function. Compared with clinical and other laboratory measurements, urinary concentrations of DKK3:creatinine significantly improved AKI prediction (net reclassification improvement 0·32, 95% CI 0·23-0·42, p<0·0001). High urinary DKK3:creatinine concentrations were independently associated with significantly lower kidney function at hospital discharge and after a median follow-up of 820 days (IQR 733-910). In the RenalRIP trial, preoperative urinary DKK3:creatinine concentrations higher than 471 pg/mg were associated with a significantly higher risk for AKI (OR 1·94, 95% CI 1·08-3·47, p=0·026), persistent renal dysfunction (OR 6·67, 1·67-26·61, p=0·0072), and dialysis dependency (OR 13·57, 1·50-122·77, p=0·020) after 90 days compared with DKK3:creatinine concentrations of 471 pg/mg or less. Urinary DKK3:creatinine concentrations higher than 471 pg/mg were associated with significantly higher risk for AKI (OR 2·79, 95% CI 1·45-5·37) and persistent renal dysfunction (OR 3·82, 1·32-11·05) only in patients having a sham procedure, but not remote ischaemic preconditioning (AKI OR 1·35, 0·76-2·39 and persistent renal dysfunction OR 1·05, 0·12-9·45). INTERPRETATION: Preoperative urinary DKK3 is an independent predictor for postoperative AKI and for subsequent loss of kidney function. Urinary DKK3 might aid in the identification of patients in whom preventive treatment strategies are effective. FUNDING: No study funding.

Relapsing and Progressive Complications of Severe Hypertriglyceridemia: Effective Long-Term Treatment with Double Filtration Plasmapheresis.

BACKGROUND: Severe hypertriglyceridemia (HTG) is associated with major complications such as acute or relapsing pancreatitis (AP) and atherosclerotic cardiovascular disease (ASCVD). Rapid elimination of triglyceride (TG)-rich lipoproteins (LP) with double filtration plasmapheresis (DFPP) without need for substitution has been found to be effective for the acute, short-term treatment of HTG-induced AP. Data on the long-term use of DFPP to prevent HTG-associated complications are scarce. OBJECTIVES: To evaluate the use and efficacy of regular DFPP treatment in clinical practice for preventing recurrence of HTG-associated complications in thera-py refractory patients. METHODS: Retrospective multicenter study in patients with severe symptomatic drug and diet refractory HTG with regular DFPP treatment. Patients' incidence of HTG-associated pancreatic or cardiovascular complications was compared before treatment and with regular DFPP treatment. RESULTS: Ten patients (3 female) were identified with baseline maximal TG concentrations of 2,587-28,090 mg/dL (median 5,487 mg/dL; interquartile range [IQR] 4,340-12,636). The mean observation period was 3.9 ± 3.4 years before and 3.8 ± 3.0 years after commencement of DFPP. In 5 patients, severe HTG was related to chylomicronemia, 2 patients had familial partial lipodystrophy Dunnigan, and 1 patient had additional LP(a)-hyperlipoproteinemia. The main HTG-associated complication was recurrent AP in 8 patients, including 1 patient treated during pregnancy. Two patients presented severe progressive ASCVD. With long-term DFPP treatment, the annual rate of HTG-associa-ted pancreatic or cardiovascular complications declined from median 1.4 (IQR 0.7-2.6) to 0 (IQR 0.0-0.4; p < 0.005). The absolute number of events was reduced by 77%. In 6 patients (60%) episodes of AP did not occur, nor was progression of ASCVD detected clinically or by routine imaging techniques. DFPP was effective in the elimination of TG-rich LP from plasma, and was safe and well-tolerated. CONCLUSION: Long-term, regular DFPP treatment resulted in stabilization of patients with severe HTG and related recurrent AP or progression of ASCVD, who were refractory to conventional dietary and drug therapy.

Consequences of chronic kidney disease in chronic obstructive pulmonary disease.

BACKGROUND: The combination of chronic obstructive pulmonary disease (COPD) and chronic kidney disease (CKD) is associated with a higher prevalence of comorbidities and increased mortality. The impact of kidney function on patient-centered outcomes in COPD has not been evaluated. METHODS: Patients from the German COPD and Systemic Consequences - Comorbidities Network (COSYCONET) cohort COPD were analysed. CKD was diagnosed if the estimated glomerular filtration rate (eGFR) measurements were < 60 mL/min/1.73m2 at study inclusion and six month later. The effect of CKD, on comorbidities, symptoms [modified British Medical Research Council dyspnoea scale], physical capacity [six-minute walk test, and timed up and go] and St George's Respiratory Questionnaire were analysed. Restricted cubic spline models were used to evaluate a nonlinear relationship between eGFR with patient-centered outcomes, cox survival analysis was applied to evaluate mortality. RESULTS: 2274 patients were analysed, with CKD diagnosed in 161 (7.1%). Spline models adjusted for age, gender, BMI, FEV1 and cardiovascular comorbidities revealed independent associations between eGFR with modified British Medical Research Council dyspnoea scale, St George's Respiratory Questionnaire, (p < 0.001 and p = 0.011), six-minute walk test (p = 0.015) and timed up and go (p < 0.001). CKD was associated with increased mortality, independently from for other cardiovascular comorbidities (hazard ratio 2.3; p < 0.001). CONCLUSION: These data show that CKD is a relevant comorbidity in COPD patients which impacts on patient-centered outcomes and mortality. TRIAL REGISTRATION: NCT01245933.

Dickkopf-3 (DKK3) in Urine Identifies Patients with Short-Term Risk of eGFR Loss.

BACKGROUND: The individual course of CKD may vary, and improved methods for identifying which patients will experience short-term eGFR loss are needed. Assessing urinary Dickkopf-3 (DKK3), a stress-induced tubular epithelia-derived profibrotic glycoprotein, may provide information about ongoing tubulointerstitial fibrosis and short-term eGFR loss. METHODS: To investigate urinary DKK3's potential as a biomarker of short-term eGFR loss (over 12 months), we prospectively assessed eGFR and urinary DKK3 levels in patients with CKD of various etiologies at baseline and annual follow-ups. We also measured urinary DKK3 in a general population sample and patients with diagnostic kidney biopsies or IgA nephropathy under treatment. RESULTS: Median urinary DKK3-to-creatinine concentration at baseline was significantly higher in patients with CKD than the general population sample (431 versus 33 pg/mg). In the CKD cohort, having a urinary DKK3-to-creatinine level >4000 pg/mg was independently and significantly associated after multiple adjustments with mean annual decline in eGFR of 7.6% over 12 months. Urinary DKK3 significantly improved prediction of kidney function decline compared with eGFR or albuminuria alone. Urinary DKK3-to-creatinine levels were related to the extent of tubulointerstitial fibrosis in kidney biopsies. In patients with IgA nephropathy, a rise in urinary DKK3 was associated with significant eGFR decline within 6 months, whereas stable or decreasing urinary DKK3 indicated a more favorable course. CONCLUSIONS: Urinary DKK3 levels identify patients at high risk for eGFR decline over the next 12 months regardless of the cause of kidney injury and beyond established biomarkers, potentially providing a tool to monitor CKD progression and assess effects of interventions.

Potassium: an ion with dangerous airs and graces.

Take home figureFactors promoting hypokalaemia and hyperkalaemia. CHF, chronic heart failure; CKD, chronic kidney disease.

Hyperkalaemia in Heart Failure-Pathophysiology, Implications and Therapeutic Perspectives.

PURPOSE OF REVIEW: Hyperkalaemia is a frequent and sometimes life-threatening condition that may be associated with arrhythmia and cardiac dysfunction. Evaluating the prevalence of hyperkalaemia in patients with heart failure (HF) and potential treatments of this condition is essential for patients using renin-angiotensin-aldosterone system inhibitors or angiotensin receptor-neprilysin inhibitor and mineralocorticoid receptor antagonists, which represent the cornerstone and highly proven life-saving therapy. RECENT FINDINGS: Novel findings from the past few years include data regarding the epidemiology, pathomechanisms, implications and novel therapeutic approaches to counteract hyperkalaemia in patients with HF. Whilst older potassium-binding agents are associated with serious adverse events, novel potassium-binding drugs are effective in lowering potassium levels and are generally well tolerated. Hyperkalaemia represents both a direct risk of cardiovascular complication and an indirect biomarker of the severity of the underlying disease such as neurohormonal activation and renal dysfunction. Novel potassium-binding drugs such as patiromer and sodium zirconium cyclosilicate may help to optimize therapy in HF and achieve guideline-recommended doses.

Symmetric dimethylarginine, high-density lipoproteins and cardiovascular disease.

AIMS: The vascular effects of high-density lipoproteins (HDL) differ under certain clinical conditions. The composition of HDL is modified in patients with chronic kidney disease (CKD). As a consequence, uremic HDL induces endothelial dysfunction. We have previously shown that accumulation of symmetric dimethylarginine (SDMA) in HDL causes these adverse effects of HDL in CKD. The aim of the study is to determine the impact of the accumulation of SDMA on the association between HDL and mortality. METHODS AND RESULTS: Mortality, renal function, serum SDMA and HDL-cholesterol (HDL-C) were assessed in the LURIC study including 3310 subjects undergoing coronary angiography. All-cause mortality was 30.0% during median follow-up of 9.9 years. Serum SDMA levels significantly predicted all-cause and cardiovascular mortality, and were significantly correlated with SDMA accumulation in HDL. Notably, higher serum SDMA was independently associated with lower cholesterol efflux (P = 0.004) as a measure of HDL functionality. In subjects with low SDMA levels, higher HDL-C was associated with significantly lower mortality. In contrast, in subjects with high SDMA, HDL-C was associated with higher mortality. These findings were confirmed in 1424 participants of the MONICA/KORA S3 cohort. Of note, we derived an algorithm allowing for calculation of biologically effective HDL-C' based on measured HDL-C and SDMA. We corroborated these clinical findings with invitro evidence showing that SDMA accumulation abolishes the anti-inflammatory and regenerative properties of HDL. CONCLUSION: The data identify SDMA as a marker of HDL dysfunction. These findings highlight on the pivotal role of SDMA accumulation in HDL as a mediator of pre-mature cardiovascular disease in patients with CKD.

Innate immunity in CKD-associated vascular diseases.

Chronic kidney disease (CKD) is associated with an increased risk for cardiovascular events. Therefore, the activation of the innate immune system plays an important role. In contrast to the adaptive immunity, unspecific recognition of conserved endogenous and exogenous structures by pattern recognition receptors (PRRs) represents a key feature of the innate immunity. Of these PRRs, Toll-like receptors (TLRs) as well as the inflammasome complex have been documented to be involved in the pathogenesis of cardiovascular diseases (CVDs). They are not only expressed in leukocytes but also in a variety of cell types such as endothelial cells or fibroblasts. While activation of TLRs on the cell surface leads to nuclear factor κB-dependent expression of pro-inflammatory mediators, the inflammasome is a cytosolic multimeric protein complex, which cleaves cytokines such as interleukin-1ß into their biologically active forms. Several endogenous ligands for these PRRs have been identified as contributing to the development of a CKD-specific pro-inflammatory microenvironment. Notably, activation of TLRs as well as the inflammasome is associated with arterial hypertension, formation of atherosclerotic vascular lesions and vascular calcification. However, detailed molecular mechanisms on how the innate immune system contributes to CKD-associated CVDs are as yet poorly understood. Currently, several agents modulating the activation of the innate immune system are the focus of cardiovascular research. Large clinical studies will provide further information on the therapeutic applicability of these substances to reduce cardiovascular morbidity and mortality in the general population. Further trials including patients with CKD will be necessary to assess their effects on CKD-associated CVD.

Serum amyloid A: high-density lipoproteins interaction and cardiovascular risk.

AIMS: High-density lipoproteins (HDLs) are considered as anti-atherogenic. Recent experimental findings suggest that their biological properties can be modified in certain clinical conditions by accumulation of serum amyloid A (SAA). The effect of SAA on the association between HDL-cholesterol (HDL-C) and cardiovascular outcome remains unknown. METHODS AND RESULTS: We examined the association of SAA and HDL-C with mortality in the Ludwigshafen Risk and Cardiovascular Health (LURIC) study, which included 3310 patients undergoing coronary angiography. To validate our findings, we analysed 1255 participants of the German Diabetes and Dialysis study (4D) and 4027 participants of the Cooperative Health Research in the Region of Augsburg (KORA) S4 study. In LURIC, SAA concentrations predicted all-cause and cardiovascular mortality. In patients with low SAA, higher HDL-C was associated with lower all-cause and cardiovascular mortality. In contrast, in patients with high SAA, higher HDL-C was associated with increased all-cause and cardiovascular mortality, indicating that SAA indeed modifies the beneficial properties of HDL. We complemented these clinical observations by in vitro experiments, in which SAA impaired vascular functions of HDL. We further derived a formula for the simple calculation of the amount of biologically 'effective' HDL-C based on measured HDL-C and SAA from the LURIC study. In 4D and KORA S4 studies, we found that measured HDL-C was not associated with clinical outcomes, whereas calculated 'effective' HDL-C significantly predicted better outcome. CONCLUSION: The acute-phase protein SAA modifies the biological effects of HDL-C in several clinical conditions. The concomitant measurement of SAA is a simple, useful, and clinically applicable surrogate for the vascular functionality of HDL.

HDL cholesterol is not associated with lower mortality in patients with kidney dysfunction.

In the general population, HDL cholesterol (HDL-C) is associated with reduced cardiovascular events. However, recent experimental data suggest that the vascular effects of HDL can be heterogeneous. We examined the association of HDL-C with all-cause and cardiovascular mortality in the Ludwigshafen Risk and Cardiovascular Health study comprising 3307 patients undergoing coronary angiography. Patients were followed for a median of 9.9 years. Estimated GFR (eGFR) was calculated using the Chronic Kidney Disease Epidemiology Collaboration eGFR creatinine-cystatin C (eGFRcreat-cys) equation. The effect of increasing HDL-C serum levels was assessed using Cox proportional hazard models. In participants with normal kidney function (eGFR>90 ml/min per 1.73 m(2)), higher HDL-C was associated with reduced risk of all-cause and cardiovascular mortality and coronary artery disease severity (hazard ratio [HR], 0.51, 95% confidence interval [95% CI], 0.26-0.92 [P=0.03]; HR, 0.30, 95% CI, 0.13-0.73 [P=0.01]). Conversely, in patients with mild (eGFR=60-89 ml/min per 1.73 m(2)) and more advanced reduced kidney function (eGFR<60 ml/min per 1.73 m(2)), higher HDL-C did not associate with lower risk for mortality (eGFR=60-89 ml/min per 1.73 m(2): HR, 0.68, 95% CI, 0.45-1.04 [P=0.07]; HR, 0.84, 95% CI, 0.50-1.40 [P=0.50]; eGFR<60 ml/min per 1.73 m(2): HR, 1.18, 95% CI, 0.60-1.81 [P=0.88]; HR, 0.82, 95% CI, 0.40-1.69 [P=0.60]). Moreover, Cox regression analyses revealed interaction between HDL-C and eGFR in predicting all-cause and cardiovascular mortality (P=0.04 and P=0.02, respectively). We confirmed a lack of association between higher HDL-C and lower mortality in an independent cohort of patients with definite CKD (P=0.63). In summary, higher HDL-C levels did not associate with reduced mortality risk and coronary artery disease severity in patients with reduced kidney function. Indeed, abnormal HDL function might confound the outcome of HDL-targeted therapies in these patients.

HDL in children with CKD promotes endothelial dysfunction and an abnormal vascular phenotype.

Endothelial dysfunction begins in early CKD and contributes to cardiovascular mortality. HDL is considered antiatherogenic, but may have adverse vascular effects in cardiovascular disease, diabetes, and inflammatory conditions. The effect of renal failure on HDL properties is unknown. We studied the endothelial effects of HDL isolated from 82 children with CKD stages 2-5 (HDL(CKD)), who were free of underlying inflammatory diseases, diabetes, or active infections. Compared with HDL from healthy children, HDL(CKD) strongly inhibited nitric oxide production, promoted superoxide production, and increased vascular cell adhesion molecule-1 expression in human aortic endothelial cells, and reduced cholesterol efflux from macrophages. The effects on endothelial cells correlated with CKD grade, with the most profound changes induced by HDL from patients on dialysis, and partial recovery observed with HDL isolated after kidney transplantation. Furthermore, the in vitro effects on endothelial cells associated with increased aortic pulse wave velocity, carotid intima-media thickness, and circulating markers of endothelial dysfunction in patients. Symmetric dimethylarginine levels were increased in serum and fractions of HDL from children with CKD. In a longitudinal follow-up of eight children undergoing kidney transplantation, HDL-induced production of endothelial nitric oxide, superoxide, and vascular cell adhesion molecule-1 in vitro improved significantly at 3 months after transplantation, but did not reach normal levels. These results suggest that in children with CKD without concomitant disease affecting HDL function, HDL dysfunction begins in early CKD, progressing as renal function declines, and is partially reversed after kidney transplantation.

Carbamylated low-density lipoprotein induces endothelial dysfunction.

AIMS: Cardiovascular events remain the leading cause of death in Western world. Atherosclerosis is the most common underlying complication driven by low-density lipoproteins (LDL) disturbing vascular integrity. Carbamylation of lysine residues, occurring primarily in the presence of chronic kidney disease (CKD), may affect functional properties of lipoproteins; however, its effect on endothelial function is unknown. METHODS AND RESULTS: Low-density lipoprotein from healthy donors was isolated and carbamylated. Vascular reactivity after treatment with native LDL (nLDL) or carbamylated LDL (cLDL) was examined in organ chambers for isometric tension recording using aortic rings of wild-type or lectin-like-oxidized LDL receptor-1 (LOX-1) transgenic mice. Reactive oxygen species (ROS) and nitric oxide (NO) production were determined using electron spin resonance spectroscopy. The effect of LDL-carbamyl-lysine levels on cardiovascular outcomes was determined in patients with CKD during a median follow-up of 4.7 years. Carbamylated LDL impaired endothelium-dependent relaxation to acetylcholine or calcium-ionophore A23187, but not endothelium-independent relaxation to sodium nitroprusside. In contrast, nLDL had no effect. Carbamylated LDL enhanced aortic ROS production by activating NADPH-oxidase. Carbamylated LDL stimulated endothelial NO synthase (eNOS) uncoupling at least partially by promoting S-glutathionylation of eNOS. Carbamylated LDL-induced endothelial dysfunction was enhanced in LOX-1 transgenic mice. In patients with CKD, LDL-carbamyl-lysine levels were significant predictors for cardiovascular events and all-cause mortality. CONCLUSIONS: Carbamylation of LDL induces endothelial dysfunction via LOX-1 activation and increased ROS production leading to eNOS uncoupling. This indicates a novel mechanism in the pathogenesis of atherosclerotic disease which may be pathogenic and prognostic in patients with CKD and high plasma levels of cLDL.