Jan Menne

Terminal complement inhibitor eculizumab in atypical hemolytic-uremic syndrome

BACKGROUND Atypical hemolytic-uremic syndrome is a genetic, life-threatening, chronic disease of complement-mediated thrombotic microangiopathy. Plasma exchange or infusion may transiently maintain normal levels of hematologic measures but does not treat the underlying systemic disease. METHODS We conducted two prospective phase 2 trials in which patients with atypical hemolytic-uremic syndrome who were 12 years of age or older received eculizumab for 26 weeks and during long-term extension phases. Patients with low platelet counts and renal damage (in trial 1) and those with renal damage but no decrease in the platelet count of more than 25% for at least 8 weeks during plasma exchange or infusion (in trial 2) were recruited. The primary end points included a change in the platelet count (in trial 1) and thrombotic microangiopathy event-free status (no decrease in the platelet count of >25%, no plasma exchange or infusion, and no initiation of dialysis) (in trial 2). RESULTS A total of 37 patients (17 in trial 1 and 20 in trial 2) received eculizumab for a median of 64 and 62 weeks, respectively. Eculizumab resulted in increases in the platelet count; in trial 1, the mean increase in the count from baseline to week 26 was 73×10(9) per liter (P<0.001). In trial 2, 80% of the patients had thrombotic microangiopathy event-free status. Eculizumab was associated with significant improvement in all secondary end points, with continuous, time-dependent increases in the estimated glomerular filtration rate (GFR). In trial 1, dialysis was discontinued in 4 of 5 patients. Earlier intervention with eculizumab was associated with significantly greater improvement in the estimated GFR. Eculizumab was also associated with improvement in health-related quality of life. No cumulative toxicity of therapy or serious infection-related adverse events, including meningococcal infections, were observed through the extension period. CONCLUSIONS Eculizumab inhibited complement-mediated thrombotic microangiopathy and was associated with significant time-dependent improvement in renal function in patients with atypical hemolytic-uremic syndrome. (Funded by Alexion Pharmaceuticals; C08-002 ClinicalTrials.gov numbers, NCT00844545 [adults] and NCT00844844 [adolescents]; C08-003 ClinicalTrials.gov numbers, NCT00838513 [adults] and NCT00844428 [adolescents]).

Olmesartan for the delay or prevention of microalbuminuria in type 2 diabetes

BACKGROUND Microalbuminuria is an early predictor of diabetic nephropathy and premature cardiovascular disease. We investigated whether treatment with an angiotensin-receptor blocker (ARB) would delay or prevent the occurrence of microalbuminuria in patients with type 2 diabetes and normoalbuminuria. METHODS In a randomized, double-blind, multicenter, controlled trial, we assigned 4447 patients with type 2 diabetes to receive olmesartan (at a dose of 40 mg once daily) or placebo for a median of 3.2 years. Additional antihypertensive drugs (except angiotensin-converting-enzyme inhibitors or ARBs) were used as needed to lower blood pressure to less than 130/80 mm Hg. The primary outcome was the time to the first onset of microalbuminuria. The times to the onset of renal and cardiovascular events were analyzed as secondary end points. RESULTS The target blood pressure (<130/80 mm Hg) was achieved in nearly 80% of the patients taking olmesartan and 71% taking placebo; blood pressure measured in the clinic was lower by 3.1/1.9 mm Hg in the olmesartan group than in the placebo group. Microalbuminuria developed in 8.2% of the patients in the olmesartan group (178 of 2160 patients who could be evaluated) and 9.8% in the placebo group (210 of 2139); the time to the onset of microalbuminuria was increased by 23% with olmesartan (hazard ratio for onset of microalbuminuria, 0.77; 95% confidence interval, 0.63 to 0.94; P=0.01). The serum creatinine level doubled in 1% of the patients in each group. Slightly fewer patients in the olmesartan group than in the placebo group had nonfatal cardiovascular events--81 of 2232 patients (3.6%) as compared with 91 of 2215 patients (4.1%) (P=0.37)--but a greater number had fatal cardiovascular events--15 patients (0.7%) as compared with 3 patients (0.1%) (P=0.01), a difference that was attributable in part to a higher rate of death from cardiovascular causes in the olmesartan group than in the placebo group among patients with preexisting coronary heart disease (11 of 564 patients [2.0%] vs. 1 of 540 [0.2%], P=0.02). CONCLUSIONS Olmesartan was associated with a delayed onset of microalbuminuria, even though blood-pressure control in both groups was excellent according to current standards. The higher rate of fatal cardiovascular events with olmesartan among patients with preexisting coronary heart disease is of concern. (Funded by Daiichi Sankyo; ClinicalTrials.gov number, NCT00185159.).

Carotid Baroreceptor Stimulation, Sympathetic Activity, Baroreflex Function, and Blood Pressure in Hypertensive Patients

In animals, electric field stimulation of carotid baroreceptors elicits a depressor response through sympathetic inhibition. We tested the hypothesis that the stimulation acutely reduces sympathetic vasomotor tone and blood pressure in patients with drug treatment–resistant arterial hypertension. Furthermore, we tested whether the stimulation impairs the physiological baroreflex regulation. We studied 7 men and 5 women (ages 43 to 69 years) with treatment-resistant arterial hypertension. A bilateral electric baroreflex stimulator at the level of the carotid sinus (Rheos) was implanted ≥1 month before the study. We measured intra-arterial blood pressure, heart rate, muscle sympathetic nerve activity (microneurography), cardiac baroreflex sensitivity (cross-spectral analysis and sequence method), sympathetic baroreflex sensitivity (threshold technique), plasma renin, and norepinephrine concentrations. Measurements were performed under resting conditions, with and without electric baroreflex stimulation, for ≥6 minutes during the same experiment. Intra-arterial blood pressure was 193±9/94±5 mm Hg on medications. Acute electric baroreflex stimulation decreased systolic blood pressure by 32±10 mm Hg (range: +7 to −108 mm Hg; P=0.01). The depressor response was correlated with a muscle sympathetic nerve activity reduction (r2=0.42; P<0.05). In responders, muscle sympathetic nerve activity decreased sharply when electric stimulation started. Then, muscle sympathetic nerve activity increased but remained below the baseline level throughout the stimulation period. Heart rate decreased 4.5±1.5 bpm with stimulation (P<0.05). Plasma renin concentration decreased 20±8% (P<0.05). Electric field stimulation of carotid sinus baroreflex afferents acutely decreased arterial blood pressure in hypertensive patients, without negative effects on physiological baroreflex regulation. The depressor response was mediated through sympathetic inhibition.

Novel Baroreflex Activation Therapy in Resistant Hypertension Results of a European Multi-Center Feasibility Study

OBJECTIVES This study assessed the safety and efficacy of a novel implantable device therapy in resistant hypertension patients. BACKGROUND Despite the availability of potent antihypertensive drugs, a substantial proportion of patients remain hypertensive. A new implantable device (Rheos system, CVRx, Inc., Minneapolis, Minnesota) that activates the carotid baroreflex may help these patients. METHODS Forty-five subjects with systolic blood pressure ≥160 mm Hg or diastolic ≥90 mm Hg despite at least 3 antihypertensive drugs were enrolled in a prospective, nonrandomized feasibility study to assess whether Rheos therapy could safely lower blood pressure. Subjects were followed up for as long as 2 years. An external programmer was used to optimize and individualize efficacy. RESULTS Baseline mean blood pressure was 179/105 mm Hg and heart rate was 80 beats/min, with a median of 5 antihypertensive drugs. After 3 months of device therapy, mean blood pressure was reduced by 21/12 mm Hg. This result was sustained in 17 subjects who completed 2 years of follow-up, with a mean reduction of 33/22 mm Hg. The device exhibited a favorable safety profile. CONCLUSIONS The Rheos device sustainably reduces blood pressure in resistant hypertensive subjects with multiple comorbidities receiving numerous medications. This unique therapy offers a safe individualized treatment option for these high-risk subjects. This novel approach holds promise for patients with resistant hypertension and is currently under evaluation in a prospective, placebo-controlled clinical trial.

Catheter-Based Renal Nerve Ablation and Centrally Generated Sympathetic Activity in Difficult-to-Control Hypertensive Patients Prospective Case Series

Endovascular renal nerve ablation has been developed to treat resistant hypertension. In addition to lowering efferent renal sympathetic activation, the intervention may attenuate central sympathetic outflow through decreased renal afferent nerve traffic, as evidenced by a recent case report. We tested the hypothesis in 12 nonpreselected patients with difficult-to-control hypertension (aged 45–74 years) admitted for renal nerve ablation. All patients received ≥3 antihypertensive medications at full doses, including a diuretic. Electrocardiogram, respiration, brachial and finger arterial blood pressure, and muscle sympathetic nerve activity were recorded before and 3 to 6 months after renal nerve ablation. Heart rate and blood pressure variability were analyzed in the time and frequency domain. Pharmacological baroreflex slopes were determined using the modified Oxford bolus technique. Resting heart rate was 61±3 bpm before and 58±2 bpm after ablation (P=0.4). Supine blood pressure was 157±7/85±4 mm Hg before and 157±6/85±4 mm Hg after ablation (P=1.0). Renal nerve ablation did not change resting muscle sympathetic nerve activity (before, 34±2 bursts per minute; after, 32±3 bursts per minute P=0.6), heart rate variability, or blood pressure variability. Pharmacological baroreflex control of heart rate and muscle sympathetic nerve activity did not change. We conclude that reduced central sympathetic inhibition may be the exception rather than the rule after renal nerve ablation in unselected patients with difficult-to-control arterial hypertension.

Low-Dose Therapy With the Long-Acting Erythropoietin Analogue Darbepoetin Alpha Persistently Activates Endothelial Akt and Attenuates Progressive Organ Failure

Background—The hematopoietic cytokine erythropoietin has cytoprotective effects in endothelial cells in vitro that are mediated through direct activation of the pro-survival Akt tyrosine kinase signaling pathway. We tested the hypothesis that low-dose therapy with the long-acting recombinant human erythropoietin analogue darbepoetin alpha protects vascular endothelium in vivo in a classic remnant kidney rat model characterized by severe endothelial damage, progressive vascular sclerosis, and ischemia-induced tissue fibrosis. Methods and Results—Using a parallel group study design, we randomly assigned animals after 5/6 nephrectomy to treatment with either saline (n=36) or 0.1 μg/kg body wt darbepoetin (n=24) subcutaneously once weekly. We monitored hematocrit, blood pressure, and serum creatinine regularly and obtained renal tissue 6 weeks after nephrectomy for morphological and immunohistochemical analysis. Darbepoetin-treated animals had significantly improved survival compared with saline-treated controls (63% versus 33%; P<0.05), although hematocrit levels were similar in both groups. Darbepoetin treatment ameliorated endothelial damage; attenuated the composite tissue injury score (saline 1.9±0.4; darbepoetin 0.4±0.2; P<0.001), which included vascular sclerosis, glomerulosclerosis, and tubulointerstitial damage; and preserved renal function. We found persistent activation of the pro-survival Akt signaling pathway in endothelial and epithelial glomerular cells in darbepoetin-treated animals, accompanied by a significant reduction of apoptotic cell death in renal tissue. Conclusions—Low-dose darbepoetin treatment confers vascular and tissue protection that is associated with persistent stimulation of the pro-survival Akt signaling pathway. The use of recombinant human erythropoietin or analogues may have utility in preventing ischemia-related progressive vascular injury and organ failure.

ADMA Increases Arterial Stiffness and Decreases Cerebral Blood Flow in Humans

Background and Purpose— Preclinical studies have revealed that the endogenous nitric oxide synthase inhibitor, asymmetric dimethylarginine (ADMA), increases vascular tone in cerebral blood vessels. Marked elevations of ADMA blood levels were found in patients with diseases characterized by decreased cerebral perfusion, such as ischemic stroke. Arterial stiffness is an independent predictor of stroke and other adverse cardiovascular events. The aim of this study was to investigate the influence of a systemic subpressor dose of ADMA on arterial stiffness and cerebral perfusion in humans. Methods— Using a double-blind, vehicle-controlled study design, we allocated 20 healthy men in random order to infusion of either ADMA (0.10 mg ADMA/kg per min) or vehicle over a period of 40 minutes. Arterial stiffness was assessed noninvasively by pulse wave analysis. All volunteers underwent measurement of cerebral perfusion by dynamic contrast-enhanced perfusion magnetic resonance imaging of the brain. Results— Infusion of ADMA significantly decreased total cerebral perfusion by 15.1±4.5% (P=0.007), whereas blood flow in the vehicle group increased by 7.7±2.8% (P=0.02). ADMA also increased arterial stiffness as assessed by measurement of the augmentation index (−12.6±1.9 to −9.6±1.5, P=0.007). Conclusions— Our results document for the first time that subpressor doses of ADMA increase vascular stiffness and decrease cerebral perfusion in healthy subjects. Thus, ADMA is an important endogenous modulator of cerebral vascular tone and may be involved in the pathogenesis of cerebrovascular disease.

Diagnosis and Prediction of CKD Progression by Assessment of Urinary Peptides

Progressive CKD is generally detected at a late stage by a sustained decline in eGFR and/or the presence of significant albuminuria. With the aim of early and improved risk stratification of patients with CKD, we studied urinary peptides in a large cross-sectional multicenter cohort of 1990 individuals, including 522 with follow-up data, using proteome analysis. We validated that a previously established multipeptide urinary biomarker classifier performed significantly better in detecting and predicting progression of CKD than the current clinical standard, urinary albumin. The classifier was also more sensitive for identifying patients with rapidly progressing CKD. Compared with the combination of baseline eGFR and albuminuria (area under the curve [AUC]=0.758), the addition of the multipeptide biomarker classifier significantly improved CKD risk prediction (AUC=0.831) as assessed by the net reclassification index (0.303±-0.065; P<0.001) and integrated discrimination improvement (0.058±0.014; P<0.001). Correlation of individual urinary peptides with CKD stage and progression showed that the peptides that associated with CKD, irrespective of CKD stage or CKD progression, were either fragments of the major circulating proteins, suggesting failure of the glomerular filtration barrier sieving properties, or different collagen fragments, suggesting accumulation of intrarenal extracellular matrix. Furthermore, protein fragments associated with progression of CKD originated mostly from proteins related to inflammation and tissue repair. Results of this study suggest that urinary proteome analysis might significantly improve the current state of the art of CKD detection and outcome prediction and that identification of the urinary peptides allows insight into various ongoing pathophysiologic processes in CKD.

Complement 5a Receptor Inhibition Improves Renal Allograft Survival

Complement activation plays a key role in mediating apoptosis, inflammation, and transplant rejection. In this study, the role of the complement 5a receptor (C5aR) was examined in human renal allografts and in an allogenic mouse model of renal transplant rejection. In human kidney transplants with acute rejection, C5aR expression was increased in renal tissue and in cells infiltrating the tubulointerstitium. Similar findings were observed in mice. When recipient mice were treated once daily with a C5aR antagonist before transplantation, long-term renal allograft survival was markedly improved compared with vehicle-treatment (75 versus 0%), and apoptosis was reduced. Furthermore, treatment with a C5aR antagonist significantly attenuated monocyte/macrophage infiltration, perhaps a result of reduced levels of monocyte chemoattractant protein 1 and the intercellular adhesion molecule 1. In vitro, C5aR antagonism inhibited intercellular adhesion molecule 1 upregulation in primary mouse aortic endothelial cells and reduced adhesion of peripheral blood mononuclear cells. Furthermore, C5aR blockade markedly reduced alloreactive T cell priming. These results demonstrate that C5aR plays an important role in mediating acute kidney allograft rejection, suggesting that pharmaceutical targeting of C5aR may have potential in transplantation medicine.

Deletion of Protein Kinase C-β Isoform In Vivo Reduces Renal Hypertrophy but Not Albuminuria in the Streptozotocin-Induced Diabetic Mouse Model

The protein kinase C (PKC)-β isoform has been implicated to play a pivotal role in the development of diabetic kidney disease. We tested this hypothesis by inducing diabetic nephropathy in PKC-β–deficient (PKC-β−/−) mice. We studied nondiabetic and streptozotocin-induced diabetic PKC-β−/− mice compared with appropriate 129/SV wild-type mice. After 8 weeks of diabetes, the high-glucose–induced renal and glomerular hypertrophy, as well as the increased expression of extracellular matrix proteins such as collagen and fibronectin, was reduced in PKC-β−/− mice. Furthermore, the high-glucose–induced expression of the profibrotic cytokine transforming growth factor (TGF)-β1 and connective tissue growth factor were significantly diminished in the diabetic PKC-β−/− mice compared with diabetic wild-type mice, suggesting a role of the PKC-β isoform in the regulation of renal hypertrophy. Notably, increased urinary albumin-to-creatinine ratio persisted in the diabetic PKC-β−/− mice. The loss of the basement membrane proteoglycan perlecan and the podocyte protein nephrin in the diabetic state was not prevented in the PKC-β−/− mice as previously demonstrated in the nonalbuminuric diabetic PKC-α−/− mice. In summary, the differential effects of PKC-β deficiency on diabetes-induced renal hypertrophy and albuminuria suggest that PKC-β contributes to high-glucose–induced TGF-β1 expression and renal fibrosis, whereas perlecan, as well as nephrin, expression and albuminuria is regulated by other signaling pathways.