Neeraj Dhaun

Circulating microRNAs as potential markers of human drug‐induced liver injury

New biomarkers of liver injury are required in the clinic and in preclinical pharmaceutical evaluation. Previous studies demonstrate that two liver‐enriched microRNAs (miR‐122 and miR‐192) are promising biomarkers of acetaminophen‐induced acute liver injury (APAP‐ALI) in mice. We have examined these molecules, for the first time, in humans with APAP poisoning. Serum miR‐122 and miR‐192 were substantially higher in APAP‐ALI patients, compared to healthy controls (median ΔΔCt [25th, 75th percentile]) (miR‐122: 1,265 [491, 4,270] versus 12.1 [7.0, 26.9], P < 0.0001; miR‐192: 6.9 [2.0, 29.2] versus 0.44 [0.30, 0.69], P < 0.0001). A heart‐enriched miR‐1 showed no difference between APAP‐ALI patients and controls, whereas miR‐218 (brain‐enriched) was slightly higher in the APAP‐ALI cohort (0.17 [0.07, 0.50] versus 0.07 [0.04, 0.12]; P = 0.01). In chronic kidney disease (CKD) patients, miR‐122 and ‐192 were modestly higher, compared to controls (miR‐122: 32.0 [21.1, 40.9] versus 12.1 [7.0, 26.9], P = 0.006; miR‐192: 1.2 [0.74, 1.9] versus 0.44 [0.30, 0.69], P = 0.005), but miR‐122 and ‐192 were substantially higher in APAP‐ALI patients than CKD patients (miR‐122: P < 0.0001; miR‐192: P < 0.0004). miR‐122 correlated with peak ALT levels in the APAP‐ALI cohort (Pearson R = 0.46, P = 0.0005), but not with prothrombin time. miR‐122 was also raised alongside peak ALT levels in a group of patients with non‐APAP ALI. Day 1 serum miR‐122 levels were almost 2‐fold higher in APAP‐ALI patients who satisfied Kings College Criteria (KCC), compared to those who did not satisfy KCC, although this did not reach statistical significance (P = 0.15). Conclusion: This work provides the first evidence for the potential use of miRNAs as biomarkers of human drug‐induced liver injury. (HEPATOLOGY 2011;)

The Endothelin System and Its Antagonism in Chronic Kidney Disease

The incidence of chronic kidney disease (CKD) is increasing worldwide. Cardiovascular disease (CVD) is strongly associated with CKD and constitutes one of its major causes of morbidity and mortality. Treatments that slow the progression of CKD and improve the cardiovascular risk profile of patients with CKD are needed. The endothelins (ET) are a family of related peptides, of which ET-1 is the most powerful endogenous vasoconstrictor and the predominant isoform in the cardiovascular and renal systems. The ET system has been widely implicated in both CVD and CKD. ET-1 contributes to the pathogenesis and maintenance of hypertension and arterial stiffness and more novel cardiovascular risk factors such as oxidative stress and inflammation. Through these, ET also contributes to endothelial dysfunction and atherosclerosis. By reversal of these effects, ET antagonists may reduce cardiovascular risk. In particular relation to the kidney, antagonism of the ET system may be of benefit in improving renal hemodynamics and reducing proteinuria. ET likely also is involved in progression of renal disease, and data are emerging to suggest a synergistic role for ET receptor antagonists with angiotensin-converting enzyme inhibitors in slowing CKD progression.

Role of Endothelin-1 in Clinical Hypertension 20 Years On

Hypertension is the most common risk factor worldwide for cardiovascular morbidity and mortality.1,2 Currently it is estimated that a quarter of the world’s adult population is hypertensive, and this number is projected to increase to ≈30% by 2025.1 Although, there exist a number of drug therapies for hypertension, blood pressure (BP) control to target is still only achieved in ≈30% of patients.3 Over the last 20 years, novel licensed therapies have primarily focused on the renin-angiotensin-aldosterone system. Endothelin (ET) receptor antagonism represents an innovative, but as yet only partially explored, alternative approach in the management of hypertension. A review in Hypertension 10 years ago outlined the potential role that ET-1 may play in the development of hypertension,4 as proposed by Yanagisawa et al in their original Nature article in 1988.5 This largely focused on preclinical data because, at that time, there was only 1 published study of ET receptor antagonism in patients with essential hypertension.6 There were also few data that focused on the relative benefits of selective or mixed ET blockade. Finally, the lack of longer-term data on safety and tolerability for these drugs made their place in the antihypertensive armamentarium unclear. In this review we aim to answer many of these questions and outline some of the key findings in this field from the last decade. The ET family consists of three 21-amino acid peptides (ET-1, ET-2, and ET-3) with powerful vasoconstrictor and pressor properties.7 Of the 3 peptides, ET-1 is the major vascular isoform and of most importance in the cardiovascular system.8 The gene product is the 212-amino acid prepro-ET-1. This is cleaved to big ET-1, after which an ET-converting enzyme (ECE) catalyzes the generation of the biologically active ET-1 and a C-terminal fragment. ET-1 acts by binding to …

Comparative Toxicity of Citalopram and the Newer Antidepressants After Overdose

Objective: To compare the toxicity of citalopram, venlafaxine, mirtazapine, and nefazadone after overdose. Methods: Two‐year retrospective review of consecutive patients admitted to the toxicology unit of Edinburgh Royal Infirmary. Outcome measure included physiological variables, ECG recordings, peak creatine kinase, development of arrhythmias, seizure, tremor or agitation, and the need for admission to a critical care facility. Results: A total of 225 patients were studied. Venlafaxine was associated with a significantly higher pulse rate (p < 0.0001) and tremor (p = 0.007) than other antidepressants. Citalopram was associated with a significantly longer QT interval on ECG recording (p < 0.0001) but mean QTc durations were not significantly different between all drugs studied. No arrhythmias were recorded. Only venlafaxine and citalopram caused seizures and were associated with the need for admission to Intensive Care, but there was no significant difference between them. Conclusions: Mirtazapine and nefazadone appear safe in overdose and were associated with minimal features of neurological or cardiovascular toxicity. Citalopram is more likely to cause QT prolongation but other features of cardiovascular toxicity were uncommon. Both citalopram and venlafaxine are proconvulsants. Venlafaxine also causes more frequent features of the serotonin syndrome.

Blood Pressure–Independent Reduction in Proteinuria and Arterial Stiffness After Acute Endothelin-A Receptor Antagonism in Chronic Kidney Disease

Endothelin 1 is implicated in the development and progression of chronic kidney disease and associated cardiovascular disease. We, therefore, studied the effects of selective endothelin-A receptor antagonism with BQ-123 on key independent surrogate markers of cardiovascular risk (blood pressure, proteinuria and renal hemodynamics, arterial stiffness, and endothelial function) in patients with nondiabetic chronic kidney disease. In a double-blind, randomized crossover study, 22 subjects with proteinuric chronic kidney disease received, on 2 separate occasions, placebo or BQ-123. Ten of these subjects also received nifedipine (10 mg) as an active control for the antihypertensive effect of BQ-123. Blood pressure, pulse wave velocity, flow-mediated dilation, renal blood flow, and glomerular filtration rate were monitored after drug dosing. BQ-123 reduced blood pressure (mean arterial pressure: −7±1%; P<0.001 versus placebo) and increased renal blood flow (17±4%; P<0.01 versus placebo). Glomerular filtration rate remained unchanged. Proteinuria (−26±4%; P<0.01 versus placebo) and pulse wave velocity (−5±1%; P<0.001 versus placebo) fell after BQ-123, but flow-mediated dilation did not change. Nifedipine matched the blood pressure and renal blood flow changes seen with BQ-123. Nevertheless, BQ-123 reduced proteinuria (−38±3% versus 26±11%; P<0.001) and pulse wave velocity (−9±1% versus −3±1%; P<0.001) to a greater extent than nifedipine. Selective endothelin-A receptor antagonism reduced blood pressure, proteinuria, and arterial stiffness on top of standard treatment in renal patients. Furthermore, these studies suggest that the reduction in proteinuria and arterial stiffness is partly independent of blood pressure. If maintained longer term, selective endothelin-A receptor antagonism may confer cardiovascular and renal benefits in patients with chronic kidney disease.

Selective Endothelin-A Receptor Antagonism Reduces Proteinuria, Blood Pressure, and Arterial Stiffness in Chronic Proteinuric Kidney Disease

Proteinuria is associated with adverse cardiovascular and renal outcomes that are not prevented by current treatments. Endothelin 1 promotes the development and progression of chronic kidney disease and associated cardiovascular disease. We, therefore, studied the effects of selective endothelin-A receptor antagonism in proteinuric chronic kidney disease patients, assessing proteinuria, blood pressure (BP), and arterial stiffness, key independent, surrogate markers of chronic kidney disease progression and cardiovascular disease risk. In a randomized, double-blind, 3-way crossover study, 27 subjects on recommended renoprotective treatment received 6 weeks of placebo, 100 mg once daily of sitaxsentan, and 30 mg once daily of nifedipine long acting. Twenty-four–hour proteinuria, protein:creatinine ratio, 24-hour ambulatory BP, and pulse wave velocity (as a measure of arterial stiffness) were measured at baseline and week 6 of each treatment. In 13 subjects, renal blood flow and glomerular filtration rate were assessed at baseline and week 6 of each period. Compared with placebo, sitaxsentan reduced 24-hour proteinuria (−0.56±0.20 g/d; P=0.0069), protein:creatinine ratio (−38±15 mg/mmol; P=0.0102), BP (−3.4±1.2 mm Hg; P=0.0069), and pulse wave velocity (−0.64±0.24 m/s; P=0.0052). Nifedipine matched the BP and pulse wave velocity reductions seen with sitaxsentan but did not reduce proteinuria. Sitaxsentan alone reduced both glomerular filtration rate and filtration fraction. It caused no clinically significant adverse effects. Endothelin-A receptor antagonism may provide additional cardiovascular and renal protection by reducing proteinuria, BP, and arterial stiffness in optimally treated chronic kidney disease subjects. The antiproteinuric effects of sitaxsentan likely relate to changes in BP and renal hemodynamics.

Blood pressure and not uraemia is the major determinant of arterial stiffness and endothelial dysfunction in patients with chronic kidney disease and minimal co-morbidity

INTRODUCTION Patients with chronic kidney disease (CKD) have increased risk of cardiovascular disease to which co-morbidity and associated conventional risk factors contribute. We hypothesised that arterial stiffness (AS) and endothelial dysfunction (ED), as surrogates of cardiovascular risk, would worsen as renal function declined even in patients without co-morbidity and that this would relate to emerging cardiovascular risk factors. METHODS Carotid-femoral pulse wave velocity (PWV), as a measure of AS, and flow-mediated dilatation (FMD) of the brachial artery, as a measure of ED, were assessed in CKD patients without established cardiovascular disease or diabetes mellitus. RESULTS PWV increased linearly as renal function declined (r(2) = 0.08, p < 0.01) whereas FMD was reduced only in patients with advanced kidney disease. In multivariable analysis, blood pressure was the major determinant of PWV and FMD. High-sensitivity C-reactive protein and asymmetric dimethylarginine, and isoprostanes and endothelin-1, were independent predictors of PWV and FMD, respectively. However, renal function did not independently predict either AS or ED. CONCLUSIONS These findings suggest that declining renal function, in the absence of significant co-morbidity, is associated with progressive arterial stiffness, but only patients close to dialysis exhibit endothelial dysfunction. Whilst blood pressure remains the major determinant of PWV and FMD, inflammation, oxidative stress and endothelin-nitric oxide balance contribute to cardiovascular risk, in this non-comorbid cohort.

Urinary endothelin-1 in chronic kidney disease and as a marker of disease activity in lupus nephritis

Chronic inflammation contributes to the development and progression of chronic kidney disease (CKD). Identifying renal inflammation early is important. There are currently no specific markers of renal inflammation. Endothelin-1 (ET-1) is implicated in the pathogenesis of CKD. Thus, we investigated the impact of progressive renal dysfunction and renal inflammation on plasma and urinary ET-1 concentrations. In a prospective study, plasma and urinary ET-1 were measured in 132 subjects with CKD stages 1 to 5, and fractional excretion of ET-1 (FeET-1) was calculated. FeET-1, serum C-reactive protein (CRP), urinary ET-1:creatinine ratio, and urinary albumin:creatinine ratio were also measured in 29 healthy volunteers, 85 subjects with different degrees of inflammatory renal disease but normal renal function, and in 10 subjects with rheumatoid arthritis without renal involvement (RA). In subjects with nephritis associated with systemic lupus erythematosus (SLE), measurements were done before and after 6 mo of treatment. In subjects with CKD, plasma ET-1 increased linearly as renal function declined, whereas FeET-1 rose exponentially. In subjects with normal renal function, FeET-1 and urinary ET-1:creatinine ratio were higher in SLE subjects than in other groups (7.7 +/- 2.7%, 10.0 +/- 3.0 pg/mumol, both P < 0.001), and correlated with CRP, and significantly higher than in RA subjects (both P < 0.01) with similar CRP concentrations. In SLE patients, following treatment, FeET-1 fell to 3.6 +/- 1.4% (P < 0.01). Renal ET-1 production increases as renal function declines. In subjects with SLE, urinary ET-1 may be a useful measure of renal inflammatory disease activity while measured renal function is still normal.

Endothelin-1 and the kidney - beyond BP

Since its discovery over 20 years ago endothelin‐1 (ET‐1) has been implicated in a number of physiological and pathophysiological processes. Its role in the development and progression of chronic kidney disease (CKD) is well established and is an area of ongoing intense research. There are now available a number of ET receptor antagonists many of which have been used in trials with CKD patients and shown to reduce BP and proteinuria. However, ET‐1 has a number of BP‐independent effects. Importantly, and in relation to the kidney, ET‐1 has clear roles to play in cell proliferation, podocyte dysfunction, inflammation and fibrosis, and arguably, these actions of ET‐1 may be more significant in the progression of CKD than its prohypertensive actions. This review will focus on the potential role of ET‐1 in renal disease with an emphasis on its BP‐independent actions.

Endothelin-A Receptor Antagonism Modifies Cardiovascular Risk Factors in CKD

Arterial stiffness and impaired nitric oxide (NO) bioavailability contribute to the high risk for cardiovascular disease in CKD. Both asymmetric dimethylarginine (ADMA), an endogenous inhibitor of NO production, and endothelin-1 (ET-1) oppose the actions of NO, suggesting that ET-1 receptor antagonists may have a role in cardiovascular protection in CKD. We conducted a randomized, double-blind, three-way crossover study in 27 patients with proteinuric CKD to compare the effects of the ET(A) receptor antagonist sitaxentan, nifedipine, and placebo on proteinuria, BP, arterial stiffness, and various cardiovascular biomarkers. After 6 weeks of treatment, placebo and nifedipine did not affect plasma urate, ADMA, or urine ET-1/creatinine, which reflects renal ET-1 production; in contrast, sitaxentan led to statistically significant reductions in all three of these biomarkers. No treatment affected plasma ET-1. Reductions in proteinuria and BP after sitaxentan treatment was associated with increases in urine ET-1/creatinine, whereas reduction in pulse-wave velocity, a measure of arterial stiffness, was associated with a decrease in ADMA. Taken together, these data suggest that ET(A) receptor antagonism may modify risk factors for cardiovascular disease in CKD.