Endothelin but Not Angiotensin II May Mediate Hypertension-Induced Coronary Vascular Calcification in Chronic Kidney Disease

Role of crosstalk between endothelial cells and smooth muscle cells in vascular calcification in chronic kidney disease

Chronic kidney disease (CKD) is a severe health problem worldwide, and vascular calcification (VC) contributes substantially to the cardiovascular morbidity and high mortality of CKD. CKD is often accompanied by a variety of pathophysiological states, such as inflammation, oxidative stress, hyperglycaemia, hyperparathyroidism and haemodynamic derangement, that can cause injuries to smooth muscle cells (SMCs) and endothelial cells (ECs) to promote VC. Similar to SMCs, whose role has been widely explored in VC, ECs may contribute to VC via osteochondral transdifferentiation, apoptosis, etc. In addition, given their location in the innermost layer of the blood vessel lumen and preferential reception of various pro‐calcification stimuli, ECs can pass messages to vascular wall cells and communicate with them. Crosstalk between ECs and SMCs via cytokines through a paracrine mechanism, extracellular vesicles, miRNAs and myoendothelial gap junctions also plays a role in VC. In this review, we emphasize the role of intercellular crosstalk between ECs and SMCs in VC associated with CKD.

Copeptin is independently associated with vascular calcification in chronic kidney disease stage 5

BACKGROUND

Vascular calcification (VC) is an independent predictor of cardiovascular disease (CVD) present in 30-70% of patients with chronic kidney disease (CKD). Copeptin is a sensitive surrogate marker of arginine vasopressin (AVP), which is involved in many pathophysiologic processes in CKD. The aim of the present study was to explore the association of copeptin with VC in CKD stage 5.

METHODS

Copeptin was investigated in conjunction with living donor kidney transplantation in 149 clinically stable CKD stage 5 patients (CKD5), including 53 non-dialyzed (CKD5-ND) and 96 dialysis patients treated by peritoneal dialysis (PD) (n = 43) or hemodialysis (HD) (n = 53). We analyzed the association of copeptin with presence and extent of VC ascertained both histologically in biopsies from the inferior epigastric artery (n = 137) and by coronary artery calcification (CAC) score measured by computed tomography.

RESULTS

Patients with higher copeptin were older, had higher systolic blood pressure, higher prevalence of CVD and their preceding time on chronic dialysis was longer. In Spearman's rank correlations (Rho), copeptin concentrations were significantly associated with CAC score (Rho = 0.27; p = 0.003) and presence of medial VC (Rho = 0.21; p = 0.016). Multivariate logistic regression analysis showed that 1-SD higher age, male gender, diabetes and 1-SD higher copeptin were significantly associated with the presence of moderate-extensive VC.

CONCLUSIONS

High circulating levels of copeptin in CKD5 patients are independently associated with the degree of medial calcification ascertained by histology of arterial biopsies. Thus, plasma copeptin may serve as a marker of the uremic calcification process.

The Value of Big Endothelin-1 in the Assessment of the Severity of Coronary Artery Calcification

Progression of coronary artery calcification (CAC) was significantly associated with all-cause mortality, and high coronary artery calcium score (CACS) portends a particularly high risk of cardiovascular events. But how often one should rescan is still an unanswered question. Preliminary screening by testing circulating biomarker may be an alternative before repeat computed tomography (CT) scan. The aim of this study was to investigate the value of big endothelin-1 (bigET-1), the precursor of endothelin-1 (ET-1), in predicting the severity of CAC. A total of 428 consecutively patients who performed coronary computed tomography angiography (CCTA) due to chest pain in Fuwai Hospital were included in the study. The clinical characteristics, CACS, and laboratory data were collected, and plasma bigET-1 was detected by enzyme-linked immunosorbent assay (ELISA). The bigET-1 was positively correlated with the CACS (r = .232, P < .001), and the prevalence of CACS >400 increased significantly in the highest bigET-1 tertile than the lowest tertile. Multivariate analysis showed that bigET-1was the independent predictor of the presence of CACS >400 (odds ratio [OR] = 1.721, 95% confidence interval [CI], 1.002-2.956, P = .049). The receiver operating characteristic (ROC) curve analysis showed that the optimal cutoff value of bigET-1 for predicting CACS >400 was 0.38 pmol/L, with a sensitivity of 59% and specificity of 68% (area under curve [AUC] = 0.65, 95% CI, 0.58-0.72, P < .001). The present study demonstrated that the circulating bigET-1 was valuable in the assessment of the severity of CAC.

Can antihypertensive medication interfere with the vicious cycle between hypertension and vascular calcification?

Vascular calcification is a phenomenon of disturbed calcium deposition, as part of the calcium that is supposed to be deposited to our bones, is lodged to our vessels. There are two forms of vascular calcification, each with a distinct anatomical distribution and clinical relevance, namely the intimal and medial calcification. Studies have demonstrated that hypertension may cause vascular calcification but also that both types of calcification, especially medial, promote arterial rigidity and hence hypertension. Implications of this two-way road are largely unknown as there is no consensus yet on their exact clinical value. However, several antihypertensive medications seem to be able to interfere with the cycle of high blood pressure and vascular calcium deposits. The present review summarizes the up-to-date data regarding the effect of antihypertensive medication on vascular calcification.

Endothelin antagonists for diabetic and non-diabetic chronic kidney disease

Numerous pre-clinical studies have implicated endothelin-1 in the pathogenesis of diabetic and non-diabetic chronic kidney disease (CKD). Renal endothelin-1 production is almost universally increased in kidney disease. The pathologic effects of endothelin-1, including vasoconstriction, proteinuria, inflammation, cellular injury and fibrosis, are likely mediated by the endothelin A (ETA) receptor. ETA antagonism alone, and/or combined ETA/B blockade, reduces CKD progression. Based on the strong pre-clinical data, several clinical trials using ETA antagonists were conducted. Small trials involving acute intravenous endothelin receptor blockade suggest that ETA, but not ETB, blockade exerts protective renal and vascular effects in CKD patients. A large phase 3 trial (ASCEND) examined the effects of avosentan, an endothelin receptor antagonist, on renal disease progression in diabetic nephropathy. Proteinuria was reduced after 3-6 months of treatment. However the study was terminated due to increased morbidity and mortality associated with avosentan-induced fluid retention. Several phase 2 trials using avosentan at lower doses than in ASCEND, atrasentan or sitaxsentan (the latter two being highly ETA-selective) showed reductions in proteinuria on top of renin-angiotensin system blockade. Infrequent and clinically insignificant fluid retention was observed at the most effective doses. Additional trials using ETA blockers are ongoing or being planned in patients with diabetic nephropathy or focal segmental glomerulosclerosis. Moving forward, such studies must be conducted with careful patient selection and attention to dosing in order to minimize adverse side effects. Nonetheless, there is cause for optimism that this class of agents will ultimately prove to be effective for the treatment of CKD.

Ankle–Brachial Index as an Indicator of Arterial Stiffness in Patients Without Peripheral Artery Disease

We tested the hypothesis that the Ankle-Brachial Index (ABI) in patients without peripheral arterial disease ([PAD] ABI > 1.0) is an indicator of arterial stiffness. Fifty-five patients had measurement of carotid pulse wave contour, pulse wave velocity (PWV), and ABI. Vascular stiffness as assessed by augmentation index (AIx) showed a significant ( P = .002) inverse correlation with ABI. Dichotomizing ABI into groups above and below the median showed that persons with a lower ABI, >1.0 to 1.5 (n = 27) had a significantly ( P < .01) higher AIx than those with a higher ABI > 1.5 (n = 28). In contrast, vascular stiffness assessed by brachial-ankle or carotid femoral PWV did not correlate with ABI. In summary, ABI is an indicator of arterial stiffness assessed by AIx. Vascular changes detected by AIx are not the same as those detected by PWV. Assessment of ABI may have utility in cardiovascular risk assessment in patients without PAD.