Erythropoietin mediates brain-vascular-kidney crosstalk and may be a treatment target for pulmonary and resistant essential hypertension

Organ crosstalk pathways represent the next frontier for target-mining in molecular medicine for existing syndromes. Pulmonary hypertension and resistant essential hypertension are syndromes that have been proven elusive in etiology, and frequently refractory to first-line management. Underlying crosstalk mechanisms, not yet considered in these treatments, may hinder outcomes or unlock novel treatments. This review focuses systematically on erythropoietin, a synthesizable molecule, as a mediator of brain-kidney crosstalk. Insights gained from this review will be applied to cardiovascular diseases in a clinician-directed fashion.

Serum and tissue endothelin-1 are independent from intima-media thickness of peripheral arteries in patients with chronic kidney disease

AIM

We aimed to study the relationship of peripheral arteries' atherosclerosis with serum and tissue endothelin-1 in chronic kidney disease patients.

METHODS

Ninety patients were enrolled, including 35 patients with chronic kidney disease (case group), 31 patients with coronary artery diseases who were candidates for coronary artery bypass grafting (positive control group), and 24 living kidney donors (negative control group). Intima-media thickness of the common carotid and femoral arteries was determined by ultrasonography. Serum and tissue endothelin-1 were measured by ELISA method.

RESULTS

The mean serum and tissue endothelin-1 levels in the donor group were significantly lower than other groups (p < 0.001 for both). The coronary artery bypass grafting group had higher carotid and femoral intima-media thickness than other groups (p < 0.001), and the chronic kidney disease group had higher carotid and femoral intima-media thickness than the donor group (p < 0.001). Regression analysis in all groups did not reveal any correlation between the carotid intima-media thickness/femoral intima-media thickness and the serum/tissue endothelin-1. There was a direct linear correlation between the carotid and femoral intima-media thickness (p < 0.001) in all groups.

CONCLUSIONS

Endothelin-1 level and intima-media thickness were higher in the chronic kidney disease patients and coronary artery bypass grafting candidates, without any correlation between endothelin-1 and peripheral arteries' intima-media thickness of both groups. Perhaps endothelin-1 rises and remains high upon endothelial damage and initiation of atherosclerosis.

Endothelin-1 Plasma Levels in Hemodialysis Treatment—The Influence of Type 2 Diabetes

In patients on chronic hemodialysis the prevalence of atherosclerosis is increased and is by far the leading cause of morbidity and mortality. Endothelin-1, an endothelium-derived peptide with vasoconstrictive and mitogenic effects on vascular smooth muscles, is involved in the pathogenesis of atherosclerosis. The aim of the present study was to investigate the time course of plasma endothelin-1 levels during a hemodialysis session and to explore the influence of preexisting type 2 diabetes mellitus. Forty-five clinically stable hemodialysis patients (21 females, 24 males; mean age 62 +/- 12 years) were evaluated. Patients with type 2 diabetes (n= 11) were compared with the group of patients without diabetes (n=34). Relative blood volume (BV) changes (hemoglobinometry) and blood pressure (BP) was measured. Samples were taken before, every hour during, and after hemodialysis. Plasma endothelin-1 levels were measured by enzyme-linked immunoassay (ELISA) and results were corrected according to hemoconcentration. Hemodialysis with an ultrafiltration of 2215 +/- 952 mL was performed. Total BV at the end of hemodialysis was 89.3% +/- 8.3% of the pretreatment volume. Plasma endothelin-1 was enhanced in hemodialysis patients compared to normal subjects and increased from 1.28 +/- 0.47 before to 1.44 +/- 0.54 pg/mL (ref. 0.3-0.9) at the end of hemodialysis (p<0.05). The BV change (r=0.41) and the BP (mean BP: r=0.34) correlated with plasma endothelin-1 at the end of hemodialysis (p<0.05). The levels of endothelin-1 were significantly higher in the group of dialysis patients with type 2 diabetes compared to nondiabetics in all measurements (p<0.05). These findings suggest a potential role of endothelin-1 in the pathogenesis of vascular dysfunction in diabetes mellitus. The dialysis procedure per se, through vasoconstriction due to BV decrease, local endothelial injury (a.v. fistula), or bioincompatibility reactions (foreign surface contact) may additionally alter endothelial cell functions.

Arterial hypertension induced by erythropoietin and erythropoiesis-stimulating agents (ESA)

This review summarizes the evidence for a hypertensinogenic effect of Erythropoietin (Epo) in normal human subjects and predialysis, hemodialysis, and continuous ambulatory peritoneal dialysis (CAPD) patients. The possible mechanisms of Epo-induced hypertension are examined with in vivo animal and in vitro data, as well as pathophysiological human studies in both normal subjects and CKD patients. The evidence for a hypertensinogenic effect of erythropoiesis-stimulating agents (ESAs) in normal subjects, predialysis CKD, hemodialysis, and CAPD patients is compelling. Epo increases BP directly and notably independently of its erythropoietic effect and its effect on blood rheology. The potential for the development of future agents that might act as specific stimulators of erythropoiesis, devoid of direct hemodynamic side effects is underscored.

Impact of rHuEPO therapy initiation on soluble adhesion molecule levels in haemodialysis patients

BACKGROUND

Increased levels of soluble adhesion molecules have been reported in haemodialysis (HD) patients. Recent studies have shown that recombinant human erythropoietin (rHuEPO) elicits proliferation and migration of endothelial cells and modifies endothelial function. The present study was design to explore the effects of rHuEPO on serum levels of soluble adhesion molecules in HD patients.

METHODS

Soluble serum levels of E-selectin (sE-selectin), intracellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) were measured by ELISA in 29 rHuEPO naïve HD patients (20 males, 9 females) and 10 control subjects at baseline and second month. The HD patients with a haemoglobin level lower than 10.0 mg/dL (n = 19) were administered rHuEPO therapy and other HD patients (n = 10) were followed as a placebo group.

RESULTS

Serum levels of soluble adhesion molecules were significantly higher in HD patients compared with the control group. A significant rise from the baseline in sE-selectin levels (77 +/- 70 vs 100 +/- 86 ng/mL, P < 0.05) was observed 2 months after rHuEPO initiation, while sICAM-1 and sVCAM-1 levels decreased (271 +/- 261 vs 197 +/- 89 and 1043 +/- 243 vs 990 +/- 236 ng/mL, respectively, P < 0.05).

CONCLUSIONS

The present data indicate that rHuEPO could have an important action on serum levels of soluble adhesion molecules in HD patients. rHuEPO might modify the expression of adhesion molecules from endothelial cells either. However, the exact mechanism responsible for the serum elevation of these molecules in HD patients is yet to be fully elucidated.

Should hemoglobin be normalized in patients with chronic kidney disease?

In the last decade the nephrology community has learned much about the impact of anemia on patients with kidney disease. Therapy of anemia can correct many of the symptoms which seriously compromise patient function. Despite the obvious benefits, controversy continues regarding the optimal target hemoglobin concentration both in patients prior to dialysis and in dialysis populations. In this editorial we review the clinical data that contribute to this controversy and the physiologic concepts underlying the treatment of anemia. Furthermore, we discuss the need to individualize hemoglobin targets for specific patient populations and the importance of early identification and treatment of anemia in patients with kidney disease. The economic impact of normalizing hemoglobin with the use of erythropoietin and intravenous or oral iron has affected clinical practice over the last decade. Current guidelines published by Kidney Disease Outcomes and Quality Initiative (KDOQI), the European Working Group on Anemia Management, and the Canadian Society of Nephrology all recommend target hemoglobin concentrations and thresholds for initiation of therapy and also suggest the need for reevaluation of current targets in light of new evidence. This editorial supports those guidelines and challenges the reader to critically evaluate current practice in the context of the accumulating data and the physiologic principles discussed herein. The therapy of anemia in patients with chronic kidney disease (CKD) is becoming increasingly sophisticated and is an essential component of care in patients with CKD. However, the effects of therapy will be most impressive when accompanied by the optimal care of all hemodynamic and metabolic abnormalities that are associated with CKD.