The influence of the pleiotropic action of erythropoietin and its derivatives on nephroprotection

The Role of Erythropoietin Levels in Predicting Long-Term Outcomes following Severe Acute Kidney Injury

INTRODUCTION

Acute kidney injury (AKI) survivors are at an increased risk of chronic kidney disease, end-stage kidney disease, and mortality. Little is known about the effect of erythropoietin (EPO), a kidney-producing hormone, in post-AKI setting. We aimed to investigate the role of EPO as a predictor of long-term outcomes in post-severe AKI survivors.

METHODS

We performed a retrospective analysis of post-AKI cohort conducted between August 2018 and December 2021. Adults who survived severe AKI stages 2-3 were enrolled. Serum EPO was obtained at 1 month after hospital discharge. We explored whether EPO level could predict long-term kidney outcomes at 12 months including mortality, kidney replacement therapy, doubling serum creatinine, and major adverse kidney events at 365 days.

RESULTS

One hundred and twelve patients were enrolled. Median EPO level was significantly higher in non-survivors than survivors (28.9 [interquartile range: 16.2-50.7] versus 11.6 mU/mL [7.5-22.3], p = 0.003). The best EPO level cut-off was 16.2 mU/mL (sensitivity 77.8%, specificity 62.1%). Serum EPO predicted 12-month mortality with an area under the curve (AUC) of 0.69. Combining clinical model using age, baseline, and discharge kidney function with serum EPO improved prediction with AUC of 0.74. Multivariable analysis demonstrated that high-level of EPO group had significantly higher mortality compared with low-level EPO group (15.2% vs. 3.0%, p = 0.020). Hematocrit was significantly lower in high-level EPO group compared with low-level EPO group at 12 months (33.4 ± 1.1% vs. 36.0 ± 0.9%, p = 0.038).

CONCLUSIONS

Plasma EPO appears to be a useful marker for predicting long-term outcome in post-severe AKI survivors.

Is the relationship between erythropoiesis and renal function one of the secrets of extreme longevity?

BACKGROUND AND AIMS

Renal function and erythropoiesis could be impaired with advancing age. Neutrophil gelatinase-associated lipocalin (NGAL) as well as erythropoietin (EPO) levels are two useful biomarkers of the renal status. In advanced age, the relationships between NGAL, EPO and hemoglobin (Hb) levels remains unknown. The aim of the present study is to evaluate the relationship between renal function and erythropoiesis in a small cohort of centenarians.

METHODS AND RESULTS

We observed thirty-one healthy centenarians with normal hemoglobin levels, a mild reduction in eGFR and no need of erythropoiesis support. We found a significant inverse association between NGAL and GFR, hemoglobin levels and EPO, confirming the key role of the renal function on erythropoiesis also in extreme longevity. A gender difference emerged, showing female participants with lower eGFR and Hb values more than males.

CONCLUSIONS

Our findings suggested a new link between renal function, erythropoiesis and longevity in centenarians and these could have relevant implications in clinical practice. These findings could explain why very old subjects presenting a slight GFR reduction seemed not to be exposed to a significant risk of mortality.

Interaction Between Intrinsic Renal Cells and Immune Cells in the Progression of Acute Kidney Injury

A growing number of studies have confirmed that immune cells play various key roles in the pathophysiology of acute kidney injury (AKI) development. After the resident immune cells and intrinsic renal cells are damaged by ischemia and hypoxia, drugs and toxins, more immune cells will be recruited to infiltrate through the release of chemokines, while the intrinsic cells promote macrophage polarity conversion, and the immune cells will promote various programmed deaths, phenotypic conversion and cycle arrest of the intrinsic cells, ultimately leading to renal impairment and fibrosis. In the complex and dynamic immune microenvironment of AKI, the bidirectional interaction between immune cells and intrinsic renal cells affects the prognosis of the kidney and the progression of fibrosis, and determines the ultimate fate of the kidney.

Erythropoietin alters the pharmacokinetics of organic anions mainly eliminated by the kidney in rats

Erythropoietin (EPO) is a cytokine originally used for its effects on the hematopoietic system, and is widely prescribed around the world. In the present study, the effects of EPO administration on p-aminohippurate (PAH, a prototype organic anion) pharmacokinetics and on the renal expression of PAH transporters were evaluated. Male Wistar rats were treated with EPO or saline (control group). After 42 h, PAH was administered, and plasma samples were obtained at different time points to determine PAH levels. PAH levels in renal tissue and urine were also assessed. The renal expression of PAH transporters was evaluated by Western blotting. EPO-treated rats showed an increase in PAH systemic clearance, in its elimination rate constant, and in urinary PAH levels, while PAH in renal tissue was decreased. Moreover, EPO administration increased the expression of the transporters of the organic anions evaluated. The EPO-induced increase in PAH clearance is accounted for by the increase in its renal secretion mediated by the organic anion transporters. The goal of this study is to add important information to the wide knowledge gap that exists regarding drug-drug interactions. Owing to the global use of EPO, these results are useful in terms of translation into clinical practice.

Recombinant Erythropoietin Provides Protection against Renal Fibrosis in Adenine-Induced Chronic Kidney Disease

Chronic kidney disease (CKD) causes anemia by renal damage. In CKD, the kidney is submitted to hypoxia, persistent inflammation, leading to fibrosis and permanent loss of renal function. Human recombinant erythropoietin (rEPO) has been widely used to treat CKD-associated anemia and is known to possess organ-protective properties that are independent from its well-established hematopoietic effects. Nonhematopoietic effects of EPO are mediated by an alternative receptor that is proposed to consist of a heterocomplex between the erythropoietin receptor (EPOR) and the beta common receptor (βcR). The present study explored the effects of rEPO to prevent renal fibrosis in adenine-induced chronic kidney disease (Ad-CKD) and their association with the expression of the heterodimer EPOR/βcR. Male Wistar rats were randomized to control group (CTL), adenine-fed rats (Ad-CKD), and Ad-CKD with treatment of rEPO (1050 IU/kg, once weekly for 4 weeks). Ad-CKD rats exhibited anemia, uremia, decreased renal function, increased infiltration of inflammatory cells, tubular atrophy, and fibrosis. rEPO treatment not only corrected anemia but reduced uremia and partially improved renal function as well. In addition, we observed that rEPO diminishes tubular injury, prevents fibrosis deposition, and induces the EPOR/βcR heteroreceptor. The findings may explain the extrahematopoietic effects of rEPO in CKD and provide new strategies for the treatment of renal fibrosis in CKD.

Among Children Born Extremely Preterm a Higher Level of Circulating Neurotrophins Is Associated with Lower Risk of Cognitive Impairment at School Age

OBJECTIVES

To test the hypothesis that higher blood levels of neurotrophic proteins (proteins that support neuronal survival and function) in the first 2 weeks of life are associated with a lower risk of cognitive impairment at 10 years.

STUDY DESIGN

We evaluated 812 10-year-old children with neonatal blood specimens enrolled in the multicenter prospective Extremely Low Gestational Age Newborn Study, assessing 22 blood proteins collected on 3 days over the first 2 weeks of life. Using latent profile analysis, we derived a cognitive function level based on standardized cognitive and executive function tests. We defined high exposure as the top quartile neurotrophic protein blood level on ≥2 days either for ≥4 proteins or for a specific cluster of neurotrophic proteins (defined by latent class analysis). Multinomial logistic regression analyzed associations between high exposures and cognitive impairment.

RESULTS

Controlling for the effects of inflammatory proteins, persistently elevated blood levels of ≥4 neurotrophic proteins were associated with reduced risk of moderate (OR, 0.35; 95% CI, 0.18-0.67) and severe cognitive impairment (OR, 0.22; 95% CI, 0.09-0.53). Children with a cluster of elevated proteins including angiopoietin 1, brain-derived neurotrophic factor, and regulated upon activation, normal T-cell expressed, and secreted had a reduced risk of adverse cognitive outcomes (OR range, 0.31-0.6). The risk for moderate to severe cognitive impairment was least with 0-1 inflammatory and >4 neurotrophic proteins.

CONCLUSIONS

Persisting elevations of circulating neurotrophic proteins during the first 2 weeks of life are associated with lowered risk of impaired cognition at 10 years of age, controlling for increases in inflammatory proteins.

Circulating biomarkers in extremely preterm infants associated with ultrasound indicators of brain damage

AIM

To assess to what extent the blood concentrations of proteins with neurotrophic and angiogenic properties measured during the first postnatal month convey information about the risk of sonographically-identified brain damage among very preterm newborns.

METHODS

Study participants were 1219 children who had a cranial ultrasound scan during their stay in the intensive care nursery and blood specimens collected on 2 separate days at least a week apart during the first postnatal month. Concentrations of selected proteins in blood spots were measured with electrochemiluminescence or with a multiplex immunobead assay and the risks of cranial ultrasound images associated with top-quartile concentrations were assessed.

RESULTS

High concentrations of multiple inflammation-related proteins during the first 2 postnatal weeks were associated with increased risk of ventriculomegaly, while high concentrations of just 3 inflammation-related proteins were associated with increased risk of an echolucent/hypoechoic lesion (IL-6, IL-8, ICAM-1), especially on day 7. Concomitant high concentrations of IL6R and bFGF appeared to modulate the increased risks of ventriculomegaly and an echolucent lesion associated with inflammation. More commonly high concentrations of putative protectors/repair-enhancers did not appear to diminish these increased risks.

CONCLUSION

Our findings provide support for the hypothesis that endogenous proteins are capable of either protecting the brain against damage and/or enhancing repair of damage.

Early low-dose erythropoiesis-stimulating agent therapy and progression of moderate chronic kidney disease: a randomized, placebo-controlled trial

Background

It is unknown whether early intervention with low-dose erythropoiesis-stimulating agents (ESAs) in non-anaemic patients delays progression of chronic kidney disease (CKD).

Methods

In a single-blind, 24-month trial, adults with estimated glomerular filtration rate (eGFR) 30–59 mL/min/1.73 m2 and either Type 2 diabetes mellitus or previous kidney transplantation were randomized to low-dose continuous erythropoiesis receptor activator (CERA; monthly dose 30–75 µg; n = 115) or placebo (n = 120). The primary endpoint was the annual change in eGFR (abbreviated Modification of Diet in Renal Disease formula).

Results

Mean (standard deviation) eGFR was 40.7 (9.8) mL/min/1.73 m2 versus 39.8 (9.2) mL/min/1.73 m2 at baseline for CERA and placebo, respectively, and 39.0 (11.6) g/dL versus 39.7 (10.6) g/dL at the final visit. The median (interquartile range) annual reduction in eGFR was 0.5 (−2.2, 3.8) mL/min/1.73 m2 with CERA versus 0.4 (−2.0, 3.2) mL/min/1.73 m2 with placebo (P = 0.657). No significant difference in the annual change in eGFR was observed between treatment groups in the subpopulations with Type 2 diabetes or kidney transplant. Adverse events with a suspected relation to study drug occurred in 22.0% and 16.2% of patients randomized to CERA or placebo, respectively, and adverse events led to study drug discontinuation in 11.0% and 8.5% of patients.

Conclusions

Patients with moderate CKD and Type 2 diabetes or previous kidney transplantation showed stable renal function that was unaffected by administration of low-dose ESA. In addition, there was no clinically meaningful effect of 2-year low-dose ESA treatment on albuminuria, an important surrogate marker of kidney injury.

Renoprotective effect of erythropoietin in zebrafish after administration of gentamicin: an immunohistochemical study for β-catenin and c-kit expression

BACKGROUND

Gentamicin is an aminoglycoside antibiotic widely used in the treatment of infections caused by Gram-negative bacteria. The main limitation to its therapeutic effectiveness is the potential nephrotoxicity. Erythropoietin has a tissue protective effect widely demonstrated in the kidney. The aim of the present study was to evaluate the renoprotective effects of erythropoietin in a model of zebrafish (Danio rerio) after administration of gentamicin.

METHODS

Sixty adult zebrafish were subdivided into three groups: group A was treated with gentamicin; group B received gentamicin and, 24 h later, epoetin alpha; group C received drug diluent only. In order to analyze the renoprotective activity of erythropoietin, the expression of c-kit and β-catenin was evaluated by immunohistochemistry.

RESULTS

Generally, the zebrafish renal tubule regenerates 15 days after an injury. Conversely, 7 days after gentamicin administration, animals treated with erythropoietin (group B) showed a better renal injury repair as documented by: increased expression of β-catenin, less degenerated tubules, greater number of centers of regeneration, positivity for c-kit only in immature-looking tubules and lymphohematopoietic cells.

CONCLUSION

The expression of c-kit and β-catenin suggests that erythropoietin may exert a role in regeneration reducing the extent of tubular damage from the outset after gentamicin administration.

Bridging Translation by Improving Preclinical Study Design in AKI

Despite extensive research, no therapeutic interventions have been shown to prevent AKI, accelerate recovery of AKI, or reduce progression of AKI to CKD in patients. This failure in translation has led investigators to speculate that the animal models being used do not predict therapeutic responses in humans. Although this issue continues to be debated, an important concern that has not been addressed is whether improvements in preclinical study design can be identified that might also increase the likelihood of translating basic AKI research into clinical practice using the current models. In this review, we have taken an evidence-based approach to identify common weaknesses in study design and reporting in preclinical AKI research that may contribute to the poor translatability of the findings. We focused on use of N-acetylcysteine or sodium bicarbonate for the prevention of contrast-induced AKI and use of erythropoietin for the prevention of AKI, two therapeutic approaches that have been extensively studied in clinical trials. On the basis of our findings, we identified five areas for improvement in preclinical study design and reporting. These suggested and preliminary guidelines may help improve the quality of preclinical research for AKI drug development.

Emerging EPO and EPO receptor regulators and signal transducers

As essential mediators of red cell production, erythropoietin (EPO) and its cell surface receptor (EPO receptor [EPOR]) have been intensely studied. Early investigations defined basic mechanisms for hypoxia-inducible factor induction of EPO expression, and within erythroid progenitors EPOR engagement of canonical Janus kinase 2/signal transducer and activator of transcription 5 (JAK2/STAT5), rat sarcoma/mitogen-activated protein kinase/extracellular signal-regulated kinase (RAS/MEK/ERK), and phosphatidylinositol 3-kinase (PI3K) pathways. Contemporary genetic, bioinformatic, and proteomic approaches continue to uncover new clinically relevant modulators of EPO and EPOR expression, and EPO's biological effects. This Spotlight review highlights such factors and their emerging roles during erythropoiesis and anemia.

Effect of high-dose erythropoietin on graft function after kidney transplantation: a meta-analysis of randomized controlled trials

PURPOSE

Current evidence suggests that preconditioning with erythropoietin (EPO) can protect against ischemia reperfusion injury in rodents. However, randomized controlled trials (RCTs) assessing the efficacy and safety of high-dose EPO in kidney transplantation have yielded inconclusive results. Herein, we performed a meta-analysis of RCTs to assess whether the administration of high-dose EPO can improve graft function and the potential adverse events.

METHODS

Relevant RCT studies that investigated high-dose EPO on graft function after kidney transplantation were comprehensively searched in Pubmed, Embase, and Cochrane Library until July 10, 2014. All statistical analyses were performed using Review Manager 5.0 and STATA 12.0.

RESULTS

A total of 4 RCTs involving 356 patients were identified. Comprehensively, a trend of reduction in the incidence of delayed graft function could be observed in the EPO group (EPO vs. placebo groups: RR=0.88); however, the result did not reach the significance level (95% CI, 0.72-1.08; P=0.21). Furthermore, no significant difference in the incidences of adverse events was observed between the two groups.

CONCLUSIONS

The current meta-analysis indicates that the administration of high-dose EPO is, to some extent, prone to protect kidney function without increasing the susceptibility to adverse events.

Combination of hemoglobin and left ventricular ejection fraction as a new predictor of contrast induced nephropathy in patients with non-ST elevation myocardial infarction

BACKGROUND

Hemoglobin concentration (Hb) and left ventricular ejection fraction (EF) are known predictors of contrast induced nephropathy (CIN). We hypothesized that combination of Hb concentration and left ventricular EF is superior to either variable alone in predicting contrast induced nephropathy in patients with acute coronary syndrome (ACS).

MATERIAL AND METHODS

Consecutive patients with ACS were prospectively enrolled. Patients considered for invasive strategy were included. Baseline creatinine levels were detected on admission and 24, 48 and 72 hours after coronary intervention. 25% or 0,5 umol/L increase in creatinine level was considered as CIN.

RESULTS

268 patients with ACS (mean age 58±11 years, 77% male) were enrolled. Contrast induced nephropathy was observed in 26 (9.7%) of patients. Baseline creatinine concentration, left ventricular EF, and Hemoglobin was significantly different between two groups. Contrast volume to estimated glomerular filtration rate ratio (OR: 1.310, 95% CI: 1.077-1.593, p=0.007) and the combination of Hb and left ventricular EF (OR: 0.996, 95% CI: 0.994-0.998, p=0.001) were found to be independent predictors for CIN. Hb × LVEF ≤690 had 85% sensitivity and 57% specificity to predict CIN (area under curve: 0.724, 95% CI: 0.625-0.824, p<0.001). In addition, Hb × LVEF ≤690 had a negative predictive value of 97% in our analysis

CONCLUSIONS

The combination of Hb and left ventricular EF is better than either variable alone at predicting CIN in patients with ACS that undergone percutaneous coronary intervention. The prediction was independent of baseline renal function and volume of contrast agent.