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

Abstract

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.

Low‐dose erythropoietin improves cardiac function in experimental heart failure without increasing haematocrit

“…Lower doses of EPO have also been shown to confer vascular and tissue protection in the kidney [22]. Low-dose darbepoetin treatment in a rat remnant kidney model improved the survival, ameliorated endothelial damage and preserved renal function, without an increase in haematocrit levels.…”

“…Moreover, chronic EPO administration in a dose that was insufficient to increase haematocrit, was shown to improve survival, ameliorate endothelial damage and preserve renal function in a rat remnant kidney model, suggesting a different dose-response relationship for the erythropoietic and pleiotropic effects [22]. Lowdose EPO might therefore exert similar beneficial effects on the myocardium, without the deleterious effects on haematocrit.…”

Erythropoietin and Oxidative Stress

“…Activation of Akt is usually cytoprotective, such as during free radical exposure , Matsuzaki, et al, 1999, hyperglycemia (Anitha, et al, 2006), endothelial cell hypoxia (Chong, et al, 2002b), β-amyloid toxicity , Chong, et al, 2005d, cardiomyopathy (Kim, et al, 2008), and oxidative stress . EPO uses the PI 3-K/Akt pathway in a variety of experimental models of injury (Bahlmann, et al, 2004, Chong, et al, 2002b, Chong, et al, 2003e, Chong and Maiese, 2007a, Miki, et al, 2006, Parsa, et al, 2003, Sharples, et al, 2004, Um, et al, 2007, Um and Lodish, 2006, Wu, et al, 2007b. These can involve transcription factor regulation (Chong and Maiese, 2007a), maintenance of ΔΨ m , prevention of cytochrome c release , and blockade of caspase activity , Chong, et al, 2002b.…”

Effect of darbepoetin alfa on endothelial progenitor cells and vascular reactivity in chronic kidney disease

“…26 A study of a mixed population of patients with varying degrees of CKD, including patients on hemodialysis and peritoneal dialysis, found a reduction in EPC number and function with worsening kidney disease. 27 The administration of hormones such as rhEPO [9][10][11] and drugs such as HMG-CoA reductase inhibitors 7,28,29 increase the circulating pool of EPCs, supposedly via increased mobilization from bone marrow. As demonstrated in the present study, impairment of EPCs in the setting of decreased glomerular filtration rate does not appear permanent as EPC levels increased in response to short-term (4-week) darbepoetin alfa administration.…”

“…A series of studies indicates that administration of recombinant human erythropoietin (rhEPO) or its analogue darbepoetin alfa enhances EPC differentiation in vitro and in vivo. 9,10 In addition, studies in laboratory animals indicate that rhEPO mobilizes EPCs from the bone marrow. 11 The diabetic state, common in patients with CKD, results in impaired endothelial function and reduced levels of circulating EPCs.…”