Carbamylated erythropoietin protects the kidneys from ischemia-reperfusion injury without stimulating erythropoiesis

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Abstract

Several studies have shown that erythropoietin (EPO) can protect the kidneys from ischemia-reperfusion injury and can raise the hemoglobin (Hb) concentration. Recently, the EPO molecule modified by carbamylation (CEPO) has been identified and was demonstrated to be able to protect several organs without increasing the Hb concentration. We hypothesized that treatment with CEPO would protect the kidneys from tubular apoptosis and inhibit subsequent tubulointerstitial injury without erythropoiesis. The therapeutic effect of CEPO was evaluated using a rat ischemia-reperfusion injury model. Saline-treated kidneys exhibited increased tubular apoptosis with interstitial expression of α-smooth muscle actin (α-SMA), while EPO treatment inhibited tubular apoptosis and α-SMA expression to some extent. On the other hand, CEPO-treated kidneys showed minimal tubular apoptosis with limited expression of α-SMA. Moreover, CEPO significantly promoted tubular epithelial cell proliferation without erythropoiesis. In conclusion, we identified a new therapeutic approach using CEPO to protect kidneys from ischemia-reperfusion injury.

Section snippets

Materials and methods

Experimental design. Forty-two male Sprague--Dawley rats weighing 220–280 g were purchased from Japan SLC Inc. (Shizuoka, Japan) and were maintained under standard conditions until the experiments were done. All studies were performed in accordance with the principles of the Guideline on Animal Experimentation of Osaka University. The rats were randomly allocated into three groups: (1) the saline-treatment group (control group; n = 15); (2) the EPO-treatment group (EPO group; n = 15); and (3) the

Effect on erythropoiesis and renal function

When compared to saline-treated rats, EPO-treatment (100 IU/kg × 3/wk × 2wk) significantly increased Hb concentration (saline, 13.5 ± 0.9 g/dl vs. EPO, 14.9 ± 1.0 g/dl; p < 0.01). On the other hand, CEPO-treatment neither enhanced nor reduced Hb concentration (13.1 ± 0.2 g/dl; p = 0.73), suggesting that CEPO, unlike EPO, does not stimulate erythropoiesis. Saline-treated rats demonstrated the increment of serum creatinine (1.54 ± 0.68 mg/dl) 24 h after I/R injury, and EPO-treatment showed the tendency to suppress the

Discussion

In this paper, we examined whether EPO or CEPO may have therapeutic effects on tubulointerstitial injury in a rat model of I/R injury. Untreated kidneys exhibited increased tubular apoptosis and interstitial α-SMA expression, while EPO-treatment inhibited tubular apoptosis and α-SMA expression to some extent. On the other hand, CEPO-treated kidneys showed minimal tubular apoptosis and limited α-SMA expression. In addition, CEPO administration did not increase the Hb concentration, while

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