EPO and α-MSH prevent ischemia/reperfusion-induced down-regulation of AQPs and sodium transporters in rat kidney

Erythropoietin prevented the decreased expression of aquaporin1-3 in ureteral obstructive kidneys in juvenile rats

BACKGROUND

Urinary tract obstruction is associated with impaired renal urinary concentration; even after the release of the obstruction, patients still suffer from polyuria. It has been reported that the decreased expression of aquaporins (AQPs) is associated with postobstructive polyuria, and erythropoietin (EPO) can promote the recovery of decreased AQP2 expression induced by bilateral ureteral obstruction. However, whether EPO can promote the recovery of the expression of AQP1-3 after the release of unilateral ureteral obstruction (UUO) has not yet been reported.

AIMS

To investigate the effects of EPO treatment on the expression of renal AQP1-3 after the release of UUO.

METHODS

UUO was established in rats by 24-h temporary unilateral obstruction of renal ureters. Three days following EPO treatment, the kidneys were removed to determine the expression levels of AQP1-3, NLRP3, caspase-1, and IL-1β via semiquantitative immunoblotting and immunohistochemistry.

RESULTS

EPO inhibited the expression of NLRP3, caspase-1, and IL-1β; reduced plasma creatinine and urea; and promoted the recovery of AQP1-3 expression in UUO rats.

CONCLUSIONS

EPO treatment prevented the decreased expression of renal AQPs and the development of impaired urinary concentration capacity after the release of UUO, which may partially occur by way of anti-inflammasome effects.

IMPACT

EPO treatment could prevent the decreased expression of renal water transporter proteins AQP1-3 and the development of impaired renal functions, which may be associated with its anti-inflammasome effects. EPO regulated the expression of renal water transporter proteins AQP1-3, which could provide the potential for the treatment of postobstructive polyuresis. EPO treatment could be one of the effective methods by participating in multiple dimensions for patients with obstructive nephropathy.

Anti-inflammatory α-Melanocyte-Stimulating Hormone Protects Retina After Ischemia/Reperfusion Injury in Type I Diabetes

Retinal ischemia/reperfusion (I/R) injury is a major cause of vision loss in many ocular diseases. Retinal I/R injury is common in diabetic retinopathy, which as a result of hyperglycemia damages the retina and can cause blindness if left untreated. Inflammation is a major contributing factor in the pathogenesis of I/R injury. α-Melanocyte-stimulating hormone (α-MSH) is an anti-inflammatory peptide hormone that has displayed protective effects against I/R-induced organ damages. Here, we aimed to investigate the protective role of α-MSH on I/R-induced diabetic retinal damage using hyperglycemic C57BL/6J Ins2Akita/+ mice. Experimental I/R injury was induced by blocking the right middle cerebral artery (MCA) for 2 h followed by 2 h or 22 h of reperfusion using the intraluminal method. Since ophthalmic artery originates proximal to the origin of the MCA, the filament also blocked blood supply to the retina. Upon treatment with α-MSH at 1 h after ischemia and 1 h after reperfusion, animals displayed significant improvement in amplitudes of b-wave and oscillatory potentials during electroretinography. α-MSH also prevented I/R-induced histological alterations and inhibited the development of retinal swelling. Loss of retinal ganglion cells as well as oxidative stress were significantly attenuated in the α-MSH-treated retinae. Level of interleukin 10 was significantly increased after α-MSH treatment. Moreover, gene expression of glutamate aspartate transporter 1, monocarboxylate transporter (MCT) 1 and MCT-2 were significantly higher after α-MSH administration. In conclusion, α-MSH mitigates the severity of I/R-induced retinal damage under hyperglycemic condition. These beneficial effects of α-MSH may have important therapeutic implications against retinal I/R injury under hyperglycemic condition.

Aquaglyceroporin Modulators as Emergent Pharmacological Molecules for Human Diseases

Aquaglyceroporins, a sub-class of aquaporins that facilitate the diffusion of water, glycerol and other small uncharged solutes across cell membranes, have been recognized for their important role in human physiology and their involvement in multiple disorders, mostly related to disturbed energy homeostasis. Aquaglyceroporins dysfunction in a variety of pathological conditions highlighted their targeting as novel therapeutic strategies, boosting the search for potent and selective modulators with pharmacological properties. The identification of selective inhibitors with potential clinical applications has been challenging, relying on accurate assays to measure membrane glycerol permeability and validate effective functional blockers. Additionally, biologicals such as hormones and natural compounds have been revealed as alternative strategies to modulate aquaglyceroporins via their gene and protein expression. This review summarizes the current knowledge of aquaglyceroporins’ involvement in several pathologies and the experimental approaches used to evaluate glycerol permeability and aquaglyceroporin modulation. In addition, we provide an update on aquaglyceroporins modulators reported to impact disease, unveiling aquaglyceroporin pharmacological targeting as a promising approach for innovative therapeutics.

GSK-3β inhibitor TDZD-8 prevents reduction of aquaporin-1 expression via activating autophagy under renal ischemia reperfusion injury

Renal ischemia/reperfusion (I/R) injury is a main cause of acute kidney injury (AKI). Aquaporin (AQP)-1 water channel in the kidney is critical for the maintenance of water homeostasis and the urinary concentrating ability. Increasing evidence supports an important role of autophagy in the pathogenesis of AKI induced by renal I/R. The purpose of the present study is to investigate whether activation of autophagy prevents downregulation of AQP1 protein induced by renal I/R and potential molecular mechanisms. Renal I/R induced consistently reduced protein expression of AQP1, 2, and 3, as well as sodium cotransporters Na⁺ -K⁺ -2Cl^- cotransporter and α-Na,K-ATPase, which was associated with increased urine output and decreased creatinine clearance in rats. Renal I/R also suppressed autophagy and increased inflammatory responses in the kidney. 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), the glycogen synthase kinase-3β inhibitor, ameliorated renal injury under I/R, activated autophagy and markedly increased expression of AQPs and sodium transporters in the kidney, which was associated with improved urine output and creatinine clearance in rats. Hypoxia/reoxygenation (H/R) induced suppression of autophagy and downregulation of AQP1 in murine inner medullary collecting duct 3 (IMCD3) cells, which was fully prevented by TDZD-8 treatment. Inhibition of autophagy by 3-methyladenine or Atg5 gene knockdown attenuated recovery of AQP1 protein expression induced by TDZD-8 in IMCD3 cells with H/R. Interleukin-1 beta (IL-1β) decreased the abundance of AQP1 protein in IMCD3 cells. H/R induced increases in protein expression of nod-like receptor pyrin domain-containing 3 and IL-1β, which was reversed by TDZD-8. In conclusion, TDZD-8 treatment prevented downregulation of AQP1 expression under renal I/R injury, likely via activating autophagy and decreasing IL-1β production.

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.

Effect of erythropoietin on mercury-induced nephrotoxicity: Role of membrane transporters

Mercury is a widespread pollutant. Mercuric ions uptake into tubular cells is supported by the Organic anion transporter 1 (Oat1) and 3 (Oat3) and its elimination into urine is through the Multidrug resistance-associated protein 2 (Mrp2). We investigated the effect of recombinant human erythropoietin (Epo) on renal function and on renal expression of Oat1, Oat3, and Mrp2 in a model of mercuric chloride (HgCl2)-induced renal damage. Four experimental groups of adult male Wistar rats were used: Control, Epo, HgCl2, and Epo + HgCl2. Epo (3000 IU/kg, b.w., i.p.) was administered 24 h before HgCl2 (4 mg/kg, b.w., i.p.). Experiments were performed 18 h after the HgCl2 dose. Parameters of renal function and structure were evaluated. The protein expression of Oat1, Oat3 and Mrp2 in renal tissue was assessed by immunoblotting techniques. Mercury levels were determined by cold vapor atomic absorption spectrometry. Pretreatment with Epo ameliorated the HgCl2-induced tubular injury as assessed by histopathology and urinary biomarkers. Immunoblotting showed that pretreatment with Epo regulated the renal expression of mercury transporters in a way to decrease mercury content in the kidney. Epo pretreatment ameliorates HgCl2-induced renal tubular injury by modulation of mercury transporters expression in the kidneys.

A nonbiodegradable scaffold-free cell sheet of genome-engineered mesenchymal stem cells inhibits development of acute kidney injury

Cell therapy using genome-engineered stem cells has emerged as a novel strategy for the treatment of kidney diseases. By exploiting genome editing technology, human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) secreting an angiogenic factors or an anti-inflammatory factor were generated for therapeutic application in acute kidney injury. Junction polymerase chain reaction analysis verified zinc finger nucleases-assisted integration of the desired gene into the hUC-MSCs. Flow cytometry and differentiation assays indicated that genome editing did not affect the differentiation potential of these mesenchymal stem cells. Protein measurement in conditioned media with the use of ELISA and immunoblotting revealed the production and secretion of each integrated gene product. For cell therapy in the bilateral ischemia-reperfusion mouse model of acute kidney injury, our innovative scaffold-free cell sheets were established using a non-biodegradable temperature-responsive polymer. One of each type of scaffold-free cell sheets of either the angiogenic factor vascular endothelial grown factor or angiopoietin-1, or the anti-inflammatory factor erythropoietin, or α-melanocyte-stimulating hormone-secreting hUC-MSCs was applied to the decapsulated kidney surface. This resulted in significant amelioration of kidney dysfunction in the mice with acute kidney injury, effects that were superior to intravenous administration of the same genome-engineered hUC-MSCs. Thus, our scaffold-free cell sheets of genome-engineered mesenchymal stem cells provides therapeutic effects by inhibiting acute kidney injury via angiogenesis or anti-inflammation.

Investigation of Neuroprotective Effects of Erythropoietin on Chronic Neuropathic Pain in a Chronic Constriction Injury Rat Model

Introduction

Neuropathic pain is pretty common in modern society, and the treatment effect is far from satisfactory. This study aimed to find evidence of the neuroprotective effect of erythropoietin (EPO) in the treatment of neuropathic pain in a rat model of chronic constriction injury (CCI).

Methods

A total of 30 rats were randomly divided into sham operation group, CCI group, or CCI+EPO group. The mechanical and thermal nociception thresholds are evaluated as behavioral assessments. The dorsal root ganglion cells were morphologically evaluated by hematoxylin and eosin staining, and AMPK, p-AMPK, mTOR, p70S6K, and AQP-2 proteins were compared and analyzed by Western blotting. Compared with the sham operation group, rats in the CCI group had shorter paw withdrawal threshold and paw withdrawal latency, abnormal morphology, and increased satellite glial cells.

Results

After treatment with EPO, these changes were significantly reversed. In vivo administration of erythropoietin seems to be able to regulate the expression of AQP-2 through the AMPK/mTOR/p70S6K pathway. Our study provides behavioral, morphological, and immunoblot evidence to prove the neuroprotective effect of EPO in the treatment of chronic neuropathic pain in the CCI rat model.

Conclusion

Our results indicate that EPO has the potential to treat neuropathic pain caused by peripheral nerve injury, although further verification is needed.

Effects of early high-dose erythropoietin on acute kidney injury following cardiac arrest: exploratory post hoc analyses from an open-label randomized trial

BACKGROUND

Acute kidney injury (AKI) is frequent in patients resuscitated from cardiac arrest (CA) and may worsen outcome. Experimental data suggest a renoprotective effect by treating these patients with a high dose of erythropoietin (Epo) analogues. We aimed to evaluate the efficacy of epoetin alpha treatment on renal outcome after CA.

METHODS

We did a post hoc analysis of the Epo-ACR-02 trial, which randomized patients with a persistent coma after a witnessed out-of-hospital CA. Only patients admitted in one intensive care unit were analysed. In the intervention group, patients received five intravenous injections of Epo spaced 12 h apart during the first 48 h, started as soon as possible after resuscitation. In the control group, patients received standard care without Epo. The main endpoint was the proportion of patients with persistent AKI defined by Kidney Disease: Improving Global Outcomes criteria at Day 2. Secondary endpoints included the occurrence of AKI through Day 7, estimated glomerular filtration rate (eGFR) at Day 28, haematological indices and adverse events.

RESULTS

A total of 162 patients were included in the primary analysis (74 in the Epo group, 88 in the control group). Baseline characteristics were similar in the two groups. At Day 2, 52.8% of the patients (38/72) in the intervention group had an AKI, as compared with 54.4% of the patients (46/83) in the control group (P = 0.74). There was no significant difference between the two groups regarding the proportion of patients with AKI through Day 7. Among patients with persistent AKI at Day 2, 33% (4/12) in the intervention group had an eGFR <75 mL/min/1.73 m2 compared with 25% (3/12) in the control group at Day 28 (P = 0.99). We found no significant differences in haematological indices or adverse events.

CONCLUSION

After CA, early administration of Epo did not confer any renal protective effect as compared with standard therapy.

Urinary extracellular vesicular release of aquaporins in patients with renal transplantation

Background

Diuresis has been observed within a week following renal transplantation, suggesting that the procedure causes acute disturbance of renal water homeostasis. Aquaporin (AQP) 1 and AQP2, important proteins for renal water reabsorption, have been identified in urinary extracellular vesicles (uEV-AQP1 and -AQP2), and experimental studies have shown that the presence of uEV-AQP1 and -AQP2 may be an indicator of their levels of expression in the kidney. However, the release patterns of uEV-AQP1 and -AQP2 during the acute phase following renal transplantation are largely unknown.

Methods

In this study, we examined the release of uEV-AQP1 and -AQP2 in recipients until 6 days (day 6) after renal transplantation. At Miyazaki prefectural Miyazaki Hospital, Japan, uEVs were obtained from 7 recipients, all of whom had received renal allografts from living donors. uEVs were isolated by differential centrifugation.

Results

Immunoblotting analysis showed that the release of uEV-AQP2 was significantly decreased on day 1 in comparison with a control sample (from 3 healthy volunteers), accompanied by high urine output and low urine osmolality. Thereafter, the level increased gradually to the control level by day 6. The release pattern of uEV-AQP1 was similar to that of uEV-AQP2, but the levels did not reach statistical significance in comparison with the control level at any of the time points examined. Evaluation of the relationship between urinary osmolality and uEV-AQPs revealed a significant correlation for uEV-AQP2, but not for uEV-AQP1.

Conclusion

These results indicate that acute diuresis after renal transplantation might be due to a decrease in the renal expression of AQP2, whose level can be estimated from the amount released in uEVs.

Renal ischemia-reperfusion injury impairs renal calcium, magnesium, and phosphate handling in mice

Fibroblast growth factor 23 (FGF23) levels are elevated in patients with acute kidney injury (AKI). The consequences on renal Ca²⁺, Mg²⁺, and P_i regulatory mechanisms are unknown. We hypothesized that renal ischemia-reperfusion (I/R) injury alters the expression of important renal Ca²⁺, Mg²⁺, and P_i transport proteins. I/R injury was induced in male C57BL/6 mice by clamping both renal arteries for 27 min. Mice were investigated 18 h later. The mRNA and protein levels of renal Ca²⁺, Mg²⁺, and P_i transport proteins were measured by RT-qPCR and western blot analysis. I/R injury-induced hyperphosphatemia and hypermagnesemia were paralleled by a decrease in glomerular filtration rate and an increase in the fractional excretion of Ca²⁺, Mg²⁺, and P_i. I/R injury affected the fibroblast growth factor 23 (FGF23)-klotho-vitamin D axis by increasing plasma levels of FGF23 and downregulation of renal klotho expression. Plasma levels of PTH and 1,25-dihydroxyvitamin D₃ were unchanged. Further, downregulation of key genes for paracellular reabsorption of Ca²⁺ and Mg²⁺ (claudin (Cldn)2, Cldn10b, Cldn16, Cldn19) and for active transcellular transport of Ca²⁺, Mg²⁺, and P_i (calbindin-D_28K, Ncx1, Pmca4, Cnnm2, Trpm7, NaP_i-2a, and NaP_i-2c) was observed. However, renal expression of Trpv5 and Trpv6 was increased. In vitro studies support a direct effect of proinflammatory cytokines on the mRNA expression of Cldn16, Cldn19, and Trpv6. Our findings indicate that renal I/R injury increases FGF23 blood levels independent of PTH and 1,25-dihydroxyvitamin D₃. This increase is associated with hypermagnesemia, hyperphosphatemia, and increased or decreased expression of specific renal Ca²⁺, Mg²⁺, and P_i transporters, respectively.

The renal protect function of erythropoietin after release of bilateral ureteral obstruction in a rat model

Congenital urinary tract obstruction is one of the most frequent malformations in fetuses or neonates, which usually causes profound impairment of renal function including reductions in both glomerular filtration rate (GFR) and tubular handling of water and solutes. Although obstruction can be released by surgical operation, the child will suffer from diuresis for sometime. It has been reported that erythropoietin (EPO) could prevent the down-regulation of aquaporin-2 (AQP2) and urinary-concentrating defects induced by renal ischemia/reperfusion (I/R) injury. However, whether EPO could promote the recovery of renal function and AQP2 expression after releasing of ureteral obstruction has not been reported yet. The purposes of the present study were to investigate the effects of EPO on renal function and AQP2 expression after release of bilateral ureteral obstruction (BUO-R) in rats. The results showed that EPO could promote interleukin (IL) 10 (IL-10) expression; inhibit tumor necrosis factor-α (TNF-α), IL-6, and inducible nitric oxide synthase (iNOS) expressions; reduce the fractional excretion of sodium (FENa) and plasma creatinine (CREA) and urea; and promote the recovery of water and salt handling and AQP2 expression in BUO-R rats, especially in the high dose of EPO-treated group rats. In conclusion, EPO could promote the recovery of renal function and AQP2 expression in BUO-R rats, which may partially associate with its anti-inflammation effect.

Effects of erythropoietin receptor activity on angiogenesis, tubular injury, and fibrosis in acute kidney injury: a "U-shaped" relationship

The erythropoietin receptor (EpoR) is widely expressed but its renoprotective action is unexplored. To examine the role of EpoR in vivo in the kidney, we induced acute kidney injury (AKI) by ischemia-reperfusion in mice with different EpoR bioactivities in the kidney. EpoR bioactivity was reduced by knockin of wild-type human EpoR, which is hypofunctional relative to murine EpoR, and a renal tubule-specific EpoR knockout. These mice had lower EPO/EpoR activity and lower autophagy flux in renal tubules. Upon AKI induction, they exhibited worse renal function and structural damage, more apoptosis at the acute stage (<7 days), and slower recovery with more tubulointerstitial fibrosis at the subacute stage (14 days). In contrast, mice with hyperactive EpoR signaling from knockin of a constitutively active human EpoR had higher autophagic flux, milder kidney damage, and better renal function at the acute stage but, surprisingly, worse tubulointerstitial fibrosis and renal function at the subacute stage. Either excess or deficient EpoR activity in the kidney was associated with abnormal peritubular capillaries and tubular hypoxia, creating a "U-shaped" relationship. The direct effects of EpoR on tubular cells were confirmed in vitro by a hydrogen peroxide model using primary cultured proximal tubule cells with different EpoR activities. In summary, normal erythropoietin (EPO)/EpoR signaling in renal tubules provides defense against renal tubular injury maintains the autophagy-apoptosis balance and peritubular capillary integrity. High and low EPO/EpoR bioactivities both lead to vascular defect, and high EpoR activity overides the tubular protective effects in AKI recovery.

Long Term Osmotic Mini Pump Treatment with Alpha-MSH Improves Myocardial Function in Zucker Diabetic Fatty Rats

The present investigation evaluates the cardiovascular effects of the anorexigenic mediator alpha-melanocyte stimulating hormone (MSH), in a rat model of type 2 diabetes. Osmotic mini pumps delivering MSH or vehicle, for 6 weeks, were surgically implanted in Zucker Diabetic Fatty (ZDF) rats. Serum parameters, blood pressure, and weight gain were monitored along with oral glucose tolerance (OGTT). Echocardiography was conducted and, following sacrifice, the effects of treatment on ischemia/reperfusion cardiac injury were assessed using the isolated working heart method. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was measured to evaluate levels of oxidative stress, and force measurements were performed on isolated cardiomyocytes to determine calcium sensitivity, active tension and myofilament co-operation. Vascular status was also evaluated on isolated arterioles using a contractile force measurement setup. The echocardiographic parameters ejection fraction (EF), fractional shortening (FS), isovolumetric relaxation time (IVRT), mitral annular plane systolic excursion (MAPSE), and Tei-index were significantly better in the MSH-treated group compared to ZDF controls. Isolated working heart aortic and coronary flow was increased in treated rats, and higher Hill coefficient indicated better myofilament co-operation in the MSH-treated group. We conclude that MSH improves global heart functions in ZDF rats, but these effects are not related to the vascular status.

Topical Erythropoietin Treatment Accelerates the Healing of Cutaneous Burn Wounds in Diabetic Pigs Through an Aquaporin-3-Dependent Mechanism

We have previously reported that the topical application of erythropoietin (EPO) to cutaneous wounds in rats and mice with experimentally induced diabetes accelerates their healing by stimulating angiogenesis, reepithelialization, and collagen deposition, and by suppressing the inflammatory response and apoptosis. Aquaporins (AQPs) are integral membrane proteins whose function is to regulate intracellular fluid hemostasis by enabling the transport of water and glycerol. AQP3 is the AQP that is expressed in the skin where it facilitates cell migration and proliferation and re-epithelialization during wound healing. In this report, we provide the results of an investigation that examined the contribution of AQP3 to the mechanism of EPO action on the healing of burn wounds in the skin of pigs with experimentally induced type 1 diabetes. We found that topical EPO treatment of the burns accelerated their healing through an AQP3-dependent mechanism that activates angiogenesis, triggers collagen and hyaluronic acid synthesis and the formation of the extracellular matrix (ECM), and stimulates reepithelialization by keratinocytes. We also found that incorporating fibronectin, a crucial constituent of the ECM, into the topical EPO-containing gel, can potentiate the accelerating action of EPO on the healing of the burn injury.

Aquaporin-3 deletion in mice results in renal collecting duct abnormalities and worsens ischemia-reperfusion injury

Aquaporin-3 (AQP3), a transporter of water, glycerol and H₂O₂, is expressed in basolateral membranes of principal cells in kidney collecting duct. Here, we report that AQP3 deletion in mice affects renal function and modulates renal injury. We found collecting duct hyperplasia and cell swelling in kidneys of adult AQP3 null mice. After mild renal ischemia-reperfusion (IR), AQP3 null mice had significantly greater blood urea nitrogen (57mg/dl) and creatinine (136μM) than wild-type mice (35mg/dl and 48μM, respectively), and showed renal morphological changes, including tubular dilatation, erythrocyte diapedesis and collecting duct incompletion. MPO, MDA and SOD following IR in AQP3 null mice were significantly different from that in wild-type mice (1.7U/g vs 0.8U/g, 3.9μM/g vs 2.4μM/g, 6.4U/mg vs 11U/mg, respectively). Following IR, AQP3 deletion inhibited activation of mitogen-activated protein kinase (MAPK) signaling and produced an increase in the ratios of Bax/Bcl-2, cleaved caspase-3/caspase-3 and p-p53/p53. Studies in transfected MDCK cells showed that AQP3 expression attenuated reduced cell viability following hypoxia-reoxygenation, with reduced apoptosis and increased MAPK signaling. Our results support a novel role for AQP3 in modulating renal injury and suggest the mechanisms involved in protection against hypoxic injury.

Prevention of contrast-induced nephropathy with single bolus erythropoietin in patients with diabetic kidney disease: A randomized controlled trial

AIM

Contrast-induced-nephropathy (CIN) is associated with poor outcomes, thus prevention of CIN may be of clinical value. Erythropoietin (EPO) has been shown to elicit tissue-protective effects in experimental models and in clinical studies of acute kidney injury. We therefore evaluated its effectiveness for prevention of CIN after coronary angiography (CA) ± percutaneous coronary intervention (PCI) in diabetic patients with chronic kidney disease.

METHODS

A prospective, randomized, controlled trial was carried out in 138 diabetic patients with eGFR <60 mL/min who underwent non-urgent CA ± PCI. Patients received normal saline and n-acetyl cysteine before CA, with or without 50,000 U of EPO administered 30 min prior to CA. CIN was defined as an increase in serum creatinine of at least 0.5 mg/dL during the first 2 days after exposure to contrast media. Primary outcome was the incidence of CIN. Secondary outcomes were the sensitivity and positive predictive value (PPV) of Cystatin C (CC) and Neutrophil-gelatinase-associated-lipocalin (NGAL) for diagnosis of CIN.

RESULTS

The observed incidence of CIN was 8.7%, significantly lower than the expected for such high-risk population. The administration of EPO prior to CA did not reduce the incidence of CIN (9.7% vs. 7.6%, P = 0.65). CC and NGAL demonstrated a low sensitivity (16.6%) and low PPV (6.7 and 33.3%, respectively) for detecting CIN.

CONCLUSION

The administration of EPO prior to CA did not reduce the incidence of CIN. Additional prospective research with a larger sample size and in other patient categories is essential to further define the potential protective effect of EPO on prevention of CIN.

Vasopressin analog terlipressin attenuates kidney injury in hemorrhagic shock

Background

In hemorrhagic shock (HS), volume replacement with crystalloid solution can restore the hemodynamic status and decrease mortality. However, it can also lead to tissue edema and pulmonary congestion, as well as increasing vascular permeability. Here, we analyzed the effects that resuscitation with lactated Ringer's solution (LRS) or administration of the vasopressin analog terlipressin has on renal function in a porcine model of HS.

Methods

Using pressure-controlled bleeding, we induced pigs to HS, maintaining mean arterial pressure (MAP) at 40 mm Hg for 30 min. Animals were divided into 4 groups: sham (anesthesia only); shock-only (HS induction); shock+LRS (HS induction and subsequent resuscitation with LRS at 3 times the volume of blood removed); and shock+Terli (HS induction and subsequent bolus administration of 2 mg of terlipressin). Parameters were evaluated at baseline, then at 30, 60, and 120 min after treatment (T30, T60, and T120, respectively). Animals were euthanized at T60 or T120.

Results

Both treatments restored MAP to baseline values. At T30 and T60, creatinine clearance was highest in shock+LRS pigs, whereas it was highest in shock+Terli pigs at T120. Both treatments initially induced hyponatremia, although urinary excretion of all ions was higher in shock+LRS pigs at T30. Both treatments restored Na-K-2Cl cotransporter expression, whereas only terlipressin restored aquaporin 2 expression. Both treatments also prevented HS-induced acute tubular necrosis. Expression of the vasopressin receptors V1a and V2 was highest in shock-only pigs. At T120, V1a expression was lowest in shock+LRS pigs.

Discussion

Terlipressin might be useful for preventing HS-induced acute kidney injury.

Remote ischemic perconditioning attenuates ischemia/reperfusion-induced downregulation of AQP2 in rat kidney

Renal ischemia/reperfusion (I/R) can lead to impaired urine concentration ability and increased fractional excretion of sodium (FeNa). Local ischemic preconditioning improves renal water and sodium handling after I/R injury. Here, we investigate whether remote ischemic perconditioning (rIPeC) prevents dysregulation of renal water and salt handling in response to I/R injury and mechanisms that may be involved. Rats were subjected to right nephrectomy and randomized into a sham group or an I/R group. In the I/R group, rats were subjected to 37 min of renal ischemia and 3 days of reperfusion. rIPeC was applied to the abdominal aorta. Blood and urine were collected on day 3 postoperatively for clearance studies. The expression of aquaporins (AQPs) and the sodium transporter Na-K-ATPase were analyzed using immunoblotting and immunohistochemistry. I/R injury resulted in polyuria, increased FeNa, and decreased urine osmolality compared to sham rats. rIPeC attenuated the increase in FeNa and the decrease in urine osmolality. Expression of AQP1, AQP2, phosphorylated AQP2 (pAQP2), and Na-K-ATPase was downregulated in I/R rats. rIPeC attenuated the reductions in AQP2 and pAQP2 expression. Immunohistochemistry revealed decreased labeling of Na-K-ATPase in the outer medulla in I/R kidneys compared to kidneys from sham and I/R + rIPeC rats. After renal ischemia, the expression of Na-K-ATPase was substantially reduced in the outer medullary thick ascending limb. In conclusion, our data suggest that rIPeC might prevent dysregulation of renal water and salt handling via regulation of AQP2 expression and phosphorylation as well as via regulation of Na-K-ATPase expression in I/R rat kidneys.

Restoration of Haemoglobin Level Using Hydrodynamic Gene Therapy with Erythropoietin Does Not Alleviate the Disease Progression in an Anaemic Mouse Model for TGFβ1-Induced Chronic Kidney Disease

Erythropoietin, Epo, is a 30.4 kDa glycoprotein hormone produced primarily by the fetal liver and the adult kidney. Epo exerts its haematopoietic effects by stimulating the proliferation and differentiation of erythrocytes with subsequent improved tissue oxygenation. Epo receptors are furthermore expressed in non-haematopoietic tissue and today, Epo is recognised as a cytokine with many pleiotropic effects. We hypothesize that hydrodynamic gene therapy with Epo can restore haemoglobin levels in anaemic transgenic mice and that this will attenuate the extracellular matrix accumulation in the kidneys. The experiment is conducted by hydrodynamic gene transfer of a plasmid encoding murine Epo in a transgenic mouse model that overexpresses TGF-β1 locally in the kidneys. This model develops anaemia due to chronic kidney disease characterised by thickening of the glomerular basement membrane, deposition of mesangial matrix and mild interstitial fibrosis. A group of age matched wildtype littermates are treated accordingly. After a single hydrodynamic administration of plasmid DNA containing murine EPO gene, sustained high haemoglobin levels are observed in both transgenic and wildtype mice from 7.5 ± 0.6 mmol/L to 9.4 ± 1.2 mmol/L and 10.7 ± 0.3 mmol/L to 15.5 ± 0.5 mmol/L, respectively. We did not observe any effects in the thickness of glomerular or tubular basement membrane, on the expression of different collagen types in the kidneys or in kidney function after prolonged treatment with Epo. Thus, Epo treatment in this model of chronic kidney disease normalises haemoglobin levels but has no effect on kidney fibrosis or function.

Sex-dependent expression of water channel AQP1 along the rat nephron

In the mammalian kidney, nonglycosylated and glycosylated forms of aquaporin protein 1 (AQP1) coexist in the luminal and basolateral plasma membranes of proximal tubule and descending thin limb. Factors that influence AQP1 expression in (patho)physiological conditions are poorly known. Thus far, only angiotensin II and hypertonicity were found to upregulate AQP1 expression in rat proximal tubule in vivo and in vitro (Bouley R, Palomino Z, Tang SS, Nunes P, Kobori H, Lu HA, Shum WW, Sabolic I, Brown D, Ingelfinger JR, Jung FF. Am J Physiol Renal Physiol 297: F1575-F1586, 2009), a phenomenon that may be relevant for higher blood pressure observed in men and male experimental animals. Here we investigated the sex-dependent AQP1 protein and mRNA expression in the rat kidney by immunochemical methods and qRT-PCR in tissue samples from prepubertal and intact gonadectomized animals and sex hormone-treated gonadectomized adult male and female animals. In adult rats, the overall renal AQP1 protein and mRNA expression was ∼80% and ∼40% higher, respectively, in males than in females, downregulated by gonadectomy in both sexes and upregulated strongly by testosterone and moderately by progesterone treatment; estradiol treatment had no effect. In prepubertal rats, the AQP1 protein expression was low compared with adults and slightly higher in females, whereas the AQP1 mRNA expression was low and similar in both sexes. The observed differences in AQP1 protein expression in various experiments mainly reflect changes in the glycosylated form. The male-dominant expression of renal AQP1 in rats, which develops after puberty largely in the glycosylated form of the protein, may contribute to enhanced fluid reabsorption following the androgen- or progesterone-stimulated activities of sodium-reabsorptive mechanisms in proximal tubules.

Recombinant human erythropoietin pretreatment attenuates acute renal tubular injury against ischemia-reperfusion by restoring transient receptor potential channel-6 expression and function in collecting ducts

OBJECTIVE

Acute renal tubular injury is a serious complication in the postoperative period, which is associated with high mortality and increased ICU stay. We aimed to demonstrate the protective effect of rhEPO against acute tubular injury induced by ischemia-reperfusion and to explore the mechanism of canonical transient receptor potential channel-6.

DESIGN

Randomized laboratory animal study.

SETTINGS

Animal research laboratory.

INTERVENTIONS

Male Sprague-Dawley rats were randomly divided into three groups: the sham group, the control group, and the rhEPO group. Experimental acute tubular injury was established in rats by bilateral renal arterial occlusion for 30 minutes followed by reperfusion.

MEASUREMENTS AND MAIN RESULTS

Blood samples were obtained for cystatin-C and neutrophil gelatinase-associated lipocalin measurements by enzyme-linked immunosorbance assays. Seventy-two hours after reperfusion, urine samples were collected for osmolality and fractional excretion of sodium (%) assays on a chemistry analyzer. Kidneys were harvested at 24, 48, and 72 hours after reperfusion. Transient receptor potential channel-6, aquaporin-2, and Na,K-ATPase expression in collecting ducts were studied by immunofluorescence and Western blot. Coimmunoprecipitations were also performed to identify the possible signalplex relation between transient receptor potential channel-6 and aquaporin-2 or Na,K-ATPase channels. RhEPO pretreatment significantly inhibited serum cystatin-C (2 hr: 453 ± 64 μg/L vs 337 ± 28 μg/L, p < 0.01), serum neutrophil gelatinase-associated lipocalin (72 hr: 1,175 ± 107 ng/L vs 1,737 ± 402 ng/L, p < 0.05), and urinary fractional excretion of sodium (%) increase (0.9 ± 0.1 vs 2.2 ± 0.8, p < 0.05) and alleviated the decrease of urinary osmolality (1,293 ± 101 mosmol/kg H2O vs 767 ± 91 mosmol/kg H2O, p < 0.05) induced by ischemia-reperfusion injury. Meanwhile, recombinant human erythropoietin greatly improved the ischemia-reperfusion-induced attenuation of transient receptor potential channel-6 expression (48 hr: 42% ± 2% vs 67% ± 2% and 72 hr: 55% ± 2% vs 66% ± 2%), as well as aquaporin-2 and Na,K-ATPase expression in collecting ducts. Transient receptor potential channel-6 functionally interacted with Na,K-ATPase but not aquaporin-2.

CONCLUSIONS

Recombinant human erythropoietin pretreatment at the dose of 5,000 IU/kg potently prevented ischemia-reperfusion-induced acute tubular injury, which might be partly attributed to the restoring the effect of transient receptor potential channel-6 expression and collecting duct function.

Development of intestinal ischemia/reperfusion-induced acute kidney injury in rats with or without chronic kidney disease: Cytokine/chemokine response and effect of α-melanocyte-stimulating hormone

Background

The primary aim of the study was to investigate the cytokine/chemokine response in the kidney, lung, and liver following acute kidney injury (AKI). The secondary aim was to test whether α-melanocyte-stimulating hormone (α-MSH) could prevent a reduction in organ function, and attenuate the inflammatory cytokine/chemokine response within the kidney, lung, and liver following AKI in rats with or without preexisting chronic kidney disease (CKD).

Methods

A two-stage animal model, in which AKI was induced in rats with preexisting CKD, induced by 5/6 nephrectomy (Nx), was used. Six weeks later, AKI was induced by intestinal ischemia and reperfusion (IIR). Sham procedures [S(Nx) and S(IIR)] were also performed.

Results

Increasing levels of serum creatinine (sCr) demonstrated progressive development of CKD in response to Nx, and following IIR sCr levels increased further significantly, except in the S(Nx) group treated with α-MSH. However, no significant differences in the fractional increase in sCr were observed between any of the groups exposed to IIR. In kidney, lung, and liver tissue the levels of interleukin (IL)-1β were significantly higher in rats undergoing IIR when compared to the S(IIR) and control rats. The same pattern was observed for the chemokine monocyte chemoattractant protein (MCP)-1 in lung and liver tissue. Furthermore, kidney IL-1β and RANTES levels were significantly increased after IIR in the Nx rats compared to the S(Nx) rats.

Conclusion

Both the functional parameters and the cytokine/chemokine response are as dramatic when AKI is superimposed onto CKD as onto non-CKD. No convincing protective effect of α-MSH was detected.

α-Melanocyte stimulating hormone treatment in pigs does not improve early graft function in kidney transplants from brain dead donors

Delayed graft function and primary non-function are serious complications following transplantation of kidneys derived from deceased brain dead (DBD) donors. α-melanocyte stimulating hormone (α-MSH) is a pleiotropic neuropeptide and its renoprotective effects have been demonstrated in models of acute kidney injury. We hypothesized that α-MSH treatment of the recipient improves early graft function and reduces inflammation following DBD kidney transplantation. Eight Danish landrace pigs served as DBD donors. After four hours of brain death both kidneys were removed and stored for 18 hours at 4°C in Custodiol preservation solution. Sixteen recipients were randomized in a paired design into two treatment groups, transplanted simultaneously. α-MSH or a vehicle was administered at start of surgery, during reperfusion and two hours post-reperfusion. The recipients were observed for ten hours following reperfusion. Blood, urine and kidney tissue samples were collected during and at the end of follow-up. α-MSH treatment reduced urine flow and impaired recovery of glomerular filtration rate (GFR) compared to controls. After each dose of α-MSH, a trend towards reduced mean arterial blood pressure and increased heart rate was observed. α-MSH did not affect expression of inflammatory markers. Surprisingly, α-MSH impaired recovery of renal function in the first ten hours following DBD kidney transplantation possibly due to hemodynamic changes. Thus, in a porcine experimental model α-MSH did not reduce renal inflammation and did not improve short-term graft function following DBD kidney transplantation.

Glutaraldehyde erythropoietin protects kidney in ischaemia/reperfusion injury without increasing red blood cell production

BACKGROUND AND PURPOSE

Recombinant human erythropoietin (rHuEPO) is currently the mainstay of renal anaemia treatment. Recently, rHuEPO has been shown to provide pleiotrophic tissue protection in various pathological conditions. However, the benefits of rHuEPO beyond anaemia treatment are limited because it increases red blood cell mass. Carbamylated erythropoietin (CEPO) is the first rHuEPO derivative that lacks erythropoietic activity but retains tissue protection properties. Since carbamylation targets lysine residues on rHuEPo, we hypothesized that targeted lysine modifications of rHuEPO may result in a novel non-erythropoietic erythropoietin.

EXPERIMENTAL APPROACH

rHuEPO was subjected to various targeted lysine modifications. In vitro cytoprotection and apoptosis were evaluated using P19 and HEK293 cells. In vivo erythropoiesis was performed by administering the derivatives to animals for 2 weeks. Renoprotection was tested on an ischaemia/reperfusion (I/R) model.

KEY RESULTS

We synthesized a novel derivative, a glutaraldehyde erythropoietin (GEPO). This construct abolished in vivo erythropoiesis. Biochemical characterization showed that GEPO was more electrostatically negative than rHuEPO. Immunoprecipitation experiments revealed that GEPO bound to the IL3RB/EPOR heterotrimeric receptor and ameliorated cellular apoptosis via the activation of Bcl-2. Notably, Bcl-2 activation was suppressed by the JAK2 inhibitor, tyrphostin AG490. In vivo experiments showed that GEPO also ameliorated kidney damage due to I/R injury both functionally and histologically.

CONCLUSIONS AND IMPLICATIONS

Herein, we describe a novel lysine-modified rHuEPO, glutaradehyde-EPO (GEPO), obtained from a simple reaction. This derivative has no erythropoietic properties but retains cell-protective characteristics both in vitro and in vivo, with promise for future use as an adjunctive treatment of kidney disease.

Protective effects of erythropoietin on endotoxin-related organ injury in rats

The protective effect of erythropoietin (EPO) on tissues following ischemia and reperfusion injuries remains poorly understood. We aimed to investigate the effect of EPO in preventing endotoxin-induced organ damage. Rat model of multiple organ failure (MOF) was established by tail vein injection of 10 mg/kg lipopolysaccharide (LPS). Recombinant human EPO treatment (5000 U/kg) was administered by tail vein injection at 30 min after LPS challenge. Twenty-four h after EPO treatment, changes in serum enzyme levels, including aspartate aminotransferase (AST), alanine transaminase (ALT), blood urea nitrogen (BUN) and creatinine (Cr), were evaluated by biochemical analysis. Serum levels of tumor necrosis factor-α (TNF-α) were determined by using immunoradiometric assay. Histological examination of tissue sections was carried out by hematoxylin and eosin staining, while ultrastructure evaluation of organ tissues was assessed by transmission electron microscopy. Protein expression levels were detected by using Western blotting. EPO treatment showed a modest effect in preventing LPS-induced elevation of AST, ALT, BUN, Cr, and TNF-α levels, and in protecting against LPS-induced tissue degeneration and injured ultrastructure in the lung, liver, and kidney. Moreover, LPS promoted phosphorylation of alanine aminotransferase (AKT) and increased nuclear factor-κB (NF-κB) activation in the lung, liver, and kidney (P<0.05 vs. control). However, EPO treatment significantly decreased the LPS-induced pAKT up-regulation in these tissues (P<0.05 vs. LPS treatment alone). The present study demonstrates that EPO may play a protective role against LPS-induced MOF by reducing the inflammatory response and tissue degeneration, possibly via the phosphatidylinositol 3-kinase/AKT and NF-κB signaling pathways.

Adrenocorticotropic hormone ameliorates acute kidney injury by steroidogenic-dependent and -independent mechanisms

Adrenocorticotropic hormone (ACTH) has a renoprotective effect in chronic kidney disease; however, its effect on acute kidney injury (AKI) remains unknown. In a rat model of tumor necrosis factor (TNF)–induced AKI, we found that ACTH gel prevented kidney injury, corrected acute renal dysfunction, and improved survival. Morphologically, ACTH gel ameliorated TNF-induced acute tubular necrosis, associated with a reduction in tubular apoptosis. While the steroidogenic response to ACTH gel plateaued, the kidney-protective effect continued to increase at even higher doses, suggesting steroid-independent mechanisms. Of note, ACTH also acts as a key agonist of the melanocortin system, with its cognate melanocortin 1 receptor (MC1R) abundantly expressed in renal tubules. In TNF-injured tubular epithelial cells in vitro, ACTH reinstated cellular viability and eliminated apoptosis. This beneficial effect was blunted in MC1R-silenced cells, suggesting that this receptor mediates the anti-apoptotic signaling of ACTH. Moreover, ACTH gel protected mice against cecal ligation puncture–induced septic AKI better than α-melanocyte-stimulating hormone: a protein equal in biological activity to ACTH except for steroidogenesis. Thus, ACTH has additive renoprotective actions achieved by both steroid-dependent mechanisms and MC1R-directed anti-apoptosis. ACTH may represent a novel therapeutic strategy to prevent or treat AKI.

Erythropoietin ameliorates oxidative stress and tissue injury following renal ischemia/reperfusion in rat kidney and lung

OBJECTIVE

To study the effect of erythropoietin (EPO) treatment on renal and lung injury following renal ischemia/reperfusion (I/R).

MATERIALS AND METHODS

Thirty male Wistar rats were assigned to three groups of 10 rats each. The first group was sham-operated, the second was subjected to renal I/R (30 min of ischemia followed by 24 h of reperfusion). The third group was subjected to renal I/R and treated with EPO in two doses: the first dose 1 h prior to ischemia (1,000 U/kg) and the second dose 6 h after ischemia (1,000 U/kg).

RESULTS

The renal and lung tissue injury index, tissue serum blood urea nitrogen and creatinine (Cr) were higher in the renal I/R group compared to the renal I/R + EPO group; the difference was statistically significant (p < 0.05). Kidney and lung tissue glutathione peroxidase and superoxide dismutase levels were higher in the renal I/R + EPO group than the renal I/R group; the difference was also statistically significant (p < 0.05).

CONCLUSION

The data showed that EPO pretreatment could be effective in reducing renal and lung injury following renal I/R and could improve the cellular antioxidant defense system. Hence EPO pretreatment may be effective for attenuating renal and lung injury after renal I/R-induced injury during surgical procedures, hypotension, renal transplantation and other conditions inducing renal I/R.

NFAT5 is activated by hypoxia: role in ischemia and reperfusion in the rat kidney

The current hypothesis postulates that NFAT5 activation in the kidney's inner medulla is due to hypertonicity, resulting in cell protection. Additionally, the renal medulla is hypoxic (10–18 mmHg); however there is no information about the effect of hypoxia on NFAT5. Using in vivo and in vitro models, we evaluated the effect of reducing the partial pressure of oxygen (PO₂) on NFAT5 activity. We found that 1) Anoxia increased NFAT5 expression and nuclear translocation in primary cultures of IMCD cells from rat kidney. 2) Anoxia increased transcriptional activity and nuclear translocation of NFAT5 in HEK293 cells. 3) The dose-response curve demonstrated that HIF-1α peaked at 2.5% and NFAT5 at 1% of O₂. 4) At 2.5% of O₂, the time-course curve of hypoxia demonstrated earlier induction of HIF-1α gene expression than NFAT5. 5) siRNA knockdown of NFAT5 increased the hypoxia-induced cell death. 6) siRNA knockdown of HIF-1α did not affect the NFAT5 induction by hypoxia. Additionally, HIF-1α was still induced by hypoxia even when NFAT5 was knocked down. 7) NFAT5 and HIF-1α expression were increased in kidney (cortex and medulla) from rats subjected to an experimental model of ischemia and reperfusion (I/R). 7) Experimental I/R increased the NFAT5-target gene aldose reductase (AR). 8) NFAT5 activators (ATM and PI3K) were induced in vitro (HEK293 cells) and in vivo (I/R kidneys) with the same timing of NFAT5. 8) Wortmannin, which inhibits ATM and PI3K, reduces hypoxia-induced NFAT5 transcriptional activation in HEK293 cells. These results demonstrate for the first time that NFAT5 is induced by hypoxia and could be a protective factor against ischemic damage.

Erythropoietin ameliorates genetamicin-induced renal toxicity: A biochemical and histopathological study

BACKGROUND

Investigations have attempted to modify the outcome of tubular injury by either ameliorating renal tubular damage or promoting tubular regeneration in the case of acute tubular necrosis.

OBJECTIVES

We investigated the protective effect of Eprex an erythropoietin analogue on tubular injury induced by gentamicin (GM).

MATERIALS AND METHODS

Forty male Wistar rats were randomly divided into four groups. In group 1,rats were served as a sham group. In group 2, rats were injected intraperitoneally with 100 mg/kg of GM for 10 consecutive days (positive control group) and then were sacrificed. In group 3, rats received GM for 10 days then Eprex 100U/kg was injected intraperitoneally for the next 10 days and then they were sacrificed at the day 20th. In group 4 rats were injected a combination of GM (80 mg/kg) and Eprex 100U/kg intraperitoneally for 10 days and then were sacrificed.

RESULTS

The results indicated that, Eprex prevented the increase in serum creatinine (Cr) and blood urea nitrogen (BUN). The effect of Eprex on damage score, showed that co-administration of GM and Eprex (group 3 and 4) reduced the kidney tissue damage compared to positive control group (P<0.05). This result indicat that Eprex potentially can reduce or prevent the kidney tissue damage.

CONCLUSIONS

Ameliorative effect of Eprex when the drug was given in combination with GM and also when the drug was applied after GM-induced tubular damage, revealed the renoprotective potency of Eprex. Eprex is a promising drug to prevent or attenuate tubular damage induced by GM or other nephrotoxic agents which act through the same mechanisms as gentamicin.

N-Glycosylation engineering of tobacco plants to produce asialoerythropoietin

Erythropoietin (EPO) is a glycoprotein hormone that displays both hematopoietic and tissue-protective functions by binding to two distinct receptors. Recombinant human EPO (rhuEPO) is widely used for the treatment of anemia, but its use for tissue protection is limited because of potentially harmful increases in red blood cell mass when higher doses of rhuEPO are used. Recent studies have shown that asialoerythropoietin (asialo-rhuEPO), a desialylated form of rhuEPO, lacks hematopoietic activity, but retains cytoprotective activity. Currently, a small amount of asialo-rhuEPO is produced by enzymatic desialylation of rhuEPO. The prohibitive cost of rhuEPO, however, is a major limitation of this method. Plants have the ability to synthesize complex N-glycans, but lack enzymatic activities to add sialic acid and β1,4-galactose to N-glycan chains. Plants could be genetically engineered to produce asialo-rhuEPO by introducing human β1,4-galactosyltransferase. The penultimate β1,4-linked galactose residues are important for in vivo biological activity. In this proof of concept study, we show that tobacco plants co-expressing human β1,4-galactosyltransferase and EPO genes accumulated asialo-rhuEPO. Purified asialo-rhuEPO binds to an Erythrina cristagalli lectin column, indicating that its N-glycan chains bear terminal β1,4-galactose residues and that the co-expressed GalT is functionally active. Asialo-rhuEPO interacted with the EPO receptor (EPOR) with similar affinity as rhuEPO, implying that it was properly folded. The strategy described here provides a straightforward way to produce asialo-rhuEPO for research and therapeutic purposes.

KEY MESSAGE

N-glycosylation pathway in tobacco plants could be genetically engineered to produce a tissue-protective cytokine, asialoerythropoietin (a desialylated form of human hormone erythropoietin).

Deciphering the mechanisms of the Na+/H+ exchanger-3 regulation in organ dysfunction

The Na+/H+ exchanger-3 (NHE3) belongs to the mammalian NHE protein family and catalyzes the electro-neutral exchange of extracellular sodium for intracellular proton across cellular membranes. Its transport function is of essential importance for the maintenance of the body's salt and water homeostasis as well as acid-base balance. Indeed, NHE3 activity is finely regulated by a variety of stimuli, both acutely and chronically, and its transport function is fundamental for a multiplicity of severe and world-wide infection-pathological conditions. This review aims to provide a concise overview of NHE3 physiology and discusses the role of NHE3 in clinical conditions of prominent importance, specifically in hypertension, diabetic nephropathy, heart failure, acute kidney injury, and diarrhea. Study of NHE3 function in models of these diseases has contributed to the deciphering of mechanisms that control the delicate ion balance disrupted in these disorders. The majority of the findings indicate that NHE3 transport function is activated before the onset of hypertension and inhibited thereafter; NHE3 transport function is also upregulated in diabetic nephropathy and heart failure, while it is reported to be downregulated in acute kidney injury and in diarrhea. The molecular mechanisms activated during these pathological conditions to regulate NHE3 transport function are examined with the aim of linking NHE3 dysfunction to the analyzed clinical disorders.

Renal ischaemia/reperfusion injury: possible role of aquaporins

Renal ischaemia/reperfusion (I/R) injury is a common problem that occurs when blood flow is interrupted to the kidney in case of kidney transplantation, aortic cross-clamping and shock with subsequent resuscitation. Renal I/R injury is a complex conditions which includes the onset of an inflammatory process, which is associated with impairment of concentrating ability of the kidney and impairment of solute transport. Characteristically, renal I/R injury is associated with marked reduction in the protein expression of renal aquaporins (AQPs) mainly (AQP1, AQP2 and AQP3), and solute transporters were observed in this condition and could account for the impaired urinary concentration that observed in this condition. Recently, many agents were tested for a possible protective effect against this insult such as erythropoietin (EPO), α-melanocyte-stimulating hormone (α-MSH) and α-lipoic acid which were proved to prevent downregulation of AQPs and solute transporters. The aim of this short review is to outline the potential pathophysiological role of AQPs in renal I/R injury and to put a spotlight on the modulation of renal functions impairment in renal ischaemia by new drugs that prevent downregulation of AQPs.

The reduction of Na/H exchanger-3 protein and transcript expression in acute ischemia-reperfusion injury is mediated by extractable tissue factor(s)

Ischemic renal injury is a formidable clinical problem, the pathophysiology of which is incompletely understood. As the Na/H exchanger-3 (NHE3) mediates the bulk of apical sodium transport and a significant fraction of oxygen consumption in the proximal tubule, we examined mechanisms by which ischemia-reperfusion affects the expression of NHE3. Ischemia-reperfusion dramatically decreased NHE3 protein and mRNA (immunohistochemistry, immunoblot, and RNA blot) in rat kidney cortex and medulla. The decrease in NHE3 protein was uniform throughout all tubules, including those appearing morphologically intact. In the kidney cortex, a decrease in NHE3 surface protein preceded that of NHE3 total protein and mRNA. Kidney homogenates from rats exposed to mild renal ischemia-reduced cell surface NHE3 protein expression in opossum kidney cells in vitro, whereas homogenates from animals with moderate-to-severe ischemia reduced both total NHE3 protein and mRNA. The decrease in total NHE3 protein was dependent on the proteasomal degradation associated with NHE3 ubiquitylation measured by coimmunoprecipitation. The transferable factor(s) from the ischemic homogenate that reduce NHE3 expression were found to be heat sensitive and to be associated with a lipid-enriched fraction, and did not include regulatory RNAs. Thus, transferable factor(s) mediate the ischemia-reperfusion injury-induced decrease in NHE3 of the kidney.

Erythropoietin as a novel brain and kidney protective agent

Erythropoietin is a 30.4 kDa glycoprotein produced by the kidney, which is mostly known for its physiological function in regulating red blood cell production in the bone marrow Accumulating evidence, however suggests that erythropoietin has additional organ protective effects, which may specifically be useful in protecting the brain and kidneys from injury. Experimental evidence suggests that these protective mechanisms are multi-factorial in nature and may include inhibition of apoptotic cell death, stimulation of cellular regeneration, inhibition of deleterious pathways and promotion of recovery. In this article we review the physiology of erythropoietin, assess previous work that supports the role of erythropoietin as a general tissue protective agent and explain the mechanisms by which it may achieve this tissue protective effect. We then focus on specific laboratory and clinical data that suggest that erythropoietin has a strong brain protective and kidney protective effect. In addition, we comment on the implications of these studies for clinicians at the bedside and for researchers designing controlled trials to further elucidate the true clinical utility of erythropoietin as a neuroprotective and nephroprotective agent. Finally, we describe EPO-TBI, a double-blinded multi-centre randomised controlled trial involving the authors that is being conducted to investigate the organ protective effects of erythropoietin on the brain, and also assesses its effect on the kidneys.

Lung injury following acute kidney injury: kidney-lung crosstalk

The mortality of acute kidney injury (AKI) remains unacceptably high, especially associated with acute respiratory failure. Lung injury complicated with AKI was previously considered as "uremic lung", which is characterized by volume overload and increased vascular permeability. New experimental data using rodent models of renal ischemia-reperfusion and bilateral nephrectomy have emerged recently focusing on kidney-lung crosstalk in AKI, and have highlighted the pathophysiological significance of increased cytokine concentration, enhanced inflammatory responses, and neutrophil activation. In this review, we outline the history of uremic lung and acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), the epidemiological data on the synergistic effect of AKI and lung injury on mortality, and recent basic research which has identified possible pathways in AKI-induced lung injury. These findings will enable us to develop new therapeutic strategies against lung injury associated with AKI and improve the outcomes of critically ill patients in intensive care units.

Renoprotective effect of erythropoietin in rats subjected to ischemia/reperfusion injury: gender differences

BACKGROUND

Renal ischemia reperfusion injury induces gender-dependent heat-shock protein 72 expression, which maintains membrane localization of renal Na(+)/K(+)ATPase-α1. The erythropoietin has a protecting effect against ischemia reperfusion injury in various organs. In this study, we investigated whether erythropoietin exerts a beneficial effect against post-ischemic renal injury. Furthermore, we studied the erythropoietin signaling on heat-shock protein 72 and Na(+)/K(+)ATPase-α1 expression and localization.

METHODS

In male and female Wistar rats, rHuEPO (1000 IU/bwkg intraperitoneal) or vehicle was administered 24 hours prior to unilateral left renal ischemia reperfusion (50 minutes). Kidneys were subsequently removed at hours 2 or 24 of the reperfusion; sham-operated rats served as controls (C) (n = 8/group). We measured serum erythropoietin, renal function, evaluated histological injury, and observed heat-shock protein 72 as well as Na(+)/K(+)ATPase-α1 protein level and localization. Additional groups were followed for 7-day survival.

RESULTS

Erythropoietin treatment was associated with better post-ischemic survival and less impaired renal function in males while diminishing the renal structural damage in both sexes. Endogenous erythropoietin was higher in males and increased in both genders after erythropoietin treatment. The erythropoietin treatment elevated protein levels of heat-shock protein 72 and Na(+)/K(+)ATPase-α1 in 24 hours in males, whereas in females, the already higher expression of heat-shock protein 72 and Na(+)/K(+)ATPase-α1 was not increased. Moreover, erythropoietin prevented ischemia reperfusion induced Na(+)/K(+)ATPase-α1 translocation from the basolaterale membrane in males.

CONCLUSION

Erythropoietin diminishes gender difference in the susceptibility to renal post-ischemic injury and reduces post-ischemic structural damage while preserving kidney function, particularly in males. This additional protection may be associated with a heat-shock protein 72-mediated effect on Na(+)/K(+)ATPase-α1 expression and translocation.

Pre-treatment with isoflurane ameliorates renal ischemic-reperfusion injury in mice

AIMS

Perioperative renal dysfunction is associated with a high mortality. The aim of this study was to investigate whether isoflurane preconditioning provides a protection against renal ischemic-reperfusion injury and whether hypoxia inducible factor 1 α (HIF-1 α) is responsible for the protection afforded by isoflurane in mice.

MAIN METHODS

Adult male C57BL/6 mice received vehicle (PBS), scrambled siRNA or HIF-1 α siRNA via hydrodynamic injection through tail vein. Twenty-four hours after injection, they were exposed to 1.5% isoflurane in oxygen enriched air for 2h while controls without injection were exposed to oxygen enriched air. Twenty-four hours after gas exposure, mice were sacrificed and their kidney were harvested for western blot while other cohorts underwent renal ischemia-reperfusion injury induced by bilateral renal pedicle clamping for 25 min for renal histological or functional analysis 24h after reperfusion or by unilateral clamping for 40 min for survival rate analysis.

KEY FINDINGS

Survival rate and the expression of HIF-1 α and erythropoietin were significantly increased while apoptosis, renal tubule score, blood plasma creatinine and urea were decreased by isoflurane preconditioning. HIF-1 α siRNA but not scrambled siRNA injection abrogated the protective effect of isoflurane preconditioning.

SIGNIFICANCE

Our data suggested that isoflurane preconditioning provided a protection against renal ischemic-reperfusion injury which is very likely due to hypoxia inducible factor-1 α upregulation.

Erythropoietin (EPO) in acute kidney injury

Erythropoietin (EPO) is a 30.4 kDa glycoprotein produced by the kidney, and is mostly well-known for its physiological function in regulating red blood cell production in the bone marrow. Accumulating evidence, however, suggests that EPO has additional organ protective effects, which may be useful in the prevention or treatment of acute kidney injury. These protective mechanisms are multifactorial in nature and include inhibition of apoptotic cell death, stimulation of cellular regeneration, inhibition of deleterious pathways, and promotion of recovery.

In this article, we review the physiology of EPO, assess previous work that supports the role of EPO as a general tissue protective agent, and explain the mechanisms by which it may achieve this tissue protective effect. We then focus on experimental and clinical data that suggest that EPO has a kidney protective effect.

The changes of aquaporin 2 in the graft of acute rejection rat renal transplantation model

AIM

To investigate the significance and changes of Aquaporin 2 (AQP2) in the rat renal graft of acute rejection (AR).

METHODS

Wistar recipients of Spraque-Dawley or Wistar renal grafts were treated with cyclosporine (CsA). Renal grafts were harvested at various times after transplantation for analysis of the levels of AQP2 mRNA and protein of by RT-PCR and immunohistochemistry.

RESULTS

The expression of AQP2 mRNA and protein in the acutely rejecting were grafts significantly decreased (P < 0.05) compared with the control group. But the expression of AQP2 mRNA and protein in the syngeneic grafts (sTX) versus the immunosuppression group (aTX+CsA) showed no difference compared with a control group (P > 0.05). Furthermore, at day 5 and day 7 after transplantation the expressions of AQP2 expression in the allogeneic group (aTX) were decreased significantly compared with day 3 after transplantation (P < 0.05). In addition, there was no remarkable difference at day 5 or 7 after transplantation.

CONCLUSION

AQP2 mRNA and protein expressions were down-regulated during renal transplant acute rejection, which had no relationship to the ischemia reperfusion injury and denervation damage. Furthermore, CsA administration after kidney transplantation blunted this down-regulation (P > 0.05).

Renoprotective effect of erythropoietin against ischaemia-reperfusion injury in a non-human primate model

BACKGROUND

The renoprotective effect of erythropoietin (Epo) against ischaemia-reperfusion injury (IR/I) was evaluated in a non-human primate model.

METHODS

Crab-eating macaques were divided into two groups: Control (n = 10), treated with saline, and EPO (n = 10), treated with Epo. Epo was injected intravenously at a dose of 12,000 units, 5 min before clamping the renal pedicle and 5 min before declamping. Renal IR/I was created by clamping the left renal artery for 90 min following right nephrectomy. Haemoglobin (Hb), haematocrit (Ht), creatinine (Cr), blood urea nitrogen (BUN), cystatin C and interleukin-6 (IL-6) were measured before (Pre) and after (Day 0) the operation, and on post-operative days: Day 1, Day 3, Day 5 and Day 7. Apoptotic cells were counted on Day 1.

RESULTS

There were no differences in Hb and Ht between the two groups. Cr, BUN, cystatin C and IL-6 levels in the EPO group were lower than those in the Control group at most of the observation points. The number of apoptotic cells in the Control was significantly higher than that of and EPO group.

CONCLUSIONS

Epo significantly ameliorates renal IR/I in this non-human primate model. Our findings justify the clinical application of Epo, not only for acute renal failure, but also in transplantation.

Neutrophil gelatinase-associated lipocalin at ICU admission predicts for acute kidney injury in adult patients

RATIONALE

Measured at intensive care unit admission (ICU), the predictive value of neutrophil gelatinase-associated lipocalin (NGAL) for severe acute kidney injury (AKI) is unclear.

OBJECTIVES

To assess the ability of plasma and urine NGAL to predict severe AKI in adult critically ill patients.

METHODS

Prospective-cohort study consisting of 632 consecutive patients.

MEASUREMENTS AND MAIN RESULTS

Samples were analyzed by Triage immunoassay for NGAL expression. The primary outcome measure was occurrence of AKI based on Risk-Injury-Failure (RIFLE) classification during the first week of ICU stay. A total of 171 (27%) patients developed AKI. Of these 67, 48, and 56 were classified as RIFLE R, I, and F, respectively. Plasma and urine NGAL values at ICU admission were significantly related to AKI severity. The areas under the receiver operating characteristic curves for plasma and urine NGAL were for RIFLE R (0.77 ± 0.05 and 0.80 ± 0.04, respectively), RIFLE I (0.80 ± 0.06 and 0.85 ± 0.04, respectively), and RIFLE F (0.86 ± 0.06 and 0.88 ± 0.04, respectively) and comparable with those of admission estimated glomerular filtration rate (eGFR) (0.84 ± 0.04, 0.87 ± 0.04, and 0.92 ± 0.04, respectively). Plasma and urine NGAL significantly contributed to the accuracy of the "most efficient clinical model" with the best four variables including eGFR, improving the area under the curve for RIFLE F prediction to 0.96 ± 0.02 and 0.95 ± 0.01. Serial NGAL measurements did not provide additional information for the prediction of RIFLE F.

CONCLUSIONS

NGAL measured at ICU admission predicts the development of severe AKI similarly to serum creatinine-derived eGFR. However, NGAL adds significant accuracy to this prediction in combination with eGFR alone or with other clinical parameters and has an interesting predictive value in patients with normal serum creatinine.

Differential effects of taurine treatment and taurine deficiency on the outcome of renal ischemia reperfusion injury

Taurine possesses membrane stabilization, osmoregulatory and antioxidant properties, aspects of relevance to ischemic injury. We tested the hypothesis that body taurine status is a determinant of renal ischemic injury. Accordingly, renal function and structure were examined in control (C), taurine-treated (TT) and taurine deficient (TD) rats that were subjected to bilateral renal ischemia (60 min) followed by reperfusion (IR); sham operated rats served as controls. Baseline urine osmolality was greater in the TD group than in the control and the TT groups, an effect associated with increased renal aquaporin 2 level. The IR insult reduced urine osmolality (i.e., day-1 post insult); the TD/IR group displayed a more marked recovery in urine osmolality by day-6 post insult than the other two groups. Fluid and sodium excretions were lower in the TD/IR group, suggesting propensity to retention. Histopathological examination revealed the presence of tubular necrotic foci in the C/IR group than sham controls. While renal architecture of the TD/IR group showed features resembling sham controls, the TT/IR group showed dilated tubules, which lacked immunostaining for aquaporin 2, but not 1, suggestive of proximal tubule origin. Finally, assessment of cell proliferation and apoptosis revealed lower proliferation but higher apoptotic foci in the TT/IR group than other IR groups. Collectively, the results indicate that body taurine status is a major determinant of renal IR injury.

Cardioprotection by a nonerythropoietic, tissue-protective peptide mimicking the 3D structure of erythropoietin

Erythropoietin (EPO), originally identified for its critical hormonal role in regulating production and survival of erythrocytes, is a member of the type 1 cytokine superfamily. Recent studies have shown that EPO has cytoprotective effects in a wide variety of tissues, including the heart, by preventing apoptosis. However, EPO also has undesirable effects, such as thrombogenesis. In the present study, we investigated whether a helix B-surface peptide (HBSP), a nonerythropoietic, tissue-protective peptide mimicking the 3D structure of erythropoietin, protects cardiomyocytes from apoptosis in vitro and in vivo. In cultured neonatal rat cardiomyocytes, HBSP clearly inhibited apoptosis (approximately 80%) induced by TNF-alpha, which was comparable with the effect of EPO, and activated critical signaling pathways of cell survival, including Akt, ERK1/2, and STAT3. Among these pathways, Akt was shown to play an essential role in HBSP-induced prevention of apoptosis, as assessed by using a small interfering RNA approach. In the dilated cardiomyopathic hamster (J2N-k), whose cardiac tissues diffusely expressed TNF-alpha, HBSP also inhibited apoptosis (approximately 70%) and activated Akt in cardiomyocytes. Furthermore, the levels of serum creatine kinase activity and of cardiac expression of atrial natriuretic peptide, a marker of chronic heart failure, were down-regulated in animals treated with HBSP. These data demonstrate that HBSP protects cardiomyocytes from apoptosis and leads to a favorable outcome in failing hearts through an Akt-dependent pathway. Because HBSP does not have the undesirable effects of EPO, it could be a promising alternative for EPO to treat cardiovascular diseases, such as myocardial infarction and heart failure.