Tracking and protection of transplanted stem cells using a ferrocenecarboxylic acid-conjugated peptide that mimics hTERT.

In vivo tracking of transplanted stem cells has been a central aim of stem cell therapy. Although many tracking systems have been introduced, no method has yet been validated for clinical applications. We developed a novel sophisticated peptide (GV1001) that mimics hTERT (human telomerase reverse transcriptase) and analysed its ability to track and protect stem cells after transplantation. Ferrocenecarboxylic acid-conjugated GV1001 (Fe-GV1001) efficiently penetrated stem cells with no adverse effects. Moreover, Fe-GV1001 improved the viability, proliferation, and migration of stem cells under hypoxia. After Fe-GV1001-labelled stem cells were transplanted into the brains of rats after stroke, the labelled cells were easily tracked by MRI. Our findings indicate that Fe-GV1001 can be used for the in vivo tracking of stem cells after transplantation into the brain and can improve the efficacy of stem cell therapy by sustaining and enhancing stem cell characteristics under disease conditions.

The erythropoietin-derived peptide MK-X and erythropoietin have neuroprotective effects against ischemic brain damage.

Erythropoietin (EPO) has been well known as a hematopoietic cytokine over the past decades. However, recent reports have demonstrated that EPO plays a neuroprotective role in the central nervous system, and EPO has been considered as a therapeutic target in neurodegenerative diseases such as ischemic stroke. Despite the neuroprotective effect of EPO, clinical trials have shown its unexpected side effects, including undesirable proliferative effects such as erythropoiesis and tumor growth. Therefore, the development of EPO analogs that would confer neuroprotection without adverse effects has been attempted. In this study, we examined the potential of a novel EPO-based short peptide, MK-X, as a novel drug for stroke treatment in comparison with EPO. We found that MK-X administration with reperfusion dramatically reduced brain injury in an in vivo mouse model of ischemic stroke induced by middle cerebral artery occlusion, whereas EPO had little effect. Similar to EPO, MK-X efficiently ameliorated mitochondrial dysfunction followed by neuronal death caused by glutamate-induced oxidative stress in cultured neurons. Consistent with this effect, MK-X significantly decreased caspase-3 cleavage and nuclear translocation of apoptosis-inducing factor induced by glutamate. MK-X completely mimicked the effect of EPO on multiple activation of JAK2 and its downstream PI3K/AKT and ERK1/2 signaling pathways, and this signaling process was involved in the neuroprotective effect of MK-X. Furthermore, MK-X and EPO induced similar changes in the gene expression patterns under glutamate-induced excitotoxicity. Interestingly, the most significant difference between MK-X and EPO was that MK-X better penetrated into the brain across the brain-blood barrier than did EPO. In conclusion, we suggest that MK-X might be used as a novel drug for protection from brain injury caused by ischemic stroke, which penetrates into the brain faster in comparison with EPO, even though MK-X and EPO have similar protective effects against excitotoxicity.

Neuroprotective Effects of an Erythropoietin-Derived Peptide in PC1 2 Cells under Oxidative Stress.

Erythropoietin (EPO) has been shown to be a key cytokine in the production of erythrocytes from erythroblasts. Recently, attempts have been made to adopt EPO as a drug target for neuroprotection in selected neurological pathologies. In the current study, a novel EPO-derived peptide which mimics the weak binding site of EPO to its receptor (MK-X) was generated. Experimental results demonstrated that MK-X was able to ameliorate neuronal death due to reactive oxygen species and conditions of oxidative stress similar to EPO. In addition, MK-X induced long-lasting Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and Akt activation. Furthermore, treatment with inhibitors of ERK1/2 and Akt abolished the neuroprotective effect of MK-X. Unlike EPO, however, MK-X did not induce cellular proliferation. Collectively, the results of the current study suggested that MK-X may be useful as a novel neuroprotective reagent.

Neuroprotective Effects of an Erythropoietin-Derived Peptide in PC12 Cells under Oxidative Stress.

Erythropoietin (EPO) has been shown to be a key cytokine in the production of erythrocytes from erythroblasts. Recently, attempts have been made to adopt EPO as a drug target for neuroprotection in selected neurological pathologies. In the current study, a novel EPO-derived peptide which mimics the weak binding site of EPO to its receptor (MK-X) was generated. Experimental results demonstrated that MK-X was able to ameliorate neuronal death due to reactive oxygen species and conditions of oxidative stress similar to EPO. In addition, MK-X induced long-lasting Extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) and Akt activation. Furthermore, treatment with inhibitors of ERK1/2 and Akt abolished the neuroprotective effect of MK-X. Unlike EPO, however, MK-X did not induce cellular proliferation. Collectively, the results of the current study suggested that MK-X may be useful as a novel neuroprotective reagent.

Phase I trial of repeated intrathecal autologous bone marrow-derived mesenchymal stromal cells in amyotrophic lateral sclerosis.

UNLABELLED: Stem cell therapy is an emerging alternative therapeutic or disease-modifying strategy for amyotrophic lateral sclerosis (ALS). The aim of this open-label phase I clinical trial was to evaluate the safety of two repeated intrathecal injections of autologous bone marrow (BM)-derived mesenchymal stromal cells (MSCs) in ALS patients. Eight patients with definite or probable ALS were enrolled. After a 3-month lead-in period, autologous MSCs were isolated two times from the BM at an interval of 26 days and were then expanded in vitro for 28 days and suspended in autologous cerebrospinal fluid. Of the 8 patients, 7 received 2 intrathecal injections of autologous MSCs (1 × 10(6) cells per kg) 26 days apart. Clinical or laboratory measurements were recorded to evaluate the safety 12 months after the first MSC injection. The ALS Functional Rating Scale-Revised (ALSFRS-R), the Appel ALS score, and forced vital capacity were used to evaluate the patients' disease status. One patient died before treatment and was withdrawn from the study. With the exception of that patient, no serious adverse events were observed during the 12-month follow-up period. Most of the adverse events were self-limited or subsided after supportive treatment within 4 days. Decline in the ALSFRS-R score was not accelerated during the 6-month follow-up period. Two repeated intrathecal injections of autologous MSCs were safe and feasible throughout the duration of the 12-month follow-up period. SIGNIFICANCE: Stem cell therapy is an emerging alternative therapeutic or disease-modifying strategy for amyotrophic lateral sclerosis (ALS). To the authors' best knowledge, there are no clinical trials to evaluate the safety of repeated intrathecal injections of autologous bone marrow mesenchymal stromal cells in ALS. After the clinical trial (phase I/II) was conducted, the stem cell (HYNR-CS, NEURONATA-R) was included in the revision of the regulations on orphan drug designation (number 160; December 31, 2013) and approved as a New Drug Application (Department of Cell and Gene Therapy 233; July 30, 2014) by the Korean Food and Drug Administration. The phase II trial is expected to be reported later.

Recombinant human erythropoietin in amyotrophic lateral sclerosis: a pilot study of safety and feasibility.

BACKGROUND AND PURPOSE: It has been shown that erythropoietin is neuroprotective in animal models of neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). The aim of this study was to determine the safety and feasibility of repetitive high-dose recombinant human erythropoietin (rhEPO) therapy in ALS patients. METHODS: Two consecutive studies were conducted. We first recruited 26 subjects for an initial single-arm safety study. After a lead-in period of 3 months to assess the disease progression, rhEPO was infused intravenously (35,000 IU) once per month for 3 months, and the subjects were followed for an additional 3 months. The ALS Functional Rating Scale-Revised (ALSFRS-R) was used for clinical assessment. After confirming the safety of rhEPO, 60 subjects were recruited for the second controlled study (rhEPO and control groups), which involved a total of 6 infusions at a rate of 1/month. RESULTS: There were no serious adverse events in the first study. The mean rate of decline in the ALSFRS-R score was lower during the treatment period than during the lead-in period (mean±SD: 2.6±1.8 and 3.7±2.6, respectively; p=0.02). However, the rate of decline during the subsequent 3 months returned to that observed in the lead-in period. In the second study, the mean rate of decline in ALSFRS-R score was significantly lower in the rhEPO group than in the control group (during months 0-3, 1.8±1.7 vs. 3.1±2.3, p=0.03; during months 4-6, 2.1±2.2 vs. 3.5±2.3, p=0.02). CONCLUSIONS: Intravenous high-dose rhEPO is both safe and feasible for the treatment of ALS. Further investigation using different intervals and doses should be considered.

Identification of peptides that selectively bind to myoglobin by biopanning of phage displayed-peptide library.

Biopanning of phage displayed-peptide library was performed against myoglobin, a marker for the early assessment of acute myocardial infarction (AMI), to identify peptides that selectively bind to myoglobin. Using myoglobin-conjugated magnetic beads, phages that bound to myoglobin were collected and amplified for the next round of screening. A 148-fold enrichment of phage titer was observed after five rounds of screening relative to the first round. After phage binding ELISA, three phage clones were selected (3R1, 3R7 and 3R10) and the inserted peptides were chemically synthesized. The analysis of binding affinity showed that the 3R7 (CPSTLGASC) peptide had higher binding affinity (Kd=57 nM) than did the 3R1 (CNLSSSWIC) and 3R10 (CVPRLSAPC) peptide (Kd=125 nM and 293 nM, respectively). Cross binding activity to other proteins, such as bovine serum albumin, troponin I, and creatine kinase-MB, was minimal. In a peptide-antibody sandwich ELISA, the selected peptides efficiently captured myoglobin. Moreover, the concentrations of myoglobin in serum samples measured by a peptide-peptide sandwich assay were comparable to those measured by a commercial antibody-based kit. These results indicate that the identified peptides can be used for the detection of myoglobin and may be a cost effective alternative to antibodies.

In vivo imaging of myocardial cell death using a peptide probe and assessment of long-term heart function.

During acute myocardial infarction (AMI), both apoptosis and necrosis of myocardial cells could occur and lead to left ventricular (LV) functional decline. Here we determined whether in vivo imaging signals of myocardial cell death by ApoPep-1 (CQRPPR), a peptide probe that binds to apoptotic and necrotic cells through histone H1, at an early stage after AMI showed correlation with the long-term heart function. AMI was induced using a rat model of ischemia and reperfusion (I/R) injury. Fluorescence-labeled ApoPep-1 was administered by intravenous injection into rats 2h after reperfusion. Ex vivo imaging of hearts isolated 2h after peptide injection showed higher levels of near-infrared fluorescence (NIRF) signals at hearts of I/R rats than those of sham-operated rats. The fluorescent peptide was rapidly cleared from the blood and did not bind to red and white blood cells. Localization of fluorescent ApoPep-1 at the area of cell death was demonstrated by co-staining of myocardial tissue with TUNEL. The intensity of in vivo NIRF imaging signals by homing of ApoPep-1 to injured myocardium of I/R rats obtained 2h after peptide injection (equivalent to 4h after injury) showed strong and moderate correlation with the change in the LV ejection fractions (r(2)=0.82) and the size of the fibrotic area (r(2)=0.64), respectively, observed at four weeks after injury. These results suggest that ApoPep-1-mediated in vivo imaging signals of myocardial cell death, including both apoptosis and necrosis, at an early stage of AMI could be a potential biomarker for assessment of long-term outcome of heart function.

Differential cell death and Bcl-2 expression in the mouse retina after glutathione decrease by systemic D,L-buthionine sulphoximine administration.

Glutathione (GSH) plays a critical role in cellular defense against unregulated oxidative stress in mammalian cells including neurons. We previously demonstrated that GSH decrease using [D, L]-buthionine sulphoximine (BSO) induces retinal cell death, but the underlying mechanisms of this are still unclear. Here, we demonstrated that retinal GSH level is closely related to retinal cell death as well as expression of an anti-apoptotic molecule, Bcl-2, in the retina. We induced differential expression of retinal GSH by single and multiple administrations of BSO, and examined retinal GSH levels and retinal cell death in vivo. Single BSO administration showed a transient decrease in the retinal GSH level, whereas multiple BSO administration showed a persistent decrease in the retinal GSH level. Retinal cell death also showed similar patterns: transient increases of retinal cell death were observed after single BSO administration, whereas persistent increases of retinal cell death were observed after multiple BSO administration. Changes in the retinal GSH level affected Bcl-2 expression in the retina. Immunoblot and immunohistochemical analyses showed that single and multiple administration of BSO induced differential expressions of Bcl-2 in the retina. Taken together, the results of our study suggest that the retinal GSH is important for the survival of retinal cells, and retinal GSH appears to be deeply related to Bcl-2 expression in the retina. Thus, alteration of Bcl-2 expression may provide a therapeutic tool for retinal degenerative diseases caused by retinal oxidative stress such as glaucoma or retinopathy.

The plasma membrane redox enzyme NQO1 sustains cellular energetics and protects human neuroblastoma cells against metabolic and proteotoxic stress.

The plasma membrane redox system (PMRS) of nicotinamide adenine dinucleotide (NADH)-related enzymes plays a key role in the maintenance of cellular energetics. During the aging process, neural cells are particularly sensitive to impaired energy metabolism and oxidative damage, but the involvement of the PMRS in these processes is unknown. Here, we used human neuroblastoma cells with either elevated or reduced levels of the PMRS enzyme NADH-quinone oxidoreductase 1 (NQO1) to investigate how the PMRS regulates neuronal stress responses. Cells with elevated NQO1 levels were more resistant to death induced by 2-deoxyglucose, potassium cyanide (energetic stress), and lactacystin (proteotoxic stress), but were not protected from being killed by H(2)O(2) and serum withdrawal. The NAD(+)(an oxidized form of NADH)/NADH ratio was maintained at a significantly higher level in cells overexpressing NQO1, consistent with enhanced levels of NQO1 activity. Levels of the neuroprotective transcription factors nuclear factor kappa-light-chain-enhancer of activated B cells and nuclear factor (erythroid-derived 2)-like 2, and the protein chaperone HSP70 were elevated in cells overexpressing NQO1. Cells in which NQO1 levels were decreased by RNA interference exhibited increased vulnerability to death induced by 2-deoxyglucose and lactacystin. Thus, a higher NAD(+)/NADH ratio and activation of adaptive stress response pathways are enhanced by the PMRS in neuroblastoma cells, enabling them to maintain redox homeostasis under conditions of energetic and proteotoxic stress. These findings have implications for the development of therapeutic interventions for neural tumors and neurodegenerative conditions.

Exendin-4 protects against sulfonylurea-induced ß-cell apoptosis.

Sulfonylurea is one of the commonly used anti-diabetic drugs that stimulate insulin secretion from ß-cells. Despite their glucose lowering effects in type 2 diabetes mellitus, long-term treatment brought on secondary failure characterized by ß-cell exhaustion and apoptosis. ER stress induced by Ca(2+) depletion in endoplasmic reticulum (ER) is speculated be one of the causes of secondary failure, but it remains unclear. Glucagon like peptide-1 (GLP-1) has anti-apoptotic effects in ß-cells after the induction of oxidative and ER stress. In this study, we examined the anti-apoptotic action of a GLP-1 analogue in ß-cell lines and islets against ER stress induced by chronic treatment of sulfonylurea. HIT-T15 and dispersed islet cells were exposed to glibenclamide for 48 h, and apoptosis was evaluated using Annexin/PI flow cytometry. Expression of the ER stress-related molecules and sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) 2/3 was determined by real-time PCR and western blot analysis. Chronic exposure to glibenclamide increased apoptosis by depletion of ER Ca(2+) concentration through reduced expression of SERCA 2/3. Pretreatment with Exendin-4 had an anti-apoptotic role through ER stress modulation and ER Ca(2+) replenishing by SERCA restoration. These findings will further the understanding of one cause of glibenclamide-induced ß-cell loss and therapeutic availability of GLP-1-based drugs in secondary failure by sulfonylurea during treatment of diabetes.

Exendin-4 Protects Against Sulfonylurea-Induced ß-Cell Apoptosis.

Sulfonylurea is one of the commonly used anti-diabetic drugs that stimulate insulin secretion from ß-cells. Despite their glucose lowering effects in type 2 diabetes mellitus, long-term treatment brought on secondary failure characterized by ß-cell exhaustion and apoptosis. ER stress induced by Ca2+ depletion in endoplasmic reticulum (ER) is speculated be one of the causes of secondary failure, but it remains unclear. Glucagon like peptide-1 (GLP-1) has anti-apoptotic effects in ß-cells after the induction of oxidative and ER stress. In this study, we examined the antiapoptotic action of a GLP-1 analogue in ß-cell lines and islets against ER stress induced by chronic treatment of sulfonylurea. HIT-T15 and dispersed islet cells were exposed to glibenclamide for 48 h, and apoptosis was evaluated using Annexin/PI flow cytometry. Expression of the ER stress-related molecules and sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) 2/3 was determined by real-time PCR and western blot analysis. Chronic exposure to glibenclamide increased apoptosis by depletion of ER Ca2+ concentration through reduced expression of SERCA 2/3. Pretreatment with Exendin-4 had an anti-apoptotic role through ER stress modulation and ER Ca2+ replenishing by SERCA restoration. These findings will further the understanding of one cause of glibenclamide-induced ß-cell loss and therapeutic availability of GLP-1-based drugs in secondary failure by sulfonylurea during treatment of diabetes.

Protective effect of aminophylline against cigarette smoke extract-induced apoptosis in human lung fibroblasts (MRC-5 cells).

Cigarette smoking is the principal cause of chronic obstructive pulmonary disease (COPD), especially emphysema, which is characterized by alveolar wall destruction and airspace enlargement. Apoptosis of lung structural cells is involved in the pathogenesis of COPD. Xanthine derivatives (aminophylline or theophylline) have been used for the treatment of COPD as a bronchodilator. But the effects of xanthine derivatives on apoptosis of the lung structural cells remain poorly understood, even though it is known that theophylline protects against ultraviolet irradiation-induced cell death in corneal epithelial cells. This study was designed to determine whether aminophylline would protect against cigarette smoke extract (CSE)-induced apoptosis in lung fibroblasts. We demonstrated that aminophylline protected against apoptosis of MRC-5 cells at a relatively lower therapeutic range (10 µg/ml), resulting in a significant increase in cell viability occurring at 20% concentration after 8-hr exposure. Annexin staining decreased from 68 ± 4% of the control to 12 ± 2% of aminophylline (10 µg/ml) pre-treatment after 20% CSE exposure for 12 hr (p < 0.05). Aminophylline decreased caspase 3 and 8 activities and nuclear condensation or fragmentation in MRC-5 cells after exposure to 20% CSE for 12 hr compared with control and high levels of aminophylline (>50 µg/ml) pre-treatment. These findings suggest that aminophylline protected apoptosis of MRC-5 cells through the inactivation of caspases 3 and 8 and could be an effective agent to reduce cigarette smoking-induced lung structural cell apoptosis.

Erythropoietin promotes hair shaft growth in cultured human hair follicles and modulates hair growth in mice.

BACKGROUND: Recent studies have shown that erythropoietin (EPO)/erythropoietin receptor (EPOR) signaling exist in both human and mouse hair follicles (HFs). OBJECTIVE: To investigate whether dermal papilla cells (DPCs) express functional EPOR and, if so, to investigate effects of EPO on hair shaft growth in cultured human scalp hair follicles and hair growth in mice. METHODS: EPOR expression in DPCs and follicular keratinocytes was examined by RT-PCR and immunoblot. Phosphorylation of EPOR signaling pathway mediators by EPO treatment was examined by immunoblot. MTT assay was employed to check cell viability after EPO treatment. Hair shaft growth was measured in the absence or presence of EPO and matrix keratinocyte proliferation was examined by Ki-67 immunostaining in cultured hair follicles. Agarose beads containing EPO were implanted into dorsal skin of C57BL/6 mice to examine effects of EPO on hair growth in vivo. RESULTS: EPOR mRNA and protein are expressed in cultured human DPCs. EPOR signaling pathway mediators such as EPOR and Akt are phosphorylated by EPO in DPCs. EPO significantly promoted the growth of DPCs and elongated hair shafts with increased proliferation of matrix keratinocytes in cultured human hair follicles. In addition, EPO not only promoted anagen induction from telogen but also prolonged anagen phase. CONCLUSIONS: EPO may modulate hair growth by stimulating DPCs that express functional EPOR.

Extracellular signal-regulated kinase (ERK) inhibition attenuates cigarette smoke extract (CSE) induced-death inducing signaling complex (DISC) formation in human lung fibroblasts (MRC-5) cells.

Cigarette smoke (CS), a major risk factor in emphysema, causes cell death by incompletely understood mechanisms. Death-inducing signaling complex (DISC) formation is an initial event in Fas-mediated apoptosis. We demonstrated cigarette smoke extract (CSE) induced DISC formation in human lung fibroblasts (MRC-5). The aim of this study was to investigate the involvement of extracellular signal-regulated kinase (ERK) MAPK activation in CSE induced DISC formation. Immunoprecipitation (IP) for Fas and Western Immunoblot (IB) analysis for caspase 8 were then performed to show DISC. Lactate dehydrogenase (LDH) release was measured using a cytotoxicity detection kit. MTT assay was used as a measure of cell viability. We demonstrated that CSE induces DISC formation in MRC-5 using IP for Fas and IB for caspase 8. ERK was expressed in MRC-5 exposed to CSE. MEK-1 inhibitor (PD98059) decreased DISC formation in MRC-5 exposed to 20% CSE at 1 hr, and cell viability, as assessed by colorimetric MTT assay, was increased in MEK-1 inhibitor treated MRC-5 cells after 24 hr CSE exposure compared to the control. Inhibiting ERK significantly decreased the caspase-3,-8 activity in MEK-1 inhibitor treated MRC-5 cells compared to the control.The DISC formation, initial event of extrinsic apoptotic pathway, is a primary component of CSE- induced death in MRC-5, and ERK activation plays an active role in the DISC formation and downstream pathway. These results suggest that modulation of ERK may have therapeutic potential in the prevention of smoke-related lung injury.

The pro-angiogenic cytokine pleiotrophin potentiates cardiomyocyte apoptosis through inhibition of endogenous AKT/PKB activity.

Pleiotrophin is a development-regulated cytokine and growth factor that can promote angiogenesis, cell proliferation, or differentiation, and it has been reported to have neovasculogenic effects in damaged heart. Developmentally, it is prominently expressed in fetal and neonatal hearts, but it is minimally expressed in normal adult heart. Conversely, we show in a rat model of myocardial infarction and in human dilated cardiomyopathy that pleiotrophin is markedly up-regulated. To elucidate the effects of pleiotrophin on cardiac contractile cells, we employed primary cultures of rat neonatal and adult cardiomyocytes. We show that pleiotrophin is released from cardiomyocytes in vitro in response to hypoxia and that the addition of recombinant pleiotrophin promotes caspase-mediated genomic DNA fragmentation in a dose- and time-dependent manner. Functionally, it potentiates the apoptotic response of neonatal cardiomyocytes to hypoxic stress and to ultraviolet irradiation and of adult cardiomyocytes to hypoxia-reoxygenation. Moreover, UV-induced apoptosis in neonatal cardiomyocytes can be partially inhibited by small interfering RNA-mediated knockdown of endogenous pleiotrophin. Mechanistically, pleiotrophin antagonizes IGF-1 associated Ser-473 phosphorylation of AKT/PKB, and it concomitantly decreases both BAD and GSK3beta phosphorylation. Adenoviral expression of constitutively active AKT and lithium chloride-mediated inhibition of GSK3beta reduce the potentiated programmed cell death elicited by pleiotrophin. These latter data indicate that pleiotrophin potentiates cardiomyocyte cell death, at least partially, through inhibition of AKT signaling. In conclusion, we have uncovered a novel function for pleiotrophin on heart cells following injury. It fosters cardiomyocyte programmed cell death in response to pro-apoptotic stress, which may be critical to myocardial injury repair.

Therapeutic effectiveness of a single vs multiple doses of erythropoietin after experimental myocardial infarction in rats.

BACKGROUND: Systemic application of recombinant human erythropoietin (rhEPO) greatly limits cardiac tissue damage and attenuates left ventricular (LV) remodeling after experimentally induced myocardial infarction (MI). However, multiple injections of rhEPO stimulate red blood cell production and elevate the hematocrit (Htc), which might negatively affect the outcome of acute MI. We compared the outcome of experimental MI in rats treated with a single or multiple doses of rhEPO. MATERIALS AND METHODS: Sprague-Dawley male rats were subjected to a permanent ligation of the left descending coronary artery (CL) or sham operation. Immediately after CL animals received either a single i.v. injection of 3,000 IU/kg of rhEPO, or a single injection plus additional injections of the same dose of rhEPO repeated daily for six more days. Echocardiography and blood collection for measurement of Htc were performed prior to, and at 2 and 4 weeks after CL; MI size was measured histologically 4 weeks after CL. RESULTS: A single injection of rhEPO elevated Htc by 11% (p < 0.05) 1 week after CL, but after multiple rhEPO injections Htc increased by 40%. In untreated rats a 140 and 340% expansion in end-diastolic and end-systolic LV volumes, respectively, and 55% decline in ejection fraction (EF) occurred during the 4 week period following CL. A single rhEPO dose attenuated the LV remodeling and EF reduction by 50%. Repeated rhEPO injections did not elicit any additional benefits in respect to LV remodeling. Moreover, at the end of 4 weeks, MI size was significantly reduced (by 40%) by a single injection, while after repeated rhEPO injections the reduction of MI size was not statistically significant. CONCLUSION: The results of this study indicate that multiple dosing of rhEPO after induced myocardial infarction in rats has no added therapeutic benefits over those achieved by a single dose.

Erythropoietin, modified to not stimulate red blood cell production, retains its cardioprotective properties.

Erythropoietin (EPO), a hematopoietic cytokine, possesses strong antiapoptotic, tissue-protective properties. For clinical applications, it is desirable to separate the hematopoietic and tissue-protective properties. Recently introduced carbamylated erythropoietin (CEPO) does not stimulate the erythropoiesis but retains the antiapoptotic and neuroprotective effects. We tested the ability of CEPO to protect cardiac tissue from toxin-induced and oxidative stress in vitro and ischemic damage in vivo and compared these effects with the effects of EPO. CEPO reduced by 50% the extent of staurosporine-induced apoptosis in isolated rats' cardiomyocytes and increased by 25% the reactive oxygen species threshold for induction of the mitochondrial permeability transition. In an experimental model of myocardial infarction induced by permanent ligation of a coronary artery in rats, similarly to EPO, a single bolus injection of 30 mug/kg b.wt. of CEPO immediately after coronary ligation reduced apoptosis in the myocardial area at risk, examined 24 h later, by 50%. Left ventricular remodeling (ventricular dilation) and functional decline (fall in ejection fraction) assessed by repeated echocardiography were significantly and similarly attenuated in CEPO- and EPO-treated rats. Four weeks after coronary ligation, the myocardial infarction (MI) size in CEPO- and EPO-treated rats was half of that in untreated coronary-ligated animals. Unlike EPO, CEPO had no effect on hematocrit. The antiapoptotic cardioprotective effects of CEPO, shown by its ability to limit both post-MI left ventricular remodeling and the extent of the myocardial scar in the model of permanent coronary artery ligation in rats, demonstrate comparable potency to that of native (nonmodified) EPO.

Cardioprotection by recombinant human erythropoietin following acute experimental myocardial infarction: dose response and therapeutic window.

BACKGROUND: Recombinant human erythropoietin (rhEPO) protects tissue from ischemic damage, but translation of this finding into useful guidelines with respect to human trials for myocardial infarction (MI) requires a determination of the minimum effective rhEPO dose and the therapeutic window following MI. METHOD AND RESULTS: Serial echocardiography revealed that during four weeks following MI, induced by a permanent coronary ligation in rats, the LV end-diastolic and end-systolic volumes in untreated rats expanded from 0.35 +/- 0.01 and 0.14 +/- 0.01 ml to 0.84 +/- 0.04 and 0.61 +/- 0.06 ml, respectively, and ejection fraction (EF) reduced by 50%. A single i.v. injection of rhEPO immediately following MI in a dose of 150 IU/kg was as effective as 3,000 IU/kg in causing a 2-fold reduction of the number of apoptotic nuclei in the AAR 24-h later, a 2-fold reduction of the MI size measured 4 weeks later, attenuation of progressive LV dilatation and fall in EF. A 3000 IU/kg dose had similar therapeutic effects when delayed by 4, 8, or 12 h following MI, but was not effective after a 24-h delay. A single dose of 150 IU/kg was effective within 4 h post-MI, but was without effect if administered after an 8-h delay. CONCLUSION: Cell death, final MI size, myocardial remodeling and functional decline are significantly reduced in rats by a single injection of rhEPO in a dose as low as 150 IU/kg if administered during the first 4 h after the ischemic event. Higher doses extend the therapeutic window up to 12 h.

Beneficial effects of chronic pharmacological manipulation of beta-adrenoreceptor subtype signaling in rodent dilated ischemic cardiomyopathy.

BACKGROUND: Studies in isolated cardiac myocytes have demonstrated that signaling via specific beta1-adrenergic receptor subtypes (beta1ARs) promotes but that signaling via beta2ARs protects from cell death. We hypothesized that prolonged beta(2)AR stimulation or beta1AR blockade would each protect myocytes from death and thereby ameliorate cardiac remodeling in chronic heart failure. METHODS AND RESULTS: A large myocardial infarction (MI) induced in rats by coronary artery ligation resulted in a dilated cardiomyopathy (DCM) characterized by infarct expansion and a progressive increase in left ventricular (LV) end-diastolic volume, accompanied by a reduction in ejection fraction (EF), as assessed by repeated echocardiography. Pressure-volume analysis at 8 weeks after ligation showed that diastolic stiffness (Eed) and arterial elastance (Ea) were increased, end-systolic elastance (Ees) was decreased, and arterioventricular (AV) coupling (Ea/Ees) had deteriorated. Apoptosis was present in both peri-infarct and remote myocardium. Chronic (6-week) administration of the beta2AR agonists fenoterol or zinterol, starting at 2 weeks after MI, reduced the extent of LV dilation, infarct expansion, and EF decline. The beta1AR blocker metoprolol did not affect the former and preserved EF to a lesser extent than did the beta2AR agonists. At 8 weeks after ligation, apoptosis was reduced by all drugs but to a greater extent by beta2AR agonists than by the beta1AR blocker. Both beta2AR agonists and the beta1AR blocker improved AV coupling, the former mainly by reducing Ea and the latter mainly by increasing Ees. Only the beta2AR agonists reduced the Eed and the MI size by reducing infarct expansion. CONCLUSIONS: These results provide proof of concept for the efficacy of chronic beta2AR stimulation in this DCM model.