Novel, selective EPO receptor ligands lacking erythropoietic activity reduce infarct size in acute myocardial infarction in rats

Rosiglitazone Does Not Show Major Hidden Cardiotoxicity in Models of Ischemia/Reperfusion but Abolishes Ischemic Preconditioning-Induced Antiarrhythmic Effects in Rats In Vivo

Clinical observations are highly inconsistent with the use of the antidiabetic rosiglitazone regarding its associated increased risk of myocardial infarction. This may be due to its hidden cardiotoxic properties that have only become evident during post-marketing studies. Therefore, we aimed to investigate the hidden cardiotoxicity of rosiglitazone in ischemia/reperfusion (I/R) injury models. Rats were treated orally with either 0.8 mg/kg/day rosiglitazone or vehicle for 28 days and subjected to I/R with or without cardioprotective ischemic preconditioning (IPC). Rosiglitazone did not affect mortality, arrhythmia score, or infarct size during I/R. However, rosiglitazone abolished the antiarrhythmic effects of IPC. To investigate the direct effect of rosiglitazone on cardiomyocytes, we utilized adult rat cardiomyocytes (ARCMs), AC16, and differentiated AC16 (diffAC16) human cardiac cell lines. These were subjected to simulated I/R in the presence of rosiglitazone. Rosiglitazone improved cell survival of ARCMs at 0.3 μM. At 0.1 and 0.3 μM, rosiglitazone improved cell survival of AC16s but not that of diffAC16s. This is the first demonstration that chronic administration of rosiglitazone does not result in major hidden cardiotoxic effects in myocardial I/R injury models. However, the inhibition of the antiarrhythmic effects of IPC may have some clinical relevance that needs to be further explored.

Cardiac Protection of a Novel Lupane-Type Triterpenoid from Injuries Induced by Hypoxia-Reperfusion

Myocardial ischemia-reperfusion injury (MIRI) leads to cardiac remodeling and heart failure associated with acute myocardial infarction, which is one of the leading causes of death worldwide. Betulinic acid (BA), a widely distributed lupane-type triterpenoid, has been reported to possess antioxidative activity and inhibit apoptosis in MIRI. Due to the low bioavailability and water insolubility of BA, a previous study found a series of BA-derivative compounds by microbial transformation. In this study, we observe whether there are anti-MIRI effects of BTA07, a BA derivative, on cardiac injuries induced by hypoxia/reoxygenation (H/R) in adult rat cardiomyocytes in vitro and in Langendorff-perfused hearts ex vivo, and further explore its mechanism of cardioprotection to find more efficient BA derivatives. The hemodynamic parameters of isolated hearts were monitored and recorded by a Lab Chart system. The markers of oxidative stress and apoptosis in isolated hearts and adult rat cardiomyocytes (ARCMs) were evaluated. The expression levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X (Bax), protein kinase B (Akt) and phospho-Akt (pAkt, Ser473) induced by H/R were detected via Western blot. The Langendorff experiments showed that BTA07 improves hemodynamic parameters, reduces myocardium damage and infarct size, inhibits levels of myocardial tissue enzymes lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary outflow and reduces oxidative stress and the activation of caspase-3 in the myocardium. In vitro, BTA07 reduced cell death and caspase-3 activation and inhibited reactive oxygen species (ROS) generation. Furthermore, the protective effects of BTA07 were attenuated by inhibition of the PI3K/Akt signaling pathway with LY294002 in ARCMs. BTA07 protects ARCMs and isolated hearts from hypoxia-reperfusion partly by inhibiting oxidative stress and cardiomyocyte apoptosis.

Ischemic preconditioning protects the heart against ischemia-reperfusion injury in chronic kidney disease in both males and females

BACKGROUND

Uremic cardiomyopathy is a common cardiovascular complication of chronic kidney disease (CKD) characterized by left ventricular hypertrophy (LVH) and fibrosis enhancing the susceptibility of the heart to acute myocardial infarction. In the early stages of CKD, approximately 60% of patients are women. We aimed to investigate the influence of sex on the severity of uremic cardiomyopathy and the infarct size-limiting effect of ischemic preconditioning (IPRE) in experimental CKD.

METHODS

CKD was induced by 5/6 nephrectomy in 9-week-old male and female Wistar rats. Two months later, serum and urine laboratory parameters were measured to verify the development of CKD. Transthoracic echocardiography was performed to assess cardiac function and morphology. Cardiomyocyte hypertrophy and fibrosis were measured by histology. Left ventricular expression of A- and B-type natriuretic peptides (ANP and BNP) were measured by qRT-PCR and circulating BNP level was measured by ELISA. In a subgroup of animals, hearts were perfused according to Langendorff and were subjected to 35 min global ischemia and 120 min reperfusion with or without IPRE (3 × 5 min I/R cycles applied before index ischemia). Then infarct size or phosphorylated and total forms of proteins related to the cardioprotective RISK (AKT, ERK1,2) and SAFE (STAT3) pathways were measured by Western blot.

RESULTS

The severity of CKD was similar in males and females. However, CKD males developed more severe LVH compared to females as assessed by echocardiography. Histology revealed cardiac fibrosis only in males in CKD. LV ANP expression was significantly increased due to CKD in both sexes, however, LV BNP and circulating BNP levels failed to significantly increase in CKD. In both sexes, IPRE significantly decreased the infarct size in both the sham-operated and CKD groups. IPRE significantly increased the phospho-STAT3/STAT3 ratio in sham-operated but not in CKD animals in both sexes. There were no significant differences in phospho-AKT/AKT and phospho-ERK1,2/ERK1,2 ratios between the groups.

CONCLUSION

The infarct size-limiting effect of IPRE was preserved in both sexes in CKD despite the more severe uremic cardiomyopathy in male CKD rats. Further research is needed to identify crucial molecular mechanisms in the cardioprotective effect of IPRE in CKD.

Cardioprotective Effect of Novel Matrix Metalloproteinase Inhibitors

Background: We recently developed novel matrix metalloproteinase-2 (MMP-2) inhibitor small molecules for cardioprotection against ischemia/reperfusion injury and validated their efficacy in ischemia/reperfusion injury in cardiac myocytes. The aim of the present study was to test our lead compounds for cardioprotection in vivo in a rat model of acute myocardial infarction (AMI) in the presence or absence of hypercholesterolemia, one of the major comorbidities affecting cardioprotection. Methods: Normocholesterolemic adult male Wistar rats were subjected to 30 min of coronary occlusion followed by 120 min of reperfusion to induce AMI. MMP inhibitors (MMPI)-1154 and -1260 at 0.3, 1, and 3 µmol/kg, MMPI-1248 at 1, 3, and 10 µmol/kg were administered at the 25th min of ischemia intravenously. In separate groups, hypercholesterolemia was induced by a 12-week diet (2% cholesterol, 0.25% cholic acid), then the rats were subjected to the same AMI protocol and single doses of the MMPIs that showed the most efficacy in normocholesterolemic animals were tested in the hypercholesterolemic animals. Infarct size/area at risk was assessed at the end of reperfusion in all groups by standard Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining, and myocardial microvascular obstruction (MVO) was determined by thioflavine-S staining. Results: MMPI-1154 at 1 µmol/kg, MMPI-1260 at 3 µmol/kg and ischemic preconditioning (IPC) as the positive control reduced infarct size significantly; however, this effect was not seen in hypercholesterolemic animals. MVO in hypercholesterolemic animals decreased by IPC only. Conclusions: This is the first demonstration that MMPI-1154 and MMPI-1260 showed a dose-dependent infarct size reduction in an in vivo rat AMI model; however, single doses that showed the most efficacy in normocholesterolemic animals were abolished by hypercholesterolemia. The further development of these promising cardioprotective MMPIs should be continued with different dose ranges in the study of hypercholesterolemia and other comorbidities.

Renoprotective potential of exogen erythropoietin on experimental ruptured abdominal aortic aneurysm model: An animal study

Objective(s):

The aim of this study is to investigate the renoprotective effect of erythropoietin (EPO) on hypovolemic shock and ischemia/reperfusion (IR) injury on kidneys as end-organs in an experimentally-created ruptured abdominal aortic aneurysm (rAAA) model.

Materials and Methods:

Thirty anesthetized Sprague-Dawley male rats were randomized to sham ((Sh n:6) (Sh+EPO n:6)) or shock and I/R groups ((S/IR n:9) (S/IR+EPO n:9)). Additional surgical procedure except aortic exploration was not performed on Sh and Sh+EPO groups. 60 min of shock, 60 min of ischemia, and 120 min of reperfusion were applied on S/IR and S/IR+EPO groups. In the S/IR and S/IR+EPO groups, hemorrhagic shock, lower torso ischemia, and reperfusion were created. At the end of the shock period, saline solutions were separately and equally administered to Sh and S/IR groups, whereas 2000 U/kg EPO was intraperitoneally administered to Sh+EPO and S/IR+EPO groups. At the end of the experimental study, some biochemical and histological parameters were studied in serum and kidney tissues.

Results:

Biochemical parameters were all significantly increased in the S/IR group compared with the Sh group. These parameters were not statistically significantly different between S/IR+EPO and Sh+EPO groups. In histopathologic examination, EPO prevented high-grade injury.

Conclusion:

Our data indicate that EPO may have a renoprotective effect and reduce the systemic inflammatory response that resulted from shock and I/R in an experimental model of rAAA.

[Characterisation of the protective role of erythropoetin in a murine model of acute lung injury]

In addition to its role in erythropoiesis, erythropoietin (Epo) plays a role in tissue protection, which includes cardioprotective, nephroprotective and neuroprotective effects. The presence of Epo and its receptor (Epo-R) in pulmonary tissue also suggests a cytoprotective effect of Epo in the lung. Our project aims to document this role in a murine model under-expressing Epo. The obtained results will lead to a better understanding of the cytoprotective effects of Epo and will also give an appreciation of its beneficial effects in cases of lung injury.

Daily Consumption of Bilberry ( Vaccinium myrtillus L.) Extracts Increases the Absorption Rate of Anthocyanins in Rats

The effects of daily consumption of anthocyanins on bioavailability has remained unclear. In this study, we evaluated whether daily consumption affects the absorption rate of anthocyanins in rats when consumed during the active and sleep phase. Eighty rats were randomly divided into two groups. The first group consumed AIN-93G control diets, and the second group consumed AIN-93G diets containing 1% bilberry extract for 2 weeks. After 12 h fast, anthocyanins were not detected in plasma of rats. Bilberry extract (500 mg/kg body weight) was then orally administered at the beginning of the diurnal light period (ZT0, sleep phase) or at the end of the diurnal light period (ZT12, active phase). Blood concentrations of anthocyanins peaked 1 h after administration in both groups. Maximum blood concentration in rats that consumed bilberry extract daily (852 nM) was higher than that in control rats (630 nM) when the extract was administered at ZT0 but not at ZT12. Daily consumption of anthocyanins increases their absorption rate, but this effect is limited to the beginning of the sleep phase.

Pretreatment with Erythropoietin Attenuates Lung Ischemia/Reperfusion Injury via Toll-Like Receptor-4/Nuclear Factor-κB (TLR4/NF-κB) Pathway

Background

Lung ischemia/reperfusion injury (LIRI) is a medical problem featuring pulmonary dysfunction and damage. The present study aimed to investigate the protective effects of erythropoietin (EPO), which has been reported to be an anti-inflammatory agent, on LIRI through inhibiting the TLR-4/NF-κB signaling pathway.

Material/Methods

All rats were randomly divided into 3 groups (n=8): a control group, a vehicle+LIRI group, and an EPO+LIRI group. LIRI included 90-min ischemia and 120-min reperfusion, while RhEpo was administered (3 kU/kg) intraperitoneally 2 h before the operation. Levels of pulmonary inflammatory responses were examined by analyzing pulmonary permeability index (PPI), oxygenation index, histology, and expressions of inflammatory cytokines.

Results

Pretreatment with EPO significantly decreased lung W/D ratio, BALF leukocytes count and percentage, and PPI but increased oxygenation index compared with the LIRI group (P<0.05). More importantly, with EPO pretreatment there was less pathological damage compared with the vehicle group. Expressions of inflammatory cytokines (TNF-α, IL-6, and IL-1β) in the serum were significantly lower in the EPO group than in the LIRI group (P<0.05). In addition, gene expression and protein expression of TLR-4 and NF-κB were significantly inhibited with EPO pretreatment compared with the LIRI group (P<0.05).

Conclusions

Our study id the first to report that EPO protects lung injuries after LIRI through inhibiting the TLR4-NF-κB signaling pathway, which provides solid evidence for the use of EPO as a therapeutic agent for treating LIRI in the future.

Erythropoietin reduces collagen deposition after myocardial infarction but does not improve cardiac function

Myocardial remodeling includes inappropriate collagen deposition in the interstitium. Erythropoietin (EPO) may have cardioprotective effects. We aimed to assess the role of EPO on myocardial remodeling during the chronic phase. We studied 60 Wistar rats divided into the following groups: control (CT), control + EPO (CT + EPO), myocardial infarction + EPO (MI + EPO), and myocardial infarction (MI). The interstitial collagen volume fraction (ICVF) was quantified and echocardiography was performed. We quantified asymmetric dimethylarginine and glutathione by ELISA, and used real-time PCR to assess apoptosis and inflammation. Western blotting was used to evaluate inflammatory proteins and tissue inhibitors of metalloproteinases (TIMPs), and TUNEL staining was used to detect apoptosis. For matrix metalloproteinases (MMPs), we performed zymography. Parametric and nonparametric analyses were performed according to normality testing. ICVF was greater in MI groups (p < 0.001) and was attenuated by EPO (p = 0.05). The MMP-2 did not show any difference between groups. The TIMP-1 and TIMP-2 did not have difference between groups. The MI groups had worse fraction shortening (p < 0.001), without EPO protection (p = 0.666). The MI groups had increased left ventricle diastolic dimension (p < 0.001) without EPO attenuation (p = 0.79). EPO did not act on oxidative stress. Apoptosis and inflammation were not modulated by EPO. We concluded that EPO attenuated interstitial collagen accumulation, but did not protect from heart dilation or dysfunction.

Erythropoietin Reduces Insulin Resistance via Regulation of Its Receptor-Mediated Signaling Pathways in db/db Mice Skeletal Muscle

Erythropoietin (EPO) can reduce insulin resistance (IR) in adipocytes; however, it is unknown whether EPO can decrease IR in skeletal muscle. Here we investigated whether EPO could reduce IR in type 2 diabetic mouse skeletal muscle and its possible signaling mechanisms of action. Twelve-week-old db/db diabetic mice were employed in this study. Systemic use of EPO improved glucose profiles in type 2 diabetic mice after 4 and 8 weeks treatment. EPO up-regulated EPOR protein expression in skeletal muscle, and subsequently activated downstream signaling molecules such as JAK2, IRS-1, PI3K, AKT, and eNOS. We next constructed lentivirally-delivered shRNAs against EPOR and transfected skeletal muscle cells to knockdown EPOR. EPOR knockdown inhibited EPO induced JAK2, IRS-1, PI3K, AKT, eNOS signaling transduction, autophagy and Glut 4 translocation, as well as promoted apoptosis in skeletal muscle. Thus, EPO reduces skeletal muscle IR in type 2 diabetic mice via its specific receptor, EPOR. Possible mechanisms involved in its action may include increased autophagy and reduced apoptosis in type 2 diabetic skeletal muscles, which provides a new strategy for the treatment of IR.

Protective effects of cyclic helix B peptide on aristolochic acid induced acute kidney injury

BACKGROUND

Aristolochic acid (AA) injuries remain a serious condition associated with acute renal dysfunction. Herein, the effect and mechanism of a novel tissue protective peptide, cyclic helical B-peptide (CHBP) derived from erythropoietin, were investigated in a mice model.

METHODS

Mice were randomly divided into four groups, receiving the following treatments (1: saline; 2: AA 10mg/kg; 3: AA 10mg/kg +CHBP 4nmol/kg; 4: AA 10mg/kg +CHBP 8nmol/kg).

RESULTS

Blood urea nitrogen and serum creatinine was increased by AA but decreased by CHBP in a dose-dependent fashion. CHBP also significantly improved renal tubular injury and inflammatory infiltration, which was gradually increased by AA. Apoptotic cells, infiltrating inflammatory cells, and active caspase-3+ cells were greatly reduced by CHBP. In addition, CHBP inhibited caspase-3, 9 and improved bcl-2, bcl-xl protein expression in vivo.

CONCLUSION

Taken together, we demonstrated, for the first time, that CHBP effectively improved renal function and tissue damage caused by AA, which maybe through reducing caspase-3 activation, apoptosis, and inflammation.

Development of a new model for acute myocardial infarction in rabbits

The rabbit left anterior descending coronary artery is not macroscopically apparent; this often leads to failure in creation of an acute myocardial infarction (AMI) model. In order to devise a simple method with good reproducibility and high success rate for use as a rabbit AMI model, a new surgical technique was developed, in which the obtuse marginal (OM) branch of the left circumflex coronary artery was coagulated with an electric knife using a left parasternal approach. Four weeks after OM branch coagulation, an electrocardiogram (ECG), blood biochemistry analysis, echocardiographic measurements and pathologic analysis were performed. The left parasternal approach provided the surgeon clear visualization of the targeted blood vessel to accurately identify the proper site to occlude. The successful development of AMI was confirmed by ST segment elevation on the ECG, by high levels of AMI-related markers in blood samples, by cardiac functional damage reflected on echocardiographic images and by changes in pathological sections. Furthermore, an acceptable success rate and low mortality were achieved. Hence, this surgical technique was suggested to be a highly reliable and reproducible method to induce AMI in rabbits for the assessment of new therapeutic interventions or regenerative approaches.