B-Type Natriuretic Peptide Pretreatment Attenuates Heart Ischemia-Reperfusion Injury in Rats

Recombinant human brain natriuretic peptide attenuates ischemic brain injury in mice by inhibiting oxidative stress and cell apoptosis via activation of PI3K/AKT/Nrf2/HO-1 pathway

Ischemic stroke followed by cerebral artery occlusion is a main cause of chronic disability worldwide. Recombinant human brain natriuretic peptide (rhBNP) has been reported to alleviate sepsis-induced cognitive dysfunction and brain I/R injury. However, the function and molecular mechanisms of rhBNP in ischemic brain injury have not been clarified. For establishment of an animal model of ischemic brain injury, C57BL/6 mice were treated with middle cerebral artery occlusion (MCAO) surgery for 1 h and reperfusion for 24 h. After subcutaneous injection of rhBNP into model mice, neurologic deficits were assessed by evaluating behavior of mice according to Longa scoring system, and TTC staining was utilized to determine the brain infarct size of mice. The levels of oxidative stress markers, superoxide dismutase (SOD), catalase (CAT), glutathione (GSH) and malondialdehyde (MDA), were detected in hippocampal tissues of mice by corresponding kits. Cell apoptosis in hippocampus tissues was examined by TUNEL staining. Protein levels of antioxidant enzymes (HO-1 and NQO1) in cerebral cortex, apoptotic markers (Bax, Bcl-2, and cleaved caspase), and PI3K/AKT pathway-associated factors in hippocampus were tested by western blot analysis. The results revealed that injection of rhBNP decreased neurologic deficit scores, the percent of brain water content, and infarct volume. Additionally, rhBNP downregulated MDA level, upregulated the levels of SOD, CAT, and GSH in hippocampus of mice, and increased protein levels of HO-1 and NQO1 in the cortex. Cell apoptosis in hippocampus tissues of model mice was inhibited by rhBNP which was shown as the reduced TUNEL-positive cells, the decreased Bax, cleaved caspase-3, and cleaved caspase-9 protein levels, and the enhanced Bcl-2 protein level. In addition, rhBNP treatment activated the PI3K/AKT signaling pathway and upregulated the protein levels of HO-1 and NRF2. Overall, rhBNP activates the PI3K/AKT/HO-1/NRF2 pathway to attenuate ischemic brain injury in mice after MCAO by suppression of cell apoptosis and oxidative stress.

Natriuretic-like Peptide Lebetin 2 Mediates M2 Macrophage Polarization in LPS-Activated RAW264.7 Cells in an IL-10-Dependent Manner

Snake natriuretic peptide (NP) Lebetin 2 (L2) has been shown to improve cardiac function and reduce fibrosis as well as inflammation by promoting M2-type macrophages in a reperfused myocardial infarction (MI) model. However, the inflammatory mechanism of L2 remains unclear. Therefore, we investigated the effect of L2 on macrophage polarization in lipopolysaccharide (LPS)-activated RAW264.7 cells in vitro and explored the associated underlying mechanisms. TNF-α, IL-6 and IL-10 levels were assessed using an ELISA assay, and M2 macrophage polarization was determined by flow cytometry. L2 was used at non-cytotoxic concentrations determined by a preliminary MTT cell viability assay, and compared to B-type natriuretic peptide (BNP). In LPS-activated cells, both peptides reduced TNF-α and IL-6 release compared to controls. However, only L2 increased IL-10 release in a sustained manner and promoted downstream M2 macrophage polarization. Pretreatment of LPS-activated RAW264.7 cells with the selective NP receptor (NPR) antagonist isatin abolished both IL-10 and M2-like macrophage potentiation provided by L2. In addition, cell pretreatment with the IL-10 inhibitor suppressed L2-induced M2 macrophage polarization. We conclude that L2 exerts an anti-inflammatory response to LPS by regulating the release of inflammatory cytokines via stimulating of NP receptors and promoting M2 macrophage polarization through activation of IL-10 signaling.

Recombinant Human Brain Natriuretic Peptide Attenuates Myocardial Ischemia-Reperfusion Injury by Inhibiting CD4+ T Cell Proliferation via PI3K/AKT/mTOR Pathway Activation

Inflammation plays a major role in the development of myocardial ischemia-reperfusion (IR) injury. Recombinant human brain natriuretic peptide (rhBNP), a man-made version of a peptide that is elevated in heart failure, exhibits anti-inflammatory effects in various tissues. However, its role in myocardial IR injury remains unclear. In this study, we demonstrate that treatment with rhBNP provided protection for mice against myocardial IR injury as manifested by reduced infarct size and well-preserved myocardial, attenuated inflammatory infiltration and CD4⁺ T cell proliferation function, and inhibited expression of proinflammatory related genes. Furthermore, mechanistic studies revealed that rhBNP inhibited Jurkat T proliferation by promoting PI3K/AKT/mTOR phosphorylation. Collectively, our data suggest that the administration of rhBNP during IR injury could expand our understanding of the cardioprotective effects of rhBNP.

Involvement of brain natriuretic peptide signaling pathway in the cardioprotective action of sitagliptin

BACKGROUND

The current study is focusing on the role of brain natriuretic peptide (BNP), a substrate of dipeptidyl peptidase-4 (DPP-4) enzyme, and its signaling survival pathway in the cardioprotective mechanism of sitagliptin, a DPP-4 inhibitor.

METHODS

Male Wistar rats were randomized into 7 groups, sham, I/R, KT-5823 (selective protein kinase (PK) G inhibitor), 5-HD (selective mito-KATP channel blocker), sitagliptin (300mg/kg, po), sitagliptin+KT-5823, and sitagliptin+5-HD. Sitagliptin was administered for 3 days prior to induction of coronary I/R, while either KT-5823 or 5-HD was administered intravenously 5min before coronary ligation.

RESULTS

Pretreatment with sitagliptin provided significant protection against I/R injury as manifested by decreasing, percentage of infarct size, suppressing the elevated ST segment, reducing the increased cardiac enzymes, as well as DPP-4 activity and elevating both heart rate (HR) and left ventricular developed pressure (LVDP). However, the addition of either blocker to sitagliptin regimen reversed partly its cardioprotective effects. Although I/R increased BNP content, it unexpectedly decreased that of cGMP; nevertheless, sitagliptin elevated both parameters, an effect that was not affected by the use of the two blockers. On the molecular level, sitagliptin decreased caspase-3 activity and downregulated the mRNA levels of BNP, Bax, and Cyp D, while upregulated that of Bcl2. The use of either KT-5823 or 5-HD with sitagliptin hindered its effect on the molecular markers tested.

CONCLUSIONS

The results of the present study suggest that the cardioprotective effect of sitagliptin is mediated partly, but not solely, through the BNP/cGMP/PKG survival signaling pathway.

Nesiritide Therapy Is Associated With Better Clinical Outcomes Than Dobutamine Therapy in Heart Failure

To evaluate the therapeutic effects of dobutamine and nesiritide in the treatment of heart failure (HF), a meta-analysis of published studies was conducted. Computerized bibliographic databases in Chinese and English languages were carefully searched to identify the relevant literature. A total of 6 cohort studies were enrolled in current meta-analysis for statistical analyses. The effect of dobutamine and nesiritide in patients with HF was estimated by odds ratios (ORs) and 95% confidence interval (CI). Our results revealed a significantly higher survival rate in nesiritide-treated patients, compared with those treated with dobutamine (OR = 1.97; 95% CI, 1.43-2.71; P < 0.001). In addition, a lower readmission rate was also associated with the nesiritide-treated group in comparison with the dobutamine-treated group (OR = 1.96; 95% CI, 1.39-2.78; P < 0.001). A stratified analysis revealed that the subgroup of patients with HF treated with nesiritide showed higher survival outcomes than those patients with HF treated with dobutamine when follow-up period was greater than 6 months (OR = 1.70; 95% CI, 1.21-2.38; P = 0.002) but not under 6 months (P > 0.05). This indicated that nesiritide treatment had longer term benefits as well. Interestingly, based on the reason for readmission, a subgroup analysis of the HF subgroup and the "all-cause" subgroup showed that higher readmission rates were associated with dobutamine treatment in both subgroups (HF: OR = 2.71; 95% CI, = 1.51-4.83; P = 0.001; all-cause: OR = 1.64; 95% CI, 1.06-2.53; P = 0.026; respectively). Our results suggest that nesiritide therapy is associated with a lower in-hospital mortality rates and decreased readmission rates compared with dobutamine treatment in patients with HF.

Lebetin 2, a Snake Venom-Derived Natriuretic Peptide, Attenuates Acute Myocardial Ischemic Injury through the Modulation of Mitochondrial Permeability Transition Pore at the Time of Reperfusion

Cardiac ischemia is one of the leading causes of death worldwide. It is now well established that natriuretic peptides can attenuate the development of irreversible ischemic injury during myocardial infarction. Lebetin 2 (L2) is a new discovered peptide isolated from Macrovipera lebetina venom with structural similarity to B-type natriuretic peptide (BNP). Our objectives were to define the acute cardioprotective actions of L2 in isolated Langendorff-perfused rat hearts after regional or global ischemia-reperfusion (IR). We studied infarct size, left ventricular contractile recovery, survival protein kinases and mitochondrial permeability transition pore (mPTP) opening in injured myocardium. L2 dosage was determined by preliminary experiments at its ability to induce cyclic guanosine monophosphate (cGMP) release without changing hemodynamic effects in normoxic hearts. L2 was found to be as effective as BNP in reducing infarct size after the induction of either regional or global IR. Both peptides equally improved contractile recovery after regional IR, but only L2 increased coronary flow and reduced severe contractile dysfunction after global ischemia. Cardioprotection afforded by L2 was abolished after isatin or 5-hydroxydecanote pretreatment suggesting the involvement of natriuretic peptide receptors and mitochondrial K_ATP (mitoK_ATP) channels in the L2-induced effects. L2 also increased survival protein expression in the reperfused myocardium as evidenced by phosphorylation of signaling pathways PKCε/ERK/GSK3β and PI3K/Akt/eNOS. IR induced mitochondrial pore opening, but this effect was markedly prevented by L2 treatment. These data show that L2 has strong cardioprotective effect in acute ischemia through stimulation of natriuretic peptide receptors. These beneficial effects are mediated, at least in part, by mitoK_ATP channel opening and downstream activated survival kinases, thus delaying mPTP opening and improving IR-induced mitochondrial dysfunction.

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

Erythropoietin (EPO) has been shown to protect the heart against acute myocardial infarction in pre-clinical studies, however, EPO failed to reduce infarct size in clinical trials and showed significant safety problems. Here, we investigated cardioprotective effects of two selective non-erythropoietic EPO receptor ligand dimeric peptides (AF41676 and AF43136) lacking erythropoietic activity, EPO, and the prolonged half-life EPO analogue, darbepoetin in acute myocardial infarction (AMI) in rats. In a pilot study, EPO at 100U/mL significantly decreased cell death compared to vehicle (33.8±2.3% vs. 40.3±1.5%, p<0.05) in rat neonatal cardiomyocytes subjected to simulated ischemia/reperfusion. In further studies (studies 1-4), in vivo AMI was induced by 30min coronary occlusion and 120min reperfusion in male Wistar rats. Test compounds and positive controls for model validation (B-type natriuretic peptide, BNP or cyclosporine A, CsA) were administered iv. before the onset of reperfusion. Infarct size (IS) was measured by standard TTC staining. In study 1, 5000U/kg EPO reduced infarct size significantly compared to vehicle (45.3±4.8% vs. 59.8±4.5%, p<0.05). In study 2, darbepoetin showed a U-shaped dose-response curve with maximal infarct size-reducing effect at 5μg/kg compared to the vehicle (44.4±5.7% vs. 65.9±2.7%, p<0.01). In study 3, AF41676 showed a U-shaped dose-response curve, where 3mg/kg was the most effective dose compared to the vehicle (24.1±3.9% vs. 44.3±2.5%, p<0.001). The positive control BNP significantly decreased infarct size in studies 1-3 by approximately 35%. In study 4, AF43136 at 10mg/kg decreased infarct size, similarly to the positive control CsA compared to the appropriate vehicle (39.4±5.9% vs. 58.1±5.4% and 45.9±2.4% vs. 63.8±4.1%, p<0.05, respectively). This is the first demonstration that selective, non-erythropoietic EPO receptor ligand dimeric peptides AF41676 and AF43136 administered before reperfusion are able to reduce infarct size in a rat model of AMI. Therefore, non-erythropoietic EPO receptor peptide ligands may be promising cardioprotective agents.

Dobutamine Therapy is Associated with Worse Clinical Outcomes Compared with Nesiritide Therapy for Acute Decompensated Heart Failure: A Systematic Review and Meta-Analysis

BACKGROUND

Inotropes and natriuretic peptides are essential components of current therapeutic options for acute decompensated heart failure (ADHF). This systematic review examines the therapeutic effectiveness of dobutamine and brain natriuretic peptide, nesiritide, in reducing mortality and readmission rates for ADHF treatment.

METHODS

Published studies related to dobutamine and nesiritide therapy in ADHF were identified via an exhaustive search of scientific literature databases. The identified studies, published between 2002 and 2012, were carefully screened based on our predefined inclusion criteria. Selected studies were pooled, and odds ratios (ORs) and 95% confidence intervals (95% CI) for each outcome were calculated. Subgroup analysis was conducted to assess the influence of ethnicity on the study outcome.

RESULTS

Seven cohort studies were selected for this meta-analysis. These seven studies included 959 ADHF patients who underwent nesiritide treatment and 1748 ADHF patients who received dobutamine therapy. Our meta-analysis revealed a significantly lower survival rate in dobutamine-treated patients compared with nesiritide-treated patients (OR 0.48, 95% CI 0.36-0.63, P < 0.001). Additionally, a markedly higher readmission rate was associated with dobutamine treatment compared with nesiritide treatment (OR 0.52, 95% CI 0.36-0.73, P < 0.001). A stratified analysis based on ethnicity revealed a significantly lower survival in dobutamine-treated ADHF patients in Caucasian and mixed populations compared with nesiritide treatment (Caucasian: OR 0.60, 95% CI 0.38-0.94, P = 0.024; Mixed: OR 0.38, 95% CI 0.26-0.56, P < 0.001). However, a similar association was not detected in Asian populations (P = 0.738). Further, dobutamine-treated ADHF patients displayed higher readmission rates than did nesiritide-treated patients in both Caucasian and mixed-race populations (all P < 0.05).

CONCLUSIONS

Our study suggests that dobutamine therapy is associated with poorer outcomes, with higher in-hospital mortality rates and increased readmission rates compared with nesiritide therapy in ADHF patients. Thus, current treatment strategies need to be redesigned for better outcomes.

Retraction. rhBNP therapy can improve clinical outcomes and reduce in-hospital mortality compared with dobutamine in heart failure patients: a meta-analysis

AIMS

A meta-analysis was performed to compare the therapeutic outcomes in patients treated for heart failure (HF) with recombinant human brain natriuretic peptide (rhBNP) and dobutamine.

METHODS

PubMed, Embase and the Chinese Biomedical Database were exhaustively searched to identify studies relevant to this meta-analysis. Eight cohort studies were found suitable for inclusion. Data regarding trial validity, methodological processes and clinical outcomes were extracted.

RESULTS

Patients treated with rhBNP showed statistically significant reduction of in-hospital mortality and re-admission rates compared with the dobutamine treated patient group (both P < 0.05). Further, the rhBNP treated patient group showed higher survival outcomes, compared with dobutamine treated patients, when the post-treatment follow-up period was longer than 6 months (P < 0.05). Stratified analysis based on ethnicity showed a dramatic decrease of in-hospital mortality among mixed race HF patients receiving rhBNP treatment (P < 0.05), but such decreases were not statistically significant in Asian and Caucasian populations (both P > 0.05). On the other hand, re-admission rates were significantly lower in rhBNP treated Caucasian and mixed race populations (both P < 0.05). Notably, in rhBNP treated group, dose levels of 0.015 and 0.03 incrementally lowered the re-admission rates, displaying dose effect, and the re-admission rates at both rhBNP doses were significantly lower than the dobutamine treated group (both P < 0.05).

CONCLUSIONS

Our meta-analysis results suggested that rhBNP therapy is associated with lower in-hospital mortality and re-admission rates in HF patients compared to the dobutamine regimen. Nevertheless, large scale prospective, randomized trials are necessary to confirm these findings.