Neuregulin-1 promotes mitochondrial biogenesis, attenuates mitochondrial dysfunction, and prevents hypoxia/reoxygenation injury in neonatal cardiomyocytes.

Neuregulin-1 (NRG-1)/erythroblastic leukaemia viral oncogene homologues (ErbB) pathway activation plays a crucial role in regulating the adaptation of the adult heart to physiological and pathological stress. In the present study, we investigate the effect of recombined human NRG-1 (rhNRG-1) on mitochondrial biogenesis, mitochondrial function, and cell survival in neonatal rat cardiac myocytes (NRCMs) exposed to hypoxia/reoxygenation (H/R). The results of this study showed that, in the H/R-exposed NRCMs, mitochondrial biogenesis was impaired, as manifested by the decrease of the expression of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) and mitochondrial membrane proteins, the inner membrane (Tim23), mitofusin 1 (Mfn1), and mitofusin 2 (Mfn2). RhNRG-1 pretreatment effectively restored the expression of PGC-1α and these membrane proteins, upregulated the expression of the anti-apoptosis proteins Bcl-2 and Bcl-xL, preserved the mitochondrial membrane potential, and attenuated H/R-induced cell apoptosis. Blocking PGC-1 expression with siRNA abolished the beneficial role of rhNRG-1 on mitochondrial function and cell survival. The results of the present study strongly suggest that NRG-1/ErbB activation enhances the adaption of cardiomyocytes to H/R injury via promoted mitochondrial biogenesis and improved mitochondrial homeostasis. SIGNIFICANCE OF THE STUDY: The results of this research revealed for the first time the relationship between neuregulin-1 (NRG-1)/erythroblastic leukaemia viral oncogene homologues (ErbB) activation and mitochondrial biogenesis in neonatal cardiomyocytes and verified the significance of this promoted mitochondrial biogenesis in attenuating hypoxia/reoxygenation injury. This finding may open a new field to further understand the biological role of NRG-1/ErbB signalling pathway in cardiomyocyte.

Transanal endorectal pull-through procedure versus transabdominal surgery for Hirschsprung disease: A systematic review and meta-analysis.

OBJECTIVE: To analyze the clinical results of transanal endorectal pull-through (TERPT) and transabdominal approach (TAB) in the treatment of Hirschsprung disease. METHODS: We searched all publications in the PubMed, MEDLINE, EMBASE, and Cochrane library databases between January 2003 and November 2018. The study included randomized controlled trials (RCTs) and observational clinical studies (OCSs), to compare the surgery duration, length of postoperative hospital stay, incidence of postoperative incontinence/soiling, constipation, and enterocolitis between the TERPT and TAB groups. Mantel-Haenszel method was used for continuous variables, the combined odds ratios (ORs) and 95% confidence intervals (CIs) for dichotomous variables were used. RESULTS: In the 87 studies, we include 1 case of RCTs and 9 cases of OCSs. Including 392 cases of TERPT and 332 cases of TAB groups. TERPT has a short postoperative hospitalization [mean difference (MD) = -6.74 day; 95% CIs; -13.26 to -0.23; P = .04], and a low incidence of postoperative incontinence (ORs = 0.54; 95% CIs, 0.35-0.83; P = .006) and constipation (ORs = 0.50; 95% CIs, 0.28-0.90; P = .02). There was no difference in duration of surgery (MD = -30.59 min; 95% CIs, -98.01-36.83; P = .37) and incidence of postoperative enterocolitis (ORs = 0.78; 95% CIs, 0.53-1.17; P = .23). CONCLUSION: TERPT is superior to TAB in terms of hospitalization time, postoperative incontinence, and constipation. However, there are still a large number of RCTs to verify, and more trials are expected to be testified in the future.

[Impact of loop diuretics on blood sodium in patients hospitalized for heart failure].

OBJECTIVE: To observe the level of blood sodium in patients hospitalized for heart failure with water-sodium retention treated with loop diuretics and risk factors of low blood sodium. METHODS: We selected 1 378 acute decompensated heart failure patients who visited Anzhen Hospital, and they are treated with loop diuretics, 259 patients with weight loses more than 1 kg in one week was enrolled in the final analysis, and divided into 3 groups: Group A (weight reduction between 1-3 kg), Group B (weight reduction between 3-5 kg) and Group C (weight reduction over 5 kg). Blood sodium, creatinine and uric acid were compared among groups and risk factors of low blood sodium were analyzed. RESULTS: Blood sodium was similar before and post loop diuretics treatment in Group A, and reduced in group B ((138.28 ± 3.73) mmol/L vs. (139.34 ± 3.66) mmol/L, P < 0.05) and in Group C((137.60 ± 4.07) mmol/L vs. (139.44 ± 4.12) mmol/L, P < 0.05). Forty-six (17.8%) patients developed hyponatremia post loop diuretics treatment. Duration of loop diuretics use was the independent risk infector for hyponatremia (OR = 1.191, 95%CI 1.010-1.385). CONCLUSIONS: Loop diuretics use is safe for treating hospitalized patients for heart failure with water-sodium retention and the risk of developing hyponatremia is low. Duration of loop diuretics use is the independent risk factor of hyponatremia.

Neuregulin-1 protects myocardial cells against H2 O2 -induced apoptosis by regulating endoplasmic reticulum stress.

Neuregulin-1 (NRG-1) is a stress-mediated growth factor secreted by cardiovascular endothelial cells and provides the protection to myocardial cells, but the underlying mechanisms are not fully understood. This study aimed to demonstrate that NRG-1 protects myocardial cells exposed to oxidative damage by regulating endoplasmic reticulum (ER) stress. Neonatal rat cardiac myocytes (NRCMs) were isolated and treated with H2 O2 as a cellular model of ER stress. NRCMs were pretreated with different concentrations of NRG-1. We found that NRG-1 increased the viability and reduced the apoptosis of NRCMs treated by H2 O2 . Moreover, NRG-1 reduced lactate dehydrogenase level, increased superoxide dismutase activity and decreased malondialdehyde content in NRCMs treated by H2 O2 . Finally, we demonstrated that NRG-1 alleviated ER stress and decreased CHOP and GRP78 protein levels in NRCMs treated by H2 O2 . Taken together, these data indicate that NRG-1 relieves oxidative and ER stress in NRCMs and suggest that NRG-1 is a promising agent for cardioprotection.

Long term outcomes of saphaneous vein graft intervention in elderly patients with prior coronary artery bypass graft.

OBJECTIVES: To investigate the procedure characteristics and long term follow-up of percutaneous coronary intervention (PCI) for saphaneous vein graft (SVG) lesions in the elderly patients. METHODS: From December 2005 to December 2011, 84 graft lesions were treated percutaneously. Seventeen were located at proximal anastomosis, 48 were located at SVG body, 19 were located at distal anastomosis. Primary endpoint was defined as major adverse cardiovascular events (MACE, composite of cardiac death, target vessel revascularization, acute myocardial infarction). RESULTS: The graft age was 6.7 ± 4.0 years. Most anastomosis lesions (80.0%) presented within one year post coronary artery bypass grafting (CABG). Proximal anastomosis lesion had the lowest successful rate for PCI compared with graft body and distal anastomosis lesions (70.6% vs. 91.7%, 79.0%, P < 0.05). The distal embolic protection device was used in 19.1% of patients, most frequently used in body graft PCI (29.2%, P < 0.01). The diameter of the stent was smallest in distal anastomosis group (2.9 ± 0.4 mm, P < 0.05). The highest post dilatation pressure was required in the proximal anastomosis (17.8 ± 2.7 atm, P < 0.05). The patients were followed up for 24.3 ± 16.9 months. MACE occurred in 18.57% of patients. Incidence of MACE was highest among proximal anastomosis PCI (47.1% vs. body graft PCI 16.7%, distal anastomosis PCI 21.1%; P < 0.05). Old myocardial infarction was the predictive factor for the poor clinical outcomes (P = 0.04). CONCLUSIONS: PCI of SVG lesions is feasible with lower success rate. PCI of ostial graft anastomosis lesions had the lowest procedure success rate and highest MACE rate compared with graft body and distal anastomosis lesions. Old myocardial infarction was a predictive factor of poor outcomes.

Neuregulin-1 suppresses cardiomyocyte apoptosis by activating PI3K/Akt and inhibiting mitochondrial permeability transition pore.

Neuregulin-1 (NRG-1) has been shown to attenuate cardiomyocyte apoptosis but the underlying signaling mechanism remains elusive. In this study, we focused on mitochondrial permeability transition pore (mPTP) opening and PI3K/Akt pathway to investigate the effects of NRG-1 on oxidative stress-induced apoptosis of cardiomyocyte. Human cardiac myocytes and neonatal rat cardiac myocytes were exposed to hydrogen peroxide with or without pre-treatment with recombinant human neuregulin-1 (rhNRG-1). Cell apoptosis and mPTP opening were assayed by flow cytometry and confocal microscopy. The activation of Akt was detected by western blot analysis. The results showed that H(2)O(2) induced cardiomyocyte apoptosis and activated mPTP. rhNRG-1 inhibited mPTP and activated Akt in the presence of H(2)O(2) and further protected the cells from H(2)O(2)-induced apoptosis. However, rhNRG-1 failed to inhibit mPTP opening and cell apoptosis in the presence of PI3K inhibitor LY294002. Taken together, these findings suggest that NRG-1 activates PI3K/Akt signaling and inhibits mPTP opening, and downstream apoptotic events in cardiac myocytes subjected to oxidative stress.

Coronary stenting versus bypass surgery in heart failure patients with preserved ejection fraction.

BACKGROUND: The optimal revascularization strategy in patients with heart failure with preserved ejection fraction (HFPEF) remains unclear. The aim of the present study was to compare the effects of percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) in patients with HFPEF. METHODS: From July 2003 through September 2005, a total of 920 patients with coronary artery disease (CAD) and HFPEF (ejection fraction ≥ 50%) underwent PCI (n = 350) or CABG (n = 570). We compared the groups with respect to the primary outcome of mortality, and the secondary outcomes of main adverse cardiac and cerebral vascular events (MACCE), including death, myocardial infarction, stroke and repeat revascularization, at a median follow-up of 543 days. RESULTS: In-hospital mortality was significantly lower in the PCI group than in the CABG group (0.3% vs. 2.5%, adjusted P = 0.016). During follow-up, there was no significant difference in the two groups with regard to mortality rates (2.3% vs. 3.5%, adjusted P = 0.423). Patients receiving PCI had higher MACCE rates as compared with patients receiving CABG (13.4% vs. 4.0%, adjusted P < 0.001), mainly due to higher rate of repeat revascularization (adjusted P < 0.001). Independent predictors of mortality were age, New York Heart Association (NYHA) class and chronic total occlusion. CONCLUSION: Among patients with CAD and HFPEF, PCI was shown to be as good as CABG with respect to the mortality rate, although there was a higher rate of repeat revascularization in patients undergoing PCI.

Neuregulin-1 attenuates mitochondrial dysfunction in a rat model of heart failure.

BACKGROUND: Mitochondrial dysfunction plays a pivotal role in the progression of left ventricular (LV) remodeling and heart failure (HF). Recombinant human neuregulin-1 (rhNRG-1) improves cardiac function in models of experimental HF and in clinical trials; however, its impact on mitochondrial function during chronic HF remains largely unknown. The purpose of this study was to investigate whether rhNRG-1 could attenuate the functional and structural changes that occur in cardiac mitochondria in a rat model of HF induced by myocardial infarction. METHODS: Sixty adult rats underwent sham or coronary ligation to induce HF. Four weeks after ligation, 29 animals with LV ejective fraction ≤ 50% were randomized to receive either vehicle or rhNRG-1 (10 µg×kg(-1)×d(-1), I.V.) for 10 days, another 12 sham-operated animals were given no treatment. Echocardiography was used to determine physiological changes. Mitochondrial membrane potential (MMP), respiratory function and tissue adenosine triphosphate (ATP) production were analyzed. Cytochrome c expression and cardiomyocyte apoptosis were determined. Oxidative stress was evaluated by reactive oxygen species production using fluorescence assays and gene expression of glutathione peroxidase measured by real-time quantitative PCR. RESULTS: Compared with sham-operated animals, vehicle treated HF rats exhibited severe LV remodeling and dysfunction, significant mitochondrial dysfunction, increased mitochondrial cytochrome c release, increased myocyte apoptosis and enhanced oxidative stress. Short-term treatment with rhNRG-1 significantly attenuated LV remodeling and cardiac function. Concomitant with this change, mitochondrial dysfunction was significantly attenuated; with ATP production, MMP and respiratory function restored, cytochrome c release and apoptosis inhibited, and oxidative stress reduced. CONCLUSION: The present study demonstrated that rhNRG-1 can significantly improve LV remodeling and cardiac function in the failing heart, this beneficial effect is related to reducing mitochondrial dysfunction, myocyte apoptosis and oxidative stress.

[Impact of anemia on long-term outcome in elderly patients with acute coronary syndrome undergoing percutaneous coronary interventions].

OBJECTIVE: To assess the impact of pre-procedure anemia on the long-term mortality in elderly patients with acute coronary syndrome (ACS) after percutaneous coronary interventions. METHODS: A total of 1014 ACS patients (≥ 60 years of age) with hemoglobin data and without previous treatment with thrombolytic agents and without end-stage renal failure before the interventional procedure were included. Patients were classified as anemia using the definition of World Health Organization: hemoglobin < 130 g/L in men, and < 120 g/L in women. A total of 253 patients were anemia. The clinical features of patients with and without anemia and association of pre-procedure anemia with long-term mortality were analyzed. RESULTS: Incidence of diabetes and serum creatinine level were significantly higher in anemia patients than in non-anemia patients while systolic blood pressure and low-density lipoprotein cholesterol were significantly lower in anemia patients than in non-anemia patients (P < 0.05 or P < 0.01). The patients were followed up for 528 (178 - 675) days. After adjustment for potential co-variants in Cox regression analysis, pre-procedure anemia was associated with a significantly higher long-term mortality (RR: 3.293, 95%CI: 1.431 - 7.578, P < 0.01). CONCLUSION: Pre-procedure anemia is an independent predictor of long-term mortality in elderly patients with acute coronary syndrome after percutaneous coronary interventions.

Factors influencing recovery of left ventricular structure in patients with chronic heart failure.

BACKGROUND: Angiotensin converting enzyme (ACE) inhibitors and ß-blockers (ßB) have beneficial effects on left ventricular (LV) remodeling, alleviate symptoms and reduce morbidity and mortality in patients with chronic heart failure (CHF). However the correlation between the d osages of ACE inhibitors, ßB, and recovery of LV structure remains controversial. Clinical factors associated with recovery of normal ventricular structure in CHF patients receiving medical therapy are poorly defined. Here we aimed to identify variables associated with recovery of normal or near-normal structure in patients with CHF. METHODS: We recruited 231 consecutive CHF outpatients, left ventricular ejection fraction (LVEF) ≤ 40% and left ventricular end diastolic diameter (LVEDD) > 55/50 mm (male/female), who were receiving optimal pharmacotherapy between January 2001 and June 2009, and followed them until December 31, 2009. They were divided into three groups according to LVEDD and whether they were still alive at final follow-up: group A, LVEDD ≤ 60/55 mm (male/female); group B, LVEDD > 60/55 mm (male/female); and group C, those who died before final follow-up. Apart from group C, univariate analysis was performed followed by Logistic multivariate analysis to determine the predictors of recovery of LV structure. RESULTS: A total of 217 patients completed follow-up, and median follow-up time was 35 months (range 6 - 108). Twenty-five patients died during that period; the all-cause mortality rate was 11.5%. Group A showed clinical characteristics as follows: the shortest duration of disease and shortest QRS width, the lowest N-terminal brain natriuretic peptide (NT-proBNP) at baseline, the highest dose of ßB usage, the highest systolic blood pressure (SBP), diastolic blood pressure (DBP) and the lowest New York Heart Association (NYHA) classification, serum creatinine, uric acid, total bilirubin and NT-proBNP after treatment. Logistic multivariate analysis was performed according to recovery or no recovery of LV structure. Data showed that LVEF at follow-up (P = 0.013), mitral regurgitation at baseline (P = 0.020), LVEDD at baseline (P = 0.031), and ßB dosage (P = 0.041) were independently associated with recovery of LV diameter. CONCLUSION: Our study suggests that four clinical variables may predict recovery of LV structure to normal or near-normal values with optimal drug therapy alone, and may be used to discriminate between patients who should receive optimal pharmacotherapy and those who require more aggressive therapeutic interventions.

[Optimal pharmacotherapy according to guideline improved prognosis of outpatients with chronic heart failure].

OBJECTIVE: To evaluate the effects of optimal pharmacotherapy according to guideline on treating chronic heart failure(CHF) in real world clinical practice. METHODS: A total of 231 consecutive outpatients with reduced left ventricular ejection fraction (LVEF ≤ 40%) and enlarged left ventricular end diastolic diameter (male > 55 mm, female > 60 mm) were recruited from January 2001 to June 2009. All patients were treated with optimal pharmacotherapy according to guideline recommendations and followed up to December 31, 2009. Mortality, rehospitalization and changes of heart size and cardiac function at baseline and at the end of follow-up period were analyzed. RESULTS: (1) 14 patients were lost during follow-up (6.1%), and follow-up was complete in 217 patients (93.9%). 97.2% and 98.2% patients were prescribed angiotensin converting enzyme (ACE) inhibitors and ß-blockers (ßB). Combined of ACE inhibitors and BB use was applied in 95.3% patients. The target dose of ACE inhibitors and ßB were reached in 50.7% and 37.3% patients. (2) Lower mortality and re-hospitalization rates were observed in this cohort: all-cause morality, average annual mortality was 11.5% and 3.9% respectively. Re-hospitalization rate was 27.6%. (3) Left ventricular end-diastolic diameter (LVEDD) decreased from (68.2 ± 7.2) mm to (62.2 ± 9.6) mm. LVEDD value was normal or near normal (male ≤ 60 mm, female ≤ 55 mm) in 43.2% patients. LVEF improved form (29.8 ± 7.5)% to (43.3 ± 11.8)%, LVEF was > 40% in 60.4% patients, LVEF was ≤ 40% but increased ≥ 10% after treatment in 22.9% patients. CONCLUSION: Optimal pharmacotherapy according to guideline can improve prognosis of outpatients with CHF.

Prognostic value of baseline C-reactive protein levels in patients undergoing coronary revascularization.

BACKGROUND: C-reactive protein (CRP) is a lowly expressed marker for inflammatory response. This study aimed to evaluate the prognostic value of baseline CRP levels in patients undergoing coronary revascularization in the context of modern medical treatment. METHODS: This was a retrospective study in a single center. Four hundred and fourteen patients were enrolled, who underwent coronary revascularization and received adequate medication for secondary prevention of coronary heart disease. The study compared the follow-up clinical outcomes between high level CRP group (CRP > 5 mg/L) and low level one. The median follow-up time was 551 days. RESULTS: Compared with low CRP group, the relative risk (RR) of the major adverse cardiovascular and cerebral events (MACCE) in high CRP group was 5.131 (95%CI: 1.864-14.123, P = 0.002). There were no significant differences in death, myocardial infarction and stroke during the follow-up between two groups, but a higher risk of re-revascularization was found in high CRP group (RR 6.008, 95%CI: 1.667-21.665, P = 0.006). Cox regression analysis showed that only CRP level could contribute to MACCE during the follow-up. MACCE-free rate was much lower in high CRP group (Kaplan-Meier log-rank P < 0.001). CONCLUSION: In the context of modern medical treatment, the baseline level of CRP is an independent predictor for long-term prognosis in patients with coronary revascularization.

[Impact of overweight on clinical outcomes in patients undergoing coronary revascularization].

OBJECTIVES: To determine the impact of BMI on clinical outcome in patients with heart failure underwent coronary revascularization. METHODS: The DESIRE-plus (Drug-Eluting Stent Impact on Revascularization-plus) was a single-center registry of coronary revascularization in our institution between July 1, 2004 and September 30, 2005. We analyzed heart failure patients with the complete data of body mass index (BMI) data from the DESIRE-plus trial and grouped them by BMI (normal BMI group, BMI < 24; overweight group, BMI 24-27.9; obesity group, BMI > or = 28). Total mortality, cardiac mortality and MACCE including death, neo-myocardial infarction, stroke, re-revascularization were recorded. We evaluated risk estimates for three bodyweight groups. RESULTS: 1010 patients were included in the study (295 in normal BMI group; 495 in overweight group and 220 obesity group). Median follow-up was 542 days. Overweight and obese patients were younger (59.3 +/- 10.14 years, 58.6 +/- 10.30 years vs 62.6 +/- 9.93 years, P < 0.01) and had a significantly higher incidence of hypertension (61.2, 66.8% vs 52.5%, P = 0.017), stable angina pectoris (21.2%, 23.7% vs 17.0%, P = 0.05) and higher triglyceride [(1.90 +/- 1.05) mmol/L, (2.10 +/- 1.12) mmol/L vs (1.48 +/- 0.92) mmol/L, P < 0.01)], fasting blood glucose level [(6.07 +/- 2.09) mmol/L, (5.96 +/- 1.53) mmol/L vs (5.67 +/- 1.92) mmol/L, P = 0.021), blood creatinine (84.9 +/- 21.7) micromol/L, (90.2 +/- 30.9) micromol/L vs (82.2 +/- 25.8) micromol/L, P = 0.002] compared with normal BMI patients. Multivariate Cox regression model showed obese patients had an decreased hazard risk (HR) for total mortality (0.285, 95%CI 0.104 - 0.777) and MACCE (0.596, 95%CI 0.401 - 0.885) compared with those for patients with normal BMI, overweight patients had no increased risk for total mortality (HR 0.769, 95%CI 0.442 - 1.338) and MACCE (0.998, 95%CI 0.754 - 1.322), there was hardly any significantly difference in cardiac mortality between three groups (P = 0.223). CONCLUSION: There were more risk factors in heart failure patients with coronary heart disease complicated with obesity or overweight, but the prognosis after revascularization of them is at least no worse than the normal weight coronary heart disease patients.

A Phase II, randomized, double-blind, multicenter, based on standard therapy, placebo-controlled study of the efficacy and safety of recombinant human neuregulin-1 in patients with chronic heart failure.

OBJECTIVES: The purpose of this study was to assess the safety and efficacy of recombinant human neuregulin-1 (rhNRG-1) in chronic heart failure (CHF) patients. BACKGROUND: Neuregulin-1 plays important roles in maintaining cardiomyocyte structure and cardiac pumping functionality and physiology. Previously, rhNRG-1 was proven to be effective in treating heart failure in animals by reducing end-diastolic volume (EDV) and end-systolic volume (ESV) and increasing left ventricular ejection fraction (LVEF%). METHODS: A total of 44 CHF patients designated as New York Heart Association functional class II or III were enrolled in a double-blind, randomized manner and treated with a placebo or rhNRG-1 (0.3, 0.6, or 1.2 microg/kg/day) for 10 days, in addition to standard therapies. The follow-up period was 90 days; left ventricular function and structure measured by magnetic resonance imaging were the primary end points. RESULTS: Although not statistically different from placebo, the LVEF% was significantly increased by 27.11 +/- 31.12% (p = 0.009) at day 30 after rhNRG-1 treatment in the 0.6-microg/kg group, whereas it was only increased 5.83 +/- 25.75% in the placebo group (p = 0.49). In addition, there were decreases in ESV (-11.58 +/- 12.74%, p = 0.002) and EDV (-5.64 +/- 10.03%, p = 0.05) in the 0.6-microg/kg/day group at day 30; more importantly, both ESV and EDV levels continued to decrease at day 90 (-20.79 +/- 17.03% and -14.03 +/- 13.17%, respectively), accompanied by a sustained increase in LVEF%. This suggests that short-term treatment with rhNRG-1 results in a long-term reversal of remodeling. The effective dose was proven to be tolerable and safe for CHF patients. CONCLUSIONS: rhNRG-1 improved the cardiac function of CHF patients by increasing the LVEF% and showed the capability of antiremodeling by decreasing ESV and EDV compared with pre-treatment. (A Randomized, Double-Blind, Multi-Center, Placebo Parallel controlled, Standard Therapy Based Phase II Clinical Trial to Evaluate the Efficacy and Safety of Recombinant Human Neuregulin-1 for Injection in Patients with Chronic Heart Failure; ChiCTR-TRC-00000414).

Neuregulin-1 preconditioning protects the heart against ischemia/reperfusion injury through a PI3K/Akt-dependent mechanism.

BACKGROUND: Neuregulin-1 (NRG-1), the ligand of the myocardial ErbB receptor, is a protein mediator with regulatory actions in the heart. This study investigated whether NRG-1 preconditioning has protective effects on myocardial ischemia/reperfusion (I/R) injury and its potential mechanism. METHODS: We worked with an in vivo rat model with induced myocardial ischemia (45 minutes) followed by reperfusion (3 hours). NRG-1 message was detected in the heart using RT-PCR and the protein levels of NRG-1 and ErbB4 were detected by Western blotting analysis. Infarct size was assessed using the staining agent triphenyltetrazolium chloride and cardiac function was continuously monitored. The levels of creatine kinase and lactate dehydrogenase in plasma were analyzed to assess the degree of cardiac injury. The extent of cardiac apoptosis was evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay and by Western blotting analysis of cleaved caspase-3. We examined the phosphorylation of Akt in the myocardium and the effect of PI3K/Akt inhibition on NRG-1-induced cardioprotection. RESULTS: Transcription and expression of NRG-1 and phosphorylation of its ErbB4 receptor were significantly upregulated in the I/R hearts. NRG-1 pretreatment reduced the infarct size following cardiac I/R in a concentration-dependent manner with an optimal concentration of 4 µg/kg in vivo. NRG-1 pretreatment with 4 µg/kg, i.v. markedly reduced the plasma creatine kinase and lactate dehydrogenase levels. Pretreatment with NRG-1 also significantly reduced the percentage of TUNEL positive myocytes and the level of cleaved caspase-3 in the I/R hearts. Pretreatment with NRG-1 significantly increased phosphorylation of Akt following I/R. Furthermore, the cardioprotective effect limiting the infarct size that was induced by NRG-1 was abolished by co-administration of the PI3K inhibitor LY294002. CONCLUSIONS: The concentration of NRG-1, a new autacoid, was rapidly upregulated after myocardial I/R. NRG-1 preconditioning has cardioprotective effects against I/R injury through a PI3K/Akt-dependent mechanism in vivo.