ABSTRACT
Objective:To investigate the protective role of extracellular signal-regulated kinase (ERK) signaling pathway in the process that vasonatrin peptide (VNP) reduces hepatic ischemia-reperfusion injury in rats.Methods:Twenty SD rats, weighting 200-250 g, were randomly divided into four groups and each group has five rats. The four groups were sham operation group (S group), ischemia-reperfusion group (I/R group), VNP group (V group) and PD98059+ VNP group (P+ V group). In the rat model of hepatic warm ischemia and reperfusion, the hepatic artery and portal vein of the left lobe and middle lobe of the liver were clamped with arterial clamp for 45 min followed by reperfusion for 120 min. In the V group, VNP (50 μg/kg) was injected 10 minutes before ischemia. In the P+ V group, PD98059 (2 mg/kg) was injected 20 min before VNP injection followed by VNP administration and I/R treatment. The serum levels of alanine amino transaminase (ALT), aspartate amino transferase (AST), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and the superoxide dismutase (SOD) in liver tissue homogenate and malondialdehyde (MDA) were measured. The histopathology of liver tissue was observed. The contents of p-ERK1/2 were detected by Western blot.Results:Compared with S group, in I/R group and P+ V group the serum levels of ALT [(489.65±11.22), (333.05±24.77) vs. (33.78±4.88) U/L], AST [(651.43±14.99), (503.18±21.48) vs. (154.84±12.32) U/L], TNF-α [(12.83±1.09), (9.64±0.57) vs. (2.11±0.11) ng/L], IL-1β [(7.19±0.62), (5.12±0.22) vs. (1.10±0.49) ng/L], MDA [(8.00±0.88), (5.60±1.01) vs. (2.76±1.29) μmol/mg] increased, while SOD [(54.89±10.60), (68.85±8.33) vs. (126.10±15.63) nmol/mg]decreased (all P<0.05). The histopathology of liver tissue revealed that liver structure damaged more seriously in I/R group and P+ V group. Western blot analysis showed that p-ERK1/2 decreased significantly in I/R group and P+ V group. Compared with I/R group, ALT, AST, MDA, TNF-α and IL-1β decreased significantly and SOD increased significantly in V group (all P<0.05). The histopathology of liver tissue revealed that liver structure was damaged slightly, and p-ERK1/2 increased significantly in V group compared with I/R group ( P<0.05). Conclusion:VNP can significantly reduce hepatic ischemia-reperfusion injury through activation of p-ERK1/2 signaling pathway and inhibition of hepatocyte inflammatory response.
ABSTRACT
Isoprenaline-induced cardiac hypertrophy can deteriorate to heart failure, which is a leading cause of mortality. Endogenous vasonatrin peptide (VNP) has been reported to be cardioprotective against myocardial ischemia/reperfusion injury in diabetic rats. However, little is known about the effect of exogenous VNP on cardiac hypertrophy. We further explored whether VNP attenuated isoprenaline-induced cardiomyocyte hypertrophy by examining the levels and activities of cGMP and PKG. In this study, we found that VNP significantly attenuated isoprenaline-induced myocardial hypertrophy and cardiac fibroblast activation in vivo. Moreover, VNP effectively halted the activation of apoptosis and oxidative stress in the isoprenaline-treated myocardium. VNP promoted superoxide dismutase (SOD) activity. Further study revealed that the protective effects of VNP might be mediated by the activity of the cGMP-PKG signaling pathway in vivo or in vitro, while the use of agonists and antagonists confirmed these results. Therefore, we demonstrated that the antiapoptosis and antioxidative stress effects of VNP depends on elevated cGMP-PKG signaling activity both in vivo and in vitro. These results suggest that VNP may be used in the treatment of myocardial hypertrophy.
Subject(s)
Atrial Natriuretic Factor/pharmacology , Cardiomegaly/drug therapy , Cardiotonic Agents/pharmacology , Myocardial Reperfusion Injury/drug therapy , Myocytes, Cardiac/drug effects , Animals , Animals, Newborn , Cardiomegaly/chemically induced , Cardiomegaly/pathology , Cyclic GMP/genetics , Humans , Isoproterenol/toxicity , Mice , Myocardial Reperfusion Injury/chemically induced , Myocardial Reperfusion Injury/pathology , Myocardium/metabolism , Myocardium/pathology , Myocytes, Cardiac/pathology , Oxidative Stress/drug effects , Primary Cell Culture , Rats , Signal Transduction/drug effects , Superoxide Dismutase/geneticsABSTRACT
Diabetes mellitus increases morbidity/mortality of ischemic heart disease. Although atrial natriuretic peptide and C-type natriuretic peptide reduce the myocardial ischemia-reperfusion damage in nondiabetic rats, whether vasonatrin peptide (VNP), the artificial synthetic chimera of atrial natriuretic peptide and C-type natriuretic peptide, confers cardioprotective effects against ischemia-reperfusion injury, especially in diabetic patients, is still unclear. This study was designed to investigate the effects of VNP on ischemia-reperfusion injury in diabetic rats and to further elucidate its mechanisms. The high-fat diet-fed streptozotocin-induced diabetic Sprague-Dawley rats were subjected to ischemia-reperfusion operation. VNP treatment (100 µg/kg iv, 10 min before reperfusion) significantly improved the instantaneous first derivation of left ventricle pressure (±LV dP/dtmax) and LV systolic pressure and reduced LV end-diastolic pressure, apoptosis index, caspase-3 activity, plasma creatine kinase (CK), and lactate dehydrogenase (LDH) activities. Moreover, VNP inhibited endoplasmic reticulum (ER) stress by suppressing glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP). These effects were mimicked by 8-bromine-cyclic guanosinemonophosphate (8-Br-cGMP), a cGMP analog, whereas they were inhibited by KT-5823, the selective inhibitor of PKG. In addition, pretreatment with tauroursodeoxycholic acid (TUDCA), a specific inhibitor of ER stress, could not further promote the VNP's cardioprotective effect in diabetic rats. In vitro H9c2 cardiomyocytes were subjected to hypoxia/reoxygenation and incubated with or without VNP (10(-8) mol/l). Gene knockdown of PKG1α with siRNA blunted VNP inhibition of ER stress and apoptosis, while overexpression of PKG1α resulted in significant decreased ER stress and apoptosis. VNP protects the diabetic heart against ischemia-reperfusion injury by inhibiting ER stress via the cGMP-PKG signaling pathway. These results suggest that VNP may have potential therapeutic value for the diabetic patients with ischemic heart disease.
Subject(s)
Atrial Natriuretic Factor/pharmacology , Diabetes Mellitus, Experimental/metabolism , Heart Ventricles/drug effects , Myocardial Reperfusion Injury/metabolism , Animals , Apoptosis , Atrial Natriuretic Factor/therapeutic use , Carbazoles/pharmacology , Caspase 3/metabolism , Cell Hypoxia , Cell Line , Creatine Kinase/blood , Cyclic GMP/analogs & derivatives , Cyclic GMP/pharmacology , Cyclic GMP-Dependent Protein Kinase Type I/antagonists & inhibitors , Cyclic GMP-Dependent Protein Kinase Type I/genetics , Cyclic GMP-Dependent Protein Kinase Type I/metabolism , Diabetes Mellitus, Experimental/complications , Endoplasmic Reticulum Stress , Heart Ventricles/metabolism , Heart Ventricles/pathology , Male , Myocardial Reperfusion Injury/complications , Myocardial Reperfusion Injury/drug therapy , Myocytes, Cardiac/drug effects , Myocytes, Cardiac/metabolism , Rats , Rats, Sprague-Dawley , Taurochenodeoxycholic Acid/pharmacology , Transcription Factor CHOP/metabolism , Ventricular Function/drug effectsABSTRACT
Vasonatrin peptide (VNP) is an active cardiovascular factor and a novel synthetic natriuretic peptide with unknown natriuretic peptide receptor (NPR) binding properties. We set out to design binding models of NPRA/VNP and NPRB/VNP, and then assessed their recognition and binding affinities using molecular dynamics. Molecular dynamics analysis indicated decreases in the values of Van der Waals, electrostatic energy and potential energy of NPRB/VNP compared to NPRA/VNP. There was a 25% increase in H-bond formation between VNP and NPRB. The cGMP stimulated by VNP in NPRB-transfected HEK-293 cells was 11-fold higher than that of NPRA. We therefore demonstrated that VNP binds with both NPRA and NPRB, but with a preference for NPRB.
