Manganese and the heart: acute cardiodepression and myocardial accumulation of manganese

The aim of study was to assess acute effects of the divalent manganese ion (Mn²⁺) in an intact but isolated heart preparation. Rat hearts were perfused in the Langendorff mode at constant flow rate. Left ventricular (LV) developed pressure (LVDP), LV pressure first derivatives (LVdp/dt max and min), heart rate (HR) and aortic pressure (AoP) were recorded. Ventricular contents of high energy phosphate compounds (HEP) and Mn metal were measured at the end of experiment. Infusion of MnCl₂ for 5 min with perfusate concentrations 1–3000 μM induced an immediate depression of contractile function at and above 30 μM and negative chronotropy at and above 300 μM . These EC₅₀ values were found (μM ): LVDP 250; LVdp/dt max 160; LVdp/dp min 120; HR 1000; and increase in AoP 80. Recovery of function during a 14 min washout period was rapid and extensive, except for Mn²⁺ 3000 μM . Somewhat unexpected, Mn²⁺ 30–1000 μM raised coronary vascular resistance up to about twice the control level, whereas the vasoconstrictory response was overcome at 3000 μM . Mn²⁺ 3000 μM reduced tissue HEP. Ventricular Mn content rose stepwise for perfusate Mn²⁺ above 1 μM up to about 55 times the control level for perfusate Mn²⁺ 3000 μM . It is concluded that: acute effects of Mn²⁺ like depression of contractility and rate is rapidly reversible; and rat hearts accumulate and buffer large amounts of Mn²⁺ without affecting cardiac function or energy metabolism in the acute stage.     

神经调节蛋白1对冠状动脉平滑肌细胞表达血管生成因子的影响

目的:探讨神经调节蛋白1(neuregulin-1,NRG-1)对人冠状动脉平滑肌细胞(HCASMCs)表达血管生成因子的影响。方法:培养HCASMCs,实验使用第3代细胞。用Western blot法检测细胞Erb B的表达和磷酸化。在正常、缺氧缺血清或NRG-1(100μg/L)处理条件下,用Western blot法检测血管内皮生长因子(VEGF)、血管生成素1(Ang-1)和血管生成素2(Ang-2)表达的改变。结果:Erb B2、Erb B3和Erb B4均能在HCASMCs中表达,加入NRG-1后,这3种Erb B的磷酸化水平均增加。与对照组比较,在缺氧缺血清组HCASMCs中VEGF和Ang-1的表达明显增加(P0.05),而Ang-2的表达差异无统计学显著性。与缺氧缺血清组比较,NRG-1处理组的HCASMCs表达VEGF和Ang-1进一步显著增加(P0.05),而Ang-2的表达差异无统计学显著性。结论:HCASMCs能表达Erb B2、Erb B3和Erb B4,加入NRG-1增强Erb B2、Erb B3和Erb B4的磷酸化。缺氧缺血清和NRG-1处理均能增加VEGF和Ang-1在HCASMCs中的表达。     

An improved isolated, left ventricular ejecting, murine heart model

 An improved, isolated, left ventricular-ejecting, murine heart model is described and evaluated. Special attention was paid to the design and impedance characteristics of the artificial aortic outflow tract and perfusate composition, which contained glucose (10 mM plus insulin) and pyruvate (1.5 mM) as substrates. Temperature of the isolated perfused hearts was maintained at 38.5 °C. During antegrade perfusion (preload 10 mm Hg, afterload 50 mm Hg, 2.5 mM Ca²⁺) proper design of the aortic outflow tract provided baseline values for cardiac output (CO), left ventricular developed pressure (LVDP) and the maximum first derivative of left ventricular pressure (LV dP/dt _max) of 11.1±1.7 ml min^–1, 83±5 mm Hg and 6283±552 mm Hg s^–1, respectively, resembling findings in the intact mouse. During 100 min normoxic antegrade perfusion CO declined non-significantly by less than 10%. Varying pre- and afterloads resulted in typical Frank-Starling relationships with maximal CO values of 18.6±1.8 ml min^–1 at pre- and afterload pressures of 25 and 50 mm Hg, respectively. Left ventricular function curves were constructed at free [Ca²⁺] of 1.5 and 2.5 mM in the perfusion medium. Significantly higher values for CO, LVDP and LV dP/dt _max and LV dP/dt _min were obtained at 2.5 mM Ca²⁺ at all loading conditions investigated. Phosphocreatine and creatine levels remained stable throughout the perfusion period. Despite a small but significant decline in tissue ATP content, the sum of adenine nucleotides did not change during the normoxic perfusion period. The tissue content of glycogen increased significantly. Received: 28 April 1998 / Received after revision and accepted: 10 September 1998     

Phe45 of NRG2β is critical for the affinity of NRG2β for ErbB4 and for potent stimulation of ErbB4 signaling by NRG2β

The Neuregulins (NRGs) are members of the epidermal growth factor (EGF) family of growth factors. EGF family members regulate the signaling of ErbB family receptor tyrosine kinases, including the epidermal growth factor receptor (EGFR/ErbB1), ErbB2/HER2/Neu, ErbB3/HER3 and ErbB4/HER4. We have previously demonstrated that the EGF family hormone NRG2β is a potent ErbB4 agonist, whereas NRG2α is a weak ErbB4 agonist. We have also previously demonstrated that Phe45 of NRG2β regulates the potency of NRG2β. Here, we address the hypotheses that Phe45 regulates the potency of NRG2β by regulating the affinity of NRG2β for ErbB4. We demonstrate that Phe45 of NRG2β indeed regulates the affinity of NRG2β for ErbB4. Furthermore, a hydrophobic or uncharged amino acid side chain at residue 45 contributes to NRG2β binding to ErbB4. These data indicate that Phe45 of NRG2β may regulate the affinity of NRG2β for ErbB4 by interacting with hydrophobic amino acids in ErbB4.     

Acute and chronic adrenergic stimulation of submandibular salivary glands. Effects on the endocrine function of epidermal growth factor in mice

Submandibular salivary glands are the major source of epidermal growth factor (EGF) in mice. Acute secretion of EGF from these glands protects the heart against catecholamine-induced injury. Little is known about chronic adrenergic stimulation of salivary glands and the contribution of accumulated EGF to the adaptive hypertrophic response of the heart to such chronic adrenergic stimulation. Here we show that the EGF content of submandibular glands did not recover to normal values 24 h after a single phenylephrine injection or an aggressive encounter. Repeated (twice a day for 2 days) adrenergic stimulation resulted in an almost 90% decrease in EGF content in the submandibular glands. In these conditions, new adrenergic stimulation did not result in an increase in plasma EGF concentration, or in the activation of liver ErbB1 (the EGF receptor). Chronic isoproterenol or phenylephrine administration (7 days) induced atrial natriuretic factor expression in the heart and an increase in both ventricular weight and protein. The surgical removal of submandibular glands (sialoadenectomy) did not affect these adaptive responses of the heart. We conclude that EGF from submandibular glands does not contribute to heart hypertrophy, one of the adaptive responses induced by chronic adrenergic stimulation.     

ATP-dependent potassium channels and mitochondrial permeability transition pores play roles in the cardioprotection of theaflavin in young rat

Previous studies have confirmed that tea polyphenols possess a broad spectrum of biological functions such as anti-oxidative, anti-bacterial, anti-tumor, anti-inflammatory, anti-viral and cardiovascular protection activities, as well as anti-cerebral ischemia-reperfusion injury properties. But the effect of tea polyphenols on ischemia/reperfusion heart has not been well elucidated. The aim of this study was to investigate the protective effect of theaflavin (TF1) and its underlying mechanism. Young male Sprague-Dawley (SD) rats were randomly divided into five groups: (1) the control group; (2) TF1 group; (3) glibenclamide + TF1 group; (4) 5-hydroxydecanoate (5-HD) + TF1 group; and (5) atractyloside + TF1 group. The Langendorff technique was used to record cardiac function in isolated rat heart before and after 30 min of global ischemia followed by 60 min of reperfusion. The parameters of cardiac function, including left ventricular developing pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximal differentials of LVDP (±LVdP/dt _max) and coronary flow (CF), were measured. The results showed: (1) compared with the control group, TF1 (10, 20, 40 μmol/l) displayed a better recovery of cardiac function after ischemia/reperfusion in a concentration-dependent manner. At 60 min of reperfusion, LVDP, ±LVdP/dt _max and CF in the TF1 group were much higher than those in the control group, whereas left ventricular end-diastolic pressure (LVEDP) in the TF1 group was lower than that in the control group (P < 0.01). (2) Pretreatment with glibenclamide (10 μmol/l), a K_ATP antagonist, completely abolished the cardioprotective effects of TF1 (20 μmol/l). Also, most of the effects of TF1 (20 μmol/l) on cardiac function after 60 min of reperfusion were reversed by 5-HD (100 μmol/l), a selective mitochondria K_ATP antagonist. (3) Atractyloside (20 μmol/l), a mitochondrial permeability transition pore (mPTP) opener, administered at the beginning of 15 min of reperfusion completely abolished the cardioprotection of TF1 (20 μmol/l). The results indicate that TF1 protects the rat heart against ischemia/reperfusion injury through the opening of K_ATP channels, particularly on the mitochondrial membrane, and inhibits mPTP opening.     

甘氨酰谷氨酰胺在大鼠离体心脏缺血/再灌注损伤中的保护作用研究

目的： 研究甘氨酰谷氨酰胺对缺血再灌注大鼠离体心脏的保护作用。方法：应用Langendorff离体心脏灌注系统建立心肌缺血再灌注模型。30只SD雄性大鼠随机分为正常对照组(control)、甘氨酰谷氨酰胺对照组(Gly-Gln)、缺血再灌注组(I/R)、缺血/再灌注+甘氨酰谷氨酰胺组(I/R+ Gly-Gln)。I/R组及I/R+ Gly-Gln组分别灌注30 min后,全心停灌20 min,再灌注40 min,I/R+ Gly-Gln组于再灌注时在灌流液中加入Gly-Gln;正常对照组连续灌流90 min,Gly-Gln对照组灌流液中加入Gly-Gln。记录各组灌注时,左室舒张末压(LVEDP)、左室发展压(LVDP)、左室压力最大变化速率(±dp/dtmax)、心率(HR)及心肌细胞单相动作电位(MAP);同时在相应的时点分别测定冠脉流出液中的乳酸脱氢酶（LDH)、肌酸激酶(CK)活性。结果：离体大鼠心脏缺血20min,再灌注40 min,导致严重的心功能抑制,表现为LVEDP升高,LVDP、±dp/dtmax降低;再灌注液中加入Gly-Gln后,LVEDP降低,LVDP、±dp/dtmax明显升高（P<0.01)。I/R+ Gly-Gln组冠脉流出液中LDH、CK活性明显低于I/R组(均P<0.01)。结论： Gly-Gln能有效减轻缺血再灌注引起的左室功能下降,减少心肌细胞LDH、CK的释出,表明Gly-Gln对缺血再灌注损伤的大鼠离体心脏具有保护作用。     

Neuregulin-1β attenuates sepsis-induced diaphragm atrophy by activating the PI3K/Akt signaling pathway

The aim of this study was to investigate the protective effects of neuregulin-1β (NRG-1β) on sepsis-induced diaphragm atrophy and the possible underlying mechanisms. Sprague–Dawley rats were randomly divided into sham, sepsis and NRG groups. Sepsis was induced by cecal ligation and puncture (CLP). In the NRG group, rats received tail vein injections of NRG-1β (10 μg/kg) every 12 h for 72 h after CLP. At 3 days after surgery, diaphragm contractile forces were measured by determining the force-frequency curve and muscle fiber areas by hematoxylin–eosin staining. Moreover, the NRG-1 expression level in the diaphragm was detected by Western blotting. Furthermore, the proteins in the PI3K/Akt signaling pathway and its downstream Akt-mTOR and Akt-FOXO axes were detected by Western blotting analysis. In L6 myotubes treated with lipopolysaccharide (LPS) and NRG-1β, PI3K/Akt signaling pathway-related protein expression was further determined using the PI3K inhibitor LY294002. Exogenous NRG-1β could compensate for sepsis-induced diminished NRG-1 in the diaphragm and attenuate the reduction in diaphragm contractile forces and muscle fiber areas during sepsis. Moreover, NRG-1β treatment could activate the PI3K/Akt signaling pathway in the diaphragm during sepsis. The inhibition of p70S6K and 4E-BP1 on the Akt-mTOR axis and the increased expression of Murf1 on the Akt-FOXO axis were reversed after NRG-1 treatment. In addition, NRG-1β could activate the PI3K/Akt signaling pathway in L6 myotubes treated with LPS, while the PI3K inhibitor LY294002 blocked the effects of NRG-1β. NRG-1 expression in the diaphragm was reduced during sepsis, and exogenously administered recombinant human NRG-1β could attenuate sepsis-induced diaphragm atrophy by activating the PI3K/Akt signaling pathway.

     

HO-1在保护缺氧-复氧心脏中的作用及其机制研究

目的：研究血红素氧化酶1（HO-1）在对抗 心肌缺氧-复氧损伤中的作用，并探讨环氧化酶2（COX-2）是否参与其作用机制。 方法：采用离体大鼠心脏Langendorff灌流模型，观察心功能和酶学等指标。 结果：（1）HO-1的诱导剂高铁血红素可明显抑制缺氧-复氧心脏LVEDP增高 ，LVDP和±dp/dtmax的下降；减少复氧期LDH释放，缩小心肌梗死面积（P <0.01）。（2）HO-1的抑制剂可加重缺氧-复氧心脏LVDP和±dp/dtmax下 降，LDH释放和梗死面积明显高于单纯缺氧-复氧组（P<0.05）。（3）GC的抑制剂亚甲 蓝和COX-2的抑制剂塞来昔布均可部分取消高铁血红素降低缺氧-复氧心脏LVEDP，增加LVDP 和±dp/dtmax的作用，使LDH的释放和梗死面积明显增加（P<0.05） 。 结论：诱导HO-1增加可保护缺氧-复氧心肌，其作用可能通过激动鸟苷酸 环化酶途径，继而调节COX-2的活性来完成。     

Oxidative stress promotes d-GalN/LPS-induced acute hepatotoxicity by increasing glycogen synthase kinase 3β activity

Objective

Our previous studies have demonstrated that glycogen synthase kinase 3β (GSK3β) activity is increased in the progression of acute liver failure (ALF), which aggravates liver injury, while its regulatory mechanism remains elusive. This study is designated to address whether oxidative stress activates GSK3β to promote ALF.

Methods

In a murine model induced by d-galactosamine (d-GalN) (700 mg/kg) and LPS (10 μg/kg), N-acetylcysteine (300 mg/kg) or SB216763 (25 mg/kg) was used to inhibit oxidative stress or GSK3β activity, respectively. Serum alanine aminotransferase and aspartate aminotransferase levels were assessed. The parameters of oxidative stress were evaluated in liver tissue. Whether GSK3β inhibition protects hepatocytes from oxidative stress-induced cell apoptosis was investigated in vitro. Moreover, the activity of GSK3β was measured in the liver of chronic hepatitis B (CHB) patients and ALF patients.

Results

In vivo, N-acetylcysteine ameliorated the d-GalN/LPS-induced hepatotoxicity and reduced GSK3β activity; GSK3β inhibition increased hepatic superoxide dismutase activity and the glutathione content, decreased malondialdehyde production in the liver tissues; while GSK3β inhibition suppressed the JNK activation in the liver and decreased cytochrome c release from mitochondria. In vitro, GSK3β inhibition lessened hepatocytes apoptosis induced by H₂O₂ or Antimycin A, as demonstrated by decreased LDH activity, and reduced cleavage of caspase-3 expression. Furthermore, GSK3β activity in the CHB patients was increased in the phase of ALF.

Conclusions

Results indicate that GSK3β activation contributes to liver injury by participating in oxidative stress response in ALF and is, therefore, a potential therapeutic target for ALF.     

Specific effects of neuregulin-1β on the communication between DRG neurons and skeletal muscle cells in vitro

The communication between primary afferent neuron and skeletal muscle (SKM) is one of the important factors on maintaining the structure and function of SKM cells. Neuregulin-1β (NRG-1β) signaling is essential for regulating synaptic neurotransmission. Here, we established a neuromuscular coculture model of dorsal root ganglion (DRG) sensory neurons and SKM cells to explore the nerve-muscle communication in the presence of exogenous NRG-1β. The expression of three distinct subtypes (TrkA, TrkB, and TrkC) of tyrosine kinase receptors was monitored for the phenotypical alterations of the neurons. The aggregation extent of acetylcholine receptor (AChR) represents the specific changes of SKM cells after NRG-1β incubation in this neuromuscular coculture model. The results showed that NRG-1β not only enhanced neurite outgrowth of DRG neurons but also increased the length and branches of SKM cells. NRG-1β treatment not only induced expression of all the three subtypes of Trk receptors in neurons but also promoted AChR aggregation on the surface of SKM cells. The effects of NRG-1β could be blocked by administration of ERK1/2 inhibitor PD98059, PI3K inhibitor LY294002, and JAK2 inhibitor AG490, respectively. These data imply that NRG-1β is essential for the nerve-muscle communication by enhancing growth and modifying phenotypes of the two different kinds of cells. The specific effects produced by NRG-1β add novel interpretation for nerve-muscle communication between sensory neurons and SKM cells.     

The effects of neuregulin-1β on neuronal phenotypes of primary cultured dorsal root ganglion neurons by activation of PI3K/Akt

Neuregulin-1β (NRG-1β) signaling has multiple functions in neurons. NRG-1 signaling regulates neuronal development, migration, myelination, and synaptic maintenance. The neuropeptide- and neurofilament (NF)-immunoreactive (IR) neurons are two major phenotypical classes in dorsal root ganglion (DRG). Whether NRG-1β influences DRG neuronal phenotypes remains unknown. To assess the effects of NRG-1β on DRG neuronal phenotypes, dissociated embryonic rat DRG neuronal culture model was established. Primary cultured DRG neurons were exposed to NRG-1β (5nmol/L), NRG-1β (10nmol/L), NRG-1β (20nmol/L), NRG-1β (20nmol/L) plus LY294002 (10μmol/L) for 3 days, respectively. The DRG neurons were continuously exposed to growth media as control. After that, all above cultured DRG neurons were processed for double fluorescent labeling of calcitonin gene-related peptide (CGRP) or neurofilament-200 (NF-200) and microtubule associated protein 2 (MAP2). The percentage of CGRP-IR neurons and NF-200-IR neurons was counted. The expression of CGRP mRNA and NF-200 mRNA was analyzed by real time-PCR analysis. The percentage of CGRP-IR neurons but not NF-200-IR neurons increased significantly in the presence of NRG-1β as compared with that in the absence of NRG-1β. The levels of CGRP mRNA but not NF-200 mRNA increased significantly in the presence of NRG-1β as compared with that in the absence of NRG-1β. PI3K inhibitor LY294002 blocked the effects of NRG-1β. These results support an important role for exogenous NRG-1β in induction of the distinct neuronal phenotype response by activation of PI3K/Akt in sensory neurons.     

低氧刺激诱导体外培养的大鼠脑皮质星形胶质细胞内neuregulin-1表达上调

Neuregulin-1(NRG-1)是神经胶质及神经元产生的细胞间信号转导蛋白。该蛋白通过与ErbB受体结合,对神经系统的正常发育、成熟发挥重要作用,也在缺血性脑损伤时起神经保护作用。为探讨体外培养的星形胶质细胞受缺氧刺激后NRG-1的表达特点,本实验利用体外培养的大鼠脑皮质星形胶质细胞,采用免疫组织化学和Westernblot方法,比较了正常培养和低氧复氧条件下星形胶质细胞中NRG1的表达。结果显示:正常培养的星形胶质细胞中有NRG-1的表达,但含量不高;低氧复氧培养后星形胶质细胞NRG1的表达量随着复氧时间的延长缓慢增加,至复氧8h,其表达量陡然升高,达到峰值后又逐渐降低,甚至降至正常水平以下。本研究表明,在低氧缺血性脑损伤后,星形胶质细胞反应性大量产生NRG1的时间相对滞后。由此提示,低氧缺血性脑损伤后,立即使用外源性神经保护剂为宜。     

In situ hybridization reveals developmental regulation of ErbB1-4 mRNA expression in mouse midbrain: Implication of ErbB receptors for dopaminergic neurons

Although epidermal growth factor (EGF) and neuregulin-1 are neurotrophic factors for mesencephalic dopaminergic neurons and implicated in schizophrenia, the cellular localization and developmental regulation of their receptors (ErbB1-4) remain to be characterized. Here we investigated the distributions of mRNA for ErbB1-4 in the midbrain of the developing mouse with in situ hybridization and immunohistochemistry. The expression of ErbB1 and ErbB2 mRNAs was relatively high at the perinatal stage and frequently colocalized with mRNA for S100β and Olig2, markers for immature astrocytes or oligodendrocyte precursors. Modest signal for ErbB1 mRNA was also detected in a subset of dopaminergic neurons. ErbB3 mRNA was detectable at postnatal day 10, peaked at postnatal day 18, and colocalized with 2′,3′-cyclic nucleotide 3′-phosphodiesterase, a marker for oligodendrocytes. In contrast, ErbB4 mRNA was exclusively localized in neurons throughout development. Almost all of ErbB4 mRNA-expressing cells (94%–96%) were positive for tyrosine hydroxylase in the substantia nigra pars compacta but 66%–78% in the ventral tegmental area and substantia nigra pars lateralis. Conversely, 92%–99% of tyrosine hydroxylase-positive cells expressed ErbB4 mRNA. The robust and restricted expression of ErbB4 mRNA in the midbrain dopaminergic neurons suggests that ErbB4 ligands, neuregulin-1 and other EGF-related molecules, contribute to development or maintenance of this neuronal population.     

Interleukin-1 receptor expression by ovine afferent lymph dendritic cells: response to secondary antigen challenge

Interleukin(IL)-1 is thought to enhance the function of antigen presenting cells of the dendritic cell lineage. To investigate the interaction of IL-1 and dendritic cells, recombinant ovine IL-1α and IL-1β have been used to determine IL-1 receptor (R) expression on fresh dendritic cells (ALDC) collected from cannulated sheep pseudoafferent lymph ducts, both prior to and in response to localized ovalbumin challenge. Resting ovine ALDC express ～ 510 IL-1R per cell for IL-1α (K_d ～ 30 pM ) and ～ 350 IL-1R/cell for IL-β (K_d ～ 160 pM ). Saturation binding and in situ analyses show an initial transient but dramatic increase in IL-1α binding to ALDC by 4 h in response to ovalbumin challenge of primed sheep. Maximal IL-1R expression, reaching ? 21700 IL-1R/cell for IL-1α detected by around 48 h, was followed by a gradual return to resting level by 8 days post challenge. Fewer than 0.5% of resting ALDC expressed IL-1R but at least 5% of ALDC bound IL-1α after ovalbumin challenge. There was no evidence of specific up-regulation of receptors for IL-1β on these cells. Fresh ovine alveolar macrophages, used as a positive control for specific IL-1R expression, were found to express ～ 2600 sites/cell for IL-1α (K_d ～ 56 pM ) and 16500 sites/cell for IL-1β (K_d ～ 4.6 pM ). In view of the differing IL-1 binding characteristics displayed by the receptors on the two cell types, it is postulated that afferent lymph dendritic cells and macrophages are not expressing the same form of IL-1R.     

神经调节素对大鼠脑缺血再灌注损伤AQP-4及GFAP表达的影响

应用线栓法经颈外-颈内动脉插线建立大脑中动脉闭塞再灌注(MCAO/R)大鼠动物模型,经颈内动脉单剂量注射1.5%神经调节素-1β(NRG-1β,0.3μg/kg)干预治疗。用干湿重法、免疫组化、免疫荧光双标记法和免疫印迹法观察NRG-1β对大鼠脑缺血再灌注损伤水通道蛋白(AQP-4)及胶质纤维酸性蛋白(GFAP)表达的影响。结果显示:随着缺血时间延长,对照组脑组织含水量逐渐增加,NRG-1β治疗能减少MCAO/R后脑组织含水量,与对照组相比,缺血1.5～2.0h组存在显著性差异(P<0.05)。脑缺血再灌注损伤可诱导脑组织AQP-4及GFAP表达,且随着缺血缺氧时间的延长,AQP-4及GFAP蛋白的表达逐渐增加。尽管它们均在胶质细胞中表达,但在脑组织中的分布略有不同。NRG-1β治疗可以增加二者在脑中的表达水平,与对照组相比具有显著性差异(P<0.01)。以上结果提示,NRG-1β可能通过激活内在的保护机制,增强胶质细胞的活性,从而抑制MCAO/R早期脑水肿的形成过程,改善神经元的生存环境,进而干扰脑缺血再灌注损伤的病理生理过程,对缺血性脑损伤具有积极的保护作用。     

Neuregulin-1β对压力超负荷心肌肥大大鼠治疗作用及机制的研究

 目的：研究神经调节蛋白 1β（NRG-1β）对压力超负荷所致大鼠心肌肥大的治疗作用并探讨其机制。方法：Wistar雄性大鼠采用腹主动脉缩窄的方法复制心肌肥大模型。术后8周,将模型动物随机分成模型（model）组、NRG-1β治疗组（尾静脉注射NRG-1β,10 μg·kg-1·d-1）和NRG-1β+赫赛汀(Herceptin, HERCE)治疗组（尾静脉注射NRG-1β的同时给予注射HERCE 10 μg·kg-1·d-1）。假手术（sham）组除不以银夹缩窄腹主动脉外,其余操作同腹主动脉缩窄组。7　d后分别采用心动超声、血流动力学评价心功能;Masson染色观察心肌组织的超微结构;放射免疫法检测心肌组织中血管紧张素II（Ang II）,酶联免疫吸附法测定心肌组织中肿瘤坏死因子 α（TNF-α）的变化;RT-PCR法检测心肌中bcl-2和bax mRMA表达的改变。结果：（1）心动超声显示,和模型组比较,NRG-1β组左室射血分数(LVEF)及短轴缩短率(LVFS)升高,左室收缩末内径(LVESD)及舒张末内径(LVEDD)减小（P<0.01）。（2）血流动力学检测显示,NRG-1β治疗组左室收缩末压(LVESP)和左室内压最大上升和下降速率(±dp/dtmax)均明显高于模型组（P<0.01）;左室舒张末压(LVEDP)低于模型组（P<0.01）。（3）与模型组比较,NRG-1β组心肌胶原容积分数（CVF）下降,心肌中Ang II和TNF-α明显减少,bcl-2 mRNA表达显著升高,而bax mRNA表达下降（P<0.01）。（4）NRG-1β+ HERCE治疗组与模型组相比各项指标无明显改变（P>0.05）。结论：NRG-1可以减少压力超负荷大鼠心肌Ang II和TNF-α的生成,从而减轻Ang II和TNF-α介导的心肌间质重构; NRG-1可通过上调bcl-2 mRNA表达、下调bax mRNA表达,抑制心肌细胞的凋亡,改善压力超负荷大鼠的心功能,进而在心肌肥大的过程中发挥作用。