Platelet nitric oxide synthase is activated by tyrosine dephosphorylation: possible role for SHP-1 phosphatase

BACKGROUND: Endothelial nitric oxide synthase (eNOS) activity in endothelial cells is regulated by post-translational phosphorylation of critical serine, threonine and tyrosine residues in response to a variety of stimuli. However, the post-translational regulation of eNOS in platelets is poorly defined. OBJECTIVES: We investigated the role of tyrosine phosphorylation in the regulation of platelet eNOS activity. METHODS: Tyrosine phosphorylation of eNOS and interaction with the tyrosine phosphatase SHP-1 were investigated by coimmunoprecipitation and immunoblotting. An in vitro immunoassay was used to determine eNOS activity together with the contribution of protein tyrosine phosphorylation. RESULTS: We found platelet eNOS was tyrosine phosphorylated under basal conditions. Thrombin induced a dose- and time-dependent increase in eNOS activity without altering overall level of tyrosine phosphorylation, although we did observe evidence of minor tyrosine dephosphorylation. In vitro tyrosine dephosphorylation of platelet eNOS using a recombinant protein tyrosine phosphatase enhanced thrombin-induced activity compared to thrombin alone, but had no effect on endothelial eNOS activity either at basal or after stimulation with bradykinin. Having shown that dephosphorylation could modulate platelet eNOS activity we examined the role of potential protein phosphatases important for platelet eNOS activity. We found SHP-1 protein tyrosine phosphatase, co-associated with platelet eNOS in resting platelets, but does not associate with eNOS in endothelial cells. Stimulation of platelets with thrombin increased SHP-1 association with eNOS, while inhibition of SHP-1 abolished the ability of thrombin to induce elevated eNOS activity. CONCLUSIONS: Our data suggest a novel role for tyrosine dephosphorylation in platelet eNOS activation, which may be mediated by SHP-1.     

中脑导水管周围灰质NO对大鼠血压的影响及其机制探讨

目的 探讨大鼠中脑导水管周围灰质(PAG)NO对血压的影响及作用机制。方法 采用微量注射法，观察大鼠血压的变化，放免法检测Ach含量。结果 PAG内微量注射L-NNA后，大鼠平均动脉压升高，延髓头端腹外侧区(RVLM)内Ach含量增多，且这一升压效应可被PALG内预注L-Arg或RVLM内预注东莨菪碱所阻断。结论PAG内NO可能经RVLM内Ach介导对血压有紧张性抑制作用。     

一氧化氮与肺缺血再灌注损伤的研究进展

一氧化氮（nitricoxide，NO）是一种活性很强的自由基，具有广泛的生物学活性。多项研究提示NO在急性肺缺血／再灌注（ischemia／reperfusion，I／R）损伤中具有重要作用。本文重点描述有关一氧化氮在肺I／R损伤中作用的研究进展。     

诱导型一氧化氮合酶在前列腺增生组织中表达的研究

目的：探讨诱导型一氧化氮合酶(iNOS)与前列腺增生(BPH)病理生理变化的关系。方法:用免疫组化法检测10例正常和30例有膀胱出口梗阻的BPH患者膀胱和前列腺组织中iNOS的表达。结果：BPH组前列腺组织中iNOS呈阳性染色，主要分布于前列腺的上皮细胞及上皮下组织中，间质平滑肌组织中均为阴性；对照组的膀胱壁、膀胱颈部和前列腺组织中均无iNOS阳性染色。结论：iNOS仅在BPH患者前列腺组织中有特异性表达，提示它参与了前列腺增生的病理生理过程。     

二乙基二硫代氨基甲酸钠对沙土鼠脑缺血再灌注损伤的影响

沙土鼠脑缺血60min后,脑组织氧自由基和MDA含量无明显升高,而Mn-SOD的活性下降。缺血60min再灌注5min时,氧自由基显著升高。再灌注30min时,MDA的生成显著增多,Mn-SOD和Cu,Zn-SOD活性显著降低。缺血前15 min,iv DTC对缺血再灌注脑组织中氧自由基和MDA升高有显著抑制作用,对Mn-SOD活性有显著保护作用,且呈剂量依赖关系。     

实验性癫痫大鼠海马结构内一氧化氮-环磷酸鸟苷途径的研究

目的研究实验性癫痫发作大鼠海马结构内一氧化氮（ＮＯ）环磷酸鸟苷（ｃＧＭＰ）信使机制及其意义。方法雄性ＳＤ大鼠４１只，随机分为对照组（５只）、红藻氨酸（ＫＡ）１０、３０、６０分钟组（每组６只）和Ｌ硝基精氨酸甲酯（ＬＮＡＭＥ）＋ＫＡ１０、３０、６０分钟组（每组６只）。用放射免疫法测定ＫＡ诱导性癫痫发作中各时点海马结构内ｃＧＭＰ含量及ＬＮＡＭＥ的干预效应。结果ＫＡ注射引起大鼠海马结构内ｃＧＭＰ浓度升高，并加重大鼠癫痫发作（湿狗样摇动提早出现和发生次数增多）；ＫＡ注射前３０分钟给予ＬＮＡＭＥ可明显抑制ＫＡ１０、３０分钟组ｃＧＭＰ浓度的升高，但ＬＮＡＭＥ对ＫＡ６０分钟组ｃＧＭＰ的抑制作用不显著。结论在ＫＡ发作早期，ｃＧＭＰ浓度升高与内源性ＮＯ有关；ＮＯ的抗发作效应可能与ｃＧＭＰ信使机制存在某种联系。     

腺苷A1受体诱导预处理延迟效应对供心保存的影响及机制探讨

目的　探讨腺苷A1受体激动剂预处理延迟效应对保存大鼠心脏的影响及其机制。方法　Wistar大鼠随机分为 8组 ,A、C组以高选择性腺苷A1受体激动剂 (CCPA)预处理 ;D、E、F组在CCPA预处理前分别注射锰 超氧化物歧化酶 (Mn SOD)反义、有意义、错配寡核苷酸 (ODN) ;B、G组注射生理盐水 ,H组只注射反义寡核苷酸。 2 4h后 ,A、B组用 4℃St.Thomas液保存 4h ,复灌 1h ,而另 6组采取低温缺血 3h ,复灌 1h。观测心功能、磷酸肌酸激酶 (CK mb)、三磷酸腺苷 (ATP)含量等。结果　A组左室内压上升与下降最大速率恢复率 (±dp/dtmax,% )为 6 2 .83± 17.2 7,6 6 .81± 18.99,心肌ATP含量 (10 3 μmol/g)为3.6 7± 1.4 2 ;而B组分别为 4 0 .4 1± 18.2 9,4 4 .70± 2 5 .14 ,1.4 6± 0 .5 4 ;A组均明显高于B组 ,差异均有显著性 (P <0 .0 1orP <0 .0 5 )。C组±dp/dtmax恢复率、ATP、Mn SOD活性均明显高于D、G、H组 (P <0 .0 1orP <0 .0 5 ) ,而与E、F组比较 ,差异无显著性。结论　腺苷A1受体激动剂能诱导预处理的延迟效应 ,改善离体大鼠心脏的保存效果 ,而该效应与Mn SOD的高表达有关。     

超细α-FeOOH制备过程研究 Ⅰ.制备工艺

以制备晶形、粒度、轴比等满足高性能磁粉要求的铁黄为目标,研究了碱法超细α-FeOOH合成的工艺配方和工艺条件对粒子性能的影响,包括碱比、气量、转速、Fe(OH)_2结晶条件、熟化时间等工艺参数的影响规律。重复稳定地制备出三类超微粒α-FeOOH粒子,其粒度分别为0.18、0.28、0.39μm,分布均匀,无枝叉。     

Exacerbation of lymphocytic choriomeningitis in mice treated with the inducible nitric oxide synthase inhibitor aminoguanidine

To elucidate the possible involvement of the inducible nitric oxide synthase (iNOS) and NO in the development of lymphocytic choriomeningitis (LCM), the consequences of inhibition of iNOS by the inhibitor aminoguanidine was examined in mice following intracerebral infection with LCM virus (LCMV). Aminoguanidine administration to mice infected with LCMV completely blocked increased plasma nitrate/nitrite levels and led to increased proinflammatory cytokine gene expression at early stages of lesion development in the brain, enhanced clinical severity and decreased survival time. The levels of LCMV recovered from the brain of aminoguanidine treated mice did not differ from those in infected control mice. These findings argue against either an anti-viral or pathogenic role of NO in LCM but rather suggest a possible protective action of this mediator.     

Antioxidant and glutathione-related enzymatic activities in rat sciatic nerve

The present work tries to establish the antioxidant capacity of the peripheral nervous tissue of the rat, in terms of the enzymatic activities present in this tissue that either prevent the formation of activated species as the semiquinone radical (DT-diaphorase), protect against activated oxygen species (superoxide dismutase, glutathione peroxidase), conjugate natural toxic products or xenobiotics (glutathione S-transferases, especially the activity conjugating 4-hydroxy-nonenal), or complete the glutathione system metabolism (glutathione disulfide reductase, γ-glutamyl transpeptidase). All the activities studied are lower in this tissue than they are in liver, except for γ-glutamyl transpeptidase. The relevance of the results obtained and its possible relationship with different neuropathies is discussed. It is concluded that the peripheral nervous tissue is by far less protected than the liver against oxidative damage.