Hypoxic pulmonary vasoconstriction: redox regulation of O2-sensitive K+ channels by a mitochondrial O2-sensor in resistance artery smooth muscle cells

Hypoxic pulmonary vasoconstriction (HPV) is a widely-conserved mechanism for matching ventilation and perfusion that optimizes systemic PO(2). HPV is elicited by moderate alveolar hypoxia through a mechanism that is intrinsic to the pulmonary circulation, particularly the resistance pulmonary arteries (PA), and is robust even in isolated perfused lungs. Although modulated by the endothelium, HPV persists in denuded PA rings and PA smooth muscle cells (PASMC). Beginning within seconds of hypoxia, HPV plateaus in minutes and persists for hours. During focal hypoxia (e.g. atelectasis), HPV is restricted to the vascular segments serving hypoxic lobes, and diverts blood to better-ventilated segments without causing pulmonary hypertension (PHT). However, with global hypoxia, as occurs at high altitude or in the fetal lung, HPV increases pulmonary vascular resistance (PVR) and may contribute to PHT. This review focuses on a comprehensive Redox Theory of HPV but considers relevant modulatory factors (endothelin), triggering stimuli (cyclic ADP-ribose-induced release of sarcoplasmic reticulum (SR) Ca(2+)) and sustaining pathways (Rho kinase-modulated Ca(2+) sensitization of the contractile apparatus). The Redox Theory proposes that an O(2)-sensor in resistance PASMC (complexes I and III of the mitochondrial electron transport chain (ETC)) generates reactive O(2) species (ROS) in proportion to PO(2). During normoxia, a redox mediator, like hydrogen peroxide (H(2)O(2)), maintains voltage-gated O(2)-sensitive K(+) channels (Kv) in an oxidized open state. Hypoxic withdrawal of ROS inhibits Kv channels, thereby depolarizing PASMCs, activating L-type voltage-gated Ca(2+) channels, enhancing Ca(2+) influx and promoting vasoconstriction. The role of O(2)-sensitive K(+) channels is conserved in most specialized O(2)-sensitive tissues, including the ductus arteriosus and carotid body. The unique occurrence of hypoxic vasoconstriction in the pulmonary circulation relates to the colocalization of an O(2)-sensor and O(2)-sensitive Kv channels in resistance PAs. HPV has relevance to human physiology, pathophysiology (high altitude pulmonary edema (HAPE) and PHT) and therapy (single lung anesthesia).     

华支睾吸虫Rho GTPase重组蛋白免疫保护效果

目的探讨华支睾吸虫(Clonorchis sinensis,Cs)Rho GTPase重组蛋白的免疫保护效果。方法将20只8周龄SD大鼠随机均分为2组,重组蛋白实验组(A组)和PBS对照组(B组)。A组共免疫5次,首次和第2周分别用Cs-Rho GTPase重组蛋白(90μg/ml)1ml加等体积福氏完全佐剂和福氏不完全佐剂稀释后背部、足垫多点皮下注射,第4、7和11周分别用Cs-Rho GTPase重组蛋白(90μg/ml)1ml腹腔注射。B组用PBS加佐剂免疫小鼠。末次免疫后,即灌胃感染华支睾吸虫囊蚴(50个/只),感染后第21天起每隔3～5d粪检1次,待查见虫卵后,计数虫卵数,并用乙醚麻醉处死大鼠,剖检胆管和胆囊中华支睾吸虫成虫。采集各次免疫前小鼠尾静脉血,ELISA法测定血清IgG、IgG1和IgG2a抗体水平。统计分析各组平均成虫数、虫卵数及抗体水平差异。结果 A组检获平均成虫数为(9.2±9.9)条、每克粪便平均虫卵数为(956.8±1062.5)个,B组分别为(23.25±15.75)条和(3062.5±2501.8)个,两组差异有统计学意义(P0.05)。A组血清的抗体吸光度(A450值)分别为IgG(0.1、0.45、0.65、0.6、0.65)、IgG1(0.1、0.45、1.1、1.0、1.1)、IgG2a(0.1、0.7、1.1、1.1、1.1),而B组IgG、IgG1和IgG2a吸光度(A450值)均维持在0.1水平,两组间差异有统计学意义(P0.05)。结论 Cs-Rho GTPase重组蛋白可诱导SD大鼠产生较好的抗华支睾吸虫感染的免疫保护作用。     

Disruption of ROCK1 gene attenuates cardiac dilation and improves contractile function in pathological cardiac hypertrophy

The development of left ventricular cardiomyocyte hypertrophy in response to increased hemodynamic load and neurohormonal stress is initially a compensatory response. However, persistent stress eventually leads to dilated heart failure, which is a common cause of heart failure in human hypertensive and valvular heart disease. We have recently reported that Rho-associated coiled-coil containing protein kinase 1 (ROCK1) homozygous knockout mice exhibited reduced cardiac fibrosis and cardiomyocyte apoptosis, while displaying a preserved compensatory hypertrophic response to pressure overload. In this study, we have tested the effects of ROCK1 deficiency on cardiac hypertrophy, dilation, and dysfunction. We have shown that ROCK1 deletion attenuated left ventricular dilation and contractile dysfunction, but not hypertrophy, in a transgenic model of Gαq overexpression-induced hypertrophy which represents a well-characterized and highly relevant genetic mouse model of pathological hypertrophy. Although the development of cardiomyocyte hypertrophy was not affected, ROCK1 deletion in Gαq mice resulted in a concentric hypertrophic phenotype associated with reduced induction of hypertrophic markers indicating that ROCK1 deletion could favorably modify hypertrophy without inhibiting it. Furthermore, ROCK1 deletion also improved contractile response to β-adrenergic stimulation in Gαq transgenic mice. Consistent with this observation, ROCK1 deletion prevented down-regulation of type V/VI adenylyl cyclase expression, which is associated with the impaired β-adrenergic signaling in Gαq mice. The present study establishes for the first time a role for ROCK1 in cardiac dilation and contractile dysfunction.     

NADPH氧化酶与Rho/Rho-激酶激活在外膜介导的血管重塑中的作用

目的　探讨NADPH氧化酶与Rho/Rho 激酶在外膜介导的血管重塑中的作用。方法在体去除兔颈动脉外膜 ,于术后即刻、1周及 2周取出颈动脉。用图像分析系统测定内膜及中层面积 ;应用多道生理仪测血管反应性 ;原位杂交及RT PCR检测mRNA表达。结果　 (1)血管外膜去除后内膜增生 ,2周时内膜增生较 1周时更为明显。对照侧无内膜增生。 (2 )与对照侧比较 ,去外膜侧血管在术后即刻、1周对去甲肾上腺素的收缩反应减弱 (P <0 0 5)。 (3 )与对照侧比较 ,去外膜侧NADPH氧化酶P2 2PhoxmRNA表达在 1周时增高 (P <0 0 5)。 (4)与对照侧比较 ,去外膜侧Rho 激酶mRNA表达在 2周时增高 (P <0 0 5)。结论　外膜去除后血管内膜增生 ,血管舒缩功能改变 ,其发生机制与NADPH氧化酶及Rho 激酶激活有关     

An integrin and Rho GTPase-dependent pinocytic vacuole mechanism controls capillary lumen formation in collagen and fibrin matrices

A major question that remains unanswered concerning endothelial cell (EC) morphogenesis is how lumens are formed in three-dimensional extracellular matrices (ECMs). Studies from many laboratories have revealed a critical role for an ECM-integrin-cytoskeletal signaling axis during EC morphogenesis. We have discovered a mechanism involving intracellular vacuole formation and coalescence that is required for lumen formation in several in vitro models of morphogenesis. In addition, a series of studies have observed vacuoles in vivo during angiogenic events. These vacuoles form through an integrin-dependent pinocytic mechanism in either collagen or fibrin matrices. In addition, we have shown that the Cdc42 and Rac1 guanosine triphosphatases (GTPases), which control actin and microtubule cytoskeletal networks, are required for vacuole and lumen formation. These GTPases are also known to regulate integrin signaling and are activated after integrin-matrix interactions. Furthermore, the expression of green fluorescent protein-Rac1 or -Cdc42 chimeric proteins in ECs results in the targeting of these fusion proteins to intracellular vacuole membranes during lumen formation. Thus, a matrix-integrin-cytoskeletal signaling axis involving both the Cdc42 and Rac1 GTPases regulates the process of EC lumen formation in three-dimensional collagen or fibrin matrices.     

TNF-α对肺微血管内皮细胞ERM蛋白表达的研究

目的 观察肿瘤坏死因子-α(TNF-α)对大鼠肺微血管内皮细胞(PMVEC)表达埃兹蛋白-根蛋白-膜突蛋白(ezrin-radixin-moesin,ERM)及磷酸化ERM蛋白(p-ERM)的影响,并初步探讨Rho激酶(ROCK)与ERM蛋白磷酸化的关系.方法 体外培养大鼠PMVEC,随机(随机数字法)分为TNF-α量效组(0、0.1、1、10 μg/L TNF-α与PMVEC孵育60 min)、TNF-α时效组(10 μg/LTNF-α分别与PMVEC孵育0、15、30、60、90、120、180 min)和ROCK抑制剂(Y-27632)干预组:分别以10μg/L的TNF-α和30 μmol/L Y-27632+ 10 μg/LTNF-α与PMVEC孵育60min.Western印迹检测ERM蛋白及p-ERM相对表达量.采用SPSS 16.0软件进行分析,多组变量间比较采用单因素方差分析,以P＜ 0.05为差异具有统计学意义.结果 Western印迹检测到大鼠PMVEC均表达ERM蛋白和p-ERM,量效组p-ERM表达量随TNF-α浓度(0、0.1、1、10 μg/L)增加逐渐升高,分别为0.648±0.102、0.728±0.082、0.926±0.121、1.245±0.134(均P=0.000).时效组p-ERM相对表达量于15 min开始上升(0.777±0.151),90 min达高峰(1.295±0.176),之后渐下降,120 min (0.802±0.139),180 min仍维持较高水平(0.769±0.128),分别与未刺激0 min组(0.631±0.123)比较,P=0.004,0.000,0.001,0.016.ROCK抑制剂预处理PMVEC后再给予TNF-α刺激,p-ERM相对表达量(0.634±0.112)较单独TNF-α刺激组(0.875±0.164)显著减少(P =0.002),而较单独ROCK抑制剂组(0.661±0.108)和未处理组(0.654±0.125)差异无统计学意义(分别为P=0.973,P=0.900).结论 TNF-α诱导大鼠PMVEC中的ERM蛋白磷酸化表达增加,ROCK参与其磷酸化调控.     

Rho and ROCK signaling in VEGF-induced microvascular endothelial hyperpermeability

OBJECTIVES: Vascular endothelial growth factor (VEGF) plays an important role in the regulation of microvascular permeability under various physiological and pathological conditions. The authors tested the hypothesis that the small GTPase Rho and its downstream effector ROCK (Rho-associated coiled-coil-containing protein kinase) mediate VEGF-induced increases in venular permeability. They also investigated myosin light chain (MLC) phosphorylation and actin polymerization, two well-characterized targets of the Rho-ROCK pathway that are implicated in the regulation of endothelial barrier function. METHODS: The apparent permeability coefficient of albumin (P(a)) was measured in intact isolated porcine coronary venules and in cultured coronary venular endothelial cell (CVEC) monolayers. RhoA activation was determined using a Rhotekin-agarose pull down assay. MLC phosphorylation was evaluated by immunoblotting with phospho-specific antibodies, and endothelial cellular F-actin was viewed using fluorescence microscopy. RESULTS: VEGF increased P(a) in both isolated coronary venules and CVEC monolayers. The hyperpermeability response occurred in a similar time course to that of Rho activation, MLC phosphorylation, and actin stress fiber formation. Selective blockage of ROCK with Y27632 dose-dependently inhibited VEGF-induced venular hyperpermeability. Moreover, inhibition of either Rho with exoenzyme C3 or ROCK with Y-27632 attenuated VEGF-induced increases in permeability, MLC phosphorylation, and actin-stress fiber formation in CVEC monolayers. CONCLUSIONS: Collectively, these findings suggest that the Rho-ROCK signal pathway contributes to VEGF-induced hyperpermeability. Myosin light-chain phosphorylation and actin stress fiber formation occur concomitantly with the increase in permeability upon VEGF stimulation.     

Blockade of Rho/Rho-associated coiled coil-forming kinase signaling can prevent progression of hepatocellular carcinoma in matrix metalloproteinase-dependent manner

Aim:  There is growing evidence that the Rho/Rho-associated coiled coil-forming kinase (ROCK) signaling pathway is upregulated in tumors and plays a key role in cancer invasion and metastasis. Our aim was to test the anticancer effects of Rho/ROCK inhibitor, Y-27632, including possible mechanisms in a highly-metastasizing hepatocellular carcinoma (HCC) mouse model on its secretion of matrix metalloproteinase (MMP) and tumor progression.
Methods:  Following orthotopic implantation of CBO140C12 HCC tumor fragments into the liver of mice, the mice were randomly assigned to a Y-27632-treated group or control group. After treatment for 4 weeks, specimens were obtained to evaluate tumor size, metastases, and immunohistochemical findings. In vitro , we examined the effects of Y-27632 and RhoC siRNA on MMP-2 and -9 expressions, invasiveness, and apoptosis in cultured tumor cells.
Results:  Both RhoA and RhoC were upregulated in HCC-bearing livers, and Y-27632 significantly inhibited not only tumor growth and intrahepatic metastasis ( P  < 0.05), but also tumoral MMP-9 expression. Moreover, Y-27632 treatment resulted in large necrotic areas in tumors. In vitro , Y-27632 and RhoC siRNA reduced MMP-2 and -9 expressions, as well as the chemotactic migration of tumor cells dose-dependently, and increased apoptosis eight times.
Conclusion:  Y-27632 suppresses progression and limits the intrahepatic metastasis of established HCC. This could be linked to the decreased MMP expression and induction of apoptosis in tumor cells. Rho signaling may prove to be a productive target in anticancer therapy.     

Distinct molecular underpinnings of Drosophila olfactory trace conditioning

Trace conditioning is valued as a simple experimental model to assess how the brain associates events that are discrete in time. Here, we adapted an olfactory trace conditioning procedure in Drosophila melanogaster by training fruit flies to avoid an odor that is followed by foot shock many seconds later. The molecular underpinnings of the learning are distinct from the well-characterized simultaneous conditioning, where odor and punishment temporally overlap. First, Rutabaga adenylyl cyclase (Rut-AC), a putative molecular coincidence detector vital for simultaneous conditioning, is dispensable in trace conditioning. Second, dominant-negative Rac expression, thought to sustain early labile memory, significantly enhances learning of trace conditioning, but leaves simultaneous conditioning unaffected. We further show that targeting Rac inhibition to the mushroom body (MB) but not the antennal lobe (AL) suffices to achieve the enhancement effect. Moreover, the absence of trace conditioning learning in D1 dopamine receptor mutants is rescued by restoration of expression specifically in the adult MB. These results suggest the MB as a crucial neuroanatomical locus for trace conditioning, which may harbor a Rac activity-sensitive olfactory "sensory buffer" that later converges with the punishment signal carried by dopamine signaling. The distinct molecular signature of trace conditioning revealed here shall contribute to the understanding of how the brain overcomes a temporal gap in potentially related events.     

Unraveling the interface of signal recognition particle and its receptor by using chemical cross-linking and tandem mass spectrometry

Among the methods used to unravel protein interaction surfaces, chemical cross-linking followed by identification of the cross-linked peptides by mass spectrometry has proven especially useful in dynamic and complex systems. During the signal recognition particle (SRP)-dependent targeting of proteins to the bacterial plasma membrane, the specific interaction between Ffh (the protein component of SRP) and FtsY (the SRP receptor) is known to be essential for the efficiency and fidelity of this process. In this work, we studied the Escherichia coli and Thermus aquaticus Ffh.FtsY complexes by using chemical cross-linking and tandem mass spectrometry to identify nine intermolecular cross-linked peptides. This information was used in conjunction with a previously undescribed model-building approach that combines geometric restraint optimization with macromolecular docking. The resulting model of the Ffh.FtsY complex is in good agreement with the crystal structure solved shortly thereafter. Intriguingly, four of the cross-linked pairs involve the M domain of Ffh, which is absent from the crystal structure, providing previously undocumented experimental evidence that the M domain is positioned in close proximity to the Ffh.FtsY interface in the complex.