热休克蛋白B1对大鼠心肌细胞氧化应激性损伤的作用

目的探讨线粒体在热休克蛋白 B1(HSPB1)抗氧化应激诱导的大鼠心肌细胞株 H9c2损伤中的作用。方法以培养的稳定高表达 HSPB1 H9c2(HSPB1细胞)和空载体转染的 H9c2(对照细胞)为模型,0～1000/μmol/L H_2O_2刺激2h,观察细胞形态学、线粒体内膜跨膜电位、内源性活性氧自由基(ROS)水平。结果 (1)HSPB1高表达显著减轻 H_2O_2诱导的细胞形态学的损伤变化;(2)HSPB1高表达显著减轻 H_2O_2诱导的线粒体跨膜电位丧失:0、75、150、300、500、1000μmol/LH_2O_2刺激后,HSPB1和对照细胞的跨膜电位分别为10.0±0.11和7.01±0.26,9.11±0.17和6.05±0.19,7.69±0.28和5.14±0.28,6.95±0.13和4.66±0.11,6.61±0.20和1.85±0.35,6.60±0.05和1.19±0.01,各组差异均有统计学意义(P<0.01);(3)HSPB1和对照细胞在0、75、150、300、500、1000μmol/L H_2O_2诱导后,内源性 ROS 水平分别为5527±248和5964±387、6719±336和8528±411、6469+160和7795±136、7042±12和7591±203、6148±208和6911±136、5468±546和6822±371,除0 μmol/L 外,其他各组差异均有统计学意义(P<0.05)。结论HSPB1高表达显著保护了大鼠心肌细胞因氧化应激诱导的形态学变化,这可能与稳定线粒体膜电位和抑制线粒体产生的 ROS 有关。     

Dopaminergic inhibition of anterior pituitary adenylate cyclase activity and prolactin release: the effects of perturbing calcium on catalytic adenylate cyclase activity

The dopaminergic inhibition of anterior pituitary adenylate cyclase activity, cAMP accumulation, and prolactin release was studied in the presence of the Ca2+ channel activator, maitotoxin. In isobutylmethylxanthine (IBMX)-treated cells, maitotoxin stimulated prolactin secretion within 30 s and cAMP accumulation within 1 min. Although dopamine reduced cAMP accumulation and prolactin release, the effectiveness of the catecholamine was reduced in the presence of maitotoxin. When hemipituitary glands were exposed for 10 min to 100 ng maitotoxin/ml, their membranes showed increased adenylate cyclase activity. The hypothesis that maitotoxin stimulates adenylate cyclase activity by increasing Ca2+ availability was supported by the observation that, at concentrations up to 100 microM, Ca2+-stimulated anterior pituitary adenylate cyclase activity. Although dopamine decreased basal and maitotoxin-stimulated pituitary cAMP accumulation, via changes in adenylate cyclase activity, the decrement in cyclic nucleotide production, but not prolactin release, can be ascribed to the effect of the catecholamine on the basal activities of these parameters. These data provide additional evidence that an increased Ca2+ flux is stimulating to cAMP generation and prolactin release, whereas dopamine is inhibitory to these processes.     

H9c2细胞株在心肌缺氧/复氧实验中的应用

目的本实验对H9e2细胞株进行缺氧／复氧,旨在引进一种操作、培养简便,可传代且功能与分离培养的原代细胞相似的大鼠心肌细胞株。方法培养的H9c2细胞随机均匀分为常氧对照组（NC组,6只）和缺氧／复氧组（H／R组,6只）。细胞置于含95％N2,5％CO2的三气培养箱内缺氧3h,置于含95％空气、5％CO2的CO2培养箱中进行复氧培养。台盼蓝染色记数细胞,MTT法检测细胞存活率,检测培养基上清中乳酸脱氢酶（LDH）含量反映细胞损伤程度,并与在分离培养的乳鼠原代心肌细胞上进行的研究做对比。结果与常氧组相比,H9c2细胞缺氧／复氧处理后,存活率明显降低[（68．65±7．55）％比（91．95±9．13）％,P〈0．01],LDH漏出量增加[（132．38±24．07）U／L比（34．69±9．86）U／L,P〈0．01]。原代乳鼠心肌细胞缺氧／复氧处理后,LDH漏出量增加[（428．62±56．65）U／L比（116．02±23．01）U／L,P〈0．01]。结论H9c2细胞株具有与原代培养乳鼠心肌细胞相似的功能特性,易于分离培养,并可传代,在缺氧／复氧等实验中具有广阔的应用前景。     

Hormone sensitivity of adenylate cyclase activity in cardiac sarcolemma and sarcoplasmic reticulum preparations.

The functional significance of the adenylate cyclase activity found in cardiac microsomal preparations enriched in sarcoplasmic reticulum vesicles was examined by comparing the effects of agents known to modify this enzyme in sarcolemmal and sarcoplasmic reticulum fractions prepared from guinea pig ventricles. The sensitivity of the sarcolemmal adenylate cyclase to adrenergic agonists resembled that of a typical β-receptor. Although the response to these agonists was similar in the case of the sarcoplasmic reticulum enzyme, the extent of stimulation was much less than in the sarcolemma. The pH optimum of the sarcoplasmic reticulum enzyme of 7.5 was slightly lower than that of the sarcolemmal enzyme, which was 8.0; and NaF shifted the pH optimum of the latter, but not the former. The sarcoplasmic reticulum adenylate cyclase was less sentitive to alkali metal salts and GTP than was the sarcolemmal enzyme. While these studies cannot exclude the possibility that the lesser response of the sarcoplasmic reticulum enzyme to catecholamines, alkali metal salts, and GTP arose from contaminating sarcolemmal fragments that were modified during the preparation of these subcellular fractions, they are consistent with the view that the cardiac cell sarcoplasmic reticulum contains an adenylate cyclase that is less regulated, or regulated by different factors, than those which modulate sarcolemmal adenylate cyclase.     

Evidence for A2 adenosine receptor-mediated effects on adenylate cyclase activity in rat ovarian membranes

Effects of adenosine analogues on adenylate cyclase activity in preovulatory rat ovarian membranes were studied. Adenosine analogues stimulated adenylate cyclase activity in the following rank order of potency: NECA (5'-(N-ethyl)carboxamidoadenosine) greater than 2-chloroadenosine greater than N6-(R-phenylisopropyl)-adenosine greater than N6-(S-phenylisopropyl)adenosine. The apparent EC50 for NECA was 0.28 microM. The adenosine receptor antagonist 8-phenyltheophylline (10 microM) displaced the dose-response curve for NECA to the right, increasing the EC50 for NECA about one order of magnitude. NECA also additively increased maximally FSH-stimulated adenylate cyclase activity. These results suggest that adenosine stimulates adenylate cyclase in rat ovarian membranes via adenosine receptors of the A2 type.     

The role of zinc status in altered cardiac adenylate cyclase activity in diabetic rats

Zinc deficiency and altered myocardial adenylate cyclase activity commonly occur in diabetes. To determine whether the zinc intake of the animal can account for the altered beta-adrenergic receptor activity in the diabetic heart, we determined the beta-adrenergic receptor number and isoproterenol-, NaF- and forskolin-stimulated adenylate cyclase activity in diabetic and control rats maintained on low, normal and high zinc diets for 3 weeks. Scatchard analysis of [125I]iodocyanopindolol binding to control heart membrane preparations revealed a binding capacity of 17.3 +/- 1.3 fmol/mg protein with a Kd of 35 +/- 1.0 pmol/l. Neither the diabetic state nor the zinc status altered these binding parameters. The isoproterenol-stimulated adenylate cyclase activity was significantly lower in diabetic rats on low zinc diets compared with controls. The NaF- (65.1 +/- 5.4 vs 60.8 +/- 6.4 pmol cAMP.mg protein-1.min-1) and forskolin-stimulated adenylate cyclase activities (161 +/- 9.3 vs 154 +/- 21.2 pmol cAMP.mg protein-1. min-1) were not significantly altered in diabetic rats. Low dietary zinc intake compared with high zinc diet significantly increased NaF- and forskolin-stimulated adenylate cyclase activity both in diabetic rats and controls. The effect of dietary zinc content on isoproterenol-stimulated adenylate cyclase was significant in control rats only. Thus zinc intake appears to be an important determinant of cardiac adenylate cyclase activity level. Additional factors peculiar to the diabetic state are involved in the modulation of beta-adrenergic responsiveness of the diabetic heart.     

人心肌热休克蛋白27基因克隆及其高表达对大鼠心肌细胞氧化损伤的保护作用

目的克隆和重组人心肌热休克蛋白27(HSP27)基因,观察HSP27高表达对大鼠心肌细胞氧化应激的影响。方法将RTPCR获得的人心肌HSP27基因全长cDNA,重组入质粒载体pCDNA31 。将重组体pCDNA31 /HSP27转染大鼠心肌细胞系H9c2,经G418选择性培养获得稳定转染细胞系;观察HSP27高表达对H2O2诱导的乳酸脱氢酶(LDH)释放和细胞凋亡的影响。结果(1)pCDNA31 /HSP27在293T和H9c2中表达良好;(2)0、100、250、500、1000μmol/LH2O2引起的LDH释放,在HSP27高表达组和野生型组分别为0396±0017和0390±0009、0437±0014和0416±0015、0471±0018和0417±0009、0505±0030和0657±0022、0547±0027和0661±0011(均为P<0001);(3)150μmol/LH2O2诱导的细胞凋亡在HSP27高表达和野生型组分别为总细胞数的(10693±1122)%和(4027±1628)%,P<001。结论人心肌HSP27基因被成功克隆和重组,其在大鼠心肌细胞系H9c2的高度表达显著保护了该细胞的过氧化损伤。     

Thermodependence of basal and stimulated cardiac adenylate cyclase activity in normotensive and spontaneously hypertensive rats

The cardiac adenylate cyclase activity from normotensive and spontaneously hypertensive (SHR) rats was studied as a function of temperature between 17° and 37°C. Arrhenius plots of adenylate cyclase activity displayed a break around 31°C when tested under basal conditions or in the presence of GTP but were linearized after activation with p[NH]ppG, NaF, secretin, glucagon or isoproterenol. The energy of activation of adenylate cyclase activity in the presence of GTP (9.5 ± 0.5 kcal/mol) was significantly lower than in the presence of p[NH]ppG (17.7 ± 0.8 kcal/mol). A hormone was without effect on the energy of activation observed with either GTP or p[NH]ppG but the simultaneous presence of hormone and nucleotide increased markedly the activity of the enzyme. The energies of activation were analyzed in terms of variation of enthalpy and entropy and discussed in relation with the process of activation and coupling of the guanine nucleotide regulatory protein. These thermodynamic characteristics were similar in cardiac membranes from normotensive and spontaneously hypertensive rats, suggesting that the impairment of hormone-stimulated adenylate cyclase activity observed in the heart membranes of hypertensive rats was not a consequence of a defect in the activation process of the enzyme.     

Chinese hamster ovary cell population density affects intracellular concentrations of calcium-dependent regulator and ability of regulator to inhibit adenylate cyclase activity

The adenylate cyclase activity [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] of crude Chinese hamster ovary cell membranes was inhibited 30-40% by low concentrations (6-600 ng/ml) of calcium-dependent regulator (CDR). This inhibitory effect was lost at concentrations of CDR above 600 ng/ml. The adenylate cyclase activity of membranes prepared from low population density Chinese hamster ovary cells was not appreciably altered by CDR. However, with increasing cell population density there was a significant increase in the ability of CDR to inhibit cyclic AMP formation. Further, the intracellular levels of CDR determined in the 12,000 x g supernatant and particulate fractions varied inversely with increasing cell population density. As cell number increased from 2 x 10(6) to 10 x 10(6) cells per dish the CDR concentration present in the supernatant fraction increased from 0.4 to 0.8 mug of CDR per mg of protein, while the amount of endogenous CDR associated with the particulate fraction decreased from 0.6 to 0.4 mug of CDR per mg of protein. This suggests that possible changes in the distribution of CDR between the supernatant and membrane fractions might serve as a regulatory mechanism for activities under CDR control.     

Paradoxical effects of short- and long-term interleukin-6 exposure on liver injury and repair

Interleukin-6 (IL-6) is an important mediator of liver regeneration and repair that is also elevated in chronic liver diseases, including fatty liver of obesity and cirrhosis. IL-6 has been reported both to delay and accelerate liver regeneration. We examined the effects on liver injury and regeneration of a continuous administration of exogenous IL-6 to mice by injection of an IL-6-expressing CHO-cell line in athymic nude mice and by osmotic mini-pump delivery of recombinant murine IL-6. Short-term IL-6 administration (1-2 days) accelerated early recovery of liver mass, whereas more long-term administration (5-7 days) markedly impaired liver regeneration. Similarly, short-term IL-6 treatment increased hepatic resistance to the lethal effects of the Fas agonist Jo-2, but on more prolonged IL-6 exposure the Jo-2 resistance vanished. IL-6 administration initially induced expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, correlating with protection against Fas-mediated cell death. More prolonged IL-6 administration, however, resulted in marked induction of the pro-apoptotic protein Bax. This result coincided with increased activation of the type II or intrinsic, mitochondrial path to cell death, manifested by increased caspase-9 activation and increased cytochrome c release after Jo-2 exposure. These data demonstrate that IL-6 can function acutely to improve hepatic regeneration and repair, but that more chronic exposure not only abolishes the protective effects of IL-6, but actually sensitizes the liver to injury and death. In conclusion, elevated IL-6 in certain chronic liver diseases contributes to an increased likelihood of liver failure after injury.     

硒对砷诱导的大鼠H9c2心肌细胞氧化损伤的抑制作用和可能机制

目的探讨硒对砷诱导的H9c2心肌细胞氧化损伤的保护作用及其可能机制。方法H9c2细胞按处理方法不同分对照组、Na2SeO3（1μmol/L）组、As2O3（5μmol/L）组、As2O3（5μmol/L）＋Na2SeO3（1μmol/L）组以及NF-κB抑制剂PDTC（100 nmol/L）不同处理组。应用MTT法检测细胞存活率;DTNB法检测细胞内还原型谷胱甘肽（GSH）含量;二氢乙啶（Dihydroethidium,DHE）染色法检测细胞活性氧（reactive oxygen species,ROS）产生;提取细胞核蛋白,Western blotting法检测核蛋白中NF-κB的p65亚单位表达。结果与对照组相比,5μmol/L As2O3作用下,H9c2细胞生存率、细胞内GSH含量降低,ROS生成和核蛋白中NF-κB p65的表达增加;1μmol/L Na2SeO3可以提高As2O3损伤的H9c2细胞存活率和细胞内GSH含量,减少ROS生成和p65的表达。PDTC干预可减轻砷所致心肌细胞的损伤,表现为细胞ROS产生减少;Na2SeO3和抑制剂PDTC共同作用时,H9c2细胞生成ROS进一步减少。结论NF-κB信号途径参与了As2O3诱导的H9c2心肌细胞氧化应激反应,Na2SeO3可能通过抑制NF-κB减轻氧化应激诱导的H9c2细胞损伤。     

Uptake of tri-iodothyronine and thyroxine in myoblasts and myotubes of the embryonic heart cell line H9c2(2-1)

Uptake of tri-iodothyronine (T(3)) was compared with that of thyroxine (T(4)) in the embryonic heart cell line H9c2 (2-1). These cells propagate as myoblasts and form differentiated myotubes upon reduction of the serum concentration, as indicated by a 31-fold increase in creatine kinase activity. Protein and DNA content per well were around 2-fold higher in myotubes than in myoblasts. When expressed per well, T(3) and T(4) uptake were, compared with myoblasts, 1.9- to 2-fold and 3.1- to 4-fold higher in myotubes respectively. On the other hand, the characteristics of T(3) and T(4) uptake were similar in myoblasts and myotubes. At any time-point, T(4) uptake was 2-fold higher than that of T(3), and both uptakes were energy but not Na(+) dependent. T(3) and T(4) uptake exhibited mutual inhibition in myoblasts and myotubes: 10 microM unlabeled T(3) reduced T(4) uptake by 51-60% (P<0.001), while 10 microM T(4) inhibited T(3) uptake by 48-51% (P<0.001). Furthermore, T(3) and T(4) uptake in myoblasts was dose-dependently inhibited by tryptophan (maximum inhibition around 70%; P<0.001). Exposure of the cells to T(3) or T(4) during differentiation significantly increased the fusion index (35 and 40%; P < 0.01). Finally, both myoblasts and myotubes showed a small deiodinase type I activity, while deiodinase type II activity was undetectable. In conclusion, T(3) and T(4) share a common energy-dependent transport system in H9c2(2-1) cells, that may be important for the availability of thyroid hormone during differentiation.     

Muscarinic cholinergic-receptor stimulation of specific GTP hydrolysis related to adenylate cyclase activity in canine cardiac sarcolemma

One component of muscarinic receptor inhibition of the function of cardiac ventricles is mediated by the inhibition of activated adenylate cyclase activity in sarcolemma. We have shown previously that muscarinic agonists inhibit GTP- but not Gpp(NH)p-activated adenylate cyclase activity, and various studies in other tissues indicate that nonhydrolyzable GTP analogues prevent inactivation of the enzyme. These data have suggested a role for GTP hydrolysis in the mechanism of inhibition of adenylate cyclase. The present study demonstrates that purified canine cardiac sarcolemma displays high-affinity GTPase activity that is reciprocally related to adenylate cyclase activity. The high-affinity GTPase activity was stimulated by muscarinic agonists and blocked by atropine. Furthermore, the one-half maximal effects of oxotremorine for binding to muscarinic receptors, stimulation of high-affinity GTPase activity, and inhibition of adenylate cyclase activity were similar. Muscarinic stimulation of GTPase activity and inhibition of adenylate cyclase activity required functional activity of the pertussis toxin (IAP) substrate(s). Treatment of sarcolemmal membranes with IAP attenuated the ability of oxotremorine to both stimulate high-affinity GTPase activity and inhibit adenylate cyclase activity. These studies indicate that muscarinic receptor stimulation of high-affinity GTPase activity dependent on functional IAP substrate(s) is closely linked to the mechanism of muscarinic inhibition of adenylate cyclase activity.     

Epinephrine-sensitive adenylate cyclase of human fat cell ghosts: Stabilization of enzyme activity by fluoride and nucleotides

The effects of fluoride and nucleotides on the stability of the human fat cell adenylate cyclase were studied. Preincubation of fat cell ghosts in 1 mM KHCO₃ at 30°C for 20 min resulted in a substantial loss of basal, epinephrine- and NaF-stimulated enzyme activities. Inactivation was almost completely prevented by nucleotides (ATP, GTP and GMP-P(NH)P). ¹ Epinephrine was without influence on the time course and degree of inactivation. NaF (20 mM), however, like the nucleotides protected from inactivation. In contrast to epinephrine NaF failed to stimulate enzyme activity in membranes pretreated with GMP-P(NH)P (0.1 mM). Our results show that NaF exerts two distinct effects on the human fat cell adenylate cyclase: stimulation of enzyme activity and protection from inactivation. Both effects appear to be related to the binding of nucleotides.     

Protein metabolism in acromegaly: differential effects of short- and long-term treatment

CONTEXT: GH acutely increases body protein by stimulating protein synthesis and reducing protein oxidation. OBJECTIVE: The objective of the study was to determine whether these changes in protein metabolism are sustained in long-term GH excess and reversed by correction. DESIGN: We conducted a cross-sectional study in 16 acromegalic and 18 normal subjects and a longitudinal study in which acromegalic subjects were studied before and after short-term (n=8) or long-term (n=10) treatment. SETTING: The study was conducted at a clinical research center. MAIN OUTCOME MEASURES: Whole-body rates of leucine appearance (leucine Ra; an index of protein breakdown), leucine oxidation, and nonoxidative leucine disposal (NOLD; an index of protein synthesis) estimated using infusion of 1-[13C] leucine were measured. RESULTS: Leucine Ra and NOLD were greater (P<0.01) in acromegalic compared with normal subjects, whereas leucine oxidation did not differ. Leucine oxidation increased significantly (P<0.05) after short-term treatment but returned to baseline after long-term treatment. Both leucine Ra and NOLD decreased significantly (P<0.05) after short- and long-term treatment. Adjustment for body composition did not affect results. CONCLUSIONS: In acromegalic subjects, protein breakdown and synthesis are increased, whereas protein oxidation does not differ from normal subjects. Protein oxidation increases transiently, whereas protein breakdown and synthesis are stably reduced after treatment. Because protein oxidation represents irreversible loss, we conclude that the normal state of protein oxidation found in acromegaly and after long-term treatment represents metabolic adaptation, which maintains protein mass at a steady state after stable changes in GH status.     

ANXA2敲除的A549细胞系的构建及其对H1N1和H9N2流感病毒复制的影响北大核心CSCD

目的旨在利用CRISPR/Cas9基因编辑技术构建ANXA2敲除的A549细胞,并探索ANXA2敲除对流感病毒复制的影响。方法本研究设计了3对靶向ANXA2基因外显子的特异性sgRNAs,分别将sgRNAs构建到LentiCRISPRv2载体上获得重组质粒,与辅助质粒共转染293T细胞包装成慢病毒后感染A549细胞,通过嘌呤霉素压力及有限稀释法筛选ANXA2基因敲除的单克隆细胞株,用靶基因测序及Western-blot验证ANXA2的敲除效果,并通过CCK-8试验比较ANXA2敲除细胞和野生型A549细胞的细胞活力。再分别用人流感病毒WSN(H1N1)和禽流感病毒SD98(H9N2)感染ANXA2敲除和野生型A549细胞,经TCID_(50)检测ANXA2敲除对流感病毒复制的影响。结果成功获得了ANXA2敲除的A549细胞系,且与野生型A549细胞相比,细胞活力无显著差异;ANXA2敲除后WSN(H1N1)和SD98(H9N2)流感病毒的病毒滴度均升高,其中ANXA2对SD98(H9N2)流感病毒的影响要大于WSN(H1N1)。结论本研究利用CRISPR/Cas9基因编辑技术构建了ANXA2敲除的A549细胞,并发现ANXA2敲除促进了流感病毒的复制,本研究为流感病毒复制和致病机制的研究奠定了基础。