Hydrogen peroxide-induced oxidative stress in MC3T3-E1 cells: The effects of glutamate and protection by purines

Glutamate has toxic effects on a number of tissues, partly by inducing toxic (e.g., oxidative) stress, whereas adenosine can be protective. Since there is evidence that glutamate and adenosine receptors are present in bone, we set out to study whether oxidative stress, induced by hydrogen peroxide (H2O2), affected viability in the MC3T3-E1 osteoblast-like cell line and whether treatment with adenosine receptor ligands attenuated this. Hydrogen peroxide (100 microM to 5 mM) reduced the viability of the MC3T3-E1 cells, while catalase reversed this cell loss and itself had some mitogenic effect. Superoxide dismutase (SOD) increased the number of viable cells alone but failed to modify significantly the effect of H2O2 treatments. Glutamate (100 microM, 1 mM) and NMDA (10 microM), applied alone for up to 1 h, had a mitogenic effect (P < 0.05). Adenosine A1 and A2A receptor agonists and antagonists at low and high concentrations showed some mitogenic effects when added singly, but only high concentrations of the agonists showed significant protection against cell death resulting from H2O2 treatments. Contributions from both apoptotic and necrotic pathways were implicated in the H2O2-induced cell loss as was demonstrated by the use of the caspase-3 inhibitor (Z-DEVD-fmk) and the PARP-1 inhibitor (DPQ). The results demonstrate that hydrogen peroxide was toxic to MC3T3-E1 cells, whereas glutamate was not and may even have a trophic influence. Adenosine and its receptors afforded some protection to osteoblasts against cellular death mediated partly by apoptosis and partly by necrosis.     

Etiologic mechanism and prevention of perioperative stroke

Despite advances in surgical techniques and improvements in perioperative care, the incidence of perioperative strokes has not decreased, reflecting the aging of the population and the increased number of patients with complication. We investigated the cases who were consulted due to perioperative stroke. From April, 2004 to March, 2007, a total of 102 patients were referred for neurological evaluation because of perioperative stroke. Types of planned or performed surgery, risk factors, types of stroke and timing of the events were analyzed. Sixty-seven cases were consulted preoperatively for history or risk factors of stroke. Forty-seven cases had ischemic risk factors and cerebral vascular recanalization was carried out in four patients who experienced severe cerebral hypoperfusion. The other patients with ischemic risk factors were treated to avoid dehydration or hypotension perioperatively. Nine cases with hemorrhagic risk factors, such as cerebral aneurysm, were treated to avoid significant hypertension during surgery. The types of planned surgery were cardiovascular surgery in 29 cases, abdominal surgery in 13, cervical surgery in 7, and thoracic surgery in 6. Except for one case, who suffered cerebral embolism due to cardiac surgery, those who were consulted preoperatively did not experience stroke. Neurological events had occurred in 35 patients and they were consulted postoperatively. The surgical procedures were cardiovascular surgery in 19 patients, thoracic surgery in 6, abdominal surgery in 6. The types of stroke were cerebral infarction in 20 cases, hypoxic brain in 8, and transient ischemic attack in 5. The cause of the cerebral infarction was considered as cerebral embolism in 19 cases. Those who were consulted preoperatively were treated to prevent intraoperative stroke and did not suffer neurological complication. Most stoke in patients undergoing surgery were not related to hypoperfusion but due to embolism.     

Nitric oxide synthesis in the in vivo allograft response: a possible regulatory mechanism.

Activated macrophages are known to oxidatively metabolize L-arginine to nitric oxide and citrulline. We have recently shown that nitric oxide is a potent inhibitory molecule in the in vitro rat mixed-splenocyte culture, resulting in inhibition of proliferation and cytolytic T-cell induction. We undertook this study using the sponge matrix allograft model in the rat to determine whether nitric oxide plays a role in an in vivo allograft response. Our experiments showed that on day 6 after grafting, when cytolytic activity of allograft-infiltrating cells is first detected, allogeneic graft fluid contains higher levels of NO2-/NO3- (the stable endproducts of nitric oxide metabolism) than syngeneic graft fluid. Furthermore, evaluation of the supernatants of cultured graft-infiltrating cells revealed that allogeneic graft-infiltrating cells spontaneously produce higher amounts of nitric oxide than syngeneic graft-infiltrating cells. The nitric oxide production was inhibited in the presence of NG-monomethyl-L-arginine (NMA), the competitive inhibitor of nitric oxide production. Most of the nitric oxide production was observed in the adherent macrophage fraction of the allograft-infiltrating cells. When allograft-infiltrating cells were cultured in the presence of NMA, donor-specific cytolytic activity was observed, whereas allograft-infiltrating cells cultured in the absence of NMA showed no cytolytic activity. These data show that nitric oxide production may play an important regulatory role in the allograft response.     

In vivo tracking of human mesenchymal stem cells in experimental stroke

To understand the fates of human mesenchymal stem cells (hMSCs) following transplantation into a rodent model of middle cerebral artery occlusion (MCAo), magnetic resonance imaging (MRI) techniques were employed, hMSCs were labeled with ferumoxides (Feridex)--protamine sulfate complexes, which were visualized and examined by MRI up to 10 weeks following transplantation. Migration of the transplanted cells to the infarcted area was further confirmed by histological methods. We found that the hMSCs transplanted in MCAo models possess the capacity to migrate to the infarcted area extensively in both ipsilateral and contralateral injections, exhibiting a pathotropism. We also analyzed the detailed migration patterns of transplanted hMSCs. We speculate that the extensive migratory ability of hMSCs may represent a therapeutic potential for developing efficient cell transplantation strategies in stroke.     

Recent in vivo surgical robot and mechanism developments

The surgical landscape is quickly changing because of the major driving force of robotics. Well-established technology that provides robotic assistance from outside the patient may soon give way to alternative approaches that place the robotic mechanisms inside the patient, whether through traditional laparoscopic ports or through other, natural orifices. While some of this technology is still being developed, other concepts are being evaluated through clinical trials. This article examines the state of the art in surgical robots and mechanisms by providing an overview of the ex vivo robotic systems that are commercially available to in vivo mechanisms, and robotic assistants that are being tested in animal models.     

sigma-1受体在缺血性脑卒中的作用及机制研究进展

缺血性脑卒中(ischemic stroke, IS)是最常见的神经系统疾病,因其高致残率和病死率,且治疗时间窗口窄,迫切需要寻找新的治疗手段来减少IS后的脑损伤。sigma-1受体(sigma-1 receptor, Sig-1R)是一种特异性分子伴侣蛋白,在中枢神经系统中高表达,参与神经元可塑性调节。文章通过对Sig-1R结构、分布、相关通路及配体的阐述,针对Sig-1R在IS中的作用及其机制进行综述,为探索Sig-1R相关配体发展为抗IS候选药物提供理论依据。     

In vivo activity of leflunomide: pharmacokinetic analyses and mechanism of immunosuppression.

BACKGROUND: Leflunomide is an experimental drug with demonstrated ability to prevent and reverse acute allograft and xenograft rejection. The two biochemical activities reported for the active metabolite of leflunomide, A77 1726, are inhibition of tyrosine phosphorylation and inhibition of dihydroorotate dehydrogenase, an enzyme necessary for de novo pyrimidine synthesis. These activities can be distinctly separated in vitro by the use of uridine, which reverses the anti-proliferative effects of A77 1726 caused by inhibition of de novo pyrimidine synthesis. We report the effect of uridine on the in vivo immunosuppressive activities of leflunomide. METHODS: We first quantified the serum levels of A77 1726, the active metabolite of leflunomide, after a single treatment of leflunomide (5, 15, and 35 mg/kg). Additionally, we quantified the levels of serum uridine and of nucleotide triphosphates in the liver, spleen, and lymph nodes of Lewis rats after the administration of a single dose of uridine (500 mg/kg; i.p.). Lewis rats heterotopically transplanted with brown Norway or Golden Syrian hamster hearts were treated for 50 or 75 days with leflunomide (5, 15, and 35 mg/kg/day; gavage) alone or in combination with uridine (500 mg/ kg/day; i.p.). Hematocrits were determined and the levels of alloreactive or xenoreactive immunoglobulin (Ig)M and IgG were determined by flow cytometric analysis. The allograft and xenografts, small bowel, liver, kidney, and spleen were subjected to pathological examination. RESULTS: A linear relationship was observed between the serum A77 1726 concentrations in Lewis rats and the dose of leflunomide administered. Peak A77 1726 concentrations were 20.9, 71.8 and 129.3 mg/l (77.5, 266.1 and 478.8 microM) for the 5, 15, and 35 mg/kg doses of leflunomide, respectively. The concentration of uridine in the serum of normal Lewis rats is 6.5 microM; after i.p. administration of 500 mg/kg uridine, the serum uridine concentrations peaked at 384.1 microM in 15-30 min. The rapid elimination of uridine was not reflected in the lymphoid compartments, and the pharmacokinetics of pyrimidine nucleotides in the spleen resembled that of A77 1726. This dose of uridine, when administered daily (500 mg/kg/day, i.p.), weakly antagonized the immunosuppressive activities of leflunomide (5, 15, and 35 mg/kg/day) in the allotransplantation model. In contrast, in the xenotransplantation model, the same concentration of uridine completely antagonized the immunosuppressive activities of low-dose leflunomide (15 mg/kg/day) and partially antagonized the immunosuppressive activities of high-dose leflunomide (35 mg/kg/day). Toxicities associated with high-dose leflunomide (35 mg/kg/day) were anemia, diarrhea, and pathological changes in the small bowel and liver. These toxicities were significantly reduced by uridine co-administration. CONCLUSION: These studies reveal that the blood levels of A77 1726 in Lewis rats satisfy in vitro requirements for both inhibition of de novo pyrimidine synthesis and protein tyrosine kinase activity. Our data also illustrate that the in vivo mechanism of immunosuppression by leflunomide is complex and is affected by at least the following four factors: type and vigor of the immune response, availability of uridine for salvage by proliferating lymphocytes, species being investigated, and concentration of serum A77 1726.     

肝细胞癌SMC7721体内外多药耐药模型的建立及其耐药机制

目的 建立肝细胞癌SMC7721体内外多药耐药细胞株并探讨其耐药机制.方法 通过阿霉素浓度递增筛选出SMC7721/ADM肝癌多药耐药细胞株并建立裸鼠移植瘤模型;噻唑蓝(MTr)检测各组移植瘤对化疗药物的耐药性;逆转录-聚合酶链反应(RT-PCR)和Western blot检测MDR1和BCRP在各组移植瘤中的表达.结果 SMC7721/ADM对阿霉素,丝裂霉素,5-Fu的耐药性均较亲本细胞明显降低(P<0.01);其移植瘤对3种化疗药物的IC50.均明显低于亲本细胞(P<0.05);SMC7721/ADM细胞中MDR1 mRNA表达是亲本细胞的40.13倍(P<0.01);BCRP mRNA表达与亲本细胞差异无统计学意义(P>0.05).其移植瘤中BCRP mRNA表达是亲本细胞移植瘤的3.69倍(P<0.01);而MDR1 mRNA表达与亲本细胞差异无统计学意义(P>0.05);SMC7721/ADM细胞株中两种蛋白表达显著高于亲本细胞株(P<0.01);SMC7721/ADM移植瘤中BCRP蛋白表达显著高于亲本移植瘤(P<0.01),而两者中MDR1表达差异无统计学意义(JP>0.05).结论 MDR1和BCRP在SMC7721/ADM多药耐药的不同阶段起作用并介导肝细胞癌对不同药物的耐药性.     

Studies on the mechanism whereby acidemia stimulates collecting duct hydrogen ion secretion in vivo

The purpose of these studies was to elucidate the mechanism whereby collecting duct hydrogen ion secretion was augmented by acidemia. The urine minus blood PCO2 difference in alkaline urine (U-B PCO2) was used to evaluate this parameter. In dogs with a normal ECF volume, the U-B PCO2 factored was high, and there was no significant relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentrations unless amiloride, an agent that abolishes the transtubular potential difference, was present. In this latter case, the U-B PCO2 was a linear function of the urine bicarbonate concentration, and the U-B PCO2 factored for the urine bicarbonate concentration was directly proportional to the blood hydrogen ion concentration. To extend the pH range considerably, we used lysine to induce bicarbonaturia in dogs with an expanded ECF volume. Amiloride now caused only a small decrease in the U-B PCO2 at any urine bicarbonate concentration, and furthermore, it did not influence the linear relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentration. These results suggests that acidemia stimulates collecting duct hydrogen ion secretion by a mechanism that appears to be independent of the amiloride-sensitive component of the U-B PCO2. We speculate that the mechanism might involve an increased intracellular hydrogen ion concentration during acidemia.     

Propofol prevents peroxide-induced inhibition of glutamate transport in cultured astrocytes.

BACKGROUND: Glutamate transporters located in the plasma membrane of cerebral astrocytes take up excitatory neurotransmitters from the synaptic cleft. In diseases characterized by oxidative stress, the extracellular glutamate concentration increases and contributes to neuronal death. The authors wanted to determine whether propofol defends brain cells against oxidant-induced changes in their transport of glutamate. METHODS: Primary cultures of rat cerebral astrocytes were exposed to tert-butyl hydroperoxide (1 mM) to serve as an in vitro model of oxidative stress. Astrocytes were incubated with propofol for 2 h and tert-butyl hydroperoxide was added for the final hour. Alternatively, astrocytes were incubated with tert-butyl hydroperoxide for 30 min and then with propofol for another 30 min. Control cells received drug vehicle rather than propofol. The rate of uptake of glutamate, the efflux of the nonmetabolizable analog D-aspartate, and the intracellular concentration of the endogenous antioxidant glutathione were measured. RESULTS: Tert-butyl hydroperoxide decreased the glutathione concentration and inhibited glutamate uptake but had a negligible effect on D-aspartate efflux. At clinically relevant concentrations, propofol did not affect the glutathione concentration but did prevent the effect of tert-butyl hydroperoxide on glutamate transport. Furthermore, the addition of propofol after tert-butyl hydroperoxide reversed the inhibition of glutamate uptake. CONCLUSIONS: Propofol prevents and reverses the inhibition of excitatory amino acid uptake in astrocytes exposed to tert-butyl hydroperoxide. The ability of propofol to defend against peroxide-induced inhibition of glutamate clearance may prevent the pathologic increase in extracellular glutamate at synapses, and thus delay or prevent the onset of excitotoxic neuronal death.     

去甲斑蝥素对荷瘤裸鼠胆囊癌移植瘤的抗癌作用机制

目的 探讨去甲斑蝥素（NCTD）对荷瘤裸鼠胆囊癌移植瘤的抗癌作用机制。方法 在建立裸鼠胆囊癌移植瘤动物模型的基础上进行肿瘤增殖、侵袭、转移体内干预实验,实验分空白对照、氟尿嘧啶、NCTD、NCTD＋氟尿嘧啶4组。6周末应用链霉素亲和生物素复合物（SABC）法检测移植瘤增殖细胞核抗原（PCNA）、Ki-67、细胞周期素D1（cyclin D1）、p27、Bcl-2蛋白,逆转录PCR（RT-PCR）检测PCNA、cyclin D1、p27、Bcl-2、Bax、存活素（Survivin）基因mRNA。HE染色观察瘤周癌细胞浸润、侵袭,解剖显微镜下观察肺组织转移瘤结节,并采用SABC和RT-PCR检测nm23、金属蛋白酶2（MMP2）及其组织抑制剂（TIMP2）蛋白和mRNA。结果 NCTD组增殖相关PCNA、Ki-67、cyclin D1蛋白表达下降,p27蛋白表达上升;PCNA mRNA、cyclin D1 mRNA表达下降,p27 mRNA表达增高。NCTD组凋亡相关Bcl-2蛋白表达下降;Bcl-2 mRNA、Survivin mRNA表达下降,Bax mRNA表达增高。NCTD显著减少荷瘤鼠移植瘤的瘤周癌细胞浸润和肺转移结节（P〈0．01）;NCTD组转移相关MMP2蛋白表达下降,nm23、TIMP2蛋白表达上升;nm23-H,mRNA、TIMP2 mRNA表达增高。结论 NCTD抑制荷瘤裸鼠胆囊癌移植瘤增殖、侵袭和转移的机制可能与NCTD干扰胆囊癌移植瘤细胞周期,抑制细胞增殖,诱导细胞凋亡,阻止细胞迁移运动,以及影响细胞增殖、细胞周期调控、细胞凋亡、细胞基质溶解和转移相关基因蛋白表达有关。     

Acute management of stroke – II: haemorrhagic stroke

Haemorrhagic strokes are relatively less common compared to ischaemic strokes, with the vast majority of haemorrhages being intracerebral as opposed to subarachnoid. The definitive diagnosis of a haemorrhagic stroke is based on non-contrast CT imaging of the brain. Acute care should focus on prompt identification of the cause, minimizing the risk of haemorrhage expansion by controlling blood pressure and correcting any underlying coagulopathy, and obliterating vascular lesions with a high risk of rebleeding. Patients should be closely monitored, and emergent surgery should be considered in those patients who display signs of clinical deterioration, especially in the presence of posterior fossa haemorrhages. Future directions include refining the use of bedside neuro-monitoring and neuro-imaging techniques as well as developing novel approaches to minimize the complications of haemorrhagic stroke.     

Halothane potentiation of hydrogen peroxide-induced inhibition of surfactant synthesis: the role of type II cell energy status

Small concentrations of inhaled anesthetics can affect Type II cell surfactant production and exacerbate oxidant-mediated lung injury. We hypothesized that inhaled anesthetics augment oxidant-induced Type II pneumocyte dysfunction related to their different effects on cellular adenosine triphosphate (ATP) status. Freshly isolated Type II cells were exposed to different concentrations of hydrogen peroxide (H2O2) in the presence or absence of an in vitro halothane exposure. Cells exposed to 100 microM H2O2 alone demonstrated a 23% decrease in ATP levels and a 32% decrease in phosphatidylcholine (PC) synthesis compared with controls. Halothane alone decreased PC synthesis by only 12% and reduced ATP levels by 20%. However, when exposed to both halothane and H2O2 together, ATP levels decreased by 40%, and PC synthesis rates decreased by 51%. Pretreatment of cells with nicotinamide, an inhibitor of poly adenosine diphosphate ribose polymerase, completely prevented the ATP loss and PC synthesis decline caused by H2O2 alone, but it had no effect on the halothane-augmented portion of the cell injury. These data suggest that the ability of halothane to enhance oxidative damage may be related to its own specific effects on cell energetics that may not be amenable to the same treatments used to mitigate other cellular mechanisms of oxidative stress. IMPLICATIONS: A mediator of inflammation (hydrogen peroxide) and an inhaled anesthetic (halothane) interact to decrease cell energy and secretion of a substance (surfactant) required for healthy lung function from cells that line gas-exchange compartments. This interaction represents a possible mechanism by which inflammatory lung disease may become more severe intraoperatively.     

Renal hypothermia: in vivo and ex vivo

Temporary occlusion of the renal artery may be necessary for operations to remove renal calculi in situ, such as partial nephrectomy, nephrolithotomy, and extended pyelolithotomy. Performance of these operations requires an understanding of renal responses to warm ischemia and available methods of protecting the kidney in situ when the period of arterial occlusion exceeds that which may be safely tolerated. Methods of extracorporeal renal preservation are also reviewed because autotransplantation and bench surgery may occasionally be employed to treat patients with renal calculous disease.     

脑卒中供者心脏的心肌损伤机制与临床研究进展

脑死亡供者心脏是目前心脏移植最主要的器官来源。脑死亡发生后会出现严重的血流动力学改变和一系列器官功能变化,进而造成组织器官的功能损害甚至丧失,尤其是心脏。神经系统和心血管系统的生理、病理生理之间存在密切联系和相互作用,脑卒中发生后,通过脑-心轴反应导致自主神经失调、神经内分泌紊乱和强烈而持续的炎症反应,引发交感风暴、儿茶酚胺风暴、炎症风暴等导致脑卒中所致心脏损伤。本文旨在对近年来有关脑卒中供者心脏心肌损伤的机制研究及其对心脏移植术后疗效和预后影响的相关研究进行综述,为临床实践和进一步研究提供参考。