杜鹃花总黄酮对在体大鼠心肌缺血再灌注损伤的保护作用及其机制

目的 观察杜鹃花总黄酮(TFRS)对大鼠心肌缺血再灌注损伤的保护作用及其机制.方法 采用在体结扎大鼠心脏冠状动脉左前降支法,观察心电图ST段和T波的变化,TTC染色法测定心肌梗死面积并测定大鼠血清乳酸脱氢酶(LDH)、肌酸激酶(CK)活性,血清丙二醛(MDA)及一氧化氮(NO)水平,并应用逆转录酶链式反应(RT-PCR)方法测大鼠心肌中诱导型一氧化氮合酶(iNOS)mRNA表达情况.结果 TFRS 100 mg/kg对缺血30 min时ST段的抬高有明显抑制作用,TFRS 25、50、100 mg/kg对再灌注30 min时ST段的抬高有明显抑制作用;TFRS 50 mg/kg能显著的降低心肌梗死面积;TFRS 50、100 mg/kg能不同程度降低血清中的LDH、CK的活性.TFRS 50 mg/kg可降低血清中MDA的水平;TFRS 100 mg/kg能显著提高心肌iNOS mRNA的表达.结论 TFRS对心肌和缺血再灌注损伤有一定的保护作用,其作用机制可能与抗自由基和提高心肌iNOS基因mRNA的表达及增加NO产生有关.     

刺五加注射液对庆大霉素耳中毒豚鼠耳蜗iNOS表达的影响

目的:观察刺五加注射液是否对豚鼠庆大霉素耳毒性具有拮抗作用.方法:随机将动物分成正常对照组,庆大霉素组(GM),刺五加注射液组(ASS),庆大霉素 刺五加注射液组(GM ASS),采用听性脑干反应(ABR)、免疫组化、透射电镜方法观察用药前后各组ABR阈值iNOS表达情况及形态学变化.结果:用药后GM组ABR阈值明显升高,ASS组与正常对照组ABR阈值无明显差异,但ASS组ABR阈值比GM组和ASS GM组降低明显;透射电镜下观察到GM组毛细胞损伤严重,而ASS GM组毛细胞损伤情况与GM组相比损伤较轻.免疫组化结果表明与正常对照组相比GM组iNOS的表达明显升高,ASS GM组iNOS的表达稍有增多.结论:刺五加注射液可能通抑制iNOS的表达来拮抗庆大霉素耳毒性.     

EPA、DHA对人单核细胞NO的产生、iNOSmRNA表达及NFκB活性的影响

目的探讨n-3多不饱和脂肪酸(Eicosapentaenoic acid EPA,Docosahexenoic acid DHA)对人单核细胞炎症因子——一氧化氮(NO)的分泌和诱导型NO合酶(iNOS mRNA)表达的影响,以及EPA、DHA对核转录因子(NFκB)与DNA结合活性的影响。方法硝酸还原酶法测定NO的含量,RT-PCR技术分析iNOS mRNA表达水平,凝胶电泳迁移实验检测NFκB与DNA的结合活性。结果EPA、DHA在10~20μg/ml浓度范围内能够降低体外培养的人外周血单核细胞NO的分泌和iNOS mRNA的表达并降低NFκB的DNA结合活性。结论EPA,DHA能够抑制单核细胞炎症因子NO的产生,减少iNOS mRNA的表达,并通过抑制信号转导途径中NFκB与DNA的结合活性这一通路来抑制炎症因子分泌,产生抑制炎症作用。     

吲哚美辛对大鼠C6 胶质瘤细胞增生和iNOS 酶活性的影响

目的探索吲哚美辛(IND)对大鼠C6胶质瘤细胞增生和诱导型一氧化氮合酶(iNOS)酶活性的作用。方法用含5?S的高糖DMEM培养C6细胞,用无血清的DMEM培养24h后,加入终浓度分别为60、125、250μmol/L的IND作用24h,用MTT法检测细胞增生情况;细胞常规培养,用无血清的DMEM培养24h后,分别加入LPS、LPS加入30min后分别加60,125,250μmol/L的IND,作用24h后提取细胞培养上清液检测iNOS的酶活性。结果各浓度的IND使C6细胞增生明显降低,并显示出剂量依赖性;各浓度的IND能明显降低LPS诱导的iNOS的酶活性。结论IND强烈抑制C6细胞增生,并且显著抑制LPS诱导的C6细胞iNOS的酶活性。     

缺氧复氧损伤对血管内皮细胞一氧化氮合成酶基因表达的影响及辛伐他汀的干预作用

目的探讨缺氧、复氧损伤对血管内皮细胞一氧化氮合成酶基因表达的影响及辛伐他汀的干预作用,并探讨其可能的机制。方法体外培养人脐静脉内皮细胞株ECV304,使用自制的缺氧小室对ECV304进行缺氧、复氧处理。第1组:仅进行缺氧、复氧处理。第2组:不同浓度的辛伐他汀(0.1、1.0、10.0μmol/L)及10.0μmol/L辛伐他汀 0.2mmol/L甲羟戊酸预处理ECV304,再行缺氧2h、复氧2h处理。RT-PCR分别检测内皮细胞eNOS、iNOS基因的相对表达量。结果缺氧2h、复氧2hECV304eNOS相对表达量明显减少(均P≤0.01);缺氧2hiNOS相对表达量明显减少(P≤0.01),复氧2、4、8hiNOS相对表达量明显增加(均P<0.05);辛伐他汀(0.1、1.0、10.0μmol/L)预处理后再给予缺氧、复氧刺激则均使eNOS相对表达量增加(均P<0.05),并呈浓度依赖增加,同时iN-OS相对表达量减少;同时用辛伐他汀和甲羟戊酸预处理后则以上辛伐他汀的作用消失。结论缺氧、复氧应激下血管内皮细胞eNOS表达减少,iNOS表达增加;辛伐他汀可以阻止因缺氧、复氧刺激导致的eNOS低表达和iNOS高表达,该作用可被甲羟戊酸逆转。     

iNOS和COX-2在过氧化氢预处理诱导的适应性细胞保护中的作用

目的探讨H2O2预处理对PC12细胞iNOS与COX-2蛋白表达的影响及其在适应性细胞保护中的作用。方法在PC12细胞建立H2O2预处理对抗H2O2诱导细胞凋亡的实验模型,采用甲氮甲唑蓝(MTT)法检测细胞存活率,碘化丙啶(PI)染色流式细胞术检测细胞凋亡,流式细胞仪(FCM)检测iNOS与COX-2蛋白表达水平。结果用10μmol.L-1H2O2预处理PC12细胞90min可明显地抑制20～100μmol.L-1H2O2作用24h后引起的细胞毒性和细胞凋亡,并可明显地促进PC12细胞iNOS与COX-2蛋白表达;选择性iNOS抑制剂AG和COX-2抑制剂NS-398分别阻断H2O2预处理诱导的抗细胞凋亡作用。结论H2O2预处理可诱导适应性细胞保护作用,其机制之一可能与促进PC12细胞的iNOS与COX-2蛋白表达有关。     

Cancer chemoprevention by tea polyphenols through modulating signal transduction pathways

The action mechanisms of several chemopreventive agents derived from herbal medicine and edible plants have become attractive issues in cancer research. Tea is the most widely consumed beverage worldwide. Recently, the cancer chemopreventive actions of tea have been intensively investigated. It have been demonstrated that the active principles of tea were attributed to their tea polyphenols. Recently, tremendous progress has been made in elucidating the molecular mechanisms of cancer chemoprevention by tea and tea polyphenols. The suppression of various tumor biomarkers including growth factor receptor tyrosine kinases, cytokine receptor kinases, PI3K, phosphatases, ras, raf, MAPK cascades, N x FB, I x B kinase, PKA, PKB, PKC, c-jun, c-fos, c-myc, cdks, cyclins, and related transducing proteins by tea polyphenols has been studied in our laboratory and others. The I x B kinase (IKK) activity in LPS-activated murine macrophages (RAW 264.7 cells) was found to be inhibited by various tea polyphenols including (-) epigallocatechin-3-gallate (EGCG), theaflavin (TF-1), theaflavin-3-gallate (TF-2) and theaflavin-3,3'-digallate (TF-3). TF-3 inhibited IKK activity in activated macrophages more strongly than did the other tea polyphenols. TF-3 inhibited both IKK1 and IKK2 activity and prevented the degradation of I x B x and I x B x in activated macrophage cells. The results suggested that the inhibition of IKK activity by TF-3 and other tea polyphenols could occur by a direct effect on IKKs or on upstream events in the signal transduction pathway. TF-3 and other tea polyphenols blocked phosphorylation of IB from the cytosolic fraction, inhibited NFB activity and inhibited increases in inducible nitric oxide synthase levels in activated macrophage. TF-3 and other tea polyphenols also inhibited strongly the activities of xanthine oxidase, cyclooxygenase, EGF-receptor tyrosine kinase and protein kinase C. These results suggest that TF-3 and other tea polyphenols may exert their cancer chemoprevention through suppressing tumor promotion and inflammation by blocking signal transduction. The mechanisms of this inhibition may be due to the blockade of the mitogenic and differentiating signals through modulating EGFR function, MAPK cascades, NFkappaB activation as well as c-myc, c-jun and c-fos expression.     

The effect of linarin on LPS-induced cytokine production and nitric oxide inhibition in murine macrophages cell line RAW264.7

The herb, Chrysanthemum zawadskii var, latilobum commomly known as Gu-Jul-Cho in Korea, used in traditional medicine to treat pneumonia, bronchitis, cough, common cold, pharyngitis, bladder-related disorders, gastroenteric disorders, and hypertension. Linarin is the main active compound and the biological mechanisms of its activity are unclear. It is believed that effects of this herb may be exerted through the pluripotent effectors of linarin due to its ability to treat a variety of afflictions. In this study, the effects of linarin on the mouse macrophages cell line, RAW 264.7, were investigated. It was found that linarin could activate macrophages by producing cytokines. Monocytes and tissue macrophages produce at least two groups of protein mediators of inflammation, interleukin 1 (IL-1) and the tumor necrosis factor (TNF). Recent studies have shown that TNF and IL-1 modulate the inflammatory function of endothelial cells, leukocytes, and fibroblasts. TNF-alpha production by macrophages treated with linarin occured in a dose dependent manner. However, IL-1 production was largely unaffected by this natural product. This study demonstrated the ability of linarin to activate macrophages both directly and indirectly. Linarin also affect both cytokine production and nitric oxide inhibition, in addition to the expression of some surface molecules. Nitric oxide (NO), derived from L-argin-ine, is produced by two forms(constitutive and inducible) of nitric oxide synthase (NOS). The NO produced in large amounts by inducible NOS is known to be responsible for the vasodilation and hypotension observed in septic shock. Linarin was found to inhibit NO production in the LPS-activated RAW 264.7 cells. Linarin may be a useful candidate as a new drug for treating endotoxemia and the inflammation accompanied by NO overproduction. The linarin-treated total lymphocytes exhibited cytotoxicity in a dose dependent manner between 20 microg/ml and 40 microg/ml. These results suggest that linarin may function through macrophage activation.     

Expression of brain-derived neurotrophic factor (BDNF) and inducible nitric oxide synthase (iNOS) in rat astrocyte cultures treated with Levetiracetam

The aim of the present study was to investigate the effects of Levetiracetam, a new antiepileptic drug, on the synthesis of brain-derived neurotrophic factor (BDNF) and inducible nitric oxide synthase (iNOS) in rat cortical astrocyte cultures. The astrocytes were treated for 48 h with different concentrations of Levetiracetam and the expression of BDNF and iNOS was analyzed by immunostaining and immunoblotting analyses. We observed that Levetiracetam is able to stimulate expression of both BDNF and iNOS in a concentration-dependent manner on rat cortical astrocyte cultures. For the BDNF, this effect appears at very low concentrations (1 and 10 microgram/ml), while expression of iNOS appears only at higher dosages (50 microgram/ml). We conclude that Levetiracetam might exert neuroprotective effects, at least in part, via stimulation of neurotrophic factors, thus reducing the extent of inflammation and neuronal death under pathological conditions such as epilepsy.     

Expression of nitric oxide synthases in keratinocytes after UVB irradiation

The importance of nitric oxide (NO) in mediating vasodilation, neurotransmission, and immune and inflammatory responses has been demonstrated. Human keratinocyte express inducible nitric oxide synthase (iNOS) and the neuronal constitutive isoform of NOS (ncNOS). We established an in vitro model in keratinocytes to investigate changes in NO, iNOS and ncNOS expression after UVB exposure. We demonstrated a large induction of NO after UVB exposure and that the source of NO produced in UVB-exposed keratinocytes was increased expression of iNOS and ncNOS. The increased NO production with increased expression of iNOS and ncNOS may contribute to the pathological and physiological features of UVB-induced erythema and skin inflammation.