Effects of hydrogen peroxide on the transient outward current in rabbit atrial myocytes

1. In the present study, we investigated the effects of hydrogen peroxide (H2O2) on the 4-aminopyridine-sensitive transient outward current (I(TO)) in rabbit atrial myocytes using the amphotericin B-perforated patch voltage-clamp method. 2. Superfusion of myocytes with H2O2 at 100 micromol/L gradually slowed the time-course of inactivation of I(TO) and increased the peak by 9% (n = 9). The H2O2-induced slowing of I(TO) inactivation was concentration dependent (over the concentration range 10 micromol/L to 1 mmol/L). These effects were hardly reversed by washout of H2O2, but were quickly abolished by dithiothreitol (2 mmol/L). 3. Bisindolylmaleimide (100 nmol/L), an inhibitor of protein kinase C, significantly attenuated the H2O2-induced effects on I(TO). 4. These results suggest that rabbit atrial I(TO) is susceptible to oxidation by H2O2 at concentrations relevant to those encountered during ischaemia/reperfusion and that protein kinase C modulates the effects of H2O2.     

Ebselen attenuates cadmium-induced testicular damage in mice

This study was designed to examine if ebselen, an organoselenium compound with antioxidant and glutathione peroxidase-mimetic properties, attenuates testicular injury caused by intraperitoneal administration of CdCl(2). A number of toxicological parameters were evaluated in the testes of mice, such as delta-aminolevulinic acid dehydratase (delta-ALA-D) activity, lipid peroxidation, ascorbic acid levels and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities. Ebselen attenuated lipid peroxidation levels altered by CdCl(2). delta-ALA-D activity inhibited by the highest dose of CdCl(2) was attenuated by ebselen. A significant negative correlation between lipid peroxidation levels and delta-ALA-D activity was observed. Ebselen restored ascorbic acid levels reduced by CdCl(2). A significant negative correlation between ascorbic acid levels and delta-ALA-D activity reinforces the idea that ebselen attenuated the damage induced by CdCl(2) via its antioxidant property. The significant correlation between ALT and delta-ALA-D activity supports the assumption that ebselen prevented damage caused by CdCl(2). The results show that ebselen attenuated oxidative stress, a process important for CdCl(2) toxicity.     

DNA damage by dimethylformamide: role of hydrogen peroxide generated during degradation

Dimethylformamide (DMF) has been suspected to associate with cancers in exposed workers, whereas there has been inadequate evidence for carcinogenicity in experimental animals. We demonstrated that H(2)O(2) was generated during the degradation of DMF under aerobic conditions, and that the amount of H(2)O(2) was enhanced by exposure to solar light or by the contamination of trace metal. Experiments using (32)P-5'-end-labeled DNA fragments revealed that the degraded DMF induced DNA damage in the presence of Cu(II). However, purified DMF did not induce DNA damage even in the presence of Cu(II). Addition of purified DMF enhanced DNA damage induced by H(2)O(2) in the presence of Cu(II). The degraded DMF caused Cu(II)-mediated DNA cleavage frequently at thymine and cytosine residues. The similar pattern of site-specific DNA damage was observed with purified DMF and H(2)O(2). Bathocuproine and catalase inhibited the DNA damage, indicating the involvement of Cu(I) and H(2)O(2). A typical free hydroxy radical scavenger showed no inhibitory effect on the DNA damage. Addition of purified DMF enhanced about 3-4-fold 8-oxo-7, 8-dihydro-2'-deoxyguanosine formation induced by H(2)O(2) and Cu(II). ESR spectroscopic study demonstrated that carbon-centered radicals and nitrogen-centered radicals were generated in the reaction mixture of DMF, H(2)O(2), and Cu(II). Inhibitory effects of scavengers on radical formation and DNA damage suggest that carbon-centered radicals and/or nitrogen-centered radicals may contribute to the DNA damage. These results suggest that H(2)O(2) generation during DMF degradation is related to the possible carcinogenic activity of DMF.     

Involvement of H2O2 in superoxide-dismutase-induced enhancement of endothelium-dependent relaxation in rabbit mesenteric resistance artery

1 The mechanism underlying the enhancement by superoxide dismutase (SOD) of endothelium-dependent relaxation was investigated in rabbit mesenteric resistance arteries. 2 SOD (200 U ml(-1)) increased the production of H(2)O(2) in smooth muscle cells (as indicated by the use of an H(2)O(2)-sensitive fluorescent dye). 3 Neither SOD nor catalase (400 U ml(-1)) modified either the resting membrane potential or the hyperpolarization induced by acetylcholine (ACh, 1 micro M) in smooth muscle cells. 4 In arteries constricted with noradrenaline, the endothelium-dependent relaxation induced by ACh (0.01-1 micro M) was enhanced by SOD (200 U ml(-1)) (P<0.01). This action of SOD was inhibited by L-N(G)-nitroarginine (nitric oxide (NO)-synthase inhibitor) but not by either charybdotoxin+apamin (Ca(2+)-activated-K(+)-channel blockers) or diclofenac (cyclooxygenase inhibitor). 5 Neither ascorbate (50 micro M) nor tiron (0.3 mM), superoxide scavengers, had any effect on the ACh-induced relaxation, but each attenuated the enhancing effect of SOD on the ACh-induced relaxation. Similarly, catalase (400 U ml(-1)) inhibited the effect of SOD without changing the ACh-induced relaxation. 6 In endothelium-denuded strips constricted with noradrenaline, SOD enhanced the relaxation induced by the NO donor 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC-7) (P<0.05). Ascorbate and catalase each attenuated this effect of SOD. 7 H(2)O(2) (1 micro M) enhanced the relaxation on the noradrenaline contraction induced by NOC-7 and that induced by 8-bromo-cGMP, a membrane-permeable analogue of guanosine 3',5' cyclic monophosphate (cGMP). 8 SOD had no effect on cGMP production, whether measured in endothelium-intact strips following an application of ACh (0.1 micro M) or in endothelium-denuded strips following an application of NOC-7 (0.1 micro M). 9 It is suggested that in rabbit mesenteric resistance arteries, SOD increases the ACh-induced, endothelium-dependent relaxation by enhancing the action of NO in the smooth muscle via its H(2)O(2)-producing action (rather than via a superoxide-scavenging action).     

Prostanoid receptors involved in the relaxation of human bronchial preparations

1. Iloprost and cicaprost (IP-receptor agonists) induced relaxations in the histamine- (50 microM) contracted human bronchial preparations (pD2 values, 6.63+/-0.12 and 6.86+/-0.08; Emax values, 90+/-04 and 65+/-08% of the papaverine response for iloprost (n=6) and cicaprost (n=3), respectively). 2. Prostaglandin E2 (PGE2) and misoprostol (EP-receptor agonist) relaxed the histamine-contracted human bronchial preparations (pD2 values, 7.13+/-0.07 and 6.33+/-0.28; Emax values, 67+/-04 and 57+/-08% of the papaverine response for PGE2 (n=14) and misoprostol (n=4), respectively). In addition, both relaxations were inhibited by AH6809 (DP/EP1/EP2-receptor antagonist; 3 microM; n=5-6). 3. The PGE2-induced relaxations of human bronchial preparations were not modified by treatment with AH23848B (TP/EP4-receptor antagonist; 30 microM; n=4). 4. The contracted human bronchial preparations were significantly relaxed by prostaglandin D2 (PGD2) or by BW245C a DP-receptor agonist. However, these responses did not exceed 40% of the relaxation induced by papaverine. In addition, the relaxations induced by PGD2 were significantly inhibited by treatment with a DP-receptor antagonist BWA868C (0.1 microM; n=3). 5. These data suggest that the relaxation of human isolated bronchial preparations induced by prostanoids involved IP-, EP2- and to a lesser extent DP-receptors but not EP4-receptor.     

Effect of riluzole on cytosolic Ca2+ increase in human osteosarcoma cells

In human osteosarcoma MG63 cells, the effect of the neuroprotective drug riluzole on the intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured using fura-2. Riluzole (50-500 micromol/l) caused a rapid and sustained plateau increase in [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 150 micromol/l). The riluzole-induced rise in [Ca(2+)](i) was prevented by 58 and 20% by extracellular Ca(2+) removal and nifedipine, respectively, but was not changed by La(3+) and verapamil. In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum (ER) Ca(2+)-ATPase, caused a monophasic increase in [Ca(2+)](i), after which the increasing effect of riluzole on [Ca(2+)](i) was attenuated by 84%; also, pretreatment with riluzole abolished the thapsigargin-induced [Ca(2+)](i) increase. U73122, an inhibitor of phospholipase C, abrogated the ATP (but not riluzole)-induced rise in [Ca(2+)](i). A low concentration (6 micromol/l) of riluzole selectively potentiated the bradykinin (but not ATP and histamine)-induced increase in [Ca(2+)](i). These results suggest that riluzole rapidly increases [Ca(2+)](i) by stimulating both the extracellular Ca(2+) influx via a nifedipine-sensitive pathway and intracellular Ca(2+) release from the ER via an as yet unidentified mechanism(s).     

Inactivation of creatine kinase by Adriamycin during interaction with horseradish peroxidase

Oxidative damage of creatine kinase (CK) induced by Adriamycin((R)) (ADM) with peroxidase was investigated using horseradish peroxidase (HRP). ADM oxidatively inactivated CK during its interaction with HRP in the presence of H(2)O(2) (HRP-H(2)O(2)). The red color of ADM was lost during oxidation by HRP-H(2)O(2). Adding catalase stopped the color change of ADM induced by HRP-H(2)O(2), indicating that ADM was oxidized by HRP complex I or II. CK was inactivated readily, even when it was added to the reaction mixture containing colorless ADM. Some sulfhydryl groups of CK, which have an important role in its enzyme activity, were very sensitive to ADM activated by HRP-H(2)O(2), suggesting that inactivation of CK is due to oxidation of SH groups at the active center. Presumably, oxidative ADM quinone is involved dominantly in the inactivation of CK. Among the anthracycline drugs tested in this study, only ADM and epirubicin caused inactivation of CK and alcohol dehydrogenase and loss of the red color during oxidation by HRP-H(2)O(2).     

The effect of the PKC inhibitor GF109203X on the release of Ca2+ from internal stores and Ca2+ entry in DDT1 MF-2 cells.

1. The effects of the specific protein kinase C (PKC) inhibitor, GF109203X, were measured on the cytoplasmic Ca2+ concentration ([Ca2+]i), and on histamine H1 receptor- and thapsigargin-mediated increases in [Ca2+]i in DDT1 MF-2 smooth muscle cells. 2. After pretreatment of cells with GF109203X (5 microM, 45 min), the histamine (100 microM)-induced initial rise in [Ca2+]i, representing Ca2+ mobilization from internal stores, was inhibited (by 59 +/- 7%). The slowly declining phase of the histamine induced Ca2+ response, reflecting Ca2+ entry, was enhanced (83 +/- 26%) in the presence of the PKC inhibitor. 3. The histamine induced release of Ca2+ from internal stores, measured after blocking Ca2+ entry with LaCl3 was inhibited by GF109203X in a concentration-dependent manner (IC50: 3.1 +/- 1.1 microM). 4. Histamine-induced formation of inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) was not changed in the presence of GF109203X. 5. The PKC activating phorbol ester, phorbol 12-myristate 13-acetate (PMA, 1 microM), strongly reduced histamine-induced Ins(1,4,5)P3 formation (58 +/- 16%). This effect was reversed by GF109203X (5 microM). Furthermore, PMA diminished histamine evoked Ca2+ release (50 +/- 6%) and blocked Ca2+ entry completely. 6. The rise in [Ca2+]i caused by blocking endoplasmic reticulum Ca2(+)-ATPase with thapsigargin (1 microM), was strongly reduced (57 +/- 3%) after pretreatment of cells with GF109203X. Downregulation of PKC by long-term pretreatment of cells with PMA (1 microM, 48 h) did not abolish this effect of GF109203X (48 +/- 3% inhibition). 7. In permeabilized DDT, MF-2 cells preloaded with 45Ca2+ in the presence of GF109203X, the amount of 45Ca2+ released by Ins(1,4,5)P3 (10 microM) was markedly reduced (42 +/- 9%). GF109203X did not release Ca2+ itself and did not impair Ins(1,4,5)P3 receptor function. 8. Uptake of 45Ca2+ by intact cells, representing Ca2+ entry, was enhanced by GF109203X (65 +/- 11%), by histamine (24 +/- 6%) and also by thapsigargin (121 +/- 10%). The GF109203X- and the thapsigargin-induced uptake of 45Ca2+ were not additive. 9. These data suggest that GF109203X reduces the filling-state of intracellular Ins(1,4,5)P3 sensitive Ca2+ stores by inhibiting the Ca2+ uptake into these stores, thereby promoting store-dependent (capacitive) Ca2+ entry.     

Evaluation of the probes 2',7'-dichlorofluorescin diacetate,luminol, and lucigenin as indicators of reactive species formation

This study attempts to provide a critical assessment of three different common approaches to identifying teactive species formed in biological systems: the 2',7'-dichlorofluorescin diacetate (DCFH-DA) assay, and the luminol- and lucigenin-amplified chemiluminescence assays. There have been several contradictory reports about the specificity of these methods. Our results show that DCFH is oxidized to the fluorescent compound 2',7'-dichlorofluorescin (DCF) in human neutrophils exposed to the following compounds: Aroclor (A)1242, hydrogen peroxide (H(2)O(2)), nitric oxide (NO), and FeSO(4). Use of a cell-free DCFH system showed increased formation of DCF by peroxynitrite (ONOO(-)), horseradish peroxidase (HRP) alone, and HRP in combination with H(2)O(2), FeSO(4) alone, and a mixture of FeSO(4) and H(2)O(2). The hydroxyl radical (z.rad;OH) scavenger formate and the iron ion chelator deferoxamine reduced the DCF formation induced by FeSO(4) in combination with H(2)O(2). DCFH was insensitive to NO and H(2)O(2) in the cell-free system. In the presence of neutrophils, the A1242-induced luminol chemiluminescence was decreased by the superoxide dismutase inhibitor diethyldithiocarbamic acid (DDC) and the myeloperoxidase inhibitor salicylhydroxamic acid (SHA). Exposure of the neutrophils to NO, FeSO(4), or H(2)O(2) alone did not have any effect. A1242-induced lucigenin chemiluminescence in the neutrophils was increased slightly by DDC, but was not affected by SHA, NO, FeSO(4), or H(2)O(2). In conclusion, we suggest that the DCF assay is only suitable for measurements of ONOO(-), H(2)O(2) in combination with cellular peroxidases, and z.rad;OH. Luminol is sensitive towards HOCl, while lucigenin is oxidized by O(2)z.rad;(-).     

CYP1A2低表达增强何首乌水提物及其相关单体成分肝细胞毒性的研究

目的建立CYP1A2低表达人正常肝细胞株,探究何首乌水提物(PMR)及其相关单体成分的肝细胞毒性与CYP1A2低表达的关系。方法运用RNA干扰技术构建稳定转染shCYP1A2的2种人正常肝细胞系L02、HepaRG,RT-qPCR验证干扰效果;PMR及其相关单体成分:二苯乙烯苷(2,3,5,4’-tetrahydroxystilbene-2-O-β-D-glucoside,TSG)、大黄素-8-O-β-D-葡萄糖苷(emodin-8-O-β-D-glucopyranoside,EG)、没食子酸(gallic acid,GA)、大黄素(emodin,EM)、大黄素甲醚(physcion,PH)、芦荟大黄素(aloe-emodin,AE)、大黄酸(rhein,RH)作用CYP1A2敲低的L02及HepaRG细胞48 h,MTT检测细胞活力。结果成功构建了稳定转染shCYP1A2的2种人正常肝细胞系,L02-shCYP1A2、HepaRG-shCYP1A2与相应空质粒对照组相比,CYP1A2 mRNA表达分别下降了59.81%(L02-shCYP1A2)和66.60%(HepaRG-shCYP1A2)。1.5~3 mg/mL PMR作用CYP1A2敲低的L02-shCYP1A2细胞48 h,细胞毒性显著增加(P<0.01);2.5~3 mg/mL PMR作用CYP1A2敲低的HepaRG-shCYP1A2细胞48 h,细胞毒性显著增加(P<0.05、P<0.01);40~120μmol/L GA作用CYP1A2敲低的L02-shCYP1A2及HepaRGshCYP1A2细胞48 h,细胞毒性显著增加(P<0.01、P<0.01);AE作用CYP1A2敲低的HepaRG-shCYP1A2细胞48 h,细胞毒性显著增加(P<0.01)。结论CYP1A2低表达显著增加PMR的肝细胞毒性,推测GA和AE可能为相关的增毒成分。     

New adjacent Bis-tetrahydrofuran Annonaceous acetogenins from Annona muricata

Bioactivity-guided fractionation led to the isolation of two new Annonaceous acetogenins, annocatacin A ( 1). and annocatacin B ( 2). from the seeds and the leaves, respectively, of Annona muricata. Compounds 1 and 2 are the first examples where the adjacent bis-tetrahydrofuran ring system is located at C-15. The new structures were elucidated and characterized by spectral and chemical methods. Both Annonaceous acetogenins 1 and 2 showed significant in vitro cytotoxicity toward the human hepatoma cell lines, Hep G2 and 2,2,15, and were compared with the known adjacent bis-tetrahydrofuran acetogenins, neoannonin ( 3). desacetyluvaricin ( 4). bullatacin ( 5). asimicin ( 6). annoglaucin ( 7). squamocin ( 8). and rollimusin ( 9).     

Effect of Salvia miltiorrhiza Bunge injection on anticardiolipin antibody production induced by beta2 glycoprotein.

AIM: To explore the therapeutic effect and the mechanism of Chinese herbs on antiphospholipid syndrome (APS) by observing the effect of Salvia miltiorrhiza Bunge injectio (SmBI) on anticardiolipin antibody (aCL) induced by beta2 glycoprotein I (beta2-GP I). METHODS: Sixty female mice randomly fell into 6 groups: group A, B, C, D was injected through abdominal cavity with different dosage of SmBI daily; after 14 d, group A, B, C, E was immunized with 150 microg of purified human beta2-GP I in complete Freund's adjuvant subcutaneously; group F as control. The titre of aCL were detected by enzyme linked immunosorbent assay; subsets of T cell were grouped by streptavidin-biotin complex technique; and the activity of IL-2 was measured by MTT chromatometry. RESULTS: (1) Compared with group E, the absorbance (A) of aCL in group A, B, and C was decreased (P < 0.05 or P < 0.01). By linear correlation, the dosage is negatively correlated with the A values of aCL in 1, 2, and 3 weeks (P < 0.01). (2) Compared with group E, TH/TS ratio was reduced in group A, B, and C (P < 0.05 or P < 0.01); there is no significant differences between group D and F (P>0.05). By linear correlation, the dosage is negatively correlated with TH/TS ratio (P < 0.01). (3) Compared with E, the activity of IL-2 in group B and C decreased significantly (P < 0.01). By linear correlation, there is negative correlation between dosage and IL-2 activity (P < 0.01). There is no significant difference between D and F (P > 0.05). (4) There is positive correlation between TH/TS ratio and IL-2 activity in different dilutions (P<0.01). CONCLUSION: The mechanism of suppressive effect of SmBI on aCL induced by beta2-GP I may be realized by resuming the elevated TH/TS ratio and IL-2 activity. The state that SmBI have no effect on normal mice indicates that SmBI has selective immunoregulative functive.     

活性维生素D_3 顺铂对卵巢癌HO-8910细胞株的凋亡研究

目的观察1,25(OH)2维生素D3单独及其与顺铂合用对人卵巢癌细胞株凋亡的影响及Bax蛋白的表达情况。方法四甲基偶氮唑蓝(MTT)法检测细胞抑制率,流式细胞术测定细胞周期及凋亡率,免疫组织化学法检测Bax蛋白表达情况。结果1,25(OH)2维生素3、顺铂均可抑制HO-8910细胞的生长(P<0.01)、均可阻滞细胞于G0/G1期并诱导HO-8910细胞凋亡(P<0.01),当两者合用时上述作用加强,凋亡率明显上升(P<0.01),两者均可上调Bax蛋白表达(P<0.01),两者合用时Bax蛋白表达增强(P<0.01)。结论1,25(OH)2维生素D3与顺铂合用能协同抑制HO-8910细胞的生长并进一步诱导其凋亡。     

Double stage activity in aminoglycoside antibiotics

Fourteen different aminoglycoside antibiotics (AGs) were challenged with aminoglycoside acetyltransferases (AACs) of actinomycete origin in order to examine their 'double stage activity' that is arbitrarily defined as antibiotic activity retainable after enzymatic modification. In kanamycin (KM)-group AGs tested [KM, dibekacin (DKB), amikacin and arbekacin (ABK)], ABK retained activity after acetylations by AAC(3), AAC(2') and AAC(6'). DKB also retained a weak activity after acetylation by AAC(2'). In gentamicin (GM)-group AGs tested [GM, micronomicin, sisomicin (SISO), netilmicin (NTL) and isepamicin], GM, SISO and NTL retained activites after acetylation by AAC(2'). In neomycin (NM)-group AGs tested [ribostamycin, NM, paromomycin], NM retained activity after acetylation by AAC(6') and AAC(2'). None of astromicin (ASTM)-group AGs tested (ASTM and istamycin B) retained activity after acetylation by AAC(2') and AAC(6'). The activities of acetylated ABK derivatives by AAC(3) and AAC(2') were distinctively high, compared to the others. Streptomyces lividans TK21 containing the cloned aac genes were markedly sensitive to AGs that retained activities after acetylation, indicating the substantial effect of 'double stage activity'.     

白藜芦醇通过线粒体调控血吸虫感染小鼠M1/M2极化

目的探讨白藜芦醇对血吸虫病巨噬细胞极化的作用及机制。方法45只血吸虫感染小鼠3周后,随机分3组,A组感染组,B组白藜芦醇治疗组,C组吡喹酮治疗组,另取15只小鼠为健康对照D组。感染第9周,流式细胞术检测肝脏M1、M2,ATP试剂盒检测肝脏巨噬细胞ATP,实时定量PCR检测M1和M2相关因子、mtDNA。采用虫卵可溶性抗原(SEA)刺激RAW264.7,再给予白藜芦醇处理,检测M1、M2比例,细胞上清中M1和M2相关因子,PGC-1α,mtDNA和ATP。结果B组M1比例高于A组(P<0.01),M2比例低于A组(P<0.05),肝脏巨噬细胞M2相关因子、PGC-1α、mtDNA、ATP、基础耗氧率均低于A组(P<0.05),M1相关因子高于A组(P<0.05)。白藜芦醇使RAW264.7往M1分化增多(P<0.01),往M2分化减少(P<0.01),M2相关因子降低(P<0.05),mtDNA、PGC-1α、ATP、基础耗氧率降低(P<0.05),M1相关因子增高(P<0.05)。结论白藜芦醇通过抑制巨噬细胞线粒体数量和功能促进其往M1分化,抑制其往M2分化。     

Characterization of human recombinant alpha(2A)-adrenoceptors expressed in Chinese hamster lung cells using intracellular Ca(2+) changes: evidence for cross-talk between recombinant alpha(2A)- and native alpha(1)-adrenoceptors

1. Human alpha(2A)-adrenoceptors expressed in Chinese hamster lung (CHL) fibroblasts have been pharmacologically characterized by measuring intracellular calcium (Ca(2+)(i)) changes using the Ca(2+)-sensitive dye Fluo3-AM, in conjunction with a fluorometric imaging plate reader (FLIPR). 2. Several alpha-adrenoceptor agonists were examined including the alpha(2)-adrenoceptor agonists UK-14304, B-HT 920, dexmedetomidine and A-54741, the selective alpha(1)-adrenoceptor agonist phenylephrine and the non-selective adrenergic agonist noradrenaline. Of these only noradrenaline (mean pEC(50)=6.49) and A-54741 (6.90) evoked changes in Ca(2+)(i); A-54741 was a partial agonist relative to noradrenaline, achieving only 33% of the noradrenaline maximum. 3. Ca(2+)(i) changes induced by noradrenaline and A-54741 were antagonized by the alpha(2)-selective antagonist rauwolscine (10 nM) and by the alpha(1)-selective antagonists prazosin (0.1 nM) and doxazosin (1.0 nM). 4. Phenylephrine (100 microM) and UK-14304 (10 microM) alone were ineffective in causing Ca(2+)(i) increase. In the presence of a fixed concentration of UK-14304 (3.0 microM), phenylephrine induced concentration-dependent increases in Ca(2+)(i) (mean pEC(50)=5.33). In the presence of phenylephrine (30.0 microM) UK-14304 induced Ca(2+)(i) release (pEC(50)=6.92). The effects of phenylephrine were abolished by prazosin (1.0 nM) or rauwolscine (100 nM). 5. In saturation radioligand binding experiments using membranes of parental (non-transfected) CHL cells there was a small, specific binding of [(3)H]-prazosin (B(max)=24 fmol mg protein(-1); pK(D)=10. 24). 6. Collectively, these data suggest that alpha-adrenoceptor agonist-induced Ca(2+)(i) release in CHL fibroblasts transfected with the human alpha(2A)-adrenoceptor is dependent upon co-activation of the recombinant receptor and a native alpha(1)-adrenoceptor.     

Regulation of nicotine-induced cyclooxygenase-2 protein expression in human gingival fibroblasts

AIM: Activation of cyclooxygenase-2 (COX-2) expression by nicotine suggests a potential role for nicotine in the pathogenesis of smoking-associated periodontal disease. The aim of this study was to investigate whether chemical interactions can modulate nicotine-induced COX-2 expression in human gingival fibroblasts (HGF). METHODS: Cytotoxicity was investigated by using lactate dehydrogenase leakage assays and Western blotting was used to assess COX-2 expression. Furthermore, buthionine sulfoximine (BSO; an intracellular glutathione synthesis inhibitor), 2-oxothiazolidine-4-carboxylic acid (OTZ; the precursor of cysteine), and PD98059 (extracellular signal-regulated protein kinase inhibitor) were added to search for the possible regulation mechanisms of nicotine-induced COX-2 expression. RESULTS: Nicotine was found to elevate lactate dehydrogenase leakage in a dose-dependent manner (P<0.05). Treatment of HGF with nicotine was shown to mediate COX-2 protein expression. Pretreatment with OTZ decreased nicotine-induced COX-2 protein level by approximately 60 % (P<0.05). However, BSO enhanced nicotine-induced COX-2 protein level up to approximately 3-fold (P<0.05). Treatment of HGF with PD98059 decreased nicotine-induced COX-2 protein expression. In addition, nicotine induced extracellular signal-regulated protein kinase phosphorylation in a time-dependent manner (P<0.05). CONCLUSION: Nicotine may play a significant role in the pathogenesis of cigarette smoking associated-periodontitis via the activation of COX-2 which is augmented by oxidative stress and mediated by extracellular signal-regulated protein kinase signaling.     

A novel model of pain sensation using superfused gastrosplenic omentum preparation of anesthetized rats

A pain model for screening analgesics was established in anesthetized rats. The omenta of urethane-anesthetized rats were exteriorized, fixed in a plastic chamber, and superfused with Tyrode solution. Administration of bradykinin (BK) in the chamber elicited the reflex hypertensive response (RHR). Modification of the RHR was tested by topical (in the chamber) or intravenous administration of drugs. The BK dose-response curve was shifted to the right by topical indomethacin. The RHR by BK was inhibited by topical application of a BK B(2) antagonist, (Thi(5,8)-D-Phe(7)-BK), a local anesthetic (2% carbocaine), and by intravenous administration of a ganglion blocker (hexamethonium) or an alpha-adrenergic blocker (dibenamine). The RHR by topical BK was almost completely inhibited by morphine and the suppression was largely reversed by naloxone. The RHR, induced by a threshold dose of BK and inhibited by indomethacin, was potentiated by pretreatment of the omentum with prostaglandin (PG) E(2) or PGI(2). PGE(2) was less potent, but the effect lasted longer than that of PGI(2). Topical administration of a non-acidic analgesic, mepirizole, inhibited the RHR by topical BK by only 20%, but intravenous mepirizole inhibited topical BK by 96.2%, indicating its major central action. This model may be useful for studying analgesics.     

Regulation of epithelial Na+ channels by aldosterone: role of Sgk1

1. The epithelial sodium channel (ENaC) is tightly regulated by hormonal and humoral factors, including cytosolic ion concentration and glucocorticoid and mineralocorticoid hormones. Many of these regulators of ENaC control its activity by regulating its surface expression via neural precursor cell-expressed developmentally downregulated (gene 4) protein (Nedd4-2). 2. During the early phase of aldosterone action, Nedd4-2-dependent downregulation of ENaC is inhibited by the serum- and glucocorticoid-induced kinase 1 (Sgk1). 3. Sgk1 phosphorylates Nedd4-2. Subsequently, phosphorylated Nedd4-2 binds to the 14-3-3 protein and, hence, reduces binding of Nedd4-2 to ENaC. 4. Nedd4-2 is also phosphorylated by protein kinase B (Akt1). Both Sgk1 and Akt1 are part of the insulin signalling pathway that increases transepithelial Na(+) absorption by inhibiting Nedd4-2 and activating ENaC.     

Mechanism of inhibitory action of tranilast on the release of slow reacting substance of anaphylaxis (SRS-A) in vitro: effect of tranilast on the release of arachidonic acid and its metabolites

We investigated the mechanism of inhibitory action of tranilast, one of the anti-allergic drugs, on the release of slow reacting substance of anaphylaxis (SRS-A). Ionophore A23187 (0.5 or 0.2 micrograms/ml)-induced SRS-A release from rat peritoneal exudate cells (PEC) or human leucocytes was inhibited by tranilast (10(-5)-10(-3) M). The IC50 (the concentration which gives 50% inhibition) of tranilast on these reactions was approx. 10(-4) M. Prostaglandin (PG)E2 release from sensitized purified rat mast cells (PMC) by a specific antigen (DNP-Ascaris) was markedly suppressed by tranilast (10(-3) M). Similarly, ionophore A23187-induced PGE2 and 6-keto-PGF1 alpha releases from rat PEC were inhibited by tranilast (10(-5)-10(-3) M). DNP-Ascaris antigen-induced 3H-arachidonic acid (AA), 3H-PGE2, 3H-PGF2 alpha and 3H-PGD2 releases from rat PMC were markedly suppressed by tranilast (10(-5)-10(-3) M), DSCG (10(-5)-10(-4) M) and mepacrine (10(-3) M). The activity of AA-converting enzymes such as 5-lipoxygenase, cyclooxygenase, PGI2 synthetase, and glutathione-S-transferase was hardly influenced by tranilast (10(-5)-10(-3) M). From these results, we suggest that the mechanism of the inhibitory action of tranilast on the release of SRS-A is related to the processes prior to dissociation of AA from the membrane phospholipids.