OBJECTIVETo examine the inhibition of nitric oxide (NO) synthesis during ischemic preconditioning (IP) upon the induction of heat-shock protein 72 (HSP72) and the size-limiting effect of the second window of protection on infarction.

METHODSRabbits were subjected to either 4 cycles of 5-min long coronary artery occlusion separated by 10 min of reperfusion, or a sham operation. During this procedure, we administered 10 mg/kg of N(G)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase) intravenously 5 min before IP followed by its continuous infusion (1.5 mg/kg/min). Twenty-four hours after IP or the sham operation, the hearts were rapidly excised for assay of HSP72 expression or were subjected to 30 min of coronary artery occlusion followed by 120 min of reperfusion, at which point infarct size (IS) was measured.

RESULTSTwenty-four hours after IP or the sham operation, there was no difference in heart rate or mean arterial pressure between the groups. Immunoblotting revealed an increase in HSP72 protein levels in the IP group, which was blocked by L-NAME. IS in the IP rabbits was reduced compared with controls (29.8 +/- 3.7% vs. 50.8 +/- 4.3%, P < 0.01). IS in the IP rabbits was elevated as a result of L-NAME treatment (46.0 +/- 5.1%). Administration of L-arginine reversed the effects of L-NAME on the induction of HSP72 and IS (33.5 +/- 4.0%). The intravenous administration of S-nitroso-N-acetylpenicillamine (an NO donor, 15 microg/kg/min) over 20 min increased the induction of HSP72 and reduced IS (31.3 +/- 5.7%, P < 0.01 vs. control) 24 h later.

CONCLUSIONThese findings suggest that NO may be involved in the induction of HSP72 and the opening of the second window of protection of IP.

Animals ; HSP72 Heat-Shock Proteins ; Heat-Shock Proteins ; biosynthesis ; Hemodynamics ; drug effects ; Ischemic Preconditioning, Myocardial ; Male ; Myocardial Infarction ; pathology ; Nitric Oxide ; physiology ; Penicillamine ; analogs & derivatives ; pharmacology ; Rabbits

OBJECTIVETo investigate the effect of Ca(2+) mobilization on release and activation of matrix metalloproteinases (MMPs) in human hepatocellular carcinoma cells.

METHODSCa(2+) and chemicals which can induce or inhibit Ca(2+) mobilization were added into human SMMC-7721 hepatoma cells in vitro. SDS-PAGE protein electrophoresis and gelatin zymography analysis were carried out to detect the changes of release and activation of MMPs in the cell culture supernatant.

RESULTSAddition of CaCl(2) into culture system resulted in an enhanced secretion and activation of MMP-2 and MMP-9 in a dose-dependent manner. At a dose of 0.8 mmol/L CaCl(2), it maintained a stable high level of MMPs, especially of MMP-2 with (109.71 +/- 27.93)% elevation as compared to the cells without CaCl(2) addition (P < 0.001). SDS-PAGE analysis showed that most secreted proteins were MMPs (MMP-2 and MMP-9) when the cells cultured in media without serum. Thapsigargin (Tg, 4 micromol/L), an inducer of intracellular Ca(2+) stores depletion, significantly enhanced the release and activation of MMP-2 and MMP-9, compared to the control with (58.63 +/- 31.04)% elevation (P < 0.05), while the inducing effect of Tg on MMPs release and activation was significantly inhibited by S-nitro-N-acetylpenicillamine (SNAP, 200 micromol/L), an NO donor.

CONCLUSIONIntracellular Ca(2+) regulation pathways may play an important role in the process of release and activation of MMPs.

Calcium ; metabolism ; Carcinoma, Hepatocellular ; enzymology ; pathology ; Cell Line, Tumor ; Dose-Response Relationship, Drug ; Humans ; Liver Neoplasms ; enzymology ; pathology ; Matrix Metalloproteinase 2 ; metabolism ; secretion ; Matrix Metalloproteinase 9 ; metabolism ; secretion ; Nitric Oxide Donors ; pharmacology ; Penicillamine ; analogs & derivatives ; pharmacology ; Thapsigargin ; pharmacology

The expression of inducible nitric oxide synthase (iNOS) is a critical factor in both normal physiological functions and the pathogenesis of disease. This study was undertaken to determine the molecular mechanism by which nitric oxide (NO) exerts negative feedback regulation on iNOS gene expression. Isolated rat hepatocytes stimulated with cytokines exhibited a marked increase in NO production as well as iNOS mRNA and protein levels, which were significantly reduced by pretreatment of the NO donors S-nitroso-N-acetyl-D, L-penicillamine (SNAP) and V-PYRRO/NO. This effect of SNAP was inhibited when NO was scavenged using red blood cells. Pretreatment with oxidized SNAP, 8-Br-cGMP, NO2-, or NO3- did not suppress the cytokine-induced NO production. Moreover, LPS/ IFN-gamma-stimulated RAW264.7 cells, which produce endogenous NO, expressed lower levels of iNOS, IL-1beta, IL-6 and TNF-alpha mRNAs, without changes in their mRNA half-lives, than those in the presence of the iNOS inhibitor NG-monomethyl- L-arginine. The iNOS gene transcription rate exhibited an 18-fold increase after cytokine stimulation, which was significantly inhibited by SNAP pretreatment. SNAP also blocked cytokine- induced increase in NF-kappa B activation, iNOS promoter activity, nuclear translocation of cytosolic NF-kappa B p65 subunit, and I kappa B alpha degradation, which correlated with its inhibitory effect on phosphorylation and ubiquitination of I kappa B. These data indicate that NO down-regulates iNOS gene expression and NO production by inhibiting the post-translational processes of I kappa B alpha thereby preventing NF-kappa B activation. These results identify a novel negative feedback mechanism whereby NO down-regulates iNOS gene expression.
Animals ; Cell Line ; Cell Nucleus/metabolism ; Cyclic GMP/*analogs & derivatives/pharmacology ; Cytokines/genetics/metabolism ; *Down-Regulation ; Hepatocytes/metabolism ; I-kappa B/*metabolism ; Lipopolysaccharides/pharmacology ; Nitric Oxide/biosynthesis/*physiology ; Nitric-Oxide Synthase/biosynthesis/*genetics ; Penicillamine/*analogs & derivatives/pharmacology ; Phosphorylation ; Promoter Regions (Genetics)/genetics ; *Protein Processing, Post-Translational ; Protein Transport ; Rats ; Research Support, Non-U.S. Gov't

OBJECTIVETo observe the role of G protein in the dual regulation of opioid receptor agonist on the delayed rectified potassium channels.

METHODSUsing whole-cell patch-clamp techniques applied to NG108-15 cells, investigate the effect of opioid receptor agonist on the delayed rectified potassium channels by administration of Guanosine-5'-0'-2-thiociphosphate (GDP beta S), Pertusis Toxin (PTX), Tetroacetic acid nueleoside diphosphate kinase (NDPK) and Adenosine-3' 5' cyclic monophosphate cAMP in the pipette solution.

RESULTS(1) GDP beta S could block the changes induced by both high and low concentration of (D-Pen2.5)-enkephalin (DPDPE) (P < 0.05). (2) PTX could inhibit the excitative regulation on K+ channel by high concentration of DPDPE (P < 0.05). But CTX had no effect on K+ channel caused by DPDPE. (3) UDP could block the excitative effect of K+ channel by high concentration of NDPK, while have no changes on the inhibitory effect caused by low concentration of opioid agonists. (4) cAMP took part in the regulation in high concentration of agonist administration (P < 0.05), while no changes for low concentration of agonists.

CONCLUSIONSDual changes were observed on delayed rectifier potassium channel by agonist treatment on NG108-15 cells. The excitative effect was Gi/o coupled in high concentration of agonist incubation, related to cAMP. While the inhibitory effect was possibly induced by G protein beta gamma subunit directly.

Animals ; Enkephalin, D-Penicillamine (2,5)- ; pharmacology ; GTP-Binding Proteins ; physiology ; Glioma ; metabolism ; pathology ; Guanosine Monophosphate ; analogs & derivatives ; pharmacokinetics ; Hybrid Cells ; metabolism ; pathology ; Mice ; Neuroblastoma ; metabolism ; pathology ; Patch-Clamp Techniques ; Pertussis Toxin ; pharmacology ; Potassium Channels, Inwardly Rectifying ; metabolism ; Rats ; Receptors, Opioid ; agonists ; Thionucleotides ; pharmacokinetics

To investigate the protective effects of nitric oxide (NO) on cardiomyocytes against hydrogen peroxide (H2O2)-induced injury, cultured neonatal cardiomyocytes were divided into three groups: (1) normal group; (2) H2O2 group: cells were treated with H2O2 (0.1 mmol/L) for 4 h; (3) SNAP+ H2O2 group: cells were pretreated with NO donor S-nitroso-N-acetyl-1,1-penicillamine (SNAP, 0.5 mmol/L) 10 min before H2O2 treatment. Colorimetric assay was used to detect cell viability and lactate dehydrogenase (LDH) activity to evaluate cell injury. Apoptotic rate of cardiomyocytes were determined by flow cytometer. Superoxide dismutase (SOD) activity and malonaldehyde (MDA) content were measured by colorimetric assay to evaluate cell antioxidant ability. Intracellular calcium was tested by laser confocal microscopy. The results showed that after treatment with H2O2, cell viability was significantly reduced to 58.3+/-7.6% compared with normal group (93.1+/-6.2 %). LDH activity and apoptotic rates were 1580.5+/-186.7 U/L and 26.4+/-5.7% respectively, significantly higher than that of normal group (631.4+/-75.6 U/L and 0). SNAP pretreatment markedly improved cell viability to 79.7+/-9.3% and reduced LDH activity and apoptotic rates to 957.8+/-110.9 U/L and 9.1+/-3.3%, respectively. Cells treated with H2O2 had a lower SOD activity of 14.73+/-1.68 NU/ml and a higher MDA content of (15.35+/-3.49) micromol/L compared with normal cells (19.67+/-0.85 NU/ml) and (6.95+/-0.83 micromol/L), respectively. Cells with SNAP pretreatment had a higher SOD activity of 21.36+/-3.11 NU/ml and a lower MDA content of 9.12+/-1.47 micromol/L compared with H2O2 group. Intracellular calcium content was reduced by SNAP administration while enhanced by H2O2. Pretreatment with SNAP could antagonize the effect of H2O2 of accelerating intracellular calcium content. Based on the results observed, it is concluded that NO donor SNAP may protect cardiomyocytes from being injured by H2O2. The underlying mechanisms may include improving cell antioxidant ability and reducing intracellular calcium overload.
Animals ; Animals, Newborn ; Cells, Cultured ; Free Radical Scavengers ; pharmacology ; Hydrogen Peroxide ; antagonists & inhibitors ; L-Lactate Dehydrogenase ; metabolism ; Malondialdehyde ; metabolism ; Myocardium ; cytology ; metabolism ; Myocytes, Cardiac ; metabolism ; pathology ; Nitric Oxide ; metabolism ; Nitric Oxide Donors ; pharmacology ; Penicillamine ; analogs & derivatives ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Superoxide Dismutase ; metabolism

OBJECTIVETo investigate the dual effects by the delta opioid receptor agonists DPDPE on the delayed rectified potassium channels in NG108-15 cells.

METHODSA series of outward currents were evoked in NG108-15 cells by depolarizing voltage from -50 mV to +80 mV at holding potential of -90 mV. These currents were delayed rectified potassium currents. Relatively selected delta opioid receptor agonists DPDPE of higher and lower concentrations were used to modulate the delayed rectified K+ current in NG108-15 cells. Opioid receptor antagonist Naloxone (NAL) and relatively selected delta opioid receptor antagonist Naltrindole (NTI) were used in the present experiments for the characterization of the actions of opioid receptors.

RESULTSThe relatively higher concentrations of delta opioid receptor agonist DPDPE (> or = 10(-6) mol/L) significantly increased the amplitude of the delayed rectified K+ current. On the contrary, the relatively lower concentrations of DPDPE (< or = 10(-12) mol/L) decreased the amplitude of the delayed rectified K+ current (P < 0.05). Furthermore both the increase and decrease were time-dependent.

CONCLUSIONSdelta opioid receptor agonist has dual regulatory effects on the delayed rectified potassium channels in NG108-15 cells.

Animals ; Cell Membrane ; metabolism ; Enkephalin, D-Penicillamine (2,5)- ; pharmacology ; Glioma ; metabolism ; pathology ; Hybrid Cells ; metabolism ; Mice ; Naloxone ; pharmacology ; Naltrexone ; analogs & derivatives ; pharmacology ; Neuroblastoma ; metabolism ; pathology ; Patch-Clamp Techniques ; Potassium Channels, Inwardly Rectifying ; drug effects ; metabolism ; Rats ; Receptors, Opioid, delta ; agonists ; Tumor Cells, Cultured

OBJECTIVETo examine the effect of angiotensin-converting enzyme inhibitor (ACEI) on hydrogen peroxide (H(2)O(2))-induced decrease in contraction of isolated rataortic rings, and to investigate its mechanisms.

METHODSThe thoracic aortic rings with endothelium of male Sprague-Dawley rats were mounted on a bath system. Isometric contractions of aortic rings were measured.

RESULT(1) After incubation with captopril (an ACEI with sulfhydryl groups) or perindoprilate (an ACEI without sulfhydryl groups), the decrease in contraction response to PE was prevented in arteries which were pretreated with 300 micromol/L H(2)O(2). (2) Captopril enhanced the HO-1 activity of thoracic aorta. After inhibition of HO-1 activity by ZnPP IX, the protection effect of captopril was abrogated. Hemin (an inducer of HO-1) and bilirubin (a product of HO-1) could mimic the antioxidative effect of captopril. (3) Both L-NAME (an inhibitor of NOS) and methylene blue (an inhibitor of GC) could abolish the protective effect of captopril. (4) SNAP could protect aortic rings against H(2)O(2) attack, and ZnPP IX could cancel the effect of SNAP.

CONCLUSIONBoth ACEI with or without sulfhydryl groups could prevent the H(2)O(2) induced decrease in contraction responses to PE in intact aortic rings. The increase of NO and activation of HO-1 might be involved in the mechanism.

Angiotensin-Converting Enzyme Inhibitors ; pharmacology ; Animals ; Antioxidants ; pharmacology ; Aorta, Thoracic ; drug effects ; metabolism ; physiology ; Bilirubin ; pharmacology ; Captopril ; pharmacology ; Heme Oxygenase-1 ; metabolism ; Hemin ; pharmacology ; Hydrogen Peroxide ; pharmacology ; In Vitro Techniques ; Male ; Methylene Blue ; pharmacology ; NG-Nitroarginine Methyl Ester ; pharmacology ; Nitric Oxide ; metabolism ; Penicillamine ; analogs & derivatives ; pharmacology ; Protoporphyrins ; pharmacology ; Rats ; Rats, Sprague-Dawley ; Vasoconstriction ; drug effects

OBJECTIVETo investigate the postburn change in hypothalamic paraventricular beta-endorphin and the roles of delta-receptor in scalded rats.

METHODSMale Sprague-Dawley (SD) rats were randomly divided into 3 groups, i.e. ICI174864, DPDPE and control groups. The rats were inflicted with 20% TBSA of III degree scalding on the back by boiling (100 degrees ) water. The postburn change in the tissue content of the hypothalamic paraventricular beta-endorphin was determined by radioimmuno assay (RIA). The effects of delta-receptor in scalded shock rats were investigated by observing the change of the rats'survival time and cardiac indices after the micro-injection of delta-receptor agonist DPDPE or antagonist ICI174864 into the hypothalamic paraventricle.

RESULTS(1) The tissue content of the hypothalamic paraventricular beta-endorphin increased significantly (P < 0.01) at 1, 2 and 4 postburn hours (PBHs) in the scalded rats. (2) When compared with that of control group, the ratio of the cardiovascular parameters [mean arterial pressure (MAP), dp/dt(max) and HR] were obviously increased at different time points in rats with pre-injection of ICI174864 whereas the ratio was decreased when DPDPE was used. Nevertheless, the change in the heart rate ratio was not obvious whether ICI174864 or DPDPE was used. (3) The average animal survival time in ICI174864 group was much longer than that in DPDPE group.

CONCLUSIONAn excessive increase in hypothalamic paraventricular beta-endorphin was one of the factors leading to the aggravation of burn shock and earlier death. delta-receptor located in the tissue might have played important roles in the mediation of the action of hypothalamic paraventricular beta-endorphin. It is beneficial to antagonize the action of delta-receptor for the correction of burn shock and for the prolongation of the of life of animals.

Analgesics, Opioid ; pharmacology ; Animals ; Blood Pressure ; drug effects ; Burns ; physiopathology ; Enkephalin, D-Penicillamine (2,5)- ; pharmacology ; Enkephalin, Leucine ; analogs & derivatives ; pharmacology ; Heart Rate ; drug effects ; Male ; Narcotic Antagonists ; pharmacology ; Paraventricular Hypothalamic Nucleus ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, delta ; drug effects ; physiology ; Survival Analysis ; beta-Endorphin ; metabolism

The role of nitric oxide (NO) in the ocular surface remains unknown. We investigated the conditions leading to an increase of NO generation in tear and the main sources of NO in ocular surface tissue. We evaluated the dual action (cell survival or cell death) of NO depending on its amount. We measured the concentration of nitrite plus nitrate in the tears of ocular surface diseases and examined the main source of nitric oxide synthase (NOS). When cultured human corneal fibroblast were treated with NO producing donor with or without serum, the viabilities of cells was studied. We found that the main sources of NO in ocular surface tissue were corneal epithelium, fibroblast, endothelium, and inflammatory cells. Three forms of NOS (eNOS, bNOS, and iNOS) were expressed in experimentally induced inflammation. In the fibroblast culture system, the NO donor (SNAP, S-nitroso-N-acetyl-D, L-penicillamine) prevented the death of corneal fibroblast cells caused by serum deprivation in a dose dependent manner up to 500 micrometer SNAP, but a higher dose decreased cell viability. This study suggested that NO might act as a doubleedged sword in ocular surface diseases depending on the degree of inflammation related with NO concentration.
Animals ; Apoptosis/drug effects/physiology ; Aqueous Humor/metabolism ; Blood Proteins/pharmacology ; Cell Survival/drug effects/physiology ; Cells, Cultured ; Epithelium, Corneal/*cytology/*enzymology ; Fibroblasts/cytology/enzymology ; Humans ; Nitric Oxide/biosynthesis/*physiology ; Nitric Oxide Donors/pharmacology ; Nitric Oxide Synthase/metabolism ; Nitric Oxide Synthase Type I ; Nitric Oxide Synthase Type II ; Nitric Oxide Synthase Type III ; Penicillamine/*analogs & derivatives/pharmacology ; Peroxynitrous Acid/biosynthesis ; Rabbits ; Tears/metabolism ; Uveitis/metabolism