Biomedical subjects

D Li

Publications and source records attributed to D Li.

At least 109 records · Page 6Linked to original sources

PubMed2001

Silyl derivatization of alkylphenols, chlorophenols, and bisphenol A for simultaneous GC/MS determination.

A fast silyl derivatization technique for simultaneous GC/ MS analysis of alkylphenols, chlorophenols, and bisphenol A was developed. The analytes were silylized with an excess amount of bis(trimethylsilyl)trifluoroacetamide (BSTFA) followed by hydrolysis of excess silyl reagent with water. Reaction rates of derivatization were studied in various solvents and found to be fastest in acetone. Derivatization reaction in acetone was completed quantitatively within 15 s at room temperature while it took more than 1 h in other solvents studied. Similar results were obtained in mixed solvents with acetone if the content of acetone was higher than 60% (v/v). Since water-immiscible solvents such as dichloromethane or hexane are frequently used in the extraction of phenolic analytes in various sample matrixes, acetone can be added to the extracts in order to accelerate the reaction rate of derivatization. Stability of the derivatives in sample for long-term storage was ensured by hydrolyzing excess derivatizing reagent, BSTFA, with a spike of water followed by dehydration using anhydrous sodium sulfate. On the basis of the above results, a derivatizing treatment kit was designed to improve the convenience of analysis. It was possible to treat sample within several minutes successfully by using the kit. So fast simultaneous determination of those anlaytes by GC/MS was possible with improved convenience as well as sensitivity and reproducibility.

Gas Chromatography-Mass Spectrometry↗

PubMed2001

Activation of estrogen receptor blocks interleukin-6-inducible cell growth of human multiple myeloma involving molecular cross-talk between estrogen receptor and STAT3 mediated by co-regulator PIAS3.

Estrogen receptors (ERs)(1) highly expressed by multiple myeloma (MM) cells and stimulation of estrogenic ligands leads to cell apoptosis. Interleukin (IL)-6 is a major growth factor in the pathogenesis of MM. However, little is known concerning the molecular consequences of ER activation on IL-6-regulated MM cell growth. Here we show that the ER agonist 17 beta-estradiol completely abolished IL-6-inducible MM cell proliferation. By contrast, the ER antagonist ICI 182,780 overcame the inhibitory effect of estrogen. Estrogen blocked STAT3 DNA binding and transactivation but failed to affect the mRNA expression of IL-6 receptor chains or activation of JAK2 and STAT3. Estrogen-activated ER did not associate directly with STAT3. Estrogen induced the mRNA expression of PIAS3 (protein inhibitor of activated STAT3) and increased PIAS3 physical association with STAT3, suggesting a possible mechanism of STAT3 inhibition requiring PIAS3 as a co-regulator modulating the cross-talk between ER and STAT3. These data directly demonstrate STAT3 to be a molecular participant in ER inhibition of the IL-6 signaling pathway in human MM cells and provides the molecular basis for the potential use of estrogenic ligands in the treatment of MM or other tumors where IL-6 has an autocrine or paracrine role.

Base Sequence↗

PubMed2001

Genomic organization and isoform-specific tissue expression of human NAPOR (CUGBP2) as a candidate gene for familial arrhythmogenic right ventricular dysplasia.

Neuroblastoma apoptosis-related RNA-binding protein (NAPOR; HGMW-approved symbol CUGBP2) is a newly discovered gene prominently induced during apoptosis, suggesting that it plays a role during apoptosis. We have found that it is encoded by a gene located on chromosome 10p13-p14 between Généthon markers D10S547 and D10S223, a region to which we have recently localized a gene responsible for arrhythmogenic right ventricular dysplasia (ARVD). To examine its possible role in the pathogenesis of ARVD, we determined the genomic organization of the human NAPOR gene including its exon-intron boundaries and the putative promoter sequence, which provide a plausible mechanism for its alternative mRNA splicing. We also demonstrated that three isoforms of the NAPOR transcript were differently expressed, with NAPOR-3 being nearly neuron specific while the other two forms were ubiquitously expressed. The expression of NAPOR is differentially regulated during development. Finally, we screened the members of the ARVD family for mutations and identified two DNA sequence variants in the protein-coding exons of NAPOR, neither of which was responsible for ARVD. While the function of NAPOR remains to be elucidated, our current characterization of the NAPOR gene will be valuable for further clinical and functional study.

Alternative Splicing↗

PubMed2001

Potential ionic mechanism for repolarization differences between canine right and left atrium.

Experimental and clinical evidence suggests a critical role for the left atrium (LA) in atrial fibrillation (AF). In animal models, repolarization is faster in the LA than in the right atrium (RA), leading to more stable reentry circuits with a shorter intrinsic period in the LA. The ionic mechanisms underlying LA-RA repolarization differences are unknown. Therefore, we evaluated ionic currents and action potentials (APs) with the whole-cell patch clamp in isolated canine atrial myocytes. The density of the rapid delayed rectifier current (I(Kr)) was greater in the LA (eg, 1.83+/-0.10 pA/pF at +20 mV) than in the RA (1.15+/-0.07 pA/pF, P<0.01; n=16 cells per group). The slow and ultrarapid delayed rectifier, the inward rectifier, L-type Ca(2+), and transient outward K(+) currents were all comparable in the LA and RA. There were no differences in kinetic or voltage-dependent properties of currents in LA versus RA. Western blots of ether-a-go-go-related gene (ERG) protein in three RA and corresponding LA regions showed significantly greater ERG expression in LA. AP duration (APD) was shorter in the LA versus RA in both isolated cells and multicellular preparations, and the effective refractory period (ERP) was shorter in the LA compared with the RA in vivo. Dofetilide had significantly larger APD- and ERP-increasing effects in the LA compared with RA, and LA-RA repolarization differences were eliminated by exposure to dofetilide. We conclude that LA myocytes have larger I(Kr) than do RA myocytes, contributing importantly to the shorter APD and ERP in LA. The larger LA I(Kr) may participate in the ability of the LA to act as a "driver region" for AF, with potentially important implications for understanding AF mechanisms and antiarrhythmic therapy.

Action Potentials↗

PubMed2001

Isolation and purification of the ovulation-inducing factor from seminal plasma in the bactrian camel (Camelus bactrianus).

The purpose of this study was to extract, identify and partially characterize a newly found ovulation-inducing factor, and thus gain our understanding of induced ovulation in biology. In our preliminary research, an ovulation-inducing factor (OIF) was isolated and purified from seminal plasma of the bactrian camel by ion-exchange chromatography on DEAE-cellulose, HPLC and reverse-phase HPLC. The OIF is a peptide with 74 residues and GnRH-like bioactivity, which is heat-stable in camel seminal plasma because the OIF is wrapped up in several protein layers with different properties. However, purified OIF is degraded when it is exposed to oxygen or is heated in water. According to the analysis of amino acid components and partial amino acid sequence aminated N-terminus, and its molecular weight, the OIF is completely different from the native-LHRH, LH, HCG, PMSG and PGF-2alpha. The OIF is a novel ovulation hormone in the bactrian camel, but is similar to that reported in the bull.

Amino Acid Sequence↗

PubMed2001

Structure of complement receptor 2 in complex with its C3d ligand.

Complement receptor 2 (CR2/CD21) is an important receptor that amplifies B lymphocyte activation by bridging the innate and adaptive immune systems. CR2 ligands include complement C3d and Epstein-Barr virus glycoprotein 350/220. We describe the x-ray structure of this CR2 domain in complex with C3d at 2.0 angstroms. The structure reveals extensive main chain interactions between C3d and only one short consensus repeat (SCR) of CR2 and substantial SCR side-side packing. These results provide a detailed understanding of receptor-ligand interactions in this protein family and reveal potential target sites for molecular drug design.

Amino Acid Sequence↗

PubMed2001

Exploring the potential for subtype-selective muscarinic agonists in glaucoma.

Pilocarpine has been used to lower intraocular pressure (IOP) in glaucoma patients for more than 100 years. Since the identification of five muscarinic receptor subtypes, there has been an interest in separating the IOP-lowering effects from the ocular side effects of pupil constriction and lens accommodation. However, all these actions seem to be mediated by the M3 receptor. A novel muscarinic receptor agonist, AGN 199170, that has no activity on the M3 subtype was compared to pilocarpine in a monkey glaucoma model. This compound lowered IOP suggesting that muscarinic agonists targeted at muscarinic receptors other than the M3 subtype may be able to selectively lower IOP.

Animals↗

PubMed2001

[26S rDNA D1/D2 domain sequence analysis of the pathogenic strain from the first case of disseminated trichosporonosis in China].

OBJECTIVE: To determine the large-subunit (26S) rDNA D1/D2 domain sequence of AS 2.217 4, the pathogenic strain from the first case of disseminated trichosporosis in China, and study the feasibility of applying DNA sequencing in rapid identification of pathogenic yeast. METHOD: The strain of Trichosporon (AS 2.2174) was collected from the skin lesion of a case of disseminated trichosporosis. Nuclear DNA was extracted from the cells of AS 2.2174 by a simplified protocol and the 26S rDNA D1/D2 domain was amplified by PCR. The PCR product was then directly sequenced with the ABI PRISM BigDye cycle sequencing kit. RESULTS: The 26S rDNA D1/D2 domain of strain AS 2.2174 was determined (GenBank accession number: AF337949). Comparison analysis indicated that the D1/D2 sequence of AS 2.2174 is identical with that of the type strain of Trichosporon asahii, and differs from those T. asteroides, T. faecale and T. coremiiforme in 3, 5 and 8 nucleotides, respectively. The latter three species are phenotypically indistinguishable from T. asashii. CONCLUSION: The strain AS 2.2174 was confirmed to belong to Trichosporon asahii. This species is the first record in China clinically and taxonomically. DNA sequencing shows an advantage in fast and accurate identification of clinically relevant yeast species.

Adult↗

PubMed2001

Precision calculation of magnetization and specific heat of vortex liquids and solids in type-II superconductors.

A new systematic calculation of magnetization and specific heat contributions of vortex liquids and solids is presented. We develop an optimized perturbation theory for the Ginzburg-Landau description of thermal fluctuations effects in the vortex liquids. The expansion is convergent in contrast to the conventional high temperature expansion which is asymptotic. In the solid phase we calculate the first two orders which are already quite accurate. The results are in good agreement with existing Monte Carlo simulations and experiments. Limitations of various nonperturbative and phenomenological approaches are noted. In particular, we show that there is no exact intersection point of the magnetization curves.

Journal Article↗

PubMed2001

Interligand Overhauser effects in type II dihydrofolate reductase.

R67 dihydrofolate reductase (DHFR) is a type II DHFR produced by bacteria as a resistance mechanism to the increased clinical use of the antibacterial drug trimethoprim. Type II DHFRs are not homologous in either sequence or structure with chromosomal DHFRs. The type II enzymes contain four identical subunits which form a homotetramer containing a single active site pore accessible from either end. Although the crystal structure of the complex of R67 DHFR with folate has been reported [Narayana et al. (1995) Nat. Struct. Biol. 2, 1018], the nature of the ternary complex which must form with substrate and cofactor is unclear. We have performed transferred NOE and interligand NOE (ILOE) studies to analyze the ternary complexes formed from NADP(+) and folate in order to probe the structure of the ternary complex. Consistent with previous studies of the binary complex formed from another type II DHFR, the ribonicotinamide bond of NADP(+) was found to adopt a syn conformation, while the adenosine moiety adopts an anti conformation. Large ILOE peaks connecting NADP(+) H4 and H5 with folate H9 protons are observed, while the absence of a large ILOE connecting NADP(+) H4 and H5 with folate H7 indicates that the relative orientation of the two ligands differs significantly from the orientation in the chromosomal enzyme. To obtain more detailed insight, we prepared and studied the folate analogue 2-deamino-2-methyl-5,8-dideazafolate (DMDDF) which contains additional protons in order to provide additional NOEs. For this analogue, the exchange characteristics of the corresponding ternary complex were considerably poorer, and it was necessary to utilize higher enzyme concentrations and higher temperature in order to obtain ILOE information. The results support a structure in which the NADP(+) and folate/DMDDF molecules extend in opposite directions parallel to the long axis of the pore, with the nicotinamide and pterin ring systems approximately stacked at the center. Such a structure leads to a ternary complex which is in many respects similar to the gas-phase theoretical calculations of the dihydrofolate-NADPH transition state by Andres et al. [(1996) Bioorg. Chem. 24, 10-18]. Analogous NMR studies performed on folate, DMDDF, and R67 DHFR indicate formation of a ternary complex in which two symmetry-related binding sites are occupied by folate and DMDDF.

Binding Sites↗

PubMed2001

Hyperosmolarity reduces GLUT4 endocytosis and increases its exocytosis from a VAMP2-independent pool in l6 muscle cells.

The intracellular traffic of the glucose transporter 4 (GLUT4) in muscle cells remains largely unexplored. Here we make use of L6 myoblasts stably expressing GLUT4 with an exofacially directed Myc-tag (GLUT4myc) to determine the exocytic and endocytic rates of the transporter. Insulin caused a rapid (t(12) = 4 min) gain, whereas hyperosmolarity (0.45 m sucrose) caused a slow (t(12) = 20 min) gain in surface GLUT4myc molecules. With prior insulin stimulation followed by addition of hypertonic sucrose, the increase in surface GLUT4myc was partly additive. Unlike the effect of insulin, the GLUT4myc gain caused by hyperosmolarity was insensitive to wortmannin or to tetanus toxin cleavage of VAMP2 and VAMP3. Disappearance of GLUT4myc from the cell surface was rapid (t(12) = 1.5 min). Insulin had no effect on the initial rate of GLUT4myc internalization. In contrast, hyperosmolarity almost completely abolished GLUT4myc internalization. Surface GLUT4myc accumulation in response to hyperosmolarity was only partially blocked by inhibition of tyrosine kinases with erbstatin analog (erbstatin A) and genistein. However, neither inhibitor interfered with the ability of hyperosmolarity to block GLUT4myc internalization. We propose that hyperosmolarity increases surface GLUT4myc by preventing GLUT4 endocytosis and stimulating its exocytosis via a pathway independent of phosphatidylinositol 3-kinase activity and of VAMP2 or VAMP3. A tetanus toxin-insensitive v-SNARE such as TI-VAMP detected in these cells, might mediate membrane fusion of the hyperosmolarity-sensitive pool.

Androstadienes↗

PubMed2001

Prediction of electrophoretic mobilities. 4. Multiply charged aromatic carboxylates in capillary zone electrophoresis.

The electrophoretic mobilites of aromatic carboxylates and sulfonates at zero ionic strength were correlated with models incorporating both hydrodynamic and dielectric friction. The hydrodynamic friction was predicted using either the Hückel spherical ion model or the Perrin ellipsoidal model. Dielectric friction is the charge-induced drag caused by the reorientation of the solvent dipoles in response to the analyte charge. Based on the Hubbard-Onsager and Zwanzig expressions, the dielectric friction is related to z2/V. Expressions incorporating both the hydrodynamic and dielectric frictional terms successfully predicted infinite-dilution mobilities to within 4.4%. The influence of dielectric friction ranged from 3-8% of the overall drag for singly charged analytes to 39% of the total frictional drag for 1,2,4,5-benzenetetracarboxylate.

Journal Article↗

PubMed2001

Pharmacophore analysis of the nuclear oxysterol receptor LXRalpha.

A cell-free assay was developed for the orphan nuclear receptor LXRalpha that measures the ligand-dependent recruitment of a peptide from the steroid receptor coactivator 1 (SRC1) to the nuclear receptor. Using this ligand-sensing assay (LiSA), the structural requirements for activation of the receptor by oxysterols and related compounds were studied. The minimal pharmacophore for receptor activation was shown to be a sterol with a hydrogen bond acceptor at C24. 24(S),25-Epoxycholesterol (1), which meets this criterion, is among the most efficacious of the oxysterols and is an attractive candidate as the LXRalpha natural hormone. Cholenic acid dimethylamide (14) showed increased efficacy compared to 1, whereas the unnatural oxysterol 22(S)-hydroxycholesterol (4) was shown to be an antagonist of 1 in the LiSA. The structural requirements for SRC1 recruitment in the LiSA correlated with the transcriptional activity of compounds in a cell-based reporter assay employing LXRalpha-GAL4 chimeric receptors. Site-directed mutagenesis identified Trp(443) as an amino acid critical for activation of LXRalpha by oxysterol ligands. This information was combined with the structure-activity relationship developed from the LiSA to develop a 3D homology model of LXRalpha. This model may aid the design of synthetic drugs targeted at this transcriptional regulator of cholesterol homeostasis.

Amino Acid Sequence↗

PubMed2001

Interaction of phospholipase D1 with a casein-kinase-2-like serine kinase.

Phospholipase D (PLD)1 was phosphorylated in vivo and by an associated kinase in vitro following immunoprecipitation. Both phosphorylation events were greatly reduced in a catalytically inactive point mutant in which the serine residue at position 911 was converted into alanine (S911A). The kinase could be enriched from detergent-extracted brain membranes and bind and phosphorylate PLD1 that was immunoprecipitated from COS-7 cells. Using in-gel kinase assays we determined that the size of the kinase is approximately 40 kDa and that PLD1 is more effective than S911A in binding the kinase. Preliminary analysis of the phosphorylation sites on PLD1 suggested that the kinase belongs to the casein kinase 2 (CK2) family. Consistent with this, we found that the kinase could utilize GTP, and could be inhibited by heparin and 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB). Membrane fractions from Chinese hamster ovary (CHO) cell lines that inducibly express PLD1 contained an endogenous kinase activity that phosphorylated PLD1 using GTP and was inhibited by DRB. Direct evidence that the kinase is CK2 came from observations that immunoprecipitates using PLD1 antibodies contained immunoreactive CK2alpha, and immunoprecipitates using CK2alpha antibodies contained immunoreactive PLD1. Co-expression of PLD1 in COS-7 cells with the two recombinant CK2 subunits, alpha or beta, suggests that the association of PLD1 with the kinase is through the beta subunit. Supporting this, phosphorylation of PLD1 by purified recombinant CK2alpha was enhanced by purified recombinant CK2beta. Assays measuring PLD1 catalytic activity following phosphorylation by CK2 suggest that this phosphorylation event does not influence PLD1-mediated hydrolysis of phosphatidylcholine in vitro.

Animals↗

PubMed2001

The role of Glu39 in MnII binding and oxidation by manganese peroxidase from Phanerochaete chrysoporium.

Manganese peroxidase (MnP) is a heme-containing enzyme produced by white-rot fungi and is part of the extracellular lignin degrading system in these organisms. MnP is unique among Mn binding enzymes in its ability to bind and oxidize Mn(II) and efficiently release Mn(III). Initial site-directed mutagenesis studies identified the residues E35, E39, and D179 as the Mn binding ligands. However, an E39D variant was recently reported to display wild-type Mn binding and rate of oxidation, calling into question the role of E39 as an Mn ligand. To investigate this hypothesis, we performed computer modeling studies which indicated metal-ligand bond distances in the E39D variant and in an E35D--E39D--D179E triple variant which might allow Mn binding and oxidation. To test the model, we reconstructed the E35D and E39D variants used in the previous study, as well as an E39A single variant and the E35D--E39D--D179E triple variant of MnP isozyme 1 from Phanerochaete chrysosporium. We find that all of the variant proteins are impaired for Mn(II) binding (K(m) increases 20--30-fold) and Mn(II) oxidation (k(cat) decreases 50--400-fold) in both the steady state and the transient state. In particular, mutation of the E39 residue in MnP decreases both Mn binding and oxidation. The catalytic efficiency of the E39A variants decreased approximately 10(4)-fold, while that of the E39D variant decreased approximately 10(3)-fold. Contrary to initial modeling results, the triple variant performed only as well as any of the single Mn ligand variants. Interestingly, the catalytic efficiency of the triple variant decreased only 10(4)-fold, which is approximately 10(2)-fold better than that reported for the E35Q--D179N double variant. These combined studies indicate that precise geometry of the Mn ligands within the Mn binding site of MnP is essential for the efficient binding, oxidation, and release of Mn by this enzyme. The results clearly indicate that E39 is a Mn ligand and that mutation of this ligand decreases both Mn binding and the rate of Mn oxidation.

Amino Acid Substitution↗

PubMed2001

Sensitivity to DNA damage induced by benzo(a)pyrene diol epoxide and risk of lung cancer: a case-control analysis.

Levels of DNA adducts vary greatly in vivo, attributable to individual differences in enzymatic bioactivation of benzo(a)pyrene. We developed an assay to measure the levels of DNA adducts induced in vitro by benzo(a)pyrene diol epoxide (BPDE), a bioactivated form of benzo(a)pyrene. In this large molecular epidemiological study of lung cancer, we tested the hypothesis that the level of in vitro BPDE-induced adducts is associated with risk of lung cancer. This hospital-based case-control study included 221 newly diagnosed lung cancer cases and 229 healthy controls frequency matched on age, sex, ethnicity, and smoking status. Short-term cultured peripheral blood lymphocytes from each subject were exposed in vitro to BPDE (4 microm) for 5 h, and the 32P-postlabeling method was then used to measure BPDE-induced DNA adducts in the host cells. Overall, the patients had significantly higher levels of BPDE-DNA adducts than did the controls (mean +/- SD per 107 nucleotides, 93.2+/-89.3 for cases versus 63.7+/-61.1 for controls; P = 0.001). Univariate and multivariate logistic regression analyses were performed to calculate the crude and adjusted odds ratios and their 95% confidence intervals. When the median adduct level of controls (46/10(7) nucleotides) was used as the cutoff point, 64% of cases had higher levels (odds ratio, 2.15; 95% confidence interval, 1.39-3.33, adjusted for age, sex, ethnicity, body mass index, recent weight loss, pack-years smoked, smoking in the last 24 h, and family history of cancer). Stratified analyses showed consistently higher levels of BPDE-induced adducts in cases than in controls, regardless of subgroup of age, sex, ethnicity, body mass index, recent weight loss, pack-years smoked, smoking in the last 24 h, and family history of cancer. A significant dose-response relationship between the quartile levels of BPDE-induced DNA adducts and the risk of lung cancer was observed (trend test, P < 0.001). The significant association between the level of in vitro BPDE-induced DNA adducts and risk for lung cancer suggests that subjects very sensitive to BPDE-induced DNA damage may have a suboptimal ability to remove the BPDE-DNA adducts and so are susceptible to tobacco carcinogen exposure and, therefore, may be at increased risk of lung cancer.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗

PubMed2001

Heterologous expression of athermostable manganese peroxidase from Dichomitus squalens in Phanerochaete chrysosporium.

Dichomitus squalens belongs to a group of white-rot fungi which express manganese peroxidase (MnP) and laccase but do not express lignin peroxidase (LiP). To facilitate structure/function studies of MnP from D. squalens, we heterologously expressed the enzyme in the well-studied basidiomycete, Phanerochaete chrysosporium. The glyceraldehyde-3-phosphate-dehydrogenase (gpd) promoter of P. chrysosporium was fused to the coding region of the mnp2 gene of D. squalens, 5 bp upstream of the translation start site, and placed in a vector containing the ural gene as a selectable marker. Purified recombinant protein (rDsMnP) was similar in kinetic and spectral characteristics to both the wild-type MnPs from D. squalens and P. chrysosporium (PcMnP). The N-terminal amino acid sequence of the rDsMnP was determined and was identical to the predicted sequence. Cleavage of the propeptide followed a conserved amino acid motif (A-A-P-S/T) in both rDsMnP and PcMnP. However, the protein from D. squalens was considerably more thermostable than its P. chrysosporium homolog with half-lives 15- to 40-fold longer at 55 degrees C. As previously demonstrated for PcMnP, addition of exogenous MnII and CdII conferred additional thermal stability to rDsMnP. However, unlike PcMnP, ZnII also confers some additional thermal stability to rDsMnP at 55 degrees C. Some differences in the metal-specific effects on thermal stability of rDsMnP at 65 degrees C were noted.

Amino Acid Motifs↗

PubMed2001

Epinephrine upregulates superoxide dismutase in human coronary artery endothelial cells.

Regular exercise resulting in release of catecholamines is an oxidant stress, and yet it protects humans from acute cardiac events. We designed this study to examine the effect of epinephrine on free radical release and endogenous superoxide dismutase (SOD) gene and protein expression in human coronary artery endothelial cells (HCAECs). HCAECs were incubated with epinephrine (10(-9) to 10(-5) M) alone or with the water-soluble analog of vitamin E (trolox) (10(-5) M), the lipid-soluble vitamin E (5 x 10(-5) M), or the beta(1)-adrenergic blocker atenolol (10(-5) M). At 1 and 24 h of incubation with epinephrine, superoxide anion generation increased by 102 and 81% in the HCAECs. There was a marked increase in both MnSOD and Cu/ZnSOD mRNA and protein, as determined by RT-PCR and Western Analysis, respectively. Both MnSOD and Cu/ZnSOD activities were also increased. Pretreatment of HCAECs with trolox and vitamin E decreased superoxide anion generation (p <.05 vs. epinephrine alone) and blocked the subsequent upregulation of SOD mRNA and protein. Treatment of cells with the beta-blocker atenolol also blocked the upregulation of SOD (p <.05 vs. epinephrine alone). These observations suggest that epinephrine via beta(1)-adrenoceptor activation causes superoxide anion generation, and the superoxide subsequently upregulates the endogenous antioxidant species SOD. These observations may be the basis of long-term benefits of exercise.

Adrenergic beta-Antagonists↗