Biomedical subjects

Hong-Yu Zhang

Publications and source records attributed to Hong-Yu Zhang.

At least 37 records · Page 2Linked to original sources

PubMed2005

Beta-lactam antibiotics are multipotent agents to combat neurological diseases.

Recently, Rothstein et al. reported that beta-lactam antibiotics, including penicillin and ceftriaxone, are potential therapeutic drugs to treat some neurological disorders, e.g., amyotrophic lateral sclerosis (ALS), by modulating the expression of glutamate transporter GLT1 via gene activation. However, considering the facts that: (i) many neurological diseases (including ALS) are associated with transition metal ions and redox stress, and ALS can be efficiently prevented by metal chelators, e.g., diethyl-dithiocarbamate (DDC); (ii) beta-lactam antibiotics have long been known as metal chelators, we argue that the beneficial effect of beta-lactam antibiotics on ALS likely involves Cu(II)-attenuating ability. This is partially supported by our theoretical calculations.

Anti-Bacterial Agents↗

PubMed2005

A theoretical study on the structure-activity relationships of metabolites of folates as antioxidants and its implications for rational design of antioxidants.

To elucidate the structure-activity relationships of metabolites of folates as antioxidants, the O-H bond dissociation enthalpies (BDEs) and ionization potentials (IPs) for these compounds were calculated by density functional theory (DFT) on B3LYP/6-31+G(,3pd) level. Accordingly, the antioxidant activity difference for metabolites of folates can be elucidated by O-H BDE and IP values and can be further explained in terms of electronic effect and intramolecular hydrogen bond effect of substituents. Furthermore, the potential of the active center of metabolites of folates, 4-hydroxypyrimidine (4-HP), as lead antioxidant, was evaluated by comparing the BDEs and IPs of 4-HP with those of 5-hydroxypyrimidine (5-HP). It was revealed that 4-HP and 5-HP held identical IPs, but the O-H BDE of the former was 22.84 kcal/mol higher than that of the latter, which meant 4-HP was inert in H-atom donation. Nevertheless, the O-H BDE of 4-HP was very sensitive to the substituents, which made NH2-derivatives of 4-HP very active as antioxidants. Therefore, 4-HP is also a potential lead antioxidant and deserves attention in rational design of antioxidants.

Antioxidants↗

PubMed2005

Radical scavenging potential of phenolic compounds encountered in O. europaea products as indicated by calculation of bond dissociation enthalpy and ionization potential values.

The radical scavenging potential of phenolic compounds occurring in Olea europaea and of recently identified hydroxytyrosol metabolites was evaluated by means of quantum chemical calculations. The bond dissociation enthalpy (BDE) of phenolic hydroxyl groups and the ionization potential (IP) were calculated as descriptors to predict the H-atom-donating and electron-donating abilities of antioxidants, respectively. Catechol derivatives had the lowest BDE values (77.7-80.1 kcal/mol) whereas the lignans, pinoresinol and 1-acetoxypinoresinol, and other monophenols had much higher BDE values (85.1-88.0 kcal/mol), which suggested a lower potential for radical scavenging. Side chain characteristics were not found to affect the size of BDE values although differences in lipophilicity (on the basis of calculated Log P values) indicate variability in the activity in real systems. Conclusions for the antioxidant potential could not be drawn based on the IP values. Lack of experimental data for most of the studied compounds due to oxidative instability and difficulties in synthesis or isolation supports the usefulness of a computational approach for those interested in the antioxidant potential of phenolics encountered in O. europaea products.

Chemical Phenomena↗

PubMed2005

Successful application of TD-DFT in transient absorption spectra assignment.

[Reaction: see text] Despite the wide application of time-resolved spectra technology in investigating various chemical and biological processes, it is still a great challenge to give an unambiguous spectra assignment for observed transient species, e.g., the curcumin-derived radicals. Here we report that time-dependent density functional theory with the B3LYP functional and an appropriate basis set can give reliable absorption spectra for carbon- and oxygen-centered radicals derived from curcumin, which indicates the potential of theoretical methods in helping assign transient spectra.

Acetonitriles↗

PubMed2005

A new strategy to combat Alzheimer's disease. Combining radical-scavenging potential with metal-protein-attenuating ability in one molecule.

Oxidative stress and excessive redox metals have been implicated in the pathogenesis of Alzheimer's disease (AD), which leads to the tentative employment of radical scavengers and metal chelators in clinical therapy of AD. The preliminary successes of both therapy strategies inspire us to propose that better clinical effects can be expected for a compound combining radical-scavenging potential with metal-protein-attenuating ability. Based on theoretical investigation, we indicate that two novel metal chelators (1-(benzimidazole-2-ylmethyl)-1,4,7-triazacyclononane and 1,4-bis(benzimidazole-2-ylmethyl)-1,4,7-triazacyclonone), especially the latter, are promising to fulfill this new strategy.

Alzheimer Disease↗

PubMed2005

A theoretical study of the different radical-scavenging activities of catechin, quercetin, and a rationally designed planar catechin.

To improve the radical-scavenging activity of catechin, a planar catechin analogue was designed and synthesized by Fukuhara [J. Am. Chem. Soc. 124 (2002) 5952]. Although the planar catechin is less active than quercetin, it is much more active than catechin in its ability to scavenge galvinoxyl radical, suggesting that the rational design was successful. However, an interesting question remains: what is the basis for the enhanced radical-scavenging activity of the planar catechin? By DFT calculations, we determined that the galvinoxyl radical is scavenged through an electron-transfer mechanism rather than a hydrogen-atom-transfer mechanism. Moreover, the antioxidant anion, derived from proton dissociation, plays a key role in the radical-scavenging process. Hence, the different radical-scavenging activities of the three antioxidants may result from the different ionization potentials of their anions.

Antioxidants↗

PubMed2005

Solvent effects are important in elucidating radical-scavenging mechanisms of antioxidants. A case study on genistein.

In two recent researches on antioxidant mechanisms of flavonoids and isoflavonoids, quantum chemical method was employed to calculate the proton dissociation energies, the bond dissociation energies and the ionization potentials for the phenols and derived radicals to help determine the radical-scavenging mechanisms. As the solvent effect was left out of consideration, the conclusion drawn from the calculation incurred some controversies. In the current study, we re-calculated the parameters for genistein and its anion by employing a B3LYP/6-311+G(d,p)//6-31G(d,p) method with solvent effect. Accordingly, a more reasonable explanation on the experimentally observed behavior of genistein as a radical scavenger was obtained. Therefore, solvent effect should be considered in the investigation of radical-scavenging mechanisms of antioxidants in polar solvents.

Anions↗

PubMed2005

The role of electrostatic interaction in triggering the unraveling of stable helix 1 in normal prion protein. A molecular dynamics simulation investigation.

The conversion of normal prion protein (PrPC) into scrapie isoform (PrPSc) is a key event in the pathogenesis of prion diseases. However, the conversion mechanism has given rise to much controversy. For instance, there is much debate on the behavior of helix 1 (H1) in the conversion. A series of experiments demonstrated that H1 in isolated state was very stable under a variety of conditions. But, other experiments indicated that helices 2 and 3 rather than H1 were retained in PrPSc. In this paper, molecular dynamics (MD) simulation is employed to investigate the dynamic behavior of H1. It is revealed that although the helix 1 of Human PrPC (HuPrPC) is very stable in the isolated state, it becomes unstable when incorporated into native HuPrPC, which likely results from the long-range electrostatic interaction between Asp147 and Arg208 located in the helices 1 and 3, respectively. This explanation is supported by experimental evaluation and MD simulation on D147N mutant of HuPrPC that the mutant becomes a little more stable than the wild type HuPrPC. This finding not only help to reconcile the existing debate on the role of helix 1 in the PrPC-->PrPSc transition, but also reveals a possible mechanism for triggering the PrPC-->PrPSc conversion.

Aspartic Acid↗

PubMed2005

The discovery,genetic analysis and gene mapping of earliness rice (Oryza sativa L.) D64B.

D64B, an achromatic early mutation, was discovered from indica rice preserver line D63B. D64B were crossed with inhomogeneous sterile lines, preserver lines and restorer lines, most of their F1 shared the same heading dates as D64B. The results indicated that D64B possessed the characteristic of dominant earliness. To analyze the earliness trait, positive and negative crosses F2 and BC1 from the cross of D64B and Shuhui 527 were cultivated. Their heading dates showed double apices distributing with same apex values. According to apex vale value -103 d, plants of the F2 and BC1 were separated into early plants and late plants, which were tested with Chi2 value. The results suggested that the segregation ratio of number of early to late plant fitted to 3:1 and 1:1 for positive and negative cross F2 and BC1, respectively, and that the earliness of D64B was controlled by a single dominant major gene. To map the gene, the polymorphisms between D64B and Shuhui 527 was analyzed with reported 356 SSR primers and 59 primers showed polymorphisms. The earliness-lateness near isogenic pools, early plants and late plants from F2 of Shuhui 527 x D64B were further amplified with the 59 primers. The results indicated that there were polymorphisms on both RM279 and RM71. Their results being analyzed with MAPMAKER/EXP3.0 software, the dominant major gene was located on the top arm of rice chromosome 2 and between the two SSR markers, RM279 and RM71, with genetic distance of 12.6 cM and 13.3 cM, respectively. According to reported data, the gene was first discovered and tentatively named as Ef-3(t). In breeding practice, sterile line D64A had been bred with D64B.

Chromosome Mapping↗

PubMed2005

[Comparison between R-CHOP regimen and CHOP regimen in treating naive diffuse large B-cell lymphoma in China--a multi-center randomized trail].

BACKGROUND & OBJECTIVE: CHOP regimen is a standard treatment for patients with diffuse large B-cell non-Hodgkin's lymphoma (NHL), and its 5-year overall survival (OS) rate is 30%-40%. Rituximab is a chimeric monoclonal antibody (MoAb) directly against CD20-positive B cells, and has good effect on diffuse large B-cell NHL. Rituximab combined with standard chemotherapy has been approved for treating aggressive B-cell NHL in Europe and the US. This study was to determine efficacy and safety of the combination of Rituximab and CHOP regimen in treating Chinese patients with CD20-positive diffuse large B-cell NHL. METHODS: From Sep. 2003 to Nov. 2004, a total of 63 patients in 9 centers were enrolled. All the patients were randomized into 2 groups: 32 received CHOP regimen alone (CHOP group), and 31 received Rituximab and CHOP regimen (R-CHOP group). All patients signed informed consent. The complete response rates, overall response rates, and side events of the 2 groups were compared. RESULTS: The complete response rates were similar in R-CHOP and CHOP groups (41.9% vs. 37.5%, P=0.719); the overall response rates were slightly higher in R-CHOP group than in CHOP group (83.8% vs. 65.6%, P=0.096). Disease progression during treatment was reported for 7 (21.9%) patients in CHOP group and 1 (3.2%) patient in R-CHOP group (P=0.026). The occurrence rates of adverse events were similar in R-CHOP and CHOP groups (65.6% vs. 67.7%, P=0.859). The most common adverse event was leukopenia; fever and chills were rather common in R-CHOP group. Clinically relevant toxicity was similar in both groups. CONCLUSION: When compared with standard CHOP alone, the addition of Rituximab to standard CHOP regimen reduces the risk of treatment failure in patients with diffuse large B-cell NHL, and doesn't increase the occurrence of chemotherapy-related adverse events.

Adolescent↗

PubMed2004

Methylation profile of the promoter CpG islands of 14 "drug-resistance" genes in hepatocellular carcinoma.

AIM: To establish the DNA methylation patterns of the promoter CpG islands of 14 "drug-resistance" genes in hepatocellular carcinoma (HCC). METHODS: The methylation specific polymerase chain reaction in conjunction with sequencing verification was used to establish the methylation patterns of the 14 genes in the liver tissues of four healthy liver donors, as well as tumor and the paired non-cancerous tissues of 30 HCC patients. RESULTS: While 11 genes (ATP-binding cassette, sub-family G (WHITE), member 2(ABCG2), activating transcription factor (ATF2), beta-2-microglobulin (B2M), deoxycytidine kinase (DCK), occludin (OCLN), v-raf-1 murine leukemia viral oncogene homolog (RAF1), ralA binding protein 1 (RALBP1), splicing factor (45 kD) (SPF45), S-phase kinase-associated protein 2 (p45) (SKP2), tumor protein p53 (Li-Fraumeni syndrome) (TP53) and topoisomerase (DNA) II beta (TOP2B)) maintained the unmethylated patterns, three genes displayed to various extents the hypermethylation state in tumor tissues in comparison with the normal counterparts. The catalase (CAT) was hypermethylated in tumor and the neighboring non-cancerous tissue of one case (3.3%). Both glutathione S-transferase pi (GSTpi) (80%, 24/30 in tumor and 56.7%, 17/30 in the paired non-cancerous tissues) and cystic fibrosis transmembrane conductance regulator, ATP-binding cassette (sub-family C, member 7) (CFTR) (77%, 23/30 in tumor and 50%, 15/30 in the paired non-cancerous tissues) genes were prevalently hypermethylated in HCC as well as their neighboring non-cancerous tissues. No significant difference in the hypermethylation occurrence was observed between the HCC and its neighboring non-cancerous tissues. CONCLUSION: Hypermethylation of promoter CpG islands of both CFTR and GSTpi genes occurs prevalently in HCC, which may correlate with the low expression of these two genes at the mRNA level and has the profound etiological and clinical implications. It is likely to be specific to the early phase of HCC carcinogenesis.

Acyltransferases↗

PubMed2004

Methylation profile of the promoter CpG islands of 31 genes that may contribute to colorectal carcinogenesis.

AIM: To establish the methylation profile of the promoter CpG islands of 31 genes that might play etiological roles in colon carcinogenesis. METHODS: The methylation specific PCR in conjunction of sequencing verification was used to establish the methylation-profile of the promoter CpG islands of 31 genes in colorectal cancer (n = 65), the neighboring non-cancerous tissues (n = 5), colorectal adenoma (n = 8), and normal mucosa (n = 1). Immunohistochemically, expression of 10 genes was assessed on the home-made tissue microarrays of tissues from 58 patients. The correlation of tumor specific changes with each of clinical-pathologic features was scrutinized with relevant statistic tools. RESULTS: In comparison with the normal mucosa of the non-cancer patients, the following 14 genes displayed no tumor associated changes: breast cancer 1, early onset (BRCA1), cadherin 1, type 1, E-cadherin (epithelial) (CDH1), death-associated protein kinase 1 (DAPK1), DNA (cytosine-5-)-methyltransferase 1 (DNMT1), melanoma antigen, family A, 1 (directs expression of antigen MZ2-E) (MAGEA1), tumor suppressor candidate 3 (N33), cyclin-dependent kinase inhibitor 1A (p21, Cip1) (p21(WAF1)), cyclin-dependent kinase inhibitor 1B (p27, Kip1) (p27(KIP1)), phosphatase and tensin homolog (mutated in multiple advanced cancers 1) (PTEN), retinoic acid receptor, beta (RAR- , Ras association (RalGDS/AF-6) domain family 1 C (RASSF1C), secreted frizzled-related protein 1 (SFRP1), tissue inhibitor of metalloproteinase 3 (Sorsby fundus dystrophy, pseudoinflammatory) (TIMP3), and von Hippel-Lindau syndrome (VHL). The rest 17 targets exhibited to various extents the tumor associated changes. As changes in methylation of the following genes occurred marginally, their impact on the formation of colorectal cancer were trivial: adenomatous polyposis coli (APC) (8%, 5/65), Ras association (RalGDS/AF-6) domain family 1A (RASSF1A) (3%, 2/65) and cyclin-dependent kinase inhibitor 2A, alternated reading frame (p14(ARF)) (6%, 4/65). The following genes exhibited moderate changes in methylation: O-6-methylguanine-DNA methyltransferase (MGMT) (20%, 13/65), mutL homolog 1, colon cancer, nonpolyposis type 2 (E. coli) (hMLH1) (18%, 12/65), cyclin-dependent kinase inhibitor 2A (melanoma, p16, inhibits CDK4) (p16(INK4a)) (10%, 10/65), methylated in tumor 1 (MINT1) (15%, 10/65), methylated in tumor 31 (MINT31) (11%, 7/65). The rest changed greatly in the methylation pattern in colorectal cancer (CRC): cyclin A1 (cyclin a1) (100%, 65/65), caudal type homeobox transcription factor 1 (CDX1) (100%, 65/65), RAR- (85%, 55/65), myogenic factor 3 (MYOD1) (69%, 45/65), cyclin-dependent kinase inhibitor 2B (p15, inhibits CDK4) (p15(INK4b)) (68%, 44/65), prostaglandin-endoperoxide synthase 2 (prostaglandin G/H synthase and cyclooxygenase) (COX2) (72%, 47/65), cadherin 13, H-cadherin (heart) (CDH13) (65%, 42/65), CAAX box 1 (CXX1) (58%, 38/65), tumor protein p73 (p73) (63%, 41/65) and Wilms tumor 1 (WT1) (58%, 38/65). However, no significant correlation of changes in methylation with any given clinical-pathological features was detected. Furthermore, the frequent changes in methylation appeared to be an early phase event of colon carcinogenesis. The in situ expression of 10 genes was assessed by the immunohistochemical approach at the protein level: CDH1, CDH13, COX2, cyclin A1, hMLH1, MGMT, p14(ARF), p73, RAR- , and TIMP3 genes in the context of the methylation status in colorectal cancer. No clear correlation between the hypermethylation of the promoter CpG islands and the negative expression of the genes was established. CONCLUSION: The methylation profile of 31 genes was established in patients with colon cancer and colorectal adenomas, which provides new insights into the DNA methylation mediated mechanisms underlying the carcinogenesis of colorectal cancer and may be of prognostic values for colorectal cancer.

ADP-Ribosylation Factor 6↗

PubMed2004

Estimation of scavenging activity of phenolic compounds using the ABTS(*+) assay.

Observations on the applicability of the ABTS(*+) assay to define structure-activity relationships (SARs) among phenols (AH) were based on experimental data and theoretical calculations. All AH examined (hydroxycinnamic derivatives, simple polyphenols, polyhydroxybenzoates, and flavonoids) were found to be active toward ABTS(*+). Moreover, known weak radical scavengers (i.e., coumaric and isoferulic acids) were found to be efficient or comparatively active to caffeic or rosmarinic acids in contradiction to the AH classification based on 1,1-diphenyl-2-picrylhydrazyl (DPPH) data or the bond dissociation enthalpy values. This behavior was observed both in ethanol and in buffered (pH 7.4) environment. Resorcinol and phloroglucin were found to be more active than catechol and hydroquinone, whereas, among polyhydroxybenzoates, 2,4-dihydroxybenzoic acid was the least active, in line with the DPPH and theoretical data. Therefore, it can be argued that the ABTS(*+) assay may give an indication for the presence of antioxidants in a certain system but SARs cannot be readily inferred.

Benzothiazoles↗

PubMed2004

Serum level of TSGF, CA242 and CA19-9 in pancreatic cancer.

AIM: To establish a method to detect the expression of the tumor specific growth factor TSGF, CA242 and CA19-9 in serum and evaluate their value in diagnosis of pancreatic cancer. METHODS: ELISA and Biochemical colorimetric assay were used to detect the serum content of TSGF, CA242 and CA19-9 in 200 normal cases, 52 pancreatitis patients and 96 pancreatic cancer patients. RESULTS: The positive likelihood ratios of TSGF, CA242 and CA19-9 were 5.4, 12.6 and 6.3, respectively, and their negative likelihood ratios were 0.10, 0.19 and 0.17, respectively. With single tumor marker diagnosed pancreatic cancer, the highest sensitivity and specificity of TSGF were 91.6% and 93.5%. In combined test with 3 markers, when all of them were positive, the sensitivity changed to 77.0% and the specificity and the positive predictive value were 100%. The levels of TSGF and CA242 were significantly higher in the patients with pancreatic cancer of head than those in the patients with pancreatic cancer of body, tail and whole pancreas, but the expression of CA19-9 had no correlation with the positions of the pancreatic cancer. The sensitivity of TSGF, CA242 and CA19-9 was increased with the progress in stages of pancreatic cancer. In stage I, the sensitivity of TSGF was markedly higher than CA242 and CA19-9. CONCLUSION: The combined use of TSGF, CA242 and CA19-9 expressions can elevate the specificity for pancreatic cancer diagnosis. And it shows that it plays an important role to differentiate positions and tissue typing. It is a forepart diagnosis for the pancreatic cancer by combination checking. There is very important correlation between the three markers and the pancreatic cancer.

Adult↗

PubMed2004

Unexpected role of 5-OH in DPPH radical-scavenging activity of 4-thiaflavans. Revealed by theoretical calculations.

The O-H bond dissociation enthalpies (BDEs) of 4-thiaflavans were calculated by a combined density functional theory method (RO)B3LYP/6-311 + G(2d,2p)//AM1/AM1. The calculated BDEs not only gave a reasonable explanation on the DPPH radical-scavenging activity difference of 4-thiaflavans, but also revealed the unexpected role of 5-OH in enhancing the antioxidant activity of A-ring.

Antioxidants↗

PubMed2004

A theoretical study on Cu(II) binding modes and antioxidant activity of mammalian normal prion protein.

In this paper, the density functional theory (DFT) method B3LYP/LANL2DZ was used to calculate binding energies and electron affinities for various Cu(II) binding modes of mammalian normal prion protein (PrP(c)). The calculation results not only provide solid evidence to support one of the experimentally determined Cu(II) binding modes of PrP(c) but also shed new light on the normal function of the elusive protein; that is, PrP(c) is rather a Cu(II) transporter than an antioxidant. In addition, the employed theoretical methodology is also useful to investigate the metal chelating properties of other proteins and to rationally design Cu,Zn-superoxide dismutase mimics.

Antioxidants↗

PubMed2004

Antioxidative effect of schisanhenol on human low density lipoprotein and its quantum chemical calculation.

AIM: To investigate the effect of schisanhenol (Sal) on copper ion-induced oxidative modulation of human low density lipoprotein (LDL). METHODS: The antioxidative activity of eight schisandrins (DCL) on microsome lipid peroxidation induced by Vit C/NADPH system was first observed, and then, the effect of Sal on Cu2+-induced human LDL oxidation was studied. The generation of malondialdehyde (MDA), lipofuscin, reactive oxygen species (ROS), consumption of a-tocopherol as well as electrophoretic mobility of LDL were determined as criteria of LDL oxidation. Finally, the quantum chemical method was used to calculate the theoretical parameters of eight DCL for elucidating the difference of their antioxidant ability. RESULTS: Sal was shown to be the most active one among eight schizandrins in inhibiting microsome lipid oxidation induced by Vit C/NADPH. Sal 100, 50, and 10 micromol/L inhibited production of MDA, lipofuscin and ROS as well as the consumption of a-tocopherol in Cu2+-induced oxidation of human LDL in a dose-dependent manner. Sal also reduced electrophoretic mobility of the oxidized human LDL. Further study of quantum chemistry found that Sal was the strongest one among eight DCL to scavenge O2, R, RO and ROO radicals. CONCLUSION: Sal has antioxidative effect on human LDL oxidation. The mechanism of Sal against LDL oxidation may be through scavenging free radicals.

Animals↗

PubMed2004

Correlation between methylation profile of promoter cpg islands of seven metastasis-associated genes and their expression states in six cell lines of liver origin.

BACKGROUND & OBJECTIVE: DNA methylation has been regarded as an important epigenetic signature reflecting the transcription state of DNA in cells. This study was to assess the correlation between methylation state of promoter CpG islands of metastasis-associated genes and their expression in 6 liver cell lines, including 5 cancerous. METHODS: Methylation specific polymerase chain reaction method (MSP) and DNA sequencing verification were used to analyze the methylation state of promoter CpG islands of 7 genes (ASPH, ENO3, ITGA9, LRP6, MTHFD2, OXCT, and SRP72) in 5 liver cancer cell lines (BEL-7402, SMMC-7721, Hep3B, HepG2, and HCCLM3), and 1 immortalized liver cell line (L-02). Expression of 6 genes in this list was assessed by the semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method. RESULTS: The methylation state of genes was either unmethylated or heterozygously methylated in these 7 liver cell lines. Except for no expression of OXCT gene was detected by RT-PCR in both HepG2 and HCCLM3 cells where it was heterozygously methylated, there was expression of genes in all the remaining cases. CONCLUSION: Although expression state of genes in this study supported the general notion that hypermethylation state of promoter CpG islands of genes represents the silenced state of gene transcription, there were exceptions. Therefore, other mechanisms are likely to contribute to the observed expression state of these 7 genes in this study.

Calcium-Binding Proteins↗