Biomedical subjects

W Guan

Publications and source records attributed to W Guan.

At least 19 recordsLinked to original sources

PubMed2001

A novel phosphotyrosine mimetic 4'-carboxymethyloxy-3'-phosphonophenylalanine (Cpp): exploitation in the design of nonpeptide inhibitors of pp60(Src) SH2 domain.

The novel phosphotyrosine (pTyr) mimetic 4'-carboxymethyloxy-3'-phosphonophenylalanine (Cpp) has been designed and incorporated into a series of nonpeptide inhibitors of the SH2 domain of pp60(c-Src) (Src) tyrosine kinase. A 2.2 A X-ray crystal structure of 1a bound to a mutant form of Lck SH2 domain provides insight regarding the structure-activity relationships and supports the design concept of this new pTyr mimetic.

Animals↗

PubMed2001

The phase-shift mutation in the glucocorticoid receptor gene: potential etiologic significance of neuroendocrine mechanisms in lupus nephritis.

BACKGROUND: Glucocorticoid (GC), a mediator of the hypothalamo-pituitary-adrenal axis, has been found to play an important role in maintaining the stability of immune endo-environment of the body. The pathogenesis of lupus nephritis, an autoimmune disease, is thought to be related to the intrinsic hyposensitivity to GC secreted by adrenal gland, and impairs the regulation of the immuno-neuro-endocrine axis. METHODS: To test this hypothesis, we examined the response of 39 clinic patients with lupus nephritis to GC and analyzed the molecular structure and function of the GC receptor (GR) on peripheral blood mononuclear cells. RESULTS: There was no difference in the level of ACTH, GC and ligand affinity of GR between the patients and the controls. The GR number on mononuclear cells of lupus patients was lower than that of the controls. There was no difference in GR number between the patients with heterogeneous response, i.e. sensitive, dependent and resistance, to GC. The analysis of exon 9 of the GC receptor with PCR-amplified single strand conformation polymorphism (PCR-SSCP) method showed the polymorphism in exon 9 of GC receptor in 8 of the 39 lupus nephritis patients. DNA sequence analysis revealed an adenine insertion at the 2439 base pair of the GC receptor gene. This phase-shift mutation caused an additional 20 amino acids being translated into protein of GC receptor. CONCLUSION: The decreased number of GC receptor and the molecular variation of GR on mononuclear cells could explain the phenomenon of GC resistance, potentially to endogenous GC, which suggested an etiological significance of neuro-endocrine-immune mechanism in lupus nephritis. This may be useful in the design of lupus nephritis therapy.

Adolescent↗

PubMed2001

Bone-targeted Src SH2 inhibitors block Src cellular activity and osteoclast-mediated resorption.

Src, a nonreceptor tyrosine kinase, is an important regulator of osteoclast-mediated resorption. We have investigated whether compounds that bind to the Src SH2 domain inhibit Src activity in cells and decrease osteoclast-mediated resorption. Compounds were examined for binding to the Src SH2 domain in vitro using a fluorescence polarization binding assay. Experiments were carried out with compounds demonstrating in vitro binding activity (nmol/L range) to determine if they inhibit Src SH2 binding and Src function in cells, demonstrate blockade of Src signaling, and lack cellular toxicity. Cell-based assays included: (1) a mammalian two-hybrid assay; (2) morphological reversion and growth inhibition of cSrcY527F-transformed cells; and (3) inhibition of cortactin phosphorylation in csk-/- cells. The Src SH2 binding compounds inhibit Src activity in all three of these mechanism-based assays. The compounds described were synthesized to contain nonhydrolyzable phosphotyrosine mimics that bind to bone. These compounds were further tested and found to inhibit rabbit osteoclast-mediated resorption of dentine. These results indicate that compounds that bind to the Src SH2 domain can inhibit Src activity in cells and inhibit osteoclast-mediated resorption.

Actins↗

PubMed2001

Cross talk between prostacyclin and nitric oxide under shear in smooth muscle cell: role in monocyte adhesion.

We tested the hypothesis that at sites of vascular damage, vessel homeostasis is maintained through the cross talk of shear-induced production of prostacyclin and nitric oxide (NO) in vascular smooth muscle cells (VSMC). Confluent A7r5 cells derived from rat aortic VSMC and mesenteric VSMC were exposed to shear stress at 15 dyn/cm(2) for 90 min with the use of a cone-plate device, and productions of prostacyclin and NO were examined. Shear stress increased cumulative production of prostacyclin by 3- to 3.5-fold and that of NO by 6- to 7.5-fold. Western blot analysis showed that inducible NO synthase protein was expressed after shear stress in both types of VSMC. Inhibition of NO synthase enhanced the shear-induced production of prostacyclin from 40 to 60%. Shear-induced production of NO was suppressed by 70% after treatment with 10(-4) M of indomethacin. A7r5 cells adhesiveness for monocytes was suppressed by 50% after shear stress. This suppression was abolished by pretreatment with 10(-4) M of indomethacin, whereas inhibition of NO synthase only minimally inhibited it. We conclude that there is a cross talk of shear-induced production of prostacyclin and NO in VSMC. At sites of vascular damage, prostacyclin synthesis may prevent monocyte adhesiveness for VSMC through the concomitant enhancement of NO production.

Animals↗

PubMed2001

[The construction and evaluation of antisense RNA expression vector targeting at HCV 5'NCR].

Antisense RNA is an important field of antisense technique. In order to explore a novel approach for the treatment of hepatitis C virus (HCV) infection and prove the availability of transgenic cellular model HepG2. 9706, an antisense RNA was designed targeting at the highly conserved 5'NCR and translation initiation site of HCV RNA at nt positions 13-397. It was inserted into the downstream of SV40 promotor sequence of pGL3 control vector in which luciferase gene is deleted. The antisense RNA expression vector (pHCV-asR) was constructed and identified by PCR, endonucleases reaction and DNA sequencing. Its expression in transfected HepG2 cells was tested by RT-PCR. To evaluate the inhibitory activities of pHCV-asR, HepG2. 9706 cells were transfected using this construct via Lipofectin method. Luciferase activity in cell lysates was measured for quantitative determining antiviral effects within the cells. The results showed that the inserted sequence of the pHCV-asR is the same as the designed sequence and can express in HepG2 cells. It was also found that pHCV-asR in HepG2. 9706 has a dose-dependent inhibitory effects on luciferase expression controlled by HCV 5'NCR with a inhibitory rate of 57%.

5' Untranslated Regions↗

PubMed2001

[Inhibitory effects of phosphorothioate antisense oligonucleotides on gene expression controlled by HCV 5'NCR in nude mice xenograft].

OBJECTIVE: To evaluate the activity in vivo of 3 phosphorothioate antisense oligonucleotides, HCV363, HCV279 and HCV349 using nude mice xenograft models based on the establishment of HCV 5' NCR transgenic cellular model (HepG2.9706). METHODS: Female BALB/C nude mice, aged 4 to 6 weeks and weighing around 20g, were implanted s.c. with 100mul (106 cells) of the HepG2.9706 cells suspension in the lower-back region. In approximate 1 weeks, the animals were randomly grouped and intraperitoneally administrated the antisense drugs at 10 mg/kg body weight. RESULTS: HCV363, HCV279 and HCV349 had obvious sequence-specific inhibitory effects on luciferase expression controlled by HCV 5' NCR in xenograft cells with the inhibitory rates of 80.4%, 78.6% and 47.9%, respectively. The effects of three different concentrations (5, 10, 20 mg/kg body weight) of HCV363 indicated that HCV363 increased the inhibitory activities on luciferase expression following the concentration raise and its inhibitory rate was up to 82.7%. CONCLUSIONS: This study suggests that antisense oligonucleotides may provide a novel therapeutic approach to the treatment of HCV infection.

Animals↗

PubMed2001

[CAG microsatellite polymorphisms of androgen receptor gene and the stage and grade of prostate cancer].

OBJECTIVE: To explore the relationship between the CAG microsatellite in androgen receptor (AR) gene and the stage and grade of prostate cancer(PC). METHODS: The number of CAG repeats in exon 1 of the AR gene was measured in 37 PC tissues by PCR-SSCP analysis, and its association with stages and grades of PC determined. RESULTS: The average number of CAG repeats of AR gene differed significantly between PC in stage B (25.04 +/- 1.88) and in stage C-D (24.14 +/- 2.64) (P = 0.002). The frequency of short CAG(< 22) was 13.0% (3/23) in stage B and 28.6%(4/14) in stage C-D, while that of long CAG(> or = 22) was 87.0% (20/23) and 71.4% (10/14) (P = 0.029), respectively. The average number of CAG repeats increased with the decrease in tumor cell differentiation. The frequency of short CAG repeats dropped with the increase in tumor cell differentiation while the opposite was true for that of long CAG repeats. CONCLUSION: The number of CAG repeats in AR gene may be one of the factors determining the biologic characteristics PC. Short CAG repeats may signify aggressiveness of PC.

Aged↗

PubMed2001

[Alteration of Fas/FasL gene expression in oral squamous cell carcinoma cell line Tca83 by retinoid acid].

OBJECTIVE: To study the induction of apoptosis by retinoid acid(RA) in Tca83 cell line and the expression of correlative Fas/FasL gene. METHODS: Apoptosis of Tca83 was detected by TUNEL, the expression of Fas/FasL-mRNA was detected by RT-PCR and cell immunohistochemical technique. RESULTS: The cell apoptosis number of Tca83 in RA group was significantly higher than that in non-RA groupe on day 5(P < 0.05). The expression of Fas-mRNA in RA group was also much higher than that in non-RA group on day 5(P < 0.05), but the level of FasLmRNR had no change. Immunohistochemistry also showed, after RA treatment, the Fas stain was enhanced. CONCLUSION: The result suggests that apoptosis induced by RA may be resulted from the enhancement of Fas gene transcription and translation.

Antineoplastic Agents↗

PubMed2001

[The inhibitory effects of hepatocyte targeting pH-sensitive liposome mediated phosphorothioate antisense oligonucleotide on gene expression controlled by HCV 5'NCR].

Antisense oligodeoxynucleotide is a negative charged macromolecule and hence is difficult to penetrate cell membrane and liable to degradation. To increase the effective concentration of antisense drugs in the target cells, a hepatocyte-targeting liposome directed to asialoglycoprotein receptors exclusively expressing on the hepatocyte membrane was designed and prepared based on the receptor-mediated gene transfer. In order to accelerate endosomal exit of nucleic acid drugs, the liposomal formulation with pH-sensitive property was adopted. The hepatocyte-targeting and pH-sensitivity of liposome were analyzed by galactose-receptor competitive inhibition and hemolysis of chicken red blood cell. Antisense oligodeoxynucleotide, HCV363 against HCV 5'NCR, was delivered via prepared liposome to transgenic cell HepG2.9706 and evaluated for its inhibitory effect on luciferase expression controlled by HCV 5'NCR in HepG2.9706 using Luciferase Assay System The results showed that different concentrations (10, 20, 30 mmol/L) of galactose solutions reduce the delivery effects of liposome to some extend that were up to saturation when the concentrations of galactose solution exceed 20 mmol/L. Prepared liposomes mixed with chicken RBC are put into PBS buffers with different pH values(4.0-8.0), it was observed that the amount of heme is greatly released in acidic PBS (pH < 6) due to the fusion of liposome and RBC membranes. Liposome-mediated HCV363 has dose-dependent inhibitory activities on luciferase expression controlled by HCV 5'NCR in HepG2.9706 and the inhibitory rate is 86% at a concentration of 1.0 mumol/L. In conclusion, the liposome is proven to be a hepatocyte-targeting pH-sensitive delivery system that can increase the pharmaceutical effects of antisense drugs.

Carcinoma, Hepatocellular↗

PubMed2000

Structure-based design of an osteoclast-selective, nonpeptide src homology 2 inhibitor with in vivo antiresorptive activity.

Targeted disruption of the pp60(src) (Src) gene has implicated this tyrosine kinase in osteoclast-mediated bone resorption and as a therapeutic target for the treatment of osteoporosis and other bone-related diseases. Herein we describe the discovery of a nonpeptide inhibitor (AP22408) of Src that demonstrates in vivo antiresorptive activity. Based on a cocrystal structure of the noncatalytic Src homology 2 (SH2) domain of Src complexed with citrate [in the phosphotyrosine (pTyr) binding pocket], we designed 3',4'-diphosphonophenylalanine (Dpp) as a pTyr mimic. In addition to its design to bind Src SH2, the Dpp moiety exhibits bone-targeting properties that confer osteoclast selectivity, hence minimizing possible undesired effects on other cells that have Src-dependent activities. The chemical structure AP22408 also illustrates a bicyclic template to replace the post-pTyr sequence of cognate Src SH2 phosphopeptides such as Ac-pTyr-Glu-Glu-Ile (1). An x-ray structure of AP22408 complexed with Lck (S164C) SH2 confirmed molecular interactions of both the Dpp and bicyclic template of AP22408 as predicted from molecular modeling. Relative to the cognate phosphopeptide, AP22408 exhibits significantly increased Src SH2 binding affinity (IC(50) = 0.30 microM for AP22408 and 5.5 microM for 1). Furthermore, AP22408 inhibits rabbit osteoclast-mediated resorption of dentine in a cellular assay, exhibits bone-targeting properties based on a hydroxyapatite adsorption assay, and demonstrates in vivo antiresorptive activity in a parathyroid hormone-induced rat model.

Adsorption↗

PubMed2000

A Src SH2 selective binding compound inhibits osteoclast-mediated resorption.

BACKGROUND: The observations that Src(-/-) mice develop osteopetrosis and Src family tyrosine kinase inhibitors decrease osteoclast-mediated resorption of bone have implicated Src in the regulation of osteoclast-resorptive activity. We have designed and synthesized a compound, AP22161, that binds selectively to the Src SH2 domain and demonstrated that it inhibits Src-dependent cellular activity and inhibits osteoclast-mediated resorption. RESULTS: AP22161 was designed to bind selectively to the Src SH2 domain by targeting a cysteine residue within the highly conserved phosphotyrosine-binding pocket. AP22161 was tested in vitro for binding to SH2 domains and was found to bind selectively and with high affinity to the Src SH2 domain. AP22161 was further tested in mechanism-based cellular assays and found to block Src SH2 binding to peptide ligands, inhibit Src-dependent cellular activity and diminish osteoclast resorptive activity. CONCLUSIONS: These results indicate that a compound that selectively inhibits Src SH2 binding can be used to inhibit osteoclast resorption. Furthermore, AP22161 has the potential to be further developed for treating osteoporosis.

Amino Acid Sequence↗

PubMed2000

Salt-induced exacerbation of morning surge in blood pressure in patients with essential hypertension.

The morning surge in blood pressure (BP) is related to the morning occurrence of lethal cardiovascular events. We tested the hypothesis that salt intake may be associated with the morning surge in BP in essential hypertension. Seventy-six patients were admitted and placed on a low salt diet (2 g/day) for 7 days followed by a high salt diet (20-23 g/day) for another 7 days. At the end of each salt diet, 24-h ambulatory BP and heart rate monitorings and head-up tilt (HUT) test were performed. Patients whose average mean BP (MBP) was increased by more than 10% by salt loading were assigned to the salt-sensitive (SS) group (n = 37); the remaining patients, whose MBP was increased by less than 10%, were assigned to the non-salt-sensitive (NSS) group (n = 39). The increase in ambulatory MBP during 6.30-8.00 am above the baseline (2.00-4.00 am) was significantly enhanced by salt loading in the NSS group (P < 0.05), but not in the SS group. The coefficient of variation of 24-h MBP and heart rate was increased by salt loading only in the NSS group. The significant elevation of plasma noradrenaline concentration after awakening, which was noted during the low salt diet period, was unchanged during the high salt diet period in the NSS group, but abolished in the SS group. Salt loading enhanced HUT-induced decrease in systolic BP without affecting the heart rate response only in the NSS group. We conclude that the morning surge in BP is enhanced by salt loading in the NSS type of essential hyper- tension, presumably by the excessive activation of the sympathetic nervous system. Journal of Human Hypertension (2000) 14, 57-64.

17-Hydroxycorticosteroids↗

PubMed2000

Cross talk of shear-induced production of prostacyclin and nitric oxide in endothelial cells.

We tested the hypothesis that vessel homeostasis is maintained through the cross talk of shear-induced production of prostacyclin and nitric oxide (NO). Confluent human umbilical vein endothelial cells (HUVEC) were exposed to fluid shear stress at 15 dyn/cm(2) using a cone-plate device, and the concentrations of 6-keto-PGF(1alpha) and NO metabolites (nitrate and nitrite) in the medium were measured with radioimmunoassay and the Greiss method, respectively. Compared with static control, shear stress increased cumulative prostacyclin production by twofold after 90 min of exposure. Inhibition of NO synthase enhanced flow-induced prostacyclin production by twofold without affecting the baseline production. Guanylyl cyclase inhibitor enhanced flow-induced prostacyclin production to the same degree. In contrast, a stable agonist of cGMP attenuated the rapid early phase of flow-dependent prostacyclin production. Shear-induced NO metabolite production was unaffected even after indomethacin inhibited prostacyclin production. We conclude that NO shows an inhibitory effect on prostacyclin production under shear stress and that vessel homeostasis may be maintained through an increase in prostacyclin production when NO synthesis is impaired in endothelial cells.

Cell Survival↗

PubMed2000

Specific regulatory inhibition of transfected HepG(2) with HCV 5'NCR by antisense phosphorothioate oligodeoxynucleotides.

OBJECTIVE: To screen efficient and specific new drugs against hepatitis C virus (HCV) and find the best target sequence of antisense oligodeoxynucleotides (ASODNs) targeting at HCV gene. METHODS: Fifteen S-ASODNs targeting at the 5'NCR and start AUG of HCV RNA were designed and synthesized according to the predicted RNA secondary structure of the HCV 5'NCR and the adjacent AUG region. HepG(2) cells were co-transfected with pHCV-neo4 and S-ASODN. The inhibitory effects of S-ASODNs on gene expression controlled by HCV 5'NCR were determined by the assay of luciferase activity. RESULTS: Five S-ASODNs, i.e. HCV65, HCV279, HCV363, HCV349 and HCV352, showed sequence-specific and dose-dependent inhibitory activities with an inhibition rate of more than 80% at a concentration of 100 nmol/L. According to 50% inhibitory concentrations, the inhibitory activity of HCV363 was the best. On the other hand, ASODNs had only little non-specific effect by negative control trials. In addition, the results also indicated that there were some coordinate effects between ASODNs at different targets. CONCLUSION: Stem-loop 2a and 3d of HCV 5'NCR and the start AUG of polyprotein precursor are candidate targets of S-ASODNs.

5' Untranslated Regions↗

PubMed2000

[Ecological study on relationship between desertification process and vegetation dynamics in west of northeast China: vegetation classification].

Based on the data obtained from 72 plant community plots and 276 plant species in Hulunbeier Sandy Land and Kerqin Sandy Land in the northeast desertification region of China, TWINSPAN analysis was carried out. Meanwhile the practical classification result was obtained by Detrended correspondence Analysis (DCA). Under the vegetation classification principles of China, the vegetation classification system of the desertification regions in northeast China was preliminarily established, which includes 6 vegetation types, 11 subtypes, 40 formations, and 55 associations.

China↗

PubMed2000

Treating traumatic tattoo by micro-incision.

OBJECTIVE: To design a micro-incision operation for treating traumatic tattoo. METHODS: With an 11-gauge blade, a micro-incision was made on each side of the small tattoo spot and the tattoo skin was removed. For a longer tattoo particle, a longer incision was needed. The skin incision was sutured with 6-0 silk. For a complex tattoo, dermabrasion could be used first to remove the superficial one so as to expose the deep one which was removed in the same way as mentioned above. When there was a large number of tattoo particles, many operations were needed. RESULTS: Fourteen patients were treated by this method with good to excellent result. CONCLUSION: Micro-incision for treating traumatic tattoo is an effective method.

Adult↗

PubMed2000

[In vitro antiviral activity of antisense oligonucleotides against influenza virus].

For developing of antisense oligonucleotides as potential antiviral therapeutic agents against influenza A virus, phosphorothioate oligodeoxynucleotides(PS-ODN) targeted to part to the 3' and 5' end sequences which are common to the eight RNAs of type A influenza virus were synthesized. The in vitro cytotoxicity of these PS-ODNs was assayed and then antiviral activity of these PS-ODNs was evaluated by using cultured MDCK cells infected by A/JingFang/86-1(H1N1). It was found that(1) No in vitro cytotoxicity was seen when concentration of PS-ODN was up to 50 mumol/L. (2) Oligonucleotides(IV4 #) complementary to 5' terminal conserved sequences and ODN(IV6 #, IV7 #)composed by 3'/5' terminal conserved sense sequences or antisense sequences all exhibited the most potent antiviral activity. IV4 # ODN exhibited significant antiviral activity with reduced hemegglutination titer about 50% at concentration of 1 mumol/L, and over 70% at 10 mumol/L. The antiviral activity of IV4 # was in a dose- and sequence-dependent manner. (3) IV4 # ODN showed significant antiviral activity not only against H1N1 subtype strains of influenza virus, but also against H3N2 subtype strains. (4) The multiplicity of infection(MOI) of influenza virus had effects on antiviral activity of IV4 # ODN. IV4 # ODN showed better dose-dependent antiviral activity when there was lower MOI. These results suggested the the 3'/5' terminal sequences of influenza A virus could be used as a target for designing antiviral oligonucleotides against influenza A virus.

Animals↗

PubMed1999

Time course of free radical production after primary coronary angioplasty for acute myocardial infarction and the effect of vitamin C.

Reactive oxygen species are thought to mediate reperfusion injury after rapid revascularization for acute myocardial infarction (AMI) and 8-epi prostaglandin (PG) F2alpha, a free-radical catalyzed product of arachidonic acid, has been proposed as an indicator of oxidative stress in vivo during myocardial reperfusion. The time course of urinary 8-epi PGF2alpha excretion after primary coronary angioplasty (PTCA) for AMI was investigated, as well as the effect of prior administration of vitamin C. Urine samples, 1 before and 5 after primary PTCA (0-30, 30-60, 60-90, 90-120 and 120-150 min), were collected in 11 patients with AMI undergoing primary PTCA (Group 1), 10 patients with AMI treated with water-soluble vitamin C at an initial dose of 2.0 g followed by a constant infusion at 20mg/min prior to primary PTCA (Group 2), and 6 patients with stable effort angina undergoing elective PTCA (Group 3). 8-epi PGF2alpha was measured by enzyme immunoassay. There were no significant differences in urinary 8-epi PGF2alpha excretion at baseline among the 3 groups. In Group 1, urinary 8-epi PGF2alpha excretion (ng/mmol creatinine) significantly increased from 60+/-8 at baseline to 122+/-16 at 60-90 min (p<0.001), and declined to the baseline level at 120-150 min after primary PTCA. In Group 2, it also increased from 72+/-12 to 123+/-15 at 60-90 min (p<0.01), and the percent increase did not differ from that in Group 1. In Group 3, it remained unchanged during the study period. The free radical production is rapidly and transiently enhanced after primary PTCA for AMI, and vitamin C fails to suppress it.

Aged↗