Cloning, Expression, and Functional Characterization of Two Highly Efficient Flavonoid-di-O-glycosyltransferases ZmUGT84A1 and ZmUGT84A2 from Maize (Zea mays L.)

The maize (Zea mays L.) glycosyltransferase family 1 comprises many uridine diphosphate glycosyltransferase (UGT) members. However, UGT activities and biochemical functions have seldom been revealed. In this study, the genes of two flavonoid di-O-glycosyltransferases ZmUGT84A1 and ZmUGT84A2 were cloned from maize plant and expressed in Escherichia coli. Phylogenetic analysis showed that the two enzymes were homologous to AtUGT84A1 and AtUGT84A3. The two recombinant enzymes showed a high conversion rate of luteolin to its glucosides, mainly 4',7-di-O-glucoside and minorly 3',7-di-O-glucoside in two-step glycosylation reactions in vitro. Moreover, the recombinant ZmUGT84A1 and ZmUGT84A2 had a broad substrate spectrum, converting eriodictyol, naringenin, apigenin, quercetin, and kaempferol to monoglucosides and diglucosides. The highly efficient ZmUGT84A1 and ZmUGT84A2 may be used as a tool for the effective synthesis of various flavonoid O-glycosides and as markers for crop breeding to increase O-glycosyl flavonoid content in food.

An activatable near-infrared molecular reporter for fluoro-photoacoustic imaging of liver fibrosis

Noninvasive and accurate detection of liver fibrosis is extremely significant for well-timed intervention and treatment to prevent or reverse its progression. Fluorescence imaging probes hold great potential for imaging of liver fibrosis, but they always encounter the inherent limitation of shallow penetration depth, which compromises their ability of in vivo detection. To overcome this issue, an activatable fluoro-photoacoustic bimodal imaging probe (IP) is herein developed for specific visualization of liver fibrosis. The probe IP is constructed on a near-infrared thioxanthene-hemicyanine dye that is caged with gamma-glutamyl transpeptidase (GGT) responsive substrate and linked with integrin-targeted peptide (cRGD). Such molecular design permits IP to effectively accumulate in the liver fibrosis region through specific recognition of cRGD towards integrin and activate its fluoro-photoacoustic signal after interaction with overexpressed GGT to precisely monitor the liver fibrosis. Thus, our study presents a potential strategy to design dual-target fluoro-photoacoustic imaging probes for noninvasive detection of early-stage liver fibrosis.

Blood pressure reducing effects of piromelatine and melatonin in spontaneously hypertensive rats

BACKGROUND

Recently, widespread interest has grown regarding melatonin treatment of hypertension including its cardioprotective effects. Studies in rodents indicate that melatonin plays a role in the pathogenesis of hypertension in rats with metabolic syndrome. Piromelatine, a melatonin agonist, serotonin 5-HT-1A and 5-HT-1D agonist and serotonin 5-HT2B antagonist is a multimodal agent with sleep promoting, anti-diabetic, analgesic, anti-neurodegenerative, anxiolytic and antidepressant potential, currently in development for the treatment of insomnia.

AIM

In this report we assessed the effects of piromelatine and melatonin treatment on blood pressure in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats.

MATERIALS AND METHODS

Five groups of 12-wk-old rats (10/group) were treated for 5 weeks with a vehicle, piromelatine (5, 15 and 50 mg/kg BW) and melatonin (10 mg/kg BW) and an age-matched WKY control group. Systolic blood pressure (tail-cuff method) was measured weekly at 9:00 a.m. and at 9:00 p.m. The rats body weight, plasma glucose, insulin, triglyceride, adiponectin, total cholesterol, HDL and LDL/VLDL cholesterol were also measured.

RESULTS

Our results showed that both piromelatine and melatonin reduced SHR blood pressure significantly both during the morning and the evening. Piromelatine, but not melatonin, also reduced SHR body weight gain and both significantly decreased plasma glucose and insulin levels and increased adiponectin levels.

CONCLUSIONS

Piromelatine, similar to melatonin, has an antihypertensive effect and also attenuates body weight, improves metabolic profiles and might be useful in the treatment of hypertension and the metabolic syndrome.

Associated factors for HIV and syphilis infection among men who have sex with men only and men who have sex with both men and women in cities of China

Summary

The aims of this paper were to find out the status of HIV and syphilis infection and to examine the sexual behaviours between men who have sex with men only (MSM/M) and men who have sex with both men and women (MSM/W), as well as to determine the correlates for HIV and syphilis infection among MSM/M and MSM/W, respectively. Among 1693 MSM who participated in the study, the proportions of MSM/M and MSM/W were 82.1% and 17.9%, respectively. The prevalences of HIV infection were 7.0% in MSM/M and 6.6% in MSM/W and the prevalences of syphilis infection were 11.9% and 13.2%, respectively. Among the MSM/M subset, the correlates both for HIV and syphilis infection included having more sexual partners, and being receptive or both insertive and receptive for anal sex. Among the MSM/W subset, living in Chengdu was associated with HIV infection and using condoms inconsistently during anal sex was associated with syphilis infection. The findings of this survey call for interventions tailored according to the needs of different subsets of MSM.

Enhancement of manumycin A-induced apoptosis by methoxyamine in myeloid leukemia cells

Farnesyltransferase inhibitors (FTIs) are currently under investigation for leukemia treatment. We evaluated the FTI manumycin A (manumycin) in two myeloid leukemia cell lines (U937 and HL-60). Manumycin induced nitric oxide production and apoptosis of the leukemia cells. Nitric oxide or other reactive oxygen species may induce oxidative DNA damage, and the number of apurinic sites increased after manumycin treatment, which was reversed by concurrent treatment with N-acetyl-L-cysteine. Since repair of DNA damage is important to cell survival, we hypothesized that methoxyamine, an inhibitor of base-excision repair, would enhance the antineoplastic effect of manumycin. The combination of manumycin and methoxyamine resulted in enhanced apoptosis by six criteria increased annexin V binding, release of mitochondrial cytochrome c into the cytosol, activation of caspase-9, activation of caspase-3, specific cleavage of poly-adenosyl ribose polymerase, and increase in the sub-G1 cell cycle fraction. The drug combination enhanced inhibition on the soft agar clonogenic assay and on the formazan dye cell viability assay. The effects of manumycin or manumycin plus methoxyamine on apoptosis were blocked by N-acetyl-L-cysteine, and partially by nitric oxide synthase inhibitors or scavenger of peroxide. We conclude that methoxyamine enhances manumycin-induced apoptosis in myeloid leukemia cells.

Factors contributing to troponin exchange in myofibrils and in solution

The troponin complex in a muscle fiber can be replaced with exogenous troponin by using a gentle exchange procedure in which the actin-tropomyosin complex is never devoid of a full complement of troponin (Brenner et al. (1999) Biophys J 77: 2677-2691). The mechanism of this exchange process and the factors that influence this exchange are poorly understood. In this study, the exchange process has now been examined in myofibrils and in solution. In myofibrils under rigor conditions, troponin exchange occurred preferentially in the region of overlap between actin and myosin when the free Ca2+ concentration was low. At higher concentrations of Ca2+, the exchange occurred uniformly along the actin. Ca2+ also accelerated troponin exchange in solution but the effect of S1 could not be confirmed in solution experiments. The rate of exchange in solution was insensitive to moderate changes in pH or ionic strength. Increasing the temperature resulted in a two-fold increase in rate with each 10 degrees C increase in temperature. A sequential two step model of troponin binding to actin-tropomyosin could simulate the observed association and dissociation transients. In the absence of Ca2+ or rigor S1, the following rate constants could describe the binding process: k1 = 7.12 microM(-1) s(-1), k(-1) = 0.65 s(-1), k2 = 0.07 s(-1), k(-2) = 0.0014 s(-1). The slow rate of detachment of troponin from actin (k(-2)) limits the rate of exchange in solution and most likely contributes to the slow rate of exchange in fibers.

Molecular basis for the effect of lipid lowering drugs on growth factors after de-endothelialization

OBJECTIVE

To study the mechanism and effect of lipid lowering drugs in arresting the development of arterial restenosis after angioplasty.

METHODS

De-endothelialization injury of rabbit aortae, common iliac and femoral arteries using balloon angioplasty and the expression of growth factors such as platelet derived growth factor-B (PDGF-B), transforming growth factor beta-1 (TGF beta-1), and fibroblast growth factors (bFGF) were investigated. Total serum cholesterol (TC) and triglycerides (TG) were analyzed during and after the treatment using either simvastatin combined with gemfibrozil or simvastatin alone for 6 weeks.

RESULTS

Serum total cholesterol and triglycerides were only slightly to moderately increased after high cholesterol ration intake lasting for 6 weeks in rabbits of two therapeutic groups (simvastatin plus gemfibrozil or only simvastatin). A positive correlation was found between TC and intimal/medial ratio (r = 0.5873, P < 0.05). PDGF-B detected by immuno-histochemistry and RT-PCR analysis showed that the release of PDGF-B was inhibited by simvastatin and gemfibrozil after de-endothelialization. RT-PCR analysis showed that TGF beta-1 was increased in the neointima in two treatment groups but no definite change was seen in the mRNA of bFGF in the smooth muscle cell (SMC) of the balloon-injured arteries even under lipid lowering drug treatment.

CONCLUSION

In addition to the lipid lowering effect, both simvastatin and gemfibrozil also influence the release of PDGF-Band TGF-1 in the neointima after de-endothelialization.

Development of serine protease inhibitors displaying a multicentered short (<2.3 A) hydrogen bond binding mode: inhibitors of urokinase-type plasminogen activator and factor Xa

Novel scaffolds that bind to serine proteases through a unique network of short hydrogen bonds to the catalytic Ser195 have been developed. The resulting potent serine protease inhibitors were designed from lead molecule 2-(2-hydroxyphenyl)1H-benzoimidazole-5-carboxamidine, 6b, which is known to display several modes of binding. For instance, 6b can recruit zinc and bind in a manner similar to that reported by bis(5-amidino-2-benzimidazolyl)methane (BABIM) (Nature 1998, 391, 608-612).(1) Alternatively, 6b can bind in the absence of zinc through a multicentered network of short (<2.3 A) hydrogen bonds. The lead structure was optimized in the zinc-independent binding mode toward a panel of six human serine proteases to yield optimized inhibitors such as 2-(3-bromo-2-hydroxy-5-methylphenyl)-1H-indole-5-carboxamidine, 22a, and 2-(2-hydroxybiphenyl-3-yl)-1H-indole-5-carboxamidine, 22f. Structure-activity relationships determined that, apart from the amidine function, an indole or benzimidazole and an ortho substituted phenol group were also essential components for optimal potency. The affinities (K(i)) of 22a and 22f, for example, bearing these groups ranged from 8 to 600 nM toward a panel of six human serine proteases. High-resolution crystal structures revealed that the binding mode of these molecules in several of the enzymes was identical to that of 6b and involved short (<2.3 A) hydrogen bonds among the inhibitor hydroxyl oxygen, Ser195, and a water molecule trapped in the oxyanion hole. In summation, novel and potent trypsin-like serine protease inhibitors possessing a unique mode of binding have been discovered.

[Activation of NF-kappa B and its effect on induction of platelet-derived growth factor-B transcription by angiotensin II in ECV304 cell line]

OBJECTIVES

The renin-angiotensin system may contribute to the pathogenesis of atherosclerosis. The transcription factor nuclear factor-kappa B (NF-kappa B) participates in most signal pathways involved in the inflammatory process. In this project the effect of angiotensin II (Ang II) on NF-kappa B activation and the promotion of PDGF-B mRNA expression in human endothelial cell line ECV304 was studied.

METHODS

Electrophoretic mobility shift assay, immunofluorescence and immunoelectronic microscope techniques, including confocal microscopy and gold particle labelled electronic microscopy were applied to investigate the mechanism by which Ang II activates NF-kappa B, ECV304 cells were transiently transfected with an NF-kappa B/luciferase reporter gene and catalytically inactive NIK, IKK alpha, IKK beta mutants respectively. Northern blot was carried out to detect PDGF-B mRNA.

RESULTS

By the findings of immunofluorescence confocal microscopy, immunoelectronic microscopy and Northern blot, Ang II was effective in stimulating NF-kappa B activation and there was definited cytoplasmic-to-nuclear translocation of NF-kappa B subunits p50 and p65 and overexpression of PDGF-B mRNA expression. Over-expression of the transiently transfected IKK alpha-KM, IKK beta-KM and NIK-KM mutant genes enabled to block the reporter gene activation induced by ang II.

CONCLUSION

Ang II is effective to activate NF-kappa B through a pathway dependent on NIK, IKK alpha and IKK beta, and induces PDGF-B transcription in the endothelial cell line ECV304.

[Influence of a G/A substitution at -75 bp promoter region of apolipoprotein A I gene and wine consumption on the plasma apolipoprotein A I levels in Yi and Han Chinese]

OBJECTIVE

To study the influence of a common polymorphism of the human apolipoprotein A I gene promoter at a position of -75 bp upstream of the transcription start site and wine consumption on plasma lipid levels.

METHODS

742 healthy Yi and Han healthy subjects all above 15 years old to be the total population which was divided into three samples, namely, Yi-farmer sample, Yi-emigrant sample and Han-resident sample for this study. Estimations of plasma lipids and apolipoproteins were carried on through an auto-analyzer. Genetic DNA was prepared from the frozen blood clot using Triton x-100 lysis technique. Amplification of a 432 bp fragment of the apoA I gene promoter was performed via the PCR, followed by restriction digestion, electrophoresis and identification of the genotypes involved. Data analysis was done at last.

RESULTS

Four groups of alcohol consumption were defined: the non-drinkers, 1 - 25 g alcohol intake/day, 26 - 75 g alcohol/day and > 75 g alcohol/day. A tendency of a mild persistent elevation of plasma HDL-C and apoA I was noticed corresponding to an increase of the amount of alcohol intake, and with no evidence of threshold effect observed in the samples of both the Yi-farmers and the Han people. Similar phenomenon was obtained in the sample of Yi-emigrants, but no statistical significance. The frequencies of the A allele of all 3 samples were similar. In Han and Yi-emigrant samples, the drinkers with genotypes of GG had a higher plasma HDL-C and apoA I level than that of the non-drinkers with the same genotypes. Drinkers with A allele had a lower plasma HDL-C and apoA I level than that of drinkers without A allele, and the non-drinkers with A allele had a higher levels of apoA I than of non-drinkers with genotypes of GG. It is estimated that 18% of the variability of plasma apoA I level could be explained by the G/A polymorphism in non-drinkers of Yi-emigrants (F = 8.94, P < 0.01).

CONCLUSIONS

Current data suggest that a moderate alcohol consumption or a G to A substitution could make a lower incidence of CHD, but the beneficial effect of one will be negated by the other when both factors occur simultaneously. This finding is seemed valuable for a further study on the effect of the environmental factor or genetic factor in effecting the plasma apoA I level afterwards.

Suppression of induced atherosclerosis in h-apo AI transgenic mice by overexpression of human apo AI in the aortic wall

OBJECTIVES

To investigate the inhibitory effect of expressed human apolipoprotein AI (h-apo AI) and high density lipoprotein (HDL) on atherosclerosis development in transgenic mice, and cultivation of smooth muscle cells isolated from the aortic wall of transgenic mice that are able to produce human apo AI in vitro.

METHODS

Both h-apo AI transgenic mice and normal C57 mice were fed with either a regular chow or a high-fat diet containing 5% pork lard, 1.25% cholesterol and 0.25% sodium cholate for 14 or 24 weeks respectively. Human apo AI mRNA were detected by Northern blot. Plasma apo AI levels were measured using a radio-immuno-diffusion assay, and plasma lipid levels were measured using a colorimetric assay. Image analysis was performed in order to quantify the fatty streak areas stained with oil red O. In addition, smooth muscle cells isolated from the media layer of the aortic wall of h-apo AI transgenic mice were cultured for the detection of human apo AI produced.

RESULTS

Higher levels of h-apo AI mRNA were found in liver, small intestine, kidneys and aortae in transgenic mice than in the controls all on a high-fat diet. The transgenic mice had an increased level of serum apo AI and HDL-cholesterol and the fatty streak area counted at the aortic sinus was approximately 5-fold less in the transgenic mice after feeding with a high fat ration, particularly after 24 weeks. SMC isolated from the transgenic mice aortae were cultivated and able to express h-apo AI mRNA and its related protein.

CONCLUSION

Elevation of h-apo AI and HDL in serum and aortic wall of the transgenic mice has a remarkably inhibitory effect on the development of experimental atherosclerosis.

Interaction of alcohol and the G to a substitution at the promoter region of the apolipoprotein AI gene in determining plasma apolipoprotein AI levels in Yi and Han Chinese

OBJECTIVE

To investigate the influence on plasma lipid levels of alcohol and a common polymorphism in the human apolipoprotein AI gene promoter at a position 75 bp upstream of the transcription start site.

METHODS

For this study, 742 healthy Yi and Han subjects all above 15 years old formed the total population which was divided into three groups: the Yi-farmer group, the Yi-emigrant group and the Han-resident group. All estimates of plasma lipids and apolipoproteins were performed using an auto-analyzer. Genetic DNA was prepared from the blood clots using the Triton X-100 lysis technique. Amplification of a 432 bp fragment of the apoAI gene promoter was performed using PCR followed by restriction digestion, electrophoresis and identification of the genotypes involved.

RESULTS

The samples were divided on the basis of alcohol consumption: non-drinkers, 1-25 g/day, 26-75 g/day and > 75 g/day. Comparing the four alcohol consumption groups, plasma HDLC and apoAI levels were increased as the alcohol consumption increased with no evidence of threshold effects in the Yi-farmers and the Han people groups. A similar association was found in the Yi-emigrant group, but was not statistically significant. The frequencies of the A allele in the three populations were similar, and no significant difference of lipid and apolipoprotein levels was found between subjects with and without the A allele in the three populations. But, in Han and Yi-emigrant samples, the drinkers with the GG genotype had higher plasma HDLC and apoAI levels than non-drinkers with the same genotype, while the drinkers with the A allele had lower plasma HDLC and apoAI levels than drinkers without the A allele. Non-drinkers with the A allele had higher levels of apoAI than non-drinkers with GG genotypes. It was estimated that 18% of the variability of plasma apoAI level could be explained by the G to A polymorphism in non-drinkers of Yi-emigrants (F = 8.94, P < 0.01).

CONCLUSIONS

The present data suggest that moderate alcohol consumption and the G to A substitution could lower the risk of coronary heart disease (CHD), but the beneficial effects of one will be negated by the other.

[Inhibition of monocytes adhesion to the intima of arterial wall by local expression of antisense monocyte chemotactic protein-1]

OBJECTIVE

To study the mechanism of monocyte recruitment in atherogenesis and to clarify the effect of monocyte chemotactic protein-1 (MCP-1) in this process.

METHODS

Femoral arteries isolated from the rabbits which had been fed with a high cholesterol diet and locally perfused with MM-LDL within the artery beforehand, were used as the models. Antisense MCP-1cDNA was transferred into the arterial wall by injecting recombinant LNCX-anti-MCP-1/liposomal complex in the femoral sheath and the periarterial tissue.

RESULTS

Expression of antisense MCP-1 mediated by recombinant LNCX plasmid/lipsomal complex gene transfer enabled to inhibit MCP-1 gene expression and adhesion of monocyte to the intima.

CONCLUSION

MCP-1 plays an important role on the recruitment of monocytes in the arterial wall, which provides a potential clue in developing a gene therapy project for the prevention and treatment of atherogenesis.

Inhibition of intimal lipid deposition in human apolipoprotein A1 transgenic mice

1. Southern blot confirmed the emergence of the human apolipoprotein A1 (h-apoA1) gene (four to 15 copies) in newborn transgenic mice. The inheritance pattern of h-apoA1 transgene in three generations of progeny was compatible with a single autosomal integration site. 2. Northern blot showed h-apoA1 mRNA expressed mainly in liver, kidney and aorta. The total plasma apoA1 (murine plus human) level was significantly increased to 58 and 118 in transgenic mice without or under zinc induction, respectively. The majority was h-apoA1. Plasma lecithin:cholesterol acyltransferase activity was positively correlated with h-apoA1 levels in transgenic mice (r = 0.43; P < 0.01). 3. After a high cholesterol intake for 14 weeks, the incidence of fatty streak at the aortic sinus was 40% in transgenic mice and 80% in controls. Expression of platelet-derived growth factor-B, c-myc and c-fos proteins was much weaker in smooth muscle cells at the aortic sinus in transgenic mice.

[Cloning whole length cDNA of related genes responsible for smooth muscle cells proliferation in atherogenesis and study on its function]

OBJECTIVE

To clone whole length cDNA of the related genes responsible for vascular smooth muscle cell (SMC) proliferation in atherogenesis, and to study its function.

METHODS

ox-LDL was added as a stimulant to the SMC culture medium. Subtractive library was established using subtractive hybridization technique in order to clone the related genes fragments. With the whole length cDNA library established, the whole length cDNA of the related gene was cloned. The protein expressed was studied.

RESULTS

4 new gene fragments and one whole length cDNA were cloned. The new cloned gene is able to express a protein of about 44000 daltons and closely related to the activity of ox-LDL.

CONCLUSIONS

The new cloned gene is considered responsible for SMC proliferation.

[Morphometric study of inflammatory cells and smooth muscle cells in coronary plaques and their relation with plaque stability]

OBJECTIVE

To compare the content of inflammatory cells and smooth muscle cells in stable and unstable coronary plaques in order to clarify the role of these cells in the vulnerability of plaques.

METHODS

Hearts from 12 postmortem acute myocardial infarction cases were studied. The epicardial coronary arteries were dissected en bloc, fixed, decalcified, cut at 4 mm intervals and routinely processed for HE sections. 163 stable plaques (with no or only little lipid core) and 163 unstable plaques (with lipid core size > 40% of plaque area) were studied immunohistochemically using monoclonal antibodies specific for macrophages (CD68), T lymphocytes (UCHL-1) and smooth muscle cells (actin). Computor aided planimetry was used to measure the positive area of different cells.

RESULTS

The content of macrophage and T lymphocytes in unstable plaques were significantly higher than that in stable plaques (P < 0.05).

CONCLUSIONS

Stable plaques and unstable plaques not only had different lipid core size but also had different inflammatory cell and smooth muscle cell content. The larger the lipid core and the more macrophages and T lymphocytes in the fibrous cap, the more unstable the plaque. The lipid core and inflammatory cells (including macrophages and T lymphocytes) are the two major determinants of the vulnerability of coronary plaques.

Minimally modified low-density lipoprotein induces monocyte chemotactic protein-1 expression in vivo and a novel model for monocyte adhesion to arterial intima

OBJECTIVE

To test whether minimally modified low-density lipoprotein (MM-LDL) can stimulate the arterial cells expressing MCP-1 in vivo and thus induce monocyte adherence to endothelium.

METHODS

An animal model was constructed to study the function of MM-LDL in vivo. MM-LDL (600 micrograms/ml) was perfused into a segment of the femoral artery of rabbits (both ends of which were occluded with removable ligatures). After exposure to MM-LDL for 2 h, the arterial segments were taken out 6 or 18 h later. The arteries were subjected to in situ hybridization with 35S-labeled antisense monocyte chemotactic protein-1 (MCP-1) RNA probe and processed for scanning electron microscopy.

RESULTS

The expression of MCP-1 mRNA of the arterial endothelial cells and smooth muscle cells were increased by 60% and 90% 6 h after perfusion and had a 3.2 folds and 1.6 folds increase 18 h after perfusion respectively as compared with control (arteries perfused with saline). There was also apparent monocyte adherence to the endothelium observed by scanning electron microscopy.

CONCLUSION

MM-LDL can stimulate vascular cells in expressing MCP-1 mRNA and enhance monocyte adherence to endothelium in vivo.

[The modulation of collagen synthesis and expressions of type I and III collagen mRNAs in aorta smooth muscle cell by PDGF and heparin]

OBJECTIVE

The effect of platelet derived growth factor (PDGF) and heparin on the modulation of human aorta smooth muscle cell(hASMC) proliferation, collagen synthesis, expressions of type I and III collagen mRNAs as well as transforming growth factor-beta (TGF-beta) mRNA were investigated.

METHODS

3H-TdR and 3H-proline incorporation and Northern blot analysis were done. 3H-TdR and 3H-proline incorporation was statistically analyzed with t test among different experimental groups.

RESULTS

In comparison to the control group, PDGF possessed the ability in promoting markedly the DNA synthesis (3H-TdR incorporation: PDGF group vs control, P < 0.01), synthesis and secretion of collagen protein (3H-proline incorporation of SMC and medium: PDGF group vs control, P < 0.01), expressions of type I and type III collagen mRNAs, and transforming growth factor mRNA in hASMC. Whereas heparin significantly decreased the DNA synthesis (heparin group vs control, P < 0.01), synthesis and secretion of collagen protein (heparin group vs control, P < 0.01) of hASMC in vitro. Heparin also inhibited the promoting effect of PDGF on DNA synthesis, the synthesis and secretion of collagen protein, and reduced the up-regulation of expressions of type I and type III collagen mRNAs as well as TGF-beta mRNA that stimulated by PDGF.

CONCLUSIONS

PDGF could promote the collagen synthesis through upregulating type I and type III collagen mRNA expressions while heparin just inhibiting SMC DNA and collagen synthesis effected in the way of anti-atherosclerosis.

Calcium binding to the regulatory domain of skeletal muscle troponin C induces a highly constrained open conformation

We have used fluorescence resonance energy transfer to investigate the conformation of the apo and calcium-loaded states of the regulatory N-terminal domain of full-length troponin C mutants from skeletal muscle. The mutants studied each contained a single tryptophan residue (position 22 or 90) and a single cysteine residue (position 52 or 101). The intrinsic fluorophore in each mutant served as an energy donor and the cysteine was conjugated to the acceptor probe 5-(iodoacetamidoethyl)amino-naphthalene-1-sulfonic acid. The distributions of two intersite distances (between residues 22 and 52, and residues 90 and 52) were broad in the apo state, indicative of considerable structural dynamics. These distributions were shifted to longer distances and considerably sharpened in the calcium-loaded state. The shifts to longer distances by 8 to 11 A indicate a calcium-induced opening of the N-terminal domain conformation. The transition of the troponin C structure from a closed conformation to an open conformation is accompanied by a substantial reduction of structural fluctuations that dominate in the apo structure as evidenced from the large decrease of the widths of the distributions. This highly constrained open conformation is required as part of the structural basis to facilitate productive interaction between troponin C and troponin I to trigger contraction in skeletal muscle.

[The effect of expressed human apolipoprotein AI on plasma high density lipoprotein level in transgenic mice]

OBJECTIVE

To study the regulation of human apolipoprotein AI(h-apo AI) gene expression and its role in high density lipoprotein (HDL) metabolism.

METHODS

Transgenic C57BL/6 mice established in this laboratory with human apoAI gene containing mouse metallothionein-I(MT-I) promoter were used for investigation.

RESULTS

Southern blot identified the presence of 4-15 copies of h-apo AI gene in the transgenic mice. Northern blot showed that human apo AI mRNA was expressed mainly in the liver and kidneys, and the high level of h-apo AI mRNA was obtained in liver, kidneys and small intestine after Zinc(Zn) induction. Total Plasma apoAI Level in transgenic mice was significantly increased than that in the controls, and a high h-apoAI level was detected in the transgenic mice (46% increased after Zn induction). Additionally, total and HDL cholesterol levels were noticed to be highly increased to 47% before and 103% after Zn induction in the transgenic mice comparing to that of the controls. The plasma HDL and h-apoAI levels were significantly correlated (r = 0.85, P < 0.01) in the transgenic mice.

CONCLUSION

Apo AI has a profound effect on regulating HDL levels in the transgenic mice. This animal model is considered appropriate for studying the effect of apoAI on lipid metabolism and the mechanism combating atherogenesis.

[The dynamic change of extracellular matrix in human coronary atherogenesis]

OBJECTIVE

To investigate the expression of type I, III procollagen mRNAs and chondroitin sulfate proteoglycan (CSPG) genes, as well as the distribution of type I, III collagen fibers and CSPG in human coronary atherogenesis.

METHODS

Staining for HE, picrosirius red, immunohistochemistry and hybridization in situ technique were included.

RESULTS

(1) Along with the development of atherosclerotic lesion, collagen type I, III and CSPG were increased simultaneously in the coronary wall; The expressions of type I, III procollagen, biglycan, and decorin mRNAs were noticed to be increased in the plaques. (2) beta-lipoprotein was seen coexistently with CSPG in the AS plaques of the coronary arteries. (3) There were more SMC proliferation, predominant augmentation of type III collagen fibers and accumulation of CSPG in the early plaques of most young subjects; but less SMC, amount of type I collagen fibers and deposition of CSPG in the advanced plaques of most aged people.

CONCLUSION

Over-expression of type I, III procollagen, biglycan and decorin mRNAs was related to the increase of type I, III collagen and CSPG in the atherosclerotic lesions. Proliferation of SMC, augmentation of type I, III collagen and CSPG and change of the proportion between collagen and CSPG are considered to play an important role in the development of coronary atherosclerosis.

Tryptophan mutants of troponin C from skeletal muscle--an optical probe of the regulatory domain

We have generated a series of chicken skeletal muscle troponin C mutants to study the conformation of the regulatory domain in the N-terminal half of the molecule. These mutants each contained a single Trp at position 22 (helix A), 52 (linker of helices B and C), or 90 (central helix). Some of these mutants also contained additional mutations to introduce a single Cys at a desired position. The mutants were characterized by molecular graphics and CD and found to have a minimum of structural perturbations when compared with the native structure. They also retained the ability to regulate myofibrillar ATPase activity. The fluorescence of Trp22 was sensitive to Ca2+ binding only to the regulatory sites, whereas Trp52 and Trp90 responded to Ca2+ binding to both the regulatory and the Ca2+/Mg2+ sites. The tryptophan quantum yield (Q) of all Trp22-containing mutants was very high (0.33) in the absence of bound Ca2+, compared to that of L-tryptophan in aqueous solution (0.14). Q decreased 25% upon binding of Ca2+ to the regulatory sites. The quantum yields of Trp52 and Trp90 in apo mutants were close to 0.14. In the presence of bound Ca2+ at the regulatory sites, the quantum yield of Trp52 decreased 16%, whereas that of Trp90 increased 25%. Results from acrylamide quenching of the fluorescence of the three Trp residues indicated that Trp22 was the least exposed and Trp52 was the most exposed, consistent with other spectral data that Trp22 was in a relatively nonpolar environment and Trp52 was in a highly polar environment. The ability of Trp52 and Trp90 to sense Ca2+ binding to sites located at both domains suggests inter-domain communication in the protein. These single Trp TnC mutants provide specific signals for probing Ca2+-induced conformational changes in the regulatory domain.

Time-resolved fluorescence study of the single tryptophans of engineered skeletal muscle troponin C

The regulatory domain of troponin C (TnC) from chicken skeletal muscle was studied using genetically generated mutants which contained a single tryptophan at positions 22, 52, and 90. The quantum yields of Trp-22 are 0.33 and 0.25 in the presence of Mg2+ (2-Mg state) and Ca2+ (4-Ca state), respectively. The large quantum yield of the 2-Mg state is due to a relatively small nonradiative decay rate and consistent with the emission peak at 331 nm. The intensity decay of this state is monoexponential with a single lifetime of 5.65 ns, independent of wavelength. In the 4-Ca state, the decay is biexponential with the mean of the two lifetimes increasing from 4.54 to 4.92 ns across the emission band. The decay-associated spectrum of the short lifetime is red-shifted by 19 nm relative to the steady-state spectrum. The decay of Trp-52 is biexponential in the 2-Mg state and triexponential in the 4-Ca state. The decay of Trp-90 requires three exponential terms for a satisfactory fit, but can be fitted with two exponential terms in the 4-Ca state. The lower quantum yields (< 0.15) of these two tryptophans are due to a combination of smaller radiative and larger nonradiative decay rates. The results from Trp-22 suggest a homogeneous ground-state indole ring in the absence of bound Ca2+ at the regulatory sites and a ground-state heterogeneity induced by activator Ca2+. The Ca(2+)-induced environmental changes of Trp-52 and Trp-90 deviate from those predicted by a modeled structure of the 4-Ca state. The anisotropy decays of all three tryptophans show two rotational correlation times. The long correlation times (phi 1 = 8.1-8.3 ns) derived from Trp-22 and Trp-90 suggest an asymmetric hydrodynamic shape. TnC becomes more asymmetric upon binding activator Ca2+ (phi 1 = 10.1-11.6 ns). The values of phi 1 obtained from Trp-52 are 3-4 ns shorter than those from Trp-22 and Trp-90, and these reduced correlation times may be related to the mobility of the residue and/or local segmental flexibility.

Phosphorylation-induced distance change in a cardiac muscle troponin I mutant

Phosphorylation of two adjacent serine residues in the unique N-terminal extension of cardiac muscle troponin I (cTnI) is known to decrease the Ca2+-sensitivity of cardiac myofilaments. To probe the structural significance of the N-terminal extension, we have constructed two cTnI mutants each containing a single cysteine: (1) a full-length cTnI mutant (S5C/C81I/C98S) and (2) a truncated cTnI mutant (S9C/C50I/C67S) in which the N-terminal 32 amino acid residues were deleted. We determined the apparent binding constants for the complex formation between IAANS-labeled cardiac troponin C (cTnC) and the two cTnI mutants. The affinities of the cTnC for the truncated cTnI mutant were: (1) 1.5 x 10(6) M(-1) in EGTA, (2) 28.9 x 10(6) M(-1) in Mg2+, and (3) 87.5 x 10(6) M(-1) in Mg2+ + Ca2+. These binding constants were approximately 1.4-fold smaller than the corresponding values obtained with the full-length cTnI mutant, suggesting a very small contribution of the N-terminal extension to the binding of cTnI to cTnC. Cys-5 in the full-length cTnI mutant was labeled with IAANS, and the distribution of the separation between this site and Trp-192 was determined by analysis of the efficiency of fluorescence resonance energy transfer from Trp-192 to IAANS. The following mean distances were obtained with the unphosphorylated full-length mutant: 44.4 A (cTnI alone), 48.3 A (cTnI + cTnC), 46.3 A (cTnI + cTnC in Mg2+), and 51.6 A (cTnI + cTnC in Mg2+ + Ca2+). The corresponding values of the mean distance determined with the phosphorylated full-length cTnI mutant were 35.8, 36.6, 34.8, and 37.3 A. The phosphorylation of cTnI reduced the half-width of the distribution from 9.5 to 3.7 A. Similar but less pronounced decreases of the half-widths were also observed with the phosphorylated cTnI complexed with cTnC in different ionic conditions. Thus, phosphorylation of cTnI resulted in a decrease of 9-12 A in the mean distance between the sites located at the N- and C-terminal portion of cTnI. Our results indicate that phosphorylation elicits a change in the conformation of cTnI which underlies the basis of the phosphorylation-induced modulation of cTnI activity.

A study of apolipoprotein A-IV genetic polymorphism, serum lipids and lipoproteins in Beijing habitants

OBJECTIVES

Apolipoprotein (apo) A-IV genetic polymorphism and its effect on serum lipids, apoA-I and apoA-IV were investigated in order to clarify the role of apoA-IV gene during the development of hyperlipidemia.

METHODS

Four polymorphic sites (codon 127, 167, 347 and 360) of apoA-IV gene (exon 3) were determined in two groups of inhabitants in Beijing (Group I: 145 healthy individuals; Group II: 41 cases of hyperlipidemic patients and controls) by PCR-RFLP technique. Serum concentrations of HDL-cholesterol (HDL-C), HDL3-C, HDL2-C, triglyceride (TG), total cholesterol (TC), apoA-I and apoA-IV were studied among the individuals with different genotypes of apoA-IV.

RESULTS

In Group I, frequencies of the alleles were 0.648 and 0.352 in codon 127; 0.972 and 0.028 in codon 167; 0.817 and 0.183 in codon 347. Two common alleles were 0.941 and 0.059 in codon 360. The results indicated that cases of codon 127 heterozygotes had a significantly higher serum TC level and cases of apoA-IV Ser127 homozygotes kept a markedly low TG level. Both homozygotes and heterozygotes which carried apoA-IV His 360 exhibited a significantly higher concentration of TC in comparing with that of apoA-IV Gln 360 homozygotes. The data from Group II showed that the allele frequency of His 360 had a significant difference between patients and controls.

CONCLUSIONS

Certain polymorphic sites of apoA-IV gene might influence the serum lipid levels in both healthy persons and hyperlipidemic patients. His 360 polymorphic position might have a relationship with the development of hyperlipidemia.

Expression of tissue-type plasminogen activator in smooth muscle cells of injured iliac arteries in rabbits

In this experiment, expression of tissue-type plasminogen activator (t-PA) in smooth muscle cells (SMCs) was measured at different intervals after the arterial injury. In the normal iliac arteries, only low levels of t-PA activity were estimated. t-PA activity in extracts of the iliac arteries increased significantly at the 4th day after the injury, equivalent to the process that SMCs migrated from the media to the intima, and the t-PA activity was then decreased approximately to the normal level at the 7th day. Coexistent to the above data, results from in situ hybridization showed that the expression of t-PA mRNA in the intima as well as media increased also significantly at the 4th day after the arterial injury, and at the 7th day, t-PA mRNA was detected only in those SMCs locating closely adjacent to the internal elastic lamina. These results suggest that t-PA might play an important role in SMC migration following endothelial injury, and antagonism of t-PA expression and/or activity within the vessel wall might be helpful in intervening the development of restenosis following angioplasty.

[Expression of tissue-type plasminogen activator (t-PA) in smooth muscle cells of injured iliac arteries in rabbits]

To investigate the mechanism of atherogenesis and development of restenosis following angioplasty, the expression of t-PA in SMC at different intervals after the arterial injury was measured by morphological analysis, plasmin generation assay and in situ hybridization. t-PA activity of the iliac arteries was noticed to be significantly increased on the 4th day after injury, signalling the commencement of SMC migration from the media to intima, t-PA activity then decreased to approximately the normal level on the 7th day. Results from in situ hybridization also showed that the expression of t-PA mRNA in the intima and media increased significantly on the 4th day after the arterial injury, by the 7th day, t-PA mRNA was detected only in SMC located adjacent to the internal elastic lamina. These results suggest that t-PA might play an important role in SMC proliferation and migration following arterial injury.

[Apolipoprotein A-IV and transportation of cholesterol from smooth muscle cells in experimental hyperlipidemia]

The effects of apolipoprotein (apo) A-IV and apoA-IV/phosphatidylcholine (PC) liposome on cholesterol efflux from the smooth muscle cells originating from the aorta of hypercholesterolemic rabbit model and control rabbits, and on the activation of lecithin cholesterol acyltransferase (LCAT) were studied respectively. Both apoA-IV/PC and apoA-I/PC liposomes have similar efficiency as the HDL's, i.e. a strong ability to clear intracellular cholesterol and the ability to activate LCAT. There were no differences noticed on the clearance ability between apoA-IV and apoA-I or between apoA-IV/PC and apoA-I/PC liposomes. These results suggest that apoA-IV may play an important role in the process of reverse cholesterol transport and apoA-IV/PC liposome may be effectively used instead of natural HDL to prevent the development of atherosclerosis.