Evolution of an organophosphate-degrading enzyme: a comparison of natural and directed evolution

Organophosphate-degrading enzyme from Agrobacterium radiobacter P230 (OPDA) is a recently discovered enzyme that degrades a broad range of organophosphates. It is very similar to OPH first isolated from Pseudomonas diminuta MG. Despite a high level of sequence identity, OPH and OPDA exhibit different substrate specificities. We report here the structure of OPDA and identify regions of the protein that are likely to give it a preference for substrates that have shorter alkyl substituents. Directed evolution was used to evolve a series of OPH mutants that had activities similar to those of OPDA. Mutants were selected for on the basis of their ability to degrade a number of substrates. The mutations tended to cluster in particular regions of the protein and in most cases, these regions were where OPH and OPDA had significant differences in their sequences.

[Purification and characterization of L-amino acid oxidase from Agkistrodon halys pallas venom]

L-amino acid oxidase (LAO, EC 1.4.3.2) is widely found in snake venoms and is thought to contribute to the toxicity in envenoming. By using of Sephadex G-150, DEAE-Sepharose CL-6B and FPLC Superose 12 chromatography, a protein with L-amino acid oxidase activity was purified and characterized from Agkistrodon haly Pallas venom. Its molecular mass was 57 kD as determined by SDS-PAGE analysis under both reducing and non-reducing conditions, and its pI was about 4.9. The protein catalysed the stereospecific oxidative deamination of L-amino acid substrate. It inhibited the platelet aggregation induced by ADP and collagen dose-dependently, even at low concentrations of 0.2 micromol/L and 0.08 micromol/L, respectively. The LAO had antibacterial effect to E.coli K12D31, and the effective concentration was as low as 0.03 g/L. Furthermore, the LAO showed cytotoxicity in crystal violet assay and apoptosis-inducing activity in the A549 cells. After 24h treatment with 5 mg/L LAO, the typical DNA fragmentation pattern of apoptotic cells was observed by using of agrose gel electrophoresis.

Experience with a bone bank operation and allograft bone infection in recipients at a medical centre in southern Taiwan

To assess the contamination rate of allograft bones at retrieval and the infection rate of the implanted allograft bone, we audited a bone bank retrospectively and reviewed the medical charts of allograft bone recipients between June 1999 and June 2000 at a medical centre in southern Taiwan. The bone bank did its utmost to minimize allograft contamination with hospital-acquired pathogens by adopting purposefully designed criteria for selection of donors. This protocol included sterilization with soaking of the retrieved allograft in a solution of a first-generation cephalosporin before storage and prophylaxis in recipients with first-generation cephalosporin. The contamination rates at allograft retrieval from living and cadaveric donors were 2.7% and 12.4%, respectively (P<0.001). Culture of 262 specimens taken at allograft implant revealed 12 (4.6%) positive for culture. Of the 12 patients implanted with allograft bones positive for culture, nine (75.0%) had allograft bone infection, while three (25.0%) did not. Among the 250 recipients with sterile allograft bones, four (1.6%) were found to have allograft infection. None of the cases of infection required removal of the allograft bones, and all cases were successfully treated with tailored antimicrobial therapy based on susceptibility tests on isolated bacteria. The overall infection rate was 5.0%, which compared favourably with those in other series. A prospective cohort study is needed to determine which of the varied sterilization methodologies gives the best and/or most cost-effective outcome.

Streptococcus pneumoniae bacteremia in southern Taiwan

Streptococcus pneumoniae bacteremia was diagnosed in 33 patients between June 1999 and November 2000 at the Chang Gung Memorial Hospital-Kaohsiung in southern Taiwan. Antimicrobial susceptibility and serotyping of the clinical isolates were performed. Pneumonia was diagnosed in 19 patients, primary bacteremia in 13, and meningitis in one. The most common serotypes were types 14, 3, and 23F. Fourteen (42.4%) isolates of S. pneumoniae were non-susceptible to penicillin. High antimicrobial resistance rates were found to erythromycin (81.9%), tetracycline (69.7%), clindamycin (69.7%), trimethoprim-sulfamethoxazole (33.1%), and chloramphenicol (12.1%). The mortality was 42.4% and liver cirrhosis was an independent risk factor for mortality (odds ratio = 9.998; 95% confidence interval, 1.011-98.85; p=0.049). All isolated strains were covered by 23-valent the pneumococcal vaccine. Given the increasing prevalence of penicillin non-susceptible S. pneumoniae infection in the community, ongoing periodic monitoring of the evolutionary clinical situation is needed. Results of this study suggest that patients with liver cirrhosis should be inoculated with pneumococcal vaccine.

Nosocomial blood-stream infection in patients with end-stage renal disease: excess length of hospital stay, extra cost and attributable mortality

Patients with end-stage renal disease undergoing haemodialysis are at high risk of nosocomial blood-stream infection (BSI), but data on the associated costs in this patient population are not available. Therefore, we conducted a retrospective matched (1:2) case-control study of such patients undergoing haemodialysis from January 1998 to December 1998 in a medical centre in southern Taiwan to determine the excess length of hospital stay, attributable mortality, and the extra cost caused by nosocomial BSI. The excess length of hospital stay was 30 days for cases vs. 16 days for controls (P<0.001), the mortality rate was 26.3% for cases vs. 0 for controls (P=0.003) (attributable mortality being 26.3%), and the median of overall costs was 131,584 dollars NT for cases vs. 65,282 dollars NT for controls (P<0.001). Based on these findings, we believe that an effective programme to minimize nosocomial BSI in this patient population would greatly reduce their medical and economic burdens.

Inhibitory effect of conjugated linoleic acid on linoleic acid elongation in transformed yeast with human elongase

Conjugated linoleic acid (CLA; 18:2) refers to a group of positional and geometric isomers derived from linoleic acid (LA; delta9,12-18:2). Using a growing baker's yeast (Saccharomyces cerevisiae) transformed with human elongase gene, we examined the inhibitory effect of CLA at various concentrations (10, 25, 50, and 100 microM) on elongation of LA (25 microM) to eicosadienoic acid (EDA; delta11,14-20:2). Among four available individual CLA isomers, only c9,t11- and t10,c12-isomers inhibited elongation of LA to EDA. The extent of inhibition (ranging from 20 to 60%) was related to the concentration of CLA added to the medium. In the meantime, only these two isomers, when added at 50 microM to the media, were elongated to conjugated FDA (c11,t13- and t12,c14-20:2) by the same recombinant elongase at the rate of 28 and 24%, respectively. The inhibitory effect of CLA on LA elongation is possibly due to competition between CLA isomers and LA for the recombinant elongase. Thus, results from this study and a previous study suggest that the biological effect of CLA is exerted through its inhibitory effect on delta6-desaturation as well as elongation of LA which results in a decrease in long-chain n-6 fatty acids and consequently the eicosanoid synthesis.

Effect of occlusal trauma on healing of periapical pathoses: report of two cases

AIM

To present two clinical cases and demonstrate that occlusal trauma may affect healing of periapical pathoses.

SUMMARY

Two teeth with periradicular disease did not respond successfully to conventional root canal treatment or endodontic surgery. Occlusal adjustment was finally performed on both cases. After occlusal adjustment, uncomplicated healing and periapical repair occurred in both cases. The findings in these two cases suggest that occlusal trauma may play a role in the healing of periapical pathoses.

KEY LEARNING POINTS

Occlusal trauma is positively correlated with changes in periodontal tissues. Although experiments in animals have shown that application of forces to teeth will not induce further periodontal destruction, we believe that some failures of root canal treatment may be due to the presence of occlusal trauma modulating the responses of inflamed periapical tissues or apical pathoses with persistent infection.

[Research progresses on degradation mechanism in vivo and medical applications of polylactic acid]

Polylactic acid (PLA), a kind of aliphatic polyester, is a biodegradable polymer with outstanding biocompatibility. The degradation of PLA is a complex process involving four main phenomena, namely water absorption, ester cleavage, diffusion of soluble oligomers, and solubilization of fragments. This paper emphasizes on the following aspects: 1) present understanding of the hydrolytic degradation and enzymatic degradation of PLA and autocatalystic degradation mechanism in the bulk PLA; 2) main factors influencing PLA degradation; 3) biological results; 4) the development in application of PLA.

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta). I. Nitrogen storage under nitrogen enrichment and starvation

This paper deals with the N storage of Gracilaria tenuistipitata var. liui and Ulva pertusa under ammonium enrichment and starvation. After 10 days of ammonium enrichment, ammonium NH4+, free amino acid (FAA), protein (pro), chlorophyll (Chl), phycoerythrin (PE) and total dissolved nitrogen (TDN) of the two macroalgae increased significantly. Total nitrogen (TN) increased significantly from 3.65% to 5.78% dry weight of G. tenuistipitata var. liui and 2.82% to 5.07% dw of U. pertusa, respectively. Protein and FAA were the most important N storage pools in the macroalgae. During N-starvation period, individual N pools of the two species were depleted at exponential rates. Each N pool in U. pertusa decreased more rapidly than in G. tenuistipitata, var. liui and the latter was able to sustain fast growth for more time (> 20 days) than U. pertusa. N demands for supporting growth were different between the two species, U. pertusa grew more rapidly and had higher N demands than G. tenuistipitata var. liui did.

Comparative studies on utilizing nitrogen capacity between two macroalgae Gracilaria tenuistipitata var. liui (rhodophyta) and Ulva pertusa (chlorophyta). II. Feedback controls of intracellular nitrogen pools on nitrogen uptake

The potential feedback by intracellular nitrogen pools on maximum N uptake (NH4+) rate were determined for Gracilaria tenuistipitata var. liui and Ulva pertusa. The results of correlation matrix analyzing showed that the surge uptake of ammonium seemed related to rapid changes in small intracellular pools of inorganic nitrogen or small peptide and amino acids rather than to changes in TN content of the macroalgae. The assimilation rates of nitrogen of U. pertusa and G. tenuistipitata increased slowly during N starvation and were mainly regulated by amino acids and some incorporation of amino acids into macromolecules. From ecological point of view, the fast-growing and uptaking nutrient U. pertusa is more suitable to improve water quality in integrated shrimp culture ponds in which external nutrient supplies are usually high and constant during the culture period, while G. tenuistipitata var. liui is more suitable to be polycultured in a waters with intermittence supply of nutrients.

Effect of conjugated linoleic acid on fungal delta6-desaturase activity in a transformed yeast system

Conjugated linoleic acid (CLA; 18:2), a group of positional and geometric isomers of linoleic acid (LA; 18:2n-6), has been shown to modulate immune function through its effect on eicosanoid synthesis. This effect has been attributed to a reduced production of n-6 polyunsaturated fatty acid (PUFA), the precursor of eicosanoids. Since delta6-desaturase is the rate-limiting enzyme of the n-6 PUFA production, it is our hypothesis that CLA, which has similar chemical structure to LA, interacts directly with delta6-desaturase. A unique and simple model, i.e., baker's yeast (Saccharomyces cerevisiae) transformed with fungal delta6-desaturase gene, previously established, was used to investigate the direct effect of CLA on delta6-desaturase. This model allows LA to be converted to y-linolenic acid (GLA; 18:3n-6) but not GLA to its metabolite(s). No metabolites of CLA were found in the lipids of the yeast transformed with delta6-desaturase. The inability to convert CLA to conjugated GLA was not due to the failure of yeast cells to take up the CLA isomers. CLA mixture and individual isomers significantly inhibited the activity of delta6-desaturase of the transformed yeast in vivo. Even though its uptake by the yeast was low, CLA c9,t11 isomer was found to be the most potent inhibitor of the four isomers tested, owing to its high inhibitory effect on delta6-desaturase. Since CLA did not cause significant changes in the level of delta6-desaturase mRNA, the inhibition of GLA production could not be attributed to suppression of delta6-desaturase gene expression at the transcriptional level.

Modulation of cholesterol concentration in Caco-2 cells by incubation with different n-6 fatty acids

Incorporation of exogenous cholesterol was compared in human adenocarcinoma colon cells (Caco-2) after incubation with 100 microM of either linoleic acid (LA, 18:2n-6), gamma-linolenic acid (GLA, 18:3n-6), arachidonic acid (AA, 20:4n-6) or adrenic acid (or n-6 docosatetraenoic acid, DTA, 22:4n-6). In both cells 7 days after seeding and 14 days after confluency, incubation with LA significantly raised the proportion of 18:2n-6 but not its long-chain metabolites in cellular phospholipid. Incubation with GLA increased the levels of 18:3n-6, 20:3n-6, and 20:4n-6. Incubation with AA increased the levels of 20:4n-6 and 22:4n-6, and incubation with DTA increased the levels of 22:4n-6 as well as its retro-conversion metabolite, 20:4n-6. A subsequent addition of cholesterol (180 microM) to the medium significantly raised the cellular cholesterol level but less so in the cells 7 days after seeding incubated with GLA. The increase in cellular cholesterol level was generally greater in the cells of 7 days after seeding, particularly those incubated with long-chain highly unsaturated n-6 fatty acids, than in those of 14 days after confluency. These findings suggest that the cell growth and the extent of unsaturation in cell membrane phospholipid fatty acids modulate the incorporation of the exogenous cholesterol into the Caco-2 cells.

Purification, characterization, and cDNA sequence of halysetin, a disintegrin-like/cysteine-rich protein from the venom of Agkistrodon halys Pallas

By means of DEAE-Sepharose CL-6B column chromatography, gel filtration on Sephadex G-75 and Superose 12 FPLC, halysetin, an antiplatelet protein, was purified from the venom of Agkistrodon halys Pallas with molecular mass of 29 kDa on SDS-PAGE and 23,168 Da by mass spectrometry. The p1 was about 5.0. Halysetin was devoid of phospholipase A2, fibrino-(geno)lytic, esterase, hemorrhagenic activities. Halysetin dose-dependently inhibited the aggregation of human platelet, which was stimulated by collagen with IC50 of 420 nM, but not that stimulated by ADP. The N-and C-terminal sequences of halysetin were characterized. Its full-length cDNA was cloned by RT-PCR from the total RNA extracted from the snake venom gland. It encoded a protein of 212-amino-acid residues with disintegrin-like/cysteine-rich domains and was highly homologous with SYMPs (snake venom metalloprotease).

[MDM2 gene expression in nasopharyngeal carcinoma and its relationship with p53 protein expression and EB virus latent infection]

OBJECTIVE

To define the expression levels of MDM2 gene in nasopharyngeal carcinoma (NPC) and its relationship with p53 protein expression and EB virus latent infection.

METHOD

MDM2 gene expression at mRNA and protein levels, p53 protein and EB virus DNA were detected by nonradioactive in situ hybridization (ISH), immunohistochemistry(IHC) and polymerase chain reaction (PCR) separately in 46 cases of NPC tissues and 12 cases of chronic inflammation of nasopharyngeal epithelium (CINE).

RESULT

Fourteen cases of NPC showed MDM2 mRNA and protein overexpression, 38 cases were p53 protein positive, and 43 cases were EBV-DNA positive. Neither MDM2 nor p53 protein was expressed in any case of CINE. MDM2 expression was significantly related to p53 protein expression (P < 0.05), but not to EB virus latent infection in NPC.

CONCLUSION

MDM2 gene may play an important role in the pathogenesis of NPC through interacting with p53 protein.

Reconciling conflicting findings regarding postcessation weight concerns and success in smoking cessation

Correlates of concern about weight gain following smoking cessation and self-efficacy about controlling weight gain were examined in 940 men and 1,166 women who were surveyed on 2 occasions as part of a randomized trial of work-site interventions for smoking cessation. Weight concerns were positively associated with female sex, body weight, dieting for weight control, nicotine addiction, and social encouragement to quit. Bivariate analyses replicated prior findings that elevated weight concerns are associated with a reduced likelihood of quitting smoking, at least in women. Analyses controlling for demographics, nicotine dependence, and social factors replicated prior findings that weight concerns are not negatively related to smoking cessation and that some measures of concern are positively related to cessation. These analyses suggest that conflicting findings found in this literature are due primarily to how weight concerns are defined and whether covariates like nicotine addiction are used in data analyses.

Comparison of growth and fatty acid metabolism in rats fed diets containing equal levels of gamma-linolenic acid from high gamma-linolenic acid canola oil or borage oil

We have utilized transgenic technology to develop a new source of gamma-linolenic acid (GLA) using the canola plant as a host. The aim of the present study was to compare the growth and fatty acid metabolism in rats fed equal amounts of GLA obtained from the transgenic canola plant relative to GLA from the borage plant. Young male Sprague-Dawley rats (n = 10/group) were randomized and fed a purified AIN93G diet (10% lipid by weight) containing either a mixture of high GLA canola oil (HGCO) and corn oil or a control diet containing borage oil (BO) for 6 wk. GLA accounted for 23%, of the triglyceride fatty acids in both diets. Growth and diet consumption were monitored every 2-3 d throughout the study. At study termination, the fatty acid composition of the liver and plasma phospholipids was analyzed by gas chromatography. The growth and diet consumption of the HGCO group were similar to the BO group. There were no adverse effects of either diet on the general health or appearance of the rats, or on the morphology of the major organs. There was no significant difference between the diet groups for total percentage of n-6 polyunsaturated fatty acids present in either the total or individual phospholipid fractions of liver or plasma. The relative percentage of GLA and its main metabolite, arachidonic acid, in each phospholipid fraction of liver or plasma were also similar between groups. The percentage of 18:2n-6 in liver phosphatidylethanolamine and phosphatidylinositol/serine was higher (P < 0.05) and 22:5n-6 was lower in the HGCO group than the BO group. This finding could be attributed to the higher 18:3n-3 content in the HGCO diet than the BO diet. Results from this long-term feeding study of rats show for the first time that a diet containing transgenically modified canola oil was well-tolerated, and had similar biological effects, i.e., growth characteristics and hepatic metabolism of n-6 fatty acids, as a diet containing borage oil.

[Isolation and verification of Triticum aestivum-Eremopyrum orientale addition lines and substitution lines by GISH]

Eremopyrum is a potential genus in wheat improvement. To breed T. aestivum-Er. orientale additional and substitutional lines, chromosome number of 96 BC2F3 individuals were accounted. Fifteen plants with 2n = 43 and eight plants with 2n = 44 were checked out. GISH results of the individuals with 43 chromosomes showed that they blonged to three different monosomic additions. Two disomic additions, one double-monosomic addition, one trible-monosomic addition and one monosomic addition were found in the 2n = 44 individuals. One double-monosomic substitution and one monosomic substitution were obtained. We also proved that it is relatively easier to obtain addition lines in the selfing population than to obtain double-monosomic additions.

Antimetastatic and anti-invasive ability of phospho-ascorbyl palmitate through intracellular ascorbate enrichment and the resultant antioxidant action

A lipophilic and auto-oxidation-resistant derivative of ascorbic acid (Asc), Asc-2-O-phosphate-6-O-palmitate (Asc2P6Plm), was shown to exert an invasion-inhibitory action as promptly as 30-40 min for 50% inhibition and 60-90 min for 80% inhibition after entering fibrosarcoma HT-1080 cells. Invasive inhibition of 95-97% was accomplished by Asc2P6Plm of doses exhibiting no cytotoxicity under the same conditions. Asc2P6Plm was dephosphorylated and esterolyzed to Asc, which enriched the intracellular Asc dose dependently in invasion-suppressed cells, contrasting with no detectable Asc in invasive cells fed without Asc2P6Plm. Intracellular dehydroAsc (DehAsc), unexpectedly, amounted to 1.02-1.65-fold as much as intracellular Asc, suggesting that invasive cells underwent oxidative stress, the repression of which resulted in both inhibition of tumor invasion and oxidative conversion of Asc to DehAsc. Correspondingly, intracellular oxidants fluorometrically detected with a redox indicator CDCFH were more abundant in invasive cells than in invasion-suppressed cells fed with Asc2P6Plm. Invasion inhibitory effects of Asc2P6Plm necessitated the extensive inhibition of the major gelatinases MMP-9 and MMP-2, as shown by zymography and Western blots, but did not necessitate direct expression of the metastasis suppressor gene nm23, taking as long as 6-18 h in contrast to a prompt action of Asc2P6Plm. Antimetastatic effects on melanoma B16BL6 cells were given dose dependently by intravenous administration or pretreatment with Asc2P6Plm. Thus, Asc2P6Plm is anticipated as an antimetastatic agent via the potent antioxidant activity.

Expression, purification and preliminary crystallographic studies of a hyperthermophilic esterase from Archaeoglobus fulgidus

An esterase from the hyperthermophilic archeon Archaeoglobus fulgidus has been expressed, purified and crystallized in a form suitable for structure analysis. The enzyme has a molecular mass of 35 467 Da and shows sequence similarity to other esterases known to possess the alpha/beta hydrolase fold. The crystals diffract to 2.8 A and belong to space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 155.6, b = 155.0, c = 162.4 A.

Reconciling conflicting findings regarding postcessation weight concerns and success in smoking cessation

Correlates of concern about weight gain following smoking cessation and self-efficacy about controlling weight gain were examined in 940 men and 1,166 women who were surveyed on 2 occasions as part of a randomized trial of work-site interventions for smoking cessation. Weight concerns were positively associated with female sex, body weight, dieting for weight control, nicotine addiction, and social encouragement to quit. Bivariate analyses replicated prior findings that elevated weight concerns are associated with a reduced likelihood of quitting smoking, at least in women. Analyses controlling for demographics, nicotine dependence, and social factors replicated prior findings that weight concerns are not negatively related to smoking cessation and that some measures of concern are positively related to cessation. These analyses suggest that conflicting findings found in this literature are due primarily to how weight concerns are defined and whether covariates like nicotine addiction are used in data analyses.

Cholesterol supplementation attenuates the hypocholesterolemic effect of rice bran oil in rats

Rice bran oil (RBO), when blended with safflower oil (SFO) at the ratio of 7 to 3, has been shown to lower serum cholesterol in humans consuming cholesterol. The mechanism as to how this oil blend exerts its effect is not yet clear. This study examined the effect of cholesterol supplementation on the cholesterol-lowering ability of different RBO/SFO blends. Male Sprague Dawley rats (4 wk old) were fed purified diets containing 10% fat with or without the addition of 0.5% cholesterol for 3 wk. The fat was either SFO or RBO alone, or the mixture of these two oils at the ratio of 7: 3 (7S/3R), 5:5 (5S/5R), or 3:7 (3S/7R). Without cholesterol supplementation, there were no significant differences in the serum and liver total cholesterol levels among different dietary fats. However, the HDL cholesterol level of rats fed the RBO-containing diets (especially in rats fed the 3S/7R diet) was higher than that of rats fed the diet containing SFO alone. This resulted in an increase in the ratio of HDL/total cholesterol-a desirable outcome. Supplementation of the diets with 0.5% cholesterol significantly increased the cholesterol level in both the serum and the liver. Increasing the proportion of RBO in the diet further raised the total cholesterol level in the serum whereas it reduced liver cholesterol. Then, the specific effect of the 3S/7R mixture on the ratio of HDL/total cholesterol disappeared. These findings suggest that cholesterol supplemented at the level of 0.5% in this study masked the cholesterol-lowering effect of RBO. Smaller percentages of polyunsaturated fatty acid (i.e., 18:2n-6) in the RBO-containing diets than in the SFO diet might have reduced their ability to dispose the circulating serum cholesterol into the liver.

Depletion of a fatty acid-binding protein impairs neurite outgrowth in PC12 cells

Epithelial fatty acid-binding protein (E-FABP) is up-regulated in rat dorsal root ganglia after sciatic nerve crush and in differentiating neurons during development. The present study investigates the role of E-FABP during nerve growth factor (NGF)-mediated neurite outgrowth in PC12 cells. Undifferentiated PC12 cells express low levels of E-FABP, while NGF triggers a 6- and 8-fold induction of E-FABP mRNA and protein, respectively. Up-regulation of E-FABP mRNA occurs as early as 24 h after NGF treatment and remains highly expressed over the course of several days, corresponding to NGF-mediated neurite outgrowth. Withdrawal of NGF leads to down-regulation of E-FABP mRNA and retraction of neurites. Immunofluorescence microscopy reveals E-FABP immunoreactivity in the perinuclear cytoplasm, neurites and growth cones of NGF-differentiated cells. To examine the role of E-FABP during neurite outgrowth, PC12 cells were transfected with a constitutive antisense E-FABP vector to create the E-FABP-deficient line PC12-AS. By morphometric analysis, PC12-AS cells treated for 2, 4, and 7 days with NGF exhibited significantly decreased neurite expression relative to control (mock-transfected) cells. Taken together, these data indicate that E-FABP is important in normal NGF-mediated neurite outgrowth in PC12 cells, a finding that is consistent with a potential role in axonal development and regeneration.

Anti-metastatic effect of an autooxidation-resistant and lipophilic ascorbic acid derivative through inhibition of tumor invasion

The invasion of human fibrosarcoma HT-1080 cells through Matrigel was shown to be inhibited by pretreatment with ascorbic acid (Asc) or its four derivatives, such as Asc-6-O-palmitate (Asc6Plm), Asc-2-O-phosphate (Asc2P), Asc-2-O-phosphate-6-O-palmitate (Asc2P6Plm), and Asc-5,6-benzylidene (Asc5,6Bz) of non-cytotoxic concentrations for 1 or 18 hr. Two lipophilic derivatives such as Asc6Plm and Asc2P6Plm exerted an invasiveness-inhibitory activity more markedly with 1-hr pretreatment, being a more practical index in terms of the plasma half-life, than Asc, Asc5,6Bz or Asc2P being less lipophilic. Considerably less cytotoxicity (a > 3.3-fold higher IC50 for 1-hr pretreatment) of Asc2P6Plm sufficiently compensated a slightly lower invasiveness-inhibitory activity (a < 1.8-fold higher EC50) as compared with Asc6Plm. Pulmonary metastasis of mouse melanoma B16BL6 cells injected into the tail vein was also inhibited by intravenous administration with Asc2P6Plm dose-dependently. Thus Asc2P6Plm, a lipophilicity-hydrophilicity balanced molecule protectively blockd in the autooxidation-prone moiety, is anticipated as a potent anti-metastatic agent via inhibition of tumor invasion.