Biomedical subjects

W C Chang

Publications and source records attributed to W C Chang.

At least 109 records · Page 6Linked to original sources

PubMed1999

Weekly 24-h infusion of high-dose 5-flurouracil and leucovorin in patients with advanced gastric cancer.

The effect of biochemical modulation of weekly high-dose 5-fluorouracil (5-FU) 24 h infusion by leucovorin (LV) in the treatment of 39 consecutive patients with advanced gastric cancer without prior chemotherapy from October 1996 to August 1997 was examined. There were 21 male and 18 female patients with a median age of 56 years. The regimen consisted of 5-FU 2600 mg/m2 and LV 150 mg administered by 24 h infusion weekly for 6 weeks followed by a 2 week break. The treatment was repeated every 8 weeks until disease progression, patient refusal or unacceptable toxicity. Placement of a central vascular device and a portable external infusion pump was required in all patients and was used for outpatient treatment. The response to treatment was evaluated every 8 weeks. A total of 395 chemotherapy treatments were given with a mean of 10 (2-24). This response rate was: 33% (12 of 36) partial response (PR) rate, 33% (12 of 36) stable disease (SD) and 33% (12 of 36) progressive disease (PD). In general, the toxicity was mild but two toxic deaths occurred, one due to neutropenic sepsis and the other due to hyperammonemia. The median time to progression was 4 months. The overall median survival was 7 months. The survivals of the PR, SD and PD were 12, 8 and 5 months, respectively. This regimen showed a modest activity against gastric cancer with acceptable toxicity. Weekly 24 h infusion of high-dose 5-FU with LV in an outpatient setting for patients with gastric cancer is feasible and deserves further study as a basis for combination therapy.

Adult↗

PubMed1999

Study of Cardiovascular Risk Intervention by Pharmacists (SCRIP): a randomized trial design of the effect of a community pharmacist intervention program on serum cholesterol risk.

OBJECTIVE: To determine the efficacy of a program of intervention by pharmacists on lipid risk management in patients at high risk for cardiovascular events. METHODS: Randomized, multicenter (44 sites in Alberta and Saskatchewan) study of community pharmacist intervention versus usual care in 1000 patients. Patients are those at high risk of vascular events (existing atherosclerotic vascular disease, or diabetes with > or = 1 other risk factor). After obtaining consent, the pharmacist calls the Project Office to randomize. Patients allocated to intervention receive a brochure and education about cardiovascular risk factors. Pharmacists also complete a physician contact form, which lists the patient's risk factors, medications, and any recommendations. A point-of-care cholesterol test is performed, the result is discussed with the patient, and it is entered on the contact form. If appropriate, the patient is asked to see his or her primary care physician for further assessment and/or treatment, and the form is faxed to the physician. Patients are followed up at two, four, eight, 12, and 16 weeks. During follow-up visits, pharmacists provide educational reinforcement and check for primary end point occurrence. Patients allocated to usual care receive the brochure only, with minimal follow-up. The primary end point is a composite of measurement of a complete lipid panel by the physician, or addition or modification of lipid-lowering drug therapy. Substudies will evaluate economics (third-party payer and pharmacy manager perspective), patient satisfaction, and quality of life. CONCLUSIONS: SCRIP (Study of Cardiovascular Risk Intervention by Pharmacists) is a unique ongoing trial that is evaluating a community pharmacist intervention designed to optimize cholesterol risk management in patients at high risk for cardiovascular events.

Aged↗

PubMed1999

Efficacy of pelvic floor rehabilitation for treatment of genuine stress incontinence.

To assess the clinical efficacy of a pelvic floor rehabilitation (PFR) program for treatment of genuine stress incontinence (GSI), we studied 72 patients with slight to moderate (2-10 g of urine loss per hour) or severe (11-50 g of urine loss per hour) GSI who underwent PFR. Objective and subjective assessments were performed before and 3, 6, 12, 18, and 24 months after the start of treatment. The overall success rate (complete cure or marked improvement in symptoms) was 61% (44/72) at the 2-year follow-up. The number of leakages per 24 hours and urine loss in the 1-hour pad test were significantly reduced, and vaginal muscle strength was significantly increased in successfully-treated patients. Significant changes were also observed in symptoms of micturition frequency and nocturia and in volume at first desire to void during cystometry in the treatment success group. Patient compliance with the exercise program was a significant predictor of success. The success rate during the 2-year follow-up period, estimated according to patient compliance, also differed significantly among groups, with good, moderate, and poor compliance. Patients experienced no serious adverse effects. These results show that the PFR program used in this study is an effective alternative to surgical intervention for the treatment of GSI in selected patients.

Adult↗

PubMed1999

Effects of the butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) on the arylamines N-acetyltransferase activity in rat white blood cells.

Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) were used to determine any effects on the N-acetyltransferase (NAT) activity in rat whole blood and white blood cells as measured by high performance liquid chromatography assay for the amounts of N-acetyl-2-aminofluorene (AAF) and 2-aminofluorene (AF). Two assay systems were performed, one with cellular cytosols, the other with intact white blood cells. The NAT activity in the whole blood and white blood cell cytosols was suppressed by BHA and BHT in a dose-dependent manner, i.e. the higher the concentrations of BHA and BHT, the higher the inhibition of NAT activity. Time-course experiments showed that NAT activity measured from the intact white blood cells was inhibited by BHA and BHT up to 24 h. The results suggest that BHA and BHT suppressed AF acetylation in rat blood with intact white blood cells.

Acetylation↗

PubMed1998

Characterization of gammaS-crystallin isoforms from a catfish: evolutionary comparison of various gamma-, gammaS-, and beta-crystallins.

gammaS-Crystallin from catfish eye lenses, formerly designated betas-crystallin in mammalian lenses, is structurally characterized in this study by cDNA cloning and sequencing. To facilitate sequence characterization of gammaS-crystallin with structural properties lying between beta- and gamma-crystallins, a cDNA mixture was constructed from the poly(A)+ mRNA isolated from catfish eye lenses, and amplification by polymerase chain reaction (PCR) was carried out to obtain nucleotide segments encoding multiple gammaS-crystallin isoforms. Sequencing several positive clones revealed that at least two distinct isoforms exist in the gammaS-crystallin class of this teleostean fish, similar to the authentic gamma-crystallin family characterized previously in species of the piscine class. Comparison of protein sequences encoded by two representative catfish gammaS1 and gammaS2 cDNAs with the published sequences of beta-, gamma-, and gammaS-crystallins from shark, carp, bullfrog, bovine, and human lenses indicates that there is about 20-50% sequence homology between catfish gammaS-crystallins and various members of the related beta/gamma-crystallin superfamily from different evolutionary classes, with a higher sequence similarity being found between catfish gammaS- and mammalian gamma-crystallins than between catfish gammaS- and bovine or carp gammaS-crystallins. Phylogenetic trees constructed on the basis of the nucleotide and protein sequence divergence among various beta-, gamma-, and gammaS-crystallins corroborate the closer relatedness of catfish gammaS- to authentic gamma-crystallin than to bovine and carp gammaS-crystallins. The results suggest that evolution of catfish gammaS-crystallins follows a different path from that of bovine and carp gammaS-crystallins and may represent a more ancient offshoot from the ancestral gamma/gammaS coding gene than carp and bovine gammaS-crystallins.

Amino Acid Sequence↗

PubMed1998

Acute coronary syndromes in the GUSTO-IIb trial: prognostic insights and impact of recurrent ischemia. The GUSTO-IIb Investigators.

BACKGROUND: Recurrent ischemia after an acute coronary syndrome portends an unfavorable outcome and has major resource-use implications. This issue has not been studied systematically among the spectrum of patients with acute coronary presentations, encompassing those with and without ST-segment elevation. METHODS AND RESULTS: We assessed the 1-year prognosis of the 12 142 patients enrolled in the GUSTO-IIb trial by the presence (n=4125) or absence (n=8001) of ST-segment elevation. This latter group was further categorized into those with baseline myocardial infarction (n=3513) or unstable angina (n=4488). We also assessed the incidence of recurrent ischemia and its impact on outcomes. Recurrent ischemia was significantly rarer in those with ST-segment elevation (23%) than in those without (35%; P<0.001). Mortality at 30 days was greater among patients with ST-segment elevation (6.1% versus 3.8%; P<0.001) but less so at 6 months; by 1 year, mortality did not differ significantly (9.6% versus 8.8%). Patients with non-ST-segment-elevation infarction had higher rates of reinfarction at 6 months (9.8% versus 6.2%) and higher 6-month (8.8% versus 5.0%) and 1-year mortality rates (11.1% versus 7.0%) than such patients who had unstable angina. CONCLUSIONS: Refractory ischemia was associated with an approximate doubling of mortality among patients with ST-segment elevation and a near tripling of risk among those without ST elevation. This study highlights not only the substantial increase in late mortality and reinfarction with non-ST-segment-elevation infarction but also the opportunities for better triage and application of therapeutic strategies for patients with recurrent ischemia.

Acute Disease↗

PubMed1998

The C-terminal segment is essential for maintaining the quaternary structure and enzyme activity of the nitric oxide forming nitrite reductase from Achromobacter cycloclastes.

We have constructed and expressed a series of mutated nitrite reductase (NIR) mutants based on the sequence of NIR from Achromobacter cycloclastes. Deleting a pentapeptide, an undecapeptide, or a heptadecapeptide from the C-terminus of NIR resulted in a series of C-terminal deletion mutated proteins designated as NIR-5, NIR-11, and NIR-17, respectively. A C-terminally extended mutated protein, NIR+8, was also produced, which contains an extra octapeptide attached to the C-terminus of the wild-type NIR. An SDS-PAGE system using tris-tricine buffer could retain the native NIR in its trimeric form, thus offering a convenient method to check the quaternary structure of NIR analogs. By using this system it was found that NIR-5 was maintained as trimer and retained 72% of wild-type enzyme activity. However, both NIR-11 and NIR-17 behaved as monomers in the SDS-PAGE and lost all their enzyme activity. Although NIR+8 maintained its trimeric structure it was enzymatically inactive. These results clearly indicate that the C-terminal undecapeptide is essential for maintaining the quaternary structure as well as the full enzymatic activity, as expected from the X-ray crystallography studies.

Alcaligenes↗

PubMed1998

HIV, but not murine leukemia virus, vectors mediate high efficiency gene transfer into freshly isolated G0/G1 human hematopoietic stem cells.

Recent studies have opened the possibility that quiescent, G0/G1 hematopoietic stem cells (HSC) can be gene transduced; lentiviruses (such as HIV type 1, HIV) encode proteins that permit transport of the viral genome into the nucleus of nondividing cells. We and others have recently demonstrated efficient transduction by using an HIV-1-based vector gene delivery system into various human cell types including human CD34(+) cells or terminally differentiated neurons. Here we compare the transduction efficiency of two vectors, HIV-based and murine leukemia virus (MuLV)-based vectors, on untreated and highly purified human HSC subsets that are virtually all in G0/G1. The HIV vector, but not MuLV vector supernatants, transduced freshly isolated G0/G1 HSC from mobilized peripheral blood. Single-step transduction using replication-defective HIV resulted in HSC that expressed the green fluorescent protein (GFP) transgene while retaining their stem cell phenotype; clonal outgrowths of these GFP+ HSC on bone marrow stromal cells fully retained GFP expression for at least 5 weeks. MuLV-based vectors did not transduce resting HSC, as measured by transgene expression, but did so readily when the HSC were actively cycling after culture in vitro for 3 days in a cytokine cocktail. These results suggest that resting HSC may be transduced by lentiviral-based, but not MuLV, vectors and maintain their primitive phenotype, pluripotentiality, and at least in vitro, transgene expression.

Antigens, CD34↗

PubMed1998

Proteolytic cleavage and activation of PAK2 during UV irradiation-induced apoptosis in A431 cells.

Exposure of mammalian cells to ultraviolet (UV) light elicits a cellular response and can also lead to apoptotic cell death. In this report, we show that a 36-kDa myelin basic protein (MBP) kinase detected by an in-gel kinase assay can be dramatically activated during the early stages of UV irradiation-triggered apoptosis of A431 cells. Immunoblot analysis revealed that this 36-kDa MBP kinase could be recognized by an antibody against the C-terminal regions of a family of p21Cdc42/Rac-activated kinases (PAKs). By using this antibody and a PAK2-specific antibody against the N-terminal region of PAK2 as studying tools, we further demonstrated that UV irradiation caused cleavage of PAK2 to generate a 36-kDa C-terminal catalytic fragment and a 30-kDa N-terminal fragment in A431 cells. The appearance of the 36-kDa C-terminal catalytic fragment of PAK2 matched exactly with the activation of the 36-kDa MBP kinase in A431 cells upon UV irradiation. In addition, UV irradiation also led to activation of CPP32/caspase-3, but not ICH-1L/caspase-2 and ICE/caspase-1, in A431 cells and the kinetics of activation of CPP32/caspase-3 appeared to correlate well with that of DNA fragmentation and of cleavage/activation of PAK2, respectively. Moreover, blockage of activation of CPP32/caspase-3 by pretreating the cells with two specific tetrapeptidic inhibitors for caspases (Ac-DEVD-cho and Ac-YVAD-cmk) could significantly attenuate the extent of cleavage/activation of PAK2 induced by UV irradiation. Collectively, the results demonstrate that cleavage and activation of PAK2 can be induced during the early stages of UV irradiation-triggered apoptosis and indicate the involvement of CPP32/caspase-3 in this process.

Amino Acid Sequence↗

PubMed1998

Characterization of phospholipase A2 (PLA2) from Taiwan Cobra: isoenzymes and their site-directed mutants.

Extracellular and secretory phospholipase A2 (PLA2), a class of phospholipid digesting enzyme, is widely distributed in animal venoms of reptiles and insects. Two cDNAs encoding PLA2 isoenzymes from Taiwan Cobra (Naja naja atra) were cloned into pQE-30 plasmid vector and expressed in Escherichia coli. The recombinant products were subjected to refolding using sulfonation under reduction/oxidation conditions with glutathione and enterokinase removal of His-tag, resulting in the active recombinant PLA2 with the same molecular masses of native enzymes as determined by mass spectrometry. The recombinant PLA2 was also shown by circular dichroism to possess a secondary structure similar to native PLA2. The enzymatic activity of the major isoenzyme (PLA2-1) is higher than the other minor isoenzyme (PLA2-2), which shows two amino acid difference from PLA2-1. Site-directed mutagenesis was used to probe the structure/function relationship of two highly conserved residues among all reported PLA2, i.e., His-47 and Asp-93. Replacement of His-47 residue by either Ala or Arg resulted in the complete loss of activity. Similarly, the mutant Asp-93 --> Asn (D93N) also retained little activity. These results suggest that both His-47 and Asp-93 are essential for the catalytic activity of PLA2. Computer graphic study, based on homology modelling, highlights the differences between native PLA2 isoenzymes and their site-directed mutants, which may account for the differences in the observed biological activity.

Base Sequence↗

PubMed1998

Identification of a lipoxygenase inhibitor in A431 cells as a phospholipid hydroperoxide glutathione peroxidase.

An endogenous lipoxygenase inhibitor, purified from the cytosol of human epidermoid carcinoma A431 cells, was analyzed by N-terminal microsequencing and mass spectrometric analysis. The inhibitor was purified by SDS-PAGE, then subjected to in-gel CNBr cleavage and trypsin digestion. The N-terminal sequence data obtained from a 6-8 kDa band of in-gel CNBr cleavage and the three isolated peptides of in-gel trypsin digestion, and the C-terminal peptide sequence from matrix-assisted laser desorption ionization mass spectrometry matched the sequence of human phospholipid hydroperoxide glutathione peroxidase. The purified inhibitor exhibited peroxidase activity using phosphatidylcholine hydroperoxides as the substrate. We therefore concluded that the lipoxygenase inhibitor present in A431 cells was a phospholipid hydroperoxide glutathione peroxidase.

Amino Acid Sequence↗

PubMed1998

Selective deamidation of recombinant human stem cell factor during in vitro aging: isolation and characterization of the aspartyl and isoaspartyl homodimers and heterodimers.

During in vitro aging, deamidation of recombinant human stem cell factor produced in Escherichia. coli was detected by HPLC analysis and by the release of soluble ammonia. The deamidation rate is very slow in buffers at low pH or at low temperatures; however, the rate is significantly accelerated in alkaline buffers such as sodium bicarbonate in combination with elevated temperatures. HPLC isolation of various deamidated forms followed by peptide mapping and mass spectrometric analyses revealed that the deamidation involves Asn10 in the sequence -T9NNV- near the N-terminus of the protein. Following peptide mapping analysis, significant amounts of aspartyl and isoaspartyl peptides were identified, indicating the conversion of asparagine into both aspartate and isoaspartate residues. As a result of spontaneous association-dissociation of stem cell factor dimer, a total of five deamidated forms, including two homodimers and three heterodimers, were detected and isolated. Cell proliferation assays showed that two rhSCF heterodimeric species, derived from dimerization between isoaspartyl and other stem cell factor monomers, retain only approximately half of the biological activity. The homodimer with isoaspartic acid in place of Asn10 is 50-fold less potent, while the aspartyl homodimer, either isolated during deamidation experiments or recombinantly prepared by site-directed mutagenesis (e.g., N10D and N10D/N11D variants), exhibits higher activity than the standard molecule. In comparison, synthetic N10A and N10E variants, though missing the deamidation site, are significantly less active. All these variants lacking the Asn10 deamidation site are relatively more stable than those containing the asparagine residue. The results indicate that the biological function and chemical stability of stem cell factor are influenced by the nature of the residue at position 10.

Amides↗

PubMed1998

Induction of 12-lipoxygenase expression by phorbol 12-myristate 13-acetate in human epidermoid carcinoma A431 cells.

Phorbol 12-myristate 13-acetate (PMA) increased the expression of 12-lipoxygenase activity and mRNA in a time-dependent manner in human epidermoid carcinoma A431 cells. The increase of 12-lipoxygenase was accompanied by the increase in protein level in microsomes prepared from A431 cells. The PMA-induced expression of 12-lipoxygenase activity and mRNA was inhibited by the treatment of cells with a protein kinase C inhibitor GF 109203X. Promoters of different DNA lengths for human 12-lipoxygenase gene were used to prepare the luciferase fusion vectors. These plasmid constructs were transiently transfected into A431 cells. Following treatment of PMA for 18 h, a 4- to 5-fold increase in luciferase reporter activity was observed in plasmids with the 5'-flanking region length of -951 bp and that of -224 bp upstream from translation starting site. A time-dependent induction of luciferase activity by PMA was found to parallel the PMA-induced enzyme activity and mRNA expression. Transient transfection with a series of 5'-deletion constructs showed that the 5'-flanking region spanning from -224 to -100 bp from translation starting site played an important role for PMA response. Gel mobility shift assay and site-directed mutagenesis indicated that two Sp1 binding sequences residing at -158 to -150 bp and -123 to -114 bp were responsible for the PMA response in activating the transcription of human 12-lipoxygenase gene.

Arachidonate 12-Lipoxygenase↗

PubMed1998

Promotional effect of N-nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (a nitrosated Maillard reaction product) in mouse fibroblast cells.

N-Nitroso-N-(3-keto-1,2-butanediol)-3'-nitrotyramine (NO-NTA) is a product of model browning system generated in the presence of sodium nitrite. The chemical structure of this compound has been confirmed by UV, mass and nuclear magnetic resonance, and infrared spectroscopy in our previous study. A two-stage transformation protocol was used to chemically transform the mouse embryo fibroblasts C3H10T1/2 cells. To initiate transformation, the cells were treated with benzo[a]pyrene (BaP) (0.1 mg/ml), and NO-NTA (0.01, 0.1 and 1 mg/ml) was employed subsequently to complete the transformation process. Malignant transformed foci were formed in BaP-initiated and NO-NTA promoted C3H10T1/2 cells after 8 wk. Cells treated with NO-NTA alone failed to induce transformation. However, cells initiated with BaP and promoted by cells initiated with BaP and promoted by NO-NTA demonstrated oncogenic properties. Cell lines transformed with NO-NTA-transformed colonies exhibited enhanced growth rate, anchorage independence and tumorigenicity in animals relative to parent cells. These results indicate that NO-NTA is a new tumour promoter and may induce tumour promotion by two-stage oncogenesis. Further studies on the mechanism of action of NO-NTA are now in progress.

Animals↗

PubMed1998

Weekly 24 h infusion of high-dose 5-fluorouracil and leucovorin in patients with biliary tract carcinomas.

From October 1995 to June 1997, 19 chemotherapy-naive patients with pathology-proven locally advanced or metastatic biliary tract carcinomas (BTC) were enrolled. The regimen consisted of 5-fluorouracil (5-FU) 2600 mg/m2 and leucovorin (LV) 150 mg by weekly 24 h infusion for 6 weeks and followed by a 2 week break. The treatment was terminated if disease progressed, the patient refused or unacceptable toxicity occurred. All patients required a Port-A catheter insertion and were treated at outpatient clinics by portable infusion pumps. There were 12 males and seven females with a median age of 62 years (range 45-77). The primary tumor sites were nine intrahepatic cholangiocarcinomas (CC), three perihilar CC, one distal BTC and six gallbladder cancers. A total of 179 chemotherapy sessions were given with a mean of 9.5 (range 2-18). Eighteen patients were evaluable for response. The response rates were: 33% (six of 18) partial response (PR), 39% (seven of 18) stable disease (SD) and 28% (five of 18) progressive disease (PD). All of the patients were evaluable for toxicity. The most common toxicities were mild fatigue (nine of 19, 47%), loss of appetite (nine of 19, 47%), skin hyperpigmentation (five of 19, 26%) and diarrhea (two of 19, 11%). Only one patient had grade IV myelotoxicity with sepsis but without treatment-related death. The median time to progression was 4 months. The overall median survival time was 7.0 months. The median survival time of the PR was not reached, SD was 8.0 months and PD 3.5 months. In conclusion, weekly high-dose 5-FU with LV by 24 h infusion in an outpatient setting for patients with BTC is effective, only mildly toxic and deserves further study.

Aged↗

PubMed1998

Effects of insulin on protein phosphorylation and protein kinase C activity in human malignant gliomas.

Modulation of protein phosphorylation activities by insulin was investigated in glioma and normal glial cells. Insulin suppressed the in vitro protein phosphorylation of glioma cells in a dose-dependent manner while it stimulated that of meningiomas, neurilemmomas and glial cells. Although gliomas and glial cells contained different species of tyrosyl phosphoproteins before treatment, they expressed similar kinds of tyrosyl phosphoproteins in response to insulin. Insulin increased the activities of casein kinase II and total protein kinase C (PKC) in glioma and normal glial cells. The membrane-bound PKC activity in U373-MG cells was elevated by insulin. The PKC isozymes, including subtypes alpha, beta, delta, epsilon and gamma, were detected in gliomas, but few were found in glial cells. Insulin down regulated the cytosolic PKC-gamma and the membrane-bound PKC-epsilon proteins in gliomas. These results indicate that an altered insulin signaling pathway exists in human gliomas, which might involve differential regulation of PKC isozymes.

Casein Kinase II↗

PubMed1997

SARPs: a family of secreted apoptosis-related proteins.

Quiescent mouse embryonic C3H/10T1/2 cells are more resistant to different proapoptotic stimuli than are these cells in the exponential phase of growth. However, the exponentially growing 10T1/2 cells are resistant to inhibitors of RNA or protein synthesis, whereas quiescent cells die upon these treatments. Conditioned medium from quiescent 10T1/2 cells possesses anti-apoptotic activity, suggesting the presence of protein(s) that function as an inhibitor of the apoptotic program. Using differential display technique, we identified and cloned a cDNA designated sarp1 (secreted apoptosis-related protein) that is expressed in quiescent but not in exponentially growing 10T1/2 cells. Hybridization studies with sarp1 revealed two additional family members. Cloning and sequencing of sarp2 and sarp3 revealed 38% and 40% sequence identity to sarp1, respectively. Human breast adenocarcinoma MCF7 cells stably transfected with sarp1 or infected with SARP1-expressing adenovirus became more resistant, whereas cells transfected with sarp2 displayed increased sensitivity to different proapoptotic stimuli. Expression of sarp family members is tissue specific. sarp mRNAs encode secreted proteins that possess a cysteine-rich domain (CRD) homologous to the CRD of frizzled proteins but lack putative membrane-spanning segments. Expression of SARPs modifies the intracellular levels of beta-catenin, suggesting that SARPs interfere with the Wnt-frizzled proteins signaling pathway.

Amino Acid Sequence↗

PubMed1997

Characterization and purification of a lipoxygenase inhibitor in human epidermoid carcinoma A431 cells.

A lipoxygenase inhibitor in the cytosolic fraction of human epidermoid carcinoma A431 cells was characterized and purified. The cytosolic inhibitor lost the inhibitory activity upon heating at 75 degrees C for 15 min or pretreating with 1 mg/ml trypsin at 37 degrees C for 60 min. Cytosol, after dialysis, lost the inhibitory activity but its inhibitory activity recovered when 1 mM GSH was added to the dialysate. The inhibitory activity of cytosol was also abolished by treatment either with 1 mM iodoacetate at 4 degrees C for 1 h or with 0.5 mM H2O2. The pI of the inhibitor was approx. 7.0. In addition to 12-lipoxygenase, the inhibitor inhibited the activities of 5-lipoxygenase and fatty acid cyclo-oxygenase in a cell-free system. The inhibitor was purified by a series of column chromatographies using CM Sephadex C-50, Sephadex G-100 SF and Mono P columns. A major 22 kDa protein was obtained that was distinct from selenium-dependent glutathione peroxidase.

Arachidonic Acid↗