Long-term follow-up of craniovertebral junction arteriovenous fistulas surgically treated by feeder obliteration: report of three cases

Craniovertebral junction arteriovenous fistulas are still rare and are viewed differently from other arteriovenous fistulas because of their specificity of location and treatment. Intravascular treatment has come to play an important role in this area, but it is still controversial in terms of safety and reliability for complete obliteration. From the anatomical point of view, direct surgery seems to be more efficient and safe than endovascular therapy based on our experience with three surgically treated cases. In all three cases, the surgical approach was intended to obliterate the feeders in the vicinity of the nidus. In 2 of 3 cases, follow-up angiography showed complete obliteration of the fistulas and one case showed partial obliteration. No recurrence of symptoms was encountered 4-7 years postoperatively. Surgical treatment is still advantageous over intravascular treatment in this type of arteriovenous malformation. Simple surgical fistulous obliteration may lead to the gradual complete disappearance of this malformation.

Diffusion tensor tractography of the Meyer loop in cases of temporal lobe resection for temporal lobe epilepsy: correlation between postsurgical visual field defect and anterior limit of Meyer loop on tractography

BACKGROUND AND PURPOSE

Visual field defects sometimes occur after temporal resection surgery. Our purpose was to evaluate the correlation between visual field defects caused by temporal lobe resection and the degree of resection of the Meyer loop, as assessed by diffusion tensor tractography.

MATERIALS AND METHODS

We examined 14 patients who underwent temporal resection for temporal lobe epilepsy. We obtained presurgical tractographies and then measured the distance between the temporal tip and the anterior limit of the Meyer loop (T-M distance). The degree of resection of the Meyer loop was defined as the distance from the anterior limit of the Meyer loop to the posterior limit of the temporal lobe resection (M-R distance). This was calculated by subtracting the T-M distance from the measured distance between the temporal tip and the posterior limit of the resection (T-R distance).

RESULTS

The mean T-M distance was 36.6 mm. The interindividual variation of the distance ranged from 30.0 to 43.2 mm. Although there was no statistically significant correlation between the extent of the visual field defect and the T-R distance, there was a statistically significant correlation between the degree of the visual field defect and the M-R distance.

CONCLUSION

The range of interindividual variation for the position of the Meyer loop was rather large, indicating that this variation is the key factor in visual field defects after temporal lobectomy, and the visual field defect appears to be predicted by presurgical tractography. Evaluation of the Meyer loop through the use of tractography seems to be a feasible method, which can be used to predict the visual field defect after temporal lobe resection.

Crystal structure of CYP105A1 (P450SU-1) in complex with 1alpha,25-dihydroxyvitamin D3

Vitamin D 3 (VD 3), a prohormone in mammals, plays a crucial role in the maintenance of calcium and phosphorus concentrations in serum. Activation of VD 3 requires 25-hydroxylation in the liver and 1alpha-hydroxylation in the kidney by cytochrome P450 (CYP) enzymes. Bacterial CYP105A1 converts VD 3 into 1alpha,25-dihydroxyvitamin D 3 (1alpha,25(OH) 2D 3) in two independent reactions, despite its low sequence identity with mammalian enzymes (<21% identity). The present study determined the crystal structures of a highly active mutant (R84A) of CYP105A1 from Streptomyces griseolus in complex and not in complex with 1alpha,25(OH) 2D 3. The compound 1alpha,25(OH) 2D 3 is positioned 11 A from the iron atom along the I helix within the pocket. A similar binding mode is observed in the structure of the human CYP2R1-VD 3 complex, indicating a common substrate-binding mechanism for 25-hydroxylation. A comparison with the structure of wild-type CYP105A1 suggests that the loss of two hydrogen bonds in the R84A mutant increases the adaptability of the B' and F helices, creating a transient binding site. Further mutational analysis of the active site reveals that 25- and 1alpha-hydroxylations share residues that participate in these reactions. These results provide the structural basis for understanding the mechanism of the two-step hydroxylation that activates VD 3.

Hepatic UDP-glucuronosyltransferases responsible for glucuronidation of thyroxine in humans

To clarify the UDP-glucuronosyltransferase (UGT) isoform(s) responsible for the glucuronidation of the thyroid hormone thyroxine (T(4)) in the human liver, the T(4) glucuronidation activities of recombinant human UGT isoforms and microsomes from seven individual human livers were comparatively examined. Among the 12 recombinant human UGT1A and UGT2B subfamily enzymes examined, UGT1A1, UGT1A3, UGT1A9, and UGT1A10 showed definite activities for T(4) glucuronidation. These UGT1A enzymes, with the exception of UGT1A10, were detected in all of the human liver microsomes examined. Interindividual differences in T(4) glucuronidation activity were observed among the microsomes from the seven individual human livers, and the T(4) glucuronidation activity was closely correlated with beta-estradiol 3-glucuronidation activity. Furthermore, Spearman correlation analysis for a relationship between the T(4) glucuronidation activity and the level of UGT1A1, UGT1A3, and UGT1A9 in the microsomes revealed that levels of UGT1A1 and UGT1A3, but not that of UGT1A9, were closely correlated with T(4) glucuronidation activity. T(4) glucuronidation activity in human liver microsomes was strongly inhibited by 26,26,26,27,27,27-hexafluoro-1alpha,23(S),25-trihydroxyvitamin D(3) (an inhibitor of UGT1A3), moderately inhibited by either bilirubin (an inhibitor of UGT1A1) or beta-estradiol (an inhibitor of UGT1A1 and UGT1A9), but not inhibited by propofol (an inhibitor of UGT1A9). These findings indicated strongly that glucuronidation of T(4) in the human liver was mediated by UGT1A subfamily enzymes, especially UGT1Al and UGT1A3, and further suggested that the interindividual differences would come from differences in the expression levels of UGT1A1 and UGT1A3 in individual human livers.

Changes in hepatic gene expression associated with the hypocholesterolaemic activity of royal jelly

Royal jelly (RJ) has various pharmacological actions, including hypolipidaemic, hypocholesterolaemic and anti-atherosclerotic effects, in experimental animals but the molecular mechanisms involved remain unclear. Here, we investigated changes in the expression of lipid metabolism-associated genes in the liver of RJ-treated mice by means of a DNA microarray technique to obtain clues to the mechanism of the hypocholesterolaemic action of RJ. We compared the hepatic gene expression profiles in three groups of mice fed a diet containing 5% RJ, a diet containing 5% RJ stored at 40 degrees C for 7 days (40-7d RJ) or a control diet which provided the same total energy as the other diets. RJ decreased gene expression of squalene epoxidase (SQLE), which is a key enzyme in cholesterol biosynthesis, and sterol regulatory element-binding protein (SREB)-1, which may be a transcriptional factor of SQLE. It increased gene expression of low-density lipoprotein receptor (LDLR), which is involved in cholesterol incorporation in liver. Thus, the hypocholesterolaemic action of RJ appears to be associated with a decrease of SQLE and an increase of LDLR in mice.

A novel mechanism for polychlorinated biphenyl-induced decrease in serum thyroxine level in rats

We have previously suggested that the decrease in the levels of serum total thyroxine (T(4)) and free T(4) by a single administration to rats of Kanechlor-500 (KC500) at a dose of 100 mg/kg is not necessarily dependent on the increase in hepatic T(4)-UDP-glucuronosyltransferase (UDP-GT). In the present study, we determined whether or not a consecutive treatment with KC500 at a relatively low dose (10 mg/kg i.p., once daily for 10 days) results in a decrease in the level of serum total T(4) and further investigated an exact mechanism for the KC500-induced decrease in the T(4). At 4 days after final treatment with KC500, the serum total T(4) and free T(4) levels were markedly decreased in both Wistar and UGT1A-deficient Wistar (Gunn) rats, whereas significant increases in hepatic T(4)-UDP-GT activity were observed in Wistar rats but not in Gunn rats. The level of serum thyroid-stimulating hormone was not significantly changed in either Wistar or Gunn rats. Clearance from serum of the [(125)I]T(4) administered to the KC500-pretreated Wistar and Gunn rats was faster than that to the corresponding control (KC500-untreated) rats. The accumulated level of [(125)I]T(4) was increased in several tissues, especially the liver, in the KC500-pretreated rats. The present findings demonstrated that a consecutive treatment with KC500 resulted in a significant decrease in the level of serum total T(4) in both Wistar and Gunn rats and further indicated that the KC500-induced decrease would occur through increase in accumulation of T(4) in several tissues, especially the liver, rather than increase in hepatic T(4)-UDP-GT activity.

Kinetic Studies of 25-Hydroxy-19-nor-vitamin D3 and 1α,25-Dihydroxy-19-nor-vitamin D3 Hydroxylation by CYP27B1 and CYP24A1

Our previous study demonstrated that 25-hydroxy-19-nor-vitamin D(3) [25(OH)-19-nor-D(3)] inhibited the proliferation of immortalized noncancerous PZ-HPV-7 prostate cells similar to 1 alpha,25-dihydroxyvitamin D(3) [1 alpha,25(OH)(2)D(3)], suggesting that 25(OH)-19-nor-D(3) might be converted to 1 alpha,25-dihydroxy-19-nor-vitamin D(3) [1 alpha,25(OH)(2)-19-nor-D(3)] by CYP27B1 before exerting its antiproliferative activity. Using an in vitro cell-free model to study the kinetics of CYP27B1-dependent 1 alpha-hydroxylation of 25(OH)-19-nor-D(3) and 25-hydroxyvitamin D(3) [25(OH)D(3)] and CYP24A1-dependent hydroxylation of 1 alpha,25(OH)-19-nor-D(3) and 1 alpha,25(OH)(2)D(3), we found that k(cat)/K(m) for 1 alpha-hydroxylation of 25(OH)-19-nor-D(3) was less than 0.1% of that for 25(OH)D(3), and the k(cat)/K(m) value for 24-hydroxylation was not significantly different between 1 alpha,25(OH)(2)-19-nor-D(3) and 1 alpha,25(OH)(2)D(3). The data suggest a much slower formation and a similar rate of degradation of 1 alpha,25(OH)(2)-19-nor-D(3) compared with 1 alpha,25(OH)(2)D(3). We then analyzed the metabolites of 25(OH)D(3) and 25(OH)-19-nor-D(3) in PZ-HPV-7 cells by high-performance liquid chromatography. We found that a peak that comigrated with 1 alpha,25(OH)(2)D(3) was detected in cells incubated with 25(OH)D(3), whereas no 1 alpha,25(OH)(2)-19-nor-D(3) was detected in cells incubated with 25(OH)-19-nor-D(3). Thus, the present results do not support our previous hypothesis that 25(OH)-19-nor-D(3) is converted to 1 alpha,25(OH)(2)-19-nor-D(3) by CYP27B1 in prostate cells to inhibit cell proliferation. We hypothesize that 25(OH)-19-nor-D(3) by itself may have a novel mechanism to activate vitamin D receptor or it is metabolized in prostate cells to an unknown metabolite with antiproliferative activity without 1 alpha-hydroxylation. Thus, the results suggest that 25(OH)-19-nor-D(3) has potential as an attractive agent for prostate cancer therapy.

Effects of Coexpression of UGT1A9 on Enzymatic Activities of Human UGT1A Isoforms

We established stable HEK293 cell lines expressing double isoforms, UGT1A1 and UGT1A9, UGT1A4 and UGT1A9, or UGT1A6 and UGT1A9, as well as stable cell lines expressing each single isoform. To analyze the protein-protein interaction between the UGT1As, we investigated the thermal stability and resistance to detergent. UGT1A9 uniquely demonstrated thermal stability, which was enhanced in the presence of UDP-glucuronic acid (>90% of control), and resistance to detergent. Interestingly, UGT1A1, UGT1A4, and UGT1A6 acquired thermal stability and resistance to detergent by the coexpression of UGT1A9. An immunoprecipitation assay revealed that UGT1A6 and UGT1A9 interact in the double expression system. Using the single expression systems, it was confirmed that estradiol 3-O-glucuronide, imipramine N-glucuronide, serotonin O-glucuronide, and propofol O-glucuronide formations are specific for UGT1A1, UGT1A4, UGT1A6, and UGT1A9, respectively. By kinetic analyses, we found that the coexpressed UGT1A9 significantly affected the kinetics of estradiol 3-O-glucuronide formation (decreased Vmax), imipramine N-glucuronide formation (increased Km and Vmax), and serotonin O-glucuronide formation (decreased Vmax) catalyzed by UGT1A1, UGT1A4, and UGT1A6, respectively. On the other hand, the coexpressed UGT1A1 increased Km and decreased the Vmax of the propofol O-glucuronide formation catalyzed by UGT1A9. The coexpressed UGT1A4 and UGT1A6 also increased the Vmax of the propofol O-glucuronide formation by UGT1A9. This is the first study showing that human UGT1A isoforms interact with other isoforms to change the enzymatic characteristics.

Role of Gln 85 of human CYP27A1 in 25-hydroxyvitamin D(3)-binding and protein folding

CYP27A1 catalyzes vitamin D(3) 25-hydroxylation and further hydroxylation at C-1alpha, C-24 or C-26(27). Molecular modeling of human CYP27A1 and docking with 25-hydroxyvitamin D(3) predicted that Gln 85 might be important for 1alpha-hydroxylation activity of CYP27A1 by forming a hydrogen bond with the 25-OH group of 25-hydroxyvitamin D(3). Expectedly, the mutant Q85H expressed in Escherichia coli showed no detectable 1alpha-hydroxylation activity toward 25-hydroxyvitamin D(3). In addition, Q85H prefers 24-hydroxylation toward 25-hydroxyvitamin D(3) whereas the wild-type prefers 26(27)-hydroxylation. A molecular modeling study also suggests that Gln 85 of CYP27A1 simultaneously interacts with Asn 107 and the hydroxyl group of the substrate. The fact that Q85L did not contain a heme molecule suggests that the hydrogen bond between Gln 85 and Asn 107 is important for protein folding of CYP27A1. Based on these results, it is possible that Gln 85 plays essential roles in both substrate-binding and protein folding.

cDNA cloning and characterization of feline CYP1A1 and CYP1A2

Deficiency of drug glucuronidation in the cat is one of the major reasons why this animal is highly sensitive to the side effects of drugs. The characterization of cytochrome P450 isoforms belonging to the CYP1A subfamily, which exhibit important drug oxidation activities such as activation of pro-carcinogens, was investigated. Two cDNAs, designated CYP1A-a and CYP1A-b, corresponding to the CYP1A subfamily were obtained from feline liver. CYP1A-a and CYP1A-b cDNAs comprise coding regions of 1554 bp and 1539 bp, and encode predicted amino acid sequences of 517 and 512 residues, respectively. These amino acid sequences contain a heme-binding cysteine and a conserved threonine. The cDNA identities, as well as the predicted amino acid sequences containing six substrate recognition sites, suggest that CYP1A-a and CYP1A-b correspond to CYP1A1 and CYP1A2, respectively. This was confirmed by the kinetic parameters of the arylhydrocarbon hydroxylase and 7-ethoxyresorufin O-deethylase activities of expressed CYPs in yeast AH22 cells and by the tissue distribution of each mRNA. However, theophylline 3-demethylation is believed to be catalyzed by CYP1A1 in cats, based on the high V(max) and low K(m) seen, in contrast to other animals. Because feline CYP1A2 had a higher K(m) for phenacetin O-deethylase activity with acetaminophen, which cannot be conjugated with glucuronic acid due to UDP-glucuronosyltransferase deficiency, it is supposed that the side effects of phenacetin as a result of toxic intermediates are severe and prolonged in cats.

[Recent studies on vitamin D metabolizing enzymes]

CYP27A1, CYP27B1, and CYP24A1 are members of the cytochrome P450 superfamily, and key enzymes of vitamin D(3) metabolism. CYP27A1 produced at least seven forms of minor metabolites including 1alpha, 25 (OH) (2)D(3) in addition to the major metabolite 25 (OH) D(3). In contrast, CYP27B1 appears to be a special enzyme to catalyze the hydroxylation at C-1alpha position of 25 (OH) D(3). Mutagenesis studies of CYP27B1 revealed the amino acid residues involved in substrate binding or interaction between CYP27B1 and adreno-doxin. On CYP24A1-dependent metabolism, remarkable metabolic processes of 1alpha, 25 (OH) (2)D(3) were observed. Rat CYP24A1 catalyzed six sequential monooxygenation reactions that convert 1alpha, 25 (OH) (2)D(3) into calcitroic acid. In addition to the C-24 oxidation pathway, human CYP24A1 catalyzed also C-23 oxidation pathway to produce 1alpha, 25 (OH) (2)D(3)-26, 23-lactone. Surprisingly, more than 70% of the vitamin D metabolites observed in a living body were found to be the products formed by the activities of CYP27A1, CYP27B1, and CYP24A1. In addition to the mitochondrial P450s, microsomal P450s also play important roles in vitamin D metabolism. Recent reports suggest that human microsomal CYP2R1 is more important than CYP27A1 as a vitamin D 25-hydroxylase. The decline in bone mineral density that occurs after long-term treatment with some antiepileptic drugs appears to be due to the increased 1alpha, 25 (OH) (2)D(3) metabolism by CYP3A4. Some vitamin D analogs are good substrates for CYP3A1 while CYP24A1 is responsible for metabolism of most of vitamin D analogs.

Interaction between mitochondrial CYP27B1 and adrenodoxin: role of arginine 458 of mouse CYP27B1

A molecular modeling study of CYP27B1 suggests that Arg458 of mouse CYP27B1 is involved in interaction with adrenodoxin (ADX). Thus, we generated CYP27B1 mutants R458K and R458Q and revealed their enzymatic properties. Substrate-induced difference spectra and K(m) values for 1alpha-hydroxylation of 25(OH)D3 indicate that the replacement of Arg458 with Lys or Gln does not affect substrate binding. However, these mutants showed remarkable decreases of both kcat values and the ratio of product formation to NADPH oxidation (coupling efficiency). A high K(m) value of R458Q for ADX concentration and a decrease of rate constant of the first electron transfer seem reasonable considering that the conversion from Arg to noncharged Gln abolishes salt-bridge formation with the acidic residue of ADX. On the other hand, R458K showed atypical kinetics for ADX concentration with Hill's constant of 2.0 and high catalytic activity at high ADX concentration by increase of coupling efficiency. These results suggest that conformational change of R458K by binding the two ADX molecules is essential for 1alpha-hydroxylation of 25(OH)D3. On the other hand, binding one ADX molecule is sufficient for the conformational change of the wild-type CYP27B1, judging from its Michaelis-Menten-type kinetics for ADX concentration with high coupling efficiency. These results suggest that ADX functions as an effector for the oxygen transfer reaction in addition to being an electron donor for CYP27B1.

Enzymatic properties of human CYP2W1 expressed in Escherichia coli

The human genome project revealed a new member of the P450 family 2, CYP2W1, which has orthologous form in other vertebrate species, suggesting CYP2W1's significant physiological function. Recently, it was reported that CYP2W1 can metabolize arachidonic acid. In this study, we isolated human CYP2W1 cDNA, and successfully expressed truncated CYP2W1 lacking N-terminal 20 amino acids in Escherichia coli cells. In the bicistronic expression system for human CYP2W1 and NADPH-P450 reductase, the formation of blue pigment, indigo, was observed in bacterial cultures. Based on this result, we revealed that CYP2W1 catalyzes the oxidation of indole. In addition, CYP2W1 showed monooxygenase activity towards 3-methylindole and chlorzoxazone. However, no activity was observed towards fatty acids including arachidonic acid. Further analysis using an E. coli expression system will reveal substrate specificity of CYP2W1 and why this P450 isoform is universally conserved in vertebrates.

Structure-function analysis of vitamin D 24-hydroxylase (CYP24A1) by site-directed mutagenesis: amino acid residues responsible for species-based difference of CYP24A1 between humans and rats

Our previous studies revealed the species-based difference of CYP24A1-dependent vitamin D metabolism. Although human CYP24A1 catalyzes both C-23 and C-24 oxidation pathways, rat CYP24A1 shows almost no C-23 oxidation pathway. We tried to identify amino acid residues that cause the species-based difference by site-directed mutagenesis. In the putative substrate-binding regions, amino acid residue of rat CYP24A1 was converted to the corresponding residue of human CYP24A1. Among eight mutants examined, T416M and I500T showed C-23 oxidation pathway. In addition, the mutant I500F showed quite a different metabolism of 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] from both human and rat CYP24A1. These results strongly suggest that the amino acid residues at positions 416 and 500 play a crucial role in substrate binding and greatly affect substrate orientation. A three-dimensional model of CYP24A1 indicated that the A-ring and triene part of 1alpha,25(OH)2D3 could be located close to amino acid residues at positions 416 and 500, respectively. Our findings provide useful information for the development of new vitamin D analogs for clinical use.

Biodegradation of dioxins by recombinant Escherichia coli expressing rat CYP1A1 or its mutant

Among polychlorinated dibenzo-p-dioxins (PCDDs), 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TetraCDD) is the most toxic one. Recently, we reported that rat CYP1A1 mutant, F240A, expressed in yeast showed metabolic activity toward 2,3,7,8-TetraCDD. In this study, we successfully expressed N-terminal truncated P450s (Delta1A1 and DeltaF240A) in Escherichia coli cells. Kinetic analysis using membrane fractions prepared from the recombinant E. coli cells revealed that DeltaF240A has enzymatic properties similar to F240A expressed in yeast. The metabolism of PCDDs by recombinant E. coli cells expressing both DeltaF240A and human NADPH-P450 reductase was also examined. When 2,3,7-TriCDD was added to the E. coli cell culture at a final concentration of 10 microM, approximately 90% of the 2,3,7-TriCDD was converted into multiple metabolites within 8 h. These results indicate the possible application of prokaryotic cells expressing DeltaF240A to the bioremediation of PCDD-contaminated soil.

A hypopharyngeal gland protein of the worker honeybee Apis mellifera L. enhances proliferation of primary-cultured rat hepatocytes and suppresses apoptosis in the absence of serum

The worker honeybees of Apis mellifera L. age-dependently change from nurse bees which take care of their brood to forager bees which collect for nectar and convert it into honey during their lifespan of 30-40 days. A 56-kDa protein (p56kP-4) was shown to be present only in the nurse-bee hypopharyngeal gland. Here, we investigated the physiological effects of p56kP-4 on primary-cultured rat hepatocytes in the absence of serum. The p56kP-4 recombinant protein expressed in Escherichia coli significantly stimulated hepatocyte DNA synthesis and protected cells from apoptosis induced by serum deprivation. It also activated mitogen-activated protein kinase, as well as protein kinase B, which is a key regulator of cell survival. These findings suggest that p56kP-4 has a growth factor-like action on primary-cultured rat hepatocytes.

The use of ultrasonic bone curettes in spinal surgery

OBJECT

The author describes a clinical applications, procedure, and efficacy of ultrasonic bone curette (UBC) (bone-removal bar) in spinal surgery.

METHODS

From July 2003 to March 2005, we operated on 98 consecutive spinal disorders by using UBC, Sonopet UST-2001; Chiari type-1 malformation (6 cases), cervical disorders (64 cases), thoracic disorders (5 cases), and lumbar disorders (23 cases). The instrument was devoid of any spinning parts, and the risk of grabbing cotton pledgets and damaging normal tissue was thereby avoided. Support from assistants for irrigation and suction was not required.

FINDINGS

In this series, there were no iatrogenically induced injuries for example, direct or heat damage to surrounding soft tissues, including nerves, vessels, spinal cord, and dura matter. Considering potential complications of mechanical injuries by ultrasonic technique, intermittent usage and cotton protection during use under an operating microscope are recommended. We found that the ultrasonic device is easy to handle; however, it is time consuming for removing a large amount of bone and ossified lesions. Therefore, we recommend the combined use of this method with standard drilling.

CONCLUSIONS

This system appears to be versatile, safe, and efficient in spinal surgery and could be improved by the development of a better handpiece.

Platelets treated with ticlopidine are less reactive to unusually large von Willebrand factor multimers than are those treated with aspirin under high shear stress

Much attention has recently been focused on the interaction between unusually large von Willebrand factor multimers (UL-VWFM) and platelets under high shear stress in pathological thrombus formation. The antiplatelet drugs acetylsalicylic acid (aspirin) and a thienopyridine derivative (ticlopidine) are commonly used to treat cerebral ischemia but exert different effects on high-shear-stress-induced platelet aggregation (H-SIPA) in the plasma. To examine the effects of these drugs in the absence of plasma factors, we studied H-SIPA using washed platelets (WPs) and purified UL-VWFM. WPs were prepared from the blood of 9 aspirin-treated and 11 ticlopidine-treated patients with cerebral ischemia, and H-SIPA in the presence of UL-VWFM was measured using a cone plate aggregometer. Plasma levels of VWF antigen with its multimer analysis, ristocetin cofactor and VWF-cleaving protease (ADAMTS13) activity were also measured. Forty-six healthy volunteers from 2 age groups, 20-40 years (n=20) and 41-60 years old (n=26), were also tested as controls. H-SIPA was significantly inhibited for ticlopidine-treated platelets, but it was observed to a lesser extent for aspirin-treated platelets. For both groups, no difference in the plasma levels of VWF antigen, ristocetin cofactor and ADAMTS13 activity was noted. All patients possessed UL-VWFM, and it was detected in healthy volunteers with increasing frequency with increasing age. Under plasma-free conditions, platelets from aspirin-treated patients exhibit marginal but significant inhibition of H-SIPA. Furthermore, the presence of UL-VWFM in the plasma of patients and normal volunteers is directly related to their age rather than being a consequence of underlying disease.

Monospecific Antipeptide Antibodies Against Human Hepatic UDP-Glucuronosyltransferase 1A Subfamily (UGT1A) Isoforms

Expression of UDP-glucuronosyltransferases (UGT) in mammals is thought to be regulated in both a tissue- and developmental-specific manner. Furthermore, induction of genes encoding UGT occurs after exposure to xenobiotics including drugs, environmental pollutants and dietary compounds. In human, isoforms of UGT 1A subfamily catalyze the glucuronidation of a greater proportion of drugs, suggesting that the expression of UGT1A isoforms is responsible for the clearance of a diverse range of drugs. To analyze the expression of human UGT1A isoforms, we have developed polyclonal antibodies against specific peptide regions within the isoforms (UGT1A1, 1A3, 1A4, 1A6 and 1A9). The prepared antipeptide antibodies were found to be highly monospecific for each UGT1A isoform and no cross-reactivity with UGT2B isoforms was detected. Analysis of UGT1A protein levels in hepatic microsomes using these antibodies demonstrated interindividual differential expression of each isoform. These highly specific antipeptide antibodies provide an important tool to analyze tissue distribution and interindividual expression levels of human UGT1As.

Cytochrome P450 2E polymorphism in feline liver

Only one isoform of cytochrome P450 (CYP) 2E subfamily was known in human and various animals. Three cDNAs corresponding to CYP 2E subfamily members (CYP2E-a, CYP2E-b and CYP2E-c) were obtained from feline liver. These cDNAs each had a 1488-bp nucleotide coding region encoding a predicted amino acid sequence of 495 residues. Eleven amino acid substitutions were observed between CYP2E-a and CYP2E-b, but only one substitution between CYP2E-b and CYP2E-c. The CO difference spectrums about 450 nm wave length and similar values of Vmax and Km of 6-hydoxygenase activity toward chlorzoxazone were observed in all three isoforms expressed in AH22 yeast cells. By PCR-RFLP, mRNA of the CYP2E-a was found to be expressed in liver, mononuclear cells, kidney, lung, stomach, intestine and pancreas, whereas CYP2E-b and CYP2E-c were expressed mainly in the liver and mononuclear cells. Expression of CYP2E-a was observed in the livers of all felines tested, but CYP2E-b and CYP2E-c were not expressed in all cats. The sequences of two different introns between exons I and II and between exons VII and VIII were obtained in genomic DNA from the feline liver. Based on these results, we conclude that cats have two highly similar CYP2E genes.

Practical application of mammalian cytochrome P450

Heterologous expression systems play an important role in the analysis of structure-function relationships of mammalian P450s. In addition, these expression systems allow practical application of mammalian P450s. Genetically engineered fused enzymes between mammalian P450 and yeast NADPH-P450 reductase have possible applications in bioconversion processes. Combined use of techniques reported thus far could produce steroid hormones in the recombinant yeast cells harboring four P450 species, CYP11A1, CYP17A1, CYP21B1 and CYP11B1. In an Escherichia coli expression system, the technology of the construction of the mitochondrial P450 electron transport chain has been established. The recombinant E. coli cells expressing CYP27B1, adrenodoxin and NADPH-adrenodoxin reductase would be applicable to a bioconversion process to produce 1alpha,25-dihydroxyvitamin D3. We also demonstrated the usefulness of heterologous expression systems for human liver microsomal P450s for the prediction of drug metabolism in the human body. Microsomal fractions prepared from recombinant yeast, insect and mammalian cells are commercially available and play an important role in preclinical drug development. Application of mammalian P450 to bioremediation with genetic engineering has also been developed. Thus, mammalian P450s appear to have great potential for a wide range of practical applications.

Intestinal and hepatic CYP3A4 catalyze hydroxylation of 1alpha,25-dihydroxyvitamin D(3): implications for drug-induced osteomalacia

The decline in bone mineral density that occurs after long-term treatment with some antiepileptic drugs is thought to be mediated by increased vitamin D(3) metabolism. In this study, we show that the inducible enzyme CYP3A4 is a major source of oxidative metabolism of 1alpha,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)] in human liver and small intestine and could contribute to this adverse effect. Heterologously-expressed CYP3A4 catalyzed the 23- and 24-hydroxylation of 1,25(OH)(2)D(3). No human microsomal cytochrome P450 enzyme tested, other than CYP3A5, supported these reactions. CYP3A4 exhibited opposite product stereochemical preference compared with that of CYP24A1, a known 1,25(OH)(2)D(3) hydroxylase. The three major metabolites generated by CYP3A4 were 1,23R,25(OH)(3)D(3), 1,24S,25(OH)(3)D(3), and 1,23S,25(OH)(3)D(3). Although the metabolic clearance of CYP3A4 was less than that of CYP24A1, comparison of metabolite profiles and experiments using CYP3A-specific inhibitors indicated that CYP3A4 was the dominant source of 1,25(OH)(2)D(3) 23- and 24-hydroxylase activity in both human small intestine and liver. Consistent with this observation, analysis of mRNA isolated from human intestine and liver (including samples from donors treated with phenytoin) revealed a general absence of CYP24A1 mRNA. In addition, expression of CYP3A4 mRNA in a panel of duodenal samples was significantly correlated with the mRNA level of a known vitamin D receptor gene target, calbindin-D9K. These and other data suggest that induction of CYP3A4-dependent 1,25(OH)(2)D(3) metabolism by antiepileptic drugs and other PXR ligands may diminish intestinal effects of the hormone and contribute to osteomalacia.