Transporter-Mediated Hepatic Uptake Plays an Important Role in the Pharmacokinetics and Drug-Drug Interactions of Montelukast.

Montelukast, a leukotriene receptor antagonist commonly prescribed for treatment of asthma, is primarily metabolized by cytochrome P450 (CYP)2C8, and has been suggested as a probe substrate for investigating CYP2C8 activity in vivo. We evaluated the quantitative role of hepatic uptake transport in its pharmacokinetics and drug-drug interactions (DDIs). Montelukast was characterized with significant active uptake in human hepatocytes, and showed affinity towards organic anion transporting polypeptides (OATPs) in transfected cell systems. Single-dose rifampicin, an OATP inhibitor, decreased montelukast clearance in rats and monkeys. Clinical DDIs of montelukast were evaluated using physiologically based pharmacokinetic modeling; and simulation of the interactions with gemfibrozil-CYP2C8 and OATP1B1/1B3 inhibitor, clarithromycin-CYP3A and OATP1B1/1B3 inhibitor, and itraconazole-CYP3A inhibitor, implicated OATPs-CYP2C8-CYP2C8 interplay as the primary determinant of montelukast pharmacokinetics. In conclusion, hepatic uptake plays a key role in the pharmacokinetics of montelukast, which should be taken into account when interpreting clinical interactions.

Body fat mass and lean mass as predictors of survival in hemodialysis patients.

A higher body mass index (BMI) is a predictor of better survival in hemodialysis patients, although the relative importance of body fat and lean mass has not been examined in the dialysis population. We performed an observational cohort study in 808 patients with end-stage renal disease on maintenance hemodialysis. At baseline, fat mass was measured by dual-energy X-ray absorptiometry and expressed as fat mass index (FMI; kg/m2). Lean mass index (LMI) was defined as BMI minus FMI. During the mean follow-up period of 53 months, 147 deaths, including 62 cardiovascular (CV) and 85 non-CV fatal events, were recorded. In univariate analysis, LMI was not significantly associated with CV or non-CV death, whereas a higher FMI was predictive of lower risk for non-CV death. Analyses with multivariate Cox models, which took other confounding variables as covariates, indicated the independent associations between a higher LMI and a lower risk of CV death, as well as between a higher FMI and a lower risk of non-CV death. These results indicate that increased fat mass and lean mass were both conditions associated with better outcomes in the dialysis population.

Atherogenic lipoprotein changes in diabetic nephropathy.

Cardiovascular risk is increased in patients with diabetic nephropathy. The aim of this study was to examine the relative impacts of albuminuria and renal failure, the two important features of diabetic nephropathy, on potentially atherogenic lipoprotein changes in this condition. The subjects were 160 non-diabetic healthy controls and a total of 200 type 2 diabetes patients with various degrees of nephropathy. The diabetic patients were divided into four groups by urinary albumin/creatinine ratio (U-ACR) and serum creatinine (S-Cr) levels: DM-1 (U-ACR< 30 mg/g, N=85), DM-2 (U-ACR=30-300 mg/g, N=48), DM-3 (U-ACR > 300 mg/g, N=29) and DM-4 (S-Cr>177 micromol/l or 2.0mg/dl, N=38). Lipids in very low (VLDL), intermediate (IDL), low (LDL), and high density (HDL) lipoproteins were measured following ultracentrifugation. VLDL-cholesterol (VLDL-C) was elevated (by 73-100%) in diabetic patients and it did not differ among the stages of nephropathy. IDL-C was higher as the nephropathy stage was advanced, and the elevation was significant in the DM-3 (by 75%) and DM-4 (by 131%) groups. LDL-C was not elevated in diabetic patients and was not different among the stages of nephropathy. Reduction of HDL-C was significant in DM-1, DM-2 and DM-3 (by 12-16%) and it was more exaggerated in DM-4 (by 35%). Multiple regression analyses indicated that elevated S-Cr, but not U-ACR, was an independent factor associated with raised IDL-C and lowered HDL-C in diabetic patients. These results indicate that diabetic patients with nephropathy show multiple lipoprotein changes, and that renal failure has greater impact than albuminuria on abnormalities in IDL and HDL. These lipoprotein alterations may contribute to an increased cardiovascular risk in diabetic nephropathy, especially in diabetic renal failure.

Primary structure and autoproteolysis of brevilysin H6 from the venom of Gloydius halys brevicaudus.

The complete amino acid sequence of brevilysin H6 (H6), a zinc-protease isolated from Gloydius halys brevicaudus venom, was determined by a manual Edman degradation method. H6 has an amino-terminal pyroglutamic acid and consists of a total of 419 residues. An N-linked sugar chain is attached at Asn-181. The molecule is composed of three domains (metalloprotease, disintegrin-like and cysteine-rich domains), as commonly found in other high molecular mass metalloproteases from snake venoms. In the absence of calcium ions, H6 is autocatalytically degraded with a half-life of 47 min to give 29 and 45 kDa fragments, which correspond to residues 208-419 and 99-419 of H6, respectively. Thus, the autoproteolysis seemed to start from the cleavage of either the Leu(98)-Leu(99) or Asp(207)-Ile(208) bond. Calcium ions suppressed both the formation of the 45 kDa fragment and the rate of autoproteolysis. Calcium ions also contributed to the stability of H6 against pH, heating, urea and cysteine. More than twenty-five peptide bonds adjacent to hydrophobic residues in the metalloprotease domain were progressively cleaved during the autoproteolysis.

Purification and amino acid sequence of brevilysin L6, a non-hemorrhagic metalloprotease from Agkistrodon halys brevicaudus venom.

A non-hemorrhagic proteinase, brevilysin L6 (L6), has been purified to homogeneity from Agkistrodon halys brevicaudus venom by gel filtration and DEAE-Toyopearl 650M chromatography. It is an acidic protein with an isoelectric point of 4.8, and its molecular mass was estimated to be 21.5 kDa by SDS-PAGE. The optimum pH of L6 was about 9. EDTA and o-phenanthroline inhibited the proteolytic activity, suggesting that L6 is a metalloprotease. Cysteine also inhibited the activity of L6, but glutathione did not. The protein was stable in the pH range of 5-8.5 and below 40 degreesC. Calcium ions had no effect on the proteolytic activity of L6 or on its thermal stability. The enzyme preferentially cleaved X-Leu, X-Phe, X-Val, and X-His bonds. L6 showed weak alpha-fibrinogenase activity. The complete amino acid sequence of L6 was also determined by manual Edman degradation. L6 is a non-glycosylated single-chain polypeptide consisting of 203 residues with an N-terminal pyroglutamic acid and a calculated molecular weight of 22,713 Da. Its entire sequence is highly homologous to those of other metalloproteases from various snake venoms. A zinc-binding motif, HEXXHXXGXXH, is located at residues 143-153 in the sequence of L6.

Inhibition of the proliferation of Ehrlich ascites tumor cells by hydrostatic pressure.

The effect of high pressure on the viability of Ehrlich ascites tumor cells was examined. The tumor cells were subjected to various pressures (0.1-150 MPa) for 30 min at 37 degrees C. The viability of pressure-treated cells was examined by the dye exclusion method. The number of stained cells increased significantly at pressures above 130 MPa. In addition, the pressure-treated cells were intraperitoneally inoculated into the mice. The tumor cells which were subjected to pressures below 110 MPa proliferated in the peritoneal cavity of the mice, so that the mice died. In contrast, the mice, which were inoculated with the tumor cells treated at pressures above 130 MPa, remained alive. These results suggest that the destruction of the tumor cells begins to occur at about 130 MPa.

Granulocyte-colony stimulating factor produced by pancreatic carcinoma.

CONCLUSION: A rare case of granulocyte-colony stimulating factor (G-CSF) produced by carcinoma of the pancreas has been reported. BACKGROUND: This is the first case showing high G-CSF concentration in the aspirated tumor fluid (mucin) at its early stage without leukocytosis. METHODS: The tumor, detected incidentally in a 64-yr-old male, was removed by a distal pancreatectomy. The mass was 7.0 x 6.5 x 4.5 cm, and was histologically diagnosed as cystadenocarcinoma with prominent sarcomatous transformation. It was classified as anaplastic carcinoma. RESULTS: After 4 wk of resection, progressive leukocytosis was observed. Seven weeks after the operations, the peripheral leukocyte count increased to 126,000/mL. After 8 wk of resection, the patient died of recurrence. The serum G-CSF concentration was elevated after recurrence. The preserved mucin contained in the cystic components of the resected specimen had a G-CSF concentration higher than 2400 pg/mL. G-CSF is a known cytokine and an etiologic agent in paraneoplastic syndromes. An early diagnosis can, therefore, be made prior to the manifestation of clinical symptoms by the evaluation of the aspirated tumor fluid. This can lead to the prevention of the paraneoplastic syndrome with inhibitory cytokines in future.

Effects of intracellular pH on high pressure-induced hemolysis of anion transport inhibitor-treated erythrocytes.

Effects of anion transport inhibitors such as 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonate on hemolysis of human erythrocytes at 200 MPa were examined by changing intracellular pH (7.2-7.9). These inhibitors suppressed the hemolysis at neutral pH but enhanced it at alkaline pH. However, such an enhancement was suppressed by cross-linking of membrane proteins using diamide. From the near-UV CD spectra of band 3 and the relation between hemolysis and anion transport in intact or trypsin-treated erythrocytes, it was found that such hemolytic properties were characterized by the binding of inhibitors to band 3. In addition, spectrin detachment from the erythrocyte membrane by high pressure was considerably suppressed by DIDS treatment at neutral pH, but not by DIDS labeling at alkaline pH. These results suggest that the interaction of the cytoplasmic domain of band 3 with the cytoskeleton, which is induced by the binding of ligands to the exofacial domain of band 3, is dependent on the intracellular pH, i.e., the linking is tightened at neutral pH but relaxed at alkaline pH.

Release of spectrin-containing vesicles from human erythrocyte ghosts by dimyristoylphosphatidylcholine.

Membrane vesicles, which were released from human erythrocyte ghosts by dimyristoylphosphatidylcholine (DMPC), showed a protein composition similar to that of the erythrocyte membrane, despite a reduction of in spectrin content. The spectrin content of vesicles decreased with increasing hemoglobin concentration within ghost membranes, but increased upon exposure of hemoglobin-free ghosts to a pressure of 100 MPa. The ESR spectra of spin-labeled membrane proteins showed that membrane proteins in ghosts became unfolded at high pressure. Furthermore, spectrin-poor and protein 4.1-rich vesicles were released by DMPC from diamide-treated ghosts in which spectrin was cross-linked and stabilized. Taking into account that the spectrin tetramer is stabilized by hemoglobin [Liu and Palek (1984) J. Biol. Chem. 259, 11556-11562], these results suggest that the spectrin content of DMPC-induced vesicles from erythrocyte ghosts increases with increasing instability of the cytoskeletal network in parent cells.

Effects of anion transport inhibitors on hemolysis of human erythrocytes under hydrostatic pressure.

Effects of anion transport inhibitors on hemolysis of human erythrocytes at 200 mPa were examined. The degree of hemolysis was decreased by treating intact cells with 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS), 4,4'-dinitrostilbene-2,2'-disulfonate and pyridoxal 5'-phosphate (PLP) had little effect on the hemolysis. In contrast, the degree of hypotonic hemolysis increased upon treatment with anion transport, inhibitors. From the relationship between the hemolysis at 200 mPa and anion transport, it was found that high-pressure-induced hemolysis was suppressed by the covalent binding of anion transport inhibitors to band 3. This idea was supported by the finding that the hemolysis at 200 mPa of trypsin-treated erythrocytes was suppressed by DIDS. Furthermore, the spectrin content in vesicles which are released from erythrocyte ghost by dimyristoyl-phosphatidylcholine decreased upon DIDS labeling of band 3, but did not change upon PLP labeling. These results suggest that the interaction of the cytoplasmic domain of band 3 with spectrin, perhaps via ankyrin, is tightened by the covalent binding of bulky ligands to the exofacial domain of band 3.

Purification and characterization of a non-hemorrhagic metalloprotease from Agkistrodon halys brevicaudus venom.

A non-hemorrhagic metalloprotease (protease L4) was purified from the venom of Chinese Mamushi (Agkistrodon halys brevicaudus) by gel filtration and anion-exchange chromatography. Protease L4 has the molecular weight of 22,000 and its optimum pH was 8.5. The protein was stable in the pH range of 5-9 and below 40 degrees C. The proteolytic activity was inhibited by metal-chelating agents and some metal ions. Calcium ion activated the activity dose-dependently, but had only a minor effect on the thermal and pH stability. L4 showed fibrinogenase activity, hydrolyzing only the A alpha chain of fibrinogen. The protease cleaved preferentially at the N-terminal of Leu and His residues of some peptides.

Effects of chemical modification of membrane thiol groups on hemolysis of human erythrocytes under hydrostatic pressure.

Membrane stability of the human erythrocyte under high pressure was examined by modifying membrane SH-groups with NEM or diamide. Hemolysis at 200 MPa of chemically modified erythrocytes was significantly suppressed by the prolonged incubation of them in a reagent-free medium above 30 degrees C prior to the application of high pressure. However, there was no detectable change regarding membrane phospholipid distribution, CD spectra and SDS-PAGE of membrane proteins, and intracellular K+ concentration during the incubation. On the other hand, the data of protein-spin labeling and SH-group content showed that the SH-groups buried in membrane proteins appeared on their surface by conformational changes of membrane proteins induced during the incubation. The extraction of peripheral proteins from NEM-treated membranes in 0.1 N NaOH was considerably suppressed by the incubation. These results suggest that, upon chemical modification of membrane SH-groups, protein-protein interactions are modulated during prolonged incubation above 30 degrees C so that high pressure-induced hemolysis is suppressed.

Property and amino acid sequence of a subtilisin inhibitor from seeds of beach canavalia (Canavalia lineata).

A subtilisin inhibitor was purified from the seeds of Canavalia lineata by ammonium sulfate precipitation, ultrafiltration on a YM-30 membrane, column chromatography on DEAE-Toyopearl and SP-Toyopearl, followed by reverse-phase HPLC. The inhibitor (CLSI-I) is a low molecular weight protein (M(r) about 6500) containing no half-cystine residue, and quite stable as to extreme heat and pH treatment. CLSI-I inhibited subtilisin-type serine proteases including S. griseus alkaline protease. The amino acids of CLSI-I were sequenced by manual Edman degradation after enzymatic digestion with Achromobacter lyticus lysyl endopeptidase and Staphylococcus aureus V8 protease. CLSI-I contains 65 amino acid residues and showed a high homology to potato inhibitor I family proteins.

Hemolytic properties of Ca(2+)-treated human erythrocytes under hydrostatic pressure.

The effect of intracellular Ca2+ on high pressure-induced hemolysis of human erythrocytes was examined. Red cells were incubated with Ca2+ (0.01-1 mM) in the presence of ionophore A23187. The Ca(2+)-loaded cells were subjected to a pressure of 200 mPa. Treatment with 0.1 mM Ca2+ had the greatest suppressive effect on the hemolysis. On removal of intracellular Ca2+, red cells showed a morphological change from echinocytes to normal discocytes but the hemolysis remained unaltered. Measurement of intracellular K+ and viscosity demonstrated that the suppressive effect of Ca2+ on the hemolysis is irreversible and is largely associated with the increase of intracellular viscosity induced by K+ efflux.

Effects of cross-linking of membrane proteins on vesiculation induced by dimyristoylphosphatidylcholine in human erythrocytes.

To study the effect of cross-linking of membrane proteins on vesiculation of human erythrocytes by dimyristoylphosphatidylcholine (DMPC), red cells were treated with diamide at atmospheric pressure or 100 MPa and then incubated with DMPC in buffers of pH 6.5-8.5. Irrespective of buffer pH, the amount of released vesicles increased upon cross-linking of membrane proteins but approached the control level upon reduction of the cross-linking by dithiothreitol. Similar enhancement of vesicle release was also observed in N-ethylmaleimide-treated red cells. Hemolysis during vesiculation was observed only in red cells treated with diamide at 100 MPa. Furthermore, the composition of membrane proteins in released vesicles was analyzed by SDS-PAGE. Membrane vesicles released from intact red cells or the cells treated with diamide at atmospheric pressure contained band 3 as a major membrane protein. On the other hand, membrane vesicles from red cells treated with diamide at 100 MPa contained protein 4.1 in addition to band 3 and the orientation of these proteins was similar to that in intact cells. These results indicate that the amount and membrane protein composition of DMPC-induced vesicles are much affected by chemical modification of SH-groups in red cell membrane proteins.