Tomoaki Shinkawa

Protective action of ulinastatin against cisplatin nephrotoxicity in mice and its effect on the lysosomal fragility.

The development of azotemia after cisplatin injection in mice was inhibited by ulinastatin treatment in a dose-dependent manner. Reduction in creatinine clearance and elevation in fractional excretion of sodium in mice receiving cisplatin was ameliorated by ulinastatin administration. Epithelial necrosis and hyaline cast formation in the proximal tubule were also suppressed. Ulinastatin showed no influence on the kidney platinum level after cisplatin injection. In LLC-PK1 cells, addition of ulinastatin to the incubation medium markedly reduced the release of N-acetyl-beta-D-glucosaminidase, on of the lysosomal enzymes, during hypotonic treatment only when cells were damaged with cisplatin. On the other hand, ulinastatin showed no effect on the elevation of malondialdehyde concentration in the murine kidney cortical slices after the treatment with cisplatin. These results indicate that ulinastatin has a protective effect against cisplatin nephrotoxicity, and its prevention of the increase in lysosomal fragility is a probable mechanism involved in the renal protection.

Synthesis and diuretic activity of 4,5-dihydro-6H-imidazo[4,5,1-ij]quinoline-6-one6-oxime-O-sulfonic acid derivatives

Abstract Using our previously reported 7-chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(1H)-quinolinone 4-oxime-O-sulfonic acid potassium salt 1a (M17055) as a lead, a series of tricyclic (2a-o, 3, 4, 5) and tetracyclic (6) quinolinone oxime O-sulfonic acid derivatives were synthesized by ring annulation of the 1-(2-methylbenzoyl) moiety to the quinolinone skeleton. They were compared with furosemide and compound 1a for diuretic activity in dogs; some tricyclic 4,5-dihydro-6H-imidazo[4,5,1-ij]quinoline-6-one 6-oxime-O-sulfonic acid derivatives showed diuretic activity comparable (2c,e) or superior (2m) to the lead compound 1a. These results are discussed on the basis of a comparison of the conformational and electronic characteristics of the relevant compounds with the aid of computer graphics.

A novel quinolinone diuretic, M12285, and its activation mechanism through sulfate conjugation.

The diuretic activity of a quinolinone oxime diuretic, M12285, was examined after renal arterial, i.v. and portal injection in rats. M12285 injected into the renal artery at a dose of 1 mg/kg caused no diuretic effect, whereas i.v. and portal injections induced marked diuresis dose dependently. The minimum effective dose with portal injection was lower (1 mg/kg) than that with i.v. injection (3 mg/kg) and the start of the effect was faster with portal injection. These results indicated that some metabolic modification in the liver is necessary for the diuretic activity to appear. Accordingly, we performed in situ rat liver perfusion with M12285 and obtained several metabolites. Renal arterial injection of each fractionated metabolite of M12285 revealed that all the diuretic activity derived from one of these metabolites. From IR and 1H-nuclear magnetic resonance (1HNMR) measurements, the chemical structure of this active metabolite was assumed to be a sulfate-conjugated form of M12285 at the oxime moiety. Based on this tentative chemical structure, we synthesized the oxime sulfate of M12285 (potassium salt, M17000) and confirmed the identity of IR and 1HNMR spectra. Administration of M17000 into the renal artery induced apparent diuresis in a dose-dependent manner in both rats and dogs. These results indicate that the oxime sulfate of M12285 is responsible for the diuretic activity of M12285. Therefore, we synthesized several derivatives of M17000 and confirmed their possible therapeutic value as a novel family of diuretics, namely quinolinone oxime sulfonic acids.

Uptake of human urinary trypsin inhibitor by the kidney epithelial cell line, LLC-PK1

Abstract We investigated the uptake of human urinary trypsin inhibitor (UTI) by the kidney epithelial cells, LLC-PK1. Indirect immunogold techniques with an electron microscope demonstrated the localization of UTI within the cells after an incubation during which UTI was added to the apical side. Immunoreactivities were found in endocytic vesicles, vacuoles and lysosomes. Subsequently, we tried to characterize the property of the uptake of UTI using the fluorescein isothiocyanate-labelled UTI (FITC-UTI). FITC-UTI uptake was decreased by an incubation with an excess of unlabelled UTI and showed concentration-dependent saturation. This process was markedly suppressed during the incubation at 4°C. The uptake was significantly lessened with 2,4-dinitrophenol and antimycin A, inhibitors of oxidative phosphorylation, and colchicine, a microtubule-depolymerizing agent. These results indicate that exogenous UTI is internalized by LLC-PK1 cells through an endocytic pathway. From uptake studies, it is suggested that an adsorptive process is partially involved in the mechanisms of endocytosis.

Synthesis and diuretic activity of 2,3-dihydro-4(1H)-quinolinone 4-oxime-O-sulfonic acid derivatives

Abstract The diuretic activity of 6-chloro-2,3-dihydro-1-propionyl-4(1H)-quinolinone 4-oxime 1 (M12285) was previously shown to derive from a 6-chloro-2,3-dihydro-1-propionyl-4(1H)-quinolinone 4-oxime-O-sulfonic acid salt as a rat metabolite. Thus, in the present study, the potassium salt 2 (M17000) was synthesized to unambiguously establish the structure as well as the stereochemistry of the oxime. The structural features of compounds 1 and 2 were compared with those of conventional diuretics by electrostatic potential maps. Using compound 2 as a lead compound, various quinolinone oxime sulfonic acid derivatives were synthesized and the diuretic activity for elucidation of the structure-activity relationships examined. Among the compounds synthesized, 7-chloro-2,3-dihydro-1-(2-methylbenzoyl)-4(1H)-quinolinone 4-oxime-O-sulfonic acid potassium salt 3 (M17055) showed a particularly high activity.

Cytoprotective Effect of Ulinastatin on LLC-PK1 Cells Treated with Antimycin A, Gentamicin, and Cisplatin

The cytoprotective effect of ulinastatin was studied in LLC-PK1 cells treated with antimycin A, gentamicin, or cisplatin. All of the three agents induced a concentration-dependent increase in the release of lactate dehydrogenase and a decrease in the amount of remaining protein. In the cell injury models treated with 1.5 microM antimycin A, 10 mM gentamicin, and 0.3 mM cisplatin, ulinastatin tended to show a cytoprotective effect at a concentration of 3,000 U/ml and provided a significant protective effect at 10,000 U/ml. LLC-PK1 cells treated with 0.3 mM cisplatin, bovine serum albumin, and alpha1-acid glycoprotein at a concentration of 3.54 mg/ml, which is a comparable protein concentration to that of 10,000 U/ml ulinastatin, showed no protective effect but rather enhanced cell injury. These results suggest that ulinastatin exerts a direct protective effect on LLC-PK1 cells against various renal toxicities.