Thiazolidinedione-dependent activation of sphingosine kinase 1 causes an anti-fibrotic effect in renal mesangial cells.

BACKGROUND AND PURPOSE: PPARγ agonists [thiazolidinediones (TZDs)] are known to exert anti-fibrotic effects in the kidney. In addition, we previously demonstrated that sphingosine kinase 1 (SK-1) and intracellular sphingosine-1-phosphate (S1P), by reducing the expression of connective tissue growth factor (CTGF), have a protective role in the fibrotic process. EXPERIMENTAL APPROACH: Here, we investigated the effect of TZDs on intracellular sphingolipid levels and the transcriptional regulation of SK-1 in mesangial cells to evaluate potential novel aspects of the anti-fibrotic capacity of TZDs. KEY RESULTS: Stimulation with the TZDs, troglitazone and rosiglitazone, led to increased S1P levels in rat mesangial cells. This was paralleled by increased SK-1 activity as a consequence of direct effects of the TZDs on SK-1 expression. GW-9662, a PPARγ antagonist, inhibited the stimulating effect of TZDs on SK-1 mRNA and activity levels and intracellular S1P concentrations. Furthermore, SK-1 up-regulation by TZDs was functionally coupled with lower amounts of pro-fibrotic CTGF. SK-1 inhibition with SKI II almost completely abolished this effect in a dose-dependent manner. Moreover, the CTGF lowering effect of TZDs was fully blocked in MC isolated from SK-1 deficient mice (SK-1(-/-) ) as well as in glomeruli of SK-1(-/-) mice compared with wild-type mice treated with TRO and RSG. CONCLUSION AND IMPLICATIONS: These data show that TZD-induced SK-1 up-regulation results in lower amounts of CTGF, demonstrating novel facets for the anti-fibrotic effects of this class of drugs.

Pharmacokinetics and metabolism of the new thromboxane A2 receptor antagonist ramatroban in animals. 1st communication: absorption, concentrations in plasma, metabolism, and excretion after single administration to rats and dogs.

The absorption, concentrations in plasma, metabolism and excretion of ramatroban ((+)-(3R)-3-(4-fluorophenylsulfonamido)-1,2,3,4-tetrahydro-9- carbazolepropanoic acid, CAS 116649-85-5, BAY u 3405) have been studied following a single intravenous, oral, or intraduodenal administration of 14C-labeled or nonlabeled compound to rats and dogs (dose range: 1-10 mg.kg-1). After intraduodenal administration of [14C]ramatroban, enteral absorption of radioactivity was rapid and almost complete both in bile duct-cannulated male rats (83%) and female dogs (95%). The oral bioavailability of ramatroban was complete in the dog but amounted to about 50% in the rat due to presystemic elimination. A marked food effect on the rate but not on the extent of absorption was observed in rats. The elimination of the parent compound from plasma occurred rapidly with total clearance of 1.2 l.h-1.kg-1 in male rats and 0.7 l.h-1.kg-1 in dogs. After oral administration to male rats AUC increased dose-proportionally between 1 and 10 mg.kg-1, whereas in Cmax an over-proportional increase was observed. Excretion of total radioactivity was fast and occurred predominantly via the biliary/fecal route in both species. The residues were low, 144 h after dosing less than 0.2% of the radioactivity remained in the body of rats. A considerable sex difference was found in rats following oral administration of ramatroban. In females a 3-fold higher AUC and a 1.7-fold longer half-life of unchanged compound, as well as 3-fold higher renal excretion of total radioactivity was observed. A marked species difference exists in the metabolism of ramatroban. In dogs the drug was almost exclusively metabolized via conjugation with glucuronic acid, whereas in rats oxidative phase I metabolism and glucuronidation were equally important. As a consequence enterohepatic circulation was much more pronounced in dogs (77%) than in rats (17% of the initial dose).

Structures of BAY o 6997 and BAY q 1313 microbial ACE inhibitors.

BAY o 6997 and BAY q 1313 are two novel ACE inhibitors produced by Streptomyces WS 464 and Streptomyces WS 1065, respectively. Their structures were elucidated by NMR and MS analysis of the inhibitors and a substance which formed on decomposition of BAY o 6997 on heating in 4 M acetic acid. Both inhibitors are composed of the same amino acids, namely His and 2-methylamino-4-aminobutyric acid. The 2-amino group of His and the 4-amino group of the 2-methylamino-4-aminobutyric acid are bridged by differently substituted ethylene moieties. As determined by gas chromatography on a chiral phase, both amino acids isolated from the total hydrolysate after derivatisation, at least in BAY o 6997, possess the L-configuration.

Biotransformation of nimodipine in rat, dog, and monkey.

14C-labelled (+/-) 3-isopropyl5-(2-methoxyethyl)1,4-dihydro-2,6-dimethyl-4- (3-nitrophenyl)-pyridine-3,5-dicarboxylate (nimodipine, Bay e 9736, Nimotop; CAS 66085-59-4) was administered orally to rat, dog, and monkey (each 5, 10, or 20 mg/kg) and intraduodenally to rat (5 mg/kg). Urine was collected over a period of 24 h (bile 6 h). Dog bile was obtained from the gall bladder 4 h after oral dosing. Rat plasma was taken 1 h p. appl. of the unlabelled compound and additionally at different times following administration of [14C]nimodipine. The metabolite profiles in the excreta were established by TLC (radioscan/autoradiography). The unchanged drug was neither detectable in urine nor in bile, but was present in rat plasma. Nimodipine was extensively metabolized. 18 metabolites were isolated by LC, HPLC, and preparative TLC and identified by comparison with the reference substances using two-dimensional TLC, HPLC, GC/radio-GC, 1H-NMR-spectroscopy, MS, and GC/MS. About 75% of the renally excreted biotransformation products, more than 50% of the metabolites present in the bile (rat, dog) and approx. 80% of the plasma metabolites (rat only) have been identified. The large number of metabolites was produced by some common biotransformation reactions: dehydrogenation of the 1,4-dihydropyridine system, oxidative ester cleavage, oxidative O-demethylation and subsequent oxidation of the resulting primary alcohol to the carboxylic acid, hydroxylation of the methyl groups at 2- or 6-position, hydroxylation of one methyl group of the isopropyl ester moiety, reduction of the aromatic nitro group, and glucuronidation as phase II-reaction.

Isolation and structural elucidation of biotransformation products from acarbose.

Following oral administration the a-glucosidase inhibitor acarbose (O-4,6-dideoxy-4-[[(1S,4R,5S,6S)-4,5,6-trihydroxy-3-(hydroxymethyl) -2-cyclohexen-1-yl]amino]-a-D-glucopyranosyl-(1----4)-O-a-D-glu copyranosyl-(1----4)-D-glucopyranose, Bay g 5421) is degraded by digestive enzymes and/or intestinal microorganism. The effect of anaerobic intestinal bacteria can be studied in an in vitro model which involves the incubation of acarbose with human or animal intestinal flora. Acarbose and nine biotransformation products can be isolated from the incubation mixture. These products were identified by nuclear magnetic resonance and mass spectrometry as so-called component 2 (loss of the terminal glucose), component 1 (loss of both glucose rings), hexose homologues of acarbose and component 2, methyl homologues of acarbose, butyric acid ester of component 2, basic disaccharide (loss of the cyclitol ring of component 2), delta-aminovaleric acid and gamma-aminobutyric acid. Following oral administration of [14C]-acarbose to healthy volunteers, 35% of the radioactivity was excreted in the form of at least 13 metabolites in the urine. Three of the metabolites were isolated by Craig countercurrent distribution and ion-pair HPLC and characterized by virtue of their nuclear magnetic resonance and mass spectra as derivatives of 4-methylpyrogallol. Two were shown to be monomethylether-monosulphates while the third was a monosulphate-monoglucuronide. The synthesis of ten reference substances and the comparison of HPLC and UV data clearly indicated that the majority of the non-isolated metabolites were also 4-methylpyrogallol derivatives. The peculiarities of the nuclear magnetic resonance and mass spectra of this type of compound are discussed.

Pharmacokinetics of acarbose. Part I: Absorption, concentration in plasma, metabolism and excretion after single administration of [14C]acarbose to rats, dogs and man.

The absorption, disposition, metabolism, and excretion of acarbose (O-4,6-dideoxy-4-[[(1S, 4R, 5S, 6S)-4,5,6-trihydroxy-3- (hydroxymethyl)-2- cyclohexen-1-yl]amino]-a-D-glucopyranosyl- (1----4)-O-a-D-glucopyranosyl- (1----4) -D-glucopyranose, Bay g 5421) have been studied following a single administration of the 14C-labelled compound to rats and dogs via different routes (intravenous, oral, intraduodenal) in the dose range of 2-200 mg.kg-1 as well as to man in a single oral dose of 200 mg. After intravenous administration [14C]acarbose was eliminated rapidly and completely via the renal route. There was no indication for a systemic metabolization of [14C]acarbose. The (renal) clearance for [14C]acarbose was in the range of the glomerular filtration rate. After oral administration [14C]acarbose was very poorly absorbed (1-2% of dose in rats and man and 4% in dogs). Additionally, up to 35% of the radioactivity of [14C]acarbose were absorbed after degradation by digestive enzymes and/or intestinal microorganisms. The delayed and biphasic absorption of the radioactivity strongly influenced the plasma concentration vs time profiles of total radioactivity. Maximum concentrations dependent on the degree of microbial degradation (dog less than rat, man) and on the intestinal transit time were reached at 1.2 h (dogs), 8 h (rats) and 14-24 h (man). The excretion of the radioactivity absorbed occurred rapidly and completely mostly via the renal route.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic fate of rioprostil in the rat--in vivo and in liver perfusion.

The metabolic fate of rioprostil is investigated in the rat--in vivo and in liver perfusions--using the tritriated drug. Seven metabolites are isolated from the perfusion model and identified by 1H-NMR spectroscopy, mass spectrometry (EI/CI/FAB) and combined GC-MS (EI/CI). Rioprostil is extensively metabolized. The main metabolite in urine (81.2%) and bile (50.1%) is the tetranor-1,16-dicarboxylic acid. The tetranor carboxylic acid is isolated in smaller amounts (8.1 and 18.2% resp.). Rioprostil itself can be detected neither in the urine nor in the bile of the in vivo studies. Thus, the metabolism of rioprostil proceeds via the biotransformation pathways of the naturally occurring prostaglandins.

Viriplanin A, a new anthracycline antibiotic of the nogalamycin group. I. Isolation, characterization, degradation reactions and biological properties.

Viriplanin A, a new anthracycline antibiotic produced by Ampullariella regularis strain SE 47, was isolated from a raw product that demonstrated activity against Herpes simplex viruses. Based on spectroscopic data, the structure of the aglycone, viriplanol, was determined, and the antibiotic was found to contain the sugar moieties 2-deoxy-L-fucose, 4-O-mesaconoyl-L-diginose and decilonitrose. In solution viriplanin A is very unstable to light. The antibiotic belongs to the nogalamycin group and is related to arugomycin and decilorubicin.

Influence of muzolimine on arterial wall elastin.

Muzolimine, 3-amino-1-(3,4-dichloro-alpha-methylbenzyl)-2- pyrazolin -5-one, an antihypertensive and diuretic drug, accumulates in the arterial tissue of rats and dogs after oral administration. Two weeks after the administration of 3 mg [14C]muzolimine, the aorta of rats contained 60-300 times more 14C-radioactivity/weight unit than the skin or tail tendon. The 14C-radioactivity was exclusively bound to the isolated aortic elastin and corresponded to 0.04% of the applied muzolimine dose. Up to ca 250 ng bound muzolimine/mg elastin was found in the aorta of dogs treated with non-labelled muzolimine for 52 weeks. The elastin-bound [14C]muzolimine was not extractable by organic solvents or by weak acids or bases but was released in a soluble form by pancreatic elastase and extracted from the elastase digest by dichloromethane. In the dichloromethane extract muzolimine was detected by HPLC and HPTLC, and was identified by mass spectrometry. Muzolimine pretreatment of rats for 2 months did not influence the elastin content of arterial tissue or [3H]glycine incorporation into aortic elastin under organ culture conditions, but after labelling the elastin with [4,5-3H]lysine, the [3H]desmosine and [3H]-isodesmosine isolated from the elastin of muzolimine-pretreated rats and incorporated under organ culture conditions was lower than that of control animals. In addition, aortic elastin of rats pretreated for 2 months with 800 ppm muzolimine in the diet was more resistant to elastase degradation. This effect might give some implications for muzolimine in the therapy of cardiovascular disorders with impaired arterial elastin metabolism.