Role of nuclear factor-kappaB and heme oxygenase-1 in the mechanism of action of an anti-inflammatory chalcone derivative in RAW 264.7 cells.

The synthetic chalcone 3',4',5',3,4,5-hexamethoxy-chalcone (CH) is an anti-inflammatory compound able to reduce nitric oxide (NO) production by inhibition of inducible NO synthase protein synthesis. In this work, we have studied the mechanisms of action of this compound. CH (10-30 microm) prevents the overproduction of NO in RAW 264.7 macrophages stimulated with lipopolysaccharide (1 microg ml(-1)) due to the inhibition of nuclear factor kappaB (NF-kappaB) activation. We have shown that treatment of cells with CH results in diminished degradation of the NF-kappaB-IkappaB complex leading to inhibition of NF-kappaB translocation into the nucleus, DNA binding and transcriptional activity. We also demonstrate the ability of this compound to activate NfE2-related factor (Nrf2) and induce heme oxygenase-1 (HO-1). Our results indicate that CH determines a rapid but nontoxic increase of intracellular oxidative species, which could be responsible for Nrf2 activation and HO-1 induction by this chalcone derivative. This novel anti-inflammatory agent simultaneously induces a cytoprotective response (HO-1) and downregulates an inflammatory pathway (NF-kappaB) with a mechanism of action different from antioxidant chalcones.

Effect of cyclosporine A on the tissue distribution and pharmacokinetics of etoposide.

PURPOSE: Cyclosporine A (CyA) is able to inhibit P-glycoprotein (P-gp) and to increase cytotoxicity of some anticancer drugs, including etoposide. However, the effect of CyA on the distribution of etoposide in normal tissues, which could affect their toxicity, has not been studied extensively. The purpose of this study was to investigate the effect of CyA on the pharmacokinetics and tissue distribution of etoposide in rats. METHODS: Etoposide was administered as an i.v. bolus injection (3 mg) or as a constant-rate i.v. infusion (8 mg/h) 1 h after the beginning of infusion of CyA or saline. Animals were killed 1 h after the bolus administration or after the beginning of infusion of etoposide, and plasma and tissue (testicle, muscle, heart, lung, spleen, kidney, liver, colon, and intestine) concentrations of etoposide, blood concentrations of CyA were determined. All analyses were performed by HPLC. RESULTS: Infusion of CyA (1 mg/h) in rats treated with an i.v. bolus of etoposide caused a decrease in the plasma clearance (5.4+/-2.1 vs 9.3+/-2.4 ml/min), and an increase in plasma and tissue concentrations of etoposide, but the tissue-to-plasma concentration ratios of etoposide were not affected. When etoposide was infused at a constant rate to reach a steady-state plasma level, coinfusion of CyA (10 mg/h) also caused a decrease in the plasma clearance (4.8+/-1.5 vs 9.8+/-4.7 ml/min), and an increase in plasma and tissue concentrations of etoposide. Only lung and spleen showed tissue-to-plasma ratios of etoposide significantly higher than obtained in rats coinfused with saline, but the differences were small. CONCLUSIONS: The higher tissue concentrations of etoposide caused by CyA administration were mainly a direct consequence of the higher plasma concentration resulting from a decrease in the clearance of etoposide rather than a consequence of changes in the tissue distribution of etoposide. Extrapolation of the results obtained in rats to clinical practice suggests that the coadministration of etoposide and CyA would not lead to an increase in the toxicity of etoposide if the dose were decreased in the same proportion as clearance of etoposide is decreased by CyA administration.

Pharmacokinetics of the time-dependent elimination of all-trans-retinoic acid in rats.

The time-dependent elimination kinetics of all-trans-retinoic acid (ATRA) has been associated with autoinduction of its metabolism and has led to the hypothesis that rapid development of acquired clinical resistance to ATRA may be prevented by coadministration of metabolic inhibitors. This study in rats was performed to investigate the pharmacokinetics and onset of time-dependent elimination of ATRA, with the purpose of establishing an animal model suitable for in vivo preclinical studies of compounds capable of inhibiting ATRA metabolism. After the intravenous (IV) bolus administration of single doses of ATRA (1.60 mg kg(-1) and 0.40 mg kg(-1)), the plasma concentration-time curves showed an accelerated decline at 180 minutes after dosing. The plasma clearance (Cl) of ATRA, determined after IV administration of a second dose (1.60 mg kg(-1)), at 180 minutes was greater than Cl after a single dose, thus indicating the existence of a time-dependent elimination process detectable 180 minutes after administration of the first dose. Such time-dependent elimination was confirmed by means of an IV constant-rate infusion of 0.48 mg h(-1) kg(-1) of ATRA during 10 hours. Peak plasma ATRA concentration was achieved at 180 minutes, after which the plasma concentration decreased to reach a much lower apparent steady-state drug concentration at 420 minutes. The area under the plasma concentration-time curve (AUC) obtained after oral administration of a second ATRA dose (1.60 mg kg(-1)) was approximately 8% of the AUC obtained after a single oral dose; consistent with a time-dependent increase in the elimination of ATRA, as was observed after IV administration.

Effect of cytochrome P450 inhibitors (diethyl dithiocarbamate, ketoconazole and grapefruit juice) on the pharmacokinetics of all-trans-retinoic acid.

Diethyl dithiocarbamate (DEDTC) has been reported to be a more powerful inhibitor of all-trans-retinoic acid (ATRA) in vitro metabolism than the well-established cytochrome P450 (CYP) inhibitor ketoconazole (KC). In recent years grapefruit juice (GJ) has been shown to be able to increase the oral bioavailability of several drugs by inhibiting intestinal CYP. This study investigated the in vivo effect of these CYP inhibitors on the pharmacokinetics of ATRA. The latter was administered to rats as a constant-rate intravenous (i.v.) infusion (0.48 mg h(-1) kg(-1)) during 10 h and orally (1.6 mg kg(-1)). DEDTC (320 mg kg(-1) x 2 i.v., 6.4 and 32 mg kg(-1) per os (p.o.)) did not change the ATRA concentration-time profiles, whereas KC (320 and 32 mg kg(-1) p.o.)--with i.v. infused or orally dosed ATRA--increased the mean concentration-time curve value by 160% and 78%, respectively. A high dose of DEDTC (320 mg kg(-1) p.o.) caused a marked decrease in plasma levels of ATRA. GJ (6.4 ml kg(-1) p.o.) did not affect the plasma levels of ATRA. It is concluded that the in vivo effect of CYP inhibitors (DEDTC and KC) on the elimination rate of ATRA is qualitatively different from that expected from in vitro studies.