Molecular mechanisms of biliary excretion of cefditoren and the effects of cefditoren on the expression levels of hepatic transporters

Pharmacokinetic changes of cefdinir and cefditoren and its molecular mechanisms in acute kidney injury in rats

OBJECTIVES

Acute kidney injury (AKI) was a common organ damage that often occurred after cisplatin. This study was aimed at investigating the pharmacokinetic changes of cefdinir and cefditoren in AKI rats, and elucidating the possible molecular mechanisms.

METHODS

The renal injury model was established by intraperitoneal injection of cisplatin (12 mg/kg). Plasma creatinine, blood urea nitrogen, the mRNA expression of Kim-1, hematoxylin and eosin staining and Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling (TUNEL) assay were used to measure the degree of renal damage. On this basis, the pharmacokinetic changes of cefdinir and cefditoren were investigated in normal and AKI rats. RT-PCR and Western blot were performed to clarify the molecular mechanisms for the changes in the related transporters expression.

KEY FINDINGS

The cumulative urinary excretion of cefdinir was significantly decreased and the plasma concentration was remarkably increased in AKI rats. The expression of organic anion transporter 1 (Oat1) and Oat3 in kidney was decreased. However, pharmacokinetics of cefditoren was not influenced. The expression of organic anion-transporting polypeptide 1a1 (Oatp1a1), Oatp1a4, Oatp1b2 and multidrug resistance-associated protein 2 (Mrp2) in liver was unchanged in AKI rats.

CONCLUSIONS

The molecular mechanism of decreased expression of Oat1 and Oat3 was achieved through activating p53, and then increasing the expression of Bax and Caspase-3 and down regulating Bcl-2 in AKI rats. On this basis, the cumulative urinary excretion of cefdinir was significantly decreased and the plasma concentration of cefdinir was remarkably increased in AKI rats. However, the pharmacokinetic changes of cefditoren were not observed. Accordingly, cephalosporin antibiotics such as cefditoren should be firstly selected for the treatment in patients with AKI in clinic.

Liver uptake of cefditoren is mediated by OATP1B1 and OATP2B1 in humans and Oatp1a1, Oatp1a4, and Oatp1b2 in rats

OATPs and Oatps mediated liver uptake of cefditoren in humans and in rats.

Targeting P-glycoprotein expression and cancer cell energy metabolism: combination of metformin and 2-deoxyglucose reverses the multidrug resistance of K562/Dox cells to doxorubicin

P-glycoprotein (P-gp) is one of the major obstacles to efficiency of cancer chemotherapy. Here, we investigated whether combination of metformin and 2-deoxyglucose reverses the multidrug resistance (MDR) of K562/Dox cells and tried to elucidate the possible mechanisms. The combination of metformin and 2-deoxyglucose selectively enhanced the cytotoxicity of doxorubicin against K562/Dox cells. Metformin was not a substrate of P-gp but suppressed the elevated level of P-gp in K562/Dox cells. The downregulation of P-gp may be partly attributed to the inhibition of extracellular signal-regulated kinase pathway. The addition of 2-deoxyglucose to metformin initiated a strong metabolic stress in both K562 and K562/Dox cells. Combination of metformin and 2-deoxyglucose inhibited glucose uptake and lactate production in K562 and K562/Dox cells leading to a severe depletion in ATP and a enhanced autophagy. Above all, P-gp substrate selectively aggravated this ATP depletion effect and increased cell apoptosis in K562/Dox cells. In conclusion, metformin decreases P-gp expression in K562/Dox cells via blocking phosphorylation of extracellular signal-regulated kinase. P-gp substrate increases K562/Dox cell apoptosis via aggravating ATP depletion induced by combination of metformin and 2-deoxyglucose. Our observations highlight the importance of combination of metformin and 2-deoxyglucose in reversing multidrug resistance.

OATP and MRP2-mediated hepatic uptake and biliary excretion of eprosartan in rat and human

BACKGROUND

Eprosartan is an angiotensin II receptor antagonist, used in the treatment of hypertension and heart failure in clinical patients. The objective of this study was to clarify the mechanism underlying hepatic uptake and biliary excretion of eprosartan in rats and humans.

METHODS

Perfused rat liver in situ, rat liver slices, isolated rat hepatocytes and human organic anion-transporting polypeptide (OATP)-transfected cells in vitro were used in this study.

RESULTS

Extraction ratio of eprosartan was decreased by rifampicin in perfused rat livers. Uptake of eprosartan in rat liver slices and isolated rat hepatocytes was significantly inhibited by Oatp modulators such as ibuprofen, digoxin, rifampicin and cyclosporine A, but not by tetraethyl ammonium or p-aminohippurate. Uptake of eprosartan in rat hepatocytes indicated a saturable process. Although uptake of eprosartan in OATP1B3-human embryonic kidney cells (HEK) 293 cells was not observed, significant differences in cellular accumulations of eprosartan between vector- and OATP1B1-Madin-Darby canine kidney strain (MDCK) II cells were found in transcellular transport study. Moreover, cumulative biliary excretion rate of eprosartan in the presence of probenecid (Multidrug resistance-associated protein 2 (Mrp2) inhibitor) was significantly decreased in perfused rat livers. Vectorial basal-to-apical transport of eprosartan was also observed in OATP1B1/MRP2 double transfectants.

CONCLUSIONS

Eprosartan was transported by multiple Oatps (at least Oatp1a1 and Oatp1a4)/Mrp2 in rat and OATP1B1/MRP2, at least, in human.

Involvement of organic anion-transporting polypeptides in the hepatic uptake of dioscin in rats and humans

The objective of this study was to clarify the mechanism underlying hepatic uptake of dioscin (diosgenyl 2,4-di-O-a-L-rhamnopyranosyl-p-D-glucopyranoside), an herbal ingredient with antihepatitis activity, in rats and humans. The liver uptake index (LUI) in vivo, perfused rat liver in situ, rat liver slices, isolated rat hepatocytes, and human organic anion-transporting polypeptide (OATP)-transfected cells in vitro were used to evaluate hepatic uptake of dioscin. Values of 11.9% ± 1.6% and 15.0% ± 0.9% of dose for uptake of dioscin were observed by LUI in vivo and perfused rat livers in situ, respectively. The time course of dioscin uptake by rat liver slices was temperature-dependent. Uptake of dioscin by rat liver slices and isolated rat hepatocytes was inhibited significantly by Oatp modulators, such as ibuprofen (Oatp1a1 inhibitor), digoxin (Oatp1a4 substrate), and glycyrrhizic acid (Oatp1b2 inhibitor), but not by TEA or p-aminohippurate. Uptake of dioscin in rat hepatocytes and OATP1B3-human embryonic kidney (HEK) 293 cells indicated a saturable process with a Km of 3.75 ± 0.51 μM and 2.08 ± 0.27 μM, respectively. (-)-Epigallocatechin gallate, cyclosporin A, rifampicin, and telmisartan inhibited transport of dioscin in OATP1B3-HEK293 cells. However, transcellular transport of dioscin in OATP1B1- or OATP1B1/multidrug resistance-associated protein 2-Madin-Darby canine kidney strain II cells was not observed. These results indicate that hepatic uptake of dioscin is involved in OATP1B3 in humans, and multiple Oatps might participate in this process in rats.

The elimination of MTC-220, a novel anti-tumor agent of conjugate of paclitaxel and muramyl dipeptide analogue, in rats

PURPOSE

MTC-220, a conjugate of paclitaxel and muramyl dipeptide analogue, was reported to exhibit anti-tumor ability and anti-metastatic effect. The aim of present study was to investigate the elimination of MTC-220 and the related mechanisms in rats.

METHODS

The excretion of MTC-220 and its metabolites in bile and urine were determined in rats after intravenous administration at 4 mg/kg. Caco-2 cell monolayer, in situ liver perfusion model and in vivo pharmacokinetics with selected inhibitors in rats were used to confirm the involvement of hepatic transporters in the elimination of MTC-220. The metabolic stability of MTC-220 was assessed by the incubation with rat liver microsomes and plasma.

RESULTS

Approximately 72 % of MTC-220 was excreted into bile and less than 0.02 % into urine after administration in rats. The Caco-2 cell monolayer was impermeable to MTC-220. In in situ liver perfusion model, the hepatic extraction ratio of MTC-220 was reduced to 40 % of control in the presence of rifampicin, an Oatps inhibitor, and the cumulative biliary excretion rates of MTC-220 were reduced to 52.9, 71.5 and 62.9 % of control when concomitant perfusion with probenecid, novobiocin and verapamil, the inhibitors of Mrp2, Bcrp and P-gp, respectively. Co-administration of rifampicin, probenecid, novobiocin and verapamil with MTC-220 increased the AUC0-t and decreased the CL of MTC-220 in certain extents in rats. MTC-220 remained metabolically intact in rat liver microsomes, but less stable in plasma incubation.

CONCLUSIONS

In summary, the elimination of MTC-220 was mainly through the biliary excretion in unchanged form in rats. Liver transporters including Oatps, Mrp2, Bcrp and P-gp might be all involved in the hepatic elimination of MTC-220. MTC-220 exhibited the high metabolic stability in liver microsomes, but less stable in plasma. The esterases might involve in the metabolism of MTC-220 in plasma.

Effect of JBP485 on obstructive jaundice is related to regulation of renal Oat1, Oat3 and Mrp2 expression in ANIT-treated rats

The objective was to determine whether protective effects of JBP485 on biliary obstruction induced by alpha-naphthylisothiocyanate (ANIT) are mediated by the organic anion transporters Oat1, Oat3 and the multidrug resistance-associated protein Mrp2. The ANIT-induced increases in bilirubin (BIL), alanine aminotransferase (ALT) and aspartate transaminase (AST) in rat serum were inhibited significantly by oral administration of JBP485. The plasma concentration of JBP485 which is the substrate of Oat1 and Oat3 determined by LC-MS/MS was markedly increased after intravenous administration in ANIT-treated rats, whereas cumulative urinary excretion of JBP485 in vivo and the uptake of JBP485 in kidney slices were decreased remarkably. RT-PCR and Western blot showed the decreased expression of Oat1 and Oat3, increased expression of Mrp2 in ANIT-induced rats, meanwhile, the expression levels of Mrp2 and Oat1 were up-regulated after administration of JBP485. The up-regulation of Mrp2 and Oat1 was associated with a concomitant increase in urinary BIL after treatment with JBP485 in ANIT-treated rats. The mechanism for JBP485 to restore liver function might be related to improvement of the expression and function for Oat1 and Mrp2 as well as facilitation of urinary excretion for hepatoxic substance.