Lack of therapeutic improvement of liver fibrosis in rats by dexamethasone in spite of ascites amelioration

Pathophysiology of liver fibrosis (LF) includes hepatic parenchymal cell destruction and connective tissue formation. Although dexamethasone has been used in the liver diseases, there is controversy over the beneficial effects of dexamethasone on LF. Previous studies showed that CCAAT/enhancer binding protein-beta (C/EBPbeta) activation contributes to hepatocyte regeneration and dissolution of fibrosis and that dexamethasone activates C/EBPbeta whereas C/EBPbeta-mediated gene induction by dexamethasone is antagonized by a corepressor. The present study investigated the possible therapeutic effect of dexamethasone for the treatment of LF in rats. We injected rats with multiple doses of dimethylnitrosamine (DMN) for 4 weeks and then used the LF rats to determine whether dexamethasone treatment therapeutically improved liver functions and resolved fibers accumulated in the liver. Dexamethasone (100 microg/kg, po, three times per week for 4 weeks) failed to restore the body weight gain and liver weight decreased by LF. The body weight gain reduced during LF was further decreased by dexamethasone treatment. Animals were subjected to blood biochemical, liver histopathological and immunochemical analyses. Although dexamethasone treatment significantly reduced ascites in LF rats, the plasma albumin and total protein levels decreased in fibrotic rats were not restored. Impaired liver functions during LF including elevated plasma aminotransferases and bilirubin levels along with GSTA2 repression were not recovered by dexamethasone. Dexamethasone failed to decrease the fibrosis score and to eliminate the extracellular matrix and alpha-smooth muscle actin accumulated in the fibrotic liver. The results of the present study showed that dexamethasone ameliorated ascites in LF rats but failed to improve the liver functions and fiber accumulation, and that the possible beneficial effect of dexamethasone might result from anti-inflammatory effect but not from liver improvement.     

Effects of JBP485 on the expression and function of PEPT1 in indomethacin-induced intestinal injury in rats and damage in Caco-2 cells

To investigate the effect of JBP485 (an anti-inflammatory dipeptide) on PEPT1 in indomethacin-induced intestinal injury in rats and damage in Caco-2 cells, the activity and expression of PEPT1 were examined. The effects of treatment with indomethacin and co-treatment with JBP485 were examined in terms of intestinal histological changes, MDA and MPO levels in rats; as well as LDH-release and oxidative stress in Caco-2 cells. Uptake of glycylsarcosine (Gly-Sar) by PEPT1 was determined by in vivo, in vitro and in situ studies. RT-PCR and Western blot were used to assess the expression of PEPT1 in rat intestine and Caco-2 cells. JBP485 caused a significant decrease in MDA and MPO levels, and improved the pathological condition of rat intestine, while attenuating Caco-2 cells damage induced by indomethacin. Uptake of Gly-Sar by PEPT1 was decreased by indomethacin treatment, whereas the Gly-Sar plasma concentration was markedly increased in JBP485 co-treated rats. Indomethacin down-regulated the expression of PEPT1 mRNA and protein in rat intestine and Caco-2 cells, and the effects were reversed after administration of JBP485. These results indicated that JBP485 not only improved intestinal injury and cell damage but also partially blocked the down-regulation of PEPT1 expression and function induced by indomethacin.     

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.