Influence of Matrigel-overlay on constitutive and inducible expression of nine genes encoding drug-metabolizing enzymes in primary human hepatocytes

1. Previous studies reported that rat hepatocytes overlaid with extracellular matrix components (Matrigel) maintain the expression and responsiveness of drug-metabolizing enzymes. However, whether Matrigel provides similar advantages in human hepatocytes remains largely uncertain.2. The influence of Matrigel-overlay on the constitutive and phenobarbital- and oltipraz-inducible expression of nine biotransformation enzymes, cytochrome P450s 1A1, 1A2, 2B6, 3A4, and glutathione S-transferases A1, A2, M1, T1, P1, in primary human hepatocytes was evaluated.3. Hepatocytes from five livers were maintained on a rigid collagen substratum with or without Matrigel overlay and treated for 48?h with two doses of each inducer. Quantitative RT-PCR, and for selected genes, immunoblot and enzyme activity analyses, demonstrated that human hepatocytes overlaid with Matrigel showed consistently higher constitutive and inducible expression of biotransformation genes. 4. Phenobarbital-mediated responsiveness of cytochrome P450 2B6, a potential indicator of hepatocyte differentiation status, was markedly higher in overlaid relative to non-overlaid hepatocytes. 5. It is concluded that an Matrigel overlay facilitates the maintenance and induction of xenobiotic metabolizing enzymes in primary cultures of human hepatocytes.

Phytochemical-induced changes in gene expression of carcinogen-metabolizing enzymes in cultured human primary hepatocytes

1. The naturally occurring compounds curcumin (CUR), 3,3'-diindolylmethane (DIM), isoxanthohumol (IXN), 8-prenylnaringenin (8PN), phenethyl isothiocyanate (PEITC) and sulforaphane (SFN) protect animals against chemically induced tumours. Putative chemoprotective mechanisms include modulated expression of hepatic biotransformation enzymes. However, few, if any, studies have used human primary cells as test models. 2. The present study investigated the effects of these phytochemicals on the expression of four carcinogenesis-relevant enzymes--cytochrome P450 (CYP)1A1 and 1A2, NAD(P)H:quinone oxidoreductase (NQO1) and glutathione S-transferase A1 (GSTA1)--in primary cultures of freshly isolated human hepatocytes. 3. Quantitative RT-PCR analyses demonstrated that CYP1A1 was up-regulated by PEITC and DIM in a dose-dependent manner. CYP1A2 transcription was significantly activated following DIM, IXN, 8PN and PEITC treatments. DIM exhibited a remarkably effective induction response of CYP1A1 (474-, 239- and 87-fold at 50, 25 and 10 microM, respectively) and CYP1A2 (113-, 70- and 31-fold at 50, 25 and 10 microM, respectively), that was semiquantitatively reflected in protein levels. NQO1 expression responded to PEITC (11 x at 25 microM), DIM (4.5 x at 50 microM) and SFN (5 x at 10 microM) treatments. No significant effects on GSTA1 transcription were seen. 4. The findings show novel and unexpected effects of these phytochemicals on the expression of human hepatic biotransformation enzymes that play key roles in chemical-induced carcinogenesis.