Characterization of CYP1A in hepatocytes of cynomolgus monkeys ( Macaca fascicularis ) and induction by different substituted polychlorinated biphenyls (PCBs)

Abstract

Cynomolgus monkeys (Macaca fascicularis) have been used previously as a model to study effects on cytochrome P450 (CYP) regulation. Until now it has not been elucidated which CYP1A proteins are present in this primate species. The aim of this study was to characterize CYP1A in untreated hepatocytes of cynomolgus monkey using two specific CYP1A inhibitors (alpha-naphthoflavone and furafylline). The effect of different substituted polychlorinated biphenyls (PCBs) on CYP1A regulation was also studied in these hepatocytes. Small quantities of CYP1A2 have been identified in untreated hepatocytes. Northern blots showed the presence of a CYP1A mRNA in untreated hepatocytes, when hybridizations where performed with human CYP1A2 cDNA. Inhibitions with furafylline and alpha-naphthoflavone also suggested the presence of CYP1A2 properties. After induction with different PCBs, (probably) CYP1A1 mRNA and enzyme activity were induced in cynomolgus monkey hepatocytes. As expected, 2,3',4,4',5-PeCB (PCB no. 118), a mono-ortho substituted congener, was a potent CYP1A inducer but 2,2',3,4,4',5',5'-HpCB (PCB no. 180), a di-ortho and 2,2',3,4',5,5',6-HpCB (PCB no. 187), a tri-ortho substituted PCB, could induce CYP1A mRNA and enzyme activity in cynomolgus monkey hepatocytes as well.

Multivariate modeling of polychlorinated biphenyl–induced CYP1A activity in hepatocytes from three different species: Ranking scales and species differences

“…A suitable model could be a nonhuman primate, such as a cy‐nomolgus monkey. In the applied monkey system and in human liver, the CYP1A2 protein has been identified [35]. Further, CYP1A1 is probably induced in monkey hepatocytes after exposure to different PCBs [35].…”

“…In the applied monkey system and in human liver, the CYP1A2 protein has been identified [35]. Further, CYP1A1 is probably induced in monkey hepatocytes after exposure to different PCBs [35]. The cytochrome P450 system of the pig is the least known; consequently, the pig isoforms involved here have not yet been identified [10].…”

Polychlorinated Biphenyls and Polybrominated Biphenyls

“…AhR is present in several tissues and cells of the immune system as shown in rodents (e.g. Mason & Okey, 1982), in non-human primates (Van Der Burght et al, 1998) and in humans (Hakkola et al, 1997).…”

“…It uses relative effective potencies (REP) of individual compounds to activate the AhR, and AhR-dependent toxic or biological effects relative to the reference toxicant TCDD; toxic equivalency factors (TEFs) for individual compounds were established/extrapolated from the database of many in-vivo studies. Since the 1980s, the TEF concept has been developed and refined Safe, 1990;Ahlborg et al, 1994;Van den Berg et al, 1998). Current TEF values were reevaluated recently using a refined TEF database (Haws et al, 2006;Van den Berg et al, 2006).…”

Determination of in vitro relative potency (REP) values for mono-ortho polychlorinated biphenyls after purification with active charcoal

“…In addition, although PCB-156 could induce CYP1A1 in fish (PLHC-1) hepatoma cells, two other MO-PCBs, -105 and -118, induced little or no CYP1A1 activity (Hestermann et al, 2000). In primary cultures of rat and cynomolgus monkey hepatocytes, MO-PCBs were found to induce CYP1A1-dependent EROD activity (Chen and Bunce, 2004;Van der Burght et al, 1998Zeiger et al, 2001). …”