In Vitro Hepatic Assessment of Cineole and Its Derivatives in Common Brushtail Possums (Trichosurus vulpecula) and Rodents

Abstract

Folivore marsupials, such as brushtail possum (Trichosurus Vulpecula) and koala (Phascolarctos cinereus), can metabolise higher levels of dietary terpenes, such as cineole, that are toxic to eutherian mammals. While the highly efficient drug metabolising enzymes, cytochrome P450 3A (CYP3A) and phase II conjugating enzymes (UDP-glucuronosyltransferase, UGT), are involved in the metabolism of high levels of dietary terpenes, evidence for inhibitory actions on these enzymes by these terpenes is scant. Thus, this study investigated the effect of cineole and its derivatives on catalytic activities of hepatic CYP3A and UGT in mice, rats, and possums. Results showed that cineole (up to 50 µM) and its derivatives (up to 25 µM) did not significantly inhibit CYP3A and UGT activities in mice, rats, and possums (both in silico and in vitro). Interestingly, basal hepatic CYP3A catalytic activity in the possums was ~20% lower than that in rats and mice. In contrast, possums had ~2-fold higher UGT catalytic activity when compared to mice and rats. Thus, these basal enzymatic differences may be further exploited in future pest management strategies.

Investigating the Contribution of Major Drug-Metabolising Enzymes to Possum-Specific Fertility Control

“…This study found that possum had significantly higher basal UGT2B glucuronidation activity than avian (~8-fold). It should be noted that there are no previous reports in the literature of basal UGT2B glucuronidation activity in possums using p-nitrophenol glucuronidation, except for the study previously published by our research team [17]. In that study, possums had ~2-fold higher UGT catalytic activity compared to rodents, consistent with the findings of the present study.…”

“…Western blotting showed that CYP3A4 protein levels varied between the 4 species examined. Interestingly, possum liver had higher levels of hepatic CYP3A4 protein than avian (~4-fold), mouse (~2-fold), and human (~2-fold), similar to our previous study in possums and rodents [17]. The high CYP3A protein levels in possums could be due to the use of a mammalian CYP3A polyclonal antibody, which may have also detected other highly homologous isoforms of CYP3A in possums.…”

“…The low catalytic activity of CYP3A in possums may mean that the rate of metabolism of contraceptives in possums is likely to be slower than in rodents and humans. For comparison purposes, it should be noted that there are no previous reports in the literature of basal CYP3A catalytic activity in possum using erythromycin N-demethylation, with the exception of the study previously published by our research team [17]. Our previous study also showed that the basal hepatic CYP3A catalytic activity was approximately 20% lower in possums than in rats and mice.…”

“…enzymes were found compared to rodents (mice and rats). The results showed that possums had ~2fold higher UGT catalytic activity and ~20% lower CYP3A catalytic activity compared to mice and rats [17]. Therefore, the present study aimed to further investigate possum-specific differences in the major drug-metabolising enzymes (CYP3A and UGT2B) using CYP450-based compounds in rodent, avian and human liver samples.…”

In vitro effects and in silico analysis of newly synthetized pyrrole derivatives on the activity of different isoforms of Cytochrome P450: CYP1A2, CYP2D6 and CYP3A4

“…Recently, the reliability and robustness of the in silico methods for the assessment of CYP450 activities has increased substantially. Studies based on the implementation of web servers (Ekroos and Sjogren 2006) and molecular docking simulations (Chand et al 2021) have displayed good correlation with the in vitro results.…”