Mouse Cyp a is a homologous isoform of
Mouse Cyp3a11 is a homologous isoform of the human CYP3A4 gene, and both are highly expressed in the liver (Hart, Cui, Klaassen, & Zhong, 2009). CYP3A4 is the most abundant CYP450 in hepatic microsomes responsible for drug and xenobiotic metabolism (Zanger & Schwab, 2013), and it is the most active CYP450 isoform that catalyzes NADPH oxidation and superoxide production (Hrycay & Bandiera, 2015a). Thus, the activity of this enzyme may be an important cause of ROS generation. The induction of CYP3A2 activity by phenobarbital, a CYP3A inducer, worsens lipopolysaccharide-induced hepatic injury in rats with increases in ROS, hydroxy-2-nonenal, and 8-hydroxydeoxyguanosine production, indicating a stage of oxidative stress (Minamiyama et al., 2004). In the present study, ENDM-associated CYP3A activity was significantly induced in the HFFD mice, which corroborated our previous data showing that expression of CYP3A11 mRNA was extensively upregulated in HFFD mice (Jearapong et al., 2015). THC lowered CYP3A activity in the HFFD mice, demonstrating its ability to promote a balance of the CYP450 profile and improve the hepatic histopathology in these mice (Jearapong et al., 2015). The links between microsomal ROS generation and total CYP450 content and CYP3A2 activities were noted in a previous study, where oxidative stress and liver injury were attenuated by inhibition of CYP450 enzymes (Shaik & Mehvar, 2010).
Enzymes involved in phase II detoxification, such as UGT, GST, and the antioxidant enzyme NQO, also play an important role in protecting 5-moUTP from oxidative damage (Hasegawa, Miwa, Tsutsumiuchi, & Miwa, 2010). Thus, the impacts of HFFD and THC on phase II enzymatic activities were investigated in this study. THC did not increase GST activity in either the RD or the HFFD mice, and it did not affect UGT activity in the HFFD mice. THC did not modify NQO activity in the RD or HFFD mice. These observations were inconsistent with the observed effects of other antioxidant compounds, such as astaxanthin (Wu et al., 2014), epigallocatechin-3-gallate (You et al., 2014), and silymarin, which regulated antioxidant-related transcription factors that induce NQO1 expression (Surai, 2015). Nevertheless, THC was superior to VitE in restoring the HFFD-induced UGT activity and in not disrupting GST activity in either RD or HFFD mice. Therefore, our findings suggest that oxidative stress resulted from an increase in ROS generation via the CYP450 biotransformation cycle in phase I. Furthermore, as an antioxidant, THC was shown to have the potential to balance the redox state in HFFD mice primarily through phase I, rather than the phase II, biotransformation.
Conclusions The HFFD induced hepatic injury in mice through CYP450-induced oxidative stress and modification of CYP450 profiles. THC attenuated oxidative stress in the HFFD mice via decreases in glucose tolerance, alanine aminotransferase, and aspartate aminotransferase, downregulation of phase I metabolizing enzymes, suppression of HFFD-induced NADPH-CYP450 reductase, reduction in ROS production by CYP2E1 and CYP3A11, and also by restoring the mRNA levels of anti-oxidative related genes. While both THC and VitE showed similar effects via several approaches, THC did not affect the expression of anti-oxidative related genes while VitE induced the expressions of CuZn-Sod, Cat, and Gpx mRNA. THC did not improve the activity of HFFD-induced phase II metabolizing enzymes. These observations suggest that the mechanism by which THC delays the progression of HFFD-induced liver injury is related to phase I biotransformation, particularly via the CYP450-associated pathway and antioxidation pathways.
Introduction In aquaculture, a large number of fish are typically maintained in relatively small and confined areas where they can be kept under controlled conditions. In spite of attempts to maintain optimal culture conditions, outbreaks of disease are almost inevitable. Such situations require immediate action to reduce losses. Unfortunately, in the United States there are currently only three FDA-approved and available antibiotic drugs for use in fish. They are oxytetracycline (OTC, Terramycin for Fish®, Phibro Animal Health, Inc., Fairfield, NJ), ormetoprim and sulfadimethoxine (Romet-30®, Pharmaq AS, Oslo, Norway) (Stoffregen et al., 1996), and florfenicol (Aquaflor®, Intervet/Schering-Plough, Animal Health Corp. Summit, NJ).