There are few in vivo knockout models available to study the function of the Cyp2 members of the P450 superfamily. Cyp2bs are thought be involved in the metabolism of drugs, environmental toxicants, and endobiotics such as steroid hormones. We produced a Cyp2b-knockdown (KD) mouse for subsequent study of Cyp2b function. There are multiple Cyp2b members in mice (only one, CYP2B6 in humans), therefore we made a quintuple Cyp2b-KD mouse using lentiviral-promoted shRNA homologous to all five Cyp2b subfamily members (Cyp2b10, 2b9, 2b13, 2b19, and 2b23). The Cyp2b-KD mice are viable and fertile. Expression of the three hepatic Cyp2b members, 2b9, 2b10, and 2b13, is significantly repressed as demonstrated by QPCR and Western blotting. Furthermore, the CAR activator and potent Cyp2b inducer was unable to outcompete the shRNA-mediated repression of Cyp2b as Cyp2b induction was 6-11X lower in Cyp2b-KD individuals than WT mice; despite increased CAR expression in TC-treated mice. Cyp2b-KD mice show an increase in liver weight probably due to compensatory mechanisms. In addition, we observed increased abdominal and renal fat in individuals younger than 10-weeks old. This is associated with higher serum cholesterol, HDL, and LDL concentrations. Serum triglycerides are increased in Cyp2b-KD mice treated with TCPOBOP relative to WT mice treated with TCPOBOP. Interestingly, using corn oil as a carrier has some side effects as the mice show induction of CYPs relative to untreated Cyp2b-KD mice and WT corn oil treated mice, indicating perturbations in the normal response to unsaturated fatty acids. A study investigating older mice is currently underway. In summary, we have developed a Cyp2b-knockdown mouse using RNAi and evidence based on this mouse model suggests that Cyp2b isoforms have an endogenous functions that include dietary lipid metabolism.
Sources of Research Support: NIH grant ES017321 awarded to WSB.