Opposing Roles of Peroxisome Proliferator-activated Receptor α and Growth Hormone in the Regulation of CYP4A11 Expression in a Transgenic Mouse Model

Abstract

CYP4A11 transgenic mice (CYP4A11 Tg) were generated to examine in vivo regulation of the human CYP4A11 gene. Expression of CYP4A11 in mice yields liver and kidney P450 4A11 levels similar to those found in the corresponding human tissues and leads to an increased microsomal capacity for -hydroxylation of lauric acid. Fasted CYP4A11 Tg mice exhibit 2-3-fold increases in hepatic CYP4A11 mRNA and protein, and this response is absent in peroxisome proliferator-activated receptor ␣ (PPAR␣) null mice. Dietary administration of either of the PPAR␣ agonists, fenofibrate or clofibric acid, increases hepatic and renal CYP4A11 levels by 2-3-fold, and these responses were also abrogated in PPAR␣ null mice. Basal liver CYP4A11 levels are reduced differentially in PPAR␣ ؊/؊ females (>95%) and males (<50%) compared with PPAR␣ ؊/؉ mice. Quantitative and temporal differences in growth hormone secretion are known to alter hepatic lipid metabolism and to underlie sexually dimorphic gene expression, respectively. Continuous infusion of low levels of growth hormone reduced CYP4A11 expression by 50% in PPAR␣-proficient male and female transgenic mice. A larger decrease was observed for the expression of CYP4A11 in PPAR␣ ؊/؊ CYP4A11 Tg male mice to levels similar to that of female PPAR␣-deficient mice. These results suggest that PPAR␣ contributes to the maintenance of basal CYP4A11 expression and mediates CYP4A11 induction in response to fibrates or fasting. In contrast, increased exposure to growth hormone down-regulates CYP4A11 expression in liver.

Altered Cytochrome P450 Expression in Mice during Pregnancy

“…The decreased PPAR␣ expression strongly correlated with the reduced expression levels of Cyp2d22 and Cyp2e1 ( Table 2), suggesting that PPAR␣ potentially participates in regulation of P450 expression during mouse pregnancy. In fact, it has been shown that a peroxisome proliferator activator (such as WY-14,643) down-regulates CYP2C11 and CYP2C12 while up-regulating CYP4A in rats (Corton et al, 1998;Graham and Lake, 2008) and mice (Savas et al, 2009). However, it is uncertain whether these results can be extrapolated to humans.…”

Genistein, Resveratrol, and 5-Aminoimidazole-4-carboxamide-1-β-d-ribofuranoside Induce Cytochrome P450 4F2 Expression through an AMP-Activated Protein Kinase-Dependent Pathway

“…The cross-reactivity of the resultant antibody with P450 4F11 and 4F12 was then removed by back-adsorption of anti-P450 4F2 IgG against a Affi-Gel 10 agarose gel solid-phase support to which P450 4F11 and 4F12 Sf9 lysate proteins had been coupled. We previously used a similar procedure to remove the cross-reactivity of murine CYP4A proteins with antibodies to human P450 4A11 (Savas et al, 2009). The final back-absorbed antibody exhibited cross-reactivity with P450 4F2 and P450 4F3 and was designated as anti-P450 4F2/3 IgG (Supplemental Fig.…”

5-Aminoimidazole-4-carboxyamide-ribonucleoside (AICAR)-Stimulated Hepatic Expression ofCyp4a10,Cyp4a14,Cyp4a31, and Other Peroxisome Proliferator-Activated Receptor α-Responsive Mouse Genes Is AICAR 5′-Monophosphate-Dependent and AMP-Activated Protein Kinase-Independent

“…The RNA concentration was determined spectrophotomically. The primers used for measurement of Cyp4a12, Cyp4a14, L27, and PPAR␣ mRNA were described previously (Savas et al, 2009). The sequences for all other primers used for qPCR are listed in Table 1.…”