Effects of gonadectomy and sex hormones on the induction of hepatic CYP4A by clofibrate in rats

Detrimental Effects of Testosterone Addition to Estrogen Therapy Involve Cytochrome P-450-Induced 20-HETE Synthesis in Aorta of Ovariectomized Spontaneously Hypertensive Rat (SHR), a Model of Postmenopausal Hypertension

Postmenopausal period has been associated to different symptoms such as hot flashes, vulvovaginal atrophy, hypoactive sexual desire disorder (HSDD) and others. Clinical studies have described postmenopausal women presenting HSDD can benefit from the association of testosterone to conventional hormonal therapy. Testosterone has been linked to development of cardiovascular diseases including hypertension and it also increases cytochrome P-450-induced 20-HETE synthesis which in turn results in vascular dysfunction. However, the effect of testosterone plus estrogen in the cardiovascular system is still very poorly studied. The aim of the present study is to evaluate the role of cytochrome P-450 pathway in a postmenopausal hypertensive female treated with testosterone plus estrogen. For that, hypertensive ovariectomized rats (OVX-SHR) were used as a model of postmenopausal hypertension and four groups were created: SHAM-operated (SHAM), ovariectomized SHR (OVX), OVX treated for 15 days with conjugated equine estrogens [(CEE) 9.6 μg/Kg/day/po] or CEE associated to testosterone [(CEE+T) 2.85 mg/kg/weekly/im]. Phenylephrine-induced contraction and generation of reactive oxygen species (ROS) were markedly increased in aortic rings from OVX-SHR compared to SHAM rats which were restored by CEE treatment. On the other hand, CEE+T abolished vascular effects by CEE and augmented both systolic and diastolic blood pressure of SHR. Treatment of aortic rings with the CYP/20-HETE synthesis inhibitor HET0016 (1 μM) reduced phenylephrine hyperreactivity and the augmented ROS generation in the CEE+T group. These results are paralleled by the increased CYP4F3 protein expression and activity in aortas of CEE+T. In conclusion, we showed that association of testosterone to estrogen therapy produces detrimental effects in cardiovascular system of ovariectomized hypertensive females via CYP4F3/20-HETE pathway. Therefore, our findings support the standpoint that the CYP/20-HETE pathway is an important therapeutic target for the prevention of cardiovascular disease in menopausal women in the presence of high levels of testosterone.

Effect of biliary obstruction and internal biliary drainage on hepatic cytochrome P450 isozymes in rats

AIM: To investigate the total cytochrome P450 (CYP) content, microsomal mixed-function oxidase (MFO) activity, and expression of mRNAs for various CYP isozymes in a simple rat model of reversible obstructive jaundice.

METHODS: Obstructive jaundice was created in male rats by causing bile duct obstruction with polyester tape. In another group of rats, bile duct obstruction was followed by internal biliary drainage after releasing the tape. The expression of various CYP isozyme mRNAs was semi-quantitatively assessed by competitive RT-PCR.

RESULTS: The total CYP content and microsomal MFO activity showed a significant decrease after biliary obstruction, but returned to respective control levels after biliary drainage. A marked reduction in the expression of CYP1A2, 2B1/2, 2C11, 2E1, 3A1, and 3A2 mRNA was detected during biliary obstruction, while expression increased significantly toward the control level after biliary drainage. Although expression of CYP4A1 mRNA showed no reduction during biliary obstruction, it still increased significantly after biliary drainage.

CONCLUSION: These results suggest that not only obstructive jaundice, but also the subsequent internal biliary drainage may affect regulatory medications of the synthesis of individual CYP isozymes differently.

The up-regulation of hepatic acyl-coA oxidase and cytochrome P450 4A1 mRNA expression by dietary oxidized frying oil is comparable between male and female rats

We previously demonstrated that oxidized frying oil (OFO) activates peroxisome proliferator-activated receptor alpha (PPARalpha) and up-regulates hepatic acyl-CoA oxidase (ACO) and cytochrome P450 4A1 (CYP4A1) genes in male rats. As female rats were shown to be less responsive to some peroxisome proliferators (PP), this study compared the expression of a few PPARalpha target genes in male and female rats fed diets containing OFO. Male and female rats were fed a diet containing 20 g/100 g OFO (O diet) or fresh soybean oil (F diet) for 6 wk. Both male and female rats fed the O diet showed significantly higher liver weight, hepatic ACO and catalase activities, CYP4A protein, and expression of ACO and CYP4A1 mRNA (P < 0.05) compared with their control groups. The mRNA expression of two other PPARalpha target genes, FA-binding protein and HMG-CoA synthase, were marginally increased by dietary OFO (P = 0.0669 and 0.0521, respectively). Female rats fed the O diet had significantly lower CYP4A protein than male rats fed the same diet. The remaining OFO-induced effects were not significantly different between male and female rats fed the O diet. These results indicate that dietary OFO, unlike clofibrate or other PP, had minimal sexual dimorphic effect on the induction of hepatic PPARalpha target gene expression.

Juvenile hormone inhibition of gene expression for cytochrome P4504C1 in adult females of the cockroach, Blaberus discoidalis

The regulation and pattern of gene expression for cytochrome P4504C1 was measured in the fat body of adult females of the cockroach, Blaberus discoidalis. The level of CYP4C1-mRNA was high at adult emergence but disappeared after 4 days of adult life. In starved females, CYP4C1-mRNA levels declined by day 4 but increased steadily thereafter; by 25 days, the levels were nearly twice those observed at eclosion. Both the rapid early disappearance of the transcript and the starvation-related increase failed to occur following decapitation. Allatectomy also prevented the disappearance of CYP4C1-mRNA at day 4, and treatment of decapitated females with methoprene (JHA) stimulated a 70% decrease in transcript within 24 h. Injection of synthetic Blaberus hypertrehalosemic hormone (HTH) increased CYP4C1-mRNA by six-fold in the fat body of both intact and decapitated females. CYP4C1-mRNA in the fat body of males did not respond to JHA treatment. The dynamics of CYP4C1-mRNA in the fat body of females could be explained based on an inhibition of CYP4C1 expression by JH that was overcome by HTH.