Suppression of hepatic CYP3A1/2 and CYP2C11 by cyclosporine is not mediated by altering growth hormone levels

Albumin is a secret factor involved in multidirectional interactions among the serotoninergic, immune and endocrine systems that supervises the mechanism of CYP1A and CYP3A regulation in the liver

This review focuses on albumin, which is involved in multidirectional interactions among the immune, endocrine and serotoninergic systems and supervises the regulation of cytochrome P450 (CYP) isoforms under conditions of both normal liver function and liver insufficiency. Special attention is paid to albumin, thyroid hormones, testosterone and tryptophan hydroxylase in these interactions as well as their potential roles in liver regeneration. The association of these factors with inflammation and the modification of the mechanism of hepatic drug-metabolizing CYP isoform regulation are also presented because changes in the expression of CYP isoforms in the liver may result in subsequent changes to a marker substance used for testing CYP activity, thus providing a simple way to control the liver regeneration process or the dangerous stimulation of hepatocarcinogenesis.

Effect of kanglaite on rat cytochrome P450

CONTEXT

Kanglaite (KLT) is an oily substance extracted from Coix lacryma-jobi Linn. (Cramineae) and has been proved to significantly improve the life span and quality of life of patients, when combined with chemotherapy, radiotherapy, or surgery.

OBJECTIVE

The purpose of this study was to find out whether KLT influences the effect on rat cytochrome P450 (CYP) enzymes (CYP1A2, CYP2B6, CYP2C9, CYP2C19, and CYP3A4) by using cocktail probe drugs in vivo.

MATERIALS AND METHODS

A cocktail solution at a dose of 5 mL/kg, which contained phenacetin (20 mg/kg), bupropion (20 mg/kg), tolbutamide (5 mg/kg), omeprazole (20 mg/kg), and midazolam (10 mg/kg), was given as oral administration to rats treated with 7 d intraperitoneal injection of KLT. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by HPLC-MS/MS. The corresponding pharmacokinetic parameters were calculated by the software of DAS 2.0 (SPPS Inc., Chicago, IL).

RESULTS

In the experiment, there was a statistically significant difference in the t1/2, Cmax, AUC(0-∞), and CL for phenacetin, bupropion, tolbutamide, omeprazole, and midazolam. Our study showed that treatment with multiple doses of KLT had induction effect on rat CYP1A2, while CYP2B6, CYP2C9, CYP2C19, and CYP3A4 enzyme activities had been inhibited after multiple doses of KLT treatment.

CONCLUSIONS

KLT can either induce or inhibit activities of CYP. Therefore, caution is needed when KLT is co-administration with some CYP substrates in clinic, which may result in herb-drug interactions.

Dioxin-induced fetal growth retardation: the role of a preceding attenuation in the circulating level of glucocorticoid

Exposure of pregnant rats to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) at a low dose causes developmental disorders such as growth retardation and sexual immaturity in their pups. Our previous studies have demonstrated that TCDD attenuates the expression of pituitary luteinizing hormone in fetuses, resulting in the impairment of sexual behavior after they reach maturity. In this study, we focused on growth disturbance and investigated whether TCDD affects the expression of growth hormone (GH), another pituitary hormone which is essential for normal development in perinatal pups. The result showed that maternal exposure to TCDD (1 µg/kg) at gestational day (GD) 15 reduced the fetal expression of GH from the onset at GD18. In accordance with this, TCDD attenuated the pup weight during the perinatal period. We then examined the effect of TCDD on the serum concentration of corticosterone, which plays a key role in the proliferation of GH-producing cells, and found that TCDD reduces the circulating level of corticosterone in the mothers at GD18 and the male fetuses at GD19. The reduction in fetuses seems to be due to increased inactivation rather than reduced synthesis, because TCDD induces the fetal expression of hepatic enzymes participating in the metabolism of glucocorticoids without changing the expression of steroidogenic proteins in the pituitary-adrenal axis. Supplying corticosterone to TCDD-exposed mothers restored or tended to restore a TCDD-induced reduction in pup weight as well as the levels of pituitary GH mRNA and serum GH. These results suggest that TCDD lowers GH expression and growth retardation owing, at least partially, to a reduction in the circulating level of glucocorticoid in pregnant mothers and their fetuses.

Macrophage heterogeneity in liver injury and fibrosis

Hepatic macrophages are central in the pathogenesis of chronic liver injury and have been proposed as potential targets in combatting fibrosis. Recent experimental studies in animal models revealed that hepatic macrophages are a remarkably heterogeneous population of immune cells that fulfill diverse functions in homeostasis, disease progression, and regression from injury. These range from clearance of pathogens or cellular debris and maintenance of immunological tolerance in steady state conditions; central roles in initiating and perpetuating inflammation in response to injury; promoting liver fibrosis via activating hepatic stellate cells in chronic liver damage; and, finally, resolution of inflammation and fibrosis by degradation of extracellular matrix and release of anti-inflammatory cytokines. Cellular heterogeneity in the liver is partly explained by the origin of macrophages. Hepatic macrophages can either arise from circulating monocytes, which are recruited to the injured liver via chemokine signals, or from self-renewing embryo-derived local macrophages, termed Kupffer cells. Kupffer cells appear essential for sensing tissue injury and initiating inflammatory responses, while infiltrating Ly-6C(+) monocyte-derived macrophages are linked to chronic inflammation and fibrogenesis. In addition, proliferation of local or recruited macrophages may possibly further contribute to their accumulation in injured liver. During fibrosis regression, monocyte-derived cells differentiate into Ly-6C (Ly6C, Gr1) low expressing 'restorative' macrophages and promote resolution from injury. Understanding the mechanisms that regulate hepatic macrophage heterogeneity, either by monocyte subset recruitment, by promoting restorative macrophage polarization or by impacting distinctive macrophage effector functions, may help to develop novel macrophage subset-targeted therapies for liver injury and fibrosis.

Effects of aescin on cytochrome P450 enzymes in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Aescin, the main active component found in extracts of horse chestnut (Aesculus hippocastanum) seed a traditional medicinal herb, is a mixture of triterpene saponins. It has been shown to be effective in inflammatory, chronic venous and edematous treatment conditions in vitro and in vivo, and is broadly used to treat chronic venous insufficiency. The purpose of this study was to find out whether aescin influences the effect on rat cytochrome P450 (CYP) enzymes (CYP1A2, CYP2C9, CYP2E1 and CYP3A4) by using cocktail probe drugs in vivo; the influence on the levels of CYP mRNA was also studied.

MATERIALS AND METHODS

A cocktail solution at a dose of 5mL/kg, which contained phenacetin (20mg/kg), tolbutamide (5mg/kg), chlorzoxazone (20mg/kg) and midazolam (10mg/kg), was given as oral administration to rats treated with a single dose or multiple doses of intravenous aescin via the caudal vein. Blood samples were collected at a series of time-points and the concentrations of probe drugs in plasma were determined by HPLC-MS/MS. The corresponding pharmacokinetic parameters were calculated by the software of DAS 2.0. In addition, real-time RT-PCR was performed to determine the effects of aescin on the mRNA expression of CYP1A2, CYP2C9, CYP2E1 and CYP3A4 in rat liver.

RESULTS

Treatment with a single dose or multiple doses of aescin had inductive effects on rat CYP1A2, while CYP2C9 and CYP3A4 enzyme activities were inhibited. Moreover, aescin has no inductive or inhibitory effect on the activity of CYP2E1. The mRNA expression results were in accordance with the pharmacokinetic results.

CONCLUSIONS

Aescin can either inhibit or induce activities of CYP1A2, CYP2C9 and CYP3A4. Therefore, caution is needed when aescin is co-administration with some CYP1A2, CYP2C9 or CYP3A4 substrates in clinic, which may result in treatment failure and herb-drug interactions.

Effects of schizonepetin on activity and mRNA expression of cytochrome p450 enzymes in rats

The aim of this study was to find out whether Schizonepetin influences the pharmacokinetics of the main substrates drugs of CYP1A2, CYP3A1/2, CYP2E1, CYP2C19 and CYP2D6 in rats; the influence on the levels of CYP mRNA was also studied. Phenacetin, dapsone, chlorzoxazone, omeprazole and metoprolol were selected as probe substrates for CYP1A2, CYP3A1/2, CYP2E1, CYP2C19 and CYP2D6 respectively. HPLC methods were employed for the determination of these substrates in plasma and the pharmacokinetic parameters were calculated. Real-time RT-PCR was used to determine the effects of Schizonepetin on the mRNA expression of CYP3A1, CYP1A2 and CYP2E1 in the rat liver. After the rats were orally administrated with Schizonepetin once a day for seven consecutive days, there were significant differences in plasma concentration of phenacetin, dapsone, chlorzoxazone and metoprolol, but not omeprazole, as compared with pre-administration. In addition, Schizonepetin induced the expression of CYP3A1, CYP1A and CYP2E1 at dosages of 24 and 48 mg/kg. Our results indicated that Schizonepetin had significant induction effects on CYP3A1/2 and inhibition effects on CYP1A2, CYP2E1 or CYP2D6 as oriented from the pharmacokinetic profiles of the substrates. Moreover, in the mRNA expression levels, Schizonepetin could induce the mRNA expression of CYP3A1, CYP1A and CYP2E1. In conclusion, co-administration of some CYP substrates with Schizonepetin may lead to an undesirable herb-drug interaction.

Hepatotoxicity and gene expression down-regulation of CYP isozymes caused by renal ischemia/reperfusion in the rat

Renal ischemia/reperfusion (I/R) occurs in many clinical scenarios, including trauma, elective surgery, and transplantation. Events initiated by this process can lead to inflammation in the kidneys, culminating in local injury as well as distant organ dysfunction. The objectives of this study were to investigate the changes in the functions of the liver and the regulation of gene expression of cytochrome P450 (CYP) isozymes after renal I/R. Hepatoxocity was assessed by serum alanine aminotransferase (sALT), serum aspartate aminotransferase (sAST) and liver glutathione-S-transferase (GST) activities, liver glutathione (GSH) level, and histopathological examination. Hepatic cytochrome P4503A1 (CYP3A1) and cytochrome P4502E1 (CYP2E1) activities were measured by erythromycin N-demethylase (ERD) and aniline hydroxylase (ANH) activities, respectively. CYP3A1 and CYP2E1 mRNA expression was determined by RT-PCR. Results showed that activities of sALT and sAST were significantly increased, while hepatic CYP3A1and CYP2E1 activities as well as their respective mRNA levels were significantly decreased after renal I/R. Moreover, hepatic tissue congestion, degeneration, and local necrosis were observed in rats after 1, 4, and 8h renal reperfusion following 2h renal ischemia. In conclusion, the present study suggests that renal I/R can cause hepatotoxicity and gene expression down-regulation of CYP isozymes in rats.

Controlled inactivation of recombinant viruses with vitamin B2

Inactivated viruses are important tools for vaccine development and gene transfer. 8-Methoxypsoralen (8-MOP) and long-wavelength ultraviolet irradiation (LWUVI) inactivates many viruses. Toxicity limits its use in animals and humans. Toxicological and photosensitizing properties of riboflavin make it suitable for virus inactivation in preparations for biological use. Viruses expressing beta-galactosidase were mixed with either 8-MOP (1.5mM) or riboflavin (50 microM) and exposed to LWUVI (365 nm) for 2 h. Virus activity was determined by limiting dilution. The half-life of the adenovirus preparation treated with 8-MOP was 8.28 ns(-1) and 36.5 ns(-1) after treatment with riboflavin. Despite the difference in half-life, both preparations were completely inactivated within 45 min. In contrast, the half-lives for adeno-associated virus (AAV) preparations were similar (63 ns(-1) 8-MOP vs. 67 ns(-1) riboflavin). Each AAV preparation was fully inactivated within 90 min. The half-life of lentivirus was 193.4 ns(-1) after treatment with 8-MOP and 208 ns(-1) after exposure to riboflavin. Virus treated with riboflavin was inactivated within 20 min. Virus exposed to 8-MOP was inactivated in 90 min. DNA and RNA viruses can be inactivated by riboflavin and LWUVI and used in physiological systems sensitive to other photochemicals.

Cyclosporine and bromocriptine-induced suppressions of CYP3A1/2 and CYP2C11 are not mediated by prolactin

The purpose of this study was to determine if the suppression of hepatic CYP3A1/2 (cytochrome P450 3A1/2) and CYP2C11 (cytochrome P450 2C11) by cyclosporine is mediated by prolactin. Male intact rats were given subcutaneous doses of either 15 mg/kg/day of cyclosporine or 1 ml/kg/day of cyclosporine vehicle concomitantly with one of the following: 500 mg/kg prolactin, 1 ml/kg prolactin vehicle, 4 mg/kg bromocriptine, or 1 ml/kg bromocriptine vehicle for 14 days. Protein expressions were measured using Western blot analysis and activities were measured using an in vitro testosterone hydroxylation assay. The administration of prolactin did not significantly alter CYP3A1/2 protein expression. Hypoprolactinemia, produced by bromocriptine, caused a significant suppression of CYP3A1/2 activity levels when bromocriptine was administered alone and in combination with cyclosporine (P<0.001, P<0.05; respectively). However, the cause of the suppression by bromocriptine was likely not the result of lowering prolactin levels. Bromocriptine administration also lowered CYP2C11 protein expression and activity, while prolactin administration had virtually no effect on CYP2C11. Chronic cyclosporine administration caused a 140% increase in prolactin area under the curve (AUC) (P<0.001). Bromocriptine caused a significant decline in endogenous prolactin secretion, however, concurrent cyclosporine administration did not recover these levels. Overall, while both cyclosporine and bromocriptine, separately, can significantly alter the fate of hepatic P450 enzymes, the suppression is likely not due to an alteration in prolactin levels.

Considerations for use of recombinant adenoviral vectors: dose effect on hepatic cytochromes P450

Recombinant adenovirus (Ad) serotype 5 is a vector commonly used for gene delivery. Although this vector has a natural tropism for the liver, there is a limited understanding of how Ad administration affects one of the primary hepatic processes, drug metabolism. The effects of systemic administration of a model recombinant adenoviral vector on two hepatic cytochrome P450 (P450) enzymes, CYP3A2 and 2C11, were investigated. Sprague-Dawley rats were treated with one of six vector doses, ranging from 5.7 x 10(6) to 5.7 x 10(12) virus particles (vp)/kg. Hepatic P450 protein expression, catalytic activity, and mRNA levels were measured over 14 days. Ad administration (5.7 x 10(10)-5.7 x 10(12) vp/kg) reduced CYP3A2 over the duration of the study. Six hours after administration of 5.7 x 10(12) vp/kg, CYP3A2 activity and mRNA levels were suppressed by 45 and 65%, respectively (P < or = 0.01). This continued throughout the study with levels dropping to 36 and 45% of controls by 14 days, respectively (P < or = 0.01). A similar trend was detected for CYP2C11 within this dosing range. Administration of 5.7 x 10(6), 5.7 x 10(8), and 5.7 x 10(9) vp/kg of Ad significantly increased both CYP2C11 protein expression by 86, 71, and 107% and activity 110, 118, and 53%, respectively, above those of animals treated with saline (P < or = 0.01). These results clearly indicate that a single dose of adenovirus significantly alters key drug metabolizing enzymes for an extended period of time and should be investigated further in the context of the design and implementation of clinical trial protocols.