Section of Toxicology and Environmental Chemistry, Department of Pharmaceutics and Analytical Chemistry, Faculty of Pharmaceutical Sciences, University of Copenhagen, Universitetsparken 2, DK-2100 Copenhagen Ø, Denmark.
Toxicology in Vitro (Impact Factor: 2.9). 03/2008; 22(1):146-53. DOI: 10.1016/j.tiv.2007.09.004
Antiepileptic drugs and epilepsy are often associated with sexual disorder in women such as hyperandrogenism, menstrual disorders and ovarian cysts. In children, until puberty, a hormone imbalance may influence many aspects of development, e.g. growth and sexual maturation. The aromatase complex is the enzyme system that converts androgens to estrogens and consequently an inhibition may induce a hormone imbalance. Twelve antiepileptic drugs, used in mono or polytherapy for the treatment of children, were tested for their ability to inhibit aromatase (CYP19) with commercially available microsomes from transfected insect cells using dibenzylfluorescein as substrate. The drugs inhibiting CYP19 were: lamotrigine, oxcarbazepine, tiagabine, phenobarbital, phenytoin, ethosuximide, and valproate. The inhibitory effects (50% reduction in activity compared to enzymes without inhibitor present) were in the range of 1.4-49.7 mM. Carbamazepine, gabapentin, primidone, topiramate and vigabatrin showed no inhibition. Additionally, binary drug combinations were tested to investigate if combination therapy could potentiate the aromatase inhibition. Additive inhibition was seen in combination experiments with valproate and phenobarbital. When adding carbamazepine to a range of valproate concentrations no additional inhibition was seen. The data for some of the AEDs show that side effects on steroid synthesis in humans due to inhibition of aromatase should be considered.
"These findings offer leads into prospective new strategies for epilepsy treatment, made especially valuable given the challenges involved in treating this condition. For example, it is known that 30% of the newly diagnosed patients do not respond sufficiently to monotherapy . Therefore, compounds capable of inhibiting aromatase should be investigated for potential in polytherapy, based on mechanism of action, in addition to being tested for antiepileptic properties. "
[Show abstract][Hide abstract] ABSTRACT: The present study compares antiepileptic drugs and aromatase (CYP19) inhibitors for chemical and structural similarity. Human aromatase is well known as an important pharmacological target in anti-breast cancer therapy, but recent research demonstrates its role in epileptic seizures, as well. The current antiepileptic treatment methods cause severe side effects that endanger patient health and often preclude continued use. As a result, less toxic and more tolerable antiepileptic drugs (AEDs) are needed, especially since every individual responds differently to given treatment options.
Through a pharmacophore search, this study shows that a model previously designed to search for new classes of aromatase inhibitors is able to identify antiepileptic drugs from the set of drugs approved by the Food and Drug Administration. Chemical and structural similarity analyses were performed using five potent AIs, and these studies returned a set of AEDs that the model identifies as hits.
The pharmacophore model returned 73% (19 out of 26) of the drugs used specifically to treat epilepsy and approximately 82% (51 out of 62) of the compounds with anticonvulsant properties. Therefore, this study supports the possibility of identifying AEDs with a pharmacophore model that had originally been designed to identify new classes of aromatase inhibitors. Potential candidates for anticonvulsant therapy identified in this manner are also reported. Additionally, the chemical and structural similarity between antiepileptic compounds and aromatase inhibitors is proved using similarity analyses.
This study demonstrates that a pharmacophore search using a model based on aromatase inhibition and the enzyme's structural features can be used to screen for new candidates for antiepileptic therapy. In fact, potent aromatase inhibitors and current antiepileptic compounds display significant - over 70% - chemical and structural similarity, and the similarity analyses performed propose a number of antiepileptic compounds with high potential for aromatase inhibition.
"The reduced expression observed for CYP19 at 900 and 1,500 lM VPA exposure provides a possible explanation for the increased T/E2 ratio. However, down-regulation of CYP19 expression following VPA exposure has not been previously observed (Ohnishi & Ichikawa, 1997; Gustavsen et al., 2009), except when high exposure levels have been used (Jacobsen et al., 2008). "
[Show abstract][Hide abstract] ABSTRACT: Endocrine disruptive effects have been frequently observed in patients using antiepileptic drugs (AEDs). Two different AEDs, valproate (VPA) and levetiracetam (LEV), were tested in forskolin-stimulated human adrenal carcinoma (H295R) cells to explore their effect on steroidogenesis. VPA has a long history as an anticonvulsant and is linked with many of the endocrine disorders associated with AED use. LEV is a newer AED, and no endocrine disruptive effects have been reported in humans to date.
H295R cells, which are capable of full steroidogenesis, were stimulated with forskolin and exposed to either VPA or LEV for 48 h. Medium was collected and analyzed for hormone production. For the VPA-exposed cells, steroidogenic gene expression analysis was also conducted.
VPA exposure resulted in a significant reduction in progesterone and estradiol (E2) production, whereas testosterone (T) levels remained unchanged. There were also significant alterations in expression level for most genes analyzed. LEV exposure resulted in a minor, but statistically significant, reduction in T and E2 production.
Exposure of forskolin-stimulated H295R cells to VPA led to an increased T/E2 ratio through a significant decrease in estradiol production. Gene analysis suggested that VPA affects NR0B1 expression. NR0B1 inhibits promoters of other genes involved in steroidogenesis, and the altered expression of NR0B1 might explain the observed down-regulation in hormone production. The effects of LEV exposure on hormone secretion were not considered to be biologically significant.
"Recently, Jacobsen et al. (2008) reported that some of the AEDs used in our patients (PB, PHT, VPA, OXC, LTG), but not CBZ and PRM, inhibit in vitro the aromatase complex (CYP19) activity that converts testosterone into E2. Additive enzyme inhibition has been observed in combination experiments with multiple AEDS, and was also found in a number of the subjects we studied. "
[Show abstract][Hide abstract] ABSTRACT: Reproductive dysfunction in epilepsy is attributed to the seizures themselves and also to antiepileptic drugs (AEDs), which affect steroid production, binding, and metabolism. In turn, neuroactive steroids may influence neuronal excitability. A previous study in this cohort of consecutive women with epilepsy showed that patients with more frequent seizures had higher cortisol and lower dehydroepiandrosterone sulfate levels than those with rare or absent seizures. The present study was aimed at evaluating, in these same women, the possible relationship between some clinical parameters, seizure frequency, AED therapies, and sex hormone levels.
Estradiol (E2), progesterone (Pg), sex hormone-binding globulin (SHBG), and free estrogen index (FEI) were measured during the luteal phase in 113 consecutive females, 16-47 years old, with different epilepsy syndromes on enzyme-inducing AED (EIAED) and/or non-enzyme-inducing AED (NEIAED) treatments, and in 30 age-matched healthy women. Hormonal data were correlated with clinical parameters (age, epilepsy syndrome, disease onset, and duration), seizure frequency assessed on the basis of a seizure frequency score (SFS), and AED therapies.
E2, Pg, and FEI were lower, whereas SHBG levels were higher in the epilepsy patients than in the controls. However, sex steroid and SHBG levels were not different between groups of patients categorized according to SFS. Therapies with EIAEDs accounted for changes in E2 levels and FEI.
Despite globally decreased sex steroid levels in serum, actual hormone titers were not significantly correlated with SFS in consecutive epilepsy women; rather, these hormonal changes were explained by AED treatments, mainly when EIAED polytherapies were given.
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