The influence of ovariectomy on anti-convulsant effect of pioglitazone in mice

Sex and gonadectomy modify behavioral seizure susceptibility and mortality in a repeated low-dose kainic acid systemic injection paradigm in mice

OBJECTIVE

Sex differences in epilepsy appear driven in part due to effects of gonadal steroids, with varying results in experimental models based on species, strain, and method of seizure induction. Furthermore, removing the main source of these steroids via gonadectomy may impact seizure characteristics differently in males and females. Repeated low-dose kainic acid (RLDKA) systemic injection paradigms were recently shown to reliably induce status epilepticus (SE) and hippocampal histopathology in C57BL/6J mice. Here, we investigated whether seizure susceptibility in a RLDKA injection protocol exhibits a sex difference and whether gonadectomy differentially influences response to this seizure induction paradigm in males and females.

METHODS

Adult C57BL/6J mice were left gonad-intact as controls or gonadectomized (females: ovariectomized, OVX; males: orchidectomized, ORX). At least 2 weeks later, KA was injected ip, every 30 minutes at 7.5 mg/kg or less until the animal reached SE, defined by at least 5 generalized seizures (GS, Racine stage 3 or higher). Parameters of susceptibility to GS induction, SE development, and mortality rates were quantified.

RESULTS

No differences in seizure susceptibility or mortality were observed between control males and control females. Gonadectomized mice exhibited increased susceptibility and reduced latency to both GS and SE in comparison to corresponding controls of the same sex, but the effects were stronger in males. In addition, ORX males, but not OVX females, exhibited strongly increased seizure-induced mortality.

SIGNIFICANCE

The RLDKA protocol is notable for its efficacy in inducing SE and seizure-induced histopathology in C57BL/6J mice, the background for many transgenic strains in current use in epilepsy research. The present results indicate that this protocol may be beneficial for investigating the effects of gonadal hormone replacement on seizure susceptibility, mortality, and seizure-induced histopathology, and that gonadectomy unmasks sex differences in susceptibility to seizures and mortality not observed in gonad-intact controls.

Sex and gonadectomy modify behavioral seizure susceptibility and mortality in a repeated low-dose kainic acid systemic injection paradigm in mice

Objective

Sex differences in epilepsy appear driven in part due to effects of gonadal steroids, with varying results in experimental models based on species, strain, and method of seizure induction. Furthermore, removing a main source of these steroids via gonadectomy may impact seizure characteristics differently in males and females. Repeated low-dose kainic acid (RLDKA) systemic injection paradigms were recently shown to reliably induce status epilepticus (SE) and hippocampal histopathology in C57BL/6J mice. Here, we investigated whether seizure susceptibility in a RLDKA injection protocol exhibits a sex difference, and whether gonadectomy differentially influences response to this seizure induction paradigm in males and females.

Methods

Adult C57BL/6J mice were left gonad-intact as controls or gonadectomized (females: ovariectomized, OVX; males: orchidectomized, ORX). At least 2 weeks later, KA was injected i.p. every 30 minutes at 7.5 mg/kg or less until the animal reached SE, defined by at least 5 generalized seizures (GS, Racine stage 3 or higher). Parameters of susceptibility to GS induction, SE development, and mortality rates were quantified.

Results

No differences in seizure susceptibility or mortality were observed between control males and control females. ORX males exhibited increased susceptibility and reduced latency to both GS and SE, but OVX females exhibited increased susceptibility and reduced latency to SE only. However, ORX males, but not OVX females, exhibited strongly increased seizure-induced mortality.

Significance

The RLDKA protocol is notable for its efficacy in inducing SE and seizure-induced histopathology in C57BL/6J mice, the background for many transgenic strains in current use in epilepsy research. The present results indicate that this protocol may be beneficial for investigating the effects of gonadal hormone replacement on seizure susceptibility, mortality, and seizure-induced histopathology, and that gonadectomy unmasks sex differences in susceptibility to seizures and mortality not observed in gonad-intact controls.

Is the peroxisome proliferator-activated receptor gamma a putative target for epilepsy treatment? Current evidence and future perspectives

The peroxisome proliferator-activated receptor gamma (PPARγ), which belongs to the family of nuclear receptors, has been mainly studied as an important factor in metabolic disorders. However, in recent years the potential role of PPARγ in different neurological diseases has been increasingly investigated. Especially, in the search of therapeutic targets for patients with epilepsy the question of the involvement of PPARγ in seizure control has been raised. Epilepsy is a chronic neurological disorder causing a major impact on the psychological, social, and economic conditions of patients and their families, besides the problems of the disease itself. Considering that the world prevalence of epilepsy ranges between 0.5% - 1.0%, this condition is the fourth for importance among the other neurological disorders, following migraine, stroke, and dementia. Among others, temporal lobe epilepsy (TLE) is the most common form of epilepsy in adult patients. About 65% of individuals who receive antiseizure medications (ASMs) experience seizure independence. For those in whom seizures still recur, investigating PPARγ could lead to the development of novel ASMs. This review focuses on the most important findings from recent investigations about the potential intracellular PPARγ-dependent processes behind different compounds that exhibited anti-seizure effects. Additionally, recent clinical investigations are discussed along with the promising results found for PPARγ agonists and the ketogenic diet (KD) in various rodent models of epilepsy.

Pioglitazone Ameliorates Hippocampal Neurodegeneration, Disturbances in Glucose Metabolism and AKT/mTOR Signaling Pathways in Pentyelenetetrazole-Kindled Mice

Disturbance of glucose metabolism, nerve growth factor (NGF) and m-TOR signaling have been associated with the pathophysiology of epilepsy. Pioglitazone (PGZ) is an anti-diabetic drug that shows a protective effect in neurodegenerative diseases including epilepsy; however, its exact mechanism is not fully elucidated. The present study aimed to investigate the potential neuroprotective effect of PGZ in pentylenetetrazole (PTZ) kindled seizure in mice. Swiss male albino mice were randomly distributed into four groups, each having six mice. Group 1 was considered the control. Epilepsy was induced by PTZ (35 mg/kg i.p.) thrice a week for a total of 15 injections in all other groups. Group 2 was considered the untreated PTZ group while Group 3 and Group 4 were treated by PGZ prior to PTZ injection at two dose levels (5 and 10 mg/kg p.o., respectively). Seizure activity was evaluated after each PTZ injection according to the Fischer and Kittner scoring system. At the end of the experiment, animals were sacrificed under deep anesthesia and the hippocampus was isolated for analysis of glucose transporters by RT-PCR, nerve growth factor (NGF) by ELISA and mTOR by western blotting, in addition to histopathological investigation. The PTZ-treated group showed a significant rise in seizure score, NGF and m-TOR hyperactivation, along with histological abnormalities compared to the control group. Treatment with PGZ demonstrated a significant decrease in NGF, seizure score, m-TOR, GLUT-1 and GLUT-3 in comparison to the PTZ group. In addition, improvement of histological features was observed in both PGZ treated groups. These findings suggest that PGZ provides its neuroprotective effect through modulating m-TOR signaling, glucose metabolism and NGF levels.