BDNF mediated activity dependent maturation of visual Wulst following prenatal repetitive auditory stimulation at a critical developmental period in domestic chicks (Gallus domesticus)

Altered hippocampal kynurenine pathway metabolism contributes to hyperexcitability in human mesial temporal lobe epilepsy-hippocampal sclerosis

BACKGROUND AND PURPOSE

Glutamate receptor-mediated enhanced excitatory neurotransmission is typically associated with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). Kynurenic acid and quinolinic acid are two important tryptophan-kynurenine pathway metabolites that modulate glutamate receptor activity. This study was designed to test the hypothesis that alteration in metabolism of tryptophan-kynurenine pathway metabolites in the hippocampus of patients with MTLE-HS contributes to abnormal glutamatergic transmission.

EXPERIMENTAL APPROACH

Levels of tryptophan-kynurenine pathway metabolites were determined using HPLC and LC-MS/MS in hippocampal samples from patients with MTLE-HS, compared with autopsy and non-seizure control samples. mRNA and protein expressions of tryptophan-kynurenine pathway enzymes were determined by qPCR and Western blot. Spontaneous glutamatergic activities were recorded from pyramidal neurons in the presence of kynurenine and kynurenic acid, using whole-cell patch clamp.

KEY RESULTS

Levels of kynurenic acid were reduced and quinolinic acid levels were raised in hippocampal samples from MTLE-HS patients, whereas kynurenine levels remained unaltered, compared with levels in non-seizure controls. Spontaneous glutamatergic activity in MTLE-HS hippocampal samples was higher than that in non-seizure controls. Treatment with kynurenine inhibited glutamatergic activity in non-seizure control samples but not in MTLE-HS samples. However, exogenously applied kynurenic acid inhibited glutamatergic activity in both non-seizure control and MTLE-HS hippocampal samples. Also, levels of kynurenine aminotransferase II and its cofactor pyridoxal phosphate were reduced in MTLE-HS samples.

CONCLUSION AND IMPLICATIONS

Our findings indicate that altered metabolism of tryptophan-kynurenine pathway metabolites in hippocampus could contribute to hyperglutamatergic tone in patients with MTLE-HS.

Embelin ameliorates cognitive dysfunction and progression of kindling in pentylenetetrazol-induced kindling in mice by attenuating brain inflammation

OBJECTIVE

This study was conducted to evaluate the effect of embelin (EMB) on various epileptic models and related brain inflammation.

METHODS

Male Swiss albino mice were administered EMB (5, 10, and 20 mg/kg/p.o.) in acute and chronic study for 7 days and 35 days, respectively. Acute study included increasing current electroshock (ICES) and pentylenetetrazol (PTZ)-induced seizure test. Step-down latency (SDL) and forced swim test (FST) were performed to evaluate cognitive functions and depression-like behavior, respectively. Chronic study included PTZ-induced kindling. Levels of inflammatory biomarkers, namely interleukin-1 beta (IL-1β), interleukin-1 receptor antagonist (IL-1Ra), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), were estimated in the hippocampus and cortex of the kindled brains by ELISA technique. Further, neurotransmitters (NTs), namely gamma aminobutyric acid (GABA), glutamate, and dopamine, were estimated by using validated liquid chromatography-mass spectrometry (LC-MS) method followed by ultra-high-performance liquid chromatography (UHPLC).

RESULTS

Embelin (EMB) treatment increased the seizure threshold to hind limb extension (HLE) in the ICES test and decreased the seizure scores in the kindling experiment. Significantly low levels of IL-1β, IL-1Ra, IL-6, and TNF-α were observed in the hippocampus of PTZ + EMB (10 and 20 mg/kg)-treated groups compared with PTZ+ vehicle-treated group. Significantly lower levels of IL-1Ra, IL-6, and TNF-α compared with PTZ+ vehicle-treated group were observed in the cortex of PTZ + EMB (10 and 20 mg/kg)-treated groups, while IL-1β levels were found to be significantly lower only in the cortex of PTZ + EMB (20 mg/kg)-treated group. Increased levels of dopamine and GABA and decreased levels of glutamate in both hippocampus and cortex were observed in EMB + PTZ-treated groups compared with vehicle + PTZ-treated group. Latency of step down was found to be increased and immobility time in FST was decreased in EMB + PTZ groups compared with vehicle + PTZ group.

CONCLUSION

Embelin suppressed epileptogenesis in the kindled mice via neurochemical modulation of neurotransmitters and inhibiting the inflammatory pathway. Further, EMB was also observed to be protecting the kindled animals from cognition and depression-like behavior.