Quantitative expression and localization of GABAB receptor protein subunits in hippocampi from patients with refractory temporal lobe epilepsy. (1st July 2018)

• Record Type: Journal Article
• Authors: Sheilabi, Mariam A.; Battacharyya, Dev; Caetano, Laura; Thom, Maria; Reuber, Markus; Duncan, John S.; Princivalle, Alessandra P.
• Is Part Of: Neuropharmacology. Volume 136:Part A(2018)
• Page Start: 117
• Page End: 128
• Publication Date: 2018-07-01
• Subjects: Human temporal lobe epilepsy -- Hippocampal sclerosis -- GABAB qRT-PCR -- Quantitative Western blot -- Immunohistochemistry; Neuropsychopharmacology -- Periodicals; Autonomic Agents -- Periodicals; Neuropsychopharmacologie -- Périodiques; Neuropsychopharmacology; Periodicals; Electronic journals; 615.78
• DOI: 10.1016/j.neuropharm.2017.08.001
• Languages: English
• ISSNs: 0028-3908

Abstract

Abstract: This study investigates GABAB protein expression and mRNA levels in three types of specimens. Two types of specimens from patients with temporal lobe epilepsy (TLE), secondary to hippocampal sclerosis, sclerotic hippocampal samples (TLE-HS), and tissue from the structurally preserved non-spiking ipsilateral superior temporal gyrus (TLE-STG) removed from the same patient during epilepsy surgery; and third specimen is hippocampal tissue from individuals with no history of epilepsy ( post-mortem controls, PMC). mRNA expression of GABAB subunits was quantified in TLE-HS, TLE-STG and PMC specimens by qRT-PCR. Qualitative and quantitative Western blot (WB) and immunohistochemistry techniques were employed to quantify and localize GABAB proteins subunits. qRT-PCR data demonstrated an overall decrease of both GABAB1 isoforms in TLE-HS compared to TLE-STG. These results were mirrored by the WB findings. GABAB2 mRNA and protein were significantly reduced in TLE-HS samples compared to TLE-STG; however they appeared to be upregulated in TLE-HS compared to the PMC samples. Immunohistochemistry (IHC) showed that GABAB proteins were widely distributed in PMC and TLE-HS hippocampal sections with regional differences in the intensity of the signal. The higher expression of mature GABAB protein in TLE-HS than PMC is in agreement with previous studies. However, these findings could be due to post-mortem changes in PMC specimens. The TLE-STG samples examined here represent a better 'control' tissue compared to TLE-HS samples characterised by lower than expected GABAB expression. This interpretation provides a better explanation for previous functional studies suggesting reduced inhibition in TLE-HS tissue due to attenuated GABAB currents. This article is part of the "Special Issue Dedicated to Norman G. Bowery". Highlights: This study investigates GABAB in three types of human specimens: two from patients with TLE-HS, TLE-STG and PMC. This study investigates GABAB with three different quantitative techniques: RT-PCR, Western blot, and immunohistochemistry in human specimens. The higher expression of mature GABAB protein in TLE-HS than PMC is in agreement with previous studies. On the other hand, this study shows a statistically significant lower expression of GABAB2 in TLE-HS samples than in non-epileptogenic. Downregulated GABAB2 in TLE-HS could represent one reason for impaired GABAergic inhibition in epileptogenic hippocampus.