Protective effects of γ-aminobutyric acid against H

γ-Aminobutyric acid (GABA) is a major inhibitory neurotransmitter in the central nervous system and reported to maintain the redox homeostasis and insulin secretion function of pancreatic β cells. This study tested the hypothesis that GABA maintains cellular redox status, and modulates glycogen synthase kinase (GSK)-3β and antioxidant-related nuclear factor erythroid 2-related factor 2 (NRF2) nuclear mass ratio in the H2O2-injured RINm5F cells.

RINm5F cells were treated with/without GABA (50, 100 and 200 μmol/L) for 48 h and then exposed to 100 μmol/L H2O2 for 30 min. Viable cells were harvested, and dichloro-dihydro-fluorescein diacetate (DCFH-DA) was used to detect reactive oxygen species (ROS) level; cellular redox status and insulin secretion were measured; cell viability was determined by 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay; mitochondrial membrane potential (MMP) was detected by flow cytometry; relative genes levels were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR); western blotting was used to determine protein expression of GSK-3β and p-GSK-3β (Ser9), and nuclear and cytoplasmic NRF2.

H2O2 increased ROS production, and induced adverse affects in relation to antioxidant defense systems and insulin secretion. These changes were restored by treatment with 100 and 200 μmol/L GABA. In addition, 100 or 200 μmol/L GABA induced membrane depolarization and increased cell viability. These effects were mediated by Caspase-3, Bcl-2 associated X protein (Bax) and B-cell lymphoma-2 (Bcl-2) expression. Western blotting indicated that GABA inhibited GSK-3β by increasing p-GSK-3β (Ser9) level, and directed the transcription factor NRF2 to the nucleus.

In rat insulin-producing RINm5F cells, GABA exerts its protective effect by regulating GSK-3β and NRF2, which governs redox homeostasis by inhibiting apoptosis and abnormal insulin secretion by exposure to H2O2.