GABA receptor x GAD1

Gamma amino butyric acid (GABA) is a neurotransmitter inhibitor molecule functioning in the central nervous system of mammals, found in all the suprachiasmatic nucleus (SCN) and has a critical role in refining circadian rhythm since the SCN sends signals to peripheral clocks for synchronization. GABA may function in plants in a similar way to animals in relation to circadian rhythm. Previously, we found that GABA biosynthesis was affected at transcriptional level in Nicotiana tabaccum under drought stress during 24 h periodicity. In the light of these findings we hypothesized that, GABA might be an internal cue for circadian rhythm and disruption of this interaction by different stresses might affect phase rhythms in tobacco. We conducted experiments with N. tabaccum plants under salt stress in 72 h periodicity. Physiological parameters along with GABA content, GAD and GABA-T activities were measured and the transcript profiles of genes related to the morning, central and evening loops of the circadian rhythm were also analyzed. According to our findings, under control conditions, GABA-shunt was found to be associated with CCA1, PRR7, TOC, PRR3 and GI, while H₂O₂ content was negatively correlated with GABA catabolism. Salt stress reversed the daily rhythm of GABA biosynthesis (day and night cycle) as compared to the control plants. The morning and the night/central genes' transcript abundances were impaired during day-night transitions in salt-stressed groups. Moreover, under salt stress, GABA catabolism was associated more with the morning phase genes and the correlation between GABA-shunt and the circadian rhythm was adversely affected. It is possible that increased H₂O₂ content under salt stress may also play a regulatory role in this interplay.

GAD67 impacts insomnia as a key enzyme catalysing the conversion of glutamate (Glu) to gamma‐aminobutyric acid (GABA). Senegenin enhances neuroprotection and is used widely to treat insomnia and other neurological diseases. This study aimed to investigate how senegenin regulates insomnia through a GAD67‐mediated signalling pathway. We measured GAD67 expression levels in insomnia patients and evaluated the expression levels of GAD67 and Keap1/Nrf2/Parkin/PINK1‐related cytokines following GAD67 lentiviral transfection in PC12 cells and in rat models. We also assessed cellular reactive oxygen species (ROS) and mitochondrial membrane potential levels. Additionally, EEG/EMG was used to analyse the sleep phases of rats and to assess memory and exploration functions. Pathological changes and the expression of GAD67 and sleep‐related proteins in the hippocampus were examined. The results showed that GAD67 expression was increased in insomnia patients, ROS levels were elevated, and the mitochondrial membrane potential was decreased in the GAD67‐KD group. Insomnia rats exhibited changes in sleep rhythm, learning, and exploration dysfunction, pathological changes in the CA1 region of the hippocampus, and differential expression of GAD67 and sleep‐related factors. Inhibitory neurofactor expression levels were decreased in insomnia rats, showing a positive correlation in the GAD67‐KD group and a negative correlation in the GAD67‐OE group. Conversely, excitatory factor expression levels were increased in insomnia rats, showing a positive correlation in the GAD67‐KD group and a negative correlation in the GAD67‐OE group. Senegenin intervention modulated cytokine expression levels. In conclusion, GAD67 negatively regulates insomnia, and senegenin can regulate insomnia by mediating the expression of cytokines in the GAD67‐regulated Keap1/Nrf2/Parkin/PINK1 pathway.

This study aimed to examine the efficacy and underlying mechanisms of action of cinnamic acid (CA) in the treatment of insomnia.

An insomnia model was established using parachlorophenylalanine (PCPA) in rats. Pathological changes in the rat hippocampal CA3 region were assessed using hematoxylin and eosin staining. Sleep duration and sleep-wake states were assessed using a pentobarbital-induced sleep test and electroencephalogram analysis. Neurotransmitters, including 5-hydroxytryptophan (5-HTP), 5-hydroxy tryptamine (5-HT), γ-aminobutyric acid (GABA), and glutamic acid (Glu), were detected via enzyme-linked immunosorbent assay. Changes in glutamic acid decarboxylase (GAD)67, GABA_AR γ2, GABA_AR β2, and GABA_AR α proteins were assessed using western blotting. Bulk RNA sequencing (RNA-seq) analysis and molecular docking were used to explore the mechanism of action of CA in insomnia treatment.

In the rat model with PCPA-induced insomnia, CA treatment increased body weight and food intake, reduced water intake, and alleviated damage to the hippocampal CA3 region. CA treatment also reduced sleep latency and wake time and enhanced sleep duration, rapid eye movement sleep, and non-rapid eye movement sleep. In the hypothalamus, CA treatment increased 5-HTP, 5-HT, GABA, GAD67, GABAAR γ2, GABAAR β2, and GABAAR α1 levels, but reduced Glu levels. Using the data from bulk RNA-seq, GSEA analysis indicated neurotrophin signaling pathway was activated by CA treatment. CA could bind with LHPP and reduced its protein expression.

CA treatment prolonged sleep duration and improved sleep quality in a rat model of insomnia, mediated by LHPP inhibition.