838-P: Lipotoxicity-Induced Liver Cell Injury Is Prevented by a Novel Positive Allosteric Modulator of the GABAA Receptor

NAFLD is a highly prevalent condition currently lacking an approved pharmacological therapy. GABA, besides being a neurotransmitter, has been proposed to protect from liver toxicity in both in vivo an in vitro models. We aimed to determine if a novel positive allosteric modulator (PAM) of the GABA_A receptor, the thioacrylamide-derivative HK4 which is devoid of blood brain barrier penetration, can protect human hepatocytes against lipotoxicity-induced injury.

Patch clamping in HEK-293 cells and calcium influx measurements in INS-1E cells proved HK4 as a selective PAM of the GABA_A receptor. The expression of several main GABA_A receptor subunits (α₁, α₃, α₅, β_2/3 and γ₂) was demonstrated by Western blotting of HepG2 cells. Next generation sequencing was performed and an effect of HK4 on the gene expression profile in response to palmitate was observed. A preventive effect of HK4 on palmitate-induced apoptosis was demonstrated by reduced caspase 3/7 activity both in HepG2 (47.32 ± 6.92 % vs. 1065 ± 98.68 %) and human primary hepatocytes (57.13 ± 21.47 % vs. 155.1 ± 3.78 %) . This effect was further confirmed by the TUNEL assay (6.41 ± 1.42 % vs. 11.62 ± 0.99 % TUNEL positive cells) . This anti-apoptotic effect was mediated through reduced protein expression of cleaved PARP-1, reduced phosphorylation of NF-κB, and by upregulation of the ER chaperone PDI, as measured by Western blotting.

In conclusion, GABAergic signaling reduces lipotoxic-induced apoptosis in hepatocytes by preventing inflammation, DNA damage and ER stress. Therefore, we propose that HK4 may arise as an innovative pharmacological tool to treat or prevent NASH as a first-in-class drug.