Activation of hydroxycarboxylic acid receptor 1 attenuates glutamate-induced excitotoxic neuronal injury

The aim of this study is to investigate the role of hydroxycarboxylic acid receptor 1 (HCAR1) in glutamate-induced excitotoxic neuronal injury. The effective and safe concentrations of an endogenous HCAR1 agonist (L-lactic acid) and an exogenous HCAR1 agonist (3,5-dihydroxybenzoic acid, 3,5-DHBA) were determined using a CCK-8 assay. An excitotoxic injury model was established by stimulating mouse hippocampal neuronal cells (HT22 cells) with 20 mM glutamate, followed by intervention with safe concentrations of L-lactic acid and 3,5-DHBA. Neuronal survival and apoptosis were assessed by NeuN immunofluorescence staining and a TUNEL assay. The effects of HCAR1 agonists on glutamate transport were evaluated using vesicular glutamate transporter 1 (VGLUT1) immunofluorescence staining and qRT‒PCR. Additionally, qRT‒PCR was performed to quantify the expression of a neuronal excitability marker gene ( c-fos ), inflammatory factors and hcar1 . The results showed that HCAR1 agonists (L-lactic acid and 3,5-DHBA) significantly improved neuronal survival, reduced glutamate-induced apoptosis and decreased neuronal excitability ( p < 0.05). The activation of HCAR1 inhibited the transport of the excitatory neurotransmitter glutamate ( p < 0.05). The upregulation of HCAR1 expression led to the significant downregulation of the expression of inflammatory factors ( il-1β , il-6 and tnf-α ) ( p < 0.05). In conclusion, HCAR1 activation effectively suppresses glutamate-induced neuronal apoptosis, reduces the uptake of excitatory neurotransmitters, and downregulates proinflammatory factor expression, thereby exerting neuroprotective effects.