Acidosis induces autophagic cell death through ASIC1-mediated Akt/mTOR signaling in HT22 neurons

Although it has been confirmed that acid-sensing ion channel 1 (ASIC1) plays a critical role in acidosis-induced neuronal injury and death, its underlying mechanisms remain largely unclear. In the present study, we investigated the involvement of ASIC1 in acidosis-induced neuronal death and its underlying mechanisms in HT22 neurons. The neurons were cultured in acidic medium to mimic extracellular acidosis. Cell viability and death, autophagy, ASIC1 expression, and the phosphorylation of Akt and mTOR were evaluated. Our results demonstrated that acidosis markedly increased the cell death rate, which was profoundly reversed by 3-MA (an autophagy inhibitor) but exacerbated by rapamycin (an autophagy activator). Moreover, our results indicated that acidosis induced excessive autophagy by increasing the expression and translocation of ASIC1, and decreasing the phosphorylation of the Akt and mTOR proteins. Intriguingly, inhibiting the activation of ASIC1 with its blocker PcTx-1 not only significantly decreased acidosis-induced neurotoxicity but also markedly compromised acidosis-induced autophagy and Akt/mTOR signaling inactivation, as evidenced by a decrease in the neuronal death rate, LC3Ⅱ/LC3Ⅰ ratio, and autophagosome number as well as p62 degradation and an increase in the phosphorylation of Akt and mTOR. Collectively, these results indicate that acidosis exerts its cytotoxic effects on HT22 neurons by inducing autophagic cell death through the ASIC1-related Akt/mTOR signaling pathway.