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Figure 1. Lowering extracellular pH activates ASIC1a currents in HEK293 cells and these currents are potentiated by reducing Zn2+ concentrations. A, Representative current traces demonstrating the activation of ASIC1a-like current in HEK293 cells. The current is largely inhibited by PcTX venom (150 ng/mL), a specific blocker for homomeric ASIC1a channels. Reducing the concentration of Zn2+ by perfusion with 10 μmol/L TPEN dramatically increased the amplitude of the ASIC current. In contrast, perfusion of the cells with 10 μmol/L ZnCl2 slightly inhibited the ASIC current. B, Summary bar graph demonstrating the effect of changing the concentration of Zn2+ on ASIC current in HEK293 cells. n=5. **P<0.01 compared with control group.Show Less

Figure 3. Acid-induced injury of HEK293 cells is inhibited by specific ASIC1a blockade. Summary bar graph showing the inhibition of acidosis induced injury of HEK293 cells by PcTX venom (150 ng/mL), a specific blocker for homomeric ASIC1a channels. n=4. **P<0.01 between control (pH 7.4) and pH 5.5, and *P<0.05 between pH 5.5 and pH 5.5+PcTX venom.Show Less

Figure 2. Acid incubation induces injury of HEK293 cells. A, Representative black and white images showing the acid-induced injury of HEK293 cells. Cells were incubated with extracellular solutions with pH buffered at either 7.4 or 5.5 for 3 hours before switching back to neurobasal medium. Photographs were taken 24 hours after the acid incubation. B, Bar graph summarizing time-dependent injury of HEK293 cells as indicated by increase in LDH release, after the acid incubation. LDH release at various time points has been normalized to the maximal releasable amount obtained by incubating cells with 1% Triton X-100 for 15 minutes. *P<0.05 and **P<0.01 compared with pH 7.4 treated group at the same time points.Show Less

Figure 4. Effect of Zn2+ on acid-induced injury of HEK293 cells. A, Fluorescent images (upper panel) and summary bar graph (lower panel) showing the potentiation of acidosis-induced injury of HEK293 cells by Zn2+ chelation with TPEN (10 μmol/L). n=4. **P<0.01 between control (pH 7.4) and pH 5.5, and between pH 5.5 and pH 5.5+TPEN. B. Summary bar graph showing inhibition of acid-induced injury of HEK293 cells by addition of 10 μmol/L Zn2+. n=4. **P<0.01 between control and pH 5.5, and *P<0.05 between pH 5.5 and pH 5.5+10 μmol/L Zn2+.Show Less