Calcium-permeable Acid-sensing Ion Channel Is a Molecular Target of the Neurotoxic Metal Ion Lead

Abstract

Acid-sensing ion channels (ASICs) are emerging as fundamental players in the regulation of neural plasticity and in pathological conditions. Here we showed that lead (Pb2+), a well known neurotoxic metal ion, reversibly and concentration-dependently inhibited ASIC currents in the acutely dissociated spinal dorsal horn and hippocampal CA1 neurons of rats. In vitro expression of ASIC subunits in combination demonstrated that both ASIC1 and -3 subunits were sensitive to Pb2+. Mechanistically, Pb2+ reduced the pH sensitivity of ASICs independent of membrane voltage change. Moreover, Pb2+ inhibited the ASIC-mediated membrane depolarization and the elevation of intracellular Ca2+ concentration. In addition, we compared the effect of Pb2+ with that of Ca2+ or amiloride to explore the possible interactions of Pb2+ and Ca2+ in regulating ASICs, and we found that Pb2+ inhibited ASIC currents independent of the amiloride/Ca2+ blockade. Because ASIC1b and -3 subunits are mainly expressed in peripheral neurons, our data identified ASIC1a-containing Ca2+-permeable ASIC as a novel central target of Pb2+ action, which may contribute to Pb2+ neurotoxicity.

Upregulation of Acid-Sensing Ion Channel ASIC1a in Spinal Dorsal Horn Neurons Contributes to Inflammatory Pain Hypersensitivity

“…All constructs were expressed in Chinese hamster ovary (CHO) cells. Transient transfection of CHO cells was performed as reported previously (Wu et al, 2004;Wang et al, 2006). Cotransfection with a green fluorescent protein (GFP) expression vector, pEGFP-N1, was used to enable identification of transfected cells for patch clamping by monitoring GFP fluorescence in some experiments.…”

“…Ca 2ϩ imaging. Intracellular Ca 2ϩ imaging was performed as previously described (Gao et al, 2005;Wang et al, 2006). Primary cultured SDH neurons at 4 d in vitro (DIV) were incubated with 1 M Fura-2-acetoxymethyl ester for 20 min at 37°C, washed three times, and incubated in standard extracellular solution for 30 min.…”

Subunit‐dependent cadmium and nickel inhibition of acid‐sensing ion channels

“…are sensitive to metal ions (Baron et al, 2001(Baron et al, , 2002Segal et al, 2002;Sheng et al, 2002;Cucu et al, 2003Cucu et al, , 2005Chu et al, 2004;Gao et al, 2004;Wang et al, 2006). While the effects of extracellular Zn 2þ , Pb 2þ , and Gd 3þ on ASIC and acid-sensing currents in neurons have been explored (Babinski et al, 2000;Baron et al, 2001Baron et al, , 2002Chu et al, 2004;Gao et al, 2004;Wang et al, 2006), possible regulation by Ni 2þ and Cd 2þ have not.…”

“…While the effects of extracellular Zn 2þ , Pb 2þ , and Gd 3þ on ASIC and acid-sensing currents in neurons have been explored (Babinski et al, 2000;Baron et al, 2001Baron et al, , 2002Chu et al, 2004;Gao et al, 2004;Wang et al, 2006), possible regulation by Ni 2þ and Cd 2þ have not. This is in contrast to ENaC, which is recognized to be modulated by extracellular Ni 2þ (Segal et al, 2002;Sheng et al, 2002;Cucu et al, 2003Cucu et al, , 2005.…”

“…While ASIC1a, 2a, 2b, and 4 are widely expressed in both central and peripheral sensory neurons, ASIC1b and 3 are found primarily in sensory neurons (Waldmann et al, 1999;Krishtal, 2003 (Stockand et al, 1993;Chen et al, 1997;Paoletti et al, 1997;Shafer, 1998;Fayyazuddin et al, 2000;Sharonova et al, 2000;Gavazzo et al, 2001;Erreger and Traynelis, 2005). For endogenous and recombinant ASIC, the effects of Zn 2þ and Pb 2þ are dose-dependent and reversible with the actions of these metals often being subunit specific (Baron et al, 2001(Baron et al, , 2002Chu et al, 2004;Gao et al, 2004;Wang et al, 2006). Regulation of ASIC by Cd 2þ and Ni 2þ , in contrast, has not been reported.…”