Genistein inhibits voltage-gated sodium currents in SCG neurons through protein tyrosine kinase-dependent and kinase-independent mechanisms

摘要

Voltage-gated sodium channels play a crucial role in the initiation and propagation of neuronal action potentials. Genistein, an isoflavone phytoestrogen, has long been used as a broad-spectrum inhibitor of protein tyrosine kinases (PTK). In addition, genistein-induced modulation of ion channels has been described previously in the literature. In this study, we investigated the effect of genistein on voltage-gated sodium channels in rat superior cervical ganglia (SCG) neurons. The results show that genistein inhibits Na+ currents in a concentration-dependent manner, with a concentration of half-maximal effect (IC₅₀) at 9.1 ± 0.9 μM. Genistein positively shifted the voltage dependence of activation but did not affect inactivation of the Na+ current. The inactive genistein analog daidzein also inhibited Na+ currents, but was less effective than genistein. The IC₅₀ for daidzein-induced inhibition was 20.7 ± 0.1 μM. Vanadate, an inhibitor of protein tyrosine phosphatases, partially but significantly reversed genistein-induced inhibition of Na+ currents. Other protein tyrosine kinase antagonists such as tyrphostin 23, an erbstatin analog, and PP2 all had small but significant inhibitory effects on Na+ currents. Among all active and inactive tyrosine kinase inhibitors tested, genistein was the most potent inhibitor of Na+ currents. These results suggest that genistein inhibits Na+ currents in rat SCG neurons through two distinct mechanisms: protein tyrosine kinase-independent, and protein tyrosine kinase-dependent mechanisms. Furthermore, the Src kinase family may be involved in the basal phosphorylation of the Na+ channel.