Angiotensin II induces protein overexpression of hyperpolarization-activated cyclic nucleotide-gated channels in primary cultured nodose neurons

Modulating ion channel function includes acutely affecting the kinetics of the ion channels and chronically changing the expression of ion channels. Our previous study showed that angiotensin II (Ang II) acutely increased hyperpolarization-activated cyclic nucleotide-gated (HCN) currents in nodose ganglion (NG) neurons via NADPH oxidase-superoxide signaling. Therefore, the present study was to measure chronic treatment with Ang II on protein expression of the HCN channels in the primary cultured rat NG neurons. Immunofluorescent staining data showed that HCN1 was expressed in the A-type NG neurons, and HCN2 was expressed in the C-type NG neurons. Chronic treatment of Ang II (100. nM, 12. h) induced the protein expression of HCN2 besides the overexpression of HCN1 in the A-type NG neurons; and the overexpression of HCN2 in the C-type NG neurons. An Ang II type I receptor antagonist (1 μM losartan), a NADPH oxidase inhibitor (100 μM apocynin), or a superoxide dismutase mimetic (1. mM tempol) attenuated the effect of Ang II to increase the protein expression of the HCN channels in rat nodose neurons. Whole cell patch-clamp data further confirmed that chronic treatment of Ang II (100. nM, 12. h) significantly enhanced the density of HCN currents in A- and C-type NG neurons. Above three inhibitors significantly inhibited the Ang II-induced increase of the HCN channel density in rat NG neurons. These findings suggest that Ang II-NADPH oxidase-superoxide signaling chronically regulates the protein expression of the HCN channels in rat nodose neurons.