Angiotensin type 2 receptor neuroprotection against chemical hypoxia is dependent on the delayed rectifier K ⁺ channel, Na ⁺/Ca ²⁺ exchanger and Na ⁺/K ⁺ ATPase in primary cortical cultures

We have previously reported that angiotensin II (Ang II) protects cortical neurons from chemical-induced hypoxia through activation of the angiotensin type 2 (AT ₂) receptor. Here, we show in mouse primary neuronal cultures that the AT ₂ receptor neuroprotection results from the activation of the delayed rectifier K ⁺ channel as well as the involvement of the Na ⁺/Ca ²⁺ exchanger (NCX) and Na ⁺/K ⁺ ATPase (ATPase). Roles of the K ⁺ channel, NCX and ATPase were determined using the specific blockers α-dendrotoxin, KB-R7943 and ouabain, respectively. Sodium azide (10 mM) induced apoptosis in 40% of neurons. Inhibition of the AT ₁ receptor with losartan (1 μM) facilitated angiotensin II mediated neuroprotection by reducing sodium azide-induced apoptosis 61.8 ± 5.6%, while inhibition of the AT ₂ receptor with PD123319 (1 μM) showed no neuroprotection. These results suggest that angiotensin II neuroprotection is mediated through the AT ₂ receptor and requires inhibition of the AT ₁ receptor in order to facilitate its effect. To determine the roles of delayed rectifier K ⁺ channel, NCX and ATPase cultures were pretreated with α-dendrotoxin (10 nM), KB-R7943 (100 nM) and ouabain (100 nM), which significantly attenuated AT ₂ receptor mediated neuroprotection. These findings further suggest that the mechanism of AT ₂ receptor mediated neuroprotection is coupled to activation of the delayed rectifier K ⁺ channel, NCX and ATPase.