Fig. 2.

Digoxin blocks HIF-1 activation and Nox2 up-regulation by IH. A: Digoxin inhibits IH₆₀-evoked HIF-1α accumulation in a concentration-dependent manner. Top part, representative HIF-1α immunoblot. Bottom part, densitometric analysis of HIF-1α protein levels normalized to tubulin protein levels and expressed as percent change from normoxic control (N). B: Digoxin inhibits HIF-1-dependent reporter gene expression by IH. PC12 cells were cotransfected with p2.1, containing an HRE upstream of SV40 promoter and luciferase coding sequences, and pRSV-LacZ, containing RSV promoter and β-gal coding sequences. Transfected cells were exposed to either 20% O₂ (N) or 120 cycles of IH (IH 120). C,D: Digoxin inhibits up-regulation of Nox2 mRNA expression (C) and Nox enzyme activity (D) in response to IH. Mean ± SEM (n = 3–5) are shown, **P < 0.01 compared with control (N).