Fig. 4

Both in vitro and in vivo sGC activation is directly neuroprotective in a cGMP-PKG-CREB dependent manner. a Improved outcome in treated mice (see Fig. 3) was associated with decreased cortical neuronal apoptosis (n = 4, p < 0.001) suggesting a novel neuroprotective mechanism. b shows an in vitro ischemia model free of vascular and blood-brain-barrier components. After dissection, hippocampal brain slices were subjected to oxygen and glucose deprivation (OGD)/re-oxygenation (ReOx) in the absence or presence of the sGC activators, BAY58-2667 or BAY60-2770, with and without the cGMP-dependent protein kinase inhibitor, KT5823.⁶¹ Both BAY58-2667 (n = 7, p < 0.05) or BAY60-2667 (n = 13, p < 0.05) increased cell viability after OGD/Re-Ox. Adding the PKG-inhibitor KT5823 reversed this effect for both BAY58-2667 (n = 8, p < 0.05) and BAY60-2770 (n = 7, p < 0.05). c BAY60-2770 treatment increased the ratio of the PKG substrate p-CREB/t-CREB upon OGD/ReOx (n = 8, p < 0.05), an effect was completely prevented in the presence of the PKG-inhibitor KT5823 (n = 4, p < 0.05), suggesting a neuroprotective link. d Similarly, p-CREB/t-CREB ratio was significantly increased in vivo 24 h post-stroke (n = 4, p < 0.05). e Schematic representation of the suggested neuroprotective signaling events: BAY58-2667/60-2770 specifically activates the predominant post-stroke form of sGC (heme-free apo-sGC) and thereby recovers lost sGC-dependent cGMP formation, which leads to CREB phosphorylation and direct neuroprotection