Abstract
Brain-derived neurotrophic factor (BDNF) is a well-known and well-studied neurotrophin. Most biological effects of BDNF are mediated by the activation of TrkB receptors. This neurotrophin regulates several neuronal functions as cell proliferation, viability, and differentiation. Ouabain is a steroid that binds to the Na(+)/K(+) ATPase, inducing the activation of several intracellular signaling pathways. Previous data from our group described that ouabain treatment increases retinal ganglion cells survival (RGC). The aim of the present study was to evaluate, if this cardiac glycoside can have a synergistic effect with BDNF, the classical trophic factor for retinal ganglion cells, as well as investigate the intracellular signaling pathways involved. Our work demonstrated that the activation of Src, PLC, and PKCδ participates in the signaling cascade mediated by 50 ng/mL BDNF, since their selective inhibitors completely blocked the trophic effect of BDNF. We also demonstrated a synergistic effect on RGC survival when we concomitantly used ouabain (0.75 nM) and BDNF (10 ng/mL). Moreover, the signaling pathways involved in this synergistic effect include Src, PLC, PKCδ, and JNK. Our results suggest that the synergism between ouabain and BDNF occurs through the activation of the Src pathway, JNK, PLC, and PKCδ.