Fig. 10. Scheme of the proposed signal transduction cascade activated by ROS and hypoxia. Either hypoxia (initiating elevated ROS generation) or exogenous addition of ROS induces phosphorylation of gp130 and initiates a feed-forward cycle of NADPH oxidase activity and expression. ROS generated by NADPH oxidase act as signalling molecules within the CT-1/gp130 signalling cascade which finally results in HIF-1 upregulation and stimulation of CT-1 expression.