Figure 7. Summary of the proposed relaxin signaling during lung IR.

Upper panel: In a short-term IR cycle in rat isolated lungs, relaxin induced iNOS in a manner (early in ischemia but moderately in level) distinct from the natural course (later but marked in reperfusion). This moderately elevated NO generation suppresses the IR-related ET-1 surge, both effects act in concert to inhibit cell activation and subsequent tissue damage. Lower panel: Early and moderate iNOS induction by relaxin is dependent on a subtle balance between stimulatory ERK-1/2-NF-κB and inhibitory PI3K-FKHRL-1 pathways.