Summary of Mechanisms by which Gasotransmitters can Induce Cytoprotection. The gasotransmitters share unique and similar pathways by which they protect against tissue and cellular injury. Both CO and NO have been shown to regulate smooth muscle relaxation through the sGC/cGMP pathway. NO and H2S have been shown to regulate cell proliferation and vascular smooth muscle relaxation balance through mitogen-activated protein kinases (MAPK), and ATP-sensitive potassium channels (KATP ). In addition, H2S and CO regulate oxidant/antioxidant balance through the transcription factor NF-E2-related factor (Nrf2).