8-Nitroguanosine is a nitrated nucleic acid which is formed from the reactions of guanosine with peroxynitrite, myeloperoxidase, nitrite, and peroxide. It is known that the nitration of guanine is enhanced in virus infection, bacterial infection, inflammatory disease , cancers , and diseases associated with smoking . 8-Nitroguanosine is thought to be one of the makers of DNA damage caused by oxidative stress. Cyclic GMP (cGMP) is a second messenger that activates protein kinase G. 8-Nitro-cGMP (nitrated cGMP) has been identified as a nitrated cGMP formed in vivo . 8-Nitro-cGMP can act as a unique second messenger distinct from cGMP to induce antioxidative adaptive responses. Mode of actions of 8-nitro-cGMP mainly relies on its adduction to protein cysteine residues called “protein S-guanylation”, as a post translational modification.