MnDPDP: Contrast Agent for Imaging and Protection of Viable Tissue

Figure 5

ROS-RNS with intrinsic cell defence (outer box) and exogenous antioxidants (inner box). The diagram presents free radicals with unpaired electrons (.marked) and other oxidizing byproducts of respiration. Secondary pathways activated by ROS-RNS are not included. Observe the dependence of NO· upon MnSOD and H₂O₂ upon CAT and GPx or upon binding of prooxidant Cu⁺ and Fe²⁺. Suboptimal control of and Fe²⁺ or Cu⁺ may release highly toxic ONOO⁻ and ·OH, radicals which initiate protein nitration and secondary chain reactions attacking most cell constituents. The strategic position of MnDPDP/MnPLED as direct (MnSOD mimetic) and indirect (Fe²⁺/Cu⁺ chelation) catalytic antioxidants is indicated. Material derived from [34, 43, 53–59]. , superoxide; H₂O₂, hydrogen peroxide;·OH, hydroxyl radical; NO·, nitric oxide; ONOO⁻, peroxynitrite; NOS, nitric oxide synthase; MnSOD, mitochondrial SOD; CAT, catalase; GPx, glutathion peroxidase; NAC, N-acetyl-cysteine; scavengers, antioxidants consumed by ROS-RNS and chain reactants in a one-to-one manner.