Free Radical Injury

Overview

• Free radicals are chemical compounds with unpaired electrons in the valence shell
  • a cascade is initiated whereby a free radical steals an electron from a cellular molecule
  • the intial free radical is quenched but has created another free radical
  • results in cell membrane peroxidation, DNA and protein damage
• Causes of free radical generation
  • radiation exposure
  • metabolism of drugs (phase I)
    • e.g.) acetaminophen
  • redox reactions
    • naturally as part of oxidative ATP generation
  • nitric oxide
  • transition metals
    • e.g.) copper and iron
  • leukocyte oxidative burst
  • reperfusion after anoxia 
    • a major cause of injury after thrombolytic therapy
  • carbon tetrachloride exposure 
    • solvent used in dry cleaning industry
    • leads to hepatocyte damage and resultant fatty change
• Degradation of free radicals occus by
  • enzymes
    • catalase
    • superoxide dismutase
    • glutathione peroxidase
  • spontaneous decay
  • antioxidants
    • vitamins A, C, E