title: Hemoglobin redox reactions and red blood cell aging.
abstract: CONCLUSIONS
  The physiological mechanism(s) for recognition and removal of red blood cells (RBCs) from circulation after 120 days of its lifespan is not fully understood. Many of the processes thought to be associated with the removal of RBCs involve oxidative stress. We have focused on hemoglobin (Hb) redox reactions, which is the major source of RBC oxidative stress.
  
  
  BACKGROUND
  The importance of Hb redox reactions have been shown to originate in large parts from the continuous slow autoxidation of Hb producing superoxide and its dramatic increase under hypoxic conditions. In addition, oxidative stress has been shown to be associated with redox reactions that originate from Hb reactions with nitrite and nitric oxide (NO) and the resultant formation of highly toxic peroxynitrite when NO reacts with superoxide released during Hb autoxidation.
  
  
  RESULTS
  The interaction of Hb, particularly under hypoxic conditions with band 3 of the RBC membrane is critical for the generating the RBC membrane changes that trigger the removal of cells from circulation. These changes include exposure of antigenic sites, increased calcium leakage into the RBC, and the resultant leakage of potassium out of the RBC causing cell shrinkage and impaired deformability.
  
  
  CONCLUSIONS
  The need to understand the oxidative damage to specific membrane proteins that result from redox reactions occurring when Hb is bound to the membrane. Proteomic studies that can pinpoint the specific proteins damaged under different conditions will help elucidate the cellular aging processes that result in cells being removed from circulation.
authors.affiliation: Molecular Dynamics Section, National Institute on Aging, Baltimore, MD 21224, USA. rifkindj@mail.nih.gov
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Rifkind
authors.forename: Enika
authors.initials: E
authors.lastname: Nagababu
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D016922:Cellular Senescence / Q000502:physiology*; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D011485:Protein Binding; D026361:Reactive Nitrogen Species / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D000975:Antioxidants; D006454:Hemoglobins; D026361:Reactive Nitrogen Species; D017382:Reactive Oxygen Species