title: Caffeine inhibits erythrocyte membrane derangement by antioxidant activity and by blocking caspase 3 activation.
abstract: The aim of this research was to investigate the effect of caffeine on band 3 (the anion exchanger protein), haemoglobin function, caspase 3 activation and glucose-6-phosphate metabolism during the oxygenation-deoxygenation cycle in human red blood cells. A particular attention has been given to the antioxidant activity by using in vitro antioxidant models. Caffeine crosses the erythrocyte membrane and interacts with the two extreme conformational states of haemoglobin (the T and the R-state within the framework of the simple two states allosteric model) with different binding affinities. By promoting the high affinity state (R-state), the caffeine-haemoglobin interaction does enhance the pentose phosphate pathway. This is of benefit for red blood cells since it leads to an increase of NADPH availability. Moreover, caffeine effect on band 3, mediated by haemoglobin, results in an extreme increase of the anion exchange, particularly in oxygenated erythrocytes. This enhances the transport of the endogenously produced CO(2) thereby avoiding the production of dangerous secondary radicals (carbonate and nitrogen dioxide) which are harmful to the cellular membrane. Furthermore caffeine destabilizes the haeme-protein interactions within the haemoglobin molecule and triggers the production of superoxide and met-haemoglobin. However this damaging effect is almost balanced by the surprising scavenger action of the alkaloid with respect to the hydroxyl radical. These experimental findings are supported by in silico docking and molecular dynamics studies and by what we may call the "caspase silence"; in fact, there is no evidence of any caspase 3 activity enhancement; this is likely due to the promotion of positive metabolic conditions which result in an increase of the cellular reducing power.
authors.affiliation: Organic and Biological Chemistry Department, University of Messina, V. le Ferdinando Stagno d'Alcontres 31, 98166 Messina, Italy. etellone@unime.it
authors.forename: Ester
authors.initials: E
authors.lastname: Tellone
authors.forename: Silvana
authors.initials: S
authors.lastname: Ficarra
authors.forename: Annamaria
authors.initials: A
authors.lastname: Russo
authors.forename: Ersilia
authors.initials: E
authors.lastname: Bellocco
authors.forename: Davide
authors.initials: D
authors.lastname: Barreca
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Laganà
authors.forename: Ugo
authors.initials: U
authors.lastname: Leuzzi
authors.forename: Davide
authors.initials: D
authors.lastname: Pirolli
authors.forename: Maria Cristina
authors.initials: MC
authors.lastname: De Rosa
authors.forename: Bruno
authors.initials: B
authors.lastname: Giardina
authors.forename: Antonio
authors.initials: A
authors.lastname: Galtieri
mesh_terms: D001457:Anion Exchange Protein 1, Erythrocyte / Q000819:agonists* / Q000378:metabolism; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D053148:Caspase 3 / Q000378:metabolism; D004910:Erythrocyte Membrane / Q000187:drug effects* / Q000378:metabolism; D004912:Erythrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D017665:Hydroxyl Radical / Q000037:antagonists & inhibitors / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D009249:NADP / Q000096:biosynthesis; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010427:Pentose Phosphate Pathway / Q000187:drug effects*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D013816:Thermodynamics
chemical_list: D001457:Anion Exchange Protein 1, Erythrocyte; D006454:Hemoglobins; D017665:Hydroxyl Radical; D002110:Caffeine; D006418:Heme; D009249:NADP; D053148:Caspase 3; D010100:Oxygen