title: Protective effect of polyphenols on presbycusis via oxidative/nitrosative stress suppression in rats.
abstract: Age-related hearing loss (AHL) -presbycusis- is the number one neurodegenerative disorder and top communication deficit of our aged population. Experimental evidence suggests that mitochondrial dysfunction associated with reactive oxygen species (ROS) plays a central role in the aging process of cochlear cells. Dietary antioxidants, in particular polyphenols, have been found to be beneficial in protecting against the generation of ROS in various diseases associated with oxidative stress, such as cancer, neurodegenerative diseases and aging.
  
  
  
  This study was designed to investigate the effects of polyphenols on AHL and to determine whether oxidative stress plays a role in the pathophysiology of AHL.
  
  
  
  Sprague-Dawley rats (n=100) were divided into five groups according to their age (3, 6, 12, 18 and 24months old) and treated with 100mg/kg/day body weight of polyphenols dissolved in tap water for half of the life of the animal. Auditory steady-state responses (ASSR) threshold shifts were measured before sacrificing the rats. Then, cochleae were harvested to measure total superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, reactive oxidative and nitrogen species levels, superoxide anions and nitrotyrosine levels.
  
  
  
  Increased levels of ROS and RNS in cochlea observed with age decreases with polyphenol treatment. In addition, the activity of SOD and GPx enzymes in older rats recovered after the administration of polyphenols.
  
  
  
  The reduction in oxidative and nitrosative stress in the presence of polyphenols correlates with significant improvements in ASSR threshold shifts.
authors.affiliation: European University of Madrid, Calle del Tajo S/N 28670 Villaviciosa de Odón, Madrid, Spain. Electronic address: carolina.sanchez2@universidadeuropea.es.
authors.forename: Carolina
authors.initials: C
authors.lastname: Sánchez-Rodríguez
authors.affiliation: Department of Otolaryngology, University Hospital of Getafe, Carretera de Toledo, km 12, 500, Getafe (Madrid), Spain. Electronic address: edurloc@gmail.com.
authors.forename: Eduardo
authors.initials: E
authors.lastname: Martín-Sanz
authors.affiliation: Department of Biochemistry, University Hospital of Getafe, Carretera de Toledo, km 12, 500, Getafe (Madrid), Spain. Electronic address: esperanza.cuadrado@salud.madrid.org.
authors.forename: Esperanza
authors.initials: E
authors.lastname: Cuadrado
authors.affiliation: Clinical Epidemiology Unit, Infanta Cristina Hospital, Avenida 9 de junio, 2. 28981 - Parla, Madrid, Spain. Electronic address: jjgranizo@granadatos.com.
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Granizo
authors.affiliation: Department of Otolaryngology, University Hospital of Getafe, Carretera de Toledo, km 12, 500, Getafe (Madrid), Spain. Electronic address: rsanzf@salud.madrid.org.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Sanz-Fernández
mesh_terms: D000375:Aging / Q000187:drug effects*; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D003051:Cochlea / Q000187:drug effects / Q000378:metabolism; D005072:Evoked Potentials, Auditory; D005979:Glutathione Peroxidase / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress / Q000187:drug effects*; D059808:Polyphenols / Q000494:pharmacology*; D011304:Presbycusis / Q000188:drug therapy* / Q000503:physiopathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D059808:Polyphenols; D017382:Reactive Oxygen Species; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase
keywords: Auditory steady-state responses (ASSR); Oxidative and nitrosative stress; Polyphenols; Presbycusis