title: Epigenetic mechanisms are involved in the regulation of ethanol consumption in mice.
abstract: BACKGROUND
  Repeated alcohol exposure is known to increase subsequent ethanol consumption in mice. However, the underlying mechanisms have not been fully elucidated. One postulated mechanism involves epigenetic modifications, including histone modifications and DNA methylation of relevant genes such as NR2B or BDNF.
  
  
  METHODS
  To investigate the role of epigenetic mechanisms in the development of alcohol drinking behavior, an established chronic intermittent ethanol exposure reinforced ethanol drinking mouse model with vapor inhalation over two 9-day treatment regimens was used. The DNA methyltransferase inhibitor, 5-azacytidine or the histone deacetylase inhibitor, Trichostatin A was administered (intraperitoneally) to C57BL/6 mice 30 min before daily exposure to chronic intermittent ethanol. Changes in ethanol consumption were measured using the 2-bottle choice test.
  
  
  RESULTS
  The results indicated that systemic administration of Trichostatin A (2.5 µg/g) facilitated chronic intermittent ethanol-induced ethanol drinking, but systemic administration of 5-azacytidine (2 µg/g) did not cause the same effect. However, when 5-azacytidine was administered by intracerebroventricular injection, it facilitated chronic intermittent ethanol-induced ethanol drinking. Furthermore, the increased drinking caused by chronic intermittent ethanol was prevented by injection of a methyl donor, S-adenosyl-L-methionine. To provide evidence that chronic intermittent ethanol- or Trichostatin A-induced DNA demethylation and histone modifications of the NR2B promoter may underlie the altered ethanol consumption, we examined epigenetic modifications and NR2B expression in the prefrontal cortex of these mice. Chronic intermittent ethanol or Trichostatin A decreased DNA methylation and increased histone acetylation in the NR2B gene promoter, as well as mRNA levels of NR2B in these mice.
  
  
  CONCLUSIONS
  Taken together, these results indicate that epigenetic modifications are involved in regulating ethanol drinking behavior, partially through altering NR2B expression.
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang). qiang@uthscsa.edu.
authors.forename: Mei
authors.initials: M
authors.lastname: Qiang
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Ji G
authors.initials: JG
authors.lastname: Li
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Ashley D
authors.initials: AD
authors.lastname: Denny
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Jie-Min
authors.initials: JM
authors.lastname: Yao
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Mai
authors.initials: M
authors.lastname: Lieu
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Kerang
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Department of Pharmacology, The University of Texas Health Science Center at San Antonio, San Antonio, Texas (Drs Qiang, Li, Denny, Lieu, and Carreon); Department of Neurology, Third Hospital of Guangxi Medical University, Nanning, Guangxi, China (Dr Yao); Department of Psychiatry, First Clinical Medical College (Dr Zhang), and School of Public Health, Shanxi Medical University, Taiyuan, China (Dr Qiang).
authors.forename: Stephanie
authors.initials: S
authors.lastname: Carreon
mesh_terms: D000107:Acetylation / Q000187:drug effects; D000428:Alcohol Drinking / Q000235:genetics* / Q000503:physiopathology; D000818:Animals; D001374:Azacitidine / Q000494:pharmacology; D002492:Central Nervous System Depressants / Q000008:administration & dosage; D019175:DNA Methylation / Q000187:drug effects; D015254:DNA Modification Methylases / Q000037:antagonists & inhibitors / Q000378:metabolism; D044127:Epigenesis, Genetic; D000431:Ethanol / Q000008:administration & dosage; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006657:Histones / Q000187:drug effects / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D008297:Male; D008810:Mice, Inbred C57BL; D017397:Prefrontal Cortex / Q000503:physiopathology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate / Q000235:genetics / Q000378:metabolism
chemical_list: D002492:Central Nervous System Depressants; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; C121001:NR2B NMDA receptor; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D000431:Ethanol; C012589:trichostatin A; D015254:DNA Modification Methylases; D001374:Azacitidine
keywords: 5-azacytidine; NR2B; SAM; Trichostatin-A; alcohol drinking; epigenetics; mice