title: Promoter methylation represses AT2R gene and increases brain hypoxic-ischemic injury in neonatal rats.
abstract: Perinatal nicotine exposure downregulated angiotensin II type 2 receptor (AT2R) in the developing brain and increased brain vulnerability to hypoxic-ischemic injury in male neonatal rats. We tested the hypothesis that site-specific CpG methylation at AT2R gene promoter contributes to the increased vulnerability of brain injury in the neonate. Nicotine was administered to pregnant rats from day 4 of gestation to day 10 after birth. Brain hypoxic-ischemic injury was induced in day 10 male pups. CpG methylation at AT2R promoter was determined in the brain by quantitative methylation-specific PCR. Nicotine exposure significantly increased the methylation of a single CpG-52 locus near the TATA-box at AT2R promoter. Electrophoretic mobility shift assay indicated that the methylation of CpG-52 significantly decreased the binding affinity of TATA-binding protein (TBP). Chromatin immunoprecipitation assay further demonstrated an increase in the binding of a methyl-binding protein and a decrease in TBP binding to AT2R promoter in vivo in neonatal brains of nicotine-treated animals. This resulted in AT2R gene repression in the brain. Intracerebroventricular administration of a demethylating agent 5-aza-2'-deoxycytidine abrogated the enhanced methylation of CpG-52, rescued the TBP binding, and restored AT2R gene expression. Of importance, 5-aza-2'-deoxycytidine reversed the nicotine-increased vulnerability of brain hypoxic-ischemic injury in the neonate. The finding provides mechanistic evidence of increased promoter methylation and resultant AT2R gene repression in the developing brain linking perinatal stress and a pathophysiological consequence of heightened vulnerability of brain hypoxic-ischemic encephalopathy in the neonate.
authors: Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA 92350, USA; Department of Neurology, First Affiliated Hospital of Chongqing Medical University, Chongqing 400016, China.
authors: Yong
authors: Y
authors: Li
authors: Daliao
authors: D
authors: Xiao
authors: Shumei
authors: S
authors: Yang
authors: Lubo
authors: L
authors: Zhang
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000187:drug effects / Q000473:pathology; D018899:CpG Islands; D019175:DNA Methylation; D005260:Female; D020925:Hypoxia-Ischemia, Brain / Q000235:genetics* / Q000473:pathology; D008297:Male; D009538:Nicotine / Q000633:toxicity; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D044139:Receptor, Angiotensin, Type 2 / Q000235:genetics* / Q000378:metabolism; D016385:TATA Box; D035181:TATA-Box Binding Protein / Q000378:metabolism
chemical_list: D044139:Receptor, Angiotensin, Type 2; D035181:TATA-Box Binding Protein; D009538:Nicotine
keywords: AT(2)R; Hypoxic–ischemic encephalopathy; Methylation; Nicotine
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