Perinatal nicotine exposure increases vulnerability of hypoxic-ischemic brain injury in neonatal rats: role of angiotensin II receptors.
OBJECTIVE
Maternal cigarette smoking increases the risk of neonatal morbidity. We tested the hypothesis that perinatal nicotine exposure causes heightened brain vulnerability to hypoxic-ischemic (HI) injury in neonatal rats through aberrant expression patterns of angiotensin II type 1 (AT(1)R) and type 2 (AT(2)R) receptors in the developing brain.


METHODS
Nicotine was administered to pregnant rats through subcutaneous osmotic minipumps. HI brain injury was determined in 10-day-old pups. AT(1)R and AT(2)R expression patterns were assessed through Western blotting, quantitative polymerase chain reaction, immunofluorescence, and confocal imaging.


RESULTS
Perinatal nicotine exposure significantly increased HI brain infarct size in male, but not female, pups. In fetal brains, nicotine caused a decrease in mRNA and protein abundance of AT(2)R but not AT(1)R. The downregulation of AT(2)R persisted in brains of male pups, and nicotine treatment resulted in a significant increase in methylation of CpG locus 3 bases upstream of TATA-box at the AT(2)R gene promoter. In female brains, there was an increase in AT(2)R but a decrease in AT(1)R expression. Both AT(1)R and AT(2)R expressed in neurons but not in astrocytes in the cortex and hippocampus. Central application of AT(1)R antagonist losartan or AT(2)R antagonist PD123319 increased HI brain infarct size in both male and female pups. In male pups, AT(2)R agonist CGP42112 abrogated nicotine-induced increase in HI brain infarction. In females, PD123319 uncovered the nicotine's effect on HI brain infarction.


CONCLUSIONS
Perinatal nicotine exposure causes epigenetic repression of the AT(2)R gene in the developing brain resulting in heightened brain vulnerability to HI injury in neonatal male rats in a sex-dependent manner.
Center for Perinatal Biology, Division of Pharmacology, Department of Basic Sciences, Loma Linda University, School of Medicine, Loma Linda, CA 92350, USA.
Yong
Y
Li
Daliao
D
Xiao
Chiranjib
C
Dasgupta
Fuxia
F
Xiong
Wenni
W
Tong
Shumei
S
Yang
Lubo
L
Zhang
D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D015153:Blotting, Western; D001921:Brain / Q000473:pathology; D020208:Brain Injury, Chronic / Q000473:pathology*; D002545:Brain Ischemia / Q000473:pathology*; D019175:DNA Methylation / Q000187:drug effects; D005260:Female; D005317:Fetal Growth Retardation / Q000139:chemically induced / Q000473:pathology; D002534:Hypoxia, Brain / Q000473:pathology*; D007093:Imidazoles / Q000494:pharmacology / Q000627:therapeutic use; D007150:Immunohistochemistry; D008297:Male; D018613:Microscopy, Confocal; D009538:Nicotine / Q000633:toxicity*; D018722:Nicotinic Agonists / Q000633:toxicity*; D011247:Pregnancy; D011725:Pyridines / Q000494:pharmacology / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D060888:Real-Time Polymerase Chain Reaction; D044140:Receptor, Angiotensin, Type 1 / Q000096:biosynthesis / Q000235:genetics; D044139:Receptor, Angiotensin, Type 2 / Q000096:biosynthesis / Q000235:genetics; D011945:Receptors, Angiotensin / Q000502:physiology*
D047228:Angiotensin II Type 1 Receptor Blockers; D007093:Imidazoles; D018722:Nicotinic Agonists; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D000804:Angiotensin II; C073402:PD 123319; D009538:Nicotine