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The formation of learning and memory is regulated by synaptic plasticity in hippocampal neurons. Here we explored how gestational exposure to dexamethasone, a synthetic glucocorticoid commonly used in clinical practice, has lasting effects on offspring's learning and memory. Adult offspring rats of prenatal dexamethasone exposure (PDE) displayed significant impairments in novelty recognition and spatial learning memory, with some phenotypes maintained transgenerationally. PDE impaired synaptic transmission of hippocampal excitatory neurons in offspring of F1 to F3 generations, and abnormalities of neurotransmitters and receptors would impair synaptic plasticity and lead to impaired learning and memory, but these changes failed to carry over to offspring of F5 and F7 generations. Mechanistically, altered hippocampal miR-133a-3p-SIRT1-CDK5-NR2B signaling axis in PDE multigeneration caused inhibition of excitatory synaptic transmission, which might be related to oocyte-specific high expression and transmission of miR-133a-3p. Together, PDE affects hippocampal excitatory synaptic transmission, with lasting consequences across generations, and CDK5 in offspring's peripheral blood might be used as an early-warning marker for fetal-originated learning and memory impairment.
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Developmental programming of the embryo is controlled by both genetic information and epigenetic information. During fertilization, this information carried by sperms can be delivered to thezygote, where they can regulate early embryonic development. Mature sperms are highly abundant in epigenetic information, and including small non-coding RNAs (sncRNAs), which play important roles during spermatogenesis, fertilization, and early embryo development. Recent studies revealed that sncRNAs can regulate gene expression, mediate protein translation, transmit the epigenetic information, and so on. Recently, increasing evidences showed that parental environment exposure, such as diet, toxicant, pressure, may cause the inheritance of acquired characteristics, and they can be stored and transmitted to the next generation by epigenetic information in germ cells. Recent advances of transgenerational inheritance revealed that sncRNAs are environmentally responsive epigenetic molecules in sperms. This review summarized current knowledge about the sncRNAs information in sperms, including transfer RNA-derived small RNAs (tsRNAs), rsRNAs (risbosome-RNA derived small RNAs), microRNAs (miRNAs) and PIWI-interacting RNAs (piRNAs), that are responsive to environmental factors and are capable of affecting embryonic development and the phenotype of the offspring later in life. Furthermore, this review also delineated potential molecular mechanisms that might regulate sperm sncRNAs.
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OBJECTIVE To investigate the transgenerational effect of neuroendocrine metabolic programmed alteration in adult intrauterine growth retardation (lUGR) offspring rats with prenatal nicotine exposure. METHODS Pregnant Wistar rats were administered daily with nicotine (2 mg.kg-1 ) by sc from gestational day 11 until delivery. F1 offspring was fed with a standard diet before four groups in F2 were set up according to the cross-mating between F1 normal adult rats and nicotine-induced lUGR adult rats. CC group was mated by F1 normal adult rats, CN group by F1 normal adult male rats and lUGR adult female rats, NC group by F1 lUGR adult male rats and normal adult female rats, while NN group was mated by F1 lUGR adult rats. F2 adult rats were subjected to a fortnight ice water swimming stimulus. Blood samples were collected before and after stress and then detected for the levels of adrenocortico-tropic hormone ( ACTH), corticosterone ( CORT), glucose, triglycerides ( TG) and total cholesterol (TCH). RESULTS Before stress, the level of serum CORT in F2 male rats of NN group was decreased to 73.9% of that of the CC group (P<0.05),while the level of serum TG in F2 male rats of CN and NC groups was increased to 1.43 and 1.52 times that of the CC group, respectively ( P<0.05). Meanwhile, the level of serum TG in F2 female rats of CN, NC and NN groups was increased to 1.71, 1.80 and 1.81 times that of the CC group, respectively (P<0.05). After stress, the serum CORT gain rate in F2 male rats of CC group was -1.67%, but was 36.0% in NN group. The serum glucose level in male NC group and in female CN group was increased to 1.61 and 1.62 times that of the corresponded CC groups, respectively (P<0.01). Furthermore, the serum TG gain rate in F2 rats of each nicotine group was decreased markedly in comparison with their corresponding controls (P<0.05), ie, the serum TG gain rates in F2 male rats of CN, NC and NN groups were decreased to 46.4%, 16.7% and 7.7% of the CC group, while the serum TG gain rates in F2 female rats of these groups were decreased to 20.6%, 4.0% and 8.4% of the CC group, respectively. Compared with CC group, TCH level of females and males in NN group was decreased by 40.5% and 21.9%(P<0.01) before stress, respectively, and the TCH gain rate of females in NN group was increased by 49.7%(P<0.05) after stress. CONCLUSION The reproductive and developmental toxicities and the neuroendocrine metabolic programming alterations induced by prenatal nicotine exposure are transgenerated to F2 offspring and these effects exhibit gender and parental differences.
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OBJECTIVE To investigate the transgenerational effects of a hypothala mic-pituitary-ad-renal (HPA)axis -associated neuroendocrine metabolic progra mming alteration fro m F1 to adult second generation (F2)with prenatal ethanol ingestion.METHODS Pregnant Wistar rats were ad ministered with ethanol (4 mg·kg -1·d -1 )fro m gestational day 1 1 until delivery.F1 rats were fed a high-fat diet fro m postnatal week 4 (PW4)and were cross-mated in PW 16 -20.F2 rats were fed a standard diet fro m PW4 and rectal te mperature was measured in PW20,oral glucose tolerance test (OGTT)was con-ducted in PW21 ,blood sa mples and hypothala mus were collected in PW24 to investigate seru m lipids and HPA axis activity.RESULTS Co mparing to the F2 control group ,rectal te mperature in F2 ethanol group were higher (P<0.01 ),sugar tolerance in F2 male group was i mpaired (P<0.05),seru m corti-costerone and hypothala mus arginine vasopressin (AVP) mRNA were increased (P <0.05);seru m insulin were decreased (P<0.05)and male rats showed i mpaired glucose tolerance (P<0.05);seru m high-density lipoproteincholesterol (HDL-C)decrease (P <0.05)and total cholesterol (TCH)/HDL-C and low density lipoproteincholesterol (LDL-C)/HDL-C ratios were markedly increased (P <0.05,P <0.01 ).CONCLUSION Prenatal ethanol exposure induced metabolic syndro me has transgenerational effects,which may originate fro m the intrauterine progra mming of altered HPA axis-associated neuroen-docrine metabolis m.