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Prenatal nicotine changes the response to postnatal chlorpyrifos: Interactions targeting serotonergic synaptic function and cognition.

ABSTRACT: Nicotine and chlorpyrifos are developmental neurotoxicants that target serotonin systems. We examined whether prenatal nicotine exposure alters the subsequent response to chlorpyrifos given postnatally. Pregnant rats received nicotine throughout gestation at 3mg/kg/day, a regimen designed to achieve plasma levels seen in smokers; chlorpyrifos was given to pups on postnatal days (PN) 1-4 at 1mg/kg, just above the detection threshold for brain cholinesterase inhibition. We assessed long-term effects from adolescence (PN30) through full adulthood (PN150), measuring the expression of serotonin receptors and serotonin turnover (index of presynaptic impulse activity) in cerebrocortical brain regions encompassing the projections that are known targets for nicotine and chlorpyrifos. Nicotine or chlorpyrifos individually increased the expression of serotonin receptors, with greater effects on males than on females and with distinct temporal and regional patterns indicative of adaptive synaptic changes rather than simply an extension of initial injury. This interpretation was confirmed by our finding an increase in serotonin turnover, connoting presynaptic serotonergic hyperactivity. Animals receiving the combined treatment showed a reduction in these adaptive effects on receptor binding and turnover relative to the individual agents, or even an effect in the opposite direction; further, normal sex differences in serotonin receptor concentrations were dissipated or reversed, an effect that was confirmed by behavioral evaluations in the Novel Objection Recognition Test. In addition to the known liabilities associated with maternal smoking during pregnancy, our results point to additional costs in the form of heightened vulnerability to neurotoxic chemicals encountered later in life.

SUBMITTER: Slotkin TA

PROVIDER: S-EPMC4324014 | biostudies-other | 2015 Feb

REPOSITORIES: biostudies-other

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Prenatal nicotine changes the response to postnatal chlorpyrifos: Interactions targeting serotonergic synaptic function and cognition.

Slotkin Theodore A TA Skavicus Samantha S Levin Edward D ED Seidler Frederic J FJ

Brain research bulletin 20150112

Nicotine and chlorpyrifos are developmental neurotoxicants that target serotonin systems. We examined whether prenatal nicotine exposure alters the subsequent response to chlorpyrifos given postnatally. Pregnant rats received nicotine throughout gestation at 3mg/kg/day, a regimen designed to achieve plasma levels seen in smokers; chlorpyrifos was given to pups on postnatal days (PN) 1-4 at 1mg/kg, just above the detection threshold for brain cholinesterase inhibition. We assessed long-term effec ...[more]

PMID: 25592617

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Project description:Chlorpyrifos (CPF), one of the most widely-used organophosphorus (OP) insecticides in agriculture, is degraded in the field to its oxon form, chlorpyrifos-oxon (CPO), which can represent a significant contaminant in exposures to adults and children. CPO is also responsible for the acetylcholinesterase (AChE) inhibition associated with CPF exposures; CPF is converted by liver CYP450 enzymes to CPO, which binds to and inhibits AChE and other serine active-site esterases, lipases and proteases. Young children represent a particularly susceptible population for exposure to CPF and CPO, in part because levels of the plasma enzyme, paraoxonase (PON1), which hydrolyzes CPO, are very low during early development. While a number of studies have demonstrated developmental neurotoxicity associated with CPF exposure, including effects at or below the threshold levels for AChE inhibition, it is unclear whether these effects were due directly to CPF or to its active metabolite, CPO. PON1 knockout (PON1-/-) mice, which lack PON1, represent a highly sensitive mouse model for toxicity associated with exposure to CPF or CPO. To examine the neurobehavioral consequences of CPO exposure during postnatal development, PON1-/- mice were exposed daily from PND 4 to PND 21 to CPO at 0.15, 0.18, or 0.25 mg/kg/d. A neurobehavioral test battery did not reveal significant effects of CPO on early reflex development, motor coordination, pre-pulse inhibition of startle, startle amplitude, open field behavior, or learning and memory in the contextual fear conditioning, Morris water maze, or water radial-arm maze tests. However, body weight gain and startle latency were significantly affected by exposure to 0.25 mg/kg/d CPO. Additionally, from PNDs 15-20 the mice exposed repeatedly to CPO at all three doses exhibited a dose-related transient hyperkinesis in the 20-min period following CPO administration, suggesting possible effects on catecholaminergic neurotransmission. Our previous study demonstrated wide-ranging effects of neonatal CPO exposure on gene expression in the brain and on brain AChE inhibition, and modulation of both of these effects by the PON1(Q192R) polymorphism. The current study indicates that the neurobehavioral consequences of these effects are more elusive, and suggests that alternative neurobehavioral tests might be warranted, such as tests of social interactions, age-dependent effects on learning and memory, or tests designed specifically to assess dopaminergic or noradrenergic function.

Project description:Prenatal exposure to synthetic corticosteroids can significantly alter postnatal development through changes in neurotransmitters, peptides and their receptors, and thus having long-lasting behavioral effects. Some of these changes have been observed in animal experiments, others also in humans prenatally exposed to synthetic corticosteroids. Here, we focused on transcriptomic changes within the ARC of rats prenatally exposed to either betamethasone or saline. The expression of transcriptome has been assessed by novel computational tools to determine complex changes that may have life-long effects on phenotype, i.e., behavior. Total of 18,094 unigenes were quantified in the hypothalamic ARC of P14 male and female rats prenatally exposed to betametasone used in this experiment. Out of these genes, Kyoto Encyclopedia for Genes and Genomes (http://www.genome.jp) selected 112 for the dopaminergic synapse, 75 for the GABAergic and 97 for the glutamatergic synapse. We further analyzed composition, topology and modulatory networks of the genomic fabric of the dopaminergic, GABAergic, and glutamatergic synapse (the transcriptome of the most interconnected and stably expressed gene network responsible for specific transmission). Finally we investigated the M-bM-^@M-^\transcriptomic landscapeM-bM-^@M-^] of the GSF in the ARC of P14 males (M) and females (F) prenatally (G15) exposed to betamethasone (B) or saline (S). We combined in one measure (PWR = Pair-Wise Relevance) expression levels, controls and coordination of all pairs that can be formed by synapse genes with the other synapse genes, higher PWRs indicating larger influence of that gene pair to the fabric modulation. We found that prenatal exposure to betamethasone caused sex-dependent changes in the dopaminergic/GABA/glutamatergic synapse genes:. In males, 10 dopaminergic (9%), 4 GABAergic (5%) and 5 glutamatergic synapse genes (5%) were down-regulated. While in females, 9 dopaminergic (8%), 3 GABAergic (4%) and 6 glutamatergic (6%) synapse genes were downregulated. The data indicate that in both sexes the dopaminergic synapse was the most affected. In contrast, in control animals, no significant differences between male and female were present in these synapse genes. Since the most noticeable transcritpomic changes were found in the transcriptome of DA glutamatergic synapse, we investigated the expression of tyrosine-hydroxylase (TH) NMDA receptor subunits in the ARC. The western blot analyses and immunohistochemistry confirmed the sex-specific differences between prenatally betamethasone-exposed and saline-exposed P15 rats. Accordingly to the changes in gene expression, prenatal exposure to synthetic corticosteroids was associated with postnatal changes in behavior and susceptibility to certain types of seizures. While we did not find any significant impairements in normal behavioral patterns (open field activity), there was a sex-specific change in the novel object recognition test. We found that behavioral lateralization in females is lost after prenatal betamethasone exposure and both male and female prenatally betamethasone exposed rats were avoiding novelty. This trait is similar to children with autism and suggests that certain elements of autistic behaviors can be present after prenatal exposure to synthetic corticosteroids. Additionally, there were changes in the search patterns in the Morris water maze as well as in the Barnes maze. In conclusion, our work is consistent with findings of profound reprogramming changes in the brain after prenatal corticosteroid exposure associated with alterations cognitive functions and seizure susceptibility. Two-sexes (M, F) x two-condition (B = betamethasone prenataly exposed vs S = saline prenataly exposed) experiment. Biological replicates: 4 MS, 4 FS, 4 MB, 4 FB.

Project description:Prenatal exposure to synthetic corticosteroids can significantly alter postnatal development through changes in neurotransmitters, peptides and their receptors, and thus having long-lasting behavioral effects. Some of these changes have been observed in animal experiments, others also in humans prenatally exposed to synthetic corticosteroids. Here, we focused on transcriptomic changes within the ARC of rats prenatally exposed to either betamethasone or saline. The expression of transcriptome has been assessed by novel computational tools to determine complex changes that may have life-long effects on phenotype, i.e., behavior. Total of 18,094 unigenes were quantified in the hypothalamic ARC of P14 male and female rats prenatally exposed to betametasone used in this experiment. Out of these genes, Kyoto Encyclopedia for Genes and Genomes (http://www.genome.jp) selected 112 for the dopaminergic synapse, 75 for the GABAergic and 97 for the glutamatergic synapse. We further analyzed composition, topology and modulatory networks of the genomic fabric of the dopaminergic, GABAergic, and glutamatergic synapse (the transcriptome of the most interconnected and stably expressed gene network responsible for specific transmission). Finally we investigated the “transcriptomic landscape” of the GSF in the ARC of P14 males (M) and females (F) prenatally (G15) exposed to betamethasone (B) or saline (S). We combined in one measure (PWR = Pair-Wise Relevance) expression levels, controls and coordination of all pairs that can be formed by synapse genes with the other synapse genes, higher PWRs indicating larger influence of that gene pair to the fabric modulation. We found that prenatal exposure to betamethasone caused sex-dependent changes in the dopaminergic/GABA/glutamatergic synapse genes:. In males, 10 dopaminergic (9%), 4 GABAergic (5%) and 5 glutamatergic synapse genes (5%) were down-regulated. While in females, 9 dopaminergic (8%), 3 GABAergic (4%) and 6 glutamatergic (6%) synapse genes were downregulated. The data indicate that in both sexes the dopaminergic synapse was the most affected. In contrast, in control animals, no significant differences between male and female were present in these synapse genes. Since the most noticeable transcritpomic changes were found in the transcriptome of DA glutamatergic synapse, we investigated the expression of tyrosine-hydroxylase (TH) NMDA receptor subunits in the ARC. The western blot analyses and immunohistochemistry confirmed the sex-specific differences between prenatally betamethasone-exposed and saline-exposed P15 rats. Accordingly to the changes in gene expression, prenatal exposure to synthetic corticosteroids was associated with postnatal changes in behavior and susceptibility to certain types of seizures. While we did not find any significant impairements in normal behavioral patterns (open field activity), there was a sex-specific change in the novel object recognition test. We found that behavioral lateralization in females is lost after prenatal betamethasone exposure and both male and female prenatally betamethasone exposed rats were avoiding novelty. This trait is similar to children with autism and suggests that certain elements of autistic behaviors can be present after prenatal exposure to synthetic corticosteroids. Additionally, there were changes in the search patterns in the Morris water maze as well as in the Barnes maze. In conclusion, our work is consistent with findings of profound reprogramming changes in the brain after prenatal corticosteroid exposure associated with alterations cognitive functions and seizure susceptibility.

Dataset Information

Prenatal nicotine changes the response to postnatal chlorpyrifos: Interactions targeting serotonergic synaptic function and cognition.

Publications

Prenatal nicotine changes the response to postnatal chlorpyrifos: Interactions targeting serotonergic synaptic function and cognition.

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