Perinatal dietary supplementation with a soy lecithin preparation: effects on development of central catecholaminergic neurotransmitter systems

Re-evaluation of lecithins (E 322) as a food additive

The present opinion deals with the re-evaluation of lecithins (E 322) when used as a food additive. Lecithins (E 322) is an authorised food additive in the EU according to Annex II and Annex III to Regulation (EC) No 1333/2008 on food additives, and have been previously evaluated by JECFA in 1973 and by the SCF in 1982. Among lecithins, phosphatidylcholine is hydrolysed in choline in the cytidine-5-diphosphate-choline pathway in all cells of the body. Following the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010, the Panel concluded that there was no need for a numerical ADI for lecithins (E 322) and that there was no safety concern for the general population from more than 1 year of age at the refined exposure assessment for the reported uses of lecithins (E 322) as a food additive. The Panel further concluded that there is no safety concern for the exposure to the choline from lecithins (E 322) as a food additive at use and use levels reported by industry. For infants (from 12 weeks up to 11 months of age), the Panel concluded that there was no safety concern at the refined exposure assessment for the reported uses of lecithins (E 322) as a food additive and for the choline from lecithins (E 322) as a food additive at use and use levels reported by industry. For infants and young children consuming foods for special medical purposes, the Panel concluded that there was no safety concern with respect to the refined exposure assessment for the reported uses of lecithins (E 322) as a food additive and for exposure to choline resulting from these uses of lecithins (E 322).

Intake of Fermented Soybean (Natto) Increased Locomotor Activity in Mice

We fed mice food granules containing fermented soybean (natto in Japanese) powder (hereafter "natto granules") for 14 d to investigate whether natto granules had any effects on mouse behavior. We noted an enhancement of locomotor activity in natto-granule-fed mice compared to control and soybean-pellet-fed mice. This enhanced locomotor activity was blocked by a low dose of haloperidol (1 microg/kg i.p.), a dopamine receptor antagonist, but not by methysergide, a serotonin 5-HT(1/2) receptor antagonist. The results suggest that the enhanced locomotor activity induced by continuous intake of natto granules in mice is sensitive to haloperidol.

Effects of prenatal nicotine exposure on primate brain development and attempted amelioration with supplemental choline or vitamin C: neurotransmitter receptors, cell signaling and cell development biomarkers in fetal brain regions of rhesus monkeys

Studies in developing rodents indicate that nicotine is a neuroteratogen that disrupts brain development by stimulating nicotinic acetylcholine receptors (nAChRs) that control neural cell replication and differentiation. We administered nicotine to pregnant Rhesus monkeys from gestational day 30 through 160 by continuous infusion, achieving maternal plasma levels comparable to those in smokers (30 ng/ml). Fetal brain regions and peripheral tissues were examined for nAChR subtypes, other neurotransmitter receptors, and indices of cell signaling and cell damage. Nicotine evoked nAChR upregulation, but with distinct regional disparities indicative of selective stimulatory responses. Similarly, indices of cell loss (reduced DNA), cell size and neuritic outgrowth (protein/DNA and membrane/total protein ratios) were distinct for each region and did not necessarily follow the rank order of nAChR upregulation, suggesting the involvement of additional mechanisms such as oxidative stress. We then attempted to offset the adverse effects of nicotine with standard dietary supplements known to interact with nicotine. By itself, choline elicited nicotine-like actions commensurate with its promotion of cholinergic neurotransmission. When given in combination with nicotine, choline protected some regions from damage but worsened nicotine's effects in other regions. Similarly, Vitamin C supplementation had mixed effects, increasing nAChR responses while providing protection from cell damage in the caudate, the brain region most susceptible to oxidative stress. Our results indicate that nicotine elicits neurodevelopmental damage that is highly selective for different brain regions, and that dietary supplements ordinarily thought to be neuroprotectant may actually worsen some of the adverse effects of nicotine on the fetal brain.

Neonatal chlorpyrifos exposure alters synaptic development and neuronal activity in cholinergic and catecholaminergic pathways

After routine home application of chlorpyrifos (CPF), infant and child exposures can exceed acceptable levels. We treated neonatal rats daily on postnatal days (PN) 1-4 (1 mg/kg) or days 11-14 (5 mg/kg), treatments that evoked no overt signs of toxicity. Effects on the development of cholinergic neuronal function were assessed using choline acetyltransferase (ChAT) activity and hemicholinium-3 (HC-3) binding as indices of synaptic proliferation and synaptic activity, respectively. In the forebrain, early CPF treatment caused a decrease in ChAT without affecting HC-3 binding; late treatment decreased HC-3 binding without affecting ChAT. In the brainstem, early treatment had no effect on either parameter but late treatment decreased both ChAT and HC-3 binding. Effects of CPF were not limited to development of cholinergic synapses but also involved catecholamine pathways. For norepinephrine or dopamine, either early or late CPF treatment evoked an increase in synaptic activity (transmitter turnover). The cerebellum, a region with sparse cholinergic innervation, was affected the most. Effects on catecholamine systems were unrelated to the magnitude or temporal pattern of cholinesterase inhibition. Our results suggest that CPF exposure during the postnatal period of synaptogenesis elicits widespread disruption of cholinergic and catecholaminergic pathways. As this is the period in which patterns of synaptic responsiveness is programmed by neural input, the period of developmental vulnerability to CPF is likely to extend into childhood.

Fetal dexamethasone exposure interferes with establishment of cardiac noradrenergic innervation and sympathetic activity

Endogenous glucocorticoids provide natural differentiation signals for adrenergic neurons, and exposure to high exogenous steroid levels thus disrupts the timing of neuronal maturation. In the current study, pregnant rats were given 0.05, 0.2, or 0.8 mg/kg dexamethasone on gestational days 17, 18, and 19, and the effects on development of cardiac sympathetic function were assessed postnatally in the offspring. Dexamethasone produced a dose-dependent retardation of body and heart weight gains; at the highest dose, heart weight deficits were smaller than those for body weight, producing a relative cardiomegaly. The weight effects were accompanied by abnormalities of noradrenergic innervation, as assessed with measurements of norepinephrine levels and turnover. Norepinephrine levels were significantly reduced at all doses of dexamethasone, with the magnitude of effect exceeding that on heart or body weights; thus the levels were reduced even when corrected for tissue weight (ng norepinephrine/g heart weight). Norepinephrine turnover, a measure of neuronal impulse activity, showed delayed development at the lowest dose of dexamethasone and displayed profound suppression throughout development at the higher doses. Adverse effects of dexamethasone on norepinephrine turnover were still apparent in young adulthood, despite the recovery of weight variables to within 15% of normal values. In light of the release of steroids during maternal stress and the use of steroids in the therapy of neonatal respiratory distress, developing adrenergic neurons are likely to be targeted for adverse effects even when standard growth indices have normalized.

Fetal dexamethasone exposure alters macromolecular characteristics of rat brain development: a critical period for regionally selective alterations?

Fetal glucocorticoid exposure retards postnatal growth and evokes abnormalities of nervous system structure and function. To examine the underlying mechanisms, we administered 0.2 or 0.8 mg/kg of dexamethasone to pregnant rats on gestational days 17, 18, and 19 and assessed brain region cell development with indices of DNA content (total cell numbers), DNA concentration (cell packing density), and protein/DNA ratio (relative cell size). Dexamethasone evoked deficits of pup body and brain region weights, but the brain regions displayed growth-sparing associated initially with preservation of cell numbers (normal or elevated DNA content and concentration), at the expense of relative cell size (decreased protein/DNA). Subsequently, brain cell acquisition lagged behind that of controls, with deficits in DNA and elevations of protein/DNA. In midbrain + brainstem and in cerebellum, cell markers returned to normal by weaning. However, the forebrain showed persistent elevations of DNA and reduced protein/DNA, indicative of replacement of neurons with glia. Because the treatment period coincided with the timing of neuronal cell replication in the forebrain, but not in the other regions, these results suggest that the critical period for lasting deficits of dexamethasone coincides with the peak of neuronal mitosis.

Fetal dexamethasone exposure sensitizes neonatal rat brain to hypoxia: effects on protein and DNA synthesis

Fetal exposure to glucocorticoids is known to produce long-term alterations in cell development within the central nervous system. The current study examines whether some of the adverse effects of prenatal dexamethasone treatment on brain development represent sensitization to hypoxia-induced damage. Pregnant rats were given 0.2 or 0.8 mg/kg of dexamethasone on gestational days 17, 18 and 19 and their offspring were challenged by exposure to 7% O2 on postnatal days 1 and 8. In control rats at 1 day of age, hypoxia evoked an acute decrease in protein synthesis, assessed by [3H]leucine incorporation, in both the midbrain + brainstem and forebrain. The decrease was also seen in animals receiving the low dose of dexamethasone, but was of smaller magnitude in the midbrain + brainstem than in the control cohort. At the higher dose of dexamethasone, hypoxia failed to evoke a decrease in protein synthesis; instead, protein synthesis was significantly increased. By 8 days of age, the animals receiving the lower dose of dexamethasone also displayed the anomalous increment in [3H]leucine incorporation during hypoxic challenge, whereas the effect in the high dose group was less notable. Similarly, parallel examination of incorporation of [3H]thymidine into DNA on postnatal day 1 indicated that control animals would reduce their macromolecule synthetic rate in a hypoxic environment, but that animals exposed to the high dose of dexamethasone would not; unlike the case with protein synthesis, however, the dexamethasone group never showed an increase in DNA synthesis during hypoxia. By 8 days of age, the interaction between the high dose of dexamethasone and hypoxia was no longer apparent for DNA synthesis.2

Effects of acute hypoxia on neonatal rat brain: regionally selective, long-term alterations in catecholamine levels and turnover

Neonatal rats were exposed to 2 hr of hypoxia (7% O2) on the day after birth and examined for effects on development of noradrenergic and dopaminergic systems. Measurements were made of transmitter levels and turnover, the latter a biochemical index of neuronal activity. Hypoxia had a regionally selective effect, characterized by a long-lasting increase in turnover of norepinephrine and dopamine in midbrain and brainstem, with little or no effect in cerebral cortex or cerebellum. The effects of hypoxia were exacerbated when peripheral alpha-adrenergic receptors were blocked with phenoxybenzamine during the hypoxic exposure; in this case, the same abnormalities were then seen in the cerebral cortex as well. Thus, the release of peripheral catecholamines during the hypoxic insult, and their actions at alpha-adrenergic receptors, may play a role in protecting the neonatal nervous system from hypoxia-induced alterations.

Prenatal exposure to nicotine impairs nervous system development at a dose which does not affect viability or growth

Prenatal exposure to high doses of nicotine (greater than 6 mg/kg/day) via maternal infusions has been shown to impair nervous system development and to decrease viability and growth. In the current study, we have examined the effects of infusing pregnant rats with 2 mg/kg of nicotine per day from gestational days 4 through 20. At this lower dose, there was neither interference with maternal weight gain nor any increase in resorption rate. Intrauterine and postnatal growth was maintained at normal or supranormal rates in the exposed offspring. Nevertheless, sufficient nicotine penetrated the fetal brain to cause persistent alterations in [3H]nicotine binding sites, abnormalities of cellular development [assessed by measurements of ornithine decarboxylase (ODC) activity and deoxyribonucleic acid (DNA)], and impairment of development of peripheral noradrenergic projections (assessed by kidney norepinephrine levels); in each case, the neural alterations were virtually equivalent to those obtained previously at the higher, growth-suppressant dosage. These findings indicate that growth impairment alone is insufficient to predict the adverse effects of nicotine on development.

Effects of prenatal nicotine exposure on neuronal development: selective actions on central and peripheral catecholaminergic pathways

The effects of prenatal nicotine exposure on development of catecholaminergic pathways were examined through measurements of transmitter turnover and levels in both the central and peripheral nervous system. Administration of nicotine (3 mg/kg SC, twice daily) to pregnant rats on gestational days 3 through 20 resulted in growth retardation which did not spare the brain and which did not resolve until after weaning. Nicotine exposure produced an elevation in transmitter turnover in central noradrenergic pathways with a regional selectivity reflecting the timetable of cellular development: the most profound effects were seen in late-developing regions (cerebellum), intermediate effects were found in earlier-developing areas (cerebral cortex) and the least effect was obtained where maturation occurs earliest (midbrain + brainstem). Dopaminergic pathways were much less vulnerable than was the noradrenergic system. Effects on the peripheral sympathetic nervous system also were targeted toward specific neuronal populations: renal, cardiac and adrenal pathways were activated by prenatal nicotine exposure, whereas sympathetic innervation of the lung showed reduced activity. All the peripheral effects appeared only after the second postnatal week. These results indicate that prenatal nicotine exposure produces profound alterations in transmitter disposition which are targeted toward specific neuronal populations and which may depend upon generalized effects on cellular development of specific brain regions. Because altered peripheral nerve activity was seen only after the onset of central control of sympathetic tone, actions on central regulation may play a role in the relatively more profound effects in the autonomic nervous system.

Perinatal dietary exposure to soy lecithin: altered sensitivity to central cholinergic stimulation

The effects of perinatal exposure to soy lecithin preparation (SLP) on the development of cholinergic responses in the rat brain were examined by assessing the ability of intracisternally administered carbachol to stimulate 33Pi incorporation into phospholipids in vivo, an effect of carbachol mediated by muscarinic cholinergic receptors. Maternal intake of SLP produced a suppression of the cholinergic response in the offspring, an effect which was specific in that basal (unstimulated) incorporation rates were not reduced (in fact, they eventually became elevated), nor was the response to another neurotransmitter (dopamine) compromised. The effect occurred early in the preweanling stage, a period in which SLP exposure also enhances development of cholinergic nerve terminals. These results suggest that SLP exposure has a major effect on cholinergic synaptic development and reactivity, followed by secondary changes in other neurotransmitter pathways and by more generalized effects on basal membrane phospholipid turnover.