Sylvia Lam

Upregulation of Erythropoietin and its Receptor Expression in the Rat Carotid Body During Chronic and Intermittent Hypoxia

The carotid body (CB) plays important roles in cardiorespiratory changes in intermittent hypoxia (IH). Erythropoietin (EPO), a hypoxia-inducible factor (HIF)-1 target gene, is present in the chemoreceptive type-I cells in the CB but its expression and role in IH resembling sleep apnoeic conditions are not known. We hypothesized that IH upregulates the expression of EPO and its receptor (EPOr) in the rat CB. The CB expressions of EPO and EPOr were examined in rats breathing 10% O(2) (in isobaric chamber for CH, 24 hour/day) or in IH (cyclic between air and 5% O(2) per minute, 8 hour/day) for 3-28 days. Immunohistochemical studies revealed that the EPO and EPOr proteins were localized in CB glomic clusters. The proportional amount of cells with positive staining of EPO immunoreactivities was significantly increased in both IH and CH groups when compared with the normoxic control. The EPO expression was more markedly increased in the CH than that of the IH groups throughout the time course, reaching a peak level at day 14. The positive EPOr immunostaining was increased significantly in the 3-day CH group. By day 14, the EPOr expression elevated considerably at peak levels in both IH and CH rats, whereas the elevation was greater in the CH rats. These results suggest an upregulation of EPO and its receptor expression in the rat CB under IH and CH conditions, presumably mediated by the activation of HIF-1 pathway. The increased EPO binding to its receptor might play a role in the enhancement of CB excitability during the early pathogenesis in patients with sleep-disordered breathing.

Frontal-Subcortical Protein Expression following Prenatal Exposure to Maternal Inflammation

Background Maternal immune activation (MIA) during prenatal life is a risk factor for neurodevelopmental disorders including schizophrenia and autism. Such conditions are associated with alterations in fronto-subcortical circuits, but their molecular basis is far from clear. Methodology/Principal Findings Using two-dimensional differential in-gel electrophoresis (2D-DIGE) and mass spectrometry, with targeted western blot analyses for confirmation, we investigated the impact of MIA on the prefrontal and striatal proteome from an established MIA mouse model generated in C57B6 mice, by administering the viral analogue PolyI:C or saline vehicle (control) intravenously on gestation day (GD) 9. In striatum, 11 proteins were up-regulated and 4 proteins were down-regulated in the PolyI:C mice, while 10 proteins were up-regulated and 7 proteins down-regulated in prefrontal cortex (PFC). These were proteins involved in the mitogen-activated protein kinase (MAPK) signaling pathway, oxidation and auto-immune targets, including dual specificity mitogen-activated protein kinase kinase 1 (MEK), eukaryotic initiation factor (eIF) 4A-II, creatine kinase (CK)-B, L-lactate dehydrogenase (LDH)-B, WD repeat-containing protein and NADH dehydrogenase in the striatum; and guanine nucleotide-binding protein (G-protein), 14-3-3 protein, alpha-enolase, olfactory maker protein and heat shock proteins (HSP) 60, and 90-beta in the PFC. Conclusions/Significance This data fits with emerging evidence for disruption of critical converging intracellular pathways involving MAPK pathways in neurodevelopmental conditions and it shows considerable overlap with protein pathways identified by genetic modeling and clinical post-mortem studies. This has implications for understanding causality and may offer potential biomarkers and novel treatment targets for neurodevelopmental conditions.

Dietary supplementation with n-3 fatty acids from weaning limits brain biochemistry and behavioural changes elicited by prenatal exposure to maternal inflammation in the mouse model.

Prenatal exposure to maternal immune activation (MIA) increases the risk of schizophrenia and autism in the offspring. The MIA rodent model provides a valuable tool to directly test the postnatal consequences of exposure to an early inflammatory insult; and examine novel preventative strategies. Here we tested the hypotheses that behavioural differences in the MIA mouse model are accompanied by in vivo and ex vivo alterations in brain biochemistry; and that these can be prevented by a post-weaning diet enriched with n-3 polyunsaturated fatty acid (PUFA). The viral analogue PolyI:C (POL) or saline (SAL) was administered to pregnant mice on gestation day 9. Half the resulting male offspring (POL=21; SAL=17) were weaned onto a conventional lab diet (n-6 PUFA); half were weaned onto n-3 PUFA-enriched diet. In vivo magnetic resonance spectroscopy measures were acquired prior to behavioural tests; glutamic acid decarboxylase 67 (GAD67) and tyrosine hydroxylase protein levels were measured ex vivo. The main findings were: (i) Adult MIA-exposed mice fed a standard diet had greater N-acetylaspartate/creatine (Cr) and lower myo-inositol/Cr levels in the cingulate cortex in vivo. (ii) The extent of these metabolite differences was correlated with impairment in prepulse inhibition. (iii) MIA-exposed mice on the control diet also had higher levels of anxiety and altered levels of GAD67 ex vivo. (iv) An n-3 PUFA diet prevented all the in vivo and ex vivo effects of MIA observed. Thus, n-3 PUFA dietary enrichment from early life may offer a relatively safe and non-toxic approach to limit the otherwise persistent behavioural and biochemical consequences of prenatal exposure to inflammation. This result may have translational importance.

Upregulation of Pituitary Adenylate Cyclase Activating Polypeptide and Its Receptor Expression in the Rat Carotid Body in Chronic and Intermittent Hypoxia

The carotid body (CB) plays important roles in cardiorespiratory changes in chronic and intermittent hypoxia. Pituitary adenylate cyclase activating polypeptide (PACAP) is involved in the regulation of respiratory chemoresponse. We hypothesized an upregulation of the expressions of PACAP and its receptor (PAC1) in the rat CB in chronic and intermittent hypoxia. The CB expressions of PACAP and PAC1 were examined in rats breathing 10% O(2) (in isobaric chamber for chronic hypoxia, 24 h/day) or in intermittent hypoxia (cyclic between air and 5% O(2) per minute, 8 h/day) for 7 days. Immunohistochemical studies showed that the PACAP and PAC1 proteins were localized in CB glomic clusters containing tyrosine hydroxylase. The proportional amount of cells with positive staining of PACAP and PAC1 was significantly increased in both hypoxic groups when compared with the normoxic control. In addition, the mRNA level of PAC1 expression was markedly elevated in the hypoxic groups, despite no changes in the PACAP expression. These results suggest an upregulation of PACAP and its receptor expression in the rat CB under chronic and intermittent hypoxic conditions. The PACAP binding to its receptor could activate the PKA signaling pathway leading to an increased CB excitability under hypoxic conditions.

The effect of oxytocin on social and non-social behaviour and striatal protein expression in C57BL/6N mice

Oxytocin has been suggested as a promising new treatment for neurodevelopmental disorders. However, important gaps remain in our understanding of its mode of action, in particular, to what extent oxytocin modulates social and non-social behaviours and whether its effects are generalizable across both sexes. Here we investigated the effects of a range of oxytocin doses on social and non-social behaviours in C57BL/6N mice of both sexes. As the striatum modulates social and non-social behaviours, and is implicated in neurodevelopmental disorders, we also conducted a pilot exploration of changes in striatal protein expression elicited by oxytocin. Oxytocin increased prepulse inhibition of startle but attenuated the recognition memory in male C57BL/6N mice. It increased social interaction time and suppressed the amphetamine locomotor response in both sexes. The striatum proteome following oxytocin exposure could be clearly discriminated from saline controls. With the caveat that these results are preliminary, oxytocin appeared to alter individual protein expression in directions similar to conventional anti-psychotics. The proteins affected by oxytocin could be broadly categorized as those that modulate glutamatergic, GABAergic or dopaminergic signalling and those that mediate cytoskeleton dynamics. Our results here encourage further research into the clinical application of this peptide hormone, which may potentially extend treatment options across a spectrum of neurodevelopmental conditions.

Poster #20 MATERNAL IMMUNE ACTIVATION IN THE EARLY OR LATE PREGNANCY LEADS TO THE DIFFERENT BEHAVIORAL ABNORMALITIES OF THE ADULT OFFSPRING RELEVANT TO THE SCHIZOPHRENIA

This journal supplement has title: Abstracts of the 3rd Biennial Conference of the Schizophrenia International Research Society

Poster #223 GENDER DIFFERENCES AND EFFECTS OF ACUTE AND CHRONIC OXYTOCIN ON SOCIAL INTERACTION IN MICE

This journal supplement has title: Abstracts of the 3rd Biennial Conference of the Schizophrenia International Research Society