P4-222: Defects in IGF-1 receptor, insulin receptor and insulin receptor substrate proteins in Alzheimer's disease neurons indicate resistance to insulin and IGF-1 signaling

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Poster Presentations P4:

identified in the brain. Recently we demonstrated that neurons respond to gonadotropin-releasing hormone 1 (GnRH1) by producing luteinizing hormone (LH) that in turn induces neurosteroid synthesis. Methods: To test whether there may be an autocrine/paracrine feedback mechanism within the brain that modulates neurosteroid synthesis, as is the case for the regulation of gonadal sex steroid production by the HPG axis, 3-month old female BALB/c mice were either left intact, ovariectomized (OVX) or OVX and treated with a cholesterol (control), E2, P4 or E2 ⫹ P4 pellet for 3 d. Results: Ovariectomy, which induces a dramatic increase in GnRH and gonadotropin synthesis, decreased the expression of GnRH receptor 1 (GnRHR1) and LH␤ variants but did not alter estrogen receptor (ER␣) expression. Ovariectomy had a differential affect on steroidogenic acute regulatory protein (StAR) expression, increasing the 30- and 32-kDa StAR variants. Treatment of OVX animals with E2, P4 or E2 ⫹ P4 all potently suppressed the expression of brain LH␤, GnRHR1 and ER␣, but increased the 37-kDa StAR variant. Conclusions: These results indicate that negative feedback loop(s) exist within the brain to regulate GnRH and LH signaling, and neurosteroid production via the regulation of StAR expression. Thus, circulating sex steroids can regulate the expression of components of the neurosteroid synthesis pathway in the brain, and may therefore play a major role in the regulation of neurosteroid synthesis. Given the importance of sex steroids to brain function, it is possible that autocrine/paracrine neurosteroid production may be a mechanism to fine-tune the level of sex steroids in the brain. Understanding the feedback loops in the brain that regulate neurosteroid production has important implications for developing therapeutic strategies to maintain brain sex steroid levels and cognition. P4-221

GABA-LINKED ACCELERATION OF AGINGASSOCIATED MEMORY DECLINE IN APP/PS1 TRANSGENIC MOUSE AND ITS PHARMACOLOGICAL TREATMENT BY PICROTOXIN

Yuji Yoshiike1, Tetsuya Kimura1, Shunji Yamashita1, Hiroyuki Furudate2, Tatsuya Mizoroki1, Miyuki Murayama1, Akihiko Takashima1, 1RIKEN Brain Science Institute, Wako-shi, Saitama, Japan; 2Saitama University, Saitama-shi, Saitama, Japan. Contact e-mail: [email protected] Background: It is increasingly recognized that cognitive deficits in Alzheimer’s disease (AD) is not perfectly matched with pathological hallmarks. Some of complex and fluctuating symptoms of AD patients cannot be explained simply by toxic mechanisms of aggregated Ab. Instead, AD can be seen as a failure in neural systems that is characterized by degeneracy, the ability of structurally different elements to perform the same function or yield the same output. However, it is unclear how neural systems failure or network dysfunction is triggered by aging or AD linked genes such as APP and PS1 and how it leads to cognitive impairment. Methods: We examined hippocampal slice LTP and spatial reference memory in APP/PS1 mice in comparison with NTG mice at two ages, namely adult (9-15 mon) and old (19-25 mon). Results: Reduction in LTP level and decline in memory performance were observed in both adult APP/PS1 mice and old NTG mice. Surprisingly, when the measurements were taken in the presence of bicuculline, a GABAA receptor antagonist, the levels of LTP in adult APP/PS1 mice and old NTG mice turned out to be higher than adult NTG mice, indicating an over excitation. Moreover, the increased gap in LTP levels measured in the presence and absence of bicuculline suggested that GABA-mediated inhibition in adult APP/PS1 mice and old NTG mice was upregulated in a possible compensatory response to over excitatory signals originated from aging or mutant APP/ PS1 gene products. Assuming that this compensatory upregulation of GABA inhibition on synaptic plasticity accelerates aging-associated memory decline, we treated mice chronically by GABAA receptor antagonist, picrotoxin, at a non-epileptic dose and rescued memory deficits in adult APP/PS1 mice by normalizing GABAA receptor level. Conclusions: These results suggest that altered synaptic plasticity associated with upregulated GABA inhibition, that is likely a compensatory response to over

excitatory signals induced by aging or by familial AD linked gene products like Ab and mutant PS1, leads to cognitive impairment that is pharmacologically reversible. Therefore, it may be not only toxic mechanisms but also compensatory mechanisms that play important roles in neural systems failure of at least mouse brain. P4-222

DEFECTS IN IGF-1 RECEPTOR, INSULIN RECEPTOR AND INSULIN RECEPTOR SUBSTRATE PROTEINS IN ALZHEIMER’S DISEASE NEURONS INDICATE RESISTANCE TO INSULIN AND IGF-1 SIGNALING

Cora O’ Neill1, Aileen M. Moloney1, Rebecca J. Griffin2, Meghan F. Coakley1, Suzanne Timmons1, Rosemary O’Connor1, Rivka Ravid3, 1University College Cork, Cork, Ireland; 2Trinity College, Dublin, Ireland; 3The Netherlands Brain Bank, Amsterdam, Netherlands. Contact e-mail: [email protected] Background: Several reports infer that neurons become resistant to insulin receptors (IRs) in AD, and also indicate resistance to the closely related IGF-1 receptor (IGF-1R) in the disease. These defects in IR and IGF-1R signalling are believed to be mechanistically important in AD pathogenesis. In line with this soluble A␤ and soluble A␤ oligomers (ADDLs) inhibit IR tyrosine autophosphorylation and signalling, with ADDLs causing a redistribution and internalisation of IR. Detailed knowledge of IGF-1R and IR protein status in AD brain is lacking. Methods: We have performed a comparative analysis of IGF-1R and IR status in AD and control brain, as well as investigating their key adaptor insulin receptor substrate proteins, IRS-1 and IRS-2, whose loss and inactivation is a major cause of insulin and IGF-1 receptor resistance in other cell types. Results: IGF-1R levels are significantly increased in AD temporal cortex as analysed by western immunoblot. Immunoflourescence microscopy shows increased IGF-1R levels within and surrounding A␤ plaques, and in GFAP immunopositive astrocytes in AD. However, in contrast, IGF-1R levels are significantly decreased in AD neurons, with aberrant IGF-1R distribution particularly evident in degenerating neurons with NFTs. IR levels are unchanged in AD temporal cortex as analysed by comparative western immunoblot with matched control cases. However, immunofluorescence microscopy shows IR is internalised in AD neurons and not visible at the cell membrane or within dendrites as in control neurons. Significant reductions of IRS-2 and IRS-1 protein levels were detected in AD cases correlating with the pathological severity of the disease, and are found together with a significant increase in levels of inactivated IRS-1 phosphorylated at Ser312 and Ser616, colocalising strongly with neurons containing NFTs. Conclusions: These IRS changes would be predicted to cause insulin and IGF-1 receptor resistance in AD neurons, uncoupling IR and IGF-1R from signals downstream of IRS, particularly the PI3-kinase-Akt pathway. Mechanistically, inactivation and loss of IRS1/2 may be due to pathological hyper-activation of Akt-mTOR signalling which we have found to be excessively activated in AD neurons, and which is a major cause of similar IRS defects and IR/IGF-1R resistance in other cell types. P4-223

FATTY ACID AMIDE HYDROLASE INHIBITION ENHANCES LEARNING AND MEMORY THROUGH ACTIVATION OF PPAR-ALPHA NUCLEAR RECEPTORS

Sevil Yasar1, Carmen Mazzola2,3, Julie Medalie4, Maria Scherma4, Leigh Panlilio4, Jean Lud Cadet2, Steven Goldberg4, 1Johns Hopkins University, School of Medicine, Baltimore, MD, USA; 2Intramural Research Program, NIDA, NIH, DHHS, Baltimore, MD, USA; 3 University of Catania, School of Medicine, Catania, Italy; 4Intramural Research Program, NIDA, NIH, DHHS, Baltimore, MD, USA. Contact e-mail: [email protected] Background: Fatty acid amide hydrolase (FAAH) is an intracellular enzyme catalyzing hydrolysis of endogenous lipid mediators, such as anandamide, an endogenous cannabinoid , oleoyethanolamide (OEA) and palmitoyethanolamide (PEA). OEA and PEA are structurally similar to anandamide, but do not