The threshold optical density that discriminated staining from background was decided and kept constant for all those quantifications. the 5LO pathway affects key neuropathological features of the AD-like phenotype (behavior, Abeta, microgliosis, astrocytosis) but Capn1 not others (tau pathology) in the LPS-dependent neuroinflammation model. The opposite ways whereby 5LO influences the LPS-dependent effects in vivo supports the complex nature of the neuroinflammatory response JMV 390-1 in AD and its differential role in modulating amyloid and tau neuropathology. Keywords:Alzheimers disease, Transgenic mouse models, Amyloid beta, LPS, Behavior, Neuroinflammation == 1. INTRODUCTION == Alzheimers disease (AD) is the most common aging-associated neurodegenerative dementia. While the hallmark pathology of AD includes accumulation of amyloid- plaques and neurofibrillary tau tangles, inflammation is also a constant characteristic of the AD brain. Astrocytosis and microgliosis follow progression of AD pathology, and elevation of pro-inflammatory cytokines such as interleukin 1 (IL-1) is also seen in AD patients (Sheng et al. 1997a,Sheng et al. 1997b,Griffin et JMV 390-1 al. 1989). Several reports have shown significantly higher amounts of bacterial and viral genetic material in the brains of AD patients compared to controls, and contamination with mouse hepatitis computer virus in the triple transgenic (3xTg) mouse model of AD results in acceleration of AD pathology (Hammond et al. 2010,Balin et al. 1998,Itzhaki et al. 2008,Kountouras et al. 2006,Sy et al. 2011). This evidence suggests that inflammatory says accelerate the development of the AD phenotype. Several pro-inflammatory enzymes have been linked to AD, among which is the 5-lipoxygenase protein (5LO). 5LO uses arachidonic acid as substrate to produce inflammatory leukotriene metabolites, which then can modulate increased vascular permeability as well as immune cell adhesion and activation (Radmark and Samuelsson, 2010). 5LO is usually elevated in AD brains compared to age-matched controls, and aging increases 5LO expression in several areas of the brain including cortex and hippocampus (Firuzi et al., 2008;Chinnici et al., 2007;Ikonomovic, et al. 2008). We have previously reported that 5LO is an endogenous modulator of both A production and tau phosphorylation (Chu and Pratico, 2011;Chu and Pratico, 2013;Chu et al., 2012). Pharmacological inhibition of 5LO in an AD mouse model of amyloidosis results in fewer plaques as well as attenuation of learning and memory deficits (Chu and Pratico, 2011). However, it is not known whether 5LO plays a role in the inflammation-induced worsening of the AD-like phenotype. To address this question we challenged 3xTg and 3xTg mice genetically deficient for 5LO (3xTg/5LOKO) with a chronic course of lipopolysaccharide (LPS) injection. Chronic peripheral LPS injection in transgenic AD animals closely simulates inflammatory says caused by contamination, which are able to modulate AD brain pathology (Sy et al. 2011). We found that 3xTg animals treated with LPS had impaired fear-conditioned contextual recall which was not seen in 3xTg/5LOKO animals. 3xTg animals treated with LPS did not have significantly greater amyloid levels than controls, however we found that LPS significantly elevated the presenilin-1 and presenilin-enhancer 2 components of the -secretase, suggesting a misprocessing of APP. 3xTg animals without 5LO had lower A levels than control 3xTg animals. Additionally, 3xTg animals lacking 5LO also resisted LPS-mediated elevations in -secretase protein levels. By contrast, compared with controls, knockout of 5LO did not protect 3xTg animals against LPS-mediated hyper-phosphorylation of tau. Finally, LPS induced astrocytosis and microgliosis and a significant up-regulation of inflammatory cytokines in 3xTg mice, JMV 390-1 but it failed to do so in 3xTg/5LOKO. == 2. METHODS == == 2.1 Animals == All animal procedures were approved by the Institutional Animal Care and Usage Committee, in accordance with the U.S. National Institutes of Health guidelines and approved by the Temple Universitys Animal Care and Use Committee. The 3xTg mice used in this study contain a mutant amyloid precursor protein (APP; KM670/671NL), a human mutant PS1 (M146V) knockin, and tau (P301L) transgenes; 3xTg, and mice genetically deficient for 5LO (5LOKO) were crossed as previously described to create 3xTg/5LOKO mice (Oddo et al., 2003;Goulet et al., 1994). Nave male 3xTg and 3xTg/5LO-/- mice aged 6 months were used for this study. All mice were housed on a 12 hours light/dark cycle in the Medical Research Building at the Temple University Health Sciences Campus, which is fully accredited by the Association for the Assessment and Accreditation of Laboratory Animal Care International. Standard mouse chow and water were providedad libitum. Animals were intra-peritoneally either given phosphate-buffered saline (PBS) as control, or lipopolysaccharide (LPS;Escherichia coli055:B5; Sigma, St. Louis, MO at a dose of 0.5mg/kg, twice a week for 6 weeks (n=4, 3xTg (PBS), n = 5 3xTg (LPS), n = 4 3xTg/5LO-/- (PBS), n = 6 3xTg/5LO-/- (LPS)). == 2.2 Behavioral paradigms == Following treatment with PBS or LPS, all.
