Gene expression profile in Alzheimer's brain screened by molecular indexing

Thymoquinone alleviates the experimentally induced Alzheimer’s disease inflammation by modulation of TLRs signaling

Alzheimer’s disease (AD) is characterized by a robust inflammatory response elicited by the accumulation and deposition of amyloid-β (Aβ) within the brain. Aβ induces detrimental inflammatory responses through toll-like receptors (TLRs) signaling pathway. Thymoquinone (TQ), the main active constituent of Nigella sativa oil, has been reported by several previous studies for its potent anti-inflammatory effect. The aim of this study is to elucidate the effect of TQ in improving learning and memory, using a rat model of AD induced by a combination of aluminum chloride (AlCl3) and d-galactose (d-Gal). TQ was administered orally at doses of 10, 20, and 40 mg/kg/day for 14 days after AD induction. Memory functions were assessed using the step through passive avoidance test. Amyloid plaques were shown to be present using hematoxylin and eosin staining. Tumor necrosis factor-alpha (TNF-α) and Interleukin-1beta (IL-1β) levels in brain were assessed via ELISA and profiling TLR-2, TLR-4, myeloid differential factor 88, toll–interleukin-1 receptor domain-containing adapter-inducing interferon-β, interferon regulatory factor 3 (IRF-3), and nuclear factor-κB (NF-κB) expressions via real-time polymerase chain reaction. TQ improved AD rat cognitive decline, decreased Aβ formation and accumulation, significantly decreased TNF-α and IL-1β at all levels of doses and significantly downregulated the expression of TLRs pathway components as well as their downstream effectors NF-κB and IRF-3 mRNAs at all levels of doses ( p < 0.05). We concluded that TQ reduced the inflammation induced by d-Gal/AlCl3 combination. It is therefore reasonable to assign the anti-inflammatory responses to the modulation of TLRs pathway.

Alzheimer's disease pathogenesis and therapeutic interventions

Alzheimer's disease (AD) is a neurodegenerative disorder of the central nervous system associated with progressive cognitive and memory loss. Molecular hallmarks of the disease are characterized by extracellular deposition of the amyloid beta peptide (Abeta) in senile plaques, the appearance of intracellular neurofibrillary tangles (NFT), cholinergic deficit, extensive neuronal loss and synaptic changes in the cerebral cortex and hippocampus and other areas of brain essential for cognitive and memory functions. Abeta deposition causes neuronal death via a number of possible mechanisms including oxidative stress, excitotoxicity, energy depletion, inflammation and apoptosis. Despite their multifactorial etiopathogenesis, genetics plays a primary role in progression of disease. To date genetic studies have revealed four genes that may be linked to autosomal dominant or familial early onset AD (FAD). These four genes include: amyloid precursor protein (APP), presenilin 1 (PS1), presenilin 2 (PS2) and apolipoprotein E (ApoE). Plaques are formed mostly from the deposition of Abeta, a peptide derived from APP. The main factors responsible for Abeta formation are mutation of APP or PS1 and PS2 genes or ApoE gene. All mutations associated with APP and PS proteins can lead to an increase in the production of Abeta peptides, specifically the more amyloidogenic form, Abeta42. In addition to genetic influences on amyloid plaque and intracellular tangle formation, environmental factors (e.g., cytokines, neurotoxins, etc.) may also play important role in the development and progression of AD. A direct understanding of the molecular mechanism of protein aggregation and its effects on neuronal cell death could open new therapeutic approaches. Some of the therapeutic approaches that have progressed to the clinical arena are the use of acetylcholinesterase inhibitors, nerve growth factors, nonsteroidal inflammatory drugs, estrogen and the compounds such as antioxidants, neuronal calcium channel blockers or antiapoptotic agents. Inhibition of secretase activity and blocking the formation of beta-amyloid oligomers and fibrils which may inhibit fibrilization and fibrilization-dependent neurotoxicity are the most promising therapeutic strategy against the accumulation of beta-amyloid fibrils associated with AD. Furthermore, development of immunotherapy could be an evolving promising therapeutic approach for the treatment of AD.

Mapping cellular transcriptosomes in autopsied Alzheimer's disease subjects and relevant animal models

Alzheimer's disease (AD) is a late-onset and progressive neurodegenerative disorder characterized clinically by memory loss, impairment of other cognitive functions, and changes in behavior and personality. The overall aim of this review is to summarize recent advances in studies of AD progression and the use of animal models in gene expression studies of AD progression. Genetic causes of AD are known only for early-onset AD patients. For a majority of late-onset AD patients, causal factors are still unknown. Currently, there are no early detectable biomarkers for late-onset AD, and there is a lack of understanding of AD pathophysiology, particularly at the early stages of disease progression, before pathology develops. Human histopathological and biochemical studies provide valuable information regarding the last stages of AD pathogenesis. However, to understand early cellular changes in AD progression before symptoms develop, animal models are still our only alternative. Several research groups have created genetically engineered animal models, particularly models of the mouse, rat, fly, and worm, which have allowed us to better, understand the initiating events of AD progression. Recently, state-of-the-art methods have helped elucidate gene expression changes in affected and unaffected tissues from postmortem AD brains and from animal models developed for AD studies. These methods allow the investigation of mRNA-based transcriptosomal profiles of brain specimens from AD humans and transgenic animals. The major finding from these studies is that AD progression and pathogenesis involve multiple cellular pathways, which suggests that AD is a complex and heterogeneous disease.

Cell line dependent RNA expression profiles of prion-infected mouse neuronal cells

The overall impact of prion disease on gene expression is not well characterized. We have carried out a large-scale expression analysis of specific cell types commonly employed in studies of prion disease. Neuroblastoma cells (N2a) and hypothalamic neuronal cells (GT1) can be persistently infected with mouse-adapted scrapie prions, the latter demonstrating cytopathologic effects associated with prion neuropathology. Exploiting a mouse DNA microarray containing approximately 21,000 spotted cDNAs, we have identified several hundred differentially expressed sequences in the two cell lines when infected with prion strain RML. ScN2a and ScGT1 cells demonstrate unique changes in RNA profiles and both differ from the reported changes in human microglia and prion-infected brain studies albeit with some overlap. In addition, several of the identified changes are shared in common with other neurodegenerative diseases such as Alzheimer's disease. The results illustrate that prion infection differs in effect depending on cell type, which could be exploited for diagnostic or therapeutic intervention.

Gene expression profiles of transcripts in amyloid precursor protein transgenic mice: up-regulation of mitochondrial metabolism and apoptotic genes is an early cellular change in Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by the impairment of cognitive functions and by beta amyloid (Abeta) plaques in the cerebral cortex and the hippocampus. Our objective was to determine genes that are critical for cellular changes in AD progression, with particular emphasis on changes early in disease progression. We investigated an established amyloid precursor protein (APP) transgenic mouse model (the Tg2576 mouse model) for gene expression profiles at three stages of disease progression: long before (2 months of age), immediately before (5 months) and after (18 months) the appearance of Abeta plaques. Using cDNA microarray techniques, we measured mRNA levels in 11 283 cDNA clones from the cerebral cortex of Tg2576 mice and age-matched wild-type (WT) mice at each of the three time points. This gene expression analysis revealed that the genes related to mitochondrial energy metabolism and apoptosis were up-regulated in 2-month-old Tg2576 mice and that the same genes were up-regulated at 5 and 18 months of age. These microarray results were confirmed using northern blot analysis. Results from in situ hybridization of mitochondrial genes-ATPase-6, heat-shock protein 86 and programmed cell death gene 8-suggest that the granule cells of the hippocampal dentate gyrus and the pyramidal neurons in the hippocampus and the cerebral cortex are up-regulated in Tg2576 mice compared with WT mice. Results from double-labeling in situ hybridization suggest that in Tg2576 mice only selective, over-expressed neurons with the mitochondrial gene ATPase-6 undergo oxidative damage. These results, therefore, suggest that mitochondrial energy metabolism is impaired by the expression of mutant APP and/or Abeta, and that the up-regulation of mitochondrial genes is a compensatory response. These findings have important implications for understanding the mechanism of Abeta toxicity in AD and for developing therapeutic strategies for AD.

The use of real-time PCR analysis in a gene expression study of Alzheimer’s disease post-mortem brains

The measurement of gene expressions in brains with neurodegenerative diseases is a major area of brain research. The objective of our research was to determine whether quantitative real-time PCR could measure messenger RNA (mRNA) expression in brains with post-mortem intervals beyond 12h. In the present paper, we examined the quality of RNA from brain specimens of both Alzheimer's disease (AD) patients (n = 13) and non-demented normal control subjects (n = 6). To determine a unregulated endogenous reference gene in AD, we measured mRNA expressions of the commonly used reference genes beta-actin, 18S rRNA, and GAPDH. In addition, we determined whether post-mortem interval, brain weight, or age at death influences mRNA expression. Our real-time PCR analysis results indicate that mRNA expression can be detected in all brain specimens for beta-actin, 18S rRNA, GAPDH, and also synaptophysin, a known marker for AD. Further, using real-time PCR analysis, we found that beta-actin and 18S rRNA are differentially expressed in the brain specimens of both AD and control subjects, while GAPDH is similarly expressed in AD and control brain specimens. These findings suggest that GAPDH can be used as a endogenous reference gene in the study of AD brains. A comparative gene expression analysis also suggests that synaptophysin is down-regulated in AD brain specimens compared to control brain specimens.

Differentially expressed genes in sporadic amyotrophic lateral sclerosis spinal cords--screening by molecular indexing and subsequent cDNA microarray analysis

To analyze the genes related to the pathophysiology of sporadic amyotrophic lateral sclerosis (SALS) we performed gene profiling of SALS spinal cords using molecular indexing combined with cDNA microarray. Eighty-four fragments were cloned in the first screening procedure with molecular indexing. Subsequent quantitative microarray screening revealed 11 genes which were differentially expressed in SALS. Real-time RT-PCR verified that the expression level of the following six genes was altered in SALS: dorfin, metallothionein-3, 30 kDa TATA-binding protein-associated factor, neugrin, ubiquitin-like protein 5 and macrophage-inhibiting factor-related protein-8. These results indicated that genes associated with the ubiquitin-proteasome system, oxidative toxicity, transcription, neuronal differentiation and inflammation might be involved in the pathogenesis of SALS.

X-Linked inhibitor of apoptosis protein is involved in mutant SOD1-mediated neuronal degeneration

Mutations in the superoxide dismutase 1 (SOD1) gene cause the degeneration of motor neurons in familial amyotrophic lateral sclerosis (FALS). An apoptotic process including caspase-1 and -3 has been shown to participate in the pathogenesis of FALS transgenic (Tg) mouse model. Here we report that IAP proteins, potent inhibitors of apoptosis, are involved in the FALS Tg mouse pathologic process. The levels of X-linked inhibitor of apoptosis protein (XIAP) mRNA and protein were significantly decreased in the spinal cord of symptomatic G93A-SOD1 Tg mice compared with littermates. In contrast, the levels of cIAP-1 mRNA and protein were increased in symptomatic G93A-SOD1 Tg mice, whereas the levels of cIAP-2 mRNA and protein were unchanged. In situ hybridization showed that the expression of XIAP was remarkably reduced in the motor neurons of Tg mice, and the expression of cIAP-1 was strongly increased in the reactive astrocytes of Tg mice. Overexpression of XIAP markedly inhibited the cell death and caspase-3 activity in the neuro2a cells expressing mutant SOD1. Deletional mutant analysis revealed that the N-terminal domain of XIAP, the BIR1-2 domains, was essential for this inhibitory activity. These results suggest that XIAP plays a role in the apoptotic mechanism in the progression of disease in mutant SOD1 Tg mice and holds therapeutic possibilities for FALS.

Functional genomics in neuropsychiatric disorders and in neuropharmacology

The rapidly accumulating amount of information concerning gene and protein expression patterns produced by functional genomics, proteomics and bioinformatics is presently providing new targets for drug development. Furthermore, the analysis of gene expression in cells and tissues affected by a disease may reveal the underlying metabolic pathways and cellular processes affected. Finally, changes in gene expression may be used in either diagnostics or the monitoring of drug responses. This review focuses on advances in the use of functional genomics in neurological and neuropsychiatric diseases and neuropsychopharmacology. Although the number of published studies in this field is still limited, it already appears that this strategy may become a fruitful means in the analysis of the aetiology of neuropsychiatric disorders and the search for novel neuropharmacological drugs.