Alzheimer's disease: inside, outside, upside down

Comparative Gene-Expression Analysis of Alzheimer's Disease Progression with Aging in Transgenic Mouse Model

Alzheimer’s disease (AD) is a multifactorial neurodegenerative disorder characterized by progressive memory dysfunction and a decline in cognition. One of the biggest challenges to study the pathological process at a molecular level is that there is no simple, cost-effective, and comprehensive gene-expression analysis tool. The present study provides the most detailed (Reverse transcription polymerase chain reaction) RT-PCR-based gene-expression assay, encompassing important genes, based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) disease pathway. This study analyzed age-dependent disease progression by focusing on pathological events such as the processing of the amyloid precursor protein, tau pathology, mitochondrial dysfunction, endoplasmic reticulum stress, disrupted calcium signaling, inflammation, and apoptosis. Messenger RNA was extracted from the cortex and hippocampal region of APP/PS1 transgenic mice. Samples were divided into three age groups, six-, nine-, and 12-month-old transgenic mice, and they were compared with normal C57BL/6J mice of respective age groups. Findings of this study provide the opportunity to design a simple, effective, and accurate clinical analysis tool that can not only provide deeper insight into the disease, but also act as a clinical diagnostic tool for its better diagnosis.

sRAGE induces human monocyte survival and differentiation

The receptor for advanced glycation end products (RAGE) is produced either as a transmembrane or soluble form (sRAGE). Substantial evidence supports a role for RAGE and its ligands in disease. sRAGE is reported to be a competitive, negative regulator of membrane RAGE activation, inhibiting ligand binding. However, some reports indicate that sRAGE is associated with inflammatory disease. We sought to define the biological function of sRAGE on inflammatory cell recruitment, survival, and differentiation in vivo and in vitro. To test the in vivo impact of sRAGE, the recombinant protein was intratracheally administered to mice, which demonstrated monocyte- and neutrophil-mediated lung inflammation. We also observed that sRAGE induced human monocyte and neutrophil migration in vitro. Human monocytes treated with sRAGE produced proinflammatory cytokines and chemokines. Our data demonstrated that sRAGE directly bound human monocytes and monocyte-derived macrophages. Binding of sRAGE to monocytes promoted their survival and differentiation to macrophages. Furthermore, sRAGE binding to cells increased during maturation, which was similar in freshly isolated mouse monocytes compared with mature tissue macrophages. Because sRAGE activated cell survival and differentiation, we examined intracellular pathways that were activated by sRAGE. In primary human monocytes and macrophages, sRAGE treatment activated Akt, Erk, and NF-kappaB, and their activation appeared to be critical for cell survival and differentiation. Our data suggest a novel role for sRAGE in monocyte- and neutrophil-mediated inflammation and mononuclear phagocyte survival and differentiation.

Advanced glycation end products and diabetic foot disease

Diabetic foot disease is an important complication of diabetes. The development and outcome of foot ulcers are related to the interplay between numerous diabetes-related factors such as nerve dysfunction, impaired wound healing and microvascular and/or macrovascular disease.The formation of advanced glycation end products (AGEs) has been recognized as an important pathophysiological mechanism in the development of diabetic complications. Several mechanisms have been proposed by which AGEs lead to diabetic complications such as the accumulation of AGEs in the extracellular matrix causing aberrant cross-linking, the binding of circulating AGEs to the receptor of AGEs (RAGE) on different cell types and activation of key cell signalling pathways with subsequent modulation of gene expression, and intracellular AGE formation leading to quenching of nitric oxide and impaired function of growth factors. In the last decade, many experimental studies have shown that these effects of AGE formation may play a role in the pathogenesis of micro- and macrovascular complications of diabetes, diabetic neuropathy and impaired wound healing. In recent years also, several clinical studies have shown that glycation is an important pathway in the pathophysiology of those complications that predispose to the development of foot ulcers. Currently, there are a number of ways to prevent or decrease glycation and glycation-induced tissue damage. Although not in the area of neuropathy or wound healing, recent clinical studies have shown that the AGE-breakers may be able to decrease adverse vascular effects of glycation with few side effects.

S100A8 and S100A9 in inflammation and cancer

Calprotectin (S100A8/A9), a heterodimer of the two calcium-binding proteins S100A8 and S100A9, was originally discovered as immunogenic protein expressed and secreted by neutrophils. Subsequently, it has emerged as important pro-inflammatory mediator in acute and chronic inflammation. More recently, increased S100A8 and S100A9 levels were also detected in various human cancers, presenting abundant expression in neoplastic tumor cells as well as infiltrating immune cells. Although, many possible functions have been proposed for S100A8/A9, its biological role still remains to be defined. Altogether, its expression and potential cytokine-like function in inflammation and in cancer suggests that S100A8/A9 may play a key role in inflammation-associated cancer.

Oxidative Stress Increases Expression and Activity of BACE in NT2 Neurons

Recently an aspartyl protease with beta-secretase activity called BACE was identified. In the present paper we showed that BACE is modulated by the oxidative stress product 4-hydroxynonenal (HNE). Exposure of NT(2) neurons to the two classical pro-oxidant stimuli ascorbate/FeSO(4) and H(2)O(2)/FeSO(4) resulted in a significant generation of HNE, which is temporally followed by an increased production of BACE protein levels. HNE mediated BACE induction is accompanied by a proportional elevation of carboxy-terminal fragments of amyloid precursor protein. Moreover, the direct relationship between BACE induction and lipid peroxidation products was strongly confirmed by the protection exerted by a short pretreatment with alpha-tocopherol, the most important antioxidant known to prevent the formation of aldehydic end-products of lipid peroxidation, including HNE. Our results support the hypothesis that oxidative stress and A beta production are strictly interrelated events and suggest that inhibition of BACE may have a therapeutic effect synergic with antioxidant compounds.