AGE- RAGE stressor pathway involved in Alzheimer disease: possible beneficial strategies

MAIN AREA: neurodegenerative diseases, chronic inflammatory diseases, glyco-oxidation products

KEYWORDS: AGE, inflammation, RAGE

Ageing is the most important risk factor for the development of neurodegenerative diseases such as Alzheimer disease (AD). Among the evidence present in the early stage of AD, oxidative stress and inflammation are important hallmarks strictly related to the production of advanced glycation end-products (AGEs). They can form both endogenously and exogenously through different mechanisms, from diverse precursors. AGE formation in vivo occurs during physiologic aging and is accelerated in conditions of hyperglycemia, oxidative stress and inflammation, but also dietary AGEs, abundant in processed food, can contribute to the total AGE body load. It is known that the levels of AGEs and their receptors (among them RAGE) are elevated, while the levels of the scavenger soluble receptor for AGE (sRAGE) are reduced in patients with AD. The term “AGE–RAGE stress” has been proposed and high level of AGE–RAGE stress is a universal risk factor for the onset of various diseases. Stressor agents in the AGE–RAGE axis include AGEs and amyloid β (Aβ). Neuronal RAGE binds to Aβ and upregulates RAGE expression, followed by more Aβ generation, causing neuronal toxicity and synaptic dysfunction. Our study aims to manipulate the AGE-RAGE axis in the treatment of AD.

Stressor agents in the AGE–RAGE axis include AGEs and amyloid β (Aβ). The AGE’s interaction with its cell receptor RAGE generates reactive oxygen species  involving the activation of nuclear factor-kappa B (NF-kB) transcription. NF-kB activates numerous inflammatory cytokine genes. A high index of AGE-RAGE stress would result in tissue damage and the development of diseases. Neuronal RAGE binds to Aβ and upregulates RAGE expression, followed by more Aβ generation, causing neuro-inflammation, neuronal toxicity and synaptic dysfunction. 

Our study aims to manipulate the AGE-RAGE axis in the treatment of AD.  We will take advantage of already established experimental models of AD  used from  Prof.  Guglielmotto, which consist of several types of human Induced Pluripotent Stem Cells (hiPSCs). The project proposes two pathways for the modulation of the AGE-RAGE axis: 1. Elevation of sRAGE: hiPSCs derived from AD and control patients will be treated with increasing concentration of sRAGE; 2. Reduction of RAGE expression through two different approaches: a) pharmacological inhibition: hiPSCs and cells from control patients will be treated with drugs able to downregulate the expression of RAGE, these studies can elicit a drug repurposing strategy; b) RNA interference (RNAi) strategies: to enhance the specificity of the anti-RAGE treatments, RNAi strategies with small interfering RNA (siRNA) targeting RAGE will be used (Prof.ssa S. Pizzimenti). Thus, ad hoc synthesized nanovehicles loaded with siRAGE (NV-siRAGE) will be prepared in collaboration with Prof. Roberta Cavalli (Dip. Scienza e Tecnologia del Farmaco, Unito).  End-point analyses: we will detect Aβ levels, β- and γ-secretases activity, RAGE activity, proinflammatory cytokine production, oxidative stress levels, sRAGE and AGE classes, cell viability by using techniques such as western blot (WB), real-time polymerase chain reaction (real-time PCR), hplc coupled to mass detection (hplc–MS), ELISA kits, and MTT assay. Future Planning: based on the results, we can address our studies on experimental animals. Interestingly, ad hoc synthesized nanovehicles loaded with siRAGE used in this study can be patented. The project presented here takes advantage of our expertise on the AGE-RAGE axis, specific cell cultures and specific siRNA protocols (M.Aragno, M. Guglielmotto, S.Pizzimenti).