Influence of lipid type and amyloid beta peptide on membrane perturbance and consequences on neuronal cell toxicity observed by the luminescent responses of the RuApy complex

• Grant number: 21/02436-7
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2021
• End date: August 31, 2023
• Field of knowledge: Interdisciplinary Subjects
• Principal Investigator: Rose Maria Carlos
• Grantee: Maria Laura da Cruz Garcia
• Host Institution: Centro de Ciências Exatas e de Tecnologia (CCET). Universidade Federal de São Carlos (UFSCAR). São Carlos , SP, Brazil
• Associated scholarship(s): 22/03380-8 - Interactions between amyloid beta peptide and lipid membrane models with complex cis-[Ru(phen)2(3,4Apy)2]2+ as a luminescent probe, BE.EP.MS

Abstract

Alzheimer's disease (AD) is characterized mainly by the accumulation of aggregates of beta-amyloid peptide (bA) in the patient's brain that lead to severe synaptic and cognitive dysfunctions not available in neurodegenerative dementia. Several studies indicate that bA toxicity comes from the process of aggregation and interaction with a neuronal membrane. Other studies suggest that non-amyloidogenic factors, such as the type of membrane that is responsible for the toxicity exerted by bA. As all these characteristics are variables to be considered in elucidating the impact of biological membranes on the structure of bA and the effect of bA on the integrity of the cell membrane it is important that the effects on these factors are investigated. Despite the extensive literature on membrane-bA interactions, a discussion at the molecular level is still an excipient and is often controversial. Furthermore, there are few systematic and mechanistic studies of the bA-membrane interaction due to the lack of sufficiently sensitive techniques for these interactions without the need for a membrane-bound chromophore. Recent studies of the interaction of the complex cis-[Ru(phen)2(3,4-Apy)2]2+ (RuApy) where phen = 1,10-phenanthroline and 3,4-Apy = 3,4-aminopyridine, with negatively charged phospholipids (DOPG), carried out by Maria Laura during her scientific research project (FAPESP 2019/15813-3) shows that this complex is a luminescent probe sensitive to the lipid environment. These results motivated us to (1) explore the behavior of non-amyloidogenic bA peptides (p3-17-40, p3-17-42) and amyloidogenic (1-40, 1-42, 25-35) in the native and fibrillar form in the presence of membranes (liposomes, SUVs, LUVs, GUVs and SLBs) varying the concentration of bA; (2) determine how these conditions interfere with the integrity of the membrane; (3) Compare the results obtained on the bA effects on the toxicity and integrity of neuronal cells (PC12 and /or SH-SY5Y). For this, we intend to use RuApy's luminescent responses as a molecular probe for bA-membrane interaction. Once RuApy is positively charged, explore the effects of zwitterionic phospholipids (POPC), as well as negatively charged phospholipids (POPG) and if possible, with additional membrane components such as gangliosides and cholesterol. The studies will be carried out using luminescence spectroscopy (steady state and time resolved), fluorescent image microscopy, pH sensitive dyes, isothermal calorimetric titration and Langmuir isotherms. The studies proposed in this project were designed to contribute to elucidating membrane-bA interactions which are associated with AD and to recognize the potential of the RuApy complex as a luminescent sensor in biological environment. (AU)