Tetramodal Chemical Imaging Delineates the Lipid-Amyloid Peptide Interplay at Single Plaques in Transgenic Alzheimer?s Disease Models

Beta-amyloid (AP) plaque pathology is one of the most prominent histopathological feature of Alzheimer's disease (AD). The exact pathogenic mechanisms linking AP to AD pathogenesis remain however not fully understood. Recent advances in amyloid-targeting pharmacotherapies highlight the critical relevance of AP aggregation for understanding the molecular basis of AD pathogenesis. We developed a novel, integrated, tetramodal chemical imaging paradigm for acquisition of trimodal mass spectrometry imaging (MSI) and interlaced fluorescent microscopy from a single tissue section. We used this approach to comprehensively investigate lipid-AP correlates at single plaques in two different mouse models of AD (tgAPPSwe and tgAPPArcSwe) with varying degrees of intrinsic properties affecting amyloid aggregation. Integration of the multimodal imaging data and multivariate data analysis identified characteristic patterns of plaque-associated lipid-and peptide localizations across both mouse models. Correlative fluorescence microscopy using structure-sensitive amyloid probes identified intra-plaque structure-specific lipid and AP patterns, including AP 1-40 and AP 1-42 along with gangliosides (GM), phosphoinositols (PI), conjugated ceramides (CerP and PE-Cer), and lysophospholipids (LPC, LPA, and LPI). Single plaque correlation analysis across all modalities further revealed how these distinct lipid species were associated with AP peptide deposition across plaque heterogeneity, indicating different roles for those lipids in plaque growth and amyloid fibrillation, respectively. Here, conjugated ceramide species correlated with AP core formation indicating their involvement in initial plaque seeding or amyloid maturation. In contrast, LPI and PI were solely correlated with general plaque growth. In addition, GM1 and LPC correlated with continuous AP deposition and maturation. The results highlight the potential of this comprehensive multimodal imaging approach and implement distinct lipids in amyloidogenic proteinopathy.