Correlative optical photothermal infrared and X-ray fluorescence for chemical imaging of trace elements and relevant molecular structures directly in neurons

Alzheimer's disease(AD)is the most common cause of dementia,costing about 1%of the global economy.Failures of clinical trials targeting amyloid-βprotein(Aβ),a key trigger of AD,have been explained by drug inefficiency regardless of the mechanisms of amyloid neurotoxicity,which are very difficult to address by available technologies.Here,we combine two imaging modalities that stand at opposite ends of the electromagnetic spectrum,and therefore,can be used as complementary tools to assess structural and chemical information directly in a single neuron.Combining label-free super-resolution microspectroscopy for sub-cellular imaging based on novel optical photothermal infrared(O-PTIR)and synchrotron-based X-ray fluorescence(S-XRF)nano-imaging techniques,we capture elemental distribution and fibrillary forms of amyloid-βproteins in the same neurons at an unprecedented resolution.Our results reveal that in primary AD-like neurons,iron clusters co-localize with elevated amyloidβ-sheet structures and oxidized lipids.Overall,our O-PTIR/S-XRF results motivate using high-resolution multimodal microspectroscopic approaches to understand the role of molecular structures and trace elements within a single neuronal cell.

Differential seeding and propagating efficiency ofα-synuclein strains generated in different conditions

Background:Accumulation of alpha-synuclein(α-syn)is a main pathological hallmark of Parkinson’s and related diseases,which are collectively known as synucleinopathies.Growing evidence has supported that the same protein can induce remarkably distinct pathological progresses and disease phenotypes,suggesting the existence of strain difference amongα-syn fibrils.Previous studies have shown thatα-syn pathology can propagate from the peripheral nervous system(PNS)to the central nervous system(CNS)in a“prion-like”manner.However,the difference of the propagation potency from the periphery to CNS among differentα-syn strains remains unknown and the effect of different generation processes of these strains on the potency of seeding and propagation remains to be revealed in more detail.Methods:Three strains of preformedα-syn fibrils(PFFs)were generated in different buffer conditions which varied in pH and ionic concentrations.Theα-syn PFFs were intramuscularly(IM)injected into a novel bacterial artificial chromosome(BAC)transgenic mouse line that expresses wild-type humanα-syn,and the efficiency of seeding and propagation of these PFFs from the PNS to the CNS was evaluated.Results:The three strains ofα-syn PFFs triggered distinct propagation patterns.The fibrils generated in mildly acidic buffer led to the most severeα-syn pathology,degeneration of motor neurons and microgliosis in the spinal cord.Conclusions:The differentα-syn conformers generated in different conditions exhibited strain-specific pathology and propagation patterns from the periphery to the CNS,which further supports the view thatα-syn strains may be responsible for the heterogeneity of pathological features and disease progresses among synucleinopathies.