Alzheimer’s Disease (AD), commonly known as senile dementia, is a neurodegenerative disease most commonly occurring in people over 65 years old. The pathological features of AD include senile plaques, neuronal fiber tangles, granulovacuolar degeneration of hippocampal pyramidal neurons, and neuronal deficits. As an insidious disease, clinical symptoms for AD include cognitive impairment, non-cognitive neuropsychiatric disorders, and reduced social function. Although increasing evidence demonstrate that the cause of AD is related to the aggregation of Aβ peptides and the emergence of Aβ oligomers, few anti-aggregation therapeutics have been approved by the U.S. Food and Drug Administration in the past decades. On September 15, 2023, Professor Ruhong Zhou and his team at Shanghai Institute for Advanced Study, Zhejiang University published ‘C3N Nanodots Inhibit Aggregation of Aβ Peptides and Aβ Oligomers’ in Nature Communications, reporting ultrasmall C3N nanodots as an inhibitor to Aβ peptide aggregation. By combining experiments and multi-scale theoretical calculations, they systematically investigated biological effects and detailed molecular mechanisms of how C3N nanodots inhibit Aβ peptide aggregation and intervene in the pathological progression in mice with AD at molecular and cellular levels respectively, providing new insights to develop highly efficient and low-toxicity anti-AD drugs.
Through thioflavin T(ThT) fluorescence experiments, dot hybridization experiments and AFM morphology observation, the authors found that C3N nanodots could efficiently inhibit the aggregation of Aβ42 peptide (Figure 1b-d), and alleviate neurotoxicity induced by the aggregation through stimulated primary neuron model for Aβ42 peptide. In addition, C3N nanodots could effectively prevent the aggregation of other fragments in Aβ peptide family, such as the N-truncated Aβ peptide (AβpE3) and the Aβ40 peptide. To further explore molecular mechanism by which C3N nanodots inhibit Aβ aggregation, the authors employed all-atom molecular dynamics (MD) simulation to reveal structural change of C3N nanodots during Aβ42 aggregation. Results showed that C3N nanodots strongly inhibited the formation of ordered β-sheets in Aβ42 peptide self-assembly and induced disordered structures to form (Fig. 1e-f). Detailed binding mechanism was obtained by analyzing C3N-peptide interactions together with key binding conformations. In addition, they comparatively analyzed the inhibition of Aβ42 aggregation by C3N nanodots, graphene nanorods (GRA), and fullerenes (C60), and found C3N nanodots inhibited Aβ42 aggregation most.
Cognitive deficit is typical in AD patients, and the authors found that C3N nanodots could pass through blood-brain barrier in mice by labeling C3N nanodots with Cy5.5. Water maze experiments showed that C3N nanodots administration (1 mg/kg/d) greatly shortened the time to hidden platform. After the platform was removed, residence time and number of crossings in target area were significantly increased in intervened mice (Figure 2b-f). In new object recognition experiment, C3N nanodot administration prolonged exploration time (Figure 2g-h). These results consistently showed that C3N nanodot administration improved learning and memory in AD mice.
In addition, the authors discovered that C3N nanodots reduced Aβ polypeptide accumulation in slices and homogenates of brains in mice with AD, which in turn alleviated neuronal synaptic damage as well as neuronal death (Figure 3). These results further demonstrated C3N nanodots effectively ameliorated AD pathology by inhibiting Aβ polypeptide aggregation.
To sum up, the work demonstrated that C3N nanodots attenuated Aβ aggregation-induced neuronal cytotoxicity and overall Aβ peptide, and effectively blocked synaptic loss, thus significantly ameliorated behavioral deficits in APP/PS1 double-transgenic mice with AD. Besides, no inflammatory response andvmajor organ damage was detected in mice administered for C3N nanodots up to six months in the experiment. This study provides experimental and theoretical evidence for C3N nanodots in AD prevention and treatment, and could serve as reference for designing subsequent drugs inhibiting Aβ aggregation.
The work was supported by from the National Key Research and Development Program of China, the National Key R&D Program of China, the National Natural Science Foundation of China, the National Independent Innovation Demonstration Zone Shanghai Zhangjiang Major Projects, the Starry Night Science Fund at Shanghai Institute for Advanced Study of Zhejiang University, and BirenTech Research. To access the article please go to https://www.nature.com/articles/s41467-023-41489-y.