Mechanistic insight into female predominance in Alzheimer's disease based on aberrant protein S-nitrosylation of C3.
Level 4 - case-series / case-control
Case-control postmortem human brain tissue analysis coupled with mechanistic laboratory experiments
PubMed 36516243 · doi:10.1126/sciadv.ade0764
What was done
Authors used triaryl phosphine (SNO TRAP) coupled with mass spectrometry to analyze protein S-nitrosylation in 40 postmortem human brains from male and female donors with Alzheimer's disease (AD) and non-AD controls. Candidate proteins were ranked bioinformatically, and laboratory experiments were performed to examine the mechanism connecting sex hormones, S-nitrosylated complement component 3 (SNO-C3), and synaptic loss.
What was found
Mass spectrometry identified 1,449 S-nitrosylated proteins across 2,809 SNO sites. Integrative ranking identified complement component 3 (C3), p62 (SQSTM1), and phospholipase D3 among the top 10 elevated SNO proteins. SNO-C3 was increased in female compared with male AD brains. Mechanistic experiments demonstrated that SNO-C3 formation was dependent on declining beta-estradiol levels, leading to increased synaptic phagocytosis, synapse loss, and cognitive decline (specific quantitative effect sizes were not reported in the abstract).
Why it matters
The findings provide a molecular hypothesis for female predominance in Alzheimer's disease, linking estrogen decline to complement-driven synaptic elimination.
Limits
The human tissue sample was small (40 postmortem brains) and no exact numerical values, statistical effect sizes, or demographic breakdowns were reported in the abstract. Causal links from falling estradiol to synapse loss and cognitive impairment rely on preclinical mechanistic systems rather than human longitudinal data.
Cited by
- supports Complement C3 marks synapses for microglial phagocytosis/digestion, and synaptic binding of C3 is reduced by estradiol.
- supports In Alzheimer's disease brains, C3-bound synapses show a 5-fold increase in men and up to a 28-fold increase in women compared to controls.