What is the evidence that blood-brain barrier (BBB) permeability changes serve as early biomarkers for neurodegeneration?
Focus areas:
- CSF biomarker panels for BBB dysfunction (tight junction proteins like claudin-5, zonula occludens-1; pericyte markers like PDGFR-beta)
- Blood-based BBB permeability indicators (S100B, NFL, GFAP in plasma vs CSF)
- Dynamic contrast-enhanced MRI measures of BBB leakage as early AD/PD markers
- Relationship between BBB disruption and neurovascular uncoupling preceding motor/cognitive symptoms
- Comparative utility of BBB permeability markers vs amyloid/tau PET for early detection
CSF soluble PDGFR-β shedding from pericytes as the earliest detectable molecular event in AD, preceding amyloid/tau pathology and exploitable as a 'zero-stage' biomarker via ADAM10/17-mediated ectodomain shedding. Biomarker utility is strong; therapeutic translation requires novel PDGFR-β agonism or ADAM10/17-selective CNS inhibition.
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Curated Mechanism Pathway
Curated pathway diagram from expert analysis
flowchart TD
A["PDGFRB Activation PDGF-BB Ligand Binding"]
B["Pericyte Recruitment Blood-Brain Barrier Maintenance"]
C["PDGFRB Signaling PI3K/AKT and MAPK Pathways"]
D["Pericyte Coverage Capillary Integrity"]
E["BBB Integrity Loss Pericyte Dropout in AD"]
F["Neurovascular Coupling Functional Hyperemia Impaired"]
G["Amyloid Deposition Cerebral Amyloid Angiopathy"]
H["Hypoperfusion Chronic Ischemia"]
I["Cognitive Decline Vascular contributions to dementia"]
A --> B
B --> C
C --> D
D --> E
E --> F
F --> H
E --> G
G --> H
H --> I
style A fill:#1a237e,stroke:#4fc3f7,color:#4fc3f7
style I fill:#b71c1c,stroke:#ef9a9a,color:#ef9a9a
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5 citations5 with PMID5 mediumValidation: 0%5 supporting / 0 opposing
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No opposing evidence
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Presenilins mediate phosphatidylinositol 3-kinase/AKT and ERK activation via select signaling receptors. Selec…MEDIUM▼
Presenilins mediate phosphatidylinositol 3-kinase/AKT and ERK activation via select signaling receptors. Selectivity of PS2 in platelet-derived growth factor signaling.
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IF cognitively normal individuals aged 60-80 with elevated baseline CSF sPDGFR-β (top quartile) are stratified and followed longitudinally for 36 months, THEN they will demonstrate significantly faster accumulation of amyloid pathology (≥15% greater decline in CSF Aβ42/40 ratio) and tau pathology (≥20% greater increase in CSF p-tau217) compared to individuals in the lowest sPDGFR-β quartile.
pendingconf: 0.65
Expected outcome: sPDGFR-β elevation precedes and predicts accelerated amyloid/tau pathology accumulation over 36 months, with effect size ≥15% difference in biomarker trajectories between quartiles.
Falsified by: No significant difference in amyloid/tau biomarker change rates between sPDGFR-β quartiles (p>0.05 for group × time interaction), OR sPDGFR-β changes occur after rather than before amyloid/tau changes in the temporal sequence analysis.
Method: Longitudinal analysis of the Alzheimer's Disease Neuroimaging Initiative (ADNI) cohort or similar multicenter cohort of cognitively normal elderly (N≥300) with serial CSF sampling at baseline, 12, 24, and 36 months, using Simoa sPDGFR-β assay, Lumipulse Aβ42/40, and p-tau217 measurements.
IF human brain pericytes in primary culture are treated with selective ADAM10 (Ro 28-1663) and ADAM17 (TMI-005) inhibitors either individually or in combination (25μM each, 48h), THEN combined ADAM10/17 inhibition will reduce secreted sPDGFR-β in conditioned media by ≥60% compared to vehicle control, with single-agent inhibition achieving ≤30% reduction each.
pendingconf: 0.45
Expected outcome: sPDGFR-β shedding from pericytes requires coordinated ADAM10 and ADAM17 activity, with ≥60% reduction when both are inhibited simultaneously.
Falsified by: Combined ADAM10/17 inhibition produces <40% reduction in sPDGFR-β (fails to implicate these sheddases); OR single-agent inhibition produces ≥50% reduction (suggesting single sheddase is sufficient, contradicting the hypothesis of dual enzyme requirement).
Method: Primary human brain pericyte cultures (ScienCell or generated from iPSC-derived pericytes) treated with selective pharmacological inhibitors; sPDGFR-β measured by ELISA in conditioned media; validity confirmed with siRNA knockdown of ADAM10/17 as positive control.