Minimal penetration of lipopolysaccharide across the murine blood-brain barrier.
Level 5 - mechanism / opinion, no new human data
Mechanistic bench and animal research
PubMed 19735725 · doi:10.1016/j.bbi.2009.09.001
What was done
Radioiodine-labeled lipopolysaccharide (I-LPS) was coinjected intravenously with radioactively labeled albumin (I-Alb, a vascular space marker) in mice to measure blood-brain barrier (BBB) association and penetration. Uptake was also tested following repeated LPS injections to assess the effect of BBB disruption, and I-LPS was injected into the lateral ventricle to evaluate CNS-to-blood clearance.
What was found
Measurable I-LPS associated with the BBB, mostly by reversible binding to brain endothelia, with small amounts sequestered. Approximately 0.025% of an intravenous I-LPS dose crossed the BBB into the CNS. Disruption of the BBB via repeated LPS injections did not increase uptake. Intracerebroventricularly injected I-LPS entered systemic circulation via cerebrospinal fluid bulk flow reabsorption.
Why it matters
Direct penetration of peripheral LPS into the CNS is negligible, indicating that systemic LPS-induced neuroinflammation is predominantly mediated by targets outside the BBB (e.g., circumventricular organs, afferent nerves, or brain endothelial signaling) rather than direct parenchymal exposure.
Limits
The study was conducted in a murine model and findings may not fully translate to human BBB physiology. Sample sizes, exact LPS doses, and statistical variance metrics were not provided in the abstract. Neuroinflammatory events were not directly co-measured but inferred from historical literature dose-response curves.
Cited by
- contradicts Lipopolysaccharide (LPS) can cross the blood-brain barrier and activate microglial immune cells, inducing brain inflammation.