Microglia drive diurnal variation in susceptibility to inflammatory blood-brain barrier breakdown.
Level 5 - mechanism / opinion, no new human data
Preclinical animal laboratory experiment
PubMed 39513366 · doi:10.1172/jci.insight.180081
What was done
Mice under standard light-dark cycles received repeated systemic lipopolysaccharide (LPS) injections in the morning (ZT1) or evening (ZT13). Blood-brain barrier (BBB) permeability was evaluated using sodium fluorescein (a non-transporter polar marker). The researchers assessed glial activation and inflammatory markers in the brain versus periphery, and tested the effects of microglial depletion and constant darkness housing on BBB disruption.
What was found
The abstract reports no specific numerical values or p-values. It reports a striking increase in paracellular BBB leak specifically after evening LPS injection compared to morning injection. Evening LPS led to sustained glial activation and neuroinflammation that was not mirrored in peripheral tissues. The elevated evening neuroinflammation and BBB leak were suppressed by microglial depletion and by housing mice in constant darkness.
Why it matters
This work demonstrates that inflammatory BBB disruption is subject to diurnal variation driven by microglial activation and light cues. It suggests that time of day may influence susceptibility and severity in inflammatory central nervous system conditions.
Limits
The study was conducted entirely in a rodent model using LPS-induced systemic inflammation; findings cannot be directly extrapolated to human clinical pathology without human validation, especially given differences between nocturnal and diurnal circadian physiology. The abstract does not disclose sample sizes, effect sizes, or variance metrics.
Cited by
- supports LPS-driven immune activation and glial cell activation disrupt the blood-brain barrier, contributing to early-stage neurodegeneration.