FEXI MRI detects increased blood-brain barrier water permeability in response to mild lung infection

Non-disruption alterations to the blood-brain barrier (BBB) can be difficult to detect and therefore require highly sensitive tools for reliable measurement. Here, we apply a BBB filter exchange imaging (BBB-FEXI) technique to assess the rat brain in response to mild Streptococcus pneumoniae lung infection. We observe a significant 78 ± 39 % increase in BBB water permeability during infection. Higher water exchange measures were associated with higher levels of vascular inflammation, while BBB tight junction proteins remained unchanged. The expression of aquaporin-4 water channel was 38% higher in infected animals, which may drive the increase in water exchange during infection.