Calpeptin attenuates LPS-induced ventriculomegaly in neonatal mice

Acute inflammatory insults in the developing brain can produce ventriculomegaly, but underlying mechanisms remain incompletely defined. We tested whether preventive calpeptin treatment modified the phenotype induced by intraventricular lipopolysaccharide (LPS) in neonatal mice. Ventricular-volume analysis included vehicle (12 pups/4 litters), LPS (8 pups/3 litters), and LPS + calpeptin (10 pups/2 litters). Calpeptin reduced mean ventricular volume by 72% relative to LPS (2.48 versus 8.92 mm 3 ); the difference persisted in a mixed-effects model with litter as a random intercept (−0.61 log 10 mm 3 , 95% CI −1.02 to −0.20, p = 0.004). Survival analysis included vehicle (13 pups/4 litters), LPS (26 pups/5 litters), and LPS + calpeptin (12 pups/2 litters). Observed endpoint survival was 10/12 with calpeptin versus 10/26 with LPS, but the litter-level comparison was not significant, and pronounced between-litter heterogeneity and only two calpeptin litters preclude a definitive treatment-effect inference; survival remains exploratory. Cortical DiI vascular labeling and VE-cadherin immunofluorescence were obtained from one litter per group and are descriptive, not measures of blood-brain barrier permeability. In cultured primary brain microvascular endothelial cells, LPS increased permeability and the approximately 95/130 kDa VE-cadherin-immunoreactive band ratio. Calpeptin and TLR4 inhibition reduced the band-ratio increase but did not significantly attenuate permeability relative to LPS. Calpeptin is not protease- or isoform-selective, and target engagement was not measured. Thus, the findings suggest a contribution from calpeptin-sensitive protease activity without identifying the responsible protease, confirming cleavage of the lower band, or demonstrating endothelial barrier protection in vivo.