Calpeptin mitigates ventriculomegaly and microvascular impairment in a novel LPS- dependent mouse model of acquired hydrocephalus

Hydrocephalus, characterized by ventricular distension due to impaired cerebrospinal fluid (CSF) pathways, is a multifactorial condition with perinatal infection as a predominant global cause. Over three decades, alterations in periventricular cell junctions, especially cadherins, have been linked to pediatric hydrocephalus pathogenesis. We propose that the Toll-like receptor (TLR)–calpain (calcium-dependent proteinase) pathway induces cadherin cleavage, playing a central role in initiating vascular impairment associated with vascular permeability and ventriculomegaly—hallmark events in acquired hydrocephalus (AH). In this manuscript, perinatal C57BL/6 mice and endothelial cell cultures were exposed to lipopolysaccharide (LPS) toxin, a gram-negative bacteria component, modeled post-infectious hydrocephalus. For treatment, calpain inhibitor (calpeptin) and TLR-4 receptor inhibitor were employed in cell cultures, with calpeptin used in mice. Magnetic resonance imaging (MRI) quantified ventricular volume, and immunofluorescence and DiI assessed microvascular integrity. Additionally, endothelial permeability was evaluated using a transwell system. Results showed that in vitro LPS induced increased endothelial permeability associated with calpain-dependent cleavage of VE-cadherin. In vivo, intraventricular LPS-induced ventriculomegaly linked to microvascular impairments dorsally to the ventricles (p<0.05). In vitro, TLR and calpain inhibition exhibited similar vascular permeability and VE-cadherin cleavage after LPS exposure compared to the control. In vivo, calpain inhibition prevented or attenuated ventriculomegaly and significantly improved survival after LPS injection (p<0.05). This research offers a comprehensive analysis from in vitro experiments on C57BL/6 mice primary brain microvascular endothelial cells to in vivo mouse models, highlighting the pivotal role of the TLR4-Calpain pathway, VE-cadherin cleavage, and vascular impairment in acquired hydrocephalus pathogenesis. The findings emphasize the potential of calpain inhibition in preventing the physiopathology associated with LPS exposure.