Pulmonary glycosaminoglycans and fucosylation regulate lung barrier function and defense against S.pneumoniae

<bold>Background</bold>: Lung epithelial glycosaminoglycans are shed during lung injury, while certain individuals may have mutations in fucosyltransferase genes, lacking the ability to secrete terminally fucosylated glycans and resulting in susceptibility to infection by certain pathogens. <bold>Aims</bold>: Investigating how heparan sulfate and hyaluronan, as well as terminally fucosylated glycans influence <italic>Streptococcus pneumoniae</italic> (S.pn.) infection and lung barrier function. <bold>Methods</bold>: Murine models of pneumonia were employed utilizing enzymatic cleavage of pulmonary hyaluronan and heparan sulfate, as well as systemic inhibition of terminal fucosylation using 2-deoxy-D-galactose (2d-Gal). The murine glycome was evaluated using LC-MS/MS. Epithelial barrier function was assessed through impedance sensing and use of an alveolus-on-a-chip model. <bold>Results</bold>: Heparinase treatment of mice resulted in increased lung barrier permeability during pneumonia. Exposure to heparinase <italic>in vitro</italic> accelerated loss of barrier function of human alveolar epithelial cells following S.pn. infection. In a human alveolus-on-a-chip model, heparinase treatment combined with S.pn. infection resulted in increased epithelial permeability. Systemic inhibition of fucosylation <italic>in vivo</italic> using 2d-Gal led to reduced bacterial burden and quicker resolution of neutrophilic inflammation in BAL of infected mice. Treatment with 2d-Gal led to reduced lung permeability and lower cytokine levels in BAL fluid of infected mice. <bold>Conclusions</bold>: Our findings reveal a protective role of intact heparan sulfate on lung epithelial barrier function, while biochemical inhibition of fucosylation prevents establishment of S.pn. infection in mice.