Functional role of the alveolar epithelial glycocalyx in pulmonary defense and inflammation

The overarching aim of this project is to comprehensively dissect how the alveolar epithelial glycocalyx regulates susceptibility to infection, lung barrier function and pneumonia pathogenesis from micro- to macromolecular mechanisms.

Using animal models, we have demonstrated that glycosaminoglycan (GAG) polysaccharides, such as hyaluronan and heparan sulfate, are crucial in preventing severe courses of murine pneumococcal pneumonia. Enzymatic cleavage of pulmonary hyaluronan gave rise to significantly increased bacterial dissemination in addition to perivascular and systemic inflammation in mice. Cleavage of heparan sulfate, on the other hand, resulted in pronounced bronchoalveolar bacterial burden, pulmonary inflammation and extensive increase in alveolar permeability, an indicator of lung barrier failure. Our in vivo findings of barrier disruption were corroborated in vitro using human epithelial barrier models and organ-on-chip platforms. Modulating the glycocalyx microarchitecture through biochemical inhibition of fucosylation in vivo in wild-type (WT) mice culminated in significant improvement in physiological parameters, reduced bacterial burden and improved lung barrier integrity following pneumococcal infection. Using our expertise in glycan synthesis technology, we successfully synthesized various fucosylated glycan structures such as blood group antigens and Globo-H, the latter of which was also utilized to generate glycan-specific nanobodies in alpacas. Further investigations into the lung barrier revealed an epithelial-specific neutrophil-attracting chemokine CXCL5 which was stored in the alveolar glycocalyx. Through the use of Cxcl5-knockout (Cxcl5^–/–) mice, we discovered that this specific chemokine acted detrimentally on the lung barrier, potentiating barrier permeability during pneumococcal infection.