Regulation of eosinophil recruitment and allergic airway inflammation by heparan sulfate proteoglycan (HSPG) modifying enzymes.

<bold>Background:</bold> HSPGs are glycoproteins containing covalently attached heparan sulfate (HS) chains which bind to growth factors, chemokines, etc., and regulate various aspects of inflammation including cell recruitment. We previously showed that deletion of endothelial <italic>N</italic>-acetylglucosamine <italic>N</italic>-deacetylase-<italic>N</italic>-sulfotransferase-1 (Ndst1), an enzyme responsible for <italic>N</italic>-sulfation during HS biosynthesis, reduces allergic airway inflammation (AAI). Here, we investigated the importance of <italic>O</italic>-sulfation mediated by uronyl 2-<italic>O</italic>-sulfotransferase (Hs2st) in development of AAI relative to <italic>N</italic>-sulfation. <bold>Methods:</bold> Mice deficient in endothelial and leukocyte <italic>Hs2st</italic> (<italic>Hs2st</italic>f/f<italic>Tie2Cre</italic>+) or <italic>Ndst1</italic> (<italic>Ndst1</italic>f/f<italic>Tie2Cre</italic>+) and WT mice were challenged with <italic>Alternaria alternata</italic> and evaluated for airway inflammation. Trafficking of murine eosinophils on lung endothelial cells was examined <italic>in vitro</italic> under conditions of flow. <bold>Results:</bold> Exposure to <italic>Alternaria</italic> decreased expression level of <italic>Hs2st</italic> in WT mice while level of <italic>Ndst1</italic> remained unchanged. Compared to WT mice, <italic>Alternaria</italic>-challenged <italic>Hs2st</italic>f/f<italic>Tie2Cre</italic>+ mice exhibited significantly increased eosinophils in the bone marrow, bronchoalveolar lavage fluid [BALF] and lung tissue associated with persistent airway hyperresponsiveness, airway mucus hypersecretion and elevated Th2 cytokines. In contrast, <italic>Alternaria</italic>-challenged <italic>Ndst1</italic>f/f<italic>Tie2Cre</italic>+ mice exhibited a marked reduction in airway eosinophilia, mucus secretion and smooth muscle mass compared to WT counterparts. While BALF eotaxins were lower in <italic>Alternaria</italic>-challenged <italic>Hs2st</italic>f/f<italic>Tie2Cre</italic>+ relative to WT mice, they were not reduced to background levels as in allergen-challenged <italic>Ndst1</italic>f/f<italic>Tie2Cre</italic>+ mice. Trafficking of murine eosinophils under conditions of flow <italic>in vitro</italic> was similar on <italic>Hs2st</italic>-deficient and WT endothelial cells. Expression of ZO-1 in <italic>Hs2st</italic>-deficient lung blood vessels in control and allergen-challenged mice was significantly lower than in WT counterparts. <bold>Conclusions:</bold> Our study demonstrates that allergen exposure reduces expression of Hs2st; loss of uronyl 2-<italic>O</italic>-sulfation in endothelial and leukocyte HSPG amplifies recruitment of eosinophils likely due to a compromised vascular endothelium resulting in persistent inflammation whereas loss of <italic>N</italic>-sulfation limits eosinophilia and attenuates inflammation underscoring the importance of site-specific sulfation in HSPG to their role in AAI. [ABSTRACT FROM AUTHOR]