Extracellular adenosine enhances the ability of PMNs to killStreptococcus pneumoniaeby inhibiting IL-10 production

Abstract

PMNs are crucial for initial control of Streptococcus pneumoniae (pneumococcus) lung infection; however, as the infection progresses their persistence in the lungs becomes detrimental. Here we explored why the anti-microbial efficacy of PMNs declines over the course of infection. We found that the progressive inability of PMNs to control infection correlated with phenotypic differences characterized by a decrease in CD73 expression, an enzyme required for production of extracellular adenosine (EAD). EAD production by CD73 was crucial for the ability of both murine and human PMNs to kill S. pneumoniae. In exploring the mechanisms by which CD73 controlled PMN function, we found that CD73 mediated its anti-microbial activity by inhibiting IL-10 production. PMNs from wild type mice did not increase IL-10 production in response to S. pneumoniae, however, CD73-/- PMNs up-regulated IL-10 production upon pneumococcal infection in vitro and during lung challenge. IL-10 inhibited the ability of wild type PMNs to kill pneumococci. Conversely, blocking IL-10 boosted the bactericidal activity of CD73-/- PMNs as well as host resistance of CD73-/- mice to pneumococcal pneumonia. CD73/IL-10 did not affect apoptosis, bacterial uptake and intracellular killing or production of anti-microbial Neutrophil Elastase and Myeloperoxidase. Rather, inhibition of IL-10 production by CD73 was important for optimal ROS production by PMNs. ROS contributed to PMN anti-microbial function as their removal or detoxification impaired the ability of PMNs to efficiently kill S. pneumoniae. This study demonstrates that CD73 controls PMN anti-microbial phenotype during S. pneumoniae infection.

Extracellular adenosine signaling reverses the age‐driven decline in the ability of neutrophils to kill Streptococcus pneumoniae

“…We previously found that extracellular adenosine (EAD) production by PMNs is required for their antimicrobial activity against S . pneumoniae (Siwapornchai et al, 2020). To test if aging is associated with changes in the expression of EAD‐producing and degrading enzymes, we compared the basal expression of CD73, CD39, and ADA on the surface of bone marrow‐derived PMNs using flow cytometry.…”

“…CD73 expression is crucial for the antimicrobial phenotype of PMNs during S pneumoniae infection (Siwapornchai et al, 2020). As pulmonary infection progresses, unresolved PMN presence in the lungs becomes detrimental for host resistance (Bou Ghanem, Clark, Roggensack, et al, 2015).…”

“…We previously found that this was in part because S . pneumoniae manipulated the host by targeting the surface expression of CD73 on pulmonary PMNs later in the infection, blunting the ability of these cells to kill bacteria (Siwapornchai et al, 2020). Thus, initial expression of CD73 on PMNs is crucial for host resistance, which suggests that the reduced basal expression of this enzyme in PMNs of old mice contributes to the innate age‐driven susceptibility to infection (Bou Ghanem, Clark, Du, et al, 2015).…”

“…Streptococcus pneumoniae TIGR4 AC316 strain (serotype 4) was a kind gift from Andrew Camilli. Bacteria were grown at 37°C in 5% CO 2 in Todd Hewitt broth supplemented with 0.5% yeast extract and oxyrase until mid‐exponential phase as previously described (Siwapornchai et al, 2020).…”

“…pneumoniae lung infection (Bou Ghanem, Clark, Roggensack, et al, 2015). Importantly, CD73 controlled PMN antimicrobial activity (Siwapornchai et al, 2020). CD73 expression and EAD production by PMNs was required for their ability to kill and clear S .…”