Abstract
Introduction: Extracellular ATP (eATP) was one of the DAMPs to stimulate the immune response. Our work has showed that polymicrobial sepsis causes the eATP release into circulation of sepsis mice and eATP regulated PMNs function via purinergic signaling.
Objective: To understand how systemic ATP affects the PMNs chemotaxis and to explore the potential of removal of ATP as treatment.
Methods: Human PMNs were isolated from healthy volunteers. Chemotaxis was assessed using a live cell imaging system. Cells were coated in a plate and chemoattractant gradient was generated with a micropipette loaded with 100nM bacterial product fMLP. The movement of cells was recorded with/without ATPase Apyrase. Migration speeds and directionality of cells were calculated. We determined the bacterial burden in blood and peritoneum in Cecal ligation and puncture (CLP) induced sepsis mice with/without apyrase treatment.
Results: We found that eATP at levels in sepsis significantly impairs the ability of PMNs to properly orient in the chemotactic gradient field, reducing the percentage of PMNs that migrate in the correct direction to the focus of infection. Apyrase completely recovers chemotaxis of PMNs in the presence of external ATP. Correspondingly, Apyrease significantly reduced the bacteria numbers in both blood and peritoneum in CLP-induced sepsis mice.
Conclusions: We conclude that eATP in sepsis impairs PMN chemotaxis by obscuring the endogenous purinergic guidance system of PMNs and that the removal of systemic ATP can restore PMN chemotaxis and the ability of PMNs to find and kill bacteria.
This work was funded by grants from the NNSF of China (FQ.Wen and X.Li), the NIGMS, NIAID (WG.Junger).
- Copyright ©the authors 2016
