Mechanism And Characteristic Of Polymorphonuclear Leukocyte Chemotaxis In Oxygen Gradient

Hypoxia is a common pathological process of various types of inflammatory diseases and is the most common cause of cell damage, polymorphonuclear leukocytes (PMN) have a key regulatory role in vascular inflammation. Inflamed lesions often become severely hypoxic. Infiltration and function execution of inflammatory cells need more oxygen. As PMN migrate from the circulation to sites of inflammation, they are required to adapt to and function within oxygen tensions much lower than those encountered in the circulatory system. However, it is unclear how inflammatory cells resolve the contradiction of oxygen supply and need.Objective:In this studies, we used advanced techniques to recover the characteristics and mechanism of PMN chemotaxis in oxygen gradient.Methods:The Ibidi six-channel cell chemotaxis assay to observe PMN movement in 21→0%O2 gradient. Chemoattractant-induced chemotaxis was measured in a 48-well chamber. After hypoxia or fMLP (N-formylmethionyl-leucyl-phenylalanine, a agonist of formylpeptide receptor (FPR)) treatment, Expression of CYGB of PMN were assayed by Western blot.Result:The directed migration of PMN toward hypoxia terminal was observed in oxygen gradient. PMNs chemotaxis was enhanced with the increase of oxygen gradient. The supernatants of hypoxia-cultured PMN induced chemotaxis in a hypoxic time-dependent way, the supernatants of normoxia-cultured PMN did not. Hypoxia promoted PMN to produce chemoattractants. With the O2 concentrations decreasing, the PMN supernatant-induced chemotaxis was strengthened gradually. FPR antagonist tBoc attenuated partially the supernatant-induced chemotaxis. Hypoxia or FPR agonist fMLP precondition increased the expression of cytoglobin of PMN and chemotaxis of PMN to serum under hypoxia.Conclusion:These results suggest that hypoxia promotes PMN in hypoxia terminal of oxygen gradient to produce chemoattractants such FPR agonists, which attract PMN to hypoxia terminal. The chemoattractants and hypoxia upregulate the expression of oxygen metabolism related proteins such as cytoglobin in PMN and enhance the capacity of PMN infiltration to hypoxic inflammatory microenvironment.