Intraperitoneal injection of lipopolysaccharide induces dynamic migration of Gr-1high polymorphonuclear neutrophils in the murine abdominal cavity.

Intraperitoneal injection of lipopolysaccharide (LPS; 100 microg) in mice resulted in the disappearance of almost all proteose peptone-induced polymorphonuclear neutrophils (PMNs) with high-level fluorescence for the cell surface marker Gr-1 (Gr-1(high)) at 15 min postinjection, followed by doubling of their proportion at 30 min postinjection. High staining levels of 3'-acetyl-2'-carboxyl-6',7'-(dihyropyran-2'-one)-5 or 6-carboxyfluorescein diacethoxylmethyl ester-labeled PMNs injected into the peritoneal cavity were detected in mesenteric lymph nodes 15 min postinjection of LPS. Therefore, the time of decrease of Gr-1(high) PMNs coincided with that of the increase in cell accumulation in mesenteric lymph nodes. Since milk fat globule-EGF factor 8 (MFG-E8), which is secreted by macrophages, bound many PMNs exhibiting Gr-1(high) and Gr-1(medium) at 30 min postinjection of LPS, the staining level of annexin V on those cells was very low because its binding site is the same as the receptor for MFG-E8. At 60 min postinjection of LPS, the proportion of Gr-1(high) PMNs decreased, and almost all Gr-1(medium) PMNs tended to shift to the right compared with those at 30 min postinjection. The geomeans of Toll-like receptor 4 (TLR4) expression on PMNs at 15, 30, and 60 min postinjection of LPS were 63, 66, and 24%, respectively, compared with that on normal PMNs, indicating that the expression of TLR4 decreases in response to exposure to LPS. Our results suggest that LPS induced PMN death and that many PMNs expressing Gr-1(high) undergo apoptosis 180 min postinjection of LPS.