To explore the regulated effect of exogenous carbon monoxide releasing molecule 2 (CORM-2) on phagocytosis of LPS-chanllanged neutrophils and its relevant mechanism.

Venous blood of a healthy adult volunteer was collected and neutrophils were isolated. Then the neutrophils were divided into five groups according to the random number table, including control, LPS, LPS+ CORM-2 (10 and 50 μmol/L) and LPS+ iCORM-2 group. The control group did not receive any treatment. The LPS group treated with LPS (1 μg/ml) for 60 min. The CORM-2 group and iCORM-2 group underwent the same stimulation and immediate administrated indicated dosage of CORM-2 (10 and 50 μmol/L) and iCORM-2 (50 μmol/L). After neutrophils isolation and individual treatment, the chemotaxis was measured using agarosechemotaxis model. Besides, the early apoptosis rate and phagocytosis of neutrophils was determined by flow cytometry and the level of Akt phosphorylation in MAPK signaling were detected by Western blot. The parameters above were processed with 3 times repeated assayed and all values were analyzed using one-way analysis of variation, and SNK test.

As shown in chemotaxis measured, compared with control group, there was a significant decrease of the chemotaxis distance when neutrophils stimulated with LPS and iCORM-2, (both P<0.05). Compared with LPS group, treated with CORM-2 (10 μmol/L and 50 μmol/L) sharply recovered the chemotaxis of neutrophil (both P< 0.01). The chemotaxis distanceof neutrophil of iCORM-2 group was similar with LPS group (P>0.05). As shown in neutrophil exocytosis, there was a slightly increase of exocytosis when neutrophil stimulate with LPS compared with control group (P>0.05). Whereas there was a significant decrease of exocytosis when treated with CORM-2 (10 μmol/L and 50 μmol/L) (both P<0.01). The exocytosis of neutrophil of iCORM-2 group was similar with LPS group (P>0.05). In terms of phagocytosis, compared with control group, there was a significant increase with LPS (P<0.05). Compared with LPS group, treated with CORM-2 (10 μmol/L and 50 μmol/L) sharply elevated the phagocytosis of neutrophil (both P<0.01). The phagocytosis of iCORM-2 group was similar with LPS group (both P>0.05). Compared with control group, it was similar of the level of Akt phosphorylation with LPS and iCORM-2 (all P>0.05). Compared with control group, the level of Akt phosphorylation was increased in CORM-2 (10 μmol/L and 50 μmol/L) groups (both P<0.05). Compared with LPS group, the level of Akt phosphorylation was increased in CORM-2 (10 μmol/L and 50 μmol/L) groups (both P<0.05).

CORM-2 can promote the apoptosis in LPS-chanllaged neutrophils, sharply recover the chemotaxis and promoted the phagocytosis. The possible mechanism of CORM-2 regulated the apoptosis and phagocytosis of LPS-induced neutrophil is related with the elevation of phosphorylation of Akt.