Protective effect of granulocyte colony-stimulating factor (G-CSF) in a granulocytopenic mouse model of Pseudomonas aeruginosa lung infection through enhanced phagocytosis and killing by alveolar macrophages through priming tumour necrosis factor-alpha (TNF-α) production

Abstract

SUMMARYWe investigated the effects of G-CSF in a granulocytopenic mouse model of Pseudomonas aeruginosa lung infection. The model was prepared by intratracheal instillation of the bacteria, while granulocytopenia was induced by intraperitoneal injection of 4 . 0 mg of cyclophosphamide (CPA). There was no difference in the survival rate between G-CSF-treated animals and the normal group, and the number of neutrophils in the blood and lung recovered to normal in the former group. However, the phagocytic and killing activities of neutrophils were lower in G-CSF-treated mice than in controls. Interestingly, the mortality rate increased significantly when anti-TNF-a antibody was combined with G-CSF, although it was intermediate between CPA alone and CPA-G-CSF-treated mice. However, the improved mortality was not associated with a change in the number of neutrophils in the circulation and lung. Administration of anti-TNF-a antibody resulted in a significant suppression of TNF-a in bronchoalveolar lavage fluid and of enhanced alveolar macrophage function (phagocytic and bactericidal activity) against P. aeruginosa in G-CSF-treated granulocytopenic mice. We showed also increased TNF-a mRNA expression and TNF-a production in vitro using G-CSF-pretreated alveolar macrophages compared with control untreated macrophages. Our results are the first evidence to suggest that G-CSF provides a synergistic protective effect against lethal P. aeruginosa lung infection in the granulocytopenic host. This effect is probably due to enhancement of alveolar macrophage function through endogenous TNF-a production, in addition to increasing the number of circulating neutrophils.

Intrapulmonary TNF Gene Therapy Reverses Sepsis-Induced Suppression of Lung Antibacterial Host Defense

“…Furthermore, our studies indicated that intrapulmonary TNF expression in vivo enhanced the ability of AM to ingest P. aeruginosa when cultured ex vivo. Similar effects of TNF on macrophage phagocytic activity have been shown by others (61). The mechanism for enhanced phagocytic function in response to in vivo expression of the TNF transgene remains unclear, as we observed no significant change in the expression of several AM cell surface molecules involved in the phagocytic response, including CD54, CD11b, CD11c, and CD16 (data not shown).…”

Reduced tissue macrophage population in the lung by anticancer agent cyclophosphamide: restoration by local granulocyte macrophage–colony-stimulating factor gene transfer

“…[1][2][3][4] Indeed, experimental studies carried out by us (data not shown) and others [7][8][9] demonstrate that mice subjected to a CP regimen easily succumb to pulmonary gram-negative bacterial infection elicited by otherwise nonlethal inocula of bacteria. It has long been believed that granulocytopenianeutropenia is the only cause of such increased susceptibility.…”

“…It has long been believed that granulocytopenianeutropenia is the only cause of such increased susceptibility. [7][8][9] Lung tissue residential macrophages, however, are also an integral part of innate immunity, 19,30 and the lack of these cells, regardless of a normal level of peripheral blood neutrophils, predisposes hosts to acute lung bacterial infection. [12][13][14] The critical requirement of a normal number of AMs in the lung for innate immunity was further demonstrated in a recent study by Broug-Holub et al 15 showing that the host deficient in AMs succumbed to Klebsiella pneumonia despite a higher than normal level of neutrophilic infiltration in the lung.…”

Cyclophosphamide Decreases Nitrotyrosine Formation and Inhibits Nitric Oxide Production by Alveolar Macrophages in Mycoplasmosis

“…These toxic metabolites have been shown to reduce lung microsomal enzyme activity and decrease antioxidant defenses (29). Studies with Pseudomonas aeruginosa demonstrated that pretreatment of mice with CYP did not affect the ability of isolated AMs to phagocytize bacteria (34) and control B6 iNOS ϩ/ϩ mice were pretreated with CYP or saline i.p. and infected intranasally with 1.5 ϫ 10 7 CFU of M. pulmonis.…”

“…Mice were injected i.p. with 200 mg of CYP (Bristol-Myers Squibb, Princeton, N.J.)/kg (ϳ4 mg) (26,34) and again 72 h later with 100 mg of CYP/kg (ϳ2 mg) i.p. Control mice were injected with sterile saline.…”