[The changes in secretory function of pulmonary intravascular macrophages after challenge of lipopolysaccharide].

OBJECTIVE: To investigate the role of pulmonary intravascular macrophages (PIMs) in the pathogenesis of acute lung injury (ALI) due to infection. METHODS: Porcine pulmonary blood vessels were flushed by modified Morton method, and PIMs were isolated and cultured. The adhered PIMs were collected with adhesion method and incubated in RPMI 1640 medium. They were challenged with lipopolysaccharide (LPS, 10 mg/L). The activity of interleukin-1ß (IL-1ß), and contents of IL 6 and IL 8 in the culture supernatant were measured by method of thymocyte proliferation and enzyme linked immunoadsorbent assay (ELISA). RESULTS: The released contents of IL-1ß, IL-6 and IL-8 from PIMs were increased significantly compared with those before LPS challenge , and they peaked at 2 hours [IL-1ß activity: (10 400 ± 2 389) scintillant count/min], 4 hours [IL-6 content: (0.80 ± 0.36) µg/L], and 6 hours [IL-8 content: (4.94 ± 1.19) µg/L ] after LPS challenge , and the differences were significant compared with hose before LPS challenge [IL-1ß activity: (213 ± 85) scintillant count/min, IL-6 content: (0.27 ± 0.12) µg/L, IL-8 content: (1.84 ± 0.53) µg/L, all P <0.01]. CONCLUSION: Among the cytokines released from PIMs after LPS challenge , the increase in IL-1ß occurred earlier in comparison with that of IL-6 and IL-8, suggesting that the former might play an important role at the early stage of ALI; on the other hand, though the increase in IL-6 and IL-8 contents occurred later than that of IL- 1ß but it lasted for a longer duration, suggesting that they might be associated with the advancement of ALI. The Results also suggested that interaction of these cytokines played a more important role in the pathogenesis of ALI.

[Changes in inflammatory cytokines released by pulmonary intravascular macrophages after stimulation with lipopolysaccharide].

OBJECTIVE: To investigate the roles of pulmonary intravascular macrophages (PIMs) in the pathogenesis of infective acute lung injury (ALI). METHODS: Porcine pulmonary blood vessels were flushed by modified Morton's method, PIMs were isolated with adhesion method and incubated in RPMI 1640 medium. They were stimulated with lipopolysaccharide (LPS, 10 mg/L). The contents of interleukin-6 (IL-6), IL-8 and tumor necrosis factor-alpha (TNF-alpha) in the culture supernatants were respectively measured by enzyme linked immunoadsorbent assay (EILSA). RESULTS: The release of TNF-alpha, IL-6 and IL-8 by PIMs was increased significantly as compared with the levels before stimulation by LPS, peaking at 1, 4, and 6 hours after LPS stimulation, respectively. The differences were significant (all P<0.01). CONCLUSION: Among the cytokines released by PIMs after LPS challenge, the increase in TNF-alpha content occurs earlier in comparison with that of IL-6 and IL-8, suggesting that the former may play an important role at the early stage of ALI. On the other hand, the increase in IL-6 and IL-8 contents is later than that of TNF-alpha and lasts for a longer time, suggesting that they may be associated with the development of ALI. The results also suggest that interaction of these cytokines is more important in the pathogenesis of ALI.

LPS induces pulmonary intravascular macrophages producing inflammatory mediators via activating NF-kappaB.

Pulmonary intravascular macrophages (PIMs) are often responsible for the clearance of blood-borne pathogens, including endotoxin, lipopolysaccharide of Gram-negative bacteria. It is well accepted that PIMs play a pivotal role in the pathogenesis of endotoxin-induced acute lung injury. However, the mechanisms by which PIMs are involved in the lipopolysaccharide-induced inflammatory responses remain unclear. Through the present study the following results were found: (1) When challenged with lipopolysaccharide (10 micrograms/ml), PIMs underwent marked cellular enlargement, intercellular adhesion plaques became longer, and some particulates were enwrapped in the pseudopods. (2) Lipopolysaccharide could up-regulate the expression of some inflammatory mediators in PIMs, including TNF-alpha, IL-1beta, IL-6, IL-8, and COX-2, and these up-regulated expression of inflammatory mediators correlated with NF-kappaB activation. (3) Dexamethasone as well as acetylsalicylic acid reduced the expression of TNF-alpha in lipopolysaccharide-challenged PIMs, and the decreased expression of TNF-alpha was also consistent with decreased NF-kappaB activation. Our results suggest that NF-kappaB activation in PIMs followed by phagocytizing lipopolysaccharide resulted in the up-regulation of TNF-alpha, IL-1beta, IL-6, IL-8, and COX-2, which could be alleviated by dexamethasone.