Tuberc Respir Dis.  1998 Dec;45(6):1236-1251.

Lung Injury Indices Depending on Tumor Necrosis Factor-alpha Level and Novel 35 kDa Protein Synthesis in Lipopolysaccharide-Treated Rat

Affiliations
  • 1Department of Internal Medicine, Division of Pulmonology, College of Medicine, the Catholic University of Korea, Seoul, Korea.

Abstract

BACKGROUND: TNF-alpha appears to be a central mediator of the host response to sepsis. While TNF-alpha is mainly considered a proinflammatory cytokine, it can also act as a direct cytotoxic cytokine. However, there are not so many studies about the relationship between TNF-alpha level and lung injury severity in ALI, particularly regarding the case of ALI caused by direct lung injury such as diffuse pulmonary infection. Recently, a natural defense mechanism, known as the stress response or the heat shock response, has been reported in cellular or tissue injury reaction. There are a number of reports examining the protective role of pre-induced heat stress proteins on subsequent LPS-induced TNF-alpha release from monocyte or macrophage and also on subsequent LPS-induced ALI in animals. However it is not well established whether the stress protein synthesis such as HSP can be induced from rat alveolar macrophages by in vitro or in vivo LPS stimulation.
METHODS
We measured the level of TNF-alpha, the percentage of inflammatory cells in bronchoalveolar lavage fluid, protein synthesis in alveolar macrophages isolated from rats at 1, 2, 3, 4, 6, 12, and 24 hours after intratracheal LPS instillation. We performed histologic examination and also obtained histologic lung injury index score in lungs from other rats at 1, 2, 3, 4, 6, 12, 24 h after intratracheal LPS instillation. Isolated non-stimulated macrophages were incubated for 2 h with different concentration of LPS (0, 1, 10, 100 ng/ml, 1, or 10 microgram/ml). Other non-stimulated macrophages were exposed at 43dgrees C for 15 min, then returned to at 37dgrees C in 5% CO2-95% for 1 hour, and then incubated for 2 h with LPS (0, 1, 10, 100ng/ml, 1, or 10 microgram/ml).
RESULTS
TNF-alpha levels began to increase significantly at 1 h, reached a peak at 3 h (P<0.0001), began to decrease at 6 h, and returned to control level at 12 h after LPS instillation. The percentage of inflammatory cells (neutrophils and alveolar macrophages) began to change significantly at 2 h, reached a peak at 6 h, began to recover but still showed significant change at 12 h, and showed insignificant change at 24 h after LPS instillation compared with the normal control. After LPS instillation, the score of histologic lung injury index reached a maximum value at 6 h and remained steady for 24 hours. 35 kDa protein band was newly synthesized in alveolar macrophage from 1 hour on for 24 hours after LPS instillation. Inducible heat stress protein 72 was not found in any alveolar macrophages obtained from rats after LPS instillation. TNF-alpha levels in supernatants of LPS-stimulated macrophages were significantly higher than those of non-stimulated macrophages(p0.05). Following LPS stimulation, TNF-alpha levels in supernatants were significantly lower after heat treatment than in those without heat treatment(p0.05). The inducible heat stress protein 72 was not found at any concentrations of LPS stimulation. Whereas the 35 kDa protein band was exclusively found at dose of LPS of 10 microgram/ml.
CONCLUSION
TNF-alpha has a direct or indirect close relationship with lung injury severity in acute lung injury or acute respiratory distress syndrome. In vivo and in vitro LPS stimulation dose not induce heat stress protein 72 in alveolar macrophages. It is likely that 35 kDa protein, synthesized by alveolar macrophage after LPS instillation, does not have a defense role in acute lung injury.

Keyword

Tumor Necrosis Factor-alpha

MeSH Terms

Acute Lung Injury
Animals
Bronchoalveolar Lavage Fluid
Heat-Shock Proteins
Heat-Shock Response
Hot Temperature
Lung Injury*
Lung*
Macrophages
Macrophages, Alveolar
Monocytes
Rats*
Respiratory Distress Syndrome, Adult
Sepsis
Tumor Necrosis Factor-alpha*
Heat-Shock Proteins
Tumor Necrosis Factor-alpha
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