[Studies on effects of cytokine released from alveolar macrophage induced by mineral dust on lung fibroblast].

OBJECTIVE

To understand the role of cytokine released from alveolar macrophage (AM) in lung fibrosis caused by mineral dust.

METHODS

Rabbit's AM obtained by lavage was cultured with mineral dust in vitro. Activities of tumor necrosis factor (TNF) and interleukin 6 (IL-6) in its supernatant were determined with isotope labelling method and MTT colorimetry, respectively. Human fetal lung fibroblast WI-138 was cultured with this supernatant. Proliferation of fibroblast and synthesis of collagen were examined by 3H-thymidine (3H-TdR) and 14C-proline (14C-Pro) incorporation and its total hydroxyproline (HOP) level was analyzed by chloramine-T method.

RESULTS

Proliferation of lung fibroblast and synthesis of collagen could be enhanced by the supernatant containing AM induced by quartz, asbestos and uranium mineral dust, with 3H-TdR incorporated counts per minute (cpm) of 6,584, 3,848 and 6,893 in the group of 100 micrograms 3H-TdR and 14C-Pro incorporated 27,952, 13,416 and 18,538 in the group of 200 micrograms respectively, which were significantly higher than those in the control group. Total HOP levels in the culture media for lung fibroblast enhanced by AM supernatant were 22.41, 24.00 and 21.39 micrograms/ml, respectively, and was significantly higher than that in the control group (12.91 micrograms/ml). Release of TNF and IL-6 could be stimulated by mineral dust, such as quartz, asbestos and uranium mineral dust, and their activities were significantly higher than those in the control group, with those of 1,396, 1,198 and 852 U/ml in TNF group and 1,336, 1511 and 1,335 U/ml in IL-6 group, respectively. Proliferation of lung fibroblast and synthesis of collagen could be inhibited by antibody against TNF and interferon-r (gamma), and the effect of the latter was weaker than that of the former on inhibition of fibroblast proliferation and the effect on collagen synthesis was just in the opposite direction.

CONCLUSION

Lung fibrosis caused by mineral dust correlated with abnormal expression of TNF and IL-6. Antibody against TNF and gamma interferon could antagonize the effect of NTF and IL-6.