[Expression and role of nuclear transcription factor Sp1 in macrophages stimulated by silicon dioxide].
OBJECTIVE
To study the expression and localization of nuclear transcription factor Sp1 in macrophages after stimulated by silicon dioxide in vivo and in vitro.


METHODS
Forty Sprague Dawley rats were randomly divided into the control group and the silica exposure group, 20 in each group. The rat silicosis models were established by direct tracheal instillation of silica into rat lung (0.2 g/kg) only once while the control group was instilled with equal amount of saline. Animals were killed at 1st, 7th, 14th, 21st and 28th day after instillation. Dynamic changes of Sp1 protein expression and its cellular localization were detected by immunohistochemistry in pulmonary macrophages. In vitro, Sp1 mRNA and protein expression and their dynamic changes were monitored by RT-PCR and western blotting after stimulated by silicon dioxide in cultured RAW264.7 macrophages respectively. Cellular localization of Sp1 protein was characterized by immunocytochemistry.


RESULTS
Compared to the control group, the Sp1 protein expression was increased in pulmonary macrophages and reached the peak at the 14th day in the silica exposure group. In vitro, the Sp1 mRNA level began to rise at 30 minutes after the administration of silicon dioxide and reached the peak at 240 minutes and then decreased to the minimal level at 960 minutes. The Sp1 total protein and nuclear protein also exhibited the similar trend. The former reached the peak at 240 minutes and the latter at 480 minutes. The significant nuclear translocation of Sp1 protein was observed at 120 minutes after the administration of silicon dioxide and became most significant at 480 minutes.


CONCLUSIONS
Silicon dioxide can activate nuclear transcription factor Sp1 in macrophages in vivo and in vitro. Sp1 might play an important pathogenic role in the development of silicosis.
Wang
Jin-sheng
JS
Department of Pathology, Xiangya School of Medicine, Centre South University, Changsha 410078, China.
Zeng
Qing-fu
QF
Feng
De-yun
DY
Hu
Yong-bin
YB
Wen
Ji-fang
JF
D000818:Animals; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000187:drug effects; D007150:Immunohistochemistry; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000378:metabolism*; D017737:Macrophages, Peritoneal / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012822:Silicon Dioxide / Q000494:pharmacology*; D016329:Sp1 Transcription Factor / Q000096:biosynthesis* / Q000235:genetics
D012333:RNA, Messenger; D016329:Sp1 Transcription Factor; D012822:Silicon Dioxide