Role of proto-oncogenes in the regulation of proenkephalin mRNA expression induced by repeated nicotine injections in rat adrenal medulla.
We have studied the effect of repeated systemic administrations of nicotine (3 mg/kg) at 30 min intervals on proenkephalin (proENK) mRNA level in rat adrenal gland. Northern blot analysis has shown that proENK mRNA expression was enhanced by repeated nicotine administrations. Additionally, repeated administrations of nicotine transiently induced the c-fos and c-jun mRNA levels after the first-third nicotine administration, and the c-fos and c-jun mRNA levels were returned to the basal level after the seventh administration of nicotine. c-Fos, c-Jun and Fra-2 protein levels were persistently increased until the seventh administration. The repeated nicotine administrations also elevated phospho-CREB without altering total CREB level in all tested groups. Immunohistochemical analysis showed that the increase of c-Fos and c-Jun proteins by repeated nicotine administrations is mostly medulla specific, while Fra-2 immuno reactivity was shown both in medulla and cortex. The repeated nicotine administrations enhanced the AP-1 and ENKCRE-2 DNA binding activities. Furthermore, the cross-competition studies revealed that the AP-1 proteins, rather than CREB, actively bind to ENKCRE-2 DNA domain. These results suggest that proENK mRNA expression induced by repeated nicotine administrations may be mediated by AP-1 proteins, such as c-Fos, c-Jun and Fra-2 rather than CREB via interacting to the ENKCRE-2 DNA binding domain in rat adrenal medulla.
Kim
Yung-Hi
YH
Department of Pharmacology and Institute of Natural Medicine, College of Medicine, Hallym University, Chunchon, Kangwon-Do, South Korea.
Won
Je-Seong
JS
Won
Moo-Ho
MH
Lee
Jin-Koo
JK
Suh
Hong-Won
HW
D000313:Adrenal Medulla / Q000187:drug effects* / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000502:physiology; D024202:Electrophoretic Mobility Shift Assay; D004745:Enkephalins / Q000235:genetics*; D051921:Fos-Related Antigen-2; D005786:Gene Expression Regulation; D007124:Immunoenzyme Techniques; D007274:Injections, Intraperitoneal; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D011498:Protein Precursors / Q000235:genetics*; D016760:Proto-Oncogene Proteins c-fos / Q000502:physiology*; D016755:Proto-Oncogene Proteins c-jun / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020218:Response Elements / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000378:metabolism; D014157:Transcription Factors / Q000502:physiology
D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004745:Enkephalins; D051921:Fos-Related Antigen-2; C497874:Fosl2 protein, rat; D011498:Protein Precursors; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D012333:RNA, Messenger; D018808:Transcription Factor AP-1; D014157:Transcription Factors; C029992:proenkephalin; D009538:Nicotine