Expression of protein kinase C-delta (PKC delta) is up-regulated by apoptosis-inducing stimuli. However, very little is known about the signaling pathways that control PKC delta gene transcription. In the present study, we demonstrate that JNK stimulates PKC delta gene expression via c-Jun and ATF2 in response to the anticancer agent doxorubicin (DXR) in mouse lymphocytic leukemia L1210 cells. Luciferase reporter assays showed that DXR-induced activation of the PKC delta promoter was enhanced by ectopic expression of JNK1, c-Jun, or ATF2, whereas it was strongly reduced by expression of dominant negative JNK1 or by treatment with the JNK inhibitor SP600125. Furthermore, point mutations in the core sequence of the c-Jun/ATF2 binding site suppressed DXR-induced activation of the PKC delta promoter. Our results suggest an additional role for a JNK signaling cascade in DXR-induced PKC delta gene expression.
Activating Transcription Factor 2/*physiology ; Animals ; Anthracenes/pharmacology ; Antibiotics, Antineoplastic/*pharmacology ; Apoptosis ; Cell Line, Tumor ; Doxorubicin/*pharmacology ; Mice ; Mitogen-Activated Protein Kinase 8/*physiology ; Mutation ; Promoter Regions, Genetic ; Protein Kinase C-delta/genetics/*metabolism ; Proto-Oncogene Proteins c-jun/antagonists & inhibitors/*physiology ; Signal Transduction/physiology ; Transcription, Genetic

Formation of the periodontium begins following onset of tooth-root formation in a coordinated manner after birth. Dental follicle progenitor cells are thought to form the cementum, alveolar bone and Sharpey's fibers of the periodontal ligament (PDL). However, little is known about the regulatory morphogens that control differentiation and function of these progenitor cells, as well as the progenitor cells involved in crown and root formation. We investigated the role of bone morphogenetic protein-2 (Bmp2) in these processes by the conditional removal of the Bmp2 gene using the Sp7-Cre-EGFP mouse model. Sp7-Cre-EGFP first becomes active at E18 in the first molar, with robust Cre activity at postnatal day 0 (P0), followed by Cre activity in the second molar, which occurs after P0. There is robust Cre activity in the periodontium and third molars by 2 weeks of age. When the Bmp2 gene is removed from Sp7(+) (Osterix(+)) cells, major defects are noted in root, cellular cementum and periodontium formation. First, there are major cell autonomous defects in root-odontoblast terminal differentiation. Second, there are major alterations in formation of the PDLs and cellular cementum, correlated with decreased nuclear factor IC (Nfic), periostin and α-SMA(+) cells. Third, there is a failure to produce vascular endothelial growth factor A (VEGF-A) in the periodontium and the pulp leading to decreased formation of the microvascular and associated candidate stem cells in the Bmp2-cKO(Sp7-Cre-EGFP). Fourth, ameloblast function and enamel formation are indirectly altered in the Bmp2-cKO(Sp7-Cre-EGFP). These data demonstrate that the Bmp2 gene has complex roles in postnatal tooth development and periodontium formation.
Actins ; analysis ; Activating Transcription Factor 2 ; genetics ; Age Factors ; Ameloblasts ; pathology ; Amelogenesis ; genetics ; Animals ; Bone Morphogenetic Protein 2 ; genetics ; Cell Adhesion Molecules ; analysis ; Cell Differentiation ; genetics ; Cementogenesis ; genetics ; Dental Cementum ; pathology ; Dental Pulp ; blood supply ; Fluorescent Dyes ; Green Fluorescent Proteins ; Male ; Mice ; Mice, Knockout ; Microvessels ; pathology ; Molar ; growth & development ; Molar, Third ; growth & development ; NFI Transcription Factors ; analysis ; Odontoblasts ; pathology ; Odontogenesis ; genetics ; Periodontal Ligament ; growth & development ; Sp7 Transcription Factor ; Stem Cells ; physiology ; Tooth Root ; growth & development ; Transcription Factors ; genetics ; Vascular Endothelial Growth Factor A ; analysis ; Zinc Fingers ; genetics

OBJECTIVETo study the role of antenatal glucocorticoid (dexamethasone and betamethasone) on bone morphogenetic protein (BMP) signal transduction of the rat fetal lungs.

METHODSFifteen pregnant rats were randomly divided into five groups: the rats treated with dexamethasone for 1 day (1D-DEX) or 3 days (3D-DEX), with betamethasone for 1 day (1D-BEX) or 3 days (3D-BEX) or with normal saline (control group), followed cesarean section on the 19th day of gestation. The mRNA levels of BMP4, BMPR-II, Smad1 and ATF-2 of fetal rat lungs were ascertained by reverse transcriptase polymerase chain reaction (RT-PCR). The expression of BMP4, BMPR-II, Smad1 and ATF-2 antigen expression in fetal lungs was assessed by immune histochemical staining. The expression of BMP4 and BMPR-II was determined by Western blot.

RESULTSThe levels of BMP4, BMPR-II and Smad1 mRNA expression were up-regulated in the 1D-BEX, 3D-BEX and 3D-DEX groups compared with those in the control group (P<0.05). The immune histochemiscal analysis showed that the expression of BMP4, BMPR-II, Phospho-Smad1 (pSmad1) and ATF-2 in the 1D-BEX, 3D-BEX and 3D-DEX groups was significantly higher than that in the control group (P<0.01). The results of Western blot demonstrated that the expression of BMP4 and BMPR-II protein increased significantly in the 1D-BEX, 3D-BEX and 3D-DEX groups when compared with the control group (P<0.01).

CONCLUSIONSBetamethasone and dexamethasone may play important roles in the regulation of BMP signal transduction in the rat fetal lungs. Up-regulation of BMP4, BMPR-II and Smad1 might be one of crucial factors for the glucocorticoid-induced maturity of fetal lungs.

Activating Transcription Factor 2 ; analysis ; genetics ; Animals ; Betamethasone ; pharmacology ; Bone Morphogenetic Protein 4 ; analysis ; genetics ; physiology ; Bone Morphogenetic Protein Receptors, Type II ; analysis ; genetics ; Dexamethasone ; pharmacology ; Female ; Fetus ; drug effects ; metabolism ; Lung ; drug effects ; metabolism ; Pregnancy ; Rats ; Rats, Sprague-Dawley ; Reverse Transcriptase Polymerase Chain Reaction ; Signal Transduction ; drug effects ; Smad1 Protein ; analysis ; genetics