1,25‐Dihydroxyvitamin D₃ induction of the tissue‐type plasminogen activator gene is mediated through its multihormone‐responsive enhancer

Abstract

Tissue-type plasminogen activator (t-PA) is a positive modulator of the plasminogen-plasmin system, which is involved in bone remodeling. In the present study, 1,25-dihydroxyvitamin D 3 [1,25(OH) 2 D 3 ] was found to stimulate t-PA gene expression in ROS17/2.8 osteosarcoma cells. Transient transfection analysis and in vitro DNA binding studies identified two vitamin D-responsive elements (VDRE) in the human t-PA enhancer. The first VDRE (bp 3 37175 to 3 37146) comprised an inverted palindrome separated by 9 bp (IP9) overlapping a palindrome separated by 3 bp. The second VDRE (bp 3 37315 to 3 37302) is an IP2 element overlapping the previously identified retinoic acidresponsive element. 1,25(OH) 2 D 3 treatment of primary osteoblasts derived from t-PAlacZ transgenic mice containing 9 kb of 5P P sequence of the human t-PA gene increased the number of lacZ-positive cells, fitting with the probability model of enhancer function.z 1999 Federation of European Biochemical Societies.

Transcriptional and posttranscriptional regulation of the plasminogen activator system

“…TheVDRElocated at -7315 is an inverted palindrome overlapping the previously identified RARE. Moreover, vitamin D3 treatment of primaryosteoblasts derivedfrom t-PA -LacZ transgenic micecontaining 9kbofthe 5'sequence of the human tPAgene increased the number of lacZpositive cells, reinforcing the modelofenhancer function (87).…”

“…The multihormone responsive enhancer also contains ag lucocorticoid-responsive unit (GRU) withfour functional binding sites for the glucocorticoid receptor, located between -7,501 and -7,974 (80).Site-specific mutagenesis of the fourG REs eliminatedd examethasone-mediated induction of the tPAm ultihormone-responsive enhancer.T herefore, the human tPAgene is adirect target forglucocorticoids,albeit throughanunusuallycomplexGRU composedofmultiple binding sites for GR. In addition, 1,25-dihydroxyvitamin D3 was found to stimulate tPAexpression in osteosarcoma cells via two newlyi dentified vitamin D-responsive elements( VDRE) located at -7175a nd -7315 in the multihormone-responsive enhancer of the tPApromoter (87). TheVDRElocated at -7315 is an inverted palindrome overlapping the previously identified RARE.…”

“…In contrast, thetPA proximal promoter,which is primarilyregulated through acAMP-responsive element and twoSp1 binding sites, contains no hormone-responsive elements. Steroid hormoness uch as glucocorticoids and androgens,retinoidssuch as vitamin Aand retinoicacid, and 1,25-dihydroxyvitamin D3 have beenshown to increase tPAsynthesis in vivo and in vitro (49,(80)(81)(82)(83)(84)(85)(86)(87)(88). RetinoicacidinducestPA expression in microvascularendothelial, oralsquamous carcinoma and neuroblastoma cells (89,90).…”

Matrix metalloproteinases MMP‐2, ‐9 and tissue inhibitors TIMP‐1, ‐2 expression and secretion by primary human osteoblast cells in response to titanium, zirconia, and alumina ceramics

“…12,30 Osteoblasts produce collagenase in response to 1,25(OH) 2 vitamin D 3 or interleukin-1 stimulation. 25,26 This protease is also secreted by osteoclasts in sub-osteoclastic zones at sites of bone resorption. 18,29,30 Despite the numerous studies undertaken on osteoblast/biomaterial interactions, the regulation of their proteolytic activity and ECM remodeling remains to be understood.…”