Dynamic binding of Ku80, Ku70 and NF90 to the IL-2 promoter in vivo in activated T-cells.

IL-2 gene expression in activated T-cells is initiated by chromatin remodeling at the IL-2 proximal promoter and conversion of a transcriptional repressor into a potent transcriptional activator. A purine-box regulator complex was purified from activated Jurkat T-cell nuclei based on sequence-specific DNA binding to the antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target DNA sequence in the proximal IL-2 promoter. ARRE DNA-binding subunits were identified as NF90, NF45 and systemic lupus erythematosis autoantigens, Ku80 and Ku70. Monoclonal antibodies to Ku80, Ku70 and NF90 specifically inhibit constitutive and inducible ARRE DNA-binding activity in Jurkat T-cells. Ku80, Ku70 and NF90 bind specifically to the IL-2 gene promoter in vivo, as demonstrated by chromatin immunoprecipitation. Activation of Jurkat T-cells and mouse primary spleen cells induces binding of Ku80 and NF90 to the IL-2 promoter in vivo, and decreases binding of Ku70 to the IL-2 promoter in vivo, and these dynamic changes are inhibited by immunosuppressants cyclosporin A and triptolide. Dynamic changes in binding of Ku80, Ku70 and NF90 to the IL-2 proximal promoter in vivo correlate with chromatin remodeling and transcriptional initiation in activated T-cells.

Simvastatin rescues rats from fatal pulmonary hypertension by inducing apoptosis of neointimal smooth muscle cells.

BACKGROUND: Pulmonary vascular injury by toxins can induce neointimal formation, pulmonary arterial hypertension (PAH), right ventricular failure, and death. We showed previously that simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in pneumonectomized rats injected with the alkaloid toxin monocrotaline. The present study was undertaken to investigate the efficacy of simvastatin and its mechanism of reversing established neointimal vascular occlusion and pulmonary hypertension. METHODS AND RESULTS: Pneumonectomized rats injected with monocrotaline at 4 weeks demonstrated severe PAH at 11 weeks (mean pulmonary artery pressure [mPAP]=42 versus 17 mm Hg in normal rats) and death by 15 weeks. When rats with severe PAH received simvastatin (2 mg x kg(-1) x d(-1) by gavage) from week 11, there was 100% survival and reversal of PAH after 2 weeks (mPAP=36 mm Hg) and 6 weeks (mPAP=24 mm Hg) of therapy. Simvastatin treatment reduced right ventricular hypertrophy and reduced proliferation and increased apoptosis of pathological smooth muscle cells in the neointima and medial walls of pulmonary arteries. Longitudinal transcriptional profiling revealed that simvastatin downregulated the inflammatory genes fos, jun, and tumor necrosis factor-alpha and upregulated the cell cycle inhibitor p27Kip1, endothelial nitric oxide synthase, and bone morphogenetic protein receptor type 1a. CONCLUSIONS: Simvastatin reverses pulmonary arterial neointimal formation and PAH after toxic injury.

Longitudinal transcriptional analysis of developing neointimal vascular occlusion and pulmonary hypertension in rats.

Pneumonectomized rats injected with the alkaloid toxin, monocrotaline, develop progressive neointimal pulmonary vascular obliteration and pulmonary hypertension resulting in right ventricular failure and death. The antiproliferative immunosuppressant, triptolide, attenuates neointimal formation and pulmonary hypertension in this disease model (Faul JL, Nishimura T, Berry GJ, Benson GV, Pearl RG, and Kao PN. Am J Respir Crit Care Med 162: 2252-2258, 2000). Pneumonectomized rats, injected with monocrotaline on day 7, were killed at days 14, 21, 28, and 35 for measurements of physiology and gene expression patterns. These data were compared with pneumonectomized, monocrotaline-injected animals that received triptolide from day 5 to day 35. The hypothesis was tested that a group of functionally related genes would be significantly coexpressed during the development of disease and downregulated in response to treatment. Transcriptional analysis using total lung RNA was performed on replicate animals for each experimental time point with exploratory data analysis followed by statistical significance analysis. Marked, statistically significant increases in proteases (particularly derived from mast cells) were noted that parallel the development of vascular obliteration and pulmonary hypertension. Mast-cell-derived proteases may play a role in regulating the development of neointimal pulmonary vascular occlusion and pulmonary hypertension in response to injury.

Immunosuppressive and anti-inflammatory mechanisms of triptolide, the principal active diterpenoid from the Chinese medicinal herb Tripterygium wilfordii Hook. f.

Extracts of Tripterygium wilfordii hook. f. (leigong teng, Thundergod vine) are effective in traditional Chinese medicine for treatment of immune inflammatory diseases including rheumatoid arthritis, systemic lupus erythematosus, nephritis and asthma. Characterisation of the terpenoids present in extracts of Tripterygium identified triptolide, a diterpenoid triepoxide, as responsible for most of the immunosuppressive, anti-inflammatory and antiproliferative effects observed in vitro. Triptolide inhibits lymphocyte activation and T-cell expression of interleukin-2 at the level of transcription. In all cell types examined, triptolide inhibits nuclear factor-kappaB transcriptional activation at a unique step in the nucleus after binding to DNA. Further characterisation of the molecular mechanisms of triptolide action will serve to elucidate pathways of immune system regulation.

Simvastatin enhances bone morphogenetic protein receptor type II expression.

Statins confer therapeutic benefits in systemic and pulmonary vascular diseases. Bone morphogenetic protein (BMP) receptors serve essential signaling functions in cardiovascular development and skeletal morphogenesis. Mutations in BMP receptor type II (BMPR2) are associated with human familial and idiopathic pulmonary arterial hypertension, and pathologic neointimal proliferation of vascular endothelial and smooth muscle cells within small pulmonary arteries. In severe experimental pulmonary hypertension, simvastatin reversed disease and conferred a 100% survival advantage. Here, modulation of BMPR2 gene expression by simvastatin is characterized in human embryonic kidney (HEK) 293T, pulmonary artery smooth muscle, and lung microvascular endothelial cells (HLMVECs). A 1.4kb BMPR2 promoter containing Egr-1 binding sites confers reporter gene activation in 293T cells which is partially inhibited by simvastatin. Simvastatin enhances steady-state BMPR2 mRNA and protein expression in HLMVEC, through posttranscriptional mRNA stabilization. Simvastatin induction of BMPR2 expression may improve BMP-BMPR2 signaling thereby enhancing endothelial differentiation and function.

NF45/ILF2 tissue expression, promoter analysis, and interleukin-2 transactivating function.

NF45/ILF2 associates with NF90/ILF3 in the nucleus and regulates IL-2 gene transcription at the antigen receptor response element (ARRE)/NF-AT DNA target sequence (P.N. Kao, L. Chen, G. Brock, J. Ng, A.J. Smith, B. Corthesy, J. Biol. Chem. 269 (1994) 20691-20699). NF45 is widely expressed in normal tissues, especially testis, brain, and kidney, with a predominantly nuclear distribution. NF45 mRNA expression is increased in lymphoma and leukemia cell lines. The human and murine NF45 proteins differ only by substitution of valine by isoleucine at amino acid 142. Fluorescence in situ hybridization localized the human NF45 gene to chromosome 1q21.3, and mouse NF45 gene to chromosome 3F1. Promoter analysis of 2.5 kB of the murine NF45 gene reveals that significant activation is conferred by factors, possible including NF-Y, that bind to the CCAAT-box sequence. The function of human NF45 in regulating IL-2 gene expression was characterized in Jurkat T-cells stably transfected with plasmids directing expression of NF45 cDNA in sense or antisense orientations. NF45 sense expression increased IL-2 luciferase reporter gene activity 120-fold, and IL-2 protein expression 2-fold compared to control cells. NF45 is a highly conserved, regulated transcriptional activator, and one target gene is IL-2.

NF90 regulates cell cycle exit and terminal myogenic differentiation by direct binding to the 3'-untranslated region of MyoD and p21WAF1/CIP1 mRNAs.

NF90 and splice variant NF110/ILF3/NFAR are double-stranded RNA-binding proteins that regulate gene expression. Mice with targeted disruption of NF90 were engineered. NF90(-/-) mice were born small and weak and succumbed to perinatal death within 12 h because of neuromuscular respiratory failure. Lung inflation and morphology were normal in NF90(-/-) mice. The diaphragm and other skeletal muscles in NF90(-/-) mice demonstrated disorganized arrangement and paucity of myofibers, evidence of myocyte degeneration and increased apoptosis. The expression of myogenic regulators, MyoD, myogenin, and p21WAF1/CIP1, was severely decreased in NF90(-/-) mice. These myogenic transcription factors and cell cycle inhibitors are regulated in part through post-transcriptional mRNA stabilization. Northwestern blotting revealed that NF90 is the principal and specific p21WAF1/CIP1 and MyoD 3'-untranslated region RNA-binding protein in developing skeletal muscles. NF90 regulates transcription factors and a cell cycle inhibitor essential for skeletal muscle differentiation and for survival.

Simvastatin attenuates smooth muscle neointimal proliferation and pulmonary hypertension in rats.

Hypertensive pulmonary vascular disease is characterized by abnormal proliferation of vascular endothelial and smooth muscle cells, leading to occlusion of pulmonary arterioles, pulmonary hypertension, right ventricular failure, and death. Compounds with antiproliferative effects on vascular endothelial and smooth muscle cells, such as 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors, may prevent the development of experimental hypertensive pulmonary vascular disease. Pneumonectomized rats injected with monocrotaline at 7 days develop severe hypertensive pulmonary vascular disease with neointimal formation. Rats were randomized to receive either vehicle or treatment with the HMG-CoA reductase inhibitor simvastatin (2 mg/kg per day). By Day 35, rats that received vehicle had higher mean pulmonary arterial pressures (53 +/- 2 mm Hg) and right ventricular hypertrophy (right ventricle/[left ventricle plus septum] [RV/LV+S] = 0.78 +/- 0.09) than rats in Group PMS5-35 that received simvastatin from Day 5 to 35 (mean pulmonary arterial pressure = 27 +/- 3 mm Hg, RV/LV+S = 0.34 +/- 0.08; p < or = 0.001). Pulmonary vascular remodeling with neointimal formation consisting of vascular smooth muscle cells was more severe in vehicle-treated rats (vascular occlusion score, 1.98 +/- 0.02) than in Group PMS5-35 (vascular occlusion score, 0.59 +/- 0.46; p < 0.001). In addition, lung endothelial nitric oxide synthase gene expression was decreased in vehicle-treated animals but was restored toward normal levels in simvastatin-treated animals. Simvastatin attenuates monocrotaline-induced pulmonary vascular remodeling with neointimal formation, pulmonary arterial hypertension, and right ventricular hypertrophy in rats.