Biomedical subjects

John A Schoenhard

Publications and source records attributed to John A Schoenhard.

5 recordsLinked to original sources

PubMed2004

Tumor necrosis factor alpha activates the human plasminogen activator inhibitor-1 gene through a distal nuclear factor kappaB site.

Plasminogen activator inhibitor-1 (PAI-1) is the major inhibitor of plasminogen activation and likely plays important roles in coronary thrombosis and arteriosclerosis. Tumor necrosis factor-alpha (TNFalpha) is one of many recognized physiological regulators of PAI-1 expression and may contribute to elevated plasma PAI-1 levels in sepsis and obesity. Although TNFalpha is a potent inducer of PAI-1 expression in vitro and in vivo, the precise location of the TNFalpha response site in the PAI-1 promoter has yet to be determined. Transient transfection studies using luciferase reporter constructs containing PAI-1 promoter sequence up to 6.4 kb failed to detect a response to TNFalpha. Moreover, TNFalpha failed to induce expression of enhanced green fluorescent protein under the control of a 2.9-kb human PAI-1 promoter in transgenic mice, although endogenous murine PAI-1 was strongly induced. These data suggested that the TNFalpha response element in the PAI-1 gene is remote from the proximal promoter region. In this study, seven candidate regulatory regions were identified using cross-species sequence homology analysis as well as DNase I-hypersensitive site analysis. We identified a 5' distal TNFalpha-responsive enhancer of the PAI-1 gene located 15 kb upstream of the transcription start site containing a conserved NFkappaB-binding site that mediates the response to TNFalpha. This newly recognized site is fully capable of binding NFkappaB subunits p50 and p65, whereas overexpression of the NFkappaB inhibitor IkappaB prevents TNFalpha-induced activation of this enhancer element.

Animals↗

PubMed2003

Regulation of the PAI-1 promoter by circadian clock components: differential activation by BMAL1 and BMAL2.

Circadian variation in plasminogen activator inhibitor-1 (PAI-1) production likely contributes to increased risk of myocardial infarction and decreased efficacy of thrombolytic therapy during the morning. In this study, we characterize the abilities of fundamental molecular components of intrinsic circadian clocks to regulate the human PAI-1 promoter in transfected endothelial cells. Both CLOCK:BMAL1 and CLOCK:BMAL2 heterodimers activate the PAI-1 promoter through requisite proximal (-565 to -560 bp) and distal (-680 to -675 bp) E-box enhancers. Although the distal E-box overlaps the 4G/5G polymorphism of the PAI-1 promoter, allelic variation at this site does not influence CLOCK:BMAL1-and CLOCK:BMAL2-mediated transactivation. Together, CLOCK:BMAL1 and CLOCK:BMAL2 make additive contributions to PAI-1 gene transcription. While the abilities of these heterodimers to activate gene expression differ by twofold, the susceptibilities of these circadian activators to inhibition by period and cryptochrome proteins are equivalent and redox independent. Given that BMAL1 and BMAL2 differ in their spatiotemporal distributions, such distinctions may allow intrinsic circadian clocks to modulate the amplitudes of their oscillators, while maintaining circadian periodicity. In this way, fundamental circadian clock components may drive circadian variation in PAI-1, which in turn influences the pathogenesis, timing, and treatment of acute atherothrombotic events.

ARNTL Transcription Factors↗

PubMed2002

Comparative effects of estrogen and angiotensin-converting enzyme inhibition on plasminogen activator inhibitor-1 in healthy postmenopausal women.

BACKGROUND: This study compares the effect of estrogens and ACE inhibition on plasminogen activator inhibitor-1 (PAI-1) concentrations in healthy postmenopausal women, genotyped for a 4G/5G polymorphism in the PAI-1 promoter, a polymorphism shown to influence PAI-1 concentrations. Methods and Results- Morning estradiol, PAI-1, tissue plasminogen activator, plasma renin activity, angiotensin II, and aldosterone were measured in 19 postmenopausal women (5G/5G:4G/5G:4G4G=5:10:4, respectively) at baseline and during randomized, single-blind, crossover treatment with conjugated equine estrogens 0.625 mg per os per day, ramipril 10 mg per os per day, and combination estrogens and ramipril. Estradiol (P<0.005) and angiotensin II (P<0.01) were significantly higher during estrogens. Plasma renin activity was significantly increased during ACE inhibition (P<0.05). Both conjugated estrogens [PAI-1 antigen from 12.5 (7.6, 17.4) [mean (95% CI)] baseline to 6.6 (2.6, 10.7) ng/mL, P<0.01] and ACE inhibition [8.3 (4.9, 11.7) ng/mL, P<0.005] decreased PAI-1 without decreasing tissue plasminogen activator. The effect of combined therapy on PAI-1 [5.6 (2.3, 8.8) ng/mL] was significantly greater than that of ramipril alone (P<0.05). There was a significant effect of PAI-1 4G/5G genotype on baseline PAI-1 concentrations (P=0.001) and a significant interactive effect of 4G/5G genotype and treatment, such that genotype influenced the change in PAI-1 during ramipril (P=0.011) or combined therapy (P=0.006) but not during estrogens (P=0.715). CONCLUSIONS: ACE inhibition with ramipril and conjugated estrogens similarly decrease PAI-1 antigen concentrations in postmenopausal women. Larger studies that use clinical outcomes are needed to determine whether PAI-1 4G/5G genotype should influence the choice of conjugated estrogens or ACE inhibition for the treatment of healthy postmenopausal women.

Aldosterone↗

PubMed2002

Potential roles of plasminogen activator system in coronary vascular remodeling induced by long-term nitric oxide synthase inhibition.

Recent studies have indicated that a number of factors contribute to the pathophysiology in response to nitric oxide synthase (NOS) inhibition. We previously demonstrated that plasminogen activator inhibitor-1 deficient (PAI-1-/-) mice are protected against hypertension and perivascular fibrosis induced by relatively short-term NOS inhibition. In this study, we compared the temporal changes in systolic blood pressure and coronary perivascular fibrosis induced by long-term treatment with N(omega)-nitro- L -arginine methyl ester (L -NAME) in wild type (WT), PAI-1(-/-) and tissue-type plasminogen activator deficient (t-PA-/-) mice. After initiating L -NAME, systolic blood pressure increased in all groups at 2 weeks. Over a 16 week study period, systolic blood pressure increased to 143+/-3 mmHg (mean+/-SEM) in WT animals, 139+/-2 in t-PA-/- mice vs 129+/-2 in PAI-1-/- mice (P < 0.01). Coronary perivascular fibrosis increased in L -NAME-treated WT and t-PA(-/-) mice compared to each control group (P<0.01 in WT, P<0.05 in t-PA-/-), while PAI-1-/- mice were protected against fibrosis induced by L -NAME. t-PA deficiency did not accentuate the vascular pathology or the changes in blood pressure. In situ zymography demonstrated augmented gelatinolytic activity in PAI-1-/- mice at baseline, suggesting that PAI-1 deficiency prevents the increase of collagen deposition by promoting matrix degradation. Plasma TGF-beta1 levels increased in L -NAME-treated WT and PAI-1-/- mice (P < 0.01), but not in L -NAME-treated t-PA-/- mice. These findings support the hypothesis that the plasminogen activator system protects against the structural vascular changes induced by long-term NOS inhibition. While PAI-1 deficiency protects against L -NAME-induced hypertension and perivascular fibrosis, t-PA deficiency does not exacerbate the vascular pathology or hypertension.

Animals↗

PubMed2002

Alternative splicing yields novel BMAL2 variants: tissue distribution and functional characterization.

The BMAL2 gene encodes a member of the basic helix-loop-helix PER-ARNT-SIM family of transcription factors, which control diverse physiological processes including circadian rhythms. We identified four novel human BMAL2 transcripts that differ by alternative splicing within their NH2-terminal regions. Divergent expression of these and previously reported transcripts was observed among human tissues. The functional consequences of alternative splicing for transcriptional activation by CLOCK:BMAL2 heterodimers were assessed using luciferase reporter gene constructs that contained one of three diurnally regulated promoters, namely, those of the mouse period1, mouse vasopressin, and human plasminogen activator inhibitor-1 genes. These studies revealed that alternative splicing generates BMAL2 isoforms possessing high, medium, low, or no transcriptional activity. Similar results were obtained with each promoter, suggesting that alternative splicing may influence the amplitudes of both central and peripheral oscillators. Indeed, alternative splicing of BMAL2 may provide tissues with a rheostat capable of regulating CLOCK:BMAL2 heterodimer function across a broad continuum of potential transcriptional activities to accommodate varied metabolic demands and physiological roles.

ARNTL Transcription Factors↗