Coordinated expression of tissue-type plasminogen activator and plasminogen activator inhibitor type 1 during corpus luteum formation and luteolysis in the adult pseudopregnant rat

Proteolytic activity generated by the plasminogen activator (PA) system is associated with many biological processes. Using an adult pseudopregnant rat model, we have studied how two components of the PA system, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type 1 (PAI-1), are expressed temporally and spatially during different developmental stages of the corpus luteum (CL). Northern blot analysis, in situ hybridization, in situ zymography, and fibrin overlay were used to analyze the expression and distribution of tPA and PAI-1 messenger RNA (mRNA) as well as PA activity in CL of different ages. We demonstrated that during the luteinization period (approximately days 1-2), tPA mRNA was highly and evenly expressed in newly formed CL, whereas PAI-1 mRNA was mainly detected in the central part of the same CL. In accordance with these findings, proteolytic activity generated by tPA was detected in the outer region of newly formed CL by in situ zymography. During the luteotropic period (approximately days 3-10), tPA mRNA expression was very low. PAI-1 mRNA expression was also low, but increased on day 10. As expected, proteolytic activity was very low during this period. During functional luteolysis (days 13-14) and subsequent structural luteolysis, tPA mRNA was elevated. PAI-1 mRNA was also expressed during this period. Moreover, the net PA activity, as determined by fibrin overlay, was relatively high during this period. Our studies indicate that tPA and PAI-1 are coordinately expressed in the CL, resulting in increased proteolytic activities during the luteinization and luteolytic periods. PA-mediated proteolysis may, therefore, play a role in both CL formation and luteolysis in rats.     

Plasminogen activator activity during decidualization of human endometrial stromal cells is regulated by plasminogen activator inhibitor 1

Progesterone acts on the estradiol (E2)-conditioned human endometrium to induce decidualization of stromal cells. Consistent with these differential hormone actions in vivo, progestins regulate several end points of decidualization in human endometrial stromal cell monolayers, and E2 augments the effects of progestin. This study shows that in vitro decidualization of the stromal cells is accompanied by diminished plasminogen activator (PA) expression. Polyacrylamide gel electrophoretic separation after immunoprecipitation of biosynthetically labeled PAs revealed that medroxyprogesterone acetate (MPA) lowered levels of secreted tissue type PA (tPA) at 67 kilodaltons and urokinase type PA (uPA) at 55 kilodaltons. These levels were reduced further by E2 plus MPA despite a lack of response to E2 alone. Although tPA activity was readily measured by a chromogenic assay, detection of uPA activity required prior activation, indicating that uPA is released as the pro-uPA zymogen. Comparisons of levels of immunogenic PAs, as measured by specific enzyme-linked immunosorbent assays, with the corresponding catalytic activities revealed selective progestational inhibition of PA activity vs. antigen after 3 days of experimental incubation. Thus, 10(-7) mol/L MPA produced about a 2-fold greater reduction of levels of PA activity than that of its corresponding antigen. More strikingly, 10(-8) mol/L E2 plus 10(-7) mol/L MPA virtually eliminated both tPA activity (99% inhibition; P < 0.005) and uPA activity (93% inhibition; P < 0.005); the reductions in levels of the corresponding antigens were only about 50% of the control levels and did not attain statistical significance. Only after 3-6 days of incubation with E2 plus MPA was statistically significant inhibition achieved for immunogenic levels of both tPA (P < 0.05) and uPA (P < 0.005). Preferential inhibition of levels of PA activities compared with those of the corresponding PA antigens reflects the action of the potent PA inhibitor PAI-1. Thus, the concentration of PAI-1 in the stromal cell-conditioned medium at the end of 0-3 days exceeded those of tPA and uPA, respectively, by 28- and 12-fold in response to MPA and by 52- and 25-fold in response to E2 plus MPA. Extrapolation of these in vitro results to the events of the luteal phase, whose steroidal milieu is mimicked by E2 plus MPA, indicates that decidual cell-derived PAI-1 is a key regulator of proteolytic degradation of extracellular matrix and fibrinolysis during implantation and menstruation.     

Plasminogen activation in synovial tissues: differences between normal, osteoarthritis, and rheumatoid arthritis joints

OBJECTIVE: To analyse the functional activity of the plasminogen activators urokinase (uPA) and tissue type plasminogen activator (tPA) in human synovial membrane, and to compare the pattern of expression between normal, osteoarthritic, and rheumatoid synovium. The molecular mechanisms underlying differences in PA activities between normal and pathological synovial tissues have been further examined. METHODS: Synovial membranes from seven normal (N) subjects, 14 osteoarthritis (OA), and 10 rheumatoid arthritis (RA) patients were analysed for plasminogen activator activity by conventional zymography and in situ zymography on tissue sections. The tissue distribution of uPA, tPA, uPA receptor (uPAR), and plasminogen activator inhibitor type-1 (PAI-1) was studied by immunohistochemistry. uPA, tPA, uPAR, and PAI-1 mRNA values and mRNA distribution were assessed by northern blot and in situ hybridisations respectively. RESULTS: All normal and most OA synovial tissues expressed predominantly tPA catalysed proteolytic activity mainly associated to the synovial vasculature. In some OA, tPA activity was expressed together with variable amounts of uPA mediated activity. By contrast, most RA synovial tissues exhibited considerably increased uPA activity over the proliferative lining areas, while tPA activity was reduced when compared with N and OA synovial tissues. This increase in uPA activity was associated with increased levels of uPA antigen and its corresponding mRNA, which were localised over the synovial proliferative lining areas. In addition, in RA tissues, expression of the specific uPA receptor (uPAR) and of the plasminogen activator inhibitor-type 1     

High plasminogen activator inhibitor and tissue plasminogen activator levels in plasma precede a first acute myocardial infarction in both men and women: evidence for the fibrinolytic system as an independent primary risk factor

BACKGROUND: In patients with established ischemic heart disease, prospective cohort studies have indicated that plasminogen activator inhibitor (PAI-1), the inhibitor of the fibrinolytic system, may predict cardiovascular events. So far, there have been no primary prospective studies of PAI-1. METHODS AND RESULTS: The aim of the present study was to test whether plasma levels of PAI-1, tissue-type plasminogen activator (tPA), von Willebrand factor (vWF), and thrombomodulin (TM) could predict the occurrence of a first acute myocardial infarction (AMI) in a population with high prevalence of coronary heart disease by use of a prospective nested case-control design. Mass concentrations of PAI-1 and tPA were significantly higher for the 78 subjects who developed a first AMI compared with the 156 references matched for age, sex, and sampling time; for tPA, this increase was independent of smoking habits, body mass index, hypertension, diabetes, cholesterol, and apolipoprotein A-I. The ratio of quartile 4 to 1 for tPA was 5.9 for a patient to develop a first AMI. The association between tPA and AMI was seen in both men and women. Increased levels of vWF were associated with AMI in a univariate analysis. High levels of TM were associated with AMI in women but not in men. CONCLUSIONS: The plasma levels of PAI-1, tPA, and vWF are associated with subsequent development of a first AMI; for PAI-1 and tPA, this relation was found in both men and women. For tPA but not for PAI-1 and vWF, this association is independent of established risk factors.     

Regulation of tissue-type plasminogen activator (tPA) and type-1 plasminogen activator inhibitor (PAI-1) gene expression in rat hepatocytes in primary culture

We have performed a comparative study on tPA and PAI-1 mRNA expression in primary cultures of rat hepatocytes and elucidated the possible regulation of these factors by certain hormonal stimulation. The tPA mRNA increased 2- to 4-fold in the presence of cholera toxin (CT), dibutyryl cyclic AMP (dbcAMP), or 3-isobutyl-1-methyl xanthine (IBMX), but slightly decreased in the presence of dexamethasone. The tPA activity was also changed by these agents in a similar fashion. On the contrary, PAI-1 mRNA decreased with CT, dbcAMP, or IBMX, but increased transiently with dexamethasone. From results obtained with cycloheximide, ongoing protein synthesis was judged to be required for both PAI-1 induction with dexamethasone and PAI-1 suppression with IBMX, but not for the tPA induction with IBMX. Dexamethasone exerted opposite regulatory effects on the tPA mRNA expression depending on its concentration: at 10(-8) to 10(-6) M, it suppressed the expression; whereas at 10(-10) M, it elevated the expression.     

Abnormal expression of type 1 plasminogen activator inhibitor and tissue factor in severe preeclampsia

Preeclampsia is a multisystemic obstetric disease of unknown etiology that is commonly associated with fibrin deposition, occlusive lesions in placental vasculature, and intrauterine fetal growth retardation. We previously reported that type 1 plasminogen activator inhibitor (PAI-1) levels are significantly increased in plasma and placenta from pregnant women with preeclampsia compared to normal pregnant women. In the present report we localize the expression of placental PAI-1 in greater detail and compare it with that of tissue factor (TF), a procoagulant molecule, and vitronectin (Vn), a PAI-1 cofactor. We also examine the expression of two cytokines, tumor necrosis factor alpha (TNFalpha) and interleukin-1 (IL-1), in order to begin to define the underlying mechanisms responsible for the elevated levels of PAI-1 and fibrin deposits observed in placenta from preeclampsia. We demonstrate a significant increase in PAI-1, TF and TNFalpha antigen and PAI-1 and TF mRNA in placentas from preeclamptic patients. PAI-1 mRNA was increased not only in syncytiotrophoblast and infarction areas, but also in fibroblasts and in some endothelial cells of fetal vessels in placentas from preeclamptic patients. However, there was no colocalization between PAI-1, TF, Vn and TNFalpha in placental villi. The elevated TNFalpha in the placenta may induce PAI-1 and TF, and thus promote the thrombotic alterations associated with preeclampsia.     

Immunohistochemical characterization of the plasminogen activator system in psoriatic epidermis

The relative topographical distribution of urokinase-type plasminogen activator (uPA), tissue-type PA (tPA), PA-inhibitor-1 (PAI-1), PA-inhibitor-2 (PAI-2), plasmin(ogen), alpha 2-antiplasmin, and alpha 2-macroglobulin was studied in lesional epidermis of psoriasis vulgaris, and in normal epidermis, by immunohistochemistry. In psoriatic epidermis, tPA predominated, although uPA was found in some biopsies. PAs were not detected in normal epidermis. PAI-1 was not detected in normal epidermis and was only present in a proportion of biopsies of psoriatic lesions. PAI-2 was found in normal and psoriatic epidermis. Plasmin(ogen) was confined to the basal cell layer of normal epidermis, whereas in lesional psoriatic skin it was scattered throughout the epidermis. Alpha 2-antiplasmin and alpha 2-macroglobulin were not found in the epidermis of normal skin. In psoriatic epidermis alpha 2-antiplasmin was confined to the subcorneal layer, whereas staining for alpha 2-macroglobulin was found only in a proportion of biopsies, in the upper epidermis. Our immunohistological findings indicate that colocalization of tPA and its substrate plasminogen may allow efficient generation of plasmin, and that the focal absence of plasmin inhibitors may then favour the persistence of plasmin activity.     

Torsional injury resulting in disc degeneration: I. An in vivo rabbit model

OBJECTIVE: To substantiate in a premenopausal population of women, the link between visceral adipose tissue and circulating plasminogen activator inhibitor 1 (PAI-1) levels. DESIGN: Study of correlations between anthropometric parameters and PAI-1 and evaluation of the changes induced by weight loss. SUBJECTS: Forty-two healthy pre-menopausal women (aged 18-51 y, with a wide range of body mass index (BMI, 21-48.8 kg/m2). Thirteen women were evaluated after weight loss (6.6+/-3.3 kg). MEASUREMENTS: BMI, waist and hip circumferences. Total, subcutaneous and visceral adipose tissue areas at the L3-L4 level by computed tomography. Insulin, cholesterol, triglyceride, HDL cholesterol, PAI-1 activity, PAI-1 antigen and tissue plasminogen activator (tPA) antigen. RESULTS: PAI-1 activity, PAI antigen and tPA antigen were positively correlated with visceral adipose tissue, but not with subcutaneous adipose tissue. This correlation was independent of insulin or triglyceride levels. The amount of visceral adipose tissue explained 28% of the PAI-1 activity variance. Weight loss confirmed this link, PAI-1 diminution being correlated only with visceral adipose tissue loss and not with total fat, insulin or triglyceride decrease. CONCLUSION: This study suggests, like in vitro studies, that visceral fat may be an important contributor to the circulating PAI-1.     

Urokinase plasminogen activator is elevated in human astrocytic gliomas relative to normal adjacent brain

We assayed urokinase plasminogen activator (uPA), tissue type plasminogen activator (tPA), and plasminogen activator inhibitor-1 (PAI-1) in 43 human brain tumors (predominantly astrocytic gliomas) and in histologically disease-free brain tissue resected with 21 of the tumors. Levels of uPA, tPA, and PAI-1, measured by enzyme-linked immunosorbent assay, varied widely among individuals in neoplastic and in normal tissue but did not correlate with age or sex. Pairwise comparison of neoplastic and normal tissue from 21 individuals revealed that mean tumor uPA level was elevated 6-fold (P < 0.001). Mean tumor tPA and PAI-1 were 2.5-fold greater than those of normal brain, but these differences were not statistically significant. Tumor uPA was elevated 2- to 30-fold in 16/21 paired samples (76%). In contrast, tumor tPA was elevated 2- to 22-fold in 7/21 (33%) of pairs, whereas tumor PAI-1 was 2- to 13-fold greater in 10/21 (48%) of pairs. Our results demonstrate that elevation of uPA content is frequent in astroglial tumors, as is the case in other major human cancers.     

Angiotensin II type 2 receptor is upregulated in human heart with interstitial fibrosis, and cardiac fibroblasts are the major cell type for its expression

The expression pattern of angiotensin (Ang) II type 2 receptor (AT2-R) in the remodeling process of human left ventricles (LVs) remains poorly defined. We analyzed its expression at protein, mRNA, and cellular levels using autopsy, biopsy, or operation LV samples from patients with failing hearts caused by acute (AMI) or old (OMI) myocardial infarction and idiopathic dilated cardiomyopathy (DCM) and also examined functional biochemical responses of failing hearts to Ang II. In autopsy samples from the nonfailing heart group, the ratio of AT1-R and AT2-R was 59% and 41%, respectively. The expression of AT2-R was markedly increased in DCM hearts at protein (3.5-fold) and mRNA (3.1-fold) levels compared with AMI or OMI. AT1-R protein and mRNA levels in AMI hearts showed 1.5- and 2.1-fold increases, respectively, whereas in OMI and DCM hearts, AT1-R expression was significantly downregulated. AT1-R-mediated response in inositol phosphate production was significantly attenuated in LV homogenate from failing hearts compared with nonfailing hearts. AT2-R sites were highly localized in the interstitial region in either nonfailing or failing heart, whereas AT1-R was evenly distributed over myocardium at lower densities. Mitogen-activated protein kinase (MAPK) activation by Ang II was significantly decreased in fibroblast compartment from the failing hearts, and pretreatment with AT2-R antagonist caused an additional significant increase in Ang II-induced MAPK activity (36%). Cardiac hypertrophy suggested by atrial and brain natriuretic peptide levels was comparably increased in OMI and DCM, whereas accumulation of matrix proteins such as collagen type 1 and fibronectin was much more prominent in DCM than in OMI. These findings demonstrate that (1) AT2-R expression is upregulated in failing hearts, and fibroblasts present in the interstitial regions are the major cell type responsible for its expression, (2) AT2-R present in the fibroblasts exerts an inhibitory effect on Ang II-induced mitogen signals, and (3) AT1-R in atrial and LV tissues was downregulated during chronic heart failure, and AT1-R-mediated functional biochemical responsiveness was decreased in the failing hearts. Thus, the expression level of AT2-R is likely determined by the extent of interstitial fibrosis associated with heart failure, and the expression and function of AT1-R and AT2-R are differentially regulated in failing human hearts.     

Concentration of endogenous tPA antigen in coronary artery disease: relation to thrombotic events, aspirin treatment, hyperlipidemia, and multivessel disease

Tissue plasminogen activator (tPA) is the major plasminogen activator responsible for dissolving blood clots found in blood vessels. However, elevated concentrations of tPA antigen were found to be related to adverse events in patients with coronary artery disease (CAD). Considerable controversy about the significance of these results exists. The goal of this cross-sectional study was to identify independent determinants for tPA antigen concentrations in patients with CAD, to possibly clarify the above paradoxical relationship. The baseline tPA antigen concentrations of 366 patients with angiographic evidence of coronary sclerosis were determined. Univariate analysis showed that age (P=0.013), angiographic extent of disease (P<0.001), presence of angina at rest (P<0.001), diabetes mellitus (P=0.004), hypercholesterolemia (P=0. 045), hypertriglyceridemia (P=0.015), and chronic intake of nitrates (P<0.001) were significantly and positively related to tPA antigen concentration, while the chronic intake of aspirin was inversely related to tPA antigen (P<0.001). In addition, plasminogen activator inhibitor type 1 (PAI-1) activity was found to be significantly and positively associated with tPA antigen concentration (P<0.001). A multivariate analysis identified chronic low-dose aspirin therapy (P<0.001), PAI-1 activity (P<0.001), hypertriglyceridemia (P=0.005), the type of angina (P=0.026), multivessel disease (P=0.041), and hypercholesterolemia (P=0.043) as significant and independent determinants of tPA antigen. While hypertriglyceridemia and hypercholesterolemia both are related to the underlying disease, the type of angina and the number of involved vessels are linked to the severity and extent of disease, and all of them are indicators of a prothrombotic state found during the progression of CAD. In contrary, low-dose aspirin rather would decrease the likelihood of thrombotic events. The relation of tPA antigen to PAI-1 activity furthermore underlines the relation between tPA antigen concentration and a prothrombotic state. Therefore, the positive or-in case of aspirin therapy-negative correlation of these parameters with tPA antigen concentration would indicate that thrombus formation and simultaneous endothelial cell activation might be major determinants for tPA antigen concentration in CAD.     

Repositioning of human interphase chromosomes by nucleolar dynamics in the reverse transformation of HT1080 fibrosarcoma cells

OBJECTIVES: The effects of norepinephrine on expression of cardiac genes during pathological cardiac growth and heart failure are not fully understood. Tissue insulin-like growth factor 1 (IGF-1) and its receptor (IGF-1R) play an important role in the regulation of the hyperplastic capacity of cardiac myocytes. Sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2), on the other hand, is important in regulating cardiac contractile function. The present study examined the effects of elevated levels of NE on expression of IGF-1/IGF-1R and SERCA2 mRNAs. METHODS: Rats were infused with NE using osmotic minipumps for 3 and 6 days at a rate of 50 micrograms/kg/h and also at a higher dose (130 micrograms/kg/h) for 6 and 14 days. Levels of expression of IGF-1/IGF-1R and SERCA2 mRNAs were determined by ribonuclease protection assay and by Northern blotting, respectively. RESULTS: NE treatment significantly increased IGF-1 mRNA levels in both left- and right-ventricle; however, levels of IGF-1R increased in the left- but not the right-ventricle. By contrast, NE infusion at both the lower dose and the higher dose failed to alter expression of SERCA2 mRNA. CONCLUSION: Our results suggest that NE treatment differentially regulates expression of IGF-1 and IGF-1R in the ventricles of rat heart and that NE appears not to affect expression of SERCA2 mRNA.     

In-vitro effect of oncostatin M on the release by endothelial cells of von Willebrand factor, tissue-type plasminogen activator and plasminogen activator inhibitor-1

Epidemiological studies have demonstrated that levels of plasma fibrinogen, von Willebrand factor (vWf), plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPA) are associated with the incidence of vascular disease. Since oncostatin M dramatically induces fibrinogen biosynthesis by hepatocytes and could be implicated in vascular injury leading to atherosclerosis, we have analyzed the effect of oncostatin M on PAI-1, vWf and tPA secretion by endothelial cells. A 2-h incubation of human umbilical vein endothelial cells with oncostatin M increases thrombin-induced secretion of vWf to the same extent as tumour necrosis factor-alpha or interleukin-1 (137+/-26% of control for 5 ng/ml oncostatin M, P < 0.001, n=5). The effects on tPA and PAI-1 secretion were different depending on the type of endothelial cells tested. On human umbilical vein endothelial cells, oncostatin M induced an increase in PAI-1 and a decrease in tPA secretion, which could explain the thrombogenicity of oncostatin M on large vessels. On a human microvasculature endothelial cell line, oncostatin M did not modify PAI-1 but induced an increase in tPA secretion. This observation of the effects of oncostatin M on both macro- and microvasculature could explain the increased levels of vWf, PAI-1 and tPA in the plasma of atherosclerotic subjects identified in epidemiological studies, suggesting that oncostatin M could play a key role in the development of atherosclerotic lesions.     

Identification of tissue-type plasminogen activator-specific plasminogen activator inhibitor-1 mutants. Evidence that second sites of interaction contribute to target specificity

Plasminogen activator inhibitor-1 (PAI-1) is the primary inhibitor of the plasminogen activators (PAs), tissue-type plasminogen activator (tPA), and urokinase-type plasminogen activator (uPA). A library of PAI-1 mutants containing substitutions at the P1 and P1' positions was screened for functional activity against tPA and thrombin. Several PAI-1 variants that were inactive against uPA in a previous study (Sherman, P. M., Lawrence, D. A., Yang, A. Y., Vandenberg, E. T., Paielli, D., Olson, S. T., Shore, J. D., and Ginsburg, D. (1992) J. Biol. Chem. 267, 7588-7595) had significant inhibitory activity toward tPA. This set of tPA-specific PAI-1 mutants contained a wide range of amino acid substitutions at P1 including Asn, Gln, His, Ser, Thr, Leu, Met, and all the aromatic amino acids. This group of mutants also demonstrated a spectrum of substitutions at P1'. Kinetic analyses of selected variants identified P1Tyr and P1His as the most efficient tPA-specific inhibitors, with second-order rate constants (ki) of 4.0 x 10(5) M-1s-1 and 3.6 x 10(5) M-1s-1, respectively. Additional PA-specific PAI-1 variants containing substitutions at P3 through P1' were constructed. P3Tyr-P2Ser-P1Lys-P1'Trp and P3Tyr-P2Ser-P1Tyr-P1'Met had ki values of 1.7 x 10(6) M-1s-1 and 2.5 x 10(6) M-1s-1 against tPA, respectively, but both were inactive against uPA. In contrast, P2Arg-P1Lys-P1'Ala inhibited uPA 74-fold more rapidly than tPA. The mutant PAI-1 library was also screened for inhibitory activity toward thrombin in the presence and absence of the cofactor heparin. While wild-type PAI-1 and several P1Arg variants inhibited thrombin in the absence of heparin, a number of variants were thrombin inhibitors only in the presence of heparin. These results demonstrate the importance of the reactive center residues in determining PAI-1 target specificity and suggest that second sites of interaction between inhibitors and proteases can also contribute to target specificity. Finally, the PA-specific mutants described here should provide novel reagents for dissecting the physiological role of PAI-1 both in vitro and in vivo.     

Prolactin delays gonadotrophin-induced ovulation and down-regulates expression of plasminogen-activator system in ovary

This study was conducted to determine whether prolactin (PRL) suppresses gonadotrophin-induced ovulation and disturbs the co-ordinated gene expression of tissue type plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1) in rat ovary. Immature female rats were injected with 10 IU pregnant mare's serum gonadotrophin to stimulate follicle growth, and 48 h received different doses of prolactin followed by 7 IU human chorionic gonadotrophin (HCG). The oviducts were examined for the presence of ova, and the amounts of tPA and PAI-1 mRNA present in the ovary were measured at various times after the hormone treatment. PRL had no significant effect on ovarian weight but caused a dose-dependent decrease in ovulation number. In the control animals receiving HCG alone, 13.3 +/- 1.3 (mean +/- SEM) ova/oviduct were found; while in animals receiving HCG plus 50, 100 or 200 microg PRL, the ovulation number was dose-dependently suppressed by 53.6, 66.9 and 76% respectively at 18 h after treatment. PRL suppression of HCG-induced ovulation was time-dependent. By 24 h after treatment, the number of ova in the oviducts in HCG- and HCG plus PRL-treated groups was not significantly different. PRL also suppressed HCG-induced tPA gene expression in a dose- and time-dependent manner. At all time points examined, tPA mRNA content of whole ovaries and granulosa cells (GC) in PRL-treated groups was lower than in the HCG-treated controls. The activities of PAI-1 in ovarian extracellular fluid (OEF) and PAI-1 mRNA in the theca-interstitial cells (TI) in the PRL-treated groups were higher than in the HCG-treated controls. The highest stimulation by PRL of PAI-1 activity in OEF and of PAI-1 mRNA in TI was observed at 9 h and 6 h after HCG treatment respectively. The localization of tPA and PAI-1 antigens in the ovaries was consistent with changes in the mRNA and activity levels. These data suggest that PRL temporarily delays, but does not completely inhibit, HCG-induced ovulation, which may be caused by a suppression of PA-mediated proteolysis.     

PAI-1, obesity, insulin resistance and risk of cardiovascular events

Circulating (PAI-1) levels are elevated in patients with coronary heart disease and may play an important role in the development of atherothrombosis. Many clinical studies have indicated that the insulin resistance syndrome, which is a situation predisposing to diabetes and ischemic heart disease, may be a major regulator of PAI-1 expression, especially in determining plasma PAI-1 levels. Central obesity is a characteristic of insulin resistance and is a well recognized risk factor for coronary heart disease. Recently the production of PAI-1 by adipose tissue, in particular by tissue from omentum, has been demonstrated and could be an important contributor to the elevated plasma PAI-1 levels observed in insulin resistant patients. Besides the effect of the metabolic status on plasma PAI-1 levels, the role of a genetic control has been emphasized, but according to recent results obtained in a family segregation study, its participation seems limited. Prospective cohort studies of patients with previous myocardial infarction or angina pectoris have underlined the association between increased plasma PAI-1 levels and the risk of coronary events, but the predictive capacity of PAI-1 disappears after insulin resistance marker adjustments. Taken together these results support the notion that PAI-1 can be a link between obesity, insulin resistance and cardiovascular disease.     

2-Arachidonoylglycerol, a putative endogenous cannabinoid receptor ligand, induces rapid, transient elevation of intracellular free Ca2+ in neuroblastoma x glioma hybrid NG108-15 cells

The hypothesis that tea drinking may protect against coronary heart disease (CHD) through effects on clotting as measured by plasma fibrinogen, tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) was tested in 65 healthy volunteers (31 men and 34 women; aged 20-74 years) in a randomized, blind, placebo-controlled, crossover study lasting 10 weeks (run-in phase 2 weeks, tea and placebo phases 4 weeks). During the placebo phase, intakes of milk, sugar, water and caffeine were matched to those in the tea phase during which 6 mugs of tea were drunk daily. Compliance with tea intake was measured by marking tea bags with p-aminobenzoic acid and measuring recovery in 24-hour urine collections. The mean +/- SD fibrinogen level, PAI-1 activity and tPA antigen level at baseline of 2.91 +/- 0.81 g/l, 7.9 +/- 5.3 U/ml and 4.76 +/- 2.17 ng/ml, respectively, were in the normal range. No significant differences in these variables between the run-in, tea or placebo phases were observed. The putative protective effect of tea against development of CHD is not mediated through effects of black tea on fibrinogen, tPA or PAI-1.     

Angiotensin II receptor type 1 mRNA is upregulated in atria of patients with end-stage heart failure

There is increasing evidence that pathological changes in the myocardium during chronic heart failure (CHF) are partly regulated through the activation of the renin-angiotensin system (RAS), an effect mediated by the angiotensin II type 1 receptor (AT1R). We examined the expression of cardiac AT1R mRNA in normal (atria, n=7; ventricle, n=3) and end-stage CHF human hearts (atria, n=8; ventricle, n=14). Tissue was snap-frozen immediately after explantation during orthotopic cardiac transplantation; control specimens were obtained from healthy donor hearts rejected for technical reasons. Northern blots of purified total mRNA from each tissue were hybridized with a random primed radiolabeled probe for the coding sequence of AT1R. Stringent conditions were used for both hybridization (5X SSC, 65 degrees C) and washing (0.5X SSC, 0.1% SDS, 65 degrees C) of the membrane. Left and right atrial tissue showed low levels of AT1R mRNA expression in the controls, with statistically significant upregulation of expression in tissue from pathological hearts; CHF atria 1.28+/-0.86 optical density (OD) units, control atria 0.56+/-0.31 OD units, P=0.05 (mean+/-s.d.). There were undetectable levels in ventricles from either control (2/2) or dilated hearts (7/7). The results were independent of the etiology of the heart failure and suggest that increased levels of atrial AT1R mRNA may occur in response to elevated atrial pressures in heart failure.