Impact of statins on modulation by insulin of expression of plasminogen activator inhibitor type-1

Mesenchymal stromal cells-based therapy in a murine model of elastase-induced emphysema: Simvastatin as a potential adjuvant in cellular homing

Chronic Obstructive Pulmonary Disease - COPD is characterized by the destruction of alveolar walls associated to a chronic inflammatory response of the airways. There is no clinical therapy for COPD. In this context, cell-based therapies represent a promising therapeutic approach for chronic lung disease. The goal of this work was to evaluate the effect of simvastatin on cell-based therapy in a mice emphysema model. Female FVB mice received intranasal instillation of elastase (three consecutive doses of 50 μL) in order to promote pulmonary emphysema. After 21 days of the first instillation, the animals were treated with Adipose-Derived Mesenchymal Stromal Cells (AD-MSC, 2.6 × 10⁶) via retro-orbital infusion associated or not with simvastatin administrated daily via oral gavage (15 mg/kg/15d). Before and after these treatments, the histological and morphometrical analyses of the lung tissue, as so as lung function (whole body plethysmography) were evaluated. PAI-1 gene expression, an upregulated factor by ischemia that indicate a low survival of transplanted MSC, was also evaluated. The result regarding morphological and functional aspects of both lungs, presented no significant difference among the groups (AD-MSC or AD-MSC + Simvastatin). However, significant anatomical difference was observed in the right lung of the both groups of mice. The results shown a higher deposition of cells in the right lung, with might to be explained by anatomical differences (slightly higher right bronchi). Decreased levels of PAI-1 were observed in the simvastatin treated groups. The pulmonary ventilation was similar between the groups with only a tendency to a lower in the elastase treated animals due to a low respiratory frequency. In conclusion, the results suggest that both AD-MSC and simvastatin treatments could promote an improvement of morphological recovery of pulmonary emphysema, that it was more pronounced in the right lung.

Statin Therapy Negatively Impacts Skeletal Muscle Regeneration and Cutaneous Wound Repair in Type 1 Diabetic Mice

Those with diabetes invariably develop complications including cardiovascular disease (CVD). To reduce their CVD risk, diabetics are generally prescribed cholesterol-lowering 3-hydroxy-methylglutaryl coenzyme A reductase inhibitors (i.e., statins). Statins inhibit cholesterol biosynthesis, but also reduce the synthesis of a number of mevalonate pathway intermediates, leading to several cholesterol-independent effects. One of the pleiotropic effects of statins is the reduction of the anti-fibrinolytic hormone plasminogen activator inhibitor-1 (PAI-1). We have previously demonstrated that a PAI-1 specific inhibitor alleviated diabetes-induced delays in skin and muscle repair. Here we tested if statin administration, through its pleiotropic effects on PAI-1, could improve skin and muscle repair in a diabetic rodent model. Six weeks after diabetes onset, adult male streptozotocin-induced diabetic (STZ), and WT mice were assigned to receive control chow or a diet enriched with 600 mg/kg Fluvastatin. Tibialis anterior muscles were injured via Cardiotoxin injection to induce skeletal muscle injury. Punch biopsies were administered on the dorsal scapular region to induce injury of skin. Twenty-four days after the onset of statin therapy (10 days post-injury), tissues were harvested and analyzed. PAI-1 levels were attenuated in statin-treated diabetic tissue when compared to control-treated tissue, however no differences were observed in non-diabetic tissue as a result of treatment. Muscle and skin repair were significantly attenuated in Fluvastatin-treated STZ-diabetic mice as demonstrated by larger wound areas, less mature granulation tissue, and an increased presence of smaller regenerating muscle fibers. Despite attenuating PAI-1 levels in diabetic tissue, Fluvastatin treatment impaired cutaneous healing and skeletal muscle repair in STZ-diabetic mice.

Posttranscriptional regulation of expression of plasminogen activator inhibitor type-1 by cAMP in HepG2 liver cells

Altered expression of plasminogen activator inhibitor type-1 (PAI-1), a physiologic fibrinolysis inhibitor, is implicated in atherosclerosis. Cyclic adenosine monophosphate (cAMP) alters PAI-1 expression in several cells. Nevertheless, posttranscriptional regulation of PAI-1 has not been elucidated. To determine whether cAMP affects PAI-1 expression at posttranscriptional level, we determined promoter activity, mRNA levels, 3'-untranslated region (UTR) activity and protein levels of PAI-1 using HepG2 cells. cAMP decreased PAI-1 promoter activity at 24 h and mRNA expression at 4 h while it increased mRNA expression and accumulation of PAI-1 protein into media at 24 h. Human PAI-1 mRNA exists in two subspecies (3.2 and 2.2 kb), and cAMP increased baseline luciferase activity of 3'-UTR of the 3.2 kb PAI-1 mRNA [3'-UTR (+1358-3176)] and 1 kb fragment of 3'-terminus of 3'-UTR of 3.2 kb mRNA [3'-UTR (+2177-3176)]. cAMP increased PAI-1 protein expression despite decrease in promoter activity, presumably by regulating PAI-1 expression at the posttranscriptional level and thereby affecting mRNA stability. The 53-nt fragment in 3'-UTR (+2591 to +2643 nt) was involved in posttranscriptional regulation by cAMP. Thus, cAMP can stabilize 3.2 kb PAI-1 mRNA mediated by specific effects on 3'-UTR, and these effects are associated with increased expression of PAI-1 protein.

Simvastatin suppresses dexamethasone-induced secretion of plasminogen activator inhibitor-1 in human bone marrow adipocytes

Background

Osteonecrosis of the femoral head is a common complication of high-dose glucocorticoid treatment. Intravascular thrombosis is thought to be associated with the ischemic state of the femoral head. Plasminogen activator inhibitor-1 (PAI-1) is an adipokine, which are physiologically active substances secreted from visceral and subcutaneous adipocytes. PAI-1 suppresses fibrinolysis by binding tissue-type plasminogen activator. Several reports have described the relationship between PAI-1 and steroid-induced osteonecrosis of the femoral head, and the preventive effects of lipid-lowering agents (statins) against steroid-induced osteonecrosis of the femoral head. We previously reported that adipokines and dexamethasone induced PAI-1 secretion from bone marrow adipocytes. The purpose of the present study is to examine the effects of simvastatin on PAI-1 secretion from human bone marrow adipocytes in vitro.

Methods

Primary bone marrow adipocytes were extracted from collagenase-treated bone marrow fluid obtained from the femoral necks of 40 patients (6 men, 34 women; age range, 52-81 years) undergoing hip joint replacement surgery. After suspended culture with or without dexamethasone or simvastatin, PAI-1 mRNA expression was assessed by real-time RT-PCR. Total PAI-1 protein secretion in culture medium was assessed by enzyme-linked immunosorbent assay.

Results

PAI-1 mRNA expression was up-regulated by 388% (P = 0.002) with dexamethasone, and down-regulated by 45% (P = 0.002) with simvastatin, as compared to control levels. Dexamethasone increased total PAI-1 secretion by 166% (P = 0.001) and simvastatin decreased total PAI-1 secretion by 64% (P = 0.002). No significant changes were observed in adiponectin mRNA expression and secretion by dexamethasone and simvastatin, while pre-treatment with simvastatin reversed dexamethasone induced PAI-1 secretion by 89%, as compared to control levels.

Conclusion

The present study confirmed the suppressive effects of simvastatin on PAI-1 expression and secretion from bone marrow adipocytes. Furthermore, pre-treatment with simvastatin reversed dexamethasone induced PAI-1 secretion. Simvastatin may thus exhibit preventive effects against steroid-induced osteonecrosis of the femoral head by suppressing PAI-1 secretion.

Increased expression of plasminogen activator inhibitor type-1 (PAI-1) in HEPG2 cells induced by insulin mediated by the 3'-untranslated region of the PAI-1 gene and its pharmacologic implications

OBJECTIVE

Insulin increases, through several molecular mechanisms, expression of plasminogen activator inhibitor-1 (PAI-1), the major physiologic inhibitor of fibrinolysis. This phenomenon has been implicated as a cause of accelerated coronary artery disease and the increased incidence of acute coronary syndromes associated with type 2 diabetes. We have previously reported that physiologic and pharmacologic concentrations of insulin induce PAI-1 synthesis in human HepG2 cells and that simvastatin can attenuate its effects. This study was performed to further elucidate mechanisms responsible for the insulin-induced PAI-1 production.

METHODS

Concentrations of PAI-1 mRNA were determined by real-time PCR, and PAI-1 protein was assayed by western blotting. PAI-1 promoter (-829 to +36 bp) activity was assayed with the use of luciferase reporter assays. The potential role of the 3'-untranslated region (UTR) in the PAI-1 gene was assayed with the use of luciferase constructs containing the 3'-UTR. Oxidative stress was measured by loading cells with carboxy-2,7 dichlorodihydrofluorescein.

RESULTS

Insulin increased PAI-1 promoter activity, PAI-1 mRNA, and accumulation of PAI-1 protein in the conditioned media. Insulin-inducible PAI-1 promoter activity was attenuated by simvastatin. Experiments performed with luciferase reporters containing the 3'-UTR showed that insulin increased luciferase activity through this region. Insulin also increased oxidative stress. Both insulin-inducible luciferase activity through the 3'-UTR and oxidative stress were attenuated by simvastatin.

CONCLUSION

Insulin can increase PAI-1 expression through multiple mechanisms including induction mediated by the 3'-UTR of the PAI-1 gene. Accordingly, beneficial pleiotropic effects of statins on coronary artery disease may be attributable, in part, to attenuation of overexpression of PAI-1 mediated by the 3'-UTR in syndromes of insulin resistance (such as the metabolic syndrome) and type 2 diabetes.

Primary prevention of vascular events in patients with high levels of C-reactive protein: the JUPITER study

The Justification for the Use of Statins in Primary Prevention: An Intervention Trial Evaluating Rosuvastatin (JUPITER) study was the first large-scale, prospective study to examine the benefits of statin therapy in subjects with elevated levels of high-sensitivity C-reactive protein but with low-to-normal LDL-cholesterol levels, who were not qualified for lipid-lowering treatment according to the current guidelines for primary prevention. The JUPITER study aimed to determine whether rosuvastatin 20 mg daily would reduce the rate of first major cardiovascular events, including cardiovascular death, nonfatal stroke, nonfatal myocardial infarction, hospitalization for unstable angina or arterial revascularization. Rosuvastatin reduced LDL-cholesterol levels by 50% and high-sensitivity C-reactive protein by 37%. Compared with placebo, the combined primary end point was reduced in 44% (p < 0.00001), and total mortality in 20% (p = 0.02). The trial confirmed the relationship between the rates of major cardiovascular events with both high-sensitivity C-reactive protein and LDL-cholesterol levels achieved after statin treatment. Interestingly, this was the first large, prospective statin trial to show benefit in the reduction of venous thromboembolism.