P2577Losartan diminishes the expression of TGF-beta and improves cardiomyopathy in mice with Marfan syndrome

Introduction

Marfan syndrome (MFS) is caused by mutations in the fibrillin-1 gene, leading to abnormal signaling of the transforming growth factor beta (TGF-β). This results in aortic root dilation, dissection and rupture, which are the main causes of morbidity and mortality of MFS patients. Current treatment with losartan, an angiotensin-II receptor-1 blocker, has shown beneficial effect on aortic disease in MFS murine models. However, the mechanisms whereby the treatment with losartan improves cardiac remodeling and function of the left ventricle (LV) in MFS are still unknown.

Purpose

To investigate the effects of losartan on mechanisms of the cardiomyopathy in mice with MFS.

Methods

mgΔloxPneo MFS murine model from C129/sv background was utilized in this study. To evaluate the effect of the treatment with losartan on the LV of MFS and wild-type mice, animals were allocated in 2 groups of treatments: Losartan group: mice were kept with water supplemented with losartan (0.6g/L); Untreated control group: mice were kept with water only. The animals received treatment from 1 month of age until completing 6 months. After five months of treatment, LV echocardiography was performed, and fragments of LV tissue were analyzed by morphometry and protein expression analysis by Western blot.

Results

Losartan MFS mice showed decrease in interventricular septum and posterior wall thickness and LV mass. Furthermore, losartan prevented aortic and mitral regurgitation, arrhythmia, bradycardia, septal hypokinesia and pulmonary hypertension when compared with control MFS mice. Systolic and diastolic LV function were not different between groups. Collagen volume fraction and the disorganization and disruptions of the elastic fibers in coronary arteries were lower in losartan treatment than in controls. The protein expression of pro-apoptotic factors (BAX/Bcl-2 and caspase 3 and 9), proliferating cell nuclear antigen and hypoxia-inducible factor 1 and 2α were lower in losartan treatment, whereas the expression of vascular endothelial growth factor was increased in losartan group when compared with control MFS mice. Moreover, the treatment with losartan strongly reduced the TGF-β, ERK and p38MAPK protein expression compared to controls.

Conclusion

In this murine model of MFS, losartan treatment has the ability to change several pathophysiological mechanisms related with the fibrillin-1 mutation, by decreasing apoptosis, cell proliferation and increasing angiogenesis. Overall, the treatment resulted in improved structural rearrangement and attenuation of the rupture of elastic fibers in the coronary arteries, of the cardiac hypertrophy and myocardial fibrosis. These effects were possibly related with the decreased TGF-β expression by ERK and p38MAPK signaling pathways by losartan. Our findings shed a new light on the mechanisms of action of losartan on MFS cardiomyopathy.

Acknowledgement/Funding

FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo)

P6295Methotrexate reduces cardiac remodeling and improves left ventricle function in rats with Takotsubo cardiomyopathy

Introduction

Takotsubo cardiomyopathy (TC) is characterized by cardiac disfunction and left ventricle (LV) remodeling caused, mainly, by physical or emotional stress. Previously, we have shown in atherosclerotic rabbits that methotrexate (MTX), an anti-inflammatory chemotherapeutic agent, is capable of reducing the inflammatory process and atherosclerotic lesions.

Purpose

To investigate the effect of MTX treatment in rats with TC.

Methods

TC was induced in Wistar rats with 2 injections of isoproterenol (85mg/kg) with a 24h interval. Animals were allocated in 3 experimental groups: CT: animals induced and treated with saline; TK: animal induced with isoproterenol and treated with saline; TK-MTX: animals induced with isoproterenol and treated with MTX (1mg/kg). Animals were treated every week for 4 weeks. After the treatment, echocardiography, morphometry and molecular analysis (Western blot) of the LV were performed.

Results

TK and TK-MTX groups did not show cardiac dilation or LV intraventricular septum and posterior wall thickening. However, compared to TK, the treatment with MTX improved both LV systolic and diastolic function. In addition, the treatment diminished myocytes diameter and subendocardial and interstitial fibrosis of the LV. Protein expression of pro-apoptotic factors (caspase 3 and BAX), pro-inflammatory cytokine TNF-α, metalloproteinase 2, transforming growth factor beta, collagen I and III and hypoxia-inducible factor 2 alfa were all decreased. Vascular endothelial growth factor (VEGF) and adenosine A1 receptor showed increased protein expression in TK-MTX group when compared to CT and TK. There was correlation of myocardial fibrosis (r2=-0.57), myocytes diameter (r2=-0.78) and VEGF expression (r2=0.58) with LV systolic disfunction. Also, myocardial fibrosis (r2=0.57) and VEGF expression (r2=-0.68) correlated with diastolic disfunction in the LV. Animals treated with MTX did not present any toxicity.

Conclusion

Treatment with MTX diminished apoptosis, the expression of TNF-α and metalloproteinases, cardiac hypertrophy and myocardial fibrosis. Besides that, the treatment increased angiogenesis and strongly improved cardiac function of the LV. MTX, possibly through an increase in the production of intracellular adenosine, could be considered as a feasible treatment for TC.

Acknowledgement/Funding

FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo)

Ha-ras oncogene-induced transcription of human papillomavirus type 18 E6 and E7 oncogenes

Human papillomavirus (HPV) DNA sequences are found in most carcinomas originating from the uterine cervix. HPV E6 and E7 oncogenes have been shown to cooperate with ras oncogenes to fully transform human epithelial cells. We investigated the effect of the Ha-ras oncogene on the transcriptional activity of HPV-18 and found that it induced the transcriptional activity of the viral promoter, whereas the normal gene had only a minimal effect. However, transfection of the normal Ha-ras gene and simultaneous inhibition of protein phosphatase sensitive to okadaic acid (OA) resulted in a cooperative transactivation of the viral promoter. When cloned upstream of a minimal promoter, the AP-1 binding sites present in the viral promoter conferred transcriptional responsiveness to Ha-ras and OA. Furthermore, HeLa cell clones permanently expressing the Ha-ras oncogene or high levels of the normal gene exhibited a twofold to threefold increase in E6*E7/E1 and E6*E7 transcripts. We propose that both Ha-ras and a protein phosphatase sensitive to OA regulate HPV oncogene expression through modulation of AP-1 activity and suggest that increased levels of E6 and E7, resulting from activated viral transcription in the presence of ras oncogenes, may in part explain the observed cooperation between these viral and cellular oncogenes in the transformation of human cells.

Early promoters of genital and cutaneous human papillomaviruses are differentially regulated by the bovine papillomavirus type 1 E2 gene product

The physical state of the human papillomavirus (HPV) genome is usually different in malignant lesions of the skin, in which it is generally found in episomal form, and genital mucosa, in which it is frequently integrated with disruption of the E2 gene. Using chimeric or natural HPV promoters in the presence of the bovine papillomavirus type 1 E2 gene product, we observed transcription activation or repression, depending on the distance of E2-binding motifs from the start site. We found a clear difference in the positions of E2-binding motifs in cutaneous and genital HPVs that may partly explain the selective pressure for genome integration of genital HPV types in malignant lesions.