Effects of simvastatin on pulmonary fibrosis, pulmonary hypertension and exercise capacity in bleomycin-treated rats.

AIM: Pulmonary fibrosis is often complicated by pulmonary hypertension. Statins reduce fibroblast activity in vitro and pulmonary hypertension in vivo. We investigated whether Simvastatin exerts beneficial effects on pulmonary fibrosis and pulmonary hypertension in Bleomycin-treated rats in vivo. METHODS: Rats were randomly assigned to controls, Bleomycin, Bleomycin plus Simvastatin from day 1 to 28 and Bleomycin plus Simvastatin from day 13 to 28. 28 days after Bleomycin instillation, right ventricular systolic pressure (RVSP), right ventricular mass (RV/(LV+S)), right ventricular and circulating brain natriuretic peptide (BNP) levels were determined to assess pulmonary hypertension. Pulmonary hydroxyproline content (HPC), pulmonary connective tissue growth factor (CTGF) transcription and lung compliance (LC) were analysed to characterize pulmonary fibrosis. Exercise capacity was determined by treadmill tests. RESULTS: Compared with controls, Bleomycin increased RVSP, RV/(LV+S), BNP levels, HPC and CTGF transcription and decreased LC significantly. Simvastatin administered from day 1 to 28 normalized all these parameters. Simvastatin administered from day 13 to 28 had no effect on HPC and LC, but reduced RV/(LV+S) significantly and induced a strong trend to lower RVSP and BNP levels. Exercise capacity was reduced by Bleomycin. Simvastatin significantly improved exercise intolerance in both treatment groups. CONCLUSIONS: Simvastatin prevents the development of pulmonary fibrosis, but fails to attenuate already established pulmonary fibrosis. In contrast, it ameliorates pulmonary hypertension and thereby exercise capacity in the prevention and the treatment group regardless of its effects on pulmonary fibrosis. Whether statins are a treatment option in humans with pulmonary fibrosis needs to be investigated by further study.

Effects of selective and unselective endothelin-receptor antagonists on prostacyclin synthase gene expression in experimental pulmonary hypertension.

OBJECTIVE: Compared to the unselective endothelin (ET) receptor antagonist (Bosentan), superior effects of selective ET-A-receptor blockage (Ambrisentan) for the treatment of pulmonary hypertension (PH) are expected due to ET-B-receptor mediated beneficial effects. Our hypothesis was that treatment with Ambrisentan leads to an increase in prostacyclin synthase I (PGIS) expression compared to Bosentan. MATERIAL AND METHODS: To test this hypothesis, rats were treated with either monocrotaline (MCT) only, MCT+Ambrisentan or MCT+Bosentan. After 4 weeks, right ventricular systolic pressure (RVSP), pulmonary vascular remodelling and right ventricular hypertrophy (RV/(LV+S)) were measured. RESULTS: In MCT only treated animals, significantly greater expression of PGIS mRNA was found in the lungs compared to control animals, and this was confirmed by immunohistochemical analysis indicating increased staining of PGIS in the very small pulmonary arteries (17 % greater expression of PGIS mRNA in MCT versus control, p = 0.002; Remmele score (RS): 51 versus 102, p = 0.009). Treatment with Bosentan resulted in a significantly lower expression of PGIS mRNA compared to Ambrisentan and MCT only (7 % versus 18 %, p = 0.003 and 7 % versus 17 %, p = 0.004). This observation was also confirmed by immunohistochemical analysis (RS very small arteries: 45 versus 81, p = 0.003; RS small arteries: 45 versus 108, p = 0.014). No difference was observed in RVSP, RV/(LV+S) or pulmonary vascular remodelling between the two treatment groups (RVSP: 28 versus 39 mmHg, p = 0.189; RV/(LV+S) 0.46 versus 0.48, p = 0.818; medial area: 78.3 % versus 75.2 %, p = 0.823). CONCLUSIONS: Treatment with Bosentan leads to lower PGIS expression in pulmonary arteries compared to Ambrisentan, although the greater PGIS expression by Ambrisentan treatment had no benefical effect on pulmonary haemodynamics.

The NO donor molsidomine reduces endothelin-1 gene expression in chronic hypoxic rat lungs.

We investigated the effects of the nitric oxide (NO) donor molsidomine and the nitric oxide synthase inhibitor N-nitro-L-arginine methyl ester (L-NAME) on pulmonary endothelin (ET)-1 gene expression and ET-1 plasma levels in chronic hypoxic rats. Two and four weeks of hypoxia (10% O2) significantly increased right ventricular systolic pressure, the medial cross-sectional vascular wall area of the pulmonary arteries, and pulmonary ET-1 mRNA expression (2-fold and 3.2-fold, respectively). ET-1 plasma levels were elevated after 4 wk of hypoxia. In rats exposed to 4 wk of hypoxia, molsidomine (15 mg x kg(-1) x day(-1)) given either from the beginning or after 2 wk of hypoxia significantly reduced pulmonary hypertension, pulmonary vascular remodeling, pulmonary ET-1 gene expression, and ET-1 plasma levels. L-NAME administration (45 mg x kg(-1) x day(-1)) in rats subjected to 2 wk of hypoxia did not modify these parameters. Our findings suggest that in chronic hypoxic rats, exogenously administered NO acts in part by suppressing the formation of ET-1. In contrast, inhibition of endogenous NO production exerts only minor effects on the pulmonary circulation and pulmonary ET-1 synthesis in these animals.

Role of endothelins for the regulation of renal renin gene expression.

Endothelin-1, -2 and -3 (ET-1, -2, -3) have suppressive effects on the renin system in different experimental in vitro models, whereas a modulation of renin secretion or renin gene expression by endothelins (ETs) in in vivo studies has not so far been found. In a recent study we observed a significant stimulation of the renin system by acute hypoxia over 6 h in rats. In the study reported here, we investigated the more chronic effects of hypoxia (10% O2 for 4 weeks) on renin gene expression and the influence of the ET system on its regulation. Renin mRNA levels decreased after 2 weeks of hypoxia to 76% of control and after 4 weeks to 49% of control (p < 0.05). Concomitant administration of the ET(A)-receptor antagonist LU135252 led to a significant increase in renin gene expression compared to control or hypoxia alone. ET-1 mRNA increased to 120% after 2 weeks and 173% after 4 weeks of hypoxia (NS), while ET-3 was not affected by hypoxia. We therefore conclude that ETs have a suppressive effect on renal renin gene expression in the setting of chronic hypoxia in rats in vivo.

Effects of chronic hypoxia on renal PDGF-A, PDGF-B, and VEGF gene expression in rats.

BACKGROUND: There is evidence from in vitro studies to suggest that the genes of platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF) are, like the erythropoietin gene, regulated by oxygen tension. Hypoxia-induced stimulation of, for example, PDGF or VEGF might be involved in the pathogenesis of acute or chronic renal failure and in renal 'inflammatory' diseases (glomerulonephritis, vasculitis, allograft rejection). METHODS: Male Wistar rats were exposed to chronic normobaric hypoxia (10% O(2), 90% N(2)) for 4 weeks. Additional groups of rats were treated with the endothelin receptor antagonist LU13525 and the NO donor molsidomine. Renal mRNA levels of PDGF-A, PDGF-B, and VEGF were semiquantitated using RNase protection assays. RESULTS: Renal gene expression of PDGF-A and PDGF-B was neither affected by 2 or 4 weeks of hypoxia nor by concomitant treatment with LU135252 or molsidomine. Chronic hypoxia did also not change VEGF gene expression; however, concomitant treatment with LU135252 increased all VEGF subtypes (188, 164, 120). CONCLUSIONS: The findings of the present study suggest that renal PDGF and VEGF gene expression in vivo during chronic hypoxia for 2 and 4 weeks is not sensitive to tissue hypoxia in contrast to cell culture experiments. During chronic hypoxia with concomitant blockade of endothelin receptors, all VEGF subtypes were increased, suggesting an inhibitory action of endothelins with regard to renal VEGF gene expression.

Effects of chronic hypoxia on renal renin gene expression in rats.

BACKGROUND: The effects of hypoxia on renin secretion and renin gene expression have been controversial. In recent studies, we have demonstrated that acute hypoxia of 6 h duration caused a marked stimulation of renin secretion and renal renin gene expression. This hypoxia-induced stimulation of the renin-angiotensin system might contribute, for example, to the progression of chronic renal failure and to the development of hypertension in the sleep-apnoea syndrome. For this reason, we were interested in the more chronic effects of hypoxia on renal renin gene expression and its possible regulation. METHODS: Male rats were exposed to chronic normobaric hypoxia (10% O(2)) for 2 and 4 weeks. Additional groups of rats were treated with an endothelin ET(A) receptor antagonist, LU135252, or a NO donor, molsidomine, respectively. Systolic blood pressure and right ventricular pressures were measured. Renal renin, endothelin-1 and endothelin-3 gene expression were quantitated using RNAase protection assays. RESULTS: During chronic hypoxia, haematocrit increased to 72+/-2%, and right ventricular pressure increased by a mean of 26 mmHg. Renal renin gene expression was halved during 4 weeks of chronic hypoxia. This decrease was reversed by endothelin receptor blockade (105 or 140% of baseline values after treatment for weeks 3-4 or 1-4). Furthermore, there was a trend of increasing renal endothelin-1 gene expression (to 173% of baseline values) after 4 weeks of hypoxia. Systolic blood pressure increased moderately during 4 weeks of chronic hypoxia from 129+/-2 to 150+/-4 mmHg. This blood pressure increase was higher in rats treated for 4 weeks with an endothelin receptor antagonist (196+/-11 mmHg). CONCLUSIONS: Chronic hypoxia (in contrast to acute hypoxia) suppresses renal renin gene expression. This inhibition presumably is mediated by endothelins.

Quantification of aortic stenosis in mechanically ventilated patients using multiplane transesophageal Doppler echocardiography.

STUDY OBJECTIVES: To evaluate the feasibility and accuracy of multiplane transesophageal Doppler echocardiographic assessment of the severity of aortic stenosis in mechanically ventilated patients using modified transgastral views of the left ventricular outflow tract and the aortic valve. DESIGN: A prospective study comparing the results of transesophageal echocardiography (TEE) with transthoracic echocardiography (TTE) and cardiac catheterization. SETTING: A university hospital. PATIENTS: Twenty-eight American Society of Anesthesiologists class III and IV patients with aortic stenosis undergoing elective cardiac surgery for valve replacement. INTERVENTIONS: Intubated and mechanically ventilated patients with aortic stenosis undergoing cardiac surgery for valve replacement were studied by multiplane transesophageal Doppler echocardiography to determine transvalvular pressure gradients (Bernoulli formula) and valve areas (continuity equation). These findings were compared with the respective preoperative data from TTE and cardiac catheterization. MEASUREMENTS AND RESULTS: In 25 of 28 patients (89%), adequate transgastral Doppler recordings of the aortic jet could be obtained. The TEE measurements correlated well with the respective data obtained by TTE (maximal pressure gradient: r=0.93, p<0.0001, mean difference=5.9+/-5.8 mm Hg [mean+/-SD]; mean pressure gradient: r=0.91, p<0.0001, mean difference=5.4+/-4.6 mm Hg; aortic valve area: r=0.97, p<0.0001, mean difference=0.07+/-0.05 cm2) and cardiac catheterization (n=16) (maximal vs peak-to-peak pressure gradient: r=0.84, p<0.0001, mean difference=10.9+/-8.8 mm Hg; mean pressure gradient: r=0.80, p<0.0002, mean difference=9.7+/-5.9 mm Hg; aortic valve area: r=0.84, p<0.0001, mean difference=0.1+/-0.08 cm2). CONCLUSION: Multiplane transesophageal Doppler echocardiography offers an alternative approach for assessing the severity of aortic stenosis in mechanically ventilated patients in whom conventional TTE is not feasible.

Vascular remodeling and growth factor gene expression in the rat lung during hypoxia.

Recent studies suggest that the vasoactive peptides endothelin-1 and -3 and the mitogens VEGF and PDGF-A and -B could be involved in the pathogenesis of hypoxic pulmonary hypertension. We were interested to investigate whether these peptides could also be involved in the vascular remodeling occurring during chronic hypoxia (10% oxygen; 1 and 3 weeks) in the rat. Hypoxia increased significantly systolic right ventricular pressure and typical morphological signs of vascular remodeling were found. This was accompanied by increased ET-1 and the ET-3 mRNA expression after acute (6 h; P < 0.05) and chronic hypoxia of 1 (P < 0.05) and 3 weeks (P < 0.05). In contrast, we found no effects of hypoxia on the gene expression of VEGF and PDGF-A and -B in the lung. Our findings indicate that ET-3 in addition to ET-1 could be involved in the process of hypoxia-induced vascular remodeling, whereas it appears less likely that the mitogens VEGF and PDGF-A and -B are essentially involved in the pathogenesis of hypoxic pulmonary hypertension.

Transgastric Doppler echocardiographic assessment of the severity of aortic stenosis using multiplane transesophageal echocardiography.

We investigated whether multiplane transesophageal Doppler echocardiography using transgastral views allows determination of pressure gadients and valve areas in patients with aortic stenosis. This technique was feasible in 35 of 39 patients (90%), with highly significant correlations with results obtained from transthoracic Doppler echocardiography and cardiac catheterization, thus offering an alternative approach for quantification of aortic stenosis.

ANP gene expression in rat hearts during hypoxia.

It is unclear whether the increase in plasma atrial natriuretic peptide (ANP) concentration during hypoxia is due to direct, hypoxia-induced upregulation of ANP secretion in the heart, or to pressure overload of the right ventricle (RV) following hypoxia-induced pulmonary hypertension. To test the hypothesis that hypoxia leads to an early upregulation of the ANP gene, we examined the influence of acute and prolonged inspiratory hypoxia (6 h, 1 or 3 weeks) on the expression of ANP messenger ribonucleic acid (mRNA) in rat heart and compared the results with the expression of the ANP gene after acute pressure overload induced by experimental coarctation of the main pulmonary artery. As a molecular marker for hypertrophy we determined the ratio of alpha- and beta-myosin gene expression. Hypoxia increased systolic RV pressure from 20.0 +/- 1.6 mmHg to 27.8 +/- 1.6 mmHg (P < 0.01) and 41.6 +/- 2.1 mmHg (P < 0. 05) after 1 and 3 weeks hypoxia respectively. The ANP plasma concentration did not change significantly after 6 h or 1 week: 232 +/- 21 pg/ml (control), 246 +/- 25 pg/ml (6 h), 268 +/- 25 pg/ml (1 week), but increased significantly after 3 weeks hypoxia (446.8 +/- 99.56 pg/ml; P < 0.05). ANP mRNA levels in different regions of the heart did not change after 6 h or 1 week hypoxia. After 3 weeks hypoxia ANP mRNA had increased 2.7-fold in the RV (P < 0.05), 4. 2-fold in the left ventricle (LV, P < 0.05), 3.5-fold in the septum (S, P < 0.05) and about 1.4-fold in the right (n.s.) and left atrium (n.s.). Relative ventricular masses increased significantly only for the RV (190%, P < 0.05) during hypoxia. The beta/alpha-myosin mRNA ratio did not change after 6 h hypoxia but, contrary to ANP gene expression, increased after just 1 week (6.1-fold in RV, 7.8-fold in LV, 6-fold in S; P < 0.05) and was more pronounced in the RV after 3 weeks (9.4-fold in RV, 7.6-fold in LV, 9.1-fold in S; P < 0.05). The increase in the beta/alpha-myosin mRNA ratio in the LV contrasts with a lack of increase in relative ventricular mass. Acute pressure overload in the RV after pulmonary arterial banding significantly increased ANP-mRNA and the beta/alpha-myosin mRNA ratio after 1 day in the RV. In the LV ANP mRNA was unchanged. The delayed upregulation of the ANP gene suggests that hypoxia per se is not a significant stimulus for ANP gene expression in the heart and that hypoxia-induced ANP-gene expression in the heart is regulated predominantly by the increase in RV afterload due to hypoxia-induced increased pulmonary pressure. The upregulation of ANP and beta-myosin mRNA in the LV during chronic hypoxia has yet to be elucidated.

The concept of dimensions in developmental research.

In the present article, the terms attribute, concept, and category were deliberately used to demonstrate how such terms share a common meaning, at least at one level. This is precisely the level at which interpretive misunderstandings seem to abound. The misunderstandings are not limited to any group of theorists, but apply equally to many of us. Actually, the problem is not very different from that which exists for similarity. In an extensive analysis of the similarity construct, Gregson (1975) remarked that one reason for its popularity was that the lack of a precise definition could be "dangerously versatile." Versatility at the expense of precise definition does not improve either predictability or our understanding of complex developmental processes. That understanding is our goal, and if the suggestions we have made lead to more clearly defined research designs and more consistent results, our goals shall have been achieved.