Improvement of bleomycin-induced pulmonary hypertension and pulmonary fibrosis by the endothelin receptor antagonist Bosentan

Rationale

There is evidence that endothelin plays a key role in the development of pulmonary hypertension (PH) in pulmonary fibrosis (PF). However, the functional consequence of the unselective endothelin receptor antagonist Bosentan in PH and PF has not yet been studied. Therefore, we investigated the effects of Bosentan on the development of PH in the model of Bleomycin-induced PF in rats.

Methods

Adult male Wistar rats were randomly assigned to the following groups: untreated animals (controls), Bleomycin-induced PF (Bleomycin) and Bleomycin-induced PF treated with Bosentan (Bleomycin + Bosentan). Exercise capacity was evaluated by treadmill exercise testing. PH was assessed by right ventricular systolic pressure (RVSP) and right ventricular hypertrophy. For quantification of PF the hydroxyproline content in lung tissue (HPC) was measured.

Results

Compared to controls, animals with Bleomycin-induced PF showed a significant reduction in exercise capacity (44% vs. 100%), significantly higher RVSP (65 mmHg vs. 23 mmHg), significantly more right ventricular hypertrophy (0.55 vs. 0.24) and significantly higher HPC (60.5 vs. 14.8). Bosentan treatment in animals with Bleomycin-induced PF resulted in significantly greater exercise capacity (98% vs. 44%) and a trend towards lower RVSP (52 mmHg vs. 65 mmHg), significantly less right ventricular hypertrophy (0.34 vs. 0.55) and significantly lower HPC (16.7 vs. 60.5) compared to untreated Bleomycin-induced PF.

Conclusion

Application of Bosentan in Bleomycin rats resulted in significantly higher exercise capacity as a result of improvements in PH and PF.     

Pulmonary vasodilator strategies in neonates with acute hypoxemic respiratory failure and pulmonary hypertension

The management of acute hypoxemic respiratory failure (AHRF) in newborns continues to be a clinical challenge with elevated risk for significant morbidities and mortality, especially when accompanied with persistent pulmonary hypertension of the newborn (PPHN). PPHN is a syndrome characterized by marked hypoxemia secondary to extrapulmonary right-to-left shunting across the ductus arteriosus and/or foramen ovale with high pulmonary artery pressure and increased pulmonary vascular resistance (PVR). After optimizing respiratory support, cardiac performance and systemic hemodynamics, targeting persistent elevations in PVR with inhaled nitric oxide (iNO) therapy has improved outcomes of neonates with PPHN physiology. Despite aggressive cardiopulmonary management, a significant proportion of patients have an inadequate response to iNO therapy, prompting consideration for additional pulmonary vasodilator therapy. This article reviews the pathophysiology and management of PPHN in term newborns with AHRF while highlighting both animal and human data to inform a physiologic approach to the use of PH-targeted therapies.     

Pulmonary arterial hypertension related to HIV: is inflammation related to IL-6 the cornerstone?

Vascular diseases have become the leading cause of mortality in the population treated for HIV infection. Pulmonary arterial hypertension (PAH) related to HIV (PAH–HIV), the fourth cause of PAH in France, has the same histological pattern as other PAH from the group 1 of Dana Point classification. But, conversely to idiopathic PAH in the general population, PAH–HIV is particular by its high frequency in HIV-infected population. This raises the question for the role of inflammation in the PAH–HIV pathophysiology. Its constant occurrence over the decades, despite introduction of combination antiretroviral therapy (CAT), does not preclude the hypothesis of an involvement of inflammation in the genesis of PAH–HIV. Indeed, it is well known that normalization of CD4+ by the CAT does not mean no inflammation. Especially, it persists an increased and continuous production of IL-6, a main cytokine in the genesis of PAH lesions. This inflammation mainly involves the endothelin-1 pathway, which has an action on endothelium and macrophages, leading to high production of IL-6. Moreover, plasmatic level of IL-6 has a prognostic value in PAH–HIV, independently from conventional (functional or hemodynamic) parameters. The use of endothelin receptor antagonist permits major effect on IL-6 production and dramatic effect on PAH in so-called “bosentan responders”.     

Effects of Pulmonary Vasodilator Therapy on Ventilatory Efficiency during Exercise in Adults with Eisenmenger Syndrome

Objective. Eisenmenger syndrome, characterized by systemic‐level pulmonary arterial resistance with resultant right‐to‐left shunt, is associated with low exercise capacity and hyperpnea at rest and exercise. Because ventilatory requirements are augmented by right‐to‐left shunting, we hypothesized that if pulmonary vasodilator treatment improved pulmonary perfusion in this condition, this would also improve ventilatory efficiency during exercise. Design. To investigate this, data from incremental cardiopulmonary exercise tests performed by Eisenmenger patients before and after beginning therapy with pulmonary hypertension medications were retrospectively analyzed. Setting. Ahmanson/University of California, Los Angeles Adult Congenital Heart Disease Center. Patients. Ten adults with Eisenmenger syndrome treated with either bosentan or sildenafil. Outcome Measures. The primary analysis was comparison, before and after treatment, of the efficiency of exercise ventilation as reflected in the ratio of ventilation () to carbon dioxide output () measured at the anaerobic threshold (AT), the slope of during incremental exercise, and end tidal partial pressure of CO₂ (PETCO₂) at the AT. Secondary measures included peak oxygen uptake () and AT. Results. Following treatment there were significant reductions in the slope (59.5 ± 12.9 vs. 50.0 ± 7.2, P= .003), and significant decrease in ratio (56.9 ± 6.2 vs. 50.2 ± 5.9, P= .00004) and increase in PETCO₂ (21.12 ± 2.43 vs. 23.9 ± 2.62 torr, P= .0092) measured at the AT. Increases in peak (0.73 ± 0.25 vs. 0.78 ± 0.32 L/min, P= .333) and AT (0.61 ± 0.20 vs. 0.68 ± 0.25 L/min, P= .154) were not significant. Conclusions. These findings are consistent with reduction in right‐to‐left shunt due to improved pulmonary blood flow, though attenuation of ventilatory drive is not excluded. Treatment of adult Eisenmenger patients with pulmonary the pulmonary vasodilators bosentan or sildenafil leads to improvement in parameters of ventilatory efficiency during exercise.     

A Phase II study of bosentan, a dual endothelin receptor antagonist, as monotherapy in patients with stage IV metastatic melanoma

There is no effective systemic therapy for disseminated metastatic melanoma. Data suggest that endothelin may play a role in pathophysiology of melanoma and that the dual endothelin receptor antagonist bosentan may have anti-tumor activity. This multicenter, open-label, single-arm, prospective, proof-of-concept study assessed the effects of bosentan monotherapy (500 mg oral tablets, bid) on tumor response in patients with stage IV metastatic melanoma. Patients were treated until disease progression, death or serious adverse event leading to premature study drug discontinuation. Tumor response was assessed at 6-weekly intervals using the Response Evaluation Criteria in Solid Tumors (RECIST). Among the 35 patients included in this study with stage IV metastatic melanoma, 21 (60%) were stage M1C, 10 (29%) stage M1B and 4 (11%) stage M1A (American Joint Committee on Cancer [AJCC] classification). Nine patients (26%) had received prior therapy for stage IV melanoma. Disease stabilization was observed in 6 of the 32 patients analyzed per protocol at week 6 with confirmatory evaluation at week 12, 5 of whom were still stable at > or =24 weeks. Of the 6 patients with disease stabilization, 2 were stage M1A, 1 was stage M1B and the remaining 3 were stage M1C. Partial or complete response was not observed. Progressive disease was observed in 17 (49%) patients at week 12 and in 25 (71%) patients at the end of the study (data base closure). The most frequent adverse events were typical for the underlying disease or known to be associated with bosentan: headache (43%), fatigue (34%), nausea (31%), back pain (23%) and abnormal hepatic function (23%). Bosentan might have benefit in disease stabilization in certain patients with metastatic melanoma and deserves further investigation in combination with other anticancer drugs.     

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.     

Role of angiotensin and endothelin in testicular ischemia reperfusion injury

Objectives: To determine whether angiotensin and endothelin have any role in testicular ischemia reperfusion injury by investigating the effects of the angiotensin converting enzyme inhibitor enalapril, selective non‐peptide angiotensin‐II type I blocker losartan and dual endothelin receptor blocker bosentan. Methods: Rats were anesthetized with thiopental sodium (50 mg/kg i.p.) before the operation. The left testicular artery and vein of rats were occluded for 1 h; before the bilateral orchiectomy, the organ was allowed to reperfuse for 3 h or 24 h. Enalapril (20 mg/kg i.p.), losartan (30 mg/kg i.p.), bosentan (10 mg/kg i.p.) or vehicle (saline) were given 30 min before reperfusion. Malondialdehyde level was measured in testicular tissue after 3 h of reperfusion. Histological examination was carried out after 24 h of reperfusion. Results: Ischemia reperfusion caused a significant increase in malondialdehyde level of ipsilateral testis, and histopathological injury in both ipsilateral and contralateral testes. Enalapril, losartan and bosentan treatments prevented the ischemia reperfusion‐induced augmentation in malondialdehyde levels. Only bosentan treatment ameloriated ischemia reperfusion‐induced histopathological alterations. Conclusions: Endothelin might play a more important role in pathogenesis of testicular ischemia reperfusion injury when compared with angiotensin.     

波生坦治疗儿童先天性心脏病相关肺动脉高压的疗效观察

目的 评价非选择性内皮素受体拮抗剂波生坦用于儿童先天性心脏病(CHD)相关肺动脉高压(PAH)治疗的临床效果.方法 32例具备用药指征的CHD患儿接受口服波生坦治疗,其中18例为左向右分流,男10例,女8例,年龄2个月至15岁;14例为功能性单心室(FSV),男8例,女6例,年龄5个月至15岁.术前90 d至术后8年开始口服波生坦治疗,用药后定期随访,评估临床效果和药物不良反应.结果 左向右分流患儿口服波生坦后1、2、3个月肺动脉压(mm Hg,1 m Hg=0.133 kPa)分别为57±26、52±31、46±22,均明显低于用药前(74±15,均P<0.05);用药后3个月心功能分级明显改善(Ⅳ、Ⅲ、Ⅱ级构成比分别为55.6%、33.3%、11.1%比0、16.7%、83.3%,P<0.01).其中7例8～15岁患儿用药后3个月6 min步行距离较用药前明显增加[(497±56)比(424±31)m,P<0.01)].FSV组患儿末次随访(用药2～5个月)经皮血氧饱和度比用药前明显提高[(86±5)%比(78±6)%,P<0.01];心功能分级明显改善(Ⅳ、Ⅲ、Ⅱ级构成比分别为0、21.4%、71.5%比35.7%、42.9%、21.4%,P<0.01);颜面部水肿和胸腔积液发生率明显降低(均为7.1%比57.1%,均P<0.05),未发现因服用波生坦而发生的明显不良反应.结论 波生坦用于治疗儿童CHD相关PAH是安全的.对左向右分流患儿可有效降低术后肺动脉压,改善心功能分级和活动耐量;对FSV患儿可改善血氧饱和度和心功能,降低肺血管阻力增高所致并发症的发生率.