Optimizing endothelin receptor antagonist use in the management of pulmonary arterial hypertension

Nrf2 Activation With CDDO-Methyl Promotes Beneficial and Deleterious Clinical Effects in Transgenic Mice With Sickle Cell Anemia

Activation of Nrf2, a major transcription factor that drives the antioxidant defense system, is an emerging therapeutic strategy in Sickle Cell Disease (SCD). In this study, transgenic Sickle Cell Anemia mice (SS mice) treated with CDDO-Methyl (CDDO-Me), a potent Nrf2 activator, showed reduced progression of hemolytic anemia with aging, but surprisingly also showed reduced endothelial function. Pulmonary vessels isolated from SS mice treated for 4 months with CDDO-Me displayed a diminished response to nitric oxide (NO)-induced vasodilation compared to littermates given vehicle. It is unclear what molecular mechanism underly the vascular impairment, however, our in vitro assays revealed that CDDO-Me induced the expression of the endothelin receptor (ETA and ETB) in vascular smooth muscle cells. Endothelin signaling is associated with increased vascular tone and vasoconstriction. This study underscores the importance of pre-clinical benefit-risk investigations of Nrf2 activating compounds which may be used to treat patients with SCD.

Comparative assessment of efficacy and safety of ambrisentan and bosentan in patients with pulmonary arterial hypertension: A meta-analysis

WHAT IS KNOWN AND OBJECTIVE

Two endothelin receptor antagonists, ambrisentan and bosentan, have been demonstrated to be effective individually compared with placebo in the treatment of patients with pulmonary arterial hypertension (PAH). This network meta-analysis compared the efficacy and safety of ambrisentan and bosentan in patients with PAH.

METHODS

Clinical trials were identified from the Cochrane Central Register of Controlled Trials (CENTRAL/CCTR), EMBASE and PubMed databases. Weighted mean differences (MD) with 95% confidence intervals (CI) were calculated for continuous outcomes (6-min walk distance [6MWD] and Borg dyspnoea index [BDI]). Hazard ratio (HR) was calculated for binary outcomes, including clinical worsening, discontinuation due to adverse events (AEs) and liver dysfunction. Surface under cumulative ranking curve (SUCRA) was used to rank the treatments in each index.

RESULTS

Five clinical trials from four published studies (total patients: n = 920) were included. Ambrisentan and bosentan showed no significant difference in 6MWD (MD: -1.32; 95% CI: -27.87, 25.31, SUCRA score: ambrisentan 0.73, bosentan 0.77), BDI (MD: -0.16; 95% CI: -0.98, 0.65, SUCRA score: ambrisentan 0.83, bosentan 0.66), clinical worsening (HR: 0.99; 95% CI: 0.33, 2.94, SUCRA score: ambrisentan 0.75, bosentan 0.74) and discontinuation due to AEs (HR: 0.84; 95% CI: 0.11, 5.86, SUCRA score: ambrisentan 0.47, bosentan 0.57). However, ambrisentan was significantly better than bosentan with respect to abnormal liver function (HR: 23.18; 95% CI: 2.24, 377.20, SUCRA score: ambrisentan 0.99, bosentan 0.02).

WHAT IS NEW AND CONCLUSION

The results of this network meta-analysis suggest that ambrisentan was similar to bosentan in efficacy, while it exhibited better tolerability with respect to abnormal liver function in comparison with bosentan, in patients with PAH.

DDCI-01, a novel long acting phospdiesterase-5 inhibitor, attenuated monocrotaline-induced pulmonary hypertension in rats

Pulmonary arterial hypertension is a progressive, malignant heart disease, characterized by pulmonary arteriole remodeling and increased pulmonary vascular resistance, which eventually leads to right heart failure. This study sought to evaluate the effects of a novel long-acting phospdiesterase-5 inhibitor, namely DDCI-01, as an early intervention for monocrotaline-induced pulmonary hypertensive rats. To establish this model, 50 mg/kg of monocrotaline was intraperitoneally injected into rats. At Day 7 after monocrotaline injection, two doses of DDCI-01 (3 or 9 mg/kg/day) or tadalafil (at 3 or 9 mg/kg/day) were intragastrically administered. The rats were anesthetized with pentobarbital for hemodynamic and echocardiographic measurements, at Day 21 after monocrotaline injection. Compared to the monocrotaline group, DDCI-01 at 3 and 9 mg/kg/day (P) reduced the mean pulmonary arterial pressure (mPAP), right ventricular systolic pressure, right ventricular transverse diameter, pulmonary arterial medial wall thickness (WT%), and right ventricle hypertrophy. However, no significant difference in the indices mentioned as above was found between DDCI-01 (3 mg/kg/day) and tadalafil (3 mg/kg/day). In addition, DDCI-01 at 9 mg/kg/day resulted in lower mPAP and WT%, as well as higher cyclic guanosine monophosphate levels in the lung and plasma compared with the same dose of tadalafil (9 mg/kg/day) (all P < 0.05). These findings suggested that DDCI-01 improved monocrotaline-induced pulmonary hypertension in rats, and a dose of DDCI-01 of 9 mg/kg/day might be more effective than the same dose of tadalafil in monocrotaline-induced pulmonary hypertension in rats.

Cytokines in the immunopathology of systemic sclerosis

Cytokines and growth factors are key regulators of immune activation, vascular alteration and excessive production of extracellular matrix which are hallmark events in the pathogenesis of systemic sclerosis (SSc). They modulate cell-cell and cell-matrix interactions. In particular, cytokines play a central role in the immunopathogenesis of SSc on the basis of molecular pathways which are complex and not completely understood. The majority of cytokines that may be involved in SSc pathogenesis have effect upon or are derived from cells of the immune system, including both the innate and adaptive compartments. Novel therapies that block key mediators that drive the fibrotic response are being developed and appear as potential therapeutic tools in the treatment of SSc, highlighting the importance for an effective therapy targeted towards the molecular and cellular pathways. This article reviews cytokine biology in that context, with particular emphasis on immunopathology of the disease, therapeutic targeting and the way that current or emerging treatments for SSc might impact on cytokine biology.

Bosentan treatment for Raynauds phenomenon and skin fibrosis in patients with Systemic Sclerosis and pulmonary arterial hypertension: an open-label, observational, retrospective study

Raynaud?s phenomenon (RP) and cutaneous fibrosis are the distinctive manifestations of scleroderma, in which Endothelin-1 plays a fundamental pathogenetic role. Bosentan, an Endothelin-1 receptor antagonist used for the treatment of pulmonary arterial hypertension, retards the beginning of new sclerodermic digital ulcers (DU). This open-label, observational, retrospective study verified the effect of Bosentan on RP and skin fibrosis in sclerodermic outpatients affected by pulmonary arterial hypertension without DU. Fourteen subjects (13 women, 1 man; mean age 60 ± 7.5 years; ten with limited and four with diffuse scleroderma) were observed at baseline (T0) and after four (T1), twelve (T2), twenty-four (T3) and forty-eight (T4) weeks during treatment with Bosentan. They were evaluated for daily quantity and duration of RP attacks and skin thickness (using modified Rodnan total skin score, MRSS). Videocapillaroscopic evaluation was performed at T0 and T4. Bosentan decreased significantly the number and duration of RP attacks, beginning at T2 (p<0.05). Videocapillaroscopy showed significant improvement of microcirculatory patterns at T4 (p<0.05). MRSS decreased throughout the study, reaching the statistical significance at T3 and T4 (p<0.01) in the whole cohort. The present data suggest that Bosentan is effective in stabilizing the microcirculation involvement and in improving skin fibrosis irrespective of scleroderma patterns.

Endothelin receptor antagonists for pulmonary arterial hypertension: an overview

The last decade has seen major advances in the pharmacotherapy of pulmonary arterial hypertension (PAH). One of these advances has been the discovery of endothelin receptor antagonists (ERAs). ERAs are a class of potent vasodilators and antimitotic substances, which could specifically dilate and remodel pulmonary arterial system, and have been proposed as an alternative to traditional therapies for PAH. Current available evidence suggests that ERAs improve exercise capacity, functional status, pulmonary hemodynamics, and delay the time to clinical worsening for patients with PAH. This review attempts to provide an overview of the pharmacology, therapeutic benefits, and safety profile of ERAs in patients with PAH.

Endothelin-dependent vasoconstriction in human uterine artery: application to preeclampsia

BACKGROUND

Reduced uteroplacental perfusion, the initiating event in preeclampsia, is associated with enhanced endothelin-1 (ET-1) production which feeds the vasoconstriction of uterine artery. Whether the treatments of preeclampsia were effective on ET-1 induced contraction and could reverse placental ischemia is the question addressed in this study. We investigated the effect of antihypertensive drugs used in preeclampsia and of ET receptor antagonists on the contractile response to ET-1 on human uterine arteries.

METHODOLOGY/PRINCIPAL FINDINGS

Experiments were performed, ex vivo, on human uterine artery samples obtained after hysterectomy. We studied variations in isometric tension of arterial rings in response to the vasoconstrictor ET-1 and evaluated the effects of various vasodilators and ET-receptor antagonists on this response. Among antihypertensive drugs, only dihydropyridines were effective in blocking and reversing the ET-1 contractile response. Their efficiency, independent of the concentration of ET-1, was only partial. Hydralazine, alpha-methyldopa and labetalol had no effect on ET-1 induced contraction which is mediated by both ET(A) and ET(B) receptors in uterine artery. ET receptors antagonists, BQ-123 and BQ-788, slightly reduced the amplitude of the response to ET-1. Combination of both antagonists was more efficient, but it was not possible to reverse the maximal ET-1-induced contraction with antagonists used alone or in combination.

CONCLUSION

Pharmacological drugs currently used in the context of preeclampsia, do not reverse ET-1 induced contraction. Only dihydropyridines, which partially relax uterine artery previously contracted with ET-1, might offer interesting perspectives to improve placental perfusion.

Targeted oral therapies in the treatment of pulmonary arterial hypertension

Recent advances in our understanding of the pathophysiology of pulmonary arterial hypertension (PAH) have led to the US FDA's approval of eight drugs for its treatment. Although guidelines for the use of PAH therapies are available and regularly updated, there is a lack of information on how these agents differ and what characteristics may enable one agent to be of greater relative clinical utility than another. Oral agents may be compared across a variety of measures, including clinical efficacy, safety and tolerability, dosing and pharmacology, potential for drug interactions, treatment adherence and suitability for use in combination regimens. Although no large, prospective, head-to-head trial has been conducted with oral agents for PAH, data from placebo-controlled studies indicate that the enrolled patient populations were remarkably homogeneous with respect to demographic and disease severity parameters. In general, data suggest that these agents improve functional capacity, delay disease progression and improve haemodynamics. Additionally, long-term sustainability of response has been demonstrated. However, there was no consistently superior agent across the primary and secondary endpoints assessed in these trials, and the magnitudes of improvements were in a fairly defined range across agents. Consequently, treatment choice may shift to other aspects such as drug safety and tolerability, potential for drug interactions, dosing convenience, treatment adherence, effect on quality of life and access to medication. In this review, the four targeted oral agents approved for the treatment of PAH in the US are reviewed, and clinical results are placed into context.

The management of acute pulmonary arterial hypertension

Acute pulmonary arterial hypertension (PAH), which may complicate the course of many complex disorders, is always underdiagnosed and its treatment frequently begins only after serious complications have developed. Acute PAH is distinctive because they differ in their clinical presentation, diagnostic findings, and response to treatment from chronic PAH. The acute PAH may take either the form of acute onset of chronic PAH or acute PAH or surgery-related PAH. Significant pathophysiologic differences existed between acute and chronic PAH. Therapy of acute PAH should generally be aimed at acutely relieving right ventricular (RV) pressure overload and preventing RV dysfunction. There are three classes of drugs targeting the correction of abnormalities in endothelial dysfunction, which have been approved recently for the treatment of PAH: (1) prostanoids; (2) endothelin receptor antagonists; and (3) phosphodiesterase-5 inhibitors. The efficacy and safety of these compounds have been confirmed in uncontrolled studies in patients with PAH. Intravenous epoprostenol is suggested to serve as the first-line treatment for the most severe patients. In the other situations, the first-line therapy may include bosentan, sildenafil, or a prostacyclin analogue. Recent advances in the management of PAH have markedly improved prognosis.