Effect of Ambrisentan Therapy on the Expression of Endothelin Receptor, Endothelial Nitric Oxide Synthase and NADPH Oxidase 4 in Monocrotaline-induced Pulmonary Arterial Hypertension Rat Model

BACKGROUND AND OBJECTIVES: Elevated endothelin (ET)-1 level is strongly correlated with the pathogenesis of pulmonary arterial hypertension (PAH). Expression level of nicotinamide adenine dinucleotide phosphate oxidase (NOX) 4 is increased in the PAH patients. Ambrisentan, a selective endothelin receptor A (ERA) antagonist, is widely used in PAH therapy. The current study was undertaken to evaluate the effects of ambrisentan treatment in the monocrotaline (MCT)-induced PAH rat model. METHODS: Rats were categorized into control group (C), monocrotaline group (M) and ambrisentan group (Am). The M and Am were subcutaneously injected 60 mg/kg MCT at day 0, and in Am, ambrisentan was orally administered the day after MCT injection for 4 weeks. The right ventricle (RV) pressure was measured and pathological changes of the lung tissues were observed by Victoria blue staining. Protein expressions of ET-1, ERA, endothelial nitric oxide synthase (eNOS) and NOX4 were confirmed by western blot analysis. RESULTS: Ambrisentan treatment resulted in a recovery of the body weight and RV/left ventricle+septum at week 4. The RV pressure was lowered at weeks 2 and 4 after ambrisentan administration. Medial wall thickening of pulmonary arterioles and the number of intra-acinar arteries were also attenuated by ambrisentan at week 4. Protein expression levels of ET-1 and eNOS were recovered at weeks 2 and 4, and ERA levels recovered at week 4. CONCLUSIONS: Ambrisentan administration resulted in the recovery of ET-1, ERA and eNOS protein expression levels in the PAH model. However, the expression level of NOX4 remained unaffected after ambrisentan treatment.

Benign Prostatic Hyperplasia: Current and Future Therapeutics.

Benign prostatic hyperplasia (BPH) is one of the most common diseases of old-aged men affecting >90% of men in their 70s and 80s. Although the exact cause is not known, most people agree that dihydrotestosterone plays a strong role in pathogenesis. BPH can be a progressive disease. Severe BPH can cause serious problems including renal insufficiency. Surprisingly the risk factors for BPH are found to be the same as for cardiovascular diseases. Management of BPH has changed significantly in the last decade. α-blockers and 5α-reductase inhibitors are the most commonly used drugs. A number of other drugs belonging to newer groups like phosphodiesterase inhibitors, hexokinase inhibitors like lonidamine, antagonists of endothelin, vanilloid and purine receptors and modulators of JM-27 expression are also showing promise. These are in different stages of clinical trials. The surgical counterpart of treatment has also witnessed recent advancements. Newer techniques like potassium-titanylphosphate (KTP) laser and photo selective vaporization of prostate have been shown to have nearly equal efficacy as that of transurethral resection of prostate (TURP) with less side effects.

Pharmacotherapy for pulmonary arterial hypertension

Although pulmonary arterial hypertension (PAH) is an orphan disease with high mortality and for which there is no cure, current treatment have led to considerable gains in the outcomes of these patients. Oral anticoagulation is proposed for most patients; diuretic treatment and supplemental oxygen are indicated in cases of fluid retention and hypoxemia. High doses of calcium-channel blockers are indicated only in the minority of patients who respond to acute vasoreactivity testing. Nonresponders to acute vaoreactivity testing or who remain in World Health Organization (WHO) functional class III, should be considered candidates for treatment with either an oral phophodiesterase-5 inhibitor or an oral endothelin-receptor antagonist. Continuous intravenous administration of epoprostenol remains the treatment of choice in WHO functional class IV patients. Combination therapy is recommended for patients treated with PAH monotherapy who remain in WHO functional class III. The pharmacologic management of PAH is rapidly evolving as newer therapeutic targets that stabilize or reverse pulmonary vascular disease and as clinical practice pattern shift in favor of earlier diagnosis and aggressive treatment. Questions about preferred first-line therapy and when to institute combination therapies remain. Future drug development targeting other molecular pathways of PAH is essential for definitively improving patient survival. The search for novel treatment continues, with promising new concepts arising from a better understanding of the pathobiology of PAH.

The mechanism and pulmonary-protective effects of endothelin-1 receptor antagonist in chronic obstructive pulmonary diseases rat model / 中华内科杂志

Objective To investigate whether the endothelin (ET) receptor antagonists have protective role in the development of emphysema. Methods Spragne-Dawley rats (n = 24) were divided into four groups: control group, cigarette smoke extract (CSE) group, BQ123 group and Bosentan group. CSE was injected intraperitoneally once a week for three weeks and BQ123 and Bosentan were administered daily for the same duration. TdT-mediated dUTP nick end labeling(TUNEL) was performed to observe the deoxyribonucleic acid (DNA) damaged cells and the expression of caspase-3 was determined by immunohistochemistry and Western blot. Matrix metalloproteinase-2 (MMP-2) and MMP-9 activities were investigated by gelatin zymography and tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) concentrations were measured by enzyme linked immunosorbent assay (ELISA). Results We confirmed the emphysematous destruction in the lungs of experimental rats induced by the intraperitoneal injection of CSE within 3 weeks. The mean lining inteval (MLI) and damage index (DI) were significantly increased in the CSE group compared with control group. However, the MLI and DI were significantly decreased in the BQI23 and bosentan groups compared with CSE rats (P < 0. 01, respectively). The TUNEL-positive cells were markedly distributed in the peribronchioles, intra-alveoli, and septal areas of the emphysematous lungs in CSE rats comparing with the lungs of control rats. The apoptosis index (AI) was significantly higher in CSE group than control group. And the AI was significantly reduced in BQ123 group and bosentan group compared with that in CSE group. The caspase-3 positive ceils were markedly distributed in the emphysematous lungs of CSE group comparing with the stained cells in the lungs of control rats. These positive cells were apparently reduced in the BQ123 and bosentan groups compared with the stained cells in CSE group. Comparing with the control group, expression of caspase-3 was prominently enhanced in CSE groups, but both BQ123 and bosentan treatments markedly inhabited the increases of the cleaved caspase-3 protein levels in rats injected with CSE. Rats injected with CSE showed increased MMP-2 and MMP-9 activities in their lung tissue homogenates and MMP-2 and MMP-9 activities were reduced significantly in both BQ123 and bosentan groups. The levels of TNFα and IL-1β were significantly increased in the CSE group in comparison to those in controls. BQ123 and bosentan significantly prevented the increases of the levels of TNFα and IL-1β in lungs of rats with injection of CSE. Condusions ET-1 may have an important role in the pathological process of emphysema and ET receptor antagonists protect against the development of emphysema probably by decelerating apoptosis, inhibiting proteolytic enzyme activity and reducing inflammatory cytokine levels.

Endothelins system and myocardial hypertrophy / 中国药理学通报

Cardiac hypertrophy is a major adaptational mechanism in stresses such as pressure overload and neurohumoral stimulation.As powerful vasoconstrictor peptides in cardiovascular system,especially the vascular endothelium,smooth muscle cells and cardiocyte,ETs play important physiological roles in the regulation of normal cardiovascular function.Excessive generation of ETs in local cardiac muscle has been linked to myocardial hypertrophy.Endothelin-1(ET-1) in cardiac muscle exerts its actions in the development of myocardial hypertrophy through binding to specific receptors and interacting with other vasoactive substance of local tissues.ET-1 can induce the hypertrophy for cardiocytes and the proliferation for cardiac fibroblasts by ETA.ETB receptors are implicated both in initiating and maintaining myocardial hypertrophy.As a new target of drug,ET receptors have become the research focus,and great progress has been made on the development of the ET antagonists.