Current and Future Therapeutic Targets for Pulmonary Arterial Hypertension

Natural plant products in treatment of pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a severe disease characterized by progressive remodeling of distal pulmonary arteries and persistent elevation of pulmonary vascular resistance (PVR), which leads to right ventricular dysfunction, heart failure, and eventually death. Although treatment responsiveness for this disease is improving, it continues to be a life-threatening condition. With the clinical efficacy of natural plant products being fully confirmed by years of practice, more and more recognition and attention have been obtained from the international pharmaceutical industry. Moreover, studies over the past decades have demonstrated that drugs derived from natural plants show unique advantages and broad application prospects in PAH treatment, not to mention the historical application of Chinese traditional medicine in cardiopulmonary diseases. In this review, we focus on summarizing natural plant compounds with therapeutic properties in PAH, according to the extracts, fractions, and pure compounds from plants into categories, hoping it to be helpful for basic research and clinical application.

Statins may be beneficial for patients with pulmonary hypertension secondary to lung diseases

BACKGROUND

Previous animal studies and clinical trials report inconsistent findings regarding the role of statins in pulmonary hypertension (PH). Systematic reviews have shown no use of statins on pulmonary arterial hypertension (PAH). This is the first meta-analysis of randomized controlled trials (RCTs) determining the clinical impacts of statin therapy on patients with PH secondary to lung diseases.

METHODS

Electronic databases and manual bibliographical searches were conducted. Eligible studies included RCTs of at least 3 months that evaluated statin therapy as compared with control in adult patients with PH due to pulmonary diseases. Statistical analyses were performed to calculate mean difference, relative risks (RRs), and 95% confidence intervals (CIs) using random-effect model.

RESULTS

A total of 6 RCTs were identified and included in this study. Five trials reported the effects of statins in patients with both chronic obstructive pulmonary disease (COPD) and PH, and the remaining 1 was based on PH due to pneumoconiosis. We found that statin therapy was associated with increased 6-minute walk distance and reduced pulmonary artery systolic pressure. There was no observed difference in the incidence of death, drug withdrawal, and adverse event between statin and control group.

CONCLUSIONS

Our findings suggest that statins might be safe and beneficial for patients with PH due to chronic lung diseases. However, larger RCTs with more patients and longer observational duration are needed.

Statins Have No Additional Benefit for Pulmonary Hypertension: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

We performed a meta-analysis to explore the effects of adding statins to standard treatment on adult patients of pulmonary hypertension (PH).

METHODS

A systematic search up to December, 2015 of Medline, EMBASE, Cochrane Database of Systematic reviews and Cochrane Central Register of Controlled Trials was performed to identify randomized controlled trials with PH patients treated with statins.

RESULTS

Five studies involving 425 patients were included into this meta-analysis. The results of our analysis showed that the statins can't significantly increase 6-minute walking distance (6MWD, mean difference [MD] = -0.33 [CI: -18.25 to 17.59]), decrease the BORG dyspnea score (MD = -0.72 [CI: -2.28 to 0.85]), the clinical worsening risk (11% in statins vs. 10.1% in controls, Risk ratio = 1.06 [CI: 0.61, 1.83]), or the systolic pulmonary arterial pressure (SPAP) (MD = -0.72 [CI: -2.28 to 0.85]). Subgroup analysis for PH due to COPD or non-COPD also showed no significance.

CONCLUSIONS

Statins have no additional beneficial effect on standard therapy for PH, but the results from subgroup of PH due to COPD seem intriguing and further study with larger sample size and longer follow-up is suggested.

Lung Circulation

The circulation of the lung is unique both in volume and function. For example, it is the only organ with two circulations: the pulmonary circulation, the main function of which is gas exchange, and the bronchial circulation, a systemic vascular supply that provides oxygenated blood to the walls of the conducting airways, pulmonary arteries and veins. The pulmonary circulation accommodates the entire cardiac output, maintaining high blood flow at low intravascular arterial pressure. As compared with the systemic circulation, pulmonary arteries have thinner walls with much less vascular smooth muscle and a relative lack of basal tone. Factors controlling pulmonary blood flow include vascular structure, gravity, mechanical effects of breathing, and the influence of neural and humoral factors. Pulmonary vascular tone is also altered by hypoxia, which causes pulmonary vasoconstriction. If the hypoxic stimulus persists for a prolonged period, contraction is accompanied by remodeling of the vasculature, resulting in pulmonary hypertension. In addition, genetic and environmental factors can also confer susceptibility to development of pulmonary hypertension. Under normal conditions, the endothelium forms a tight barrier, actively regulating interstitial fluid homeostasis. Infection and inflammation compromise normal barrier homeostasis, resulting in increased permeability and edema formation. This article focuses on reviewing the basics of the lung circulation (pulmonary and bronchial), normal development and transition at birth and vasoregulation. Mechanisms contributing to pathological conditions in the pulmonary circulation, in particular when barrier function is disrupted and during development of pulmonary hypertension, will also be discussed.