Activation of Nicotinic Acetylcholine α7 Receptor Attenuates Progression of Monocrotaline-Induced Pulmonary Hypertension in Rats by Downregulating the NLRP3 Inflammasome.

Yan Deng,Yan Deng,Sheng-Lan Guo,Jia-Quan Li,Ying-Chuan Zhou,Ying-Chuan Zhou,Xing-Cui Gao,Xing-Cui Gao,Bin Wei,Bin Wei

doi:10.3389/fphar.2019.00128

Abstract

Background: Inflammation and altered immunity contribute to the development of pulmonary arterial hypertension (PH). The alpha 7 nicotinic acetylcholine receptor (α7nAChR) possesses anti-inflammatory activities. The current study was performed to investigate the effects of a selective α7nAChR agonist, PNU-282987, on controlling a monocrotaline (MCT)-induced rat model of PH and explored the underlying mechanisms.Methods: Sprague-Dawley rats were injected with MCT and treated with PNU-282987 at the prevention (starting 1 week before MCT) and treatment (starting 2 weeks after MCT) settings. Four weeks after MCT injection, hemodynamic changes, right ventricular structure, and lung morphological features were assessed. Enzyme-linked immunosorbent assay, Western blot and qRT-PCR were performed to assess levels of inflammatory cytokines and NLRP3 (Nod-like receptor family pyrin domain-containing 3) inflammasome pathway in the rat lung tissues. In addition, the lung macrophage line NR8383 was used to confirm the in vivo data.Results: Monocrotaline injection produced PH in rats and downregulated α7nAChR mRNA and protein expression in rat lung tissues compared to sham controls. Pharmacological activation of α7nAChR by PNU-282987 therapy improved the rat survival rate, attenuated the development of PH as assessed by remodeling of pulmonary arterioles, reduced the right ventricular (RV) systolic pressure, and ameliorated the hypertrophy and fibrosis of the RV in rats with MCT-induced PH. The expression of TNF-α, IL-6, IL-1β, and IL-18 were downregulated in rat lung tissues, which implied that PNU-282987 therapy may help regulate inflammation. These protective effects involved the inhibition of the NLRP3 inflammasome. In vitro assays of cultured rat lung macrophages confirmed that the anti-inflammation effect of PNU-282987 therapy may contribute to the disturbance of NLRP3 inflammasome activation.Conclusion: Targeting α7nAChR with PNU-282987 could effectively prevent and treat PH with benefits for preventing ongoing inflammation in the lungs of rats with MCT-induced PH by inhibiting NLRP3 inflammasome activation.

Highlights

Pulmonary hypertension (PH) is characterized by progressive pulmonary vascular remodeling, microvascular loss, and elevated pulmonary vascular resistance leading to increased right-sided heart failure and high rates of morbidity and mortality (No authors, 2015; Potus et al, 2015; Mendes-Ferreira et al, 2016)
We assessed hemodynamics and histology data on these rats and found that the MCT-treated rats developed severe PH due to a significant elevation of the RV systolic pressure and thickened the vessel walls compared with those of the sham group (P < 0.05; Figures 3A,B), which is consistent with previous studies (Kim et al, 2017); PNU282987 treatment effectively suppressed the MCT-induced increase in the RV systolic pressure (P < 0.05; Figures 3A,B)
We explored whether the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and the potential downstream signaling are involved in regulating inflammation cytokines by detecting the NLRP3 inflammasome markers, including NLRP3, pro-cas-1, caspase-1, and IL-1β

Summary

Introduction

Pulmonary hypertension (PH) is characterized by progressive pulmonary vascular remodeling, microvascular loss, and elevated pulmonary vascular resistance leading to increased right-sided heart failure and high rates of morbidity and mortality (No authors, 2015; Potus et al, 2015; Mendes-Ferreira et al, 2016). Macrophages are generated from circulating monocytes and differentiate into macrophages, which produce inflammatory cytokines, thereby promoting pulmonary artery smooth muscle cells (PASMC) proliferation via growth factor signaling (Gurtu and Michelakis, 2015; Florentin et al, 2018). The role of a macrophage is dependent on its microenvironment, with which it can interact through its large repertoire of surface receptors (Zhou et al, 2014; Layhadi and Fountain, 2017; Rojas et al, 2018). In this regard, identifying and targeting inflammatory “upstream” receptors could represent novel therapeutic strategies. The current study was performed to investigate the effects of a selective α7nAChR agonist, PNU-282987, on controlling a monocrotaline (MCT)-induced rat model of PH and explored the underlying mechanisms

Methods

Results

Discussion

Conclusion