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Activation of Nicotinic Acetylcholine ?7 Receptor Attenuates Progression of Monocrotaline-Induced Pulmonary Hypertension in Rats by Downregulating the NLRP3 Inflammasome.

ABSTRACT: Background: Inflammation and altered immunity contribute to the development of pulmonary arterial hypertension (PH). The alpha 7 nicotinic acetylcholine receptor (?7nAChR) possesses anti-inflammatory activities. The current study was performed to investigate the effects of a selective ?7nAChR 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 ?7nAChR mRNA and protein expression in rat lung tissues compared to sham controls. Pharmacological activation of ?7nAChR 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-?, IL-6, IL-1?, 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 ?7nAChR 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.

SUBMITTER: Deng Y

PROVIDER: S-EPMC6399137 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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

Deng Yan Y Guo Sheng-Lan SL Wei Bin B Gao Xing-Cui XC Zhou Ying-Chuan YC Li Jia-Quan JQ

Frontiers in pharmacology 20190226

<b>Background:</b> 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. <b>Methods:</b> Sprague-Dawley rats were injected with MCT and treated with P ...[more]

PMID: 30863307

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Project description:BackgroundMast cells (MCs) are implicated in inflammation and tissue remodeling. Accumulation of lung MCs is described in pulmonary hypertension (PH); however, whether MC degranulation and c-kit, a tyrosine kinase receptor critically involved in MC biology, contribute to the pathogenesis and progression of PH has not been fully explored.MethodsPulmonary MCs of idiopathic pulmonary arterial hypertension (IPAH) patients and monocrotaline-injected rats (MCT-rats) were examined by histochemistry and morphometry. Effects of the specific c-kit inhibitor PLX and MC stabilizer cromolyn sodium salt (CSS) were investigated in MCT-rats both by the preventive and therapeutic approaches. Hemodynamic and right ventricular hypertrophy measurements, pulmonary vascular morphometry and analysis of pulmonary MC localization/counts/activation were performed in animal model studies.ResultsThere was a prevalence of pulmonary MCs in IPAH patients and MCT-rats as compared to the donors and healthy rats, respectively. Notably, the perivascular MCs were increased and a majority of them were degranulated in lungs of IPAH patients and MCT-rats (p < 0.05 versus donor and control, respectively). In MCT-rats, the pharmacological inhibitions of MC degranulation and c-kit with CSS and PLX, respectively by a preventive approach (treatment from day 1 to 21 of MCT-injection) significantly attenuated right ventricular systolic pressure (RVSP) and right ventricular hypertrophy (RVH). Moreover, vascular remodeling, as evident from the significantly decreased muscularization and medial wall thickness of distal pulmonary vessels, was improved. However, treatments with CSS and PLX by a therapeutic approach (from day 21 to 35 of MCT-injection) neither improved hemodynamics and RVH nor vascular remodeling.ConclusionsThe accumulation and activation of perivascular MCs in the lungs are the histopathological features present in clinical (IPAH patients) and experimental (MCT-rats) PH. Moreover, the accumulation and activation of MCs in the lungs contribute to the development of PH in MCT-rats. Our findings reveal an important pathophysiological insight into the role of MCs in the pathogenesis of PH in MCT-rats.

Project description:BackgroundRats with chronic hypoxia-induced non-inflammatory pulmonary hypertension (PH) are resistant to ventilator-induced lung injury. We investigated the effect of high tidal volume ventilation in another model of PH, monocrotaline (MCT)-induced PH, which is a type of inflammatory PH.MethodsPH was induced in rats by subcutaneous injection with 60 mg/kg MCT. Normal control rats, rats at 2 weeks after MCT injection (MCT2), and rats at 3 weeks after MCT injection (MCT3) were ventilated with low tidal volume (LV, 6 mL/kg) or high tidal volume (HV, 35 mL/kg) for 2 h with room air without positive end-expiratory pressure. Arterial oxygen pressure (PaO2) and Evans blue dye (EBD) extravasation were measured. Hypertensive pulmonary vascular remodeling was assessed morphometrically by the percentage of muscularized peripheral pulmonary arteries (%Muscularization) and the media wall thickness to external diameter ratio, namely percentage medial wall thickness (%MWT). To assess inflammation, lung IκB protein and cytokine mRNA expression levels were assessed.ResultsBaseline mean pulmonary arterial pressure was significantly higher in MCT rats (normal, 15.4 ± 0.5 mmHg; MCT2, 23.7 ± 0.9; and MCT3, 34.5 ± 1.5). After 2-h ventilation, PaO2 was significantly lower in the HV groups compared with the LV groups in normal and MCT2 rats, but not in MCT3 rats. Impairment of oxygenation with HV was less in MCT3 rats compared with normal and MCT2 rats. Among the HV groups, MCT3 rats showed significantly lower levels of EBD extravasation than normal and MCT2 rats. HV significantly downregulated IκB protein expression in normal and MCT3 rats and increased IL-6, MCP-1, CXCL-1 (MIP-1), and IL-10 mRNA levels in MCT3 rats. %Muscularization, %MWT, and the expression of lung elastin were significantly higher in MCT3 rats than in normal and MCT2 rats.ConclusionWe found that HV-associated damage might be reduced in MCT-induced PH rats compared with normal rats. The results of this and earlier studies suggest that hypertensive pulmonary vascular structural changes might be protective against the occurrence of ventilator-induced lung injury, irrespective of the etiology of PH.

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Activation of Nicotinic Acetylcholine ?7 Receptor Attenuates Progression of Monocrotaline-Induced Pulmonary Hypertension in Rats by Downregulating the NLRP3 Inflammasome.

Publications

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

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