Pulmonary inflammation is regulated by the levels of the vesicular acetylcholine transporter.

Nathalia M Pinheiro,Iolanda F L C Tibério,Mílton A Martins,Vânia F Prado,Soraia K P Costa,Claudia J C P Miranda,Carla M Prado,Marco Antônio M Prado,Niels O S Câmara,Adenir Perini,Luciana C Caperuto,Maria Isabel C Alonso-Vale

doi:10.1371/journal.pone.0120441

Abstract

Acetylcholine (ACh) plays a crucial role in physiological responses of both the central and the peripheral nervous system. Moreover, ACh was described as an anti-inflammatory mediator involved in the suppression of exacerbated innate response and cytokine release in various organs. However, the specific contributions of endogenous release ACh for inflammatory responses in the lung are not well understood. To address this question we have used mice with reduced levels of the vesicular acetylcholine transporter (VAChT), a protein required for ACh storage in secretory vesicles. VAChT deficiency induced airway inflammation with enhanced TNF-α and IL-4 content, but not IL-6, IL-13 and IL-10 quantified by ELISA. Mice with decreased levels of VAChT presented increased collagen and elastic fibers deposition in airway walls which was consistent with an increase in inflammatory cells positive to MMP-9 and TIMP-1 in the lung. In vivo lung function evaluation showed airway hyperresponsiveness to methacholine in mutant mice. The expression of nuclear factor-kappa B (p65-NF-kB) in lung of VAChT-deficient mice were higher than in wild-type mice, whereas a decreased expression of janus-kinase 2 (JAK2) was observed in the lung of mutant animals. Our findings show the first evidence that cholinergic deficiency impaired lung function and produce local inflammation. Our data supports the notion that cholinergic system modulates airway inflammation by modulation of JAK2 and NF-kB pathway. We proposed that intact cholinergic pathway is necessary to maintain the lung homeostasis.

Highlights

Pulmonary diseases such as asthma, acute lung inflammation and chronic obstructive pulmonary disease (COPD) represent major threats to human health
The cholinergic anti-inflammatory pathway is a modulator of innate immune responses by neuronal and non-neuronal mechanisms [3,4,5,6]. This statement is supported by the fact that during the inflammatory process, ACh released by the vagus nerve and acting via α7 nicotinic receptors (α7nAChR) present on macrophage and other immune cells, seems to inhibit cytokine production and contributing to counteract an ongoing state of inflammation [6,7,8,9]. α7nAChR activation inhibits the nuclear translocation of transcription factor NF-kB [10] but it activates the Janus kinase-2 and signal transducer and activator of transcription 3 pathway (JAK-STAT3)
These results suggest that long-term cholinergic deficiency affects pulmonary inflammation, pointing out the importance of acetylcholine in control pulmonary homeostasis

Summary

Introduction

Pulmonary diseases such as asthma, acute lung inflammation and chronic obstructive pulmonary disease (COPD) represent major threats to human health In common, they involve complex immune responses in which inflammatory and epithelial cells release elevated levels of pro-inflammatory Th1/Th2 cytokines such as IL-6, TNF-α, IL-4 and the regulatory cytokine IL-10 [1]. The cholinergic anti-inflammatory pathway is a modulator of innate immune responses by neuronal and non-neuronal mechanisms [3,4,5,6] This statement is supported by the fact that during the inflammatory process, ACh released by the vagus nerve and acting via α7 nicotinic receptors (α7nAChR) present on macrophage and other immune cells, seems to inhibit cytokine production and contributing to counteract an ongoing state of inflammation [6,7,8,9]. JAK2-STAT3 can in turn counteracts inflammation by regulating the activity of suppressor of cytokine signaling 3 (SOCS-3) [11]

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Conclusion